• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.170-174
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• 2004

Most of thin film composite reverse osmosis membranes include amide linkages, which are susceptible to chlorine attack resulting in N-chloro derivatives. This study examined a new method based on post-treatment of reverse osmosis membrane with various silane derivatives to improve chlorine resistance. The silane derivatives contain one alkyl group and three alkoxy groups such as trifluoromethyltrimethoxysilane, 3-aminopropylmethoxydiethoxysilane and 3, 3, 3-trifluoropropyltrimethoxysilane. Compared to commercial membranes, silane derivatives coated membranes showed significantly enhanced chlorine durability.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.705-720
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• 2023

In South Korea, ongoing incidents related to drinking water quality have eroded consumer trust. Specifically, beyond quality incidents, there have been complaints about taste, odor, and other issues stemming from the presence of chlorine. To address this, water service operators are employing various management strategies from both temporal (scheduling) and spatial (rechlorination) perspectives to ensure uniform and safe distribution of chlorine residuals. In this study, we focus on the optimal monthly management of chlorine residuals, based on water distribution network analysis. Water quality reaction coefficients, including bulk fluid and wall reaction coefficients, were estimated through lab-scale tests and EPANET water quality simulations, respectively, accounting for temperature variations in a large-scale water distribution network. Utilizing these estimated coefficients, we examined the monthly variations in chlorine residual distribution under different chlorine injection conditions. The results indicate that the efficient concentration for chlorine injection, which satisfies the residual chlorine limit range, varies with temperature changes. Consequently, it is imperative to establish a specific and quantitative chlorine injection plan that considers the accurate spatial distribution of monthly chlorine residuals.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.4
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• pp.109-114
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• 2015

In this study, the effects of chlorine dioxide (D) bleaching conditions on the delignification of hemp bast fiber were elucidated. Chlorine dioxide bleaching was carried out through three stages (DED) and five stages (DEDED), respectively. Applied amounts of chlorine dioxide at $D_1$ and $D_2$ stages were varied to find the optimum bleaching condition. It was found that the optical properties of its handsheet as well as the delignification of hemp bast fiber increased as the concentration of chlorine dioxide at $D_1$ stage increased. It was also notable that the bleachability of the DEDED bleaching stages was slightly more effective than that of the DED bleaching stages. The burst index of the handsheets made with bleached hemp bast fiber was higher than that of the unbleached samples, but the burst index of these samples decreased as their delignification increased. These results indicated that the higher concentration of chlorine dioxide at $D_1$ stage was major factor to improve the bleaching efficiency of hemp bast fiber.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.531-539
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• 2015

Chlor-alkali industry is one of the largest electrochemical processes which annually producing 70 million tons of sodium hydroxide and chlorine from sodium chloride solution. $DSA^{(R)}$ (Dimensionally Stable Anodes) electrodes such as $RuO_2$ and $IrO_2$, which is popular in chlor-alkali process, have been investigated to improve the chlorine generation efficiency. Although DSA electrode has been developed with various researches, understanding of the chlorine evolution mechanism is essential to the development of highly efficient DSA electrode. In this review paper, chlorine generation mechanisms are summarized and that of key factors are identified to systematically understand the chlorine generation mechanism. Rate determining step, effect of pH, reaction intermediate, and electrode crystal structure were intensively overviewed as key factors of the chlorine mechanism.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.5
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• pp.601-607
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• 2007

In order to maintain constant residual chlorine in sedimentation basin, It is necessary to develop real time prediction model of residual chlorine considering water treatment plant data such as water qualities, weather, and plant operation conditions. Based on the operation data acquired from K water treatment plant, prediction models of residual chlorine in sediment basin were accomplished. The input parameters applied in the models were water temperature, turbidity, pH, conductivity, flow rate, alkalinity and pre-chlorination dosage. The multiple regression models were established with linear and non-linear model with 5,448 data set. The corelation coefficient (R) for the linear and non-linear model were 0.39 and 0.374, respectively. It shows low correlation coefficient, that is, these multiple regression models can not represent the residual chlorine with the input parameters which varies independently with time changes related to weather condition. Artificial neural network models are applied with three different conditions. Input parameters are consisted of water quality data observed in water treatment process based on the structure of auto-regressive model type, considering a time lag. The artificial neural network models have better ability to predict residual chlorine at sediment basin than conventional linear and nonlinear multi-regression models. The determination coefficients of each model in verification process were shown as 0.742, 0.754, and 0.869, respectively. Consequently, comparing the results of each model, neural network can simulate the residual chlorine in sedimentation basin better than mathematical regression models in terms of prediction performance. This results are expected to contribute into automation control of water treatment processes.

