After preliminary treatment, industrial wastewater passes through primary treatment, where physicochemical processes are used to remove BOD, COD, oils, fats, and remaining TSS.

Typical primary treatment methods include dissolved air flotation (DAF) electrocoagulation, coagulation-flocculation, and sedimentation.

In this way, process wastewater is prepared either for direct discharge into the sewer system or natural receiving body, or for further biological wastewater treatment.