• 상하수도학회지
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• 제23권3호
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• pp.331-337
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• 2009

Electrolysis produces hypochlorous acid by using a small quantity of NaCl as electrolyte. This process maximizes the stabilization of drinking water through the control of chlorine residual concentration. This study investigated free chlorine generation by an electrolytic method using $Ti/IrO_2$ and stainless steel. The generation of free chlorine was increased with increasing hydraulic retention time, voltage, chlorine ion concentration and the number of electrodes. However, the change of pH did not affect the generation of free chlorine. There was no significant difference on the behavior of chlorine concentration between electrolytic method and NaOCl injection. In this study, the concentration of free chlorine predicted model based on power functional model was developed various under conditions. Electrolysis free chlorine generation model can be effective tool in the estimation of free chlorine generation.

• 한국환경보건학회지
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• 제25권3호
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• pp.83-88
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• 1999

This study was carried out to examine the behavior of THM formation in water treated with chlorine dioxide where humic acid was used as THM precursor. THM was not detected in bromide-free water, but formed in water containing bromide. When 10 mg/l of chlorine dioxide was added to water containing 5 mg/l of humic acid and bromide respectively, 20.46 ${\mu}$g/l of THM was formed. It is postulated that chlorine dioxide oxidize bromide to hydrobromous acid, which subsequently reacted with humic acids similar to chlorine reaction. The formation of THM could be reduced at low pH. Among THM formed, CHBr$_3$ was the predominant species in the alkaline solution, while CHCl$_3$ in the acidic solution. A sample pretreated with chlorine dioxide for 24h before addition of chlorine showed a reduction of 75.1% in THM formation, compared with a sample not pretreated with chlorine dioxide and a sample treated by chlorine for 24h prior to addition of chlorine dioxide also showed a reduction of 37.8% in THM formation, compared with a sample not added with chlorine dioxide. It may explain that chlorine dioxide oxidizes directly a fraction of THM.

• 상하수도학회지
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• 제30권1호
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• pp.9-17
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• 2016

Disinfectant/oxidation process is a crucial process in water treatment for supplying safe drinking water. Chlorination is still widely used for water treatment area due to its effectiveness on microbial inactivation and economic feasibility. Recently, disinfection concern in marine environment is increasing, for example, movement of hazardous marine organism due to ballast water, marine environmental degradation due to power plant cooling water discharge, and increase of the amount of disinfectant in the offshore plant. It is needed to conduct the assessment of disinfectant behavior and the development of disinfectant prediction model in seawater. The appropriate prediction model for disinfectant behavior is not yet provided. The objective of the study is to develop chlorine decay model in seawater. Various model types were applied to develop the seawater chlorine decay model, such as first order decay model, EPA model, and two-phase model. The model simulation indicated that chlorine decay in seawater is influenced by both organic and inorganic matter in seawater. While inorganic matter has a negative correlation with the chlorine decay, organic matter has a positive correlation with the chlorine decay.

• 한국응용곤충학회지
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• 제54권3호
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• pp.151-158
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• 2015

이산화염소($ClO_2$) 훈증제는 살충효과를 나타낸다. 그러나 일부 곤충은 이산화염소에 대해 회피행동을 보여, 이 훈증제에 대한 방제효율을 크게 떨어뜨리고 있다. 본 연구는 이를 해결하기 위해 이산화염소 처리에 열처리를 추가하여 곤충의 이산화염소에 대한 회피행동을 줄여 살충효과를 극대화하는 전략을 세웠다. 이산화염소 훈증 처리는 거짓쌀도둑거저리(Tribolium castaneum)에 대해 살충효과를 주었으며, 시험 곤충이 노출된 조건에서 12 시간 처리할 때 유충에 대해서 383.67 ppm (153.63 - 955.78 ppm: 95% 신뢰구간), 성충에 대해서 397.75 ppm (354.46 - 446.13 ppm: 95% 신뢰구간)의 반수치사농도를 나타냈다. 그러나 먹이인 밀가루를 충분히 제공한 상태에서 이산화염소를 처리하면, 처리 약제에 반응하여 시험 곤충이 먹이 속으로 들어가는 회피행동을 보이면서 방제효과는 크게 낮아졌다. Y 튜브를 이용한 이 곤충의 먹이 선호성 행동을 분석한 결과 거짓쌀도둑거저리 성충은 이산화염소가 처리된 먹이를 회피하는 행동을 보였다. 그러나 촉각을 제거한 경우 이러한 회피행동은 둔화 되었다. 거짓쌀도둑거저리에 6 시간 동안 $46^{\circ}C$ 열처리를 하면 살충효과는 10% 이하로 낮지만, 처리된 성충들이 먹이 밖으로 나와 있는 것을 관찰하였다. 반면 400 ppm의 이산화염소를 단독으로 6 시간 처리한 결과 회피행동에 따라 전혀 살충효과를 보이지 않았다. 그러나 $46^{\circ}C$ 열처리와 400 ppm의 이산화염소를 병행하여 6 시간 처리한 결과 살충효과는 95%로 크게 증가하였다. 따라서 열처리는 거짓쌀도둑거저리의 이산화염소에 대한 회피행동을 억제하여 살충효과를 증가시켰다.

