• 한국물환경학회지
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• 제29권3호
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• pp.409-419
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• 2013

In this study, the analytical method for 27 residual pharmaceuticals in raw water was developed. Online sample preconcentration/extraction and analysis with high resolution Orbitrap mass spectrometry (LC-ESI/Orbitrap MS) were performed. The calibration curves showed good linearities (above $r^2$ = 0.998) in the range of 5 ~ 1,000 ng/L. The method detection limit and the limit of quantification were 1.1 ~ 10.0 ng/L and 3.4 ~ 31.7 ng/L, respectively. Recoveries of the target compounds were between 70.1% and 115.8% (except cefadroxil, cefradine, vancomycin, and iopromide (50.2 ~ 67.0%)). The optimized analytical method can be useful to determine the residual pharmaceuticals in raw water.

• 한국터널지하공간학회 논문집
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• 제13권6호
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• pp.463-499
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• 2011

지중에 건설되는 터널은 대부분 지하수위 하부에 위치하므로 지하수 처리문제는 터널의 장기운영에 있어 매우 중요하다. 배수형 터널의 경우 수리기능이 원활하면 라이닝에 수압이 작용하지 않으나 장기 운영으로 인해 배수시스템의 열화가 진행되면서 라이닝 배면에 잔류수압이 작용할 수 있다. 본 연구에서는 배수재 및 배수공 폐색 조건에 따른 터널에 작용하는 수압분포를 ICFEP프로그램을 활용하여 수치해석적으로 고찰하고 현재 적용중인 잔류수압과의 비교 분석을 통해 라이닝에 작용하는 합리적인 잔류수압 적용 방안을 검토하였다.

• Journal of Welding and Joining
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• 제19권3호
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• pp.285-291
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• 2001

Large steel water pipes are joined prevalently by the bell end method, and are welded both at inside and outside of lapped parts. In practice, welded joints of water pipes are very critical, because in most cases failure of pipes causing leakage occurs at the welded joint. Therefore some methods have been developed to ensure the soundness of welded joints of water pipes, like leakage tests and nondestructive tests (NDTs). But one of the major characteristics that affects the soundness of welded Joints is the stress distribution caused by welding and external forces. Some studies have been carried out on the residual stress of steel water popes, but complex stress distributions by welding and external forces are rarely studied. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Also, stress values are measured from real steel water pipes by the hole-drilling methods, and compared with predicted ones. The influence of some typical post weld treatments on residual stress distribution was also investigated by residual stress measurements.

• 상하수도학회지
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• 제22권2호
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• pp.227-232
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• 2008

The masking effect of chlorine on algae-related taste and odor(T&O) compounds has long been an important issue for water suppliers. In this study, masking experiments with chlorine were performed on two kinds of treated water and one of raw water. After adding chlorine(0 to 0.8 mg/L) to water samples, odor intensity was evaluated by a newly developed sensory method(2-out-of-5 odor test) for three days along with the measurement of residual chlorine concentration. Even though the relationship between the residual chlorine concentration and odor reported by the sensory analysts was not always coincident, it was proved that residual chlorine more than a certain concentration could completely mask both added geosmin and naturally occurring T&O compounds. For the sand-filtered water spiked with 10 ng/L of geosmin, 0.12-0.18 mg/L of residual chlorine was necessary to achieve complete masking. In the case of GAC-filtered water, 10 ng/L of spiked geosmin was completely masked by 0.15-0.1 mg/L of residual chlorine. Combined ozone and GAC was not enough to treat raw water spiked with 300 ng/L of geosmin. In this experiment, sensory analysts were able to detect earthy or musty odors from the treated water. From a masking experiment with raw water taken from the Daechung Reservoir, it was found that fishy odor was more difficult to mask with chlorine than earthy odor. As the chlorine residual declined, the analysts began to notice the original odor and the fishy odor was noticed earlier than the earthy odor.

