The significance of sewage treatment: after the sewage is treated, it can be recycled, reducing the consumption of water resources for our production. Water treatment technology utilizes relevant technical means to purify sewage so that it can continue to use, so sewage treatment is extremely important.
Categorized by the source of sewage, sewage treatment is generally divided into production sewage treatment and domestic sewage treatment. Production of sewage, including industrial sewage, agricultural sewage, and medical sewage, etc., while the domestic sewage is the sewage generated by daily life, refers to a variety of forms of inorganic and organic matter of the complex mixture, including:
① Floating and suspended solid particles of various sizes;
② gelatinous and gel-like diffusive matter;
③ pure solution.
By the quality of water pollution, water pollution has two categories:
A class of natural pollution; the other
A class of man-made pollution, the current harm to the water body is more man-made pollution.
Sewage treatment is widely used in construction, agriculture, transportation, energy, petrochemicals, environmental protection, cityscape, medical care, food and beverage and other fields, but also more and more into the daily life of ordinary people.
Expanded Information
Sewage treatment can be divided into physical, biological and chemical methods according to its role.
①Physical method: the main use of physical separation of 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, used for village and town water capacity, self-purification ability, the degree of sewage treatment requirements are not high.
② biological method: the use of microbial metabolism, the sewage is dissolved or colloidal state of organic matter decomposition and oxidation into 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 for industrial wastewater. Commonly used are coagulation, neutralization, oxidation reduction, 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.
After primary treatment of wastewater BOD removal rate of only 20%, is still not suitable for discharge, but also must carry out secondary treatment. The main task of secondary treatment is to substantially remove the colloidal and dissolved organic matter in the state of sewage, BOD removal rate of 80% to 90%.
Generally after secondary treatment of sewage can meet the discharge standards, commonly used activated sludge and biofilm treatment. The purpose of tertiary treatment is to further remove a particular pollutant, such as fluoride, phosphorus removal, etc., belongs to the depth of treatment, commonly used chemical method.
Baidu Encyclopedia - Wastewater Treatment