Basic technology of sewage treatment plant

The purpose of treatment process selection is to select a mature process which is safe, reliable, advanced in technology, energy-saving, low in operating cost, less in investment, less in land occupation and convenient in operation and management according to the sewage quantity, sewage quality and environmental capacity, and taking into account the economic conditions and management level. According to the water quality, water quantity and treatment requirements of this project, in order to achieve the best effluent effect with the lowest construction cost and operation cost, we recommend adopting the internationally advanced Barak sewage treatment process, and the sewage treatment effect is good.

The purpose of treatment process selection is to select a mature process which is safe, reliable, advanced in technology, energy-saving, low in operating cost, less in investment, less in land occupation and convenient in operation and management according to the sewage quantity, sewage quality and environmental capacity, and taking into account the economic conditions and management level. According to the water quality, water quantity and treatment requirements of this project, in order to achieve the best effluent effect with the lowest construction cost and operation cost, we recommend adopting the internationally advanced Barak sewage treatment process, and the sewage treatment effect is good. Ballack process originated in Germany, which is a new process developed on the basis of traditional activated sludge process and aerated oxidation pond. It is designed with low sludge load and high sludge age, and oxygen is supplied by floating mobile aeration system. Due to the oxygenation characteristics of the mobile aeration system, multiple anoxic and aerobic zones can be generated in the biochemical pool, so the process has good nitrogen and phosphorus removal function. The main characteristics of this new process are: 1, floating aeration delayed activated sludge process, long sludge age, full oxidation of organic matter, reliable effluent and strong impact load resistance; Multi-stage A/O aeration process is adopted, and the efficiency of nitrogen and phosphorus removal is extremely high. Compared with the traditional oxidation ditch, A/A/O and SBR processes, the project investment is low, the floor space is small, and the operation and management are simple. 2. The residence time of bubbles produced by floating microporous aeration system in water is three times that of traditional fixed mode, so the oxygen transfer efficiency is high and the power consumption is low. At the same time, the floating aeration system is simple to operate, does not need fixed installation, is convenient to maintain (does not need an emptying tank), and can effectively reduce labor costs. 3. A biological selection tank is set in front of the aeration tank, which can inhibit the growth of filamentous bacteria by using the growth law of microorganisms, and at the same time provide an anaerobic environment for phosphorus accumulating bacteria to release phosphorus and strengthen the biochemical phosphorus removal effect. 4. Using the dissolved oxygen online control system to adjust the output air volume of the blower economically can greatly save the aeration power cost. 5. The pool body has strong civil flexibility, combined layout, small and compact floor space, and can be adapted to local conditions. Slope protection can adopt various civil construction methods, such as concrete, rubble, earth pool, impervious board, etc., and the civil investment is extremely economical. Sewage treatment project is an infrastructure project with complex technology, large investment and strong policy. Although there is no obvious economic benefit, the environmental benefit and long-term social benefit are immeasurable. Based on this feature, even developed countries attach great importance to the development and construction of sewage treatment projects. However, we should also consider how to reduce the capital investment and operation cost, and study how to simplify the sewage treatment process, occupy less land, save electricity, facilitate management and improve the treatment effect. This is exactly what the Black Process has done. Compared with the traditional secondary biochemical treatment and the existing oxidation ditch and SBR processes, the process flow is simple, the applicability is strong and the effluent quality is excellent. It has obvious advantages in construction investment, floor space and operating cost. 2.2 process scheme design 2.2. 1 sewage treatment process 2.2.65438 fine grid technology for sewage coarse grid pumping station desanding metering channel The sewage discharged from the contact pool of Baileke comprehensive pool is introduced into the factory from the south side of the factory, and then lifted by water pump into the fine grid, process desanding and Baileke comprehensive pool for physical and chemical treatment, and finally the effluent is discharged or reused through Tanhe. 