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1
Bergstrom, D. W., and E. G. Beauchamp. "Relationships between denitrification rate and determinant soil properties under barley." Canadian Journal of Soil Science 73, no. 4 (November 1, 1993): 567–78. http://dx.doi.org/10.4141/cjss93-056.
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To better understand environmental regulation of denitrification, we examined relationships between denitrification rate and six determinant soil properties: moisture content, air-filled porosity, NO3− content, respiration rate, mineralizable-C concentration and denitrifying enzyme activity (DEA). Soil cores were collected on 27 sampling dates over a growing season at a site seeded to barley (Hordeum vulgare). Denitrification rate was measured using a static core technique and acetylene blockage. Moisture content and air-filled porosity and, to a lesser extent, mineralizable-C concentration and respiration rate were more strongly related to denitrification rate than was DEA. Denitrification rate was unrelated to NO3− content. On most sampling dates, mean denitrification rate increased substantially only below an air-filled porosity of 0.3. Moreover, the distribution of individual measurements of denitrification rate was less skewed at lower air-filled porosities. Approximately 60% of variation in mean values of denitrification rate for each sampling date could be accounted for by measurements of bulk soil properties, of which moisture content and air-filled porosity were most important. Measurements of bulk soil properties did not account for nil values of denitrification rate at low air-filled porosities or for small-scale spatial variability. Such measurements were better indicators of temporal variation — that is, when denitrification occurred — than of actual rates. Key words: Denitrification, air-filled porosity, denitrifying enzyme activity
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Kozub, D. D., and S. K. Liehr. "Assessing Denitrification Rate Limiting Factors in a Constructed Wetland Receiving Landfill Leachate." Water Science and Technology 40, no. 3 (August 1, 1999): 75–82. http://dx.doi.org/10.2166/wst.1999.0140.
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The focus of this research was to investigate denitrification in constructed wetlands to improve the nitrogen treatment capabilities of these systems. A free water surface flow constructed wetland located at the New Hanover County Solid Waste Management Facility, near Wilmington, North Carolina, USA, was used for this research. Field water sampling in conjunction with a laboratory acetylene block method was used to quantify nitrogen removals in the wetland. Background denitrification rates as well as potential denitrification rates using sodium acetate and sodium phosphate were measured in the laboratory. According to field measurements, average nitrate nitrogen loading and removal rates in the constructed wetland during 1997 were 11.1 ± 3.4 g N/m3/d and 4.5 ± 2.2 g N/m3/d, respectively. Denitrification rates measured in the laboratory with the addition of sodium acetate were higher than background denitrification rates while the addition of sodium phosphate had no effect on the denitrification rates. Results suggested denitrification in the wetland was limited by the availability of easily degradable sources of organic carbon. Background denitrification rates measured using the laboratory method were comparable to the nitrate nitrogen removal rates measured by field water sampling.
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Vabolienė, Giedrė, and Algirdas Bronislovas Matuzevičius. "ASSESMENT OF NITRIFICATION AND DENITRIFICATION RATE IN BIOLOGICAL NITROGEN REMOVAL FROM WASTEWATER." JOURNAL OF ENVIRONMENTAL ENGINEERING AND LANDSCAPE MANAGEMENT 15, no. 2 (June 30, 2007): 77–84. http://dx.doi.org/10.3846/16486897.2007.9636912.
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Biological nitrogen removal from wastewater is based on nitrification and denitrification processes in biological treatment plants with activated sludge. Slowed growth of nitrification bacteria is one of basic problems in biological nitrogen removal from wasterwater. Using biological nitrogen removal technologies at changing nitrification and denitrification rate, it is very important to evaluate properly aeration and reduced aeration duration and to estimate nitrification and denitrification rate. To this purpose an investigation was carried out at Utena Wastewater Treatment Plant. Nitrification and denitrification rate was estimated during five experiments in aeration tanks when the duration of aeration and reduced aeration was from 120 to 180 min. Nitrification and denitrification rate at a different aeration regime and impact of aeration regime on biological nitrogen removal was estimated in the work.
4
Bode, H., C. F. Seyfried, and A. Kraft. "High-Rate Denitrification of Concentrated Nitrate Wastewater." Water Science and Technology 19, no. 1-2 (January 1, 1987): 163–74. http://dx.doi.org/10.2166/wst.1987.0198.
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The principles of high-rate denitrification are explained. In the experimental section of the paper the results of nine lab-scale experiments are described and compared with data gained from reviewed literature. The tests were performed in continuous flow stirred-tank and wash-out reactors under mesophilic and thermophilic conditions. The experimental results confirm that high-rate denitrification is an extremely efficient process. Removal rates of up to 25 kg NOx-Nel./ (m3·d) were achieved with the activated sludge systems. The nitrate sludge loading was found to be the significant design parameter for the process if there is an excess of organic substrate. The maximum rate achieved by thermophilic bacteria was 10 kg NOx-Nel./(kg MLVSS·d) which exceeded by 33 % that for mesophilic organisms. Due to this, in the wash-out reactors the thermophilic system was superior to the mesophilic at system-related, inevitably similar MLVSS concentrations. But because of a temperature-dependent type of growth (thermophilic: disperse; mesophilic: flocculating), in the case of systems with recycling of biomass, higher removal rates (per volume) were obtained for the mesophilic reactors.
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Walczak, J., and M. Zubrowska-Sudol. "The rate of denitrification using hydrodynamically disintegrated excess sludge as an organic carbon source." Water Science and Technology 77, no. 9 (March 17, 2018): 2165–73. http://dx.doi.org/10.2166/wst.2018.125.
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Abstract This study investigates the potential of hydrodynamically disintegrated excess activated sludge when used as a supplementary carbon source for denitrification. Two objectives constituted this study: (i) to analyse the denitrification rate by using excess sludge subjected to hydrodynamic disintegration (HD), performed at different energy densities, as an organic carbon source, and (ii) to analyse the impact of hydrolysis of disintegrated sludge on the denitrification rate. Nitrate reduction tests were conducted to assess the denitrification rate for the following sources of organic carbon: thickened excess sludge disintegrated at three levels of energy density (70, 140 and 210 kJ/L), acetic acid solution and municipal wastewater after mechanical treatment. It was found that the HD of excess sludge conducted at different levels of energy density led to dissolved organic compounds characterised by various properties as donors of H+ in the denitrification process. The susceptibility of disintegrated sludge to anaerobic hydrolysis decreased along with the increasing energy density. The obtained organic carbon contributed to a lower increase in the denitrification rate in comparison to that when disintegrated sludge not subjected to hydrolysis was applied.
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Jiang, Feng, Zhen-Sheng Liang, Guo-Liang Peng, Jin Qian, and Guang-Hao Chen. "Nitrogen removal capacity of simultaneously autotrophic and heterotrophic denitrification in a sewer receiving nitrified source-separated urine." Water Practice and Technology 8, no. 1 (March 1, 2013): 33–40. http://dx.doi.org/10.2166/wpt.2013.005.
