For the whole world, the storage of water resources is limited in itself. With the continuous discharge of various industrial wastewater and domestic sewage, a large number of original clean water quality has been polluted, making available water in life increasingly scarce. With the continuous increase of various industrial construction, this kind of harm is also expanding. Only by making more rational use of limited resources can this vicious circle be alleviated. For the wastewater discharged from our daily life or production, due to different sewage substances and pollution levels, targeted sewage purification treatment can be carried out, so that the sewage with less pollution and purification can be reused. With the development of sewage treatment, it will effectively improve the discharge of domestic sewage and other sewage, so as to avoid large-scale pollution of clean water sources.
The basic methods of wastewater treatment are as follows:
Primary treatment is a physical treatment method, which uses grids and grids, grit chamber, sedimentation tank, oil separation tank and other structures to remove suspended solids and floating oil in wastewater, and then reduces the decomposition degree of wastewater through preliminary adjustment of pH value. After primary treatment, wastewater generally does not meet the discharge standard (BOD removal rate is only 25-40%). Therefore, it is usually a pretreatment stage, which can reduce the load of subsequent processes and improve the treatment effect.
The second is environmental protection of sewage treatment. Among all kinds of wastewater discharged, industrial wastewater is the most difficult to treat. Because these industrial wastewater discharges contain a large number of metals or other toxic substances, which can be mixed together to produce various chemical reactions, aggravating water pollution. At the same time, when using some sewage treatment equipment to treat these wastewater, due to the existence of these special substances, Electroplating wastewater treatment equipment It will also cause corrosion and damage to equipment and reinjection system. Not only that, because the polluted water quality is difficult to control, it has also caused great pollution to our living environment.
Secondary treatment is a biological treatment method and some chemical methods to remove degradable organics and some colloidal pollutants from wastewater. After secondary treatment, the removal rate of BOD in wastewater can reach 80-90%, that is, the BOD content can be less than 30 mg/L. After secondary treatment, it can generally meet the agricultural irrigation and wastewater discharge standards. Therefore, secondary treatment is the main body of wastewater treatment. However, a certain amount of suspended solids, soluble organic matter, soluble inorganic matter and algal value-added nutrients that cannot be decomposed by organisms, such as nitrogen and phosphorus, remain in the secondary treatment water and contain viruses and bacteria.
In fact, one industry can discharge several different types of wastewater, and one wastewater will produce different pollutants and different pollution effects. For example, dye plants discharge acidic and alkaline wastewater. Textile printing and dyeing wastewater has different pollutants and pollution effects due to different fabrics and dyes. Even the wastewater from the production plant may contain multiple pollutants at the same time. For example, the overhead oil vapor condensate of distillation, cracking, coking, stacking and other units contains phenol, oil and sulfide. In different industrial enterprises, although the products, raw materials and processing technology are very different, they may also discharge wastewater with similar performance. Oil refinery, chemical plant and coking plant may discharge oily and phenolic wastewater.
