• Journal of Korean Society of Water and Wastewater
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• v.14 no.2
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• pp.164-173
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• 2000

Fluoridation of drinking water to a level of about 0.8mg/l (below 1.5mg/l) for reducing the incidence of tooth decay is recommended. However, concerns about potential problems of unknown effects and overdosing hinders the fluoridation. This study describes the work performed to obtain information on the behavior of fluoride under various conditions in the process of water fluoridation. Effects of water treatment chemicals, water treatment unit, and water distribution on water fluoridation were investigated at both lab and an actual water treatment plant. Residual fluoride concentration was not affected by lime and chlorine dosage up to 20mg/l. Flocculation with PAC slightly decreased the residual fluoride concentration as PAC dosage increased. Average fluoride concentration of 0.87mg/l at an intake basin was decreased to 0.83mg/l by sedimentation, 0.81mg/l by dual media(sand+anthracite) filtration, and 0.79mg/l by granular activated carbon filtration in the water treatment plant.

• The Korean Journal of Food And Nutrition
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• v.30 no.3
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• pp.591-598
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• 2017

To prolong the shelf-life of strawberry, samples were treated with gel packs containing slow-released chlorine dioxide($ClO_2$) gas at 3~7 ppm for 6 days at room temperature. The weight loss and decay ratio as well as changes in pH, color and texture properties of the treated samples were investigated. The weight of the control and $ClO_2$ gas treated samples decreased slightly, but the weight of the control changed faster than those of the $ClO_2$ gas treated samples during the storage period. The decay ratio of control was higher than those of the $ClO_2$ gas treatments since 4 days of storage. The pH and acidity in the control and in the $ClO_2$ gas treated samples were no differences during storage period. The lightness of strawberry decreased during storage, but there was no difference in lightness among the treatments even when storage time was extended. The redness and yellowness of the control showed higher change than those of the $ClO_2$ gas treatments during 6 days. The firmness of the control changed more rapidly than those of the $ClO_2$ gas treatments during 6 days. Especially, the samples treated 3 and 5 ppm $ClO_2$ gas were the least changed. And the scores for appearance, firmness and overall acceptance control and 7 ppm $ClO_2$ gas treatment decreased more rapidly than those of 3 and 5 ppm treatment.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.4
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• pp.411-416
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• 2010

Interest in application of ultraviolet light technology for primary disinfection of potable water in drinking water treatment plants has increased significantly in recent years. The efficacy of disinfection processes in water purification systems is governed by several key factors, including reactor hydraulics, disinfectant chemistry, and microbial inactivation kinetics. The objective of this work was to develop a computational fluid dynamics(CFD) model to predict velocity fields, mass transport, chlorine decay, and microbial inactivation in a continuous flow reactor. In this paper, It describe the how to design optimal UV disinfection device for ground water, BWT and rainwater. Spring shape instrument silver coated located in inner side of disinfection chamber. It make lead the active flowing movement target water and maximize disinfection performance. To search the optimal design method, it was performed computer simulation with 3D-CFD discrete ordinates model and manufactured prototype. Using proposed design method, performed simulation and proved satisfied performance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.9
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• pp.17-23
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• 2009

Interest in application of ultraviolet light technology for primary disinfection of potable water in drinking water treatment plants has increased significantly in recent years. The efficacy of disinfection processes in water purification systems is governed by several key factors, including reactor hydraulics, disinfectant chemistry, and microbial inactivation kinetics. The objective of this work was to develop a computational fluid dynamics(CFD) model to predict velocity fields, mass transport, chlorine decay, and microbial inactivation in a continuous flow reactor. The CFD model was also used to evaluate disinfection efficiency in alternative reactor designs. In a typical operation, water enters the inlet of a UV lamp and flows through the annular space between the quartz sleeve and the outside chamber wall. The irradiated water leaves through the outlet nozzle. In this paper, it describe the how to design optimal ultraviolet disinfection device for ground water and rainwater. To search the optimal design method, it was performed computer simulation with 3D-CFD discrete ordinates model and manufactured prototype. Using proposed design method, performed simulation and proved satisfied performance.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.4
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• pp.619-624
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• 2016

