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


    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. stel...

  2. Denitrification of nitrate waste solutions

    Energy Technology Data Exchange (ETDEWEB)

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


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

  3. Modeling nitrate removal in a denitrification bed. (United States)

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


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

  4. 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


    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

  5. Nitrate removal with lateral flow sulphur autotrophic denitrification reactor. (United States)

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


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

  6. Seasonal variation in denitrification and dissimilatory nitrate reduction to ammonia process rates and corresponding key functional genes along an estuarine nitrate gradient

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    Cindy J Smith


    Full Text Available This research investigated spatial-temporal variation in benthic bacterial community structure, rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA processes and abundances of corresponding genes and transcripts at three sites – the estuary-head, mid-estuary and the estuary mouth along the nitrate gradient of the Colne estuary over an annual cycle. Denitrification rates declined down the estuary, while DNRA rates were higher at the estuary head and middle than the estuary mouth. In four out of the six two-monthly time-points, rates of DNRA were greater than denitrification at each site. Abundance of gene markers for nitrate-reduction (nitrate reductase narG and napA, denitrification (nitrite reductase nirS and DNRA (DNRA nitrite reductase nrfA declined along the estuary with significant relationships between denitrification and nirS abundance, and DNRA and nrfA abundance. Spatially, rates of denitrification, DNRA and corresponding functional gene abundances decreased along the estuary. However, temporal correlations between rate processes and functional gene and transcript abundances were not observed.

  7. 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


    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.

  8. The nitrogen isotope effect of benthic remineralization-nitrification-denitrification coupling in an estuarine environment (United States)

    Alkhatib, M.; Lehmann, M. F.; Del Giorgio, P. A.


    The nitrogen (N) stable isotopic composition of pore water nitrate and total dissolved N (TDN) was measured in sediments of the St. Lawrence Estuary and the Gulf of St. Lawrence. The study area is characterized by gradients in organic matter reactivity, bottom water oxygen concentrations, as well as benthic respiration rates. Benthic N isotope exchange, as well as the nitrate and TDN isotope effects of benthic nitrification-denitrification coupling on the water column, ϵapp and ϵsed, respectively, were investigated. The sediments were a major sink for nitrate and a source of reduced dissolved N (RDN = DON + NH4+). We observed that both the pore water nitrate and RDN pools were enriched in 15N relative to the water column, with increasing δ15N downcore in the sediments. As in other marine environments, the biological nitrate isotope fractionation of net nitrate elimination was barely expressed at the scale of sediment-water-exchange, with ϵapp values water oxygen concentrations and the organic matter reactivity can modulate ϵapp. For the first time, actual measurements of δ15N of pore water RDN were included in the calculations of ϵsed. We argue that large fractions of the sea-floor-derived DON are reactive and, hence, involved in the development of the δ15N of dissolved inorganic N (DIN) in the water column. In the St. Lawrence sediments, the combined benthic N transformations yield a flux of 15N-enriched RDN that can significantly enhance ϵsed. Calculated ϵsed values were within the range of 4.6 ± 2‰, and were related to organic matter reactivity and oxygen penetration depth in the sediments. ϵsed reflects the δ15N of the N2 lost from marine sediments and thus best describes the isotopic impact of N elimination on the oceanic fixed N pool. Our mean value for ϵsed is larger than assumed by earlier work, questioning current ideas with regards to the state of

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


    Bowles, Marshall; Joye, Samantha


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

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

    NARCIS (Netherlands)

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


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

  11. High rates of denitrification and nitrate removal in cold seep sediments. (United States)

    Bowles, Marshall; Joye, Samantha


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

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

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


    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.

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

    Institute of Scientific and Technical Information of China (English)

    WANG XuMing; WANG JianLong


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

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

    Directory of Open Access Journals (Sweden)

    Pierluigi VIAROLI


    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.

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

    Institute of Scientific and Technical Information of China (English)

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


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

  17. Culture Studies of Nitrogen and Oxygen Isotope Effects Associated with Nitrate Assimilation and Denitrification (United States)

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


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


    Directory of Open Access Journals (Sweden)

    A. Sabzali, M. Gholami, A. R. Yazdanbakhsh, A. Khodadadi, B. Musavi, R. Mirzaee


    Full Text Available Nitrate contamination in drinking water can cause methemoglobinemia, which is especially detrimental to infants and nursing mothers. Batch experiments in two units for catalytic reduction of nitrate from groundwater with Zn catalyst and sulfamic acid were conducted. The system includes chemical denitriphication (ChemDen reactor and electrolytic recovery reactoers. A batch study was conducted to optimize parameters like pH, sulfamic acid concentration, Zn concentration, temperature and reaction time governing the ChemDen process. The concentrations of remained nitrate and Zn were measured at the end of the reactions. Results showed that near to 100% of nitrate decreased and the quantity of remained nitrate was <1 mg/L. pH and agitation had great effect on denitrification, and the nitrate removal rate changed rapidly when pH value ranged between 3-4. Two water quality parameters which limit this process were sulfate and chloride ions concentrations in nitrate contaminated water.

  19. Sulfur-based autotrophic denitrification with eggshell for nitrate-contaminated synthetic groundwater treatment. (United States)

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


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

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

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

  2. Enhancement of bacterial denitrification for nitrate removal in groundwater with electrical stimulation from microbial fuel cells (United States)

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


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

  3. Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification (United States)

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


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

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

    Institute of Scientific and Technical Information of China (English)


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

  5. 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;


    ) 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...

  6. Nitrate removal from groundwater driven by electricity generation and heterotrophic denitrification in a bioelectrochemical system. (United States)

    Tong, Yiran; He, Zhen


    This research aims to develop a new approach for in situ nitrate removal from groundwater by using a bioelectrochemical system (BES). The BES employs bioelectricity generated from organic compounds to drive nitrate moving from groundwater into the anode and reduces nitrate to nitrogen gas by heterotrophic denitrification. This laboratory study of a bench-scale BES demonstrated effective nitrate removal from both synthetic and actual groundwater. It was found that applying an electrical potential improved the nitrate removal and the highest nitrate removal rate of 208.2 ± 13.3g NO3(-)-Nm(-3) d(-1) was achieved at 0.8 V. Although the open circuit condition (no electricity generation) still resulted in a nitrate removal rate of 158.5 ± 4.2 gm(-3) d(-1) due to ion exchange, electricity production could inhibit ion exchange and prevent introducing other undesired ions into groundwater. The nitrate removal rate exhibited a linear relationship with the initial nitrate concentration in groundwater. The BES produced a higher current density of 33.4 Am(-3) and a higher total coulomb of 244.7 ± 9.1C from the actual groundwater than the synthetic groundwater, likely because other ions in the actual groundwater promoted ion movement to assist electricity generation. Further development of this BES will need to address several key challenges in anode feeding solution, ion competition, and long-term stability.

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

    Directory of Open Access Journals (Sweden)

    Arzu KILIÇ


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

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

    Sahinkaya, Erkan; Kilic, Adem


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

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

    DEFF Research Database (Denmark)

    Wunderlich, Anja; Meckenstock, Rainer; Einsiedl, Florian


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

  10. Evaluation on the Nanoscale Zero Valent Iron Based Microbial Denitrification for Nitrate Removal from Groundwater. (United States)

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


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

  11. Denitrification by plant roots? New aspects of plant plasma membrane-bound nitrate reductase. (United States)

    Eick, Manuela; Stöhr, Christine


    A specific form of plasma membrane-bound nitrate reductase in plants is restricted to roots. Two peptides originated from plasma membrane integral proteins isolated from Hordeum vulgare have been assigned as homologues to the subunit NarH of respiratory nitrate reductase of Escherichia coli. Corresponding sequences have been detected for predicted proteins of Populus trichocarpa with high degree of identities for the subunits NarH (75%) and NarG (65%), however, with less accordance for the subunit NarI. These findings coincide with biochemical properties, particularly in regard to the electron donors menadione and succinate. Together with the root-specific and plasma membrane-bound nitrite/NO reductase, nitric oxide is produced under hypoxic conditions in the presence of nitrate. In this context, a possible function in nitrate respiration of plant roots and an involvement of plants in denitrification processes are discussed.

  12. Optimization and evaluation of a bottom substrate denitrification tank for nitrate removal from a recirculating aquaculture system. (United States)

    Pungrasmi, Wiboonluk; Playchoom, Cholticha; Powtongsook, Sorawit


    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.

  13. 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


    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.

  14. 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


    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 SMDDC...

  15. 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)



    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.

  16. Denitrification of nitrate and nitrite by 'Candidatus Accumulibacter phosphatis' clade IC. (United States)

    Saad, Sondos A; Welles, Laurens; Abbas, Ben; Lopez-Vazquez, Carlos M; van Loosdrecht, Mark C M; Brdjanovic, Damir


    Phosphate accumulating organisms (PAO) are assumed to use nitrate as external electron acceptor, allowing an efficient integration of simultaneous nitrogen and phosphate removal with minimal organic carbon (COD) requirements. However, contradicting findings appear in literature regarding the denitrification capacities of PAO due to the lack of clade specific highly enriched PAO cultures. Whereas some studies suggest that only PAO clade I may be capable of using nitrate as external electron acceptor for anoxic P-uptake, other studies indicate that PAO clade II may be responsible for anoxic P-removal. In the present study, a highly enriched PAO clade IC culture (>99% according to FISH) was cultivated in an SBR operated under Anaerobic/Oxic conditions and subsequently exposed to Anaerobic/Anoxic/Oxic conditions using nitrate as electron acceptor. Before and after acclimatization to the presence of nitrate, the aerobic and anoxic (nitrate and nitrite) activities of the PAO I culture were assessed through the execution of batch tests using either acetate or propionate as electron donor. In the presence of nitrate, significant P-uptake by PAO I was not observed before or after acclimatization. Using nitrite as electron acceptor, limited nitrite removal rates were observed before acclimatization with lower rates in the acetate fed reactor without P-uptake and slightly higher in the propionate fed reactor with a marginal anoxic P-uptake. Only after acclimatization to nitrate, simultaneous P and nitrite removal was observed. This study suggests that PAO clade IC is not capable of using nitrate as external electron acceptor for anoxic P-removal. The elucidation of the metabolic capacities for individual PAO clades helps in better understanding and optimization of the relation between microbial ecology and process performance in enhanced biological phosphate removal processes.

  17. Biological Denitrification of High Nitrate Processing Wastewaters from Explosives Production Plant. (United States)

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


    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.

  18. 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


    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.

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

    Directory of Open Access Journals (Sweden)

    N. Glock


    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

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

    Directory of Open Access Journals (Sweden)

    N. Glock


    Full Text Available The discovery that foraminifera are able to use nitrate instead of oxygen as an electron acceptor for respiration has challenged our understanding of nitrogen cycling in the ocean. It was thought before that only prokaryotes and some fungi are able to denitrify. Rate estimates of foraminiferal denitrification have been very sparse and limited to specific regions in the oceans, not comparing stations along a transect of a certain region. 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 probably account for the total denitrification in shelf sediments between 80 and 250 m water depth. The estimations also imply that foraminifera are still important denitrifiers in the centre of the OMZ around 320 m (29–50% of the benthic denitrification, but play only a minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m (2–6% of total benthic denitrification. Furthermore, foraminiferal denitrification has been compared to the total benthic nitrate loss measured during benthic chamber experiments. The estimated foraminiferal denitrification rates contribute 2 to 46% to the total nitrate loss across a depth transect from 80 to 700 m, respectively. Flux rate estimates range 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 3955 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

  1. Pilot and full scale applications of sulfur-based autotrophic denitrification process for nitrate removal from activated sludge process effluent. (United States)

    Sahinkaya, Erkan; Kilic, Adem; Duygulu, Bahadir


    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).

  2. Scale-dependent linkages between nitrate isotopes and denitrification in surface soils: implications for isotope measurements and models. (United States)

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


    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.

  3. Summer nitrate uptake and denitrification in an upper Mississippi River backwater lake: The role of rooted aquatic vegetation (United States)

    Kreiling, Rebecca M.; Richardson, W.B.; Cavanaugh, J.C.; Bartsch, L.A.


    In-stream nitrogen processing in the Mississippi River has been suggested as one mechanism to reduce coastal eutrophication in the Gulf of Mexico. Aquatic macrophytes in river channels and flood plain lakes have the potential to temporarily remove large quantities of nitrogen through assimilation both by themselves and by the attached epiphyton. In addition, rooted macrophytes act as oxygen pumps, creating aerobic microsites around their roots where coupled nitrification-denitrification can occur. We used in situ 15N-NO3- tracer mesocosm experiments to measure nitrate assimilation rates for macrophytes, epiphyton, and microbial fauna in the sediment in Third Lake, a backwater lake of the upper Mississippi River during June and July 2005. We measured assimilation over a range of nitrate concentrations and estimated a nitrate mass balance for Third Lake. Macrophytes assimilated the most nitrate (29.5 mg N m-2 d-1) followed by sediment microbes (14.4 mg N m-2 d-1) and epiphytes (5.7 mg N m-2d-1. Assimilation accounted for 6.8% in June and 18.6% in July of total nitrate loss in the control chambers. However, denitrification (292.4 mg N m-2 d-1) is estimated to account for the majority (82%) of the nitrate loss. Assimilation and denitrification rates generally increased with increasing nitrate concentration but denitrification rates plateaued at about 5 mg N L-1. This suggests that backwaters have the potential to remove a relatively high amount of nitrate but will likely become saturated if the load becomes too large. ?? 2010 US Government.

  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;


    A mixed beech and spruce forest soil was incubated under potential denitrification assay (PDA) condition with 10% acetylene (C2H2) in the headspace of soil slurry bottles. Nitrous oxide (N2O) concentration in the headspace, as well as nitrate, nitrite and ammonium concentrations in the soil slurr...

  5. Nitrate removal and microbial analysis by combined micro-electrolysis and autotrophic denitrification. (United States)

    Xing, Wei; Li, Desheng; Li, Jinlong; Hu, Qianyi; Deng, Shihai


    A process combining micro-electrolysis and autotrophic denitrification (CEAD) with iron-carbon micro-electrolysis carriers was developed for nitrate removal. The process was performed using organic-free influent with a NO3(-)-N concentration of 40.0±3.0mg/L and provided an average nitrate removal efficiency of 95% in stable stages. The total nitrogen removal efficiency reached 75%, with 21% of NO3(-)-N converted into NH4(+)-N. The corresponding hydraulic retention time was 8-10h, and the optimal pH ranged from 8.5 to 9.5. Microbial analysis with high-throughput sequencing revealed that dominant microorganisms in the reactor belonged to the classes of β-, γ-, and α-Proteobacteria. The abundance of the genera Thermomonas significantly increased during the operation, comprising 21.4% and 24.1% in sludge attached to the carriers in the middle and at the bottom of the reactor, respectively. The developed CEAD achieved efficient nitrate removal from water without organics, which is suitable for practical application.

  6. Numerical simulation of a fine-grained denitrification layer for removing septic system nitrate from shallow groundwater (United States)

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


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

  7. Nitrate and nitrite inhibition of methanogenesis during denitrification in granular biofilms and digested domestic sludges. (United States)

    Banihani, Qais; Sierra-Alvarez, Reyes; Field, James A


    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.

  8. Remediation of nitrate-contaminated wastewater using denitrification biofilters with straws of ornamental flowers added as carbon source. (United States)

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

    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 nitrate-contaminated wastewater, although further optimization of carbon source addition is still required.

  9. Denitrification constitutes an import N sink in subtropical N-saturated forests - a nitrate dual isotope study (United States)

    Yu, Lonfei; Zhu, Jing; Mulder, Jan; Dörsch, Peter


    Forests in China receive variable but increasing amounts of nitrogen from the atmosphere causing N saturation and nitrate runoff. Surprisingly high N-retention has been reported from subtropical forests, suggesting active mechanisms of N removal. Here we report a multi-site study of 15N and 18O abundances in soil nitrate (NO3-) across seven forested catchments spanning from temperate to subtropical China. In each catchment, samples were taken on one date during one or two summer along the hydrological continuum comprising hillslope positions and riparian zones. We had found previously in an intensive multi-year study at one of the sites, that the spatial pattern of summertime 15N and 18O in soil nitrate was remarkably stable across climatically distinct years, suggesting persistent N removal by denitrification at the foot of hill slopes and in groundwater discharge zones (Yu et al., submitted). In the present study, we extended the scope to five subtropical Chinese catchments and compared them with two temperate forests. Our data confirm the general pattern of efficient nitrification on hillslopes and strong denitrification in riparian zones in the subtropical catchments but not in the temperate ones. This is likely because high summer rainfalls at the monsoonal sites connect N mineralization and oxidation in upland positions with NO3- reduction in ground water discharge zones via NO3- runoff, rendering subtropical forests an efficient sink for reactive N with implications for regional N budgets. The impact of N deposition level, hydrology and edaphic factors on the predictive power of nitrate isotope signatures for N removal processes will be discussed. Yu L, Zhu J, Mulder J, Dörsch P: Spatiotemporal patterns in dual nitrate isotopes reveal efficient N transformation and denitrification along a hydrological continuum in N-saturated, subtropical forest. Submitted

  10. Denitrification of high strength nitrate waste from a nuclear industry using acclimatized biomass in a pilot scale reactor. (United States)

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


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

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

    Zhang, Yifeng; Angelidaki, Irini


    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 SMDDC, which was composed of an anode and a cathode chamber, can be easily applied to subsurface environments. When current was produced by bacteria on the anode, [Formula: see text] and Na(+) were transferred into the anode and cathode through anion and cation exchange membrane, respectively; the anode effluent was directed to the cathode where [Formula: see text] was reduced to N(2) through autotrophic denitrification. For proof-of-concept, the SMDDC was fed with synthetic wastewater as fuel and submerged into a glass reactor filled with synthetic groundwater. The SMDDC produced 3.4 A/m(2) of current density, while removing 90.5% of nitrate from groundwater with 12 h wastewater hydraulic retention time (HRT) and 10 Ω of external resistance. The nitrate concentration and ionic strength of groundwater were the main limiting factors to the system performance. Besides, the external resistance and HRT were also affecting the system performance. Furthermore, the SMDDC showed improved performance with high ionic strength of groundwater (2200 μS/cm) and was able to reduce groundwater salinity as well. External nitrification was beneficial to the current generation and nitrate removal rate, but was not affecting total nitrogen removal. Results clearly indicate that this system holds a great potential for efficient and cost-effective treatment of nitrate-containing groundwater and energy recovery.

  12. Nitrate removal, communities of denitrifiers and adverse effects in different carbon substrates for use in denitrification beds. (United States)

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


    Denitrification beds are containers filled with wood by-products that serve as a carbon and energy source to denitrifiers, which reduce nitrate (NO(3)(-)) from point source discharges into non-reactive dinitrogen (N(2)) gas. This study investigates a range of alternative carbon sources and determines rates, mechanisms and factors controlling NO(3)(-) removal, denitrifying bacterial community, and the adverse effects of these substrates. Experimental barrels (0.2 m(3)) filled with either maize cobs, wheat straw, green waste, sawdust, pine woodchips or eucalyptus woodchips were incubated at 16.8 °C or 27.1 °C (outlet temperature), and received NO(3)(-) enriched water (14.38 mg N L(-1) and 17.15 mg N L(-1)). After 2.5 years of incubation measurements were made of NO(3)(-)-N removal rates, in vitro denitrification rates (DR), factors limiting denitrification (carbon and nitrate availability, dissolved oxygen, temperature, pH, and concentrations of NO(3)(-), nitrite and ammonia), copy number of nitrite reductase (nirS and nirK) and nitrous oxide reductase (nosZ) genes, and greenhouse gas production (dissolved nitrous oxide (N(2)O) and methane), and carbon (TOC) loss. Microbial denitrification was the main mechanism for NO(3)(-)-N removal. Nitrate-N removal rates ranged from 1.3 (pine woodchips) to 6.2 g N m(-3) d(-1) (maize cobs), and were predominantly limited by C availability and temperature (Q(10) = 1.2) when NO(3)(-)-N outlet concentrations remained above 1 mg L(-1). The NO(3)(-)-N removal rate did not depend directly on substrate type, but on the quantity of microbially available carbon, which differed between carbon sources. The abundance of denitrifying genes (nirS, nirK and nosZ) was similar in replicate barrels under cold incubation, but varied substantially under warm incubation, and between substrates. Warm incubation enhanced growth of nirS containing bacteria and bacteria that lacked the nosZ gene, potentially explaining the greater N(2)O emission in

  13. Sequential in situ hydrotalcite precipitation and biological denitrification for the treatment of high-nitrate industrial effluent. (United States)

    Cheng, Ka Yu; Kaksonen, Anna H; Douglas, Grant B


    A sequential process using hydrotalcite precipitation and biological denitrification was evaluated for the treatment of a magnesium nitrate (Mg(NO3)2)-rich effluent (17,000mgNO3(-)-N/L, 13,100mgMg/L) generated from an industrial nickel-mining process. The hydrotalcite precipitation removed 41% of the nitrate (7000mgNO3(-)-N/L) as an interlayer anion with an approximate formula of Mg5Al2(OH)14(NO3)2·6H2O. The resultant solute chemistry was a Na-NO3-Cl type with low trace element concentrations. The partially treated effluent was continuously fed (hydraulic retention time of 24h) into a biological fluidised bed reactor (FBR) with sodium acetate as a carbon source for 33days (1:1 v/v dilution). The FBR enabled >70% nitrate removal and a maximal NOx (nitrate+nitrite) removal rate of 97mg NOx-N/Lh under alkaline conditions (pH 9.3). Overall, this sequential process reduced the nitrate concentration of the industrial effluent by >90% and thus represents an efficient method to treat Mg(NO3)2-rich effluents on an industrial scale.

  14. Effect of nitrate and acetylene on nirS, cnorB, and nosZ expression and denitrification activity in Pseudomonas mandelii. (United States)

    Saleh-Lakha, Saleema; Shannon, Kelly E; Henderson, Sherri L; Zebarth, Bernie J; Burton, David L; Goyer, Claudia; Trevors, Jack T


    Nitrate acts as an electron acceptor in the denitrification process. The effect of nitrate in the range of 0 to 1,000 mg/liter on Pseudomonas mandelii nirS, cnorB, and nosZ gene expression was studied, using quantitative reverse transcription-quantitative PCR. Denitrification activity was measured by using the acetylene blockage method and gas chromatography. The effect of acetylene on gene expression was assessed by comparing denitrification gene expression in P. mandelii culture grown in the presence or absence of acetylene. The higher the amount of NO(3)(-) present, the greater the induction and the longer the denitrification genes remained expressed. nirS gene expression reached a maximum at 2, 4, 4, and 6 h in cultures grown in the presence of 0, 10, 100, and 1,000 mg of KNO(3)/liter, respectively, while induction of nirS gene ranged from 12- to 225-fold compared to time zero. cnorB gene expression also followed a similar trend. nosZ gene expression did not respond to NO(3)(-) treatment under the conditions tested. Acetylene decreased nosZ gene expression but did not affect nirS or cnorB gene expression. These results showed that nirS and cnorB responded to nitrate concentrations; however, significant denitrification activity was only observed in culture with 1,000 mg of KNO(3)/liter, indicating that there was no relationship between gene expression and denitrification activity under the conditions tested.

  15. Control of nitratation in an oxygen-limited autotrophic nitrification/denitrification rotating biological contactor through disc immersion level variation. (United States)

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


    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.

  16. Biological nitrate transport in sediments on the Peruvian margin mitigates benthic sulfide emissions and drives pelagic N loss during stagnation events (United States)

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


    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.

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

    NARCIS (Netherlands)

    Hoek, van der J.P.


    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

  18. 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


    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...

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

    DEFF Research Database (Denmark)

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


    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...

  20. Denitrification in soil amended with thermophile-fermented compost suppresses nitrate accumulation in plants. (United States)

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


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

  1. Multi-scale measurements and modeling of denitrification in streams with varying flow and nitrate concentration in the upper Mississippi River basin, USA (United States)

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


    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



    A. Sabzali, M. Gholami, A. R. Yazdanbakhsh, A. Khodadadi, B. Musavi, R. Mirzaee


    Nitrate contamination in drinking water can cause methemoglobinemia, which is especially detrimental to infants and nursing mothers. Batch experiments in two units for catalytic reduction of nitrate from groundwater with Zn catalyst and sulfamic acid were conducted. The system includes chemical denitriphication (ChemDen reactor) and electrolytic recovery reactoers. A batch study was conducted to optimize parameters like pH, sulfamic acid concentration, Zn concentration, temperature and reacti...

  3. Growth and uptake kinetics of nitrate and phosphate by benthic microalgae for phytoremediation of eutrophic coastal sediments. (United States)

    Kwon, Hyeong Kyu; Oh, Seok Jin; Yang, Han-Soeb


    In the present study, the effect of monochromatic light (blue, yellow and red) and mixed wavelength on the nutrient uptake and growth kinetics of benthic microalgae Achnanthes sp., Amphora sp., Navicula sp. and Nitzschia sp. were investigated. The maximum uptake rate (ρmax) for nitrate and phosphate obtained by short-term experiments were high in the order of blue, mixed, red, yellow wavelength, and among the 4 benthic microalgae, Nitzschia sp. was the highest ρmax. The half-saturation constant (Ks) was higher than other taxon. The specific maximum growth rate (μmax') and minimum cell quota (q0) for the nitrogen and phosphorus-limited condition, Nitzschia sp. showed the highest μmax' and q0 values among the 4 benthic microalgae. These results suggest that the benthic microalgae are adapted to high nutrient concentration. In particular, Nitzschia sp., which have a higher capability of storage and uptake, may be a useful species for phytoremediation.

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

    Directory of Open Access Journals (Sweden)

    Federico Rossi


    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.

  5. Elucidating the impact of nitrate and labile carbon application on spatial heterogeneity of denitrification by 15N modelling (United States)

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


    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.

  6. Enhancing nitrogen removal efficiency and reducing nitrate liquor recirculation ratio by improving simultaneous nitrification and denitrification in integrated fixed-film activated sludge (IFAS) process. (United States)

    Bai, Yang; Zhang, Yaobin; Quan, Xie; Chen, Shuo


    An integrated fixed-film activated sludge (IFAS) process (G1) and an activated sludge anoxic-oxic process (G2) were operated at nitrate liquor recirculation ratio (R) of 100, 200 and 300% to investigate the feasibility of enhancing nitrogen removal efficiency (RTN) and reducing R by improving simultaneous nitrification and denitrification (SND) in the IFAS process. The results showed that the effluent NH4(+)-N and total nitrogen (TN) of G1 at R of 200% were less than 1.5 and 14.5 mg/L, satisfying the Chinese discharge standard (NH4(+)-N removal efficiency ranged 15-19%, which was the main reason that the RTN was improved in the IFAS process. Therefore, the IFAS process was an effective method for improving RTN and reducing R. In practical application, this advantage of the IFAS process can decrease the electricity consumption for nitrate liquor recirculation flow, thereby saving operational costs.

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

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


    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 springs and suggest that ammonia oxidation may be a major source of energy fuelling primary production.

  8. Denitrification by Rhizobium meliloti

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, A.


