• 한국환경농학회지
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• 제28권2호
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• pp.202-208
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• 2009

유기염소계 살충제 endosulfan과 이의 토양 중 주 분해산물인 endosulfan sulfate의 ZVI에 의한 분해정도와 분해산물을 조사하였다. ZVI처리에 의해서 수용액내에서 endosulfan과 endosulfan sulfate는 pH가 낮을수록 분해율이 높았으며 pH 3.0에서 ${\alpha}$-endosulfan은 28%, endosulfan sulfate는 90%정도 분해되었고 acetone/water(50/50, v/v) 용액에서는 ${\alpha}$-endosulfan은 65%, endosulfan sulfate는 92%정도 분해되었다. ZVI에 의해 ${\alpha}$-endosulfan 및 endosulfan sulfate는 분해되어 2개의 미확인 물질을 생성하였다. 반응시간에 따른 반응속도와 반감기를 비교해 보면 endosulfan sulfate가 ${\alpha}$-endosulfan에 비해 빠르게 분해되는 양상을 보였다. ZVI의 처리에 인해 ${\alpha}$-endosulfan과 endosulfan sulfate에서 생성된 2개의 미확인 물질은 GC-MS로 분석한 결과, 하나의 $Cl^-$가 $H^+$로 치환된 구조이성질체로 나타났다.

• 한국환경과학회지
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• 제23권4호
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• pp.737-742
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• 2014

This study aimed for evaluating the applicability of the two stage dual media filtration system in field water treatment plant. The field plant of two stage and dual media filtration system was operated for 2 months. Average iron concentrations of the settled water, existing filtered water and second stage filtered water was 0.041 mg/L, 0.007 mg/L and 0.005 mg/L, respectively. Removal efficiency of iron concentration in the second stage is appropriately 35% more than in existing filtered water. Also removal efficiency of residual chlorine in the dual media filtration system is relatively 42.3% more than in existing filtered water due to adsorption of activated carbon, but the removal of ammonia nitrogen by adsorption is insufficient. Average concentrations of THM and chloroform in the settled water are 0.033 mg/L, 0.026 mg/L, respectively and in existing filtered water are 0.023 mg/L and 0.023 mg/L. Average concentrations of THM and chloroform in the dual media filtration system are 0.008 mg/L and 0.013 mg/L. Therefore removal efficiency of THM concentration in second stage is more than 66.4% in existing filtrated water. Also removal efficiency of chloroform in the dual media filtration system is more than 50.0% in existing filtered water because of the adsorption of activated carbon. In this case backwashing period in dual stage system is 4~5 days, but in existing filtration system is 1~2 days.

• 한국환경보건학회지
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• 제39권1호
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• pp.32-42
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• 2013

Objectives: Cryptosporidium, a protozoan parasite, has been recognized as a frequent cause of waterborne disease due to its extremely strong resistance against chlorine disinfection. Although there has as yet been no report of a Cryptosporidium outbreak through drinking water in Korea, it is important to estimate the health risk of Cryptosporidium in water supply systems because of the various infection cases in human and domestic animals and frequent detection reports on their oocysts in water environments. Methods: This study evaluated the annual infection risk of Cryptosporidium in tap water using the quantitative microbial risk assessment technique. Exposure assessment was performed upon the results of a national survey on Cryptosporidium on the water sources of 97 large-scale water purification plants in Korea, water treatment efficacy, and daily unboiled tap water consumption. The estimates of the US Environmental Protection Agency on the mean likelihood of infection from ingesting one oocyst were applied for effect assessment. Results: Using probabilistic methods, mean annual infection risk of Cryptosporidiosis by the intake of tap water was estimated to fall within the range of $2.3{\times}10^{-4}$ to $1.0{\times}10^{-3}$ (median $5.7{\times}10^{-4}$). The risk in using river sources was predicted to be four times higher than with lake sources. With 0.5-log higher removal efficacy, the risk was estimated to be $1.8{\times}10^{-4}$, and could then be lowered by one-third. Conclusions: These estimations can be compared with acceptable risk and then used to determine the adequacy and priority of various drinking water quality strategies such as the establishment of new treatment technology.

