• 상하수도학회지
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• 제21권5호
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• pp.539-549
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• 2007

To establish effective and prompt measures for energy conservation in public wastewater treatment plants in Korea, energy consumption rates in 233 utilities in 9 provinces and 7 metropolitan cities are investigated and compared to the rest of the world. Mean load factor for wastewater treatment utilities is 74.9% and those for influent pumps and aeration blowers are 56.2% and 61.0%, respectively. Mean electrical energy usages as the key performance indicators are $0.243kWh/m^3$ for overall sewage treatments and 2.07 kWh per unit kg BOD removal. Digester gas as one of major byproducts in the process amounts to $382,000m^3/day$ nationwide. While major part of the digester gas is used for sludge heating, only 7.3% of the gas is utilized for electricity generation. Both efficiencies for BOD removal and digestion gas generation are considerably lower than those in USA and EU utilities due to low concentration of organic material in influent wastewater. Such low energy regeneration, in turn, results in significantly higher energy consumption in Korean plants, compared to that in USA and EU ones.

• 상하수도학회지
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• 제8권3호
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• pp.19-25
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• 1994

In this research, characteristics of nitrification and denitrification using the microorganism attached on sponge and plates were examined. The denitrification and nitrification performance were investigated under the anaerobic and aerobic condition for about 2 months. Because the basins of denitrification and nitrification were connected in series, wastewater was flowed from denitrification basin to nitrification one. The 90% of influent flowrate was returned from nitrification basin to denitrification one. Most of organic material was removed in nitrification basin, wherease the only exact amount of organics required in denitrification process was removed in denitrification one. This experiment resulted in that heterotrophic bacteria existing in aerobic basin governed the removal efficiency of organic compounds. In case the influent BOD concentration into nitrification basin was 80mg/l, it did not affect to accumulation of nitrifying bacteria, the balance of heterotrophic bacteria was proved to be an important factor in nitrification/denitrification method such as anaerobic and aerobic cycling type.

• 대한환경공학회지
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• 제35권1호
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• pp.38-44
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• 2013

D하수처리장의 송풍량을 효과적으로 조절하는 시스템을 구축하기 위해 2011년 1월 1일부터 2012년 8월 31일까지 포기조 DO 농도를 평균 2.1 mg/L로 유지하면서 유입유량, 유입농도, 유입부하, 수온, F/M비, 생물반응조의 MLSS 농도 변화에 따른 송풍량 변화를 검토하였다. 그 결과 동일한 DO 농도를 유지하기 위한 송풍량 변화폭은 매우 크며, 송풍량 산정을 결정하는 주요 인자는 수온, F/M비, $BOD_5$ 유입 부하, T-N 유입 부하로 나타났다. 그 중 가장 큰 영향을 주는 지표는 수온으로 수온 $1^{\circ}C$ 증가는 $45.8m^3/h$의 송풍량을 증가시키는 것으로 나타났으며, 이는 계절의 영향이 반영된 것으로 사료 된다. 하절기에는 유입 유량증가, 낮은 MLSS농도, F/M비 증가의 영향과, 동절기에는 유입 유량감소, 높은 MLSS농도, F/M비 감소 등의 영향이 송풍량에 반영되어, 수온 변화에 따른 필요 송풍량 변화를 더욱 가중시킨 것으로 사료된다. 따라서 호기조 송풍량 산정 시에는 유입유량, 유입 $BOD_5$농도, 유입 T-N농도 및 생물반응조의 MLSS농도 중 하나의 인자를 이용하는 것보다, 유입부하나 F/M비로 연산하여 접근이 필요한 것으로 사료된다.

• 상하수도학회지
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• 제13권1호
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• pp.51-60
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• 1999

An intermittently-aerated, intermittently-decanted single-reactor process (KIDEA process : KIST intermittently decanted extended aeration process) was applied for nitrogen removal from wastewater. Synthetic wastewater with chemical oxygen demand (COD): nitrogen (N) ratio of approximately 5.25: 1 was used. The average COD removal efficiency reached above 95%, and under optimal conditions nitrogen removal efficiency also reached above 90%. This process consisted of 72 minute aeration, 48 minute settling and 24 minute effluent decanting with continuous feeding of influent wastewater from the bottom of the reactor, and did not require a separate anoxic mixing-phase. In this process, nitritation ($1^{st}$ step of nitrification) was induced but nitratation($2^{nd}$ step of nitrification) was suppressed. Main factors responsible for the accumulation of nitrite ion in the experimental condition were free ammonium and dissolved oxygen. This condition of nitrite build-up accelerated by continuous feed flow in the bottom of the KIDEA reactor because of high concentration of ammonia nitrogen in the influent. This research provides one of answers to control nitrate build-up.

