• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.4
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• pp.87-95
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• 2000

A vegetation purification system was applied to improve water quality of Masan Reservoir in Korea, which was composed of constructed wetlands in series. Five different kinds of macrophytes were planted in each wetland. The system was operated with the condition of low concentrations and high hydraulic loadings. Removal efficiencies(%) of chemical oxygen demand(COD) , total nitrogen(T-N) and total phosphorus(T-P) in this system were 9.0, 12.8, 20.1% , respectively. and removal rates(g/$m^2$/d) were 1.9(COD), 0.34(T-N) and 0.05(T-P) . Comparing this system with other wetlands operated at low hydraulic loadings, average removal efficiencies were low but removal rates were relatively high. Accordingly, this system could be applied to imporve reservoir water quality, because removal rates are more important than removal efficiencies in case of reservoir water quality improvement . However, the removal efficiencies and rates of this system are less than those of the hydroponic biofilter method which is a kind of a constructed wetland and utilize root zones of emergent macrophytes for trapping pollutants. Therefore, it is recommended that this system should be modified to utilize root zones of emergent macrophytes enough to improve reservoir water quality more efficiently.

• Journal of Environmental Science International
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• v.27 no.11
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• pp.1073-1081
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• 2018

In this study, an operational data set was analysed by establishing a path model to figure out the actual cause-effect relationship of a wastewater treatment plant (WWTP); in particular, for the effluent concentrations of T-N and T-P. To develop the path models, data sets of operational records including effluent concentrations and operational factors were obtained from a field scale WWTP of $680,000m^3$ of treatment capacity. The models showed that the relationship networks with the correlation coefficients between variables for objective expressions indicated the strength of each relationship. The suggested path models were verified according to whether the analyzation results matched known theories well, but sophisticated minute theoric relationships could not be cropped out distinctly. This indicates that only a few paths with strong theoric casual relationships were represented as measured data due to the high non-linearity of the mechanism of the removal process in a biological wastewater treatment.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.3
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• pp.189-194
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• 2012

In this study, a 3-stage biological aerated filter (BAF) system was proposed to enhance nitrogen removal in the treatment of low carbon to nitrogen ratio (C/N ratio) municipal wastewater. Laboratory experiments were conducted to evaluate the effects of dynamic-flow at the HRT of 6 h. Results of the long-term operation of 3-stage BAF systems showed that the dynamic-flow enabled the total nitrogen removal (T-N) removal efficiency of the system to be about 7 % higher than that of non-dynamic-flow system in treating domestic wastewater due to the more efficient use of organic substrates. The overall $NH_4$-N removal performance was stable during the operational period due to the unique system configuration where independent nitrification occurred. It was concluded that the 3-stage BAF system proposed in this study provided excellent performance in the removal of nitrogen by employing dynamic-flow and three columns functioning as sorption, denitrification and nitrification, respectively.

• Biomedical Science Letters
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• v.3 no.2
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• pp.77-82
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• 1997

One of the most important prerequisites of the industrial microorganism is that it should not be virulent to humans or economically important animals or plants. In this investigation, the microbiological characterization of T. madida N-5-3 strain was performed. And then, the virulence of the test strain in mouse model was examined systematically. The microbiological characteristics of the test strain were found to be fully consistent with those of typical T. madida. The i.p. lethal dose(LD)$_{50}$ of the test strain was greater than 1$\times$10$^8$, because there was no dead animal with the challenge doses upto the level of 1$\times$10$^8$. When 1$\times$10$^8$ yeast cells were challenged to the laboratory mice, T. madida N-5-3 strain was completely cleared from the liver and spleen in 4 days after challenge. And no pathological changes in the histological examination of the internal organs from challenged mice was observed. Above results can provide the predictability of the safety of T. madida N-5-3 strain for the industrial use in the view point of the public health aspect.

