What are the common methods of industrial wastewater treatment?

Basic method of wastewater treatment: (1) Physical treatment is adopted in the primary treatment, that is, structures such as grating, screen, grit chamber, sedimentation tank and grease trap are used to remove solid suspended solids and oil slick in wastewater, and the pH value is preliminarily adjusted to reduce the degree of wastewater corruption. After primary treatment, wastewater generally can't meet the discharge standard (BOD removal rate is only 25-40%). Therefore, it is usually a pretreatment stage to reduce the load of the subsequent treatment process and improve the treatment effect.

Basic methods of wastewater treatment: (2) Secondary treatment is to remove degradable organic matter and some colloidal pollutants from wastewater through biological treatment and some chemical methods. After secondary treatment, the removal rate of BOD in wastewater can reach 80-90%, that is, the total BOD can be less than 30 mg/L, and the water after secondary treatment can generally meet the standards of agricultural irrigation and wastewater discharge, so secondary treatment is the main body of wastewater treatment. However, after secondary treatment, there are still a certain amount of suspended solids, dissolved organic matter, dissolved inorganic matter, nitrogen and phosphorus and other algae value-added nutrients in the water, and there are also viruses and bacteria. Therefore, higher emission standards cannot be achieved. If it is discharged into a river with small flow and poor dilution ability after treatment, it may cause pollution and cannot be directly used as a supply source of tap water, industrial water and groundwater.

Basic methods of wastewater treatment: (3) Tertiary treatment is to further remove pollutants that cannot be removed by secondary treatment, such as phosphorus, nitrogen, biodegradable organic pollutants, inorganic pollutants and pathogens. The tertiary treatment of wastewater is a "advanced treatment" method which further adopts chemical methods (chemical oxidation, chemical precipitation, etc.) on the basis of secondary treatment. ) and physical and chemical methods (adsorption, ion exchange, membrane separation technology, etc. ) remove some specific pollutants. Obviously, the cost of tertiary treatment of wastewater is high, but water resources can be fully utilized.