• Journal of environmental and Sanitary engineering
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• v.7 no.2
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• pp.37-52
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• 1992

Since the first sewage treatment plant was constructed in 1976, the sewerage systems of Korea have been rapidly expanded. As of the end of 1991, 22 sewage treatment plants with total capacity of 5.4 million tons/day are in operation which is equivalent of 3395 total daily sewage generation. Total extension of sewer 39.534 km in 1990 which is 55% of the target extension for the year 2001. However, the most sewage treatment plants employ activated sludge process which may not be suitable for medium and/or small scale plants. The poor existing sewer systems do not effectively collect and transport sewage to adversely affect the function of sewage treatment plant. To select the appropriate treatment system, the cities are classified into 3 categories such as large and medium size inland cities, small size cities and coastal cities. Considering the criteria suggested during this study, appropriate treatment processes were selected for each category. Conventional activated sludge process and step aeration process were found to be the most appropriate for big inland cities while biological nutrient removal processes should be considered for the cities discharge the effluent to lakes or reservoirs. RBC or Oxidation Ditch process might be appropriate for the medium size cities while several processes which do not require skilled operation and maintenance were suggested for the small cities. Ocean discharge after primary treatment can be considered for some east coast cities, Appropriate methodology to rehabilitate the existing sewers and strategy to convert combined sewer system to separate sewer system were proposed. This paper also include the appropriate management system for industrial wastewater, sludge and nightsoil.

• 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 Industrial Technology
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• v.22 no.B
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• pp.95-101
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• 2002

Much of domestic city is served by combined sewer system rather than separate sanitary or storm sewers. During wet weather, when the volume of sanitary sewage and storm water entering the combined sewers exceeds the system capacity, the system is designed to overflow at several designated CSOs. The objective of this research is to have grasp of characteristics of combined sewer runoff and to evaluate efficiently the intercepted volume of CSOs. During the wet weather in first rainfall, SS load at each site H-1, H-2, and H-3 were 600kg/event, 370kg/event, and 289kg/event, SS load at each site in second rainfall were 216kg/event, 113kg/event, and 37.2kg/event. EMCs at each site were 702mg/L, 816mg/L, 861mg/L in first rainfall and 99.9mg/L, 161.9mg/L, 103.6mg/L in second rainfall, respectively. First flush coefficients b at each site were 0.237, 0.166, and 0.151.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.585-594
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• 2006

This study focused on the causes of fish kills and its prevention methods in Yudeung Stream, Daejeon, Korea. Intense field data, continuous water quality monitoring system and water quality modeling were applied to analyze the causes. Pollutant can be delivered to urban streams by surface runoff and combined sewer overflows in rainfall events. However, water quality analysis and water quality modeling results indicate that the abrupt fish kills in the Yudeung stream seems to be caused by combined effect of DO depletion, increase in turbidity and other toxic material. Excessive fish population in the study area may harm the aesthetic value of the stream and also has greater potential for massive fish kills. It is suggested to implement methods to reduce delivery of pollutants to the stream not only to prevent fish kills but also to keep balance of ecosystem including human uses. Frequent clean up of the urban surface and CSO, installation of detention basin will be helpful. In the long run, it seems combined sewer system has be replaced with separate sewer system for more effective pollutant removal in the urban area.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.21-26
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• 2004

It is muck important to determine the intercepting capacities as measures for reducing the load of contamination influenced by CSOs during wet weather period. Intercepting and treating the whole rainfalls can be best measured for reducing the contamination load, but it is not desirable in view of scale and preservation of the wastewater treatment facilities. This study analyzed the quantity and quality of the water in the combined sewer by method of changing the type and size of drainage basin and intercepting capacities in rainfalls, estimate the influence the other CSOs at the change of planned intercepted quantity, and compared the degree of contamination load between the combined system and separate system by examining the influence of the other CSOs at the change of planned intercepted quantity.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.5
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• pp.557-564
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• 2005

The objective of this study is to evaluate a criteria of intercepting capacity and a reduction goal of overflow pollution load in combined sewer system. In the current criteria of intercepting capacity in the domestic sewage facility standard, it is known that three times of peak sewage (Q) in dry period or runoff flow by 2mm/hr is not appropriate since the intercepted flow is estimated by runoff and show different result even in the same watershed. Though a reduction goal of overflow pollution load can be determined from 1) same level of storm-water runoff pollution load in separated storm sewer, 2) less than 5% sewage load in dry weather period, by the domestic sewage facility standard, the simulated results from storm-water model show large differences between two criteria. While it is predicted that sewage pollution load standard three time larger than separated storm sewer standard in high population density and urbanized area, it is shown that separate storm sewer standard larger than sewage pollution load standard in middle population density and developing area. Accordingly, it is proposed that more reasonable intercepting flow and reduction goal of overflows pollution load should be established to minimize discharging pollution load in combined sewer systems. For the purpose, a resonable standard has to be amended by pollution load balance considering the characteristics of a watershed for generation, collection, treatment, and discharging flow.