• Korean journal of food and cookery science
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• v.21 no.5
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• pp.703-708
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• 2005

The purposes of this study were to establish washing conditions for vegetable salad to reduce the microbial hazard by using sodium hypochlorite solution and eventually to implement HACCP for salad processing. By using the salad production line of Shinkeum Co. located in Gwacheon, Gyunggi-do, salad samples were washed under several washing conditions (chlorine dip period, chlorine concentration, rinse time, etc.) to determine the most effective conditions. The original washing line consisted of 3 baths (100 ppm chlorine water dip, water rinse, and water rinse), each with a capacity of 100 L of tap water and 5 kg of salad. First, the salad samples were washed with 100 ppm of sodium hypochlorite solution for various dip times (3, 6, 9, 12 min); however, only a 1 log- or less-reduction in total microbial counts was achieved in all groups and the time of chlorine water dip was not a significant factor in reducing the microbial hazard. When another water bath was added before the chlorine water dip (4-bath washing), a 2 log-reduction in total microbial counts was achieved. This result suggested the importance of pre-dipping salad materials in water before chlorine treatment to reduce the organic load on the surface of the vegetables. Coliforms were not detected at all after washing. As the concentration of chlorine $(50{\sim}150\;ppm)$ and rinse time $(0.5{\sim}2\;min)$ increased, greater microbial reduction was achieved; however, physical damage of the salad was observed. Finally, the optimum washing conditions for salad were determined as 3 min-water dip, 3 min-chlorine (100 ppm) dip, 2 min-rinse, and 2 min-rinse.

• Journal of Korean Society on Water Environment
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• v.33 no.4
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• pp.487-493
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• 2017

This study was conducted to propose measures of water quality management as the water criteria for waterscape facilities which have been highlighted as alternatives to wading pools in summer season was legislated. The number of public waterscape facilities has reached 290 sites in Gyeounggi province and 971 sites in South Korea in 2017. The water tank capacity of 80.3 % public waterscape facilities was less than $100m^3$. Facilities with disinfection system were only 6.5 % and facilities with filtration function were also very low at 6.9 %. Most of the waterscape facilities, about 93%, are expected to be vulnerable to complying with revised water quality criteria because they have to be disinfected by handling. Chlorine disinfectants, which are more persistent than ozone or ultraviolet sterilization methods, are more preferred. However, care should be taken when adding disinfectans because hypochlorous acid, which is an effective component of chlorine disinfectant, remains after the disinfection, but it is easily decomposed with time. For this study, ${\bigcirc}{\bigcirc}$ park floor fountain with a capacity of $63m^3$ was selected and the amount of free residual chlorine concentration was measured by injecting a certain amount of chlorine bleach. As a result, it took 5 hours to decrease from the water quality standard of 4 mg/L to 0.04 mg/L. If the waterscape facility is operated for 7 to 8 hours, the chlorine bleach should be re-injected after 5 hours. In addition, the problem of pH increase due to the input of chlorine disinfectant is expected, and the neutralization method using vinegar was proposed.

