• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.642-649
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• 2007

The effectiveness of add-on tertiary treatment processes for the polishing of the effluent of a biological nutrient removal (BNR) system from a modified $A^2/O$ process has been examined under the field condition with pilot-scale plants. The add-on treatment processes of 1) combined biofilm anoxic reactor and sand filtration, and 2) two-stage denitrification filter had been operated with various operating conditions. The experimental results indicated that two-stage denitrification filter could produced a better polished tertiary effluent. Filtration rate of $150m^3/m^2{\cdot}d$ for the 2-stage denitrifying filter could decrease the nitrate removal probably due to shorter detention time that caused insufficient reaction for denitrification. Two stage denitrification filter operated with M/N ratio of 3.0 and filtration rate of $100m^3/m^2{\cdot}d$ produced the tertiary effluent with nitrate and SS concentraitons of 2.8 mg/L and 2.3 mg/L, respectively. When the operating temperature reduced $30^{\circ}C$ to $18^{\circ}C$, $NO_3{^-}-N$ removal efficiency decreased from 73% to 68%.

• Environmental Engineering Research
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• v.10 no.6
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• pp.283-293
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• 2005

Characteristics of sulfur-based autotrophic denitrification in a semi-continuous type reactor and the kinetic parameters were studied. Enriched autotrophic denitrifying culture was used for the reactor operation. Biomass growth on sulfur particles and in the liquid medium was monitored using the DAPI staining method. From the result of ion concentration changes and the biomass growth, maximum specific growth rate, ${\mu}_{max}$, and the half velocity constant, $K_M$, were estimated as $0.61\;d^{-1}$ and 3.66 mg/L, respectively. Growth yield coefficient, Y values for electron acceptor and donor were found as 0.49 gVSS/g N and 0.16 gVSS/g S. The biomass showed specific denitrification rate, ranging 0.86-1.13 gN/g VSS-d. A half-order equation was found to best simulate the denitrification process in the packed bed reactor operated in the semi-continuous mode.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.602-608
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• 2005

A laboratory-scale experiment was conducted to investigate control of soluble microbial products (SMP) by the internal recycle rate in the submerged membrane separation activated sludge process. The internal recycle rate of the reactor RUN 1 and RUN 2 were 100 % and 200 %, respectively. SMP concentration was rapidly accumulated in the reactor (RUN 1). The variation of accumulated SMP concentration was related to the denitrification rate at the beginning experiment however SMP concentration decreased without correlatively to the denitrification rate during long operation time. The microbial kinetic model was rapidly presented in the both microbial growth and extinction in the reactor (RUN 1). In the SMP kinetic model, Internal recycle rate is the lower, value of UAP and BAP which SMP matter were presented low. The study about development of kinetic model is relatively well adjusted to the experiment exception SMP. In the future, SMP formation equation must be thought that continually research is necessary.

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1826-1835
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• 2008

An autotrophic denitrification reactor (ADR-l) and a heterotrophic denitrification reactor (HDR-2) were operated to remove nitrate and nitrite in an anoxic environment in raw sewage. The $NO_3$-N removal rate of ADR-l was shown to range from 52.8% to 78.7%, which was higher than the $NO_3$-N removal rate of HDR-2. Specific denitrification rates (SDNR) of ADR-l and HDR-2 were 3.0 to 4.0 and 1.1 to $1.2\;mgNO_3$-N/gVSS/h, respectively. From results of restriction fragment length polymorphism (RFLP) of the 16S rRNA gene, Aquaspirillum metamorphum, Alcaligenes defragrans, and Azoarcus sp. were $\beta$-Proteobacteria that are affiliated with denitritying bacteria in the ADR-l. Specifically, Thiobacillus denitrificans was detected as an autotrophic denitrification bacteria. In HDR-2, the $\beta$-Proteobacteria such as Denitritying-Fe-oxidizing bacteria, Alcaligenes defragrans, Acidovorax sp., Azoarcus denitrificans, and Aquaspirillum metamorphum were the main bacteria related to denitrifying bacteria. The $\beta$-and $\alpha$-Proteobacteria were the important bacterial groups in ADR-l, whereas the $\beta$-Proteobacteria were the main bacterial group in HDR-2 based on results of fluorescent in situ hybridization (FISH). The number of Thiobacillus denitrificans increased in ADR-l during the operation period but not in HRD-2. Overall, the data presented here demonstrate that many heterotrophic denitritying bacteria coexisted with autotrophic denitrifying bacteria such as Thiobacillus denitrificans for nitrate removal in ADR-l. On the other hand, only heterotrophic denitritying bacteria were identified as dominant bacterial groups in HDR-2. Our research may provide a foundation for the complete nitrate removal in raw sewage of low-COD concentration under anoxic condition without any external organic carbon or the requirement of post-treatment.

