• Journal of Korean Society on Water Environment
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• v.34 no.6
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• pp.650-660
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• 2018

The objective of this study was to compare the rainfall-runoff characteristics in streams of classified urban and rural watershed using land use and population density. EMC (event mean concentration) of BOD, COD, TP and SS increased significantly in urban and rural watershed, but that of TN remained unchanged. Although there were no significant differences in EMC of BOD, COD, TN, TP depending on the watershed characteristics, EMC of BOD and COD significantly increased in the urban watershed, while EMC of TP increased in the rural watershed. In the urban watershed, the first flush time was faster and the first flush effect was stronger in BOD, COD, and TP. However, the difference between cumulative mass and cumulative volume was found to be less than 0.2 in the rural watershed, indicating a weak first flush effect. The discharged masses of BOD (70 %), COD (64 %), and TP (66 %) in the first flush of runoff were higher in urban watershed, while TN (67 %) was higher in rural watershed. The reproducibility of first flush time and the strength of first flush using CV (coefficient of variation) was found to be more reproducible for first flush time in both watersheds. In rural watershed, the CV value of first flush time for TP out of water quality parameters was lower. Whereas the CV values of first flush time for BOD, COD and TP in urban watersheds were similar.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.641-646
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• 2004

Vehicle emissions from highway landuse include different pollutants such as heavy metals, oil and grease and particulates from fuels, brake pad wear and tire wear. Since highways are impervious and have high pollutant mass emissions from vehicular activity, it is considered as stormwater intensive landuses. Therefore this research was performed to understand the magnitude of first flush and to suggest the criteria of first flush for storm runoff management in highways. The fractions of washed-off mass are very high in first 30% of runoff volume, which suggests a definition of first flush. The washed-off mass stabilizes after 30% of the runoff volume and it is apparent that treatment capacity in the early part of a storm is more valuable than treatment capacity in the later part of the storm. Using the criteria of "high" first flush and "medium" first flush, as 50% of the mass in the first 30% of the volume, and 30 to 50% in the first 30% volume, respectively, more than 30% of the storms showed high first flush. A "first flush friendly" best management practice(BMP), meaning a BMP that can treat a high percentage or all of the initial flow, would be advantageous up to 80% of the events.

• Journal of Korean Society on Water Environment
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• v.30 no.6
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• pp.622-631
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• 2014

The purpose of this research was to find a proper disposal rainfall extent to improve water quality. SWMM was applied to select catchment area and tested first flush load and rainfall extent. BOD 40mg/L was selected to dispose the first flush and sewer overflow with the same as the criteria of Sewerage Act. Design rainfall, BOD load ratio of first flush sewer overflow, and the ratio of disposal flow were analyzed under various rainfall distribution. BOD load and design rainfall to treat overflow in situation of first flush extent with 4.3~17.4% were 56~87% and 3.8~6.8 mm/day, respectively. In urban area, first flush loads were not correspond to land activities, but tend to increase with increasing rainfall amount and drainage area. The more the distribution of rainfall is similar to Huff-frontal or central distribution of rainfall, the more increase the first flush loads.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.475-485
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• 2011

Lake Sihwa has a very unique watershed environment, surrounded by industrial, urban and rural catchment area with different land use. The first flush phenomenon was investigated in 3 catchment area. 4TG, representing the industrial area, shows rapid discharges of highly concentrated pollutants during the early stages of a storm and it is indicating a strong first flush effect. At AS, representing the urban area, the pollutant concentration reached its peak approximately 2~3 hours after the start of storm, which is a strong first flush effect did not appear. JJB and MS represent the rural areas, the PEMC analysis results suggest that highly concentrated pollutants were discharged during the middle and latter stages of a storm, instead of early pollutant runoff due to the effects of rainwater runoff.

• Journal of Environmental Impact Assessment
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• v.16 no.5
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• pp.341-350
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• 2007

Lake Youngrang is a lagoon whose effluent flows into the East Sea. Because two resort towns and two golf courses are situated at the lake basin, many tourists visit this area. Stormwater runoff surveys were carried out for the eight storm events from 2004 to 2005 in the eutrophic lake watershed to give a basic data for the diffuse pollution control of the lake. Dimensionless mass-volume curves indicating the distribution of pollutant mass vs. volume were used to analyze the first flush phenomenon. The mass-volume curves were fitted with a power function and polynomial equation curves. The regression analysis showed that the polynomial equation curves were better than the power function in representing the tendency of the first flush, and second degree polynomial equation curves indicated the strength of the first flush effectively.

