Modern sewage treatment technology

Modern sewage treatment technology, according to degree of treatment, can be divided into one, two and three class treatment.

Primary treatment (physical treatment), mainly to remove suspended solid pollutants in sewage, most of physical treatment can only complete the requirements of treatment. After treatment, BOD  can generally be removed by about 30%, cannt satisfy the discharge standards.

Secondary treatment, mainly to remove colloidal and dissolved organic pollutants (BOD, COD substances) in sewage, removal rate can reach more than 90%, so that organic pollutants meet discharge standards. 

Thirdly treatment, further treatment of difficult-to-degrade organic matter, nitrogen and phosphorus, etc. which can lead to the eutrophication of water insoluble inorganics. Main methods include bio-nitrogen and phosphorus removal , coagulation precipitation, sand rate, activated carbon adsorption, ion exchange and electro seepage analysis.