• 한국환경보건학회지
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• 제19권2호
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• pp.1-9
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• 1993

In public water supply systems, Alum and/or PAC being used as a coagulant. It is well known that their use increased frequently the concentration of residual aluminum in filtered water upon operating conditions. This study was conducted to find the optimum conditions that both the concentration of residual aluminum and turbidity are minimized by changing such factors as pH, temperature, alum dosage, mixing rate, alkalinity and hardness. The results can be summarized as follows: The pH values for the minimum concentration of residual aluminum and turbidity as a given experimental condition were found at pH 6 and pH 7 respectively, the apparent clarity was best at pH 8. The floc settling rate was the greatest at pH 6.5, but the turbidity was high at the same condition. The more alum dosage, the higher the concentration of residual aluminum. However the alum dosage less than 15 mg/l tend to decrease in turbidity. Restabilization and enmeshment occurred near 15 mg/l and 20 mg/l of alum dose respectively. With the increase of mixing rate (rapid and slow), the concentration of residual aluminum and turbidity are increased and the same trend was found in increment of mixing time. At low water temperature, the concentration of residual aluminum was decreased, but turbidity was increased. It was confirmed that alkalinity had an effect on the coagulation efficiency, but hardness did not.

• 상하수도학회지
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• 제23권4호
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• pp.499-505
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• 2009

Many other countries have investigated the residual sludge treatment process to save the existing water resource and produce the high suspended solid concentration sludge. There are various methods for concentrating residual sludge, but the membrane system has received the most interest for its efficiency. The objective of this study was to evaluate the application of membrane filtration system for the residual sludge treatment. The experiment equipment was composed of Lab scale Crossflow tubular membrane filtration system. Generally, crossflow operation mode demands high electric cost mainly for the pump energy. So to cut off electric cost, very low Crossflow velocity was used in this experiment. Results confirmed that suspended solid concentration of residual sludge could be concentrated to 57,000mg/L in low Crossflow velocity tubular membrane system,. This concentration can be directly injected into the dehydrator. Based on the results, we know that the Crossflow tubular membrane system should be replaced conventional residual sludge treatment system.

• 상하수도학회지
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• 제14권1호
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• pp.108-116
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• 2000

Chlorine is widely used as a disinfectant in drinking-water systems throughout the world. Chlorine residual was used as an indicator for prediction of water quality in water distribution systems. The variation of chlorine residual in drinking water distribution systems of Suwon city was simulated using EPANET. EPANET is a computerized simulation model which predicts the dynamic hydraulic and water quality behavior within a water distribution system operating over an extended time period. Sampling and analysis were performed to calibrated the computer model in 1999 (Aug. Summer). Water quality variables used in simulations are temperature, roughness coefficient, pipe diameter, pipe length, water demand, velocity and so on. Extended water residence time affected water quality due to the extended reaction time in some areas. All area showed the higher concentration of chlorine residual than 0.2mg/l(standard). So it can be concluded that any area in Suwon city is not in biological regrowth problem. Rechlorination turned out to be an useful method for uniform concentration of free chlorine residual in distribution system. The cost of disinfectant could be saved remarkably by cutting down the initial chlorine concentration to the level which guarantees minimum concentration (0.2mg/l) throughout the distribution system.

• 한국수자원학회논문집
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• 제55권spc1호
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• pp.1197-1210
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• 2022

최근 국내에서는 관로 노후화 및 다양한 수질사고 발생으로 인해 상수도 분야에 대한 관심이 급증함에 따라, 상수도 서비스에 대한 이용자들의 수질민원 또한 증가하고 있다. 수질민원의 경우 실제 수질오염뿐만 아니라 소독을 위한 잔류염소농도에 대한 불편을 포함하고 있으며, 따라서 사용자에게 공급되는 잔류염소농도를 균등하게 유지하기 위해 재염소 처리와 같은 다양한 노력이 시도되고 있다. 본 연구에서는 상수관망 내 잔류염소농도 모의를 위해 적용 대상지역의 수질반응계수를 추정하였으며, 수질기준을 만족시키는 동시에 잔류염소농도 균등화를 고려하기 위한 염소 투입 및 재투입 최적화 방법을 제안하였다. 제안된 방법은 국내 대규모 지방상수도를 대상으로 적용하였으며, 격자탐색법을 통해 다양한 염소 투입/재투입 계획을 비교 분석하고, 공급 잔류염소농도의 적합성 및 균등성을 중심으로 최적화한 결과를 제시하였다.

