Aruto ASAKURA
Solution of Polluting Load Based on Long-term Continuous Observation
Shuji HIMENO, Toshiya KOMATSU
Combined sewer overflow has come to be regarded as a serious issue in Japan, and there is a pressing need for improvement works to provide a solution. In this paper, based on the observation data, the evaluation about the effects of the countermeasures for the improvement is quantitatively pollution load on public water area using the CSO long-term monitoring data. Automatic sampling system installed in the Nagaoka City public sewerage system, and the quality and quantity of the combined sewer overflow were continuously observed for more than 75 months. There is no clear relation between the number of CSO”Ēs and the volume of CSO discharge. The factor is neither the population change nor the mean annual rainfall in monitoring area. Then, Other factors were enumerated. It is a decrease in unclear water by having executed pipe rehabilitation to sewer that becomes superannuated. The volume of CSO increases when there is crack in the upper part of sewer. When it is one side, there is crack also in lower sides, sewer issue to geological layer and land contamination is caused. They are canceled by executing pipe rehabilitation. In the region that outflows exceed more than inflows of unclear water, the effect of the pollution load reduction on public water can be expected by executing pipe rehabilitation.
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