Sewage treatment according to its role can be divided into physical process, biological process and chemical process three.

1, physical process: the main use of physical separation of sewage in the non-soluble substances, 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, used in villages and towns with a large capacity of water, self-purification ability, sewage treatment is not required to a high degree of the case.

2, biological processes: the use of microbial metabolism, the sewage is dissolved or colloidal organic decomposition and oxidation of stable inorganic substances, so that the sewage is purified. Commonly used activated sludge and biofilm method. Biological method of treatment is higher than the physical method.

3, chemical process: is the use of chemical reactions to treat or recover sewage dissolved substances or colloidal substances, mostly used for 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.

Sewage treatment guidelines:

1, urban sewage treatment process should be based on the scale of treatment, water quality characteristics, the environmental function of the receiving body of water and the actual situation and requirements of the local area, after a comprehensive technical and economic comparison of the preferred to determine.

2, process selection of the main technical and economic indicators include: treatment of unit water investment, reduce the unit of pollutant investment, treatment of unit water consumption and cost, reduce the unit of pollutant consumption and cost, footprint, operational performance and reliability, management and maintenance of the degree of difficulty, the overall environmental benefits.

3, should realistically determine the quality of sewage water intake, optimize process design parameters. Must be the current status of the water quality characteristics of sewage, pollutant composition of a detailed investigation or determination, to make a reasonable analysis and prediction. Complex or special in the composition of water quality, sewage treatment process should be carried out when the dynamic test, if necessary, should carry out pilot studies.

4, active and prudent use of efficient and economical new processes. For the first time in the domestic application of new processes, must be after pilot and production tests to provide reliable design parameters before application.

Reference to the above? Baidu Encyclopedia - Wastewater Treatment

Reference? Baidu Encyclopedia - Wastewater Treatment Process