According to the viewpoint of sewage source, sewage can be defined as liquid or water with waste discharged from houses, institutions, businesses or industrial areas and mixed with groundwater, surface water and snowstorms. There are many kinds of sewage, and there are many technologies and processes to reduce the impact of sewage on the environment accordingly. According to the source of sewage, sewage can be divided into these four categories.

category I: industrial wastewater comes from sewage from mining and industrial production activities, including runoff leachate from industrial or commercial storage and processing, and other wastewater that is not domestic sewage.

category ii: domestic sewage comes from houses, office buildings, institutions or similar sewage; Sanitary sewage; Sewer sewage, including industrial wastewater mixed with domestic sewage in sewer system.

the third category: non-toxic and harmless sewage with commercial sewage coming from commercial facilities and some components exceeding domestic sewage [2]. Such as restaurant sewage. Laundry sewage, animal feeding sewage, hair salon sewage, etc.

category iv: surface runoff comes from rainwater, snow water, expressway sewage, water from urban and industrial areas, etc. surface runoff does not penetrate into soil, but enters groundwater along streets and land.