AOA energy-saving land-saving nitrogen and phosphorus removal sewage treatment process using MBR (membrane bioreactor) to replace secondary sedimentation tank

Abstract

The invention relates to an AOA energy-saving and land-saving nitrogen and phosphorus removal sewage treatment process by replacing a secondary sedimentation tank with an MBR. The AOA energy-saving and land-saving nitrogen and phosphorus removal sewage treatment process comprises a water feeding procedure; anaerobic zone treatment: completing anaerobic degradation of organic matters in the sewage and release reaction of phosphorus, converting macromolecular organic matters into micromolecular organic matters and intracellular carbon sources, and inputting the sewage into an aerobic zone; treating in an aerobic zone to remove ammonia nitrogen; phosphorus-accumulating bacteria absorb phosphorus and store the phosphorus in cells in the form of polyphosphate so as to remove the phosphorus, and then the sewage is input into the anoxic zone; anoxic zone treatment: carrying out denitrification reaction to realize denitrification; treating in a membrane biological reaction area, intercepting suspended matters and microorganisms in the sewage by using a membrane component, and completing mud-water separation, water recycling or discharging and regular sludge discharging; refluxing I: refluxing the sludge discharged from the membrane biological reaction zone to the aerobic zone; and 2, refluxing, namely refluxing the sewage treated in the anoxic zone to the anaerobic zone. Through the arrangement, the occupied area is greatly reduced, the energy consumption is reduced, and the sewage treatment effect is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to an AOA energy-saving and land-saving nitrogen and phosphorus removal sewage treatment process using an MBR instead of a secondary sedimentation tank. Background Art

[0002] The AOA (Anaerobic-Oxic-Anoxic) process is an efficient deep denitrification process for urban sewage. Compared with traditional sewage treatment processes, the AOA process requires almost no additional carbon source, can fully utilize the organic matter in the raw water, can reduce the aeration and deodorization air volume by half, can reduce the sludge production by 20%, and can reduce the overall operating cost by 10%. It has the advantages of efficient denitrification and energy saving and consumption reduction, and has been proven to have excellent sewage treatment efficiency in actual projects.

[0003] After the sewage treated by the AOA process flows out of the anoxic tank, it is still mixed with a large amount of activated sludge and needs to be transported to the secondary sedimentation tank. Through the solid-liquid separation process, the water and sludge are separated to achieve the purpose of effluent clarification and sludge recovery. However, due to the high sludge concentration and poor sedimentation performance in the sewage flowing out of the anoxic tank, directly entering the secondary sedimentation tank may affect the sedimentation performance of the secondary sedimentation tank, resulting in poor effluent water quality. Therefore, it is often necessary to pre-treat it before transporting it to the secondary sedimentation tank. This requires the addition of a pre-treatment unit, resulting in an increase in the demand for floor space, increased complexity of the process flow, and increased difficulty in operation and maintenance. Summary of the invention

[0004] In order to solve the above defects, the present invention proposes an AOA energy-saving and land-saving nitrogen and phosphorus removal sewage treatment process in which MBR is used instead of a secondary sedimentation tank.

[0005] The technical solution adopted by the present invention is an AOA energy-saving and land-saving nitrogen and phosphorus removal sewage treatment process using MBR instead of a secondary sedimentation tank, comprising the following steps:

[0006] The influent process receives sewage and pumps it to the anaerobic zone;

[0007] Anaerobic zone treatment, through the action of anaerobic microorganisms, completes the anaerobic degradation of organic matter in sewage and the release of phosphorus, converts macromolecular organic matter into small molecular organic matter and intracellular carbon source, and then the sewage is input into the aerobic zone;

[0008] In the aerobic zone, the organic matter in the sewage undergoes nitrification reaction, converting ammonia nitrogen into nitrate nitrogen, thus removing ammonia nitrogen; polyphosphate bacteria absorb phosphorus and store it in the cells in the form of polyphosphate, thus removing phosphorus, and then the sewage is input into the anoxic zone;

[0009] The anoxic zone is treated to carry out denitrification reaction, reducing nitrate nitrogen to nitrogen gas to achieve denitrification, and then the sewage is input into the membrane biological reaction zone;

[0010] Membrane biological reaction zone treatment uses membrane components to intercept suspended solids and microorganisms in sewage, completes mud and water separation, water is reused or discharged, and sludge is discharged regularly;

[0011] Among them, it also includes:

[0012] Backflow 1: the sludge discharged from the membrane biological reaction zone flows back to the aerobic zone;

[0013] Backflow 2: The sewage treated in the anoxic zone flows back to the anaerobic zone.

[0014] Furthermore, the sludge discharged from the membrane biological reaction zone is returned to the aerobic zone, specifically including: the sewage treated in the membrane biological reaction zone carries activated sludge and dissolved oxygen back to the aerobic zone, the activated sludge participates in the nitrification reaction in the aerobic zone, and converts ammonia nitrogen into nitrate nitrogen; the dissolved oxygen enables the polyphosphate bacteria to absorb excessive phosphorus in the aerobic environment.

[0015] Furthermore, the reflux ratio of reflux one is 200%.

[0016] Furthermore, the sewage treated in the anoxic zone is returned to the anaerobic zone, which specifically includes: the sewage treated in the anoxic zone carries activated sludge and returns to the anaerobic zone, and the activated sludge supplements the biomass in the anaerobic zone.

[0017] Furthermore, the reflux ratio of the reflux 2 is 100%.

