WorldWideScience

Sample records for biological denitrification process

  1. Microbial ecology of denitrification in biological wastewater treatment.

    Science.gov (United States)

    Lu, Huijie; Chandran, Kartik; Stensel, David

    2014-11-01

    Globally, denitrification is commonly employed in biological nitrogen removal processes to enhance water quality. However, substantial knowledge gaps remain concerning the overall community structure, population dynamics and metabolism of different organic carbon sources. This systematic review provides a summary of current findings pertaining to the microbial ecology of denitrification in biological wastewater treatment processes. DNA fingerprinting-based analysis has revealed a high level of microbial diversity in denitrification reactors and highlighted the impacts of carbon sources in determining overall denitrifying community composition. Stable isotope probing, fluorescence in situ hybridization, microarrays and meta-omics further link community structure with function by identifying the functional populations and their gene regulatory patterns at the transcriptional and translational levels. This review stresses the need to integrate microbial ecology information into conventional denitrification design and operation at full-scale. Some emerging questions, from physiological mechanisms to practical solutions, for example, eliminating nitrous oxide emissions and supplementing more sustainable carbon sources than methanol, are also discussed. A combination of high-throughput approaches is next in line for thorough assessment of wastewater denitrifying community structure and function. Though denitrification is used as an example here, this synergy between microbial ecology and process engineering is applicable to other biological wastewater treatment processes. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Applying the Nernst equation to simulate redox potential variations for biological nitrification and denitrification processes.

    Science.gov (United States)

    Chang, Cheng-Nan; Cheng, Hong-Bang; Chao, Allen C

    2004-03-15

    In this paper, various forms of Nernst equations have been developed based on the real stoichiometric relationship of biological nitrification and denitrification reactions. Instead of using the Nernst equation based on a one-to-one stoichiometric relation for the oxidizing and the reducing species, the basic Nernst equation is modified into slightly different forms. Each is suitable for simulating the redox potential (ORP) variation of a specific biological nitrification or denitrification process. Using the data published in the literature, the validity of these developed Nernst equations has been verified by close fits of the measured ORP data with the calculated ORP curve. The simulation results also indicate that if the biological process is simulated using an incorrect form of Nernst equation, the calculated ORP curve will not fit the measured data. Using these Nernst equations, the ORP value that corresponds to a predetermined degree of completion for the biochemical reaction can be calculated. Thus, these Nernst equations will enable a more efficient on-line control of the biological process.

  3. Design of fluidized-bed, biological denitrification systems

    International Nuclear Information System (INIS)

    Patton, B.D.; Hancher, C.W.; Pitt, W.W.; Walker, J.F.

    1982-01-01

    Many commercial processes yield nitrate-containing wastewaters that are being discharged to the environment because traditional recovery or disposal methods are economically unacceptable. The anticipated discharge limits (i.e., 10 to 20 g (NO 3 - )/m 3 ) being considered by many states will not allow continued release of these wastewaters. The new discharge standards can be met economically by use of the fluidizied-bed, biological denitrification process. Research and development studies were conducted with 0.05-, 0.10-, 0.20-, and 0.50-m-diam fluidized-bed bioreactor systems. Feed nitrate concentrations were in the 0 to 10,000 g (NO 3 - )/m 3 range. Using the data from these studies, rate expressions were developed for the destruction of nitrate as a function of nitrate concentration. Methods were also developed for sizing bioreactors and biomass control systems. The sizing methods for fluidized-bed denitrification systems are described, and support systems such as sampling and analysis, instrumentation and controls, utilities, and bacteria storage are discussed. Operation of the process is also briefly discussed to aid the designer. Using the methods presented in this report, fluidized-bed, biological denitrification systems can be designed to treat nitrate wastewater streams

  4. Controlled Carbon Source Addition to an Alternating Nitrification-Denitrification Wastewater Treatment Process Including Biological P Removal

    DEFF Research Database (Denmark)

    Isaacs, Steven Howard; Henze, Mogens

    1995-01-01

    The paper investigates the effect of adding an external carbon source on the rate of denitrification in an alternating activated sludge process including biological P removal. Two carbon sources were examined, acetate and hydrolysate derived from biologically hydrolyzed sludge. Preliminary batch ...

  5. Denitrification of acid wastes from uranium purification processes

    International Nuclear Information System (INIS)

    Clark, F.E.; Francis, C.W.; Francke, H.C.; Strohecker, J.W.

    1975-11-01

    Laboratory and pilot-plant investigations have shown the technical feasibility of removing nitrates from neutralized acid wastes from uranium purification processes by biological denitrification, a dissimilatory process in which the nitrate ion is reduced to nitrogen gas by specific bacteria. The process requires anaerobic conditions and an organic carbon source, as well as other life-sustaining constituents. These denitrification studies produced process design information on a columnar denitrification plant and on continuous-flow, stirred-bed reactors. Denitrification, using packed columns, was found to be desirable for soluble salts, such as those of sodium and ammonium; denitrification, using stirred reactors, was found to be desirable for mixtures containing insoluble salts, such as those of calcium and aluminum. Packed columns were found to have denitrification rates ranging up to 122 grams of nitrate per day per cubic decimeter of column volume; stirred-bed reactors have been shown to have reaction rates near 10 grams of nitrate per day per cubic decimeter of reactor volume. The continuous-flow, stirred-bed reactors were selected for scaleup studies because of the solids-removal problems associated with packed columns when operating on feeds containing high concentrations of insoluble salts or ions which form insoluble salts with the products of the denitrification reaction

  6. Biological nitrate removal from water and wastewater by solid-phase denitrification process.

    Science.gov (United States)

    Wang, Jianlong; Chu, Libing

    2016-11-01

    Nitrate pollution in receiving waters has become a serious issue worldwide. Solid-phase denitrification process is an emerging technology, which has received increasing attention in recent years. It uses biodegradable polymers as both the carbon source and biofilm carrier for denitrifying microorganisms. A vast array of natural and synthetic biopolymers, including woodchips, sawdust, straw, cotton, maize cobs, seaweed, bark, polyhydroxyalkanoate (PHA), polycaprolactone (PCL), polybutylene succinate (PBS) and polylactic acid (PLA), have been widely used for denitrification due to their good performance, low cost and large available quantities. This paper presents an overview on the application of solid-phase denitrification in nitrate removal from drinking water, groundwater, aquaculture wastewater, the secondary effluent and wastewater with low C/N ratio. The types of solid carbon source, the influencing factors, the microbial community of biofilm attached on the biodegradable carriers, the potential adverse effect, and the cost of denitrification process are introduced and evaluated. Woodchips and polycaprolactone are the popular and competitive natural plant-like and synthetic biodegradable polymers used for denitrification, respectively. Most of the denitrifiers reported in solid-phase denitrification affiliated to the family Comamonadaceae in the class Betaproteobacteria. The members of genera Diaphorobacter, Acidovorax and Simplicispira were mostly reported. In future study, more attention should be paid to the simultaneous removal of nitrate and toxic organic contaminants such as pesticide and PPCPs by solid-phase denitrification, to the elucidation of the metabolic and regulatory relationship between decomposition of solid carbon source and denitrification, and to the post-treatment of the municipal secondary effluent. Solid-phase denitrification process is a promising technology for the removal of nitrate from water and wastewater. Copyright © 2016

  7. Effect of pine bark and compost on the biological denitrification process of non-hazardous landfill leachate: Focus on the microbiology

    International Nuclear Information System (INIS)

    Trois, Cristina; Coulon, Frederic; Polge de Combret, Cecile; Martins, Jean M.F.; Oxarango, Laurent

    2010-01-01

    In an attempt to optimize the cost-efficiency of landfill leachate treatment by biological denitrification process, our study focused on finding low-cost alternatives to traditional expensive chemicals such as composted garden refuse and pine bark, which are both available in large amount in South African landfill sites. The overall objective was to assess the behaviour of the bacterial community in relation to each substrate while treating high strength landfill leachates. Denitrification processes in fixed bed reactors were simulated at laboratory scale using anaerobic batch tests with immature compost and pine bark. High strength leachate was simulated using a solution of water and nitrate at a concentration of 500 mg l -1 . Results suggest that pine bark released large amounts of phenolic compounds and hydroxylated benzene rings, which both can delay the acclimatization time and inhibit the biological denitrification (only 30% efficiency). Furthermore, presence of potential pathogens like Enterobacter and Pantoea agglomerans prevents the applicability of the pine bark in full-scale operations. On the other hand, lightly composted garden refuse (CGR) offered an adequate substrate for the formation of a biofilm necessary to complete the denitrification process (total nitrate removal observed within 7 days). CGR further contributed to a rapid establishment of an active consortium of denitrifiers including Acinetobacter, Rhizobium, Thermomonas, Rheinheimera, Phaeospirillum and Flavobacterium. Clearly the original composition, nature, carbon to nitrogen ratio (C/N) and degree of maturity and stability of the substrates play a key role in the denitrification process, impacting directly on the development of the bacterial population and, therefore, on the long-term removal efficiency.

  8. Effect of pine bark and compost on the biological denitrification process of non-hazardous landfill leachate: Focus on the microbiology

    Energy Technology Data Exchange (ETDEWEB)

    Trois, Cristina, E-mail: troisc@ukzn.ac.za [Centre for Research in Environmental, Coastal and Hydrological Engineering, School of Civil Engineering, Surveying and Construction, University of KwaZulu-Natal, Howard College Campus, Durban 4041 (South Africa); Coulon, Frederic; Polge de Combret, Cecile [Centre for Resource Management and Efficiency, School of Applied Sciences, Cranfield University, MK43 0AL (United Kingdom); Martins, Jean M.F.; Oxarango, Laurent [Laboratoire d' etude de Transferts en Hydrologie et Environnement, UMR 5564 (CNRS/INPG/IRD/UJF), Universite de Grenoble, BP 53, 38041 Grenoble Cedex 9 (France)

    2010-09-15

    In an attempt to optimize the cost-efficiency of landfill leachate treatment by biological denitrification process, our study focused on finding low-cost alternatives to traditional expensive chemicals such as composted garden refuse and pine bark, which are both available in large amount in South African landfill sites. The overall objective was to assess the behaviour of the bacterial community in relation to each substrate while treating high strength landfill leachates. Denitrification processes in fixed bed reactors were simulated at laboratory scale using anaerobic batch tests with immature compost and pine bark. High strength leachate was simulated using a solution of water and nitrate at a concentration of 500 mg l{sup -1}. Results suggest that pine bark released large amounts of phenolic compounds and hydroxylated benzene rings, which both can delay the acclimatization time and inhibit the biological denitrification (only 30% efficiency). Furthermore, presence of potential pathogens like Enterobacter and Pantoea agglomerans prevents the applicability of the pine bark in full-scale operations. On the other hand, lightly composted garden refuse (CGR) offered an adequate substrate for the formation of a biofilm necessary to complete the denitrification process (total nitrate removal observed within 7 days). CGR further contributed to a rapid establishment of an active consortium of denitrifiers including Acinetobacter, Rhizobium, Thermomonas, Rheinheimera, Phaeospirillum and Flavobacterium. Clearly the original composition, nature, carbon to nitrogen ratio (C/N) and degree of maturity and stability of the substrates play a key role in the denitrification process, impacting directly on the development of the bacterial population and, therefore, on the long-term removal efficiency.

  9. High rates of denitrification and nitrous oxide emission in arid biological soil crusts from the Sultanate of Oman

    DEFF Research Database (Denmark)

    Abed, Raeid M M; Lam, Phyllis; De Beer, Dirk

    2013-01-01

    Using a combination of process rate determination, microsensor profiling and molecular techniques, we demonstrated that denitrification, and not anaerobic ammonium oxidation (anammox), is the major nitrogen loss process in biological soil crusts from Oman. Potential denitrification rates were 584...... that nitrogen loss via denitrification is a dominant process in crusts from Oman, which leads to N 2 O gas emission and potentially reduces desert soil fertility....

  10. Modeling nitrous oxide production during biological nitrogen removal via nitrification and denitrification: extensions to the general ASM models.

    Science.gov (United States)

    Ni, Bing-Jie; Ruscalleda, Maël; Pellicer-Nàcher, Carles; Smets, Barth F

    2011-09-15

    Nitrous oxide (N(2)O) can be formed during biological nitrogen (N) removal processes. In this work, a mathematical model is developed that describes N(2)O production and consumption during activated sludge nitrification and denitrification. The well-known ASM process models are extended to capture N(2)O dynamics during both nitrification and denitrification in biological N removal. Six additional processes and three additional reactants, all involved in known biochemical reactions, have been added. The validity and applicability of the model is demonstrated by comparing simulations with experimental data on N(2)O production from four different mixed culture nitrification and denitrification reactor study reports. Modeling results confirm that hydroxylamine oxidation by ammonium oxidizers (AOB) occurs 10 times slower when NO(2)(-) participates as final electron acceptor compared to the oxic pathway. Among the four denitrification steps, the last one (N(2)O reduction to N(2)) seems to be inhibited first when O(2) is present. Overall, N(2)O production can account for 0.1-25% of the consumed N in different nitrification and denitrification systems, which can be well simulated by the proposed model. In conclusion, we provide a modeling structure, which adequately captures N(2)O dynamics in autotrophic nitrification and heterotrophic denitrification driven biological N removal processes and which can form the basis for ongoing refinements.

  11. The Effects of Different External Carbon Sources on Nitrous Oxide Emissions during Denitrification in Biological Nutrient Removal Processes

    Science.gov (United States)

    Hu, Xiang; Zhang, Jing; Hou, Hongxun

    2018-01-01

    The aim of this study was to investigate the effects of two different external carbon sources (acetate and ethanol) on the nitrous oxide (N2O) emissions during denitrification in biological nutrient removal processes. Results showed that external carbon source significantly influenced N2O emissions during the denitrification process. When acetate served as the external carbon source, 0.49 mg N/L and 0.85 mg N/L of N2O was produced during the denitrificaiton processes in anoxic and anaerobic/anoxic experiments, giving a ratio of N2O-N production to TN removal of 2.37% and 4.96%, respectively. Compared with acetate, the amount of N2O production is negligible when ethanol used as external carbon addition. This suggested that ethanol is a potential alternative external carbon source for acetate from the point of view of N2O emissions.

  12. Carbon source recovery from excess sludge by mechanical disintegration for biological denitrification.

    Science.gov (United States)

    Zubrowska-Sudol, M

    2018-04-01

    The goal of the study was to evaluate the possibility of carbon source recovery from excess sludge by mechanical disintegration for biological denitrification. The total efficiency of denitrification, unit demand for organic compounds for denitrification, unit volume of disintegrated sludge and unit cost of nitrogen removal as a function of energy density used for excess sludge disintegration (70, 140 and 210 kJ/L) were analyzed. In the study a full-scale disc disintegrator was used (motor power: 30 kWh, motor speed: 2,950 rpm). It was shown that the amounts of organic compounds released from the activated sludge flocs at all tested levels of energy density are high enough to be used to intensify the removal of nitrogen compounds from wastewater. It was also documented that the energy density provided during process of disintegration was an important factor determining the characteristics of organic compounds obtained under the disintegration for their use in order to intensify the process of denitrification. The highest value of total efficiency of denitrification (50.5 ± 3.1 mg N/L) was obtained for carbon source recovery from excess sludge at 70 kJ/L, but the lowest unit cost of nitrogen removal occurred for 140 kJ/L (0.0019 ± 0.0011 EUR/g N).

  13. Biological and geochemical processes involved during denitrification in Callovo-Oxfordian clay

    International Nuclear Information System (INIS)

    Ollivier, P.; Parmentier, M.; Joulian, C.; Pauwels, H.; Albrecht, A.

    2012-01-01

    Document available in extended abstract form only. The clay-rich Callovo-Oxfordian (COx) formation has been selected for the disposal of medium and high level, long-lived radioactive waste. After waste cell closure and degradation of package some intermediate-level waste will release nitrate. The latter is likely to diffuse into the surrounding environment (engineered barriers and geological host formation) and interact with a variety compounds present in the barrier components and the rocks. These interactions may result in modification of chemical conditions and impact storage conditions and radionuclide retention. Our work is focused on the understanding of the fate of nitrates released during and after degradation of waste package. We developed a coupled approach considering both geochemical and biological processes of nitrate reduction to simulate reactions occurring at the interface of the engineered barrier and the clay-rich COx formation. Laboratory experiments have been carried out in order to acquire data on kinetics of denitrification coupled with a molecular approach using enzymatic and metabolic activities as a tool for an accurate estimation of biomass. Denitrification has been monitored in a synthetic solution comparable to COx pore water supplemented with acetate and nitrate and amended with a heterotrophic denitrifying strain, Pseudomonas mandelii. Several conditions are applied considering different acetate/nitrate ratios in the presence or absence of COx clay. Before the beginning of experiments, the headspace is flushed with N 2 gas to remove oxygen from flasks. Acetylene is used to stop denitrification reaction after the production of N 2 O gas and thus avoid the formation of N 2 gas. Two successive redox reactions are thus expected to occur in experiments. Samples are regularly collected to analyze physical and chemical parameters as well as biological parameters. Biomass is estimated and monitored using both optical microscopy and

  14. Modeling Nitrous Oxide Production during Biological Nitrogen Removal via Nitrification and Denitrification: Extensions to the General ASM Models

    DEFF Research Database (Denmark)

    Ni, Bing-Jie; Ruscalleda, Maël; Pellicer i Nàcher, Carles

    2011-01-01

    on N2O production from four different mixed culture nitrification and denitrification reactor study reports. Modeling results confirm that hydroxylamine oxidation by ammonium oxidizers (AOB) occurs 10 times slower when NO2– participates as final electron acceptor compared to the oxic pathway. Among......Nitrous oxide (N2O) can be formed during biological nitrogen (N) removal processes. In this work, a mathematical model is developed that describes N2O production and consumption during activated sludge nitrification and denitrification. The well-known ASM process models are extended to capture N2O...

  15. Biological denitrification process based on the Fe(0)-carbon micro-electrolysis for simultaneous ammonia and nitrate removal from low organic carbon water under a microaerobic condition.

    Science.gov (United States)

    Deng, Shihai; Li, Desheng; Yang, Xue; Xing, Wei; Li, Jinlong; Zhang, Qi

    2016-11-01

    A combined process between micro-electrolysis and biological denitrification (MEBD) using iron scraps and an activated carbon-based micro-electrolysis carrier was developed for nitrogen removal under a microaerobic condition. The process provided NH4(+)-N and total nitrogen (TN) removal efficiencies of 92.6% and 95.3%, respectively, and TN removal rate of 0.373±0.11kgN/(m(3)d) at corresponding DO of 1.0±0.1mg/L and HRT of 3h, and the optimal pH of 7.6-8.4. High-throughput sequencing analysis verified that dominant classes belonged to β-, α-, and γ-Proteobacteria, and Nitrospira. The dominant genera Hydrogenophaga and Sphaerotilus significantly increased during the operation, covering 13.2% and 6.1% in biofilms attached to the carrier in the middle of the reactor, respectively. Autotrophic denitrification contributed to >80% of the TN removal. The developed MEBD achieved efficient simultaneous nitrification and autotrophic denitrification, presenting significant potential for application in practical low organic carbon water treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Assessment of denitrification process in lower Ishikari river system, Japan.

    Science.gov (United States)

    Jha, Pawan Kumar; Minagawa, Masao

    2013-11-01

    Sediment denitrification rate and its role in removal of dissolved nitrate load in lower Ishikari river system were examined. Denitrification rate were measured using acetylene inhibition technique on the sediment samples collected during August 2009-July 2010. The denitrification rate varied from 0.001 to 1.9 μg Ng(-1) DM h(-1) with an average value of 0.21 μg Ng(-1) DM h(-1) in lower Ishikari river system. Denitrification rate showed positive correlation with dissolved nitrate concentration in the river basin, indicating overlying water column supplied nitrate for the sediment denitrification processes. Nutrient enrichment experiments result showed that denitrification rate increased significantly with addition of nitrate in case of samples collected from Barato Lake however no such increase was observed in the samples collected from Ishikari river main channel and its major tributaries indicating that factors other than substrate concentration such as population of denitrifier and hydrological properties of stream channel including channel depth and flow velocity may affects the denitrification rate in lower Ishikari river system. Denitrification rate showed no significant increase with the addition of labile carbon (glucose), indicating that sediment samples had sufficient organic matter to sustain denitrification activity. The result of nutrient spiraling model indicates that in- stream denitrification process removes on an average 5%d(-1) of dissolve nitrate load in Ishikari river. This study was carried out to fill the gap present in the availability of riverine denitrification rate measurement and its role in nitrogen budget from Japanese rivers characterize by small river length and high flow rate. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. A Tire-Sulfur Hybrid Adsorption Denitrification (T-SHAD) process for decentralized wastewater treatment.

    Science.gov (United States)

    Krayzelova, Lucie; Lynn, Thomas J; Banihani, Qais; Bartacek, Jan; Jenicek, Pavel; Ergas, Sarina J

    2014-09-15

    Nitrogen discharges from decentralized wastewater treatment (DWT) systems contribute to surface and groundwater contamination. However, the high variability in loading rates, long idle periods and lack of regular maintenance presents a challenge for biological nitrogen removal in DWT. A Tire-Sulfur Hybrid Adsorption Denitrification (T-SHAD) process was developed that combines nitrate (NO3(-)) adsorption to scrap tire chips with sulfur-oxidizing denitrification. This allows the tire chips to adsorb NO3(-) when the influent loading exceeds the denitrification capacity of the biofilm and release it when NO3(-) loading rates are low (e.g. at night). Three waste products, scrap tire chips, elemental sulfur pellets and crushed oyster shells, were used as a medium in adsorption, leaching, microcosm and up-flow packed bed bioreactor studies of NO3(-) removal from synthetic nitrified DWT wastewater. Adsorption isotherms showed that scrap tire chips have an adsorption capacity of 0.66 g NO3(-)-N kg(-1) of scrap tires. Leaching and microcosm studies showed that scrap tires leach bioavailable organic carbon that can support mixotrophic metabolism, resulting in lower effluent SO4(2-) concentrations than sulfur oxidizing denitrification alone. In column studies, the T-SHAD process achieved high NO3(-)-N removal efficiencies under steady state (90%), variable flow (89%) and variable concentration (94%) conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Denitrification gene density across a wastewater-impacted riparian buffer zone

    Science.gov (United States)

    Riparian buffers are a best management practice used extensively to protect water bodies from agriculturally-generated nitrate pollution. In particular, the biological process of denitrification has been shown to be a sink for this nitrate. Denitrification results in the reduction of nitrate under a...

  19. Biological denitrification of high-nitrates wastes generated in the nuclear industry

    International Nuclear Information System (INIS)

    Francis, C.W.

    1980-01-01

    Biological denitrification appears to be one of the most effective methods to remove nitrates from wastewater streams (Christenson and Harremoes, 1975). However, most of the research and development work has been centered on removal of nitrates from sewage or agricultural drainage waters, nitrate nitrogen concentration usually less than 50 g/m 3 . Work was initiated at Oak Ridge National Laboratory (ORNL) in 1974 to test the use of biological nitrification in the removal of high concentrations of nitrate (in excess of 1.0 kg NO 3 -N/m 3 ) from uranium purification waste streams. Since then, a full-scale treatment facility, a stirred reactor, has been installed at the Y-12 plant; and a pilot-plant, using a fluidized bed, has been proposed at Portsmouth Gaseous Diffusion Plant. The objective of this manuscript is to present some applied microbiological research relating to possible constraints in biologically denitrifying certain waste streams in the nuclear industry and comparing the effectiveness of denitrification of these waste streams in three bench scale reactors, (1) a continuous flow-stirred reactor, (2) stirred bed rector, and (3) a fluidized bed reactor

  20. Effect of dissolved oxygen on biological denitrification using biodegradable plastic as the carbon source

    Science.gov (United States)

    Zhang, Xucai; Zhang, Jianmei

    2018-02-01

    Biological denitrification is currently a common approach to remove nitrate from wastewater. This study was conducted to evaluate the influence of dissolved oxygen on denitrification in wastewater treatment using biodegradable plastic as carbon source by designing the aerated, anoxic, and low-oxygen experimental treatment groups. The results showed that the removal rates of nitrate in anoxic and low-oxygen groups were 30.6 g NO3 --Nm-3 d-1 and 30.8 g NO3 --N m-3 d-1 at 83 h, respectively, both of which were higher than that of the aerated group. There was no significant difference between the anoxic and low-oxygen treatment groups for the nitrate removal. Additional, the nitrite accumulated during the experiments, and the nitrite concentrations in anoxic and aerated groups were lower than those in low-oxygen group. No nitrite was detected in all groups at the end of the experiments. These findings indicated that dissolved oxygen has important influence on denitrification, and anoxic and low-oxygen conditions can support completely denitrification when using BP as carbon source in nitrate-polluted wastewater treatment.

  1. The use of a rubble chimney for denitrification of irrigation return waters

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Roy B; Kruger, Paul [Civil Engineering Department, Stanford University (United States)

    1970-05-15

    Biological denitrification has been proposed as a means of removing nitrates from waste waters to control eutrophication in receiving waters. A potential use for this method is the treatment of irrigation return waters containing high concentrations of nitrate-nitrogen, since direct discharge of such wastes may cause objectionable algal growth in the receiving waters. For example, the process may be used to treat agricultural waste waters in the San Joaquin Valley in California, where an estimated 580,000 acre-feet/year of return waters, containing 20 mg/l of nitrate-nitrogen, will require disposal by A.D. 2020. Two methods of biological denitrification are presently under study for possible use in the San Joaquin Valley. In one method nitrates are reduced to nitrogen gas by bacterial action in deep ponds; in the other method bacterial denitrification takes place in biological filters. In biological filters, bacteria are grown on columns of submerged stones. A possible alternative to the conventional construction of these filters is the creation of a rubble chimney by a contained nuclear explosion. This paper presents the results of a preliminary investigation of the feasibility of using a rubble chimney as a biological filter for denitrification. (author)

  2. The use of a rubble chimney for denitrification of irrigation return waters

    International Nuclear Information System (INIS)

    Evans, Roy B.; Kruger, Paul

    1970-01-01

    Biological denitrification has been proposed as a means of removing nitrates from waste waters to control eutrophication in receiving waters. A potential use for this method is the treatment of irrigation return waters containing high concentrations of nitrate-nitrogen, since direct discharge of such wastes may cause objectionable algal growth in the receiving waters. For example, the process may be used to treat agricultural waste waters in the San Joaquin Valley in California, where an estimated 580,000 acre-feet/year of return waters, containing 20 mg/l of nitrate-nitrogen, will require disposal by A.D. 2020. Two methods of biological denitrification are presently under study for possible use in the San Joaquin Valley. In one method nitrates are reduced to nitrogen gas by bacterial action in deep ponds; in the other method bacterial denitrification takes place in biological filters. In biological filters, bacteria are grown on columns of submerged stones. A possible alternative to the conventional construction of these filters is the creation of a rubble chimney by a contained nuclear explosion. This paper presents the results of a preliminary investigation of the feasibility of using a rubble chimney as a biological filter for denitrification. (author)

  3. Denitrification in groundwater at uranium mill tailings sites

    International Nuclear Information System (INIS)

    Goering, Timothy J.; Groffman, Armando; Thomson, Bruce

    1992-01-01

    Nitrates are a major contaminant in groundwater at many Uranium Mill Tailings Remedial Action (UMTRA) sites. Microbial denitrification, the transformation of nitrate to nitrogen gas, may be occurring in groundwater at several UMTRA sites. Denitrification is a biologically mediated process whereby facultative anaerobes use nitrate for respiration under anaerobic conditions. Denitrifying bacteria are ubiquitous in soils, sediments, and water. Denitrification requires nitrate, organic carbon, oxygen-limiting conditions, and trace nutrients, especially phosphorus. The lack of organic carbon is the most common limiting factor for denitrification. Denitrification occurs under a limited range of temperature and pH. The uranium milling processes used at UMTRA sites provided a readily available source of carbon and nitrates for denitrifying bacteria. At the Maybell, Colorado, site, the denitrifying organisms Pseudomonas, Flavobacterium and Acinetobacter were identified in core samples of materials from beneath the tailings. In addition, microcosm experiments simulating aquifer conditions beneath the tailings pile showed an average 40 percent decrease in nitrate concentrations over 13 days. At the New Rifle, Colorado, site, aquifer conditions appear favorable for denitrification. Nitrate and organic carbon are readily available in the groundwater, and redox conditions beneath and downgradient of the tailings pile are relatively anoxic. Downgradient from the tailings, total nitrogen is being removed from the groundwater system at a greater rate than the geochemically conservative anion, chloride. This removal may be due to denitrification and adsorption of ammonium onto clay and silt particles. (author)

  4. Denitrification in groundwater at uranium mill tailings sites

    Energy Technology Data Exchange (ETDEWEB)

    Goering, Timothy J [Jacobs Engineering Group, Inc., Albuquerque, NM (United States); Groffman, Armando [Roy F. Weston, Inc., Albuquerque, NM (United States); Thomson, Bruce [University of New Mexico, Albuquerque, NM (United States)

    1992-07-01

    Nitrates are a major contaminant in groundwater at many Uranium Mill Tailings Remedial Action (UMTRA) sites. Microbial denitrification, the transformation of nitrate to nitrogen gas, may be occurring in groundwater at several UMTRA sites. Denitrification is a biologically mediated process whereby facultative anaerobes use nitrate for respiration under anaerobic conditions. Denitrifying bacteria are ubiquitous in soils, sediments, and water. Denitrification requires nitrate, organic carbon, oxygen-limiting conditions, and trace nutrients, especially phosphorus. The lack of organic carbon is the most common limiting factor for denitrification. Denitrification occurs under a limited range of temperature and pH. The uranium milling processes used at UMTRA sites provided a readily available source of carbon and nitrates for denitrifying bacteria. At the Maybell, Colorado, site, the denitrifying organisms Pseudomonas, Flavobacterium and Acinetobacter were identified in core samples of materials from beneath the tailings. In addition, microcosm experiments simulating aquifer conditions beneath the tailings pile showed an average 40 percent decrease in nitrate concentrations over 13 days. At the New Rifle, Colorado, site, aquifer conditions appear favorable for denitrification. Nitrate and organic carbon are readily available in the groundwater, and redox conditions beneath and downgradient of the tailings pile are relatively anoxic. Downgradient from the tailings, total nitrogen is being removed from the groundwater system at a greater rate than the geochemically conservative anion, chloride. This removal may be due to denitrification and adsorption of ammonium onto clay and silt particles. (author)

  5. Advances in wastewater nitrogen removal by biological processes: state of the art review

    Directory of Open Access Journals (Sweden)

    Andrea G. Capodaglio

    2016-04-01

    Full Text Available The paper summarizes the state-of-the-art of the most recent advances in biological nitrogen removal, including process design criteria and technological innovations. With reference to the Modified Ludzck Ettinger (MLE process (pre-denitrification and nitrification in the activated sludge process, the most common nitrogen removal process used nowadays, a new design equation for the denitrification reactor based on specific denitrification rate (SDNR has been proposed. In addition, factors influencing SDNR (DO in the anoxic reactor; hydrodynamic behavior are analyzed, and technological solutions are proposed. Concerning technological advances, the paper presents a summary of various “deammonification” processes, better known by their patent names like ANAMMOX®, DEMON®, CANON®, ANITA® and others. These processes have already found applications in the treatment of high-strength wastewater such as digested sludge liquor and landfill leachate. Among other emerging denitrification technologies, consideration is given to the Membrane Biofilm Reactors (MBfRs that can be operated both in oxidation and reduction mode.

  6. In Situ Denitrification and Biological Nitrogen Fixation Under Enhanced Atmospheric Reactive Nitrogen Deposition in UK Peatlands

    Science.gov (United States)

    Ullah, Sami; Saiz Val, Ernesto; Sgouridis, Fotis; Peichl, Matthias; Nilsson, Mats

    2017-04-01

    Dinitrogen (N2) and nitrous oxide (N2O) losses due to denitrification and biological N2 fixation (BNF) are the most uncertain components of the nitrogen (N) cycle in peatlands under enhanced atmospheric reactive nitrogen (Nr) deposition. This uncertainty hampers our ability to assess the contribution of denitrification to the removal of biologically fixed and/or atmospherically deposited Nr in peatlands. This uncertainty emanates from the difficulty in measuring in situ soil N2 and N2O production and consumption in peatlands. In situ denitrification and its contribution to total N2O flux was measured monthly between April 2013 and October 2014 in peatlands in two UK catchments. An adapted 15N-Gas Flux method1 with low level addition of 15N tracer (0.03 ± 0.005 kg 15N ha-1) was used to measure denitrification and its contribution to net N2O production (DN2O/TN2O). BNF was measured in situ through incubation of selected sphagnum species under 15N2 gas tracer. Denitrification2 varied temporally and averaged 8 kg N-N2 ha-1 y-1. The contribution of denitrification was about 48% to total N2O flux3 of 0.05 kg N ha-1 y-1. Soil moisture, temperature, ecosystem respiration, pH and mineral N content mainly regulated the flux of N2 and N2O. Preliminary results showed suppression of BNF, which was 1.8 to 7 times lower in peatland mosses exposed to ˜15 to 20 kg N ha-1 y-1 Nr deposition in the UK than in peatland mosses in northern Sweden with background Nr deposition. Overall, the contribution of denitrification to Nr removal in the selected peatlands was ˜50% of the annual Nr deposition rates, making these ecosystems vulnerable to chronic N saturation. These results point to a need for a more comprehensive annual BNF measurement to more accurately account for total Nr input into peatlands and its atmospheric loss due to denitrification. References Sgouridis F, Stott A & Ullah S, 2016. Application of the 15N-Gas Flux method for measuring in situ N2 and N2O fluxes due to

  7. Thermal hydrolysis of sludge and the use of hydrolysate as carbon source for denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Barlindhaug, J

    1995-10-01

    As a consequence of the North Sea- and the Baltic Sea Treaties as well as the Wastewater Directive of the EU, several large wastewater treatment plants discharging to sensitive receiving waters have to include phosphorus as well as nitrogen removal. This thesis evaluates the so called NTH-process for nutrient removal. In this process pre-precipitation is used in front of a biological nitrogen removal step that is based on a combination of pre- and post-denitrification in moving bed biofilm reactors. The biological step is followed by a final separation step, possibly after coagulant addition. Carbon source for the post denitrification step is made available by hydrolysis of the sludge produced. The idea is that the particulate organic matter, which in a traditional pre-denitrification step would have to be enzymatically hydrolyzed, can be more efficiently hydrolyzed in a concentrated sidestream and used in a post-denitrification step. In the thesis hydrolyzed sludge is used as a carbon source for denitrification. The objective is to investigate the influence of varying hydrolysis conditions on the composition and amount of the thermal hydrolysate produced, as well as the quality of the hydrolysate as a carbon source for denitrification. 201 refs., 78 refs., 53 tabs.

  8. Simultaneous biological nutrient removal: evaluation of autotrophic denitrification, heterotrophic nitrification, and biological phosphorus removal in full-scale systems.

    Science.gov (United States)

    Littleton, Helen X; Daigger, Glen T; Strom, Peter F; Cowan, Robert A

    2003-01-01

    Simultaneous biological nutrient removal (SBNR) is the biological removal of nitrogen and phosphorus in excess of that required for biomass synthesis in a biological wastewater treatment system without defined anaerobic or anoxic zones. Evidence is growing that significant SBNR can occur in many systems, including the aerobic zone of systems already configured for biological nutrient removal. Although SBNR systems offer several potential advantages, they cannot be fully realized until the mechanisms responsible for SBNR are better understood. Consequently, a research program was initiated with the basic hypothesis that three mechanisms might be responsible for SBNR: the reactor macroenvironment, the floc microenvironment, and novel microorganisms. Previously, the nutrient removal capabilities of seven full-scale, staged, closed-loop bioreactors known as Orbal oxidation ditches were evaluated. Chemical analysis and microbiological observations suggested that SBNR occurred in these systems. Three of these plants were further examined in this research to evaluate the importance of novel microorganisms, especially for nitrogen removal. A screening tool was developed to determine the relative significance of the activities of microorganisms capable of autotrophic denitrification and heterotrophic nitrification-aerobic denitrification in biological nutrient removal systems. The results indicated that novel microorganisms were not substantial contributors to SBNR in the plants studied. Phosphorus metabolism (anaerobic release, aerobic uptake) was also tested in one of the plants. Activity within the mixed liquor that was consistent with current theories for phosphorus-accumulating organisms (PAOs) was observed. Along with other observations, this suggests the presence of PAOs in the facilities studied.

  9. Integrating anammox with the autotrophic denitrification process via electrochemistry technology.

    Science.gov (United States)

    Qiao, Sen; Yin, Xin; Zhou, Jiti; Wei, Li'e; Zhong, Jiayou

    2018-03-01

    In this study, an autotrophic denitrification process was successfully coupled with anammox to remove the nitrate by-product via electrochemical technology. When the voltage applied to the combined electrode reactor was 1.5 V, the electrode reaction removed nitrate by using the autotrophic denitrification biomass without affecting the anammox biomass. The nitrogen removal efficiency of the combined electrode reactor reached 99.1% without detectable nitrate at an influent NO 2 - -N/NH 4 + -N ratio of 1.5. On day 223, using the model calculations based on reaction equations, 19.7% of total nitrogen was removed via the autotrophic denitrification process, while the majority of nitrogen removal (approximately 79.4%) was attributed to the anammox reaction. Small variations of the population numbers and community structure of artificial bacteria according to electron microscopy predicted that the anammox and autotrophic denitrifying biomasses could coexist in the electrode reactor. Then, 16S rRNA analysis determined that the anammox biomass group was always dominant in mixed flora during continuous cultivation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Warming can boost denitrification disproportionately due to altered oxygen dynamics.

    Directory of Open Access Journals (Sweden)

    Annelies J Veraart

    Full Text Available BACKGROUND: Global warming and the alteration of the global nitrogen cycle are major anthropogenic threats to the environment. Denitrification, the biological conversion of nitrate to gaseous nitrogen, removes a substantial fraction of the nitrogen from aquatic ecosystems, and can therefore help to reduce eutrophication effects. However, potential responses of denitrification to warming are poorly understood. Although several studies have reported increased denitrification rates with rising temperature, the impact of temperature on denitrification seems to vary widely between systems. METHODOLOGY/PRINCIPAL FINDINGS: We explored the effects of warming on denitrification rates using microcosm experiments, field measurements and a simple model approach. Our results suggest that a three degree temperature rise will double denitrification rates. By performing experiments at fixed oxygen concentrations as well as with oxygen concentrations varying freely with temperature, we demonstrate that this strong temperature dependence of denitrification can be explained by a systematic decrease of oxygen concentrations with rising temperature. Warming decreases oxygen concentrations due to reduced solubility, and more importantly, because respiration rates rise more steeply with temperature than photosynthesis. CONCLUSIONS/SIGNIFICANCE: Our results show that denitrification rates in aquatic ecosystems are strongly temperature dependent, and that this is amplified by the temperature dependencies of photosynthesis and respiration. Our results illustrate the broader phenomenon that coupling of temperature dependent reactions may in some situations strongly alter overall effects of temperature on ecological processes.

  11. Acid Fermentation Process Combined with Post Denitrification for the Treatment of Primary Sludge and Wastewater with High Strength Nitrate

    Directory of Open Access Journals (Sweden)

    Allen Kurniawan

    2016-03-01

    Full Text Available In this study, an anaerobic baffled reactor (ABR, combined with a post denitrification process, was applied to treat primary sludge from a municipal wastewater treatment plant and wastewater with a high concentration of nitrate. The production of volatile fatty acids (VFAs was maximized with a short hydraulic retention time in the acid fermentation of the ABR process, and then the produced VFAs were supplied as an external carbon source for the post denitrification process. The laboratory scale experiment was operated for 160 days to evaluate the VFAs’ production rate, sludge reduction in the ABR type-acid fermentation process, and the specific denitrification rate of the post denitrification process. As results, the overall removal rate of total chemical oxygen demand (TCOD, total suspended solids (TSS, and total nitrogen (TN were found to be 97%, 92%, 73%, respectively, when considering the influent into ABR type-acid fermentation and effluent from post denitrification. We observed the specific VFAs production rate of 0.074 gVFAs/gVSS/day for the ABR type-acid fermentation, and an average specific denitrification rate of 0.166 gNO3−-N/gVSS/day for the post denitrification. Consequently, we observed that a high production of VFAs from a primary sludge, using application of the ABR type acid fermentation process and the produced VFAs were then successfully utilized as an external carbon source for the post denitrification process, with a high removal rate of nitrogen.

  12. Studies on denitrification performance of tricking filters

    International Nuclear Information System (INIS)

    Ruediger, A.

    1993-01-01

    Trickling filters are one of the oldest methods of biological waste water purification, widely used ever since they were first developed. These filters are mostly used for aerobic purification of water as highly polluted or lightly polluted reactors. While these systems are very useful for the elemination of organic pollution and the nitrification of the waste waters, denitrification of the whole plant poses considerable problems. The question is in how far trickling filters can be used as denitrification reactors. The conditions of successful denitrification in trickling filters is investigated, denitrification performance is established. Studies were conducted in laboratory, semi-industrial and industrial scale. (BBR) [de

  13. Assessment of the denitrification process in alluvial wetlands at floodplain scale using the SWAT model

    Science.gov (United States)

    As alluvial plains support intensive agricultural activities, they often suffer from groundwater nitrate pollution. Denitrification is recognized as an important process in nitrate pollution control in riparian zones. In shallow aquifer zones influenced by recharged surface water, denitrification ...

  14. Denitrification

    National Research Council Canada - National Science Library

    Payne, W. J

    1981-01-01

    .... After an introduction on the discovery of the denitrification process and the development of research into it, the author considers successively the four anerobic, reductive steps that comprise...

  15. ANAEROBIC DIGESTION AND THE DENITRIFICATION IN UASB REACTOR

    Directory of Open Access Journals (Sweden)

    José Tavares de Sousa

    2008-01-01

    Full Text Available The environmental conditions in Brazil have been contributing to the development of anaerobic systems in the treatment of wastewaters, especially UASB - Upflow Anaerobic Sludge Blanket reactors. The classic biological process for removal of nutrients uses three reactors - Bardenpho System, therefore, this work intends an alternative system, where the anaerobic digestion and the denitrification happen in the same reactor reducing the number of reactors for two. The experimental system was constituted by two units: first one was a nitrification reactor with 35 L volume and 15 d of sludge age. This system was fed with raw sanitary waste. Second unit was an UASB, with 7.8 L and 6 h of hydraulic detention time, fed with ¾ of effluent nitrification reactor and ¼ of raw sanitary waste. This work had as objective to evaluate the performance of the UASB reactor. In terms of removal efficiency, of bath COD and nitrogen, it was verified that the anaerobic digestion process was not affected. The removal efficiency of organic material expressed in COD was 71%, performance already expected for a reactor of this type. It was also observed that the denitrification process happened; the removal nitrate efficiency was 90%. Therefore, the denitrification process in reactor UASB is viable.

  16. Regulation by sliding operation of a denitrification process; Regulation par regime glissant d`un procede de denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Babary, J.P.; Bourrel, S.

    1995-12-31

    Biotechnological processing of waste waters is made through fixed bed bioreactors. Biochemical reaction kinetics can be modelled by non linear differential equations. The model is used to develop control laws. As an application, a denitrification bioreactor is modelled. Then control algorithm is checked through mathematical simulation of nitrogen compounds concentration ratio. (D.L.)

  17. Sulfur-oxidizing autotrophic and mixotrophic denitrification processes for drinking water treatment: elimination of excess sulfate production and alkalinity requirement.

    Science.gov (United States)

    Sahinkaya, Erkan; Dursun, Nesrin

    2012-09-01

    This study evaluated the elimination of alkalinity need and excess sulfate generation of sulfur-based autotrophic denitrification process by stimulating simultaneous autotrophic and heterotrophic (mixotrophic) denitrification process in a column bioreactor by methanol supplementation. Also, denitrification performances of sulfur-based autotrophic and mixotrophic processes were compared. In autotrophic process, acidity produced by denitrifying sulfur-oxidizing bacteria was neutralized by the external NaHCO(3) supplementation. After stimulating mixotrophic denitrification process, the alkalinity need of the autotrophic process was satisfied by the alkalinity produced by heterotrophic denitrifiers. Decreasing and lastly eliminating the external alkalinity supplementation did not adversely affect the process performance. Complete denitrification of 75 mg L(-1) NO(3)-N under mixotrophic conditions at 4 h hydraulic retention time was achieved without external alkalinity supplementation and with effluent sulfate concentration lower than the drinking water guideline value of 250 mg L(-1). The denitrification rate of mixotrophic process (0.45 g NO(3)-N L(-1) d(-1)) was higher than that of autotrophic one (0.3 g NO(3)-N L(-1) d(-1)). Batch studies showed that the sulfur-based autotrophic nitrate reduction rate increased with increasing initial nitrate concentration and transient accumulation of nitrite was observed. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Simultaneous bioreduction of nitrate and chromate using sulfur-based mixotrophic denitrification process

    Energy Technology Data Exchange (ETDEWEB)

    Sahinkaya, Erkan, E-mail: erkansahinkaya@yahoo.com [Istanbul Medeniyet University, Bioengineering Department, Goztepe, Istanbul (Turkey); Kilic, Adem [Harran University, Environmental Engineering Department, Osmanbey Campus, 63000 Sanliurfa (Turkey); Calimlioglu, Beste; Toker, Yasemin [Istanbul Medeniyet University, Bioengineering Department, Goztepe, Istanbul (Turkey)

    2013-11-15

    Highlights: • Simultaneous heterotrophic and autotrophic denitrification was stimulated. • Simultaneous bioreduction of nitrate and chromate was achieved. • Total chromium decreased <50 μg/L when the influent Cr(VI) was ≤5 mg/L. -- Abstract: This study aims at evaluating simultaneous chromate and nitrate reduction using sulfur-based mixotrophic denitrification process in a column reactor packed with elemental sulfur and activated carbon. The reactor was supplemented with methanol at C/N ratio of 1.33 or 2. Almost complete denitrification was achieved at influent NO{sub 3}{sup −}–N and Cr(VI) concentrations of 75 mg/L and 10 mg/L, respectively, and 3.7 h HRT. Maximum denitrification rate was 0.5 g NO{sub 3}{sup −}–N/(L.d) when the bioreactor was fed with 75 mg/L NO{sub 3}{sup −}–N, 150 mg/L methanol and 10 mg/L Cr(VI). The share of autotrophic denitrification was between 12% and 50% depending on HRT, C/N ratio and Cr(VI) concentration. Effluent total chromium was below 50 μg/L provided that influent Cr(VI) concentration was equal or below 5 mg/L. DGGE results showed stable microbial community throughout the operation and the presence of sulfur oxidizing denitrifying bacteria (Thiobacillus denitrificans) and Cr(VI) reducing bacteria (Exiguobacterium spp.) in the column bed.

  19. Effects of different external carbon sources and electron acceptors on interactions between denitrification and phosphorus removal in biological nutrient removal processes.

    Science.gov (United States)

    Hu, Xiang; Sobotka, Dominika; Czerwionka, Krzysztof; Zhou, Qi; Xie, Li; Makinia, Jacek

    The effects of two different external carbon sources (acetate and ethanol) and electron acceptors (dissolved oxygen, nitrate, and nitrite) were investigated under aerobic and anoxic conditions with non-acclimated process biomass from a full-scale biological nutrient removal-activated sludge system. When acetate was added as an external carbon source, phosphate release was observed even in the presence of electron acceptors. The release rates were 1.7, 7.8, and 3.5 mg P/(g MLVSS·h) (MLVSS: mixed liquor volatile suspended solids), respectively, for dissolved oxygen, nitrate, and nitrite. In the case of ethanol, no phosphate release was observed in the presence of electron acceptors. Results of the experiments with nitrite showed that approximately 25 mg NO 2 -N/L of nitrite inhibited anoxic phosphorus uptake regardless of the concentration of the tested external carbon sources. Furthermore, higher denitrification rates were obtained with acetate (1.4 and 0.8 mg N/(g MLVSS·h)) compared to ethanol (1.1 and 0.7 mg N/ (g MLVSS·h)) for both anoxic electron acceptors (nitrate and nitrite).

  20. Comparison of heterotrophic and autotrophic denitrification processes for nitrate removal from phosphorus-limited surface water.

    Science.gov (United States)

    Wang, Zheng; He, Shengbing; Huang, Jungchen; Zhou, Weili; Chen, Wanning

    2018-03-29

    Phosphorus (P) limitation has been demonstrated for micro-polluted surface water denitrification treatment in previous study. In this paper, a lab-scale comparative study of autotrophic denitrification (ADN) and heterotrophic denitrification (HDN) in phosphorus-limited surface water was investigated, aiming to find out the optimal nitrogen/phosphorus (N/P) ratio and the mechanism of the effect of P limitation on ADN and HDN. Furthermore, the optimal denitrification process was applied to the West Lake denitrification project, aiming to improve the water quality of the West Lake from worse than grade V to grade IV (GB3838-2006). The lab-scale study showed that the lack of P indeed inhibited HDN more greatly than ADN. The optimal N/P ratio for ADN and HDN was 25 and a 0.15 mg PO 4 3- -P L -1 of microbial available phosphorus (MAP) was observed. P additions could greatly enhance the resistance of ADN and HDN to hydraulic loading shock. Besides, The P addition could effectively stimulate the HDN performance via enriching the heterotrophic denitrifiers and the denitrifying phosphate-accumulating organisms (DNPAOs). Additionally, HDN was more effective and cost-effective than ADN for treating P-limited surface water. The study of the full-scale HDBF (heterotrophic denitrification biofilter) indicated that the denitrification performance was periodically impacted by P limitation, particularly at low water temperatures. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Denitrification of fertilizer wastewater at high chloride concentration

    DEFF Research Database (Denmark)

    Ucisik, Ahmed Süheyl; Henze, Mogens

    Wastewater from fertilizer industry is characterized by high contents of chloride concentration, which normally vary between 60 and 76 g/l. Experiments with bilogical denitrification were performed in lab-scale "fill and draw" reactors with synthetic wastewater with chloride concentrations up to 77.......4 g/l. The results of the experiments showed that biological denitrification was feasible at the extreme environmental conditions prevailing in fertilizer wastewater. Stable continuous biological denitrfication of the synthetic high chloride wastewater was performed up to 77.4 g Cl/l at 37 degree C...

  2. Characteristic of nitrous oxide production in partial denitrification process with high nitrite accumulation.

    Science.gov (United States)

    Du, Rui; Peng, Yongzhen; Cao, Shenbin; Wang, Shuying; Niu, Meng

    2016-03-01

    Nitrous oxide (N2O) production during the partial denitrification process with nitrate (NO3(-)-N) to nitrite (NO2(-)-N) transformation ratio of 80% was investigated in this study. Results showed that N2O was seldom observed before complete depletion of NO3(-)-N, but it was closely related to the reduction of NO2(-)-N rather than NO3(-)-N. High COD/NO3(-)-N was in favor of N2O production in partial denitrification with high NO2(-)-N accumulation. It was seriously enhanced at constant acidic pH due to the free nitrous acid (FNA) inhibition. However, the N2O production was much lower at initial pH of 5.5 and 6.5 due to the pH increase during denitrification process. Significantly, the pH turning point could be chosen as a controlled parameter to denote the end of NO3(-)-N reduction, which could not only achieve high NO2(-)-N accumulation but also decrease the N2O production significantly for practical application. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Treatment of domestic wastewater by anaerobic denitrification ...

    African Journals Online (AJOL)

    SALAMA YOUSSEF

    for the denitrification process could be deduced from the. pH variation. The alkalinity and pH increased in heterotrophic and H2-based autotrophic denitrification because nitrite reduction consumed protons (H+). Proton consumption is illustrated in Equations (1 to 4) (Rittmann and McCarty, 2001). Heterotrophic denitrification.

  4. Denitrification processes in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.

    rate in the vicinity of 30 Tg Ny@u-1@@, but the extent of benthic contribution remains unknown. A decoupling of denitrification from primary production, unique to the Arabian Sea, is revealed by nitrite, Electron Transport System (ETS) activity...

  5. Impact of partial nitritation degree and C/N ratio on simultaneous Sludge Fermentation, Denitrification and Anammox process.

    Science.gov (United States)

    Wang, Bo; Peng, Yongzhen; Guo, Yuanyuan; Yuan, Yue; Zhao, Mengyue; Wang, Shuying

    2016-11-01

    This study presents a novel process (i.e. PN/SFDA) to remove nitrogen from low C/N domestic wastewater. The process mainly involves two reactors, a pre-Sequencing Batch Reactor for partial nitritation (termed as PN-SBR) and an anoxic reactor for integrated Denitrification and Anammox with carbon sources produced from Sludge Fermentation (termed as SFDA). During long-term Runs, NO2(-)/NH4(+) ratio (i.e. NO2(-)-N/NH4(+)-N calculated by mole) in the PN-SBR effluent was gradually increased from 0.2 to 37 by extending aerobic duration, meaning that partial nitritation turning to full nitritation could be achieved. Impact of partial nitritation degree on SFDA process was investigated and the result showed that, NO2(-)/NH4(+) ratios between 2 and 10 were appropriate for the co-existence of denitrification and anammox together in the SFDA reactor, and denitrification instead of anammox contributed greater for nitrogen removal. Further batch tests indicated that anammox collaborated well with denitrification at low C/N (1.0 in this study). Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Stoichiometric evaluation of partial nitritation, anammox and denitrification processes in a sequencing batch reactor and interpretation of online monitoring parameters.

    Science.gov (United States)

    Langone, Michela; Ferrentino, Roberta; Cadonna, Maria; Andreottola, Gianni

    2016-12-01

    A laboratory-scale sequencing batch reactor (SBR) performing partial nitritation - anammox and denitrification was used to treat anaerobic digester effluents. The SBR cycle consisted of a short mixing filling phase followed by oxic and anoxic reaction phases. Working at 25 °C, an ammonium conversion efficiency of 96.5%, a total nitrogen removal efficiency of 88.6%, and an organic carbon removal efficiency of 63.5% were obtained at a nitrogen loading rate of 0.15 kg N m -3 d -1 , and a biodegradable organic carbon to nitrogen ratio of 0.37. The potential contribution of each biological process was evaluated by using a stoichiometric model. The nitritation contribution decreased as the temperature decreased, while the contribution from anammox depended on the wastewater type and soluble carbon to nitrogen ratio. Denitrification improved the total nitrogen removal efficiency, and it was influenced by the biodegradable organic carbon to nitrogen ratio. The characteristic patterns of conductivity, oxidation-reduction potential (ORP) and pH in the SBR cycle were well related to biological processes. Conductivity profiles were found to be directly related to the decreasing profiles of ammonium. Positive ORP values at the end of the anoxic phases were detected for total nitrogen removal efficiency of lower than 85%, and the occurrence of bending points on the ORP curves during the anoxic phases was associated with nitrite depletion by the anammox process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Simultaneous heterotrophic and sulfur-oxidizing autotrophic denitrification process for drinking water treatment: control of sulfate production.

    Science.gov (United States)

    Sahinkaya, Erkan; Dursun, Nesrin; Kilic, Adem; Demirel, Sevgi; Uyanik, Sinan; Cinar, Ozer

    2011-12-15

    A long-term performance of a packed-bed bioreactor containing sulfur and limestone was evaluated for the denitrification of drinking water. Autotrophic denitrification rate was limited by the slow dissolution rate of sulfur and limestone. Dissolution of limestone for alkalinity supplementation increased hardness due to release of Ca(2+). Sulfate production is the main disadvantage of the sulfur autotrophic denitrification process. The effluent sulfate concentration was reduced to values below drinking water guidelines by stimulating the simultaneous heterotrophic and autotrophic denitrification with methanol supplementation. Complete removal of 75 mg/L NO(3)-N with effluent sulfate concentration of around 225 mg/L was achieved when methanol was supplemented at methanol/NO(3)-N ratio of 1.67 (mg/mg), which was much lower than the theoretical value of 2.47 for heterotrophic denitrification. Batch studies showed that sulfur-based autotrophic NO(2)-N reduction rate was around three times lower than the reduction rate of NO(3)-N, which led to NO(2)-N accumulation at high loadings. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Investigation on thiosulfate-involved organics and nitrogen removal by a sulfur cycle-based biological wastewater treatment process.

    Science.gov (United States)

    Qian, Jin; Lu, Hui; Cui, Yanxiang; Wei, Li; Liu, Rulong; Chen, Guang-Hao

    2015-02-01

    Thiosulfate, as an intermediate of biological sulfate/sulfite reduction, can significantly improve nitrogen removal potential in a biological sulfur cycle-based process, namely the Sulfate reduction-Autotrophic denitrification-Nitrification Integrated (SANI(®)) process. However, the related thiosulfate bio-activities coupled with organics and nitrogen removal in wastewater treatment lacked detailed examinations and reports. In this study, S2O3(2-) transformation during biological SO4(2-)/SO3(2-) co-reduction coupled with organics removal as well as S2O3(2-) oxidation coupled with chemolithotrophic denitrification were extensively evaluated under different experimental conditions. Thiosulfate is produced from the co-reduction of sulfate and sulfite through biological pathway at an optimum pH of 7.5 for organics removal. And the produced S2O3(2-) may disproportionate to sulfide and sulfate during both biological S2O3(2-) reduction and oxidation most possibly carried out by Desulfovibrio-like species. Dosing the same amount of nitrate, pH was found to be the more direct factor influencing the denitritation activity than free nitrous acid (FNA) and the optimal pH for denitratation (7.0) and denitritation (8.0) activities were different. Spiking organics significantly improved both denitratation and denitritation activities while minimizing sulfide inhibition of NO3(-) reduction during thiosulfate-based denitrification. These findings in this study can improve the understanding of mechanisms of thiosulfate on organics and nitrogen removal in biological sulfur cycle-based wastewater treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Mineralization of 2-chlorophenol by sequential electrochemical reductive dechlorination and biological processes

    Energy Technology Data Exchange (ETDEWEB)

    Arellano-González, Miguel Ángel; González, Ignacio [Universidad Autónoma Metropolitana-Iztapalapa, Departamento de Química, Av. San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico D.F. (Mexico); Texier, Anne-Claire, E-mail: actx@xanum.uam.mx [Universidad Autónoma Metropolitana-Iztapalapa, Departamento de Biotecnología, Av. San Rafael Atlixco No. 186, Col. Vicentina, 09340 Mexico, D.F. (Mexico)

    2016-08-15

    Highlights: • Dechlorination of 2-chlorophenol to phenol was 100% efficient on Pd-Ni/Ti electrode. • An ECCOCEL reactor was efficient and selective to obtain phenol from 2-chlorophenol. • Phenol was totally mineralized in a coupled denitrifying biorreactor. • Global time of 2-chlorophenol mineralization in the combined system was 7.5 h. - Abstract: In this work, a novel approach was applied to obtain the mineralization of 2-chlorophenol (2-CP) in an electrochemical-biological combined system where an electrocatalytic dehydrogenation process (reductive dechlorination) was coupled to a biological denitrification process. Reductive dechlorination of 2-CP was conducted in an ECCOCEL-type reactor on a Pd-Ni/Ti electrode at a potential of −0.40 V vs Ag/AgCl{sub (s)}/KCl{sub (sat)}, achieving 100 percent transformation of 2-CP into phenol. The electrochemically pretreated effluent was fed to a rotating cylinder denitrifying bioreactor where the totality of phenol was mineralized by denitrification, obtaining CO{sub 2} and N{sub 2} as the end products. The total time required for 2-CP mineralization in the combined electrochemical-biological process was 7.5 h. This value is close to those previously reported for electrochemical and advanced oxidation processes but in this case, an efficient process was obtained without accumulation of by-products or generation of excessive energy costs due to the selective electrochemical pretreatment. This study showed that the use of electrochemical reductive pretreatment combined with biological processes could be a promising technology for the removal of recalcitrant molecules, such as chlorophenols, from wastewaters by more efficient, rapid, and environmentally friendly processes.

  10. Evaluating vertical concentration profile of carbon source released from slow-releasing carbon source tablets and in situ biological nitrate denitrification activity

    Science.gov (United States)

    Yeum, Y.; HAN, K.; Yoon, J.; Lee, J. H.; Song, K.; Kang, J. H.; Park, C. W.; Kwon, S.; Kim, Y.

    2017-12-01

    Slow-releasing carbon source tablets were manufactured during the design of a small-scale in situ biological denitrification system to reduce high-strength nitrate (> 30 mg N/L) from a point source such as livestock complexes. Two types of slow-releasing tablets, precipitating tablet (PT, apparent density of 2.0 g/mL) and floating tablet (FT), were prepared to achieve a vertically even distribution of carbon source (CS) in a well and an aquifer. Hydroxypropyl methylcellulose (HPMC) was used to control the release rate, and microcrystalline cellulose pH 101 (MCC 101) was added as a binder. The #8 sand was used as a precipitation agent for the PTs, and the floating agents for the FTs were calcium carbonate and citric acid. FTs floated within 30 min. and remained in water because of the buoyance from carbon dioxide, which formed during the acid-base reaction between citric acid and calcium carbonate. The longevities of PTs with 300 mg of HPMC and FTs with 400 mg of HPMC were 25.4 days and 37.3 days, respectively. We assessed vertical CS profile in a continuous flowing physical aquifer model (release test, RT) and its efficiency on biological nitrate denitrification (denitrification test, DT). During the RT, PTs, FTs and a tracer (as 1 mg rhodamine B/L) were initially injected into a well of physical aquifer model (PAM). Concentrations of CS and the tracer were monitored along the streamline in the PAM to evaluate vertical profile of CS. During the DT, the same experiment was performed as RT, except continuous injection of solution containing 30 mg N/L into the PAM to evaluate biological denitrification activity. As a result of RT, temporal profiles of CS were similar at 3 different depths of monitoring wells. These results suggest that simultaneous addition of PT and FT be suitable for achieving a vertically even distribution of the CS in the injection well and an aquifer. In DT, similar profile of CS was detected in the injection well, and nitrate was biologically

  11. Microbial nitrate removal in biologically enhanced treated coal gasification wastewater of low COD to nitrate ratio by coupling biological denitrification with iron and carbon micro-electrolysis.

    Science.gov (United States)

    Zhang, Zhengwen; Han, Yuxing; Xu, Chunyan; Ma, Wencheng; Han, Hongjun; Zheng, Mengqi; Zhu, Hao; Ma, Weiwei

    2018-04-21

    Mixotrophic denitrification coupled biological denitrification with iron and carbon micro-electrolysis (IC-ME) is a promising emerging bioprocess for nitrate removal of biologically enhanced treated coal gasification wastewater (BECGW) with low COD to nitrate ratio. TN removal efficiency in R1 with IC-ME assisted was 16.64% higher than R2 with scrap zero valent iron addition, 23.05% higher than R3 with active carbon assisted, 30.51% higher than R4 with only active sludge addition, 80.85% higher than R5 utilizing single IC-ME as control. Fe 2+ generated from IC-ME decreased the production of N 2 O and enriched more Nitrate-reducing Fe(Ⅱ) oxidation bacteria (NRFOB) Acidovorax and Thiobacillus, which could convert nitrate to nitrogen gas. And the presence of Fe 3+ , as the Fe 2+ oxidation product, could stimulate the growth of Fe(III)-reducing strain (FRB) that indicated by redundancy analysis. Microbial network analysis demonstrated FRB Geothrix had a co-occurrence relationship with other bacteria, revealing its dominant involvement in nitrate removal of BECGW. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Denitrification as the dominant nitrogen loss process in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Ward, B.B.; Devol, A.H.; Rich, J.J.; Chang, B.X.; Bulow, S.E.; Naik, H.; Pratihary, A.K.; Jayakumar, A.

    experiments in the Arabian Sea denitrification is responsible for 87-99% of the total N sub(2) production. The dominance of denitrification is reproducible using two independent isotope incubation methods. In contrast, anammox is dominant in the Eastern...

  13. Influence of Pyrolytic Biochar on Settleability and Denitrification of Activated Sludge Process

    Institute of Scientific and Technical Information of China (English)

    Xiao-feng Sima; Bing-bing Li; Hong Jiang

    2017-01-01

    Biochar is a massively produced by-product of biomass pyrolysis to obtain renewable energy and has not been fully used.Incomplete separation of sludge and effluent and insufficient denitrification of sewage are two of main factors that influence the efficiency of activated sludge process.In this work,we proposed a new utilization of biochar and investigated the effect of biochar addition on the performance of settleability and denitrification of activated sludge.Results show that the addition of biochar can improve the settleability of activated sludge by changing the physicochemical characteristics of sludge (e.g.,flocculating ability,zeta-potential,hydrophobicity,and extracellular polymeric substances constituents).Moreover,the dissolved organic carbon released from biochar obtained at lower pyrolysis temperature can improve the nitrate removal efficiency to a certain extent.

  14. Nitrate removal properties of solid-phase denitrification processes using acid-blended poly(L-lactic acid) as the sole substrate

    International Nuclear Information System (INIS)

    Yamada, T; Matsuoka, H; Sun, J; Tsuji, H; Hiraishi, A; Yoshikawa, S

    2013-01-01

    The large amount of waste that is discharged along with the diffusion of poly(L-lactic acid) (PLLA) articles in use is persistent concern. Previously, we studied solid-phase denitrification (SPD) processes using PLLA to establish an effective re-use of PLLA waste. We found that PLLA with a weight-average molecular weight (M w ) of approximately 10,000 was suitable for SPD processes; however, the recycling of PLLA waste consumes a high energy. A new PLLA plastic including 5% poly(ethylene oxalate) (PEOxPLLA) as a blend material has attracted attention because recycling of PEOxPLLA consumes less electricity than that of PLLA. In this study, our main objectives were to evaluate whether PEOxPLLA can be used for SPD processes by changing its M w and to investigate the bioavailability for denitrification of hydrolysates released from PEOxPLLA. The predicted hydrolysates, including oxalic acid, ethylene glycol, and lactate, are abiotically released, leading to different biological nitrate removal rates. Consequently, the nitrate removal rate of PEOxPLLA ranged from 0.9–4.1 mg-NO 3 − -N·g-MLSS·h −1 by changing the M w in the range of 8,500–238,000. In culture-dependent approaches, denitrifying bacteria using each substrate as an electron donor are found in activated sludge, suggesting that all hydrolysates functioned in the SPD processes using PEOxPLLA.

  15. Denitrification across landscapes and waterscapes: A synthesis

    Science.gov (United States)

    Seitzinger, S.; Harrison, J.A.; Böhlke, J.K.; Bouwman, A.F.; Lowrance, R.; Peterson, B.; Tobias, C.; Van Drecht, G.

    2006-01-01

    Denitrification is a critical process regulating the removal of bioavailable nitrogen (N) from natural and human-altered systems. While it has been extensively studied in terrestrial, freshwater, and marine systems, there has been limited communication among denitrification scientists working in these individual systems. Here, we compare rates of denitrification and controlling factors across a range of ecosystem types. We suggest that terrestrial, freshwater, and marine systems in which denitrification occurs can be organized along a continuum ranging from (1) those in which nitrification and denitrification are tightly coupled in space and time to (2) those in which nitrate production and denitrification are relatively decoupled.In aquatic ecosystems, N inputs influence denitrification rates whereas hydrology and geomorphology influence the proportion of N inputs that are denitrified. Relationships between denitrification and water residence time and N load are remarkably similar across lakes, river reaches, estuaries, and continental shelves.Spatially distributed global models of denitrification suggest that continental shelf sediments account for the largest portion (44%) of total global denitrification, followed by terrestrial soils (22%) and oceanic oxygen minimum zones (OMZs; 14%). Freshwater systems (groundwater, lakes, rivers) account for about 20% and estuaries 1% of total global denitrification. Denitrification of land-based N sources is distributed somewhat differently. Within watersheds, the amount of land-based N denitrified is generally highest in terrestrial soils, with progressively smaller amounts denitrified in groundwater, rivers, lakes and reservoirs, and estuaries. A number of regional exceptions to this general trend of decreasing denitrification in a downstream direction exist, including significant denitrification in continental shelves of N from terrestrial sources. Though terrestrial soils and groundwater are responsible for much

  16. Biological denitrification from mature landfill leachate using a food-waste-derived carbon source.

    Science.gov (United States)

    Yan, Feng; Jiang, Jianguo; Zhang, Haowei; Liu, Nuo; Zou, Quan

    2018-05-15

    The mature landfill leachate containing high ammonia concentration (>1000 mg/L) is a serious threat to environment; however, the low COD to TN ratio (C/N, waste and oil-added food waste, were first applied as external carbon sources for the biological nitrogen removal from mature landfill leachate in an aerobic/anoxic membrane bioreactor. "Acidogenic liquid b" served quite better than commercial sodium acetate, considering the higher denitrification efficiency and the slightly rapider denitrification rate. The effect of C/N and temperature were investigated under hydraulic retention time (HRT) of 7 d, which showed that C/N ≥ 7 (25 °C) was enough to meet the general discharge standards of NH 4 + -N, TN and COD in China. Even for some special areas of China, the more stringent discharge standards (NH 4 + -N ≤ 8 mg/L, TN ≤ 20 mg/L) could also be achieved under longer HRT of 14 d and C/N ≥ 6. Notably, the COD concentration in effluent could also be well reduced to 50-55 mg/L, without further physical-chemical treatment. This proposed strategy, involving the high-value utilization of food waste, is thus promising for efficient nitrogen removal from mature landfill leachate. Copyright © 2018 Elsevier Ltd. All rights reserved.

  17. Edaphic Conditions Regulate Denitrification Directly and Indirectly by Altering Denitrifier Abundance in Wetlands along the Han River, China.

    Science.gov (United States)

    Xiong, Ziqian; Guo, Laodong; Zhang, Quanfa; Liu, Guihua; Liu, Wenzhi

    2017-05-16

    Riparian wetlands play a critical role in retaining nitrogen (N) from upland runoff and improving river water quality, mainly through biological processes such as soil denitrification. However, the relative contribution of abiotic and biotic factors to riparian denitrification capacity remains elusive. Here we report the spatiotemporal dynamics of potential and unamended soil denitrification rates in 20 wetlands along the Han River, an important water source in central China. We also quantified the abundance of soil denitrifying microorganisms using nirK and nirS genes. Results showed that soil denitrification rates were significantly different between riparian and reservoir shoreline wetlands, but not between mountain and lowland wetlands. In addition, soil denitrification rates showed strong seasonality, with higher values in August (summer) and April (spring) but lower values in January (winter). The potential and unamended denitrification rates were positively correlated with edaphic conditions (moisture and carbon concentration), denitrifier abundance, and plant species richness. Path analysis further revealed that edaphic conditions could regulate denitrification rates both directly and indirectly through their effects on denitrifier abundance. Our findings highlight that not only environmental factors, but also biotic factors including denitrifying microorganisms and standing vegetation, play an important role in regulating denitrification rate and N removal capacity in riparian wetlands.

  18. Using natural biomass microorganisms for drinking water denitrification.

    Science.gov (United States)

    Costa, Darleila Damasceno; Gomes, Anderson Albino; Fernandes, Mylena; Lopes da Costa Bortoluzzi, Roseli; Magalhães, Maria de Lourdes Borba; Skoronski, Everton

    2018-07-01

    Among the methods that are studied to eliminate nitrate from drinking water, biological denitrification is an attractive strategy. Although several studies report the use of denitrifying bacteria for nitrate removal, they usually involve the use of sewage sludge as biomass to obtain the microbiota. In the present study, denitrifying bacteria was isolated from bamboo, and variable parameters were controlled focusing on optimal bacterial performance followed by physicochemical analysis of water adequacy. In this way, bamboo was used as a source of denitrifying microorganisms, using either Immobilized Microorganisms (IM) or Suspended Microorganisms (SM) for nitrate removal. Denitrification parameters optimization was carried out by analysis of denitrification at different pH values, temperature, nitrate concentrations, carbon sources as well as different C/N ratios. In addition, operational stability and denitrification kinetics were evaluated. Microorganisms present in the biomass responsible for denitrification were identified as Proteus mirabilis. The denitrified water was submitted to physicochemical treatment such as coagulation and flocculation to adjust to the parameters of color and turbidity to drinking water standards. Denitrification using IM occurred with 73% efficiency in the absence of an external carbon source. The use of SM provided superior denitrification efficiency using ethanol (96.46%), glucose (98.58%) or glycerol (98.5%) as carbon source. The evaluation of the operational stability allowed 12 cycles of biomass reuse using the IM and 9 cycles using the SM. After physical-chemical treatment, only SM denitrified water remained within drinking water standards parameters of color and turbidity. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Drinking water decontamination by biological denitrification using fresh bamboo as inoculum source.

    Science.gov (United States)

    Bucco, Samuel; Padoin, Natan; Netto, Willibaldo Schmidell; Soares, Hugo Moreira

    2014-10-01

    Groundwater contamination is becoming a serious problem in many Brazilian regions. European countries started to deal with this issue in the 1980s, mainly caused by the extensive usage of nitrogenous fertilizers and the absence of domestic wastewater treatment. Due to its high solubility, nitrate readily passes through the soil and reaches the aquifer. Thereafter, this ion moves, following groundwater flow, and can be found several kilometers from the area where the pollution occurred. Concern about nitrate contamination is due to the link found between this contaminant and various human health diseases, such as methemoglobin and cancer. Studies carried out in France enabled the design and implementation of several biological denitrification plants throughout the country, in order to remove nitrate from its contaminated groundwater. Heterotrophic denitrification facilities shown to be adequate to treat high water flows with satisfactory nitrate removal efficiency, especially when static media supports are employed. The objective of this research was to evaluate the existence of denitrifying microorganisms in bamboo (Bambusa tuldóides) and verify the feasibility of their use to inoculate a pilot-scale fixed-bed bioreactor. The support material selected to fill the bioreactor bed was commercial polypropylene Pall rings, since such support has a high porosity associated with a wide superficial area. The bioreactor was able to produce and retain a large amount of cells. Using ethanol as carbon source, nitrate (N-NO3(-)) removal efficiency of the bioreactor stood around 80 % for a maximum nitrogen loading rate of approximately 6.5 mg N-NO3 (-) L(-1) h(-1).

  20. The relationship between anammox and denitrification in the sediment of an inland river

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Sheng, E-mail: zhous@outlook.com [Eco-environmental Protection Research Institute, Shanghai Academy of Agricultural Sciences, No. 1000 Jinqi Road, Shanghai 201403 (China); Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Borjigin, Sodbilig; Riya, Shohei; Terada, Akihiko; Hosomi, Masaaki [Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)

    2014-08-15

    This study measured the microbial processes of anaerobic ammonium oxidation (anammox) and denitrification in sediment sampled from two sites in the estuary of an inland river (Koisegawa River, Ibaragi prefecture, Japan) using a nitrogen isotope pairing technique (IPT). The responses of anammox and denitrification activities to temperature and nitrate concentration were also evaluated. Further, to elucidate the correlation between anammox and denitrification processes, an inhibition experiment was conducted, using chlorate to inhibit the first step of denitrification. Denitrification activity was much higher than anammox activity, and it reached a maximum at the surface layer in February 2012. Denitrification activity decreased as sediment depth increased, and a similar phenomenon was observed for anammox activity in the sediment of site A, where aquatic plants were absent from the surroundings. The activities of both denitrification and anammox were temperature-dependent, but they responded differently to changes in incubation temperature. Compared to a linear increase in denitrification as temperature rose to 35 °C, the optimal temperature for anammox was 25 °C, after which the activity decreased sharply. At the same time, both anammox and denitrification activities increased with NO{sub 3}{sup −} concentration. The Michaelis–Menten kinetic constants (V{sub max} and K{sub m}) of denitrification were significantly higher than those of the anammox process. Furthermore, anammox activity decreased accordingly when the first step of denitrification was inhibited, which probably reduced the amount of the intermediate NO{sub 2}{sup −}. Our study provides the first direct exploration of the denitrification-dependent correlation of anammox activity in the sediment of inland river. - Highlights: • The activity of denitrification in river sediment was much higher than anammox. • Denitrification and anammox respond differently to changes in temperature.

  1. Bacterial community evolutions driven by organic matter and powder activated carbon in simultaneous anammox and denitrification (SAD) process.

    Science.gov (United States)

    Ge, Cheng-Hao; Sun, Na; Kang, Qi; Ren, Long-Fei; Ahmad, Hafiz Adeel; Ni, Shou-Qing; Wang, Zhibin

    2018-03-01

    A distinct shift of bacterial community driven by organic matter (OM) and powder activated carbon (PAC) was discovered in the simultaneous anammox and denitrification (SAD) process which was operated in an anti-fouling submerged anaerobic membrane bio-reactor. Based on anammox performance, optimal OM dose (50 mg/L) was advised to start up SAD process successfully. The results of qPCR and high throughput sequencing analysis indicated that OM played a key role in microbial community evolutions, impelling denitrifiers to challenge anammox's dominance. The addition of PAC not only mitigated the membrane fouling, but also stimulated the enrichment of denitrifiers, accounting for the predominant phylum changing from Planctomycetes to Proteobacteria in SAD process. Functional genes forecasts based on KEGG database and COG database showed that the expressions of full denitrification functional genes were highly promoted in R C , which demonstrated the enhanced full denitrification pathway driven by OM and PAC under low COD/N value (0.11). Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Exploring the Denitrification Proteome of Paracoccus denitrificans PD1222

    Directory of Open Access Journals (Sweden)

    Alfonso Olaya-Abril

    2018-05-01

    Full Text Available Denitrification is a respiratory process that produces nitrous oxide as an intermediate, which may escape to the atmosphere before its reduction to dinitrogen through the nitrous oxide reductase NosZ. In this work, the denitrification process carried out by Paracoccus denitrificans PD1222 has been explored through a quantitative proteomic analysis. Under anaerobic conditions, with nitrate as sole nitrogen source, the synthesis of all the enzymes involved in denitrification, the respiratory nitrate, nitrite, nitric oxide, and nitrous oxide reductases, was increased. However, the periplasmic and assimilatory nitrate reductases decreased. Synthesis of transporters for alcohols, D-methionine, sulfate and copper, most of the enzymes involved in the tricarboxylic acid cycle, and proteins involved in other metabolic processes like lysine catabolism, fatty acids degradation and acetyl-CoA synthesis, was increased during denitrification in P. denitrificans PD1222. As consequence, an enhanced production of the central metabolite acetyl-CoA was observed. After establishing the key features of the denitrification proteome, its changes by the influence of a competitive electron acceptor, oxygen, or competitive nitrogen source, ammonium, were evaluated.

  3. Use of bioreactor landfill for nitrogen removal to enhance methane production through ex situ simultaneous nitrification-denitrification and in situ denitrification.