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Discharging source-separated and nitrified urine into sewer helps to save cost and space in biological nitrogen treatment as in-sewer denitrification is induced. This unique denitrification process may become complicated in sewers with sulfide contamination as simultaneously autotrophic and heterotrophic denitrification possibly occur but may compete each other for nitrate in oxidation of sulfide and organics. The objective of this study is to estimate the mixed denitrification rate in a sulfide-contaminated sewer when nitrified urine (mainly nitrite and nitrate) is discharged. In this study two investigations were conducted: (1) determination of the autotrophic, heterotrophic and mixed denitrification rates via lab batch tests and (2) determination of the total nitrogen removal rate in a 6.5-km long force main sewer via field study with calcium nitrate dosed at an average influent rate of 15.6 mg N/L. The lab tests determined the rates of autotrophic, heterotrophic and mixed denitrification at 0.36 ± 0.06, 6.54 ± 0.04 and 1.99 ± 0.1 mg N/L/h, respectively, while the field study estimated the total in-sewer denitrification rate at 2.32 mg N/L/h in the sewer when sulfide was present. Simultaneously autotrophic and heterotrophic denitrification was found when sewage was contaminated with sulfide. However, nitrogen removal rate of heterotrophic denitrification was 3.3 times higher that of the mixed denitrification process. The results indicate that discharging source-separated and nitrified urine into sewer is meaningful to decentralized sewage treatment, especially when sulfide is absent in the sewer.
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Lie, Ewa, and Thomas Welander. "Influence of dissolved oxygen and oxidation–reduction potential on the denitrification rate of activated sludge." Water Science and Technology 30, no. 6 (September 1, 1994): 91–100. http://dx.doi.org/10.2166/wst.1994.0256.
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The influence of low concentrations of dissolved oxygen (DO) and the oxidation-reduction potential (ORP) on the denitrification activity of activated sludge has been studied in batchwise experiments. The ORP was maintained at different levels by automatic titration with air and the denitrification activity was determined by following the disappearance of nitrate. Oxygen was found to have a negative effect on denitrification even at lower concentrations than can be measured with conventional oxygen probes (<0.1 mg/L). The ORP was found to be a useful indicator of the DO concentration at this low level and the denitrification rate was found to decrease linearly with increasing ORP. However, the effect of the ORP on denitrification differed between sludges from different treatment plants. A linear relationship was also found between the ORP and the DO concentration in the region of measurable DO concentrations. Extrapolation of this straight line into the region where DO was under the detection limit indicated that oxygen exerts an inhibitory effect on denitrification at such low concentrations as a few μg/L.
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Machefert, S. E., and N. B. Dise. "Hydrological controls on denitrification in riparian ecosystems." Hydrology and Earth System Sciences 8, no. 4 (August 31, 2004): 686–94. http://dx.doi.org/10.5194/hess-8-686-2004.
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Abstract. Nitrous oxide fluxes and denitrification rates were measured in situ over a year at a riparian site in the UK. An exponential relationship was found between denitrification rates and soil moisture, with a sharp increase in denitrification rate at a water-filled pore space of 60–80%. Similar relationships were found in other studies compiled for comparison. The present study is unique in measuring denitrification in an "intact" ecosystem in the field, rather than in cores in the field or the lab. The exponential relationship between denitrification rate and soil moisture, with a "threshold" at 60–80% water-filled pore space (20–40% gravimetric moisture), has proven to be comparable across a wide range of ecosystems, treatments and study conditions. Whereas moisture content determines the potential for denitrification, the absolute rate of denitrification is determined by available nitrate (NO3-), dissolved organic carbon and temperature. As a first approximation, denitrification rates can be simply modelled by using a general exponential relationship between denitrification potential and water-filled pore space (or volumetric/gravimetric water content) multiplied by a constant value determined by the nitrogen status of the site. As such, it is recommended that the current relationship used in INCA to relate denitrification to soil moisture be amended to an exponential form, with a threshold of approximately 70% for the onset of denitrification. Keywords: nitrous oxide, denitrification, soil moisture, nitrogen, eutrophication, riparian
9
Duc, Phung Anh. "ASSESS THE DENITRIFICATION POTENTIAL OF FERMENTED BIOSOLIDS BASED ON THEIR SPECIFIC DENITRIFICATION RATE (SDNR)." Vietnam Journal of Science and Technology 54, no. 2A (March 19, 2018): 112. http://dx.doi.org/10.15625/2525-2518/54/2a/11919.
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The study examined the potential of fermented and dark-fermented biosolids as external carbon sources for denitrification improvement. This was done by up-scaling the selected two (out of seven) sludge fermentation conditions from past studies, carrying out ammonia stripping pre-treatment to fix the C/N ratio, before finding their specific denitrification rate (SDNR) using SDNR experiment set-up. The gotten SDNR were then compared to the SDNR of other substances gotten from both previous studies and literature, to weight the denitrification potential of fermented biosolids as a substance. The results found that with an initial COD of 607-704 mgCOD/L, the SDNR of the two fermented biosolids and dark fermented biosolids were found to be 8.35 ± 0.41 and 8.56 ± 0.71 respectively. This was much higher than the 1.53 -2.57 for sucrose and 1.29 ± 0.21 for wastewater found in earlier study using the same methodology; and comparable to the denitrification potential value for the well-studied methanol
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Mikawa, Kazuhiro, Hiroyoshi Emori, Tadashi Takeshima, Eiichi Ishiyama, and Kazuhiro Tanaka. "High rate and compact two-stage post-denitrification process with single-sludge pre-denitrification." Water Science and Technology 34, no. 1-2 (July 1, 1996): 467–75. http://dx.doi.org/10.2166/wst.1996.0405.
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For the sewage treatment plants near rivers and closed water bodies in urbanized areas there is a growing demand for introduction of advanced treatment processes for nitrogen and phosphorus removal for water quality conservation and environmental protection. In order to achieve the total nitrogen content of below 10 mg/L in effluent, a compact single sludge pre-denitrification process by dosing immobilized pellets in the nitrification tank (PEGASUS process) has been already developed (Tanaka et al. 1992). Furthermore, a two-stage PEGASUS process and a PEGASUS process with post-denitrification were developed and investigated for nitrogen removal. Both processes achieved the total nitrogen of less than 5mg/L.
11
Clayton, J. A., G. A. Ekama, M. C. Wentzel, and G. v. R. Marais. "Denitrification Kinetics in Biological Nitrogen and Phosphorus Removal Activated Sludge Systems Treating Municipal Waste Waters." Water Science and Technology 23, no. 4-6 (February 1, 1991): 1025–35. http://dx.doi.org/10.2166/wst.1991.0554.
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Using plugflow anoxic reactors and batch tests, an experimental investigation was undertaken into the kinetics of denitrification in nitrification denitrification biological excess phosphorus removal (NDBEPR) systems. It was found that (1) in the primary and secondary anoxic reactors, the specific rate constant for denitrification associated with the utilization of slowly biodegradable COD (SBCOD) was respectively 2½ and 1½ times higher than in these reactors in nitrification denitrification (ND) systems and (2) in the primary anoxic reactor, the rapid rate of denitrification attributable to readily biodegradable COD was absent. The increased rate is hypothesized to be due to a stimulation in the active sludge mass of an increased rate of hydrolysis of SBCOD in these anoxic reactors of the NDBEPR system apparently induced by the presence of the anaerobic reactor in these systems.
12
Bergstrom, D. W., and E. G. Beauchamp. "An empirical model of denitrification." Canadian Journal of Soil Science 73, no. 4 (November 1, 1993): 421–31. http://dx.doi.org/10.4141/cjss93-044.
