Treatment Methods of Food Processing Wastewater
Release time：
2026-05-08
Due to the wide variety of food types and extensive raw material sources, food industry wastewater is characterized by high contents of suspended solids and grease, abundant heavy metal ions, high COD and BOD values, large fluctuations in water quality and water volume, high concentrations of nitrogen and phosphorus compounds, and in some cases, relatively high water temperature. Sludge, waste oil, waste acid and waste alkali are generated during the treatment of food wastewater. In addition, animal and plant waste produced in the processing process shall also be subjected to harmless disposal.
I. Physical Treatment Methods
Physical treatment refers to the method of changing the composition of sewage by physical action. Common physical treatment methods for food industry sewage include screening, skimming, regulation, sedimentation, air flotation, centrifugal separation, filtration and microfiltration. The first five processes are mostly used for pretreatment or primary treatment, while the latter three are mainly applied to advanced treatment.
II. Chemical Treatment Methods
Chemical treatment adopts chemical principles and chemical reactions to convert pollutants in sewage into harmless substances so as to purify wastewater. Pollutants will change their chemical properties after chemical treatment, and the process is always accompanied by chemical reactions. Chemical treatment methods applied to food industry sewage include neutralization, coagulation, electrolysis, redox, ion exchange and membrane separation.
III. Biological Treatment Methods
Biochemical treatment is one of the most important processes in organic wastewater treatment systems. In food processing wastewater treatment, biological processes can be divided into aerobic processes, anaerobic processes, stabilization ponds, land treatment, and various combined processes formed by the integration of the above technologies. Food wastewater is a type of organic sewage, and biological treatment serves as the main secondary treatment process to degrade COD and BOD₅.
Aerobic biological treatment processes are classified into activated sludge processes and membrane processes according to the growth form of microorganisms utilized. The former includes conventional activated sludge process, step aeration process, biosorption process, complete mixing process, extended aeration process, oxidation ditch and sequencing batch reactor (SBR). The latter covers biological filter, tower biological filter, biological rotary disc, activated biofilter, biological contact oxidation process and aerobic fluidized bed. Generally, aerobic treatment performs well on low-concentration wastewater.
Anaerobic biological treatment processes are suitable for food processing wastewater, mainly because the wastewater contains high-concentration and easily biodegradable organic matter without toxicity. In addition, anaerobic treatment features low power consumption; the generated biogas can be used as energy source, and the excess sludge yield is low. The fully enclosed anaerobic treatment system helps improve environmental sanitation, allows seasonal or intermittent operation, and enables long-term sludge storage.
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