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Sample records for benthic denitrification nitrate

  1. Denitrification, nitrate turnover, and aerobic respiration by benthic foraminiferans in the oxygen minimum zone off Chile

    DEFF Research Database (Denmark)

    Høgslund, Signe; Revsbech, Niels Peter; Cedhagen, Tomas;

    2008-01-01

    Population density, nitrate turnover, and oxygen respiration of benthic foraminiferans were investigated in the oxygen minimum zone (OMZ) off the Chilean coast. Live foraminiferans were found predominantly in the upper 3 mm of the sediment, and the nitrate accumulating species Nonionella cf. stella...

  2. Biological denitrification of nitrate waste solutions

    International Nuclear Information System (INIS)

    The studies leading to the design of the Oak Ridge Y-12 plant biological denitrification system are briefly described. The system uses a flow-through stirred-bed reactor. Methanol and lime-neutralized acetic acid were evaluated as C sources. The acetic acid was selected because the calcium carbonate generated in the process is needed for neutralization of the acid wastes. Excess organic will be used to ensure maximum amount of nitrate destroyed. The system will generate solids in the form of calcium carbonate, aluminum hydroxide, and organic carbon and N2 and CO2 gases. (JSR)

  3. 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

  4. Potential importance of physiologically diverse benthic foraminifera in sedimentary nitrate storage and respiration

    Science.gov (United States)

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

    2012-09-01

    Until recently, the process of denitrification (conversion of nitrate or nitrite to gaseous products) was thought to be performed exclusively by prokaryotes and fungi. The finding that foraminifera perform complete denitrification could impact our understanding of nitrate removal in sediments as well as our understanding of eukaryotic respiration, especially if it is widespread. However, details of this process and the subcellular location of these reactions in foraminifera remain uncertain. For example, prokaryotic endobionts, rather than the foraminifer proper, could perform denitrification, as has been shown recently in an allogromiid foraminifer. Here, intracellular nitrate concentrations and isotope ratios (δ15NNO3 and δ18ONO3) were measured to assess the nitrate dynamics in four benthic foraminiferal species (Bolivina argentea, Buliminella tenuata, Fursenkoina cornuta, Nonionella stella) with differing cellular architecture and associations with microbial endobionts, recovered from Santa Barbara Basin, California. Cellular nitrate concentrations were high (12-217 mM) in each species, and intracellular nitrate often had elevated δ15NNO3 and δ18ONO3 values. Experiments including suboxic and anoxic incubations of B. argentea revealed a decrease in intracellular nitrate concentration and an increase in δ15NNO3 and δ18ONO3over time, indicating nitrate respiration and/or denitrification within the foraminifera. Results illustrate that nitrate reduction occurs in a range of foraminiferal species, including some possessing endobionts (including a chloroplast-sequestering species) and others lacking endobionts, implying that microbial associates may not solely be responsible for this process in foraminifera. Furthermore, we show that benthic foraminifera may represent important reservoirs of nitrate storage in sediments, as well as mediators of its removal.

  5. 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.

  6. Nitrification and denitrification in a midwestern stream containing high nitrate: In situ assessment using tracers in dome-shaped incubation chambers

    Science.gov (United States)

    Smith, R.L.; Böhlke, J.K.; Repert, D.A.; Hart, C.P.

    2009-01-01

    The extent to which in-stream processes alter or remove nutrient loads in agriculturally impacted streams is critically important to watershed function and the delivery of those loads to coastal waters. In this study, patch-scale rates of in-stream benthic processes were determined using large volume, open-bottom benthic incubation chambers in a nitrate-rich, first to third order stream draining an area dominated by tile-drained row-crop fields. The chambers were fitted with sampling/mixing ports, a volume compensation bladder, and porewater samplers. Incubations were conducted with added tracers (NaBr and either 15N[NO3-], 15N[NO2-], or 15N[NH4+]) for 24-44 h intervals and reaction rates were determined from changes in concentrations and isotopic compositions of nitrate, nitrite, ammonium and nitrogen gas. Overall, nitrate loss rates (220-3,560 ??mol N m-2 h-1) greatly exceeded corresponding denitrification rates (34-212 ??mol N m-2 h-1) and both of these rates were correlated with nitrate concentrations (90-1,330 ??M), which could be readily manipulated with addition experiments. Chamber estimates closely matched whole-stream rates of denitrification and nitrate loss using 15N. Chamber incubations with acetylene indicated that coupled nitrification/denitrification was not a major source of N2 production at ambient nitrate concentrations (175 ??M), but acetylene was not effective for assessing denitrification at higher nitrate concentrations (1,330 ??M). Ammonium uptake rates greatly exceeded nitrification rates, which were relatively low even with added ammonium (3.5 ??mol N m-2 h-1), though incubations with nitrite demonstrated that oxidation to nitrate exceeded reduction to nitrogen gas in the surface sediments by fivefold to tenfold. The chamber results confirmed earlier studies that denitrification was a substantial nitrate sink in this stream, but they also indicated that dissolved inorganic nitrogen (DIN) turnover rates greatly exceeded the rates of

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

    Science.gov (United States)

    Wang, Jianlong; Chu, Libing

    2016-11-01

    Nitrate pollution in receiving waters has become a serious issue worldwide. Solid-phase denitrification process is an emerging technology, which has received increasing attention in recent years. It uses biodegradable polymers as both the carbon source and biofilm carrier for denitrifying microorganisms. A vast array of natural and synthetic biopolymers, including woodchips, sawdust, straw, cotton, maize cobs, seaweed, bark, polyhydroxyalkanoate (PHA), polycaprolactone (PCL), polybutylene succinate (PBS) and polylactic acid (PLA), have been widely used for denitrification due to their good performance, low cost and large available quantities. This paper presents an overview on the application of solid-phase denitrification in nitrate removal from drinking water, groundwater, aquaculture wastewater, the secondary effluent and wastewater with low C/N ratio. The types of solid carbon source, the influencing factors, the microbial community of biofilm attached on the biodegradable carriers, the potential adverse effect, and the cost of denitrification process are introduced and evaluated. Woodchips and polycaprolactone are the popular and competitive natural plant-like and synthetic biodegradable polymers used for denitrification, respectively. Most of the denitrifiers reported in solid-phase denitrification affiliated to the family Comamonadaceae in the class Betaproteobacteria. The members of genera Diaphorobacter, Acidovorax and Simplicispira were mostly reported. In future study, more attention should be paid to the simultaneous removal of nitrate and toxic organic contaminants such as pesticide and PPCPs by solid-phase denitrification, to the elucidation of the metabolic and regulatory relationship between decomposition of solid carbon source and denitrification, and to the post-treatment of the municipal secondary effluent. Solid-phase denitrification process is a promising technology for the removal of nitrate from water and wastewater. PMID:27396522

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

    Directory of Open Access Journals (Sweden)

    Pierluigi VIAROLI

    2009-02-01

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

  10. Biosensor Determination of the Microscale Distribution of Nitrate, Nitrate Assimilation, Nitrification, and Denitrification in a Diatom-Inhabited Freshwater Sediment

    OpenAIRE

    Lorenzen, Jan; Larsen, Lars Hauer; Kjær, Thomas; Revsbech, Niels-Peter

    1998-01-01

    High-resolution NO3− profiles in freshwater sediment covered with benthic diatoms were obtained with a new microscale NO3− biosensor characterized by absence of interference from chemical species other than NO2− and N2O. Analysis of the microprofiles obtained indicated no nitrification during darkness, high rates of nitrification and a tight coupling between nitrification and denitrification during illumination, and substantial rates of NO3− assimilation during illumination. Nitrification dur...

  11. Effect of nitrate, organic carbon, and temperature on potential denitrification rates in nitrate-rich riverbed sediments

    Science.gov (United States)

    Pfenning, K.S.; McMahon, P.B.

    1997-01-01

    A study conducted in 1994 as part of the US Geological Survey's National Water-Quality Assessment Program, South Platte River Basin investigation, examined the effect of certain environmental factors on potential denitrification rates in nitrate-rich riverbed sediments. The acetylene block technique was used to measure nitrous oxide (N2O) production rates in laboratory incubations of riverbed sediments to evaluate the effect of varying nitrate concentrations, organic carbon concentrations and type, and water temperature on potential denitrification rates. Sediment incubations amended with nitrate, at concentrations ranging from 357 to 2142 ??mol l-1 (as measured in the field), produced no significant increase (P > 0.05) in N2O production rates, indicating that the denitrification potential in these sediments was not nitrate limited. In contrast, incubations amended with acetate as a source of organic carbon, at concentrations ranging from 0 to 624 ??mol l-1, produced significant increases (P organic carbon concentration, indicating that the denitrification potential in these sediments was organic carbon limited. Furthermore, N2O production rates also were affected by the type of organic carbon available as an electron donor. Acetate and surface-water-derived fulvic acid supported higher N2O production rates than groundwater-derived fulvic acid or sedimentary organic carbon. Lowering incubation temperatures from 22 to 4??C resulted in about a 77% decrease in the N2O production rates. These results help to explain findings from previous studies indicating that only 15-30% of nitrate in groundwater was denitrified before discharging to the South Platte River and that nitrate concentrations in the river generally were higher in winter than in summer.

  12. 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-...

  13. 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...

  14. Electrolytic denitrification of alkaline nitrate and nitrite solution

    International Nuclear Information System (INIS)

    Processing of high-level waste at the Savannah River Plant (SRP) will produce a low-level alkaline salt solution, containing approximately 17% sodium nitrate and sodium nitrite. This solution will be incorporated into a cement wasteform, saltstone, and placed in an engineered landfill. Laboratory experiments have demonstrated the technical feasibility of electrochemically reducing the nitrate and nitrite in a synthetic, nonradioactive salt solution similar in composition to that expected to be produced at SRP. Greater than ninety-five percent of the sodium nitrate and sodium nitrite can be reduced electrolytically, producing ammonia, nitrogen, oxygen, and sodium hydroxide. Reduction of the nitrate and nitrite will reduce the leaching of nitrate and nitrite from the saltstone monolith. In addition, significant reductions in the volume of saltstone may be realized if the sodium hydroxide produced by electrolysis can be recycled

  15. Bioelectrochemical denitrification on biocathode buried in simulated aquifer saturated with nitrate-contaminated groundwater.

    Science.gov (United States)

    Nguyen, Van Khanh; Park, Younghyun; Yu, Jaecheul; Lee, Taeho

    2016-08-01

    Nitrate contamination in aquifers has posed human health under high risk because people still rely on groundwater withdrawn from aquifers as drinking water and running water sources. These days, bioelectrochemical technologies have shown a great number of benefits for nitrate remediation via autotrophic denitrification in groundwater. This study tested the working possibility of a denitrifying biocathode when installed into a simulated aquifer. The reactors were filled with sand and synthetic groundwater at various ratios (10, 50, and 100 %) to clarify the effect of various biocathode states (not-buried, half-buried, and fully buried) on nitrate reduction rate and microbial communities. Decreases in specific nitrate reduction rates were found to be correlated with increases in sand/medium ratios. A specific nitrate reduction rate of 322.6 mg m(-2) day(-1) was obtained when the biocathode was fully buried in an aquifer. Microbial community analysis revealed slight differences in the microbial communities of biocathodes at various sand/medium ratios. Various coccus- and rod-shaped bacteria were found to contribute to bioelectrochemical denitrification including Thiobacillus spp. and Paracoccus spp. This study demonstrated that the denitrifying biocathode could work effectively in a saturated aquifer and confirmed the feasibility of in situ application of microbial electrochemical denitrification technology. PMID:27117152

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-09-15

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

  17. 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

    ) and the diversity and abundance of nitrate- and nitrous-oxide-reducing bacteria were investigated. Additionally, the diversity of actively nitrate- and nitrous-oxide-reducing bacteria was analyzed in the larval gut.The presence of larvae increased the total effluxes of N2O and N2+N2O up to 8.6- and 4.2-fold...... were found expressed, which may contribute to higher phylotype richness in colonized sediment. In contrast, phylotype richness of the nitrous oxide reductase gene nosZ was unaffected by the presence of larvae and very few nosZ phylotypes were expressed in the gut. Gene abundance of neither narG, nor......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...

  18. 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.

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

    Science.gov (United States)

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

    2015-12-01

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

  20. A new method for in situ nitrate removal from groundwater using submerged microbial desalination-denitrification cell (SMDDC)

    DEFF Research Database (Denmark)

    Zhang, Yifeng; Angelidaki, Irini

    2013-01-01

    A considerable increase in nitrate concentration in groundwater has become a serious concern worldwide. We developed a novel submerged microbial desalination-denitrification cell (SMDDC) to in situ remove nitrate from groundwater, produce electric energy, and potentially treat wastewater. The SMD...

  1. 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. PMID:24520693

  2. 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.

  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. 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...... different treatments. Commonly applied PDA measurement likely underestimates the nitrate removal capacity of a system. Incubation time and organic matter/nitrate ratio are the most critical factors to consider using C2H2 inhibition technique to quantify denitrification. By comparing the treatments with and...... slurries were monitored during the incubation. Results show that nitrate disappearance rate was higher than N2O production rate with C2H2 blockage during the incubation. Sum of nitrate, nitrite, and N2O with C2H2 blockage could not recover the original soil nitrate content, showing an N imbalance in such a...

  5. 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. PMID:22593607

  6. Denitrification of high concentrations of nitrites and nitrates in synthetic medium with different sources of organic carbon. III. Methanol.

    Science.gov (United States)

    Błaszczyk, M; Gałka, E; Sakowicz, E; Mycielski, R

    1985-01-01

    The denitrification of nitrites and nitrates (1000 mg N/l) in medium containing methanol as a source of organic carbon was studied. Continuous cultures of mixed population of autochtonic microflora from bottom sludge of nitrogenous wastewater reservoir were set up in a chemostat-type column and packed bed reactor. The efficiency of denitrification of nitrates in packed bed reactor was 506.7 mg N/l/h whereas denitrification of nitrites was from 8.7 to 16.0 mg N/l/h depending on the granulation of the filing material. In the latter case 83% nitrogen was removed from the medium. One of the factors causing low efficiency of denitrification of nitrites is excessive alkalization of the medium in the bed. The use of a three-step bed with adjusted pH resulted in complete denitrification of nitrites with efficiency 60 mg N/l/h. The bacteria inside the bed were dominated by Paracoccus denitrificans and by Pseudomonas aeruginosa when nitrates were present. The sensitivity of P. denitrificans to high concentrations of nitrites seems to be the second factor contributing to low efficiency of denitrification with methanol as organic substrate. PMID:2412408

  7. 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.

  8. The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone

    Directory of Open Access Journals (Sweden)

    N. Glock

    2012-12-01

    Full Text Available The discovery that foraminifera are able to use nitrate instead of oxygen as energy source for their metabolism has challenged our understanding of nitrogen cycling in the ocean. It was evident before that only prokaryotes and fungi are able to denitrify. Rate estimates of foraminiferal denitrification were very sparse on a regional scale. Here, we present estimates of benthic foraminiferal denitrification rates from six stations at intermediate water depths in and below the Peruvian oxygen minimum zone (OMZ. Foraminiferal denitrification rates were calculated from abundance and assemblage composition of the total living fauna in both, surface and subsurface sediments, as well as from individual species specific denitrification rates. A comparison with total benthic denitrification rates as inferred by biogeochemical models revealed that benthic foraminifera account for the total denitrification on the shelf between 80 and 250 m water depth. They are still important denitrifiers in the centre of the OMZ around 320 m (29–56% of the benthic denitrification but play only a minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m (3–7% of total benthic denitrification. Furthermore, foraminiferal denitrification was compared to the total benthic nitrate loss measured during benthic chamber experiments. Foraminiferal denitrification contributes 1 to 50% to the total nitrate loss across a depth transect from 80 to 700 m, respectively. Flux rate estimates ranged from 0.01 to 1.3 mmol m−2 d−1. Furthermore we show that the amount of nitrate stored in living benthic foraminifera (3 to 705 µmol L−1 can be higher by three orders of magnitude as compared to the ambient pore waters in near surface sediments sustaining an important nitrate reservoir in Peruvian OMZ sediments. The substantial contribution of foraminiferal nitrate respiration to total benthic nitrate loss at the Peruvian margin

  9. [Influence of nitrate on the simultaneous methanogenesis and denitrification reaction of anaerobic biofilm and granular sludge].

    Science.gov (United States)

    Zhong, Chen-Yu; Ye, Jie-Xu; Li, Ruo-Yu; Chen, Sheng; Sun, De-Zhi

    2012-12-01

    The aims of this study are to further investigate the impact mechanism of nitrate on the simultaneous methanogenesis and denitrification (SMD) process of anaerobic biofilm, and to extend the application of the biofilm process in the treatment of high nitrogen and COD concentration organic wastewater. The SMD reactions were successfully carried out in a hybrid anaerobic biofilm and sludge reactor (HABSR) and an up-flow anaerobic sludge blanket (UASB), and the influence of nitrate on the performance of simultaneous carbon and nitrogen removal in biofilm and granular sludge were investigated using batch tests. The results showed that the nitrate concentration could obviously affect the carbon and nitrogen removal in both biofilm and granular sludge, and the increase of nitrate concentration had more serious impact on the granular sludge, and the biofilm presented higher COD and nitrogen removal efficiency and stronger resistance to toxic materials than the granular sludge. As the nitrate concentration was increased from 75 to 600 mg x L(-1), the COD removal rates were reduced from 273.26 to 0.1 mg x (h x g)(-1) in granular sludge and reduced from 95 to 1.7 mg x (h x g)(-1) in biofilm. At the same time, the denitrification rate of biofilm and granular sludge were increased form 21.43 and 22.31 mg x (h x g)(-1) to 83.72 and 61.06 mg x (h x g)(-1), respectively. The biofilm recovered the COD degradation rate more quickly and easily than the granular sludge, and the maximum COD removal rate reached 712.44 mg x (h x g)(-1). The nitrite accumulation was observed to be the major cause that affected the simultaneous carbon and nitrogen removal of biofilm and granular sludge. It's found that the maximum nitrite accumulation in biofilm was only one tenth of that of the granular sludge at the same nitrate concentration. The HABSR was proved to be an important alternative for SMD reaction employed in the treatment of high nitrogen and COD concentration organic wastewater. PMID

  10. 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). PMID:24862952

  11. 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.

  12. 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 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. PMID:27102809

  13. 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.

  14. Dynamic Linkages between Denitrification Functional Genes/Enzymes and Biogeochemical Reaction Rates of Nitrate and Its Reduction Products

    Science.gov (United States)

    Li, M.; Shi, L.; Qian, W.; Gao, Y.; Liu, Y.; Liu, C.

    2015-12-01

    Denitrification is a respiratory process in which oxidized nitrogen compounds are used as alternative electron acceptors for energy production when oxygen is limited. Denitrification is an important process that not only accounts for the significant loss of nitrogen fertilizers from soils but also leads to NO, N2O and CO2 emissions, which are important greenhouse gas species. In this study, denitrification was investigated in Columbia River sediments, focusing on the dynamic linkages between functional genes/enzymes and biogeochemical reaction rates of nitrate and its reduction products. NO3-, NO2- and N2O were assayed in different incubation time. DNA was extracted from the sediments and functional genes were quantified as a function of time during the denitrification. Functional enzymes were extracted from the sediments and measured using a newly developed, targeted protein method. The biogeochemical, functional gene, and enzyme data were collectively used to establish the dynamic correlation of functional genes/enzymes and biogeochemical reaction rates. The results provide fundamental insights regarding the dynamic regulation of functional genes and enzymes in the processes of denitrification and greenhouse gas production, and also provide experimental data critical for the development of biogeochemical reaction models that incorporate genome-scale insights and describe macroscopic biogeochemical reaction rates in ecosystems.

  15. Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds

    OpenAIRE

    Warneke, Sören; Schipper, Louis A.; Matiasek, Michael G.; Scow, Kate M.; Cameron, Stewart; Bruesewitz, Denise A.; McDonald, Ian R.

    2011-01-01

    Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate ( NO3−) from point source discharges into non-reactive dinitrogen (N2) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO3− removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m3) filled with either maize cobs, w...

  16. Remediation of nitrate-contaminated wastewater using denitrification biofilters with straws of ornamental flowers added as carbon source.

    Science.gov (United States)

    Chang, Junjun; Ma, Luyao; Zhou, Yuanyang; Zhang, Shenghua; Wang, Weilu

    2016-01-01

    Straws of four ornamental flowers (carnation, rose, lily, and violet) were added into denitrification biofilters using gravel as matrix through vertically installed perforated polyvinylchloride pipes to provide organic carbon for the treatment of nitrate-contaminated wastewater operating in batch mode. Removal efficiencies of nitrate and phosphate, as well as temporal variations of nitrogen and carbon during batches 10 and 19, were investigated and assessed. Nitrate removal was efficiently enhanced by the addition of flower straws, but decreased gradually as the organic substances were consumed. Phosphate removal was also improved, although this very limited. High nitrate removal rates were achieved during the initial 12 h in the two batches each lasting for 3 days, along with the depletion of influent dissolved oxygen due to aerobic degradation of the organic compounds. NO2(-)-N of 0.01-2.83 mg/L and NH4(+)-N of 0.02-1.69 mg/L were formed and both positively correlated to the nitrate reduced. Inorganic carbon (IC) concentrations increased during the batches and varied conversely with the nitrate contents, and could be indicative of nitrate removal due to the highly significant positive correlation between NO3(-)-N removed and IC concentration (r(2) = 0.881, p biofilter to treat nitrate-contaminated wastewater, although further optimization of carbon source addition is still required.

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

    Science.gov (United States)

    Vavilin, V A; Rytov, S V

    2015-09-01

    A kinetic analysis of nitrate denitrification by a single or two species of denitrifying bacteria with glucose or ethanol as a carbon source and nitrite or nitrous oxide as intermediate products was performed using experimental data published earlier (Menyailo and Hungate, 2006; Vidal-Gavilan et al., 2013). Modified Monod kinetics was used in the dynamic biological model. The special equations were added to the common dynamic biological model to describe how isotopic fractionation between N species changes. In contrast to the generally assumed first-order kinetics, in this paper, the traditional Rayleigh equation describing stable nitrogen and oxygen isotope fractionation in nitrate was derived from the dynamic isotopic equations for any type of kinetics. In accordance with the model, in Vidal-Gavilan's experiments, the maximum specific rate of nitrate reduction was proved to be less for ethanol compared to glucose. Conversely, the maximum specific rate of nitrite reduction was proved to be much less for glucose compared to ethanol. Thus, the intermediate nitrite concentration was negligible for the ethanol experiment, while it was significant for the glucose experiment. In Menyailo's and Hungate's experiments, the low value of maximum specific rate of nitrous oxide reduction gives high intermediate value of nitrous oxide concentration. The model showed that the dynamics of nitrogen and oxygen isotope signatures are responding to the biological dynamics. Two microbial species instead of single denitrifying bacteria are proved to be more adequate to describe the total process of nitrate denitrification to dinitrogen. PMID:25989520

  18. Biological nitrate transport in sediments on the Peruvian margin mitigates benthic sulfide emissions and drives pelagic N loss during stagnation events

    Science.gov (United States)

    Dale, A. W.; Sommer, S.; Lomnitz, U.; Bourbonnais, A.; Wallmann, K.

    2016-06-01

    Benthic N cycling in the Peruvian oxygen minimum zone (OMZ) was investigated at ten stations along 12 °S from the middle shelf (74 m) to the upper slope (1024 m) using in situ flux measurements, sediment biogeochemistry and modeling. Middle shelf sediments were covered by mats of the filamentous bacteria Thioploca spp. and contained a large 'hidden' pool of nitrate that was not detectable in the porewater. This was attributed to a biological nitrate reservoir stored within the bacteria to oxidize sulfide during 'dissimilatory nitrate reduction to ammonium' (DNRA). The extremely high rates of DNRA on the shelf (15.6 mmol m-2 d-1 of N), determined using an empirical steady-state model, could easily supply all the ammonium requirements for anammox in the water column. The model further showed that denitrification by foraminifera may account for 90% of N2 production at the lower edge of the OMZ. At the time of sampling, dissolved oxygen was below detection limit down to 400 m and the water body overlying the shelf had stagnated, resulting in complete depletion of nitrate and nitrite. A decrease in the biological nitrate pool was observed on the shelf during fieldwork concomitant with a rise in porewater sulfide levels in surface sediments to 2 mM. Using a non-steady state model to simulate this natural anoxia experiment, these observations were shown to be consistent with Thioploca surviving on a dwindling intracellular nitrate reservoir to survive the stagnation period. The model shows that sediments hosting Thioploca are able to maintain high ammonium fluxes for many weeks following stagnation, potentially sustaining pelagic N loss by anammox. In contrast, sulfide emissions remain low, reducing the economic risk to the Peruvian fishery by toxic sulfide plume development.

  19. Control of nitratation in an oxygen-limited autotrophic nitrification/denitrification rotating biological contactor through disc immersion level variation.

    Science.gov (United States)

    Courtens, Emilie N P; Boon, Nico; De Clippeleir, Haydée; Berckmoes, Karla; Mosquera, Mariela; Seuntjens, Dries; Vlaeminck, Siegfried E

    2014-03-01

    With oxygen supply playing a crucial role in an oxygen-limited autotrophic nitrification/denitrification (OLAND) rotating biological contactor (RBC), its controlling factors were investigated in this study. Disc rotation speeds (1.8 and 3.6rpm) showed no influence on the process performance of a lab-scale RBC, although abiotic experiments showed a significant effect on the oxygenation capacity. Estimations of the biological oxygen uptake rate revealed that 85-89% of the oxygen was absorbed by the microorganisms during the air exposure of the discs. Indeed, increasing the disc immersion (50 to 75-80%) could significantly suppress undesired nitratation, on the short and long term. The presented results demonstrated that nitratation could be controlled by the immersion level and revealed that oxygen control in an OLAND RBC should be predominantly based on the atmospheric exposure percentage of the discs.

  20. Remediation of nitrate-nitrogen contaminated groundwater using a pilot-scale two-layer heterotrophic-autotrophic denitrification permeable reactive barrier with spongy iron/pine bark.

    Science.gov (United States)

    Huang, Guoxin; Huang, Yuanying; Hu, Hongyan; Liu, Fei; Zhang, Ying; Deng, Renwei

    2015-07-01

    A novel two-layer heterotrophic-autotrophic denitrification (HAD) permeable reactive barrier (PRB) was proposed for remediating nitrate-nitrogen contaminated groundwater in an oxygen rich environment, which has a packing structure of an upstream pine bark layer and a downstream spongy iron and river sand mixture layer. The HAD PRB involves biological deoxygenation, heterotrophic denitrification, hydrogenotrophic denitrification, and anaerobic Fe corrosion. Column and batch experiments were performed to: (1) investigate the NO3(-)-N removal and inorganic geochemistry; (2) explore the nitrogen transformation and removal mechanisms; (3) identify the hydrogenotrophic denitrification capacity; and (4) evaluate the HAD performance by comparison with other approaches. The results showed that the HAD PRB could maintain constant high NO3(-)-N removal efficiency (>91%) before 38 pore volumes (PVs) of operation (corresponding to 504d), form little or even negative NO2(-)-N during the 45 PVs, and produce low NH4(+)-N after 10 PVs. Aerobic heterotrophic bacteria played a dominant role in oxygen depletion via aerobic respiration, providing more CO2 for hydrogenotrophic denitrification. The HAD PRB significantly relied on heterotrophic denitrification. Hydrogenotrophic denitrification removed 10-20% of the initial NO3(-)-N. Effluent total organic carbon decreased from 403.44mgL(-1) at PV 1 to 9.34mgL(-1) at PV 45. Packing structure had a noticeable effect on its denitrification. PMID:25747301

  1. Combined ion exchange/biological denitrification for nitrate removal from ground water.

    NARCIS (Netherlands)

    Hoek, van der J.P.

    1988-01-01

    This thesis deals with the development of a new process for nitrate removal from ground water. High nitrate concentrations in ground water are a result of fertilization in agriculture. According to a directive of the European Community the maximum admissible concentration of nitrate in drinking wate

  2. Nitrate levels modulate denitrification activity in tropical mangrove sediments (Goa, India)

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; LokaBharathi, P.A.

    % of the N loss in mangrove sediments occurs through denitrification. Mangrove sediments are largely anaerobic and rich in organic matter providing favourable conditions for denitrification. The process is mediated mainly by facultatively anaerobic... Sousa 1999). Sediment cores were collected at low tide and transported in an ice box. Cores for activity measurements were maintained at 4ºC. For measurement of labile organic matter (LOM), cores were immediately sectioned at 0-2, 2-4, 4-6, 6-8 and 8...

  3. Widespread occurrence of nitrate storage and denitrification among Foraminifera and Gromiida

    DEFF Research Database (Denmark)

    Ochoa, Elisa Pina; Høgslund, Signe; Geslin, Emmanuelle;

    2010-01-01

    Benthic foraminifers inhabit a wide range of aquatic environments including open marine, brackish, and freshwater environments. Here we show that several different and diverse foraminiferal groups (miliolids, rotaliids, textulariids) and Gromia, another taxon also belonging to Rhizaria, accumulat...

  4. Effects of solid-phase denitrification on the nitrate removal and bacterial community structure in recirculating aquaculture system.

    Science.gov (United States)

    Qiu, Tianlei; Liu, Lili; Gao, Min; Zhang, Lanhe; Tursun, Haireti; Wang, Xuming

    2016-06-01

    A solid-phase denitrification (SPD) reactor packed with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) as a carbon source was incorporated into a recirculating aquaculture system (RAS) to remove accumulated nitrate. Bacterial community structures in different parts of the RAS, including biofilter unit, SPD reactor, and culture water, were analyzed using Illumina MiSeq sequencing technology. The data showed that nitrate levels decreased remarkably in the RAS connected with SPD reactor (RAS-DR). In contrast, nitrate levels increased continuously in the conventional RAS without SPD reactor (RAS-CK). Biofilter unit and culture water in RAS-DR developed lower species richness and higher bacterial community diversity than that in RAS-CK. The bacterial community structure of RAS was significantly affected by the SPD process and the changes included an increase in the proportion of Proteobacteria and Firmicutes and a decrease in Nitrospira abundance in RAS-DR. Firmicutes was the most abundant phylum (56.9 %) and mainly consisted of Clostridium sensu stricto (48.3 %) in SPD reactor. PMID:27125529

  5. Multi-scale measurements and modeling of denitrification in streams with varying flow and nitrate concentration in the upper Mississippi River basin, USA

    Science.gov (United States)

    Bohlke, Johnkarl F.; Antweiler, Ronald C.; Harvey, Judson W.; Smith, Richard L.; Voytek, Mary A.; Laursen, A.; Smith, L.K.

    2009-01-01

    Denitrification is an important net sink for NO3 - in streams, but direct measurements are limited and in situ controlling factors are not well known. We measured denitrification at multiple scales over a range of flow conditions and NO3 - concentrations in streams draining agricultural land in the upper Mississippi River basin. Comparisons of reach-scale measurements (in-stream mass transport and tracer tests) with local-scale in situ measurements (pore-water profiles, benthic chambers) and laboratory data (sediment core microcosms) gave evidence for heterogeneity in factors affecting benthic denitrification both temporally (e.g., seasonal variation in NO3 - concentrations and loads, flood-related disruption and re-growth of benthic communities and organic deposits) and spatially (e.g., local stream morphology and sediment characteristics). When expressed as vertical denitrification flux per unit area of streambed (U denit, in µmol N m-2 h-1), results of different methods for a given set of conditions commonly were in agreement within a factor of 2–3. At approximately constant temperature (~20 ± 4°C) and with minimal benthic disturbance, our aggregated data indicated an overall positive relation between U denit (~0–4,000 µmol N m-2 h-1) and stream NO3 - concentration (~20–1,100 µmol L-1) representing seasonal variation from spring high flow (high NO3 -) to late summer low flow (low NO3 -). The temporal dependence of U denit on NO3 - was less than first-order and could be described about equally well with power-law or saturation equations (e.g., for the unweighted dataset, U denit ˜26 * [NO3 -]0.44 or U denit ˜640 * [NO3 -]/[180 + NO3 -]; for a partially weighted dataset, U denit ˜14 * [NO3 -]0.54 or U denit ˜700 * [NO3 -]/[320 + NO3 -]). Similar parameters were derived from a recent spatial comparison of stream denitrification extending to lower NO3 - concentrations (LINX2), and from the combined dataset from both studies over 3 orders of magnitude

  6. Biological Denitrification of High Nitrate Processing Wastewaters from Explosives Production Plant

    OpenAIRE

    Cyplik, Paweł; Marecik, Roman; Piotrowska-Cyplik, Agnieszka; Olejnik, Anna; Drożdżyńska, Agnieszka; Chrzanowski, Łukasz

    2011-01-01

    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...

  7. 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

    - and NO3-) were followed for 3 weeks in the beginning of the growth season (May-June). During the 3 weeks two separate periods of rain gave dramatic changes in soil water content. A rainfall in the beginning of the sampling period, resulting in a short-term wetting of the soil, stimulated the potential...... 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...... and denitrifiers. The results indicate that potential activities (enzyme contents) in the four bacterial groups were less dependent on their inorganic N substrates in the bulk and rhizosphere soils, but showed distinct and different responses to duration of soil wetting after rainfall....

  8. Method of denitrification and stabilization of radioactive aqueous solutions of radioisotope nitrates

    International Nuclear Information System (INIS)

    The method is solved of denitrification and of the stabilization of aqueous solutions of radioactive isotopes produced during the reprocessing of nuclear fuel. The aqueous solution is first mixed with the vitreous component, most frequently phosphoric acid, ammonium phosphate or boric acid and if needed with the addition of alkalis, possibly with clarifying or anti-foam components, e.g., arsenic trioxide, antimony or cerium oxide. The mixture is further adjusted with ammonia to pH 5 - 9. The liquid mixture is then thermally and pyrolytically processed, e.g., by calcinator or fluid-bed reactor or by pot melting at temperatures of 3O0 to 900 degC while of a powder product or glass melt is formed in the presence of gaseous emissions composed of nitrous oxide - nitrogen. The resulting product is further processed by containerization or is sealed in a metal matrix. (B.S.)

  9. Nitrate Removal from Wastewater through Biological Denitrification with OGA 24 in a Batch Reactor

    Directory of Open Access Journals (Sweden)

    Federico Rossi

    2014-12-01

    Full Text Available Nitrates pollution of waters is a worldwide problem and its remediation is a big challenge from the technical and the scientific point of view. One of the most used and promising cleaning techniques is the biological treatment of wastewaters operated by denitrifying bacteria. In this paper we begin a thorough study of denitrifying performances of the bacterium Azospira sp. OGA 24, recently isolated from the highly polluted Sarno river in the south of Italy. Here, the kinetics of nitrates consumption operated by bacteria in a specifically devised batch bioreactor, in anoxic condition and with acetate as the organic substrate, has been characterized. Experimental data were then used in a simplified model of a real wastewater treatment plant to find that OGA 24 can clean water with efficiency up to 90%. The denitrifying performances of OGA 24 match the requirements of Italian laws and make the bacterium suitable for its employment in treatment plants.

  10. Elucidating the impact of nitrate and labile carbon application on spatial heterogeneity of denitrification by 15N modelling

    Science.gov (United States)

    Cardenas, Laura; Loick, Nadine; Dixon, Liz; Matthews, Peter; Gilsanz, Claudia; Bol, Roland; Lewicka-Szczebak, Dominika; Well, Reinhard

    2016-04-01

    N2O is considered to be an important GHG with soils representing its major source and accounting for approximately 6% of the current global warming and is also implicated in the depletion of stratospheric ozone. The atmospheric N2O concentration has been increasing since the Industrial Revolution making the understanding of its sources and removal processes very important for development of mitigation strategies. Bergstermann et al. (2011) found evidence of the existence of more than one pool of nitrate undergoing denitrification in a silty clay loam arable soil amended with glucose/nitrate solution. The Rayleigh type model was used to simulate d15N of N2O using process rates and associated fractionation factors, but assumptions for some of the model parameters had to be made due to lack of available data. In this study we carried out 2 incubation experiments in order to parameterise the model. To restrict the volume of soil reached by the amendment, we used blocks containing 3 soil cores that were incubated in one vessel to measure emissions of NO, N2O, N2 and CO2 from a clay grassland soil amended with KNO3 (N) and glucose (C) in three treatments: '1C' only 1 core received N and C (the other 2 received water), '3C' 3 cores received N and C, and 'Control' (received water only). The results showed changes in the d15Nbulk trends after day 6 post amendment application, coinciding with the decrease of N2O fluxes. We also report the results in the 15N site preference (SP) and d18O. We will show the results from the model validation based on this data.

  11. 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......-labeled water and 18O-labeled nitrite were added to the microcosm experiments to study the effect of putative backward reactions of nitrite to nitrate on the stable isotope fractionation. We found no evidence for a reverse reaction. Significant variations of the stable isotope enrichment factor ε were observed...

  12. Denitrification-Coupled Iron(II) Oxidation: A Key Process Regulating the Fate and Transport of Nitrate, Phosphate, and Arsenic in a Wastewater-Contaminated Aquifer

    Science.gov (United States)

    Smith, R. L.; Kent, D. B.; Repert, D. A.; Hart, C. P.

    2007-12-01

    Denitrification in the subsurface is often viewed as a heterotrophic process. However, some denitrifiers can also utilize inorganic electron donors. In particular, Fe(II), which is common in many aquifers, could be an important reductant for contaminant nitrate. Anoxic iron oxidation would have additional consequences, including decreased mobility for species like arsenic and phosphate, which bind strongly to hydrous Fe(III) oxide. A study was conducted in a wastewater contaminant plume on Cape Cod to assess the potential for denitrification- coupled Fe(II) oxidation. Previous changes in wastewater disposal upgradient of the study area had resulted in nitrate being transported into a portion of the anoxic zone of the plume and decreased concentrations of Fe(II), phosphate, and arsenic. A series of anoxic tracers (groundwater + nitrate + bromide) were injected into the unaffected, Fe(II)-containing zone under natural gradient conditions. Denitrification was stimulated within 1 m of transport (4 days) for both low and high (100 & 1000 μM) nitrate additions, initially producing stiochiometric quantities of nitrous oxide (>300 μM N) and trace amounts of nitrite. Subsequent injections at the same site reduced nitrate even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and this was accompanied by an increase in colloidal Fe(III) and decreases in pH, total arsenic, and phosphate concentrations. All plume constituents returned to background levels several weeks after the tracer tests were completed. Groundwater microorganisms collected on filters during the tracer test rapidly and immediately reduced nitrite and oxidized Fe(II) in 3-hr laboratory incubations. Several pure cultures of Fe(II)-oxidizing denitrifying bacteria were isolated from core material and subsequently characterized. All of the isolates were mixotrophic, simultaneously oxidizing organic carbon and Fe

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

    Science.gov (United States)

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

    2015-12-01

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

  14. Effect of nitrate concentration, pH, and hydraulic retention time on autotrophic denitrification efficiency with Fe(II) and Mn(II) as electron donors.

    Science.gov (United States)

    Su, Jun-Feng; Shi, Jing-Xin; Huang, Ting-Lin; Ma, Fang; Lu, Jin-Suo; Yang, Shao-Fei

    2016-01-01

    The role of electron donors (Fe(2+) and Mn(2+)) in the autotrophic denitrification of contaminated groundwater by bacterial strain SY6 was characterized based on empirical laboratory-scale analysis. Strain SY6 can utilize Fe(2+) more efficiently than Mn(2+) as an electron donor. This study has shown that the highest nitrate removal ratio, observed with Fe(2+) as the electron donor, was approximately 88.89%. An immobilized biological filter reactor was tested by using three levels of influent nitrate (10, 30, and 50 mg/L), three pH levels (6, 7, and 8), and three levels of hydraulic retention time (HRT; 6, 8, and 12 h), respectively. An optimal nitrate removal ratio of about 95% was achieved at pH 6.0 using a nitrate concentration of 50 mg/L and HRT of 12 h with Fe(2+) as an electron donor. The study showed that 90% of Fe(2+) and 75.52% removal of Mn(2+) were achieved at pH 8.0 with a nitrate concentration of 50 mg/L and a HRT of 12 h. Removal ratio of Fe(2+) and Mn(2+) is higher with higher influent nitrate and HRT. A weakly alkaline environment assisted the removal of Fe(2+) and Mn(2+). PMID:27642838

  15. Nitrate elimination by denitrification in hardwood forest soils of the Upper Rhine floodplain - correlation with redox potential and organic matter

    OpenAIRE

    Brettar, Ingrid; Trémolières, Michèle; Sanchez-Pérez, José-Miguel

    2002-01-01

    Denitrification in floodplains is a major issue for river- and groundwater quality. In the Upper Rhine valley, floodplain forests are about to be restored to serve as flood retention areas (polders). Besides flood attenuation in downstream areas, improvement of water quality became recently a major goal for polder construction. Redox potential monitoring was suggested as a means to support assessment of nitrogen elimination in future floodplains by denitrification during controlled flooding. ...

  16. Depletion of oxygen, nitrate and nitrite in the Peruvian oxygen minimum zone cause an imbalance of benthic nitrogen fluxes

    Science.gov (United States)

    Sommer, S.; Gier, J.; Treude, T.; Lomnitz, U.; Dengler, M.; Cardich, J.; Dale, A. W.

    2016-06-01

    Oxygen minimum zones (OMZ) are key regions for fixed nitrogen loss in both the sediments and the water column. During this study, the benthic contribution to N cycling was investigated at ten sites along a depth transect (74-989 m) across the Peruvian OMZ at 12°S. O2 levels were below detection limit down to ~500 m. Benthic fluxes of N2, NO3-, NO2-, NH4+, H2S and O2 were measured using benthic landers. Flux measurements on the shelf were made under extreme geochemical conditions consisting of a lack of O2, NO3- and NO2- in the bottom water and elevated seafloor sulphide release. These particular conditions were associated with a large imbalance in the benthic nitrogen cycle. The sediments on the shelf were densely covered by filamentous sulphur bacteria Thioploca, and were identified as major recycling sites for DIN releasing high amounts of NH4+up to 21.2 mmol m-2 d-1 that were far in excess of NH4+ release by ammonification. This difference was attributed to dissimilatory nitrate (or nitrite) reduction to ammonium (DNRA) that was partly being sustained by NO3- stored within the sulphur oxidizing bacteria. Sediments within the core of the OMZ (ca. 200-400 m) also displayed an excess flux of N of 3.5 mmol m-2 d-1 mainly as N2. Benthic nitrogen and sulphur cycling in the Peruvian OMZ appears to be particularly susceptible to bottom water fluctuations in O2, NO3- and NO2-, and may accelerate the onset of pelagic euxinia when NO3- and NO2- become depleted.

  17. Buried particulate organic carbon stimulates denitrification and nitrate retention in stream sediments at the groundwater-surface water interface

    Science.gov (United States)

    Stelzer, Robert S.; Scott, J. Thad; Bartsch, Lynn

    2015-01-01

    The interface between ground water and surface water in streams is a hotspot for N processing. However, the role of buried organic C in N transformation at this interface is not well understood, and inferences have been based largely on descriptive studies. Our main objective was to determine how buried particulate organic C (POC) affected denitrification and NO3− retention in the sediments of an upwelling reach in a sand-plains stream in Wisconsin. We manipulated POC in mesocosms inserted in the sediments. Treatments included low and high quantities of conditioned red maple leaves (buried beneath combusted sand), ambient sediment (sand containing background levels of POC), and a control (combusted sand). We measured denitrification rates in sediments by acetylene-block assays in the laboratory and by changes in N2 concentrations in the field using membrane inlet mass spectrometry. We measured NO3−, NH4+, and dissolved organic N (DON) retention as changes in concentrations and fluxes along groundwater flow paths in the mesocosms. POC addition drove oxic ground water to severe hypoxia, led to large increases in dissolved organic C (DOC), and strongly increased denitrification rates and N (NO3− and total dissolved N) retention relative to the control. In situ denitrification accounted for 30 to 60% of NO3− retention. Our results suggest that buried POC stimulated denitrification and NO3− retention by producing DOC and by creating favorable redox conditions for denitrification.

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

    Science.gov (United States)

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

    2013-04-01

    The large amount of waste that is discharged along with the diffusion of poly(L-lactic acid) (PLLA) articles in use is persistent concern. Previously, we studied solid-phase denitrification (SPD) processes using PLLA to establish an effective re-use of PLLA waste. We found that PLLA with a weight-average molecular weight (Mw) of approximately 10,000 was suitable for SPD processes; however, the recycling of PLLA waste consumes a high energy. A new PLLA plastic including 5% poly(ethylene oxalate) (PEOxPLLA) as a blend material has attracted attention because recycling of PEOxPLLA consumes less electricity than that of PLLA. In this study, our main objectives were to evaluate whether PEOxPLLA can be used for SPD processes by changing its Mw and to investigate the bioavailability for denitrification of hydrolysates released from PEOxPLLA. The predicted hydrolysates, including oxalic acid, ethylene glycol, and lactate, are abiotically released, leading to different biological nitrate removal rates. Consequently, the nitrate removal rate of PEOxPLLA ranged from 0.9-4.1 mg-NO3--N·g-MLSS·h-1 by changing the Mw in the range of 8,500-238,000. In culture-dependent approaches, denitrifying bacteria using each substrate as an electron donor are found in activated sludge, suggesting that all hydrolysates functioned in the SPD processes using PEOxPLLA.

  19. 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

  20. Ammonia oxidation, denitrification and dissimilatory nitrate reduction to ammonium in two US Great Basin hot springs with abundant ammonia-oxidizing archaea.

    Science.gov (United States)

    Dodsworth, Jeremy A; Hungate, Bruce A; Hedlund, Brian P

    2011-08-01

    Many thermophiles catalyse free energy-yielding redox reactions involving nitrogenous compounds; however, little is known about these processes in natural thermal environments. Rates of ammonia oxidation, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in source water and sediments of two ≈ 80°C springs in the US Great Basin. Ammonia oxidation and denitrification occurred mainly in sediments. Ammonia oxidation rates measured using (15)N-NO(3)(-) pool dilution ranged from 5.5 ± 0.8 to 8.6 ± 0.9 nmol N g(-1) h(-1) and were unaffected or only mildly stimulated by amendment with NH(4) Cl. Denitrification rates measured using acetylene block ranged from 15.8 ± 0.7 to 51 ± 12 nmol N g(-1) h(-1) and were stimulated by amendment with NO(3)(-) and complex organic compounds. The DNRA rate in one spring sediment measured using an (15)N-NO(3)(-) tracer was 315 ± 48 nmol N g(-1) h(-1). Both springs harboured distinct planktonic and sediment microbial communities. Close relatives of the autotrophic, ammonia-oxidizing archaeon 'Candidatus Nitrosocaldus yellowstonii' represented the most abundant OTU in both spring sediments by 16S rRNA gene pyrotag analysis. Quantitative PCR (qPCR) indicated that 'Ca. N. yellowstonii'amoA and 16S rRNA genes were present at 3.5-3.9 × 10(8) and 6.4-9.0 × 10(8) copies g(-1) sediment. Potential denitrifiers included members of the Aquificales and Thermales. Thermus spp. comprised <1% of 16S rRNA gene pyrotags in both sediments and qPCR for T. thermophilus narG revealed sediment populations of 1.3-1.7 × 10(6) copies g(-1) sediment. These data indicate a highly active nitrogen cycle (N-cycle) in these springs and suggest that ammonia oxidation may be a major source of energy fuelling primary production.

  1. Denitrification in Marl and Peat Sediments in the Florida Everglades

    OpenAIRE

    Gordon, A S; Cooper, W. J.; Scheidt, D. J.

    1986-01-01

    The potential for denitrification in marl and peat sediments in the Shark River Slough in the Everglades National Park was determined by the acetylene blockage assay. The influence of nitrate concentration on denitrification rate and N2O yield from added nitrate was examined. The effects of added glucose and phosphate and of temperature on the denitrification potential were determined. The sediments readily denitrified added nitrate. N2O was released from the sediments both with and without a...

  2. Sediment Denitrification in Two Contrasting Tropical Shallow Lagoons

    DEFF Research Database (Denmark)

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

    2016-01-01

    . There was no correlation of denitrification with nitrate or ammonium fluxes. Sediments in temperate environments with similar oxygen consumption rates usually presented a higher proportion of nitrification-denitrification rates. Sediment oxygen consumption was a good predictor of sediment denitrification in both studied...

  3. Denitrification of Spent Regenerated Brine Using Molasses

    OpenAIRE

    Tepuš, Brigita; Simonič, Marjana; Petrovič, Aleksandra; Filipič, Jasmina

    2014-01-01

    Spent BRINE from the regeneration of exhausted resins has to be properly treated before its disposal. The heterotrophic denitrification of regenerated brine was studied in present work. Molasses which served as a carbon source has until now not been applied during brine denitrification. The nitrate and nitrite consumptions were observed according to different ratios between total organic carbon and nitrate (TOC / NO3 ratios) and the influence of NaCl was studied during batch experiments. ...

  4. 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.

  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. NOx reduction is the main pathway for benthic N2O production in a eutrophic, monomictic south-alpine lake

    Directory of Open Access Journals (Sweden)

    C. V. Freymond

    2013-03-01

    Full Text Available Nitrous oxide (N2O is a potent greenhouse gas, generated through microbial nitrogen (N turnover processes, such as nitrification, nitrifier denitrification, and denitrification. Previous studies quantifying natural sources have mainly focused on soils and the ocean, but the potential role of terrestrial water bodies in the global N2O budget has been widely neglected. Furthermore, the biogeochemical controls on the production rates and the microbial pathways that produce benthic N2O in lakes are essentially unknown. In this study, benthic N2O fluxes and the contributions of the microbial pathways that produce N2O were assessed using 15N label flow-through sediment incubations in the eutrophic, monomictic south basin of Lake Lugano in Switzerland. The sediments were a significant source of N2O throughout the year, with production rates ranging between 140 and 2605 nmol N2O h−1 m−2, and the highest observed rates coinciding with periods of water column stratification and stably anoxic conditions in the overlying bottom water. Nitrate (NO3– reduction via denitrification was found to be the major N2O production pathway in the sediments under both oxygen-depleted and oxygen-replete conditions in the overlying water, while ammonium oxidation did not significantly contribute to the benthic N2O flux. A significant portion (up to 15% of the total NO3– consumed by denitrification was reduced only to N2O, without complete denitrification to N2. These fluxes were highest when the bottom water had completely stabilized to a low-oxygen state, in contrast with the notion that stable anoxia is particularly conducive to complete denitrification without accumulation of N2O. This study provides evidence that lake sediments are a~significant source of N2O to the overlying water and may produce large N2O fluxes to the atmosphere during seasonal mixing events.

  7. 饮用水中硝酸盐的反硝化动力学及微生物群落研究%Study on Denitrification Kinetics and Bacterial Community of Nitrate-contaminated Drinking Water

    Institute of Scientific and Technical Information of China (English)

    叶正芳; 王凤; 王中友

    2013-01-01

    Objective Denitrification kinetics under different carbon source and bacterial community are investigated,which provides technical support for the denitrification of drinking water in the regenerative life support system.Methods Immobilized microorganisms biological filters were used for removing nitrate in drinking water.PCR-DGGE was nsed to analyze bacterial community.Results The results showed that,when the reactors used ethanol and sodium acetate as carbon source,denitrification reaction followed zero-order kinetics in the first 2 and 1.5 h respectively,with a denitrification rate of 11.913 g NO3--N/(gVSS · d) and 15.633 g NO3--N/(gVSS · d).Moreover,when glucose was used as carbon source,NO3--N concentration curve could be fitted using two order polynomial and the mean value of denitrification rate was 7.177 g NO3--N/(gVSS ·d).Conclusion Denitrification reaction follows zero-order kinetics when carbon source is sufficient in drinking water.Nitrite first accumulates and then consumes.The denitrifying Pseudomona,Aquabacterium and Rhodocyclaceae are dominant among the immobilized microorganisms.%目的 分析饮用水中不同碳源条件下的反硝化反应动力学,研究微生物群落结构变化,鉴定出优势菌种,为解决再生式生命保障系统中饮用水的脱氮难题提供技术支持.方法 采用固定化微生物滤池工艺去除饮用水中的硝酸盐,并进行水质分析;利用PCR-DGGE技术分析微生物群落结构变化.结果 乙醇和乙酸钠系统分别在前0~2 h和0~1.5h内表现为零级动力学反应,线性拟合得出的反硝化速率分别为11.913 g NO3--N/(gVSS·d)和15.633 g NO3--N/(gVSS·d),而葡萄糖系统在0~3h内,硝态氮浓度曲线可由二阶多项式拟合,平均反硝化速率为7.177 g NO3--N/(gVSS·d).结论 饮用水中碳源充足时反硝化过程遵循零级反应,亚硝酸盐先累积后消耗,脱氮效果较好的微生物种属主要有假单胞菌属Pseudomona、水杆菌属Aquabacterium和红环菌科Rhodocyclaceae.