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We used a simple empirical model to predict denitrification rates from measurements of bulk soil properties. Boundary analysis was used to define relationships between denitrification rate and each of air-filled porosity, respiration rate and mineralizable-C content. The ratio of measured denitrifying enzyme activity to the maximum measured value was used to account for variation in amounts of enzymes and numbers of denitrifiers in soil. Nitrate content had little effect on denitrification rate and was excluded from the model. Because the model did not account for microscale variability, it did not accurately predict rates in individual soil cores. Nevertheless, population means and distributions of predicted and measured values were similar. The seasonal patterns of mean values of predicted and measured denitrification rates were also similar over the second half of the sampling period, which extended from May to November. The model did not account for appreciable denitrification on three dates in May. This discrepancy indicated that environmental regulation of denitrification may not be uniform over the season. The model was not sufficiently sensitive to factors influencing episodic events. Key words: Denitrification rate, model, boundary line
13
Komori, M., and Y. Sakakibara. "High-rate hydrogenotrophic denitrification in a fluidized-bed biofilm reactor using solid-polymer-electrolyte membrane electrode (SPEME)." Water Science and Technology 58, no. 7 (October 1, 2008): 1441–46. http://dx.doi.org/10.2166/wst.2008.725.
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A fluidized-bed biofilm reactor equipped with a Solid-Polymer-Electrolyte Membrane Electrode (SPEME) cell was developed in order to enhance hydrogenotrophic denitrification of groundwater. Porous cubes made of polyvinylalcohol (PVA) were used as a biofilm carrier and continuous treatments using synthetic groundwater were carried out for 105 days. Electric current was changed step-wise from 0.4 to 4.0 A. Experimental results showed that efficient production and dissolution of hydrogen were achieved by application of electric current as well as high-rate denitrification simultaneously. Denitrification rates of nitrite increased with the increase of electric current. Overall denitrification rates attained to about 90 mg-N/L/h, which was 3 to 9 times as high as those reported in former studies. Supplying electric current of about two times of stoichiometric equivalent to the cell considered necessary for complete denitrification. Water quality in effluent was very stable and electrolytic voltage was low around 3 V. In addition, simple and secure operation was demonstrated over the experiment. From these results, it was concluded that the present fluidized-bed biofilm reactor equipped with a SPEME cell could be very feasible for high-rate hydrogenotrophic denitrification of ground water.
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Bragan, R. J., J. L. Starr, and T. B. Parkin. "Shallow Groundwater Denitrification Rate Measurement by Acetylene Block." Journal of Environmental Quality 26, no. 6 (November 1997): 1531–38. http://dx.doi.org/10.2134/jeq1997.00472425002600060012x.
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Johnson, R., M. LaMontagne, and I. Valiela. "Rate of Denitrification in Submerged Salt Marsh Sediments." Biological Bulletin 187, no. 2 (October 1994): 289–90. http://dx.doi.org/10.1086/bblv187n2p289.
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Epsztein, Razi, Michael Beliavski, Sheldon Tarre, and Michal Green. "High-rate hydrogenotrophic denitrification in a pressurized reactor." Chemical Engineering Journal 286 (February 2016): 578–84. http://dx.doi.org/10.1016/j.cej.2015.11.004.
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Hwang, Yongwoo, Hiroshi Sakuma, and Toshihiro Tanaka. "Denitrification with isopropanol as a carbon source in a biofilm system." Water Science and Technology 30, no. 11 (December 1, 1994): 69–78. http://dx.doi.org/10.2166/wst.1994.0547.
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Several batch tests and pilot-scale investigations on biological denitrification with isopropanol were performed. Isopropanol was converted to acetone by microbial oxidation during denitrification. Isopropanol itself little contributed to denitrification in practice while the converted acetone played a role of a main hydrogen donor. A larger quantity of nitrite intermediate was formed by using methanol compared to the case of isopropanol. The measured requirement of isopropanol was 2.0 mg mg−1 NO3-N, and was 2/3 of methanol. The oxygen equivalent of isopropanol for nitrate removal was almost the same as that of methanol. The denitrifier net growth yield for isopropanol was greater than for methanol. In order to maximize the denitrification rate, it is essential to convert isopropanol to acetone rapidly by accurate dosing for nitrogen load because the denitrification rate was accelerated by using acetone only. Excessive dose of isopropanol can cause a decrease in the denitrification rate as well as an increase of BOD in the effluent.
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Chen, G. H., H. Ozaki, and Y. Terashima. "Endogenous Denitrification in Biofilm." Water Science and Technology 26, no. 3-4 (August 1, 1992): 523–34. http://dx.doi.org/10.2166/wst.1992.0432.
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The model on endogenous denitrification in a biofilm, previously presented by the authors, was verified well with bench scale experiments. Production of the secondary substrate due to lysis of microorganisms, which is necessary for the progress of endogenous denitrification, was experimentally proved. In order to investigate metabolic characteristics of the substrate, molecular weight distributions of the substrate on CODcr or carbohydrate bases were measured. The percentage of the secondary substrate with molecular weight less than 10,000, was more than 50% on both bases. The experimental results demonstrated that the production rate of the substrate can be expressed by the first order type expression with respect to the concentration of biomass. The specific constants for microorganisms lysis and maximum endogenous denitrification rate were determined (0.45 day−1 and 0.141 day−1, respectively).
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Abbasi, M. K., and W. A. Adams. "Assessment of the contribution of denitrification to N losses from compacted grassland soil by NO3− disappearance and N2O production during anaerobic incubation." Canadian Journal of Soil Science 79, no. 1 (February 1, 1999): 57–64. http://dx.doi.org/10.4141/s98-022.
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Decreases in herbage production and of N uptake and utilization have been observed on Denbigh series soils in mid-Wales after several years in permanent pasture. Laboratory experiments were conducted to examine the contribution of denitrification to N loss from these wet grassland soils. Denitrification capacity was measured in seived soil following the addition of KNO3 and maintained at 20°C under anoxic conditions. Emission of N2O was measured from intact field cores equilibrated under conditions of simulated "field capacity" using glucose as C substrate. The rate of loss of NO3−–N decreased with depth and in the 0–2.5 cm layer all added NO3−–N was lost in 10 d incubation. Net mineralization of NH4+–N occurred at about one-sixth of the rate of NO3−–N disappearance. The presence of NO3− reduced the rate of decrease in redox potential (Eh) and the Eh did not fall below about +200 mV until all NO3−–N had been lost. Emission of N2O was greatest between 6 and 48 h and denitrification rate decreased with depth. Addition of glucose increased N2O emission in the 2.5–5.7 cm layers indicating that C limitation to denitrification may occur at shallow depths in the soil profile of compacted grassland. On average, the total denitrification ranged between 15 and 20 kg N ha−1, equivalent to 20–30% of applied N. The potential rates of denitrification change markedly over quite shallow depths in these compacted grassland soils. Furthermore, since denitrification occurred at substantial rates under simulated field capacity, conditions conducive to denitrification are likely to persist for quite long periods in the moist climatic conditions. Key words: Compacted soil, denitrification, glucose, grassland, nitrous oxide
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Liang, B. C., and A. F. MacKenzie. "Seasonal denitrification rates under corn (Zea mays L.) in two Quebec soils." Canadian Journal of Soil Science 77, no. 1 (February 1, 1997): 21–25. http://dx.doi.org/10.4141/s96-018.
