The authors discovered large differences in the characteristics of overflows by the calculation of 1) intercepting volume of overflows for sewer systems using SWMM model which takes into consideration the runoff and pollutants from rainfalls and 2) the intercepted volume in the total flow at an investigation site. The intercepting rate at the investigation point of CSOs showed higher values than the SSDs. Based on the modeling of the receiving water quality after calculating the intercepting amount of overflows by considering the characteristics of outflows for a proper management of the overflow of sewer systems with rainfalls, it is clear that the BOD decreased by 82.9%-94.0% for the discharge after intercepting a specific amount of flows compared to the discharge from unprocessed overflows.

Objectives : To recycle the wasted activated carbon from water purifiers and reuse stormwater runoff, this study evaluated water quality of stormwater runoff with regeneration using granular activated carbon containing commercial activated carbon for water treatment and wasted activated carbon from household water purifiers.Methods : The removal of total coliforms, chloride, BOD, T-N, T-P, turbidity, and pH in stormwater runoff were analyzed by down-flow column test using granular activated carbon with varied mixing ratios. In addition, chemical modification with ferrous sulfate and ultrasonic treatment were conducted to improve the removal efficiency of total coliforms, and turbidity.Results and Discussion : The optimal mixing ratio of granular activated carbon was 7:3 (GAC:WGAC), which showed high removal efficiency of 88.2% for total coliforms, 70.8% for chloride, 72.6% for BOD, 88.4% for T-N, 50.7% for T-P, and 85.9% for turbidity. The granular activated carbon with surface modification using a 0.2 M FeSO₄ solution with ultrasonic treatment demonstrated the highest removal efficiency, with a reduction of 11.8% in total coliforms, 29.2% in chloride, 12.1% in BOD, 20.3% in T-P, and 13.2% in turbidity, while T-N showed a decrease of 19.4% in removal efficiency.Conclusion : The granular activated carbon with a 7:3 mixing ratio showed highest removal efficiencies for all water quality parameters, while the total coliforms and turbidity did not meet the water quality standards for reclaimed water. This indicated that further physicochemical surface modification with FeSO₄ and ultrasonic treatment was needed to improve the removal performance and meet the water quality standards for reclaimed water. This approach explored in this study using wasted activated carbon should be continued in the area of resource and water circulation to properly utilize resources of wastes.

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