    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

  9. Denitrification in Sinorhizobium meliloti. (United States)

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


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

  10. Ultrasound-assisted activation of zero-valent magnesium for nitrate denitrification: identification of reaction by-products and pathways. (United States)

    Ileri, Burcu; Ayyildiz, Onder; Apaydin, Omer


    Zero-valent magnesium (Mg(0)) was activated by ultrasound (US) in an aim to promote its potential use in water treatment without pH control. In this context, nitrate reduction was studied at batch conditions using various doses of magnesium powder and ultrasound power. While neither ultrasound nor zero-valent magnesium alone was effective for reducing nitrate in water, their combination removed up to 90% of 50 mg/L NO3-N within 60 min. The rate of nitrate reduction by US/Mg(0) enhanced with increasing ultrasonic power and magnesium dose. Nitrogen gas (N2) and nitrite (NO2(-)) were detected as the major reduction by-products, while magnesium hydroxide Mg(OH)2 and hydroxide ions (OH(-)) were identified as the main oxidation products. The results from SEM-EDS measurements revealed that the surface oxide level decreased significantly when the samples of Mg(0) particles were exposed to ultrasonic treatment. The surface passivation of magnesium particles was successfully minimized by mechanical forces of ultrasound, which in turn paved the way to sustain the catalyst activity toward nitrate reduction.

  11. Vertical distribution of denitrification in an estuarine sediment: integrating sediment flowthrough reactor experiments and microprofiling via reactive transport modeling. (United States)

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


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

  12. Cloth catalysts in water denitrification. II. Removal of nitrates using Pd-Cu supported on glass fibers


    Matatov-Meytal, Yu.; Barelko, V.; Yuranov, I.; Kiwi-Minsker, L.; Renken, A.; Sheintuch, M.


    The use of glass fibers in the form of woven cloth (GFC), as a new type of catalytic support, was studied for the reduction of aqueous nitrate solutions using a Pd/Cu–GFC catalyst. The activity (per gram Pd) and selectivity to nitrogen were found to be comparable with those found for Pd–Cu catalysts supported on the other carriers. The maximal initial removal activity was found for a catalyst with a Pd/(Pd+Cu) ratio of 0.81. The corresponding activity was 0.7 mmol min-1 (gPd)-1, and the selec...

  13. Natural Denitrification in the Saturated Zone: A Review (United States)

    Korom, Scott F.


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

  14. Nitrates (United States)

    ... Blockers Angiotensin-Converting Enzyme (ACE) Inhibitors Antiarrhythmics Anticoagulants Antiplatelet Therapy Aspirin Beta-Blockers Blood Thinners Calcium Channel Blockers Digitalis Medicines Diuretics Inotropic Agents Statins, Cholesterol-Lowering Medicines Nitrates Disclaimer The information ...

  15. Patch-scale controls on denitrification in stream bed sediments (United States)

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


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

  16. The enzymes associated with denitrification (United States)

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


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

  17. The potential of dairy wastewater for denitrification

    Directory of Open Access Journals (Sweden)

    Tibela Landeka Dragičević


    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.

  18. Bedforms as Biocatalytic Filters: A Pumping and Streamline Segregation Model for Nitrate Removal in Permeable Sediments. (United States)

    Azizian, Morvarid; Grant, Stanley B; Kessler, Adam J; Cook, Perran L M; Rippy, Megan A; Stewardson, Michael J


    Bedforms are a focal point of carbon and nitrogen cycling in streams and coastal marine ecosystems. In this paper, we develop and test a mechanistic model, the "pumping and streamline segregation" or PASS model, for nitrate removal in bedforms. The PASS model dramatically reduces computational overhead associated with modeling nitrogen transformations in bedforms and reproduces (within a factor of 2 or better) previously published measurements and models of biogeochemical reaction rates, benthic fluxes, and in-sediment nutrient and oxygen concentrations. Application of the PASS model to a diverse set of marine and freshwater environments indicates that (1) physical controls on nitrate removal in a bedform include the pore water flushing rate, residence time distribution, and relative rates of respiration and transport (as represented by the Damkohler number); (2) the biogeochemical pathway for nitrate removal is an environment-specific combination of direct denitrification of stream nitrate and coupled nitrification-denitrification of stream and/or sediment ammonium; and (3) permeable sediments are almost always a net source of dissolved inorganic nitrogen. The PASS model also provides a mechanistic explanation for previously published empirical correlations showing denitrification velocity (N2 flux divided by nitrate concentration) declines as a power law of nitrate concentration in a stream (Mulholland et al. Nature, 2008, 452, 202-205).

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

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


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

  20. Denitrification in human dental plaque

    Directory of Open Access Journals (Sweden)

    Verstraete Willy


    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.

  1. The kinetics of denitrification in permeable sediments

    DEFF Research Database (Denmark)

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


    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...... 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...

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

    DEFF Research Database (Denmark)

    Klitten, Laura Line; Alhede, Morten; Kolpen, Mette;


    Chronic Pseudomonas aeruginosa lung infection is the most severe complication in patients with cystic fibrosis (CF). The infection is characterized by the formation of biofilm surrounded by numerous polymorphonuclear leukocytes (PMNs) and strong O2 depletion in the endobronchial mucus. We have...... reported that O2 is mainly consumed by the activated PMNs, while O2 consumption by aerobic respiration is diminutive and nitrous oxide (N2O) is produced in infected CF sputum. This suggests that the reported growth rates of P. aeruginosa in lungs and sputum may result from anaerobic respiration using...... comparable to our reported growth rates in the majority of P. aeruginosa cells in CF lungs and sputum. Thus, we have demonstrated that denitrification is required for P. aeruginosa growth in infected endobronchial CF mucus....

  3. Heterotrophic denitrification of aquaculture effluent using fluidized sand biofilters (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...

  4. 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


    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.

  5. 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


    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.

  6. Biological denitrification in a fluidized bed. (United States)

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


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

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

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

  9. Nitrate removal from high strength nitrate-bearing wastes in granular sludge sequencing batch reactors. (United States)

    Krishna Mohan, Tulasi Venkata; Renu, Kadali; Nancharaiah, Yarlagadda Venkata; Satya Sai, Pedapati Murali; Venugopalan, Vayalam Purath


    A 6-L sequencing batch reactor (SBR) was operated for development of granular sludge capable of denitrification of high strength nitrates. Complete and stable denitrification of up to 5420 mg L(-1) nitrate-N (2710 mg L(-1) nitrate-N in reactor) was achieved by feeding simulated nitrate waste at a C/N ratio of 3. Compact and dense denitrifying granular sludge with relatively stable microbial community was developed during reactor operation. Accumulation of large amounts of nitrite due to incomplete denitrification occurred when the SBR was fed with 5420 mg L(-1) NO3-N at a C/N ratio of 2. Complete denitrification could not be achieved at this C/N ratio, even after one week of reactor operation as the nitrite levels continued to accumulate. In order to improve denitrification performance, the reactor was fed with nitrate concentrations of 1354 mg L(-1), while keeping C/N ratio at 2. Subsequently, nitrate concentration in the feed was increased in a step-wise manner to establish complete denitrification of 5420 mg L(-1) NO3-N at a C/N ratio of 2. The results show that substrate concentration plays an important role in denitrification of high strength nitrate by influencing nitrite accumulation. Complete denitrification of high strength nitrates can be achieved at lower substrate concentrations, by an appropriate acclimatization strategy.

  10. 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.


    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

  11. Linkages between denitrification and dissolved organicmatter quality, Boulder Creek watershed, Colorado (United States)

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


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

  12. Physicochemical properties influencing denitrification rate and microbial activity in denitrification bioreactors (United States)

    Schmidt, C. A.


    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;

  13. Impact of Aquifer Heterogeneities on Autotrophic Denitrification. (United States)

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


    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.

  14. A Network Biology Approach to Denitrification in Pseudomonas aeruginosa (United States)

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


    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

  15. Analysis of denitrification process in the groundwater of floodplains using a modelling approach (United States)

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


    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

  16. Pore-water distribution and quantification of diffusive benthic fluxes of nutrients in the Huanghai and East China Seas sediments

    Institute of Scientific and Technical Information of China (English)


    The distribution of nitrate, nitrite, ammonia, phosphate and silicate in pore-water and their exchange between sediments and overlying waters (benthic flux) were determined at nine locations on the shelve of Huanghai and East China Seas. On the basis of the redox potential of sediments and nutrients distributions in the pore-waters, it is found that the benthic sediments are being in a suboxic to anoxic environment in the Huanghai and East China Seas. The nutrients distribution in the pore-waters is mainly controlled by the sediment environment, and ammonia is the major inorganic nitrogen in the pore-waters. On the basis of benthic fluxes of untrients calculated using Fick's first law, there is remarkable efflux of ammonia, dissolved inorganic nitrogen(DIN), phosphate and silicate from the sediments to the overlying waters in the study area, and their benthic fluxes are 299.3~2 214.8, 404.4~2 159.5 , 5.5~18.8 and cate for the overlying water. At most stations, the nitrate flux was from the overlying waters to the sediments, which suggests that suboxic organic matter decomposition via denitrification is dominated in the most area of Huanghai and East China Seas. High benthic fluxes appearing in the coastal area and relatively low benthic fluxes occurring in the shelf area are found and are consistent with primary productivity zoning in the study area. On the other hand, the ammonia flux displays an exponential decrease with water depth increase and an exponential increase with the bottom water temperature. However, others do not display this trend.

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

    DEFF Research Database (Denmark)

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

    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...... 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...

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

    Directory of Open Access Journals (Sweden)

    Annelies J Veraart

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Sheng, E-mail: [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)


    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.

  20. Stimulating nitrate removal processes of restored wetlands. (United States)

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


    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.

  1. Linking denitrification and infiltration rates during managed groundwater recharge. (United States)

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


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

  2. Numerical Modeling of Natural and Enhanced Denitrification Processes in Aquifers (United States)

    Kinzelbach, Wolfgang; SchäFer, Wolfgang; Herzer, JöRg


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

  3. Nitrate Removal from Ground Water: A Review


    Archna *; Surinder K. Sharma; Ranbir Chander Sobti


    Nitrate contamination of ground water resources has increased in Asia, Europe, United States, and various other parts of the world. This trend has raised concern as nitrates cause methemoglobinemia and cancer. Several treatment processes can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that biological denitrification is more acceptable for nitrate removal than reverse osmosis and ion ex...

  4. Impact of Sulfide on Nitrate Conversion in Eutrophic Nitrate-Rich Marine Sludge

    DEFF Research Database (Denmark)

    Schwermer, Carsten U.; Krieger, Bärbel; Lavik, Gaute


    IMPACT OF SULFIDE ON NITRATE CONVERSION IN EUTROPHIC NITRATE-RICH MARINE SLUDGE C.U. Schwermer 1, B.U. Krieger 2, G. Lavik 1, A. Schramm 3, J. van Rijn 4, D. de Beer 1, D. Minz 5, E. Cytryn 4, M. Kuypers 1, A. Gieseke 1 1 Max Planck Institute for Marine Microbiology, Bremen, Germany; 2 Dept...... nitrate conversion from denitrification to dissimilatory nitrate-reduction to ammonium (DNRA). In situ microsensor profiling in stagnant sludge revealed the typical stratification of nitrate reduction on top of sulfate reduction. Increasing the bulk nitrate concentration lead to a downward shift....... Our results show that the presence of sulfide generally decreased growth rates but increased N2O production. We conclude that sulfide plays a key role in causing incomplete denitrification, presumably by inhibiting the N2O reductase, and enhancing DNRA compared to denitrification.  ...

  5. Biological nitrate removal using wheat straw and PLA as substrate. (United States)

    Fan, Zhenxing; Hu, Jun; Wang, Jianlong


    Biological nitrate removal using wheat straw and polylactic acid (PLA) as both carbon source and biofilm support was investigated. The results showed that biofilm could develop on the surface of wheat straw within 15 d, the denitrification rate was 0.067 mg-N/(g-wheat straw x h) and nitrate removal efficiency was about 100%. For PLA, the time required for biofilm development was 40 d, the denitrification rate was 0.0026 mg-N/(g-PLA x h) and nitrate removal efficiency could also reach 100%. Temperature had a substantial influence on the denitrification performance of both wheat straw and PLA. The FTIR analysis and SEM observation confirmed that wheat straw and PLA were used for denitrification, and explained some reasons for the differences between the two substrates. The wheat straw was superior to PLA when used as carbon source for nitrate removal, in terms of the denitrification rate.

  6. Autotrophic denitrification using hydrogen generated from metallic iron corrosion. (United States)

    Sunger, Neha; Bose, Purnendu


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

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

    Directory of Open Access Journals (Sweden)

    Petrovič Aleksandra


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

  8. Internal hydraulics of an agricultural drainage denitrification bioreactor (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...

  9. Combined denitrification and phosphorus removal in a biofilter

    DEFF Research Database (Denmark)

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


    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...

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

    NARCIS (Netherlands)

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


    Background - Global warming and the alteration of the global nitrogen cycle are major anthropogenic threats to the environment. Denitrification, the biological conversion of nitrate to gaseous nitrogen, removes a substantial fraction of the nitrogen from aquatic ecosystems, and can therefore help to

  11. Behavior of solid carbon sources for biological denitrification in groundwater remediation. (United States)

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


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

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

    Energy Technology Data Exchange (ETDEWEB)

    Bergwall, C.


    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

  13. [Study on hydrogen autotrophic denitrification of bio-ceramic reactor]. (United States)

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


    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.

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

    Institute of Scientific and Technical Information of China (English)

    LU Songliu; HU Hongying; SUN Yingxue; YANG Jia


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

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

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, J.M.


    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

  16. Denitrification 'Woodchip' Bioreactors for Productive and Sustainable Agricultural Systems (United States)

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


    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.

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

    Directory of Open Access Journals (Sweden)

    Haryun Kim


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

  18. 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


    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.

  19. Seasonal variability of denitrification efficiency in northern salt marshes: an example from the St. Lawrence Estuary. (United States)

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


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

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

    DEFF Research Database (Denmark)

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


    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...... was in some situations driven by organic matter alone. Nitrous oxide (N2O) became an increasingly important product of denitrification with increasing sulfide concentration and was >80% of the total N gas formation at 10 μM sulfide. The potential rates of denitrification measured in incubations at elevated...

  1. Denitrification and a nitrogen budget of created riparian wetlands. (United States)

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


    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.

  2. Evaluation of the denitrification rate of terraced paddy fields (United States)

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


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

  3. Benthic Cover (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 moderate-depth...

  4. Benthic foraminifera

    Digital Repository Service at National Institute of Oceanography (India)

    Saraswat, R.; Nigam, R.

    (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... (2009) Deep-sea benthic diversity linked to seasonality of pelagic productivity. Deep Sea Research Part I: Oceanographic Research Papers 56: 835-841. Culver S (1988) New foraminiferal depth zonation of the northwestern Gulf of Mexico. Palaios 3: 69...

  5. 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


    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.

  6. Denitrification and inference of nitrogen sources in the karstic Floridan Aquifer (United States)

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


    Aquifer denitrification is among the most poorly constrained fluxes in global and regional nitrogen budgets. The few direct measurements of denitrification in groundwaters provide limited information about its spatial and temporal variability, particularly at the scale of whole aquifers. Uncertainty in estimates of denitrification may also lead to underestimates of its effect on isotopic signatures of inorganic N, and thereby confound the inference of N source from these data. In this study, our objectives are to quantify the magnitude and variability of denitrification in the Upper Floridan Aquifer (UFA) and evaluate its effect on N isotopic signatures at the regional scale. Using dual noble gas tracers (Ne, Ar) to generate physical predictions of N2 gas concentrations for 112 observations from 61 UFA springs, we show that excess (i.e. denitrification-derived) N2 is highly variable in space and inversely correlated with dissolved oxygen (O2). Negative relationship between O2 and ??15NNO 3 across a larger dataset of 113 springs, well-constrained isotopic fractionation coefficients, and strong 15N: 18O covariation further support inferences of denitrification in this uniquely organic-matter-poor system. Despite relatively low average rates, denitrification accounted for 32% of estimated aquifer N inputs across all sampled UFA springs. Back-calculations of source ??15NNO 3 based on denitrification progression suggest that isotopically-enriched nitrate (NO3-) in many springs of the UFA reflects groundwater denitrification rather than urban- or animal-derived inputs. ?? Author(s) 2011.

  7. 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


    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.

  8. Effects of restoration and reflooding on soil denitrification in a leveed Midwestern floodplain. (United States)

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


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

  9. Nitrous Oxide Production by Abundant Benthic Macrofauna

    DEFF Research Database (Denmark)

    Stief, Peter; Schramm, Andreas

    Detritivorous macrofauna species co-ingest large quantities of microorganisms some of which survive the gut passage. Denitrifying bacteria, in particular, become metabolically induced by anoxic conditions, nitrate, and labile organic compounds in the gut of invertebrates. A striking consequence...... of the short-term metabolic induction of gut denitrification is the preferential production of nitrous oxide rather than dinitrogen. On a large scale, gut denitrification in, for instance, Chironomus plumosus larvae can increase the overall nitrous oxide emission of lake sediment by a factor of eight. We...... 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...

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

    Directory of Open Access Journals (Sweden)

    T. DeVries


    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.

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

    DEFF Research Database (Denmark)

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


    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...

  12. 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


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

  13. Nitrate reduction functional genes and nitrate reduction potentials persist in deeper estuarine sediments. Why?

    Directory of Open Access Journals (Sweden)

    Sokratis Papaspyrou

    Full Text Available Denitrification and dissimilatory nitrate reduction to ammonium (DNRA are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the

  14. Nitrate Reduction Functional Genes and Nitrate Reduction Potentials Persist in Deeper Estuarine Sediments. Why? (United States)

    Papaspyrou, Sokratis; Smith, Cindy J.; Dong, Liang F.; Whitby, Corinne; Dumbrell, Alex J.; Nedwell, David B.


    Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This

  15. Operation of a fluidized-bed denitrification bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, P.A.


    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.

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

    Institute of Scientific and Technical Information of China (English)


    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.

  17. Simultaneous nitrification and denitrification based on internal circulation baffled reactor

    Directory of Open Access Journals (Sweden)

    LU Xiaoya


    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.

  18. Study on crystallization of ammonium sulfate and ammonium nitrate by-produced from desulfurization and denitrification with oxidation and ammonia methods%氧化法、氨法脱硫、脱硝副产物硫酸铵、硝酸铵结晶研究

    Institute of Scientific and Technical Information of China (English)

    范学友; 贾勇; 钟秦


    Ammonium sulfate and ammonium nitrate were by-produced during the simultaneous desulfurization and denitrification for the flue gas by the combined oxidation and ammonia process.Ammonium nitrate was added on the basis of single crystallization of ammonium sulfate.The products were analyzed by laser particle size distribution meter,XRD,and SEM.Effects of evaporation temperature ,pH, stirring speed, and fly ash content on mixed crystallization of ammonium sulfate and ammonium nitrate were investigated.Results showed that the product of mixed crystals was cubic crystal; under the conditions of pH = 5, temperature of 60 ℃, stirring speed of 200 r/min,and no fly ash existed the distribution of particle size was even; the crystal size was the biggest when the fly ash content was 4 g/L.%运用氧化和氨法脱硫相结合的烟气同时脱硫、脱硝技术得到的副产物中主要含有硫酸铵和硝酸铵.在原有硫酸铵单独结晶的基础上加入了硝酸铵,利用激光粒度分布仪、XRD、扫描电镜对产物进行了分析,考察了蒸发温度、pH、搅拌速度、飞灰含量对二者混合结晶的影响.结果发现:混合结晶的产物为立方晶型;当结晶的pH控制在5左右、温度为60℃、搅拌速度为200r/min、无飞灰存在时得到的晶体粒径分布均匀;飞灰含量为4g/L时得到的晶体的平均粒径最大.

  19. Denitrification controls in urban riparian soils: implications for reducing urban nonpoint source nitrogen pollution. (United States)

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


    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

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


    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.

  1. Monitoring induced denitrification in an artificial aquifer recharge system. (United States)

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


    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

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

    Institute of Scientific and Technical Information of China (English)



    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.

  3. 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))


    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.

  4. Modeling the Effects of Hydrological and Biogeochemical Processes on Denitrification and Stream Nitrogen Losses in River Networks (United States)

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


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

  5. Microbiological Denitrification and Denitrifying Activity of Paracoccus Denitrificans

    Institute of Scientific and Technical Information of China (English)

    万曦; 万国江; 等


    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 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.

  6. O2 reduction and denitrification rates in shallow aquifers (United States)

    Tesoriero, Anthony J.; Puckett, Larry J.


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

  7. Effects of pentachlorophenol on the bacterial denitrification process

    Directory of Open Access Journals (Sweden)

    Bairen Yang


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

  8. Operation of a fluidized-bed bioreactor for denitrification

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

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

    Directory of Open Access Journals (Sweden)

    J. L. Riera


    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

  10. 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


    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

  11. Denitrification in a Sand and Gravel Aquifer: An Overview of a Long-Term Study (United States)

    Smith, R. L.


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

  12. Modeling and mitigation of denitrification 'woodchip' bioreactor phosphorus releases during treatment of aquaculture wastewater (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. Measuring potential denitrification enzyme activity rates using the membrane inlet mass spectrometer (United States)

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

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

  15. Dissimilatory nitrate reduction by Pseudomonas alcaliphila with an electrode as the sole electron donor. (United States)

    Su, Wentao; Zhang, Lixia; Li, Daping; Zhan, Guoqiang; Qian, Junwei; Tao, Yong


    Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were considered two alternative pathways of dissimilatory nitrate reduction. In this study, we firstly reported that both denitrification and DNRA occurred in Pseudomonas alcaliphila strain MBR with an electrode as the sole electron donor in a double chamber bio-electrochemical system (BES). The initial concentration of nitrate appeared as a factor determining the type of nitrate reduction with electrode as the sole electron donor at the same potential (-500 mV). As the initial concentration of nitrate increased, the fraction of nitrate reduced through denitrification also increased. While nitrite (1.38 ± 0.04 mM) was used as electron acceptor instead of nitrate, the electrons recovery via DNRA and denitrification were 43.06 ± 1.02% and 50.51 ± 1.37%, respectively. The electrochemical activities and surface topography of the working electrode catalyzed by strain MBR were evaluated by cyclic voltammetry and scanning electron microscopy. The results suggested that cells of strain MBR were adhered to the electrode, playing the role of electron transfer media for nitrate and nitrite reduction. Thus, for the first time, the results that DNRA and denitrification occurred simultaneously were confirmed by powering the strain with electricity. The study further expanded the range of metabolic reactions and had potential value for the recognization of dissimilatory nitrate reduction in various ecosystems.

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

    DEFF Research Database (Denmark)

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


    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...

  17. Denitrification characteristics of a sulfur autotrophic denitrification reactor

    Directory of Open Access Journals (Sweden)

    Chenxiao ZHANG


    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%.

  18. Molecular Approaches to Studying Denitrification (United States)

    Voytek, M. A.


    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.

  19. Tradeoffs in regulating ecosystem services in East African Papyrus Wetlands: Denitrification as a case study (United States)

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


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

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

    Directory of Open Access Journals (Sweden)

    J. B. Heffernan


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

  1. Preparation of Pd-Cu Bimetal Catalyst Loaded on Ion Exchange Resin and its Catalytic Denitrification for Water Containing Nitrate%离子交换树脂负载Pd-Cu双金属催化剂的制备及其对硝酸盐的催化脱除作用

    Institute of Scientific and Technical Information of China (English)

    高建峰; 徐春彦; 高保娇; 庄源益


      The loading-type Pd-Cu bimetal catalyst was prepared using anion exchange resin (AIER) as carrier and complex reagent EDTA as an intermedium. The as-prepared catalyst was used in reduction of nitrate in water to remove nitrate using H2 as reductant. The effects of the composition of bimetal, the property of the carrier and the presence of NaCl on the denitrification were investigated. The results showed that the metal ions (Cu2+and Pd2+) can be combined onto resin surface by the strong adsorption of AIER towards EDTA and the strong chelation of EDTA for metal ions. Via reduction of hydrazine hydrate for the metal ions, the loading-type catalyst Pd-Cu/AIER with high bimetal capacity and firm combination property were obtained. For the aqueous solution mere containing nitrate, NO3- only was reduced into NH4+ by the catalysis of Pd-Cu/ AIER. In the presence of higher concentration NaCl, the reduction of NO3-into N2 could be accelerated greatly. The activity and selectivity of the catalyst prepared is poorer if the weak alkaline anion exchange resins were used.%  采用阴离子交换树脂(AIER)为载体,以络合剂EDTA为媒介物,制备了Pd-Cu双金属负载性型催化剂;以H2为还原剂,将催化剂应用于水介质中NO3-还原为N2的脱除反应;考察了双金属催化剂组成、载体阴离子交换树脂的性质及水介质中NaCl存在对还原脱除反应的影响规律.研究结果表明,凭借阴离子交换树脂对EDTA强烈的吸附作用及EDTA对金属离子的强螯合作用,可将大量的金属离子(Cu2+与Pd2+)结合到树脂表面,再通过水合肼的还原作用,可制得金属负载量高且结合程度牢的双金属负载性型催化剂Pd-Cu/AIER.在单纯含有硝酸盐的水溶液中,在催化剂Pd-Cu/AIER的作用下,NO3-只能被还原为NH4+离子,不能还原为N2;水介质中大量氯离子的存在,能大大促进NO3-转变为N2的还原反应;载体阴离子交换树脂的碱性越弱,最终制得的催化剂活性与选择性越差.

  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


    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. The effect of floating vegetation on denitrification and greenhouse gas production in wetland mesocosms (United States)

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


    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

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

    Directory of Open Access Journals (Sweden)

    F. Oehler


    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.

  5. Autohydrogenotrophic denitrification of drinking water using a polyvinyl chloride hollow fiber membrane biofilm reactor. (United States)

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


    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.

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

    Institute of Scientific and Technical Information of China (English)

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


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

  7. 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


    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.

  8. 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


    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.

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


    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.

  10. Use of agro-food wastewaters for the optimisation of the denitrification process. (United States)

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


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

  11. Lateral Transfer of the Denitrification Pathway Genes among Thermus thermophilus Strains▿ (United States)

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


    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

  12. 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


    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...

  13. Benthic fluxes in a tropical estuary and their role in the ecosystem

    Digital Repository Service at National Institute of Oceanography (India)

    Pratihary, A; Naqvi, S.W.A; Naik, H.; Thorat, B.R.; Narvenkar, G.; Manjunatha, B.R.; Rao, V.P.

    ) sup(4-) and acted as a net sink of combined N because of the high rate of benthic denitrification as it could remove 22% of riverine DIN influx thereby protecting the eco system from eutrophication and consequent degradation. The estuarine sediment...


    Directory of Open Access Journals (Sweden)

    José Tavares de Sousa


    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.