1. The main function of the coarse grid is to intercept large floating objects and suspended substances in sewage, prevent the water pump unit from being blocked, and reduce the treatment load of subsequent treatment structures. And make it run normally. Structure type: design parameters of underground reinforced concrete vertical wall parallel passage: design flow Qmax=3300m3/h, flow velocity V=0.8m/s, passage width B= 1400mm, number of passages, two main equipments: rotary grate and supporting grate slag conveying system, equipment type: high chain plane grate, and shaftless screw conveyor is selected as the conveying system. Design parameters: grille gap e=20mm, grille width B= 1200 mm, grille passing speed v=0.9m/s, grille passing loss h=200mm, and motor power n =1.5kw. Control mode: two sets of cleaning and conveying equipment are controlled according to the liquid level difference before and after the grille, and a grille slag conveyor is equipped. 2. The main function of lifting pump house: lifting sewage to meet the hydraulic requirements of subsequent treatment facilities. Structural type: underground steel-concrete rectangular submersible pump station design parameters: design flow Qmax=3300m3/h, sump volume V=400m3, pool number: 1, Main equipment: submersible pump equipment type: anti-blocking automatic coupling system equipment parameters: flow Q=700m3/ H, lift H= 1 1m, power N=55KW, control mode: number of operating equipment is controlled according to the liquid level of the sump: 6 underground (1 standby) pump houses, with a plane size of 8.3x/kloc. Structural type: design parameters of parallel passage of elevated reinforced concrete vertical wall: design flow qmax = 3300 m3/h, grid crossing speed v = 1.0m/s, channel width b = 1.240mm, number of channels: two main equipments: grid machine and supporting grid slag conveying system; Equipment type: rotary. Design parameters with conveying and dewatering functions: grille flow Qmax=3300m3/h, grille gap b=6mm, grille loss δ h = 300mm, grille width B= 1200mm, motor power n = 2.2kw. Control mode: two sets of equipment for cleaning and conveying actions are controlled according to the liquid level difference before and after the grille: two fine grilles, one for use and one for standby. 4. Process sand removal The traditional sand removal process covers a large area. Barak process adopts the internationally popular rotary fine grid to remove sand particles and other impurities larger than 1mm in sewage at one time. The process is simple, easy to operate and low in operating cost. At the same time, Barak's suspended aeration method makes up for the influence of fine sand precipitation. Main equipment: rotary fine grating and screw extruder equipment type: NOVA fine grating, which has both conveying and extrusion functions. Design parameters: grid-crossing flow QMAX = 3300 m3/h, drum grid diameter d=900mm, drum grid length L = 2,500mm, grid gap width B = 1mm, number of equipment: 3 rotating fine grids, 2 in use 1 standby. 5. Metering wells In order to improve the working efficiency and operation management level of the sewage treatment plant, accumulate technical data, sum up operation experience, correctly grasp the sewage treatment capacity and power consumption, and reflect the operation cost, metering wells are set up behind the fine grid, electromagnetic flowmeters are designed and selected, and information is input into the computer to know and record the water treated by the biochemical reaction tank at any time. 6. Baileke comprehensive pond Baileke comprehensive pond is designed according to 66,000m3/d and checked according to 80,000m3/d ... This design adopts two parallel production lines. (1) The main function of the biological selection tank is to adjust the water quality and quantity, and at the same time, it has the function of anaerobic treatment, which can inhibit the growth of filamentous bacteria and prevent sludge bulking. At the same time, it has the function of hydrolysis and acidification, which can not only remove phosphorus biologically but also decolorize, creating conditions for the reuse of reclaimed water. Structure type: design parameters of reinforced concrete: hydraulic retention time HRT=3.8hr Pool depth: H=5.5m Total volume: V = 3,300m3 Quantity: 1 Main equipment: 2 submersible mixers Equipment type: high-speed mixed submersible mixer equipment parameters: rotating speed: n=960rpm Power: N=9KW Control mode: controlled by programmable control system. The main function of biochemical reaction tank: in aerobic environment, BOD and COD can be degraded by microorganisms, and nitrogen and phosphorus can be effectively removed by wave oxidation process. Structural type: rectangular tank body of semi-above-ground earth dam, masonry slope protection, geotextile seepage control design parameters: volume load NV = 0.3kgbod/(m3 d) sludge concentration MLSS = 4500mg/ L sludge age: θ=30 days, sludge reflux ratio R= 100%, hydraulic retention time HRT =/kloc-. H oxygen transfer efficiency E=25% Effective length L=2000mm Number of equipment: two sets, 30 aeration chains (3) The main function of the integrated clarifier is to vertically separate activated sludge from water, and the sludge is concentrated and then returned to the biological selection tank. Structure type: design parameters of reinforced concrete: surface load q=0.75m/h, total volume V=5800m3, main equipment: 65438. 