Sewage treatment process is a variety of economical, reasonable, scientific and effective process methods for urban domestic sewage and industrial wastewater. Sewage treatment is widely used in construction, agriculture, transportation, energy, petrochemical, environmental protection, urban landscape, medical, catering and other fields. The urban sewage treatment process should be determined according to the treatment scale, water quality characteristics, environmental functions of the receiving water body, and local actual conditions and requirements, after technical and economic comparison.
A. Classification of sewage treatment processes
1. According to the nature of the treatment method
Physical method: sedimentation method, filtration, oil separation, air flotation, centrifugal separation, magnetic separation;
Chemical method: coagulation precipitation method, neutralization method, redox method, chemical precipitation method;
Physical and chemical methods: adsorption, ion exchange, extraction, stripping, stripping;
Biological method: activated sludge method, biofilm method, anaerobic process, biological nitrogen and phosphorus removal process.
2. According to the water quality status and the destination of the treated water
Primary treatment: mechanical treatment (pretreatment stage)
Coarse grille and fine grille, grit chamber, primary sedimentation tank, air flotation tank, adjustment tank.
Secondary treatment: the main process is biochemical treatment (main body)
Activated sludge process, CASS process, A2/O process, A/O process, SBR, oxidation ditch, hydrolysis acidification tank.
Tertiary Treatment: Control Eutrophication and Reuse
Advanced catalytic oxidation, aerated biological filter, fiber filter, active sand filtration, reverse osmosis, membrane treatment, and reclaimed water reuse generally include disinfection tanks, ultraviolet ozone disinfection tanks, and chlorine dioxide disinfection tanks.
Under normal circumstances, the actual sewage often contains a variety of pollutants, and only a single treatment method often fails to achieve the expected effect. In order to obtain a better treatment effect at a lower treatment cost, it is often necessary to select several treatment technologies according to certain factors, such as the quality of the sewage, the amount of water, the degree of treatment, the possibility of recycling useful substances, and the conditions of the capital and site. The primary and secondary relationship and the sequence before and after are reasonably combined to form a complete purification treatment system.