  15. [Nitrate removal by a strain of nitrate-dependent Fe (II) -oxidizing bacteria]. (United States)

    Wang, Hong-Yu; Yang, Kai; Zhang, Qian; Ji, Bin; Chen, Dan; Sun, Yu-Chong; Tian, Jun


    A nitrate-dependent Fe(II)-oxidizing bacterial strain, named W5, was isolated from the sediment of the East Lake in Wuhan. Strain W5 was studied for its characteristics of denitrification and nitrogen removal. According to its physiological and biochemical characteristics and the analysis of its 16S rRNA gene sequence, strain W5 was identified as Microbacterium sp. The optimal denitrification performance can be obtained under conditions of NO3(-) -N 40 mg x L(-1), Fe2+ 500 mg x L(-1) and pH 6.8-7.0. After one week of cultivation under optimal conditions, nitrate removal percentage reached 87.0%. During the process of the culture, the nitrite nitrogen concentration was no more than 0.31 mg x L(-1) and there was no ammonia nitrogen production. It was indicated that the nitrate was mostly converted into N2. The consumption rate of Fe2+ was 95.2%.

  16. Nitrate removal using different carbon substrates in a laboratory model. (United States)

    Hashemi, Seyyed Ebrahim; Heidarpour, Manouchehr; Mostafazadeh-Fard, Behrouz


    Agricultural fields have been frequently identified as major contributors of nitrate leaching into surface and ground waters. Tile drains can act as direct pathways, transferring leached nitrate to surface water. Bioreactor filters are useful for the removal of nitrate from drainage waters; however, these filters require an external carbon supply to sustain denitrification. In this study, four organic carbon sources including wood, barley straw, rice husks, and date palm leaf, were used to enhance denitrification and the effects of water velocity and influent nitrate concentration on the nitrate removal were evaluated. Cumulative nitrate removal was highest for the date palm leaf treatments and was lowest for the wood treatments. The effects were in decreasing order for date palm leaf, barley straw, rice husks, and wood, respectively. The performance of the biofilters improved with increasing influent nitrate concentration and decreasing water velocity, allowing for high nitrate removal rates to be achieved. The results showed that all of the treatments had reduced the effluent nitrate concentrations below the USEPA maximum contaminant level for drinking water of 45 mg L(-1) nitrate at the end of the study.

  17. Long term performance of the Waterloo denitrification barrier

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  18. Comparison of denitrification performances using PLA/starch with different mass ratios as carbon source. (United States)

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


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

  19. A Microbial Fuel Cell Modified with Carbon Nanomaterials for Organic Removal and Denitrification

    Directory of Open Access Journals (Sweden)

    Njud S. Alharbi


    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.

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

    DEFF Research Database (Denmark)

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


    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....

  1. Identifying functional zones of denitrification in heterogeneous aquifer systems by numerical simulations - a case study (United States)

    Jang, E.; Kalbacher, T.; He, W.; Shao, H.; Schueth, C.; Kolditz, O.


    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

  2. Biological processes for environmental control of effluent streams in the nuclear fuel cycle. [Denitrification; removal of heavy metals

    Energy Technology Data Exchange (ETDEWEB)

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


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

  3. Nitrogen dose-response relationships: benthic algae and macroinvertebrates in running water


    R Wright; Eriksen, T.; Schneider, S.


    Nitrogen deposition affects freshwater biodiversity in two ways: by contributing to acidification via nitrate in runoff, and by acting as a nutrient. We used data for two organism groups, benthic algae (224 sites) and benthic invertebrates (62 sites), to test if N as a nutrient affects the species numbers of these groups in running water. Neither of these groups showed significant relationships with nitrogen, except for a positive relationship between nitrate concentration and the number of b...

  4. Nitrate removal by microbial enhancement in a riparian wetland. (United States)

    Pei, Yuansheng; Yang, Zhifeng; Tian, Binghui


    A riparian wetland (RW) was constructed in a river bend to study the effect of the addition of Bacillus subtilis FY99-01 on nitrate removal. Nitrate was removed more efficiently in the summer than in the winter owing to integrated hydraulic, microbial and environmental effects. The maximal nitrate removal and the mean nitrate loss rate in the RW were 36.1% and 50.5 g/m(2)/yr, respectively. Statistic analyses indicated that the redox potential was very significant to denitrification while organic matter in the outflow, temperature and nitrate in the inflow significantly affected nitrate removal. These results suggest that an RW can be a cost-effective approach to enhance microbial nitrate removal and can potentially be extended to similar river bends.

  5. 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.


    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

  6. Nitrate removal in deep sediments of a nitrogen-rich river network: A test of a conceptual model (United States)

    Stelzer, Robert S.; Bartsch, Lynn


    Many estimates of nitrogen removal in streams and watersheds do not include or account for nitrate removal in deep sediments, particularly in gaining streams. We developed and tested a conceptual model for nitrate removal in deep sediments in a nitrogen-rich river network. The model predicts that oxic, nitrate-rich groundwater will become depleted in nitrate as groundwater upwelling through sediments encounters a zone that contains buried particulate organic carbon, which promotes redox conditions favorable for nitrate removal. We tested the model at eight sites in upwelling reaches of lotic ecosystems in the Waupaca River Watershed that varied by three orders of magnitude in groundwater nitrate concentration. We measured denitrification potential in sediment core sections to 30 cm and developed vertical nitrate profiles to a depth of about 1 m with peepers and piezometer nests. Denitrification potential was higher, on average, in shallower core sections. However, core sections deeper than 5 cm accounted for 70%, on average, of the depth-integrated denitrification potential. Denitrification potential increased linearly with groundwater nitrate concentration up to 2 mg NO3-N/L but the relationship broke down at higher concentrations (> 5 mg NO3-N/L), a pattern that suggests nitrate saturation. At most sites groundwater nitrate declined from high concentrations at depth to much lower concentrations prior to discharge into the surface water. The profiles suggested that nitrate removal occurred at sediment depths between 20 and 40 cm. Dissolved oxygen concentrations were much higher in deep sediments than in pore water at 5 cm sediment depth at most locations. The substantial denitrification potential in deep sediments coupled with the declines in nitrate and dissolved oxygen concentrations in upwelling groundwater suggest that our conceptual model for nitrate removal in deep sediments is applicable to this river network. Our results suggest that nitrate removal rates

  7. Nitrate removal in deep sediments of a nitrogen-rich river network: A test of a conceptual model (United States)

    Stelzer, Robert S.; Bartsch, Lynn A.


    Many estimates of nitrogen removal in streams and watersheds do not include or account for nitrate removal in deep sediments, particularly in gaining streams. We developed and tested a conceptual model for nitrate removal in deep sediments in a nitrogen-rich river network. The model predicts that oxic, nitrate-rich groundwater will become depleted in nitrate as groundwater upwelling through sediments encounters a zone that contains buried particulate organic carbon, which promotes redox conditions favorable for nitrate removal. We tested the model at eight sites in upwelling reaches of lotic ecosystems in the Waupaca River Watershed that varied by three orders of magnitude in groundwater nitrate concentration. We measured denitrification potential in sediment core sections to 30 cm and developed vertical nitrate profiles to a depth of about 1 m with peepers and piezometer nests. Denitrification potential was higher on average in shallower core sections. However, core sections deeper than 5 cm accounted for 70% on average of the depth-integrated denitrification potential. Denitrification potential increased linearly with groundwater nitrate concentration up to 2 mg NO3-N/L, but the relationship broke down at higher concentrations (>5 mg NO3-N/L), a pattern that suggests nitrate saturation. At most sites groundwater nitrate declined from high concentrations at depth to much lower concentrations prior to discharge into the surface water. The profiles suggested that nitrate removal occurred at sediment depths between 20 and 40 cm. Dissolved oxygen concentrations were much higher in deep sediments than in pore water at 5 cm sediment depth at most locations. The substantial denitrification potential in deep sediments coupled with the declines in nitrate and dissolved oxygen concentrations in upwelling groundwater suggest that our conceptual model for nitrate removal in deep sediments is applicable to this river network. Our results suggest that nitrate removal rates can

  8. Nitrate reduction in geologically heterogeneous catchments

    DEFF Research Database (Denmark)

    Refsgaard, Jens Christian; Auken, Esben; Bamberg, C.A.;


    In order to fulfil the requirements of the EU Water Framework Directive nitrate load from agricultural areas to surface water in Denmark needs to be reduced by about 40%. The regulations imposed until now have been uniform, i.e. the same restrictions for all areas independent of the subsurface...... conditions. Studies have shown that on a national basis about 2/3 of the nitrate leaching from the root zone is reduced naturally, through denitrification, in the subsurface before reaching the streams. Therefore, it is more cost-effective to identify robust areas, where nitrate leaching through the root...... the entire catchment. However, as distributed models often do not include local scale hydrogeological heterogeneities, they are typically not able to make accurate predictions at scales smaller than they are calibrated. We present a framework for assessing nitrate reduction in the subsurface...

  9. 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

  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


    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. Denitrifying bioreactors for nitrate removal from tile drained cropland (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 ...

  12. Models of oxic respiration, denitrification and sulfate reduction in zones of coastal upwelling (United States)

    Canfield, D. E.


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

  13. Denitrification in a BTEX Contaminated Aquifer Containing Reduced Sulfur (United States)

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


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

  14. Ammonium removal by Agrobacterium sp. LAD9 capable of heterotrophic nitrification-aerobic denitrification. (United States)

    Chen, Qian; Ni, Jinren


    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.

  15. 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;


    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...

  16. 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


    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.

  17. 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 (United States)

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


    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.

  18. 伊乐藻和氮循环菌技术对太湖氮素吸收和反硝化的影响%Nitrogen Uptake and Denitrification Study on the Joint Treatment of Aquatic Vegetation and Immobilized Nitrogen Cycling Bacteria in Taihu Lake

    Institute of Scientific and Technical Information of China (English)

    刘丹丹; 李正魁; 叶忠香; 张万广


    Undisturbed sediment cores were collected from Meiliang Bay, Taihu Lake. Immobilized nitrogen cycling bacteria (INCB), Elodea nuttallii were added to four groups of restoration incubation chambers respectively to explore the nitrogen removal mechanism in different restoration treatments. 15N tracer and isotope pairing technique were used to determine the rates of plant uptake and denitrification in different treatments. The results showed that denitrification rates were significantly different among the treatments, while cores with addition of both INCB and Elodea nuttallii achieved the highest denitrification rate of 99. 35 μmol·( m2·h) -1 and plant uptake rate of 36. 55μg·( m2·h) -1 . Elodea nuttallii in the cores could assimilate nitrate itself and enhance coupled nitrification-denitrification. Compared with plant uptake, denitrification was the main pathway of nitrogen removal. The results also showed that the combination of Elodea nuttallii and INCB could promote benthic nitrogen removal and purification of water body.%从太湖梅梁湾采集无扰动泥芯样,分别添加固定化氮循环细菌、水生植物伊乐藻建立室内微宇宙,模拟生态修复,探讨不同修复处理下,硝氮的去除机制.采用15N标记结合同位素配对技术测定了各生态模拟柱中的反硝化速率和植物吸收速率.结果表明,不同处理的实验柱反硝化速率差异明显,同时添加了水生植物和固定化氮循环细菌的实验柱反硝化速率最高,为99.35μmol·( m2·h)-1,植物氮吸收速率为36.55μg·( m2·h)-1.沉水植物伊乐藻在自身吸收氮素的同时也提高了耦合硝化反硝化的作用.与植物吸收相比,反硝化过程是主要的氮去除途径.沉水植物与固定化氮循环菌组合生态修复技术促进了湖泊水体氮素的脱除,起到了净化作用.

  19. Reductive denitrification using zero-valent iron and bimetallic iron. (United States)

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


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

  20. Nitrous oxide emission from denitrification in stream and river networks (United States)

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


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

  1. Spatial-seasonal variation of soil denitrification under three riparian vegetation types around the Dianchi Lake in Yunnan, China. (United States)

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


    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.

  2. 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;


    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...

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

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


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

  4. Numerical modeling of coupled nitrification-denitrification in sediment perfusion cores from the hyporheic zone of the Shingobee River, MN (United States)

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


    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.

  5. Engineered bioretention for removal of nitrate from stormwater runoff. (United States)

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


    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.

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

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


    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.

  7. Eddies reduce denitrification and compress habitats in the Arabian Sea (United States)

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


    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.

  8. Mustard catch crop enhances denitrification in shallow groundwater beneath a spring barley field. (United States)

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


    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.

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


    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.

  10. Non-linear hydraulic properties of woodchips necessary to design denitrification beds (United States)

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


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

  11. Drinking Water Denitrification using Autotrophic Denitrifying Bacteria in a Fluidized Bed Bioreactor 

    Directory of Open Access Journals (Sweden)

    Abdolmotaleb Seid-mohammadi


    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.

  12. [Denitrification and kinetic characteristics using biodegradable polymers as carbon source and biofilm carrier]. (United States)

    Lai, Cai-sheng; Tan, Hong-xin; Luo, Guo-zhi; Ruan, Yun-jie; Zhou, Wei; Sun, Da-chuan


    The PBS material that in the form of insoluble biodegradable polymers pellets was investigated as the solid carbon source and the biofilm carrier for nitrate removal from wastewater. The denitrification of nitrate removal and kinetic process were carried out in a packed-bed reactor in order to remove nitrate in recirculation aquaculture system. The experimental results indicated that the optimal influent loading rate was in the range of 0.107-1.098 kg/(m3 x d), when the water temperature was (29 +/- 1) degrees C and the influent nitrate concentration was in the range of 25-334 mg/L. The maximum nitrate volumetric removal rate of 0.577 kg/(m3 x d) was achieved at the influent loading rate of 1.098 kg/(m3 x d). When the influent loading rate exceeded 1.098 kg/(m3 x d), the nitrate volumetric removal rate was declined. The kinetic experimental results show that the denitrification rate of PBS as the solid carbon source and the biofilm carrier corresponds to first-order kinetics. Based on the kinetics characteristics, constants n and K used in Eckenfelder model were deduced, which can be successfully applied for the prediction of effluent nitrate concentration. The two groups' predictive values and actual values were analyzed by using SPSS 16.0 software for Paired-Samples t test analysis. The Paired-Samples t test analysis indicates that the corresponding p > 0.05 values are 0.553 and 0.632, which proved that no significant differences exist between the predictive values and actual values of the model.

  13. 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.


    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

  14. Comparison of nitrate attenuation characterization methods at the Uranium mill tailing site in Monument Valley, Arizona (United States)

    Carroll, Kenneth C.; Jordan, Fiona L.; Glenn, Edward P.; Jody Waugh, W.; Brusseau, Mark L.


    SummarySeveral methods for characterizing the occurrence and rate of nitrate attenuation were tested at a field site near Monument Valley, Arizona. Spatial and temporal nitrate concentration data collected from a transect of monitoring wells located along the plume centerline were analyzed to evaluate the overall rates of natural attenuation. The occurrence and rate of denitrification was evaluated through microcosm experiments, nitrogen isotopic fractionation analysis, and solute-transport modeling. First-order denitrification-rate coefficients calculated with each method were comparable. In addition, the composite natural attenuation rate coefficient was similar to the denitrification-rate coefficients, which suggests that microbially induced decay primarily controls nitrate attenuation at the site. This

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

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


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

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

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


    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.

  17. 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


    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.

  18. Dissimilatory nitrate reduction processes in sediments of urban river networks: Spatiotemporal variations and environmental implications. (United States)

    Cheng, Lv; Li, Xiaofei; Lin, Xianbiao; Hou, Lijun; Liu, Min; Li, Ye; Liu, Sai; Hu, Xiaoting


    Urbanizations have increased the loadings of reactive nitrogen in urban riverine environments. However, limited information about dissimilatory nitrate reduction processes and associated contributions to nitrogen removal is available for urban riverine environments. In this study, sediment slurry experiments were conducted with nitrogen isotope-tracing technique to investigate the potential rates of denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) and their contributions to nitrate reduction in sediments of urban river networks, Shanghai. The potential rates of denitrification, anammox and DNRA measured in the study area ranged from 0.193 to 98.7 nmol N g(-1) h(-1) dry weight (dw), 0.0387-23.7 nmol N g(-1) h(-1) dw and 0-10.3 nmol N g(-1) h(-1) dw, respectively. Denitrification and DNRA rates were higher in summer than in winter, while anammox rates were greater in winter than in summer for most sites. Dissolved oxygen, total organic carbon, nitrate, ammonium, sulfide, Fe(II) and Fe(III) were found to have significant influence on these nitrate reduction processes. Denitrification contributed 11.5-99.5%% to total nitrate reduction, as compared to 0.343-81.6% for anammox and 0-52.3% for DNRA. It is estimated that nitrogen loss of approximately 1.33 × 10(5) t N year(-1) was linked to both denitrification and anammox processes, which accounted for about 20.1% of total inorganic nitrogen transported annually into the urban river networks of Shanghai. Overall, these results show the potential importance of denitrification and anammox in nitrogen removal and provide new insight into the mechanisms of nitrogen cycles in urban riverine environments.

  19. 2,4-D removal via denitrification using volatile fatty acids. (United States)

    He, X; Wareham, D G


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

  20. Evaluation of gasoline-denatured ethanol as a carbon source for denitrification. (United States)

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


    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.

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

    Directory of Open Access Journals (Sweden)

    Pradyut Kundu


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

  2. Ammonium assimilation: An important accessory during aerobic denitrification of Pseudomonas stutzeri T13. (United States)

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


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

  3. 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


    Anaerobic methane oxidation coupled to denitrification, also known as “nitrate/nitrite-dependent anaerobic methane oxidation” (n-damo), was discovered in 2006. Since then, only a few studies have identified this process and the associated microorganisms in natural environments. In aquatic sediments......, the close proximity of oxygen- and nitrate-consumption zones can mask n-damo as aerobic methane oxidation. We therefore investigated the vertical distribution and the abundance of denitrifying methanotrophs related to Candidatus Methylomirabilis oxyfera with cultivation-independent molecular techniques...... in the sediments of Lake Constance. Additionally, the vertical distribution of methane oxidation and nitrate consumption zones was inferred from high-resolution microsensor profiles in undisturbed sediment cores. M. oxyfera-like bacteria were virtually absent at shallow-water sites (littoral sediment) and were...

  4. Removal of nutrients in denitrification system using coconut coir fibre for the biological treatment of aquaculture wastewater. (United States)

    Manoj, Valsa Remony; Vasudevan, Namasivayam


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

  5. Box-modelling of the impacts of atmospheric nitrogen deposition and benthic remineralisation on the nitrogen cycle of the eastern tropical South Pacific (United States)

    Su, Bei; Pahlow, Markus; Oschlies, Andreas


    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.

  6. Insensitive Ammonium Nitrate. (United States)

    is reduced by replacing the ammonium nitrate with a solid solution of potassium nitrate in form III ammonium nitrate wherein the potassium nitrate...constitutes from more than zero to less than 50 weight percent of the solid solution . (Author)

  7. Excess nitrate loads to coastal waters reduces nitrate removal efficiency: mechanism and implications for coastal eutrophication. (United States)

    Lunau, Mirko; Voss, Maren; Erickson, Matthew; Dziallas, Claudia; Casciotti, Karen; Ducklow, Hugh


    Terrestrial ecosystems are becoming increasingly nitrogen-saturated due to anthropogenic activities, such as agricultural loading with artificial fertilizer. Thus, more and more reactive nitrogen is entering streams and rivers, primarily as nitrate, where it is eventually transported towards the coastal zone. The assimilation of nitrate by coastal phytoplankton and its conversion into organic matter is an important feature of the aquatic nitrogen cycle. Dissolved reactive nitrogen is converted into a particulate form, which eventually undergoes nitrogen removal via microbial denitrification. High and unbalanced nitrate loads to the coastal zone may alter planktonic nitrate assimilation efficiency, due to the narrow stochiometric requirements for nutrients typically shown by these organisms. This implies a cascade of changes for the cycling of other elements, such as carbon, with unknown consequences at the ecosystem level. Here, we report that the nitrate removal efficiency (NRE) of a natural phytoplankton community decreased under high, unbalanced nitrate loads, due to the enhanced recycling of organic nitrogen and subsequent production and microbial transformation of excess ammonium. NRE was inversely correlated with the amount of nitrate present, and mechanistically controlled by dissolved organic nitrogen (DON), and organic carbon (Corg) availability. These findings have important implications for the management of nutrient runoff to coastal zones.

  8. [Element Sulfur Autotrophic Denitrification Combined Anaerobic Ammonia Oxidation]. (United States)

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


    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.

  9. 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


    FROM THE GUT OF AN INSECT TO THE GLOBAL CLIMATE: DENITRIFICATION AND NITROUS OXIDE PRODUCTION INSIDE LAKE CHIRONOMIDAE P. Stief, L.P. Nielsen, N.P. Revsbech, A. Schramm Department of Biological Sciences, Microbiology, University of Aarhus, Denmark Denitrifying bacteria in lake sediments drive...... an environmentally relevant ecosystem function by reducing nitrate to dinitrogen gas. Thereby, they remove inorganic nitrogen that originates from organic matter mineralisation and anthropogenic pollution. Nitrous oxide, a greenhouse gas 300 times more potent than carbon dioxide, is emitted from lakes only...... as a minor fraction of the nitrate reduced. However, when lake sediments are densely colonised by macrofauna, the rates of nitrous oxide emission increase significantly. We hypothesise that the guts of bacterivorous macrofauna represent short-term habitats in which high denitrification activity...

  10. 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

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

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


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

  12. Inhibition of denitrification by ultraviolet radiation (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.


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

  14. Long-term Effects of Ethanol Addition on Denitrification At The Uranium Mill Tailing Site In Monument Valley, Arizona (United States)

    McMillan, A. L.; Borden, A. K.; Brusseau, M. L.; Carroll, K. C.; Akyol, N. H.; Berkompas, J. L.; Miao, Z.; Jordan, F.; Tick, G. R.; Waugh, J.; Glenn, E. P.


    Due to mining and processing of uranium at a site near Monument Valley, AZ, an extensive nitrate plume was produced in a shallow alluvial aquifer. Two pilot tests were conducted to evaluate the addition of ethanol as a carbon substrate to enhance natural denitrification. Aqueous geochemistry was characterized based upon groundwater samples collected before and after the addition of ethanol. Compound specific stable isotope analysis was also conducted. The results of the field tests showed that the concentration of nitrate decreased, while the concentration of nitrous oxide (a product of denitrification) increased. In addition, changes in aqueous concentrations of sulfate, iron, and manganese indicated that the ethanol amendment caused a change in prevailing redox conditions. The results of compound-specific stable isotope analysis for nitrate-nitrogen indicated that the nitrate concentration reductions were biologically mediated. Denitrification rate coefficients estimated for the pilot tests were approximately 50 times larger than resident-condition (non-enhanced) values obtained from prior characterization studies conducted at the site. Using the time at which nitrate concentrations began to decline for downgradient monitoring wells, and the associated inter-well distances, rough estimates of approximately 0.1-0.17 m/day were obtained for the effective reactive-front velocity. These values are within the range of mean pore-water velocities expected for the measured hydraulic conductivities and gradient. The nitrate concentrations in the injection zone have remained at levels three orders of magnitude below the initial values for many months, indicating that the ethanol amendments had a long-term impact on the local subsurface environment.

  15. 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


    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.

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

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


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

  17. Microbiological and molecular characterization of denitrification in biofilters treating pig manure. (United States)

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


    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.

  18. 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.


    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.

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

    Directory of Open Access Journals (Sweden)

    E. Martí


    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

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

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


    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.

  1. Drinking water decontamination by biological denitrification using fresh bamboo as inoculum source. (United States)

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


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

  2. Experimental evidence for aerobic bio-denitrification

    Institute of Scientific and Technical Information of China (English)


    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.

  3. Effect of carbon source and COD/NO₃⁻-N ratio on anaerobic simultaneous denitrification and methanogenesis for high-strength wastewater treatment. (United States)

    Xie, Li; Chen, Jinrong; Wang, Rui; Zhou, Qi


    The effect of carbon source and COD/NO(3)(-)-N ratio on denitrification and methanogenesis in mixed methanogenic matrix was investigated in this study. Industrial wastewater, anaerobic treated cassava stillage (CS) and glucose synthetic wastewater were used as carbon sources respectively for comparison. Experimental results showed that denitrification was the main nitrate reduction pathway for all COD/NO(3)(-)-N ratios tested in two substrates. Simultaneous denitrification and methanogenesis occurred at COD/NO(3)(-)-N higher than 7 regardless of carbon sources. Incomplete denitrification was observed at COD/NO(3)(-)-N ratio below 7 in both the anaerobic effluent of CS and glucose-fed cultures due to the insufficient available organic carbon. The nature of carbon sources was observed to play a key role in the nitrate and organic carbon utilization rates. COD/NO(3)(-)-N ratio had a strong effect on the organic matter utilization pathways. Methanization consumed more organic matter than denitrification with further increase of COD/NO(3)(-)-N ratio above 7 in two substrates. Results of VFA variation suggested that propionate and butyrate were preferably utilized by the denitrifiers than acetate.

  4. Biological filter capable of simultaneous nitrification and denitrification for Aquatic Habitat in International Space Station. (United States)

    Uemoto, H; Shoji, T; Uchida, S


    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

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

    KAUST Repository

    Balk, Melike


    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.

  6. Nitrate ammonification in mangrove soils: a hidden source of nitrite? (United States)

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


    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.

  7. Combined used of natural zeolites and microalgaes for the denitrification of wastewater from fertilizer plants; Uso combinado de zeolitas naturales y microalgas en la denitrificacion de aguas residuales

    Energy Technology Data Exchange (ETDEWEB)

    Soca Olazabal, N.; Blanco Toledo, F.; Pizarro Camacho, D.


    In our work we investigated the process of denitrification of waster-water with high percentage of nitrate and ammonia using natural zeolites that can be used later in agricultures fertilizer, because of the nitrogen load received. This effluents was used for micro algae growth reducing the nitrate concentration, the micro algae was Chlorella Vulgaris. The zeolite reduced the NH``+{sub 4} concentration up to 5 mg/l. and the NH``+{sub 4} concentration in the zeolite, it si very important in the agriculture. The chlorella Vulgaris reduces 30 mg/l of nitrate in six hours in the steady state. (Author) 9 refs.

  8. 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...

  9. Heterotrophic-autotrophic sequential system for reductive nitrate and perchlorate removal. (United States)

    Ucar, Deniz; Cokgor, Emine Ubay; Sahinkaya, Erkan


    Nitrate and perchlorate were identified as significant water contaminants all over the world. This study aims at evaluating the performances of the heterotrophic-autotrophic sequential denitrification process for reductive nitrate and perchlorate removal from drinking water. The reduced nitrate concentration in the heterotrophic reactor increased with increasing methanol concentrations and the remaining nitrate/nitrite was further removed in the following autotrophic denitrifying process. The performances of the sequential process were studied under varying nitrate loads of [Formula: see text] at a fixed hydraulic retention time of 2 h. The C/N ratio in the heterotrophic reactor varied between 1.24 and 2.77 throughout the study. Nitrate and perchlorate reduced completely with maximum initial concentrations of [Formula: see text] and 1000 µg/L, respectively. The maximum denitrification rate for the heterotrophic reactor was [Formula: see text] when the bioreactor was fed with [Formula: see text] and 277 mg/L methanol. For the autotrophic reactor, the highest denitrification rate was [Formula: see text] in the first period when the heterotrophic reactor performance was low. Perchlorate reduction was initiated in the heterotrophic reactor, but completed in the following autotrophic process. Effluent sulphate concentration was below the drinking water standard level of 250 mg/L and pH was in the neutral level.

