What are the methods of sewage treatment？
1. Traditional activated sludge method
The traditional activated sludge treatment method is one of the oldest industrial sewage treatment processes, and the key components of its industrial sewage treatment are biogas digesters and sedimentation tanks.
When the organic matter in the sewage stays in the aeration tank, the microorganisms in the aeration tank absorb most of the organic matter in the sewage, and are oxidized into inorganic matter in the aeration tank, and then partially activated in the sedimentation tank after precipitation. The mud needs to be returned to the aeration tank. The advantages of this process are: high removal rate of organic matter, high sludge load, small pool volume, low power consumption and low operating cost. The disadvantages of this process are: the common aeration tank occupies a lot of land, the construction investment is large, the range of relevant indicators to meet the national standards is small, the sludge bulking phenomenon is easy to occur, and the removal rate of phosphorus and nitrogen is low.
2. A/O method
The A/O method is an industrial sewage treatment process developed on the basis of the traditional activated sludge method, where A stands for Anoxic (anoxic) and O stands for Oxic (aerobic). A/O method is an anoxic-aerobic biological industrial sewage treatment process. By increasing the nitrification-denitrification reaction system formed by the aerobic tank and the anoxic tank, the process can well treat the nitrogen content in the sewage and has an obvious denitrification effect. However, the nitrification-denitrification reaction system needs to be well controlled, which puts forward higher management requirements for the process, which also becomes a major disadvantage of the process.
3. A2/O method
The A2/O method is also an industrial sewage treatment process developed on the basis of the traditional activated sludge method. A2, namely A-A, the former A stands for Anaerobic (anaerobic), and the latter A stands for Anoxic (anoxic). ); O stands for (aerobic). A2/O is an anaerobic-anoxic-aerobic industrial wastewater treatment process. The phosphorus and nitrogen removal effect of the A2O method is very good, and it is very suitable for industrial sewage treatment that requires phosphorus and nitrogen removal. Therefore, in urban industrial sewage treatment plants with special requirements for phosphorus and nitrogen removal, the A2/O process is generally preferred.
4. A/B method
A/B method is the abbreviation of adsorption biodegradation method. There is no initial precipitation in this process. The aeration tank is divided into two sections with high and low loads, and there are separate sedimentation and sludge return systems. The residence time in the high load section is about 20~40min, mainly due to biological flocculation and adsorption, and incomplete oxidation reaction occurs at the same time, and the removal of BOD is more than 50%. Section B is acquainted with the conventional activated sludge method and has a lower load. Section A in the AB method has high efficiency and strong buffering capacity. Section B plays the role of water effluent gatekeeper and has better processing stability. For high-concentration industrial sewage treatment, the AB method has good applicability and high energy-saving benefits. Especially in the use of sludge digestion and biogas utilization processes, the advantages are most obvious. However, the sludge yield of the AB method is relatively large, and the organic content of the A stage sludge is extremely high, so it is necessary to add sludge for subsequent stabilization treatment, which will increase a certain investment and cost. In addition, due to the removal of more BOD in the A stage, the carbon source is insufficient, and it is difficult to achieve the requirements of the denitrification process. For the occasions with low sewage concentration, the B section is also more difficult, and it is difficult to exert its advantages.
In general, the AB method is more suitable for large and medium-sized urban industrial sewage treatment plants with high sewage concentration and subsequent treatment facilities such as sludge digestion, and has obvious energy saving effect, while for urban industrial sewage that requires denitrification. Treatment plants are generally not suitable for use.
5. SBR method
The SBR method is the abbreviation of the batch activated sludge method. It is a sewage biological treatment technology that operates intermittently according to a certain time sequence. Sequencing batch activated sludge process. The reaction mechanism and the mechanism of removing pollutants are basically the same as the traditional activated sludge method, but the operation mode is different. The biggest difference between the SBR method and the traditional water treatment process is that it divides each unit of the process in time sequence, replaces the space division operation with time division operation, replaces biochemical reaction with unsteady biochemical reaction, and replaces dynamic sedimentation with ideal precipitation. The whole process is carried out intermittently for a single operation unit, but it is continuous after being scheduled by the combination of multiple units, realizing the combination of orderly and intermittent operation in operation.