  8. [Heterotrophic Nitrification and Aerobic Denitrification of the Hypothermia Aerobic Denitrification Bacterium: Arthrobacter arilaitensis].

    Science.gov (United States)

    He, Teng-xia; Ni, Jiu-pai; Li, Zhen-lun; Sun, Quan; Ye Qing; Xu, Yi

    2016-03-15

    High concentrations of ammonium, nitrate and nitrite nitrogen were employed to clarify the abilities of heterotrophic nitrification and aerobic denitrification of Arthrobacter arilaitensis strain Y-10. Meanwhile, by means of inoculating the strain suspension into the mixed ammonium and nitrate, ammonium and nitrite nitrogen simulated wastewater, we studied the simultaneous nitrification and denitrification ability of Arthrobacter arilaitensis strain Y-10. In addition, cell optical density was assayed in each nitrogen removal process to analyze the relationship of cell growth and nitrogen removal efficiency. The results showed that the hypothermia denitrification strain Arthrobacter arilaitensis Y-10 exhibited high nitrogen removal efficiency during heterotrophic nitrification and aerobic denitrification. The ammonium, nitrate and nitrite removal rates were 65.0%, 100% and 61.2% respectively when strain Y-10 was cultivated for 4 d at 15°C with initial ammonium, nitrate and nitrite nitrogen concentrations of 208.43 mg · L⁻¹, 201.16 mg · L⁻¹ and 194.33 mg · L⁻¹ and initial pH of 7.2. Nitrite nitrogen could only be accumulated in the medium containing nitrate nitrogen during heterotrophic nitrification and aerobic denitrification process. Additionally, the ammonium nitrogen was mainly removed in the inorganic nitrogen mixed synthetic wastewater. In short, Arthrobacter arilaitensis Y-10 could conduct nitrification and denitrification effectively under aerobic condition and the ammonium nitrogen removal rate was more than 80.0% in the inorganic nitrogen mixed synthetic wastewater. PMID:27337904

  9. Denitrification in human dental plaque

    Directory of Open Access Journals (Sweden)

    Verstraete Willy

    2010-03-01

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

  10. The kinetics of denitrification in permeable sediments

    DEFF Research Database (Denmark)

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

    2013-01-01

    to study experimentally. The realistic implementation of such models requires reliable experimentally derived data on the kinetics of denitrification. Here we undertook measurements of denitrification kinetics as a function of nitrate concentration in carefully controlled flow through reactor experiments...... 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...

  11. Mechanism Study on a Combined Denitrification Approach for Nitrate-Contaminated Groundwater Remediation%联合脱氮法用于硝酸盐污染地下水修复的机理研究

    Institute of Scientific and Technical Information of China (English)

    黄国鑫; 高云鹤; Howard Fallowfield; Huade Guan; 刘菲

    2012-01-01

    Nitrate in groundwater has become a worldwide environmental and public health issue. Nitrate can cause methaemoglobinaemia, septicemia, hepatopathy, and even cancers. Currently, single chemical reduction (CR), autotrophic denitrification (AD) and heterotrophic denitrification (HD) have been reported worldwide, however theircombined denitrification approaches are rarely studied. In this paper the denitrification capacities, by products, pathways and mechanisms of a combined denitrification approach via batch experiments are explored, which are supported by zero valent iron, methanol and mixed bacteria. The results indicate that the elimination rates of 5.79% , 14.30% and 63. 03% were achieved by single zero valent iron-based CR, AD and HD respectively after 5 days, whereas close to 100% was attained by the combined approach. The combined approach is superior to single CR, AD or HD. Nitrite accumulation did not occur in the single CR or AD, but did take place in the single HD. Ammonium variations of <0. 6 mg/L were respectively found in CR, AD and HD. Nitrate was reduced to nitrogenous gas by CR, AD and HD. The combined system, in which HD played a dominant role, included three denitrification pathways, those of CR, AD and HD. Anaerobic zero valent iron corrosion provided cathodic hydrogen and ferrous iron for autotrophic denitrifiers. HD provided carbon dioxide for autotrophic denitrifiers. The combined system improved the elimination rate, which was not achieved by single AD and HD system. This combined approach was a potential, feasible and effective approach for groundwater in situ remediation.%地下水硝酸盐已经成为了世界性环境和健康问题.目前针对硝酸盐的化学还原脱氮、自养脱氮、异养脱氮等单一脱氮方法研究较多;联合脱氮体系包括化学还原、自养脱氮和畀养脱氮三种脱氮途径,综合了单一脱氮法的优点,但研究甚少.本研究通过静态批试验,采用零价铁、甲醇和混合菌

  12. Effects of nitrate contamination and seasonal variation on the denitrification and greenhouse gas production in La Rocina stream (Doñana National Park, SW Spain)

    OpenAIRE

    Tortosa, Germán; Galeote, David; Sánchez-Raya, Juan A.; Delgado Huertas, Antonio; Sánchez-Monedero, Miguel Ángel; Bedmar, Eulogio J.

    2011-01-01

    Climatic influence (global warming and decreased rainfall) could lead to an increase in the ecological and toxicological effects of the pollution in aquatic ecosystems, especially contamination from agricultural nitrate (NO3 −) fertilizers. Physicochemical properties of the surface waters and sediments of four selected sites varying in NO3 − concentration along La Rocina Stream, which feeds Marisma del Rocio in Do˜nana National Park (South West, Spain), were studied. Electri...

  13. 生物反硝化去除地下水中硝酸盐的混合碳源研究%Biological denitrification for nitrate removal from groundwater using mixed carbon sources

    Institute of Scientific and Technical Information of China (English)

    沈志红; 张增强; 王豫琪; 王珍; 陈园; 魏素娜

    2011-01-01

    选取麦秸、锯末、乙醇为碳源,比较了这3种物质单独或两两组合作为碳源的情况下,生物反硝化去除模拟地下水中硝酸盐的效果.结果表明,以麦秸为碳源的反应体系具有较好的反硝化效果,但反应器出水具有颜色和异味;锯末+乙醇作为混合碳源的反应体系比单独添加锯末或乙醇反应体系的脱氮效果好;碳氮比(C/N)为40的混合碳源用量有利于硝酸盐的去除;添加0.5%(乙醇占总碳源量的百分比)的乙醇对以锯末为碳源的反应体系的硝酸盐去除具有显著的促进作用.%Wheat straw, sawdust and ethanol were selected as carbon soureas for denitdfication microorganisms to remediate nitrate from groundwater. The effect of wheat straw, sawdust, ethanol, wheat straw + ethanol, sawdust + ethanol as well as wheat straw + sawdust as carbon sources to remove nitrate from the simulated groundwater were compared. The results showed that the reactor packed with wheat straw had good nitrate removal efficiency, but the effluent from the reactor was colored and had a bad odor. The reactor packed with sawdust + ethanol had a better performance than the reactor packed with sawdust or ethanol alone. The ratio of carbon and nitrogen (C/N) 40 was beneficial to nitrate removal. When using sawdust as carbon source, 0.5% ethanol (the percentage of ethanol to the amount of carbon sources) had a significant effect on improving denitrification.

  14. 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...

  15. 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.

  16. Seasonal enhancement of submarine groundwater discharge (SGD)-derived nitrate loading into the Ria Formosa coastal lagoon assessed by 1-D modeling of benthic NO

    NARCIS (Netherlands)

    Ibánhez, J.S.P.; Leote, C.; Rocha, C.

    2013-01-01

    The role of benthic sandy ecosystems in mitigating View the MathML sourceNO3- loads carried by Submarine Groundwater Discharge (SGD) to coastal marine ecosystems is uncertain. Benthic biogeochemical mediation of View the MathML sourceNO3--rich submarine groundwater discharge was studied at the seepa

  17. 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...

  18. 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...

  19. Comparison of denitrification between Paracoccus sp. and Diaphorobacter sp.

    Science.gov (United States)

    Chakravarthy, Srinandan S; Pande, Samay; Kapoor, Ashish; Nerurkar, Anuradha S

    2011-09-01

    Denitrification was compared between Paracoccus sp. and Diaphorobacter sp. in this study, both of which were isolated from activated sludge of a denitrifying reactor. Denitrification of both isolates showed contrasting patterns, where Diaphorobacter sp. showed accumulation of nitrite in the medium while Paracoccus sp. showed no accumulation. The nitrate reduction rate was 1.5 times more than the nitrite reduction in Diaphorobacter sp., as analyzed by the resting state denitrification kinetics. Increasing the nitrate concentration in the medium increased the nitrite accumulation in Diaphorobacter sp., but not in Paracoccus sp., indicating a branched electron transfer during denitrification. Diaphorobacter sp. was unable to denitrify efficiently at high nitrate concentrations from 1 M, but Paracoccus sp. could denitrify even up to 2 M nitrate. Paracoccus sp. was found to be an efficient denitrifier with insignificant amounts of nitrite accumulation, and it could also denitrify high amounts of nitrate up to 2 M. Efficient denitrification without accumulation of intermediates like nitrite is desirable in the removal of high nitrates from wastewaters. Paracoccus sp. is shown to suffice this demand and could be a potential organism to remove high nitrates effectively. PMID:21509603

  20. The kinetics of denitrification in permeable sediments

    Science.gov (United States)

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

    2013-04-01

    Permeable sediments comprise the majority of shelf sediments, yet the rates of denitrification remain highly uncertain in these environments. Computational models are increasingly being used to understand the dynamics of denitrification in permeable sediments, which are complex environments to study experimentally. The realistic implementation of such models requires reliable experimentally derived data on the kinetics of denitrification. Here we undertook measurements of denitrification kinetics as a function of nitrate concentration and in the presence and absence of oxygen, in carefully controlled flow through reactor experiments 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 Km) ranging between 1.5 and 19.8 μM, and maximum denitrification rate (Vmax) were in the range of 0.9-7.5 nmol mL-1 h-1. The production of N2 through anaerobic ammonium oxidation (anammox) was generally found to be less than 10% that of denitrification. Vmax were in the same range as previously reported in cohesive sediments despite organic carbon contents one order of magnitude lower for the sediments studied here. The ratio of sediment O2 consumption to Vmax was in the range of 0.02-0.09, and was on average much lower than the theoretical ratio of 0.8. The most likely explanation for this is that the microbial community is not able to instantaneously shift or optimally use a particular electron acceptor in the highly dynamic redox environment experienced in permeable sediments. Consistent with this explanation, subsequent longer-term experiments over 5 days showed that denitrification rates increased by a factor of 10 within 3 days of the permanent onset of anoxia. In contrast to previous studies, we did not observe any significant

  1. 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;

  2. 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.

  3. Hydrologic connectivity increases denitrification in the hyporheic zone and restored floodplains of an agricultural stream

    Science.gov (United States)

    Roley, Sarah S.; Tank, Jennifer L.; Williams, Maureen A.

    2012-09-01

    Stream ecotones, specifically the lateral floodplain and subsurface hyporheic zone, can be important sites for nitrogen (N) removal via denitrification, but their role in streams with constructed floodplains has not been examined. We studied denitrification in the hyporheic zone and floodplains of an agriculturally influenced headwater stream in Indiana, USA, that had floodplains added as part of a "two-stage ditch" restoration project. To examine the potential for N removal in the hyporheic zone, we seasonally measured denitrification rates and nitrate concentrations by depth into the stream sediments. We found that nitrate concentration and denitrification rates declined with depth into the hyporheic zone, but denitrification was still measureable to a depth of at least 20 cm. We also measured denitrification rates on the restored floodplains over the course of a flood (pre, during, and post-inundation), and also compared denitrification rates between vegetated and non-vegetated areas of the floodplain. We found that floodplain denitrification rates increased over the course of a floodplain inundation event, and that the presence of surface water increased denitrification rates when vegetation was present. Stream ecotones in midwestern, agriculturally influenced streams have substantial potential for N removal via denitrification, particularly when they are hydrologically connected with high-nitrate surface water.

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

    OpenAIRE

    Vries, de, H.J.C.; 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 denitrification had higher greenhouse gas emission, whereas nitrification only had higher nitrate leaching and ammonia emission from field application of discharge water

  5. Alternative nitrate reduction pathways in experimentally fertilized New England salt marshes

    DEFF Research Database (Denmark)

    Uldahl, Anne; Banta, Gary Thomas; Boegh, Eva;

    ongoing ecosystem level nutrient additions experiments in two New England salt marshes, Plum Island Sound (NO3- additions since 2003) and Great Sippewissett Marsh (fertilizer additions since the 1970's) to examine the relative importance of these NO3- reduction pathways in salt marshes. Sediments from......Nitrate present or generated in any benthic ecosystem can be reduced by a number of microbial pathways, most notably denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA). The first two processes remove of biologically available N from...... the ecosystem in the form of gaseous N2, while the last process transforms of NO3- to another biologically available form, NH4+, and thus merely recycles N. Salt marshes are important ecosystems for the cycling, retention and removal of biologically available N transported from land to the oceans. We used...

  6. 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

  7. A network biology approach to denitrification in Pseudomonas aeruginosa.

    Directory of Open Access Journals (Sweden)

    Seda Arat

    Full Text Available 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.

  8. 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

  9. Stimulating nitrate removal processes of restored wetlands.

    Science.gov (United States)

    Ballantine, Kate A; Groffman, Peter M; Lehmann, Johannes; Schneider, Rebecca L

    2014-07-01

    The environmental and health effects caused by nitrate contamination of aquatic systems are a serious problem throughout the world. A strategy proposed to address nitrate pollution is the restoration of wetlands. However, although natural wetlands often remove nitrate via high rates of denitrification, wetlands restored for water quality functions often fall below expectations. This may be in part because key drivers for denitrification, in particular soil carbon, are slow to develop in restored wetlands. We added organic soil amendments that range along a gradient of carbon lability to four newly restored wetlands in western New York to investigate the effect of carbon additions on denitrification and other processes of the nitrogen cycle. Soil carbon increased by 12.67-63.30% with the use of soil amendments (p ≤ 0.0001). Soil nitrate, the carbon to nitrogen ratio, and microbial biomass nitrogen were the most significant predictors of denitrification potential. Denitrification potential, potential net nitrogen nitrification and mineralization, and soil nitrate and ammonium, were highest in topsoil-amended plots, with increases in denitrification potential of 161.27% over control plots. While amendment with topsoil more than doubled several key nitrogen cycling processes, more research is required to determine what type and level of amendment application are most effective for stimulating removal of exogenous nitrate and meeting functional goals within an acceptable time frame. PMID:24915604

  10. Nitrogen, carbon, and sulfur isotopic change during heterotrophic (Pseudomonas aureofaciens) and autotrophic (Thiobacillus denitrificans) denitrification reactions

    Science.gov (United States)

    Hosono, Takahiro; Alvarez, Kelly; Lin, In-Tian; Shimada, Jun

    2015-12-01

    In batch culture experiments, we examined the isotopic change of nitrogen in nitrate (δ15NNO3), carbon in dissolved inorganic carbon (δ13CDIC), and sulfur in sulfate (δ34SSO4) during heterotrophic and autotrophic denitrification of two bacterial strains (Pseudomonas aureofaciens and Thiobacillus denitrificans). Heterotrophic denitrification (HD) experiments were conducted with trisodium citrate as electron donor, and autotrophic denitrification (AD) experiments were carried out with iron disulfide (FeS2) as electron donor. For heterotrophic denitrification experiments, a complete nitrate reduction was accomplished, however bacterial denitrification with T. denitrificans is a slow process in which, after seventy days nitrate was reduced to 40% of the initial concentration by denitrification. In the HD experiment, systematic change of δ13CDIC (from - 7.7‰ to - 12.2‰) with increase of DIC was observed during denitrification (enrichment factor εN was - 4.7‰), suggesting the contribution of C of trisodium citrate (δ13C = - 12.4‰). No SO42 - and δ34SSO4 changes were observed. In the AD experiment, clear fractionation of δ13CDIC during DIC consumption (εC = - 7.8‰) and δ34SSO4 during sulfur use of FeS2-S (around 2‰), were confirmed through denitrification (εN = - 12.5‰). Different pattern in isotopic change between HD and AD obtained on laboratory-scale are useful to recognize the type of denitrification occurring in the field.

  11. Application of a widely used denitrification model to Dutch data sets

    NARCIS (Netherlands)

    Heinen, M.

    2006-01-01

    In many modelling studies on N cycling, denitrification is considered by a simplified process model. A widely used model describes denittification as potential denitrification reduced by the soil conditions nitrate N content (N), degree of water saturation (S) and temperature (7). Henault and Germon

  12. 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.

  13. Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea

    Directory of Open Access Journals (Sweden)

    K. Dähnke

    2013-05-01

    Full Text Available The global marine nitrogen cycle is constrained by nitrogen fixation as a source of reactive nitrogen, and denitrification or anammox on the sink side. These processes with their respective isotope effects set the marine nitrate 15N-isotope value (δ15N to a relatively constant average of 5‰. This value can be used to better assess the magnitude of these sources and sink terms, but the underlying assumption is that sedimentary denitrification and anammox, processes responsible for approximately one-third of global nitrogen removal, have little to no isotope effect on nitrate in the water column. We investigated the isotope fractionation in sediment incubations, measuring net denitrification and nitrogen and oxygen stable isotope fractionation in surface sediments from the coastal Baltic Sea (Boknis Eck, northern Germany, a site with seasonal hypoxia and dynamic nitrogen turnover. Sediment denitrification was fast, and regardless of current paradigms assuming little fractionation during sediment denitrification, we measured fractionation factors of 18.9‰ for nitrogen and 15.8‰ for oxygen in nitrate. While the input of nitrate to the water column remains speculative, these results challenge the current view of fractionation during sedimentary denitrification and imply that nitrogen budget calculations may need to consider this variability, as both preferential uptake of light nitrate and release of the remaining heavy fraction can significantly alter water column nitrate isotope values at the sediment–water interface.

  14. Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea

    Directory of Open Access Journals (Sweden)

    K. Dähnke

    2013-01-01

    Full Text Available The global marine nitrogen cycle is constrained by nitrogen fixation as a source of reactive nitrogen, and denitrification or anammox on the sink side. These processes with their respective isotope effects set the marine nitrate 15N-isotope value (δ15N to a relatively constant average of 5‰. This value can be used to better assess the magnitude of these sources and sink terms, but the underlying assumption is that sedimentary denitrification and anammox, processes responsible for approximately one third of global nitrogen removal, have little to no isotope effect on nitrate in the water column.

    We investigated the isotope fractionation in sediment incubations, measuring net denitrification and nitrogen and oxygen stable isotope fractionation in surface sediments from the coastal Baltic Sea (Boknis Eck, Northern Germany, a site with seasonal hypoxia and dynamic nitrogen turnover.

    We found tremendously high denitrification rates, and regardless of current paradigms assuming little fractionation during sediment denitrification, we measured fractionation factors of 18.9‰ for nitrogen and 15.8‰ for oxygen in nitrate. While the input of nitrate to the water column remains speculative, these results challenge the current view of fractionation during sedimentary denitrification and imply that nitrogen budget calculations may need to consider this variability, as both preferential uptake of light nitrate and release of the remaining heavy fraction can significantly alter water column nitrate isotope vales at the sediment-water interface.

  15. 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...

  16. 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...

  17. Regulation of denitrification in the genus Thauera; response pattern in the transition from oxic to anoxic environment, life on the energetic edge

    OpenAIRE

    Andreassen, Øystein Andre

    2010-01-01

    Denitrification is a taxonomically widespread process used by more than 60 different genera of bacteria including archaea and some fungi, where nitrate is reduced to dinitrogen gas (N2) by four enzymes; nitrate reductase (NAR & NAP), nitrite reductase (NIR), nitric oxide reductase (NOR) and nitrous oxide reductase (N2OR). The end product of denitrification depends on the different bacteria species ability to synthesize the required enzymes involved in the denitrification process, some bacteri...

  18. The role of benthic macrofauna on nitrogen cycling in eutrophic lake sediment

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, J.M.

    1998-12-01

    This thesis concerns the role of sediment-living macrobenthos in the cycling of nitrogen species and nitrogen transformation in eutrophic freshwater sediments. In my thesis I have, employing {sup 15}N-isotope techniques in laboratory experiments, shown the importance of infaunal chironomid larvae and oligochaetes on denitrification in eutrophic lake sediments. Investigated benthic organisms not only expand the sediment surface with their permanent or non-permanent burrow constructions, they also transport water through the burrows continuously. This behaviour of intermittent water-pumping activity, provides the burrows with oxygen, and in addition, mediates the supply of nitrate to denitrifying zones. The highly dynamic oxygen climate within and narrow oxic zones around burrows, due to their radial geometry, provides a very short diffusion path for nitrate into surrounding anoxic zones. In my studies rates of denitrification were enhanced c. 3 to 6-fold by the influence of chironomids (Chironomus plumosus) and c. 2-fold by the influence of oligochaetes at comparable biomass. The difference in degree of stimulation is explained by species-specific habitat exploitation which could also be observed between different tube-dwelling species of chironomids. Besides chironomid biomass, the degree of enhancement of denitrification by chironomids was dependent on nitrate concentration in the overlying water, and water temperature. Nitrification was also seen to be stimulated by the infaunal macrobenthos but to a lesser degree than denitrification. It is suggested that bioturbated eutrophic sediment, under predominantly oxic bottom water conditions may act more pronouncedly as a sink for inorganic nitrogen relative to non-bioturbated sediment, and that bioturbated sediment above all, may be an important factor contributing to lowered transport of nitrogen to the coast. In order to sustain high nitrogen removal capacity in wetlands, ponds and lakes, it is further suggested

  19. Benthic Cover

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic cover (habitat) maps are derived from aerial imagery, underwater photos, acoustic surveys, and data gathered from sediment samples. Shallow to...

  20. Nitrous oxide concentration and nitrification and denitrification in Zhujiang River Estuary, China

    Institute of Scientific and Technical Information of China (English)

    XU Jirong; WANG Youshao; WANG Qinji; YIN Jianping

    2005-01-01

    The concentrations of nitrous oxide varies between 57 and 329 nmol/dm3, saturation is 674%~4 134% in the Zhujiang River Estuary.This suggests that the area is an emissive source of nitrous oxide. The acetylene inhibition technique is employed to evaluate the rates ofnitrification, denitrification and nitrate reduction by bacterial activities in the sediments at three sites. The average of nitrification,tical profiles of the sediments show that the nitrification and denitrification processes mainly take place in the depth from 0 to 4 cm and depend on regional conditions. The rates of nitrification, denitrification and nitrate reduction are dominated by Eh, nitrate and ammonium concentrations in sediments and DO in overlay water. There is a coupling between nitrification and denitrification.

  1. 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

  2. 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.

  3. [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.

  4. Estimates of Denitrification and Nitrification in Coastal and Estuarine Sediments

    OpenAIRE

    Nishio, Takashi; Koike, Isao; Hattori, Akihiko

    1983-01-01

    Denitrification and nitrification in sediments of Tama Estuary and Odawa Bay, Japan, were investigated by the combined use of a continuous-flow sediment-water system and a 15N tracer technique. At Odawa Bay, the nitrification rate was comparable to the nitrate reduction rate, and 70% of the N2 evolved originated from nitrogenous oxides (nitrate and nitrite) which were produced by the action of nitrifying bacteria in the sediments. At Tama Estuary, the nitrate reduction rate was 11 to 17 times...

  5. Research Progress on the Simultaneous Removal of Nitrate and Pesticides from Groundwater using Solid-phase Denitrification Process%固相反硝化技术同时去除地下水中的硝酸盐与农药进展

    Institute of Scientific and Technical Information of China (English)

    王旭明; 孙立娇; 仇天雷; 张兰河

    2012-01-01

    概述了固相反硝化技术及其特点,综述了固相反硝化技术在去除地下水中硝酸盐与农药的研究现状,分析了反应机理及当前研究中存在的问题,并在此基础上对固相反硝化的未来核心研究方向进行了展望.%Groundwater pollution by pesticides and nitrate from intensive agricultural practices is a common and growing problem in the major agricultural areas of the world. A novel water treatment process termed as "solid-phase denitrification (SPD)" is introduced, and the present research status and development for the simultaneous removal of nitrate and pesticides using SPD process are reviewed. The mechanisms and problems for SPD research are also analyzed. Finally, the future research emphasis and prospect are proposed.

  6. 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.

  7. Potential nitrosamine formation and its prevention during biological denitrification of red beet juice.

    Science.gov (United States)

    Kolb, E; Haug, M; Janzowski, C; Vetter, A; Eisenbrand, G

    1997-02-01

    High nitrate intake has been shown to result in an increased risk of endogenous formation of N-nitroso compounds. Certain vegetables and vegetable juices contain high concentrations of nitrate. Biological denitrification using strains of Paracoccus denitrificans (P.d.) has been proposed as effective means to reduce nitrate contents in such vegetable juices. During this bacterial denitrification process, substantial nitrite concentrations are transiently formed. This study investigated whether N-nitrosation reactions might occur. The easily nitrosatable amine morpholine was added to red beet juice at high concentration (100 ppm) during denitrification 10 different batches of red beet juice served as raw material. Each batch was submitted to denitrification in the presence and absence of ascorbic acid. In the absence of ascorbic acid, formation of N-nitrosomorpholine (NMOR) was observed in the low ppb range (0.5-8 ppb). Addition of ascorbic acid (500 mg/litre) inhibited the formation of NMOR, except for those instances where the pH was less than 6 and/or nitrate turnover was low (high rates of nitrate turnover (> 200 mg NO3-/litre/hr), nitrosamine formation can reliably be prevented by ascorbic acid. The results show that bacterial denitrification of red beet juice high in nitrate can be accomplished without the risk of nitrosamine formation. PMID:9146735

  8. Effects of sulfide on the integration of denitrification with anaerobic digestion.

    Science.gov (United States)

    Yin, Zhixuan; Xie, Li; Zhou, Qi

    2015-10-01

    The effects of sulfide on the integration of denitrification with anaerobic digestion using anaerobic effluents of cassava stillage as carbon source were investigated. Batch tests indicated that nitrate reduction efficiencies decreased from 96.5% to 15.8% as sulfide/nitrate (S/NO3(-)-N) ratios increased from 0.27 to 1.60. At low S/NO3(-)-N ratios (0.27-1.08) anaerobic acidogenesis was accelerated. Nitrate was reduced to nitrite via sulfur-based autotrophic denitrification, after which the formed nitrite and residual nitrate were converted to N2 via heterotrophic denitrification. Increases in the S/NO3(-)-N ratio (1.60) caused a shift (76.3%) in the nitrate reduction pathway from denitrification to dissimilatory nitrate reduction to ammonia (DNRA). Sulfide concentrations (S/NO3(-)-N ratio of 1.60) suppressed not only heterotrophic denitrification but also acidogenesis. The potentially toxic effect of sulfide on acid production was mitigated by its rapid oxidation to sulfur, allowing the recovery of acidogenesis. PMID:25801462

  9. 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.

  10. Potential rates and environmental controls of denitrification and nitrous oxide production in a temperate urbanized estuary.

    Science.gov (United States)

    Teixeira, Catarina; Magalhães, Catarina; Boaventura, Rui A R; Bordalo, Adriano A

    2010-12-01

    Denitrification may play a major role in inorganic nitrogen removal from estuarine ecosystems, particularly in those subjected to increased nitrate and organic matter loads. The Douro estuary (NW Portugal) suffers from both problems: freshwater input of nitrate and organic load from untreated wastewater discharges. To assess how these factors might control sediment denitrification, a 12-month survey was designed. Denitrification potential and nitrous oxide (N(2)O) production were measured at different locations using the slurry acetylene blockage technique. Denitrification rate ranged from 0.4 to 38 nmol N g⁻¹ h⁻¹, increasing towards the river mouth following an urban pollution gradient. N(2)O production, a powerful greenhouse gas implicated on the destruction of the ozone layer, was significantly related with sediment organic matter and accounted for 0.5-47% of the N gases produced. Additional enrichment experiments were consistent with the results found in the environment, showing that sediments from the upper less urban stretch of the estuary, mostly sandy, respond positively to carbon and, inversely, in organic rich sediments from the lower estuary, the denitrification potential was limited by nitrate availability. The obtained results confirmed denitrification as an important process for the removal of nitrate in estuaries. The presence of wastewater discharges appears to stimulate nitrogen removal but also the production of N(2)O, a powerful greenhouse gas, exacerbating the N(2)O:N(2) ratio and thus should be controlled. PMID:20688382

  11. Benthic processes in fresh water fluffy sediments undergoing resuspension

    Directory of Open Access Journals (Sweden)

    Daniele Longhi

    2013-02-01

    Full Text Available In the Po river plain relict freshwater wetlands are characterised by a low free water to emergent macrophyte surface ratio, rapid infilling and fluffy sediments, undergoing frequent resuspension. Particle mixing should alter the steep gradients of dissolved gas, nutrient and organic matter quality that generally characterise sediments, with implications for benthic processes. Sediment features and solute fluxes were studied from December 2003 to February 2005 within the Busatello swamp complex (Northern Italy by means of a combination of core incubation, porewater extraction and microprofiling. At the study site, along a 10 cm vertical profile, sediment organic matter content (32.5%, porosity (0.94 and density (1.02 g cm–3 were nearly constant. Oxygen demand measured by dark core incubation (12.7-56.9 mmol m–2 d–1 was strongly correlated with water temperature. Rates agreed reasonably well with diffusive oxygen fluxes calculated from microprofiles while ammonium and phosphorus regeneration rates predicted from porewater gradients (-309.3-43.4 and -0.1-0.7 μmol m–2 d–1, respectively were significantly lower than rates measured via core incubations (-129.8-5420.5 and -120.4-35.4 μmol m–2 d–1, respectively. This is a probable consequence of insufficient vertical resolution of nutrient profiles and lack of steady state conditions. A sediment resuspension experiment, carried out under controlled laboratory conditions, indicated large instantaneous oxygen and nitrate consumption, a transient increase of denitrification rates and the rapid release of ammonium and soluble reactive phosphorus. In unconsolidated sediments, resuspension and mixing of sediment particles are key processes regulating mineralisation rates and benthic-pelagic coupling.

  12. 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.

  13. 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.

  14. 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...... View the MathML source or sulfide concentrations were converted to in situ rates using the measured water column concentrations of View the MathML source and sulfide and the actual measured relations between View the MathML source and sulfide concentrations and denitrification rates. In situ...... extrapolated to the entire Baltic Proper (BP) denitrification in the water column was in the range of 132–547 kton N yr−1 and was thus at least as important as sediment denitrification which has recently been estimated to 191 kton N yr−1. With a total external N-input of 773 kton N yr−1 it is clear that...

  15. 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.

  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

    wastewaters from fish, potato and onion industries all stimulated denitrification. Reject water from anaerobic treatment of excess sludge had no significant effect on the denitrification processes. For isobutyric, isovaleric and n-valeric acid the undissociated compounds appear to act as the inhibitor......The effect of volatile fatty acids and trimethylamine on denitrification activity of activated sludge was studied in laboratory batch experiments. Formic acid had no effect on the denitrification rates. Acetic acid, n-butyric acid and trimethylamine all enhanced the rates. Acetate is the compound...... 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. Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea

    OpenAIRE

    Dähnke, K.; B. Thamdrup

    2013-01-01

    The global marine nitrogen cycle is constrained by nitrogen fixation as a source of reactive nitrogen, and denitrification or anammox on the sink side. These processes with their respective isotope effects set the marine nitrate N-15-isotope value (delta N-15) to a relatively constant average of 5 parts per thousand. This value can be used to better assess the magnitude of these sources and sink terms, but the underlying assumption is that sedimentary denitrification and anammox, processes re...

  18. Biological denitrification of brine: the effect of compatible solutes on enzyme activities and fatty acid degradation

    OpenAIRE

    Cyplik, Paweł; Piotrowska-Cyplik, Agnieszka; Marecik, Roman; Czarny, Jakub; Drożdżyńska, Agnieszka; Chrzanowski, Łukasz

    2012-01-01

    The effect of the addition of compatible solutes (ectoine and trehalose) on the denitrification process of saline wastewater was studied. In saline wastewater, it was observed that the initial concentration of nitrates was 500 mg N l−1. A fatty substance isolated from oiled bleaching earth (waste of vegetable oil refining process) was used as a source of carbon. The consortium, which was responsible for the denitrification process originated from the wastewater of the vegetable oil industry. ...

  19. Influence of organic carbon sources and isotope exchange processes between water and nitrate on the fractionation of the stable isotopes 15N/14N and 18O/16O in dissolved nitrate during microbial dentrification in groundwater

    International Nuclear Information System (INIS)

    Stable isotopes of nitrate are commonly used to determine sources and degradation of nitrate. In this study, nitrite oxidizing bacteria were found to promote an oxygen isotope exchange between water and nitrate under anoxic conditions. Also, different carbon sources were found to influence the enrichment of stable isotopes in nitrate during microbial denitrification. Both results refine the stable isotope model of nitrate in respect to nitrate source determination and microbial nitrate reduction.

  20. Benthic foraminifera

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.

    less prone to diagenetic changes and degrade in a more arbitrary manner, indicating that their degradation is not only depend on test architecture, but also the physical/mechanical processes (Berkeley et al., 2009). There is a net, and species... (Nolet and Corliss, 1990). Differences in the abundance of oxygen-sensitive and dissolution-prone benthic foraminiferal species between the Last Glacial Maximum (LGM) and the Holocene in the abyssal waters of the southwestern Gulf of Mexico were used...

  1. Denitrification in Low pH Spodosols and Peats Determined with the Acetylene Inhibition Method

    OpenAIRE

    1980-01-01

    Potential denitrification rates were determined for predominantly acid (pH ≥ 3.6) horizons of forestal, miry, and agricultural soils from 22 locations in southern Finland. The acetylene inhibition method was used with nitrate-amended water-logged soils incubated in an N2 atmosphere containing 2.5 or 5% C2H2. Complete inhibition of the reduction of N2O to N2 was observed in 99.3% of the samples. The denitrification rates varied from 0.12 to 53.8 μg of N·cm-3·day-1. Correlation between denitrif...

  2. [Biocatalyst of redox mediators on the denitrification by Paracoccus versutus strain GW1].

    Science.gov (United States)

    Li, Hai-Bo; Lian, Jing; Guo, Yan-Kai; Zhao, Li-Jun; Du, Hai-Feng; Yang, Jing-Liang; Guo, Jian-Bo

    2012-07-01

    The quinone respiration process of Paracoccus versutus strain GW1 was characterized and the effects of the four redox mediators on the denitrification process were studied. The experiment results suggested that quinones were utilized by Paracoccus versutus strain GW1 as electron acceptors in the respiratory chain and reduced to hydroquinone. Batch experiments were carried out to investigate the biocatalyst effect of redox mediators as catalyst on the denitrification process at 35 degrees C. All four redox mediators tested were able to enhance the nitrate removal efficiency and the denitrification efficiency by 1.14-1.63 fold and 1.12-2.02 fold, respectively. The accelerating effect from high to low was AQDS > 1,5-AQDS > AQS > alpha-AQS. In the presence of redox mediators, the stabilized ORP values in the nitrate decomposition process were reduced by 33-75 mV. The pH variations in denitrification with redox mediators showed similar tendency to that of the conventional nitrate removal process. In the concentration range of 0-0.32 mmol x L(-1), AQDS had the best accelerating effect and a linear correlation was found for the denitrification rate K and the AQDS concentration cAQDS. This study indicated that the application of redox mediators significantly improved the denitrification process by enhancing the decomposition rate. PMID:23002627

  3. Inhibition of existing denitrification enzyme activity by chloramphenicol.

    OpenAIRE

    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. Chlo...

  4. Dietary carbohydrates and denitrification in recirculating aquaculture systems

    OpenAIRE

    Meriac, A.

    2014-01-01

    Due to overfishing of global fish stocks and increasing fish meal prices, plant ingredients are being increasingly used as an alternative source of protein in fish feeds. However, the inclusion of unpurified plant ingredients will also increase the content of fibers in feeds. Fibers are nearly indigestible and will therefore increase solid waste production in aquaculture. This solid waste can be used to as a carbon source for denitrification to control nitrate levels in recirculating aquacult...

  5. Treatment of hydroponic wastewater by denitrification filters using plant prunings as the organic carbon source.

    Science.gov (United States)

    Park, J B K; Craggs, R J; Sukias, J P S

    2008-05-01

    This study investigated the feasibility of using pre-treated plant liquors as organic carbon sources for the treatment of hydroponic wastewater containing high nitrate-N (>300 mg N/L). The waste plant material was pre-treated to extract organic carbon-rich liquors. When this plant liquor was used as an organic carbon source in denitrification filters at the organic carbon:nitrogen dose rate of 3C:N, nitrate removal efficiencies were >95% and final effluent nitrate concentrations were consistently 140 mg/L) of organic carbon (fBOD5) remained in the final effluents. Therefore, a 'compromise' organic carbon:nitrogen dose rate (2C:N) was trialled, at which nitrate removal efficiencies were maintained at >85%, final effluent nitrate concentrations were consistently below 45 mg N/L, and effluent fBOD5 concentrations were hydroponic wastewater in a denitrification filter. PMID:17714940

  6. Operation of a fluidized-bed denitrification bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, P.A.

    1978-11-15

    In the fluidized-bed denitrification process developed, bacteria are allowed to grow and attach themselves to 0.25 to 0.60-mm-OD coal particles, and nitrate-containing solution is pumped up through the column at a velocity sufficient to fluidize the bacteria-coated coal particles. The denitrification bacteria convert the nitrate ions to nitrogen gas. A 10-cm-ID column has been operated by Oak Ridge Y-12 Plant personnel to test the scale-up and operational characteristics of the fluidized bed process. The reactor consists of a tapered bottom section for flow distribution, several straight 10-cm-ID cylindrical sections, and a tapered top section for solid/liquid disengaging. Increasing the diameter of the reactor by a factor of two did not cause any decrease in reactor performance. The fluidized-bed reactor is characterized by short-residence-time requirements (about 2 minutes per meter of height), and by high, but variable, denitrification rates (2 to 35 g NO/sub 3//sup -/-N/dm/sup 3//day). The reactor is best suited for relatively low-concentration nitrate wastes (<1 wt% NO/sub 3//sup -/). The economics of using the reactor for high-concentration wastes (>20 wt% NO/sub 3//sup -/) is less favorable, but still may be competitive with other reactor types. 9 figs, 2 tables.

  7. 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.

  8. 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.

  9. Eutrophication in the northern Adriatic Sea: Benthic fluxes and nutrient budgets

    Energy Technology Data Exchange (ETDEWEB)

    Berelson, W.M.; Hammond, D.E. (Univ. of Southern California, Los Angeles (United States)); Giordani, P. (Inst. di Geologia Marina-CNR, Bologna (Italy))

    1990-01-09

    The northern Adriatic Sea has been plagued by problems of eutrophication. This area is relatively shallow (maximum depth = 60m), becoming stratified during the summer months which inhibits oxygen transport to bottom waters. Anthropogenic nutrient loading in rivers entering the northern Adriatic has increased nutrient input to this system and stimulated algai growth. Five stations in the western Adriatic (south of the Po River Delta) were occupied during September, 1988 and benthic flux chambers used to measure nutrient fluxes. These sites included 3 stations previously studied in 1982. Flux measurements of dissolved silica, nitrate, oxygen, ammonia, phosphate, CO[sub 2], alkalinity and radon were made during 24 hour incubations of flux chambers (area covered - 0.07 m[sup 2], volume = [approximately]81) that were continuously stirred and sampled periodically. Nutrient fluxes measured were generally consistent with the fluxes measured previously in June, 1982 except for radon fluxes which were 203 times greater in the earlier field season. There was a general trend in nutrient fluxes to decrease offshore, a pattern probably controlled by the sedimentation patterns because fine grained, organic matter-rich sediment are concentrated in a zone near shore. Average regional fluxes were (in mmol m[sup -2]d[sup -1], negative values indicate flux into sediment): Oxygen (-12), CO[sub 2] (19), Alkalinity (4), Silica (3.3), Ammonia (1.5), Phosphate (0.1) and Nitrate (0.3). The carbon/ammonia flux ratio is about twice the C/N ratio in marine phytoplankton, suggesting that large amounts of denitrification may be occuring in these sediments. Comparisons of benthic fluxes and sediment burial rates indicate that 50-90% of the carbon, silica, phosphorus and nitrogen arriving at the sediment-water interface is recycled before burial. The nutrient input to the water column from NW Adriatic sediments is about equal to the input from coastal rivers.

  10. Significance of dredging on sediment denitrification in Meiliang Bay, China: A year long simulation study

    Science.gov (United States)

    Zhong, Jicheng; Fan, Chengxin; Zhang, Lu; Edward, Hall; Ding, Shiming; Li, Bao; Liu, Guofeng

    2010-01-01

    An experiment for studying the effects of sediment dredging on denitrification in sediments was carried out through a one-year incubation of undredged (control) and dredged cores in laboratory. Dredging the upper 30 cm of sediment can significantly affect physico-chemical characteristics of sediments. Less degradation of organic matter in the dredged sediments was found during the experiment. Denitrification rates in the sediments were estimated by the acetylene blockage technique, and ranged from 21.6 to 102.7 nmol N2/(g dry weight (dw) x hr) for the undredged sediment and from 6.9 to 26.9 nmol N2/(g dw x hr) for dredged sediments. The denitrification rates in the undredged sediments were markedly higher (p < 0.05) than those in the dredged sediments throughout the incubation, with the exception of February 2006. The importance of various environmental factors on denitrification was assessed, which indicated that denitrification was regulated by temperature. Nitrate was probably the key factor limiting denitrification in both undredged and dredged sediments. Organic carbon played some role in determining the denitrification rates in the dredged sediments, but not in the undredged sediments. Sediment dredging influenced the mineralization of organic matter and denitrification in the sediment; and therefore changed the pattern of inherent cycling of nitrogen.

  11. Membrane bioreactor for drinking water denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Barreiros, A.M. [Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa (Portugal)]|[Escola Superior de Tecnologia, Instituto Politecnico de Setubal, Rua do Vale de Chaves, Estefanilha, 2900 Setubal (Portugal); Rodrigues, C.M.; Crespo, J.P.S.G.; Reis, M.A.M. [Departamento de Quimica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa (Portugal)

    1998-04-01

    The aim of this study is to evaluate the performance of a membrane bioreactor with cell recycle to be used for drinking water denitrification, when operated with a high nitrate load (up to 7.68 kgNO{sub 3}{sup -}/m{sup 3} day) and low hydraulic retention time (down to 0.625 h). Nitrate and nitrite were always completely removed for all the operational conditions used. The effluent`s nitrite concentration kept below 0.1 mg NO{sub 2}{sup -}/l with exception of a short period, during the reactor start-up, when it accumulates. The performance of the membrane bioreactor was also evaluated using a groundwater containing 148 mg NO{sub 3}{sup -}/l. Nitrate and nitrite concentration in the effluent were below the recommended values for drinking water when the reactor was controlled at pH 7.0. The membrane flux decreases during operation as a consequence of membrane fouling. The flux decrease was more severe during operation with synthetic medium than with contaminated groundwater due to the existence of molecular complexes in the synthetic broth. A backshock technique was used to reduce the surface fouling of the membrane. Combining this technique with the use of a reserve asymmetric structured membrane it was found that the membrane flux remains nearly unchanged. (orig.) With 7 figs., 14 refs.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. Benthic fluxes of dissolved organic nitrogen in the Lower St. Lawrence Estuary and implications for selective organic matter degradation

    Directory of Open Access Journals (Sweden)

    M. Alkhatib

    2013-05-01

    Full Text Available The distribution of dissolved organic nitrogen (DON and carbon (DOC in sediment pore waters was determined at nine locations along the St. Lawrence Estuary and in the Gulf of St. Lawrence. The study area is characterized by gradients in the sedimentary particulate organic matter (POM reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. Based on pore water profiles we estimated the benthic diffusive fluxes of DON and DOC. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m−2 d−1. DON fluxes were positively correlated with sedimentary POM reactivity and sediment oxygen exposure time (OET, suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30% to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange. This result is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. The ratio of the DON to nitrate flux increased from 0.6 in the Lower Estuary to 1.5 in the Gulf. In contrast to DON, DOC fluxes did not show any significant spatial variation along the Laurentian Channel (LC between the Estuary and the Gulf (2100 ± 100μmol m−2 d−1, suggesting that production and consumption of labile DOC components proceed at similar rates, irrespective of the overall benthic characteristics and the reactivity of POM. As a consequence, the molar C/N ratio of dissolved organic matter (DOM in pore water and the overlying bottom water varied significantly along the transect, with lowest C/N in the Lower Estuary (5–6 and highest C/N (> 10 in the Gulf. We observed large differences between the C/N of pore water DOM with respect to POM, and the degree of

  17. Denitrification in diffuse hydrothermal vent fluids of Axial Volcano and the Endeavour Segment on the Juan de Fuca Ridge

    Science.gov (United States)

    Bourbonnais, A.; Lehmann, M. F.; Butterfield, D. A.; Devol, A.; Chang, B. X.; Juniper, K.

    2009-12-01

    Denitrification is a major and well-investigated sink of bio-available nitrogen (N) in the ocean. However, little is known about the removal of N in diffuse hydrothermal vents. Hydrothermal vent fluids are known to harbor diverse bacterial populations, and the use of nitrate as an electron acceptor for the microbially mediated oxidation of hydrogen sulphide has previously been documented in these extreme environments, but no direct measurements of denitrification rates have been reported. We present the first denitrification rate estimates (i.e. the conversion of nitrate to nitrogen gas) derived from 15N-label incubations at 7 diffuse hydrothermal vent sites along the Juan de Fuca Ridge (North-East Pacific). Incubation samples (in-situ temperatures between 6.8 and 40.8οC) were collected during research cruises in June and August 2008. We also measured the isotopic composition of nitrate and ammonium from low-T sites collected during several cruises from 2006 to 2009. Mixing between ambient seawater and sub-seafloor hydrothermal reservoirs is the dominant process that modulates DIN concentration and isotope dynamics. However, clear signs of isotope fractionation of the N (and O of nitrate) isotopes at some sites suggests the presence of nitrate consuming processes, likely denitrification and/or the assimilation by vent microorganisms. 15N incubation-based denitrification rates ranged from 0 to 0.6 μM N/day, with no consistent relationship with the in-situ temperature of the vent fluids. With only one exception, detectable denitrification rates were determined at all sites, suggesting that denitrification is an important N-elimination process in diffuse vent fluids. Ongoing work that aims at studying the environmental factors that potentially control rates of denitrification (e.g. temperature, flow rate, fluid chemistry), as well as other possible N removal pathways (e.g. anammox and DNRA coupled to anammox), will also be discussed.

  18. 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.

  19. Nitrate retention and removal in Mediterranean streams with contrasting land uses: a 15N tracer study

    Directory of Open Access Journals (Sweden)

    J. L. Riera

    2008-08-01

    Full Text Available We used 15N-labelled nitrate (NO−3 additions to investigate nitrogen (N cycling at the whole-reach scale in three Mediterranean streams subjected to contrasting land uses (i.e. forested, urban and agricultural. Our aim was to examine: i the magnitude and relative importance of NO−3 retention (i.e. assimilatory uptake, and removal, (i.e. denitrification, ii the relative contribution of the different primary uptake compartments to NO−3 retention, and iii the regeneration, transformation and export pathways of the retained N. The concentration of NO−3 increased and that of dissolved oxygen (DO decreased from the forested to the agricultural stream, with intermediate values in the urban stream. Standing stocks of primary uptake compartments were similar among streams and dominated by detritus compartments (i.e. fine and coarse benthic organic matter. In agreement, metabolism was net heterotrophic in all streams, although the degree of heterotrophy increased from the forested to the agricultural stream. The NO−3 uptake length decreased along this gradient, whereas the NO−3 mass-transfer velocity and the areal NO−3 uptake rate were highest in the urban stream. Denitrification was not detectable in the forested stream, but accounted for 9% and 68% of total NO−3 uptake in the urban and the agricultural stream, respectively. The relative contribution of detritus compartments to NO−3 assimilatory uptake was highest in the forested and lowest in the agricultural stream. In all streams, the retained N was rapidly transferred to higher trophic levels and regenerated back to the water column. Due to a strong coupling between regeneration and nitrification, most retained N was exported from the experimental reaches in the form of NO−3. This study evidences fast N cycling in Mediterranean streams. Moreover, results indicate that permanent NO−3 removal via denitrification may be enhanced over temporary NO−3 retention via assimilatory

  20. Reintroduction of flooding and change in denitrification rates on a leveed Midwestern floodplain

    Science.gov (United States)

    Orr, C. H.; Stanley, E.; Wilson, K.; Finlay, J.

    2005-05-01

    We examined the response of soil denitrification to a floodplain restoration project that reintroduced controlled flooding to a previously isolated 900 hectare site adjacent to the Baraboo River, Wisconsin. Monthly June-August for one year prior and two years post restoration we measured denitrification in static cores (SC μgN2O-N/kgsoil-hr) and potential denitrification in carbon and nitrate amended soil slurry samples (DEA μgN2O-N/kgsoil-hr). Rates showed high temporal and spatial variability. Individual sample SC rates ranged widely (0.00 to 16.7) with a mean value of 1.10 (SD = 3.02). DEA rates were in the same general range (0.00 to 15.0) but with a slightly higher mean (mean 1.41, comparison psoil nutrient content. However, the difference in rates between SC and DEA samples pre-restoration was higher than post-restoration, suggesting that denitrification was less limited after the reintroduction of flooding. Vegetation type and history of flooding were better predictors of denitrification than current soil water content. Despite large variability in measured rates, these results demonstrate that there is potential for denitrification to remove significant amounts nitrate from river systems. Management of water levels to provide adequate exchange between river and floodplain is important to this process.

  1. Concurrence of Anaerobic Ammonium Oxidation and Organotrophic Denitrification in Presence of p-Cresol.

    Science.gov (United States)

    González-Blanco, G; Cervantes, F J; Beristain-Cardoso, R; Gómez, J

    2015-08-01

    This study was carried out to evaluate the capacity of anaerobic granular sludge for oxidizing ammonium and p-cresol with nitrate as terminal electron acceptor. Kinetics for the anaerobic oxidation of ammonium and p-cresol is described in this paper. The phenolic compound was very efficiently consumed, achieving 65 % of mineralization. Ammonium and nitrate were also consumed at 83 and 92 %, respectively, being the main product N2. Anaerobic ammonium oxidation was promoted owing to accumulation of nitrite, and it allowed the synergy of anaerobic ammonium oxidation and organotrophic denitrification for the simultaneous removal of ammonium, nitrate, and p-cresol. A carbonaceous intermediate partially identified was transiently accumulated, and it transitorily truncated the respiratory process of denitrification. These experimental results might be considered for defining strategies in order to remove nitrate, ammonium, and phenolic compounds from wastewaters. PMID:26062920

  2. 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.

  3. N₂O accumulation from denitrification under different temperatures.

    Science.gov (United States)

    Poh, Leong Soon; Jiang, Xie; Zhang, Zhongbo; Liu, Yu; Ng, Wun Jern; Zhou, Yan

    2015-11-01

    The effects of temperature on nitrous oxide (N2O) accumulation during denitrification and denitritation were investigated. Batch experiments were performed to measure N2O accumulation at 25 and 35 °C. More N2O accumulation was observed during denitritation at the higher temperature as compared with full denitrification and low temperature tests. The highest nitrite concentration tested in this study (25 mg/L NO2 (-)N and pH 8.0) did not show inhibitory effect on N2O reduction. It was found that the major cause of more N2O accumulation during denitrification at higher temperature was due to higher N2O production rate and lower N2O solubility. Specific nitrate, nitrite, and N2O reduction rates increased 62, 61, and 41 %, respectively, when temperature rose from 25 to 35 °C. The decrease of N2O solubility in mixed liquor at 35 °C (when compared to 25 °C) resulted in faster diffusing rate of N2O from liquid to gas phase. It was also more difficult for gas phase N2O to be re-dissolved. The diffused N2O was then accumulated in the headspace, which was not available for denitrification by denitrifiers. The results of this study suggest higher temperature may worsen N2O emission from wastewater treatment plants (WWTPs). PMID:26129949

  4. O 2 reduction and denitrification rates in shallow aquifers

    Science.gov (United States)

    Tesoriero, A.J.; Puckett, L.J.