    Science.gov (United States)

    Sun, Xiaojie; Zhang, Hongxia; Cheng, Zhaowen

    2017-08-01

    High concentrations of nitrate-nitrogen (NO 3 - -N) derived from ex situ nitrification phase can inhibit methane production during ex situ nitrification and in situ denitrification bioreactor landfill. A combined process comprised of ex situ simultaneous nitrification-denitrification (SND) in an aged refuse bioreactor (ARB) and in situ denitrification in a fresh refuse bioreactor (FRB) was conducted to reduce the negative effect of high concentrationsof NO 3 - -N. Ex situ SND can be achieved because NO 3 - -N concentration can be reduced and the removal rate of ammonium-nitrogen (NH 4 + -N) remains largely unchanged when the ventilation rate of ARB-A2 is controlled. The average NO 3 - -N concentrations of effluent were 470mg/L in ex situ nitrification ARB-A1 and 186mg/L in ex situ SND ARB-A2. The average NH 4 + -N removal rates of ARB-A1 and ARB-A2 were 98% and 94%, respectively. Based on the experimental data from week 4 to week 30, it is predicted that NH 4 + -N concentration in FRB-F1 of the ex situ nitrification and in situ denitrification process would reach 25mg/L after 63weeks, and about 40weeks for the FRB-F2 of ex situ SND and in situ denitrification process . Ex situ SND and in situ denitrification process can improve themethane production of FRB-F2. The lag phase time of methane production for the FRB-F2 was 11weeks. This phase was significantly shorter than the 15-week phases of FRB-F1 in ex situ nitrification and in situ denitrification process. A seven-week stabilizationphase was required to increase methane content from 5% to 50% for FRB-F2. Methane content in FRB-F1 did not reach 50% but reached the 45% peak after 20weeks. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. The effect of millennial-scale changes in Arabian Sea denitrification on atmospheric CO2

    International Nuclear Information System (INIS)

    Altabet, M.A.; Higginson, M.J.; Murray, D.W.

    2002-01-01

    Most global biogeochemical processes are known to respond to climate change, some of which have the capacity to produce feedbacks through the regulation of atmospheric greenhouse gases. Marine denitrification - the reduction of nitrate to gaseous nitrogen - is an important process in this regard, affecting greenhouse gas concentrations directly through the incidental production of nitrous oxide, and indirectly through modification of the marine nitrogen inventory and hence the biological pump for C0 2 . Although denitrification has been shown to vary with glacial-interglacial cycles, its response to more rapid climate change has not yet been well characterized. Here we present nitrogen isotope ratio, nitrogen content and chlorin abundance data from sediment cores with high accumulation rates on the Oman continental margin that reveal substantial millennial-scale variability in Arabian Sea denitrification and productivity during the last glacial period. The detailed correspondence of these changes with Dansgaard-Oeschger events recorded in Greenland ice cores indicates rapid, century-scale reorganization of the Arabian Sea ecosystem in response to climate excursions, mediated through the intensity of summer monsoonal upwelling. Considering the several-thousand-year residence time of fixed nitrogen in the ocean, the response of global marine productivity to changes in denitrification would have occurred at lower frequency and appears to be related to climatic and atmospheric C0 2 oscillations observed in Antarctic ice cores between 20 and A kyr ago. (author)

  5. Plant effects on soil denitrification - a review of potential mechanisms

    Science.gov (United States)

    Malique, Francois; Butterbach-Bahl, Klaus; Dannenmann, Michael

    2017-04-01

    Denitrification is a microbial process occurring in soils, both producing and consuming the potent greenhouse gas nitrous oxide (NO), competing for nitrate with plants and hydrological leaching pathways, removing nutrients and reactive nitrogen from the biosphere, and closing the global nitrogen cycle. Despite its obvious importance, denitrification remained among the least well quantified biogeochemical processes in soils. This is due to enormous methodological difficulties involved in the direct quantification of soil microbial denitrification rates (mainly with regard to the terminal product N2) and the denitrification nitrogen gas product ratios (NO:N2O:N2), Plants may affect denitrification through a myriad of mechanisms such as e.g., competition for nitrate and water, through oxygen consumption, by regulating litter quality and changing soil pH, and via the exudation of labile carbon or secondary plant compounds involved in shaping the rhizospheric microbial community. However, plant effects on denitrification so far hardly were quantified so that the actual extent of plant control on denitrification is largely unknown. Here, we summarize the current knowledge on mechanisms how plants can affect denitrification rates and N gas product ratios in soils at temporal scales from hours to days and years. We review earlier research to quantify plant effects on denitrification as well as critically discuss the limited methods currently available to quantify plant-soil-denitrifier interactions. Finally, we provide pointers to use plants as tools to manage denitrification, e.g. to improve N use efficiency in agricultural ecosystems and to minimize soil nitrous oxide emissions.

  6. Alternative solutions for the bio-denitrification of landfill leachates using pine bark and compost

    International Nuclear Information System (INIS)

    Trois, Cristina; Pisano, Giulia; Oxarango, Laurent

    2010-01-01

    Nitrified leachate may still require an additional bio-denitrification step, which occurs with the addition of often-expensive chemicals as carbon source. This study explores the applicability of low-cost carbon sources such as garden refuse compost and pine bark for the denitrification of high strength landfill leachates. The overall objective is to assess efficiency, kinetics and performance of the substrates in the removal of high nitrate concentrations. Garden refuse and pine bark are currently disposed of in general waste landfills in South Africa, separated from the main waste stream. A secondary objective is to assess the feasibility of re-using green waste as by-product of an integrated waste management system. Denitrification processes in fixed bed reactors were simulated at laboratory scale using anaerobic batch tests and leaching columns packed with immature compost and pine bark. Biologically treated leachate from a Sequencing Batch Reactor (SBR) with nitrate concentrations of 350, 700 and 1100 mgN/l were used for the trials. Preliminary results suggest that, passed the acclimatization step (40 days for both substrates), full denitrification is achieved in 10-20 days for the pine bark and 30-40 days for the compost.

  7. Distributed denitrification in a northeastern agricultural landscape

    Science.gov (United States)

    Anderson, T. R.; Groffman, P. M.; Walter, M. T.

    2011-12-01

    Denitrification may be an important sink of anthropogenic nitrogen (N) in eastern US watersheds. Denitrification occurs primarily under anaerobic conditions by heterotrophic microbes, and is therefore expected to be vigorous in wet soils containing large amounts of organic carbon. Actual rates of denitrification, however, have been difficult to quantify, and remain one of the critical unresolved N processes at the landscape scale. We measured denitrification rates in situ along hydrologic flow paths and across gradients of hydroperiodicities, i.e., frequencies and durations of saturated conditions, at Cornell University's Teaching & Research Center in Harford, NY (an active dairy farm). Denitrification rates were measured monthly using the 15N push-pull method from 14 mini-piezometers arrayed along a gradient of hydroperiodicity as indicated by a soil topographic index (STI). Measured rates of denitrification were spatially variable across sites and ranged from undetectable to over 4500 μg N/kg soil/day with a mean of 572 ± 167 μg N/kg soil/day. Mean rates of denitrification increased with STI, which ranged from 8.7 to 23.0 across our mini-piezometer sites. This relationship was used to estimate denitrification rates across the landscape and resolve a missing piece of the N budget for the farm. Only 14% of the farm fell into areas of STI greater than 8.7; however, denitrification in these areas account for more than 60% of the missing N balance for the entire landscape. Improved understanding of the distribution and magnitudes of denitrification in agricultural landscapes has good potential to facilitate new, novel, and better management practices for controlling N loading to streams and rivers. Indeed, the very areas that appear to have a propensity to harbor denitrification, i.e., areas prone to be wet, are often artificially drained as part of standard agricultural practices which reduces the frequency that these areas are likely to be anaerobic and

  8. Biological groundwater denitrification systems: Lab-scale trials aimed at nitrous oxide production and emission assessment.

    Science.gov (United States)

    Capodici, Marco; Avona, Alessia; Laudicina, Vito Armando; Viviani, Gaspare

    2018-07-15

    Bio-trenches are a sustainable option for treating nitrate contamination in groundwater. However, a possible side effect of this technology is the production of nitrous oxide, a greenhouse gas that can be found both dissolved in the liquid effluent as well as emitted as off gas. The aim of this study was to analyze NO 3 - removal and N 2 O production in lab-scale column trials. The column contained olive nut as organic carbon media. The experimental study was divided into three phases (I, II and III) each characterized by different inlet NO 3 - concentrations (30, 50, 75mgNO 3 -NL -1 respectively). Sampling ports deployed along the length of the column allowed to observe the denitrification process as well as the formation and consumption of intermediate products, such as nitrite (NO 2 - ) and nitrous oxide (N 2 O). In particular, it was observed that N 2 O production represent only a small fraction of removed NO 3 - during Phase I and II, both for dissolved (0.007%) and emitted (0.003%) phase, and it was recorded a high denitrification efficiency, over 99%. Nevertheless, significantly higher values were recorded for Phase 3 concerning emitted phase (0.018%). This fact is due to increased inlet concentration which resulted in a carbon limitation and in a consequent decrease in denitrification efficiency (76%). Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Desulphurization and denitrification processes in the energy industry

    Directory of Open Access Journals (Sweden)

    Virèíková Edita

    1998-09-01

    Full Text Available The world´s problem of environmental pollution is also an important problem in the Slovak Republic. One of the biggest sources of air pollution is the combustion of low quality fossil fuels. During the burning of coal, combustible types of sulfur, like organic and pyritic, are oxidized and form sulfur dioxide or trioxide. Nitrogen oxides in chimney gases are generally found in three forms: NO, NO2 and N2O. It is more difficult to remove NOX than SO2 because of the structure of NOx. For this reason it is necesary to keep lower NOx emissions in the system by various methods. This paper surveys the current status of the desulphurization and denitrification processes in the energy industry.

  10. Denitrification pathways and rates in the sandy sediments of the Georgia continental shelf, USA

    Directory of Open Access Journals (Sweden)

    Ingall Ellery

    2005-02-01

    Full Text Available Denitrification in continental shelf sediments has been estimated to be a significant sink of oceanic fixed nitrogen (N. The significance and mechanisms of denitrification in organic-poor sands, which comprise 70% of continental shelf sediments, are not well known. Core incubations and isotope tracer techniques were employed to determine processes and rates of denitrification in the coarse-grained, sandy sediments of the Georgia continental shelf. In these sediments, heterotrophic denitrification was the dominant process for fixed N removal. Processes such as coupled nitrification-denitrification, anammox (anaerobic ammonium oxidation, and oxygen-limited autotrophic nitrification-denitrification were not evident over the 24 and 48 h time scale of the incubation experiments. Heterotrophic denitrification processes produce 22.8–34.1 μmole N m-2 d-1 of N2 in these coarse-grained sediments. These denitrification rates are approximately two orders of magnitude lower than rates determined in fine-grained shelf sediments. These lower rates may help reconcile unbalanced marine N budgets which calculate global N losses exceeding N inputs.

  11. Denitrification by Rhizobium meliloti

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, A

    1996-10-01

    Rhizobium meliloti strains were investigated for their denitrification activity as free-living cells and in nodules on lucerne (Medicago sativa) roots. They were also investigated for presence of nitrous oxide reductase (nos) activity and for genes using a nosZ probe derived from the Pseudomonas stutzeri. To decide whether R. meliloti strains used as inoculants contribute to the total denitrification activity in a lucerne ley, strains with different denitrifying capacities were used in field and laboratory experiments. The nitrate reduction activity of R. meliloti during anaerobic respiration was compared with that of a strain of Pseudomonas aeruginosa. A great diversity in the denitrification activity was found within strains of R. meliloti, and four of thirteen investigated strains showed an obvious denitrification activity. Two denitrifying bacteria were used as references, one strain each of Bradyrhizobium japonicum and P. aeruginosa. All but one of the R. meliloti strains hybridized to the PstI-fragment of the nosZ-gene from P. stutzeri. Two sizes of the hybridizing fragment, 5 and 7 kb, were noticed. Nos activity was only shown in three R. meliloti strains, and these were all characterized by a high denitrification activity. The potential denitrification activity was about 20, 40, and 80 times higher than the actual denitrification activity for lucerne, fallow, and grass, respectively. The potential denitrification activity was almost the same in lucerne and grass planted soils. Compared with the unplanted soil, the presence of lucerne roots in the soil increased the actual denitrification activity, while roots of both plant species, grass and lucerne, increased the potential denitrification activity in the soil. 32 refs, 7 figs, 1 tab

  12. Nitrate removal from drinking water with a focus on biological methods: a review.

    Science.gov (United States)

    Rezvani, Fariba; Sarrafzadeh, Mohammad-Hossein; Ebrahimi, Sirous; Oh, Hee-Mock

    2017-05-31

    This article summarizes several developed and industrial technologies for nitrate removal from drinking water, including physicochemical and biological techniques, with a focus on autotrophic nitrate removal. Approaches are primarily classified into separation-based and elimination-based methods according to the fate of the nitrate in water treatment. Biological denitrification as a cost-effective and promising method of biological nitrate elimination is reviewed in terms of its removal process, applicability, efficiency, and associated disadvantages. The various pathways during biological nitrate removal, including assimilatory and dissimilatory nitrate reduction, are also explained. A comparative study was carried out to provide a better understanding of the advantages and disadvantages of autotrophic and heterotrophic denitrification. Sulfur-based and hydrogen-based denitrifications, which are the most common autotrophic processes of nitrate removal, are reviewed with the aim of presenting the salient features of hydrogenotrophic denitrification along with some drawbacks of the technology and research areas in which it could be used but currently is not. The application of algae-based water treatment is also introduced as a nature-inspired approach that may broaden future horizons of nitrate removal technology.

  13. Rising Sludge in Secondary Settlers Due to Denitrification

    DEFF Research Database (Denmark)

    Henze, Mogens; Dupont, Rene; Grau, Peter

    1993-01-01

    High suspended solids concentrations in settler effluents can be caused by rising sludge, which is the effect of flotation of solids by nitrogen gas resulting from biological denitrification. Many factors influence the nitrogen gas bubble evolution. The most important factor is the rate...

  14. Physicochemical properties influencing denitrification rate and microbial activity in denitrification bioreactors

    Science.gov (United States)

    Schmidt, C. A.

    2012-12-01

    The use of N-based fertilizer will need to increase to meet future demands, yet existing applications have been implicated as the main source of coastal eutrophication and hypoxic zones. Producing sufficient crops to feed a growing planet will require efficient production in combination with sustainable treatment solutions. The long-term success of denitrification bioreactors to effectively remove nitrate (NO¬3), indicates this technology is a feasible treatment option. Assessing and quantifying the media properties that affect NO¬3 removal rate and microbial activity can improve predictions on bioreactor performance. It was hypothesized that denitrification rates and microbial biomass would be correlated with total C, NO¬3 concentration, metrics of organic matter quality, media surface area and laboratory measures of potential denitrification rate. NO¬3 removal rates and microbial biomass were evaluated in mesocosms filled with different wood treatments and the unique influence of these predictor variables was determined using a multiple linear regression analysis. NO3 reduction rates were independent of NO¬3 concentration indicating zero order reaction kinetics. Temperature was strongly correlated with denitrification rate (r2=0.87; Q10=4.7), indicating the variability of bioreactor performance in differing climates. Fiber quality, and media surface area were strong (R>0.50), unique predictors of rates and microbial biomass, although C:N ratio and potential denitrification rate did not predict actual denitrification rate or microbial biomass. Utilizing a stepwise multiple linear regression, indicates that the denitrification rate can be effectively (r2=0.56;pdetergent fiber and surface area alone are quantified. These results will assist with the widespread implementation of denitrification bioreactors to achieve significant N load reductions in large watersheds. The nitrate reduction rate as a function of groundwater temperature for all treatments

  15. Alternative solutions for the bio-denitrification of landfill leachates using pine bark and compost.

    Science.gov (United States)

    Trois, Cristina; Pisano, Giulia; Oxarango, Laurent

    2010-06-15

    Nitrified leachate may still require an additional bio-denitrification step, which occurs with the addition of often-expensive chemicals as carbon source. This study explores the applicability of low-cost carbon sources such as garden refuse compost and pine bark for the denitrification of high strength landfill leachates. The overall objective is to assess efficiency, kinetics and performance of the substrates in the removal of high nitrate concentrations. Garden refuse and pine bark are currently disposed of in general waste landfills in South Africa, separated from the main waste stream. A secondary objective is to assess the feasibility of re-using green waste as by-product of an integrated waste management system. Denitrification processes in fixed bed reactors were simulated at laboratory scale using anaerobic batch tests and leaching columns packed with immature compost and pine bark. Biologically treated leachate from a Sequencing Batch Reactor (SBR) with nitrate concentrations of 350, 700 and 1100 mgN/l were used for the trials. Preliminary results suggest that, passed the acclimatization step (40 days for both substrates), full denitrification is achieved in 10-20 days for the pine bark and 30-40 days for the compost. Copyright 2010 Elsevier B.V. All rights reserved.

  16. Denitrification in human dental plaque

    Directory of Open Access Journals (Sweden)

    Verstraete Willy

    2010-03-01

    Full Text Available Abstract Background Microbial denitrification is not considered important in human-associated microbial communities. Accordingly, metabolic investigations of the microbial biofilm communities of human dental plaque have focused on aerobic respiration and acid fermentation of carbohydrates, even though it is known that the oral habitat is constantly exposed to nitrate (NO3- concentrations in the millimolar range and that dental plaque houses bacteria that can reduce this NO3- to nitrite (NO2-. Results We show that dental plaque mediates denitrification of NO3- to nitric oxide (NO, nitrous oxide (N2O, and dinitrogen (N2 using microsensor measurements, 15N isotopic labelling and molecular detection of denitrification genes. In vivo N2O accumulation rates in the mouth depended on the presence of dental plaque and on salivary NO3- concentrations. NO and N2O production by denitrification occurred under aerobic conditions and was regulated by plaque pH. Conclusions Increases of NO concentrations were in the range of effective concentrations for NO signalling to human host cells and, thus, may locally affect blood flow, signalling between nerves and inflammatory processes in the gum. This is specifically significant for the understanding of periodontal diseases, where NO has been shown to play a key role, but where gingival cells are believed to be the only source of NO. More generally, this study establishes denitrification by human-associated microbial communities as a significant metabolic pathway which, due to concurrent NO formation, provides a basis for symbiotic interactions.

  17. Oxygen at Nanomolar Levels Reversibly Suppresses Process Rates and Gene Expression in Anammox and Denitrification in the Oxygen Minimum Zone off Northern Chile

    OpenAIRE

    Dalsgaard, Tage; Stewart, Frank J.; Thamdrup, Bo; De Brabandere, Loreto; Revsbech, Niels Peter; Ulloa, Osvaldo; Canfield, Don E.; DeLong, Edward

    2014-01-01

    A major percentage (20 to 40%) of global marine fixed-nitrogen loss occurs in oxygen minimum zones (OMZs). Concentrations of O[subscript 2] and the sensitivity of the anaerobic N[subscript 2]-producing processes of anammox and denitrification determine where this loss occurs. We studied experimentally how O[subscript 2] at nanomolar levels affects anammox and denitrification rates and the transcription of nitrogen cycle genes in the anoxic OMZ off Chile. Rates of anammox and denitrification w...

  18. Citric acid application for denitrification process support in biofilm reactor.

    Science.gov (United States)

    Mielcarek, Artur; Rodziewicz, Joanna; Janczukowicz, Wojciech; Dabrowska, Dorota; Ciesielski, Slawomir; Thornton, Arthur; Struk-Sokołowska, Joanna

    2017-03-01

    The study demonstrated that citric acid, as an organic carbon source, can improve denitrification in Anaerobic Sequencing Batch Biofilm Reactor (AnSBBR). The consumption rate of the organic substrate and the denitrification rate were lower during the period of the reactor's acclimatization (cycles 1-60; 71.5 mgCOD L -1  h -1 and 17.81 mgN L -1  h -1 , respectively) than under the steady state conditions (cycles 61-180; 143.8 mgCOD L -1  h -1 and 24.38 mgN L -1  h -1 ). The biomass yield coefficient reached 0.04 ± 0.02 mgTSS· mgCOD re -1 (0.22 ± 0.09 mgTSS mgN re -1 ). Observations revealed the diversified microbiological ecology of the denitrifying bacteria. Citric acid was used mainly by bacteria representing the Trichoccocus genus, which represented above 40% of the sample during the first phase of the process (cycles 1-60). In the second phase (cycles 61-180) the microorganisms the genera that consumed the acetate and formate, as the result of citric acid decomposition were Propionibacterium (5.74%), Agrobacterium (5.23%), Flavobacterium (1.32%), Sphaerotilus (1.35%), Erysipelothrix (1.08%). Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Heterotrophic Anodic Denitrification in Microbial Fuel Cells

    Directory of Open Access Journals (Sweden)

    Jakub Drewnowski

    2016-06-01

    Full Text Available Nowadays, pollution caused by energy production systems is a major environmental concern. Therefore, the development of sustainable energy sources is required. Amongst others, the microbial fuel cell (MFC seems to be a possible solution because it can produce clean energy at the same time that waste is stabilized. Unfortunately, mainly due to industrial discharges, the wastes could contain nitrates, or nitrates precursors such ammonia, which could lead to lower performance in terms of electricity production. In this work, the feasibility of coupling anodic denitrification process with electricity production in MFC and the effect of the nitrates over the MFC performance were studied. During the experiments, it was observed that the culture developed in the anodic chamber of the MFC presented a significant amount of denitrificative microorganisms. The MFC developed was able to denitrify up to 4 ppm, without affecting the current density exerted, of about 1 mA/cm2. Regarding the denitrification process, it must be highlighted that the maximum denitrification rate achieved with the culture was about 60 mg·NO3−·L−1·h−1. Based on these results, it can be stated that it is possible to remove nitrates and to produce energy, without negatively affecting the electrical performance, when the nitrate concentration is low.

  20. The effect of millennial-scale changes in Arabian Sea denitrification on atmospheric CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Altabet, M.A.; Higginson, M.J. [University of Massachusetts, New Bedford, MA (United States). School for Marine Science and Technology; Murray, D.W. [Brown University, Providence, RI (United States). Center for Environmental Studies

    2002-07-01

    Most global biogeochemical processes are known to respond to climate change, some of which have the capacity to produce feedbacks through the regulation of atmospheric greenhouse gases. Marine denitrification - the reduction of nitrate to gaseous nitrogen - is an important process in this regard, affecting greenhouse gas concentrations directly through the incidental production of nitrous oxide, and indirectly through modification of the marine nitrogen inventory and hence the biological pump for C0{sub 2}. Although denitrification has been shown to vary with glacial-interglacial cycles, its response to more rapid climate change has not yet been well characterized. Here we present nitrogen isotope ratio, nitrogen content and chlorin abundance data from sediment cores with high accumulation rates on the Oman continental margin that reveal substantial millennial-scale variability in Arabian Sea denitrification and productivity during the last glacial period. The detailed correspondence of these changes with Dansgaard-Oeschger events recorded in Greenland ice cores indicates rapid, century-scale reorganization of the Arabian Sea ecosystem in response to climate excursions, mediated through the intensity of summer monsoonal upwelling. Considering the several-thousand-year residence time of fixed nitrogen in the ocean, the response of global marine productivity to changes in denitrification would have occurred at lower frequency and appears to be related to climatic and atmospheric C0{sub 2} oscillations observed in Antarctic ice cores between 20 and A kyr ago. (author)

  1. Anaerobic columnar denitrification of high nitrate wastewater

    International Nuclear Information System (INIS)

    Francis, C.W.; Malone, C.D.

    1975-01-01

    Anaerobic columns were used to test the effectiveness of biological denitrification of nitrate solutions ranging in concentration from 1 to 10 kg NO 3 /m 3 . Several sources of nitrate (Ca(CNO 3 ) 2 , NaNO 3 , NH 4 NO 3 , and actual nitrate wastes from a UO 2 fuel fabrication plant) were evaluated as well as two packing media. The packing media were anthracite coal particles, whose effective diameter size ranged between 2 and 3 mm, and polypropylene Raschig rings 1.6 x 1.6 diameter. The anthracite coal proved to be the better packing media as excessive hydraulic short circuiting occurred in a 120 x 15 cm diameter glass column packed with the polypropylene rings after 40 days operation. With anthracite coal, floatation of the bed occurred at flow rates greater than 0.80 cm 3 /s. Tapered columns packed with anthracite coal eliminated the floatation problem, even at flow rates as high as 5 cm 3 /s. Under optimum operating conditions the anthracite coal behaved as a fluidized bed. Maximum denitrification rates were 1.0--1.4 g NO 3 /m 3 /s based on initial bed volume. Denitrification kinetics indicated that rates of denitrification became substrate inhibited at nitrate concentrations greater than 6.5 kg NO 3 /m 3 Anaerobic columns packed with anthracite coal appear to be an effective method of nitrate disposal for nitrate rich wastewater generated at UO 2 fuel fabrication plants and fuel reprocessing facilities. (U.S.)

  2. Performance of nitrate-dependent anaerobic ferrous oxidizing (NAFO) process: a novel prospective technology for autotrophic denitrification.

    Science.gov (United States)

    Zhang, Meng; Zheng, Ping; Li, Wei; Wang, Ru; Ding, Shuang; Abbas, Ghulam

    2015-03-01

    Nitrate-dependent anaerobic ferrous oxidizing (NAFO) is a valuable biological process, which utilizes ferrous iron to convert nitrate into nitrogen gas, removing nitrogen from wastewater. In this work, the performance of NAFO process was investigated as a nitrate removal technology. The results showed that NAFO system was feasible for autotrophic denitrification. The volumetric loading rate (VLR) and volumetric removal rate (VRR) under steady state were 0.159±0.01 kg-N/(m(3) d) and 0.073±0.01 kg-N/(m(3) d), respectively. In NAFO system, the effluent pH was suggested as an indicator which demonstrated a good correlation with nitrogen removal. The nitrate concentration was preferred to be less than 130 mg-N/L. Organic matters had little influence on NAFO performance. Abundant iron compounds were revealed to accumulate in NAFO sludge with peak value of 51.73% (wt), and they could be recycled for phosphorus removal, with capacity of 16.57 mg-P/g VS and removal rate of 94.77±2.97%, respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. SNCR method of flue gas denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Kuropka, J. [Politechniki Wroclawskiej, Wroclaw (Poland). Instytut Inzynierii Ochrony Srodowiska

    1998-12-31

    Current achievements in experiments on selective non-catalytic reduction of nitrogen oxides from flue gases were presented. Some basic parameters of denitrification process (temperature of reaction, contact time, molar ratio of agents, additions to reacting substances) which influence the rate of nitrogen oxides emission from flue gases were analysed. On the basis of conducted experiments with calcium hydroxide and urea or calcium carbonate and urea on full-scale FGD installation on WP-120 boiler it was found that SNCR method can be applied to simultaneous denitrification and desulfurisation of flue gases. 27 refs., 10 figs.

  4. Linking denitrification and infiltration rates during managed groundwater recharge.

    Science.gov (United States)

    Schmidt, Calla M; Fisher, Andrew T; Racz, Andrew J; Lockwood, Brian S; Huertos, Marc Los

    2011-11-15

    We quantify relations between rates of in situ denitrification and saturated infiltration through shallow, sandy soils during managed groundwater recharge. We used thermal methods to determine time series of point-specific flow rates, and chemical and isotopic methods to assess denitrification progress. Zero order denitrification rates between 3 and 300 μmol L(-1) d(-1) were measured during infiltration. Denitrification was not detected at times and locations where the infiltration rate exceeded a threshold of 0.7 ± 0.2 m d(-1). Pore water profiles of oxygen and nitrate concentration indicated a deepening of the redoxocline at high flow rates, which reduced the thickness of the zone favorable for denitrification. Denitrification rates were positively correlated with infiltration rates below the infiltration threshold, suggesting that for a given set of sediment characteristics, there is an optimal infiltration rate for achieving maximum nitrate load reduction and improvements to water supply during managed groundwater recharge. The extent to which results from this study may be extended to other managed and natural hydrologic settings remains to be determined, but the approach taken in this study should be broadly applicable, and provides a quantitative link between shallow hydrologic and biogeochemical processes.

  5. Denitrification potential and its relation to organic carbon quality in three coastal wetland soils

    International Nuclear Information System (INIS)

    Dodla, Syam K.; Wang, Jim J.; DeLaune, Ron D.; Cook, Robert L.

    2008-01-01

    Capacity of a wetland to remove nitrate through denitrification is controlled by its physico-chemical and biological characteristics. Understanding these characteristics will help better to guide beneficial use of wetlands in processing nitrate. This study was conducted to determine the relationship between soil organic carbon (SOC) quality and denitrification rate in Louisiana coastal wetlands. Composite soil samples of different depths were collected from three different wetlands along a salinity gradient, namely, bottomland forest swamp (FS), freshwater marsh (FM), and saline marsh (SM) located in the Barataria Basin estuary. Potential denitrification rate (PDR) was measured by acetylene inhibition method and distribution of carbon (C) moieties in organic C was determined by 13 C solid-state NMR. Of the three wetlands, the FM soil profile exhibited the highest PDR on both unit weight and unit volume basis as compared to FS and SM. The FM also tended to yield higher amount of N 2 O as compared to the FS and SM especially at earlier stages of denitrification, suggesting incomplete reduction of NO 3 - at FM and potential for emission of N 2 O. Saline marsh soil profile had the lowest PDR on the unit volume basis. Increasing incubation concentration from 2 to 10 mg NO 3 - -N L -1 increased PDR by 2 to 6 fold with the highest increase in the top horizons of FS and SM soils. Regression analysis showed that across these three wetland systems, organic C has significant effect in regulating PDR. Of the compositional C moieties, polysaccharides positively influenced denitrification rate whereas phenolics (likely phenolic adehydes and ketonics) negatively affected denitrification rate in these wetland soils. These results could have significant implication in integrated assessment and management of wetlands for treating nutrient-rich biosolids and wastewaters, non-point source agricultural runoff, and nitrate found in the diverted Mississippi River water used for coastal

  6. Implication of using different carbon sources for denitrification in wastewater treatments.

    Science.gov (United States)

    Cherchi, Carla; Onnis-Hayden, Annalisa; El-Shawabkeh, Ibrahim; Gu, April Z

    2009-08-01

    Application of external carbon sources for denitrification becomes necessary for wastewater treatment plants that have to meet very stringent effluent nitrogen limits (e.g., 3 to 5 mgTN/L). In this study, we evaluated and compared three carbon sources--MicroC (Environmental Operating Solutions, Bourne, Massachusetts), methanol, and acetate-in terms of their denitrification rates and kinetics, effect on overall nitrogen removal performance, and microbial community structure of carbon-specific denitrifying enrichments. Denitrification rates and kinetics were determined with both acclimated and non-acclimated biomass, obtained from laboratory-scale sequencing batch reactor systems or full-scale plants. The results demonstrate the feasibility of the use of MicroC for denitrification processes, with maximum denitrification rates (k(dmax)) of 6.4 mgN/gVSSh and an observed yield of 0.36 mgVSS/mgCOD. Comparable maximum nitrate uptake rates were found with methanol, while acetate showed a maximum denitrification rate nearly twice as high as the others. The maximum growth rates measured at 20 degrees C for MicroC and methanol were 3.7 and 1.2 day(-1), respectively. The implications resulting from the differences in the denitrification rates and kinetics of different carbon sources on the full-scale nitrogen removal performance, under various configurations and operational conditions, were assessed using Biowin (EnviroSim Associates, Ltd., Flamborough, Ontario, Canada) simulations for both pre- and post-denitrification systems. Examination of microbial population structures using Automated Ribosomal Intergenic Spacer Analysis (ARISA) throughout the study period showed dynamic temporal changes and distinct microbial community structures of different carbon-specific denitrifying cultures. The ability of a specific carbon-acclimated denitrifying population to instantly use other carbon source also was investigated, and the chemical-structure-associated behavior patterns observed

  7. Assessment of sulfide production risk in soil during the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification process.

    Science.gov (United States)

    Ghorbel, L; Coudert, L; Gilbert, Y; Mercier, G; Blais, J F

    2016-10-01

    This study aimed to determine the potential of sulfide generation during infiltration through soil of domestic wastewater treated by a sulfur-utilizing denitrification process. Three types of soil with different permeability rates (K s = 0.028, 0.0013, and 0.00015 cm/s) were investigated to evaluate the potential risk of sulfur generation during the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification system. These soils were thoroughly characterized and tested to assess their capacity to be used as drainages for wastewaters. Experiments were conducted under two operating modes (saturated and unsaturated). Sulfate, sulfide, and chemical oxygen demand (COD) levels were determined over a period of 100 days. Despite the high concentration of sulfates (200 mg/L) under anaerobic conditions (ORP = -297 mV), no significant amount of sulfide was generated in the aqueous (soil permeability did not have a noticeable effect on the infiltration of domestic wastewater treated by a sulfur-utilizing denitrification system due to low contents of organic matter (i.e., dissolved organic carbon, DOC). The autotrophic denitrification process used to treat the domestic wastewater allowed the reduction of the concentration of biochemical oxygen demand (BOD5) below 5 mg/L, of DOC below 7 mg/L, and of COD below 100 mg/L.

  8. Respirometry applied for biological nitrogen removal process; Aplicacion de la respirometria al tratamiento biologico para la eliminacion del nitrogeno

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, E.

    2004-07-01

    In waste water treatment plants, the Biological Nitrogen Removal (BNR) has acquired a fundamental importance. The BNR processes are Nitrification ( aerobic) and Denitrification (anoxic). Since both processes are carried on living microorganisms, a lack of their bioactivity information might cause serious confusion about their control criteria and following up purposes. For this reason, the Re spirometry applied to those processes has reached an important role by getting an essential information in a timely manner through respiration rate measurements in static and dynamic modes and applications such as AUR (Ammonium Uptake Rate), Nitrification Capacity. RBCOD (Readily Biodegradable COD) as well as AUR related to SRT (Sludge age), RBCOD related to NUR (Specific Nitrate Uptake Rate) and others. By other side in this article we have introduced a not very well known applications related to denitrification, about the methanol acclimatization and generated bioactivity. (Author) 6 refs.

  9. Oxygen at nanomolar levels reversibly suppresses process rates and gene expression in anammox and denitrification in the oxygen minimum zone off northern Chile.

    Science.gov (United States)

    Dalsgaard, Tage; Stewart, Frank J; Thamdrup, Bo; De Brabandere, Loreto; Revsbech, Niels Peter; Ulloa, Osvaldo; Canfield, Don E; DeLong, Edward F

    2014-10-28

    A major percentage (20 to 40%) of global marine fixed-nitrogen loss occurs in oxygen minimum zones (OMZs). Concentrations of O2 and the sensitivity of the anaerobic N2-producing processes of anammox and denitrification determine where this loss occurs. We studied experimentally how O2 at nanomolar levels affects anammox and denitrification rates and the transcription of nitrogen cycle genes in the anoxic OMZ off Chile. Rates of anammox and denitrification were reversibly suppressed, most likely at the enzyme level. Fifty percent inhibition of N2 and N2O production by denitrification was achieved at 205 and 297 nM O2, respectively, whereas anammox was 50% inhibited at 886 nM O2. Coupled metatranscriptomic analysis revealed that transcripts encoding nitrous oxide reductase (nosZ), nitrite reductase (nirS), and nitric oxide reductase (norB) decreased in relative abundance above 200 nM O2. This O2 concentration did not suppress the transcription of other dissimilatory nitrogen cycle genes, including nitrate reductase (narG), hydrazine oxidoreductase (hzo), and nitrite reductase (nirK). However, taxonomic characterization of transcripts suggested inhibition of narG transcription in gammaproteobacteria, whereas the transcription of anammox narG, whose gene product is likely used to oxidatively replenish electrons for carbon fixation, was not inhibited. The taxonomic composition of transcripts differed among denitrification enzymes, suggesting that distinct groups of microorganisms mediate different steps of denitrification. Sulfide addition (1 µM) did not affect anammox or O2 inhibition kinetics but strongly stimulated N2O production by denitrification. These results identify new O2 thresholds for delimiting marine nitrogen loss and highlight the utility of integrating biogeochemical and metatranscriptomic analyses. The removal of fixed nitrogen via anammox and denitrification associated with low O2 concentrations in oceanic oxygen minimum zones (OMZ) is a major sink in

  10. Denitrification prevails over anammox in tropical mangrove sediments (Goa, India)

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; Michotey, V.D.; Guasco, S.; Bonin, P.C.; LokaBharathi, P.A.

    denitrification as the main process of N sub(2) production in mangrove sediments. At Divar, denitrification was approx 3 times higher than at Tuvem with maximum activity of 224.51 + or -6.63 nmol N sub(2) g sup(−1) h sup(−1) at 0–2 cm. Denitrifying genes (nos...

  11. Atmospheric nitrogen deposition influences denitrification and nitrous oxide production in lakes.

    Science.gov (United States)

    McCrackin, Michelle L; Elser, James J

    2010-02-01

    Microbially mediated denitrification is an important process that may ameliorate the effects of nitrogen (N) loading by permanently removing excess N inputs. In this study, we measured the rate of denitrification and nitrous oxide (N2O) production during denitrification in sediments from 32 Norwegian lakes at the high and low ends of a gradient of atmospheric N deposition. Denitrification and N2O production rates averaged 41.7 and 1.1 micromol N x m(-2) x h(-1), respectively, for high-deposition lakes. There was no detectable denitrification or N2O production in low-deposition lakes. Epilimnetic nitrate concentration was strongly correlated with denitrification rate (r2 = 0.67). We also measured the denitrification rate in response to experimental additions of organic carbon, nitrate, and phosphorus. Experimental nitrate additions stimulated denitrification in sediments of all lakes, regardless of N deposition level. In fact, the rate of denitrification in nitrate-amended treatments was the same magnitude for lakes in both deposition areas. These findings suggest that lake sediments possess considerable capacity to remove nitrate and that this capacity has not been saturated under conditions of chronic N loading. Further, nitrous oxide was nearly 3% of the total gaseous product during denitrification in high-deposition lakes, a fraction that is comparable to polluted marine sediments. Our findings suggest that, while lakes play an important role in N removal in the landscape, they may be a source of N2O emissions, especially in areas subject to elevated N inputs.

  12. Potential Denitrification: Concept and Conditions of its Measurement ...

    African Journals Online (AJOL)

    Denitrification plays important roles in nitrogen cycling and management affecting both the environment and agricultural systems. Potential denitrification has a role in comparison of denitrification magnitudes in different soils. This paper discusses the concept of potential denitrification in relation to denitrification rate and ...

  13. Modelling the soil nitrogen denitrification

    International Nuclear Information System (INIS)

    Budoi, G.H.; Danuso, F.; Giovanardi, R.; Gavriluta, A.; Alexandrescu, A.; Bireescu, L.

    1999-01-01

    The paper presents the differential equations used to compute the daily amounts of N denitrified and to compute the amount of N denitrified in a given period of time. It shows also the equations which compute the correction factors of the maximum denitrification rate as a function of soil temperature (F td ), moisture (F md ) and pH (F pHd ), original equations used by NICROS - nitrogen crop simulation model to describe the influence of these abiotic factors. The temperature factor, F td . The optimum temperature for denitrification is between 25-37 o C. The process is slow at temperatures below 10 o C, there is an increased inhibition below 5 o C and stop completely at 0 o C. The maximum temperature for denitrification is practically that which limits the soil microbiological activity, generally 75 o C. The following relations are used to compute the F td factor: F td 1/(1 + e -0,3347 tmed+ 4,99 ) if t med ≤ 37; F td = 1 - (t med - 37)/38 if 75 > t med > 37; F td = 0 if t med ≥ 75, where t med is the average daily soil temperature. The moisture factor, F md . The denitrification has maximum intensity at soil water saturation, U sat , and stop below 80 % from U sat . F md = 0 if soil moisture U s ≤ 0,8*U sat , and F md = (U s - 0,8*U sat )/(U sat - 0,8*U sat ) if U s > 0,8*U sat . The pH factor, F pHd . Denitrification takes place at pH between 4-9 and is maximum at pH between 7-8. The relations used to compute the F pHd factor are: F pHd = 1/(1 + e -3,1923 pH + 18,87 ) if pH ≤ 8; F pHd = (9 - pH) when pH is between 8-9, and F pHd = 0 if pH > 9. Refs. 6 (author)

  14. Effect of Volatile Fatty Acids and Trimethylamine on Denitrification in Activated Sludge

    DEFF Research Database (Denmark)

    Eilersen, Ann Marie; Henze, Mogens; Kløft, Lene

    1995-01-01

    The effect of volatile fatty acids and trimethylamine on denitrification activity of activated sludge was studied in laboratory batch experiments. Formic acid had no effect on the denitrification rates. Acetic acid, n-butyric acid and trimethylamine all enhanced the rates. Acetate is the compound...... wastewaters from fish, potato and onion industries all stimulated denitrification. Reject water from anaerobic treatment of excess sludge had no significant effect on the denitrification processes. For isobutyric, isovaleric and n-valeric acid the undissociated compounds appear to act as the inhibitor...... with the strongest effect, n-butyric acid has a moderate effect, while TMA only have a small effect in stimulating the rates. Propionic, isobutyric, n-valeric, isovaleric and caproic acid inhibit denitrification, nitrate reduction being more inhibited than nitrite reduction. The inhibitor concentration, KI, at which...

  15. Denitrification potential and its relation to organic carbon quality in three coastal wetland soils

    Energy Technology Data Exchange (ETDEWEB)

    Dodla, Syam K. [School of Plant, Environmental and Soil Sciences, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803 (United States); Wang, Jim J. [School of Plant, Environmental and Soil Sciences, Louisiana State Univ. Agricultural Center, Baton Rouge, LA 70803 (United States)], E-mail: jjwang@agctr.lsu.edu; DeLaune, Ron D. [Wetland Biogeochemistry Institute, School of the Coast and Environment, Louisiana State University, Baton Rouge, LA 70803 (United States); Cook, Robert L. [Chemistry Department, Louisiana State University, Baton Rouge, LA 70803 (United States)

    2008-12-15

    Capacity of a wetland to remove nitrate through denitrification is controlled by its physico-chemical and biological characteristics. Understanding these characteristics will help better to guide beneficial use of wetlands in processing nitrate. This study was conducted to determine the relationship between soil organic carbon (SOC) quality and denitrification rate in Louisiana coastal wetlands. Composite soil samples of different depths were collected from three different wetlands along a salinity gradient, namely, bottomland forest swamp (FS), freshwater marsh (FM), and saline marsh (SM) located in the Barataria Basin estuary. Potential denitrification rate (PDR) was measured by acetylene inhibition method and distribution of carbon (C) moieties in organic C was determined by {sup 13}C solid-state NMR. Of the three wetlands, the FM soil profile exhibited the highest PDR on both unit weight and unit volume basis as compared to FS and SM. The FM also tended to yield higher amount of N{sub 2}O as compared to the FS and SM especially at earlier stages of denitrification, suggesting incomplete reduction of NO{sub 3}{sup -} at FM and potential for emission of N{sub 2}O. Saline marsh soil profile had the lowest PDR on the unit volume basis. Increasing incubation concentration from 2 to 10 mg NO{sub 3}{sup -}-N L{sup -1} increased PDR by 2 to 6 fold with the highest increase in the top horizons of FS and SM soils. Regression analysis showed that across these three wetland systems, organic C has significant effect in regulating PDR. Of the compositional C moieties, polysaccharides positively influenced denitrification rate whereas phenolics (likely phenolic adehydes and ketonics) negatively affected denitrification rate in these wetland soils. These results could have significant implication in integrated assessment and management of wetlands for treating nutrient-rich biosolids and wastewaters, non-point source agricultural runoff, and nitrate found in the diverted

  16. Denitrification coupled with methane anoxic oxidation and microbial community involved identification

    Directory of Open Access Journals (Sweden)

    Renata Medici Frayne Cuba

    2011-02-01

    Full Text Available In this work, the biological denitrification associated with anoxic oxidation of methane and the microbial diversity involved were studied. Kinetic tests for nitrate (NO3- and nitrite (NO2- removal and methane uptake were carried out in 100 mL batch reactors incubated in a shaker (40 rpm at 30 ºC. Denitrificant/methanotrophic biomass was taken from a laboratory scale reactor fed with synthetic nitrified substrates (40 mgN L-1 of NO3- and subsequently NO2- and methane as carbon source. Results obtained from nitrate removal followed a first order reaction, presenting a kinetic apparent constant (kNO3 of 0.0577±0.0057d-1. Two notable points of the denitrification rate (0.12gNO3--N g-1 AVS d-1 and 0.07gNO3--N g-1 AVS d-1 were observed in the beginning and on the seventh day of operation. When nitrite was added as an electron acceptor, denitrification rates were improved, presenting an apparent kinetic constant (kNO2 of 0.0722±0.0044d-1, a maximum denitrification rate of 0.6gNO2--N g-1AVS d-1, and minimum denitrification rate of 0.1gNO2--N g-1AVS d-1 at the beginning and end of the test, respectively. Endogenous material supporting denitrification and methane concentration dissolved in the substrate was discarded from the control experiments in the absence of methane and seed, respectively. Methylomonas sp. was identified in the reactors fed with nitrate and nitrite as well as uncultured bacterium.

  17. Denitrification using a monopolar electrocoagulation/flotation (ECF) process.

    Science.gov (United States)

    Emamjomeh, Mohammad M; Sivakumar, Muttucumaru

    2009-01-01

    Nitrate levels are limited due to health concerns in potable water. Nitrate is a common contaminant in water supplies, and especially prevalent in surface water supplies and shallow wells. Nitrate is a stable and highly soluble ion with low potential for precipitation or adsorption. These properties make it difficult to remove using conventional water treatment methods. A laboratory batch electrocoagulation/flotation (ECF) reactor was designed to investigate the effects of different parameters such as electrolysis time, electrolyte pH, initial nitrate concentration, and current rate on the nitrate removal efficiency. The optimum nitrate removal was observed at a pH range of between 9 and 11. It appeared that the nitrate removal rate was 93% when the initial nitrate concentration and electrolysis time respectively were 100 mg L(-1)-NO(3)(-) and 40 min. The results showed a linear relationship between the electrolysis time for total nitrate removal and the initial nitrate concentration. It is concluded that the electrocoagulation technology for denitrification can be an effective preliminary process when the ammonia byproduct must be effectively removed by the treatment facilities.

  18. Screening identification of aerobic denitrification bacteria with high soil desalinization capacity

    Science.gov (United States)

    Jin, H.; Chen, H.; Jin, H.; Qian, Y.; Zhang, K.

    2017-08-01

    In order to study the mechanism of bacteria used in the saline soil remediation process, the aerobic denitrification bacteria were isolated from an agricultural greenhouse soil in a farm in East China’s Zhejiang Province. The identification, nitrogen reducing characteristics and the denitrification effect of bacteria from different soils at various locations were investigated. The results showed that the NO3- removal rate was 91% with bacteria from the greenhouse soil under aerobic conditions in 52 h, and the bacteria were identified as Gram-positive Castellaniella denitrification bacteria.

  19. Correlations between in situ denitrification activity and nir-gene abundances in pristine and impacted prairie streams

    International Nuclear Information System (INIS)

    Graham, David W.; Trippett, Clare; Dodds, Walter K.; O'Brien, Jonathan M.; Banner, Eric B.K.; Head, Ian M.; Smith, Marilyn S.; Yang, Richard K.; Knapp, Charles W.

    2010-01-01

    Denitrification is a process that reduces nitrogen levels in headwaters and other streams. We compared nirS and nirK abundances with the absolute rate of denitrification, the longitudinal coefficient of denitrification (i.e., K den , which represents optimal denitrification rates at given environmental conditions), and water quality in seven prairie streams to determine if nir-gene abundances explain denitrification activity. Previous work showed that absolute rates of denitrification correlate with nitrate levels; however, no correlation has been found for denitrification efficiency, which we hypothesise might be related to gene abundances. Water-column nitrate and soluble-reactive phosphorus levels significantly correlated with absolute rates of denitrification, but nir-gene abundances did not. However, nirS and nirK abundances significantly correlated with K den , as well as phosphorus, although no correlation was found between K den and nitrate. These data confirm that absolute denitrification rates are controlled by nitrate load, but intrinsic denitrification efficiency is linked to nirS and nirK gene abundances. - Denitrification efficiency best correlated to nirS and nirK gene abundances.

  20. The role of nitrifier denitrification in the production of nitrous oxide revisited

    NARCIS (Netherlands)

    Wrage-Mönnig, Nicole; Horn, Marcus A.; Well, Reinhard; Müller, Christoph; Velthof, Gerard; Oenema, Oene

    2018-01-01

    Nitrifier denitrification is the reduction of nitrite (NO2 −) by ammonia-oxidizing bacteria. This process may account for up to 100% of nitrous oxide (N2O) emissions from ammonium (NH4 +) in soils and is more significant than classical denitrification under some conditions. Investigations of

  1. Effects of process operating conditions on the autotrophic denitrification of nitrate-contaminated groundwater using bioelectrochemical systems.

    Science.gov (United States)

    Cecconet, D; Devecseri, M; Callegari, A; Capodaglio, A G

    2018-02-01

    Nitrates have been detected in groundwater worldwide, and their presence can lead to serious groundwater use limitations, especially because of potential health problems. Amongst different options for their removal, bioelectrochemical systems (BESs) have achieved promising results; in particular, attention has raised on BES-driven autotrophic denitrification processes. In this work, the performance of a microbial electrolysis cell (MEC) for groundwater autotrophic denitrification, is assessed in different conditions of nitrate load, hydraulic retention time (HRT) and process configuration. The system obtained almost complete nitrate removal under all conditions, while nitrite accumulation was recorded at nitrate loads higher than 100mgNO 3 - L -1 . The MEC system achieved, in different tests, a maximum nitrate removal rate of 62.15±3.04gNO 3 - -Nm -3 d -1 , while the highest TN removal rate observed was 35.37±1.18gTNm -3 d -1 . Characteristic of this process is a particularly low (in comparison with other reported works) energy consumption: 3.17·10 -3 ±2.26·10 -3 kWh/gNO 3 - N removed and 7.52·10 -2 ±3.58·10 -2 kWhm -3 treated. The anolyte configuration in closed loop allowed the process to use less clean water, while guaranteeing identical performances as in other conventional configurations. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Denitrification and potential nitrous oxide and carbon dioxide production in brownfield wetland soils.

    Science.gov (United States)

    Palta, Monica M; Ehrenfeld, Joan G; Groffman, Peter M

    2013-09-01

    Brownfields, previously developed sites that are derelict, vacant, or underused, are ubiquitous in urban areas. Wetlands on brownfields often retain rain and stormwater longer than the surrounding landscape because they are low-lying; this increases the possibility for these areas to process waterborne contaminants from the urban environment. In the northeastern United States, atmospheric deposition of nitrate (NO) is high. Denitrification, a microbial process common in wetlands, is a means of removing excess NO. Nitrogen gas is the desired end product of denitrification, but incomplete denitrification results in the production of NO, a greenhouse gas. The goal of this study was to investigate the potential of brownfield wetlands to serve as sinks for inorganic nitrogen and sources of greenhouse gases. We examined limitations to denitrification and NO production in brownfield wetland soils in New Jersey. Soil C:N ratios were high (18-40) and intact core denitrification (-0.78 to 11.6 μg NO-N kg dry soil d) and N mineralization (0.11-2.97 mg N kg dry soil d) were low for all sites. However, soil NO increased during dry periods. Nitrate additions to soil slurries increased denitrification rates, whereas labile C additions did not, indicating that soil denitrifiers were nitrogen limited. Incubations indicated that the end product of denitrification was primarily NO and not N. These results indicate that brownfield wetlands can develop significant denitrification capacity, potentially causing NO limitation. They might be significant sinks for atmospheric NO but may also become a significant source of NO if NO deposition were to increase. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  3. Process of nourishment staggered for elimination of nitrogen. Specific characteristics of the process. Strategies of control; Proceso de alimentacion escalonada para eliminacion de nitrogeno. Caracteristicas especificas del proceso. Estrategias de control

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigo, J. C.; Cortacans, J. A. [Infilco Espanola, s.a (Spain)

    2002-07-01

    This article illustrates the step fed activated sludge process advantages for biological nitrogen removal. This configuration, also known as ALP-HA (alternative phase step feed) process, reduces biological reactor volume, avoids internal sludge recycling and optimizes organic matter consumption for denitrification. Besides, it is offered the possibility to work with a calibrated specific model as a tool for the evaluation, design and operation of the process. To end up, some efficient operation strategies for the three-step ALPHA process in denitrification-nitrification reactors are proposed. (Author) 13 refs.

  4. The development and application of SCR denitrification technology in power plant

    Science.gov (United States)

    Wu, Junnan

    2017-12-01

    In recent decades, the emission of the nitrogen oxides (NOX) has been increasing with the years of the thermal power plant. The environment pollution caused by the emission of quantities of nitrogen oxides became more and more serious, so people now put more emphasis on the control of the emission of the nitrogen oxides. Especially, our country and the society are paying much more attention to the environment protection and the environment problems cannot be neglected. In this paper, we introduced the related research background of the technology of SCR denitrification which was as the symbol of the technology of the catalytic denitrification and discussed the reaction principles of the SCR denitrification and frequently used catalysts, the process of the technology, and the configuration. In the end, we pointed the way of the future research of the technology of the SCR denitrification.

  5. Environmental and Microbial Features Affecting Denitrification and Anammox Hotspots in an Estuarine Ecosystem

    Science.gov (United States)

    Lisa, J.; Song, B.; Lefcheck, J. S.; Tobias, C. R.

    2016-02-01

    Biogeochemical hotspots are characterized as a few sites that exhibit extremely high reaction rates relative to surrounding area, and often account for a high percentage of the overall reaction rates in an ecosystem. Criteria for quantitatively identifying these sites have not been well established. Further, the underlying mechanisms of hotspots have been described in terms of environmental conditions, with little attention paid to the microbial community. The objectives of this study were to establish quantitative criteria to identify denitrification and anammox hotspots, and determine the underlying microbial and environmental factors responsible for elevated N2 production. We used 15N isotope pairing incubation experiments to measure denitrification and anammox rates in the New River Estuary, NC. Quantitative PCR assays of nitrous oxide reductase (nosZ Clades I and II) and hydrazine oxidoreductase (hzo) genes were conducted to estimate denitrifier and anammox abundance. Structural Equation Modeling (SEM) was used to elucidate complex causal relationships between environmental and biological variables. Denitrification hotspots, quantitatively defined as statistical outliers, accounted for 35.6% total denitrification while comprising only 7.3% of the sites. Anammox hotspots,10.6% of the sites, accounted for 60.9% of total anammox. SEM revealed increased sediment organics at lower salinities supported higher functional gene abundance, which in turn resulted in higher N2 production. Surprisingly, denitrification rates were significantly and positively correlated with nosZ Clade II gene abundance, after accounting for the non-significant contributions of the naturally more abundant nosZ Clade I, and other environmental covariates. This is the first time that a quantitative definition of biogeochemical hotspots was put forth and used to determine the importance of anammox and denitrification hotspots in estuarine nitrogen removal capacity. Despite the low area

  6. Discovery of Fungal Denitrification Inhibitors by Targeting Copper Nitrite Reductase from Fusarium oxysporum.

    Science.gov (United States)

    Matsuoka, Masaki; Kumar, Ashutosh; Muddassar, Muhammad; Matsuyama, Akihisa; Yoshida, Minoru; Zhang, Kam Y J

    2017-02-27

    The efficient application of nitrogenous fertilizers is urgently required, as their excessive and inefficient use is causing substantial economic loss and environmental pollution. A significant amount of applied nitrogen in agricultural soils is lost as nitrous oxide (N 2 O) in the environment due to the microbial denitrification process. The widely distributed fungus Fusarium oxysporum is a major denitrifier in agricultural soils and its denitrification activity could be targeted to reduce nitrogen loss in the form of N 2 O from agricultural soils. Here, we report the discovery of first small molecule inhibitors of copper nitrite reductase (NirK) from F. oxysporum, which is a key enzyme in the fungal denitrification process. The inhibitors were discovered by a hierarchical in silico screening approach consisting of pharmacophore modeling and molecular docking. In vitro evaluation of F. oxysporum NirK activity revealed several pyrimidone and triazinone based compounds with potency in the low micromolar range. Some of these compounds suppressed the fungal denitrification in vivo as well. The compounds reported here could be used as starting points for the development of nitrogenous fertilizer supplements and coatings as a means to prevent nitrogen loss by targeting fungal denitrification.

  7. Denitrification and Biodiversity of Denitrifiers in a High-Mountain Mediterranean Lake

    Directory of Open Access Journals (Sweden)

    Antonio Castellano-Hinojosa

    2017-10-01

    Full Text Available Wet deposition of reactive nitrogen (Nr species is considered a main factor contributing to N inputs, of which nitrate (NO3− is usually the major component in high-mountain lakes. The microbial group of denitrifiers are largely responsible for reduction of nitrate to molecular dinitrogen (N2 in terrestrial and aquatic ecosystems, but the role of denitrification in removal of contaminant nitrates in high-mountain lakes is not well understood. We have used the oligotrophic, high-altitude La Caldera lake in the Sierra Nevada range (Spain as a model to study the role of denitrification in nitrate removal. Dissolved inorganic Nr concentration in the water column of la Caldera, mainly nitrate, decreased over the ice-free season which was not associated with growth of microbial plankton or variations in the ultraviolet radiation. Denitrification activity, estimated as nitrous oxide (N2O production, was measured in the water column and in sediments of the lake, and had maximal values in the month of August. Relative abundance of denitrifying bacteria in sediments was studied by quantitative polymerase chain reaction of the 16S rRNA and the two phylogenetically distinct clades nosZI and nosZII genes encoding nitrous oxide reductases. Diversity of denitrifiers in sediments was assessed using a culture-dependent approach and after the construction of clone libraries employing the nosZI gene as a molecular marker. In addition to genera Polymorphum, Paracoccus, Azospirillum, Pseudomonas, Hyphomicrobium, Thauera, and Methylophaga, which were present in the clone libraries, Arthrobacter, Burkholderia, and Rhizobium were also detected in culture media that were not found in the clone libraries. Analysis of biological activities involved in the C, N, P, and S cycles from sediments revealed that nitrate was not a limiting nutrient in the lake, allowed N2O production and determined denitrifiers’ community structure. All these results indicate that

  8. Denitrification and Biodiversity of Denitrifiers in a High-Mountain Mediterranean Lake

    Science.gov (United States)

    Castellano-Hinojosa, Antonio; Correa-Galeote, David; Carrillo, Presentación; Bedmar, Eulogio J.; Medina-Sánchez, Juan M.

    2017-01-01

    Wet deposition of reactive nitrogen (Nr) species is considered a main factor contributing to N inputs, of which nitrate (NO3−) is usually the major component in high-mountain lakes. The microbial group of denitrifiers are largely responsible for reduction of nitrate to molecular dinitrogen (N2) in terrestrial and aquatic ecosystems, but the role of denitrification in removal of contaminant nitrates in high-mountain lakes is not well understood. We have used the oligotrophic, high-altitude La Caldera lake in the Sierra Nevada range (Spain) as a model to study the role of denitrification in nitrate removal. Dissolved inorganic Nr concentration in the water column of la Caldera, mainly nitrate, decreased over the ice-free season which was not associated with growth of microbial plankton or variations in the ultraviolet radiation. Denitrification activity, estimated as nitrous oxide (N2O) production, was measured in the water column and in sediments of the lake, and had maximal values in the month of August. Relative abundance of denitrifying bacteria in sediments was studied by quantitative polymerase chain reaction of the 16S rRNA and the two phylogenetically distinct clades nosZI and nosZII genes encoding nitrous oxide reductases. Diversity of denitrifiers in sediments was assessed using a culture-dependent approach and after the construction of clone libraries employing the nosZI gene as a molecular marker. In addition to genera Polymorphum, Paracoccus, Azospirillum, Pseudomonas, Hyphomicrobium, Thauera, and Methylophaga, which were present in the clone libraries, Arthrobacter, Burkholderia, and Rhizobium were also detected in culture media that were not found in the clone libraries. Analysis of biological activities involved in the C, N, P, and S cycles from sediments revealed that nitrate was not a limiting nutrient in the lake, allowed N2O production and determined denitrifiers’ community structure. All these results indicate that denitrification could be a

  9. Impact of chloride on denitrification potential in roadside wetlands

    International Nuclear Information System (INIS)

    Lancaster, Nakita A.; Bushey, Joseph T.; Tobias, Craig R.; Song, Bongkeun; Vadas, Timothy M.

    2016-01-01

    Developed landscapes are exposed to changes in hydrology and water chemistry that limit their ability to mitigate detrimental impacts to coastal water bodies, particularly those that result from stormwater runoff. The elevated level of impervious cover increases not only runoff but also contaminant loading of nutrients, metals, and road salt used for deicing to water bodies. Here we investigate the impact that road salt has on denitrification in roadside environments. Sediments were collected from a series of forested and roadside wetlands and acclimated with a range of Cl − concentrations from 0 to 5000 mg L −1 for 96 h. Denitrification rates were measured by the isotope pairing technique using 15 N–NO 3 − , while denitrifying community structures were compared using terminal restriction fragment length polymorphism (T-RFLP) of nitrous oxide reductase genes (nosZ). Chloride significantly (p < 0.05) inhibited denitrification in forested wetlands at a Cl − dosage of 2500 or 5000 mg L −1 , but the decrease in denitrification rates was less and not significant for the roadside wetlands historically exposed to elevated concentrations of Cl − . The difference could not be attributed to other significant changes in conditions, such as DOC concentrations, N species concentrations, or pH levels. Denitrifying communities, as measured by T-RFs of the nosZ gene, in the roadside wetlands with elevated concentration of Cl − were distinctly different and more diverse compared to forested wetlands, and also different in roadside wetlands after 96 h exposures to Cl − . The shifts in denitrifying communities seem to minimize the decrease in denitrification rates in the wetlands previously exposed to Cl. As development results in more Cl − use and exposure to a broad range of natural or manmade wetland structures, an understanding of the seasonal effect of Cl on denitrification processes in these systems would aid in design or mitigation of the effects on

  10. Transient competitive complexation in biological kinetic isotope fractionation explains nonsteady isotopic effects: Theory and application to denitrification in soils

    Science.gov (United States)

    Maggi, Federico; Riley, William J.

    2009-12-01

    The theoretical formulation of biological kinetic isotope fractionation often assumes first-order or Michaelis-Menten kinetics, the latter solved under the quasi-steady state assumption. Both formulations lead to a constant isotope fractionation factor, therefore they may return incorrect estimations of isotopic effects and misleading interpretations of isotopic signatures when fractionation is not a steady process. We have analyzed the isotopic signature of denitrification in biogeochemical soil systems by Menyailo and Hungate (2006) in which high and variable 15N-N2O enrichment during N2O production and inverse isotope fractionation during N2O consumption could not be explained with first-order kinetics and the Rayleigh equation, or with Michaelis-Menten kinetics. When Michaelis-Menten kinetics were coupled to Monod kinetics to describe biomass and enzyme dynamics, and the quasi-steady state assumption was relaxed, transient Michaelis-Menten-Monod kinetics accurately reproduced the observed concentrations, and variable and inverse isotope fractionations. These results imply a substantial revision in modeling isotopic effects, suggesting that steady state kinetics such as first-order, Rayleigh, and classic Michaelis-Menten kinetics should be superseded by transient kinetics in conjunction with biomass and enzyme dynamics.

  11. Effect of growing plants on denitrification at high soil nitrate concentrations

    International Nuclear Information System (INIS)

    Haider, K.; Mosier, A.; Heinemeyer, O.

    1987-01-01

    The availability of plant rhizosphere C deposits and its influence on microbial denitrification is not clearly defined. Conflicting reports as to the influence of plants and root exudation on denitrification continue to appear in the literature. The results of the authors earlier phytotron study indicated that denitrification was not stimulated in soils planted with corn or wheat compared to unplanted soils. Lower nitrate concentrations in the planted soils, however, may have led to misinterpretation of this data. A second study was conducted, to evaluate the effect of actively growing plants on denitrification where the NO 3 7 content of planted soils was maintained similar to unplanted soils. Simultaneously the C fixed by corn (Zea mays) and the fate of fertilizer N applied to the soil during the growing season were quantified. The corn was grown in a phytotron under a continuous supply of 14 CO 2 in 15 N fertilized soils to which 15 N-NO 3 - was added periodically during the growing season. The results of these studies showed that denitrification was not stimulated in soils planted with corn during active plant growth phase even when soil NO 3 - was relatively high. Denitrification was, however, greater in corn planted than unplanted soil when the recoverable root biomass began to decrease. Less N was immobilized and net 15 N immobilization was lower in planted soils than in unplanted soils. As denitrification was lower in planted soils during the time of active plant growth, the study suggests that root exudates did not stimulate either process

  12. Denitrification activity and oxygen dynamics in Arctic sea ice

    DEFF Research Database (Denmark)

    Glud, Ronnie Nøhr; Stahl, Henrik J.; Rysgaard, Søren

    2008-01-01

    denitrification activity (5-194 mu mol N m(-2) day(-1)) and anammox activity (3-5 mu mol N m(-2) day(-1)) in melt water from both first-year and multi-year sea ice was found. These values correspond to 27 and 7%, respectively, of the benthic denitrification and anammox activities in Arctic sediments. Although we...... a mosaic of microsites of high and low O-2 concentrations. Brine enclosures and channels were strongly O-2 depleted in actively melting sea ice, and anoxic conditions in parts of the brine system would favour anaerobic processes....

  13. Nitrifier-induced denitrification is an important source of soil nitrous oxide and can be inhibited by a nitrification inhibitor 3,4-dimethylpyrazole phosphate.

    Science.gov (United States)

    Shi, Xiuzhen; Hu, Hang-Wei; Zhu-Barker, Xia; Hayden, Helen; Wang, Juntao; Suter, Helen; Chen, Deli; He, Ji-Zheng

    2017-12-01

    Soil ecosystem represents the largest contributor to global nitrous oxide (N 2 O) production, which is regulated by a wide variety of microbial communities in multiple biological pathways. A mechanistic understanding of these N 2 O production biological pathways in complex soil environment is essential for improving model performance and developing innovative mitigation strategies. Here, combined approaches of the 15 N- 18 O labelling technique, transcriptome analysis, and Illumina MiSeq sequencing were used to identify the relative contributions of four N 2 O pathways including nitrification, nitrifier-induced denitrification (nitrifier denitrification and nitrification-coupled denitrification) and heterotrophic denitrification in six soils (alkaline vs. acid soils). In alkaline soils, nitrification and nitrifier-induced denitrification were the dominant pathways of N 2 O production, and application of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) significantly reduced the N 2 O production from these pathways; this is probably due to the observed reduction in the expression of the amoA gene in ammonia-oxidizing bacteria (AOB) in the DMPP-amended treatments. In acid soils, however, heterotrophic denitrification was the main source for N 2 O production, and was not impacted by the application of DMPP. Our results provide robust evidence that the nitrification inhibitor DMPP can inhibit the N 2 O production from nitrifier-induced denitrification, a potential significant source of N 2 O production in agricultural soils. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  14. Removal of nutrients in denitrification system using coconut coir fibre for the biological treatment of aquaculture wastewater.

    Science.gov (United States)

    Manoj, Valsa Remony; Vasudevan, Namasivayam

    2012-03-01

    Ideal bacterial support medium for fixed film denitrification processes/bioreactors must be inexpensive, durable and possess large surface area with sufficient porosity. The present study has been focussed on removing nitrate nitrogen at two different nitrate nitrogen loading rates (60 (NLR I) and 120 (NLR II) mg l(-1)) from simulated aquaculture wastewater. Coconut coir fibre and a commercially available synthetic reticulated plastic media (Fujino Spirals) were used as packing medium in two independent upflow anaerobic packed bed column reactors. Removal of nitrate nitrogen was studied in correlation with other nutrients (COD, TKN, dissolved orthophosphate). Maximum removal of 97% at NLR-I and 99% at NLR - II of nitrate nitrogen was observed in with either media. Greater consistency in the case of COD removal of upto 81% was observed at NLR II where coconut coir was used as support medium compared to 72% COD removal by Fujino Spirals. The results observed indicate that the organic support medium is just as efficient in nitrate nitrogen removal as conventionally used synthetic support medium. The study is important as it specifically focuses on denitrification of aquaculture wastewater using cheaper organic support medium in anoxic bioreactors for the removal of nitrate nitrogen; which is seldom addressed as a significant problem.

  15. Shortcut nitrification-denitrification by means of autochthonous halophilic biomass in an SBR treating fish-canning wastewater.

    Science.gov (United States)

    Capodici, Marco; Corsino, Santo Fabio; Torregrossa, Michele; Viviani, Gaspare

    2018-02-15

    Autochthonous halophilic biomass was cultivated in a sequencing batch reactor (SBR) aimed at analyzing the potential use of autochthonous halophilic activated sludge in treating saline industrial wastewater. Despite the high salt concentration (30 g NaCl L -1 ), biological oxygen demand (BOD) and total suspended solids (TSS), removal efficiencies were higher than 90%. More than 95% of the nitrogen was removed via a shortcut nitrification-denitrification process. Both the autotrophic and heterotrophic biomass samples exhibited high biological activity. The use of autochthonous halophilic biomass led to high-quality effluent and helped to manage the issues related to nitrogen removal in saline wastewater treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Integrated real-time control strategy in multi-tank A2O process for biological nutrient removal treating real domestic wastewater

    Directory of Open Access Journals (Sweden)

    Saad Abualhail

    2017-02-01

    Full Text Available An integrated real-time anaerobic–anoxic/oxic (A2O operated with multi-tank called IMT–A2O process was designed and operated with fluctuating influent loads for biological nutrient removal for treating real domestic wastewater. IMT–A2O process, a “phased isolation tank” technology, varies both aeration pattern and flow path in a continuous flow multi-tank system to force fluctuation of organic and nutrient concentrations in process reactors. Using an eight-phase cycle, desired biochemical transformations, are accomplished at different times in the same tank. On-line sensors (pH, ORP, and DO were used as real-time control parameters to adjust the duration of each operational phase in the IMT–A2O process. The control system is an algorithm that automatically adjusts the cycle length to the influent wastewater characteristics according to the end points. It was found that on-line sensor values of pH, ORP, and DO were somehow related with the dynamic behaviors of nutrient concentrations in IMT–A2O. The algorithm acts in the reaction phases of the IMT–A2O cycle using ORP and pH break points of tank one to distinguish the end of denitrification and the beginning of phosphorus release, pH break point of tank two to control the end of denitrification and beginning of phosphorus release and a sudden increase in DO pattern, pH break point and ORP to control phosphorus uptake and the end of the nitrification process. Although the fluctuations in raw wastewater concentration are extreme; an influent with a low C/N ratio is deficient in organic carbon, and a low carbon source level can limit the overall biological denitrification process, the average removal efficiencies achieved for COD, ammonia–nitrogen, total nitrogen and total phosphorus were not less than 76.11%, 87.78%, 76.45% and 83.75%, respectively, using the integrated real-time control strategy. The integrated IMT–A2O exhibited a better performance in nutrient removal than the

  17. Comparison of Simultaneous Nitrification and Denitrification for Three Different Reactors

    Directory of Open Access Journals (Sweden)

    W. Khanitchaidecha

    2015-01-01

    Full Text Available Discharge of high NH4-N containing wastewater into water bodies has become a critical and serious issue due to its negative impact on water and environmental quality. In this research, the performance of three different reactors was assessed and compared with regard to the removal of NH4-N from wastewater. The highest nitrogen removal efficiency of 98.3% was found when the entrapped sludge reactor (ESR, in which the sludge was entrapped in polyethylene glycol polymer, was used. Under intermittent aeration, nitrification and denitrification occurred simultaneously in the aerobic and anaerobic periods. Moreover, internal carbon was consumed efficiently for denitrification. On the other hand, internal carbon consumption was not found to occur in the suspended sludge reactor (SSR and the mixed sludge reactor (MSR and this resulted in nitrogen removal efficiencies of SSR and MSR being 64.7 and 45.1%, respectively. Nitrification and denitrification were the main nitrogen removal processes in the aerobic and anaerobic periods, respectively. However, due to the absence of sufficient organic carbon, denitrification was uncompleted resulting in high NO3-N contents in the effluent.

  18. Nitrogen removal and electricity production at a double-chamber microbial fuel cell with cathode nitrite denitrification.

    Science.gov (United States)

    Yu, Yangyang; Zhao, Jianqiang; Wang, Sha; Zhao, Huimin; Ding, Xiaoqian; Gao, Kun

    2017-12-01

    Double-chamber microbial fuel cell was applied to investigate the performance of the electricity production and nitrite denitrification through feeding nitrite into the cathode. Factors influencing denitrification performance and power production, such as external resistance, influent nitrite concentration and Nitrite Oxygen Bacteria inhibitors, were studied. The results show that when the concentration of nitrite nitrogen and external resistance were 100 mg L -1 and 10 Ω, respectively, the nitrite denitrification reached the best state. The NaN 3 can inhibit nitrite oxidation effectively; meanwhile, the nitrite denitrification with N 2 O as the final products was largely improved. The [Formula: see text] was reduced to [Formula: see text], causing the cathode denitrification coulombic efficiency to exceed 100%. In chemoautotrophic bio-nitrification, microorganisms may utilize H 2 O to oxidize nitrite under anaerobic conditions. Proteobacteria might play a major role in the process of denitrification in MFC.

  19. Molecular Approaches to Studying Denitrification

    Science.gov (United States)

    Voytek, M. A.

    2001-05-01

    Denitrification is carried out by a diverse array of microbes, mainly as an alternative mode of respiration that allows the organisms to respire using oxidized N compounds instead of oxygen. A common approach in biogeochemistry to the study of the regulation of denitrification is to assess activity by mass balance of substrates and products or direct rate measurements and has intrinsically assumed resource regulation of denitrification. Reported rates can vary significantly even among ecosystems characterized by similar environmental conditions, thus indicating that direct control by abiotic factors often is not sufficient to predict denitrification rates accurately in natural environments. Alternatively, a microbiological approach would proceed with the identification of the organisms responsible and an evaluation of the effect of environmental factors on the biochemical pathways involved. Traditional studies have relied on culturing techniques, such as most probable number enrichments, and have failed to assess the role of the predominately uncultivable members of the microbial community. A combination of biogeochemical measurements and the assessment of the microbial community is necessary and becoming increasingly possible with the development and application of molecular techniques. In order to understand how the composition and physiological behavior of the microbial community affects denitrification rates, we use a suite of molecular techniques developed for phylogenetic and metabolic characterization of denitrifying communities. Molecular tools available for quantifying denitrifying bacteria and assessing their diversity and activity are summarized. Their application is illustrated with examples from marine and freshwater environments. Emerging techniques and their application to ground water studies will be discussed.

  20. Denitrification activity in mangrove sediments varies with associated vegetation

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; Dutta, P.; Gonsalves, M.J.B.D.; Bonin, P.C.; LokaBharathi, P.A.

    . Eng.: 95; 2016; 671-681 Denitrification activity in mangrove sediments varies with associated vegetation Sheryl Oliveira Fernandes a, #, Pinky Dutta b, Maria-Judith Gonsalves a, Patricia C. Bonin c, P. A. LokaBharathi a, *  a Biological... in tropical and subtropical regions of the world (Giri et al., 2011). They provide a range of ecosystem services like soil formation, wood production, fish spawning grounds, carbon (C) storage and nutrient cycling (Murdiyarso et al., 2015). However, over...

  1. Exposure Time Distributions reveal Denitrification Rates along Groundwater Flow Path of an Agricultural Unconfined Aquifer

    Science.gov (United States)

    Kolbe, T.; Abbott, B. W.; Thomas, Z.; Labasque, T.; Aquilina, L.; Laverman, A.; Babey, T.; Marçais, J.; Fleckenstein, J. H.; Peiffer, S.; De Dreuzy, J. R.; Pinay, G.

    2016-12-01

    Groundwater contamination by nitrate is nearly ubiquitous in agricultural regions. Nitrate is highly mobile in groundwater and though it can be denitrified in the aquifer (reduced to inert N2 gas), this process requires the simultaneous occurrence of anoxia, an electron donor (e.g. organic carbon, pyrite), nitrate, and microorganisms capable of denitrification. In addition to this the ratio of the time groundwater spent in a denitrifying environment (exposure time) to the characteristic denitrification reaction time plays an important role, because denitrification can only occur if the exposure time is longer than the characteristic reaction time. Despite a long history of field studies and numerical models, it remains exceedingly difficult to measure or model exposure times in the subsurface at the catchment scale. To approach this problem, we developed a unified modelling approach combining measured environmental proxies with an exposure time based reactive transport model. We measured groundwater age, nitrogen and sulfur isotopes, and water chemistry from agricultural wells in an unconfined aquifer in Brittany, France, to quantify changes in nitrate concentration due to dilution and denitrification. Field data showed large differences in nitrate concentrations among wells, associated with differences in the exposure time distributions. By constraining a catchment-scale characteristic reaction time for denitrification with water chemistry proxies and exposure times, we were able to assess rates of denitrification along groundwater flow paths. This unified modeling approach is transferable to other catchments and could be further used to investigate how catchment structure and flow dynamics interact with biogeochemical processes such as denitrification.

  2. [Denitrification study of Elodea nuttallii-nitrogen cycling bacteria restoration in Meiliang Bay, Taihu Lake].

    Science.gov (United States)

    Zhao, Lin; Li, Zheng-Kui; Zhou, Tao; Wu, Ning-Mei; Ye, Zhong-Xiang; Liu, Dan-Dan

    2013-08-01

    Undisturbed sediment cores were collected from Meiliang Bay, Taihu Lake, and the integrated Elodea nuttallii-nitrogen cycling bacteria technology was applied as a restoration method. The effects of the Elodea nuttallii-nitrogen cycling bacteria technology on sediment denitrification was observed by isotope pairing technique. The highest denitrification rate of 104.64 micromol x (m2 x h)(-1) was achieved in sediments with Elodea nuttallii-nitrogen cycling bacteria assemblage. The abundance of nirS, nirK and nosZ genes involved in denitrification processes in the sediments (within 2 cm below the water-sediment interface) were measured by real-time quantitative PCR (RT-qPCR). The abundance of nirS and nosZ genes in the sediments with restoration treatments was increased, which was more than one order of magnitudes higher than that in bare sediments. The results indicated that the presence of macrophyte and nitrogen cycling bacteria could increase benthic nitrogen removal by facilitating coupled nitrification-denitrification and uncoupled nitrification-denitrification.

