• KSBB Journal
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• v.8 no.5
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• pp.438-445
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• 1993

Raw cow manure was treated by a 4-step integrated system with phase separation anaerobic digestion and algal culture. When the first methane fermentation was performed by the effluent from the acid fermenter with retention time of 4 days, the elrerage blogas production rate was 977m1/1 culture/day Gas productivity compared to conventional single-stage anaerobic digestion increased up to 31.4%. As the 2nd methane fermenter was fed by the effluent from the first methane fermenter with 4 days of retention time, average amount of 428m1/1 culture/day of biogas was produced. The reduction rate of COD in the effluent from the acid fermenter, the 1st and the 2nd methane fermenter were 71.8%, 42.6% and 24.0% respectively. Finally, we examined algal treatment process for the effluent from the 2nd methane fermenter. A semi-continuous culture of Chlorella sp. PSH3 was conducted by feeding the effluent with retention time of 10days. In this process, the production rate of algal biomass and COD reduction rate were averaged 1.8g/1 culture/day(2.8$\times$106 cells/ml) and 73%, respectively. Through the 4-setp treatments, the total chemical oxygen demand was reduced from 51,300ppm to 85ppm. Therefore, the reduction rate of total chemical oxygen demand reached about 99.8%. The results indicate that the integrated system could be applicable for treatment of organic wastes, concurrently producing biogas and algal biomass.

• Korean Journal of Microbiology
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• v.34 no.3
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• pp.126-131
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• 1998

Reduction of hexavalent chromium to its trivalent form by leachate microorganisms was studied in batch and bench-scale continuous stirred tank reactor. The inoculum was a culture of microorganisms in leachate and capable of providing up to 90% chromate reduction during 72 h batch assay with $20mg\;Cr(VI)\;L^{-1}$ in minimal media containing different levels of leachate (10 to 60%) and glucose (50 to 200 mM). Addition of glucose increased the efficiency of chromate reduction, but adverse effect was observed with increase of leachate probably due to the competitive inhibition between chromate and sulfate ions. The continuous culture experiment was conducted for 124 days using synthetic feed containing different levels of chromate (5 to $65mg\;L^{-1}$) at room temperature. With a hydraulic retention time of 36 h, chromate reduction efficiency was mostly 100% when Cr(VI) concentrations in the reactor were in the range of 5 to $50mg\;L^{-1}$ Specific rate of Cr(VI) removal was calculated as $3.492mg\;g^{-1}\;protein\;h^{-1}$ during the period of 101~124 days from the start-up which showed 81.2% of average reduction efficiency. The results indicate the potential application of using leachate microorganisms for detoxification of hexavalent chromium in various chromium-contaminated wastewater from landfill or tannery sites.

• Journal of Korea Water Resources Association
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• v.40 no.9
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• pp.735-742
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• 2007

In this study, a methodology which is based on segments and minimum outsets to estimate the reliability of a real water distribution system efficiently and accurately is suggested. The current reliability assessment models based on minimum cutset consider a pipe as only area impacted by a pipe failure which incurs underestimation of pipe failure impact. In contrary, the suggested methodology adopts "segment" and "unintended isolation" with the hydraulic pressure failure area to define the actual service interruption area in a water distribution system due to a pipe failure, which is different from the Previous reliability estimating methodologies. In addition, a minimum cutset is defined as a single segment incurring abnormal operating conditions and the success mode approach is used to account for the probability of multiple failure combinations of minimum outsets. The model considers numbers and locations of on-off valves when the service interruption area is defined. Once the methodology is applied to a real water distribution system, it is possible to define actual service interruption areas and using the defined areas, the reliability of the water distribution system is estimated reliably, compared with the previous reliability assessment methodologies.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.405-415
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• 2000

Experiments for autotrophic denitrification were performed using an upf10w reac1.or packed with sulfur particles as an electron donor. The influent $NO_3{^-}$-N concentration was kept almost constant, but the hydraulic retention time(HRT) and temperature varied. Results of the research showed that the denitrification efficiency and gas generation rate decreased as the HRT and temperature were reduced. During the HRT effect experiment, alkalinities of 3.44~5.71g, with an average of 4.67 g which is close to the theoretical value of 4.57g were consumed for each gram of $NO_3{^-}$-N removed. During the temperature effect experiment, however, the values were 6.58~13.41 g with an average of 9.12 g which is almost twice the theoretical value Denitrification along the length of the reactor appeared to be a first-order reaction with a reaction rate constant of 0.1648/hr. On the other hand, the sulfate generation showed a zero-order reaction with a reaction rate constant of 241/hr. There was some discrepancy in the nitrogen mass balance between the theoretical and measured values, requiring further researches.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.159-166
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• 2009

