The separation of clean water and sewage is mainly to separate the highly polluted water from the unpolluted water or the low polluted water, and treat them separately, so as to reduce the amount of discharged pollutants and reduce the cost of water treatment. Clear water and sewage is a relative concept, which is closely related to the quality of raw water and discharge standards. At present, the national and provincial departments have not issued clear definition standards.
The separation of rainwater and sewage is a way to separate urban sewage from rainfall runoff and use a drainage pipe for discharge or subsequent treatment. Rainwater can be directly discharged into the river through the rainwater pipe network, or can be used as landscape water and municipal water after natural precipitation; sewage needs to be collected through the sewage pipe network and sent to the sewage treatment plant for treatment, and then discharged into the river after the water quality reaches the corresponding national or local standards. The separation of rainwater and sewage facilitates rainwater collection and centralized management and discharge, reduces the impact of water volume on the sewage treatment plant, avoids the pollution of sewage on river and groundwater, and ensures the treatment efficiency of sewage treatment plant.