Multi-section AAO-MBR (anaerobic-anoxic-oxic-membrane bioreactor) composite sewage treatment device

Abstract

The utility model discloses a multi-section AAO-MBR (anaerobic-anoxic-oxic-membrane bioreactor) composite sewage treatment device, which relates to the technical field of sewage treatment and comprises a pretreatment section, a primary treatment section, a secondary treatment section, an advanced treatment section and a sludge treatment section. The pretreatment section comprises a coarse screen, a lifting pump room, a fine screen and an aerated grit chamber which are sequentially connected through pipelines; the primary treatment section comprises a membrane grid and a primary sedimentation tank; the secondary treatment section comprises a multi-section AAO biochemical tank; the multi-section AAO biochemical tank comprises an anaerobic tank, a first anoxic tank, a first aerobic tank, a second anoxic tank and a second aerobic tank. According to the device, gradient utilization of a carbon source and efficient synergistic removal of nitrogen and phosphorus are realized through symmetrical layout, rotary circulation and graded reflux. The advanced treatment system adopts an MBR membrane tank, and ensures that suspended solids and total phosphorus in effluent stably reach the standard through a membrane separation technology. And the sludge treatment section is combined with a low-temperature vacuum drying technology, so that the water content of the sludge is reduced to be less than 40%, and efficient treatment and resource utilization of the sludge are realized.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, and in particular to a multi-stage AAO-MBR composite wastewater treatment device. Background Technology

[0002] With rapid urbanization and increasingly stringent environmental protection requirements, wastewater treatment technologies face multiple challenges, including improving treatment efficiency, optimizing operating costs, and optimizing resource utilization. While traditional AAO (anaerobic-anoxic-aerobic) processes can simultaneously remove organic matter and nitrogen and phosphorus pollutants, their single-process design suffers from issues such as unbalanced carbon source distribution, insufficient synergy of microbial functions, and large fluctuations in water quality and quantity, leading to unstable nitrogen and phosphorus removal efficiencies. Furthermore, conventional processes rely on secondary sedimentation tanks for sludge-water separation, resulting in low sludge concentrations and a tendency for sludge bulking, causing significant fluctuations in treatment effectiveness.

[0003] Current multi-stage AAO processes enhance the synergistic effect of nitrogen and phosphorus removal by adding anoxic and aerobic reaction zones, but still face bottlenecks in advanced treatment stages, such as difficulty in controlling suspended solids in the effluent and insufficient water quality stability. Membrane bioreactor (MBR) technology replaces traditional sedimentation units with membrane separation, significantly improving biomass concentration and effluent quality. However, single MBR systems suffer from insufficient regulation of the microbial metabolic environment and difficulties in controlling membrane fouling. While processes such as sequencing batch reactor (SBR) offer flexibility, they require high levels of automation control and struggle to achieve stable and efficient nitrogen and phosphorus removal in continuous flow treatment. Existing technologies that simply combine multi-stage AAO with MBR often suffer from insufficient functional zoning matching and poor synergy of operating parameters, resulting in low carbon source utilization and rapid membrane module lifespan degradation. Utility Model Content

[0004] The purpose of this invention is to address the problems existing in the prior art by proposing a multi-stage AAO-MBR composite wastewater treatment device. Through an innovative design of the multi-stage AAO biological treatment structure and the synergistic operation mechanism of the membrane separation unit, it optimizes the distribution of microbial populations and the metabolic environment, significantly improving the synergistic efficiency of nitrogen and phosphorus removal. Combined with a dynamically controlled membrane fouling inhibition strategy, it ensures stable effluent quality while reducing system energy consumption and operation and maintenance requirements, providing a more adaptable solution for advanced wastewater treatment and resource utilization.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A multi-stage AAO-MBR composite wastewater treatment device includes a pretreatment stage, a primary treatment stage, a secondary treatment stage, an advanced treatment stage, and a sludge treatment stage.

[0007] The pretreatment section includes a coarse screen, a booster pump station, a fine screen, and an aerated grit chamber connected sequentially by pipelines; the primary treatment section includes a membrane screen and a primary sedimentation tank; the secondary treatment section includes a multi-stage AAO biological treatment tank, which comprises an anaerobic tank, a first anoxic tank, a first aerobic tank, a second anoxic tank, and a second aerobic tank; the advanced treatment section includes an MBR membrane tank and equipment room; and the sludge treatment section comprises a sludge thickener, a low-temperature vacuum dryer, an inclined scraper conveyor, and a sludge silo.

