• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.2
• /
• pp.199-206
• /
• 2008

Simultaneous nitrification and denitrification means that nitrification and denitrification occur concurrently in the same reaction vessel under low DO concentration. Some mathematical models developed to simulate simultaneous nitrification and denitrification reaction, but they have the complex model structures or have limitations of model application. To solve these problems, if possible that predict the behavior of simultaneous nitrification and denitrification reaction by activated sludge model, structures of the model is less complex than previous models and applies the various operation conditions. But original activated sludge models have difficulties in representing the denitrification reaction under aerobic condition. So the aim of this study is to interpret simultaneous nitrification and denitrification reaction by modifying activated sludge model. Original activated sludge model No.1(ASM1) was selected and modified. The simulation result in modified ASM1 predicted appropriately for the measured data. This indicates the structures of ASM1 are properly improved for interpretation of simultaneous nitrification and denitrification reaction.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.5
• /
• pp.542-548
• /
• 2005

A fluidized bed reactor containing porous media has been known to be effective for nitrogen and organic matters removal in wastewater. The porous media which attached microbes plays important roles in simultaneous nitrification/denitrification (SND) due to coexistence of oxic, anaerobic and anoxic zone. For SND reaction, oxygen and organic substrates should be effectively diffused from wastewater into the intra-carrier zone. However, the overgrowth heterotrophic microbes at the surface of porous media may restrict from substrates diffusion. From these viewpoints, the existence and effect of heterotrophic bacteria at surface of porous media might be the key point for nitrogen removal. A porous media-membrane hybrid process was found to have improved nitrogen removal efficiency, due to stimulated denitrification as well as nitrification. Microelectrode studies revealed that although intra-media denitrification rate in a conventional fluidized bed was limited by organic carbon, this limitation was reduced in the hybrid process, resulting in the increased denitrification rate from 0.5 to $4.2\; mgNO_3-N/L/hr$.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 1994.11a
• /
• pp.97-100
• /
• 1994

산화구리가 담지된 알루미나 흡수제/촉매를 이용하여 유황산화물과 질소산화물의 제거반응 특성을 고정층 반응기를 이용하여 고찰하였다. 반응온도가 증가할 수록 $350^{\circ}C$까지 탈질 효율이 증가하였으며 그 이상의 온도에서는 암모니아의 산화에 의하여 탈질효율이 감소하였다. 암모니아의 $NO_{x}$ 선택성은 $SO_{x}$ 가 존재하지 않는 경우에 $NH_3/NO_{x}$mole 비 1.0 까지 유지되었으나 $SO_{x}$ 가 존재하면 선택성은 매우 감소하였다. 동시제거 반응의 경우 $400^{\circ}C$ 이상에서 효과적이었으며 $350^{\circ}C$ 이하에서는 암모늄 염의 생성으로 인하여 탈질효율의 감소가 반응시간이 증가함에 따라서 감소하였다.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.11
• /
• pp.1995-2005
• /
• 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 Korean Society of Environmental Engineers
• /
• v.27 no.11
• /
• pp.1174-1179
• /
• 2005

Up-flow sludge blanket(USB) reactors were used to investigate the effects of N/C(${NO_3}^--N/COD$) ratio on simultaneous denitrification and methanogenesis processes. Without nitrate feeding, 84% of the influent COD was converted into methane. With the increase of N/C ratio, nitrogen gas increased while methane production decreased and stopped finally at the N/C ratio over 0.20. Influent nitrate was completely denitrified into nitrogen gas while nitrate removal efficiency dropped below 40% at N/C ratio of 0.40 because of deficiency in organic carbon. Fraction of COD utilized by denitrification increased at higher N/C ratios. Methanogenesis started to be effected at N/C ratio of 0.05, which could explain the competition for organic carbon between these microorganisms such as denitrifiers and methanogens, rather than inhibitory effect of nitrate and its intermediates. Critical N/C ratio for simultaneous denitrification and methanogenesis was found to be 0.20. Influent COD was removed over 92% by denitrification, methanogenesis and other biochemical reactions including cell growth at these N/C ratios.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.8
• /
• pp.944-949
• /
• 2007

The profiles of on-line sensors such as DO, ORP and pH can provide useful information about pollutant removal reaction in sequencing batch reactor. For detection of denitrification completion, the nitrate hee point from ORP profile has been considered as a main indicator of denitrification completion. However, many researchers pointed out that the nitrate knee usually disappeared been the progress of denitrification is so fast and it makes the fault at detection of denitrification completion. In this paper, dynamic time warping(DTW) method and discriminant analysis were used to detect and isolate the profiles of two cases, denitrification completed and uncompleted. As the results, proposed methods can detect state of denitrification successfully.