Chlorine dioxide ($ClO_2$) gas treatment (75 ppmv, 30 min) has been suggested to improve the microbial safety of postharvest paprika in a previous study. Based on these results, in this study, an additional combined treatment using low-concentration $ClO_2$ gas-generating sticks (3 ppmv) in paprika samples during storage was carried out at $8^{\circ}C$ and 90% relative humidity to further enhance the quality and reduce the decay rate of paprika for the purpose of lengthy storage. After the combined treatment, the initial populations of total aerobic bacteria as well as yeast and molds in the paprika samples decreased by 3.04 and 2.70 log CFU/g, respectively, compared with those of the control samples, and this microbial inactivation was maintained by the low-concentration $ClO_2$ gas-generating sticks during storage. In particular, the decay rate of samples with combined treatment was significantly lower than that of the control. Vitamin C content, hardness, and color quality parameters of paprika samples were not altered by treatment, while weight loss of the samples treated with the combined $ClO_2$ gas was lower than that of the control during storage. These results indicate that the combination of two different $ClO_2$ gas treatments is effective for retaining the quality of paprika during prolonged storage.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.887-894
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• 2000

The purposes of this study are investigation of species of attached algae and the relation between attached algae and odor in tap water, Oscillatoria sp. and Mougeotia sp. were colonized at sedimentation basin in water treatment plant. Resulting from analysis, 3.7ppt of geosmin and dimethyl-disulfide with trace were detected in sample of Oscillatoria sp. only, 22 compounds were found in each of sample that had been incubated in room temperature for 5 days, 17 compounds were generated by algal decay. Decayed products were sulfur compounds of 10 species such as dimethyl-sulfide and phenol, p-cresol, indole and scatole. So, it is assumed that attached algae which tolerant to chlorine was the origin of odor in tap water. They usually formed big colonies. Colonies on the bottom were decayed because of anaerobic state. While decaying they were detached from colonies and so, odorous compounds are originated from this decayed algae.

• Korean Journal of Food Science and Technology
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• v.43 no.1
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• pp.98-104
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• 2011

The storage quality of fresh buckwheat sprouts, as influenced by pretreatment and packaging within processing steps, was investigated to establish appropriate postharvest handling treatment for the commodity. After harvest, the sprouts were dipped in chlorine water (100 ppm), rinsed twice with clean water, pre-cooled with iced water, de-watered, and packed in plastic trays. Sprout samples taken from each processing step were stored at $5^{\circ}C$ for 6 days to measure quality attributes. Viable cell counts of mesophilic aerobes and coliform bacteria were lower by about 1 log scale in the postharvest treated samples compared to an untreated control, although the initial microbial reduction due to the postharvest treatments was offset by cell growth during storage. All sprout samples showed a decrease of fresh weight by approximately 4% after 6 days of storage. However, moisture and soluble solid contents were maintained at the initial levels of the sprouts. No significant difference in surface color was observed among sample treatments. For sensory properties including discoloration, wilting, decay, and visual quality, there were no significant differences among sample treatments. The present results suggest that proper postharvest processing treatments can exert positive effects on extending the shelf-life of fresh buckwheat sprout.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.20 no.1
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• pp.17-24
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• 2014

The purpose of this study was to review the brief physiological characteristics and some factors of the quality decay of strawberry harvested in Korea. Strawberries are highly perishable with soft surface. Surface injury and fungus growth are common as a result of handling and distribution. Many growers and distributers are considered to protect the physical impact and inhibit the fungus growth for prolonging the shelf life in the distribution and market channels. Post-harvest treatments of precooling, carbon dioxide, chlorine dioxide, ozone, and ultrasound are practiced on strawberry in order to extend shelf-life and preserve the quality. Modified atmosphere packaging, edible coating, and oxygen absorbent application can be used as supplemental treatments to extend postharvest-life of strawberry. The packaging types for current domestic and export strawberry in Korea were summarized. The findings from this study can be lead to a better understanding of strawberry packaging development associated with the proper handling and distribution of strawberry. This could be useful for the strawberry growers, distributors, and buyers.