• Environmental Engineering Research
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• v.16 no.4
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• pp.231-236
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• 2011

Biological nitrogen removal, using a continuous flow packed-bed reactor (CPBR) in a consecutive nitrification and denitrification process, was evaluated. An apparent decline in the nitrification efficiency coincided with the steady increase in $NH_4{^+}$-N load. Sustained nitrification efficiency was found to be higher at longer empty bed contact times (EBCTs). The relationship between the rate of alkalinity consumption and $NH_4{^+}$-N utilization ratio followed zero-order reaction kinetics. The heterotrophic denitrification rate at a carbon-tonitrogen (C/N) ratio of >4 was found to be >74%. This rate was higher by a factor of 8.5 or 8.9 for $NO_3{^-}$-N/volatile solids (VS)/day or $NO_3{^-}-N/m^3$ ceramic media/day, respectively, relative to the rates measured at a C/N ratio of 1.1. Autotrophic denitrification efficiencies were 80-90%. It corresponds to an average denitrification rate of 0.96 kg $NO_3{^-}-N/m^3$ ceramic media/day and a relevant average denitrification rate of 0.28 g $NO_3{^-}$-N/g VS/day, were also obtained. Results presented here also constitute the usability of an innovative porous sulfur ceramic media. This enhanced the dissolution rate of elemental sulfur via a higher contact surface area.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.429-437
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• 2007

This study aims to develop a sulfur-using denitrification process which is possible a renovation to advanced treatment plant submerging a simple module in activated sludge aeration tank. At first, the impact factor of sulfur-using denitrification was appreciated by the batch test. Secondly, reflecting a dissolved oxygen effect of sulfur-using denitrification that was confirmed by the batch test, in a continuous nitrification/sulfur-using denitrification, high-rate nitrogen removal reaction was induced at optimum condition controlling DO concentration according to phases. Also, inside and outside of sulfur-using denitrification module was covered with microfilter and the module was considered as an alternative of clarifier. Result of batch test for sulfur-using denitrification, $NO_2{^-}N$ was lower for consumption of alkalinity and sulfur than that of $NO_3{^-}-N$. These results revealed the accordance of theoretical prediction. In continuous nitrification/sulfur-using denitrification experiment, actual wastewater was used as a influent, and influent nitrogen loading rates were increased 0.04, 0.07, 0.11, $0.14kg\;N/m^3-day$ by changing hydraulic retention times. At this time, nitrogen loading rates of packed sulfur were increased 0.23, 0.46, 0.69, $0.93kg\;N/m^3-day$. As a result, nitrification efficiency was about 100% and denitrification efficiency was 93, 81, 79, 72%. Accordingly, nitrogen removal was a high-rate. Also the module of sulfur-using denitrification covered with microfilter did not make a fouling phenomena according to increased flux. And the module was achieved effluent suspended solids of below 10 mg/L without a clarifier. In conclusion, it is possible a renovation to advanced treatment plant submerging a simple module packed sulfur in activated sludge aeration tank of traditional facilities. And the plant used the module packed sulfur is expected as a effective facilities of high-rate and the smallest.

• Journal of Environmental Health Sciences
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• v.29 no.1
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• pp.62-66
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• 2003

The biological denitrification batch tests were conducted to optimize the operating conditions with various temperature and initial SCO $D_{Cr}$ /N $O_3$-N ratio. and the denitrification rates were analyzed various SCO $D_{Cr}$ /N $o_3$-N ratio of influent with swine wastes fermented and temperature. The finishing time of denitrification was within 15 hours, 12 hours, and 6 hours as the temperature of denitrification applied were 15$\pm$1$^{\circ}C$, 25$\pm$1$^{\circ}C$, and 31$\pm$1$^{\circ}C$, respectively. From the batch tests, denitrification rate was operated with over 3 of SCO $D_{Cr}$ /N $O_3$-N ratio. Denitrification rate was increased as the temperature of denitrification, increased such as 2.40-3.90 mg N $O_3$-N/gMLVSSㆍhr, 6.10-7.60 mgN $O_3$-N/gMLVSSㆍhr, and 14.40-15.88 mgN $O_3$-N/gMLVSSㆍhr, respectively. The denitrification rate was increased as the ratio of initial SCO $D_{Cr}$ N $O_3$-N increased. However, it was found that the suitable ratio of SCO $D_{Cr}$ /N $O_3$-N for denitrification should be considered because the ratio of mg SCO $D_{Cr}$ , consumed per mg N $O_3$-N removed varied depend on the influent SCO $D_{Cr}$ /TKN ratios.

