• 한국대기환경학회지
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• 제4권2호
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• pp.38-46
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• 1988

NOx is an important air pollution material which is generated when fossil fuels are burning, NOx removal in flue gas by selective catalytic reduction was studied over various catalysts in a fixed bed continuous flow reactor. The ranges of experimental conditions were at the temperatures between $200^\circ$C and $350^\circ$C, the $NH_3/NOx$ mole ratios between 0.8 and 1.4, oxygen concentrations between 1.5% and 3% and the space velocities between 5, 000 $hr^-1$ and 12, 500 $hr^-1$. The efficiency of NOx removal in the ranges of experimental conditions was highest at the temp. of 300$^\circ$C, oxygen concentration of 2.5-2.6% and $NH_3/NOx$ mole ratios of 1.0-1.2. The catalyst with high activity for NOx removal in flue gas was found to be $MoO_3-V_2O_5/TiO_2$.

• 대한환경공학회지
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• 제28권7호
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• pp.764-769
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• 2006

미생물을 접종하지 않은 동전기 공정에서 전기분해에 의한 양극조에서 산소의 발생은 전류밀도에 비례하였으며 전해질을 순환시킴에 따라 생물반응기내 전해질과 함께 용존산소농도가 증가하였다. 전류의 공급과 함께 미생물 농도는 급격히 증가하였으며 이때 미생물의 산소소비량이 증가되어 용존산소농도가 감소되었다. Pentadecane-오염토양에 대한 동전기 생물학적 복원의 결과에서 높은 전류밀도 1.88 $mA/cm^2$에서 비록 산소의 발생량은 많았지만 오히려 증가된 유기산이 전해질 pH와 미생물 활성을 감소시키므로 미생물 농도와 제거효율이 0.63 $mA/cm^2$보다 낮게 나타났다. 0.63 $mA/cm^2$에서 적절한 산소의 공급과 동시에 전해액 pH의 감소가 작았으므로 최적의 미생물 농도와 제거효율을 얻을 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제22권4호
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• pp.362-366
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• 2001

To show the effects of metallothionein (MT) on the activity of enzymes involved in the removal of reactive oxygen species, MT has been added to the assay systems of superoxide dismutase (SOD), catalase and peroxidase. We have used assay systems of SOD based on NADPH oxidation and nitrite formation from hydroxylammonium chloride as an assay of superoxide breakdown rate. The two assay systems showed different results at the high concentration of MT. MT showed the scavenging of superoxide in the SOD assay system in the presence and absence of SOD. MT added to the SOD assay system behaved as an activator of SOD, but apo-MT behaved as an inhibitor. When MT was added to the assay system in the presence of a fixed amount of SOD, the breakdown rate of superoxide increased. The effects of MT on the decomposition of hydrogen peroxide and the activity of catalase and peroxidase decomposing hydrogen peroxide were evaluated. MT decreased the activities of catalase and peroxidase. We have concluded that the function of MT as an antioxidant might effect the level of superoxide scavenging and not the level of hydrogen peroxide.

• 한국물환경학회지
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• 제28권5호
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• pp.717-722
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• 2012

Fluoride can be easily found in semiconductor and display industry. However, there is a lack of research for its effects on the related wastewater treatment. The objective of this study is to evaluate the microbial inhibitory effect by fluoride injection. The research entailed the assessment of removal efficiency of $TCOD_{Cr}$ according to the fluoride concentration and also the Specific Oxygen Uptake Rate (SOUR) was measured. The laboratory scale reactor was prepared and operated with the fluoride concentrations of 0, 10, 50, 100, and 200 mg/L based on concentrations frequently occurring in the wastewater. The results from this study showed that, as the fluoride concentration increase, the Specific Substrate Utilization Rate (SSUR) tend to decrease as expected. Also, the increase in fluoride concentrations resulted in the decrease in SOUR. It is determined that fluoride injection affects the microbial activity. Especially, The addition of above 200 mg/L fluoride into reactor caused rapidly decreased SSUR and SOUR due to the inhibitory effects of fluoride.

• Environmental Engineering Research
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• 제24권1호
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• pp.144-149
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• 2019

Landfill leachate constitutes one of the most polluting wastewaters. Their treatment was considered difficult due to the presence of high concentration of organic matter, ammonia, toxic organic compounds and heavy metals. Biological processes were found to be effective in several cases, but they are limited by the presence of inhibitory compounds in leachate. In this study we develop a biological process for the leachate biodetoxification using Trametes trogii (T. trogii; CLBE55). Results show that laccase activity, mycelia growth and chemical oxygen demand (COD) removal efficiencies varied depending on the leachate and ammonium concentration. Indeed T. trogii was able to grow in the presence of low concentration of landfill leachate of 10 and 30%. In fact, the biomass produced was 4.7 and 3.7 g/L, respectively leading to a COD removal of 66 and 53%, respectively. However, when the concentration of the introduced leachate exceeds 30%, the treatment efficiency and particularly the COD removal decreases to reach 15% at 100% leachate. The effect of the ammonia was also studied and results showed that the addition of 5 g/L of ammonia inhibited totally the production of laccase and the COD removal.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권6호
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• pp.352-356
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• 2002

Aeration was found to affect the biological denitrification by Ochrobactrum authropi SY509. Although cell growth was vigorous under 1 vvm of aeration and an agitation speed of 400 rpm in a 3-L jar fermentor, almost no nitrate was removed. Yet under low agitation speeds (100, 200, and 300 rpm), denitrification occurred when the dissolved oxygen was exhausted shortly af-ter the inoculation of the microorganism. Ochrobactrum authropi SY509 was found to express highly active denitrifying enzymes under anaerobic conditions. The microorganism also synthesized denitrifying enzymes under aerobic conditions (1 vvm and 400 rpm), yet their activity was only 60% of the maximum level under anaerobic conditions and the nitrate removal efficiency was merely 15%. However, although the activities of the denitrifying enzymes were inhibited in the presence of oxygen, they were fully recovered when the conditions were switched to anaerobic conditions.