• Journal of Environmental Science International
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• v.7 no.4
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• pp.493-500
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• 1998

An experimental study was conducted to Indentify the dlrpct denitrification of ammonium nitrogen In culture water by ozone. During the experimnet period, pH was 7.8-8.8. pH was grdually lower after ammonium nitrogen was reacted with ozone under Br . In addition, it can be tmown that the culturing water was improved greatly form the inverstigation of T-N by biofilm and ozonation. As the results of a variation of recirculation rate, denitrification of ammonium nitrogen was in increased in proportion to the recirculation rate. But Nitrification of microorganism was opposite to the recirculation rate. With the increasing injected ozone in ozonation tank uner 21 clrculation/day(6.71 /min), dinitrification of ammonium nitrogen was Increased lineraly in propotion to the Increasing of injected ozone concentration.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.6
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• pp.779-786
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• 1996

The main purpose of this study was to estimate the role of dissolved inorganic nitrogen (DIN) released from sediment and denitrification process in sediment on the nitrogen budget of Hiroshima Bay by means of collecting data on distributions and budgets of nitrogen and phosphorus in the bay, DIN fluxes across sediment-water interface and denitrification rates in the sediments of the same area. The TN : TP and DIN:DIP atomic ratios of the discharged freshwater were about 26 and 21, respectively. The standing stocks in the seawater of the TN : TP atomic ratio varied from 8 to 14 with an annual mean value of 11, while the DIN : DIP atomic ratio varied from 10 to 15 with an annual mean value of 12 in the bay. The residence time of nitrogen and phosphorus were estimated to be about 109 days and 200 days in the bay, respectively. The proportion of DIN released from sediment and denitrification rate to the loading of total nitrogen into Hiroshima Bay were $45\%\;(37\~82\%)\;and\;13\%(0.0\~37\%)$, respectively, and the amount of nitrogen through denitrification process was 6.5 times larger than the outflow of nitrogen from the bay. The results show that DIN released from sediment and denitrification process in sediment play important roles on the nitrogen budget in Hiroshima Bay.

• Journal of environmental and Sanitary engineering
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• v.12 no.3
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• pp.9-17
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• 1997

This research aims to remove nitrogen in the piggery wastewater by combined process with upflow anaerobic sludge blanket (UASB) and biofilm process. For the effective denitrification. anaerobic and anoxic reactors were connected to a reactor. The effluent of aerobix reactor was recycled equally with influent in the upper filter of anaerobic reactor for denitrification and outlet of UBF reactor was connected to the settling tank with $1.5{\;}{\ell}$ capacity and the settling sludge was repeatedly recycled to UASB zone. The organic loading rate of total reactor was operated from 0.4 to $3.1kgCOD/m^{3}/d$ and it was observed that the removal rate of TCOD was 80 to 95 percentage. Ammonia nitrogen was removed over 90 percentage in the less volumetric loading rate than $0.1{\;}kgN/m^{3}/d$. But because of non-limitation of organic materials, it was reduced to 70 percentage in the more volumetric loading rate than $0.6{\;}kgN/m^{3}/d$. But denitrification rate was observed 100 percentage in the all of loading rate. This is caused by the maintenance of optimum temperature, sufficient carbon source, and competition of electron acceptors. The results of COD mass balance at the $1.21{\;}kgCOD/m^{3}/d$ was observed with the 71.7% percentage of influent COD. It was revealed that the most part of organic materials was removed in the aerobic and the anaerobic reactor because 38.4 percentage was conversed into $CH_{4}$ gas and 11 percentage was removed in the aerobic reactor with cell synthesis and metabolism. Besides, 5.7% organics was used to denitrification reaction and 3.7% organics related to sulfate reduction.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.1
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• pp.94-98
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• 1985