    2011-01-01

    O 2 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. O 2 reduction rates varied widely within and between sites, with zero-order rates ranging from 100 mol 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 O 2 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 O 2 reduction rates and negatively correlated at sites with lower rates. Furthermore, electron donors from recharging DOC are not sufficient to account for appreciable O 2 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. copyright 2011 by the American Geophysical Union.

  5. Operation of a fluidized-bed bioreactor for denitrification

    Energy Technology Data Exchange (ETDEWEB)

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

    1978-01-01

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

  6. Operation of a fluidized-bed bioreactor for denitrification

    International Nuclear Information System (INIS)

    Two denitrification fluidized-bed bioreactors of the same length (i.e., 5 m) but with different inside diameters (i.e., 5 and 10 cm) have been operated on feed ranging in nitrate concentration from 200 to 2000 g/m3; thus far, good agreement has been obtained. Two 10-cm-ID bioreactors operating in series have also been tested; the results are in accordance with predicted results based on the performance of a 5-cm-ID bioreactor. The overall denitrification rate in the dual 10-cm-ID bioreactor system was found to be 23 kg N(NO3-)/day-m3 using feed with a nitrate concentration of 1800 g/m3. Data obtained in operating-temperature tests indicate that the maximum denitrification rate is achieved between 22 and 300C. These data will form the basis of the design of our mobile pilot plant which consists of dual 20-cm-ID by 7.3-m-long bioreactors

  7. Enhancing denitrification using a carbon supplement generated from the wet oxidation of waste activated sludge.

    Science.gov (United States)

    Strong, P J; McDonald, B; Gapes, D J

    2011-05-01

    This study compared the effect of four pure carbon supplements on biological denitrification to a liquor derived as a by-product from the wet oxidation (WO) of waste activated sludge. Sequencing batch reactors were used to acclimate sludge biomass, which was used in batch assays. Acetate, WO liquor and ethanol-supplementation generated the fastest denitrification rates. Acetate and WO liquor were efficiently utilised by all acclimated biomass types, while poor rates were achieved with methanol and formate. When comparing an inoculum from an ethanol-supplemented and non-supplemented wastewater treatment plant (WWTP), the ethanol-acclimated sludge obtained superior denitrification rates when supplemented with ethanol. Similarly high nitrate removal rates were achieved with both sludge types with acetate and WO liquor supplementation, indicating that WO liquors could achieve excellent rates of nitrate removal. The performance of the WO liquor was attributed to the variety of organic carbon substrates (particularly acetic acid) present within the liquor. PMID:21196117

  8. Kinetic analysis of simultaneous denitrification and biomineralization of novel Acinetobacter sp. CN86.

    Science.gov (United States)

    Su, Jun-Feng; Shi, Jing-Xin; Huang, Ting-Lin; Ma, Fang

    2016-08-15

    A novel aerobic denitrification and biomineralization strain CN86 was isolated from the Qu Jiang artificial lake. Based on phylogenetic characteristics, the isolated strain was identified as Acinetobacter species. Strain CN86 was confirmed to have the ability to perform simultaneous denitrification and biomineralization. Exponential decay equation was used for the matching of kinetic processes on denitrification and biomineralization. A highest nitrate removal rate was achieved at the pH7.0, organic concentration of 1.5g/L and temperature of 30°C. An optimal hardness removal rate was obtained at the pH9.0, organic concentration of 2.0g/L and temperature of 30°C. Strain CN86 is a suitable candidate for the simultaneous removal of nitrate and hardness in groundwater treatment. PMID:27287863

  9. Oxidation of humic substances supports denitrification reactions in agricultural soils.

    Science.gov (United States)

    van Trump, J. I.; Coates, J. D.

    2007-12-01

    Humic substances (HS) are a ubiquitous, recalcitrant, and diverse class of compounds arising from degradation and condensation of plant and microbial biopolymers. Many bacteria oxidize hydroquinones within humic substances to their quinone analogs, providing electrons for respiratory processes such as nitrate reduction. Microbial hydroquinone oxidation contributes to the redox state of HS and supports denitrification, which may be of import to agricultural soils where nitrate retention is critical and HS are prevalent. Most probable number counts were performed on soils collected from a Nebraska farm, with the model humic hydroquinone 2,6- anthrahydroquinone disulfonate (AHDS) serving as an electron donor and nitrate as the electron acceptor. Results indicated that AHDS oxidizing, nitrate reducing bacteria were present in soils from bluegrass fields (104 cells/g) and aspen groves (106 cells/g), as well as in plots of corn (106 cells/g), and soybean treated (106 cells/g) and un-treated (105 cells/g) with pig slurry. These results demonstrate that microorganisms participating in the proposed metabolism are prevalent within agricultural soils. Upflow glass columns were constructed, containing a support matrix of glass beads amended with 10% w/w soil from the corn plot previously mentioned. All columns were subjected to a continual flow of phosphate-buffered water amended with sodium nitrate. Above the point source for nitrate injection, phosphate-buffered water containing electron donor treatments were continually injected. The impacts of electron donor treatments (no donor, oxidized HS, reduced HS, and acetate) on denitrification and other geochemical parameters were observed. Column studies were able to resolve effects of electron donor treatment both spatially as a function of distance from the injection point source, and temporally, as a function of time of donor treatment. Four sample ports in each column were routinely analyzed for concentrations of nitrate

  10. 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...

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

    DEFF Research Database (Denmark)

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

    2014-01-01

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

  12. 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 ...

  13. Isotopic and microbiological signatures of pyrite-driven denitrification in a sandy aquifer

    NARCIS (Netherlands)

    Zhang, Y.C.; Slomp, C.P.; Broers, H.P.; Bostick, B.; Passier, H.F.; Böttcher, M.E.; Omoregie, E.O.; Lloyd, J.R.; Polya, D.A.; Cappellen, P. van

    2012-01-01

    Denitrification driven by pyrite oxidation can play a major role in the removal of nitrate from groundwater systems. As yet, limited information is available on the interactions between the micro-organisms and aqueous and mineral phases in aquifers where pyrite oxidation is occurring. In this study,

  14. Microbial Oxidation of Pyrite Coupled to Nitrate Reduction in Anoxic Groundwater Sediment

    DEFF Research Database (Denmark)

    Jørgensen, Christian Juncher; Elberling, Bo; Jacobsen, Ole Stig;

    2009-01-01

    denitrification process with pyrite as the primary electron donor. The process demonstrates a temperature dependency (Q10) of 1.8 and could be completely inhibited by addition of a bactericide (NaN3). Experimentally determined denitrification rates show that more than 50% of the observed nitrate reduction can...

  15. Molecular characterization of a microbial consortium involved in methane oxidation coupled to denitrification under micro-aerobic conditions

    OpenAIRE

    Liu, Jingjing; Sun, Faqian; Wang, Liang; Ju, Xi; Wu, Weixiang; Chen, Yingxu

    2013-01-01

    Methane can be used as an alternative carbon source in biological denitrification because it is nontoxic, widely available and relatively inexpensive. A microbial consortium involved in methane oxidation coupled to denitrification (MOD) was enriched with nitrite and nitrate as electron acceptors under micro-aerobic conditions. The 16S rRNA gene combined with pmoA phylogeny of methanotrophs and nirK phylogeny of denitrifiers were analysed to reveal the dominant microbial populations and functi...

  16. A standardised method for measuring in situ denitrification in shallow aquifers: numerical validation and measurements in riparian wetlands

    OpenAIRE

    Sánchez-Pérez, J. M.; C. Bouey; Sauvage, S.; Teissier, S.; Antiguedad, I.; Vervier, P.

    2003-01-01

    A tracer test to examine in situ denitrification in shallow groundwater by a piezometer with a packer system used bromide as a tracer of dilution and acetylene (10%) to block the denitrification process at the nitrous oxide stage. During the test, dissolved oxygen, nitrate (NO3‾), bromide (Br‾), nitrous oxide (N2O) and dissolved organic carbon (DOC) were measured. To calibrate the experimental method, comparison with numerical simula...

  17. A standardised method for measuring in situ denitrification in shallow aquifers: numerical validation and measurements in riparian wetlands

    OpenAIRE

    Sánchez-Pérez, J. M.; C. Bouey; Sauvage, S.; Teissier, S.; Antiguedad, I.; Vervier, P.

    2003-01-01

    A tracer test to examine in situ denitrification in shallow groundwater by a piezometer with a packer system used bromide as a tracer of dilution and acetylene (10%) to block the denitrification process at the nitrous oxide stage. During the test, dissolved oxygen, nitrate (NO3‾), bromide (Br‾), nitrous oxide (N2O) and dissolved organic carbon (DOC) were measured. To calibrate the experimental method, comparison with numerical simulations of the groundwater transfer were carried o...

  18. Denitrification characteristics of a sulfur autotrophic denitrification reactor

    Directory of Open Access Journals (Sweden)

    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%.

  19. Molecular Approaches to Studying Denitrification

    Science.gov (United States)

    Voytek, M. A.

    2001-05-01

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

  20. Box-modeling of the impacts of atmospheric nitrogen deposition and benthic remineralization on the nitrogen cycle of the eastern tropical South Pacific

    Directory of Open Access Journals (Sweden)

    B. Su

    2015-09-01

    Full Text Available Both atmospheric deposition and benthic remineralization influence the marine nitrogen cycle, and hence ultimately also marine primary production. The biological and biogeochemical relations of the eastern tropical South Pacific (ETSP to nitrogen deposition, benthic denitrification and phosphate regeneration are analysed in a prognostic box model of the oxygen, nitrogen and phosphorus cycles in the ETSP. In the model, atmospheric nitrogen deposition based on estimates for the years 2000–2009 is offset by half by reduced N2 fixation, with the other half transported out of the model domain. Both model- and data-based benthic denitrification are found to trigger nitrogen fixation, partly compensating for the NO3− loss. Since phosphate is the ultimate limiting nutrient in the model, enhanced sedimentary phosphate regeneration under suboxic conditions stimulates primary production and subsequent export production and NO3− loss in the oxygen minimum zone (OMZ. A sensitivity analysis of the local response to both atmospheric deposition and benthic remineralization indicates dominant stabilizing feedbacks in the ETSP, which tend to keep a balanced nitrogen inventory, i.e., nitrogen input by atmospheric deposition is counteracted by decreasing nitrogen fixation; NO3− loss via benthic denitrification is partly compensated by increased nitrogen fixation; enhanced nitrogen fixation stimulated by phosphate regeneration is partly removed by the stronger water-column denitrification. Even though the water column in our model domain acts as a NO3− source, the ETSP including benthic denitrification might become a NO3− sink.

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

    Science.gov (United States)

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

    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 S1-1 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 level accumulation of nitrite, suggesting that the aerobic denitrification process of strain S1-1 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 S1-1 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 degrees C and initial pH 6.5. PMID:22432315

  2. 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.

  3. Comparative evaluation of nitrate removal technologies

    International Nuclear Information System (INIS)

    Due to the extensive application of artificial nitrogen-based fertilizers and animal manure on land, many water agencies face problems of increasing concentrations of nitrate in groundwater. The contamination of groundwater by nitrate may pose a significant public health problem. The threat of methemoglobinemia is well documented and reflected in the U.S. drinking water standard of 10 mg/L as nitrate-nitrogen. Approximately 45% of Saskatchewan's population use groundwater for drinking purposes, out of which, approximately 23% (230,000) are rural residents. The water used is made available from over 48,000 privately owned wells in regions where there is an extensive application of chemical fertilizers. Biological denitrification, ion exchange and reveres osmosis (RO) processes were selected for further study. Field studies were conducted on these processes. The sulfur/limestone autotrophic denitrification (SLAD) process was selected to achieve biological removal of nitrate from groundwater. The feasibility of the system was evaluated under anaerobic conditions. An ion exchange study was conducted using Ionac A554 which is strong anion exchange resins. In the case of groundwater containing low sulfate concentrations, A554 offered high nitrate removal. However, the disposal of regenerant brine can be a problem. A reverse osmosis unit with Filmtec membrane elements (FT30-Element Family) was used in the study on nitrate removal. The unit effluent average nitrate concentration was less than the maximum allowable concentration. (author)

  4. 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

  5. Cloth catalysts in water denitrification: I. Pd on glass fibers

    OpenAIRE

    Matatov-Meytal, Y.; Barelko, V.; Yuranov, I.; Sheintuch, M.

    2000-01-01

    Fiber catalysts are easy to handle and free of mass-transfer resistance. This report is the first application of cloth catalysts to water denitrification. In this work, cloths woven from glass fibers (GF) of 7–10 mm in diameter, impregnated with Pd, were tested in a semi-batch reactor to evaluate their effectiveness in the catalytic liquid phase hydrogenation of nitrites and nitrates. The catalytic properties of Pd-GF cloths were evaluated as a function of Pd loading as well of chemical comp...

  6. 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.

  7. 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.

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

    Science.gov (United States)

    Cathrine, Sumathi J; Raghukumar, Chandralata

    2009-01-01

    Denitrification is a microbial process during which nitrate or nitrite is reduced under anaerobic condition to gaseous nitrogen. The Arabian Sea contains one of the major pelagic denitrification zones and in addition to this, denitrification also takes places along the continental shelf. Prokaryotic microorganisms were considered to be the only players in this process. However recent studies have shown that higher microeukaryotes such as fungi can also adapt to anaerobic mode of respiration and reduce nitrate to harmful green house gases such as NO and N2O. In this study we examined the distribution and biomass of fungi in the sediments of the seasonal anoxic region off Goa from two stations. The sampling was carried out in five different periods from October 2005, when dissolved oxygen levels were near zero in bottom waters to March 2006. We isolated mycelial fungi, thraustochytrids and yeasts. Species of Aspergillus and thraustochytrids were dominant. Fungi were isolated under aerobic, as well as anaerobic conditions from different seasons. Four isolates were examined for their denitrification activity. Two cultures obtained from the anoxic sediments showed better growth under anaerobic condition than the other two cultures that were isolated from oxic sediments. Our preliminary results suggest that several species of fungi can grow under oxygen deficient conditions and participate in denitrification processes. PMID:18834939

  9. Cross effect of temperature, pH and free ammonia on autotrophic denitrification process with sulphide as electron donor.

    Science.gov (United States)

    Fajardo, Carmen; Mora, Mabel; Fernández, Isaac; Mosquera-Corral, Anuska; Campos, José Luis; Méndez, Ramón

    2014-02-01

    Autotrophic denitrification is a suitable technology to simultaneously remove oxidised nitrogen compounds and reduced sulphur compounds yielding nitrogen gas, sulphur and sulphate as the main products. In this work, several batch tests were conducted to investigate the cross effect of temperature, pH and free ammonia on the autotrophic denitrification. Denitrification efficiencies above 95% were achieved at 35°C and pH 7.5-8.0 with maximum specific autotrophic denitrifying activities up to 188mgN2g(-1)VSSd(-1). Free ammonia did not show any effect on denitrification at concentrations up to 53mg NH3-NL(-1). Different sulphide concentrations were also tested with stoichiometric nitrite and nitrate concentrations. Sulphide inhibited denitrification at concentrations higher than 200mgS(2-)L(-1). A 50% inhibition was also found at nitrite concentrations above 48mg NO2(-)-NL(-1). The maximum specific activity decreased until a value of 25mgN2g(-1) VSSd(-1) at 232mg NO2(-)-NL(-1). The Haldane model was used to describe denitrification inhibition caused by nitrite. Kinetic parameters determined from the fitting of experimental data were rmax=176mgN2g(-1)VSSd(-1), Ks=10.7mg NO2(-)-NL(-1) and Ki=34.7mg NO2(-)-NL(-1). The obtained model allowed optimising an autotrophic denitrification process by avoiding situations of inhibition and thus obtaining higher denitrification efficiencies. PMID:24216266

  10. Sulfur-based denitrification: Effect of biofilm development on denitrification fluxes.

    Science.gov (United States)

    Wang, Yue; Bott, Charles; Nerenberg, Robert

    2016-09-01

    Elemental sulfur (S(o)) can serve as an electron donor for denitrification. However, the mechanisms and rates of S(o)-based denitrification, which depend on a biofilm development on a solid S(o) surface, are not well understood. We used completely-mixed reactors packed with S(o) chips to systematically explore the behavior of S(o)-based denitrification as a function of the bulk nitrate (NO3(-)) concentration and biofilm development. High-purity (99.5%) and agricultural-grade (90% purity) S(o) chips were tested to explore differences in performance. NO3(-) fluxes followed a Monod-type relationship with the bulk NO3(-) concentration. For high-purity S(o), the maximum NO3(-) flux increased from 0.4 gN/m(2)-d at 21 days to 0.9 g N/m(2)-d at around 100 days, but then decreased to 0.65 gN/m(2)-d at 161 days. The apparent (extant) half-saturation constant for NO3(-) KSapp, based on the bulk NO3(-) concentration and NO3(-) fluxes into the biofilm, increased from 0.1 mgN/L at 21 days to 0.8 mgN/L at 161 days, reflecting the increasing mass transfer resistance as the biofilm thickness increased. Nitrite (NO2(-)) accumulation became significant at bulk NO3(-) concentration above 0.2 mgN/L. The behavior of the agricultural-grade S(o) was very similar to the high-purity S(o). The kinetic behavior of S(o)-based denitrification was consistent with substrate counter-diffusion, where the soluble sulfur species diffuse from the S(o) particle into the base of the biofilm, while NO3(-) diffuses into the biofilm from the bulk. Initially, the fluxes were low due to biomass limitation (thin biofilms). As the biofilm thickness increased with time, the fluxes first increased, stabilized, and then decreased. The decrease was probably due to increasing diffusional resistance in the thick biofilm. Results suggest that fluxes comparable to heterotrophic biofilm processes can be achieved, but careful management of biofilm accumulation is important to maintain high fluxes. PMID:27187050

  11. 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.

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

    Directory of Open Access Journals (Sweden)

    Renata Medici Frayne Cuba

    2011-02-01

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

  13. 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.

  14. Soil nitrate reducing processes – drivers, mechanisms for spatial variation, and significance for nitrous oxide production

    OpenAIRE

    Giles, Madeline; Morley, Nicholas; Baggs, Elizabeth M; Daniell, Tim J.

    2012-01-01

    The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate ( NO 3 − ) and production of the potent greenhouse gas, nitrous oxide (N2O). A number of factors are known to control these processes, including O2 concentrations and moisture content, N, C, pH, and the size and community structure of nitrate reducing organisms responsible for the processes. There...

  15. Soil nitrate reducing processes – drivers, mechanisms for spatial variation and significance for nitrous oxide production

    OpenAIRE

    TimJohnDaniell; MadelineEleanoreGiles

    2012-01-01

    The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate (NO3-¬) and production of the potent greenhouse gas, nitrous oxide (N2O). A number of factors are known to control these processes, including O2 concentrations and moisture content, N, C, pH and the size and community structure of nitrate reducing organisms responsible for the processes. Ther...

  16. Response of benthic metabolism and nutrient cycling to reductions in wastewater loading to Boston Harbor, USA

    Science.gov (United States)

    Tucker, Jane; Giblin, Anne E.; Hopkinson, Charles S.; Kelsey, Samuel W.; Howes, Brian L.

    2014-12-01

    We describe the long-term response of benthic metabolism in depositional sediments of Boston Harbor, MA, to large reductions in organic matter and nutrient loading. Although Boston Harbor received very high loadings of nutrients and solids it differs from many eutrophic estuaries in that severe hypoxia was prevented by strong tidal flushing. Our study was conducted for 9 years during which a series of improvements to sewage treatment were implemented, followed by 10 years after the culminating step in the clean-up, which was to divert all wastewater effluent offshore. Counter to expectations, sediment oxygen demand and nutrient effluxes initially increased at some stations, reaching some of the highest rates recorded in the literature, and were spatially and temporally quite variable. Early increases were attributed to macrofaunal effects, as sediments at some sites were rapidly colonized by tube-building amphipods, Ampelisca spp., which dominated a dense macrofaunal mat community. As reductions in loading progressed, however, mean rates in oxygen uptake and release of ammonium, nitrate, and phosphate all decreased. At the point of outfall diversion, rates and variability had already decreased substantially. By the end of the study, average oxygen uptake had decreased from 74 to 41 mmol m-2 d-1 and spatial and temporal variability had decreased. Similarly, nutrient fluxes were less than half the rates measured at the start of the project and also less variable. Other evidence of improved conditions included a decrease in the carbon content of sediments at most stations and higher Eh values at all stations, illustrating less reducing conditions. Denitrification also showed an overall decrease from the beginning to the end of the 19-year study, but was highest during the intermediate phases of the cleanup, reaching 9 mmol N m-2 d-1. At the end of the study denitrification averaged for all sites was 2.2 mmol N m-2 d-1, but when compared to current loadings, had become

  17. 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

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

    Science.gov (United States)

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

    2013-04-01

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

  19. 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...... of Amx 820 and EUB 338 mixed. Denitrification was observed through the reductions of both COD and nitrate–nitrite concentrations under anaerobic/anoxic conditions. By providing a stoichiometric ratio of nitrite to ammonium nitrogen with addition nitrate nitrogen, a gradual reduction of ANAMMOX activity...

  20. 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...

  1. Modelling the soil nitrogen denitrification

    International Nuclear Information System (INIS)

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

  2. 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.

  3. Simulation of three-phase fluidized bioreactors for denitrification

    International Nuclear Information System (INIS)

    Fluidized-bed bioreactors were developed and operated at three scales (diameters of 0.1, 0.2, and 0.5 m) by the Chemical Technology Division. The performance of these reactors in denitrification was simulated using the following modified form of Monod kinetics to describe the reaction kinetics: rate = V/sub max/ (NO3-/K/sub s/ + NO3-) (% biomass). In the fluids-movement portion of the simulation the tanks-in-series approximation to backmixing was used. This approach yielded a V/sub max/ of 3.5 g/m3-min (% biomass) and a K/sub s/ of 163 g/m3 for the 0.5-m bioreactor. Values of V/sub max/ and K/sub s/ were also determined for data derived from the 0.1-m bioreactor, but inadequate RTD data reduced the confidence level in these results. A complication in denitrification is the multi-step nature of the reduction from nitrate to nitrite to hyponitrite and finally to nitrogen. An experimental study of the effect of biomass loading upon denitrification was begun. It is recommended that the experimental work be continued

  4. Hyporheic zone denitrification: controls on effective reaction depth and contribution to whole-stream mass balance

    Science.gov (United States)

    Harvey, Judson W.; Böhlke, John Karl; Voytek, Mary A.; Scott, Durelle; Tobias, Craig R.

    2013-01-01

    Stream denitrification is thought to be enhanced by hyporheic transport but there is little direct evidence from the field. To demonstrate at a field site, we injected 15NO3−, Br (conservative tracer), and SF6 (gas exchange tracer) and compared measured whole-stream denitrification with in situ hyporheic denitrification in shallow and deeper flow paths of contrasting geomorphic units. Hyporheic denitrification accounted for between 1 and 200% of whole-stream denitrification. The reaction rate constant was positively related to hyporheic exchange rate (greater substrate delivery), concentrations of substrates DOC and nitrate, microbial denitrifier abundance (nirS), and measures of granular surface area and presence of anoxic microzones. The dimensionless product of the reaction rate constant and hyporheic residence time, λhzτhz define a Damköhler number, Daden-hz that was optimal in the subset of hyporheic flow paths where Daden-hz ≈ 1. Optimal conditions exclude inefficient deep pathways transport where substrates are used up and also exclude inefficient shallow pathways that require repeated hyporheic entries and exits to complete the reaction. The whole-stream reaction significance, Rs (dimensionless), was quantified by multiplying Daden-hz by the proportion of stream discharge passing through the hyporheic zone. Together these two dimensionless metrics, one flow-path scale and the other reach-scale, quantify the whole-stream significance of hyporheic denitrification. One consequence is that the effective zone of significant denitrification often differs from the full depth of the hyporheic zone, which is one reason why whole-stream denitrification rates have not previously been explained based on total hyporheic-zone metrics such as hyporheic-zone size or residence time.

  5. Hyporheic zone denitrification: Controls on effective reaction depth and contribution to whole-stream mass balance

    Science.gov (United States)

    Harvey, Judson W.; Böhlke, J. K.; Voytek, Mary A.; Scott, Durelle; Tobias, Craig R.

    2013-10-01

    Stream denitrification is thought to be enhanced by hyporheic transport but there is little direct evidence from the field. To investigate at a field site, we injected 15NO3-, Br (conservative tracer), and SF6 (gas exchange tracer) and compared measured whole-stream denitrification with in situ hyporheic denitrification in shallow and deeper flow paths of contrasting geomorphic units. Hyporheic denitrification accounted for between 1 and 200% of whole-stream denitrification. The reaction rate constant was positively related to hyporheic exchange rate (greater substrate delivery), concentrations of substrates DOC and nitrate, microbial denitrifier abundance (nirS), and measures of granular surface area and presence of anoxic microzones. The dimensionless product of the reaction rate constant and hyporheic residence time, λhzτhz define a Damköhler number, Daden-hz that was optimal in the subset of hyporheic flow paths where Daden-hz ≈ 1. Optimal conditions exclude inefficient deep pathways where substrates are used up and also exclude inefficient shallow pathways that require repeated hyporheic entries and exits to complete the reaction. The whole-stream reaction significance, Rs (dimensionless), was quantified by multiplying Daden-hz by the proportion of stream discharge passing through the hyporheic zone. Together these two dimensionless metrics, one flow-path scale and the other reach-scale, quantify the whole-stream significance of hyporheic denitrification. One consequence is that the effective zone of significant denitrification often differs from the full depth of the hyporheic zone, which is one reason why whole-stream denitrification rates have not previously been explained based on total hyporheic-zone metrics such as hyporheic-zone size or residence time.

  6. High nitrate removal from synthetic wastewater with the mixed bacterial culture.

    Science.gov (United States)

    Foglar, Lucija; Briski, Felicita; Sipos, Laszlo; Vuković, Marija

    2005-05-01

    The applicability of the mixed bacterial culture, originated from two-stage anaerobic-aerobic industrial yeasts production wastewater treatment plant for high rate denitrification processes was investigated. After acclimation to nitrate, the dominant strains were Pseudomonas and Paracoccus sp. Complete denitrification with low accumulation of nitrite-N (0.1 mg/l) was found in synthetic wastewater, obeying a zero-order reaction with respect to nitrate and a first-order reaction with respect to biomass concentration. Denitrification was then monitored in the continuous-flow stirred reactor at different hydraulic retention time, HRT (62-28 h) in order to achieve the optimal HRT. Nitrate was completely removed during following 45 days, at 25 degrees C with HRT, which we reduced from 62 to 28 h. Yet still, at 28 h HRT, high average specific denitrification rate of 142 mg NO3- -N/g VSS h was obtained. PMID:15627558

  7. Anoxic Activated Sludge Monitoring with Combined Nitrate and Titrimetric Measurements

    DEFF Research Database (Denmark)

    Petersen, B.; Gernaey, Krist; Vanrolleghem, P.A.

    2002-01-01

    An experimental procedure for anoxic activated sludge monitoring with combined nitrate and titrimetric measurements is proposed and evaluated successfully with two known carbon sources, (-)acetate and dextrose. For nitrate measurements an ion-selective nitrate electrode is applied to allow...... was with the carbon source in excess, since excess nitrate provoked nitrite build-up thereby complicating the data interpretation. A conceptual model could quantitatively describe the experimental observations and thus link the experimentally measured proton production with the consumption of electron acceptor...... and carbon source during denitrification....

  8. Long term performance of the Waterloo denitrification barrier

    International Nuclear Information System (INIS)

    Beginning in 1991 a series of laboratory tests and small scale field trials were initiated to test the performance of an innovative permeable reactive barrier for treatment of nitrate from septic systems. The barrier promotes denitrification by providing an energy source in the form of solid organic carbon mixed into the porous media material. Advantages of the system for nitrate treatment are that the reaction is passive and in situ and it is possible to incorporate sufficient carbon mass in conveniently sized barriers to potentially provide treatment for long periods (decades) without the necessity for maintenance. However, longevity can only be demonstrated by careful long term monitoring of field installations. This paper documents four years of operating history at three small scale field trials; two where the denitrification barrier is installed as a horizontal layer positioned in the unsaturated zone below conventional septic system infiltration beds and one where the barrier is installed as a vertical wall intercepting a septic system plume at a downgradient location. The barriers have successfully attenuated 50-100% of NO-3-N levels of up to 170 mg/L and treatment has remained consistent over the four year period in each case, thus considerable longevity is indicated. Other field trials have demonstrated this technology to be equally effective in treating nitrogen contamination from other sources such as landfill leachate and farm field runoff

  9. Biological denitrification using poly(butanediol succinate) as electron donor.

    Science.gov (United States)

    Shen, Zhiqiang; Yin, Yanan; Wang, Jianlong

    2016-07-01

    Poly(butanediol succinate) (PBS), a biodegradable polymer, was used as both solid carbon source and biofilm carrier for biological nitrate removal process, in which PBS was filled in a packed-bed bioreactor. The denitrification performance and the microbial diversity of biofilm attached on the surface of PBS were investigated. The experimental results showed that the volumetric denitrification rate was 0.60 kg m(-3) day(-1) when NO3-N loading rate was 0.63 kg m(-3) day(-1), and the average NO2-N concentration was below 0.20 mg L(-1). The effluent pH value decreased slightly from a range of 6.98-7.87 to 6.46-7.18. The analysis of microbial community structure of biofilm by pyrosequencing method showed that Proteobacteria was the most abundant phylum (89.87 %), and β-Proteobacteria represented the most abundant class. Among the 76 identified genera, Dechloromonas (10.26 %), Alicycliphilus (9.15 %), Azospira (8.92 %), and Sinobacteraceae-uncultured (8.75 %) were the abundant genera. PBS, as a promising alternative carbon source, is a suitable solid carbon source and biofilm carrier for nitrate removal. PMID:26960320

  10. Examining thiosulfate-driven autotrophic denitrification through respirometry.

    Science.gov (United States)

    Mora, Mabel; Guisasola, Albert; Gamisans, Xavier; Gabriel, David

    2014-10-01

    Anoxic respirometry was applied to characterize a sulfide-oxidizing nitrate-reducing (SO-NR) culture obtained from an anoxic biogas desulfurizing biotrickling filter treating high loads of H2S. Immobilized biomass extracted from the biotrickling filter was grown in a suspended culture with thiosulfate as electron donor to obtain the biomass growth yield and the S2O3(2)(-)/NO3(-) consumed ratio. Afterward, respirometry was applied to describe thiosulfate oxidation under anoxic conditions. A pure culture of Thiobacillus denitrificans was also used as a control culture in order to validate the procedure proposed in this work to characterize the SO-NR biomass. Respirometric profiles obtained with this microbial culture showed that nitrite was formed as intermediate during nitrate reduction and revealed that no competitive inhibition appeared when both electron acceptors were present in the medium. Although final bioreaction products depended on the initial S2O3(2)(-)/NO3(-) ratio, such ratio did not affect thiosulfate oxidation or denitrification rates. Moreover, respirometric profiles showed that the specific nitrite uptake rate depended on the biomass characteristics being that of a SO-NR mixed culture (39.8mgNg(-1) VSSh(-1)) higher than that obtained from a pure culture of T. denitrificans (19.7mgNg(-1) VSSh(-1)). For the first time, the stoichiometry of the two-step denitrification mechanism with thiosulfate oxidation and biomass growth associated was solved for both reactions. PMID:25065782

  11. 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.

  12. 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.

  13. Biological denitrification of brine: the effect of compatible solutes on enzyme activities and fatty acid degradation.

    Science.gov (United States)

    Cyplik, Paweł; Piotrowska-Cyplik, Agnieszka; Marecik, Roman; Czarny, Jakub; Drozdzyńska, Agnieszka; Chrzanowski, Łukasz

    2012-09-01

    The effect of the addition of compatible solutes (ectoine and trehalose) on the denitrification process of saline wastewater was studied. In saline wastewater, it was observed that the initial concentration of nitrates was 500 mg N l⁻¹. A fatty substance isolated from oiled bleaching earth (waste of vegetable oil refining process) was used as a source of carbon.The consortium, which was responsible for the denitrification process originated from the wastewater of the vegetable oil industry. The consortium of microorganisms was identified by the use of restriction fragment length polymorphism of 16S rRNA gene amplicons and sequencing techniques. It was noted that ectoine affects significantly the activity of lipase and nitrate reductase, and resulted in faster denitrification compared to saline wastewater with the addition of trehalose or control saline wastewater (without compatible solutes). It was observed that relative enzyme activities of lipase and nitrate reductase increased by 32 and 35%, respectively, in the presence of 1 mM ectoine. This resulted in an increase in specific nitrate reduction rate in the presence of 1 mM ectoine to 5.7 mg N g⁻¹ VSS h⁻¹, which was higher than in the absence of ectoine (3.2 mg N g⁻¹ VSS h⁻¹). The addition of trehalose did not have an effect on nitrate removals. Moreover, it was found that trehalose was used up completely by bacteria as a source of carbon in the denitrification process. The fatty acids were biodegraded by 74% in the presence of 1 mM ectoine. PMID:22286267

  14. 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 (ppapyrus vegetation, whereas organic carbon was limiting in all agricultural sites. Multivariate analysis showed that this pattern also corresponded significantly with low soil organic matter in the agricultural sites and low soil NO3 (by KCl extraction) in papyrus vegetation (ppapyrus vegetation than in the agricultural sites, and likely resulted in a greater availability of anaerobic microzones. On an areal basis, papyrus vegetation may provide hotspots for denitrification (up to 0.2 kg N

  15. 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

  16. Paracoccus denitrificans for the effluent recycling during continuous denitrification of liquid food.

    Science.gov (United States)

    Tippkötter, Nils; Roikaew, Wipa; Ulber, Roland; Hoffmann, Alexander; Denzler, Hans-Jörg; Buchholz, Heinrich

    2010-01-01

    Nitrate is an undesirable component of several foods. A typical case of contamination with high nitrate contents is whey concentrate, containing nitrate in concentrations up to 25 l. The microbiological removal of nitrate by Paracoccus denitrificans under formation of harmless nitrogen in combination with a cell retention reactor is described here. Focus lies on the resource-conserving design of a microbal denitrification process. Two methods are compared. The application of polyvinyl alcohol-immobilized cells, which can be applied several times in whey feed, is compared with the implementation of a two step denitrification system. First, the whey concentrate's nitrate is removed by ion exchange and subsequently the eluent regenerated by microorganisms under their retention by crossflow filtration. Nitrite and nitrate concentrations were determined by reflectometric color measurement with a commercially available Reflectoquant device. Correction factors for these media had to be determined. During the pilot development, bioreactors from 4 to 250 mg x L(-1) and crossflow units with membrane areas from 0.02 to 0.80 m(2) were examined. Based on the results of the pilot plants, a scaling for the exemplary process of denitrifying 1,000 tons per day is discussed. PMID:20187124

  17. The mechanisms governing low denitrification capacity and high nitrogen oxide gas emissions in subtropical forest soils in China

    Science.gov (United States)

    Zhang, Jinbo; Yu, Yongjie; Zhu, Tongbin; Cai, Zucong

    2014-08-01

    Previous studies have demonstrated that denitrification rates are low in subtropical forest soils. However, the mechanisms governing this process are not well known. This study seeks to identify the mechanisms responsible for the low denitrification capacity and high nitrogen oxide gas ratio in subtropical forest soils in China. The denitrification capacity and nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2) emission rates were measured using the acetylene inhibition method under conditions of added nitrate and anoxia. The abundance of nitrate reductase (narG), nitrite reductase (nirK), nitric oxide reductase (cnorB), and nitrous oxide reductase (nosZ) was measured using real-time, quantitative polymerase chain reaction, and sequencing of the nirK and norB products was performed to analyze the population structure of denitrifying bacteria. These results showed that the denitrification capacity in subtropical forest soils was lower than in temperate forest soils (p soil pH or soil organic C, was the key soil variable influencing denitrification, and Ehi alone could explain 68% of the variations in denitrification capacity. The high Ehi in subtropical soils led to a low abundance of nirK and significant differences in the population structure of denitrifying bacteria between subtropical and temperate soils. Therefore, Ehi was responsible for the low denitrification capacity in subtropical forest soils. The ratio of NO to total denitrification gas products (p forest soils than in temperate forest soils, while the reverse trend was observed for the ratio of N2 to total denitrification gas products (p soils. Thus, NO and N2O, but not N2, were the dominant denitrification gas products, accounting for 80%, even under the highly anaerobic conditions in subtropical forest soils and despite low denitrification capacity. These results were significant for understanding the "Hole in the Pipe" model and NO and N2O gases emission in subtropical forest soils. Despite

  18. Influence of macrophytes on nitrate removal in wetlands

    Energy Technology Data Exchange (ETDEWEB)

    Weisner, S.E.B.; Eriksson, Peder G.; Graneli, W.; Leonardson, L. (Lund Univ. (Sweden). Dept. of Ecology)

    1994-01-01

    Efficient nitrate removal from wetlands depends on denitrification. Macrophytes support denitrification by supplying organic carbon. Organic carbon available to denitrifying bacteria is released from plant litter and from living macrophytes. Macrophytes offer attachment surfaces for epiphytes, also producing organic matter, and for denitrifying bacteria. Emergent macrophytes are generally more productive than submerged macrophytes, but submerged macrophytes have more epiphytes and offer a larger attachment area in the water column for denitrifying bacteria. Emergent and submerged vegetation differ in their seasonal patterns of release of organic carbon. We conclude that a mixture of emergent and submerged macrophytes may be beneficial for nitrogen removal in wetlands with a surface-flow of nitrate-rich water. The influence of vegetation on wetland hydraulics must also be considered. A wetland design with deeper parts favoring submerged macrophytes alternating, along the water flow, with shallower parts covered by emergent macrophytes, may promote denitrification processes and distribution of water flow. 41 refs, 5 figs

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Yasumoto, J.

    2014-12-01

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

  1. 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...

  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. 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

  4. Single-sludge denitrification in recirculating aquaculture systems: effects of pre-fermentation and pH

    DEFF Research Database (Denmark)

    Suhr, Karin Isabel; Letelier-Gordo, Carlos Octavio; Prat Busquets, Pau

    2015-01-01

    Single-sludge denitrification (DN) reactors in aquaculture use the carbonous solid fish waste produced in the system to reduce the discharged nitrate load. The solid waste is available for denitrifiers when present in soluble, readily biodegradable form, and the transformation is accomplished...

  5. Denitrification alternates between a source and sink of nitrous oxide in the hypolimnion of a thermally stratified reservoir

    Science.gov (United States)

    Nitrogen loading from developed watersheds to aquatic ecosystems can stimulate microbial denitrification, a process which reduces nitrate (NO3-) to dinitrogen (N2) or nitrous oxide (N2O), the latter a potent greenhouse gas. While aquatic ecosystems are a globally significant sou...

  6. Denitrifying bioreactors for nitrate removal from tile drained cropland

    Science.gov (United States)

    Denitrification bioreactors are a promising technology for mitigation of nitrate-nitrogen (NO3-N) losses in subsurface drainage water. Bioreactors are constructed with carbon substrates, typically wood chips, to provide a substrate for denitrifying microorganisms. Researchers in Iowa found that for ...

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Trois, Cristina, E-mail: troisc@ukzn.ac.za [CRECHE Centre for Research in Environmental, Coastal and Hydrological Engineering. School of Civil Engineering, Surveying and Construction. University of KwaZulu-Natal, Howard College Campus, Durban, 4041 (South Africa); Pisano, Giulia [CRECHE Centre for Research in Environmental, Coastal and Hydrological Engineering. School of Civil Engineering, Surveying and Construction. University of KwaZulu-Natal, Howard College Campus, Durban, 4041 (South Africa); Oxarango, Laurent [LTHE (UMR 5564 CNRS/INPG/IRD/UJF), Universite de Grenoble, BP 53, 38041 Grenoble Cedex 9 (France)

    2010-06-15

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

  9. Geomorphic and chemical controls on sediment denitrification in restored urban streams

    Science.gov (United States)

    Tuttle, A. K.; McMillan, S. K.

    2011-12-01

    In the Southeastern United States, recent endeavors in stream restoration address bank destabilization, catastrophic flooding, and water quality issues resulting from urban stream syndrome. Several projects in the city of Charlotte, North Carolina are underway with goals of stabilizing stream banks, improving local water quality and enhancing ecological functions. Restoration of natural stream pattern and profile provides an opportunity to mitigate eutrophication by enhancing nitrogen uptake and removal in stream sediments. Four restored headwater streams, and a degraded and reference stream were included in this study to examine sediment denitrification rates. Several environmental factors (e.g. NO3¬ concentration, dissolved organic carbon, sediment carbon) as well as proximity to engineered grade-control structures, riffles, and pools are examined as possible drivers affecting nitrogen removal. We used an acetylene block method to measure denitrification rates using slurries of stream sediments from different locations in each reach, including steps, riffles, and pools. Although average denitrification rates were variable (ranging from 64 to 864 μmol N hr-1 m-2), restored streams had the highest denitrification rates, especially those with a restored floodplain. At the NO3-concentrations typically observed in these streams during baseflow, (0.50 ±0.2 ¬ mg/L), NO3- availability appears to be the primary limiting factor for denitrification rates. Generally, sediments collected immediately downstream of grade control structures had highest rates of NO3- removal, which we hypothesize is linked to deposition and burial of benthic organic material, enhancing development of active microbial populations at anaerobic microsites. Laboratory experiments amended with NO3- and labile carbon as glucose showed that while NO3- was likely primarily controlling rates, labile carbon increased denitrification rates with NO3- saturation at approximately 1 mg/L.

  10. 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.

  11. 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

  12. Hyporheic Zone Denitrification: Flow Path Controls and Scaling Consequences for N budgets for the Whole Stream

    Science.gov (United States)

    Harvey, J. W.; Bohlke, J. K.; Voytek, M. A.; Scott, D.; Tobias, C. R.

    2013-12-01

    Denitrification is thought to be enhanced by hyporheic transport but there is little direct evidence from the field that relates controlling processes to whole-stream consequences for N budgets. To demonstrate at a field site we injected 15 NO3-, Br (conservative tracer) and SF6 (gas exchange tracer) and compared measures of whole-stream denitrification with in situ hyporheic denitrification measurements in both shallow and deeper flow paths of contrasting geomorphic units such as channel thalwegs and side cavities. Hyporheic denitrification accounted for between a few percent and 200% of whole-stream denitrification. The reaction rate constant was positively related to hyporheic exchange rate (which increases substrate delivery), concentrations of substrates DOC and nitrate, microbial denitrifier abundance as indicated by nirS, and measures related to granular surface area and presence of anoxic microzones in otherwise suboxic porewater. Reaction efficiency in individual hyporheic flow paths was quantified as the dimensionless product of reaction rate constant and hyporheic residence time, λhzτhz (also defined as a Damköhler number, Daden-hz). At the stream reach scale the reaction significance was quantified by a dimensionless index Rs that combines the product of Da hz and the proportion of stream discharge passing through the hyporheic zone. Reaction progress was optimal in the subset of hyporheic flow paths where Da den-hz ~ 1, which avoids inefficient transport through very long flow paths after substrates have been used up but also avoids inefficient pathways that require repeated entries and exits through very short hyporheic flow paths to complete the reaction. We conclude that the zone of significant denitrification in the streambed can be substantially less than the full depth of the hyporheic zone, which is one reason previous researchers were not able to explain whole-stream denitrification rates based on total hyporheic-zone metrics such as

  13. Enhanced denitrification of Pseudomonas stutzeri by a bioelectrochemical system assisted with solid-phase humin.

    Science.gov (United States)

    Xiao, Zhixing; Awata, Takanori; Zhang, Dongdong; Zhang, Chunfang; Li, Zhiling; Katayama, Arata

    2016-07-01

    The denitrification reactions performed by Pseudomonas stutzeri JCM20778 were enhanced electrochemically with the use of solid-phase humin, although P. stutzeri itself was incapable of receiving electrons directly from the graphite electrode. Electrochemically reduced humin enhanced the microbial, but not abiotic, denitrification reactions. Electric current and cyclic voltammetry analyses suggested that the solid-phase humin functioned as an electron donor for the denitrification reactions of P. stutzeri. Nitrogen balance study and the estimation of the first-order rate constants of the consecutive denitrification reactions suggested that the solid-phase humin enhanced all reducing reactions from nitrate to nitrogen gas. Considering the wide distribution of humin in the environment, the findings that solid-phase humin can assist in electron transfer, from the electrode to a denitrifying bacterium that has little ability to directly utilize external electrons, has important implications for the widespread application of bioelectrochemical systems assisted by solid-phase humin for enhancing microbial denitrification.

  14. Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea

    OpenAIRE

    Dähnke, K.; B. Thamdrup

    2013-01-01

    The global marine nitrogen cycle is constrained by nitrogen fixation as a source of reactive nitrogen, and denitrification or anammox on the sink side. These processes with their respective isotope effects set the marine nitrate 15N-isotope value (δ15N) to a relatively constant average of 5‰. This value can be used to better assess the magnitude of these sources and sink terms, but the underlying assumption is that sedimentary...

  15. Impact of carbon-dosing on micro-pollutants removal in MBBR post-denitrification systems

    OpenAIRE

    Escola Casas, Monica; Torresi, Elena; Plósz, Benedek G.; Bester, Kai; Christensen, M.

    2015-01-01

    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 efficient...

  16. Simultaneous Nitrification and Denitrification in Aerobic Chemostat Cultures of Thiosphaera pantotropha

    OpenAIRE

    Robertson, L.A.; van Niel, E.W.; Torremans, R.A.; Kuenen, J. G.

    1988-01-01

    Thiosphaera pantotropha is capable of simultaneous heterotrophic nitrification and aerobic denitrification. Consequently, its nitrification potential could not be judged from nitrite accumulation, but was estimated from complete nitrogen balances. The maximum rate of nitrification obtained during these experiments was 93.9 nmol min−1 mg of protein−1. The nitrification rate could be reduced by the provision of nitrate, nitrite, or thiosulfate to the culture medium. Both nitrification and denit...

  17. Denitrification using immersed membrane bioreactors

    OpenAIRE

    McAdam, Ewan J.

    2008-01-01

    Nitrate is practically ubiquitous in waters abstracted for municipal potable water production in Europe due to decades of intensive agricultural practice. Ion exchange is principally selected to target abstracted waters with elevated nitrate concentrations. However, the cost associated with disposal of the waste stream has re-ignited interest in destructive rather concentrative technologies. This thesis explores the potential of membrane bioreactor (MBR) technology for the remo...

  18. Diversity of Nitrate-Reducing and Denitrifying Bacteria in a Marine Aquaculture Biofilter and their Response to Sulfide

    DEFF Research Database (Denmark)

    Krieger, Bärbel; Schwermer, Carsten U.; Rezakhani, Nastaran;

    2006-01-01

    DIVERSITY OF NITRATE-REDUCING AND DENITRIFYING BACTERIA IN A MARINE AQUACULTURE BIOFILTER AND THEIR RESPONSE TO SULFIDE B.U. Krieger 1,5, C. Schwermer 2, N. Rezakhani 5, M.A. Horn 1, A. Gieseke 2, E. Cytryn 3, D. Minz 3, J. van Rijn 4, H.L. Drake 1, A. Schramm 5 1 Dept. of Ecological Microbiology...... was developed containing a 3-stage biofilter for nitrification, denitrification/anaerobic sludge digestion, and sulfide oxidation. Sulfate reduction in the anaerobic part of the system leads to sulfide concentrations exceeding 5 mM, which may affect nitrate reduction and denitrification. Sulfide can inhibit...... nitrous oxide reductase, trigger a shift from denitrification to dissimilatory nitrate reduction to ammonium (DNRA), or be used as electron donor for nitrate reduction. The goal of this study was to identify and isolate nitrate-reducing and denitrifying bacteria from the biofilter and to investigate...

  19. Sediment Nitrification, Denitrification, and Nitrous Oxide Production in a Deep Arctic Lake †

    OpenAIRE

    Klingensmith, K. M.; Alexander, V.

    1983-01-01

    We used a combination of 15N tracer methods and a C2H2 blockage technique to determine the role of sediment nitrification and denitrification in a deep oligotrophic arctic lake. Inorganic nitrogen concentrations ranged between 40 and 600 nmol · cm−3, increasing with depth below the sediment-water interface. Nitrate concentrations were at least 10 times lower, and nitrate was only detectable within the top 0 to 6 cm of sediment. Eh and pH profiles showed an oxidized surface zone underlain by m...

  20. 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.

  1. 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  +50, and correlate inversely with NO3 -N concentrations. This variation occurs in basalt 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.

  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. Simplified denitrification models: overview and properties

    NARCIS (Netherlands)

    Heinen, M.

    2006-01-01

    This paper reviews simplified process models for denitrification. More than fifty models were considered. The majority of these (simple) models are based on potential denitrification-either measured as a soil's property or computed from organic C dynamics-or consider denittification as a first-order

  4. Chemical, isotopic, and microbiological evidence for denitrification during transport of domestic wastewater through a thick unsaturated zone in the Mojave Desert, San Bernardino County, California

    Science.gov (United States)

    Schroeder, R.A.; Martin, P.M.; Böhlke, J.K.

    1993-01-01

    Nitrogen in downward-infiltrating wastewater discharged from seepage pits (dry wells) at residences in the upper Mojave River Basin, California represents a significant potential source of nitrate contamination to the underlying ground water. However, increases in nitrate concentration in the ground water have not yet been observed. The low nitrate concentration in the ground water may be the result of lateral dispersion in the unsaturated zone, dilution below the water table, or denitrification of wastewater nitrate in the unsaturated zone. Measured vertical rates indicate that some wastewater has reached the water table beneath communities that are older than 5 to 10 years. As wastewater percolates from seepage pits into the unsaturated zone, reduced nitrogen is converted rapidly to nitrate at shallow depths and the nitrate concentrations commonly decrease with depth. The largest nitrate decreases seem to coincide with increased content of fine-grained sediments or with proximity to the water table. Between lysimeters at 160 and 199 feet at one residence, the decrease in nitrate concentration coincided with a large increase in sulfate, decrease in alkalinity, and increase in 815N in nitrate. Those data are consistent with denitrification by oxidation of iron sulfide to produce ferric oxides; but if such a reaction occurs, it must be in domains that are small in comparison with the sampled volumes because the waters also contain substantial quantities of dissolved oxygen. The predominantly low nitrate concentrations in the area's ground water are consistent with the operation of a nitrogen-removal mechanism, possibly denitrification; however, the reducing capacity of the sediments to maintain denitrification is not known.

  5. Mass Spectrometric Studies of the Effect of pH on the Accumulation of Intermediates in Denitrification by Paracoccus denitrificans

    OpenAIRE

    Thomsen, Jens K.; Geest, Torben; Cox, Raymond P.

    1994-01-01

    We have used a quadrupole mass spectrometer with a gas-permeable membrane inlet for continuous measurements of the production of N2O and N2 from nitrate or nitrite by cell suspensions of Paracoccus denitrificans. The use of nitrate and nitrite labeled with 15N was shown to simplify the interpretation of the results when these gases were measured. This approach was used to study the effect of pH on the production of denitrification intermediates from nitrate and nitrite under anoxic conditions...

  6. The importance of dissimilatory nitrate reduction to ammonium (DNRA) in the nitrogen cycle of coastal ecosystems

    DEFF Research Database (Denmark)

    Giblin, Anne E.; Tobias, Craig R.; Song, Bongkeun;

    2013-01-01

    be ignored. Measurements comparing the importance of denitrification vs. DNRA in 55 coastal sites found that DNRA accounted for more than 30% of the nitrate reduction at 26 sites. DNRA was the dominant pathway at more than one-third of the sites. Understanding what controls the relative importance......Until recently, it was believed that biological assimilation and gaseous nitrogen (N) loss through denitrification were the two major fates of nitrate entering or produced within most coastal ecosystems. Denitrification is often viewed as an important ecosystem service that removes reactive N from...... of denitrification and DNRA, and how the balance changes with increased nitrogen loading, is of critical importance for predicting eutrophication trajectories. Recent improvements in methods for assessing rates of DNRA have helped refine our understanding of the rates and controls of this process, but accurate...