• 한국안전학회지
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• 제6권3호
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• pp.5-11
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• 1991

To remove NO from flue gas, a direct decomposition method to $N_2$ and $O_2$ was investigated by using copper / zeolite catalyst. The copper ion-exchanged HY type zeolite has high activity on NO decomposition. The decomposition activity was increased with the increase of ion-exchange level, contacting time and reaction temperature in the range of 30$0^{\circ}C$ -50$0^{\circ}C$ , and decreased with the oxygen addition.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.32-44
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• 2002

Selective catalytic reduction of nitric oxide by methane in the presence of excess oxygen was investigated over copper and cobalt ion-exchanged ZSM-5 zeolites. Copper ion-exchanged ZSM-5(Cu-ZSM-5) has the limitations for commercial applications to lean-bum gasoline and diesel engines due to low thermal stability and resistance to water vapor and sulfur dioxide. But cobalt ion-exchanged ESM-5(Co-ZSM-5) is more active at high temperatures and also stable to water vapor and sulfur dioxide for catalytic reduction of nitric oxide by methane. The catalytic activity of Cu-ZSM-5 for NO reduction increases with increasing temperatures, reaches the maximum conversion of 23.0% at 350\"C. and then decreases with higher temperatures. In the meantime catalytic activities of Co-ZSM-5 show the maximum conversion of 25.8% at $500^{\circ}C$ Therefore Co-ZSM-5 catalysts have higher thermal stability at high temperatures. Catalytic activities of both zeolites were remarkably enhanced with the existence of oxygen in the exhaust. It is noted that the catalytic activity of Cu-ZSM-5 decreases with the increasing concentration of methane while the catalytic activity of Co-ZSM-5 decreases with increasing contents of methane in the exhaust. This may imply the existence of different paths of NO reduction by methane in the presence of excess oxygen fur Cu-ZSM-5 and Co-ZSM-5 catalysts. For binary metal ionexchanged ZSM-5, the primary ion-exchanged metal may be masked by secondary ion-exchanged component, which plays the important role for catalytic activities of binary metal ion-exchanged ZSM-5, Therefore CuCo-ZSM-5 catalysts show the similar volcano-shaped curves to Cu-ZSM-5 catalysts between the activity and temperature. It Is interesting that the activities of CoCu-ZSM-5 catalysts indicate almost no dependence on the concentration of methane in the exhaust.aust.

• Journal of Plant Biology
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• 제33권4호
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• pp.277-283
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• 1990

Inactivation and reactivation of photosynthetic oxygen evolving complex were studied with isolated spinach (Spinacia oleraceda. L.) photosystem II particles by the activity of oxygen evolution and chlorophyll fluorescence. When the particles were treated with Tris and urea, the oxygen evolution was inactivated and three polypeptides having molecular weights of 33 kDa, 24 kDa and 18 kDa were simultaneously released. But in NaCl-treated particles, two polypeptides of 24 kDa and 18 kDa were removed from PS II particles. The oxygen evolution activities of Tris and urea-treated particles were not restored by adding cation ions (Mg2+, Mn2+ and Ca2+), but the NaCl-treated particles were restored by exogenously added Ca2+. The removal of these extrinsic polypeptides, especially 33 kDa, markedly showed the decrease of the variable fluorescence (Fv). These results are likely to be due to dissipate thermal energy by antenna of photosystem II complexes.

• 한국환경과학회지
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• 제17권11호
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• pp.1265-1271
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• 2008

Aerated submerged bio-film (ASBF) pilot plant has been developed. The presented studies optimized an inexpensive method of enhanced wastewater treatment. The objectives of this research were to describe pilot scale experiments for efficient removal of dissolved organic and nitrogen compounds by using ASBF reactor in plug-flow reactor (PFR) and improve understanding of dissolved organic matter and nitrogen compounds removal rates with dynamic relationships between heterotrophs and autotrophs in the fixed-film reactor. This research explores the possibility of enhancing the performance of shallow wastewater treatment lagoons through the addition of specially designed structures. This direct gas-phase contact should increase the oxygen transfer rate into the bio-film, as well as increase the micro-climate mixing of water, nutrients, and waste products into and out of the bio-film. This research also investigated the efficiency of dissolved organic matter and ammonia nitrogen removals in the ASBF. As it was anticipated, nitrification activity was highest during periods when the flow rate was lower, but it seemed to decline during times when the flow rate was highest. And ammonia nitrogen removal rates were more sensitive than dissolved organic matter removal rates when flow rates exceeded 2.2 L/min.