• 한국환경과학회지
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• 제2권4호
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• pp.325-330
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• 1993

A number of experiments were conducted in order to investigate the organic removal efficiency and biomass characteristics according to the organic shock loading rate in a fluidized bed biofilm reactor. At the operation conditions of HRT, 8.44 hour, superficial upflow velocity, 0.9 cm/sec and temperature, 22$\pm$$1^{\circ}C$, the removal efficiency of SCOD was founded to be 96.5, 92 and 90 % with the organic shock loading rate of 3.5, 10.8 and 33 kgCOD/m$^3$ㆍday, respectively. Within the F/M ratio ranged 0.4 to 2.0 kgCOD/kgVSSㆍday, the SCOD removal efficiency was shown as 90% at F/M ratio of 2.0 kgCOD/kgVSSㆍday, but the TCOD removal efficiency was 72 % at F/M ratio of 1.8 kgCOD/kgVSSㆍday. The average biomass concentrations were 7800, 14950 and 27532 mg/l on the organic shock loading rate of 3.5, 10.8 and 33 kgCOD/$\textrm{m}^3$ㆍday, respectively. This result was agreed with the fact that more biomass could be produced at high concentration of substrate, but some biomass was detached at the onset of shock and easily acclimated at the shock condition.

• KSBB Journal
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• 제10권3호
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• pp.241-248
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• 1995

염색가공 폐수 중 난분해성 물질이 PYA를 처리 하기 위하여, 한천-acrylamide를 이용한 bead를 제 조한 후 air-lift 반응기에서 연속실험을 행하였다. 합성폐수의 PYA놓도가 $3,100mg/\ell$. 체류시간 24hr일 때 유출수의 농도는 $4500mg/\ell$ 이며, 제거효율은 85% 이상을 나타내었다. 실제 호발폐수의 경우 PYA 및 COD농도가 $3,253mg/\ell$, $4,500mg/\ell$일 때, 체류시간 24hr에서 유출수의 농도는 $840mg/\ell, 480mg/\ell$이며, 제거효 율은 81.3%와 85.2%로 각각 나타났다. bead의 지름이 lmm일 때는 내부의 미생물 성장 이 양호하였으나 bead의 지름이 2mm일 때는 기질 과 산소전달저항에 의하여 반지름의 48% 이상은 미 생물의 성장이 저해를 받았다. 고정화 반응기에서 전체 기질 제거속도 중 bead 내 고정화 cell의 제거 분율은 평균 70%로 나타났다. 현탁 반응기에서 희석율 $0.083hr^{-1}$ 이상에서는 기질 이용속도가 감소하였으나 고정화 반응기에서는 희석율 $0.125hr^{-1}$까지 거의 선형척으로 증가하였다. PYA 제거속도식에서 포화상수 $K_s=6.60(g PVA/\ell)$와 최대 비기질 이용속도 k=0.175(g PVA/g cell.hr)를 얻었다.

• 상하수도학회지
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• 제8권2호
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• pp.25-34
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• 1994

In this research, investigations were made on the effect of type and load of organic substrate on phosphorus release. Reactors of three different sizes were operated, being fed on five kinds of organic substrates. The quantitative analyses were made on phosphorus release and substrate utilization under anaerobic condition. The molar ratios of the uptaken organic substrate to the released phosphorus were 0.5 with acetate, 0.6 with glucose, 0.8 with glucose/acetate, and 1.2 with glucose/acids, respectively. The phosphorus release was inhibited at the higher organic load than the normal at stead state. Both acetate and acids/glucose enhanced phosphorus release- as well as uptake-rate, however, the complete phosphorus removal was achieved after the microbial adaptation to the new environment. In case with acetate, operation was hampered by the poor sludge settleability and phosphorus uptake was not enough although the phosphorus release was active. But with milk/starch, the phosphorus release and uptake was well developed even though phosphorus release was not comparatively high. From this study, it was concluded that organic substrates, such as glucose seemed to be converted fatty acids after fast bio-sorption, followed by concurrent uptake of these acids by excess phosphorus removing bacteria.

• 한국물환경학회지
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• 제21권5호
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• pp.448-457
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• 2005

The conventional activated sludge processes were operated as a combined organic substrate removal and nitrification. So, it was necessary to provide with oxygen for both carbon and ammonia removal. But, in the BNR processes, nitrification is separated from carbon removal that causes fast ammonia oxidation and reduced oxygen demands. And most of the substrate is utilized by denitrification organisms and phosphorus accumulating organisms. with these appearances, mathematical model for BNR processes different from IWA ASM can be simplified and applied. In this study, it was performed that the existing equations as McKinney model, nitrification model published by U.S. EPA and oxygen demands from stoichiometry and the relationship between NUR and OUR were applied to full-scale BNR processes and the results were compared with the measured. and it is possible to make out the optimum design parameter from those equations.

• Tribology and Lubricants
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• 제37권6호
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• pp.208-212
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• 2021

Chemical mechanical polishing (CMP) is a key technology used for the global planarization of thin films in semiconductor production and smoothing the surface of substrate materials. CMP is a type of hybrid process using a material removal mechanism that forms a chemically reacted layer on the surface of a material owing to chemical elements included in a slurry and mechanically removes the chemically reacted layer using abrasive particles. Sapphire is known as a material that requires considerable time to remove materials through CMP owing to its high hardness and chemical stability. This study introduces a technology using electrolytic ionization and ultraviolet (UV) light in sapphire CMP and compares it with the existing CMP method from the perspective of the material removal rate (MRR). The technology proposed in the study experimentally confirms that the MRR of sapphire CMP can be increased by approximately 29.9, which is judged as a result of the generation of hydroxyl radicals (·OH) in the slurry. In the future, studies from various perspectives, such as the material removal mechanism and surface chemical reaction analysis of CMP technology using electrolytic ionization and UV, are required, and a tribological approach is also required to understand the mechanical removal of chemically reacted layers.

