Sewage collection facilities [including sewage pipes, rainwater pipes, factory drainage pipes, etc. ]-> sewage pumping station->; Grid interception->; Grit chamber->; Primary sedimentation tank->; Core treatment processes such as aeration tank and anaerobic tank->; Secondary sedimentation tank->; Drain pipe or canal into water [①]
The core treatment process can be divided into primary treatment and secondary and above advanced treatment. Advanced treatment process mainly includes aerobic treatment process, anaerobic treatment process and their combination.
At present, aerobic treatment methods include SBR, UASB, oxidation ditch and oxidation pond. Fill the aeration tank with air or oxygen, so that aerobic bacteria can remove organic impurities from sewage. The anaerobic treatment process mainly includes anaerobic fluidized bed, two-phase anaerobic fermentation, anaerobic filtration and other methods. Anaerobic bacteria are used for anaerobic fermentation to remove organic matter from sewage. In addition, the commonly used processes such as A20 and its variants are the combination of aerobic treatment and anaerobic treatment, and its treatment effect is often much better than that of a single treatment method.
Advanced treatment structures are nothing more than the following: aeration tank, anaerobic tank, oxidation pond, anaerobic reactor and special phosphorus and nitrogen removal equipment, or their variant processes, but the treatment principles are similar.
With the increasing awareness of environmental pollution and the strengthening of environmental awareness, sewage treatment plants have been built in most cities, and the treatment process has been upgraded from simple primary treatment to secondary or advanced treatment. But for large and medium-sized cities, Pu Yin still takes centralized treatment. The sewage treated by the sewage treatment plant has a large area, so it is necessary to use the lifting pump station to lift the distant sewage to the sewage treatment plant for centralized treatment. These sewage lifting pumping stations should not only ensure that all sewage is lifted to the sewage treatment plant, but also meet the requirements of sewage volume change. Generally, they have large flow and long transportation distance. Moreover, sewage pipes are generally buried deeply, and pumping stations need high lift and consume considerable power.
Electricity charge is the main energy consumption of sewage pumping station. The longer the transportation distance, the higher the electricity price. For example, Wuhan Longwangzui Sewage Treatment Plant has five sewage lifting pumping stations, which collect a large area of sewage nearby, but the flow is still not large. At present, the treatment flow of the expansion project is only 6.5438+0.5 million tons.
Reuse of effluent from urban sewage treatment China has invested a lot of money to build urban sewage treatment plants, but the treated reclaimed water has not been fully utilized, so the reuse of sewage should be fully considered in urban sewage treatment decision. Develop the utilization of reclaimed water in agricultural irrigation, green land irrigation, urban miscellaneous use, ecological restoration and industrial cooling.
In the recycling of urban sewage, the water consumption and water quality should be reasonably determined according to the needs and uses of users. Advanced treatment technologies such as coagulation, filtration, disinfection or natural purification can be used for sewage reuse. Therefore, in water-deficient cities and areas with serious water pollution, before planning and constructing long-distance water transfer, the urban sewage recycling project should be actively implemented, and at the same time, water saving and pollution reduction should be done with no investment or low investment.
The planning and construction of urban sewage recycling should be based on objective needs and practical possibilities, the final scale should be determined according to long-term planning, and the implementation scale should be determined according to the current water quantity and water demand. The national conditions, actual conditions and users' needs should be considered in the selection of urban sewage recycling technology and the implementation of the project. The scale, treatment degree, treatment technology, water delivery mode, reclaimed water quality and purpose of urban sewage recycling should not only meet the requirements, but also be economical and reasonable. At present, the reuse of urban sewage should focus on agricultural irrigation, municipal miscellaneous use, landscape water, domestic miscellaneous use, industrial cooling, ecological environment and surface water supply.
However, the process of urban sewage reclamation and reclaimed water utilization should ensure the health and safety of the public and operators, as well as the safety of the surrounding environment, especially to effectively control the pollution and spread of pathogenic bacteria. The use of reclaimed water shall conform to the national and local water quality standards and the regulations on sewage recycling. The selection of treatment process, especially the guarantee of the reliability and safety of the process, should be strictly demonstrated and evaluated by experts and approved by the competent department.
In the process of sewage treatment, each sewage treatment structure has many energy-saving ways. The following are the energy-saving methods of various structures in the process of sewage treatment.
Energy-saving ways of sewage lifting pumping station. Changing the existing centralized sewage treatment into decentralized treatment and making full use of the reclaimed water after primary treatment can reduce the pressure of urban sewage treatment plants and greatly reduce the cost of advanced treatment. At the same time, the water volume of sewage lifting pumping station will be reduced or even cancelled, and all of them will be treated in a decentralized way. The sewage treatment plant is only responsible for treating the sewage discharged by users with a large amount of sewage near the factory.
Energy-saving ways of power grid. Installing sewage treatment equipment in low-lying places as far as possible can reduce the power of lifting pump. When sewage passes through the grid, it can pass through the grid bars with its fast flow rate, and if necessary, it can be lifted to the sedimentation tank with a lifting pump.
Energy-saving ways of aeration equipment [③]. Both aerobic and anaerobic treatment facilities consume a lot of energy. Because we want to use electric equipment to air the sewage, but we can use multi-layer aerobic filtration to reduce this energy consumption. In aerobic filtration, the thickness of each filter layer is different, and the filtration effect is also very different
The specific method of aerobic filtration is that the sewage can directly enter the first layer of aerobic filtration after being intercepted by the grid. The pore of the first layer of aerobic filtration is very large, and it is generally paved with coarse sand and gravel, mainly to remove large suspended solids in sewage, and to mix oxygen in the air into sewage through the turbulence of water in sand and gravel. Then the sewage enters the second aerobic filter layer, the grain size of the sand in the second aerobic filter layer is relatively small, and the sewage stays in this layer for a long time, mainly due to the oxidation process of organic matter by aerobic microorganisms. In this aerobic filter layer, it is easy to generate biofilm, similar to biofilm treatment. If the organic content of sewage is not very high, the treated water has basically reached the discharge standard, and the treated water can also be collected for reclaimed water use. If the organic content of sewage is high, the next layer of aerobic filtration can be continued, and the pores of the filtration layer will be smaller, the treatment time will be longer and the effect will be better. In this layer, because of the long residence time of sewage, it also has a good removal effect on N and P in sewage.
The discharged water after aerobic filtration can meet the discharge requirements, and there is no need to set up a secondary sedimentation tank for mud-water separation. This treatment process is suitable to be built beside rivers and lakes, and the treated water can be discharged nearby without using clean water pipes or pipes.