  3. Denitrification as an adaptive trait in soil and groundwater bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Bergwall, C

    1997-09-01

    The focus of this thesis is on selection and adaptation processes in bacteria with emphasis on denitrifying bacteria in groundwater. Other nitrogen transformation processes such as dissimilatory nitrate reduction to ammonium (nitrate ammonification) and nitrification of forest soil bacteria are briefly discussed. Microcosms with sterile sediment and groundwater were inoculated with single denitrifying strains isolated from three groundwater aquifers, two of which are agricultural aquifers (in situ NO{sub 3}{sup -}-N was 24.1 and 35.2 mg1{sup -1}) and the third which is a pristine lake water infiltration aquifer (in situ NO{sub 3}{sup -}-N was 6.3 mg1{sup -1}). The average denitrification activity for strains from the nitrate contaminated sites were twice as high as the activity of the strains from the pristine site. Denitrification were carbon limited and glucose amendment increased the denitrification activity about a 2-fold for all strains. The strain specific differences in denitrification rates increased to a 2.5-fold after carbon addition indicating that the differences in reduction rates cannot be explained by different carbon utilisation rates but rather reflect innate differences in the reductases of the strains. A preliminary identification of the molecular target for adaptation was performed with artificial electron donors and electron acceptors for all enzymatic steps in the denitrification pathway. Nitrous oxide reductase activity was significantly higher in denitrifiers from the nitrate contaminated sites. This suggests that nos genes may be the molecular target, possibly by mutation or gene duplication for adaptation to high nitrate concentrations. Two anaerobic denitrifiers from each of the contaminated sites were capable of aerobic denitrification indicating that high nitrate concentrations may select for strains that denitrifies in the presence of both oxygen and nitrate. Microcosm experiments with fertilized coniferous forest soil showed that the

  4. Rapid Start-up and Loading of an Attached Growth, Simultaneous Nitrification/Denitrification Membrane Aerated Bioreactor

    Science.gov (United States)

    Meyer, Caitlin E.; Pensinger, Stuart; Pickering, Karen D.; Barta, Daniel; Shull, Sarah A.; Vega, Letticia M.; Christenson, Dylan; Jackson, W. Andrew

    2015-01-01

    Membrane aerated bioreactors (MABR) are attached-growth biological systems used for simultaneous nitrification and denitrification to reclaim water from waste. This design is an innovative approach to common terrestrial wastewater treatments for nitrogen and carbon removal and implementing a biologically-based water treatment system for long-duration human exploration is an attractive, low energy alternative to physiochemical processes. Two obstacles to implementing such a system are (1) the "start-up" duration from inoculation to steady-state operations and (2) the amount of surface area needed for the biological activity to occur. The Advanced Water Recovery Systems (AWRS) team at JSC explored these two issues through two tests; a rapid inoculation study and a wastewater loading study. Results from these tests demonstrate that the duration from inoculation to steady state can be reduced to under two weeks, and that despite low ammonium removal rates, the MABRs are oversized.

  5. Rapid Startup and Loading of an Attached Growth, Simultaneous Nitrification/Denitrification Membrane Aerated Bioreactor

    Science.gov (United States)

    Meyer, Caitlin; Vega, Leticia

    2014-01-01

    The Membrane Aerated Bioreactor (MABR) is an attached-growth biological system for simultaneous nitrification and denitrification. This design is an innovative approach to common terrestrial wastewater treatments for nitrogen and carbon removal. Implementing a biologically-based water treatment system for long-duration human exploration is an attractive, low energy alternative to physiochemical processes. Two obstacles to implementing such a system are (1) the "start-up" duration from inoculation to steady-state operations and (2) the amount of surface area needed for the biological activity to occur. The Advanced Water Recovery Systems (AWRS) team at JSC explored these two issues through two tests; a rapid inoculation study and a wastewater loading study. Results from these tests demonstrate that the duration from inoculation to steady state can be reduced to two weeks and that the surface area to volume ratio baseline used in the Alternative Water Processor (AWP) test was higher than what was needed to remove the organic carbon and ammonium from the system.

  6. Nitrous oxide emissions and denitrification rates: A blueprint for smart management and remediation of agricultural landscapes.

    Science.gov (United States)

    Tomasek, A.; Hondzo, M.; Kozarek, J. L.

    2015-12-01

    Anthropogenic activities have greatly altered the global nitrogen cycle, especially in the agriculturally dominated Midwest, with severe consequences on human and aquatic health. Complete microbial denitrification can be viewed as a nitrogen sink, converting soluble nitrate into inert nitrogen gas. This research aims to quantify and correlate the driving parameters in microbial denitrification and explore the relationship to the abundance of denitrifying genes and the microbial communities at these sites. Denitrifying genes for each step in the denitrification process have been quantified. Data from a field site in Southern Minnesota has been collected throughout the season for two years enabling investigation into the temporal variability of denitrification. Data was collected at two cross-sections across the channel to determine the effect of bank location and moisture content on denitrification. Data were collected in an experimental basin in the summer of 2015 to determine the effect of flooding and benthic organic matter content and quality on microbial denitrification and nitrous oxide production. Four sediment types were investigated in three different flood regimes. After each raising or lowering of the water level, soil cores were taken to determine soil characteristics, the potential denitrification using the denitrification enzyme activity method, nitrous oxide production using a static core method, and the denitrifying gene abundance. Chambers were also deployed over each soil amendment in each flood regime to determine the nitrous oxide production over time. Results from these studies will convey a more complete explanation of denitrification and nitrous oxide production under varying environmental conditions. By determining the driving parameters for microbial denitrification, denitrification hot spots and hot moments can be created and enhanced. One potential consequence of increased denitrification is the possibility of incomplete denitrification

  7. Impact of direct greenhouse gas emissions on the carbon footprint of water reclamation processes employing nitrification-denitrification.

    Science.gov (United States)

    Schneider, Andrew G; Townsend-Small, Amy; Rosso, Diego

    2015-02-01

    Water reclamation has the potential to reduce water supply demands from aquifers and more energy-intensive water production methods (e.g., seawater desalination). However, water reclamation via biological nitrification-denitrification is also associated with the direct emission of the greenhouse gases (GHGs) CO₂, N₂O, and CH₄. We quantified these direct emissions from the nitrification-denitrification reactors of a water reclamation plant in Southern California, and measured the (14)C content of the CO₂ to distinguish between short- and long-lived carbon. The total emissions were 1.5 (±0.2) g-fossil CO₂ m(-3) of wastewater treated, 0.5 (±0.1) g-CO₂-eq of CH₄ m(-3), and 1.8 (±0.5) g-CO₂-eq of N₂O m(-3), for a total of 3.9 (±0.5) g-CO₂-eqm(-3). This demonstrated that water reclamation can be a source of GHGs from long lived carbon, and thus a candidate for GHG reduction credit. From the (14)C measurements, we found that between 11.4% and 15.1% of the CO₂ directly emitted was derived from fossil sources, which challenges past assumptions that the direct CO₂ emissions from water reclamation contain only modern carbon. A comparison of our direct emission measurements with estimates of indirect emissions from several water production methods, however, showed that the direct emissions from water reclamation constitute only a small fraction of the plant's total GHG footprint. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Denitrification in the Mississippi River network controlled by flow through river bedforms

    Science.gov (United States)

    Gomez-Velez, Jesus D.; Harvey, Judson W.; Cardenas, M. Bayani; Kiel, Brian

    2015-01-01

    Increasing nitrogen concentrations in the world’s major rivers have led to over-fertilization of sensitive downstream waters1, 2, 3, 4. Flow through channel bed and bank sediments acts to remove riverine nitrogen through microbe-mediated denitrification reactions5, 6, 7, 8, 9, 10. However, little is understood about where in the channel network this biophysical process is most efficient, why certain channels are more effective nitrogen reactors, and how management practices can enhance the removal of nitrogen in regions where water circulates through sediment and mixes with groundwater - hyporheic zones8, 11, 12. Here we present numerical simulations of hyporheic flow and denitrification throughout the Mississippi River network using a hydrogeomorphic model. We find that vertical exchange with sediments beneath the riverbed in hyporheic zones, driven by submerged bedforms, has denitrification potential that far exceeds lateral hyporheic exchange with sediments alongside river channels, driven by river bars and meandering banks. We propose that geomorphic differences along river corridors can explain why denitrification efficiency varies between basins in the Mississippi River network. Our findings suggest that promoting the development of permeable bedforms at the streambed - and thus vertical hyporheic exchange - would be more effective at enhancing river denitrification in large river basins than promoting lateral exchange through induced channel meandering. 

  9. Effects of specific inhibitors on anammox and denitrification in marine sediments.

    Science.gov (United States)

    Jensen, Marlene Mark; Thamdrup, Bo; Dalsgaard, Tage

    2007-05-01

    The effects of three metabolic inhibitors (acetylene, methanol, and allylthiourea [ATU]) on the pathways of N2 production were investigated by using short anoxic incubations of marine sediment with a 15N isotope technique. Acetylene inhibited ammonium oxidation through the anammox pathway as the oxidation rate decreased exponentially with increasing acetylene concentration; the rate decay constant was 0.10+/-0.02 microM-1, and there was 95% inhibition at approximately 30 microM. Nitrous oxide reduction, the final step of denitrification, was not sensitive to acetylene concentrations below 10 microM. However, nitrous oxide reduction was inhibited by higher concentrations, and the sensitivity was approximately one-half the sensitivity of anammox (decay constant, 0.049+/-0.004 microM-1; 95% inhibition at approximately 70 microM). Methanol specifically inhibited anammox with a decay constant of 0.79+/-0.12 mM-1, and thus 3 to 4 mM methanol was required for nearly complete inhibition. This level of methanol stimulated denitrification by approximately 50%. ATU did not have marked effects on the rates of anammox and denitrification. The profile of inhibitor effects on anammox agreed with the results of studies of the process in wastewater bioreactors, which confirmed the similarity between the anammox bacteria in bioreactors and natural environments. Acetylene and methanol can be used to separate anammox and denitrification, but the effects of these compounds on nitrification limits their use in studies of these processes in systems where nitrification is an important source of nitrate. The observed differential effects of acetylene and methanol on anammox and denitrification support our current understanding of the two main pathways of N2 production in marine sediments and the use of 15N isotope methods for their quantification.

  10. Small scale denitrification variability in riparian zones: Results from a high-resolution dataset

    Science.gov (United States)

    Gassen, Niklas; Knöller, Kay; Musolff, Andreas; Popp, Felix; Lüders, Tillmann; Stumpp, Christine

    2017-04-01

    Riparian zones are important compartments at the interface between groundwater and surface water where biogeochemical processes like denitrification are often enhanced. Nitrate loads of either groundwater entering a stream through the riparian zone or streamwater infiltrating into the riparian zone can be substantially reduced. These processes are spatially and temporally highly variable, making it difficult to capture solute variabilities, estimate realistic turnover rates and thus to quantify integral mass removal. A crucial step towards a more detailed characterization is to monitor solutes on a scale which adequately resemble the highly heterogeneous distribution and on a scale where processes occur. We measured biogeochemical parameters in a spatial high resolution within a riparian corridor of a German lowland river system over the course of one year. Samples were taken from three newly developed high-resolution multi-level wells with a maximum vertical resolution of 5 cm and analyzed for major ions, DOC and N-O isotopes. Sediment derived during installation of the wells was analyzed for specific denitrifying enzymes. Results showed a distinct depth zonation of hydrochemistry within the shallow alluvial aquifer, with a 1 m thick zone just below the water table with lower nitrate concentrations and EC values similar to the nearby river. Conservative parameters were consistent inbetween the three wells, but nitrate was highly variable. In addition, spots with low nitrate concentrations showed isotopic and microbial evidence for higher denitrification activities. The depth zonation was observed throughout the year, with stronger temporal variations of nitrate concentrations just below the water table compared to deeper layers. Nitrate isotopes showed a clear seasonal trend of denitrification activities (high in summer, low in winter). Our dataset gives new insight into river-groundwater exchange processes and shows the highly heterogeneous distribution of

  11. Study of a combined heterotrophic and sulfur autotrophic denitrification technology for removal of nitrate in water

    International Nuclear Information System (INIS)

    Liu Huijuan; Jiang Wei; Wan Dongjin; Qu Jiuhui

    2009-01-01

    A combined two-step process of heterotrophic denitrification in a fluidized reactor and sulfur autotrophic denitrification processes (CHSAD) was developed for the removal of nitrate in drinking water. In this process, the advantage of high efficiency of heterotrophic denitrification with non-excessive methanol and the advantage of non-pollution of sulfur autotriphic denitrification were integrated in this CHSAD process. And, this CHSAD process had the capacity of pH balance and could control the concentration of SO 4 2- in effluent by adjusting the operation condition. When the influent nitrate was 30 mg NO 3 - -N/L, the reactor could be operated efficiently at the hydraulic retention time (HRT) ranging from 20 to 40 min with C:N ratio (mg CH 3 OH:mg NO 3 - -N) of 2.0 (methanol as carbon source). The nitrate removal was nearly 100% and there was no accumulated nitrite or residual methanol in the effluent. The effluent pH was about 7.5 and the sulfate concentration was lower than 130 mg/L. The maximum volume-loading rate of the reactor was 2.16 kg NO 3 - -N/(m 3 d). The biomass and scanning electron microscopy graphs of biofilm were also analyzed.

  12. Oxygen at nanomolar levels reversibly suppresses process rates and gene expression in anammox and denitrification in the oxygen minimum zone off Northern Chil

    DEFF Research Database (Denmark)

    Dalsgaard, Tage; Stewart, Frank J.; Thamdrup, Bo

    2014-01-01

    at nanomolar levels affects anammox and denitrification rates and the transcription of nitrogen cycle genes in the anoxic OMZ off Chile. Rates of anammox and denitrification were reversibly suppressed, most likely at the enzyme level. Fiftypercent inhibition of N2 and N2O production by denitrification...

  13. Using rates of oxygen and nitrate reduction to map the subsurface distribution of groundwater denitrification

    Science.gov (United States)

    Kolbe, T.; De Dreuzy, J. R.; Abbott, B. W.; Aquilina, L.; Babey, T.; Green, C. T.; Fleckenstein, J. H.; Labasque, T.; Laverman, A.; Marçais, J.; Peiffer, S.; Thomas, Z.; Pinay, G.

    2017-12-01

    Widespread fertilizer application over the last 70 years has caused serious ecological and socioeconomic problems in aquatic and estuarine ecosystems. When surplus nitrogen leaches as nitrate (a major groundwater pollutant) to the aquifer, complex flow dynamics and naturally occurring degradation processes control its transport. Under the conditions of depleted oxygen and abundant electron donors, microorganisms reduce NO3- to N2 (denitrification). Denitrification rates vary over orders of magnitude among sites within the same aquifer, complicating estimation of denitrification capacity at the catchment scale. Because it is impractical or impossible to access the subsurface to directly quantify denitrification rates, reactivity is often assumed to occur continuous along flowlines, potentially resulting in substantial over- or underestimation of denitrification. Here we investigated denitrification in an unconfined crystalline aquifer in western France using a combination of common tracers (chlorofluorocarbons, O2, NO3-, and N2) measured in 16 wells to inform a time-based modeling approach. We found that spatially variable denitrification rates arise from the intersection of nitrate rich water with reactive zones defined by the abundance of electron donors (primarily pyrite). Furthermore, based on observed reaction rates of the sequential reduction of oxygen and nitrate, we present a general framework to estimate the location and intensity of the reactive zone in aquifers. Accounting for the vertical distribution of reaction rates results in large differences in estimations of net denitrification rates that assume homogeneous reactivity. This new framework provides a tractable approach for quantifying catchment and regional groundwater denitrification rates that could be used to improve estimation of groundwater resilience to nitrate pollution and develop more realistic management strategies.

  14. Applicability of industrial wastewater as carbon source for denitrification of a sludge dewatering liquor.

    Science.gov (United States)

    Chen, Jiazhong; Lee, Yoomin; Oleszkiewicz, Jan A

    2013-01-01

    The applicability of four industrial waste streams from potato processing, canola processing and oil refining, biodiesel production (glycerol), and glycol as substitutes to methanol and ethanol in denitrification of anaerobically digested sludge dewatering liquor (centrate) was evaluated in bench-scale sequencing batch reactors. It was found that glycerol was the best substitute with the specific denitrification rate (SDNR) of 13 mg NO3-N/(g VSS x h) followed by potato processing wastewater at 12mg NO3-N/(g VSS x h). Both substrates produced faster SDNR than methanol's 10mg NO3-N/(g VSS x h); however, they were inferior to ethanol's 17 mg NO3-N/(g VSS x h). Glycol had SDNR of 8 mg NO3-N/(g VSS x h) and demonstrated a very fast acclimation rate, i.e. the response in increased denitrification rate was visible in three days following glycol addition. Canola processing and oil refining wastewater was considered an inappropriate carbon source due to a low SDNR of 5 mg NO3-N/(g VSS x h) and apparent inhibitory effect on nitrification.

  15. Biological processes for environmental control of effluent streams in the nuclear fuel cycle

    International Nuclear Information System (INIS)

    Shumate, S.E. II; Hancher, C.W.; Strandberg, G.W.; Scott, C.D.

    1978-01-01

    Nitrates and radioactive heavy metals need to be removed from aqueous effluent streams in the fuel cycle. Biological methods are being developed for reducing nitrate or nitrite to N 2 gas and for decreasing dissolved metal concentration to less than 1 g/m 3 . Fluidized-bed denitrification bioreactors are being tested. Removal of uranium from solution by Saccharomyces cerevisiae and Pseudomonas aeruginosa was studied

  16. Use of microbial analysis to evaluate denitrification in the karstic aquifer of Okinawa, Japan

    Science.gov (United States)

    Yasumoto, J.

    2014-12-01

    Denitrification, a microbial process in the nitrogen cycle, is a facultative respiratory pathway in which nitrate (NO3-), nitrite (NO2-), nitric oxide (NO), and nitrous oxide (N2O), successively, are reduced to nitrogen gas (N2). This study explores the use of microbial analysis to evaluate the processes involved in nitrate attenuation in groundwater. Polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) is used to identify denitrifiers based only on their 16SrRNA gene sequences, and Real-Time PCR analysis is used to quantify nitrite reducing genes (nirK and nirS), this suggest that a new methods for detecting denitrification activity by comparing the gene dosage that has been detected by RT-PCR and the value of the δ15NNO3- and δ18ONO3-. This study focuses on a zone of significant NO3- attenuation occurring at underground dam catchment area in the karstic Ryukyu limestone aquifer, which is located southern part of Okinawa, Japan. As a result of microbial analysis, the bacteria were detected at all observation points which have been reported to have denitrification ability. And it has been confirmed that the bacteria has a gene nirS which is related to denitrification. In addition, many bacteria related to denitrification have been extracted from suspended solids more than from groundwater in the aquifer. And, the correlation was high between nirK /nirS gene dosage that has been detected by RT-PCR and the value of the δ15N and δ18O; therefore, this study demonstrates the effectiveness of using Real-Time PCR analysis for providing insights into the processes affecting nitrate attenuation in ground water.

  17. High-Resolution Denitrification Kinetics in Pasture Soils Link N2O Emissions to pH, and Denitrification to C Mineralization.

    Directory of Open Access Journals (Sweden)

    Md Sainur Samad

    Full Text Available Denitrification in pasture soils is mediated by microbial and physicochemical processes leading to nitrogen loss through the emission of N2O and N2. It is known that N2O reduction to N2 is impaired by low soil pH yet controversy remains as inconsistent use of soil pH measurement methods by researchers, and differences in analytical methods between studies, undermine direct comparison of results. In addition, the link between denitrification and N2O emissions in response to carbon (C mineralization and pH in different pasture soils is still not well described. We hypothesized that potential denitrification rate and aerobic respiration rate would be positively associated with soils. This relationship was predicted to be more robust when a high resolution analysis is performed as opposed to a single time point comparison. We tested this by characterizing 13 different temperate pasture soils from northern and southern hemispheres sites (Ireland and New Zealand using a fully automated-high-resolution GC detection system that allowed us to detect a wide range of gas emissions simultaneously. We also compared the impact of using different extractants for determining pH on our conclusions. In all pH measurements, soil pH was strongly and negatively associated with both N2O production index (IN2O and N2O/(N2O+N2 product ratio. Furthermore, emission kinetics across all soils revealed that the denitrification rates under anoxic conditions (NO+N2O+N2 μmol N/h/vial were significantly associated with C mineralization (CO2 μmol/h/vial measured both under oxic (r2 = 0.62, p = 0.0015 and anoxic (r2 = 0.89, p<0.0001 conditions.

  18. GeoChip-based analysis of the microbial community functional structures in simultaneous desulfurization and denitrification process.

    Science.gov (United States)

    Yu, Hao; Chen, Chuan; Ma, Jincai; Liu, Wenzong; Zhou, Jizhong; Lee, Duu-Jong; Ren, Nanqi; Wang, Aijie

    2014-07-01

    The elemental sulfur (S°) recovery was evaluated in the presence of nitrate in two development models of simultaneous desulfurization and denitrification (SDD) process. At the loading rates of 0.9 kg S/(m³·day) for sulfide and 0.4 kg N/(m³·day) for nitrate, S° conversion rate was 91.1% in denitrifying sulfide removal (DSR) model which was higher than in integrated simultaneous desulfurization and denitrification (ISDD) model (25.6%). A comprehensive analysis of functional diversity, structure and metabolic potential of microbial communities was examined in two models by using functional gene array (GeoChip 2.0). GeoChip data indicated that diversity indices, community structure, and abundance of functional genes were distinct between two models. Diversity indices (Simpson's diversity index (1/D) and Shannon-Weaver index (H')) of all detected genes showed that with elevated influent loading rate, the functional diversity decreased in ISDD model but increased in DSR model. In contrast to ISDD model, the overall abundance of dsr genes was lower in DSR model, while some functional genes targeting from nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), such as Thiobacillus denitrificans, Sulfurimonas denitrificans, and Paracoccus pantotrophus were more abundant in DSR model which were highly associated with the change of S(0) conversion rate obtained in two models. The results obtained in this study provide additional insights into the microbial metabolic mechanisms involved in ISDD and DSR models, which in turn will improve the overall performance of SDD process. Copyright © 2014. Published by Elsevier B.V.

  19. Particulate Pyrite Autotrophic Denitrification (PPAD) for Remediation of Nitrate-contaminated Groundwater

    Science.gov (United States)

    Tong, S.; Rodriguez-Gonzalez, L. C.; Henderson, M.; Feng, C.; Ergas, S. J.

    2015-12-01

    The rapid movement of human civilization towards urbanization, industrialization, and increased agricultural activities has introduced a large amount of nitrate into groundwater. Nitrate is a toxic substance discharged from groundwater to rivers and leads to decreased dissolved oxygen and eutrophication. For this experiment, an electron donor is needed to convert nitrate into non-toxic nitrogen gas. Pyrite is one of the most abundant minerals in the earth's crust making it an ideal candidate as an electron donor. The overall goal of this research was to investigate the potential for pyrite to be utilized as an electron donor for autotrophic denitrification of nitrate-contaminated groundwater. Batch studies of particulate pyrite autotrophic denitrification (PPAD) of synthetic groundwater (100 mg NO3--N L-1) were set up with varying biomass concentration, pyrite dose, and pyrite particle size. Reactors were seeded with mixed liquor volatile suspended solids (VSS) from a biological nitrogen removal wastewater treatment facility. PPAD using small pyrite particles (exhibited substantial nitrate removal rate, lower sulfate accumulation (5.46 mg SO42-/mg NO3--N) and lower alkalinity consumption (1.70 mg CaCO3/mg NO3--N) when compared to SOD (7.54 mg SO42-/mg NO3--N, 4.57 mg CaCO3/mg NO3--N based on stoichiometric calculation). This research revealed that the PPAD process is a promising technique for nitrate-contaminated groundwater treatment and promoted the utilization of pyrite in the field of environmental remediation.

  20. Denitrification, anammox and fixed nitrogen removal in the water column of a tropical great lake

    Science.gov (United States)

    Darchambeau, François; Roland, Fleur; Crowe, Sean A.; De Brabandere, Loreto; Llirós, Marc; Garcia-Armisen, Tamara; Inceoglu, Ozgul; Michiels, Céline; Servais, Pierre; Morana, Cédric D. T.; Bouillon, Steven; Meysman, Filip; Veuger, Bart; Masilya, Pascal M.; Descy, Jean-Pierre; Borges, Alberto V.

    2013-04-01

    If rates of microbial denitrification in aquatic systems are poorly constrained, it is much more the case for tropical water bodies. Lake Kivu [2.50° S 1.59° S, 29.37° E 28.83° E] is one of the great lakes of the East African Rift. It is an oligotrophic lake characterized by anoxic deep waters rich in dissolved gases (methane and carbon dioxide) and nutrients, and by well oxygenated and nutrient-depleted surface waters. During the seasonally stratified rainy season (October to May), a nitrogenous zone characterized by the accumulation of nitrite (NO2-) and nitrate (NO3-) is often observed in the lower layer of the mixolimnion. It results from nitrification of ammonium released by decaying organic matter. With the seasonal uplift of the oxygen minimum zone, the nitrogenous zone becomes anoxic and might be the most preferential area for fixed nitrogen (N) removal in Lake Kivu. Our work aimed at identifying and quantifying the processes of N losses by denitrification and/or anammox in the nitrogenous zone of the Lake Kivu water column. During 5 sampling campaigns (March 2010, October 2010, June 2011, February 2012 and September 2012), isotopic labelling experiments were used to quantify denitrification and anammox rates along vertical profiles at two pelagic stations of the main lake. Moreover, N2:Ar ratios were estimated during the September 2012 campaign, and 16S rDNA pyrosequencing was used to describe bacterial community composition during the last 2 campaigns. No bacteria related to organisms performing anammox was observed and labelling experiments failed to detect anammox at any locations and any depths. In Lake Kivu, denitrifying bacteria were mainly related to Denitratisoma and Thiobacillus genus. Significant denitrification rates were observed at several occasions, especially under the oxic-anoxic interface in the bottom of the nitracline. The annual average denitrification rate was estimated at ~150 μmoles N m-2 d-1. Denitrification was not the only

  1. Impact of chloride on denitrification potential in roadside wetlands.

    Science.gov (United States)

    Lancaster, Nakita A; Bushey, Joseph T; Tobias, Craig R; Song, Bongkeun; Vadas, Timothy M

    2016-05-01

    Developed landscapes are exposed to changes in hydrology and water chemistry that limit their ability to mitigate detrimental impacts to coastal water bodies, particularly those that result from stormwater runoff. The elevated level of impervious cover increases not only runoff but also contaminant loading of nutrients, metals, and road salt used for deicing to water bodies. Here we investigate the impact that road salt has on denitrification in roadside environments. Sediments were collected from a series of forested and roadside wetlands and acclimated with a range of Cl(-) concentrations from 0 to 5000 mg L(-1) for 96 h. Denitrification rates were measured by the isotope pairing technique using (15)N-NO3(-), while denitrifying community structures were compared using terminal restriction fragment length polymorphism (T-RFLP) of nitrous oxide reductase genes (nosZ). Chloride significantly (p wetlands at a Cl(-) dosage of 2500 or 5000 mg L(-1), but the decrease in denitrification rates was less and not significant for the roadside wetlands historically exposed to elevated concentrations of Cl(-). The difference could not be attributed to other significant changes in conditions, such as DOC concentrations, N species concentrations, or pH levels. Denitrifying communities, as measured by T-RFs of the nosZ gene, in the roadside wetlands with elevated concentration of Cl(-) were distinctly different and more diverse compared to forested wetlands, and also different in roadside wetlands after 96 h exposures to Cl(-). The shifts in denitrifying communities seem to minimize the decrease in denitrification rates in the wetlands previously exposed to Cl. As development results in more Cl(-) use and exposure to a broad range of natural or manmade wetland structures, an understanding of the seasonal effect of Cl on denitrification processes in these systems would aid in design or mitigation of the effects on N removal rates. Copyright © 2016 Elsevier Ltd. All rights

  2. Denitrification controls in urban riparian soils: implications for reducing urban nonpoint source nitrogen pollution.

    Science.gov (United States)

    Li, Yangjie; Chen, Zhenlou; Lou, Huanjie; Wang, Dongqi; Deng, Huanguang; Wang, Chu

    2014-09-01

    The purpose of this research was to thoroughly analyze the influences of environmental factors on denitrification processes in urban riparian soils. Besides, the study was also carried out to identify whether the denitrification processes in urban riparian soils could control nonpoint source nitrogen pollution in urban areas. The denitrification rates (DR) over 1 year were measured using an acetylene inhibition technique during the incubation of intact soil cores from six urban riparian sites, which could be divided into three types according to their vegetation. The soil samples were analyzed to determine the soil organic carbon (SOC), soil total nitrogen (STN), C/N ratio, extractable NO3 (-)-N and NH4 (+)-N, pH value, soil water content (SWC), and the soil nitrification potential to evaluate which of these factors determined the final outcome of denitrification. A nitrate amendment experiment further indicated that the riparian DR was responsive to added nitrate. Although the DRs were very low (0.099 ~ 33.23 ng N2O-N g(-1) h(-1)) due to the small amount of nitrogen moving into the urban riparian zone, the spatial and temporal patterns of denitrification differed significantly. The extractable NO3 (-)-N proved to be the dominant factor influencing the spatial distribution of denitrification, whereas the soil temperature was a determinant of the seasonal DR variation. The six riparian sites could also be divided into two types (a nitrate-abundant and a nitrate-stressed riparian system) according to the soil NO3 (-)-N concentration. The DR in nitrate-abundant riparian systems was significantly higher than that in the nitrate-stressed riparian systems. The DR in riparian zones that were covered with bushes and had adjacent cropland was higher than in grass-covered riparian sites. Furthermore, the riparian DR decreased with soil depth, which was mainly attributed to the concentrated nitrate in surface soils. The DR was not associated with the SOC, STN, C/N ratio, and

  3. A simple model for simultaneous methanogenic-denitrification systems

    DEFF Research Database (Denmark)

    Garibay-Orijel, C.; Ahring, Birgitte Kiær; Rinderknecht-Seijas, N.

    2006-01-01

    We describe a useful and simple model for studies of simultaneous methanogenic-denitrification (M-D) systems. One equation predicts an inverse relationship between the percentage of electron donor channeled into dissimilatory denitrification and the loading ratio X given by grams degradable COD per...

  4. Nitrate denitrification with nitrite or nitrous oxide as intermediate products: Stoichiometry, kinetics and dynamics of stable isotope signatures.

    Science.gov (United States)

    Vavilin, V A; Rytov, S V

    2015-09-01

    A kinetic analysis of nitrate denitrification by a single or two species of denitrifying bacteria with glucose or ethanol as a carbon source and nitrite or nitrous oxide as intermediate products was performed using experimental data published earlier (Menyailo and Hungate, 2006; Vidal-Gavilan et al., 2013). Modified Monod kinetics was used in the dynamic biological model. The special equations were added to the common dynamic biological model to describe how isotopic fractionation between N species changes. In contrast to the generally assumed first-order kinetics, in this paper, the traditional Rayleigh equation describing stable nitrogen and oxygen isotope fractionation in nitrate was derived from the dynamic isotopic equations for any type of kinetics. In accordance with the model, in Vidal-Gavilan's experiments, the maximum specific rate of nitrate reduction was proved to be less for ethanol compared to glucose. Conversely, the maximum specific rate of nitrite reduction was proved to be much less for glucose compared to ethanol. Thus, the intermediate nitrite concentration was negligible for the ethanol experiment, while it was significant for the glucose experiment. In Menyailo's and Hungate's experiments, the low value of maximum specific rate of nitrous oxide reduction gives high intermediate value of nitrous oxide concentration. The model showed that the dynamics of nitrogen and oxygen isotope signatures are responding to the biological dynamics. Two microbial species instead of single denitrifying bacteria are proved to be more adequate to describe the total process of nitrate denitrification to dinitrogen. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Nitrogen removal from sludge digester liquids by nitrification/denitrification or partial nitritation/anammox: environmental and economical considerations.

    Science.gov (United States)

    Fux, C; Siegrist, H

    2004-01-01

    In wastewater treatment plants with anaerobic sludge digestion, 15-20% of the nitrogen load is recirculated to the main stream with the return liquors from dewatering. Separate treatment of this ammonium-rich digester supernatant significantly reduces the nitrogen load of the activated sludge system. Two biological applications are considered for nitrogen elimination: (i) classical autotrophic nitrification/heterotrophic denitrification and (ii) partial nitritation/autotrophic anaerobic ammonium oxidation (anammox). With both applications 85-90% nitrogen removal can be achieved, but there are considerable differences in terms of sustainability and costs. The final gaseous products for heterotrophic denitrification are generally not measured and are assumed to be nitrogen gas (N2). However, significant nitrous oxide (N2O) production can occur at elevated nitrite concentrations in the reactor. Denitrification via nitrite instead of nitrate has been promoted in recent years in order to reduce the oxygen and the organic carbon requirements. Obviously this "achievement" turns out to be rather disadvantageous from an overall environmental point of view. On the other hand no unfavorable intermediates are emitted during anaerobic ammonium oxidation. A cost estimate for both applications demonstrates that partial nitritation/anammox is also more economical than classical nitrification/denitrification. Therefore autotrophic nitrogen elimination should be used in future to treat ammonium-rich sludge liquors.

  6. From the Gut of an Insect to the Global Climate: Denitrification and Nitrous Oxide Production inside Lake Chironomidae

    DEFF Research Database (Denmark)

    Stief, Peter; Nielsen, Lars Peter; Revsbech, Niels Peter

    2006-01-01

    FROM THE GUT OF AN INSECT TO THE GLOBAL CLIMATE: DENITRIFICATION AND NITROUS OXIDE PRODUCTION INSIDE LAKE CHIRONOMIDAE P. Stief, L.P. Nielsen, N.P. Revsbech, A. Schramm Department of Biological Sciences, Microbiology, University of Aarhus, Denmark Denitrifying bacteria in lake sediments drive...

  7. Denitrification in the water column of the central Baltic Sea

    DEFF Research Database (Denmark)

    Dalsgaard, Tage; De Brabandere, Loreto; Hall, Per O. J.

    2013-01-01

    Removal of fixed nitrogen in the water column of the eastern Gotland Basin, central Baltic Sea, was studied during two cruises in September 2008 and August 2010. The water column was stratified with anoxic sulfidic bottom water meeting oxic nitrate containing water at the oxic–anoxic interface......3 or sulfide concentrations were converted to in situ rates using the measured water column concentrations of NO3 and sulfide and the actual measured relations between NO3 and sulfide concentrations and enitrification rates. In situ denitrification ranged from 0.24 to 15.9 nM N2 h1. Assuming...... area. Even with an active denitrification layer of 3–6 m thickness the pelagic denitrification per unit area clearly exceeded sediment denitrification rates elsewhere in the Baltic Sea. When extrapolated to the entire Baltic Proper (BP) denitrification in the water column was in the range of 132...

  8. Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer

    Directory of Open Access Journals (Sweden)

    J. B. Heffernan

    2012-05-01

    Full Text Available Aquifer denitrification is among the most poorly constrained fluxes in global and regional nitrogen budgets. The few direct measurements of denitrification in groundwaters provide limited information about its spatial and temporal variability, particularly at the scale of whole aquifers. Uncertainty in estimates of denitrification may also lead to underestimates of its effect on isotopic signatures of inorganic N, and thereby confound the inference of N source from these data. In this study, our objectives are to quantify the magnitude and variability of denitrification in the Upper Floridan Aquifer (UFA and evaluate its effect on N isotopic signatures at the regional scale. Using dual noble gas tracers (Ne, Ar to generate physical predictions of N2 gas concentrations for 112 observations from 61 UFA springs, we show that excess (i.e. denitrification-derived N2 is highly variable in space and inversely correlated with dissolved oxygen (O2. Negative relationships between O2 and δ15NNO3 across a larger dataset of 113 springs, well-constrained isotopic fractionation coefficients, and strong 15N:18O covariation further support inferences of denitrification in this uniquely organic-matter-poor system. Despite relatively low average rates, denitrification accounted for 32 % of estimated aquifer N inputs across all sampled UFA springs. Back-calculations of source δ15NNO3 based on denitrification progression suggest that isotopically-enriched nitrate (NO3 in many springs of the UFA reflects groundwater denitrification rather than urban- or animal-derived inputs.

  9. Effective Biological Nitrogen Removal Treatment Processes for Domestic Wastewaters with Low C/N Ratios: A Review

    DEFF Research Database (Denmark)

    Sun, Sheng-Peng; Pellicer i Nàcher, Carles; Merkey, Brian

    2010-01-01

    with high efficiency and relative low costs. However, the removal of nitrogen from domestic wastewater with a low carbon/nitrogen (C/N) ratio can often be limited in municipal wastewater plants (WWTPs) because organic carbon is a limiting factor for denitrification. The present work reviews innovative....... They can effectively be used for nitrogen removal from low C/N domestic wastewater without external carbon addition. In addition, conventional and alternative carbon sources for enhanced biological nitrogen removal were also reviewed. We conclude that alternative carbon sources such as wine distillery...... at large scale for nitrogen removal from low C/N domestic wastewater, (2) further method logic are explored to introduce the Anammox pathway into domestic wastewater treatment, and (3) alternative carbon sources are explored and optimized for supporting the denitrification. With these efforts, cost...

  10. Illumina MiSeq sequencing reveals the key microorganisms involved in partial nitritation followed by simultaneous sludge fermentation, denitrification and anammox process.

    Science.gov (United States)

    Wang, Bo; Peng, Yongzhen; Guo, Yuanyuan; Zhao, Mengyue; Wang, Shuying

    2016-05-01

    A combined process including a partial nitritation SBR (PN-SBR) followed by a simultaneous sludge fermentation, denitrification and anammox reactor (SFDA) was established to treat low C/N domestic wastewater in this study. An average nitrite accumulation rate of 97.8% and total nitrogen of 9.4mg/L in the effluent was achieved during 140days' operation. The underlying mechanisms were investigated by using Illumina MiSeq sequencing to analyze the microbial community structures in the PN-SBR and SFDA. Results showed that the predominant bacterial phylum was Proteobacteria in the external waste activated sludge (WAS, added to the SFDA) and SFDA while Bacteroidetes in the PN-SBR. Further study indicated that in the PN-SBR, the dominant nitrobacteria, Nitrosomonas genus, facilitated nitritation and little nitrate was generated in the PN-SBR effluent. In the SFDA, the co-existence of functional microorganisms Thauera, Candidatus Anammoximicrobium and Pseudomonas were found to contribute to simultaneous sludge fermentation, denitrification and anammox. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Denitrification in Soil Aggregate Analogues-Effect of Aggregate Size and Oxygen Diffusion

    Directory of Open Access Journals (Sweden)

    Steffen Schlüter

    2018-04-01

    Full Text Available Soil-borne nitrous oxide (N2O emissions have a high spatial and temporal variability which is commonly attributed to the occurrence of hotspots and hot moments for microbial activity in aggregated soil. Yet there is only limited information about the biophysical processes that regulate the production and consumption of N2O on microscopic scales in undisturbed soil. In this study, we introduce an experimental framework relying on simplified porous media that circumvents some of the complexities occuring in natural soils while fully accounting for physical constraints believed to control microbial activity in general and denitrification in particular. We used this framework to explore the impact of aggregate size and external oxygen concentration on the kinetics of O2 consumption, as well as CO2 and N2O production. Model aggregates of different sizes (3.5 vs. 7 mm diameter composed of porous, sintered glass were saturated with a defined growth medium containing roughly 109 cells ml−1 of the facultative anaerobic, nosZ-deficient denitrifier Agrobacterium tumefaciens with N2O as final denitrification product and incubated at five different oxygen levels (0–13 vol-%. We demonstrate that the onset of denitrification depends on the amount of external oxygen and the size of aggregates. Smaller aggregates were better supplied with oxygen due to a larger surface-to-volume ratio, which resulted in faster growth and an earlier onset of denitrification. In larger aggregates, the onset of denitrification was more gradual, but with comparably higher N2O production rates once the anoxic aggregate centers were fully developed. The normalized electron flow from the reduced carbon substrate to N-oxyanions (edenit-/etotal- ratio could be solely described as a function of initial oxygen concentration in the headspace with a simple, hyperbolic model, for which the two empirical parameters changed with aggregate size in a consistent way. These findings confirm the

  12. Simultaneous denitrification and anaerobic digestion in GRAnular Bed Baffled Reactor (GRABBR)

    International Nuclear Information System (INIS)

    Baloch, M.I.; Akunna, J.C.

    2002-01-01

    This study elucidates the characteristics of compartmentalised anaerobic system seeded with UASB granules, called GRAanular Bed Baffled Reactor (GRABBR), for combined denitrification and anaerobic digestion processes. The reactor was used for the treatment of glucose enriched synthetic wastewater with various nitrate concentrations. The study was carried out with a 10 litre working volume GRABBR divided into 5 equal compartments operating at organic loading rate (OLR) of 20 kg COD/m 3 .d with a hydraulic retention time (HRT) of 6 hours. At these conditions, phase separation (between acidogenesis and methanogenesis) was created in the system and then the effect of varying nitrate concentrations (50-200 mg/l NO 3 -N) in the acidogenic zone (i.e. first compartment) was studied. Due to its unique compartmentalised design, denitrification was the major pathway for nitrate reduction with no noticeable dissimilatory nitrate reduction to ammonia (DNRA). More than 84% of all added nitrates were removed in the acidogenic zone, showing that acidogens possess high denitrifying capabilities. The denitrification rate increased with increase in nitrate concentration, with maximum value estimated as 175 mg NO 3 -N/l.h at influent nitrate concentration of 200 mg/l NO 3 -N in the acidogenic zone. Although nitrate addition resulted in lower methane production, COD removal efficiencies improved by up to 8% when compared with the reactor performance before nitrate addition. Furthermore, the alkalinity produced during denitrification improved the stability of the system by controlling the decrease in pH resulting from acidogenesis. The system encouraged simultaneous denitrification and anaerobic digestion in a single unit by accommodating denitrifiers in the early compartments and allowing methanogenesis to flourish in the downstream compartments of the system, thus minimising inhibition to methane producing bacteria by nitrates. (author)

  13. Denitrification in the karstic Floridan Aquifer

    Science.gov (United States)

    Fork, M.; Albertin, A. R.; Heffernan, J. B.; Katz, B. G.; Cohen, M. J.

    2010-12-01

    Nitrate concentrations in the karstic Floridan Aquifer have increased dramatically over the past 50 years, owing to agricultural intensification and urbanization. Due to low concentrations of organic matter and moderately oxic conditions in the Floridan Aquifer, groundwater denitrification has been assumed to be negligible. In this study, we evaluate that assumption using both existing and new data describing dissolved gases (Ne, N2, O2, Ar) and NO3- concentration and isotopic composition (δ18O- and δ15N-NO3) in the aquifer’s artesian springs. For new data, we collected samples from 33 spring vents representing a gradient of both DO and NO3- concentrations in northern Florida and used Membrane Inlet Mass Spectrometry (MIMS) to directly measure dissolved N2 and Ar. We modeled the physical processes (recharge temperature, dissolution of excess air) driving super-saturation of N2 gas using Ne and Ar where data describing Ne were available. Ar concentrations were correlated closely with recharge temperature, which ranged from 15.7 - 22.2°C, while Ne was closely correlated with excess air, which ranged from 1.05 to 2.66 mg L-1 and averaged 1.83 mg L-1. Estimates of physical mechanisms allowed calculation of expected N2 concentrations that were compared to observed N2 concentrations. Where Ne data were unavailable, we assumed excess air equal to the empirical average. Overall, observed N2 exceeded expectations based on physical processes in 33 of 47 cases; average excess N2 was 0.48 mg L-1 across all sites. In addition, excess N2 was negatively correlated with DO (r2 = 0.46); springs with low DO (Aquifer. Low DOC concentrations indicate that alternative electron donors may fuel nitrate reduction. Scaling to regional estimates of N2 production based on springs discharge and DO concentrations indicates that subsurface denitrification may account for some of the imbalance in springshed nutrient budgets. In addition, we conclude that use of δ15N-NO3- to diagnose

  14. Controls on denitrification potential in nitrate-rich waterways and riparian zones of an irrigated agricultural setting.

    Science.gov (United States)

    Webster, Alex J; Groffman, Peter M; Cadenasso, Mary L

    2018-02-21

    Denitrification, the microbial conversion of NO 3 - to N gases, is an important process contributing to whether lotic and riparian ecosystems act as sinks for excess NO 3 - from agricultural activities. Though agricultural waterways and riparian zones have been a focus of denitrification research for decades, almost none of this research has occurred in the irrigated agricultural settings of arid and semi-arid climates. In this study, we conducted a broad survey of denitrification potential in riparian soils and channel sediment from 79 waterway reaches in the irrigated agricultural landscape of California's Central Valley. With this approach, we sought to capture the wide range of variation that arose from diverse waterway management and fluctuating flow conditions, and use this variation to identify promising management interventions. We explored associations of denitrification potentials with surface water NO 3 - -N, organic matter, flow conditions, vegetation cover, near-channel riparian bank slope, and channel geomorphic features using generalized linear mixed models. We found strong associations of sediment denitrification potentials with reach flow conditions, which we hypothesize was the result of variation in microbial communities' tolerance to dry-wet cycles. Denitrification potentials in riparian soils, in contrast, did not appear affected by flow conditions, but instead were associated with organic matter, vegetation cover, and bank slope in the riparian zone. These results suggest a strong need for further work on how denitrification responds to varying flow conditions and dry-wet cycles in non-perennial lotic ecosystems. Our findings also demonstrate that denitrifier communities respond to key features of waterway management, which can therefore be leveraged to control denitrification through a variety of management actions. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  15. The kinetics of denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Evrard, Victor; Glud, Ronnie N.; Cook, Perran L. M.

    2013-01-01

    Permeable sediments comprise the majority of shelf sediments, yet the rates of denitrification remain highly uncertain in these environments. Computational models are increasingly being used to understand the dynamics of denitrification in permeable sediments, which are complex environments...... on sediments taken from six shallow coastal sites in Port Phillip Bay, Victoria, Australia. The results showed that denitrification commenced rapidly (within 30 min) after the onset of anoxia and the kinetics could be well described by Michaelis-Menten kinetics with half saturation constants (apparent K...... in cohesive sediments despite organic carbon contents one order of magnitude lower for the sediments studied here. The ratio of sediment O-2 consumption to V-max was in the range of 0.02-0.09, and was on average much lower than the theoretical ratio of 0.8. As a consequence, models implemented...

  16. Characterization of a halophilic heterotrophic nitrification-aerobic denitrification bacterium and its application on treatment of saline wastewater.

    Science.gov (United States)

    Duan, Jinming; Fang, Hongda; Su, Bing; Chen, Jinfang; Lin, Jinmei

    2015-03-01

    A novel halophilic bacterium capable of heterotrophic nitrification-aerobic denitrification was isolated from marine sediments and identified as Vibrio diabolicus SF16. It had ability to remove 91.82% of NH4(+)-N (119.77 mg/L) and 99.71% of NO3(-)-N (136.43 mg/L). The nitrogen balance showed that 35.83% of initial NH4(+)-N (119.77 mg/L) was changed to intracellular nitrogen, and 53.98% of the initial NH4(+)-N was converted to gaseous denitrification products. The existence of napA gene further proved the aerobic denitrification ability of strain SF16. The optimum culture conditions were salinity 1-5%, sodium acetate as carbon source, C/N 10, and pH 7.5-9.5. When an aerated biological filter system inoculated with strain SF16 was employed to treat saline wastewater, the average removal efficiency of NH4(+)-N and TN reached 97.14% and 73.92%, respectively, indicating great potential of strain SF16 for future full-scale applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Nitrous oxide production by nitrification and denitrification in the Eastern Tropical South Pacific oxygen minimum zone

    Science.gov (United States)

    Ji, Qixing; Babbin, Andrew R.; Jayakumar, Amal; Oleynik, Sergey; Ward, Bess B.

    2015-12-01

    The Eastern Tropical South Pacific oxygen minimum zone (ETSP-OMZ) is a site of intense nitrous oxide (N2O) flux to the atmosphere. This flux results from production of N2O by nitrification and denitrification, but the contribution of the two processes is unknown. The rates of these pathways and their distributions were measured directly using 15N tracers. The highest N2O production rates occurred at the depth of peak N2O concentrations at the oxic-anoxic interface above the oxygen deficient zone (ODZ) because slightly oxygenated waters allowed (1) N2O production from both nitrification and denitrification and (2) higher nitrous oxide production yields from nitrification. Within the ODZ proper (i.e., anoxia), the only source of N2O was denitrification (i.e., nitrite and nitrate reduction), the rates of which were reflected in the abundance of nirS genes (encoding nitrite reductase). Overall, denitrification was the dominant pathway contributing the N2O production in the ETSP-OMZ.

  18. The Evolution of Indian and Pacific Ocean Denitrification and Nitrogen Dynamcs since the Miocene

    Science.gov (United States)

    Ravelo, A. C.; Carney, C.; Rosenthal, Y.; Holbourn, A.; Kulhanek, D. K.

    2017-12-01

    The feedbacks between geochemical cycles and physical climate change are poorly understood; however, there has been tremendous progress in developing coupled models to help predict the direction and strength of these feedbacks. As such, there is a need for more data to validate and test these models. To this end, the nitrogen (N) cycle, and its links to the biological pump and to climate, is an active area of paleoceanographic research. Using N isotope records, Robinson et al. (2014) showed that pelagic denitrification in the Indian and Pacific Oceans intensified as climate cooled and subsurface ventilation decreased since the Pliocene. They pointed out that a more ventilated warm Pliocene contrasts with glacial-interglacial patterns wherein more ventilation occurs during cold phases, indicating that different mechanisms may occur at different timescales. Our objective is to better understand the nature of the feedbacks between the oceanic N cycle and climate by focusing on the large dynamic range of conditions that occurred during and since the Miocene. We used new cores drilled during IODP Expedition 363 to generate bulk sediment N isotope records at three western tropical Pacific sites (U1486, U1488, U1490) and one southeastern tropical Indian Ocean site (U1482). We find that the N isotope trends since the Pliocene are in agreement with previous studies showing increasing denitrification as climate cooled. In the Miocene, the Indian Ocean record shows no long-term N isotope trend whereas the Pacific Ocean records show a trend that is roughly coupled to changes in global climate suggesting that pelagic denitrification in the Pacific was strongly influenced by greater ventilation during global warmth. However, there are notable deviations from this coupling during several intervals in the Miocene, and there are site-to-site differences in trends. These deviations and differences can be explained by changes in tropical productivity (e.g., late Miocene biogenic

  19. Studies on benthic denitrification in the Chwaka Bay mangrove ...

    African Journals Online (AJOL)

    Spatial variations in denitrification rates were due to variations in concentration levels of organic matter and possibly to disproportionate competition for inorganic nitrogen between denitrifiers and benthic autotrophs among sites. There were no seasonal differences in denitrification rates. Results from the present study ...

  20. Oxygen requirement for denitrification by the fungus Fusarium oxysporum.

    Science.gov (United States)

    Zhou, Z; Takaya, N; Sakairi, M A; Shoun, H

    2001-01-01

    The effects of dioxygen (O2) on the denitrification activity of the fungus Fusarium oxysporum MT-811 in fed-batch culture in a stirred jar fermentor were examined. The results revealed that fungal denitrifying activity requires a minimal amount of O2 for induction, which is repressed by excess O2. The optimal O2 supply differed between the denitrification substrates : 690 micromol O2 x h(-1) (g dry cell wt.)(-1) for nitrate (NO3-) and about 250 micromol O2 x h(-1) (g dry cell wt.)(-1) for nitrite (NO2-). The reduction of NO3- required more O2 than that of NO2- . With an optimal O2 supply, 80% and 52% of nitrogen atoms in NO3- and NO2-, respectively, were recovered as the denitrification product N2O. These features of F. oxysporum differ from those of bacterial denitrifiers that work exclusively under anoxic conditions. The denitrification activity of F. oxysporum MT-811 mutants with impaired NO3- assimilation was about double that of the wild-type strain, suggesting competition for the substrate between assimilatory and dissimilatory types of NO3- reduction. These results showed that denitrification by F. oxysporum has unique features, namely, a minimal O2 requirement and competition with assimilatory NO3-.

  1. Fractionation of Nitrogen and Oxygen Isotopes and Roles of Bacteria during Denitrification

    Science.gov (United States)

    Kang, J.; Buyanjargal, A.; Jeen, S. W.

    2017-12-01

    Nitrate in groundwater can cause health and environmental problems when not properly treated. The purpose of this study was to develop a treatment method for nitrate in groundwater using organic carbon-based reactive mixtures (i.e., wood chips and gravel) through column experiments and to evaluate reaction mechanisms responsible for the treatment. The column experiments were operated for a total of 19 months. The results from the geochemical analyses for the experiments suggest that cultures of denitrifying bacteria used organic carbon while utilizing nitrate as their electron acceptor via denitrification process. Proteobacteria was the most abundant phylum in all samples, accounting for 45.7% of the bacterial reads, followed by Firmicutes (22.6%) and Chlorobi (10.6%). Bacilli, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Actinobacteria_c consisted of 32, 30, 23, 11, and 2% of denitrifying bacteria class. The denitrification process caused fractionation of nitrogen and oxygen isotopes of nitrate while nitrate concentration decreased. When fitted to the Rayleigh's fractionation model, enrichment factors (ɛ) were 11.5‰ and 5.6‰ for 15N and 18O isotopes, respectively. Previous studies suggested that nitrogen isotope enrichment factors of denitrification are within the range of 4.7 to 40‰ and oxygen isotopic enrichment factors are between 8 and 18.3‰. This study shows that nitrate in groundwater can be effectively treated using passive treatment systems, such as permeable reactive barriers (PRBs), and denitrificaton is the dominant process reponsible for the removal of nitrate.

  2. Nitrate removal from groundwater by cooperating heterotrophic with autotrophic denitrification in a biofilm-electrode reactor

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yingxin [School of Water Resources and Environment, China University of Geosciences, Beijing 100083 (China); Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 3058572 (Japan); Feng, Chuanping, E-mail: fengchuangping@gmail.com [School of Water Resources and Environment, China University of Geosciences, Beijing 100083 (China); Wang, Qinghong; Yang, Yingnan; Zhang, Zhenya; Sugiura, Norio [Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 3058572 (Japan)

    2011-09-15

    Highlights: {yields} Intensified biofilm-electrode reactor using cooperative denitrification is developed. {yields} IBER combines heterotrophic and autotrophic denitrification. {yields} CO{sub 2} formed by heterotrophic denitrification is used by autotrophic bacteria. {yields} Optimum running conditions are C/N = 0.75, HRT = 8 h, and I = 40 mA. {yields} A novel degradation mechanism for cooperating denitrification process is proposed. - Abstract: An intensified biofilm-electrode reactor (IBER) combining heterotrophic and autotrophic denitrification was developed for treatment of nitrate contaminated groundwater. The reactor was evaluated with synthetic groundwater (NO{sub 3}{sup -}N50 mg L{sup -1}) under different hydraulic retention times (HRTs), carbon to nitrogen ratios (C/N) and electric currents (I). The experimental results demonstrate that high nitrate and nitrite removal efficiency (100%) were achieved at C/N = 1, HRT = 8 h, and I = 10 mA. C/N ratios were reduced from 1 to 0.5 and the applied electric current was changed from 10 to 100 mA, showing that the optimum running condition was C/N = 0.75 and I = 40 mA, under which over 97% of NO{sub 3}{sup -}N was removed and organic carbon (methanol) was completely consumed in treated water. Simultaneously, the denitrification mechanism in this system was analyzed through pH variation in effluent. The CO{sub 2} produced from the anode acted as a good pH buffer, automatically controlling pH in the reaction zone. The intensified biofilm-electrode reactor developed in the study was effective for the treatment of groundwater polluted by nitrate.

  3. Seasonal effects of the zebra mussel (Dreissena polymorpha) on sediment denitrification rates in Pool 8 of the Upper Mississippi River

    Science.gov (United States)

    Bruesewitz, Denise A.; Tank, Jennifer L.; Bernot, Melody J.; Richardson, William B.; Strauss, Eric A.

    2006-01-01

    Zebra mussels (Dreissena polymorpha) have altered the structure of invaded ecosystems and exhibit characteristics that suggest they may influence ecosystem processes such as nitrogen (N) cycling. We measured denitrification rates seasonally on sediments underlying zebra mussel beds collected from the impounded zone of Navigation Pool 8 of the Upper Mississippi River. Denitrification assays were amended with nutrients to characterize variation in nutrient limitation of denitrification in the presence or absence of zebra mussels. Denitrification rates at zebra mussel sites were high relative to sites without zebra mussels in February 2004 (repeated measures analysis of variance (RM ANOVA), p = 0.005), potentially because of high NO3-N variability from nitrification of high NH4+ zebra mussel waste. Denitrification rates were highest in June 2003 (RM ANOVA, p 3-N concentrations during the study (linear regression, R2 = 0.72, p p ≤ 0.01). Examining how zebra mussels influence denitrification rates will aid in developing a more complete understanding of the impact of zebra mussels and more effective management strategies of eutrophic waters.

  4. End-of-pipe single-sludge denitrification in pilot-scale recirculating aquaculture systems

    DEFF Research Database (Denmark)

    Suhr, Karin Isabel; Pedersen, Lars-Flemming; Nielsen, J.L.

    2014-01-01

    A step toward environmental sustainability of recirculat aquaculture systems (RAS) is implementation ofsingle-sludge denitrification, a process eliminating nitrate from the aqueous environment while reduc-ing the organic matter discharge simultaneously. Two 1700 L pilot-scale RAS systems each...

  5. Molecular identification of potential denitrifying bacteria and use of D-optimal mixture experimental design for the optimization of denitrification process.

    Science.gov (United States)

    Ben Taheur, Fadia; Fdhila, Kais; Elabed, Hamouda; Bouguerra, Amel; Kouidhi, Bochra; Bakhrouf, Amina; Chaieb, Kamel

    2016-04-01

    Three bacterial strains (TE1, TD3 and FB2) were isolated from date palm (degla), pistachio and barley. The presence of nitrate reductase (narG) and nitrite reductase (nirS and nirK) genes in the selected strains was detected by PCR technique. Molecular identification based on 16S rDNA sequencing method was applied to identify positive strains. In addition, the D-optimal mixture experimental design was used to optimize the optimal formulation of probiotic bacteria for denitrification process. Strains harboring denitrification genes were identified as: TE1, Agrococcus sp LN828197; TD3, Cronobacter sakazakii LN828198 and FB2, Pedicoccus pentosaceus LN828199. PCR results revealed that all strains carried the nirS gene. However only C. sakazakii LN828198 and Agrococcus sp LN828197 harbored the nirK and the narG genes respectively. Moreover, the studied bacteria were able to form biofilm on abiotic surfaces with different degree. Process optimization showed that the most significant reduction of nitrate was 100% with 14.98% of COD consumption and 5.57 mg/l nitrite accumulation. Meanwhile, the response values were optimized and showed that the most optimal combination was 78.79% of C. sakazakii LN828198 (curve value), 21.21% of P. pentosaceus LN828199 (curve value) and absence (0%) of Agrococcus sp LN828197 (curve value). Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Inhibition of existing denitrification enzyme activity by chloramphenicol

    Science.gov (United States)

    Brooks, M.H.; Smith, R.L.; Macalady, D.L.

    1992-01-01

    Chloramphenicol completely inhibited the activity of existing denitrification enzymes in acetylene-block incubations with (i) sediments from a nitrate-contaminated aquifer and (ii) a continuous culture of denitrifying groundwater bacteria. Control flasks with no antibiotic produced significant amounts of nitrous oxide in the same time period. Amendment with chloramphenicol after nitrous oxide production had begun resulted in a significant decrease in the rate of nitrous oxide production. Chloramphenicol also decreased (>50%) the activity of existing denitrification enzymes in pure cultures of Pseudomonas denitrificans that were harvested during log- phase growth and maintained for 2 weeks in a starvation medium lacking electron donor. Short-term time courses of nitrate consumption and nitrous oxide production in the presence of acetylene with P. denitrificans undergoing carbon starvation were performed under optimal conditions designed to mimic denitrification enzyme activity assays used with soils. Time courses were linear for both chloramphenicol and control flasks, and rate estimates for the two treatments were significantly different at the 95% confidence level. Complete or partial inhibition of existing enzyme activity is not consistent with the current understanding of the mode of action of chloramphenicol or current practice, in which the compound is frequently employed to inhibit de novo protein synthesis during the course of microbial activity assays. The results of this study demonstrate that chloramphenicol amendment can inhibit the activity of existing denitrification enzymes and suggest that caution is needed in the design and interpretation of denitrification activity assays in which chloramphenicol is used to prevent new protein synthesis.

  7. Effect of Co-Contaminant on Denitrification Removal of Nitrate in Drinking Water

    Directory of Open Access Journals (Sweden)

    Arzu KILIÇ

    2012-12-01

    Full Text Available In recent years, nitrogenous fertilizers used in agriculture, unconscious and without treatment wastewater is discharged led to an increase in groundwater nitrate pollution. In many countries, nitrate concentration in the ground waters used as drinking water source exceeded the maximum allowable concentration of 10 mg/L NO3-N. According to a study, some wells in the Harran Plain contain nitrate as high as 180 mg/L NO3--N and the average concentration for whole plain is 35 mg/L NO3--N (Yesilnacar et al., 2008. Additionally, increased water consumption, unconscious use of fertilizers and pesticides has led to the emergence of co-contaminant in drinking water. Recently, hazardous to human health co-contaminant such as arsenic, pesticides, perchlorate, selenate, chromate, uranium are observed in the nitrate pollution drinking water. There are many processes used for the removal of nitrate. The physical–chemical technologies that can be used for nitrate removal are reverse osmosis, ion exchange and electrodialysis (Alvarez et al., 2007. Important disadvantages of these processes are their poor selectivity, high operation and maintenance costs and the generation of brine wastes after treatment. Consequently, biological treatment processes to convert nitrates to benign dinitrogen gas, could be an interesting alternative for the remediation of groundwater contaminated with nitrates. The aim of this article, effective and cheap method for the removal of nitrate from drinking water biological denitrification is to examine the usability of contaminated drinking water with co-contaminant pollutions.

  8. Simultaneous nitrification, denitrification and phosphorus removal (SNDPR) in a full-scale water reclamation plant located in warm climate.

    Science.gov (United States)

    Yang, Qin; Shen, Nan; Lee, Zarraz M-P; Xu, Guangjing; Cao, Yeshi; Kwok, Beehong; Lay, Winson; Liu, Yu; Zhou, Yan

    The combination of simultaneous nitrification-denitrification (SND) with enhanced biological phosphorus removal (EBPR) provides a more efficient and economically viable option for nutrient removal from municipal wastewater compared to conventional two-step nitrification-denitrification. This study analyzed the nutrients (N and P) profiles in a full-scale municipal wastewater reclamation plant (WRP) located in the tropical region, in which more than 90% of nitrogen was removed. Interestingly, average SND efficiency in aerobic zones was found to be up to 50%, whereas phosphorus profile displayed a clear cyclic release and uptake pattern with a phosphorus removal efficiency of up to 76%. The capability of sludge to perform SND and EBPR was further confirmed through a series of batch experiments. Microbial analysis revealed the presence of Accumulibacter and Tetrasphaera phosphate accumulating organisms in the plant, while few glycogen accumulating organisms (GAO) was observed. This study showed the significant occurrence of combined SND and EBPR, known as simultaneous nitrification, denitrification and phosphorus removal (SNDPR), in the studied WRP under warm climate. The possible causes behind the observed SNDPR were also discussed.

  9. Regulation and role of epiphytic nitrification and denitrification in macrophyte-dominated systems

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Peder G.

    2000-02-01

    This thesis examines mechanisms regulating bacterial nitrification and denitrification in attached microbial communities on surfaces of aquatic macrophytes. It also evaluates the role of epiphytic nitrification and denitrification for the nitrogen turnover in macrophyte-dominated nutrient-rich freshwater. Epiphytic nitrification is promoted in light and epiphytic denitrification occurs mainly in dark, because the metabolic activity of the aquatic macrophyte and its epiphytes induce in light high and in dark low oxygen concentrations in epiphytic communities. Epiphytic nitrification and denitrification are also affected by the physical and chemical characteristics of the aquatic macrophyte. The spatial distribution of nitrification in emergent macrophyte wetlands is related to the species composition of the emergent vegetation, possibly because of a macrophyte species-related release of organic nitrification inhibitors. Contrasting to nitrifying bacteria, which are lithotrophic, denitrifying bacteria use organic substances as an energy source and are therefore stimulated by the release of organic matter from aquatic macrophytes. Epiphytic communities support more denitrification in nutrient-rich than in nutrient-poor environments. In lakes and ponds, epiphytic denitrification is higher at sheltered locations than at locations exposed to wind-induced water movements or currents. In flowing water, epiphytic denitrification occurs mainly at low oxygen concentrations in the surrounding water. However, because aquatic macrophytes impede water flow and induce low oxygen concentrations in dark, epiphytic denitrification can be present within dense vegetation despite of high oxygen concentrations in the surrounding water. Epiphytic nitrification is almost unaffected by flow conditions, and can occur both in light and in dark. In shallow-water systems such as treatment wetlands, aquatic macrophytes often provide most of the accessible surface area for attached nitrifying and

  10. Simultaneous nitrogen and phosphorus removal in the sulfur cycle-associated Enhanced Biological Phosphorus Removal (EBPR) process.

    Science.gov (United States)

    Wu, Di; Ekama, George A; Wang, Hai-Guang; Wei, Li; Lu, Hui; Chui, Ho-Kwong; Liu, Wen-Tso; Brdjanovic, Damir; van Loosdrecht, Mark C M; Chen, Guang-Hao

    2014-02-01

    Hong Kong has practiced seawater toilet flushing since 1958, saving 750,000 m(3) of freshwater every day. A high sulfate-to-COD ratio (>1.25 mg SO4(2-)/mg COD) in the saline sewage resulting from this practice has enabled us to develop the Sulfate reduction, Autotrophic denitrification and Nitrification Integrated (SANI(®)) process with minimal sludge production and oxygen demand. Recently, the SANI(®) process has been expanded to include Enhanced Biological Phosphorus Removal (EBPR) in an alternating anaerobic/limited-oxygen (LOS-EBPR) aerobic sequencing batch reactor (SBR). This paper presents further development - an anaerobic/anoxic denitrifying sulfur cycle-associated EBPR, named as DS-EBPR, bioprocess in an alternating anaerobic/anoxic SBR for simultaneous removal of organics, nitrogen and phosphorus. The 211 day SBR operation confirmed the sulfur cycle-associated biological phosphorus uptake utilizing nitrate as electron acceptor. This new bioprocess cannot only reduce operation time but also enhance volumetric loading of SBR compared with the LOS-EBPR. The DS-EBPR process performed well at high temperatures of 30 °C and a high salinity of 20% seawater. A synergistic relationship may exist between sulfur cycle and biological phosphorus removal as the optimal ratio of P-release to SO4(2-)-reduction is close to 1.0 mg P/mg S. There were no conventional PAOs in the sludge. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Biological reduction of nitrates in wastewaters from nuclear processing using a fluidized-bed bioreactor

    International Nuclear Information System (INIS)

    Pitt, W.W.; Hancher, C.W.; Patton, B.D.

    1981-01-01

    There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt.% NO 3 - and as large as 2000 m 3 /day, in the nuclear fuel cycle. The biological reduction of nitrate in wastewater to gaseous nitrogen, accompanied by the oxidation of a nutrient carbon source to gaseous carbon dioxide, is an ecologically sound and cost-effective method of treating wastewaters containing nitrates. These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 gN(NO 3 - )/m 3 by the use of a fluidized-bed bioreactor. The denitrification bacteria are a mixed culture derived from garden soil; the major strain is Pseudomonas. In the fluidized-bed bioreactor the bacteria are allowed to attach to 0.25- to 0.50-mm-diam coal fluidization particles, which are then fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m 3 . This paper describes the results of a biodenitrification R and D program based on the use of fluidized bioreactors capable of operating at nitrate levels up to 7000 g/m 3 and achieving denitrification rates as high as 80 g N(NO 3 - ) per day per liter of empty bioreactor volume. 4 figures, 7 tables

  12. The influence of stormwater management practices on denitrification rates of receiving streams in an urban watershed

    Science.gov (United States)

    Cronenberger, M. S.; McMillan, S. K.

    2011-12-01

    Increasing urbanization and the subsequent disruption of floodplains has led to the need for implementing stormwater management strategies to mitigate the effects of urbanization, including soil and streambank erosion, increased export of nutrients and contaminants and decreased biotic richness. Excessive stormwater runoff due to the abundance of impervious surfaces associated with an urban landscape has led to the ubiquitous use of best management practices (BMPs) to attenuate runoff events and prevent the destructive delivery of large volumes of water to stream channels. As a result, effluent from BMPs (i.e. wetlands and wet ponds) has the potential to alter the character of the receiving stream channel and thus, key ecosystem processes such as denitrification. The purpose of this study was to determine the extent to which BMPs, in the form of constructed wetlands and wet ponds, influence in-stream denitrification rates in the urban landscape of Charlotte, NC. Four sites, two of each BMP type, were evaluated. Sediment samples were collected upstream and downstream of the BMP outflow from May-July 2011 to determine the effect of wetland discharge on in-stream nitrogen removal via denitrification. Denitrification rates were determined using the acetylene block method; water column nutrient and carbon concentrations and sediment organic matter content were also measured. Generally, wetland sites exhibited higher denitrification rates, nitrate concentrations and sediment organic matter content. Our work and others has demonstrated a significant positive correlation between nitrate concentration and denitrification rates, which is the likely driver of the higher observed rates at the wetland sites. Geomorphology was also found to be a key factor in elevated denitrification rates at sites with riffles and boulder jams. Sediment organic matter was found to be higher downstream of BMP outflows at all four sites, but demonstrated no significant relationship with

  13. Denitrification of nitrate waste solutions

    International Nuclear Information System (INIS)

    Michaels, S.L.; Michel, R.C.; Terpandjian, P.D.; Vora, J.N.

    1976-01-01

    Bacterial denitrification by Pseudomonas Stutzeri has been chosen as the method for removing nitrate from the effluent stream of the Y-12 uranium purification process. A model was developed to predict bacterial growth and carbon and nitrate depletion during the induction period and steady state operation. Modification of analytical procedures and automatic control of the pH in the reactor are recommended to improve agreement between the prediction of the model and experimental data. An initial carbon-to-nitrogen (C/N) mass ratio of 1.4-1.5 insures adequate population growth during the induction period. Further experiments in batch reactors and in steady state flow reactors are recommended to obtain more reliable kinetic rate constants

  14. Isolation of high-salinity-tolerant bacterial strains, Enterobacter sp., Serratia sp., Yersinia sp., for nitrification and aerobic denitrification under cyanogenic conditions.

    Science.gov (United States)

    Mpongwana, N; Ntwampe, S K O; Mekuto, L; Akinpelu, E A; Dyantyi, S; Mpentshu, Y

    2016-01-01

    Cyanides (CN(-)) and soluble salts could potentially inhibit biological processes in wastewater treatment plants (WWTPs), such as nitrification and denitrification. Cyanide in wastewater can alter metabolic functions of microbial populations in WWTPs, thus significantly inhibiting nitrifier and denitrifier metabolic processes, rendering the water treatment processes ineffective. In this study, bacterial isolates that are tolerant to high salinity conditions, which are capable of nitrification and aerobic denitrification under cyanogenic conditions, were isolated from a poultry slaughterhouse effluent. Three of the bacterial isolates were found to be able to oxidise NH(4)-N in the presence of 65.91 mg/L of free cyanide (CN(-)) under saline conditions, i.e. 4.5% (w/v) NaCl. The isolates I, H and G, were identified as Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Results showed that 81% (I), 71% (G) and 75% (H) of 400 mg/L NH(4)-N was biodegraded (nitrification) within 72 h, with the rates of biodegradation being suitably described by first order reactions, with rate constants being: 4.19 h(-1) (I), 4.21 h(-1) (H) and 3.79 h(-1) (G), respectively, with correlation coefficients ranging between 0.82 and 0.89. Chemical oxygen demand (COD) removal rates were 38% (I), 42% (H) and 48% (G), over a period of 168 h with COD reduction being highest at near neutral pH.

  15. Inactivation of ANAMMOX communities under concurrent operation of anaerobic ammonium oxidation (ANAMMOX) and denitrification

    DEFF Research Database (Denmark)

    Chamchoi, N.; Nitisoravut, S.; Schmidt, Jens Ejbye

    2008-01-01

    of Amx 820 and EUB 338 mixed. Denitrification was observed through the reductions of both COD and nitrate–nitrite concentrations under anaerobic/anoxic conditions. By providing a stoichiometric ratio of nitrite to ammonium nitrogen with addition nitrate nitrogen, a gradual reduction of ANAMMOX activity...... was found with an increase of COD concentration in a range of 100–400 mg l−1. This is equivalent to the COD to N ratio of 0.9–2.0. The COD concentration was found to be a control variable for process selection between ANAMMOX reaction and denitrification. A reduction of COD and nitrite–nitrate...

  16. The mechanism of oxygen isotopic fractionation during fungal denitrification - A pure culture study

    Science.gov (United States)

    Wrage-Moennig, Nicole; Rohe, Lena; Anderson, Traute-Heidi; Braker, Gesche; Flessa, Heinz; Giesemann, Annette; Lewicka-Szczebak, Dominika; Well, Reinhard

    2014-05-01

    Nitrous oxide (N2O) from soil denitrification originates from bacteria and - to an unknown extent - also from fungi. During fungal denitrification, oxygen (O) exchange takes place between H2O and intermediates of the denitrification process as in bacterial exchange[1,2]. However, information about enzymes involved in fungal O exchanges and the associated fractionation effects is lacking. The objectives of this study were to estimate the O fractionation and O exchange during the fungal denitrifying steps using a conceptual model[2] adapted from concepts for bacterial denitrification[3], implementing controls of O exchange proposed by Aerssens, et al.[4] and using fractionation models by Snider et al.[5] Six different pure fungal cultures (five Hypocreales, one Sordariales) known to be capable of denitrification were incubated under anaerobic conditions, either with nitrite or nitrate. Gas samples were analyzed for N2O concentration and its isotopic signatures (SP, average δ15N, δ18O). To investigate O exchange, both treatments were also established with 18O-labelled water as a tracer in the medium. The Hypocreales strains showed O exchange mainly at NO2- reductase (Nir) with NO2- as electron acceptor and no additional O exchange at NO3- reductase (Nar) with NO3- as electron acceptor. The only Hypocreales species having higher O exchange with NO3- than with NO2- also showed O exchange at Nar. The Sordariales species tested seems capable of O exchange at NO reductase (Nor) additionally to O exchange at Nir with NO2-. The data will help to better interpret stable isotope values of N2O from soils. .[1] D. M. Kool, N. Wrage, O. Oenema, J. Dolfing, J. W. Van Groenigen. Oxygen exchange between (de)nitrification intermediates and H2O and its implications for source determination of NO?3- and N2O: a review. Rapid Commun. Mass Spec. 2007, 21, 3569. [2] L. Rohe, T.-H. Anderson, B. Braker, H. Flessa, A. Giesemann, N. Wrage-Mönnig, R. Well. Fungal Oxygen Exchange between

  17. Denitrification in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Noronha, R.J.; Reddy, C.V.G.

    deficits because the approach requires denitrification to be restricted to Persian Gulf water. A method involving oxidative ratios has been modified and used to calculate nitrate deficits. The deficits so calculated lie between the values reported earlier...

  18. Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003

    Directory of Open Access Journals (Sweden)

    S. Davies

    2006-01-01

    Full Text Available Observations of gas-phase HNO3 and N2O in the polar stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding aboard the ENVISAT satellite (MIPAS-E were made during the cold Arctic winter of 2002/2003. Vortex temperatures were unusually low in early winter and remained favourable for polar stratospheric cloud formation and denitrification until mid-January. MIPAS-E observations provide the first dataset with sufficient coverage of the polar vortex in mid-winter which enables a reasonable estimate of the timing of onset and spatial distribution of denitrification of the Arctic lower stratosphere to be performed. We use the observations from MIPAS-E to test the evolution of denitrification in the DLAPSE (Denitrification by Lagrangian Particle Sedimentation microphysical denitrification model coupled to the SLIMCAT chemical transport model. In addition, the predicted denitrification from a simple equilibrium nitric acid trihydrate-based scheme is also compared with MIPAS-E. Modelled denitrification is compared with in-vortex NOy and N2O observations from the balloon-borne MarkIV interferometer in mid-December. Denitrification was clearly observed by MIPAS-E in mid-December 2002 and reached 80% in the core of the vortex by early January 2003. The DLAPSE model is broadly able to capture both the timing of onset and the spatial distribution of the observed denitrification. A simple thermodynamic equilibrium scheme is able to reproduce the observed denitrification in the core of the vortex but overestimates denitrification closer to the vortex edge. This study also suggests that the onset of denitrification in simple thermodynamic schemes may be earlier than in the MIPAS-E observations.

  19. Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification

    Science.gov (United States)

    Mulholland, P.J.; Hall, R.O.; Sobota, D.J.; Dodds, W.K.; Findlay, S.E.G.; Grimm, N. B.; Hamilton, S.K.; McDowell, W.H.; O'Brien, J. M.; Tank, J.L.; Ashkenas, L.R.; Cooper, L.W.; Dahm, Clifford N.; Gregory, S.V.; Johnson, S.L.; Meyer, J.L.; Peterson, B.J.; Poole, G.C.; Valett, H.M.; Webster, J.R.; Arango, C.P.; Beaulieu, J.J.; Bernot, M.J.; Burgin, A.J.; Crenshaw, C.L.; Helton, A.M.; Johnson, L.T.; Niederlehner, B.R.; Potter, J.D.; Sheibley, R.W.; Thomasn, S.M.

    2009-01-01

    We measured denitrification rates using a field 15N-NO- 3 tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (SWden) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N2 production rates far exceeded N2O production rates in all streams. The fraction of total NO-3 removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NHz 4 concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling SWden were specific discharge (discharge / width) and NO-3 concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (Uden) and NO- 3 concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although Uden increased with increasing NO- 3 concentration, the efficiency of NO-3 removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO-3 load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO-3 concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO-3 concentration. ?? 2009.