• Korean Journal of Ecology and Environment
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• v.39 no.4 s.118
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• pp.481-488
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• 2006

The field scale experiment was performed to examine the performance of the constructed wetland for nonpoint source (NPS) pollution loading reduction. Four sets (0.88 ha each) of wetland and pond system were used. After three growing seasons of the wetland construction, plant coverage increased to about 90% even without plantation from bare soil surfaces at the initial stage. During the start up period of constructed wetlands, lower water levels should be maintained to avoid flooding newly plants, if wetland plants are to start from germinating seeds. The average removal rate of $BOD_5$, TSS, T-N and T-P during the first two years was 5.6%, 46.6%, 45.7%, and 54.8%, respectively. The $BOD_5$ removal rate was low and it might be attributed to the low influent concentration. The early stage of wetland performance demonstrated the effectiveness of water quality improvement and was satisfactory for treating polluted stream waters. From the first-order analysis, T-P was virtually not temperature dependent, and $BOD_5$ and TSS were more temperature dependent than T-N. A pond-wetland system was more effective than a wetland-pond or a wetland alone system in water quality improvement, particularly to reduce T-P. Overall, the wetland system was found to be an adequate alternative for treating a polluted stream water with stable removal efficiency and recommended as a NPS control measures.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.2
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• pp.259-265
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• 2008

Generally speaking, there are two widely used methods of Nitrogen removal from waste water: 1) nitrification using autotrophic microorganisms, and 2) denitrification using heterotrophic microorganisms. The C/N ratio is an important factor of the denitrification process. In this case, if methanol is added to increase the lacking organic matter, a high economic cost is incurred and methanol is left in the processed water. In an effort to fix these issues, autotrophic denitrification through the use of Hydrogen, Iron and Sulfur is being studied, and among those Sulfur is cheaper and carries out denitrification effectively, and therefore is being studied the most. In this study, after cultivating T. denitrificans, the presence of T. denitrificans was determined and the effectiveness of denitirification via T. denitrificans was studied. In order to find out about the inhibition of T. denitrificans from the loading of organic matter, this shows that the greater the loading of organic matter, the more the denitrification ability of T. denitrificans is hindered. In order to research the hindrance of T. denitrificans resulting from the loading of $NO_3{^-}-N$, these results show that concentrations less than 100mg/L per 100mL of gel volume do not hinder T. denitrificans. In order to research the optimization of denitrification resulting from T. denitrificans, three 500mL samples of Sulfur granules were prepared: 1) one with only T. denitrificans attached (Mode I), 2) one with both T. denitrificans and active sludge attached (Mode II), and 3) one with only active sludge attached (Mode III). The results showed that autotrophic denitrification using S from Mode I was the most active.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.438-444
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• 2005

This study is to install the flexible vertical in order to separate not only the time but also the space in the single reactor by opening and closing the flexible vertical, and to intensify the aerobic, anaerobic and anoxic reactions by reducing the time to activate the microorganism for nitrification, denitrification, release of organic phosphate and luxury uptake of ortho-phosphate. Eventually the result of this study obtained each 90.9%, 76.4% for the removal efficiency of total nitrogen and phosphate. Also, content rate of phosphate at excess sludge was higher $25{\sim}30%$ for SBR reactor with the flexible verticals than existing SBR process. It would be concluded that SBR reactor with flexible verticals is promising for nitrogen and phosphate removal conditions than conventional SBR processes.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.108-108
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• 1998

