• 상하수도학회지
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• 제32권6호
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• pp.535-550
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• 2018

Total organic carbon (TOC) will replace chemical oxygen demand ($COD_{Mn}$) as an effluent water quality standard in public sewage treatment works (PSTWs) from 2021 in Korea. To ensure effective control of TOC in the effluent, investigation was carried out into TOC levels and sewage treatment operation factors in five target PSTWs using anaerobic-anoxic-aerobic ($A_2O$) processes, media, membrane, and sequencing batch reactor (SBR) technologies. TOC removal efficiencies appeared to be 93-96% on average. As a fraction of TOC, biodegradable dissolved organic carbon (BDOC) was reduced from 64% in the influent to 9% in the effluent in these PSTWs. During the investigation, biological treatment processes were applied flexibly for operation factors such as HRT, SRT, MLSS, F/M ratios and BOD volume loads, based on the influent characteristics and design conditions. As a result, we suggest efficient operating conditions in PSTWs by evaluating relationships between TOC removal and operation factors.

• 한국물환경학회지
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• 제36권6호
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• pp.535-545
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• 2020

This study aims to conserve and monitor energy use in public sewage treatment plants by utilizing data from the SCADA system and by controlling the aeration rate required for maintaining effluent water quality. Power consumption in the sewage treatment process was predicted using the equipment's uptime, efficiency, and inherent power consumption. The predicted energy consumption was calibrated by measured data. Additionally, energy efficiency indicators were proposed based on statistical data for energy use, capacity, and effluent quality. In one case study, a sewage treatment plant operated via the SBR process used ~30% of energy consumed in maintaining the bioreactors and treated water tanks (included decanting pump and cleaning systems). Energy consumption analysis with the K-ECO Tool-kit was conducted for unit processing. The results showed that about 58.7% of total energy consumed was used in the preliminary and biological treatment rotating equipment such as the blower and pump. In addition, the energy consumption rate was higher to the order of 19.2% in the phosphorus removal process, 16.0% during sludge treatment, and 6.1% during disinfection and discharge. In terms of equipment energy usage, feeding and decanting pumps accounted for 40% of total energy consumed following 27% for blowers. By controlling the aeration rate based on the proposed feedback control system, the DO concentration was reduced by 56% compared pre-controls and the aeration amount decreased by 28%. The overall power consumption of the plant was reduced by 6% via aeration control.

• 한국수처리학회지
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• 제26권6호
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• pp.53-59
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• 2018

Water pollution is drastically increasing day by day, because of the enhancement in use of livestock, urban sewage detergents and fertilizers. Moreover increase in concentration of phosphorous and nitrogen contained in sewage, leads to green tide problem in the rivers and causes marine pollution. For this problem to solve, several technologies are being researched and developed. Among them, this experiment is a study on Bench-scale STP based on internationally certified sewage treatment equipment by MEPC. 227(64) of IMO. The purpose of this study is to compare the biological treatment efficiency of phosphorus of Bench-scale STP. The ratio of C : N : P was set to 10 : 5 : 3 and 10 : 3 : 1 as the operating conditions. And the operation cycle was set to anoxic(mixed) 70 min - aeration 50 min (70-50), anoxic(mixed) 90 min - aeration 60 min (90-60). As a result, the phosphorous treatment efficiency was 88% at average, and the treatment efficiency was steady at 90-60 better than 70-50. The efficiency of the bench-scale STP has been verified through this experiment and additional experiments are required to derive the optimal operating conditions.

