The significance of sewage treatment: After sewage is treated, it can be recycled to reduce the consumption of water resources for our country's production. Water treatment technology uses relevant technical means to purify sewage so that it can continue to be used, so sewage treatment is extremely important.

According to the classification of sewage sources, sewage treatment is generally divided into production sewage treatment and domestic sewage treatment. Production sewage includes industrial sewage, agricultural sewage and medical sewage, etc., while domestic sewage is the sewage produced in daily life, which refers to a complex mixture of various forms of inorganic and organic matter, including:

① Floating and suspended The size of solid particles;

② Colloidal and gelatinous diffusers;

③Pure solution.

According to the nature of water pollution, there are two types of water pollution:

One is natural pollution; the other

The other is man-made pollution. At present, man-made pollution is more harmful to water bodies.

Sewage treatment is widely used in various fields such as construction, agriculture, transportation, energy, petrochemicals, environmental protection, urban landscape, medical care, catering, etc., and is increasingly entering the daily lives of ordinary people.

Extended information

Sewage treatment can be divided into three types according to its functions: physical method, biological method and chemical method.

①Physical method: Mainly uses physical effects to separate insoluble substances in sewage without changing the chemical properties during the treatment process. Commonly used ones include gravity separation, centrifugal separation, reverse osmosis, air flotation, etc. The physical treatment structure is relatively simple and economical, and is used in villages and towns where water bodies have large capacity, strong self-purification capabilities, and low sewage treatment requirements.

②Biological method: Utilize the metabolic function of microorganisms to decompose and oxidize dissolved or colloidal organic matter in the sewage into stable inorganic substances, so that the sewage can be purified. Commonly used methods include activated sludge method and biofilm method. The degree of treatment by biological methods is higher than that by physical methods.

③Chemical method: It is a method that uses chemical reactions to treat or recover dissolved substances or colloidal substances in sewage. It is mostly used for industrial wastewater. Commonly used methods include coagulation method, neutralization method, redox method, ion exchange method, etc. Chemical treatment method has good treatment effect but high cost. It is mostly used as the effluent after biochemical treatment for further treatment to improve the quality of the effluent.

The BOD removal rate of wastewater after primary treatment is only 20%, which is still not suitable for discharge and requires secondary treatment. The main task of secondary treatment is to significantly remove colloidal and dissolved organic matter in sewage, with a BOD removal rate of 80% to 90%.

Generally, sewage that has undergone secondary treatment can meet the discharge standards. The activated sludge method and biofilm treatment method are commonly used. The purpose of tertiary treatment is to further remove certain special pollutants, such as fluorine removal, phosphorus removal, etc. It is an advanced treatment and chemical methods are commonly used.

Baidu Encyclopedia-Sewage Treatment