• Mycobiology
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• 제50권5호
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• pp.345-356
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• 2022

The fungal distribution, diversity, and load were analyzed in the geographically segregated island groundwater systems in Korea. A total of 79 fungal isolates were secured from seven islands and identified based on the internal transcribed spacer (ITS) sequences. They belonged to three phyla (Ascomycota, Basidiomycota, and Chlorophyta), five classes, sixteen orders, twenty-two families, and thirty-one genera. The dominant phylum was Ascomycota (91.1%), with most fungi belonging to the Cladosporium (21.5%), Aspergillus (15.2%), and Stachybotrys (8.9%) genera. Cladosporium showed higher dominance and diversity, being widely distributed throughout the geographically segregated groundwater systems. Based on the diversity indices, the genera richness (4.821) and diversity (2.550) were the highest in the groundwater system of the largest scale. As turbidity (0.064-0.462) increased, the overall fungal count increased and the residual chlorine (0.089-0.308) had low relevance compared with the total count and fungal diversity. Cladosporium showed normal mycelial growth in de-chlorinated sterilized samples. Overall, if turbidity increases under higher fungal diversity, bio-deterioration in groundwater-supplying facilities and public health problems could be intensified, regardless of chlorine treatment. In addition to fungal indicators and analyzing methods, physical hydrostatic treatment is necessary for monitoring and controlling fungal contamination.

• 대한환경공학회지
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• 제22권4호
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• pp.661-669
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• 2000

본 연구는 6개 관종으로 구성된 모의순환관로시스템에서 정수의 부식성을 조절하여 관로내의 부식을 저감시킬 목적으로 pH 및 알칼리도 조절 수질제어시스템을 운전하여 관로의 금속용출 저감 및 부식성 지수의 변화를 파악하고, 수질제어에 따른 다른 수질인자들 즉, 미생물, 잔류염소농도, 그리고 소독부산물(THMs) 및 이온류 등의 농도 변화를 평가하고자 하였다. 실험결과, pH 및 알칼리도 조절을 통한 수질제어시스템은 부식성 지수의 변화와 함께 금속의 용출율이 감소하였으며, 소독부산물(THMs)의 형성 및 미생물의 재성장에도 별다른 영향을 미치지 않는 것으로 나타나 수질제어에 따라 관 표면에 형성된 탄산칼슘 피막은 부식저감과 함께 관로내 수질의 안정화를 가져오는 것으로 판단된다. 따라서 pH 및 알칼리도 동시 조절을 통한 부식성 수질 제어시스템은 고형물의 침전 및 용출에 가장 큰 영향을 미치는 pH 및 TIC 등 수질인자들을 안정화시켜 전체적인 수돗물의 수질관리에 매우 효과적일 것으로 사료된다.

• 한국산학기술학회논문지
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• 제9권1호
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• pp.170-175
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• 2008

본 연구에서는 상수도관의 부식방지를 위해 관망 내부에서 탄산칼슘의 침전 및 용해 여부를 판단할 수 있는 지표인 CCPP를 산정할 수 있는 프로그램을 개발하였다. CCPP 산정은 9단계 절차를 통하여 이루어지며, 평형상태의 pH를 가정하고 결정 식의 왼쪽 항의 합과 오른 쪽 항의 합이 오차의 범위에서 유사한 값을 주도록 반복계산을 수행하고, 다음 단계에서 초기 및 평형상태의 알칼리도를 대입하여 CCPP를 구한다. 프로그램 개발은 계산을 위해 포트란 언어를, 결과 값을 그래프로 표현하여 쉽게 판단할 수 있도록 비쥬얼베이직 언어를 사용하였다. 개발된 프로그램을 적용하여 한강 수계 Y정수사업소의 수질을 평가한 결과, 탄산칼슘의 불포화 상태가 심한 수질로 판명되어 부식성이 높은 것으로 평가되었다.

