• KSBB Journal
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• 제25권1호
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• pp.103-107
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• 2010

Oil degradation agent was developed with organic sludge and modified peat moss (MPM) to recover oil contaminated soil. Waste sludge discharged from wastewater treatment plant of chemical plant in Ulsan National Industrial Park was used as organic sludge, and MPM was purchased. Organic sludge was adequate to use as growth medium for microorganism, the surface of MPM had porous structure which could enhance the cultivation condition of oil degradation microorganisms. Water contents and TPH variation with time were observed to investigate the degradation capacity of developed degradation agent. Water contents were rapidly decreased with higher contents of MPM, however, in case of TPH, high MPM content decreased the degradation capacity. Therefore, it was recommended that the content of MPM was controlled to below 10% in degradation agent as mixing organic sludge with MPM.

• 한국환경과학회지
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• 제11권10호
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• pp.1103-1108
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• 2002

In order to evaluate the degradation organophosphorus pesticide, EPN, in water environment, the effects of water temp.(10$^{circ}C,\;30^{\circ}C$), pH(3-11) and sunlight on its degradation were investigated during 10 days. The degradation rate of EPN(200 rpm) was faster at higher water temp. and higher pH, i.e., its degradation rate at pH 3, 5, 7, 9, 11 was 57, 63, 66, 69, 75%(1$0^{\circ}C$), and 70, 74, 79, 91, 97%(3$0^{\circ}C$) after 10 days, respectively. The effect of water temp. on its degradation was little in acidic condition, but was rather great in alkaline condition, with time. EPN was degraded fast at the alkaline condition by photolysis. At the condition of pH 11, EPN was degraded fast at the early stage in the first 2 days, but after that the degradation rate was weakened.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.607-613
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• 2001

The biodegradation rates of diesel oil by a selected diesel-degrading bacterium, Pseudomonas stutzeri strain Y2G1, and microbial consortia composed of combinations of 5 selected diesel-degrading bacterial were determined in liquid and soil systems. The diesel degradation rate by strain Y2G1 linearly increased $(R^2=0.98)$ as the diesel concentration increased up to 12%, and a degradation rate as high as 5.64 g/l/day was obtained. The diesel degradation by strain Y2G1 was significantly affected by several environmental factors, and the optimal conditions for pH, temperature, and moisture content were at pH8, $25^{\circ}C$, and 10%, respectively. In the batch soil microcosm tests, inoculation, especially in the form of a consortium, and the addition of nutrients both significantly enhanced the diesel degradation by a factor of 1.5 and 4, respectively. Aeration of the soil columns effectively accelerated the diesel degradation, and the initial degradation rate was obviously stimulated with the addition of inorganic nutrients. Based on these results, it was concluded that the major rate-limiting factors in the tested diesel-contaminated soil were the presence of inorganic nutrients, oxygen, and diesel-degrading microorganisms. To resolve these limiting parameters, bioremediation strategies were specifically designed for the tested soil, and the successful mitigation of the limiting parameters resulted in an enhancement of the bioremediation efficiency by a factor of 11.

• 한국환경과학회지
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• 제23권9호
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• pp.1635-1642
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• 2014

Haloacetic acids (HAAs) concentrations have been observed to decreased at drinking water distribution system extremities. This decrease is associated with microbiological degradation by pipe wall biofilm. The objective of this study was to evaluate HAAs degradation in a drinking water system in the presence of a biofilm and to identify the factors that influence this degradation. Degradation of monochloroacetic acid (MCAA), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) was observed in a simulated distribution system. The results obtained showed that different parameters came into play simultaneously in the degradation of HAAs, including retention time, water temperature, biomass, and composition of organic matter. Seasonal variations had a major effect on HAAs degradation and biomass quantity (ATP concentration) was lower by 25% in the winter compared with the summer.

• 한국환경농학회지
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• 제17권3호
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• pp.234-238
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• 1998

Anaerobic degradation characteristics of dewatered liquid of household food waste including methane conversion efficiency and degradation kinetics were studied in an anaerobic batch reactor of 5 L volume. The ultimate methane production for dewatered liquid of household food waste tested was over 0.31L $CH_4/L{\cdot}dewatered$ liquid of household food waste. The kinetic constant of dewatered liquid of household food waste tested was $0.223d^{-1}/L$. The kinetic behavior of anaerobic degradation was described as a first order series reaction. The determinant of rate-limiting step(DR) that is balanced out from the rates of reaction steps was defined by the logarithmic difference of the maximum acidification rate and the maximum methanation rate. Anaerobic degradation characteristics of organic materials were evaluated by the value of DR. The DR of dewatered liquid of household food waste tested was 1.17.