  7. Engineered bioretention for removal of nitrate from stormwater runoff.

    Science.gov (United States)

    Kim, Hunho; Seagren, Eric A; Davis, Allen P

    2003-01-01

    A bioretention unit is a simple, plant- and soil-based, low-impact treatment and infiltration facility for treating stormwater runoff in developed areas. Nitrate, however, is not attenuated in conventional bioretention facilities. Thus, this study systematically evaluated a reengineered concept of bioretention for nitrate removal via microbial denitrification, which incorporates a continuously submerged anoxic zone with an overdrain. Experimental studies were performed in four phases. In the first two phases, column studies demonstrated that, overall, newspaper is the best solid-phase electron-donor substrate for denitrification out of the set studied (alfalfa, leaf mulch compost, newspaper, sawdust, wheat straw, wood chips, and elemental sulfur) based on superior nitrate removal and effluent water quality. The nitrate loading and hydraulic loading studies in the second phase provided design information. In the third phase, system viability after 30- and 84-day dormant periods was evaluated in column studies, demonstrating that newspaper-supported biological denitrification should be effective under conditions of intermittent loadings. Finally, in the fourth phase, pilot-scale bioretention studies demonstrated the effectiveness of the proposed design, showing nitrate plus nitrite mass removals of up to 80%. These results indicate that engineered bioretention for the removal of nitrogen from stormwater runoff has the potential for successful application as an urban stormwater treatment practice.

  8. 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.

  9. 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.

  10. Nitrification—Denitrification Loss of Added Nitrogen in Flooded RIce Rhizosphere

    Institute of Scientific and Technical Information of China (English)

    LIXIN-HUI; ZHUZHAO-LIANG; 等

    1994-01-01

    Nitrification-denitrification losses of 15N-labelled nitrate and ammonium applied to the rhizos phere and nonrhizosphere of flooded rice were evaluated in 2 greenhouse rhizobox experiments.The loss of added N via denitrification was estimated directly by measuring the total fluxes of (N2O+N2)12N,It was found that 67% and 51%-56% of 15N-nitrate added to rice rhizosphere were lost as (N2O+N2)-15N in the 2 experiments,respectively,which were comparable to that added to norhizosphere soil(70%and 47%,respectively),implying that the denitrifying activity in rice rhizosphere was as high as that in nonrhizosphere soil.However,only trace amounts (0-0\\3% of added N)were recovered as (N2O+N2)-15N when 15N-ammonium was applied to either rhizosphere or nonrhizosphere,which seems to indicate that the nitrifying activity in the either rhizosphere of nonrhizosphere soils was quite low.The apparent denitrification calculated from 15N balance studies was 10%-47% higher than the total flux of (N2O+N2)-15N.Reasons for the large differences can not be explained satisfactorily.Though the denitrifying activity in rhizosphere was high and comparable to that in nonrhizosphere soil.presumably due to the low nitrifying activity and /or the strong competition of N uptake against denitrification.the nitrification-denitrification taking place in rhizosphere could not be an important mechanism of loss of ammonium N in flooded rice-soil system.

  11. Effects of polybrominated diphenyl ethers and plant species on nitrification, denitrification and anammox in mangrove soils.

    Science.gov (United States)

    Chen, Juan; Zhou, Hai Chao; Pan, Ying; Shyla, Farzana Shazia; Tam, Nora Fung-Yee

    2016-05-15

    Little is known about polybrominated diphenyl ethers (PBDEs) and planting affect biogeochemical processes, and their impact on microbial nitrogen (N) transformation in soil. A 12-month microcosm experiment was conducted to understand the effects of a mixture of PBDEs at two contamination levels, 2 and 20 mg kg(-1)dry weight representing low and high soil contamination, respectively, using two mangrove plant species, namely Kandelia obovata (Ko) and Bruguiera gymnorrhiza (Bg), on nitrification, denitrification and anammox in mangrove soils. No significant changes in these N transformation processes were found at month 3 and at a low level of PBDEs in both plant species, suggesting that short-term exposure to 2 mg kg(-1) contamination did not affect microbial N transformation. At month 12, a high level of PBDE contamination significantly decreased the nitrification potential activity and the copy numbers of archaeal amoA and bacterial amoA gene in Ko soil, but such inhibitory effect was not significant in Bg soil. On the contrary, the denitrification-related parameters, including the activities of nitrate reductase and nitrite reductase, potential denitrification activity and copy numbers of nirK, nirS and nosZ gene, were stimulated by a high level of PBDE contamination in both Ko and Bg soils, and the stimulation was higher in the more anaerobic Bg soil. Different from denitrification, a high level of PBDE contamination decreased the copy numbers of anammox bacterial 16S rRNA gene in Bg soil but not in Ko soil; this was possibly related to the lower nitrate concentration in Bg soil that might inhibit the growth of anammox bacteria. These results indicated that the effects of PBDEs on microbial N transformation were plant species-specific, with the nitrifying microorganisms in Ko soil more susceptible to PBDE contamination, while denitrification and anammox in Bg soil were more sensitive. PMID:26901803

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

    International Nuclear Information System (INIS)

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

  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. 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.

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

    Science.gov (United States)

    Morita, Masahiko; Uemoto, Hiroaki; Watanabe, Atsushi

    2007-08-15

    A simple denitrification bioreactor for nitrate-containing wastewater without organic compounds was developed. This bioreactor consisted of packed gel envelopes in a single tank. Each envelope comprised two plates of gels containing Paracoccus denitrificans cells with an internal space between the plates. As an electron donor for denitrification, ethanol was injected into the internal space and not directly into the wastewater. P. denitrificans cells in the gel reduced nitrate to nitrogen gas by using the injected ethanol. Nitrate-containing desulfurization wastewater derived from a coal-fired thermal power plant was continuously treated with 20 packed gel envelopes (size, 1,000 x 900 x 12 mm; surface area, 1.44 m(2)) in a reactor tank (volume 1.5 m(3)). When the total nitrogen concentration in the inflow was around 150 mg-N x L(-1), the envelopes removed approximately 60-80% of the total nitrogen, and the maximum nitrogen removal rate was 5.0 g-N x day(-1) per square meter of the gel surface. This value corresponded to the volumetric nitrogen removal performance of 0.109 kg-N x m(-3) x day(-1). In each envelope, a high utilization efficiency of the electron donor was attained, although more than the double amount of the electron donor was empirically injected in the present activated sludge system to achieve denitrification when compared with the theoretical value. The bioreactor using the envelopes would be extremely effective as an additional denitrification system because these envelopes can be easily installed in the vacant spaces of preinstalled water treatment systems, without requiring additional facilities for removing surplus ethanol and sludge. PMID:17252606

  16. Reaction chain modeling of denitrification reactions during a push-pull test

    Science.gov (United States)

    Boisson, A.; de Anna, P.; Bour, O.; Le Borgne, T.; Labasque, T.; Aquilina, L.

    2013-05-01

    Field quantitative estimation of reaction kinetics is required to enhance our understanding of biogeochemical reactions in aquifers. We extended the analytical solution developed by Haggerty et al. (1998) to model an entire 1st order reaction chain and estimate the kinetic parameters for each reaction step of the denitrification process. We then assessed the ability of this reaction chain to model biogeochemical reactions by comparing it with experimental results from a push-pull test in a fractured crystalline aquifer (Ploemeur, French Brittany). Nitrates were used as the reactive tracer, since denitrification involves the sequential reduction of nitrates to nitrogen gas through a chain reaction (NO3- → NO2- → NO → N2O → N2) under anaerobic conditions. The kinetics of nitrate consumption and by-product formation (NO2-, N2O) during autotrophic denitrification were quantified by using a reactive tracer (NO3-) and a non-reactive tracer (Br-). The formation of reaction by-products (NO2-, N2O, N2) has not been previously considered using a reaction chain approach. Comparison of Br- and NO3- breakthrough curves showed that 10% of the injected NO3- molar mass was transformed during the 12 h experiment (2% into NO2-, 1% into N2O and the rest into N2 and NO). Similar results, but with slower kinetics, were obtained from laboratory experiments in reactors. The good agreement between the model and the field data shows that the complete denitrification process can be efficiently modeled as a sequence of first order reactions. The 1st order kinetics coefficients obtained through modeling were as follows: k1 = 0.023 h- 1, k2 = 0.59 h- 1, k3 = 16 h- 1, and k4 = 5.5 h- 1. A next step will be to assess the variability of field reactivity using the methodology developed for modeling push-pull tracer tests.

  17. 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.

  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. Model-based integration and analysis of biogeochemical and isotopic dynamics in a nitrate-polluted pyritic aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Prommer, H.; Broers, H.P.; Slomp, C.P.; Greskowiak, J.; Van Der Grift, B.; Van Cappellen, P.

    2013-01-01

    Leaching of nitrate from agricultural land to groundwater and the resulting nitrate pollution are a major environmental problem worldwide. Its impact is often mitigated in aquifers hosting sufficiently reactive reductants that can promote autotrophic denitrification. In the case of pyrite acting as

  20. 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.

  1. 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.

  2. Oxygen isotope fractionation during N2O production by soil denitrification

    Science.gov (United States)

    Lewicka-Szczebak, Dominika; Dyckmans, Jens; Kaiser, Jan; Marca, Alina; Augustin, Jürgen; Well, Reinhard

    2016-02-01

    The isotopic composition of soil-derived N2O can help differentiate between N2O production pathways and estimate the fraction of N2O reduced to N2. Until now, δ18O of N2O has been rarely used in the interpretation of N2O isotopic signatures because of the rather complex oxygen isotope fractionations during N2O production by denitrification. The latter process involves nitrate reduction mediated through the following three enzymes: nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR). Each step removes one oxygen atom as water (H2O), which gives rise to a branching isotope effect. Moreover, denitrification intermediates may partially or fully exchange oxygen isotopes with ambient water, which is associated with an exchange isotope effect. The main objective of this study was to decipher the mechanism of oxygen isotope fractionation during N2O production by soil denitrification and, in particular, to investigate the relationship between the extent of oxygen isotope exchange with soil water and the δ18O values of the produced N2O. In our soil incubation experiments Δ17O isotope tracing was applied for the first time to simultaneously determine the extent of oxygen isotope exchange and any associated oxygen isotope effect. We found that N2O formation in static anoxic incubation experiments was typically associated with oxygen isotope exchange close to 100 % and a stable difference between the 18O / 16O ratio of soil water and the N2O product of δ18O(N2O / H2O) = (17.5 ± 1.2) ‰. However, flow-through experiments gave lower oxygen isotope exchange down to 56 % and a higher δ18O(N2O / H2O) of up to 37 ‰. The extent of isotope exchange and δ18O(N2O / H2O) showed a significant correlation (R2 = 0.70, p fractionation model was used to test various scenarios with different magnitudes of branching isotope effects at different steps in the reduction process. The results suggest that during denitrification, isotope exchange occurs prior to

  3. Box-modelling of the impacts of atmospheric nitrogen deposition and benthic remineralisation on the nitrogen cycle of the eastern tropical South Pacific

    Science.gov (United States)

    Su, Bei; Pahlow, Markus; Oschlies, Andreas

    2016-09-01

    Both atmospheric deposition and benthic remineralisation influence the marine nitrogen cycle, and hence ultimately also marine primary production. The biological and biogeochemical relations in the eastern tropical South Pacific (ETSP) among nitrogen deposition, benthic denitrification and phosphorus regeneration are analysed in a prognostic box model of the oxygen, nitrogen and phosphorus cycles in the ETSP. Atmospheric nitrogen deposition ( ≈ 1.5 Tg N yr-1 for the years 2000-2009) is offset by half in the model by reduced N2 fixation, with the other half transported out of the model domain. Model- and data-based benthic denitrification in our model domain are responsible for losses of 0.19 and 1.0 Tg Tg N yr-1, respectively, and both trigger nitrogen fixation, partly compensating for the NO3- loss. Model- and data-based estimates of enhanced phosphate release via sedimentary phosphorus regeneration under suboxic conditions are 0.062 and 0.11 Tg N yr-1, respectively. Since phosphate is the ultimate limiting nutrient in the model, even very small additional phosphate inputs stimulate primary production and subsequent export production and NO3- loss in the oxygen minimum zone (OMZ). A sensitivity analysis of the local response to both atmospheric deposition and benthic remineralisation indicates dominant stabilising feedbacks in the ETSP, which tend to keep a balanced nitrogen inventory; i.e. nitrogen input by atmospheric deposition is counteracted by decreasing nitrogen fixation; NO3- loss via benthic denitrification is partly compensated for by increased nitrogen fixation; enhanced nitrogen fixation stimulated by phosphate regeneration is partly counteracted by stronger water-column denitrification. Even though the water column in our model domain acts as a NO3- source, the ETSP including benthic denitrification might be a NO3- sink.

  4. Denitrification by Pseudomonas stutzeri coupled with CO2 reduction by Sporomusa ovata with hydrogen as an electron donor assisted by solid-phase humin.

    Science.gov (United States)

    Xiao, Zhixing; Awata, Takanori; Zhang, Dongdong; Katayama, Arata

    2016-09-01

    A co-culture system comprising an acetogenic bacterium, Sporomusa ovata DSMZ2662, and a denitrifying bacterium, Pseudomonas stutzeri JCM20778, enabled denitrification using H2 as the sole external electron donor and CO2 as the sole external carbon source. Acetate produced by S. ovata supported the heterotrophic denitrification of P. stutzeri. A nitrogen balance study showed the reduction of nitrate to nitrogen gas without the accumulation of nitrite and nitrous oxide in the co-culture system. S. ovata did not show nitrate reduction to ammonium in the co-culture system. Significant proportions of the consumed H2 were utilized for denitrification: 79.9 ± 4.6% in the co-culture system containing solid-phase humin and 62.9±11.1% in the humin-free co-culture system. The higher utilization efficiency of hydrogen in the humin-containing system was attributed to the higher denitrification activity of P. stutzeri under the acetate deficient conditions. The nitrogen removal rate of the humin-containing co-culture system reached 0.19 kg NO3(-)-N·m(-3)·d(-1). Stable denitrification activity for 61 days of successive sub-culturing suggested the robustness of this co-culture system. This study provides a novel strategy for the in situ enhancement of microbial denitrification. PMID:26975755

  5. Solid phase electron donors control denitrification in groundwater at agricultural sites

    Science.gov (United States)

    Green, C. T.; Liao, L.; Bekins, B. A.; Bohlke, J. K.

    2011-12-01

    Increased concentrations of nitrate in groundwater caused by agricultural use of chemical and organic fertilizers are a concern because of possible risks to environmental and human health. At many sites, these problems are mitigated by natural attenuation of nitrate as a result of microbially mediated denitrification of nitrate to nitrogen gas. Recent studies have clarified the factors affecting the rates and extents of denitrification in groundwater in agricultural areas. Intensive studies were conducted by the US Geological Survey to study agricultural chemicals in California, Nebraska, Washington, and Maryland using laboratory analyses, field measurements, and flow and transport modeling for monitoring well transects (0.5 to 2.5 km in length) and vertical profiles (0 to 50 m in depth). Groundwater analyses included major ion chemistry, dissolved gases, nitrogen and oxygen stable isotopes, and atmospheric age-tracers. Sediments were analyzed for concentrations of potential electron donors for denitrification, including reduced iron and sulfur, and organic carbon. Geochemical data and mass balance calculations indicated that solid-phase electron donors were an important factor controlling denitrification at these sites. To examine the generality of this result, a mathematical model of vertical flux of water, oxygen, and nitrate was developed and applied at these study sites along with 2 new study sites in Iowa and Mississippi and 8 additional sites from previous studies in Nebraska, Texas, Minnesota, Wisconsin, North Carolina, Maryland (2 sites), and New York. Model results confirmed the importance of solid phase electron donors. The normalized reaction rates on an electron flux basis tended to increase with depth from the shallow oxygen reduction zone to the underlying nitrate reduction zone. The pattern of higher rates at depth is consistent with a reaction rate controlled by solid phase donors that are depleted under oxidizing conditions near the surface and in

  6. Biological denitrification using poly(butylene succinate) as carbon source and biofilm carrier for recirculating aquaculture system effluent treatment.

    Science.gov (United States)

    Zhu, Song-Ming; Deng, Ya-Le; Ruan, Yun-Jie; Guo, Xi-Shan; Shi, Ming-Ming; Shen, Jia-Zheng

    2015-09-01

    Nitrate removal is essential for the sustainable operation of recirculating aquaculture system (RAS). This study evaluated the heterotrophic denitrification using poly(butylene succinate) as carbon source and biofilm carrier for RAS wastewater treatment. The effect of varied operational conditions (influent type, salinity and nitrate loading) on reactor performance and microbial community was investigated. The high denitrification rates of 0.53 ± 0.19 kg NO3(-)-N m(-3) d(-1) (salinity, 0‰) and 0.66 ± 0.12 kg NO3(-)-Nm(-3) d(-1) (salinity, 25‰) were achieved, and nitrite concentration was maintained below 1mg/L. In addition, the existence of salinity exhibited more stable nitrate removal efficiency, but caused adverse effects such as excessive effluent dissolved organic carbon (DOC) and dissimilation nitrate reduce to ammonia (DNRA) activity. The degradation of PBS was further confirmed by SEM and FTIR analysis. Illumina sequencing revealed the abundance and species changes of functional denitrification and degradation microflora which might be the primary cause of varied reactor performance. PMID:26093254

  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. Southern ocean controls on the extent of denitrification in the southeast Pacific (ODP Site 1234)

    Science.gov (United States)

    Robinson, R. S.; Mix, A.; Martinez, P.

    2005-12-01

    A mechanistic understanding of the observed temporal changes in oceanic denitrification, the bacterial reduction of nitrate under suboxic conditions, has been sought due to the potential importance of N inventory changes and the production of N2O on the climate system. High-resolution oxygen isotope and bulk sediment δ15N records from ODP Site 1234 on the Chile Margin are presented as a record of denitrification changes within the Peru-Chile Upwelling system over the last 65ky. The character of the Site 1234 δ15N record is quite similar to that of its northern hemisphere counterparts with the exception of timing. Denitrification changes in the southeast Pacific show coherent variation with Antarctic climate, as indicated by the Byrd ice core δ18O record, rather than with northern hemisphere climate change. The high latitude polar oceans play a fundamental role in setting the physical and biological controls on subsurface oxygen supply and demand. The southern hemisphere character of the Chile margin record suggests that episodes of reduced denitrification in the SE Pacific likely represent times when more oxygen was supplied as the result of changes in the chemical composition of Subantarctic Mode Water (SAMW), which forms in the Subantarctic zone of the Southern Ocean and ventilates the low latitude thermocline. An increase in oxygen can be achieved through (1) lower temperatures/ higher ventilation rates and/or (2) reduced oxygen demand in the low latitude subsurface due to reduction in the preformed nutrient content of SAMW.

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

    Science.gov (United States)

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

    2015-12-01

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

  10. 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. PMID:24922353

  11. 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.

  12. 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.

  13. Determining Roles of Accessory Genes in Denitrification by Mutant Fitness Analyses.

    Science.gov (United States)

    Vaccaro, Brian J; Thorgersen, Michael P; Lancaster, W Andrew; Price, Morgan N; Wetmore, Kelly M; Poole, Farris L; Deutschbauer, Adam; Arkin, Adam P; Adams, Michael W W

    2016-01-01

    Enzymes of the denitrification pathway play an important role in the global nitrogen cycle, including release of nitrous oxide, an ozone-depleting greenhouse gas. In addition, nitric oxide reductase, maturation factors, and proteins associated with nitric oxide detoxification are used by pathogens to combat nitric oxide release by host immune systems. While the core reductases that catalyze the conversion of nitrate to dinitrogen are well understood at a mechanistic level, there are many peripheral proteins required for denitrification whose basic function is unclear. A bar-coded transposon DNA library from Pseudomonas stutzeri strain RCH2 was grown under denitrifying conditions, using nitrate or nitrite as an electron acceptor, and also under molybdenum limitation conditions, with nitrate as the electron acceptor. Analysis of sequencing results from these growths yielded gene fitness data for 3,307 of the 4,265 protein-encoding genes present in strain RCH2. The insights presented here contribute to our understanding of how peripheral proteins contribute to a fully functioning denitrification pathway. We propose a new low-affinity molybdate transporter, OatABC, and show that differential regulation is observed for two MoaA homologs involved in molybdenum cofactor biosynthesis. We also propose that NnrS may function as a membrane-bound NO sensor. The dominant HemN paralog involved in heme biosynthesis is identified, and a CheR homolog is proposed to function in nitrate chemotaxis. In addition, new insights are provided into nitrite reductase redundancy, nitric oxide reductase maturation, nitrous oxide reductase maturation, and regulation. PMID:26452555

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

    Science.gov (United States)

    Grebliunas, Brian D; Perry, William L

    2016-01-01

    Nutrient stoichiometry within a wetland is affected by the surrounding land use, and may play a significant role in the removal of nitrate (NO3-N). Tile-drained, agricultural watersheds experience high seasonal inputs of NO3-N, but low phosphorus (PO4-P) and dissolved organic carbon (DOC) loads relative to surface water dominated systems. This difference may present stoichiometric conditions that limit denitrification within receiving waterways. We investigated how C:N:P ratios affected denitrification rates of sediments from tile-drained mitigation wetlands incubated for: 0, 5, 10, and 20 days. We then tested whether denitrification rates of sediments from surface-water and tile-drained wetlands responded differently to C:N ratios of 2:1 versus 4:1. Ratios of C:N:P (P maintenance of anaerobic conditions, the availability of labile DOC is playing an important limiting role in sediment denitrification within mitigation wetlands. PMID:27064357

  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...

  16. Nitrate-transformations during simulated drought on a restored floodplain

    Science.gov (United States)

    Hoagland, B.; Russo, T. A.; Schmidt, C. M.; Tran, D.

    2015-12-01

    Water resources in the California Central Valley face challenges due to recurring drought, aging levee systems, and nitrate contamination. As decisions are made to restore floodplain connectivity, soil microbial metabolic pathways such as denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) transform nitrate under saturated soil conditions and may each affect downstream water quality. However, few studies have quantified the contribution of all three pathways to nitrate retention in freshwater systems, and specifically in restored floodplains. Additionally, no former studies quantify the rates of these microbial nitrate transformations during floods after prolonged periods of drought. To test how flood duration impacts nitrogen cycling we added 15N-enriched tracer to soil mesocosms to measure denitrification, anammox, and DNRA transformation rates. In July 2015, we extracted seven soil mesocosms from the floodplain and riverbed of the Lower Cosumnes River in the San Joaquin Basin of California. Cosumnes River water enriched with 15N-NO3- tracer was pumped into each mesocosm at a constant rate simulating flood durations of 20 h, 30 h, and 96 h. Samples were collected from the surface water, soil pore water, drain water, and sediment for measurements of NO3-, NO2-, NH4+, gas isotopes, and DNA extraction. This study aims to demonstrate the relevance of anammox and DNRA to total nitrate retention and characterize the hydrologic conditions most favorable to each pathway.

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

    Directory of Open Access Journals (Sweden)

    W. Eschenbach

    2013-02-01

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

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

  18. Nitrate transport and its regulation by O2 in Pseudomonas aeruginosa.

    Science.gov (United States)

    Hernandez, D; Dias, F M; Rowe, J J

    1991-04-01

    Pseudomonas aeruginosa is an obligate respirer which can utilize nitrate as a terminal electron acceptor under anaerobic conditions (denitrification). Immediate, transient regulation of nitrate respiration is mediated by oxygen through the inhibition of nitrate uptake. In order to gain an understanding of the bioenergetics of nitrate transport and its regulation by oxygen, the effects of various metabolic inhibitors on the uptake process and on oxygen regulation were investigated. Nitrate uptake was stimulated by the protonophores carbonyl cyanide m-chlorophenylhydrazone and 2,4-dinitrophenol, indicating that nitrate uptake is not strictly energized by, but may be affected by the proton motive force. Oxygen regulation of nitrate uptake might in part be through redox-sensitive thiol groups since N-ethylmaleimide at high concentrations decreased the rate of nitrate transport. Cells grown with tungstate (deficient in nitrate reductase activity) and azide-treated cells transported nitrate at significantly lower rates than untreated cells, indicating that physiological rates of nitrate transport are dependent on nitrate reduction. Furthermore, tungstate grown cells transported nitrate only in the presence of nitrite, lending support to the nitrate/nitrite antiport model for transport. Oxygen regulation of nitrate transport was relieved (10% that of typical anaerobic rates) by the cytochrome oxygen reductase inhibitors carbon monoxide and cyanide. PMID:1910283

  19. [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.

  20. Denitrification of agricultural drainage line water via immobilized denitrification sludge.

    Science.gov (United States)

    Hunt, Patrick G; Matheny, Terry A; Ro, Kyoung S; Stone, Kenneth C; Vanotti, Matias B

    2008-07-15

    Nonpoint source nitrogen is recognized as a significant water pollutant worldwide. One of the major contributors is agricultural drainage line water. A potential method of reducing this nitrogen discharge to water bodies is the use of immobilized denitrifying sludge (IDS). Our objectives were to (1) produce an effective IDS, (2) determine the IDS reaction kinetics in laboratory column bioreactors, and (3) test a field bioreactor for nitrogen removal from agricultural drainage line water. We developed a mixed liquor suspended solid (MLSS) denitrifying sludge using inoculant from an overland flow treatment system. It had a specific denitrification rate of 11.4 mg NO(3)-N g(-1) MLSS h(-1). We used polyvinyl alcohol (PVA) to immobilize this sludge and form IDS pellets. When placed in a 3.8-L column bioreactor, the IDS had a maximum removal rate (K(MAX)) of 3.64 mg NO(3)-N g(-1) pellet d(-1). In a field test with drainage water containing 7.8 mg NO(3)-N L(-1), 50% nitrogen removal was obtained with a 1 hr hydraulic retention time. Expressed as a 1 m(3) cubically-shaped bioreactor, the nitrogen removal rate would be 94 g NO(3)-N m(-2)d(-1), which is dramatically higher than treatment wetlands or passive carbonaceous bioreactors. IDS bioreactors offer potential for reducing nitrogen discharge from agricultural drainage lines. More research is needed to develop the bioreactors for agricultural use and to devise effective strategies for their implementation with other emerging technologies for improved water quality on both watershed and basin scales. PMID:18569323

  1. Periplasmic nitrate reductases: structural and spectroscopic studies

    OpenAIRE

    Javier Gonzalez, Pablo

    2006-01-01

    Dissertação apresentada para obtenção do grau de Doutor em Bioquímica, especialidade Bioquímica-Física, pela Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa Nitrate reduction occurs in the cell in order to incorporate nitrogen into biomolecules(assimilatory ammonification), as the final electron acceptor when bacteria are grown in anaerobic conditions (denitrification/dissimilatory ammonification) and to eliminate energy excess generated by the cell metabolism (dissimi...

  2. [Simultaneous Biotransformation of Ammonium and Nitrate via Zero-Valent Iron on Anaerobic Conditions].

    Science.gov (United States)

    Zhou, Jian; Huang, Yong; Yuan, Yi; Liu, Xin; Li, Xiang; Shen, Jie; Yang, Peng-bing

    2015-12-01

    Zero-valent iron (ZVI) was used to improve the biological autotrophic denitrification process between nitrate and ammonia by anaerobic ammonia oxidation ( ANAMMOX) bacteria. With the addition of ZVI, the biological autotrophic denitrification process could be reacted in the influent condition of pH was 7-8, at 35°C ±0.5°C, the concentration of ammonia was 50-100 mg · L⁻¹ and the concentration of nitrate was 50-100 mg · L⁻¹. The highest conversion rate could be reached to 17.2 mg · (L·h) ⁻¹. With the change of reaction time and the molar ratio of nitrate and ammonia in influent, the final molar conversion ratio of nitrate and ammonia in effluent fluctuated between 1.2-3. 5. The result showed that this autotrophic denitrification process was not belonged to elementary reaction. The mechanism of this autotrophic denitrification process could be summarized that with the reduction of ZVI, the nitrate could be reduced to nitrite. Hereafter, the ANAMMOX process reacted between the nitrite and ammonia. PMID:27011992

  3. A standardised method for measuring in situ denitrification in shallow aquifers: numerical validation and measurements in riparian wetlands

    Directory of Open Access Journals (Sweden)

    J. M. Sánchez-Pérez

    2003-01-01

    Full Text Available A tracer test to examine in situ denitrification in shallow groundwater by a piezometer with a packer system used bromide as a tracer of dilution and acetylene (10% to block the denitrification process at the nitrous oxide stage. During the test, dissolved oxygen, nitrate (NO3‾, bromide (Br‾, nitrous oxide (N2O and dissolved organic carbon (DOC were measured. To calibrate the experimental method, comparison with numerical simulations of the groundwater transfer were carried out, taking into account the environmental characteristics. The method was tested by measurements undertaken in different environmental conditions (geology, land use and hydrology in two riparian wetlands. Denitrification rates measured by this method ranged from 5.7 10-6 g N-NO3‾L-1 h-1 to 1.97 10-3 g N-NO3‾L-1 h-1 The method is applicable in shallow aquifers with a permeability from 10-2 to 10-4m s-1. Keywords: denitrification, shallowaquifer, groundwater modelling, wetlands, nitrate-nitrogen, packer system

  4. Biodiversity in Benthic Ecology

    DEFF Research Database (Denmark)

    Friberg, Nikolai; Carl, J. D.

    Foreword: This proceeding is based on a set of papers presented at the second Nordic Benthological Meeting held in Silkeborg, November 13-14, 1997. The main theme of the meeting was biodiversity in benthic ecology and the majority of contributions touch on this subject. In addition, the proceeding...

  5. The effects of temperature and resource availability on denitrification and relative N2O production in boreal lake sediments.

    Science.gov (United States)

    Myrstener, Maria; Jonsson, Anders; Bergström, Ann-Kristin

    2016-09-01

    Anthropogenic environmental stressors (like atmospheric deposition, land use change, and climate warming) are predicted to increase inorganic nitrogen and organic carbon loading to northern boreal lakes, with potential consequences for denitrification in lakes. However, our ability to predict effects of these changes is currently limited as northern boreal lakes have been largely neglected in denitrification studies. The aim of this study was therefore to assess how maximum potential denitrification and N2O production rates, and the relationship between the two (relative N2O production), is controlled by availability of nitrate (NO3(-)), carbon (C), phosphorus (P), and temperature. Experiments were performed using the acetylene inhibition technique on sediments from a small, nutrient poor boreal lake in northern Sweden in 2014. Maximum potential denitrification and N2O production rates at 4°C were reached already at NO3(-) additions of 106-120μg NO3(-)-N/L, and remained unchanged with higher NO3 amendments. Higher incubation temperatures increased maximum potential denitrification and N2O production rates, and Q10 was somewhat higher for N2O production (1.77) than for denitrification (1.69). The relative N2O production ranged between 13% and 64%, and was not related to NO3(-) concentration, but the ratio increased when incubations were amended with C and P (from a median of 16% to 27%). Combined, our results suggests that unproductive northern boreal lakes currently have low potential for denitrification but are susceptible to small changes in NO3 loading especially if these are accompanied by enhanced C and P availability, likely promoting higher N2O production relative to N2. PMID:27593275

  6. Nitrate bioreduction in redox-variable low permeability sediments

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Sen; Liu, Yuanyuan; Liu, Chongxuan; Shi, Liang; Shang, Jianying; Shan, Huimei; Zachara, John M.; Fredrickson, Jim K.; Kennedy, David W.; Resch, Charles T.; Thompson, Christopher J.; Fansler, Sarah J.

    2015-09-09

    Denitrification is a microbial process that reduces nitrate and nitrite to nitrous oxide (N2O) or dinitrogen (N2) with a strong implication to global nitrogen cycling and climate change. This paper reports the effect of sediment redox conditions on the rate and end product of denitrification. The sediments were collected from a redox transition zone consisting of oxic and reduced layers at US Department of Energy’s Hanford Site where N2O was locally accumulated in groundwater. The results revealed that denitrification rate and end product varied significantly with initial sediment redox state. The denitrification rate was relatively faster, limited by organic carbon content and bioavailability in the oxic sediment. In contrast, the rate was much slower in the reduced sediment, limited by biomass and microbial function. A significant amount of N2O was accumulated in the reduced sediment; while in the oxic sediment, N2O was further reduced to N2. RT-PCR analysis revealed that nosZ, the gene that codes for N2O reductase, was below detection in the reduced sediment. The results implied that redox transition zones can be important sinks or sources of N2O depending on local biogeochemical and microbial conditions, and are important systems for understanding and modeling denitrification in subsurface environments.

  7. 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

  8. 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.

  9. Nitrate retention and removal in Mediterranean streams bordered by contrasting land uses: a 15N tracer study

    Directory of Open Access Journals (Sweden)

    E. Martí

    2009-02-01

    Full Text Available We used 15N-labelled nitrate (NO3− additions to investigate pathways of nitrogen (N cycling at the whole-reach scale in three stream reaches with adjacent forested, urban and agricultural land areas. Our aim was to explore among-stream differences in: (i the magnitude and relative importance of NO3− retention (i.e. assimilatory uptake and removal (i.e. denitrification, (ii the relative contribution of the different primary uptake compartments to NO3− retention, and (iii the regeneration, transformation and export pathways of the retained N. Streams varied strongly in NO3− concentration, which was highest in the agricultural stream and lowest in the forested stream. The agricultural stream also showed the lowest dissolved oxygen (DO concentration and discharge. Standing stocks of primary uptake compartments were similar among streams and dominated by detritus compartments (i.e. fine and coarse benthic organic matter. Metabolism was net heterotrophic in all streams, although the degree of heterotrophy was highest in the agricultural stream. The NO3− uptake length was shortest in the agricultural stream, intermediate in the urban stream, and longest in the forested stream. Conversely, the NO3− mass-transfer velocity and the areal NO3− uptake rate were highest in the urban stream. Denitrification was not detectable in the forested stream, but accounted for 9% and 68% of total NO3− uptake in the urban and the agricultural stream, respectively. The relative contribution of detritus compartments to NO3− assimilatory uptake was greatest in the forested and lowest in the agricultural stream. In all streams, the retained N was rapidly regenerated back to the water column. Due to a strong coupling between regeneration and nitrification, most retained N was exported from the experimental reaches in the form of NO3−. This study provides evidence of fast in-stream N cycling, although the relative importance of N retention and removal

  10. 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

  11. 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.

  12. Heterotrophic denitrification at extremely high salt and pH by haloalkaliphilic Gammaproteobacteria from hypersaline soda lakes

    OpenAIRE

    Shapovalova, A. A.; Khijniak, T. V.; Tourova, T. P.; Muyzer, G.; Sorokin, Y

    2008-01-01

    In this paper we describe denitrification at extremely high salt and pH in sediments from hypersaline alkaline soda lakes and soda soils. Experiments with sediment slurries demonstrated the presence of acetate-utilizing denitrifying populations active at in situ conditions. Anaerobic enrichment cultures at pH 10 and 4 M total Na+ with acetate as electron donor and nitrate, nitrite and N2O as electron acceptors resulted in the dominance of Gammaproteobacteria belonging to the genus Halomonas. ...

  13. 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.

  14. Nitrate contamination of groundwater as a factor of atmospheric pollution

    International Nuclear Information System (INIS)

    High nitrate concentrations of ground water in agricultural regions not only enhance denitrification in gravel pit lakes but also increase the proportion of nitrous oxide (N2O) in the gaseous products released to the atmosphere. Thereby they contribute to the greenhouse effect and destruction of the stratospheric ozone layer. However, due to the present small area of the lakes, their effect may be considered as important at the global scale

  15. Nitrate ammonification in mangrove soils: A hidden source of nitrite?

    Directory of Open Access Journals (Sweden)

    Melike eBalk

    2015-03-01

    Full Text Available Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests.The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden under the nitrate-limited conditions of most mangrove forest soils.

  16. Nitrate ammonification in mangrove soils: a hidden source of nitrite?

    KAUST Repository

    Balk, Melike

    2015-03-02

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils.

  17. Nitrate ammonification in mangrove soils: a hidden source of nitrite?

    Science.gov (United States)

    Balk, Melike; Laverman, Anniet M; Keuskamp, Joost A; Laanbroek, Hendrikus J

    2015-01-01

    Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils. PMID:25784903

  18. Predicting long-term denitrification capacity of sandy aquifers from incubation experiments and sediment properties

    Directory of Open Access Journals (Sweden)

    W. Eschenbach

    2012-07-01

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

    For this purpose, we incubated aquifer material from two sandy Pleistocene aquifers in Northern Germany under anaerobic conditions in the laboratory using the 15N tracer technique. The measured long-term denitrification capacities ranged from 0.18 to 56.2 mg N kg−1 yr−1. The laboratory incubations exhibited high differences between non-sulphidic and sulphidic aquifer material in both aquifers with respect to all investigated sediment parameters. Denitrification rates and the estimated lifetime of denitrification were higher in the sulphidic samples. Denitrification capacity measured during one year of incubation (Dcap was predictable from sediment variables within a range of uncertainty of 0.5 to 2 (calculated Dcap/measured Dcap for aquifer material with a Dcap > 20 mg N kg−1 yr−1. Predictions were poor for samples with lower Dcap like samples from the NO3-bearing groundwater zone, which includes the non-sulphidic samples, from the upper part of both aquifers where Dcap is not sufficient to protect groundwater from anthropogenic NO3 input. Calculation of Dcap from initial denitrification rates was only successful for samples from the NO

  19. /sup 13/N, /sup 15/N isotope and kinetic evidence against hyponitrite as an intermediate in denitrification

    Energy Technology Data Exchange (ETDEWEB)

    Hollocher, T.C. (Brandeis Univ., Waltham, MA); Garber, E.; Cooper, A.J.L.; Reiman, R.E.

    1980-06-10

    /sup 13/N- and /sup 15/N-labeling experiments were carried out with Paracoccus denitrificans, grown anaerobically on nitrate, to determine whether hyponitrite might be an obligatory intermediate in denitrification and a precursor of nitrous oxide. From experiments designed to trap (/sup 13/N)- or (/sup 15/N, /sup 15/N)hyponitrite by dilution into authentic hyponitrite it was calculated that the intracellular concentration of a presumptive hyponitrite pool must be less than 0.4 mm. In order for a pool of this size to turn over rapidly enough to handle the flux of nitrogen during denitrification, the spontaneous rate of hyponitrite dehydration must be enhanced by a factor of several thousand through enzyme catalysis. Cell extracts failed to catalyze this reaction under a variety of conditions. It is concluded that hyponitrite cannot be an intermediate in denitrification. In addition, the assimilation of inorganic nitrogen was studied in P. dentrificans using /sup 13/N as tracer. At low concentrations (<10/sup -8/ M) of labeled nitrate and nitrite 5 to 10% of the label was assimilated into non-volatile metabolites and 90 to 95% was reduced to N/sub 2/. Similarly, with 15 mm (/sup 13/N)nitrate, 5% of the label went into metabolites and 95% to N/sub 2/. High pressure liquid chromatography analysis of the labeled metabolites indicated that the major pathway for assimilation of inorganic nitrogen in P. denitrificans under these conditions is through ammonia incorporation via the aspartase reaction.

  20. Experimental evidence for aerobic bio-denitrification

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Nitrate pollution of groundwater is paid more and more attention for its hazardous to environments and human health. A strain of DN11 was isolated from soil and used in the laboratory columns filled with various media for nitrate removal. The experimental results showed that DN11could reduce nitrate at different rates in different media under the aerobic condition. The mechanism for nitrate removal with DN11 is explained meanwhile.

  1. In-Stream Microbial Denitrification Potential at Wastewater Treatment Plant Discharge Sites

    Science.gov (United States)

    Hill, N. B.; Rahm, B. G.; Shaw, S. B.; Riha, S. J.

    2014-12-01

    Reactive nitrogen loading from municipal sewage discharge provides point sources of nitrate (NO3-) to rivers and streams. Through microbially-mediated denitrification, NO3- can be converted to dinitrogen (N2) and nitrous oxide (N2O) gases, which are released to the atmosphere. Preliminary observations made throughout summer 2011 near a wastewater treatment plant (WWTP) outfall in the Finger Lakes region of New York indicated that NO3- concentrations downstream of the discharge pipe were lower relative to upstream concentrations. This suggested that nitrate processing was occurring more rapidly and completely than predicted by current models and that point "sources" can in some cases be point "sinks". Molecular assays and stable isotope analyses were combined with laboratory microcosm experiments and water chemistry analyses to better understand the mechanism of nitrate transformation. Nitrite reductase (nirS and nirK) and nitrous oxide reductase (nosZ) genes were detected in water and sediment samples using qPCR. Denitrifcation genes were present attached to stream sediment, in pipe biofilm, and in WWTP discharge water. A comparison of δ18-O and δ15-N signatures also supported the hypothesis that stream NO3- had been processed biotically. Results from microcosm experiments indicated that the NO3- transformations occur at the sediment-water interface rather than in the water column. In some instances, quantities of denitrification genes were at higher concentrations attached to sediment downstream of the discharge pipe than upstream of the pipe suggesting that the wastewater discharge may be enriching the downstream sediment and could promote in-stream denitrification.

  2. Interaction of Cr(VI) reduction and denitrification by strain Pseudomonas aeruginosa PCN-2 under aerobic conditions.

    Science.gov (United States)

    He, Da; Zheng, Maosheng; Ma, Tao; Li, Can; Ni, Jinren

    2015-06-01

    Inhibition of efficient denitrification in presence of toxic heavy metals is one of the current problems encountered in municipal wastewater treatment plants. This paper presents how to remove hexavalent chromium (Cr(VI)) and nitrate simultaneously by the novel strain Pseudomonas aeruginosa PCN-2 under aerobic conditions. The capability of strain PCN-2 for Cr(VI) and nitrate reduction was confirmed by PCR analysis of gene ChrR, napA, nirS, cnorB, nosZ, while Cr(VI) reduction was proved via an initial single-electron transfer through Cr(V) detection using electron paramagnetic resonance. Experimental results demonstrated that Cr(VI) and nitrate reduction by strain PCN-2 was much faster at pH 8-9 and higher initial cell concentration. However, increasing Cr(VI) concentration would inhibit aerobic denitrification process and result in an significant delay of nitrate reduction or N2O accumulation, which was attributed to competition between three electron acceptors, i.e., Cr(VI), O2 and nitrate in the electron transport chain.

  3. Interaction of Cr(VI) reduction and denitrification by strain Pseudomonas aeruginosa PCN-2 under aerobic conditions.

    Science.gov (United States)

    He, Da; Zheng, Maosheng; Ma, Tao; Li, Can; Ni, Jinren

    2015-06-01

    Inhibition of efficient denitrification in presence of toxic heavy metals is one of the current problems encountered in municipal wastewater treatment plants. This paper presents how to remove hexavalent chromium (Cr(VI)) and nitrate simultaneously by the novel strain Pseudomonas aeruginosa PCN-2 under aerobic conditions. The capability of strain PCN-2 for Cr(VI) and nitrate reduction was confirmed by PCR analysis of gene ChrR, napA, nirS, cnorB, nosZ, while Cr(VI) reduction was proved via an initial single-electron transfer through Cr(V) detection using electron paramagnetic resonance. Experimental results demonstrated that Cr(VI) and nitrate reduction by strain PCN-2 was much faster at pH 8-9 and higher initial cell concentration. However, increasing Cr(VI) concentration would inhibit aerobic denitrification process and result in an significant delay of nitrate reduction or N2O accumulation, which was attributed to competition between three electron acceptors, i.e., Cr(VI), O2 and nitrate in the electron transport chain. PMID:25795449

  4. Denitrification in an anoxic rotating biological contactor under two carbon/nitrogen ratios

    OpenAIRE

    Cortez, Susana; Teixeira, P; Oliveira, Rosário; Mota, M.

    2008-01-01

    The aim of the present work was to compare the performance of an anoxic bench-scale rotating biological contactor (RBC), in terms of the denitrification process, applied to treat synthetic wastewater under two carbon/nitrogen (C/N) molar ratios (1.5 and 3). The average removal efficiency in terms of nitrogen-nitrate was of about 90.4% at a C/N=1.5 lowering to 73.7% at a C/N=3. Considering carbon-acetate removal an overall efficiency of 82.0% and 63.6% was attained at a C/N rati...

  5. 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

  6. 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

  7. Benthic diatoms in lakes

    OpenAIRE

    Gottschalk, Steffi

    2014-01-01

    In order to protect or improve surface waters ecosystem response to pressures needs to be quantified. Diatoms are frequently used for assessing ecological status in streams and for reconstructing water quality of lakes. However, ecological status assessment of European lakes based on extant diatom assemblages is rare. The overall aim of this thesis is to facilitate the application of benthic diatoms in water quality assessment of boreal lakes, using methods developed for stream assessmen...

  8. The feasibility of applying immature yard-waste compost to remove nitrate from agricultural drainage effluents: A preliminary assessment

    Science.gov (United States)

    Tsui, L.; Krapac, I.G.; Roy, W.R.

    2007-01-01

    Nitrate is a major agricultural pollutant found in drainage waters. Immature yard-waste compost was selected as a filter media to study its feasibility for removing nitrate from drainage water. Different operation parameters were tested to examine the denitrification efficiency, including the amounts of compost packed in columns, the flow rate, and the compost storage periods. The experimental results suggested that hydraulic retention time was the major factor to determine the extent of nitrate removal, although the amount of compost packed could also contribute to the nitrate removal efficiency. The effluent nitrate concentration increased as the flow rate decreased, and the compost column reduced nitrate concentrations from 20 mg/L to less than 5 mg/L within 1.5 h. The solution pH increased at the onset of experiment because of denitrification, but stabilized at a pH of about 7.8, suggesting that the compost had a buffering capacity to maintain a suitable pH for denitrification. Storing compost under air-dried conditions may diminish the extent nitrate removed initially, but the effects were not apparent after longer applications. It appeared that immature yard-waste compost may be a suitable material to remove nitrate from tile drainage water because of its relatively large organic carbon content, high microbial activity, and buffering capacity. ?? 2006 Elsevier B.V. All rights reserved.

  9. [Nitrate removal from recirculating aquaculture system using polyhydroxybutyrate-co-hydroxyvalerate as carbon source ].

    Science.gov (United States)

    Zhang, Lanhe; Liu, Lili; Qiu, Tianlei; Gao, Min; Han, Meilin; Yuan, Ding; Wang, Xuming

    2014-09-01

    [ OBJECTIVE] Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) was used as solid carbon source and biofilm carrier to remove nitrate from recirculating aquaculture system (RAS). Dynamics of microbial community structure in biofilm coating on carbon source packed into denitrification reactor were investigated. [METHODS] Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the microbial community in biofilm from denitrifiation reactor. Bacteria degrading PHBV were isolated from the reactor using pure culture method. [RESULTS] Nitrate decreased remarkably in the RAS connected with dentrification reactor. In contrast, Nitrate increased continuously in the conventional RAS without dentrification reactor. According to the phylogenetic analysis, the microbes in the biofilm samples from denitrification reactor were divided into Proteobacteria ( p-proteobacteria, γ-proteobacteria and δ- proteobacteria) , Firmicutes and Bacteroidetes. The major advantageous populations were Acidovorax and Bacillus in the 40-day reactor. The advantageous populations in the 150-day reactor were in order of Clostridium, Desulfitobacterium, Dechloromonas, Pseudoxanthomonas and Flavobacterium. Pure cultures of bacteria degrading PHBV isolated from denitrification reactor were classified into Acidovorax, Methylibium, Pseudoxanthomonas and Dechloromonas. [CONCLUSION] Nitrate could be removed effectively from RAS using PHBV as carbon source. Advantageous bacteria and their dynamic changes were ascertained in biofilm from denitrification reactor packed with PHBV. PMID:25522594

  10. Microbial degradation of high nitrogen contents (primarily nitrate) in industrial waste water

    International Nuclear Information System (INIS)

    This study deals with the denitrification of industrial waste water of high nitrate content, including waste water from the recovery process for nuclear material. At first the autotrophic process employing Thiob. denitrificans was investigated: kinetics, stoichiometry, application of a packed bed reactor; effect of nitrate concentration, retention time, loading and height of the reactor on denitrification. The system proved to be useful for waste water with nitrate up to 4.5 g/L; the highest rate of denitrification achieved was 1.5 g/L.h when the retention time was 2.5 h and the nitrate concentration (in-flow) 4.3 g/L (i.e. reactor loadung 41 kg NO3-/m3.d). Equally good results were obtained by the heterotrophic process: ethanol allowed a reactor loading of 60 kg NO3-/m3.d; however, in this case bacterial growth tended to clog the column. - Enrichments made with ethanol yielded Ps. aeruginosa as main component of the population; in contrast, those with methanol resulted in a mixture of Hyphomicrobium spec. and Paracoccus denitrificans; this bacterial culture was used to determine the stoichiometry of denitrification in continuous culture; it was also employed to denitrify a diluted solution of nitric acid (0.1 ml HNO3/L) which could be achieved in continuous culture using a retention time of 25 h. (orig.)

  11. Patterns of gaseous nitrogen losses from cattle slurries enriched with urea of urea ammonium nitrate

    NARCIS (Netherlands)

    Postma, R.; Velthof, G.L.; Oenema, O.

    2000-01-01

    A study was conducted to investigate the potential of using mixtures of cattle slurry with cheap urea (U) or urea-ammonium nitrate (UAN). The kinetics of NH3 volatilization, nitrous oxide (N2O) emission and denitrification after the addition of U and

  12. One method is not enough to determine denitrification in a Histic Gleysol following different grassland renovation techniques in Northwest Germany

    Science.gov (United States)

    Well, Reinhard; Buchen, Caroline; Eschenbach, Wolfram; Lewicka-Szczebak, Dominika; Helfrich, Mirjam; Gensior, Andreas; Flessa, Heinz

    2014-05-01

    Grassland renovation by reseeding is a common practices to improve productivity, but knowledge on enhanced nitrate leaching and N2O emission due to disturbance during associated soil tillage is scarce. Denitrification in hydromorphic soils under agricultural management is potentially extremely high due to the coincidence of high nitrate concentrations, labile organic carbon and oxygen depletion during extended periods of water saturation close to the soil surface (Well et al. 2003; Well et al. 2005). We investigated the impact of grassland renewal or conversion to arable land on greenhouse gas fluxes and N losses in field plot experiments. One of the two sites is a hydromorphic soil (Histic Gleysol) rich in organic C, with groundwater level always within the rooting zone and close to the surface during winter. Assessment of the N budget to estimate enhanced N mineralization following grassland renewal as well as associated N leaching is complicated by potentially complete NO3- consumption via denitrification. Robust estimation on denitrification losses at this site is crucial to assess the impact of grassland renewal on its N dynamics and budget. One aim of this study is to determine denitrification in the surface and subsoil in order to close the N budget. We apply five approaches to investigate spatial and temporal dynamics of denitrification and will report first results. (1) N balance approach: The N budget is obtained by weekly measurement of N2O fluxes and mineral N in the top soil, mineral N twice a year at 0 to 90 cm depth, N uptake, N fertilization and modeling N leaching based on mineral N and hydrological model data. Unaccounted N is attributed to possible denitrification. (2) Isotopologue approach: δ18O, average δ15N and 15N site preference of N2O as well as δ15N and δ18O of NO3- are measured at times to estimate N2O reduction to N2 in the topsoil during periods of unsaturated conditions using the N2O isotope fractionation approach (Lewicka

  13. Influence of zero-valent iron nanoparticles on nitrate removal by Paracoccus sp.

    Science.gov (United States)

    Liu, Yan; Li, Shibin; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravi

    2014-08-01

    Nitrate contamination in drinking water is a major threat to public health. This study investigated the efficiency of denitrification of aqueous solutions in the co-presence of synthesized nanoscale zero-valent iron (nZVI; diameter: 20-80 nm) and a previously isolated Paracoccus sp. strain YF1. Various influencing factors were studied, such as oxygen, pH, temperature, and anaerobic corrosion products (Fe(2+), Fe(3+) and Fe3O4). With slight toxicity to the strain, nZVI promoted denitrification efficiency by providing additional electron sources under aerobic conditions. For example, 50 mg L(-1) nZVI increased the nitrate removal efficiency from 66.9% to 85.2%. However, a high concentration of nZVI could lead to increased production of Fe(2+), a toxic ion which could compromise the removal efficiency. Kinetic studies suggest that denitrification by both free cells, and nZVI-amended cells fitted well to the zero-order model. Temperature and pH are the major factors affecting nitrate removal and cell growth, with or without the presence of nZVI. In this study, nitrate removal and cell growth increased in the pH range of 6.5-8.0, and temperature range of 25-35 °C. These conditions favor the growth of the strain, which dominated denitrification in all scenarios involved. As for anaerobic corrosion products, compared with Fe(2+) and Fe(3+), Fe3O4 promoted denitrification by serving as an electron donor. Finally, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) confirmed attachments of nZVI on the surface of the cell, and the formation of iron oxides. This study indicated that, as an electron donor source with minimal cellular toxicity, nZVI could be used to promote denitrification efficiency under biotic conditions. PMID:24630453

  14. Deep Nitrate Deficit Observed in the Highly Oxygenated East/Japan Sea and Its Possible Cause

    Directory of Open Access Journals (Sweden)

    Il-Nam Kim

    2012-01-01

    Full Text Available We present evidence of denitrification on the continental slopes of the Ulleung Basin (UB and the Eastern Japan Basin (EJB near the Tatar Strait (TtS in the East/Japan Sea (EJS, despite its high water column dissolved oxygen concentrations. Some nutrient concentration data deviate significantly from the fitted regression line of nitrate (N vs. phosphate (P in deep waters, indicating a loss of nitrate in the region. The EJS has a lower N/P ratio (ca. 12.4 below 300 dbar than a traditional Redfield ratio (16. The N/P ratio and oxygen concentration are substantially lower at several locations whose depths are close to the sediment-water interface, near TtS (500 - 1100 dbar and in UB (1100 - 2200 dbar. The decreased nitrate concentration is smaller than the expected nitrate level (a low N/P ratio of < 12.4, and a secondary nitrite peak near the bottom of these two regions: taken collectively, both indicate the presence of denitrification in the bottom layer. It is speculated that active re-mineralization and denitrification may occur simultaneously along the rich organic matter bottom layer on the slope environment. Denitrification rates are estimated at ~3 - 33 μmol N m-2 d-1. Current estimates do not support the previous idea of basin-wide denitrification in EJS, although the N/P ratio is low like in other hypoxic/anoxic seas. A better understanding of the denitrification process is necessary for predicting future changes of nitrogen cycle in the well-oxygenated EJS considering the decadal-scale physical and biogeochemical changes that have occurred.