[0008] Preferably, the inlet end of the membrane grid is connected to the outlet end of the aerated grit chamber, and the outlet end of the membrane grid is connected to the inlet end of the primary sedimentation tank.

[0009] Preferably, the anaerobic tank is located on the side near the primary sedimentation tank. The effluent from the anaerobic tank enters the first anoxic tank through the flow hole in the middle of the corridor. The first anoxic tank is located in the middle corridor of the multi-segment AAO. There are two first aerobic tanks, which are symmetrically arranged and located on both sides of the first anoxic tank. There are also two second anoxic tanks, which are symmetrically arranged and located on both sides of the first aerobic tank. There are also two second aerobic tanks, which are symmetrically arranged and located near the rear half of the second anoxic tank. The end of the first anoxic tank near the second aerobic tank is connected to the first aerobic tank, and the end of the first aerobic tank near the anaerobic tank is connected to the second anoxic tank.

[0010] The effluent from the anaerobic tank enters the first anoxic tank through the flow hole in the middle of the corridor. The wastewater from the first anoxic tank enters the first aerobic tank through the flow hole near the second aerobic tank. The wastewater from the first aerobic tank enters the second anoxic tank through the flow hole near the anaerobic tank. The wastewater from the second anoxic tank enters the second aerobic tank through the flow hole in the side wall.

[0011] Preferably, both the first aerobic tank and the second aerobic tank are equipped with disc aerators along the water flow direction, and the bottom of the first anoxic tank, the second anoxic tank, the first aerobic tank, and the second aerobic tank are equipped with a flow-pushing agitator. The first anoxic tank and the second anoxic tank are equipped with carbon source dosing devices with adjustable opening.

[0012] Preferably, the first anoxic tank is equipped with a first return pump for returning the digestate to the anaerobic tank; the second aerobic tank is equipped with a second return pump for returning the sludge to the first anoxic tank; and the effluent from the second aerobic tank enters the MBR membrane tank through the upper effluent channel.

[0013] Preferably, there are two MBR membrane tanks, which are symmetrically arranged on both sides of the second aerobic tank. The sludge pump and permeate pump of the MBR membrane tank are all located in the middle corridor of the MBR membrane tank.

[0014] Preferably, the sludge pump of the MBR membrane tank is used to shunt and transport sludge to the sludge treatment section and the first aerobic tank, and the water production pump is used to lift the effluent of the MBR membrane tank to the subsequent treatment unit for treatment.

[0015] Preferably, the sludge treatment section further includes a sludge power distribution room, a chemical dosing room, and a blower room that are配套 with sludge dewatering.

[0016] Compared with the prior art, the advantages and positive effects of the present utility model are as follows:

[0017] 1. In this application, through the deep coupling design of multi-stage AAO and MBR, the comprehensive efficiency of sewage treatment is significantly improved. The system adopts a multi-stage anaerobic-anoxic-aerobic segmented structure. Through the symmetric layout of biochemical tanks and precise dissolved oxygen control, the function of denitrifying phosphorus-removing bacteria groups is strengthened, realizing the cascade utilization of carbon sources and the efficient synergistic removal of nitrogen and phosphorus. The total nitrogen, total phosphorus, and suspended solids in the effluent stably reach the first-class A standard. The two-way cooperation mechanism between the MBR membrane tank and the biochemical unit (such as a 300% high reflux ratio and symmetric flow pattern design) greatly improves the sludge concentration gradient and the ability to resist impact load, effectively alleviates the risk of membrane fouling, extends the operation cycle of the membrane module, and significantly reduces the overall energy consumption of the system.

[0018] 2. In this application, through the compact series layout of multi-stage AAO and MBR, while reducing the floor area, the efficient connection of treatment units is achieved, especially suitable for new construction or renovation projects of sewage treatment plants with limited land use. The sludge treatment unit adopts low-temperature vacuum drying technology, combined with the linkage design of an inclined scraper conveyor and a sludge silo, significantly improving the dewatering efficiency, and the sludge moisture content is reduced to less than 40%. In addition, through the synergistic effect of hierarchical reflux control and a pusher agitator, the dynamic balance of nitrogen and phosphorus removal is strengthened, ensuring stable operation under water quality fluctuations, and the comprehensive operation cost is reduced by 15%-20% compared with the traditional process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic plan view of a multi-stage AAO-MBR composite sewage treatment device proposed by the present utility model.

