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Sample records for waterloo denitrification barrier

  1. Long term performance of the Waterloo denitrification barrier

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, W.D.; Cherry, J.A. [Univ. of Waterloo, Ontario (Canada)

    1997-12-31

    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{sup -}{sub 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.

  2. Institutional Motivations and Barriers to the Construction of Green Buildings on Campus: A Case Study of the University of Waterloo, Ontario

    Science.gov (United States)

    Richardson, Gregory R. A.; Lynes, Jennifer K.

    2007-01-01

    Purpose: To explore the barriers and motivations to the construction of green buildings at the University of Waterloo (UW) by documenting and analysing the UW building process. Design/methodology/approach: The authors conducted 13 semi-structured in-depth interviews with key UW individuals as well as analyzing numerous internal reports in order to…

  3. Applying Reactive Barrier Technology to Enhance Microbially-mediated Denitrification during Managed Aquifer Recharge

    Science.gov (United States)

    Beganskas, S.; Weir, W. B.; Harmon, R. E.; Gorski, G.; Fisher, A. T.; Saltikov, C.; Young, K. S.; Runneals, D.; Teo, E. K.; Stoneburner, B.; Hernandez, J.

    2015-12-01

    We are running field experiments to observe and quantify microbially-mediated water quality improvement via denitrification during infiltration in the shallow subsurface. Nitrate is a pervasive groundwater contaminant, and nitrate removal through denitrification can occur during infiltration in natural and anthropogenic systems, including during managed aquifer recharge (MAR). The rate of denitrification can vary depending on factors such as infiltration rate; previous work suggests that denitrification rates can increase monotonically with infiltration rates until reaching a critical threshold. We are performing controlled field tests of variables that affect denitrification rate, including sampling to link water chemistry changes to microbial ecology and activity. This study explores how microbial activity and denitrification rates respond to different infiltration rates and the presence or absence of a reactive material (wood chips, a carbon source). We are conducting four two-week-long tests, each under different conditions. For each test, we measure bulk infiltration rate (the sum of lateral and vertical infiltration), vertical infiltration rate using heat as a tracer, and water level. We collect surface and subsurface water samples daily, and we collect soil samples at the start and end of each test. For each water sample, we are measuring NO3-, NO2-, NH3, DOC, and N and O isotopes in nitrate. Soil samples will be tested for grain size, total C/N, and the presence of microbiological genes associated with denitrification. These results will expand our knowledge of the conditions under which denitrification occurs by implicating specific microorganisms and physical infiltration parameters. Our design has the potential for additional experimentation with variables that impact water chemistry during infiltration. This study has broad applications for designing MAR systems that effectively improve water supply and water quality.

  4. Forging Collaborative Partnerships: The Waterloo Neighborhood Project.

    Science.gov (United States)

    Gruenewald, Anne

    The Forging Collaborative Partnerships Project in Waterloo, Iowa is a collaborative venture to assist voluntary agencies in developing tools and strategies to strengthen collaborative relationships among public and nonprofit child welfare agencies and other key stakeholders as they adopt a family-focused philosophy. This monograph details how the…

  5. Historical Air Photo Digitization Project University of Waterloo Map Library

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    Eva Dodsworth

    2008-12-01

    Full Text Available The University Map Library (UML at the University of Waterloo developed an onlinecollection of digitized and georeferenced aerial photography of the Kitchener-Waterlooarea from the 1930s and 1940s. Using GIS technology, the air photos were digitizedwith geographical coordinate tags for use in GIS software programs including onlinemapping applications such as Google Earth (GE. By creating and offeringdownloadable georeferenced images compatible with popular mapping tools, the airphotos have gained significant popularity and utilization by not only regular library usersbut by community groups, organizations and corporations who have never used libraryresources before. The integration of modern technology with traditional paper mappinghas proven to be both a method of preservation and a means of increasing and varyingutilization of the collection.

  6. University of Waterloo's Historical Air Photo Digitization Project

    Directory of Open Access Journals (Sweden)

    Eva Dodsworth

    2008-12-01

    Full Text Available The University of Waterloo Map Library is a cartographic and GIS academic resource centre to academics, community organizations and interested members of the local community. With a collection of over 100,000 maps, 49,000 air photos and being the campus’ hub for geospatial data, the library is frequented by many user groups and individuals – serving a variety of interests and purposes. Until most recently, many of these users were able to only access the collection in person, during library hours. Now, one of the library’s most popular paper collection used by the local community, the historical aerial photographs, have become available online for users to view and download from their home and business computers. The Map Library’s air photo collection includes stereoscopic images of the Region of Waterloo taken as early as 1930 to as recent as 1995. The air photos are widely used by students, business contractors, history buffs and home owners who like to study the air photos for land cover, property information, feature identification and changes in these over time. Due to several access limitations, the Map Library wanted to provide the community with easier access, available 24/7 and remotely from the internet. The Map Library scanned, digitized, and georeferenced photos from the 1930s and 1940s and uploaded them to a website that provides easy access for viewing and downloading the imagery. Using GIS technology, the air photos were digitized with geographical coordinate tags for use in GIS software programs including online mapping applications such as Google Earth (GE. By creating and offering downloadable georeferenced images compatible with popular mapping tools, the air photos have gained significant popularity and utilization by not only regular library users but by community groups, organizations and corporations who have never used library resources in the past. The integration of modern technology with traditional paper

  7. Place Branding – Geographical Approach. Case Study: Waterloo

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    Marius-Cristian Neacşu

    2016-11-01

    Full Text Available This study represents an exploratory analysis of the evolution of the place branding concept, with an important focus on the geographical perspective. How has this notion, a newcomer into the geographers' analysis, changed over time and what role does it have in the decision making process of intervening into the way a certain place is organised or as an instrument of economic revival and territorial development? At least from the perspective of Romanian geographical literature, the originality and novelty of this study is obvious. An element of the originality of this research is the attempt of redefining the concept of place branding so that it is more meaningful from the perspective of spatial analyses. The reason for which Waterloo was chosen as a case study is multi-dimensional: the case studies so far have mainly focused on large cities (urban branding instead of place branding and this site has all the theoretical elements to create a stand-alone brand.

  8. 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.

    . The degree of denitrification decreases steadily southward. The results indicate that denitrification extends up to 11 or 12 degrees N latitude. Taking 30 years as the average residence time of water for the layer in which denitrification occurs...

  9. 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

  10. Denitrification in Sinorhizobium meliloti.

    Science.gov (United States)

    Torres, María J; Rubia, María I; Bedmar, Eulogio J; Delgado, María J

    2011-12-01

    Denitrification is the complete reduction of nitrate or nitrite to N2, via the intermediates nitric oxide (NO) and nitrous oxide (N2O), and is coupled to energy conservation and growth under O2-limiting conditions. In Bradyrhizobium japonicum, this process occurs through the action of the napEDABC, nirK, norCBQD and nosRZDFYLX gene products. DNA sequences showing homology with nap, nirK, nor and nos genes have been found in the genome of the symbiotic plasmid pSymA of Sinorhizobium meliloti strain 1021. Whole-genome transcriptomic analyses have demonstrated that S. meliloti denitrification genes are induced under micro-oxic conditions. Furthermore, S. meliloti has also been shown to possess denitrifying activities in both free-living and symbiotic forms. Despite possessing and expressing the complete set of denitrification genes, S. meliloti is considered a partial denitrifier since it does not grow under anaerobic conditions with nitrate or nitrite as terminal electron acceptors. In the present paper, we show that, under micro-oxic conditions, S. meliloti is able to grow by using nitrate or nitrite as respiratory substrates, which indicates that, in contrast with anaerobic denitrifiers, O2 is necessary for denitrification by S. meliloti. Current knowledge of the regulation of S. meliloti denitrification genes is also included.

  11. Spatial analysis of participation in the Waterloo Residential Energy Efficiency Project

    Science.gov (United States)

    Song, Ge Bella

    Researchers are in broad agreement that energy-conserving actions produce economic as well as energy savings. Household energy rating systems (HERS) have been established in many countries to inform households of their house's current energy performance and to help reduce their energy consumption and greenhouse gas emissions. In Canada, the national EnerGuide for Houses (EGH) program is delivered by many local delivery agents, including non-profit green community organizations. Waterloo Region Green Solutions is the local non-profit that offers the EGH residential energy evaluation service to local households. The purpose of this thesis is to explore the determinants of household's participation in the residential energy efficiency program (REEP) in Waterloo Region, to explain the relationship between the explanatory variables and REEP participation, and to propose ways to improve this kind of program. A spatial (trend) analysis was conducted within a geographic information system (GIS) to determine the spatial patterns of the REEP participation in Waterloo Region from 1999 to 2006. The impact of sources of information on participation and relationships between participation rates and explanatory variables were identified. GIS proved successful in presenting a visual interpretation of spatial patterns of the REEP participation. In general, the participating households tend to be clustered in urban areas and scattered in rural areas. Different sources of information played significant roles in reaching participants in different years. Moreover, there was a relationship between each explanatory variable and the REEP participation rates. Statistical analysis was applied to obtain a quantitative assessment of relationships between hypothesized explanatory variables and participation in the REEP. The Poisson regression model was used to determine the relationship between hypothesized explanatory variables and REEP participation at the CDA level. The results show that

  12. Epidemiology of Enteric Disease in C-EnterNet’s Pilot Site – Waterloo Region, Ontario, 1990 to 2004

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    Victoria A Keegan

    2009-01-01

    Full Text Available OBJECTIVE: The objective of the present study was to describe the epidemiology of reportable enteric illness in Ontario’s Waterloo region, including comparing calculated incidence rates with published rates, and adjusting for under-reporting to determine the number of community cases, where published data were available.

  13. Denitrification characteristics of a sulfur autotrophic denitrification reactor

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    Chenxiao ZHANG

    2016-02-01

    Full Text Available The denitrification characteristics of a sulfur autotrophic denitrification reactor are investigated. The results show that domestication of sulfur autotrophic bacteria is completed within 15 days after biofilm formation in the reactor, which is shorter than other similar researches. The nitrogen removal rate remains over than 90%, and the denitrification rate reaches 18.5 mg N/(L·h with influent NO-3-N of 70 mg/L , influent pH of 8 and HRT of 4.3 h . Thiobacillus denitrificans are observed in the whole reactor when domestication finishes, while it is more abundant in the middle and lower part. The optimal influent NO-3-N concentration for the reactor is 50 mg/L, the optimal temperature is 30~35 ℃, the optimal influent pH is 7~8, and the nitrogen removal rate is over than 90%.

  14. 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.

  15. Denitrification in human dental plaque

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    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.

  16. The enzymes associated with denitrification

    Science.gov (United States)

    Hochstein, L. I.; Tomlinson, G. A.

    1988-01-01

    The enzymes involved in the reduction of nitrogenous oxides are thought to be intermediates in denitrification processes. This review examines the roles of nitrate reductase, nitrite reductases, nitric oxide reductase, mechanisms of N-N bond formation, and nitrous oxide reductases.

  17. 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 Reef...... consumption and N-2 production. The N:O-2 slope of 0.114 implied that about 75% of all the nitrogen mineralized was denitrified. A 4-fold increase in sediment column length (from 10 to 40 cm) resulted in an overall increase in oxygen consumption (1.6-fold), TCO2 production (1.8-fold), and denitrification (1...... enhance the development of microniches (i.e., steep oxygen gradients) within porous carbonate sands, perhaps providing optimum conditions for denitrification. The denitrification peak fell within the broad range of advection rates (often on scales of 1-100 L m(-2) h(-1)) typically found on continental...

  18. Food consumption patterns in the Waterloo Region, Ontario, Canada: a cross-sectional telephone survey

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    Cook Angela

    2008-10-01

    Full Text Available Abstract Background The demographics and lifestyles of Canadians are changing, thereby influencing food choices and food preparation in the home. Although different dietary practices are associated with increased risk of foodborne illness, our ability to evaluate food consumption trends and assess risks associated with foodborne illness is limited by lack of data on current eating habits and consumer food safety practices. The objective of this study was to describe, for the first time, the food consumption patterns in a Canadian-based population from a food safety perspective, in order to establish baseline data on actual food intake of individuals. Method A cross-sectional telephone survey of 2,332 randomly selected residents of Waterloo Region, Ontario, Canada (C-EnterNet pilot site was conducted between November 2005 and March 2006. Food intake was assessed using a 7-day dietary recall method. Results Certain food items were consumed more than others among the same food groups, and consumption of many food items varied by gender and age. Specific foods considered high-risk for the transmission of certain enteric pathogens were significantly more likely to be consumed by males (i.e. unpasteurized juice, bean sprouts, and undercooked meat and elderly individuals (i.e. undercooked eggs. The majority of households prepared and consumed most meals at home, allocating an average of 44 minutes to prepare a meal. Conclusion Baseline data on actual food intake is useful to public health professionals and food safety risk assessors for developing communication messages to consumers and in foodborne outbreak investigations.

  19. The impacts of hypnotic susceptibility on chaotic dynamics of EEG signals during standard tasks of Waterloo-Stanford Group Scale.

    Science.gov (United States)

    Yargholi, Elahe'; Nasrabadi, Ali Motie

    2013-05-01

    Chaotic features of hypnotic EEG (electroencephalograph), recorded during standard tasks of Waterloo-Stanford Group Scale of hypnotic susceptibility (WSGS), were used to investigate the underlying dynamic of tasks and analyse the effect of hypnotic depth and concentration on EEG signals. Results demonstrate: (1) More efficiency of Higuchi dimension in comparison with Correlation dimension to distinguish subjects from different hypnotizable groups, (2) Channels with significantly different chaotic features among people from various hypnotizability levels in tasks, (3) High level of consistency among discriminating channels of tasks with function of brain's lobes, (4) Most affectability of medium hypnotizable subjects and (5) Rise in fractal dimensions due to increase in hypnosis depth.

  20. Great Historical Events That Were Significantly Affected by the Weather. Part 11: Meteorological Aspects of the Battle of Waterloo.

    Science.gov (United States)

    Neumann, J.

    1993-03-01

    The Waterloo Campaign extended from 15 to 18 June 1815, with the decisive Battle of Waterloo taking place on the 18th. The campaign involved the "Army of the North" of Napoleon on the one hand, and the Anglo-Dutch and Prussian armies on the other. The latter were commanded, respectively, by the Duke of Wellington and Prince Blücher. A shallow but active low and associated warm and cold fronts crossed the battle area on the 16th and 17th.The weather had important effects on the battles. On the 16th, in a battle between part of the French army and part of the Prussian army, at the village of Ligny, about 40 km south-southeast of Brussels, thunderstorms connected with the passage of the aforementioned warm front made the use of muskets impracticable.However, the most important weather effects developed on the 17th and during the night from the 17th to the 18th. Violent thunderstorms occurred early in the afternoon of the 17th close to Ligny, while Napoleon was in the process of attacking the Anglo-Dutch force at Quatre Bras. The rains turned the ground into a quagmire, making it impossible for the French artillery and cavalry, and even for the infantry, to move across the fields in extended order, as required by the emperor. The French advance was so greatly slowed down that Wellington was able to withdraw his lighter force to a better position near Waterloo. Thus, the Anglo-Dutch force was almost completely preserved for the decisive battle of the next day.The rainshowers of the 17th and the night from the 17th to the 18th softened the ground to an extent that, on the morning of the 18th, Napoleon and his artillery experts judged that the battle-the Battle of Waterloo-could not be started before a late hour of the forenoon [1130 local standard time (LST)]. Until the arrival of the Prussian force, about 1600 LST and later, the battle tended to go in favor of the French, but the Prussians turned the tide of the fighting.The paper quotes judgments of military

  1. Denitrification of nitrate waste solutions

    Energy Technology Data Exchange (ETDEWEB)

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

    1976-04-26

    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.

  2. ENVIRONMENTAL TECHNOLOGY VERIFICATION: JOINT (NSF-EPA) VERIFICATION STATEMENT AND REPORT FOR THE REDUCTION OF NITROGEN IN DOMESTIC WASTEWATER FROM INDIVIDUAL RESIDENTIAL HOMES, WATERLOO BIOFILTER® MODEL 4-BEDROOM (NSF 02/03/WQPC-SWP)

    Science.gov (United States)

    Verification testing of the Waterloo Biofilter Systems (WBS), Inc. Waterloo Biofilter® Model 4-Bedroom system was conducted over a thirteen month period at the Massachusetts Alternative Septic System Test Center (MASSTC) located at Otis Air National Guard Base in Bourne, Mas...

  3. Natural Denitrification in the Saturated Zone: A Review

    Science.gov (United States)

    Korom, Scott F.

    1992-06-01

    Denitrification is increasingly recognized for its ability to eliminate or reduce nitrate concentrations in groundwater. With this awareness comes a desire to predict the rate and extent of denitrification in aquifers. The limiting factor in making predictive models, however, is our limited knowledge of the physical characteristics of this process. This review synthesizes the published literature on natural aquifer denitrification. A background section discusses denitrification requirements and dissimilatory nitrate reduction to ammonium, which occurs in environments similar to those where denitrification occurs, and gives a historical perspective on denitrification. Other sections discuss denitrification with organic carbon serving as the electron donor (heterotrophic denitrification) and with reduced inorganic compounds serving as the electron donor (autotrophic denitrification). The section on heterotrophic denitrification is structured around two tables that summarize natural aquifer denitrification rates reported by laboratory studies and natural aquifer denitrification rates reported by field studies. The section on autotrophic denitrification discusses denitrification with reduced iron and reduced sulfur. Thus far, most studies only consider a single electron donor or donor type, whether heterotrophic or autotrophic. This review demonstrates, however, that multiple electron donors may be present in a given aquifer. Future research efforts are recommended to determine the factors affecting the availability of electron donors and their denitrification rates. Additional research is also suggested on how dissolved oxygen affects denitrification rates and on the factors influencing the partitioning of nitrate reduction products to nitrous oxide, a potential contributor to the destruction of the ozone layer, and to ammonium.

  4. Denitrification in marine shales in northeastern Colorado

    Science.gov (United States)

    McMahon, P.B.; Böhlke, J.K.; Bruce, B.W.

    1999-01-01

    Parts of the South Platte River alluvial aquifer in northeastern Colorado are underlain by the Pierre Shale, a marine deposit of Late Cretaceous age that is water in the aquifer is contaminated with NO3/-, and the shale contains abundant potential electron donors for denitrification in the forms of organic carbon and sulfide minerals. Nested piezometers were sampled, pore water was squeezed from cores of shale, and an injection test was conducted to determine if denitrification in the shale was a sink for alluvial NO3/- and to measure denitrification rates in the shale. Measured values of NO3/-, N2, NH4/+, ??15[NO3/-], ??15N[N2], and ??15N[NH4/+] in the alluvial and shale pore water indicated that denitrification in the shale was a sink for alluvial NO3/-. Chemical gradients, reaction rate constants, and hydraulic head data indicated that denitrification in the shale was limited by the slow rate of NO3/- transport (possibly by diffusion) into the shale. The apparent in situ first-order rate constant for denitrification in the shale based on diffusion calculations was of the order of 0.04-0.4 yr-1, whereas the potential rate constant in the shale based on injection tests was of the order of 60 yr-1. Chemical data and mass balance calculations indicate that organic carbon was the primary electron donor for denitrification in the shale during the injection test, and ferrous iron was a minor electron donor in the process. Flux calculations for the conditions encountered at the site indicate that denitrification in the shale could remove only a small fraction of the annual agricultural NO3/- input to the alluvial aquifer. However, the relatively large potential first-order rate constant for denitrification in the shale indicated that the percentage of NO3/- uptake by the shale could be considerably larger in areas where NO3/- is transported more rapidly into the shale by advection.

  5. The potential of dairy wastewater for denitrification

    Directory of Open Access Journals (Sweden)

    Tibela Landeka Dragičević

    2010-09-01

    Full Text Available In this work the potential of dairy wastewater for denitrification process by means of a microbial culture of nitrificants and denitrificants was investigated. The aim of this work was to remove nitrate by using organic compounds from the dairy wastewater as an electron donors. The minimal ratio of COD/NO3-N of 10 (COD-chemical oxygen demand/NO3-N-nitrate nitrogen was required to achieve complete reduction of NO3-N. The microbial culture of nitrificants and denitrificants, that was previously adapted on the dairy wastewater, carried out nitrate reduction with a different substrate utilization rate. The denitrification rate of 5.75 mg NO3-N/Lh was achieved at the beginning of denitrification when the microbial culture utilizes readily biodegradable COD. Further degradation occurred with the denitrification rate of 1.7 mg NO3-N/Lh.

  6. Denitrification processes in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.

    Recent information on some consequences of the acute mid-water oxygen deficiency in the Arabian Sea, especially on carbon-nitrogen cycling, is reviewed. An evaluation of published estimates of water column denitrification rate suggests an overall...

  7. Temperature effect on aerobic denitrification and nitrification

    Institute of Scientific and Technical Information of China (English)

    XIE Shu-guang; ZHANG Xiao-jian; WANG Zhan-sheng

    2003-01-01

    Nitrogen loss without organic removal in biofilter was observed and its possible reason was explained. A lower hydraulic loading could improve aerobic denitrification rate. Aerobic denitrification was seriously affected by low temperature(below 10oC). However, nitrification rate remained high when the temperature dropped from 15oC to5oC. It seemed the autotrophic biofilm in BAF could alleviate the adverse effect of low temperature.

  8. Modeling nitrate removal in a denitrification bed.

    Science.gov (United States)

    Ghane, Ehsan; Fausey, Norman R; Brown, Larry C

    2015-03-15

    Denitrification beds are promoted to reduce nitrate load in agricultural subsurface drainage water to alleviate the adverse environmental effects associated with nitrate pollution of surface water. In this system, drainage water flows through a trench filled with a carbon media where nitrate is transformed into nitrogen gas under anaerobic conditions. The main objectives of this study were to model a denitrification bed treating drainage water and evaluate its adverse greenhouse gas emissions. Field experiments were conducted at an existing denitrification bed. Evaluations showed very low greenhouse gas emissions (mean N2O emission of 0.12 μg N m(-2) min(-1)) from the denitrification bed surface. Field experiments indicated that nitrate removal rate was described by Michaelis-Menten kinetics with the Michaelis-Menten constant of 7.2 mg N L(-1). We developed a novel denitrification bed model based on the governing equations for water flow and nitrate removal kinetics. The model evaluation statistics showed satisfactory prediction of bed outflow nitrate concentration during subsurface drainage flow. The model can be used to design denitrification beds with efficient nitrate removal which in turn leads to enhanced drainage water quality.

  9. Denitrification mechanism in combustion of biocoal briquettes.

    Science.gov (United States)

    Kim, Heejoon; Li, Tianji

    2005-02-15

    Pulp black liquor (PBL), an industrial waste from paper production, has been previously shown to be an effective binder and denitrification agent for coal briquettes. This study investigated the denitrification mechanism of PBL in both the volatile combustion and char combustion stages of coal briquettes. X-ray diffraction and ion chromatography were used to analyze the residual ashes of combustion. The exhaust gas was analyzed by a flue gas analysis system and a Q-mass spectrometry system. The denitrification mechanism of PBL in the volatile combustion stage was found to result from the emission of NH3. The denitrification of PBL in the char combustion stage was associated with the NaOH contained in PBL. The direct reaction of NaOH with NO gas was examined, and some interesting phenomena were observed. Pure carbon or pure NaOH showed only limited reaction with NO. However, the mixture of NaOH and carbon (NaOH + C) significantly enhanced the reaction. This mixture increased the NO removal up to 100%. Subsequently, denitrification lasted for a long time period, with about 25% of NO removal. The pyrolysis characteristic of NaNO3, a compound resulting from denitrification, was also affected by the presence of carbon. In the presence of carbon, the NOx emission resulting from the pyrolysis of NaNO3 was reduced by a factor of 6. Since the denitrification phenomena appeared only in the absence of oxygen, a model of oxygen distribution in a burning coal briquette was employed to explain the reactions occurring in real combustion of coal briquettes.

  10. The Extent of Denitrification in Long Island Groundwater using MIMS

    Science.gov (United States)

    Young, C.; Hanson, G. N.; Kroeger, K. D.

    2009-12-01

    Long Island drinking water is provided by a sole source aquifer with nitrate levels in some North Shore communities approaching or exceeding the drinking water standard of 10 mgL-1. Previous workers, using mass balance approaches, suggested that the primary source of nitrogen is sewage effluent and observed a 50% deficit of nitrate in Long Island’s groundwater system. We analyzed dissolved N2/Ar ratios in groundwater from wells to determine if groundwater denitrification is the cause of the nitrogen deficit at two locations where septic tanks are used for sewage treatment and the effluent leaches to the groundwater; a suburban community on the north shore of Long Island (Northport, NY) and parkland on a barrier island at the south shore of Long Island (Watch Hill, Fire Island National Seashore). In Northport we found 0 to 20 % of the nitrate in groundwater denitrified with excess N-NO3- concentrations ranging from 0 to 1.5 mgL-1. These samples had concentrations high in dissolved oxygen (DO), 6 to 11 mgL-1, and low in dissolved organic carbon (DOC), 0.4 to 2.8 mgL-1. At Watch Hill nitrogen is primarily retained as ammonium or dissolved organic nitrogen. Where nitrate is formed, we found up to 99% denitrification. Excess N-NO3- ranged from 0 to 8 mgL-1 with concentrations low in DO, 0.3 to 3.4 mgL-1, and high in DOC, 5.3 to 18.4 mgL-1. The vadose zone in the Northport area has an average thickness of 10-100 feet whereas at Watch Hill it is 1 - 2 feet thick. We hypothesize that the vadose zone thickness affects the extent of denitrification by controlling the amount of DOC and DO that reaches the groundwater. A thick vadose zone allows for more extensive interaction of infiltrating sewage effluent with atmospheric oxygen in the vadose zone which oxidizes DOC. In Northport groundwater has high DO, low DOC and essentially no denitrification leaving 2 to 11 mgL-1 N-NO3- remaining. At the Watch Hill site a thin vadose zone below the sewage leach field provides

  11. Inhibition of denitrification by ultraviolet radiation

    Science.gov (United States)

    Mancinelli, R. L.; White, M. R.

    It has been shown that UV-A (λ = 320- 400 nm) and UV-B (λ = 280 - 320 nm) inhibit photosynthesis, nitrogen fixation and nitrification. The purpose of this study was to determine the effects, if any, on denitrification in a microbial community inhabiting the intertidal. The community studied is the microbial mat consisting primarily of Lyngbya that inhabits the Pacific marine intertidal, Baja California, Mexico. Rates of denitrification were determined using the acetylene blockage technique. Pseudomonas fluorescens (ATCC # 17400) was used as a control organism, and treated similarly to the mat samples. Samples were incubated either beneath a PAR transparent, UV opaque screen (OP3), or a mylar screen to block UV-B, or a UV transparent screen (UVT) for 2 to 3 hours. Sets of samples were also treated with nitrapyrin to inhibit nitrification, or DCMU to inhibit photosynthesis and treated similarly. Denitrification rates were greater in the UV protected samples than in the UV exposed samples the mat samples as well as for the Ps. fluorescens cultures. Killed controls exhibited no activity. In the DCMU and nitrapyrin treated samples denitrification rates were the same as in the untreated samples. These data indicate that denitrification is directly inhibited by UV radiation.

  12. Denitrification potential enhancement by addition of external carbon sources in a pre-denitrification process

    Institute of Scientific and Technical Information of China (English)

    PENG Yong-zhen; MA Yong; WANG Shu-ying

    2007-01-01

    The aim of this study is to investigate the denitrification potential enhancement by addition of external carbon sources and to estimate the denitrification potential for the predenitrification system using nitrate utilization rate(NUR)batch tests.It is shown that the denitrification potential Can be substantially increased with the addition of three external carbon sources,i.e.methanol,ethanol,and acetate.and the denitrification rates of ethanol,acetate,and methanol reached up to 9.6,12,and 3.2 mgN/(gVSS·h),respectively,while mat of starch wastewater was only 0.74 mgN/(gVSS·h).By comparison,ethanol was found to be the best extemal carbon source.NUR batch tests with starch wastewater and waste ethanol were carried out.The denitrification potential increased from 5.6 to 16.5 mg NO.-N/L owing to waste ethanol addition.By means of NUR tests,the wastewater characteristics and kinetic parameters can be estimated.which are used to determine the denitrification potential of wastewater,to calculate the denitrification potential of the plant and to predict the nitrate effluent quality,as well as provide information for developing carbon dosage conlxol strategy.

  13. The kinetics of denitrification in permeable sediments

    DEFF Research Database (Denmark)

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

    2013-01-01

    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...

  14. 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

  15. Enhanced Denitrification in Roadside Ditches with Bioreactors

    Science.gov (United States)

    Pluer, W.; Schneider, R.; Walter, M. T.

    2016-12-01

    Nitrate (NO3) pollution remains a water quality problem in agriculture-dominated watersheds despite decades of research and concerted efforts. Excess NO3 causes eutrophication in estuarine and marine ecosystems far downstream of the pollution source. Denitrification reduces NO3 to inert dinitrogen gas; this process occurs naturally in saturated areas of the landscape but this rate cannot keep up with the runoff rate due to fertilizer and manure applications. Researchers developed denitrifying bioreactors as a solution to encourage denitrification at the field level. Denitrifying bioreactors remove NO3 at a significantly higher rate (>2 g N m-2 d-1) than natural systems such as wetlands (<0.5 g N m-2 d-1). Most current designs of denitrifying bioreactors necessitate connection with tile drainage as the inflow source of water and NO3. It also requires a portion of farmland (typically <1% of field area is needed) which farmers can be reluctant to relinquish. Meanwhile, road ditches commonly run along agricultural fields, channeling runoff and NO3 to surface water. Because the ditches are designed to avoid flooding, they channel water rapidly and minimize time and contact with soil microbes for denitrification (denitrification rates in ditches are typically <0.1 g N m-2 d-1). Modified denitrifying bioreactors placed in road ditches could provide high NO3 removal in already marginal land, especially at baseflow conditions. A pilot study of this shows instantaneous NO3 removal rates up to 110 g N m-2 d-1 in the first year. Continued results similar to this pilot study and wider application could significantly increase ditch denitrification and help mitigate NO3 pollution.

  16. 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;pbioreactors to achieve significant N load reductions in large watersheds. The nitrate reduction rate as a function of groundwater temperature for all treatments. Correlations between nitrate reduction rate and properties of carbon media;

  17. Genetic basis for denitrification in Ensifer meliloti.

    Science.gov (United States)

    Torres, Maria J; Rubia, Maria I; de la Peña, Teodoro Coba; Pueyo, José J; Bedmar, Eulogio J; Delgado, María J

    2014-06-02

    Denitrification is defined as the dissimilatory reduction of nitrate or nitrite to nitric oxide (NO), nitrous oxide (N2O), or dinitrogen gas (N2). N2O is a powerful atmospheric greenhouse gas and cause of ozone layer depletion. Legume crops might contribute to N2O production by providing nitrogen-rich residues for decomposition or by associating with rhizobia that are able to denitrify under free-living and symbiotic conditions. However, there are limited direct empirical data concerning N2O production by endosymbiotic bacteria associated with legume crops. Analysis of the Ensifer meliloti 1021 genome sequence revealed the presence of the napEFDABC, nirK, norECBQD and nosRZDFYLX denitrification genes. It was recently reported that this bacterium is able to grow using nitrate respiration when cells are incubated with an initial O2 concentration of 2%; however, these cells were unable to use nitrate respiration when initially incubated anoxically. The involvement of the nap, nirK, nor and nos genes in E. meliloti denitrification has not been reported. E. meliloti nap, nirK and norC mutant strains exhibited defects in their ability to grow using nitrate as a respiratory substrate. However, E meliloti nosZ was not essential for growth under these conditions. The E. meliloti napA, nirK, norC and nosZ genes encode corresponding nitrate, nitrite, nitric oxide and nitrous oxide reductases, respectively. The NorC component of the E. meliloti nitric oxide reductase has been identified as a c-type cytochrome that is 16 kDa in size. Herein, we also show that maximal expression of the E. meliloti napA, nirK, norC and nosZ genes occurred when cells were initially incubated anoxically with nitrate. The E. meliloti napA, nirK, norC and nosZ genes are involved in nitrate respiration and in the expression of denitrification enzymes in this bacterium. Our findings expand the short list of rhizobia for which denitrification gene function has been demonstrated. The inability of E

  18. Impact of Aquifer Heterogeneities on Autotrophic Denitrification.

    Science.gov (United States)

    McCarthy, A.; Roques, C.; Selker, J. S.; Istok, J. D.; Pett-Ridge, J. C.

    2015-12-01

    Nitrate contamination in groundwater is a big challenge that will need to be addressed by hydrogeologists throughout the world. With a drinking water standard of 10mg/L of NO3-, innovative techniques will need to be pursued to ensure a decrease in drinking water nitrate concentration. At the pumping site scale, the influence and relationship between heterogeneous flow, mixing, and reactivity is not well understood. The purpose of this project is to incorporate both physical and chemical modeling techniques to better understand the effect of aquifer heterogeneities on autotrophic denitrification. We will investigate the link between heterogeneous hydraulic properties, transport, and the rate of autotrophic denitrification. Data collected in previous studies in laboratory experiments and pumping site scale experiments will be used to validate the models. The ultimate objective of this project is to develop a model in which such coupled processes are better understood resulting in best management practices of groundwater.

  19. Biological denitrification in a fluidized bed.

    Science.gov (United States)

    Narjari, N K; Khilar, K C; Mahajan, S P

    1984-12-01

    A fluidized bed biofilm reactor using sand as the carrier particle was employed to study the effects of superficial velocity on the removal of nitrates as well as on the growth of the biofilm. Velocity was found to affect significantly both nitrate removal and biofilm growth. An analysis based on heterogenous catalysis was used to describe the denitrification process. There is good agreement between analysis and experimental measurements for startup and steady-state operating conditions.

  20. Denitrification in upland of China: Magnitude and influencing factors

    Science.gov (United States)

    Wang, Jinyang; Yan, Xiaoyuan

    2016-12-01

    A better understanding of influencing factors and accurate estimate of soil denitrification is a global concern. Here we present a synthesis of 300 observations of denitrification in Chinese upland soils from 39 field and laboratory studies using the acetylene inhibition technique. The results of a linear mixed model analysis showed that the rates of soil denitrification were significantly affected by crop type, soil organic carbon, soil pH, the measurement period, and the rate of N application. The emission factor (EF) and N2O/(N2O + N2) ratio for soil denitrification were on average 2.11 ± 0.17% and 0.508 ± 0.020, respectively. Our meta-analysis indicated that N fertilization increased soil denitrification by 311% (95% CI: 279-346%) and 112% (95% CI: 66-171%) in the field and laboratory studies, respectively. Substantial interactive effects between soil properties and N fertilization on soil denitrification were found. Although the highest values of both the rate of denitrification and the EF were found in vegetable fields, the size of the stimulating effect of N fertilization on soil denitrification was lower in vegetable fields than in maize and wheat fields. These results suggest that the crop-specific effect is important and that vegetable fields are potential hot spots of denitrification in Chinese uplands. Based on either the EF or the N2O/(N2O + N2) ratio obtained, the estimated amount of total denitrification from the upland soils was an order of magnitude lower than that from budget calculations, suggesting that the acetylene inhibition technique may significantly underestimate denitrification in Chinese upland soils.

  1. Reductive denitrification of nitrate by scrap iron filings

    Institute of Scientific and Technical Information of China (English)

    HAO Zhi-wei; XU Xin-hua; WANG Da-hui

    2005-01-01

    Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed.

  2. 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.

  3. A PRELIMINARY EXPERIMENT ON DENITRIFICATION OF WASTE LANDFILL LEACHATE

    Science.gov (United States)

    Wada, Nariaki; Nakamichi, Tamihiro; Yagi, Masahiro; Matsumoto, Toshihide; Kugimiya, Akikazu; Michioku, Kohji

    A laboratory experiment on denitrification was carried out in order to reduce nitrogen load from municipal landfill leachate. Nitrogen was efficiently removed by feeding sludge of the leachate pond into the tanks, which could activate denitrification bacteria. Although inorganic reducing agent such as iron powder was not able to make the whole water mass anoxic, denitrification took place by supplying organic matters such as methanol, hydrogen feeding agent, etc.. It is considered that small amount of anoxic water film produced on surfaces of container and carriers might contribute to denitrification, although the bulk water is kept aerobic. It is found that organic matters contained in the leachate is so insufficient that nitrification liquid circulation does not work well for denitrification.

  4. 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.

  5. Analysis and monitoring of a denitrification process; Analyse et controle d`un procede de denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Bourrel, S.V.; Babary, J.P.; Dochain, D.

    1995-12-31

    The working of a denitrification fixed bed bioreactor strongly depends on time and location of observing point, resulting in partial differential equations systems for the functional model. This model has to be simplified to perform efficient computerized simulation. The simplifying method chosen is orthogonal collocation (belonging to to ponderated residues class methods). Then, Runge-Kutta method was used to perform open loop simulation. (D.L.) 18 refs.

  6. Study on Soil Denitrification in Wheat-Maize Rotation System

    Institute of Scientific and Technical Information of China (English)

    ZOU Guo-yuan; ZHANG Fu-suo; JU Xiao-tang; CHEN Xin-ping; LIU Xue-jun

    2006-01-01

    Soil denitrification was studied in wheat-maize rotation cropping system on an aquic cambisol. Results showed that the N loss amount by denitrification ranged from 4.7 to 9.7 kg per hectare with different levels of nitrogen application and the key stage for denitification was during summer maize-growth-period, especially within 1-2 weeks after fertilizer nitrogen was applied. Similar trend was found between soil N2O production/emission dynamic and denitrification dynamic in the rotation system, which may indicate that mainly N2O is produced in nitrification process.

  7. The Denitrification Characteristics and Microbial Community in the Cathode of an MFC with Aerobic Denitrification at High Temperatures.

    Science.gov (United States)

    Zhao, Jianqiang; Wu, Jinna; Li, Xiaoling; Wang, Sha; Hu, Bo; Ding, Xiaoqian

    2017-01-01

    Microbial fuel cells (MFCs) have attracted much attention due to their ability to generate electricity while treating wastewater. The performance of a double-chamber MFC with simultaneous nitrification and denitrification (SND) in the cathode for treating synthetic high concentration ammonia wastewater was investigated at different dissolved oxygen (DO) concentrations and high temperatures. The results showed that electrode denitrification and traditional heterotrophic denitrification co-existed in the cathode chamber. Electrode denitrification by aerobic denitrification bacterium (ADB) is beneficial for achieving a higher voltage of the MFC at high DO concentrations (3.0-4.2 mg/L), while traditional heterotrophic denitrification is conducive to higher total nitrogen (TN) removal at low DO (0.5-1.0 mg/L) concentrations. Under high DO conditions, the nitrous oxide production and TN removal efficiency were higher with a 50 Ω external resistance than with a 100 Ω resistance, which demonstrated that electrode denitrification by ADB occurred in the cathode of the MFC. Sufficient electrons were inferred to be provided by the electrode to allow ADB survival at low carbon:nitrogen ratios (≤0.3). Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) results showed that increasing the DO resulted in a change of the predominant species from thermophilic autotrophic nitrifiers and facultative heterotrophic denitrifiers at low DO concentrations to thermophilic ADB at high DO concentrations. The predominant phylum changed from Firmicutes to Proteobacteria, and the predominant class changed from Bacilli to Alpha, Beta, and Gamma Proteobacteria.

  8. Heterotrophic denitrification of aquaculture effluent using fluidized sand biofilters

    Science.gov (United States)

    The ability to consistently and cost-effectively reduce nitrate-nitrogen loads in effluent from recirculating aquaculture systems would enhance the industry's environmental stewardship and allow improved facility proximity to large markets in sensitive watersheds. Heterotrophic denitrification techn...

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

    DEFF Research Database (Denmark)

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

    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...... 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 (may produce View the Math......ML source and once the O2 has been depleted denitrification will follow resulting in enormous rates per unit 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...

  10. Denitrification and a nitrogen budget of created riparian wetlands.

    Science.gov (United States)

    Batson, Jacqulyn A; Mander, Ulo; Mitsch, William J

    2012-01-01

    Riparian wetland creation and restoration have been proposed to mediate nitrate-nitrogen (NO-N) pollution from nonpoint agricultural runoff. Denitrification by anaerobic microbial communities in wetland soils is believed to be one of the main sinks for NO-N as it flows through wetlands. Denitrification rates were quantified using an in situ acetylene inhibition technique at 12 locations in three wetland/riverine sites at the Olentangy River Wetland Research Park, Columbus, Ohio for 1 yr. Sites included two created flow-through experimental wetlands and one bottomland forest/river-edge site. Points were spatially distributed at inflows, center, and outflows of the two wetlands to include permanently flooded open water, intermittently flooded transitions, and upland. Annual denitrification rates (median [mean]) were significantly higher ( wetlands (266 [415] μg NO-N m h) than in shallower transition zones (58 [37.5] μg NO-N m h). Median wetland transition zone denitrification rates did not differ significantly ( ≥ 0.05) from riverside or upland sites. Denitrification rates peaked in spring; for the months of April through June, median denitrification rates ranged from 240 to 1010 μg NO-N m h in the permanently flooded zones. A N mass balance analysis showed that surface water flux of N was reduced by 57% as water flowed through the wetland, but only about 3.5% of the N inflow was permanently removed through denitrification. Most N was probably lost through groundwater seepage. Comparison with denitrification rates measured previously in these wetlands suggests that these rates have remained steady over the past 4 to 5 yr.

  11. Evaluation of the denitrification rate of terraced paddy fields

    Science.gov (United States)

    Onishi, Takeo; Nakamura, Kimihito; Horino, Haruhiko; Adachi, Toru; Mitsuno, Toru

    2012-05-01

    SummaryRice is one of the most important staple foods in the world. Lowland paddy fields are well known for functioning as denitrification areas, but few studies have been conducted of paddy fields situated on hill slopes (terraced paddy fields). These terraced paddy fields have a characteristic artificial stepped shape, and this unique shape and periodic ponding from rice production may configure unique hydrological properties that might be different from lowland paddy fields. The shape and hydrological properties may also affect transport of nutrients such as nitrogen. This study is particularly focused on the denitrification rate in terraced paddy fields. To understand the hydrological properties of terraced paddy fields, a detailed water budget including the subsurface flow components was calculated. Combining the water budget components and chemical measurements of surface and subsurface water, a nitrogen budget was calculated. The results showed that about 10% of the total nitrogen input, mainly from fertilizers, was lost, suggesting the occurrence of denitrification in the area. The average denitrification rate of the study site was estimated at about 0.53-0.67 g N m-2 year-1. Spatial variations in the measured groundwater nitrate concentration suggest that denitrification is important in both the plough layer and the sloping area. The denitrification rate in the sloping area was estimated at 0.67-0.78 g N m-2 year-1, which is slightly higher than the estimates of denitrification rate in paddy lots, i.e., 0.56-0.61 g N m-2 year-1. The result indicates the importance of sloping areas for denitrification in terraced paddy fields.

  12. Denitrification likely catalyzed by endobionts in an allogromiid foraminifer.

    Science.gov (United States)

    Bernhard, Joan M; Edgcomb, Virginia P; Casciotti, Karen L; McIlvin, Matthew R; Beaudoin, David J

    2012-05-01

    Nitrogen can be a limiting macronutrient for carbon uptake by the marine biosphere. The process of denitrification (conversion of nitrate to gaseous compounds, including N(2) (nitrogen gas)) removes bioavailable nitrogen, particularly in marine sediments, making it a key factor in the marine nitrogen budget. Benthic foraminifera reportedly perform complete denitrification, a process previously considered nearly exclusively performed by bacteria and archaea. If the ability to denitrify is widespread among these diverse and abundant protists, a paradigm shift is required for biogeochemistry and marine microbial ecology. However, to date, the mechanisms of foraminiferal denitrification are unclear, and it is possible that the ability to perform complete denitrification is because of the symbiont metabolism in some foraminiferal species. Using sequence analysis and GeneFISH, we show that for a symbiont-bearing foraminifer, the potential for denitrification resides in the endobionts. Results also identify the endobionts as denitrifying pseudomonads and show that the allogromiid accumulates nitrate intracellularly, presumably for use in denitrification. Endobionts have been observed within many foraminiferal species, and in the case of associations with denitrifying bacteria, may provide fitness for survival in anoxic conditions. These associations may have been a driving force for early foraminiferal diversification, which is thought to have occurred in the Neoproterozoic era when anoxia was widespread.

  13. A Network Biology Approach to Denitrification in Pseudomonas aeruginosa

    Science.gov (United States)

    Arat, Seda; Bullerjahn, George S.; Laubenbacher, Reinhard

    2015-01-01

    Pseudomonas aeruginosa is a metabolically flexible member of the Gammaproteobacteria. Under anaerobic conditions and the presence of nitrate, P. aeruginosa can perform (complete) denitrification, a respiratory process of dissimilatory nitrate reduction to nitrogen gas via nitrite (NO2), nitric oxide (NO) and nitrous oxide (N2O). This study focuses on understanding the influence of environmental conditions on bacterial denitrification performance, using a mathematical model of a metabolic network in P. aeruginosa. To our knowledge, this is the first mathematical model of denitrification for this bacterium. Analysis of the long-term behavior of the network under changing concentration levels of oxygen (O2), nitrate (NO3), and phosphate (PO4) suggests that PO4 concentration strongly affects denitrification performance. The model provides three predictions on denitrification activity of P. aeruginosa under various environmental conditions, and these predictions are either experimentally validated or supported by pertinent biological literature. One motivation for this study is to capture the effect of PO4 on a denitrification metabolic network of P. aeruginosa in order to shed light on mechanisms for greenhouse gas N2O accumulation during seasonal oxygen depletion in aquatic environments such as Lake Erie (Laurentian Great Lakes, USA). Simulating the microbial production of greenhouse gases in anaerobic aquatic systems such as Lake Erie allows a deeper understanding of the contributing environmental effects that will inform studies on, and remediation strategies for, other hypoxic sites worldwide. PMID:25706405

  14. Factors Controlling Sediment Denitrification Rates in Grassland and Forest Streams

    Directory of Open Access Journals (Sweden)

    Haryun Kim

    2014-01-01

    Full Text Available Sediment denitrification is an important nitrate (NO3- removal process from agricultural streams. The direct and indirect factors that control denitrification rates in tributary sediments can vary depending on the types of agricultural activities and vegetation. Our research investigated (1 tributary sediment denitrification rates in a grassland stream affected by pasture ecosystems and a forest stream affected by N fertilization; and (2 the environmental factors that determine denitrification rates in tributary sediments. The denitrification enzyme activity (DEA in grassland stream sediments is positively correlated with precipitation likely due to the increased nutrient exchange rates between stream water and sediments, and was higher than in forest stream sediments, leading to a decrease in NO3- concentration ([NO3-] in stream sediments. The DEA in riparian sediments was regulated by carbon concentrations and did not contribute to NO3- removal from the riparian sediment in grassland and forest streams. Thus, environmental factors affected by different types of agricultural activities and vegetation might regulate denitrification rates and [NO3-] in agricultural stream ecosystems.

  15. 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.

  16. Does denitrification occur within porous carbonate sand grains?

    Directory of Open Access Journals (Sweden)

    P. L. M. Cook

    2017-09-01

    Full Text Available Permeable carbonate sands form a major habitat type on coral reefs and play a major role in organic matter recycling. Nitrogen cycling within these sediments is likely to play a major role in coral reef productivity, yet it remains poorly studied. Here, we used flow-through reactors and stirred reactors to quantify potential rates of denitrification and the dependence of denitrification on oxygen concentrations in permeable carbonate sands at three sites on Heron Island, Australia. Our results showed that potential rates of denitrification fell within the range of 2–28 µmol L−1 sediment h−1 and were very low compared to oxygen consumption rates, consistent with previous studies of silicate sands. Denitrification was observed to commence at porewater oxygen concentrations as high as 50 µM in stirred reactor experiments on the coarse sediment fraction (2–10 mm and at oxygen concentrations of 10–20 µM in flow-through and stirred reactor experiments at a site with a median sediment grain size of 0.9 mm. No denitrification was detected in sediments under oxic conditions from another site with finer sediment (median grain size: 0.7 mm. We interpret these results as confirmation that denitrification may occur within anoxic microniches present within porous carbonate sand grains. The occurrence of such microniches has the potential to enhance denitrification rates within carbonate sediments; however further work is required to elucidate the extent and ecological significance of this effect.

  17. The Denitrification Characteristics and Microbial Community in the Cathode of an MFC with Aerobic Denitrification at High Temperatures

    Science.gov (United States)

    Zhao, Jianqiang; Wu, Jinna; Li, Xiaoling; Wang, Sha; Hu, Bo; Ding, Xiaoqian

    2017-01-01

    Microbial fuel cells (MFCs) have attracted much attention due to their ability to generate electricity while treating wastewater. The performance of a double-chamber MFC with simultaneous nitrification and denitrification (SND) in the cathode for treating synthetic high concentration ammonia wastewater was investigated at different dissolved oxygen (DO) concentrations and high temperatures. The results showed that electrode denitrification and traditional heterotrophic denitrification co-existed in the cathode chamber. Electrode denitrification by aerobic denitrification bacterium (ADB) is beneficial for achieving a higher voltage of the MFC at high DO concentrations (3.0–4.2 mg/L), while traditional heterotrophic denitrification is conducive to higher total nitrogen (TN) removal at low DO (0.5–1.0 mg/L) concentrations. Under high DO conditions, the nitrous oxide production and TN removal efficiency were higher with a 50 Ω external resistance than with a 100 Ω resistance, which demonstrated that electrode denitrification by ADB occurred in the cathode of the MFC. Sufficient electrons were inferred to be provided by the electrode to allow ADB survival at low carbon:nitrogen ratios (≤0.3). Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) results showed that increasing the DO resulted in a change of the predominant species from thermophilic autotrophic nitrifiers and facultative heterotrophic denitrifiers at low DO concentrations to thermophilic ADB at high DO concentrations. The predominant phylum changed from Firmicutes to Proteobacteria, and the predominant class changed from Bacilli to Alpha, Beta, and Gamma Proteobacteria. PMID:28154554

  18. 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.

  19. Microbial Community Structure and Denitrification in a Wetland Mitigation Bank▿

    Science.gov (United States)

    Peralta, Ariane L.; Matthews, Jeffrey W.; Kent, Angela D.

    2010-01-01

    Wetland mitigation is implemented to replace ecosystem functions provided by wetlands; however, restoration efforts frequently fail to establish equivalent levels of ecosystem services. Delivery of microbially mediated ecosystem functions, such as denitrification, is influenced by both the structure and activity of the microbial community. The objective of this study was to compare the relationship between soil and vegetation factors and microbial community structure and function in restored and reference wetlands within a mitigation bank. Microbial community composition was assessed using terminal restriction fragment length polymorphism targeting the 16S rRNA gene (total bacteria) and the nosZ gene (denitrifiers). Comparisons of microbial function were based on potential denitrification rates. Bacterial community structures differed significantly between restored and reference wetlands; denitrifier community assemblages were similar among reference sites but highly variable among restored sites throughout the mitigation bank. Potential denitrification was highest in the reference wetland sites. These data demonstrate that wetland restoration efforts in this mitigation bank have not successfully restored denitrification and that differences in potential denitrification rates may be due to distinct microbial assemblages observed in restored and reference (natural) wetlands. Further, we have identified gradients in soil moisture and soil fertility that were associated with differences in microbial community structure. Microbial function was influenced by bacterial community composition and soil fertility. Identifying soil factors that are primary ecological drivers of soil bacterial communities, especially denitrifying populations, can potentially aid the development of predictive models for restoration of biogeochemical transformations and enhance the success of wetland restoration efforts. PMID:20453124

  20. Nitrate removal with lateral flow sulphur autotrophic denitrification reactor.

    Science.gov (United States)

    Lv, Xiaomei; Shao, Mingfei; Li, Ji; Xie, Chuanbo

    2014-01-01

    An innovative lateral flow sulphur autotrophic denitrification (LFSAD) reactor was developed in this study; the treatment performance was evaluated and compared with traditional sulphur/limestone autotrophic denitrification (SLAD) reactor. Results showed that nitrite accumulation in the LFSAD reactor was less than 1.0 mg/L during the whole operation. Denitrification rate increased with the increased initial alkalinity and was approaching saturation when initial alkalinity exceeded 2.5 times the theoretical value. Higher influent nitrate concentration could facilitate nitrate removal capacity. In addition, denitrification efficiency could be promoted under an appropriate reflux ratio, and the highest nitrate removal percentage was achieved under reflux ratio of 200%, increased by 23.8% than that without reflux. Running resistance was only about 1/9 of that in SLAD reactor with equal amount of nitrate removed, which was the prominent excellence of the new reactor. In short, this study indicated that the developed reactor was feasible for nitrate removal from waters with lower concentrations, including contaminated surface water, groundwater or secondary effluent of municipal wastewater treatment with fairly low running resistance. The innovation in reactor design in this study may bring forth new ideas of reactor development of sulphur autotrophic denitrification for nitrate-contaminated water treatment.

  1. Enzyme diversity and mosaic gene organization in denitrification.

    Science.gov (United States)

    Zumft, W G; Körner, H

    1997-02-01

    Denitrification is a main branch of the global nitrogen cycle. In the past ten years unravelling the underlying biochemistry and genetics has proceeded at an increasing pace. Fungal denitrification has become a new field. The biochemical investigation of denitrification has culminated in the description of the crystal structures of the two types of nitrite reductases. The N2O reductase shares with cytochrome c oxidase the CuA center as a structurally novel metal site. The cytochrome b subunit of NO reductase has a striking conservation of heme-binding transmembrane segments versus the subunit I of cytochrome c oxidase. Another putative denitrification gene product shows structural relation to the subunit III of the oxidase. N2O reductase and NO reductase may be ancestors of energy-conserving enzymes of the heme-copper oxidase superfamily. More than 30 genes for denitrification are located in a > 30-kb cluster in Pseudomonas stutzeri, and comparable gene clusters have been identified in Pseudomonas aeruginosa and Paracoccus denitrificans. Genes necessary for nitrite reduction and NO reduction have a mosaic arrangement with very few conserved locations within these clusters and relative to each other.

  2. [Study on hydrogen autotrophic denitrification of bio-ceramic reactor].

    Science.gov (United States)

    Chen, Dan; Wang, Hong-Yu; Song, Min; Yang, Kai; Liu, Chen

    2013-10-01

    Nitrate wastewater is processed in a bio-ceramic reactor based on hydrogen autotrophic denitrification. The implementation procedure of biological denitrification by hydrogen autotrophic denitrification was investigated. The effects of hydraulic retention time, influent nitrate load, influent pH, temperature and the amount of hydrogen were assessed throughout this trial. The results showed that the removal rate of NO-(3) -N was 94. 54% and 97. 47% when the hydraulic retention time was 24 h and 48 h, respectively. When the hydraulic retention time was in the range of 5-16 h, the removal rate gradually dropped with the shortening of the hydraulic retention time. When the influent NO-(3) -N concentration was low, with the increase in the influent NO-(3) -N concentration, the degradation rate also increased. The denitrification was inhibited when the NO-(3) -N concentration was higher than 110 mg.L-1. Neutral and alkaline environment was more suitable for the reactor. The reactor showed a wide range of temperature adaptation and the optimum temperature of the reactor was from 25 to 30 degrees C. When hydrogen was in short supply, the effect of denitrification was significantly reduced. These results indicated the specificity of hydrogen utilization by the denitrifying bacteria. The effluent nitrite nitrogen concentration was maintained at low levels during the operation.

  3. 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.

  4. How Do Vegetation Density and Transportation Network Density Affect Crime across an Urban Central-Peripheral Gradient? A Case Study in Kitchener—Waterloo, Ontario

    Directory of Open Access Journals (Sweden)

    Yikang Du

    2016-07-01

    Full Text Available The relationship between vegetation, transportation networks, and crime has been under debate. Vegetation has been positively correlated with fear of crime; however, the actual correlation between vegetation and occurrences of crime is uncertain. Transportation networks have also been connected with crime occurrence but their impact on crime tends to vary over different circumstances. By conducting spatial analyses, this study explores the associations between crime and vegetation as well as transportation networks in Kitchener-Waterloo. Further, geographically weighted regression modeling and a dummy urban variable representing the urban center/other urban areas were employed to explore the associations across an urban central-peripheral gradient. Associations were analyzed for crimes against persons and crimes against property for four specific crime types (assaults, vehicle theft, sex offences, and drugs. Results suggest that vegetation has a reverse association with crimes against persons and crimes against property while transportation networks have a positive relationship with these two types of crime. Additionally, vegetation can be a deterrent to vehicle theft crime and drugs, while transportation networks can be a facilitator of drug-related crimes. Besides, these two associations appear stronger in the urban center compared to the urban periphery.

  5. Nitrification and denitrification as sources of gaseous nitrogen emission from different forest soils in Changbai Mountain

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The contributions of nitrification and denitrification to N2O and N2 emissions from four forest soils on northern slop of Changbai Mountain were measured with acetylene inhibition methods. In incubation experiments, 0.06% and 3% C2H2 were used to inhibit nitrification and denitrification in these soils, respectively. Both nitrification and denitification existed in these soils except tundra soil, where only denitrification was found. The annually averaged rates of nitrification and denitrification in mountain dark brown forest soil were much higher than that in other three soils. In mountain brown coniferous soil, contributions of different processes to gaseous nitrogen emissions were Denitrification N2O > Nitrification N2O > Denitrification N2. The same sequence exists in mountain soddy soil as that in the mountain brown coniferous soil. The sequence in mountain tundra soil was Denitrification N2O > Denitrification N2.

  6. Anammox transited from denitrification in upflow biofilm reactor

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shao-hui; ZHENG Ping; HUA Yu-mei

    2004-01-01

    Anammox was successfully transited from heterotrophic denitrification and autotrophic denitrification in two upflow biofilm reactors, respectively. The results showed that the volumetric loading rate and nitrogen removal efficiency in the reactor transited from heterotrophic denitrification were higher than that in its counterpart. When the hydraulic retention time was 12 h or so, the total nitrogen loading rate was about 0.609 kg N/(m3·d), and the effluent ammonia and nitrite concentrations were less than 8.5 mg/L and 2.5 mg/L, respectively. The upflow anammox biofilm reactor was capable of keeping and accumulating the slow-growing bacteria efficiently. During operation of the reactor, the biomass color was gradually turned from brownish to red, and the ratio of ammonia consumption, nitrite consumption and nitrate production approached the theoretical one. These changes could be used as an indicator for working state of the reactor.

  7. 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.

  8. Denitrification 'Woodchip' Bioreactors for Productive and Sustainable Agricultural Systems

    Science.gov (United States)

    Christianson, L. E.; Summerfelt, S.; Sharrer, K.; Lepine, C.; Helmers, M. J.

    2014-12-01

    Growing alarm about negative cascading effects of reactive nitrogen in the environment has led to multifaceted efforts to address elevated nitrate-nitrogen levels in water bodies worldwide. The best way to mitigate N-related impacts, such as hypoxic zones and human health concerns, is to convert nitrate to stable, non-reactive dinitrogen gas through the natural process of denitrification. This means denitrification technologies need to be one of our major strategies for tackling the grand challenge of managing human-induced changes to our global nitrogen cycle. While denitrification technologies have historically been focused on wastewater treatment, there is great interest in new lower-tech options for treating effluent and drainage water from one of our largest reactive nitrogen emitters -- agriculture. Denitrification 'woodchip' bioreactors are able to enhance this natural N-conversion via addition of a solid carbon source (e.g., woodchips) and through designs that facilitate development of anoxic conditions required for denitrification. Wood-based denitrification technologies such as woodchip bioreactors and 'sawdust' walls for groundwater have been shown to be effective at reducing nitrate loads in agricultural settings around the world. Designing these systems to be low-maintenance and to avoid removing land from agricultural production has been a primary focus of this "farmer-friendly" technology. This presentation provides a background on woodchip bioreactors including design considerations, N-removal performance, and current research worldwide. Woodchip bioreactors for the agricultural sector are an accessible new option to address society's interest in improving water quality while simultaneously allowing highly productive agricultural systems to continue to provide food in the face of increasing demand, changing global diets, and fluctuating weather.

  9. 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.

    , as reflected by the distribu- tion of NO-2 (Fig. 2d), denitrification intensifies away from the coast. This pattern is opposite to that observed in the two other major oceanic suboxic zones, especially off Peru-Chile, where the poleward undercurrents, in fact..., support bulk of the denitrification (Codispoti et al., 1989). This difference probably owes to a lower respiration rate within the WIUC, which, in turn, may be caused by two factors. Firstly, un- like its counterpart off Peru-Chile the WIUC does not occur...