• Journal of Korean Neurosurgical Society
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• 제65권4호
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• pp.572-581
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• 2022

Objective : Compared to microscopes, exoscopes have advantages in field-depth, ergonomics, and educational value. Exoscopes are especially well-poised for adaptation into fluorescence-guided surgery (FGS) due to their excitation source, light path, and image processing capabilities. We evaluated the feasibility of near-infrared FGS using a 3-dimensional (3D), 4 K exoscope with near-infrared fluorescence imaging capability. We then compared it to the most sensitive, commercially-available near-infrared exoscope system (3D and 960 p). In-vitro and intraoperative comparisons were performed. Methods : Serial dilutions of indocyanine-green (1-2000 ㎍/mL) were imaged with the 3D, 4 K Olympus Orbeye (system 1) and the 3D, 960 p VisionSense Iridium (system 2). Near-infrared sensitivity was calculated using signal-to-background ratios (SBRs). In addition, three patients with brain tumors were administered indocyanine-green and imaged with system 1, with two also imaged with system 2 for comparison. Results : Systems 1 and 2 detected near-infrared fluorescence from indocyanine green concentrations of >250 ㎍/L and >31.3 ㎍/L, respectively. Intraoperatively, system 1 visualized strong near-infrared fluorescence from two, strongly gadolinium-enhancing meningiomas (SBR=2.4, 1.7). The high-resolution, bright images were sufficient for the surgeon to appreciate the underlying anatomy in the near-infrared mode. However, system 1 was not able to visualize fluorescence from a weakly-enhancing intraparenchymal metastasis. In contrast, system 2 successfully visualized both the meningioma and the metastasis but lacked high resolution stereopsis. Conclusion : Three-dimensional exoscope systems provide an alternative visualization platform for both standard microsurgery and near-infrared fluorescent guided surgery. However, when tumor fluorescence is weak (i.e., low fluorophore uptake, deep tumors), highly sensitive near-infrared visualization systems may be required.

• Korean Chemical Engineering Research
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• 제53권6호
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• pp.783-791
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• 2015

바이오매스 가스화 공정을 위하여 내경이 0.1 m이고 높이가 1.2 m인 유동층 반응기에서 수증기 및 촉매의 첨가가 프로듀서가스(Producer gas)에 미치는 영향을 파악하였다. 가스화 장치는 유동층 반응기, 연료공급 장치, 사이클론, 2개의 냉각기, 수증기 발생장치 및 가스분석기로 구성하였다. 층물질 및 촉매물질로 평균입자크기 $380{\mu}m$의 비구형 silica sand 와 평균입자 $356{\mu}m$ 크기의 소성된 백운석을 사용하였다. 사용된 바이오매스는 국산 우드펠릿(Korea woody pellet) 및 동남아 팜 부산물인 EFB(empty fruit bunch)를 펠릿 형태로 가공하여 사용하였다. 실험 고정 변수로는 연료공급량 50 g/min(EFB), 38 g/min(KWP) 반응 온도 $800^{\circ}C$, ER(equivalence ratio) 0.25로 설정하였다. 조업 변수로 촉매인 소성된 백운석을 층물질 0~100 wt%의 혼합비로 사용하였다. 가스화매체로 공기 또는 Air-Steam을 사용하였다. 이때 수증기 첨가량은 SBR(steam to biomass ratio) 기준 0.3으로 하였다. 생성된 가스의 조성, 타르(Tar) 및 저위발열량을 측정하였다. 실험의 결과로 소성된 백운석은 모든 실험조건에서 프로듀서가스 타르의 함량을 감소시키며 최대 67.3 wt%의 감소율을 보였다. 저위발열량은 공기가스화에서 소성된 백운석 첨가량이 증가할수록 감소하였다. 하지만 Air-steam 가스화에서 저위발열량은 변화가 적거나 오히려 소폭 증가한 경향을 보였다.

• Journal of Microbiology and Biotechnology
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• 제11권6호
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• pp.994-1001
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• 2001