• 대한환경공학회지
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• 제28권9호
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• pp.926-934
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• 2006

본 연구에서는 TPA 생산부산물의 대체 탄소원으로의 적용가능성을 검토하기 위해 호흡률 실험과 탈질 실험을 수행하고 기질 분해 특성을 평가하기 위해 수행된 실험결과를 활성슬러지 모델(ASM1)이 포함된 GPS-X로 전산모사 하였다. 호흡률 측정 결과 TPA 생산 부산물의 RBDCOD(readily biodegradable COD) 분율이 90% 이상으로 높았다. 탈질실험 결과 비탈질률이 약 8.00 mg ${NO_3^-$-N/g VSS/hr로 상용 외부탄소원과 유사한 높은 탈질능을 나타내었다. ASM1 모델의 heterotrophs 미생물에 관련된 매개변수들의 민감도 분석을 수행하였다. RUN1의 호흡률 실험과 탈질 실험결과를 통해 추정된 ${\mu}_{max,H}$, $K_s$, ${\eta}_g$, $b_H$의 값은 각각 6.60/day, 23.3 mg/L, 0.88, 0.54/day였고 default 값을 사용하였을 때와 비교하여 매개변수 추정을 통해 RMSE(Relative Mean Squared Error)가 40% 감소하였다. 추정된 매개 변수 해들은 호흡률 실험의 높은 최대 비호흡률과 최종 내생비호흡률, 무산소 조건에서의 높은 비탈질률로 나타난 TPA 부산물의 기질 제거 특성을 잘 반영하였다.

• Environmental Engineering Research
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• 제11권3호
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• pp.156-163
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• 2006

In this study, substrate removal characteristics were analyzed to reduce the cost of external carbon dosage at Sudokwon Landfill Site Management Corporation in Korea by utilizing oxygen uptake rate (OUR) and nitrate uptake rate (NUR) tests. To estimate and evaluate the substrate removal characteristics obtained by the batch tests, the lab-scale MLE process was operated. By-products of J Co. (sugar manufactory) and S Co. (fine chemical industry) were selected as the concerned carbon sources through a comparison of carbon and nitrogen contents. MeOH was tested as a control experiment. Until the steady state, the fraction of $RBDCOD_{OUR}$ concentration to COD concentration of J Co., S Co. by-products and MeOH increased and reached levels of 98%, 82%, and 100%, respectively. During the 20th operating day, the fraction of $RBDCOD_{NUR}$ concentration to COD concentration was 95%, 81%, and 83%, respectively. These fractions of $RBDCOD_{NUR}$ concentration to $RBDCOD_{OUR}$ concentration increased according to acclimation periods and reached levels of 99%, 97%, and 81%, respectively, on the 20th day. The results obtained from the lab-scale MLE process operation using the concerned carbon sources as external carbon were similar to that observed by OUR and NUR tests.

• 한국환경과학회지
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• 제4권3호
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• pp.221-228
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• 1995

Stability of reactor and effect on biofilm characteristics were investigated by varying the hydraulic residence time in an inverse fluidized bed biofilm reactor(IFBBR). The SCOD removal efficiency was maintained above 90 % in the HRT range of 12hr to 2hr, but the TCOD removal efficiency was dropped down to 50% because of biomass detachment from overgrown bioparticles. The reactor was stably operated up to the conditions of HRT of 2hr and F/M ratio of 4.5kgCOD/$m^3$/day, but above the range there was an abrupt increase of filamentous microorganisms. The optimum biofilm thickness and the biofilm dry density in this experiment were shown as $200\mu\textrm{m}$ and $0.08 g/cm^3$, respectively. The substrate removal rate of this system was found as 1st order because the biofilm was maintained slightly thin by the increased hydraulic loading rate.

• 환경위생공학
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• 제16권3호
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• pp.22-27
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• 2001

It have been investigated how algal and bacterial symbiotic reaction influences on removal of organic carbon in river ecosystem. And artificial experimentation apparatus was made for algae'and bacteia'culture as lab scale. Investigating and researching minutely the change of concentration of organic carbon substrate and the change of population density of algae'and of bacteria'with this artificial experimentation apparatus, the next results could be obtained. 1. Successful decrease of DOC(dissolved organic carbon) could not be expected unless algal and bacterial biomass floe was nut formed effectively and unless biosorption was not proceeded effectively in the very culture system in which artificial synthetic wastewater was supplied continuously at constant rate. 2. In conditions of culture liquid of 1335 glucnse mg/L(type 1) and of 267 glucose mg:L(type 2), the algal dominant species was always Chlorella vulgaris in both types in which artificial synthetic wastewater were supplied continuously at constant rate and algae population density was around maximum 107 cells/mL. 3. It was around 108 ~ 107 cells/mL that the population density of heterotrophic bacterium. In culture medium systems type 1 and type 2 in which artificial wastewater were supplied continuously at constant rate, the same density appeared initially when using the population density of Escherichia coli w 3110 as indirect indicator. And this density decreased rapidly till the culturing date 35 days were passed away, while this density increased with gentle slope after same date and then the trend of change at type 2 was more severe than one at type 1. 4. When seeing such a change of population density of Escherichia coli w 3110, the growth of heterotrophic bacterium appeared as survival instinct pattern of broader requirement of nutrient at condition of low concentration of organic carbon substrate than condition of high concentration of same substrate.

• Environmental Engineering Research
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• 제24권3호
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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.