1, sewage discharged into Class III waters of GB3838 and Class II waters of GB3097 shall be subject to Class I standards;

2. Sewage discharged into Class V and VI waters in GB3838 and Class III waters in GB3097 shall be subject to Class II standards;

3. The sewage discharged into the urban drainage system after being treated by the secondary sewage treatment plant shall implement the three-level standard.

Legal basis: Article 14 of People's Republic of China (PRC) Water Pollution Prevention Law.

The competent department of environmental protection in the State Council shall, according to the national water environmental quality standards and the national economic and technical conditions, formulate the national water pollutant discharge standards.

The people's governments of provinces, autonomous regions and municipalities directly under the Central Government may formulate local standards for the discharge of water pollutants for projects not specified in the national standards for the discharge of water pollutants; For projects that have been stipulated in the national water pollutant discharge standards, local water pollutant discharge standards that are stricter than the national water pollutant discharge standards can be formulated. Local water pollutant discharge standards shall be reported to the competent department of environmental protection of the State Council for the record.

Where pollutants are discharged into water bodies with local water pollutant discharge standards, the local water pollutant discharge standards shall be implemented.

Article 15

The competent department of environmental protection in the State Council and the people's governments of provinces, autonomous regions and municipalities directly under the Central Government shall, according to the requirements of water pollution prevention and control and the national or local economic and technological conditions, revise the water environmental quality standards and water pollutant discharge standards in a timely manner.

Article 16

The prevention and control of water pollution shall be in accordance with the unified planning of river basins or regions. Plans for the prevention and control of water pollution in important rivers and lakes determined by the state shall be formulated by the competent department of environmental protection of the State Council in conjunction with the comprehensive macro-control department of the State Council's economy, the competent department of water administration and the people's governments of relevant provinces, autonomous regions and municipalities directly under the Central Government, and submitted to the State Council for approval.

Plans for the prevention and control of river basin water pollution in other provinces, autonomous regions and municipalities directly under the Central Government other than those specified in the preceding paragraph shall be prepared by the competent environmental protection department of the people's government of the province, autonomous region and municipality directly under the Central Government in conjunction with the water administrative department at the same level and the relevant municipal and county people's governments, and shall be reviewed by the people's government of the province, autonomous region and municipality directly under the Central Government and submitted to the State Council for approval.

Plans for the prevention and control of water pollution in rivers and lakes across counties, autonomous regions and municipalities directly under the Central Government shall be formulated by the competent environmental protection department of the people's governments of provinces, autonomous regions and municipalities directly under the Central Government in conjunction with the water administrative department at the same level, and submitted to the people's governments of provinces, autonomous regions and municipalities directly under the Central Government for approval and to the State Council for the record.

The approved water pollution prevention and control plan is the basic basis for water pollution prevention and control, and the modification of the plan must be approved by the original approving authority.

The local people's governments at or above the county level shall organize the formulation of water pollution prevention and control plans in their respective administrative areas in accordance with the legally approved water pollution prevention and control plans for rivers and lakes.

What is the process of sewage treatment?

1. mainly removes suspended solid pollutants from sewage, and most physical treatment methods can only meet the requirements of primary treatment. After primary treatment, BOD can generally be removed by about 30%, which can not meet the discharge standard. Primary treatment belongs to the pretreatment of secondary treatment;

2. It mainly removes colloid and dissolved organic pollutants in sewage, and the removal rate can reach above 90%, so that the organic pollutants can meet the discharge standard, and the removal rate of suspended solids can reach 95%, with good effluent effect;

3. Further treatment of refractory organic matter and soluble inorganic matter, such as nitrogen and phosphorus, which can lead to water eutrophication. The main methods include biological nitrogen and phosphorus removal, coagulation and sedimentation, sand filtration, activated carbon adsorption, ion exchange and electrodialysis.