  20. Direct contribution of clams (Ruditapes philippinarum) to benthic fluxes, nitrification, denitrification and nitrous oxide emission in a farmed sediment

    Science.gov (United States)

    Welsh, David T.; Nizzoli, Daniele; Fano, Elisa A.; Viaroli, Pierluigi

    2015-03-01

    The influence of the manila clam (Ruditapes philippinarum) on N-cycle processes, and oxygen and nutrient fluxes in a farmed sediment was investigated using a multiple core incubation approach and parallel incubations of individual clams. Clam population/biomass density varied ∼8-fold between cores and all sediment-water column solute (O2. N2, N2O, NH4+, NOX and DIN) fluxes and benthic process (N-regeneration, nitrification and denitrification) rates were strongly and significantly correlated with clam density/biomass. Isolated clams exhibited high rates of respiration, N-excretion, nitrification and denitrification of 2050 ± 70, 395 ± 49, 201 ± 42 and 235 ± 40 nmol individual-1 h-1, respectively. The direct contribution of the clams and their associated microbiota to benthic processes was estimated by multiplying the per individual rates by the number of clams in each incubated core. The clams on average directly accounted for 64-133% of total rates of sediment oxygen demand, N-regeneration, nitrification and denitrification, indicating that they regulated processes primarily through their own metabolic activity and that of bacteria that colonise them. Clams and the farmed sediments were significant sources of the greenhouse gas N2O, but this was primarily due to their high nitrification and denitrification rates, rather than high specific N2O yields, as N2O emissions represented farmed sediments had a high denitrification efficiency of 67 ± 10%, but this ecosystem service came at the environmental cost of increased N-regeneration and N2O emission rates. The measured N2O emissions indicate that bivalve aquaculture may be a significant source of N2O. It is therefore recommended that N2O emissions should be included in the impact assessments of current and future bivalve-farming projects.

  1. Quantifying denitrification in rippled permeable sands through combined flume experiments and modeling

    DEFF Research Database (Denmark)

    Kessler, Adam J.; Glud, Ronnie N.; Cardenas, M. Bayani

    2012-01-01

    We measured denitrification in permeable sediments in a sealed flume tank with environmentally representative fluid flow and solute transport behavior using novel measurements. Numerical flow and reactive transport models representing the flume experiments were implemented to provide mechanistic...... insight into the coupled hydrodynamic and biogeochemical processes. There was broad agreement between the model results and experimental data. The model showed that the coupling between nitrification and denitrification was relatively weak in comparison to that in cohesive sediments. This was due...... of permeable sediments with nonmigratory ripples to remove bioavailable nitrogen from coastal ecosystems is lower than that of cohesive sediments. We conclude that while experimental measurements provide a good starting point for constraining key parameters, reactive transport models with realistic kinetic...

  2. Biological nitrate removal processes from drinking water supply-a review.

    Science.gov (United States)

    Mohseni-Bandpi, Anoushiravan; Elliott, David Jack; Zazouli, Mohammad Ali

    2013-12-19

    This paper reviews both heterotrophic and autotrophic processes for the removal of nitrate from water supplies. The most commonly used carbon sources in heterotrophic denitrification are methanol, ethanol and acetic acid. Process performance for each feed stock is compared with particular reference nitrate and nitrite residual and to toxicity potential. Autotrophic nitrate removal has the advantages of not requiring an organic carbon source; however the slow growth rate of autotrophic bacteria and low nitrate removal rate have contributed to the fact that relatively few full scale plants are in operation at the present time.

  3. Branching processes in biology

    CERN Document Server

    Kimmel, Marek

    2015-01-01

    This book provides a theoretical background of branching processes and discusses their biological applications. Branching processes are a well-developed and powerful set of tools in the field of applied probability. The range of applications considered includes molecular biology, cellular biology, human evolution and medicine. The branching processes discussed include Galton-Watson, Markov, Bellman-Harris, Multitype, and General Processes. As an aid to understanding specific examples, two introductory chapters, and two glossaries are included that provide background material in mathematics and in biology. The book will be of interest to scientists who work in quantitative modeling of biological systems, particularly probabilists, mathematical biologists, biostatisticians, cell biologists, molecular biologists, and bioinformaticians. The authors are a mathematician and cell biologist who have collaborated for more than a decade in the field of branching processes in biology for this new edition. This second ex...

  4. Simultaneous selenate reduction and denitrification by a consortium of enriched mine site bacteria.

    Science.gov (United States)

    Subedi, Gaurav; Taylor, Jon; Hatam, Ido; Baldwin, Susan A

    2017-09-01

    Increasing selenium concentrations in aquatic environments downstream of mine sites is of great concern due to selenium's bioaccumulation propensity and teratogenic toxicity. Removal of selenium from mine influenced water is complicated by the presence of nitrate, which is also elevated in mine influenced water due to the use of explosives in mining. In many biological treatment processes, nitrate as a thermodynamically more preferable electron acceptor inhibits selenate reduction. Here we report on an enrichment of a bacterial assemblage from a mine impacted natural marsh sediment that was capable of simultaneous selenate reduction and denitrification. Selenate reduction followed first order kinetics with respect to the concentration of total dissolved selenium. The kinetic rate constant was independent of initial nitrate concentration over the range 3-143 mg L -1 -NO 3 - -N. The initial concentration of selenate inhibited selenate reduction kinetics over the range 1-24 mg-Se L -1 . Dominant taxa that grew in selenate only medium were classified in the genera Pseudomonas, Lysinibacillus and Thauera. When nitrate was introduced in addition to selenate, previously rare taxa that became dominant were relatives of Exiguobacterium, Tissierella and Clostridium. Open reading frames (ORFs) associated with dissimilatory denitrification were identified for Pseudomonas, Thauera and Clostridium. In addition, ORFs were found that were homologous with known selenate reductase subunits (SerA and SerB). These findings suggest that native mine site bacteria can be used for removing selenate and nitrate from mine wastewater. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

  5. Denitrification gene expression in clay-soil bacterial community

    Science.gov (United States)

    Pastorelli, R.; Landi, S.

    2009-04-01

    Our contribution in the Italian research project SOILSINK was focused on microbial denitrification gene expression in Mediterranean agricultural soils. In ecosystems with high inputs of nitrogen, such as agricultural soils, denitrification causes a net loss of nitrogen since nitrate is reduced to gaseous forms, which are released into the atmosphere. Moreover, incomplete denitrification can lead to emission of nitrous oxide, a potent greenhouse gas which contributes to global warming and destruction of ozone layer. A critical role in denitrification is played by microorganisms and the ability to denitrify is widespread among a variety of phylogenetically unrelated organisms. Data reported here are referred to wheat cultivation in a clay-rich soil under different environmental impact management (Agugliano, AN, Italy). We analysed the RNA directly extracted from soil to provide information on in situ activities of specific populations. The expression of genes coding for two nitrate reductases (narG and napA), two nitrite reductases (nirS and nirK), two nitric oxide reductases (cnorB and qnorB) and nitrous oxide reductase (nosZ) was analyzed by reverse transcription (RT)-nested PCR. Only napA, nirS, nirK, qnorB and nosZ were detected and fragments sequenced showed high similarity with the corresponding gene sequences deposited in GenBank database. These results suggest the suitability of the method for the qualitative detection of denitrifying bacteria in environmental samples and they offered us the possibility to perform the denaturing gradient gel electrophoresis (DGGE) analyzes for denitrification genes.. Earlier conclusions showed nirK gene is more widely distributed in soil environment than nirS gene. The results concerning the nosZ expression indicated that microbial activity was clearly present only in no-tilled and no-fertilized soils.

  6. Impact of direct greenhouse gas emissions on the carbon footprint of water reclamation processes employing nitrification–denitrification

    International Nuclear Information System (INIS)

    Schneider, Andrew G.; Townsend-Small, Amy; Rosso, Diego

    2015-01-01

    Water reclamation has the potential to reduce water supply demands from aquifers and more energy-intensive water production methods (e.g., seawater desalination). However, water reclamation via biological nitrification–denitrification is also associated with the direct emission of the greenhouse gases (GHGs) CO 2 , N 2 O, and CH 4 . We quantified these direct emissions from the nitrification–denitrification reactors of a water reclamation plant in Southern California, and measured the 14 C content of the CO 2 to distinguish between short- and long-lived carbon. The total emissions were 1.5 (± 0.2) g-fossil CO 2 m −3 of wastewater treated, 0.5 (± 0.1) g-CO 2 -eq of CH 4 m −3 , and 1.8 (± 0.5) g-CO 2 -eq of N 2 O m −3 , for a total of 3.9 (± 0.5) g-CO 2 -eq m −3 . This demonstrated that water reclamation can be a source of GHGs from long lived carbon, and thus a candidate for GHG reduction credit. From the 14 C measurements, we found that between 11.4% and 15.1% of the CO 2 directly emitted was derived from fossil sources, which challenges past assumptions that the direct CO 2 emissions from water reclamation contain only modern carbon. A comparison of our direct emission measurements with estimates of indirect emissions from several water production methods, however, showed that the direct emissions from water reclamation constitute only a small fraction of the plant's total GHG footprint. - Highlights: • Direct greenhouse gas emissions were measured at a wastewater reclamation plant. • These greenhouse gas emissions amounted to 3.9 (± 0.5) g-CO 2 -eq m −3 of wastewater. • 14 C analysis of the CO 2 emissions was conducted to determine the fossil component. • 11.4% to 15.1% of the emitted CO 2 was derived from fossil sources

  7. Adaptation and monitoring of microorganisms in petroleum industry wastewater nitrification processes

    Directory of Open Access Journals (Sweden)

    A. Madero

    1998-07-01

    Full Text Available Biological removal of ammonia nitrogen is carried out in two successive stages, nitrification and denitrification. This work studied the nitrification process on microorganisms isolated from different aquifer sources: a eutrophicate pond and residual waters from two treatment plants (petrochemical and domestic

  8. Compared microbiology of granular sludge under autotrophic, mixotrophic and heterotrophic denitrification conditions.

    Science.gov (United States)

    Fernández, N; Sierra-Alvarez, R; Amils, R; Field, J A; Sanz, J L

    2009-01-01

    Water contamination by nitrate is a wideworld extended phenomena. Biological autotrophic denitrification has a real potential to face this problem and presents less drawbacks than the most extended heterotrophic denitrification. Three bench-scale UASB reactors were operated under autotrophic (R1, H2S as electron donor), mixotrophic (R2, H2S plus p-cresol as electron donors) and heterotrophic (R3, p-cresol as electron donor) conditions using nitrate as terminal electron acceptor. 16S rDNA genetic libraries were built up to compare their microbial biodiversity. Six different bacteria phyla and three archaeal classes were observed. Proteobacteria was the main phyla in all reactors standing out the presence of denitrifiers. Microorganisms similar to Thiobacillus denitrificans and Acidovorax sp. performed the autotrophic denitification. These OTUs were displaced by chemoheterotrophic denitrifiers, especially by Limnobacter-like and Ottowia-like OTUs. Other phyla were Bacteroidetes, Chloroflexi, Firmicutes and Actinobacteria that--as well as Archaea members--were implicated in the degradation of organic matter, as substrate added as coming from endogenous sludge decay under autotrophic conditions. Archaea diversity remained low in all the reactors being Methanosaeta concilii the most abundant one.

  9. Benthic metabolism and denitrification in a river reach: a comparison between vegetated and bare sediments

    Directory of Open Access Journals (Sweden)

    Pierluigi VIAROLI

    2009-02-01

    Full Text Available This study aims at comparing biogeochemical processes in a Vallisneria spiralis meadow and in unvegetated sediments in the upper reach of the Mincio River (Northern Italy. The main hypothesis of this work is that meadows of rooted macrophytes affect benthic metabolism, enhancing capacity to retain nutrients (assimilation and dissipate (denitrification nitrogen loadings. In order to highlight how plants affect benthic processes in the riverbed, oxygen, dissolved inorganic carbon (DIC, soluble reactive phosphorus (SRP and inorganic nitrogen fluxes, together with denitrification rates, were measured from February to November 2007 in intact cores collected from stands of V. spiralis and bare sediments. V. spiralis biomass, elemental composition and growth rates were concurrently measured. Macrophyte biomass ranged from 60 to 120 g m-2 (as dry matter; growth rates followed a seasonal pattern from 0.001 in winter up to 0.080 d-1 in summer. On an annual basis, the macrophyte meadow was autotrophic with net O2 production and dissolved inorganic carbon uptake, while the bare sediment was net heterotrophic. The concurrent N assimilation by macrophytes and losses through denitrification led to similar N uptake/dissipation rates, up to 2500 mmol m-2 y-1. Under the very high NO3 - concentrations of the Mincio River, the competition between primary production and denitrification processes was also avoided. A significant ammonium regeneration from sediments to the water column occurred in the V. spiralis meadow, where plant debris and particulate matter accumulated. Here, SRP was also released into the water column, whilst in the bare sediment SRP fluxes were close to zero. Overall, V. spiralis affected the benthic metabolism enhancing the ecosystem capacity to control nitrogen contamination. However, the actual N removal rates were not sufficient to mitigate the pollution discharge.

  10. Electron transfer rates and energy releases during denitrification of municipal wastewater

    DEFF Research Database (Denmark)

    Abdul-Talib, S.; Ujang, Z; Vollertsen, J.

    2004-01-01

    could be simplified by a two-stage process. In the first stage, nitrate was utilised with significant accumulation of nitrite. In the second stage nitrite was utilised when nitrate depleted. Denitrification rates during the two stages were expressed in terms of electron equivalents (e-eq.) in order...... to compare the process when differennt electron acceptors namlely, nitrate and nitrite were utilised. The energy release rates during the two stages were calculated and compared....

  11. Operation of a fluidized-bed bioreactor for denitrification

    International Nuclear Information System (INIS)

    Hancher, C.W.; Taylor, P.A.; Napier, J.M.

    1978-01-01

    Two denitrification fluidized-bed bioreactors of the same length (i.e., 5 m) but with different inside diameters (i.e., 5 and 10 cm) have been operated on feed ranging in nitrate concentration from 200 to 2000 g/m 3 ; thus far, good agreement has been obtained. Two 10-cm-ID bioreactors operating in series have also been tested; the results are in accordance with predicted results based on the performance of a 5-cm-ID bioreactor. The overall denitrification rate in the dual 10-cm-ID bioreactor system was found to be 23 kg N(NO 3 - )/day-m 3 using feed with a nitrate concentration of 1800 g/m 3 . Data obtained in operating-temperature tests indicate that the maximum denitrification rate is achieved between 22 and 30 0 C. These data will form the basis of the design of our mobile pilot plant which consists of dual 20-cm-ID by 7.3-m-long bioreactors

  12. The diversity of the N2O reducers matters for the N2O:N2 denitrification end-product ratio across an annual and a perennial cropping system.

    Science.gov (United States)

    Domeignoz-Horta, Luiz A; Spor, Aymé; Bru, David; Breuil, Marie-Christine; Bizouard, Florian; Léonard, Joël; Philippot, Laurent

    2015-01-01

    Agriculture is the main source of terrestrial emissions of N2O, a potent greenhouse gas and the main cause of ozone layer depletion. The reduction of N2O into N2 by microorganisms carrying the nitrous oxide reductase gene (nosZ) is the only biological process known to eliminate this greenhouse gas. Recent studies showed that a previously unknown clade of N2O-reducers was related to the capacity of the soil to act as an N2O sink, opening the way for new strategies to mitigate emissions. Here, we investigated whether the agricultural practices could differently influence the two N2O reducer clades with consequences for denitrification end-products. The abundance of N2O-reducers and producers was quantified by real-time PCR, and the diversity of both nosZ clades was determined by 454 pyrosequencing. Potential N2O production and potential denitrification activity were used to calculate the denitrification gaseous end-product ratio. Overall, the results showed limited differences between management practices but there were significant differences between cropping systems in both the abundance and structure of the nosZII community, as well as in the [rN2O/r(N2O+N2)] ratio. More limited differences were observed in the nosZI community, suggesting that the newly identified nosZII clade is more sensitive than nosZI to environmental changes. Potential denitrification activity and potential N2O production were explained mainly by the soil properties while the diversity of the nosZII clade on its own explained 26% of the denitrification end-product ratio, which highlights the importance of understanding the ecology of this newly identified clade of N2O reducers for mitigation strategies.

  13. Effect of soil saturation on denitrification in a grassland soil

    Directory of Open Access Journals (Sweden)

    L. M. Cardenas

    2017-10-01

    Full Text Available Nitrous oxide (N2O is of major importance as a greenhouse gas and precursor of ozone (O3 destruction in the stratosphere mostly produced in soils. The soil-emitted N2O is generally predominantly derived from denitrification and, to a smaller extent, nitrification, both processes controlled by environmental factors and their interactions, and are influenced by agricultural management. Soil water content expressed as water-filled pore space (WFPS is a major controlling factor of emissions and its interaction with compaction, has not been studied at the micropore scale. A laboratory incubation was carried out at different saturation levels for a grassland soil and emissions of N2O and N2 were measured as well as the isotopocules of N2O. We found that flux variability was larger in the less saturated soils probably due to nutrient distribution heterogeneity created from soil cracks and consequently nutrient hot spots. The results agreed with denitrification as the main source of fluxes at the highest saturations, but nitrification could have occurred at the lower saturation, even though moisture was still high (71 % WFSP. The isotopocules data indicated isotopic similarities in the wettest treatments vs. the two drier ones. The results agreed with previous findings where it is clear there are two N pools with different dynamics: added N producing intense denitrification vs. soil N resulting in less isotopic fractionation.

  14. Denitrification Potential, Root Biomass, and Organic Matter in Degraded and Restored Urban Riparian Zones

    Science.gov (United States)

    Hydrologic changes associated with urbanization often lead to lower water tables and drier, more aerobic soils in riparian zones. These changes reduce the potential for denitrification, an anaerobic microbial process that converts nitrate, a common water pollutant, into nitrogen...

  15. Compaction stimulates denitrification in an urban park soil using 15N tracing technique

    DEFF Research Database (Denmark)

    Li, Shun; Deng, Huan; Rensing, Christopher Günther T

    2014-01-01

    Soils in urban areas are subjected to compaction with accelerating urbanization. The effects of anthropogenic compaction on urban soil denitrification are largely unknown. We conducted a study on an urban park soil to investigate how compaction impacts denitrification. By using 15N labeling method...... and acetylene inhibition technique, we performed three coherent incubation experiments to quantify denitrification in compacted soil under both aerobic and anaerobic conditions. Uncompacted soil was set as the control treatment. When monitoring soil incubation without extra substrate, higher nitrous oxide (N2O......) flux and denitrification enzyme activity were observed in the compacted soil than in the uncompacted soil. In aerobic incubation with the addition of K15NO3, N2O production in the compacted soil reached 10.11 ng N h-1 g-1 as compared to 0.02 ng N h-1 g-1 in the uncompacted soil. Denitrification...

  16. Studies on yeasts and yeast-like microorganisms in the denitrification unit biocenosis

    Directory of Open Access Journals (Sweden)

    Elena Sláviková

    2014-08-01

    Full Text Available It was found that Candida famata, Hansenula californica and Rhodotorula rubra occurred in reactor UASB-type biocenosis in the course of denitrification carried out in the presence of lactic acid as a carbon source. The role of those species in nitrogen removal process was discussed with respect to their physiology.

  17. Denitrification of high strength nitrate waste from a nuclear industry using acclimatized biomass in a pilot scale reactor.

    Science.gov (United States)

    Dhamole, Pradip B; Nair, Rashmi R; D'Souza, Stanislaus F; Pandit, Aniruddha B; Lele, S S

    2015-01-01

    This work investigates the performance of acclimatized biomass for denitrification of high strength nitrate waste (10,000 mg/L NO3) from a nuclear industry in a continuous laboratory scale (32 L) and pilot scale reactor (330 L) operated over a period of 4 and 5 months, respectively. Effect of substrate fluctuations (mainly C/NO3-N) on denitrification was studied in a laboratory scale reactor. Incomplete denitrification (95-96 %) was observed at low C/NO3-N (≤2), whereas at high C/NO3-N (≥2.25) led to ammonia formation. Ammonia production increased from 1 to 9 % with an increase in C/NO3-N from 2.25 to 6. Complete denitrification and no ammonia formation were observed at an optimum C/NO3-N of 2.0. Microbiological studies showed decrease in denitrifiers and increase in nitrite-oxidizing bacteria and ammonia-oxidizing bacteria at high C/NO3-N (≥2.25). Pilot scale studies were carried out with optimum C/NO3-N, and sustainability of the process was checked on the pilot scale for 5 months.

  18. Nitric oxide in denitrification - an elusive signal molecule emitted from soil

    Science.gov (United States)

    Bakken, L. R.; Frostegard, A.

    2010-12-01

    Soils emit variable amounts of NO and N2O, with environmental consequences (atmosphere chemistry and global warming). Nitrification was for some time considered the main source of NO emission, but several investigations have indicated that denitrification may be a potent source as well. However, strong emission of NO from denitrifying organisms is in some conflict with common understanding of the role of NO in the regulation of denitrification, as based on paradigm model strains. NO appears to be an important signal molecule for denitrifying organisms by exerting a positive feedback on the expression of the genes coding for denitrification. On the other hand, a careful control of the NO concentrations at nanomolar concentrations has long been considered an essential fitness character for denitrifying organisms, since micromolar concentrations of NO is toxic to many organisms. For the same reason, organisms lacking genes encoding NO reductase (NOR) have been considered unfit for denitrification. This view is challenged by isolation of organisms whose primary product of denitrification is NO, either because they lack the genes for NO reductase, or because their synthesis of the denitrification proteome is extremely unbalanced, resulting in transient NO accumulation to micromolar concentrations when grown in pure culture. Such paralyzing NO concentrations are probably never reached in natural environments, however, due to diffusion and NO-absorption by adjacent organisms, be it by NOR or other NO scavenging enzymes. Hypothetically, the production of NO by denitrifying organisms may be an advantage by fending off nearby competitors. We have embarked on a comparative study of denitrification phenotypes regarding their denitrification gene expression and control of NO and N2O concentrations in response to anoxic spells. This includes model strains (Paracoccus denitrificans and Agrobacterium tumefaciens) and recently isolated strains within several genera. Some are found

  19. Development of a method for in situ measurement of denitrification in aquifers using 15N tracer tests and membrane inlet mass spectrometry

    Science.gov (United States)

    Eschenbach, W.; Well, R.; Flessa, H.; Walther, W.; Duijnisveld, W. H. M.

    2009-04-01

    In NO3- contaminated aquifers containing reduced compounds like organic carbon or sulfides, denitrification is an intense process. Its characterization is of interest because NO3- consump-tion improves water quality and N2O production can cause emission of this greenhouse gas to the atmosphere. Spatial distribution of NO3- and N2 produced by denitrification in groundwa-ter (excess N2) reflects the NO3- input as well as cumulative denitrification during aquifer pas-sage. Reaction progress (RP) at a given location, i.e. the relative consumption by denitrifica-tion of the NO3- that had been leached to the aquifers, characterizes the stage of the denitrifi-cation process. RP can be derived from the ratio between accumulated gaseous denitrification products and initial NO3- concentrations. The amount and spatial distribution of reduced com-pounds within denitrifying aquifers is not well known. Recent findings from parallel investi-gations on in situ denitrification and reactive compounds suggests that single-well 15N tracer tests might be suitable to characterize the stock of reduced compounds in aquifers (Konrad 2007). The overall objective of our studies is measure the spatial dynamics of denitrification within two sandy aquifers in northern Germany. This includes measurement of the actually occurring denitrification process. Moreover we want to determine the long-term denitrification potential which is governed by the stock of reactive material. Here we present a new approach for in situ-measurement of denitrification at monitoring wells using a combination of 15N-tracer push-pull experiments with in situ analysis of 15N-labled N2 and N2O using membrane inlet mass spectrometry (MIMS). We will present first results from a laboratory test with aquifer mesocosms using the MIMS method. In this test we supplemented aquifer material of two depths (2 and 7 m below surface) of a drinking water catchment in Northwest Germany with K15NO3 solution. After tracer application we

  20. Heterotrophic nitrification and aerobic denitrification bacterium ...

    African Journals Online (AJOL)

    Jane

    2011-07-18

    Jul 18, 2011 ... nutrient agar plates 3 times from the enrichment liquid medium. The isolates ..... growing in the logarithmic phase, the decomposition rate was higher than .... denitrification in bench-scale sequencing batch reactors. Water Res.

  1. Assessment of denitrification gaseous end-products in the soil profile under two water table management practices using repeated measures analysis.

    Science.gov (United States)

    Elmi, Abdirashid A; Astatkie, Tess; Madramootoo, Chandra; Gordon, Robert; Burton, David

    2005-01-01

    The denitrification process and nitrous oxide (N2O) production in the soil profile are poorly documented because most research into denitrification has concentrated on the upper soil layer (0-0.15 m). This study, undertaken during the 1999 and 2000 growing seasons, was designed to examine the effects of water table management (WTM), nitrogen (N) application rate, and depth (0.15, 0.30, and 0.45 m) on soil denitrification end-products (N2O and N2) from a corn (Zea mays L.) field. Water table management treatments were free drainage (FD) with open drains and subirrigation (SI) with a target water table depth of 0.6 m. Fertility treatments (ammonium nitrate) were 120 kg N ha(-1) (N120) and 200 kg N ha(-1) (N200). During both growing seasons greater denitrification rates were measured in SI than in FD, particularly in the surface soil (0-0.15 m) and at the intermediate (0.15-0.30 m) soil depths under N200 treatment. Greater denitrification rates under the SI treatment, however, were not accompanied with greater N2O production. The decrease in N2O production under SI was probably caused by a more complete reduction of N2O to N2, which resulted in lower N2O to (N2O + N2) ratios. Denitrification rate, N2O production and N2O to (N2O + N2) ratios were only minimally affected by N treatments, irrespective of sampling date and soil depth. Overall, half of the denitrification occurred at the 0.15- to 0.30- and 0.30- to 0.45-m soil layers, and under SI, regardless of fertility treatment level. Consequently, sampling of the 0- to 0.15-m soil layer alone may not give an accurate estimation of denitrification losses under SI practice.

  2. Simulation of three-phase fluidized bioreactors for denitrification

    International Nuclear Information System (INIS)

    Hamza, A.V.; Dolan, J.F.; Wong, E.W.

    1981-03-01

    Fluidized-bed bioreactors were developed and operated at three scales (diameters of 0.1, 0.2, and 0.5 m) by the Chemical Technology Division. The performance of these reactors in denitrification was simulated using the following modified form of Monod kinetics to describe the reaction kinetics: rate = V/sub max/ (NO 3 - /K/sub s/ + NO 3 - ) (% biomass). In the fluids-movement portion of the simulation the tanks-in-series approximation to backmixing was used. This approach yielded a V/sub max/ of 3.5 g/m 3 -min (% biomass) and a K/sub s/ of 163 g/m 3 for the 0.5-m bioreactor. Values of V/sub max/ and K/sub s/ were also determined for data derived from the 0.1-m bioreactor, but inadequate RTD data reduced the confidence level in these results. A complication in denitrification is the multi-step nature of the reduction from nitrate to nitrite to hyponitrite and finally to nitrogen. An experimental study of the effect of biomass loading upon denitrification was begun. It is recommended that the experimental work be continued

  3. Denitrification in the Arabian Sea: A 3D ecosystem modelling study

    Science.gov (United States)

    Anderson, Thomas R.; Ryabchenko, Vladimir A.; Fasham, Michael J. R.; Gorchakov, Victor A.

    2007-12-01

    A three-dimensional hydrodynamic-ecosystem model was used to examine the factors determining the spatio-temporal distribution of denitrification in the Arabian Sea. The ecosystem model includes carbon and nitrogen as currencies, cycling of organic matter via detritus and dissolved organic matter, and both remineralization and denitrification as sinks for material exported below the euphotic zone. Model results captured the marked seasonality in plankton dynamics of the region, with characteristic blooms of chlorophyll in the coastal upwelling regions and central Arabian Sea during the southwest monsoon, and also in the northern Arabian Sea during the northeast monsoon as the mixed layer shoals. Predicted denitrification was 26.2 Tg N yr -1,the greatest seasonal contribution being during the northeast monsoon when primary production is co-located with the zone of anoxia. Detritus was the primary organic substrate consumed in denitrification (97%), with a small (3%) contribution by dissolved organic matter. Denitrification in the oxygen minimum zone was predicted to be fuelled almost entirely by organic matter supplied by particles sinking vertically from the euphotic zone above (0.73 mmol N m -2 d -1) rather than from lateral transport of organic matter from elsewhere in the Arabian Sea (less than 0.01 mmol N m -2 d -1). Analysis of the carbon budget in the zone of denitrification (north of 10°N and east of 55°E) indicates that the modelled vertical export flux of detritus, which is similar in magnitude to estimates from field data based on the 234Th method, is sufficient to account for measured bacterial production below the euphotic zone in the Arabian Sea.

  4. Report on Influence of Physical and Biological Soil Processes on NO3- Fertilizer

    International Nuclear Information System (INIS)

    Rolston, D.E.

    1981-01-01

    Denitrification of nitrate (NO 3 - ) fertilizer was simulated using a mathematical model. The rate of denitrification was considered to be a function of NO 3 - concentration, available carbon (C) concentration, degree of soil-water saturation, and temperature. Available C concentrations were calculated from initial amounts of soil C and additions of plant residues or animal manure. The consumption of added C in the soil system was assumed to occur in 2 or 3 stages with different rate constants for each stage and C source. A Q 10 value of 2 was used in correcting denitrification rate constants and C consumption constants at two temperatures. Model simulations for denitrification were compared with measured N 2 and N 2 O gas fluxes during nitrate leaching in field plots of Yolo soil at different soil-water content, C additions, soil temperature, and irrigation frequencies

  5. Denitrification and Ecosystem Services: Mapping and Modeling Conservation Effects

    Science.gov (United States)

    Morris, C. K.; Walter, T.

    2012-12-01

    Precision conservation is the latest effort to increase higher efficiency in agricultural best management practices by considering the spatial and temporal variability in agroecosystems. The authors have developed a framework for incorporating the ecosystem service of denitrification into an existing precision conservation mapping tool. The model identifies areas of denitirification and quantifies potential denitrification when a conservation practice is adopted. The methodology is being tested in a small subwatershed in the Upper Susquehanna Basin of New York State.

  6. Marine denitrification rates determined from a global 3-D inverse model

    Directory of Open Access Journals (Sweden)

    T. DeVries

    2013-04-01

    Full Text Available A major impediment to understanding long-term changes in the marine nitrogen (N cycle is the persistent uncertainty about the rates, distribution, and sensitivity of its largest fluxes in the modern ocean. We use a global ocean circulation model to obtain the first 3-D estimate of marine denitrification rates that is maximally consistent with available observations of nitrate deficits and the nitrogen isotopic ratio of oceanic nitrate. We find a global rate of marine denitrification in suboxic waters and sediments of 120–240 Tg N yr−1, which is lower than many other recent estimates. The difference stems from the ability to represent the 3-D spatial structure of suboxic zones, where denitrification rates of 50–77 Tg N yr−1 result in up to 50% depletion of nitrate. This depletion reduces the effect of local isotopic enrichment on the rest of the ocean, allowing the N isotope ratio of oceanic nitrate to be achieved with a sedimentary denitrification rate about 1.3–2.3 times that of suboxic zones. This balance of N losses between sediments and suboxic zones is shown to obey a simple relationship between isotope fractionation and the degree of nitrate consumption in the core of the suboxic zones. The global denitrification rates derived here suggest that the marine nitrogen budget is likely close to balanced.

  7. Glacial-interglacial changes and Holocene variations in Arabian Sea denitrification

    Science.gov (United States)

    Gaye, Birgit; Böll, Anna; Segschneider, Joachim; Burdanowitz, Nicole; Emeis, Kay-Christian; Ramaswamy, Venkitasubramani; Lahajnar, Niko; Lückge, Andreas; Rixen, Tim

    2018-01-01

    At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ) at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which is contrary to the trend in the other two regions of water column denitrification in the eastern tropical North and South Pacific. We calculated composite sea surface temperature (SST) and δ15N ratios in time slices of 1000 years of the last 25 kyr to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. Low δ15N values of 4-7 ‰ during the last glacial maximum (LGM) and stadials (Younger Dryas and Heinrich events) suggest that denitrification was inactive or weak during Pleistocene cold phases, while warm interstadials (ISs) had elevated δ15N. Fast changes in upwelling intensities and OMZ ventilation from the Antarctic were responsible for these strong millennial-scale variations during the glacial. During the entire Holocene δ15N values > 6 ‰ indicate a relatively stable OMZ with enhanced denitrification. The OMZ develops parallel to the strengthening of the SW monsoon and monsoonal upwelling after the LGM. Despite the relatively stable climatic conditions of the Holocene, the δ15N records show regionally different trends in the Arabian Sea. In the upwelling areas in the western part of the basin, δ15N values are lower during the mid-Holocene (4.2-8.2 ka BP) compared to the late Holocene ( ventilation of the OMZ during the period of the most intense southwest monsoonal upwelling. In contrast, δ15N values in the northern and eastern Arabian Sea rose during the last 8 kyr. The displacement of the core of the OMZ from the region of maximum productivity in the western Arabian Sea to its present position in the northeast was established during the middle and late Holocene. This was

  8. Glacial–interglacial changes and Holocene variations in Arabian Sea denitrification

    Directory of Open Access Journals (Sweden)

    B. Gaye

    2018-01-01

    Full Text Available At present, the Arabian Sea has a permanent oxygen minimum zone (OMZ at water depths between about 100 and 1200 m. Active denitrification in the upper part of the OMZ is recorded by enhanced δ15N values in the sediments. Sediment cores show a δ15N increase during the middle and late Holocene, which is contrary to the trend in the other two regions of water column denitrification in the eastern tropical North and South Pacific. We calculated composite sea surface temperature (SST and δ15N ratios in time slices of 1000 years of the last 25 kyr to better understand the reasons for the establishment of the Arabian Sea OMZ and its response to changes in the Asian monsoon system. Low δ15N values of 4–7 ‰ during the last glacial maximum (LGM and stadials (Younger Dryas and Heinrich events suggest that denitrification was inactive or weak during Pleistocene cold phases, while warm interstadials (ISs had elevated δ15N. Fast changes in upwelling intensities and OMZ ventilation from the Antarctic were responsible for these strong millennial-scale variations during the glacial. During the entire Holocene δ15N values  >  6 ‰ indicate a relatively stable OMZ with enhanced denitrification. The OMZ develops parallel to the strengthening of the SW monsoon and monsoonal upwelling after the LGM. Despite the relatively stable climatic conditions of the Holocene, the δ15N records show regionally different trends in the Arabian Sea. In the upwelling areas in the western part of the basin, δ15N values are lower during the mid-Holocene (4.2–8.2 ka BP compared to the late Holocene ( <  4.2 ka BP due to stronger ventilation of the OMZ during the period of the most intense southwest monsoonal upwelling. In contrast, δ15N values in the northern and eastern Arabian Sea rose during the last 8 kyr. The displacement of the core of the OMZ from the region of maximum productivity in the western Arabian Sea to its present position

  9. The effect of floating vegetation on denitrification and greenhouse gas production in wetland mesocosms

    Science.gov (United States)

    Jacobs, A. E.; Harrison, J. A.

    2012-12-01

    Anthropogenic intensification of nitrogen (N) loading to aquatic ecosystems is widespread and can lead to the degradation of these systems. Wetlands are important sites for N removal via denitrification, the microbially mediated reduction of reactive nitrate to inert N2 gas, but they can also produce high levels of greenhouse gases. Floating plants play an important role in encouraging denitrification, since they create low oxygen conditions that may favor denitrification. We investigated whether wetland sediments with floating plant cover had higher denitrification and greenhouse gas production rates than wetland sediments without floating plants. Replicate flow-through mesocosms with wetland sediment and water were constructed in a growth chamber to mimic the wetland where the sediment and water were collected. Mesocosm treatments were covered with floating vegetation (duckweed), an opaque tarp, or no cover to determine how cover type affects denitrification and greenhouse gas production and whether biotic or abiotic factors are likely responsible for observed differences. Denitrification and greenhouse gas production rates were calculated by measuring excess N2 gas, methane, and nitrous oxide concentrations in the water column and measuring the gas exchange rates between the water column and the atmosphere. Gas exchange rates were measured using an inert volatile tracer added to the water column and accumulation of gas in the mesocosm headspace. Additional mesocosm experiments were performed to determine how duckweed-dominated wetland systems respond to nitrogen loading and which mechanism for lowering dissolved oxygen concentrations is important in affecting denitrification under floating vegetation. Mesocosms with floating vegetation had lower dissolved oxygen than no cover or tarp-covered mesocosms, which is consistent with field and literature observations. Water flowing out of the mesocosms had statistically lower total nitrogen and nitrate concentrations

  10. Effect of Temperature on Oxygen Profiles and Denitrification Rates in Freshwater Sediments

    NARCIS (Netherlands)

    Klein, de Jeroen J.M.; Overbeek, Ciska C.; Juncher Jørgensen, Christian

    2017-01-01

    Vegetated ditches and wetlands are important sites for nutrient removal in agricultural catchments. About half of the influx of inorganic nitrogen can be removed from these ecosystems by denitrification. Previous studies have shown that denitrification in aquatic ecosystems is strongly temperature

  11. Transport zonation limits coupled nitrification-denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Kessler, Adam John; Glud, R.N.; Cardenas, M.B.

    2013-01-01

    - and N-15-N-2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N-2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification......-denitrification is severely limited in permeable sediments because the flow and transport field limits interaction between oxic and anoxic pore water. The approach allowed for new detailed insight into subsurface denitrification zones in complex permeable sediments....

  12. Copepod carcasses as microbial hot spots for pelagic denitrification

    DEFF Research Database (Denmark)

    Glud, Ronnie N.; Grossart, Hans-Peter; Larsen, Morten

    2015-01-01

    Copepods are exposed to a high non-predatory mortality and their decomposing carcasses act as microniches with intensified microbial activity. Sinking carcasses could thereby represent anoxic microenvironment sustaining anaerobic microbial pathways in otherwise oxic water columns. Using non...... investigated carcass samples and thereby documented the potential for microbial denitrification in carcasses. The nirS gene was occasionally expressed in live copepods, but not as consistently as in carcasses. Incubations of sinking carcasses in 15NO2 3 amended seawater demonstrated denitrification, of which...

  13. Impact of direct greenhouse gas emissions on the carbon footprint of water reclamation processes employing nitrification–denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Andrew G., E-mail: andrew.schneider@yale.edu [University of Cincinnati, Department of Geology, Cincinnati, OH 45221 (United States); Townsend-Small, Amy [University of Cincinnati, Department of Geology, Cincinnati, OH 45221 (United States); University of Cincinnati, Department of Geography, Cincinnati, OH 45221 (United States); Rosso, Diego [Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175 (United States)

    2015-02-01

    Water reclamation has the potential to reduce water supply demands from aquifers and more energy-intensive water production methods (e.g., seawater desalination). However, water reclamation via biological nitrification–denitrification is also associated with the direct emission of the greenhouse gases (GHGs) CO{sub 2}, N{sub 2}O, and CH{sub 4}. We quantified these direct emissions from the nitrification–denitrification reactors of a water reclamation plant in Southern California, and measured the {sup 14}C content of the CO{sub 2} to distinguish between short- and long-lived carbon. The total emissions were 1.5 (± 0.2) g-fossil CO{sub 2} m{sup −3} of wastewater treated, 0.5 (± 0.1) g-CO{sub 2}-eq of CH{sub 4} m{sup −3}, and 1.8 (± 0.5) g-CO{sub 2}-eq of N{sub 2}O m{sup −3}, for a total of 3.9 (± 0.5) g-CO{sub 2}-eq m{sup −3}. This demonstrated that water reclamation can be a source of GHGs from long lived carbon, and thus a candidate for GHG reduction credit. From the {sup 14}C measurements, we found that between 11.4% and 15.1% of the CO{sub 2} directly emitted was derived from fossil sources, which challenges past assumptions that the direct CO{sub 2} emissions from water reclamation contain only modern carbon. A comparison of our direct emission measurements with estimates of indirect emissions from several water production methods, however, showed that the direct emissions from water reclamation constitute only a small fraction of the plant's total GHG footprint. - Highlights: • Direct greenhouse gas emissions were measured at a wastewater reclamation plant. • These greenhouse gas emissions amounted to 3.9 (± 0.5) g-CO{sub 2}-eq m{sup −3} of wastewater. • {sup 14}C analysis of the CO{sub 2} emissions was conducted to determine the fossil component. • 11.4% to 15.1% of the emitted CO{sub 2} was derived from fossil sources.

  14. Simultaneous denitrification and phosphorus removal by Agrobacterium sp. LAD9 under varying oxygen concentration.

    Science.gov (United States)

    Ma, Tao; Chen, Qian; Gui, Mengyao; Li, Can; Ni, Jinren

    2016-04-01

    Although efficient aerobic denitrification has received increasing attention, few studies have been made on simultaneous denitrification and phosphorus removal (SDPR) under aerobic condition. In this study, SDPR by an efficient aerobic denitrifier, Agrobacterium sp. LAD9, was firstly demonstrated. High nitrate and phosphorus removal rates of 7.50 and 1.02 mg L(-1) h(-1) were achieved in wide range of O2 concentration from 5.92 to 20.02 mg L(-1). The N2O production would be inhibited as O2 concentration exceeded 11.06 mg L(-1), while the phosphorus removal efficiency would be generally improved with increasing O2 concentration. (15)N mass spectrometry revealed that nitrogen removal accorded with the typical aerobic denitrification pathway, while (31)P nuclear magnetic resonance spectroscopy ((31)P NMR) indicated the fate of phosphorus to cells, extracellular polymeric substances (EPS), and polyphosphate (poly-P) of the denitrifier. EPS acted as a reservoir of phosphorus and the transformation of poly-P was dynamic and depended on initial orthophosphate (ortho-P) content. The aerobic SDPR would greatly simplify the conventional wastewater treatment processes which required separated considerations of nitrogen and phosphorus removal.

  15. Modeling nitrous oxide production and reduction in soil through explicit representation of denitrification enzyme kinetics.

    Science.gov (United States)

    Zheng, Jianqiu; Doskey, Paul V

    2015-02-17

    An enzyme-explicit denitrification model with representations for pre- and de novo synthesized enzymes was developed to improve predictions of nitrous oxide (N2O) accumulations in soil and emissions from the surface. The metabolic model of denitrification is based on dual-substrate utilization and Monod growth kinetics. Enzyme synthesis/activation was incorporated into each sequential reduction step of denitrification to regulate dynamics of the denitrifier population and the active enzyme pool, which controlled the rate function. Parameterizations were developed from observations of the dynamics of N2O production and reduction in soil incubation experiments. The model successfully reproduced the dynamics of N2O and N2 accumulation in the incubations and revealed an important regulatory effect of denitrification enzyme kinetics on the accumulation of denitrification products. Pre-synthesized denitrification enzymes contributed 20, 13, 43, and 62% of N2O that accumulated in 48 h incubations of soil collected from depths of 0-5, 5-10, 10-15, and 15-25 cm, respectively. An enzyme activity function (E) was defined to estimate the relative concentration of active enzymes and variation in response to environmental conditions. The value of E allows for activities of pre-synthesized denitrification enzymes to be differentiated from de novo synthesized enzymes. Incorporating explicit representations of denitrification enzyme kinetics into biogeochemical models is a promising approach for accurately simulating dynamics of the production and reduction of N2O in soils.

  16. Relationships Between Denitrifier Abundance, Denitrifier Diversity and Denitrification in Gulf of Mexico Hypoxic Zone Sediments.

    Science.gov (United States)

    Proctor, L. M.; Childs, C.; MacAuley, S.

    2002-12-01

    The largest zone of anthropogenic bottom water hypoxia in the Western Hemisphere occurs seasonally in the northern Gulf of Mexico. This hypoxic zone reaches its greatest extent in the summer months and is a consequence of seasonal stratification of the water column combined with the decomposition of organic matter derived from accelerated rates of primary production. The enhanced primary production is driven by inorganic nitrogen input from the Mississippi River and these conditions would seem ideal for supporting high levels of denitrification. Yet sediment denitrification exhibited a wide range, even at the height of the seasonal hypoxia. Therefore, we compared benthic denitrifier abundances and denitrifier diversity at several stations over two seasons exhibiting extremes in denitrification to evaluate the relationship between abundances, diversity and denitrification levels. Sediment denitrification ranged from 20 to 100 umol m-2 h-1, with rates in July, 2000 approximately half that observed in July, 2001. The highest rates were generally observed at stations with bottom water DO concentrations between 1 and 3 mg l-1. Relative denitrifier abundances, using nirS and nirK as proxies for denitrifiers, suggested a direct relationship between abundances and denitrification while denitrifier diversity, measured by T-RFLPs of nirS and nirK, suggested an inverse relationship between diversity and denitrification. These results suggest that several factors are important in understanding what controls denitrification in Gulf of Mexico hypoxic zone sediments.

  17. Glacial-Holocene variability in pelagic denitrification and OMZ intensity along the NW Mexican Margin

    Science.gov (United States)

    Ontiveros Cuadras, J. F.; Thunell, R.; Ruiz-Fernandez, A. C.; Machain-Castillo, M. L.; Tappa, E.

    2017-12-01

    Denitrification of fixed nitrogen represents a substantial loss of bioavailable nitrogen from the ocean, thus playing a major role in the global nitrogen cycle. Water-column (pelagic) denitrification occurs mostly in the oxygen minimum zones (OMZs), which are situated beneath coastal upwelling areas that are characterized by high settling fluxes of organic detritus and high rates of oxygen utilization from remineralization. Our study uses biogenic components (total organic carbon and opal) and δ15N values of sediments from the NW Mexican Margin to reconstruct variations in denitrification and strength of the OMZ in the eastern tropical North Pacific (ETNP) for the last 36,000 years. During the last glacial period (LGM, 23-18 kyr) the associations between relatively low δ15N values (7-8‰) and low TOC (2-4%) and opal (1-4%) content indicates reduced denitrification due to reduced upwelling and decreased flux of organic matter through the OMZ. This was followed by abrupt acceleration of water-column denitrification (δ15N, 7-10‰) and the strengthening of the OMZ during the latter half of Heinrich Stadial 1 (HS1; 18-14.7 kyr). However, the biogenic component of sediments deposited during HS1 do not increase appreciably, suggesting that the increase in denitrification was not driven by an increase in productivity. Furthermore, the increase in δ15N precedes the deglacial decrease in planktonic foraminiferal δ18O which mostly occurs during the Bolling Alerod (14.7-12.9 kyr). This suggests that the increase in denitrification was not a response to surface warming. Rather, we attribute the rapid increase in denitrification during HS1 to reduced ventilation of the ETNP OMZ. Following the peak in denitrification at the end of HS1, we observe a small but steady decline in δ15N over the last 15 kyr. Higher TOC in Holocene sediments relative to glacial sediments suggests that increased productivity has played a role in maintaining a strong OMZ throughout the Holocene.

  18. Evaluation and adjustment of description of denitrification in the DailyDayCent and COUP models based on N2 and N2O laboratory incubation system measurements

    Science.gov (United States)

    Grosz, Balázs; Well, Reinhard; Dannenmann, Michael; Dechow, René; Kitzler, Barbara; Michel, Kerstin; Reent Köster, Jan

    2017-04-01

    Denitrification is an anaerobic key process by microbes where the NO3- is step-by-step reduced and emitted as NO, N2O and finally N2 gas from the soil. The accurate knowledge of the reduction of nitrate (NO3-) and nitrite (NO2-) to N2O and molecular N2 is important because the N2O fraction is further reduced to N2 and constitutes the main emission source of this greenhouse gas from agricultural soils. Hence, our understanding and ability to quantify soil denitrification is crucial for mitigating nitrogen fertilizer loss as well as for reducing N2O emissions. Models can be an important tool to predict mitigation effects and help to develop climate smart mitigation strategies. Ideally, commonly used biogeochemical models could provide adequate predictions of denitrification processes of agricultural soils but often simplified process descriptions and inadequate model parameters prevent models from simulating adequate fluxes of N2 and N2O on field scale. Model development and parametrization often suffers from limited availability of empirical data describing denitrification processes in agricultural soils. While in many studies N2O emissions are used to develop and train models, detailed measurements on NO, N2O, N2 fluxes and concentrations and related soil conditions are necessary to develop and test adequate model algorithms. Composition of denitrifying communities, coinciding effects of management and local conditions on the development of denitrification hotspots are highly variable in space and time. To address this issue the coordinated research unit „Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM)" was initiated to more closely investigate N-fluxes caused by denitrification in response to environmental effects, soil properties and microbial communities. Data suitable to validate denitrification models are still scarce due to previous technical and/or methodical limitations of measuring N2 fluxes, but large

  19. Irrigation of DOC-rich liquid promotes potential denitrification rate and decreases N

    NARCIS (Netherlands)

    Qin, Shuping; Hu, Chunsheng; Clough, Tim J.; Luo, Jiafa; Oenema, Oene; Zhou, Shungui

    2017-01-01

    Lack of dissolved organic carbon (DOC) is generally one of the key factors limiting denitrification in subsoil beneath the root zone. Despite a number of laboratory DOC amendment studies, the effects of in situ DOC infiltration on subsoil denitrification, and on subsequent end product

  20. Cause analysis and suggestion of urea consumption in denitrification system of coal-fired power plant

    Science.gov (United States)

    Zhang, Xueying; Dong, Ruifeng; Guo, Yang; Wang, Fangfang; Yang, Shuo

    2018-02-01

    In the daily operation of many power plants, the urea consumption of denitration system is much more than normal. Therefore, the process of site testing and laboratory analysis are carried out. Several suggestions are given out. (1) The position of sampling hole on the exit flue of denitrification system should be redesigned. (2) The denitrification optimization and adjustment should be carried out based on the technical specifications for the operation system. (3) The flue gas CEMS system for single point sampling should be transformed into two or three point sampling mode. (4) When the coal - fired unit is shutting down, examine the ammonia injection and nozzle branch, in order to improve the operation reliability of denitration system.

  1. [Numerical simulation and operation optimization of biological filter].

    Science.gov (United States)

    Zou, Zong-Sen; Shi, Han-Chang; Chen, Xiang-Qiang; Xie, Xiao-Qing

    2014-12-01

    BioWin software and two sensitivity analysis methods were used to simulate the Denitrification Biological Filter (DNBF) + Biological Aerated Filter (BAF) process in Yuandang Wastewater Treatment Plant. Based on the BioWin model of DNBF + BAF process, the operation data of September 2013 were used for sensitivity analysis and model calibration, and the operation data of October 2013 were used for model validation. The results indicated that the calibrated model could accurately simulate practical DNBF + BAF processes, and the most sensitive parameters were the parameters related to biofilm, OHOs and aeration. After the validation and calibration of model, it was used for process optimization with simulating operation results under different conditions. The results showed that, the best operation condition for discharge standard B was: reflux ratio = 50%, ceasing methanol addition, influent C/N = 4.43; while the best operation condition for discharge standard A was: reflux ratio = 50%, influent COD = 155 mg x L(-1) after methanol addition, influent C/N = 5.10.

  2. Denitrification in the water column of the central Baltic Sea

    DEFF Research Database (Denmark)

    Dalsgaard, Tage; De Brabandere, Loreto; Hall, Per

    2013-01-01

    denitrification ranged from 0.24 to 15.9 nM N2 h−1. Assuming that these rates were valid throughout the anoxic View the MathML source containing zone, depth integrated in situ denitrification rates of 0.06–2.11 mmol N m−2 d−1 were estimated. The thickness of this zone was generally 3–6 m, which is probably what...... View the MathML source or sulfide concentrations were converted to in situ rates using the measured water column concentrations of View the MathML source and sulfide and the actual measured relations between View the MathML source and sulfide concentrations and denitrification rates. In situ...... can be maintained through regular turbulent mixing induced by internal waves at the oxic–anoxic interface. However, layers of up to 55 m thickness with low O2 water (Math...

  3. Novel MBR_based main stream biological nutrient removal process: high performance and microbial community.

    Science.gov (United States)

    Zhang, Chuanyi; Xu, Xinhai; Zhao, Kuixia; Tang, Lianggang; Zou, Siqi; Yuan, Limei

    2018-02-01

    For municipal wastewater treatment, main stream biological nutrient removal (BNR) process is becoming more and more important. This lab-scale study, novel MBR_based BNR processes (named A 2 N-MBR and A 2 NO-MBR) were built. Comparison of the COD removal, results obtained demonstrated that COD removal efficiencies were almost the same in three processes, with effluent concentration all bellowed 30 mg L -1 . However, the two-sludge systems (A 2 N-MBR and A 2 NO-MBR) had an obvious advantage over the A 2 /O for denitrification and phosphorus removal, with the average TP removal rates of 91.20, 98.05% and TN removal rates of 73.00, 79.49%, respectively, higher than that of 86.45 and 61.60% in A 2 /O process. Illumina Miseq sequencing revealed that Candidatus_Accumulibacter, which is capable of using nitrate as an electron acceptor for phosphorus and nitrogen removal simultaneously, was the dominant phylum in both A 2 N-MBR and A 2 NO-MBR process, accounting for 28.74 and 23.98%, respectively. Distinguishingly, major organism groups related to nitrogen and phosphorus removal in A 2 /O system were Anaerolineaceae_uncultured, Saprospiraceae_uncultured and Thauera, with proportions of 11.31, 8.56 and 5.00%, respectively. Hence, the diversity of dominant PAOs group was likely responsible for the difference in nitrogen and phosphorus removal in the three processes.

  4. Orbital-scale denitrification changes in the Eastern Arabian Sea during the last 800 kyrs.

    Science.gov (United States)

    Kim, Ji-Eun; Khim, Boo-Keun; Ikehara, Minoru; Lee, Jongmin

    2018-05-04

    Denitrification in the Arabian Sea is closely related to the monsoon-induced upwelling and subsequent phytoplankton production in the surface water. The δ 15 N values of bulk sediments collected at Site U1456 of the International Ocean Discovery Program (IODP) Expedition 355 reveal the orbital-scale denitrification history in response to the Indian Monsoon. Age reconstruction based on the correlation of planktonic foraminifera (Globigerinoides ruber) δ 18 O values with the LR04 stack together with the shipboard biostratigraphic and paleomagnetic data assigns the study interval to be 1.2 Ma. Comparison of δ 15 N values during the last 800 kyrs between Site U1456 (Eastern Arabian Sea) and Site 722B (Western Arabian Sea) showed that δ 15 N values were high during interglacial periods, indicating intensified denitrification, while the opposite was observed during glacial periods. Taking 6‰ as the empirical threshold of denitrification, the Eastern Arabian Sea has experienced a persistent oxygen minimum zone (OMZ) to maintain strong denitrification whereas the Western Arabian Sea has undergone OMZ breakdown during some glacial periods. The results of this study also suggests that five principal oceanographic conditions were changed in response to the Indian Monsoon following the interglacial and glacial cycles, which controls the degree of denitrification in the Arabian Sea.

  5. Isotopologue fractionation during N(2)O production by fungal denitrification.

    Science.gov (United States)

    Sutka, Robin L; Adams, Gerard C; Ostrom, Nathaniel E; Ostrom, Peggy H

    2008-12-01

    Identifying the importance of fungi to nitrous oxide (N2O) production requires a non-intrusive method for differentiating between fungal and bacterial N2O production such as natural abundance stable isotopes. We compare the isotopologue composition of N2O produced during nitrite reduction by the fungal denitrifiers Fusarium oxysporum and Cylindrocarpon tonkinense with published data for N2O production during bacterial nitrification and denitrification. The fractionation factors for bulk nitrogen isotope values for fungal denitrification were in the range -74.7 to -6.6 per thousand. There was an inverse relationship between the absolute value of the fractionation factors and the reaction rate constant. We interpret this in terms of variation in the relative importance of the rate constants for diffusion and enzymatic reduction in controlling the net isotope effect for N2O production during fungal denitrification. Over the course of nitrite reduction, the delta(18)O values for N2O remained constant and did not exhibit a relationship with the concentration characteristic of an isotope effect. This probably reflects isotopic exchange with water. Similar to the delta(18)O data, the site preference (SP; the difference in delta(15)N between the central and outer N atoms in N2O) was unrelated to concentration during nitrite reduction and, therefore, has the potential to act as a conservative tracer of production from fungal denitrification. The SP values of N2O produced by F. oxysporum and C. tonkinense were 37.1 +/- 2.5 per thousand and 36.9 +/- 2.8 per thousand, respectively. These SP values are similar to those obtained in pure culture studies of bacterial nitrification but quite distinct from SP values for bacterial denitrification. The large magnitude of the bulk nitrogen isotope fractionation and the delta(18)O values associated with fungal denitrification are distinct from bacterial production pathways; thus multiple isotopologue data holds much promise for

  6. Microbially induced carbonate precipitation (MICP) by denitrification as ground improvement method - Process control in sand column experiments

    Science.gov (United States)

    Pham, Vinh; van Paassen, Leon; Nakano, Akiko; Kanayama, Motohei; Heimovaara, Timo

    2013-04-01

    Calcite precipitation induced by microbes has been proven to be efficient in stabilizing granular soils, especially with urea hydrolysis, as it has been successfully demonstrated in a pilot application 2010. However, as a byproduct highly concentrated ammonium chloride (NH4Cl) solution is produced, which has to be removed and disposed and forms a significant disadvantage of the technique that makes an alternative process like denitrification preferred. The proof of principle of microbially induced calcite precipitation (MICP) by denitrification has been demonstrated by Van Paassen et al (2010) who suggested that instead of producing waste as a byproduct, different pre-treated waste streams could be used as substrates for in situ growth of denitrifying bacteria and simultaneous cementation without producing waste to be removed. In this study sand column experiments are performed in which calcium carbonate was successfully precipitated by indigenous denitrifying micro-organisms, which were supplied weekly with a pulse of a substrate solution containing calcium acetate and calcium nitrate. Besides the production of calcite and the growth of bacteria in biofilms, the reduction of nitrate resulted in the production of (nitrogen) gas. It was observed that this gas partly fills up the pore space and consequently contributed to a reduction of the permeability of the treated sand. The presence of gas in the pore space affected the flow of the injected substrates and influenced to the distribution of calcium carbonate. The effect of the mean particle size (D50) on the flow and transport of solutes and gas in the porous media has been evaluated by treating several columns with varying grain size distribution and comparing the change in permeability after each incubation period and analyzing the distribution of the gas throughout the columns using X-ray computed tomography (CT) scanning. The present results show that there is a considerable decrease of permeability - a

  7. Optimization aspects of the biological nitrogen removal process in a full-scale twin sequencing batch reactor (SBR) system in series treating landfill leachate.

    Science.gov (United States)

    Remmas, Nikolaos; Ntougias, Spyridon; Chatzopoulou, Marianna; Melidis, Paraschos

    2018-03-29

    Despite the fact that biological nitrogen removal (BNR) process has been studied in detail in laboratory- and pilot-scale sequencing batch reactor (SBR) systems treating landfill leachate, a limited number of research works have been performed in full-scale SBR plants regarding nitrification and denitrification. In the current study, a full-scale twin SBR system in series of 700 m 3 (350 m 3 each) treating medium-age landfill leachate was evaluated in terms of its carbon and nitrogen removal efficiency in the absence and presence of external carbon source, i.e., glycerol from biodiesel production. Both biodegradable organic carbon and ammonia were highly oxidized [biochemical oxygen demand (BOD 5 ) and total Kjehldahl nitrogen (TKN) removal efficiencies above 90%], whereas chemical oxygen demand (COD) removal efficiency was slightly above 40%, which is within the range reported in the literature for pilot-scale SBRs. As the consequence of the high recalcitrant organic fraction of the landfill leachate, dissimilatory nitrate reduction was restricted in the absence of crude glycerol, although denitrification was improved by electron donor addition, resulting in TN removal efficiencies above 70%. Experimental data revealed that the second SBR negligibly contributed to BNR process, since carbon and ammonia oxidation completion was achieved in the first SBR. On the other hand, the low VSS/SS ratio, due to the lack of primary sedimentation, highly improved sludge settleability, resulting in sludge volume indices (SVI) below 30 mL g -1 .

  8. Field tracer test for denitrification in a pyrite-bearing schist aquifer

    International Nuclear Information System (INIS)

    Pauwels, H.; Kloppmann, W.; Foucher, J.-C.; Martelat, A.; Fritsche, V.

    1998-01-01

    A small-scale artificial tracer test performed on a schist aquifer in Brittany has helped clarify mechanisms and kinetics of in situ autotrophic denitrification. NO 3 was injected as a pulse simultaneously with a conservative tracer - Br - . During the test, which lasted 210 h, 73% of the injected Br - was recovered, as against only 47% of the NO 3 . The 26% difference in the recovery of the two injected species is interpreted as being the result of denitrification, in part due to the direct oxidation of pyrite present in the solid aquifer according to the reaction: 5FeS 2 +14NO 3 - +4H + approaches7N 2 +10SO 4 2- +5Fe 2+ +2H 2 O, and in part due to subsequent iron oxidation according to the reaction: NO 3 - +5Fe 2+ +6H + approaches1/2N 2 +5Fe 3+ +3H 2 O. Despite the potential increase in SO 4 and Fe resulting from denitrification through pyrite oxidation, the concentrations of these elements in the groundwater remain moderate due to the precipitation of minerals such as jarosite and/or natroalunite. Tracer transfer takes place in a heterogeneous medium which, according to the breakthrough curves, can be simplified to a dual-porosity aquifer comprising a high-permeability (fractures or large fissures) medium of low porosity from which only minor denitrification of circulating NO 3 -bearing water was observed and a low-permeability (small fissures) medium of high porosity which induces a higher denitrification rate in the circulating NO 3 -bearing water. The kinetics of the denitrification reaction are high compared with results obtained for other environments and can be described by a first-order model with a half life of 7.9 days for the low-porosity medium and only 2.1 days for the high-porosity medium. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  9. Enhanced heterotrophic denitrification: effect of dairy industry sludge acclimatization and operating conditions.

    Science.gov (United States)

    Akbari Shahabi, Zeinab; Naeimpoor, Fereshteh

    2014-06-01

    Heterotrophic denitrification of drinking water was enhanced by selection of an anoxic sludge taken from a dairy industry among the sludges taken from various industries, and the effect of carbon sources was examined. Acclimatization to high nitrate concentration was then carried out in a five-stage process. Considering removals of both nitrate and nitrite, the sludge taken from anoxic unit of Tehran Pegah dairy industry was shown to be the superior microbial culture, with ethanol as carbon source as compared to acetate. To enhance the rate of denitrification, acclimatization to nitrate (at 100, 200, 400, 800, and 1,600 mg N-NO3/L) was carried out in sequencing batch reactors over a 3-month period under anoxic condition, and comparisons were made between the performances of acclimated and non-acclimated sludges at each stage. It was found that acclimatization up to the fourth stage enhanced the specific denitrification rate to a high value of 29.6 mg N-NO3/h/g mixed liquor suspended solids (MLSS), with no significant nitrite accumulation. Additionally, the effect of initial pH (6, 6.5, 7, and 7.5) and carbon-to-nitrogen (C/N) ratio (1, 1.5, 2, and 3) on the performance of this final acclimated sludge was assessed, where initial pH of 7 and C/N ratio of 1.5 resulted in the best performances considering both nitrate and nitrite removal.

  10. Denitrification of nitrate waste solutions

    International Nuclear Information System (INIS)

    Bertolami, R.J.; Chao, E.I.; Choi, W.M.; Johnson, B.R.; Varlet, J.L.P.

    1976-01-01

    Growth rates for the denitrifying bacteria Pseudomonas Stutzeri were studied to minimize the time necessary to start up a bacterial denitrification reactor. Batch experiments were performed in nine 250-ml Erlenmeyer flasks, a 7-liter fermentor, and a 67-liter fermentor. All reactors maintained an anaerobic environment. Initial microorganism inoculum concentration was varied over four orders of magnitude. Initial nitrate and substrate carbon concentrations were varied from 200 to 6000 ppm and from 56 to 1596 ppm, respectively, with a carbon-to-nitrogen weight ratio of 1.18. In all experiments, except those with the highest initial substrate-to-bacteria ratio, no growth was observed due to substrate depletion during the lag period. In those experiments which did exhibit an increase in bacterial population, growth also stopped due to substrate depletion. A model simulating microbe growth during the induction period was developed, but insufficient data were available to properly adjust the model constants. Because of this, the model does not accurately predict microbe growth. The metabolism of Pseudomonas Stutzeri was studied in detail. This resulted in a prediction of the denitrification stoichiometry during steady state reactor operation. Iron was found to be an important component for bacterial anabolism

  11. Predicting the denitrification capacity of sandy aquifers from shorter-term incubation experiments and sediment properties

    Directory of Open Access Journals (Sweden)

    W. Eschenbach

    2013-02-01

    Full Text Available Knowledge about the spatial variability of denitrification rates and the lifetime of denitrification in nitrate-contaminated aquifers is crucial to predict the development of groundwater quality. Therefore, regression models were derived to estimate the measured cumulative denitrification of aquifer sediments after one year of incubation from initial denitrification rates and several sediment parameters, namely total sulphur, total organic carbon, extractable sulphate, extractable dissolved organic carbon, hot water soluble organic carbon and potassium permanganate labile organic carbon.

    For this purpose, we incubated aquifer material from two sandy Pleistocene aquifers in Northern Germany under anaerobic conditions in the laboratory using the 15N tracer technique. The measured amount of denitrification ranged from 0.19 to 56.2 mg N kg−1 yr−1. The laboratory incubations exhibited high differences between non-sulphidic and sulphidic aquifer material in both aquifers with respect to all investigated sediment parameters. Denitrification rates and the estimated lifetime of denitrification were higher in the sulphidic samples. For these samples, the cumulative denitrification measured during one year of incubation (Dcum(365 exhibited distinct linear regressions with the stock of reduced compounds in the investigated aquifer samples. Dcum(365 was predictable from sediment variables within a range of uncertainty of 0.5 to 2 (calculated Dcum(365/measured Dcum(365 for aquifer material with a Dcum(365 > 20 mg N kg−1 yr−1. Predictions were poor for samples with lower Dcum(365, such as samples from the NO3 bearing groundwater zone, which includes the non-sulphidic samples, from the upper part of both aquifers where denitrification is not sufficient to

  12. Experimental and modelling study of drinking water hydrogenotrophic denitrification in packed-bed reactors

    International Nuclear Information System (INIS)

    Vasiliadou, I.A.; Karanasios, K.A.; Pavlou, S.; Vayenas, D.V.

    2009-01-01

    The aim of this work was to study hydrogenotrophic denitrification in packed-bed reactors under draw-fill and continuous operation. Three bench-scale packed-bed reactors with gravel in different sizes (mean diameter 1.75, 2.41 and 4.03 mm) as support media were used, in order to study the effect of particle size on reactors performance. The maximum denitrification rate achieved under draw-fill operation was 4.4 g NO 3 - -N/ld for the filter with gravel of 2.41 mm. This gravel size was chosen to perform experiments under continuous operation. Feed NO 3 - -N concentrations and hydraulic loadings (HL) ranged between 20-200 mg/l and 5.7-22.8 m 3 /m 2 d, respectively. A comparison between the two operating modes showed that, for low HL the draw-fill operation achieved higher denitrification rates, while for high HL and intermediate feed concentrations (40-60 mg NO 3 - -N/l) the continuous operation achieved higher denitrification rates (4.67-5.65 g/ld). Finally, experiments with three filters in series (with gravels of 4.03, 2.41 and 1.75 mm mean diameter) were also performed under continuous operation. The maximum denitrification rate achieved was 6.2 g NO 3 - -N/ld for feed concentration of 340 mg/l and HL of 11.5 m 3 /m 2 d. A model, which describes denitrification in packed-bed reactors, was also developed. The model predicts the concentration profiles of NO 3 - -N along filter height, in draw-fill as well as in continuous operation, satisfactorily.

  13. Simultaneous desulfurization and denitrification by microwave reactor with ammonium bicarbonate and zeolite

    International Nuclear Information System (INIS)

    Wei Zaishan; Lin Zhehang; Niu Hejingying; He Haiming; Ji Yongfeng

    2009-01-01

    Microwave reactor with ammonium bicarbonate (NH 4 HCO 3 ) and zeolite was set up to study the simultaneous removal of sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) from flue gas. The results showed that the microwave reactor filled with NH 4 HCO 3 and zeolite could reduce SO 2 to sulfur with the best desulfurization efficiency of 99.1% and reduce NO x to nitrogen with the best NO x purifying efficiency of 86.5%. Microwave desulfurization and denitrification effect of the experiment using ammonium bicarbonate and zeolite together is much higher than that using ammonium bicarbonate or zeolite only. NO x concentration has little effect on denitrification but has no influence on desulfurization, SO 2 concentration has no effect on denitrification. The optimal microwave power and empty bed residence time (EBRT) on simultaneous desulfurization and dentrification are 211-280 W and 0.315 s, respectively. The mechanism for microwave reduced desulfurization and denitrification can be described as the microwave-induced catalytic reduction reaction between SO 2 , NO x and ammonium bicarbonate with zeolite being the catalyst and microwave absorbent

  14. Hydrogenotrophic denitrification in a packed bed reactor: effects of hydrogen-to-water flow rate ratio.

    Science.gov (United States)

    Lee, J W; Lee, K H; Park, K Y; Maeng, S K

    2010-06-01

    Hydrogen dissolution and hydrogenotrophic denitrification performance were investigated in a lab-scale packed bed reactor (PBR) by varying the hydrogen flow rate and hydraulic retention time (HRT). The denitrification performance was enhanced by increasing the hydrogen flow rate and HRT as a result of high dissolved hydrogen concentration (0.39mg/L) and utilization efficiencies (79%). In this study, the hydrogen-to-water flow rate ratio (Q(g)/Q(w)) was found to be a new operating factor representing the two parameters of hydrogen flow rate and HRT. Hydrogen dissolution and denitrification efficiency were nonlinearly and linearly correlated with the Q(g)/Q(w), respectively. Based on its excellent linear correlation with denitrification efficiency, Q(g)/Q(w) should be greater than 2.3 to meet the WHO's guideline of nitrate nitrogen for drinking water. This study demonstrates that Q(g)/Q(w) is a simple and robust factor to optimize hydrogen-sparged bioreactors for hydrogenotrophic denitrification. Copyright 2010 Elsevier Ltd. All rights reserved.

  15. Nitrous oxide production in grassland soils: assessing the contribution of nitrifier denitrification

    NARCIS (Netherlands)

    Wrage, N.; Velthof, G.L.; Laanbroek, H.J.; Oenema, O.

    2004-01-01

    Nitrifier denitrification is the reduction of NO2- to N2 by nitrifiers. It leads to the production of the greenhouse gas nitrous oxide (N2O) as an intermediate and possible end product. It is not known how important nitrifier denitrification is for the production of N2O in soils. We explored N2O

  16. Mixing-induced groundwater denitrification beneath a manured field in southern Alberta, Canada

    International Nuclear Information System (INIS)

    McCallum, J.E.; Ryan, M.C.; Mayer, B.; Rodvang, S.J.

    2008-01-01

    Contamination of shallow groundwater by NO 3 - from manure may occur under fields where manure is spread as fertilizer and for disposal. Attenuation of NO 3 - in groundwater occurs through denitrification under certain conditions, or NO 3 - -contaminated younger groundwater may mix with older groundwater, lowering the NO 3 - concentration. In this study, δ 15 N and δ 18 O values of NO 3 - , and δ 18 O and δ 2 H values in groundwater under a manured field were evaluated to determine if groundwater NO 3 - concentrations were influenced through mixing of shallower, manure-impacted groundwater with older groundwater, or if denitrification was reducing NO 3 - concentrations. The younger groundwater showed clear evidence of manure impact with elevated Cl - (∼85 mg L -1 ) and NO 3 - concentrations (∼50 mg NO 3 -N L -1 ), and δ 15 N and δ 18 O values of NO 3 - consistent with a manure source. Vertical hydraulic gradients and δ 18 O and δ 2 H values in groundwater suggest older, more reduced groundwater is upwelling locally and mixing with the shallow groundwater. Decreasing NO 3 :Cl ratios, decreasing dissolved O 2 concentrations, and increasing δ 15 N and δ 18 O values of NO 3 - suggest that denitrification occurs locally in the aquifer. The extent of denitrification is proportional to the fraction of deeper groundwater in the aquifer. Denitrification apparently does not proceed in the younger, manure-impacted groundwater in the absence of mixing

  17. Mechanism and rate of denitrification in an agricultural watershed: Electron and mass balance along groundwater flow paths

    Science.gov (United States)

    Tesoriero, Anthony J.; Liebscher, Hugh; Cox, Stephen E.

    2000-01-01

    The rate and mechanism of nitrate removal along and between groundwater flow paths were investigated using a series of well nests screened in an unconfined sand and gravel aquifer. Intensive agricultural activity in this area has resulted in nitrate concentrations in groundwater often exceeding drinking water standards. Both the extent and rate of denitrification varied depending on the groundwater flow path. While little or no denitrification occurred in much of the upland portions of the aquifer, a gradual redox gradient is observed as aerobic upland groundwater moves deeper in the aquifer. In contrast, a sharp shallow redox gradient is observed adjacent to a third‐order stream as aerobic groundwater enters reduced sediments. An essentially complete loss of nitrate concurrent with increases in excess N2 provide evidence that denitrification occurs as groundwater enters this zone. Electron and mass balance calculations suggest that iron sulfide (e.g., pyrite) oxidation is the primary source of electrons for denitrification. Denitrification rate estimates were based on mass balance calculations using nitrate and excess N2 coupled with groundwater travel times. Travel times were determined using a groundwater flow model and were constrained by chlorofluorocarbon‐based age dates. Denitrification rates were found to vary considerably between the two areas where denitrification occurs. Denitrification rates in the deep, upland portions of the aquifer were found to range from from 1.0 to 2.7 mM of N per year. Potential denitrification rates in groundwater adjacent to the stream may be much faster, with rates up to 140 mM per year based on an in situ experiment conducted in this zone.

  18. Regulation-Structured Dynamic Metabolic Model Provides a Potential Mechanism for Delayed Enzyme Response in Denitrification Process

    Energy Technology Data Exchange (ETDEWEB)

    Song, Hyun-Seob; Thomas, Dennis G.; Stegen, James C.; Li, Minjing; Liu, Chongxuan; Song, Xuehang; Chen, Xingyuan; Fredrickson, Jim K.; Zachara, John M.; Scheibe, Timothy D.

    2017-09-29

    In a recent study of denitrification dynamics in hyporheic zone sediments, we observed a significant time lag (up to several days) in enzymatic response to the changes in substrate concentration. To explore an underlying mechanism and understand the interactive dynamics between enzymes and nutrients, we developed a trait-based model that associates a community’s traits with functional enzymes, instead of typically used species guilds (or functional guilds). This enzyme-based formulation allows to collectively describe biogeochemical functions of microbial communities without directly parameterizing the dynamics of species guilds, therefore being scalable to complex communities. As a key component of modeling, we accounted for microbial regulation occurring through transcriptional and translational processes, the dynamics of which was parameterized based on the temporal profiles of enzyme concentrations measured using a new signature peptide-based method. The simulation results using the resulting model showed several days of a time lag in enzymatic responses as observed in experiments. Further, the model showed that the delayed enzymatic reactions could be primarily controlled by transcriptional responses and that the dynamics of transcripts and enzymes are closely correlated. The developed model can serve as a useful tool for predicting biogeochemical processes in natural environments, either independently or through integration with hydrologic flow simulators.

  19. Effects of aquatic vegetation type on denitrification

    NARCIS (Netherlands)

    Veraart, A.J.; Bruijne, de W.J.J.; Peeters, E.T.H.M.; Klein, de J.J.M.; Scheffer, M.

    2011-01-01

    In a microcosm 15N enrichment experiment we tested the effect of floating vegetation (Lemna sp.) and submerged vegetation (Elodea nuttallii) on denitrification rates, and compared it to systems without macrophytes. Oxygen concentration, and thus photosynthesis, plays an important role in regulating

  20. Simultaneous desulfurization and denitrification by microwave reactor with ammonium bicarbonate and zeolite

    Energy Technology Data Exchange (ETDEWEB)

    Wei Zaishan [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China)], E-mail: weizaishan98@163.com; Lin Zhehang; Niu Hejingying; He Haiming; Ji Yongfeng [School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

    2009-03-15

    Microwave reactor with ammonium bicarbonate (NH{sub 4}HCO{sub 3}) and zeolite was set up to study the simultaneous removal of sulfur dioxide (SO{sub 2}) and nitrogen oxides (NO{sub x}) from flue gas. The results showed that the microwave reactor filled with NH{sub 4}HCO{sub 3} and zeolite could reduce SO{sub 2} to sulfur with the best desulfurization efficiency of 99.1% and reduce NO{sub x} to nitrogen with the best NO{sub x} purifying efficiency of 86.5%. Microwave desulfurization and denitrification effect of the experiment using ammonium bicarbonate and zeolite together is much higher than that using ammonium bicarbonate or zeolite only. NO{sub x} concentration has little effect on denitrification but has no influence on desulfurization, SO{sub 2} concentration has no effect on denitrification. The optimal microwave power and empty bed residence time (EBRT) on simultaneous desulfurization and dentrification are 211-280 W and 0.315 s, respectively. The mechanism for microwave reduced desulfurization and denitrification can be described as the microwave-induced catalytic reduction reaction between SO{sub 2}, NO{sub x} and ammonium bicarbonate with zeolite being the catalyst and microwave absorbent.

  1. Mathematical modeling of biological processes

    CERN Document Server

    Friedman, Avner

    2014-01-01

    This book on mathematical modeling of biological processes includes a wide selection of biological topics that demonstrate the power of mathematics and computational codes in setting up biological processes with a rigorous and predictive framework. Topics include: enzyme dynamics, spread of disease, harvesting bacteria, competition among live species, neuronal oscillations, transport of neurofilaments in axon, cancer and cancer therapy, and granulomas. Complete with a description of the biological background and biological question that requires the use of mathematics, this book is developed for graduate students and advanced undergraduate students with only basic knowledge of ordinary differential equations and partial differential equations; background in biology is not required. Students will gain knowledge on how to program with MATLAB without previous programming experience and how to use codes in order to test biological hypothesis.

  2. Piecewise deterministic processes in biological models

    CERN Document Server

    Rudnicki, Ryszard

    2017-01-01

    This book presents a concise introduction to piecewise deterministic Markov processes (PDMPs), with particular emphasis on their applications to biological models. Further, it presents examples of biological phenomena, such as gene activity and population growth, where different types of PDMPs appear: continuous time Markov chains, deterministic processes with jumps, processes with switching dynamics, and point processes. Subsequent chapters present the necessary tools from the theory of stochastic processes and semigroups of linear operators, as well as theoretical results concerning the long-time behaviour of stochastic semigroups induced by PDMPs and their applications to biological models. As such, the book offers a valuable resource for mathematicians and biologists alike. The first group will find new biological models that lead to interesting and often new mathematical questions, while the second can observe how to include seemingly disparate biological processes into a unified mathematical theory, and...

  3. A comparative study of methanol as a supplementary carbon source for enhancing denitrification in primary and secondary anoxic zones.