• 공업화학
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• 제34권5호
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• pp.541-547
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• 2023

The effect of temperature and influent alkalinity/ammonia (K/A) ratio on the start-up of the partial nitrification (PN) process for an activated sludge-based domestic wastewater treatment was studied. Two different sequence batch reactors (SBR) were operated at 26 ℃ and 32 ℃. The relationship between temperature and the concentration of free ammonia (FA) and free acid nitrite (FNA) was investigated. A stable PN process was achieved in the 32 ℃ reactor when the influent ammonium concentration was lower than 150 mg-N/L. In contrast, the PN process in the 26 ℃ reactor had a higher nitrite accumulation rate (NAR) and ammonium removal efficiency (ARE) when the influent ammonia concentration was increased to more than 150 mg-N/L. Then three different ranges of the K/A ratio were applied to an SBR reactor. In the K/A range of 2.48~1.65, the SBR reactor achieved the highest NAR ratio (75.78%). This ratio helps to achieve the appropriate level of alkalinity to maintain a stable pH and provide a sufficient amount of inorganic carbon source for the activity of microorganisms. At the same time, FA and FNA values also reached the threshold to inhibit nitrite-oxidizing bacteria (NOB) without a significant effect on ammonia-oxidizing bacteria (AOB). Results showed that the control of temperature and K/A ratio during the start-up period may be important in establishing a stable and steady PN process for the treatment of domestic wastewater.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2000년도 추계학술대회 학술발표 논문집
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• pp.452-455
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• 2000

There are increasingly important financial incentives and environmental consideration to improve the effluent quality of wastewater from domestic and industrial users. The activated sludge process is a widely used biological wastewater treatment process. The activated sludge process is complicated due to the many factors such as the variation of influent flowrate and concentration, the complexity of biological reactions and the various operation conditions. Nowadays, not only suspended solids and residual carbon, but also nitrogen and phosphorous concentration of the effluent water must be taken into account for the design and operation of wastewater treatment plants. Also, the effluent quality to be met are more stringent. Therefore, an intelligent control approach is required in order to successful biological nitrogen removal. In this paper, the strategies for dosage of extra carbon in the anoxic zone and DO concentration in the aerobic zone are presented and evaluated through the simulation using the denitrification layout of the IWA simulation benchmark implemented by Matlab$\^$/5.3/Simulink$\^$/3.0. The control strategy to achieve sufficient denitrification rates in an anoxic zone. Methanol is used as an external extra carbon source. The external extra carbon source is required for the nitrogen removal process because nitrogen and organic concentration are fluctuated in the influent flowrate. The dissolved oxygen is calculated by So concentration in the activated sludge model NO.1. The air flowrate of each aerobic reactor is intelligently controlled to achieve the predefined setpoints. Air flowrate is adjusted by the fuzzy logic controller that includes two inputs and one output. The objective function for the optimization procedure is designed to improve effluent quality and reduce the operating cost.

• 상하수도학회지
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• 제27권4호
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• pp.489-494
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• 2013

Effects of operating parameters such as hydraulic retention time(HRT), recycle ratio and influent COD concentration on the performance of a continuous flow microbial fuel cell(MFC) were investigated. Decrease of HRT improved mass transfer of substrate to electrogenic microorganisms, therefore resulting in increased electrode voltage and power generation of MFC. Increase of HRT promoted COD removal by elongating retention time for COD removal in MFC. Recycling of effluent increased the COD removal and coulombic efficiencies by returning suspended microorganisms into MFC. Increase of influent COD enhanced COD removal due to the improved mass transfer of substrate. Decrease of coulombic efficiency by the increase of the HRT and influent COD concentration indicated that they enhanced the activities of fermentative bacteria.

• 한국환경보건학회지
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• 제23권1호
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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$^3$.

• 상하수도학회지
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• 제23권4호
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• pp.431-438
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• 2009

The purpose of this study was to evaluate the performances of zero-valent iron (ZVI) combined SBR (Z-SBR) process in decolorization and organic removal of synthetic dye wastewater. The batch test for optimizing the operation parameters of ZVI column showed that the appropriate EBCT was around 11 min and the pH of the dye wastewater was below 7.0. During the step increase of influent color unit from 300 to 1,000cu, about 53 to 79% decolorization efficiency could be achieved in control SBR (C-SBR, without ZVI column), which resulted from destroying azo bond of synthetic dye in anaerobic condition. For the same influent color loading, Z-SBR showed always higher decolorization efficiency than C-SBR with an aid of ZVI reducing power. The TCOD concentration in Z-SBR effluent was 20-30mg/L lower than C-SBR effluent although the TCOD before and after ZVI column was nearly same. It means that breakdown of azo bond by ZVI reducing power could increase biodegradability of synthetic dye wastewater.

• 한국미생물·생명공학회지
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• 제23권6호
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• pp.755-762
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• 1995

A phenolic resin industrial wastewater containing about 41,000 mg/l of phenol and 2,800 mg/l of formaldehyde was biologically treated by a mixed culture GE2 immobilized on ceramic beads. This study was carried out with three experimental groups : Control-only added the sludge of papermill wastewater ; GE2 treatment-added GE2 to Control ; Ceramic treatment-applied ceramic carrier to GE2 treatment. When the original wastewater was diluted 80 times with aerated tap-water, influent COD$_{Mn}$ WaS 1,140 mg/l and that of the effluent was in the range of 22-35 mg/l, which was not much different among the experimental groups. However, at 20-times dilution, influent COD$_{Mn}$ was 4,800 mg/l and the effluent COD$_{Mn}$ of Control, GE2 treatment and Ceramic treatment was 179, 128 and 94 mg/l, respectively. COD$_{Mn}$, removal efficiency by Ceramic treatment was the highest, at 98.0%. At this time, the effluent phenol concentration of Control, GE2 treatment and Ceramic treatment was 10.71, 7.93 and 5.60, respectively. As the dilution times decreased, the removal efficiency of COD$_{Mn}$ and phenol did not change much, but COD$_{Mn}$ and phenol concentration of the effluent increased. Consequently, it is likely that the phenolic industrial wastewater containing phenol and formaldehyde can be biologically treated using a GE2 and ceramic carrier and that at 40-times dilution, the effluent completely meets the effluent standards for industrial wastewater treatment plant.