Wastewater Discharge Requirements for Ceramic Manufacturing

Ceramic production is a water-intensive industry. Wastewater originates from raw material preparation, forming, glazing, polishing, and equipment cleaning, and typically contains high concentrations of suspended solids, organic matter, and trace heavy metals. In China, the discharge of these effluents is governed by a dedicated national standard supported by supplementary technical guidelines and, in some regions, stricter local requirements.

The Core National Standard

The primary regulatory instrument is GB 25464–2010, the Emission Standard of Pollutants for Ceramics Industry. It specifies limits, monitoring, and control requirements for both water and air pollutant discharge from ceramic enterprises. The standard applies to architectural ceramics, sanitary ware, domestic and decorative porcelain, and special ceramics. Once it took effect, ceramic manufacturers were no longer subject to the wastewater provisions of the older Integrated Wastewater Discharge Standard (GB 8978–1996); GB 25464–2010 became the controlling standard.

A 2014 amendment revised certain provisions of GB 25464–2010. It is important to note that the amendment focused on air pollutant parameters—specifically the reference oxygen content and emission limits for particulate matter, sulfur dioxide, and nitrogen oxides from spray dryers and kilns. The water pollutant limits in the original standard were not altered by this amendment.

Key Discharge Limits and Monitoring Locations

The standard distinguishes between direct discharge and indirect discharge (discharge to a municipal sewer or centralized treatment facility). Direct discharge limits are considerably stricter. For direct discharge, chemical oxygen demand is limited to 50 mg/L, suspended solids to 50 mg/L, and ammonia nitrogen to 3.0 mg/L. Total phosphorus is capped at 1.5 mg/L. For indirect discharge, the corresponding limits are relaxed: COD at 110 mg/L, suspended solids at 120 mg/L, and ammonia nitrogen at 10 mg/L.

Heavy metals are subject to a different monitoring regime. Rather than being controlled only at the final plant outfall, parameters such as total cadmium, total chromium, total lead, and total nickel are monitored at the outlet of the specific workshop or production facility where they may be generated. This “workshop outlet” approach prevents dilution from masking heavy metal contributions before they reach the final discharge point. The pH value for all discharge must remain between 6 and 9.