  10. Granulation of sulfur-oxidizing bacteria for autotrophic denitrification.

    Science.gov (United States)

    Yang, Weiming; Lu, Hui; Khanal, Samir K; Zhao, Qing; Meng, Liao; Chen, Guang-Hao

    2016-11-01

    Sulfur-oxidizing bacteria (SOB) was successfully employed for effective autotrophic denitrification and sludge minimization in a full-scale application of saline sewage treatment in Hong Kong. In this study, a Granular Sludge Autotrophic Denitrification (GSAD) reactor was continuously operated over 600 days for SOB granulation, and to evaluate the long-term stability of SOB granules, microbial communities and denitrification efficacy. Sludge granulation initiated within the first 40 days of start-up with an average particle size of 186.4 μm and sludge volume index (SVI5) of 40 mL/g in 5 min. The sludge granules continued to grow reaching a nearly uniform size of mean diameter 1380 ± 20 μm with SVI5 of 30 mL/g during 600 days of GSAD reactor operation at hydraulic retention time of 5 h and nitrate loading rate of 0.33 kg-N/m(3)/d. The GSAD reactor with SOB granular sludge achieved 93.7 ± 2.1% nitrogen and complete sulfide removal with low sludge yield of 0.15 g-volatile suspended solids (VSS)/g-N, and much lower nitrous oxide (N2O) emission than the heterotrophic denitrifying process. Microbial community analysis using fluorescence in situ hybridization (FISH) technique revealed that granules were enriched with SOB contributing to autotrophic denitrification. Furthermore, 16S rRNA analysis showed diverse autotrophic denitrification related genera, namely Thiobacillus (32.6%), Sulfurimonas (31.3%), and Arcobacter (0.01%), accounting for 63.9% of total operational taxonomic units at the generic level. No heterotrophic denitrification related genera were detected. The results from this study could provide useful design and operating conditions with respect to SOB sludge granulation and its subsequent application in a full-scale autotrophic denitrification in the Sulfate reduction-Autotrophic denitrification-Nitrification Integrated (SANI) process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Denitrification of fertilizer wastewater at high chloride concentration

    DEFF Research Database (Denmark)

    Ucisik, Ahmed Süheyl; Henze, Mogens

    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......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...

  12. 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 of biolog...

  13. Denitrification and the denitrifier community in a coastal microbial mats

    NARCIS (Netherlands)

    Fan, H.; Bolhuis, H.; Stal, L.J.

    2015-01-01

    Denitrification was measured in three structurally different coastal microbial mats by using the stable isotope technique. The composition of the denitrifying community was determined by analyzing the nitrite reductase (nirS and nirK) genes using clone libraries and the GeoChip. The highest

  14. Effects of pentachlorophenol on the bacterial denitrification process

    Directory of Open Access Journals (Sweden)

    Bairen Yang

    2016-10-01

    Full Text Available The use of pentachlorophenol (PCP was banned or restricted in many countries worldwide because of its adverse influences on the ecological environment and humans. However, the potential disrupting effects of PCP on denitrifying microorganisms have warranted more analysis. In this study, the impacts of PCP on denitrification were investigated by using Paracoccus denitrificans as a model denitrifying bacterium. Compared with the control, the presences of 10 and 50 μM of PCP were found to significantly decrease the denitrification efficiencies from 98.5 to 87.2% and 68.7%, respectively. The mechanism studies showed that PCP induced the generation of reactive oxygen species, which decreased the vital enzymes activities related to glycolysis process, causing the disturbance of the metabolism of P. denitrificans utilizing carbon source (glucose and the growth of the cell, and subsequently the generation of electron donor (NADH for denitrification via NAD+ reduction was severely depressed. Further studies indicated that PCP also decreased the genes expression of several key enzymes responsible for denitrification, such as napA of nitrate reductase (NAR, nirS of nitrite reductase, norB of nitric oxide reductase, and nosZ of nitrous oxide reductase; however, there was only the enzyme activity of NAR was remarkably inhibited.

  15. Internal hydraulics of an agricultural drainage denitrification bioreactor

    Science.gov (United States)

    Denitrification bioreactors to reduce the amount of nitrate-nitrogen in agricultural drainage are now being deployed across the U.S. Midwest. However, there are still many unknowns regarding internal hydraulic-driven processes in these "black box" engineered treatment systems. To improve this unders...

  16. Formaldehyde biodegradation and its effect on the denitrification process.

    Science.gov (United States)

    Eiroa, M; Vilar, A; Kennes, C; Veiga, M C

    2007-09-01

    Simultaneous formaldehyde biodegradation and denitrification in batch assays and in a continuous lab-scale reactor were studied. In batch assays, initial biodegradation rates between 0.7 and 3.3 g CKH2O g VSS(-1) d(-1) were obtained at formaldehyde concentrations between 300 and 2150 mg l(-1). The denitrification process was affected by the presence of formaldehyde. The nitrite accumulation increased with the initial formaldehyde concentration. In the continuous reactor, removal efficiencies above 98.5% were obtained at formaldehyde loading rates between 0.37 and 2.96 kg COD m(-3) d(-1) (625-5000 mg CH2O l(-1)). Formaldehyde removal led to the appearance of methanol and formic acid in the medium. Denitrification process was almost complete (around 99.7%) at nitrogen loading rates up to 0.44 kg N-NO3- m(-3) d(-1). Nitrite occasionally appeared in the effluent at concentrations less than 2.9 mg l(-1). The composition of the biogas indicated that denitrification and methanogenesis occurred simultaneously in the same unit.

  17. Microbiological Denitrification and Denitrifying Activity of Paracoccus Denitrificans

    Institute of Scientific and Technical Information of China (English)

    万曦; 万国江; 等

    2000-01-01

    With rapidly industrial and agricultural development,more and more fertilizers,chemicals and heavy ions will be discharged into lakes and rivers,which would cause lake eutrophication and quality deterioration in drinking water sources.Therefore,denitrification is essential for controlling the amounts of nitrogen,During the transformation process from nitrate to the end products-nitrogen and several intermediated[e.g.nitrite(NO2-),nitrous oxide(N2O) and nitric oxide(NO)]may be accumulated,which have more toxic influences on the environment.in This study,the denitrification effect of Paracoccus Denitrificans was examined on the changes between oxic and anoxic conditions at varying pH.At pH=7.5,denitrification proceeded well after 3 switches from oxic to anoxic conditions and vice versa,Production of N2 was constant and the amounts of NO2-,N2O and NO were extremely low.How ever,at pH=6.8,denitrification activity was inhitied and there large amounts of the intermaediates.The denitrifying bacteria decreased violently in dry weight and were washed out.

  18. 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...

  19. Denitrification and the denitrifier community in coastal microbial mats

    NARCIS (Netherlands)

    Fan, H.; Bolhuis, H.; Stal, L.J.

    2015-01-01

    Denitrification was measured in three structurally different coastal microbial mats by using the stable isotope technique. The composition of the denitrifying community was determined by analyzing the nitrite reductase (nirS and nirK) genes using clone libraries and the GeoChip. The highest potentia

  20. Sediment Denitrification in Two Contrasting Tropical Shallow Lagoons

    DEFF Research Database (Denmark)

    Enrich-Prast, Alex; Santoro, Ana Lucia; Countinho, Rodrigo S.

    2016-01-01

    . Oxygen consumption varied from 426 to 4248 mu mol O-2 m(-2) h(-1) and was generally three times higher in the meso-eutrophic than the oligotrophic lagoon. The low denitrification activity was ascribed to both low water NO3- concentrations (supply from nitrification...

  1. Estimation of denitrification potential with respiration based techniques

    NARCIS (Netherlands)

    Kujawa-Roeleveld, K.

    2000-01-01

    Denitrification with its prerequisite process nitrification, is a common practice to remove nitrogen from wastewater in activated sludge systems. Although the key factors detrimental to its performance are well recognised, not all links are implemented for optimal design and operation performance. T

  2. O2 reduction and denitrification rates in shallow aquifers

    Science.gov (United States)

    Tesoriero, Anthony J.; Puckett, Larry J.

    2011-12-01

    O2 reduction and denitrification rates were determined in shallow aquifers of 12 study areas representing a wide range in sedimentary environments and climatic conditions. Zero- and first-order rates were determined by relating reactant or product concentrations to apparent groundwater age. O2 reduction rates varied widely within and between sites, with zero-order rates ranging from 100 μmol N L-1 yr-1; >0.36 yr-1) occur when changes in lithology result in a sharp increase in the supply of electron donors. Denitrification lag times (i.e., groundwater travel times prior to the onset of denitrification) ranged from 80 yr. The availability of electron donors is indicated as the primary factor affecting O2 reduction rates. Concentrations of dissolved organic carbon (DOC) and/or sulfate (an indicator of sulfide oxidation) were positively correlated with groundwater age at sites with high O2 reduction rates and negatively correlated at sites with lower rates. Furthermore, electron donors from recharging DOC are not sufficient to account for appreciable O2 and nitrate reduction. These relations suggest that lithologic sources of DOC and sulfides are important sources of electrons at these sites but surface-derived sources of DOC are not. A review of published rates suggests that denitrification tends to occur more quickly when linked with sulfide oxidation than with carbon oxidation.

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

    NARCIS (Netherlands)

    Veraart, A.J.; Klein, de J.J.M.; Scheffer, M.

    2011-01-01

    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

  4. 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.

  5. 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

  6. 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

  7. EDITORIAL: Theory Meets Data Analysis at Comparable and Extreme Mass Ratios Conference (NRDA/Capra 2010), Perimeter Institute for Theoretical Physics, Waterloo, Canada, 20-26 June 2010 Theory Meets Data Analysis at Comparable and Extreme Mass Ratios Conference (NRDA/Capra 2010), Perimeter Institute for Theoretical Physics, Waterloo, Canada, 20-26 June 2010

    Science.gov (United States)

    Lehner, L.; Pfeiffer, H.; Poisson, E.

    2011-07-01

    This special issue of Classical and Quantum Gravity contains articles submitted in relation to the 'Theory Meets Data Analysis at Comparable and Extreme Mass Ratios' conference held at the Perimeter Institute for Theoretical Physics, Waterloo, Canada, 20-26 June 2010. This conference, organized by S Fairhurst, G Gonzalez, L Lehner, Y Liu, H Pfeiffer, and E Poisson brought together researchers from three gravitational wave communities: experiment, theory and data analysis, who discussed the latest advances and challenges for detecting and exploiting gravitational waves. Approximately 60 talks spread over one week, together with many lively discussions provided an excellent atmosphere for debate. With so much packed in over seven days there were too many highlights to list specifics here. However, several common themes could be clearly discerned: the tremendous progress achieved in the detector level; the understanding of key comparable-mass systems and the data analysis techniques required for searching for their signals; the significant progress achieved in obtaining predictions in extreme mass ratio scenarios and the understanding of remaining challenges; as well as several new efforts towards making multi-messenger astronomy a reality. This issue contains research articles presented at this conference which, together with online talks (all of which can be found at pirsa.org/C10015), illustrate the level of maturity the field has reached. Many challenges still remain and the communities involved are actively working towards addressing them.

  8. 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

    Measurement of biogeochemical processes in permeable sediments (including the hyporheic zone) is difficult because of complex multidimensional advective transport. This is especially the case for nitrogen cycling, which involves several coupled redox-sensitive reactions. To provide detailed insig......- 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....

  9. Monitoring induced denitrification in an artificial aquifer recharge system.

    Science.gov (United States)

    Grau-Martinez, Alba; Torrentó, Clara; Folch, Albert; Domènech, Cristina; Otero, Neus; Soler, Albert

    2014-05-01

    As demands on groundwater increase, artificial recharge is becoming a common method for enhancing groundwater supply. The Llobregat River is a strategic water supply resource to the Barcelona metropolitan area (Catalonia, NE Spain). Aquifer overexploitation has leaded to both a decrease of groundwater level and seawater intrusion, with the consequent deterioration of water quality. In the middle section of the aquifer, in Sant Vicenç del Horts, decantation and infiltration ponds recharged by water from the Llobregat River (highly affected from wastewater treatment plant effluents), were installed in 2007, in the framework of the ENSAT Life+ project. At the bottom of the infiltration pond, a vegetal compost layer was installed to promote the growth of bacteria, to induce denitrification and to create favourable conditions for contaminant biodegradation. This layer consists on a mixture of compost, aquifer material, clay and iron oxide. Understanding the fate of contaminants, such as nitrate, during artificial aquifer recharge is required to evaluate the impact of artificial recharge in groundwater quality. In order to distinguish the source of nitrate and to evaluate the capability of the organic reactive layer to induce denitrification, a multi-isotopic approach coupled with hydrogeochemical data was performed. Groundwater samples, as well as river samples, were sampled during artificial and natural recharge periods. The isotopic analysis included: δ15N and δ18O of dissolved nitrate, δ34S and δ18O of dissolved sulphate, δ13C of dissolved inorganic carbon, and δ2H and δ18O of water. Dissolved nitrate isotopic composition (δ15NNO3 from +9 to +21 o and δ18ONO3 from +3 to +16 ) demonstrated that heterotrophic denitrification induced by the reactive layer was taking place during the artificial recharge periods. An approximation to the extent of nitrate attenuation was calculated, showing a range between 95 and 99% or between 35 and 45%, by using the extreme

  10. DENITRIFICATION PROCESS ENHANCING IN FOUR-STAGES ROTATING BIOLOGICAL CONTACTOR

    Directory of Open Access Journals (Sweden)

    Artur Mielcarek

    2016-06-01

    Full Text Available The aim of the study was to determine the degree of an organic substrate consumption in the denitrification process involving a biofilm in four-stages laboratory scale rotating biological contactor (RBC. The discs submergence was 40% of their diameter. Acetic acid, used as external carbon source, was fed to the fourth stage of RBC. Consumption of substrate was observed for 2 and 24 hours. For a shorter period there was the removal of 37.9 ± 1.8 mg N·m-2, while using 499,9 ± 33.2 mg O2·m-2 of organic compounds. The prolongation of the experiment duration guaranteed higher efficiency of denitrification. The ratio of organic substrate used to the amount of nitrogen removed was 13: 1 and 21: 1 for 2 and 24 hours respectively.

  11. Numerical Modeling of Natural and Enhanced Denitrification Processes in Aquifers

    Science.gov (United States)

    Kinzelbach, Wolfgang; SchäFer, Wolfgang; Herzer, JöRg

    1991-06-01

    Nitrate modeling in the groundwater environment must incorporate microbial denitrification as the major process of nitrate elimination. A multispecies transport model is presented which describes the interaction of oxygen, nitrate, organic carbon, and bacteria. Three phases (mobile pore water, biophase, and aquifer material) are taken into account. The model is applied to a natural aquifer situation as well as to an in situ remediation case where nitrate is employed as an oxidant. In the natural aquifer it is shown that the release of organic carbon from the matrix is the controlling factor for denitrification. In the remediation case, on the other hand, the data suggest that diffusion limitation of the nutrient supply to the biophase controls bacterial growth.

  12. Patch-scale controls on denitrification in stream bed sediments

    Science.gov (United States)

    Voytek, M. A.; Harvey, J. W.; Smith, L. K.; Smith, R. L.; Bohlke, J. K.

    2001-12-01

    Denitrification is usually considered one of the most important processes controlling nitrogen loads in streams and rivers because it has the capability of permanently removing fixed nitrogen. Denitrification requires an electron donor, i.e. DOC and nitrate which is often abundant in agriculturally impacted systems. However, it is inhibited by oxygen and therefore occurs primarily in sediments where the supply and delivery of these substrates might be more limited. The goal of this study was to assess the interaction of chemical, biological and physical controls on in-stream denitrification. The influence of stream velocities, sediment grain size, carbon content and reactivity, hyporheic exchange, benthic algal coverage and microbial community distribution and activity were evaluated on sediments collected from two small streams located in the Upper Illinois River watershed, where elevated loads of nitrogen species are commonly observed. In general, sediment microbial community structure and activity reflected the observed differences in channel characteristics. Denitrifiers tended to be more abundant and active in sediment with coarser grain size distributions and greater periphyton coverage. Coarser grain size distributions were associated with deeper penetration of surface water nitrate into the sediments and periphyton coverage appeared to be correlated with higher sediment carbon concentrations and a higher C/N ratios, indicating a greater availability of labile carbon. Conversely, finer grained sediment with little or no periphyton exhibited poorly developed and less active denitrifying communities at depth. This study suggests that in-situ denitrification rates are controlled by a balance of physical mechanisms of substrate delivery and biologically controlled processes that alter porewater concentrations of essential and inhibitory substrates, which are controlled in turn by both physical and biological properties of the sediment.

  13. Improved Denitrification of Municipal Sludge in Biofilm-electrode Reactor

    Institute of Scientific and Technical Information of China (English)

    ZHANG Le-hua; JIA Jin-ping; WANG Ya-lin; YANG Ji

    2004-01-01

    The denitrification of municipal sludge was improved by combining biofilm process with the electrochemical effect in a single novel reactor. Experiments in this reactor[electric current 60 mA, hydraulic retention time (HRTs) 6.0 h] showed that the removal of CODCr, ammonia nitrogen and total nitrogen in the biofilm-electrode reactor were 2.5%, 1.2%, 14.9%, respectively, higher than those in a traditional biofilm reactor.

  14. Effect of carbon source on the denitrification in constructed wetlands

    Institute of Scientific and Technical Information of China (English)

    LU Songliu; HU Hongying; SUN Yingxue; YANG Jia

    2009-01-01

    The constructed wetlands with different plants in removal of nitrate were investigated.The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated.The results showed that the additional carbon source (glucose) can remarkably improve the nitrate removal ability of the constructed wetland.It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in the summer and from 10% to 30% in the winter, when the nitrate concentration was 30-40 mg/L, the retention time was 24 h and 25 mg/L dissolved organic carbon (DOC) was ploughed into the constructed wetland.However, the nitrite in the constructed wetland accumulated a litter with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the effluent.It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands, and the seasonal change may impact the denitrification.

  15. 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.

  16. 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.

  17. Denitrification 'hot spots' in soil following surface residue application

    Science.gov (United States)

    Kuntz, Marianne; Morley, Nicholas J.; Hallett, Paul D.; Watson, Christine; Baggs, Elizabeth M.

    2015-04-01

    The availability of organic C is an important driver for the production and reduction of the greenhouse gas nitrous oxide (N2O) during denitrification. Denitrification as a response to plant residue amendments to soil surfaces has been extensively researched. However, the nature of hotspot sites of N2O production and reduction within the soil profile, especially in relation to the location of applied residues, is unknown. In a laboratory experiment we investigated the relationship between denitrifier N2O surface fluxes and N2O production and reduction sites. Probes which equilibrate with the soil gas phase by diffusion were developed to quantify denitrification products and product ratios at 1-2 cm, 4.5-5.5 cm or 8-9 cm from the surface. 13C labelled barley straw was incorporated at rates of 0, 2 and 4 t ha-1 into the top 3 cm of soil and subsequently amended with 14NH415NO3. In a three week experiment the soil gas phase at the three depths was analysed for 15N-N2O, 15N-N2, 13C-CO2 and O2 concentrations. Additionally, cores were destructively sampled for mineral 15N as well as microbial C and dissolved C in the respective depths. 15N-N2O and CO2 surface fluxes peaked one day after N application, with residue application resulting in significantly higher 15N-N2O emission rates compared to the non-amended control. The timing of the 15N-N2O surface flux on day 1 was related to maximum 15N-N2O concentrations of 36.6 μg 15N L-1 within the pore space at 5 cm depth. Three days after fertilizer application 15N-N2O pore space concentrations had significantly increased to 193 μg 15N L-1 at 9 cm depth indicating denitrifier activity at greater depth. Denitrification below the soil surface could be explained by increased microbial activity, oxygen depletion with increasing depth and progressive downwards diffusion of fertilizer NO3-. However, C availability appeared to only affect denitrification in the surface layer in which the residue was incorporated. Our results provide

  18. 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......, no statistical difference in total N losses and 15N-(N2O+N2) flux between the uncompacted soil and the compacted soil was detected. Compaction promoted soil denitrification and may impact urban N biogeochemical cycling....

  19. High rates of denitrification and nitrate removal in cold seep sediments

    OpenAIRE

    Bowles, Marshall; Joye, Samantha

    2010-01-01

    We measured denitrification and nitrate removal rates in cold seep sediments from the Gulf of Mexico. Heterotrophic potential denitrification rates were assayed in time-series incubations. Surficial sediments inhabited by Beggiatoa exhibited higher heterotrophic potential denitrification rates (32 μ N reduced day−1) than did deeper sediments (11 μ N reduced day−1). Nitrate removal rates were high in both sediment horizons. These nitrate removal rates translate into rapid turnover times (...

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

    Science.gov (United States)

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

    2011-01-01

    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 relationship between O2 and ??15NNO 3 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 ??15NNO 3 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. ?? Author(s) 2011.

  1. Research progress of Anammox-denitrification coupling start up and Influencing Factors

    Institute of Scientific and Technical Information of China (English)

    GUO Pi-jian

    2014-01-01

    Since anammox can simultaneously remove ammonia and nitrite nitrogen,And low cost,have been researched by many scholars,Its high ammonia wastewater treatment has great application value. However, high concentrations of organic carbon on anaerobic ammonium oxidation significantly inhibited. How to achieve anaerobic ammonium oxidation and denitrification coupling, is now a focus of research in the training process, anammox bacteria and denitrifying bacteria on pH, organic matter with different requirements, this paper summarizes the anammox and denitrification startup method and pH, organic matter on anaerobic ammonia oxidation and denitrification coupling and explore control strategies for anaerobic ammonium oxidation and denitrification coupling recommendations.

  2. Feasibility of two low-cost organic substrates for inducing denitrification in artificial recharge ponds: Batch and flow-through experiments.

    Science.gov (United States)

    Grau-Martínez, Alba; Torrentó, Clara; Carrey, Raúl; Rodríguez-Escales, Paula; Domènech, Cristina; Ghiglieri, Giorgio; Soler, Albert; Otero, Neus

    2017-03-01

    Anaerobic batch and flow-through experiments were performed to assess the capacity of two organic substrates to promote denitrification of nitrate-contaminated groundwater within managed artificial recharge systems (MAR) in arid or semi-arid regions. Denitrification in MAR systems can be achieved through artificial recharge ponds coupled with a permeable reactive barrier in the form of a reactive organic layer. In arid or semi-arid regions, short-term efficient organic substrates are required due to the short recharge periods. We examined the effectiveness of two low-cost, easily available and easily handled organic substrates, commercial plant-based compost and crushed palm tree leaves, to determine the feasibility of using them in these systems. Chemical and multi-isotopic monitoring (δ(15)NNO3, δ(18)ONO3, δ(34)SSO4, δ(18)OSO4) of the laboratory experiments confirmed that both organic substrates induced denitrification. Complete nitrate removal was achieved in all the experiments with a slight transient nitrite accumulation. In the flow-through experiments, ammonium release was observed at the beginning of both experiments and lasted longer for the experiment with palm tree leaves. Isotopic characterisation of the released ammonium suggested ammonium leaching from both organic substrates at the beginning of the experiments and pointed to ammonium production by DNRA for the palm tree leaves experiment, which would only account for a maximum of 15% of the nitrate attenuation. Sulphate reduction was achieved in both column experiments. The amount of organic carbon consumed during denitrification and sulphate reduction was 0.8‰ of the total organic carbon present in commercial compost and 4.4% for the palm tree leaves. The N and O isotopic fractionation values obtained (εN and εO) were -10.4‰ and -9.0‰ for the commercial compost (combining data from both batch and column experiments), and -9.9‰ and -8.6‰ for the palm tree column, respectively. Both

  3. Carbon nanotubes affect the toxicity of CuO nanoparticles to denitrification in marine sediments by altering cellular internalization of nanoparticle

    Science.gov (United States)

    Zheng, Xiong; Su, Yinglong; Chen, Yinguang; Wan, Rui; Li, Mu; Huang, Haining; Li, Xu

    2016-06-01

    Denitrification is an important pathway for nitrate transformation in marine sediments, and this process has been observed to be negatively affected by engineered nanomaterials. However, previous studies only focused on the potential effect of a certain type of nanomaterial on microbial denitrification. Here we show that the toxicity of CuO nanoparticles (NPs) to denitrification in marine sediments is highly affected by the presence of carbon nanotubes (CNTs). It was found that the removal efficiency of total NOX--N (NO3--N and NO2--N) in the presence of CuO NPs was only 62.3%, but it increased to 81.1% when CNTs appeared in this circumstance. Our data revealed that CuO NPs were more easily attached to CNTs rather than cell surface because of the lower energy barrier (3.5 versus 36.2 kT). Further studies confirmed that the presence of CNTs caused the formation of large, incompact, non-uniform dispersed, and more negatively charged CuO-CNTs heteroaggregates, and thus reduced the nanoparticle internalization by cells, leading to less toxicity to metabolism of carbon source, generation of reduction equivalent, and activities of nitrate reductase and nitrite reductase. These results indicate that assessing nanomaterial-induced risks in real circumstances needs to consider the “mixed” effects of nanomaterials.

  4. Tidal controls on riverbed denitrification along a tidal freshwater zone

    Science.gov (United States)

    Knights, Deon; Sawyer, Audrey H.; Barnes, Rebecca T.; Musial, Cole T.; Bray, Samuel

    2017-01-01

    In coastal rivers, tidal pumping enhances the exchange of oxygen-rich river water across the sediment-water interface, controlling nitrogen cycling in riverbed sediment. We developed a one-dimensional, fluid flow and solute transport model that quantifies the influence of tidal pumping on nitrate removal and applied it to the tidal freshwater zone (TFZ) of White Clay Creek (Delaware, USA). In field observations and models, both oxygenated river water and anoxic groundwater deliver nitrate to carbon-rich riverbed sediment. A zone of nitrate removal forms beneath the aerobic interval, which expands and contracts over daily timescales due to tidal pumping. At high tide when oxygen-rich river water infiltrates into the bed, denitrification rates decrease by 25% relative to low tide. In the absence of tidal pumping, our model predicts that the aerobic zone would be thinner, and denitrification rates would increase by 10%. As tidal amplitude increases toward the coast, nitrate removal rates should decrease due to enhanced oxygen exchange across the sediment-water interface, based on sensitivity analysis. Denitrification hot spots in TFZs are more likely to occur in less permeable sediment under lower tidal ranges and higher rates of ambient groundwater discharge. Our models suggest that tidal pumping is not efficient at removing surface water nitrate but can remove up to 81% of nitrate from discharging groundwater in the TFZ of White Clay Creek. Given the high population densities of coastal watersheds, the reactive riverbeds of TFZs play a critical role in mitigating new nitrogen loads to coasts.

  5. 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.

  6. Denitrification and N2 fixation in the Pacific Ocean

    Science.gov (United States)

    Deutsch, Curtis; Gruber, Nicolas; Key, Robert M.; Sarmiento, Jorge L.; Ganachaud, Alexandre

    2001-06-01

    We establish the fixed nitrogen budget of the Pacific Ocean based on nutrient fields from the recently completed World Ocean Circulation Experiment (WOCE). The budget includes denitrification in the water column and sediments, nitrogen fixation, atmospheric and riverine inputs, and nitrogen divergence due to the large-scale circulation. A water column denitrification rate of 48±5 Tg N yr -1 is calculated for the Eastern Tropical Pacific using N* [Gruber and Sarmiento, 1997] and water mass age tracers. On the basis of rates in the literature, we estimate sedimentary denitrification to remove an additional 15±3 Tg N yr-1. We then calculate the total nitrogen divergence due to the large scale circulation through the basin, composed of flows through a zonal transect at 32°S, and through the Indonesian and Bering straits. Adding atmospheric deposition and riverine fluxes results in a net divergence of nitrogen from the basin of -4±12 Tg N yr-1. Pacific nitrogen fixation can be extracted as a residual component of the total budget, assuming steady state. We find that nitrogen fixation would have to contribute 59±14 Tg N yr-1 in order to balance the Pacific nitrogen budget. This result is consistent with the tentative global extrapolations of Gruber and Sarmiento [1997], based on nitrogen fixation rates estimated for the North Atlantic. Our estimated mean areal fixation rate is within the range of direct and geochemical rate estimates from a single location near Hawaii [Karl et al., 1997]. Pacific nitrogen fixation occurs primarily in the western part of the subtropical gyres where elevated N* signals are found. These regions are also supplied with significant amounts of iron via atmospheric dust deposition, lending qualitative support to the hypothesis that nitrogen fixation is regulated in part by iron suppy.

  7. Production of ammonia-derived radicals in a dielectric barrier discharge and their injection for denitrification

    DEFF Research Database (Denmark)

    Kusano, Y.; Leipold, F.; Fateev, A.

    2005-01-01

    and laser diode absorption spectroscopy was employed for detection of NH and NE, in the discharge respectively, while ultraviolet absorption and Fourier transform infrared spectroscopy was used for detection of nitrogen oxides, ammonia, ammonia-derived radicals, and other products after mixing the plasma...... efficiency and no generation of corrosive acids. In the present work ammonia-derived radicals were generated using an atmospheric pressure Ar/NH3 DBD and subsequently injected into an exhaust chamber where a synthetic flue gas of an NO/N-2 mixture was fed for demonstration of NO reduction. Optical emission...... activated gas with the synthetic flue gas. Although NE and NH2 radicals were observed in the discharge, due to their short lifetimes it is unlikely that they would be simply transported, mixed with the flue gas and react with NO to form N-2. On the other hand, hydrazine (N2H4), which is a stable ammonia...

  8. 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

  9. Hydraulic properties of four-year old woodchips from a denitrification bed

    Science.gov (United States)

    Denitrification beds are being used to reduce the transport of water-soluble nitrate via subsurface drainage systems to surface water. Only recently has the non-linearity of water flow through woodchips been ascertained. To successfully design and model denitrification beds for optimum nitrate remov...

  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. Denitrification in the root zone using a simple empirical model SimDen

    DEFF Research Database (Denmark)

    Vinther, Finn Pilgaard

    2006-01-01

    Only by knowing soil type and amount of nitrogen applied, an estimate of the annual denitrification can be obtained with the simple empirical model SimDen.......Only by knowing soil type and amount of nitrogen applied, an estimate of the annual denitrification can be obtained with the simple empirical model SimDen....

  12. Linkages between denitrification and dissolved organicmatter quality, Boulder Creek watershed, Colorado

    Science.gov (United States)

    Barnes, Rebecca T.; Smith, Richard L.; Aiken, George R.

    2012-01-01

    Dissolved organic matter (DOM) fuels the majority of in-stream microbial processes, including the removal of nitrate via denitrification. However, little is known about how the chemical composition of DOM influences denitrification rates. Water and sediment samples were collected across an ecosystem gradient, spanning the alpine to plains, in central Colorado to determine whether the chemical composition of DOM was related to denitrification rates. Laboratory bioassays measured denitrification potentials using the acetylene block technique and carbon mineralization via aerobic bioassays, while organic matter characteristics were evaluated using spectroscopic and fractionation methods. Denitrification potentials under ambient and elevated nitrate concentrations were strongly correlated with aerobic respiration rates and the percent mineralized carbon, suggesting that information about the aerobic metabolism of a system can provide valuable insight regarding the ability of the system to additionally reduce nitrate. Multiple linear regressions (MLR) revealed that under elevated nitrate concentrations denitrification potentials were positively related to the presence of protein-like fluorophores and negatively related to more aromatic and oxidized fractions of the DOM pool. Using MLR, the chemical composition of DOM, carbon, and nitrate concentrations explained 70% and 78% of the observed variability in denitrification potential under elevated and ambient nitrate conditions, respectively. Thus, it seems likely that DOM optical properties could help to improve predictions of nitrate removal in the environment. Finally, fluorescence measurements revealed that bacteria used both protein and humic-like organic molecules during denitrification providing further evidence that larger, more aromatic molecules are not necessarily recalcitrant in the environment.

  13. Denitrification at pH 4 by a soil-derived Rhodanobacter-dominated community.

    Science.gov (United States)

    van den Heuvel, R N; van der Biezen, E; Jetten, M S M; Hefting, M M; Kartal, B

    2010-12-01

    Soil denitrification is a major source of nitrous oxide emission that causes ozone depletion and global warming. Low soil pH influences the relative amount of N₂O produced and consumed by denitrification. Furthermore, denitrification is strongly inhibited in pure cultures of denitrifying microorganisms below pH 5. Soils, however, have been shown to denitrify at pH values as low as pH 3. Here we used a continuous bioreactor to investigate the possibility of significant denitrification at low pH under controlled conditions with soil microorganisms and naturally available electron donors. Significant NO₃⁻ and N₂O reduction were observed for 3 months without the addition of any external electron donor. Batch incubations with the enriched biomass showed that low pH as well as low electron donor availability promoted the relative abundance of N₂O as denitrification end-product. Molecular analysis of the enriched biomass revealed that a Rhodanobacter-like bacterium dominated the community in 16S rRNA gene libraries as well as in FISH microscopy during the highest denitrification activity in the reactor. We conclude that denitrification at pH 4 with natural electron donors is possible and that a Rhodanobacter species may be one of the microorganisms involved in acidic denitrification in soils.

  14. Biodiesel waste as source of organic carbon for municipal WWTP denitrification.

    Science.gov (United States)

    Bodík, I; Blstáková, A; Sedlácek, S; Hutnan, M

    2009-04-01

    This paper presents the results of experiments to test biodiesel waste (glycerine--g-phase) as an organic carbon source for the removal of nitrate in a WWTP denitrification process. Investigation of g-phase was first centered on g-phase utilization as an external source for denitrification under laboratory conditions and consequently, after positive results from the laboratory investigation, g-phase was applied in the denitrification process in the WWTP Vrútky (35,000 PE). This WWTP had insufficient nitrogen removal via denitrification. Denitrification was insufficient due to an influent with a low BOD5/N ratio (1.7:1) entering into the activated sludge tank. Laboratory experiments and calculations showed that, to reach Ntotal concentration under 10 mg l(-1) in effluent, a biodiesel waste dose of 500 kg(COD) d(-1) was necessary. Glycerol phase (g-phase) dosing into the denitrification tank increased denitrification efficiency by 2.0 - 5.0 mg(NO)(3)(-N)l(-1) per 100 l of g-phase dose into the denitrification tank.

  15. Simultaneous biological removal of sulfide and nitrate by autotrophic denitrification in an activated sludge system

    NARCIS (Netherlands)

    Manconi, I.; Carucci, A.; Lens, P.N.L.; Rossetti, S.

    2006-01-01

    The feasibility of an autotrophic denitrification process in an activated sludge reactor, using sulphide as the electron donor, was tested for simultaneous denitrification and sulphide removal. The reactor was operated at nitrate (N) to sulphide (S) ratios between 0.5 and 0.9 to evaluate their effec

  16. [Potential of nitrification and denitrification in water purification system with hydroponic bio-filter method].

    Science.gov (United States)

    Li, Xian-ing; Lu, Xi-wu; Song, Hai-liang; Osamu, Nishimura; Yuhei, Inamori

    2005-03-01

    The potential of nitrification and denitrification of sediment and the density of ammonium-oxidizing bacteria and nitrite-oxidizing bacteria in sediment in water quality purifying system with hydroponic bio-filter method (HBFM) were measured. The variation of nitrification and denitrification potential of the sediment along the stream way was quantitatively studied. The results show that among the sediments from front, middle and retral part of the stream way, the sediment from middle part reached a maximum nitrification potential . nitrification potential of 4.76 x 10(-6) g/(g x h), while the sediment from front part reached a maximum denitrification potential of 8 .1 x 10(-7) g/(g x h). The distribution of nitrification potential accords with the ammonium-oxidizing bacteria density. The key for improving nitrogen removal efficiency of HBFM system consists in changing nitrification & denitrification region distributing and accordingly enhances denitrification process.

  17. Can Membrane Inlet Mass Spectrometer Measure Short-term Denitrification Enzyme Activity and Denitrification Potentials of Soils?

    Science.gov (United States)

    Khalil, M. I.; Richards, K. G.

    2009-04-01

    Denitrifier population size and potential activity combined with the relevant environmental factors regulate the rates of denitrification in terrestrial and aquatic ecosystems. Due to the high atmospheric background of di-nitrogen (N2), denitrification enzyme activity (DEA) in soils is traditionally measured using the acetylene block or stable isotope techniques under non-limiting substrates and anaerobic/saturated conditions for periods from a few hours to several days so as to estimate denitrification potential (DP). This research investigated the estimation of DEA and DP by quantifying the N2/Ar ratio changes in waters/sediments using membrane inlet mass spectrometry (MIMS). Two experiments were conducted with soils of A, B and C horizons collected from grazed grassland to obtain optimal NO3- and available carbon (C) rates. In experiment 1, 30 g soil (oven dry basis) followed by helium-flushed deionized water was taken in triplicate 160 mL glass bottles and sealed with rubber stoppers without any air entrapments. Then N as potassium nitrate (0 to 120 mg NO3 - N kg-1 soil) and readily available C as glucose (0 to 240 mg glucose-C) plus 30 mg NO3 - N, kg-1 soil were amended. Laboratory incubation was performed in the dark at 21oC under water to reduce the risk of N2 contamination. After six hours, the treated water samples were transferred into 12 mL exetainers and kept under water at 4oC before analysis using MIMS. The N2/Ar ratios, representing DEA, varied between soil horizons and declined with decreasing soil depths. The maximum peak for N2/Ar ratios were observed with the 30 mg NO3 - N kg-1 soil in all soil horizons and coupled with the 60 mg glucose-C kg-1 soil for C horizon, and 120 mg glucose-C kg-1 for A and B horizons. Experiment 2 was conducted to assess simulated unsaturated and saturated subsoil (C horizon) denitrification capacity (NO3 - Nonly amendment), and DP (both C and N amendment) using the same methodology as experiment 1 and incubated for 3

  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· mgCODre(-1) (0.22 ± 0.09 mgTSS mgNre(-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%).

  19. Autotrophic denitrification using hydrogen generated from metallic iron corrosion.

    Science.gov (United States)

    Sunger, Neha; Bose, Purnendu

    2009-09-01

    Hydrogenotrophic denitrification was demonstrated using hydrogen generated from anoxic corrosion of metallic iron. For this purpose, a mixture of hydrogenated water and nitrate solution was used as reactor feed. A semi-batch reactor with nitrate loading of 2000 mg m(-3) d(-1) and hydraulic retention time (HRT) of 50 days produced effluent with nitrate concentration of 0.27 mg N L(-1) (99% nitrate removal). A continuous flow reactor with nitrate loading of 28.9 mg m(-3) d(-1) and HRT of 15.6 days produced effluent with nitrate concentration of approximately 0.025 mg N L(-1) (95% nitrate removal). In both cases, the concentration of nitrate degradation by-products, viz., ammonia and nitrite, were below detection limits. The rate of denitrification in the reactors was controlled by hydrogen availability, and hence to operate such reactors at higher nitrate loading rates and/or lower HRT than reported in the present study, hydrogen concentration in the hydrogenated water must be significantly increased.

  20. Cocurrent biological nitrification and denitrification in wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Spector, M.

    1998-11-01

    Repetitive conditioning of recycle activated sludge (RAS) under strict anaerobic conditions gradually changes the products of ammonia oxidation from nitrite and nitrate to nitrous oxide (N{sub 2}O) and nitrogen (N{sub 2}). Nitrite inhibits oxygen respiration of anaerobically conditioned sludge; biochemical oxygen demand (BOD) is then oxidized by nitrite, which is reduce to N{sub 2}O and N{sub 2}. When anaerobic RAS conditioning is initially imposed on a nitrifying system, Nitrobacter species continue to oxidize nitrite to nitrate and thus reduce the nitrite available to oxidize BOD. However, Nitrobacter in the mixed liquor gradually tend to wash out because the sole source of Nictrobacter energy, the oxidation of nitrite to nitrate, is diminished to the extent that nitrite is reduced. Incorporation of an RAS conditioning zone to the activate-sludge process results in evolution of a nonfilamentous biomass, which affects both cocurrent biological nitrification and denitrification (CBND) and biological phosphorus removal (BPR). The initial feed zone may be either aerobic or anaerobic. A final anoxic denitrification zone is desirable for removal of residual nitrite plus nitrate (NO{sub x}) from aeration effluent. Nitrous oxide, the main reaction product of CBND, promotes both global warming and destruction of the stratospheric ozone layer.

  1. Denitrification characteristics of a marine origin psychrophilic aerobic denitrifying bacterium

    Institute of Scientific and Technical Information of China (English)

    Haiyan Zheng; Ying Liu; Guangdong Sun; Xiyan Gao; Qingling Zhang; Zhipei Liu

    2011-01-01

    A psychrophilic aerobic denitrifying bacterium,strain S1-1,was isolated from a biological aerated filter conducted for treatment of recirculating water in a marine aquaculture system.Strain S1-1 was preliminarily identified as Psychrobacter sp.based on the analysis of its 16S rRNA gene sequence,which showed 100% sequence similarity to that of Psychrobacter sp.TSBY-70.Strain S 1-1 grew well either in high nitrate or high nitrite conditions with a removal of 100% nitrate or 63.50% nitrite,and the total nitrogen removal rates could reach to 46.48% and 31.89%,respectively.The results indicated that nitrate was mainly reduced in its logarithmic growth phase with a very low leve 1 accumulation of nitrite,suggesting that the aerobic denitrification process of strain S l-1 occurred mainly in this phase.The GC-MS results showed that N2O was formed as the major intermediate during the aerobic denitrifying process of strain S1-1.Finally,factors affecting the growth of strain Sl-1 and its aerobic denitrifying ability were also investigated.Results showed that the optimum aerobic denitrification conditions for strain S1-1 were sodium succinate as carbon source,C/N ratio15,salinity 10 g/L NaCl,incubation temperature 20℃ and initial pH 6.5.

  2. Analysis of denitrification process in the groundwater of floodplains using a modelling approach

    Science.gov (United States)

    Bernard-Jannin, Léonard; Brito, David; Sun, Xiaoling; Teissier, Samuel; Neves, Ramiro; Sauvage, Sabine; Sánchez-Pérez, José-Miguel

    2016-04-01

    Nitrate contamination of freshwater systems is a global concern. In alluvial floodplains, highly vulnerable to nitrate pollution due to widespread agricultural activities, riparian areas have been proven to be efficient in nitrate removal through denitrification. However, denitrification presents complex spatio-temporal patterns and is controlled by many factors. Hence, modelling can provide useful knowledge about this biogeochemical process, by helping to identify key factors involved in denitrification process and its spatio-temporal variability. In this study, a modelling approach combining i) a distributed hydrodynamic model, coupling surface and subsurface flow (MOHID Land), with ii) a simplified denitrification calculation module including dissolved organic carbon (DOC borned by the river) and particulate organic carbon (POC present in soil) have been applied to a monitored meander area of the Garonne river (6.6 km²). The dataset include hydrological data and nitrates concentrations collected in a network of 25 piezometers during 12 monthly campaigns allowing the set up and the validation of the model application. The average denitrification rate was estimated to 28 kg N/ha/yr representing 38% of the lateral nitrate input from the agricultural area. Denitrification was the highest in the low elevation riparian area in relation with inundated soils releasing topsoil organic carbon fueling denitrification. In addition high denitrification rates were simulated in downstream part of the meander in relation with the high nitrates flux coming from the agricultural area. Geomorphological settings and groundwater flows in the area play a major role in controlling denitrification in floodplain area. Flood events lead to high denitrification periods by increasing topsoil layer POC availability with higher water level in the aquifer. However, the role of DOC borne by the river seems restricted. The model can be applied to estimate nitrate removal capacity of riparian

  3. Tradeoffs in regulating ecosystem services in East African Papyrus Wetlands: Denitrification as a case study

    Science.gov (United States)

    Gettel, G. M.; Tshering, K.; Nakitende, H.; van Dam, A.

    2012-12-01

    Papyrus wetlands are important to the livelihoods of millions of people in East Africa, partly because they converted to grazing and agricultural lands during during dry seasons. At the same time, papyrus wetlands fringe important water bodies - e.g. Lake Victoria - and may help protect these ecosystems from the impacts of increased nutrient inputs. Denitrification -- the production of gaseous nitrogen (N) from the microbial reduction of nitrate (NO3) in anaerobic environments -- is likely an important mechanism for nitrogen retention in these systems. However, few measurements have been made, and the effect of wetland exploitation on denitrification has not yet been determined. In particular, we were interested in whether the hydrologic status (wet vs dry) is as important as agricultural activities in controlling denitrification potential. Using acetylene block technique to measure potential denitrification (denitrification enzyme assay), we measured potential denitrification rates in natural papyrus vegetation and in grazing, rice, maize, and sugarcane fields in the Nyando and Mara wetlands in Kenya and Tanzania (respectively) in November - December 2010. We also determined whether denitrification was limited by soil organic carbon or by NO3 in different patch types, and further assessed controls using multivariate analysis relating soil characteristics to potential denitrification rates. Potential denitrification in papyrus vegetation was the highest of all measured sites (price fields (2.3 - 303 ug N20 g soil dry weight-1 hour-1), and intermediate in maize and sugarcane (6.5 - 75 ug N20 g soil dry weight-1 hour-1 and 5 - 30 ug N20 g soil dry weight-1 hour-1 respectively). Controls of denitrification in different land uses were similar in the Nyando and Mara sites, and showed that NO3 limited denitrification in papyrus vegetation, whereas organic carbon was limiting in all agricultural sites. Multivariate analysis showed that this pattern also corresponded

  4. Fluidized-bed denitrification for mine waters. Part I: low pH and temperature operation.

    Science.gov (United States)

    Papirio, S; Ylinen, A; Zou, G; Peltola, M; Esposito, G; Puhakka, J A

    2014-06-01

    Mining often leads to nitrate and metal contamination of groundwater and water bodies. Denitrification of acidic water was investigated in two up-flow fluidized-bed reactors (FBR) and using batch assays. Bacterial communities were enriched on ethanol plus nitrate in the FBRs. Initially, the effects of temperature, low-pH and ethanol/nitrate on denitrification were revealed. Batch assays showed that pH 4.8 was inhibitory to denitrification, whereas FBR characteristics permitted denitrification even at feed pH of 2.5 and at 7-8 °C. Nitrate and ethanol were removed and the feed pH was neutralized, provided that ethanol was supplied in excess to nitrate. Subsequently, Fe(II) and Cu impact on denitrification was investigated within batch tests at pH 7. Iron supplementation up to 100 mg/L resulted in iron oxidation and soluble concentrations ranging from 0.4 to 1.6 mg/L that stimulated denitrification. On the contrary, 0.7 mg/L of soluble Cu significantly slowed denitrification down resulting in about 45 % of inhibition in the first 8 h. Polymerase chain reaction-denaturant gradient gel electrophoresis demonstrated the co-existence of different denitrifying microbial consortia in FBRs. Dechloromonas denitrificans and Hydrogenophaga caeni were present in both FBRs and mainly responsible for nitrate reduction.

  5. Nitrate removal and denitrification affected by soil characteristics in nitrate treatment wetlands.

    Science.gov (United States)

    Lin, Ying-Feng; Jing, Shuh-Ren; Lee, Der-Yuan; Chang, Yih-Feng; Shih, Kai-Chung

    2007-03-01

    Several small-scale surface flow constructed wetlands unplanted and planted (monoculture) with various macrophytes (Phragmites australis, Typha orientalis, Pennisetum purpureum, Ipomoea aquatica, and Pistia stratiotes) were established to continuously receive nitrate-contaminated groundwater. Soil characteristics and their effects on nitrate removal and soil denitrification were investigated. The results showed that planted wetland cells exhibited significantly higher (P wetland cell (1%, 0.11 microg N2O-N/g/h). However, the unplanted uncovered wetland cell showed a nitrate removal efficiency (55%) lower than but a soil denitrification rate (9.12 microg N2O-N/g/h) comparable to the planted cells. The nitrate removal rate correlated closely and positively with the soil denitrification rate for the planted cells, indicating that soil denitrification is an important process for removing nitrate in constructed wetlands. The results of nitrogen budget revealed that around 68.9-90.7% of the overall nitrogen removal could be attributed to the total denitrification. The soil denitrification rate was found to correlate significantly (P wetland soil, which accordingly were concluded as suitable indicators of soil denitrification rate and nitrate removal rate in nitrate treatment wetlands.

  6. Denitrification of soil nitrogen in coastal and inland salt marshes with different flooding frequencies

    Science.gov (United States)

    Bai, Junhong; Wang, Xin; Jia, Jia; Zhang, Guangliang; Wang, Yuying; Zhang, Shuai

    2017-02-01

    Denitrification is an important process for removing nitrogen in wetlands, and it is influenced by many environmental factors. However, little information is available on the relationship between hydrologic conditions and denitrification. In this study three typical sampling sites with different flooding frequencies, including short-term flooding wetlands (STFW), seasonal-flooding wetlands (SFW) and tidal flooding wetlands (TFW) were chosen as the study sites in the Yellow River Delta. In contrast, five typical sampling sites with different flooding frequencies, including 100-year floodplain (H), 10-year floodplain (T), 5-year floodplain (F), 1-year floodplain (O) and permanently flooded floodplain (B) were chosen as the study sites in Xianghai wetlands. This study reflected that the denitrification rates decreased with depth along soil profiles in both inland and coastal salt marsh soils. Flooding periods, soil depth and their interaction showed significant effects on the denitrification processes. Generally, higher flooding frequencies will cause higher denitrification rates in salt marshes. Moreover, the denitrification rates were significantly positively correlated with soil moisture content in both wetlands. Additionally, the denitrification rates were significantly positively correlated with organic matter and NO3-_N content while negatively correlated with soil pH and salinity in inland salt marshes. Therefore, the changes in soil properties (e.g. SOM, TN, pH and salinity) can become an important way to control NO3- levels in inland salt marshes.

  7. Direct Estimation of Nitrogen Gases Emitted from Flooded Soils During Denitrification of Applied Nitrogen

    Institute of Scientific and Technical Information of China (English)

    CAIGUI-XIN; YANGNAN-CHANG; 等

    1991-01-01

    Denitrification losses measured by direct method (measuring the evolution of (N2+N2O)-15N) were compared with the apparent denitrification losses (calculated from the difference between the total N loss and ammonia loss), for fertilizers applied to flooded soils.The direct measured denitrification losses from potassium nitrate were 23.0%,40.0%,and 63.1-79.7% of applied N in rice field,and in incubations of 7 cm deep layer of soil and 2 cm deep layer of soil,respectively;while the corresponding apparent denitrification losses were 96.0%,98.4%,and 97.7-97.9%,respectively.In field experiments with urea,the direct measured denitrification losses ranged from 0.1-1.8%,which were much less than the apparent denitrification losses (41.3-45.7%).Such discrepancies were primarily due to the entrapment of the gaseous products of denitrification in the soil as revealed by the facts:(1) stirring the floodwater and the surface soil markedly increased the fluxes of (N2_N2O)-15N from urea or potassium nitrate applied to the flooded rice field,and (2) reducing the pressure in the headspace of the incubation bottle with the 7 cm soil layer during gas sampling decreased the discrepance between the direct measured and apparent denitrifecation losses from 58.4% to 21.2%.The advantage of reducing the pressure in the headspace is that there is minimal disturbance of the soil.Further testing of this technique in rice field is needed to determine its effectiveness in releasing the entrapped gaseous products of denitrification so that denitrification losses can be quantified directly.

  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. Simultaneous nitrification and denitrification based on internal circulation baffled reactor

    Directory of Open Access Journals (Sweden)

    LU Xiaoya

    2014-06-01

    Full Text Available Nitrogen removal experiments were carried out by using an internal circulation baffled bioreactor (ICBBR. Nitrate, nitrite and ammonia were used as N source for nitrogen removal experiments. The ICBBR has high nitrogen removal capacity. The removal rates of total nitrogen, nitrate, and nitrite are almost the same. When nitrate and nitrite were used as N sources their kinetic orders were 0.88. When ammonia was used as N source simultaneous nitrification and denitrification (SND was realized in ICBBR and ammonia removal fitted also 0.88 order kinetics, but total nitrogen removal fitted third-order kinetics. Nitrate and nitrite removal rates were faster than ammonia removal rate under the same C/N ratio, and total nitrogen removal rate increased with increasing C/N ratio.

  10. Isolation and denitrification characteristic of an aerobic denitrifier

    Institute of Scientific and Technical Information of China (English)

    ZHOU Dan-dan; MA Fang; WANG Hong-yu; DONG Shuang-shi; WANG Ai-jie

    2006-01-01

    Aerobic denitrifiers were enriched by activated sludge cultivation method. By this way, 105 strains were isolated from the activated sludge and 25 strains were confirmed to be capable of obtaining energy by deoxidization of nitrate to nitrogen gas under aerobic condition. The characteristic of one denitrifier, Pseudomonas chloritidismutans strain, was particularly studied due to its higher nitrogen removal rate. It was found that Pseudomonas chloritidismutans can use nitrite, nitrate and oxygen for aerobic respiration in liquid medium, and the pH increased and ORP decreased by activated denitrifier. When they used nitrite or nitrate for respiration, nitrogen removal effect was high and nitrite could be reduced more efficiently than nitrate. Denitrification process was accomplished faster when both nitrite and nitrate existed in the medium compared to each of which existed alone. Particularly, at denitrifying activity, the nitrogen removal rate of strain was not affected by the DO concentration in the culture media.

  11. Electrolytically aided denitrification on a rotating biological contactor.

    Science.gov (United States)

    Rodziewicz, Joanna; Filipkowska, Urszula; Dziadkiewicz, Ewa

    2011-01-01

    The study was conducted at a bench scale on a rotating biological contactor under both conventional conditions (without the flow of electric current) and with the passage of an electric current having the following densities: 0.2 A m(-2), 0.8 A m(-)2 and 1.5 A m(-2). Stainless-steel discs covered with an immobilized biofilm served as a cathode, whereas an electrode made of stainless steel immersed in the wastewater of the flow tank of the contactor served as an anode. Experiments were carried out on municipal wastewater containing nitrogen in the organic and ammonium forms. The highest efficiency of nitrogen removal was observed with the passage of electric current at the density of 0.2 A m(-2). The efficiency of the denitrification process was over 64% and the nitrification efficiency was 93.4%.

  12. Stoichiometries of remineralisation and denitrification in global biogeochemical ocean models

    Directory of Open Access Journals (Sweden)

    A. Paulmier

    2009-05-01

    Full Text Available Since the seminal paper of Redfield (1934, constant stoichiometric elemental ratios linking biotic carbon and nutrient fluxes are often assumed in marine biogeochemistry, and especially in coupled biogeochemical circulation models, to couple the global oxygen, carbon and nutrient cycles. However, when looking in more detail, some deviations from the classical Redfield stoichiometry have been reported, in particular with respect to remineralization of organic matter changing with depth or with ambient oxygen levels. We here compare the assumptions about the stoichiometry of organic matter and its remineralization that are used explicitly and implicitly in common biogeochemical ocean models. We find that the implicit assumptions made about the hydrogen content of organic matter can lead to inconsistencies in the modeled remineralization and denitrification stoichiometries. It is suggested that future marine biogeochemical models explicitly state the chemical composition assumed for the organic matter, including its oxygen and hydrogen content.

  13. Eddies reduce denitrification and compress habitats in the Arabian Sea

    Science.gov (United States)

    Lachkar, Zouhair; Smith, Shafer; Lévy, Marina; Pauluis, Olivier

    2016-09-01

    The combination of high biological production and weak oceanic ventilation in regions, such as the northern Indian Ocean and the eastern Pacific and Atlantic, cause large-scale oxygen minimum zones (OMZs) that profoundly affect marine habitats and alter key biogeochemical cycles. Here we investigate the effects of eddies on the Arabian Sea OMZ—the world's thickest—using a suite of regional model simulations with increasing horizontal resolution. We find that isopycnal eddy transport of oxygen to the OMZ region limits the extent of suboxia so reducing denitrification, increasing the supply of nitrate to the surface, and thereby enhancing biological production. That same enhanced production generates more organic matter in the water column, amplifying oxygen consumption below the euphotic zone, thus increasing the extent of hypoxia. Eddy-driven ventilation likely plays a similar role in other low-oxygen regions and thus may be crucial in shaping marine habitats and modulating the large-scale marine nitrogen cycle.

  14. 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.

  15. The Effects of Different Fertilizing Methods on Nitrification and Denitrification in Black Soil in Songnen Plain

    Institute of Scientific and Technical Information of China (English)

    LIU Shu-yu; WANG Hong-yan; WANG Xu-mei; QI Zhi-yong

    2004-01-01

    The paper compared the effects of application of farm manure with chemical fertilizers on nitrification and denitrification in black soil, the result showed that the numbers of nitrobacterias and denitrobacterias in farm manure treatment were both higher than that of other treatments. The intensity of denitrification in chemical treatment was higher than that of manure treatment. The content of organic matter in soil was correlated with the intensity of nitrification and denitrification, and the coefficients were respectively 0.9981 and 0.8693.

  16. High rates of denitrification and nitrate removal in cold seep sediments.

    Science.gov (United States)

    Bowles, Marshall; Joye, Samantha

    2011-03-01

    We measured denitrification and nitrate removal rates in cold seep sediments from the Gulf of Mexico. Heterotrophic potential denitrification rates were assayed in time-series incubations. Surficial sediments inhabited by Beggiatoa exhibited higher heterotrophic potential denitrification rates (32 μM N reduced day(-1)) than did deeper sediments (11 μM N reduced day(-1)). Nitrate removal rates were high in both sediment horizons. These nitrate removal rates translate into rapid turnover times (cold seeps and the requirement for novel mechanisms to provide nitrate to the sediment microbial community.

  17. Directly measured denitrification reveals oyster aquaculture and restored oyster reefs remove nitrogen at comparable high rates

    Science.gov (United States)

    Coastal systems are increasingly impacted by over-enrichment of nutrients, which has cascading effects for ecosystem functioning. Oyster restoration and aquaculture are both hypothesized to mitigate excessive nitrogen (N) loads via benthic denitrification (DNF). However, this has...

  18. 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...

  19. Ecology of fungi in the denitrification zones of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Manohar, C.S.

    The microbial process, denitrification was considered to be an inherent character of a few specialized groups of bacteria. But recently, the involvement of micro-eukaryotes such as fungi and foraminiferans are reported (Takaya et al., 2002; Risgaard...

  20. 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.

    regimes. It is suggested that ammonium actively produced by detrital breakdown (ammonification) is efficiently consumed through nitrification process. The three processes in concert viz. ammonification, nitrification and denitrification appear to operate...

  1. Denitrification and polar stratospheric cloud formation during the Arctic winter 2009/2010

    National Research Council Canada - National Science Library

    F. Khosrawi; J. Urban; M. C. Pitts; P. Voelger; P. Achtert; M. Kaphlanov; M. L. Santee; G. L. Manney; D. Murtagh; K.-H. Fricke

    2011-01-01

    The sedimentation of HNO3 containing Polar Stratospheric Cloud (PSC) particles leads to a permanent removal of HNO3 and thus to a denitrification of the stratosphere, an effect which plays an important role in stratospheric ozone depletion...

  2. Behavior of solid carbon sources for biological denitrification in groundwater remediation.

    Science.gov (United States)

    Zhang, Jianmei; Feng, Chuanping; Hong, Siqi; Hao, Huiling; Yang, Yingnan

    2012-01-01

    The present study was conducted to compare the behavior of wheat straw, sawdust and biodegradable plastic (BP) as potential carbon sources for denitrification in groundwater remediation. The results showed that a greater amount of nitrogen compounds were released from wheat straw and sawdust than from BP in leaching experiments. In batch experiments, BP showed higher nitrate removal efficiency and longer service life than wheat straw and sawdust, which illustrated that BP is the most appropriate carbon source for stimulation of denitrification activity. In column experiments, BP was able to support complete denitrification at influent nitrate concentrations of 50, 60, 70, 80, and 90 mg NO(3)(-)-N/L, showing corresponding denitrification rates of 0.12, 0.14, 0.17, 0.19, and 0.22 mg NO(3)(-)-N.L(-1).d(-1).g(-1), respectively. These findings indicate that BP is applicable for use as a carbon source for nitrate-polluted groundwater remediation.

  3. Dynamics of partial anaerobiosis denitrification, and water in soil : experiments and simulation

    NARCIS (Netherlands)

    Leffelaar, P.A.

    1987-01-01

    Dynamic interactions between biological respiration and denitrification, and physical transport processes that modify the abiotic soil environment in which bacteria live, were studied through the development of a new type of experimental respirometer system and an explanatory simulation

  4. Removal of nitrate from groundwater by heterotrophic denitrification using the solid carbon source

    Institute of Scientific and Technical Information of China (English)

    WANG XuMing; WANG JianLong

    2009-01-01

    Removal of nitrate from groundwater was investigated using biodegradable meal box (BMB) and poly(ε-caprolactone) (PCL) as carbon source and biofilm carrier. The experimental results show that nitrate in groundwater can be effectively removed using BMB and PCL as carbon source. Denitrification 7.5. The pH value of effluent ranged from 7 to 8, and NO2-N concentration was less than 0.1 mg/L. Compared with BMB, PCL could decrease nitrite accumulation; however, more significant influence of temperature on denitrification was observed for PCL as carbon source. Temperature constants for BMB and PCL were 0.045 and 0.068, respectively, at 10-30℃. Based on denitrification efficiency and cost, BMB is more suitable as a carbon source for denitrification of groundwater than PCL.

  5. Combined effects of carbon, nitrogen and phosphorus on CH4 production and denitrification in wetland sediments

    NARCIS (Netherlands)

    Kim, Sang Yun; Veraart, Annelies; Meima-Franke, M.; Bodelier, Paul

    2015-01-01

    Anthropogenic impacts and associated climate change are anticipated to change nutrient availability in wetlands. Changes in nutrient availability can affect major biogeochemical reactions (i.e., methanogenesis, denitrification) which impact greenhouse gas emissions and trophic status of ecosystems.

