Wastewater Discharge Standards for Large Central Kitchens

Large central kitchens, as the core hubs of concentrated and scaled food production, generate substantial volumes of wastewater with distinctive characteristics. The effluent originates from multiple sources—ingredient washing, equipment and container cleaning, floor flushing, and cooking processes—and typically contains high concentrations of chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), suspended solids (SS), ammonia nitrogen, and animal/vegetable oils. 

Given the large flow rates and concentrated discharge patterns, strict compliance with national and local standards is essential to prevent adverse impacts on municipal drainage systems and receiving water bodies.

The Regulatory Framework

The wastewater discharge from central kitchens is primarily governed by two national standards: the Integrated Wastewater Discharge Standard (GB 8978-1996) and the Wastewater Quality Standard for Discharge into Municipal Sewers (GB/T 31962-2015). The applicable requirements depend on the discharge destination. 

For wastewater discharged into municipal sewer networks after pretreatment, the GB 8978-1996 tertiary standard applies. For direct discharge into natural water bodies such as rivers or lakes, the primary or secondary standards of the same regulation must be met. Additionally, the GB/T 31962-2015 sets forth specific concentration limits for pH, COD, ammonia nitrogen, and other indicators for discharges into urban sewers.

Pretreatment Requirements

Given the high oil and grease content in central kitchen wastewater, pretreatment is mandatory before the effluent enters any treatment facility or municipal pipeline. According to the Technical Specification for Environmental Protection in Catering Industry (HJ 554-2010), oil-bearing wastewater must be treated through grease traps. 

The design and construction of these traps must adhere to technical specifications: the hydraulic retention time should not be less than 0.5 hours; the tank should be divided into at least two compartments with three baffles; and the oil-storage volume in manually cleaned traps should not be less than 25% of the effective tank volume.

The New Industry-Specific Standard

A significant development in recent years is the issuance of the Discharge Standard of Water Pollutants for Food Processing and Manufacturing Industry (GB 46817-2025), published on November 4, 2025. This standard, which took effect on January 1, 2026, for new facilities and will apply to existing ones from January 1, 2028, supersedes the relevant provisions of GB 8978-1996. 

It establishes discharge limits specifically tailored to food processing operations, including central kitchens. Facilities involved in meat processing may also need to comply with the Discharge Standard of Water Pollutants for Meat Processing Industry (GB 13457)！