  10. The interplay between transport and reaction rates as controls on nitrate attenuation in permeable, streambed sediments (United States)

    Lansdown, K.; Heppell, C. M.; Trimmer, M.; Binley, A.; Heathwaite, A. L.; Byrne, P.; Zhang, H.


    Anthropogenic nitrogen fixation and subsequent use of this nitrogen as fertilizer have greatly disturbed the global nitrogen cycle. Rivers are recognized hot spots of nitrogen removal in the landscape as interaction between surface water and sediments creates heterogeneous redox environments conducive for nitrogen transformations. Our understanding of riverbed nitrogen dynamics to date comes mainly from shallow sediments or hyporheic exchange flow pathways with comparatively little attention paid to groundwater-fed, gaining reaches. We have used 15N techniques to quantify in situ rates of nitrate removal to 1 m depth within a groundwater-fed riverbed where subsurface hydrology ranged from strong upwelling to predominantly horizontal water fluxes. We combine these rates with detailed hydrologic measurements to investigate the interplay between biogeochemical activity and water transport in controlling nitrogen attenuation along upwelling flow pathways. Nitrate attenuation occurred via denitrification rather than dissimilatory nitrate reduction to ammonium or anammox (range = 12 to >17,000 nmol 15N L-1 h-1). Overall, nitrate removal within the upwelling groundwater was controlled by water flux rather than reaction rate (i.e., Damköhler numbers rates of denitrification and short water residence time close to the riverbed surface balanced by slower rates of denitrification and water flux at depth. Within this permeable riverbed >80% of nitrate removal occurs within sediments not exposed to hyporheic exchange flows under base flow conditions, illustrating the importance of deep sediments as nitrate sinks in upwelling systems.

  11. Green Infrastructure Benefits for Communities Managing Nitrate in their Drinking Water Sources (United States)

    Nitrate in water moving through the “biologically active soil zone” of riparian zones, wetlands and streams may undergo denitrification. Therefore GI techniques such as conservation and restoration of riparian zones, wetlands and streams (daylighting) have the potential to remov...

  12. The feasibility of applying immature yard-waste compost to remove nitrate from agricultural drainage effluents: A preliminary assessment (United States)

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


    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.

  13. Microbial degradation of acenapthene and napthalene under denitrification conditions in soil--water systems: Annual report, October 1987

    Energy Technology Data Exchange (ETDEWEB)

    Mihelcic, J.R.; Luthy, R.G.


    This study examined the microbial degradation of acenaphthene and naphthalene under denitrification conditions at soil-to-water ratios of 1:25 and 1:50 with soil containing approximately 10/sup 5/ denitrifying organisms per gram of soil. Under nitrate-excess conditions, both acenaphthene and naphthalene were degraded microbially from initial aqueous-phase concentrations of about one and several mg/l, respectively, to nondetectable levels (<0.01 mg/l) in time periods less than 9 weeks. Acclimation periods of 12 to 36 days were observed prior to the onset of microbial degradation in tests with soil not previously exposed to PAH, while acclimation periods were absent in tests with soil reserved from prior PAH degradation tests. It was judged that the apparent acclimation period resulted from the time for a small population of organisms capable of PAH degradation to attain sufficient densities to exhibit detectable PAH reduction. About 0.9 percent of the naturally occurring soil organic carbon could be mineralized under denitrification conditions, and this accounted for the greater proportion of the nitrate depletion. The mineralization of the labile fraction of the soil organic carbon via microbial denitrification occurred without an observed acclimation period, and was rapid compared to PAH degradation. Under nitrate-limiting conditions the PAH compounds were stable owing to the depletion of nitrate via the more rapid process of soil organic carbon mineralization. The microbial degradation of the PAH compound depends on the interrelationships between: the desorption kinetics and the reversibility of desorption of sorbed compound from the soil, the concentration of PAH-degrading microorganisms, and the competing reaction for nitrate utilization via mineralization of the labile fraction of naturally occurring soil organic carbon. 44 refs., 10 figs.

  14. Influence of zero-valent iron nanoparticles on nitrate removal by Paracoccus sp. (United States)

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


    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.

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

    Directory of Open Access Journals (Sweden)

    Il-Nam Kim


    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.

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

    DEFF Research Database (Denmark)

    Carter, Mette Sustmann


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

  17. Characteristic of nitrous oxide production in partial denitrification process with high nitrite accumulation. (United States)

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


    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.

  18. Syringe test screening of microbial gas production activity: Cases denitrification and biogas formation. (United States)

    Østgaard, Kjetill; Kowarz, Viktoria; Shuai, Wang; Henry, Ingrid A; Sposob, Michal; Haugen, Hildegunn Hegna; Bakke, Rune


    Mass produced plastic syringes may be applied as vessels for cheap, simple and large scale batch culture testing. As illustrated for the cases of denitrification and of biogas formation, metabolic activity was monitored by direct reading of the piston movement due to the gas volume formed. Pressure buildup due to friction was shown to be moderate. A piston pull and slide back routine can be applied before recording gas volume to minimize experimental errors due to friction. Inoculum handling and activity may be conveniently standardized as illustrated by applying biofilm carriers. A robust set of positive as well as negative controls ("blanks") should be included to ensure quality of the actual testing. The denitrification test showed saturation response at increasing amounts of inoculum in the form of adapted moving bed biofilm reactor (MBBR) carriers, with well correlated nitrate consumption vs. gas volume formed. As shown, the denitrification test efficiently screened different inocula at standardized substrates. Also, different substrates were successfully screened and compared at standardized inocula. The biogas potential test showed efficient screening of different substrates with effects of relative amounts of carbohydrate, protein, fat. A second case with CO2 capture reclaimer waste as substrate demonstrated successful use of co-feeding to support waste treatment and how temperature effects on kinetics and stoichiometry can be observed. In total, syringe test screening of microbial gas production seems highly efficient at a low cost when properly applied.

  19. Dual nitrate isotopes in the Dutch and German Wadden Sea and its tributary rivers (United States)

    Sanders, Tina; Wiese, Philipp; Dähnke, Kirstin


    The Dutch and German Wadden Sea is threatened by the river-induced eutrophication due to riverine nitrate. Despite reduction of nutrient inputs to rivers in the past decades, nitrate inputs remain problematic, also because the estuary of one of the main contributing rivers, the Elbe River, has now developed from a net nitrate sink to a nitrate source. During a sampling campaign in August 2014 we measured nitrate concentration and dual isotope signatures in the Wadden Sea and in two contributing rivers, the Ems and the Elbe River. Our goal was to assess individual riverine contributions and turnover mechanisms of nitrate in the estuaries and the Wadden Sea itself using dual nitrate isotopes as fingerprint signatures. Nitrate concentration in the Ems River and Estuary twice exceeded that of the Elbe River. δ15N and δ18O of nitrate nevertheless showed that denitrification was active in the Ems estuary, removing nitrate, whereas nitrification produced new nitrate in the Elbe Estuary. Surprisingly, Wadden Sea samples appeared not to be entirely dominated by these two riverine source signatures. This suggests that additional turnover mechanisms in the Wadden Sea itself or inputs of nitrate from the open North Sea additionally affect the isotope composition of nitrate in the Dutch and German Wadden Sea.

  20. Effect of organic loading on nitrification and denitrification in a marine sediment microcosm (United States)

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


    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.

  1. Technical Note: Alternative in-stream denitrification equation for the INCA-N model (United States)

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


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

  2. Fluidized-bed denitrification of mining water tolerates high nickel concentrations. (United States)

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


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

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

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


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

  4. Fate and impact of organics in an immersed membrane bioreactor applied to brine denitrification and ion exchange regeneration. (United States)

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


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

  5. Stochastic Controls on Nitrate Transport and Cycling (United States)

    Botter, G.; Settin, T.; Alessi Celegon, E.; Marani, M.; Rinaldo, A.


    In this paper, the impact of nutrient inputs on basin-scale nitrates losses is investigated in a probabilistic framework by means of a continuous, geomorphologically based, Montecarlo approach, which explicitly tackles the random character of the processes controlling nitrates generation, transformation and transport in river basins. This is obtained by coupling the stochastic generation of climatic and rainfall series with simplified hydrologic and biogeochemical models operating at the hillslope scale. Special attention is devoted to the spatial and temporal variability of nitrogen sources of agricultural origin and to the effect of temporally distributed rainfall fields on the ensuing nitrates leaching. The influence of random climatic variables on bio-geochemical processes affecting the nitrogen cycle in the soil-water system (e.g. plant uptake, nitrification and denitrification, mineralization), is also considered. The approach developed has been applied to a catchment located in North-Eastern Italy and is used to provide probabilistic estimates of the NO_3 load transferred downstream, which is received and accumulated in the Venice lagoon. We found that the nitrogen load introduced by fertilizations significantly affects the pdf of the nitrates content in the soil moisture, leading to prolonged risks of increased nitrates leaching from soil. The model allowed the estimation of the impact of different practices on the probabilistic structure of the basin-scale hydrologic and chemical response. As a result, the return period of the water volumes and of the nitrates loads released into the Venice lagoon has been linked directly to the ongoing climatic, pluviometric and agricultural regimes, with relevant implications for environmental planning activities aimed at achieving sustainable management practices.

  6. Storage and mobilization of natural and septic nitrate in thick unsaturated zones, California (United States)

    Izbicki, John A.; Flint, Alan L.; O'Leary, David R.; Nishikawa, Tracy; Martin, Peter; Johnson, Russell D.; Clark, Dennis A.


    Mobilization of natural and septic nitrate from the unsaturated zone as a result of managed aquifer recharge has degraded water quality from public-supply wells near Yucca Valley in the western Mojave Desert, California. The effect of nitrate storage and potential for denitrification in the unsaturated zone to mitigate increasing nitrate concentrations were investigated. Storage of water extractable nitrate in unsaturated alluvium up to 160 meters (m) thick, ranged from 420 to 6600 kilograms per hectare (kg/ha) as nitrogen (N) beneath undeveloped sites, from 6100 to 9200 kg/ha as N beneath unsewered sites. Nitrate reducing and denitrifying bacteria were less abundant under undeveloped sites and more abundant under unsewered sites; however, δ15N–NO3, and δ18O–NO3 data show only about 5–10% denitrification of septic nitrate in most samples—although as much as 40% denitrification occurred in some parts the unsaturated zone and near the top of the water table. Storage of nitrate in thick unsaturated zones and dilution with low-nitrate groundwater are the primary attenuation mechanisms for nitrate from septic discharges in the study area. Numerical simulations of unsaturated flow, using the computer program TOUGH2, showed septic effluent movement through the unsaturated zone increased as the number and density of the septic tanks increased, and decreased with increased layering, and increased slope of layers, within the unsaturated zone. Managing housing density can delay arrival of septic discharges at the water table, especially in layered unsaturated alluvium, allowing time for development of strategies to address future water-quality issues.

  7. Disentangling the rhizosphere effect on nitrate reducers and denitrifiers: insight into the role of root exudates. (United States)

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


    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.

  8. The fate of nitrate in riparian wetlands: results from a pan-European study (United States)

    Burt, T.; Pinay, G.


    Subsurface flow through the soil and deeper sediments of the riparian zone is known to be of crucial importance to denitrification and other nitrogen cycling processes. Since denitrification potential generally increases towards the soil surface, water table elevation can control the degree to which nitrate reduction is optimised. This paper presents data collected as part of a pan-European study of nitrate buffer zones, the NICOLAS project (Nitrogen Control by Landscape Structures in Agricultural Environments). An identical experimental design was employed at each site, allowing climatic controls on hydrology and nitrogen cycling processes to be explored. Nitrate elimination occurred at most of the 13 study sites spread out within Europe (between latitude 40\\deg and 55\\deg N) with an efficiency ranging from 5 to 30% of N concentration abatement per metre. This elimination usually occurred within the first few tens of metres at the upland-wetland interface depending on local geomorphological and hydrological conditions.

  9. 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


    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.

  10. Denitrification in a deep basalt aquifer: implications for aquifer storage and recovery. (United States)

    Nelson, Dennis; Melady, Jason


    Aquifer storage and recovery (ASR) can provide a means of storing water for irrigation in agricultural areas where water availability is limited. A concern, however, is that the injected water may lead to a degradation of groundwater quality. In many agricultural areas, nitrate is a limiting factor. In the Umatilla Basin in north central Oregon, shallow alluvial groundwater with elevated nitrate-nitrogen of 9 mg/L is injected into the Columbia River Basalt Group (CRBG), a transmissive confined aquifer(s) with low natural recharge rates. Once recovery of the injected water begins, however, NO3 -N in the recovered water decreases quickly to storage. In contrast to NO3 -N, other constituents in the recovered water show little variation, inconsistent with migration or simple mixing as an explanation of the NO3 -N decrease. Nitrogen isotopic ratios (δ(15) N) increase markedly, ranging from +3.5 to > +50, and correlate inversely with NO3 -N concentrations. This variation occurs in recovery of aquifer, averaging 3.0 mg/L. Similar to nitrate concentrations, TOC drops in the recovered water, consistent with this component contributing to the denitrification of nitrate during storage.

  11. Autotrophic denitrification performance and bacterial community at biocathodes of bioelectrochemical systems with either abiotic or biotic anodes. (United States)

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


    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.

  12. High-quality draft genome sequence of the Thermus amyloliquefaciens type strain YIM 77409(T) with an incomplete denitrification pathway. (United States)

    Zhou, En-Min; Murugapiran, Senthil K; Mefferd, Chrisabelle C; Liu, Lan; Xian, Wen-Dong; Yin, Yi-Rui; Ming, Hong; Yu, Tian-Tian; Huntemann, Marcel; Clum, Alicia; Pillay, Manoj; Palaniappan, Krishnaveni; Varghese, Neha; Mikhailova, Natalia; Stamatis, Dimitrios; Reddy, T B K; Ngan, Chew Yee; Daum, Chris; Shapiro, Nicole; Markowitz, Victor; Ivanova, Natalia; Spunde, Alexander; Kyrpides, Nikos; Woyke, Tanja; Li, Wen-Jun; Hedlund, Brian P


    Thermus amyloliquefaciens type strain YIM 77409(T) is a thermophilic, Gram-negative, non-motile and rod-shaped bacterium isolated from Niujie Hot Spring in Eryuan County, Yunnan Province, southwest China. In the present study we describe the features of strain YIM 77409(T) together with its genome sequence and annotation. The genome is 2,160,855 bp long and consists of 6 scaffolds with 67.4 % average GC content. A total of 2,313 genes were predicted, comprising 2,257 protein-coding and 56 RNA genes. The genome is predicted to encode a complete glycolysis, pentose phosphate pathway, and tricarboxylic acid cycle. Additionally, a large number of transporters and enzymes for heterotrophy highlight the broad heterotrophic lifestyle of this organism. A denitrification gene cluster included genes predicted to encode enzymes for the sequential reduction of nitrate to nitrous oxide, consistent with the incomplete denitrification phenotype of this strain.

  13. Nitrate removal from groundwater in columns packed with reed and rice stalks. (United States)

    Qian, Jiazhong; Wang, Zhiping; Jin, Song; Liu, Yong; Chen, Tianhu; Fallgren, Paul H


    Nitrate leaching contaminates groundwater. The objective of this study was to determine if reed and rice stalks could enhance denitrification and reduce nitrate leaching into groundwater. Artificial groundwater spiked with nitrate and field groundwater samples were tested in the columns in sand reactors packed with either reed or rice stalks. The maximum nitrate removal rates were determined to be 1.93 and 1.97 mg nitrate-N l(-1) h(-1), respectively, in the reed and rice stalk-packed columns. The maximum nitrate-nitrogen removal rate in reactors packed with reed stalk was 1.33 mg nitrate-N l(-1) h(-1) when experimented with natural groundwater. Chemical oxygen demand consumption was higher when rice stalk (176.1 mg l(-1)) was used as the substrate, compared to reed stalk (35.2 mg l(-1)) at the same substrate dosage. No nitrite accumulation was detected during the test. The results demonstrate that agricultural byproducts, such as reed and rice stalks, may be used as substrate amendments for enhanced denitrification in natural settings, such as lakeside lagoons, ditches or wetlands.

  14. Anaerobic Growth of Haloarchaeon Haloferax volcanii by Denitrification Is Controlled by the Transcription Regulator NarO (United States)

    Hattori, Tatsuya; Shiba, Hiromichi; Ashiki, Ken-ichi; Araki, Takuma; Nagashima, Yoh-kow; Yoshimatsu, Katsuhiko


    ABSTRACT The extremely halophilic archaeon Haloferax volcanii grows anaerobically by denitrification. A putative DNA-binding protein, NarO, is encoded upstream of the respiratory nitrate reductase gene of H. volcanii. Disruption of the narO gene resulted in a loss of denitrifying growth of H. volcanii, and the expression of the recombinant NarO recovered the denitrification capacity. A novel CXnCXCX7C motif showing no remarkable similarities with known sequences was conserved in the N terminus of the NarO homologous proteins found in the haloarchaea. Restoration of the denitrifying growth was not achieved by expression of any mutant NarO in which any one of the four conserved cysteines was individually replaced by serine. A promoter assay experiment indicated that the narO gene was usually transcribed, regardless of whether it was cultivated under aerobic or anaerobic conditions. Transcription of the genes encoding the denitrifying enzymes nitrate reductase and nitrite reductase was activated under anaerobic conditions. A putative cis element was identified in the promoter sequence of haloarchaeal denitrifying genes. These results demonstrated a significant effect of NarO, probably due to its oxygen-sensing function, on the transcriptional activation of haloarchaeal denitrifying genes. IMPORTANCE H. volcanii is an extremely halophilic archaeon capable of anaerobic growth by denitrification. The regulatory mechanism of denitrification has been well understood in bacteria but remains unknown in archaea. In this work, we show that the helix-turn-helix (HTH)-type regulator NarO activates transcription of the denitrifying genes of H. volcanii under anaerobic conditions. A novel cysteine-rich motif, which is critical for transcriptional regulation, is present in NarO. A putative cis element was also identified in the promoter sequence of the haloarchaeal denitrifying genes. PMID:26787768

  15. Oyster Reef Restoration and Aquaculture Impacts on Denitrification and the Benthic Community (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. Optimizing nitrate removal in woodchip beds treating aquaculture effluents

    DEFF Research Database (Denmark)

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


    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...

  17. Regional oxygen reduction and denitrification rates in groundwater from multi-model residence time distributions, San Joaquin Valley, USA (United States)

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


    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.

  18. Regional oxygen reduction and denitrification rates in groundwater from multi-model residence time distributions, San Joaquin Valley, USA (United States)

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


    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.

  19. Denitrification in upland of China: Magnitude and influencing factors (United States)

    Wang, Jinyang; Yan, Xiaoyuan


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

  20. 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


    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.

  1. Modeled Wet Nitrate Deposition (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...

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

    Digital Repository Service at National Institute of Oceanography (India)

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

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

  3. Micromachined Amperometric Nitrate Sensor


    Dohyun Kim; Ira Goldberg; Jack Judy


    A nitrate-sensing system that consists of a micromachined sensor substrate, nitrate-permeable membrane, integrated microfluidic channels, and standard fluidic connectors has been designed, fabricated, assembled, and tested. Our microsensor was designed for in-situ monitoring of nitrate concentrations in ground water. A silver electrode was patterned for amperometric nitrate detection. An electrochemically oxidized silver electrode was used as a reference electrode. Microfluidic channels were ...

  4. American Samoa ESI: BENTHIC (Benthic Marine Habitat Polygons) (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains sensitive biological resource data for benthic habitats in American Samoa. Vector polygons in this data set represent the distribution of...


    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.

  6. 21 CFR 181.33 - Sodium nitrate and potassium nitrate. (United States)


    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  7. 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


    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.

  8. Evaluating Ecosystem Services for Reducing Groundwater Nitrate Contamination: Nitrate Attenuation in the Unsaturated and Saturated Zones (United States)

    Wang, J.


    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

  9. Probabilistic dynamics of soil nitrate: Coupling of ecohydrological and biogeochemical processes (United States)

    Botter, G.; Daly, E.; Porporato, A.; Rodriguez-Iturbe, I.; Rinaldo, A.


    In this paper we analyze the probabilistic dynamics resulting from a simplified model of soil moisture and nitrate mass in relatively arid environments, which accounts for relevant hydrologic and biogeochemical processes and for the random characters of rainfall. The soil nitrate balance includes uptake through transpiration, mineralization, nitrification, and denitrification. To allow an exact mathematical treatment, all nitrate fluxes are assumed to be linear functions of the state variables, namely, soil moisture and nitrate mass stored in soils. The range of applicability of the above simplification is investigated by means of numerical Monte Carlo simulations, showing that the linear approach is meaningful in relatively arid environments, where soil moisture contents are generally low. The moment-generating function of the joint probability distribution (pdf) of soil nitrate and water content is derived, thereby allowing a linkage between the main features of soil nitrate statistics and the underlying soil, vegetation, rainfall, and biogeochemical parameters. Exact expressions for the moments of the nitrate pdf and for the covariance of soil moisture and nitrate mass are derived. The pdf of the nitrate mass in storage within the soil is shown to be reasonably approximated by a gamma distribution in many cases of practical interest. Interestingly, nitrogen limitation for the ecosystem is shown to be directly related to low values of the product between the rate of rainfall arrivals and the characteristic time of nitrate removal.

  10. 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


    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...

  11. 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


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

  12. Biological denitrification in drinking water treatment using the seaweed Gracilaria verrucosa as carbon source and biofilm carrier. (United States)

    Ovez, B; Mergaert, J; Saglam, M


    Chemical and microbiological aspects were investigated with regard to biological denitrification of drinking water using the seaweed Gracilaria verrucosa as the carbon and energy substrate and as physical support for the microbial flora in semibatch, fixed-bed reactors. Complete removal of nitrate (100 mg/L) was readily achieved without accumulation of nitrite. Microbiological analysis indicated that the effluent of the reactor contained high numbers of bacteria (>10(6)/mL total count). Among the 44 bacterial strains isolated directly from the samples or isolated after enrichment at 37 degrees C, 25 different fatty acid profiles were found, indicating a complex microflora, including potential pathogens.

  13. Feasibility of two low-cost organic substrates for inducing denitrification in artificial recharge ponds: Batch and flow-through experiments. (United States)

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


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

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


    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.

  15. A novel nonwoven hybrid bioreactor (NWHBR) for enhancing simultaneous nitrification and denitrification. (United States)

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


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

  16. 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


    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.

  17. Effects of heavy metals on aerobic denitrification by strain Pseudomonas stutzeri PCN-1. (United States)

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


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

  18. NEPR Benthic Habitat Map 2015 (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...

  19. National Benthic Infaunal Database (NBID) (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...

  20. 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...

  1. Analysis of Microbial Communities in Biofilms from CSTR-Type Hollow Fiber Membrane Biofilm Reactors for Autotrophic Nitrification and Hydrogenotrophic Denitrification. (United States)

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


    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.

  2. [Identification of a high ammonia nitrogen tolerant and heterotrophic nitrification-aerobic denitrification bacterial strain TN-14 and its nitrogen removal capabilities]. (United States)

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


    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.

  3. 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: [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)


    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.

  4. Effect of dissolved oxygen on elemental sulfur generation in sulfide and nitrate removal process: characterization, pathway, and microbial community analysis. (United States)

    Wang, Xiaowei; Zhang, Yu; Zhang, Tingting; Zhou, Jiti


    Microaerobic bioreactor treatment for enriched sulfide and nitrate has been demonstrated as an effective strategy to improve the efficiencies of elemental sulfur (S(0)) generation, sulfide oxidation, and nitrate reduction. However, there is little detailed information for the effect and mechanism of dissolved oxygen (DO) on the variations of microbial community in sulfur generation, sulfide oxidation, and nitrate reduction systems. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was employed to evaluate the variations of microbial community structures in a sulfide oxidation and nitrate reduction reactor under different DO conditions (DO 0-0.7 mg · L(-1)). Experimental results revealed that the activity of sulfide-oxidizing bacteria (SOB) and nitrate-reducing bacteria (NRB) could be greatly stimulated in 0.1-0.3 mg-DO · L(-1). However, when the DO concentration was further elevated to more than 0.5 mg · L(-1), the abundance of NRB was markedly decreased, while the heterotrophic microorganisms, especially carbon degradation species, were enriched. The reaction pathways for sulfide and nitrate removal under microaerobic conditions were also deduced by combining batch experiments with functional species analysis. It was likely that the oxidation of sulfide to sulfur could be performed by both aerobic heterotrophic SOB and sulfur-based autotrophic denitrification bacteria with oxygen and nitrate as terminal electron acceptor, respectively. The nitrate could be reduced to nitrite by both autotrophic and heterotrophic denitrification, and then the generated nitrite could be completely converted to nitrogen gas via heterotrophic denitrification. This study provides new insights into the impacts of microaerobic conditions on the microbial community functional structures of sulfide-oxidizing, nitrate-reducing, and sulfur-producing bioreactors, which revealing the potential linkage between functional microbial communities and

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

    KAUST Repository

    Keuskamp, J.A.


    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.

  6. 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


    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.

  7. 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;


    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...

  8. Nitrate removal under different ecological remediation measures in Taihu Lake: a 15N mass-balance approach. (United States)

    Liu, Dandan; Li, Zhengkui; Zhang, Wanguang


    Ecological remediation is an important measure for the protection of lake water quality in removing nutrients, such as nitrate (NO3 (-)). In this study, four bioremediation processes (bare sediment, immobilized nitrogen cycling bacteria (INCB) added, Elodea nuttallii added, E. nuttallii-INCB assemblage) were operated at a lab to elucidate the effect of macrophyte appearance and INCB addition on NO3 (-) removal and achieve the optimal processes for biomediation. (15) N-NO3 solution was added to microcosms to identify the key nitrogen transformation processes responsible for NO3 (-) removal. Results showed that nitrate removal was significantly enhanced after the addition of INCB and E. nuttallii. In the treatments with INCB added, E. nuttallii added, and INCB and E. nuttallii-INCB assemblage, nitrate removal ratio achieved 94.74, 98.76, and 99.15 %, respectively. In contrast, only 23.47 % added nitrate was removed in the control. Plant uptake and denitrification played an important role in nitrogen removal. The water quality was substantially improved by the addition of INCB and macrophyte that can accelerate denitrification and promote nitrogen assimilation of plants. The results indicated that plant uptake and microbial denitrification were key processes for nitrate removal.

