빗물 침투 저류조를 위한 모래 정화층의 비점오염 정화 특성에 관한 연구 Study on filtration characteristics of sand filter layers to non-point source pollutant for artificial rainwater reservoirs원문보기
Prevalent construction of impermeable pavements in urban areas causes diverse water-related environmental issues, such as lowering ground water levels and shortage of water supply for the living. In order to resolve such problems, an artificial rainwater reservoir (ARR) can be an effective and usefu...
Prevalent construction of impermeable pavements in urban areas causes diverse water-related environmental issues, such as lowering ground water levels and shortage of water supply for the living. In order to resolve such problems, an artificial rainwater reservoir (ARR) can be an effective and useful solution. ARR facilitates the hydrologic cycle in urban areas by temporarily retaining precipitation-runoff within a shallow subsurface layer for later use in a dry season. However, in order to use the stored water of precipitation-runoff, non-point source pollutants mostly retained in initial rainfall should be removed before being stored in the reservoir. Therefore, the purification system to filter out the non-point source pollutants is essential for ARR. The conventional soil filtration technology is well known to be able to capture non-point source pollutants in a economical and efficient way. This study adopted a sand filter layer (SFL) as a non-point pollutant source removal system in ARR, and conducted a series of lab-scale chamber tests and field tests to evaluate the pollutant removal efficiency and applicability of SFL. Firstly, for the laboratory chamber experiments, five types of SFL of different grain size distributions were set in two kinds of chambers with dimensions of 20cm×30cm×60cm and 40cm×30cm×60cm as the type of artificially contaminated water made by clay and real non-point source pollutants collected on the road of Seoul, Korea, and then the artificially contaminated water was spilt into SFL at a constant rate. This step was repeated over 100 times for each type of SFL. To evaluate the performance of the purification systems, the concentration of the polluted water in terms of TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) were measured and compared. In addition, a reduction in hydraulic conductivity of SFL due to pollutant clogging was estimated indirectly. Secondly, to study on the clogging characteristics of SFL on the grain distribution of filter soils, the accumulated weights of non-point source pollutant particles that clogged the pores of SFL were estimated by the analytical modeling solution and the lab-scale tests. The effects of the lumped parameter θ introduced in the clogging theory on the clogging situation were studied by comparing the results from the analytical modeling solution and the lab-scale tests. During the process of the analytical modeling solution, the condition of the variation in the hydraulic conductivity and the porosity of sand filter layers had different grain size distributions and layer compositions as effective particle sizes were utilized. Through this research, it was found that the results from the analytical modeling solution and the lab-scale test were positively correlated, and verified that the lumped parameter θ is closely related to the pore size distribution of SFL. In conclusion, from the results of the laboratory chamber experiments, the double sand filter layers consisted of effective particle sizes of 1.49mm in the upper layer and 0.93mm in the lower layer were proposed as the optimum removal system for the non-point source pollutants in the in-situ artificial rainwater reservoir. The optimum SFL selected through the laboratory chamber experiments was verified on the in-situ ARR for field applicability.
Prevalent construction of impermeable pavements in urban areas causes diverse water-related environmental issues, such as lowering ground water levels and shortage of water supply for the living. In order to resolve such problems, an artificial rainwater reservoir (ARR) can be an effective and useful solution. ARR facilitates the hydrologic cycle in urban areas by temporarily retaining precipitation-runoff within a shallow subsurface layer for later use in a dry season. However, in order to use the stored water of precipitation-runoff, non-point source pollutants mostly retained in initial rainfall should be removed before being stored in the reservoir. Therefore, the purification system to filter out the non-point source pollutants is essential for ARR. The conventional soil filtration technology is well known to be able to capture non-point source pollutants in a economical and efficient way. This study adopted a sand filter layer (SFL) as a non-point pollutant source removal system in ARR, and conducted a series of lab-scale chamber tests and field tests to evaluate the pollutant removal efficiency and applicability of SFL. Firstly, for the laboratory chamber experiments, five types of SFL of different grain size distributions were set in two kinds of chambers with dimensions of 20cm×30cm×60cm and 40cm×30cm×60cm as the type of artificially contaminated water made by clay and real non-point source pollutants collected on the road of Seoul, Korea, and then the artificially contaminated water was spilt into SFL at a constant rate. This step was repeated over 100 times for each type of SFL. To evaluate the performance of the purification systems, the concentration of the polluted water in terms of TSS (Total Suspended Solids) and COD (Chemical Oxygen Demand) were measured and compared. In addition, a reduction in hydraulic conductivity of SFL due to pollutant clogging was estimated indirectly. Secondly, to study on the clogging characteristics of SFL on the grain distribution of filter soils, the accumulated weights of non-point source pollutant particles that clogged the pores of SFL were estimated by the analytical modeling solution and the lab-scale tests. The effects of the lumped parameter θ introduced in the clogging theory on the clogging situation were studied by comparing the results from the analytical modeling solution and the lab-scale tests. During the process of the analytical modeling solution, the condition of the variation in the hydraulic conductivity and the porosity of sand filter layers had different grain size distributions and layer compositions as effective particle sizes were utilized. Through this research, it was found that the results from the analytical modeling solution and the lab-scale test were positively correlated, and verified that the lumped parameter θ is closely related to the pore size distribution of SFL. In conclusion, from the results of the laboratory chamber experiments, the double sand filter layers consisted of effective particle sizes of 1.49mm in the upper layer and 0.93mm in the lower layer were proposed as the optimum removal system for the non-point source pollutants in the in-situ artificial rainwater reservoir. The optimum SFL selected through the laboratory chamber experiments was verified on the in-situ ARR for field applicability.
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