• Korean Chemical Engineering Research
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• 제48권1호
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• pp.103-109
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• 2010

하폐수 처리과정에서 발생되는 슬러지는 주로 혐기소화에 의해 처리되며 슬러지를 감량하고 메탄을 생산할 수 있어 많이 이용되고 있다. 슬러지의 전처리는 혐기소화의 율속단계인 가수분해를 높여 처리속도를 향상시키므로 많은 연구가 진행 중이다. 본 연구에서는 열, 초음파, 열-알칼리의 전처리 기술에 따른 슬러지의 가수분해(가용화) 효과와 전처리한 슬러지를 혐기소화하여 메탄 생산량과 슬러지의 감량 효과를 비교하였다. 하수와 폐수 슬러지 가용화율은 열-알칼리 동시 처리한 경우에는 67과 70%로 가장 높았고 다음으로 초음파 처리와 열처리가 40% 이상의 비슷한 가용화율을 보였다. 혐기소화 가스의 메탄 함량은 45~70% 범위로 유지되었고 전처리한 슬러지가 control에 비해 높게 나타났다. 메탄 생산량은 열처리, 초음파 처리, 열-알칼리를 같이 처리한 경우가 control에 비해 각각 하수슬러지는 2.6, 2.7, 3.5배, 폐수 슬러지는 3.5, 4.1, 4.2배 증가하였다. 혐기소화 슬러지의 감량효과는 전처리한 슬러지가 control에 비해 5~19% 포인트 높게 나타났으며 열-알칼리 처리한 경우가 초음파와 열처리에 비해 우수한 감량 효과를 보였다. 위의 결과로부터 전처리가 메탄 생산량에서 뿐만 아니라 슬러지 처리처분 비용 절감에 있어서도 중요한 역할을 함을 확인할 수 있었고 열-알칼리 동시 처리가 가장 우수한 성능을 보였다.

• 한국물환경학회지
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• 제25권1호
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• pp.120-124
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• 2009

This study was performed to investigate the application of submerged membrane bioreactor (MBR) system for biological nutrient removal of municipal wastewater. MBR bioreactor consists of four reactors such as anaerobic, stabilization, anoxic and submerged membrane aerobic reactors with two internal recycles. The hydraulic retention time (HRT), sludge retention time (SRT) and flux were 6.2 hr, 34.1 days and $19.6L/m^2/hr$ (LMH), respectively. As a result of operation, the removal efficiency of $COD_{Cr}$, SS, TN and TP were 94.3%, 99.9%, 69.4%, and 74.6%, respectively. There was no significant effect of microbial activity after the maintenance cleaning using 200 mg/L of NaOCl. Membrane filtration for the treatment of municipal wastewater was performed for longer than 9 months without chemical recovery cleaning.

• 대한환경공학회지
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• 제27권1호
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• pp.93-100
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• 2005

본 연구는 1차슬러지와 생물학적 영양소제거 슬러지의 처리에 있어서 분리 및 혼합처리에 대한 농축과 탈수특성을 조사하였다. 슬러지의 탈수를 위해서는 고분자 폴리머, 증기주입 및 초음파처리등의 슬러지 개량방법을 이용하여 슬러지의 개량특성을 분석하였고, 비저항계수측정법과 Wedge zone simulator 그리고 원심분리를 이용하여 탈수특성을 분석하였다. 농축실험결과 1차슬러지와 생물학적 2차슬러지를 분리농축하는 것이 바람직한 것으로 나타났으며, 특히 3.5%이상의 고농도 1차슬러지의 경우는 농축단계에서 상징수의 고액분리는 부정적이었다. 농축된 슬러지의 개량에 있어서는 폴리머 주입, 증기처리 및 초음파처리 등의 개랑법중에서 폴리머를 주입한 경우가 가장 우수한 탈수성을 나타내었다. 1차와 2차 및 혼합슬러지의 최적 폴리머 주입조건은 건조고형물 기준으로 각각 0.26%, 0.43% 및 0.38%이었다. 농축슬러지의 탈수실험에서는 1차와 2차슬러지를 혼합하여 처리하는 것이 고액분리측면에서나 반류수의 수질측면에서 보다 효과적으로 나타났다. 여과포를 이용하는 탈수방식은 폴리머의 사용이 필수적이었으나 이 경우 2차슬러지의 단독탈수는 효과가 없었다. 원심탈수 방법은 가장 우수한 탈수효율을 보였으며, 이때 폴리머의 주입으로 탈수케익의 고형물함량을 조금 더 향상시킬 수 있었다. 이상의 실험결과에 근거하여 반류수의 수질특성과 고형물회수를 고려한 합리적인 슬러지 처리공정을 제안하였다.