This study has been attempted to generate electricity, while simultaneously treating artificial organic wastewater using both batch and continuous microbial fuel cells (MFCs). In the batch MFC, current-voltage curve showed an onset potential of -0.69 V vs. Ag/AgCl. The potential range between this potential and 0 potential displayed an available voltage for an automatic production of electric energy and glucose, which was oxidized and treated at the same time. The 486 mg/L glucose solution showed the maximum power of $30mW/m^2$ and the maximum current density of $75mA/m^2$ shown in the power curve. As a result, discharging of the cell containing COD 423 mg/L at the constant current density of $60mA/m^2$ showed a continuous electricity generation for about 22 hours that dropped rapidly due to dissipating of organic material. Total electric energy production was 18.0 Wh. While discharging, the pH change was low and dropped from pH 6.53 to 6.20 then increased to 6.47, then stabilized at this charge. The COD treatment efficiency was found to be 72%. In the continuous MFC, COD removal tends to increase as the hydraulic retention time is increased. At one day of hydraulic retention time as the maximum value reaches the COD removal efficiency, power production rate and power production rate per COD removal that were obtained were 68.8%, $14mW/m^2$, and $20.8mW/m^2/g$ CODrm, respectively. In the continuous MFC, the power production rate per COD removal increases as the hydraulic retention time is increased and decreases as the organic loading rate is increased. At the values lower than an organic loading rate of $1kgCOD/m^3/d$, the values higher than about $18.1mW/m^2/g$ CODrm could be obtained.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.117-122
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• 2007

The hydrodynamic behaviors of the clarifier with an interior baffle in a wastewater treatment plant was investigated by using a radiotracer $^{99m}Tc$(30 40 mCi) to verify the results of CFD(computational fluid dynamics) modelling in the previous study. The clarifier model was manufactured with consideration to the hydraulic similarity(1/21) of a real plant($L{\times}W{\times}H:2.6{\times}0.4{\times}0.2m$). By installation of an interior baffle to the clarifier, the strong density current at the bottom of the clarifier decreased substantially and increased the area of sludge settling zone, which were visualized successfully from the radiotracer experiment. Also the portion of short circuit stream changed from 48 % to 32 % and the mean residence time of sludge decreased from 940 sec to 810 sec, which corresponds to the results of CFD modelling. As a result, it is anticipated that radiotracer technology can be used as an important tool for designing new wastewater treatment plants and verifying their performances after structural modifications.

• Journal of the Korean GEO-environmental Society
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• v.17 no.9
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• pp.21-28
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• 2016

The purpose of this study is to compare the three areas that each estimated by using three different river topographic maps. For construction of river topographic maps, the data used in this study are ASTER, SRTM and a 1:5,000 scale digital map data sets in 14 streams of the Cheongdo-gun and Uiseong-gun. HEC-GeoRAS, RAS Mapper, and RiverCAD model are applied for the flooding area analysis using observed data and design rainfalls. The result of analysis is to compare observed flooding area based on the flood plain maps with estimated inundation area by hydraulic models and constructed river topographic maps. The results of this study are as follows; Flooding area by HEC-GeoRAS model is similar to the inundation area of flood plain map and appears in order of RAS Mapper, and RiverCAD model in all watersheds. Flood inundation area by SRTM DEM is similar to the result of 1:5,000 scale digital map in all watersheds and all analysis models. The SRTM DEM shows the most similarity to the digital map than ASTER DEM in all of the watershed scale and analysis models. HEC-GeoRAS and RiverCAD model are efficient models for flood inundation analysis in small watershed and HEC-GeoRAS and Ras Mapper model are efficient in medium to large watershed.

• KSBB Journal
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• v.23 no.1
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• pp.70-76
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• 2008

Surface of hydrophobic media was modified to become hydrophilic by ion beam irradiation. Fixed bed biofilm reactors packed with or without surface modification were used to remove organics, nitrogen, and phosphorus from sewage. This system composed of anoxic/oxic cycles to increase the nutrient removal. A cylindrical polyethylene was used as a packing media in this study. With 12 hours of hydraulic retention time (HRT), the reactors with and without surface modification showed 95% and 92% $COD_{cr}$ removal, respectively. Both reactors showed over 95% $COD_{cr}$ removals for a longer HRT of 16 hours. Nitrogen removal ranged 54.8% to 70.2% for the surface modified system and 57.5% to 76.5% for the non-modified system under same condition. Finally, phosphorus removal ranged 59.4% to 69.8% for the surface modified system and 51.3% to 63.4% for the non-modified system under same condition. From this study organics and phosphorus were better removed in using surface modified media and vice versa for nitrogen removal.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.1
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• pp.79-89
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• 2001

