Sewage into the plant first through the interceptor (so that the plant can handle the sewage into the plant for treatment) into the coarse grating (salvage the larger dregs) to the sewage pump (elevate the height of the sewage) to the fine grating (salvage the smaller dregs) to the sedimentation tank (gravity separation based on the sewage gravity of the inorganic particles to precipitate and exclude the larger particles of the specific gravity of the sewage) to biochemical tanks (activated sludge method to remove BOD5, SS and various forms of nitrogen or phosphorus) into the final settling tank (excluding residual sludge and backflow sludge) Activated sludge method to remove BOD5, SS and various forms of nitrogen or phosphorus in the sewage) into the final sedimentation tank (excluding the remaining sludge and return sludge) into the D-type filter tank (to further reduce SS, so that the effluent reaches the national level standard) into the ultraviolet light disinfection (to kill Escherichia coli bacteria in the water) and then out of the water
Biochemical tank, the final sedimentation tank out of a part of the sludge as a biochemical tank of the return sludge, and the rest is sent to the sludge dewatering room dewatering. The sludge is sent to the sludge dewatering room for dewatering and transportation
Mainly physical treatment, biochemical treatment and chemical treatment, biochemical treatment is often used, the mainstream treatment method depends on the quality of the water being treated and the receiving body of water, the mainstream treatment of urban sewage treatment method for biochemical treatment methods, such as activated sludge, mbr and other methods.
Sewage treatment
sewage treatment. wastewater treatment in order to make the sewage after a certain method of treatment. Wastewater treatment is the process by which sewage is treated in a certain way to meet certain standards. Discharge into a body of water. Wastewater treatment is a measure or method of discharging wastewater into a body of water or reusing it.
Modern wastewater treatment technology. According to the degree of treatment. Can be divided into primary. Secondary and tertiary treatment.
Primary treatment. Mainly removes the solid pollutants in the sewage in a suspended state. Most of the physical treatment method can only complete the requirements of primary treatment. After primary treatment of sewage. BOD can generally remove about 30%. Can not meet the discharge standard. Primary treatment belongs to the pretreatment of secondary treatment.
Secondary treatment. The main removal of colloidal and dissolved organic pollutants in the sewage state (BOD.COD substances). Removal rate of up to 90% or more. Organic pollutants to meet the discharge standards.
Tertiary treatment. Further treatment of difficult to degrade organic matter. Nitrogen and phosphorus and other soluble inorganic substances that can lead to eutrophication of water bodies. The main methods include biological nitrogen and phosphorus removal. Coagulation and precipitation method. Sand rate method. Activated carbon adsorption. Ion exchange method and electroosmosis analysis method.
The whole process of raw sewage through the coarse grid deletion through the sewage lifting pump after lifting. Through the grid deletion or sieve rate. After that, it enters the sand sedimentation tank. After the sand-water separation of sewage into the initial sedimentation tank. Above is the primary treatment (i.e. physical treatment). The effluent from the primary sedimentation tank enters the biological treatment equipment. There are activated sludge method and biofilm method. (The reactor of activated sludge method has aeration tank. Oxidation ditch and so on. Biofilm method includes biofilter. Bio-turntable. Biological contact oxidation and biological fluidized bed). The effluent from the biological treatment plant enters the secondary sedimentation tank. The effluent from the secondary sedimentation tanks is either disinfected and discharged or goes to tertiary treatment. At the end of the primary treatment, the secondary treatment is completed. Tertiary treatment includes biological nitrogen and phosphorus removal. Coagulation and sedimentation. Sand filtration. Activated carbon adsorption. Ion exchange and electrodialysis. A portion of the sludge from the secondary sedimentation tank is returned to the primary sedimentation tank or biological treatment plant. A part of the sludge goes to the sludge thickener. Afterwards, it enters the sludge digester. After dewatering and drying equipment. The sludge is finally utilized.