    Science.gov (United States)

    Ginige, Maneesha P; Bowyer, Jocelyn C; Foley, Leah; Keller, Jürg; Yuan, Zhiguo

    2009-04-01

    A comparative study on the use of methanol as a supplementary carbon source to enhance denitrification in primary and secondary anoxic zones is reported. Three lab-scale sequencing batch reactors (SBR) were operated to achieve nitrogen and carbon removal from domestic wastewater. Methanol was added to the primary anoxic period of the first SBR, and to the secondary anoxic period of the second SBR. No methanol was added to the third SBR, which served as a control. The extent of improvement on the denitrification performance was found to be dependent on the reactor configuration. Addition to the secondary anoxic period is more effective when very low effluent nitrate levels are to be achieved and hence requires a relatively large amount of methanol. Adding a small amount of methanol to the secondary anoxic period may cause nitrite accumulation, which does not improve overall nitrogen removal. In the latter case, methanol should be added to the primary anoxic period. The addition of methanol can also improve biological phosphorus removal by creating anaerobic conditions and increasing the availability of organic carbon in wastewater for polyphosphate accumulating organisms. This potentially provides a cost-effective approach to phosphorus removal from wastewater with a low carbon content. New fluorescence in situ hybridisation (FISH) probes targeting methanol-utilising denitrifiers were designed using stable isotope probing. Microbial structure analysis of the sludges using the new and existing FISH probes clearly showed that the addition of methanol stimulated the growth of specific methanol-utilizing denitrifiers, which improved the capability of sludge to use methanol and ethanol for denitrification, but reduced its capability to use wastewater COD for denitrification. Unlike acetate, long-term application of methanol has no negative impact on the settling properties of the sludge.

  4. Modeling Electron Competition among Nitrogen Oxides Reduction and N2O Accumulation in Hydrogenotrophic Denitrification

    DEFF Research Database (Denmark)

    Liu, Yiwen; Ngo, Huu Hao; Guo, Wenshan

    2018-01-01

    Hydrogenotrophic denitrification is a novel and sustainable process for nitrogen removal, which utilizes hydrogen as electron donor and carbon dioxide as carbon source. Recent studies have shown that nitrous oxide (N2O), a highly undesirable intermediate and potent greenhouse gas, can accumulate...

  5. In Situ Groundwater Denitrification in the Riparian Zone of a Short-Rotation Woody Crop Experimental Watershed

    Science.gov (United States)

    Jeffers, J. B.; Jackson, C. R.; Rau, B.; Pringle, C. M.; Matteson, C.

    2017-12-01

    The southeastern United States has potential to become a major producer of short rotation woody crops (SRWC) for the production of biofuels, but this will require converting to more intensive forest management practices that will increase nitrate (NO3-) loading and alter nitrogen cycling in nearby freshwater ecosystems. Water quality monitoring in an experimental short-rotation woody crop watershed in the Coastal Plain of South Carolina has shown increased concentrations of NO3- in groundwater but no evidence of increased NO3- in riparian groundwater or surface waters. Forested riparian areas established as streamside management zones (SMZ) are known to act as buffers to surface water bodies by mitigating nutrients. The objectives of this study were to quantify denitrification by measuring dinitrogen (N2) and nitrous oxide (N2O) concentrations along groundwater flow paths and analyze relationships between denitrification estimates, nutrients, and water chemistry parameters. A network of piezometers has been established in the Fourmile Experimental Watershed at the Department of Energy - Savannah River Site. Water samples were collected monthly and were analyzed for concentrations of nutrients (temperature, specific conductivity, dissolved oxygen, pH, dissolved organic carbon) and dissolved gases (N2, Ar, N2O). Preliminary data showed greater dissolved N2O concentrations than dissolved N2 concentrations in groundwater. The ratios of N2O to combined end products of denitrification (N2O / N2O+N2) ranged from 0.33 to 0.99. Mean N2O+N2 concentrations were greater in groundwater samples in the SRWC plot and along the SMZ boundary than along the ephemeral stream within the riparian zone. Correlations between water chemistry parameters and N2 concentrations are indicative of known biogeochemical driving factors of denitrification. Continued monthly sampling will be coupled with analysis of nutrient concentrations (NO3-, NH4+, TN) to help determine transport and processing

  6. Denitrification in agriculturally impacted streams: seasonal changes in structure and function of the bacterial community.

    Directory of Open Access Journals (Sweden)

    Erin Manis

    Full Text Available Denitrifiers remove fixed nitrogen from aquatic environments and hydrologic conditions are one potential driver of denitrification rate and denitrifier community composition. In this study, two agriculturally impacted streams in the Sugar Creek watershed in Indiana, USA with different hydrologic regimes were examined; one stream is seasonally ephemeral because of its source (tile drainage, whereas the other stream has permanent flow. Additionally, a simulated flooding experiment was performed on the riparian benches of the ephemeral stream during a dry period. Denitrification activity was assayed using the chloramphenicol amended acetylene block method and bacterial communities were examined based on quantitative PCR and terminal restriction length polymorphisms of the nitrous oxide reductase (nosZ and 16S rRNA genes. In the stream channel, hydrology had a substantial impact on denitrification rates, likely by significantly lowering water potential in sediments. Clear patterns in denitrification rates were observed among pre-drying, dry, and post-drying dates; however, a less clear scenario was apparent when analyzing bacterial community structure suggesting that denitrifier community structure and denitrification rate were not strongly coupled. This implies that the nature of the response to short-term hydrologic changes was physiological rather than increases in abundance of denitrifiers or changes in composition of the denitrifier community. Flooding of riparian bench soils had a short-term, transient effect on denitrification rate. Our results imply that brief flooding of riparian zones is unlikely to contribute substantially to removal of nitrate (NO3- and that seasonal drying of stream channels has a negative impact on NO3- removal, particularly because of the time lag required for denitrification to rebound. This time lag is presumably attributable to the time required for the denitrifiers to respond physiologically rather than a change

  7. European-scale modelling of groundwater denitrification and associated N2O production

    International Nuclear Information System (INIS)

    Keuskamp, J.A.; Drecht, G. van; Bouwman, A.F.

    2012-01-01

    This paper presents a spatially explicit model for simulating the fate of nitrogen (N) in soil and groundwater and nitrous oxide (N 2 O) production in groundwater with a 1 km resolution at the European scale. The results show large heterogeneity of nitrate outflow from groundwater to surface water and production of N 2 O. This heterogeneity is the result of variability in agricultural and hydrological systems. Large parts of Europe have no groundwater aquifers and short travel times from soil to surface water. In these regions no groundwater denitrification and N 2 O production is expected. Predicted N leaching (16% of the N inputs) and N 2 O emissions (0.014% of N leaching) are much less than the IPCC default leaching rate and combined emission factor for groundwater and riparian zones, respectively. - Highlights: ► Groundwater denitrification and N 2 O production was modelled at the European scale. ► In large parts of Europe no groundwater denitrification is expected. ► N leaching and N 2 O emission in Europe are much less than the IPCC default values. - European groundwater denitrification is spatially variable, and associated nitrous oxide production is much less than based on the IPCC default estimate.

  8. Advanced phosphorus recovery using a novel SBR system with granular sludge in simultaneous nitrification, denitrification and phosphorus removal process.

    Science.gov (United States)

    Lu, Yong-Ze; Wang, Hou-Feng; Kotsopoulos, Thomas A; Zeng, Raymond J

    2016-05-01

    In this study, a novel process for phosphorus (P) recovery without excess sludge production from granular sludge in simultaneous nitrification-denitrification and P removal (SNDPR) system is presented. Aerobic microbial granules were successfully cultivated in an alternating aerobic-anaerobic sequencing batch reactor (SBR) for removing P and nitrogen (N). Dense and stable granular sludge was created, and the SBR system showed good performance in terms of P and N removal. The removal efficiency was approximately 65.22 % for N, and P was completely removed under stable operating conditions. Afterward, new operating conditions were applied in order to enhance P recovering without excess sludge production. The initial SBR system was equipped with a batch reactor and a non-woven cloth filter, and 1.37 g of CH3COONa·3H2O was added to the batch reactor after mixing it with 1 L of sludge derived from the SBR reactor to enhance P release in the liquid fraction, this comprises the new system configuration. Under the new operating conditions, 93.19 % of the P contained in wastewater was released in the liquid fraction as concentrated orthophosphate from part of granular sludge. This amount of P could be efficiently recovered in the form of struvite. Meanwhile, a deterioration of the denitrification efficiency was observed and the granules were disintegrated into smaller particles. The biomass concentration in the system increased firstly and then maintained at 4.0 ± 0.15 gVSS/L afterward. These results indicate that this P recovery operating (PRO) mode is a promising method to recover P in a SNDPR system with granular sludge. In addition, new insights into the granule transformation when confronted with high chemical oxygen demand (COD) load were provided.

  9. Effects of Bubble-Mediated Processes on Nitrous Oxide Dynamics in Denitrifying Bioreactors

    Science.gov (United States)

    McGuire, P. M.; Falk, L. M.; Reid, M. C.

    2017-12-01

    To mitigate groundwater and surface water impacts of reactive nitrogen (N), agricultural and stormwater management practices can employ denitrifying bioreactors (DNBs) as low-cost solutions for enhancing N removal. Due to the variable nature of hydrologic events, DNBs experience dynamic flows which can impact physical and biological processes within the reactors and affect performance. A particular concern is incomplete denitrification, which can release the potent greenhouse gas nitrous oxide (N2O) to the atmosphere. This study aims to provide insight into the effects of varying hydrologic conditions upon the operation of DNBs by disentangling abiotic and biotic controls on denitrification and N2O dynamics within a laboratory-scale bioreactor. We hypothesize that under transient hydrologic flows, rising water levels lead to air entrapment and bubble formation within the DNB porous media. Mass transfer of oxygen (O2) between trapped gas and liquid phases creates aerobic microenvironments that can inhibit N2O reductase (NosZ) enzymes and lead to N2O accumulation. These bubbles also retard N2O transport and make N2O unavailable for biological reduction, further enhancing atmospheric fluxes when water levels fall. The laboratory-scale DNB permits measurements of longitudinal and vertical profiles of dissolved constituents as well as trace gas concentrations in the reactor headspace. We describe a set of experiments quantifying denitrification pathway biokinetics under steady-state and transient hydrologic conditions and evaluate the role of bubble-mediated processes in enhancing N2O accumulation and fluxes. We use sulfur hexafluoride and helium as dissolved gas tracers to examine the impact of bubble entrapment upon retarded gas transport and enhanced trace gas fluxes. A planar optode sensor within the bioreactor provides near-continuous 2-D profiles of dissolved O2 within the bioreactor and allows for identification of aerobic microenvironments. We use qPCR to

  10. The efficiency of a membrane bioreactor in drinking water denitrification

    Directory of Open Access Journals (Sweden)

    Petrovič Aleksandra

    2015-01-01

    Full Text Available The membrane bioreactor (MBR system was investigated regarding its nitrate removal capacity from drinking water. The performance of a pilot-scale MBR was tested, depending on the operational parameters, using sucrose as a carbon source. Drinking water from the source was introduced into the reactor in order to study the influence of flow-rate on the nitrate removal and denitrification efficiency of drinking water. The content of the nitrate was around 70 mg/L and the C/N ratio was 3:1. Nitrate removal efficiencies above 90% were obtained by flow-rates lower than 4.8 L/h. The specific denitrification rates varied between 0.02 and 0.16 g/L NO3/ (g/L MLSS•d. The efficiencies and nitrate removal were noticeably affected by the flow-rate and hydraulic retention times. At the maximum flow-rate of 10.2 L/h still 68% of the nitrate had been removed, whilst the highest specific denitrification rate was achieved at 0.2738 g/L NO3/ (g/L MLSS•d. The maximum reactor removal capacity was calculated at 8.75 g NO3/m3•h.

  11. Combined denitrification and phosphorus removal in a biofilter

    DEFF Research Database (Denmark)

    Falkentoft, Christina Maria; Harremoes, Poul; Mosbæk, Hans

    2000-01-01

    A lab-scale biofilter was run continuously for 11/2 years for combined denitrification and phosphorus removal. Alternation between anaerobic and anoxic (nitrate) conditions was used to obtain an enriched culture of denitrifying, phosphate accumulating organisms. Batch experiments were performed...

  12. Coastal versus open-ocean denitrification in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Naik, H.; Pratihary, A.K.; DeSouza, W.; Narvekar, P.V.; Jayakumar, D.A.; Devol, A.H.; Yoshinari, T.; Saino, T.

    through advection from the south. The waters Published by Copernicus GmbH on behalf of the European Geosciences Union. 622 S. W. A. Naqvi et al.: Arabian Sea denitrification 60 E 70 E 10 N 20 N 3204 3939 3201 TN039/18 CATS � � (a) o o o 0 500 1000 1500....: Arabian Sea denitrification 625 150 100 50 Temperature (oC) 100 50 O2 (M) Distance from coast (km) 150 100 50 Salinity G2 CATS G9 �P�P 150 100 50 150 100 50 150 NO2- (M) 150 100 50 NO3-(M) N2O (nM) 150 100 50 NH4+(M) 80 60 40 20 0 Distance from coast (km...

  13. Denitrification nitrogen gas formation and gene expression in alpine grassland soil as affected by climate change conditions

    Science.gov (United States)

    Chen, Zhe; Wang, Changhui; Gschwendtner, Silvia; Schloter, Michael; Butterbach-Bahl, Klaus; Dannenmann, Michael

    2013-04-01

    Due to methodological problems, reliable data on soil dinitrogen (N2) emission by denitrification are extremely scarce, and the impacts of climate change on nitrogen (N) gas formation by denitrification and N gas product ratios as well as the underlying microbial drivers remain unclear. We combined the helium-gas-flow-soil-core technique for simultaneously quantification of nitrous oxide (N2O) and N2 emission with the reverse transcript qPCR technology. Our goals were to characterize denitrification dynamics and N gas product ratios in alpine grassland soil as affected by climate change conditions and to evaluate relationships between denitrification gene expression and N gas emission. We used soils from the pre-alpine grassland Terrestrial Environmental Observatory (TERENO), exposed to ambient temperature and precipitation (control treatment), or three years of simulated climate change conditions (increased temperature, reduction of summer precipitation and reduced snow cover). Soils were amended with glucose and nitrate and incubated subsequently at 1) 5°C and 20% oxygen; 2) 5°C and 0% oxygen; 3) 20°C and 0% oxygen until stabilization of N gas emissions in each incubation step. After switching incubation conditions to 0% oxygen and 20°C, N2O emission peaked immediately and declined again, followed by a delayed peak in N2 emission. The dynamics of cnorB gene expression, encoding the reduction of nitric oxide (NO) to N2O, followed the N2O emission pattern, while nosZ gene expression, encoding N2O reduction to N2 followed the course of N2 emission. The mean N2O:N2 ratios were 1.31 + 0.10 and 1.56 + 0.16 for control and climate change treatment respectively, but the denitrification potential was overall lower in climate change treatment. Hence, simulated climate change promoted N2O but lessened N2 emission. This stimulation of N2O was in accordance with increased cnorB gene expression in soil of the climate change treatment. N mass balance calculations revealed

  14. Soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification for domestic wastewater treatment.

    Science.gov (United States)

    Kong, Zhe; Li, Lu; Feng, Chuanping; Chen, Nan; Dong, Shanshan; Hu, Weiwu

    2015-01-01

    In this study, an integrated two-stage soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification (SIBPD) was designed for domestic wastewater treatment. Benefited from excellent adsorption ability and water-permeability, soil infiltration could avoid clogging, shorten operating time and lower maintenance cost. Respiration and nitrification were mostly engaged in aerobic stage (AES), while nitrate was majorly removed by pyrite-based mixotrophic denitrification mainly occurred in anaerobic stage (ANS). Fed with synthetic and real wastewater for 120days at 1.5h HRT, SIBPD demonstrated good removal performance showing 87.14% for COD, 92.84% for NH4(+)-N and 82.58% for TP along with 80.72% of nitrate removed by ANS. TN removal efficiency was 83.74% when conducting real wastewater. Compared with sulfur-based process, the effluent pH of SIBPD was maintained at 6.99-7.34 and the highest SO4(2-) concentration was only 64.63mgL(-1). This study revealed a promising and feasible application prospect for on-site domestic wastewater treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Nitrous oxide emissions from denitrification and the partitioning of gaseous losses as affected by nitrate and carbon addition and soil aeration

    International Nuclear Information System (INIS)

    Gillam, K.M.; Nova Scotia Agricultural College, Truro, NS; Zebarth, B.J.; Burton, D.L.

    2008-01-01

    The factors controlling nitrous oxide (N 2 O) emissions vary with different soil and environmental conditions and management practices. This study was conducted to determine the importance of soil aeration, nitrate (NO 3 ) addition, carbon (C) additions, and C sources on gaseous nitrogen (N) losses from the denitrification of arable soils at a potato farm in Atlantic Canada. Denitrification and N 2 O emissions were measured using acetylene inhibition. An N 2 O and nitrogen gas (N 2 ) ratio of 0.7 showed that most emissions occurred as N 2 O. Emissions at water-filled pore spaces (WFPs) of 0.45 m 3 per m 3 were negligible. N 2 O emissions increased with NO 3 and C additions. Results suggested that soil aeration plays a dominant role in controlling the magnitude of denitrification and N 2 O emissions. However, soil NO 3 supplies in this study did not limit the denitrification process. The study showed that N 2 O emissions are controlled by C availability when there is a high degree of soil disturbance and high fertilizer N inputs. The relationship between the demand and supply of terminal electron acceptors (TEAs) was used to explain the spatial distribution of the N 2 O emissions. Higher WFPs and lower soil NO 3 concentrations resulted in higher rates of total denitrification. It was concluded that further research is needed to examine the role of overall soil and crop management in relation to C availability when developing mitigation strategies. 52 refs., 4 tabs

  16. Investigation of the effects of hydrogenotrophic denitrification and anammox on the improvement of the quality of the drinking water supply system.

    Science.gov (United States)

    Khanitchaidecha, W; Koshy, P; Kamei, T; Shakya, M; Kazama, F

    2013-01-01

    A drinking water supply system operates at Chyasal (in the Kathmandu Valley, Nepal) for purifying the groundwater that has high levels of ammonium nitrogen (NH4-N). However, high NO3-N concentrations were seen in the water after treatment. To further improve the quality of the drinking water, two types of attached growth reactors were developed for the purification system: (i) a hydrogenotrophic denitrification (HD reactor) and (ii) a concurrent reactor with anammox and hydrogenotrophic denitrification (AnHD reactor). For the HD reactor fed by water containing NO3-N, the denitrification efficiency was high (95-98%) for all NO3-N feed rates (20-40 mg/L). The nitrite-nitrogen (NO2-N) and nitrate-nitrogen (NO3-N) concentrations in the effluent were ∼0.5 mg/L. On the other hand, the AnHD reactor fed with water containing NH4-N and NO2-N was operated under varying flow rates of H2(30-70 mL/min) and intermittent supply periods (1-2 h). The efficiency of the anammox process was found to increase with decreasing H2flow rates or with increasing intermittency of the H2supply, while the efficiency of denitrification decreased under these conditions. For the optimal condition of 1.5 h intermittent H2supply, the anammox and denitrification efficiencies of the AnHD reactor reached 80% and 42%, respectively, while the concentrations of both NH4-N and NO2-N in the effluent were water purification system.

  17. Indian Monsoon and denitrification change in the Laxmi Basin (IODP Exp. 355 Site U1456) of the Eastern Arabian Sea during the last 800 kyrs

    Science.gov (United States)

    Kim, J. E.; Khim, B. K.; Ikehara, M.; Lee, J.

    2017-12-01

    The Arabian Sea is a famous site for the basin-wide denitrification in the globe. The Western Arabian Sea has been acknowledged by its upwelling-induced denitrification related to the Indian Monsoon system (Altabet et al., 1999). It was recently reported that the denitrification in the Eastern Arabian Sea (IODP Exp. 355 Site U1456) has been persistent and consistent during the mid-Pleistocene as reflected in the bulk sediment δ15N values (Tripathi et al., 2017). Based on the age model reconstructed by δ18O stratigraphy of planktonic foraminifera (Globigerinoides ruber) together with shipboard biostratigraphic and paleomagnetic data at Site U1456 drilled in the Laxmi Basin of the Eastern Arabian Sea, the glacial-interglacial fluctuations of denitrification in association with the development of oxygen minimum zone (OMZ) were resolved in the context of Indian Monsoon activity. One of striking features in the Eastern Arabian Sea is that the δ15N values of bulk sediment show clear and consistent denitrification with minimum δ15N values exceeding 6‰ even during glacial periods, when its western counterpart experienced a temporal collapse of OMZ and denitrification. The Eastern Arabian Sea is fed not only by the upwelling-induced productivity in the western margin during the summer monsoon but also by the high productivity during the winter monsoon, both of which maintain the increased productivity affecting the OMZ through the consumption of dissolved oxygen by the degradation of sinking organic particles. The Eastern Arabian Sea is further influenced by the clockwise surface currents, intermediate water ventilation change by the blockage of Antarctic Intermediate Water, limited inflow from the Red Sea/Persian Gulf, and the freshwater salinity stratification due to nearby riverine discharges, all of which make the denitrification process more complicated than the Western Arabian Sea. Nonetheless, the glacial-interglacial denitrification change in the Eastern

  18. Phylogenetic analysis of nitrite, nitric oxide, and nitrous oxide respiratory enzymes reveal a complex evolutionary history for denitrification.

    Science.gov (United States)

    Jones, Christopher M; Stres, Blaz; Rosenquist, Magnus; Hallin, Sara

    2008-09-01

    Denitrification is a facultative respiratory pathway in which nitrite (NO2(-)), nitric oxide (NO), and nitrous oxide (N2O) are successively reduced to nitrogen gas (N(2)), effectively closing the nitrogen cycle. The ability to denitrify is widely dispersed among prokaryotes, and this polyphyletic distribution has raised the possibility of horizontal gene transfer (HGT) having a substantial role in the evolution of denitrification. Comparisons of 16S rRNA and denitrification gene phylogenies in recent studies support this possibility; however, these results remain speculative as they are based on visual comparisons of phylogenies from partial sequences. We reanalyzed publicly available nirS, nirK, norB, and nosZ partial sequences using Bayesian and maximum likelihood phylogenetic inference. Concomitant analysis of denitrification genes with 16S rRNA sequences from the same organisms showed substantial differences between the trees, which were supported by examining the posterior probability of monophyletic constraints at different taxonomic levels. Although these differences suggest HGT of denitrification genes, the presence of structural variants for nirK, norB, and nosZ makes it difficult to determine HGT from other evolutionary events. Additional analysis using phylogenetic networks and likelihood ratio tests of phylogenies based on full-length sequences retrieved from genomes also revealed significant differences in tree topologies among denitrification and 16S rRNA gene phylogenies, with the exception of the nosZ gene phylogeny within the data set of the nirK-harboring genomes. However, inspection of codon usage and G + C content plots from complete genomes gave no evidence for recent HGT. Instead, the close proximity of denitrification gene copies in the genomes of several denitrifying bacteria suggests duplication. Although HGT cannot be ruled out as a factor in the evolution of denitrification genes, our analysis suggests that other phenomena, such gene

  19. The study of a pilot-scale aerobic/Fenton/anoxic/aerobic process system for the treatment of landfill leachate.

    Science.gov (United States)

    Hu, Wenyong; Zhou, Yu; Min, Xiaobo; Liu, Jingyi; Li, Xinyu; Luo, Lin; Zhang, Jiachao; Mao, Qiming; Chai, Liyuan; Zhou, YaoYu

    2017-06-29

    In this study, a combined aerobic-Fenton-anoxic/aerobic system was designed for the remediation of raw landfill leachate in a pilot-scale experiment. This system included (i) a granular sludge biological oxidation procedure that achieves the accumulation of nitrite nitrogen ([Formula: see text]) under aerobic conditions; (ii) a Fenton process that improves the biodegradability of the biotreated leachate and (iii) an activated sludge biological oxidation component under anoxic and aerobic conditions. Additionally, a shortcut nitrification and denitrification pathway was achieved. The effects of free ammonia, temperature and pH on nitrite accumulation were discussed. The change in the biochemical oxygen demand/chemical oxygen demand ratio of the effluent after shortcut nitrification was also analysed. The microbial community in the reactor were also investigated. The problem of the lack of carbon source in the denitrification process can be solved by the Fenton reagent method. Moreover, it was beneficial to achieving nitrogen removal as well as the more extensive removal of organic matter. The treatment strategy employed in this study exhibited good results and provided the potential practical application for treating landfill leachate.

  20. Characterization of novel Bacillus strain N31 from mariculture water capable of halophilic heterotrophic nitrification-aerobic denitrification.

    Science.gov (United States)

    Huang, Fei; Pan, Luqing; Lv, Na; Tang, Xianming

    2017-11-01

    The development of an intensive aquaculture industry has been accompanied by increasing environmental impacts, especially nitrogen pollution. In this study, a novel halophilic bacterium capable of heterotrophic nitrification and aerobic denitrification was isolated from mariculture water and identified as Bacillus litoralis N31. The efficiency of ammonium, nitrite and nitrate removal by N31 were 86.3%, 89.3% and 89.4%, respectively, after a 48-h cultivation in sole N-source medium with initial nitrogen approximately 20 mg/L. However, ammonium was removed preferentially, and no obvious nitrite accumulated during the simultaneous nitrification and denitrification process in mixed N-source media. The existence of hao, napA and nirS genes further proved the heterotrophic nitrification-aerobic denitrification capability of N31. The optimal conditions for ammonium removal were 30°C, initial pH 7.5-8.5, C/N ratio 5-20 and salinity 30-40‰, and the nitrification rate of N31 increased with increasing initial [Formula: see text] from 10 to 250 mg/L. Biosecurity assessment with shrimp indicated that strain N31 could be applied in the marine aquaculture industry safely for culture water remediation and effluent treatment. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  1. Establishing Ideal Conditions for Complete Denitrification by Pseudomonas Aureofaciens - An Update on Determining Isotopic Composition of Dissolved Nitrate Using Bacterial Denitrification and Laser Spectroscopy

    International Nuclear Information System (INIS)

    Yi, Amelia Lee Zhi; Heiling, Maria; Toloza, Arsenio; Heng, Lee K.

    2017-01-01

    This serves as update on research entitled “Determining isotopic composition of dissolved nitrate using bacterial denitrification and laser spectroscopy” first published in the Vol. 39, No. 1, July 2016 SWMCN Soils Newsletter. In this research, isotopic δ"1"5N and δ"1"8O composition of dissolved nitrates is measured by laser spectroscopy after reduction of nitrate to N_2O by Pseudomonas aureofaciens. Quantifying the isotopic composition of nitrates in aqueous samples allows for better identification of potential nitrate sources, which in turn assists in remediation of nitrate-contaminated water and design of future agricultural management practises. The overall objective of the project is to establish a technical guide in the form of a standard operating procedure outlining best practises for denitrification method.

  2. Performance of heterotrophic partial denitrification under feast-famine condition of electron donor: a case study using acetate as external carbon source.

    Science.gov (United States)

    Gong, Lingxiao; Huo, Mingxin; Yang, Qing; Li, Jun; Ma, Bin; Zhu, Rulong; Wang, Shuying; Peng, Yongzhen

    2013-04-01

    Recently, the combination of anammox and post heterotrophic partial denitrification (nitrate to nitrite) was increasingly popular to treat anammox effluent with excessive nitrate, whereas achieving nitrite accumulation stably was a major bottleneck for post-denitrification. This work focused on the performance of heterotrophic partial denitrification under acetate feast-famine condition. The results showed that readily biodegradable COD to nitrate (RBCOD/NO3(-)) ratio of 2.5 facilitated an ideal nitrite accumulation ratio (NAR) of 71.7% under complete nitrate reduction. When RBCOD/NO3(-) ratio was below 3.5, in terms of efficiency and nitrite accumulation, higher NAR obtained during exogenous denitrification identified that the external acetate depletion was the optimal ending point of denitrification, which could be indicated by pH accurately. The indication of pH realized NAR of 60% ideally under batch-flow mode with RBCOD/NO3(-) ratio of 2.7, which might promote the scale-up of partial denitrification. Furthemore, alkaline environment (pH 9.0-9.6) repressed N2O emission even during endogenous denitrification. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Denitrification: an important pathway for nitrous oxide production in tropical mangrove sediments (Goa, India).

    Science.gov (United States)

    Fernandes, Sheryl Oliveira; Bharathi, P A Loka; Bonin, Patricia C; Michotey, Valérie D

    2010-01-01

    Net nitrous oxide production and denitrification activity were measured in two mangrove ecosystems of Goa, India. The relatively pristine site Tuvem was compared to Divar, which is prone to high nutrient input. Stratified sampling at 2-cm intervals within the 0- to 10-cm depth range showed that N2O production at both the locations decreased with depth. Elevated denitrification activity at Divar resulted in maximum production of up to 1.95 nmol N2O-N g(-1) h(-1) at 2 to 4 cm, which was three times higher than at Tuvem. Detailed investigations to understand the major pathway contributing to N2O production performed at Tuvem showed that incomplete denitrification was responsible for up to 43 to 93% of N2O production. Nitrous oxide production rates closely correlated to nitrite concentration (n = 15; r = -0.47; p production. Nitrous oxide production through nitrification was below detection, affirming that denitrification is the major pathway responsible for production of the greenhouse gas. Net N2O production in these mangrove systems are comparatively higher than those reported from other natural estuarine sediments and therefore warrant mitigation measures.

  4. Marine N2O Emissions From Nitrification and Denitrification Constrained by Modern Observations and Projected in Multimillennial Global Warming Simulations

    Science.gov (United States)

    Battaglia, G.; Joos, F.

    2018-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas (GHG) and ozone destructing agent; yet global estimates of N2O emissions are uncertain. Marine N2O stems from nitrification and denitrification processes which depend on organic matter cycling and dissolved oxygen (O2). We introduce N2O as an obligate intermediate product of denitrification and as an O2-dependent by-product from nitrification in the Bern3D ocean model. A large model ensemble is used to probabilistically constrain modern and to project marine N2O production for a low (Representative Concentration Pathway (RCP)2.6) and high GHG (RCP8.5) scenario extended to A.D. 10,000. Water column N2O and surface ocean partial pressure N2O data serve as constraints in this Bayesian framework. The constrained median for modern N2O production is 4.5 (±1σ range: 3.0 to 6.1) Tg N yr-1, where 4.5% stems from denitrification. Modeled denitrification is 65.1 (40.9 to 91.6) Tg N yr-1, well within current estimates. For high GHG forcing, N2O production decreases by 7.7% over this century due to decreasing organic matter export and remineralization. Thereafter, production increases slowly by 21% due to widespread deoxygenation and high remineralization. Deoxygenation peaks in two millennia, and the global O2 inventory is reduced by a factor of 2 compared to today. Net denitrification is responsible for 7.8% of the long-term increase in N2O production. On millennial timescales, marine N2O emissions constitute a small, positive feedback to climate change. Our simulations reveal tight coupling between the marine carbon cycle, O2, N2O, and climate.

  5. Using Pure Cultures to Define the Site Preference of Nitrous Oxide Produced by Microbial Nitrification and Denitrification

    Science.gov (United States)

    Sutka, R. L.; Breznak, J. A.; Ostrom, N. E.; Ostrom, P. H.; Gandhi, H.

    2004-12-01

    Defining the site preference of nitrous oxide (N2O) produced in pure culture studies is crucial to interpreting field data. We have previously demonstrated that the intramolecular distribution of nitrogen isotopes (isotopomers) can be used to differentiate N2O produced by nitrifier denitrification and nitrification in cultures of Nitrosomonas europaea. Here, we have expanded on our initial results and evaluated the isotopomeric composition of N2O produced during nitrification and nitrifier denitrification with cultures of Nitrosospira multiformis. In addition, we have analyzed N2O produced during methanotrophic nitrification, denitrification, and fungal denitrification. To evaluate N2O production during nitrification and nitrifier denitrification, we compared the site preference of N2O formed as a result of nitrite reduction and hydroxylamine oxidation with Nitrosomonas europaea and Nitrosospira multiformis. The average site preference of N2O produced by hydroxylamine oxidation was similar for Nitrosomonas europaea (33.0 ± 3.5 ‰ ) and Nitrosospira multiformis (33.1 ± 4.2 ‰ ). Nitrous oxide produced by nitrifier-denitrification by Nitrosomonas europaea and Nitrosospira multiformis had a similar site preference of - 1.4 ± 4.4 ‰ and - 1.1 ± 2.6 ‰ respectively. The results indicate that it is possible to differentiate between N2O produced by nitrite reduction and hydroxylamine oxidation by ammonia oxidizing bacteria. Methanotrophic nitrification was evaluated by analyzing the N2O produced during hydroxylamine oxidation in concentrated cell suspensions of two methane oxidizing bacteria. The site preference of N2O produced by the two methane oxidizers, Methylococcus capsulatus Bath and Methylosinus trichosporium was 31.8 ± 4.7 ‰ and 33.0 ± 4.5 ‰ respectively. The results indicate that a site preference of 33 ‰ is applicable for nitrification regardless of whether a methane oxidizer or ammonia oxidizer is involved in the reaction. To determine the site

  6. Relative importance of plant uptake and plant associated denitrification for removal of nitrogen from mine drainage in sub-arctic wetlands.

    Science.gov (United States)

    Hallin, Sara; Hellman, Maria; Choudhury, Maidul I; Ecke, Frauke

    2015-11-15

    Reactive nitrogen (N) species released from undetonated ammonium-nitrate based explosives used in mining or other blasting operations are an emerging environmental problem. Wetlands are frequently used to treat N-contaminated water in temperate climate, but knowledge on plant-microbial interactions and treatment potential in sub-arctic wetlands is limited. Here, we compare the relative importance of plant uptake and denitrification among five plant species commonly occurring in sub-arctic wetlands for removal of N in nitrate-rich mine drainage in northern Sweden. Nitrogen uptake and plant associated potential denitrification activity and genetic potential for denitrification based on quantitative PCR of the denitrification genes nirS, nirK, nosZI and nosZII were determined in plants growing both in situ and cultivated in a growth chamber. The growth chamber and in situ studies generated similar results, suggesting high relevance and applicability of results from growth chamber experiments. We identified denitrification as the dominating pathway for N-removal and abundances of denitrification genes were strong indicators of plant associated denitrification activity. The magnitude and direction of the effect differed among the plant species, with the aquatic moss Drepanocladus fluitans showing exceptionally high ratios between denitrification and uptake rates, compared to the other species. However, to acquire realistic estimates of N-removal potential of specific wetlands and their associated plant species, the total plant biomass needs to be considered. The species-specific plant N-uptake and abundance of denitrification genes on the root or plant surfaces were affected by the presence of other plant species, which show that both multi- and inter-trophic interactions are occurring. Future studies on N-removal potential of wetland plant species should consider how to best exploit these interactions in sub-arctic wetlands. Copyright © 2015 Elsevier Ltd. All rights

  7. Spies and Bloggers: New Synthetic Biology Tools to Understand Microbial Processes in Soils and Sediments

    Science.gov (United States)

    Masiello, C. A.; Silberg, J. J.; Cheng, H. Y.; Del Valle, I.; Fulk, E. M.; Gao, X.; Bennett, G. N.

    2017-12-01

    Microbes can be programmed through synthetic biology to report on their behavior, informing researchers when their environment has triggered changes in their gene expression (e.g. in response to shifts in O2 or H2O), or when they have participated in a specific step of an elemental cycle (e.g. denitrification). This use of synthetic biology has the potential to significantly improve our understanding of microbes' roles in elemental and water cycling, because it allows reporting on the environment from the perspective of a microbe, matching the measurement scale exactly to the scale that a microbe experiences. However, synthetic microbes have not yet seen wide use in soil and sediment laboratory experiments because synthetic organisms typically report by fluorescing, making their signals difficult to detect outside the petri dish. We are developing a new suite of microbial programs that report instead by releasing easily-detected gases, allowing the real-time, noninvasive monitoring of behaviors in sediments and soils. Microbial biosensors can, in theory, be programmed to detect dynamic processes that contribute to a wide range of geobiological processes, including C cycling (biofilm production, methanogenesis, and synthesis of extracellular enzymes that degrade organic matter), N cycling (expression of enzymes that underlie different steps of the N cycle) and potentially S cycling. We will provide an overview of the potential uses of gas-reporting biosensors in soil and sediment lab experiments, and will report the development of the systematics of these sensors. Successful development of gas biosensors for laboratory use will require addressing issues including: engineering the intensity and selectivity of microbial gas production to maximize the signal to noise ratio; normalizing the gas reporter signal to cell population size, managing gas diffusion effects on signal shape; and developing multiple gases that can be used in parallel.

  8. Flood-controlled excess-air formation favors aerobic respiration and limits denitrification activity in riparian groundwater

    Directory of Open Access Journals (Sweden)

    Simone ePeter

    2015-11-01

    Full Text Available The saturated riparian zones of rivers act as spatially and temporally variable biogeochemical reactors. This complicates the assessment of biogeochemical transport and transformation processes. During a flood event, excess-air formation, i.e. the inclusion and dissolution of air bubbles into groundwater, can introduce high amounts of dissolved O2 and thereby affect biogeochemical processes in groundwater. With the help of a field-installed membrane-inlet mass-spectrometer we resolved the effects of flood induced excess-air formationon organic carbon and nitrogen transformations in groundwater of different riparian zones of a restored section of the River Thur, Switzerland. The results show that the flood event triggered high aerobic respiration activity in the groundwater below a zone densely populated with willow plants. The flood introduced high concentrations of O2 (230 µmol L–1 to the groundwater through the formation of excess air and transported up to ~400 µmol L 1 organic carbon from the soil/root layer into groundwater during the movement of the water table. A rapid respiration process, quantified via the measurements of O2, CO2 and noble-gas concentrations, led to fast depletion of the introduced O2 and organic carbon and to high CO2 concentration (590 µmol L–1 in the groundwater shortly after the flood. The synchronous analysis of different nitrogen species allowed studying the importance of denitrification activity. The results indicate that in the willow zone excess-air formation inhibited denitrification through high O2 concentration input. Instead, the observed decrease in nitrate concentration (~50 µmol N L 1 may be related to fostered nitrate uptake by plants. In the other riparian zones closer to the river, no significant excess-air formation and corresponding respiration activity was observed. Overall, analyzing the dissolved gases in the groundwater significantly contributed to deciphering biogeochemical processes in

  9. Stochastic processes in cell biology

    CERN Document Server

    Bressloff, Paul C

    2014-01-01

    This book develops the theory of continuous and discrete stochastic processes within the context of cell biology.  A wide range of biological topics are covered including normal and anomalous diffusion in complex cellular environments, stochastic ion channels and excitable systems, stochastic calcium signaling, molecular motors, intracellular transport, signal transduction, bacterial chemotaxis, robustness in gene networks, genetic switches and oscillators, cell polarization, polymerization, cellular length control, and branching processes. The book also provides a pedagogical introduction to the theory of stochastic process – Fokker Planck equations, stochastic differential equations, master equations and jump Markov processes, diffusion approximations and the system size expansion, first passage time problems, stochastic hybrid systems, reaction-diffusion equations, exclusion processes, WKB methods, martingales and branching processes, stochastic calculus, and numerical methods.   This text is primarily...

  10. Hybrid Thermochemical/Biological Processing

    Science.gov (United States)

    Brown, Robert C.

    The conventional view of biorefineries is that lignocellulosic plant material will be fractionated into cellulose, hemicellulose, lignin, and terpenes before these components are biochemically converted into market products. Occasionally, these plants include a thermochemical step at the end of the process to convert recalcitrant plant components or mixed waste streams into heat to meet thermal energy demands elsewhere in the facility. However, another possibility for converting high-fiber plant materials is to start by thermochemically processing it into a uniform intermediate product that can be biologically converted into a bio-based product. This alternative route to bio-based products is known as hybrid thermochemical/biological processing. There are two distinct approaches to hybrid processing: (a) gasification followed by fermentation of the resulting gaseous mixture of carbon monoxide (CO), hydrogen (H2), and carbon dioxide (CO2) and (b) fast pyrolysis followed by hydrolysis and/or fermentation of the anhydrosugars found in the resulting bio-oil. This article explores this "cart before the horse" approach to biorefineries.

  11. USBF-system of biological wastewater treatment; Elsistema USBF en la depuracion biologica de aguas residuales

    Energy Technology Data Exchange (ETDEWEB)

    Ampudia Gutierrez, J.

    2003-07-01

    An advanced system of biological wastewater treatment, has been developed by the company Depuralia. This system brings up a technological innovation, which has been awarded with several international awards. The wastewater treatment, occurs in an activated sludge reactor of extended aeration with a very low mass loading, with a nitrification-denitrification process, and water separation-clarification by upflow sludge blanket-filtration. The arrangement of a compact biological reactor enables complex wastewater treatment. High efficiency of the separation through sludge filtration provides functionality of the equipment with high concentration of activated sludge, with less implementation surface and volume. The elements of the biological reactor are described, the advantages are enumerated, and the results obtained in several accomplishments are shown; in the industrial as well as in the urban water treatment plants. (Author) 9 refs.

  12. Nutrient and carbon availability influences on denitrification in the regulated Lower Colorado River, Austin

    Science.gov (United States)

    Spector, J.

    2016-12-01

    The Lower Colorado River in Austin, Texas receives nitrogen-rich runoff and treated wastewater effluent and is subject to periodic water releases from the Longhorn Dam, which cause fluctuations in groundwater stage downstream. This research examined groundwater denitrification at the Hornsby Bend riparian area (located approximately 24 km downstream of downtown Austin) and characterized how dam-induced hyporheic exchange affects denitrification rates. Conductivity, temperature, water level, and dissolved oxygen concentrations were measured continuously throughout flood pulses for six months using dataloggers installed in a transect of seven monitoring wells on the river bank. Hourly samples were collected using an autosampler in one monitoring well (MW-5) during various flood conditions during the six month monitoring period. Water samples were analyzed for total organic carbon, total nitrogen, anions (NO3- and NO2-), NH4+ concentrations, alkalinity, and specific ultraviolet absorbance (SUVA) to characterize dissolved organic matter. Following large flood events (up to 4 m of water level stage increase), average conductivity increased 300 µs/centimeter in MW-5 as the water level receded. Analysis of water samples indicated that NO3- reduction occurred as conductivity and alkalinity increased. In addition, NH4+ concentrations increased during high conductivity periods. Increased denitrification activity corresponded with high SUVA. High conductivity and alkalinity increase the availability of electron donors (HCO3- and CO32-) and enhances denitrification potential. Higher SUVA values indicate increased dissolved organic carbon aromaticity and corresponding NO3- reduction. Additionally, changes in dissolved organic matter lability indicate the residence times of possible reactive organic carbon in the riparian area. This study has implications for determining advantageous geochemical conditions for hyporheic zone denitrification following large flood events.

  13. Heterotrophic denitrification vs. autotrophic anammox – quantifying collateral effects on the oceanic carbon cycle

    Directory of Open Access Journals (Sweden)

    W. Koeve

    2010-08-01

    Full Text Available The conversion of fixed nitrogen to N2 in suboxic waters is estimated to contribute roughly a third to total oceanic losses of fixed nitrogen and is hence understood to be of major importance to global oceanic production and, therefore, to the role of the ocean as a sink of atmospheric CO2. At present heterotrophic denitrification and autotrophic anammox are considered the dominant sinks of fixed nitrogen. Recently, it has been suggested that the trophic nature of pelagic N2-production may have additional, "collateral" effects on the carbon cycle, where heterotrophic denitrification provides a shallow source of CO2 and autotrophic anammox a shallow sink. Here, we analyse the stoichiometries of nitrogen and associated carbon conversions in marine oxygen minimum zones (OMZ focusing on heterotrophic denitrification, autotrophic anammox, and dissimilatory nitrate reduction to nitrite and ammonium in order to test this hypothesis quantitatively. For open ocean OMZs the combined effects of these processes turn out to be clearly heterotrophic, even with high shares of the autotrophic anammox reaction in total N2-production and including various combinations of dissimilatory processes which provide the substrates to anammox. In such systems, the degree of heterotrophy (ΔCO2:ΔN2, varying between 1.7 and 6.5, is a function of the efficiency of nitrogen conversion. On the contrary, in systems like the Black Sea, where suboxic N-conversions are supported by diffusive fluxes of NH4+ originating from neighbouring waters with sulphate reduction, much lower values of ΔCO2:ΔN2 can be found. However, accounting for concomitant diffusive fluxes of CO2, the ratio approaches higher values similar to those computed for open ocean OMZs. Based on this analysis, we question the significance of collateral effects concerning the trophic

  14. Temporary storage or permanent removal? The division of nitrogen between biotic assimilation and denitrification in stormwater biofiltration systems.

    Directory of Open Access Journals (Sweden)

    Emily G I Payne

    Full Text Available The long-term efficacy of stormwater treatment systems requires continuous pollutant removal without substantial re-release. Hence, the division of incoming pollutants between temporary and permanent removal pathways is fundamental. This is pertinent to nitrogen, a critical water body pollutant, which on a broad level may be assimilated by plants or microbes and temporarily stored, or transformed by bacteria to gaseous forms and permanently lost via denitrification. Biofiltration systems have demonstrated effective removal of nitrogen from urban stormwater runoff, but to date studies have been limited to a 'black-box' approach. The lack of understanding on internal nitrogen processes constrains future design and threatens the reliability of long-term system performance. While nitrogen processes have been thoroughly studied in other environments, including wastewater treatment wetlands, biofiltration systems differ fundamentally in design and the composition and hydrology of stormwater inflows, with intermittent inundation and prolonged dry periods. Two mesocosm experiments were conducted to investigate biofilter nitrogen processes using the stable isotope tracer 15NO3(- (nitrate over the course of one inflow event. The immediate partitioning of 15NO3(- between biotic assimilation and denitrification were investigated for a range of different inflow concentrations and plant species. Assimilation was the primary fate for NO3(- under typical stormwater concentrations (∼1-2 mg N/L, contributing an average 89-99% of 15NO3(- processing in biofilter columns containing the most effective plant species, while only 0-3% was denitrified and 0-8% remained in the pore water. Denitrification played a greater role for columns containing less effective species, processing up to 8% of 15NO3(-, and increased further with nitrate loading. This study uniquely applied isotope tracing to biofiltration systems and revealed the dominance of assimilation in stormwater

  15. Hydrogeological and multi-isotopic approach to define nitrate pollution and denitrification processes in a coastal aquifer (Sardinia, Italy)

    Science.gov (United States)

    Pittalis, Daniele; Carrey, Raul; Da Pelo, Stefania; Carletti, Alberto; Biddau, Riccardo; Cidu, Rosa; Celico, Fulvio; Soler, Albert; Ghiglieri, Giorgio

    2018-02-01

    Agricultural coastal areas are frequently affected by the superimposition of various processes, with a combination of anthropogenic and natural sources, which degrade groundwater quality. In the coastal multi-aquifer system of Arborea (Italy)—a reclaimed morass area identified as a nitrate vulnerable zone, according to Nitrate Directive 91/676/EEC—intensive agricultural and livestock activities contribute to substantial nitrate contamination. For this reason, the area can be considered a bench test for tuning an appropriate methodology aiming to trace the nitrate contamination in different conditions. An approach combining environmental isotopes, water quality and hydrogeological indicators was therefore used to understand the origins and attenuation mechanisms of nitrate pollution and to define the relationship between contaminant and groundwater flow dynamics through the multi-aquifer characterized by sandy (SHU), alluvial (AHU), and volcanic hydrogeological (VHU) units. Various groundwater chemical pathways were consistent with both different nitrogen sources and groundwater dynamics. Isotope composition suggests a mixed source for nitrate (organic and synthetic fertilizer), especially for the AHU and SHU groundwater. Moreover, marked heterotrophic denitrification and sulfate reduction processes were detected; although, for the contamination related to synthetic fertilizer, the attenuation was inefficient at removing NO3 - to less than the human consumption threshold of 50 mg/L. Various factors contributed to control the distribution of the redox processes, such as the availability of carbon sources (organic fertilizer and the presence of lagoon-deposited aquitards), well depth, and groundwater flow paths. The characterization of these processes supports water-resource management plans, future actions, and regulations, particularly in nitrate vulnerable zones.

  16. River water infiltration enhances denitrification efficiency in riparian groundwater.

    Science.gov (United States)

    Trauth, Nico; Musolff, Andreas; Knöller, Kay; Kaden, Ute S; Keller, Toralf; Werban, Ulrike; Fleckenstein, Jan H

    2018-03-01

    Nitrate contamination in ground- and surface water is a persistent problem in countries with intense agriculture. The transition zone between rivers and their riparian aquifers, where river water and groundwater interact, may play an important role in mediating nitrate exports, as it can facilitate intensive denitrification, which permanently removes nitrate from the aquatic system. However, the in-situ factors controlling riparian denitrification are not fully understood, as they are often strongly linked and their effects superimpose each other. In this study, we present the evaluation of hydrochemical and isotopic data from a 2-year sampling period of river water and groundwater in the riparian zone along a 3rd order river in Central Germany. Based on bi- and multivariate statistics (Spearman's rank correlation and partial least squares regression) we can show, that highest rates for oxygen consumption and denitrification in the riparian aquifer occur where the fraction of infiltrated river water and at the same time groundwater temperature, are high. River discharge and depth to groundwater are additional explanatory variables for those reaction rates, but of minor importance. Our data and analyses suggest that at locations in the riparian aquifer, which show significant river water infiltration, heterotrophic microbial reactions in the riparian zone may be fueled by bioavailable organic carbon derived from the river water. We conclude that interactions between rivers and riparian groundwater are likely to be a key control of nitrate removal and should be considered as a measure to mitigate high nitrate exports from agricultural catchments. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Nitrous oxide production and consumption by denitrification in a grassland: Effects of grazing and hydrology.

    Science.gov (United States)

    Hu, Jing; Inglett, Kanika S; Clark, Mark W; Inglett, Patrick W; Ramesh Reddy, K

    2015-11-01

    Denitrification is generally recognized as a major mechanism contributing to nitrous oxide (N2O) production, and is the only known biological process for N2O consumption. Understanding factors controlling N2O production and consumption during denitrification will provide insights into N2O emission variability, and potentially predict capacity of soils to serve as sinks or sources of N2O. This study investigated the effects of hydrology and grazing on N2O production and consumption in a grassland based agricultural watershed. A batch incubation study was conducted on soils (0-10 cm) collected along a hydrological gradient representing isolated wetland (Center), transient zone (Edge) and pasture upland (Upland), from both grazed and ungrazed areas. Production and consumption potentials of N2O were quantified on soils under four treatments, including (i) ambient condition, and amended with (ii) NO3(-), (iii) glucose-C, and (iv) NO3(-) +glucose-C. The impacts of grazing on N2O production and consumption were not observed. Soils in hydrologically distinct zones responded differently to N2O production and consumption. Under ambient conditions, both production and consumption rates of Edge soils were higher than those observed for Center and Upland soils. Results of amended incubations suggested NO3(-) was a key factor limiting N2O production and consumption rates in all hydrological zones. Over 5-d incubation with NO3(-) amendment, cumulative production and consumption of N2O for Center soils were 1.6 and 3.3 times higher than Edge soils, and 3.6 and 7.6 times higher than Upland soils, respectively. However, cumulative N2O net production for Edge soils was the highest, with 2 to 3 times higher than Upland and Center soils. Our results suggest that the transient areas between wetland and upland are likely to be "hot spots" of N2O emissions in this ecosystem. Wetlands within agricultural landscapes can potentially function to reduce both NO3(-) leaching and N2O emissions

  18. Development of mixed microbial granular biofilms for denitrification of concentrated wastes

    International Nuclear Information System (INIS)

    Krishna Mohan, T.V.; Nancharaiah, Y.V.; Venugopalan, V.P.; Narasimhan, S.V.; Satyasai, P.M.

    2010-01-01

    Nitrate containing wastes are generated at various stages of the nuclear fuel cycle; fuel fabrication and reprocessing. A treatment process for removing nitrate from such concentrated nitrate bearing effluents is needed. Among other available options, biological denitrification is an economical and technically feasible method for nitrate removal. Granular biofilm based sequencing batch reactors (SBRs) may allow designing a compact and high rate processes suitable for the treatment of concentrated effluents. Hence, experiments were carried out in laboratory scale sequencing batch reactors (SBRs) to develop granular biofilms (composed of mixed microbes) for removing nitrate from the concentrated nitrate containing-media. Microbial granular biofilms, capable of consuming nitrate up to 2710 mg/l nitrate-N, were developed under anaerobic conditions in a 6-litre volume sequencing batch reactor (SBR). The SBR was inoculated with activated sludge flocs and operated with 24-h cycle and 50% volumetric exchange ratio. Synthetic media containing acetate as the energy source and electron donor, at carbon to nitrogen molar ratio of 2:1 and 3:1 was fed into the SBRs. Nitrate-N concentration in the SBR was increased in a step-wise manner starting from 677 to 2710 mg/l (1355 to 5420 mg/l in the feed). Complete removal of influent nitrate occurred within the first few hours of SBR cycle period. Effluent nitrate and nitrite levels (∼3 mg/l nitrate-N or nitrite-N) at the end of SBR cycle period (24 h) were found to be below the discharge limits. Under these conditions biomass predominantly consisted of granular biofilms. Results show the potential of granular biofilm based SBR for converting nitrate to nitrogen gas from concentrated nitrate bearing industrial effluents. (author)

  19. The role of C:N:P stoichiometry in affecting denitrification in sediments from agricultural surface and tile-water wetlands.

    Science.gov (United States)

    Grebliunas, Brian D; Perry, William L

    2016-01-01

    Nutrient stoichiometry within a wetland is affected by the surrounding land use, and may play a significant role in the removal of nitrate (NO3-N). Tile-drained, agricultural watersheds experience high seasonal inputs of NO3-N, but low phosphorus (PO4-P) and dissolved organic carbon (DOC) loads relative to surface water dominated systems. This difference may present stoichiometric conditions that limit denitrification within receiving waterways. We investigated how C:N:P ratios affected denitrification rates of sediments from tile-drained mitigation wetlands incubated for: 0, 5, 10, and 20 days. We then tested whether denitrification rates of sediments from surface-water and tile-drained wetlands responded differently to C:N ratios of 2:1 versus 4:1. Ratios of C:N:P (P tile-drained wetland sediments. Carbon limitation of denitrification became evident at elevated NO3-N concentrations (20 mg L(-1)). Denitrification measured from tile water and surface water wetland sediments increased significantly (P < 0.05) at the 2:1 and 4:1 C:N treatments. The results from both experiments suggest wetland sediments provide a limiting pool of labile DOC to maintain prolonged NO3-N removal. Also, DOC limitation became more evident at elevated NO3-N concentrations (20 mg L(-1)). Irrespective of NO3-N concentrations, P did not limit denitrification rates. In addition to wetting period, residence time, and maintenance of anaerobic conditions, the availability of labile DOC is playing an important limiting role in sediment denitrification within mitigation wetlands.

  20. Achieving mainstream nitrogen removal through simultaneous partial nitrification, anammox and denitrification process in an integrated fixed film activated sludge reactor.

    Science.gov (United States)

    Wang, Chao; Liu, Sitong; Xu, Xiaochen; Zhang, Chaolei; Wang, Dong; Yang, Fenglin

    2018-07-01

    The anaerobic ammonium oxidation (anammox) is becoming a critical technology for energy neutral in mainstream wastewater treatment. However, the presence of chemical oxygen demanding in influent would result in a poor nitrogen removal efficiency during the deammonification process. In this study, the simultaneous partial nitrification, anammox and denitrification process (SNAD) for mainstream nitrogen removal was investigated in an integrated fixed film activated sludge (IFAS) reactor. SNAD-IFAS process achieved a total nitrogen (TN) removal efficiency of 72 ± 2% and an average COD removal efficiency was 88%. The optimum COD/N ratio for mainstream wastewater treatment was 1.2 ± 0.2. Illumina sequencing analysis and activity tests showed that anammox and denitrifying bacteria were the dominant nitrogen removal microorganism in the biofilm and the high COD/N ratios (≥2.0) leaded to the proliferation of heterotrophic bacteria (Hydrogenophaga) and nitrite-oxidizing bacteria (Nitrospira) in the suspended sludge. Network analysis confirmed that anammox bacteria (Candidatus Kuenenia) could survive in organic matter environment due to that anammox bacteria displayed significant co-occurrence through positive correlations with some heterotrophic bacteria (Limnobacter) which could protect anammox bacteria from hostile environments. Overall, the results of this study provided more comprehensive information regarding the community composition and assemblies in SNAD-IFAS process for mainstream nitrogen removal. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Combined Pre-Precipitation, Biological Sludge Hydrolysis and Nitrogen Reduction - A Pilot Demonstration of Integrated Nutrient Removal

    DEFF Research Database (Denmark)

    Kristensen, G. H.; Jørgensen, P. E.; Strube, R.

    1992-01-01

    solubilization was 10-13% of the suspended COD. The liquid phase of the hydrolyzed sludge, the hydrolysate, was separated from the suspended fraction by centrifugation and added to the biological nitrogen removal stage to support denitrification. The hydrolysate COD consisted mainly of volatile fatty acids......A pilot study was performed to investigate advanced wastewater treatment by pre-precipitation in combination with biological nitrogen removal supported by biological sludge hydrolysis. The influent wastewater was pretreated by addition of a pre-polymerized aluminum salt, followed by flocculation......, resulting in high denitrification rates. Nitrogen reduction was performed based on the Bio-Denitro principle in an activated sludge system. Nitrogen was reduced from 45 mg/l to 9 mg/l and phosphorus was reduced from 11 mg/l to 0.5 mg/l. The sludge yield was low, approx. 0.3-0.4 gCOD/gCOD removed...

  2. Evaluation of gasoline-denatured ethanol as a carbon source for denitrification.

    Science.gov (United States)

    Kazasi, Anna; Boardman, Gregory D; Bott, Charles B

    2013-06-01

    In this study concerning denitrification, the performance of three carbon sources, methanol (MeOH), ethanol (EtOH) and gasoline-denatured ethanol (dEtOH), was compared and evaluated on the basis of treatment efficiency, inhibition potential and cost. The gasoline denaturant considered here contained mostly aliphatic compounds and little of the components that typically boost the octane rating, such as benzene, toluene, ethylbenzene and xylenes. Results were obtained using three lab-scale SBRs operated at SRT of 12.0 +/- 0.9 days. After biomass was acclimated, denitrification rates with dEtOH were similar to those of EtOH (201 +/- 50 and 197 +/- 28 NO3-N/g MLVSS x d, respectively), and higher than those of MeOH (165 +/- 49 mg NO3-N/g MLVSS x d). The denaturant did not affect biomass production, nitrification or denitrification. Effluent soluble COD concentrations were always less than the analytical detection limit. Although the cost of dEtOH ($2.00/kg nitrate removed) was somewhat higher than that of methanol ($1.63/kg nitrate removed), the use of dEtOH is very promising and utilities will have to decide if it is worth paying a little extra to take advantage of its benefits.

  3. Fluctuating Thermodynamics for Biological Processes

    Science.gov (United States)

    Ham, Sihyun

    Because biomolecular processes are largely under thermodynamic control, dynamic extension of thermodynamics is necessary to uncover the mechanisms and driving factors of fluctuating processes. The fluctuating thermodynamics technology presented in this talk offers a practical means for the thermodynamic characterization of conformational dynamics in biomolecules. The use of fluctuating thermodynamics has the potential to provide a comprehensive picture of fluctuating phenomena in diverse biological processes. Through the application of fluctuating thermodynamics, we provide a thermodynamic perspective on the misfolding and aggregation of the various proteins associated with human diseases. In this talk, I will present the detailed concepts and applications of the fluctuating thermodynamics technology for elucidating biological processes. This work was supported by Samsung Science and Technology Foundation under Project Number SSTF-BA1401-13.

  4. Removal of highly elevated nitrate from drinking water by pH-heterogenized heterotrophic denitrification facilitated with ferrous sulfide-based autotrophic denitrification.

    Science.gov (United States)

    Huang, Bin; Chi, Guangyu; Chen, Xin; Shi, Yi

    2011-11-01

    The performance of acetic acid-supported pH-heterogenized heterotrophic denitrification (HD) facilitated with ferrous sulfide-based autotrophic denitrification (AD) was investigated in upflow activated carbon-packed column reactors for reliable removal of highly elevated nitrate (42 mg NO(3)-Nl(-1)) in drinking water. The use of acetic acid as substrate provided sufficient internal carbon dioxide to completely eliminate the need of external pH adjustment for HD, but simultaneously created vertically heterogenized pH varying from 4.8 to 7.8 in the HD reactor. After 5-week acclimation, the HD reactor developed a moderate nitrate removal capacity with about one third of nitrate removal occurring in the acidic zone (pH 4.8-6.2). To increase the treatment reliability, acetic acid-supported HD was operated under 10% carbon limitation to remove >85% of nitrate, and ferrous sulfide-based AD was supplementally operated to remove residual nitrate and formed nitrite without excess of soluble organic carbon, nitrite or sulfate in the final effluent. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Quantifying denitrification losses from a sub-tropical pasture in Queensland/Australia - use of the 15N gas flux method

    Science.gov (United States)

    Friedl, Johannes; Scheer, Clemens; Warner, Daniel; Grace, Peter

    2014-05-01

    denitrification. This study highlights denitrification as a major pathway of N loss for sub-tropical pasture systems with a substantial amount of applied fertiliser lost as N2 at high WFPS. The 15N gas flux method proved an effective tool in assessing N losses from fertilised soils. However, its suitability to determine N2 fluxes from soils with lower denitrification rates needs to be confirmed in future studies. The high variation between soil cores emphasises the need for field measurements with a high spatial and temporal resolution in order to capture the dynamics of N2 emissions. Mulvaney, R. L. and L. T. Kurtz. 1984. "Evolution of Dinitrogen and Nitrous Oxide from Nitrogen-15 Fertilized Soil Cores Subjected to Wetting and Drying Cycles1." Soil Sci. Soc. Am. J. 48 (3): 596-602. https://www.soils.org/publications/sssaj/abstracts/48/3/596. doi: 10.2136/sssaj1984.03615995004800030026x. Stevens, R. J. and R. J. Laughlin. 2001. "Lowering the detection limit for dinitrogen using the enrichment of nitrous oxide." Soil Biology and Biochemistry 33 (9): 1287-1289. http://www.sciencedirect.com/science/article/pii/S0038071701000360. doi: http://dx.doi.org/10.1016/S0038-0717(01)00036-0.

  6. Selective enhancement and verification of woody biomass digestibility as a denitrification carbon source.

    Science.gov (United States)

    Hu, Rongting; Zheng, Xilai; Xin, Jia; Sun, Zhaoyue; Zheng, Tianyuan

    2017-11-01

    The denitrification efficiency of woody biomass as carbon source is low because of its poor carbon availability. In this study, representative poplar sawdust was pretreated with lime and peracetic acid to enhance the biomass digestibility to different degrees; sawdust was then mixed with soil to investigate its denitrification efficiency. Under controllable conditions (25-95°C, 12-24h, varying dosages), sawdust digestibility (characterized by reducing sugar yield) was selectively enhanced 1.0-21.8 times over that of the raw sawdust (28.8mgeq.glucoseg -1 dry biomass). This increase was mainly attributed to the removal of lignin from the biomass. As a carbon source, the sawdust (digestibility enhanced by 5.4 times) increased the nitrate removal rate by 4.7 times, without N 2 O emission. However, the sawdust with high digestibility (12.6 or 18.0 times), despite releasing more dissolved organic carbon (DOC), did not exhibit further increase in denitrification efficiency, and emitted N 2 O. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. From Partial nitrification to canon in an aerobic granular SBR

    International Nuclear Information System (INIS)

    Vazquez-Padin, J.; Figueroa, M.; Campos, J. L.; Mosquera-Corral, A.; Mendez, R.

    2009-01-01

    Nitrogen removal via nitrification-denitrification processes is commonly used in biology wastewater treatment plants to remove nitrogen compounds. In recent years new technologies emerged bringing solutions to remove nitrogen from wastewaters with not enough COD content to complete the denitrification process. An alternative strategy to the conventional nitrification-denitrification processes has been developed in the nine tries consisting of a combination of the oxidation of half of the ammonium from the wastewater to nitrite via partial nitrification and the removal of both, ammonium and formed nitrite by the Anammox process. (Author)

  8. Comparing cost and process performance of activated sludge (AS) and biological aerated filters (BAF) over ten years of full sale operation.

    Science.gov (United States)

    Hansen, R; Thogersen, T; Rogalla, F

    2007-01-01

    In the early 1990s, the Wastewater Treatment Plant (WWTP) of Frederikshavn, Denmark, was extended to meet new requirements for nutrient removal (8 mg/L TN, 1.5 mg TP/L) as well as to increase its average daily flow to 16,500 m(3)/d (4.5 MGD). As the most economical upgrade of the existing activated sludge (AS) plant, a parallel biological aerated filter (BAF) was selected, and started up in 1995. Running two full scale processes in parallel for over ten years on the same wastewater and treatment objectives enabled a direct comparison in relation to operating performance, costs and experience. Common pretreatment consists of screening, an aerated grit and grease removal and three primary settlers with chemical addition. The effluent is then pumped to the two parallel biological treatment stages, AS with recirculation and an upflow BAF with floating media. The wastewater is a mixture of industrial and domestic wastewater, with a dominant discharge of fish processing effluent which can amount to 50% of the flow. The maximum hydraulic load on the pretreatment section as a whole is 1,530 m(3)/h. Approximately 60% of the sewer system is combined with a total of 32 overflow structures. To avoid the direct discharge of combined sewer overflows into the receiving waters, the total hydraulic wet weather capacity of the plant is increased to 4,330 m(3)/h, or 6 times average flow. During rain, some of the raw sewage can be directed through a stormwater bypass to the BAF, which can be modified in its operation to accommodate various treatment needs: either using simultaneous nitrification/denitrification in all filters with recirculation introducing bottom aeration with full nitrification in some filters for storm treatment and/or post-denitrification in one filter. After treatment, the wastewater is discharged to the Baltic Sea through a 500 m outfall. The BAF backwash sludge, approximately 1,900 m(3) per 24 h in dry weather, is redirected to the AS plant. Primary settler

  9. Global sensitivity analysis for identifying important parameters of nitrogen nitrification and denitrification under model uncertainty and scenario uncertainty

    Science.gov (United States)

    Chen, Zhuowei; Shi, Liangsheng; Ye, Ming; Zhu, Yan; Yang, Jinzhong

    2018-06-01

    Nitrogen reactive transport modeling is subject to uncertainty in model parameters, structures, and scenarios. By using a new variance-based global sensitivity analysis method, this paper identifies important parameters for nitrogen reactive transport with simultaneous consideration of these three uncertainties. A combination of three scenarios of soil temperature and two scenarios of soil moisture creates a total of six scenarios. Four alternative models describing the effect of soil temperature and moisture content are used to evaluate the reduction functions used for calculating actual reaction rates. The results show that for nitrogen reactive transport problem, parameter importance varies substantially among different models and scenarios. Denitrification and nitrification process is sensitive to soil moisture content status rather than to the moisture function parameter. Nitrification process becomes more important at low moisture content and low temperature. However, the changing importance of nitrification activity with respect to temperature change highly relies on the selected model. Model-averaging is suggested to assess the nitrification (or denitrification) contribution by reducing the possible model error. Despite the introduction of biochemical heterogeneity or not, fairly consistent parameter importance rank is obtained in this study: optimal denitrification rate (Kden) is the most important parameter; reference temperature (Tr) is more important than temperature coefficient (Q10); empirical constant in moisture response function (m) is the least important one. Vertical distribution of soil moisture but not temperature plays predominant role controlling nitrogen reaction. This study provides insight into the nitrogen reactive transport modeling and demonstrates an effective strategy of selecting the important parameters when future temperature and soil moisture carry uncertainties or when modelers face with multiple ways of establishing nitrogen

  10. Industrial residues as an external carbon source in denitrification; Industrielle Reststoffe als externe Kohlenstoffquelle fuer die Denitrifikation

    Energy Technology Data Exchange (ETDEWEB)

    Schories, G. [TECON GmbH, Clausthal-Zellerfeld (Germany); Geissen, S.U.; Vogelpohl, A. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). Inst. fuer Thermische Verfahrenstechnik

    1999-07-01

    Biological waste water treatment requires biologically readily degradable carbon in order to permit elimination of as much nitrogen as possible. Often now this type of carbon is no longer present in waste water in an appropriate quantity, so that external carbon must be added. Apart from industrially fabricated substrates, the use of industrial residues and waste products as well as of partial waste water streams with a high organic pollutant load is lately being considered for cost reasons. But this is not altogether harmless. Those partial streams may contain substances that inhibit denitrification, impose an additional burden on subsequent cleaning stages or may even pass them unmodified, so that they are emitted into the environment and pose an ecological hazard potential. Hence, industrial residual products need to be specifically selected for use as an external carbon source in denitrification. A suitable strategy is described and demonstrated by means of different examples. (orig.) [German] In der biologischen Abwasserbehandlung ist fuer eine weitestgehende Stickstoffelimination oftmals biologisch gut abbaubarer Kohlenstoff im Abwasser nicht (mehr) in ausreichendem Masse vorhanden. Dann ist die Zugabe einer sog. externen Kohlenstoffquelle erforderlich. Neben industriell hergestellten Substraten wird in letzter Zeit aus Kostengruenden vielfach der Einsatz industrieller Rest- und Abfallstoffe sowie organisch hochbelasteter Abwasserteilstroeme erwogen. Dies ist jedoch nicht unproblematisch, da in diesen Stoffstroemen auch Substanzen enthalten sein koennen, die die Denitrifikation hemmen, nachfolgende Reinigungsstufen zusaetzlich belasten oder diese sogar unveraendert passsieren, dadurch in die Umwelt emittiert werden und damit moeglicherweise aus oekologischer Sicht ein Gefahrenpotential darstellen koennen. Es muss also eine besondere Auswahl der Pruefung industrieller Reststoffe im Hinblick auf den Einsatz als externe Kohlenstoffquelle in der Denitrifikation

  11. A soil infiltration system incorporated with sulfur-utilizing autotrophic denitrification (SISSAD) for domestic wastewater treatment.

    Science.gov (United States)

    Kong, Zhe; Feng, Chuanping; Chen, Nan; Tong, Shuang; Zhang, Baogang; Hao, Chunbo; Chen, Kun

    2014-05-01

    To enhance the denitrification performance of soil infiltration, a soil infiltration system incorporated with sulfur-utilizing autotrophic denitrification (SISSAD) for domestic wastewater treatment was developed, and the SISSAD performance was evaluated using synthetic domestic wastewater in this study. The aerobic respiration and nitrification were mainly taken place in the upper aerobic stage (AES), removed 88.44% COD and 89.99% NH4(+)-N. Moreover, autotrophic denitrification occurred in the bottom anaerobic stage (ANS), using the CO2 produced from AES as inorganic carbon source. Results demonstrated that the SISSAD showed a remarkable performance on COD removal efficiency of 95.09%, 84.86% for NO3(-)-N, 95.25% for NH4(+)-N and 93.15% for TP. This research revealed the developed system exhibits a promising application prospect for domestic wastewater in the future. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Evidence for denitrification as main source of N2O emission from residue-amended soil

    DEFF Research Database (Denmark)

    Li, Xiaoxi; Sørensen, Peter; Olesen, Jørgen Eivind

    2016-01-01

    -leguminous species (ryegrass). Plant material was placed in a discrete layer surrounded by soil in which the nitrate View the MathML source pool was enriched with 15N to distinguish N2O derived from denitrification and nitrification. Net N mineralisation from leguminous catch crops was significant (30–48 mg N kg−1....... Emission of N2O occurred at all moisture levels, but was higher at 50 and 60% WFPS than at 40% in soil with leguminous residues. The 15N enrichment of N2O indicated that denitrification was the dominant source independent of moisture level and residue type. We conclude that catch crop residues...... will stimulate N2O emissions via denitrification over a wide range of soil moisture conditions, but that emission levels may depend significantly on residue quality and soil moisture....

  13. Biological Water Processor and Forward Osmosis Secondary Treatment

    Science.gov (United States)

    Shull, Sarah; Meyer, Caitlin

    2014-01-01

    The goal of the Biological Water Processor (BWP) is to remove 90% organic carbon and 75% ammonium from an exploration-based wastewater stream for four crew members. The innovative design saves on space, power and consumables as compared to the ISS Urine Processor Assembly (UPA) by utilizing microbes in a biofilm. The attached-growth system utilizes simultaneous nitrification and denitrification to mineralize organic carbon and ammonium to carbon dioxide and nitrogen gas, which can be scrubbed in a cabin air revitalization system. The BWP uses a four-crew wastewater comprised of urine and humidity condensate, as on the ISS, but also includes hygiene (shower, shave, hand washing and oral hygiene) and laundry. The BWP team donates 58L per day of this wastewater processed in Building 7.

  14. Autoxidation and acetylene-accelerated oxidation of NO in a 2-phase system; implications for the expression of denitrification in ex situ experiments

    Science.gov (United States)

    Nadeem, Shahid; Dörsch, Peter; Bakken, Lars

    2013-04-01

    Denitrification allows microorganisms to sustain respiration under anoxic conditions. The typical niche for denitrification is an environment with fluctuating oxygen concentrations such as soils and borders between anoxic and oxic zones of biofilms and sediments. In such environments, the organisms need adequate regulation of denitrification in response to changing oxygen availability to tackle both oxic and anoxic spells. The regulation of denitrification in soils has environmental implications, since it affects the proportions of N2, N2O and NO emitted to the atmosphere. The expression of denitrification enzymes is regulated by a complex regulatory network involving one or several positive feedback loops via the intermediate nitrogen oxides. Nitric oxide (NO) is known to induce denitrification in model organisms, but the quantitative effect of NO and its concentration dependency has not been assessed for denitrification in soils. NO is chemically unstable in the presence of oxygen due to autoxidation, and the oxidation of NO is accelerated by acetylene (C2H2) which is commonly used as an inhibitor of N2O reductase in denitrification studies. As a first step to a better understanding of NO's role in soil denitrification, we investigated NO oxidation kinetics for a closed "two phase" system (i.e. liquid phase + headspace) typically used for denitrification experiments with soil slurries, with and without acetylene present. Models were developed to adequately predict autoxidation and acetylene-accelerated oxidation. The minimum oxygen concentration in the headspace ([O2]min, mL L-1) for acetylene-accelerated NO oxidation was found to increase linearly with the NO concentration ([NO], mL L-1); [O2]min= 0.192 + [NO]*0.1 (r2=0.978). The models for NO oxidation were then used to assess NO-oxidation rates in denitrification experiments with batches of bacterial cells extracted from soil. The batches were exposed to low initial oxygen concentrations in gas tight serum

  15. A Friendly-Biological Reactor SIMulator (BioReSIM for studying biological processes in wastewater treatment processes

    Directory of Open Access Journals (Sweden)

    Raul Molina

    2014-12-01

    Full Text Available Biological processes for wastewater treatments are inherently dynamic systems because of the large variations in the influent wastewater flow rate, concentration composition and the adaptive behavior of the involved microorganisms. Moreover, the sludge retention time (SRT is a critical factor to understand the bioreactor performances when changes in the influent or in the operation conditions take place. Since SRT are usually in the range of 10-30 days, the performance of biological reactors needs a long time to be monitored in a regular laboratory demonstration, limiting the knowledge that can be obtained in the experimental lab practice. In order to overcome this lack, mathematical models and computer simulations are useful tools to describe biochemical processes and predict the overall performance of bioreactors under different working operation conditions and variations of the inlet wastewater composition. The mathematical solution of the model could be difficult as numerous biochemical processes can be considered. Additionally, biological reactors description (mass balance, etc. needs models represented by partial or/and ordinary differential equations associated to algebraic expressions, that require complex computational codes to obtain the numerical solutions. Different kind of software for mathematical modeling can be used, from large degree of freedom simulators capable of free models definition (as AQUASIM, to closed predefined model structure programs (as BIOWIN. The first ones usually require long learning curves, whereas the second ones could be excessively rigid for specific wastewater treatment systems. As alternative, we present Biological Reactor SIMulator (BioReSIM, a MATLAB code for the simulation of sequencing batch reactors (SBR and rotating biological contactors (RBC as biological systems of suspended and attached biomass for wastewater treatment, respectively. This BioReSIM allows the evaluation of simple and complex

  16. Denitrification capacity and greenhouse gas emissions of soils in channelized and restored reaches along an Alpine river corridor

    Science.gov (United States)

    Shrestha, Juna; Niklaus, Pascal; Samaritani, Emanuela; Frossard, Emmanuel; Tockner, Klement; Luster, Jörg

    2010-05-01

    In order to assess the effects of river restoration on water and air quality, the biogeochemical functions of channelized and restored river reaches have to be quantified. The objective of this study was to compare denitrification potential and greenhouse gas emissions of functional processing zones (FPZ) in a channelized and a recently restored reach of the alpine river Thur in north-eastern Switzerland. The study was part of the project cluster RECORD of the ETH domain, Switzerland, which was initiated to increase the mechanistic understanding of coupled hydrological and ecological processes in river corridors. The denitrification potential represents an important aspect of the soil filter function related to water quality. Besides, it also contributes to the emission of greenhouse gases. Extensively used pasture growing on a sandy loam is the characteristic FPZ of the channelized section. The restored section encompasses five FPZ: (i) bare gravel bars sparsely colonized by plants, (ii) gravel bars densely colonized by grass (mainly canary reed grass with up to 80 cm sandy deposits), (iii) mixed forest dominated by ash and maple, (iv) riparian forest dominated by willow (Salix alba), (v) older overbank sediments stabilized during restoration with young willows separating the forests from the river-gravel bar system (willow bush). The FPZ were sampled in January, April, August and October 2009. In addition, in June and July 2009 two flood events were monitored in the restored section with more frequent samplings. At each date, topsoil samples were collected in each FPZ (four replicates per samples) and analyzed for denitrifier enzyme activity (DEA). In addition, gas samples were taken in-situ using the closed chamber technique to measure soil respiration as well as N2O and CH4 fluxes. In all FPZ, the denitrification potential was mainly governed by soil moisture. It was highest in the willow forest exhibiting low spatial variability. The DEA in pasture, grass zone

  17. Physiological levels of nitrate support anoxic growth by denitrification of Pseudomonas aeruginosa at growth rates reported in cystic fibrosis lungs and sputum

    DEFF Research Database (Denmark)

    Line, Laura; Alhede, Morten; Kolpen, Mette

    2014-01-01

    denitrification. The growth rate of P. aeruginosa achieved by denitrification at physiological levels (~400 μM) of nitrate (NO(-) 3) is however, not known. Therefore, we have measured growth rates of anoxic cultures of PAO1 and clinical isolates (n = 12) in LB media supplemented with NO(-) 3 and found...... a significant increase of growth when supplementing PAO1 and clinical isolates with ≥150 μM NO(-) 3 and 100 μM NO(-) 3, respectively. An essential contribution to growth by denitrification was demonstrated by the inability to establish a significantly increased growth rate by a denitrification deficient Δnir...... of the four N-oxide reductases in PAO1 (Nar, Nir, Nor, Nos) further verified the engagement of denitrification, showing a transient increase in activation and expression and rapid consumption of NO(-) 3 followed by a transient increase of NO(-) 2. Growth rates obtained by denitrification in this study were...

