2. Biological method: The organic matter in dissolved or colloidal state in sewage is decomposed and oxidized into stable inorganic matter by using the metabolic function of microorganisms, so that the sewage can be purified. Activated sludge process and biofilm process are commonly used. The treatment degree of biological method is higher than physical method.
3. Chemical method: it is a method to treat or recover dissolved or colloidal substances in sewage through chemical reaction, which is mostly used in industrial wastewater. Coagulation, neutralization, redox and ion exchange are commonly used methods. Chemical treatment has good treatment effect and high cost, and it is mostly used as the effluent after biochemical treatment for further treatment to improve the effluent quality.
Causes of extended data pollution:
Among the water pollution caused by human production activities, industrial water pollution is the most serious. Such as industrial wastewater, which has many pollutants and complex components, is not only difficult to purify in water, but also difficult to treat.
Industrial wastewater is the main cause of water pollution caused by industrial pollution. It accounts for most of the pollutants discharged by industry. Due to different types of factories, the pollutants contained in industrial wastewater vary widely. Even in similar factories, the quality and quantity of pollutants are different due to different production processes. In addition to the direct injection of industrial wastewater into the water body, solid waste and waste gas will also pollute the water body.
Agricultural pollution is firstly caused by loose surface caused by farming or land reclamation. When the soil and terrain are unstable, a large amount of sediment flows into the water, which increases the suspended solids in the water.
Another important reason is that the use of pesticides and fertilizers is increasing day by day. Only a small amount of pesticides and fertilizers are attached or absorbed, and most of the rest remain in the soil, floating in the atmosphere, entering and infiltrating into surface water through rainfall and surface runoff, forming pollution.
Urban pollution sources are water pollution caused by urban population concentration and urban domestic sewage, garbage and waste gas. The pollution of urban pollution sources to water bodies is mainly domestic sewage, which is a mixture of various kinds of sewage produced in people's daily life, including sewage discharged from kitchens, bathrooms and toilets.
In the world, the industrial and domestic wastewater discharged from urban areas alone is as much as 500 cubic kilometers every year, and each drop of sewage will cause several times or even dozens of times of pollution to the water body.
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