Wastewater Discharge Standards for the Soy Sauce Industry

Soy sauce production generates large volumes of highly concentrated organic wastewater, characterized by deep color, high salinity, elevated suspended solids, and exceptionally high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) levels. 

If discharged without proper treatment, such effluent can severely pollute receiving water bodies, causing eutrophication and disrupting aquatic ecosystems. Understanding the applicable discharge standards is therefore essential for regulatory compliance and environmental protection.

The Foundational Standard: GB 8978-1996

The soy sauce industry falls within the broader food fermentation sector, and its wastewater discharge is primarily governed by the national mandatory standard Integrated Wastewater Discharge Standard (GB 8978-1996). This foundational standard classifies discharge limits into three tiers based on the receiving environment:

Class I applies to discharge into Class III waters (as defined in GB 3838) or Class II seawater areas.

Class II applies to discharge into Class IV or V waters or Class III seawater areas.

Class III applies to discharge into municipal sewer systems that feed into secondary wastewater treatment plants.

For new, expanded, or renovated facilities, the Class I limits for key pollutants are set at COD ≤ 100 mg/L, BOD₅ ≤ 30 mg/L, and suspended solids (SS) ≤ 70 mg/L.

The Emerging Industry-Specific Standard

A significant development is the recent introduction of Emission Standard for Water Pollutants from Food Processing and Manufacturing Industry (GB 46817-2025), which specifically covers soy sauce, vinegar, and fermented sauce manufacturers. 

This standard establishes a more tailored regulatory framework for the sector, addressing pollutants including pH, color (dilution factor), SS, COD, BOD₅, ammonia nitrogen, total nitrogen, total phosphorus, and—for applicable subsectors—animal/vegetable oils and total coliforms.

Crucially, this standard introduces benchmark effluent volume per unit of product—a measure designed to prevent enterprises from simply diluting wastewater to meet concentration limits. For general areas, the limit is set at 6.5 m³ per tonne of product for existing enterprises and 6.0 m³ per tonne for new facilities. This approach combines concentration control with total quantity control, ensuring genuine pollution reduction rather than mere dilution！