• Journal of Wetlands Research
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• v.23 no.1
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• pp.85-93
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• 2021

Sewage separation which often involves installing a new pipe to separate wastewater flow from stormwater runoff flow can be costly and depends highly on its feasibility in a site. To be able to develop a potentially more economical alternative that can also lessen major road traffic disturbance during this process, a different approach where a smaller sewage separator pipe is installed inside an existing combined sewer pipe was investigated. A small-scale of a box sewer and the proposed sewage separator pipe was constructed in the laboratory to observe and compare the deposition of solids and other solid-associated major pollutants at different flow rates. In addition, three-dimensional flow simulations considering five different scenarios were conducted using Ansys Fluent to observe the effect of the proposed sewage separator pipe to the hydraulic flow if installed inside the combined sewer pipe. Results revealed that the deposition of TSS, TCOD, TN, and TP were reduced by at least 60% when the wastewater was conveyed by the sewage separator pipe instead of the combined sewer pipe. Moreover, the flow simulations conducted showed that there was little to no major disturbance in hydraulic flow and velocity distribution when the sewage separator was installed inside a straight pipe and even at pipe transitions such as intersections, turns, and drop in elevation. Considering the pipe dimensions and the results of the study, the proposed approach can be promising in terms of reduction in pollutant deposition without a major effect on the hydraulic flow. Further investigation and cost-analysis should be done in the future to support these preliminary findings and help alleviate the problems caused by combined sewer overflows by introducing an alternative approach.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.63-70
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• 2012

This study was carried out to investigate change in influent concentration of domestic wastewater flowed from a newly constructed separate sewer system (SSS) and biological nutrients removal efficiency of a full scale Air-vent sequential batch reactor (SBR, $600m^3/d$). The average concentration of $BOD_5$, SS, T-N and T-P from SSS were 246.5 mg/L, 231.6 mg/L, 42.974 mg/L, 5.360 mg/L, respectively which corresponds to 2.2times, 1.2times, 1.8times and 2.1times higher than those from the conventional combined sewer system (CSS). The removal efficiency of $BOD_5$, SS, T-N, and T-P for the Air-vent SBR operated with influent from SSS averaged 99.1%, 99.0%, 91.2%, and 93.5%, respectively. Especially the respective nitrogen and phosphorus removal was 15% greater than that of the SBR operated with influent from CSS. Simultaneous nitrification and denitrification (SND) was observed in an aerobic reactor(II) as a result of DO concentration gradient developed along the depth by the Air-vent system. In order to achieve T-N removal greater than 90%, the C/N ratio should be over 6.0 and the difference between $BOD_5$ loading and nitrogen loading rate be over 100 kg/day (0.130 kg $T-N/m^3{\cdot}d$). Even with high influent T-P concentration of 5.360 mg/L from SSS (compared with 2.465 mg/L from CSS) T-P removal achieved 93.5% which was 15.5% higher than that of the SBR with influent from CSS. This is probably due to high influent $BOD_5$ concentration from SSS that could provide soluble carbon source to release phosphorus at anaerobic condition. In order to achieve T-P removal greater than 90%, the difference between $BOD_5$ loading and phosphorus loading rate should be over 100 kg /day (0.130 kg $T-N/m^3{\cdot}d$).

• Journal of Intelligence and Information Systems
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• v.8 no.2
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• pp.205-227
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• 2002

Our study is focused on a multiple-agent system to provide efficient collaborative work by automating the conference calling process with the help of intelligent agents. Automating the meeting scheduling requires a careful consideration of the individual official schedule as well as the privacy and personal preferences. Therefore, the automation of conference calling needs the distributed processing task where a separate calendar management process is associated for increasing the reliability and inherent parallelism. This paper describes in detail the design and implementation issues of a multiple-agent system for conference calling that allows the convener and participants to minimize their efforts in creating a meeting. Our system is based on the client-sewer model. In the sewer side, a scheduling agent, a negotiating agent, a personal information managing agent, a group information managing agent, a session managing agent, and a coordinating agent are operating. In the client side, an interface agent, a media agent, and a collaborating agent are operating. Agents use a standardized knowledge manipulation language to communicate amongst themselves. Communicating through a standardized knowledge manipulation language allows the system to overcome heterogeneity which is one of the most important problems in communication among agents for distributed collaborative computing. The agents of our system propose the dates on which as many participants as possible are available to attend the conference using the forward chaining algorithm and the back propagation network algorithm.