  18. Temperature response of denitrification rate and greenhouse gas production in agricultural river marginal wetland soils.

    Science.gov (United States)

    Bonnett, S A F; Blackwell, M S A; Leah, R; Cook, V; O'Connor, M; Maltby, E

    2013-05-01

    Soils are predicted to exhibit significant feedback to global warming via the temperature response of greenhouse gas (GHG) production. However, the temperature response of hydromorphic wetland soils is complicated by confounding factors such as oxygen (O2 ), nitrate (NO3-) and soil carbon (C). We examined the effect of a temperature gradient (2-25 °C) on denitrification rates and net nitrous oxide (N2 O), methane (CH4 ) production and heterotrophic respiration in mineral (Eutric cambisol and Fluvisol) and organic (Histosol) soil types in a river marginal landscape of the Tamar catchment, Devon, UK, under non-flooded and flooded with enriched NO3- conditions. It was hypothesized that the temperature response is dependent on interactions with NO3--enriched flooding, and the physicochemical conditions of these soil types. Denitrification rate (mean, 746 ± 97.3 μg m(-2)  h(-1) ), net N2 O production (mean, 180 ± 26.6 μg m(-2)  h(-1) ) and net CH4 production (mean, 1065 ± 183 μg m(-2)  h(-1) ) were highest in the organic Histosol, with higher organic matter, ammonium and moisture, and lower NO3- concentrations. Heterotrophic respiration (mean, 127 ± 4.6 mg m(-2)  h(-1) ) was not significantly different between soil types and dominated total GHG (CO2 eq) production in all soil types. Generally, the temperature responses of denitrification rate and net N2 O production were exponential, whilst net CH4 production was unresponsive, possibly due to substrate limitation, and heterotrophic respiration was exponential but limited in summer at higher temperatures. Flooding with NO3- increased denitrification rate, net N2 O production and heterotrophic respiration, but a reduction in net CH4 production suggests inhibition of methanogenesis by NO3- or N2 O produced from denitrification. Implications for management and policy are that warming and flood events may promote microbial interactions in soil between distinct microbial communities and increase

  19. Nitrous oxide emission from denitrification in stream and river networks

    Science.gov (United States)

    Beaulieu, J.J.; Tank, J.L.; Hamilton, S.K.; Wollheim, W.M.; Hall, R.O.; Mulholland, P.J.; Peterson, B.J.; Ashkenas, L.R.; Cooper, L.W.; Dahm, Clifford N.; Dodds, W.K.; Grimm, N. B.; Johnson, S.L.; McDowell, W.H.; Poole, G.C.; Maurice, Valett H.; Arango, C.P.; Bernot, M.J.; Burgin, A.J.; Crenshaw, C.L.; Helton, A.M.; Johnson, L.T.; O'Brien, J. M.; Potter, J.D.; Sheibley, R.W.; Sobota, D.J.; Thomas, S.M.

    2011-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N 2O via microbial denitrification that converts N to N2O and dinitrogen (N2). The fraction of denitrified N that escapes as N2O rather than N2 (i.e., the N2O yield) is an important determinant of how much N2O is produced by river networks, but little is known about the N2O yield in flowing waters. Here, we present the results of whole-stream 15N-tracer additions conducted in 72 headwater streams draining multiple land-use types across the United States. We found that stream denitrification produces N2O at rates that increase with stream water nitrate (NO3-) concentrations, but that production, but does not increase the N2O yield. In our study, most streams were sources of N2O to the atmosphere and the highest emission rates were observed in streams draining urban basins. Using a global river network model, we estimate that microbial N transformations (e.g., denitrification and nitrification) convert at least 0.68 Tg??y -1 of anthropogenic N inputs to N2O in river networks, equivalent to 10% of the global anthropogenic N2O emission rate. This estimate of stream and river N2O emissions is three times greater than estimated by the Intergovernmental Panel on Climate Change.

  20. Simultaneous desulfurization and denitrification of flue gas by electron beam

    International Nuclear Information System (INIS)

    Baumann, W.; Jordan, S.; Maetzing, H.; Paur, H.R.; Schikarski, W.; Wiens, H.

    1987-05-01

    The simultaneous desulfurization and denitrification by the irradiation with 300 keV electrons in the presence of stoichiometric amounts of ammonia yields removal efficiencies of more than 90%. NO X -removal efficiencies depend on the absorbed dose, NO X -concentration and NH 3 -stoichiometry. SO 2 -removal proceeds by thermal and radiation induced mechanisms. The efficiency of the SO 2 -removal process is highest for low temperatures and high NH 3 -stoichiometries. By recycling of scrubbed gas into the reaction chamber (multiple irradiation) the efficiency of the process is increased by 50%. The product aerosol has mass median diameters of 2 and NO x removals in the absence of NH 3 are predicted with reasonable accuracy by the computer model. In the presence of NH 3 experimental data show higher SO 2 removal efficiencies than calculated. This is probably due to additional heterogeneous reactions on particles, which are not covered by the computer model. With 119 figs., 86 refs [de

  1. Long-term operation of oxygen-limiting membrane bioreactor (MBR) for the development of simultaneous partial nitrification, anammox and denitrification (SNAD) process.

    Science.gov (United States)

    Zhao, Chuanqi; Wang, Gang; Xu, Xiaochen; Yang, Yuesuo; Yang, Fenglin

    2017-07-18

    In this study, an oxygen-limiting membrane bioreactor (MBR) with recirculation of biogas for relieving membrane fouling was successfully operated to realize the simultaneous partial nitrification, anammox and denitrification (SNAD) process. The MBR operation was considered effective in the long-term test with total nitrogen (TN) and chemical oxygen demand (COD) removal efficiencies of 94.86% and 98.91%, respectively. Membrane fouling was significantly alleviated due to the recirculation of biogas and the membrane had been cleaned four times with a normal filtration period of 52 days. The co-existence of ammonia-oxidizing bacteria (AOB), anammox and denitrifying bacteria in MBR was confirmed by scanning electron microscopy (SEM) and fluorescence in situ hybridizations (FISH) analysis. Furthermore, AOB were found close to the granule surface, while denitrifying bacteria and anammox were in the deeper layer of granules. Potential in excellent TN and COD removal, operational stability and sustainability, as well as in alleviating membrane fouling is expected by using this oxygen-limiting MBR.

  2. Effect of solids retention time and wastewater characteristics on biological phosphorus removal

    DEFF Research Database (Denmark)

    Henze, Mogens; Aspegren, H.; Jansen, J.l.C.

    2002-01-01

    with time which has importance in relation to modelling. The overall conclusion of the comparison between the two plants is that the biological phosphorus removal efficiency under practical operating conditions is affected by the SRT in the plant and the wastewater composition. Thus great care should......The paper deals with the effect of wastewater, plant design and operation in relation to biological nitrogen and phosphorus removal and the possibilities to model the processes. Two Bio-P pilot plants were operated for 2.5 years in parallel receiving identical wastewater. The plants had SRT of 4...... and 21 days, the latter had nitrification and denitrification. The plant with 4 days SRT had much more variable biomass characteristics, than the one with the high SRT. The internal storage compounds, PHA, were affected significantly by the concentration of fatty acids or other easily degradable organics...

  3. Graphics processing units in bioinformatics, computational biology and systems biology.

    Science.gov (United States)

    Nobile, Marco S; Cazzaniga, Paolo; Tangherloni, Andrea; Besozzi, Daniela

    2017-09-01

    Several studies in Bioinformatics, Computational Biology and Systems Biology rely on the definition of physico-chemical or mathematical models of biological systems at different scales and levels of complexity, ranging from the interaction of atoms in single molecules up to genome-wide interaction networks. Traditional computational methods and software tools developed in these research fields share a common trait: they can be computationally demanding on Central Processing Units (CPUs), therefore limiting their applicability in many circumstances. To overcome this issue, general-purpose Graphics Processing Units (GPUs) are gaining an increasing attention by the scientific community, as they can considerably reduce the running time required by standard CPU-based software, and allow more intensive investigations of biological systems. In this review, we present a collection of GPU tools recently developed to perform computational analyses in life science disciplines, emphasizing the advantages and the drawbacks in the use of these parallel architectures. The complete list of GPU-powered tools here reviewed is available at http://bit.ly/gputools. © The Author 2016. Published by Oxford University Press.

  4. Nitrous oxide emission from denitrification in stream and river networks

    Science.gov (United States)

    Nitrous oxide (N2O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N2O via microbial denitrification which converts N to N2O and dinitrog...

  5. Nitrite accumulation in continuous-flow partial autotrophic denitrification reactor using sulfide as electron donor.

    Science.gov (United States)

    Liu, Chunshuang; Li, Wenfei; Li, Xuechen; Zhao, Dongfeng; Ma, Bin; Wang, Yongqiang; Liu, Fang; Lee, Duu-Jong

    2017-11-01

    The nitrite accumulation in handling nitrate and sulfide-laden wastewater in a continuous-flow upflow anaerobic sludge blanket reactor was studied. At sulfide/nitrate-nitrogen ratio of 1:0.76 and loading rates of 1.2kg-Sm -3 d -1 and 0.4kg-Nm -3 d -1 , the elemental sulfur and nitrite accumulation rates peaked at 90% and 70%, respectively, with Acrobacter, Azoarcus and Thauera presenting the functional strains in the studied reactor. The accumulated nitrite was proposed a promising feedstock for anaerobic ammonia oxidation process. An integrated partial autotrophic denitrification-anaerobic ammonia oxidation-aeration process for handling the ammonia and sulfide-laden wastewaters is proposed for further studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Thermal denitrification of evaporators concentrates in reactor with fluidized bed

    International Nuclear Information System (INIS)

    Brugnot, C.

    1993-11-01

    As part of the treatments of liquid wastes coming from the Marcoule reprocessing plant, the study of a thermal denitrification process for evaporator concentrates has been chosen by the CEA/CEN Cadarache: the fluidized-bed calcination. This work presents the study of a calcination pilot-plant for wastes with a very high sodium nitrate content. After a reactional analysis carried out in a thermobalance on samples which are representative of the fluidized-bed compounds, the perfecting of many of the plant parameters - such as the solution injection system - was carried out on a scale-model at first. Then, it was verified on the pilot-plant, and some experiments have been carried out. A mathematical model for the particle growth inside the fluidized-bed is proposed. (author). 179 refs., 65 figs., 23 tabs

  7. Kinetics of nitrous oxide production by denitrification in municipal solid waste.

    Science.gov (United States)

    Wu, Chuanfu; Shimaoka, Takayuki; Nakayama, Hirofumi; Komiya, Teppei

    2015-04-01

    As one of the Nitrous Oxide (N2O) production pathways, denitrification plays an important role in regulating the emission of N2O into the atmosphere. In this study, the influences of different substrate concentrations and transient conditions on the denitrification rate and N2O-reducing activities were investigated. Results revealed that N2O production rates (i.e. denitrification rates) were stimulated by increased total organic carbon (TOC) concentration, while it was restrained under high oxygen concentrations. Moreover, the impact of nitrate concentrations on N2O production rates depended on the TOC/NO3--N ratios. All the N2O production rate data fitted well to a multiplicative Monod equation, with terms describing the influence of TOC and nitrate concentrations, and an Arrhenius-type equation. Furthermore, results demonstrated that high temperatures minimized the N2O-reducing activities in aged municipal solid waste, resulting in an accumulation of N2O. On the other hand, a transient condition caused by changing O2 concentrations may strongly influence the N2O production rates and N2O-reducing activities in solid waste. Finally, based on the results, we believe that a landfill aeration strategy properly designed to prevent rising temperatures and to cycle air injection is the key to reducing emissions of N2O during remediation of old landfills by means of in situ aeration. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Correlation of denitrification-accepted fraction of electrons with NAD(P)H fluorescence for Pseudomonas aeruginosa performing simultaneous denitrification and respiration at extremely low dissolved oxygen conditions.

    Science.gov (United States)

    Chen, Fan; Xia, Qing; Ju, Lu-Kwang

    2004-01-01

    In cystic fibrosis airway infection, Pseudomonas aeruginosa forms a microaerobic biofilm and undergoes significant physiological changes. It is important to understand the bacterium's metabolism at microaerobic conditions. In this work, the culture properties and two indicators (the denitrification-accepted e- fraction and an NAD(P)H fluorescence fraction) for the culture's "fractional approach" to a fully anaerobic denitrifying state were examined in continuous cultures with practically zero DO but different aeration rates. With decreasing aeration, specific OUR decreased while specific NAR and NIR increased and kept Y(ATP/S) relatively constant. P. aeruginosa thus appeared to effectively compensate for energy generation at microaerobic conditions with denitrification. At the studied dilution rate of 0.06 h(-1), the maximum specific OUR was 2.8 mmol O2/g cells-h and the Monod constant for DO, in the presence of nitrate, was extremely low (Y(X/S) increased significantly (from 0.24 to 0.34) with increasing aeration, attributed to a roughly opposite trend of Y(ATP/X) (ATP generation required for cell growth). As for the denitrification-accepted e- fraction and the fluorescence fraction, both decreased with increasing aeration as expected. The two fractions, however, were not directly proportional. The fluorescence fraction changed more rapidly than the e- fraction at very low aeration rates, whereas the opposite was true at higher aeration. The results demonstrated the feasibility of using online NAD(P)H fluorescence to monitor sensitive changes of cellular physiology and provided insights to the shift of e- -accepting mechanisms of P. aeruginosa under microaerobic conditions.

  9. Spatial variability in denitrification rates in an Oregon tidal salt marsh

    Science.gov (United States)

    Modeling denitrification (DeN) is particularly challenging in tidal systems, which play a vital role in buffering adjacent coastal waters from nitrogen inputs. These systems are hydrologically and biogeochemically complex, varying on fine temporal and spatial scales. As part of a...

  10. Fludized-bed process for complex municipal sewage treatment systems using micro-organisms immobilized on heterogenous polymer structures (biocompounds); Wirbelbettverfahren zur komplexen kommunalen Abwasserreinigung unter Verwendung von auf heterogenen Polymerstrukturen (Biocompounds) immobilisierten Mikroorganismen

    Energy Technology Data Exchange (ETDEWEB)

    Ochmann, C.

    2004-07-01

    Within the context of the present work, novel carriers for immobilizing microorganisms have been developed and tested both in the laboratory and on a semi-industrial scale. It was the primary target to optimize the known processes in deep biofilms such that, besides carbon compounds decomposition and nitrification, a directed (and sufficient) denitrification would also become possible. Prerequisite for purposefully influencing denitrification processes is to realize biofilms of a definite thickness. This cannot be ensured by means of the carriers used hitherto in practice. The approach consists in the use of heterogeneous polymer structures (biocompounds) made of two differently rapidly degradable biopolymers. The biopolymer that is more slowly degradable forms a matrix into which the rapidly degradable biopolymer is inserted in form of particles arranged from one another at a distance. Based on the primary biological decomposition of the more rapidly degradable component (''biocorrosion''), porosity is generated in the substrate, releasing carbon at the same time. In this way, anoxic zones are formed based on the existent material gradient, besides protection of the biofilm forming in the pores from mechanical wear and tear. Simultaneously this ensures the supply of carbon to the anoxic zone for denitrification. In examinations (laboratory and semi-technology), it has been shown that simultaneous and continuous degradation of carbon and nitrogen compounds can be achieved in a completely and steadily aerated reaction space through the use of biocompounds. No problems arose both in carbon compounds degradation and nitrification. The removal of nitrogen compounds from wastewater was limited by the denitrification performance, which allowed to identify denitrification as the limiting process within the total process. It was possible to show that the N{sub tot} elimination rate is a function of the C/N ratio in crude wastewater. (orig.)

  11. Nitrogen speciation and trends, and prediction of denitrification extent, in shallow US groundwater

    Science.gov (United States)

    Hinkle, Stephen R.; Tesoriero, Anthony J.

    2014-01-01

    Uncertainties surrounding nitrogen cycling complicate assessments of the environmental effects of nitrogen use and our understanding of the global carbon–nitrogen cycle. In this paper, we synthesize data from 877 ambient-monitoring wells across the US to frame broad patterns of nitrogen speciation and trends. At these sites, groundwater frequently contains substantial co-occurring NO3− and XSN2 (N2 from denitrification), reflecting active/ongoing denitrification and/or a mixture of undenitrified and denitrified groundwater. NO3− and NH4+ essentially do not co-occur, indicating that the dominant source of NH4+ at these sites likely is not dissimilatory reduction of NO3− to NH4+. Positive correlations of NH4+ with apparent age, CH4, dissolved organic carbon, and indicators of reduced conditions are consistent with NH4+ mobilization from degradation of aquifer organic matter and contraindicate an anthropogenic source of NH4+ for most sites. Glacial aquifers and eastern sand and gravel aquifers generally have lower proportions of NO3− and greater proportions of XSN2 than do fractured rock and karst aquifers and western sand and gravel aquifers. NO3− dominates in the youngest groundwater, but XSN2 increases as residence time increases. Temporal patterns of nitrogen speciation and concentration reflect (1) changing NO3− loads over time, (2) groundwater residence-time controls on NH4+ mobilization from solid phases, and (3) groundwater residence-time controls on denitrification. A simple classification tree using readily available variables (a national coverage of soil water depth, generalized geology) or variables reasonably estimated in many aquifers (residence time) identifies categorical denitrification extent (50%) with 79% accuracy in an independent testing set, demonstrating a predictive application based on the interconnected effects of redox, geology, and residence time.

  12. Autotrophic and heterotrophic nitrification-anoxic denitrification dominated the anoxic/oxic sewage treatment process during optimization for higher loading rate and energy savings.

    Science.gov (United States)

    Zhang, Xueyu; Zheng, Shaokui; Zhang, Hangyu; Duan, Shoupeng

    2018-04-30

    This study clarified the dominant nitrogen (N)-transformation pathway and the key ammonia-oxidizing microbial species at three loading levels during optimization of the anoxic/oxic (A/O) process for sewage treatment. Comprehensive N-transformation activity analysis showed that ammonia oxidization was performed predominantly by aerobic chemolithotrophic and heterotrophic ammonia oxidization, whereas N 2 production was performed primarily by anoxic denitrification in the anoxic unit. The abundances of ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria, and anaerobic AOB in activated sludge reflected their activities on the basis of high-throughput sequencing data. AOB amoA gene clone libraries revealed that the predominant AOB species in sludge samples shifted from Nitrosomonas europaea (61% at the normal loading level) to Nitrosomonas oligotropha (58% and 81% at the two higher loading levels). Following isolation and sequencing, the predominant culturable heterotrophic AOB in sludge shifted from Agrobacterium tumefaciens (42% at the normal loading level) to Acinetobacter johnsonii (52% at the highest loading level). Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. Implication of two in-stream processes in the fate of nutrients discharged by sewage system into a temporary river.

    Science.gov (United States)

    David, Arthur; Perrin, Jean-Louis; Rosain, David; Rodier, Claire; Picot, Bernadette; Tournoud, Marie-George

    2011-10-01

    The aim of this study was to better understand the fate of nutrients discharged by sewage treatment plants into an intermittent Mediterranean river, during a low-flow period. Many pollutants stored in the riverbed during the low-flow period can be transferred to the downstream environments during flood events. The study focused on two processes that affect the fate and the transport of nutrients, a physical process (retention in the riverbed sediments) and a biological process (denitrification). A spatial campaign was carried out during a low-flow period to characterize the nutrient contents of both water and sediments in the Vène River. The results showed high nutrient concentrations in the water column downstream of the treated wastewater disposal (up to 13,315 μg N/L for ammonium and 2,901 μg P/L for total phosphorus). Nutrient concentrations decreased rapidly downstream of the disposal whereas nutrient contents in the sediments increased (up to 1,898 and 784 μg/g for total phosphorus and Kjeldahl nitrogen, respectively). According to an in situ experiment using sediment boxes placed in the riverbed for 85 days, we estimated that the proportion of nutrients trapped in the sediments represents 25% (respectively 10%) of phosphorus (respectively nitrogen) loads lost from the water column. In parallel, laboratory tests indicated that denitrification occurred in the Vène River, and we estimated that denitrification likely coupled to nitrification processes during the 85 days of the experiment was significantly involved in the removal of nitrogen loads (up to 38%) from the water column and was greater than accumulation processes.

  14. Environmental conditions influence the plant functional diversity effect on potential denitrification.

    Directory of Open Access Journals (Sweden)

    Ariana E Sutton-Grier

    2011-02-01

    Full Text Available Global biodiversity loss has prompted research on the relationship between species diversity and ecosystem functioning. Few studies have examined how plant diversity impacts belowground processes; even fewer have examined how varying resource levels can influence the effect of plant diversity on microbial activity. In a field experiment in a restored wetland, we examined the role of plant trait diversity (or functional diversity, (FD and its interactions with natural levels of variability of soil properties, on a microbial process, denitrification potential (DNP. We demonstrated that FD significantly affected microbial DNP through its interactions with soil conditions; increasing FD led to increased DNP but mainly at higher levels of soil resources. Our results suggest that the effect of species diversity on ecosystem functioning may depend on environmental factors such as resource availability. Future biodiversity experiments should examine how natural levels of environmental variability impact the importance of biodiversity to ecosystem functioning.

  15. An additional simple denitrification bioreactor using packed gel envelopes applicable to industrial wastewater treatment.

    Science.gov (United States)

    Morita, Masahiko; Uemoto, Hiroaki; Watanabe, Atsushi

    2007-08-15

    A simple denitrification bioreactor for nitrate-containing wastewater without organic compounds was developed. This bioreactor consisted of packed gel envelopes in a single tank. Each envelope comprised two plates of gels containing Paracoccus denitrificans cells with an internal space between the plates. As an electron donor for denitrification, ethanol was injected into the internal space and not directly into the wastewater. P. denitrificans cells in the gel reduced nitrate to nitrogen gas by using the injected ethanol. Nitrate-containing desulfurization wastewater derived from a coal-fired thermal power plant was continuously treated with 20 packed gel envelopes (size, 1,000 x 900 x 12 mm; surface area, 1.44 m(2)) in a reactor tank (volume 1.5 m(3)). When the total nitrogen concentration in the inflow was around 150 mg-N x L(-1), the envelopes removed approximately 60-80% of the total nitrogen, and the maximum nitrogen removal rate was 5.0 g-N x day(-1) per square meter of the gel surface. This value corresponded to the volumetric nitrogen removal performance of 0.109 kg-N x m(-3) x day(-1). In each envelope, a high utilization efficiency of the electron donor was attained, although more than the double amount of the electron donor was empirically injected in the present activated sludge system to achieve denitrification when compared with the theoretical value. The bioreactor using the envelopes would be extremely effective as an additional denitrification system because these envelopes can be easily installed in the vacant spaces of preinstalled water treatment systems, without requiring additional facilities for removing surplus ethanol and sludge. (c) 2007 Wiley Periodicals, Inc.

  16. Nitrogen removal from landfill leachate via ex situ nitrification and sequential in situ denitrification

    International Nuclear Information System (INIS)

    Zhong Qi; Li Daping; Tao Yong; Wang Xiaomei; He Xiaohong; Zhang Jie; Zhang Jinlian; Guo Weiqiang; Wang Lan

    2009-01-01

    Ex situ nitrification and sequential in situ denitrification represents a novel approach to nitrogen management at landfills. Simultaneous ammonia and organics removal was achieved in a continuous stirred tank reactor (CSTR). The results showed that the maximum nitrogen loading rate (NLR) and the maximum organic loading rate (OLR) was 0.65 g N l -1 d -1 and 3.84 g COD l -1 d -1 , respectively. The ammonia and chemical oxygen demand (COD) removal was over 99% and 57%, respectively. In the run of the CSTR, free ammonia (FA) inhibition and low dissolved oxygen (DO) were found to be key factors affecting nitrite accumulation. In situ denitrification was studied in a municipal solid waste (MSW) column by recalculating nitrified leachate from CSTR. The decomposition of MSW was accelerated by the recirculation of nitrified leachate. Complete reduction of total oxidized nitrogen (TON) was obtained with maximum TON loading of 28.6 g N t -1 TS d -1 and denitrification was the main reaction responsible. Additionally, methanogenesis inhibition was observed while TON loading was over 11.4 g N t -1 TS d -1 and the inhibition was enhanced with the increase of TON loading

  17. Instream large wood: Denitrification hotspots with low N2O production

    Science.gov (United States)

    We examined the effect of instream large wood on denitrification capacity in two contrasting, lower order streams — one that drains an agricultural watershed with no riparian forest and minimal stores of instream large wood and another that drains a forested watershed with an ext...

  18. Dietary carbohydrates and denitrification in recirculating aquaculture systems

    OpenAIRE

    Meriac, A.

    2014-01-01

    Due to overfishing of global fish stocks and increasing fish meal prices, plant ingredients are being increasingly used as an alternative source of protein in fish feeds. However, the inclusion of unpurified plant ingredients will also increase the content of fibers in feeds. Fibers are nearly indigestible and will therefore increase solid waste production in aquaculture. This solid waste can be used to as a carbon source for denitrification to control nitrate levels in recirculating aquacul...

  19. Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2O and NO under low oxygen availability.

    Science.gov (United States)

    Zhu, Xia; Burger, Martin; Doane, Timothy A; Horwath, William R

    2013-04-16

    The continuous increase of nitrous oxide (N2O) abundance in the atmosphere is a global concern. Multiple pathways of N2O production occur in soil, but their significance and dependence on oxygen (O2) availability and nitrogen (N) fertilizer source are poorly understood. We examined N2O and nitric oxide (NO) production under 21%, 3%, 1%, 0.5%, and 0% (vol/vol) O2 concentrations following urea or ammonium sulfate [(NH4)2SO4] additions in loam, clay loam, and sandy loam soils that also contained ample nitrate. The contribution of the ammonia (NH3) oxidation pathways (nitrifier nitrification, nitrifier denitrification, and nitrification-coupled denitrification) and heterotrophic denitrification (HD) to N2O production was determined in 36-h incubations in microcosms by (15)N-(18)O isotope and NH3 oxidation inhibition (by 0.01% acetylene) methods. Nitrous oxide and NO production via NH3 oxidation pathways increased as O2 concentrations decreased from 21% to 0.5%. At low (0.5% and 3%) O2 concentrations, nitrifier denitrification contributed between 34% and 66%, and HD between 34% and 50% of total N2O production. Heterotrophic denitrification was responsible for all N2O production at 0% O2. Nitrifier denitrification was the main source of N2O production from ammonical fertilizer under low O2 concentrations with urea producing more N2O than (NH4)2SO4 additions. These findings challenge established thought attributing N2O emissions from soils with high water content to HD due to presumably low O2 availability. Our results imply that management practices that increase soil aeration, e.g., reducing compaction and enhancing soil structure, together with careful selection of fertilizer sources and/or nitrification inhibitors, could decrease N2O production in agricultural soils.

  20. Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

    Directory of Open Access Journals (Sweden)

    Alfred Obia

    Full Text Available Biochar (BC application to soil suppresses emission of nitrous- (N2O and nitric oxide (NO, but the mechanisms are unclear. One of the most prominent features of BC is its alkalizing effect in soils, which may affect denitrification and its product stoichiometry directly or indirectly. We conducted laboratory experiments with anoxic slurries of acid Acrisols from Indonesia and Zambia and two contrasting BCs produced locally from rice husk and cacao shell. Dose-dependent responses of denitrification and gaseous products (NO, N2O and N2 were assessed by high-resolution gas kinetics and related to the alkalizing effect of the BCs. To delineate the pH effect from other BC effects, we removed part of the alkalinity by leaching the BCs with water and acid prior to incubation. Uncharred cacao shell and sodium hydroxide (NaOH were also included in the study. The untreated BCs suppressed N2O and NO and increased N2 production during denitrification, irrespective of the effect on denitrification rate. The extent of N2O and NO suppression was dose-dependent and increased with the alkalizing effect of the two BC types, which was strongest for cacao shell BC. Acid leaching of BC, which decreased its alkalizing effect, reduced or eliminated the ability of BC to suppress N2O and NO net production. Just like untreated BCs, NaOH reduced net production of N2O and NO while increasing that of N2. This confirms the importance of altered soil pH for denitrification product stoichiometry. Addition of uncharred cacao shell stimulated denitrification strongly due to availability of labile carbon but only minor effects on the product stoichiometry of denitrification were found, in accordance with its modest effect on soil pH. Our study indicates that stimulation of denitrification was mainly due to increases in labile carbon whereas change in product stoichiometry was mainly due to a change in soil pH.

  1. Engineering application of anaerobic ammonium oxidation process in wastewater treatment.

    Science.gov (United States)

    Mao, Nianjia; Ren, Hongqiang; Geng, Jinju; Ding, Lili; Xu, Ke

    2017-08-01

    Anaerobic ammonium oxidation (Anammox), a promising biological nitrogen removal process, has been verified as an efficient, sustainable and cost-effective alternative to conventional nitrification and denitrification processes. To date, more than 110 full-scale anammox plants have been installed and are in operation, treating industrial NH 4 + -rich wastewater worldwide, and anammox-based technologies are flourishing. This review the current state of the art for engineering applications of the anammox process, including various anammox-based technologies, reactor selection and attempts to apply it at different wastewater plants. Process control and implementation for stable performance are discussed as well as some remaining issues concerning engineering application are exposed, including the start-up period, process disturbances, greenhouse gas emissions and especially mainstream anammox applications. Finally, further development of the anammox engineering application is proposed in this review.

  2. What is the so-called optimum pH for denitrification in soil?

    Czech Academy of Sciences Publication Activity Database

    Šimek, Miloslav; Jíšová, Linda; Hopkins, D. W.

    2002-01-01

    Roč. 34, - (2002), s. 1227-1234 ISSN 0038-0717 Institutional research plan: CEZ:AV0Z6066911 Keywords : pH * denitrifying enzyme activity * denitrification potential Subject RIV: EH - Ecology, Behaviour Impact factor: 1.902, year: 2002

  3. Biological nitrogen removal from sewage via anammox: Recent advances.

    Science.gov (United States)

    Ma, Bin; Wang, Shanyun; Cao, Shenbin; Miao, Yuanyuan; Jia, Fangxu; Du, Rui; Peng, Yongzhen

    2016-01-01

    Biological nitrogen removal from sewage via anammox is a promising and feasible technology to make sewage treatment energy-neutral or energy-positive. Good retention of anammox bacteria is the premise of achieving sewage treatment via anammox. Therefore the anammox metabolism and its factors were critically reviewed so as to form biofilm/granules for retaining anammox bacteria. A stable supply of nitrite for anammox bacteria is a real bottleneck for applying anammox in sewage treatment. Nitritation and partial-denitrification are two promising methods of offering nitrite. As such, the strategies for achieving nitritation in sewage treatment were summarized by reviewing the factors affecting nitrite oxidation bacteria growth. Meanwhile, the methods of achieving partial-denitrification have been developed through understanding the microorganisms related with nitrite accumulation and their factors. Furthermore, two cases of applying anammox in the mainstream sewage treatment plants were documented. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Mixing effects on apparent reaction rates and isotope fractionation during denitrification in a heterogeneous aquifer

    Science.gov (United States)

    Green, Christopher T.; Böhlke, John Karl; Bekins, Barbara A.; Phillips, Steven P.

    2010-01-01

    Gradients in contaminant concentrations and isotopic compositions commonly are used to derive reaction parameters for natural attenuation in aquifers. Differences between field‐scale (apparent) estimated reaction rates and isotopic fractionations and local‐scale (intrinsic) effects are poorly understood for complex natural systems. For a heterogeneous alluvial fan aquifer, numerical models and field observations were used to study the effects of physical heterogeneity on reaction parameter estimates. Field measurements included major ions, age tracers, stable isotopes, and dissolved gases. Parameters were estimated for the O2 reduction rate, denitrification rate, O2 threshold for denitrification, and stable N isotope fractionation during denitrification. For multiple geostatistical realizations of the aquifer, inverse modeling was used to establish reactive transport simulations that were consistent with field observations and served as a basis for numerical experiments to compare sample‐based estimates of “apparent” parameters with “true“ (intrinsic) values. For this aquifer, non‐Gaussian dispersion reduced the magnitudes of apparent reaction rates and isotope fractionations to a greater extent than Gaussian mixing alone. Apparent and true rate constants and fractionation parameters can differ by an order of magnitude or more, especially for samples subject to slow transport, long travel times, or rapid reactions. The effect of mixing on apparent N isotope fractionation potentially explains differences between previous laboratory and field estimates. Similarly, predicted effects on apparent O2threshold values for denitrification are consistent with previous reports of higher values in aquifers than in the laboratory. These results show that hydrogeological complexity substantially influences the interpretation and prediction of reactive transport.

  5. Long term performance of the Waterloo denitrification barrier

    International Nuclear Information System (INIS)

    Robertson, W.D.; Cherry, J.A.

    1997-01-01

    Beginning in 1991 a series of laboratory tests and small scale field trials were initiated to test the performance of an innovative permeable reactive barrier for treatment of nitrate from septic systems. The barrier promotes denitrification by providing an energy source in the form of solid organic carbon mixed into the porous media material. Advantages of the system for nitrate treatment are that the reaction is passive and in situ and it is possible to incorporate sufficient carbon mass in conveniently sized barriers to potentially provide treatment for long periods (decades) without the necessity for maintenance. However, longevity can only be demonstrated by careful long term monitoring of field installations. This paper documents four years of operating history at three small scale field trials; two where the denitrification barrier is installed as a horizontal layer positioned in the unsaturated zone below conventional septic system infiltration beds and one where the barrier is installed as a vertical wall intercepting a septic system plume at a downgradient location. The barriers have successfully attenuated 50-100% of NO - 3 -N levels of up to 170 mg/L and treatment has remained consistent over the four year period in each case, thus considerable longevity is indicated. Other field trials have demonstrated this technology to be equally effective in treating nitrogen contamination from other sources such as landfill leachate and farm field runoff

  6. Substrate-dependent denitrification of abundant probe-defined denitrifying bacteria in activated sludge.

    Science.gov (United States)

    Morgan-Sagastume, Fernando; Nielsen, Jeppe Lund; Nielsen, Per Halkjaer

    2008-11-01

    The denitrification capacity of different phylogenetic bacterial groups was investigated on addition of different substrates in activated sludge from two nutrient-removal plants. Nitrate/nitrite consumption rates (CRs) were calculated from nitrate and nitrite biosensor, in situ measurements. The nitrate/nitrite CRs depended on the substrate added, and acetate alone or combined with other substrates yielded the highest rates (3-6 mg N gVSS(-1) h(-1)). The nitrate CRs were similar to the nitrite CRs for most substrates tested. The structure of the active denitrifying population was investigated using heterotrophic CO2 microautoradiography (HetCO2-MAR) and FISH. Probe-defined denitrifiers appeared as specialized substrate utilizers despite acetate being preferentially used by most of them. Azoarcus and Accumulibacter abundance in the two different sludges was related to differences in their substrate-specific nitrate/nitrite CRs. Aquaspirillum-related bacteria were the most abundant potential denitrifiers (c. 20% of biovolume); however, Accumulibacter (3-7%) and Azoarcus (2-13%) may have primarily driven denitrification by utilizing pyruvate, ethanol, and acetate. Activated sludge denitrification was potentially conducted by a diverse, versatile population including not only Betaproteobacteria (Aquaspirillum, Thauera, Accumulibacter, and Azoarcus) but also some Alphaproteobacteria and Gammaproteobacteria, as indicated by the assimilation of 14CO2 by these probe-defined groups with a complex substrate mixture as an electron donor and nitrite as an electron acceptor in HetCO2-MAR-FISH tests.

  7. Nitrogen mineralization and denitrification as influenced by crop residue particle size

    DEFF Research Database (Denmark)

    Ambus, P.; Jensen, E.S.

    1997-01-01

    1: N-15-labelled ground (less than or equal to 3 mm) and cut (25 mm) barley residue, and microcrystalline cellulose+glucose were mixed into a sandy loam soil with additional inorganic N. Experiment 2: inorganic N-15 and C2H2 were added to soils with barley and pea material after 3, 26, and 109 days......Managing the crop residue particle size has the potential to affect N conservation in agricultural systems. We investigated the influence of barley (Hordeum vulgare) and pea (Pisum sativum) crop residue particle size on N mineralization and denitrification in two laboratory experiments. Experiment...... for measuring gross N mineralization and denitrification. Net N immobilization over 60 days in Experiment 1 cumulated to 63 mg N kg(-1) soil (ground barley), 42 (cut barley), and 122 (cellulose+glucose). More N was seemingly net mineralized from ground barley (3.3 mg N kg(-1) soil) than from cut barley (2.7 mg...

  8. Denitrification capacity of bioreactors filled with refuse at different landfill ages

    International Nuclear Information System (INIS)

    Chen Yingxu; Wu Songwei; Wu Weixiang; Sun Hua; Ding Ying

    2009-01-01

    The denitrification capacity of refuse at different landfill ages in bioreactor landfill system was studied. Three reactors filled with 1-year-old refuse (R1), 6-year-old refuse (R6) and 11-year-old refuse (R11), respectively, were operated in the experiment. Nitrate solution (1000 mg NO 3 - -N L -1 ) was added into each reactor. The results showed that the reactors were all able to consume nitrate. However, 1-year-old refuse in R1 had both a higher nitrate reduction rate and concentration of N 2 . In addition, vertical differences in nitrate removal along the depth of R1 were observed. The bottom-layer refuse and the middle-layer refuse both showed higher efficiency in nitrate depletion than the top layer. Furthermore, N 2 O accumulation was found in R11 with the concentration up to 19.3% of the released gas. These results suggested that 1-year-old refuse, which was partly degraded, was more suitable to use as denitrification medium.

  9. Method of denitrification and stabilization of radioactive aqueous solutions of radioisotope nitrates

    International Nuclear Information System (INIS)

    Pecak, V.; Matous, V.

    1983-01-01

    The method is solved of denitrification and of the stabilization of aqueous solutions of radioactive isotopes produced during the reprocessing of nuclear fuel. The aqueous solution is first mixed with the vitreous component, most frequently phosphoric acid, ammonium phosphate or boric acid and if needed with the addition of alkalis, possibly with clarifying or anti-foam components, e.g., arsenic trioxide, antimony or cerium oxide. The mixture is further adjusted with ammonia to pH 5 - 9. The liquid mixture is then thermally and pyrolytically processed, e.g., by calcinator or fluid-bed reactor or by pot melting at temperatures of 3O0 to 900 degC while of a powder product or glass melt is formed in the presence of gaseous emissions composed of nitrous oxide - nitrogen. The resulting product is further processed by containerization or is sealed in a metal matrix. (B.S.)

  10. Mathematical modeling of nitrous oxide production in an anaerobic/oxic/anoxic process.

    Science.gov (United States)

    Ding, Xiaoqian; Zhao, Jianqiang; Hu, Bo; Chen, Ying; Ge, Guanghuan; Li, Xiaoling; Wang, Sha; Gao, Kun; Tian, Xiaolei

    2016-12-01

    This study incorporates three currently known nitrous oxide (N 2 O) production pathways: ammonium-oxidizing bacteria (AOB) denitrification, incomplete hydroxylamine (NH 2 OH) oxidation, and heterotrophic denitrification on intracellular polymers, into a mathematical model to describe N 2 O production in an anaerobic/oxic/anoxic (AOA) process for the first time. The developed model was calibrated and validated by four experimental cases, then evaluated by two independent anaerobic/aerobic (AO) studies from literature. The modeling results displayed good agreement with the measured data. N 2 O was primarily generated in the aerobic stage by AOB denitrification (67.84-81.64%) in the AOA system. Smaller amounts of N 2 O were produced via incomplete NH 2 OH oxidation (15.61-32.17%) and heterotrophic denitrification on intracellular polymers (0-12.47%). The high nitrite inhibition on N 2 O reductase led to the increased N 2 O accumulation in heterotrophic denitrification on intracellular polymers. The new model was capable of modeling nitrification-denitrification dynamics and heterotrophic denitrification on intracellular polymers in the AOA system. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Using the Triple Labelling Technique to apportion N2O Emissions to Nitrification and Denitrification from different Nitrogen Sources at different Water-Filled-Pore-Spaces

    Science.gov (United States)

    Loick, Nadine; Dixon, Elizabeth R.; Repullo Ruibérriz de Torres, Miguel A.; Ciganda, Veronica; Lopez-Aizpun, Maria A.; Matthews, G. Peter; Müller, Christoph; Cardenas, Laura M.

    2017-04-01

    Nitrous oxide (N2O) is considered to be an important greenhouse gas (GHG) accounting for approximately 6% of the current global warming. The atmospheric N2O concentration has been increasing since the Industrial Revolution, with soils representing its major source, making the understanding of its sources and removal processes very important for the development of mitigation strategies. In soils N gases are mainly produced via nitrification and denitrification. It is assumed that under dry/aerobic conditions nitrification is the dominant N consuming process, while denitrification becomes dominant under wetter conditions promoting anaerobicity. Nitrification and denitrification may occur simultaneously in different microsites of the same soil but there is often uncertainty associated with which process dominates in a particular soil under specific conditions. N2O predominantly derives from incomplete denitrification of nitrate (NO3-). The existence of different pools of NO3- in soils, namely the native soil pool, and the fertiliser-added one, has been suggested through a series of laboratory incubation experiments (Meijide et al., 2010; Bergstermann et al., 2011) using the denitrification incubation system, DENIS (Cardenas et al., 2003), in which soil cores are incubated under an N-free atmosphere, allowing direct measurements of all emitted N gases (NO, N2O and N2) as well as CO2. A third pool, NO3- produced from nitrification of applied NH4+, can also be a source of N2O via denitrification and also from nitrification. In this study labelling of substrate-N with 15N is used to quantify the underlying gross N transformation rates and link them to N-emissions to identify the production and consumption pathways and temporal dynamics of N2O. In three experiments twelve soil cores each were incubated in the DENIS to measure gaseous emissions, while parallel incubations under the same conditions were set up for destructive soil sampling at 7 time points. Using the triple

  12. Introductory Biology Textbooks Under-Represent Scientific Process

    Directory of Open Access Journals (Sweden)

    Dara B. Duncan

    2011-08-01

    Full Text Available Attrition of undergraduates from Biology majors is a long-standing problem. Introductory courses that fail to engage students or spark their curiosity by emphasizing the open-ended and creative nature of biological investigation and discovery could contribute to student detachment from the field. Our hypothesis was that introductory biology books devote relatively few figures to illustration of the design and interpretation of experiments or field studies, thereby de-emphasizing the scientific process.To investigate this possibility, we examined figures in six Introductory Biology textbooks published in 2008. On average, multistep scientific investigations were presented in fewer than 5% of the hundreds of figures in each book. Devoting such a small percentage of figures to the processes by which discoveries are made discourages an emphasis on scientific thinking. We suggest that by increasing significantly the illustration of scientific investigations, textbooks could support undergraduates’ early interest in biology, stimulate the development of design and analytical skills, and inspire some students to participate in investigations of their own.

  13. Some aspects of the oxygen-deficient conditions and denitrification in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.

    Utilizing a fairly large amount of recently collected data, some outstanding questions concerning the Arabian Sea denitrification problem are addressed. The true level of dissolved oxygen, determined colorimetrically, are about an order of magnitude...

  14. Performance evaluation of pilot scale sulfur-oxidizing denitrification for treatment of metal plating wastewater.

    Science.gov (United States)

    Flores, Angel S P; Gwon, Eun-Mi; Sim, Dong-Min; Nisola, Grace; Galera, Melvin M; Chon, Seung-Se; Chung, Wook-Jin; Pak, Dae-Won; Ahn, Zou Sam

    2006-01-01

    A full-scale and two pilot-scale upflow sulfur-oxidizing denitrification (SOD) columns were evaluated using metal plating wastewater as feed. The sludge was autotrophically enriched, and inoculated in the SOD columns attached to the effluent line of three metal plating wastewater treatment facilities. The effects of activated carbon and aeration were also studied, and found effective for the removal of suspended solids and ammonia, respectively. The results showed that the constituents, such as the total nitrogen, nitrates, nitrites, ammonia, chemical oxygen demand (COD), and heavy metals, were effectively removed. The pH was observed to be maintained at 7-8 due to the alkalinity supplied by the sulfur-calcium carbonate (SC) pellet. The denitrification efficiency and start-up period were observed to be affected by the influent quality. Chromium, iron, nickel, copper, and zinc--the major heavy metal components of the influent--were effectively reduced at certain concentrations. Other metal ions were also detected and reduced to undetectable concentrations, but no trends in the comparison with denitrification were observed. From the results it can be concluded that SOD is effective for the removal of nitrogen, particularly nitrates, without a drastic pH change, and can effectively remove minute concentrations of heavy metals and COD in metal plating wastewaters.

  15. Woody Debris: Denitrification Hotspots and N2O Production in Fluvial Systems

    Science.gov (United States)

    The maintenance and restoration of forested riparian cover is important for watershed nitrogen (N) cycling. Forested riparian zones provide woody debris to streams that may stimulate in-stream denitrification and control nitrous oxide (N2O) production. We examined the effects of ...

  16. Profile of science process skills of Preservice Biology Teacher in General Biology Course

    Science.gov (United States)

    Susanti, R.; Anwar, Y.; Ermayanti

    2018-04-01

    This study aims to obtain portrayal images of science process skills among preservice biology teacher. This research took place in Sriwijaya University and involved 41 participants. To collect the data, this study used multiple choice test comprising 40 items to measure the mastery of science process skills. The data were then analyzed in descriptive manner. The results showed that communication aspect outperfomed the other skills with that 81%; while the lowest one was identifying variables and predicting (59%). In addition, basic science process skills was 72%; whereas for integrated skills was a bit lower, 67%. In general, the capability of doing science process skills varies among preservice biology teachers.

  17. Decadal- to Orbital-Scale Links Between Climate, Productivity and Denitrification on the Peru Margin

    Science.gov (United States)

    Higginson, M. J.; Altabet, M. A.; Herbert, T. D.

    2002-12-01

    Denitrification is the predominant global loss term for combined nitrogen and can exert a major control on its oceanic inventory, global productivity and atmospheric CO2. Our prior work demonstrates that proxy records for changing denitrification, oxygenation and productivity in the recent geological past in the Arabian Sea exhibit unprecedented similarity with abrupt climate fluctuations recorded in high-latitude ice-cores. Since the Peru Margin and Arabian Sea together constitute almost two-thirds of global marine water-column denitrification, changes in concert in these two regions could potentially have effected rapid global climate changes through an oceanic mechanism. The Peru Margin is intimately coupled to the Equatorial Pacific, source of El Ni&ño-La Niña SST, productivity and precipitation anomalies. Here, biogeochemical cycles are especially sensitive to abrupt climatic changes on decadal time-scales by virtue of this ENSO coupling. The purpose of our research is to investigate whether longer changes in tropical Pacific oceanography represent a 'scaling up' of anomalous ENSO conditions, modulated by both internal (e.g. nutrient inventory or WPWP heat budget) and external (e.g. orbital) forcing throughout the last glacial/inter-glacial cycle. Here we present first results of a detailed investigation of recently-recovered sediments from ODP Site 1228 on the Peru margin upper continental slope, in an attempt to capture some of the essential aspects of ENSO-like variability. Despite the existing availability of high quality sediment cores from this margin, little detailed paleoclimatic information currently exists because of poor sedimentary carbonate preservation (exacerbated post-recovery) which has limited generation of essential chronostratigraphic controls. Instead, we rely on the development and novel application of compound-specific AMS dating verified and supplemented by intermittent foraminiferal and bulk-carbon AMS dates, a magnetic paleo

  18. N2O isotopomers and N2:N2O ratio as indicators of denitrification in ecosystems

    International Nuclear Information System (INIS)

    Mander, Ülo; Zaman, Mohammad

    2015-01-01

    The world is experiencing climate change and variability due to increased greenhouse gas (GHG) emissions. The main GHG’s of concern are nitrous oxide (N 2 O), carbon dioxide (CO 2 ) and methane (CH 4 ). Agriculture contributes approximately 14% of the world’s GHG emissions. Nitrous oxide is one of the key GHG and ozone (O 3 ) depleting gas, constituting 7% of the anthropogenic greenhouse effect. On a molecular basis, N 2 O has a 310- and 16-fold greater global warming potential than each of CO 2 and CH 4 , respectively, over a 100-year period. Nitrous oxide can be produced through both chemical and biochemical pathways. They occur during denitrification (the stepwise conversion of nitrate (NO 3 - ) to nitrogen gas (N 2 ) and during nitrification by ammonia-oxidizing archea (bacteria) during the oxidation of hydroxylamine (NH 2 OH) to nitrite (NO 2 - ) which is then reduced to N 2 O and N 2 by nitrifier denitrification or heterotrophic denitrification

  19. Micro-electrolysis/retinervus luffae-based simultaneous autotrophic and heterotrophic denitrification for low C/N wastewater treatment.

    Science.gov (United States)

    Li, Jinlong; Li, Desheng; Cui, Yuwei; Xing, Wei; Deng, Shihai

    2017-07-01

    Nitrogen bioremediation in organic insufficient wastewater generally requires an extra carbon source. In this study, nitrate-contaminated wastewater was treated effectively through simultaneous autotrophic and heterotrophic denitrification based on micro-electrolysis carriers (MECs) and retinervus luffae fructus (RLF), respectively. The average nitrate and total nitrogen removal rates reached 96.3 and 94.0% in the MECs/RLF-based autotrophic and heterotrophic denitrification (MRAHD) system without ammonia and nitrite accumulation. The performance of MRAHD was better than that of MEC-based autotrophic denitrification for the wastewater treatment with low carbon nitrogen (COD/N) ratio. Real-time quantitative polymerase chain reaction (qPCR) revealed that the relative abundance of nirS-type denitrifiers attached to MECs (4.9%) and RLF (5.0%) was similar. Illumina sequencing suggested that the dominant genera were Thiobacillus (7.0%) and Denitratisoma (5.7%), which attached to MECs and RLF, respectively. Sulfuritalea was discovered as the dominant genus in the middle of the reactor. The synergistic interaction between autotrophic and heterotrophic denitrifiers played a vital role in the mixotrophic substrate environment.

  20. Syringe test screening of microbial gas production activity: Cases denitrification and biogas formation.

    Science.gov (United States)

    Østgaard, Kjetill; Kowarz, Viktoria; Shuai, Wang; Henry, Ingrid A; Sposob, Michal; Haugen, Hildegunn Hegna; Bakke, Rune

    2017-01-01

    Mass produced plastic syringes may be applied as vessels for cheap, simple and large scale batch culture testing. As illustrated for the cases of denitrification and of biogas formation, metabolic activity was monitored by direct reading of the piston movement due to the gas volume formed. Pressure buildup due to friction was shown to be moderate. A piston pull and slide back routine can be applied before recording gas volume to minimize experimental errors due to friction. Inoculum handling and activity may be conveniently standardized as illustrated by applying biofilm carriers. A robust set of positive as well as negative controls ("blanks") should be included to ensure quality of the actual testing. The denitrification test showed saturation response at increasing amounts of inoculum in the form of adapted moving bed biofilm reactor (MBBR) carriers, with well correlated nitrate consumption vs. gas volume formed. As shown, the denitrification test efficiently screened different inocula at standardized substrates. Also, different substrates were successfully screened and compared at standardized inocula. The biogas potential test showed efficient screening of different substrates with effects of relative amounts of carbohydrate, protein, fat. A second case with CO 2 capture reclaimer waste as substrate demonstrated successful use of co-feeding to support waste treatment and how temperature effects on kinetics and stoichiometry can be observed. In total, syringe test screening of microbial gas production seems highly efficient at a low cost when properly applied. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Isotopic and microbiological signatures of pyrite-driven denitrification in a sandy aquifer

    NARCIS (Netherlands)

    Zhang, Y.C.; Slomp, C.P.; Broers, H.P.; Bostick, B.; Passier, H.F.; Böttcher, M.E.; Omoregie, E.O.; Lloyd, J.R.; Polya, D.A.; Cappellen, P. van

    2012-01-01

    Denitrification driven by pyrite oxidation can play a major role in the removal of nitrate from groundwater systems. As yet, limited information is available on the interactions between the micro-organisms and aqueous and mineral phases in aquifers where pyrite oxidation is occurring. In this study,

  2. Effect of organic enrichment and thermal regime on denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in hypolimnetic sediments of two lowland lakes.

    Science.gov (United States)

    Nizzoli, Daniele; Carraro, Elisa; Nigro, Valentina; Viaroli, Pierluigi

    2010-05-01

    We analyzed benthic fluxes of inorganic nitrogen, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in hypolimnetic sediments of lowland lakes. Two neighbouring mesotrophic (Ca' Stanga; CS) and hypertrophic (Lago Verde; LV) lakes, which originated from sand and gravel mining, were considered. Lakes are affected by high nitrate loads (0.2-0.7 mM) and different organic loads. Oxygen consumption, dissolved inorganic carbon, methane and nitrogen fluxes, denitrification and DNRA were measured under summer thermal stratification and late winter overturn. Hypolimnetic sediments of CS were a net sink of dissolved inorganic nitrogen (-3.5 to -4.7 mmol m(-2)d(-1)) in both seasons due to high nitrate consumption. On the contrary, LV sediments turned from being a net sink during winter overturn (-3.5 mmol m(-2)d(-1)) to a net source of dissolved inorganic nitrogen under summer conditions (8.1 mmol m(-2)d(-1)), when significant ammonium regeneration was measured at the water-sediment interface. Benthic denitrification (0.7-4.1 mmol m(-2)d(-1)) accounted for up to 84-97% of total NO(3)(-) reduction and from 2 to 30% of carbon mineralization. It was mainly fuelled by water column nitrate. In CS, denitrification rates were similar in winter and in summer, while in LV summer rates were 4 times lower. DNRA rates were generally low in both lakes (0.07-0.12 mmol m(-2)d(-1)). An appreciable contribution of DNRA was only detected in the more reducing sediments of LV in summer (15% of total NO(3)(-) reduction), while during the same period only 3% of reduced NO(3)(-) was recycled into ammonium in CS. Under summer stratification benthic denitrification was mainly nitrate-limited due to nitrate depletion in hypolimnetic waters and parallel oxygen depletion, hampering nitrification. Organic enrichment and reducing conditions in the hypolimnetic sediment shifted nitrate reduction towards more pronounced DNRA, which resulted in the inorganic nitrogen recycling and

  3. Effect of substrate availability on nitrous oxide production by deammonification processes under anoxic conditions.

    Science.gov (United States)

    Schneider, Yvonne; Beier, Maike; Rosenwinkel, Karl-Heinz

    2012-05-01

    Due to its high global warming potential, nitrous oxide (N(2)O) emissions from wastewater treatment processes have recently received a high degree of attention. Nevertheless, there is still a lack of information regarding the microbiological processes leading to N(2)O production. In this study, two lab-scale sequencing batch reactors were operated with deammonification biomass to investigate the role of denitrification and the influence of substrate availability regarding N(2)O formation during the anoxic phase of deammonification. Three different operational phases were established: within the first phase conversion by anammox was favoured and after a transition phase, denitrification activity was promoted. Low nitrous oxide production was observed during stable operation aiming for anammox conversion. Pulsed inflow of the wastewater containing ammonium (NH(4)(+)) and nitrite (NO(2)(-)) led to increased N(2)O production rates. Within the period of denitrification as dominating nitrogen conversion process, the nitrous oxide concentration level was higher during continuous inflow conditions, but the reaction to pulsed inflow was less pronounced. The results indicated that denitrification was responsible for N(2)O formation from the deammonification biomass. Operational settings to achieve suppression of denitrification processes to a large extend were deducted from the results of the experiments. © 2012 The Authors. Microbial Biotechnology © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

  4. Biological nutrients removal from the supernatant originating from the anaerobic digestion of the organic fraction of municipal solid waste.

    Science.gov (United States)

    Malamis, S; Katsou, E; Di Fabio, S; Bolzonella, D; Fatone, F

    2014-09-01

    This study critically evaluates the biological processes and techniques applied to remove nitrogen and phosphorus from the anaerobic supernatant produced from the treatment of the organic fraction of municipal solid waste (OFMSW) and from its co-digestion with other biodegradable organic waste (BOW) streams. The wide application of anaerobic digestion for the treatment of several organic waste streams results in the production of high quantities of anaerobic effluents. Such effluents are characterized by high nutrient content, because organic and particulate nitrogen and phosphorus are hydrolyzed in the anaerobic digestion process. Consequently, adequate post-treatment is required in order to comply with the existing land application and discharge legislation in the European Union countries. This may include physicochemical and biological processes, with the latter being more advantageous due to their lower cost. Nitrogen removal is accomplished through the conventional nitrification/denitrification, nitritation/denitritation and the complete autotrophic nitrogen removal process; the latter is accomplished by nitritation coupled with the anoxic ammonium oxidation process. As anaerobic digestion effluents are characterized by low COD/TKN ratio, conventional denitrification/nitrification is not an attractive option; short-cut nitrogen removal processes are more promising. Both suspended and attached growth processes have been employed to treat the anaerobic supernatant. Specifically, the sequencing batch reactor, the membrane bioreactor, the conventional activated sludge and the moving bed biofilm reactor processes have been investigated. Physicochemical phosphorus removal via struvite precipitation has been extensively examined. Enhanced biological phosphorus removal from the anaerobic supernatant can take place through the sequencing anaerobic/aerobic process. More recently, denitrifying phosphorus removal via nitrite or nitrate has been explored. The removal of

  5. Groundwater denitrification in two agricultural river catchments: influence of hydro-geological setting and aquifer geochemistry

    Science.gov (United States)

    McAleer, Eoin; Mellander, Per-Erik; Coxon, Catherine; Richards, Karl G.; Jahangir, Mohammad M. R.

    2015-04-01

    Identifying subsurface environments with a natural capacity for denitrification is important for improving agricultural management. At the catchment scale, a complex hierarchy of landscape, hydro-geological and physico-chemical characteristics combine to affect the distribution of groundwater nitrate (NO3-). This study was conducted along four instrumented hillslopes in two ca. 10km2 agricultural river catchments in Ireland, one dominated by arable and one by grassland agriculture. Both catchments are characterised by well drained soils, but have differing aquifer characteristics. The arable catchment is underlain by weathered Ordovician slate bedrock which is extensively fractured with depth. The grassland catchment is characterised by Devonian sandstone bedrock, exhibiting both lateral (from upslope to near stream) and vertical variations in permeability along each hillslope. The capacity for groundwater denitrification was assessed by examining the concentration and distribution patterns of N species (total nitrogen, nitrate, nitrite, ammonium), dissolved organic carbon (DOC), dissolved oxygen (DO) and redox potential (Eh) in monthly samples from shallow and deep groundwater piezometers (n=37). Additionally, the gaseous products of denitrification: nitrous oxide (N2O) and excess dinitrogen (excess N2) were measured seasonally using gas chromatography and membrane inlet mass spectroscopy, respectively. The slate catchment was characterised by uniformity, both laterally and vertically, in aquifer geochemistry and gaseous denitrification products. The four year spatial mean groundwater NO3--N concentration was 6.89 mg/l and exhibited low spatial and temporal variability (temporal SD: 1.19 mg/l, spatial SD: 1.185 mg/l). Elevated DO concentrations (mean: 9.75 mg/l) and positive Eh (mean: +176.5mV) at all sample horizons indicated a setting with little denitrification potential. This non-reducing environment was reflected in a low accumulation of denitrification

  6. Conditions and mechanisms affecting simultaneous nitrification and denitrification in a Pasveer oxidation ditch

    NARCIS (Netherlands)

    Hao, X.; Doddema, H.J.; Groenestijn, J.W. van

    1997-01-01

    Simultaneous nitrification and denitrification in a Pasveer oxidation ditch was studied. The purpose was to evaluate the performances of both nitrification and dentrification in oxidation ditches, and to pursue some possible approaches to enhance nitrogen removal. Almost complete nitrification was

  7. Towards the understanding of network information processing in biology

    Science.gov (United States)

    Singh, Vijay

    Living organisms perform incredibly well in detecting a signal present in the environment. This information processing is achieved near optimally and quite reliably, even though the sources of signals are highly variable and complex. The work in the last few decades has given us a fair understanding of how individual signal processing units like neurons and cell receptors process signals, but the principles of collective information processing on biological networks are far from clear. Information processing in biological networks, like the brain, metabolic circuits, cellular-signaling circuits, etc., involves complex interactions among a large number of units (neurons, receptors). The combinatorially large number of states such a system can exist in makes it impossible to study these systems from the first principles, starting from the interactions between the basic units. The principles of collective information processing on such complex networks can be identified using coarse graining approaches. This could provide insights into the organization and function of complex biological networks. Here I study models of biological networks using continuum dynamics, renormalization, maximum likelihood estimation and information theory. Such coarse graining approaches identify features that are essential for certain processes performed by underlying biological networks. We find that long-range connections in the brain allow for global scale feature detection in a signal. These also suppress the noise and remove any gaps present in the signal. Hierarchical organization with long-range connections leads to large-scale connectivity at low synapse numbers. Time delays can be utilized to separate a mixture of signals with temporal scales. Our observations indicate that the rules in multivariate signal processing are quite different from traditional single unit signal processing.

  8. Analysis of Microbial Communities in Biofilms from CSTR-Type Hollow Fiber Membrane Biofilm Reactors for Autotrophic Nitrification and Hydrogenotrophic Denitrification.

    Science.gov (United States)

    Shin, Jung-Hun; Kim, Byung-Chun; Choi, Okkyoung; Kim, Hyunook; Sang, Byoung-In

    2015-10-01

    Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH4(+)-N/m(3)/d and 0.10-0.21 kg NO3(-)-N/m(3)/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH4(+) or NO3(-) loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.

  9. Efficiency comparison of different biofilm carriers concerning the P- and N-elimination in a fluidized bed system under alternating anaerobic/anoxic conditions; Leistungsvergleich verschiedener Traegermaterialien - hinsichtlich ihrer Eignung zur N- und P-Elimination in einem alternierend anaerob/anoxisch betriebenen Wirbelbettverfahren

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, D.; Hegemann, W. [Techn. Univ. Berlin, Fachgebiet Siedlungswasserwirtschaft, Berlin (Germany)

    2001-09-01

    Objective of the depicted research was the selection of a carrier material that is suitable for the the use in the Sorption-Denitrification-P-Removal-process (S-DN-P-process) realized in a Fluidized-Bed-Biofilm-Reactor. The S-DN-P-process is a biofilmprocess which combines denitrification and biological P-removal in a new way. The biomass is exposed to a sequential change of anaerobic, substrate-rich wastewater and anoxic, substrate-poor wastewater. Under these conditions phosphate-accumulating organisms (PAO) are enriched which are able to use nitrate as electron acceptor. Consequently, the readily biodegradable wastewater components are used simultaneously for denitrification and biological P-removal. In the described investigations special carriers were compared which were especially developed for fluidized-bed-processes and moving-bed-processes. With one exception, it was established that all materials had similar performances although they had different specific surfaces. Therefore the material costs will be crucially for a particular application case. At the moment the costs per m{sup 3} carrier material range between 450 and 1000 DM. (orig.)

  10. Synthetic Biology: Tools to Design, Build, and Optimize Cellular Processes

    Science.gov (United States)

    Young, Eric; Alper, Hal

    2010-01-01

    The general central dogma frames the emergent properties of life, which make biology both necessary and difficult to engineer. In a process engineering paradigm, each biological process stream and process unit is heavily influenced by regulatory interactions and interactions with the surrounding environment. Synthetic biology is developing the tools and methods that will increase control over these interactions, eventually resulting in an integrative synthetic biology that will allow ground-up cellular optimization. In this review, we attempt to contextualize the areas of synthetic biology into three tiers: (1) the process units and associated streams of the central dogma, (2) the intrinsic regulatory mechanisms, and (3) the extrinsic physical and chemical environment. Efforts at each of these three tiers attempt to control cellular systems and take advantage of emerging tools and approaches. Ultimately, it will be possible to integrate these approaches and realize the vision of integrative synthetic biology when cells are completely rewired for biotechnological goals. This review will highlight progress towards this goal as well as areas requiring further research. PMID:20150964

  11. Synthetic Biology: Tools to Design, Build, and Optimize Cellular Processes

    Directory of Open Access Journals (Sweden)

    Eric Young

    2010-01-01

    Full Text Available The general central dogma frames the emergent properties of life, which make biology both necessary and difficult to engineer. In a process engineering paradigm, each biological process stream and process unit is heavily influenced by regulatory interactions and interactions with the surrounding environment. Synthetic biology is developing the tools and methods that will increase control over these interactions, eventually resulting in an integrative synthetic biology that will allow ground-up cellular optimization. In this review, we attempt to contextualize the areas of synthetic biology into three tiers: (1 the process units and associated streams of the central dogma, (2 the intrinsic regulatory mechanisms, and (3 the extrinsic physical and chemical environment. Efforts at each of these three tiers attempt to control cellular systems and take advantage of emerging tools and approaches. Ultimately, it will be possible to integrate these approaches and realize the vision of integrative synthetic biology when cells are completely rewired for biotechnological goals. This review will highlight progress towards this goal as well as areas requiring further research.

  12. Synthetic biology: tools to design, build, and optimize cellular processes.

    Science.gov (United States)

    Young, Eric; Alper, Hal

    2010-01-01

    The general central dogma frames the emergent properties of life, which make biology both necessary and difficult to engineer. In a process engineering paradigm, each biological process stream and process unit is heavily influenced by regulatory interactions and interactions with the surrounding environment. Synthetic biology is developing the tools and methods that will increase control over these interactions, eventually resulting in an integrative synthetic biology that will allow ground-up cellular optimization. In this review, we attempt to contextualize the areas of synthetic biology into three tiers: (1) the process units and associated streams of the central dogma, (2) the intrinsic regulatory mechanisms, and (3) the extrinsic physical and chemical environment. Efforts at each of these three tiers attempt to control cellular systems and take advantage of emerging tools and approaches. Ultimately, it will be possible to integrate these approaches and realize the vision of integrative synthetic biology when cells are completely rewired for biotechnological goals. This review will highlight progress towards this goal as well as areas requiring further research.

  13. Potential denitrification and nitrous oxide production in the sediments of the Seine River Drainage Network (France).

    Science.gov (United States)

    Garnier, Josette A; Mounier, Emmanuelle M; Laverman, Anniet M; Billen, Gilles F

    2010-01-01

    To investigate bottom sediment denitrification at the scale of the Seine drainage network, a semi-potential denitrification assay was used in which river sediments (and riparian soils) were incubated for a few hours under anaerobic conditions with non limiting nitrate concentrations. This method allowed the nitrous oxide (N(2)O) concentration in the headspace, as well as the nitrate, nitrite, and ammonium concentrations to be determined during incubation. The rates at which nitrate decreased and N(2)O increased were then used to assess the potential denitrification activity and associated N(2)O production in the Seine River Basin. We observed a longitudinal pattern characterized by a significant increase of the potential rate of denitrification from upstream sectors to large downstream rivers (orders 7-8), from approximately 3.3 to 9.1 microg NO(3)(-)-N g(-1) h(-1), respectively, while the N(2)O production rates was the highest both in headwaters and in large order rivers (0.14 and 0.09 N(2)O-N g(-1) h(-1), respectively) and significantly lower in the intermediate sectors (0.01 and 0.03 N(2)O-N g(-1) h(-1)). Consequently, the ratio N(2)O production:NO(3) reduction was found to reach 5% in headstreams, whereas it averaged 1.2% in the rest of the drainage network, an intermediate percentage being found for the riparian soils. Finally, the ignition loss of sediments, together with other redundant variables (particulate organic carbon content: g C 100 g(-1) dry weight [dw], moisture: g water 100 g(-1) dw, sediment size production.

  14. Biological processes influencing contaminant release from sediments

    International Nuclear Information System (INIS)

    Reible, D.D.

    1996-01-01

    The influence of biological processes, including bioturbation, on the mobility of contaminants in freshwater sediments is described. Effective mass coefficients are estimated for tubificid oligochaetes as a function of worm behavior and biomass density. The mass transfer coefficients were observed to be inversely proportional to water oxygen content and proportional to the square root of biomass density. The sediment reworking and contaminant release are contrasted with those of freshwater amphipods. The implications of these and other biological processes for contaminant release and i n-situ remediation of soils and sediments are summarized. 4 figs., 1 tab

  15. Pre-digestion to enhance volatile fatty acids (VFAs) concentration as a carbon source for denitrification in treatment of liquid swine manure.

    Science.gov (United States)

    Wu, Sarah Xiao; Chen, Lide; Zhu, Jun; Walquist, McKenzie; Christian, David

    2018-04-30

    Insufficient denitrification in biological treatment is often a result of the lack of a carbon source. In this study, use of the volatile fatty acids (VFAs) generated via pre-digestion as a carbon source to improve denitrification in sequencing batch reactor (SBR) treatment of liquid swine manure was investigated. The pre-digestion of swine manure was realized by storing the manure in a sealed container in room temperature and samples were taken periodically from the container to determine the VFA levels. The results showed that after 14 days of pre-digestion, the VFA level in the digested liquid was increased by 200%. A polynomial relationship for the VFA level in the digested manure with the digestion time was observed with a correlation coefficient being 0.9748. Two identical SBRs were built and operated on 8-h cycles in parallel, with one fed with pre-digested and the other raw swine manure. There were five phases included in each cycle, i.e., anaerobic (90 min), anoxic (150 min), anoxic/anaerobic (90 min), anoxic/aerobic (120 min), and settle/decant (30 min), and the feeding was split to 600 mL/200 mL and performed at the beginning of and 240 min into the cycle. The SBR fed on pre-digested swine manure achieved successful denitrification with only 0.35 mg/L nitrate left in the effluent, compared to 15.9 mg/L found in the effluent of the other SBR. Nitrite was not detected in the effluent from both SBRs. The results also indicated that there was no negative impact of feeding SBRs with the pre-digested liquid swine manure for treatment on the removal of other constituents such as total solids (TS), volatile solids (VS), suspended solids (SS), volatile suspended solids (VSS), and soluble chemical oxygen demand (COD). Therefore, anaerobic digestion as a pretreatment can be an effective way to condition liquid swine manure for SBR treatment to achieve sufficient nitrate removal.

  16. Treatment of slaughter wastewater by coagulation sedimentation-anaerobic biological filter and biological contact oxidation process

    Science.gov (United States)

    Sun, M.; Yu, P. F.; Fu, J. X.; Ji, X. Q.; Jiang, T.

    2017-08-01

    The optimal process parameters and conditions for the treatment of slaughterhouse wastewater by coagulation sedimentation-AF - biological contact oxidation process were studied to solve the problem of high concentration organic wastewater treatment in the production of small and medium sized slaughter plants. The suitable water temperature and the optimum reaction time are determined by the experiment of precipitation to study the effect of filtration rate and reflux ratio on COD and SS in anaerobic biological filter and the effect of biofilm thickness and gas water ratio on NH3-N and COD in biological contact oxidation tank, and results show that the optimum temperature is 16-24°C, reaction time is 20 min in coagulating sedimentation, the optimum filtration rate is 0.6 m/h, and the optimum reflux ratio is 300% in anaerobic biological filter reactor. The most suitable biological film thickness range of 1.8-2.2 mm and the most suitable gas water ratio is 12:1-14:1 in biological contact oxidation pool. In the coupling process of continuous operation for 80 days, the average effluent’s mass concentrations of COD, TP and TN were 15.57 mg/L, 40 mg/L and 0.63 mg/L, the average removal rates were 98.93%, 86.10%, 88.95%, respectively. The coupling process has stable operation effect and good effluent quality, and is suitable for the industrial application.

  17. Influence oFe3+ Ions on Nitrate Removal by Autotrophic Denitrification Using Thiobacillus denitrificans

    Directory of Open Access Journals (Sweden)

    Z. Blažková

    2017-07-01

    Full Text Available he sulphur-based autotrophic denitrification process utilizing Thiobacillus denitrificans was studied experimentally as an alternative method of removing nitrates from industrial wastewater. The objective of the work was to examine the effect of ferric iron addition to the reaction mixture and determine optimal dosage for specific conditions. All experiments were carried out in anoxic batch bioreactor, and elemental sulphur was used as an electron donor. Compared to the control operation without ferric iron addition, significant increases in nitrates removal were demonstrated for the concentration of ferric iron equal to 0.1 mg L–1. However, under these conditions, increased nitrite content was detected in the reaction mixture which exceeds the limits for drinking water.

  18. Endogenous influences on anammox and sulfocompound-oxidizing autotrophic denitrification coupling system (A/SAD) and dynamic operating strategy.

    Science.gov (United States)

    Sun, Xinbo; Du, Lingfeng; Hou, Yuqian; Cheng, Shaoju; Zhang, Xuxiang; Liu, Bo

    2018-02-21

    The anaerobic ammonia oxidation (anammox) and sulfocompound-oxidizing autotrophic denitrification coupling system (A/SAD) was initiated in an expanded granular sludge bed (EGSB) reactor for nitrogen removal from high-strength wastewater. Owing to cooperation between anammox and partial sulfocompound-oxidation autotrophic denitrification coupling system (PSAD), the highest nitrogen removal efficiency (NRE) of 98.1% ± 0.4% achieved at the optimal influent conditions of conversion efficiency of ammonium (CEA) of 55% and S 2 O 3 2- -S/NO 3 - -N (S/N) of 1.4 mol mol -1 . The activity of the short-cut sulfocompound-oxidizing autotrophic denitrification (SSAD) was also regulated to cope with dynamic CEA in the influent by changing the S/N, which was demonstrated to be effective in alleviating nitrite accumulation when the CEA was between 57% and 61%. Both the anammox and SAD bacteria enriched in the reactor after long-term incubation. Candidatus Brocadia and Candidatus Jettenia might be potentially contributing the most to anammox, while the Thiobacillus was the dominant taxa related to SAD. Copyright © 2018. Published by Elsevier Ltd.

  19. Characterization of sulfate-reducing granular sludge in the SANI(®) process.

    Science.gov (United States)

    Hao, Tianwei; Wei, Li; Lu, Hui; Chui, Hokwong; Mackey, Hamish R; van Loosdrecht, Mark C M; Chen, Guanghao

    2013-12-01

    Hong Kong practices seawater toilet flushing covering 80% of the population. A sulfur cycle-based biological nitrogen removal process, the Sulfate reduction, Autotrophic denitrification and Nitrification Integrated (SANI(®)) process, had been developed to close the loop between the hybrid water supply and saline sewage treatment. To enhance this novel process, granulation of a Sulfate-Reducing Up-flow Sludge Bed (SRUSB) reactor has recently been conducted for organic removal and provision of electron donors (sulfide) for subsequent autotrophic denitrification, with a view to minimizing footprint and maximizing operation resilience. This further study was focused on the biological and physicochemical characteristics of the granular sulfate-reducing sludge. A lab-scale SRUSB reactor seeded with anaerobic digester sludge was operated with synthetic saline sewage for 368 days. At 1 h nominal hydraulic retention time (HRT) and 6.4 kg COD/m(3)-d organic loading rate, the SRUSB reactor achieved 90% COD and 75% sulfate removal efficiencies. Granular sludge was observed within 30 days, and became stable after 4 months of operation with diameters of 400-500 μm, SVI5 of 30 ml/g, and extracellular polymeric substances of 23 mg carbohydrate/g VSS. Fluorescence in situ hybridization (FISH) analysis revealed that the granules were enriched with abundant sulfate-reducing bacteria (SRB) as compared with the seeding sludge. Pyrosequencing analysis of the 16S rRNA gene in the sulfate-reducing granules on day 90 indicated that the microbial community consisted of a diverse SRB genera, namely Desulfobulbus (18.1%), Desulfobacter (13.6%), Desulfomicrobium (5.6%), Desulfosarcina (0.73%) and Desulfovibrio (0.6%), accounting for 38.6% of total operational taxonomic units at genera level, with no methanogens detected. The microbial population and physicochemical properties of the granules well explained the excellent performance of the granular SRUSB reactor. Copyright © 2013 Elsevier

  20. The effects of oxygen on process rates and gene expression of anammox and denitrification in the Eastern South Pacific oxygen minimum zone

    DEFF Research Database (Denmark)

    Dalsgaard, Tage; Stewart, Frank; De Brabandere, Loreto

    Oxygen concentrations were consistently below our detection limit of 90 nM for a distance of > 2000 km in the oxygen minimum zone (OMZ) along the coasts of Chile and Peru. In most cases, anammox and denitrification were only detected when in situ oxygen concentrations were below detection...... differently to oxygen. When normalized to a housekeeping gene (rpoB), the expression of 4 out of 9 N-cycle-genes changed with increasing oxygen concentration: The expression of ammonium monooxygenase (amoC) was stimulated, whereas expression of nitrite reductase (nirS), nitric oxide reductase (nor...

  1. Removal of nitrogen and organic matter in a submerged-membrane bioreactor operating in a condition of simultaneous nitrification and denitrification

    Directory of Open Access Journals (Sweden)

    Izabela Major Barbosa

    2016-04-01

    Full Text Available This study evaluated the removal of nitrogen and organic matter in a membrane bioreactor system operating in a condition of simultaneous nitrification and denitrification controlled by intermittent aeration. A submerged-membrane system in a bioreactor was used in a pilot scale to treat domestic wastewater. The dissolved oxygen concentration was maintained between 0.5 and 0.8 mg L-1. The concentration of the mixed liquor suspended solids (MLSS in the system ranged from 1 to 6 g L-1. The system efficiency was evaluated by the removal efficiency of organic matter, quantified by Chemical Oxygen Demand (COD, Biochemical Oxygen Demand (BOD5 and Total Organic Carbon (TOC. Nitrogen removal was assessed by quantifying Total Kjeldahl Nitrogen (TKN and ammonia nitrogen. During the system start-up, the removal efficiencies of COD and NTK were around 90% and 80%, respectively. After the simultaneous nitrification and denitrification (SND conditions were established, the removal efficiencies of COD and NTK were 70% and 99%, respectively. These results showed that sewage treatment with the membrane bioreactor (MBR system, operating with simultaneous nitrification and denitrification conditions, was able to remove organic matter and promote nitrification and denitrification in a single reactor, producing a high-quality permeate.