While the Industrial Revolution in the 1960s brought economic development, people gradually noticed the increasingly serious river pollution. The pollution of the river has gradually affected their work and life. For this reason, people have to pay attention to the treatment of drinking sewage. It was not until the 1980s that he learned that engineering must conform to the principles of ecology, and proposed governance concepts such as building multi-natural rivers. At present, there are three commonly used river sewage treatment methods, namely physical methods, chemical methods, ecological-biological methods, ecological-biological methods (including river aeration and reoxygenation, biofilm methods, bioremediation methods, and land treatment methods). , aquatic plant purification method)
1. Physical method
Physical methods mainly refer to dredging of sediment, mechanical algae removal, diversion of water to scour sediment and water transfer. Dredging the polluted bottom means removing the pollutants from the (river) system. It can greatly reduce the pollution contribution rate of sediment to the overlying water body, thereby improving the water quality. The purpose of water transfer is to introduce clean water sources upstream or near polluted rivers through the regulation of water conservancy facilities (such as gates and pumping stations) to improve the water quality of downstream polluted rivers. Such methods often treat the symptoms rather than the root causes.
2. Chemical method
Chemical methods such as coagulation and precipitation, adding chemical agents to kill algae, adding iron salts to promote the precipitation of phosphorus, adding lime to denitrify and other methods. Studies have shown that this method has a good removal effect on turbidity, eoD, ss, and TP, and also has a certain removal effect on TN, heavy metals, etc., and the daily dosage of chemicals is small. However, this method of river sewage treatment is easy to cause secondary pollution.
3. Ecology-biological methods Ecological-biological methods (mainly including aeration and re-oxygenation of river channels, biofilm methods, bioremediation methods, land treatment methods, aquatic plant purification methods, etc.)
(1) Channel aeration method
Artificial aeration and reoxygenation refers to the artificial oxygenation of the river in anoxic (or anaerobic) state to enhance the self-purification ability of the river, improve the water quality, and improve or restore the ecological environment of the river. River aeration and reoxygenation generally adopts two forms: fixed oxygenation station and mobile oxygenation platform. The process has the advantages of simple equipment, flexible operation, reliable security, low investment, quick effect, convenient operation, wide adaptability, and no harm to aquatic ecology.
(2) Biofilm technology Biofilm technology
It means that the microbial population is attached to the surface of some carriers in a film-like form, and is in contact with sewage. The microorganisms on the biofilm absorb and assimilate the organic matter in the sewage as nutrients, so that the sewage can be purified. At present, the biofilm technologies commonly used in river sewage treatment mainly include inter-gravel contact oxidation method, contact oxidation method of water holding ditch (canal), biological activated carbon packed column purification method, thin laminar flow method and voltaic flow purification method, which are widely used. It is a contact oxidation method.
(3) Bioremediation technology Bioremediation technology
It refers to an engineering technology system that uses microorganisms and other organisms to degrade toxic and harmful pollutants in water or soil into CO2 and water, or convert them into non-toxic and harmless substances. There are two main types of bioremediation technologies used for river sewage treatment. One is to directly add one or more microbial strains that have been cultured and screened to the polluted river water. Tests have shown that the COD removal rate is above 9096. Another type is to add microbial growth promoters (nutrients) to polluted river water to promote the growth of "indigenous" microorganisms. After administering the drug. Through the promotion of growth, the growth of pollutant-degrading microorganisms is promoted. The microorganisms in the river channel change from anaerobic to aerobic, and the organisms change from low to high. , the dissolved oxygen rises significantly, and the black odor is eliminated. This method has obvious effects on eliminating black and odor in water and increasing dissolved oxygen in water.
(4) Land treatment technology
Land treatment technology is an ancient but effective technology for river sewage treatment. It uses the land as a treatment facility, and uses the adsorption, filtration and purification functions and self-regulation functions of the seven soils and plant systems to achieve a certain degree of water purification. Foreign practical experience shows that. The land treatment system has a good removal effect on organic compounds, especially organic chlorine and ammonia nitrogen.
(5) Aquatic plant purification method
This method is a sewage purification method which fully utilizes the natural purification function of aquatic plants. For example, duckweed, reeds in wetlands, etc. are used for purification treatment in a certain water area. However, the discharge of domestic sewage will cause problems such as odor, pests and landscape impact, so the above problems should be comprehensively considered when selecting, such as choosing to plant reeds at the downwind in spring and summer.
