• Journal of Korean Society of Water and Wastewater
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• v.18 no.3
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• pp.320-330
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• 2004

Most of domestic city is served combined sewer system among various sewer system like as separate sanitary, combined sewer system and storm sewers. During the wet weather, sewer and rainfall have been overflowed because it is over capacity of the combined sewer system; that is called combined sewer overflows(CSOs) This research was carried out to investigate runoff characteristics of combined sewer and to evaluate the effective CSOs volume in Hong-Chun gun. During wet weather, SS load of first rainfall at H-1, H-2, and H-3 were 600kg/event, 370kg/event, and 289kg/event, respectively. 55 load of second rainfall were 216kg/event, 113kg/event, and 37.2kg/event. When the first rainfall, event mean concentrations(EMCs) at each site were 702mg/L, 816mgjL and 861.5mg/L. The second rainfall's event mean concentrations(EMCs) were 99.9gm/L, 161.9mg/L, 103.6mg/L. Rrst flush coefficient b at each site were 0.237,0.166, and 0.151. When the first rainfall, the flow containing 80% of pollutant mass of CSOs at each site were 0.55, 0.23, 0.48 in first rainfall, respectively. The case of second rainfall were 0.79, 0.83, 0.81. Most of all, characteristics of rainfall like as analysis of first-flush, CSOs volume, pollutant loadings is investigated to decide intercepted volume for control of CSOs.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.229-235
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• 2011

In order to manage a sewer system effectively, flow conditions such as flux, water quality, Infiltration and Inflow (I/I), Combined Sewer Overflows (CSOs), etc need to be monitored on a regular base. Therefore, in sewer networks, a monitoring is so important to prevent the river disaster. Monitoring all nodes of an entire sewer system is not necessary and cost-prohibitive. Water quality monitoring points that can represent a sewer system should be selected in a economical manner. There is no a standard for the selection of monitoring points and the quantitative analysis of the observed data has not been applied in sewer system. In this study, the entropy method was applied for a sewer network to evaluate and determine the optimal water quality monitoring points using genetic algorithm. The entropy method allows to analyze the observed data for the pattern and magnitude of temporal water quality change. Since water quality measurement usually accompanies with flow measurement, a set of installation locations of flowmeters was chosen as decision variables in this study.

• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.543-550
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• 2007

In this study, combined sewer overflows (CSOs) from five independent rainfall events in rural city area were collected and investigated. First flush effect in sewage pumping station located near the WWTP was retarded 30 to 60 minutes from booster pumping station. The ratios between SS, COD and TP concentrations prior to rainfall and peak concentrations during the period of rainfall were highly increased but nitrogen was relatively constant, which indicates that it is not associated with particles washed off from the surface of watershed. Mass balance results show that 30% of CSO was generated from booster pump station and 66.5% of CSO was from the whole runoff area. In the area of newly constructed sewer system, CSO problem was related with pump and sewer capacities, but in other old sewer system equipped area, it was due to the collection efficiency. Finally, Log-Log pollutant rating equations were suggested.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.557-564
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• 2009

A combined sewer system can quickly drain both storm water and sewage, improve the living environment and resolve flood measures. A combined sewer system is much superior to separate sewer system in reduction of the non-point source pollutant load. However, during rainfall. it is impossible in time, space and economic terms to cope with the entire volume of storm water. A sewage system that exceeds the capacity of the sewer facilities drain into the river mixed with storm-water. In addition, high concentration of CSOs by first-flush increase pollution load and reduce treatment efficiency in sewage treatment plant. The aim of this study was to develope a processing unit for the removal of high CSOs concentrations in relation to water quality during rainfall events in a combined sewer. The most suitable operational design for processing facilities under various conditions was also determined. With a designed discharge of 19.89 m/min, the removal efficiency was good, without excessive overflow, but it was less effective in relation to underflow, and decreased with decreasing particle size and specific gravity. It was necessary to lessen radius of vortex separator for increasing inlet velocity in optimum range for efficient performance, and removal efficiency was considered to high because of rotation increases through enlargement of comparing height of vortex separator in diameter. By distribution of influent particle size, the actual turbulent flow and experimental results was a little different from the theoretical removal efficiency due to turbulent effect in device.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.1
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• pp.47-55
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• 2009

Sewers are important national infrastructure and play an essential part by handling both wastewater and stormwater to minimise problems caused to human life and the environment. However, they can cause urban flooding when rainfall exceeds the system capacity. Sewer flooding is an unwelcome and increasingly frequent problem in many urban areas, and its frequency will increase over time with urbanisation and climate change. Under current standards, sewers are designed to drain stormwater generated by up to 10 year return period storms, but data suggests that many in practice have been experienced flooding with exceeding system capacity under increased storm events. A large number of studies has considered upgrading or increasing the design standard but there are still lack of information to propose a suitable return period with the corresponding system quantity to achieve. A methodology is required to suggest a proper level of standard within a suitable sewerage rehabilitation planning that can avoid the exceedance problem. This study aimed to develop a methodology to support effective sewer rehabilitation that could prevent urban flooding mainly resulted from the exceedance of existing storm sewer system capacity. Selected sewerage rehabilitation methods were examined under different storm return periods and compared to achieve the best value for money.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.1
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• pp.75-84
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• 2011