  9. 氮负荷对烟气脱硫脱硝废水反硝化过程的影响%Effects of Nitrogen Load on Flue Gas Desulfurization and Denitrification of Wastewater Denitrification Treatment

    Institute of Scientific and Technical Information of China (English)

    赵樑; 倪伟敏; 贾秀英; 范慧婷


    Wastewater is simulated according to the main characteristics of flue gas desulfurization and denitrification of wastewater ,and the effects of different nitrate nitrogen loads on the change rules of C and N as well as the nitrogen removal effects in the process of wastewater denitrification .The results show that the nitrate removal rate is more than 95% after 12 h under the nitrate nitrogen load of 50~400 mg/L ,and there is 10% ~ 20% nitrate transformed into nitrite in the reaction .The consumption of TOC is increasing with the increase of nitrogen load ,however ,the degradation rate is decreasing ,it needs 5 .40 ,4 .03 ,3 .15 , 2.96 ,2 .88 ,2 .32 and 1 .9 mg TOC to degrade per mg nitrate nitrogen .TN removal includes the removals of nitrate ,nitrate and some organic nitrogen .TN removal and nitrate nitrogen removal happen almost simultaneously .At the end of the reaction ,the demand of △TOC/△TN is 1 .9~4 .0 under different nitrogen loads .The volume of denitrification rate increases from 2 .73 to 21.90 mg NO3-‐N/(L · h) when the nitrogen load increases from 50 to 400 mg/L .△TOC/△TN ,volume denitrification rate and nitrogen load have good linear relationship .%依据烟气脱硫脱硝废水的主要特征配制模拟废水,研究不同硝态氮负荷对该废水反硝化过程中C和N的变化规律及脱氮效果的影响.间歇式批次实验结果表明:氮负荷为50~400 mg/L时,经过12 h后硝态氮去除率达到95%以上,反应过程中有10%~20%硝态氮转化为亚硝态氮.随着氮负荷的增加,T OC的消耗量也在增加,但降解率逐渐减小,去除每毫克硝态氮所需TOC依次为5.40、4.03、3.15、2.96、2.88、2.32和1.9 mg . TN的去除包括硝态氮、亚硝态氮和部分有机氮的去除,亚硝态氮完全去除时TN也基本去除.反应结束时,不同氮负荷下所需的△TOC/△TN为1.9~4.0.氮负荷从50 mg/L增加至400 mg/L ,容积反硝化速率由2

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

    Energy Technology Data Exchange (ETDEWEB)

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


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

  11. Groundwater nitrate reduction versus dissolved gas production: A tale of two catchments. (United States)

    McAleer, E B; Coxon, C E; Richards, K G; Jahangir, M M R; Grant, J; Mellander, Per E


    At the catchment scale, a complex mosaic of environmental, hydrogeological and physicochemical characteristics combine to regulate the distribution of groundwater and stream nitrate (NO3(-)). The efficiency of NO3(-) removal (via denitrification) versus the ratio of accumulated reaction products, dinitrogen (excess N2) & nitrous oxide (N2O), remains poorly understood. Groundwater was investigated in two well drained agricultural catchments (10km(2)) in Ireland with contrasting subsurface lithologies (sandstone vs. slate) and landuse. Denitrification capacity was assessed by measuring concentration and distribution patterns of nitrogen (N) species, aquifer hydrogeochemistry, stable isotope signatures and aquifer hydraulic properties. A hierarchy of scale whereby physical factors including agronomy, water table elevation and permeability determined the hydrogeochemical signature of the aquifers was observed. This hydrogeochemical signature acted as the dominant control on denitrification reaction progress. High permeability, aerobic conditions and a lack of bacterial energy sources in the slate catchment resulted in low denitrification reaction progress (0-32%), high NO3(-) and comparatively low N2O emission factors (EF5g1). In the sandstone catchment denitrification progress ranged from 4 to 94% and was highly dependent on permeability, water table elevation, dissolved oxygen concentration solid phase bacterial energy sources. Denitrification of NO3- to N2 occurred in anaerobic conditions, while at intermediate dissolved oxygen; N2O was the dominant reaction product. EF5g1 (mean: 0.0018) in the denitrifying sandstone catchment was 32% less than the IPCC default. The denitrification observations across catchments were supported by stable isotope signatures. Stream NO3(-) occurrence was 32% lower in the sandstone catchment even though N loading was substantially higher than the slate catchment.

  12. Quantitative importance of denitrification and N2O emission in an N-saturated subtropical forest catchment, southwest China (United States)

    Zhu, J.; Dörsch, P.; Mulder, J.


    Anthropogenic emission of nitrogen in the environment has increased rapidly, due to fast economic growth. This has resulted in increased deposition rates of reactive nitrogen, primarily as NOx (from fossil fuel combustion) and NH3 (from fertilizer production and animal husbandry). In response, temperate and boreal forests may develop nitrogen saturation, characterized by increased leaching of nitrate. In addition, elevated emission of N2 and N2O, due to nitrification and denitrification, may occur. To date, few studies exist quantifying the nitrogen balance, including N2 and N2O production, in nitrogen-saturated, monsoonal, sub-tropical forest ecosystems in south-west China. Since nitrate contributes to the eutrophication of stream water, and N2O is a potent greenhouse gas, it is important to quantitatively understand the role of nitrification and denitrification in the nitrogen cycle. Several subtropical forests in southwest China, receiving elevated nitrogen deposition (30-73 kg N ha-1 a-1; Zhang. et al., 2008), are characterized by high temperature and soil moisture content in much of the growing season. This may cause a much stronger intensity of denitrification compared with that in temperate and boreal forests. In turn this may lead to decreased nitrate leaching and a higher potential of N2O emission. In my PhD project, I will investigate the nitrogen cycle in a forest catchment (TieShanPing; TSP), which is near one of the biggest cities, Chongqing, in southwest China. Previous research suggests high nitrogen deposition (3.52 gN m-2 a-1), but low nitrogen flux (0.57 gN m-2 a-1) in runoff (Chen & Mulder, 2007). Tree growth, and thus plant N uptake, is limited and nitrate fluxes below the root zone are relatively large, suggesting ‘N-saturation'. Based on this, we hypothesize that significant amounts of nitrogen are emitted as gases, with denitrification playing an important role, and N2 and N2O (especially N2) being major components of the emitted gases

  13. 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


    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.

  14. Removal of organic matter and nitrogen from distillery wastewater by a combination of methane fermentation and denitrification/nitrification processes. (United States)

    Li, Jun; Zhang, Zhen-jia; Li, Zhi-rong; Huang, Guang-yu; Abe, Naoki


    The distillery wastewater of Guangdong Jiujiang Distillery, which is characteristic of containing high organic matters and rich total nitrogen, was treated by a combination of methane fermentation and denitrification/nitrification processes. 80% of COD in the raw wastewater was removed by methane fermentation at the COD volumetric loading rate of 20 kg COD/(m3 x d) using the expanded granule sludge bed (EGSB) process. However, almost all the organic nitrogen in the raw wastewater was converted into ammonia by ammonification there. Ammonia and volatile fatty acids (VFA) remaining in the anaerobically treated wastewater were simultaneously removed utilizing VFA as an electron donor by denitrification occurring in the other EGSB reactor and nitrification using PEG-immobilized nitrifying bacteria with recirculation process. An aerobic biological contact oxidization reactor was designed between denitrification/nitrification reactor for further COD removal. With the above treatment system, 18000-28000 mg/L of COD in raw wastewater was reduced to less than 100 mg/L. Also, ammonia in the effluent of the system was not detected and the system had a high removal rate for 900-1200 mg/L of TN in the raw wastewater, only leaving 400 mg/L of nitrate nitrogen.

  15. 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


    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.

  16. 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


    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.

  17. Metolachlor metabolite (MESA) reveals agricultural nitrate-N fate and transport in Choptank River watershed (United States)

    McCarty, Gregory W.; Hapeman, Cathleen J.; Rice, Clifford P.; Hively, W. Dean; McConnell, Laura L.; Sadeghi, Ali M.; Lang, Megan W.; Whitall, David R.; Bialek, Krystyna; Downey, Peter


    Over 50% of streams in the Chesapeake Bay watershed have been rated as poor or very poor based on the index of biological integrity. The Choptank River estuary, a Bay tributary on the eastern shore, is one such waterway, where corn and soybean production in upland areas of the watershed contribute significant loads of nutrients and sediment to streams. We adopted a novel approach utilizing the relationship between the concentration of nitrate-N and the stable, water-soluble herbicide degradation product MESA {2-[2-ethyl-N-(1-methoxypropan-2-yl)-6-methylanilino]-2-oxoethanesulfonic acid} to distinguish between dilution and denitrification effects on the stream concentration of nitrate-N in agricultural subwatersheds. The ratio of mean nitrate-N concentration/(mean MESA concentration * 1000) for 15 subwatersheds was examined as a function of percent cropland on hydric soil. This inverse relationship (R2 = 0.65, p 2 ≤ 0.99) for all eight sampling dates except one where R2 = 0.90. This very strong correlation indicates that nitrate-N was conserved in much of the Choptank River estuary, that dilution alone is responsible for the changes in nitrate-N and MESA concentrations, and more importantly nitrate-N loads are not reduced in the estuary prior to entering the Chesapeake Bay. Thus, a critical need exists to minimize nutrient export from agricultural production fields and to identify specific conservation practices to address the hydrologic conditions within each subwatershed. In well drained areas, removal of residual N within the cropland is most critical, and practices such as cover crops which sequester the residual N should be strongly encouraged. In poorly drained areas where denitrification can occur, wetland restoration and controlled drained structures that minimize ditch flow should be used to maximize denitrification.


    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...

  19. Experimental effects of grazers on autotrophic species assemblages across a nitrate gradient in Florida springs (United States)

    Springs face accelerated degradation of ecosystem structure, namely in the form of autotrophic species assemblage shifts from submerged vascular macrophytes to benthic filamentous algae. Increasing nitrate concentrations have been cited as a primary driver of this shift and numeric nutrient criteria...

  20. Aerobic respiration along isopycnals leads to overestimation of the isotope effect of denitrification in the ocean water column (United States)

    Marconi, Dario; Kopf, Sebastian; Rafter, Patrick A.; Sigman, Daniel M.


    The nitrogen (N) isotopes provide an integrative geochemical tool for constraining the fixed N budget of the ocean. However, N isotope budgeting requires a robust estimate for the organism-scale nitrogen isotope effect of denitrification, in particular as it occurs in water column denitrification zones (εwcd). Ocean field data interpreted with the Rayleigh model have typically yielded estimates for εwcd of between 20 and 30‰. However, recent findings have raised questions about this value. In particular, culture experiments can produce a substantially lower isotope effect (∼13‰) under conditions mimicking those of ocean suboxic zones. In an effort to better understand prior field estimates of εwcd, we use a geochemical multi-box model to investigate the combined effects of denitrification, aerobic respiration, and isopycnal exchange on the δ15N of nitrate. In the context of this admittedly simplistic model, we consider three isopycnals extending from the Southern Ocean to the Eastern Tropical North Pacific (ETNP). We show that the data from the ETNP suboxic zone can be reproduced with an εwcd of 13‰, given a rate of aerobic respiration consistent with the nutrient data on these isopycnals and a plausible range in the δ15N of the sinking flux being remineralized. We discuss the limitations of our analysis, additional considerations, as well as possible data-based tests for the proposal of a lower εwcd than previously estimated. All else held constant, a lower εwcd would imply a lower global ocean rate of denitrification that is more similar to the estimated rate of N input to the global ocean, providing a major impetus for further investigation.

  1. 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

  2. Use of an industrial effluent as a carbon source for denitrification of a high-strength waste water

    Energy Technology Data Exchange (ETDEWEB)

    Bernet, N. [Inst. National de la Recherche Agronomique, Lab. de Biotechnologie de l`Environnement, Narbonne (France); Habouzit, F. [Inst. National de la Recherche Agronomique, Lab. de Biotechnologie de l`Environnement, Narbonne (France); Moletta, R. [Inst. National de la Recherche Agronomique, Lab. de Biotechnologie de l`Environnement, Narbonne (France)


    Denitrification of a high-strength synthetic wastewater (150 g NO{sub 3}{sup -} l{sup -1}) was carried out using a wine distillery effluent as an example of an industrial carbon source (22.7 g chemical oxygen demand l{sup -1}). Two configurations were tested: One consisted of an acidogenesis reactor followed by a denitrifying reactor and the other was a single reactor directly fed with the raw effluents. In both cases, denitrification was achieved at a nitrate load of 9.54 g NO{sub 3}{sup -} l{sup -1} day{sup -1} (2.19 gN as NO{sub 3}{sup -} l{sup -1} day{sup -1}) with good specific reduction rates: 32.6 mg and 35.2 mg N as NO{sub x} g volatile suspended solids h{sup -1}, calculated on a single day, for the two-step and the one-step process respectively. Dissimilatory nitrate reduction to ammonium did not occur, even in the one-step process. (orig.)

  3. Sulfur-based mixotrophic denitrification corresponding to different electron donors and microbial profiling in anoxic fluidized-bed membrane bioreactors. (United States)

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


    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.

  4. Simultaneous urea hydrolysis, formaldehyde removal and denitrification in a multifed upflow filter under anoxic and anaerobic conditions. (United States)

    Garrido, J M; Méndez, R; Lema, J M


    A multifed upflow filter (MUF), working under anoxic or anaerobic conditions, coupled with an aerobic biofilm airlift suspension (BAS) reactor was operated in order to treat a wastewater with high formaldehyde (up to 1.5 g L-1) and urea (up to 0.46 g L-1) concentrations. In the MUF, formaldehyde removal, denitrification and urea hydrolysis took place simultaneously. The MUF was operated at 37 degrees C, at a hydraulic retention time (HRT) ranging from 1 to 0.3 d. An organic loading rate (OLR) of 0.5 kg-formaldehyde m-3 d-1 was efficiently eliminated during anaerobic operation and transformed into methane, while a much higher OLR (up to 2 kg-formaldehyde m-3 d-1) was oxidised under anoxic conditions by the nitrite or nitrate from the nitrifying airlift. However, only 80% of urea was hydrolysed to ammonia in an anoxic environment while complete conversion occurred under anaerobic conditions. Moreover, formaldehyde concentrations higher than 50 mg L-1 provoked a loss of efficiency of urea hydrolysis, decreasing to 10% at formaldehyde concentrations above 300 mg L-1. Methane production rate during the anaerobic stage was adversely affected by accumulations of formaldehyde in the reactor causing lower formaldehyde removal efficiency. However, denitrification proceeded properly even at a formaldehyde concentration of 700 mg L-1 in the reactor, although nitrous oxide appears in the off-gas. The COD/N ratios required for complete nitrite and nitrate denitrification with formaldehyde were estimated at 2.1 and 3.5 kg-COD/kg-N, respectively.

  5. 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

  6. Effect of nitrate concentration on filamentous bulking under low level of dissolved oxygen in an airlift inner circular anoxic-aerobic incorporate reactor

    Institute of Scientific and Technical Information of China (English)

    Yiming Su; Yalei Zhang; Xuefei Zhou; Ming Jiang


    This laboratory research investigated a possible cause of filamentous bulking under low level of dissolved oxygen conditions (dissolved oxygen value in aerobic zone maintained between 0.6-0.8 mg O2/L) in an airlift inner-circular anoxic-aerobic reactor.During the operating period,it was observed that low nitrate concentrations affected sludge volume index significantly.Unlike the existing hypothesis,the batch tests indicated that filamentous bacteria (mainly Thiothrix sp.) could store nitrate temporarily under carbon restricted conditions.When nitrate concentration was below 4 mg/L,low levels of carbon substrates and dissolved oxygen in the aerobic zone stimulated the nitrate-storing capacity of filaments.When filamentous bacteria riched in nitrate reached the anoxic zone,where they were exposed to high levels of carbon but limited nitrate,they underwent denitrification.However,when nonfilamentous bacteria were exposed to similar conditions,denitrification was restrained due to their intrinsic nitrate limitation.Hence,in order to avoid filamentous bulking,the nitrate concentration in the return sludge (from aerobic zone to the anoxic zone) should be above 4 mg/L,or alternatively,the nitrate load in the anoxic zone should be kept at levels above 2.7 mg NO-3-N/g SS.

  7. Carbon nanotubes affect the toxicity of CuO nanoparticles to denitrification in marine sediments by altering cellular internalization of nanoparticle (United States)

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


    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.

  8. Benthic mineralization and nutrient exchange over the inner continental shelf of western India (United States)

    Pratihary, A. K.; Naqvi, S. W. A.; Narvenkar, G.; Kurian, S.; Naik, H.; Naik, R.; Manjunatha, B. R.


    The western Indian continental shelf is one of the most productive coastal systems of the world ocean. This system experiences extreme changes in its oxygen regime, being normoxic from November to May and suboxic (denitrifying)/anoxic from June to October, owing to the biogeochemical response to cyclical monsoonal influence. In order to understand the impact of the seasonally varying oxygen regime on benthic mineralization, nutrient exchange and, in turn, on the shelf ecosystem, we carried out the first ever intact-core incubations during two contrasting seasons - spring intermonsoon and fall intermonsoon (late southwest monsoon) at a 28 m-deep fixed site on the inner shelf off Goa, dominated by fine-grained cohesive sediments. The results showed that incomplete sediment oxygen consumption (SOC) occurred during April as opposed to the complete SOC and subsequent sulfide flux observed in the fall intermonsoon incubations. The sediments acted as a perennial net source of DIN (dissolved inorganic nitrogen i.e. NO3- + NO2- + NH4+), PO43- and SiO44- to the overlying water column. The efflux of DIN increased from 1.4 to 3.74 mmol m-2 d-1 from April to October, of which NH4+ flux comprised 59-100%. During the oxic regime, ∼75% of diffusing NH4+ appeared to be nitrified (2.55 mmol m-2 d-1), of which ∼77% remained coupled to benthic denitrification. Consequently, 58% of NH4+ flux was lost in active coupled nitrification-denitrification, resulting in substantial N loss (1.98 mmol m-2 d-1) in the sediments. The continental shelf sediments switched over from being a NO3- source during the oxic regime to a NO3- sink during the anoxic regime. During suboxia, benthic denitrification that is fed by NO3- from the overlying water caused N loss at the rate of 1.04 mmol m-2 d-1. Nitrogen loss continued even under sulfidic conditions during October, possibly through the chemolithoautotrophic denitrification, at a potential rate of 3.21 mmol m-2 d-1. Phosphate flux increased more

  9. Fractionation of Nitrogen and Oxygen Isotopes During Microbial Nitrate Reduction (United States)

    Lehmann, M. F.; Bernasconi, S. M.; Reichert, P.; Barbieri, A.; McKenzie, J. A.


    reduction barely contributes to the observed nitrate depletion in the water column. However, being mainly fuelled by NO3- from nitrifying activity at the sediment-water interface above the redoxcline, sedimentary nitrate reduction may still play an important role in the overall N budget of Lake Lugano without affecting the water column signal. The combined measurements of N and O isotope ratios in nitrate revealed that a significant contribution from coupled nitrification-denitrification in the open-water column could be excluded. The determination of δ 15N and δ 18O values in the water-column nitrate proved to be an effective tool to assess nitrate dissimilation in a hypolimnetic redox-transition zone. Moreover, the dual-isotope approach allowed deconvolving the effects of coexisting N-cycling processes. Hence, this study confirms the high potential of δ 18O values for nitrate as a valuable biogeochemical tracer in aquatic systems, complementing nitrate δ 15N values. Brandes J.A. and Devol, A. H., Geochim. Cosmochim. Acta 61(9), 1997.

  10. Agricultural nitrate pollution

    DEFF Research Database (Denmark)

    Anker, Helle Tegner


    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...

  11. Nitrate Leaching Index (United States)

    The Nitrate Leaching Index is a rapid assessment tool that evaluates nitrate (NO3) leaching potential based on basic soil and climate information. It is the basis for many nutrient management planning efforts, but it has considerable limitations because of : 1) an oversimplification of the processes...

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

    NARCIS (Netherlands)

    Hoang, N.K.L.


    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

  13. Nitrate removal and denitrification in headwater agricultural streams of the Pacific Northwest (United States)

    Headwater streams can serve as important sites for nitrogen (N) removal in watersheds. Here we examine the influence of agricultural streams on watershed N export in the Willamette River Basin of western Oregon, USA, a region with mixed agricultural, urban and forestry land uses...

  14. 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

    amended with organic carbon were prepared using glucose as a substrate with concentrations ranging from 0%, 0.1%, 0.3%, 0.5%, 0.75% to 1%. No significant increase in N2O production was observed on organic C addition. When both the substrates were in excess...

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

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


    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.

  16. Nitrate respiration associated with detrital aggregates in aerobic bottom waters of the abyssal NE Pacific (United States)

    Wolgast, D. M.; Carlucci, A. F.; Bauer, J. E.

    Rates of nitrate utilization in tube core respirometers (TCR) placed over aggregates on the seafloor at an abyssal site (Station M) in the eastern North Pacific Ocean increased at times of high particle flux. In the presence of aggregates, both oxygen and nitrate were used in respiration. The ratio of O 2 : NO 3 concentrations in ambient waters was 3.9, while O 2 : NO 3 utilization rates in TCR overlying and TCR aggregate pore waters were 2.6 and 0.6, respectively. We postulated that denitrification was occurring in microzones of the particle-rich oxygenated (135 μM) waters. To test this, nitrate respiration was measured aboard a ship in oxygen-minimum (˜26 μM) water supplemented with particulate matter collected by a surface net tow. Dissolved oxygen consumption occurred immediately, followed by nitrate utilization while oxygen was still present. Calculations from cell densities indicated 0.6 μM of the original 42 μM of nitrate was assimilated into bacterial biomass during 36 h of incubation, suggesting the major portion of the utilized nitrate was used in respiration. Nitrate utilization rates in the in situ incubation study and those of the shipboard experiment were 3.1 and 2.7 μM d -1, respectively. The results of the present studies suggest nitrate respiration occurs in microzones of aggregates in oxygenated bottom waters at times of high particle flux and causes some loss of fixed nitrogen.

  17. A tale of two interfaces: Dynamic nitrate removal in the hyporheic zone of a tidal fresh river (United States)

    Sawyer, A. H.; Knights, D. H.; Barnes, R. T.; Wallace, C.; Bray, S. N.; Musial, C.


    At the interface of rivers and oceans, tidal freshwater zones (TFZs) stretch for tens to hundreds of kilometers but are rarely monitored for nitrogen export due to their complex hydrodynamics. Field observations from the TFZ of White Clay Creek (Delaware, USA) show that river discharge and nitrate export rates decrease during rising tide, while hyporheic storage increases. During falling tide, river discharge and nitrate export rates increase, while stored hyporheic water is released to the river. We estimate that 11% of river water exchanges through the hyporheic zone of this TFZ due to tidal pumping alone. We developed a one-dimensional, coupled fluid flow and solute transport model to quantify the influence of tidal pumping on nitrate removal in the riverbed. Tidal pumping promotes a deep, oscillating zone of aerobic respiration that limits denitrification near the sediment-water interface. As tide rises, groundwater residence times in shallow riverbed sediments increase, which causes a doubling of denitrification rates relative to falling tide. Given a uniform substrate along TFZs, removal rates of groundwater-borne nitrate should decrease as tidal amplitude increases downstream. Denitrification hot spots should occur in less permeable, organic-rich sediment under low tidal ranges. Because TFZs connect lowland nitrogen sources to the ocean, it is imperative that we expand monitoring efforts and elucidate their role in nitrogen export to the coast.

  18. Investigating the nitrification and denitrification kinetics under aerobic and anaerobic conditions by Paracoccus denitrificans ISTOD1. (United States)

    Medhi, Kristina; Singhal, Anjali; Chauhan, D K; Thakur, Indu Shekhar


    Municipal wastewater contains multiple nitrogen contaminants such as ammonia, nitrate and nitrite. Two heterotrophic nitrifier and aerobic denitrifiers, bacterial isolates ISTOD1 and ISTVD1 were isolated from domestic wastewater. On the basis of removal efficiency of ammonia, nitrate and nitrite under both aerobic and anaerobic conditions, ISTOD1 was selected and identified as Paracoccus denitrificans. Aerobically, NH4(+)-N had maximum specific nitrogen removal rate (Rxi) of 7.6g/gDCW/h and anaerobically, NO3(-)N showed Rxi of 2.5*10(-1)g/g DCW/h. Monod equation described the bioprocess kinetic coefficients, µmax and Ks, obtained by regression. Error functions were calculated to validate the Monod equation experimental data. Aerobic NO3(-)N showed the highest YW of 0.372mg DCW/mg NO3(-)N among the five conditions. ISTOD1 serves as a potential candidate for treating nitrogen rich wastewater using simultaneous nitrification and aerobic denitrification. It can be used in bioaugmentation studies under varied condition.

  19. Modeling the long-term fate of agricultural nitrate in groundwater in the San Joaquin Valley, California (United States)

    Chapelle, Francis H.; Campbell, Bruce G.; Widdowson, Mark A.; Landon, Mathew K.


    Nitrate contamination of groundwater systems used for human water supplies is a major environmental problem in many parts of the world. Fertilizers containing a variety of reduced nitrogen compounds are commonly added to soils to increase agricultural yields. But the amount of nitrogen added during fertilization typically exceeds the amount of nitrogen taken up by crops. Oxidation of reduced nitrogen compounds present in residual fertilizers can produce substantial amounts of nitrate which can be transported to the underlying water table. Because nitrate concentrations exceeding 10 mg/L in drinking water can have a variety of deleterious effects for humans, agriculturally derived nitrate contamination of groundwater can be a serious public health issue. The Central Valley aquifer of California accounts for 13 percent of all the groundwater withdrawals in the United States. The Central Valley, which includes the San Joaquin Valley, is one of the most productive agricultural areas in the world and much of this groundwater is used for crop irrigation. However, rapid urbanization has led to increasing groundwater withdrawals for municipal public water supplies. That, in turn, has led to concern about how contaminants associated with agricultural practices will affect the chemical quality of groundwater in the San Joaquin Valley. Crop fertilization with various forms of nitrogen-containing compounds can greatly increase agricultural yields. However, leaching of nitrate from soils due to irrigation has led to substantial nitrate contamination of shallow groundwater. That shallow nitrate-contaminated groundwater has been moving deeper into the Central Valley aquifer since the 1960s. Denitrification can be an important process limiting the mobility of nitrate in groundwater systems. However, substantial denitrification requires adequate sources of electron donors in order to drive the process. In many cases, dissolved organic carbon (DOC) and particulate organic carbon

  20. Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer (United States)

    Bohlke, Johnkarl F.; Hatzinger, P.B.; Sturchio, N.C.; Gu, B.; Heraty, L.J.; Borden, R.C.


    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 (e18O/e37Cl) 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 (e18O/e15N), which is within the range of values reported previously for denitrification. However, the magnitudes of the individual apparent in situ isotope fractionation effects for perchlorate and nitrate were appreciably smaller than those reported in homogeneous closed systems (0.2 to 0.6 times), even after adjustment for dilution. These results indicate that (1) isotope fractionation factor ratios (e18O/e37Cl, e18O/e15N) derived from homogeneous laboratory systems (e.g. pure culture studies) can be used qualitatively to confirm the occurrence of in situ biodegradation of both perchlorate and nitrate, but (2) the magnitudes of the individual apparent e values cannot be used quantitatively to estimate the in situ extent of biodegradation of either anion.