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Nitrogen losses in soil through denitrification are important due to reduced agronomic effectiveness and environmental concerns with nitrous oxide emissions. Knowledge of denitrification may allow for management procedures to reduce these losses. Field experiments were conducted in 1991 and 1992 to investigate N fertilizer effects on denitrification under corn (Zea mays L.) on two soils of contrasting texture in southwestern Quebec. Soil core incubation with C2H2 was used to assess denitrification rates. Total calculated denitrification rate from April to November in 1991 and 1992 varied from 4 to 41 kg N ha−1 on a Chicot sandy clay loam and from 29 to 53 kg N ha−1 on a Ste. Rosalie clay. Denitrification rates increased linearly with increasing fertilizer N rates only in the Ste. Rosalie clay in 1991. Denitrification in the Ste. Rosalie soil was positively related to temperature and NO3− levels in April and May, moisture content from August to November, and temperature in October and November. Denitrification in the Chicot soil was positively related to soil moisture content and NO3− levels in April and May, and soil moisture content in June. Reducing soil NO3− concentrations in April and May could decrease denitrification rate in both Chicot and Ste. Rosalie soils. Key words: Denitrification, fertilizer N, temperature, moisture content
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Matsui, Saburo, and Ryoko Yamamoto. "A New Method of Sulphur Denitrification for Sewage Treatment by a Fluidized Bed Reactor." Water Science and Technology 18, no. 7-8 (July 1, 1986): 355–62. http://dx.doi.org/10.2166/wst.1986.0308.
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Anaerobic treatment of sewage has a problem of denitrification, because that organic carbon and hydrogen are recoverd mainly in the form of methane and not used for denitrification. Other electron donors must be introduced. Promising donors are reduced forms of sulphur. In this study, thiosulphate and elemental sulphur were used in fluidized bed reactor systems. Denitrification by oxidation of sulphur was unstable due to poor solubility of sulphur into sewage. Thiosulphate denitrification was very stable. Stoichiometric relationship of the denitrification and thiosulphate oxidation for the reactor was obtained. The denitrification process was described by the first order consecutive reactions. The rate constant of nitrate to nitrite reduction, kl varied between 2.05×10−2 and 1.09×10−1 (1/gVSS/l*min.). The rate constant of nitrite to nitrogen reduction, k2 varied between 1.41×10−1 and 9.08×10−1 (l/gVSS/l*min.).
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Liu, W., L. Yao, Z. Wang, Z. Xiong, and G. Liu. "Human land uses enhance sediment denitrification and N<sub>2</sub>O production in Yangtze lakes primarily by influencing lake water quality." Biogeosciences Discussions 12, no. 10 (May 22, 2015): 7815–44. http://dx.doi.org/10.5194/bgd-12-7815-2015.
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Abstract. Sediment denitrification in lakes alleviates the effects of eutrophication through removal of nitrogen to the atmosphere as N2O and N2. However, N2O contributes notably to the greenhouse effect and global warming. Human lands uses (e.g., agricultural and urban areas) strongly affect lake water quality and sediment characteristics, which, in turn, may regulate lake sediment denitrification and N2O production. In this study, we investigated sediment denitrification and N2O production and their relationships to within-lake variables and watershed land uses in 20 lakes from the Yangtze River basin in China. The results indicated that both lake water quality and sediment characteristics were significantly influenced by watershed land uses. Increased background denitrification rate would result in increased N2O production rate. Background denitrification and N2O production rates were positively related to water nitrogen concentrations but were not significantly correlated with sediment characteristics and plant community structure. A significant positive relationship was observed between background denitrification rate and percentage of human-dominated land uses (HDL) in watersheds. Structural equation modelling revealed that the indirect effects of HDL on sediment denitrification and N2O production in Yangtze lakes were mediated primarily through lake water quality. Our findings also suggest that although sediments in Yangtze lakes can remove large quantities of nitrogen through denitrification, they may also be an important source of N2O, especially in lakes with high nitrogen content.
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Raboni, Massimo, Paolo Viotti, Elena Cristina Rada, Fabio Conti, and Maria Rosaria Boni. "The Sensitivity of a Specific Denitrification Rate under the Dissolved Oxygen Pressure." International Journal of Environmental Research and Public Health 17, no. 24 (December 14, 2020): 9366. http://dx.doi.org/10.3390/ijerph17249366.
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The biological denitrification process is extensively discussed in scientific literature. The process requires anoxic conditions, but the influence of residual dissolved oxygen (DO) on the efficiency is not yet adequately documented. The present research aims to fill this gap by highlighting the effects of DO on the specific denitrification rate (SDNR) and consequently on the efficiency of the process. SDNR at a temperature of 20 °C (SDNR20°C) is the parameter normally used for the sizing of the denitrification reactor in biological-activated sludge processes. A sensitivity analysis of SNDR20°C to DO variations is developed. For this purpose, two of the main empirical models illustrated in the scientific literature are taken into consideration, with the addition of a deterministic third model proposed by the authors and validated by recent experimentations on several full-scale plants. In the first two models, SDNR20°C is expressed as a function of the only variable food:microrganism ratio in denitrification (F:MDEN), while in the third one, the dependence on DO is made explicit. The sensitivity analysis highlights all the significant dependence of SDNR20°C on DO characterized by a logarithmic decrease with a very pronounced gradient in correspondence with low DO concentrations. Moreover, the analysis demonstrates the relatively small influence of F:MDEN on the SDNR20°C and on the correlation between SDNR20°C and DO. The results confirm the great importance of minimizing DO and limiting, as much as possible, the transport of oxygen in the denitrification reactor through the incoming flows and mainly the mixed liquor recycle. Solutions to achieve this result in full-scale plants are reported.
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Laverman, Anniet M., Christof Meile, Philippe Van Cappellen, and Elze B. A. Wieringa. "Vertical Distribution of Denitrification in an Estuarine Sediment: Integrating Sediment Flowthrough Reactor Experiments and Microprofiling via Reactive Transport Modeling." Applied and Environmental Microbiology 73, no. 1 (October 27, 2006): 40–47. http://dx.doi.org/10.1128/aem.01442-06.
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ABSTRACT Denitrifying activity in a sediment from the freshwater part of a polluted estuary in northwest Europe was quantified using two independent approaches. High-resolution N2O 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 N2O 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.
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Mann, G. W., S. Davies, K. S. Carslaw, and M. P. Chipperfield. "Factors controlling Arctic denitrification in cold winters of the 1990s." Atmospheric Chemistry and Physics 3, no. 2 (April 3, 2003): 403–16. http://dx.doi.org/10.5194/acp-3-403-2003.
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Abstract. Denitrification of the Arctic winter stratosphere has been calculated using a 3-D microphysical model for the winters 1994/95, 1995/96, 1996/97 and 1999/2000. Denitrification is assumed to occur through the sedimentation of low number concentrations of large nitric acid trihydrate (NAT) particles (as inferred by e.g. Fahey et al., 2001). We examine whether the meteorological conditions that allowed particles to grow to the very large sizes observed in 1999/2000 also occurred in the other cold winters. The results show that winter 1999/2000 had conditions that were optimum for denitrification by large NAT particles, which are a deep concentric NAT area and vortex. Under these conditions, NAT particles can circulate in the NAT-supersaturated air for several days, reaching several micrometres in radius and leading to a high downward flux of nitric acid. The other winters had shorter periods with optimum conditions for denitrification. However, we find that NAT particles could have grown to large sizes in all of these winters and could have caused significant denitrification. We define the quantity "closed-flow area'' (the fraction of the NAT area in which air parcel trajectories can form closed loops) and show that it is a very useful indicator of possible denitrification. We find that even with a constant NAT nucleation rate throughout the NAT area, the average NAT number concentration and size can vary by up to a factor of 10 in response to this meteorological quantity. These changes in particle properties account for a high degree of variability in denitrification between the different winters. This large meteorologically induced variability in denitrification rate needs to be compared with that which could arise from a variable nucleation rate of NAT particles, which remains an uncertain quantity in models. Sensitivity studies show that although denitrification was likely approaching asymptotic minimum values throughout much of the 1999/2000 vortex, decreases in the volume-averaged nucleation rate would have substantially reduced the denitrification.