• 상하수도학회지
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• 제26권6호
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• pp.825-831
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• 2012

The retrofitting of a thickening unit process is widely considered in municipal wastewater treatment plants in Korea to enhance the anaerobic digestion efficiency. The authors examined the effect of feed concentration (2-34.1 g VS/L) and feed to microorganism (F/M) ratio (0.50-1.35 g VS/g VS) on anaerobic batch digestion of sewage sludge. Methane yield over 90 mL $CH_4/g$ $VS_{feed}$ was found at a feed concentration in the range of 12-26 g VS/L and a F/M ratio below 0.6 g VS/g VS. A high F/M ratio decreased methane yield and rate with oragnic acid accumulation. As sudden increase of sewage sludge concentration prior to anaerobic digestion would jeopardize the digester performance due to the rasied F/M ratio, gradual increase of the sludge feed concentration or an additional biomass retention in the digester is recommended.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제1권2호
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• pp.125-136
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• 1997

Digestion of a municipal wastewater sludge by the anaerobic sequencing batch reactor(ASBR) was investigated to evaluate the performance of the ASBR process at a critical condition of high-solids-content feed. The reactors were operated at an HRT of 10 days with an equivalent loading rate of 0.8-1.5 gVS/L/d at $35^{\circ}C.$ The main conclusions drawn from this study were as follows: 1. Digestion of a municipal wastewater sludge was possible using the ASBR in spite of high concentration of settleable solids in the sludge. The ASBRS with 3- and 4-day cycle period showed almost identical high digestion performances. 2. No adverse effect on digestion stability was observed in the ASBRS in spite of withdrawal and replenishment of $30\%\;or\;40\%$ of liquid contents. A conventional anaerobic digester could be easily converted to the ASBR without any stability problem. 3. Flotation thickening occurred in thicken step of the ASBRS throughout steady state, and floating bed volume at the end of thicken period occupied about $70\%$ of the working volume of the reactor. Efficiency of flotation thickening in the ASBRS could be comparable to that of additional gravity thickening of a completely mixed digester. 4. Solids were accumulated rapidly in the ASBR during start-up period. Solids concentrations in the ASBRS were 2.6 times higher than that in the completely mixed control reactor at steady state. Dehydrogenase activity had a strong correlation with the solids concentration. Dehydrogenase activity of the digested sludge in the ASBR was 2.9 times higher than that of the sludge in the control reactor, and about 25 times higher than that of the subnatant in the ASBR. 5. Remarkable increase in equivalent gas production of $52\%$ was observed at the ASBRS compared with the control reactor in spite of similar Quality of clarified effluent from the ASBRS and control reactor. The increase in gas production from the ASBRS was believed to be combined results of accumulation of microorganisms, higher driving force applied, and additional long-term degradation of organics continuously accumulated.

• 대한환경공학회지
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• 제33권5호
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• pp.314-324
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• 2011

하수를 이용해서 배양된 조류는 바이오디젤 생산에 유용한 자원이다. 그러나 실제 하수에서 조류의 영양염류 신진대사와 하수 세균과의 상호작용에 관한 연구는 미흡하다. 본 연구에서는 하수로 배양되는 대표적 조류균주인 Ankistrodesmus gracilis SAG 278-2에 의한 하수 내 질소, 인 제거 거동을 평가하였고, 조류와 상호작용하는 하수 내의 세균 군집을 분석하였다. 하수 슬러지 세균 군집과 비교하였을 때, 조류-세균 복합 군집은 하수 내보다 높은 영양염류 제거를 보였다. 16S rRNA 유전자 분석 결과, 조류-세균 군집에서 조류가 성장함에 따라 Unclassified Alcaligenaceae 세균이 선택적으로 우점됨을 알 수 있었고, 조류에 의해서 선택적으로 우점화된 하수세균은 자연 수질 환경에서 조류와 공생적으로 상호작용 하는 것으로 알려진 Alcaligenes faecalis subsp. 5659-H와 계통학적으로 가까운 것으로 밝혀졌다. 본 연구의 결과, 하수 내의 높은 영양염류 제거를 보이는 조류-세균 복합 군집에서의 조류의 성장 및 신진대사가 특정 세균의 분포에 영향을 주는 것을 알 수 있었다.