• 한국물환경학회지
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• 제27권1호
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• pp.104-109
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• 2011

The removal efficiencies of 2-methylisoborneol (MIB) and geosmin were investigated to reveal removal characteristics of typical organic compounds causing disagreeable taste and odor at the conventional water treatment plant installed with pulsator clarifier patented by the French company $Degr{\acute{e}}mont$. The injection rate of Powdered Activated Carbon (PAC) into water was changed step wisely as we conducted jar tests in the laboratory and water treatment in the actual plant. 2-MIB concentration decreased linearly while geosmin did exponentially along with the injection rate of PAC at our jar tests. The removal efficiency of geosmin by PAC injection was considerably higher than that of 2-MIB. In the real pulsator clarifier, 2-MIB concentration started decreasing as the injection rate reached up to 10 mg/L of PAC. On the other hand, the concentration of geosmin in water decreased proportional to the injection rate of PAC. In the sand filtration, removal efficiencies of 2-MIB and geosmin on July were much higher than those on March. It was carefully suggested beforehand and found afterwards that general microorganisms notably existed in the sand filter with no chlorine in filter influent and backwash water and the sand filter biologically activated removed much more odor compounds. It was considered as the reason why the removal efficiency of 2-MIB and geosmin was increased. The microbial activity maybe increased in summer with water temperature rising and low filtration rate possibly increased contact time between odor compounds and general microorganisms.

• 한국재료학회지
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• 제31권12호
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• pp.704-709
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• 2021

In the flux used in the batch galvanizing process, the effect of the component ratio of NH₄Cl to ZnCl₂ on the microstructure, coating adhesion, and corrosion resistance of Zn-Mg-Al ternary alloy-coated steel is evaluated. Many defects such as cracks and bare spots are formed inside the Zn-Mg-Al coating layer during treatment with the flux composition generally used for Zn coating. Deterioration of the coating property is due to the formation of AlCl_x mixture generated by the reaction of Al element and chloride in the flux. The coatability of the Zn-Mg-Al alloy coating is improved by increasing the content of ZnCl₂ in the flux to reduce the amount of chlorine reacting with Al while maintaining the flux effect and the coating adhesion is improved as the component ratio of NH₄Cl to ZnCl₂ decreases. Zn-Mg-Al alloy-coated steel products treated with the optimized flux composition of NH₄Cl·3ZnCl₂ show superior corrosion resistance compared to Zn-coated steel products, even with a coating weight of 60 %.

• Journal of Dairy Science and Biotechnology
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• 제41권4호
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• pp.203-210
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• 2023

Bacterial contamination negatively affects the quality, functionality, and safety of dairy products. Adherent populations of bacteria, referred to as biofilms, grow on the surfaces of dairy processing equipment and are the primary cause of dairy contamination. In addition, microorganisms present in the farm environment and dairy factory can contaminate the Clear-In-Place (CIP) line through raw milk transport pipes; therefore, exhaustive management is required. In dairy manufacturing facilities, biofilm formation is controlled using CIP systems that primarily require sodium hydroxide and nitric acid. However, the leakage or incomplete removal of these potently active compounds can be harmful to humans. In the present study, we compared the eradication of Escherichia coli and other bacteria using commercially available combinations of sodium hypochlorite (NaClO) and citric acid, which are recognized by the Korean Ministry of Food and Drug Safety (MFDS) as food disinfectants. When considered in the CIP system of the field manufacturing process, E. coli was not detected (compared to detection before treatment), and other bacteria were detected at 0-32 culture-forming units (CFU)/cm². The residual amount of chlorine ions after CIP treatment was similar to that in tap water, and there was no significant difference in the overall components of the fermented dairy products. Therefore, the NaClO/citric acid CIP system can be safely applied in dairy manufacturing processes.

• 한국식품영양과학회지
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• 제38권9호
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• pp.1265-1270
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• 2009

조리기구 및 도구의 재질 표면에 오염된 병원성 세균은 외식 및 단체급식에서 교차 오염의 원인으로 작용할 수 있으며, 이들이 표면에 형성시킨 biofilm은 세척 및 살균소독 과정에서도 살아남아 식중독의 위험을 증가시킨다. 따라서 본 연구에서는 상업적 살균소독제와 $71^{\circ}C$ 건열 살균을 하였을 때 스테인리스 스틸과 폴리프로필렌에 오염된 5종류의 병원성 미생물(E. coli O157:H7, S. Typhimurium, P. aeruginosa, L. monocytogenes, S. aureus)의 부착세포와 biofilm에 대한 저해 효과를 평가하였다. 결과로 염소계와 $71^{\circ}C$ 건열처리는 모두 유의적인 저해효과를 나타내지 않았다. 알코올계살균소독제는 스테인리스 스틸과 폴리프로필렌에서 각각 3.4$\sim$6.4 log, 5.5$\sim$7.4 log CFU/coupon 수준의 감소를 보여 강한 살균력을 나타내는 것으로 관찰되었다. 살균소독제 처리는 단체급식소에서 가장 일반적으로 사용하고 있는 소독방법이지만, 살균소독제 종류에 따라서 살균 효과 차이가 크고, 미생물의 오염되어 있는 물질 및 오염 방법 등 처리 조건의 차이에 따라 결과가 달라질 수 있다. 그러므로 효과적인 살균 소독을 위해 보다 다양한 조건과 처리방법에 대한 연구가 이루어져야 할 것으로 사료된다.