  1. Evidence for the Existence of Autotrophic Nitrate-Reducing Fe(II)-Oxidizing Bacteria in Marine Coastal Sediment. (United States)

    Laufer, Katja; Røy, Hans; Jørgensen, Bo Barker; Kappler, Andreas


    Nitrate-reducing Fe(II)-oxidizing microorganisms were described for the first time ca. 20 years ago. Most pure cultures of nitrate-reducing Fe(II) oxidizers can oxidize Fe(II) only under mixotrophic conditions, i.e., when an organic cosubstrate is provided. A small number of nitrate-reducing Fe(II)-oxidizing cultures have been proposed to grow autotrophically, but unambiguous evidence for autotrophy has not always been provided. Thus, it is still unclear whether or to what extent Fe(II) oxidation coupled to nitrate reduction is an enzymatically catalyzed and energy-yielding autotrophic process or whether Fe(II) is abiotically oxidized by nitrite from heterotrophic nitrate reduction. The aim of the present study was to find evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments. Microcosm incubations showed that with increasing incubation times, the stoichiometric ratio of reduced nitrate/oxidized Fe(II) [NO3(-)reduced/Fe(II)oxidized] decreased, indicating a decreasing contribution of heterotrophic denitrification and/or an increasing contribution of autotrophic nitrate-reducing Fe(II) oxidation over time. After incubations of sediment slurries for >10 weeks, nitrate-reducing activity ceased, although nitrate was still present. This suggests that heterotrophic nitrate reduction had ceased due to the depletion of readily available organic carbon. However, after the addition of Fe(II) to these batch incubation mixtures, the nitrate-reducing activity resumed, and Fe(II) was oxidized, indicating the activity of autotrophic nitrate-reducing Fe(II) oxidizers. The concurrent reduction of (14)C-labeled bicarbonate concentrations unambiguously proved that autotrophic C fixation occurred during Fe(II) oxidation and nitrate reduction. Our results clearly demonstrated that autotrophic nitrate-reducing Fe(II)-oxidizing bacteria were present in the investigated coastal marine sediments.

  2. Biological nitrate removal using a food waste-derived carbon source in synthetic wastewater and real sewage. (United States)

    Zhang, Haowei; Jiang, Jianguo; Li, Menglu; Yan, Feng; Gong, Changxiu; Wang, Quan


    The production of volatile fatty acids (VFAs) from food waste to improve biological nutrient removal has drawn much attention. In this study, acidogenic liquid from food waste was used as an alternative carbon source for synthetic wastewater treatment. C/N ratios of 5 and 6 were suitable for denitrification, and the change in acidogenic liquid composition had no negative effect on denitrification. The denitrification rates using optimal carbon-to-nitrate ratios of acidogenic liquid were more than 25 mg NO3-N/(gVSS·h). At the same time, acidogenic liquid was used to improve nutrient removal from summer and winter sewage. C/N ratios of 5 and 6 were acceptable for summer sewage treatment. Total nitrogen in the final effluent was less than 7 mg/L. Two additional hours were required for winter sewage treatment, and the C/N ratio had to be >6.

  3. 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


    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.

  4. The Denitrification Characteristics and Microbial Community in the Cathode of an MFC with Aerobic Denitrification at High Temperatures (United States)

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


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

  5. Enzyme diversity and mosaic gene organization in denitrification. (United States)

    Zumft, W G; Körner, H


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

  6. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer (United States)

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


    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 weeks

  7. Anoxic nitrate reduction coupled with iron oxidation and attenuation of dissolved arsenic and phosphate in a sand and gravel aquifer (United States)

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


    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

  8. Distribution of Land Use to Purify Contaminated Groundwater by Nitrate (United States)

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


    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. Bioactivation of organic nitrates and the mechanism of nitrate tolerance. (United States)

    Klemenska, Emila; Beresewicz, Andrzej


    Organic nitrates, such as nitroglycerin, are commonly used in the therapy of cardiovascular disease. Long-term therapy with these drugs, however, results in the rapid development of nitrate tolerance, limiting their hemodynamic and anti-ischemic efficacy. In addition, nitrate tolerance is associated with the expression of potentially deleterious modifications such as increased oxidative stress, endothelial dysfunction, and sympathetic activation. In this review we discuss current concepts regarding the mechanisms of organic nitrate bioactivation, nitrate tolerance, and nitrate-mediated oxidative stress and endothelial dysfunction. We also examine how hydralazine may prevent nitrate tolerance and related endothelial dysfunction.

  10. Small-scale, hydrogen-oxidizing-denitrifying bioreactor for treatment of nitrate-contaminated drinking water. (United States)

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


    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.


    Institute of Scientific and Technical Information of China (English)

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


    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.

  12. Mobilisation or dilution? Nitrate response of karst springs to high rainfall events (United States)

    Huebsch, M.; Fenton, O.; Horan, B.; Hennessy, D.; Richards, K. G.; Jordan, P.; Goldscheider, N.; Butscher, C.; Blum, P.


    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 on 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 the high

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

    Directory of Open Access Journals (Sweden)

    M. Huebsch


    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

  14. Agricultural nitrate pollution

    DEFF Research Database (Denmark)

    Anker, Helle Tegner


    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...... in nitrogen leaching since the mid-80s. Nevertheless, further effort is needed, particularly in ecologically sensitive areas. This article discusses different regulatory approaches – and in particular the need for a differentiated nitrate regulation tailored to meet site-specific ecological demands – from...... of the mandatory specification standards of the Nitrates Directive combined with additional instruments to address the need for severe restrictions on fertiliser use or cultivation practices in the most ecologically vulnerable areas....

  15. Long-term fertilization alters the relative importance of nitrate reduction pathways in salt marsh sediments (United States)

    Peng, Xuefeng; Ji, Qixing; Angell, John H.; Kearns, Patrick J.; Yang, Hannah J.; Bowen, Jennifer L.; Ward, Bess B.


    Salt marshes provide numerous valuable ecological services. In particular, nitrogen (N) removal in salt marsh sediments alleviates N loading to the coastal ocean. N removal reduces the threat of eutrophication caused by increased N inputs from anthropogenic sources. It is unclear, however, whether chronic nutrient overenrichment alters the capacity of salt marshes to remove anthropogenic N. To assess the effect of nutrient enrichment on N cycling in salt marsh sediments, we examined important N cycle pathways in experimental fertilization plots in a New England salt marsh. We determined rates of nitrification, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) using sediment slurry incubations with 15N labeled ammonium or nitrate tracers under oxic headspace (20% oxygen/80% helium). Nitrification and denitrification rates were more than tenfold higher in fertilized plots compared to control plots. By contrast, DNRA, which retains N in the system, was high in control plots but not detected in fertilized plots. The relative contribution of DNRA to total nitrate reduction largely depends on the carbon/nitrate ratio in the sediment. These results suggest that long-term fertilization shifts N cycling in salt marsh sediments from predominantly retention to removal.

  16. Sulfide oxidation and nitrate reduction for potential mitigation of H2S in landfills. (United States)

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


    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.

  17. 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)


    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.

  18. Biochemical and genomic analysis of the denitrification pathway within the genus Neisseria. (United States)

    Barth, Kenneth R; Isabella, Vincent M; Clark, Virginia L


    Since Neisseria gonorrhoeae and Neisseria meningitidis are obligate human pathogens, a comparison with commensal species of the same genus could reveal differences important in pathogenesis. The recent completion of commensal Neisseria genome draft assemblies allowed us to perform a comparison of the genes involved in the catalysis, assembly and regulation of the denitrification pathway, which has been implicated in the virulence of several bacteria. All species contained a highly conserved nitric oxide reductase (NorB) and a nitrite reductase (AniA or NirK) that was highly conserved in the catalytic but divergent in the N-terminal lipid modification and C-terminal glycosylation domains. Only Neisseria mucosa contained a nitrate reductase (Nar), and only Neisseria lactamica, Neisseria cinerea, Neisseria subflava, Neisseria flavescens and Neisseria sicca contained a nitrous oxide reductase (Nos) complex. The regulators of the denitrification genes, FNR, NarQP and NsrR, were highly conserved, except for the GAF domain of NarQ. Biochemical examination of laboratory strains revealed that all of the neisserial species tested except N. mucosa had a two- to fourfold lower nitrite reductase activity than N. gonorrhoeae, while N. meningitidis and most of the commensal Neisseria species had a two- to fourfold higher nitric oxide (NO) reductase activity. For N. meningitidis and most of the commensal Neisseria, there was a greater than fourfold reduction in the NO steady-state level in the presence of nitrite as compared with N. gonorrhoeae. All of the species tested generated an NO steady-state level in the presence of an NO donor that was similar to that of N. gonorrhoeae. The greatest difference between the Neisseria species was the lack of a functional Nos system in the pathogenic species N. gonorrhoeae and N. meningitidis.

  19. Comparison of denitrification activity measurements in groundwater using cores and natural-gradient tracer tests (United States)

    Smith, R.L.; Garabedian, S.P.; Brooks, M.H.


    The transport of many solutes in groundwater is dependent upon the relative rates of physical flow and microbial metabolism. Quantifying rates of microbial processes under subsurface conditions is difficult and is most commonly approximated using laboratory studies with aquifer materials. In this study, we measured in situ rates of denitrification in a nitrate- contaminated aquifer using small-scale, natural-gradient tracer tests and compared the results with rates obtained from laboratory incubations with aquifer core material. Activity was measured using the acetylene block technique. For the tracer tests, co-injection of acetylene and bromide into the aquifer produced a 30 ??M increase in nitrous oxide after 10 m of transport (23-30 days). An advection-dispersion transport model was modified to include an acetylene-dependent nitrous oxide production term and used to simulate the tracer breakthrough curves. The model required a 4-day lag period and a relatively low sensitivity to acetylene to match the narrow nitrous oxide breakthrough curves. Estimates of in situ denitrification rates were 0.60 and 1.51 nmol of N2O produced cm-3 aquifer day-1 for two successive tests. Aquifer core material collected from the tracer test site and incubated as mixed slurries in flasks and as intact cores yielded rates that were 1.2-26 times higher than the tracer test rate estimates. Results with the coring-dependent techniques were variable and subject to the small- scale heterogeneity within the aquifer, while the tracer tests integrated the heterogeneity along a flow path, giving a rate estimate that is more applicable to transport at the scale of the aquifer.

  20. 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


    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

  1. Isotopic composition of nitrate in the central Arabian Sea and eastern tropical North Pacific: A tracer for mixing and nitrogen cycles

    Digital Repository Service at National Institute of Oceanography (India)

    Brandes, J.A.; Devol, A.H.; Yoshinari, T.; Jayakumar, D.A.; Naqvi, S.W.A.

    . Shaded region denotes depths with < 10 µM O2 concentrations. dence of reduced denitrification activity as only a weak sec- ondary nitrite maximum was observed. Nitrate deficits calculated with the potential temperature-expected nitrate re...- lationships of Naqvi et al. (1990) exhibited a similar pattern with B5N-N0,, with peak deficits of 9 µM at 300 m for September 1993 and January 1995 and 7.5 µM for April 1994. Negative nitrate deficits were observed for near-sur- face (80 m) samples were...

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

    Directory of Open Access Journals (Sweden)

    Madeline Eleanore Giles


    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.

  3. Use of continuous monitoring to assess stream nitrate flux and transformation patterns. (United States)

    Jones, Christopher; Kim, Sea-Won; Schilling, Keith


    Delivery of nitrogen from farmed fields to the stream network is an ongoing water quality issue in central North America and other parts of the world. Although fertilization and other farming practices have been refined to produce environmental improvements, stemming loss of nitrogen, especially in the soluble nitrate form, is a problem that has seemingly defied solution. The Iowa Nutrient Reduction Strategy is a policy initiative designed to implement conservation and other farm management practices to produce reductions in nitrate loading. The strategy does not focus on how the streams themselves may or may not be processing nitrogen and reducing downstream loading. We used continuous high-frequency nitrate and discharge monitoring over 3 years at two sites separated by 18 km in a low-order, agricultural stream in eastern Iowa to estimate how nitrogen is processed, and whether or not these processes are reducing downstream loading. We conclude that the upstream to downstream nitrate concentration decline between the two sites was not driven by denitrification. These data also show that nitrate concentrations are closely coupled to discharge during periods of adequate moisture, but decoupling of concentration from discharge occurs during dry periods. This decoupling is a possible indicator of in-stream nitrate processing. Finally, nitrate concentrations are likely diluted by water sourced from non-row crop land covers in the lower reaches of the watershed.

  4. Tentative Study on a New Way of Simultaneous Desulfurization and Denitrification%一种利用脱氮硫杆菌的同步脱硫反硝化新工艺研究

    Institute of Scientific and Technical Information of China (English)

    王爱杰; 杜大仲; 任南琪; 程翔; 刘春爽


    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-/NO-3) in the respectively, in order to achieve high conversion of sulfur.

  5. Identification of the autotrophic denitrifying community in nitrate removal reactors by DNA-stable isotope probing. (United States)

    Xing, Wei; Li, Jinlong; Cong, Yuan; Gao, Wei; Jia, Zhongjun; Li, Desheng


    Autotrophic denitrification has attracted increasing attention for wastewater with insufficient organic carbon sources. Nevertheless, in situ identification of autotrophic denitrifying communities in reactors remains challenging. Here, a process combining micro-electrolysis and autotrophic denitrification with high nitrate removal efficiency was presented. Two batch reactors were fed organic-free nitrate influent, with H(13)CO3(-) and H(12)CO3(-) as inorganic carbon sources. DNA-based stable-isotope probing (DNA-SIP) was used to obtain molecular evidence for autotrophic denitrifying communities. The results showed that the nirS gene was strongly labeled by H(13)CO3(-), demonstrating that the inorganic carbon source was assimilated by autotrophic denitrifiers. High-throughput sequencing and clone library analysis identified Thiobacillus-like bacteria as the most dominant autotrophic denitrifiers. However, 88% of nirS genes cloned from the (13)C-labeled "heavy" DNA fraction showed low similarity with all culturable denitrifiers. These findings provided functional and taxonomical identification of autotrophic denitrifying communities, facilitating application of autotrophic denitrification process for wastewater treatment.

  6. 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...

  7. California GAMA Program: Sources and transport of nitrate in shallow groundwater in the Llagas Basin of Santa Clara County, California

    Energy Technology Data Exchange (ETDEWEB)

    Moran, J E; McNab, W; Esser, B; Hudson, G; Carle, S; Beller, H; Kane, S; Tompson, A B; Letain, T; Moore, K; Eaton, G; Leif, R; Moody-Bartel, C; Singleton, M


    A critical component of the State Water Resource Control Board's Groundwater Ambient Monitoring and Assessment (GAMA) Program is to assess the major threats to groundwater resources that supply drinking water to Californians (Belitz et al., 2004). Nitrate is the most pervasive and intractable contaminant in California groundwater and is the focus of special studies under the GAMA program. This report presents results of a study of nitrate contamination in the aquifer beneath the cities of Morgan Hill and Gilroy, CA, in the Llagas Subbasin of Santa Clara County, where high nitrate levels affect several hundred private domestic wells. The main objectives of the study are: (1) to identify the main source(s) of nitrate that issue a flux to the shallow regional aquifer (2) to determine whether denitrification plays a role in the fate of nitrate in the subbasin and (3) to assess the impact that a nitrate management plan implemented by the local water agency has had on the flux of nitrate to the regional aquifer. Analyses of 56 well water samples for major anions and cations, nitrogen and oxygen isotopes of nitrate, dissolved excess nitrogen, tritium and groundwater age, and trace organic compounds, show that synthetic fertilizer is the most likely source of nitrate in highly contaminated wells, and that denitrification is not a significant process in the fate of nitrate in the subbasin except in the area of recycled water application. In addition to identifying contaminant sources, these methods offer a deeper understanding of how the severity and extent of contamination are affected by hydrogeology and groundwater management practices. In the Llagas subbasin, the nitrate problem is amplified in the shallow aquifer because it is highly vulnerable with high vertical recharge rates and rapid lateral transport, but the deeper aquifers are relatively more protected by laterally extensive aquitards. Artificial recharge delivers low-nitrate water and provides a means of

  8. 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


    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.

  9. Flood survey of nitrate behaviour using nitrogen isotope tracing in the critical zone of a French agricultural catchment (United States)

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


    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.

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

    Institute of Scientific and Technical Information of China (English)


    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.

  11. Vulnerability of recently recharged groundwater in principal [corrected] aquifers of the United States to nitrate contamination. (United States)

    Gurdak, Jason J; Qi, Sharon L


    Recently recharged water (defined here as aquifer to subaquifer scale. New logistic regression models were developed using data from the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program and National Water Information System for 17 principal aquifers of the U.S. to identify important source, transport, and attenuation factors that control nonpoint source nitrate concentrations greater than relative background levels in recently recharged groundwater and were used to predict the probability of detecting elevated nitrate in areas beyond the sampling network. Results indicate that dissolved oxygen, crops and irrigated cropland, fertilizer application, seasonally high water table, and soil properties that affect infiltration and denitrification are among the most important factors in predicting elevated nitrate concentrations. Important differences in controlling factors and spatial predictions were identified in the principal aquifer and national-scale models and support the conclusion that similar spatial scales are needed between informed groundwater management and model development.

  12. California GAMA Special Study: An isotopic and dissolved gas investigation of nitrate source and transport to a public supply well in California's Central Valley

    Energy Technology Data Exchange (ETDEWEB)

    Singleton, M J; Moran, J E; Esser, B K; Roberts, S K; Hillegonds, D J


    This study investigates nitrate contamination of a deep municipal drinking water production well in Ripon, CA to demonstrate the utility of natural groundwater tracers in constraining the sources and transport of nitrate to deep aquifers in the Central Valley. The goal of the study was to investigate the origin (source) of elevated nitrate and the potential for the deep aquifer to attenuate anthropogenic nitrate. The site is ideal for such an investigation. The production well is screened from 165-325 feet below ground surface and a number of nearby shallow and deep monitoring wells were available for sampling. Furthermore, potential sources of nitrate contamination to the well had been identified, including a fertilizer supply plant located approximately 1000 feet to the east and local almond groves. A variety of natural isotopic and dissolved gas tracers including {sup 3}H-{sup 3}He groundwater age and the isotopic composition of nitrate are applied to identify nitrate sources and to characterize nitrate transport. An advanced method for sampling production wells is employed to help identify contaminant contributions from specific screen intervals. Nitrate transport: Groundwater nitrate at this field site is not being actively denitrified. Groundwater parameters indicate oxic conditions, the dissolved gas data shows no evidence for excess nitrogen as the result of denitrification, and nitrate-N and -O isotope compositions do not display patterns typical of denitrification. Contaminant nitrate source: The ambient nitrate concentration in shallow groundwater at the Ripon site ({approx}12 mg/L as nitrate) is typical of shallow groundwaters affected by recharge from agricultural and urban areas. Nitrate concentrations in Ripon City Well 12 (50-58 mg/L as nitrate) are significantly higher than these ambient concentrations, indicating an additional source of anthropogenic nitrate is affecting groundwater in the capture zone of this municipal drinking water well. This

  13. 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


    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.

  14. Nitrate dynamics within a stream-lake network through time and space (United States)

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


    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

  15. Biological removal of nitrate by an oil reservoir culture capable of autotrophic and heterotrophic activities: kinetic evaluation and modeling of heterotrophic process. (United States)

    An, Shijie; Stone, Heather; Nemati, Mehdi


    Kinetics of heterotrophic denitrification was investigated using an oil reservoir culture with the ability to function under both autotrophic and heterotrophic conditions. In the batch system nitrate at concentrations up to 30 mM did not influence the kinetics but with 50mM slower growth and removal rates were observed. A kinetic model, representing the denitrification as reduction of nitrate to nitrite, and subsequent reduction of nitrite to nitrous oxides and nitrogen gas was developed. The value of various kinetic coefficients, including maximum specific growth rate, saturation constant, yield and activation energy for nitrate and nitrite reductions were determined by fitting the experimental data into the developed model. In continuous bioreactors operated with 10 or 30 mM nitrate, complete removal of nitrate (no residual nitrite) and linear dependency between nitrate loading and removal rates were observed for loading rates up to 0.21 and 0.58 mM h(-1), respectively. The highest removal rates of 0.31 and 0.94 mM h(-1) observed at loading rates of 0.42 mM h(-1) and 1.26 mM h(-1), with corresponding removal percentages of nitrate and total nitrogen being 75.4, 54.4%, and 74.4 and 17.9%, respectively. Developed kinetic model predicted the performance of the continuous bioreactors with accuracy.

  16. Impacts of shrimp farm effluent on water quality, benthic metabolism and N-dynamics in a mangrove forest (New Caledonia) (United States)

    Molnar, Nathalie; Welsh, David T.; Marchand, Cyril; Deborde, Jonathan; Meziane, Tarik


    Water quality parameters, sediment oxygen demand (SOD), dissolved organic and inorganic nutrient fluxes, and N-cycle processes (nitrification; denitrification; dissimilatory nitrate reduction to ammonium (DNRA)) were determined in a New Caledonian mangrove receiving shrimp farm effluent and a natural mangrove. Effluent was enriched in nutrients and organic matter, and significantly stimulated SOD and nutrient regeneration rates in the receiving sediments. All N-cycling processes were stimulated between ˜2 and 12-fold in the sediments receiving effluents compared to the natural mangrove. However, due to the preferential enhancement of DNRA compared to denitrification, there was no significant increase in net nitrogen elimination compared to the significant increase in sediment nutrient regeneration rates. These results indicate that the mangroves are only a partial filter for the shrimp farm effluent, as confirmed by the elevated nutrient concentrations measured in an external, marine creek of the effluent receiving mangrove.

  17. Kinetics and corrosion products of aqueous nitrate reduction by iron powder without reaction conditions control

    Institute of Scientific and Technical Information of China (English)

    FAN Xiaomeng; GUAN Xiaohong; MA Jun; AI Hengyu


    Although considerable research has been conducted on nitrate reduction by zero-valent iron powder (Fe0), these studies were mostly operated under anaerobic and invariable pH conditions that was unsuitable for practical application.Without reaction conditions (dissolved oxygen or reaction pH) control, this study aimed at subjecting the kinetics of denitrification by microscale Fe0 (160-200 mesh) to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface.Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant.Additional test results showed that the reduction rate of nitrate increased with increasing Fe0 dosage.The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe0 dosage.Experimental results also suggested that nitrate reduction by microscale Fe0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration.X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO(OH), was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5.The proportion of FeO(OH) increased as reaction time went on, whereas the proportion of Fe3O4 decreased.

  18. Statistical evaluation of effects of riparian buffers on nitrate and ground water quality (United States)

    Spruill, T.B.


    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

  19. Simultaneous biological removal of endosulfan (alpha+beta) and nitrates from drinking waters using wheat straw as substrate. (United States)

    Aslan, Sükrü; Türkman, Ayşen


    Nitrate and endosulfan (alpha+beta) removal was studied in an upflow biological denitrification reactor packed with wheat straw as carbon source and support particles for microorganisms. While almost complete nitrate elimination and between 65% and 70% endosulfan (alpha+beta) elimination occurred when the temperature was higher than 20 degrees C; below that value, nitrate removal efficiency decreased to about 10%. Nitrate, dissolved organic carbon (DOC), and endosulfan (alpha+beta) removal efficiencies decreased considerably at 1500 microg/l endosulfan concentration in the batch experiments. Although a high removal efficiency was observed for endosulfan (alpha+beta) and nitrate in the biological denitrification continuous reactor, the effluent water could not be used for drinking purpose because of the unacceptable levels of endosulfan (alpha+beta), colour and dissolved organic content. During the continuous study, 23.4% of the initial weight of wheat straw was lost and 24 g was consumed per gram of nitrogen removed. The results of the continuous study showed that 21.3% of the endosulfan removal was achieved by adsorption onto the wheat straw and 68.2% of the endosulfan removal occurred by biological activity and the remaining portion was detected in the effluent water.

  20. 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


    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.

  1. Application of light-weight filtration media in an anoxic biofilter for nitrate removal from micro-polluted surface water. (United States)

    Wang, Zheng; Fei, Xiang; He, Shengbing; Huang, Jungchen; Zhou, Weili

    The research investigated nitrate removal from micro-polluted surface water by the single-stage process of anoxic biofilter using light-weight polystyrene beads as filtration media. In this study, sodium acetate was used as an external carbon source and the nitrate removal efficiency under different regimes of hydraulic loading rate (HLR), water temperature, and C/N ratio was studied. In addition, the effect of backwash on denitrification efficiency was investigated. The results show that the biofilter achieved a high nitrate removal efficiency in 2 weeks at water temperatures ranging between 22 and 25 °C at a C/N ratio (COD:NO3(-)-N) of 6:1. Besides, the average removal efficiency of nitrate at HLRs of 5.66, 7.07 and 8.49 m(3) m(-2) h(-1) were 87.5, 87.3 and 87.1%, respectively. The average removal efficiency of nitrate nitrogen was 13.9% at a HLR of 5.66 m(3) m(-2) h(-1) at water temperatures of 12-14 °C, then it increased to 93.7% when the C/N ratio increased to 10. It suggests that the optimal hydraulic retention time is at water temperatures of 8-10 °C. The water consumption rate of backwash was about 0.2-0.3%, and denitrification efficiency returned to the normal level in 12 h after backwash.

  2. Intracellular Nitrate of Marine Diatoms as a Driver of Anaerobic Nitrogen Cycling in Sinking Aggregates

    Directory of Open Access Journals (Sweden)

    Anja Kamp


    Full Text Available Diatom-bacteria aggregates are key for the vertical transport of organic carbon in the ocean. Sinking aggregates also represent pelagic microniches with intensified microbial activity, oxygen depletion in the center, and anaerobic nitrogen cycling. Since some of the aggregate-forming diatom species store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom-bacteria aggregates. Stable 15N isotope incubations under dark and anoxic conditions revealed that axenic S. marinoi is able to reduce intracellular nitrate to ammonium that is immediately excreted by the cells. When exposed to a light:dark cycle and oxic conditions, S. marinoi stored nitrate intracellularly in concentrations > 60 mmol L-1 both as free-living cells and associated to aggregates. Intracellular nitrate concentrations exceeded extracellular concentrations by three orders of magnitude. Intracellular nitrate was used up within 2-3 days after shifting diatom-bacteria aggregates to dark and anoxic conditions. Thirty-one percent of the diatom-derived nitrate was converted to nitrogen gas, indicating that a substantial fraction of the intracellular nitrate pool of S. marinoi becomes available to the aggregate-associated bacterial community. Only 5% of the intracellular nitrate was reduced to ammonium, while 59% was recovered as nitrite. Hence, aggregate-associated diatoms accumulate nitrate from the surrounding water and sustain complex nitrogen transformations, including loss of fixed nitrogen, in anoxic, pelagic microniches. Additionally, it may be expected that intracellular nitrate not converted before the aggregates have settled onto the seafloor could fuel benthic nitrogen transformations.

  3. 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.


    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.