최근의 GaN에 관한 연구는 주로 MOCVD법과 MBE법이 이용되고 있으며 대부분 800¬1$\alpha$)()t 정도의 고옹에서 이루어지고 었다. 그러나 이러한 고온 성장은 GaN 성장 과청에서 질 소 vacancy를 생성시켜 광특성을 저하시키고 청색 발광충인 InGaN 화합물에 In의 유입울 어 렵게 하며 저온에서보다 탄소 오염이 증가하는 동의 문제캠을 가지고 있다. 이러한 고온 생장 의 문제점을 해결하기 위한 방법중의 한 가지로 제시되고 있는 것이 저온 성장법이다. 본 연구 에 사용된 RPE-UHVCVD법은 Nz률 rf plasma로 $\sigma$acking하여 공급함으로써 NI-h롤 질소원으 로 사용하는 고온 성장의 청우와는 다르게 온도에 크게 의존하지 고 질소원올 공급할 수 있 어 저옹 성장이 가능하였다. 기판으로는 a - Alz03($\alpha$)()1)를 사용하였고 3족원은 TEGa(triethylgallium)이며,5족원으로는 6 6-nine Nz gas를 rf plasma로 cracking하여 활성 질소원올 공급하였다 .. Nz plasma로 질화처리 를 한 sapphire 표면 위에 G따애 핵생성충을 성장 옹도(350 t, 375 t, 400 t)와 성장시간(30 분,50 분) 그리고 VIllI비(1$\alpha$)(), 2뼈)둥을 변화시키면서 성장시킨 후 GaN 에피택시충을 450 $^{\circ}C$에서 120 분 동안 성장시켰다 .. XPS(x-ray photoelectron spectroscopy), XRD(x-ray d diffraction), AFM(atomic force microscope)둥올 이용하여 표면의 조성 및 morphology 변화와 결정성을 관찰하였다. X XPS 분석 결과 질화처리를 한 sapphire 표면에는 AlN가 형성되었다는 것을 확인 할 수 있 었으며 질화처리를 한 후 G따J 핵생성충올 성장시킨 경우에 morphology 변화를 AFM으로 살 펴본 결과 표면에 facet shape의 island가 형성되었고 이러한 결파는 질화처리 과청이 facet s shape의 island 형성을 촉진시킨다는 것을 알 수 있었다. 핵생성충의 성장온도가 중가함에 따 라 island의 모양은 round shape에서 facet shape으로 변화하였다. 이러한 표면의 morphology 변화와 GaN 에피택시충의 결정성과의 관계를 살펴보면 GaN 에피택시충 표면의 rms(root m mean square) roughness가 중가하는 경 우 XRD (j -rocking curve의 FWHM(full width half m maximum) 값이 감소하는 것으로 나타났다. 이러한 현상은 결정성의 향상이 columnar 성장과 관계가 었다는 것올 알 수 있었다 .. columnar 성장은 결함의 밀도가 낮은 column의 형생과 G GaN 에피택시충의 웅력 제거로 인해 G값{의 결정성을 향상시킬 수 있는 것으로 생각된다. 톡 히 고온 성장의 경우와는 달리 rms roughness의 중가가 100-150 A청도로 명탄한 표면올 유 지하면서 결정성을 향상시킬 수 있었다. 본 실험에서는 핵생성충올 375 t에서 30 분 생장시킨 경우에 hexagonal 모양의 island로 columnar 성장을 하였고 GaN 에피태시충의 결정성도 가장 향상되었다 이상의 결과로부터 RPE-UHVCVD법용 이용한 GaN 저온 성장에서도 GaN의 결청성올 향 상시킬 수 있음융 확인할 수 있었다.

• Korean Journal of Environmental Agriculture
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• v.27 no.1
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• pp.44-49
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• 2008

The purpose of this study is to investigate the current status, including the maintenance problems and removal efficiency, of small sewage treatment facilities in Chung-nam province(Asan, Buyeo, and Gongju city). Our results showed that inflow water quality of Asan city was 19.1 mg/L of BOD, 29.0 mg/L of COD, 13.4 mg/L of T-N and 1.5 mg/L of T-P, respectively, which was much higher than any other site. Among the factors known to be an important index of water quality, the SS and BOD removal efficiency was about 70% and 50% respectively. However, the nitrogen removal efficiency was less than 10%. The total removal efficiency of pollutant was 71.1% of SS, 52.6% of BOD, 46.2% of COD, 9.2% of T-P and 4.6% of T-N respectively. Therefore nitrogen removal processes are required to prevent serious eutrophication of small river. Removal efficiency for BOD and SS of high-efficient sewage treatment facilities (STFs) and contact oxidation process was much higher than another process. Performance of these sewage treatment facilities(STFs) is not optimal due to ineffective planning for the inflow water quality. To improve these facilities, it is proposed that a technical expert analysis of water quality at these facilities is periodically required.

• Journal of Animal Environmental Science
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• v.10 no.2
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• pp.81-86
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• 2004

This experiment was conducted to evaluate combination system of wood chip trickling system and activated sludge process. The results obtained are summarized as tallows. The trickling filter system using wood chip was used as a biological pre-treatment system for treating piggery wastewater. At pre-treatment the removal efficiencies were BOD $91\%$ CODmn $65\%$, SS $75\%$ T-N $73\%$, T-P $69\%$. After pre-treatment the removal efficiencies in activated sludge process were BOD $99\%$ CODmn $94.6\%$, SS $97.8\%$ T-N $91.1\%$, T-P $91\%$. This study shows a very stable method with pre-treatment of trickling filter using wood chip. These combined treatment system was very useful for piggery wastewater.