  6. Advances in Nitrogen Denitrification and N2O Emission in Agro-ecosystem

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yu-shu; DING Hong; QIN Sheng-jin

    2011-01-01

    Nitrification and denitrification are two key links of nitrogen flow cycle in soil. N2O and N2, generated from biochemical process of nitrogen, can cause not only the nitrogen losses and reduction of nitrogen use efficiency, but also the boosted concentration of greenhouse gases,severely endangering the environment. Accordingly, nitrification-denitrification has been more and more concerned from whether an agricultural view, or an environmental one. Referring to the related literatures published at home and abroad in recent years, we overviewed the denitrification-caused N loss and N2O emission in various agro-ecosystems, and based on which we put forward countermeasures to reduce the denitrification-caused N loss and N2O emission and its research prospects in the future.

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

    National Research Council Canada - National Science Library

    Koeve, W; Kähler, P

    2010-01-01

    .... 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...

  8. 3-D microphysical model studies of Arctic denitrification: comparison with observations

    Directory of Open Access Journals (Sweden)

    S. Davies

    2005-01-01

    Full Text Available Simulations of Arctic denitrification using a 3-D chemistry-microphysics transport model are compared with observations for the winters 1994/1995, 1996/1997 and 1999/2000. The model of Denitrification by Lagrangian Particle Sedimentation (DLAPSE couples the full chemical scheme of the 3-D chemical transport model, SLIMCAT, with a nitric acid trihydrate (NAT growth and sedimentation scheme. We use observations from the Microwave Limb Sounder (MLS and Improved Limb Atmospheric Sounder (ILAS satellite instruments, the balloon-borne Michelsen Interferometer for Passive Atmospheric Sounding (MIPAS-B, and the in situ NOy instrument on-board the ER-2. As well as directly comparing model results with observations, we also assess the extent to which these observations are able to validate the modelling approach taken. For instance, in 1999/2000 the model captures the temporal development of denitrification observed by the ER-2 from late January into March. However, in this winter the vortex was already highly denitrified by late January so the observations do not provide a strong constraint on the modelled rate of denitrification. The model also reproduces the MLS observations of denitrification in early February 2000. In 1996/1997 the model captures the timing and magnitude of denitrification as observed by ILAS, although the lack of observations north of ~67° N make it difficult to constrain the actual timing of onset. The comparison for this winter does not support previous conclusions that denitrification must be caused by an ice-mediated process. In 1994/1995 the model notably underestimates the magnitude of denitrification observed during a single balloon flight of the MIPAS-B instrument. Agreement between model and MLS HNO3 at 68 hPa in mid-February 1995 was significantly better. Sensitivity tests show that a 1.5 K overall decrease in vortex temperatures or a factor 4 increase in assumed NAT nucleation rates produce the best

  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. Effects of restoration and reflooding on soil denitrification in a leveed Midwestern floodplain.

    Science.gov (United States)

    Orr, Cailin H; Stanley, Emily H; Wilson, Karen A; Finlay, Jacques C

    2007-12-01

    River floodplains have the potential to remove nitrate from water through denitrification, the anaerobic microbial conversion of nitrate to nitrogen gas. An important factor in this process is the interaction of river water with floodplain soil; however, many rivers have been disconnected from their historic floodplains by levees. To test the effect of reflooding a degraded floodplain on nitrate removal, we studied changes in soil denitrification rates on the Baraboo River floodplain in Wisconsin, USA, as it underwent restoration. Prior to this study, the site had been leveed, drained, and farmed for more than 50 years. In late fall 2002, the field drainage system was removed, and a gate structure was installed to allow controlled flooding of this site with river water. Soil moisture was extremely variable among zones and months and reflected local weather. Soil organic matter was stable over the study period with differences occurring along the elevation gradient. High soil nitrate concentrations occurred in dry, relatively organic-poor soil samples and, conversely, all samples with high moisture soils characterized by low nitrate. We measured denitrification in static cores and potential denitrification in bulk samples amended with carbon and nitrogen, one year before and two years following the manipulation. Denitrification rates showed high temporal and spatial variability. Static core rates of individual sites ranged widely (from 0.00 to 16.7 microg N2O-N x [kg soil](-1) x h(-1), mean +/- SD = 1.10 +/- 3.02), and denitrification enzyme activity (DEA) rates were similar with a slightly higher mean (from 0.00 to 15.0 microg N2O-N x [kg soil](-1) x h(-1), 1.41 +/- 1.98). Denitrification was not well-correlated with soil nitrate, organic matter content, or moisture levels, the three parameters typically thought to control denitrification. Static core denitrification rates were not significantly different across years, and DEA rates decreased slightly the second

  11. 3-D microphysical model studies of Arctic denitrification: comparison with observations

    Directory of Open Access Journals (Sweden)

    S. Davies

    2005-01-01

    Full Text Available Simulations of Arctic denitrification using a 3-D chemistry-microphysics transport model are compared with observations for the winters 1994/95, 1996/97 and 1999/2000. The model of Denitrification by Lagrangian Particle Sedimentation (DLAPSE couples the full chemical scheme of the 3-D chemical transport model, SLIMCAT, with a nitric acid trihydrate (NAT growth and sedimentation scheme. We use observations from the Microwave Limb Sounder (MLS and Improved Limb Atmospheric Sounder (ILAS satellite instruments, the balloon-borne Michelsen Interferometer for Passive Atmospheric Sounding (MIPAS-B, and the in situ NOy instrument on-board the ER-2. As well as directly comparing model results with observations, we also assess the extent to which these observations are able to validate the modelling approach taken. For instance, in 1999/2000 the model captures the temporal development of denitrification observed by the ER-2 from late January into March. However, in this winter the vortex was already highly denitrified by late January so the observations do not provide a strong constraint on the modelled rate of denitrification. The model also reproduces the MLS observations of denitrification in early February 2000. In 1996/97 the model captures the timing and magnitude of denitrification as observed by ILAS, although the lack of observations north of ~67° N in the beginning of February make it difficult to constrain the actual timing of onset. The comparison for this winter does not support previous conclusions that denitrification must be caused by an ice-mediated process. In 1994/95 the model notably underestimates the magnitude of denitrification observed during a single balloon flight of the MIPAS-B instrument. Agreement between model and MLS HNO3 at 68 hPa in mid-February 1995 is significantly better. Sensitivity tests show that a 1.5 K overall decrease in vortex temperatures, or a factor 4 increase in assumed NAT nucleation rates, produce the best

  12. Denitrification potential in stream sediments impacted by acid mine drainage: effects of pH, various electron donors, and iron.

    Science.gov (United States)

    Baeseman, J L; Smith, R L; Silverstein, J

    2006-02-01

    Acid mine drainage (AMD) contaminates thousands of kilometers of stream in the western United States. At the same time, nitrogen loading to many mountain watersheds is increasing because of atmospheric deposition of nitrate and increased human use. Relatively little is known about nitrogen cycling in acidic, heavy-metal-laden streams; however, it has been reported that one key process, denitrification, is inhibited under low pH conditions. The objective of this research was to investigate the capacity for denitrification in acidified streams. Denitrification potential was assessed in sediments from several Colorado AMD-impacted streams, ranging from pH 2.60 to 4.54, using microcosm incubations with fresh sediment. Added nitrate was immediately reduced to nitrogen gas without a lag period, indicating that denitrification enzymes were expressed and functional in these systems. First-order denitrification potential rate constants varied from 0.046 to 2.964 day(-1). The pH of the microcosm water increased between 0.23 and 1.49 pH units during denitrification. Additional microcosm studies were conducted to examine the effects of initial pH, various electron donors, and iron (added as ferrous and ferric iron). Decreasing initial pH decreased denitrification; however, increasing pH had little effect on denitrification rates. The addition of ferric and ferrous iron decreased observed denitrification potential rate constants. The addition of glucose and natural organic matter stimulated denitrification potential. The addition of hydrogen had little effect, however, and denitrification activity in the microcosms decreased after acetate addition. These results suggest that denitrification can occur in AMD streams, and if stimulated within the environment, denitrification might reduce acidity.

  13. Denitrification potential in stream sediments impacted by acid mine drainage: Effects of pH, various electron donors, and iron

    Science.gov (United States)

    Baeseman, J.L.; Smith, R.L.; Silverstein, J.

    2006-01-01

    Acid mine drainage (AMD) contaminates thousands of kilometers of stream in the western United States. At the same time, nitrogen loading to many mountain watersheds is increasing because of atmospheric deposition of nitrate and increased human use. Relatively little is known about nitrogen cycling in acidic, heavy-metal-laden streams; however, it has been reported that one key process, denitrification, is inhibited under low pH conditions. The objective of this research was to investigate the capacity for denitrification in acidified streams. Denitrification potential was assessed in sediments from several Colorado AMD-impacted streams, ranging from pH 2.60 to 4.54, using microcosm incubations with fresh sediment. Added nitrate was immediately reduced to nitrogen gas without a lag period, indicating that denitrification enzymes were expressed and functional in these systems. First-order denitrification potential rate constants varied from 0.046 to 2.964 day-1. The pH of the microcosm water increased between 0.23 and 1.49 pH units during denitrification. Additional microcosm studies were conducted to examine the effects of initial pH, various electron donors, and iron (added as ferrous and ferric iron). Decreasing initial pH decreased denitrification; however, increasing pH had little effect on denitrification rates. The addition of ferric and ferrous iron decreased observed denitrification potential rate constants. The addition of glucose and natural organic matter stimulated denitrification potential. The addition of hydrogen had little effect, however, and denitrification activity in the microcosms decreased after acetate addition. These results suggest that denitrification can occur in AMD streams, and if stimulated within the environment, denitrification might reduce acidity. ?? Springer Science+Business Media, Inc. 2006.

  14. Fluctuations in productivity and denitrification in the southeastern Arabian Sea during the Late Quaternary

    Digital Repository Service at National Institute of Oceanography (India)

    Kessarkar, P.M.; Rao, V.P.; Naqvi, S.W.A.; Chivas, A.R.; Saino, T.

    , D. W., The effect of millennial-scale changes in Arabian Sea denitrification on atmos- pheric CO 2 . Nature, 2002, 415, 159–162. 8. Reichart, G. J., Lourens, L. J. and Zachariasse, W. J., Temporal variability in the northern Arabian Sea Oxygen.... Suthhof, A., Ittekkot, V. and Gaye-Haake, B., Millennial-scale oscillations of denitrification intensity in the Arabian Sea during the late Quaternary and its potential influence on atmospheric N 2 O and global climate. Glob. Biogeochem. Cycles, 2001...

  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

    A concurrent operation of anaerobic ammonium oxidation (ANAMMOX) and denitrification was investigated in a well known UASB reactor seeding with both ANAMMOX and anaerobic granular sludges. ANAMMOX activity was confirmed by hydroxylamine test and the hybridization of biomass using the gene probes......–nitrate concentrations in all reactors confirmed the undergone concurrent denitrification which thrives when sufficient organic matter is available. COD concentration over 300 mg l−1 was found to inactivate or eradicate ANAMMOX communities....

  16. 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.

  17. Interaction between nitrification, denitrification and nitrous oxide production in fumigated soils

    Science.gov (United States)

    Yan, Dongdong; Wang, Qiuxia; Mao, Liangang; Ma, Taotao; Li, Yuan; Ouyang, Canbin; Guo, Meixia; Cao, Aocheng

    2015-02-01

    Soil fumigation can increase mineral nitrogen due to the mineralization of soil microbial biomass killed during the fumigation, and as a result nitrous oxide (N2O) emission would increase. In addition, a fumigant's impact on soil nitrification and denitrification would also alter the dynamics of N2O production in fumigated soils. Laboratory incubation studies were conducted to quantify the dynamic changes in N2O production following various fumigant treatments, and to determine the interaction between nitrification, denitrification and N2O production in fumigated soils. Results showed a substantial increase in NH4+-N and dissolved amino acids (DAA) during 7 days fumigation at 1WAF (week after fumigation). The application of fumigants caused significant inhibition of nitrification. However the results relating to potential denitrification were quite different. The rates of potential denitrification in chloropicrin (Pic) and dazomet (DZ) treatments at 1WAF were 3.5 and 5.6 times higher than the untreated control. Potential denitrification was greatly stimulated after Pic and DZ fumigation. The N2O production rates in Pic and DZ fumigated soil were significantly higher than the untreated control at 1WAF in the tested soil type. The cumulative N2O emissions in Pic and DZ fumigated soil were also significantly higher than the untreated control, but there were no significant differences among 1,3-dichloropropene (1,3-D), dimethyl disulfide (DMDS) and untreated control. A positive relationship between N2O production and potential denitrification (PDN) was observed (r = 0.951, P products of Pic and DZ would be available for microbial-aided denitrification reactions as nitrogen sources leading to N2O production, indicating that Pic and DZ degradation stimulated denitrification activity responsible for soil N2O production.

  18. Use of agro-food wastewaters for the optimisation of the denitrification process.

    Science.gov (United States)

    Rodríguez, L; Villaseñor, J; Fernández, F J

    2007-01-01

    The aim of this work was to study the feasibility of the denitrification process enhancement, in the Ciudad Real (Spain) WWTP, by dosing agro-food wastewaters generated nearby the city. The studied agro-food wastewaters were characterised by a high COD and low nutrients concentration. The denitrification rates with these wastewaters were lower than those obtained either with acetate or urban sewage, however the dose of agro-food wastewaters raised significantly the denitrification capacity in the WWTP because of the significant increase of easily biodegradable substrates in the wastewater. From the laboratory NUR batch test it was observed that the best agro-food wastewater to enhance the denitrification process was that coming from tomato processing, which presented an average denitrification rate of 1.9 mg NOx-N/(g VSS.h) and an average denitrification yield of 0.2 mg NOx-N/mg COD. The viability of the use of tomato processing wastewater was checked in a pilot plant optimised for urban sewage treatment with biological nutrient removal. The optimum dose, 5.9 mg COD/mg NOx-N, was applied and 99% of the nitrate was removed from the wastewater without influencing negatively either the COD or P effluent concentrations.

  19. Study on enhanced denitrification using particulate organic matter in membrane bioreactor by mechanism modeling.

    Science.gov (United States)

    Zheng, Min; Liu, Yan-Chen; Wang, Cheng-Wen; Xu, Kang-Ning

    2013-11-01

    Particulate organic matter (POM) in wastewater is a potential denitrification carbon source, while the optimal operational mode using denitrification mechanism with POM is still unclear in wastewater treatment plants. In this work, we investigated the denitrification rates (DNRs) in a full-scale membrane bioreactor (MBR) coupled with two-stage pre-anoxic (pre-AN), and then evaluated the POM denitrification efficiency using mechanism modeling. The results indicate that POM related fraction accounted for the majority of the obtained specific DNR of 1.39±0.46mgNg(-1) MLVSS h(-1) in the second pre-AN without available soluble carbon source. The modeling approaches with calibration and validation procedures estimated a high residual POM concentration of 0.17g COD g(-1) MLVSS in the activated sludge, which provided specific DNR of 1.14mgNg(-1) MLVSS h(-1). High POM retention time in the reactor was the result of high solid retention time used in the MBR. In particular, post-AN of high biomass concentration could provide the highest POM denitrification efficiency in MBR. The MBR process combined with additional sludge reduction technology could further enhance denitrification by POM.

  20. 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.

  1. [Element Sulfur Autotrophic Denitrification Combined Anaerobic Ammonia Oxidation].

    Science.gov (United States)

    Zhou, Jian; Huang, Yong; Liu, Xin; Yuan, Yi; Li Xiang; Wangyan, De-qing; Ding, Liang; Shao, Jing-wei; Zhao, Rong

    2016-03-15

    A novel element sulfur autotrophic denitrification combined anaerobic ammonia oxidation process, reacted in CSTR, was used to investigate the sulfate production and alkalinity consumption during the whole process. The element sulfur dosage was 50 g · L⁻¹. The inoculation volume of ANAMMOX granular sludge was 100 g · L⁻¹. The agitation rate and environment reaction temperature of the CSTR were set to 120 r · min⁻¹ and 35°C ± 0.5°C, respectively. The pH of influent was maintained in range of 8. 0-8. 4. During the start-up stage of sulfur based autotrophic denitrification, the nitrogen removal loading rate could reach 0.56-0.71 kg · (m³ · d) ⁻¹ in the condition of 5.3 h hydrogen retention time and 200 mg · L⁻¹ nitrate nitrogen. After the addition of 60 mg · L⁻¹ ammonia nitrogen, Δn(SO₄²⁻):Δn(NO₃⁻) decreased from 1.21 ± 0.06 to 1.01 ± 0.10, Δ(IC): Δ(NO₃⁻-N) decreased from 0.72 ± 0.1 to 0.51 ± 0.11, and the effluent pH increased from 6.5 to 7.2. During the combined stage, the ammonia concentration of effluent was 10.1-19.2 mg · L⁻¹, and the nitrate-nitrogen removal loading rate could be maintained in range of 0.66-0.88 kg · (m³ · d)⁻¹. The Δn (NH₄⁺): Δn (NO₃⁻) ratio reached 0.43, and the NO₃⁻ removal rate was increased by 60% in the simultaneous ammonia and nitrate removal reaction under the condition of G(T) = 22-64 s⁻¹ and pH = 8.08, while improper conditions reduced the efficiency of simultaneous reaction.

  2. Simulating microbial denitrification with EPIC: Model description and initial testing

    Energy Technology Data Exchange (ETDEWEB)

    Izaurralde, Roberto C.; Mcgill, William B.; Williams, Jimmy R.; Jones, Curtis D.; Link, Robert P.; Manowitz, D.; Schwab, D. E.; Zhang, Xuesong; Robertson, G. P.; Milar, Neville

    2017-09-01

    Microbial denitrification occurs in anaerobic soil microsites and aquatic environments leading to production of N2O and N2 gases, which eventually escape to the atmosphere. Atmospheric concentrations of N2O have been on the rise since the beginning of the industrial revolution due to large-scale manipulations of the N cycle in managed ecosystems, especially the use of synthetic nitrogenous fertilizer. Here we document and test a microbial denitrification model identified as IMWJ and implemented as a submodel in the EPIC terrestrial ecosystem model. The IMWJ model is resolved on an hourly time step using the concept that C oxidation releases electrons that drive a demand for electron acceptors such as O2 and oxides of N (NO3-, NO2-, and N2O). A spherical diffusion approach is used to describe O2 transport to microbial surfaces while a cylindrical diffusion method is employed to depict O2 transport to root surfaces. Oxygen uptake by microbes and roots is described with Michaelis-Menten kinetic equations. If insufficient O2 is present to accept all electrons generated, the deficit for electron acceptors may be met by oxides of nitrogen, if available. The movement of O2, CO2 and N2O through the soil profile is modeled using the gas transport equation solved on hourly or sub-hourly time steps. Bubbling equations also move N2O and N2 through the liquid phase to the soil surface under highly anaerobic conditions. We used results from a 2-yr field experiment conducted in 2007 and 2008 at a field site in southwest Michigan to test the ability of EPIC, with the IMWJ option, to capture the non-linear response of N2O fluxes as a function of increasing rates of N application to maize [Zea mays L.]. Nitrous oxide flux, soil inorganic N, and ancillary data from 2007 were used for EPIC calibration while 2008 data were used for independent model validation. Overall, EPIC reproduced well the timing and magnitude of N2O fluxes and NO3- mass in surficial soil layers after N

  3. 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

    2017-02-17

    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 NaN3 can inhibit nitrite oxidation effectively; meanwhile, the nitrite denitrification with N2O 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 H2O to oxidize nitrite under anaerobic conditions. Proteobacteria might play a major role in the process of denitrification in MFC.

  4. Optimization and reconstruction technology of SCR flue gas denitrification ultra low emission in coal fired power plant

    Science.gov (United States)

    Li, Xinhao

    2017-09-01

    In recent decades, nitrogen oxides (NOx) emissions from thermal power plant increased year by year in China. A large number of nitrogen oxides (NOx) emissions caused by the growing environmental problems have been widely attached importance to people. SCR denitrification technology has the advantages of cleanliness and high efficiency. At present, it has been the major technology to control NOx emission because of its high denitrification efficiency, reliable operation, no by-products and simple structure of the device. The denitrification efficiency can be stabilized at 70%. In this paper, three different denitrification methods are compared. The factors influencing the denitrification efficiency, the system arrangement and the key factors of the denitrification system are discussed in detail. And the numerical simulation of how to use this calculation software in the SCR reactor flue, baffle, reactor, spray ammonia grille and spray ammonia, mixer, etc. are reviewed, as well as the effect of system operation control on the deoxidation performance.

  5. 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

  6. Development of electrochemical denitrification from waste water containing ammonium nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Sawa, Toshio; Hirose, Yasuo; Ishii, Yoshinori; Takatsudo, Atsushi; Wakasugi, Kazuhico; Hayashi, Hiroshi

    1995-12-31

    The authors developed processes to dentrify waste water containing ammonium nitrate discharged from the nuclear fuel manufacturing works and to recover nitric acid and ammonia. For denitrification they applied the operating method and the conditions of operation to make 0.4mM or less from NH{sub 4}NO{sub 3} waste water of 1.5 M by 3 stages of electrodialysis cells. To recover nitric acid and ammonium water, they separated HNO{sub 3} solution of 6 M and NH{sub 4}OH solution with one unit of electrolysis cell, then absorbed NH{sub 3} gas from NH{sub 4}OH solution with water and applied the condition of operation to recover 8 M NH{sub 4}OH solution. The authors demonstrated that treatment and recovery can be carried out stably with actual waste water with a system through the combination of previously mentioned electrodialysis cells, electrolysis cells and an ammonia gas absorber. At present they are planning a plant where NH{sub 4}NO{sub 3} waste water of 4,500 mol can be treated per day.

  7. Reductive denitrification using zero-valent iron and bimetallic iron.

    Science.gov (United States)

    Choi, Jeong-Hak; Shinb, Won Sik; Choi, Sang June; Kim, Young-Hun

    2009-08-01

    A study of reductive denitrification of nitrate was conducted. Microscale zero-valent iron (ZVI) and palladium-coated iron (Pd/Fe) were used in the reduction of nitrate with variable pH. The solution pH was controlled by an auto controlling system instead of chemical buffers. Higher reduction rates were achieved with lower pH and lower pH gave the pseudo-first-order kinetics while it was close to the zero-order reaction when the pH of the solution was becoming high and nitrate concentration was higher. As it took several hours to convert intermediates to ammonia completely, the assumption, under which mass loss calculated from the measured ammonia concentration right after the reaction was the mass of nitrogen evolved, could lead to overestimation of the nitrogen selectivity. The current study confirmed that the palladium coating on the iron could increase the nitrogen selectivity, and the Pd/Fe system could also achieve the advantages of coupling of electron source and catalyst with regard to the engineering aspects.

  8. REMOVAL OF ADDED NITRATE IN THE SINGLE, BINARY, AND TERNARY SYSTEMS OF COTTON BURR COMPOST, ZEROVALENT IRON, AND SEDIMENT: IMPLICATIONS FOR GROUNDWATER NITRATE REMEDIATION USING PERMEABLE REACTIVE BARRIERS

    Science.gov (United States)

    Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe0) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and ...

  9. REMOVAL OF ADDED NITRATE IN THE SINGLE, BINARY, AND TERNARY SYSTEMS OF COTTON BURR COMPOST, ZEROVALENT IRON, AND SEDIMENT: IMPLICATIONS FOR GROUNDWATER NITRATE REMEDIATION USING PERMEABLE REACTIVE BARRIERS

    Science.gov (United States)

    Recent research has shown that carbonaceous solid materials and zerovalent iron (Fe0) may potentially be used as media in permeable reactive barriers (PRBs) to degrade groundwater nitrate via heterotrophic denitrification in the solid carbon system, and via abiotic reduction and ...

  10. 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.

  11. Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/3

    Directory of Open Access Journals (Sweden)

    S. Davies

    2005-11-01

    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 2002/3. 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.

  12. [Turning points in world history: urological comments on pathography of famous people: did Napoleon Bonaparte have a cystitis during the battle of Waterloo and was the battle lost because of that?].

    Science.gov (United States)

    Hatzinger, M; Stastny, M; Haferkamp, A

    2011-03-01

    Apparently unimportant diseases of some prominent figures can have a considerable effect on the course of time at turning points in world history. It is quite conceivable that the Battle of Waterloo on 18 June 1815 had been lost by France because Napoleon was not in full possession of his powers, because he was suffering from acute cystitis. Adverse weather conditions with continuous rain and coldness in advance of the battle, extremely primitive hygienic conditions and more than simple quarters for the night led to the development of cystitis. Based on the records of his biographers, his personal physician and the letters to his brother, we know that Napoleon was not able to give the command to attack in the early morning as intended, but in the early noon, only because of his bad general condition. This delay of several hours led, as we all know, to the intervention of Prussia and the devastating defeat of France. Thus it appears that a relatively unimportant urological disease influenced the course of world history crucially.

  13. Denitrification Losses and N2O Emissions from Nitrogen Fertilizer Applied to a Vegetable Field

    Institute of Scientific and Technical Information of China (English)

    CAO Bing; He Fa-Yun; Xu Qiu-Ming; Yin Bin; CAI Gui-Xin

    2006-01-01

    A field experiment was conducted on Chinese cabbage (Brassica campestris L. ssp. pekinensis (Lour.) Olsson) in a Nanjing suburb in 2003. The experiment included 4 treatments in a randomized complete block design with 3 replicates: zero chemical fertilizer N (CK); urea at rates of 300 kg N ha-1 (U300) and 600 kg N ha-1 (U600), both as basal and two topdressings; and polymer-coated urea at a rate of 180 kg N ha-1 (PCU180) as a basal application. The acetylene inhibition technique was used to measure denitrification (N2 + N2O) from intact soil cores and N2O emissions in the absence of acetylene. Results showed that compared to CK total denitrification losses were significantly greater (P ≤ 0.05) in the PCU180, U300, and U600 treatments, while N2O emissions in the U300 and U600 treatments were significantly higher (P ≤ 0.05) than CK. In the U300 and U600 treatments peaks of denitrification and N2O emission were usually observed after N application. In the polymer-coated urea treatment (PCU180) during the period 20 to 40 days after transplanting, higher denitrification rates and N2O fluxes occurred. Compared with urea, polymer-coated urea did not show any effect on reducing denitrification losses and N2O emissions in terms of percentage of applied N. As temperature gradually decreased from transplanting to harvest, denitrification rates and N2O emissions tended to decrease. A significant (P ≤ 0.01) positive correlation occurred between denitrification (r = 0.872) or N2O emission (r = 0.781) flux densities and soil temperature in the CK treatment with a stable nitrate content during the whole growing season.

  14. Seasonal variability of denitrification efficiency in northern salt marshes: an example from the St. Lawrence Estuary.

    Science.gov (United States)

    Poulin, Patrick; Pelletier, Emilien; Saint-Louis, Richard

    2007-06-01

    In coastal ecosystems, denitrification is a key process in removing excess dissolved nitrogen oxides and participating in the control of eutrophication process. Little is known about the role of salt marshes on nitrogen budgets in cold weather coastal areas. Although coastal salt marshes are important sites for organic matter degradation and nutrient regeneration, bacterial-mediated nitrogen cycling processes, such as denitrification, remain unknown in northern and sub-arctic regions, especially under winter conditions. Using labelled nitrogen (15N), denitrification rates were measured in an eastern Canadian salt marsh in August, October and December 2005. Freshly sampled undisturbed sediment cores were incubated over 8h and maintained at their sampling temperatures to evaluate the influence of low temperatures on the denitrification rate. From 2 to 12 degrees C, average denitrification rate and dissolved oxygen consumption increased from 9.6 to 25.5 micromol N2 m-2 h-1 and from 1.3 to 1.8 mmol O2 m-2 h-1, respectively, with no statistical dependence of temperature (p>0.05). Nitrification has been identified as the major nitrate source for denitrification, supplying more than 80% of the nitrate demand. Because no more than 31% of the nitrate removed by sediment is estimated to be denitrified, the presence of a major nitrate sink in sediment is suspected. Among possible nitrate consumption mechanisms, dissimilatory reduction of nitrate to ammonium, metal and organic matter oxidation processes are discussed. Providing the first measurements of denitrification rate in a St. Lawrence Estuary salt marsh, this study evidences the necessity of preserving and restoring marshes. They constitute an efficient geochemical filter against an excess of nitrate dispersion to coastal waters even under cold northern conditions.

  15. 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

  16. Denitrification in a Sand and Gravel Aquifer: An Overview of a Long-Term Study

    Science.gov (United States)

    Smith, R. L.

    2002-12-01

    Denitrification can be a key process affecting the concentration and transport of nitrate in the subsurface. As a dissimilatory process, it has the potential to consume significant amounts of nitrate, once oxygen has been depleted, while serving as the predominant terminal electron-accepting reaction for the microbial food chain. Although denitrification has been extensively studied in soils and some surface water systems, relatively little is known about the process in the saturated subsurface. Consequently, a long-term study was established to examine the occurrence of denitrification in a sewage-contaminated, sand and gravel aquifer on Cape Cod, Massachusetts. This study included a characterization of the effect of the process on spatial and temporal distribution of inorganic nitrogen species along aquifer flow paths, the effect on nitrogen stable isotope distributions, and the overall effect on the process of dispersion and consumption of dissolved oxygen and dissolved organic carbon. A variety of laboratory and field studies have been conducted to quantify the overall rate of denitrification relative to subsurface flow, factors that control the process in the Cape Cod aquifer, and the steady-state dynamics of electron flow through the individual steps of the denitrification pathway. Under some conditions, the pathway was found to be unbalanced in the aquifer, causing accumulation of nitrogen oxide intermediates (nitrite, nitrous oxide, and nitric oxide) in the groundwater. Another aspect of this study was utilization of denitrification as a tool to remediate subsurface nitrate contamination. This included in situ enhancement tests using formate as an added electron donor and a laboratory project testing specific groups of denitrifiers isolated from the aquifer. Overall this long-term study has demonstrated that small-scale heterogeneity is a major factor that dictates and controls denitrification in an aquifer at any given locale, even systems viewed as

  17. Nitrification and denitrification in subalpine coniferous forests of different restoration stages in western Sichuan,China

    Institute of Scientific and Technical Information of China (English)

    LIU Yi; CHEN Jinsong; LIU Qing; WU Yan

    2007-01-01

    Nitrification is the biological conversion of organic or inorganic nitrogen compounds from a reduced to a more oxidized state.Denitrification is generally referred to as the microbial reduction of nitrate to nitrite and further gaseous forms of nitric oxide,nitrous oxide and molecular nitrogen.They are functionally interconnected processes in the soil nitrogen cycle that are involved in the control of longterm nitrogen losses in ecosystems through nitrate leaching and gaseous N losses.In" order to better understand how nitrification and denitrification change during the process of ecosystem restoration and how they are affected by various controlling factors,gross nitrification rates and denitrification rates were determined using the barometric process separation (BaPS) technique in subalpine coniferous forests of different restoration stages.The results showed that forest restoration stage had no significant effects on gross nitrification rates or denitrification rates (One-way ANOVA (analysis of variance),p < 0.05).There was no significant difference in the temperature coefficient (Q10) for gross nitrification rate among all the forest sites (One-wayANOVA,p < 0.05).Gross nitrification rates were positively correlated with water content (p <0.05),but not with soil pH,organic matter,total nitrogen,or C/N ratios.Denitrification rates in all the forest soils were low and not closely correlated with water content,soil pH,organic matter,or total nitrogen.Nevertheless,we found that C/N ratios obviously affected denitrification rates (p < 0.05).Results from this research suggest that gross nitrification is more responsible for the nitrogen loss from soils compared with denitrification.

  18. Influence of nutrient inputs, hexadecane, and temporal variations on denitrification and community composition of river biofilms.

    Science.gov (United States)

    Chénier, M R; Beaumier, D; Fortin, N; Roy, R; Driscoll, B T; Lawrence, J R; Greer, C W

    2006-01-01

    Biofilms were cultivated on polycarbonate strips in rotating annular reactors using South Saskatchewan River water during the fall of 1999 and the fall of 2001, supplemented with carbon (glucose), nitrogen (NH4Cl), phosphorus (KH2PO4), or combined nutrients (CNP), with or without hexadecane, a model compound representing aliphatic hydrocarbons used to simulate a pollutant. In fall 1999 and fall 2001, comparable denitrification activities and catabolic potentials were observed in the biofilms, implying that denitrifying populations showed similar activity patterns and catabolic potentials during the fall from year to year in this river ecosystem, when environmental conditions were similar. Both nirS and nirK denitrification genes were detected by PCR amplification, suggesting that both denitrifying bacterial subpopulations can potentially contribute to total denitrification. Between 91.7 and 99.8% of the consumed N was emitted in the form of N2, suggesting that emission of N2O, a major potent greenhouse gas, by South Saskatchewan River biofilms is low. Denitrification was markedly stimulated by the addition of CNP, and nirS and nirK genes were predominant only in the presence of CNP. In contrast, individual nutrients had no impact on denitrification and on the occurrence of nirS and nirK genes detected by PCR amplification. Similarly, only CNP resulted in significant increases in algal and bacterial biomass relative to control biofilms. Biomass measurements indicated a linkage between autotrophic and heterotrophic populations in the fall 1999 biofilms. Correlation analyses demonstrated a significant relationship (P < or = 0.05) between the denitrification rate and the biomass of algae and heterotrophic bacteria but not cyanobacteria. At the concentration assessed (1 ppb), hexadecane partially inhibited denitrification in both years, slightly more in the fall of 2001. This study suggested that the response of the anaerobic heterotrophic biofilm community may be

  19. Low molecular carbon compounds present in the rhizosphere control denitrification kinetics

    Science.gov (United States)

    Herold, M.; Morley, N.; Baggs, E.

    2013-12-01

    Nitrogen and carbon cycles play key roles in plant-microbe interactions in soils. Carbon is supplied by plants to microbes in the form of root exudates which includes both high and low molecular compounds. Nitrogen in turn is taken up by plants and rhizosphere microbes metabolise nitrogen compounds in several biochemical pathways. The conversion of nitrogen compounds to volatile products in the process of denitrification leads to increasing amounts of nitrous oxide (N2O) in the atmosphere. Nitrous oxide is a potent greenhouse gas and increasing emissions of N2O through intense agriculture have lead to intensified research to find possible mitigation strategies to reduce N2O production from soil. In our study we show the effect of low molecular carbon compounds, typically found in root exudates, on the dynamics of denitrification as well as the dose response effect of the single compounds. The hypothesis was tested that different compound groups change the kinetics of the different reduction steps in the biochemical pathway of denitrification, which results in lower N2O production. Experiments were performed in soil-microcosms using 15N labelling approaches to monitor denitrification products . Microcosms were maintained as slurries in order to create oxygen limiting conditions, which favours denitrification. Carbon dioxide and N2O were monitored throughout the experiments and on three destructive sampling days NO3, NO2, NO and 15N-N2 were measured. Results showed that the denitrification process was differently affected by amino acids and organic acids with higher denitrification activity observed in the presence of organic acids. The dynamics of the single reduction steps were time dependent which indicates that substrate availability plays an important role in soil microbial activity. We concluded that the activity of denitrifiers are significantly influenced by different carbon compounds, and that further studies on the effects of the composition of root

  20. Factors affecting simultaneous nitrification and denitrification in an SBBR treating domestic wastewater

    Institute of Scientific and Technical Information of China (English)

    LI Jun; PENG Yongzhen; GU Guowei; WEI Su

    2007-01-01

    An aerobic sequencing batch biofilm reactor(SBBR)packed with Bauer rings was used to treat real domestic wastewater for simultaneous nitrification and denitrification.The SBBR is advantageous for creating an anoxic condition,and the biofilm can absorb and store carbon for good nitrification and denitrification.An average concentration of oxygen ranging from 0.8 to 4.0 mg/L was proved very efficient for nitrification and denitrification.Volumetric loads of TN dropped dramatically and effiueut TN concentration increased quickly when the concentration of average dissolved oxygen was more than 4.0 mg/L.The efficiency of simultaneous nitritication and denitrification(SND)increased with increasing thickness of the biofilm.The influent concentration hardly affected the TN removal efficiency,but the effluent TN increased with increasing influent concentration.It is suggested that a subsequence for denitrification be added or influent amount be decreased to meet effluent quality requirements.At optimum operating parameters,the TN removal efficiency of 74%-82% could be achieved.

  1. 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.

  2. 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 (N2O) 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 N2O 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.

  3. Innovative slow-release organic carbon-source material for groundwater in situ denitrification.

    Science.gov (United States)

    Zhang, Dayi; Zhang, Xu; Wang, Yun; Zhou, Guizhong; Li, Guanghe

    2015-01-01

    Slow-release organic carbon-source (SOC) material, a new kind of electron donor for in situ groundwater denitrification, was prepared and evaluated in this study. With starch as a biologically utilized carbon source and polyvinyl alcohol (PVA) as a frame, this material performed controllable carbon release rates and demonstrated stable behaviour during the simulated denitrification process. Raman spectrum analysis showed that the PVA skeleton formed cross-linking network structures for hydrogen-bonded water molecules reset in low temperatures, and the starchy molecules filled in the interspace of the skeleton to form a two-phase interlocking/disperse phase structure. In a static system, carbon release processes followed the Fickian law with (1.294-6.560)×10(-3) mg g(-1) s(-1/2) as the release coefficient. Under domestication and in situ groundwater simulation conditions, SOC material played a favourable role during denitrification, with 1.049±0.165 as an average carbon-nitrogen ratio. The denitrification process followed the law of zero-order kinetics, while the dynamics parameter kN was 0.563-8.753 gN m(-3) d(-1). Generally, SOC material was suggested to be a potential carbon source (electron donor) suitable for in situ groundwater denitrification.

  4. Performance of simultaneous nitrification and denitrification in lateral flow biological aerated filter

    Institute of Scientific and Technical Information of China (English)

    LONG Teng-rui; CAO Yan-xiao; ZHANG Hong-jing; GAO Xiao-tao

    2006-01-01

    A new wastewater treatment facility-lateral flow biological aerated filter (LBAF) was developed aiming at solving energy consumption and operational problems in wastewater treatment facilities in small towns. It has the function of nitrification and removing organic substrate. In this study, we focused on the denitrification performance of LBAF and its possible mechanism under thorough aeration. We identified the existence of simultaneous nitrification and denitrification (SND)by analyzing nitrogenous compounds along the flow path of LBAF and supportive microbial microscopy, and studied the effects of air/water ratio and hydraulic loading on the performance of nitrogen removal and on SND in LBAF to find out the optimal operation condition. It is found that for saving operation cost, aeration can be reduced to some degree that allows desirable removal efficiency of pollutants, and the optimal air/water ratio is 10:1. Hydraulic loading less than 0.43 m h-1 hardly affects the nitrification and denitrification performance; whereas higher hydraulic loading is unfavorable to both nitrification and denitrification, far more unfavorable to denitrification than to nitrification.

  5. [Inhibition of Denitrification by Total Phenol Load of Coal Gasification Wastewater].

    Science.gov (United States)

    Zhang, Yu-ying; Chen, Xiu-rong; Wang, Lu; Li, Jia-hui; Xu, Yan; Zhuang, You-jun; Yu, Ze-ya

    2016-03-15

    High loaded phenolic pollutants, refractory and high toxic, which existed in coal gasification wastewater, could cause the inhibition of sludge activity. In biological denitrification process of activated sludge treatment system, people tend to focus on the phenol inhibition on the efficiency and activity of nitrifying bacteria while there are few researches on the denitrification process. In order to investigate the inhibition of phenolic compounds from coal gasification wastewater on the denitrification and sludge activity, we used anoxic denitrification system to indentify the influence of different phenol load on denitrification efficiency (removal efficiency of NO₃⁻-N and NO₂⁻-N) as well as the stress and degradation activity of sludge. The results showed that when the concentration of total phenol was changed from 50 mg · L⁻¹ to 200 mg · L⁻¹, the removal rates of NO₃⁻-N and NO₂⁻-N were changed from 55% and 25% to 83% and 83% respectively. In the process of sludge domestication, the characteristics of denitrifying sludge were influenced to a certain degree.

  6. Experimental Study on Denitrification Using Coated Electrode of Immobilized Denitrifying Bacteria

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Objective To develop a coated electrode of immobilized denitrificants and to evaluate the performance of a bioelectrochemical reactor to enhance and control denitrification. Methods Denitrifying bacteria were developed by batch incubation and immobilized with polyvinyl alcohol (PVA) on the surface of activated carbon fiber (ACF) to make a coated electrode. Then the coated electrode (cathode) and graphite electrode (anode) were transferred to the reactor to reduce nitrate. Results After acclimated to the mixtrophic and autotrophic denitrification stages, the denitrifying bacteria could use hydrogen as an electron donor to reduce nitrate. When the initial nitrate concentration was 30.2 mg NO3--N/L, the denitrification efficiency was 57.3% at an applied electric current of 15 mA and a hydraulic retention time (HRT) of 12 hours.Correspondingly, the current density was 0.083 mA / cm2. The nitrate removal rate of the reactor was 34.4 g NO3--N / m3·d, and the surface area loading was 1.34 g NO3--N / m2·d. Conclusion The coated electrode may keep high quantity of biomass, thus achieving a high denitrification rate. Denitrification efficiencies are related to HRT, current density, oxidation reduction potential (ORP), dissolved oxygen (DO), pH value, and temperature.

  7. The use of machine learning algorithms to design a generalized simplified denitrification model

    Science.gov (United States)

    Oehler, F.; Rutherford, J. C.; Coco, G.

    2010-10-01

    We propose to use machine learning (ML) algorithms to design a simplified denitrification model. Boosted regression trees (BRT) and artificial neural networks (ANN) were used to analyse the relationships and the relative influences of different input variables towards total denitrification, and an ANN was designed as a simplified model to simulate total nitrogen emissions from the denitrification process. To calibrate the BRT and ANN models and test this method, we used a database obtained collating datasets from the literature. We used bootstrapping to compute confidence intervals for the calibration and validation process. Both ML algorithms clearly outperformed a commonly used simplified model of nitrogen emissions, NEMIS, which is based on denitrification potential, temperature, soil water content and nitrate concentration. The ML models used soil organic matter % in place of a denitrification potential and pH as a fifth input variable. The BRT analysis reaffirms the importance of temperature, soil water content and nitrate concentration. Generalization, although limited to the data space of the database used to build the ML models, could be improved if pH is used to differentiate between soil types. Further improvements in model performance and generalization could be achieved by adding more data.

  8. Relative importance of time, land use and lithology on determining aquifer-scale denitrification

    Science.gov (United States)

    Kolbe, Tamara; de Dreuzy, Jean-Raynald; Abbott, Benjamin W.; Marçais, Jean; Babey, Tristan; Thomas, Zahra; Peiffer, Stefan; Aquilina, Luc; Labasque, Thierry; Laverman, Anniet; Fleckenstein, Jan; Boulvais, Philippe; Pinay, Gilles

    2017-04-01

    Unconfined shallow aquifers are commonly contaminated by nitrate in agricultural regions, because of excess fertilizer application over the last decades. Watershed studies have indicated that 1) changes in agricultural practices have caused changes in nitrate input over time, 2) denitrification occurs in localized hotspots within the aquifer, and 3) heterogeneous groundwater flow circulation has led to strong nitrate gradients in aquifers that are not yet well understood. In this study we investigated the respective influence of land use, groundwater transit time distribution, and hotspot distribution on groundwater denitrification with a particular interest on how a detailed understanding of transit time distributions could be used to upscale the point denitrification measurements to the aquifer-scale. We measured CFC-based groundwater age, oxygen, nitrate, and dinitrogen gas excess in 16 agricultural wells of an unconfined crystalline aquifer in Brittany, France. Groundwater age data was used to calibrate a mechanistic groundwater flow model of the study site. Historical nitrate inputs were reconstructed by using measured nitrate concentrations, dinitrogen gas excess and transit time distributions of the wells. Field data showed large differences in denitrification activity among wells, strongly associated with differences in transit time distribution. This suggests that knowing groundwater flow dynamics and consequent transit time distributions at the catchment-scale could be used to estimate the overall denitrification capacity of agricultural aquifers.

  9. The use of machine learning algorithms to design a generalized simplified denitrification model

    Directory of Open Access Journals (Sweden)

    F. Oehler

    2010-04-01

    Full Text Available We designed generalized simplified models using machine learning algorithms (ML to assess denitrification at the catchment scale. In particular, we designed an artificial neural network (ANN to simulate total nitrogen emissions from the denitrification process. Boosted regression trees (BRT, another ML was also used to analyse the relationships and the relative influences of different input variables towards total denitrification. To calibrate the ANN and BRT models, we used a large database obtained by collating datasets from the literature. We developed a simple methodology to give confidence intervals for the calibration and validation process. Both ML algorithms clearly outperformed a commonly used simplified model of nitrogen emissions, NEMIS. NEMIS is based on denitrification potential, temperature, soil water content and nitrate concentration. The ML models used soil organic matter % in place of a denitrification potential and pH as a fifth input variable. The BRT analysis reaffirms the importance of temperature, soil water content and nitrate concentration. Generality of the ANN model may also be improved if pH is used to differentiate between soil types. Further improvements in model performance can be achieved by lessening dataset effects.

  10. 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

    2015-12-01

    Increasing nitrogen concentrations in the world's major rivers have led to over-fertilization of sensitive downstream waters. Flow through channel bed and bank sediments acts to remove riverine nitrogen through microbe-mediated denitrification reactions. 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 zones. 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.

  11. Monsoon related changes in sea surface productivity and water column denitrification in the Eastern Arabian Sea during the last glacial cycle

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Oba, T.; Chodankar, A; Kuramoto, T.; Yamamoto, M.; Minagawa, M.

    indicates, however, diminished water column denitrification in spite of increased productivity. The distinct decoupling of denitrification from productivity during the LGM can be explained by vigorous ventilation of the thermocline as a result...

  12. Environmental controls on denitrifying communities and denitrification rates: insights from molecular methods.

    Science.gov (United States)

    Wallenstein, Matthew D; Myrold, David D; Firestone, Mary; Voytek, Mary

    2006-12-01

    The advent of molecular techniques has improved our understanding of the microbial communities responsible for denitrification and is beginning to address their role in controlling denitrification processes. There is a large diversity of bacteria, archaea, and fungi capable of denitrification, and their community composition is structured by long-term environmental drivers. The range of temperature and moisture conditions, substrate availability, competition, and disturbances have long-lasting legacies on denitrifier community structure. These communities may differ in physiology, environmental tolerances to pH and O2, growth rate, and enzyme kinetics. Although factors such as O2, pH, C availability, and NO3- pools affect instantaneous rates, these drivers act through the biotic community. This review summarizes the results of molecular investigations of denitrifier communities in natural environments and provides a framework for developing future research for addressing connections between denitrifier community structure and function.

  13. Phosphorus removal in a sulfur-limestone autotrophic denitrification (SLAD) biofilter.

    Science.gov (United States)

    Li, Ruihua; Yuan, Yulin; Zhan, Xinmin; Liu, Bo

    2014-01-01

    The sulfur-limestone autotrophic denitrification (SLAD) biofilter was able to remove phosphorous from wastewater during autotrophic denitrification. Parameters influencing autotrophic denitrification in the SLAD biofilter, such as hydraulic retention time (HRT), influent nitrate (NO3(-)), and influent PO4(3-) concentrations, had significant effects on P removal. P removal was well correlated with total oxidized nitrogen (TON) removed in the SLAD biofilter; the more TON removed, the more efficient P removal was achieved. When treating the synthetic wastewater containing NO3(-)-N of 30 mg L(-1) and PO4(3-)-P of 15 mg L(-1), the SLAD biofilter removed phosphorus of 45% when the HRT was 6 h, in addition with TN removal of nearly 100%. The optimal phosphorus removal in the SLAD biofilter was around 60%. For the synthetic wastewater containing a PO4(3-)-P concentration of 15 mg L(-1), the main mechanism of phosphorus removal was the formation of calcium phosphate precipitates.

  14. Human land uses enhance sediment denitrification and N2O production in Yangtze lakes primarily by influencing lake water quality

    Directory of Open Access Journals (Sweden)

    W. Liu

    2015-05-01

    Full Text Available Sediment denitrification in lakes alleviates the effects of eutrophication through removal of nitrogen to the atmosphere as N2O and N2. However, N2O contributes notably to the greenhouse effect and global warming. Human lands uses (e.g., agricultural and urban areas strongly affect lake water quality and sediment characteristics, which, in turn, may regulate lake sediment denitrification and N2O production. In this study, we investigated sediment denitrification and N2O production and their relationships to within-lake variables and watershed land uses in 20 lakes from the Yangtze River basin in China. The results indicated that both lake water quality and sediment characteristics were significantly influenced by watershed land uses. Increased background denitrification rate would result in increased N2O production rate. Background denitrification and N2O production rates were positively related to water nitrogen concentrations but were not significantly correlated with sediment characteristics and plant community structure. A significant positive relationship was observed between background denitrification rate and percentage of human-dominated land uses (HDL in watersheds. Structural equation modelling revealed that the indirect effects of HDL on sediment denitrification and N2O production in Yangtze lakes were mediated primarily through lake water quality. Our findings also suggest that although sediments in Yangtze lakes can remove large quantities of nitrogen through denitrification, they may also be an important source of N2O, especially in lakes with high nitrogen content.

  15. 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.

  16. Post-denitrification in a sandfilter with methanol as carbon source. Nachgeschaltete Methanol-Denitrifikation im Sandfilter

    Energy Technology Data Exchange (ETDEWEB)

    Mitsdoerffer, R.; Gerhart, U. (Ingenieurbuero Gerhart und Fuchs, Muenchen (Germany))

    1992-09-01

    Nitrification with following methanol-denitrification in the sand filter was discussed by the enlargement of the sewage treatment plant of Starnberg. The results and the costs were compared with the conventional activated sludge process with nitrification, denitrification and enhanced biological phosphorus removal. (orig.).

  17. Nitrogen losses due to denitrification from cattle slurry injected into grassland soil with and without a nitrification inhibitor

    NARCIS (Netherlands)

    Klein, de C.A.M.; Logtestijn, van R.S.P.; Meer, van der H.G.; Geurink, J.H.

    1996-01-01

    Injection of cattle slurry into a grassland soil decreases NH3 volatilisation and increases N utilisation by the sward, but may also increase denitrification losses. Denitrification rates were measured using a soil core incubation technique involving acetylene inhibition, following injection of catt

  18. Denitrification in Agricultural Soils: Integrated control and Modelling at various scales (DASIM)

    Science.gov (United States)

    Müller, Christoph; Well, Reinhard; Böttcher, Jürgen; Butterbach-Bahl, Klaus; Dannenmann, Michael; Deppe, Marianna; Dittert, Klaus; Dörsch, Peter; Horn, Marcus; Ippisch, Olaf; Mikutta, Robert; Senbayram, Mehmet; Vogel, Hans-Jörg; Wrage-Mönnig, Nicole; Müller, Carsten

    2016-04-01

    The new research unit DASIM brings together the expertise of 11 working groups to study the process of denitrification at unprecedented spatial and temporal resolution. Based on state-of-the art analytical techniques our aim is to develop improved denitrification models ranging from the microscale to the field/plot scale. Denitrification, the process of nitrate reduction allowing microbes to sustain respiration under anaerobic conditions, is the key process returning reactive nitrogen as N2to the atmosphere. Actively denitrifying communities in soil show distinct regulatory phenotypes (DRP) with characteristic controls on the single reaction steps and end-products. It is unresolved whether DRPs are anchored in the taxonomic composition of denitrifier communities and how environmental conditions shape them. Despite being intensively studied for more than 100 years, denitrification rates and emissions of its gaseous products can still not be satisfactorily predicted. While the impact of single environmental parameters is well understood, the complexity of the process itself with its intricate cellular regulation in response to highly variable factors in the soil matrix prevents robust prediction of gaseous emissions. Key parameters in soil are pO2, organic matter content and quality, pH and the microbial community structure, which in turn are affected by the soil structure, chemistry and soil-plant interactions. In the DASIM research unit, we aim at the quantitative prediction of denitrification rates as a function of microscale soil structure, organic matter quality, DRPs and atmospheric boundary conditions via a combination of state-of-the-art experimental and analytical tools (X-ray μCT, 15N tracing, NanoSIMS, microsensors, advanced flux detection, NMR spectroscopy, and molecular methods including next generation sequencing of functional gene transcripts). We actively seek collaboration with researchers working in the field of denitrification.

  19. Evaluation of antibacterial and antifungal compounds for selective inhibition of denitrification in soils.

    Science.gov (United States)

    Ladan, Shiva; Jacinthe, Pierre-André

    2016-12-08

    Nitrous oxide (N2O) is an atmospheric constituent implicated in climate warming and stratospheric ozone depletion. Both bacteria and fungi participate in N2O production, but information is lacking with regard to the relative contribution of bacterial and fungal denitrifiers to the denitrification process in agricultural soils. The selective inhibition (SI) technique is widely used to assess the contribution of different groups of microbes to soil processes, but success of the technique depends on the effectiveness of the inhibitors. In this study, laboratory experiments were conducted to assess the contribution of bacteria and fungi to denitrification using soils from a woodlot, agricultural fields under conventional plowing (PT), and no-till for either 50 years (long-term) or 11 years (medium-term). A selective inhibition (SI) technique was developed using two bactericides (streptomycin and bronopol) and two fungicides (cycloheximide and captan) applied at different rates (0-32 mg per g soil). Regardless of the application rate, streptomycin and cycloheximide were not effective inhibitors of denitrification, with a degree of inhibition only between 2 and 20% relative to controls. These results are significant given the wide use of these products in SI studies. However, the bactericide bronopol and the fungicide captan effectively inhibited denitrification, with the strongest inhibition observed at an application rate of 16 mg per g soil. The ratio of fungal to bacterial denitrification activity (F : B) was generally less than 1, indicating a dominance of bacteria in denitrification activity in the soils investigated. However, an increase in the F : B ratio from 0.24 in medium-term NT to 0.87 in long-term NT soils was noted, suggesting perhaps a progressive increase in the role of fungal denitrifiers with a longer duration of NT farming.

  20. Mustard catch crop enhances denitrification in shallow groundwater beneath a spring barley field.

    Science.gov (United States)

    Jahangir, M M R; Minet, E P; Johnston, P; Premrov, A; Coxon, C E; Hackett, R; Richards, K G

    2014-05-01

    Over-winter green cover crops have been reported to increase dissolved organic carbon (DOC) concentrations in groundwater, which can be used as an energy source for denitrifiers. This study investigates the impact of a mustard catch crop on in situ denitrification and nitrous oxide (N2O) emissions from an aquifer overlain by arable land. Denitrification rates and N2O-N/(N2O-N+N2-N) mole fractions were measured in situ with a push-pull method in shallow groundwater under a spring barley system in experimental plots with and without a mustard cover crop. The results suggest that a mustard cover crop could substantially enhance reduction of groundwater nitrate NO3--N via denitrification without significantly increasing N2O emissions. Mean total denitrification (TDN) rates below mustard cover crop and no cover crop were 7.61 and 0.002 μg kg(-1) d(-1), respectively. Estimated N2O-N/(N2O-N+N2-N) ratios, being 0.001 and 1.0 below mustard cover crop and no cover crop respectively, indicate that denitrification below mustard cover crop reduces N2O to N2, unlike the plot with no cover crop. The observed enhanced denitrification under the mustard cover crop may result from the higher groundwater DOC under mustard cover crop (1.53 mg L(-1)) than no cover crop (0.90 mg L(-1)) being added by the root exudates and root masses of mustard. This study gives insights into the missing piece in agricultural nitrogen (N) balance and groundwater derived N2O emissions under arable land and thus helps minimise the uncertainty in agricultural N and N2O-N balances.

  1. ENUMERATION OF MICROBES AND GAS PRODUCTION DURING DENITRIFICATION AND NITROGEN FIXATION PROCESSES IN SOIL

    Directory of Open Access Journals (Sweden)

    A. E. Ghaly

    2012-01-01

    Full Text Available Dry plant material contains 2-4% nitrogen, making it an essential nutrient for all plants. The nitrogen cycle regulates the pathways which transform nitrogen from a relatively inert dinitrogen gas to forms of organic nitrogen such as proteins and nucleic acids. Denitrification and nitrogen fixation are the two most important processes that remove and add nitrogen to the soil, respectively. The aim of the study was to gain information on the denitrification and nitrogen fixing activities in soil and sediment employing the acetylene technique and assuring the gas chromatography analysis by total plate count and most probably number. The results indicated that acetylene (0.1 atm inhibited N2O reduction and caused stoichiometric accumulation of N2O during the conversion of NO3- to N2. N2O was an obligatory intermediate in the sequence of steps between N2O- and N2. The appearance of CO2 and accumulation of N2O would be suitable criteria for the presence of denitrifiers in appropriately enriched media and the acetylene reduction test is a suitable assay for nitrogen fixing activity. There was an obligatory requirement for organic carbon as a carbon and energy source for denitrification and nitrogen fixation to take place. The results showed that acetylglucosamine can be used as a carbon and energy source for denitrification but not as a nitrogen source (C:N ratio of 5:1. NH4+ has no effect on denitrification activity but it inhibited the nitrogenase activity. The presence of air in the gas phase affects both the denitrification and nitrogen fixing activity while adding H2O encouraged anaerobic conditions.

  2. Simultaneous measurement of denitrification and nitrogen fixation using isotope pairing with membrane inlet mass spectrometry analysis.

    Science.gov (United States)

    An, S; Gardner, W S; Kana, T

    2001-03-01

    A method for estimating denitrification and nitrogen fixation simultaneously in coastal sediments was developed. An isotope-pairing technique was applied to dissolved gas measurements with a membrane inlet mass spectrometer (MIMS). The relative fluxes of three N(2) gas species ((28)N(2), (29)N(2), and (30)N(2)) were monitored during incubation experiments after the addition of (15)NO(3)(-). Formulas were developed to estimate the production (denitrification) and consumption (N(2) fixation) of N(2) gas from the fluxes of the different isotopic forms of N(2). Proportions of the three isotopic forms produced from (15)NO(3)(-) and (14)NO(3)(-) agreed with expectations in a sediment slurry incubation experiment designed to optimize conditions for denitrification. Nitrogen fixation rates from an algal mat measured with intact sediment cores ranged from 32 to 390 microg-atoms of N m(-2) h(-1). They were enhanced by light and organic matter enrichment. In this environment of high nitrogen fixation, low N(2) production rates due to denitrification could be separated from high N(2) consumption rates due to nitrogen fixation. Denitrification and nitrogen fixation rates were estimated in April 2000 on sediments from a Texas sea grass bed (Laguna Madre). Denitrification rates (average, 20 microg-atoms of N m(-2) h(-1)) were lower than nitrogen fixation rates (average, 60 microg-atoms of N m(-2) h(-1)). The developed method benefits from simple and accurate dissolved-gas measurement by the MIMS system. By adding the N(2) isotope capability, it was possible to do isotope-pairing experiments with the MIMS system.

  3. Limited occurrence of denitrification in four shallow aquifers in agricultural areas of the United States

    Science.gov (United States)

    Green, C.T.; Puckett, L.J.; Böhlke, J.K.; Bekins, B.A.; Phillips, S.P.; Kauffman, L.J.; Denver, J.M.; Johnson, H.M.

    2008-01-01

    The ability of natural attenuation to mitigate agricultural nitrate contamination in recharging aquifers was investigated in four important agricultural settings in the United States. The study used laboratory analyses, field measurements, and flow and transport modeling for monitoring well transects (0.5 to 2.5 km in length) in the San Joaquin watershed, California, the Elkhorn watershed, Nebraska, the Yakima watershed, Washington, and the Chester watershed, Maryland. Ground water analyses included major ion chemistry, dissolved gases, nitrogen and oxygen stable isotopes, and estimates of recharge date. Sediment analyses included potential electron donors and stable nitrogen and carbon isotopes. Within each site and among aquifer-based medians, dissolved oxygen decreases with ground water age, and excess N2 from denitrification increases with age. Stable isotopes and excess N2 imply minimal denitrifying activity at the Maryland and Washington sites, partial denitrification at the California site, and total denitrification across portions of the Nebraska site. At all sites, recharging electron donor concentrations are not sufficient to account for the losses of dissolved oxygen and nitrate, implying that relict, solid phase electron donors drive redox reactions. Zero-order rates of denitrification range from 0 to 0.14 ??mol N L-1d-1, comparable to observations of other studies using the same methods. Many values reported in the literature are, however, orders of magnitude higher, which is attributed to a combination of method limitations and bias for selection of sites with rapid denitrification. In the shallow aquifers below these agricultural fields, denitrification is limited in extent and will require residence times of decades or longer to mitigate modern nitrate contamination. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  4. " Innovation Hub":The Entrepreneurial Road of the University of Waterloo%“创新枢纽”:滑铁卢大学的创业之道

    Institute of Scientific and Technical Information of China (English)

    邵玉华

    2015-01-01

    关于大学理念的争论———是“象牙塔”,还是为社会服务,一直未有定论。滑铁卢大学的创新实践给出了很好的回答。在处理大学与社会关系上,其体验式教学、创新孵化平台、合作教育、科技园、对外服务的成功,给了我国大学以启示:以创新为灵魂,坚持全面持久的创新;坚持自身主体地位,积极开展跨界合作;以创业为追求,培育创业文化。%University is the " Ivory Tower", or for social services have not been conclusive argu-ment. The innovative practice of the University of Waterloo gives a good answer. In dealing with the relationship between university and community,the success of the experience of teaching,innovation incubator platform, cooperation in education,science and technology park,external services,gives our university some enlight-enments:take innovation as the soul,persist in comprehensive and persistent innovation;adhere to its sub-ject status,actively carry out cross-border cooperation;pursuit entrepreneurship,fostering an entrepreneur-ial culture.