  4. In-stream bioreactor for agricultural nitrate treatment. (United States)

    Robertson, W D; Merkley, L C


    Nitrate from agricultural activity contributes to nutrient loading in surface water bodies such as the Mississippi River. This study demonstrates a novel in-stream bioreactor that uses carbonaceous solids (woodchips) to promote denitrification of agricultural drainage. The reactor (40 m3) was trenched into the bottom of an existing agricultural drainage ditch in southern Ontario (Avon site), and flow was induced through the reactor by construction of a gravel riffle in the streambed. Over the first 1.5 yr of operation, mean influent NO3-N of 4.8 mg L(-1) was attenuated to 1.04 mg L(-1) at a mean reactor flow rate of 24 L min(-1). A series of flow-step tests, facilitated by an adjustable height outlet pipe, demonstrated that nitrate mass removal generally increased with increasing flow rate. When removal rates were not nitrate-limited, areal mass removal ranged from 11 mg N m(-2) h(-1) at 3 degrees C to 220 mg N m(-2) h(-1) at 14 degrees C (n = 27), exceeding rates reported for some surface-flow constructed wetlands in this climatic region by a factor of about 40. Over the course of the field trial, reactor flow rates decreased as a result of silt accumulation on top of the gravel infiltration gallery. Design modifications are currently being implemented to mitigate the effects of siltation. In-stream reactors have the potential to be scaled larger and could be more manageable than attempting to address nitrate loading from individual tile drains. They could also work well in combination with other nitrate control techniques.

  5. Estimation of denitrification potential with respiration based techniques

    NARCIS (Netherlands)

    Kujawa-Roeleveld, K.


    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

  6. Formaldehyde biodegradation and its effect on the denitrification process. (United States)

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


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

  7. Sediment Denitrification in Two Contrasting Tropical Shallow Lagoons

    DEFF Research Database (Denmark)

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


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

  8. Rising Sludge in Secondary Settlers Due to Denitrification

    DEFF Research Database (Denmark)

    Henze, Mogens; Dupont, Rene; Grau, Peter


    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...

  9. Denitrification and the denitrifier community in coastal microbial mats

    NARCIS (Netherlands)

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


    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

  10. 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


    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.

  11. Seasonal carbon cycling in a Greenlandic fjord: an integrated pelagic and benthic study

    DEFF Research Database (Denmark)

    Sørensen, Heidi Louise; Meire, Lorenz; Juul-Pedersen, Thomas


    Climate change is expected to have a pronounced effect on biogeochemical cycling in Arctic fjords, but current insight on the biogeochemical functioning of these systems is limited. Here, we present seasonal data on primary production, export of particulate organic carbon (POC), and the coupling...... carbon amounted to 3.2 and 5.3 mol C m−2 yr−1, respectively. Sulfate reduction was the most prominent mineralization pathway, accounting for 69% of the benthic mineralization, while denitrification accounted for 2%. Overall, the carbon mineralization and burial in Kobbefjord were significantly higher...... in ice coverage in higher Arctic Greenlandic fjords will, as a first approximation, entail proportional increases in productivity, mineralization, and burial of organic carbon in the fjords, which will thus become similar to present-day southerly systems....

  12. Impact of chloride on denitrification potential in roadside wetlands. (United States)

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


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

  13. Effect of phosphorus load on nutrients removal and N₂O emission during low-oxygen simultaneous nitrification and denitrification process. (United States)

    Jia, Wenlin; Liang, Shuang; Ngo, Huu Hao; Guo, Wenshan; Zhang, Jian; Wang, Rong; Zou, Yina


    Three laboratory scale anaerobic-aerobic (low-oxygen) SBRs (R1, R2 and R3) were conducted at different influent phosphorus concentration to evaluate the impacts of phosphorus load on nutrients removal and nitrous oxide (N₂O) emission during low-oxygen simultaneous nitrification and denitrification (SND) process. The results showed that TP and TN removals were enhanced simultaneously with the increase in phosphorus load. It was mainly caused by the enrichment of polyphosphate accumulating organisms (PAOs) under high phosphorus load and low COD/P ratio (<50), which could use nitrate/nitrite as electron acceptors to take up the phosphorus. N₂O emission was reduced with increasing phosphorus load. N₂O-N emission amount per cycle of R3 was 24.1% lower than that of R1. It was due to the decrease of N₂O yield by heterotrophic denitrification. When the phosphorus load increased from R1 to R3, heterotrophic denitrification (D) ranged from 42.6% to 36.6% of the N₂O yield.

  14. 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


    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.

  15. 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: [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)


    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

  16. Benthic nutrient fluxes along the Laurentian Channel: Impacts on the N budget of the St. Lawrence marine system (United States)

    Thibodeau, Benoît; Lehmann, Moritz F.; Kowarzyk, Jacqueline; Mucci, Alfonso; Gélinas, Yves; Gilbert, Denis; Maranger, Roxane; Alkhatib, Mohammad


    Water column concentrations and benthic fluxes of dissolved inorganic nitrogen (DIN) and oxygen (DO) were measured in the Gulf of St. Lawrence and the Upper and Lower St. Lawrence Estuary (USLE and LSLE, respectively) to assess the nitrogen (N) budget in the St. Lawrence (SL) system, as well as to elucidate the impact of bottom water hypoxia on fixed-N removal in the LSLE. A severe nitrate deficit, with respect to ambient phosphate concentrations (N*˜-10 μmol L -1), was observed within and in the vicinity of the hypoxic bottom water of the LSLE. Given that DO concentrations in the water column have remained above 50 μmol L -1, nitrate reduction in suboxic sediments, rather than in the water column, is most likely responsible for the removal of fixed N from the SL system. Net nitrate fluxes into the sediments, derived from pore water nitrate concentration gradients, ranged from 190 μmol m -2 d -1 in the hypoxic western LSLE to 100 μmol m -2 d -1 in the Gulf. The average total benthic nitrate reduction rate for the Laurentian Channel (LC) is on the order of 690 μmol m -2 d -1, with coupled nitrification-nitrate reduction accounting for more than 70%. Using average nitrate reduction rates derived from the observed water column nitrate deficit, the annual fixed-N elimination within the three main channels of the Gulf of St. Lawrence and LSLE was estimated at 411 × 10 6 t N, yielding an almost balanced N budget for the SL marine system.

  17. Benthic nutrient fluxes in the intertidal flat within the Changjiang (Yangtze River) Estuary

    Institute of Scientific and Technical Information of China (English)

    GAO Lei; LI Daoji; WANG Yanming; YU Lihua; KONG Dingjiang; LI Mei; LI Yun; FANG Tao


    In an annual cycle from March 2005 to February 2006, benthic nutrient fluxes were measured monthly in the Dongtan intertidal flat within the Changjiang (Yangtze River) Estuary. Except for NH4+, there always showed high fluxes from overlying water into sediment for other four nutrients. Sediments in the high and middle marshes, covered with halophyte and consisting of macrofauna, demonstrated more capabilities of assimilating nutrients from overlying water than the low marsh. Sampling seasons and nutrient concentrations in the overlying water could both exert significant effects on these fluxes. Additionally, according to the model provided by previous study, denitrification rates, that utilizing NO3- transported from overlying water (DW) in Dongtan sediments, were estimated to be from -16 to 193 μmol·h-1·m-2 with an average value of 63 μmol·h-1·m-2 (n=18). These estimated values are still underestimates of the in-situ rates owing to the lack of consideration of DN, I.e., denitrification supported by the local NO3- production via nitrification.

  18. Mechanisms of temporary adhesion in benthic animals

    NARCIS (Netherlands)

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


    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

  19. Nitrate Leaching Management (United States)

    Nitrate (NO3) leaching is a significant nitrogen (N) loss process for agriculture that must be managed to minimize NO3 enrichment of groundwater and surface waters. Managing NO3 leaching should involve the application of basic principles of understanding the site’s hydrologic cycle, avoiding excess ...

  20. State of the benthic ecosystem on western Black Sea shelf in spring 2008 (United States)

    Friedrich, J.; Aleynik, D.; Eulenburg, A.; Kusch, St.; Mee, L. D.; Minicheva, G.; Stevens, T. F.; Teaca, A.; Shapiro, G. I.; Soloviev, D.


    : thermal heating and freshwater input created a double front structure on the western shelf, and intrusion of the Cold Intermediate Layer (CIL) into shelf waters was observed. Surface distribution of dissolved nutrients reflects clear signals of silica and total dissolved nitrogen input from the Danube River. Phosphate appears to have a different source, e.g. benthic and/or from the CIL. The benthic ecosystem remains fragile; diversity indices reflect small recovery, quantities in biomass of both zoo- and phytobenthos indicate ongoing perturbations in nearshore areas. A full recovery of historical beds of Phyllophora is not evident, coverage both in winter and summer is less than 10%, and its role as habitat could be compromised by overgrowth of filamentous algae. The benthic system with an epibenthic community in balance releases less nutrients than a disturbed system without benthic life. Nutrients release from the sediment is lower in winter than in summer. The oxygen penetration depth in the sediment triggers denitrification. A spectacular population development of opportunistic species both in zoo- and phytobenthos was observed. The question remains whether or not those opportunistic species can ensure ecosystem functionality and stability. Our findings will help to identify locations crucial for the functioning for the benthic shelf ecosystem, to define "Good Environmental Status" and help to provide recommendations for Marine protected areas on the western Black Sea shelf. It is hoped that the data will make an important contribution to the information base underpinning the new European Marine Strategy Directive and the Bucharest Convention for the Protection of the Black Sea.

  1. Nitrate absorption through hydrotalcite reformation. (United States)

    Frost, Ray L; Musumeci, Anthony W


    Thermally activated hydrotalcite based upon a Zn/Al hydrotalcite with carbonate in the interlayer has been used to remove nitrate anions from an aqueous solution resulting in the reformation of a hydrotalcite with a mixture of nitrate and carbonate in the interlayer. X-ray diffraction of the reformed hydrotalcites with a d(003) spacing of 7.60 A shows that the nitrate anion is removed within a 30 min period. Raman spectroscopy shows that two types of nitrate anions exist in the reformed hydrotalcite (a) nitrate bonded to the 'brucite-like' hydrotalcite surface and (b) aquated nitrate anion in the interlayer. Kinetically the nitrate is replaced by the carbonate anion over a 21 h period. Two types of carbonate anions are observed. This research shows that the reformation of a thermally activated hydrotalcite can be used to remove anions such as nitrate from aqueous systems.

  2. Insights on Biogeochemistry from the Triple Isotope System of Nitrate (Invited) (United States)

    Meixner, T.; Michalski, G. M.; Dejwahk, N.; Riha, K. M.; Lohse, K. A.; Gallo, E. L.; McIntosh, J. C.; Brooks, P. D.


    Given its central role in biogeochemistry, its multiple valences and the reactive and unreactive gaseous forms, the nitrogen cycle has long proven a difficult biogeochemical system to unravel. The oxidized form of nitrogen, nitrate, has been of particular interest due to its hydrologic mobility and role as a common groundwater contaminant. While the use of δ15N and δ18O of nitrate have long helped us over the last decade to distinguish sources of contaminant and biogeochemical processes, such as nitrate reduction, the addition of Δ17O (the triple isotope approach) has quantified the variability and importance of atmospheric contributions of nitrate, as well as the fate and transport of nitrate in natural environments. In the process of following this atmospherically sourced nitrate through hydrologic systems we have been further able to elucidate the loss and transformation processes that influence nitrate of all origins in the environment. Here, we will highlight the utility of the triple isotope system in a semi-arid system with reference to studies in other settings. The Tucson basin has four main sources of nitrogen- atmospheric deposition, terrestrial N fixation, anthropogenic fertilizer, and sewage effluent. The triple isotope system enabled the identification of denitrification as a major loss pathway after effluent discharge. We were also able to quantify the contribution of atmospheric nitrate directly to the regional groundwater system, and identify spatial patterns in surface water and groundwater. By bringing additional nitrogen budget and tracer data to bear we were able to constrain the biogeochemical cycling of N in the Tucson basin. This study offers lessons for those working on the N cycle in other settings and the triple isotope system offers a unique tool to help isolate the different processes that influence nitrate concentrations in natural waters.

  3. Treatment of dissolved perchlorate, nitrate, and sulfate using zero-valent iron and organic carbon. (United States)

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


    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.

  4. Benthic flux of nutrients and trace metals in the northern component of San Francisco Bay, California (United States)

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


    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

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

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


    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.

  6. Nitrogen cycling in the deep sedimentary biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic (United States)

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


    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 (

  7. Autonomous Marine Robotic Technology Reveals an Expansive Benthic Bacterial Community Relevant to Regional Nitrogen Biogeochemistry. (United States)

    Valentine, David L; Fisher, G Burch; Pizarro, Oscar; Kaiser, Carl L; Yoerger, Dana; Breier, John A; Tarn, Jonathan


    Benthic accumulations of filamentous, mat-forming bacteria occur throughout the oceans where bisulfide mingles with oxygen or nitrate, providing key but poorly quantified linkages between elemental cycles of carbon, nitrogen and sulfur. Here we used the autonomous underwater vehicle Sentry to conduct a contiguous, 12.5 km photoimaging survey of sea-floor colonies of filamentous bacteria between 80 and 579 m water depth, spanning the continental shelf to the deep suboxic waters of the Santa Barbara Basin (SBB). The survey provided >31 000 images and revealed contiguous, white-colored bacterial colonization coating > ∼80% of the ocean floor and spanning over 1.6 km, between 487 and 523 m water depth. Based on their localization within the stratified waters of the SBB we hypothesize a dynamic and annular biogeochemical zonation by which the bacteria capitalize on periodic flushing events to accumulate and utilize nitrate. Oceanographic time series data bracket the imaging survey and indicate rapid and contemporaneous nitrate loss, while autonomous capture of microbial communities from the benthic boundary layer concurrent with imaging provides possible identities for the responsible bacteria. Based on these observations we explore the ecological context of such mats and their possible importance in the nitrogen cycle of the SBB.

  8. Distillery wastes as external carbon sources for denitrification in municipal wastewater treatment plants. (United States)

    Czerwionka, K; Makinia, J; Kaszubowska, M; Majtacz, J; Angowski, M


    In this study, by-products from alcohol production were examined in terms of their potential application as external carbon sources for enhancing denitrification in biological nutrient removal systems. Three types of batch tests were used to compare the effects of the distillery by-products, such as fusel oil, syrup and reject water, on the non-acclimated activated sludge. Much higher nitrate utilization rates (NURs) were observed for the latter two carbon sources. In the conventional NUR measurements (one-phase experiments), the observed NURs with syrup and reject water were 3.2-3.3 g N/(kg VSS h) compared with 1.0 g N/(kg VSS h) obtained for fusel oils from two different distilleries. When the carbon sources were added at the beginning of the anoxic phase preceded by an anaerobic phase (two-phase experiments), the NURs were 4.2 g N/(kg VSS h) (syrup and reject water) and 2.4-2.7 g N/(kg VSS h) (fusel oils). The heterotrophic yield coefficient, determined based on the conventional OUR measurements, varied in a relatively narrow range (0.72-0.79 g COD/g COD) for all the examined carbon sources. Due to advantageous composition (much higher COD concentrations and COD/N ratios), fusel is a preferred carbon source for practical handling in full-scale wastewater treatment plants.

  9. Effect of high electron donor supply on dissimilatory nitrate reduction pathways in a bioreactor for nitrate removal. (United States)

    Behrendt, Anna; Tarre, Sheldon; Beliavski, Michael; Green, Michal; Klatt, Judith; de Beer, Dirk; Stief, Peter


    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 conditions where DNRA would be thermodynamically favorable. Remarkably, the microbial community exposed to a high C/NO3(-) ratio and sulfide concentration did not use the most energy-gaining process.

  10. Quantifying nitrate dynamics in an oligotrophic lake using Δ17O

    Directory of Open Access Journals (Sweden)

    A. Tanaka


    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.

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

    Directory of Open Access Journals (Sweden)

    A. Canion


    Full Text Available Despite decades of research on the physiology and biochemistry of nitrate/nitrite-respiring microorganisms, little is known regarding their metabolic response to temperature, especially under in situ conditions. The temperature regulation of microbial communities that mediate anammox and denitrification was investigated in near shore permeable sediments at polar, temperate, and subtropical sites with annual mean temperatures ranging from −5 to 23 °C. Total N2 production rates were determined using the isotope pairing technique in intact core incubations under diffusive and simulated advection conditions and ranged from 2 to 359 μmol N m−2 d−1. For the majority of sites studied, N2 removal was 2 to 7 times more rapid under advective flow conditions. Anammox comprised 6 to 14% of total N2 production at temperate and polar sites and was not detected at the subtropical site. Potential rates of denitrification and anammox were determined in anaerobic slurries in a temperature gradient block incubator across a temperature range of −1 to 42 °C. The highest optimum temperature (Topt for denitrification was 36 °C and was observed in subtropical sediments, while the lowest Topt of 21 °C was observed at the polar site. Seasonal variation in the Topt was observed at the temperate site with values of 26 and 34 °C in winter and summer, respectively. The Topt values for anammox were 9 and 26 °C at the polar and temperate sites, respectively. The results demonstrate adaptation of denitrifying communities to in situ temperatures in permeable marine sediments across a wide range of temperatures, whereas marine anammox bacteria may be predominately psychrophilic to psychrotolerant. To our knowledge, we provide the first rates of denitrification and anammox from permeable sediments of a polar permanently cold ecosystem. The adaptation of microbial communities to in situ temperatures suggests that the relationship between temperature and rates of N

  12. Isotopologue fractionation during N(2)O production by fungal denitrification. (United States)

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


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

  13. Molecular identification of potential denitrifying bacteria and use of D-optimal mixture experimental design for the optimization of denitrification process. (United States)

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


    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).

  14. 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


    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.

  15. 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


    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

  16. 'NO', a useful tool for the estimation of nitrate deficits in the Arabian Sea (United States)

    Naqvi, S. W. A.; Sen Gupta, R.


    The property 'NO', defined as the sum of O 2 and 8.65 NO 3, varies linearly with potential temperature (θ) outside the denitrification zone in the Arabian Sea, but a change in slope of the 'NO'—θ regression line occurs at θ ≈ 15°C. The 'NO'-θ relationships have been utilized to compute the 'original' nitrate concentrations which are combined with the observed data to calculate the nitrate deficits within the denitrification zone. This procedure, which approximately accounts for the 'reserved' nitrate, eliminates the errors associated with the use of the variable ΔAOU:ΔPO 4 ratio in earlier methods. In upper layers, the present method yields deficits close to those deduced from the oxidative ratios and (NO 3) r-(PO 4) r relationship. In deep layers (depth > 500 m), however, slightly higher values are obtained with the present method, presumably due to the variability of relationships between 'reserved' nutrients. Distribution of nitrate anomaly (ΔN) along a section running from 15°N, 67°E to 21°N, 63°E closely follows the distribution of nitrite at the secondary maximum. Nitrate anomalies in excess of 8 μg-at. dm -3 are observed frequently along this section. An intermediate minimum in ΔN is observed at some stations at depths where the Subantarctic Mode Water is encountered. This water mass, relatively rich in oxygen, appears to be a source of limited oxygen supply which probably prevents the intermediate layers from becoming completely anoxic.

  17. 33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate... (United States)


    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate; general provisions. 126.28 Section 126...) WATERFRONT FACILITIES HANDLING OF DANGEROUS CARGO AT WATERFRONT FACILITIES § 126.28 Ammonium...


    Directory of Open Access Journals (Sweden)

    Artur Mielcarek


    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.

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

    DEFF Research Database (Denmark)

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


    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....

  20. Nitrate in drinking water

    DEFF Research Database (Denmark)

    Schullehner, Jörg; Hansen, Birgitte; Sigsgaard, Torben

    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......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....... 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...

  1. 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


    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.

  2. Diurnal variation of dominant nitrate retention processes in an agricultural headwater stream (United States)

    Schuetz, Tobias; Ryabenko, Evgenia; Stumpp, Christine


    Nitrate and ammonium are introduced by agricultural practice into the environment and are transformed and retained on their pathway through aquatic environments. In particular, biological transformation processes (i.e. microbial denitrification or ammonium oxidation and assimilation) are responsible for the largest part of nitrate removal, which are also crucial processes in headwater streams. It is well known, that most of the biological processes are influenced by available (solar) energy fluxes, temperatures and dissolved oxygen concentrations, which vary with time and space. However, looking at biogeochemical hot spots in the landscapes` hydrological interface, the stream and river network (e.g. stream sections with a high biological activity), the temporal variability of biological processes can be an important control on total nitrate export. In this study, we therefore identified most important diurnal time periods for nitrate retention in a 75 m impervious section of an agricultural headwater stream using oxygen saturation dynamics and nitrate isotopes. We regularly measured discharge, hydro-geochemical and climate parameters, as well as nitrate and water isotopes in grab samples at three locations along the reach. On average, we observed a decrease of 10% in nitrate concentration from up- to downstream, which was only caused by biological processes and not by dilution. Nitrate isotope analysis indicated distinct trends along the reach and with time of the day. Both nitrate assimilation and nitrification caused significant changes in nitrate isotope distribution in the early day. To explain the distinct observed process dynamics from the morning to the afternoon, we simulated net primary production (NEP) and respiration using the river metabolism model RIVERMETC with observed oxygen concentrations and water temperatures. Comparing the results with the observed nitrate dynamics, the short time period when NEP occurs (~10:30 -12:30) seems to be crucial for

  3. Physiology and enzymology involved in denitrification by Shewanella putrefaciens (United States)

    Krause, B.; Nealson, K. H.


    Nitrate reduction to N2O was investigated in batch cultures of Shewanella putrefaciens MR-1, MR-4, and MR-7. All three strains reduced nitrate to nitrite to N2O, and this reduction was coupled to growth, whereas ammonium accumulation was very low (0 to 1 micromol liter-1). All S. putrefaciens isolates were also capable of reducing nitrate aerobically; under anaerobic conditions, nitrite levels were three- to sixfold higher than those found under oxic conditions. Nitrate reductase activities (31 to 60 micromol of nitrite min-1 mg of protein-1) detected in intact cells of S. putrefaciens were equal to or higher than those seen in Escherichia coli LE 392. Km values for nitrate reduction ranged from 12 mM for MR-1 to 1.3 mM for MR-4 with benzyl viologen as an artifical electron donor. Nitrate and nitrite reductase activities in cell-free preparations were demonstrated in native gels by using reduced benzyl viologen. Detergent treatment of crude and membrane extracts suggested that the nitrate reductases of MR-1 and MR-4 are membrane bound. When the nitrate reductase in MR-1 was partially purified, three subunits (90, 70, and 55 kDa) were detected in denaturing gels. The nitrite reductase of MR-1 is also membrane bound and appeared as a 60-kDa band in sodium dodecyl sulfate-polyacrylamide gels after partial purification.

  4. Tracing atmospheric nitrate in groundwater using triple oxygen isotopes: evaluation based on bottled drinking water

    Directory of Open Access Journals (Sweden)

    F. Nakagawa


    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.

  5. Biohydrogen facilitated denitrification at biocathode in bioelectrochemical system (BES). (United States)

    Liu, Hao; Yan, Qun; Shen, Wei


    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.

  6. Denitrification 'hot spots' in soil following surface residue application (United States)

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


    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

  7. 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


    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.

  8. Quantifying denitrification losses from a sub-tropical pasture in Queensland/Australia - use of the 15N gas flux method (United States)

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


    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

  9. Development of hydraulic properties and nitrate turnover processes in minerotrophic fen soil on differnet scales (United States)

    Kleimeier, Christian; Lennartz, Bernd


    Generally, it is recommended to remove the uppermost highly degraded peat layer from fens prior to rewetting to eliminate a potential source of organic pollutants for downstream water bodies. We investigated this material as a potential medium for denitrifying filters to further use the organic material. We are aiming to remove nitrate from tile drainage runoff at the outlet drainage dominated catchments to fullfill the requirements of the European Water Framework Directive. In a lysimeter scale long term mesocosm experiments we were aiming to reveal the peats behavior after disturbing and rewetting under constant flow conditions. Tracer experiments revealed a restructuring of the peat ending up at 20/80 percentage of mobile immobile pore volume. Additionally we observed the nitrate turnover. The turnover rate was determined by the hydraulic load. Absolute turnover rates were equal at lower and higher concentrations as well as flow rates, whereas the turnover reached higher percentages at lower concentrations. To further reveal the nitrate turnover processes flow through rector experiments were conducted in an anaerobic environment. We found that strongly reducing conditions can be created in peat even at the presence of nitrate. Thus we can conclude that the minerotrophic peat with its high iron and sulfur concentrations also enables autotrophic denitrification oxidizing iron and sulfur. While the conditions are favorable to re-reduce iron and sulfur,thus an electron shuttling system developed transporting electrons from the organic material as initial e- donor to nitrate as terminal e- acceptor.

  10. Nitrate removal performance of Diaphorobacter nitroreducens using biodegradable plastics as the source of reducing power (United States)

    Khan, S. T.; Nagao, Y.; Hiraishi, A.


    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.

  11. 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


    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.

  12. A record of ozone variability in South Pole Antarctic snow: Role of nitrate oxygen isotopes (United States)

    McCabe, Justin R.; Thiemens, Mark H.; Savarino, Joel


    The information contained in polar nitrate has been an unresolved issue for over a decade. Here we demonstrate that atmospheric nitrate's oxygen isotopic composition (Δ17O-NO3) reflects stratospheric chemistry in winter and tropospheric chemistry in summer. Surface snow isotope mass balance indicates that nitrate oxygen isotopic composition is the result of a mixture of 25% stratospheric and 75% tropospheric origin. Analysis of trends in Δ17O-NO3 in a 6 m snow pit that provides a 26-year record reveals a strong 2.70-year cycle that anticorrelates (R = -0.77) with October-November-December column ozone. The potential mechanisms linking the records are either denitrification or increased boundary layer photochemical ozone production. We suggest that the latter is dominating the observed trend and find that surface ozone and Δ17O-NO3 correlate well before 1991 (R = 0.93). After 1991, however, the records show no significant relationship, indicating an altered oxidative environment consistent with current understanding of a highly oxidizing atmosphere at the South Pole. The disappearance of seasonal Δ17O-NO3 trends in the surface layer at depth remain unresolved and demand further investigation of how postdepositional processes affect nitrate's oxygen isotope composition. Overall, the findings of this study present a new paleoclimate technique to investigate Antarctic nitrate records that appear to reflect trends in stratospheric ozone depletion by recording tropospheric surface ozone variability.

  13. Feasibility of remote sensing benthic microalgae (United States)

    Zingmark, R. G.


    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.

  14. Benthic Habitats of the Florida Keys (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...


    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...

  16. Assessment of sources and fate of nitrate in shallow groundwater of an agricultural area by using a multi-tracer approach. (United States)

    Pastén-Zapata, Ernesto; Ledesma-Ruiz, Rogelio; Harter, Thomas; Ramírez, Aldo I; Mahlknecht, Jürgen


    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.

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

    Institute of Scientific and Technical Information of China (English)

    GUO Pi-jian


    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.

  18. Effects on water chemistry, benthic invertebrates and brown trout following forest fertilization in central Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Goethe, L.; Soederberg, H.; Sjoelander, E. (County Administrative Board of Vaesternorrland, Haernoesand (Sweden). Environmental Unit); Nohrstedt, H.Oe. (Inst. for Forest Improvement, Uppsala (Sweden))


    Two coniferous forest drainage areas in central Sweden were partially fertilized with ammonium nitrate and calcium ammonium nitrate respectively, both at a dose of 150 kg N per ha. During the following years observations were made on stream water chemistry, invertebrates and brown trout (Salmo trutta L.). Upstream stations were used as controls. Very high concentrations of inorganic N (up to 45 mg l[sup -1]) were recorded immediately after the fertilization. Thereafter, concentration decreased rapidly but remained elevated during the whole study period. Acidity conditions (pH, alkalinity, aluminium) were unaffected by both treatments. The only registered effect on the benthic fauna was a three- to five-fold increase of drifting invertebrates during the first four-five days after the treatment. However, this did not reduce the population density at the treated stations. No effects on population of trout were recorded. (22 refs., 6 figs., 3 tabs.).