• 한국환경보건학회지
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• 제29권1호
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• pp.8-15
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• 2003

In this study, chlorine dose at water storage tank was predicted to meet the recommended guideline for free chlorine residual in drinking water distribution system, using EPANET which is a computer program that performs extended Period simulation of hydraulic and water quality behavior within pressurized pipe networks. The results may be summarized as follows. The decay of chlorine residual by season varied considerably in the following order; in summer ($25^{\circ}C$) > spring and fall (15$^{\circ}C$) > winter (5$^{\circ}C$). For re-chlorination at water storage tank by season, season-varying chlorine dose was required at its maximum of 1.00 mg/l in summer and minimum of 0.40 mg/l in winter as free chlorine residual. The decay of chlorine residual through out the networks increased with water age spent by a parcel of water in the network except for some points with low water demand. In conclusion, the season-varying chlorine dose as well as the monitoring of water quality parameters at the some points which showed high decay of chlorine residual may be necessary to deliver the safe drinking water.

• Environmental Analysis Health and Toxicology
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• 제13권3_4호
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• pp.77-85
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• 1998

It is very frequent that LAS meets the chlorine bleaches not only in the processes but also in the path from the sewages to the rivers. Therefore, it is not difficult to imagine that the harmful substances like DBPs are produced when LAs reacts with free chlorine. THMs are the major components of DBPs which are formed by reactions of organic substances with the chlorine oxidants. Among them, chloroform is the most noteworthy material. Since the major behavior observed was the formation of chloroform during reaction of LAS with free chlorine, the models were developed to grasp the tendency of chloroform formation depending on condition. According to these models, the effect of pH in the formation of chloroform is most grave.

• Corrosion Science and Technology
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• 제17권4호
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• pp.176-182
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• 2018

Corrosion of the Cu alloy with 10wt% Ni in stagnant seawater with residual free chlorine was investigated. Despite that fact that Cu alloys are widely used for seawater applications due to their stubborn resistance to chloride attack, not much is known as to how the residual free chlorine in seawater affects corrosion of Cu and its alloys. In this work, immersion tests were conducted in the presence of different levels of chlorine for 90-10 Cu-Ni samples, one of the most frequently used Cu alloys for seawater application, mostly in shipbuilding. The results revealed no evidence for accelerated corrosion of the Cu-Ni alloy even in the presence of 5 ppm residual chlorine in seawater, signifying that the Cu-Ni alloy can be more tolerant to residual chlorine that has been commonly cited by the shipbuilding industry. However, comparison of polarization behavior of the alloy samples in the presence of different electrolytes with different concentrations of residual chlorine suggests that higher concentration of chlorine could increase the corrosion rate of the Cu-Ni alloy. Furthermore, it is suggested that microorganisms in the seawater could increase the corrosion rate of the Cu-Ni alloy by encouraging exfoliation of the corrosion product off the metal surface.

• 한국환경보건학회지
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• 제23권2호
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• pp.106-114
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• 1997

When surfactants meet chlorine bleaches not only in the washing drums but also through the whole path from the stream to the river, it is not difficult to expect that they produce the harmful substances like DBPs. Furthermore considering wastewater that is contaminated by surfactants is used to discharge into drinking water sources via sewer system, it also can be imagined that residual surfactants would contribute to the some extent of DBPs' formation during chlorine disinfection in water treatment plants. Although the main behavior observed was the formation of chloroform during the reaction of LAS with free chlorine, the other manifest behaviors like the trends of pH, MBAS, free chlorine, the mole concentration of benzene ring and etc. were also investigated.

• 센서학회지
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• 제29권3호
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• pp.211-214
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• 2020

Chlorine dioxide is very effective gas for sterilization or disinfection (in manufacturing), and does not produce harmful by-products after use. However, if its concentration exceeds 10 %, it become explosive and cannot be compressed or stored. Therefore, it is necessary to measure its concentration. In this study, the concentration of chlorine dioxide with a high oxidizing strength was measured using a metal oxide sensor. The sensor was a commercially available TGS series from Figaro. The sensitivity of the sensor was inversely proportional to a low concentration of chlorine dioxide gas below 6 ppm and returned to the initial resistance at about 6 ppm. When the gas concentration reached multiples of 10 ppm, resistance of the sensor increased to several megaohms.

• 상하수도학회지
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• 제28권1호
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• pp.61-72
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• 2014

Study on effluent organic matter (EfOM) characteristic and removal efficiency is required, because EfOM is important in regard to the stability of effluents reuse, quality issues of artificial recharge and water conservation of aqueous system. UV technology is widely used in wastewater treatment. Many reports have been conducted on microbial disinfection and micro pollutant reduction with UV treatment. However, the study on EfOM with UV has limited because low/medium pressure UV lamp is not sufficient to affect refractory organics. The high intensity of pulsed UV would mineralize EfOM itself as well as change the characteristics of EfOM. Chlorine demand and DBPs formation is affected on the changed amounts and properties of EfOM. The objective of this study is to investigate the effect on EfOM, chlorine residual, and chlorinated DBPs formation with low pressure and pulsed UV treatment. The removal of organic matter through low pressure UV treatment is insignificant effect. Pulsed UV treatment effectively removes/transforms EfOM. As a result, the chlorine consumption is changed and chlorine DBPs formation is decreased. However, excessive UV treatment caused problems of increasing chlorine consumption and generating unknown by-products.