An easier way of understanding the BNR system was proposed from the study on substrate, nutrient removal tendency, microbial community and its metabolic function by applying the municipal settled sewage. During the anaerobic period, the phosphorus release rate per VFACOD we varied depending on the phosphorus content in the sludge. When the phosphorus content in the sludge was $6\%$ VSS, according to influent VFACOD, the phosphorus release rate and PHA production were $0.35 gPO_4P/gVFACOD$ and 1.0 gPHA/gVFACOD, respectively. The $NO_3N$ requirement for the phosphorus uptake as an electron acceptor was about $0.5 gNO_3N/gPO_4P_{uptake}$ based on the proposed equation with PHA, biomass, production, and the concentration of phosphorus release/uptake. Bacterial-community analysis of the sludge, as determined by FISH and 16SrDNA characterization FISH, revealed that the beta-subclass proteobacteria were the most abundant group ($27.9\%$ of the proteobacteria-specific probe EUB338), and it was likely that representative of the beta-subclass played key roles in activated sludge. The next dominant group found was the gamma-protebacteria ($15.4\%$ of probe EUB338). 16S rDNA clone library analysis showed that the members of${\beta}$- and ${\gamma}$-proteobacteria were also the most abundant groups, and $21.5\%$ (PN2 and PN4) and $15.4\%$ (PN1 and PN5) of total clones were the genera of denitrifying bacteria and PAO, respectively. Prediction of the microbial community composition was made with phosphorus content (Pv, $\%$ P/VSS) in wasted sludge and profiles of COD, PHA, $PO_4P,\;and\;NO_3N$ in an anaerobic-anoxic SBR unit. Generally, the predicted microbial composition based upon metabolic function, i.e., as measured by stoichiometry, is fairly similar to that measure by the unculturable dependent method. In this study, a proposal was made on he microbial community composition that was more easily approached to analyze the reactor behavior.

• Journal of Animal Science and Technology
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• 제49권2호
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• pp.279-286
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• 2007

반응물을 연속적으로 내부 순환시키는 생물막 연속회분식모래여과 공정을 고안하고 외부 탄소원이 전혀 사용되지 않는 조건하에서의 돈사폐수 처리특성을 평가하였다. 수직형과 경사형 모래여과조에서의 NOx-N 부하량에 따른 탈질율은 각각 19%와 3.8%로 수직형에서 5배 정도 높은 효율을 보임에 따라 수직형태의 모래여과조를 생물막 연속회분식 공정과 연계하여 운전하였다. 처리공정을 HRT 15일, 내부순환율 105L/hr.m3, 평균 암모니아성 질소 부하량 54g/m3.d 조건에서 운전하였을 때 STOC, NH4- N, TN의 처리효율은 각각 75%, 97%, 85%이었다. 생물막 연속회분식 반응조와 모래여과조간의 내부순환으로 TN의 제거효율이 약 14%증진되는 것으로 나타났으며 얻어진 질소제거효율 증진은 주로 모래여과조에서의 탈질에 의한 것으로 밝혀졌다. 또한 용해성 인의 경우 내부순환이 수행되지 않았을 시에는 유출수내 농도가 오히려 증가하였으나 내부순환시에는 약 57% 정도가 제거되는 것으로 나타남에 따라 반응물의 내부순환이 용해성 인의 제거효율 증진에도 기여함을 알 수 있었다. 시스템에서의 질소제거 양상을 분석해본 결과 최종 유출수내의 NH4-N은 부하량 60g/m3.d 수준에서 약 20mg/L 이하로 비교적 일정하였고 부하량이 100g/m3.d. 이상의 수준으로 상승함에도 80% 이상의 질소 제거효율을 보였다. 그러나 부하량 100g/m3.d 수준 이상에서부터 처리효율이 감소하는 것으로 나타나 외부탄소원이 전혀 사용되지 않는 운전조건에서의 질소의 적정 부하량은 약 100g/m3.d 정도인 것으로 판단되었다.

• 미생물학회지
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• 제53권3호
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• pp.200-207
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• 2017

