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How is the sewage purified step by step?

Sewage is water that is inevitably produced in the process of production or life and has some toxic and harmful substances or other influences. It is collectively called pollutants, and enters the water through specific channels (such as floor washing, floor washing, cooling, splashing, staying at night, dew, excrement, etc.). ), form a specific water species with lost or reduced utilization performance (such as manure can be used as organic fertilizer after being divided).

There are many ways to purify sewage, but it depends on the quality and quantity of sewage. Generally speaking, there are two kinds:

One is natural purification, that is, the so-called self-purification of water;

The second is artificial purification, but most of the water produced in this process still enters the natural water body, and the final purification of sewage is realized through "self-purification of water body", and only a few water produced with specific performance or meeting specific standards will be reused (such as tap water and landscape water). ).

Natural purification is only aimed at the part of sewage with less pollution, less impact on the receiving water body and no obvious "natural accumulation". This kind of water diversion has specific requirements for water quantity and discharge point, and cannot exceed the solubility of water body. Once the self-purification of water body and the original ecological balance are broken, some pollutants are enriched (such as ammonia nitrogen, phosphorus, heavy metals, etc. ) or lack of some nutrients (such as oxygen and sunlight). ), which will lead to the deterioration of the water quality of the receiving water body, thus leading to more serious water pollution and biological pollution (such as eutrophication and red tide).

self purification of water body

Self-purification of water body is mainly to reduce the concentration of pollutants in sewage through its own physical, biological and chemical capabilities under certain conditions, and decompose them under the action of microorganisms to realize the separation, settlement and decomposition and utilization of pollutants in water body. After a period of time, the water body can often return to the state before pollution, thus making the water body clean from unclean. Specifically:

1, physical capacity-dilution, adsorption, encapsulation (mud coating, etc. ), mixing, precipitation, etc. Where the dilution energy is centered.

Force;

2, biological ability-the absorption and decomposition of algae and microorganisms (respiratory function, material transformation and absorption and utilization, chemicals can be used for animals and plants.

Absorbed nutrients-protein, amino acids, biosorption, photosynthesis, etc. );

3, chemical and physical and chemical capabilities-the use of pollutants to achieve oxidation, reduction, acid-base reaction, decomposition, combination, adsorption and

Coagulation and other effects make the existing form of pollutants change and the concentration decrease.

Physical processes such as precipitation, dilution and mixing of pollutants in water, chemical and physical-chemical processes such as oxidation-reduction, decomposition and combination, adsorption and coagulation, and biochemical processes often occur at the same time, affecting each other and interwoven with each other. Generally speaking, physical and biochemical processes play an important role in water self-purification.

It is worth noting that the self-purification ability of water body is limited. If the amount of pollutants discharged into the water body exceeds a certain limit, it will cause permanent pollution of the water body, which is called the self-purification capacity of the water body or the water environmental capacity. There are many factors that affect the self-purification of water body, among which the main factors are: geography, hydrological conditions, species and quantity of microorganisms, water temperature, reoxygenation ability, composition of water body and pollutants, pollutant concentration and so on. Once one or more of the above factors change, it will lead to more serious water pollution.

Artificial purification refers to the degradation or removal of pollutants by taking certain specific measures through various effective means in the process of sewage source or collection and discharge to nature. This method is the most direct and effective measure, which is generally realized by special treatment of sewage.

Sewage treatment is actually through various physical, chemical and biological methods. Means, and strive to achieve the "reverse process" of the formation of special sewage, that is, the process of separating (decomposing) pollutants in wastewater, optimizing the availability of wastewater as much as possible, reducing sewage into water bodies that meet specific requirements or have specific practical properties (that is, "environmental protection water bodies" or "ecological water bodies"), and the process of realizing "harmless treatment" or "resource utilization" of pollutants.

In addition, the ecological restoration of specific water bodies can be carried out through "ecosystem" processes (such as oxidation ponds and ecological wetlands). ), but this process has a long cycle, covers a large area and has specific requirements for water bodies.

Sewage treatment engineering involves many aspects, mainly including the combination of physical methods, chemical methods, materialization and biological methods (aerobic biological methods and anaerobic biological methods, each of which is divided into treatment processes with specific effects). You can look for relevant information first, and each design involves a combination of various methods. I hope you can learn other related knowledge from it.