[0018] Further, based on a sewage treatment system, the sewage treatment system includes an inlet tank, an anaerobic tank, an aerobic tank, an anoxic tank and a membrane biological reactor tank connected in sequence, and also includes:

[0019] A reflux pump 1, two ends of which are connected to the membrane biological reaction tank and the aerobic tank respectively, and the reflux pump 1 pumps the sludge discharged from the membrane biological reaction tank to the aerobic tank;

[0020] The two ends of the reflux pump 2 are respectively connected to the anoxic tank and the anaerobic tank. The reflux pump 2 pumps the sewage discharged from the anoxic tank to the anaerobic tank.

[0021] Furthermore, the water inlet tank receives sewage transported from the sewage well;

[0022] The water inlet tank transports sewage to the anaerobic tank through a water inlet pump;

[0023] The aerobic tank receives the sewage output from the anaerobic tank and transports it to the anoxic tank after treatment;

[0024] The anoxic tank receives the sewage output from the aerobic tank and transports it to the membrane biological reaction tank after treatment;

[0025] The membrane biological reaction tank receives the sewage output from the anoxic tank, and the water treated by the membrane module is discharged through the outlet pump. Part of the treated sludge is discharged regularly, and part is pumped to the aerobic tank through the reflux pump.

[0026] Further, the anaerobic tank is equipped with an output end of a first stirring device, the aerobic tank is equipped with an output end of a second stirring device and an output end of a first aeration device, the anoxic tank is equipped with an output end of a third stirring device, and the membrane biological reactor is equipped with an output end of a second aeration device;

[0027] The power of the first stirring device and the third stirring device is less than the power of the second stirring device;

[0028] The first aeration device is used to supplement oxygen to the aerobic tank, and the second aeration device is used to reduce the blockage of the membrane module.

[0029] Furthermore, the anoxic tanks are provided with two interconnected ones, and the sewage output from the aerobic tank is input into the first anoxic tank, and is output from the second anoxic tank to the membrane biological reactor tank.

[0030] Furthermore, the aerobic pool is also equipped with a detection end of a dissolved oxygen meter, and the dissolved oxygen meter is used to monitor the dissolved oxygen concentration in the aerobic pool in real time;

[0031] A pressure gauge is also provided between the membrane biological reaction tank and the outlet water pump, and the pressure gauge is used to monitor the outlet water pressure in real time and evaluate the performance of the membrane assembly;

[0032] A thermometer is also provided in the sewage treatment system, and the thermometer is used to monitor the water temperature of the sewage in the sewage treatment system in real time.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The AOA energy-saving and land-saving denitrification and phosphorus removal sewage treatment process in which MBR replaces the secondary sedimentation tank in the present invention abandons the traditional secondary sedimentation tank and uses the membrane biological reaction zone to complete the mud-water separation. The problems of high sludge concentration and poor sedimentation performance of the sewage effluent from the anoxic tank are solved, avoiding the need to add a pretreatment unit and greatly reducing the floor space; simplifying the process flow, reducing the difficulty of operation and maintenance, reducing equipment failure points, and improving the stability and reliability of the sewage treatment system; the water quality of the membrane separation effluent is stable and excellent, and the suspended matter and microbial interception rate is high, ensuring that the sewage meets the discharge standards or is reused.

[0035] 2. In the aerobic zone of the traditional sewage treatment process, the dissolved oxygen required to maintain the normal metabolism of microorganisms and nitrification reactions in the aerobic zone is almost entirely supplied by fan aeration. The fan needs to operate continuously at high power, which consumes huge energy. However, this process introduces a reflux mechanism. The mud-water mixture discharged from the membrane biological reaction zone carries a certain amount of dissolved oxygen. After returning to the aerobic zone, this part of the dissolved oxygen can directly participate in the aerobic reaction, sharing the pressure of dissolved oxygen originally provided by fan aeration. After the reflux mechanism is established, the fan can greatly reduce power and aeration air volume. Practical data show that it can be reduced by about 50%. This not only reduces the power consumption of fan equipment, extends the service life of the fan, and saves energy; it also reduces problems such as splashing water and odor emission caused by excessive aeration, and optimizes the treatment site environment.

[0036] 3. When the membrane bioreactor is in operation, the membrane components are easily attached and blocked by suspended matter, microorganisms and their secreted extracellular polymers in the sewage, causing membrane pollution, resulting in decreased membrane flux and reduced filtration efficiency. The sludge in the membrane bioreactor area is returned to the aerobic zone through reflux, changing the distribution state of colloids and particulate matter in the sewage. On the one hand, some fine particles that are prone to membrane pollution are further metabolized and decomposed by microorganisms in the aerobic zone; on the other hand, the reflux promotes a more uniform circulation of sewage in the system, avoiding excessive enrichment of local substances and deposition on the membrane surface. Reflux continuously carries away potential pollutants, greatly delaying the process of membrane pollution and reducing the frequency of membrane component cleaning.

[0037] 4. When the membrane components need to be cleaned, the physical cleaning method of blower aeration flushing is mostly used, with the help of air flow disturbance to shake off the impurities attached to the membrane surface. Because the reflux effectively reduces the degree of membrane pollution, the blower aeration air volume required for cleaning is reduced by about 40%, the energy consumption of the cleaning process is reduced, the blower equipment loss is reduced, the sewage treatment system operates more stably and efficiently, and the overall process economy and practicality are improved.

