Sewage treatment process level

  Modern sewage treatment technology can be divided into primary, secondary and tertiary treatment according to the treatment degree.

  Primary treatment mainly removes suspended solid pollutants in sewage. Most physical treatment methods can only meet the requirements of primary treatment. BOD can be removed about 30% of the sewage after primary treatment, which can not meet the discharge standard. The primary treatment belongs to the pretreatment of the secondary treatment.

  The secondary treatment mainly removes the colloidal and dissolved organic pollutants (BOD and COD) in the sewage, and the removal rate can reach more than 90%, making the organic pollutants meet the discharge standard.

  Three stage treatment, further treatment of refractory organic matter, nitrogen, phosphorus and other soluble inorganic matter that can lead to eutrophication of water body. The main methods include biological nitrogen and phosphorus removal, coagulation sedimentation, sand filtration, activated carbon adsorption, ion exchange and electroosmosis analysis.

  The whole process is that the raw sewage passing through the coarse screen is lifted by the sewage lift pump, passes through the screen or sand filter, and then enters the grit chamber. The sewage passing through the sand water separation enters the primary sedimentation tank. The above is the primary treatment (i.e. physical treatment). The effluent from the primary sedimentation tank enters the biological treatment equipment, including activated sludge method and biofilm method, (the reactors of the activated sludge method include aeration tank, oxidation ditch, etc., and the biofilm method includes biofilter, biological rotary table, biological contact oxidation method and biological fluidized bed). The effluent from the biological treatment equipment enters the secondary sedimentation tank. The effluent from the secondary sedimentation tank is disinfected and discharged or enters the tertiary treatment. The primary treatment is the secondary treatment. The tertiary treatment includes biological nitrogen and phosphorus removal, coagulation sedimentation and sand filtration, Activated carbon adsorption, ion exchange and electrodialysis. Part of the sludge from the secondary sedimentation tank returns to the primary sedimentation tank or biological treatment equipment, and part of it enters the sludge concentration tank, and then enters the sludge digestion tank. After passing through the dehydration and drying equipment, the sludge is finally used.