1 set of sludge power system equipment type: number of submersible sewage pumps: 2 (1 set for standby) equipment parameters: flow Q=3050m3/h head: H= 10m power rate: N= 18.5KW pool number: 2 (4) stabilization pond. Main equipment: floating aeration pipe 1 root air flow: Q= 12m3/ branch. H, oxygen transfer efficiency E=25%, effective length L=2000mm, number of cells: two. 5. Blower room Blower room is the key facility to ensure the normal operation of aeration system. After calculation, in order to ensure the normal operation of the aeration system, there are six special blowers that can automatically adjust the air supply. The design flow of each centrifugal blower is Q=6800m3/h, the design maximum wind pressure is P=58.8kPa, and the power is N= 160kW. Blower is the highest energy consumption equipment in sewage treatment plant, accounting for about 65% of the whole plant's energy consumption. Reducing its energy consumption is very important to reduce the annual operating cost of sewage treatment plants. The design starts with adjusting the air volume of the blower to reduce energy consumption. There is a dissolved oxygen detector in the integrated cabinet of Baileke, and the blower can automatically adjust the air supply volume according to the change of dissolved oxygen. This measure can save energy consumption by more than 10%. The inlet pipe of each fan is equipped with muffler and elastic joint, and the outlet pipe of each fan is equipped with check valve, safety valve, elastic joint of gate valve, outlet muffler and pressure switch. Pressure gauges, electric valves, flowmeters, thermometers, etc. are installed on the blower and air outlet pipe. The air filter is installed in the air inlet pipe, and the dust removal efficiency is 99% for dust larger than 1um. The blower room is equipped with lifting facilities to facilitate equipment maintenance and roof ventilation facilities. The plane size of the blower room is 2 1×7.2m, and the height is 5.5m. After secondary treatment, the water quality of urban sewage produced by chlorine dioxide generator has been improved, and the bacterial content has been greatly reduced, but its absolute value is still considerable, and there may be pathogenic bacteria. According to the requirements of health and epidemic prevention, environmental protection and other regulatory authorities, the effluent of sewage treatment plant needs disinfection, and chlorine dioxide is used for disinfection in this project. Chlorine dioxide is a broad-spectrum disinfectant, which has a high killing effect on pathogenic microorganisms in water, including viruses, spores, heterotrophic bacteria, sulfates, reducing bacteria and fungi in water distribution network. Chlorine dioxide has a strong oxidation effect, so it has a good decoloration effect. The design and operation of disinfection room should consider uninterrupted operation throughout the year. When chlorine dioxide is used for water disinfection, its dosage is 0. 1 ~ 1.3 mg/l; When it is used for deodorization, its dosage is 0.6 ~1.3 mg/L. Considering this project as 1.0mg/L, the designed dosage of chlorine dioxide is 66,000m3/d, the designed dosage of chlorine dioxide is 66 kg/d, and the chlorine dioxide generator is synthesized by sodium chlorite and hydrochloric acid or sulfuric acid. The capacity of a single unit is 3kg/h, and it is equipped with all auxiliary equipment and double-probe alarm. In order to prevent accidents, two sets of chlorine leakage absorption devices are also set up. 7. The contact tank is disinfected by adding chlorine dioxide, and the disinfection contact time is 0.5 hours. In order to ensure the disinfection contact time of chlorine dioxide, the hydraulic retention time in the contact tank is designed to be 0.5 hours, the plane size is 30m× 17m, 1 seat, the effective water depth is 4.8m, and the superelevation is 0.5m.. 2.2.2 Design of sludge treatment process The sludge dehydrator in the sludge storage tank carries out harmless treatment on the sludge cake to be transported abroad 1. The function of sludge circulation is to pump the reflux sludge discharged from the clarifier into the biological selection tank and pump the remaining activated sludge into the sludge storage tank. The returned sludge is lifted by the sludge pump in the clarifier and then flows into the biological selection tank. Four submersible sewage pumps are used for excess sludge pumps, two in use and two for standby. The main pump selection parameters are: single flow Q =45m3/h, lift 10m and power 2.2kW. The sludge output of the concentrated sludge storage tank system is 1.03kgDS/kgBOD5, and the discharged dry sludge is 7600kg/d, and its volume is 950m3/d based on the water content of 99.2%. The working time of sludge concentration tank is 24 hours, and sludge storage tank is considered as 3 hours. Its size is L×B×H=8.0m×5.0m×3.5m, and its effective water depth is 3m. Reinforced concrete structure. In order to prevent the phosphorus in the sludge from being separated out due to anaerobic, a submersible agitator was installed in the sludge storage tank, and a short sludge storage time was adopted. 