• Journal of Soil and Groundwater Environment
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• v.26 no.6
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• pp.74-81
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• 2021

A simple and efficient scheme is presented that attempts to implement the site-specific denitrification rate in the reactive transport modeling for the nitrate in groundwater. A series of correlation analyses were conducted using 133 datasets obtained from different nitrate-contaminated sites to find the empirical relationships between denitrification rates and various subsurface properties. Based on Pearson's correlation analysis, the soil organic carbon concentrations showed a statistically significant correlation (r = 0.75, p < 0.05) with the denitrification rates. A linear regression was performed, which could be utilized to effectively determine the site-specific denitrification rate based on the soil organic carbon concentration of a site. The proposed method is expected to effectively replace the conventional methods which either were too complicated for practical application or impose large uncertainties that might end up with unreliable results.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.829-836
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• 2006

The reaction rate of denitrification is primarily affected by the utilization of organics that are usually limited in the anoxic period in a sequencing batch reactor. It is necessary to add an extemal carbon source for sufficient denitrification. An adaptive model of state-space based on the extended Kalman filter is applied to manipulate the dosage rate of extemal carbon automatically. Control strategies for denitrification have been studied to improve control performance through simulations. The normal control strategy of the constant set-point results in the overdosage of external carbon and deterioration of water quality. To prevent the overdosage of external carbon, improved control strategies such as the constrained control action, variable set-point, and variable set-point after dissolved oxygen depletion are required. More stable control is obtained through the application of the variable set-point after dissolved oxygen depletion. The converging value of the estimated denitrification coefficient reflects conditions in the reactor.

• Environmental Engineering Research
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• v.19 no.1
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• pp.75-81
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• 2014

Methanotrophic denitrification under a non-aerated condition (without external supply of oxygen or air) was investigated in a bioreactor coupled with a membrane diffuser. Batch experiment demonstrated that both methane consumption and nitrogen production rates were not high in the absence of oxygen, but most of the nitrate was reduced into $N_2$ with 88% recovery efficiency. The methane utilized for nitrate reduction was determined at 1.63 mmol $CH_4$/mmol $NO_3{^-}$-N, which was 2.6 times higher than the theoretical value. In spite of no oxygen supply, methanotrophic denitrification was well performed in the bioreactor, due to enhanced mass transfer of the methane by the membrane diffuser and utilization of oxygen remaining in the influent. The denitrification efficiency and specific denitrification rate were 47% and 1.69 mg $NO_3{^-}-N/g\;VSS{\cdot}hr$, respectively, which were slightly lower than for methanotrophic denitrification under an aerobic condition. The average concentration of total organic carbon in the effluent was as low as 2.45 mg/L, which indicates that it can be applicable as a post-denitrification method for the reclamation of secondary wastewater effluent. The dominant fatty acid methyl ester of mixed culture in the bioreactor was $C_{16:1{\omega}7c}$ and $C_{18:1{\omega}7c}$, which was predominantly found in type I and II methanotrophs, respectively. This study presents the potential of methanotrophic denitrification without externally excess oxygen supply as a post-denitrification option for various water treatment or reclamation.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.1995-2005
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• 2000

The use of heterotrophic denitrification as an alternative method for supplying alkalinity during sulfur-utilizing autotrophic denitrification was evaluated by examining the effects of external carbon source (both type and concentration) and HRT on denitrification efficiency. Concentrations of $NO_3{^-}-N$ and $COD_{Cr}$ of nitrified landfill leachate used for experiment were 700-900mg/L and 900-2500mg/L. respectively, All experiment was conducted with sulfur packed bed reactors (SPBRs) which were operated at $35^{\circ}C$. The fraction of $NO_3{^-}-N$ removed by heterotrophic denitrification ($HDNR_{fraction}$) to balance the alkalinity consumption by autotrophic denitrification varied with the type of external carbon source. When methanol and sodium acetate was added at theoretical HDNRfraction value. 100% denitrification was achieved without alkalinity addition. However, glucose and molasses require $HDNR_{fraction}$ value greater than theoretical value for complete denitrification. The EBCT and volumetric loading rate at which 100% denitrification efficiency could be achieved were 6.76 h and $2.84kg-NO_3{^-}-N/m^3{\cdot}d$, respectively, based on the fact that 100% denitrification occurred within the bottom 11.5 cm layer of the SPBR. The maximum nitrogen removal rate occurred with 89% removal efficiency at loading rate of $5.05kg-NO_3{^-}-N/m^3{\cdot}d$. However, at short EBCT, clogging of SPBR was observed with excess growth of heterotrophic denitrifiers. This problem may be eliminated by back washing or by separating of heterotrophic denitrification from sulfur-utilizing denitrification.