  15. Effects of sludge disposal on groundwater nitrate concentrations

    Science.gov (United States)

    Spalding, R. F.; Exner, M. E.; Martin, G. E.; Snow, D. D.

    1993-02-01

    More than 100 groundwater samples were collectd and analyzed for nitrate-nitrogen, δ 15N of the nitrate, dissolved organic carbon (DOC), and chloride. Multilevel samplers and nested monitoring wells were located beneath and down-gradient from an irrigated cornfield on which human waste sludge was injected. The sampling delineated a 1.3km× 0.3km plume of nitrate contamination. Both the nitrate-nitrogen concentrations and the δ 15N values within the plume's centroid were homogeneous. The levels were 34 ± 3mg1 -1 and + 13.4 ± 1.2%, respectively. A retarding zone of clayey silt split the plume and separated the oxic water from the deeper anoxic water. Nitrate levels were lower in the anoxic water and declined rapidly with depth. The significant association ( r = - 0.91) between increasing δ 15N values and decreasing nitrate concentrations indicated that the nitrate was denitrified. High chloride concentrations in the anoxic zone beneath the retarding layer are thought to originate from the sludge storage lagoon and/or the sludge compost piles. Tritium and atrazine levels confirm that this is recent recharge water. Denitrification has utilized most of the original nitrate and DOC in the plume.

  16. Denitrification activity of a remarkably diverse fen denitrifier community in finnish lapland is N-oxide limited.

    Science.gov (United States)

    Palmer, Katharina; Horn, Marcus A

    2015-01-01

    Peatlands cover more than 30% of the Finnish land area and impact N2O fluxes. Denitrifiers release N2O as an intermediate or end product. In situ N2O emissions of a near pH neutral pristine fen soil in Finnish Lapland were marginal during gas chamber measurements. However, nitrate and ammonium fertilization significantly stimulated in situ N2O emissions. Stimulation with nitrate was stronger than with ammonium. N2O was produced and subsequently consumed in gas chambers. In unsupplemented anoxic microcosms, fen soil produced N2O only when acetylene was added to block nitrous oxide reductase, suggesting complete denitrification. Nitrate and nitrite stimulated denitrification in fen soil, and maximal reaction velocities (vmax) of nitrate or nitrite dependent denitrification where 18 and 52 nmol N2O h-1 gDW-1, respectively. N2O was below 30% of total produced N gases in fen soil when concentrations of nitrate and nitrite were N2O consumption was up to 36 nmol N2O h-1 gDW-1. Denitrifier diversity was assessed by analyses of narG, nirK/nirS, and nosZ (encoding nitrate-, nitrite-, and nitrous oxide reductases, respectively) by barcoded amplicon pyrosequencing. Analyses of ~14,000 quality filtered sequences indicated up to 25 species-level operational taxonomic units (OTUs), and up to 359 OTUs at 97% sequence similarity, suggesting diverse denitrifiers. Phylogenetic analyses revealed clusters distantly related to publicly available sequences, suggesting hitherto unknown denitrifiers. Representatives of species-level OTUs were affiliated with sequences of unknown soil bacteria and Actinobacterial, Alpha-, Beta-, Gamma-, and Delta-Proteobacterial sequences. Comparison of the 4 gene markers at 97% similarity indicated a higher diversity of narG than for the other gene markers based on Shannon indices and observed number of OTUs. The collective data indicate (i) a high denitrification and N2O consumption potential, and (ii) a highly diverse, nitrate limited denitrifier

  17. Denitrification activity of a remarkably diverse fen denitrifier community in finnish lapland is N-oxide limited.

    Directory of Open Access Journals (Sweden)

    Katharina Palmer

    Full Text Available Peatlands cover more than 30% of the Finnish land area and impact N2O fluxes. Denitrifiers release N2O as an intermediate or end product. In situ N2O emissions of a near pH neutral pristine fen soil in Finnish Lapland were marginal during gas chamber measurements. However, nitrate and ammonium fertilization significantly stimulated in situ N2O emissions. Stimulation with nitrate was stronger than with ammonium. N2O was produced and subsequently consumed in gas chambers. In unsupplemented anoxic microcosms, fen soil produced N2O only when acetylene was added to block nitrous oxide reductase, suggesting complete denitrification. Nitrate and nitrite stimulated denitrification in fen soil, and maximal reaction velocities (vmax of nitrate or nitrite dependent denitrification where 18 and 52 nmol N2O h-1 gDW-1, respectively. N2O was below 30% of total produced N gases in fen soil when concentrations of nitrate and nitrite were <500 μM. vmax for N2O consumption was up to 36 nmol N2O h-1 gDW-1. Denitrifier diversity was assessed by analyses of narG, nirK/nirS, and nosZ (encoding nitrate-, nitrite-, and nitrous oxide reductases, respectively by barcoded amplicon pyrosequencing. Analyses of ~14,000 quality filtered sequences indicated up to 25 species-level operational taxonomic units (OTUs, and up to 359 OTUs at 97% sequence similarity, suggesting diverse denitrifiers. Phylogenetic analyses revealed clusters distantly related to publicly available sequences, suggesting hitherto unknown denitrifiers. Representatives of species-level OTUs were affiliated with sequences of unknown soil bacteria and Actinobacterial, Alpha-, Beta-, Gamma-, and Delta-Proteobacterial sequences. Comparison of the 4 gene markers at 97% similarity indicated a higher diversity of narG than for the other gene markers based on Shannon indices and observed number of OTUs. The collective data indicate (i a high denitrification and N2O consumption potential, and (ii a highly diverse

  18. Denitrification in marine sediments: A model study

    NARCIS (Netherlands)

    Middelburg, J.J.; Soetaert, K.E.R.; Herman, P.M.J.; Heip, C.H.R.

    1996-01-01

    The rate and factors controlling denitrification in marine sediments have been investigated using a prognostic diagenetic model. The model is forced with observed carbon fluxes, bioturbation and sedimentation rates, and bottom water conditions. It can reproduce rates of aerobic mineralization, denit

  19. Effects of aquatic vegetation type on denitrification

    NARCIS (Netherlands)

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

    2011-01-01

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

  20. 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.

  1. 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. PMID:26760756

  2. [Research progress in microbial methane oxidation coupled to denitrification].

    Science.gov (United States)

    Zhu, Jing; Yuan, Meng-Dong; Liu, Jing-Jing; Huang, Xiao-Xiao; Wu, Wei-Xiang

    2013-12-01

    Methane oxidation coupled to denitrification is an essential bond to connect carbon- and nitrogen cycling. To deeply research this process will improve our understanding on the biochemical cycling of global carbon and nitrogen. As an exogenous gaseous carbon source of denitrification, methane can both regulate the balance of atmospheric methane to effectively mitigate the greenhouse effect caused by methane, and reduce the cost of exogenous carbon source input in traditional wastewater denitrification treatment process. As a result, great attention has being paid to the mechanical study of the process. This paper mainly discussed the two types of methane oxidation coupled to denitrification, i. e., aerobic methane oxidation coupled to denitrification (AME-D) and anaerobic methane oxidation coupled to denitrification (ANME-D), with the focus on the microbiological coupling mechanisms and related affecting factors. The existing problems in the engineering application of methane oxidation coupled to denitrification were pointed out, and the application prospects were approached. PMID:24697087

  3. Generality of Nitrate Removal in Streambed Sediment on the Southern Delmarva Peninsula

    Science.gov (United States)

    McFadden, G.; Flewelling, S. A.; Herman, J. S.; Mills, A. L.

    2013-12-01

    Nitrogen fertilizers have accumulated in the unconfined Columbia aquifer on the Eastern Shore of Virginia (ESVA) and increased nitrate concentrations, which could potentially affect water quality in down-gradient surface-water bodies. The streambeds and riparian zones of the small, low-gradient ESVA streams appear to be attenuating the nitrate load of discharging groundwater via denitrification, thereby reducing groundwater nitrate concentrations by an order of magnitude or more in some cases. We measured concentrations of nitrate, chloride, and dissolved oxygen in sediment pore water as well as vertical head gradients and hydraulic conductivity in the streambed of four streams on the ESVA (Coal Kiln, Machipongo, Phillips Creek, and Parker Creek). Unlike measurements made in some other streams on the ESVA, the data did not show a consistent decrease in nitrate concentrations as groundwater discharged upward through the streambed. For Coal Kiln, Machipongo, and Phillips Creek, dissolved oxygen concentrations were consistently low (generally stream (Cobb Mill Creek) on the ESVA indicated that denitrification occurred primarily in the upper 30-60 cm of the streambed sediment, the data from Coal Kiln, Machipongo, and Phillips Creek suggest that denitrification may also be important elsewhere in the catchment, perhaps deeper in the sediment profile. In Parker Creek, the streambed appeared to be reducing nitrate concentrations as groundwater discharged to the stream, however, the magnitude of nitrate removal during vertical flow through the bed was insufficient to account for the low nitrate concentrations in the stream. Perhaps a key factor contributing to the larger groundwater nitrate concentrations entering Parker Creek's streambed was due to the discrepancy in pore-water velocities. The average pore-water velocity at maximum sample depth was a magnitude of order larger at Parker Creek than the other streams and could be representative of velocities earlier along

  4. Sulfide-driven autotrophic denitrification significantly reduces N2O emissions.

    Science.gov (United States)

    Yang, Weiming; Zhao, Qing; Lu, Hui; Ding, Zhi; Meng, Liao; Chen, Guang-Hao

    2016-03-01

    The Sulfate reduction-Autotrophic denitrification-Nitrification Integrated (SANI) process build on anaerobic carbon conversion through biological sulfate reduction and autotrophic denitrification by using the sulfide byproduct from the previous reaction. This study confirmed extra decreases in N2O emissions from the sulfide-driven autotrophic denitrification by investigating N2O reduction, accumulation, and emission in the presence of different sulfide/nitrate (S/N) mass ratios at pH 7 in a long-term laboratory-scale granular sludge autotrophic denitrification reactor. The N2O reduction rate was linearly proportional to the sulfide concentration, which confirmed that no sulfide inhibition of N2O reductase occurred. At S/N = 5.0 g-S/g-N, this rate resulted by sulfide-driven autotrophic denitrifying granular sludge (average granule size = 701 μm) was 27.7 mg-N/g-VSS/h (i.e., 2 and 4 times greater than those at 2.5 and 0.8 g-S/g-N, respectively). Sulfide actually stimulates rather than inhibits N2O reduction no matter what granule size of sulfide-driven autotrophic denitrifying sludge engaged. The accumulations of N2O, nitrite and free nitrous acid (FNA) with average granule size 701 μm of sulfide-driven autotrophic denitrifying granular sludge engaged at S/N = 5.0 g-S/g-N were 4.7%, 11.4% and 4.2% relative to those at 3.0 g-S/g-N, respectively. The accumulation of FNA can inhibit N2O reduction and increase N2O accumulation during sulfide-driven autotrophic denitrification. In addition, the N2O gas emission level from the reactor significantly increased from 14.1 ± 0.5 ppmv (0.002% of the N load) to 3707.4 ± 36.7 ppmv (0.405% of the N load) as the S/N mass ratio in the influent decreased from 2.1 to 1.4 g-S/g-N over the course of the 120-day continuous monitoring period. Sulfide-driven autotrophic denitrification may significantly reduce greenhouse gas emissions from biological nutrient removal when sulfur conversion processes are applied. PMID

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

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. The clay-rich Callovo-Oxfordian (COx) formation has been selected for the disposal of medium and high level, long-lived radioactive waste. After waste cell closure and degradation of package some intermediate-level waste will release nitrate. The latter is likely to diffuse into the surrounding environment (engineered barriers and geological host formation) and interact with a variety compounds present in the barrier components and the rocks. These interactions may result in modification of chemical conditions and impact storage conditions and radionuclide retention. Our work is focused on the understanding of the fate of nitrates released during and after degradation of waste package. We developed a coupled approach considering both geochemical and biological processes of nitrate reduction to simulate reactions occurring at the interface of the engineered barrier and the clay-rich COx formation. Laboratory experiments have been carried out in order to acquire data on kinetics of denitrification coupled with a molecular approach using enzymatic and metabolic activities as a tool for an accurate estimation of biomass. Denitrification has been monitored in a synthetic solution comparable to COx pore water supplemented with acetate and nitrate and amended with a heterotrophic denitrifying strain, Pseudomonas mandelii. Several conditions are applied considering different acetate/nitrate ratios in the presence or absence of COx clay. Before the beginning of experiments, the headspace is flushed with N2 gas to remove oxygen from flasks. Acetylene is used to stop denitrification reaction after the production of N2O gas and thus avoid the formation of N2 gas. Two successive redox reactions are thus expected to occur in experiments. Samples are regularly collected to analyze physical and chemical parameters as well as biological parameters. Biomass is estimated and monitored using both optical microscopy and quantitative

  6. 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.

  7. Denitrification of groundwater using PHBV blends in packed bed reactors and the microbial diversity.

    Science.gov (United States)

    Chu, Libing; Wang, Jianlong

    2016-07-01

    In the present study, three kinds of biopolymers, PHBV, PHBV/starch and PHBV/bamboo powder (BP) blends were used as carbon source and biofilm carriers for denitrification in packed bed reactors to remove nitrate from groundwater. Results showed that a fast start-up was obtained in bioreactors filled with both PHBV/Starch and PHBV/BP blends without external inocula and it took more than 3 month for PHBV reactor to reach the same loading rate. The PHBV/BP packed reactor exhibited a better nitrate removal efficiency (87.4 ± 7.0%) and less adverse effects in nitrite accumulation and DOC release (below 0.5 mg NO2N L(-1) and 10.5 mg DOC L(-1) in the effluent) during stable operation. Pyrosequencing analysis demonstrated that bacteria belonging to genus Clostridium in phylum Firmicus, which play the primary role in degrading the biopolymers, are the most dominant (33-15% of the sequences). The predominant species in all samples is related to Clostridium crotonatovorans. All the identified 11 genera of denitrifying bacteria affiliated with phylum Proteobacteria and constituted 30-55% in the representative sequences. The PHBV/BP blend is economically attractive carbon source with good denitrification performance. PMID:27145420

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

    Science.gov (United States)

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

    2015-01-01

    In this study, an integrated two-stage soil infiltration bioreactor incorporated with pyrite-based (mixotrophic) denitrification (SIBPD) was designed for domestic wastewater treatment. Benefited from excellent adsorption ability and water-permeability, soil infiltration could avoid clogging, shorten operating time and lower maintenance cost. Respiration and nitrification were mostly engaged in aerobic stage (AES), while nitrate was majorly removed by pyrite-based mixotrophic denitrification mainly occurred in anaerobic stage (ANS). Fed with synthetic and real wastewater for 120days at 1.5h HRT, SIBPD demonstrated good removal performance showing 87.14% for COD, 92.84% for NH4(+)-N and 82.58% for TP along with 80.72% of nitrate removed by ANS. TN removal efficiency was 83.74% when conducting real wastewater. Compared with sulfur-based process, the effluent pH of SIBPD was maintained at 6.99-7.34 and the highest SO4(2-) concentration was only 64.63mgL(-1). This study revealed a promising and feasible application prospect for on-site domestic wastewater treatment. PMID:25827248

  9. Disentangling the rhizosphere effect on nitrate reducers and denitrifiers: insight into the role of root exudates.

    Science.gov (United States)

    Henry, S; Texier, S; Hallet, S; Bru, D; Dambreville, C; Chèneby, D; Bizouard, F; Germon, J C; Philippot, L

    2008-11-01

    To determine to which extent root-derived carbon contributes to the effects of plants on nitrate reducers and denitrifiers, four solutions containing different proportions of sugar, organic acids and amino acids mimicking maize root exudates were added daily to soil microcosms at a concentration of 150 microg C g(-1) of soil. Water-amended soils were used as controls. After 1 month, the size and structure of the nitrate reducer and denitrifier communities were analysed using the narG and napA, and the nirK, nirS and nosZ genes as molecular markers respectively. Addition of artificial root exudates (ARE) did not strongly affect the structure or the density of nitrate reducer and denitrifier communities whereas potential nitrate reductase and denitrification activities were stimulated by the addition of root exudates. An effect of ARE composition was also observed on N(2)O production with an N(2)O:(N(2)O + N(2)) ratio of 0.3 in microcosms amended with ARE containing 80% of sugar and of 1 in microcosms amended with ARE containing 40% of sugar. Our study indicated that ARE stimulated nitrate reduction or denitrification activity with increases in the range of those observed with the whole plant. Furthermore, we demonstrated that the composition of the ARE affected the nature of the end-product of denitrification and could thus have a putative impact on greenhouse gas emissions.

  10. Simultaneous phosphorus uptake and denitrification by EBPR-r biofilm under aerobic conditions: effect of dissolved oxygen.

    Science.gov (United States)

    Wong, Pan Yu; Ginige, Maneesha P; Kaksonen, Anna H; Cord-Ruwisch, Ralf; Sutton, David C; Cheng, Ka Yu

    2015-01-01

    A biofilm process, termed enhanced biological phosphorus removal and recovery (EBPR-r), was recently developed as a post-denitrification approach to facilitate phosphorus (P) recovery from wastewater. Although simultaneous P uptake and denitrification was achieved despite substantial intrusion of dissolved oxygen (DO >6 mg/L), to what extent DO affects the process was unclear. Hence, in this study a series of batch experiments was conducted to assess the activity of the biofilm under various DO concentrations. The biofilm was first allowed to store acetate (as internal storage) under anaerobic conditions, and was then subjected to various conditions for P uptake (DO: 0-8 mg/L; nitrate: 10 mg-N/L; phosphate: 8 mg-P/L). The results suggest that even at a saturating DO concentration (8 mg/L), the biofilm could take up P and denitrify efficiently (0.70 mmol e(-)/g total solids*h). However, such aerobic denitrification activity was reduced when the biofilm structure was physically disturbed, suggesting that this phenomenon was a consequence of the presence of oxygen gradient across the biofilm. We conclude that when a biofilm system is used, EBPR-r can be effectively operated as a post-denitrification process, even when oxygen intrusion occurs. PMID:26398030

  11. Waste generation reduction: nitrates. FY 1984 status report

    International Nuclear Information System (INIS)

    A study was initiated at Rocky Flats Plant (RFP) to develop and demonstrate technology to eliminate nitrates in low-level waste streams without generating objectionable oxides of nitrogen. Various chemical and thermal methods of denitrification were investigated earlier in this program. Work in FY 1984 was conducted on the Thagard High Temperature Fluid Wall Reactor (HTFWR) and on an aqueous two-step process. Preliminary tests were conducted on a plasma torch system. Testing was completed with actual RFP nitrate wastes on an aqueous process consisting of formic and sulfuric acid reflux, followed by evaporation of the liquid to dryness. Results from this process show promising nitrate destruction, but with production of some NO/sub x/ in the off-gas. Also completed in aqueous testing were laser excitation techniques, indicating that the high activation energy of the nitrate ion can be overcome with a simpler chemical reaction with additional energy applied. Experiments were conducted using an HTFWR to determine its nitrate/nitrite destruction efficiency on simulated RFP and Savannah River Plant waste streams. These streams included nitrate-contaminated soils and feeds containing surrogate fission products. Various additives were tested to enhance nitrate destruction, reduce NO/sub x/ off-gas generation, and produce an acceptable final waste form

  12. Removal of nitrogen by heterotrophic nitrification-aerobic denitrification of a novel metal resistant bacterium Cupriavidus sp. S1.

    Science.gov (United States)

    Sun, Zhiyi; Lv, Yongkang; Liu, Yuxiang; Ren, Ruipeng

    2016-11-01

    A novel heterotrophic nitrifying and metal resistant bacterium was isolated and identified as Cupriavidus sp. S1. The utilization of ammonium, nitrate and nitrite as well as the production of N2 proved the heterotrophic nitrification and aerobic denitrification ability of S1. The ammonium, nitrate and nitrite removal efficiencies were 99.68%, 98.03% and 99.81%, with removal rates of 10.43, 8.64 and 8.36mg/L/h, respectively. A multiple regression equation well described the relationship between carbon source utilization, cell growth and nitrification. Keeping the shaking speed at 120rpm was beneficial for denitrification. Moreover, different forms of nitrogen source could be utilize in simultaneous nitrification and denitrification. Additionally, the efficient removal of ammonium occurred at 20.0mg/LZn(2+), or 10.0mg/LNi(2+) or 8.0mg/LCu(2+) or 5.0mg/LCr(6+), 33.35mmol/L sodium pyruvate, C/N 12-28. These findings demonstrate that S1 was effective for nitrogen removal in industrial wastewater containing heavy metal. PMID:27566522

  13. Excessive use of nitrogen in Chinese agriculture results in high N2O/(N2O+N2) product ratio of denitrification, primarily due to acidification of the soils

    OpenAIRE

    Qu, Zhi; Wang, Jingguo; Almøy, Trygve; Bakken, Lars R.

    2014-01-01

    China is the world's largest producer and consumer of fertilizer N, and decades of overuse has caused nitrate leaching and possibly soil acidification. We hypothesized that this would enhance the soils' propensity to emit N2O from denitrification by reducing the expression of the enzyme N2O reductase. We investigated this by standardized oxic/anoxic incubations of soils from five long-term fertilization experiments in different regions of China. After adjusting the nitrate concentration to 2 ...

  14. Nitrogen removal influence factors in A/O process and decision trees for nitrification/denitrification system

    Institute of Scientific and Technical Information of China (English)

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

    2004-01-01

    In order to improve nitrogen removal in anoxic/oxic(A/O) process effectively for treating domestic wastewaters, the influence factors, DO(dissolved oxygen), nitrate recirculation, sludge recycle, SRT(solids residence time), influent COD/TN and HRT(hydraulic retention time) were studied. Results indicated that it was possible to increase nitrogen removal by using corresponding control strategies, such as, adjusting the DO set point according to effluent ammonia concentration; manipulating nitrate recirculation flow according to nitrate concentration at the end of anoxic zone. Based on the experiments results, a knowledge-based approach for supervision of the nitrogen removal problems was considered, and decision trees for diagnosing nitrification and denitrification problems were built and successfully applied to A/O process.

  15. Oyster Reef Restoration and Aquaculture Impacts on Denitrification and the Benthic Community

    Science.gov (United States)

    Human impacts have greatly altered coastal ecosystems through a variety of processes including nutrient enrichment and overfishing. The negative consequences of these actions are well known and include increased macroalgae blooms, low oxygen conditions, and losses of biodiversity...

  16. Autotrophic denitrification performance and bacterial community at biocathodes of bioelectrochemical systems with either abiotic or biotic anodes.

    Science.gov (United States)

    Nguyen, Van Khanh; Hong, Sungsug; Park, Younghyun; Jo, Kyungmin; Lee, Taeho

    2015-02-01

    Two-chamber bioelectrochemical systems (BESs) have recently been developed for nitrate removal from nitrate-contaminated water. In this study, we compared the nitrate removal performance of biocathodes of BESs when using abiotic and biotic anodes. Acetate was used as electron donor in BESs with biotic anode, whereas a direct current power supply was used as energy source in BESs with abiotic anode. The nitrogen removal efficiency increased from 18.1% to 43.0% when the voltage supplied to the BES with abiotic anode increased from 0.7 V to 0.9 V, whereas no higher removal efficiency was obtained at a higher supplied voltage (1.1 V). The highest efficiency (78.0%) of autotrophic nitrogen removal was achieved when electron transfer from the biotic anode chamber of BESs was used. Unexpectedly, control of the cathode potential did not enhance nitrate removal in BESs with biotic anode. Special attention was paid to elucidate the differences of bacterial communities catalysing autotrophic denitrification in the biocathodes of BESs with abiotic and biotic anodes. Data from denaturing gradient gel electrophoresis and phylogenetic analysis suggested that denitrification in BESs with abiotic anode could be attributed to Nitratireductor sp., Shinella sp., and Dyella sp., whereas the dominant bacterial denitrifiers in BESs with biotic anode were found to be Pseudomonas sp., Curtobacterium sp., and Aeromonas sp. These results implied that biocathodes of BESs with biotic anode are more efficient than those of BESs with abiotic anode for nitrate removal from nitrate-contaminated water in practical applications.

  17. 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

    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......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...... and preferential nitrous oxide production are induced. Our investigation indeed revealed the guts of Chironomus plumosus, a widely distributed insect larva, as microsites of microbial denitrification by providing anoxic conditions and enrichment of organic carbon. Both the larvae and their dissected guts emitted...

  18. A multi-tracer approach to assess fingerprints of nitrate in an aquifer under agriculturally used land

    Science.gov (United States)

    Pasten-Zapata, Ernesto; Ledesma-Ruiz, Rogelio; Ramirez, Aldo; Harter, Thomas; Mahlknecht, Jürgen

    2014-05-01

    To effectively manage groundwater quality it is essential to understand sources of contamination and underground processes. The objective of the study was to identify sources and fate of nitrate pollution occurring in an aquifer underneath a sub-humid to humid region in NE Mexico which provides 10% of national citrus production. Nitrate isotopes and halide ratios were applied to understand nitrate sources and transformations in relation to land use/land cover. It was found that the study area is subject to diverse nitrate sources including organic waste and wastewater, synthetic fertilizers and soil processes. Animal manure and sewage from septic tanks were the causes of groundwater nitrate pollution within orchards and vegetable agriculture. Dairy activities within a radius of 1,000m from a sampling point increased nitrate pollution. Leachates from septic tanks incited nitrate pollution in residential areas. Soil nitrogen and animal waste were the sources of nitrate in groundwater under shrubland and grassland. Partial denitrification processes were evidenced. The denitrification process helped to attenuate nitrate concentration in the agricultural lands and grassland particularly during summer months.

  19. Optimizing nitrate removal in woodchip beds treating aquaculture effluents

    DEFF Research Database (Denmark)

    von Ahnen, Mathis; Pedersen, Per Bovbjerg; Hoffmann, Carl Christian;

    2016-01-01

    Nitrate is typically removed from aquaculture effluents using heterotrophic denitrification reactors. Heterotrophic denitrification reactors, however, require a constant input of readily available organic carbon (C) sources which limits their application in many aquaculture systems for practical...... the potential of optimizing woodchip reactors for treating aquaculture effluent. A central composite design (CCD) was applied to assess the effects of simultaneously changing the empty bed contact time (EBCTs of 5.0-15.0 h; corresponding to theoretical hydraulic retention times of 3.3-9.9 h) and bicarbonate...... (HCO3 -) inlet concentration (0.50-1.59 g HCO3 -/l) on the removal rate of NO3 -N, and additional organic and inorganic nutrients, in effluent deriving from an experimental recirculating aquaculture system (RAS).Volumetric NO3 -N removal rates ranged from 5.20 ± 0.02 to 8.96 ± 0.19 g/m3/day and were...

  20. NEPR Benthic Habitat Map 2015

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This benthic habitat map was created from a semi-automated habitat mapping process, using a combination of bathymetry, satellite imagery, aerial imagery and...

  1. Benthic fauna of mangrove environment

    Digital Repository Service at National Institute of Oceanography (India)

    Parulekar, A.H.

    The distribution, abundance and importance of benthic fauna in a mangrove environment has been discussed. This ecosystem is enriched with terrestrial, aquatic, marshy and mudflat species mangrove environment. Qualitative and quantitative...

  2. National Benthic Infaunal Database (NBID)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NBID is a quantitative database on abundances of individual benthic species by sample and study region, along with other synoptically measured environmental...

  3. Enhanced Alcaligenes faecalis Denitrification Rate with Electrodes as the Electron Donor.

    Science.gov (United States)

    Wang, Xin; Yu, Ping; Zeng, Cuiping; Ding, Hongrui; Li, Yan; Wang, Changqiu; Lu, Anhuai

    2015-08-15

    The utilization by Alcaligenes faecalis of electrodes as the electron donor for denitrification was investigated in this study. The denitrification rate of A. faecalis with a poised potential was greatly enhanced compared with that of the controls without poised potentials. For nitrate reduction, although A. faecalis could not reduce nitrate, at three poised potentials of +0.06, -0.06, and -0.15 V (versus normal hydrogen electrode [NHE]), the nitrate was partially reduced with -0.15- and -0.06-V potentials at rates of 17.3 and 28.5 mg/liter/day, respectively. The percentages of reduction for -0.15 and -0.06 V were 52.4 and 30.4%, respectively. Meanwhile, for nitrite reduction, the poised potentials greatly enhanced the nitrite reduction. The nitrite reduction rates for three poised potentials (-0.06, -0.15, and -0.30 V) were 1.98, 4.37, and 3.91 mg/liter/h, respectively. When the potentials were cut off, the nitrite reduction rate was maintained for 1.5 h (from 2.3 to 2.25 mg/liter/h) and then greatly decreased, and the reduction rate (0.38 mg/liter/h) was about 1/6 compared with the rate (2.3 mg/liter/h) when potential was on. Then the potentials resumed, but the reduction rate did not resume and was only 2 times higher than the rate when the potential was off. PMID:26048940

  4. Modeled Wet Nitrate Deposition

    Data.gov (United States)

    U.S. Environmental Protection Agency — Modeled data on nitrate wet deposition was obtained from Dr. Jeff Grimm at Penn State Univ. Nitrate wet depostion causes acidification and eutrophication of surface...

  5. Involvement in Denitrification is Beneficial to the Biofilm Lifestyle of Comamonas testosteroni: A Mechanistic Study and Its Environmental Implications.

    Science.gov (United States)

    Wu, Yichao; Shukal, Sudha; Mukherjee, Manisha; Cao, Bin

    2015-10-01

    Comamonas is one of the most abundant microorganisms in biofilm communities driving wastewater treatment. Little has been known about the role of this group of organisms and their biofilm mode of life. In this study, using Comamonas testosteroni as a model organism, we demonstrated the involvement of Comamonas biofilms in denitrification under bulk aerobic conditions and elucidated the influence of nitrate respiration on its biofilm lifestyle. Our results showed that C. testosteroni could use nitrate as the sole electron acceptor for anaerobic growth. Under bulk aerobic condition, biofilms of C. testosteroni were capable of reducing nitrate, and intriguingly, nitrate reduction significantly enhanced viability of the biofilm-cells and reduced cell detachment from the biofilms. Nitrate respiration was further shown to play an essential role in maintaining high cell viability in the biofilms. RNA-seq analysis, quantitative polymerase chain reaction, and liquid chromatography-mass spectrometry revealed a higher level of bis(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) in cells respiring on nitrate than those grown aerobically (1.3 × 10(-4) fmol/cell vs 7.9 × 10(-6) fmol/cell; P viability and a higher level of c-di-GMP to reduce cell detachment. PMID:26327221

  6. 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.

  7. Tidal pumping facilitates dissimilatory nitrate reduction in intertidal marshes

    Science.gov (United States)

    Zheng, Yanling; Hou, Lijun; Liu, Min; Liu, Zhanfei; Li, Xiaofei; Lin, Xianbiao; Yin, Guoyu; Gao, Juan; Yu, Chendi; Wang, Rong; Jiang, Xiaofen

    2016-02-01

    Intertidal marshes are alternately exposed and submerged due to periodic ebb and flood tides. The tidal cycle is important in controlling the biogeochemical processes of these ecosystems. Intertidal sediments are important hotspots of dissimilatory nitrate reduction and interacting nitrogen cycling microorganisms, but the effect of tides on dissimilatory nitrate reduction, including denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium, remains unexplored in these habitats. Here, we use isotope-tracing and molecular approaches simultaneously to show that both nitrate-reduction activities and associated functional bacterial abundances are enhanced at the sediment-tidal water interface and at the tide-induced groundwater fluctuating layer. This pattern suggests that tidal pumping may sustain dissimilatory nitrate reduction in intertidal zones. The tidal effect is supported further by nutrient profiles, fluctuations in nitrogen components over flood-ebb tidal cycles, and tidal simulation experiments. This study demonstrates the importance of tides in regulating the dynamics of dissimilatory nitrate-reducing pathways and thus provides new insights into the biogeochemical cycles of nitrogen and other elements in intertidal marshes.

  8. Nitrate accumulation in spinach

    NARCIS (Netherlands)

    Steingröver, Eveliene Geertruda

    1986-01-01

    Leafy vegetables, like spinach, may contain high concentrations of nitrate. In the Netherlands, about 75% of mean daily intake of nitrate orginates from the consumption of vegatables. Hazards to human health are associated with the reduction of nitrate to nitrite. Acute nitrite poisoning causes meth

  9. Evaluating Ecosystem Services for Reducing Groundwater Nitrate Contamination: Nitrate Attenuation in the Unsaturated and Saturated Zones

    Science.gov (United States)

    Wang, J.

    2013-12-01

    Nitrates are the most common type of groundwater contamination in agricultural regions. Environmental policies targeting nitrates have focused on input control (e.g., restricted fertilizer application), intermediate loads control (e.g., reduce nitrate leached from crop fields), and final loads control (e.g., reduce catchment nitrate loads). Nitrate loads can be affected by hydrological processes in both unsaturated and saturated zones. Although many of these processes have been extensively investigated in literature, they are commonly modeled as exogenous to farm management. A couple of recent studies by scientists from the Lawrence Livermore National Laboratory show that in some situations nitrate attenuation processes in the unsaturated/saturated zone, particularly denitrification, can be intensified by certain management practices to mitigate nitrate loads. Therefore, these nitrate attenuation processes can be regarded as a set of ecosystem services that farmers can take advantage of to reduce their cost of complying with environmental policies. In this paper, a representative California dairy farm is used as a case study to show how such ecosystem attenuation services can be framed within the farm owner's decision-making framework as an option for reducing groundwater nitrate contamination. I develop an integrated dynamic model, where the farmer maximizes discounted net farm profit over multiple periods subject to environmental regulations. The model consists of three submodels: animal-waste-crop, hydrologic, and economic model. In addition to common choice variables such as irrigation, fertilization, and waste disposal options, the farmer can also endogenously choose from three water sources: surface water, deep groundwater (old groundwater in the deep aquifer that is not affected by farm effluent in the short term), and shallow groundwater (drainage water that can be recycled via capture wells at the downstream end of the farm). The capture wells not only

  10. Interdependence of two NarK domains in a fused nitrate/nitrite transporter.

    Science.gov (United States)

    Goddard, Alan D; Moir, James W B; Richardson, David J; Ferguson, Stuart J

    2008-11-01

    Nitrate uptake is essential for various bacterial processes and combines with nitrite export to form the usual initial steps of denitrification, a process that reduces nitrate to dinitrogen gas. Although many bacterial species contain NarK-like transporters that are proposed to function as either nitrate/proton symporters or nitrate/nitrite antiporters based on sequence homology, these transporters remain, in general, poorly characterized. Several bacteria appear to contain a transporter that is a fusion of two NarK-like proteins, although the significance of this arrangement remains elusive. We demonstrate that NarK from Paracoccus denitrificans is expressed as a fusion of two NarK-like transporters. NarK1 and NarK2 are separately capable of supporting anaerobic denitrifying growth but with growth defects that are partially mitigated by coexpression of the two domains. NarK1 appears to be a nitrate/proton symporter with high affinity for nitrate and NarK2 a nitrate/nitrite antiporter with lower affinity for nitrate. Each transporter requires two conserved arginine residues for activity. A transporter consisting of inactivated NarK1 fused to active NarK2 has a dramatically increased affinity for nitrate compared with NarK2 alone, implying a functional interaction between the two domains. A potential model for nitrate and nitrite transport in P. denitrificans is proposed. PMID:18823285

  11. Physiological roles for two periplasmic nitrate reductases in Rhodobacter sphaeroides 2.4.3 (ATCC 17025).

    Science.gov (United States)

    Hartsock, Angela; Shapleigh, James P

    2011-12-01

    The metabolically versatile purple bacterium Rhodobacter sphaeroides 2.4.3 is a denitrifier whose genome contains two periplasmic nitrate reductase-encoding gene clusters. This work demonstrates nonredundant physiological roles for these two enzymes. One cluster is expressed aerobically and repressed under low oxygen while the second is maximally expressed under low oxygen. Insertional inactivation of the aerobically expressed nitrate reductase eliminated aerobic nitrate reduction, but cells of this strain could still respire nitrate anaerobically. In contrast, when the anaerobic nitrate reductase was absent, aerobic nitrate reduction was detectable, but anaerobic nitrate reduction was impaired. The aerobic nitrate reductase was expressed but not utilized in liquid culture but was utilized during growth on solid medium. Growth on a variety of carbon sources, with the exception of malate, the most oxidized substrate used, resulted in nitrite production on solid medium. This is consistent with a role for the aerobic nitrate reductase in redox homeostasis. These results show that one of the nitrate reductases is specific for respiration and denitrification while the other likely plays a role in redox homeostasis during aerobic growth. PMID:21949073

  12. Effect of C/N Ratio,Temperature,pH on Autotrophic Denitrification Rate with Hydrogen Gas,Iron (II) and Sodium Sulfide as Electron Donors

    Institute of Scientific and Technical Information of China (English)

    Junfeng Su; Sicheng Shao; Tinglin Huang; Fang Ma; Gang Wen; Shengchen Zheng; Kai Zhang

    2016-01-01

    Nitrate is considered to be one of the most widely present pollutants leading to eutrophication of environment. The purpose of this work was to isolate and identify new anaerobic denitrifying bacteria from reservoir sediments and utilize different electron donors for isolates to improve nitrate removal efficiency. Using traditional enrichment approach, one purified anaerobic bacterium ( Y12 ) capable of NO-3⁃N removal from sediments was obtained. The species identity of Y12 was determined via 16S rRNA gene sequence analysis to be Acinetobacter. In this work, the fastest denitrification rates were observed with ferrous iron as electron donor. And, slightly slower rates were observed with hydrogen and sodium sulfide as electron donors. However, when used hydrogen gas, ferrous iron and sodium sulfide as electron donors, C/N ratios had little effect on autotrophic denitrification rate at the initial C/N ratio from 1.5 to 9.0. Meanwhile, when made use of hydrogen gas, ferrous iron and sodium sulfide as electron donors, a maximum nitrate removal ratio of 100.00%, 91.43%and 87.99% at the temperature of 30℃, respectively. Moreover, maximum denitrification activity was observed at pH 6.0-7.0.

  13. A simple model for simultaneous methanogenic-denitrification systems

    DEFF Research Database (Denmark)

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

    2006-01-01

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

  14. Nitrate Removal from Drinking Water with Sodium Citrate as Sole Carbon Source

    Institute of Scientific and Technical Information of China (English)

    YAN Bo; ZHAO Lin; TAN Xin

    2005-01-01

    This paper investigates the effect of using sodium citrate(NaC6H5O6*2H2O)as sole carbon source for nitrate removal from drinking water.With sodium citrate as sole carbon source, batch experiments have been conducted to study the law of denitrification influenced by pH, C/N and temperature. Results show that a denitrification rate reaching 1.32 g NO-3-N /(g Biomass*d) was obtained when pH was at 7.5,C/N at 1.7(atom ratio), and temperature from 20 ℃ to 30 ℃. The results also show that denitrification rate with sodium citrate as carbon source approaches to that with methanol as carbon source.

  15. Simulating nitrate response functions in watersheds: Case studies in the United States and New Zealand

    Science.gov (United States)

    Gusyev, Maksym; Abrams, Daniel; Morgenstern, Uwe; Stewart, Michael

    2016-04-01

    Non-point sources of nitrate contamination are a common concern in different parts of the world and are difficult to characterize. Due to the solubility of nitrate, it easily enters groundwater and may take years or decades to completely flush to a stream. During this time, it may undergo denitrification, in particular if dissolved oxygen levels are low, requiring a representation of spatially distributed nitrate input as well as detailed hydrogeology. In this presentation, nitrate response functions are generated with four different methodologies that are listed in the order of decreasing degrees of freedom: groundwater flow and chemical transport (MODFLOW/MT3D), groundwater flow with solute particle tracing (MODFLOW/MODPATH), cross-sectional groundwater flow model (MODFLOW), and lumped parameter models (LPMs). We tested these approaches in selected watersheds in the Eastern and Midwestern United States as well as New Zealand and found similar nitrate results in all cases despite different model complexities. It is noted that only the fully three dimensional MODFLOW models with MT3D or MODPATH could account for detailed patterns of land use and nitrate applications; the cross-sectional models and lumped parameter models could only do so approximately. Denitrification at depth could also be explicitly accounted for in all four approaches, although this was not a major factor in any of the watersheds investigated.

  16. Field test of a cross-injection scheme for stimulating in situ denitrification near a municipal water supply well

    Science.gov (United States)

    Gierczak, R.; Devlin, J. F.; Rudolph, D. L.

    2007-01-01

    A pilot-scale test of an in situ denitrification scheme was undertaken to assess an adaptation of the nutrient injection wall (NIW) technology for treating a deep (30-40 m) nitrate contamination problem (N-NO 3- ˜ 10-12 mg/L). The adaptation is called the Cross-Injection Scheme (CIS). It duplicates the NIW method without a wall; wells are installed and operated directly in the aquifer and high-flux zones of the aquifer are preferentially targeted for treatment. The test was conducted on the site of a municipal water supply well field, with the supply well pumping between 15-80 m 3/h. Acetate was periodically injected into the aquifer between an injection-extraction well pair positioned across the normal direction of flow. The injected pulses were then permitted to move with the water toward the municipal wells, providing a carbon supply to drive the desired denitrification. The fate of nitrate, nitrite, acetate and sulphate were monitored at multilevel wells located between the injection location and the municipal wells. The acetate pulsing interval was approximately weekly (9 h injections), so that the system was operating passively 95% of the time. Previous work on the site has established that the highest solute fluxes were associated with a 1-3 m thick zone about 35 m below surface. This zone was found to respond to the acetate additions as a function of the municipal pumping rate and the carbon-to-nitrogen ratio (i.e., determined by the injected acetate concentration). Initially, acetate was injected just below the theoretical stoichiometric requirement for complete denitrification and nitrate disappearance was accompanied by nitrite production. Increasing the C:N ratio (doubling the acetate injection concentration) increased the removal of nitrate and diminished the occurrence of nitrite. Slowing the municipal pumping rate, with a C:N ratio of 1.2-1.6, resulted in complete nitrate attenuation with no nitrite production and no sulfate reduction. The

  17. 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.

  18. Correlation of anaerobic ammonium oxidation and denitrification

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The feasibility of the nitrous organic wastewater treated was studied in seven anaerobic sequencing batch reactors(ASBRs)(0 #-6 #) which had been run under stable anaerobic ammonium oxidation (Anammox). By means of monitoring and data analysis of COD, NH4+-N, NO2--N, NO3--N and pH, and of microbial test, the results revealed that the optimal Anammox performance was achieved from 2# reactor in which COD/NH4+-N was 1.65, Anammox bacteria and denitrification bacteria could coexist, and Anammox reaction and denitrification reaction could occur simultaneously in the reactors. The ratio of NH4+-N consumed: NO2--N consumed: NO3--N produced was 1:1.38:0.19 in 0# reactor which was not added glucose in the wastewater. When different ratio of COD and NH4+-N was fed for the reactors, the ratio of NO2--N consumed: NH4+-N consumed was in the range of 1.51-2.29 and the ratio of NO3-N produced: NH4+-N consumed in the range of 0-0.05.

  19. Single-sludge denitrification in recirculating aquaculture systems: Effects of pre-fermentation and pH

    DEFF Research Database (Denmark)

    Suhr, Karin Isabel; Letelier Gordo, Carlos Octavio; Prat Busquets, Pau

    2014-01-01

    Single-sludge denitrification (DN) reactors in aquaculture utilize the solid fish waste produced in the system to reduce the nitrate load discharged. The solid waste is available for denitrifiers when present in soluble readily biodegradable form. A transformation accomplished by bacterial...... hydrolysis (and fermentation). The objective of this study was to quantify the effect of pre-fermentation of the solid fish waste on single-sludge DN-reactor efficiency. Pre-fermentation times tested were; 0 (no pre-fermentation), 1 d, 5 d, and 10 d. The efficiency was quantified as the potential DN...

  20. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...

    Science.gov (United States)

    2010-07-01

    ... nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126..., ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. (a) When any item of ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...

  1. Denitrification-derived nitric oxide modulates biofilm formation in Azospirillum brasilense.

    Science.gov (United States)

    Arruebarrena Di Palma, Andrés; Pereyra, Cintia M; Moreno Ramirez, Lizbeth; Xiqui Vázquez, María L; Baca, Beatriz E; Pereyra, María A; Lamattina, Lorenzo; Creus, Cecilia M

    2013-01-01

    Azospirillum brasilense is a rhizobacterium that provides beneficial effects on plants when they colonize roots. The formation of complex bacterial communities known as biofilms begins with the interaction of planktonic cells with surfaces in response to appropriate signals. Nitric oxide (NO) is a signaling molecule implicated in numerous processes in bacteria, including biofilm formation or dispersion, depending on genera and lifestyle. Azospirillum brasilense Sp245 produces NO by denitrification having a role in root growth promotion. We analyzed the role of endogenously produced NO on biofilm formation in A. brasilense Sp245 and in a periplasmic nitrate reductase mutant (napA::Tn5; Faj164) affected in NO production. Cells were statically grown in media with nitrate or ammonium as nitrogen sources and examined for biofilm formation using crystal violet and by confocal laser microscopy. Both strains formed biofilms, but the mutant produced less than half compared with the wild type in nitrate medium showing impaired nitrite production in this condition. NO measurements in biofilm confirmed lower values in the mutant strain. The addition of a NO donor showed that NO influences biofilm formation in a dose-dependent manner and reverses the mutant phenotype, indicating that Nap positively regulates the formation of biofilm in A. brasilense Sp245.

  2. 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.

  3. Effect of high electron donor supply on dissimilatory nitrate reduction pathways in a bioreactor for nitrate removal

    DEFF Research Database (Denmark)

    Behrendt, Anna; Tarre, Sheldon; Beliavski, Michael;

    2014-01-01

    The possible shift of a bioreactor for NO3- removal from predominantly denitrification (DEN) to dissimilatory nitrate reduction to ammonium (DNRA) by elevated electron donor supply was investigated. By increasing the C/NO3- ratio in one of two initially identical reactors, the production of high...... sulfide concentrations was induced. The response of the dissimilatory NO3- reduction processes to the increased availability of organic carbon and sulfide was monitored in a batch incubation system. The expected shift from a DEN- towards a DNRA-dominated bioreactor was not observed, also not under...

  4. Effects of atrazine, metolachlor, carbaryl and chlorothalonil on benthic microbes and their nutrient dynamics.

    Directory of Open Access Journals (Sweden)

    Daniel Elias

    Full Text Available Atrazine, metolachlor, carbaryl, and chlorothalonil are detected in streams throughout the U.S. at concentrations that may have adverse effects on benthic microbes. Sediment samples were exposed to these pesticides to quantify responses of ammonium, nitrate, and phosphate uptake by the benthic microbial community. Control uptake rates of sediments had net remineralization of nitrate (-1.58 NO3 µg gdm⁻¹ h⁻¹, and net assimilation of phosphate (1.34 PO4 µg gdm⁻¹ h⁻¹ and ammonium (0.03 NH4 µg gdm⁻¹ h⁻¹. Metolachlor decreased ammonium and phosphate uptake. Chlorothalonil decreased nitrate remineralization and phosphate uptake. Nitrate, ammonium, and phosphate uptake rates are more pronounced in the presence of these pesticides due to microbial adaptations to toxicants. Our interpretation of pesticide availability based on their water/solid affinities supports no effects for atrazine and carbaryl, decreasing nitrate remineralization, and phosphate assimilation in response to chlorothalonil. Further, decreased ammonium and phosphate uptake in response to metolachlor is likely due to affinity. Because atrazine target autotrophs, and carbaryl synaptic activity, effects on benthic microbes were not hypothesized, consistent with results. Metolachlor and chlorothalonil (non-specific modes of action had significant effects on sediment microbial nutrient dynamics. Thus, pesticides with a higher affinity to sediments and/or broad modes of action are likely to affect sediment microbes' nutrient dynamics than pesticides dissolved in water or specific modes of action. Predicted nutrient uptake rates were calculated at mean and peak concentrations of metolachlor and chlorothalonil in freshwaters using polynomial equations generated in this experiment. We concluded that in natural ecosystems, peak chlorothalonil and metolachlor concentrations could affect phosphate and ammonium by decreasing net assimilation, and nitrate uptake rates by

  5. Denitrification of reprocessing concentrates of middle activity

    International Nuclear Information System (INIS)

    In order to reduce the releases from the Marcoule reprocessing plant, the treatment of liquid waste of low and medium level activity by chemical precipitation has been replaced by evaporation. Due to the high nitrate content of liquid waste, encapsulation in bitumen of the concentrate leads to considerable volumes of waste to be stored in geological formation. For safety reasons and so as to reduce the volume of waste, the elimination of the nitrates is essential: there exist various means: electrodialysis, biological denitration, chemical denitration and incineration. In view of the very high sodium nitrate content of the concentrate, electrodialysis and biological denitration were discarded. Preliminary experiments carried out at Cadarache led us to choose calcination in a fluidized bed rather than chemical denitration using a mixture of formic and phosphoric acids. Tests on a low temperature mock-up have determined the choice of an injection system that operates with liquid under pressure with the nozzle situated inside the fluidized layer. So as to avoid the vaporization of the liquid within, the injection piping also requires a cooling system using air, with a double casing. Under these conditions, liquid can be injected into the reactor without encountering any special difficulty: no plugging of the nozzle, a regular flow and liquid, stable temperature and pressure levels from top to bottom of the reactor. Differential thermogravimetric and heat analyses have led to the following conclusions: - at temperatures below 500 deg C, the nitric acid, then the aluminium nitrate decompose and produce alumina. -between approximately 570 deg C and 630 deg C, the sodium nitrate in turn decomposes and reacts with the alumina to produce a sodium aluminate. -finally, these tests enabled a reaction kinetics low of sodium nitrate decomposition in the temperature range of 500 deg C to 1000 deg C to be established. (author)

  6. Analysis of Microbial Communities in Biofilms from CSTR-Type Hollow Fiber Membrane Biofilm Reactors for Autotrophic Nitrification and Hydrogenotrophic Denitrification.