• 한국식품영양학회지
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• 제29권4호
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• pp.499-505
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• 2016

To improve the shelf-life of mushrooms, Lentinula edodes GNA01 mushrooms were treated with gel packs containing slow-released chlorine dioxide ($ClO_2$) gas at 5~10 ppm for 5 days at $20^{\circ}C$ and the weight loss rate as well as the changes in pH, color and texture properties of the treated samples were investigated. The weight of the control and $ClO_2$ gas treated samples were decreased slightly, and there were no differences during the storage period. However, the weight of the control changed faster than those of the $ClO_2$ gas treated samples during storage period. The pH in the control and in the $ClO_2$ gas treated samples were decreased during storage period, but the samples treated with 5 and 7 ppm $ClO_2$ gas were the least changed. On the other hand, the samples treated with 10 ppm $ClO_2$ gas showed no difference from the other treatments during 4 days, but the pH was lower than that of the control on the fifth day. The lightness of inside and outside in mushroom were decreased whereas redness and yellowness were increased during storage period. However, color changes in the $ClO_2$ gas treated samples were lower than those of the control. Especially, the samples treated with 5 and 7 ppm $ClO_2$ gas were the least changed. The texture of the mushroom were decreased consistently during storage period. The texture of the control changed faster than those of the $ClO_2$ gas treatments during 5 days. Especially, the samples treated 5 ppm $ClO_2$ gas were the least changed.

• Journal of Advanced Marine Engineering and Technology
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• 제41권3호
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• pp.216-221
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• 2017

디젤엔진은 내연기관 중에 제동 열효율이 가장 높은 엔진이기 때문에 큰 동력을 필요로 하는 대형트럭과 같은 중 대형 운송 차량 및 선박 등의 수송분야 및 발전시스템 등의 다양한 분야에서 사용되어지고 있다. 하지만, 디젤엔진은 연소과정에서 질소산화물(이하 NOx) 발생량이 많은 단점을 가지고 있다. 따라서 본 연구에서는 선박용 디젤엔진의 NOx를 저감하기 위해서 습식 배기가스 처리 기술인 무격막식 해수 전기분해 방식을 이용하여 NOx 저감을 시도하였다. 실제 해수를 사용하여 디젤엔진에서 배출되는 유해가스에 전기 분해된 해수인 전해수를 분사하여 보았다. 전해수의 pH 농도 및 유효염소농도, 온도에 따른 NO 산화율 및 NOx 감소량을 조사하였다. 본 실험을 통해서 전해수의 pH가 약산성 영역일 경우가 중성일 경우보다 산화탑에서의 NO 산화율이 상승하였고, 유효염소농도가 높을수록 NO 산화율이 증가하는 것을 확인할 수 있었다. 또한, 전해수 온도는 NO 산화율에 영향이 없음을 추가적으로 확인할 수 있었으며 디젤엔진에서 생성된 배기배출물에 전해수를 분사함으로써 NOx가 저감됨을 확인할 수 있었다.

• Korean Chemical Engineering Research
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• 제46권6호
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• pp.1148-1152
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• 2008

용융탄산염산화(MCO; Molten Carbonate Oxidation)는 염소유기화합물을 분해할 때 거의 대부분의 염소성분을 염내에 포집하여 다이옥신류 발생을 미연에 방지할 수 있기 때문에 염소유기화합물 처리를 위한 유망한 대체기술 중 하나로 고려되고 있다. 본 연구에서는 2단 용융탄산염산화시스템에서 염소유기화합물($C_6H_5Cl$, $C_2HCl_3$ and $CCl_4$)과 PCBs 함유 절연유의 분해에 관한 연구를 수행하였다. 용융탄산염산화반응기의 온도는 염소유기화합물 분해에 큰 영향을 미치는 것으로 확인되었다. 1차 용융탄산염산화반응기에서 염소유기화합물의 분해는 효과적이었다. 그러나 CO가 현저하게 높은 농도로 배출되었다. 이러한 CO 배출농도는 1차 반응기의 온도와 산화용 공기 주입량을 증가시킴에 따라 크게 감소되었다. 2단 용융탄산염산화시스템에서 HCl 배출농도는 모든 조건에서 7 ppm 이하였으며 염내 염소성분의 포집효율은 99.95-99.99%였다. 절연유내 PCBs는 $900^{\circ}C$ 이상의 온도에서 효과적으로 분해되었으며 PCBs의 총 분해효율은 99.9999% 이상이었다.