• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.292-299
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• 2006

Batch experiments were performed to evaluate the effects of the electron donor dosage and the initial biomass on the reductive dechlorination of perchloroethene(PCE) with benzoate as an electron donor. When benzoate was added less than the theoretical requirement for dechlorination(electron donor/acceptor ratio=0.5 and 1), the dechlorination efficiency increased from 71% to 94.3% with the increase in benzoate dosage, but the fraction of electron equivalent utilized for dechlorination decreased from 92.7% to 79.6%. Methane production was observed when the hydrogen concentration was higher than the threshold value(10 nM) after PCE and trichloroethene (TCE) were reduced to cis-1,2-dichloroethene(cDCE). When benzoate was added more than the theoretical requirement, the residual hydrogen converted into methane after the completion of dechlorination. The increase in the seeding biomass shortened the lag time for dechlorination, but it did not affect the maximum dechlorination rate as it was mainly governed by the benzoate fermentation rate. When the seeding biomass concentration was high, active dechlorination during the early period increased dechlorination efficiency while decreasing methane production.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.6
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• pp.332-339
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• 2015

Nitrogen removal is one of the most important issues about wastewater treatment because nitrogen is a primary pollutant caused various problems such as eutrophication. We developed a CANON microbial community by using AOB and ANAMMOX bacteria as seeding sources. When 100 mg-N/L of influent ammonium was supplied, the DO above 0.4 mg/L showed a very low TN removal efficiency while the DO of 0.3 mg/L showed TN removal efficiency as high as 71.3%. When the influent ammonium concentration was reduced to 50 mg/L, TN removal efficiency drastically deceased. However, TN removal efficiency was recovered to above 70% after 14 day operation when the influent nitrogen concentration was changed again from 50 mg-N/L to 100 mg-N/L. According to the operating temperature from $37{\pm}1^{\circ}C$ to $20{\pm}1^{\circ}C$, TN removal efficiency also rapidly decreased but gradually increased again up to $70.0{\pm}2.6$%. The analysis of PCR-DGGE showed no substantial difference in microbial community structures under different operational conditions. This suggests that if CANON sludge is once successfully developed from a mixture of AOB and ANAMMOX bacteria, the microbial community can be stably maintained regardless of the changes in operational conditions.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.4
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• pp.25-33
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• 2019

Operating characteristics of a 30 L microbial electrolysis cell (MEC) for producing biogas from sewage sludge was studied. During the 32-day inoculation period, carbon dioxide concentration decreased and methane concentration increased with operating time, and the overall methane content of biogas was 69.1% with a production rate of 171.6 mL CH₄/L·d. In fed-batch experiments for 6 operating cycles, CH₄ concentration of 66.5~77.2% was obtained at a production rate of 184.9~372.9 mL CH₄/L·d, COD, TS and VS removal efficiency ranged from 28.2 to 42.1%, 20.7 to 37.5% and 18.5 to 36.9%, respectively. The MEC system was observed to be stabilized as operating cycles were repeated after inoculation. In the last operating cycle, 5221 mL/L of methane was produced with CH₄ yield of 316.7 L CH₄/kg COD_rem, and the energy recovery was 73%.

• Korean Journal of Ecology and Environment
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• v.50 no.4
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• pp.403-410
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• 2017

We collected fishes at the 12,873 sites in stream order (1~7) from 2008 to 2016. In the results, two populations(Zacco platypus and Zacco koreanus) represented distributional differences in the stream order gradient, and correlation analysis showed that the two populations had a potential competitive relationship. The ecological characteristics of the fish except for the Z. platypus and the Z. koreanus, according to the gradient of stream order showed a pronounced gradient in the species such as intermediate species, sensitive species, carnivores, herbivores and omnivores. The two populations showed a high correlation between intermediate species, sensitive species of the tolerance guild and omnivores, insectivores of the trophic guild. Fish assessment index (FAI) was negative relation with stream order. According to the stream order gradient, the two populations showed different correlations with FAI.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.3
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• pp.54-62
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• 2011

This study was undertaken to investigate the effects of bone waste on the conservation of nitrogen in aerobic composting process by inducing the struvite crystallization, which was known as a powerful method for conservation of nitrogen in composting reaction. Bone waste was dried at oven and crushed to less than 3 mm prior to use. It was found phosphorus content in bone waste was about 20.9% of the fixed solids from the leaching experiments using sulfuric acid. Addition of seed compost affected the progress of composting reaction substantially. In case seed compost was not used, the duration of initial low pH was greater than seed compost was added. This prolonged acidic pH may have a beneficial effect on the leaching of P from the bone waste and struvite crystallization. The struvite crystallization and resulting conservation of nitrogen by addition of bone waste was confirmed by both reduction in ammonia loss and increased ammonia content in compost. However the level of struvite crystallization observed with bone waste addition may be less than the cases water-soluble phosphate salts were used.

