1, physical method: the main use of physical action to separate the non-soluble substances in the sewage, in the treatment process does not change the chemical nature. Commonly used gravity separation, centrifugal separation, reverse osmosis, air flotation. Physical method of treatment structures are simpler, more economical, for the village water capacity, self-purification ability, sewage treatment is not required to a high degree of the case.
2, biological method: the use of microbial metabolism, the sewage is dissolved or colloidal organic decomposition and oxidation of stable inorganic substances, so that sewage is purified. Commonly used activated sludge and biofilm method. Biological method of treatment is higher than the physical method.
3, chemical method: is the use of chemical reactions to treat or recover sewage dissolved substances or colloidal substances, mostly used in industrial wastewater. Commonly used coagulation, neutralization method, redox method, ion exchange method. Chemical treatment method is good, high cost, mostly used as a biochemical treatment of the effluent, for further treatment to improve the quality of the effluent.
Extended information?
Treatment technology: primary treatment is mainly to remove the sewage is suspended solid pollutants, most of the physical treatment method can only complete the requirements of primary treatment. After primary treatment of sewage, BOD can generally remove about 30%, not up to the discharge standard. Primary treatment belongs to the pretreatment of secondary treatment.
Secondary treatment mainly removes colloidal and dissolved organic pollutants in the sewage state (BOD, COD substances), the removal rate of up to 90% or more, so that organic pollutants to meet the discharge standards, suspended solids removal rate of 95% of the effluent effect is good. Tertiary treatment to further deal with difficult to degrade organic matter, nitrogen and phosphorus, etc. can lead to eutrophication of the water body, such as soluble inorganic substances.
Baidu Encyclopedia - Wastewater Treatment