People's Republic of China (PRC) Environmental Protection Law
Article 10 "The people's governments of provinces, autonomous regions and municipalities directly under the Central Government may formulate local pollutant discharge standards for items not specified in the national pollutant discharge standards; For projects that have been stipulated in the national pollutant discharge standards, local pollutant discharge standards that are stricter than the national pollutant discharge standards can be formulated. " In the case of coexistence of two standards, local standards should be implemented.
1999 The Ministry of Construction formulated the Water Quality Standard for Sewage Discharged into Urban Sewers (CJ3082- 1999), which stipulated the maximum allowable concentration of 35 harmful substances in sewage discharged into urban sewers.