• 한국방재안전학회논문집
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• 제9권2호
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• pp.63-75
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• 2016

안전한 수돗물 공급을 위해 정수처리장부터 최종 단계인 수도꼭지까지 일정 수준 이상의 잔류염소농도가 유지되어야 한다. 하지만 국내 문헌에 따르면 상수공급의 전체 과정 중에 30-60%의 잔류염소가 소실되고, 이에 대한 주요 원인으로 정수처리 과정에서 염소 사용량 감소 추세, 급수배관 내에서 염소분해 손실, 여름철의 높은 온도에 의한 잔류염소 분해 속도 증가, 급수배관의 노후화에 따른 잔류염소 손실, 저수조 내 저장 시 잔류염소 감소 발생 등이 파악되었다. 이러한 이유로 저수조를 거치는 급수 방식의 경우 최종 수도꼭지의 잔류염소 농도가 기준치보다 낮아질 개연성이 높고, 용량과 체류시간을 단순히 고려하는 기존의 저수조 설계 방식으로 인해서 수돗물 공급의 안전성에 대한 우려가 존재한다. 이의 개선 방안 도출을 위해서 본 연구에서는 저수조 내 잔류염소 감소에 관여하는 주요 기작들인 수체 내 잔류염소 분해, 벽체 표면 흡착, 그리고 증발에 의한 물질전달을 수학적으로 묘사하는 공식들과 계수 값들을 문헌을 통해서 획득하고, 일반적 저수조 조건에서 모델 시뮬레이션을 수행하였다. 그 결과 저수조에 유입되는 수돗물 내 유기물 농도, 수돗물이 저수조에 유입되는 수리학적조건(난류 정도), 그리고 저수조 벽체 표면 재질의 흡착능 등이 저수조 내 잔류염소 감소에 주요 영향 인자들임을 알 수 있었다. 본 연구에서 획득된 결과들은 잔류염소 감소를 최소화하여 안전한 수돗물 공급을 가능하게 하는 새로운 저수조 설계기법이나 기술 개발에 유용하게 활용될 것이다.

• 한국물환경학회지
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• 제27권3호
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• pp.334-341
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• 2011

The free residual chlorine of tap water samples, collected from 266 faucets on the water pipe network in Daegu City, was between 0.1 and 0.79 mg/L. On microorganic tests, general bacteria and the coliform goup were not detected and thus the tap water was turned out to be fit to drink. In particular, samples of which free residual chlorine was 0.1 mg/L and over were cultured in R2A agar media at $25^{\circ}C$ for 7 days, and as a result heterotrophic bacteria were detected in 65.9% of samples; (1). The closer tap water got to the faucet from the stilling basin, the lower residual chlorine concentration became but the more the bacterial count became. And, more bacteria were detected in the R2A agar medium than in the PCA medium. (2). In the case of separated strains, most colonies were reddish or yellowish. 16S rRNA sequence was identified as Methylobacterium sp. and Williamsia sp., and yellow strain was identified as Sphingomonas sp., Sphingobium sp., Novosphingobium sp., Blastomonas sp., Rhodococcus sp. and Microbacterium sp. White strain was identified as Staphylococcus sp. (3). Sterilized tap water in polyethylene bottles was inoculated with separated strain and was left as it was for 2 months. As a result, bio-film was observed in tap water inoculated with Methylobacterium sp. and Sphingomonas sp. It was found that heterotrophic bacteria increased when free residual chlorine was removed from tap water in the water pipe network. Thus, there is a need to determine a base value for heterotrophic bacteria in order to check the cleanliness of tap water in the water pipe network.