The sources and places that discharge or release pollutants into water are called water pollution sources, which are the main culprits of water pollution. Water pollution sources can be classified from different angles.

Common sources of water pollution are classified as follows.

(1) According to the attributes of pollutants, there are physical pollution sources, chemical pollution sources, biological pollution sources (pathogenic bacteria, parasites and eggs) and composite pollution sources that discharge multiple pollutants at the same time.

(2) According to the spatial distribution of pollution sources, point source pollution (such as urban sewage and waste water discharge outlets of industrial and mining enterprises and ships), line source pollution (such as oil pipelines, sewage channels, roads, railways, etc.) and non-point source pollution ( Such as pesticides, fertilizers, etc. in farmland).

(3) According to the classification of pollutants, there are mercury pollution sources, phenol pollution sources, thermal pollution sources, radioactive pollution sources, etc.

(4) According to the receiving water bodies, there are surface water pollution sources, groundwater pollution sources, atmospheric water pollution sources, and marine pollution sources.

(5) According to the discharge time of pollution sources, there are continuous pollution sources, intermittent pollution sources and transient pollution sources. Continuous pollution sources can be further divided into continuous uniform pollution sources and continuous non-uniform pollution sources.

(6) According to the mobility of pollution sources, there are fixed pollution sources and mobile pollution sources. The number of fixed pollution sources is large and the harm is great, which is the main pollution source of water pollution.

(7) According to the human social activities that cause water pollution, there are industrial pollution sources, agricultural pollution sources, transportation pollution sources and domestic pollution sources. Among them, industrial pollution sources are the main source of water pollution. There are many types of industries, complex production processes, many types of pollutants, large quantities, different toxicity, difficult to purify, and the greatest harm to the water environment.