• Journal of Wetlands Research
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• v.15 no.2
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• pp.165-170
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• 2013

Pilot scale study was carried out to produce Volatile Fatty Acids with primary sludge from municipal wastewater treatment plant. An acid fermenter was operated at pH 9, $35^{\circ}C$, SRT of 3.5-4.25d, using a final effluent as elutriating water(Mode-I) and pH 9, SRT 5d, temperature of $35^{\circ}C$(Mode-II), $55^{\circ}C$(Mode-III), using a primarily treated water as elutriating water. Although solubilization rate was enhanced with the increase of temperature, the VFAs production rate was decreased. The VS reduction was shown approximately 56%, and the sludge volume reduction was 93%. The optimal conditions for solubilization was obtained at pH 9, $35^{\circ}C$ and SRT of 5d.

• Membrane Journal
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• v.26 no.5
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• pp.401-406
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• 2016

In this study, we have investigated the removal of the low level radioactive ions of Cs and I in water by the reverse osmosis (RO) process. The two RO modules produced in domestic region and the waste RO module after the cleaning process were selected. Then we compared removal performance of both Cs and I. The experiments are conducted by varying the concentration of feed, the pressure. As a results, it was confirmed that all three modules are higher I decontamination factor than Cs. And particularly, for the cleaned RO module, its decontamination factor of I was 1140. Since the results at low pressure condition were better than that at high pressure conditions, the use of the direct installation of RO modules on the tap water might be possible. In addition, it was confirmed that the waste RO module after cleaning process using EDTA, SBS and NaOH, increased the decontamination performance better than before cleaning, in particular, the recovery ratio after cleaning was 6.3% higher.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.283-286
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• 2002

유류로 오염된 부지에 토양세정기법을 적용하기 위한 전 단계로, 실험실 규모의 컬럼실험을 통하여 pilot 규모 현장 적용을 위한 설계인자 및 최적 운전조건을 규명하고자 적정 세척제 종류와 농도, 배합비 및 세정용액 주입유량을 고찰하였다. 회분식실험 결과 POE$_{14}$와 SDS(1:1)를 1%로 적용한 흔합계면활성제의 효율이 가장 우수하였으나, 예비실험 결과 음이온계 계면활성제인 SDS는 미생물에 독성을 끼치는 경향이 있는 것으로 나타나 같은 농도에서 효율이 거의 유사한 POE$_{5}$와 POE$_{14}$ 혼합계면활성제를 이용하여 실험하였다. 선정된 혼합계면활성제를 적용하여 디젤 오염토양 세척능력을 검토한 결과 세척제 농도 1%까지는 효율이 증가하다가 1% 이상의 농도에서는 다시 감소하는 경향을 나타내었으며, 계면활성제 배합비는 1:1로 혼합하였을 경우 세척효율이 가장 우수하였다. 따라서 POE$_{5}$와 POE$_{14}$ (1:1) 1% 혼합계면활성제를 세척제로 선정하였다. 컬럼실험 결과, 주입 flux가 클수록 세정 제거된 총 유류의 양이 증가하였으며, 같은 pore volume의 세정용액 통과 시에는 flux가 작을수록 제거효율이 좋았다.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.140-148
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• 1994

A qualification test was performed for the iron removal chemical cleaning of the secondary side of nuclear steam generators at the selected temperature, 1$25^{\circ}C$, higher than the standard application temperature, 93$^{\circ}C$. The field cleaning condition for a nuclear unit was tested in a bench scale test loop including a SUS 316 stainless steel autoclave with one gallon capacity as a test vessel. The kinetics of sludge dissolution, corrosion of the secondary side materials and change of solvent chemistry were monitored. Test results indicated that more thorough cleaning was accomplished in less than half of the cleaning time required at 93$^{\circ}C$. And the total corrosions of the secondary side materials were found to be less than the values at 93$^{\circ}C$. While the solvent is recirculated and heated by an external chemical cleaning equipment for the conventional 93$^{\circ}C$ process, the secondary side is heated by the lateral heat of the primary coolant without the recirculation of the cleaning solution, and the solvent is mixed by vigorous boiling induced by periodic ventilation for the high temperature process. The requirement that the reactor coolant pumps should be running during the cleaning operation is the major disadvantage of the high temperature process which also should be considered when chemical cleaning is planned for steam generators under operation.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.9
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• pp.624-629
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• 2013

The relation between performance maintenance conditions and those cost efficiency was studied to choose an optimum operating condition in the seawater desalination pretreatment system. A hollow fiber microfiltration module, which was developed with domestic technology, was tested with the various operating conditions such as chemically enhanced backwash cycles and design dosages of a cleaning chemical. Transmembrane pressure was measured to investigate membrane fouling status and cleaning degree. In addition, economic analysis was performed to compare water production costs by the operation condition. As a result, The operation mode III, chemically enhanced backwash at once a day with 100 mg/L of sodium hypochlorite (NaOCl) was selected. The concurrent evaluation between membrane filtration performance and its economic analysis will be suitable to choose an efficient optimum condition.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.113.2-113.2
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• 2011