• Journal of Environmental Health Sciences
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• v.23 no.1
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• pp.95-104
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• 1997

The objectives of this study are to investigate the effect of media on the removal efficiency of nitrate-nitrogen and the biofilm thickness in the fluidized bed biofilm reactor(FBBR) used for the high rate denitrification of nitric acid wastewater. Granular activated carbon(GAC) of 1.274 mm diameter and sand of 0.455 mm diameter were used as the media in the FBBR of 0.05 m diameter and 1.5 m height. As the nitrate-nitrogen concentration of the influent was increased stepwise from 600 to 4800 mg/l, the nitrate- and nitrite-nitrogen concentration of the effluent, biofilm thickness and biofilm dry density were measured to study the effects of media on the denitrification efficiency. The biofilm thickness increased with the substrate loading rate, and the biofilm dry density decreased with the increase of the biofilm thickness. At the influent nitrate-nitrogen concentration of 2400 mg/l, the removal efficiency in the FBBR with GAC was 88%, while that in the FBBR with sand was 99.6%. The biofilm in the FBBR with GAC was so thick, 754.9 $\mu$m, as to increase the mass transfer resistance, compared to that, 143.7 $\mu$m, in the FBBR with sand. The maximum specific denitrification rate in the FBBR with GAC was 15.0 kg-N/m$^3\cdot$ day, while that in the FBBR with sand was 18.0 kg-N/m$^3\cdot$ day. The biomass concentration in the FBBR with sand exhibited the high value 37 kg/m$^3$.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.30-35
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• 2008

In this study, we investigated the nitrification/denitrification rate and classification of output nitrogen of a sequencing batch reactor (SBR) system with the variation of COD loads ; COD loads of 0.3, 0.4, 0.6, 0.7, 0.8, 1.0 and $1.2kgCOD/m^3{\cdot}d$ were tested to determine the optimum conditions for the operation of the SBR and increase its nitrogen removal efficiency. As the COD loads increased, the nitrification rate at aerobic(I) period and the denitrification rate at anoxic(I) period were decreased. With the variation of COD loads, the amounts of nitrogen removed in the clarified water effluent were 63.9, 54.2, 34.7, 22.5, 13.7, 12.5 and 26.5 mg/cycle, respectively. The amounts of nitrogen removed during the sludge waste process were 19.5, 26.6, 41.0, 47.3, 58.1, 72.4 and 88.1 mg/cycle, respectively. The amounts of nitrogen removed by denitrification were 66.8, 69.3, 68.9, 56.5, 39.5, 7.3 and 0.0 mg/cycle, respectively, indicating that COD load more than $0.7kgCOD/m^3{\cdot}d$ decreases the amounts of denitrified nitrogen. The nitrogen mass balances were calculated as the percentages of nitrogen removed in the clarified water effluent or by denitrification and sludge waste processing in each cycle of SBR operation and were 99.0, 98.5, 95.4, 82.1, 73.0, 60.5 and 74.8% for COD loads of 0.3, 0.4, 0.6, 0.7, 0.8, 1.0 and $1.2kgCOD/m^3{\cdot}d$, respectively.

• Environmental Engineering Research
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• v.24 no.3
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• pp.443-448
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• 2019

The present study was conducted to compare the voltage generation in two-chamber microbial fuel cells (MFCs) with a biocathode where nitrate and oxygen are used as a terminal electron acceptors (TEA) and to investigate the nitrogen removal and the electrochemical characteristics depending on the separators of the MFCs for denitrification. The maximum power density in a biocathode MFC using an anion exchange membrane (AEM) was approximately 40% lower with the use of nitrate as a TEA than when using oxygen. The MFC for denitrification using an AEM allows acetate ($CH_3COO^-$) as a substrate and nitrate ($NO_3{^-}$) as a TEA to be transported to the opposite sides of the chamber through the AEM. Therefore, heterotrophic denitrification and electrochemical denitrification occurred simultaneously at the anode and the cathode, resulting in a higher COD and nitrate removal rate and a lower maximum power density. The MFC for the denitrification using a cation exchange membrane (CEM) does not allow the transport of acetate and nitrate. Therefore, as oxidation of organics and electrochemical denitrification occurred at the anode and at the cathode, respectively, the MFC using a CEM showed a higher coulomb efficiency, a lower COD and nitrate removal rate in comparison with the MFC using an AEM.