In order to ensure the water quality and health conditions of the water body, the sewage in the discharged water body should meet the requirements stipulated by the state. Due to the different uses of water bodies, their requirements are also different. For example, some water systems are used as water supply sources, while others are used only for swimming and beautifying the city.

The first-level water body is used as the centralized water supply source of the city, and is located in the second sanitary protection zone of the water supply project, or the river section used as the protection zone of the national fish farm.

The second-level water body is used as unorganized drinking water source, food industry water supply and fish spawning area. The group swims to the reaches of the river where the spawning grounds pass.

The quality of sewage at all levels of water bodies shall meet the following requirements:

①After the sewage is mixed with the water body, the increase in the amount of suspended impurities in the water body should not exceed: the first water body - 0.25 mg/L, the second water body - 0.75 mg/L, and the third water body - 1.5 mg/L.

②After the sewage is discharged into the water at all levels, the dissolved oxygen in the water should not be less than 4.0 mg/L;

③After the first-grade water body is mixed with sewage, the B∏K5 value at 20°C should not be greater than 2.0 mg/L, and if it is a second-grade water body, the B∏K5 value should not be greater than ±.0 mg/L;

4. The sewage should not produce any odor after mixing with the water in the water body, and no odor should be produced after chlorine is added in the water treatment process;

⑤ The sewage should not have a significant color after being mixed with the water body. For this reason, the sewage and distilled water are mixed according to the designed dilution of the sewage in the water body and the transparency is measured. For general water bodies, the mixed water should have no significant color when the water column is 20 cm high; for secondary water bodies, the above water column height is 10 cm; for tertiary water bodies, the gauge is 5 cm high;

⑥After the water body is mixed with sewage, the pH value should be between 6.5÷8.5;

⑦After the sewage is diluted by the water body, the concentration of toxic substances should not cause direct or indirect harm to people and living things. In addition, there should not be too much floating material in the sewage discharged into the water body. Sewage that may contain infectious bacteria is prohibited from being discharged into first-class water bodies; this water can be discharged into second- and third-class water bodies after treatment.