동물성 오일을 이용한 바이오디젤 생산 반응 후 미반응된 메탄올과 염기촉매의 처리에 관한 연구로써 바이오디젤의 순도에 영향을 미친다. 메탄올과 염기촉매는 바이오디젤 생산 반응 후 상층인 메틸 에스터 층과 하층인 글리세롤 층에 각각 포함되어 있다. 1차적으로 각각의 층에서 메탄올을 증발하게 되며 메탄올 증발은 감압 증류 장치를 이용해 분리하게 된다. BD100을 기준으로 하여 메탄올의 함량은 0.2% 이하여야 하며 수분 함량은 0.05% 이하를 유지해야 한다. 메탄올 증발은 메탄올의 끓는 온도인 $65^{\circ}C$를 기준으로 하여 끓는점 보다 낮은 온도와 높은 온도에서 각각 증발을 실시하고 각각의 메탄올 증발 제거에 따른 FAME 함량에 미치는 영향에 대해 FAME 함량 분석을 통해 조사하였으며 메탄올 증발 후 증류수를 이용한 바이오디젤 내 잔류 촉매 및 자유 글리세린 세정 제거에 대해 조사하였다. 증류수 양과 증류수 온도 및 세정 시간에 따른 FAME 함량 변화를 알아보았으며 세정 후 증류수 증발에 따른 FAME 함량 변화에 대해서 분석을 실시하였다. 본 실험을 통해 동물성 오일을 이용한 바이오디젤 생산 후처리 공정인 메탄올 증발 및 세정, 수분 증발 공정의 최적 조건을 도출하고자 하였다.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.3
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• pp.152-158
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• 2015

This paper investigated the membrane fouling potential at the state of passive adsorption which is no permeation with the test modules on COD (Chemical oxygen demand) loading rates, examined the recovery rate and resistance on membrane fouling by three cleaning manners of hydrophobic membrane in a bioreactor. The results showed that high COD loading led to the increase of extra-cellular polymeric substances and filtration resistance. The permeability resistance from 1st day to 63rd day was getting increased, however, the value of permeability resistance after 63th day during the operation period was almost same level at three COD loading rates, it was due that the biomass adhesion on membrane surface at the state of passive adsorption reached to the critical state. Also, the final recovery rates after three cleaning manners were 78%, 72% and 69% at the COD loading concentrations of 250 mg/L, 500 mg/L and 750 mg/L respectively, and then recovery rate by physical cleaning at Run 2 and Run 3 was decreased after 40th day, it proved that biomass cake, which is not easily removed, was formed on the membrane surface because of high COD loading rate and EPS concentration.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.102-109
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• 2000

It is difficult to meet the cleanliness requirement of $10^{10}/\textrm{cm}^2$ for the giga level device fabrication with mechanical cleaning techniques like scrubbing which is widely used to remove the particles generated during Chemical Mechanical Polishing (CMP) processes. Therefore, the second cleaning process is needed to remove metallic contaminants which were not completely removed during the mechanical cleaning process. In this paper the experimental results for the removal of the metallic contaminants existing on the wafer surface using remote plasma $H_2$ cleaning and UV/$O_3$ cleaning techniques are reported. In the remote plasma $H_2$ cleaning the efficiency of contaminants removal increases with decreasing the plasma exposure time and increasing the rf-power. Also the optimum process conditions for the removal of K, Fe and Cu impurities which are easily found on the wafer surface after CMP processes are the plasma exposure time of 1min and the rf-power of 100 W. The surface roughness decreased by 30-50 % after remote plasma $H_2$ cleaning. On the other hand, the highest efficiency of K, Fe and Cu impurities removal was achieved for the UV exposure time of 30 sec. The removal mechanism of the metallic contaminants like K, Fe and Cu in the remote plasma $H_2$ and the UV/$O_3$ cleaning processes is as follows: the metal atoms are lifted off by $SiO^*$ when the $SiO^*$is evaporated after the chemical $SiO_2$ formed under the metal atoms reacts with $H^+ \; and\; e^-$ to form $SiO^*$.

• Membrane Journal
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• v.25 no.3
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• pp.276-286
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• 2015

The effects of relaxation and backwashing on fouling in ultrafiltration were investigated using full-scale membrane bioreactors (MBRs) which operated at a constant flux of 30 LMH. This paper also estimated the feasibility of using intermittent aeration strategies for minimizing the hydraulic resistance to filtration in comparison with the continuous aeration for running MBRs. Multiple cycles of filtration (14.5 min each) and relaxation (0.5 min each) were repeated. Similarly, a backwash was conducted by replacing a relaxation after each filtration cycle for the comparative performance test. The attached cake thickness on the membrane rapidly increased, caused by subsequent no aeration leading to easier combining with gel layer and the formation of heterogeneous layer on the membrane surface. During periodic backwashing, it is expected that gel and thin cake layer might sufficiently be removed by heterogeneous layer. After periodic backwashing, subsequent cake layer formation during time of no aeration was rapid than frequent no aeration, acting as a prefilter and preventing further irreversible fouling. Based on the Pearson correlation analysis, overall period fouling (dTMP/min) and average of all cycles (dTMP/min) were strongly correlated with the on-off period of aeration for operating MBRs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2525-2531
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• 2012

Al-Cu alloy has been used as a circuit material for its low resistance and ease to process for long years at CMOS technology. However, basically metal is very susceptible to corrosion and which has been a long pending trouble in various fields using metal. The defect causes the reliability concerns, so improved methods are necessary to reduce the defect. In the various corrosion parameters, PR strip process conditions after metal etch and optimal cleaning solutions are controllable and increase the process margin to prevent the metal corrosion. This study proposes that chlorine residue after metal etch as the source of metal corrosion, and charges should be removed by optimizing PR strip process condition and cleaning condition.