    Science.gov (United States)

    Shin, Jung-Hun; Kim, Byung-Chun; Choi, Okkyoung; Kim, Hyunook; Sang, Byoung-In

    2015-10-01

    Two hollow fiber membrane biofilm reactors (HF-MBfRs) were operated for autotrophic nitrification and hydrogenotrophic denitrification for over 300 days. Oxygen and hydrogen were supplied through the hollow fiber membrane for nitrification and denitrification, respectively. During the period, the nitrogen was removed with the efficiency of 82-97% for ammonium and 87-97% for nitrate and with the nitrogen removal load of 0.09-0.26 kg NH4(+)-N/m(3)/d and 0.10-0.21 kg NO3(-)-N/m(3)/d, depending on hydraulic retention time variation by the two HF-MBfRs for autotrophic nitrification and hydrogenotrophic denitrification, respectively. Biofilms were collected from diverse topological positions in the reactors, each at different nitrogen loading rates, and the microbial communities were analyzed with partial 16S rRNA gene sequences in denaturing gradient gel electrophoresis (DGGE). Detected DGGE band sequences in the reactors were correlated with nitrification or denitrification. The profile of the DGGE bands depended on the NH4(+) or NO3(-) loading rate, but it was hard to find a major strain affecting the nitrogen removal efficiency. Nitrospira-related phylum was detected in all biofilm samples from the nitrification reactors. Paracoccus sp. and Aquaspirillum sp., which are an autohydrogenotrophic bacterium and an oligotrophic denitrifier, respectively, were observed in the denitrification reactors. The distribution of microbial communities was relatively stable at different nitrogen loading rates, and DGGE analysis based on 16S rRNA (341f /534r) could successfully detect nitrate-oxidizing and hydrogen-oxidizing bacteria but not ammonium-oxidizing bacteria in the HF-MBfRs.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-09-15

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

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

    International Nuclear Information System (INIS)

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

  9. [Identification of a high ammonia nitrogen tolerant and heterotrophic nitrification-aerobic denitrification bacterial strain TN-14 and its nitrogen removal capabilities].

    Science.gov (United States)

    Xin, Xin; Yao, Li; Lu, Lei; Leng, Lu; Zhou, Ying-Qin; Guo, Jun-Yuan

    2014-10-01

    A new strain of high ammonia nitrogen tolerant and heterotrophic nitrification-aerobic denitrification bacterium TN-14 was isolated from the environment. Its physiological and biochemical characteristics and molecular identification, performences of heterotrophic nitrification-aerobic, the abilities of resistance to ammonia nitrogen as well as the decontamination abilities were studied, respectively. It was preliminary identified as Acinetobacter sp. according to its physiological and biochemical characteristics and molecular identification results. In heterotrophic nitrification system, the ammonia nitrogen and total nitrogen removal rate of the bacterial strain TN-14 could reach 97.13% and 93.53% within 24 h. In nitrates denitrification system, the nitrate concentration could decline from 94.24 mg · L(-1) to 39.32 mg · L(-1) within 24 h, where the removal rate was 58.28% and the denitrification rate was 2.28 mg · (L · h)(-1); In nitrite denitrification systems, the initial concentration of nitrite could be declined from 97.78 mg · L(-1) to 21.30 mg x L(-1), with a nitrite nitrogen removal rate of 78.22%, and a denitrification rate of 2.55 mg · (L· h)(-1). Meanwhile, strain TN-14 had the capability of flocculant production, and the flocculating rate could reach 94.74% when its fermentation liquid was used to treat 0.4% kaolin suspension. Strain TN-14 could grow at an ammonia nitrogen concentration as high as 1200 mg · L(-1). In the aspect of actual piggery wastewater treatment by strain TN-14, the removal rate of COD, ammonia nitrogen, TN and TP cloud reached 85.30%, 65.72%, 64.86% and 79.41%, respectively. Strain TN-14 has a good application prospect in biological treatment of real high- ammonia wastewater.

  10. [Identification of a high ammonia nitrogen tolerant and heterotrophic nitrification-aerobic denitrification bacterial strain TN-14 and its nitrogen removal capabilities].

    Science.gov (United States)

    Xin, Xin; Yao, Li; Lu, Lei; Leng, Lu; Zhou, Ying-Qin; Guo, Jun-Yuan

    2014-10-01

    A new strain of high ammonia nitrogen tolerant and heterotrophic nitrification-aerobic denitrification bacterium TN-14 was isolated from the environment. Its physiological and biochemical characteristics and molecular identification, performences of heterotrophic nitrification-aerobic, the abilities of resistance to ammonia nitrogen as well as the decontamination abilities were studied, respectively. It was preliminary identified as Acinetobacter sp. according to its physiological and biochemical characteristics and molecular identification results. In heterotrophic nitrification system, the ammonia nitrogen and total nitrogen removal rate of the bacterial strain TN-14 could reach 97.13% and 93.53% within 24 h. In nitrates denitrification system, the nitrate concentration could decline from 94.24 mg · L(-1) to 39.32 mg · L(-1) within 24 h, where the removal rate was 58.28% and the denitrification rate was 2.28 mg · (L · h)(-1); In nitrite denitrification systems, the initial concentration of nitrite could be declined from 97.78 mg · L(-1) to 21.30 mg x L(-1), with a nitrite nitrogen removal rate of 78.22%, and a denitrification rate of 2.55 mg · (L· h)(-1). Meanwhile, strain TN-14 had the capability of flocculant production, and the flocculating rate could reach 94.74% when its fermentation liquid was used to treat 0.4% kaolin suspension. Strain TN-14 could grow at an ammonia nitrogen concentration as high as 1200 mg · L(-1). In the aspect of actual piggery wastewater treatment by strain TN-14, the removal rate of COD, ammonia nitrogen, TN and TP cloud reached 85.30%, 65.72%, 64.86% and 79.41%, respectively. Strain TN-14 has a good application prospect in biological treatment of real high- ammonia wastewater. PMID:25693403

  11. Use of cotton gin trash to enhance denitrification in restored forested wetlands

    Science.gov (United States)

    Ullah, S.; Faulkner, S.P.

    2006-01-01

    Lower Mississippi Valley (LMV) has lost about 80% bottomland hardwood forests, mainly to agriculture. This landscape scale alteration of the LMV resulted in the loss of nitrate (NO3) removal capacity of the valley, contributing to nitrogen (N)-enhanced eutrophication and potentially hypoxia in the northern Gulf of Mexico. Restoration of hardwood forests in the LMV is a highly recommended practice to reduce NO3 load of the Mississippi River. However, restored bottomland forests take decades to develop characteristic ecological functions including denitrifier activity. One way to enhance denitrifier activity in restored wetland forests is to amend the soils with an available carbon (C) source. This research investigated the effects of cotton gin trash (CGT) amendment on denitrification rate and N2O:N2 emission ratio from a restored bottomland forest soils and compared it to those from an adjacent unamended natural forest soils. CGT amendment increased denitrification rates in the restored forest soils to the level of the natural forest soils. N2O:N2 emission ratios from the restored and natural forest soils were highly variable and were not significantly different from each other. These findings suggest that restoration of bottomland hardwood forests in the LMV will require organic carbon amendment to achieve enhanced denitrifier activity for NO3 removal while the restored forest is developing into a mature state over time. ?? 2006 Elsevier B.V. All rights reserved.

  12. Online estimation of wastewater nitrifiable nitrogen, nitrification and denitrification rates, using ORP and DO dynamics.

    Science.gov (United States)

    Spérandio, M; Queinnec, I

    2004-01-01

    Biological nitrogen removal is susceptible to disturbances in activated sludge processes. Significant improvement of performances are obtained by controlling the process taking into account wastewater modifications and sludge activity. In this work a specific sensor is developed, based on oxidation-reduction potential (ORP) and dissolved oxygen (DO) measurements performed in a completely mixed reactor which can be the activated sludge basin itself. This reactor is continuously fed by wastewater and sludge issued from the recirculation stream of the process, and submitted to alternating aeration. DO profiles and ORP bending point are linked to nitrification and denitrification in the sensor. Signal dynamics are treated with a physical model for simultaneously estimating nitrifiable nitrogen concentration in wastewater, nitrification rate, and denitrification rate. Results show very good prediction of experimental oxygen profiles and the software sensor allows us to recalculate nitrate and ammonia profiles in the reactor with a good accuracy. The estimation of nitrifiable nitrogen and removal rates has been validated experimentally. The system allows us to follow highly variable influent nitrogen concentration, toxic events, and changes in the COD concentration or quality in wastewater. PMID:14979535

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

    DEFF Research Database (Denmark)

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

    2016-01-01

    (C) and N dynamics and N2O evolution after simulated incorporation of residues from three catch crop species into a loamy sand soil, with variable soil moisture (40, 50 or 60% water-filled pore space (WFPS)). The catch crops include two leguminous (red clover and winter vetch) and one non......Catch crops, especially leguminous catch crops, may increase crop nitrogen (N) supply and decrease environmental impacts in cropping systems, but they may also stimulate nitrous oxide (N2O) emissions following spring incorporation. In this 28-day laboratory incubation study, we examined the carbon......-leguminous species (ryegrass). Plant material was placed in a discrete layer surrounded by soil in which the nitrate View the MathML source pool was enriched with 15N to distinguish N2O derived from denitrification and nitrification. Net N mineralisation from leguminous catch crops was significant (30–48 mg N kg−1...

  14. 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.

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

    DEFF Research Database (Denmark)

    Carter, Mette Sustmann

    2007-01-01

    Urine deposition by grazing livestock causes an immediate increase in nitrous oxide (N(2)O) emissions, but the responsible mechanisms are not well understood. A nitrogen-15 ((15)N) labelling study was conducted in an organic grass-clover sward to examine the initial effect of urine on the rates...... 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...

  16. 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.

  17. Benthic flux of nutrients and trace metals in the northern component of San Francisco Bay, California

    Science.gov (United States)

    Kuwabara, James S.; Topping, Brent R.; Parcheso, Francis; Engelstad, Anita C.; Greene, Valerie E.

    2009-01-01

    Two sets of sampling trips were coordinated in late summer 2008 (weeks of July 8 and August 6) to sample the interstitial and overlying bottom waters at 10 shallow locations (9 sites Brown?s Island. Except for the elevated flux at Browns Island, the benthic flux of soluble reactive phosphorus (SRP) was consistently: (1) lower than previously reported for South Bay sites, (2) an order of magnitude lower than oligotrophic Coeur d?Alene Lake, (3) two orders of magnitude lower than determined for eutrophic Upper Klamath Lake, and (4) an order of magnitude or more lower than the estimated summer riverine inputs for SRP (900 to 1,300 kilograms of phosphorous per day (kg-P d-1)). In contrast to fluxes reported for the South Bay, nitrate fluxes were consistently negative (that is, drawn from the water column into the sediment), except for one site with statistically insignificant nitrate fluxes (Site 409 within Suisun Bay). The most negative nitrate flux (-7.3?0.1 mmole m-2d-1) was observed within Grizzly Bay (Site 416). Observed nitrate fluxes bracketed the estimated summer fluvial flux of nitrate (3,500 to 5,000 kg-N d-1). With the exception of the two Grizzly Bay sites (416 and 417), the consistently positive benthic flux of ammonia generally counteracted the negative flux of nitrate to yield a net balance of dissolved inorganic nitrogen. Ammonia benthic fluxes extrapolated for Suisun Bay ranged from 320 kg-N d-1 (Site SSB009 near the entrance to Honker Bay) to 1,900 kg-N d-1 (Montezuma Island). These values represent a significant ammonia source to the water column relative to summer riverine inputs (approximately 400 to 600 kg-N d-1). Dissolved silica also displayed a consistently positive benthic flux, except for Site 409 within Suisun Bay, which showed insignificant fluxes (also insignificant for nitrate and SRP). As with the nitrate fluxes, Grizzly Bay and Browns Island sites yielded the highest dissolved silica fluxes (1.3?1.2 to 2.5?0.6 mmole m-2d-1, respectively

  18. 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.

  19. N2O isotopomers and N2:N2O ratio as indicators of denitrification in ecosystems

    International Nuclear Information System (INIS)

    The world is experiencing climate change and variability due to increased greenhouse gas (GHG) emissions. The main GHG’s of concern are nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4). Agriculture contributes approximately 14% of the world’s GHG emissions. Nitrous oxide is one of the key GHG and ozone (O3) depleting gas, constituting 7% of the anthropogenic greenhouse effect. On a molecular basis, N2O has a 310- and 16-fold greater global warming potential than each of CO2 and CH4, respectively, over a 100-year period. Nitrous oxide can be produced through both chemical and biochemical pathways. They occur during denitrification (the stepwise conversion of nitrate (NO3-) to nitrogen gas (N2) and during nitrification by ammonia-oxidizing archea (bacteria) during the oxidation of hydroxylamine (NH2OH) to nitrite (NO2-) which is then reduced to N2O and N2 by nitrifier denitrification or heterotrophic denitrification

  20. 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.

  1. Field determination of nitrate using nitrate reductase

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, E.R.; Corrigan, J.S.; Campbell, W.H. [Nitrate Elimination Co., Inc., Lake Linden, MI (United States)

    1997-12-31

    Nitrate is routinely measured in a variety of substrates - water, tissues, soils, and foods - both in the field and in laboratory settings. The most commonly used nitrate test methods involve the reduction of nitrate to nitrite via a copper-cadmium reagent, followed by reaction of the nitrite with the Griess dye reagents. The resulting color is translated into a nitrate concentration by comparison with a calibrated color chart or comparator, or by reading the absorbance in a spectrophotometer. This basic method is reliable and sufficiently sensitive for many applications. However, the cadmium reagent is quite toxic. The trend today is for continued increase in concern for worker health and safety; in addition, there are increasing costs and logistical problems associated with regulatory constraints on transport and disposal of hazardous materials. Some suppliers have substituted a zinc-based reagent powder for the cadmium in an effort to reduce toxicity. We describe here an enzyme-based nitrate detection method as an improvement on the basic Griess method that demonstrates equal or superior sensitivity, superior selectivity, and is more environmentally benign. Comparisons between the enzyme-based method and some standard field test kits being used today are made.

  2. Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers.

    Science.gov (United States)

    Decleyre, Helen; Heylen, Kim; Van Colen, Carl; Willems, Anne

    2015-01-01

    The estuarine nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate). In the past, denitrification was considered to be the main ecosystem process removing reactive nitrogen from the estuarine ecosystem. However, recent reports on the contribution of dissimilatory nitrate reduction to ammonium (DNRA) to nitrogen removal in these systems indicated a similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and the key organisms carrying out the process in marine environments are largely unknown. Hence, as a first step to better understand the interplay between denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined in sediments of the Paulina polder mudflat (Westerschelde estuary). We observed high variability in dominant nitrogen removing processes over a short distance (1.6 m), with nitrous oxide, ammonium and nitrite production rates differing significantly between all sampling sites. Denitrification occurred at all sites, DNRA was either the dominant process (two out of five sites) or absent, while nitrate reduction to nitrite was observed in most sites but never dominant. In addition, novel nitrate-to-ammonium reducers assigned to Thalassospira, Celeribacter, and Halomonas, for which DNRA was thus far unreported, were isolated, with DNRA phenotype reconfirmed through nrfA gene amplification. This study demonstrates high small scale heterogeneity among dissimilatory nitrate reduction processes in estuarine sediments and provides novel marine DNRA organisms that represent valuable alternatives to the current model organisms. PMID:26528270

  3. Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers.

    Directory of Open Access Journals (Sweden)

    Helen eDecleyre

    2015-10-01

    Full Text Available The estuarine nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate. In the past, denitrification was considered to be the main ecosystem process removing reactive nitrogen from the estuarine ecosystem. However, recent reports on the contribution of dissimilatory nitrate reduction to ammonium (DNRA to nitrogen removal in these systems indicated a similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and the key organisms carrying out the process in marine environments are largely unknown. Hence, as a first step to better understand the interplay between denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined in sediments of the Paulina polder mudflat (Westerschelde estuary. We observed high variability in dominant nitrogen removing processes over a short distance (1.6 m, with nitrous oxide, ammonium and nitrite production rates differing significantly between all sampling sites. Denitrification occurred at all sites, DNRA was either the dominant process (two out of five sites or absent, while nitrate reduction to nitrite was observed in most sites but never dominant. In addition, novel nitrate-to-ammonium reducers assigned to Thalassospira, Celeribacter and Halomonas, for which DNRA was thus far unreported, were isolated, with DNRA phenotype reconfirmed through nrfA gene amplification. This study demonstrates high small scale heterogeneity among dissimilatory nitrate reduction processes in estuarine sediments and provides novel marine DNRA organisms that represent valuable alternatives to the current model organisms.

  4. Methane oxidation coupled to nitrate reduction under hypoxia by the Gammaproteobacterium Methylomonas denitrificans, sp. nov. type strain FJG1.

    Science.gov (United States)

    Kits, K Dimitri; Klotz, Martin G; Stein, Lisa Y

    2015-09-01

    Obligate methanotrophs belonging to the Phyla Proteobacteria and Verrucomicrobia require oxygen for respiration and methane oxidation; nevertheless, aerobic methanotrophs are abundant and active in low oxygen environments. While genomes of some aerobic methanotrophs encode putative nitrogen oxide reductases, it is not understood whether these metabolic modules are used for NOx detoxification, denitrification or other purposes. Here we demonstrate using microsensor measurements that a gammaproteobacterial methanotroph Methylomonas denitrificans sp. nov. strain FJG1(T) couples methane oxidation to nitrate reduction under oxygen limitation, releasing nitrous oxide as a terminal product. Illumina RNA-Seq data revealed differential expression of genes encoding a denitrification pathway previously unknown to methanotrophs as well as the pxmABC operon in M. denitrificans sp. nov. strain FJG1(T) in response to hypoxia. Physiological and transcriptome data indicate that genetic inventory encoding the denitrification pathway is upregulated only upon availability of nitrate under oxygen limitation. In addition, quantitation of ATP levels demonstrates that the denitrification pathway employs inventory such as nitrate reductase NarGH serving M. denitrificans sp. nov. strain FJG1(T) to conserve energy during oxygen limitation. This study unravelled an unexpected metabolic flexibility of aerobic methanotrophs, thereby assigning these bacteria a new role at the metabolic intersection of the carbon and nitrogen cycles. PMID:25580993

  5. Effects of salt pond restoration on benthic flux: Sediment as a source of nutrients to the water column

    Science.gov (United States)

    Topping, Brent R.; Kuwabara, James S.; Carter, James L.; Garrettt, Krista K.; Mruz, Eric; Piotter, Sarah; Takekawa, John Y.

    2016-01-01

    Understanding nutrient flux between the benthos and the overlying water (benthic flux) is critical to restoration of water quality and biological resources because it can represent a major source of nutrients to the water column. Extensive water management commenced in the San Francisco Bay, Beginning around 1850, San Francisco Bay wetlands were converted to salt ponds and mined extensively for more than a century. Long-term (decadal) salt pond restoration efforts began in 2003. A patented device for sampling porewater at varying depths, to calculate the gradient, was employed between 2010 and 2012. Within the former ponds, the benthic flux of soluble reactive phosphorus and that of dissolved ammonia were consistently positive (i.e., moving out of the sediment into the water column). The lack of measurable nitrate or nitrite concentration gradients across the sediment-water interface suggested negligible fluxes for dissolved nitrate and nitrite. The dominance of ammonia in the porewater indicated anoxic sediment conditions, even at only 1 cm depth, which is consistent with the observed, elevated sediment oxygen demand. Nearby openestuary sediments showed much lower benthic flux values for nutrients than the salt ponds under resortation. Allochthonous solute transport provides a nutrient advective flux for comparison to benthic flux. For ammonia, averaged for all sites and dates, benthic flux was about 80,000 kg/year, well above the advective flux range of −50 to 1500 kg/year, with much of the variability depending on the tidal cycle. By contrast, the average benthic flux of soluble reactive phosphorus was about 12,000 kg/year, of significant magnitude, but less than the advective flux range of 21,500 to 30,000 kg/year. These benthic flux estimates, based on solute diffusion across the sediment-water interface, reveal a significant nutrient source to the water column of the pond which stimulates algal blooms (often autotrophic). This benthic source may be

  6. ECOMAT INC. BIOLOGICAL DENITRIFICATION PROCESS, ITER

    Science.gov (United States)

    EcoMat, Inc. of Hayward, California (EcoMat) has developed an ex situ anoxic biofilter biodenitrification (BDN) process. The process uses specific biocarriers and bacteria to treat nitrate-contaminated water and employs a patented reactor that retains biocarrier within the syste...

  7. 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.

  8. Linking hydrogeochemistry to nitrate abundance in groundwater in agricultural settings in Ireland

    Science.gov (United States)

    Jahangir, M. M. R.; Johnston, P.; Khalil, M. I.; Richards, K. G.

    2012-07-01

    SummaryNitrate (NO3--N) contamination of groundwater and associated surface waters is an increasingly important global issue with multiple impacts on terrestrial, aquatic and atmospheric environments. Investigation of the distribution of hydrogeochemical variables and their connection with the occurrence of NO3--N provides better insights into the prediction of the environmental risk associated with nitrogen use within agricultural systems. The research objective was to evaluate the effect of hydrogeological setting on agriculturally derived groundwater NO3--N occurrence. Piezometers (n = 36) were installed at three depths across four contrasting agricultural research sites. Groundwater was sampled monthly for chemistry and dissolved gases, between February 2009 and January 2011. Mean groundwater NO3--N ranged 0.7-14.6 mg L-1, with site and groundwater depth being statistically significant (p < 0.001). Unsaturated zone thickness and saturated hydraulic conductivity (Ksat) were significantly correlated with dissolved oxygen (DO) and redox potential (Eh) across sites. Groundwater NO3--N occurrence was significantly negatively related to DOC and methane and positively related with Eh and Ksat. Reduction of NO3--N started at Eh potentials <150 mV while significant nitrate reduction occurred <100 mV. Indications of heterotrophic and autotrophic denitrification were observed through elevated dissolved organic carbon (DOC) and oxidation of metal bound sulphur, as indicated by sulphate (SO42-). Land application of waste water created denitrification hot spots due to high DOC losses. Hydrogeological settings significantly influenced groundwater nitrate occurrence and suggested denitrification as the main control.

  9. The kinetic and isotopic competence of nitric oxide as an intermediate in denitrification.

    Science.gov (United States)

    Goretski, J; Hollocher, T C

    1990-01-15

    Rates of NO uptake by five denitrifying bacteria were estimated by NO-electrode and gas chromatography methods under conditions of rather low cell densities and [NOaq]. The rates so measured, VmaxNO, represent lower limits for the true value of that parameter, but nevertheless exceed Vmax for nitrite uptake, VmaxNi, by a factor of two typically. Previous estimates under suboptimal conditions had placed VmaxNO at 0.3-0.5 of VmaxNi (St. John, R. T., and Hollocher, T. C. (1977) J. Biol. Chem. 252, 212-218; Garber, E. A. E., and Hollocher, T.C. (1981) J. Biol. Chem. 256, 5459-5465). The steady-state [NOaq] during denitrification of nitrite by nitrate-grown cells was less than or equal to 1 microM. The above observations, taken with a recent direct estimate for the KmNO for NO uptake of 0.4 microM (Zafiriou, O. C., Hanley, Q. S., and Snyder, G. (1989) J. Biol. Chem. 264, 5694-5699), would allow NO to be a free intermediate between nitrite and N2O with steady-state concentrations of less than or equal to 0.4 microM. As the result of special conditions during cell growth or differential inhibition by azide, it was possible to establish systems that accumulated NO during denitrification of nitrite. In all such cases, VmaxNO less than VmaxNi, and the time required to reach the maximum [NOaq] corresponded closely to the time needed to exhaust the nitrite. A semiquantitative isotope experiment with Paracoccus denitrificans demonstrated the trapping of 15NO from 15NO2- in a pool of NOaq. A quantitative isotope method using low densities of the same bacterium showed that 15N from 15NO2- and 14N from NOg combine randomly to form N2O during the simultaneous denitrification of 15NO2- and NO. The result requires that the pathways from nitrite and NO share a common mononitrogen intermediate. Results to the contrary obtained at high cell densities (first two references cited above) are now believed to have been due to technical artifacts. The present results are consistent with the

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

    International Nuclear Information System (INIS)

    There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt.% NO3- and as large as 2000 m3/day, in the nuclear fuel cycle. The biological reduction of nitrate in wastewater to gaseous nitrogen, accompanied by the oxidation of a nutrient carbon source to gaseous carbon dioxide, is an ecologically sound and cost-effective method of treating wastewaters containing nitrates. These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 gN(NO3-)/m3 by the use of a fluidized-bed bioreactor. The denitrification bacteria are a mixed culture derived from garden soil; the major strain is Pseudomonas. In the fluidized-bed bioreactor the bacteria are allowed to attach to 0.25- to 0.50-mm-diam coal fluidization particles, which are then fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m3. This paper describes the results of a biodenitrification R and D program based on the use of fluidized bioreactors capable of operating at nitrate levels up to 7000 g/m3 and achieving denitrification rates as high as 80 g N(NO3-) per day per liter of empty bioreactor volume. 4 figures, 7 tables

  11. Nitrogen release from differently aged Raphanus sativus L. nitrate catch crops during mineralization at autumn temperatures

    DEFF Research Database (Denmark)

    Thomsen, Ingrid Kaag; Elsgaard, Lars; Olesen, Jørgen Eivind;

    2016-01-01

    radish (Raphanus sativus, L.) has emerged as a promising nitrate catch crop in cereal cropping, although the course of remineralization of residue N following termination of this frost-sensitive crucifer remains obscured. We incubated radish residues of different age (different planting and harvest dates......In temperate climates with surplus precipitation and low temperatures during autumn and winter, nitrate catch crops have become crucial in reducing nitrate leaching losses. Preferably, the N retained by the catch crop should remain in the soil and become available to the next main crop. Fodder...... pool at both temperatures. The N mineralization and nitrification potential at these low soil temperatures suggest that a considerable fraction of the N captured by nitrate catch crops may be remineralized, nitrified and thus available for plant uptake but also for loss by leaching and denitrification....

  12. Agricultural nitrate pollution

    DEFF Research Database (Denmark)

    Anker, Helle Tegner

    2015-01-01

    Despite the passing of almost 25 years since the adoption of the EU Nitrates Directive, agricultural nitrate pollution remains a major concern in most EU Member States. This is also the case in Denmark, although a fairly strict regulatory regime has resulted in almost a 50 per cent reduction...

  13. Sulfur-based mixotrophic denitrification corresponding to different electron donors and microbial profiling in anoxic fluidized-bed membrane bioreactors.

    Science.gov (United States)

    Zhang, Lili; Zhang, Chao; Hu, Chengzhi; Liu, Huijuan; Bai, Yaohui; Qu, Jiuhui

    2015-11-15

    Sulfur-based mixotrophic denitrifying anoxic fluidized bed membrane bioreactors (AnFB-MBR) were developed for the treatment of nitrate-contaminated groundwater with minimized sulfate production. The nitrate removal rates obtained in the methanol- and ethanol-fed mixotrophic denitrifying AnFB-MBRs reached 1.44-3.84 g NO3 -N/L reactor d at a hydraulic retention time of 0.5 h, which were significantly superior to those reported in packed bed reactors. Compared to methanol, ethanol was found to be a more effective external carbon source for sulfur-based mixotrophic denitrification due to lower sulfate and total organic carbon concentrations in the effluent. Using pyrosequencing, the phylotypes of primary microbial groups in the reactor, including sulfur-oxidizing autotrophic denitrifiers, methanol- or ethanol-supported heterotrophic denitrifiers, were investigated in response to changes in electron donors. Principal component and heatmap analyses indicated that selection of electron donating substrates largely determined the microbial community structure. The abundance of Thiobacillus decreased from 45.1% in the sulfur-oxidizing autotrophic denitrifying reactor to 12.0% and 14.2% in sulfur-based methanol- and ethanol-fed mixotrophic denitrifying bioreactors, respectively. Heterotrophic Methyloversatilis and Thauera bacteria became more dominant in the mixotrophic denitrifying bioreactors, which were possibly responsible for the observed methanol- and ethanol-associated denitrification.

  14. Denitrification activity in mangrove sediments varies with associated vegetation

    Digital Repository Service at National Institute of Oceanography (India)

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

    + availability in the porewater which in turn could support nitrification-denitrification. Thus, degradation of vegetation-derived organic matter was important in sustaining nutrients mainly towards the landward side proving our hypothesis that vegetation could...

  15. Nitrification and denitrification gene abundances in swine wastewater anaerobic lagoons

    Science.gov (United States)

    Although anaerobic lagoons are used globally for livestock waste treatment, their detailed microbial cycling of nitrogen is only beginning to become understood. Within this cycling, nitrification can be performed by organisms which produce the enzyme ammonia monooxygenase (AMO). For denitrification,...

  16. 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

  17. Relative Magnitude and Controls of in Situ N2 and N2O Fluxes due to Denitrification in Natural and Seminatural Terrestrial Ecosystems Using (15)N Tracers.

    Science.gov (United States)

    Sgouridis, Fotis; Ullah, Sami

    2015-12-15

    Denitrification is the most uncertain component of the nitrogen (N) cycle, hampering our ability to assess its contribution to reactive N (Nr) removal. This uncertainty emanates from the difficulty in measuring in situ soil N2 production and from the high spatiotemporal variability of the process itself. In situ denitrification was measured monthly between April 2013 and October 2014 in natural (organic and forest) and seminatural ecosystems (semi-improved and improved grasslands) in two UK catchments. Using the (15)N-gas flux method with low additions of (15)NO3(-) tracer, a minimum detectable flux rate of 4 μg N m(-2) h(-1) and 0.2 ng N m(-2) h(-1) for N2 and N2O, respectively, was achieved. Denitrification rates were lower in organic and forest (8 and 10 kg N ha(-1) y(-1), respectively) than in semi-improved and improved grassland soils (13 and 25 kg N ha(-1) y(-1), respectively). The ratio of N2O/N2 + N2O was low and ranged from soil respiration, nitrate, C:N ratio, bulk density, moisture, and pH across the sites. Overall, the contribution of denitrification to Nr removal in natural ecosystems was ~50% of the annual atmospheric Nr deposition, making these ecosystems vulnerable to chronic N saturation. PMID:26509488

  18. 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.

  19. Effects of stormwater management and stream engineering on nitrogen uptake and denitrification in streams

    Science.gov (United States)

    Newcomer, T. A.; Kaushal, S.; Mayer, P. M.; Groffman, P. M.; Grese, M. M.

    2011-12-01

    Managing the N cycle and restoring urban infrastructure represent major challenges for biogeochemistry and society. We investigated how stormwater management integrated into ecologically engineered stream networks may alter coupled N and C biogeochemical cycles. Stormwater management best management practices (BMPs) such as wetlands and ponds may serve as "hot-spots" for nitrate removal by denitrification because they have ample organic carbon, low dissolved oxygen levels, and long residence times. We hypothesized that stormwater management BMPs integrated into engineered stream networks may decrease downstream N loads while increasing C loads. We examined impacts of stormwater management BMPs on coupled N and C cycles in 2 ecologically engineered stream networks and 1 forested reference watershed at the Baltimore Long-Term Ecological Research (LTER) site. Stormwater BMPs consisted of a series of inline wetlands/ponds below a storm drain at the suburban Spring Branch stream restoration site and a series of hydrologically connected oxbow wetlands/ponds at the urban Gwynns Run site. We used a combination of: (1) stream network scale mass balances of N and C conducted monthly for 2 years across streamflow and (2) 15N in situ push-pulls to measure N removal via denitrification. At Spring Branch (the ecologically engineered stream with inline stormwater BMPs), stream network mass balances showed total dissolved nitrogen (TDN) retention of 18.4 ± 5.9% (mean ± SE, N=25) and dissolved organic carbon (DOC) retention of -21.8 ± 7.9% in stormwater BMPs. At Gwynns Run (the ecologically engineered stream with hydrologically connected oxbow stormwater BMPs), stream network scale mass balances showed TDN retention of 48.7 ± 6.6% and DOC retention of -21.8 ± 15.7%. Concentration reduction in ecologically engineered streams appeared to be inversely dependent upon streamflow, thus the stormwater management BMPs may be less effective at reducing N pollution during high flows

  20. The Effect of Riparian Zones on Nitrate Removal by Denitrification at the River Basin Scale

    NARCIS (Netherlands)

    Hoang, N.K.L.

    2013-01-01

    The riparian zone, the interface between terrestrial and aquatic ecosystems, plays an important role in nitrogen removal in spite of the minor proportion of the land area that it covers. This is verified in a large number of studies related to the effect of wetlands/riparian zones on the discharge o

  1. Forensic applications of nitrogen and oxygen isotopes in tracing nitrate sources in urban environments

    Science.gov (United States)

    Silva, S.R.; Ging, P.B.; Lee, R.W.; Ebbert, J.C.; Tesoriero, A.J.; Inkpen, E.L.

    2002-01-01

    Ground and surface waters in urban areas are susceptible to nitrate contamination from septic systems, leaking sewer lines, and fertilizer applications. Source identification is a primary step toward a successful remediation plan in affected areas. In this respect, nitrogen and oxygen isotope ratios of nitrate, in conjunction with hydrologic data and water chemistry, have proven valuable in urban studies from Austin, Texas, and Tacoma, Washington. In Austin, stream water was sampled during stremflow and baseflow conditions to assess surface and subsurface sources of nitrate, respectively. In Tacoma, well waters were sampled in adjacent sewered and un-sewered areas to determine if locally high nitrate concentrations were caused by septic systems in the un-sewered areas. In both studies, sewage was identified as a nitrate source and mixing between sewage and other sources of nitrate was apparent. In addition to source identification, combined nitrogen and oxygen isotopes were important in determining the significance of denitrification, which can complicate source assessment by reducing nitrate concentrations and increasing ??15N values. The two studies illustrate the value of nitrogen and oxygen isotopes of nitrate for forensic applications in urban areas. ?? Published by Elsevier Science Ltd. on behalf of AEHS.

  2. Building a Probabilistic Denitrification Model for an Oregon Salt Marsh

    Science.gov (United States)

    Moon, J. B.; Stecher, H. A.; DeWitt, T.; Nahlik, A.; Regutti, R.; Michael, L.; Fennessy, M. S.; Brown, L.; Mckane, R.; Naithani, K. J.

    2015-12-01

    Despite abundant work starting in the 1950s on the drivers of denitrification (DeN), mechanistic complexity and methodological challenges of direct DeN measurements have resulted in a lack of reliable rate estimates across landscapes, and a lack of operationally valid, robust models. Measuring and modeling DeN are particularly challenging in tidal systems, which play a vital role in buffering adjacent coastal waters from nitrogen inputs. These systems are hydrologically and biogeochemically complex, varying on fine temporal and spatial scales. We assessed the spatial and temporal variability of soil nitrate (NO3-) levels and O2 availability, two primary drivers of DeN, in surface soils of Winant salt marsh located in Yaquina estuary, OR during the summers of 2013 and 2014. We found low temporal variability in soil NO3- concentrations across years, tide series, and tide cycles, but high spatial variability linked to elevation gradients (i.e., habitat types); spatial variability within the high marsh habitat (0 - 68 μg N g-1 dry soil) was correlated with distance to major tide creek channels and connectivity to upslope N-fixing red alder. Soil O2 measurements collected at 5 cm below ground across three locations on two spring tide series showed that O2 drawdown rates were also spatially variable. Depending on the marsh location, O2 draw down ranged from sub-optimal for DeN (> 80 % O2 saturation) across an entire tide series (i.e., across days) to optimum (i.e., ~ 0 % O2 saturation) within one overtopping tide event (i.e., within hours). We are using these results, along with empirical relationships created between DeN and soil NO3- concentrations for Winant to improve on a pre-existing tidal DeN model. We will develop the first version of a fully probabilistic hierarchical Bayesian tidal DeN model to quantify parameter and prediction uncertainties, which are as important as determining mean predictions in order to distinguish measurable differences across the marsh.

  3. Performance and microbial communities of Mn(II)-based autotrophic denitrification in a Moving Bed Biofilm Reactor (MBBR).

    Science.gov (United States)

    Su, Jun Feng; Luo, Xian Xin; Wei, Li; Ma, Fang; Zheng, Sheng Chen; Shao, Si Cheng

    2016-07-01

    In this study, Mn(II) as electron donor was tested for the effects on denitrification in the MBBR under the conditions of initial nitrate concentration (10mgL(-1), 30mgL(-1), 50mgL(-1)), pH (5, 6, 7) and hydraulic retention time (HRT) (4h, 8h, 12h) which conducted by response surface methodology (RSM), the results demonstrated that the highest nitrate removal efficiency was occurred under the conditions of initial nitrate concentration of 47.64mgL(-1), HRT of 11.96h and pH 5.21. Analysis of SEM and flow cytometry suggested that microorganisms were immobilized on the Yu Long plastic carrier media successfully before the reactor began to operate. Furthermore, high-throughput sequencing was employed to characterize and compare the community compositions and structures of MBBR under the optimum conditions, the results showed that Pseudomonas sp. SZF15 was the dominant contributor for effective removal of nitrate in the MBBR.

  4. Physiological Roles for Two Periplasmic Nitrate Reductases in Rhodobacter sphaeroides 2.4.3 (ATCC 17025)▿

    Science.gov (United States)

    Hartsock, Angela; Shapleigh, James P.

    2011-01-01

    The metabolically versatile purple bacterium Rhodobacter sphaeroides 2.4.3 is a denitrifier whose genome contains two periplasmic nitrate reductase-encoding gene clusters. This work demonstrates nonredundant physiological roles for these two enzymes. One cluster is expressed aerobically and repressed under low oxygen while the second is maximally expressed under low oxygen. Insertional inactivation of the aerobically expressed nitrate reductase eliminated aerobic nitrate reduction, but cells of this strain could still respire nitrate anaerobically. In contrast, when the anaerobic nitrate reductase was absent, aerobic nitrate reduction was detectable, but anaerobic nitrate reduction was impaired. The aerobic nitrate reductase was expressed but not utilized in liquid culture but was utilized during growth on solid medium. Growth on a variety of carbon sources, with the exception of malate, the most oxidized substrate used, resulted in nitrite production on solid medium. This is consistent with a role for the aerobic nitrate reductase in redox homeostasis. These results show that one of the nitrate reductases is specific for respiration and denitrification while the other likely plays a role in redox homeostasis during aerobic growth. PMID:21949073

  5. Multivariate benthic ecosystem functioning in the Arctic – benthic fluxes explained by environmental parameters in the southeastern Beaufort Sea

    Directory of Open Access Journals (Sweden)

    H. Link

    2013-09-01

    Full Text Available The effects of climate change on Arctic marine ecosystems and their biogeochemical cycles are difficult to predict given the complex physical, biological and chemical interactions among the ecosystem components. We studied benthic biogeochemical fluxes in the Arctic and the influence of short-term (seasonal to annual, long-term (annual to decadal and other environmental variability on their spatial distribution to provide a baseline for estimates of the impact of future changes. In summer 2009, we measured fluxes of dissolved oxygen, nitrate, nitrite, ammonia, soluble reactive phosphate and silicic acid at the sediment–water interface at eight sites in the southeastern Beaufort Sea at water depths from 45 to 580 m. The spatial pattern of the measured benthic boundary fluxes was heterogeneous. Multivariate analysis of flux data showed that no single or reduced combination of fluxes could explain the majority of spatial variation, indicating that oxygen flux is not representative of other nutrient sink–source dynamics. We tested the influence of eight environmental parameters on single benthic fluxes. Short-term environmental parameters (sinking flux of particulate organic carbon above the bottom, sediment surface Chl a were most important for explaining oxygen, ammonium and nitrate fluxes. Long-term parameters (porosity, surface manganese and iron concentration, bottom water oxygen concentrations together with δ13Corg signature explained most of the spatial variation in phosphate, nitrate and nitrite fluxes. Variation in pigments at the sediment surface was most important to explain variation in fluxes of silicic acid. In a model including all fluxes synchronously, the overall spatial distribution could be best explained (57% by the combination of sediment Chl a, phaeopigments, δ13Corg, surficial manganese and bottom water oxygen concentration. We conclude that it is necessary to consider long-term environmental variability along with

  6. Interference of Nitrite with Pyrite under Acidic Conditions: Implications for Studies of Chemolithotrophic Denitrification.

    Science.gov (United States)

    Yan, Ruiwen; Kappler, Andreas; Peiffer, Stefan

    2015-10-01

    Chemolithotrophic denitrification coupled to pyrite oxidation is regarded a key process in the removal of nitrate in aquifers. A common product is nitrite, which is a strong oxidant under acidic conditions. Nitrite may thus interfere with Fe(II) during acidic extraction, a procedure typically used to quantify microbial pyrite oxidation, in overestimating Fe(III) production. We studied the reaction between pyrite (5-125 mM) and nitrite (40-2000 μM) at pH 0, 5.5, and 6.8 in the absence and presence of oxygen. Significant oxidation of pyrite was measured at pH 0 with a yield of 100 μM Fe(III) after 5 mM pyrite was incubated with 2000 μM nitrite for 24 h. Dissolved oxygen increased the rate at pH 0. No oxidation of pyrite was observed at pH 5.5 and 6.8. Our data imply a cyclic model for pyrite oxidation by Fe(III) on the basis of the oxidation of residual Fe(II) by NO and NO2. Interference by nitrite could be avoided if nitrite was removed from the pyrite suspensions through a washing procedure prior to acidic extraction. We conclude that such interferences should be considered in studies on microbially mediated pyrite oxidation with nitrate. PMID:26335043

  7. Protein tyrosine nitration

    Science.gov (United States)

    Chaki, Mounira; Leterrier, Marina; Barroso, Juan B

    2009-01-01

    Nitric oxide metabolism in plant cells has a relative short history. Nitration is a chemical process which consists of introducing a nitro group (-NO2) into a chemical compound. in biological systems, this process has been found in different molecules such as proteins, lipids and nucleic acids that can affect its function. This mini-review offers an overview of this process with special emphasis on protein tyrosine nitration in plants and its involvement in the process of nitrosative stress. PMID:19826215

  8. Distribution of Land Use to Purify Contaminated Groundwater by Nitrate

    Science.gov (United States)

    Iizumi, Y.; Tanaka, T.; Kinouchi, T.; Tase, N.; Fukami, K.

    2006-12-01

    Groundwater contamination by nitrate results from over-fertilizing and/or inadequate disposal of livestock excreta has been large-scale problem in agricultural area. Because nitrate is primarily transported to streams via ground water flow, explaining actual condition of groundwater is needed to propose an effective measure for the conservation and restoration of sound nitrogen cycle in agricultural river catchments. The purpose of this research was to clarify a triangular relationship between the groundwater quality and flow system, river water quality and land use. The experimental field is located on a slope from Tsukuba tableland to bottomland, which is a part of Nishi- Yata River watershed in Ibaraki Prefecture, Japan. The site area is about 0.0675 square kilometers and the altitude varies from 24 m to 19 m. Land use of tableland, bottomland and intermediate between them are forestland, paddy field and cropland, respectively. Groundwater quality and level were monitored for the year 2004. During the study period significant differences were not observed in groundwater ionic concentrations. Relative high concentrations of dissolved nitrate were detected in cropland (3 - 43 mg/l) and forestland (74 - 179 mg/l). It revealed that there was a purification zone in the paddy field and the area around its 2-4m and denitrification eliminates nitrate-nitrogen. The pressure head converted into hydraulics head, and the groundwater flow were calculated. According to the results, it seems that groundwater flow from tableland to the riverbed through bottomland. It is presumed that groundwater cultivated in cropland with chemical fertilizer pass through the purification zone of nitrate. On the other hand, it is assumed that groundwater containing nitrate originated from inadequate disposal of livestock excreta discharge from forestland does not pass through the depth of this spot. It is suggested that considering flow system of groundwater to manage distribution of land use

  9. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer

    Science.gov (United States)

    Smith, Richard L.; Kent, Douglas B.; Repert, Deborah A.; Bohlke, J.K.

    2017-01-01

    Nitrate has become an increasingly abundant potential electron acceptor for Fe(II) oxidation in groundwater, but this redox couple has not been well characterized within aquifer settings. To investigate this reaction and some of its implications for redox-sensitive groundwater contaminants, we conducted an in situ field study in a wastewater-contaminated aquifer on Cape Cod. Long-term (15 year) geochemical monitoring within the contaminant plume indicated interacting zones with variable nitrate-, Fe(II)-, phosphate-, As(V)-, and As(III)-containing groundwater. Nitrate and phosphate were derived predominantly from wastewater disposal, whereas Fe(II), As(III), and As(V) were mobilized from the aquifer sediments. Multiple natural gradient, anoxic tracer tests were conducted in which nitrate and bromide were injected into nitrate-free, Fe(II)-containing groundwater. Prior to injection, aqueous Fe(II) concentrations were approximately 175 μM, but sorbed Fe(II) accounted for greater than 90% of the total reactive Fe(II) in the aquifer. Nitrate reduction was stimulated within 1 m of transport for 100 μM and 1000 μM nitrate additions, initially producing stoichiometric quantities of nitrous oxide (>300 μM N). In subsequent injections at the same site, nitrate was reduced even more rapidly and produced less nitrous oxide, especially over longer transport distances. Fe(II) and nitrate concentrations decreased together and were accompanied by Fe(III) oxyhydroxide precipitation and decreases in dissolved phosphate, As(III), and As(V) concentrations. Nitrate N and O isotope fractionation effects during nitrate reduction were approximately equal (ε15N/ε18O = 1.11) and were similar to those reported for laboratory studies of biological nitrate reduction, including denitrification, but unlike some reported effects on nitrate by denitrification in aquifers. All constituents affected by the in situ tracer experiments returned to pre-injection levels after several

  10. Thermochemical nitrate reduction

    International Nuclear Information System (INIS)

    A series of preliminary experiments was conducted directed at thermochemically converting nitrate to nitrogen and water. Nitrates are a major constituent of the waste stored in the underground tanks on the Hanford Site, and the characteristics and effects of nitrate compounds on stabilization techniques must be considered before permanent disposal operations begin. For the thermochemical reduction experiments, six reducing agents (ammonia, formate, urea, glucose, methane, and hydrogen) were mixed separately with ∼3 wt% NO3- solutions in a buffered aqueous solution at high pH (13); ammonia and formate were also mixed at low pH (4). Reactions were conducted in an aqueous solution in a batch reactor at temperatures of 200 degrees C to 350 degrees C and pressures of 600 to 2800 psig. Both gas and liquid samples were analyzed. The specific components analyzed were nitrate, nitrite, nitrous oxide, nitrogen, and ammonia. Results of experimental runs showed the following order of nitrate reduction of the six reducing agents in basic solution: formate > glucose > urea > hydrogen > ammonia ∼ methane. Airnmonia was more effective under acidic conditions than basic conditions. Formate was also effective under acidic conditions. A more thorough, fundamental study appears warranted to provide additional data on the mechanism of nitrate reduction. Furthermore, an expanded data base and engineering feasibility study could be used to evaluate conversion conditions for promising reducing agents in more detail and identify new reducing agents with improved performance characteristics

  11. Small-scale, hydrogen-oxidizing-denitrifying bioreactor for treatment of nitrate-contaminated drinking water.

    Science.gov (United States)

    Smith, Richard L; Buckwalter, Seanne P; Repert, Deborah A; Miller, Daniel N

    2005-05-01

    Nitrate removal by hydrogen-coupled denitrification was examined using flow-through, packed-bed bioreactors to develop a small-scale, cost effective system for treating nitrate-contaminated drinking-water supplies. Nitrate removal was accomplished using a Rhodocyclus sp., strain HOD 5, isolated from a sole-source drinking-water aquifer. The autotrophic capacity of the purple non-sulfur photosynthetic bacterium made it particularly adept for this purpose. Initial tests used a commercial bioreactor filled with glass beads and countercurrent, non-sterile flow of an autotrophic, air-saturated, growth medium and hydrogen gas. Complete removal of 2 mM nitrate was achieved for more than 300 days of operation at a 2-h retention time. A low-cost hydrogen generator/bioreactor system was then constructed from readily available materials as a water treatment approach using the Rhodocyclus strain. After initial tests with the growth medium, the constructed system was tested using nitrate-amended drinking water obtained from fractured granite and sandstone aquifers, with moderate and low TDS loads, respectively. Incomplete nitrate removal was evident in both water types, with high-nitrite concentrations in the bioreactor output, due to a pH increase, which inhibited nitrite reduction. This was rectified by including carbon dioxide in the hydrogen stream. Additionally, complete nitrate removal was accomplished with wastewater-impacted surface water, with a concurrent decrease in dissolved organic carbon. The results of this study using three chemically distinct water supplies demonstrate that hydrogen-coupled denitrification can serve as the basis for small-scale remediation and that pilot-scale testing might be the next logical step.

  12. Mobilisation or dilution? Nitrate response of karst springs to high rainfall events

    Directory of Open Access Journals (Sweden)

    M. Huebsch

    2014-04-01

    Full Text Available Nitrate (NO3- contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate can discharge to surface waters unabated. However, such systems also react quickest to agricultural management changes that aim to improve water quality. In response to storm events, nitrate concentrations can alter significantly, i.e., rapidly decreasing or increasing concentrations. The current study examines the response of a specific karst spring situated on a grassland farm in south Ireland to rainfall events utilising high-resolution nitrate and discharge data together with on-farm borehole groundwater fluctuation data. Specifically, the objectives of the study are to formulate a scientific hypothesis of possible scenarios relating to nitrate responses during storm events, and to verify this hypothesis using additional case studies from the literature. This elucidates the controlling key factors that lead to mobilisation and/or dilution of nitrate concentrations during storm events. These were land use, hydrological condition and karstification, which in combination can lead to differential responses of mobilised and/or diluted nitrate concentrations. Furthermore, the results indicate that nitrate response in karst is strongly dependent on nutrient source, whether mobilisation and/or dilution occur and the pathway taken. This will have consequences for the delivery of nitrate to a surface water receptor. The current study improves our understanding of nitrate responses in karst systems and therefore can guide environmental modellers, policy makers and drinking water managers with respect to the regulations of the European Union (EU Water Framework Directive (WFD. In future, more research should focus on

  13. Direct Determination of Deep Ocean Nitrate During the Last Glacial Maximum

    Science.gov (United States)

    Spivack, A. J.; Røy, H.; Brunner, B.; Graham, D.; Gribsholt, B.; Murray, R. W.; Schrum, H. N.; D'Hondt, S. L.

    2009-12-01

    Atmospheric carbon dioxide has systematically varied with the waxing and waning of Earth’s climate for at least the last 800,000 years, with peak glacial and interglacial values of approximately 180 ppm and 280 ppm, respectively. A variety of hypotheses have been presented to explain these CO2 variations. One important class of hypotheses asserts that changes in the deep ocean nitrate content or high latitude nitrate utilization are the proximal cause of the variations. These hypotheses can be tested by determination of last glacial maximum Pacific deep water total and pre-formed nitrate concentrations. . There have previously been no direct measurements, of paleo-nitrate concentrations as there have been for atmospheric CO2 (via ice core records). Various types of sedimentary evidence and proxies exist but have not produced an unequivocal test of these hypotheses. Here we present pore fluid nitrate data that are a direct measure of both pre-formed and total nitrate concentrations in the Pacific bottom water during the last glacial maximum. The data are from two 28 meter long piston cores collected in the North Pacific gyre. The approach used is similar to that used to reconstruct paleo-salinities based on pore fluid chloride concentrations. Pore fluid chloride at these sites in the North Pacific increases with depth in the sediment, as expected for fluids derived from bottom waters during the last glacial maximum. Oxygen is present in the pore fluids throughout the sediment column, from which we infer that there is no denitrification. In the absence of denitrification, pore fluids appear to reflect concentrations during the last glacial maximum and nitrate produced during oxic respiration. Using measured oxygen concentrations; calculated pre-formed nitrate is indistinguishable from present day values of Pacific bottom waters throughout both cores implying that preformed nitrate was the same during the last glacial maximum as it is today. Additionally, if

  14. Biological reduction of nitrate wastewater using fluidized-bed bioreactors

    International Nuclear Information System (INIS)

    There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt % NO3- and as large as 2000 m3/d, in the nuclear fuel cycle as well as in many commercial processes such as fertilizer production, paper manufacturing, and metal finishing. These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 gN(NO3-)/m3 by the use of a fluidized-bed bioreactor. The major strain of denitrification bacteria is Pseudomonas which was derived from garden soil. In the fluidized-bed bioreactor the bacteria are allowed to attach to 0.25 to 0.50-mm-diam coal particles, which are fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m3. A description is given of the results of two biodenitrification R and D pilot plant programs based on the use of fluidized bioreactors capable of operating at nitrate levels up to 7000 g/m3 and achieving denitrification rates as high as 80 gN(NO3-)/d per liter of empty bioreactor volume. The first of these pilot plant programs consisted of two 0.2-m-diam bioreactors, each with a height of 6.3 m and a volume of 208 liters, operating in series. The second pilot plant was used to determine the diameter dependence of the reactors by using a 0.5-m-diam reactor with a height of 6.3 m and a volume of 1200 liters. These pilot plants operated for a period of six months and two months respectively, while using both a synthetic waste and the actual waste from a gaseous diffusion plant operated by Goodyear Atomic Corporation

  15. Sulfide oxidation and nitrate reduction for potential mitigation of H2S in landfills.

    Science.gov (United States)

    Fang, Yuan; Du, Yao; Feng, Huan; Hu, Li-Fang; Shen, Dong-Sheng; Long, Yu-Yang

    2015-04-01

    Because H2S emitted by landfill sites has seriously endangered human health, its removal is urgent. H2S removal by use of an autotrophic denitrification landfill biocover has been reported. In this process, nitrate-reducing and sulfide-oxidizing bacteria use a reduced sulfur source as electron donor when reducing nitrate to nitrogen gas and oxidizing sulfur compounds to sulfate. The research presented here was performed to investigate the possibility of endogenous mitigation of H2S by autotrophic denitrification of landfill waste. The sulfide oxidation bioprocess accompanied by nitrate reduction was observed in batch tests inoculated with mineralized refuse from a landfill site. Repeated supply of nitrate resulted in rapid oxidation of the sulfide, indicating that, to a substantial extent, the bioprocess may be driven by functional microbes. This bioprocess can be realized under conditions suitable for the autotrophic metabolic process, because the process occurred without addition of acetate. H2S emissions from landfill sites would be substantially reduced if this bioprocess was introduced.