A laboratory experiment was conducted to find out the denitrification rate upon the different levels of nitrogen fertilizer in submerged sandy soil. The results obtained were summarized as follows: 1. The highest denitrification rate was observed at 25 days after incubation. The amount was reached at 1830 ug/100g soil for 20mg nitrogen was applied in 100g soil. 2. Increases of fertilizer nitrogen was enhanced the rate of ammonification and nitrification during the incubation time. 3. Deep correlation was observed between the denitrification capacities which was determined as nitrous oxide and Mitchaelis-Menten kinetic with relation to nitrate concentration. More higher denitrification rates were observed in Mitchaelis-Menten kinetic than dentrification rate with determined as nitrous oxide. 4. A Zero order (with relation to nitrate concentration) kinetic model for denitrification was presented in this experiment condition to illustrate the variability of nitrous oxide concentrations in the submerged soil atmosphere.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.6
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• pp.628-636
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• 2008

Anaerobic denitrification in a two phase anaerobic digestion(TPAD) process combined with biological nutrients removal (BNR) system was studied for a piggery wastewater treatment. Denitrification efficiency and the effects of the nitrified effluent on acidification was investigated by recycling the nitrified effluent to the acidogenic reactor. Recycle of the nitrified effluent to the acidogenic reactor enhanced the conversion efficiency of the influent COD into volatile fatty acids(VFAs) in the TPAD-BNR system treating the piggery wastewater. Acidification rate of the acidogenic sludge acclimated with the nitrified effluent showed 6 times higher than that acclimated without it. VFA could be used for denitrification as carbon sources, however, nitrate could enhance acidification activity in the acidogenic reactor. VFA production rate was affected on the COD/Nitrate(COD/N) ratio, however, it depended much more whether the acidogenic sludge acclimated with nitrate or not. Denitrification with the acidogenic sludge acclimated without nitrified effluent followed zero-order reaction and the reaction rate constants were in the range of 1.31$\sim$1.90 mg/L$\cdot$h. Denitrification reaction rate constants of the acidogenic sludge acclimated with nitrified effluent were 3.30 mg/L$\cdot$h that showed almost twice of them evaluated from the previous tests. The stoichiometric ratios of utilized COD to removed nitrate showed similar in both tests which were in the range of 5.1$\sim$6.4 at COD/N ratio of 10.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1777-1787
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• 2000

The purpose of this study was to select an effective and economical alkali source for sulfur-utilizing autotrophic denitrification. Tests on acid neutralization and denitrification at various alkali/sulfur mixing ratios were performed for charcoal, briquette ashes, sea shell, and limestone. The results of the experiments showed that sea shell was the most effective alkali source because it could provide more surface area than limestone, and the optimal alkali/sulfur mixing ratio was 1/1(V/V). In a sulfur/sea shell packed bed reactor, the denitrification efficiency was above 90% up to a loading rate of 116 g $NO_3{^-}-N/m^3-day$. but the denitrification efficiency deteriorated to 48% at the loading rate of 145 g $NO_3{^-}-N/m^3-day$. The average $SO_4{^{2-}}$ generation per g of $NO_3{^-}-N$ removed was 7.02 g, which is lower than the theoretical value of 7.54 g. Denitrification and sulfate generation appeared to be a first-order and a zero-order reaction with a reaction rate constant of 0.146 /hr and -53.1 mg/L-hr, respectively. According to nitrogen mass balance, 71~109%, with an average of 90%, of the removed nitrogen was recovered as $N_2$ gas.