[0038] 5. Backflow 2 returns the activated sludge in the sewage treated in the anoxic zone to the anaerobic zone, replenishing the biomass in the anaerobic zone without introducing dissolved oxygen, maintaining the activity and stability of the microbial community in the anaerobic zone, and ensuring that the anaerobic zone can continuously and efficiently complete the anaerobic degradation of organic matter and the release of phosphorus. Backflow 2 constructs a small cycle between the anaerobic zone and the anoxic zone. Through this small cycle, the nutrients in the sewage (such as carbon sources, nitrogen sources, and phosphorus, etc.) can be more fully utilized, reducing the input of external energy, optimizing the material cycle and energy utilization in the system, and improving the nitrogen removal and phosphorus removal effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0040] Figure 1 It is a schematic diagram of a sewage treatment system;

[0041] Figure 2 The present invention is a flow chart of an AOA energy-saving and land-saving nitrogen and phosphorus removal wastewater treatment process in which MBR is used instead of a secondary sedimentation tank.

[0042] 10. Water inlet tank; 11. Water inlet pump;

[0043] 20. anaerobic tank; 21. first stirring device;

[0044] 30. aerobic tank; 31. second stirring device;

[0045] 40. Anoxic tank; 41. Third stirring device; 42. Reflux II; 43. Reflux pump II;

[0046] 50. Membrane bioreactor tank; 51. Outlet pump; 52. Reflux 1; 53. Reflux pump 1;

[0047] 60. Dissolved oxygen meter; 61. Pressure gauge; 62. Thermometer; 63. Aeration pump. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar components or components with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0049] In one embodiment, an AOA energy-saving and land-saving nitrogen and phosphorus removal wastewater treatment process using MBR instead of a secondary sedimentation tank, such as Figure 2 As shown, the process includes the following steps: water inlet process, anaerobic zone treatment, aerobic zone treatment, anoxic zone treatment, and membrane biological reaction zone treatment. Among them, it also includes reflux 1 52 and reflux 2 42.

[0050] Among them, the water intake process is the starting link of sewage treatment. It is used to accurately receive urban sewage, and then apply appropriate pressure through a water pump to transport the sewage stably and evenly to the anaerobic area, laying the foundation for subsequent treatment.

[0051] Anaerobic zone treatment refers to the anaerobic degradation of organic matter and the release of phosphorus in sewage through the action of anaerobic microorganisms, converting large molecular organic matter into small molecular organic matter and intracellular carbon sources, and then inputting sewage into the aerobic zone. Specifically, large molecular organic matter, such as complex substances such as proteins and polysaccharides, are gradually decomposed by anaerobic microorganisms into simple organic matter such as small molecular organic acids and alcohols; at the same time, polyphosphate bacteria release the phosphorus stored in the body under anaerobic conditions, convert it into soluble phosphates, release it into sewage, and synthesize a part of the intracellular carbon source for subsequent metabolic reactions in the aerobic and anoxic stages. The treated sewage flows into the aerobic zone by relying on the water level difference or a low-power lift pump.

[0052] In the aerobic zone treatment, the organic matter in the sewage undergoes nitrification reaction, and nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen, thereby removing ammonia nitrogen; at the same time, polyphosphate-accumulating bacteria multiply in large numbers, absorb phosphorus and store it in the form of polyphosphate in the cells, achieving efficient removal of phosphorus, and the sewage enters the anoxic zone with the help of gravity or low-power pumping.

[0053] The anoxic zone is treated to carry out denitrification reaction, reducing nitrate nitrogen to nitrogen gas, achieving denitrification, and then the sewage is input into the membrane biological reaction zone. Specifically, denitrifying bacteria use the ready-made organic matter in the sewage as a carbon source to reduce the nitrate nitrogen generated in the aerobic zone to nitrogen gas, which then escapes into the atmosphere, successfully achieving the purpose of denitrification. The treated sewage is pumped to the membrane biological reaction zone by gravity or a small flow pump.

[0054] Membrane biological reaction zone treatment uses membrane components to intercept suspended solids and microorganisms in sewage, complete mud and water separation, water is reused or discharged, and sludge is discharged regularly. Membrane components mostly use ultrafiltration or microfiltration membranes, which can accurately intercept suspended solids and microorganisms in sewage with extremely small pore sizes. Driven by pressure, clean water passes through the membrane pores and is directly reused when it meets the reuse standards, or is discharged when it meets the discharge standards; the intercepted sludge is regularly discharged from the sludge outlet to maintain the stable operation and filtration efficiency of the membrane components.

[0055] Reflux 1-52, the sludge discharged from the membrane biological reaction zone is returned to the aerobic zone, specifically including: the sewage treated in the membrane biological reaction zone carries activated sludge and dissolved oxygen back to the aerobic zone, the activated sludge participates in the nitrification reaction in the aerobic zone, converts ammonia nitrogen into nitrate nitrogen; dissolved oxygen causes polyphosphate bacteria to absorb excessive phosphorus in an aerobic environment. The sludge discharged from the membrane biological reaction zone is rich in activated sludge and a certain amount of dissolved oxygen. With the help of pipelines and reflux pumps, it is accurately returned to the aerobic zone. These activated sludges carry a large number of microorganisms, and after returning, they quickly replenish the biomass of the aerobic zone; dissolved oxygen meets the oxygen requirements of the aerobic zone nitrification reaction and aerobic phosphorus absorption, promoting the efficient development of the reaction.

[0056] Return 242, the sewage treated in the anoxic zone is returned to the anaerobic zone, specifically including: the sewage treated in the anoxic zone carries activated sludge back to the anaerobic zone, and the activated sludge replenishes the biomass in the anaerobic zone. The sewage treated in the anoxic zone contains activated sludge but no dissolved oxygen, and is returned to the anaerobic zone through pipes and pumps. The activated sludge enriches the biological community in the anaerobic zone and maintains the number and activity of microorganisms; because it does not contain dissolved oxygen, it perfectly avoids interference and damage to the anaerobic environment and ensures the smooth progress of the anaerobic reaction.