  5. 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

    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...... to the direct advective transport between anoxic pore water and the overlying water column, and little interaction between the mostly oxic advective region and the underlying anoxic region. Denitrification was therefore mainly fueled by nitrate supplied from the water column. This suggests that the capacity...

  6. 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

  7. 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......±101 and 58±20 μmol N m -2 h -1 for cyanobacterial and lichen crust, respectively. Complete denitrification to N 2 was further confirmed by an 15 NO 3 - tracer experiment with intact crust pieces that proceeded at rates of 103±19 and 27±8 μmol N m -2 h -1 for cyanobacterial and lichen crust, respectively...... layer and thus apparently originated from incomplete denitrification. Using quantitative PCR, denitrification genes were detected in both the crusts and were expressed either in comparable (nirS) or slightly higher (narG) numbers in the cyanobacterial crusts. Although 99% of the nirS sequences...

  8. Denitrification in a BTEX Contaminated Aquifer Containing Reduced Sulfur

    Science.gov (United States)

    Eckert, P.; Appelo, C.; Wisotzky, F.; Obermann, P.

    2001-05-01

    At a former gasworks plant in Duesseldorf (Germany) a massive soil and groundwater contamination with BTEX (up to 100 mg/l) and to a minor extent with PAH (up to 10 mg/l) were detected. Mainly due to sulfate and iron-(III) reduction, a natural biodegradation has occurred and restricted the length of the contaminant plume in the direction of groundwater flow to only 600 m. The active remediation strategy at this site includes nitrate-enhanced in-situ bioremediation of the remaining contaminants in the plume. Nitrate was infiltrated in the contaminated aquifer during a field test to study the efficacy of enhanced natural attenuation. Degradation of hydrocarbons under denitrifying has been proved by numerous laboratory and field studies. However, at this site the competing reaction of nitrate with hydrocarbons and reduced sulfur components has to be considered. The oxidation of pyrite by nitrate in pristine aquifers is well known. The Duesseldorf aquifer contains FeS, pyrite and Fe-calcite precipitated during over 50 years of natural attenuation. The hydrogeochemical transport model PHREEQC-2 is used to simulate the distribution of chemical species and reaction rates along the flow path between the infiltration well and two multilevel wells . The complicated suite of reactions caused by the reduction of nitrate is evaluated by the comparison of modeled and measured data. At the Duesseldorf site the concomitant presence of nitrate, Fe(II) and BTEX/PAHs showed that the reactions did not evolve to thermodynamic equilibrium and were controlled by kinetics. The very good fit of observed and model calculations illustrates that the inorganic chemical reactions during the field test are generally well understood. The kinetic reactions could be modelled with rate equations from the literature based on oxygen, and which were extended with nitrate. Denitrification rates with BTEX compounds and with FeS were found to be comparable, but the oxidation of Fe(II) and FeS occurred

  9. Scale-dependent linkages between nitrate isotopes and denitrification in surface soils: implications for isotope measurements and models.

    Science.gov (United States)

    Hall, Steven J; Weintraub, Samantha R; Bowling, David R

    2016-08-01

    Natural abundance nitrate (NO3 (-)) isotopes represent a powerful tool for assessing denitrification, yet the scale and context dependence of relationships between isotopes and denitrification have received little attention, especially in surface soils. We measured the NO3 (-) isotope compositions in soil extractions and lysimeter water from a semi-arid meadow and lawn during snowmelt, along with the denitrification potential, bulk O2, and a proxy for anaerobic microsites. Denitrification potential varied by three orders of magnitude and the slope of δ(18)O/δ(15)N in soil-extracted NO3 (-) from all samples measured 1.04 ± 0.12 (R (2) = 0.64, p < 0.0001), consistent with fractionation from denitrification. However, δ(15)N of extracted NO3 (-) was often lower than bulk soil δ(15)N (by up to 24 ‰), indicative of fractionation during nitrification that was partially overprinted by denitrification. Mean NO3 (-) isotopes in lysimeter water differed from soil extractions by up to 19 ‰ in δ(18)O and 12 ‰ in δ(15)N, indicating distinct biogeochemical processing in relatively mobile water versus soil microsites. This implies that NO3 (-) isotopes in streams, which are predominantly fed by mobile water, do not fully reflect terrestrial soil N cycling. Relationships between potential denitrification and δ(15)N of extracted NO3 (-) showed a strong threshold effect culminating in a null relationship at high denitrification rates. Our observations of (1) competing fractionation from nitrification and denitrification in redox-heterogeneous surface soils, (2) large NO3 (-) isotopic differences between relatively immobile and mobile water pools, (3) and the spatial dependence of δ(18)O/δ(15)N relationships suggest caution in using NO3 (-) isotopes to infer site or watershed-scale patterns in denitrification.

  10. Sediment, water column, and open-channel denitrification in rivers measured using membrane-inlet mass spectrometry

    Science.gov (United States)

    Reisinger, Alexander J.; Tank, Jennifer L.; Hoellein, Timothy J.; Hall, Robert O.

    2016-05-01

    Riverine biogeochemical processes are understudied relative to headwaters, and reach-scale processes in rivers reflect both the water column and sediment. Denitrification in streams is difficult to measure, and is often assumed to occur only in sediment, but the water column is potentially important in rivers. Dissolved nitrogen (N) gas flux (as dinitrogen (N2)) and open-channel N2 exchange methods avoid many of the artificial conditions and expenses of common denitrification methods like acetylene block and 15N-tracer techniques. We used membrane-inlet mass spectrometry and microcosm incubations to quantify net N2 and oxygen flux from the sediment and water column of five Midwestern rivers spanning a land use gradient. Sediment and water column denitrification ranged from below detection to 1.8 mg N m-2 h-1 and from below detection to 4.9 mg N m-2 h-1, respectively. Water column activity was variable across rivers, accounting for 0-85% of combined microcosm denitrification and 39-85% of combined microcosm respiration. Finally, we estimated reach-scale denitrification at one Midwestern river using a diel, open-channel N2 exchange approach based on reach-scale metabolism methods, providing an integrative estimate of riverine denitrification. Reach-scale denitrification was 8.8 mg N m-2 h-1 (95% credible interval: 7.8-9.7 mg N m-2 h-1), higher than combined sediment and water column microcosm estimates from the same river (4.3 mg N m-2 h-1) and other estimates of reach-scale denitrification from streams. Our denitrification estimates, which span habitats and spatial scales, suggest that rivers can remove N via denitrification at equivalent or higher rates than headwater streams.

  11. 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.

  12. Denitrification in a large river: consideration of geomorphic controls on microbial activity and community structure.

    Science.gov (United States)

    Tatariw, Corianne; Chapman, Elise L; Sponseller, Ryan A; Mortazavi, Behzad; Edmonds, Jennifer W

    2013-10-01

    Ecological theory argues that the controls over ecosystem processes are structured hierarchically, with broader-scale drivers acting as constraints over the interactions and dynamics at nested levels of organization. In river ecosystems, these interactions may arise from broadscale variation in channel form that directly shapes benthic habitat structure and indirectly constrains resource supply and biological activity within individual reaches. To evaluate these interactions, we identified sediment characteristics, water chemistry, and denitrifier community structure as factors influencing benthic denitrification rates in a sixth-order river that flows through two physiographic provinces and the transitional zone between them, each with distinct geomorphological properties. We found that denitrification rates tracked spatial changes in sediment characteristics and varied seasonally with expected trends in stream primary production. Highest rates were observed during the spring and summer seasons in the physiographic province dominated by fine-grained sediments, illustrating how large-scale changes in river structure can constrain the location of denitrification hotspots. In addition, nirS and nirK community structure each responded differently to variation in channel form, possibly due to changes in dissolved oxygen and organic matter supply. This shift in denitrifier community structure coincident with higher rates of N removal via denitrification suggests that microbial community structure may influence biogeochemical processes.

  13. Isotopic signals of summer denitrification in a northern hardwood forested catchment

    Science.gov (United States)

    Sarah K. Wexler; Christine L. Goodale; Kevin J. McGuire; Scott W. Bailey; Peter M. Groffman

    2014-01-01

    Despite decades of measurements, the nitrogen balance of temperate forest catchments remains poorly understood. Atmospheric nitrogen deposition often greatly exceeds streamwater nitrogen losses; the fate of the remaining nitrogen is highly uncertain. Gaseous losses of nitrogen to denitrification are especially poorly documented and are often ignored. Here, we provide...

  14. Measuring potential denitrification enzyme activity rates using the membrane inlet mass spectrometer

    Science.gov (United States)

    The denitrification enzyme activity (DEA) assay, provides a quantitative assessment of the multi enzyme, biological process of reactive nitrogen removal via the reduction of N03 to N2. Measured in soil, usually under non limiting carbon and nitrate concentrations, this short ter...

  15. Potential rates of ammonium oxidation, nitrite oxidation, nitrate reduction and denitrification in the young barley rhizosphere

    DEFF Research Database (Denmark)

    Højberg, Ole; Binnerup, S. J.; Sørensen, Jan

    1996-01-01

    nitrification in the rhizosphere. On the other hand, potential denitrification only responded positively to the second, longer wetting of the soil. The potential activities were not affected by changes in the pools of inorganic N. As judged from the potential activities (enzyme contents), both groups...

  16. Fluidization velocity assessment of commercially available sulfur particles for use in autotrophic denitrification biofilters

    Science.gov (United States)

    There has been no evaluation of sulfur-based autotrophic denitrification using fluidized biofilters in a recirculating aquaculture system to mitigate nitrate-nitrogen loads. The objectives of this work were to quantify the particle size distribution, specific surface area, and fluidization velocitie...

  17. Nitrogen mineralization and denitrification as influenced by crop residue particle size

    DEFF Research Database (Denmark)

    Ambus, P.; Jensen, E.S.

    1997-01-01

    for the two pea treatments. In suspensions denitrification was similar for the two treatments both with barley and pea residue. We conclude that the higher microbial activity associated with the initial decomposition of ground plant material is due to a more intimate plant residue-soil contact. On the long...

  18. Dynamics of partial anaerobiosis denitrification, and water in soil : experiments and simulation

    NARCIS (Netherlands)

    Leffelaar, P.A.

    1987-01-01

    Dynamic interactions between biological respiration and denitrification, and physical transport processes that modify the abiotic soil environment in which bacteria live, were studied through the development of a new type of experimental respirometer system and an explanatory simulation model.

  19. Scaling Denitrification Fluxes from Cores to Catchments: Spatial and Temporal Controls

    Science.gov (United States)

    Duncan, J. M.; Band, L. E.; Groffman, P. M.

    2015-12-01

    The influence of spatial and temporal heterogeneity on nitrogen cycling can be profound but catchment scale understanding remains elusive. One of the largest sources of uncertainty is the importance of denitrification. Determining in situ rates of denitrification in elements of landscape that remove a disproportionately high amount of N from certain areas of catchment (hot spots) in response to seasonal and event driven conditions (hot moments) is critical to closing watershed nitrogen budgets. We develop an approach to scale denitrification flux from seasonal soil cores collected in different landscape positions to the entire watershed using a combination of laboratory core experiments, terrain analysis and in situ soil oxygen and soil moisture content sensors. In the Pond Branch watershed in the Piedmont region of Maryland, nitrogen deposition values are relatively high (9kg/ha/yr) with low stream export (0.5 kg/ha/yr). Our data suggest that at least 16-27% of this retention can be accounted for by denitrification in certain areas of the riparian zone. We highlight the importance of riparian microtopography and the need to better link observations and models.

  20. Lateral Transfer of the Denitrification Pathway Genes among Thermus thermophilus Strains▿

    Science.gov (United States)

    Alvarez, Laura; Bricio, Carlos; José Gómez, Manuel; Berenguer, José

    2011-01-01

    Nitrate respiration is a common and strain-specific property in Thermus thermophilus encoded by the nitrate respiration conjugative element (NCE) that can be laterally transferred by conjugation. In contrast, nitrite respiration and further denitrification steps are restricted to a few isolates of this species. These later steps of the denitrification pathway are under the regulatory control of an NCE-encoded transcription factor, but nothing is known about their coding sequences or its putative genetic linkage to the NCE. In this study we examine the genetic linkage between nitrate and nitrite respiration through lateral gene transfer (LGT) assays and describe a cluster of genes encoding the nitrite-nitric oxide respiration in T. thermophilus PRQ25. We show that the whole denitrification pathway can be transferred from the denitrificant strain PRQ25 to an aerobic strain, HB27, and that the genes coding for nitrite and nitric oxide respiration are encoded near the NCE. Sequence data from the draft genome of PRQ25 confirmed these results and allowed us to describe the most compact nor-nir cluster known thus far and to demonstrate the expression and activities of the encoded enzymes in the HB27 denitrificant derivatives obtained by LGT. We conclude that this NCE nor-nir supercluster constitutes a whole denitrification island that can be spread by lateral transfer among Thermus thermophilus strains. PMID:21169443

  1. Removal of nitrate from groundwater by heterotrophic denitrification using the solid carbon source

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Removal of nitrate from groundwater was investigated using biodegradable meal box(BMB) and poly(ε-caprolactone)(PCL) as carbon source and biofilm carrier.The experimental results show that nitrate in groundwater can be effectively removed using BMB and PCL as carbon source.Denitrification rates supported by BMB and PCL were 52.80 and 42.77 mg(NO3-N)/(m2h),respectively,at 30 ℃ and pH 7.5.The pH value of effluent ranged from 7 to 8,and NO2-N concentration was less than 0.1 mg/L.Compared with BMB,PCL could decrease nitrite accumulation;however,more significant influence of temperature on denitrification was observed for PCL as carbon source.Temperature constants for BMB and PCL were 0.045 and 0.068,respectively,at 10-30℃.Based on denitrification efficiency and cost,BMB is more suitable as a carbon source for denitrification of groundwater than PCL.

  2. Global trends and uncertainties in terrestrial denitrification and N2O emissions

    NARCIS (Netherlands)

    Bouwman, A.F.; Beusen, A.H.W.; Griffioen, J.; Groenigen, J.W. van; Hefting, M.M.; Oenema, O.; Puijenbroek, P.J.T.M. van; Seitzinger, S.; Slomp, C.P.; Stehfest, E.

    2013-01-01

    Soil nitrogen (N) budgets are used in a global, distributed flow-path model with 0.5° × 0.5° resolution, representing denitrification and N2O emissions from soils, groundwater and riparian zones for the period 1900-2000 and scenarios for the period 2000-2050 based on the Millennium Ecosystem As

  3. Contribution of different PSC types to Arctic ozone depletion caused by chlorine activation and denitrification

    Science.gov (United States)

    Kirner, Oliver; Khosrawi, Farah; Müller, Rolf; Weimer, Michael; Ruhnke, Roland

    2017-04-01

    Heterogeneous reactions on the surfaces of PSC particles and denitrification of the stratosphere are the cause for polar ozone depletion in spring. In a former study we investigated the impact of different types of PSCs on Antarctic ozone depletion with the help of the chemistry-climate model ECHAM5/MESSy Atmospheric chemistry (EMAC). In this study, we investigate the impact of PSCs on Arctic ozone loss. One standard and four sensitivity EMAC simulations (nudged with ERA-Interim) have been performed to evaluate the contribution of liquid, NAT and ice particles to ozone depletion in the Arctic winters 2010/2011 and 2015/2016 due to chlorine activation by heterogeneous chemistry on their surfaces and due to denitrification of the stratosphere. In the first three sensitivity simulations, we changed the heterogeneous chemistry on PSC particles by switching on and off the chemistry on liquid, NAT and ice particles. One further sensitivity simulation without NAT formation (only liquid and ice particles) was performed to evaluate the contribution of NAT to Arctic ozone depletion due to denitrification of the stratosphere. With the help of these different EMAC simulations, we will show the significance of liquid, NAT and ice particles to Arctic ozone depletion caused by chlorine activation and denitrification.

  4. Nitrate removal effectiveness of fluidized sulfur-based autotrophic denitrification biofilters for recirculating aquaculture systems

    Science.gov (United States)

    There is a need to develop practical methods to reduce nitrate -nitrogen loads from recirculating aqua-culture systems to facilitate increased food protein production simultaneously with attainment of water quality goals. The most common wastewater denitrification treatment systems utilize methanol-...

  5. Modeling and mitigation of denitrification 'woodchip' bioreactor phosphorus releases during treatment of aquaculture wastewater

    Science.gov (United States)

    Denitrification 'woodchip' bioreactors designed to remove nitrate from agricultural waters may either be phosphorus sources or sinks. A 24 d batch test showed woodchip leaching is an important source of phosphorus during bioreactor start-up with a leaching potential of approximately 20 -30 mg P per ...

  6. A pH-control model for heterotrophic and hydrogen-based autotrophic denitrification.

    Science.gov (United States)

    Tang, Youneng; Zhou, Chen; Ziv-El, Michal; Rittmann, Bruce E

    2011-01-01

    This work presents a model to predict the alkalinity, pH, and Langelier Saturation Index (LSI) in heterotrophic and H(2)-based autotrophic denitrification systems. The model can also be used to estimate the amount of acid, e.g. HCl, added to the influent (method 1) or the pH set point in the reactor (method 2: pH can be maintained stable by CO(2)-sparge using a pH-control loop) to prevent the pH from exceeding the optimal range for denitrification and to prevent precipitation from occurring. The model was tested with two pilot plants carrying out denitrification of groundwater with high hardness: a heterotrophic system using ethanol as the electron donor and an H(2)-based autotrophic system. The measured alkalinity, pH, and LSI were consistent with the model for both systems. This work also quantifies: (1) how the alkalinity and pH in Stage-1 significantly differ from those in Stage-2; (2) how the pH and LSI differ significantly in the two denitrification systems while the alkalinity increase is about the same; and (3) why CO(2) addition is the preferred method for autotrophic system, while HCl addition is the preferred method for the heterotrophic system.

  7. 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.

  8. Stream denitrification across biomes and its response to anthropogenic nitrate loading.

    Science.gov (United States)

    Mulholland, Patrick J; Helton, Ashley M; Poole, Geoffrey C; Hall, Robert O; Hamilton, Stephen K; Peterson, Bruce J; Tank, Jennifer L; Ashkenas, Linda R; Cooper, Lee W; Dahm, Clifford N; Dodds, Walter K; Findlay, Stuart E G; Gregory, Stanley V; Grimm, Nancy B; Johnson, Sherri L; McDowell, William H; Meyer, Judy L; Valett, H Maurice; Webster, Jackson R; Arango, Clay P; Beaulieu, Jake J; Bernot, Melody J; Burgin, Amy J; Crenshaw, Chelsea L; Johnson, Laura T; Niederlehner, B R; O'Brien, Jonathan M; Potter, Jody D; Sheibley, Richard W; Sobota, Daniel J; Thomas, Suzanne M

    2008-03-13

    Anthropogenic addition of bioavailable nitrogen to the biosphere is increasing and terrestrial ecosystems are becoming increasingly nitrogen-saturated, causing more bioavailable nitrogen to enter groundwater and surface waters. Large-scale nitrogen budgets show that an average of about 20-25 per cent of the nitrogen added to the biosphere is exported from rivers to the ocean or inland basins, indicating that substantial sinks for nitrogen must exist in the landscape. Streams and rivers may themselves be important sinks for bioavailable nitrogen owing to their hydrological connections with terrestrial systems, high rates of biological activity, and streambed sediment environments that favour microbial denitrification. Here we present data from nitrogen stable isotope tracer experiments across 72 streams and 8 regions representing several biomes. We show that total biotic uptake and denitrification of nitrate increase with stream nitrate concentration, but that the efficiency of biotic uptake and denitrification declines as concentration increases, reducing the proportion of in-stream nitrate that is removed from transport. Our data suggest that the total uptake of nitrate is related to ecosystem photosynthesis and that denitrification is related to ecosystem respiration. In addition, we use a stream network model to demonstrate that excess nitrate in streams elicits a disproportionate increase in the fraction of nitrate that is exported to receiving waters and reduces the relative role of small versus large streams as nitrate sinks.

  9. Evaluation of denitrification decomposition model for estimating ammonia fluxes from chemical fertilizer application

    Science.gov (United States)

    DeNitrification DeComposition (DNDC) model predictions of NH3 fluxes following chemical fertilizer application were evaluated by comparison to relaxed eddy accumulation (REA) measurements, in Central Illinois, United States, over the 2014 growing season of corn. Practical issues for evaluating closu...

  10. Denitrification coupled to pyrite oxidation and changes in groundwater quality in a shallow sandy aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Slomp, C.P.; Broers, H.P.; Passier, H.F.; Cappellen, P. van

    2009-01-01

    This study focuses on denitrification in a sandy aquifer using geochemical analyses of both sediment and groundwater, combined with groundwater age dating (3H/3He). The study sites are located underneath cultivated fields and an adjacent forested area at Oostrum, The Netherland

  11. Woodchip denitrification bioreactors: Impact of temperature and hydraulic retention time on nitrate removal

    Science.gov (United States)

    Woodchip denitrification bioreactors, a relatively new technology for edge-of-field treatment of subsurface agricultural drainage water, have shown potential for nitrate removal. However, very few studies have evaluated the performance of these reactors under controlled conditions similar to the fie...

  12. Global trends and uncertainties in terrestrial denitrification and N2O emissions

    NARCIS (Netherlands)

    Bouwman, A.F.; Beusen, A.H.W.; Griffioen, J.; Groenigen, J.W. van; Hefting, M.M.; Oenema, O.; Puijenbroek, P.J.T.M. van; Seitzinger, S.; Slomp, C.P.; Stehfest, E.

    2013-01-01

    Soil nitrogen (N) budgets are used in a global, distributed flow-path model with 0.5° × 0.5° resolution, representing denitrification and N2O emissions from soils, groundwater and riparian zones for the period 1900-2000 and scenarios for the period 2000-2050 based on the Millennium Ecosystem As

  13. The effect of metronidazole on biological denitrification of Pesudomonas stutzeri in wastewater

    Directory of Open Access Journals (Sweden)

    hossein Masoumbeigi

    2012-12-01

    Conclusion: With ergard to strong ability of Pseudomonus stutzeri to remove nitrate high concentrations and high resistance of this bacterium against metrinidazole, biological denitrification process can have a high potential to be used for removal of nitrates high concentrations from industrial wastewater, particularly pharmaceutical industries wastewater.

  14. Denitrification in Chongming east tidal flat sediment,Yangtze estuary, China

    Institute of Scientific and Technical Information of China (English)

    WANG Dongqi; CHEN Zhenlou; XU Shiyuan; HU Lingzhen; WANG Jun

    2006-01-01

    From July 2003 to July 2004, samples were collected on Chongming Island east tidal flat every two months. The research showed that the nitrous oxide (N2O) production rate was very low in the water, Chongming east tidal flat (CM) sediment was the N2O source of the water. Sediment N2O higher in the summer. The difference of the N2O natural production rate in the different tidal flats, the correlation between the N2O natural production rate and the denitrification rate, and those with the temperature and DO indicate that middle tidal flat sediment denitrification was the main process of the N2O production, while in the low tidal flat sediment, the production of the N2O came from several processes of the nitrogen cycling. Tidal flat sediment denitrification reaction was stronger in summer and winter but relatively lower in the late autumn and early spring. Seasonal change of the sediment of them had the prominent effect on the tidal flat sediment denitrification.

  15. Regulations and Practice on Flue Gas Denitrification for Coal-Fired Power Plants in China

    Institute of Scientific and Technical Information of China (English)

    Zhu Fahua; Zhao Guohua

    2008-01-01

    @@ In China, according to the relative up-to-date regulations and standards, the maincontrol measure for Nox emission of coal-fired power plants is, in principle, low Noxcombustion. However, in recent years, more and more newly approved coal-fired plantswere required to install flue gas denitrification equipment.

  16. 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

    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...

  17. 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...

  18. First evidence of denitrification vis-a-vis monsoon in the Arabian Sea since late Miocene

    Digital Repository Service at National Institute of Oceanography (India)

    Tripathi, S.; Tiwari, M.; Lee, J.; Khim, B.-K.; Pandey, D.K.; Clift, P.D.; Kulhanek, D.K.; Ando, S.; Bendle, J.A.P.; Aharonovich, S.; Griffith, E.M.; Gurumurthy, G.P.; Hahn, A.; Iwai, M.; Kumar, A.; Kumar, A.G.; Liddy, H.M.; Lu, H.; Lyle, M.W.; Mishra, R.; Radhakrishna, T.; Routledge, C.M.; Saraswat, R.; Saxena, R.; Scardia, G.; Sharma, G.K.; Singh, A.D.; Steinke, S.; Suzuki, K.; Tauxe, L.; Xu, Z.; Yu, Z.

    in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ~3.2–2.8 Ma that coincided with Mid...

  19. Understanding the Spatio-Temporal Dynamics of Denitrification in an Oregon Salt Marsh

    Science.gov (United States)

    Salt marshes are highly susceptible to a range of climate change effects (e.g., sea-level rise, salinity changes, storm severity, shifts in vegetation across watershed). It is unclear how these effects will alter the spatial and temporal dynamics of denitrification, a potential p...

  20. Determination of respiration, gross nitrification and denitrification in soil profile using BaPS system

    Institute of Scientific and Technical Information of China (English)

    CHEN Shu-tao; HUANG Yao

    2006-01-01

    A facility of BaPS (Barometric Process Separation) was used to determine soil respiration, gross nitrification and denitrification in a winter wheat field with depths of 0-7, 7-14 and 14-21 cm. N2O production was determined by a gas chromatograph. Crop root mass and relevant soil parameters were measured. Results showed that soil respiration and gross nitrification decreased with the increase of soil depth, while denitrification did not change significantly. In comparison with no-plowing plot, soil respiration increased significantly in plowing plot, especially in the surface soil of 0-7 cm, while gross nitrification and denitrification rates were not affected by plowing. Cropping practice in previous season was found to affect soil gross nitrification in the following wheat-growing season. Higher gross nitrification rate occurred in the filed plot with preceding crop of rice compared with that of maize for all the three depths of 0-7, 7-14 and 14-21 cm. A further investigation indicated that the nitrification for all the cases accounted for about 76% of the total nitrogen transformation processes of nitrification and denitrification and the N2O production correlated with nitrification significantly, suggesting that nitrification is a key process of soil N2O production in the wheat field. In addition, the variations of soil respiration and gross nitrification were exponentially dependent on root mass (P<0.001).

  1. 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.H.; Uhlenhopp, A.G.; 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...

  2. 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

  3. Effects of sulfamethazine on denitrification and the associated N2O release in estuarine and coastal sediments.

    Science.gov (United States)

    Hou, Lijun; Yin, Guoyu; Liu, Min; Zhou, Junliang; Zheng, Yanling; Gao, Juan; Zong, Haibo; Yang, Yi; Gao, Lei; Tong, Chunfu

    2015-01-01

    Denitrification is an important pathway of nitrogen removal and nitrous oxide (N2O) production in estuarine and coastal ecosystems, and plays a significant role in counteracting aquatic eutrophication induced by excessive nitrogen loads. Estuarine and coastal environments also suffer from increasing antibiotic contamination because of the growing production and usage of antibiotics. In this study, sediment slurry incubation experiments were conducted to determine the influence of sulfamethazine (SMT, a sulphonamide antibiotic) on denitrification and the associated N2O production. Genes important for denitrification and antibiotic resistance were quantified to investigate the microbial physiological mechanisms underlying SMT's effects on denitrification. SMT was observed to significantly inhibit denitrification rates, but increasing concentrations of SMT enhanced N2O release rates. The negative exponential relationships between denitrifying gene abundances and SMT concentrations showed that SMT reduced denitrification rates by restricting the growth of denitrifying bacteria, although the presence of the antibiotic resistance gene was detected during the incubation period. These results imply that the wide occurrence of residual antibiotics in estuarine and coastal ecosystems may influence eutrophication control, greenhouse effects, and atmospheric ozone depletion by inhibiting denitrification and stimulating the release of N2O.

  4. Contribution to the development of a denitrification stage connected in series with activated sludge as H donor: Design methods, operating strategies and process optimisation; Beitrag zur nachgeschalteten Denitrifikation mit Belebtschlamm als H-Donator: Auslegungsmethoden, Betriebsstrategien und Optimierung des Verfahrens

    Energy Technology Data Exchange (ETDEWEB)

    Malchow, T.

    1995-12-31

    The main topics of this dissertation are: waste water purification; denitrification; nitrification; activated sludge; process development units for the process optimization; external carbon sources for the denitrification; activated sludge as hydrogen source for the denitrification; operation results; calculation method for the velocity of the denitrification. (SR)

  5. Plant trait diversity buffers variability in denitrification potential over changes in season and soil conditions.

    Directory of Open Access Journals (Sweden)

    Bonnie M McGill

    Full Text Available BACKGROUND: Denitrification is an important ecosystem service that removes nitrogen (N from N-polluted watersheds, buffering soil, stream, and river water quality from excess N by returning N to the atmosphere before it reaches lakes or oceans and leads to eutrophication. The denitrification enzyme activity (DEA assay is widely used for measuring denitrification potential. Because DEA is a function of enzyme levels in soils, most ecologists studying denitrification have assumed that DEA is less sensitive to ambient levels of nitrate (NO(3(- and soil carbon and thus, less variable over time than field measurements. In addition, plant diversity has been shown to have strong effects on microbial communities and belowground processes and could potentially alter the functional capacity of denitrifiers. Here, we examined three questions: (1 Does DEA vary through the growing season? (2 If so, can we predict DEA variability with environmental variables? (3 Does plant functional diversity affect DEA variability? METHODOLOGY/PRINCIPAL FINDINGS: The study site is a restored wetland in North Carolina, US with native wetland herbs planted in monocultures or mixes of four or eight species. We found that denitrification potentials for soils collected in July 2006 were significantly greater than for soils collected in May and late August 2006 (p<0.0001. Similarly, microbial biomass standardized DEA rates were significantly greater in July than May and August (p<0.0001. Of the soil variables measured--soil moisture, organic matter, total inorganic nitrogen, and microbial biomass--none consistently explained the pattern observed in DEA through time. There was no significant relationship between DEA and plant species richness or functional diversity. However, the seasonal variance in microbial biomass standardized DEA rates was significantly inversely related to plant species functional diversity (p<0.01. CONCLUSIONS/SIGNIFICANCE: These findings suggest that

  6. Discerning Between Water Column and Sedimentary Denitrification in the Santa Barbara Basin Using the Nitrogen Isotopes of Nitrate

    Science.gov (United States)

    Knapp, A. N.; Sigman, D. M.; van Geen, L.; McCorkle, D. C.; Brandes, J. A.; Thunell, R. C.

    2001-05-01

    Below its sill depth, the Santa Barbara Basin (SBB) is seasonally anoxic, making the basin suitable for denitrification in both the water column and the sediments. Deviations of nitrate and phosphate concentrations from Redfield ratios provide quantitative estimates of the nitrate consumed by denitrification in the SBB. However, there are no integrative constraints on whether denitrification occurs predominantly in the water column or in the sediments. Associated with a sharp increase in the nitrate deficit across the oxic/anoxic interface within the SBB, there is an increase in the d15N of water column nitrate, as would be expected from denitrification. However, given the size of the nitrate deficit, the increase of d15N of nitrate is much smaller than would be expected from the accepted intrinsic isotope effect of denitrification of 20-30 per mil, assuming a Rayleigh model for uptake. In situations where both transport and removal are important, the Rayleigh model provides only an approximation of the actual fractionation. However, model calculations suggest that transport within the water column cannot explain the observed d15N discrepancy in the SBB. Benthic lander studies of Puget Sound sediments have demonstrated that the isotope effect of sedimentary denitrification is negligible, due to the effects of substrate diffusion in sediment porewaters (Brandes and Devol, 1997). We present new porewater measurements from the Carolina slope in the North Atlantic that confirm this conclusion for other sedimentary environments. Thus, we infer that the small magnitude of the isotopic enrichment of SBB water column nitrate is due to the importance of denitrification in the sediments relative to the water column. Assuming that water column and sedimentary denitrification have isotope effects of 25 and 0 per mil, respectively, model calculations indicate that sedimentary denitrification accounts for more than 75% of the nitrate loss within the anoxic Santa Barbara Basin.

  7. Reactive barrier system for nitrate removal from mine effluents in northern Sweden: Laboratory experiments

    Science.gov (United States)

    Herbert, Roger

    2010-05-01

    Laboratory column experiments have been conducted to determine nitrate removal rates from mine effluents by denitrification, with the purpose of providing initial data for the construction of a pilot scale reactive barrier system at the Malmberget iron mine, Sweden. Experiments were conducted at several different flow rates at 5C, 10C and room temperature; annual mean temperatures at the Malmberget site lie close to 0C. Columns were filled with an organic substrate consisting of sawdust mixed with sewage sludge, the source of denitrifying bacteria, supported by oven-dried clay pellets. Apparent denitrification rates, calculated from inflow and outflow nitrate concentrations and column hydraulic residence time, ranged from 5 to 13 mg N/L/d, with the lowest rates corresponding to the 5C experiments. These rates are, however, limited to a certain degree by the low flow rate and the supply of electrons acceptors (i.e. nitrate) to denitrifying bacteria. Results from the column experiment have been used to construct a barrier system in Malmberget, Sweden. Trial runs with the pilot-scale barrier will be conducted during 2010, with the purpose of determining the performance of the barrier as mean air temperatures increase from below to above 0C and saturated flow commences in the barrier. The barrier system is constructed as a rectangular container with steel sheet walls (9m length in flow direction, 1.5m deep), and the flow rate will be adjusted to a hydraulic residence time of 1 day. The pilot-scale barrier system currently lies above ground, but a permanent barrier system would be installed below the ground surface so that the system can be maintained at positive temperatures throughout the year.

  8. WaterlooClarke: TREC 2015 Microblog Track

    Science.gov (United States)

    2015-11-20

    Track is to develop a real-time relevancy retrieval system that monitors a stream of social media posts and recommends relevant posts according to users...interests [1]. In this track, the representative social media is Twitter, and relevant posts are tweets with respect to a user’s interest. A user’s...algorithm. 2013. [5] Michael Dinitz. Recent advances on the matroid secretary problem. SIGACT News, 44(2):126–142, June 2013. [6] PR Freeman. The

  9. Napoleon's Waterloo Wasn't Mathematics.

    Science.gov (United States)

    Maynard, Jacquelyn

    1989-01-01

    Discusses Napoleon's involvement with mathematics and education. Describes two geometric constructions dividing the circumference of a circle into four equal parts and finding the center of a given circle. Summarizes the establishment of the Institute of Egypt and the educational system in France. Twenty-seven references are listed. (YP)

  10. Waterloo or Milestone of the Bush Administration

    Institute of Scientific and Technical Information of China (English)

    YangHongxi; ChenKaiming; WangWei

    2005-01-01

    In the coming four years, the Middle East will continue to be the strategic focus of the United States. It can be seen in an analysis of the recent years's ituation that the Bush administration rather chose a war in the Middle East to achieve its strategic goals than used non-military measures to do the same thing. In the future the Bush administration might find it difficult to draw back from its policy on the Middle East, which will mean more losses than gains. This will probably continue to cause damage to both the soft and hard power of the U.S., and result in a downward trend of the U.S. power for a certain period of time.

  11. In situ denitrification and DNRA rates in soils and underlying groundwater of an integrated constructed wetland

    Science.gov (United States)

    Mofizur Rahman Jahangir, Mohammad; Fenton, Owen; McAleer, Eoin; Carroll, Paul; Harrington, Rory; Johnston, Paul; Müller, Christoph; Richards, Karl

    2015-04-01

    Nitrogen (N) removal efficiency in constructed wetlands (CW) is low and again it does not in itself explain whether the removed N species are reactive or benign. Evaluation of environmental benefits of CW necessitates knowing N removal mechanisms and the fate of the removed N in such system. In situ denitrification and DNRA (dissimilatory nitrate reduction to ammonium) rates were measured in an earthen lined 5-cell integrated CW using 15N-enriched nitrate (NO3--N) push-pull method. Measurements were conducted in 2 groundwater depths (shallow- soils in CW bed; and deep- 4 m below CW soils) in 2 contrasting cells (high vs. low nutrient loads) of the CW. Denitrification (N¬2O-N + N2-N) and DNRA were the major NO3--N removal processes accounting together for 54-79% of the total biochemical removal of the applied NO3--N. Of which 14-17 and 40-68% were removed by denitrification and DNRA, respectively. Both the processes significantly differed with CW cells indicating that N transformations depend on the rate of nutrient loads in different cells. They were significantly higher in shallow than deep groundwater. Environmental conditions were favourable for both the processes (i.e. low dissolved oxygen and low redox potential, high dissolved organic carbon, high total carbon and high dissolved organic N) but DNRA rate was favoured over denitrification by high ambient NH4+ concentrations, reduced sulphide and low pH (5.9 - 7.0). Low pH might have limited denitrification to some extent to an incomplete state, being evident by a high N2O-N/(N2O-N+N2-N) ratio (0.35 ± 0.17, SE). Relatively higher N2O-N/(N2O-N+N2-N) ratio and higher DNRA rate over denitrification suggest that the end products of N transformations are reactive. This N2O can be consumed to N2 and/or emit to atmosphere directly and indirectly. The DNRA rate and accumulation of NH4+ indicated that CW is a net source of NH4+ in groundwater. Ammonium produced by DNRA can be fixed in soils and, when exchange sites are

  12. Denitrification and polar stratospheric cloud formation during the Arctic winter 2009/2010

    Science.gov (United States)

    Khosrawi, F.; Urban, J.; Pitts, M. C.; Voelger, P.; Achtert, P.; Kaphlanov, M.; Santee, M. L.; Manney, G. L.; Murtagh, D.; Fricke, K.-H.

    2011-08-01

    The sedimentation of HNO3 containing Polar Stratospheric Cloud (PSC) particles leads to a permanent removal of HNO3 and thus to a denitrification of the stratosphere, an effect which plays an important role in stratospheric ozone depletion. The polar vortex in the Arctic winter 2009/2010 was very cold and stable between end of December and end of January. Strong denitrification between 475 to 525 K was observed in the Arctic in mid of January by the Odin Sub Millimetre Radiometer (Odin/SMR). This was the strongest denitrification that had been observed in the entire Odin/SMR measuring period (2001-2010). Lidar measurements of PSCs were performed in the area of Kiruna, Northern Sweden with the IRF (Institutet för Rymdfysik) lidar and with the Esrange lidar in January 2010. The measurements show that PSCs were present over the area of Kiruna during the entire period of observations. The formation of PSCs during the Arctic winter 2009/2010 is investigated using a microphysical box model. Box model simulations are performed along air parcel trajectories calculated six days backward according to the PSC measurements with the ground-based lidar in the Kiruna area. From the temperature history of the backward trajectories and the box model simulations we find two PSC regions, one over Kiruna according to the measurements made in Kiruna and one north of Scandinavia which is much colder, reaching also temperatures below Tice. Using the box model simulations along backward trajectories together with the observations of Odin/SMR, Aura/MLS (Microwave Limb Sounder), CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and the ground-based lidar we investigate how and by which type of PSC particles the denitrification that was observed during the Arctic winter 2009/2010 was caused. From our analysis we find that due to an unusually strong synoptic cooling event in mid January, ice particle formation on NAT may be a possible formation mechanism during

  13. Denitrification and polar stratospheric cloud formation during the Arctic winter 2009/2010

    Directory of Open Access Journals (Sweden)

    F. Khosrawi

    2011-08-01

    Full Text Available The sedimentation of HNO3 containing Polar Stratospheric Cloud (PSC particles leads to a permanent removal of HNO3 and thus to a denitrification of the stratosphere, an effect which plays an important role in stratospheric ozone depletion. The polar vortex in the Arctic winter 2009/2010 was very cold and stable between end of December and end of January. Strong denitrification between 475 to 525 K was observed in the Arctic in mid of January by the Odin Sub Millimetre Radiometer (Odin/SMR. This was the strongest denitrification that had been observed in the entire Odin/SMR measuring period (2001–2010. Lidar measurements of PSCs were performed in the area of Kiruna, Northern Sweden with the IRF (Institutet för Rymdfysik lidar and with the Esrange lidar in January 2010. The measurements show that PSCs were present over the area of Kiruna during the entire period of observations. The formation of PSCs during the Arctic winter 2009/2010 is investigated using a microphysical box model. Box model simulations are performed along air parcel trajectories calculated six days backward according to the PSC measurements with the ground-based lidar in the Kiruna area. From the temperature history of the backward trajectories and the box model simulations we find two PSC regions, one over Kiruna according to the measurements made in Kiruna and one north of Scandinavia which is much colder, reaching also temperatures below Tice. Using the box model simulations along backward trajectories together with the observations of Odin/SMR, Aura/MLS (Microwave Limb Sounder, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations and the ground-based lidar we investigate how and by which type of PSC particles the denitrification that was observed during the Arctic winter 2009/2010 was caused. From our analysis we find that due to an unusually strong synoptic cooling event in mid January, ice particle formation

  14. Influence of flow velocity and experimental setup on denitrification processes at the laboratory scale

    Science.gov (United States)

    Boisson, A.; Aquilina, L.; Bour, O.; De Ridder, J.

    2009-04-01

    In fractured media, physical heterogeneities lead to a large distribution of flow velocities that can partly control chemical reactions involving microbial activity. The aim of this project is to assess influence of fluid flow velocity on chemical reactivity at the laboratory scale. The experimental setup tries to reproduce autotrophic denitrification observed in a cristaline aquifer (Ploemeur; France) where denitrification seems to be enhanced by the exploitation of the aquifer. The experimental setup is based on a column filled with crushed granite from the Ploemeur site. Nitrate-rich water (C=40mg/l) is injected through the column under controlled flow conditions. Nitrate degradation is measured at the outlet and at different sampling plots along the column. These experiments use natural field water without treatment in order to use total available communities instead of one known bacterial community. Typically, the experiments are made during ten days at fluid flow velocities ranging from 0.5 to 5 cm/h. The first point is that the use of uncontrolled bacterial communities in experimental setup can lead to important evolution of the bacterial activity and competition. Results show that this competition is not only related to the experimental conditions but also to the experimental apparatus equipment. Batch experiments show that commonly used polymers (PVC, Tygon, Teflon) can react with nitrates via heterotrophic denitrification within the same time scale as the rock reactivity. Such reactions can even overwhelm the studied reaction. To assess the role of the experimental conditions, we control materials reactivity compared to the relevant time scale of the experiments. The first set of experiments exhibit autotrophic denitrification along the column with variations of the location of the reactive zone during the experiments. Reactivity arises all along the experiments in the first hours but becomes highly localized at the inlet of the column in the following

  15. Topographic and physicochemical controls on soil denitrification potential in prior converted croplands located on the Delmarva Peninsula, USA

    Science.gov (United States)

    Li, X.; Mccarty, G.; Lang, M. W.; Ducey, T.; Hunt, P.; Miller, J.

    2016-12-01

    Topography and soil physiochemical characteristics exert substantial controls on denitrification in agricultural lands. In order to depict these controls at a landscape scale for decision support applications, metrics (i.e., proxies) must be developed based on commonly available geospatial data. In this study, we analyzed the combined effects of eleven topography and soil physiochemical factors, including three topographic attributes (relief, topographic wetness index, and positive openness), two soil texture indices (sand and clay), and six soil properties (soil moisture, pH, electrical conductivity, SOC, TN, and C:N ratio), on soil denitrification potential in three actively farmed crop fields that were converted from forested wetlands before 1986 (i.e., prior converted croplands). Denitrification potential was measured using denitrification enzyme activity (DEA) assays, which employed the acetylene inhibition method under two treatments - a non-nitrate and carbon limiting treatment to measure potential denitrification and a control treatment to measure the capacity for denitrification without soil amendment. Nitrate and carbon addition led to a doubling in DEA rates compared to the control treatment. Topography explained the greatest amount of variation in potential denitrification across the three sites. The relationship between topography and DEA may partly be explained through the relatively robust relationship between topography and soil moisture, texture, and carbon content. For DEA under the control treatment, soil electrical conductivity (EC) exhibited the highest correlation with denitrification capacity (i.e., r2 = 35%). Denitrification capacity and potential were higher in a dry year with low soil moisture, relative to an average year with high soil moisture, which may be caused by the substantial increase in soil EC in the dry year. However, DEA rates were less responsive to soil EC at sandy sites which tend to have low soil moisture. Results of this

  16. Smart parking barrier

    KAUST Repository

    Alharbi, Abdulrazaq M.

    2016-05-06

    Various methods and systems are provided for smart parking barriers. In one example, among others, a smart parking barrier system includes a movable parking barrier located at one end of a parking space, a barrier drive configured to control positioning of the movable parking barrier, and a parking controller configured to initiate movement of the parking barrier, via the barrier drive. The movable parking barrier can be positioned between a first position that restricts access to the parking space and a second position that allows access to the parking space. The parking controller can initiate movement of the movable parking barrier in response to a positive identification of an individual allowed to use the parking space. The parking controller can identify the individual through, e.g., a RFID tag, a mobile device (e.g., a remote control, smartphone, tablet, etc.), an access card, biometric information, or other appropriate identifier.

  17. 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.

  18. Numerical modeling of coupled nitrification-denitrification in sediment perfusion cores from the hyporheic zone of the Shingobee River, MN

    Science.gov (United States)

    Sheibley, R.W.; Jackman, A.P.; Duff, J.H.; Triska, F.J.

    2003-01-01

    Nitrification and denitrification kinetics in sediment perfusion cores were numerically modeled and compared to experiments on cores from the Shingobee River MN, USA. The experimental design incorporated mixing groundwater discharge with stream water penetration into the cores, which provided a well-defined, one-dimensional simulation of in situ hydrologic conditions. Ammonium (NH+4) and nitrate (NO-3) concentration gradients suggested the upper region of the cores supported coupled nitrification-denitrification, where groundwater-derived NH+4 was first oxidized to NO-3 then subsequently reduced via denitrification to N2. Nitrification and denitrification were modeled using a Crank-Nicolson finite difference approximation to a one-dimensional advection-dispersion equation. Both processes were modeled using first-order reaction kinetics because substrate concentrations (NH+4 and NO-3) were much smaller than published Michaelis constants. Rate coefficients for nitrification and denitrification ranged from 0.2 to 15.8 h-1 and 0.02 to 8.0 h-1, respectively. The rate constants followed an Arrhenius relationship between 7.5 and 22 ??C. Activation energies for nitrification and denitrification were 162 and 97.3 kJ/mol, respectively. Seasonal NH+4 concentration patterns in the Shingobee River were accurately simulated from the relationship between perfusion core temperature and NH+4 flux to the overlying water. The simulations suggest that NH+4 in groundwater discharge is controlled by sediment nitrification that, consistent with its activation energy, is strongly temperature dependent. ?? 2003 Elsevier Ltd. All rights reserved.

  19. Pilot and full scale applications of sulfur-based autotrophic denitrification process for nitrate removal from activated sludge process effluent.

    Science.gov (United States)

    Sahinkaya, Erkan; Kilic, Adem; Duygulu, Bahadir

    2014-09-01

    Sulfur-based autotrophic denitrification of nitrified activated sludge process effluent was studied in pilot and full scale column bioreactors. Three identical pilot scale column bioreactors packed with varying sulfur/lime-stone ratios (1/1-3/1) were setup in a local wastewater treatment plant and the performances were compared under varying loading conditions for long-term operation. Complete denitrification was obtained in all pilot bioreactors even at nitrate loading of 10 mg NO3(-)-N/(L.h). When the temperature decreased to 10 °C during the winter time at loading of 18 mg NO3(-)-N/(L.h), denitrification efficiency decreased to 60-70% and the bioreactor with S/L ratio of 1/1 gave slightly better performance. A full scale sulfur-based autotrophic denitrification process with a S/L ratio of 1/1 was set up for the denitrification of an activated sludge process effluent with a flow rate of 40 m(3)/d. Almost complete denitrification was attained with a nitrate loading rate of 6.25 mg NO3(-)-N/(L.h).

  20. Using T-RFLP data on denitrifier community composition to inform understanding of denitrification in stream sediments (Invited)

    Science.gov (United States)

    Wang, S.; Somers, K.; Sudduth, E.; Hassett, B.; Bernhardt, E. S.; Urban, D. L.

    2010-12-01

    We used terminal restriction fragment length polymorphism (T-RFLP), a molecular fingerprinting method, to characterize denitrifier communities in sediments taken from 48 study streams in North Carolina, USA. In addition to characterizing denitrifier communities, we also used denitrification enzyme activity (DEA) assays to measure potential denitrification rates. Due to differences in watershed land-use, study streams covered a gradient of nitrogen and carbon concentrations, as well as a gradient of contaminant loading from stormwater and sanitary sewers. Nitrogen and carbon (i.e., substrate) concentrations are commonly used to make predictions about denitrification rates in streams. Such models do not take into account denitrifier community composition, which may be an important, independent control of denitrification rates, particularly under stressful conditions (e.g., high contaminant loading) that prevent communities from capitalizing on high substrate availability. Our results indicate that substrate availability by itself was a weak predictor of denitrification rates; the same was also true for denitrifier community composition. However, when both factors were incorporated in a multiple regression model, the percent variation explained increased substantially. These findings suggest that T-RFLP, a relatively cost-effective method, can be used to improve our understanding of controls on denitrification rates in streams with varying watershed land-uses.

  1. Comparison of combined and separated biological aerated filter (BAF) performance for pre-denitrification/nitrification of municipal wastewater.

    Science.gov (United States)

    Rother, E; Cornel, P; Ante, A; Kleinert, P; Brambach, R

    2002-01-01

    The performance of two systems of semi-industrial up-flow biological aerated filters (BAF) with pre-denitrification followed by nitrification was studied and compared under various operating and loading conditions. The first system consisted of two separate reactors for the denitrification and the nitrification step, whereas in the second system the aerobic nitrification zone was packed on top of the anoxic denitrification zone in one reactor. The second system potentially offers substantial savings in investment costs and space requirements for a large scale treatment plant. Regarding the elimination of carbonaceous pollution and denitrification the systems did not show significant differences. However, nitrification in the combined system suffered from the mixing of different biocenosis by daily backwashing and was reduced to 50-70% of the separated system's performance. Factors such as oxygen concentration, raw water composition and loading rates affected both systems' nitrification rates in similar ways. Since it is impossible to optimise the nitrification and denitrification processes separately, the combined system should only be considered for large scale applications if space is very scarce and if a stable raw water composition can be expected. If strict limit values for nitrate have to be met in the effluent, a combination of pre- and post-denitrification is advantageous and advisable.

  2. High-rate hydrogenotrophic denitrification in a fluidized-bed biofilm reactor using solid-polymer-electrolyte membrane electrode (SPEME).

    Science.gov (United States)

    Komori, M; Sakakibara, Y

    2008-01-01

    A fluidized-bed biofilm reactor equipped with a Solid-Polymer-Electrolyte Membrane Electrode (SPEME) cell was developed in order to enhance hydrogenotrophic denitrification of groundwater. Porous cubes made of polyvinylalcohol (PVA) were used as a biofilm carrier and continuous treatments using synthetic groundwater were carried out for 105 days. Electric current was changed step-wise from 0.4 to 4.0 A. Experimental results showed that efficient production and dissolution of hydrogen were achieved by application of electric current as well as high-rate denitrification simultaneously. Denitrification rates of nitrite increased with the increase of electric current. Overall denitrification rates attained to about 90 mg-N/L/h, which was 3 to 9 times as high as those reported in former studies. Supplying electric current of about two times of stoichiometric equivalent to the cell considered necessary for complete denitrification. Water quality in effluent was very stable and electrolytic voltage was low around 3 V. In addition, simple and secure operation was demonstrated over the experiment. From these results, it was concluded that the present fluidized-bed biofilm reactor equipped with a SPEME cell could be very feasible for high-rate hydrogenotrophic denitrification of ground water.

  3. Denitrification and Nitrate Reduction to Ammonium in Taihu Lake and Yellow sea Inter—Tidal Marine Sediments

    Institute of Scientific and Technical Information of China (English)

    YINSHIXUE; SHENQIRONG; 等

    1999-01-01

    Denitrification and nitrate reduction to ammonium in Taihu Lake and Yellow Sea inter-tidal marine sediments were studied.The sediment samples were made slurry containing 150g dry matter per liter.Various of glucose-C to nitrate-N.Acetylene inhibition technique was applied to measure denitrification in the slurres,All samples were incubated anaerobically under argon atmosphere,Data showed that Taihu Lake sediment produced more N2O than marine sediment,Denitrification potential was higher in Taihu Lake sediment than in marine one,Glucose added increase denitrification activity but not the denitrification potential of the sediments.Dissimilatory nitrate reduction to ammonium seemed to occur in marine sediment,but not in freshwater one.When the marine sediment was treated with 25mmol L-1 glucose,its denitrification potentail,as indicated by maximum N2O production by acetylene blockage,was lower than that treated with no or 2.5mmol L-1 glucose.Acetylene was suspected to have inhibitory effect on dissimilatory nitrate reduction to ammonium.

  4. A new reactor for denitrification and micro-particle removal in recirculated aquaculture systems.

    Science.gov (United States)

    Boley, A; Korshun, G; Boley, S; Jung-Schroers, V; Adamek, M; Steinhagen, D; Richter, S

    2017-03-01

    A 'membrane-denitrification' reactor (MDR) was developed and tested in a semi-technical recirculation aquaculture system in comparison to a double - without MDR - as reference system. The MDR consisted of a reactor with an ultrafiltration membrane unit for removal of micro-particles (e.g. sludge flocs, bacteria and parasites). Specific carrier material provided surfaces for biofilm growth in a fluidized bed reactor with ethanol as carbon source for denitrification. The continuous motion of these carriers cleaned the membrane surface. With online and laboratory measurements of water parameters and operational data the feasibility of the concept was verified. An advantage is that no chemicals are needed to clean the membranes. Examinations of the fish and water analyses proved an MDR can positively influence cortisol, as a stress marker, and the microflora of the aquatic system.

  5. N pollution sources and denitrification in waterbodies in Taihu Lake region

    Institute of Scientific and Technical Information of China (English)

    邢光熹; 曹亚澄; 施书莲; 孙国庆; 杜丽娟; 朱建国

    2001-01-01

    Herein presented are the researches of the past few years related to characteristics of N pollution of waterbodies and N transport from croplands to the waterbodies in Suzhou and Wuxi regions, the center of the Taihu Lake valley. Based on the types of waterbodies, concentrations ofinorganic N of different forms, concentrations of PO43-, δ15NH4 values in river and lake waterbodies,the pollution sources of N in the river, lake and well waters are distinguished, and comparisons are made of trend of variation and amplitude of concentration between years, seasons and N pollutants in waterbodies. The increase in N2O concentration in different waterbodies and high δ15NO3-value in different waterbodies are deemed as an evidence of the existence of denitrification in the river, lake and well waters. Moreover, the role of denitrification in the waterbodies plays in stabilizing chronically concentration of N as pollutant in the waterbodies and mitigating N load in the waterbodies.

  6. Simultaneous nitrification/denitrification in a biofilm airlift suspension (BAS) reactor with biodegradable carrier material.

    Science.gov (United States)

    Walters, Evelyn; Hille, Andrea; He, Mei; Ochmann, Clemens; Horn, Harald

    2009-10-01

    Simultaneous nitrification and denitrification in one reactor has been realized with different methods in the past. The usage of biodegradable biocompounds as biofilm carriers is new. The biocompounds were designed out of two polymers having different degradability. Together with suspended autotrophic biomass the biocompound particles were fluidized in an airlift reactor. Process water from sludge dewatering with a mean ammonium nitrogen concentration of 1150 mg L(-1) was treated in a two stage system which achieved a nitrogen removal of 75%. Batch experiments clearly indicate that nitrification can be localized in the suspended biomass and denitrification in the pore structure of the slowly degraded biocompounds. Images taken with CLSM prove the concept of the pore structure within the biocompounds, which provide both a heterotrophic biofilm and carbon source.

  7. Denitrification of aging biogas slurry from livestock farm by photosynthetic bacteria.

    Science.gov (United States)

    Yang, Anqi; Zhang, Guangming; Yang, Guang; Wang, Hangyao; Meng, Fan; Wang, Hongchen; Peng, Meng

    2017-05-01

    Huge amount of aging biogas slurry is in urgent need to be treated properly. However, due to high NH3-N concentration and low C/N ratio, this aging biogas slurry is refractory for traditional methods. Its denitrification has become a big challenge. In this paper, photosynthetic bacteria (PSB) were employed to handle this problem. The results showed denitrification of aging biogas slurry by PSB treatment was promising. The highest removal efficiency of NH3-N reached 99.75%, much higher than all other treatments. The removal of NH3-N followed pseudo zero order reaction under dark-aerobic condition. The better inoculation rate for NH3-N removal was 30%; and aerobic condition was more beneficial for NH3-N removal than anaerobic condition because of different metabolic pathways. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Feasibility of an innovative integrated process of simultaneous desulfurization and denitrification for high strength wastewater

    Institute of Scientific and Technical Information of China (English)

    WANG Ai-jie; LIU Chun-shuang; REN Nan-qi; DENG Xu-liang; WAN Chun-li; YU Zhen-guo; XU Xin

    2008-01-01

    An anaerobic expanding-bed reactor was adopted to investigate the feasibility of an innovative inte-grated process of simultaneous desulfurization and denitrification (SDD) for high strength wastewater. In the re-actor, beterotrophic bacteria (including sulfate reducing bacterium and denitrifying bacteria) and autotrophic bacteria (including Thiobacillus denitrificans) cooperated together by incubating and enriching functional bac-teria on different carriers in the anaerobic activated sludge. Synthetic wastewater with high concentrations of sul-fate and nitrate was employed. The experimental results showed that the removal efficiency of sulfate and nitrate was above 85%, elemental sulfur was observed while nitrate was absent in effluent. The balance of sulfur, ni-trogen and electron was discussed respectively, which indicated that the integrated SDD process could be actual-ized. These results might provide a guidance to further investigate the key factors affecting the integrated SDD process and to improve the efficiency of desulfurization and denitrification in wastewater treatment.

  9. N pollution sources and denitrification in waterbodies in-Taihu Lake region

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Herein presented are the researches of the past few years related to characteristics of N pollution of waterbodies and N transport from croplands to the waterbodies in Suzhou and Wuxi regions, the center of the Taihu Lake valley. Based on the types of waterbodies, concentrations of inorganic N of different forms, concentrations of , d15NH4 values in river and lake waterbodies, the pollution sources of N in the river, lake and well waters are distinguished, and comparisons are made of trend of variation and amplitude of concentration between years, seasons and N pollutants in waterbodies. The increase in N2O concentration in different waterbodies and high d 15 value in different waterbodies are deemed as an evidence of the existence of denitrification in the river, lake and well waters. Moreover, the role of denitrification in the waterbodies plays in stabilizing chronically concentration of N as pollutant in the waterbodies and mitigating N load in the water-bodies.

  10. Enhancement of bacterial denitrification for nitrate removal in groundwater with electrical stimulation from microbial fuel cells

    Science.gov (United States)

    Zhang, Baogang; Liu, Ye; Tong, Shuang; Zheng, Maosheng; Zhao, Yinxin; Tian, Caixing; Liu, Hengyuan; Feng, Chuanping

    2014-12-01

    Electricity generated from the microbial fuel cell (MFC) is applied to the bioelectrical reactor (BER) directly as electrical stimulation means for enhancement of bacterial denitrification to remove nitrate effectively from groundwater. With maximum power density of 502.5 mW m-2 and voltage outputs ranging from 500 mV to 700 mV, the nitrate removal is accelerated, with less intermediates accumulation, compared with control sets without electrical stimulation. Denitrification bacteria proliferations and activities are promoted as its number and Adenosine-5'-triphosphate (ATP) concentration increased one order of magnitude (3.5 × 107 in per milliliter biofilm solution) and about 1.5 folds, respectively. Effects of electricity from MFCs on enhancement of bacterial behaviors are demonstrated for the first time. These results indicate that MFCs can be applied in the in-situ bioremediation of nitrate polluted groundwater for efficiency improvement.