  2. System evaluation and microbial analysis of a sulfur cycle-based wastewater treatment process for Co-treatment of simple wet flue gas desulfurization wastes with freshwater sewage.

    Science.gov (United States)

    Qian, Jin; Liu, Rulong; Wei, Li; Lu, Hui; Chen, Guang-Hao

    2015-09-01

    A sulfur cycle-based wastewater treatment process, namely the Sulfate reduction, Autotrophic denitrification and Nitrification Integrated process (SANI(®) process) has been recently developed for organics and nitrogen removal with 90% sludge minimization and 35% energy reduction in the biological treatment of saline sewage from seawater toilet flushing practice in Hong Kong. In this study, sulfate- and sulfite-rich wastes from simple wet flue gas desulfurization (WFGD) were considered as a potential low-cost sulfur source to achieve beneficial co-treatment with non-saline (freshwater) sewage in continental areas, through a Mixed Denitrification (MD)-SANI process trialed with synthetic mixture of simple WFGD wastes and freshwater sewage. The system showed 80% COD removal efficiency (specific COD removal rate of 0.26 kg COD/kg VSS/d) at an optimal pH of 7.5 and complete denitrification through MD (specific nitrogen removal rate of 0.33 kg N/kg VSS/d). Among the electron donors in MD, organics and thiosulfate could induce a much higher denitrifying activity than sulfide in terms of both NO3(-) reduction and NO2(-) reduction, suggesting a much higher nitrogen removal rate in organics-, thiosulfate- and sulfide-based MD in MD-SANI compared to sulfide alone-based autotrophic denitrification in conventional SANI(®). Diverse sulfate/sulfite-reducing bacteria (SRB) genera dominated in the bacterial community of sulfate/sulfite-reducing up-flow sludge bed (SRUSB) sludge without methane producing bacteria detected. Desulfomicrobium-like species possibly for sulfite reduction and Desulfobulbus-like species possibly for sulfate reduction are the two dominant groups with respective abundance of 24.03 and 14.91% in the SRB genera. Diverse denitrifying genera were identified in the bacterial community of anoxic up-flow sludge bed (AnUSB) sludge and the Thauera- and Thiobacillus-like species were the major taxa. These results well explained the successful operation of the lab

  3. Processing scarce biological samples for light and transmission electron microscopy

    Directory of Open Access Journals (Sweden)

    P Taupin

    2008-06-01

    Full Text Available Light microscopy (LM and transmission electron microscopy (TEM aim at understanding the relationship structure-function. With advances in biology, isolation and purification of scarce populations of cells or subcellular structures may not lead to enough biological material, for processing for LM and TEM. A protocol for preparation of scarce biological samples is presented. It is based on pre-embedding the biological samples, suspensions or pellets, in bovine serum albumin (BSA and bis-acrylamide (BA, cross-linked and polymerized. This preparation provides a simple and reproducible technique to process biological materials, present in limited quantities that can not be amplified, for light and transmission electron microscopy.

  4. Denitrification: An important pathway for nitrous oxide production in tropical mangrove sediments (Goa, India)

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; LokaBharathi, P.A.; Bonin, P.C.; Michotey, V.D.

    Net nitrous oxide production and denitrification activity were measured in two mangrove ecosystems of Goa, India. The relatively pristine site Tuvem was compared to Divar, which is prone to high nutrient input. Stratified sampling at 2-cm intervals...

  5. Nitrate removal and microbial analysis by combined micro-electrolysis and autotrophic denitrification.

    Science.gov (United States)

    Xing, Wei; Li, Desheng; Li, Jinlong; Hu, Qianyi; Deng, Shihai

    2016-07-01

    A process combining micro-electrolysis and autotrophic denitrification (CEAD) with iron-carbon micro-electrolysis carriers was developed for nitrate removal. The process was performed using organic-free influent with a NO3(-)-N concentration of 40.0±3.0mg/L and provided an average nitrate removal efficiency of 95% in stable stages. The total nitrogen removal efficiency reached 75%, with 21% of NO3(-)-N converted into NH4(+)-N. The corresponding hydraulic retention time was 8-10h, and the optimal pH ranged from 8.5 to 9.5. Microbial analysis with high-throughput sequencing revealed that dominant microorganisms in the reactor belonged to the classes of β-, γ-, and α-Proteobacteria. The abundance of the genera Thermomonas significantly increased during the operation, comprising 21.4% and 24.1% in sludge attached to the carriers in the middle and at the bottom of the reactor, respectively. The developed CEAD achieved efficient nitrate removal from water without organics, which is suitable for practical application. Copyright © 2016. Published by Elsevier Ltd.

  6. Denitrification potential in sediments of headwater streams in the southern appalachian mountains, USA

    Science.gov (United States)

    Lara A. Martin; Patrick J. Mulholland; Jackson R. Webster; H. Maurice Vallett

    2001-01-01

    We investigated variations in resource availability (NOa-N and labile organic C [LOCJ] as determinants of potential denitrification in stream sediments in the southern Appalachian Mountains, USA. stream-water and sediments were sampled seasonally in 2 streams of contrasting NO3,-N availability, Noland Creek (high NO

  7. Simultaneous nitrification-denitrification achieved by an innovative internal-loop airlift MBR: comparative study.

    Science.gov (United States)

    Li, Y Z; He, Y L; Ohandja, D G; Ji, J; Li, J F; Zhou, T

    2008-09-01

    This study assessed the performance of different single-stage continuous aerated submerged membrane bioreactors (MBR) for nitrogen removal. Almost complete nitrification was achieved in each MBR irrespective of operating mode and biomass system. Denitrification was found to be the rate-limiting step for total nitrogen (T-N) removal. The MBR with internal-loop airlift reactor (ALR) configuration performed better as regards T-N removal compared with continuous stirred-tank reactor (CSTR). It was demonstrated that simultaneous nitrification and denitrification (SND) is the mechanism leading to nitrogen removal and the contribution of microenvironment on SND is more remarkable for the MBRs with hybrid biomass. Macroenvironment analyses showed that gradient distribution of dissolved oxygen (DO) level in airlift MBRs imposed a significant effect on SND. Higher mixed liquor suspended solid (MLSS) concentration led to the improvement in T-N removal by enhancing anoxic microenvironment. Apparent nitrite accumulation coupled with higher nitrogen reduction was accomplished at MLSS concentration exceeded 12.6 g/L.

  8. The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment

    Directory of Open Access Journals (Sweden)

    M. Alkhatib

    2012-05-01

    Full Text Available The nitrogen (N stable isotopic composition of pore water nitrate and total dissolved N (TDN was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. N isotope effects on the water column associated with the benthic exchange of nitrate (εapp and TDN (εsed during benthic nitrification-denitrification coupling were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+. We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net fixed N loss was barely expressed at the scale of sediment-water exchange, with ϵapp values <3‰. The strongest under-expression (i.e. lowest εapp of the biological N isotope fractionation was observed at the most oxygenated sites with the least reactive organic matter, indicating that, through their control on the depth of the denitrification zone, bottom water oxygen concentrations and the organic matter reactivity can modulate εapp. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of εsed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly elevate εsed above εapp. Calculated εsed values were within the range of 4.6 ± 2

  9. Denitrification, nitrification, and atmospheric nitrous oxide

    National Research Council Canada - National Science Library

    Delwiche, C. C

    1981-01-01

    In this book, a number of unanswered questions particularly demanding of attention are analyzed to determine the significance of various chemical and biological processes involved with the atmospheric...

  10. Accounting for the Decreasing Denitrification Potential of Aquifers in Travel-Time Based Reactive-Transport Models of Nitrate

    Science.gov (United States)

    Cirpka, O. A.; Loschko, M.; Wöhling, T.; Rudolph, D. L.

    2017-12-01

    Excess nitrate concentrations pose a threat to drinking-water production from groundwater in all regions of intensive agriculture worldwide. Natural organic matter, pyrite, and other reduced constituents of the aquifer matrix can be oxidized by aerobic and denitrifying bacteria, leading to self-cleaning of groundwater. Various studies have shown that the heterogeneity of both hydraulic and chemical aquifer properties influence the reactive behavior. Since the exact spatial distributions of these properties are not known, predictions on the temporal evolution of nitrate should be probabilistic. However, the computational effort of pde-based, spatially explicit multi-component reactive-transport simulations are so high that multiple model runs become impossible. Conversely, simplistic models that treat denitrification as first-order decay process miss important controls on denitrification. We have proposed a Lagrangian framework of nonlinear reactive transport, in which the electron-donor supply by the aquifer matrix is parameterized by a relative reactivity, that is the reaction rate relative to a standard reaction rate for identical solute concentrations (Loschko et al., 2016). We could show that reactive transport simplifies to solving a single ordinary dfferential equation in terms of the cumulative relative reactivity for a given combination of inflow concentrations. Simulating 3-D flow and reactive transport are computationally so inexpensive that Monte Carlo simulation become feasible. The original scheme did not consider a change of the relative reactivity over time, implying that the electron-donor pool in the matrix is infinite. We have modified the scheme to address the consumption of the reducing aquifer constituents upon the reactions. We also analyzed how a minimally complex model of aerobic respiration and denitrification could look like. With the revised scheme, we performed Monte Carlo simulations in 3-D domains, confirming that the uncertainty in

  11. Dimensioning and recalculation of activation systems of several different processes; Bemessung und Nachrechnung von Belebungsanlagen verschiedener Verfahrensweisen

    Energy Technology Data Exchange (ETDEWEB)

    Wichern, M.

    2000-07-01

    In this research paper, several calculation models for the description of biological nitrogen elimination and enhanced biological phosphorous elimination are developed. The steady-state methods are suitable to be used both for the design and simulation and for the extension/optimisation of biological wastewater treatment plants. All developed models are checked for their practical utility; the calculation results are counterchecked with proved models and experimental data. COD approaches for the modelling of intermittent and alternating denitrification and for the Juelich wastewater treatment method were developed. Apart from average and maximum ammonium and nitrate nitrogen effluent values, it is possible to consider states of limited BOD during the denitrification intervals. The model for Cascade denitrification is able to present any number of cascade steps with a free distribution of the influent and the return sludge flow to the denitrification cassettes. Apart from the nitrate nitrogen input, additional oxygen input and internal recycle flows are considered, in order to gain hints about the plant operation with optimal nitrate reduction by using the oxygen balances (BOD). For the design and steady simulation of wastewater treatment plants, the COD-Model calculates the hydrolysis of hardly degradable COD, the denitrification capacity with consideration of rapidly and slowly degradable COD, heterotrophic and autotrophic biomass in the influent, the oxygen input, and the autotrophic endogenous respiration. The model for enhanced biological P-Elimination offers the chance to consider denitrifying and non-denitrifying PAOs and their storage substances (PHA), as well as different decay rates, gain rates, and denitrification performances of the two heterotropic groups. (orig.) [German] Im Rahmen der vorliegenden Arbeit werden verschiedene Berechnungsmodelle zur Beschreibung der biologischen Stickstoffelimination und vermehrten biologischen Phosphorelimination

  12. Efficient H2O2/CH3COOH oxidative desulfurization/denitrification of liquid fuels in sonochemical flow-reactors.

    Science.gov (United States)

    Calcio Gaudino, Emanuela; Carnaroglio, Diego; Boffa, Luisa; Cravotto, Giancarlo; Moreira, Elizabeth M; Nunes, Matheus A G; Dressler, Valderi L; Flores, Erico M M

    2014-01-01

    The oxidative desulfurization/denitrification of liquid fuels has been widely investigated as an alternative or complement to common catalytic hydrorefining. In this process, all oxidation reactions occur in the heterogeneous phase (the oil and the polar phase containing the oxidant) and therefore the optimization of mass and heat transfer is of crucial importance to enhancing the oxidation rate. This goal can be achieved by performing the reaction in suitable ultrasound (US) reactors. In fact, flow and loop US reactors stand out above classic batch US reactors thanks to their greater efficiency and flexibility as well as lower energy consumption. This paper describes an efficient sonochemical oxidation with H2O2/CH3COOH at flow rates ranging from 60 to 800 ml/min of both a model compound, dibenzotiophene (DBT), and of a mild hydro-treated diesel feedstock. Four different commercially available US loop reactors (single and multi-probe) were tested, two of which were developed in the authors' laboratory. Full DBT oxidation and efficient diesel feedstock desulfurization/denitrification were observed after the separation of the polar oxidized S/N-containing compounds (S≤5 ppmw, N≤1 ppmw). Our studies confirm that high-throughput US applications benefit greatly from flow-reactors. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Tracing the role of endogenous carbon in denitrification using wine industry by-product as an external electron donor: Coupling isotopic tools with mathematical modeling.

    Science.gov (United States)

    Carrey, R; Rodríguez-Escales, P; Soler, A; Otero, N

    2018-02-01

    Nitrate removal through enhanced biological denitrification (EBD), consisting of the inoculation of an external electron donor, is a feasible solution for the recovery of groundwater quality. In this context, liquid waste from wine industries (wine industry by-products, WIB) may be feasible for use as a reactant to enhance heterotrophic denitrification. To address the feasibility of WIB as electron donor to promote denitrification, as well as to evaluate the role of biomass as a secondary organic C source, a flow-through experiment was carried out. Chemical and isotopic characterization was performed and coupled with mathematical modeling. Complete nitrate attenuation with no nitrite accumulation was successfully achieved after 10 days. Four different C/N molar ratios (7.0, 2.0, 1.0 and 0) were tested. Progressive decrease of the C/N ratio reduced the remaining C in the outflow and favored biomass migration, producing significant changes in dispersivity in the reactor, which favored efficient nitrate degradation. The applied mathematical model described the general trends for nitrate, ethanol, dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. This model shows how the biomass present in the system is degraded to dissolved organic C (DOC en ) and becomes the main source of DOC for a C/N ratio between 1.0 and 0. The isotopic model developed for organic and inorganic carbon also describes the general trends of δ 13 C of ethanol, DOC and DIC in the outflow water. The study of the evolution of the isotopic fractionation of organic C using a Rayleigh distillation model shows the shift in the organic carbon source from the WIB to the biomass and is in agreement with the isotopic fractionation values used to calibrate the model. Isotopic fractionations (ε) of C-ethanol and C-DOC en were -1‰ and -5‰ (model) and -3.3‰ and -4.8‰ (Rayleigh), respectively. In addition, an inverse isotopic fractionation of +10‰ was observed for

  14. Correlation between nitrous oxide (N2O) emission and carbon to nitrogen (COD/N) ratio in denitrification process: a mitigation strategy to decrease greenhouse gas emission and cost of operation.

    Science.gov (United States)

    Andalib, Mehran; Taher, Edris; Donohue, Joseph; Ledwell, Sam; Andersen, Mikkel H; Sangrey, Karla

    2018-01-01

    The reliability and accuracy of in-situ ion selective electrode and ultraviolet (NO x ) probes have been investigated at four different treatment plants with different operational conditions. This study shows that the mentioned probes tend to compromise their accuracy and trending stability at lower NO x of production at non-detect dissolved oxygen concentrations and pH of 7-7.2 were found to be a function of influent nitrogen load or the ratio of COD/N INFLUENT . Finally, using an N 2 O probe as a proxy sensor for nitrates is proposed as a measured variable in the PI feedback in the automation of the denitrification process with a NO x set point of <1.2 mg N/L).

  15. Re-use of winery wastewaters for biological nutrient removal.

    Science.gov (United States)

    Rodríguez, L; Villaseñor, J; Buendía, I M; Fernández, F J

    2007-01-01

    The aim of this study was to evaluate the feasibility of the re-use of the winery wastewater to enhance the biological nutrient removal (BNR) process. In batch experiments it was observed that the addition of winery wastewater mainly enhanced the nitrogen removal process because of the high denitrification potential (DNP), of about 130 mg N/g COD, of the contained substrates. This value is very similar to that obtained by using pure organic substrates such as acetate. The addition of winery wastewater did not significantly affect either phosphorus or COD removal processes. Based on the experimental results obtained, the optimum dosage to remove each mg of N-NO3 was determined, being a value of 6.7 mg COD/mg N-NO3. Because of the good properties of the winery wastewater to enhance the nitrogen removal, the viability of its continuous addition in an activated sludge pilot-scale plant for BNR was studied. Dosing the winery wastewater to the pilot plant a significant increase in the nitrogen removal was detected, from 58 to 75%. The COD removal was slightly increased, from 89 to 95%, and the phosphorus removal remained constant.

  16. An introduction to stochastic processes with applications to biology

    CERN Document Server

    Allen, Linda J S

    2010-01-01

    An Introduction to Stochastic Processes with Applications to Biology, Second Edition presents the basic theory of stochastic processes necessary in understanding and applying stochastic methods to biological problems in areas such as population growth and extinction, drug kinetics, two-species competition and predation, the spread of epidemics, and the genetics of inbreeding. Because of their rich structure, the text focuses on discrete and continuous time Markov chains and continuous time and state Markov processes.New to the Second EditionA new chapter on stochastic differential equations th

  17. Engineering hyporheic zones to target nitrification versus denitrification: performance data from constructed stream flumes

    Science.gov (United States)

    Herzog, S.; Portmann, A. C.; Halpin, B. N.; Higgins, C.; McCray, J. E.

    2017-12-01

    Nonpoint source nitrogen pollution from agricultural and urban runoff is one of the leading causes of impairment to US rivers and streams. The hyporheic zone (HZ) offers a natural biogeochemical hotspot for the attenuation of nitrogen within streams, thereby complementing efforts to prevent aquatic nitrogen pollution in the first place. However, HZ in urban and agricultural streams are often degraded by scouring and colmation, which limit their potential to improve stream water quality at the reach scale. A recent effort to mitigate nitrogen pollution in the Chesapeake Bay region provides denitrification credits for hyporheic restoration projects. Unfortunately, many of the featured hyporheic zone best management practices (BMP) (e.g., weirs, cross-vanes) tend to create only localized, aerobic hyporheic flows that are not optimal for the anaerobic denitrification reaction. In short, practitioners lack an adaptable BMP that can both 1) increase hyporheic exchange, and 2) tailor HZ residence times to match reactions of interest. Here we present new performance data for an HZ engineering technique called Biohydrochemical Enhancements for Streamwater Treatment (BEST). BEST are subsurface modules that utilize low-permeability sediments to drive efficient hyporheic exchange and control residence times, along with reactive geomedia to increase reaction rates within HZ sediments. This research utilized two artificial stream flumes: One flume served as an all-sand control condition, the other featured BEST modules at 1m spacing with a mixture of 70/30 sand/woodchips (v/v). Two different BEST media were tested: a coarse sand module with K 0.5 cm/s, and a fine sand module with K 0.15 cm/s. The flume with coarse sand BEST modules created aerobic HZ conditions and demonstrated rapid nitrification of ammonia at rates significantly higher than the control. However, denitrification was much slower and not significantly different between the two streams. In contrast, the fine sand

  18. Denitrification rates and excess nitrogen gas concentrations in the Arabian Sea oxygen deficient zone

    Digital Repository Service at National Institute of Oceanography (India)

    Devol, A; Uhlenhopp, A; Naqvi, S.W.A; Brandes, J.A; Jayakumar, D.A; Naik, H.; Gaurin, S.; Codispoti, L.A.; Yoshinari, T.

    Rates of canonical, i.e. heterotrophic, water-column denitrification were measured by sup(15)N incubation techniques at a number of coastal and open ocean stations in the Arabian Sea. Measurements of N2 :Ar gas ratios were also made to obtain...

  19. Single-sludge denitrification in recirculating aquaculture systems: effects of pre-fermentation and pH

    DEFF Research Database (Denmark)

    Suhr, Karin Isabel; Letelier-Gordo, Carlos Octavio; Prat Busquets, Pau

    2015-01-01

    Single-sludge denitrification (DN) reactors in aquaculture use the carbonous solid fish waste produced in the system to reduce the discharged nitrate load. The solid waste is available for denitrifiers when present in soluble, readily biodegradable form, and the transformation is accomplished by ...

  20. Single-sludge denitrification in recirculating aquaculture systems: Effects of pre-fermentation and pH

    DEFF Research Database (Denmark)

    Suhr, Karin Isabel; Letelier Gordo, Carlos Octavio; Prat Busquets, Pau

    2014-01-01

    Single-sludge denitrification (DN) reactors in aquaculture utilize the solid fish waste produced in the system to reduce the nitrate load discharged. The solid waste is available for denitrifiers when present in soluble readily biodegradable form. A transformation accomplished by bacterial hydrol...

  1. Illumina sequencing-based analysis of a microbial community enriched under anaerobic methane oxidation condition coupled to denitrification revealed coexistence of aerobic and anaerobic methanotrophs.

    Science.gov (United States)

    Siniscalchi, Luciene Alves Batista; Leite, Laura Rabelo; Oliveira, Guilherme; Chernicharo, Carlos Augusto Lemos; de Araújo, Juliana Calabria

    2017-07-01

    Methane is produced in anaerobic environments, such as reactors used to treat wastewaters, and can be consumed by methanotrophs. The composition and structure of a microbial community enriched from anaerobic sewage sludge under methane-oxidation condition coupled to denitrification were investigated. Denaturing gradient gel electrophoresis (DGGE) analysis retrieved sequences of Methylocaldum and Chloroflexi. Deep sequencing analysis revealed a complex community that changed over time and was affected by methane concentration. Methylocaldum (8.2%), Methylosinus (2.3%), Methylomonas (0.02%), Methylacidiphilales (0.45%), Nitrospirales (0.18%), and Methanosarcinales (0.3%) were detected. Despite denitrifying conditions provided, Nitrospirales and Methanosarcinales, known to perform anaerobic methane oxidation coupled to denitrification (DAMO) process, were in very low abundance. Results demonstrated that aerobic and anaerobic methanotrophs coexisted in the reactor together with heterotrophic microorganisms, suggesting that a diverse microbial community was important to sustain methanotrophic activity. The methanogenic sludge was a good inoculum to enrich methanotrophs, and cultivation conditions play a selective role in determining community composition.

  2. Anoxia over the western continental shelf of India: Bacterial indications of intrinsic nitrification feeding denitrification

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnan, K.P.; Fernandes, S.O.; LokaBharathi, P.A.; KrishnaKumari, L.; Nair, S.; Pratihary, A.K.; Rao, B.R

    consuming available nitrate (approx. 0.5 mu M) to near zero levels within approx. 72 h of incubation. These observations have been supported by concomitant increase in nitrite concentration (approx. 4 mu M). Similar studies on denitrification...

  3. Dissipation of atrazine, enrofloxacin, and sulfamethazine in wood chip bioreactors and impact on denitrification

    Science.gov (United States)

    Wood chip bioreactors are receiving increasing attention as a means of reducing nitrate in subsurface tile drainage systems. Agrochemicals in tile drainage water entering wood chip bioreactors can be retained or degraded and may impact denitrification. The degradation of 5 mg L-1 atrazine, enrofloxa...

  4. Systems Biology Graphical Notation: Process Description language Level 1 Version 1.3.

    Science.gov (United States)

    Moodie, Stuart; Le Novère, Nicolas; Demir, Emek; Mi, Huaiyu; Villéger, Alice

    2015-09-04

    The Systems Biological Graphical Notation (SBGN) is an international community effort for standardized graphical representations of biological pathways and networks. The goal of SBGN is to provide unambiguous pathway and network maps for readers with different scientific backgrounds as well as to support efficient and accurate exchange of biological knowledge between different research communities, industry, and other players in systems biology. Three SBGN languages, Process Description (PD), Entity Relationship (ER) and Activity Flow (AF), allow for the representation of different aspects of biological and biochemical systems at different levels of detail. The SBGN Process Description language represents biological entities and processes between these entities within a network. SBGN PD focuses on the mechanistic description and temporal dependencies of biological interactions and transformations. The nodes (elements) are split into entity nodes describing, e.g., metabolites, proteins, genes and complexes, and process nodes describing, e.g., reactions and associations. The edges (connections) provide descriptions of relationships (or influences) between the nodes, such as consumption, production, stimulation and inhibition. Among all three languages of SBGN, PD is the closest to metabolic and regulatory pathways in biological literature and textbooks, but its well-defined semantics offer a superior precision in expressing biological knowledge.

  5. Stochastic transport processes in discrete biological systems

    CERN Document Server

    Frehland, Eckart

    1982-01-01

    These notes are in part based on a course for advanced students in the applications of stochastic processes held in 1978 at the University of Konstanz. These notes contain the results of re­ cent studies on the stochastic description of ion transport through biological membranes. In particular, they serve as an introduction to an unified theory of fluctuations in complex biological transport systems. We emphasize that the subject of this volume is not to introduce the mathematics of stochastic processes but to present a field of theoretical biophysics in which stochastic methods are important. In the last years the study of membrane noise has become an important method in biophysics. Valuable information on the ion transport mechanisms in membranes can be obtained from noise analysis. A number of different processes such as the opening and closing of ion channels have been shown to be sources of the measured current or voltage fluctuations. Bio­ logical 'transport systems can be complex. For example, the tr...

  6. Potential denitrification in arable soil samples at winter temperatures - measurements by 15N gas analysis

    International Nuclear Information System (INIS)

    Lippold, H.; Foerster, I.; Matzel, W.

    1989-01-01

    In samples from the plough horizon of five soils taken after cereal harvest, denitrification was measured as volatilization of N 2 and N 2 O from 15 N nitrate in the absence of O 2 . Nitrate contents lower than 50 ppm N (related to soil dry matter) had only a small effect on denitrification velocity in four of the five soils. In a clay soil dependence on nitrate concentration corresponded to a first-order reaction. Available C was no limiting factor. Even at zero temperatures remarkable N amounts (on average 0.2 ppm N per day) were still denitrified. The addition of daily turnover rates in relation to soil temperatures prevailing from December to March revealed potential turnovers in the 0-to-30-cm layer of the soils to average 28 ± 5 ppm N. (author)

  7. Hidden Markov processes theory and applications to biology

    CERN Document Server

    Vidyasagar, M

    2014-01-01

    This book explores important aspects of Markov and hidden Markov processes and the applications of these ideas to various problems in computational biology. The book starts from first principles, so that no previous knowledge of probability is necessary. However, the work is rigorous and mathematical, making it useful to engineers and mathematicians, even those not interested in biological applications. A range of exercises is provided, including drills to familiarize the reader with concepts and more advanced problems that require deep thinking about the theory. Biological applications are t

  8. Nitrate levels modulate denitrification activity in tropical mangrove sediments (Goa, India)

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; LokaBharathi, P.A.

    .M., & Bundrick, C.M. (1998). Potential sediment denitrification rates in estuaries of Northern Gulf of Mexico. Journal of environmental quality, 27(4), 859-868. Gruber, N., & Sarmiento, J.L. (1997). Global. Biogeochemical Cycles, 11, 235-266. Hahndel, R... of inorganic nitrogen in mangrove sediments (Terminos Lagoon, Mexico). Limnology and Oceanography, 41, 284-296. Sardessai, S. (1993). Dissolved, particulate and sedimentary humic acids in the mangroves and estuarine ecosystem of Goa, west coast of India...

  9. Assessing nitrification and denitrification in a paddy soil with different water dynamics and applied liquid cattle waste using the {sup 15}N isotopic technique

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Sheng, E-mail: jszs@cc.tuat.ac.jp [Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Eco-environmental Protection Institute, Shanghai Academy of Agricultural Sciences, 1000 Jinqi Road, Shanghai 201403 (China); Sakiyama, Yukina; Riya, Shohei [Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Song, Xiangfu [Eco-environmental Protection Institute, Shanghai Academy of Agricultural Sciences, 1000 Jinqi Road, Shanghai 201403 (China); Terada, Akihiko; Hosomi, Masaaki [Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)

    2012-07-15

    Using livestock wastewater for rice production in paddy fields can remove nitrogen and supplement the use of chemical fertilizers. However, paddy fields have complicated water dynamics owing to varying characteristics and would influence nitrogen removal through nitrification followed by denitrification. Quantification of nitrification and denitrification is of great importance in assessing the influence of water dynamics on nitrogen removal in paddy fields. In this study, nitrification and nitrate reduction rates with different water dynamics after liquid cattle waste application were evaluated, and the in situ denitrification rate was determined directly using the {sup 15}N isotopic technique in a laboratory experiment. A significant linear regression correlation between nitrification and the nitrate reduction rate was observed and showed different regression coefficients under different water dynamics. The regression coefficient in the continuously flooded paddy soil was higher than in the drained-reflooded paddy soil, suggesting that nitrate would be consumed faster in the flooded paddy soil. However, nitrification was limited and the maximum rate was only 13.3 {mu}g N g{sup -1} day{sup -1} in the flooded paddy soil with rice plants, which limited the supply of nitrate. In contrast, the drained-reflooded paddy soil had an enhanced nitrification rate up to 56.8 {mu}g N g{sup -1} day{sup -1}, which was four times higher than the flooded paddy soil and further stimulated nitrate reduction rates. Correspondingly, the in situ denitrification rates determined directly in the drained-reflooded paddy soil ranged from 5 to 1035 mg N m{sup -2} day{sup -1}, which was higher than the continuously flooded paddy soil (from 5 to 318 mg N m{sup -2} day{sup -1}) during the vegetation period. The nitrogen removal through denitrification accounted for 38.9% and 9.9% of applied nitrogen in the drained-reflooded paddy soil and continuously flooded paddy soil, respectively

  10. Influence of porewater advection on denitrification in carbonate sands: Evidence from repacked sediment column experiments

    DEFF Research Database (Denmark)

    Santos, Isaac R.; Eyre, Bradley D.; Glud, Ronnie N.

    2012-01-01

    Porewater flow enhances mineralization rates in organic-poor permeable sands. Here, a series of sediment column experiments were undertaken to assess the potential effect of advective porewater transport on denitrification in permeable carbonate sands collected from Heron Island (Great Barrier Re...

  11. Students’ learning activities while studying biological process diagrams

    NARCIS (Netherlands)

    Kragten, M.; Admiraal, W.; Rijlaarsdam, G.

    2015-01-01

    Process diagrams describe how a system functions (e.g. photosynthesis) and are an important type of representation in Biology education. In the present study, we examined students’ learning activities while studying process diagrams, related to their resulting comprehension of these diagrams. Each

  12. Anaerobic methane oxidation coupled to denitrification is the dominant methane sink in a deep lake

    DEFF Research Database (Denmark)

    Deutzmann, Joerg S.; Stief, Peter; Brandes, Josephin

    2014-01-01

    Anaerobic methane oxidation coupled to denitrification, also known as “nitrate/nitrite-dependent anaerobic methane oxidation” (n-damo), was discovered in 2006. Since then, only a few studies have identified this process and the associated microorganisms in natural environments. In aquatic sediments......, the close proximity of oxygen- and nitrate-consumption zones can mask n-damo as aerobic methane oxidation. We therefore investigated the vertical distribution and the abundance of denitrifying methanotrophs related to Candidatus Methylomirabilis oxyfera with cultivation-independent molecular techniques...... in the sediments of Lake Constance. Additionally, the vertical distribution of methane oxidation and nitrate consumption zones was inferred from high-resolution microsensor profiles in undisturbed sediment cores. M. oxyfera-like bacteria were virtually absent at shallow-water sites (littoral sediment) and were...

  13. Anaerobic expanded granular sludge bed (EGSB) reactor for the removal of sulphide by autotrophic denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Dinamarca, Carlos [Department of Process, Energy and Environment, Faculty of Technology, Telemark University College Kjolnes ring 56, 3918 Porsgrunn (Norway)

    2013-07-01

    The Removal efficiency, load and N/S molar ratio, of an EGSB reactor for autotrophic sulphide denitrification operated for 96 days, were studied. The reactor was operated at high inlet sulphide concentrations between 0.25 to 3.00 g HS--S/L equivalents to loads between 5 to 250 g HS--S/m3-h. Sulphide removals higher than 99 % were achieved. At a N/S molar ratio of 0.3 and 12 hours HRT the process was stable even during transition periods of influent sulphide concentration and pH (9.0-12.1). At N/S molar ratio of 1.3, granules lost some of their sedimentation properties and appeared to disintegrate. On average 94 ± 4 % of the equivalent inlet sulphur ended as elemental sulphur.

  14. Students' Ability to Solve Process-Diagram Problems in Secondary Biology Education

    Science.gov (United States)

    Kragten, Marco; Admiraal, Wilfried; Rijlaarsdam, Gert

    2015-01-01

    Process diagrams are important tools in biology for explaining processes such as protein synthesis, compound cycles and the like. The aim of the present study was to measure the ability to solve process-diagram problems in biology and its relationship with prior knowledge, spatial ability and working memory. For this purpose, we developed a test…

  15. Denitrifying capabilities of Tetrasphaera and their contribution towards nitrous oxide production in enhanced biological phosphorus removal processes.

    Science.gov (United States)

    Marques, Ricardo; Ribera-Guardia, Anna; Santos, Jorge; Carvalho, Gilda; Reis, Maria A M; Pijuan, Maite; Oehmen, Adrian

    2018-06-15

    Denitrifying enhanced biological phosphorus removal (EBPR) systems can be an efficient means of removing phosphate (P) and nitrate (NO 3 - ) with low carbon source and oxygen requirements. Tetrasphaera is one of the most abundant polyphosphate accumulating organisms present in EBPR systems, but their capacity to achieve denitrifying EBPR has not previously been determined. An enriched Tetrasphaera culture, comprising over 80% of the bacterial biovolume was obtained in this work. Despite the denitrification capacity of Tetrasphaera, this culture achieved only low levels of anoxic P-uptake. Batch tests with different combinations of NO 3 - , nitrite (NO 2 - ) and nitrous oxide (N 2 O) revealed lower N 2 O accumulation by Tetrasphaera as compared to Accumulibacter and Competibacter when multiple electron acceptors were added. Electron competition was observed during the addition of multiple nitrogen electron acceptors species, where P uptake appeared to be slightly favoured over glycogen production in these situations. This study increases our understanding of the role of Tetrasphaera-related organisms in denitrifying EBPR systems. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Boolean Models of Biological Processes Explain Cascade-Like Behavior.

    Science.gov (United States)

    Chen, Hao; Wang, Guanyu; Simha, Rahul; Du, Chenghang; Zeng, Chen

    2016-01-29

    Biological networks play a key role in determining biological function and therefore, an understanding of their structure and dynamics is of central interest in systems biology. In Boolean models of such networks, the status of each molecule is either "on" or "off" and along with the molecules interact with each other, their individual status changes from "on" to "off" or vice-versa and the system of molecules in the network collectively go through a sequence of changes in state. This sequence of changes is termed a biological process. In this paper, we examine the common perception that events in biomolecular networks occur sequentially, in a cascade-like manner, and ask whether this is likely to be an inherent property. In further investigations of the budding and fission yeast cell-cycle, we identify two generic dynamical rules. A Boolean system that complies with these rules will automatically have a certain robustness. By considering the biological requirements in robustness and designability, we show that those Boolean dynamical systems, compared to an arbitrary dynamical system, statistically present the characteristics of cascadeness and sequentiality, as observed in the budding and fission yeast cell- cycle. These results suggest that cascade-like behavior might be an intrinsic property of biological processes.

  17. Simultaneous desulfurization and denitrification of flue gas by ·OH radicals produced from O2+ and water vapor in a duct.

    Science.gov (United States)

    Bai, Mindi; Zhang, Zhitao; Bai, Mindong

    2012-09-18

    In the present study, simultaneous flue gas desulfurization and denitrification are achieved with ·OH radicals generated from O(2)(+) reacting with water vapor in a duct. The O(2)(+) ions are generated by a strong ionization dielectric barrier discharge and then injected into the duct. Compared with conventional gas discharge treatment, the present method does not need a plasma reaction reactor, additional catalysts, reductants, or oxidants. The main recovered products are the liquids H(2)SO(4) and HNO(3), which can be used in many processes. Removal rates of 97% for NO and 82% for SO(2) are obtained under the following optimal experimental conditions: molar ratio of reactive oxygen species (O(2)(+), O(3)) to SO(2) and NO, 5; inlet flue gas temperature, 65 °C; reaction time, 0.94 s; and H(2)O volume fraction, 8%. Production of O(2)(+) and the plasma reaction mechanisms are discussed, and the recovered acid is characterized. The experimental results show that the present method performs better for denitrification than for desulfurization. Compared with conventional air discharge flue gas treatments, the present method has lower initial investment and operating costs, and the equipment is more compact.

  18. Denitrification exceeds anammox as a nitrogen loss pathway in the Arabian Sea oxygen minimum zone

    Digital Repository Service at National Institute of Oceanography (India)

    Bulow, S.E.; Rich, J.J.; Naik, H.; Pratihary, A.K.; Ward, B.B.

    of anammox production (4.23 plus or minus 0.35 nmoll sup(-1) d sup(-1)) occurred near the upper boundary of the OMZ at one station. Overall, denitrification dominated N sub(2) production at this time in the Arabian Sea OMZ...

  19. Redox processes in radiation biology and cancer

    International Nuclear Information System (INIS)

    Greenstock, C.L.

    1981-01-01

    Free-radical intermediates, particularly the activated oxygen species OH, O - 2 , and 1 O 2 , are implicated in many types of radiation damage to biological systems. In addition, these same species may be formed, either directly or indirectly through biochemical redox reactions, in both essential and aberrant metabolic processes. Cell survival and adaptation to an environment containing ionizing radiation and other physical and chemical carcinogens ultimately depend upon the cell's ability to maintain optimal function in response to free-radical damage at the chemical level. Many of these feedback control mechanisms are redox controlled. Radiation chemical techniques using selective radical scavengers, such as product analysis and pulse radiolysis, enable us to generate, observe, and characterize individually the nature and reactivity of potentially damaging free radicals. From an analysis of the chemical kinetics of free-radical involvement in biological damage, redox mechanisms are proposed to describe the early processes of radiation damage, redox mechanisms are proposed to describe the early processes of radiation damage, its protection and sensitization, and the role of free radicals in radiation and chemical carcinogenesis

  20. Biologic phosphorus elimination - influencing parameters, boundary conditions, process optimation

    International Nuclear Information System (INIS)

    Dai Xiaohu.

    1992-01-01

    This paper first presents a systematic study of the basic process of biologic phosphorus elimination as employed by the original 'Phoredox (Main Stream) Process'. The conditions governing the process and the factors influencing its performance were determined by trial operation. A stationary model was developed for the purpose of modelling biologic phosphorus elimination in such a main stream process and optimising the dimensioning. The validity of the model was confirmed by operational data given in the literature and by operational data from the authors' own semitechnical-scale experimental plant. The model permits simulation of the values to be expected for effluent phosphorus and phosphate concentrations for given influent data and boundary conditions. It is thus possible to dimension a plant for accomodation of the original Phoredox (Main Stream) Process or any similar phosphorus eliminating plant that is to work according to the principle of the main stream process. (orig./EF) [de

  1. The denitrification paradox: The role of O2 in sediment N2O production

    Science.gov (United States)

    Barnes, Jonathan; Upstill-Goddard, Robert C.

    2018-01-01

    We designed a novel laboratory sediment flux chamber in which we maintained the headspace O2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (∼3 cm depth) and headspace O2 regulation (headspace: sediment/water ratio ∼9:1), net N2O production was highest at 1.2% O2 (sub-oxic; 32.3 nmol N2O m-2 d-1), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m-2 d-1) or 20.85% (ambient; 2.3 nmol N2O m-2 d-1) O2. In a longer-term sealed incubation (∼490 h) without O2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O2 or N2O up to ∼ 100 h; (ii) a quasi-linear, inverse correlation between O2 and N2O to ∼360 h, in which O2 declined to ∼2.1% and N2O rose to ∼7800 natm; (iii) over the following 50 h a slower O2 decline, to ∼1.1%, and a more rapid N2O increase, to ∼12000 natm; (iv) over the next 24 h a slowed O2 decline towards undetectable levels and a sharp fall in N2O to ∼4600 natm; (iv) a continued N2O decrease at zero O2, to ∼3000 natm by ∼ 490 h. These results show clearly that rapid N2O consumption (∼115 nmol m-2 d-1), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m-2 d-1 (NH4+ addition) and 0.4-2.2 nmol N2O m-2 d-1 (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O

  2. Contrasting nutrient mitigation and denitrification potential of agricultural drainage environments with different emergent aquatic macrophytes.

    Science.gov (United States)

    Remediation of excess nitrogen (N) in agricultural runoff can be enhanced by establishing wetland vegetation but the role of denitrification in N removal is not well understood in drainage ditches. We quantified differences in N retention during experimental runoff events followed by stagnant period...

  3. The significance of denitrification of applied nitrogen in fallow and cropped rice soils under different flooding regimes. Pt. 1

    International Nuclear Information System (INIS)

    Fillery, I.R.P.; Vlek, P.L.G.

    1982-01-01

    The role of nitrification-denitrification in the loss of nitrogen from urea applied to puddled soils planted to rice and subjected to continuous and intermittent flooding was evaluated in three greenhouse pot studies. The loss of N via denitrification was estimated indirectly using the 15 N balance, after either first accounting for NH 3 volatilization or by analyzing the 15 N balance immediately before and after the soil was dried and reflooded. When urea was broadcast and incorporated the loss of 15 N from the soil-plant systems depended on the soil, being about 20% - 25% for the silt loams and only 10% - 12% for the clay. Ammonia volatilization accounted for an average 20% of the N applied in the silt loam. Denitrification losses could not account for more than 10% of the applied N in any of the continuously flooded soil-plant systems under study and were most likely less than 5%. Intermittent flooding of soil planted to rice did not increase the loss of N. Denitrification appeared to be an important loss mechanism in continuously flooded fallow soils, accounting for the loss of approximately 40% of the applied 15 N. Loss of 15 N was not appreciably enhanced in fallow soils undergoing intermittent flooding. Apparently, nitrate formed in oxidized zones in the soil was readily denitrified in the absence of plant roots. Extensive loss (66%) of 15 N-labeled nitrate was obtained when 100 mg/pot of nitrate-N was applied to the surface of nonflooded soil prior to reflooding. This result suggests that rice plants may not compete effectively with denitrifiers if large quantities of nitrate were to accumulate during intermittent dry periods. (orig.)

  4. [Identification and Nitrogen Removal Characteristics of a Heterotrophic Nitrification-Aerobic Denitrification Strain Isolated from Marine Environment].

    Science.gov (United States)

    Sun, Qing-hua; Yu, De-shuang; Zhang, Pei-yu; Lin, Xue-zheng; Li, Jin

    2016-02-15

    A heterotrophic nitrification-aerobic denitrification strain named y5 was isolated from marine environment by traditional microbial isolation method using seawater as medium. It was identified as Klebsiella sp. based on the morphological, physiological and 16S rRNA sequence analysis. The experiment results showed that the optimal carbon resource was sodium citrate; the optimal pH was 7.0; and the optimal C/N was 17. The strain could use NH4Cl, NaNO2 and KNO3 as sole nitrogen source, and the removal efficiencies were77.07%, 64.14% and 100% after 36 hours, respectively. The removal efficiency reached 100% after 36 hours in the coexistence of NH4Cl, NaNO2 and KNO3. The results showed that the strain y5 had independent and efficient heterotrophic nitrification and aerobic denitrification activities in high salt wastewater.

  5. Application of multiple-isotope and groundwater-age data to identify factors affecting the extent of denitrification in a shallow aquifer near a river in South Korea

    Science.gov (United States)

    Kaown, Dugin; Koh, Eun-Hee; Mayer, Bernhard; Kim, Heejung; Park, Dong Kyu; Park, Byeong-Hak; Lee, Kang-Kun

    2018-01-01

    The extent of denitrification in a small agricultural area near a river in Yangpyeong, South Korea, was determined using multiple isotopes, groundwater age, and physicochemical data for groundwater. The shallow groundwater at one monitoring site had high concentrations of NO3-N (74-83 mg L-1). The δ15N-NO3 values for groundwater in the study area ranged between +9.1 and +24.6‰ in June 2014 and +12.2 to +21.6‰ in October 2014. High δ15N-NO3 values (+10.7 to +12.5‰) in both sampling periods indicated that the high concentrations of nitrate in the groundwater originated from application of organic fertilizers and manure. In the northern part of the study area, some groundwater samples showed elevated δ15N-NO3 and δ18O-NO3 values, which suggest that nitrate was removed from the groundwater via denitrification, with N isotope enrichment factors ranging between -4.8 and -7.9‰ and O isotope enrichment factors varying between -3.8 and -4.9‰. Similar δD and δ18O values of the surface water and groundwater in the south appear to indicate that groundwater in that area was affected by surface-water infiltration. The mean residence times (MRTs) of groundwater showed younger ages in the south (10-20 years) than in the north (20-30 years). Hence, it was concluded that denitrification processes under anaerobic conditions with longer groundwater MRT in the northern part of the study area removed considerable amounts of nitrate. This study demonstrates that multi-isotope data combined with physicochemical data and age-dating information can be effectively applied to characterize nitrate contaminant sources and attenuation processes.

  6. Process for sewage biological treatment from uranium

    International Nuclear Information System (INIS)

    Popa, K.; Cecal, A.; Craciun, I.

    2004-01-01

    The invention relates to the sewage treatment, in particular to the sewage biological treatmen from radioactive waste, namely from uranium. The process dor sewage biological treatment from uranium includes cultivation in the sewage of the aquatic plants Lemna minor and Spirulina platensis. The plants cultivation is carried out in two stages. In the first stage for cultivation is used Lemna minor in the second stage - Spirulina platensis . After finishing the plant cultivation it is carried out separation of their biomass. The result of the invention consists in increasing the uranyl ions by the biomass of plants cultivated in the sewage

  7. Process for sewage biological treatment from uranium

    International Nuclear Information System (INIS)

    Popa, Karin; Cecal, Alexandru; Craciun, Iftimie Ionel; Rudic, Valeriu; Gulea, Aurelian; Cepoi, Liliana

    2004-01-01

    The invention relates to the sewage treatment, in particular to the sewage biological treatment from radioactive waste, namely from uranium. The process for sewage biological treatment from uranium includes cultivation in the sewage of the aquatic plants Lemna minor and Spirulina platensis. The plant cultivation is carried out in two stages. In the first stage for cultivation is used Lemna minor and in the second stage - Spirulina platensis. After finishing the plant cultivation it is carried out separation of their biomass. The result of the invention consists in increasing the uranyl ions accumulation by the biomass of plants cultivated in the sewage.

  8. Denitrification performance of Pseudomonas denitrificans in a fluidized-bed biofilm reactor and in a stirred tank reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cattaneo, C.; Nicolella, C.; Rovatti, M. [Department of Chemical and Process Engineering, Faculty of Engineering, University of Genoa, Via Opera Pia 15, 16145 Genoa (Italy)

    2003-04-09

    Denitrification of a synthetic wastewater containing nitrates and methanol as carbon source was carried out in two systems - a fluidized-bed biofilm reactor (FBBR) and a stirred tank reactor (STR) - using Pseudomonas denitrificans over a period of five months. Nitrogen loading was varied during operation of both reactors to assess differences in the response to transient conditions. Experimental data were analyzed to obtain a comparison of denitrification kinetics in biofilm and suspended growth reactors. The comparison showed that the volumetric degradation capacity in the FBBR (5.36 kg {sub N} . m{sup -3} . d{sup -1}) was higher than in the STR, due to higher biomass concentration (10 kg {sub BM} . m{sup -3} vs 1.2 kg {sub BM} m{sup -3}). (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  9. Inhibition of denitrification and N2O emission by urine-derived benzoic and hippuric acid

    NARCIS (Netherlands)

    Groenigen, van J.W.; Palermo, V.; Kool, D.M.; Kuikman, P.J.

    2006-01-01

    Hippuric acid (HA) in cattle urine acts as a natural inhibitor of soil N2O emissions. As HA concentration varies with diet, we determined critical HA levels. We also tested the hypothesis that the inhibition occurs because the HA breakdown product benzoic acid (BA) inhibits denitrification rates.

  10. Stochastic processes, multiscale modeling, and numerical methods for computational cellular biology

    CERN Document Server

    2017-01-01

    This book focuses on the modeling and mathematical analysis of stochastic dynamical systems along with their simulations. The collected chapters will review fundamental and current topics and approaches to dynamical systems in cellular biology. This text aims to develop improved mathematical and computational methods with which to study biological processes. At the scale of a single cell, stochasticity becomes important due to low copy numbers of biological molecules, such as mRNA and proteins that take part in biochemical reactions driving cellular processes. When trying to describe such biological processes, the traditional deterministic models are often inadequate, precisely because of these low copy numbers. This book presents stochastic models, which are necessary to account for small particle numbers and extrinsic noise sources. The complexity of these models depend upon whether the biochemical reactions are diffusion-limited or reaction-limited. In the former case, one needs to adopt the framework of s...

  11. Nitrous oxide emission from denitrification in stream and river networks

    OpenAIRE

    Beaulieu, Jake J.; Tank, Jennifer L.; Hamilton, Stephen K.; Wollheim, Wilfred M.; Hall, Robert O.; Mulholland, Patrick J.; Peterson, Bruce J.; Ashkenas, Linda R.; Cooper, Lee W.; Dahm, Clifford N.; Dodds, Walter K.; Grimm, Nancy B.; Johnson, Sherri L.; McDowell, William H.; Poole, Geoffrey C.

    2010-01-01

    Nitrous oxide (N2O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N2O via microbial denitrification that converts N to N2O and dinitrogen (N2). The fraction of denitrified N that escapes as N2O rather than N2 (i.e., the N2O yield) is an important determinant of how much N2O is produced by river networks, but little is known about the N2O yield in flowi...

  12. Test of Science Process Skills of Biology Students towards Developing of Learning Exercises

    Directory of Open Access Journals (Sweden)

    Judith S. Rabacal

    2016-11-01

    Full Text Available This is a descriptive study aimed to determine the academic achievement on science process skills of the BS Biology Students of Northern Negros State College of Science and Technology, Philippines with the end view of developing learning exercises which will enhance their academic achievement on basic and integrated science process skills. The data in this study were obtained using a validated questionnaire. Mean was the statistical tool used to determine the academic achievement on the above mentioned science process skills; t-test for independent means was used to determine significant difference on the academic achievement of science process skills of BS Biology students while Pearson Product Moment of Correlation Coefficient was used to determine the significant relationship between basic and integrated science process skills of the BS Biology students. A 0.05 level of significance was used to determine whether the hypothesis set in the study will be rejected or accepted. Findings revealed that the academic achievement on basic and integrated science process skills of the BS Biology students was average. Findings revealed that there are no significant differences on the academic performance of the BS Biology students when grouped according to year level and gender. Findings also revealed that there is a significant difference on the academic achievement between basic and integrated science process skills of the BS Biology students. Findings revealed that there is a significant relationship between academic achievement on the basic and integrated science process skills of the BS Biology students.

  13. Operational and biological analyses of branched water-adjustment and combined treatment of wastewater from a chemical industrial park.

    Science.gov (United States)

    Xu, Ming; Cao, Jiashun; Li, Chao; Tu, Yong; Wu, Haisuo; Liu, Weijing

    2018-01-01

    The combined biological processes of branched water-adjustment, chemical precipitation, hydrolysis acidification, secondary sedimentation, Anoxic/Oxic and activated carbon treatment were used for chemical industrial wastewater treatment in the Taihu Lake Basin. Full-scale treatment resulted in effluent chemical oxygen demand, total nitrogen, NH 3 -N and total phosphorus of 35.1, 5.20, 3.10 and 0.15 mg/L, respectively, with a total removal efficiency of 91.1%, 67.1%, 70.5% and 89.3%, respectively. In this process, short-circuited organic carbon from brewery wastewater was beneficial for denitrification and second-sulfate reduction. The concentration of effluent fluoride was 6.22 mg/L, which also met the primary standard. Gas Chromatography-Mass Spectrometry analysis revealed that many types of refractory compounds were present in the inflow. Microbial community analysis performed in the summer by PCR-denaturing gradient gel electrophoresis and MiSeq demonstrated that certain special functional bacteria, such as denitrificans, phosphorus-accumulating bacteria, sulfate- and perhafnate-reducing bacteria, aromatic compound-degrading bacteria and organic fluoride-degrading bacteria, present in the bio-tanks were responsible for the acceptable specific biological pollutant reduction achieved.

  14. Active Interaction Mapping as a tool to elucidate hierarchical functions of biological processes.

    Science.gov (United States)

    Farré, Jean-Claude; Kramer, Michael; Ideker, Trey; Subramani, Suresh

    2017-07-03

    Increasingly, various 'omics data are contributing significantly to our understanding of novel biological processes, but it has not been possible to iteratively elucidate hierarchical functions in complex phenomena. We describe a general systems biology approach called Active Interaction Mapping (AI-MAP), which elucidates the hierarchy of functions for any biological process. Existing and new 'omics data sets can be iteratively added to create and improve hierarchical models which enhance our understanding of particular biological processes. The best datatypes to further improve an AI-MAP model are predicted computationally. We applied this approach to our understanding of general and selective autophagy, which are conserved in most eukaryotes, setting the stage for the broader application to other cellular processes of interest. In the particular application to autophagy-related processes, we uncovered and validated new autophagy and autophagy-related processes, expanded known autophagy processes with new components, integrated known non-autophagic processes with autophagy and predict other unexplored connections.

  15. Denitrification potential of riparian soils in relation to multiscale spatial environmental factors: a case study of a typical watershed, China.

    Science.gov (United States)

    Wei, Jianbing; Feng, Hao; Cheng, Quanguo; Gao, Shiqian; Liu, Haiyan

    2017-02-01

    The objective of this study was to test the hypothesis that environmental regulators of riparian zone soil denitrification potential differ according to spatial scale within a watershed; consequently, a second objective was to provide spatial strategies for conserving and restoring the purification function of runoff in riparian ecosystems. The results show that soil denitrification in riparian zones was more heterogeneous at the profile scale than at the cross-section and landscape scales. At the profile scale, biogeochemical factors (including soil total organic carbon, total nitrogen, and nitrate-nitrogen) were the major direct regulators of the spatial distribution of soil denitrification enzyme activity (DEA). At the cross-section scale, factors included distance from river bank and vegetation density, while landscape-scale factors, including topographic index, elevation, and land use types, indirectly regulated the spatial distribution of DEA. At the profile scale, soil DEA was greatest in the upper soil layers. At the cross-section scale, maximum soil DEA occurred in the mid-part of the riparian zone. At the landscape scale, soil DEA showed an increasing trend towards downstream sites, except for those in urbanized areas.

  16. Simultaneous nitrification-denitrification and phosphorus removal in a fixed bed sequencing batch reactor (FBSBR)

    International Nuclear Information System (INIS)

    Rahimi, Yousef; Torabian, Ali; Mehrdadi, Naser; Shahmoradi, Behzad

    2011-01-01

    Research highlights: → Sludge production in FSBR reactor is 20-30% less than SBR reactor. → FSBR reactor showed more nutrient removal rate than SBR reactor. → FSBR reactor showed less VSS/TSS ratio than SBR reactor. - Abstract: Biological nutrient removal (BNR) was investigated in a fixed bed sequencing batch reactor (FBSBR) in which instead of activated sludge polypropylene carriers were used. The FBSBR performance on carbon and nitrogen removal at different loading rates was significant. COD, TN, and phosphorus removal efficiencies were at range of 90-96%, 60-88%, and 76-90% respectively while these values at SBR reactor were 85-95%, 38-60%, and 20-79% respectively. These results show that the simultaneous nitrification-denitrification (SND) is significantly higher than conventional SBR reactor. The higher total phosphorus (TP) removal in FBSBR correlates with oxygen gradient in biofilm layer. The influence of fixed media on biomass production yield was assessed by monitoring the MLSS concentrations versus COD removal for both reactors and results revealed that the sludge production yield (Y obs ) is significantly less in FBSBR reactors compared with SBR reactor. The FBSBR was more efficient in SND and phosphorus removal. Moreover, it produced less excess sludge but higher in nutrient content and stabilization ratio (less VSS/TSS ratio).

  17. Simultaneous nitrification-denitrification and phosphorus removal in a fixed bed sequencing batch reactor (FBSBR)

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Yousef, E-mail: you.rahimi@gmail.com [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave, Tehran (Iran, Islamic Republic of); Torabian, Ali, E-mail: atorabi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave, Tehran (Iran, Islamic Republic of); Mehrdadi, Naser, E-mail: mehrdadi@ut.ac.ir [Department of Civil and Environmental Engineering, Graduate Faculty of Environment, University of Tehran, No. 25 Qods St., Enghelab Ave, Tehran (Iran, Islamic Republic of); Shahmoradi, Behzad, E-mail: bshahmorady@gmail.com [Department of Environmental Science, University of Mysore, MGM-06 Mysore (India)

    2011-01-30

    Research highlights: {yields} Sludge production in FSBR reactor is 20-30% less than SBR reactor. {yields} FSBR reactor showed more nutrient removal rate than SBR reactor. {yields} FSBR reactor showed less VSS/TSS ratio than SBR reactor. - Abstract: Biological nutrient removal (BNR) was investigated in a fixed bed sequencing batch reactor (FBSBR) in which instead of activated sludge polypropylene carriers were used. The FBSBR performance on carbon and nitrogen removal at different loading rates was significant. COD, TN, and phosphorus removal efficiencies were at range of 90-96%, 60-88%, and 76-90% respectively while these values at SBR reactor were 85-95%, 38-60%, and 20-79% respectively. These results show that the simultaneous nitrification-denitrification (SND) is significantly higher than conventional SBR reactor. The higher total phosphorus (TP) removal in FBSBR correlates with oxygen gradient in biofilm layer. The influence of fixed media on biomass production yield was assessed by monitoring the MLSS concentrations versus COD removal for both reactors and results revealed that the sludge production yield (Y{sub obs}) is significantly less in FBSBR reactors compared with SBR reactor. The FBSBR was more efficient in SND and phosphorus removal. Moreover, it produced less excess sludge but higher in nutrient content and stabilization ratio (less VSS/TSS ratio).

  18. The importance of dissimilatory nitrate reduction to ammonium (DNRA) in the nitrogen cycle of coastal ecosystems

    DEFF Research Database (Denmark)

    Giblin, Anne E.; Tobias, Craig R.; Song, Bongkeun

    2013-01-01

    Until recently, it was believed that biological assimilation and gaseous nitrogen (N) loss through denitrification were the two major fates of nitrate entering or produced within most coastal ecosystems. Denitrification is often viewed as an important ecosystem service that removes reactive N from...... the ecosystem. However, there is a competing nitrate reduction process, dissimilatory nitrate reduction to ammonium (DNRA), that conserves N within the ecosystem. The recent application of nitrogen stable isotopes as tracers has generated growing evidence that DNRA is a major nitrogen pathway that cannot...... of denitrification and DNRA, and how the balance changes with increased nitrogen loading, is of critical importance for predicting eutrophication trajectories. Recent improvements in methods for assessing rates of DNRA have helped refine our understanding of the rates and controls of this process, but accurate...

  19. Denitrification activity is closely linked to the total ambient Fe concentration in mangrove sediments of Goa, India

    Science.gov (United States)

    Fernandes, Sheryl Oliveira; Gonsalves, Maria-Judith; Michotey, Valérie D.; Bonin, Patricia C.; Loka, A.; Bharathi, P.

    2013-10-01

    Denitrification activity (DNT) and associated environmental parameters were examined in two mangrove ecosystems of Goa, India - the relatively unimpacted Tuvem and the anthropogenically-influenced Divar. Sampling was carried out at every 2 cm interval within the 0-10 cm depth range to determine (1) seasonal (pre-monsoon, monsoon and post-monsoon) down-core variation in DNT (2) assess the environmental factors influencing the DNT and (3) to build predictive models for benthic DNT. Denitrification generally decreased with depth and showed marked seasonal variation at both the locations. Denitrification peaked during the pre-monsoon occurring at a rate of up to 21.00 ± 12.84 nmol N2O g-1 h-1 within 0-4 cm at both the locations. Further, DNT at pre-monsoon was significantly influenced by Fe content at Tuvem and Divar suggesting Fe-mediated nitrate respiration. The influence of other limiting substrates such as NO3- and NO2- was most important during the monsoon and post-monsoon especially at Divar. The multiple regression models developed could predict 67-98% of the observed variability in DNT through the seasons. About 6-9 environmental variables were required to relatively well-predict DNT in these sediments with the complexity governing DNT decreasing from pre-monsoon to post-monsoon. Our results reveal that seasonal dynamics of DNT in tropical mangrove sediments are closely linked to the total Fe at the prevailing ambient concentration in both the systems.

  20. Chironomus plumosus larvae increase fluxes of denitrification products and diversity of nitrate-reducing bacteria in freshwater sediment

    DEFF Research Database (Denmark)

    Poulsen, Morten; W. V. Kofoed, Michael; H. Larsen, Lone

    2014-01-01

    , respectively, which was mostly due to stimulation of sedimentary denitrification; incomplete denitrification in the guts accounted for up to 20% of the N2O efflux. Phylotype richness of the nitrate reductase gene narG was significantly higher in sediment with than without larvae. In the gut, 47 narG phylotypes...... were found expressed, which may contribute to higher phylotype richness in colonized sediment. In contrast, phylotype richness of the nitrous oxide reductase gene nosZ was unaffected by the presence of larvae and very few nosZ phylotypes were expressed in the gut. Gene abundance of neither narG, nor...... nosZ wasdifferent in sediments with and without larvae. Hence, C. plumosus increases activity and diversity, but not overall abundance of nitrate-reducing bacteria, probably by providing additional ecological niches in its burrow and gut....

  1. iBiology: communicating the process of science.

    Science.gov (United States)

    Goodwin, Sarah S

    2014-08-01

    The Internet hosts an abundance of science video resources aimed at communicating scientific knowledge, including webinars, massive open online courses, and TED talks. Although these videos are efficient at disseminating information for diverse types of users, they often do not demonstrate the process of doing science, the excitement of scientific discovery, or how new scientific knowledge is developed. iBiology (www.ibiology.org), a project that creates open-access science videos about biology research and science-related topics, seeks to fill this need by producing videos by science leaders that make their ideas, stories, and experiences available to anyone with an Internet connection. © 2014 Goodwin. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  2. Biological reduction of nitrate wastewater using fluidized-bed bioreactors

    International Nuclear Information System (INIS)

    Walker, J.F. Jr.; Hancher, C.W.; Patton, B.D.; Kowalchuk, M.

    1981-01-01

    There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt % NO 3 - and as large as 2000 m 3 /d, in the nuclear fuel cycle as well as in many commercial processes such as fertilizer production, paper manufacturing, and metal finishing. These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 gN(NO 3 - )/m 3 by the use of a fluidized-bed bioreactor. The major strain of denitrification bacteria is Pseudomonas which was derived from garden soil. In the fluidized-bed bioreactor the bacteria are allowed to attach to 0.25 to 0.50-mm-diam coal particles, which are fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m 3 . A description is given of the results of two biodenitrification R and D pilot plant programs based on the use of fluidized bioreactors capable of operating at nitrate levels up to 7000 g/m 3 and achieving denitrification rates as high as 80 gN(NO 3 - )/d per liter of empty bioreactor volume. The first of these pilot plant programs consisted of two 0.2-m-diam bioreactors, each with a height of 6.3 m and a volume of 208 liters, operating in series. The second pilot plant was used to determine the diameter dependence of the reactors by using a 0.5-m-diam reactor with a height of 6.3 m and a volume of 1200 liters. These pilot plants operated for a period of six months and two months respectively, while using both a synthetic waste and the actual waste from a gaseous diffusion plant operated by Goodyear Atomic Corporation

  3. Heat transfer and fluid flow in biological processes advances and applications

    CERN Document Server

    Becker, Sid

    2015-01-01

    Heat Transfer and Fluid Flow in Biological Processes covers emerging areas in fluid flow and heat transfer relevant to biosystems and medical technology. This book uses an interdisciplinary approach to provide a comprehensive prospective on biofluid mechanics and heat transfer advances and includes reviews of the most recent methods in modeling of flows in biological media, such as CFD. Written by internationally recognized researchers in the field, each chapter provides a strong introductory section that is useful to both readers currently in the field and readers interested in learning more about these areas. Heat Transfer and Fluid Flow in Biological Processes is an indispensable reference for professors, graduate students, professionals, and clinical researchers in the fields of biology, biomedical engineering, chemistry and medicine working on applications of fluid flow, heat transfer, and transport phenomena in biomedical technology. Provides a wide range of biological and clinical applications of fluid...

  4. Influence of natural and novel organic carbon sources on denitrification in forest, degraded urban, and restored streams

    Science.gov (United States)

    Organic carbon is important in regulating ecosystem function, and its source and abundance may be altered by urbanization. We investigated shifts in organic carbon quantity and quality associated with urbanization and ecosystem restoration, and its potential effects on denitrific...

  5. Phenol wastewater remediation: advanced oxidation processes coupled to a biological treatment.

    Science.gov (United States)

    Rubalcaba, A; Suárez-Ojeda, M E; Stüber, F; Fortuny, A; Bengoa, C; Metcalfe, I; Font, J; Carrera, J; Fabregat, A

    2007-01-01

    Nowadays, there are increasingly stringent regulations requiring more and more treatment of industrial effluents to generate product waters which could be easily reused or disposed of to the environment without any harmful effects. Therefore, different advanced oxidation processes were investigated as suitable precursors for the biological treatment of industrial effluents containing phenol. Wet air oxidation and Fenton process were tested batch wise, while catalytic wet air oxidation and H2O2-promoted catalytic wet air oxidation processes were studied in a trickle bed reactor, the last two using over activated carbon as catalyst. Effluent characterisation was made by means of substrate conversion (using high liquid performance chromatography), chemical oxygen demand and total organic carbon. Biodegradation parameters (i.e. maximum oxygen uptake rate and oxygen consumption) were obtained from respirometric tests using activated sludge from an urban biological wastewater treatment plant (WWTP). The main goal was to find the proper conditions in terms of biodegradability enhancement, so that these phenolic effluents could be successfully treated in an urban biological WWTP. Results show promising research ways for the development of efficient coupled processes for the treatment of wastewater containing toxic or biologically non-degradable compounds.

  6. Denitrification in a hypersaline lake–aquifer system (Pétrola Basin, Central Spain): The role of recent organic matter and Cretaceous organic rich sediments

    International Nuclear Information System (INIS)

    Gómez-Alday, J.J.; Carrey, R.; Valiente, N.; Otero, N.; Soler, A.; Ayora, C.; Sanz, D.

    2014-01-01

    Agricultural regions in semi-arid to arid climates with associated saline wetlands are one of the most vulnerable environments to nitrate pollution. The Pétrola Basin was declared vulnerable to NO 3 − pollution by the Regional Government in 1998, and the hypersaline lake was classified as a heavily modified body of water. The study assessed groundwater NO 3 − through the use of multi-isotopic tracers (δ 15 N, δ 34 S, δ 13 C, δ 18 O) coupled to hydrochemistry in the aquifer connected to the eutrophic lake. Hydrogeologically, the basin shows two main flow components: regional groundwater flow from recharge areas (Zone 1) to the lake (Zone 2), and a density-driven flow from surface water to the underlying aquifer (Zone 3). In Zones 1 and 2, δ 15 N NO 3 and δ 18 O NO 3 suggest that NO 3 − from slightly volatilized ammonium synthetic fertilizers is only partially denitrified. The natural attenuation of NO 3 − can occur by heterotrophic reactions. However, autotrophic reactions cannot be ruled out. In Zone 3, the freshwater–saltwater interface (down to 12–16 m below the ground surface) is a reactive zone for NO 3 − attenuation. Tritium data suggest that the absence of NO 3 − in the deepest zones of the aquifer under the lake can be attributed to a regional groundwater flow with long residence time. In hypersaline lakes the geometry of the density-driven flow can play an important role in the transport of chemical species that can be related to denitrification processes. - Highlights: • Denitrification comes about in a hypersaline lake–aquifer system. • Nitrate in the basin is derived from synthetic fertilizers slightly volatilized. • Organic carbon oxidation is likely to be the main electron donor in denitrification. • Density driven flow transports organic carbon to deeper zones of the aquifer

  7. Identifying functional zones of denitrification in heterogeneous aquifer systems by numerical simulations - a case study

    Science.gov (United States)

    Jang, E.; Kalbacher, T.; He, W.; Shao, H.; Schueth, C.; Kolditz, O.

    2014-12-01

    Nitrate contamination in shallow groundwater is still one of the common problems in many countries. Because of its high solubility and anionic nature, nitrate can easily leach through soil and persist in groundwater for decades. High nitrate concentration has been suggested as a major cause of accelerated eutrophication, methemoglobinemia and gastric cancer. There are several factors influencing the fate of nitrate in groundwater system, which is e.g. distribution of N- sources to soil and groundwater, distribution and amount of reactive substances maintaining denitrification, rate of nitrate degradation and its kinetics, and geological characteristics of the aquifer. Nitrate transport and redox transformation processes are closely linked to complex and spatially distributed physical and chemical interaction, therefore it is difficult to predict and quantify in the field and laboratory experiment. Models can play a key role in elucidation of nitrate reduction pathway in groundwater system and in the design and evaluation of field tests to investigate in situ remediation technologies as well. The goal of the current study is to predict groundwater vulnerability to nitrate, to identify functional zones of denitrification in heterogeneous aquifer systems and to describe the uncertainty of the predictions due to scale effects. For this aim, we developed a kinetic model using multi-component mass transport code OpenGeoSys coupling with IPhreeqc module of the geochemical solver PHREEQC. The developed model included sequential aerobic and nitrate-based respiration, multi-Monod kinetics, multi-species biogeochemical reactions, and geological characteristics of the groundwater aquifer. Moreover water-rock interaction such as secondary mineral precipitation was also included in this model. In this presentation, we focused on the general modelling approach and present the simulation results of nitrate transport simulation in a hypothetical aquifer systems based on data from

  8. Degradation alternatives for a commercial fungicide in water: biological, photo-Fenton, and coupled biological photo-Fenton processes.

    Science.gov (United States)

    López-Loveira, Elsa; Ariganello, Federico; Medina, María Sara; Centrón, Daniela; Candal, Roberto; Curutchet, Gustavo

    2017-11-01

    Imazalil (IMZ) is a widely used fungicide for the post-harvest treatment of citrus, classified as "likely to be carcinogenic in humans" for EPA, that can be only partially removed by conventional biological treatment. Consequently, specific or combined processes should be applied to prevent its release to the environment. Biological treatment with adapted microorganism consortium, photo-Fenton, and coupled biological photo-Fenton processes were tested as alternatives for the purification of water containing high concentration of the fungicide and the coadjutants present in the commercial formulation. IMZ-resistant consortium with the capacity to degrade IMZ in the presence of a C-rich co-substrate was isolated from sludge coming from a fruit packaging company wastewater treatment plant. This consortium was adapted to resist and degrade the organics present in photo-Fenton-oxidized IMZ water solution. Bacteria colonies from the consortia were isolated and identified. The effect of H 2 O 2 initial concentration and dosage on IMZ degradation rate, average oxidation state (AOS), organic acid concentration, oxidation, and mineralization percentage after photo-Fenton process was determined. The application of biological treatment to the oxidized solutions notably decreased the total organic carbon (TOC) in solution. The effect of the oxidation degree, limited by H 2 O 2 concentration and dosage, on the percentage of mineralization obtained after the biological treatment was determined and explained in terms of changes in AOS. The concentration of H 2 O 2 necessary to eliminate IMZ by photo-Fenton and to reduce TOC and chemical oxygen demand (COD) by biological treatment, in order to allow the release of the effluents to rivers with different flows, was estimated.

  9. Advances on simultaneous desulfurization and denitrification using activated carbon irradiated by microwaves.

    Science.gov (United States)

    Ma, Shuang-Chen; Gao, Li; Ma, Jing-Xiang; Jin, Xin; Yao, Juan-Juan; Zhao, Yi

    2012-06-01

    This paper describes the research background and chemistry of desulfurization and denitrification technology using microwave irradiation. Microwave-induced catalysis combined with activated carbon adsorption and reduction can reduce nitric oxide to nitrogen and sulfur dioxide to sulfur from flue gas effectively. This paper also highlights the main drawbacks of this technology and discusses future development trends. It is reported that the removal of sulfur dioxide and nitric oxide using microwave irradiation has broad prospects for development in the field of air pollution control.

  10. Variability of subsurface denitrification and surface productivity in the coastal eastern Arabian Sea over the past seven centuries

    Digital Repository Service at National Institute of Oceanography (India)

    Agnihotri, R.; Kurian, S.; Fernandes, M.; Reshma, K.; DeSouza, W.; Naqvi, S.W.A.

    isotopic ratio in sedimentary organic matter (delta sup (15) N) exhibits a moderately declining trend during this period. This is ascribed to dilution by terrestrial sources and/or to small isotopic effect associated with vigorous denitrification...

  11. Estimating N2O processes during grassland renewal and grassland conversion to maize cropping using N2O isotopocules

    Science.gov (United States)

    Buchen, Caroline; Well, Reinhard; Flessa, Heinz; Fuß, Roland; Helfrich, Mirjam; Lewicka-Szczebak, Dominika

    2017-04-01

    . Investigations were carried out over a study period of one year following grassland renewal and grassland conversion to maize cropping on two different soil sites (Plaggic Anthrosol and Histic Gleysol) near Oldenburg, Lower Saxony Germany. Our observations indicate heterotrophic bacterial denitrification and/or nitrifier denitrification as the main source of N2O production, with a significant contribution of N2O reduction to N2 rather than nitrification (i.e. hydroxylamine oxidation) and fungal denitrification throughout the entire study period. A tendency to a higher contribution of N2O reduction to N2 was observed for the often water-saturated Histic Gleysol, while lower N2O reduction was found for the Plaggic Anthrosol. For two samples, we attempt to validate our results from the isotopocule mapping approach with a parallel 15N labelling study at the field scale (Buchen et al., 2016), as conditions of soil moisture, nitrate availability and N2O flux were similar. References: Buchen, C., Lewicka-Szczebak, D., Fuß, R., Helfrich, M., Flessa, H., Well, R., 2016. Fluxes of N2 and N2O and contributing processes in summer after grassland renewal and grassland conversion to maize cropping on a Plaggic Anthrosol and a Histic Gleysol. Soil Biology and Biochemistry 101, 6-19.

  12. Influence of different natural physical fields on biological processes

    Science.gov (United States)

    Mashinsky, A. L.

    2001-01-01

    In space flight conditions gravity, magnetic, and electrical fields as well as ionizing radiation change both in size, and in direction. This causes disruptions in the conduct of some physical processes, chemical reactions, and metabolism in living organisms. In these conditions organisms of different phylogenetic level change their metabolic reactions undergo changes such as disturbances in ionic exchange both in lower and in higher plants, changes in cell morphology for example, gyrosity in Proteus ( Proteus vulgaris), spatial disorientation in coleoptiles of Wheat ( Triticum aestivum) and Pea ( Pisum sativum) seedlings, mutational changes in Crepis ( Crepis capillaris) and Arabidopsis ( Arabidopsis thaliana) seedling. It has been found that even in the absence of gravity, gravireceptors determining spatial orientation in higher plants under terrestrial conditions are formed in the course of ontogenesis. Under weightlessness this system does not function and spatial orientation is determined by the light flux gradient or by the action of some other factors. Peculiarities of the formation of the gravireceptor apparatus in higher plants, amphibians, fish, and birds under space flight conditions have been observed. It has been found that the system in which responses were accompanied by phase transition have proven to be gravity-sensitive under microgravity conditions. Such reactions include also the process of photosynthesis which is the main energy production process in plants. In view of the established effects of microgravity and different natural physical fields on biological processes, it has been shown that these processes change due to the absence of initially rigid determination. The established biological effect of physical fields influence on biological processes in organisms is the starting point for elucidating the role of gravity and evolutionary development of various organisms on Earth.

  13. 100 years after Smoluchowski: stochastic processes in cell biology

    International Nuclear Information System (INIS)

    Holcman, D; Schuss, Z

    2017-01-01

    100 years after Smoluchowski introduced his approach to stochastic processes, they are now at the basis of mathematical and physical modeling in cellular biology: they are used for example to analyse and to extract features from a large number (tens of thousands) of single molecular trajectories or to study the diffusive motion of molecules, proteins or receptors. Stochastic modeling is a new step in large data analysis that serves extracting cell biology concepts. We review here Smoluchowski’s approach to stochastic processes and provide several applications for coarse-graining diffusion, studying polymer models for understanding nuclear organization and finally, we discuss the stochastic jump dynamics of telomeres across cell division and stochastic gene regulation. (topical review)

  14. Proximal and distal control by pH of denitrification rate in a pasture soil

    Czech Academy of Sciences Publication Activity Database

    Čuhel, Jiří; Šimek, Miloslav

    2011-01-01

    Roč. 141, 1-2 (2011), s. 230-233 ISSN 0167-8809 R&D Projects: GA AV ČR IAA600660605; GA MŠk LC06066 Grant - others:Grantová agentura Jihočeské univerzity(CZ) GAJU 142/2010/P Institutional research plan: CEZ:AV0Z60660521 Keywords : denitrification * pH * nitrous oxide Subject RIV: EH - Ecology, Behaviour Impact factor: 3.004, year: 2011

  15. Ammonia oxidation, denitrification and dissimilatory nitrate reduction to ammonium in two US Great Basin hot springs with abundant ammonia-oxidizing archaea.