[0057] The AOA energy-saving and land-saving nitrogen and phosphorus removal sewage treatment process in this embodiment, which uses MBR instead of the secondary sedimentation tank, abandons the traditional secondary sedimentation tank and uses a membrane biological reaction zone to complete the mud-water separation. The problems of high sludge concentration and poor sedimentation performance of the sewage effluent from the anoxic tank 40 are solved, avoiding the need to add a pretreatment unit and greatly reducing the floor space; simplifying the process flow, reducing the difficulty of operation and maintenance, reducing equipment failure points, and improving the stability and reliability of the sewage treatment system; the water quality of the membrane separation effluent is stable and excellent, and the suspended matter and microbial interception rate is high, ensuring that the sewage meets the discharge or reuse standards. The combination of AOA and MBR processes, with reflux one 52 and reflux two 42, achieves the superposition of advantages, learns from each other's strengths and overcomes each other's weaknesses, and further optimizes the sewage treatment effect.

[0058] In the aerobic zone of the traditional sewage treatment process, the dissolved oxygen required to maintain the normal metabolism of microorganisms and nitrification reactions in the aerobic zone is almost entirely supplied by fan aeration. The fan needs to operate continuously at high power, which consumes huge energy. However, this process introduces a reflux-52 mechanism. The mud-water mixture discharged from the membrane biological reaction zone carries a certain amount of dissolved oxygen. After returning to the aerobic zone, this part of the dissolved oxygen can directly participate in the aerobic reaction, sharing the pressure of dissolved oxygen originally provided by fan aeration. After the reflux-52 mechanism is established, the fan can significantly reduce power and aeration air volume. Practical data show that it can be reduced by about 50%. This not only reduces the power consumption of fan equipment, extends the service life of the fan, and saves energy; it also reduces problems such as water splashing and odor emission caused by excessive aeration, and optimizes the treatment site environment.

[0059] When the membrane bioreactor is in operation, the membrane components are easily attached and blocked by suspended matter, microorganisms and their secreted extracellular polymers in the sewage, causing membrane fouling, resulting in decreased membrane flux and reduced filtration efficiency. The sludge in the membrane bioreactor area is returned to the aerobic zone through the return flow-52, changing the distribution state of colloids and particulate matter in the sewage. On the one hand, some fine particles that are prone to membrane fouling are further metabolized and decomposed by microorganisms in the aerobic zone; on the other hand, the return flow promotes a more uniform circulation of sewage in the system, avoiding excessive enrichment of local substances and deposition on the membrane surface. The return flow-52 continuously carries away potential pollutants, greatly delaying the process of membrane fouling and reducing the frequency of membrane component cleaning.

[0060] When the membrane assembly needs to be cleaned, the physical cleaning method of blower aeration flushing is mostly used, with the help of air flow disturbance to shake off the impurities attached to the membrane surface. Because the reflux-52 effectively reduces the degree of membrane pollution, the blower aeration air volume required for cleaning is reduced by about 40%, the energy consumption of the cleaning process is reduced, the blower equipment loss is reduced, the sewage treatment system operates more stably and efficiently, and the overall process economy and practicality are improved.

[0061] Return 242 returns the activated sludge in the sewage treated in the anoxic zone to the anaerobic zone, replenishing the biomass in the anaerobic zone without introducing dissolved oxygen, maintaining the activity and stability of the microbial community in the anaerobic zone, and ensuring that the anaerobic zone can continuously and efficiently complete the anaerobic degradation of organic matter and the release of phosphorus. Return 242 builds a small cycle between the anaerobic zone and the anoxic zone. Through this small cycle, the nutrients in the sewage (such as carbon sources, nitrogen sources, and phosphorus, etc.) can be more fully utilized, reducing the input of external energy, optimizing the material cycle and energy utilization in the system, and improving the nitrogen removal and phosphorus removal effect.

[0062] In addition, the sewage treatment plants currently use traditional AAO-MBR, improved AAO-MBR, oxidation ditch-MBR, multi-stage AO-MBR and other MBR-related processes, which have gradually become difficult to meet the discharge standards. The MBR process is transformed into a secondary sedimentation tank to match the AOA process, which requires more space. However, most of the existing sewage treatment plants do not have the remaining land space, making the transformation difficult. The process of this embodiment does not need to increase the floor area, and is easy to promote and use.

[0063] Membrane bioreactor (MBR) has the advantages of small footprint, short construction period and low concentration of suspended particles in effluent. However, in order to avoid membrane pollution, the MBR process requires a large aeration volume for scrubbing, and the energy consumption of the blower is relatively high; a large sludge return volume and nitrification liquid return volume are required, and the energy consumption of the reflux pump is relatively high; the return sludge often carries a large amount of dissolved oxygen, which leads to a decrease in the denitrification performance of the biochemical stage.

[0064] In one embodiment, the reflux ratio of reflux 1 52 is 200%, that is, the amount of sludge refluxed from the membrane biological reaction zone to the aerobic zone is twice the amount of water inflow to the aerobic zone. In the sewage treatment process, the reflux ratio refers to the ratio of the reflux liquid flow to the water inflow flow, usually expressed as a percentage. Compared with the conventional 300%-500% reflux ratio, the reflux pump power required for the 200% reflux ratio is smaller, the reflux pipe is thinner, and the procurement and operation costs are lower. And through the combination of AOA and MBR, and the coordination of reflux 1 52 and reflux 2 42, reflux 1 52 can still meet the requirements of nitrogen removal and phosphorus removal with a low reflux ratio, so that the treated sewage can meet the corresponding discharge standards, and the sludge concentration discharged from the membrane biological reaction zone is low, about 6000mg / L, which greatly reduces membrane pollution compared with the conventional sludge concentration of 8000mg / L-10000mg / L.