  11. Chemotactic Motility of Pseudomonas fluorescens F113 under Aerobic and Denitrification Conditions.

    Directory of Open Access Journals (Sweden)

    Candela Muriel

    Full Text Available The sequence of the genome of Pseudomonas fluorescens F113 has shown the presence of multiple traits relevant for rhizosphere colonization and plant growth promotion. Among these traits are denitrification and chemotactic motility. Besides aerobic growth, F113 is able to grow anaerobically using nitrate and nitrite as final electron acceptors. F113 is able to perform swimming motility under aerobic conditions and under anaerobic conditions when nitrate is used as the electron acceptor. However, nitrite can not support swimming motility. Regulation of swimming motility is similar under aerobic and anaerobic conditions, since mutants that are hypermotile under aerobic conditions, such as gacS, sadB, kinB, algU and wspR, are also hypermotile under anaerobic conditions. However, chemotactic behavior is different under aerobic and denitrification conditions. Unlike most pseudomonads, the F113 genome encode three complete chemotaxis systems, Che1, Che2 and Che3. Mutations in each of the cheA genes of the three Che systems has shown that the three systems are functional and independent. Mutation of the cheA1 gene completely abolished swimming motility both under aerobic and denitrification conditions. Mutation of the cheA2 gene, showed only a decrease in swimming motility under both conditions, indicating that this system is not essential for chemotactic motility but is necessary for optimal motility. Mutation of the cheA3 gene abolished motility under denitrification conditions but only produced a decrease in motility under aerobic conditions. The three Che systems proved to be implicated in competitive rhizosphere colonization, being the cheA1 mutant the most affected.

  12. Spatial and temporal variation of denitrification in the riparian zone during the hydrological year

    Science.gov (United States)

    Trauth, Nico; Musolff, Andreas; Knöller, Kay; Fleckenstein, Jan H.

    2017-04-01

    In the riparian zone, where stream water mixes with groundwater, biogeochemical reactions and solute transformations occur which may enhance the self-cleaning mechanisms of aquatic ecosystems. The water exchange and solute transport through the riparian zone is controlled by hydraulic gradients between stream and groundwater and thus varies seasonally and during stream discharge events. In this study, we focus on transport, mixing and the distribution of nitrate in the riparian zone of a gravelly alluvial aquifer with the aim to quantify its denitrification potential during the hydrological year. For this purpose, 25 groundwater wells were drilled along a 2 km stream section of the Selke river, a third-order stream in Germany. From the stream and the wells, water samples were taken 4-weekly over a period of 2 years. Water samples were analyzed to field parameters, major ions, dissolved organic carbon, and N-O isotopes. Results show a strong influence of the stream on the adjacent groundwater, which varies both in time and space. In general, we can distinguish between two endmembers: a) the stream water with low chloride (concentrations and b) the groundwater in 100m distance to the stream with high chloride (>70 mg/L) and nitrate (>50 mg/L) concentrations. Based on conservatively transported chloride, the mixing of the endmembers can be determined in the riparian zone. Deviations in nitrate concentrations from this mixing model may indicate nitrate degradation by e.g. denitrification. By combining this chloride-nitrate-ratio method with dissolved oxygen data and the isotopic signature of the nitrate molecule, we are able to determine the timing and the location of high denitrification patterns in the riparian aquifer. Highest variability of denitrification occurs over the year in terms of seasonality (temperature-driven) and is temporally fueled by additional organic carbon supply during discharge events.

  13. Denitrifying bacterial community composition changes associated with stages of denitrification in oxygen minimum zones

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, D.A.; O'Mullan, G.D.; Naqvi, S.W.A.; Ward, B.B.

    mixing two water masses with different cell number–nitrite relationships. In addition, the assignment of stages is somewhat complicated because it combines the net result of the history of the water and in situ microbial activity. Diversity... that are characteristic of OMZs in active stages of denitrification suggest that the removal of fixed nitrogen may occur via episodically enhanced growth of denitrifying organisms in the core of an OMZ. These hot spots are driven by the episodic blooms of surface...

  14. Autotrophic denitrification for treatment of wastewater with high concentration of sulphur and nitrogen compounds

    OpenAIRE

    Fajardo Ortiz, María del Carmen

    2011-01-01

    Anthropogenic activities have contributed to the imbalance of nitrogen and sulphur natural cycles which causes many negative effects in nature due to the emissions of sulphur and nitrogen compounds and their transformations, e.g. rain acid, eutrophication, bad odours etc. To avoid such negative effects on environment, effluents containing high concentrations of both nitrogen and sulphur compounds must be treated previously to their discharge. Nitrification/denitrification is the conventio...

  15. 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.

  16. Organic matter and concentrated nitrogen removal by shortcut nitrification and denitrification from mature municipal landfill leachate

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shu-jun; PENG Yong-zhen; WANG Shu-ying; ZHENG Shu-wen; GUO Jin

    2007-01-01

    An UASB+Anoxic/Oxic (A/O) system was introduced to treat a mature landfill leachate with low carbon-to-nitrogen ratio and high ammonia concentration. To make the best use of the biodegradable COD in the leachate, the denitrification of NOx-N in the recirculation effluent from the clarifier was carried out in the UASB. The results showed that most biodegradable organic matters were removed by the denitrification in the UASB. The NH4+-N loading rate (ALR) of A/O reactor and operational temperature was 0.28-0.60 kg NH4+-N/(m3·d) and 17-29℃ during experimental period, respectively. The short-cut nitrification with nitrite accumulation efficiency of 90%-99% was stabilized during the whole experiment. The NH4+-N removal efficiency varied between 90% and 100%. When ALR was less than 0.45 kg NH4+-N/(m3·d), the NH4+-N removal efficiency was more than 98%. With the influent NH4+-N of 1200-1800 mg/L, the effluent NH4+-N was less than 15 mg/L. The shortcut nitrification and denitrification can save 40% carbon source, with a highly efficient denitrification taking place in the UASB. When the ratio of the feed COD to feed NH4+-N was only 2-3, the total inorganic nitrogen (TIN) removal efficiency attained 67%-80%. Besides, the sludge samples from A/O reactor were analyzed using FISH. The FISH analysis revealed that ammonia oxidation bacteria (AOB) accounted for 4% of the total eubacterial population, whereas nitrite oxidation bacteria (NOB) accounted only for 0.2% of the total eubacterial population.

  17. Large-scale controls on potential respiration and denitrification in riverine floodplains.

    Science.gov (United States)

    Welti, Nina; Bondar-Kunze, Elisabeth; Singer, Gabriel; Tritthart, Michael; Zechmeister-Boltenstern, Sophie; Hein, Thomas; Pinay, Gilles

    2012-05-01

    Restoration measures of deteriorated river ecosystems generally aim at increasing the spatial heterogeneity and connectivity of these systems in order to increase biodiversity and ecosystem stability. While this is believed to benefit overall ecological integrity, consequences of such restoration projects on biogeochemical processes per se (i.e. ecosystem functioning) in fluvial systems are rarely considered. We address these issues by evaluating the characteristics of surface water connection between side arms and the main river channel in a former braided river section and the role and degree of connectivity (i.e. duration of surface water connection) on the sediment biogeochemistry. We hypothesized that potential respiration and denitrification would be controlled by the degree of hydrological connectivity, which was increased after floodplain restoration. We measured potential microbial respiration (SIR) and denitrification (DEA) and compared a degraded floodplain section of the Danube River with a reconnected and restored floodplain in the same river section. Re-establishing surface water connection altered the controls on sediment microbial respiration and denitrification ultimately impacting potential microbial activities. Meta-variables were created to characterize the effects of hydrology, morphology, and the available carbon and nutrient pools on potential microbial processing. Mantel statistics and path analysis were performed and demonstrate a hierarchy where the effects of hydrology on the available substrates and microbial processing are mediated by the morphology of the floodplain. In addition, these processes are highest in the least connected sites. Surface water connection, mediated by morphology regulates the potential denitrification rate and the ratio of N2O to N2 emissions, demonstrating the effects of restoration in floodplain systems.

  18. 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.

  19. Stimulating in situ denitrification in an aerobic, highly permeable municipal drinking water aquifer

    Science.gov (United States)

    Critchley, K.; Rudolph, D. L.; Devlin, J. F.; Schillig, P. C.

    2014-12-01

    A preliminary trial of a cross-injection system (CIS) was designed to stimulate in situ denitrification in an aquifer servicing an urban community in southern Ontario. It was hypothesized that this remedial strategy could be used to reduce groundwater nitrate in the aquifer such that it could remain in use as a municipal supply until the beneficial effects of local reduced nutrient loadings lead to long-term water quality improvement at the wellfield. The CIS application involved injecting a carbon source (acetate) into the subsurface using an injection-extraction well pair positioned perpendicular to the regional flow direction, up-gradient of the water supply wells, with the objective of stimulating native denitrifying bacteria. The pilot remedial strategy was targeted in a high nitrate flux zone within an aerobic and heterogeneous section of the glacial sand and gravel aquifer. Acetate injections were performed at intervals ranging from daily to bi-daily. The carbon additions led to general declines in dissolved oxygen concentrations; decreases in nitrate concentration were localized in aquifer layers where velocities were estimated to be less than 0.5 m/day. NO3-15N and NO3-18O isotope data indicated the nitrate losses were due to denitrification. Relatively little nitrate was removed from groundwater in the more permeable strata, where velocities were estimated to be on the order of 18 m/day or greater. Overall, about 11 percent of the nitrate mass passing through the treatment zone was removed. This work demonstrates that stimulating in situ denitrification in an aerobic, highly conductive aquifer is challenging but achievable. Further work is needed to increase rates of denitrification in the most permeable units of the aquifer.

  20. Tertiary Denitrification of the Secondary Effluent by Denitrifying Biofilters Packed with Different Sizes of Quartz Sand

    Directory of Open Access Journals (Sweden)

    Nan Wei

    2014-05-01

    Full Text Available Tertiary denitrification of the secondary effluent in wastewater treatment plants is necessary to control the eutrophication of receiving water bodies. Two denitrifying biofilters (DNBF, one packed with quart sand with sizes of 2–4 mm (DNBFS and the other of 4–6 mm (DNBFL, were operated for tertiary denitrification under empty bed retention times (EBRTs of 30 min, 15 min and 7.5 min, respectively. Under EBRTs of 30 min, 15 min and 7.5 min, the NO3−-N removal percentages were 93%, 82% and 83% in DNBFS, and were 92%, 68% and 36% in DNBFL, respectively. The nitrogen removal loading rates increased with decreasing EBRTs, and at the EBRT of 7.5 min, the rate was 2.15 kg/(m3·d in DNBFS and 1.08 kg/(m3·d in DNBFL. The half-order denitrification coefficient of DNBFS increased from 0.42 (mg/L1/2/min at the EBRT of 30 min to 0.70 (mg/L1/2/min at the EBRT of 7.5 min, while did not vary much in DNBFL with values from 0.22 to 0.25 (mg/L1/2/min. The performance of both DNBFs was stable within each backwashing cycle, with the NO3−-N removal percentage variation within 5%. Better denitrification was achieved in DNBFS but with a slightly high decreased flow rate during the operation.

  1. Effect of organic loading on nitrification and denitrification in a marine sediment microcosm

    Science.gov (United States)

    Caffrey, J.M.; Sloth, N.P.; Kaspar, H.F.; Blackburn, T.H.

    1993-01-01

    The effects of organic additions on nitrification and denitrification were examined in sediment microcosms. The organic material, heat killed yeast, had a C/N ratio of 7.5 and was added to sieved, homogenized sediments. Four treatments were compared: no addition (control, 30 g dry weight (dw) m-2 mixed throughout the 10 cm sediment column (30 M), 100 g dw m-2 mixed throughout sediments (100M), and 100 g dw m-2 mixed into top 1 cm (100S). After the microcosms had been established for 7-11 days, depth of O2 penetration, sediment-water fluxes and nitrification rates were measured. Nitrification rates were measured using three different techniques: N-serve and acetylene inhibition in intact cores, and nitrification potentials in slurries. Increased organic additions decreased O2 penetration from 2.7 to 0.2 mm while increasing both O2 consumption, from 30 to 70 mmol O2 m-2 d-1, and NO3- flux into sediments. Nitrification rates in intact cores were similar for the two methods. Highest rates occurred in the 30 M treatment, while the lowest rate was measured in the 100S treatment. Total denitrification rates (estimated from nitrification and nitrate fluxes) increased with increased organic addition, because of the high concentrations of NO3- (40 ??M) in the overlying water. The ratio of nitrification: denitrification was used as an indication of the importance of nitrification as the NO3- supply for denitrification. This ratio decreased from 1.55 to 0.05 with increased organic addition.

  2. Non-linear hydraulic properties of woodchips necessary to design denitrification beds

    Science.gov (United States)

    Ghane, Ehsan; Feyereisen, Gary W.; Rosen, Carl J.

    2016-11-01

    Denitrification beds are being used to reduce the transport of water-soluble nitrate via subsurface drainage systems to surface water. Only recently has the non-linearity of water flow through woodchips been ascertained. To successfully design and model denitrification beds with optimum nitrate removal, a better understanding of flow in denitrification beds is needed. The main objectives of this study were to characterize the hydraulic properties of old degraded woodchips and provide a better understanding of the factors affecting flow. To achieve this goal, we conducted constant-head column experiments using old woodchips that were excavated from a four-year old denitrification bed near Willmar, Minnesota, USA. For Izbash's equation, the non-Darcy exponent (n) ranged from 0.76 to 0.87 that indicates post-linear regime, and the permeability coefficient (M10) at 10°C ranged from 0.9 to 2.6 cm s-1. For Forchheimer's equation, the intrinsic permeability of 5.6 × 10-5 cm2 and ω constant of 0.40 (at drainable porosity of 0.41) closely resembled the in-situ properties found in a previous study. Forchheimer's equation was better than that of Izbash's for describing water flow through old woodchips, and the coefficients of the former provided stronger correlations with drainable porosity. The strong correlation between intrinsic permeability and drainable porosity showed that woodchip compaction is an important factor affecting water flow through woodchips. Furthermore, we demonstrated the importance of temperature effects on woodchip hydraulics. In conclusion, the hydraulic properties of old woodchips should be characterized using a non-Darcy equation to help design efficient systems with optimum nitrate removal.

  3. Cumene hydroperoxide-supported denitrification of 2-nitropropane in uninduced mouse liver microsomes.

    Science.gov (United States)

    Marker, E K; Kulkarni, A P

    1986-01-01

    Cumene hydroperoxide supported oxidative denitrification of 2-nitropropane was investigated in uninduced mouse liver microsomes. The cytochrome P-450 peroxygenase catalyzed reaction resulted in the production of nitrite and acetone. Several lines of evidence suggested the involvement of multiple forms of cytochrome P-450. Acetone production was at least two times greater than nitrite release possibly due to sequestration of nitrite in the reaction mixtures.

  4. Large-scale controls on potential respiration and denitrification in riverine floodplains

    Science.gov (United States)

    Welti, Nina; Bondar-Kunze, Elisabeth; Singer, Gabriel; Tritthart, Michael; Zechmeister-Boltenstern, Sophie; Hein, Thomas; Pinay, Gilles

    2012-01-01

    Restoration measures of deteriorated river ecosystems generally aim at increasing the spatial heterogeneity and connectivity of these systems in order to increase biodiversity and ecosystem stability. While this is believed to benefit overall ecological integrity, consequences of such restoration projects on biogeochemical processes per se (i.e. ecosystem functioning) in fluvial systems are rarely considered. We address these issues by evaluating the characteristics of surface water connection between side arms and the main river channel in a former braided river section and the role and degree of connectivity (i.e. duration of surface water connection) on the sediment biogeochemistry. We hypothesized that potential respiration and denitrification would be controlled by the degree of hydrological connectivity, which was increased after floodplain restoration. We measured potential microbial respiration (SIR) and denitrification (DEA) and compared a degraded floodplain section of the Danube River with a reconnected and restored floodplain in the same river section. Re-establishing surface water connection altered the controls on sediment microbial respiration and denitrification ultimately impacting potential microbial activities. Meta-variables were created to characterize the effects of hydrology, morphology, and the available carbon and nutrient pools on potential microbial processing. Mantel statistics and path analysis were performed and demonstrate a hierarchy where the effects of hydrology on the available substrates and microbial processing are mediated by the morphology of the floodplain. In addition, these processes are highest in the least connected sites. Surface water connection, mediated by morphology regulates the potential denitrification rate and the ratio of N2O to N2 emissions, demonstrating the effects of restoration in floodplain systems. PMID:23565037

  5. Theoretical and practical limitations of the acetylene inhibition technique to determine total denitrification losses

    Directory of Open Access Journals (Sweden)

    R. Felber

    2012-10-01

    Full Text Available The loss of N2 from intensively managed agro-ecosystems is an important part of the N budget. Flux monitoring of N2 emissions at the field scale, e.g., by eddy correlation or aerodynamic gradient method, is impossible due to the large atmospheric N2 background (78%. The acetylene (C2H2 inhibition technique (AIT is a rather simple and frequently used, albeit imperfect, method to determine N2 losses from intact soil cores. In principle, AIT allows an estimation of total denitrification at high temporal resolution and on small spatial scales, with limited workload and costs involved. To investigate its potential and limitations, a laboratory system with two different detection systems (photoacoustic IR spectroscopy and gas chromatography is presented, which allowed simultaneous measurements of up to 7 intact soil cores in air-tight glass tubes in a temperature controlled cabinet (adjusted to field conditions with automated C2H2 injection. A survey of total denitrification losses (N2 + N2O over 1.5 yr in soil cores from an intensively managed, cut grassland system in central Switzerland supports previous reports on severe limitations of the AIT, which precluded reliable estimates of total denitrification losses. Further, the unavoidable sampling and transfer of soil samples to the laboratory causes unpredictable deviations from the denitrification activity in the field.

  6. Stimulation of autotrophic denitrification by intrusions of the Bosporus Plume into the anoxic Black Sea

    Directory of Open Access Journals (Sweden)

    Clara A. Fuchsman

    2012-07-01

    Full Text Available Autotrophic denitrification was measured in the southwestern coastal Black Sea, where the Bosporus Plume injects oxidized chemical species (especially O2 and NO3- into the oxic, suboxic and anoxic layers. Prominent oxygen intrusions caused an overlap of NOx- and sulfide at the same station where autotrophic denitrification activity was detected with incubation experiments. Several bacteria that have been proposed to oxidize sulfide in other low oxygen environments were found in the Black Sea including SUP05, Sulfurimonas, Arcobacter, and BS-GSO2. Comparison of TRFLP profiles from this mixing zone station and the Western Gyre (a station not affected by the Bosporus Plume indicate the greatest relative abundance of Sulfurimonas and Arcobacter at the appropriate depths at the mixing zone station. The autotrophic gammaproteobacterium BS-GSO2 correlated with ammonium fluxes rather than with sulfide fluxes and the maximum in SUP05 peak height was shallower than the depths where autotrophic denitrification was detected. Notably, anammox activity was not detected at the mixing zone station, though low levels of DNA from the anammox bacteria Candidatus Scalindua were present. These results provide evidence for a modified ecosystem with different N2 production pathways in the southwest coastal region compared to that found in the rest of the Black Sea. Moreover, the same Sulfurimonas phylotype (BS139 was previously detected on >30 μm particles in the suboxic zone of the Western Gyre along with DNA of potential sulfate reducers, so it is possible that particle-attached autotrophic denitrification may be an overlooked N2 production pathway in the central Black Sea as well.

  7. 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 CO2 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.

  8. Autohydrogenotrophic denitrification of drinking water using a polyvinyl chloride hollow fiber membrane biofilm reactor.

    Science.gov (United States)

    Zhang, Yanhao; Zhong, Fohua; Xia, Siqing; Wang, Xuejiang; Li, Jixiang

    2009-10-15

    A hollow fiber membrane biofilm reactor (MBfR) using polyvinyl chloride (PVC) hollow fiber was evaluated in removing nitrate form contaminated drinking water. During a 279-day operation period, the denitrification rate increased gradually with the increase of influent nitrate loading. The denitrification rate reached a maximum value of 414.72 g N/m(3)d (1.50 g N/m(2)d) at an influent NO(3)(-)-N concentration of 10mg/L and a hydraulic residence time of 37.5 min, and the influent nitrate was completely reduced. At the same time, the effluent quality analysis showed the headspace hydrogen content (3.0%) was lower enough to preclude having an explosive air. Under the condition of the influent nitrate surface loading of 1.04 g N/m(2)d, over 90% removal efficiencies of the total nitrogen and nitrate were achieved at the hydrogen pressure above 0.04 MPa. The results of denaturing gel gradient electrophoresis (DGGE), 16S rDNA gene sequence analysis, and hierarchical cluster analysis showed that the microbial community structures in MBfR were of low diversity, simple and stable at mature stages; and the beta-Proteobacteria, including Rhodocyclus, Hydrogenophaga, and beta-Proteobacteria HTCC379, probably play an important role in autohydrogenotrophic denitrification.

  9. Contribution of nitrification and denitrification to N2O emissions from urine patches

    DEFF Research Database (Denmark)

    Carter, Mette Sustmann

    2007-01-01

    and N(2)O loss ratio of nitrification (i.e. moles of N(2)O-N produced per moles of nitrate produced) and denitrification (i.e. moles of NO produced per moles of N(2)O + N(2) Produced). The effect of artificial urine (52.9 g N m(-2)) and ammonium solution (52.9g N m(-2)) was examined in separate...... experiments at 45% and 35% water-filled pore space (WFPS), respectively, and in each experiment a water control was included. The N(2)O loss derived from nitrification or denitrification was determined in the field immediately after application of (15)N-labelled solutions. During the next 24 h, gross...... nitrification rates were measured in the field, whereas the denitrification rates were measured in soil cores in the laboratory. Compared with the water control, urine application increased the N(2)O emission from 3.9 to 42.3 mu g N(2)O-N m(-2) h(-1), whereas application of ammonium increased the emission from...

  10. Simultaneous Heterotrophic Nitrification and Aerobic Denitrification by Chryseobacterium sp. R31 Isolated from Abattoir Wastewater

    Directory of Open Access Journals (Sweden)

    Pradyut Kundu

    2014-01-01

    Full Text Available A heterotrophic carbon utilizing microbe (R31 capable of simultaneous nitrification and denitrification (SND was isolated from wastewater of an Indian slaughterhouse. From an initial COD value of 583.0 mg/L, 95.54% was removed whilst, from a starting NH4+-N concentration of 55.7 mg/L, 95.87% was removed after 48 h contact. The concentrations of the intermediates hydroxylamine, nitrite, and nitrate were low, thus ensuring nitrogen removal. Aerobic denitrification occurring during ammonium removal by R31 was confirmed by utilization of both nitrate and nitrite as nitrogen substrates. Glucose and succinate were superior while acetate and citrate were poor substrates for nitrogen removal. Molecular phylogenetic identification, supported by chemotaxonomic and physiological properties, assigned R31 as a close relative of Chryseobacterium haifense. The NH4+-N utilization rate and growth of strain R31 were found to be higher at C/N = 10 in comparison to those achieved with C/N ratios of 5 and 20. Monod kinetic coefficients, half saturation concentration (Ks, maximum rate of substrate utilization (k, yield coefficient, (Y and endogenous decay coefficient (Kd indicated potential application of R31 in large-scale SND process. This is the first report on concomitant carbon oxidation, nitrification, and denitrification in the genus Chryseobacterium and the associated kinetic coefficients.

  11. Structural and functional analysis of denitrification genes in Pseudomonas stutzeri A1501

    Institute of Scientific and Technical Information of China (English)

    YAN Yongliang; LIN Min; WANG Yiping; JIN Qi; YANG Jian; CHEN Lihong; YANG Fan; DONG Jie; XUE Ying; XU Xingye; ZHU Yafang; YAO Zhijian

    2005-01-01

    Four gene clusters associated with denitrification were identified in the genome of A1501 strain, nar, nir, nor and nos, including 40 genes totally, which encode proteins for substance transportation, gene regulation and reductases. The three gene clusters, nir, nor and nos are adjacent on chromosome and are far from nar gene cluster. Compared with other denitrifying bacteria, the 40 denitrification genes in A1501 strain compose a complete denitrification catalysis system. In A1501 strain, this system has the following characteristics: (i) only one copy of narK gene is found in nar gene cluster; (ii) a narM gene is present between narK and narG; (iii) two genes, dnarE and orfl are identified at downstream of narX and narL genes, of which dnrE perhaps is a transcriptional factor belonging to FNR family; (iv) there are 16 nir genes in A1501, the most in the known denitrifying bacteria; (v) it is for the first time that norR gene has been found in A1501 and also in Pseudomonas; (vi) nos gene cluster is relatively conservative, with a completely identical composition and arrangement of genome to the reference bacteria strain.

  12. Denitrification in soil amended with thermophile-fermented compost suppresses nitrate accumulation in plants.

    Science.gov (United States)

    Ishikawa, Kazuto; Ohmori, Takashi; Miyamoto, Hirokuni; Ito, Toshiyuki; Kumagai, Yoshifumi; Sonoda, Masatoshi; Matsumoto, Jirou; Miyamoto, Hisashi; Kodama, Hiroaki

    2013-02-01

    NO (3) (-) is a major nitrogen source for plant nutrition, and plant cells store NO (3) (-) in their vacuoles. Here, we report that a unique compost made from marine animal resources by thermophiles represses NO (3) (-) accumulation in plants. A decrease in the leaf NO (3) (-) content occurred in parallel with a decrease in the soil NO (3) (-) level, and the degree of the soil NO (3) (-) decrease was proportional to the compost concentration in the soil. The compost-induced reduction of the soil NO (3) (-) level was blocked by incubation with chloramphenicol, indicating that the soil NO (3) (-) was reduced by chloramphenicol-sensitive microbes. The compost-induced denitrification activity was assessed by the acetylene block method. To eliminate denitrification by the soil bacterial habitants, soil was sterilized with γ irradiation and then compost was amended. After the 24-h incubation, the N(2)O level in the compost soil with presence of acetylene was approximately fourfold higher than that in the compost soil with absence of acetylene. These results indicate that the low NO (3) (-) levels that are often found in the leaves of organic vegetables can be explained by compost-mediated denitrification in the soil.

  13. Ammonium assimilation: An important accessory during aerobic denitrification of Pseudomonas stutzeri T13.

    Science.gov (United States)

    Sun, Yilu; Feng, Liang; Li, Ang; Zhang, Xuening; Yang, Jixian; Ma, Fang

    2017-03-12

    The present study investigated effect of ammonium utilization on aerobic denitrification by Pseudomonas stutzeri T13. Per nitrogen balance calculation, all consumed ammonium was utilized as nitrogen source for cell propagation by assimilation rather than heterotrophic nitrification. Total organic carbon (TOC) and ammonium were necessary substrates to sustain heterotrophic propagation of P. stutzeri T13 at optimum proportion equal to seven. Under aerobic condition, nitrate was utilized as substitute nitrogen source when ammonium was completely exhausted. Biomass production effectively increased with increasing initial ammonium from 0mg/L to 100mg/L. Owing to enlarged biomass, average nitrate reduction rate increased from 7.36mgL(-1)h(-1) to 11.95mgL(-1)h(-1). Such process also successfully reduced nitrite accumulation from 121.8mg/L to 66.16mg/L during aerobic denitrification. As important accessory during aerobic denitrification, ammonium assimilation efficiently doubled total nitrogen (TN) removal from 54.97mg/L (no ammonium provided) to 113.1mg/L (100mg/L ammonium involved).

  14. 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.

  15. The application of moving bed biofilm reactor to denitrification process after trickling filters.

    Science.gov (United States)

    Kopec, Lukasz; Drewnowski, Jakub; Kopec, Adam

    2016-12-01

    The paper presents research of a prototype moving bed biofilm reactor (MBBR). The device was used for the post-denitrification process and was installed at the end of a technological system consisting of a septic tank and two trickling filters. The concentrations of suspended biomass and biomass attached on the EvU Perl moving bed surface were determined. The impact of the external organic carbon concentration on the denitrification rate and efficiency of total nitrogen removal was also examined. The study showed that the greater part of the biomass was in the suspended form and only 6% of the total biomass was attached to the surface of the moving bed. Abrasion forces between carriers of the moving bed caused the fast stripping of attached microorganisms and formation of flocs. Thanks to immobilization of a small amount of biomass, the MBBR was less prone to leaching of the biomass and the occurrence of scum and swelling sludge. It was revealed that the maximum rate of denitrification was an average of 0.73 gN-NO(3)/gDM·d (DM: dry matter), and was achieved when the reactor was maintained in external organic carbon concentration exceeding 300 mgO2/dm(3) chemical oxygen demand. The reactor proved to be an effective device enabling the increase of total nitrogen removal from 53.5% to 86.0%.

  16. Sulfur-based autotrophic denitrification with eggshell for nitrate-contaminated synthetic groundwater treatment.

    Science.gov (United States)

    Xu, Yaxian; Chen, Nan; Feng, Chuanping; Hao, Chunbo; Peng, Tong

    2016-12-01

    Eggshell is considered to be a waste and a significant quantity of eggshell waste is generated from food processing, baking and hatching industries. In this study, the effect of different sulfur/eggshell (w/w) ratios and temperatures was investigated to evaluate the feasibility of the sulfur-based autotrophic denitrification with eggshell (SADE) process for nitrate removal. The results showed eggshell can maintain a neutral condition in a range of pH 7.05-7.74 in the SADE process, and remove 97% of nitrate in synthetic groundwater. Compared with oyster shell and limestone, eggshell was found to be a desirable alkaline material for sulfur-based autotrophic denitrification (SAD) with no nitrite accumulation and insignificant sulfate production. Denitrification reaction was found to follow the first-order kinetic models (R(2) > .9) having nitrate removal rate constants of 0.85 and 0.93 d(-1) for raw eggshell and boiled eggshell, respectively. Sulfur/eggshell ratio of 2:3 provided the best efficiency on nitrate removal. Nitrate was removed completely by the SADE process at a low temperature of 15°C. Eggshell could be used for the SAD process due to its good effect for nitrate removal from groundwater.

  17. Autotrophic denitrification for nitrate and nitrite removal using sulfur-limestone

    Institute of Scientific and Technical Information of China (English)

    Weili Zhou; Yeiue Sun; Bingtao Wu; Yue Zhang; Min Huang; Toshiaki Miyanaga; Zhenjia Zhang

    2011-01-01

    Sulfur-limestone was used in the autotrophic denitrification process to remove the nitrate and nitrite in a lab scale upflow biofilter.Synthetic water with four levels of nitrate and nitrite concentrations of 10,40,70 and 100 mg N/L was tested.When treating the low concentration of nitrate- or nitrite-contaminated water (10,40 mg N/L),a high removal rate of about 90% was achieved at the hydraulic retention time (HRT) of 3 hr and temperature of 20-25℃.At the same HRT,50% of the nitrate or nitrite could be removed even at the low temperature of 5-10℃.For the higher concentration nitrate and nitrite (70,100 mg N/L),longer HRT was required.The batch test indicated that influent concentration,HRT and temperature are important factors affecting the denitrification efficiency.Molecular analysis implied that nitrate and nitrite were denitrified into nitrogen by the same microorganisms.The sequential two-stepreactions from nitrate to nitrite and from nitrite to the next-step product might have taken place in the same cell during the autotrophic denitrification process.

  18. Simultaneous nitrification and denitrification in a novel membrane bioelectrochemical reactor with low membrane fouling tendency.

    Science.gov (United States)

    Li, Hui; Zuo, Wei; Tian, Yu; Zhang, Jun; Di, Shijing; Li, Lipin; Su, Xinying

    2017-02-01

    Microbial fuel cells (MFCs) can use nitrate as a cathodic electron acceptor for electrochemical denitrification, yet there is little knowledge about how to apply them into current wastewater treatment process to achieve efficient nitrogen removal. In this study, two dual-chamber MFCs were integrated with an aerobic membrane bioreactor to construct a novel membrane bioelectrochemical reactor (MBER) for simultaneous nitrification and denitrification under specific aeration. The effects of chemical oxygen demand (COD) loading rate, COD/N ratio, hydraulic retention time (HRT), and external resistance on the system performance were investigated. High effluent quality was obtained in the MBER in terms of COD and ammonium. During the operation, denitrification simultaneously occurred with nitrification at the bio-cathode of the MBER, achieving a maximal nitrogen removal efficiency of 84.3 %. A maximum power density of 1.8 W/m(3) and a current density of 8.5 A/m(3) were achieved with a coulombic efficiency of 12.1 %. Furthermore, compared to the control system, the MBER exhibited lower membrane fouling tendency due to mixed liquor volatile suspended solids (MLVSSs) and extracellular polymeric substance (EPS) reductions, EPSp/EPSc ratio decrease, and particle size increase of the sludge. These results suggest that the MBER holds potential for efficient nitrogen removal, electricity production, and membrane fouling mitigation.

  19. Enhancing denitrification using a novel in situ membrane biofilm reactor (isMBfR).

    Science.gov (United States)

    Wu, Yonghong; Li, Yizhou; Ontiveros-Valencia, Aura; Ordaz-Díaz, Luis; Liu, Junzhuo; Zhou, Chen; Rittmann, Bruce E

    2017-08-01

    The insufficient supply of electron donor in surface water contaminated with nitrate leads to its incomplete reduction in natural or constructed wetlands. Although the addition of organic matter (represented as chemical oxygen demand, COD) can stimulate N removal by denitrification, direct supplementation of COD creates unacceptable risks to effluent quality. An alternative for stimulating denitrification is supplying hydrogen gas (H2) as an inorganic electron donor. We evaluate an innovative means to do H2-based denitrification of surface waters in a wetland setting: the in-situ membrane biofilm reactor (isMBfR), in which H2 is delivered to a biofilm of denitrifying bacteria on demand based on the presence of nitrate. We carried out a proof-of-concept study in which an upper "photo zone" and a lower "MBfR root zone" were combined to remove nitrate and COD from simulated surface water. Employing mass-balances for H2, COD, nitrate, and oxygen, we documented nearly complete removals of nitrate and COD, except when the H2 supply was intentionally shut off. All nitrate removal was accomplished in the "MBfR root zone," where H2 delivery supplemented the COD supply (as needed) and provided the large majority of electron equivalents to reduce nitrate to N2. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Simultaneous phenol removal, nitrification and denitrification using microbial fuel cell technology.

    Science.gov (United States)

    Feng, Chunhua; Huang, Liqiao; Yu, Hui; Yi, Xiaoyun; Wei, Chaohai

    2015-06-01

    Here we show that concomitant removal of phenol and nitrogen can be accomplished in a single dual-chamber microbial fuel cell (MFC) reactor, in which the two chambers are separated with an anion-exchange membrane. A series of experiments were performed with ammonium (230 NH4(+)-N mg L(-1)) and phenol (with concentrations varying from 0 to 1400 mg L(-1)) fed to the aerobic cathode chamber of the MFC. Experimental results demonstrated that no apparent inhibitory effect of phenol on the nitrifying reaction was noted even at the phenol concentration up to 600 mg L(-1). For all the experiments, simultaneous nitrification and denitrification was achieved in the MFC. In comparison to the traditional aerobic bioreactor (ABR) and the same MFC run under the open-circuit condition, the MFC reactor allowed less inhibition of nitrification to phenol exposure and higher rate of nitrogen removal. The data of bacterial analysis revealed that electrochemically active bacteria and denitrifiers in the anaerobic chamber play a significant role in electricity generation and anaerobic denitrification, respectively, while phenol-degrading bacteria, nitrifiers, and denitrifiers in the aerobic cathode chamber are responsible for phenol oxidation, aerobic nitrification and aerobic denitrification, respectively. These results imply that the MFC holds potential for simultaneous removal of phenolic compounds and nitrogen contained in some particular industrial wastewaters.

  1. 2,4-D removal via denitrification using volatile fatty acids.

    Science.gov (United States)

    He, X; Wareham, D G

    2011-01-01

    Many countries have waters contaminated with both herbicides and nitrates; however, information is limited with respect to removal rates for combined nitrate and herbicide elimination. This research investigates the removal of 2,4-D via denitrification, with a particular emphasis on the effect of adding naturally generated volatile fatty acids (VFAs). The acids were produced from an acid-phase anaerobic digester with a mean VFA concentration of 3153±801 mg/L (as acetic acid). Initially, 2,4-D degrading bacteria were developed in an SBR fed with both sewage and 2,4-D (30-100 mg/L). Subsequent denitrification batch tests demonstrated that the specific denitrification rate increased from 0.0119±0.0039 using 2,4-D alone to 0.0192±0.0079 g NO₃-N/g VSS per day, when 2,4-D was combined with natural VFAs from the digester. Similarly, the specific 2,4-D consumption rate increased from 0.0016±0.0009 using 2,4-D alone to 0.0055±0.0021 g 2,4-D/g VSS per day, when using 2,4-D plus natural VFAs. Finally, a parallel increase in the percent 2,4-D removal was observed, rising from 28.33±11.88 using 2,4-D alone to 54.17±21.89 using 2,4-D plus natural VFAs.

  2. Nitrite accumulation during denitrification depends on the carbon quality and quantity in wastewater treatment with biofilters.

    Science.gov (United States)

    Rocher, Vincent; Laverman, Anniet M; Gasperi, Johnny; Azimi, Sam; Guérin, Sabrina; Mottelet, Stéphane; Villières, Thierry; Pauss, André

    2015-07-01

    This study aims to understand the mechanisms of nitrite appearance during wastewater denitrification by biofilters, focusing on the role of the carbon source. Experiments were carried out at lab-scale (batch tests) and full-scale plant (Parisian plant, capacities of 240,000 m(3) day(-1)). Results showed that the nature of the carbon source affects nitrite accumulation rates. This accumulation is low, 0.05 to 0.10 g N-NO2(-) per g N-NO3(-) eliminated, for alcohols such as methanol, ethanol, or glycerol. The utilization of glycerol leads to fungal development causing clogging of the biofilters. This fungal growth and consequent clogging exclude this carbon source, with little nitrite accumulation, as carbon source for denitrification. Whatever the carbon source, the C/N ratio in the biofilter plays a major role in the appearance of residual nitrite; an optimal C/N ratio from 3.0 to 3.2 allows a complete denitrification without any nitrite accumulation.

  3. 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.

  4. Fungal denitrification: Bipolaris sorokiniana exclusively denitrifies inorganic nitrogen in the presence and absence of oxygen.

    Science.gov (United States)

    Phillips, Rebecca; Grelet, Gwen; McMillan, Andrew; Song, Bongkeun; Weir, Bevan; Palmada, Thilak; Tobias, Craig

    2016-02-01

    Fungi may play an important role in the production of the greenhouse gas nitrous oxide (N2O). Bipolaris sorokiniana is a ubiquitous saprobe found in soils worldwide, yet denitrification by this fungal strain has not previously been reported. We aimed to test if B. sorokiniana would produce N2O and CO2 in the presence of organic and inorganic forms of nitrogen (N) under microaerobic and anaerobic conditions. Nitrogen source (organic-N, inorganic-N, no-N control) significantly affected N2O and CO2 production both in the presence and absence of oxygen, which contrasts with bacterial denitrification. Inorganic N addition increased denitrification of N2O (from 0 to 0.3 μg N20-N h(-1) g(-1) biomass) and reduced respiration of CO2 (from 0.1 to 0.02 mg CO2 h(-1) g(-1) biomass). Isotope analyses indicated that nitrite, rather than ammonium or glutamine, was transformed to N2O. Results suggest the source of N may play a larger role in fungal N2O production than oxygen status.

  5. Comparison of denitrification performances using PLA/starch with different mass ratios as carbon source.

    Science.gov (United States)

    Wu, Chuanfu; Tang, Danqi; Wang, Qunhui; Wang, Juan; Liu, Jianguo; Guo, Yan; Liu, Shu

    2015-01-01

    A suitable carbon source is significant for biological nitrate removal from groundwater. In this study, slow-release carbon sources containing polylactic acid (PLA) and starch at 8:2, 7:3, 6:4, 5:5, 4:6, and 3:7 ratios were prepared using a blending and fusing technique. The PLA/starch blend was then used as a solid carbon source for biological nitrate removal. The carbon release rate of PLA/starch was found to increase with increased starch content in leaching experiments. PLA/starch at 5:5 mass ratio was found to have the highest denitrification performance and organic carbon consumption efficiency in semi-continuous denitrification experiments, and was also revealed to support complete denitrification at 50 mg-N/L influent nitrate concentration in continuous experiments. The effluent nitrate concentration was PLA/starch increased with prolonged experimental time, which may be conducive to microorganism attachment. Therefore, PLA/starch was a suitable carbon source and biofilm carrier for groundwater remediation.

  6. Achieving partial denitrification through control of biofilm structure during biofilm growth in denitrifying biofilter.

    Science.gov (United States)

    Cui, Bin; Liu, Xiuhong; Yang, Qing; Li, Jianmin; Zhou, Xueyang; Peng, Yongzhen

    2017-08-01

    Partial denitrification was one of most effective ways to provide nitrite for annamox; whereas very limited research has been done to achieve nitrite accumulation in biofilm system. In this study, partial denitrification was studied in a lab-scale denitrifying biofilter (DNBF). The results showed biofilm structure variations caused the differences between nitrate specific reduction rate (NaSRR) and nitrite specific reduction rate (NiSRR), which led to nitrite accumulation in different degree at different biofilm formation phases. Hydrodynamic conditions also significantly influenced biofilm structure, nitrate and nitrite reduction activities. At the filtration velocity of 3.86mh(-1), not only biofilm structure, NaSRR and NiSRR kept relatively stable, but also 60% of nitrite accumulation and no nitrate in the effluent were achieved. Furthermore, Thauera genus bacteria, benefited for nitrite accumulation, became the dominant communities in high nitrite accumulation conditions. The partial denitrification combine with anammox in biofilter have the great potential applied in WWTPs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. The characteristics of a novel heterotrophic nitrification-aerobic denitrification bacterium, Bacillus methylotrophicus strain L7.

    Science.gov (United States)

    Zhang, Qing-Ling; Liu, Ying; Ai, Guo-Min; Miao, Li-Li; Zheng, Hai-Yan; Liu, Zhi-Pei

    2012-03-01

    Bacillus methylotrophicus strain L7, exhibited efficient heterotrophic nitrification-aerobic denitrification ability, with maximum NH(4)(+)-N and NO(2)(-)-N removal rate of 51.58 mg/L/d and 5.81 mg/L/d, respectively. Strain L7 showed different gaseous emitting patterns from those strains ever described. When (15)NH(4)Cl, or Na(15)NO(2), or K(15)NO(3) was used, results of GC-MS indicated that N(2)O was emitted as the intermediate of heterotrophic nitrification or aerobic denitrification, while GC-IRMS results showed that N(2) was produced as end product when nitrite was used. Single factor experiments suggested that the optimal conditions for heterotrophic nitrification were sodium succinate as carbon source, C/N 6, pH 7-8, 0 g/L NaCl, 37 °C and a wide range of NH(4)(+)-N from 80 to 1000 mg/L. Orthogonal tests showed that the optimal conditions for aerobic denitrification were C/N 20, pH 7-8, 10 g/L NaCl and DO 4.82 mg/L (shaking speed 50 r/min) when nitrite was served as substrate.

  8. Ammonium removal by Agrobacterium sp. LAD9 capable of heterotrophic nitrification-aerobic denitrification.

    Science.gov (United States)

    Chen, Qian; Ni, Jinren

    2012-05-01

    Characteristics of ammonium removal by a newly isolated heterotrophic nitrification-aerobic denitrification bacterium Agrobacterium sp. LAD9 were systematically investigated. Succinate and acetate were found to be the most favorable carbon sources for LAD9. Response surface methodology (RSM) analysis demonstrated that maximum removal of ammonium occurred under the conditions with an initial pH of 8.46, C/N ratio of 8.28, temperature of 27.9°C and shaking speed of 150rpm, where temperature and shaking speed produced the largest effect. Further nitrogen balance analysis revealed that 50.1% of nitrogen was removed as gas products and 40.8% was converted to the biomass. Moreover, the occurrence of aerobic denitrification was evidenced by the utilization of nitrite and nitrate as nitrogen sources, and the successful amplifications of membrane bound nitrate reductase and cytochrome cd(1) nitrite reductase genes from strain LAD9. Thus, the nitrogen removal in strain LAD9 was speculated to comply with the mechanism of heterotrophic nitrification coupled with aerobic denitrification (NH(4)(+)-NH(2)OH-NO(2)(-)-N(2)O-N(2)), in which also accompanied with the mutual transformation of nitrite and nitrate. The findings can help in applying appropriate controls over operational parameters in systems involving the use of this kind of strain.

  9. Effects of hydraulic retention time (HRT) on denitrification using waste activated sludge thermal hydrolysis liquid and acidogenic liquid as carbon sources.

    Science.gov (United States)

    Guo, Yiding; Guo, Liang; Sun, Mei; Zhao, Yangguo; Gao, Mengchun; She, Zonglian

    2017-01-01

    Waste activated sludge (WAS) internal carbon source can efficiently and economically enhance denitrification, and hydraulic retention time (HRT) is one of the most important operational parameters for denitrification. The effects of HRT on denitrification were investigated with WAS thermal hydrolysis liquid and acidogenic liquid as carbon sources in this study. The optimal HRT was 12h for thermal hydrolysis liquid and 8h for acidogenic liquid, with NO3(-)-N removal efficiency of 91.0% and 97.6%, respectively. In order to investigate the utilization of sludge carbon source by denitrifier, the changes of SCOD (Soluble chemical oxygen demand), proteins, carbohydrates, and VFAs (Volatile fatty acids) during denitrification process were analyzed and three-dimensional fluorescence excitation-emission matrix (EEM) spectroscopy with fluorescence regional integration (FRI) analysis was introduced. The kinetics parameters of denitrification rate (VDN), denitrification potential (PDN) and heterotroph anoxic yield (YH) were also investigated using sludge carbon source at different HRT.

  10. Anaerobic ammonium oxidation, denitrification and dissimilatory nitrate reduction to ammonium in the East China Sea sediment

    Directory of Open Access Journals (Sweden)

    G. D. Song

    2013-03-01

    Full Text Available Benthic nitrogen transformation pathways were investigated in the sediment of the East China Sea in June of 2010 using the 15N isotope pairing technique. Slurry incubations indicated that denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA as well as nitrate release by nitrate storing organisms occurred in the East China Sea sediments. These four processes did not exist independently, the nitrate release therefore diluted the 15N labeling fraction of NO3−, a part of the 15NH4+ derived from DNRA also formed 30N2 via anammox. Therefore current methods of rate calculations led to over and underestimations of anammox and denitrification respectively. Following the procedure outlined in Thampdrup and Dalsgaard (2002, denitrification rates were slightly underestimated by on average 6% without regard to the effect of nitrate release, while this underestimation could be counteracted by the presence of DNRA. On the contrary, anammox rates calculated from 15NO3− experiment were significantly overestimated by 42% without considering nitrate release. In our study this overestimation could only be compensated 14% by taking DNRA into consideration. In a parallel experiment amended with 15NH4+ + 14NO3−, anammox rates were not significantly influenced by DNRA due to the high background of 15NH4+ addition. Excluding measurements in which bioirrigation was present, integrated denitrification rates decreased from 10 to 4 mmol N m−2 d−1 with water depth, while integrated anammox rates increased from 1.5 to 4.0 mmol N m−2 d−1. Consequently, the relative contribution of anammox to the total N-loss increased from 13% at the shallowest site near the Changjiang estuary to 50% at the deepest site on the outer shelf. This study represents the first time in which anammox has been demonstrated to play a significant role in benthic nitrogen cycling in the East China Sea sediment, especially on the outer shelf. N

  11. Temperature response of denitrification and anammox reveals the adaptation of microbial communities to in situ temperatures in permeable marine sediments that span 50[degrees] in latitude

    National Research Council Canada - National Science Library

    Canion, A; Kostka, J. E; Gihring, T. M; Huettel, M; van Beusekom, J. E. E; Gao, H; Lavik, G; Kuypers, M. M. M

    2014-01-01

    .... The temperature regulation of microbial communities that mediate anammox and denitrification was investigated in near shore permeable sediments at polar, temperate, and subtropical sites with annual...

  12. Distinguishing between water column and sedimentary denitrification in the Santa Barbara Basin using the stable isotopes of nitrate

    Science.gov (United States)

    Sigman, D. M.; Robinson, R.; Knapp, A. N.; van Geen, A.; McCorkle, D. C.; Brandes, J. A.; Thunell, R. C.

    2003-05-01

    Below its sill depth, the Santa Barbara Basin (SBB) is commonly suboxic ([O2] ˜ 3 μM), with only brief periods of ventilation. Associated with development of suboxia, the concentration of nitrate decreases with depth into the basin without an associated decrease in phosphate, indicating that a substantial fraction of the nitrate supplied to the basin is removed by denitrification. Coincident with the decrease in nitrate concentration across the "redoxcline" (the interface between oxic and suboxic waters) within the SBB, there is an increase in the 15N/14N of that nitrate, as would be anticipated from the isotopic fractionation associated with denitrification. However, the increase in 15N/14N of nitrate is much smaller than occurs in the open eastern tropical North Pacific (ETNP) for a comparable amount of nitrate loss. Both the concentrations of N species within the basin and measurements of nitrate 18O/16O suggest that the lower-than-expected 15N enrichment in the suboxic SBB involves denitrification, rather than being due to some unknown source of low-15N/14N N to the deep SBB. Calculations with a range of models of nitrate supply and consumption indicate that the degree of nitrate consumption in the basin is too small for differences in water circulation to explain the isotopic differences between the Santa Barbara Basin and the open ETNP. Previous studies indicate that the isotope effect of sedimentary denitrification is negligible due to nitrate diffusion in sediment pore waters. Thus we infer that the small magnitude of the isotopic enrichment of SBB water column nitrate is due to the importance of sedimentary denitrification within the basin. Assuming that water column and sedimentary denitrification have isotope effects of 25 and 1.5 per mil, respectively, our results suggest that sedimentary denitrification accounts for more than 75% of the nitrate loss within the suboxic SBB.

  13. Is denitrification driven by elevation or plant type at a Gulf coast Juncus roemerianus and Spartina alterniflora mixed saltmarsh?

    Science.gov (United States)

    Mortazavi, B.; Chanton, P. R.; Cherry, J. A.

    2016-02-01

    Wetlands provide a crucial ecosystem service by reducing anthropogenic nitrogen released from industrial and agricultural sources. Understanding the mechanisms controlling nitrogen removal in marshes is critical as human populations increase and as marsh areas decrease. Marshes in the U.S. Gulf coast are primarily populated by Spartina alterniflora or Juncus roemerianus. Previous research has indicated that sulfide concentrations are lower in J roemerianus than in S alterniflora marshes. Higher sulfide concentrations could inhibit nitrogen removal by reducing nitrification-denitrification. However, it has yet to be determined if variability in sulfide concentration is a result of differences in elevation and inundation that impact redox conditions, or higher belowground biomass allocation by J roemerianus that ultimately results in more oxygen release to anoxic sediments. We, therefore, measured denitrification rates within an S alterniflora dominated marsh that is interspersed with J roemerianus to determine if variability in sulfide concentrations impact denitrification. We quantified denitrification with intact cores and sediment slurries and examined pore water geochemistry. J roemerianus sediment sulfide concentrations (3.6-419.4 μmol) were consistently lower than those measured in S alterniflora sediments (325.1-2246.6 μmol). NH4 flux was higher in J roemerianus cores and both NH4 and PO4 were present in higher concentration in pore water. Denitrification measured with IPT was higher in J roemerianus (21.0-81.2 μmol N2 m-2 hr-1) than in S alterniflora (14.7-52.1 μmol N2 m-2 hr-1). Potential denitrification in J roemerianus (0.5-128.1 nmole N cm-3 hr-1) was generally higher than in S alterniflora (4.1-34.2 nmole N cm-3 hr-1). By affecting sediment redox conditions, plant type rather than elevation appears to drive patterns of denitrification in this marsh. The imapct of sea level rise on vegetation distribution and nitrogen removal capacity for these

  14. Optimization and evaluation of a bottom substrate denitrification tank for nitrate removal from a recirculating aquaculture system.

    Science.gov (United States)

    Pungrasmi, Wiboonluk; Playchoom, Cholticha; Powtongsook, Sorawit

    2013-08-01

    A bottom substrate denitrification tank for a recirculating aquaculture system was developed. The laboratory scale denitrification tank was an 8 L tank (0.04 m2 tank surface area), packed to a depth of 5 cm with a bottom substrate for natural denitrifying bacteria. An aquarium pump was used for gentle water mixing in the tank; the dissolved oxygen in the water was maintained in aerobic conditions (e.g. > 2 mg/L) while anoxic conditions predominated only at the bottom substrate layer. The results showed that, among the four substrates tested (soil, sand, pumice stone and vermiculite), pumice was the most preferable material. Comparing carbon supplementation using methanol and molasses, methanol was chosen as the carbon source because it provided a higher denitrification rate than molasses. When methanol was applied at the optimal COD:N ratio of 5:1, a nitrate removal rate of 4591 +/- 133 mg-N/m2 tank bottom area/day was achieved. Finally, nitrate removal using an 80 L denitrification tank was evaluated with a 610 L recirculating tilapia culture system. Nitrate treatment was performed by batch transferring high nitrate water from the nitrification tank into the denitrification tank and mixing with methanol at a COD:N ratio of 5:1. The results from five batches of nitrate treatment revealed that nitrate was successfully removed from water without the accumulation of nitrite and ammonia. The average nitrate removal efficiency was 85.17% and the average denitrification rate of the denitrification tank was 6311 +/- 945 mg-N/m2 tank bottom area/day or 126 +/- 18 mg-N/L of pumice packing volume/day.

  15. Optimization and evaluation of a bottom substrate denitrification tank for nitrate removal from a recirculating aquaculture system

    Institute of Scientific and Technical Information of China (English)

    Wiboonluk Pungrasmi; Cholticha Playchoom; Sorawit Powtongsook

    2013-01-01

    A bottom substrate denitrification tank for a recirculating aquaculture system was developed.The laboratory scale denitrification tank was an 8 L tank (0.04 m2 tank surface area),packed to a depth of 5 cm with a bottom substrate for natural denitrifying bacteria.An aquarium pump was used for gentle water mixing in the tank; the dissolved oxygen in the water was maintained in aerobic conditions (e.g.> 2 mg/L) while anoxic conditions predominated only at the bottom substrate layer.The results showed that,among the four substrates tested (soil,sand,pumice stone and vermiculite),pumice was the most preferable material.Comparing carbon supplementation using methanol and molasses,methanol was chosen as the carbon source because it provided a higher denitrification rate than molasses.When methanol was applied at the optimal COD∶N ratio of 5∶1,a nitrate removal rate of 4591 ± 133 mg-N/m2 tank bottom area/day was achieved.Finally,nitrate removal using an 80 L denitrification tank was evaluated with a 610 L recirculating tilapia culture system.Nitrate treatment was performed by batch transferring high nitrate water from the nitrification tank into the denitrification tank and mixing with methanol at a COD∶N ratio of 5∶1.The results from five batches of nitrate treatment revealed that nitrate was successfully removed from water without the accumulation of nitrite and ammonia.The average nitrate removal efficiency was 85.17% and the average denitrification rate of the denitrification tank was 6311 ± 945 mg-N/m2 tank bottom area/day or 126 ± 18 mg-N/L of pumice packing volume/day.

  16. Spatial-seasonal variation of soil denitrification under three riparian vegetation types around the Dianchi Lake in Yunnan, China.

    Science.gov (United States)

    Wang, Shaojun; Cao, Zilin; Li, Xiaoying; Liao, Zhouyu; Hu, Binghui; Ni, Jie; Ruan, Honghua

    2013-05-01

    Outbreaks of nuisance cyanobacterial bloom are predicted to occur frequently under the effect of severe eutrophication in the water body of Lake Dianchi since the 1990s. Riparian buffers are now well recognized for their roles in the removal of inorganic nitrogen mainly via denitrification. Little is known, however, about the mechanisms of nitrate removal in the riparian buffers of Lake Dianchi. We investigated the wet and dry seasonal dynamics of denitrification rate (DNR) in the soil profiles along the topographic gradient in three riparian buffers with different vegetation types (i.e. forest, open forest, and grass). A strong vertical pattern was observed in soil organic C and N concentrations (i.e. total N, DON, NO3-N, and NH4-N) along the soil layers. We also found significantly higher in situ denitrification activity in the upper horizon along each topohydrosequence while the activities of soil denitrification could be detected down to deeper soil horizons (0.1 to 0.8 mg N per kg dry soil per day), which may contribute significantly to the reduction of the ground water nitrate. Meanwhile, the DNR in the zones near the lake was significantly higher than that in zones near the border with the upland terrace, and also in the wet seasons than in dry seasons. Denitrification rates in the forest, open forest and grass sites were significantly different only in wet seasons. Especially, we found soil organic C had a strong correlation with denitrification in all sites, despite the large intersite variability of soil and vegetation. Our data suggested spatial heterogeneity of substrate availability along a hydrologic and topographic gradient can be the primary control on spatial-seasonal patterns of denitrification in riparian buffers.

  17. Safety-barrier diagrams

    DEFF Research Database (Denmark)

    Duijm, Nijs Jan

    2007-01-01

    are discussed. A simple method for quantification of safety-barrier diagrams is proposed, including situations where safety barriers depend on shared common elements. It is concluded that safety-barrier diagrams provide a useful framework for an electronic data structure that integrates information from risk......Safety-barrier diagrams and the related so-called "bow-tie" diagrams have become popular methods in risk analysis. This paper describes the syntax and principles for constructing consistent and valid safety-barrier diagrams. The relation with other methods such as fault trees and Bayesian networks...... analysis with operational safety management....

  18. Extremal surface barriers

    Energy Technology Data Exchange (ETDEWEB)

    Engelhardt, Netta; Wall, Aron C. [Department of Physics, University of California,Santa Barbara, CA 93106 (United States)

    2014-03-13

    We present a generic condition for Lorentzian manifolds to have a barrier that limits the reach of boundary-anchored extremal surfaces of arbitrary dimension. We show that any surface with nonpositive extrinsic curvature is a barrier, in the sense that extremal surfaces cannot be continuously deformed past it. Furthermore, the outermost barrier surface has nonnegative extrinsic curvature. Under certain conditions, we show that the existence of trapped surfaces implies a barrier, and conversely. In the context of AdS/CFT, these barriers imply that it is impossible to reconstruct the entire bulk using extremal surfaces. We comment on the implications for the firewall controversy.

  19. 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.

  20. Denitrification and anammox in tropical aquaculture settlement ponds: an isotope tracer approach for evaluating N2 production.

    Directory of Open Access Journals (Sweden)

    Sarah A Castine

    Full Text Available Settlement ponds are used to treat aquaculture discharge water by removing nutrients through physical (settling and biological (microbial transformation processes. Nutrient removal through settling has been quantified, however, the occurrence of, and potential for microbial nitrogen (N removal is largely unknown in these systems. Therefore, isotope tracer techniques were used to measure potential rates of denitrification and anaerobic ammonium oxidation (anammox in the sediment of settlement ponds in tropical aquaculture systems. Dinitrogen gas (N(2 was produced in all ponds, although potential rates were low (0-7.07 nmol N cm(-3 h(-1 relative to other aquatic systems. Denitrification was the main driver of N(2 production, with anammox only detected in two of the four ponds. No correlations were detected between the measured sediment variables (total organic carbon, total nitrogen, iron, manganese, sulphur and phosphorous and denitrification or anammox. Furthermore, denitrification was not carbon limited as the addition of particulate organic matter (paired t-Test; P = 0.350, n = 3 or methanol (paired t-Test; P = 0.744, n = 3 did not stimulate production of N(2. A simple mass balance model showed that only 2.5% of added fixed N was removed in the studied settlement ponds through the denitrification and anammox processes. It is recommended that settlement ponds be used in conjunction with additional technologies (i.e. constructed wetlands or biological reactors to enhance N(2 production and N removal from aquaculture wastewater.

  1. Denitrification and anammox in tropical aquaculture settlement ponds: an isotope tracer approach for evaluating N2 production.

    Science.gov (United States)

    Castine, Sarah A; Erler, Dirk V; Trott, Lindsay A; Paul, Nicholas A; de Nys, Rocky; Eyre, Bradley D

    2012-01-01

    Settlement ponds are used to treat aquaculture discharge water by removing nutrients through physical (settling) and biological (microbial transformation) processes. Nutrient removal through settling has been quantified, however, the occurrence of, and potential for microbial nitrogen (N) removal is largely unknown in these systems. Therefore, isotope tracer techniques were used to measure potential rates of denitrification and anaerobic ammonium oxidation (anammox) in the sediment of settlement ponds in tropical aquaculture systems. Dinitrogen gas (N(2)) was produced in all ponds, although potential rates were low (0-7.07 nmol N cm(-3) h(-1)) relative to other aquatic systems. Denitrification was the main driver of N(2) production, with anammox only detected in two of the four ponds. No correlations were detected between the measured sediment variables (total organic carbon, total nitrogen, iron, manganese, sulphur and phosphorous) and denitrification or anammox. Furthermore, denitrification was not carbon limited as the addition of particulate organic matter (paired t-Test; P = 0.350, n = 3) or methanol (paired t-Test; P = 0.744, n = 3) did not stimulate production of N(2). A simple mass balance model showed that only 2.5% of added fixed N was removed in the studied settlement ponds through the denitrification and anammox processes. It is recommended that settlement ponds be used in conjunction with additional technologies (i.e. constructed wetlands or biological reactors) to enhance N(2) production and N removal from aquaculture wastewater.

