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Sewage treatment have three steps
- Dec 05, 2018 -

Sewage treatment can be divided into primary treatment, secondary treatment and tertiary treatment according to the degree of treatment.

The primary treatment is mainly to remove the solid matter in the suspended state in the sewage, and the physical method is commonly used. The BOD removal rate of the primary treated wastewater is only 20%, which is still unsuitable for discharge and requires secondary treatment. The main task of the secondary treatment is to substantially remove the colloid and dissolved organic matter in the sewage, and the BOD removal rate is 80% to 90%. Generally, the secondary treated sewage can reach the discharge standard, and the activated sludge method and the biofilm treatment method are commonly used. The purpose of the tertiary treatment is to further remove certain special pollutants, such as fluorine removal and phosphorus removal, which are advanced treatments and common chemical methods.