    Science.gov (United States)

    Dodsworth, Jeremy A; Hungate, Bruce A; Hedlund, Brian P

    2011-08-01

    Many thermophiles catalyse free energy-yielding redox reactions involving nitrogenous compounds; however, little is known about these processes in natural thermal environments. Rates of ammonia oxidation, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in source water and sediments of two ≈ 80°C springs in the US Great Basin. Ammonia oxidation and denitrification occurred mainly in sediments. Ammonia oxidation rates measured using (15)N-NO(3)(-) pool dilution ranged from 5.5 ± 0.8 to 8.6 ± 0.9 nmol N g(-1) h(-1) and were unaffected or only mildly stimulated by amendment with NH(4) Cl. Denitrification rates measured using acetylene block ranged from 15.8 ± 0.7 to 51 ± 12 nmol N g(-1) h(-1) and were stimulated by amendment with NO(3)(-) and complex organic compounds. The DNRA rate in one spring sediment measured using an (15)N-NO(3)(-) tracer was 315 ± 48 nmol N g(-1) h(-1). Both springs harboured distinct planktonic and sediment microbial communities. Close relatives of the autotrophic, ammonia-oxidizing archaeon 'Candidatus Nitrosocaldus yellowstonii' represented the most abundant OTU in both spring sediments by 16S rRNA gene pyrotag analysis. Quantitative PCR (qPCR) indicated that 'Ca. N. yellowstonii'amoA and 16S rRNA genes were present at 3.5-3.9 × 10(8) and 6.4-9.0 × 10(8) copies g(-1) sediment. Potential denitrifiers included members of the Aquificales and Thermales. Thermus spp. comprised <1% of 16S rRNA gene pyrotags in both sediments and qPCR for T. thermophilus narG revealed sediment populations of 1.3-1.7 × 10(6) copies g(-1) sediment. These data indicate a highly active nitrogen cycle (N-cycle) in these springs and suggest that ammonia oxidation may be a major source of energy fuelling primary production. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  16. Denitrification and dilution along fracture flowpaths influence the recovery of a bedrock aquifer from nitrate contamination

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jonathan J., E-mail: jon.kim@vermont.gov [Vermont Geological Survey, 1 National Life Drive, Main 2, Montpelier, VT 05620 (United States); Comstock, Jeff [Vermont Agency of Agriculture, 116 State Street, Montpelier, VT 05620 (United States); Ryan, Peter [Dept. of Geology, Middlebury College, Middlebury, VT 05753 (United States); Heindel, Craig [Waite-Heindel Environmental Management, 7 Kilburn Street, Suite 301, Burlington, VT 05401 (United States); Koenigsberger, Stephan [Dept. of Geology, Middlebury College, Middlebury, VT 05753 (United States)

    2016-11-01

    In 2000, elevated nitrate concentrations ranging from 12 to 34 mg/L NO{sub 3}−N were discovered in groundwater from numerous domestic bedrock wells adjacent to a large dairy farm in central Vermont. Long-term plots and contours of nitrate vs. time for bedrock wells showed “little/no”, “moderate”, and “large” change patterns that were spatially separable. The metasedimentary bedrock aquifer is strongly anisotropic and groundwater flow is controlled by fractures, bedding/foliation, and basins and ridges in the bedrock surface. Integration of the nitrate concentration vs. time data and the physical and chemical aquifer characterization suggest two nitrate sources: a point source emanating from a waste ravine and a non-point source that encompasses the surrounding fields. Once removed, the point source of NO{sub 3} (manure deposited in a ravine) was exhausted and NO{sub 3} dropped from 34 mg/L to < 10 mg/L after ~ 10 years; however, persistence of NO{sub 3} in the 3 to 8 mg/L range (background) reflects the long term flux of nitrates from nutrients applied to the farm fields surrounding the ravine over the years predating and including this study. Inferred groundwater flow rates from the waste ravine to either moderate change wells in basin 2 or to the shallow bedrock zone beneath the large change wells are 0.05 m/day, well within published bedrock aquifer flow rates. Enrichment of {sup 15}N and {sup 18}O in nitrate is consistent with lithotrophic denitrification of NO{sub 3} in the presence of dissolved Mn and Fe. Once the ravine point-source was removed, denitrification and dilution collectively were responsible for the down-gradient decrease of nitrate in this bedrock aquifer. Denitrification was most influential when NO{sub 3}−N was > 10 mg/L. Our multidisciplinary methods of aquifer characterization are applicable to groundwater contamination in any complexly-deformed and metamorphosed bedrock aquifer. - Highlights: • Bedrock wells contaminated

  17. Diffusion processes and related topics in biology

    CERN Document Server

    Ricciardi, Luigi M

    1977-01-01

    These notes are based on a one-quarter course given at the Department of Biophysics and Theoretical Biology of the University of Chicago in 1916. The course was directed to graduate students in the Division of Biological Sciences with interests in population biology and neurobiology. Only a slight acquaintance with probability and differential equations is required of the reader. Exercises are interwoven with the text to encourage the reader to play a more active role and thus facilitate his digestion of the material. One aim of these notes is to provide a heuristic approach, using as little mathematics as possible, to certain aspects of the theory of stochastic processes that are being increasingly employed in some of the population biol­ ogy and neurobiology literature. While the subject may be classical, the nov­ elty here lies in the approach and point of view, particularly in the applica­ tions such as the approach to the neuronal firing problem and its related dif­ fusion approximations. It is a ple...

  18. Landscape-scale estimation of denitrification rates and nitrous oxide to dinitrogen ratio at Georgia and Pennsylvania LTAR sites

    Science.gov (United States)

    Dell, C. J.; Groffman, P. M.; Strickland, T.; Kleinman, P. J. A.; Bosch, D. D.; Bryant, R.

    2015-12-01

    Denitrification results in a significant loss of plant-available nitrogen from agricultural systems and contributes to climate change, due to the emissions of both the potent greenhouse gas nitrous oxide (N2O) and environmentally benign dinitrogen (N2). However total quantities of the gases emitted and the ratio of N2:N2O are often not clearly understood, because N2 emissions cannot be directly measured in the field because of the high background level of N2 in the atmosphere. While variability in soil conditions across landscapes, especially water content and aeration, is believed to greatly impact both total denitrification rates and N2:N2O, the measurement limitations have prevented a clear understanding of landscape-scale emissions of denitrification products. The Cary Institute has developed an approach where soil core are maintained in a sealed system with an N2-free airstream, allowing emitted N2 and N2O emissions to be measured without interference from atmospheric N2. Emissions of the gases are measured under a range of oxygen concentrations and soil water contents. Laboratory responses can then be correlated with measured field conditions at the sampling points and resulting emission estimates extrapolated to the field-scale. Measurements are currently being conducted on peanut/cotton rotations, dairy forage rotations (silage corn/alfalfa), and bioenergy crops (switchgrass and miscanthus) at Long Term Agricultural Research (LTAR) sites at Tifton, GA and University Park, PA.

  19. Configuration of biological wastewater treatment line and influent composition as the main factors driving bacterial community structure of activated sludge.

    Science.gov (United States)

    Jaranowska, Paulina; Cydzik-Kwiatkowska, Agnieszka; Zielińska, Magdalena

    2013-07-01

    The structure of microbial consortia in wastewater treatment facilities is a resultant of environmental conditions created by the operational parameters of the purification process. In the research, activated sludge from nine Polish wastewater treatment plants (WWTPs) was investigated at a molecular level to determine the impact of the complexity of biological treatment line and the influent composition on the species structure and the diversity of bacterial consortia. The community fingerprints and technological data were subjected to the canonical correspondence and correlation analyses. The number of separated biological processes realized in the treatment line and the presence of industrial wastewater in the influent were the key factors determining the species structure of total and ammonia-oxidizing bacteria in biomass. The N2O-reducers community composition depended significantly on the design of the facility; the highest species richness of denitrifiers was noted in the WWTPs with separated denitrification tanks. The contribution of industrial streams to the inflow affected the diversity of total and denitrifying bacterial consortia and diminished the diversity of ammonia oxidizers. The obtained data are valuable for engineers since they revealed the main factors, including the design of wastewater treatment plant, influencing the microbial groups critical for the stability of purification processes.

  20. In situ batch denitrification of nitrate rich groundwater using sawdust as a carbon source - Marydale, South Africa

    CSIR Research Space (South Africa)

    Israel, S

    2009-01-01

    Full Text Available carbon (DOC), potassium and chloride was monitored. Two soil depths, 75 to 100cm and 165 to 200cm respectively, from the Marydale area were used as matrix material during denitrification based on contrasting chemical composition with respect to major ion...

  1. Denitrification on internal carbon sources in RAS is limited by fibers in fecal waste of rainbow trout

    NARCIS (Netherlands)

    Meriac, A.; Eding, E.H.; Kamstra, A.; Busscher, J.P.; Schrama, J.W.; Verreth, J.A.J.

    2014-01-01

    Denitrification on internal carbon sources offers the advantage to control nitrate levels in recirculating aquaculture systems (RAS) by using the fecal carbon produced within the husbandry system. However, it is not clear to which extent fecal carbon can be utilized by the microbial community within

  2. Classical and spatial stochastic processes with applications to biology

    CERN Document Server

    Schinazi, Rinaldo B

    2014-01-01

    The revised and expanded edition of this textbook presents the concepts and applications of random processes with the same illuminating simplicity as its first edition, but with the notable addition of substantial modern material on biological modeling. While still treating many important problems in fields such as engineering and mathematical physics, the book also focuses on the highly relevant topics of cancerous mutations, influenza evolution, drug resistance, and immune response. The models used elegantly apply various classical stochastic models presented earlier in the text, and exercises are included throughout to reinforce essential concepts. The second edition of Classical and Spatial Stochastic Processes is suitable as a textbook for courses in stochastic processes at the advanced-undergraduate and graduate levels, or as a self-study resource for researchers and practitioners in mathematics, engineering, physics, and mathematical biology. Reviews of the first edition: An appetizing textbook for a f...

  3. A network model shows the importance of coupled processes in the microbial N cycle in the Cape Fear River Estuary

    Science.gov (United States)

    Hines, David E.; Lisa, Jessica A.; Song, Bongkeun; Tobias, Craig R.; Borrett, Stuart R.

    2012-06-01

    Estuaries serve important ecological and economic functions including habitat provision and the removal of nutrients. Eutrophication can overwhelm the nutrient removal capacity of estuaries and poses a widely recognized threat to the health and function of these ecosystems. Denitrification and anaerobic ammonium oxidation (anammox) are microbial processes responsible for the removal of fixed nitrogen and diminish the effects of eutrophication. Both of these microbial removal processes can be influenced by direct inputs of dissolved inorganic nitrogen substrates or supported by microbial interactions with other nitrogen transforming pathways such as nitrification and dissimilatory nitrate reduction to ammonium (DNRA). The coupling of nitrogen removal pathways to other transformation pathways facilitates the removal of some forms of inorganic nitrogen; however, differentiating between direct and coupled nitrogen removal is difficult. Network modeling provides a tool to examine interactions among microbial nitrogen cycling processes and to determine the within-system history of nitrogen involved in denitrification and anammox. To examine the coupling of nitrogen cycling processes, we built a nitrogen budget mass balance network model in two adjacent 1 cm3 sections of bottom water and sediment in the oligohaline portion of the Cape Fear River Estuary, NC, USA. Pathway, flow, and environ ecological network analyses were conducted to characterize the organization of nitrogen flow in the estuary and to estimate the coupling of nitrification to denitrification and of nitrification and DNRA to anammox. Centrality analysis indicated NH4+ is the most important form of nitrogen involved in removal processes. The model analysis further suggested that direct denitrification and coupled nitrification-denitrification had similar contributions to nitrogen removal while direct anammox was dominant to coupled forms of anammox. Finally, results also indicated that partial

  4. State of the art of biological hydrogen production processes

    International Nuclear Information System (INIS)

    Loubette, N.; Junker, M.

    2006-01-01

    Our report gives an overview of hydrogen production processes with bacteria or algae. 4 main processes are described: water biophotolysis, photo- fermentation biological CO conversion and dark fermentation. Chemical phenomena which lead to hydrogen generation are exp/aired. Performances, limits and outlook are given for each process. Main projects, programs and key players involved in this field of research have been listed. This paper resumes few results of this report. (authors)

  5. State of the art of biological hydrogen production processes

    International Nuclear Information System (INIS)

    Nicolas Loubette; Michel Junker

    2006-01-01

    Our report gives an overview of hydrogen production processes with bacteria or algae. 4 main processes are described: water bio-photolysis, photo-fermentation biological CO conversion and dark fermentation. Chemical phenomena which lead to hydrogen generation are explained. Performances, limits and outlook are given for each process. Main projects, programs and key players involved in this field of research have been listed. This paper resumes few results of this report. (authors)

  6. Processing laboratory of radio sterilized biological tissues

    International Nuclear Information System (INIS)

    Aguirre H, Paulina; Zarate S, Herman; Silva R, Samy; Hitschfeld, Mario

    2005-01-01

    The nuclear development applications have also reached those areas related to health. The risk of getting contagious illnesses through applying biological tissues has been one of the paramount worries to be solved since infectious illnesses might be provoked by virus, fungis or bacterias coming from donors or whether they have been introduced by means of intermediate stages before the use of these tissues. Therefore it has been concluded that the tissue allografts must be sterilized. The sterilization of medical products has been one of the main applications of the ionizing radiations and that it is why the International Organization of Atomic Energy began in the 70s promoting works related to the biological tissue sterilization and pharmaceutical products. The development of different tissue preservation methods has made possible the creation of tissue banks in different countries, to deal with long-term preservation. In our country, a project was launched in 1998, 'Establishment of a Tissue Bank in Latino america', this project was supported by the OIEA through the project INT/ 6/ 049, and was the starting of the actual Processing Laboratory of Radioesterilized Biological Tissues (LPTR), leaded by the Chilean Nuclear Energy Commission (CCHEN). This first organization is part of a number of entities compounding the Tissue Bank in Chile, organizations such as the Transplantation Promotion Corporation hospitals and the LPTR. The working system is carried out by means of the interaction between the hospitals and the laboratory. The medical professionals perform the procuring of tissues in the hospitals, then send them to the LPTR where they are processed and sterilized with ionizing radiation. The cycle ends up with the tissues return released to the hospitals, where they are used, and then the result information is sent to the LPTR as a form of feedback. Up to now, human skin has been processed (64 donors), amniotic membranes (35 donors) and pig skin (175 portions

  7. Potential denitrification rates of subsurface soil under paddy fields receiving ground water with high nitrate concentration; Konodo shosantai chisso gan`yu chikasui no ryunyusuru suiden kasodo ni okeru dacchitsu kassei

    Energy Technology Data Exchange (ETDEWEB)

    Toda, H [Shizuoka Agricultural Experiment Station, Shizuoka (Japan); Hidaka, S [Saitama Agricultural Experiment Station, Saitama (Japan)

    1996-02-10

    It is well known that the concentration of nitrate nitrogen in the surface water decreases as it flows downward in rice paddies irrigated with water high in nitrate nitrogen concentration. The decrease is attributed to absorption by rice plants and algae adherent thereto and denitrification in the reduction layer well developed in the rice paddy surface soil. In paddy fields downstream of the Kushibiki plateau in the northwestern part of Saitama Prefecture, it is occasionally observed that nitrate nitrogen concentration in the ground water decreases as it flows down (farther from the plateau) not only in the flooded period but also in the non-flooded period. This suggests that in the said paddy field denitrification takes place not only in the rice paddy surface layer soil but also in the lower layer soil. Under the circumstances, the denitrification rate in the rice paddy lower layer soil was measured using the acetylene inhibition method under anaerobic and added nitrate conditions. A denitrification rate of 0.4-46ngN/g{sup -1} wet soil/h{sup -1} was obtained from a 40-150cm deep layer soil, smaller by the order of 1-2 than that in the surface layer soil. This suggests that the lower layer soil contributes to denitrification. 17 refs., 3 figs., 1 tab.

  8. Toluene in sewage and sludge in wastewater treatment plants.

    Science.gov (United States)

    Mrowiec, Bozena

    2014-01-01

    Toluene is a compound that often occurs in municipal wastewater ranging from detectable levels up to 237 μg/L. Before the year 2000, the presence of the aromatic hydrocarbons was assigned only to external sources. The Enhanced Biological Nutrients Removal Processes (EBNRP) work according to many different schemes and technologies. For high-efficiency biological denitrification and dephosphatation processes, the presence of volatile fatty acids (VFAs) in sewage is required. VFAs are the main product of organic matter hydrolysis from sewage sludge. However, no attention has been given to other products of the process. It has been found that in parallel to VFA production, toluene formation occurred. The formation of toluene in municipal anaerobic sludge digestion processes was investigated. Experiments were performed on a laboratory scale using sludge from primary and secondary settling tanks of municipal treatment plants. The concentration of toluene in the digested sludge from primary settling tanks was found to be about 42,000 μg/L. The digested sludge supernatant liquor returned to the biological dephosphatation and denitrification processes for sewage enrichment can contain up to 16,500 μg/L of toluene.

  9. Effects of cyanobacterial-driven pH increases on sediment nutrient fluxes and coupled nitrification-denitrification in a shallow fresh water estuary

    Directory of Open Access Journals (Sweden)

    Y. Gao

    2012-07-01

    Full Text Available Summer cyanobacterial blooms caused an elevation in pH (9 to ~10.5 that lasted for weeks in the shallow and tidal-fresh region of the Sassafras River, a tributary of Chesapeake Bay (USA. Elevated pH promoted desorption of sedimentary inorganic phosphorus and facilitated conversion of ammonium (NH4+ to ammonia (NH3. In this study, we investigated pH effects on exchangeable NH4+ desorption, pore water diffusion and the flux rates of NH4+, soluble reactive phosphorus (SRP and nitrate (NO3, nitrification, denitrification, and oxygen consumption. Elevated pH enhanced desorption of exchangeable NH4+ through NH3 formation from both pore water and adsorbed NH4+ pools. Progressive penetration of high pH from the overlying water into sediment promoted the mobility of SRP and the release of total ammonium (NH4+ and NH3 into the pore water. At elevated pH levels, high sediment-water effluxes of SRP and total ammonium were associated with reduction of nitrification, denitrification and oxygen consumption rates. Alkaline pH and the toxicity of NH3 may inhibit nitrification in the thin aerobic zone, simultaneously constraining coupled nitrification–denitrification with limited NO3 supply and high pH penetration into the anaerobic zone. Geochemical feedbacks to pH elevation, such as enhancement of dissolved nutrient effluxes and reduction in N2 loss via denitrification, may enhance the persistence of cyanobacterial blooms in shallow water ecosystems.

  10. Biological floating bed and bio-contact oxidation processes for landscape water treatment: simultaneous removal of Microcystis aeruginosa, TOC, nitrogen and phosphorus.

    Science.gov (United States)

    Su, Jun Feng; Liang, Dong Hui; Fu, Le; Wei, Li; Ma, Min

    2018-06-13

    The aim of this study was to identify algicidal bacteria J25 against the Microcystis aeruginosa (90.14%), Chlorella (78.75%), Scenedesmus (not inhibited), and Oscillatoria (90.12%). Meanwhile, we evaluate the SOD activity and efficiency of denitrification characteristics with Acinetobacter sp. J25. A novel hybrid bioreactor combined biological floating bed with bio-contact oxidation (BFBO) was designed for treating the landscape water, and the average removal efficiencies of nitrate-N, ammonia-N, nitrite-N, TN, TP, TOC, and algal cells were 91.14, 50, 87.86, 88.83, 33.07, 53.95, and 53.43%, respectively. A 454-pyrosequencing technology was employed to investigate the microbial communities of the BFBO reactor samples. The results showed that Acinetobacter sp. J25 was the dominant contributor for effective removal of N, algal cells, and TOC in the BFBO reactor. And the relative abundance of Acinetobacter showed increase trend with the delay of reaction time. Graphical abstract Biological floating bed and bio-contact oxidation (BFBO) as a novel hybrid bioreactor designed for simultaneous removal Microcystis aeruginosa, TOC, nitrogen, and phosphorus. And high-throughput sequencing data demonstrated that Acinetobacter sp. J25 was the dominate species in the reactor and played key roles in the removal of N, TOC, and M. aeruginosa. Proposed reaction mechanism of the BFBO.

  11. Understanding the biological underpinnings of ecohydrological processes

    Science.gov (United States)

    Huxman, T. E.; Scott, R. L.; Barron-Gafford, G. A.; Hamerlynck, E. P.; Jenerette, D.; Tissue, D. T.; Breshears, D. D.; Saleska, S. R.

    2012-12-01

    Climate change presents a challenge for predicting ecosystem response, as multiple factors drive both the physical and life processes happening on the land surface and their interactions result in a complex, evolving coupled system. For example, changes in surface temperature and precipitation influence near-surface hydrology through impacts on system energy balance, affecting a range of physical processes. These changes in the salient features of the environment affect biological processes and elicit responses along the hierarchy of life (biochemistry to community composition). Many of these structural or process changes can alter patterns of soil water-use and influence land surface characteristics that affect local climate. Of the many features that affect our ability to predict the future dynamics of ecosystems, it is this hierarchical response of life that creates substantial complexity. Advances in the ability to predict or understand aspects of demography help describe thresholds in coupled ecohydrological system. Disentangling the physical and biological features that underlie land surface dynamics following disturbance are allowing a better understanding of the partitioning of water in the time-course of recovery. Better predicting the timing of phenology and key seasonal events allow for a more accurate description of the full functional response of the land surface to climate. In addition, explicitly considering the hierarchical structural features of life are helping to describe complex time-dependent behavior in ecosystems. However, despite this progress, we have yet to build an ability to fully account for the generalization of the main features of living systems into models that can describe ecohydrological processes, especially acclimation, assembly and adaptation. This is unfortunate, given that many key ecosystem services are functions of these coupled co-evolutionary processes. To date, both the lack of controlled measurements and experimentation

  12. Rhizosphere Biological Processes of Legume//Cereal Intercropping Systems: A Review

    Directory of Open Access Journals (Sweden)

    JIANG Yuan-yuan

    2016-09-01

    Full Text Available Intercropping, a sustainable planting pattern, was widely used in the wordwide. It not only has the advantages of yield and nutrient acquisition, but also can ensure food security and reduce the risk of crop failures. The majority of intercropping systems involve legume//cereal combinations because of interspecific facilitation or complementarity. The rhizosphere is the interface between plants and soil where there are interactions among a myriad of microorganisms and affect the uptake of nutrients, water and harmful substances. The rhizosphere biologi-cal processes not only determine the amount of nutrients and the availability of nutrients, but also affect crop productivity and nutrient use efficiency. Hence, this paper summarized the progress made on root morphology, rhizosphere microorganisms, root exudates and ecological ef-fect in the perspective of the rhizosphere biological process,which would provide theoretical basis for improving nutrient availability, remov-ing heavy metals, and plant genetic improvements.

  13. Waste water treatment: new procesos, new mentality. Depuracion de agua residual: nuevos procesos, nueva mentalidad

    Energy Technology Data Exchange (ETDEWEB)

    Cortacans, J.A. (Infilco Espanola (Spain))

    1994-01-01

    The biological nitrification-denitrification processes require, for a correct design, en adequate consideration of several parameters, which in conventional processes are not so significant: sludge age, temperature, alkalinity, BOD5/TKN ratio, readily biodegradable fraction of the organic matter, etc. This is the key for a right solution. (Author)

  14. Diurnal rhythmicity in biological processes involved in bioavailability of functional food factors.

    Science.gov (United States)

    Tsurusaki, Takashi; Sakakibara, Hiroyuki; Aoshima, Yoshiki; Yamazaki, Shunsuke; Sakono, Masanobu; Shimoi, Kayoko

    2013-05-01

    In the past few decades, many types of functional factors have been identified in dietary foods; for example, flavonoids are major groups widely distributed in the plant kingdom. However, the absorption rates of the functional food factors are usually low, and many of these are difficult to be absorbed in the intact forms because of metabolization by biological processes during absorption. To gain adequate beneficial effects, it is therefore mandatory to know whether functional food factors are absorbed in sufficient quantity, and then reach target organs while maintaining beneficial effects. These are the reasons why the bioavailability of functional food factors has been well investigated using rodent models. Recently, many of the biological processes have been reported to follow diurnal rhythms recurring every 24 h. Therefore, absorption and metabolism of functional food factors influenced by the biological processes may vary with time of day. Consequently, the evaluation of the bioavailability of functional food factors using rodent models should take into consideration the timing of consumption. In this review, we provide a perspective overview of the diurnal rhythm of biological processes involved in the bioavailability of functional food factors, particularly flavonoids.

  15. Denitrification of coking wastewater with micro-electrolysis.

    Science.gov (United States)

    Lv, Yanli; Wang, Yanqiu; Shan, Mingjun; Shen, Xue; Su, Ying

    2011-06-01

    The denitrification for the coking wastewater was conducted by means of original battery principle with Fe-C micro-electrolysis. Fe-C serves as positive and negative electrodes, by which N02(-)-N and TN were reduced to nitrogen, and then the purpose of denitrifieation for coking wastewater was realized. The influences of pH value, carbon particle size, Fe/C ratio (mass ratio), reaction time and coagulation pH value on removal rate of N02(-)-N and TN were investigated. Coking wastewater originated from Jiamusi Coal Chemistry Engineering Company. The optimum conditions of treatment were as follows: the initial pH was 3.0, the dosage of Fe 73.5 g/L, reaction time 70 min, mass ratio of Fe/C ratio 1.0:1.3, coagulation pH 9.0 and sedimentation time 40 min. Under those conditions, nitrogen removal efficiencies of N02(-)-N and TN were beyond 50% and 45%, respectively. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  16. Nitrate removal from groundwater by cooperating heterotrophic with autotrophic denitrification in a biofilm-electrode reactor.

    Science.gov (United States)

    Zhao, Yingxin; Feng, Chuanping; Wang, Qinghong; Yang, Yingnan; Zhang, Zhenya; Sugiura, Norio

    2011-09-15

    An intensified biofilm-electrode reactor (IBER) combining heterotrophic and autotrophic denitrification was developed for treatment of nitrate contaminated groundwater. The reactor was evaluated with synthetic groundwater (NO(3)(-)-N50 mg L(-1)) under different hydraulic retention times (HRTs), carbon to nitrogen ratios (C/N) and electric currents (I). The experimental results demonstrate that high nitrate and nitrite removal efficiency (100%) were achieved at C/N = 1, HRT = 8h, and I = 10 mA. C/N ratios were reduced from 1 to 0.5 and the applied electric current was changed from 10 to 100 mA, showing that the optimum running condition was C/N = 0.75 and I = 40 mA, under which over 97% of NO(3)(-)-N was removed and organic carbon (methanol) was completely consumed in treated water. Simultaneously, the denitrification mechanism in this system was analyzed through pH variation in effluent. The CO(2) produced from the anode acted as a good pH buffer, automatically controlling pH in the reaction zone. The intensified biofilm-electrode reactor developed in the study was effective for the treatment of groundwater polluted by nitrate. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Simultaneous heterotrophic nitrification and aerobic denitrification by the marine origin bacterium Pseudomonas sp. ADN-42.

    Science.gov (United States)

    Jin, Ruofei; Liu, Tianqi; Liu, Guangfei; Zhou, Jiti; Huang, Jianyu; Wang, Aijie

    2015-02-01

    Recent research has highlighted the existence of some bacteria that are capable of performing heterotrophic nitrification and have a phenomenal ability to denitrify their nitrification products under aerobic conditions. A high-salinity-tolerant strain ADN-42 was isolated from Hymeniacidon perleve and found to display high heterotrophic ammonium removal capability. This strain was identified as Pseudomonas sp. via 16S rRNA gene sequence analysis. Gene cloning and sequencing analysis indicated that the bacterial genome contains N2O reductase function (nosZ) gene. NH3-N removal rate of ADN-42 was very high. And the highest removal rate was 6.52 mg/L · h in the presence of 40 g/L NaCl. Under the condition of pure oxygen (DO >8 mg/L), NH3-N removal efficiency was 56.9 %. Moreover, 38.4 % of oxygen remained in the upper gas space during 72 h without greenhouse gas N2O production. Keeping continuous and low level of dissolved oxygen (DO <3 mg/L) was helpful for better denitrification performance. All these results indicated that the strain has heterotrophic nitrification and aerobic denitrification abilities, which guarantee future application in wastewater treatment.

  18. Physical biological coupling in the Pearl River Estuary

    Science.gov (United States)

    Harrison, Paul J.; Yin, Kedong; Lee, J. H. W.; Gan, Jianping; Liu, Hongbin

    2008-07-01

    The Pearl River Estuary is a subtropical estuary and the second largest in China based on discharge volume from the Pearl River. Processes in the estuary vary spatially and temporally (wet vs dry season). In the dry season at the head of the estuary, hypoxic and nearly anoxic conditions occur and NH 4 reaches >600 μM, NO 3 is ˜300 μM and nitrite is ˜60 μM indicating that nitrification and denitrification may be important dry season processes in the region extending 40 km upstream of the Humen outlet. There are very few biological studies conducted in this upper section of the estuary in either the dry or wet seasons and hence there is a need for further research in this region of the river. In the wet season, the salinity wedge extends to the Hongqimen outlet and oxygen is low (35-80% saturation). Nitrate is ˜100 μM, silicate ˜140 μM; and phosphate is relatively low at ˜0.5 μM, yielding an N:P ratio up to ˜200:1 in summer. Nutrients decrease in the lower estuary and primary productivity may become potentially P-limited. Eutrophication is not as severe as one would expect from the nutrient inputs from the Pearl River and from Hong Kong's sewage discharge. This estuary shows a remarkable capacity to cope with excessive nutrients. Physical processes such as river discharge, tidal flushing, turbulent dispersion, wind-induced mixing, and estuarine circulation play an important role in controlling the production and accumulation of algal blooms and the potential occurrence of hypoxia. Superimposed on the physical processes of the estuary are the chemical and biological processes involved in the production of the bloom. For example, the 100N:1P ratio indicates that P potentially limits the amount of algal biomass (and potential biological oxygen demand) in summer. While extended periods of hypoxia are rare in Hong Kong waters, episodic events have been reported to occur during late summer due to factors such as low wind, high rainfall and river discharge which

  19. Advances in downstream processing of biologics - Spectroscopy: An emerging process analytical technology.

    Science.gov (United States)

    Rüdt, Matthias; Briskot, Till; Hubbuch, Jürgen

    2017-03-24

    Process analytical technologies (PAT) for the manufacturing of biologics have drawn increased interest in the last decade. Besides being encouraged by the Food and Drug Administration's (FDA's) PAT initiative, PAT promises to improve process understanding, reduce overall production costs and help to implement continuous manufacturing. This article focuses on spectroscopic tools for PAT in downstream processing (DSP). Recent advances and future perspectives will be reviewed. In order to exploit the full potential of gathered data, chemometric tools are widely used for the evaluation of complex spectroscopic information. Thus, an introduction into the field will be given. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  20. Kinetic study on anaerobic oxidation of methane coupled to denitrification.

    Science.gov (United States)

    Yu, Hou; Kashima, Hiroyuki; Regan, John M; Hussain, Abid; Elbeshbishy, Elsayed; Lee, Hyung-Sool

    2017-09-01

    Monod kinetic parameters provide information required for kinetic analysis of anaerobic oxidation of methane coupled to denitrification (AOM-D). This information is critical for engineering AOM-D processes in wastewater treatment facilities. We first experimentally determined Monod kinetic parameters for an AOM-D enriched culture and obtained the following values: maximum specific growth rate (μ max ) 0.121/d, maximum substrate-utilization rate (q max ) 28.8mmol CH 4 /g cells-d, half maximum-rate substrate concentration (K s ) 83μΜ CH 4 , growth yield (Y) 4.76gcells/mol CH 4 , decay coefficient (b) 0.031/d, and threshold substrate concentration (S min ) 28.8μM CH 4 . Clone library analysis of 16S rRNA and mcrA gene fragments suggested that AOM-D reactions might have occurred via the syntrophic interaction between denitrifying bacteria (e.g., Ignavibacterium, Acidovorax, and Pseudomonas spp.) and hydrogenotrophic methanogens (Methanobacterium spp.), supporting reverse methanogenesis-dependent AOM-D in our culture. High μ max and q max , and low K s for the AOM-D enrichment imply that AOM-D could play a significant role in mitigating atmospheric methane efflux. In addition, these high kinetic features suggest that engineered AOM-D systems may provide a sustainable alternative to nitrogen removal in wastewater treatment. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Denitrification-derived nitric oxide modulates biofilm formation in Azospirillum brasilense.

    Science.gov (United States)

    Arruebarrena Di Palma, Andrés; Pereyra, Cintia M; Moreno Ramirez, Lizbeth; Xiqui Vázquez, María L; Baca, Beatriz E; Pereyra, María A; Lamattina, Lorenzo; Creus, Cecilia M

    2013-01-01

    Azospirillum brasilense is a rhizobacterium that provides beneficial effects on plants when they colonize roots. The formation of complex bacterial communities known as biofilms begins with the interaction of planktonic cells with surfaces in response to appropriate signals. Nitric oxide (NO) is a signaling molecule implicated in numerous processes in bacteria, including biofilm formation or dispersion, depending on genera and lifestyle. Azospirillum brasilense Sp245 produces NO by denitrification having a role in root growth promotion. We analyzed the role of endogenously produced NO on biofilm formation in A. brasilense Sp245 and in a periplasmic nitrate reductase mutant (napA::Tn5; Faj164) affected in NO production. Cells were statically grown in media with nitrate or ammonium as nitrogen sources and examined for biofilm formation using crystal violet and by confocal laser microscopy. Both strains formed biofilms, but the mutant produced less than half compared with the wild type in nitrate medium showing impaired nitrite production in this condition. NO measurements in biofilm confirmed lower values in the mutant strain. The addition of a NO donor showed that NO influences biofilm formation in a dose-dependent manner and reverses the mutant phenotype, indicating that Nap positively regulates the formation of biofilm in A. brasilense Sp245. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  2. Physical Controls on Oxygen Distribution and Denitrification Potential in the North West Arabian Sea

    Science.gov (United States)

    Queste, Bastien Y.; Vic, Clément; Heywood, Karen J.; Piontkovski, Sergey A.

    2018-05-01

    At suboxic oxygen concentrations, key biogeochemical cycles change and denitrification becomes the dominant remineralization pathway. Earth system models predict oxygen loss across most ocean basins in the next century; oxygen minimum zones near suboxia may become suboxic and therefore denitrifying. Using an ocean glider survey and historical data, we show oxygen loss in the Gulf of Oman (from 6-12 to water across the Gulf of Oman and waters exported to the wider Arabian Sea.

  3. A novel theory: biological processes mostly involve two types of mediators, namely general and specific mediators Endogenous small radicals such as superoxide and nitric oxide may play a role of general mediator in biological processes.

    Science.gov (United States)

    Mo, Jian

    2005-01-01

    A great number of papers have shown that free radicals as well as bioactive molecules can play a role of mediator in a wide spectrum of biological processes, but the biological actions and chemical reactivity of the free radicals are quite different from that of the bioactive molecules, and that a wide variety of bioactive molecules can be easily modified by free radicals due to having functional groups sensitive to redox, and the significance of the interaction between the free radicals and the bioactive molecules in biological processes has been confirmed by the results of some in vitro and in vivo studies. Based on these evidence, this article presented a novel theory about the mediators of biological processes. The essentials of the theory are: (a) mediators of biological processes can be classified into general and specific mediators; the general mediators include two types of free radicals, namely superoxide and nitric oxide; the specific mediators include a wide variety of bioactive molecules, such as specific enzymes, transcription factors, cytokines and eicosanoids; (b) a general mediator can modify almost any class of the biomolecules, and thus play a role of mediator in nearly every biological process via diverse mechanisms; a specific mediator always acts selectively on certain classes of the biomolecules, and may play a role of mediator in different biological processes via a same mechanism; (c) biological processes are mostly controlled by networks of their mediators, so the free radicals can regulate the last consequence of a biological process by modifying some types of the bioactive molecules, or in cooperation with these bioactive molecules; the biological actions of superoxide and nitric oxide may be synergistic or antagonistic. According to this theory, keeping the integrity of these networks and the balance between the free radicals and the bioactive molecules as well as the balance between the free radicals and the free radical scavengers

  4. Revealing complex function, process and pathway interactions with high-throughput expression and biological annotation data.

    Science.gov (United States)

    Singh, Nitesh Kumar; Ernst, Mathias; Liebscher, Volkmar; Fuellen, Georg; Taher, Leila

    2016-10-20

    The biological relationships both between and within the functions, processes and pathways that operate within complex biological systems are only poorly characterized, making the interpretation of large scale gene expression datasets extremely challenging. Here, we present an approach that integrates gene expression and biological annotation data to identify and describe the interactions between biological functions, processes and pathways that govern a phenotype of interest. The product is a global, interconnected network, not of genes but of functions, processes and pathways, that represents the biological relationships within the system. We validated our approach on two high-throughput expression datasets describing organismal and organ development. Our findings are well supported by the available literature, confirming that developmental processes and apoptosis play key roles in cell differentiation. Furthermore, our results suggest that processes related to pluripotency and lineage commitment, which are known to be critical for development, interact mainly indirectly, through genes implicated in more general biological processes. Moreover, we provide evidence that supports the relevance of cell spatial organization in the developing liver for proper liver function. Our strategy can be viewed as an abstraction that is useful to interpret high-throughput data and devise further experiments.

  5. Denitrification rate determined by nitrate disapperance is higher than determined by nitrous oxide production with acetylene blockage

    DEFF Research Database (Denmark)

    Yu, Kewei; Struwe, Sten; Kjøller, Annelise

    2008-01-01

    A mixed beech and spruce forest soil was incubated under potential denitrification assay (PDA) condition with 10% acetylene (C2H2) in the headspace of soil slurry bottles. Nitrous oxide (N2O) concentration in the headspace, as well as nitrate, nitrite and ammonium concentrations in the soil slurr...

  6. Full-scale operating experience of deep bed denitrification filter achieving phosphorus.

    Science.gov (United States)

    Husband, Joseph A; Slattery, Larry; Garrett, John; Corsoro, Frank; Smithers, Carol; Phipps, Scott

    2012-01-01

    The Arlington County Wastewater Pollution Control Plant (ACWPCP) is located in the southern part of Arlington County, Virginia, USA and discharges to the Potomac River via the Four Mile Run. The ACWPCP was originally constructed in 1937. In 2001, Arlington County, Virginia (USA) committed to expanding their 113,500 m³/d, (300,000 pe) secondary treatment plant to a 151,400 m³/d (400,000 pe) to achieve effluent total nitrogen (TN) to phosphorus (TP) phosphorus, to very low concentrations. This paper will review the steps from concept to the first year of operation, including pilot and full-scale operating data and the capital cost for the denitrification filters.

  7. Biclustering with Flexible Plaid Models to Unravel Interactions between Biological Processes.

    Science.gov (United States)

    Henriques, Rui; Madeira, Sara C

    2015-01-01

    Genes can participate in multiple biological processes at a time and thus their expression can be seen as a composition of the contributions from the active processes. Biclustering under a plaid assumption allows the modeling of interactions between transcriptional modules or biclusters (subsets of genes with coherence across subsets of conditions) by assuming an additive composition of contributions in their overlapping areas. Despite the biological interest of plaid models, few biclustering algorithms consider plaid effects and, when they do, they place restrictions on the allowed types and structures of biclusters, and suffer from robustness problems by seizing exact additive matchings. We propose BiP (Biclustering using Plaid models), a biclustering algorithm with relaxations to allow expression levels to change in overlapping areas according to biologically meaningful assumptions (weighted and noise-tolerant composition of contributions). BiP can be used over existing biclustering solutions (seizing their benefits) as it is able to recover excluded areas due to unaccounted plaid effects and detect noisy areas non-explained by a plaid assumption, thus producing an explanatory model of overlapping transcriptional activity. Experiments on synthetic data support BiP's efficiency and effectiveness. The learned models from expression data unravel meaningful and non-trivial functional interactions between biological processes associated with putative regulatory modules.

  8. Intergenomic comparisons highlight modularity of the denitrification pathway and underpin the importance of community structure for N2O emissions.

    Directory of Open Access Journals (Sweden)

    Daniel R H Graf

    Full Text Available Nitrous oxide (N2O is a potent greenhouse gas and the predominant ozone depleting substance. The only enzyme known to reduce N2O is the nitrous oxide reductase, encoded by the nosZ gene, which is present among bacteria and archaea capable of either complete denitrification or only N2O reduction to di-nitrogen gas. To determine whether the occurrence of nosZ, being a proxy for the trait N2O reduction, differed among taxonomic groups, preferred habitats or organisms having either NirK or NirS nitrite reductases encoded by the nirK and nirS genes, respectively, 652 microbial genomes across 18 phyla were compared. Furthermore, the association of different co-occurrence patterns with enzymes reducing nitric oxide to N2O encoded by nor genes was examined. We observed that co-occurrence patterns of denitrification genes were not randomly distributed across taxa, as specific patterns were found to be more dominant or absent than expected within different taxonomic groups. The nosZ gene had a significantly higher frequency of co-occurrence with nirS than with nirK and the presence or absence of a nor gene largely explained this pattern, as nirS almost always co-occurred with nor. This suggests that nirS type denitrifiers are more likely to be capable of complete denitrification and thus contribute less to N2O emissions than nirK type denitrifiers under favorable environmental conditions. Comparative phylogenetic analysis indicated a greater degree of shared evolutionary history between nosZ and nirS. However 30% of the organisms with nosZ did not possess either nir gene, with several of these also lacking nor, suggesting a potentially important role in N2O reduction. Co-occurrence patterns were also non-randomly distributed amongst preferred habitat categories, with several habitats showing significant differences in the frequencies of nirS and nirK type denitrifiers. These results demonstrate that the denitrification pathway is highly modular, thus

  9. Is nanotechnology the key to unravel and engineer biological processes?

    Science.gov (United States)

    Navarro, Melba; Planell, Josep A

    2012-01-01

    Regenerative medicine is an emerging field aiming to the development of new reparative strategies to treat degenerative diseases, injury, and trauma through developmental pathways in order to rebuild the architecture of the original injured organ and take over its functionality. Most of the processes and interactions involved in the regenerative process take place at subcellular scale. Nanotechnology provides the tools and technology not only to detect, to measure, or to image the interactions between the different biomolecules and biological entities, but also to control and guide the regenerative process. The relevance of nanotechnology for the development of regenerative medicine as well as an overview of the different tools that contribute to unravel and engineer biological systems are presented in this chapter. In addition, general data about the social impact and global investment in nanotechnology are provided.

  10. Conserving forest biological diversity: How the Montreal Process helps achieve sustainability

    Science.gov (United States)

    Mark Nelson; Guy Robertson; Kurt. Riitters

    2015-01-01

    Forests support a variety of ecosystems, species and genes — collectively referred to as biological diversity — along with important processes that tie these all together. With the growing recognition that biological diversity contributes to human welfare in a number of important ways such as providing food, medicine and fiber (provisioning services...

  11. Assessment of full-scale biological nutrient removal systems upgraded with physico-chemical processes for the removal of emerging pollutants present in wastewaters from Mexico.

    Science.gov (United States)

    Estrada-Arriaga, Edson Baltazar; Cortés-Muñoz, Juana Enriqueta; González-Herrera, Arturo; Calderón-Mólgora, César Guillermo; de Lourdes Rivera-Huerta, Ma; Ramírez-Camperos, Esperanza; Montellano-Palacios, Leticia; Gelover-Santiago, Silvia Lucila; Pérez-Castrejón, Sara; Cardoso-Vigueros, Lina; Martín-Domínguez, Alejandra; García-Sánchez, Liliana

    2016-11-15

    Two full-scale biological nutrient removal systems upgraded with three physico-chemical processes (coagulation, chemical precipitation, and neutral Fenton) were evaluated in order to determine the removal of emerging pollutants (EPs) present in municipal wastewater from Mexico. Between 41 and 55 EPs were detected in the influents of two wastewater treatment plants (WWTPs), including personal care products (PPCPs), antibiotics, analgesics, antiepileptics, antilipidemics, antihypertensives, antiseptics, stimulants, and hormones. Emerging pollutants were detected at concentrations ranging from 0.69ng/L to 94,600ng/L. High concentrations of emerging pollutants were found during dry season. WWTP 1, integrated by oxidation ditches and UV light lamps, showed removal efficiencies of EPs between 20% and 22%. On the other hand, WWTP 2 consisted of anaerobic/anoxic/aerobic tanks coupled with two disinfection processes; chlorine dioxide and UV light lamps, for which the removal of EPs was significant (up to 80%). The concentrations of emerging pollutants in WWTP 1 effluent was found within a rangeemerging pollutants in the effluent were below 210ng/L. WWTP 2 showed high emerging pollutant removals, compared to those of WWTP 1, due to a greater activity of the simultaneous nitrification-denitrification processes, hydraulic retention time, and solids retention time. The compounds that were more persistent with removals below 50% in both effluents were: carbamazepine, dehydronifedipine, meprobamate, sertraline, propranolol, propoxyphene, norverapamil, diazepam, alprazolam, sulfamethoxazole, metoprolol, ofloxacin, norfloxacin, fluoxetine, erythromycin-H2O, diphenhydramine, dehydronifedipine, clarithromycin, hydrochlorothiazide, and albuterol. The application of neutral Fenton reaction as post-treatment for the two effluents from the WWTPs is promising for the removal of emerging pollutants (up to 100%) and for assuring high quality of treated water. Copyright © 2016 Elsevier B

  12. Excessive use of nitrogen in Chinese agriculture results in high N2O/(N2O+N2) product ratio of denitrification, primarily due to acidification of the soils

    Science.gov (United States)

    Qu, Zhi; Wang, Jingguo; Almøy, Trygve; Bakken, Lars R

    2014-01-01

    China is the world's largest producer and consumer of fertilizer N, and decades of overuse has caused nitrate leaching and possibly soil acidification. We hypothesized that this would enhance the soils' propensity to emit N2O from denitrification by reducing the expression of the enzyme N2O reductase. We investigated this by standardized oxic/anoxic incubations of soils from five long-term fertilization experiments in different regions of China. After adjusting the nitrate concentration to 2 mM, we measured oxic respiration (R), potential denitrification (D), substrate-induced denitrification, and the denitrification product stoichiometry (NO, N2O, N2). Soils with a history of high fertilizer N levels had high N2O/(N2O+N2) ratios, but only in those field experiments where soil pH had been lowered by N fertilization. By comparing all soils, we found a strong negative correlation between pH and the N2O/(N2O+N2) product ratio (r2 = 0.759, P soil pH. The immediate effect of liming acidified soils was lowered N2O/(N2O+N2) ratios. The results provide evidence that soil pH has a marginal direct effect on potential denitrification, but that it is the master variable controlling the percentage of denitrified N emitted as N2O. It has been known for long that low pH may result in high N2O/(N2O+N2) product ratios of denitrification, but our documentation of a pervasive pH-control of this ratio across soil types and management practices is new. The results are in good agreement with new understanding of how pH may interfere with the expression of N2O reductase. We argue that the management of soil pH should be high on the agenda for mitigating N2O emissions in the future, particularly for countries where ongoing intensification of plant production is likely to acidify the soils. PMID:24249526

  13. Denitrification of groundwater using a sulfur-oxidizing autotrophic denitrifying anaerobic fluidized-bed MBR: performance and bacterial community structure.

    Science.gov (United States)

    Zhang, Lili; Zhang, Chao; Hu, Chengzhi; Liu, Huijuan; Qu, Jiuhui

    2015-03-01

    This paper investigates a novel sulfur-oxidizing autotrophic denitrifying anaerobic fluidized bed membrane bioreactor (AnFB-MBR) that has the potential to overcome the limitations of conventional sulfur-oxidizing autotrophic denitrification systems. The AnFB-MBR produced consistent high-quality product water when fed by a synthetic groundwater with NO3 (-)-N ranging 25-80 mg/L and operated at hydraulic retention times of 0.5-5.0 h. A nitrate removal rate of up to 4.0 g NO3 (-)-N/Lreactord was attained by the bioreactor, which exceeded any reported removal capacity. The flux of AnFB-MBR was maintained in the range of 1.5-15 L m(-2) h(-1). Successful membrane cleaning was practiced with cleaning cycles of 35-81 days, which had no obvious effect on the AnFB-MBR performance. The (15) N-tracer analyses elucidated that nitrogen was converted into (15) N2-N and (15) N-biomass accounting for 88.1-93.1 % and 6.4-11.6 % of the total nitrogen produced, respectively. Only 0.3-0.5 % of removed nitrogen was in form of (15)N2O-N in sulfur-oxidizing autotrophic denitrification process, reducing potential risks of a significant amount of N2O emissions. The sulfur-oxidizing autotrophic denitrifying bacterial consortium was composed mainly of bacteria from Proteobacteria, Chlorobi, and Chloroflexi phyla, with genera Thiobacillus, Sulfurimonas, and Ignavibacteriales dominating the consortium. The pyrosequencing assays also suggested that the stable microbial communities corresponded to the elevated performance of the AnFB-MBR. Overall, this research described relatively high nitrate removal, acceptable flux, indicating future potential for the technology in practice.

  14. Denitrification in a hypersaline lake–aquifer system (Pétrola Basin, Central Spain): The role of recent organic matter and Cretaceous organic rich sediments

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Alday, J.J., E-mail: JuanJose.Gomez@uclm.es [Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla–La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete (Spain); Carrey, R., E-mail: raulcarrey@ub.edu [Grup d’Mineralogia Aplicada i Medi Ambient, Dep. Cristallografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona (Spain); Valiente, N., E-mail: Nicolas.Valiente@uclm.es [Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla–La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete (Spain); Otero, N., E-mail: notero@ub.edu [Grup d’Mineralogia Aplicada i Medi Ambient, Dep. Cristallografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona (Spain); Soler, A., E-mail: albertsolergil@ub.edu [Grup d’Mineralogia Aplicada i Medi Ambient, Dep. Cristallografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona (Spain); Ayora, C., E-mail: cayora1@gmail.com [Grup d' Hidrologia Subterrània (GHS), Institut de Diagnóstic Ambiental i Estudis de l' Aigua (IDAEA-CSIC), C/Jordi Girona 18, 08028 Barcelona (Spain); Sanz, D. [Hydrogeology Group, Institute for Regional Development (IDR), University of Castilla–La Mancha (UCLM), Campus Universitario s/n, 02071 Albacete (Spain); and others

    2014-11-01

    Agricultural regions in semi-arid to arid climates with associated saline wetlands are one of the most vulnerable environments to nitrate pollution. The Pétrola Basin was declared vulnerable to NO{sub 3}{sup −} pollution by the Regional Government in 1998, and the hypersaline lake was classified as a heavily modified body of water. The study assessed groundwater NO{sub 3}{sup −} through the use of multi-isotopic tracers (δ{sup 15}N, δ{sup 34}S, δ{sup 13}C, δ{sup 18}O) coupled to hydrochemistry in the aquifer connected to the eutrophic lake. Hydrogeologically, the basin shows two main flow components: regional groundwater flow from recharge areas (Zone 1) to the lake (Zone 2), and a density-driven flow from surface water to the underlying aquifer (Zone 3). In Zones 1 and 2, δ{sup 15}N{sub NO{sub 3}} and δ{sup 18}O{sub NO{sub 3}} suggest that NO{sub 3}{sup −} from slightly volatilized ammonium synthetic fertilizers is only partially denitrified. The natural attenuation of NO{sub 3}{sup −} can occur by heterotrophic reactions. However, autotrophic reactions cannot be ruled out. In Zone 3, the freshwater–saltwater interface (down to 12–16 m below the ground surface) is a reactive zone for NO{sub 3}{sup −} attenuation. Tritium data suggest that the absence of NO{sub 3}{sup −} in the deepest zones of the aquifer under the lake can be attributed to a regional groundwater flow with long residence time. In hypersaline lakes the geometry of the density-driven flow can play an important role in the transport of chemical species that can be related to denitrification processes. - Highlights: • Denitrification comes about in a hypersaline lake–aquifer system. • Nitrate in the basin is derived from synthetic fertilizers slightly volatilized. • Organic carbon oxidation is likely to be the main electron donor in denitrification. • Density driven flow transports organic carbon to deeper zones of the aquifer.

  15. Nitrogen Removal Characteristics of Pseudomonas putida Y-9 Capable of Heterotrophic Nitrification and Aerobic Denitrification at Low Temperature

    Directory of Open Access Journals (Sweden)

    Yi Xu

    2017-01-01

    Full Text Available The cold-adapted bacterium Pseudomonas putida Y-9 was investigated and exhibited excellent capability for nitrogen removal at 15°C. The strain capable of heterotrophic nitrification and aerobic denitrification could efficiently remove ammonium, nitrate, and nitrite at an average removal rate of 2.85 mg, 1.60 mg, and 1.83 mg NL−1 h−1, respectively. Strain Y-9 performed nitrification in preference to denitrification when ammonium and nitrate or ammonium and nitrite coexisted in the solution. Meantime, the presence of nitrate had no effect on the ammonium removal rate of strain Y-9, and yet the presence of high concentration of nitrite would inhibit the cell growth and decrease the nitrification rate. The experimental results indicate that P. putida Y-9 has potential application for the treatment of wastewater containing high concentrations of ammonium along with its oxidation products at low temperature.

  16. Transformation of carbon tetrachloride by Pseudomonas sp. strain KC under denitrification conditions

    International Nuclear Information System (INIS)

    Criddle, C.S.; DeWitt, J.T.; Grbic-Galic, D.; McCarty, P.L.

    1990-01-01

    A denitrifying Pseudomonas sp. (strain KC) capable of transforming carbon tetrachloride (CT) was isolated from groundwater aquifer solids. Major products of the transformation of 14 C-labeled CT by Pseudomonas strain KC under denitrification conditions were 14 CO 2 and an unidentified water-soluble fraction. Little or no chloroform was produced. Addition of dissolved trace metals, notably, ferrous iron and cobalt, to the growth medium appeared to enhance growth of Pseudomonas strain KC while inhibiting transformation of CT. It is hypothesized that transformation of CT by this organism is associated with the mechanism of trace-metal scavenging

  17. [Key microbial processes in nitrous oxide emissions of agricultural soil and mitigation strategies].

    Science.gov (United States)

    Zhu, Yong-Guan; Wang, Xiao-Hui; Yang, Xiao-Ru; Xu, Hui-Juan; Jia, Yan

    2014-02-01

    Nitrous oxide (N2O) is a powerful atmospheric greenhouse gas, which does not only have a strong influence on the global climate change but also depletes the ozone layer and induces the enhancement of ultraviolet radiation to ground surface, so numerous researches have been focused on global climate change and ecological environmental change. Soil is the foremost source of N2O emissions to the atmosphere, and approximately two-thirds of these emissions are generally attributed to microbiological processes including bacterial and fungal denitrification and nitrification processes, largely as a result of the application of nitrogenous fertilizers. Here the available knowledge concerning the research progress in N2O production in agricultural soils was reviewed, including denitrification, nitrification, nitrifier denitrification and dissimilatory nitrate reduction to ammonium, and the abiotic (including soil pH, organic and inorganic nitrogen, organic matter, soil humidity and temperature) and biotic factors that have direct and indirect effects on N2O fluxes from agricultural soils were also summarized. In addition, the strategies for mitigating N2O emissions and the future research direction were proposed. Therefore, these studies are expected to provide valuable and scientific evidence for the study on mitigation strategies for the emission of greenhouse gases, adjustment of nitrogen transformation processes and enhancement of nitrogen use efficiency.

  18. Integrated anaerobic/aerobic biological treatment for intensive swine production.

    Science.gov (United States)

    Bortone, Giuseppe

    2009-11-01

    Manure processing could help farmers to effectively manage nitrogen (N) surplus load. Many pig farms have to treat wastewater. Piggery wastewater treatment is a complex challenge, due to the high COD and N concentrations and low C/N ratio. Anaerobic digestion (AD) could be a convenient pre-treatment, particularly from the energetic view point and farm income, but this causes further reduction of C/N ratio and makes denitrification difficult. N removal can only be obtained integrating anaerobic/aerobic treatment by taking into account the best use of electron donors. Experiences gained in Italy during development of integrated biological treatment approaches for swine manure, from bench to full scale, are reported in this paper. Solid/liquid separation as pre-treatment of raw manure is an efficient strategy to facilitate liquid fraction treatment without significantly lowering C/N ratio. In Italy, two full scale SBRs showed excellent efficiency and reliability. Current renewable energy policy and incentives makes economically attractive the application of AD to the separated solid fraction using high solid anaerobic digester (HSAD) technology. Economic evaluation showed that energy production can reduce costs up to 60%, making sustainable the overall treatment.

  19. Biological features produced by additive manufacturing processes using vat photopolymerization method

    DEFF Research Database (Denmark)

    Davoudinejad, Ali; Mendez Ribo, Macarena; Pedersen, David Bue

    2017-01-01

    of micro biological features by Additive Manufacturing (AM) processes. The study characterizes the additive manufacturing processes for polymeric micro part productions using the vat photopolymerization method. A specifically designed vat photopolymerization AM machine suitable for precision printing...

  20. WE-DE-202-03: Modeling of Biological Processes - What Happens After Early Molecular Damage?

    International Nuclear Information System (INIS)

    McMahon, S.

    2016-01-01

    Radiation therapy for the treatment of cancer has been established as a highly precise and effective way to eradicate a localized region of diseased tissue. To achieve further significant gains in the therapeutic ratio, we need to move towards biologically optimized treatment planning. To achieve this goal, we need to understand how the radiation-type dependent patterns of induced energy depositions within the cell (physics) connect via molecular, cellular and tissue reactions to treatment outcome such as tumor control and undesirable effects on normal tissue. Several computational biology approaches have been developed connecting physics to biology. Monte Carlo simulations are the most accurate method to calculate physical dose distributions at the nanometer scale, however simulations at the DNA scale are slow and repair processes are generally not simulated. Alternative models that rely on the random formation of individual DNA lesions within one or two turns of the DNA have been shown to reproduce the clusters of DNA lesions, including single strand breaks (SSBs), double strand breaks (DSBs) without the need for detailed track structure simulations. Efficient computational simulations of initial DNA damage induction facilitate computational modeling of DNA repair and other molecular and cellular processes. Mechanistic, multiscale models provide a useful conceptual framework to test biological hypotheses and help connect fundamental information about track structure and dosimetry at the sub-cellular level to dose-response effects on larger scales. In this symposium we will learn about the current state of the art of computational approaches estimating radiation damage at the cellular and sub-cellular scale. How can understanding the physics interactions at the DNA level be used to predict biological outcome? We will discuss if and how such calculations are relevant to advance our understanding of radiation damage and its repair, or, if the underlying biological

  1. WE-DE-202-03: Modeling of Biological Processes - What Happens After Early Molecular Damage?

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, S. [Massachusetts General Hospital and Harvard Medical School (United States)

    2016-06-15

    Radiation therapy for the treatment of cancer has been established as a highly precise and effective way to eradicate a localized region of diseased tissue. To achieve further significant gains in the therapeutic ratio, we need to move towards biologically optimized treatment planning. To achieve this goal, we need to understand how the radiation-type dependent patterns of induced energy depositions within the cell (physics) connect via molecular, cellular and tissue reactions to treatment outcome such as tumor control and undesirable effects on normal tissue. Several computational biology approaches have been developed connecting physics to biology. Monte Carlo simulations are the most accurate method to calculate physical dose distributions at the nanometer scale, however simulations at the DNA scale are slow and repair processes are generally not simulated. Alternative models that rely on the random formation of individual DNA lesions within one or two turns of the DNA have been shown to reproduce the clusters of DNA lesions, including single strand breaks (SSBs), double strand breaks (DSBs) without the need for detailed track structure simulations. Efficient computational simulations of initial DNA damage induction facilitate computational modeling of DNA repair and other molecular and cellular processes. Mechanistic, multiscale models provide a useful conceptual framework to test biological hypotheses and help connect fundamental information about track structure and dosimetry at the sub-cellular level to dose-response effects on larger scales. In this symposium we will learn about the current state of the art of computational approaches estimating radiation damage at the cellular and sub-cellular scale. How can understanding the physics interactions at the DNA level be used to predict biological outcome? We will discuss if and how such calculations are relevant to advance our understanding of radiation damage and its repair, or, if the underlying biological

  2. Influence of road salt on the biological removal of nitrogen

    OpenAIRE

    Eliška Horniaková; Milan Búgel

    2007-01-01

    Processes occuring in the aeration tank remove nitrogen from the organic substances in wastewater by using the bacterii. Nitrification utilize the metabolism of aerobic bacterii Nitrosomonas, Nitrococus, Nitrospira, Nitrobacter Nitrocystis a Nitrosobolus. Pseudosomonas, Chromobacterium, Denitrobacillus a Micrococus are denitrification anaerobic bacterii. The bacterii are lithotrophic and they are sensitive to pH of wastewater. Chlorine and heavy metals are toxic for these bacterii. For a corr...

  3. Radiation processing of biological tissues for nuclear disaster management

    International Nuclear Information System (INIS)

    Singh, Rita

    2012-01-01

    A number of surgical procedures require tissue substitutes to repair or replace damaged or diseased tissues. Biological tissues from human donor like bone, skin, amniotic membrane and other soft tissues can be used for repair or reconstruction of the injured part of the body. Tissues from human donor can be processed and banked for orthopaedic, spinal, trauma and other surgical procedures. Allograft tissues provide an excellent alternative to autografts. The use of allograft tissue avoids the donor site morbidity and reduces the operating time, expense and trauma associated with the acquisition of autografts. Further, allografts have the added advantage of being available in large quantities. This has led to a global increase in allogeneic transplantation and development of tissue banking. However, the risk of infectious disease transmission via tissue allografts is a major concern. Therefore, tissue allografts should be sterilized to make them safe for clinical use. Radiation processing has well appreciated technological advantages and is the most suitable method for sterilization of biological tissues. Radiation processed biological tissues can be provided by the tissue banks for the management of injuries due to a nuclear disaster. A nuclear detonation will result in a large number of casualties due to the heat, blast and radiation effects of the weapon. Skin dressings or skin substitutes like allograft skin, xenograft skin and amniotic membrane can be used for the treatment of thermal burns and radiation induced skin injuries. Bone grafts can be employed for repairing fracture defects, filling in destroyed regions of bone, management of open fractures and joint injuries. Radiation processed tissues have the potential to repair or reconstruct damaged tissues and can be of great assistance in the treatment of injuries due to the nuclear weapon. (author)

  4. Analogous simulation of nutrient transformation processes in stream ...

    African Journals Online (AJOL)

    The main transformation processes effected by the natural microbial consortium of upper Iskar River with predominant participation of sediment biofilm were simulated in the laboratory by the use of portable devices (chambers). The dynamics of real heterotrophic respiration, organic matter oxidation, denitrification and ...

  5. Combined heterogeneous Electro-Fenton and biological process for the treatment of stabilized landfill leachate.

    Science.gov (United States)

    Baiju, Archa; Gandhimathi, R; Ramesh, S T; Nidheesh, P V

    2018-03-15

    Treatment of stabilized landfill leachate is a great challenge due to its poor biodegradability. Present study made an attempt to treat this wastewater by combining electro-Fenton (E-Fenton) and biological process. E-Fenton treatment was applied prior to biological process to enhance the biodegradability of leachate, which will be beneficial for the subsequent biological process. This study also investigates the efficiency of iron molybdophosphate (FeMoPO) nanoparticles as a heterogeneous catalyst in E-Fenton process. The effects of initial pH, catalyst dosage, applied voltage and electrode spacing on Chemical Oxygen Demand (COD) removal efficiency were analyzed to determine the optimum conditions. Heterogeneous E-Fenton process gave 82% COD removal at pH 2, catalyst dosage of 50 mg/L, voltage 5 V, electrode spacing 3 cm and electrode area 25 cm 2 . Combined E-Fenton and biological treatment resulted an overall COD removal of 97%, bringing down the final COD to 192 mg/L. Copyright © 2018 Elsevier Ltd. All rights reserved.

  6. Simulation and Analysis of Complex Biological Processes: an Organisation Modelling Perspective

    NARCIS (Netherlands)

    Bosse, T.; Jonker, C.M.; Treur, J.

    2005-01-01

    This paper explores how the dynamics of complex biological processes can be modelled and simulated as an organisation of multiple agents. This modelling perspective identifies organisational structure occurring in complex decentralised processes and handles complexity of the analysis of the dynamics

  7. Using Simple Manipulatives to Improve Student Comprehension of a Complex Biological Process: Protein Synthesis

    Science.gov (United States)

    Guzman, Karen; Bartlett, John

    2012-01-01

    Biological systems and living processes involve a complex interplay of biochemicals and macromolecular structures that can be challenging for undergraduate students to comprehend and, thus, misconceptions abound. Protein synthesis, or translation, is an example of a biological process for which students often hold many misconceptions. This article…

  8. Influence of trace elements on the activity of some microbiological processes in soil

    Energy Technology Data Exchange (ETDEWEB)

    Maliszewska, W

    1972-01-01

    It was found that N fixation was stimulated by B, Zn, Mo and Co. Fe and Cu had an evident inhibiting and Cd even toxic influence on this process. Zn and Fe stimulated proteolase activity. Mo showed almost no effect on that process. The other microelements used had a more or less inhibiting influence. Ammonification was affected with B and Mo. The other treatments had different hampering effects on that process. The nitrifyers were mostly stimulated by Fe and Al. The other microelements B, Zn, Mo and Mn, stimulated the development of nitifyers, but to a lesser degree. Cu and Cd were toxic. The highest intensity of denitrification was found without any microelement addition. The most distinct inhibition of the process was caused by Cu, Zn, and Co. Hemicellulose decomposition activity was very sensitive to a deficiency of microelements investigated. Only Zn and Mo inhibited this process. In general Cu and Cd showed the most inhibiting effect on all the biological processes investigated in the experiments. The highest stimulatory effect in all experiments was caused by B and Mo. 5 references, 4 figures, 1 table.

  9. A consilience model to describe N2O production during biological N removal

    DEFF Research Database (Denmark)

    Domingo Felez, Carlos; Smets, Barth F.

    2016-01-01

    Nitrous oxide (N2O), a potent greenhouse gas, is produced during biological nitrogen conversion in wastewater treatment operations. Complex mechanisms underlie N2O production by autotrophic and heterotrophic organisms, which continue to be unravelled. Mathematical models that describe nitric oxide...... (NO) and N2O dynamics have been proposed. Here, a first comprehensive model that considers all relevant NO and N2O production and consumption mechanisms is proposed. The model describes autotrophic NO production by ammonia oxidizing bacteria associated with ammonia oxidation and with nitrite reduction......, followed by NO reduction to N2O. It also considers NO and N2O as intermediates in heterotrophic denitrification in a 4-step model. Three biological NO and N2O production pathways are accounted for, improving the capabilities of existing models while not increasing their complexity. Abiotic contributions...

  10. Microbial nitrogen sinks in the water column of a large coastal hypoxic area, the Gulf of Mexico "Dead Zone"

    Science.gov (United States)

    Rogener, M. K.; Roberts, B. J.; Rabalais, N. N.; Stewart, F. J.; Joye, S. B.

    2016-02-01

    Excess nitrogen in coastal environments leads to eutrophication, harmful algal blooms, habitat loss, oxygen depletion and reductions in biodiversity. As such, biological nitrogen (N) removal through the microbially-mediated process of denitrification is a critical ecosystem function that can mitigate the negative consequences of excess nitrogen loading. However, denitrification can produce nitrous oxide, a potent greenhouse gas, as a byproduct under some environmental conditions. To understand how excess nitrogen loading impacts denitrification, we measured rates of this process in the water column of the Gulf of Mexico "Dead Zone" three times over the summer of 2015. The Dead Zone is generated by excessive nitrogen loading from the Mississippi River co-occurring with strong water column stratification, which leads to a large summer-time hypoxic/anoxic area at the mouth of the river and along the coast of Louisiana. Rates of denitrification ranged from 31 to 153 nmol L-1 d-1. Dead Zone waters are also enriched in methane and aerobic methane oxidation rates ranged from 0.1 to 4.3 nmol L-1 d-1. Maximal denitrification rates were observed at stations with the lowest oxygen concentrations and highest methane oxidation rates, suggesting a potential coupling between nitrate reduction and methane oxidation which both scrubs reactive N and methane from the system, thus performing a duel ecosystem service.

  11. Waste water biological purification plants of dairy products industry and energy management

    Science.gov (United States)

    Stepanov, Sergey; Solkina, Olga; Stepanov, Alexander; Zhukova, Maria

    2017-10-01

    The paper presents results of engineering and economical comparison of waste water biological purification plants of dairy products industry. Three methods of purification are compared: traditional biological purification with the use of secondary clarifiers and afterpurification through granular-bed filters, biomembrane technology and physical-and-chemical treatment together with biomembrane technology for new construction conditions. The improvement of the biological purification technology using nitro-denitrification and membrane un-mixing of sludge mixture is a promising trend in this area. In these calculations, an energy management which is widely applied abroad was used. The descriptions of the three methods are illustrated with structural schemes. Costs of equipment and production areas are taken from manufacturers’ data. The research is aimed at an engineering and economical comparison of new constructions of waste water purification of dairy products industry. The experiment demonstrates advantages of biomembrane technology in waste water purification. This technology offers prospects of 122 million rubles cost saving during 25 years of operation when compared with of the technology of preparatory reagent flotation and of 13.7 million rubles cost saving compared to the option of traditional biological purification.

  12. Moving beyond a descriptive aquatic toxicology: the value of biological process and trait information.

    Science.gov (United States)

    Segner, Helmut

    2011-10-01

    In order to improve the ability to link chemical exposure to toxicological and ecological effects, aquatic toxicology will have to move from observing what chemical concentrations induce adverse effects to more explanatory approaches, that are concepts which build on knowledge of biological processes and pathways leading from exposure to adverse effects, as well as on knowledge on stressor vulnerability as given by the genetic, physiological and ecological (e.g., life history) traits of biota. Developing aquatic toxicology in this direction faces a number of challenges, including (i) taking into account species differences in toxicant responses on the basis of the evolutionarily developed diversity of phenotypic vulnerability to environmental stressors, (ii) utilizing diversified biological response profiles to serve as biological read across for prioritizing chemicals, categorizing them according to modes of action, and for guiding targeted toxicity evaluation; (iii) prediction of ecological consequences of toxic exposure from knowledge of how biological processes and phenotypic traits lead to effect propagation across the levels of biological hierarchy; and (iv) the search for concepts to assess the cumulative impact of multiple stressors. An underlying theme in these challenges is that, in addition to the question of what the chemical does to the biological receptor, we should give increasing emphasis to the question how the biological receptor handles the chemicals, i.e., through which pathways the initial chemical-biological interaction extends to the adverse effects, how this extension is modulated by adaptive or compensatory processes as well as by phenotypic traits of the biological receptor. 2011 Elsevier B.V. All rights reserved.

  13. Image processing and recognition for biological images.

    Science.gov (United States)

    Uchida, Seiichi

    2013-05-01

    This paper reviews image processing and pattern recognition techniques, which will be useful to analyze bioimages. Although this paper does not provide their technical details, it will be possible to grasp their main tasks and typical tools to handle the tasks. Image processing is a large research area to improve the visibility of an input image and acquire some valuable information from it. As the main tasks of image processing, this paper introduces gray-level transformation, binarization, image filtering, image segmentation, visual object tracking, optical flow and image registration. Image pattern recognition is the technique to classify an input image into one of the predefined classes and also has a large research area. This paper overviews its two main modules, that is, feature extraction module and classification module. Throughout the paper, it will be emphasized that bioimage is a very difficult target for even state-of-the-art image processing and pattern recognition techniques due to noises, deformations, etc. This paper is expected to be one tutorial guide to bridge biology and image processing researchers for their further collaboration to tackle such a difficult target. © 2013 The Author Development, Growth & Differentiation © 2013 Japanese Society of Developmental Biologists.

  14. The potential of the innovative SeMPAC process for enhancing the removal of recalcitrant organic micropollutants

    Energy Technology Data Exchange (ETDEWEB)

    Alvarino, T., E-mail: teresa.alvarino@usc.es [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Komesli, O. [Ataturk University, Department of Environmental Engineering, 25250 Erzurum (Turkey); Middle East Technical University, Department of Environmental Engineering, 06531 Ankara (Turkey); Suarez, S., E-mail: sonia.suarez@usc.es [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Lema, J.M., E-mail: juan.lema@usc.es [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain); Omil, F., E-mail: francisco.omil@usc.es [Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2016-05-05

    Highlights: • Complete OMPs mass balance in a combined system biological treatment plus PAC. • Improvement of the denitrification after PAC addition. • Enhancement of OMPs biotransformation after PAC addition. • Relation between hydrophobicity (log D) and sorption onto the PAC. • Progressive saturation of the activated carbon in the solid phase with the time. - Abstract: SeMPAC is an innovative process based on a membrane sequential batch reactor to which powdered activated carbon (PAC) is directly added. It was developed with the aim of obtaining a high quality effluent in terms of conventional pollutants and organic micropollutants (OMPs). High COD removal and nitrification efficiencies (>95%) were obtained already during the operation without PAC, although denitrification was enhanced by PAC addition. OMPs were followed in the solid and liquid matrixes so that biotransformation, sorption onto the sludge and adsorption onto the PAC could be assessed. Recalcitrant compounds, such as carbamazepine and diazepam, were readily removed only after PAC addition (>99%). Progressive saturation of PAC was observed, with increasing concentrations of OMPs in the solid phase. Removal efficiencies for recalcitrant compounds were used as indicators for new additions of PAC. An improvement in the moderately biodegradable OMPs removal was observed after PAC addition (e.g. fluoxetine, trimethoprim) which was attributed to the biofilm that grew onto the sorbent, as well as to adsorption onto PAC.

  15. Complementary constraints from carbon (13C) and nitrogen (15N) isotopes on the glacial ocean's soft-tissue biological pump

    Science.gov (United States)

    Schmittner, A.; Somes, C. J.

    2016-06-01

    A three-dimensional, process-based model of the ocean's carbon and nitrogen cycles, including 13C and 15N isotopes, is used to explore effects of idealized changes in the soft-tissue biological pump. Results are presented from one preindustrial control run (piCtrl) and six simulations of the Last Glacial Maximum (LGM) with increasing values of the spatially constant maximum phytoplankton growth rate μmax, which accelerates biological nutrient utilization mimicking iron fertilization. The default LGM simulation, without increasing μmax and with a shallower and weaker Atlantic Meridional Overturning Circulation and increased sea ice cover, leads to 280 Pg more respired organic carbon (Corg) storage in the deep ocean with respect to piCtrl. Dissolved oxygen concentrations in the colder glacial thermocline increase, which reduces water column denitrification and, with delay, nitrogen fixation, thus increasing the ocean's fixed nitrogen inventory and decreasing δ15NNO3 almost everywhere. This simulation already fits sediment reconstructions of carbon and nitrogen isotopes relatively well, but it overestimates deep ocean δ13CDIC and underestimates δ15NNO3 at high latitudes. Increasing μmax enhances Corg and lowers deep ocean δ13CDIC, improving the agreement with sediment data. In the model's Antarctic and North Pacific Oceans modest increases in μmax result in higher δ15NNO3 due to enhanced local nutrient utilization, improving the agreement with reconstructions there. Models with moderately increased μmax fit both isotope data best, whereas large increases in nutrient utilization are inconsistent with nitrogen isotopes although they still fit the carbon isotopes reasonably well. The best fitting models reproduce major features of the glacial δ13CDIC, δ15N, and oxygen reconstructions while simulating increased Corg by 510-670 Pg compared with the preindustrial ocean. These results are consistent with the idea that the soft-tissue pump was more efficient

  16. Nitrogen Removal from Milking Center Wastewater via Simultaneous Nitrification and Denitrification Using a Biofilm Filtration Reactor

    Directory of Open Access Journals (Sweden)

    Seung-Gun Won

    2015-06-01

    Full Text Available Milking center wastewater (MCW has a relatively low ratio of carbon to nitrogen (C/N ratio, which should be separately managed from livestock manure due to the negative impacts of manure nutrients and harmful effects on down-stream in the livestock manure process with respect to the microbial growth. Simultaneous nitrification and denitrification (SND is linked to inhibition of the second nitrification and reduces around 40% of the carbonaceous energy available for denitrification. Thus, this study was conducted to find the optimal operational conditions for the treatment of MCW using an attached-growth biofilm reactor; i.e., nitrogen loading rate (NLR of 0.14, 0.28, 0.43, and 0.58 kg m−3 d−1 and aeration rate of 0.06, 0.12, and 0.24 m3 h−1 were evaluated and the comparison of air-diffuser position between one-third and bottom of the reactor was conducted. Four sand packed-bed reactors with the effective volume of 2.5 L were prepared and initially an air-diffuser was placed at one third from the bottom of the reactor. After the adaptation period of 2 weeks, SND was observed at all four reactors and the optimal NLR of 0.45 kg m−3 d−1 was found as a threshold value to obtain higher nitrogen removal efficiency. Dissolved oxygen (DO as one of key operational conditions was measured during the experiment and the reactor with an aeration rate of 0.12 m3 h−1 showed the best performance of NH4-N removal and the higher total nitrogen removal efficiency through SND with appropriate DO level of ~0.5 mg DO L−1. The air-diffuser position at one third from the bottom of the reactor resulted in better nitrogen removal than at the bottom position. Consequently, nitrogen in MCW with a low C/N ratio of 2.15 was successfully removed without the addition of external carbon sources.

  17. Impact of glacial/interglacial sea level change on the ocean nitrogen cycle

    Science.gov (United States)

    Ren, Haojia; Sigman, Daniel M.; Martínez-García, Alfredo; Anderson, Robert F.; Chen, Min-Te; Ravelo, Ana Christina; Straub, Marietta; Wong, George T. F.; Haug, Gerald H.

    2017-08-01

    The continental shelves are the most biologically dynamic regions of the ocean, and they are extensive worldwide, especially in the western North Pacific. Their area has varied dramatically over the glacial/interglacial cycles of the last million years, but the effects of this variation on ocean biological and chemical processes remain poorly understood. Conversion of nitrate to N2 by denitrification in sediments accounts for half or more of the removal of biologically available nitrogen (“fixed N”) from the ocean. The emergence of continental shelves during ice ages and their flooding during interglacials have been hypothesized to drive changes in sedimentary denitrification. Denitrification leads to the occurrence of phosphorus-bearing, N-depleted surface waters, which encourages N2 fixation, the dominant N input to the ocean. An 860,000-y record of foraminifera shell-bound N isotopes from the South China Sea indicates that N2 fixation covaried with sea level. The N2 fixation changes are best explained as a response to changes in regional excess phosphorus supply due to sea level-driven variations in shallow sediment denitrification associated with the cyclic drowning and emergence of the continental shelves. This hypothesis is consistent with a glacial ocean that hosted globally lower rates of fixed N input and loss and a longer residence time for oceanic fixed N—a “sluggish” ocean N budget during ice ages. In addition, this work provides a clear sign of sea level-driven glacial/interglacial oscillations in biogeochemical fluxes at and near the ocean margins, with implications for coastal organisms and ecosystems.

  18. Batch studies on nitrate removal from potable water | Darbi | Water SA

    African Journals Online (AJOL)

    A sulphur / limestone autotrophic denitrification process was used to achieve the biological removal of nitrate from groundwater. The feasibility of the system was evaluated under anaerobic conditions using laboratory-scale batch reactors. The optimum sulphur / limestone ratio was determined to be 1:1 (wt/wt). Different ...

  19. Short Horizon Control Strategies for an Alternating Activated Sludge Process

    DEFF Research Database (Denmark)

    Isaacs, Steven Howard

    1996-01-01

    Three control strategies allowing improved operational flexibility of an alternating type activated sludge process are presented in a unified model based framework. The control handles employed are the addition rate of an external carbon source to denitrification, the cycle length, and the dissol...

  20. Combined ion exchange / biological denitrification for nitrate removal from ground water

    NARCIS (Netherlands)

    Hoek, van der J.P.

    1988-01-01

    This thesis deals with the development of a new process for nitrate removal from ground water. High nitrate concentrations in ground water are a result of fertilization in agriculture. According to a directive of the European Community the maximum admissible concentration of nitrate in