• Journal of Korea Water Resources Association
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• v.55 no.spc1
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• pp.1211-1222
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• 2022

Abnormal condition inevitably occurs during operation of water distribution system (WDS) and requires the isolation of certain areas using isolation valves. In general, the determination of the optimal location of isolation valves considered minimization of hydraulic failures as isolation of certain areas causes a change in hydraulic states (e.g., flow direction, velocity, pressure, etc.). Water quality failure can also be induced by changes in hydraulics, which have not been considered for isolation valve system design. Therefore, this study proposes a new isolation valve system design methodology to prevent unexpected water quality failure events. The new methodology considers flow direction change ratio (FDCR), which accounts for flow direction changes after isolation of the area, as a constraint while reliability is used as the objective function. The optimal design model has been applied to a synthetic grid network and the results are compared with the traditional design approach. Results show that considering FDCR can eliminate flow direction changes while average pressure and coefficient of variation of pressure, velocity, and hydraulic geodesic index (HGI) outperform compared to the traditional design approach. The proposed methodology is expected to be a useful approach to minimizing unexpected consequences by traditional design approaches.

• Korean Journal of Agricultural Science
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• v.47 no.2
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• pp.375-380
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• 2020

The high intrinsic water content and salinity of food waste prevent a smooth composting process and consequently cause social, economic and environmental problems. In this study, we investigated the distribution of the water content and salinity in food wastes to obtain useful primary data to ensure adequate and quality recycling. A total of 300 food waste (FW) samples were collected from residential apartments (home generated FW), a wide range of restaurants, i.e., restaurant generated FW that included Korean, Chinese, Japanese and western FWs, and several places that included food waste processing facilities (dehydrated FW cakes). The collected food wastes were oven dried for 48 hours at 80℃ after which the water and salinity contents were analyzed. The results show that the average water content of the FWs was 72.45 ± 10.51%, and the average salinity content was 2.03 ± 0.57%. Furthermore, the salinity of the collected FWs was characterized by where the FW was generated. By location, the salinity concentration of home generated FW was 2.30% while western food had the lowest salinity concentration of 1.18%. However, dehydrated cakes had the highest salinity concentration of 2.84%. Especially, the distribution of the salinity content in food wastes can form the basis for improving the compost quality in food waste recycling.

• Journal of Korean Society on Water Environment
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• v.34 no.5
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• pp.487-493
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• 2018

Urban stormwater runoff is the one of the most extensive causes of deterioration of water quality in streams in urban areas. Especially, in the Suyeong River watershed, non-point sources from urban-residential areas are the most common cause of water pollution. Also, it has been ascertained that BOD and COD as indexes of organic matter, have limitation on management of Suyeong River's water quality. In this study, changes of organic matter properties of Suyeong River from inflow of non-point source during rainfall were investigated. Fractions of organic matters were analyzed using water samples collected at two sites (Suyeong River and Oncheon Stream) during a rain event. Variations of dissolved organic carbon (DOC) concentration by rainfall were similar to flow rate change in the river. Distribution of organic matter fraction according to change of rain duration revealed that while hydrophilic component increased at initial rainfall, the hydrophobic component was similar to change in dissolved organic carbon (DOC) concentration. Also, the relative proportion of hydrophilic components in organic matter in river water increased, due to rainfall. Results of biodegradation of organic matters revealed that decomposition rate of organic matters during rainfall was higher than that of during a non-rainfall event.

• Journal of the Korean earth science society
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• v.42 no.5
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• pp.556-570
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• 2021

This study presents the data analysis results of groundwater chemistry and the occurrence of fluoride in groundwater obtained from the groundwater quality monitoring network of Korea. The groundwater data were collected from the National Groundwater Information Center and censored for erratic values and charge balance (±10%). From the geochemical graphs and various ionic ratios, it was observed that the Ca-HCO₃ type was predominant in Korean groundwater. In addition, water-rock interaction was identified as a key chemical process controlling groundwater chemistry, while precipitation and evaporation were found to be less important. According to a non-parametric trend test, at p=0.05, the concentration of fluoride in groundwater did not increase significantly and only 4.3% of the total groundwater exceeded the Korean drinking water standard of 1.5 mg/L. However, student t-tests revealed that the fluoride concentrations were closely associated with the lithologies of tuff, granite porphyry, and metamorphic rocks showing distinctively high levels. This study enhances our understanding of groundwater chemical composition and major controlling factors of fluoride occurrence and distribution in Korean groundwater.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.6
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• pp.725-736
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• 2016

There is a growing concern on the improvement of water distribution pipeline for multi-regional water supply system in Korea along with its aging infrastructure. Rehabilitation of large diameter pipeline is more efficient in cost and time compared to replacement with trenching. The procedure for rehabilitation are diagnosis, cleaning, spraying coating material, and final inspection. The internal state of pipeline was carefully diagnosed and got C grade, which required rehabilitation. We found that 17,274,787,000 Korean won could be saved after pipe surface coating because of increased C coefficient of Hazen-Williams equation. Optimal coating material was D polyurea. We also found optimal distance between spraying nozzle and pipe wall to be 70 - 80 cm, which were critical factors for coating quality. This study also illustrated the time for spray drying to be more than 30 min. These results could be used in the quality control process during rehabilitation of aged pipelines.