• Journal of Korean Society on Water Environment
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• v.31 no.1
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• pp.67-70
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• 2015

Some data into combined and sanitary sewer system were collected in order to find out the characteristics of discharge from first flush rainfall inflow. The inflow ratios of combined and sanitary sewer system were 0.46 and 0.27 during rains from various survey data. The average inflow ratio 0.31 was appropriate for general application because many watersheds were not classified clearly as combined or sanitary sewage treatment areas. The percentage of first flush loads in the whole BOD load was about 10%. This result was thought some meaningful, comparing with similarity of first flush pollution load contribution previous surveyed by KECO (2004).

• Journal of Korean Society of Environmental Engineers
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• v.39 no.4
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• pp.214-219
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• 2017

We analyzed the water quality of first flush and rainfall runoff from a building rooftop, and investigated the removal of suspended solids (SS) in first flush using various media to develop a first flush filtration system. Particle size distribution exhibited most of particles in first flush from the rooftop ranged from 10 to 30 ${\mu}m$. SS concentrations maxed in 10~20 min and decreased afterwards. Dissolved organics and inorganic materials in runoff also showed highest levels in first flush (10 min). Filtration tests using anthracite (AC), polyurethane (PU), polypropylene (PP) showed about 50% of SS removal during the first 10 min operation, but the removal rates dramatically decreased after 20 min of filtration. Based upon the results from rinse and run cycle tests, only AC could achieve nice cycles without distinct decease of SS removal. SS removal rates increased with higher depth of media bed and lower flowrate. The system achieved over 50% of SS removal with a media depth of 30 cm and flowrate < 12 L/min.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.605-616
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• 2011

The first flush phenomenon and the Mass First Flush (MFFn) were analyzed for various rainy events in trunk road. Applicability for estimate MFFn using SWMM was evaluated by comparision with observed MFFn. First flush phenomenon was investigated by normalized cumulated (NCL) curve of every pollutant based on ten times of rainfall events monitoring data from 2008 to 2009. As a result, magnitude of first flush phenomenon varied with the pollutants and rainfall events. First flush phenomenon was detected highly in the trunk road. MFFn was estimated by varying n-value from 10 to 90% on the rainfall events. The n-value increases, MFFn is closed to '1'. As time passed, the rainfall runoff was getting similar to ratio of pollutants accumulation. The result of a measure of the strength of the linear relationship between observed data and expected data under model was good ($R^2$=0.956). As the final outcome, we have good reliability, estimation and application of MFFn using model seem statistically possible.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.314-320
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• 2006

Diffuse pollution from an urban area contributes to the significant pollution loading to a receiving water body. In this paper, rainfall runoffs from an urban basin with combined sewer systems located in the city of Daejeon were monitored to measure the rainfall runoff discharge rates and pollutant concentrations. Strong first flush effects were observed for all monitored rainfall runoffs. The first flush effects were closely related to rainfall intensity, while suspended solids were closely related to pollutant constituents. The observed averaged Event Mean Concentrations (EMCs) of Combined Sewer Overflows (CSOs) were 536.1 mg SS/L, 467.7 mg CODcr/L, 142.7 mg BOD/L, 16.5 mg TN/L, and 13.5 mg TP/L. Storage volumes for containing the first flush to improve water quality of the receiving stream can be estimated based on suspended solid concentration. In this study, retainment of the first flush equivalent to 5mm of precipitation could reduce diffuse pollution loading induced by CSOs to a receiving water body by up to 80% of suspended solid loading.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.181-181
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• 2015

최근 계속적인 도시화와 개발로 인해 불투수층이 증가함에 따라, 도시비점오염물질이 동반된 표면유출수가 증가하고 있다. 또한 도시 오염물질 배출특성 중 하나인 초기세척효과(First Flush Effect)가 대두되고 있다. 초기세척효과란 강우 시 강우초반에 고농도의 오염물질 나타나는 현상을 의미한다. 최근 이와 같은 도시 오염물질을 관리 및 저감을 위해 저영향개발(Low Impact Development)이 대안으로 나타나고 있다. 하지만 이러한 저영향개발을 분석 및 정량하기 위해서는 많은 실험적인 연구와 모델링이 필요하다. 본 연구에서는 광주광역시에 위치한 상업지구에 대해 모니터링과 LID 모델링을 실시하였고, 또한 Mass First Flush (MFF)라는 지표를 이용하여 최적 LID 크기를 산정하였다. 본 연구에선 나온 LID 크기는 1.2 mm부터 3.0 mm 정도로 나타났다. 이 결과는 향후 초기세척처리를 LID의 가이드라인으로 유용할 것이다.