[0065] In one embodiment, the return ratio of return flow 2 42 is 100%, that is, the amount of sewage returned from the anoxic zone to the anaerobic zone is equal to the amount of original sewage entering the anaerobic zone. Return flow 2 42 replenishes activated sludge in time with a return ratio of 100%, so that the number of microorganisms in the anaerobic zone is maintained at a sufficient level, ensuring that large molecular organic matter is continuously and efficiently degraded by anaerobic microorganisms, and phosphorus is released stably. Even if the influent water quality and water volume fluctuate, sufficient biomass can buffer the impact and maintain the stability of the treatment efficiency of the anaerobic zone. Return flow 2 42 provides the anaerobic zone with a stable biomass supply, precise anaerobic environment maintenance and efficient material circulation with a return ratio of 100%, and the system runs more smoothly and efficiently. At this time, the sludge concentration in the anaerobic zone is about 2000mg / L, and the sludge concentration in the aerobic zone and the anoxic zone is about 4000mg / L.

[0066] In one embodiment, based on a sewage treatment system, such as Figure 1 As shown, the sewage treatment system includes an inlet tank 10, an anaerobic tank 20, an aerobic tank 30, an anoxic tank 40 and a membrane bioreactor 50 which are connected in sequence, and also includes a reflux pump 1 53 and a reflux pump 2 43. Among them, the inlet tank 10 receives sewage transported from the sewage well; the inlet tank 10 transports sewage to the anaerobic tank 20 through the inlet pump 11; the aerobic tank 30 receives sewage output from the anaerobic tank 20 and transports it to the anoxic tank 40 after treatment; the anoxic tank 40 receives sewage output from the aerobic tank 30 and transports it to the membrane bioreactor 50 after treatment; the membrane bioreactor 50 receives sewage output from the anoxic tank 40, and the water treated by the membrane module is discharged through the outlet pump 51, and part of the treated sludge is discharged regularly, and part of it is pumped to the aerobic tank 30 through the reflux pump 1 53.

[0067] As the first stop for sewage to enter, the water inlet tank 10 can balance the sewage flow and water quality, weaken the impact of water inlet, and provide relatively stable water inlet conditions for subsequent treatment processes; the interior is often equipped with pre-treatment components such as grilles and sand settling to intercept large particles of suspended solids and sediment to prevent equipment wear and pipe blockage. The anaerobic tank 20 closely receives sewage from the water inlet tank 10 and creates an anaerobic environment. Anaerobic microorganisms cause large molecular organic matter to decompose into small molecules. At the same time, polyphosphate bacteria release the phosphorus stored in the body to generate intracellular carbon sources for subsequent use. The aerobic tank 30 receives the effluent from the anaerobic tank 20, where nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen to achieve the goal of removing ammonia nitrogen; polyphosphate bacteria absorb a large amount of phosphorus to complete the removal of phosphorus; biological fillers can be installed in the tank to increase the attachment area of ​​microorganisms and enhance the treatment effect. The anoxic tank 40 receives the effluent from the aerobic tank 30, and uses denitrifying bacteria to reduce nitrate nitrogen to nitrogen gas using organic matter in the sewage as a carbon source to achieve denitrification. To ensure the smooth progress of denitrification, the tank maintains a low dissolved oxygen state, and can be equipped with a flow-pushing device to promote the uniform flow of sewage. The membrane bioreactor 50 uses high-precision membrane components to intercept suspended matter and microorganisms in the sewage. The sewage is driven by pressure, and the clean water passes through the membrane and is pressurized by the outlet pump 51 to meet the standards for discharge or reuse. A part of the intercepted sludge is regularly discharged from the sludge outlet to maintain the stability of the membrane component flux, and the other part is quickly pumped to the aerobic tank 30 under the action of the reflux pump 53.

[0068] The reflux pump 53 has two ends connected to the membrane biological reactor 50 and the aerobic tank 30 respectively. The reflux pump 53 pumps the sludge discharged from the membrane biological reactor 50 to the aerobic tank 30. Specifically, the reflux pump 53 can use a high-lift, wear-resistant centrifugal pump to accurately match the working conditions between the aerobic tank 30 and the membrane biological reactor 50; the pipeline is made of corrosion-resistant, smooth-walled HDPE material to reduce the risk of sludge accumulation. The reflux pump 53 is adjusted in real time according to the dissolved oxygen, sludge concentration and other parameters of the aerobic tank 30 to maintain a suitable reflux condition, so that the reflux ratio is 200%; the reflux sludge is rich in activated sludge and dissolved oxygen, and the activated sludge brings back a large number of nitrifying bacteria and polyphosphate bacteria, and the dissolved oxygen directly supplies the aerobic tank 30.

[0069] The two ends of the return pump 43 are connected to the anoxic tank 40 and the anaerobic tank 20 respectively. The return pump 43 pumps the sewage discharged from the anoxic tank 40 to the anaerobic tank 20. Specifically, the return pump 43 can use a low-power, precisely controllable flow centrifugal pump to adapt to the return requirements of the anoxic tank 40 and the anaerobic tank 20; the pipeline laying follows the principle of short distance and few bends to reduce resistance and sewage retention. The return pump 43 can stably maintain a 100% return ratio with the help of an intelligent control system; the return sewage carries activated sludge and has no dissolved oxygen. The activated sludge enriches the biomass of the anaerobic zone, and the anaerobic environment avoids interference with the anaerobic reaction.

