Regulatory Requirements
I. Control Items and Classification
China's urban sewage discharge standards are mainly based on Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002) and supplementary industry and local regulations, covering pollutant limits, classification standards and special requirements. The control items are divided into basic control items and selective control items. There are 19 basic control items, mainly including conventional pollutants that affect the water environment and can be removed by the general treatment processes of municipal wastewater treatment plants, as well as some category 1 pollutants. There are 43 selective control items, which are pollutants with relatively long-term environmental impacts or high toxicity, and their control shall be determined by local environmental protection administrative departments according to actual conditions.
II. Standard Classification
According to the environmental function and protection objectives of the surface water bodies into which the wastewater treatment plants discharge, as well as the treatment processes, the standard values of conventional pollutants in the basic control items are divided into Grade 1, Grade 2 and Grade 3 standards, with Grade 1 further divided into Standard A and Standard B.
Grade 1 Standard A: This is the basic requirement for the effluent of municipal wastewater treatment plants to be reused as reclaimed water. It shall be implemented when the effluent of wastewater treatment plants is discharged into rivers and lakes with low dilution capacity for use as urban landscape water and general reclaimed water.
Grade 1 Standard B: It is applicable to the discharge of wastewater treatment plant effluent into Class III functional waters of surface water as specified in GB 3838 (excluding designated drinking water source protection areas and swimming areas), Class II functional waters of marine water as specified in GB 3097, and enclosed or semi-enclosed water bodies such as lakes and reservoirs.
Grade 2 Standard: It shall be implemented when the effluent of wastewater treatment plants is discharged into Class IV and Class V functional waters of surface water as specified in GB 3838 or Class III and Class IV functional marine areas as specified in GB 3097.
Grade 3 Standard: For wastewater treatment plants in towns not located in key control basins or drinking water source protection areas that adopt enhanced primary treatment processes, Grade 3 Standard shall be implemented, but the location for secondary treatment facilities shall be reserved to meet Grade 2 Standard in phases.
III. Standard Values
In Grade 1 Standard A, the Chemical Oxygen Demand (COD) is 50 mg/L, the Biochemical Oxygen Demand (BOD) is 10 mg/L, and the Suspended Solids (SS) is 10 mg/L, etc. Details are shown in the table below (Unit: mg/L)
Table 1 Maximum Allowable Discharge Concentrations of Basic Control Items (Daily Average Value), Unit: mg/L
| No. | Basic Control Items | Grade 1 Standard | Grade 2 Standard | Grade 3 Standard |
| Standard A | Standard B |
| 1 | Chemical Oxygen Demand (COD) | 50 | 60 | 100 | 120① |
| 2 | Biochemical Oxygen Demand (BOD₅) | 10 | 20 | 30 | 60① |
| 3 | Suspended Solids (SS) | 10 | 20 | 30 | 50 |
| 4 | Animal and Vegetable Oils | 1 | 3 | 5 | 20 |
| 5 | Petroleum Substances | 1 | 3 | 5 | 15 |
| 6 | Anionic Surfactants | 0.5 | 1 | 2 | 5 |
| 7 | Total Nitrogen (as N) | 15 | 20 | - | - |
| 8 | Ammonia Nitrogen (as N)② | 5 (8) | 8 (15) | 25 (30) | - |
| 9 | Total Phosphorus (as P) | For facilities built before December 31, 2005 | 1 | 1.5 | 3 | 5 |
| For facilities built on or after January 1, 2006 | 0.5 | 1 | 3 | 5 |
| 10 | Colority (dilution multiple) | 30 | 30 | 40 | 50 |
| 11 | pH | 6-9 |
| 12 | Fecal Coliform (MPN/L) | 103 | 104 | 104 | - |
Note: This scheme only lists part of the pollutant discharge standards; please refer to the relevant contents in the standards for other pollutants.
① The removal rate indicators shall be implemented under the following conditions: when the influent COD is higher than 350 mg/L, the removal rate shall be greater than 60%; when the influent BOD is higher than 160 mg/L, the removal rate shall be greater than 50%.
② The values outside the parentheses are the control indicators when the water temperature is > 12℃, and the values inside the parentheses are the control indicators when the water temperature is ≤ 12℃.
IV. Relevant Standards
CJ/T 51-2004 Standard Methods for Examination of Urban Sewage Quality
CJ 3082-1999 Water Quality Standard for Discharge of Sewage into Urban Sewers
CJ 3025-1993 Discharge Standard of Sewage Sludge from Municipal Wastewater Treatment Plants
GB/T 19772-2005 The Reuse of Urban Recycling Water - Water Quality Standard for Groundwater Recharge
GB 18918-2002 Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant
DB44/26-2001 Emission Limits of Water Pollutants of Guangdong Province (Implementation Standard for Industrial Wastewater Testing)
GB 18918-2002 Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant
CJ 343-2010 Water Quality Standard for Discharge of Sewage into Urban Sewers
GB 3544-2008 Discharge Standard of Water Pollutants for Pulp and Paper Industry
GB 21909-2008 Discharge Standard of Water Pollutants for Sugar Industry
GB 21908-2008 Discharge Standard of Water Pollutants for Mixed Preparation Pharmaceutical Industry
GB 21906-2008 Discharge Standard of Water Pollutants for Traditional Chinese Medicine Pharmaceutical Industry
GB 21901-2008 Discharge Standard of Water Pollutants for Down and Feather Industry
GB 21523-2008 Discharge Standard of Water Pollutants for Heterocyclic Pesticide Industry
GB 18466-2005 Discharge Standard of Water Pollutants for Medical Institutions
GB 13456-1992 Discharge Standard of Water Pollutants for Iron and Steel Industry
GB 4287-1992 Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry
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