• Journal of environmental and Sanitary engineering
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• v.6 no.2
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• pp.33-47
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• 1991

1. Water supply treatment plants personnel could not test the water quality control, because most of them rely on the provincial health laboratories about water quality rely rant test. However, in future, plants have to been provided the facilities and equipment of water quality laboratory. 2. Chlorination methods are 89.5% of liquid chlorine and 10.5% of solid chlorine, and the cost per 1 $\m^{3}$ of chlorination is about 1.30 won which chlorination cost is very cheap as 1/142 of drinking water production cost. Input method of chlorine is 35% of automatic method, 56% of semi-automatic, and 9% of other methods, and this is no problem 3. Residual effects of chlorination, in the case of distilled water as a standardized material and 0.2 ppm of seperated residual chlorine, were continued 32 hours in $0^{\circ}C$, and 25 hour in $20^{\circ}C$, of water temperature and in the case of 0.4 ppm of seperated residual chlorine were continued 47 hours in $0^{\circ}C$ and 23 hours in $20^{\circ}C$. 4. In the case of 4 ppm of seperated residual chlorine, residual effects were continued 23 hours in $5^{\circ}C$, 90 hours in $10^{\circ}C$, 78 hours in $15^{\circ}C$, and 60 hours in $20^{\circ}C$ : by the temper; lure of water, continuing residual effects of chlorination are different, so we have to car for the warm season chlorination in the hider temperature. 5. Chlorination effects of drinking waters in the case of 0.4 ppm of seperated residual chlorine were continued 237 hours in $22^{\circ}C$ water : and in the case of rechlorination as 4 ppm of residual chlorine, continued 71 hours in $22^{\circ}C$ water.

• Food Quality and Culture
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• v.3 no.1
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• pp.34-39
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• 2009

This study assessed the efficacy of aqueous chlorine dioxide ($ClO_2$) and commercial chlorine sanitizer in terms of its ability to eliminate Listeria monocytogenes, Salmonella Typhimurium, and Escherichia coli O157:H7 on radish sprouts (Raphanus sativus L.). Radish sprouts were inoculated with a cocktail containing one each of three strains of three different foodborne pathogens, then treated with distilled water (control) or chemical sanitizers (100 ppm commercial chlorine, and 50, 100, 200 ppm $C1O_2$) for 1, 5, and 10 min at room temperature ($22{\pm}2^{\circ}C$). Populations of S. Typhimurium, E. coli O157:H7 and L. monocytogenes were counted at 4.64, 6.05, and 4.29 log CFU/g, respectively, after inoculation. Treatment with water did not significantly reduce the levels of any of the three foodborne pathogens. The levels of all three pathogens were reduced by treatment with chemical sanitizers; however, the observed levels of reduction of E. coli O157:H7 and L. monocytogenes were not significant as compared with the controls. The levels of the three pathogens were reduced most profoundly when treated for 10 min with 200 ppm of $C1O_2$, and the reduction levels of S. Typhimurium, E. coli O157:H7, and L. monocytogenes were 1.17, 1.63, and 0.96 log CFU/g, respectively. When chemically injured cells were investigated using SPRAB for E. coli O157 :H7 and by selective overlay methods for S. Typhimurium and L. monocytogenes, respectively, it was noted that commercial chlorine sanitizer generated more numbers of injured pathogens than did $C1O_2$. These data indicate that $C1O_2$ treatment may prove useful in reducing the numbers of pathogenic bacteria in radish sprouts.

• Korean Journal of Food Science and Technology
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• v.36 no.3
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• pp.514-517
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• 2004

O157:H7, Salmonella typhimurium, Listeria monocytogenes were treated with aqueous chlorine dioxide to elucidate effect of aqueous chlorine dioxide treatment on major food-borne pathogenic bacteria. Survival plot of E.coli O157:H7 at 5 ppm chlorine dioxide showed typical first-order rate. After 5 min of treatment, cell number decreased by 1.5 log cycle. Survival plot slope gave D value of 3.37 min. S. typhimurium and L. monocytogenes showed biphasic curve. Aqueous chlorine dioxide treatment on S. typhimurium and L. monocytogenes resulted in bactericidal effect for 5 min, and thereafter no effect was observed under experimental conditions of this study. These results suggest concentration of chlorine dioxide is more important than treatment time, and 5 ppm chlorine dioxide treatment is not sufficient for sanitizing fresh vegetables.