Sewage treatment is widely used in construction, agriculture, transportation, energy, petrochemical, environmental protection, urban landscape, medical treatment, catering and other fields. The specific processes are as follows:

1. Chemical dephosphorization technology

The basic principle of chemical dephosphorization is to form insoluble phosphate precipitate by adding chemicals, and finally phosphorus is removed from sewage by solid-liquid separation. Its main research direction focuses on the optimal selection of chemical agents.

2. Biological phosphorus removal technology

Biological phosphorus removal technology is an economical phosphorus removal method, which can effectively remove phosphorus without affecting the removal of total nitrogen, with low operating cost, and can avoid a large number of chemical sludge produced by chemical phosphorus removal method. Among them, denitrifying phosphorus removal process is the focus of current research.

3 chemical-assisted biological phosphorus removal

Due to the poor stability and flexibility of biological phosphorus removal, it is easily affected by factors such as carbon source and pH value, and the phosphorus content of effluent often fails to meet the requirements of national emission standards. The process stability of biological phosphorus removal can be improved by additional chemical precipitation.

Working procedures of sewage treatment:

1. Primary treatment

Mainly removes suspended solid pollutants in sewage, and most physical treatment methods can only meet the requirements of primary treatment. After primary treatment, BOD can generally be removed by about 31%, which can not meet the discharge standard. Primary treatment belongs to the pretreatment of secondary treatment.

2. The secondary treatment

mainly removes colloidal and dissolved organic pollutants (BOD, COD) in sewage, and the removal rate can reach over 91%, so that the organic pollutants can meet the discharge standard, and the removal rate of suspended solids can reach 95%, and the effluent effect is good.

3. Tertiary treatment

Further treatment of refractory organic matter, soluble inorganic matter such as nitrogen and phosphorus which can lead to eutrophication of water body. The main methods include biological nitrogen and phosphorus removal, coagulation and precipitation, sand filtration, activated carbon adsorption, ion exchange and electrodialysis.

above content reference: Baidu Encyclopedia-Sewage Treatment