The choice of process flow for dairy wastewater treatment depends on the characteristics of the wastewater and the effluent discharge requirements. The treatment process is primarily biological, and based on the main unit responsible for pollutant removal load, it can be divided into aerobic treatment systems and “anaerobic + aerobic” treatment systems. Generally, when the COD of dairy wastewater is <1500 mg/L, an aerobic treatment system is considered; when COD >1500 mg/L, an “anaerobic + aerobic” treatment system is considered.
Aerobic treatment systems have a lower volumetric loading rate and are suitable for treating dairy wastewater with smaller volumes and lower pollutant concentrations. They can be divided into single-stage aerobic and multi-stage aerobic systems, and require supplementary biological and physicochemical methods as pretreatment or post-treatment to meet discharge standards. Typical process flows include “air flotation + hydrolysis acidification + single-stage aerobic,” “multi-stage aerobic + chemical coagulation sedimentation,” and “air flotation + single-stage aerobic + air flotation.” The “anaerobic + aerobic” treatment system is suitable for end-of-pipe treatment in dairy processing plants with complex products and large wastewater volumes. It typically requires supplementary pretreatment methods such as oil separation, flotation, and hydrolysis acidification. Typical process flows include “flotation + anaerobic + multi-stage aerobic,” “hydrolysis acidification + flotation + anaerobic + single-stage aerobic,” and “hydrolysis acidification + anaerobic + single-stage aerobic.” With reasonable design parameter values, all of the above process flows can meet the Class II standard of the “Integrated Wastewater Discharge Standard” . Dairy wastewater discharged into natural water bodies must comply with stricter discharge standards and requires a tertiary treatment process. Typical tertiary treatment processes for dairy wastewater include “oil separation and hydrolysis + anaerobic + aerobic + filtration” and “hydrolysis + flotation + multi-stage aerobic + filtration.”