• 한국환경과학회지
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• 제31권3호
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• pp.227-235
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• 2022

In this study, a biodegradation model of based on molecular cellulose was established. It is a mathematical, kinetic model, assuming that two major enzymes randomly break glycosidic bonds of cellulose molecules, and calculates the number of molecules by applying the corresponding probability and degradation reaction coefficients. Model calculations considered enzyme dose, cellulose chain length, and reaction rate constant ratio. Degradation increased almost by two folds with increase of temperature (5℃→25℃). The change of degradation was not significant over the higher temperatures. As temperature increased, the degradation rate of the molecules increased along with higher production of shorter chain molecules. As the reaction rates of the two enzymes were comparative the degree of degradation for any combinations of enzyme application was not affected much. Enzyme dose was also tested through experiment. While enzyme dose ranged from 1 mg/L to 10 mg/L, the gap between real data and model calculations was trivial. However, at higher dose of those enzymes (>15 mg/L), the experimental result showed the lower concentrations of reductive sugar than the corresponding model calculation did. We determined that the optimal enzyme dose for maximum generation of reductive sugar was 10 mg/L.

• Environmental Engineering Research
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• 제13권1호
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• pp.28-32
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• 2008

The photocatalytic treatment of water contaminated with 2,4,6-trinitrotoluene (TNT) was explored in bench-scale experiments in batch mode using a Pyrex tube coated with a thin film of $TiO_2$ located inside a photoreactor. The reactor was aerated by purging it with compressed air before initiating the photocatalytic reaction. The rate of TNT degradation approximated first-order kinetics. The reaction rate constant decreased as the TNT concentration increased from 25 to 100 mg/L, while the first-order kinetics could be modeled using a Langmuir adsorption isotherm. The addition of the organic reductants methanol and EDTA significantly enhanced the rate of TNT degradation, with optimum results in the presence of 20% methanol by volume. EDTA increased the rate of TNT removal by enhancing the role of the reductants.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권9호
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• pp.443-448
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• 2002

The degradation characteristics of R, G, B phosphor layers in AC-PDP, which is due to the discharge of plasma, are still unknown. For the successful commercialization of AC-PDP, the degradation of phosphor layers, caused by the plasma discharge must be investigated and improved. In this paper, the degradation properties of phosphor layers in AC-$PDP_S$ are investigated. It takes long time to investigate the degradation in real condition, so that the device for accelerating the degradation is devised. To prove the performance of the device, the visible emission characteristics of phosphor layers and discharge with the environmental temperature are examined. As a result, it is shown that the phosphor layers are easily degraded when the discharge is sustained under high environmental temperature condition. After accelerating the degradation of blue Phosphor layer((Ba,Eu)Mg$AI_10$$O_17$) for 48 hours, its luminance decreases about 38 % and the corresponding color purity deteriorates severely.

• Environmental Engineering Research
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• 제25권4호
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• pp.597-604
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• 2020

In the present study, the application of sequential biological and photocatalytic process was evaluated as a feasible process for the degradation of imidacloprid (IMI) in soil. Photocatalysis was carried out as a post and pre-treatment to the biological process as Microbial Photocatalytic (MP) and Photocatalytic Microbial (PM), respectively, to enhance the degradation and mineralization of IMI in soil. By both the processes, there was an enhancement in the percentage degradation of IMI i.e 86.2% for PM and 94.6% for MP process. The obtained results indicate that MP process is apparently more efficient in degradation of IMI which was observed with 15 days of biological treatment followed by 18 h of photocatalytic degradation (15 d + 18 h). The present work also reveals that though the difference in terms of the degradation of IMI after 5 d + 18 h, 10 d + 18 h & 15 d+ 18 h of MP process is not drastic, yet significant variation has been observed in terms of mineralization that truly signifies the removal of IMI from the soil. The LC analysis has shown that the intermediates formed during MP process are more and smaller in comparison to PM process, which further provides evidence that MP process is better than PM process for effective degradation of IMI in soil.

• 대한환경공학회지
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• 제22권10호
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• pp.1869-1879
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• 2000

혐기성 소화공정 중 생성되는 주요 중간대사산물인 프로피온산의 분해대사에 대한 연구중 에탄올과의 산화 환원 반응인 coupling 반응으로써 혐기성 소화공정에서 프로피온산 축적을 저감시킬 수 있는 연구를 수행하였다. 따라서, 본 연구는 혐기성 공정에서 프로피온산의 전환에 따른 동력학적 반응과 에탄올과의 상호 반응에 따른 특정기질 선호영향을 모델에 적용하여 살펴보았다. 본 연구는 4단계의 실험으로 수행되었다. 1, 2, 3단계는 각기 다른 기질에 순화된 미생물들을 이용하여 프로피온산 1 g COD/L와 에탄올의 농도를 각각 0, 100, 200, 400과 1,000 mg/L로 주입하여 프로피온산과 에탄올의 혐기성 분해과정을 비교 연구하였으며, 4단계에서는 Glu-MCR과 HPr-MCR의 순화미생물의 혼합비를 조절하여 프로피온산 1 g COD/L를 주입하였을 때의 혐기성 분해를 연구하였다. 본 연구에서는 수정된 경쟁적 모델을 이용하여 특정기질 선호현상을 규명하였고, 에탄올 농도의 증가에 따라 아세트산 형성반응의 $K_{s2}$값의 증가와 메탄화 과정에서의 아세트산 생성 및 분해과정에 해당되는 $K_3$값이 일부 증가하는 결과를 얻을 수 있었다. 또한 순화미생물들에 따라 프로피온산과 에탄올의 분해에 미치는 영향이 다른 결과를 얻을 수 있었다.