• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.14-17
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• 2002

To increase the efficiency of a two-stage anaerobic wastewater digestion system, various polymers were added to the methanogenic reactor as supports. The addition of polyurethane addition (6%, w/v) to the methanogenic reactor facilitated the organic loading rate (2-day Hydraulic Retention Time), higher than that of the conventional methanogenic reactor (6-day HRT). During the operation of the polyurethane-added reactor, a significant decrease in the organic mass in the effluent (COD 5-6 kg/l) was achieved, compared to that of the conventional reactor (COD 15-20 kg/l). The methane gas production rate also improved about 3-fold in the polyurethane-added reactor. More biomass was found to accumulate in the polyurethane-liquid phase (volatile solid, 26-28kg) than in the free-liquid phase (volatile solid, 5- 7 kg/l) after 90 days of operation. A scaled-up experiment with a polyurethane-added 2.5-1 reactor confirmed the previous results, and no adverse effects such as plugging or channeling due to decreased efficiency was observed even after 4 months of operation.

• 상하수도학회지
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• 제20권5호
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• pp.763-770
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• 2006

The purpose of this study was to investigate the effects of mechanical(ball-mill) solubilization of excess sludge especially focused on the TSS(total suspended solid) reduction during the conventional aerobic digestion of sewage sludges including primary and/or excess sludge, HRT was examined at the 10 days and 20 days. According to the results of this study, TSS removal efficiency of solubilized excess sludge was almost two times higher than that of non-solubilized excess sludge. And as the proportion of the primary sludge increased, TSS removal efficiency became worse because primary sludge rarely contained microbial cells which could be easily solubilized physically. It was also proved that by the application of proper solubilization techniques to the excess sludge, HRT for the aerobic digestion could be lessened(above 50%) dramatically keeping the same or better digestion performance. The fact that between primary and excess sludges, only the excess sludge is quite effective in the sludge solubilization and in it's reduction says that excess sludge releasing sources are key-point in the sludge cake reduction field as a source control.

• 한국물환경학회지
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• 제30권5호
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• pp.559-567
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• 2014

Since the ocean dumping of organic wastes is prohibited under the London Convention, the need for land treatment of food waste leachate (FWL) has significantly been growing in recent years. This study was conducted to use thermal solubilization to turn FWL into a form that can easily be degraded during the anaerobic digestion process, thereby reducing the percentage of solids and increasing the production of methane. To derive the optimal operating conditions of thermal solubilization, a laboratory-scale reactor was built and operated. The optimal reaction temperature and time turned out to be $190^{\circ}C$ and 90 min, respectively. The BMP test showed a methane production of 465 mL $CH_4/g$ $COD_{Cr}$ and a biodegradation rate of 90.1%. The production of methane rose by about 15%, compared with no the application of thermal solubilization. To reduce the solid content of FWL and improve the methane production, therefore, it may be helpful to apply thermal solubilization to pre-treatment facilities for anaerobic digestion.

• Bulletin of the Korean Chemical Society
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• 제24권10호
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• pp.1433-1436
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• 2003

A new method for the simultaneous determination of heavy metal ions in cigarette material by microwave digestion and reversed-phase high-performance liquid chromatography (RP-HPLC) has been developed. The cigarette material was digested by microwave digestion. Lead, cadmium, mercury, nickel and tin ions in the digested samples were pre-column derivatized with tetra-(2-chlorophenyl)-porphyrin ($T_2$-CPP) to form color chelates, which were then enriched by solid phase extraction with a $C_{18}$ cartridge. The chelates were separated on a Waters Xterra$^{TM}RP_{18}$ column by gradient elution with methanol (containing 0.05 mol/L pyrrolidine-aceticacid buffer salt, pH = 10.0) and acetone (containin0.05 mol/L pyrrolidine-acetic acid buffer salt, pH = 10.0)as mobile phase at a flow rate of 0.5mL/min and analyzed with a photodiode array detector from 350-600 nm. The detection limits of lead, cadmium, mercury, nickel and tin were 4,3,3,8 and 5 ng/L, respectively, in the original samples. This method was afforded good results.