  2. Differential effects of crude oil on denitrification and anammox, and the impact on N2O production.

    Science.gov (United States)

    Ribeiro, Hugo; Mucha, Ana P; Azevedo, Isabel; Salgado, Paula; Teixeira, Catarina; Almeida, C Marisa R; Joye, Samantha B; Magalhães, Catarina

    2016-09-01

    Denitrification and anammox are key processes for reducing the external nitrogen loads delivered to coastal ecosystems, and these processes can be affected by pollutants. In this study, we investigated the effect of crude oil on denitrification and anammox. Controlled laboratory experiments were performed using sediment slurries from the Lima Estuary (NW Portugal). Anammox and denitrification rates were measured using (15)N-labeled NO3(-), and the production of (29)N2 and (30)N2 quantified by membrane inlet mass spectrometry. Results revealed that while denitrification rates were stimulated between 10 and 25 000 times after crude oil amendment, anammox activity was partially (between 2 and 5 times) or completely inhibited by the addition of crude oil when comparing to rates in unamended controls. Similar results were observed across four estuarine sediment types, despite their different physical-chemical characteristics. Moreover, N2O production was reduced by 2-36 times following crude oil addition. Further work is required to fully understand the mechanism(s) of the observed reduction in N2O production. This study represents one of the first contributions to the understanding of the impact of crude oil pollution on denitrification and anammox, with profound implications for the management of aquatic ecosystems regarding eutrophication (N-removal).

  3. 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. © 2013 International Society for Microbial Ecology.......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....... Strikingly, N 2 O gas was emitted at very high potential rates of 387±143 and 31±6 μmol N m -2 h -1 from the cyanobacterial and lichen crust, respectively, with N 2 O accounting for 53-66% of the total emission of nitrogenous gases. Microsensor measurements revealed that N 2 O was produced in the anoxic...

  4. Mechanism of flue gas simultaneous desulfurization and denitrification using the highly reactive absorbent

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yi; SUN Xiaojun; XU Peiyao; MA Shuangchen; WANG Lidong; LIU Feng

    2005-01-01

    Fly ash, industry-grade lime and a few oxidizing manganese compound additive were used to prepare the "Oxygen-riched" highly reactive absorbent for simultaneous desulfurization and denitrification. Experiments of simultaneous desulfurization and denitrification were carried out using the highly reactive absorbent in the flue gas circulating fluidized bed (CFB) system. Removal efficiencies of 94.5% for SO2 and 64.2% for NO were obtained respectively. The scanning electron microscope (SEM) and accessory X-ray energy spectrometer were used to observe micro-properties of the samples, including fly ash, common highly reactive absorbent, "Oxygen-riched" highly reactive absorbent and spent absorbent. The white flake layers were observed in the SEM images about surfaces of the common highly reactive absorbent and "Oxygen- riched" one, and the particle surfaces of the spent absorbent were porous. The content of calcium on surface was higher than that of the average in the highly reactive absorbent. The manganese compound additive dispersed uniformly on the surfaces of the "Oxygen- riched" highly reactive absorbent. There was a sulfur peak in the energy spectra pictures of the spent absorbent. The component of the spent absorbent was analyzed with chemical analysis methods, and the results indicated that more nitrogen species appeared in the absorbent except sulfur species, and SO2 and NO were removed by chemical absorption according to the experimental results of X-ray energy spectrometer and the chemical analysis. Sulfate being the main desulfurization products, nitrite was the main denitrification ones during the process, in which NO was oxidized rapidly to NO2 and absorbed by the chemical reaction.

  5. Comparison of the MBBR denitrification carriers for advanced nitrogen removal of wastewater treatment plant effluent.

    Science.gov (United States)

    Yuan, Quan; Wang, Haiyan; Hang, Qianyu; Deng, Yangfan; Liu, Kai; Li, Chunmei; Zheng, Shengzhi

    2015-09-01

    The moving bed biofilm reactors (MBBRs) were used to remove the residual NO3(-)-N of wastewater treatment plant (WWTP) effluent, and the MBBR carriers for denitrification were compared. The results showed that high denitrification efficiency can be achieved with polyethylene, polypropylene, polyurethane foam, and haydite carriers under following conditions: 7.2 to 8.0 pH, 24 to 26 °C temperature, 12 h hydraulic retention time (HRT), and 25.5 mg L(-1) external methanol dosage, while the WWTP effluent total nitrogen (TN) was between 2.6 and 15.4 mg L(-1) and NO3(-)-N was between 0.2 and 12.6 mg L(-1). The MBBR filled with polyethylene carriers had higher TN and NO3(-)-N removal rate (44.9 ± 19.1 and 83.4 ± 13.0%, respectively) than those with other carriers. The minimum effluent TN and NO3(-)-N of polyethylene MBBR were 1.6 and 0.1 mg L(-1), respectively, and the maximum denitrification rate reached 23.0 g m(-2) day(-1). When chemical oxygen demand (COD)/TN ratio dropped from 6 to 4, the NO3(-)- N and TN removal efficiency decreased significantly in all reactors except for that filled with polyethylene, which indicated that the polyethylene MBBR can resist influent fluctuation much better. The three-dimensional excitation-emission matrix analysis showed that all the influent and effluent of MBBRs contain soluble microbial products (SMPs)-like organics and biochemical oxygen demand (BOD), which can be removed better by MBBRs filled with haydite and polyethylene carriers. The nitrous oxide reductase (nosZ)-based terminal restriction fragment length polymorphism (T-RFLP) analysis suggested that the dominant bacteria in polyethylene MBBR are the key denitrificans.

  6. Models of oxic respiration, denitrification and sulfate reduction in zones of coastal upwelling

    Science.gov (United States)

    Canfield, D. E.

    2006-12-01

    Coastal upwelling zones support some of the highest rates of primary production in the oceans. The settling and subsequent decomposition of this organic matter promotes oxygen depletion. In the Eastern tropical North and South Pacific and the Arabian Sea, large tracts of anoxic water develop, where intensive N 2 production through denitrification and anammox accounts for about 1/3 of the total loss of fixed nitrogen in the marine realm. It is curious that despite extensive denitrification in these waters, complete nitrate removal and the onset of sulfate reduction is extremely rare. A simple box model is constructed here to reproduce the dynamics of carbon, oxygen and nutrient cycling in coastal upwelling zones. The model is constructed with five boxes, where water is exchanged between the boxes by vertical and horizontal mixing and advection. These primary physical drivers control the dynamics of the system. The model demonstrates that in the absence of nitrogen fixation, the anoxic waters in a coastal upwelling system will not become nitrate free. This is because nitrate is the limiting nutrient controlling primary production, and if nitrate concentration becomes too low, primary production rate drops and this reduces rates of nitrate removal through N 2 production. With nitrogen fixation, however, complete nitrate depletion can occur and sulfate reduction will ensue. This situation is extremely rare in coastal upwelling zones, probably because nitrogen-fixing bacteria do not prosper in the high nutrient, turbid waters as typically in these areas. Finally, it is predicted here that the chemistry of the upwelling system will develop in a similar matter regardless whether N 2 production is dominated by anaerobic ammonium oxidation (anammox) or canonical heterotrophic denitrification.

  7. Effects of heavy metals on aerobic denitrification by strain Pseudomonas stutzeri PCN-1.

    Science.gov (United States)

    Gui, Mengyao; Chen, Qian; Ma, Tao; Zheng, Maosheng; Ni, Jinren

    2017-02-01

    Effects of heavy metals on aerobic denitrification have been poorly understood compared with their impacts on anaerobic denitrification. This paper presented effects of four heavy metals (Cd(II), Cu(II), Ni(II), and Zn(II)) on aerobic denitrification by a novel aerobic denitrifying strain Pseudomonas stutzeri PCN-1. Results indicated that aerobic denitrifying activity decreased with increasing heavy metal concentrations due to their corresponding inhibition on the denitrifying gene expression characterized by a time lapse between the expression of the nosZ gene and that of the cnorB gene by PCN-1, which led to lower nitrate removal rate (1.67∼6.67 mg L(-1) h(-1)), higher nitrite accumulation (47.3∼99.8 mg L(-1)), and higher N2O emission ratios (5∼283 mg L(-1)/mg L(-1)). Specially, promotion of the nosZ gene expression by increasing Cu(II) concentrations (0∼0.05 mg L(-1)) was found, and the absence of Cu resulted in massive N2O emission due to poor synthesis of N2O reductase. The inhibition effect for both aerobic denitrifying activity and denitrifying gene expression was as follows from strongest to least: Cd(II) (0.5∼2.5 mg L(-1)) > Cu(II) (0.5∼5 mg L(-1)) > Ni(II) (2∼10 mg L(-1)) > Zn(II) (25∼50 mg L(-1)). Furthermore, sensitivity of denitrifying gene to heavy metals was similar in order of nosZ > nirS ≈ cnorB > napA. This study is of significance in understanding the potential application of aerobic denitrifying bacteria in practical wastewater treatment.

  8. A novel nonwoven hybrid bioreactor (NWHBR) for enhancing simultaneous nitrification and denitrification.

    Science.gov (United States)

    Meng, Fangang; Wang, Yuan; Huang, Li-Nan; Li, Jie; Jiang, Feng; Li, Shiyu; Chen, Guang-Hao

    2013-07-01

    This study proposed a nonwoven hybrid bioreactor (NWHBR) in which the nonwoven fabric played dual roles as a biofilm carrier and membrane-like separation of the flocculent sludge in the reactor. The results of long-term monitoring demonstrated that the NWHBR could achieve simultaneous nitrification and denitrification (SND), with nearly complete ammonium removal and 80% removal of total nitrogen. The biofilm attached to the nonwoven fabric removed 27% of the chemical oxygen demand (COD) and 36% of the nitrate in the reactor, an enhanced elimination of nutrients that was attributed to the increased mass transfer within the biofilm due to permeate drag. The results of batch experiments showed that the flocculent sludge played a more dominant role in nitrification and denitrification (79% and 61%, respectively) than the biofilm (21% and 36%, respectively). The batch experiments also revealed that the enforced mass transfer, with an effluent recirculation rate of 4.3 L/m(2)h (which was the same as the flux during the reactor's long-term operation), improved the denitrification rate by 58% (i.e., from 9.0 to 14.2 mg-NO(3)(-)-N/h). Pyrosequencing of the 16S rRNA gene amplification revealed a high microbial diversity in both the flocculent sludge and biofilm, with Proteobacteria, Bacteroidetes and Chloroflexi as the dominant groups. A phylogenetic (P) test indicated that the NWHBR contained phylogenetically distinct microbial communities: those in the biofilm differed from those in the flocculent sludge. However, the communities on the exterior and interior of the biofilm were more similar to each other. Due to its good SND performance, low physical back-washing frequency and low air-to-water ratio, the NWHBR represents an attractive alternative for the wider application of either low-cost membrane bioreactors or biofilm reactors.

  9. The feasibility study of autotrophic denitrification with iron sludge produced for sulfide control.

    Science.gov (United States)

    Wei, Yangyang; Dai, Ji; Mackey, Hamish R; Chen, Guang-Hao

    2017-10-01

    Ferric iron is widely dosed in wastewater treatment plants dealing with sulfide for septicity control, which generates a great amount of iron-rich chemical sludge that is challenging and costly to dispose. This study investigates the feasibility of using this iron sludge as the electron donor for autotrophic denitrification, not only realizing high nitrogen removal efficiency without additional carbon source requirement, but also partially mitigating iron-rich chemical sludge disposal and reduce sludge production by enriching low-yield autotrophic denitrifiers in the system. Both batch tests and performance monitoring of a lab-scale up-flow anaerobic sludge blanket reactor with a more than 300 days of operation were conducted. All the results confirmed the feasibility of using iron sludge as electron donor for autotrophic denitrification. The nitrate reduction rate with iron sludge was highly influenced by the type of ferrous electron donor and the electron donor/acceptor ratio. Ferrous hydroxide had significantly higher nitrate reduction rate than ferrous sulfide at the same electron donor/acceptor ratio. The nitrate reduction rate also accelerated with the increase of the electron donor/acceptor ratio. However, if the total surface area of the iron sludge is considered for comparison, it was shown that ferrous hydroxide and ferrous sulfide provided similar nitrate reduction rates of around 0.02 mmol N/m(2)/d in this study, indicating total surface area would be the key parameter for denitrification efficiency for the solid phase electron donor. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Soil-Column Test on Aniline Degradation in Riverbank Filtration under Denitrification Conditions

    Institute of Scientific and Technical Information of China (English)

    Wu Yaoguo; Wang Hui; Zhang Wencun; Sun Weijian

    2005-01-01

    Drinking water is at risk from aniline pollution and thus aniline degradation and its mechanism have received much attention. In this paper, a soil column, including sediments and aquifer media, was collected from the Weihe riverbed and its bank, and used to research the characteristics of aniline degradation in the riverbank filtration process under denitrification conditions. The results indicate that all aniline could be degraded by the habituated indigenous microbes, and even mostly mineralized under denitrification conditions, but with a long lag phase. Some aniline degradation must involve deamination, while the majority undergoes covalent binding with humic substances to form complexes, and the complexes are easily degraded and even mineralized. During the degradation no intermediates were harmful to denitrifiers. Therefore, under denitrifaction conditions, aniline is degraded in RBF, and up to now aniline has not been monitored in the groundwater along the polluted river. During the 153 d testing process, the nitrate-nitrogen concentration was about 23.0 mg/L, and aniline concentrations were 40, 80 or 400 mg/L at 0-74 d, 75-105 d and 106-153 d respectively in infiltrating water. Indigenous microbes pass a lag period of 37 d, and grow on aniline as the source of carbon in the RBF under denitrification conditions. Aniline concentration in leachate was lower than the detected limits, so its removal rate was 100 %. Total organic carbon (TOC) removal rates were 97.99 %, 91.39 % and 75.30 % for 40, 80 and 400 mg/L aniline concentrations respectively, based on TOC monitored in infiltrating water and leachate.

  11. Effects of chlorothalonil and carbendazim on nitrification and denitrification in soils

    Institute of Scientific and Technical Information of China (English)

    LANG Man; CAI Zucong

    2009-01-01

    The effects of chlorothalonil and carbendazim, on nitrification and denitrification in six soils in upland and rice paddy environments were investigated. Laboratory aerobic (60% water holding capacity) and anaerobic (flooded) conditions were studied at an incubation temperature of 25℃ and fungicide addition rates of 5.5 mg/kg A. I. (field rate, FR), 20 (20FR) and 40 times (40FR) field rate, respectively. The results indicated that chlorothalonil at the field rate had a slight inhibitory effect on one soil only, and that soil did not nitrify much in the first place. But chlorothalonil at higher rates inhibited nitrification significantly in all soils. For soils JXP and JXU with a pH of less than 5.0, chlorothalonil almost completely stopped their nitrification at 20FR and 40FR during the whole 14 day incubation period. For soils HNP and HNU with a pH of greater than 8.0, chlorothalonil also significantly inhibit nitrification at 20FR and 40FR (p < 0.05). However, NH4+ that was added to the soil was also almost completely nitrified by the end of the incubation period in these two soils. The effects of chlorothalonil at 20FR and 40FR on the nitrification of JSP and JSU soils, with a pH of 5.4 and 7.2, respectively, were intermediate between the other soil types. Chlorothalonil had no effect on denitrification at the field rate and had very small effects at the higher rates of application in some soils. Carbendazim had essentially no effect on nitrification and denitrification in soils assessed.

  12. Barriers to screening mammography.

    Science.gov (United States)

    Sarma, Elizabeth A

    2015-01-01

    Breast cancer (BRCA) is the second most commonly diagnosed cancer among women in the USA, and mammography is an effective means for the early detection of BRCA. Identifying the barriers to screening mammography can inform research, policy and practice aiming to increase mammography adherence. A literature review was conducted to determine common barriers to screening mammography adherence. PsycINFO and PubMed databases were searched to identify studies published between 2000 and 2012 that examined barriers associated with reduced mammography adherence. Three thematic groups of barriers, based on social ecology, were identified from the literature: healthcare system-level, social and individual-level barriers. Researchers must consider screening behaviour in context and, therefore, should simultaneously consider each level of barriers when attempting to understand screening behaviour and create interventions to increase mammography adherence.

  13. Biological filter capable of simultaneous nitrification and denitrification for Aquatic Habitat in International Space Station.

    Science.gov (United States)

    Uemoto, H; Shoji, T; Uchida, S

    2014-04-01

    The biological filter capable of simultaneous nitrification and denitrification was constructed for aquatic animal experiments in the International Space Station (ISS). The biological filter will be used to remove harmful ammonia excreted from aquatic animals in a closed water circulation system (Aquatic Habitat). The biological filter is a cylindrical tank packed with porous glass beads for nitrification and dual plastic bags for denitrification. The porous beads are supporting media for Nitrosomonas europaea and Nitrobacter winogradskyi. The N. europaea cells and N. winogradskyi cells on the porous beads, oxidize the excreted ammonia to nitrate via nitrite. On the other hand, the dual bag is composed of an outer non-woven fabric bag and an inner non-porous polyethylene film bag. The outer bag is supporting media for Paracoccus pantotrophus. The inner bag, in which 99.5% ethanol is packed, releases the ethanol slowly, since ethanol can permeate through the non-porous polyethylene film. The P. pantotrophus cells on the outer bag reduce the produced nitrate to nitrogen gas by using the released ethanol as an electron donor for denitrification. The biological filter constructed in this study consequently removed the ammonia without accumulating nitrate. Most of the excess ethanol was consumed and did not affect the nitrification activity of the N. europaea cells and N. winogradskyi cells severely. In accordance with the aquatic animal experiments in the ISS, small freshwater fish had been bred in the closed water circulation system equipped with the biological filter for 90 days. Ammonia concentration daily excreted from fish is assumed to be 1.7 mg-N/L in the recirculation water. Under such conditions, the harmful ammonia and nitrite concentrations were kept below 0.1 mg-N/L in the recirculation water. Nitrate and total organic carbon concentrations in the recirculation water were kept below 5 mg-N/L and 3 mg-C/L, respectively. All breeding fish were alive and ate

  14. Effect of Solids Retention Time on the Denitrification Potential of Anaerobically Digested Swine Waste

    Science.gov (United States)

    Kinyua, Maureen Njoki

    Three continuously stirred tank reactors (CSTR) were operated in semi continuous mode treating swine waste using anaerobic digestion. The reactors were used to test the effect of solid retention time (SRT) on CH4 yield, total ammonia nitrogen (TAN) concentrations, % volatile solids (VS), chemical oxygen demand (COD) and volatile fatty acids (VFA) removal, readily biodegradable COD concentration and the denitrification potential for the effluent in a biological nutrient removal (BNR) system. During Phase I of the study, the three reactors were operated at the same 28 day SRT for 16 weeks. SRTs were then changed during the 12 week Phase II period. The SRTs studied were 14, 21 and 28 days, with the same organic loading rate (OLR) of 1.88 ± 0.2 kg VS/ m3-day. The reactor with the lowest SRT (14 days) had the highest VS and VFA removal at 73.6 and 67.6% and lowest TAN concentration at 0.78 g NH4+-N/L, followed by the 21 day and 28 day reactors. This was likely due to the fast microbial growth rates and substrate utilization rates in this reactor compared with the other two. The 14 day reactor had the highest CH4 yield at 0.33 m3CH 4/kg VS added and readily biodegradable COD concentration at 0.93 COD/L. The variations in CH4 yield and readily biodegradable COD concentrations between the three reactors were not statistically significant. Denitrification potential for the reactors was 1.20, 0.73 and 0.56 g COD/g N for 14, 21 and 28 day reactors, respectively, and the differences were statistically significant. None of the reactors achieved a denitrification potential of 5 g COD/g N, the amount required to use effluent of anaerobically digested swine waste as an internal carbon source in a BNR. This was attributed to operating conditions such as freezing and thawing of the raw swine waste that maximized CH4 yield and lowered the readily biodegradable COD concentration. In addition the 14 day reactor had low TAN concentrations thus increasing the denitrification potential

  15. Evaluation of the persistence of micropollutants through pure-oxygen activated sludge nitrification and denitrification

    Science.gov (United States)

    Levine, A.D.; Meyer, M.T.; Kish, G.

    2006-01-01

    The persistence of pharmaceuticals, hormones, and household and industrial chemicals through a pure-oxygen activated sludge, nitrification, denitrification wastewater treatment facility was evaluated. Of the 125 micropollutants that were tested in this study, 55 compounds were detected in the untreated wastewater, and 27 compounds were detected in the disinfected effluent. The persistent compounds included surfactants, fire-retardant chemicals, pesticides, fragrance compounds, hormones, and one pharmaceutical. Physical-chemical properties of micropollutants that affected partitioning onto wastewater solids included vapor pressure and octanol-water partition coefficients.

  16. Anaerobic denitrification in fungi from the coastal marine sediments off Goa, India

    Digital Repository Service at National Institute of Oceanography (India)

    Manohar, C.S.; Raghukumar, C.

    during the denitrification process. These are among the harmful green house gases that influence the earth’s climate by the destruction of the ozone in the stratosphere. The Arabian Sea is characterized by a perennial, open ocean oxygen minimum zone... region is a hot spot for N 2 O emission, a green house gas that influences the earth’s climate by the destruction of the ozone in the stratosphere (Naqvi et al. 2000). Microbial communities of the oxygen-depleted environment have often been assumed...

  17. Effect of Different Carbon Substrates on Nitrate Stable Isotope Fractionation During Microbial Denitrification

    DEFF Research Database (Denmark)

    Wunderlich, Anja; Meckenstock, Rainer; Einsiedl, Florian

    2012-01-01

    .1 ± 0.8‰; ε18O, −23.7 ± 1.8‰ to −19.9 ± 0.8‰). The observed isotope effects did not depend on the growth kinetics which were similar for the three types of electron donors. We suggest that different carbon sources change the observed isotope enrichment factors by changing the relative kinetics...... of nitrate transport across the cell wall compared to the kinetics of the intracellular nitrate reduction step of microbial denitrification....

  18. BIOLOGICAL NITROGEN REMOVAL FROM WASTEWATER BY DENITRIFICATION OF MIX-CULTURING FUNGI AND BACTERIA

    Institute of Scientific and Technical Information of China (English)

    TAKAYA; Naoki; SHOUN; Hirofumi

    2006-01-01

    Denitrificationis a biological processin which nitrateand/or nitrite is reduced to gaseous nitrogen,dinitrogen(N2)or nitrous oxide(N2O)while carbon dioxide is thesecond gaseous product of the process.This is one of themain mechanisms of the global nitrogen cycle,and playsanimportant role as the reverse reaction of nitrogen fixa-tion in maintaining global environmental homeostasis[1].Denitrification has beenlongthought to be a unique char-acteristic of prokaryotes[2,3].Anumber of bacteria(suchasPseudomonas s...

  19. Biological filter capable of simultaneous nitrification and denitrification for Aquatic Habitat in International Space Station

    Science.gov (United States)

    Uemoto, H.; Shoji, T.; Uchida, S.

    2014-04-01

    The biological filter capable of simultaneous nitrification and denitrification was constructed for aquatic animal experiments in the International Space Station (ISS). The biological filter will be used to remove harmful ammonia excreted from aquatic animals in a closed water circulation system (Aquatic Habitat). The biological filter is a cylindrical tank packed with porous glass beads for nitrification and dual plastic bags for denitrification. The porous beads are supporting media for Nitrosomonas europaea and Nitrobacter winogradskyi. The N. europaea cells and N. winogradskyi cells on the porous beads, oxidize the excreted ammonia to nitrate via nitrite. On the other hand, the dual bag is composed of an outer non-woven fabric bag and an inner non-porous polyethylene film bag. The outer bag is supporting media for Paracoccus pantotrophus. The inner bag, in which 99.5% ethanol is packed, releases the ethanol slowly, since ethanol can permeate through the non-porous polyethylene film. The P. pantotrophus cells on the outer bag reduce the produced nitrate to nitrogen gas by using the released ethanol as an electron donor for denitrification. The biological filter constructed in this study consequently removed the ammonia without accumulating nitrate. Most of the excess ethanol was consumed and did not affect the nitrification activity of the N. europaea cells and N. winogradskyi cells severely. In accordance with the aquatic animal experiments in the ISS, small freshwater fish had been bred in the closed water circulation system equipped with the biological filter for 90 days. Ammonia concentration daily excreted from fish is assumed to be 1.7 mg-N/L in the recirculation water. Under such conditions, the harmful ammonia and nitrite concentrations were kept below 0.1 mg-N/L in the recirculation water. Nitrate and total organic carbon concentrations in the recirculation water were kept below 5 mg-N/L and 3 mg-C/L, respectively. All breeding fish were alive and ate

  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

    Benthic invertebrates affect microbial processes and communities in freshwater sediment by enhancing sediment-water solute fluxes and by grazing on bacteria. Using microcosms, the effects of larvae of thewidespread midge Chironomus plumosus on the efflux of denitrification products (N2O and N2+ N2O......, 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...... 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. 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

    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...... 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 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...

  2. Utilizing Hydrologic and Biogeochemical Observations to Model the Impact of Climate Change on Denitrification Rates Across an Agricultural Watershed in Central New York

    Science.gov (United States)

    Barclay, J. R.; Anderson, T. R.; Archibald, J. A.; Walter, T.

    2012-12-01

    An overabundance of nitrogen (N) in marine and freshwater ecosystems has been linked to diverse effects such as eutrophication and hypoxic dead zones in marine waters, human health issues, marine wildlife mortality, and annual economic losses in excess of $3 billion. One natural process that reduces N loads to downstream waters is denitrification, the microbial process of converting NO3- to N2, NO, or N2O gas. Denitrification rates tend to be highest under conditions of warm temperatures and saturated soil. The distribution of these conditions will be effected by altered precipitation and temperature in future climate scenarios. Our goal is to develop a model to predict how denitrification rates, as well as its spatial and temporal distribution on a watershed scale, will be altered by climate change. We developed a spatially distributed hydrologic and denitrification model of a small agricultural watershed utilizing field measurements of hydrologic and biogeochemical properties and isotopic measurements of denitrification. Looking forward, we used end-of-century climate scenarios to predict changes in denitrification patterns. Our analysis suggests an increase in denitrification due primarily to increased temperatures. Understanding the magnitude and distribution of denitrification rate changes will allow us to better protect this important ecosystem service.

  3. Ammonia Volatilization and Denitrification Losses from an Irrigated Maize-Wheat Rotation Field in the North China Plain

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yu-Ming; CHEN De-Li; ZHANG Jia-Bao; R. EDIS; HU Chun-Sheng; ZHU An-Ning

    2004-01-01

    Ammonia (NH3) volatilization, denitrification loss, and nitrous oxide (N2O) emission were investigated from an irrigated wheat-maize rotation field on the North China Plain, and the magnitude of gaseous N loss from denitrification and NH3 volatilization was assessed. The micrometeorological gradient diffusion method in conjunction with a Bowen Ratio system was utilized to measure actual NH3 fluxes over a large area, while the acetylene inhibition technique (intact soil cores) was employed for measurement of denitrification losses and N2O emissions. Ammonia volatilization loss was 26.62% of the applied fertilizer nitrogen (N) under maize, while 0.90% and 15.55% were lost from the wheat field at sowing and topdressing, respectively. The differences in NH3 volatilization between different measurement events may be due to differences between the fertilization methods, and to differences in climatic conditions such as soil temperature.Denitrification losses in the fertilized plots were 0.67%-2.87% and 0.31%-0.49% of the applied fertilizer N under maize and wheat after subtracting those of the controls, respectively. Nitrous oxide emissions in the fertilized plots were approximately 0.08%-0.41% and 0.26%-0.34% of the applied fertilizer N over the maize and wheat seasons after subtracting those of the controls, correspondingly. The fertilizer N losses due to NH3 volatilization were markedly higher than those through denitrification and nitrous oxide emissions. These results indicated that NH3 volatilization was an important N transformation in the crop-soil system and was likely to be the major cause of low efficiencies with N fertilizer in the study area. Denitrification was not a very important pathway of N fertilizer loss, but did result in important evolution of the greenhouse gas N2O and the effect of N2O emitted from agricultural fields on environment should not be overlooked.

  4. Numerical simulation of a fine-grained denitrification layer for removing septic system nitrate from shallow groundwater

    Science.gov (United States)

    MacQuarrie, Kerry T. B.; Sudicky, Edward A.; Robertson, William D.

    2001-11-01

    One of the most common methods to dispose of domestic wastewater involves the release of septic effluent from drains located in the unsaturated zone. Nitrogen from such systems is currently of concern because of nitrate contamination of drinking water supplies and eutrophication of coastal waters. It has been proposed that adding labile carbon sources to septic distribution fields could enhance heterotrophic denitrification and thus reduce nitrate concentrations in shallow groundwater. In this study, a numerical model which solves for variably saturated flow and reactive transport of multiple species is employed to investigate the performance of a drain field design that incorporates a fine-grained denitrification layer. The hydrogeological scenario simulated is an unconfined sand aquifer. The model results suggest that the denitrification layer, supplemented with labile organic carbon, may be an effective means to eliminate nitrogen loading to shallow groundwater. It is also shown that in noncalcareous aquifers, the denitrification reaction may provide sufficient buffering capacity to maintain near neutral pH conditions beneath and down gradient of the drain field. Leaching of excess dissolved organic carbon (DOC) from the denitrification layer is problematic, and causes an anaerobic plume to develop in simulations where the water table is less than 5-6 m below ground surface; this anaerobic plume may lead to other down gradient changes in groundwater quality. A drain field and denitrification layer of smaller dimensions is shown to be just as effective for reducing nitrate, but has the benefit of reducing the excess DOC leached from the layer. This configuration will minimize the impact of wastewater disposal in areas where the water table is as shallow as 3.5 m.

  5. Denitrification in sediments as a major nitrogen sink in the Baltic Sea: an extrapolation using sediment characteristics

    Directory of Open Access Journals (Sweden)

    B. Deutsch

    2010-04-01

    Full Text Available Rates of denitrification in sediments were measured with the isotope pairing technique at different sites in the southern and central Baltic Sea. They varied between 0.5 μmol m−2 h−1 in sands and 28.7 μmol m−2 h−1 in muddy sediments and showed a good correlation to the organic carbon contents of the surface sediments. N-removal rates via sedimentary denitrification were estimated for the entire Baltic Sea calculating sediment specific denitrification rates and interpolating them to the whole Baltic Sea area. Another approach was carried out by using the relationship between the organic carbon content and the rate of denitrification. For the entire Baltic Sea the N-removal by denitrification in sediments varied between 426–652 kt N a−1, which is around 48–73% of the external N inputs delivered via rivers, coastal point sources and atmospheric deposition. Moreover, an expansion of the anoxic bottom areas was considered under the assumption of a rising oxycline from 100 to 80 m water depth. This leads to an increase of the area with anoxic conditions and an overall decrease in sedimentary denitrification by 14%. Overall we can show here that this type of data extrapolation is a powerful tool to estimate the nitrogen losses for a whole coastal sea and may be applicable to other coastal regions and enclosed seas, too.

  6. Vertical distribution of denitrification in an estuarine sediment: integrating sediment flowthrough reactor experiments and microprofiling via reactive transport modeling.

    Science.gov (United States)

    Laverman, Anniet M; Meile, Christof; Van Cappellen, Philippe; Wieringa, Elze B A

    2007-01-01

    Denitrifying activity in a sediment from the freshwater part of a polluted estuary in northwest Europe was quantified using two independent approaches. High-resolution N(2)O microprofiles were recorded in sediment cores to which acetylene was added to the overlying water and injected laterally into the sediment. The vertical distribution of the rate of denitrification supported by nitrate uptake from the overlying water was then derived from the time series N(2)O concentration profiles. The rates obtained for the core incubations were compared to the rates predicted by a forward reactive transport model, which included rate expression for denitrification calibrated with potential rate measurements obtained in flowthrough reactors containing undisturbed, 1-cm-thick sediment slices. The two approaches yielded comparable rate profiles, with a near-surface, 2- to 3-mm narrow zone of denitrification and maximum in situ rates on the order of 200 to 300 nmol cm(-3) h(-1). The maximum in situ rates were about twofold lower than the maximum potential rate for the 0- to 1-cm depth interval of the sediment, indicating that in situ denitrification was nitrate limited. The experimentally and model-derived rates of denitrification implied that there was nitrate uptake by the sediment at a rate that was on the order of 50 (+/- 10) nmol cm(-2) h(-1), which agreed well with direct nitrate flux measurements for core incubations. Reactive transport model calculations showed that benthic uptake of nitrate at the site is particularly sensitive to the nitrate concentration in the overlying water and the maximum potential rate of denitrification in the sediment.

  7. Heterotrophic and elemental-sulfur-based autotrophic denitrification processes for simultaneous nitrate and Cr(VI) reduction.

    Science.gov (United States)

    Sahinkaya, Erkan; Kilic, Adem

    2014-03-01

    Nitrate and chromate can be present together in water resources as nitrate is a common co-contaminant in surface and ground waters. This study aims at comparatively evaluating simultaneous chromate and nitrate reduction in heterotrophic and sulfur-based autotrophic denitrifying column bioreactors. In sulfur-based autotrophic denitrification process, elemental sulfur and nitrate act as an electron donor and an acceptor, respectively, without requirement of organic supplementation. Autotrophic denitrification was complete and not adversely affected by chromate up to 0.5 mg/L. Effluent chromate concentration was water treatment due to the elimination of organic supplementation and the risk of treated effluent contamination.

  8. Comparison of ethanol, methanol and succinate effects as carbon sources on effluent biological denitrification

    Directory of Open Access Journals (Sweden)

    abbas Rezaee

    2008-04-01

    Full Text Available Abstract Background: Increase of nitrate concentration in water sources is becoming a serious problem in many parts of the world. Nitrogen containing compounds released into environment can create serious problems, such as eutrophication of water sources and hazard potential to human health, because it has potency of causing methemoglubinemia disease and cancer. Between recommended methods, biological denitrification is an effective method to remove nitrate from water and wastewater. Materials and methods: In this study, biological nitrogen removal process was evaluated using ethanol, methanol and succinate as different organic carbon sources in batch scale. The different parameters, carbon source, initial nitrate concentration, pH, and inoculated of bacteria were evaluated. Results: The experimental results were showed that bacteria can not use methanol as carbon source. The dinitrifyers bacteria can dissimilate 200 mg/L No3-N, in the optimum condition: 28 ºC, pH 7.2 and initial inoculation of 3×108 CFU/ml, respectively. In the process, produced nitrate-N was less than 1 mg/l. Conclusion: The bacterium Pseudomonas stutzeri can use ethanol as carbon source for biological denitrification, but efficiency of succinate was better than ethanol.

  9. Effects of Ce(III) and CeO₂ nanoparticles on soil-denitrification kinetics.

    Science.gov (United States)

    Dahle, Jessica T; Arai, Yuji

    2014-11-01

    Cerium (Ce)-based compounds, such as CeO₂ nanoparticles (NPs), have received much attention in the last several years due to their popular applications in industrial and commercial uses. Understanding the impact of CeO₂ NPs on nutrient cycles, a subchronic toxicity study of CeO₂ NPs on soil-denitrification process was performed as a function of particle size (33 and 78 nm), total Ce concentration (50-500 mg L(-1)), and speciation [Ce(IV) vs. Ce(III)]. The antimicrobial effect on the soil-denitrification process was evaluated in both steady-state and zero-order kinetic models to assess particle- and chemical-species specific toxicity. It was found that soluble Ce(III) was far more toxic than Ce(IV)O₂ NPs when an equal total concentration of Ce was evaluated. Particle size-dependent toxicity, species-dependent toxicity, and concentration-dependent toxicity were all observed in this study for both the steady-state and the kinetic evaluations. Changes in physicochemical properties of Ce(IV)O₂ NPs might be important in assessing the environmental fate and toxicity of NPs in aquatic and terrestrial environments.

  10. 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.

  11. Evaluation of a denitrification wall to reduce surface water nitrogen loads.

    Science.gov (United States)

    Schmidt, Casey A; Clark, Mark W

    2012-01-01

    Denitrification walls have significantly reduced nitrogen concentrations in groundwater for at least 15 yr. This has spurred interest in developing methods to efficiently increase capture volume to reduce N loads in larger watersheds. The objective of this study was to maximize treatment volume by locating a wall where a large groundwatershed was funneled toward seepage slope headwaters. Nitrogen concentration and load were measured before and after wall installation in paired treatment and control streams. Beginning 2 d after installation, nitrogen concentration in the treatment stream declined from 6.7 ± 1.2 to 3.9 ± 0.78 mg L and total N loading rate declined by 65% (391 kg yr) with no corresponding decline in the control watershed. This wall, which only comprised 10 to 11% of the edge of field area that contributed to the treatment watershed, treated approximately 60% of the stream discharge, which confirmed the targeted approach. The total load reduction measured in the stream 155 m downstream from the wall (340 kg yr) was higher than that found in another study that measured load reductions in groundwater wells immediately around the wall (228 kg yr). This indicated the possibility of an extended impact on denitrification from carbon exported beyond the wall. This extended impact was inauspiciously confirmed when oxygen levels at the stream headwaters temporarily declined for 50 d. This research indicates that targeting walls adjacent to streams can effectively reduce N loading in receiving waters, although with a potentially short-term impact on water quality.

  12. Soil denitrification fluxes from three northeastern North American forests across a range of nitrogen deposition.

    Science.gov (United States)

    Morse, Jennifer L; Durán, Jorge; Beall, Fred; Enanga, Eric M; Creed, Irena F; Fernandez, Ivan; Groffman, Peter M

    2015-01-01

    In northern forests, large amounts of missing N that dominate N balances at scales ranging from small watersheds to large regional drainage basins may be related to N-gas production by soil microbes. We measured denitrification rates in forest soils in northeastern North America along a N deposition gradient to determine whether N-gas fluxes were a significant fate for atmospheric N inputs and whether denitrification rates were correlated with N availability, soil O2 status, or forest type. We quantified N2 and N2O fluxes in the laboratory with an intact-core method and monitored soil O2, temperature and moisture in three forests differing in natural and anthropogenic N enrichment: Turkey Lakes Watershed, Ontario; Hubbard Brook Experimental Forest, New Hampshire; and Bear Brook Watershed, Maine (fertilized and reference plots in hardwood and softwood stands). Total N-gas flux estimates ranged from 100 kg N ha(-1) year(-1) in hardwood wetlands at Turkey Lakes. N-gas flux increased systematically with natural N enrichment from soils with high nitrification rates (Bear Brook forests in northeastern North America, but it does not appear to be an important sink for elevated anthropogenic atmospheric N deposition in this region.

  13. Molecular, biochemical, and physiological approaches for understanding the ecology of denitrification.

    Science.gov (United States)

    Goregues, C M; Michotey, V D; Bonin, P C

    2005-02-01

    One of the major challenges in microbial ecology for the future is to establish links between structural and functional biodiversity. This is particularly difficult when one is interested in a phylogenetically diversified function such as denitrification. The data banks are very rich in functional gene sequences (nirS in this study), but most of them were obtained from not yet cultivated bacteria, and thus must be supplemented by sequences of organisms from the environment for which we could associate a taxonomic position and physiological characteristics. Combined analysis including molecular (16S-rRNA or nirS genes), physiological, and biochemical approaches was carried out on a bacterial set of 89 strains isolated from marine sediment. The denaturing gradient gel electrophoresis (DGGE) technique was successfully applied on unclamped polymerase chain reaction (PCR) products of nirS genes to compare the picture of the biodiversity obtained with 16S rRNA and nirS genes. The diversity of nirS genes and denitrifier characteristics were found within several of the 16S rDNA phylotypes. In contrast, the nirS phylotypes were no diverse both with respect to 16S rDNA and to physiology and biochemistry of denitrification. Sequences of the nirS PCR products were very close to marine environmental clones and were analyzed within the same phylogenetic tree.

  14. Laboratory study of nitrification, denitrification and anammox processes in membrane bioreactors considering periodic aeration.

    Science.gov (United States)

    Abbassi, Rouzbeh; Yadav, Asheesh Kumar; Huang, Shan; Jaffé, Peter R

    2014-09-01

    The possibility of using membrane bioreactors (MBRs) in simultaneous nitrification-anammox-denitrification (SNAD) by considering periodic aeration cycles was investigated. Two separate reactors were operated to investigate the effect of different anammox biomass in the presence of nitrifying and denitrifying biomass on the final nitrogen removal efficiency. The results illustrated that the reactor with higher anammox biomass was more robust to oxygen cycling. Around 98% Total Nitrogen (TN) and 83% Total Organic Carbon (TOC) removal efficiencies were observed by applying one hour aeration over a four-hour cycle. Decreasing the aeration time to 30, 15, and 2 min during a four-hour cycle affected the final TN removal efficiencies. However, the effect of decreasing aeration on the TN removal efficiencies in the reactor with higher anammox biomass was much lower compared to the regular reactor. The nitrous oxide (N2O) emission was a function of aeration as well, and was lower in the reactor with higher anammox biomass. The results of q-PCR analysis confirmed the simultaneous co-existence of nitrifiers, anammox, and denitrifiers in both of the reactors. To simulate the TN removal in these reactors as a function of the aeration time, a new model, based on first order reaction kinetics for both denitrification and anammox was developed and yielded a good agreement with the experimental observations.

  15. Carboxyl-modified single-walled carbon nanotubes negatively affect bacterial growth and denitrification activity

    Science.gov (United States)

    Zheng, Xiong; Su, Yinglong; Chen, Yinguang; Wan, Rui; Li, Mu; Wei, Yuanyuan; Huang, Haining

    2014-07-01

    Single-walled carbon nanotubes (SWNTs) have been used in a wide range of fields, and the surface modification via carboxyl functionalization can further improve their physicochemical properties. However, whether carboxyl-modified SWNT poses potential risks to microbial denitrification after its release into the environment remains unknown. Here we present the possible effects of carboxyl-modified SWNT on the growth and denitrification activity of Paracoccus denitrificans (a model denitrifying bacterium). It was found that carboxyl-modified SWNT were present both outside and inside the bacteria, and thus induced bacterial growth inhibition at the concentrations of 10 and 50 mg/L. After 24 h of exposure, the final nitrate concentration in the presence of 50 mg/L carboxyl-modified SWNT was 21-fold higher than that in its absence, indicating that nitrate reduction was substantially suppressed by carboxyl-modified SWNT. The transcriptional profiling revealed that carboxyl-modified SWNT led to the transcriptional activation of the genes encoding ribonucleotide reductase in response to DNA damage and also decreased the gene expressions involved in glucose metabolism and energy production, which was an important reason for bacterial growth inhibition. Moreover, carboxyl-modified SWNT caused the significant down-regulation and lower activity of nitrate reductase, which was consistent with the decreased efficiency of nitrate reduction.

  16. Aerobic denitrification and biomineralization by a novel heterotrophic bacterium, Acinetobacter sp. H36.

    Science.gov (United States)

    Su, Jun Feng; Shi, Jing Xin; Ma, Fang

    2017-03-15

    A novel aerobic denitrification and biomineralization strain H36 was isolated from the Qu Jiang artificial lake. Based on phylogenetic characteristics, the isolated strain was identified as Acinetobacter species. Strain H36 was confirmed to have the ability to perform simultaneous denitrification and biomineralization. Results showed the strain H36 had the capability to completely reduce 96.29% of NO3(-)-N and 78.59% of Ca(2+) over 112h under aerobic condition. Response surface methodology (RSM) analysis demonstrated the highest removal ratio of Ca(2+) was 74.24% with hardness concentration of 350mg/L, pH of 8.5, organic concentration of 0.75g/L and inoculum size of 15%. The highest removal ratio of nitrate was 77.00% with hardness concentration of 350mg/L, pH of 7.5, organic concentration of 0.75g/L and inoculum size of 10%. Besides, X-ray diffraction (XRD) analysis showed calcium carbonate could be formed in the process of biomineralization. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Evaluation on the Nanoscale Zero Valent Iron Based Microbial Denitrification for Nitrate Removal from Groundwater.

    Science.gov (United States)

    Peng, Lai; Liu, Yiwen; Gao, Shu-Hong; Chen, Xueming; Xin, Pei; Dai, Xiaohu; Ni, Bing-Jie

    2015-07-22

    Nanoscale zero valent iron (NZVI) based microbial denitrification has been demonstrated to be a promising technology for nitrate removal from groundwater. In this work, a mathematical model is developed to evaluate the performance of this new technology and to provide insights into the chemical and microbial interactions in the system in terms of nitrate reduction, ammonium accumulation and hydrogen turnover. The developed model integrates NZVI-based abiotic reduction of nitrate, NZVI corrosion for hydrogen production and hydrogen-based microbial denitrification and satisfactorily describes all of the nitrate and ammonium dynamics from two systems with highly different conditions. The high NZVI corrosion rate revealed by the model indicates the high reaction rate of NZVI with water due to their large specific surface area and high surface reactivity, leading to an effective microbial nitrate reduction by utilizing the produced hydrogen. The simulation results further suggest a NZVI dosing strategy (3-6 mmol/L in temperature range of 30-40 °C, 6-10 mmol/L in temperature range of 15-30 °C and 10-14 mmol/L in temperature range of 5-15 °C) during groundwater remediation to make sure a low ammonium yield and a high nitrogen removal efficiency.

  18. Technical Note: Alternative in-stream denitrification equation for the INCA-N model

    Science.gov (United States)

    Etheridge, J. R.; Birgand, F.; Burchell, M. R., II; Lepistö, A.; Rankinen, K.; Granlund, K.

    2014-04-01

    The Integrated Catchment model for Nitrogen (INCA-N) is a semi-distributed, process based model that has been used to model the impacts of land use, climate, and land management changes on hydrology and nitrogen loading. An observed problem with the INCA-N model is reproducing low nitrate-nitrogen concentrations during the summer growing season in some catchments. In this study, the current equation used to simulate the rate of in-stream denitrification was replaced with an alternate equation that uses a mass transfer coefficient and the stream bottom area. The results of simulating in-stream denitrification using the two different methods were compared for a one year simulation period of the Yläneenjoki catchment in Finland. The alternate equation (Nash-Sutcliffe efficiency = 0.61) simulated concentrations during the periods of the growing season with the lowest flow that were closer to the observed concentrations than the current equation (Nash-Sutcliffe efficiency = 0.60), but the results were mixed during other portions of the year. The results of the calibration and validation of the model using the two equations show that the alternate equation will simulate lower nitrate-nitrogen concentrations during the growing season when compared to the current equation, but promote investigation into other errors in the model that may be causing inaccuracies in the modeled concentrations.

  19. Effects of Heavy Metals on Ammonification,Nitrification and Denitrification in Maize Rhizosphere

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The amrnonification,nitrification and denitrification in maize rhizosphere of alluvial soils were compared with those in the bulk soil after exposure to different kinds of heavy metals.The addition of cadmium at low levels (2 mg kg-1 and 5 mg kg-1) could stimulate the arnmonification and nitrification in the soils,while inhibition influences were found at high levels of Cd addition (10 mg kg-1 and 20 mg kg-1).The relationship between microbial activity and cadmium concentration varied with the kind of microorganisms.The nitrifying bacteria were more sensitive to cadmium pollution than the armonifying bacteria.When Cd(II),Cu(II) and Cr(VI) were compared at the same addition concentration of 20 mg kg-1 soil,Cd(II) was the most effective inhibitor of amronification and denitrification among the three investigated heavy metals,and Cr(VI) had the most strong inhibitory influence on the nitrifying bacteria.The microbial activities in rhizosphere were higher than those in the bulk soil for most of the treatments.Cr(VI) proved to be the most effective in enhancing the microbial activities in rhizosphere,and this could be caused by the positive reduction of Cr(VI) to Cr(III) in rhizosphere,and the relatively sufficient existence of organic matter which intensified the adsorption of the metal.It seemed that the rhizosphere had some mitigation effect on heavy metal toxicity.

  20. Microbiological and molecular characterization of denitrification in biofilters treating pig manure.

    Science.gov (United States)

    Gilbert, Yan; Le Bihan, Yann; Aubry, Geneviève; Veillette, Marc; Duchaine, Caroline; Lessard, Paul

    2008-07-01

    Aerated organic biofilters treating pig manure exhibit partial nitrogen removal. In order to optimize this process, a better comprehension of its colonization by denitrifiers was needed. Three pilot aerated biofilters, fed with variable Biological Oxygen Demand after five days: Total Kjeldahl Nitrogen (BOD(5):TKN) ratios, were constructed and monitored during 180 days. Nitrogen was analyzed in the gaseous and liquid flows, at different depths in the systems. Denitrifying biomass was characterized by evaluating its observed (nitrogen mass balances) and potential (adapted acetylene inhibition technique) activities and its quantity (real-time PCR on nirS), at different heights inside the biofilters. Denitrification was observed as soon as nitrate was produced by nitrifiers, after approximately 40 days of operation, but the potential to denitrify increased from the beginning of the monitoring period. Biofilter fed with the highest BOD(5):TKN ratio showed significant differences with the others, particularly after 80 days of operation, as its potential activity was lower with a higher observed nitrate removal. Data showed that denitrifiers were mainly localized near the surface of the filter and that a microbiological gradient was present from top to bottom. The potential denitrifying activities were always higher than what was being observed inside the sections studied, suggesting that the biomass could have reduced more nitrate and that conditions found inside the filter did not allow denitrification to completely occur.

  1. Kinetics of substrate degradation and electricity generation in anodic denitrification microbial fuel cell (AD-MFC).

    Science.gov (United States)

    Zhang, Jiqiang; Zheng, Ping; Zhang, Meng; Chen, Hui; Chen, Tingting; Xie, Zuofu; Cai, Jing; Abbas, Ghulam

    2013-12-01

    Effect of substrate concentration on substrate degradation and electricity generation in anodic denitrification microbial fuel cell (AD-MFC) was investigated over a broad range of substrate concentrations. Substrate degradation rates and power generation could be promoted with increasing substrate concentration in a certain range, but both of them would be inhibited at high substrate concentrations. Maximum denitrification rate of 1.26 ± 0.01 kg NO(-)-N/m(3)d and maximum output voltage of 1016.75 ± 4.74 mV could be achieved when initial NO3(-)-N concentration was 1999.95 ± 2.86 mg/L. Based on Han-Levenspiel model, kinetics of substrate degradation and power generation in the AD-MFC were established. According to the kinetic model, the half-saturation coefficient and the critical inhibitory concentration for nitrate were more than 200 and 4300 mg/L, respectively. The results demonstrated that AD-MFC was capable of treating nitrate-containing wastewater and generating electricity simultaneously, and tolerant to high strength nitrate-containing wastewater.

  2. Culture Studies of Nitrogen and Oxygen Isotope Effects Associated with Nitrate Assimilation and Denitrification

    Science.gov (United States)

    Sigman, D. M.; Granger, J.; Lehmann, M. F.; Difiore, P. J.; Tortell, P. D.

    2007-12-01

    The isotope effects of nitrate-consuming reactions such as nitrate assimilation and denitrification are potential indicators of the physiological state of the organisms carrying out these reactions. Moreover, an understanding of these isotope effects is needed to use the stable isotopes to investigate the fluxes associated with these reactions in modern and ancient environments. We have used batch cultures to investigate the nitrogen (N) and oxygen (O) isotope effects of (1) nitrate assimilation by eukaryotic and prokaryotic algae and by heterotrophic bacteria, and (2) nitrate reduction by denitrifying bacteria. We observe intra- and inter-specific variation in isotope effect amplitudes and, in the case of denitrifiers, indications of isotope effect decreases during individual nitrate drawdown experiments. However, the measured N and O isotope effect ratio is close to 1 for all studied organisms, with the exception of an unusual denitrifier (Rhodobacter sphaeroides) that possesses only periplasmic (non-respiratory) nitrate reductase. This observation and other findings are consistent with nitrate reductase being the predominant source of isotope fractionation and with most isotope effect amplitude variability arising from variable degrees to which nitrate imported into the cell is reduced versus effluxed back into the environment; the more efflux, the more complete the expression of the fractionation imparted by nitrate reduction. If this is the case, then isotope effect amplitudes in the field should be related to physiological conditions in the environment, a prediction that, we argue, is supported by recent studies of (1) nitrate assimilation in the polar ocean and (2) denitrification in sediment porewaters.

  3. Denitrification with methane as electron donor in oxygen-limited bioreactors

    Energy Technology Data Exchange (ETDEWEB)

    Costa, C. [Salamanca Univ. (Spain). Chemical Engineering Dept.; Wageningen Univ., Lab. of Microbiology (Netherlands); Dijkema, C. [Wageningen Univ., Lab. of Molecular Physics, Dreijenlaan 3 (Netherlands); Friedrich, M. [Max-Planck-Inst. for Terrestrial Microbiology, Marburg (Germany); Garcia-Encina, P.; Fernandez-Polanco, F. [Univ. of Valladolid, Chemical Engineering Dept. (Spain); Stams, A.J.M. [Wageningen Univ., Lab. of Microbiology (Netherlands)

    2000-07-01

    The microbial population from a reactor using methane as electron donor for denitrification under microaerophilic conditions was analyzed. High numbers of aerobic methanotrophic bacteria (3 10{sup 7} cells/ml) and high numbers of acetate-utilizing denitrifying bacteria (2 10{sup 7} cells/ml) were detected, but only very low numbers of methanol-degrading denitrifying bacteria (4 10{sup 4} cells/ml) were counted. Two abundant acetate-degrading denitrifiers were isolated which, based on 16S rRNA analysis, were closely related to Mesorhizobium plurifarium (98.4% sequence similarity) and a Stenotrophomonas sp. (99.1% sequence similarity). A methanol-degrading denitrifying bacterium isolated from the bioreactor morphologically resembled Hyphomicrobium sp. and was moderately related to H. vulgare (93.5% sequence similarity). The initial characterization of the most abundant methanotrophic bacterium indicated that it belongs to class II of the methanotrophs. ''In vivo'' {sup 13}C-NMR with concentrated cell suspensions showed that this methanotroph produced acetate under oxygen limitation. The microbial composition of reactor material together with the NMR experiments suggest that in the reactor methanotrophs excrete acetate, which serves as the direct electron donor for denitrification. (orig.)

  4. Fluidized-bed denitrification of mining water tolerates high nickel concentrations.

    Science.gov (United States)

    Zou, G; Papirio, S; van Hullebusch, E D; Puhakka, J A

    2015-03-01

    This study revealed that fluidized-bed denitrifying cultures tolerated soluble Ni concentrations up to 500 mg/L at 7-8 and 22°C. From 10 to 40 mg/L of feed Ni, denitrification resulted in complete nitrate and nitrite removal. The concomitant reduction of 30 mg/L of sulfate produced 10 mg/L of sulfide that precipitated nickel, resulting in soluble effluent Ni below 22 mg/L. At this stage, Dechloromonas species were the dominant denitrifying bacteria. From 60 to 500 mg/L of feed Ni, nickel remained in solution due to the inhibition of sulfate reduction. At soluble 60 mg/L of Ni, denitrification was partially inhibited prior to recover after 34 days of enrichment by other Ni-tolerant species (including Delftia, Zoogloea and Azospira) that supported Dechloromonas. Subsequently, the FBR cultures completely removed nitrate even at 500 mg/L of Ni. Visual Minteq speciation model predicted the formation of NiS, NiCO3 and Ni3(PO4)2, whilst only Ni3(PO4)2 was detected by XRD.

  5. 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 (treatment and promoted the utilization of pyrite in the field of environmental remediation.

  6. Partial ozonation of activated sludge to reduce excess sludge, improve denitrification and control scumming and bulking

    Energy Technology Data Exchange (ETDEWEB)

    Boehler, Marc; Siegrist, Hansruedi

    2003-07-01

    Disposal of sewage sludge is forbidden and agricultural use of stabilized sludge will be banned in 2005 in Switzerland. The sludge has to be dewatered, dried, Incinerated and the ashes disposed in landfills. These processes are cost intensive and lead also to the loss of valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Partial ozonation of the return sludge of an activated sludge system reduces significantly excess sludge production, improves settling properties of the sludge and reduces bulking and scumming. The solubilized COD will also improve denitrification if the treated sludge is recycled to the anoxic zone. But ozonation will partly inhibit and kill nitrifiers and might therefore lead to a decrease of the effective solid retention time of the nitrifier, which reduces the safety of the nitrification. This paper discusses the effect of ozonation on sludge reduction, the operation stability of nitrification, improvement of denitrification and gives also an energy and cost evaluation. (author)

  7. Tracking composition of microbial communities for simultaneous nitrification and denitrification in polyurethane foam.

    Science.gov (United States)

    Chen, Yuan; Wang, Li; Ma, Fang; Yang, Ji-xian; Qiu, Shan

    2014-01-01

    The process of simultaneous nitrification and denitrification (SND) of immobilized microorganisms in polyurethane form is discussed. The effect of different positions within the polyurethane carrier on microbial community response for the SND process is investigated by a combination of denaturing gradient gel electrophoresis profiles of the 16S rRNA gene V3 region and scanning electron microscopy. Results show that polyurethane, which consists of a unique porous structure, is an ideal platform for biofilm stratification of aerobe, anaerobe and facultative microorganisms in regard to the SND process. The community structure diversity response to different positions was distinct. The distributions of various functional microbes, detected from the surface aerobic stratification to the interior anaerobic stratification of polyurethane, were mainly nitrifying and denitrifying bacteria. Meanwhile aerobic denitrifying bacteria such as Paracoccus sp., Agrobacterium rubi and Ochrobactrum sp. were also adhered to the interior and surface of polyurethane. The SND process occurring on polyurethane foam was carried out by two independent processes: nitrogen removal and aerobic denitrification.

  8. Converse Barrier Certificate Theorems

    DEFF Research Database (Denmark)

    Wisniewski, Rafael; Sloth, Christoffer

    2016-01-01

    This paper shows that a barrier certificate exists for any safe dynamical system. Specifically, we prove converse barrier certificate theorems for a class of structurally stable dynamical systems. Other authors have developed a related result by assuming that the dynamical system has neither sing...

  9. Skin barrier function

    DEFF Research Database (Denmark)

    2016-01-01

    Renowned experts present the latest knowledge Although a very fragile structure, the skin barrier is probably one of the most important organs of the body. Inward/out it is responsible for body integrity and outward/in for keeping microbes, chemicals, and allergens from penetrating the skin. Since...... the role of barrier integrity in atopic dermatitis and the relationship to filaggrin mutations was discovered a decade ago, research focus has been on the skin barrier, and numerous new publications have become available. This book is an interdisciplinary update offering a wide range of information...... on the subject. It covers new basic research on skin markers, including results on filaggrin and on methods for the assessment of the barrier function. Biological variation and aspects of skin barrier function restoration are discussed as well. Further sections are dedicated to clinical implications of skin...

  10. Validating soil denitrification models based on laboratory N_{2} and N_{2}O fluxes and underlying processes derived by stable isotope approaches

    Science.gov (United States)

    Well, Reinhard; Böttcher, Jürgen; Butterbach-Bahl, Klaus; Dannenmann, Michael; Deppe, Marianna; Dittert, Klaus; Dörsch, Peter; Horn, Marcus; Ippisch, Olaf; Mikutta, Robert; Müller, Carsten; Müller, Christoph; Senbayram, Mehmet; Vogel, Hans-Jörg; Wrage-Mönnig, Nicole

    2016-04-01

    Robust denitrification data suitable to validate soil N2 fluxes in denitrification models are scarce due to methodical limitations and the extreme spatio-temporal heterogeneity of denitrification in soils. Numerical models have become essential tools to predict denitrification at different scales. Model performance could either be tested for total gaseous flux (NO + N2O + N2), individual denitrification products (e.g. N2O and/or NO) or for the effect of denitrification factors (e.g. C-availability, respiration, diffusivity, anaerobic volume, etc.). While there are numerous examples for validating N2O fluxes, there are neither robust field data of N2 fluxes nor sufficiently resolved measurements of control factors used as state variables in the models. To the best of our knowledge there has been only one published validation of modelled soil N2 flux by now, using a laboratory data set to validate an ecosystem model. Hence there is a need for validation data at both, the mesocosm and the field scale including validation of individual denitrification controls. Here we present the concept for collecting model validation data which is be part of the DFG-research unit "Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM)" starting this year. We will use novel approaches including analysis of stable isotopes, microbial communities, pores structure and organic matter fractions to provide denitrification data sets comprising as much detail on activity and regulation as possible as a basis to validate existing and calibrate new denitrification models that are applied and/or developed by DASIM subprojects. The basic idea is to simulate "field-like" conditions as far as possible in an automated mesocosm system without plants in order to mimic processes in the soil parts not significantly influenced by the rhizosphere (rhizosphere soils are studied by other DASIM projects). Hence, to allow model testing in a wide range of conditions

  11. 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.

  12. Degassing of 3H/3He, CFCs and SF6 by denitrification: Measurements and two-phase transport simulations

    NARCIS (Netherlands)

    Visser, A.; Schaap, J.D.; Broers, H.P.; Bierkens, M.F.P.

    2009-01-01

    The production of N2 gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of 3H/3He, CFCs and SF6 as

  13. Degassing of 3H/3He, CFCs and SF6 by denitrification: Measurements and two-phase transport simulations

    NARCIS (Netherlands)

    Visser, A.; Schaap, J.D.; Broers, H.P.; Bierkens, M.F.P.

    2009-01-01

    The production of N2 gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of 3H/3He, CFCs and SF6 as

  14. 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...

  15. 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

    experiments performed in 5 liter bottles indicated that the denitrification rate can be instantaneously increased through the addition of either carbon source. The amount by which the rate was increased depended on the amount of carbon added. In the main experiments performed in a pilot scale alternating...