  19. Coastal Benthic Boundary Layer (CBBL) Research Program (United States)


    Ecologic Atlas of Benthic Foraminifera of the Gulf of Mexico . Marine Science International, Woods Hole, MA, 174 p. Shiller, Alan, M., Brunner, Charlotte A...implications for the preservation of skeletal carbonates. Sedimentology, 45:39-51. Poag, C. Wylie, 1981. Ecologic Atlas of Benthic Foraminifera of the Gulf of...of the inner continental shelf. The shelf of the northeastern Gulf of Mexico is currently sediment-starved with most material deposited by the

  20. Simultaneous domestic wastewater and nitrate sewage treatment by DEnitrifying AMmonium OXidation (DEAMOX) in sequencing batch reactor. (United States)

    Du, Rui; Cao, Shenbin; Li, Baikun; Wang, Shuying; Peng, Yongzhen


    A novel DEAMOX system was developed for nitrogen removal from domestic wastewater and nitrate (NO3(-)-N) sewage in sequencing batch reactor (SBR). High nitrite (NO2(-)-N) was produced from NO3(-)-N reduction in partial-denitrification process, which served as electron acceptor for anammox and was removed with ammonia (NH4(+)-N) in domestic wastewater simultaneously. A 500-days operation demonstrated that the efficient and stable nitrogen removal performance could be achieved by DEAMOX. The total nitrogen (TN) removal efficiency was as high as 95.8% with influent NH4(+)-N of 63.58 mg L(-1) and NO3(-)-N of 69.24 mg L(-1). The maximum NH4(+)-N removal efficiency reached up to 94.7%, corresponding to the NO3(-)-N removal efficiency of 97.8%. The biomass of partial-denitrification and anammox bacteria was observed to be wall-growth. The deteriorated nitrogen removal performance occurred due to excess denitrifying microbial growth in the outer layer of sludge consortium, which prevented the substrate transfer for anammox inside. However, an excellent nitrogen removal could be guaranteed by scrapping the superficial denitrifying biomass at regular intervals. Furthermore, the high-throughput sequencing analysis revealed that the Thauera genera (26.33%) was possibly responsible for the high NO2(-)-N accumulation in partial-denitrification and Candidatus Brocadia (1.7%) was the major anammox species.

  1. Assimilation of nitrate by yeasts. (United States)

    Siverio, José M


    Nitrate assimilation has received much attention in filamentous fungi and plants but not so much in yeasts. Recently the availability of classical genetic and molecular biology tools for the yeast Hansenula polymorpha has allowed the advance of the study of this metabolic pathway in yeasts. The genes YNT1, YNR1 and YNI1, encoding respectively nitrate transport, nitrate reductase and nitrite reductase, have been cloned, as well as two other genes encoding transcriptional regulatory factors. All these genes lie closely together in a cluster. Transcriptional regulation is the main regulatory mechanism that controls the levels of the enzymes involved in nitrate metabolism although other mechanisms may also be operative. The process involved in the sensing and signalling of the presence of nitrate in the medium is not well understood. In this article the current state of the studies of nitrate assimilation in yeasts as well as possible venues for future research are reviewed.

  2. 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


    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.

  3. Simultaneous nitrate and organic matter removal from salmon industry wastewater: the effect of C/N ratio, nitrate concentration and organic load rate on batch and continuous process. (United States)

    Huiliñir, C; Hernández, S; Aspé, E; Roeckel, M


    Although simultaneous denitrification-anaerobic digestion has been studied extensively, the use of salmon effluents as organic matter source has received little attention. This study evaluated the effect of C/N ratio, nitrate concentration, and organic load rate (OLR) on simultaneous nitrate and organic matter removal using salmon effluents. The study was carried out in a batch reactor with suspended biomass at 37 °C and pH 7.5, and in continuous biofilm tubular reactors at 37 °C fed with a mixture of a synthetic substrate and a saline protein-rich salmon-plant effluent. The results of the batch and continuous experiments showed that nitrate abatement was greater than 95% at all the studied C/N ratios, without effect of the C/N ratio on NO(3)(-)-N transformation and ammonia production. An increase of nitrate concentration increased organic matter consumption as well as the hydrolytic rate. The organic matter reduction varied between 88% and 40% in the continuous process. For a continuous process, the increase of the OLR decreases the removal of organic matter.

  4. Nitrogen cycling in the subsurface biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic (United States)

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


    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

  5. Nitrogen cycling in the subsurface biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic

    Directory of Open Access Journals (Sweden)

    S. D. Wankel


    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

  6. Vertical activity distribution of dissimilatory nitrate reduction in coastal marine sediments

    DEFF Research Database (Denmark)

    Behrendt, A.; de Beer, D.; Stief, P.


    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...

  7. Isotopologue signatures of nitrous oxide produced by nitrate-ammonifying bacteria isolated from soil (United States)

    Behrendt, Undine; Well, Reinhard; Giesemann, Anette; Ulrich, Andreas; Augustin, Jürgen


    Agricultural soils are the largest single source of anthropogenic N2O to the atmosphere, primarily driven by microbiological processes such as denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Both processes occur under similar conditions of low oxygen concentration and therefore, source partitioning of emitted N2O is difficult. Understanding what controls the dynamics and reaction equilibrium of denitrification and DNRA is important and may allow the development of more effective mitigation strategies. 15N site preference (SP), i.e. the difference between 15N of the central and peripheral N-position of the asymmetric N2O molecule, differs depending on processes involved in N2O formation. Hence investigation of the isotopomer ratios of formed N2O potentially presents a reliable mean to identify its source. In this study, bacterial isolates obtained from organic soils were screened for their ability to reduce nitrate/nitrite to ammonium and to release N2O to the atmosphere. Taxonomic characterisation of the strains revealed that N2O formation was only detected in ammonifying strains affiliated to several genera of the family Enterobacteriaceae and strains belonging to the genus Bacillus and Paenibacillus. Sampling of N2O was conducted by incubation of strains under oxic and anoxic conditions. Investigation of the 15N site preference showed SP values in the range of 39 to 57 o . Incubation conditions had no influence on the SP. The lowest values were achieved by a strain of the species Escherichia coli which was included in this study as a DNRA reference bacterium harbouring the NrfA gene that is coding the nitrite reductase, associated with respiratory nitrite ammonification. Soil isolates showed SP-values higher than 40 o . Comparison of these results with SP-values of N2O produced by denitrifying bacteria in pure cultures (-5 to 0 o )^[1, 2]revealedsignificantdifferences.Incontrast,N_2OproducedbydenitrifyingfungidisplayedSP - valuesinarangeof

  8. 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


    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

  9. Nitrate storage and dissimilatory nitrate reduction by eukaryotic microbes

    DEFF Research Database (Denmark)

    Kamp, Anja; Høgslund, Signe; Risgaard-Petersen, Nils;


    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...

  10. Denitrification and N2 fixation in the Pacific Ocean (United States)

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


    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.

  11. A stable isotope approach and its application for identifying nitrate source and transformation process in water. (United States)

    Xu, Shiguo; Kang, Pingping; Sun, Ya


    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.

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

    Digital Repository Service at National Institute of Oceanography (India)

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

    effective subsurface water renewal along the Arabian Sea?s western boundary through advection from the south (given that the cross-equatorial exchange of subsurface wa- ters is largely confined in the western Indian Ocean ? Swal- low, 1984) as well as from... of the N2/Ar ratio in seawater have yielded estimates of ?ex- cess? N2 that are up to twice the corresponding NO-3 deficits Biogeosciences, 3, 621?633, 2006 626 S. W. A. Naqvi et al.: Arabian Sea denitrification 0 60 120...

  13. A novel stoichiometries methodology to quantify functional microorganisms in simultaneous (partial) nitrification-endogenous denitrification and phosphorus removal (SNEDPR). (United States)

    Wang, Xiaoxia; Wang, Shuying; Zhao, Ji; Dai, Xian; Li, Baikun; Peng, Yongzhen


    Although efficient removal of carbon (C), nitrogen (N) and phosphorous (P) from wastewater with low C/N ratio was achieved in anaerobic/aerobic simultaneous nitrification-endogenous denitrification and phosphorus removal (SNEDPR) systems, the removal pathways and metabolic transformations in this complex system are unclear. This work targeted at developing the stoichiometric models for denitrifying glycogen organisms (DGAOs) via nitrite and nitrate (DGAONi and DGAONa), and demonstrating a novel methodology to quantify diverse functional microorganisms (e.g. ammonia and nitrite oxidizing bacteria, aerobic phosphorus accumulating organisms (APAOs), denitrifying PAOs (DPAOs) and aerobic GAOs (AGAOs)) for the removal of C, N and P. The results showed that the anaerobic intracellular carbon storage (CODintra) was mainly accomplished by GAOs, and PAOs were only responsible for about 40% of CODintra through a stable P release. At the aerobic stage, 84.9% of P was removed by APAOs with 15.1% left by DPAOs, while 64.6% of N was removed by DGAOs (45.8% by DGAONi and 18.8% by DGAONa) with 18.1% by DPAOs and 17.3% by bacterial growth. High proportion of N removal via nitrite (partial nitrification-endogenous denitrification) (71%) saved 7.3% aeration and 38% intracellular carbon demand. However, AGAOs still activated well at the aerobic intercellular carbon consumption, which limited the further improvement of N removal efficiency. By elucidating the nutrient removal pathways among diverse functional microorganisms, the methodology developed in this study could accelerate the nutrient removal in the SNEDPR process.

  14. The influence of oceanographic processes on pelagic-benthic coupling in polar regions: A benthic perspective (United States)

    Grebmeier, Jacqueline M.; Barry, James P.


    Benthic community abundance and biomass in polar marine systems is directly influenced by food supply from the overlying water column. Variability in hydrographic regimes, ice coverage, light, water column temperature and pelagic food web structure limit the amount of organic carbon reaching the benthos. Data from the high Arctic and Antarctic indicate that a large percentage of surface-produced organic matter is consumed by both macro- and micro-zooplankton as well as recycled in the water column via the microbial loop. This results in food-limited regimes for the underlying benthos. The few exceptions are nearshore continental shelf systems, such as in the Bering and Chukchi Seas in the western Arctic and portions of the Canadian Archipelago and Barents Sea in the eastern Arctic, where high benthic abundance and biomass occurs due to a tight coupling between water column primary production and benthic secondary production. A major difference between the Antarctic and Arctic is that the nearshore deep Antarctic is characterized by relatively high benthic abundance and biomass despite low water column production, suggesting that stability, low disturbance levels and cold temperatures enable benthic organisms to grow larger than in the Arctic. Both physical and biological disturbance levels are high in the marginal seas of the Arctic may directly influence benthic productivity. The relationship between primary production and sedimentation of organic material to the benthos is nonlinear due to its dependence on the role of the pelagic food web. Therefore, in this review we will only discuss the pelagic system with respect to how it impacts the net food supply reachig the benthos. A major objective of this review paper is demonstrate the influence of oceanographic processes on pelagic-benthic coupling in polar regions from a "bottom-up" perspective, using benthic studies from various regions in both the Arctic and Antarctic. Similarities and differences in

  15. Three-dimensional Modelling Of Nitrate Tranfer In A Flooded Alluvial Zone (United States)

    Trémolières, M.; Lachenal, C.; Sánchez-Pérez, J. M.

    In the groundwater of a flooded alluvial forest in Alsace (Illwald forest, Eastern France), upstream of the forest nitrate concentrations (close to 40 mg/l) are largely higher than those downstream (lower than 5 mg/l). The objective of this study is to evaluate the effect of two factors which could be responsible for nitrogen elim- ination : drainage by streams and river (very significant in the area) and reduction by the groundwater U plant complex (bacterial denitrification and root uptake). A three-dimensional hydrodynamic model was used to estimate horizontal and vertical flows of water in the aquifer. The conception of this model required data of hydraulic conductivity, surface water - groundwater exchanges and nitrate concentrations. The model was validated with the three following variables, which were measured locally : piezometric level, volume exported by streams and chloride concentrations in ground- water (used as an hydrological tracer). The main results showed that the drainage by streams contributed to the elimination of polluted groundwater to a depth of at least 40 m. The balance input-output of the system was calculated acroos the whole surface (2100ha) over a period of three years. The total purifying capacity of this wetland was close to 240 kgN/ha/year and only 40kg/ha/year were eliminated by stream drainage, the greater part of the rest was eliminated by denitrification and/or root uptake.

  16. Evaluation of sustainable electron donors for nitrate removal in different water media. (United States)

    Fowdar, Harsha S; Hatt, Belinda E; Breen, Peter; Cook, Perran L M; Deletic, Ana


    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.

  17. Enhancement of nitrate-induced bioremediation in marine sediments contaminated with petroleum hydrocarbons by using microemulsions. (United States)

    Zhang, Zhen; Zheng, Guanyu; Lo, Irene M C


    The effect of microemulsion on the biodegradation of total petroleum hydrocarbons (TPH) in nitrate-induced bioremediation of marine sediment was investigated in this study. It was shown that the microemulsion formed with non-ionic surfactant polyoxyethylene sorbitan monooleate (Tween 80), 1-pentanol, linseed oil, and either deionized water or seawater was stable when subjected to dilution by seawater. Desorption tests revealed that microemulsion was more effective than the Tween 80 solution or the solution containing Tween 80 and 1-pentanol to desorb TPH from marine sediment. In 3 weeks of bioremediation treatment, the injection of microemulsion and NO3 (-) seems to have delayed the autotrophic denitrification between NO3 (-) and acid volatile sulfide (AVS) in sediment compared to the control with NO3 (-) injection alone. However, after 6 weeks of treatment, the delaying effect of microemulsion on the autotrophic denitrification process was no longer observed. In the meantime, the four injections of microemulsion and NO3 (-) resulted in as high as 29.73 % of TPH degradation efficiency, higher than that of two injections of microemulsion and NO3 (-) or that of four or two injections of NO3 (-) alone. These results suggest that microemulsion can be potentially applied to enhance TPH degradation in the nitrate-induced bioremediation of marine sediment.

  18. Isotope methods as a tool to characterize nitrate origin and transport in Kocinka catchment (central Poland): preliminary results (United States)

    Zurek, Anna; Wachniew, Przemyslaw; Witczak, Stanislaw; Rozanski, Kazimierz; Kania, Jaroslaw


    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. and

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

    DEFF Research Database (Denmark)

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


    Soils in urban areas are subjected to compaction with accelerating urbanization. The effects of anthropogenic compaction on urban soil denitrification are largely unknown. We conducted a study on an urban park soil to investigate how compaction impacts denitrification. By using 15N labeling metho...

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

    DEFF Research Database (Denmark)

    Vinther, Finn Pilgaard


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

  1. Denitrification at pH 4 by a soil-derived Rhodanobacter-dominated community. (United States)

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


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


    Directory of Open Access Journals (Sweden)

    A. E. Ghaly


    Full Text Available The aim of this study was to investigate nitrification activity of urea and the assimilation of nitrate in a well aerated soil using perfusion technique with addition of glucose as an energy and carbon source. In this study, urea was rapidly nitrified by the bacteria in the saturated soil but its course of transformation to NO3 was not linear. There was an initial increase in the concentration of nitrite during the nitrification experiment which indicated that the conversion of nitrite to nitrate was appreciably slower than the rate of conversion of urea to nitrite. The rate of conversion of NH4+ to NO2- was faster than the rate of conversion of NO2- to NO3- in the first 12 days and as a result the nitrate concentration reached 2.72 µg/ml on the 12th day. After day 12, the concentration of NH4+ in solution declined significantly and the rate of conversion of NO2- to NO3- became faster than the rate of conversion of NH4+ to NO2-. The concentration of NO2-N in the solution reached zero on the 23rd day. The nitrification curve has the character of a sigmoid curve whose midpoint, which representing the most rapid rate of nitrification, fell at the point of half conversion of urea to nitrite. The curve asymptotically approaches a nitrate value that represents 98% conversion of urea into nitrate. The rest of the urea (NH4 has presumably been synthesized into bacterial cells. The initial pH of the soil was 7.7 due to the presence of NH4 which decreased gradually due to the production of NO3 reaching 6.9 by day 23. A nitrate reduction was observed under aerobic conditions. Denitrification did not proceed according to the known fact that O2 prevents the denitrifying organisms from producing the enzyme responsible for the process. The alternative pathway for nitrate reduction could be by assimilatory reduction where nitrate was converted to ammonium and then to cells. The removal of nitrate and production of ammonium caused a rise in the pH. The

  3. Assessing Stream Ecosystem Metabolism and Nitrate Utilization at Reduced Nitrate Levels Using a Chamber-Based Approach: Looking Below, Scaling Up, and Thinking Inside the Box (United States)

    Reijo, C. J.; Cohen, M. J.


    As nitrate levels in lotic systems have increased, nutrient reduction strategies have become the centerpiece of water quality standards to protect and restore stream ecosystems. While reducing anthropogenic nitrate (NO3) loads has many positive effects, we lack a fundamental understanding of how lotic systems respond to changing concentrations and no methods exist to characterize nutrient uptake behavior below ambient levels. Therefore, it is difficult to predict whether nutrient reductions will meet management goals. To fill this knowledge gap, we developed a chamber-based method which allows characterization of NO3 utilization along the two major uptake pathways at reduced NO3 levels. The chamber blocks flow by insertion into upper sediments but allows light in and sediment-water-air interactions to occur. At Gum Slough Springs, Florida, high-resolution in-situ sensors measured water quality while NO3 reduced from ambient levels (1.40 mg N/L) to below regulatory thresholds (ca. 0.20 mg N/L) within one week. Daytime NO3 uptake, resulting from both plant uptake and denitrification, was consistently greater than nighttime uptake, which is denitrification alone. Using this method, we compared NO3 uptake rates (UNO3) and gross primary production (GPP) across three vegetative regimes (i.e. submerged aquatic vegetation (SAV), SAV with epiphytic algae, and algae alone) and related GPP estimates from the chamber to reach scale. Results showed that UNO3 and GPP were greatest in SAV, GPP was negatively correlated to [NO3] in algae, denitrification rates did not vary by vegetation type, and chamber GPP (e.g. 6-8 g O2/m2/day in SAV) was comparable to reach-scale estimates (6-12 g O2/m2/day). Our results suggest UNO3 and GPP differ by vegetation regimes, GPP scales from chamber to reach level, algal presence potentially reduces GPP, and a lack of nutrient limitation even at low [NO3]. Current work includes replicating measurements across systems as well as refining the

  4. Waterproofing Materials for Ammonium Nitrate

    Directory of Open Access Journals (Sweden)

    R.S. Damse


    Full Text Available This study explores the possibility of overcoming the problem of hygroscopicity of ammonium nitrate by coating the particles with selected waterproofing materials. Gravimetric analysis ofthe samples of ammonium nitrate coated with eight different waterproofing materials, vis-a-vis, uncoated ammonium nitrate, were conducted at different relative humidity and exposuretime. The results indicate that mineral jelly is the promising waterproofing material for ammonium nitrate among the materials tested, viz, calcium stearate, dioctyl phthalate, kaoline, diethylphthalate, dinitrotoluene, shelac varnish, and beeswax. Attempts were made to confirm the waterproofing ability of mineral jelly to ammonium nitrate using differential thermal analysisand x-ray diffraction patterns as an experimental tool. Suitability of mineral jelly as an additive for the gun propellant was also assessed on the basis of theoretical calculations using THERMprogram.

  5. A continuous stirred hydrogen-based polyvinyl chloride membrane biofilm reactor for the treatment of nitrate contaminated drinking water. (United States)

    Xia, Siqing; Zhang, YanHao; Zhong, FoHua


    A continuous stirred hydrogen-based polyvinyl chloride (PVC) membrane biofilm reactor (MBfR) was investigated to remove nitrate from the drinking water. The reactor was operated over 100 days, and the result showed that the average nitrate denitrification rate of 1.2 g NO(3)(-)-N/m(2) d and the total nitrogen (TN) removal of 95.1% were achieved with the influent nitrate concentration of 50 mg NO(3)(-)-N/L and the hydrogen pressure of 0.05 MPa. Under the same conditions, the average rate of hydrogen utilization by biofilm was 0.031 mg H(2)/cm(2) d, which was sufficient to remove 50 mg NO(3)(-)-N/L from the contaminated water with the effluent nitrate and nitrite concentrations below drinking water limit values. The average hydrogen utilization efficiency was achieved as high as 99.5%. Flux analysis demonstrated that, compared to sulfate reduction, nitrate reduction competed more strongly for hydrogen electron, and obtained more electrons in high influent nitrate loading.

  6. Isotopic and Chemical Analysis of Nitrate Source and Cycling in the San Joaquin River, California (United States)

    Silva, S. R.; Kendall, C.; Bemis, B.; Bergamaschi, B.; Kratzer, C.; Dileanis, P.; Erickson, D.; Avery, E.; Paxton, K.


    concentrations appears to be a function of dilution/evaporation, as river stage varied. For the minority of samples that fell below the dilution/evaporation trend (i.e. those with nitrate concentrations lower than predicted), delta 15N values indicated assimilation rather than denitrification as the cause of the lower concentration. With one notable exception, the pattern of delta 15N of the POM samples over time generally mirrored that of the RV samples and showed no correlation with nitrate or chlorophyll-a concentrations. This relationship indicates (1) that nitrate was an important and probably the primary nutrient for the plankton and (2) that nitrate concentrations remained too high for the delta 15N to be appreciably affected by phytoplankton growth. The delta 15N values of the RV samples averaged +14.4 per mil. The fairly high nitrate concentrations and lack of evidence for denitrification in the river suggests that the delta 15N values are a source signature. Although synthetic fertilizers are a likely source of nitrate in the area, the relatively high delta 15N values are consistent with a significant fraction originating from animal waste or sewage.

  7. Species diversity of benthic diatoms and its relation to environmental variables in Ton Ngachang Waterfall, Songkhla province

    Directory of Open Access Journals (Sweden)

    and Peerapornpisal, Y.


    Full Text Available The species diversity of benthic diatoms and its relation to environmental variables were studied in Ton Ngachang Waterfall, Songkhla province. Epilithic and epipsammic diatoms were sampled at 5 stations from upstream (station 1, 2 and 3 to downstream (station 4 and 5 in summer (April 2004 and February 2005, early rainy season (June and August 2004 and rainy season (November and December 2004. A total number of 15 genera, 49 species and 8 families in order Pennales were found. Achnanthes was the dominant genus throughout the study period with 8 species. A principal components analysis (PCA on relative abundance revealed that Achnanthes minutissimaK˙˙ utzing and A. lanceolata (Brebission Grunow were the most abundant species of epilithic diatoms and epipsammic diatoms respectively, whereas species richness on both substrata were not significant different (P>0.05. Analysis of variance (ANOVA indicated that the numbers of benthic diatom species between upstream and downstream were not significant different (P>0.05, while there was statistical significance (P<0.05 among the seasons in epilithic diatoms. Multivariate analysis of variance (MANOVA on physico-chemical factors showed that nitrate, ortho-phosphate, silicate, BOD, conductivity and TSS were significant different (P<0.05 between seasons. Canonical correspondence analysis (CCA ordination indicated that nitrate, silicate, BOD, pH, conductivity, temperature and velocity were correlated with the benthic diatom abundance.

  8. [Potential of nitrification and denitrification in water purification system with hydroponic bio-filter method]. (United States)

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


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

  9. Citric acid application for denitrification process support in biofilm reactor. (United States)

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


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

  10. Combining Push Pull Tracer Tests and Microbial DNA and mRNA Analysis to Assess In-Situ Groundwater Nitrate Transformations (United States)

    Henson, W.; Graham, W. D.; Huang, L.; Ogram, A.


    Nitrogen transformation mechanisms in the Upper Floridan Aquifer (UFA) are still poorly understood because of karst aquifer complexity and spatiotemporal variability in nitrate and carbon loading. Transformation rates have not been directly measured in the aquifer. This study quantifies nitrate-nitrogen transformation potential in the UFA using single well push-pull tracer injection (PPT) experiments combined with microbial characterization of extracted water via qPCR and RT-qPCR of selected nitrate reduction genes. Tracer tests with chloride and nitrate ± carbon were executed in two wells representing anoxic and oxic geochemical end members in a spring groundwater contributing area. A significant increase in number of microbes with carbon addition suggests stimulated growth. Increases in the activities of denitrification genes (nirK and nirS) as measured by RT-qPCR were not observed. However, only microbes suspended in the tracer were obtained, ignoring effects of aquifer material biofilms. Increases in nrfA mRNA and ammonia concentrations were observed, supporting Dissimilatory Reduction of Nitrate to Ammonia (DNRA) as a reduction mechanism. In the oxic aquifer, zero order nitrate loss rates ranged from 32 to 89 nmol /L*hr with no added carbon and 90 to 240 nmol /L*hr with carbon. In the anoxic aquifer, rates ranged from 18 to 95 nmol /L*hr with no added carbon and 34 to 207 nmol /L*hr with carbon. These loss rates are low; 13 orders of magnitude less than the loads applied in the contributing area each year, however they do indicate that losses can occur in oxic and anoxic aquifers with and without carbon. These rates may include, ammonia adsorption, uptake, or denitrification in aquifer material biofilms. Rates with and without carbon addition for both aquifers were similar, suggesting aquifer redox state and carbon availability alone are insufficient to predict response to nutrient additions without characterization of microbial response. Surprisingly, these

  11. Does the source of carbon influence the abundance of nirK, nirS and nosZ functional genes in laboratory denitrification bioreactors? (United States)

    Barrett, Maria; Fenton, Owen; Ibrahim, Tristan G.; O'Flaherty, Vincent; Healey, Mark G.


    Biological denitrification in soil is the main producer of nitrous oxide (N2O) emissions. Denitrifying soil microbes are capable of reducing nitrate (NO3-) to nitrite (NO2-) to N2O and di-nitrogen gas (N2). One third of these denitrifers possess a truncated functional gene pathway, which may lack the nosZ gene and emit N2O as a final emission product instead of the more benign N2. A carbon rich environment, specific to certain types of carbon sources, has been shown to foster an anaerobic environment, which positively impacts microbial denitrification rates. The present study examined the effect of varying carbon sources in laboratory-scale denitrification bioreactors on NO3- removal and also correlated performance with the abundance of the denitrifying microbial consortia possessing the denitrifying functional genes nirK, nirS and nosZ in each bioreactor. The bioreactors comprised either lodgepole pine woodchips (LPW), lodgepole pine needles (LPN), barley straw (BBS), or cardboard (CCB), each mixed with soil in a 1:1 ratio (by volume) and subject to sequentially increasing hydraulic loading rates of 3, 5 and 10 cm d-1 for a total operation period of up to 744 days. A reactor containing soil only (CSO) was used as the study control. The abundance of denitrifers was determined by targeting nirK, nirS, nosZ functional genes and the