Analysis of energy consumption of each treatment structure
1. Sewage lifting pumping station
The sewage entering the sewage treatment plant enters the sewage lifting pumping station through the coarse grid. After that, it is lifted by the sewage pump to the front pool of the sand sedimentation tank. Pump operation consumes a lot of energy. Accounting for a considerable proportion of the total energy consumption of sewage plant operation. This is related to the sewage flow and the head to be lifted.
2. Sedimentation tank
The function of the sedimentation tank is to remove inorganic particles of high specific gravity. Sand sedimentation tank is generally set up in front of the pumping station. Inverted siphon before. In order to reduce inorganic particles on the pump. Pipeline wear, can also be set up in front of the primary sedimentation tank. In order to reduce the load on the sedimentation tank and improve the conditions of sludge treatment structures. Commonly used sand sedimentation tanks are advection sand sedimentation tank. Aerated sand sedimentation tank. Dore sand sedimentation tank and bell-type sand sedimentation tank.
Sedimentation tanks require energy supply is mainly sand and water separator and sand suction machine. As well as the aeration system of the aeration sand sedimentation tank. The power system of the Dore and bell-type sedimentation tanks.
3. Primary sedimentation tank
Primary sedimentation tank is the theme of the primary sewage treatment plant treatment structures. Or as a secondary wastewater treatment plant pre-treatment structures located in front of the biological treatment structures. The object of treatment is SS and part of the BOD5. It can improve the operating conditions of the biological treatment structure and reduce its BOD5 load. Primary sedimentation tanks include advective sedimentation tanks, radial sedimentation tanks and vertical sedimentation tanks. Radial flow sedimentation tank and vertical flow sedimentation tank.
The main energy-consuming equipment of the primary sedimentation tank is the sludge removal device. Such as chain belt scraper. Scraper and skimmer. Suction pumps and so on. But due to the influence of the mud removal cycle. Primary sedimentation tank energy consumption is relatively low.
4. Biological treatment structures
The biological treatment of wastewater unit process energy consumption to account for a considerable proportion of the direct energy consumption of sewage plants. It and sludge treatment unit process energy consumption and account for more than 60% of the direct energy consumption of sewage plants. The aeration system of the activated sludge process consumes a large amount of electricity. It is basically operated in contact. And the power is large. Otherwise, it will not achieve a good aeration effect. The treatment effect is not good. Oxidation ditch treatment process installed aerator is also a large energy consumption equipment. Biofilm treatment equipment and activated sludge method compared to lower energy consumption. But the current application is less. It is a treatment process that needs to be promoted in the future.
5. Secondary sedimentation tank
The capacity consumption of the secondary sedimentation tank is mainly in the sludge pumping and sewage indicating the removal of floating materials. The energy consumption is relatively low.
6. Sludge treatment
Sludge treatment process in the thickener. Sludge dewatering. Drying consumes a lot of electricity. The energy consumption of the sludge treatment unit is quite large. The power consumption of these units is very high.
Energy-saving ways for each treatment structure
1. Sewage lifting pump room
Sewage lifting pump room to save energy. The main consideration is how the sewage lifting pumps to save electricity. Correct scientific selection of pumps. Let the pump work in the efficient section is an effective means. Reasonable use of terrain. Reduce the height of the sewage lift to reduce the pump shaft power N is also an effective way. Regular maintenance of the pump. Reduce friction can also reduce power consumption.
2. Sedimentation tank
Adopt advection sedimentation. Avoid sand sedimentation tanks that require power equipment. Such as advection sedimentation tank. Adopt gravity sand discharge. Avoid the use of mechanical sand removal. These measures can greatly save energy consumption.
3. Primary Sedimentation Tank
The energy consumption of primary sedimentation tank is low. The main energy consumption is in the sludge removal equipment. The use of hydrostatic pressure method will obviously reduce the energy consumption.
4. Biological treatment structures
Overseas scholars have compared the biological treatment process by analyzing the energy consumption and cost-effectiveness. They believe that most of the energy consumption of the treatment facility is occurring in a single piece of equipment such as the motor. Therefore, energy saving should be from improving the whole plant power factor. The energy savings should be achieved by improving the plant-wide power factor, selecting high-efficiency electromechanical equipment, and reducing peak power requirements. The energy-saving measures they propose include both improving the electrical performance of motors. They also include solving operational process problems. They also include Energy
Recovery of wastewater plant products.