  16. Comparing the environmental impact of a nitrifiying biotrickling filter with or without denitrification for ammonia abatement at animal houses

    NARCIS (Netherlands)

    Vries, de J.W.; Melse, R.W.

    2014-01-01

    The aim was to assess the environmental impact of a biotrickling filter with nitrification only and with subsequent denitrification. Life cycle assessment was applied to assess greenhouse gases, nitrate, ammonia and fossil fuel depletion. The biotrickling filter with nitrification and denitrificatio

  17. Fate and impact of organics in an immersed membrane bioreactor applied to brine denitrification and ion exchange regeneration.

    Science.gov (United States)

    McAdam, Ewan J; Pawlett, Mark; Judd, Simon J

    2010-01-01

    The application of membrane bioreactors (MBRs) to brine denitrification for ion exchange regeneration has been studied. The developed culture was capable of complete brine denitrification at 50 gNaCl.l(-1). Denitrification reduced to c.60% and c.70% when salinity was respectively increased to 75 and 100g.l(-1), presumed to be due to reduced growth rate and the low imposed solids retention time (10 days). Polysaccharide secretion was not induced by stressed cells following salt shocking, implying that cell lysis did not occur. Fouling propensity, monitored by critical flux, was steady at 12-15l.m(-2).h(-1) during salinity shocking and after brine recirculation, indicating that the system was stable following perturbation. Low molecular weight polysaccharide physically adsorbed onto the nitrate selective anion exchange resin during regeneration reducing exchange capacity by c.6.5% when operating up to complete exhaustion. However, based on a breakthrough threshold of 10 mgNO(3)(-)-N.l(-1) the exchange capacity was comparative to that determined when using freshly produced brine for regeneration. It was concluded that a denitrification MBR was an appropriate technology for IEX spent brine recovery and reuse.

  18. Denitrification in restored and constructed wetlands adjacent to crop fields on the Mid-Atlantic coastal plain

    Science.gov (United States)

    Fertilizer applications on crop fields are a significant source of nitrate (NO3), and groundwater concentrations are frequently 500-1000 µM. We show that groundwater transport of agricultural NO3 results in significant denitrification in adjacent wetlands in the Choptank Basin on the Delmarva Penins...

  19. Central Composite Design (CCD) applied for statistical optimization of glucose and sucrose binary carbon mixture in enhancing the denitrification process

    Science.gov (United States)

    Lim, Jun-Wei; Beh, Hoe-Guan; Ching, Dennis Ling Chuan; Ho, Yeek-Chia; Baloo, Lavania; Bashir, Mohammed J. K.; Wee, Seng-Kew

    2016-12-01

    The present study provides an insight into the optimization of a glucose and sucrose mixture to enhance the denitrification process. Central Composite Design was applied to design the batch experiments with the factors of glucose and sucrose measured as carbon-to-nitrogen (C:N) ratio each and the response of percentage removal of nitrate-nitrogen (NO3 --N). Results showed that the polynomial regression model of NO3 --N removal had been successfully derived, capable of describing the interactive relationships of glucose and sucrose mixture that influenced the denitrification process. Furthermore, the presence of glucose was noticed to have more consequential effect on NO3 --N removal as opposed to sucrose. The optimum carbon sources mixture to achieve complete removal of NO3 --N required lesser glucose (C:N ratio of 1.0:1.0) than sucrose (C:N ratio of 2.4:1.0). At the optimum glucose and sucrose mixture, the activated sludge showed faster acclimation towards glucose used to perform the denitrification process. Later upon the acclimation with sucrose, the glucose uptake rate by the activated sludge abated. Therefore, it is vital to optimize the added carbon sources mixture to ensure the rapid and complete removal of NO3 --N via the denitrification process.

  20. Simultaneous removal of di-(2-ethylhexyl) phthalate and nitrogen in a laboratory-scale pre-denitrification biofilter system.

    Science.gov (United States)

    Cao, Xiangsheng; Ai, Niyuan; Meng, Xuezheng

    2014-03-01

    This study demonstrated the excellent di-(2-ethylhexyl) phthalate (DEHP) removal performance of a pre-denitrification biofilter system. Experimental results showed that DEHP removal efficiency remained stable while total nitrogen removal efficiency fluctuated with the nitrate recycle ratio changes when the hydraulic loading rate at 1.1m(3)/m(2)h. DEHP removal efficiency increased from 48% to 82% while the hydraulic loading rate increased from 1.1 to 2.2m(3)/m(2)h. DEHP concentration decreased gradually along the wastewater flow direction in the denitrification biofilter and a plug flow model with the reaction order of 5 and the rate constant of 0.54 was obtained. Both the denitrification biofilter and the nitrification biofilter showed similar DEHP removal performance. The overall DEHP removal efficiency of the system was 83.8%, in which biodegradation contributed 72.3%. Biodegradation plays a key role in DEHP removal in the pre-denitrification biofilter system. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Effect of fermentation liquid from food waste as a carbon source for enhancing denitrification in wastewater treatment.

    Science.gov (United States)

    Zhang, Yongmei; Wang, Xiaochang C; Cheng, Zhe; Li, Yuyou; Tang, Jialing

    2016-02-01

    Food wastes were used for anaerobic fermentation to prepare carbon sources for enhancing nitrogen removal in wastewater treatment. Under anaerobic conditions without pH adjustment, the fermentation liquid from food wastes (FLFW) with a high organic acid content was produced at room temperature (25 °C) and initial solid concentration of 13%. Using FLFW as the sole carbon source of artificial wastewater for biological treatment by sequence batch operation, maximized denitrification (with a denitrification rate of V(DN) = 12.89 mg/gVSS h and a denitrification potential of P(DN) = 0.174 gN/gCOD) could be achieved at a COD/TN ratio of 6. The readily biodegradable fraction in the FLFW was evaluated as 58.35%. By comparing FLFW with glucose and sodium acetate, two commonly used chemical carbon sources, FLFW showed a denitrification result similar to sodium acetate but much better than glucose in terms of total nitrogen removal, V(DN), P(DN), organic matter consumption rate (V(COD)) and heterotrophy anoxic yield coefficient (Y(H)).

  2. 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

  3. Continuous fermentation of food waste leachate for the production of volatile fatty acids and potential as a denitrification carbon source.

    Science.gov (United States)

    Kim, Hakchan; Kim, Jaai; Shin, Seung Gu; Hwang, Seokhwan; Lee, Changsoo

    2016-05-01

    This study investigated the simultaneous effects of hydraulic retention time (HRT) and pH on the continuous production of VFAs from food waste leachate using response surface analysis. The response surface approximations (R(2)=0.895, pwaste-derived VFAs, an alternative carbon source for denitrification.

  4. Modeling the Effects of Climate Change on Spatio-Temporal Dynamics of Denitrification in an Oregon Salt Marsh

    Science.gov (United States)

    The highest uncertainties in net nitrogen (N) fluxes between the atmosphere and biologically active pools are predominately due to denitrification (DeN). This diminishes confidence in our assessment of wetland N removal at transition zones between upland and aquatic systems. This...

  5. Converse Barrier Certificate Theorem

    DEFF Research Database (Denmark)

    Wisniewski, Rafael; Sloth, Christoffer

    2013-01-01

    This paper presents a converse barrier certificate theorem for a generic dynamical system.We show that a barrier certificate exists for any safe dynamical system defined on a compact manifold. Other authors have developed a related result, by assuming that the dynamical system has no singular...... points in the considered subset of the state space. In this paper, we redefine the standard notion of safety to comply with generic dynamical systems with multiple singularities. Afterwards, we prove the converse barrier certificate theorem and illustrate the differences between ours and previous work...

  6. Recycler barrier RF buckets

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, C.M.; /Fermilab

    2011-03-01

    The Recycler Ring at Fermilab uses a barrier rf systems for all of its rf manipulations. In this paper, I will give an overview of historical perspective on barrier rf system, the longitudinal beam dynamics issues, aspects of rf linearization to produce long flat bunches and methods used for emittance measurements of the beam in the RR barrier rf buckets. Current rf manipulation schemes used for antiproton beam stacking and longitudinal momentum mining of the RR beam for the Tevatron collider operation are explained along with their importance in spectacular success of the Tevatron luminosity performance.

  7. Modeling the Effects of Hydrological and Biogeochemical Processes on Denitrification and Stream Nitrogen Losses in River Networks

    Science.gov (United States)

    Alexander, R. B.; Bohlke, J. K.; Boyer, E. W.; David, M. B.; Harvey, J. W.; Mulholland, P. J.; Seitzinger, S. P.; Tobias, C. R.; Tonitto, C.; Wollheim, W. M.

    2008-12-01

    Nitrogen flux in streams is the cumulative result of biogeochemical and hydrological processes that control the supply and transport of nitrogen in terrestrial and aquatic ecosystems. These processes include the effects of denitrification on stream nitrogen removal, which influence the quantities of nitrogen delivered to downstream coastal waters, where increases in nitrogen flux have contributed to eutrophication and hypoxic conditions globally in recent decades. Despite progress in measuring and modeling stream denitrification, few studies have attempted to unravel the coupled effects of biogeochemical (nitrate loadings, concentration, temperature) and hydrological (streamflow, depth, velocity) factors on denitrification and stream nitrogen losses in river networks over space and time. We apply a dynamic nitrogen transport model to assess biogeochemical vs. hydrological effects on seasonal nitrate removal by denitrification in the river networks of two watersheds. The watershed streams have widely differing levels of nitrate concentrations, but similar flows. Unique to our model is the nonlinear dependence of stream denitrification on nitrate concentration, streamflow, and temperature, as determined by regression relations estimated from more than 300 published field measurements available for a variety of U.S. streams. We use these empirical relations to parameterize the nitrogen transport model, which was then applied to the first- through fourth-order stream reaches of the two watersheds. The model results indicate that in-stream nitrate removal by denitrification becomes less efficient as nitrate concentrations and flows increase. This is denoted by the appreciably low percentage of the in-stream nitrate flux (expressed per unit length of stream channel) that is removed in reaches during the highest nitrate concentration and flow months (Feb. to June). The importance of biogeochemical factors (which includes effects of anthropogenic nitrogen loadings, land

  8. 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

    2017-07-28

    Soil ecosystem represents the largest contributor to global nitrous oxide (N2 O) production, which is regulated by a wide variety of microbial communities in multiple biological pathways. A mechanistic understanding of these N2 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 N2 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 N2 O production, and application of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) significantly reduced the N2 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 N2 O production, and was not impacted by the application of DMPP. Our results provide robust evidence that the nitrification inhibitor DMPP can inhibit the N2 O production from nitrifier-induced denitrification, a potential significant source of N2 O production in agricultural soils. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  9. Regional oxygen reduction and denitrification rates in groundwater from multi-model residence time distributions, San Joaquin Valley, USA

    Science.gov (United States)

    Green, Christopher T.; Jurgens, Bryant C.; Zhang, Yong; Starn, J. Jeffrey; Singleton, Michael J.; Esser, Bradley K.

    2016-12-01

    Rates of oxygen and nitrate reduction are key factors in determining the chemical evolution of groundwater. Little is known about how these rates vary and covary in regional groundwater settings, as few studies have focused on regional datasets with multiple tracers and methods of analysis that account for effects of mixed residence times on apparent reaction rates. This study provides insight into the characteristics of residence times and rates of O2 reduction and denitrification (NO3- reduction) by comparing reaction rates using multi-model analytical residence time distributions (RTDs) applied to a data set of atmospheric tracers of groundwater age and geochemical data from 141 well samples in the Central Eastern San Joaquin Valley, CA. The RTD approach accounts for mixtures of residence times in a single sample to provide estimates of in-situ rates. Tracers included SF6, CFCs, 3H, He from 3H (tritiogenic He), 14C, and terrigenic He. Parameter estimation and multi-model averaging were used to establish RTDs with lower error variances than those produced by individual RTD models. The set of multi-model RTDs was used in combination with NO3- and dissolved gas data to estimate zero order and first order rates of O2 reduction and denitrification. Results indicated that O2 reduction and denitrification rates followed approximately log-normal distributions. Rates of O2 and NO3- reduction were correlated and, on an electron milliequivalent basis, denitrification rates tended to exceed O2 reduction rates. Estimated historical NO3- trends were similar to historical measurements. Results show that the multi-model approach can improve estimation of age distributions, and that relatively easily measured O2 rates can provide information about trends in denitrification rates, which are more difficult to estimate.

  10. Regional oxygen reduction and denitrification rates in groundwater from multi-model residence time distributions, San Joaquin Valley, USA

    Science.gov (United States)

    Green, Christopher T.; Jurgens, Bryant; Zhang, Yong; Starn, Jeffrey; Singleton, Michael J.; Esser, Bradley K.

    2016-01-01

    Rates of oxygen and nitrate reduction are key factors in determining the chemical evolution of groundwater. Little is known about how these rates vary and covary in regional groundwater settings, as few studies have focused on regional datasets with multiple tracers and methods of analysis that account for effects of mixed residence times on apparent reaction rates. This study provides insight into the characteristics of residence times and rates of O2 reduction and denitrification (NO3− reduction) by comparing reaction rates using multi-model analytical residence time distributions (RTDs) applied to a data set of atmospheric tracers of groundwater age and geochemical data from 141 well samples in the Central Eastern San Joaquin Valley, CA. The RTD approach accounts for mixtures of residence times in a single sample to provide estimates of in-situ rates. Tracers included SF6, CFCs, 3H, He from 3H (tritiogenic He),14C, and terrigenic He. Parameter estimation and multi-model averaging were used to establish RTDs with lower error variances than those produced by individual RTD models. The set of multi-model RTDs was used in combination with NO3− and dissolved gas data to estimate zero order and first order rates of O2 reduction and denitrification. Results indicated that O2 reduction and denitrification rates followed approximately log-normal distributions. Rates of O2 and NO3− reduction were correlated and, on an electron milliequivalent basis, denitrification rates tended to exceed O2 reduction rates. Estimated historical NO3− trends were similar to historical measurements. Results show that the multi-model approach can improve estimation of age distributions, and that relatively easily measured O2 rates can provide information about trends in denitrification rates, which are more difficult to estimate.

  11. [Vascular endothelial Barrier Function].

    Science.gov (United States)

    Ivanov, A N; Puchinyan, D M; Norkin, I A

    2015-01-01

    Endothelium is an important regulator of selective permeability of the vascular wall for different molecules and cells. This review summarizes current data on endothelial barrier function. Endothelial glycocalyx structure, its function and role in the molecular transport and leukocytes migration across the endothelial barrier are discussed. The mechanisms of transcellular transport of macromolecules and cell migration through endothelial cells are reviewed. Special section of this article addresses the structure and function of tight and adherens endothelial junction, as well as their importance for the regulation of paracellular transport across the endothelial barrier. Particular attention is paid to the signaling mechanism of endothelial barrier function regulation and the factors that influence on the vascular permeability.

  12. Barriers to Effective Listening.

    Science.gov (United States)

    Hulbert, Jack E.

    1989-01-01

    Discusses the following barriers which interfere with listening efficiency: content, speaker, medium, distractions, mindset, language, listening speed, and feedback. Suggests ways to combat these obstacles to accurate comprehension. (MM)

  13. 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.

  14. Barriers to SCM implementing

    OpenAIRE

    M.E. Rosli; B. Md Dero; A. R. Ismail; M. N. Ab Rahman

    2008-01-01

    Purpose: This paper explores the barriers faced by Malaysian manufacturing companies in successfullyimplementing the Supply Chain Management (SCM). The study has highlighted some pertinent factorsperforming the barriers that are most frequently reported by the studied companies. Sixteen companies, fromservice and manufacturing companies were studied over a period of two years to assess their SCM practicesthrough survey and interview processes.Design/methodology/approach: This part discusses t...

  15. 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...

  16. Potential of Root Exudates from Wetland Plants and Their Potential Role for Denitrification and Allelopathic Interactions

    DEFF Research Database (Denmark)

    Zhai, Xu

    vary among different Phragmites haplotypes and consequently affect their invasion potential. The studies presented in this dissertation aimed at investigating the quantity and composition of the organic carbon released in root exudates from three common wetland species as affected by temperature...... wetlands. Furthermore, environmental factors such as temperature and light-regime affect the photosynthetic carbon fixation, which continuously influence the compositions and quantity of root exudates released into rhizosphere. Conversely, root exudates from invasive species might contain some phytotoxic...... and light-regime and how the root exudates potentially affect the nitrogen removal by denitrification in constructed wetlands. Also, the studies aimed at further elucidating the potential allelopathic interaction between the plants. The findings of the research suggest that the root exudates from wetland...

  17. Impact of carbon-dosing on micro-pollutants removal in MBBR post-denitrification systems

    DEFF Research Database (Denmark)

    Escola Casas, Monica; Torresi, Elena; Plósz, Benedek G.

    Dosing of methanol or ethanol is a common practice in post-denitrification steps during wastewater treatment by MBBR technology. The carbon-dosage impact on micro- pollutants removal, in terms of type (methanol or ethanol) and concentration was investigated. First, with continuous operation...... and indigenous micro-pollutants concentrations, different methanol and ethanol dosages were used to manipulate the carbon-to-nitrate ratio in two MBBRs. Atenolol, citalopram and trimethoprim were efficiently removed in both reactors. However, type or concentration of carbon did not correlate to micro-pollutant...... the removal of such compounds. In contrast, for moderately degraded micro-pollutants, the biofilm developed under methanol dosing presented the highest removal rate constants. This might mean that the primary metabolism of methanol improved the metabolism of these micro-pollutants. In general...

  18. Impact of carbon dosing on micro-pollutants removal in MBBR post-denitrification systems

    DEFF Research Database (Denmark)

    Escola, Monica; Torresi, Elena; Gy Plósz, Benedek

    Dosing of carbon as methanol or ethanol is a common practice in post-denitrification steps during wastewater treatment by MBBR technology. The impact of the carbon dosage on micro-pollutants removal, in terms of type (methanol or ethanol) and concentration was investigated. First, with continuous...... to 53% and 30 to 100 % respectively. However, type or concentration of carbon did not lead to different micro-pollutant removal rates. Second, an anoxic-batch test with the same wastewater but containing spiked micro-pollutants (2 ng/mL) was conducted. The batch test showed that acetyl...... operation and indigenous micro-pollutants concentrations, different dosages of methanol and ethanol were used to manipulate the carbon-to-nitrate ratio in the two systems. This test revealed that atenolol, citalopram and trimethoprim were efficiently removed, with removal percentages from 56 to 98%, 17...

  19. Nitrogen fixation, denitrification, and ecosystem nitrogen pools in relation to vegetation development in the Subarctic

    DEFF Research Database (Denmark)

    Sørensen, Pernille Lærkedal; Jonasson, Sven Evert; Michelsen, Anders

    2006-01-01

    measurements of temperature, light, and soil moisture. Nitrogen fixation rate was high with seasonal input estimated at 1.1 g N m2 on frostheaved sorted circles, which was higher than the total plant N content and exceeded estimated annual plant N uptake several-fold but was lower than the microbial N content......Nitrogen (N) fixation, denitrification, and ecosystem pools of nitrogen were measured in three subarctic ecosystem types differing in soil frost-heaving activity and vegetation cover. N2-fixation was measured by the acetylene reduction assay and converted to absolute N ecosystem input by estimates...... of conversion factors between acetylene reduction and 15N incorporation. One aim was to relate nitrogen fluxes and nitrogen pools to the mosaic of ecosystem types of different stability common in areas of soil frost movements. A second aim was to identify abiotic controls on N2-fixation by simultaneous...

  20. Denitrification by plant roots? New aspects of plant plasma membrane-bound nitrate reductase.

    Science.gov (United States)

    Eick, Manuela; Stöhr, Christine

    2012-10-01

    A specific form of plasma membrane-bound nitrate reductase in plants is restricted to roots. Two peptides originated from plasma membrane integral proteins isolated from Hordeum vulgare have been assigned as homologues to the subunit NarH of respiratory nitrate reductase of Escherichia coli. Corresponding sequences have been detected for predicted proteins of Populus trichocarpa with high degree of identities for the subunits NarH (75%) and NarG (65%), however, with less accordance for the subunit NarI. These findings coincide with biochemical properties, particularly in regard to the electron donors menadione and succinate. Together with the root-specific and plasma membrane-bound nitrite/NO reductase, nitric oxide is produced under hypoxic conditions in the presence of nitrate. In this context, a possible function in nitrate respiration of plant roots and an involvement of plants in denitrification processes are discussed.

  1. CHEMICAL DENITRIFICATION OF NITRATE FROM GROUNDWATER VIA SULFAMIC ACID AND ZINC METAL

    Directory of Open Access Journals (Sweden)

    A. Sabzali, M. Gholami, A. R. Yazdanbakhsh, A. Khodadadi, B. Musavi, R. Mirzaee

    2006-07-01

    Full Text Available Nitrate contamination in drinking water can cause methemoglobinemia, which is especially detrimental to infants and nursing mothers. Batch experiments in two units for catalytic reduction of nitrate from groundwater with Zn catalyst and sulfamic acid were conducted. The system includes chemical denitriphication (ChemDen reactor and electrolytic recovery reactoers. A batch study was conducted to optimize parameters like pH, sulfamic acid concentration, Zn concentration, temperature and reaction time governing the ChemDen process. The concentrations of remained nitrate and Zn were measured at the end of the reactions. Results showed that near to 100% of nitrate decreased and the quantity of remained nitrate was <1 mg/L. pH and agitation had great effect on denitrification, and the nitrate removal rate changed rapidly when pH value ranged between 3-4. Two water quality parameters which limit this process were sulfate and chloride ions concentrations in nitrate contaminated water.

  2. Tentative Study on a New Way of Simultaneous Desulfurization and Denitrification

    Institute of Scientific and Technical Information of China (English)

    王爱杰; 杜大仲; 任南琪; 程翔; 刘春爽

    2005-01-01

    Thiobacillus denitrificans, a kind of autotrophic facultative bacteria, can oxidize sulfide into elemental sulfur or sulfate when nitrate was adopted as its electron accepter and carbon dioxide as its carbon resource under anoxic or anaerobic environment. In this way, nitrate is converted into nitrogen. In addition, Thiobacillus denitrificans can accumulate sulfur extracellularly. In this study, in a process of simultaneous desulfurization and denitrification, a strain of Thiobacillus denitrificans is employed as sulfur-producer in the treatment of wastewater containing sulfide and nitrate. The key factors affecting this process are investigated through batch tests. The experimental results indicate that the sulfide concentration and the ratio of sulfide to nitrate (S2-/NO3-) in the influent are the key factors, and their suitable values are suggested to be 5/3 and no more than 300mg·L-1, respectively, in order to achieve high conversion of sulfur.

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

    KAUST Repository

    Keuskamp, J.A.

    2012-06-01

    This paper presents a spatially explicit model for simulating the fate of nitrogen (N) in soil and groundwater and nitrous oxide (N 2O) 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 2O. 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 2O production is expected. Predicted N leaching (16% of the N inputs) and N 2O 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. © 2012 Elsevier Ltd. All rights reserved.

  4. Effect of ammonium on nitrous oxide emission during denitrification with different electron donors

    Institute of Scientific and Technical Information of China (English)

    Guangxue Wu; Xiaofeng Zhai; Chengai Jiang; Yuntao Guan

    2013-01-01

    Nitrous oxide (N2O) emission during denitrification is receiving intensive attention due to its high potential to cause greenhouse effects.In this study,denitrifiers were acclimated in sequencing batch reactors with methanol or acetate as the electron donor and nitrate as the electron acceptor.The effects of ammonium on N2O emission were examined in batch experiments with various electron donors.With the addition of ammonium,N2O emission increased under all the examined conditions compared to experiments without ammonium addition.With different electron donors,the highest ratio of N2O emission to the removed oxidized nitrogen was 0.70% for methanol,5.34% for acetate,and 34.79% for polyhydroxybutyrate.

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

    Directory of Open Access Journals (Sweden)

    Ariana E Sutton-Grier

    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.

  6. A Microbial Fuel Cell Modified with Carbon Nanomaterials for Organic Removal and Denitrification

    Directory of Open Access Journals (Sweden)

    Njud S. Alharbi

    2013-01-01

    Full Text Available This paper investigated microbial denitrification using electrochemical sources to replace organic matter as reductant. The work also involved developing a system that could be optimised for nitrate removal in applied situations such as water processing in fish farming or drinking water, where high nitrate levels represent a potential health problem. Consequently, the study examined a range of developments for the removal of nitrate from water based on the development of electrochemical biotransformation systems for nitrate removal. This also offers considerable scope for the potential application of these systems in broader bionanotechnology based processes. Furthermore, the work discussed the context of improved microbial fuel cell (MFC performance, potential analytic applications, and further innovations using a bionanotechnology approach to analyse cell-electrode interactions. High nitrate removal rate of more than 95% was successfully achieved by using a MFC system modified with carbon nanomaterials.

  7. Synergistic Pollutants Removal of the Pre-denitrification Chemical and Biological Flocculation Process

    Science.gov (United States)

    Liu, Hong-bo; Xia, Si-qing

    2010-11-01

    Based on previous studies on the chemical and biological flocculation (CBF) process and the post suspended-carrier-bed CBF process, a pre-denitrification CBF process was proposed and optimized. Pollutant removing mechanisms of the process were investigated based on COD, TN, and TP removal. Nitrogen transformation in the process was investigated and particle size distributions of influent and effluent were analyzed. Operation results show that concentrations of main pollutants such as COD, TP and NH4+-N in effluent can meet the Discharging Standards for Chinese Urban WWTPs (GB18918-2002) first grade (B) stably with a total process hydraulic retention time (HRT) as short as 6hr and poly ferric sulphate (PFS, ferrous content 18.5%) dosage amount as low as 70 mgL-1. Synergistic chemical and biological pollutants removal mechanisms of the process were also discussed.

  8. Biogas-based denitrification in a biotrickling filter: Influence of nitrate concentration and hydrogen sulfide.

    Science.gov (United States)

    López, Juan C; Porca, Estefanía; Collins, Gavin; Pérez, Rebeca; Rodríguez-Alija, Alberto; Muñoz, Raúl; Quijano, Guillermo

    2017-03-01

    The feasibility of NO3(-) removal by the synergistic action of a prevailing denitrifying anoxic methane oxidising (DAMO), and nitrate-reducing and sulfide-oxidising bacterial (NR-SOB) consortium, using CH4 and H2 S from biogas as electron donors in a biotrickling filter was investigated. The influence of NO3(-) concentration on N2 O production during this process was also evaluated. The results showed that NO3(-) was removed at rates up to 2.8 g mreactor(-3)  h(-1) using CH4 as electron donor. N2 O production rates correlated with NO3(-) concentration in the liquid phase, with a 10-fold increase in N2 O production as NO3(-) concentration increased from 50 to 200 g m(-3) . The use of H2 S as co-electron donor resulted in a 13-fold increase in NO3(-) removal rates (∼18 gNO3(-)  m(-3)  h(-1) ) and complete denitrification under steady-state conditions, which was supported by higher abundances of narG, nirK, and nosZ denitrifying genes. Although the relative abundance of the DAMO population in the consortium was reduced from 60% to 13% after H2 S addition, CH4 removals were not compromised and H2 S removal efficiencies of 100% were achieved. This study confirmed (i) the feasibility of co-oxidising CH4 and H2 S with denitrification, as well as (ii) the critical need to control NO3(-) concentration to minimize N2 O production by anoxic denitrifiers. Biotechnol. Bioeng. 2017;114: 665-673. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  9. Comparison of denitrification activity measurements in groundwater using cores and natural-gradient tracer tests

    Science.gov (United States)

    Smith, R.L.; Garabedian, S.P.; Brooks, M.H.

    1996-01-01

    The transport of many solutes in groundwater is dependent upon the relative rates of physical flow and microbial metabolism. Quantifying rates of microbial processes under subsurface conditions is difficult and is most commonly approximated using laboratory studies with aquifer materials. In this study, we measured in situ rates of denitrification in a nitrate- contaminated aquifer using small-scale, natural-gradient tracer tests and compared the results with rates obtained from laboratory incubations with aquifer core material. Activity was measured using the acetylene block technique. For the tracer tests, co-injection of acetylene and bromide into the aquifer produced a 30 ??M increase in nitrous oxide after 10 m of transport (23-30 days). An advection-dispersion transport model was modified to include an acetylene-dependent nitrous oxide production term and used to simulate the tracer breakthrough curves. The model required a 4-day lag period and a relatively low sensitivity to acetylene to match the narrow nitrous oxide breakthrough curves. Estimates of in situ denitrification rates were 0.60 and 1.51 nmol of N2O produced cm-3 aquifer day-1 for two successive tests. Aquifer core material collected from the tracer test site and incubated as mixed slurries in flasks and as intact cores yielded rates that were 1.2-26 times higher than the tracer test rate estimates. Results with the coring-dependent techniques were variable and subject to the small- scale heterogeneity within the aquifer, while the tracer tests integrated the heterogeneity along a flow path, giving a rate estimate that is more applicable to transport at the scale of the aquifer.

  10. 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).

  11. 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

  12. Can nitrogen cycle feedbacks lead to runaway denitrification and deoxygenation of the ocean?

    Science.gov (United States)

    Weber, T. S.; Deutsch, C. A.

    2014-12-01

    Over millennial timescales, the oceanic reservoir of fixed nitrogen (N) is regulated by a balance between N loss in sediments and low oxygen (O2) waters, and N2-fixation by diazotrophic phytoplankton. The two processes are coupled by selection for diazotrophs under N-limited conditions that arise from denitrification, although the spatial scale of this coupling is debated. A strong local coupling has been argued against because the export of newly fixed N would boost nearby denitrification rates, stimulating further N2-fixation in overlying water, resulting in runaway N loss and deoxygenation of the ocean. Using a global ocean circulation model with a prognostic ecosystem and biogeochemical cycles, we show that no such runaway feedback arises. Even when the majority of N2-fixation occurs directly above suboxic zones, N sources and sinks quickly reach a stable equilibrium without widespread N depletion. Taking a systems dynamics approach, we derive a "feedback factor" (f) for the interaction of N inputs and losses, which depends on the stoichiometry of diazotroph biomass, ventilation of the tropical thermocline, and upwelling rate of denitrified waters. Under modern conditions of ocean circulation and O2 solubility, f is much lower than 1 - the value that separates stable and runaway amplification of a system response - and the oceanic N reservoir is remarkably insensitive to spatial proximity of N sources and sinks, as might accompany the alleviation of diazotroph Fe-limitation. Based on these parameters, we identify climatic conditions that might push the system into a runaway feedback regime, allowing for periods of catastrophic N loss and deoxygenation during Earth's history.

  13. Biochemical and genomic analysis of the denitrification pathway within the genus Neisseria.

    Science.gov (United States)

    Barth, Kenneth R; Isabella, Vincent M; Clark, Virginia L

    2009-12-01

    Since Neisseria gonorrhoeae and Neisseria meningitidis are obligate human pathogens, a comparison with commensal species of the same genus could reveal differences important in pathogenesis. The recent completion of commensal Neisseria genome draft assemblies allowed us to perform a comparison of the genes involved in the catalysis, assembly and regulation of the denitrification pathway, which has been implicated in the virulence of several bacteria. All species contained a highly conserved nitric oxide reductase (NorB) and a nitrite reductase (AniA or NirK) that was highly conserved in the catalytic but divergent in the N-terminal lipid modification and C-terminal glycosylation domains. Only Neisseria mucosa contained a nitrate reductase (Nar), and only Neisseria lactamica, Neisseria cinerea, Neisseria subflava, Neisseria flavescens and Neisseria sicca contained a nitrous oxide reductase (Nos) complex. The regulators of the denitrification genes, FNR, NarQP and NsrR, were highly conserved, except for the GAF domain of NarQ. Biochemical examination of laboratory strains revealed that all of the neisserial species tested except N. mucosa had a two- to fourfold lower nitrite reductase activity than N. gonorrhoeae, while N. meningitidis and most of the commensal Neisseria species had a two- to fourfold higher nitric oxide (NO) reductase activity. For N. meningitidis and most of the commensal Neisseria, there was a greater than fourfold reduction in the NO steady-state level in the presence of nitrite as compared with N. gonorrhoeae. All of the species tested generated an NO steady-state level in the presence of an NO donor that was similar to that of N. gonorrhoeae. The greatest difference between the Neisseria species was the lack of a functional Nos system in the pathogenic species N. gonorrhoeae and N. meningitidis.

  14. [Denitrification and kinetic characteristics using biodegradable polymers as carbon source and biofilm carrier].

    Science.gov (United States)

    Lai, Cai-sheng; Tan, Hong-xin; Luo, Guo-zhi; Ruan, Yun-jie; Zhou, Wei; Sun, Da-chuan

    2010-08-01

    The PBS material that in the form of insoluble biodegradable polymers pellets was investigated as the solid carbon source and the biofilm carrier for nitrate removal from wastewater. The denitrification of nitrate removal and kinetic process were carried out in a packed-bed reactor in order to remove nitrate in recirculation aquaculture system. The experimental results indicated that the optimal influent loading rate was in the range of 0.107-1.098 kg/(m3 x d), when the water temperature was (29 +/- 1) degrees C and the influent nitrate concentration was in the range of 25-334 mg/L. The maximum nitrate volumetric removal rate of 0.577 kg/(m3 x d) was achieved at the influent loading rate of 1.098 kg/(m3 x d). When the influent loading rate exceeded 1.098 kg/(m3 x d), the nitrate volumetric removal rate was declined. The kinetic experimental results show that the denitrification rate of PBS as the solid carbon source and the biofilm carrier corresponds to first-order kinetics. Based on the kinetics characteristics, constants n and K used in Eckenfelder model were deduced, which can be successfully applied for the prediction of effluent nitrate concentration. The two groups' predictive values and actual values were analyzed by using SPSS 16.0 software for Paired-Samples t test analysis. The Paired-Samples t test analysis indicates that the corresponding p > 0.05 values are 0.553 and 0.632, which proved that no significant differences exist between the predictive values and actual values of the model.

  15. Denitrification in the shallow ground water of a tile-drained, agricultural watershed

    Science.gov (United States)

    Mehnert, E.; Hwang, H.-H.; Johnson, T.M.; Sanford, R.A.; Beaumont, W.C.; Holm, T.R.

    2007-01-01

    Nonpoint-source pollution of surface water by N is considered a major cause of hypoxia. Because Corn Belt watersheds have been identified as major sources of N in the Mississippi River basin, the fate and transport of N from midwestern agricultural watersheds have received considerable interest. The fate and transport of N in the shallow ground water of these watersheds still needs additional research. Our purpose was to estimate denitrification in the shallow ground water of a tile-drained, Corn Belt watershed with fine-grained soils. Over a 3-yr period, N was monitored in the surface and ground water of an agricultural watershed in central Illinois. A significant amount of N was transported past the tile drains and into shallow ground water. The ground water nitrate was isotopically heavier than tile drain nitrate, which can be explained by denitrification in the subsurface. Denitrifying bacteria were found at depths to 10 m throughout the watershed. Laboratory and push-pull tests showed that a significant fraction of nitrate could be denitrified rapidly. We estimated that the N denitrified in shallow ground water was equivalent to 0.3 to 6.4% of the applied N or 9 to 27% of N exported via surface water. These estimates varied by water year and peaked in a year of normal precipitation after 2 yr of below average precipitation. Three years of monitoring data indicate that shallow ground water in watersheds with fine-grained soils may be a significant N sink compared with N exported via surface water. ?? ASA, CSSA, SSSA.

  16. Drinking Water Denitrification using Autotrophic Denitrifying Bacteria in a Fluidized Bed Bioreactor 

    Directory of Open Access Journals (Sweden)

    Abdolmotaleb Seid-mohammadi

    2013-02-01

    Full Text Available Background and Objectives: Contamination of drinking water sources with nitrate may cause adverse effects on human health. Due to operational and maintenance problems of physicochemical nitrate removal processes, using biological denitrification processes have been performed. The aim of this study is to evaluate nitrate removal efficiency from drinking water using autotrophic denitrifying bacteria immobilized on sulfur impregnated activated carbon in a fluidized bed bioreactor. Materials and Methods: After impregnating activated carbon by sulfur as a microorganism carriers and enrichment and inoculation of denitrifying bacteria, a laboratory-scale fluidized bed bioreactor was operated. Nitrate removal efficiency, nitrite, turbidity, hardness and TOC in the effluent were examined during the whole experiment under various conditions including constant influent nitrate concentration as 90 mg NO3--N/l corresponding to different HRT ranging from 5.53 to 1.5 hr. Results: We found that  the denitrification rates was depended on the hydraulic retention time and the nitrate removal efficiency was up to 98%  and nitrite concentration was lower than 1mg/l at optimum HRT=2.4 hr respectively. Moreover, there was no difference in hardness between influent and effluent due to supplying sodium bicarbonate as carbon source for denitrifying bacteria.  However pH, TOC, hardness, and turbidity of the effluent met the W.H.O guidelines for drinking water.  Conclusion: This study demonstrated that an innovative carrier as sulfur impregnated activated carbon could be used as both the biofilm carrier and energy source for treating nitrate contaminated drinking water in the lab-scale fluidized bed bioreactor.

  17. Nitrate and nitrite inhibition of methanogenesis during denitrification in granular biofilms and digested domestic sludges.

    Science.gov (United States)

    Banihani, Qais; Sierra-Alvarez, Reyes; Field, James A

    2009-11-01

    Anaerobic bioreactors that can support simultaneous microbial processes of denitrification and methanogenesis are of interest to nutrient nitrogen removal. However, an important concern is the potential toxicity of nitrate (NO(3) (-)) and nitrite (NO(2) (-)) to methanogenesis. The methanogenic toxicity of the NO (x) (-) compounds to anaerobic granular biofilms and municipal anaerobic digested sludge with two types of substrates, acetate and hydrogen, was studied. The inhibition was the severest when the NO (x) (-) compounds were still present in the media (exposure period). During this period, 95% or greater inhibition of methanogenesis was evident at the lowest concentrations of added NO(2) (-) tested (7.6-10.2 mg NO(2) (-)-N l(-1)) or 8.3-121 mg NO(3) (-)-N l(-1) of added NO(3) (-), depending on substrate and inoculum source. The inhibition imparted by NO(3) (-) was not due directly to NO(3) (-) itself, but instead due to reduced intermediates (e.g., NO(2) (-)) formed during the denitrification process. The toxicity of NO (x) (-) was found to be reversible after the exposure period. The recovery of activity was nearly complete at low added NO (x) (-) concentrations; whereas the recovery was only partial at high added NO (x) (-) concentrations. The recovery is attributed to the metabolism of the NO (x) (-) compounds. The assay substrate had a large impact on the rate of NO(2) (-) metabolism. Hydrogen reduced NO(2) (-) slowly such that NO(2) (-) accumulated more and as a result, the toxicity was greater compared to acetate as a substrate. The final methane yield was inversely proportional to the amount of NO (x) (-) compounds added indicating that they were the preferred electron acceptors compared to methanogenesis.

  18. A Novel Teflon-membrane Gas Tension Device for Denitrification-studies in Oxygen Minimum Zones

    Science.gov (United States)

    Reed, A. C.; McNeil, C. L.; D'Asaro, E. A.; Altabet, M. A.; Johnson, B.; Bourbonnais, A.

    2014-12-01

    Oxygen Minimum Zones (OMZs) are global hotspots for the biogeochemical transformation of biologically-available forms of nitrogen to unusable nitrogen-gas. We present a new Teflon-membrane based Gas Tension Device (GTD) for measuring the excess N2 signal generated by denitrification and anammox in OMZs, with a hydrostatic pressure-independent response and a depth range from 0 - 550 m, a significant advancement from previous GTD models. The GTD consists of a 4/1000" thick by 2" diameter Teflon-membrane with a water-side plenum connected to SeaBird 5T pump. Dissolved gases in the water equilibrate across the membrane with a low-dead-volume housing connected to a high-precision quart pressure sensor. Laboratory data characterizing the GTD will be presented. The e-folding (response) time ranges from 14 min at continuous (100%) pumping to 28 min at pulse (10%) pumping. We also demonstrate the pressure dependence of the partial pressures from Henry's Law in the laboratory for pure nitrogen, pure oxygen, and standard atmospheric ratios of gases. GTD's were field tested on two floats deployed in the Eastern Tropical North Pacific (ETNP) OMZ for 15 days that targeted a productive mesoscale surface eddy originating from the Mexican coast. We anticipated that high organic carbon export should stimulate denitrification within the OMZ below. The floats profiled between the surface and 400 m depth and concurrently measured T, S, PAR, O2 (SBE 43 and Optode), and nitrate (SUNA). The N2-profiles from the GTDs are validated against independently measured N2/Ar ratio data collected during the deployment.

  19. Hedging Double Barriers with Singles

    NARCIS (Netherlands)

    Sbuelz, A.

    2000-01-01

    Double barrier options provide risk managers with good-deal flexibility in tailoring portfolio returns.Their hedges offer full protection only if unwound along the barriers.This work provides non-dynamic hedges that project the risk of double barriers on to single barriers.Non-dynamic hedges overcom

  20. Vacuum barrier for excimer lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shurter, Roger P. (Jemez Springs, NM)

    1992-01-01

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  1. Vacuum barrier for excimer lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shurter, R.P.

    1992-09-15

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput. 3 figs.

  2. Denitrification Rates and Controlling Factors for Accumulated Nitrate in the 0-12 m Intensive Farmlands: a Case Study in the North China Plain

    DEFF Research Database (Denmark)

    Yuan, H; Qin, S; Dong, W

    2017-01-01

    significantly correlated with DOC. Combining with the multiple regression analysis, it was indicated that DOC rather than DEA was the key factor regulating denitrification beneath the root zone. Additional research is required to determine if the carbon addition into the subsoil can be a promising approach......Subsoil denitrification is an important mechanism to reduce nitrate leaching into groundwater. However, regulating mechanisms of soil denitrification, especially those in the subsoil beneath the crop root zone, have not been well documented. In the current study, soil columns of 0-12 m depth were...... organic carbon (SOC), pH, denitrifying enzyme activity (DEA), and anaerobic denitrification rate (ADR) were determined. Statistical comparisons among treatments were performed. The results showed that nitrate was heavily accumulated in the entire soil profile of the N600 treatment, compared to the N0...

  3. 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

    UNLABELLED: 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. Fiftypercent inhibition of N2 and N2O production by denitrification....... 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...

  4. Anaerobic ammonium oxidation-denitrification synergistic interaction of mature landfill leachate in aged refuse bioreactor: Variations and effects of microbial community structures.

    Science.gov (United States)

    Wei, Huawei; Wang, Jie; Hassan, Muhammad; Han, Lu; Xie, Bing

    2017-07-16

    In this work, anammox-denitrification process was verified by (15)N stable isotopic tracing methods and variations and effects of microbial community structures were studied using Illumina MiSeq sequencing and Quantitative Polymerase Chain Reaction (qPCR). The results showed that higher nitrogen removal efficiency and richer microbial consortia was observed at hydraulic loading rate (HLR) of 15L/m(3)·d, BOD5/TN ratio of 0.4:1, respectively. Proteobacteria, Chloroflexi, Acidobacteria and Firmicutes were the dominant phyla in the anamox-denitrification biomass. The number of amx gene changed significantly during the HLR downshift and BOD5/TN ratio upshift period. The obtained results enhance understanding regarding the microbial community structures of anammox-denitrification bacteria in aged refuse, leading to a more effective controlling of anammox-denitrification process. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Influence of Strong Diurnal Variations in Sewage Quality on the Performance of Biological Denitrification in Small Community Wastewater Treatment Plants (WWTPs

    Directory of Open Access Journals (Sweden)

    Giordano Urbini

    2013-08-01

    Full Text Available The great diurnal variation in the quality of wastewater of small communities is an obstacle to the efficient removal of high nitrogen with traditional activated sludge processes provided by pre-denitrification. To verify this problem, the authors developed a pilot plant, in which the domestic wastewater of community of 15,000 inhabitants was treated. The results demonstrate that average and peak nitrogen removal efficiencies of over 60% and 70%, respectively, are difficult to obtain because of the strong variations in the BOD5/NO3-N ratios and the unexpected abnormal accumulation of dissolved oxygen during denitrification when the BOD5 load is low. These phenomena cause inhibitory effects and BOD5 deficiency in the denitrification process. The results demonstrate the need for a more complex approach to designing and managing small wastewater treatment plants (WWTPs provided with denitrification than those usually adopted for medium- and large-size plants.

  6. 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.

  7. Effect of Soil pH Increase by Biochar on NO, N2O and N2 Production during Denitrification in Acid Soils.

    Science.gov (United States)

    Obia, Alfred; Cornelissen, Gerard; Mulder, Jan; Dörsch, Peter

    2015-01-01

    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.

  8. Barriers to cancer screening.

    Science.gov (United States)

    Womeodu, R J; Bailey, J E

    1996-01-01

    Many barriers to cancer screening have been summarized and discussed. Barriers have been documented in all patient populations, but some groups such as ethnic minorities and the elderly face unique barriers. The barriers to cancer screening, are multifactorial, but much of the responsibility for change must lie with health care providers and the health care delivery industry. This is not to free the patient of all responsibility, but some significant barriers are beyond their direct control. Take, for example, socioeconomic status, disease knowledge, and culturally related perceptions and myths about cancer detection and treatment. The health care industry must do a better job identifying and overcoming these barriers. The significant effects of provider counseling and advice must not be underestimated. Patients must first be advised, and then further actions must be taken if they reject the screening advice. Did they refuse adherence to recommendations because they do not view themselves as susceptible, because of overwhelming personal barriers, or because of a fatalistic attitude toward cancer detection and treatment? If that is the case, physicians and health care institutions must attempt to change perceptions, educate, and personalize the message so that patients accept their disease susceptibility [table: see text]. Multiple patient and provider risk factors have been identified that can be used to target patients particularly at high risk for inadequate cancer screening and providers at high risk for performing inadequate screening. Research has clearly demonstrated the effectiveness of interventions to improve tracking of patient and physician compliance with screening recommendations. Further research is needed to show the impact of managed-care penetration and payer status on screening efforts, and incentive schemes need to be tested that reward institutions and third-party payers who develop uniform standards and procedures for cancer screening. The

  9. Seasonal variation in denitrification and dissimilatory nitrate reduction to ammonia process rates and corresponding key functional genes along an estuarine nitrate gradient

    Directory of Open Access Journals (Sweden)

    Cindy J Smith

    2015-06-01

    Full Text Available This research investigated spatial-temporal variation in benthic bacterial community structure, rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA processes and abundances of corresponding genes and transcripts at three sites – the estuary-head, mid-estuary and the estuary mouth along the nitrate gradient of the Colne estuary over an annual cycle. Denitrification rates declined down the estuary, while DNRA rates were higher at the estuary head and middle than the estuary mouth. In four out of the six two-monthly time-points, rates of DNRA were greater than denitrification at each site. Abundance of gene markers for nitrate-reduction (nitrate reductase narG and napA, denitrification (nitrite reductase nirS and DNRA (DNRA nitrite reductase nrfA declined along the estuary with significant relationships between denitrification and nirS abundance, and DNRA and nrfA abundance. Spatially, rates of denitrification, DNRA and corresponding functional gene abundances decreased along the estuary. However, temporal correlations between rate processes and functional gene and transcript abundances were not observed.

  10. Effect of nitrate and acetylene on nirS, cnorB, and nosZ expression and denitrification activity in Pseudomonas mandelii.

    Science.gov (United States)

    Saleh-Lakha, Saleema; Shannon, Kelly E; Henderson, Sherri L; Zebarth, Bernie J; Burton, David L; Goyer, Claudia; Trevors, Jack T

    2009-08-01

    Nitrate acts as an electron acceptor in the denitrification process. The effect of nitrate in the range of 0 to 1,000 mg/liter on Pseudomonas mandelii nirS, cnorB, and nosZ gene expression was studied, using quantitative reverse transcription-quantitative PCR. Denitrification activity was measured by using the acetylene blockage method and gas chromatography. The effect of acetylene on gene expression was assessed by comparing denitrification gene expression in P. mandelii culture grown in the presence or absence of acetylene. The higher the amount of NO(3)(-) present, the greater the induction and the longer the denitrification genes remained expressed. nirS gene expression reached a maximum at 2, 4, 4, and 6 h in cultures grown in the presence of 0, 10, 100, and 1,000 mg of KNO(3)/liter, respectively, while induction of nirS gene ranged from 12- to 225-fold compared to time zero. cnorB gene expression also followed a similar trend. nosZ gene expression did not respond to NO(3)(-) treatment under the conditions tested. Acetylene decreased nosZ gene expression but did not affect nirS or cnorB gene expression. These results showed that nirS and cnorB responded to nitrate concentrations; however, significant denitrification activity was only observed in culture with 1,000 mg of KNO(3)/liter, indicating that there was no relationship between gene expression and denitrification activity under the conditions tested.

  11. 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.

  12. Experimental and mechanism studies on simultaneous desulfurization and denitrification from flue gas using a flue gas circulating fluidized bed

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yi; XU PeiYao; SUN XiaoJun; WANG LiDong

    2007-01-01

    The oxidizing highly reactive absorbent was prepared from fly ash, industry lime, and an oxidizing additive M. Experiments of simultaneous desulfurization and denitrification were carried out in a flue gas circulating fluidized bed (CFB). The effects of influencing factors and calcium availability were also investigated on the removal efficiencies of desulfurization and denitrification. Removal efficiencies of 95.5% for SO2 and 64.8% for NO were obtained respectively under the optimal experimental conditions. The component of the spent absorbent was analyzed with chemical analysis methods. The results indicated that more nitrogen species appeared in the spent absorbent except sulfur species. A scanning electron microscope (SEM) and an accessory X-ray energy spectrometer were used to observe micro-properties of the samples, including fly ash, oxidizing highly reactive absorbent and spent absorbent. The simultaneous removal mechanism of SO2 and NO based on this absorbent was proposed according to the experimental results.

  13. [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.

  14. High-quality draft genome sequence of the Thermus amyloliquefaciens type strain YIM 77409(T) with an incomplete denitrification pathway.

    Science.gov (United States)

    Zhou, En-Min; Murugapiran, Senthil K; Mefferd, Chrisabelle C; Liu, Lan; Xian, Wen-Dong; Yin, Yi-Rui; Ming, Hong; Yu, Tian-Tian; Huntemann, Marcel; Clum, Alicia; Pillay, Manoj; Palaniappan, Krishnaveni; Varghese, Neha; Mikhailova, Natalia; Stamatis, Dimitrios; Reddy, T B K; Ngan, Chew Yee; Daum, Chris; Shapiro, Nicole; Markowitz, Victor; Ivanova, Natalia; Spunde, Alexander; Kyrpides, Nikos; Woyke, Tanja; Li, Wen-Jun; Hedlund, Brian P

    2016-01-01

    Thermus amyloliquefaciens type strain YIM 77409(T) is a thermophilic, Gram-negative, non-motile and rod-shaped bacterium isolated from Niujie Hot Spring in Eryuan County, Yunnan Province, southwest China. In the present study we describe the features of strain YIM 77409(T) together with its genome sequence and annotation. The genome is 2,160,855 bp long and consists of 6 scaffolds with 67.4 % average GC content. A total of 2,313 genes were predicted, comprising 2,257 protein-coding and 56 RNA genes. The genome is predicted to encode a complete glycolysis, pentose phosphate pathway, and tricarboxylic acid cycle. Additionally, a large number of transporters and enzymes for heterotrophy highlight the broad heterotrophic lifestyle of this organism. A denitrification gene cluster included genes predicted to encode enzymes for the sequential reduction of nitrate to nitrous oxide, consistent with the incomplete denitrification phenotype of this strain.

  15. 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...... an environmentally relevant ecosystem function by reducing nitrate to dinitrogen gas. Thereby, they remove inorganic nitrogen that originates from organic matter mineralisation and anthropogenic pollution. Nitrous oxide, a greenhouse gas 300 times more potent than carbon dioxide, is emitted from lakes only...... as a minor fraction of the nitrate reduced. However, when lake sediments are densely colonised by macrofauna, the rates of nitrous oxide emission increase significantly. We hypothesise that the guts of bacterivorous macrofauna represent short-term habitats in which high denitrification activity...

  16. Direct impacts of biochar on N2O production during denitrification by a soil microbial community

    Science.gov (United States)

    Mishra, Akanksha; Harter, Johannes; Hagemann, Nikolas; Kappler, Andreas

    2017-04-01

    Biochar, i.e. biomass heated under O2 limitation to 350-1000°C (pyrolysis), is suggested as a beneficial soil amendment to mitigate climate change and to maintain and restore the fertility of agro-ecosystems. Its stability enables long-term carbon sequestration and biochar effectively reduces soil-borne N2O emissions. Biochar's ability to reduce N2O emissions is well recognized through field and laboratory experiments as well as meta-analyses. However, the underlying mechanisms remain widely debated. Microbial nitrogen transformations, especially denitrification, the stepwise reduction of nitrate/nitrite via NO and N2O to N2, are considered to be a major source of N2O emissions. Soil microcosm experiments showed lower N2O emissions in the presence of biochar often correlate with a higher abundance and/or activity of N2O reducing bacteria in the presence of biochar. However, it is still unknown whether these shifts in the microbial community and/or activity is cause or effect of reduced N2O production. Biochar has the potential to change the physico-chemical environment towards conditions that favor complete denitrification, i.e. decrease the N2O/(N2O+N2) product ratio. Specifically, biochar can increase soil pH, reduce the availability of nitrate and increase the entrapment of gases, including N2O. These effects are known to decrease the N2O/(N2O+N2) ratio. In addition to the observed effects in the physio-chemical environment, we hypothesized that biochar has a direct impact on the soil microbial community. For instance, it has been shown to provide a suitable habitat to microorganisms, or facilitate electron transfer between microbe and substrates by acting as an electron shuttle or as a temporary acceptor/donor of electrons. To test this hypothesis, our experiment consisted of a microbial community extracted from soil and cultivated under anoxic conditions. It was introduced as an inoculum into three different treatments: biochar, quartz (control with a solid

  17. Anaerobic Growth of Haloarchaeon Haloferax volcanii by Denitrification Is Controlled by the Transcription Regulator NarO

    Science.gov (United States)

    Hattori, Tatsuya; Shiba, Hiromichi; Ashiki, Ken-ichi; Araki, Takuma; Nagashima, Yoh-kow; Yoshimatsu, Katsuhiko

    2016-01-01

    ABSTRACT The extremely halophilic archaeon Haloferax volcanii grows anaerobically by denitrification. A putative DNA-binding protein, NarO, is encoded upstream of the respiratory nitrate reductase gene of H. volcanii. Disruption of the narO gene resulted in a loss of denitrifying growth of H. volcanii, and the expression of the recombinant NarO recovered the denitrification capacity. A novel CXnCXCX7C motif showing no remarkable similarities with known sequences was conserved in the N terminus of the NarO homologous proteins found in the haloarchaea. Restoration of the denitrifying growth was not achieved by expression of any mutant NarO in which any one of the four conserved cysteines was individually replaced by serine. A promoter assay experiment indicated that the narO gene was usually transcribed, regardless of whether it was cultivated under aerobic or anaerobic conditions. Transcription of the genes encoding the denitrifying enzymes nitrate reductase and nitrite reductase was activated under anaerobic conditions. A putative cis element was identified in the promoter sequence of haloarchaeal denitrifying genes. These results demonstrated a significant effect of NarO, probably due to its oxygen-sensing function, on the transcriptional activation of haloarchaeal denitrifying genes. IMPORTANCE H. volcanii is an extremely halophilic archaeon capable of anaerobic growth by denitrification. The regulatory mechanism of denitrification has been well understood in bacteria but remains unknown in archaea. In this work, we show that the helix-turn-helix (HTH)-type regulator NarO activates transcription of the denitrifying genes of H. volcanii under anaerobic conditions. A novel cysteine-rich motif, which is critical for transcriptional regulation, is present in NarO. A putative cis element was also identified in the promoter sequence of the haloarchaeal denitrifying genes. PMID:26787768

  18. Biological processes for environmental control of effluent streams in the nuclear fuel cycle. [Denitrification; removal of heavy metals

    Energy Technology Data Exchange (ETDEWEB)

    Shumate, II, S E; 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/sub 2/ gas and for decreasing dissolved metal concentration to less than 1 g/m/sup 3/. Fluidized-bed denitrification bioreactors are being tested. Removal of uranium from solution by Saccharomyces cerevisiae and Pseudomonas aeruginosa was studied. (DLC)

  19. Microbiology and potential applications of aerobic methane oxidation coupled to denitrification (AME-D) process: A review.

    Science.gov (United States)

    Zhu, Jing; Wang, Qian; Yuan, Mengdong; Tan, Giin-Yu Amy; Sun, Faqian; Wang, Cheng; Wu, Weixiang; Lee, Po-Heng

    2016-03-01

    Aerobic methane oxidation coupled to denitrification (AME-D) is an important link between the global methane and nitrogen cycles. This mini-review updates discoveries regarding aerobic methanotrophs and denitrifiers, as a prelude to spotlight the microbial mechanism and the potential applications of AME-D. Until recently, AME-D was thought to be accomplished by a microbial consortium where denitrifying bacteria utilize carbon intermediates, which are excreted by aerobic methanotrophs, as energy and carbon sources. Potential carbon intermediates include methanol, citrate and acetate. This mini-review presents microbial thermodynamic estimations and postulates that methanol is the ideal electron donor for denitrification, and may serve as a trophic link between methanotrophic bacteria and denitrifiers. More excitingly, new discoveries have revealed that AME-D is not only confined to the conventional synergism between methanotrophic bacteria and denitrifiers. Specifically, an obligate aerobic methanotrophic bacterium, Methylomonas denitrificans FJG1, has been demonstrated to couple partial denitrification with methane oxidation, under hypoxia conditions, releasing nitrous oxide as a terminal product. This finding not only substantially advances the understanding of AME-D mechanism, but also implies an important but unknown role of aerobic methanotrophs in global climate change through their influence on both the methane and nitrogen cycles in ecosystems. Hence, further investigation on AME-D microbiology and mechanism is essential to better understand global climate issues and to develop niche biotechnological solutions. This mini-review also presents traditional microbial techniques, such as pure cultivation and stable isotope probing, and powerful microbial techniques, such as (meta-) genomics and (meta-) transcriptomics, for deciphering linked methane oxidation and denitrification. Although AME-D has immense potential for nitrogen removal from wastewater, drinking

  20. Aerobic respiration along isopycnals leads to overestimation of the isotope effect of denitrification in the ocean water column

    Science.gov (United States)

    Marconi, Dario; Kopf, Sebastian; Rafter, Patrick A.; Sigman, Daniel M.

    2017-01-01

    The nitrogen (N) isotopes provide an integrative geochemical tool for constraining the fixed N budget of the ocean. However, N isotope budgeting requires a robust estimate for the organism-scale nitrogen isotope effect of denitrification, in particular as it occurs in water column denitrification zones (εwcd). Ocean field data interpreted with the Rayleigh model have typically yielded estimates for εwcd of between 20 and 30‰. However, recent findings have raised questions about this value. In particular, culture experiments can produce a substantially lower isotope effect (∼13‰) under conditions mimicking those of ocean suboxic zones. In an effort to better understand prior field estimates of εwcd, we use a geochemical multi-box model to investigate the combined effects of denitrification, aerobic respiration, and isopycnal exchange on the δ15N of nitrate. In the context of this admittedly simplistic model, we consider three isopycnals extending from the Southern Ocean to the Eastern Tropical North Pacific (ETNP). We show that the data from the ETNP suboxic zone can be reproduced with an εwcd of 13‰, given a rate of aerobic respiration consistent with the nutrient data on these isopycnals and a plausible range in the δ15N of the sinking flux being remineralized. We discuss the limitations of our analysis, additional considerations, as well as possible data-based tests for the proposal of a lower εwcd than previously estimated. All else held constant, a lower εwcd would imply a lower global ocean rate of denitrification that is more similar to the estimated rate of N input to the global ocean, providing a major impetus for further investigation.

  1. Biochemical Mechanism of the Eutrophication and Its Prevention--the Deep Treatment of Waste Water and Its Denitrification and Dephosphorization

    Institute of Scientific and Technical Information of China (English)

    Li Hongshan; Li Songqiang

    2003-01-01

    Biochemical mechanism of forming the red tide is discussed in this paper. The existence of a large number of nitrates and phosphates in the eutrophic water is the prerequisite of explosive increase of algae and the forming of red tide. Reduction of eutrophication is an important approach to preventing the red tide. The method of deep treatment of the waste water and its denitrification and dephosphorization are introduced, and a new opinion on the red tide formation and fundamental prevention is put forward.

  2. Summer nitrate uptake and denitrification in an upper Mississippi River backwater lake: The role of rooted aquatic vegetation

    Science.gov (United States)

    Kreiling, Rebecca M.; Richardson, W.B.; Cavanaugh, J.C.; Bartsch, L.A.