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Hwang, J. H., N. Cicek, and J. A. Oleszkiewicz. "Long-term operation of membrane biofilm reactors for nitrogen removal with autotrophic bacteria." Water Science and Technology 60, no. 9 (November 1, 2009): 2405–12. http://dx.doi.org/10.2166/wst.2009.624.
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Efficient gas delivery and biofilm development on membrane fibers in a membrane biofilm reactor (MBfR) would be well suited to autotrophic nitrification and denitrification using hydrogen. Total nitrogen removal in a two-step MBfR system incorporating sequential nitrification and hydrogen-driven autotrophic denitrification was investigated in order to achieve nitrogen removal by autotrophic bacteria alone. This study also aimed at the long-term stable operation, which proved difficult in previous studies due to excessive biofilm accumulation in autotrophic denitrification systems. Consecutive operation of nitrification and autotrophic denitrification lasted 230 days. Average specific nitrification rate of 1.87 g N/m2 d was achieved and the performance was very stable throughout the experimental periods. Nitrification performance from this study showed comparable rates to previous studies although this work was conducted at slightly lower temperature. Batch tests confirmed the presence of nitrifiers from the effluent of the nitrification reactor, which reattached to the biofilm in the denitrification reactor leading to further nitrification. Performance of autotrophic denitrification was maintained stably throughout the experimental periods, however biofilm control by nitrogen sparging was required for process stability. Average specific denitrification rate of 1.41 g N/m2 d and a maximum specific denitrification rate of 2.04 g N/m2 d was maintained. This study showed that, with an appropriate biofilm control plan, stable long-term operation of a fully autotrophic MBfR system for total nitrogen removal was possible without major membrane cleaning procedures.
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Peng, Y. Z., J. F. Gao, S. Y. Wang, and M. H. Sui. "Use pH and ORP as fuzzy control parameters of denitrification in SBR process." Water Science and Technology 46, no. 4-5 (August 1, 2002): 131–37. http://dx.doi.org/10.2166/wst.2002.0569.
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In order to achieve fuzzy control of denitrification in a Sequencing Batch Reactor (SBR) brewery wastewater was used as the substrate. The effects of brewery wastewater, sodium acetate, methanol and endogenous carbon source on the relationships between pH, ORP and denitrification were investigated. Also different quantities of brewery wastewater were examined. All the results indicated that the nitrate apex and nitrate knee occurred in the pH and ORP profiles at the end of denitrification. And when carbon was the limiting factor, through comparing the different increasing rate of pH whether the carbon was enough or not could be known, and when the carbon should be added again could be decided. On the basis of this, the fuzzy controller for denitrification in SBR was constructed, and the on-line fuzzy control experiments comparing three methods of carbon addition were carried out. The results showed that continuous carbon addition at a low rate might be the best method, it could not only give higher denitrification rate but also reduce the re-aeration time as much as possible. It appears promising to use pH and ORP as fuzzy control parameters to control the denitrification time and the addition of carbon.
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Henze, Mogens, Gert Holm Kristensen, and Rune Strube. "Rate-Capacity Characterization of Wastewater for Nutrient Removal Processes." Water Science and Technology 29, no. 7 (April 1, 1994): 101–7. http://dx.doi.org/10.2166/wst.1994.0318.
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The detailed composition of wastewater has significant impact on the biological wastewater treatment processes. The carbon sources present govern the oxygen uptake rate, the rate of denitrification and the biological phosphorus uptake rate. In this paper, the respiration rate determinations used for the bi- or tri-substrate determinations are coupled to removal capacity in order to develop rate-capacity diagrams, that gives a fuller picture of the wastewater and its influence on the biological processes. The directly degradable carbon source gives high reaction rates, but the concentration and thus the capacity can be very limited. In such a case the overall obtainable removal rate is of more interest than the peak rate. The rate-capacity diagrams are shown for raw, primary settled and primary precipitated wastewater, characterized by detailed investigations of the respiration rates obtainable. It shows the effect of pretreatment not only on the total concentrations in the pre-treated wastewater, but also in the rate-capacity curves for biological denitrification. The rate-capacity curves are in practice coupled to the design and operation of the treatment plant. These two factors determine whether the carbon sources in the influent wastewater are used for denitrification (or biological phosphorus removal), for oxidation with oxygen or for sludge production.
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Wang, Te, Zhao Xia Liu, Mei Juan Wu, Fu Hui Kang, Qing Chen, Yao Jun Song, and Ling Hua Zhang. "Screening and Characterization of a Bacterium Capable of Simultaneous Heterotrophic Nitrification and Aerobic Denitrification at High Concentrations of Ammonia-Nitrogen." Applied Mechanics and Materials 665 (October 2014): 487–90. http://dx.doi.org/10.4028/www.scientific.net/amm.665.487.
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A bacterium capable of simultaneous heterotrophic nitrification and aerobic denitrification at high concentrations of ammonia-nitrogen was screened and identified and the denitrification property was investigated in this paper. The strain was isolated from aeration tank of wastewater disposed by activated sludge and analyzed and identified by 16S rDNA. The effects of different carbon sources and carbon and nitrogen mass ratios on denitrification rate were studied. The changes of various forms of ammonia-nitrogens during the simultaneous heterotrophic nitrification and aerobic denitrification process were characterized. A strain capable of simultaneous heterotrophic nitrification and aerobic denitrification at 600 mg/L nitrogen concentration has been isolated and screened. Comparison of its 16S rDNA sequence showed 100% similarity to Bacillus licheniformis strain Lr124/6. The strain was named as Bacillus sp. A22. The optimal conditions for degradation of ammonia-nitrogen by Bacillus sp. A22 were trisodium citrate as carbon source and carbon and nitrogen mass ratios of 10. The denitrification rate was 98.2% after 96 h of culture under the optimal conditions and there was hardly any intermediates accumulation in the denitrification process. It has practical applications that the denitrification can be performed efficiently at high concentrations of ammonia-nitrogen by method of simultaneous heterotrophic nitrification and aerobic denitrification by Bacillus sp. A22 in nitrogen purification treatment of wastewater with high concentrations of ammonia-nitrogen.
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Vanhooren, H., D. De Pauw, and P. A. Vanrolleghem. "Induction of denitrification in a pilot-scale trickling filter by adding nitrate at high loading rate." Water Science and Technology 47, no. 11 (June 1, 2003): 61–68. http://dx.doi.org/10.2166/wst.2003.0587.
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Oxygen transferred from the liquid phase into a biofilm can be used for aerobic degradation of organic matter and for nitrification. A second possible pathway for the removal of organic matter is denitrification in anoxic zones deeper in the biofilm. At high organic loading rates with insufficient oxygen supply to the biofilm, denitrification could be induced by providing the biofilm with external nitrate. This possibility was tested in a pilot-scale trickling filter by adding a pulse of nitrate to a highly loaded trickling filter. The experiment showed that denitrification can indeed be induced by adding nitrate at high loading conditions and that this way a considerably increased substrate removal capacity can be obtained. The fact that denitrification occurred was confirmed by the increased production of CO2 from bioconversion processes, without a major change of the O2 consumption. The simplified mixed-culture biofilm model developed by Rauch et al. was extended for the description of off-gas measurements and was able to describe the results of the experiment very well.