[0020] Legend: 1. Pretreatment section; 11. Coarse screen; 12. Lift pump station; 13. Fine screen; 14. Aerated grit chamber; 2. Primary treatment section; 21. Membrane screen; 22. Primary sedimentation tank; 3. Secondary treatment section; 31. Anaerobic tank; 32. First anoxic tank; 321. First return pump; 33. First aerobic tank; 34. Second anoxic tank; 35. Second aerobic tank; 351. Second return pump; 36. Disc type 37. Aerator; 38. Flow mixer; 4. Carbon source dosing device; 5. Advanced treatment section; 41. MBR membrane tank; 411. Sludge pump; 412. Permeate pump; 413. Water distribution channel; 42. Equipment room; 5. Sludge treatment section; 51. Sludge thickener; 52. Low temperature vacuum dryer; 53. Inclined scraper conveyor; 54. Sludge silo; 55. Sludge power distribution room; 56. Chemical dosing room; 57. Blower room. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of this utility model, the present utility model will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed in the following specification.

[0023] like Figure 1 As shown, this utility model provides a multi-stage AAO-MBR composite wastewater treatment device, including a pretreatment stage 1, a primary treatment stage 2, a secondary treatment stage 3, a deep treatment stage 4, and a sludge treatment stage 5:

[0024] The pretreatment section 1 includes a coarse screen 11, a lift pump station 12, a fine screen 13, and an aerated grit chamber 14 connected in sequence by pipelines; the primary treatment section 2 includes a membrane screen 21 and a primary sedimentation tank 22; the secondary treatment section 3 includes a multi-stage AAO biological treatment tank, which includes an anaerobic tank 31, a first anoxic tank 32, a first aerobic tank 33, a second anoxic tank 34, and a second aerobic tank 35; the advanced treatment section 4 includes an MBR membrane tank 41 and an equipment room 42; and the sludge treatment section 5 consists of a sludge thickener 51, a low-temperature vacuum dryer 52, an inclined scraper conveyor 53, and a sludge silo 54.

[0025] Specifically, the coarse screen 11 has a filtration accuracy of 150~500μm. Wastewater first passes through the coarse screen 11 to intercept large-sized debris. After being pressurized by the booster pump station 12, it enters the rotary drum fine screen 13 with a rotation speed of 2~6r / min and a flow velocity of 0.8m / s through the screen, removing suspended solids of 1~10mm. Subsequently, the wastewater flows into the aerated grit chamber 14 through the flow holes at the bottom of the fine screen 13. The swirling flow formed at the bottom of the chamber achieves efficient separation of sand particles (≥0.2mm, retention rate ≥85%) from organic matter.

[0026] In this embodiment, the inlet end of the membrane grid 21 is connected to the outlet end of the aerated grit chamber 14, and the outlet end of the membrane grid 21 is connected to the inlet end of the primary sedimentation tank 22.

[0027] Specifically, after being regulated by the weir plate, the effluent enters the membrane grid 21. The mesh size of the membrane grid 21 is 0.2~0.5mm, which deeply intercepts residual fibers and suspended solids (SS removal rate 50%~70%), thereby significantly reducing the amount of scum and mud and sand interference in the primary sedimentation tank 22 by 30%~40%. Finally, the wastewater in the primary sedimentation tank 22 removes 60%~70% of suspended solids (SS≤100mg / L) through gravity sedimentation. The sludge from the primary sedimentation tank 22 is discharged into the sludge storage tank for subsequent treatment by static pressure, and its supernatant enters the secondary treatment section.

[0028] In this embodiment, the anaerobic tank 31 is located on the side near the primary sedimentation tank 22. The effluent from the anaerobic tank 31 enters the first anoxic tank 32 through the flow hole in the middle of the corridor. The first anoxic tank 32 is located in the middle corridor of the multi-segment AAO. There are two first aerobic tanks 33, which are symmetrically arranged and located on both sides of the first anoxic tank 32. There are two second anoxic tanks 34, which are symmetrically arranged and located on both sides of the first aerobic tank 33. There are two second aerobic tanks 35, which are symmetrically arranged and located near the rear half of the second anoxic tank 34. The end of the first anoxic tank 32 near the second aerobic tank 35 is connected to the first aerobic tank 33, and the end of the first aerobic tank 33 near the anaerobic tank is connected to the second anoxic tank 34.