    2011-01-01

    In-stream nitrogen processing in the Mississippi River has been suggested as one mechanism to reduce coastal eutrophication in the Gulf of Mexico. Aquatic macrophytes in river channels and flood plain lakes have the potential to temporarily remove large quantities of nitrogen through assimilation both by themselves and by the attached epiphyton. In addition, rooted macrophytes act as oxygen pumps, creating aerobic microsites around their roots where coupled nitrification-denitrification can occur. We used in situ 15N-NO3- tracer mesocosm experiments to measure nitrate assimilation rates for macrophytes, epiphyton, and microbial fauna in the sediment in Third Lake, a backwater lake of the upper Mississippi River during June and July 2005. We measured assimilation over a range of nitrate concentrations and estimated a nitrate mass balance for Third Lake. Macrophytes assimilated the most nitrate (29.5 mg N m-2 d-1) followed by sediment microbes (14.4 mg N m-2 d-1) and epiphytes (5.7 mg N m-2d-1. Assimilation accounted for 6.8% in June and 18.6% in July of total nitrate loss in the control chambers. However, denitrification (292.4 mg N m-2 d-1) is estimated to account for the majority (82%) of the nitrate loss. Assimilation and denitrification rates generally increased with increasing nitrate concentration but denitrification rates plateaued at about 5 mg N L-1. This suggests that backwaters have the potential to remove a relatively high amount of nitrate but will likely become saturated if the load becomes too large. ?? 2010 US Government.

  3. Denitrification activity is closely linked to the total ambient Fe concentration in mangrove sediments of Goa, India

    Digital Repository Service at National Institute of Oceanography (India)

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

    (Corredor and Morell, 1994) or wastewater treatment (Nedwell, 1975). Chiu et al. (2004) have quantified denitrification and assessed the factors affecting the process in temperate mangrove sediment. Some of the factors influencing the activity...; Corredor and Morell, 1994; Kana et al., 1998) and organic carbon (Mc Carty and Bremner, 1993; Pfenning and Mc Mahon 1997; Ward et al., 2008). Earlier studies in the mangrove swamps of Goa have shown trace metal contamination derived mainly from ferro...

  4. Support or Barrier?

    DEFF Research Database (Denmark)

    Sanden, Guro Refsum; Lønsmann, Dorte

    This study offers a critical look at how corporate-level language management influences front-line language practices among employees in three multinational corporations (MNCs) headquartered in Scandinavia. Based on interview and document data, we examine, firstly, what front-line practices emplo...... to a discussion of how a company’s language policy may be seen as both support and a barrier....

  5. Overcoming Language Barriers

    Science.gov (United States)

    De Buda, Yvonne

    1976-01-01

    Many family physicians in Canada experience language and cultural barriers between themselves and their patients. Several aspects of the ensuing problems are described and some practical suggestions for solutions are made. The importance of health education for new Canadians in the family physician's office as well as through the media and community projects is stressed. Imagesp68-ap68-bp70-a PMID:21308059

  6. Barriers to obesity treatment.

    Science.gov (United States)

    Mauro, Marina; Taylor, Valerie; Wharton, Sean; Sharma, Arya M

    2008-05-01

    Obesity, one of the most prevalent health problems in the Western world, is a chronic and progressive condition. Therefore, as with other chronic diseases, patients with obesity require lifelong treatment. Long-term efficacy and effectiveness of obesity treatments is notoriously poor. This may in part be attributable to the substantial barriers that undermine long-term obesity management strategies. These can include lack of recognition of obesity as a chronic condition, low socioeconomic status, time constraints, intimate saboteurs, and a wide range of comorbidities including mental health, sleep, chronic pain, musculoskeletal, cardiovascular, respiratory, digestive and endocrine disorders. Furthermore, medications used to treat some of these disorders may further undermine weight-loss efforts. Lack of specific obesity training of health professionals, attitudes and beliefs as well as coverage and availability of obesity treatments can likewise pose important barriers. Health professionals need to take care to identify, acknowledge and address these barriers where possible to increase patient success as well as compliance and adherence with treatments. Failure to do so may further undermine the sense of failure, low self esteem and self efficacy already common among obese individuals. Addressing treatment barriers can save resources and increase the prospect of long-term success.

  7. Nanosized iron based permeable reactive barriers for nitrate removal - Systematic review

    Science.gov (United States)

    Araújo, Rui; Castro, Ana C. Meira; Santos Baptista, João; Fiúza, António

    2016-08-01

    It is unquestionable that an effective decision concerning the usage of a certain environmental clean-up technology should be conveniently supported. Significant amount of scientific work focussing on the reduction of nitrate concentration in drinking water by both metallic iron and nanomaterials and their usage in permeable reactive barriers has been worldwide published over the last two decades. This work aims to present in a systematic review of the most relevant research done on the removal of nitrate from groundwater using nanosized iron based permeable reactive barriers. The research was based on scientific papers published between 2004 and June 2014. It was performed using 16 combinations of keywords in 34 databases, according to PRISMA statement guidelines. Independent reviewers validated the selection criteria. From the 4161 records filtered, 45 met the selection criteria and were selected to be included in this review. This study's outcomes show that the permeable reactive barriers are, indeed, a suitable technology for denitrification and with good performance record but the long-term impact of the use of nanosized zero valent iron in this remediation process, in both on the environment and on the human health, is far to be conveniently known. As a consequence, further work is required on this matter, so that nanosized iron based permeable reactive barriers for the removal of nitrate from drinking water can be genuinely considered an eco-efficient technology.

  8. 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

  9. The contribution of anammox and denitrification to sediment N2 production in a surface flow constructed wetland.

    Science.gov (United States)

    Erler, Dirk V; Eyre, Bradley D; Davison, Leigh

    2008-12-15

    This study used anaerobic slurry assays and intact core incubations to quantify potential rates of anammox (anaerobic ammonia oxidation) in sediments along the flow path of a surface flow constructed wetland receiving secondary treated sewage effluent. Anammox occurred at two of the four sites assayed with a maximum rate of 199.4 +/- 18.7 micromol N x m(-2) x hr(-1) (24% of total N2 production) at the discharge end of the wetland. Denitrification was the major producer of N2, with a maximum rate of 965.3 +/- 122.8 micromol N x m(-2) x hr(-1) at site 2. Oxygen was probably the key regulator of anammox activity within the studied CW. In addition to anammox, we found evidence that nitrifier-denitrification was potentially responsible for the production of N2O. Total production of N2O was 15.1% of the total gaseous N produced. Limitations to the methodology for quantifying anammox in CW's are outlined. This study demonstrated that denitrification is not the only pathway for gaseous production in constructed wetlands and that wetlands may be significant sources of greenhouse gases such as N2O.

  10. Nitrification and denitrification in two-chamber microbial fuel cells for treatment of wastewater containing high concentrations of ammonia nitrogen.

    Science.gov (United States)

    Du, Haixia; Li, Fusheng; Yu, Zaiji; Feng, Chunhua; Li, Wenhan

    2016-01-01

    Simultaneous nitrification and denitrification in the aerated cathode chamber of microbial fuel cells (MFCs) inoculated with nitrifying bacteria were investigated using two-chamber MFCs. Based on the variations of [Formula: see text], [Formula: see text] and [Formula: see text] in the cathode chamber of four MFCs added with different concentrations of [Formula: see text] (50, 65, 130 and 230 mg/L), the occurrence of simultaneous nitrification and denitrification leading to effective removal of nitrogen was confirmed. Electrochemical reaction with electrons transferred from the anode chamber was found to be the major mechanism responsible for the removal of [Formula: see text] in the cathode chamber. The estimated values of the first-order rate constant for nitrification and denitrification varied in the range of 0.3-1.7 day(-1) and 0.2-0.9 day(-1), revealing a decreasing trend with increases in the initial [Formula: see text] concentrations and the detected maximum concentration of the nitrification product of [Formula: see text] in the cathode chamber, respectively.

  11. Assessment of a bioaugmentation strategy with polyphosphate accumulating organisms in a nitrification/denitrification sequencing batch reactor.

    Science.gov (United States)

    Tayà, Carlota; Guisasola, Albert; Baeza, Juan A

    2011-09-01

    Different alternative configurations and strategies for the simultaneous biological removal of organic matter and nutrients (N and P) in wastewater have been proposed in the literature. This work demonstrates a new successful strategy to bring in enhanced biological phosphorus removal (EBPR) to a conventional nitrification/denitrification system by means of bioaugmentation with an enriched culture of phosphorus accumulating organisms (PAO). This strategy was tested in a sequencing batch reactor (SBR), where an 8h configuration with 3h anoxic, 4.5h aerobic and 25 min of settling confirmed that nitrification, denitrification and PAO activity could be maintained for a minimum of 60 days of operation after the bioaugmentation step. The successful bioaugmentation strategy opens new possibilities for retrofitting full-scale WWTP originally designed for only nitrification/denitrification. These systems could remove P simultaneously to COD and N if they were bioaugmented with waste purge of an anaerobic/aerobic SBR operated in parallel treating part of the influent wastewater.

  12. The acetylene inhibition technique to determine total denitrification (N2 + N2O losses from soil samples: potentials and limitations

    Directory of Open Access Journals (Sweden)

    A. Neftel

    2012-03-01

    Full Text Available The loss of N2 from intensively managed agro-ecosystems is an important part of the N budget. The monitoring of N2 emissions at the field scale is impossible due to the high atmospheric background of 78%, which precludes the measurement of fluxes. The acetylene (C2H2 inhibition technique is a rather simple, albeit imperfect, method to determine N2 losses from entire soil cores. Despites serious limitations it is one among very few methodological options to estimate total denitrification at high temporal resolution and on small spatial scale, with limited workload and costs involved. A laboratory system with two different detection systems (photoacoustic IR spectroscopy and gas chromatography is presented, which allowed parallel measurements of up to 7 intact soil cores in air-tight glass tubes in a temperature controlled cabinet (adjusted to field conditions with an automated C2H2 injection. A survey of total denitrification losses (N2 + N2O over 1.5 yr in soil from an intensively managed, cut grassland system in central Switzerland showed a lower bound loss in the range of 6 to 25 kg N ha−1 yr−1 (3–13% of added N, roughly 3.4 times higher than the N2O loss. However, several drawbacks of the C2H2 inhibition technique preclude a more precise determination of the total denitrification loss.

  13. Removal of organic matter and nitrogen from distillery wastewater by a combination of methane fermentation and denitrification/nitrification processes

    Institute of Scientific and Technical Information of China (English)

    LI Jun; ZHANG Zhen-jia; LI Zhi-rong; HUANG Guang-yu; Naoki Abe

    2006-01-01

    The distillery wastewater of Guangdong Jiujiang Distillery, which is characteristic of containing high organic matters and rich total nitrogen, was treated by a combination of methane fermentation and denitrification/nitrification processes. 80% of COD in the raw wastewater was However, almost all the organic nitrogen in the raw wastewater was converted into ammonia by ammonification there. Ammonia and volatile fatty acids (VFA) remaining in the anaerobically treated wastewater were simultaneously removed utilizing VFA as an electron donor by denitrification occurring in the other EGSB reactor and nitrification using PEG-immobilized nitrifying bacteria with recirculation process. An aerobic biological contact oxidization reactor was designed between denitrification/nitrification reactor for further COD removal. With the above treatment system,18000-28000 mg/L of COD in raw wastewater was reduced to less than 100 mg/L. Also, ammonia in the effluent of the system was not detected and the system had a high removal rate for 900-1200 mg/L of TN in the raw wastewater, only leaving 400 mg/L of nitrate nitrogen.

  14. Estimate of denitrifying microbiota in tertiary sewage treatment and kinetics of the denitrification process using different sources of carbon

    Directory of Open Access Journals (Sweden)

    Marchetto Margarida

    2003-01-01

    Full Text Available A study of the kinetics of denitrification was carried out in the laboratory based on the quantification of N2O, the final product of the activity of denitrifying microorganisms, when the enzymatic reduction of N2O to N2 was blocked by acetylene. Concentrated mixed liquor (sludge from a reactor with intermittent aeration used for sewage treatment was used as the inoculum, while methanol, acetic acid, glucose, effluent sewage from an anaerobic fluidized bed reactor and synthetic substrate simulating domestic sewage were used as carbon sources. The mean concentration of nitrate was 20 mg/L. Maxima of N2O production and NO3- consumption occurred between 0.5h and 2.0h of incubation using all the carbon sources, which characterized the denitrification process. Acetic acid and methanol were responsible for the highest rates of N2O production. The estimated number of denitrifying microorganisms in the reactor with intermittent aeration, using the MPN technique, varied from 10(9 to 10(10 MPN/g VSS, indicating a high potential for the occurrence of denitrification.

  15. Reducing NO and N₂O emission during aerobic denitrification by newly isolated Pseudomonas stutzeri PCN-1.

    Science.gov (United States)

    Zheng, Maosheng; He, Da; Ma, Tao; Chen, Qian; Liu, Sitong; Ahmad, Muhammad; Gui, Mengyao; Ni, Jinren

    2014-06-01

    As two obligatory intermediates of denitrification, both NO and N2O had harmful environmental and biological impacts. An aerobic denitrifying bacterial strain PCN-1 was newly isolated and identified as Pseudomonas stutzeri, which was capable of high efficient nitrogen removal under aerobic condition with maximal NO and N2O accumulation as low as 0.003% and 0.33% of removed NO3(-)-N, respectively. Further experiment taking nitrite as denitrifying substrate indicated similar low NO and N2O emission of 0.006% and 0.29% of reduced NO2(-)-N, respectively. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that the coordinate expression of denitrification gene nirS (for cytochrome cd1 nitrite reductase), cnorB (for NO reductase) and nosZ (for N2O reductase) was the fundamental reason of low NO and N2O accumulation. Activated sludge system bioaugmented by strain PCN-1 demonstrated a significant reduction of NO and N2O emission from wastewater during aerobic denitrification, implied great potential of PCN-1 in practical applications.

  16. Genetic associations as indices of nitrogen cycling rates in an aerobic denitrification biofilter used for groundwater remediation.

    Science.gov (United States)

    Zhang, Yan; Ji, Guodong; Wang, Rongjing

    2015-10-01

    An aerobic denitrification biofilter (ADB) for groundwater remediation was developed with high removal efficiencies (total nitrogen (TN): 82.3-95.8%; NO3(-)-N: 93.2-98.2%). Nitrate (NO3(-)-N) transformation rates stabilized between 21.0 and 23.4 g/(m(3) h), whereas nitrite (NO2(-)-N) and ammonium (NH4(+)-N) transformation rates remained less than 6.0 g/(m(3) h) as the dissolved oxygen (DO) level increased from 1.0 mg/L to 6.0 mg/L. Nitric oxide (NO) and nitrous oxide (N2O) accumulated with great fluctuations (NO: 0-1.6×10(-3) g/(m(3) h); N2O: 0.1-1.1g/(m(3)h)) throughout the experiment. This study suggested that gene associations reflect quantitative relationships with aerobic denitrification rates and can provide useful information regarding aerobic denitrification processes in groundwater. Especially, the qnorB/nosZ ratio acts as the main driver for NO3(-)-N and NH4(+)-N transformation, while the qnorB/nosZ ratio followed by the (nirS+nirK)/nosZ ratio serve a dominant role in the accumulation of N2O and NO. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Technical and economic analysis of real anaerobic digester centrate by means of partial nitrification and sustainable heterotrophic denitrification.

    Science.gov (United States)

    Bartrolí, A; Garcia-Belinchón, C; Hidalgo, J M; Rougé, P; Fàbregas, C; Fortuny, M; Lafuente, J; Prado, Ó J

    2013-01-01

    The reliability of partial nitrification coupled with heterotrophic denitrification for the treatment of real anaerobic digester centrate produced in a wastewater treatment plant was technically and economically assessed in two sequencing batch reactors. Removal efficiencies above 90% were consistently achieved at N-ammonium loads above 1.2 g N L⁻¹ d⁻¹. Ethanol, affluent from a waste water treatment plant (biological treatment inlet) and a zero-cost liquid residue from a chemical industry containing polyethylene glycol and sorbitol were employed as carbon source for denitrification. In this last case, a total organic carbon (TOC) requirement of 4.5 g TOC g⁻¹ NO₂⁻-N was calculated. The denitrification rate was 0.26 g NO₂⁻-N g VSS⁻¹ d⁻¹ (VSS: volatile suspended solids). These results show that a carbon-rich waste can serve as a no-cost feed for denitrifying bioreactors. An in-depth economic analysis considering the main investment and operating costs of the process was developed, showing that it can suppose yearly savings above 50% with respect to the most widely used alternative of returning anaerobic digester centrate untreated to the head of the facility.

  18. Quantitative importance of denitrification and N2O emission in an N-saturated subtropical forest catchment, southwest China

    Science.gov (United States)

    Zhu, J.; Dörsch, P.; Mulder, J.

    2009-04-01

    Anthropogenic emission of nitrogen in the environment has increased rapidly, due to fast economic growth. This has resulted in increased deposition rates of reactive nitrogen, primarily as NOx (from fossil fuel combustion) and NH3 (from fertilizer production and animal husbandry). In response, temperate and boreal forests may develop nitrogen saturation, characterized by increased leaching of nitrate. In addition, elevated emission of N2 and N2O, due to nitrification and denitrification, may occur. To date, few studies exist quantifying the nitrogen balance, including N2 and N2O production, in nitrogen-saturated, monsoonal, sub-tropical forest ecosystems in south-west China. Since nitrate contributes to the eutrophication of stream water, and N2O is a potent greenhouse gas, it is important to quantitatively understand the role of nitrification and denitrification in the nitrogen cycle. Several subtropical forests in southwest China, receiving elevated nitrogen deposition (30-73 kg N ha-1 a-1; Zhang. et al., 2008), are characterized by high temperature and soil moisture content in much of the growing season. This may cause a much stronger intensity of denitrification compared with that in temperate and boreal forests. In turn this may lead to decreased nitrate leaching and a higher potential of N2O emission. In my PhD project, I will investigate the nitrogen cycle in a forest catchment (TieShanPing; TSP), which is near one of the biggest cities, Chongqing, in southwest China. Previous research suggests high nitrogen deposition (3.52 gN m-2 a-1), but low nitrogen flux (0.57 gN m-2 a-1) in runoff (Chen & Mulder, 2007). Tree growth, and thus plant N uptake, is limited and nitrate fluxes below the root zone are relatively large, suggesting ‘N-saturation'. Based on this, we hypothesize that significant amounts of nitrogen are emitted as gases, with denitrification playing an important role, and N2 and N2O (especially N2) being major components of the emitted gases

  19. Removal of organic matter and nitrogen from distillery wastewater by a combination of methane fermentation and denitrification/nitrification processes.

    Science.gov (United States)

    Li, Jun; Zhang, Zhen-jia; Li, Zhi-rong; Huang, Guang-yu; Abe, Naoki

    2006-01-01

    The distillery wastewater of Guangdong Jiujiang Distillery, which is characteristic of containing high organic matters and rich total nitrogen, was treated by a combination of methane fermentation and denitrification/nitrification processes. 80% of COD in the raw wastewater was removed by methane fermentation at the COD volumetric loading rate of 20 kg COD/(m3 x d) using the expanded granule sludge bed (EGSB) process. However, almost all the organic nitrogen in the raw wastewater was converted into ammonia by ammonification there. Ammonia and volatile fatty acids (VFA) remaining in the anaerobically treated wastewater were simultaneously removed utilizing VFA as an electron donor by denitrification occurring in the other EGSB reactor and nitrification using PEG-immobilized nitrifying bacteria with recirculation process. An aerobic biological contact oxidization reactor was designed between denitrification/nitrification reactor for further COD removal. With the above treatment system, 18000-28000 mg/L of COD in raw wastewater was reduced to less than 100 mg/L. Also, ammonia in the effluent of the system was not detected and the system had a high removal rate for 900-1200 mg/L of TN in the raw wastewater, only leaving 400 mg/L of nitrate nitrogen.

  20. Study on Reaction Activity of SCR Denitrification Catalyst%SCR脱硝催化剂反应活性探讨

    Institute of Scientific and Technical Information of China (English)

    春国成

    2015-01-01

    随着我国对环保要求以及对氮氧化物排放指标要求的不断提高,SCR脱硝技术在我国得到了广泛的应用,SCR脱硝催化剂性能的好坏直接关系到脱硝系统的运行效果。通过对实际生产中因积灰堵塞、磨损和中毒使催化剂失活的原因分析,提出在设计和运行等方面的优化措施,以期能对延长催化剂寿命、降低运行费用提供参考。%With the continuous improvement of environmental protection requirements and the requirements of nitro-gen oxide emissions, the SCR denitrification technology has been widely used in our country. The performance of SCR deni-trification catalyst is directly related to the operating effect of denitrification system. Through the analysis of the causes of cat-alyst deactivation due to fouling, wear and poisoning, the optimization measures are put forward in the design and operation.

  1. Perturbation-free measurement of in situ di-nitrogen emissions from denitrification in nitrate-rich aquatic ecosystems.

    Science.gov (United States)

    Qin, Shuping; Clough, Timothy; Luo, Jiafa; Wrage-Mönnig, Nicole; Oenema, Oene; Zhang, Yuming; Hu, Chunsheng

    2017-02-01

    Increased production of reactive nitrogen (Nr) from atmospheric di-nitrogen (N2) has greatly contributed to increased food production. However, enriching the biosphere with Nr has also caused a series of negative effects on global ecosystems, especially aquatic ecosystems. The main pathway converting Nr back into the atmospheric N2 pool is the last step in the denitrification process. Despite several attempts, there is still a need for perturbation-free methods for measuring in situ N2 fluxes from denitrification in aquatic ecosystems at the field scale. Such a method is needed to comprehensively quantify the N2 fluxes from aquatic ecosystems. Here we observed linear relationships between the δ(15)N-N2O signatures and the logarithmically transformed N2O/(N2+N2O) emission ratios. Through independent measurements, we verified that the perturbation-free N2 flux from denitrification in nitrate-rich aquatic ecosystems can be inferred from these linear relationships. Our method allowed the determination of field-scale in situ N2 fluxes from nitrate-rich aquatic ecosystems both with and without overlaying water. The perturbation-free in situ N2 fluxes observed by the new method were almost one order of magnitude higher than those by the sediment core method. The ability of aquatic ecosystems to remove Nr may previously have been severely underestimated. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Toxicity of fungicides to natural bacterial communities in wetland water and sediment measured using leucine incorporation and potential denitrification.

    Science.gov (United States)

    Milenkovski, Susann; Bååth, Erland; Lindgren, Per-Eric; Berglund, Olof

    2010-02-01

    We assessed potential toxicity of fungicides to natural bacterial communities from a constructed wetland, located in southern Sweden, and compared the sensitivity of two endpoints indicating bacterial activity, leucine incorporation, and potential denitrification, in detecting toxicity. The effects of eight fungicides (benomyl, carbendazim, carboxin, captan, cycloheximide, fenpropimorph, propiconazole, and thiram), two bactericides (bronopol and chlortetracycline) as controls, and one reference compound (3,5-dichlorophenol), were tested in a water-sediment microcosm set-up. Leucine incorporation was measured in both the water and sediment column, while potential denitrification was measured for the entire microcosm. The bactericides and the reference compound gave sigmoid concentration-response curves for both endpoints in all but one case. The fungicides thiram, captan, and benomyl, and to a lesser extent fenpropimorph and propiconazole had quantifiable toxic effects on leucine incorporation, with EC(50) values ranging from 3 to 70 mg l(-1), while carbendazim, carboxin, and cycloheximide had little effect at the investigated concentrations. Only thiram and captan inhibited potential denitrification; the other fungicides showed no quantifiable effect. A greater toxic effect on leucine incorporation was recorded for bacterial communities associated with the water column, compared to the sediment column, for all tested compounds. Leucine incorporation was the more sensitive method for toxicity assessment of bacterial communities, and also allowed for a rapid and simple way of comparing exposure in the sediment and water column, making it an attractive standard method for community based toxicological assays in aquatic environments.

  3. Barrier mechanisms in the Drosophila blood-brain barrier

    OpenAIRE

    Samantha Jane Hindle; Roland Jerome Bainton

    2014-01-01

    The invertebrate blood-brain barrier field is growing at a rapid pace and, in recent years, studies have shown a physiologic and molecular complexity that has begun to rival its vertebrate counterpart. Novel mechanisms of paracellular barrier maintenance through GPCR signaling were the first demonstrations of the complex adaptive mechanisms of barrier physiology. Building upon this work, the integrity of the invertebrate blood-brain barrier has recently been shown to require coordinated funct...

  4. Geophysical characterization of subsurface barriers

    Energy Technology Data Exchange (ETDEWEB)

    Borns, D.J.

    1995-08-01

    An option for controlling contaminant migration from plumes and buried waste sites is to construct a subsurface barrier of a low-permeability material. The successful application of subsurface barriers requires processes to verify the emplacement and effectiveness of barrier and to monitor the performance of a barrier after emplacement. Non destructive and remote sensing techniques, such as geophysical methods, are possible technologies to address these needs. The changes in mechanical, hydrologic and chemical properties associated with the emplacement of an engineered barrier will affect geophysical properties such a seismic velocity, electrical conductivity, and dielectric constant. Also, the barrier, once emplaced and interacting with the in situ geologic system, may affect the paths along which electrical current flows in the subsurface. These changes in properties and processes facilitate the detection and monitoring of the barrier. The approaches to characterizing and monitoring engineered barriers can be divided between (1) methods that directly image the barrier using the contrasts in physical properties between the barrier and the host soil or rock and (2) methods that reflect flow processes around or through the barrier. For example, seismic methods that delineate the changes in density and stiffness associated with the barrier represents a direct imaging method. Electrical self potential methods and flow probes based on heat flow methods represent techniques that can delineate the flow path or flow processes around and through a barrier.

  5. Coupling autotrophic denitrification with partial nitritation-anammox (PNA) for efficient total inorganic nitrogen removal.

    Science.gov (United States)

    Dasgupta, Sunayna; Wu, Sha; Goel, Ramesh

    2017-06-27

    The performance of and the microbial ecology in an integrated lab scale set up comprising of a PN/A bioreactor and an elemental sulfur-supported packed bed autotrophic denitrification (ESSAD) are reported. The PN/A reactor exhibited an average removal rate of 0.56±0.103kgNm(-3)d(-1), whereas the ESSAD reactor removed an average of 0.0018kg NO3(-)-Nm(-3)d(-1). The combined average removal rate was 0.6kgNm(-3)d(-1), yielding an overall total inorganic nitrogen efficiency of 97%. Based on 16S rRNA gene clone libraries from the ESSAD reactor, the extracted Operational Taxonomic Units (OTUs) formed a clade with Thiobacillus denitrificans sp. indicating a common ancestral relationship. High throughput amplicon sequencing targeting V3 region of 16S rRNA gene for the biofilm in the ESSAD also revealed an abundance of the Thiobacillus genus. Additionally, 16s rRNA amplicon sequencing of the genomic DNA from the PN/A reactor reflected a dominance of the Planctomycetes phylum. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. 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).

  7. Denitrification in a deep basalt aquifer: implications for aquifer storage and recovery.

    Science.gov (United States)

    Nelson, Dennis; Melady, Jason

    2014-01-01

    Aquifer storage and recovery (ASR) can provide a means of storing water for irrigation in agricultural areas where water availability is limited. A concern, however, is that the injected water may lead to a degradation of groundwater quality. In many agricultural areas, nitrate is a limiting factor. In the Umatilla Basin in north central Oregon, shallow alluvial groundwater with elevated nitrate-nitrogen of 9 mg/L is injected into the Columbia River Basalt Group (CRBG), a transmissive confined aquifer(s) with low natural recharge rates. Once recovery of the injected water begins, however, NO3 -N in the recovered water decreases quickly to storage. In contrast to NO3 -N, other constituents in the recovered water show little variation, inconsistent with migration or simple mixing as an explanation of the NO3 -N decrease. Nitrogen isotopic ratios (δ(15) N) increase markedly, ranging from +3.5 to > +50, and correlate inversely with NO3 -N concentrations. This variation occurs in recovery of aquifer, averaging 3.0 mg/L. Similar to nitrate concentrations, TOC drops in the recovered water, consistent with this component contributing to the denitrification of nitrate during storage.

  8. Eubacteria and Archaea community of simultaneous methanogenesis and denitrification granular sludge

    Institute of Scientific and Technical Information of China (English)

    SUN Yujiao; ZUO Jiane; CHEN Lili; WANG Yong

    2008-01-01

    Based on the successful performance of a lab-scale upflow anaerobic sludge blanket (UASB) reactor with the capacity of simultaneous methanogenesis and denitrification (SMD), the specific phylogenetic groups and community structure of microbes in the SMD granule in the UASB reactor were investigated by the construction of the Eubacteria and Archaea 16S rDNA clone libraries, fragment length polymorphism, and sequence blast. Real time quantitative-polymerase chain reaction (RTQ-PCR) technique was used to quantify the contents of Eubacteria and Archaea in the SMD granule. The contents of some special predominant methanogens were also investigated. The results indicated that the Methanosaeta and Methanobacteria were the predominant methanogens in all Archaea in the SMD granule, with contents of 71. 59% and 22. 73% in all 88 random Archaea clones, respectively. The diversity of Eubacteria was much more complex than that of Archaea. The low GC positive gram bacteria and Б-Protebacteria were the main predominant Eubacteria species in SMD granule, their contents were 49. 62% and 12. 03% in all 133 random Eubacteria clones respectively. The results of RTQ-PCR indicated that the content of Archaea was less than Eubacteria, the Archaea content in total microorganisms in SMD granule was about 27. 6%.

  9. 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.

  10. Nitrate removal from groundwater driven by electricity generation and heterotrophic denitrification in a bioelectrochemical system.

    Science.gov (United States)

    Tong, Yiran; He, Zhen

    2013-11-15

    This research aims to develop a new approach for in situ nitrate removal from groundwater by using a bioelectrochemical system (BES). The BES employs bioelectricity generated from organic compounds to drive nitrate moving from groundwater into the anode and reduces nitrate to nitrogen gas by heterotrophic denitrification. This laboratory study of a bench-scale BES demonstrated effective nitrate removal from both synthetic and actual groundwater. It was found that applying an electrical potential improved the nitrate removal and the highest nitrate removal rate of 208.2 ± 13.3g NO3(-)-Nm(-3) d(-1) was achieved at 0.8 V. Although the open circuit condition (no electricity generation) still resulted in a nitrate removal rate of 158.5 ± 4.2 gm(-3) d(-1) due to ion exchange, electricity production could inhibit ion exchange and prevent introducing other undesired ions into groundwater. The nitrate removal rate exhibited a linear relationship with the initial nitrate concentration in groundwater. The BES produced a higher current density of 33.4 Am(-3) and a higher total coulomb of 244.7 ± 9.1C from the actual groundwater than the synthetic groundwater, likely because other ions in the actual groundwater promoted ion movement to assist electricity generation. Further development of this BES will need to address several key challenges in anode feeding solution, ion competition, and long-term stability.

  11. 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.

  12. 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.

  13. Investigating the nitrification and denitrification kinetics under aerobic and anaerobic conditions by Paracoccus denitrificans ISTOD1.

    Science.gov (United States)

    Medhi, Kristina; Singhal, Anjali; Chauhan, D K; Thakur, Indu Shekhar

    2017-03-16

    Municipal wastewater contains multiple nitrogen contaminants such as ammonia, nitrate and nitrite. Two heterotrophic nitrifier and aerobic denitrifiers, bacterial isolates ISTOD1 and ISTVD1 were isolated from domestic wastewater. On the basis of removal efficiency of ammonia, nitrate and nitrite under both aerobic and anaerobic conditions, ISTOD1 was selected and identified as Paracoccus denitrificans. Aerobically, NH4(+)-N had maximum specific nitrogen removal rate (Rxi) of 7.6g/gDCW/h and anaerobically, NO3(-)N showed Rxi of 2.5*10(-1)g/g DCW/h. Monod equation described the bioprocess kinetic coefficients, µmax and Ks, obtained by regression. Error functions were calculated to validate the Monod equation experimental data. Aerobic NO3(-)N showed the highest YW of 0.372mg DCW/mg NO3(-)N among the five conditions. ISTOD1 serves as a potential candidate for treating nitrogen rich wastewater using simultaneous nitrification and aerobic denitrification. It can be used in bioaugmentation studies under varied condition.

  14. Biological Denitrification of High Nitrate Processing Wastewaters from Explosives Production Plant.

    Science.gov (United States)

    Cyplik, Paweł; Marecik, Roman; Piotrowska-Cyplik, Agnieszka; Olejnik, Anna; Drożdżyńska, Agnieszka; Chrzanowski, Lukasz

    2012-05-01

    Wastewater samples originating from an explosives production plant (3,000 mg N l(-1) nitrate, 4.8 mg l(-1) nitroglycerin, 1.9 mg l(-1) nitroglycol and 1,200 mg l(-1) chemical oxygen demand) were subjected to biological purification. An attempt to completely remove nitrate and to decrease the chemical oxygen demand was carried out under anaerobic conditions. A soil isolated microbial consortium capable of biodegrading various organic compounds and reduce nitrate to atmospheric nitrogen under anaerobic conditions was used. Complete removal of nitrates with simultaneous elimination of nitroglycerin and ethylene glycol dinitrate (nitroglycol) was achieved as a result of the conducted research. Specific nitrate reduction rate was estimated at 12.3 mg N g(-1) VSS h(-1). Toxicity of wastewater samples during the denitrification process was studied by measuring the activity of dehydrogenases in the activated sludge. Mutagenicity was determined by employing the Ames test. The maximum mutagenic activity did not exceed 0.5. The obtained results suggest that the studied wastewater samples did not exhibit mutagenic properties.

  15. Mineralization of RDX-derived nitrogen to N2 via denitrification in coastal marine sediments.

    Science.gov (United States)

    Smith, Richard W; Tobias, Craig; Vlahos, Penny; Cooper, Christopher; Ballentine, Mark; Ariyarathna, Thivanka; Fallis, Stephen; Groshens, Thomas J

    2015-02-17

    Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a common constituent of military explosives. Despite RDX contamination at numerous U.S. military facilities and its mobility to aquatic systems, the fate of RDX in marine systems remains largely unknown. Here, we provide RDX mineralization pathways and rates in seawater and sediments, highlighting for the first time the importance of the denitrification pathway in determining the fate of RDX-derived N. (15)N nitro group labeled RDX ((15)N-[RDX], 50 atom %) was spiked into a mesocosm simulating shallow marine conditions of coastal Long Island Sound, and the (15)N enrichment of N2 (δ(15)N2) was monitored via gas bench isotope ratio mass spectrometry (GB-IRMS) for 21 days. The (15)N tracer data were used to model RDX mineralization within the context of the broader coastal marine N cycle using a multicompartment time-stepping model. Estimates of RDX mineralization rates based on the production and gas transfer of (15)N2O and (15)N2 ranged from 0.8 to 10.3 μmol d(-1). After 22 days, 11% of the added RDX had undergone mineralization, and 29% of the total removed RDX-N was identified as N2. These results demonstrate the important consideration of sediment microbial communities in management strategies addressing cleanup of contaminated coastal sites by military explosives.

  16. Simultaneous desulfurization and denitrification from flue gas by Ferrate(VI).

    Science.gov (United States)

    Zhao, Yi; Han, Yinghui; Ma, Tianzhong; Guo, Tianxiang

    2011-05-01

    An innovative semidry process has been developed to simultaneously remove NO and SO₂ from flue gas. According to the conditions of the flue gas circulating fluidized bed (CFB) system, ferrate(VI) absorbent was prepared and added to humidified water, and the effects of the various influencing factors, such as ferrate(VI) concentration, humidified water pH, inlet flue gas temperature, residence time, molar ratio of Ca/(S+N), and concentrations of SO₂ and NO on removal efficiencies of SO₂ and NO were studied experimentally. Removal efficiencies of 96.1% for SO₂ and 67.2% for NO were obtained, respectively, under the optimal experimental conditions, in which the concentration of ferrate(VI) was 0.03 M, the humidified water pH was 9.32, the inlet flue gas temperature was 130 °C, the residence time was 2.2 s, and the molar ratio of Ca/(S+N) was 1.2. In addition, the reaction mechanism of simultaneous desulfurization and denitrification using ferrate(VI) was proposed.

  17. Electron affinity coefficients of nitrogen oxides and biodegradation kinetics in denitrification of contaminated stream water.

    Science.gov (United States)

    Kim, Seung-Hyun; Chung, Jong-Bae; Jeong, Byeong-Ryong; Lee, Young-Deuk; Prasher, Shiv O

    2003-01-01

    During the dry season in Korea, rivers become more vulnerable to contamination by biochemical oxygen demand (BOD) and nitrogen. It is hypothesized that the natural characteristics of the streams in Korea allow the contaminated water to be treated at the tributaries. Down-stream river water quality in Korea may be improved by spraying the contaminated stream water from the tributaries over the surrounding floodplains. The consequent water filtration through the soil could remove the contaminants through aerobic and denitrifying reactions. In this study, the kinetics parameters of the denitrifying reaction in floodplain filtration were determined using contaminated stream water. For the electron donor the Monod kinetics was used, while the competitive Michaelis-Menten model was employed for the electron acceptors. The parameters to the competitive Michaelis-Menten model were found using continuous denitrifying reactions, instead of the batch reactions employed in previous studies, to match the conditions needed to apply the competitive Michaelis-Menten kinetics. From the result, it was found that continuous reactions as well as batch reactions could be used to determine the affinity coefficients in denitrification. The results of this study also showed that the affinity coefficient of NO2, using continuous reactions, was similar to that of other studies in the literature found via batch reactions, whereas the affinity coefficient of N2O was much larger than that acquired with batch reactions. The parameters obtained in this study will be used in future work to simulate the contaminant behaviors during floodplain filtration using a mathematical model.

  18. Comparative analysis of microbial community between different cathode systems of microbial fuel cells for denitrification.

    Science.gov (United States)

    Li, Chao; Xu, Ming; Lu, Yi; Fang, Fang; Cao, Jiashun

    2016-01-01

    Two types of cathodic biofilm in microbial fuel cells (MFC) were established for comparison on their performance and microbial communities. Complete autotrophic simultaneous nitrification and denitrification (SND) without organics addition was achieved in nitrifying-MFC (N-MFC) with a total nitrogen (TN) removal rate of 0.35 mg/(L·h), which was even higher than that in denitrifying-MFC (D-MFC) at same TN level. Integrated denaturing gradient gel electrophoresis analysis based on both 16S rRNA and nirK genes showed that Alpha-, Gammaproteobacteria were the main denitrifier communities. Some potential autotrophic denitrifying bacteria which can use electrons and reducing power from cathodes, such as Shewanella oneidensis, Shewanella loihica, Pseudomonas aeruginosa, Starkeya novella and Rhodopseudomonas palustris were identified and selectively enriched on cathode biofilms. Further, relative abundance of denitrifying bacteria characterized by nirK/16S ratios was much higher in biofilm than suspended sludge according to real-time polymerase chain reaction. The highest enrichment efficiency for denitrifiers was obtained in N-MFC cathode biofilms, which confirmed autotrophic denitrifying bacteria enrichment is the key factor for a D-MFC system.

  19. Nitrogen removal by Providencia rettgeri strain YL with heterotrophic nitrification and aerobic denitrification.

    Science.gov (United States)

    Ye, Jun; Zhao, Bin; An, Qiang; Huang, Yuan-Sheng

    2016-09-01

    Providencia rettgeri strain YL shows the capability of nitrogen removal under sole aerobic conditions. By using isotope ratio mass spectrometry, (15)N-labelled N2O and N2 were detected in aerobic batch cultures containing [Formula: see text], [Formula: see text] or [Formula: see text]. Strain YL converted [Formula: see text], [Formula: see text] and [Formula: see text] to produce more N2O than N2 in the presence of [Formula: see text]. An (15)N isotope tracing experiment confirmed that the nitrogen removal pathway of strain YL was heterotrophic nitrification-aerobic denitrification. The optimal treatment conditions for nitrogen removal were pH of 8, C/N ratio of 12, temperature of 25°C and shaking speed of 105 rpm. A continuous aerobic bioreactor inoculated with strain YL was developed. With an influent [Formula: see text] concentration of 90-200 mg/L, the [Formula: see text] removal efficiency ranged from 80% to 97% and the total nitrogen removal efficiency ranged from 72% to 95%. The nitrogen balance in the continuous bioreactor revealed that approximately 35-52% of influent [Formula: see text] was denitrified aerobically to form gaseous nitrogen. These findings show that the P. rettgeri strain YL has potential application in wastewater treatment for nitrogen removal under sole aerobic conditions.

  20. [Localization of denitrification genes in plasmid DNA of bacteria Azospirillum brasilense].

    Science.gov (United States)

    Petrova, L P; Varshalomidze, O É; Shelud'ko, A V; Katsy, E I

    2010-07-01

    In 85-Mda plasmid (p85) of plant-associated bacteria Azospirillum brasilense Sp245 model strain, the genes encoding copper-containing nitrite reductase (nirK); heterodimeric NO-reductase (norCB); NorQ and NorD proteins affecting synthesis and (or) activation of NirK and (or) NO-reductase (norQD); catalytic subunit I ofcytochrom c oxidase (CccoN); presumable NO sensor carrying two hemeerythrine domains (orf181); and an enzyme required for synthesis of presumable NO antagonist, homocystein (metC) were identified. In the same region of p85, orf293 encoding transcriptional regulator of LysR type, orf208 whose protein product carries a formylmethanofuran dehydrogenase subunit E domain, and an orf164-encoding conservative secretory protein with unknown function were also found. Localization of a set of denitrification genes in the plasmid DNA A. brasilense Sp245 adjacent to IS elements ISAzba1 and ISAzba2 indicates potential mobility of these genes and high probability of their horizontal transfer among populations of rhizospheric bacteria. A site homologous to p85 nirK-orf208-orf181 genes was detected in the 115 kb plasmid of A. brasilense Sp7 type strain.

  1. Distillery wastes as external carbon sources for denitrification in municipal wastewater treatment plants.

    Science.gov (United States)

    Czerwionka, K; Makinia, J; Kaszubowska, M; Majtacz, J; Angowski, M

    2012-01-01

    In this study, by-products from alcohol production were examined in terms of their potential application as external carbon sources for enhancing denitrification in biological nutrient removal systems. Three types of batch tests were used to compare the effects of the distillery by-products, such as fusel oil, syrup and reject water, on the non-acclimated activated sludge. Much higher nitrate utilization rates (NURs) were observed for the latter two carbon sources. In the conventional NUR measurements (one-phase experiments), the observed NURs with syrup and reject water were 3.2-3.3 g N/(kg VSS h) compared with 1.0 g N/(kg VSS h) obtained for fusel oils from two different distilleries. When the carbon sources were added at the beginning of the anoxic phase preceded by an anaerobic phase (two-phase experiments), the NURs were 4.2 g N/(kg VSS h) (syrup and reject water) and 2.4-2.7 g N/(kg VSS h) (fusel oils). The heterotrophic yield coefficient, determined based on the conventional OUR measurements, varied in a relatively narrow range (0.72-0.79 g COD/g COD) for all the examined carbon sources. Due to advantageous composition (much higher COD concentrations and COD/N ratios), fusel is a preferred carbon source for practical handling in full-scale wastewater treatment plants.

  2. 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.

  3. Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds.

    Science.gov (United States)

    Warneke, Sören; Schipper, Louis A; Matiasek, Michael G; Scow, Kate M; Cameron, Stewart; Bruesewitz, Denise A; McDonald, Ian R

    2011-11-01

    Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate (NO(3)(-)) from point source discharges into non-reactive dinitrogen (N(2)) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO(3)(-) removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m(3)) filled with either maize cobs, wheat straw, green waste, sawdust, pine woodchips or eucalyptus woodchips were incubated at 16.8 °C or 27.1 °C (outlet temperature), and received NO(3)(-) enriched water (14.38 mg N L(-1) and 17.15 mg N L(-1)). After 2.5 years of incubation measurements were made of NO(3)(-)-N removal rates, in vitro denitrification rates (DR), factors limiting denitrification (carbon and nitrate availability, dissolved oxygen, temperature, pH, and concentrations of NO(3)(-), nitrite and ammonia), copy number of nitrite reductase (nirS and nirK) and nitrous oxide reductase (nosZ) genes, and greenhouse gas production (dissolved nitrous oxide (N(2)O) and methane), and carbon (TOC) loss. Microbial denitrification was the main mechanism for NO(3)(-)-N removal. Nitrate-N removal rates ranged from 1.3 (pine woodchips) to 6.2 g N m(-3) d(-1) (maize cobs), and were predominantly limited by C availability and temperature (Q(10) = 1.2) when NO(3)(-)-N outlet concentrations remained above 1 mg L(-1). The NO(3)(-)-N removal rate did not depend directly on substrate type, but on the quantity of microbially available carbon, which differed between carbon sources. The abundance of denitrifying genes (nirS, nirK and nosZ) was similar in replicate barrels under cold incubation, but varied substantially under warm incubation, and between substrates. Warm incubation enhanced growth of nirS containing bacteria and bacteria that lacked the nosZ gene, potentially explaining the greater N(2)O emission in

  4. Vacuum barrier for excimer lasers

    Energy Technology Data Exchange (ETDEWEB)

    Shurter, R.P.

    1990-10-10

    This invention is comprised of a barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yearns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  5. [The cultural barrier in care].

    Science.gov (United States)

    Djadaoudjee, Lisa

    2013-11-01

    French cultural diversity is evident within French hospitals, where nurses are confronted with communication problems resulting from the language barrier. While communication is indeed essential, there is another important aspect of caring for a patient for behind the language barrier lies a cultural barrier which must be taken into account in order to provide high-quality care.

  6. Thermal barrier coating materials

    Directory of Open Access Journals (Sweden)

    David R. Clarke

    2005-06-01

    Full Text Available Improved thermal barrier coatings (TBCs will enable future gas turbines to operate at higher gas temperatures. Considerable effort is being invested, therefore, in identifying new materials with even better performance than the current industry standard, yttria-stabilized zirconia (YSZ. We review recent progress and suggest that an integrated strategy of experiment, intuitive arguments based on crystallography, and simulation may lead most rapidly to the development of new TBC materials.

  7. Barrier mechanisms in the Drosophila blood-brain barrier

    Directory of Open Access Journals (Sweden)

    Samantha Jane Hindle

    2014-12-01

    Full Text Available The invertebrate blood-brain barrier field is growing at a rapid pace and, in recent years, studies have shown a physiologic and molecular complexity that has begun to rival its vertebrate counterpart. Novel mechanisms of paracellular barrier maintenance through GPCR signaling were the first demonstrations of the complex adaptive mechanisms of barrier physiology. Building upon this work, the integrity of the invertebrate blood-brain barrier has recently been shown to require coordinated function of all layers of the compound barrier structure, analogous to signaling between the layers of the vertebrate neurovascular unit. These findings strengthen the notion that many blood-brain barrier mechanisms are conserved between vertebrates and invertebrates, and suggest that novel findings in invertebrate model organisms will have a significant impact on the understanding of vertebrate BBB functions. In this vein, important roles in coordinating localized and systemic signaling to dictate organism development and growth are beginning to show how the blood-brain barrier can govern whole animal physiologies. This includes novel functions of blood-brain barrier gap junctions in orchestrating synchronized neuroblast proliferation, and of blood-brain barrier secreted antagonists of insulin receptor signaling. These advancements and others are pushing the field forward in exciting new directions. In this review, we provide a synopsis of invertebrate blood-brain barrier anatomy and physiology, with a focus on insights from the past 5 years, and highlight important areas for future study.

  8. 根据生物脱氮除磷原理对生活污水脱氮除磷的工艺设计%The Technological Design of Domestic Sewage's Denitrification and Phosphorus Removal Process Based on Biological Denitrification and Phosphor Removal Theory

    Institute of Scientific and Technical Information of China (English)

    汤敏

    2014-01-01

    总结了目前的生活污水脱氮除磷工艺的特点,依据生物脱氮除磷工艺原理,设计了新的生活污水脱氮除磷工艺流程。%The article summarizes current characteristics of domestic sewage's denitrification and phosphorus removal process and designs a new process based on biological denitrification and phosphorus removal theo-ry .

  9. Figuring out the process of denitrification by stable isotope approaches - Prospects and limitations -

    Science.gov (United States)

    Stange, C. F.; Spott, O.

    2009-04-01

    Improvement in the analysis of stable isotopes, higher measurement capacity and faster and more complex analysis methods allow a more detailed insight into the complexity of N cycling in soils or sediments, in particular in the formation and emission of N2 gas. The knowledge about the site-specific N2 to N2O ratio of denitrification and perhaps other processes is important to develop sustainable land use strategies for reduction of GHG emissions. Adapted stable isotope approaches are an irreplaceable tool for process identification, process quantification and processes separation. In the last years a few of new processes were found (e.g. anammox, codenitrification) and new stable isotope approaches for quantification and processes separation were published (Wrage et al.). Source partitioning of N gas production in soils is inherently challenging, but is vital to better understand controls on the different processes, with a view to develope appropriate management practices for mitigation of harmful N gases (e.g.N2O) (Baggs, 2008). Recently dual-isotope labelling approaches (Wrage et al., 2005) and triplet 15N tracer experiments (TTE) with 15N labelling of different pools (e.g. Müller et al., 2006, Russow et al 2009) have been developed to differentiate between more than two processes. The high number of simultaneously occurring processes during soil N cycling (Hayatsu et al. 2008) limits an easy applicability of isotope approaches (Spott and Stange 2007 ;Wrage et al. 2005; Phillips and Gregg, 2003), and therefore partitioning and process quantification is often afflicted with high uncertainties (Ambus et al., 2006). Especially the heterogeneity of environmental conditions in soils caused by the soil structure is difficult to handle (e.g. homogeneously labelling a soil). Hence, spatially separated processes in combination with high turnover rates (gross production and consumption) can produce different pools of one substrate in the soil (Russow et al. 2009) and

  10. Effect of carbon source and COD/NO₃⁻-N ratio on anaerobic simultaneous denitrification and methanogenesis for high-strength wastewater treatment.

    Science.gov (United States)

    Xie, Li; Chen, Jinrong; Wang, Rui; Zhou, Qi

    2012-06-01

    The effect of carbon source and COD/NO(3)(-)-N ratio on denitrification and methanogenesis in mixed methanogenic matrix was investigated in this study. Industrial wastewater, anaerobic treated cassava stillage (CS) and glucose synthetic wastewater were used as carbon sources respectively for comparison. Experimental results showed that denitrification was the main nitrate reduction pathway for all COD/NO(3)(-)-N ratios tested in two substrates. Simultaneous denitrification and methanogenesis occurred at COD/NO(3)(-)-N higher than 7 regardless of carbon sources. Incomplete denitrification was observed at COD/NO(3)(-)-N ratio below 7 in both the anaerobic effluent of CS and glucose-fed cultures due to the insufficient available organic carbon. The nature of carbon sources was observed to play a key role in the nitrate and organic carbon utilization rates. COD/NO(3)(-)-N ratio had a strong effect on the organic matter utilization pathways. Methanization consumed more organic matter than denitrification with further increase of COD/NO(3)(-)-N ratio above 7 in two substrates. Results of VFA variation suggested that propionate and butyrate were preferably utilized by the denitrifiers than acetate.

  11. Achieving nitrogen removal via nitrite in a pilot-scale continuous pre-denitrification plant.

    Science.gov (United States)

    Ma, Yong; Peng, Yongzhen; Wang, Shuying; Yuan, Zhiguo; Wang, Xiaolian

    2009-02-01

    Nitrogen removal via nitrite (the nitrite pathway) is beneficial for carbon-limited biological wastewater treatment plants. However, partial nitrification to nitrite has proven difficult in continuous processes treating domestic wastewater. The nitrite pathway is achieved in this study in a pilot-scale continuous pre-denitrification plant (V=300 L) treating domestic wastewater by controlling the dissolved oxygen (DO) concentration at 0.4-0.7 mg/L. It is demonstrated that the nitrite pathway could be repeatedly and reliably achieved, with over 95% of the oxidized nitrogen compounds at the end of the aerobic zone being nitrite. The nitrite pathway improved the total nitrogen (TN) removal by about 20% in comparison to the nitrate pathway, and also reduced aeration costs by 24%. FISH analysis showed that the nitrite oxidizing bacteria (NOB) population gradually reduced at low DO levels, and reached negligible levels when stable nitrite pathway was established. It is hypothesized that NOB was washed out due to its relatively lower affinity with oxygen. A lag phase was observed in the establishment of the nitrite pathway. Several sludge ages were required for the onset of the nitrite pathway after the application of low DO levels. However, nitrite accumulation increased rapidly after that. A similar lag phase was observed for the upset of the nitrite pathway when a DO concentration of 2-3 mg/L was applied. The nitrite pathway negatively impacted on the sludge settleability. A strong correlation between the sludge volume index and the degree of nitrite accumulation was observed.

  12. Denitrification of nitrate and nitrite by 'Candidatus Accumulibacter phosphatis' clade IC.

    Science.gov (United States)

    Saad, Sondos A; Welles, Laurens; Abbas, Ben; Lopez-Vazquez, Carlos M; van Loosdrecht, Mark C M; Brdjanovic, Damir

    2016-11-15

    Phosphate accumulating organisms (PAO) are assumed to use nitrate as external electron acceptor, allowing an efficient integration of simultaneous nitrogen and phosphate removal with minimal organic carbon (COD) requirements. However, contradicting findings appear in literature regarding the denitrification capacities of PAO due to the lack of clade specific highly enriched PAO cultures. Whereas some studies suggest that only PAO clade I may be capable of using nitrate as external electron acceptor for anoxic P-uptake, other studies indicate that PAO clade II may be responsible for anoxic P-removal. In the present study, a highly enriched PAO clade IC culture (>99% according to FISH) was cultivated in an SBR operated under Anaerobic/Oxic conditions and subsequently exposed to Anaerobic/Anoxic/Oxic conditions using nitrate as electron acceptor. Before and after acclimatization to the presence of nitrate, the aerobic and anoxic (nitrate and nitrite) activities of the PAO I culture were assessed through the execution of batch tests using either acetate or propionate as electron donor. In the presence of nitrate, significant P-uptake by PAO I was not observed before or after acclimatization. Using nitrite as electron acceptor, limited nitrite removal rates were observed before acclimatization with lower rates in the acetate fed reactor without P-uptake and slightly higher in the propionate fed reactor with a marginal anoxic P-uptake. Only after acclimatization to nitrate, simultaneous P and nitrite removal was observed. This study suggests that PAO clade IC is not capable of using nitrate as external electron acceptor for anoxic P-removal. The elucidation of the metabolic capacities for individual PAO clades helps in better understanding and optimization of the relation between microbial ecology and process performance in enhanced biological phosphate removal processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Linguistic Barriers and Bridges

    DEFF Research Database (Denmark)

    Thuesen, Frederik

    2016-01-01

    The influence of language on social capital in low-skill and ethnically diverse workplaces has thus far received very limited attention within the sociology of work. As the ethnically diverse workplace is an important social space for the construction of social relations bridging different social...... and intercultural communication, this article analyses interviews with 31 employees from two highly ethnically diverse Danish workplaces. The article shows how linguistic barriers such as different levels of majority language competence and their consequent misunderstandings breed mistrust and hostility, whilst...

  14. [Barrier methods of contraception].

    Science.gov (United States)

    Goldsmith, A; Edelman, D A

    1982-01-01

    Vaginal methods of contraception were the earliest types used and some references to them date back to antiquity. Most of the vaginal contraceptive agents identified by the ancient Greeks, Indians, Japanese, and Chinese have been found in modern laboratory tests to have spermicidal properties, but it is doubtful that the methods were fully reliable or were used by many people. During the 19th century the condom, vaginal spermicides, and diaphragm became available. The development of nonoxynol-9 and other nonirritating but effective spermicidal agents improved vaginal contraceptives greatly by the 1950s, but starting in the 1960s newer methods began to replace the vaginal methods. Interest in barrier methods has been reawakened somewhat by concern about the health effects of hormonal methods. At present all barrier methods leave something to be desired. Failure rates of 3-30% for barrier methods in general have been estimated, but the higher rates are believed due to incorrect or inconsistent use. Theoretical failure rates of condoms and diaphragms have been estimated at 3/100 women-years, but in actual use failure rates may reach 15 for condoms and 13 for diaphragms used with spermicides. Use-effectiveness rates are greatly influenced by motivation. For a variety of reasons, the acceptability of barrier methods is low, especially in developing countries. New developments in spermicidal agents include sperm inhibitors, which impede the fertilizing capacity of sperm rather than attempting a spermicidal effect; a number of such agents have been studied and have proven more effective in animal tests than conventional spermicides. Neosampoon, a new spermicidal foam, has attracted an increasing number of users, especially in developing countries. A new condom, made of thin polymers and containing a standard dose of nonoxynol-9, has been designed to dissolve in the vaginal fluid. Further studies are needed of its acceptability, efficacy, and side effects before it becomes

  15. Technical barrier challenges

    Institute of Scientific and Technical Information of China (English)

    李思佳

    2014-01-01

    according to a famouse report,the foreign Technical Barriers to Trade(TBT)have some effects on the exports of the People’s Republic of China.Major findings are as follows:(1)TBT makes it more difficult for China to export;(2)TBT increases the costs of Chinese export commodities;(3)TBT causes friction and confilicts in the international trade;(4)SOME developed countries have moved their phase-outs to China and other developing countries,which have become victims of TBT.

  16. Support or Barrier?

    DEFF Research Database (Denmark)

    Sanden, Guro Refsum; Lønsmann, Dorte

    This study offers a critical look at how corporate-level language management influences front-line language practices among employees in three multinational corporations (MNCs) headquartered in Scandinavia. Based on interview and document data, we examine, firstly, what front-line practices...... employees use to cross language boundaries in their everyday work, and, secondly, how these practices relate to top-down language management in the case companies. Our findings show that employees are often dependent on ad hoc and informal solutions in cross- language situations, which leads us...... to a discussion of how a company’s language policy may be seen as both support and a barrier....

  17. 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

  18. Denitrification constitutes an import N sink in subtropical N-saturated forests - a nitrate dual isotope study

    Science.gov (United States)

    Yu, Lonfei; Zhu, Jing; Mulder, Jan; Dörsch, Peter

    2016-04-01

    Forests in China receive variable but increasing amounts of nitrogen from the atmosphere causing N saturation and nitrate runoff. Surprisingly high N-retention has been reported from subtropical forests, suggesting active mechanisms of N removal. Here we report a multi-site study of 15N and 18O abundances in soil nitrate (NO3-) across seven forested catchments spanning from temperate to subtropical China. In each catchment, samples were taken on one date during one or two summer along the hydrological continuum comprising hillslope positions and riparian zones. We had found previously in an intensive multi-year study at one of the sites, that the spatial pattern of summertime 15N and 18O in soil nitrate was remarkably stable across climatically distinct years, suggesting persistent N removal by denitrification at the foot of hill slopes and in groundwater discharge zones (Yu et al., submitted). In the present study, we extended the scope to five subtropical Chinese catchments and compared them with two temperate forests. Our data confirm the general pattern of efficient nitrification on hillslopes and strong denitrification in riparian zones in the subtropical catchments but not in the temperate ones. This is likely because high summer rainfalls at the monsoonal sites connect N mineralization and oxidation in upland positions with NO3- reduction in ground water discharge zones via NO3- runoff, rendering subtropical forests an efficient sink for reactive N with implications for regional N budgets. The impact of N deposition level, hydrology and edaphic factors on the predictive power of nitrate isotope signatures for N removal processes will be discussed. Yu L, Zhu J, Mulder J, Dörsch P: Spatiotemporal patterns in dual nitrate isotopes reveal efficient N transformation and denitrification along a hydrological continuum in N-saturated, subtropical forest. Submitted

  19. Impacts to Ecological Services: Buried Oil from the 2010 Deepwater Horizon Spill and Its Effect on Salt Marsh Denitrification

    Science.gov (United States)

    Levine, B. M.; White, J. R.; Delaune, R.

    2016-02-01

    In coastal Louisiana (LA), demands for ecosystem services are increasing while human activities continue to deteriorate coastal systems. On April 20, 2010, the largest offshore oil spill in United States history occurred in the Gulf of Mexico, known as the Deepwater Horizon (DWH) oil spill. Approximately 795 million L of crude oil were released, consequently oiling 1,773 km of Gulf Coast shoreline. Four years later, oil from the spill was found buried in the soil and seeping at the salt marsh surface in Bay Jimmy, LA. Previous studies found that immediately following oil exposure, wetland soils have suppressed microbial activity. This study seeks to understand effects of the long-term presence of oil on soil microbes and associated impacts to wetland soil denitrification. Bulk soil and intact soil cores were collected four years after the DWH spill from a heavily impacted salt marsh and a proximal site deemed unoiled in Barataria Bay, LA. Oil present in the soil subsurface increased dry weight bulk density, and decreased moisture content. Potential denitrification (acetylene block) in the top 10 cm of soil was 38% lower for oiled samples versus unoiled controls. Areal nitrate reduction rates were significantly lower in oiled samples in an intact core flux experiment under environmentally relevant nitrate conditions (2mg/L NO3-N), P-value denitrification rates in extruded sections of soil from the intact core study at 0-5 cm and 5-10 cm depths. These results demonstrate that after four years, buried oil is still toxic to denitrifying bacteria and may have significantly negative impacts on the ecosystem service of water quality improvement. Future studies should investigate impacts of oil being rebroadcasted onto marshes as land erodes in the study area.

  20. 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