• 상하수도학회지
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• 제11권3호
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• pp.67-78
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• 1997

The objective of study was to examine to transient response of hydraulic shock loading in activated sludge process for treatment of municipal sewage. The general experiment approach was to operate the system under steady-state(pre-shock), then to apply step changes during 24hours in fourfold hydraulic shock loading at the same organic loading. Performance was assessed in both the transient state and the new steady-state(post-shock). Three bench scale activated sludge reactors were operated to investigate the effect of fourfold hydraulic shock loading on TSS and COD removal efficiency. In activated sludge reactors operated with 13hours and 7hours of HRT, effluent quality of all reactors was not changed for few effects, and also showed no foaming and no sludge bulking. Those results are the same as sludge withdrawn reactors. The effect of fourfold hydraulic shock loading on the activated sludge reactors operated with 3hours of HRT was most severe. The effluent quality was deteriorated significantly and generate foaming in reactors. Less than 24hours after the fourfold shock loading applied, the activated sludge system seemed to attain a new steady-state condition as show by effluent.

• Journal of Microbiology and Biotechnology
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• 제15권1호
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• pp.14-21
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• 2005

By using PCR with nirS gene primers, three nirSharboring denitrifying bacteria (strain N6, strain N23, and strain R13) were newly isolated from activated sludge of a weak municipal wastewater treatment plant. Small-subunit rRNA gene-based analysis indicated that strain N6, strain N23, and strain R13 were closely related to Arthrobacter sp.,Staphylococcus sp., and Bacillus sp., respectively. In an attempt to identify their roles in biological nitrate and nitrite removal from sewage, we investigated their specific denitrification rates (SDNRs) for $NO_-^3$ - and $NO_-^2$ - in various cultures. All purecultures of each isolated nirS-harboring bacterial strain could remove $NO_-^3$ - and $NO_-^2$ - simultaneously in high efficiency, and the carbon requirements for $NO_-^3$ - removal of strain N6 and strain R13 were effectively low at 3.1 and 4.1 g COD/g $NO_3N$, respectively. In the case of mix-cultures of the strains (N6+N23, N6+R13, N23+R13, and N6+N23+R13), their SDNRs for $NO_-^3$ - were also effective, and their carbon requirements for $NO_-^3$ - removal were also effective at 3.0- 3.8 g COD/g NO3N. However, all tested mix-cultures accumulated $NO_-^2$ - in their culture media. On the other hand, the continuous culture of activated sludge mixed with strain N6 showed no significant increase of $NO_-^3$ - removal in comparison with strain N6's pure culture. These results suggest that nitrate and nitrite removal in biological wastewater treatment might be dependent on complicated bacterial interactions, including several effective denitrifying bacteria isolated in this study, rather than the specific bacterial types present and the number of bacterial types in activated sludge.

• 상하수도학회지
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• 제24권5호
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• pp.561-572
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• 2010

The efficiency of biological hydrolysis at $80^{\circ}C$ on municipal solid waste mixed with anaerobic digestion sludge was investigated in 100L batch reactors. The hydrolysis effect was observed within a day, when the hydrolysis reactor used for a pre-treatment reactor for methanogenesis, and the effect was observed during two days, When the reactor used for post-treatment reactor. For both configurations, methane production rate decreased, when hydrolysis was carried out more than a day. Gaseous ammonia in the hydrolysis reactors was successtully removed by the ammonia stripping system. Microbial diversity analysis on the hydrolysis reactors indicated dependency of microbial diversity on the configuration of the hydrolysis reactors. Carbohydrate and lactate degrading microbes dominated in the hydrolysis reactor, when the hydrolysis reactor used for a pre-treatment reactor for methanogenesis, while protein degrading microbes dominated in the post-treatment reactor.

• 한국물환경학회지
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• 제27권1호
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• pp.44-53
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• 2011

Membrane bio-reactor (MBR) has several advantages over the conventional activated sludge process, including a high biomass, low sludge production, and better permeate quality. Therefore, the MBR have gained popularity for municipal and industrial wastewater treatment. However the MBR usually were used for sewage and low streng th wastewater treatment because of membrane fouling problem and limitation of oxygen transfer into biomass. In this study, the hybrid process combining MBR and pure oxygen was tested for high strength organic wastewater treatment in the COD loading range from 2 to $10kgCOD/m^3{\cdot}day$. The hybrid process, membrane coupled pure oxygen high compact reactor (MPHCR), had been operated for one year and operation parameters, the effect of COD loading, MLSS concentration and the location of membrane module were studied for membrane fouling characteristic. Also membrane resistance test and the component of foulant was analyzed to investigate what is specific foulant in the MBR.