• 대한환경공학회지
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• 제32권10호
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• pp.916-927
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• 2010

일반적으로 정수처리 공정에서 염소에 의한 소독공정은 수인성 질병을 억제하고 상수도관망에서 미생물의 재성장을 억제하는 목적으로 사용되고 있다. 그러나 염소소독은 수중의 유기물과 반응하여 소독부산물(Disinfection By-products; DBPs) 과 같은 발암성 물질을 생성함으로 적절한 염소 주입이 필요하고 최근에는 관말지역에서의 잔류염소 확보를 위해 상수관로 나 배수지 등에서 재염소를 실시하는 경향이 증가하고 있는 추세이다. 따라서 본 연구에서는 정수장에서 최적의 염소주입과 재염소 주입량을 산정하기 위하여 미국 EPA에서 개발한 EPANET 2.0을 사용하여 최적 염소 주입량을 산정하고 그 효과를 모의하였다. 대상지역 상수관로에 대한 수질을 모의하기 위하여 bottle test를 통해 수체감소계수($k_{bulk}$)를 도출하였으며, syster-matic analysis method를 이용하여 관벽감소계수($k_{wall}$)를 도출하였다. 배ㆍ급수계통에서의 수질을 정확히 예측하고자 유량과 체류시간 등을 고려한 수리해석 모델을 기초로 하여 상수도관망에서의 잔류염소 농도를 예측하고 염소주입 농도에 따른 소독부산물(DBPs)인 트리할로메탄(Trihalomethanes; THMs)의 생성변화를 실험을 통해 확인하였다. 수체감소계수($k_{bulk}$)를 도출한 결과 온도가 높을수록 초기에 빠른 감소를 보였으며, $25^{\circ}C$의 경우 25시간이 지난 이후에는 절반이상이 감소하였다. 대상지역에 재염소 주입시설을 도입할 경우 최적 재염소 주입량을 산정하였으며, 관망도상에서 경제적으로 유리한 지점을 선정할 수 있었다.

• Earthquakes and Structures
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• 제18권3호
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• pp.285-296
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• 2020

Dams are important structures for management of water supply for irrigation or drinking, flood control, and electricity generation. In seismic regions, the structural safety of concrete gravity dams is important due to the high potential of life and economic loss if they fail. Therefore, the seismic analysis of existing dams in seismically active regions is crucial for predicting responses of dams to ground motions. In this paper, earthquake response of concrete gravity dams is investigated using the finite element (FE) method. The FE model accounts for dam-water-foundation rock interaction by considering compressible water, flexible foundation effects, and absorptive reservoir bottom materials. Several uncertainties regarding structural attributes of the dam and external actions are considered to obtain the fragility curves of the dam-water-foundation rock system. The structural uncertainties are sampled using the Latin Hypercube Sampling method. The Pine Flat Dam in the Central Valley of Fresno County, California, is selected to demonstrate the methodology for several limit states. The fragility curves for base sliding, and excessive deformation limit states are obtained by performing non-linear time history analyses. Tensile cracking including the complex state of stress that occurs in dams was also considered. Normal, Log-Normal and Weibull distribution types are considered as possible fits for fragility curves. It was found that the effect of the minimum principal stress on tensile strength is insignificant. It is also found that the probability of failure of tensile cracking is higher than that for base sliding of the dam. Furthermore, the loss of reservoir control is unlikely for a moderate earthquake.

• 대한환경공학회지
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• 제39권4호
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• pp.208-213
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• 2017

본 연구에서는 국내 실정에 맞는 한국형 CWS 구축의 일환으로 국내 배 급수 시스템에서 오염 사고 발생가능성이 있는 무기 오염물질 네 종류(카드뮴, 크롬, 망간, 납)를 선정하고 batch 실험을 통해 각 오염물질의 수돗물에 주입 시 감지 가능한 "최소 반응 농도(minimum response concentration)"를 결정하고자 하였다. 무기 오염물질 네 종류에 대해 수질 인자들의 최소 반응 농도를 추적한 결과 카드뮴(수질기준 0.005 mg/L)에 대한 최소 반응 농도는 0.05~0.08 mg/L, 크롬(수질기준 0.05 mg/L)에 대한 최소 반응 농도는 0.03 mg/L, 망간(수질기준 0.05 mg/L)에 대한 최소 반응 농도는 0.005 mg/L, 그리고 납(수질기준 0.01 mg/L)에 대한 최소 반응 농도는 0.02~0.08 mg/L인 것으로 분석되었다.

• 상하수도학회지
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• 제32권3호
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• pp.211-220
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• 2018

The water containing soluble manganese may cause problems such as discolored water, unpleasant taste, fouling or scaling of pipes in water distribution system, and so on. Conventional water treatment processes using sand filtration or sedimentation after oxidation, however, cannot often meet manganese standard for drinking water. Two types of oxidants, potassium permanganate ($KMnO_4$) and sodium hypochlorite (NaOCl), were utilized at the same time for manganese oxidation, and then the precipitated manganese oxides were removed by low pressure membrane filtration in this study. In batch experiments, the multiple injection of both oxidants showed more effective manganese removal than did the single injection using either of them. Moreover, the deterioration of manganese removal at low temperature was less serious for the multiple injection than that for the single injection. Manganese removal by the continuous system of oxidation by multiple injection combined with membrane filtration was higher than those by batch experiments at the same oxidation conditions. In addition, less membrane fouling was observed for membrane filtration with oxidation during continuous membrane filtration than membrane filtration without oxidation. These results indicate that the oxidation by multiple injection coupled with membrane filtration was efficient and applicable to actual water treatment for manganese removal.