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Bragan, R. J., J. L. Starr, and T. B. Parkin. "Acetylene Transport In Shallow Groundwater for Denitrification Rate Measurement." Journal of Environmental Quality 26, no. 6 (November 1997): 1524–30. http://dx.doi.org/10.2134/jeq1997.00472425002600060011x.
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MIKAMI, Yuichiro, Tadashi NITTAMI, and Futoshi KURISU. "Effect of Endogenous Carbon Source on Biological Denitrification Rate." Journal of Water and Environment Technology 11, no. 1 (2013): 1–9. http://dx.doi.org/10.2965/jwet.2013.1.
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Burton, D. L., and E. G. Beauchamp. "Denitrification rate relationships with soil parameters in the field." Communications in Soil Science and Plant Analysis 16, no. 5 (May 1985): 539–49. http://dx.doi.org/10.1080/00103628509367626.
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Onishi, Takeo, Kimihito Nakamura, Haruhiko Horino, Toru Adachi, and Toru Mitsuno. "Evaluation of the denitrification rate of terraced paddy fields." Journal of Hydrology 436-437 (May 2012): 111–19. http://dx.doi.org/10.1016/j.jhydrol.2012.03.004.
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Zou, G., S. Papirio, A.-M. Lakaniemi, S. H. Ahoranta, and J. A. Puhakka. "High rate autotrophic denitrification in fluidized-bed biofilm reactors." Chemical Engineering Journal 284 (January 2016): 1287–94. http://dx.doi.org/10.1016/j.cej.2015.09.074.
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Hasegawa, Toru, and Tokio Okino. "Seasonal variation of denitrification rate in Lake Suwa sediment." Limnology 5, no. 1 (April 1, 2004): 33–39. http://dx.doi.org/10.1007/s10201-003-0109-y.
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Mokhayeri, Y., A. Nichols, S. Murthy, R. Riffat, P. Dold, and I. Takacs. "Examining the influence of substrates and temperature on maximum specific growth rate of denitrifiers." Water Science and Technology 54, no. 8 (October 1, 2006): 155–62. http://dx.doi.org/10.2166/wst.2006.854.
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Facilities across North America are designing plants to meet stringent limits of technology (LOT) treatment for nitrogen removal (3–5 mg/L total effluent nitrogen). The anoxic capacity requirements for meeting LOT treatment are dependent on the growth rates of the denitrifying organisms. The Blue Plains Advanced Wastewater Treatment Plant (AWTP) is one of many facilities in the Chesapeake Bay region that is evaluating its ability to meet LOT treatment capability. The plant uses methanol as an external carbon source in a post-denitrification process. The process is very sensitive to denitrification in the winter. One approach to improve anoxic capacity utilization is to use an alternative substrate for denitrification in the winter to promote the growth of organisms that denitrify at higher rates. The aim of this study was to evaluate denitrification maximum specific growth rates for three substrates, acetate, corn syrup and methanol, at two temperatures (13 °C and 19 °C). These temperatures approximately reflect the minimum monthly and average annual wastewater temperature at the Blue Plains AWTP. The results suggest that the maximum specific growth rate (μmax) for corn syrup (1.3 d−1) and acetate (1.2 d−1) are higher than that for methanol (0.5 d−1) at low temperature of 13 °C. A similar trend was observed at 19 °C.
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Xu, Guihua, Cuijie Feng, Fang Fang, Shaohua Chen, Yuanjian Xu, and Xingzu Wang. "The heterotrophic-combined-with-autotrophic denitrification process: performance and interaction mechanisms." Water Science and Technology 71, no. 8 (February 26, 2015): 1212–18. http://dx.doi.org/10.2166/wst.2015.097.
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In this work, the interaction mechanisms between an autotrophic denitrification (AD) and heterotrophic denitrification (HD) process in a heterotrophic-autotrophic denitrification (HAD) system were investigated, and the performance of the HAD system under different S/Ac− molar ratios was also evaluated. The results demonstrated that the heterotrophic-combined-with-autotrophic denitrification process is a promising technology which can remove chemical oxygen demand (COD), sulfide and nitrate simultaneously. The reduction rate of NO3− to NO2− by the HD process was much faster than that of reducing NO2− to N2, while the reduction rate of NO3− to NO2− by the AD process was slower than that of NO2− to N2. Therefore, the AD process could use the surplus NO2− produced by the HD process. This could alleviate the NO2−–N accumulation and increase the denitrification rate. In addition, the inhibition effects of acetate on AD bacteria and sulfide on HD were observed, and the inhibition was compensated by the promotion effects on NO2−. Therefore, the processes of AD and HD seem to react in parallel, without disturbing each other, in our HAD system.
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Watanabe, T., S. Hashimoto, and M. Kuroda. "Simultaneous nitrification and denitrification in a single reactor using bio-electrochemical process." Water Science and Technology 46, no. 4-5 (August 1, 2002): 163–69. http://dx.doi.org/10.2166/wst.2002.0577.
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Feasibility of a bio-electrochemical process for simultaneous nitrification and denitrification in a single reactor was experimentally investigated. The reactor consisted of anodic and cathodic electrodes, on which nitrifying and denitrifying biofilms, respectively, were fixed. Effects of the applied electric current and DO concentration in the bulk solution were examined. The TN removal could be achieved through the occurrence of nitrification and denitrification in anodic and cathodic biofilms, respectively. Both nitrification and denitrification rates increased with an increase in the applied electric current. Even at low DO concentration in the bulk solution, nitrification proceeded at a high rate by utilizing oxygen generated on the anode. Denitrification rate remained relatively high at high DO concentration due to supplying hydrogen gas to the inner side of the cathodic biofilm. The higher TN removal rate tended to be obtained at lower DO concentration and higher current density. From these results, it was concluded that the bio-electrochemical process was applicable to simultaneous nitrification and denitrification due to stable formation of aerobic and anoxic regions in the single reactor.
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Maurer, M., C. Fux, M. Graff, and H. Siegrist. "Moving-bed biological treatment (MBBT) of municipal wastewater: denitrification." Water Science and Technology 43, no. 11 (June 1, 2001): 337–44. http://dx.doi.org/10.2166/wst.2001.0700.
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Denitrification in a full-scale installation and a pilot plant for moving-bed biological treatment (MBBT) was subject to detailed investigation. Two different types of carriers were used in conventional activated sludge reactors: foam cubes and plastic tubes (Kaldnes®). Both investigated carriers showed the same behavior with regard to denitrification capacity, temperature dependency and maximum COD and nitrate turnover. In contrast to the plastic tubes (Kaldnes®), the sponge cubes stored remarkable amounts of substrate. The maximum denitrification rate with acetate as a substrate was 420 gNm-3d-1 at 10°C and 730 gNm-3d-1 at 20°C. An average denitrification rate of 240 gNm-3d-1 (10°C) was achieved with wastewater. A maximum of 37% of the COD in the influent was denitrified with a volumetric loading rate in the anoxic zone of 2.2 kgCODm-3d-1.
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Lyngå, A., and P. Balmér. "Denitrificiation in a Non-Nitrifying Activated Sludge System." Water Science and Technology 26, no. 5-6 (September 1, 1992): 1097–104. http://dx.doi.org/10.2166/wst.1992.0551.
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Post-nitrification and recycling of the nitrified effluent to an anoxic zone in an activated sludge system for denitrification is proposed as a potentially cost-effective method for nitrogen removal in existing activated sludge treatment plants. Denitrification in a non-nitrifying activated sludge system with a SRT of 3-4 days has been studied in pilot scale. The results show that denitrification rates of at least 10 g N03-N/(kgVSS h) can be achieved. At COD/NO3-N ratios above 15, nitrate supply appears to control the denitrification rate while at COD/NO3-N ratios below 15 the rate appears to be controlled by the supply of easily biodegradable organic matter.