[0070] Faced with fluctuations in influent quality and volume, return pumps 153 and 2 quickly take effect. The returned activated sludge and substances buffer the impact and maintain the stability of the reactions in each pool; the dissolved oxygen in the aerobic pool 30 is stable and the oxygen-free environment in the anaerobic pool 20 is stable, ensuring the continuity of the treatment process, reducing the risk of effluent quality exceeding the standard, and enhancing the adaptability and reliability of the system.

[0071] In one embodiment, the anaerobic tank 20 is built with the output end of the first stirring device 21, the aerobic tank 30 is built with the output end of the second stirring device 31 and the output end of the first aeration device, the anoxic tank 40 is built with the output end of the third stirring device 41, and the membrane biological reactor 50 is built with the output end of the second aeration device; the power of the first stirring device 21 and the third stirring device 41 is less than the power of the second stirring device; the first aeration device is used to supplement oxygen to the aerobic tank 30, and the second aeration device is used to reduce the blockage of the membrane module. The first aeration device and the second aeration device can be set as the same aeration pump 63, and the same aeration pump 63 extends two aeration heads, which extend into the aerobic tank 30 and the membrane biological reactor 50 respectively.

[0072] Specifically, the anaerobic tank 20 is built with an output end of a first stirring device 21. The first stirring device 21 often uses a low-speed flow mixing device with relatively small power. The purpose is to gently stir the sewage to promote full contact between the sewage and anaerobic microorganisms without destroying the microbial floc structure. Anaerobic microorganisms work in an anaerobic environment. Macromolecular organic matter is gradually decomposed into small molecular substances through hydrolysis and acidification. Polyphosphate bacteria release the phosphorus stored in the body to reserve materials and energy for subsequent treatment.

[0073] The aerobic pool 30 is equipped with a second stirring device and a first aeration device. The second stirring device has a relatively large power and usually uses a high-speed stirring impeller, which cooperates with the first aeration device to create an ideal aerobic environment. The first aeration device continuously injects air into the pool through microporous aeration discs, tubular aerators and other equipment to maintain the dissolved oxygen concentration in an appropriate range to meet the needs of nitrifying bacteria to oxidize ammonia nitrogen into nitrate nitrogen and polyphosphate bacteria to absorb a large amount of phosphorus; the second stirring device further breaks up the bubbles and stirs the water to prevent the local dissolved oxygen from being too high or too low, thereby enhancing the treatment effect.

[0074] The third stirring device 41 in the anoxic tank 40 is responsible for maintaining uniform mixing of sewage in the anoxic tank 40. Since the anoxic tank 40 only needs to create a low dissolved oxygen environment for denitrification reaction to reduce nitrate nitrogen into nitrogen gas, the third stirring device 41 has a low power, and a variable frequency speed control push flow mixing device is selected to flexibly adjust the stirring intensity as needed to avoid introducing too much oxygen and ensure the activity and reaction efficiency of denitrifying bacteria.

[0075] The membrane bioreactor 50 is equipped with a second aeration device, whose main function is to use the air flow disturbance generated by aeration to flush the surface of the membrane assembly. When the sewage is filtered through the membrane assembly, some suspended matter, microorganisms and their secreted extracellular polymers tend to adhere to the membrane and cause blockage. The second aeration device performs intermittent aeration to form a gas-liquid flushing flow to shake off the attached impurities and maintain the stability of the membrane flux.

[0076] Sewage flows from the water inlet tank 10 into the anaerobic tank 20, aerobic tank 30, anoxic tank 40 and membrane biological reactor 50 in sequence, and the equipment in each tank is started and coordinated in sequence. The first stirring device 21 of the anaerobic tank 20 runs at a low speed to initially decompose organic matter; the first aeration device and the second stirring device of the aerobic tank 30 work synchronously and efficiently to quickly complete nitrification and phosphorus absorption; the third stirring device 41 of the anoxic tank 40 maintains a stable reaction environment to promote denitrification; the second aeration device of the membrane biological reactor 50 aerates at a preset time interval to ensure smooth membrane filtration and reduce overall energy consumption, which is in line with the development trend of green and low-carbon sewage treatment, reduces long-term operating costs, and improves economic benefits.

[0077] In one embodiment, the anoxic tank 40 is provided with two interconnected ones, the sewage outputted from the aerobic tank 30 is inputted into the first anoxic tank 40, and outputted from the second anoxic tank 40 to the membrane biological reactor 50, and the reflux pump 2 43 is connected to the second anoxic tank 40. The two anoxic tanks 40 are closely arranged in series, and are connected to each other through the connecting pipes at the bottom. The pipe diameter is precisely designed according to the sewage flow rate to ensure that the sewage flows steadily and uniformly from the first anoxic tank 40 to the second anoxic tank 40. A flow regulating valve can also be set at the connection point to connect to the automatic control system, monitor in real time, flexibly adjust the sewage flow rate and flow rate, and adapt to different working conditions.

[0078] The first anoxic tank 40 is equipped with a low-power plug-flow mixing device to evenly mix the sewage, avoid local material deposition, and provide suitable reaction conditions for denitrifying bacteria; some denitrification products and activated sludge flow into the second anoxic tank 40 with the sewage. The second anoxic tank 40 is also equipped with a stirring device, and an online nitrate nitrogen monitor can be added to feedback the nitrogen content in real time, and accurately control the stirring intensity and residence time; the denitrified sewage is transported to the membrane biological reactor 50 by means of the liquid level difference and a low-power lifting pump, and the suspended solids and microorganisms are intercepted by the membrane module, and the clean water is discharged for reuse or discharged in compliance with the standards, and the sludge is disposed of regularly.