• Journal of Microbiology and Biotechnology
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• 제21권2호
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• pp.115-123
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• 2011

To investigate the effects of pipe materials on biofilm accumulation and water quality, an annular reactor with the sample coupons of four pipe materials (steel, copper, stainless steel, and polyvinyl chloride) was operated under hydraulic conditions similar to a real plumbing system for 15 months. The bacterial concentrations were substantially increased in the steel and copper reactors with progression of corrosion, whereas those in stainless steel (STS) and polyvinyl chloride (PVC) reactors were affected mainly by water temperature. The heterotrophic plate count (HPC) of biofilms was about 100 times higher on steel pipe than other pipes throughout the experiment, with the STS pipe showing the lowest bacterial number at the end of the operation. Analysis of the 16S rDNA sequences of 176 cultivated isolates revealed that 66.5% was Proteobacteria and the others included unclassified bacteria, Actinobacteria, and Bacilli. Regardless of the pipe materials, Sphingomonas was the predominant species in all biofilms. PCR-DGGE analysis showed that steel pipe exhibited the highest bacterial diversity among the metallic pipes, and the DGGE profile of biofilm on PVC showed three additional bands not detected from the profiles of the metallic materials. Environmental scanning electron microscopy showed that corrosion level and biofilm accumulation were the least in the STS coupon. These results suggest that the STS pipe is the best material for plumbing systems in terms of the microbiological aspects of water quality.

• 환경위생공학
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• 제14권1호
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• pp.11-16
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• 1999

This study was performed to investigate THMs formation by chloramination as a secondary disinfection in drinking water distribution system. As the $Cl_2/NH_3-N$ ratio increased from 1:1 to 4:1, the THMs concentration had actually no change in the breakpoint curve of pH 6, 7. At pH 8, THMs level was not augmented at between 1:1 and 5:1. In the $Cl_2/NH_3-N$ ratio of more than 5:1 and 6:1 respectively, THMs level was raised. Only the chloroform of THMs was insignificantly detected by both preformed chloramine and preammoniation applications, which was probably attributed to the stoichiometrically unstable equilibrium in the preparation of chloramine, whereas $CHCl_3$, $CHCl_2Br$ and $CHClBr_2$ of THMs were found in the application of free chlorine. However it turned out that the THMs levels by chloramine was incomparably inferior to that of free chlorine.

• 한국환경보건학회지
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• 제17권1호
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• pp.57-66
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• 1991

This study was carried out for 5 years between 1984 and 1986 and 1989 and 1990. This interviewers visited 292 households to evaluate the perception of the residents using .the. Simple Piped Water Supply (SPWS), and examined the pollution source surrounding 42 SPWS facilities and water quality by the chemical and microbiological method. The purpose of this study was to find out problems linked with SPWS and to investigate more efficient way of improvement in rural water supply. The results of the study are surmnarized as follows: 1) Approximately 55% of the sampled population have been served by simple piped water supply. 2) The drinking water was mostly taken from the springs in 16 sites and valley water in 26 sites. 3) Considering the type of distribution of the SPWS, there are 28 natural gravity systems and 14 pumping systems. 4) Out of the 180 SPWS in Chun Sung Area, 74% of the SPWS facilities were used more than ten years. In addition, 40% of residents expressed the need for repairs of old facilities. 5) 48% of the SPWS facilities are neighbored with pollution source. 6) 50% of the maintenance crews were not committed totheir job but instead, the facilities were operated by some residents or community leaders who were personally concerned about quality of the facilities. 7) About 85% of the residents answered that SPWS was convenient and helpful. 8) About 57% of the residents complaind that the amount of daily water supply is not adequate. 9) About 74% of the residents felt that the water quality is high for dringking water and therefore, 52% of the facilities were not properly chlorinated. But in contrast, the biochemical tests indicated that only 28% of the SPWS met the dringking water quality standards. 10) Maintenance cost per a household ranges form 500 to 2, 000Won (1 $ = 700 Won) a month. Most of the cost was to cover the power electric charge. For the effective maintenance and arrangement of the facilities, gorvermental financial support for the maintenance is strongly recommended.