3. In the case of biological phosphorus removal technology in ZC sewage treatment plant, in order to avoid the re-release of phosphorus from surplus sludge with high phosphorus content under anaerobic conditions, mechanical concentration is adopted for sludge concentration. The water content of excess sludge discharged from Baileke biochemical system is 99.2%. After mechanical concentration, the average water content of sludge is 95%, and after mechanical dehydration, the water content can be reduced to about 75-80%. In this design, we use mechanical thickener and centrifugal dehydrator. * * * Choose three sets (two for use and one for standby). According to the calculation of three shifts per day (i.e. 24 hours), the maximum capacity of centrifugal thickener is 45m3/h, the average solid content after concentration is 5%, and the power of supporting motor is 1. 1kW. The maximum capacity of the centrifugal dehydrator is 25m3/h, the average solid content after dehydration is ≥20%, and the power of the supporting motor is 30kW. Centrifugal sludge concentration dehydrator is equipped with sludge feed pump, sludge crusher and flocculant dosing device. The sludge dewatering room is also equipped with a desliming cake screw conveyor. The sludge transfer pump adopts German Borg pump. The plane size of the concentration and dehydration machine room is 36m× 15m, and the height is 8.5m. 4. The sludge harmless treatment of urban sewage contains a lot of harmful substances, which has secondary pollution after long-term stacking, but some of them contain a lot of organic substances. After proper process treatment, the sludge is harmless treatment. The treated sludge can be directly buried, or used as nutrient soil, backfill soil, etc. The plane size of sludge harmless treatment is 48m×22m. 2.3 graphic design 1. Principles of Graphic Design The principles of graphic design are: reasonable layout, smooth water flow, compact layout, as little land occupation as possible, and clear functional zoning. 2. Functional zoning The plane of the treatment plant is divided into front area, production area and reserved area according to functions, and there are roads and green belts between the areas. The front area of the plant is arranged on the northwest side of the treatment plant, and the north is close to Gangcheng Street, so as to facilitate contact with the outside world; Indoor and production are separated by green isolation belt to ensure a beautiful environment in front of the factory. There is a comprehensive building, a machine shop, a garage and a warehouse in the front area of the factory. The front area of the factory is large, and the comprehensive building can overlook the whole factory upstairs. Because the inlet pipe is at the northwest side of the sewage treatment plant, the tail water of the treatment plant is discharged into the Weihe River. Therefore, the inlet pump house, fine grid and grit chamber are arranged on the west side, and the biochemical tank is arranged next to it, which makes the process flow smooth. Auxiliary production buildings are relatively concentrated and arranged in the upwind direction of the factory; The sludge treatment area is arranged in the downwind direction of the dominant wind direction in summer, far away from the front area of the plant, so as to maintain a good environment in the front area of the plant. 3. In order to facilitate transportation and installation and maintenance of equipment, the roads in the factory are arranged in a ring shape, and all structures (buildings) are connected by roads. The main road in the plant is 7m wide, the secondary road is 4m wide, and the turning radius of the main road is greater than 9- 12m, with concrete pavement. 4. Water supply for the factory The water supply for the factory is provided by the municipal water supply company, which comes from the surrounding water supply main, and the pressure is greater than 4kg/cm2. The water supply in the plant area is mainly used for washing, greening and fire fighting of life, structures and equipment. The pipe diameter of the main water supply pipe is DN200, and the plant area is annular pipe network, which is beneficial to fire fighting and safe water supply. 5. Drainage in the factory area The drainage in the factory area is divided into rain and sewage. The rainwater in the factory area is collected by the road rainwater outlet and then flows into the rainwater pipeline in the factory area, and then flows into the nearby rivers by itself; Domestic sewage, production sewage, cleaning pool sewage, structure drainage and clear night in the factory are collected by sewage pipes and sent to the water intake pump house for treatment together with incoming water. 6. Considering the utilization of reclaimed water, the site of reclaimed water long-term reuse system is reserved, which lays the foundation for the long-term reuse of reclaimed water in industry, farmland irrigation and urban landscape.