[0079] A double anoxic tank 40 is set up to form a relay denitrification. The first anoxic tank 40 performs preliminary reduction, and the second anoxic tank 40 performs deep purification, which greatly improves the denitrification efficiency and significantly reduces the total nitrogen content in the effluent, stably meets the standard, satisfies strict sewage discharge standards, and reduces the risk of eutrophication of water bodies.

[0080] In one embodiment, the aerobic pool 30 is also equipped with a detection end of a dissolved oxygen meter 60, which is used to monitor the dissolved oxygen concentration in the aerobic pool 30 in real time. The detection end of the dissolved oxygen meter 60 is precisely installed at a key position of the aerobic pool 30, generally around the aeration area, the center of the pool body, and near the outlet, to ensure that the dissolved oxygen concentration information in the pool can be fully and accurately captured. The detection end is mostly a polarographic or fluorescence sensor, which uses electrodes to react chemically with dissolved oxygen in sewage to generate electrical signals, or quantifies dissolved oxygen by the degree of quenching of fluorescent substances by oxygen molecules, and feeds back data to the central control system in real time.

[0081] A pressure gauge 61 is also provided between the membrane bioreactor 50 and the outlet pump 51. The pressure gauge 61 is used to monitor the outlet pressure in real time and evaluate the performance of the membrane assembly. The pressure gauge 61 is vertically installed on the connecting pipe between the membrane bioreactor 50 and the outlet pump 51, close to the outlet port of the membrane bioreactor 50, and bears the direct pressure of the water flow. A high-precision, high-pressure resistant mechanical pressure gauge 61 or a digital pressure sensor can be used to convert the water pressure into an intuitive reading or electrical signal based on the correlation between pressure and membrane flux, and continuously display the outlet pressure of the membrane assembly when it is working to the operation and maintenance personnel.

[0082] A thermometer 62 is also provided in the sewage treatment system, and is used to monitor the water temperature of the sewage in the sewage treatment system in real time. The thermometer 62 can be distributed in the water inlet tank 10, each reaction tank and key nodes of the pipeline. The sensor probe is immersed in the sewage, and the water temperature can be measured by contact. Commonly used platinum resistance thermometers 62 and thermistor thermometers 62 can accurately sense the change of water temperature by virtue of the law of material resistance changing with temperature, and the data is transmitted to the central control room in real time.

[0083] The above monitoring equipment can all be connected to the automated central control system of the sewage treatment system. The central control system integrates data such as dissolved oxygen, outlet water pressure, and water temperature, draws real-time change curves, and intelligently analyzes data trends. Based on preset thresholds, the central control system automatically adjusts the operating parameters of aeration equipment, reflux pumps, membrane flushing devices, etc. Once the detection value deviates from the normal range, an alarm is immediately triggered to notify the operation and maintenance personnel to investigate and handle it.

[0084] The dissolved oxygen meter 60 monitors the dissolved oxygen concentration in the aerobic pool 30 in real time to avoid the problem of excessive or insufficient aeration caused by the traditional process based on experience. When the dissolved oxygen is high, the central control system automatically reduces the power of the aeration equipment and reduces the air supply; when the dissolved oxygen is low, aeration is increased in time to accurately maintain the appropriate dissolved oxygen level, which not only saves about 30%-40% of the fan energy consumption, but also stabilizes the activity of nitrifying bacteria and polyphosphate bacteria, and improves the treatment efficiency.

[0085] The pressure gauge 61 continuously monitors the outlet water pressure of the membrane bioreactor 50. In the early stage of membrane module blockage, the outlet water pressure gradually rises. The operation and maintenance personnel can predict the degree of membrane contamination in advance based on the pressure change, start the membrane flushing program in time, and adjust the frequency and intensity of backwashing. Chemical cleaning can also be combined to remove stubborn pollutants, effectively delay membrane aging, extend the service life of the membrane by 1-2 years, and reduce the cost of equipment replacement.

[0086] Sewage temperature affects the metabolic activity of microorganisms, and the thermometer 62 provides real-time water temperature information. When the water temperature is low in winter, the microbial reaction slows down, and the central control system can automatically extend the hydraulic retention time and increase the return ratio to increase the contact opportunity between microorganisms and pollutants; in summer, when the water temperature is too high, appropriate cooling measures are taken, such as adding cooling towers and adjusting the water inlet flow rate, to maintain the optimal activity of microorganisms and ensure stable treatment effects throughout the year.

[0087] The automated monitoring and control system reduces the frequency of manual inspections, and operation and maintenance personnel remotely monitor equipment operation and changes in water quality parameters. Abnormal situations automatically alarm and accurately locate fault points, reducing the difficulty of troubleshooting; the big data accumulated by the system can also provide a basis for process optimization and equipment upgrades, and improve the overall operation and maintenance management efficiency and scientificity of the sewage treatment plant. Through all-round real-time monitoring, all links of the sewage treatment system are closely linked and dynamically adjusted. In the face of fluctuations in influent water quality and water volume, it can respond quickly, maintain the stability of the reaction environment of each pool, reduce the risk of effluent water quality exceeding the standard, enhance the ability of the process to adapt to complex working conditions, and ensure long-term stable operation.

[0088] In the description of this specification, if the terms "embodiment one", "this embodiment", "in an embodiment" and the like appear, it means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the invention or at least one embodiment or example of the invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in an appropriate manner.