[0029] The effluent from the anaerobic tank 31 enters the first anoxic tank 32 through the flow hole in the middle of the corridor. The sewage from the first anoxic tank 32 enters the first aerobic tank 33 through the flow hole near the second aerobic tank 35. The sewage from the first aerobic tank 33 enters the second anoxic tank 34 through the flow hole near the anaerobic tank 31. The sewage from the second anoxic tank 34 enters the second aerobic tank 35 through the flow hole in the side wall.

[0030] Both the first aerobic tank 33 and the second aerobic tank 35 are equipped with disc aerators 36 along the water flow direction. Both the first anoxic tank 32, the second anoxic tank 34, the first aerobic tank 33, and the second aerobic tank 35 are equipped with pusher agitators 37 at the bottom. Both the first anoxic tank 32 and the second anoxic tank 34 are equipped with carbon source dosing devices 38 with adjustable opening.

[0031] Both the first aerobic tank 33 and the second aerobic tank 35 are equipped with disc aerators 36 along the water flow direction. Both the first anoxic tank 32, the second anoxic tank 34, the first aerobic tank 33, and the second aerobic tank 35 are equipped with pusher agitators 37 at the bottom. Both the first anoxic tank 32 and the second anoxic tank 34 are equipped with carbon source dosing devices 38 with adjustable opening.

[0032] The first anoxic tank 32 is equipped with a first return pump 321, which is used to return the digestate (return ratio 300%) to the anaerobic tank 31; the second aerobic tank 35 is equipped with a second return pump 351, which is used to return the sludge (return ratio 60%) to the first anoxic tank 32; the effluent from the second aerobic tank 35 enters the MBR membrane tank 41 through the upper effluent channel.

[0033] Specifically, wastewater enters the anaerobic tank 31 of the secondary wastewater treatment section through the effluent channel of the primary sedimentation tank 22. In the anaerobic tank 31, anaerobic bacteria hydrolyze, acidify, and methanate organic matter to remove it, thereby improving the wastewater's biodegradability. Simultaneously, the flow mixer 37 within the anaerobic tank 31 evenly mixes the wastewater and sludge within the tank and the returned wastewater. The effluent from the anaerobic tank 31 enters the first anoxic tank 32 through the flow passage in the middle of the corridor. The flow mixer 37 at the bottom of the first anoxic tank 32 maintains thorough mixing and suspension of the wastewater and the activated sludge returned from the second aerobic tank. An adjustable carbon source dosing device 38 is installed in both the first anoxic tank 32 and the second anoxic tank 34 to achieve carbon source... With precise application, denitrifying bacteria use carbon sources as electron donors and nitrates as electron acceptors to carry out oxidation-reduction reactions, thereby achieving nitrogen removal. Simultaneously, the first return pump 321 in the first anoxic tank 32 returns the nitrate-containing mixed liquor from the first anoxic tank 32 to the anaerobic tank 31. Through the cascade utilization of carbon sources and simultaneous nitrogen and phosphorus removal regulation, total nitrogen and total phosphorus are removed. Wastewater from the first anoxic tank 32 enters the first aerobic tank 33 through a flow hole near the second aerobic tank 35. The blower room 57 continuously supplies compressed air to the disc aerators 36 at the bottom of the first aerobic tank 33 to maintain the dissolved oxygen concentration (DO) of the first aerobic tank 33 at 2.0-3.0. (mg / L) allows nitrifying bacteria to oxidize ammonia nitrogen into nitrate nitrogen and degrade organic matter. The adsorption of organic matter and the absorption of phosphorus are also factors. Wastewater from the first aerobic tank 33 enters the second anoxic tank 34 through a flow hole near the anaerobic tank 31. To further promote denitrification and achieve nitrogen removal, the length of the second anoxic tank 34 is increased, and a carbon source is added. Precise carbon source addition and internal nitrate recirculation further compensate for the limitations of nitrogen removal in a single anoxic section, thus ensuring efficient nitrogen removal. The second anoxic tank... Wastewater from tank 34 enters the second aerobic tank 35 through the flow holes in the side wall. Under the action of the pusher mixer 37, it is fully mixed with activated sludge. At the same time, the aerator provides sufficient oxygen (the air-to-water ratio is controlled at 5:1 to 8:1) to promote the efficient adsorption and degradation of organic matter by microorganisms and the absorption of phosphorus by polyphosphate-accumulating bacteria. The treated mixed liquor is returned to the first anoxic tank 32 through the second return pump 351 to replenish the microbial community in the first anoxic tank 32 and to provide the necessary electron acceptors for the denitrification process.