  16. Vegetation, soil and hydrology management influence denitrification activity and the composition of nirK-type denitrifier communities in a newly afforested riparian buffer.

    Science.gov (United States)

    Boz, Bruno; Mizanur Rahman, Md; Bottegal, Mariangela; Basaglia, Marina; Squartini, Andrea; Gumiero, Bruna; Casella, Sergio

    2013-09-25

    Soil microbial community composition and activity could be affected by suitable manipulation of the environment they live in. If correctly applied such an approach could become a very effective way to remediate excess of chemicals. The concentration of nitrogen, especially nitrate deriving from agricultural managements, is generally found to increase in water flow. Therefore, by forcing the water flow through a buffer strip specifically designed and possibly afforested with suitable plant species, may result effective in reducing high nitrogen contents. The management of a riparian buffer may definitely affect the soil microbial activities, including denitrification, as well as the composition of the community. The present study reports on the changes occurred in terms of denitrifying microbial community composition, as compared to that of a neighbouring agricultural area, as a consequence of hydraulic management coupled to the suspension of farming practices and to the development of the woody and herbaceous vegetation. With this aim, denitrification was repeatedly measured and the data obtained were related to those deriving from a specific analysis of bacterial groups involved in denitrification. nirK, encoding for nitrite reductase, an enzyme essential for the conversion of nitrite to nitric oxide and considered the key step in the denitrification process, was chosen as the target gene. The main results obtained indicated that denitrification activity changes in riparian buffer as compared to agricultural soil and it is strongly influenced by carbon availability and soil depth. Although no significant differences on the community composition between superficial (0-15 cm) and medium (40-55 cm) layers were observed, the nirK-type denitrifier community was shown to significantly differ between riparian and agricultural soils in both surface and medium layers.

  17. The influence of N-fertilization regimes on N2O emissions and denitrification in rain-fed cropland during the rainy season.

    Science.gov (United States)

    Dong, Zhixin; Zhu, Bo; Zeng, Zebin

    2014-11-01

    The effects of nitrogen fertilization regimes on N2O emissions and denitrification rates were evaluated by in situ field incubation experiments with intact soil cores and the acetylene block technique. Intact soil cores were collected from long-term field experiments involving several N fertilization regimes, including single synthetic N fertilizer (N), organic manure (OM), synthetic N, P, K fertilizer (NPK), organic manure with synthetic fertilizer (OMNPK), crop straw residue with synthetic fertilizer (SRNPK) and no nitrogen fertilizer (NF). N2O was sampled from the head space of the cylinders to determine the daily N2O emission and denitrification rate. The results showed that the N2O emissions were greatly influenced by the specific fertilization regime even when the same nitrogen rate was applied. The mean N2O emissions and denitrification rates from the N, OM, NPK, OMNPK and SRNPK treatment were 2.22, 2.66, 1.94, 2.53, 1.67 and 4.63, 5.96, 4.15, 5.41, 3.65 mg per m(2) per day, respectively. The application of OM significantly increased the N2O emission and denitrification compared to the application of NPK because of the high soil organic carbon (SOC) content of OM. However, SRNPK increased the SOC content and decreased the N2O emissions significantly compared to the OM and OMNPK treatments because the addition of crop straw with a high C/N ratio to soil with a low inorganic N content induced N immobilization. The contents of soil nitrate and ammonium were the main limiting factors for N2O emissions in a positive regression as follows: Ln (N2O) = 2.511 + 1.258 × Ln ([NH4(+)] + [NO3(-)]). Crop straw residue combined with synthetic fertilizer is recommended as an optimal strategy for mitigating N2O emissions and denitrification-induced N loss in rain-fed croplands. PMID:25220444

  18. Comparison and Optimization of Cellulose Carbon Source for Denitrification Filter%固体纤维素类废物作为反硝化碳源滤料的比选

    Institute of Scientific and Technical Information of China (English)

    李斌; 郝瑞霞

    2013-01-01

    以棉花、稻草、稻壳、玉米芯这4种农业废弃物作为反硝化碳源和微生物载体,通过对静态释碳数量和质量、长期脱氮效果以及生物附着性能等方面的比较,旨在优选出适于再生水反硝化深度脱氮生物滤池的固体纤维素碳源滤料.结果表明,玉米芯初期可溶性有机物较多,易于微生物的附着和繁殖生长;且比其它3种碳源表现出更好的长期反硝化效果,2.5g玉米芯在46 d累计去除了284.544 g的硝氮;棉花、稻草前期处理效果较好,但长期反硝化能力不如玉米芯;稻壳的处理效果最差,几乎不能被微生物有效利用.因此,玉米芯更适用于再生水反硝化深度脱氮滤池的碳源滤料.%The quantity and quality of carbon released by four agriculture wastes included of cotton, rice hull, rice straw and corncob was analyzed for selecting a suitable cellulose filter medium as well as the carbon source in advanced denitrification of the reclaimed water. And the long-term denitrification efficiency and bio-attachment capability of four agriculture wastes was contrastively estimated by running denitrification experiments in laboratory scale. The results showed that DOM amount released by corncob was the highest at the beginning, and the DOM quality was also beneficial for microorganism growth and biofilm formation. The running denitrification experiments showed that corncob had better denitrification efficiency than that of other three carbon sources, and 284. 544 g nitrate was removed by 2. 5 g corncob within 46 days. Cotton and rice hull had better denitrification efficiency than corncob in the early time, but the long-term denitrification efficiency was lower than that of corncob. Rice straw can hardly be used by microorganism so as to have the lowest denitrification. Therefore, corncob was more suitable to be the denitrification biofilter filter medium and the carbon source in advanced denitrification of the reclaimed water.

  19. BIOLOGICAL NITROGEN REMOVAL FROM WASTEWATER BY DENITRIFICATION OF MIX-CULTURING FUNGI AND BACTERIA%混合培养真菌和细菌对废水的生物去氮作用

    Institute of Scientific and Technical Information of China (English)

    LIU De-Li; ZHENG Yong-Liang; LI Ping; TAKAYA Naoki; SHOUN Hirofumi

    2006-01-01

    Denitrification has been long thought to be a unique characteristic of prokaryotes, but in recent years, several filamentous fungi and yeasts were found to exhibit denitrifying activities. This paper deals with the examination of denitrification capabilities by mix-cultures of the fungus ( Fusarium oxysporum ) and the bacterium ( Pseudomonas stutzeri TR2) in combination with a specific medium and using a synthetic wastewater of defined quality. The results revealed that P. stutzeri TR2 has strong and fast denitrifying capabilities under anaerobic conditions, and that co-denitrification of mix-cultures with F. oxysporum and P. stutzeri TR2 was more effective to remove nitrate under limited oxygen conditions. P. stutzeri TR2 was able to remove nitrate completely during cultivation for 12 hr in the specific medium and in mixed culture with F. oxysporum. A rapid N2 evolution by mixed culture with F. oxysporum and P. stutzeri TR2 was observed in both mixed culture medium and synthetic wastewater. Using synthetic wastewater with a defined composition, about 87% of the nitrate was eliminated to form about 420μmol of N2 from 1.0mmol of NO3- by co-denitrification of F. oxysporum and P. stutzeri TR2 after incubation for 6days. In co-cultures of F. oxysporum and P. stutzeri TR2, N2O produced by F. oxysporum was rapidly consumed by P. stutzeri TR2. This indicated that mixed culture of F. oxysporum and P. stutzeri TR2 can be used to remove nitrate and nitrite from wastewater effectively.

  20. Effects of nitrate injection on microbial enhanced oil recovery and oilfield reservoir souring.

    Science.gov (United States)

    da Silva, Marcio Luis Busi; Soares, Hugo Moreira; Furigo, Agenor; Schmidell, Willibaldo; Corseuil, Henry Xavier

    2014-11-01

    Column experiments were utilized to investigate the effects of nitrate injection on sulfate-reducing bacteria (SRB) inhibition and microbial enhanced oil recovery (MEOR). An indigenous microbial consortium collected from the produced water of a Brazilian offshore field was used as inoculum. The presence of 150 mg/L volatile fatty acids (VFA´s) in the injection water contributed to a high biological electron acceptors demand and the establishment of anaerobic sulfate-reducing conditions. Continuous injection of nitrate (up to 25 mg/L) for 90 days did not inhibit souring. Contrariwise, in nitrogen-limiting conditions, the addition of nitrate stimulated the proliferation of δ-Proteobacteria (including SRB) and the associated sulfide concentration. Denitrification-specific nirK or nirS genes were not detected. A sharp decrease in water interfacial tension (from 20.8 to 14.5 mN/m) observed concomitantly with nitrate consumption and increased oil recovery (4.3 % v/v) demonstrated the benefits of nitrate injection on MEOR. Overall, the results support the notion that the addition of nitrate, at this particular oil reservoir, can benefit MEOR by stimulating the proliferation of fortuitous biosurfactant-producing bacteria. Higher nitrate concentrations exceeding the stoichiometric volatile fatty acid (VFA) biodegradation demands and/or the use of alternative biogenic souring control strategies may be necessary to warrant effective SRB inhibition down gradient from the injection wells. PMID:25149457

  1. Soil nitrate reducing processes – drivers, mechanisms for spatial variation and significance for nitrous oxide production

    Directory of Open Access Journals (Sweden)

    Madeline Eleanore Giles

    2012-12-01

    Full Text Available The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate (NO3-¬ and production of the potent greenhouse gas, nitrous oxide (N2O. A number of factors are known to control these processes, including O2 concentrations and moisture content, N, C, pH and the size and community structure of nitrate reducing organisms responsible for the processes. There is an increasing understanding associated with many of these controls on flux through the nitrogen cycle in soil systems. However, there remains uncertainty about how the nitrate reducing communities are linked to environmental variables and the flux of products from these processes. The high spatial variability of environmental controls and microbial communities across small sub cm areas of soil may prove to be critical in determining why an understanding of the links between biotic and abiotic controls has proved elusive. This spatial effect is often overlooked as a driver of nitrate reducing processes. An increased knowledge of the effects of spatial heterogeneity in soil on nitrate reduction processes will be fundamental in understanding the drivers, location and potential for N2O production from soils.

  2. 水和废水中硝酸盐的去除%Removal of nitrate from water and wastewater

    Institute of Scientific and Technical Information of China (English)

    王建龙

    2000-01-01

      本文简要介绍了去除水中硝酸盐的几种方法,包括化学脱氮、催化脱氮、反渗透、电渗析、离子交换、生物脱氮等。在此基础上,重点论述了离子交换技术去除水中硝酸盐的原理、方法及应用现状,并与其他方法进行了比较。%  Several denitrifying techniques, including chemical denitrification, catalytic denitrification, reverse osmosis, electrodialysis, for removal of nitrate from water and wastewater, are briefly introduced. Based on it, ion exchange process for nitrate removal is reviewed and evaluated in detail and compared with other techniques.

  3. Development and Application of Riparian Wetland Subsurface Flow and Denitrification Models

    Science.gov (United States)

    Elci, A.; Molz, F. J.

    2001-05-01

    Wetland hydrology is far more complex than conventional subsurface hydrology; therefore, numerical modeling of wetland subsurface flow and transport requires several simplifications and assumptions to make the task easier. The study presented here illustrates an attempt at numerical simulation of ground water flow in and below a riparian wetland, and incorporation of the flow field in a denitrification transport model. The main objective is to gain understanding of this very complex and heterogeneous system, and to investigate modeling approaches. The system studied is a small wetland (approximately 200 m long and 80 m wide) that is located on a golf course near Cheraw, South Carolina. The wetland receives nutrient input from the nearby fairways in the form of runoff during and after storm events, so a flow model is required to support a nitrate reactive transport model. Flooding and tracer experiments, soil borings and slug tests were performed to obtain information about the hydrogeology of the wetland. A runoff event is simulated in the field by amending the wetland with nitrate. Drive-point piezometers (31 total) were used to monitor hydraulic head and measure horizontal and vertical head gradients. The resulting field data were then used to set up a wetland subsurface flow model using the well-known MODFLOW-96 code. Flood experiments show that runoff moves through the wetland primarily in the subsurface before emerging as a surface upwelling that discharges into a lake. The wetland is highly effective in attenuating nitrate, and nitrate levels decrease rapidly in the upstream portions of the wetland. Strong upwelling at a deeper piezometer located downstream in the wetland indicates groundwater influx from a highly permeable deep sand layer. The water table is very shallow, and is above the ground surface in some portions of the wetland. The ground water flow model is transient, consists of four layers and encompasses the boundaries of the wetland. Measured

  4. Flood survey of nitrate behaviour using nitrogen isotope tracing in the critical zone of a French agricultural catchment

    Science.gov (United States)

    Paul, Alexia; Moussa, Issam; Payre, Virginie; Probst, Anne; Probst, Jean-Luc

    2015-11-01

    Measurements of δ15N-NO3- were taken in a highly flood-responsive agricultural catchment in the southwest of France to trace the sources and transfer pathways of nitrates during flood events. From January to March 2013, surface water samples were collected every week at the outlet, and four floods were sampled with a high resolution. Sampling was also performed in surface waters and sand lenses from the rest of the basin to trace nitrate sources and processes spatially. Nitrate extractions were performed using a method based on the solubility difference between inorganic salts and organic solutions. The δ15N values were in the range of surface water contaminated by N-fertilisers. Depending on the hydroclimatic event, nitrates resulted from a combination of sources and processes. At the start of the floods, the values of δ15N-NO3- and nitrate concentrations were low, demonstrating the dilution of water with rainwater. During a second phase, the nitrate concentration and the δ15N were higher. Deeper waters and soil solutions were the second source of nitrates. When the water level was low, both nitrate concentration and isotopic composition were high. These values reflected the denitrification processes that occurred in the soil under anaerobic conditions. An analysis of δ15N-NO3- in stream water in a small agricultural catchment was efficient at determining the origin of nitrates during flood events using a simple method.

  5. Impacts of Human Activities on the Occurrence of Groundwater Nitrate in an Alluvial Plain: A Multiple Isotopic Tracers Approach

    Institute of Scientific and Technical Information of China (English)

    Zhonghe Pang; Lijuan Yuan; Tianming Huang; Yanlong Kong; Jilai Liu; Yiman Li

    2013-01-01

    Nitrate pollution is a severe problem in areas with intensive agricultural activities.This study focuses on nitrate occurrence and its constraints in a selected alluvial fan using chemical data combined with environmental isotopic tracers (18O,3H,and 15N).Results show that groundwater nitrate in the study area is as high as 258.0 mg/L (hereafter NO3-) with an average of 86.8 mg/L against national drinking water limit of 45 mg/L and a regional baseline value of 14.4 mg/L.Outside of the riparian zone,nitrate occurrence is closely related to groundwater circulation and application of chemical fertilizer.High groundwater nitrate is found in the recharge area,where nitrate enters into groundwater through vertical infiltration,corresponding to high 3H and enriched 18O in the water.In the riparian zone,on the contrary,the fate of groundwater nitrate is strongly affected by groundwater level.Based on two sampling transects perpendicular to the riverbank,we found that the high level of nitrate corresponds to the deeper water table (25 m) near the urban center,where groundwater is heavily extracted.Groundwater nitrate is much lower (<12.4 mg/L) at localities with a shallow water table (5 m),which is likely caused by denitrification in the aquifer.

  6. The effect of different carbon sources on reduction of nitrate in effluent from the mining industry : Olika kolkällors inverkan på reduktion av nitrat i processvatten från gruvindustrin

    OpenAIRE

    Lindberg, Hanna

    2014-01-01

    Mine water effluent contains high levels of nitrogen due to residues from undetonated ammonium- nitrate based explosives. Excess nitrogen in aquatic ecosystems can cause eutrophication. Within a mining area, tailings and clarification ponds have the potential to reduce nitrogen levels by biological uptake of nitrogen into growing algae and denitrification in pond sediments. A previous study at the LKAB Kiruna mine investigated the potential nitrogen removal within the tailings and clarificati...

  7. 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.

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

    Directory of Open Access Journals (Sweden)

    W. Koeve

    2010-08-01

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

  9. Mechanisms of temporary adhesion in benthic animals

    NARCIS (Netherlands)

    Dodou, D.; Breedveld, P.; Winter, J.C.F.; Dankelman, J.; Leeuwen, van J.L.

    2011-01-01

    Adhesive systems are ubiquitous in benthic animals and play a key role in diverse functions such as locomotion, food capture, mating, burrow building, and defence. For benthic animals that release adhesives, surface and material properties and external morphology have received little attention compa

  10. Nitrate levels modulate the abundance of Paracoccus sp. in a biofilm community.

    Science.gov (United States)

    Singh, Shantanu; Nerurkar, Anuradha S; Srinandan, C S

    2015-06-01

    Conditions required to enhance a particular species efficient in degradative capabilities is very useful in wastewater treatment processes. Paracoccus sp. is known to efficiently reduce nitrogen oxides (NOx) due to the branched denitrification pathway. Individual-based simulations showed that the relative fitness of Paracoccus sp. to Pseudomonas sp. increased significantly with nitrate levels above 5 mM. Spatial structure of the biofilm showed substantially less nitrite levels in the areas of Paracoccus sp. dominance. The simulation was validated in a laboratory reactor harboring biofilm community by fluorescent in situ hybridization, which showed that increasing nitrate levels enhanced the abundance of Paracoccus sp. Different levels of NOx did not display any significant effect on biofilm formation of Paracoccus sp., unlike several other bacteria. This study shows that the attribute of Paracoccus sp. to tolerate and efficiently reduce NOx is conferring a fitness payoff to the organism at high concentrations of nitrate in a multispecies biofilm community. PMID:25838197

  11. Evaluation of nitrate removal effect on groundwater using artificial neural networks

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Considering the non-linear, complex and multivariable process of biological denitrification, an activated sludge process was introduced to remove nitrate in groundwater with the aid of artificial neural networks(ANN) to evaluate the nitrate removal effect. The parameters such as COD, NH3-N, NO3--N, NO2--N, MLSS,DO, etc. , were used for input nodes, and COD , NH3 -N , NO3--N , NO2--N were selected for output nodes. Experimental ANN training results show that ANN was able to predict the output water quality parameters very well. Most of relative errors of NO3--N and COD were in the range of ± 10% and ±5% respectively. The results predicted by ANN model of nitrate removal in groundwater produced good agreement with the experimental data. Though ANN model can optimize effect of the whole system, it cannot replace the water treatment process.

  12. Denitrification of fertilizer wastewater at high chloride concentration

    DEFF Research Database (Denmark)

    Ucisik, Ahmed Süheyl; Henze, Mogens

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

  13. Nitrate dynamics within a stream-lake network through time and space

    Science.gov (United States)

    Loken, L. C.; Crawford, J. T.; Childress, E. S.; Casson, N. J.; Stanley, E. H.

    2014-12-01

    Nitrate dynamics in streams are governed by biology, hydrology, and geomorphology, and the ability to parse these drivers apart has improved with the development of accurate high-frequency sensors. By combining a stationary Eulerian and a quasi-Lagrangian sensor platform, we investigated the timing of nitrate flushing and identified locations of elevated biogeochemical cycling along a stream-lake network in Northern Wisconsin, USA. Two years of continuous oxygen, carbon dioxide, and discharge measurements were used to compute gross primary production (GPP) and ecosystem respiration (ER) downstream of a wetland reach of Allequash Creek. Metabolic rates and flow patterns were compared with nitrate concentrations measured every 30 minutes using an optical sensor. Additionally, we floated a sensor array from the headwater spring ponds through a heterogeneous stream reach consisting of wetlands, beaver ponds, forested segments, and two lakes. Two distinct temporal patterns of stream nitrate concentrations were observed. During high flow events such as spring snowmelt and summer rain events, nitrate concentrations increased from ~5 μM (baseflow) to 12 μM, suggesting flushing from catchment sources. During baseflow conditions, nitrate followed a diel cycle with a 0.3-1.0 μM daytime draw down. Daily nitrate reduction was positively correlated with GPP calculated from oxygen and carbon dioxide records. Lastly, spatial analyses revealed lowest nitrate concentrations in the wetland reach, approximately 2-3 μM lower than the upstream spring ponds, and downstream lakes and forested reaches. This snapshot implies greater nitrate removal potential in the wetland reach likely driven by denitrification in organic rich sediments and macrophyte uptake in the open canopy stream segment. Taken together the temporal and spatial results show the dynamics of hydrology, geomorphology, and biology to influence nitrate delivery and variability in ecosystem processing through a stream

  14. ArcNLET: A GIS-based software to simulate groundwater nitrate load from septic systems to surface water bodies

    Science.gov (United States)

    Rios, J. Fernando; Ye, Ming; Wang, Liying; Lee, Paul Z.; Davis, Hal; Hicks, Rick

    2013-03-01

    Onsite wastewater treatment systems (OWTS), or septic systems, can be a significant source of nitrates in groundwater and surface water. The adverse effects that nitrates have on human and environmental health have given rise to the need to estimate the actual or potential level of nitrate contamination. With the goal of reducing data collection and preparation costs, and decreasing the time required to produce an estimate compared to complex nitrate modeling tools, we developed the ArcGIS-based Nitrate Load Estimation Toolkit (ArcNLET) software. Leveraging the power of geographic information systems (GIS), ArcNLET is an easy-to-use software capable of simulating nitrate transport in groundwater and estimating long-term nitrate loads from groundwater to surface water bodies. Data requirements are reduced by using simplified models of groundwater flow and nitrate transport which consider nitrate attenuation mechanisms (subsurface dispersion and denitrification) as well as spatial variability in the hydraulic parameters and septic tank distribution. ArcNLET provides a spatial distribution of nitrate plumes from multiple septic systems and a load estimate to water bodies. ArcNLET's conceptual model is divided into three sub-models: a groundwater flow model, a nitrate transport and fate model, and a load estimation model which are implemented as an extension to ArcGIS. The groundwater flow model uses a map of topography in order to generate a steady-state approximation of the water table. In a validation study, this approximation was found to correlate well with a water table produced by a calibrated numerical model although it was found that the degree to which the water table resembles the topography can vary greatly across the modeling domain. The transport model uses a semi-analytical solution to estimate the distribution of nitrate within groundwater, which is then used to estimate a nitrate load using a mass balance argument. The estimates given by ArcNLET are

  15. In situ measurement of nitrate in deep-sea sediments with a microscale biosensor

    DEFF Research Database (Denmark)

    Marzocchi, Ugo; Revsbech, Niels Peter; Glud, Ronnie

    about 8°C. Large resources are being spent on exploration of the deep sea using sensor-equipped benthic landers, and it would be of significant value to add nitrate to the array of chemical sensors for in situ use, but it is then necessary to construct more robust sensors that work at temperatures...... conditions. It is difficult to work strictly aseptically when producing the sensors, and there is thus a risk that the bacterial culture may be contaminated with N2O reducing bacteria that will make the sensor insensitive to nitrate. However, when used continuously at room temperature they usually work well......When a bacteria-based nitrate biosensor with tip diameter down to 20 µm was invented about 12 years ago it became possible to measure detailed nitrate profiles in marine sediments, but functional tip membranes in the sensors were difficult to make, and the sensors did not work at temperatures below...

  16. Statistical evaluation of effects of riparian buffers on nitrate and ground water quality

    Science.gov (United States)

    Spruill, T.B.

    2000-01-01

    A study was conducted to statistically evaluate the effectiveness of riparian buffers for decreasing nitrate concentrations in ground water and for affecting other chemical constituents. Values for pH, specific conductance, alkalinity, dissolved organic carbon (DOC), silica, ammonium, phosphorus, iron, and manganese at 28 sites in the Contentnea Creek Basin were significantly higher (p 20 yr) discharging ground water draining areas with riparian buffers compared with areas without riparian buffers. No differences in chloride, nitrate nitrogen, calcium, sodium, and dssolved oxygen concentrations in old ground water between buffer and nonbuffer areas were detected. Comparison of samples of young (20 yr) discharging ground water draining areas with riparian buffers compared with areas without riparian buffers. No differences in chloride, nitrate nitrogen, calcium, sodium, and dissolved oxygen concentrations in old ground water between buffer and nonbuffer areas were detected. Comparison of samples of young (conservative chemical constituents in young ground water that originate from fertilizer applications and also allow denitrification in ground water by providing an adequate source of organic carbon generated by vegetation in the buffer zone. Based on the median chloride and nitrate values for young ground water in the Contentnea Creek Basin, nitrate was 95% lower in buffer areas compared with nonbuffer areas, with a 30 to 35% reduction estimated to be due to dilution and 65 to 70% due to reduction and/or denitrification.Using data derived from a study area located in the Contentnea Creek Drainage Basin in North Carolina, the presence of riparian buffers 30-m wide or more and composed of lowland hardwood vegetation was assessed statistically in terms of nitrate-nitrogen concentrations in discharging groundwater passing beneath the buffers. The groundwater and surface-water sampling sites were selected by overlaying a digital coverage of a ma

  17. Nitrous Oxide Metabolism in Nitrate-Reducing Bacteria: Physiology and Regulatory Mechanisms.

    Science.gov (United States)

    Torres, M J; Simon, J; Rowley, G; Bedmar, E J; Richardson, D J; Gates, A J; Delgado, M J

    2016-01-01

    Nitrous oxide (N2O) is an important greenhouse gas (GHG) with substantial global warming potential and also contributes to ozone depletion through photochemical nitric oxide (NO) production in the stratosphere. The negative effects of N2O on climate and stratospheric ozone make N2O mitigation an international challenge. More than 60% of global N2O emissions are emitted from agricultural soils mainly due to the application of synthetic nitrogen-containing fertilizers. Thus, mitigation strategies must be developed which increase (or at least do not negatively impact) on agricultural efficiency whilst decrease the levels of N2O released. This aim is particularly important in the context of the ever expanding population and subsequent increased burden on the food chain. More than two-thirds of N2O emissions from soils can be attributed to bacterial and fungal denitrification and nitrification processes. In ammonia-oxidizing bacteria, N2O is formed through the oxidation of hydroxylamine to nitrite. In denitrifiers, nitrate is reduced to N2 via nitrite, NO and N2O production. In addition to denitrification, respiratory nitrate ammonification (also termed dissimilatory nitrate reduction to ammonium) is another important nitrate-reducing mechanism in soil, responsible for the loss of nitrate and production of N2O from reduction of NO that is formed as a by-product of the reduction process. This review will synthesize our current understanding of the environmental, regulatory and biochemical control of N2O emissions by nitrate-reducing bacteria and point to new solutions for agricultural GHG mitigation. PMID:27134026

  18. Synthesis of nanoiron by microemulsion with Span/Tween as mixed surfactants for reduction of nitrate in water

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yunxia; LI Tielong; JIN Zhaohui; WANG Wei; WANG Shuaima

    2007-01-01

    Denitrification of nitrate in groundwater using iron nanoparticles has received increasing interest in recent years.In order to fabricate iron nanoparticles with homogeneously spherical shape and narrow size distribution,a simple and"green"method was developed to synthesize iron nanoparticles.The conventional microemulsion methods were modified by applying Span 80 and Tween 60 as mixed surfactants.The maximum content of water in the Water-in-oil(W/O) microemulsion and its appropriate forming conditions were found,and then the microemulsion system consisting of saturated Fe2+ solution was used to synthesize α-Fe ultrafine particles by redox reaction.The nanoparticles were characterized by using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM).The results show that the average diameter of the particle is about 80-90 nm.The chemical activity of the obtained iron nanoparticles was studied by the denitrification experiment of nitrate.The results show that under the experimental conditions,iron removed most of the 80 mg/L nitrate within 30 min.The mass balance of nitrate reduction with nanoscale Fe indicates that endproducts are mainly ammonia.Two possible reaction pathways for nitrate reduction by nanoscale iron particles have been proposed in this work.

  19. Mg-Cu-Al layered double hydroxides based catalysts for the reduction of nitrates in aqueous solutions

    Directory of Open Access Journals (Sweden)

    Vulić Tatjana J.

    2010-01-01

    Full Text Available The secondary waste and bacterial contamination in physico-chemical and biological separation processes used today for nitrate removal from ground water make novel catalytic technologies that convert nitrates to unharmful gaseous nitrogen, very attractive for scientific research. The Mg-Cu-Al layered double hydroxide (LDH based catalysts with different Mg/Al ratio were investigated in water denitrification reaction in the presence of hydrogen and with solely copper as an active phase. Since LDHs have ion exchange properties and their derived mixed oxides possess memory effect (restoration of layered structure after thermal decomposition, their adsorption capacity for nitrates was also measured in the same model system. All studied samples showed nitrate removal from 23% to 62% following the decrease in Al content, as well as the substantial adsorption capacity ranging from 18% to 38%. These results underlie the necessity to take into account the effects of the adsorption in all future investigations.

  20. Application of Water Quality and Ecology Indices of Benthic Macroinvertebrate to Evaluate Water Quality of Tertiary Irrigation in Malang District

    OpenAIRE

    Desi Kartikasari; Catur Retnaningdyah; Endang Arisoesilaningsih

    2013-01-01

    This research aims to determine the water quality of tertiary irrigation in several subdistricts in Malang, namely Kepanjen, Karangploso, and Tumpang. The water quality depends on the water quality indices (National Sanitation Foundation’s-NSF Indices and O’Connor’s Indices based on variables TSS, TDS, pH, DO, and Nitrate concentrate) and ecological indices of benthic macroinvertebrate (Diversity Indices Shannon-Wiener, Hilsenhof Biotic Indices-HBI, Average Score per Taxon-ASPT which is calcu...

  1. Benthic flux of nutrients and trace metals in the northern component of San Francisco Bay, California

    Science.gov (United States)

    Kuwabara, James S.; Topping, Brent R.; Parcheso, Francis; Engelstad, Anita C.; Greene, Valerie E.

    2009-01-01

    Two sets of sampling trips were coordinated in late summer 2008 (weeks of July 8 and August 6) to sample the interstitial and overlying bottom waters at 10 shallow locations (9 sites Tiburon Center for Environmental Studies, provides information to assist in developing and refining management strategies for the Bay/Delta system and supports efforts to monitor changes in food-web structure associated with regional habitat modifications directed by the California Bay-Delta Authority. On July 7, 2008, and August 5, 2008, pore-water profilers were successfully deployed at six North Bay sites per trip to measure the concentration gradient of dissolved macronutrients and trace metals near the sediment-water interface. Only two of the sites (433 and SSB009 within Honker Bay) were sampled in both series of profiler deployments. At each sampling site, profilers were deployed in triplicate, while discrete samples and dataloggers were used to collect ancillary data from both the water column and benthos to help interpret diffusive-flux measurements. Benthic flux of dissolved (0.2-micron filtered) inorganic phosphate (that is, soluble reactive phosphorus (SRP)) ranged from negligible levels (-0.003?0.005 millimole per square meter per day (mmole m-2d-1) at Site 4.1 outside Honker Bay) to 0.060?0.006 mmole m-2d-1 near the northern coast of Brown?s Island. Except for the elevated flux at Browns Island, the benthic flux of soluble reactive phosphorus (SRP) was consistently: (1) lower than previously reported for South Bay sites, (2) an order of magnitude lower than oligotrophic Coeur d?Alene Lake, (3) two orders of magnitude lower than determined for eutrophic Upper Klamath Lake, and (4) an order of magnitude or more lower than the estimated summer riverine inputs for SRP (900 to 1,300 kilograms of phosphorous per day (kg-P d-1)). In contrast to fluxes reported for the South Bay, nitrate fluxes were consistently negative (that is, drawn from the water column into the sediment

  2. Formation of anoxia and denitrification in the bottom waters of a tropical estuary, southwest coast of India

    Directory of Open Access Journals (Sweden)

    G. D. Martin

    2010-03-01

    Full Text Available Hydrographic characteristics of the southwest coast of India and its adjoining Cochin backwaters (CBW were studied during the summer monsoon period. Anomalous formation of anoxia and denitrification were observed in the bottom layers of CBW, which have not been previously reported elsewhere in any tropical estuarine systems. The prevalent upwelling in the Arabian Sea (AS brought cool, high saline, oxygen deficient and nutrient-rich waters towards the coastal zone and bottom layers of CBW during the high tide. High freshwater discharge in the surface layers brought high amount of nutrients and makes the CBW system highly productive. Intrusion of AS waters seems to be stronger towards the upstream end (~15 km, than had been previously reported, as a consequence of the lowering of river discharges and deepening of channels in the estuary. Time series measurements in the lower reaches of CBW indicated a low mixing zone with increased stratification, 3 h after the high tide (highest high tide and high variation in vertical mixing during the spring and neap phases. The upwelled waters (O2≤40 μM intruded into the estuary was found to lose more oxygen during the neap phase (suboxic O2≤4 μM than spring phase (hypoxic O2≤10 μM. Increased stratification coupled with low ventilation and presence of high organic matter have resulted in an anoxic condition (O2=0, 2–6 km away from barmouth of the estuary and leads to the formation of hydrogen sulphide. The reduction of nitrate and formation of nitrite within the oxygen deficient waters indicated strong denitrification intensity in the estuary. The expansion of oxygen deficient zone, denitrification and formation of hydrogen sulphide may lead to a destruction of biodiversity and an increase of green house gas emissions from this region.

  3. 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

  4. Sediment nitrification and denitrification rates in a Lake Superior estuary

    Science.gov (United States)

    Microbially-mediated nitrogen (N) cycling in aquatic sediments has been recognized as an ecosystem service due to mitigation of N-transport to receiving waters. In 2011 and 2012, we compared nitrification (NIT), unamended (DeNIT) and amended (DEA) denitrification rates among spat...

  5. 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...

  6. 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

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

    Science.gov (United States)

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

  8. Formation of large NAT particles and denitrification in polar stratosphere: possible role of cosmic rays and effect of solar activity

    Directory of Open Access Journals (Sweden)

    F. Yu

    2004-02-01

    Full Text Available The formation of large nitric acid trihydrate (NAT particles has important implications for denitrification and ozone depletion. Existing theories can't explain the recent observations of large NAT particles over wide Arctic regions at temperature above ice frost point. Our analyses reveal that high-energy comic rays may induce the freezing of supercooled HNO3−H2O–H2SO4 droplets when they penetrate these thermodynamically unstable droplets. The cosmic ray-induced freezing (CRIF is consistent with the observed highly selective formation of NAT particles. We suggest that the physics behind the CRIF mechanism is the reorientation of polar solution molecules into the crystalline configuration in the strong electrical fields of moving secondary ions generated by passing cosmic rays. Our simulations indicate that strong solar proton events (SPEs may significantly enhance the formation of large NAT particles and denitrification. The CRIF mechanism can explain the high correlations between the thin nitrate-rich layers in polar ice cores and major SPEs. The observed enhancement in aerosol backscattering ratio at PSC layers shortly after an SPE and the significant precipitation velocity of the enhanced PSC payers also provide strong support for the CRIF mechanism.

  9. Tracing nitrate pollution sources and transformation in surface- and ground-waters using environmental isotopes

    International Nuclear Information System (INIS)

    Water pollution in the form of nitrate nitrogen (NO3−–N) contamination is a major concern in most agricultural areas in the world. Concentrations and nitrogen and oxygen isotopic compositions of nitrate, as well as oxygen and deuterium isotopic compositions of surface and groundwater from a typical irrigated region in the North China Plain (NCP) collected from May to October in 2012 were analyzed to examine the major nitrate sources and transformations. Concentrations of NO3−–N ranged from 0.2 to 29.6 mg/L (mean of 11.2 mg/L) in surface water, and from 0.1 to 19.4 mg/L (mean of 2.8 mg/L) in groundwater. Approximately 46.7% of the surface water samples and 10% of the groundwater samples exceeded the World Health Organization (WHO) drinking water standard for NO3−–N. Surface water samples that exceeded the standard were collected mainly in the dry season (May and October), while groundwater samples that exceeded the standard were collected in the wet season (June). Overall, the highest nitrate levels were observed in surface water in May and in groundwater in June, indicating that fertilizer application, precipitation, and irrigation strongly influence the NO3−–N concentrations. Analyses of isotopic compositions suggest that the main sources of nitrate are nitrification of fertilizer and sewage in surface water, in contrast, mineralization of soil organic N and sewage is the groundwater sources during the dry season. When fertilizers are applied, nitrate will be transported by precipitation through the soil layers to the groundwater in the wet season (June). Denitrification only occurred in surface water in the wet season. Attempts should be made to minimize overuse of nitrogen fertilizers and to improve nitrogen use efficiency in irrigated agricultural regions. - Highlights: • Nitrate sources in surface and groundwater were identified by multiple isotopes. • Nitrate pollution displayed obvious seasonal variations. • Nitrate of surface water in

  10. Tracing nitrate pollution sources and transformation in surface- and ground-waters using environmental isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yan [Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Fadong, E-mail: lifadong@igsnrr.ac.cn [Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101 (China); Zhang, Qiuying [Center for Agricultural Resources Research, Chinese Academy of Sciences, Shijiazhuang 050021 (China); Li, Jing [Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101 (China); Liu, Qiang [Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2014-08-15

    Water pollution in the form of nitrate nitrogen (NO{sub 3}{sup −}–N) contamination is a major concern in most agricultural areas in the world. Concentrations and nitrogen and oxygen isotopic compositions of nitrate, as well as oxygen and deuterium isotopic compositions of surface and groundwater from a typical irrigated region in the North China Plain (NCP) collected from May to October in 2012 were analyzed to examine the major nitrate sources and transformations. Concentrations of NO{sub 3}{sup −}–N ranged from 0.2 to 29.6 mg/L (mean of 11.2 mg/L) in surface water, and from 0.1 to 19.4 mg/L (mean of 2.8 mg/L) in groundwater. Approximately 46.7% of the surface water samples and 10% of the groundwater samples exceeded the World Health Organization (WHO) drinking water standard for NO{sub 3}{sup −}–N. Surface water samples that exceeded the standard were collected mainly in the dry season (May and October), while groundwater samples that exceeded the standard were collected in the wet season (June). Overall, the highest nitrate levels were observed in surface water in May and in groundwater in June, indicating that fertilizer application, precipitation, and irrigation strongly influence the NO{sub 3}{sup −}–N concentrations. Analyses of isotopic compositions suggest that the main sources of nitrate are nitrification of fertilizer and sewage in surface water, in contrast, mineralization of soil organic N and sewage is the groundwater sources during the dry season. When fertilizers are applied, nitrate will be transported by precipitation through the soil layers to the groundwater in the wet season (June). Denitrification only occurred in surface water in the wet season. Attempts should be made to minimize overuse of nitrogen fertilizers and to improve nitrogen use efficiency in irrigated agricultural regions. - Highlights: • Nitrate sources in surface and groundwater were identified by multiple isotopes. • Nitrate pollution displayed obvious

  11. The role of the benthic-hyporheic zone in controlling nitrous oxide emissions along two stream networks draining watersheds with contrasting land use

    Science.gov (United States)

    Marzadri, Alessandra; Dee, Martha M.; Tonina, Daniele; Tank, Jennifer L.; Bellin, Alberto

    2016-04-01

    Nitrous oxide (N2O) is a potent greenhouse gas responsible of stratospheric ozone destruction. Denitrification in stream ecosystems occurs within the benthic layer at the sediment-water interface and within subsurface environments such as the hyporheic zone and results in N2O production that could be eventually emitted to the atmosphere. Here, we quantify the role of benthic and hyporheic zones as sources of N2O gas and explore the dependence of emissions from stream morphology, flow hydraulics, land use and climate using a recently-developed fully analytical framework. Variations in N2O emissions within and among catchments of contrasting land use can be explained with a new denitrification Damköhler number (DaD) that accounts for denitrification processes within both benthic and hyporheic zones. For initial model development, we found a strong relationship between DaD and stream N2O emissions using field data collected from multiple headwater streams (i.e., LINXII project) from different biomes draining contrasting land use. We then tested its generality by comparing N2O emissions predicted with DaD to those measured using a synoptic sampling campaign in two stream networks draining contrasting land use: Manistee R (Michigan, USA) and Tippecanoe R (Indiana, USA). Our dimensionless analysis shows that the effect of land use disappears after making the emissions dimensionless with respect to the nitrogen load. Reliable predictions of N2O emissions at the stream network scale can be obtained from a limited amount of information, consisting in relatively easy to obtain biogeochemical and hydromorphological quantities.

  12. Nitrates and nitrites intoxications’ management

    OpenAIRE

    Alexandra Trif

    2007-01-01

    The study pointed out the major sources for clinical and subclinical intoxications with nitrates/nitrites (drinking water and nitrates containing fertilizers), circumstances that determine fertilizers to became sources of intoxication (excessive fertilization/consecutive high level of nitrates in fodders, free access of animals to the fertilizers, administration into the diet instead of natrium chloride), factors that determine high nitrates accumulation in fodders despite optimal fertilizati...

  13. Nitrification-denitrification Loss and N2O Emission from Urea Applied to Crop-soil Systems in North China Plain

    Institute of Scientific and Technical Information of China (English)

    DING Hong; CAI Gui-xin; WANG Yue-si; CHEN De-li

    2002-01-01

    Nitrogen losses are not only important for agriculture but environment as well. Field experiments were set up in summer corn field at Fengqiu Agro-Ecological Experimental Station of CAS in North China Plain. The soil was in maize-chao soil. Nitrification-denitrification losses and N2O emission were determined by acetylene-inhibition soil-core incubation method in the soils applied urea. The results showed that urea was fast hydrolyzed and became to nitrate. The soil with non urea released 0.33kg N/ha N2O.However, the soil produced 2.91kg N/ha N2O, about 1.94% of the applied N, when the urea was spread on soil surface. N2O emission reduced to 2.50kg N/ha, about 1.67% of the applied N, when the urea was put in deep soil by digging a hole. The denitrification loss was 1.17kg N/ha in control soil. It increased to 3.00kg N/ha and 2.09kg N/ha, which were 2.00% and 1.39% of the used N, in the soils received urea on surface and sub-surface respectively. It was suggested that nitrification-denitrification was probably not a main way of fertilizer nitrogen loss in this region.

  14. Treatment of dissolved perchlorate, nitrate, and sulfate using zero-valent iron and organic carbon.

    Science.gov (United States)

    Liu, YingYing; Ptacek, Carol J; Blowes, David W

    2014-05-01

    Waters containing ClO and dissolved NO, derived from detonated explosives and solid propellants, often also contain elevated concentrations of other dissolved constituents, including SO. Four column experiments, containing mixtures of silica sand, zero-valent Fe (ZVI) and organic C (OC) were conducted to evaluate the potential for simultaneous removal of NO, SO and ClO. Initially, the flow rate was maintained at 0.5 pore volumes (PV) d and then decreased to 0.1 PV d after 100 PV of flow. Nitrate concentrations decreased from 10.8 mg L (NO-N) to trace levels through NO reduction to NH using ZVI alone and through denitrification using OC. Observations from the mixture of ZVI and OC suggest a combination of NO reduction and denitrification. Up to 71% of input SO (24.5 ± 3.5 mg L) was removed in the column containing OC, and >99.7% of the input ClO (857 ± 63 μg L) was removed by the OC- and (ZVI + OC)-containing columns as the flow rate was maintained at 0.1 PV d. Nitrate and ClO removal followed first-order and zero-order rates, respectively. Nitrate >2 mg L (NO-N) inhibited ClO removal in the OC-containing column but not in the (ZVI + OC)-containing column. Sulfate did not inhibit ClO degradation within any of the columns.

  15. Quantifying nitrate dynamics in an oligotrophic lake using Δ17O

    Directory of Open Access Journals (Sweden)

    A. Tanaka

    2011-03-01

    Full Text Available The stable isotopic compositions of nitrate, including the 17O anomalies (Δ17O, were determined twice in 1 yr (June and August 2007 in the oligotrophic water column of Lake Mashu, Japan. These data were then used to quantify the geochemical dynamics of nitrate in the lake, by using the deposition rate of the atmospheric nitrate onto the entire catchment area of the lake. The total amount of nitrate in the lake water decreased from 4.2 to 2.1 Mmol during the period between the observations, while the average Δ17O values remained uniform at +2.5‰. The Δ17O values corresponded to an small and uniform mixing ratio of atmospheric nitrate to total nitrate of 9.7 ± 0.8%. These results indicate that 0.52 ± 0.34 Mmol of the remineralized nitrate was fed into the water column through nitrification, while 2.6 ± 0.4 Mmol of nitrate was simultaneously removed from the water column by assimilation, during the period between the observations. The lake water dissolved nitrate was characterized by rapid removal through assimilation during summer until it was almost completely removed from the euphotic layer, as well as continuous feeding into the lake through nitrification (3.2 ± 0.3 Mmol a−1 and deposition (0.35 ± 0.2 Mmol a−1, regardless of the seasons. The 15N-depleted nitrogen isotopic compositions of nitrate were as low as −6.5‰ in June, which also indicates that in-lake nitrification is the major source of nitrate in the lake and suggests that there is low potential for denitrification in and around the lake. Atmospheric nitrate deposited into the lake will be assimilated quickly, having a mean residence time of 1.2 ± 0.1 yr. In addition, more than 90% of the assimilated nitrate will be remineralized to nitrate and re-assimilated via active nitrogen cycling in the lake.

  16. Nitrogen cycling in the deep sedimentary biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

    Science.gov (United States)

    Wankel, S. D.; Buchwald, C.; Ziebis, W.; Wenk, C. B.; Lehmann, M. F.

    2015-12-01

    Nitrogen (N) is a key component of fundamental biomolecules. Hence, its cycling and availability are central factors governing the extent of ecosystems across the Earth. In the organic-lean sediment porewaters underlying the oligotrophic ocean, where low levels of microbial activity persist despite limited organic matter delivery from overlying water, the extent and modes of nitrogen transformations have not been widely investigated. Here we use the N and oxygen (O) isotopic composition of porewater nitrate (NO3-) from a site in the oligotrophic North Atlantic (Integrated Ocean Drilling Program - IODP) to determine the extent and magnitude of microbial nitrate production (via nitrification) and consumption (via denitrification). We find that NO3- accumulates far above bottom seawater concentrations (~ 21 μM) throughout the sediment column (up to ~ 50 μM) down to the oceanic basement as deep as 90 m b.s.f. (below sea floor), reflecting the predominance of aerobic nitrification/remineralization within the deep marine sediments. Large changes in the δ15N and δ18O of nitrate, however, reveal variable influence of nitrate respiration across the three sites. We use an inverse porewater diffusion-reaction model, constrained by the N and O isotope systematics of nitrification and denitrification and the porewater NO3- isotopic composition, to estimate rates of nitrification and denitrification throughout the sediment column. Results indicate variability of reaction rates across and within the three boreholes that are generally consistent with the differential distribution of dissolved oxygen at this site, though not necessarily with the canonical view of how redox thresholds separate nitrate regeneration from dissimilative consumption spatially. That is, we provide stable isotopic evidence for expanded zones of co-occurring nitrification and denitrification. The isotope biogeochemical modeling also yielded estimates for the δ15N and δ18O of newly produced nitrate (

  17. Effects of integrated stormwater management and stream engineering on nitrogen uptake and denitrification in streams

    Science.gov (United States)

    Newcomer, T. A.; Kaushal, S.; Mayer, P. M.; Groffman, P. M.; Grese, M.

    2012-12-01

    Restoring urban infrastructure and managing the N cycle represent major challenges for biogeochemistry and society. We investigated how stormwater best management practices (BMPs) integrated into urban stream networks can influence removal of N pollution. We hypothesized that stormwater BMPs are greater "hot spots" for N removal through denitrification than connected floodplain areas because they have ample organic carbon, low dissolved oxygen levels, and high residence time. We tested this hypothesis by examining N cycling in 2 urban stream networks with stormwater BMPs and a forested reference watershed with a pond at the Baltimore Long-Term Ecological Research (LTER) site. At all 3 sites, we used a combination of: (1) 250 stream reach scale mass balances of N conducted monthly for 2 years across streamflow (2) 6 in-stream tracer injection studies to measure seasonal nitrate uptake and groundwater inputs, and (3) 72 15N in situ push-pull tracer experiments to measure seasonal N removal via denitrification in stormwater BMPs and floodplain features. The stormwater BMPs at Spring Branch were inline wetlands installed below a storm drain outfall and at Gwynns Run were a wetland and wet pond configured in an oxbow to receive water during high flow events. As hypothesized, total dissolved nitrogen (TDN) concentrations decreased consistently across sampling dates as water traveled through stormwater BMPs; TDN concentrations decreased from 3.13 ± 0.67 mg/L to 1.87 ± 0.23 mg/L (mean ± SE) at Spring Branch and from 3.15 ± 0.15 mg/L to 1.47 ± 0.22 mg/L at Gwynns Run. Contrary to our hypothesis, mean TDN retention at Spring Branch was higher in a stream reach with connected floodplains, 2.01 ± 0.77 kg/day (mean ± SE), than in the stormwater BMPs, 0.053 ± 0.025 kg/day. Similarly, at Gwynns Run, mean TDN retention (and export) were 3 orders of magnitude higher in the stream reaches, 2.00 ± 1.6 kg/day (mean ± SE), than in the stormwater BMPs, 0.005 ± 0.597 kg

  18. Nitrate in drinking water

    DEFF Research Database (Denmark)

    Schullehner, Jörg; Hansen, Birgitte; Sigsgaard, Torben

    Annual nationwide exposure maps for nitrate in drinking water in Denmark from the 1970s until today will be presented based on the findings in Schullehner & Hansen (2014) and additional work on addressing the issue of private well users and estimating missing data. Drinking water supply in Denmark...... is highly decentralized and fully relying on simple treated groundwater. At the same time, Denmark has an intensive agriculture, making groundwater resources prone to nitrate pollution. Drinking water quality data covering the entire country for over 35 years are registered in the public database Jupiter....... In order to create annual maps of drinking water quality, these data had to be linked to 2,852 water supply areas, which were for the first time digitized, collected in one dataset and connected to the Jupiter database. Analyses of the drinking water quality maps showed that public water supplies...

  19. Activation of accumulated nitrite reduction by immobilized Pseudomonas stutzeri T13 during aerobic denitrification.

    Science.gov (United States)

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

    2015-01-01

    The excellent removal efficiency of nitrate by the aerobic denitrifier, Pseudomonas stutzeri T13, was achieved in free cells system. However, poor nitrite reduction prevents efficient aerobic denitrification because of the nitrite accumulation. This problem could be conquered by immobilizing the cells on supports. In this study, strain T13 was immobilized by mycelial pellets (MPs), polyurethane foam cubes (PFCs) and sodium alginate beads (SABs). Higher removal percentages of TN in MP (43.78%), PFC (42.31%) and SAB (57.25%) systems were achieved compared with the free cell system (29.7%). Furthermore, the optimal condition for immobilized cell systems was as follows: 30°C, 100rpm shaking speed and pH 7. The shock-resistance of SAB system was relatively poor, which could collapse under either alkaline (pH=9) or high rotating (200rpm) conditions. The recycling experiments demonstrated that the high steady TN removal rate could be maintained for seven cycles in both MP and PFC systems. PMID:25827250

  20. Feasibility of remote sensing benthic microalgae

    Science.gov (United States)

    Zingmark, R. G.