[0089] In the description of this specification, the terms "connect", "install", "fix", "set", "have", etc. are all understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0090] In the description of this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0091] The above description of the embodiments is to facilitate ordinary technicians in the technical field to understand and apply the technology of this case. People familiar with the technology in this field can obviously easily make various modifications to these examples and apply the general principles described here to other embodiments without creative work. Therefore, this case is not limited to the above embodiments. Modifications to the following situations should all be within the scope of protection of this case: ① A new technical solution implemented based on the technical solution of the present invention and combined with existing common knowledge, the technical effect produced by the new technical solution does not exceed the technical effect of the present invention; ② The equivalent replacement of some features of the technical solution of the present invention by using known technology, the technical effect produced is the same as the technical effect of the present invention; ③ The technical solution of the present invention can be expanded, and the substantive content of the expanded technical solution does not exceed the technical solution of the present invention; ④ The equivalent transformation made by using the contents of the description and drawings of the present invention is directly or indirectly applied to other related technical fields.

Claims

1. An AOA energy-saving and land-saving nitrogen and phosphorus removal sewage treatment process using MBR instead of a secondary sedimentation tank, characterized in that: Including the following processes: The influent process receives sewage and pumps it to the anaerobic zone; Anaerobic zone treatment, through the action of anaerobic microorganisms, completes the anaerobic degradation of organic matter in sewage and the release of phosphorus, converts macromolecular organic matter into small molecular organic matter and intracellular carbon source, and then the sewage is input into the aerobic zone; In the aerobic zone, the organic matter in the sewage undergoes nitrification reaction, converting ammonia nitrogen into nitrate nitrogen, thus removing ammonia nitrogen; polyphosphate bacteria absorb phosphorus and store it in the cells in the form of polyphosphate, thus removing phosphorus, and then the sewage is input into the anoxic zone; The anoxic zone is treated to carry out denitrification reaction, reducing nitrate nitrogen to nitrogen gas to achieve denitrification, and then the sewage is input into the membrane biological reaction zone; Membrane biological reaction zone treatment uses membrane components to intercept suspended solids and microorganisms in sewage, complete mud and water separation, water is reused or discharged, and sludge is discharged regularly; Among them, it also includes: Backflow 1: the sludge discharged from the membrane biological reaction zone flows back to the aerobic zone; Backflow 2: The sewage treated in the anoxic zone flows back to the anaerobic zone.

2. The sewage treatment process according to claim 1, characterized in that: The sludge discharged from the membrane biological reaction zone is returned to the aerobic zone, specifically including: the sewage treated in the membrane biological reaction zone carries activated sludge and dissolved oxygen back to the aerobic zone, the activated sludge participates in the nitrification reaction in the aerobic zone to convert ammonia nitrogen into nitrate nitrogen; the dissolved oxygen enables the polyphosphate bacteria to absorb excessive phosphorus in the aerobic environment.

3. The sewage treatment process according to claim 2, characterized in that: The reflux ratio of the reflux one is 200%.

4. The sewage treatment process according to any one of claims 1, characterized in that: The sewage treated in the anoxic zone is returned to the anaerobic zone, which specifically includes: the sewage treated in the anoxic zone carries activated sludge and returns to the anaerobic zone, and the activated sludge supplements the biomass in the anaerobic zone.

5. The sewage treatment process according to claim 4, characterized in that: The reflux ratio of the reflux 2 is 100%.

6. The sewage treatment process according to any one of claims 1 to 5, characterized in that: Based on a sewage treatment system, the sewage treatment system includes an inlet tank, an anaerobic tank, an aerobic tank, an anoxic tank and a membrane biological reaction tank connected in sequence, and also includes: A reflux pump 1, two ends of which are connected to the membrane biological reaction tank and the aerobic tank respectively, and the reflux pump 1 pumps the sludge discharged from the membrane biological reaction tank to the aerobic tank; The two ends of the reflux pump 2 are respectively connected to the anoxic tank and the anaerobic tank. The reflux pump 2 pumps the sewage discharged from the anoxic tank to the anaerobic tank.

7. The sewage treatment process according to claim 6, characterized in that: The water inlet tank receives sewage transported from the sewage well; The water inlet tank conveys sewage to the anaerobic tank via a water inlet pump; The aerobic tank receives the sewage output from the anaerobic tank and transports it to the anoxic tank after treatment; The anoxic tank receives the sewage output from the aerobic tank and transports it to the membrane biological reaction tank after treatment; The membrane biological reaction tank receives the sewage output from the anoxic tank, and the water treated by the membrane module is discharged through the outlet pump. Part of the treated sludge is discharged regularly, and part is pumped to the aerobic tank through the reflux pump.

8. The sewage treatment process according to claim 7, characterized in that: The anaerobic tank is provided with an output end of a first stirring device, the aerobic tank is provided with an output end of a second stirring device and an output end of a first aeration device, the anoxic tank is provided with an output end of a third stirring device, and the membrane biological reaction tank is provided with an output end of a second aeration device; The power of the first stirring device and the third stirring device is less than the power of the second stirring device; The first aeration device is used to supplement oxygen to the aerobic tank, and the second aeration device is used to reduce the blockage of the membrane module.

9. The sewage treatment process according to claim 8, characterized in that: The anoxic tanks are provided with two interconnected ones. The sewage output from the aerobic tank is input into the first anoxic tank, and is output from the second anoxic tank to the membrane biological reaction tank.

10. The sewage treatment process according to claim 9, characterized in that: The aerobic pool is also equipped with a detection end of a dissolved oxygen meter, and the dissolved oxygen meter is used to monitor the dissolved oxygen concentration in the aerobic pool in real time; A pressure gauge is also provided between the membrane biological reaction tank and the outlet water pump, and the pressure gauge is used to monitor the outlet water pressure in real time and evaluate the performance of the membrane assembly; A thermometer is also provided in the sewage treatment system, and the thermometer is used to monitor the water temperature of the sewage in the sewage treatment system in real time.

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