[0034] In this embodiment, there are two MBR membrane tanks 41, which are symmetrically arranged along both sides of the second aerobic tank 35. The MBR membrane tank sludge pump 411 and the water production pump 412 are both arranged in the middle corridor of the MBR membrane tank 41. The MBR membrane tank sludge pump 411 is used to divert and transport the sludge, with a part of it being transported to the sludge treatment section 5 for concentration and drying treatment, and the other part being refluxed at a reflux ratio of 200% to the first aerobic tank 33 to supplement the biomass. The water production pump 412 is used to lift the effluent of the MBR membrane tank 41 to the subsequent treatment unit for treatment.

[0035] Specifically, the sewage enters the water distribution channel 413 of the MBR membrane tank 41 through the flow-through holes in the middle corridor of the second aerobic tank 35. In the water distribution channel 413, PAC is continuously added to form flocs from the colloidal particles and dissolved phosphorus in the sewage, creating favorable conditions for subsequent membrane separation. Subsequently, the sewage enters the reaction zone of the MBR membrane tank 41. The high-concentration activated sludge efficiently degrades organic matter (C), removes nitrogen (N), and absorbs phosphorus (P) through microbial metabolism. At the same time, the hollow fiber membrane module (pore size 0.02 - 0.04 μm) precisely filters the mixed liquid. On the one hand, it significantly increases the biological concentration and population quantity in the bioreactor, improving the biological degradation efficiency. On the other hand, it greatly reduces the effluent SS and TP concentrations. The treated clear water is transported to the subsequent disinfection unit through the water production pump. To maintain the stable operation of the system, a part of the sludge in the MBR membrane tank 41 is refluxed to the first aerobic tank 33 through the sludge pump 411 to supplement the biomass, and the other part is combined with the sludge from the primary sedimentation tank 22 and the multi-stage AAO tank and enters the sludge treatment section 5, where PAM and PAC are successively added in the sludge thickening room for conditioning and modification.

[0036] In this embodiment, the sludge treatment section 5 further includes a sludge power distribution room 55, a chemical dosing room 56, and a blower room 57 that are配套 with sludge dewatering.

[0037] Specifically, after concentration and drying, it is transported to the sludge storage bin 54 by an inclined scraper conveyor 53 for storage, and finally transported to an external center for final disposal. The entire treatment process ensures the stable operation of the equipment through the sludge power distribution room 55, ultimately achieving the coordinated optimization of sewage达标 treatment and sludge reduction disposal.

[0038] In summary, through the deep coupling design of multi-stage AAO and MBR, the comprehensive efficiency of sewage treatment is significantly improved. The system adopts a multi-stage anaerobic - anoxic - aerobic segmented structure. Through the symmetric layout of the biochemical tanks and precise dissolved oxygen control, the function of denitrifying phosphorus-removing bacteria groups is strengthened, achieving the cascade utilization of carbon sources and the efficient and coordinated removal of nitrogen and phosphorus. The total nitrogen, total phosphorus, and suspended solids in the effluent stably reach the first-class A standard of the "Discharge Standard of Pollutants for Municipal Sewage Treatment Plants".

[0039] The bidirectional synergistic mechanism between the MBR membrane tank and the biochemical unit significantly improves the sludge concentration gradient and resistance to shock loads, effectively alleviates the risk of membrane clogging, extends the operating cycle of the membrane module, and greatly reduces the overall energy consumption of the system.

[0040] By employing a compact, series-connected multi-stage AAO and MBR layout, the system achieves efficient integration of treatment units while reducing floor space, making it particularly suitable for new or renovated wastewater treatment plants with limited land availability. The sludge treatment unit utilizes low-temperature vacuum drying technology, combined with a coordinated design of the inclined scraper conveyor and sludge silo, significantly improving dewatering efficiency and reducing sludge moisture content to below 40%. Furthermore, the system enhances the dynamic balance of nitrogen and phosphorus removal through staged reflux control (e.g., 300% reflux ratio in the anoxic zone, 60% in the aerobic zone, and 200% in the MBR tank) and the synergistic effect of the flow mixer, ensuring stable operation under fluctuating water quality. Overall operating costs are reduced by 15%-20% compared to traditional processes.

[0041] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present utility model without departing from the technical solution of the present utility model shall still fall within the protection scope of the technical solution of the present utility model.