This study was conducted to provide a basic information for the establishment of operation and treatment processes in sewer system of Nakdong river basin to minimize the overall pollutants loading to water body. Sewage flowrates were regularly measured and monitored at various sampling points of newly-built separated sewer system located in G City GA sites. To assess the inflow sewage flowrate, various calculating methods such as water-use evaluation, average-minimum daily flow quality evaluation, minimum daily flow evaluation, night water-use evaluation were used. Average I/Is were calculated except water-use evaluation. Average I/Is were found to be 6.5 $m^{3}/d$, 3.5 $m^{3}/d$, 7.7 $m^{3}/d$ at GA-1, GA-2, GA-3 points respectively. I/I ratios of three areas were found to be 4.8 %, 2.0 % and 2.7 % respectively and were obviously lower than those of the other separated sewer systems as shown in the previous studies.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.4
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• pp.493-502
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• 2015

In accordance with the Watershed Sewer System Maintenance Plan enforced on February 2, 2013, the different compliance concentration of effluent limit be applied to effluent discharged from public sewage treatment works(PSTWs) in each watershed on the basis of water quality thereof. With the introduction of watershed sewer system, it is necessary to set the compliance concentration of effluent limit for PSTWs situated in the watershed, by region and PSTW size, to achieve water quality criteria for regional watersheds or target water quality under TMDL program. Watershed Environmental Agencies establish the Watershed Sewer System Maintenance Plan and set the compliance concentrations of effluent limit for PSTWs under the plan. The agencies plan to apply tougher effluent BOD concentration limits in Class I to IV areas. Effluent BOD concentration limits will be toughened from 5~10 mg/L to 3 mg/L in class II~III areas, from 10mg/L to 5mg/L in class IV areas. Uniform application of effluent BOD concentration limits to PSTWs in the watershed sewer system need to be complemented considering type of sewage treatment technology employed and watershed characteristics. Therefore, this study presents method to determine the compliance concentration of effluent limit from PSTWs in the watershed.

• Journal of Korea Water Resources Association
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• v.37 no.3
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• pp.207-217
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• 2004

Our government is interested in the rehabilitation for the old sewer rather than the construction of a new sewer system. However, the research work on the sewer rehabilitation is not sufficient as much as the interest on the rehabilitation is increased. There are some research works for the determination of rehabilitation time by the genetic algorithm in Korea and foreign countries. However, the previous studies have considered the simple elements for the determination of the rehabilitation time and so the complex decision-making according to the degree of sewer superannuation has not been performed. Therefore, in this study, we estimate the capacity and Ⅰ/Ⅰ of sewer and determine the priority of the optimal rehabilitation for each outfall within the draining system. Also we develop the optimal rehabilitation decision making system for the cost estimation of optimal rehabilitation using the genetic algorithm.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.3
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• pp.177-190
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• 2019

The purpose of this study was to analyze the effects of sewerage facilities through I/I analysis by rainfall by selecting areas where storm overflow diverging chamber is remained due to the non-maintenance drainage equipment when the sewerage system was reconstructed as a separate sewer system. Research has shown that wet weather flow(WWF) increased from 106.2% to 154.8% compared to dry weather flow(DWF) in intercepting sewers, and that the WWF increased from 122.4% to 257.6% in comparison to DWF in storm overflow diverging chamber. As a result, owing to storm overflow diverging chamber of partially separate sewer system with untreated tributary of sewage treatment plant, rainfall-derived infiltration/inflow(RDII) has been analyzed 2.7 times higher than the areas without storm overflow diverging chamber. Meanwhile, infiltration quantity of this study area was relatively higher than that of other study areas. Therefore, it is necessary to reduce infiltration quantity through sewer pipe maintenance nearby river. Drainage equipment maintenance should be performed not to operate storm overflow diverging chamber in order to handle the appropriate sewage treatment plant capacity for rainfall because it is also expected that RDII due to rain will occur after maintenance. In conclusion, it is necessary to recognize aRDII(allowance of rainfall-derived infiltration/inflow) and to be reflected it on sewage treatment plant capacity because aRDII can occur even after maintenance to the complete separate sewer system.

• Spatial Information Research
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• v.5 no.2
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• pp.185-194
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• 1997

Spatial decision support systems(SDffi), a new class of decision support system(DSS), result from the melding together of GIS and DSS, Planning support systems(PS5) add more advanced spatial analysis functions than GIS and intertemporal functions to the functions of SDSS. This paper reports the development of a planning support system providing a framework that facilitates urban planners and civil engineers in conducting coherent deliberations about the generation of satisficing sewers. 1he planning support system for the generation of satisficing sewers(PS5/GSS) was designed from the understanding that land use and development drive the demand for storm and sanitary sewers. Through four stages of supply, demand, alternative generation, and evaluation, PSS/GSS integrates basic planning, preliminary design, and engineering design of sewer. GIS and graphic user interface are excellent toolboxes for designing sewer networks, estimating the quantity of wastewater, and showing generated alternative sewers. A sewer model using simulation tedmique can generate an initial sewer. Users can define alternative sewers by the direct manipulation of sewer networks or by the manipulation of parameters in the sewer model. The sewer model evaluates the performance of the user defined alternatives.