• 한국토양비료학회지
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• 제50권4호
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• pp.293-305
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• 2017

This experiment was conducted to evaluate the effect of leachate replacement frequency on solid state anaerobic digestion (SSAD) of dairy manure using 22 L volume lab-scale digesters at mesophilic temperature ($37^{\circ}C$) in batch mode. Three different leachate replacement strategies (no replacement, once every three days, and once every nine days) were applied and three digesters per each treatment were operated for 45 days. Results showed that leachate replacement test unit every nine days resulted in 1.6 times more methane production ($53.8N{\cdot}mL\;g^{-1}{\cdot}VS$) from SSAD compared to test unit every three days ($34.0N{\cdot}mL\;g^{-1}{\cdot}VS$). No leachate replacement strategy applied group showed slightly higher methane production ($56.3N{\cdot}mL\;g^{-1}{\cdot}VS$) than every nine days replaced one. When added the methane production potential of replaced leachate itself to the methane produced from digester, leachate replacement every nine days resulted in quite similar methane production ($56.5N{\cdot}mL\;g^{-1}{\cdot}VS$) to no leachate replacement group. Even though methane production potential of replaced leachate itself added to the methane produced from digester, every three days replacement showed only $34N{\cdot}mL$ methane production per gram of volatile solids. These results suggest that farmers do not need to replace leachate during SSAD of dairy manure and sawdust mixture in order to maximize methane production. If there are any concerns with accumulation of inhibiting substances in the digester, the 9-day cycle leachate replacement is appropriate.

• 한국환경보건학회지
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• 제24권2호
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• pp.9-19
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• 1998

Laboratory experiments were carried out to investigate the performance of anaerobic sequencing batch reactor(ASBR) for digestion of a municipal sludge. Each cycle of the ASBR comprised feeding, two-or three-day reaction, one-day thickening, and withdrawal. The reactors were operated at an HRT of 10days and 5days with an equivalent organic loading rate of 0.8-1.54 gVS/l/d, 1.81-3.56 gVS/l/d at 35$\circ$C, respectively. Solids accumulation was remarkable in the ASBR during start-up period, and directly affected by settleable solids in the feed sludge. Floatation thickening occured in the ASBRs, and Solids profiles at the end of thickening step dramatically changed at solid-liquid interface. Slight difference in solids concentrations was observed within thickened sludge bed. Efficiencies through floatation thickening were comparable to that of additional thickening of the completely mixed control reactor. Average solids concentrations in the ASBRs were 2.2-2.6 times higher than that in the control throughout the total operation period. The dehydrogenase activity had a strong correlation with the solids concentration. Organics removals based on clarified effluent of the ASBRs were consistently above 86%. Remarkable increase in equivalent gas production of 27-52% was observed at the ASBRs compared with the control though the control and ASBRs showed similiar effluent quality. Thus, digestion of a municipal sludge was possible using the ASBR in spite of high concentration of solids in the sludge.

• 공업화학
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• 제29권5호
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• pp.613-619
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• 2018

본 연구에서는 유입 슬러지에 다양한 전처리 방법과 고액분리장치를 이용한 유출수의 잉여슬러지를 농축 후 내부반송을 적용하여, 중온혐기-고온호기 혼합 슬러지 처리 공정의 슬러지 소화효율과 메탄가스 생성량에 미치는 영향을 비교 검증하였다. 실험실 규모의 혼합 소화공정장치를 제작하여 서로 다른 유입 슬러지 전처리방법을 적용하여 5단계로 실험을 진행하였다. 1단계에서는 열-알칼리처리 전처리를 하여 슬러지를 공급하였고, 2, 3, 4단계에서는 유출수로부터 농축된 잉여슬러지의 내부반송과 각각 열-알칼리처리, 열처리, 알칼리 처리(7일)를 거친 유입 슬러지를 공급하였다. 마지막 5단계에서는 전처리를 하지 않은 슬러지를 공급하였다. 실험 결과, 1단계에서 4단계까지 진행되는 동안 Volatile Suspended Solid (VSS) 제거율은 유입 슬러지 전처리와 내부반송을 적용하는 경우 크게 증가하였으며, 메탄생성량 또한 2단계에서 슬러지 내부반송과 열-알칼리처리 전처리 적용의 경우 285 mL/L/day까지 크게 증가하였다. 한편, 5단계에서 전처리를 하지 않은 슬러지를 공급하였을 경우 VSS 제거율과 메탄 생성량이 크게 감소하였다. 결론적으로, 유입 슬러지의 열-알칼리처리 전처리와 유출수의 농축 잉여슬러지의 내부반송을 통해 복합 슬러지 처리 공정의 슬러지 제거 효율과 메탄생성량을 크게 증가시킬 수 있었다.

• 산업기술연구
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• 제39권1호
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• pp.21-25
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• 2019

This work experimentally determined the effect of microaerobic condition on anaerobic digestion of thickened waste activated sludge in semi-continuous mesophilic digesters at hydraulic retention time of 20 days. The concentration of hydrogen sulfide was $7{\pm}2ppm$ at the microaerobic condition and $14{\pm}2ppm$ at the anaerobic condition. Removal efficiency of volatile solid was not significantly different between microaerobic ($40{\pm}8%$) and anaerobic ($38{\pm}8%$) conditions. There was no important difference between microaerobic ($1,352{\pm}98ml/d$) and anaerobic ($1,362{\pm}104ml/d$) conditions in the biogas production, either. Therefore, it could be concluded that the application of the microaerobic condition was an efficient method of the hydrogen sulfide removal from the biogas.