Claims

1. A multi-stage AAO-MBR combined sewage treatment device, characterized in that, The utility model relates to a sewage treatment system, including: a pretreatment section (1) comprising a coarse grid (11), a lifting pump house (12), a fine grid (13) and an aerated grit chamber (14) connected by pipelines in sequence; a primary treatment section (2) comprising a membrane grid (21) and a primary sedimentation tank (22); a secondary treatment section (3) comprising a multi-section AAO biochemical tank comprising an anaerobic tank (31), a first anoxic tank (32), a first aerobic tank (33), a second anoxic tank (34) and a second aerobic tank (35); a deep treatment section (4) comprising an MBR membrane tank (41) and an equipment room (42); a sludge treatment section (5) comprising a sludge thickener (51), a low-temperature vacuum dryer (52), an inclined scraper conveyor (53) and a sludge bin (54). 2.The multi-section AAO-MBR combined sewage treatment device according to claim 1, characterized in that: The water inlet end of the membrane grid (21) is connected to the water outlet end of the aerated grit chamber (14), and the water outlet end of the membrane grid (21) is connected to the water inlet end of the primary sedimentation tank (22). 3.The multi-stage AAO-MBR combined sewage treatment device according to claim 2, characterized in that: The anaerobic tank (31) is arranged near one side of the primary sedimentation tank (22), the first anoxic tank (32) is arranged in the middle corridor of the multi-section AAO, the first aerobic tank (33) is provided with two, the two first aerobic tanks (33) are symmetrically arranged and respectively arranged on both sides of the first anoxic tank (32), the second anoxic tank (34) is provided with two, the two second anoxic tanks (34) are symmetrically arranged and respectively arranged on both sides of the first aerobic tank (33), the second aerobic tank (35) is provided with two, the two second aerobic tanks (35) are symmetrically arranged and respectively arranged near the position of the second anoxic tank (34) after the second half, and the first anoxic tank (32) is communicated with the first aerobic tank (33) near one end of the second aerobic tank (35), and the first aerobic tank (33) is communicated with the second anoxic tank (34) near one end of the anaerobic tank. The water outlet of the anaerobic tank (31) enters the first anoxic tank (32) through the flow hole in the middle corridor, the sewage of the first anoxic tank (32) enters the first aerobic tank (33) through the flow hole near the second aerobic tank (35), the sewage of the first aerobic tank (33) enters the second anoxic tank (34) through the flow hole near the anaerobic tank (31), and the sewage of the second anoxic tank (34) enters the second aerobic tank (35) through the flow hole in the side wall.

4. The multi-stage AAO-MBR combined sewage treatment device according to claim 3, characterized in that: The first aerobic tank (33) and the second aerobic tank (35) are provided with disc aerators (36) along the water flow direction, the bottoms of the first anoxic tank (32), the second anoxic tank (34), the first aerobic tank (33) and the second aerobic tank (35) are provided with push-flow mixers (37), and the first anoxic tank (32) and the second anoxic tank (34) are provided with carbon source dosing devices (38) with adjustable opening.

5. The multi-stage AAO-MBR combined sewage treatment device according to claim 4, characterized in that: The first anoxic tank (32) is provided with a first reflux pump (321) for refluxing the digestion liquid to the anaerobic tank (31); the second aerobic tank (35) is provided with a second reflux pump (351) for refluxing the sludge to the first anoxic tank (32); the effluent of the second aerobic tank (35) enters the MBR membrane tank (41) through an upper effluent channel.

6. The multi-stage AAO-MBR combined sewage treatment device according to claim 5, characterized in that: The MBR membrane tank (41) is provided with two MBR membrane tanks (41) which are symmetrically arranged along two sides of the second aerobic tank (35), and an MBR membrane tank sludge pump (411), a water production pump (412) and a water distribution channel (413) are arranged on the middle corridor of the MBR membrane tank (41), and the sewage enters the water distribution channel (413) of the MBR membrane tank (41) through the flow hole of the middle corridor of the second aerobic tank (35).

7. The multi-stage AAO-MBR combined sewage treatment device according to claim 6, characterized in that: The MBR membrane tank sludge pump (411) is used for diverting and conveying the sludge to the sludge treatment section (5) and the first aerobic tank (33), and the water production pump (412) is used for lifting the effluent of the MBR membrane tank (41) to the subsequent treatment unit for treatment. 8.The multi-stage AAO-MBR combined sewage treatment device according to claim 1, characterized in that: The sludge treatment section (5) further comprises a sludge power distribution room (55) matched with sludge dewatering, a dosing room (56) and a blower house (57).

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