• Journal of Environmental Science International
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• v.8 no.1
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• pp.101-106
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• 1999

The relationship between primary productivity and changes in water quality was investigated at Mulgum station, a site downstream of the Nakdong River, Korea. Phytoplankton production was characterized by blooms of Microcystis aeruginosa during the summer and Stephanodiscus hantzschii during the winter. Primary production and secondary production by bacterioplankton ranged from 1.5~53.5 mg-C/ι day and 0.1~0.3 mg-C/ι day, respectively. Distribution of total organic carbon appeared to be highly correlated with phytoplankton biomass, especially during blooms of M. aeruginosa, when particulate organic carbon was 81% of total organic carbon and the main source of organic materials supplied into the water. The correlation coefficient between chlorophyll-a and BOD was 0.86. Thus it was concluded that autochthonous phytoplankton mostly affected the BOD level. Total bacterial numbers were also highly correlated with chlorophyll-a ($r^2$= 0.84) and the bacterial community appears to be regulated by phytoplankton biomass in this area.

• Journal of Environmental Science International
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• v.19 no.9
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• pp.1153-1159
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• 2010

Identification of probability distribution for water quality constituents from specific land use is important to achieve successful implementation of TMDL program. In this 3-year study, distribution of discharge and BOD(Biological Oxygen Demand) concentration from paddy rice fields were monitored. Four probability distributions, normal, log-normal, Gamma and Weibull were fitted and the goodness-of-fit was assessed using probability plots and Kolmogorov-Smirnov test. $EMC_s$ of BOD in runoff from paddy field ranged 0.37 to $7.99\;mgL^{-1}$, and all four probability distributions were acceptable. But the normal distribution would be preferred for BOD from paddy fields considering nature of straight forward application.

• Korean Journal of Environmental Biology
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• v.37 no.2
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• pp.177-188
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• 2019

The objective of this study was to analyze the distribution patterns of two exotic disturbing fish species (largemouth bass, Micropterus salmoides and bluegill, Lepomis macrochirus), their physical habitat features, and chemical water qualities from 13 sites of Dongjin River. The relationships between the fish distributions and water chemistry and physical habitat characteristics (i.e., bottom substrate) were evaluated by comparing dominant vs. absent regions of largemouth bass and bluegill. The relative abundance of the two species decreased sharply with decreased in the water quality in terms of BOD, PO₄-P and pH, but not with NO₃-N and conductivity. The bluegill showed no difference in habitat preference between the two regions with regard to the bottom structure, while the largemouth bass had significant differences in the bottom structures of silt, coarse gravels and boulders. The dominant species were Zacco platypus (14.6%), Lepomis macrochirus (14.0%), and Micropterus salmoides (9.8%) in the order of relative abundance, indicating that exotic species (24% in total) dominated the fish community, perhaps ensuing large ecological disturbances on the ecosystem. In conclusion, the results of this study suggest that the distribution of the two exotic species may be largely influenced by water quality of organic matter and nutrient pollutions.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.33-40
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• 1992

Up to now, monthly water balance analysis has been dominantly used for the water resources planning. But, it is more reasonable to explain the variation of spatial and temporal distribution of water by the daily water balance model with daily streamflow data. Since we are recently facing the problems of regional unbalance of water quantity, and of multiuse of irrigation water, and of deterioration of water quality, it is urgently needed to develop the daily water balance model to solve those problems and establish the rational plannings of agricultural water resources. In the circumstances, Daily water Balance(DAWABA) model for irrigation reservoirs was developed and the operation rule of irrigation resorvoir during drought season was established.

• Journal of the Korean Society of Food Science and Nutrition
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• v.23 no.2
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• pp.328-332
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• 1994

The purpose of present paper is to compare and analyze the quality of imported Chinese products with the Korean local products in terms of proximate composition, character of external appearance , ingredient composition of dried bracken , dried radish cubers, meju , dried pollack, dried mussel , and dried brown seaweed(Undaria puinnatidifida) which were imported between Oct., and Dec. 1992 and distributed in the market. Moisture recovery of dried products resulted in changed shape and incomplete moisture recovery due to an excessive drying in consideration of hygroscopic property in the course of distribution. The amounts of water soluble brown pigment were two times greater in Korean dried pollack and bracken than those of Chinese products. The content of volatile basic nitrogen (VBN) were twice in Chinese dried pollack, and this may be due to foregin odor from a long transport time and distribution process. The contents of aflatoxin in Korean products were not detectable and these of Chinese products were 5 $\mu\textrm{g}$(%) in dried pollack, bracken and radish cuber. the remaining agricultural chemicals were not detectable in all products. Because of poor technique and facilities, the external appearance of Chinese products especially dried mussels and dried pollack were not uniformed in size and color. Discoloration and foregin substance such as hair, dust were checked , Korean products were mostly packed in small size in PP or bag, and Chinese products were packed in bulk size and distributed as a bulk.