    1979-01-01

    Results of data analyses from multispectral scanning data are presented. The data was collected in July 1977 for concentration of chlorophyll in benthic microalgae (mainly diatoms) on an estuary mudflat.

  1. BENTHIC MACROFAUNAL ALIENS IN WILLAPA BAY

    Science.gov (United States)

    Benthic macrofaunal samples were collected at random stations in Willapa Bay, WA, in four habitats [eelgrass (Zostera marina), Atlantic cordgrass (Spartina alterniflora), mud shrimp (Upogebia pugettensis), ghost shrimp (Neotrypaea californiensis)] in 1996 and in seven habitats (Z...

  2. Benthic Habitats of the Florida Keys

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The benthic habitats of the Florida Keys were mapped from a series of 450 aerial photographs. Ecologists outlined the boundaries of specific habitat types by...

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

    Directory of Open Access Journals (Sweden)

    Simone ePeter

    2015-11-01

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

  4. Nitrates and nitrites intoxications’ management

    Directory of Open Access Journals (Sweden)

    Alexandra Trif

    2007-12-01

    Full Text Available The study pointed out the major sources for clinical and subclinical intoxications with nitrates/nitrites (drinking water and nitrates containing fertilizers, circumstances that determine fertilizers to became sources of intoxication (excessive fertilization/consecutive high level of nitrates in fodders, free access of animals to the fertilizers, administration into the diet instead of natrium chloride, factors that determine high nitrates accumulation in fodders despite optimal fertilization (factors related to the plants, soil, clime, harvest methods, storage, agrotechnical measures, nitrates/nitrites toxicity (over 45 ppm nitrates in drinking water, over 0.5 g nitrate/100 g D.M fodder/diet, the factors that influence nitrates/nitrites toxicity ( species, age, rate of feeding, diet balance especially energetically, pathological effects and symptoms (irritation and congestions on digestive tract, resulting diarrhoea, transformation of hemoglobin into methemoglobin determining severe respiratory insufficiency, vascular collapse, low blood pressure inthe acute nitrates intoxication; hypotiroidism, hypovitaminosis A, reproductive disturbances(abortion, low rate of fertility, dead born offspring, diarrhoea and/or respiratory insufficiency in new born e.g. calves, immunosuppression, decrease of milk production in chronic intoxication. There were presented some suggestions concerning management practices to limit nitrate intoxication (analyze of nitrates/nitrites in water and fodders, good management of the situation of risk ,e .g. dilution of the diet with low nitrate content fodders, feeding with balanced diet in energy, protein, minerals and vitamins, accommodation to high nitrate level diet, avoid grazing one week after a frost period, avoid feeding chop green fodders stored a couple of days, monitoring of health status of animals fed with fodders containing nitrates at risk level, a.o..

  5. Denitrification with epsilon-caprolactam by acclimated mixed culture and by pure culture of bacteria isolated from polyacrylonitrile fibre manufactured wastewater treatment system.

    Science.gov (United States)

    Lee, C M; Wang, C C

    2004-01-01

    The aim of this study is to isolate denitrifying bacteria utilizing epsilon-caprolactam as the substrate, from a polyacrylonitrile fibre manufactured wastewater treatment system. The aim is also to compare the performance of PAN (polyacrylonitrile) mixed bacteria cultures acclimated to epsilon-caprolactam and isolated pure strain for treating different initial epsilon-caprolactam concentrations from synthetic wastewater under anoxic conditions. The result showed that the PAN mixed bacteria cultures acclimated to epsilon-caprolactam could utilize 1538.5 mg/l of epsilon-caprolactam as a substrate for denitrification. Sufficient time and about 2200 mg/l of nitrate were necessary for the complete epsilon-caprolactam removal. Paracoccus thiophilus was isolated from the polyacrylonitrile fibre manufactured wastewater treatment system and it could utilize 1722.5 mg/l of epsilon-caprolactam as a substrate for denitrification. About 3500 mg/l of nitrate was necessary for the complete removal of epsilon-caprolactam. When the initial epsilon-caprolactam concentration was below 784.3 mg/l, the removal efficiency of epsilon-caprolactam by Paracoccus thiophilus was better than that for the PAN mixed bacteria cultures. The growth of Paracoccus thiophilus was better. However, when the initial epsilon-caprolactam concentration was as high as 1445.8 mg/l, both the epsilon-caprolactam removal efficiency by Paracoccus thiophilus and Paracoccus thiophilus specific growth rate were similar to the PAN mixed bacteria cultures. PMID:15137443

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

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

    2016-04-01

    Three bacterial strains (TE1, TD3 and FB2) were isolated from date palm (degla), pistachio and barley. The presence of nitrate reductase (narG) and nitrite reductase (nirS and nirK) genes in the selected strains was detected by PCR technique. Molecular identification based on 16S rDNA sequencing method was applied to identify positive strains. In addition, the D-optimal mixture experimental design was used to optimize the optimal formulation of probiotic bacteria for denitrification process. Strains harboring denitrification genes were identified as: TE1, Agrococcus sp LN828197; TD3, Cronobacter sakazakii LN828198 and FB2, Pedicoccus pentosaceus LN828199. PCR results revealed that all strains carried the nirS gene. However only C. sakazakii LN828198 and Agrococcus sp LN828197 harbored the nirK and the narG genes respectively. Moreover, the studied bacteria were able to form biofilm on abiotic surfaces with different degree. Process optimization showed that the most significant reduction of nitrate was 100% with 14.98% of COD consumption and 5.57 mg/l nitrite accumulation. Meanwhile, the response values were optimized and showed that the most optimal combination was 78.79% of C. sakazakii LN828198 (curve value), 21.21% of P. pentosaceus LN828199 (curve value) and absence (0%) of Agrococcus sp LN828197 (curve value). PMID:26893037

  8. Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer

    Science.gov (United States)

    Hatzinger, P.B.; Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Heraty, L.J.; Borden, R.C.

    2009-01-01

    Environmental context. Perchlorate (ClO4-) and nitrate (NO3-) are common co-contaminants in groundwater, with both natural and anthropogenic sources. Each of these compounds is biodegradable, so in situ enhanced bioremediation is one alternative for treating them in groundwater. Because bacteria typically fractionate isotopes during biodegradation, stable isotope analysis is increasingly used to distinguish this process from transport or mixing-related decreases in contaminant concentrations. However, for this technique to be useful in the field to monitor bioremediation progress, isotope fractionation must be quantified under relevant environmental conditions. In the present study, we quantify the apparent in situ fractionation effects for stable isotopes in ClO4- (Cl and O) and NO3- (N and O) resulting from biodegradation in an aquifer. Abstract. An in situ experiment was performed in a shallow alluvial aquifer in Maryland to quantify the fractionation of stable isotopes in perchlorate (Cl and O) and nitrate (N and O) during biodegradation. An emulsified soybean oil substrate that was previously injected into this aquifer provided the electron donor necessary for biological perchlorate reduction and denitrification. During the field experiment, groundwater extracted from an upgradient well was pumped into an injection well located within the in situ oil barrier, and then groundwater samples were withdrawn for the next 30 h. After correction for dilution (using Br- as a conservative tracer of the injectate), perchlorate concentrations decreased by 78% and nitrate concentrations decreased by 82% during the initial 8.6 h after the injection. The observed ratio of fractionation effects of O and Cl isotopes in perchlorate (18O/37Cl) was 2.6, which is similar to that observed in the laboratory using pure cultures (2.5). Denitrification by indigenous bacteria fractionated O and N isotopes in nitrate at a ratio of ???0.8 (18O/15N), which is within the range of values

  9. 地下水生物反硝化碳源材料研究%Study on carbon source for biological denitrification in groundwater

    Institute of Scientific and Technical Information of China (English)

    金虎; 刘虹

    2011-01-01

    采用室内土壤柱实验装置,研究了以生物分解性塑料为反硝化碳源去除水中的硝酸盐.结果表明,以PHB为反硝化碳源,能有效去除水中的硝酸盐,最高去除率达到100%.实验结束后,PHB的重量从实验开始的40 g经73 d降到18.6 g,原有光滑的PHB表面变成粗糙,说明PHB作为碳源被反硝化菌所利用.随着时间的推移,出水的TOC浓度与进水的TOC浓度相当接近,出水的TOC浓度基本稳定在5 mg/L以内,说明PHB的碳释放量具有可控性,不易造成二次污染.%The removal of nitrate in groundwater using biodegradable plastic as carbon resource in denitrification was studied by indoor soil column.The result showed the nitrate in groundwater was removed effectively using PHB as carbon resource in denitrification and the maximal removal rate reached 100%.The weight of PHB was decreased from original 40g to 18.6g after 73 days when the experiment was finished and the smooth surface of PHB became rough,which proved that the PHB was used as carbon resource by denitrification bacteria.With the passage to time,the TOC in the effluent was closed to that in the influent and it was less than 5 mg/L,which showed that the carbon released by PHB could be controlled and it would not lead to secondary pollution

  10. Denitrification in a hypersaline lake–aquifer system (Pétrola Basin, Central Spain): The role of recent organic matter and Cretaceous organic rich sediments

    International Nuclear Information System (INIS)

    Agricultural regions in semi-arid to arid climates with associated saline wetlands are one of the most vulnerable environments to nitrate pollution. The Pétrola Basin was declared vulnerable to NO3− pollution by the Regional Government in 1998, and the hypersaline lake was classified as a heavily modified body of water. The study assessed groundwater NO3− through the use of multi-isotopic tracers (δ15N, δ34S, δ13C, δ18O) coupled to hydrochemistry in the aquifer connected to the eutrophic lake. Hydrogeologically, the basin shows two main flow components: regional groundwater flow from recharge areas (Zone 1) to the lake (Zone 2), and a density-driven flow from surface water to the underlying aquifer (Zone 3). In Zones 1 and 2, δ15NNO3 and δ18ONO3 suggest that NO3− from slightly volatilized ammonium synthetic fertilizers is only partially denitrified. The natural attenuation of NO3− can occur by heterotrophic reactions. However, autotrophic reactions cannot be ruled out. In Zone 3, the freshwater–saltwater interface (down to 12–16 m below the ground surface) is a reactive zone for NO3− attenuation. Tritium data suggest that the absence of NO3− in the deepest zones of the aquifer under the lake can be attributed to a regional groundwater flow with long residence time. In hypersaline lakes the geometry of the density-driven flow can play an important role in the transport of chemical species that can be related to denitrification processes. - Highlights: • Denitrification comes about in a hypersaline lake–aquifer system. • Nitrate in the basin is derived from synthetic fertilizers slightly volatilized. • Organic carbon oxidation is likely to be the main electron donor in denitrification. • Density driven flow transports organic carbon to deeper zones of the aquifer

  11. Research progress in the influencing factors of autohydrogenotrophic biological denitrification for drinking water%饮用水氢自养生物脱氮影响因素研究进展

    Institute of Scientific and Technical Information of China (English)

    张彦浩; 马征; 张志斌; 孙翠珍

    2014-01-01

    饮用水的氢自养反硝化技术具有脱氮效率高、运行简单、清洁无二次污染的优点。综述了氢自养反硝化技术应用于饮用水处理的最新研究进展,探讨了硝酸盐浓度、氢气浓度或压力、pH、硬度、碱度、碳源以对氢自养反硝化的影响,并对技术的发展进行了总结及展望。%Autohydrogenotrophic denitrification applied to drinking water has advantages of high denitrification effi-ciency,simple operation and no secondary pollution. The newest research progress in autohydrogenotrophic denitrifi-cation technologies used to the treatment of drinking water is reviewed. The effects of nitrate nitrogen concentration , H2 concentration or pressure,pH,hardness,alkalinity,and carbon resource on autohydrogenotrophis denitrification are discussed. In addition,the development of autohydrogenotrophic dentitrification technologies for drinking water is summarized and predicted.

  12. Accumulation of soil carbon drives denitrification potential and lab-incubated gas production along a chronosequence of salt marsh development

    Science.gov (United States)

    He, Yanlong; Widney, Sarah; Ruan, Michelle; Herbert, Ellen; Li, Xiuzhen; Craft, Christopher

    2016-04-01

    We measured sediment organic carbon and nitrogen accumulation and rates of denitrification enzyme activity and greenhouse gas (CO2, CH4, N2O) production from slurries of sediments of a mudflat that formed in 2002, a young (8-year-old) natural Spartina alterniflora salt marsh that developed on part of the mudflat, and four mature (>200 years old) salt marshes in southeastern Georgia to examine microbial processes related to carbon (C) and nitrogen (N) cycling during succession from mudflat to mature marsh. Soil organic C and N and C: N ratio (0-30 cm) increased across the chronosequence from mudflat (791 ± 35 g C/m2, 125 ± 17 g N/m2) to young marsh (2520 ± 131 g C/m2, 190 ± 10 g N/m2) to mature marshes (5827 ± 250 g C/m2, 372 ± 20 g N/m2). After 8 years of colonization by S. alterniflora, sediment organic carbon increased 3.2 times, and nitrogen increased 1.5 times relative to the mudflat. The high rate of organic C and N accumulation based on time series measurements (188 g C/m2/yr, 7.8 g N/m2/yr) and feldspar marker layers (359 g C/m2/yr, 26.2 g N/m2/yr) was attributed to high accretion (3 cm/yr) in this low elevation (0.18 m NAVD88) emerging marsh. Carbon dioxide production increased with increasing sediment organic C from mudflat to mature marshes. Un-amended denitrification enzyme activity, measured in slurry incubations, ranged from an average of 0.020 ± 0.005 μg g-1 hr-1 in the mature marshes to 0.094 ± 0.03 μg g-1 hr-1 in the young marsh. We also measured denitrification potential in slurry incubations amended with C (glucose), N (nitrate), and C + N to assess the potential for substrate limitations. Denitrification potential in the mudflat did not show strong nutrient limitation. In the young marsh, denitrification potential was C-limited, and in the mature marsh, it was co-limited by C and N. In July samples, CO2 production showed a statistically significant increase with age from the mudflat to the mature marshes. However, in both months, CO2

  13. 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.

  14. 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....

  15. Application of Water Quality and Ecology Indices of Benthic Macroinvertebrate to Evaluate Water Quality of Tertiary Irrigation in Malang District

    Directory of Open Access Journals (Sweden)

    Desi Kartikasari

    2013-12-01

    Full Text Available This research aims to determine the water quality of tertiary irrigation in several subdistricts in Malang, namely Kepanjen, Karangploso, and Tumpang. The water quality depends on the water quality indices (National Sanitation Foundation’s-NSF Indices and O’Connor’s Indices based on variables TSS, TDS, pH, DO, and Nitrate concentrate and ecological indices of benthic macroinvertebrate (Diversity Indices Shannon-Wiener, Hilsenhof Biotic Indices-HBI, Average Score per Taxon-ASPT which is calculated by Biological Monitoring Working Party-BMWP, Ephemeroptera Indices, Plecoptera, Trichoptera-EPT. Observation of the physico-chemical water quality and benthic macroinvertebrate on May 2012 to April 2013. The sampling in each subdistrict was done at two selected stations in tertiary irrigation channel with three plot at each station. The data of physico-chemical quality of water were used to calculate the water quality indices, while the benthic macroinvertebrate data were used to calculate the ecological indices. The research findings showed that 27 taxa of benthic macroinvertebrates belong 10 classes were found in the three subdistrict. The pH, DO, Nitrate, TSS and TDS in six tertiary irrigation channels in Malang still met the water quality standards based on Government Regulation No. 82 of 2001 on Management of Water Quality and Water Pollution Control Class III. Based on NSF-WQI indices and O'Connor's Indices, water qualities in these irrigation channels were categorized into medium or moderate (yellow to good (green category. However, based on benthic macroinvertebrate communities which was used to determine the HBI, the water quality in the irrigation channels were categorized into the fair category (fairly significant organic pollution to fairly poor (significant organic pollution, while based on the value of ASPT, the water were categorized into probable moderate pollution to probable severe pollution. The irrigation water which was

  16. Tracing atmospheric nitrate in groundwater using triple oxygen isotopes: evaluation based on bottled drinking water

    Directory of Open Access Journals (Sweden)

    F. Nakagawa

    2013-06-01

    Full Text Available The stable isotopic compositions of nitrate dissolved in 49 brands of bottled drinking water collected worldwide were measured, to trace the fate of atmospheric nitrate (NO3− atm that had been deposited into subaerial ecosystems, using the 17O anomalies (Δ17O of nitrate as tracers. The use of bottled water enables collection of groundwater recharged at natural, background watersheds. The nitrate in groundwater had small Δ17O values ranging from −0.2‰ to +4.5‰ n = 49. The average Δ17O value and average mixing ratio of atmospheric nitrate to total nitrate in the groundwater samples were estimated to be 0.8‰ and 3.1%, respectively. These findings indicated that the majority of atmospheric nitrate had undergone biological processing before being exported from the surface ecosystem to the groundwater. Moreover, the concentrations of atmospheric nitrate were estimated to range from less than 0.1 μmol L−1 to 8.5 μmol L−1 with higher NO3−atm concentrations being obtained for those recharged in rocky, arid or elevated areas with little vegetation and lower NO3−atm concentrations being obtained for those recharged in forested areas with high levels of vegetation. Additionally, many of the NO3−atm-depleted samples were characterized by elevated δ15N values of more than +10‰. Uptake by plants and/or microbes in forested soils subsequent to deposition and the progress of denitrification within groundwater likely plays a significant role in the removal of NO3−atm.

  17. 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.

  18. Confirmation of co-denitrification in grazed grassland

    Science.gov (United States)

    Selbie, Diana R.; Lanigan, Gary J.; Laughlin, Ronald J.; di, Hong J.; Moir, James L.; Cameron, Keith C.; Clough, Tim J.; Watson, Catherine J.; Grant, James; Somers, Cathal; Richards, Karl G.

    2015-11-01

    Pasture-based livestock systems are often associated with losses of reactive forms of nitrogen (N) to the environment. Research has focused on losses to air and water due to the health, economic and environmental impacts of reactive N. Di-nitrogen (N2) emissions are still poorly characterized, both in terms of the processes involved and their magnitude, due to financial and methodological constraints. Relatively few studies have focused on quantifying N2 losses in vivo and fewer still have examined the relative contribution of the different N2 emission processes, particularly in grazed pastures. We used a combination of a high 15N isotopic enrichment of applied N with a high precision of determination of 15N isotopic enrichment by isotope-ratio mass spectrometry to measure N2 emissions in the field. We report that 55.8 g N m-2 (95%, CI 38 to 77 g m-2) was emitted as N2 by the process of co-denitrification in pastoral soils over 123 days following urine deposition (100 g N m-2), compared to only 1.1 g N m-2 (0.4 to 2.8 g m-2) from denitrification. This study provides strong evidence for co-denitrification as a major N2 production pathway, which has significant implications for understanding the N budgets of pastoral ecosystems.

  19. Biohydrogen facilitated denitrification at biocathode in bioelectrochemical system (BES).

    Science.gov (United States)

    Liu, Hao; Yan, Qun; Shen, Wei

    2014-11-01

    Reductive removal of nitrate in bioelectrochemical system (BES) at abiotic cathode, biocathode and biohydrogen facilitated biocathode were investigated. It was found that nitrate removal efficiency reached 95% and 59% at the biohydrogen facilitated biocathode and biocathode respectively, while which was only 13% at the abiotic cathode. Meanwhile, activity of nitrate reductase reached 0.701 g-N/Lh for the biohydrogen facilitated group, which was about 9.3 times of the biocathode group. Moreover, electrochemical performances as power density, ohmic resistance, and polarization resistance of the biohydrogen facilitated group reached 76.96 mW/m(3), 8.63 ohm and 383 ohm, respectively, which were better than two other groups. Finally, an obvious shift of bacterial community responsible for the enhanced nitrate reduction between the two biocathode groups was observed. Therefore, nitrate reduction in BES could be enhanced at the biocathode than that of the abiotic cathode, and then be further boosted with the combination of biohydrogen.

  20. Nitrate Biogeochemistry and Reactive Transport in California Groundwater: LDRD Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Esser, B K; Beller, H; Carle, S; Cey, B; Hudson, G B; Leif, R; LeTain, T; Moody-Bartel, C; Moore, K; McNab, W; Moran, J; Tompson, A

    2006-02-24

    Nitrate is the number one drinking water contaminant in the United States. It is pervasive in surface and groundwater systems,and its principal anthropogenic sources have increased dramatically in the last 50 years. In California alone, one third of the public drinking-water wells has been lost since 1988 and nitrate contamination is the most common reason for abandonment. Effective nitrate management in groundwater is complicated by uncertainties related to multiple point and non-point sources, hydrogeologic complexity, geochemical reactivity, and quantification of denitrification processes. In this paper, we review an integrated experimental and simulation-based framework being developed to study the fate of nitrate in a 25 km-long groundwater subbasin south of San Jose, California, a historically agricultural area now undergoing rapid urbanization with increasing demands for groundwater. The modeling approach is driven by a need to integrate new and archival data that support the hypothesis that nitrate fate and transport at the basin scale is intricately related to hydrostratigraphic complexity, variability of flow paths and groundwater residence times, microbial activity, and multiple geochemical reaction mechanisms. This study synthesizes these disparate and multi-scale data into a three-dimensional and highly resolved reactive transport modeling framework.

  1. Hydrogeochemistry and isotopic tracing of nitrate contamination of two aquifer systems on Jeju Island, Korea.

    Science.gov (United States)

    Koh, Eun-Hee; Kaown, Dugin; Mayer, Bernhard; Kang, Bong-Rae; Moon, Hee Sun; Lee, Kang-Kun

    2012-01-01

    The groundwater of Jeju Island (Republic of Korea) is vulnerable to contamination because its aquifers are mainly composed of highly permeable geological units and its agricultural fields are often exposed to excessive use of predominantly synthetic fertilizers. In the Gosan area of Jeju Island, we investigated nitrate contamination in both a perched aquifer above an impermeable clay bed and the regional groundwater beneath this aquitard. The δO and δD values indicate that the perched groundwater is recharged by local precipitation, whereas the regional groundwater is recharged mainly by regional flow from an adjacent mountainous region. The perched groundwater contained very high NO-N concentrations of up to 87 mg/L. The isotopic composition of nitrate in the perched groundwater showed that synthetic fertilizers applied in high excesses of crop N needs were the main cause of aquifer pollution. Elevated nitrate concentrations were also observed in the regional groundwater especially after precipitation events. Concentration and isotopic data revealed that the inflow of shallow perched groundwater along the poorly cemented or uncemented annulus of regional groundwater wells was one of the main reasons for the nitrate contamination observed in the regional groundwater. In both aquifers, δN and δO values showed that the sources of nitrate were derived from synthetic fertilizers that had been recycled in the soil zone by nitrification and in some portions of the perched aquifer (dissolved oxygen concentrations <2 mg/L) indicated that denitrification occurred locally. PMID:23128740

  2. Nitrate removal performance of Diaphorobacter nitroreducens using biodegradable plastics as the source of reducing power

    International Nuclear Information System (INIS)

    Strain NA10BT and other two strains of the denitrifying betaproteobacterium Diaphorobacter nitroreducens were studied for the performance of solid-phase denitrification (SPD) using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and some other biodegradable plastics as the source of reducing power in wastewater treatment. Sequencing-batch SPD reactors with these organisms and PHBV granules or flakes as the substrate exhibited good nitrate removal performance. Vial tests using cultures from these parent reactors showed higher nitrate removal rates with PHBV granules (ca. 20 mg-NO3−‐N g−1 [dry wt cells] h−1) than with PHBV pellets and flakes. In continuous-flow SPD reactors using strain NA10BT and PHBV flakes, nitrate was not detected even at a loading rate of 21 mg-NO3−‐N L−1 h−1. This corresponded to a nitrate removal rate of 47 mg-NO3−‐N g−1 (dry wt cells) h−1. In the continuous-flow reactor, the transcription level of the phaZ gene, coding for PHB depolymerase, decreased with time, while that of the nosZ gene, involved in denitrificaiton, was relatively constant. These results suggest that the bioavailability of soluble metabolites as electron donor and carbon sources increases with time in the continuous-flow SPD process, thereby having much higher nitrate removal rates than the process with fresh PHBV as the substrate

  3. Assessment of sources and fate of nitrate in shallow groundwater of an agricultural area by using a multi-tracer approach.

    Science.gov (United States)

    Pastén-Zapata, Ernesto; Ledesma-Ruiz, Rogelio; Harter, Thomas; Ramírez, Aldo I; Mahlknecht, Jürgen

    2014-02-01

    Nitrate isotopic values are often used as a tool to understand sources of contamination in order to effectively manage groundwater quality. However, recent literature describes that biogeochemical reactions may modify these values. Therefore, data interpretation is difficult and often vague. We provide a discussion on this topic and complement the study using halides as comparative tracers assessing an aquifer underneath a sub-humid to humid region in NE Mexico. Hydrogeological information and stable water isotopes indicate that active groundwater recharge occurs in the 8000km(2) study area under present-day climatic and hydrologic conditions. Nitrate isotopes and halide ratios indicate a diverse mix of nitrate sources and transformations. Nitrate sources include organic waste and wastewater, synthetic fertilizers and soil processes. Animal manure and sewage from septic tanks were the causes of groundwater nitrate pollution within orchards and vegetable agriculture. Dairy activities within a radius of 1,000 m from a sampling point significantly contributed to nitrate pollution. Leachates from septic tanks caused nitrate pollution in residential areas. Soil nitrogen and animal waste were the sources of nitrate in groundwater under shrubland and grassland. Partial denitrification processes helped to attenuate nitrate concentration underneath agricultural lands and grassland, especially during summer months.

  4. Simultaneous heterotrophic nitrification and aerobic denitrification at high initial phenol concentration by isolated bacterium Diaphorobacter sp. PD-7

    Institute of Scientific and Technical Information of China (English)

    Qilong Ge; Xiuping Yue; Guoying Wang

    2015-01-01

    A strain capable of phenol degradation, heterotrophic nitrification and aerobic denitrification was isolated from activated sludge of coking-plant wastewater ponds under aerobic condition. Based on its morphology, physiology, biochemical analysis and phylogenetic characteristics, the isolate was identified as Diaphorobacter sp. PD-7. Biodegradation tests of phenol showed that the maximum phenol degradation occurred at the late phase of exponential growth stages, with 1400 mg·L-1 phenol completely degraded within 85 h. Diaphorobacter sp. PD-7 accumulated a vast quantity of phenol hydroxylase in this physiological phase, ensuring that the cel s quickly utilize phenol as a sole carbon and energy source. The kinetic behavior of Diaphorobacter sp. PD-7 in batch cultures was investigated over a wide range of initial phenol concentrations (0–1400 mg·L-1) by using the Haldane model, which adequately describes the dynamic behavior of phenol biodegradation by strain Diaphorobacter sp. PD-7. At initial phenol concentration of 1400 mg·L-1, batch experiments (0.25 L flask) of nitrogen removal under aerobic condition gave almost entirely removal of 120.69 mg·L-1 ammonium nitrogen within 75 h, while nitrate nitrogen removal reached 91%within 65 h. Moreover, hydroxylamine oxidase, periplasmic nitrate reductase and nitrite reductase were successful y expressed in the isolate.

  5. 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

  6. Assessment of anthropogenic nitrate pollution in groundwater in northeast Cairo using nitrogen-15 technique

    International Nuclear Information System (INIS)

    process has a major effect in lowering the value of nitrate contents in this part. At the southern part of the study area the denitrification process controls nitrate levels where the loss of NO3- can result in a marked enrichment in the δ15N content of the remaining NO3-. Nitrogen isotope technique offers a direct mean of nitrate source identification

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

    Science.gov (United States)

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

    2014-05-01

    The microbial mediated production of nitrous oxide (N2O) and its reduction to dinitrogen (N2) via denitrification represents a loss of nitrogen (N) from fertilised agro ecosystems to the atmosphere. Although denitrification remains a major uncertainty in estimating N losses from soils, the magnitude of N2 losses and related N2:N2O ratios from soils are largely unknown due to difficulties measuring N2 against a high atmospheric background. In order to address this lack of data, this study investigated the influence of different soil moisture contents on N2 and N2O emissions from a sub-tropical pasture in Queensland/Australia using the 15N gas flux method. Intact soil cores were incubated over 14 days at 80% and 100% water filled pore space (WFPS). Gas samples were taken up to six times per day after application of 15N labelled nitrate, equivalent to 50 kg N ha-1 and analysed for N2 and N2O by isotope ratio mass spectrometry. Fluxes were calculated assuming non-random 15N distribution in the headspace according to Mulvaney and Kurtz (1984) using the labelled pool of nitrate estimated from N2O measurements (Stevens and Laughlin 2001). The main product of denitrification in both treatments was N2. N2 emissions exceeded N2O emissions by a factor of 1.3 ± 0.3 at 80% WFPS and a factor of 3 ± 0.8 at 100% WFPS. The total amount of N-N2 lost over the incubation period was 13.5±1.0 kg N ha-1 at 80% WFPS and 21.8±1.8 kg ha-1 at 100% WFPS respectively. Over the entire incubation period, N2 emissions remained elevated at 100% WFPS, showing high variation between soil cores, while related N2O emissions decreased. At 80% WFPS, N2 emissions increased constantly over time showing significantly higher values after day five. At the same time, N2O fluxes declined. Consequently, N2:N2O ratios rose over the incubation period in both treatments. Overall denitrification rates and related N2:N2O ratios were higher at 100% WFPS compared to 80% WFPS, confirming WFPS as a major driver of

  8. Evaluation of nitrate source in groundwater of southern part of North China Plain based on multi-isotope

    Institute of Scientific and Technical Information of China (English)

    方晶晶; 周爱国; 马传明; 刘存富; 蔡鹤生; 甘义群; 刘运德

    2015-01-01

    Nitrate pollution in groundwater is a serious water quality problem that increases the risk of developing various cancers. Groundwater is the most important water resource and supports a population of 5 million in Anyang area of the southern part of the North China Plain. Determining the source of nitrate pollution is the challenge in hydrology area due to the complex processes of migration and transformation. A new method is presented to determine the source of nitrogen pollution by combining the composition characteristics of stable carbon isotope in dissolved organic carbon in groundwater. The source of groundwater nitrate is dominated by agricultural fertilizers, as well as manure and wastewater. Mineralization, nitrification and mixing processes occur in the groundwater recharge area, whereas the confined groundwater area is dominated by denitrification processes.

  9. Nitrogen cycling in the subsurface biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

    Directory of Open Access Journals (Sweden)

    S. D. Wankel

    2015-08-01

    Full Text Available Nitrogen (N is a key component of fundamental biomolecules. Hence, the cycling and availability of N is a central factor governing the extent of ecosystems across the Earth. In the organic-lean sediment porewaters underlying the oligotrophic ocean, where low levels of microbial activity persist despite limited organic matter delivery from overlying water, the extent and modes of nitrogen transformations have not been widely investigated. Here we use the N and oxygen (O isotopic composition of porewater nitrate (NO3− from a site in the oligotrophic North Atlantic (IODP to determine the extent and magnitude of microbial nitrate production (via nitrification and consumption (via denitrification. We find that NO3− accumulates far above bottom seawater concentrations (∼ 21 μM throughout the sediment column (up to ∼ 50 μM down to the oceanic basement as deep as 90 mbsf, reflecting the predominance of aerobic nitrification/remineralization within the deep marine sediments. Large changes in the δ15N and δ18O of nitrate, however, reveal variable influence of nitrate respiration across the three sites. We use an inverse porewater diffusion–reaction model, constrained by the N and O isotope systematics of nitrification and denitrification and the porewater NO3− isotopic composition, to estimate rates of nitrification and denitrification throughout the sediment column. Results indicate variability of reaction rates across and within the three boreholes that are generally consistent with the differential distribution of dissolved oxygen at this site, though not necessarily with the canonical view of how redox thresholds separate nitrate regeneration from dissimilative consumption spatially. That is, we provide isotope evidence for expanded zones of co-ocurring nitrification and denitrification. The isotope biogeochemical modeling also yielded estimates for the δ15N and δ18O of newly produced nitrate (δ15NNTR and δ18ONTR, as well as the

  10. Nitrogen cycling in the subsurface biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

    Science.gov (United States)

    Wankel, S. D.; Buchwald, C.; Ziebis, W.; Wenk, C. B.; Lehmann, M. F.

    2015-08-01

    Nitrogen (N) is a key component of fundamental biomolecules. Hence, the cycling and availability of N is a central factor governing the extent of ecosystems across the Earth. In the organic-lean sediment porewaters underlying the oligotrophic ocean, where low levels of microbial activity persist despite limited organic matter delivery from overlying water, the extent and modes of nitrogen transformations have not been widely investigated. Here we use the N and oxygen (O) isotopic composition of porewater nitrate (NO3-) from a site in the oligotrophic North Atlantic (IODP) to determine the extent and magnitude of microbial nitrate production (via nitrification) and consumption (via denitrification). We find that NO3- accumulates far above bottom seawater concentrations (∼ 21 μM) throughout the sediment column (up to ∼ 50 μM) down to the oceanic basement as deep as 90 mbsf, reflecting the predominance of aerobic nitrification/remineralization within the deep marine sediments. Large changes in the δ15N and δ18O of nitrate, however, reveal variable influence of nitrate respiration across the three sites. We use an inverse porewater diffusion-reaction model, constrained by the N and O isotope systematics of nitrification and denitrification and the porewater NO3- isotopic composition, to estimate rates of nitrification and denitrification throughout the sediment column. Results indicate variability of reaction rates across and within the three boreholes that are generally consistent with the differential distribution of dissolved oxygen at this site, though not necessarily with the canonical view of how redox thresholds separate nitrate regeneration from dissimilative consumption spatially. That is, we provide isotope evidence for expanded zones of co-ocurring nitrification and denitrification. The isotope biogeochemical modeling also yielded estimates for the δ15N and δ18O of newly produced nitrate (δ15NNTR and δ18ONTR), as well as the isotope effect for

  11. Vertical activity distribution of dissimilatory nitrate reduction in coastal marine sediments

    DEFF Research Database (Denmark)

    Behrendt, A.; de Beer, D.; Stief, P.

    2013-01-01

    The relative importance of two dissimilatory nitrate reduction pathways, denitrification (DEN) and dissimilatory nitrate reduction to ammonium (DNRA), was investigated in intact sediment cores from five different coastal marine field sites (Dorum, Aarhus Bight, Mississippi Delta, Limfjord...... reduction was clearly dominated by DEN (59-131% of the total NO3- reduced) rather than by DNRA, irrespective of the sedimentary inventories of electron donors such as organic carbon, sulfide, and iron. Highest ammonium production via DNRA, accounting for up to 8.9% of the total NO3- reduced, was found...... at a site with very high concentrations of total sulfide and NH4+ within and below the layer in which NO3- reduction occurred. Sediment from two field sites, one with low and one with high DNRA activity in the core incubations, was also used for slurry incubations. Now, in both sediments high DNRA activity...

  12. The effect of spatial heterogeneity on nitrate reduction in soil systems

    DEFF Research Database (Denmark)

    Pedersen, Lasse Lu

    Nitrogen is not only an abundant element on earth, making up roughly 80%of the earth's atmosphere, it is also essential for life, and a functional nitrogen cycle is of great importance to human activities and our ecosystems. The nitrogen cycle ultimately returns reactive nitrogen, which....... While both processes bring about the reduction of nitrate, their impact on ecosystems is radically different – especially in soil environments. Nitrate itself is poorly retained in soils, and its conversion to gaseous dinitrogen and nitrous oxide through denitrification only serves to further the loss...... heterogeneity and diffusive limitations result in the formation of specialized niches. It is becoming increasingly clear that these factors are of great importance for biogeochemical processes such as the carbon cycle. Studying the heterogeneity of soil and its impact on ecological processes is not merely...

  13. A regional survey on nitrate contamination of the Po valley alluvial aquifer (Northern Italy)

    International Nuclear Information System (INIS)

    The origin, distribution and abatement of nitrate contamination in surface and groundwater are traced by hydrochemical and stable isotope analyses. The studied sector of the Po Valley is approximately 3,600 km2 wide, extending from the Alps to the Apennine along a N-S transect. The phreatic aquifer is fed by local infiltration and by streams and irrigation channels, while the Po river represents the major discharge axis. The main diffuse source of nitrates is from synthetic fertilisers, exceedingly used for crop raising. Peak concentrations are instead associated to local leakage from sewage network. The distribution of groundwater contamination is closely related to the hydraulic characteristics of the unsaturated zone, to agricultural input and irrigation practices. Denitrification is observed along major draining rivers and below rice fields. Results are interpreted in terms of aquifer vulnerability, groundwater circulation and land use. (author)

  14. A regional survey on nitrate contamination of the Po Valley Alluvial Aquifer (Northern Italy)

    International Nuclear Information System (INIS)

    The origin, distribution and abatement of nitrate contamination in surface and groundwater are traced by hydrochemical and stable isotope analyses. The studied sector of the Po Valley is approximately 3 600 km2 wide, extending from the Alps to the Apennine along a N-S transect. The phreatic aquifer is fed by local infiltration and by streams and irrigation channels, while the Po river represents the major discharge axis. The main diffuse source of nitrates is from synthetic fertilisers, exceedingly used for crop raising. Peak concentrations are instead associated to local leakage from the sewage network.The distribution of groundwater contamination is closely related to the hydraulic characteristics of the unsaturated zone, to agricultural input and irrigation practices. Denitrification is observed along major draining rivers and below rice fields. Results are interpreted in terms of aquifer vulnerability, groundwater circulation and land use. (author)

  15. 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.

  16. Nitrate storage and dissimilatory nitrate reduction by eukaryotic microbes

    DEFF Research Database (Denmark)

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils;

    2015-01-01

    The microbial nitrogen cycle is one of the most complex and environmentally important element cycles on Earth and has long been thought to be mediated exclusively by prokaryotic microbes. Rather recently, it was discovered that certain eukaryotic microbes are able to store nitrate intracellularly...... and use it for dissimilatory nitrate reduction in the absence of oxygen. The paradigm shift that this entailed is ecologically significant because the eukaryotes in question comprise global players like diatoms, foraminifers, and fungi. This review article provides an unprecedented overview of nitrate...... storage and dissimilatory nitrate reduction by diverse marine eukaryotes placed into an eco-physiological context. The advantage of intracellular nitrate storage for anaerobic energy conservation in oxygen-depleted habitats is explained and the life style enabled by this metabolic trait is described...

  17. Rapid monitoring of intermediate states and mass balance of nitrogen during denitrification by means of cavity enhanced Raman multi-gas sensing.

    Science.gov (United States)

    Keiner, Robert; Herrmann, Martina; Küsel, Kirsten; Popp, Jürgen; Frosch, Torsten

    2015-03-15

    The comprehensive investigation of changes in N cycling has been challenging so far due to difficulties with measuring gases such as N2 and N2O simultaneously. In this study we introduce cavity enhanced Raman gas spectroscopy as a new analytical methodology for tracing the stepwise reduction of (15)N-labelled nitrate by the denitrifying bacteria Pseudomonas stutzeri. The unique capabilities of Raman multi-gas analysis enabled real-time, continuous, and non-consumptive quantification of the relevant gases ((14)N2, (14)N2O, O2, and CO2) and to trace the fate of (15)N-labeled nitrate substrate ((15)N2, (15)N2O) added to a P. stutzeri culture with one single measurement. Using this new methodology, we could quantify the kinetics of the formation and degradation for all gaseous compounds (educts and products) and thus study the reaction orders. The gas quantification was complemented with the analysis of nitrate and nitrite concentrations for the online monitoring of the total nitrogen element budget. The simultaneous quantification of all gases also enabled the contactless and sterile online acquisition of the pH changes in the P. stutzeri culture by the stoichiometry of the redox reactions during denitrification and the CO2-bicarbonate equilibrium. Continuous pH monitoring - without the need to insert an electrode into solution - elucidated e.g. an increase in the slope of the pH value coinciding with an accumulation of nitrite, which in turn led to a temporary accumulation of N2O, due to an inhibition of nitrous oxide reductase. Cavity enhanced Raman gas spectroscopy has a high potential for the assessment of denitrification processes and can contribute substantially to our understanding of nitrogen cycling in both natural and agricultural systems. PMID:25732425

  18. Temporal variation of diatom benthic propagules in a monsoon-influenced tropical estuary

    Science.gov (United States)

    Patil, Jagadish S.; Anil, Arga Chandrashekar

    2008-10-01

    Temporal variations in the diatom benthic propagule (DBP) community and their role in the phytoplankton community in a monsoon-affected tropical estuary, Zuari estuary, Goa (India) are presented. The DBP from the sediments was enumerated using an extinction dilution method (most probable number method), which allows estimation of resting stages through examination of germinated vegetative cells in culture. The DBP community was dominated by planktonic species belonging to the genera Skeletonema, Fragilariopsis, Thalassiosira, and Chaetoceros. Benthic propagules (BPs) of Skeletonema costatum and Fragilariopsis sp. were dominant throughout the year. Between these two species, only S. costatum showed a linear relationship between the BP and planktonic cells, indicating that this species is particularly important in coupling of pelagic and benthic ecosystems. During the onset and restart of monsoon after an intermittent break, water column was stratified, with a low-salinity layer arising from riverine discharge and precipitation at the surface and relatively cold, saline, low-oxygen waters at the bottom. Stratification favored blooming of S. costatum and Fragilariopsis sp. in nutrient-rich surface and bottom waters, respectively. The decline in these blooms ensuing nitrate depletion and salinity change resulted in an increased abundance of BP. Chaetoceros bloom was observed during the monsoon break as well as during non-monsoon period and on both the occasions the decline in bloom was coupled with freshwater discharge. During the non-monsoon season, Thalassiosira blooms were encountered subsequent to high nitrate inputs. These findings suggest that in such shallow tropical regions, physical processes during monsoon (freshwater discharge) and non-monsoon seasons (currents, waves and tides) cause resuspension of diatom BP. Since light is not a limiting factor for germination in such regions, the blooming of resuspended BP depends on nutrient availability.

  19. Evaluation of nitrate destruction methods

    International Nuclear Information System (INIS)

    A wide variety of high nitrate-concentration aqueous mixed [radioactive and Resource Conservation and Recovery Act (RCRA) hazardous] wastes are stored at various US Department of Energy (DOE) facilities. These wastes will ultimately be solidified for final disposal, although the waste acceptance criteria for the final waste form is still being determined. Because the nitrates in the wastes will normally increase the volume or reduce the integrity of all of the waste forms under consideration for final disposal, nitrate destruction before solidification of the waste will generally be beneficial. This report describes and evaluates various technologies that could be used to destroy the nitrates in the stored wastes. This work was funded by the Department of Energy's Office of Technology Development, through the Chemical/Physical Technology Support Group of the Mixed Waste Integrated Program. All the nitrate destruction technologies will require further development work before a facility could be designed and built to treat the majority of the stored wastes. Several of the technologies have particularly attractive features: the nitrate to ammonia and ceramic (NAC) process produces an insoluble waste form with a significant volume reduction, electrochemical reduction destroys nitrates without any chemical addition, and the hydrothermal process can simultaneously treat nitrates and organics in both acidic and alkaline wastes. These three technologies have been tested using lab-scale equipment and surrogate solutions. At their current state of development, it is not possible to predict which process will be the most beneficial for a particular waste stream

  20. [1-(Carboxymethylcyclohexyl]methanaminium nitrate

    Directory of Open Access Journals (Sweden)

    Elise J. C. de Vries

    2011-02-01

    Full Text Available The title compound, C9H18NO2+·NO3−, is an anhydrous nitrate salt of gabapentin, which is formed serendipitously in the presence of selected non-coordinating metals. The crystal structure involves extensive hydrogen bonding between the –NH3+ and –COOH groups and the nitrate anion.

  1. WATER QUALITY EVALUATION OF CRIŞUL ALB AND CRIŞUL NEGRU RIVERS CATCHMENTS, FROM CODRU-MOMA MOUNTAINS (WEST OF ROMANIA, USING BENTHIC INVERTEBRATES COMMUNITIES

    Directory of Open Access Journals (Sweden)

    Andreea VARGA

    2010-01-01

    Full Text Available Water quality evaluation of the two watersheds involved the collection of thirteen samples from the tributaries of Crişul Alb and Crişul Negru rivers. The samples were collected in june 2010 with a benthic net, which had the mesh size of 250 µm, by disturbing the substrate, being thus qualitative samples. To get an overview, a series of physical-chemical parameters (water temperature, pH, oxygen, conductivity, cyanide, nitrates, nitrites, phosphates was studied in parallel with the study of benthic community. In most of the sampling points the major group of benthic macroinvertebrates were found and in some EPT group (Ephemeroptera, Plecoptera, Trichoptera prevailed even, which is known as a clean freshwater group, sensitive to pollution and human impact.

  2. A stable isotope approach and its application for identifying nitrate source and transformation process in water.

    Science.gov (United States)

    Xu, Shiguo; Kang, Pingping; Sun, Ya

    2016-01-01

    Nitrate contamination of water is a worldwide environmental problem. Recent studies have demonstrated that the nitrogen (N) and oxygen (O) isotopes of nitrate (NO3(-)) can be used to trace nitrogen dynamics including identifying nitrate sources and nitrogen transformation processes. This paper analyzes the current state of identifying nitrate sources and nitrogen transformation processes using N and O isotopes of nitrate. With regard to nitrate sources, δ(15)N-NO3(-) and δ(18)O-NO3(-) values typically vary between sources, allowing the sources to be isotopically fingerprinted. δ(15)N-NO3(-) is often effective at tracing NO(-)3 sources from areas with different land use. δ(18)O-NO3(-) is more useful to identify NO3(-) from atmospheric sources. Isotopic data can be combined with statistical mixing models to quantify the relative contributions of NO3(-) from multiple delineated sources. With regard to N transformation processes, N and O isotopes of nitrate can be used to decipher the degree of nitrogen transformation by such processes as nitrification, assimilation, and denitrification. In some cases, however, isotopic fractionation may alter the isotopic fingerprint associated with the delineated NO3(-) source(s). This problem may be addressed by combining the N and O isotopic data with other types of, including the concentration of selected conservative elements, e.g., chloride (Cl(-)), boron isotope (δ(11)B), and sulfur isotope (δ(35)S) data. Future studies should focus on improving stable isotope mixing models and furthering our understanding of isotopic fractionation by conducting laboratory and field experiments in different environments.

  3. Modeling of Reactive Transport of Nitrate in a Heterogeneous Alluvial Fan Aquifer, San Joaquin Valley, California

    Science.gov (United States)

    Green, C. T.; Phillips, S. P.

    2005-12-01

    Fate of nitrate in an alluvial fan aquifer in the San Joaquin Valley, California, was investigated with combined laboratory analyses, field measurements, geostatistics, and flow and reactive transport modeling. In the summer of 2003, groundwater wells and lysimeters were installed along a 1-km transect extending upgradient from the Merced River through an unfarmed riparian zone, a corn field, and an orchard. Groundwater levels have been monitored continuously. Saturated and unsaturated pore waters were analyzed quarterly for nutrients, anions, and cations. Sediment core samples from above and below the water table were analyzed for organic matter, nutrients, inorganic chemistry, and potential denitrification using denitrification enzyme assays (DEA's) based on the acetylene block technique. Curve fitting of DEA's provided core-scale estimates of microbial populations and growth coefficients. DEA biomass was similar to values obtained with the most probable number technique. Growth coefficients were found to be relatively uniform across the site, while biomass varied by several orders of magnitude. Age dates estimated from Chlorofluorocarbon (CFC) and Sulfur Hexafluoride (SF6), together with analyses of nitrogen species and excess nitrogen gas, provided approximate aquifer-scale, zero-order denitrification rates. The field and laboratory measurements served as input for geostatistical realizations of sediment properties and simulations of reactive transport of nitrate in the saturated zone. Analyses of cores, drillers' logs, and previous interpretations of the local geology were used to generate transition probability models of hydrofacies distributions within Holocene alluvium and pre-Holocene fans, and maps of the boundaries between these stratigraphic sequences. Multiple 3-D realizations were created and ranked based on lateral and vertical bulk-flow properties. For realizations representing a range of geological conditions, 3-D flow was computed with boundary

  4. Nitrous Oxide Production by Abundant Benthic Macrofauna

    DEFF Research Database (Denmark)

    Stief, Peter; Schramm, Andreas

    that do not ingest large quantities of microorganisms produced insignificant amounts of nitrous oxide. Ephemera danica, a very abundant mayfly larva, was monitored monthly in a nitrate-polluted stream. Nitrous oxide production by this filter-feeder was highly dependent on nitrate availability...

  5. Evaluation of sustainable electron donors for nitrate removal in different water media.

    Science.gov (United States)

    Fowdar, Harsha S; Hatt, Belinda E; Breen, Peter; Cook, Perran L M; Deletic, Ana

    2015-11-15

    An external electron donor is usually included in wastewater and groundwater treatment systems to enhance nitrate removal through denitrification. The choice of electron donor is critical for both satisfactory denitrification rates and sustainable long-term performance. Electron donors that are waste products are preferred to pure organic chemicals. Different electron donors have been used to treat different water types and little is known as to whether there are any electron donors that are suitable for multiple applications. Seven different carbon rich waste products, including liquid and solid electron donors, were studied in comparison to pure acetate. Batch-scale tests were used to measure their ability to reduce nitrate concentrations in a pure nutrient solution, light greywater, secondary-treated wastewater and tertiary-treated wastewater. The tested electron donors removed oxidised nitrogen (NOx) at varying rates, ranging from 48 mg N/L/d (acetate) to 0.3 mg N/L/d (hardwood). The concentrations of transient nitrite accumulation also varied across the electron donors. The different water types had an influence on NOx removal rates, the extent of which was dependent on the type of electron donor. Overall, the highest rates were recorded in light greywater, followed by the pure nutrient solution and the two partially treated wastewaters. Cotton wool and rice hulls were found to be promising electron donors with good NOx removal rates, lower leachable nutrients and had the least variation in performance across water types. PMID:26379204

  6. BIOLOGICAL AND PRODUCTIVE RESOURCES OF LACTATING COWS AT DENITRIFICATION

    OpenAIRE

    Kokaeva M. G.; Plieva Z. K.; Temiraev R. B.; Gurtsieva D. O.

    2015-01-01

    The article presents the results obtained in the process of two scientific-practical experiments carried jut on two milk cows (Shvitskay breed) aimed at the antioxidants detoxication properties and mould inhibitor revealing. This factor is actual in the Republic of North Ossetia-Alania as the intensive technologies of the fodder crops cultivation using the nitrate fertilizers are widely applied in the region leading to the excess nitrates and nitrite penetration into the animals’ organism. Du...

  7. Isotope methods as a tool to characterize nitrate origin and transport in Kocinka catchment (central Poland): preliminary results

    Science.gov (United States)

    Zurek, Anna; Wachniew, Przemyslaw; Witczak, Stanislaw; Rozanski, Kazimierz; Kania, Jaroslaw

    2014-05-01

    point to agriculture as the main source of NO3. The isotopic data provided no evidences for natural denitrification in the aquifer. However, only water samples with considerable amounts of nitrates were analyzed for 15N and 18O. On the other hand, low NO3 concentrations in the deeper part of aquifer can be due to denitrification or long residence time of this water. Acknowledgements. The work was carried out as part of the project Soils2Sea in BONUS programme and the statutory funds of the AGH University of Science and Technology (project No.11.11.140.026 and 11.11.220.01).

  8. 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.

  9. BIOLOGICAL AND PRODUCTIVE RESOURCES OF LACTATING COWS AT DENITRIFICATION

    Directory of Open Access Journals (Sweden)

    Kokaeva M. G.

    2015-09-01

    Full Text Available The article presents the results obtained in the process of two scientific-practical experiments carried jut on two milk cows (Shvitskay breed aimed at the antioxidants detoxication properties and mould inhibitor revealing. This factor is actual in the Republic of North Ossetia-Alania as the intensive technologies of the fodder crops cultivation using the nitrate fertilizers are widely applied in the region leading to the excess nitrates and nitrite penetration into the animals’ organism. During the first experiment, the antioxidants of epophen and vitamin C were added into the ration of the lactating cows with the subtoxic dosage of nitrates both separately and in complex. The complex feeding proved to increase the milk productivity, the fat mass and protein mass in milk while reducing the fodder expenditure per product unit. Beside, the lactating cows revealed the digestive and intermediate exchange betterment and the reduction of nitrates and nitrites level in blood. The second experiment helped to study Khadoks antioxidant and mould inhibitor called Mold-Zap efficiency use for the