Anaerobic Digestion - Thermophilic Oxic Process(ADTOP) has been known to be one way reducing and composting of organic wastes without draining or forming excess sludge. It could be completely performed by the evaporation of water using the bio-energy from the microbial degradation of organic. In the present study the complete treatment of Chinese restaurant wastes was conducted and utility of bio-energy produced from the ADTOP was estimated. Base on results, it could be concluded as follows; 1) chinese restaurant wastes could be completely treated using the TOP without draining or excess sludge. Maximum volumetric loading rate was determined as $55.0kg-garbage/m^3$. Input water was almostly evaporated and 90.5% of carboneous organic wastes was conversed to carbondioxide. 2)The optimum volumetric loading rate which is acceptable to maintain over $55^{\circ}C$ in the anaerobic digester was determined as $45kg-garbage/m^3{\cdot}d$. 3) The optimum HRT was at least over 10 days in order to maintain about $50^{\circ}C$ in the anaerobic digester using bio-energy produced from TOP. Therefore the utilization of bio-energy produced from TOP could be used in the process which had long HRT such as the anaerobic digestion. 4) The efficiency of anaerobic digester rate were over 90% by the ADTOP under the organic loading rate of $1.1kg-COD/m^3{\cdot}d$, 50kg-Chinese restaurant garbage and $250{\ell}/m^3{\cdot}min$ of the aeration rate.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1145-1148
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• 2007

한국을 비롯하여 논농사 중심지역에서는 하천 주변이 과거에는 농경지로, 그리고 오늘날은 도시지역으로 개발되어 하천의 원형이 거의 유지되지 못하고 있다. 하천은 수역과 수변으로부터 거리에 따라 여러 개의 이질적 생태적 공간이 이어지는 복합생태계로서 하나의 경관으로 볼 수 있다. 하천이 하나의 온전한 생태적 계로서 기능을 발휘하기 위해서는 이들을 모두 포함하는 하천의 원형이 복원되어야 한다. 현존하는 하천복원사업이 수변 구역의 복원에 초점을 맞추고 있지만, 진정한 복원이 이루어지기 위해서는 온전한 강변 식생의 복원이 선결과제이다. 본 연구에서는 유적군락의 형태로 잔존하는 강변 식생을 조사하여 식생복원 모델로 삼고자 한다. 수위와 침수체제에 의해 하천의 횡단구조를 수변, 홍수터 및 제방으로 구분한 후 각 지소의 적합한 식생단위를 구분하여 생태적 복원을 실현하기 위한 정보를 구축하였다. 수변식생으로는 달뿌리풀군락과 갈대군락이 자주 출현하고, 홍수터에는 갯버들군락과 키버들군락이 우세하였다. 그 중 전자의 식물군락은 하상재료가 거친 입자의 지소에 성립하고, 후자의 것은 미세한 입자의 지소에 성립하는 경향이었다. 제방역에는 버드나무군락, 다릅나무군락, 귀룽나무군락, 물푸레나무군락, 산사나무군락, 신나무군락(한탄강 지류), 참느릅나무군락, 물푸레나무-갈참나무군락(한탄강 본류), 오리나무군락(민통선 북방지역), 소나무군락, 황철나무군락, 느릅나무군락(소양강 상류), 왕버들군락(금강 중류) 등이 성립하였다. 이러한 식생정보를 하천의 지리적인 위치에 따라 구분하였고, 생태적 복원 시 도입식물을 결정하기 위한 자료로 삼기 위해 각 식생단위를 이루는 종 조성을 정보 체계화하였다.을 효율적으로 하기 위하여 Solar Unit으로부터 나오는 전기를 중전기에서 밧데리로 축전을 시키고 완전 충전 후에는 나머지 전기는 방전이 되도록 회로를 구성하였다. 사통수문 자원조사 결과에 의하면 현재 저수지에 물공급을 하는 수문은 취수탑 형식이 70% 이상을 차지하고 있으며 나머지 30%의 사통수문 중 원형수문비가 98% 이상을 차지하고 있다. 현재 대체에너지를 사용하는 저수지 사통수문은 없는 것으로 조사되었으며 전력을 사용하는 사통도 조사결과에 의하면 20% 이내로 나타났다. 이러한 결과는 향후 수리시설 개보수시 적은 예산으로 사업을 시행하는 경우 사통수문의 설치방향의 지표가 될 것으로 판단되며 수리시설의 운영관리에 대한 새로운 대안으로 제시할 수 있다.분류되었다. 지표 유거가 많아 배수등급이 매우양호로 분류되던 토양은 정 등(1995)의 분류와 비교하여 대부분 강우 유출 가능성이 큰 쪽으로 조정되었다. 새로운 수문학적 토양유형을 이용할 경우 낮은 토심에서 암반층이 발견되는 산림토양이 분포한 유역이나 산림, 밭 등에 식질 토양이 많이 분포하는 유역에서는 기존의 방법을 이용하는 것보다 강우 유출량이 높게 평가될 것으로 판단된다. 앞으로 강우 유출량 실측자료와의 비교를 통해 지속적인 보정을 하여야 할 것이며 특히 불투수층의 존재시 일괄적으로 D유형으로 분류된 토양의 경우 깊이에 따라 C 또는 D 유형으로 세분하여 조정할 필요가 있다.가 있었다. 에틸아세테이트분회물의 경우 디글로로메탄 분회물에 비해 다소 낮은 저해효과를 나타내었지만 250 ${\mu}$g/ml 농도에서 약 60%의 세포독성 효과를 나타내었다. 디클로로메탄 분획물과 에틸아세테이트 분