SA-TSA 복합구를 이용해 폐활성슬러지로부터 VFAs를 생산하고, 이를 발효 기질로 이용해 PHA를 생산하기 위한 실험을 수행하였다. 30%의 SA-TSA 복합구를 처리하였을 때 폐활성슬러지의 가용화 효율이 가장 효과적으로 일어나서 약 3,900 mg/L의 SCOD값을 얻었으며, acetic acid, propionic acid, iso-butyric acid 및 butyric acid를 주성분으로 하는 2,961 mg/L 농도의 VFAs를 얻었다. VFAs를 외부탄소원으로 이용하는 SBR 공정을 통해 PHA를 생합성하는 미생물을 농화배양하는 실험을 수행하고 PCR-DGGE로 분석한 결과, 우점 미생물로 Vibrio spp.와 Corynebacterium glutamicum이 확인되었다. 폐활성슬러지로부터 얻은 VFAs를 탄소원으로 사용하여 농화된 혼합미생물배양체를 회분배양한 결과, 건체량의 25.9%에 달하는 PHB를 얻었다. 본 연구결과는 SA-TSA 복합구를 이용하여 폐활성슬러지로부터 VFAs를 얻음으로써 폐슬러지 감량화 효과를 얻고, 또 혼합미생물배양체를 이용하여 VFAs를 바이오폴리머로 전환함으로써 경제성을 확보할 수 있는 새로운 생물공정의 가능성을 보여준다.

• 한국산업보건학회지
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• 제19권4호
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• pp.321-327
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• 2009

1,3-butadiene is classified as suspected human carcinogen, group A2(American Conference of Governmental Industrial Hygienists, ACGIH). In Korea, 1,3-butadiene has been used as a raw material; monomer, homopolymer, polybutadiene latex, acrylonitrile-butadiene-styrene(ABS) and styrene-butadiene rubber(SBR), in the petrochemistry and precision chemistry industry. As petrochemistry industry in Korea has been developed, the potential exposure possibility of 1,3-butadiene to workers can be increased. Therefore the purpose of this study is to evaluate airborne 1,3-butadiene concentration and workers' exposure levels in the workplace using 1,3-butadiene. Air samples were collected with 4-tert-butyl catechol(TBC) charcoal tube(100 mg/50 mg) and were analyzed by gas chromatograph/flame ionization detector(GC/FID) according to the Choi's method(2002). Geometric mean (GM) and arithmetic mean (AM) of total 59 workers' exposure concentrations to airborne 1.3-butadiene were 0.042 ppm and 1.51 ppm, respectively. Although most samples were lower than 1ppm, 2 samples(21.5ppm and 33.1ppm as 8hr-TWA) were exceeded the Korean standard(2ppm) over 10 times at the repair process in synthetic rubber and resin manufacture industry. 14 samples(41%) of total 34 short-term air samples were exceeded the Korean standard(10ppm as STEL) of Ministry Labor. 1,3-butadiene concentration(GM) in the synthetic rubber and resin manufacture industry(7.87ppm) was significantly higher than that in the monomer manufacure industry (0.35ppm)(p<0.05). Also in the sampling and repair process, each GM(range) was 1.39ppm(N.D.-469.6ppm) and 7.85ppm(N.D.-410.2ppm). In conclusion, it depends on the industry and process, 1,3-butadiene can be exposed to workers as high concentration for short-term.

• 대한환경공학회지
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• 제30권12호
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• pp.1281-1286
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• 2008

하수처리과정에서 온실가스인 N$_2$O가 발생하는데, N$_2$O의 지구온난화 기여율은 CO$_2$의 310배에 달한다. 본 연구에서는 하수처리공정에 따라 온실가스 배출계수가 어떤 차이를 보이는지를 분석하기위해 운전 중인 4개의 하수처리공정을 대상으로 조사하였다. 배출계수 산정을 위한 시료채취는 Flux Chamber를 이용하였으며, N$_2$O 정량은 6 port gas sampling valve가 장착된 Agilent사의 GC로 분석하였으며, 검출기는 ECD를 사용하였다. 하수처리공정별 오염물질 유입 부하에 대한 N$_2$O 배출계수 산정결과 5-stage공정은 0.94 g-N$_2$O/kg-TN으로 가장 낮았으며, 다음으로 활성슬러지공정이 2.65 g-N$_2$O/kg-TN, Denipho공정이 9.30 g-N$_2$O/kg-TN, 그리고 SBR공정이 26.73 g-N$_2$O/kg-TN으로 가장 높게 나타났다. 하수처리에서 N$_2$O 배출량 감소를 위해서는 조사대상 시설 중 5-stage 공정이 가장 적절한 것으로 평가하였다.