• Journal of Digital Convergence
• /
• v.11 no.5
• /
• pp.237-243
• /
• 2013

This study aims to examine the modified $A^2/O$ process is useful to reduce the environmental pollution caused by nutrient in wastewater. Specific results are as follows: The removal rate was evaluated at each time period, ie., 18h, 8h, 6h, and 3h after the reaction started. The anoxic rate was more than 94-97% from 18h to 6h but was less than 50% before 6h. Thus, the test of nitrification was done using 6h as the optimal anoxic retention time and the aerobic retention time set at 24h. When the flow change was 1:1, the average ammonia concentration inputted was $30mg/{\ell}$. Returned top nitric acid solution and the concentration of ammonia solution falling into the anoxic reactor was about 50％ of the initial concentration, and the flow change was 1:2, the concentration of ammonia falling into the anoxic reactor was about 62% of that of influxed ammonia. And the results of this study showed that the nitrogen removal rate can be improved by inputting untreated nitric acid and changing the flow of top nitrate solution using the modified $A^2/O$ method.

• Journal of Soil and Groundwater Environment
• /
• v.11 no.2
• /
• pp.38-44
• /
• 2006

Two sulfur-based column reactors inoculated with a bacterial consortium containing autotrophic denitrifiers were operated for 100 and 500 days, respectively and nitrate removal efficiency and the adaptation of microbial communities in the columns were monitored with column depths and time. For better understanding the adaptation phenomenon, molecular techniques including 16S rDNA sequencing and DGGE analysis were employed. Although both columns showed about 99% of nitrate removal efficiency heterotrophic denitrifiers such as Cenibacterium arsenioxidans and Geothrix fermentans were found to a significant portion at the initial stage of the 100-day reactor operation. However, as operation time increased, an autotrophic denitrifier Thiobacillus denitrificans became a dominant bacterial species throughout the column. A similar trend was also observed in the 500-day column. In addition, nitrate removal efficiencies were different with column depths and thus bacterial species with different metabolic activities were found at the corresponding depths. Especially, T. denitrificans was successfully adapted and colonized at the bottom parts of the columns where most nitrate was reduced.

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

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 1998.11a
• /
• pp.52-56
• /
• 1998

최근 들어 국외에서는 오염된 지하수의 정화기술로써 0가 금속을 이용한 방법이 높은 잠재력을 가진 신기술로 알려져 있다. 본 연구에서는 0가 금속중 나노크기(1-100nm)를 가진 0가 철입자를 이용하여 수중의 NO$_3$￣를 탈질처리하는 실험을 행하였다. 본 실험에서 제조한 나노크기 0가 철입자는 상온상압의 환원적 조건에서 50, 100, 200, 400mg/$\ell$의 NO$_3$￣와 반응하여 반응시간 30분안에 95%이상 제거되는 높은 반응성을 보여주었다. 기존의 상업용 철입자(10-100$\mu\textrm{m}$)를 이용한 NO$_3$￣의 제거결과에서 보여주는 다량의 철사용, 낮은 적용 오염농도, 그리고 낮은 반응속도등의 문제점에 비하여 나노크기 철 입자는 높은 오염농도범위에서도 적은 철 주입량과 짧은 반응시간 내에 매우 높은 제거효율(10-100배)을 나타내었다. 이러한 결과로 수중의 NO$_3$￣의 고속 탈질반응속도에 영향을 주는 중요한 변수는 반응에 참여하는 철 입자의 비표면적임을 알 수 있었다. 본 연구에서 얻은 batch실험 결과를 바탕으로 NO$_3$￣로 오염된 지하수의 정화를 위한 현장 적용을 목표로 연속처리 공정의 설계를 위한 토대를 마련하고자 하였다.