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Dorland, S., and E. G. Beauchamp. "Denitrification and ammonification at low soil temperatures." Canadian Journal of Soil Science 71, no. 3 (August 1, 1991): 293–303. http://dx.doi.org/10.4141/cjss91-029.
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A laboratory study was conducted to determine the effects of temperatures from −2 to 25 °C on denitrification and ammonification in anaerobic soil treated with alfalfa or glucose. Organic C substrate as alfalfa or glucose increased denitrification rates at all temperatures within this range and lowered the threshold temperature at which denitrification occurred. The threshold temperature for denitrification was as low as −2 °C in unfrozen (supercooled) soil in contrast to most other studies where the threshold temperature was reported to be at or above 0 °C. When soil was frozen at −2 °C, the denitrification rate was much lower than in unfrozen soil at the same temperature. A square root model was employed which showed that the square root of the denitrification rate was linearly related to temperature from −2 to 25 °C. The maximum amount of [Formula: see text] produced during the incubation periods generally decreased from −2 to 25 °C and was greatest when glucose and especially alfalfa were added. The rate of ammonification increased with addition of alfalfa but the quantities of [Formula: see text] produced generally decreased from 25 to −2 °C. Key words: Threshold temperature, frozen vs. unfrozen soil, nitrite production, square root model
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Ito, Tsukasa, Toru Aoi, Naoki Miyazato, Masashi Hatamoto, Shunji Fuchigami, Takashi Yamaguchi, and Yoshimasa Watanabe. "Diversity and abundance of denitrifying bacteria in a simultaneously nitrifying and denitrifying rotating biological contactor treating real wastewater at low temperatures." H2Open Journal 2, no. 1 (January 1, 2019): 58–70. http://dx.doi.org/10.2166/h2oj.2019.021.
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Abstract Nitrification and denitrification processes occur simultaneously in aerobic wastewater biofilms. Although wide regions of the world have average temperatures of less than 15 °C for a half year, few studies have investigated the nitrogen removal by nitrification and denitrification in a single-stage aerobic biofilm reactor used for treating real wastewater under low-temperature conditions. This study showed successful wastewater treatment in a high average nitrogen removal rate of 78% at low water temperatures by simultaneous nitrification and denitrification in a rotating biological contactor (RBC) biofilm. Batch operations using the RBC to evaluate the rates of ammonium decrease at low temperatures demonstrated that the rate of ammonium decrease at 8 °C was 76% of that at 20 °C. Daily monitoring of nitrification and denitrification rates suggested that the denitrification rate was highly correlated with the nitrification rate. Next-generation sequencing (NGS) analysis revealed the presence of diverse and abundant denitrifying bacteria and aerobic bacteria in the RBC biofilm more than those in the activated sludge samples, which probably enabled the achievement of the high nitrogen removal rates at such low temperatures. Furthermore, correlation with the colony counts showed that the NGS analysis had the quantification range of three orders of magnitude (from 0.001% to 1%).
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Forte, Annachiara, and Angelo Fierro. "Denitrification Rate and Its Potential to Predict Biogenic N2O Field Emissions in a Mediterranean Maize-Cropped Soil in Southern Italy." Land 8, no. 6 (June 17, 2019): 97. http://dx.doi.org/10.3390/land8060097.
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The denitrification rate in C2H2-amended intact soil cores and soil N2O fluxes in closed static chambers were monitored in a Mediterranean irrigated maize-cropped field. The measurements were carried out during: (i) a standard fertilization management (SFM) activity and (ii) a manipulation experimental (ME) test on the effects of increased and reduced application rates of urea at the late fertilization. In the course of the SFM, the irrigations following early and late nitrogen fertilization led to pulses of denitrification rates (up to 1300 μg N2O-N m−2 h−1) and N2O fluxes (up to 320 μg N2O-N m−2 h−1), thanks to the combined action of high soil temperatures and not limiting nitrates and water filled pore space (WFPS). During the ME, high soil nitrates were noted in all the treatments in the first one month after the late fertilization, which promoted marked N-losses by microbial denitrification (from 500 to 1800 μg N2O-N m−2 h−1) every time the soil WFPS was not limiting. At similar maize yield responses to fertilizer treatments, this result suggested no competition for N between plant roots and soil microbial community and indicated a probable surplus of nitrogen fertilizer input at the investigated farm. Correlation and regression analyses (CRA) on the whole set of data showed significant relations between both the denitrification rates and the N2O fluxes with three soil physical-chemical parameters: nitrate concentration, WFPS and temperature. Specifically, the response functions of denitrification rate to soil nitrates, WFPS and temperature could be satisfactorily modelled according to simple Michaelis-Menten kinetic, exponential and linear functions, respectively. Furthermore, the CRA demonstrated a significant exponential relationship between N2O fluxes and denitrification and simple empirical functions to predict N2O emissions from the denitrification rate appeared more fitting (higher concordance correlation coefficient) than the predictive empirical algorithm based on soil nitrates, WFPS and temperature. In this regard, the empirically established relationships between the denitrification rate on intact soil cores under field conditions and the soil variables provided local-specific threshold values and coefficients which may effectively work to calibrate and adapt existing N2O process-based simulation models to the local pedo-climatic conditions.
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Chen, Jie Yun, Zhi Zhang, Li Hua Xie, Ling Kong, and Xiao Jing Yin. "Regulating Strategies of Strengthening Nitrogen Removal for Low-Carbon Wastewater in Reversed A2/O Process." Advanced Materials Research 243-249 (May 2011): 4811–16. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4811.
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According to the ineffective denitrification and the initial controlling technique flaws for low-carbon source in reversed A2/O process, and full scale experimental studies were conducted to strengthen denitrification at normal and low temperature days in 2008~2010, to ensure the best conditions of biological denitrification and promote the stable and efficient operation of the system. The results showed that in normal temperature seasons of 2008, after shortening the HRT of the primary sedimentation tank to 1/3 of design value, improving the MLSS to 4500mg/L, setting the first section of the aerobic zone as the denitrification transition section and improving the reflux ratio, available carbon source was increased by 15%, the effluent NH3-N was 2.5mg / L and the removal rate was 90%, the effluent TN was 17 mg/L and the removal rate was increased to 54% and unit power consumption was reduced by 15% to 0.22Kw•h/m3.At low temperature seasons of 2008~2009,by improving the MLSS to 6000mg/L, extending the sludge age to enrich a large number of nitrification and denitrification bacteria, controlling DO at about 1.2mg / L in the aerobic zone and so on, the effluent NH3-N was 3 mg / L and the removal rate was 88%, the effluent TN was 15.5 mg/L and the removal rate was 62%. In low temperature of 2009 ~2010, besides the same measures as before, adding a blender in the first section of the aerobic zone to provide a better anoxic environment for denitrification and to improve nitrogen removal, the effluent NH3-N was 3 mg / L and the removal rate was 87%, the effluent TN was 13.5 mg/L and the removal rate was 66%.
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Mann, G. W., S. Davies, K. S. Carslaw, and M. P. Chipperfield. "Factors controlling Arctic denitrification in cold winters of the 1990s." Atmospheric Chemistry and Physics Discussions 2, no. 6 (December 18, 2002): 2557–86. http://dx.doi.org/10.5194/acpd-2-2557-2002.