• 대한환경공학회지
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• 제31권5호
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• pp.341-345
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• 2009

음식물쓰레기와 종이류로 구성된 유기성고형폐기물(고형물 함량 30% TS)을 대상으로 중온 건식혐기성소화를 시도하였고, 연속 운전 중 수리학적 체류 시간(HRT)을 150일, 100일, 60일, 40일로 감소시켰다. 기질의 고형물 농도를 30% TS (Total Solids)로 고정하였기 때문에 각각의 HRT에 해당하는 고형물 부하는 2.0, 3.0, 5.0, 7.5 kg TS/$m^3$/d였다. HRT를 줄임에 따라 단위용적 당 바이오가스 생산 속도는 증가하였고, HRT 40일에서 3.49${\pm}$0.31 $m^3/m^3/d$로 가장 높은 성능을 보였다. 이 때, 76%의 휘발성 고형물(VS) 분해율이 유지되었고, 0.25 $m^3$/kg $TS_{added}$의 메탄 생산 전환율을 보였으며, 이는 기질의 67.4%에 해당하는 에너지가 메탄 가스로 전환된 것을 의미한다. HRT 100일에서 0.52 $m^3$/kg $TS_{added}$로 가장 높은 바이오가스 전환율을 보였지만, 모든 HRT에서 0.45${\sim}$0.52 $m^3$/kg $TS_{added}$로 큰 차이가 나지 않았다. 고형물 함량이 높은 기질의 원활한 주입을 위해 소화조 발효액의 일부를 기질 투입구로 반송하여 기질과 혼합 후 주입하였다. 주입하고자 하는 기질의 5배에 해당하는 양의 소화조 발효액을 반송하여 혼합하였을 때, 가장 효과적인 기질 주입이 이루어졌다. 중온 건식 조건에서 서식하는 메탄 소화균의 활성도를 측정한 결과, 아세트산, 뷰틸산, 프로피온산을 이용할 경우 각각 2.66, 1.94, 1.20 mL $CH_4/g$ VS/d였다.

• 한국식품영양과학회지
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• 제43권6호
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• pp.842-853
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• 2014

본 연구는 고올레산 해바라기유(high oleic sunflower oil, HOSO), palmitic ethyl ester 및 stearic ethyl ester를 이용하여 대칭형 유지와 비대칭형 유지를 합성하였으며, 이를 이용하여 in vitro digestion에서의 소화율(%)을 비교하고자 하였다. 생성된 대칭형 유지와 비대칭형 유지는 acetone을 이용하여 분별함으로써 대칭형 유지는 I, II, III으로, 비대칭형 유지는 IV, V로 분별되었다. 그 후 분별물들을 이용하여 in vitro digestion을 진행함으로써 소화율(%)과 농도변화량(mg/mL/min)을 비교하였으며, 분별물들의 위치별 지방산 및 TAG 조성 분석, DSC를 통한 흡열 및 발열곡선 분석, solid fat index와 융점 측정을 통해 특성을 알아보고자 하였다. 위치별 지방산 조성 분석 결과 I, II, III은 sn-2 위치에 palmitic acid와 stearic acid의 합이 4.9~6.5 area%로 나타나 주로 대칭형 TAG로 이루어졌고, IV와 V는 41.9~43.9 area%로 나타나 주로 비대칭형 TAG로 구성되어 있는 것으로 확인되었다. 한편 in vitro digestion을 진행하여 분별물간의 가수분해율(%)을 비교한 결과, 반응시간 120분에서는 V만 다른 분별물에 비해 약 40% 정도 소화가 되지 않았으며, V의 융점이 $49^{\circ}C$로 반응온도($37^{\circ}C$)보다 높았다. 초기 반응시간(15분)에서는 I,II>IV>III>V 순으로 소화가 되지 않았으며, 각 분별물에서 ${\bigcirc}{\bigcirc}{\bigcirc}$와 POS/PSO의 가수분해율(%)을 비교해 본 결과 TAG 간의 가수분해율 차이가 없는 것으로 나타났다. 한편 III과 IV를 비교해 보았을 때, IV가 III에 비해 두 개의 포화지방산으로 구성된 TAG 함량이 약 40 area% 적지만 complete melting point가 III과 유사한 것으로 나타나 비대칭형 TAG가 대칭형 TAG에 비해 융점이 높다는 것을 알 수 있었다. 따라서 slip melting point가 in vitro digestion 결과에 가장 큰 영향을 미치며, 융점은 총지방산 조성에서의 포화지방산 함량이 높을수록, 두 개의 포화지방산으로 구성된 TAG의 함량이 높을수록, 비대칭형 TAG로 이루어질수록 높아짐을 알 수 있었다.