The energy consumption of aeration systems is significant. The study of the energy efficiency of aeration systems always involves the modification and innovation of aeration equipment. New aeration equipment is emerging all the time. But still can be divided into two categories: the first is the use of submerged porous diffusion head or air nozzle to generate air bubbles to transfer oxygen into the aqueous solution method. The second is the use of mechanical methods to stir the sewage to promote the dissolution of atmospheric oxygen in the water method. Microporous Aeration. The layout of the aeration diffuser head and the adjustment of the aeration system are effective measures for energy saving. Front-end anaerobic zone in the aeration tank of a conventional activated sludge treatment plant. Energy-saving mixing with submerged mixers. Biological phosphorus removal program. This simple modification can save nearly 20% of the aeration energy. If the mixing energy is included. Energy savings of 12% can be achieved. Application of automatic control systems for energy saving in wastewater treatment. The aeration system carries out stage aeration. Dissolved oxygen concentration gradient. This reduces energy consumption. Improvement of treatment results. Reduce the amount of sludge.
Biofilm treatment process using anaerobic treatment can significantly reduce energy consumption.
5. Secondary sedimentation tank
Secondary sedimentation tank in the study of sludge discharge equipment and sludge discharge mode improvement is an effective way to reduce energy consumption.
6. Sludge treatment
The study of energy saving in sludge treatment system mainly focuses on the energy recovery of sludge treatment. Energy recovery from organic pollutants in sewage sludge for treatment processes has been practiced since the beginning of the last century. However, it was not emphasized before the energy crisis. Currently, there are two ways of energy recovery: one is the utilization of sludge anaerobic digestion gas. One is the utilization of sludge incineration heat.
Digestion gas is stable. It is easy to store. It can be converted into mechanical or electrical energy by internal combustion engines or fuel cells. Waste heat can also be recycled in the digestion of sludge heating. Therefore, the use of digested gas can solve the problem of energy self-sufficiency of sewage plants to varying degrees. Lin Rongzhen et al. compared the utilization of biogas generators and fuel cells. They concluded that fuel cells have high energy utilization. It has a good future. Maximizing the use of digested gas is the main way to improve energy efficiency. The research and application of grid-connected biogas generator sets have been applied in China. It is a feasible way to utilize biogas in large-scale wastewater treatment plants.
Another way of energy recovery is to build a municipal solid waste incinerator next to the sewage treatment plant. The solid waste and sewage sludge are burned together. The electricity generated is used to run the treatment plant.
Municipal wastewater treatment of energy consumption analysis and the development of energy-saving technologies and means are often not synchronized. Due to the lack of energy balance analysis of sewage treatment methods. The development and implementation of energy-saving measures are often ahead of schedule. And most of the energy-saving ways and means are often proposed by the treatment plant operators and managers in conjunction with the actual situation of each treatment facility. They are empirical and individualized. They may not be applicable to other wastewater plants or even to plants with similar processes. On the other hand. Technological innovations in the field of wastewater treatment. The use of new materials and equipment has the potential to save energy and increase efficiency. Thus, the ways and means of saving energy are often very broad.
Conclusion
Wastewater treatment is an energy intensity technology. For some time. Energy consumption is high. High operating costs have hindered the construction of urban wastewater treatment plants in China to a certain extent. Built some treatment plants are also due to energy consumption reasons in the production and semi-suspension state. In the future for a long period of time. Energy consumption will become the bottleneck of urban wastewater treatment. Can we solve the problem of energy consumption of sewage treatment plants. Reasonable energy allocation. Has become a key factor in determining the operating efficiency of sewage treatment plants. Whether the energy consumption is low. It is also a decisive factor in the feasibility analysis of new wastewater treatment plants in the future. Development of energy-efficient wastewater treatment technologies. Rational design and operation of wastewater treatment plants. This will be the way of the future for the design and operation of wastewater treatment plants.
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