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Abstract. Denitrification of the Arctic winter stratosphere has been calculated using a 3-D microphysical model for the winters 1994/95, 1995/96, 1996/97 and 1999/2000. Denitrification is assumed to occur through the sedimentation of low number concentrations of large nitric acid trihydrate (NAT) particles, as observed extensively in 1999/2000. We examine whether the meteorological conditions that allowed NAT particles to grow to the very large sizes observed in 1999/2000 also occurred in the other cold winters. The results show that winter 1999/2000 had conditions that were optimum for denitrification by large NAT particles, which are a deep concentric cold pool and vortex. Under these conditions, NAT particles can circulate in the cold pool for several days, reaching several micrometres in radius and leading to a high downward flux of nitric acid. The other winters had shorter periods with optimum conditions for denitrification. However, we find that NAT particles could have grown to large sizes in all of these winters and could have caused significant denitrification. We define the quantity "closed flow area'' (the fraction of the cold pool in which air parcel trajectories can form closed loops) and show that it is a very useful indicator of possible denitrification. We find that even with a constant NAT nucleation rate throughout the cold pool, the average NAT number concentration and size can vary by up to a factor of 10 in response to this meteorological quantity. These changes in particle properties account for a high degree of variability in denitrification between the different winters. This large meteorologically induced variability in denitrification rate needs to be compared with that which could arise from a variable nucleation rate of NAT particles, which remains an uncertain quantity in models.
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Koenig, A., and L. H. Liu. "Autotrophic denitrification of landfill leachate using elemental sulphur." Water Science and Technology 34, no. 5-6 (September 1, 1996): 469–76. http://dx.doi.org/10.2166/wst.1996.0584.
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One of the most economical means of nitrogen removal from leachate is biological treatment by nitrification, followed by heterotrophic denitrification. An alternative biological denitrification process is autotrophic denitrification using Thiobacillus denitrificans. This autotrophic bacteria oxidizes elemental sulphur to sulphate while reducing nitrate to elemental nitrogen gas, thereby eliminating the need for addition of organic carbon compounds. For this study, pilot-scale elemental sulphur packed bed columns with fixed-film denitrification have been selected as the most suitable treatment process. The effect of hydraulic retention time as well as the effect of concentration and loading rate of nitrate on nitrate removal efficiency as a function of sulphur particle size were determined. The results indicate that (i) autotrophic denitrification can effectively remove nitrate from synthetic and actual nitrified leachate at concentrations much higher than hitherto reported; (ii) the minimum hydraulic retention time necessary for complete denitrification depends on sulphur particle size; (iii) the maximum area loading rate, in g NO3−-N/m2·d, appears to be the process limiting factor and is practically independent of sulphur particle size; and (iv) the observed stoichiometric relationships compare well with those previously reported.
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Glock, Nicolaas, Alexandra-Sophie Roy, Dennis Romero, Tanita Wein, Julia Weissenbach, Niels Peter Revsbech, Signe Høgslund, David Clemens, Stefan Sommer, and Tal Dagan. "Metabolic preference of nitrate over oxygen as an electron acceptor in foraminifera from the Peruvian oxygen minimum zone." Proceedings of the National Academy of Sciences 116, no. 8 (February 6, 2019): 2860–65. http://dx.doi.org/10.1073/pnas.1813887116.
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Benthic foraminifera populate a diverse range of marine habitats. Their ability to use alternative electron acceptors—nitrate (NO3−) or oxygen (O2)—makes them important mediators of benthic nitrogen cycling. Nevertheless, the metabolic scaling of the two alternative respiration pathways and the environmental determinants of foraminiferal denitrification rates are yet unknown. We measured denitrification and O2respiration rates for 10 benthic foraminifer species sampled in the Peruvian oxygen minimum zone (OMZ). Denitrification and O2respiration rates significantly scale sublinearly with the cell volume. The scaling is lower for O2respiration than for denitrification, indicating that NO3−metabolism during denitrification is more efficient than O2metabolism during aerobic respiration in foraminifera from the Peruvian OMZ. The negative correlation of the O2respiration rate with the surface/volume ratio is steeper than for the denitrification rate. This is likely explained by the presence of an intracellular NO3−storage in denitrifying foraminifera. Furthermore, we observe an increasing mean cell volume of the Peruvian foraminifera, under higher NO3−availability. This suggests that the cell size of denitrifying foraminifera is not limited by O2but rather by NO3−availability. Based on our findings, we develop a mathematical formulation of foraminiferal cell volume as a predictor of respiration and denitrification rates, which can further constrain foraminiferal biogeochemical cycling in biogeochemical models. Our findings show that NO3−is the preferred electron acceptor in foraminifera from the OMZ, where the foraminiferal contribution to denitrification is governed by the ratio between NO3−and O2.
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Zhang, De Yong, Xiu Ying Shen, Xiao Lu Xu, Yin Lu, and Fei Lin Hao. "Evaluation of an Aerobic Denitrifying Bacterium for Wastewater Treatment." Advanced Materials Research 621 (December 2012): 278–82. http://dx.doi.org/10.4028/www.scientific.net/amr.621.278.
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An aerobic denitrifying bacterium isolated from sludge was evaluated for water treatment application. The denitrification reaction condition was optimized using orthogonal experiment as temperature 30°C,pH7.0 and shaking speed 250rpm. The highest denitrification rate observed at 24h in the optimization experiment was 94.8%. Temperature was confirmed to be the most significant one in the four factors affecting the denitrification efficiency. In a comprehensive evaluation experiment for printing-dying wastewater treatment, the bacterium showed a satisfying water purification effects with obvious decreasing of COD, total phosphorous concentration and nitrate. The highest NO3--N removal rate occurred on day 3, which reached 94.2%.
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Zheng, Xiao Ying, Wei Chen, Ji Li, Yu Jie He, Xi Huang, and Xing Nan Wang. "Effects of the DO of Nitrification Return Flow on the Nitrogen Removal of A/A-MBR Combined Process." Applied Mechanics and Materials 174-177 (May 2012): 58–63. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.58.
Full textAbstract:
In this study, the traditional A/A/O process was combined with MBR to create the A/A-MBR combined process. A 2.0 m3/h pilot scale study on the combined process was carried out. The influence mechanism of dissolved oxygen (DO) in the return flow on the A/A-MBR combined process was analyzed and the suitable dissolved oxygen concentration in MBR was further optimized. The results show that the combined process has the characteristics of rapid start and stable operation. Its COD, NH4+-N, TN and TP removals were 82.1%~92.4%, 93.0~98.3%, 48.4~70.7% and 93.8~97.9%, respectively. The return flow with high concentration of DO in MBR seriously affected the denitrification rate. The DO concentration of return flow increased gradually from 2.0 mg/L to 5.0 mg/L, the denitrification rate continuously decreased, the denitrification rate in the first stage decreased from 2.52 mg NO3--N/(gVSS•h) to 0.34mg NO3--N/(gVSS•h). When the DO of nitrification return liquid ascended to 5 mg/L, the denitrification ability of activated sludge was severely inhibited, and its denitrification activity was even lost. DO were controlled between 4.0±0.5 mg/L by adjusting the aeration rate in the MBR, effluent TN could be stably maintained between 10.82-13.94 mg/L with 62.6% average removal rate. The effluent COD, NH4+-N, TN and TP stably qualified to t criteria of the first level A of China’ s "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002). If the effective control of membrane fouling could be ensured, the DO in the MBR was controlled as much as possible fewer than 4.0 mg/L. This could decrease the inhibition of denitrification by high DO from the return flow and insure that effluent TN achieved the discharge standard.