下水道中不明水的调查及防治对策

城市下水道中的实际污水量往往超过汇入的污水与雨水量之和，在地下水位高的地区或雨水充沛的汛期这种现象尤为突出。超出的部分在日本被称为不明水量，其主要来源于地下水和雨水的渗入。不明水不仅会造成检查井溢水，还增加了污水处理厂的负荷和运行成本。通过对日本某市下水道的实地调查，就合流制管道中来源不明的水进行了定量分析，并提出了相应的防治对策。

Survey of Unknown-water in Sewers and Corresponding Countermeasure

The actual capacity of an urban drainage system usually exceeds the combined feed capacity of rain water and wastewater. This phenomenon is outstanding during the season of high groundwater level and abundant rainwater. The additional part is called as unknown-water in Japan. It stems mainly from the infiltration of groundwater and rain water. As a result, the unknown-water not only causes overflow of manhole, it also increases load and operation cost of wastewater treatment plant. On the basis of field survey of certain sewers in a city of Japan, unknown-water in combined sewers is analyzed, and some corresponding countermeasures are put forward.