• Journal of environmental and Sanitary engineering
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• v.14 no.2
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• pp.25-31
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• 1999

Energy recovery technology from municipal solid waste has been increasingly established in many countries. Anaerobic treatment of municipal sewage sludge has low digestion efficiency because of low organic loading rate of sewage sludge. The purpose of this study was to evaluate anaerobic biodegradability of food waste which was based on organic loading rate and seeding rate. From the results of anaerbic biodegration, the optimum condition for seeding rate was turn out over 40%, which did not inhibition of methane production.

• Journal of the Korean Institute of Telematics and Electronics
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• v.4 no.2
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• pp.35-37
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• 1967

통신망이 현행의 전화단일 서어비스를 벗어나 광대역정보를 포함하는 다채로운 통신서어비스가 요청되는 세계적인 추세에 입각하여 대케이블과 더불어 공간분할형기계접점교환기의 전송특성에 관한 검사결과를 언급하여, 이와같은 시설이 광대역정보의 전송에 있어서 큰 잠재능력을 갖는 것을 주장하고 있다. 따라서 통신 서어비스총합망의 시내 및 시외계ㅡ이 구성에 관해 고찰하고 새로이 사선식종속통신망을 제안하고 있다. 이 제안에 의하면 현재의 통신망으로부터 통신총합망에 전환이 원활이 된다는 것이다. 또한 시내망에 관해서는 기존과같이 예상되는 미래의 전송방식을 포함하는 한층 품질이 우수한 유연성있는 전송계가 실현 가능하다고 시사하고 있다. 여기에 그 내용을 간추려 보겠다.

• The Korean Journal of Malacology
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• v.12 no.1
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• pp.53-83
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• 1996

러시아 블라디부스톡에 위치한 극동대학 동물박물관 소장 이매패류의 목록과 주석을 기재하였다. 총 71과 520종을 기재하였는데 그 중 종의 수가 많은 과는 Arcidae, Cardiidae, Tellinidae, Unionidae, Mytilidae, Veneridae, Ostreidae, Pectinidae, and Asartidae등이다. 각 종은 lot와 표본 숫자와 함께 채집기를 기재하였으며, 모식종(type specimen)은 사진과 기재 일자 및 박물관 소장번호를 기재하였다.

• Journal of the Korea Organic Resources Recycling Association
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• v.15 no.3
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• pp.97-105
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• 2007

This study was conducted to compare the performances of acidogenic fermentation and hydrogen fermentation using bench-scale leaching-bed reactors for organic solid waste. Acidogenic fermenters were operated with dilution rates (D) of 2.0, 3.0 and $4.0d^{-1}$ after employing anaerobic sludge and hydrogen fermenters were operated with D of 2.0, 4.0 and $6.0d^{-1}$ after employing heat-treated anaerobic sludge. The highest chemical oxygen demand (COD) conversion efficiency (56.2%) was obtained in acidogenic fermentation with D of $3.0d^{-1}$. Only volatile fatty acid (VFA) was produced as a metabolite. On the other hand, hydrogen fermentation did not show higher COD conversion efficiency (49.3%) than acidogenic fermentation, but it produced hydrogen gas (5.1% of total COD) which was a clean and environmentally friendly fuel with a high energy yield. Therefore, either acidogenic fermentation or hydrogen fermentation could be applied to organic solid waste depending on the purpose of treatment, which could maximize the economics of anaerobic treatment.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.635-641
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• 2005

Batch experiments were performed to evaluate the effect of sulfate reduction on methane production and reductive dechlorination, both compete for hydrogen with sulfate reduction. Dechlorination was inhibited by sulfate reduction at lower hydrogen concentration because their threshold values for hydrogen are similar (2 nM). Unlike methane production mainly inhibited transformation of cDCE to ethene, sulfate reduction inhibited the initial dechlorination step, PCE reduction into cDCE as well as cDCE dechlorination. The presence of sulfate eliminated methanogens as hydrogen competitor because of its high threshold value of 10 nM. When sulfate coexisted with PCE, dechlorination efficiency was not affected by the increase of seed concentration as both dechlorination and sulfate reduction were stimulated simultaneously by the increased seeding culture.