MBR sewage treatment system and control method thereof

Abstract

The present invention relates to the technical field of sewage treatment, and provides an MBR sewage treatment system and a control method thereof. It comprises an anoxic tank, an anaerobic tank and an aerobic tank connected in sequence, the aerobic tank is also connected to a plurality of membrane tanks, the plurality of membrane tanks are connected to the anoxic tank, and also comprises a membrane assembly, the membrane assembly is divided into a plurality of groups and arranged in the plurality of membrane tanks, the plurality of groups of membrane assemblies are respectively connected to a membrane assembly aeration device, and the plurality of groups of membrane assembly aeration devices are connected to an air source through a diverter valve. Through the diverter valve, all the gas volume is concentrated and supplied to a group of membrane assembly aeration devices in turn, so that the aeration volume can be relatively increased without increasing energy consumption to enhance the cleaning effect of the membrane assembly; the activated sludge can be continuously converted in aerobic, anoxic and anaerobic environments to achieve the purpose of deep denitrification and phosphorus removal.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to an MBR sewage treatment system and a control method thereof. Background Art

[0002] MBR (Membrane Bioreactor) is a sewage treatment process that combines membrane separation technology with traditional biological treatment units. During operation, the membrane material has a certain service life and needs to be replaced regularly; at the same time, in order to maintain the normal operation of conventional MBR, a continuous high-intensity aeration method is used to maintain a high cross-flow velocity on the membrane surface to delay membrane pollution. Conventional MBRs mostly use perforated tube aeration, and the effective utilization rate of aeration energy consumption for membrane surface flushing is less than 30%. Therefore, the aeration energy consumption is huge, but the utilization rate is not high; at the same time, due to the huge amount of aeration in the MBR pool, the reaction pool is strictly aerobic, and the anaerobic / anoxic and aerobic hydraulic circulation conditions required for denitrification and phosphorus removal cannot be formed, resulting in very low denitrification and phosphorus removal efficiency, close to zero.

[0003] Variable aeration is achieved by dividing the membrane components into two groups and connecting them to the air supply pipe through electric valves. During operation, one electric valve is closed in turn to concentrate all the gas volume on one group of membrane components, so that the membrane group can obtain several times the scrubbing aeration volume within a certain period of time to better delay membrane pollution, while the total aeration volume remains unchanged.

[0004] In actual operation, the low-consumption integrated MBR equipment is formed by partitioning the reaction pool through partitions, which is divided into membrane pool, anoxic pool outside the membrane pool and anaerobic pool. Under normal circumstances, under the action of aeration, the mixed sludge in the membrane pool flows out of the membrane pool due to the large aeration volume, that is, flows to the anoxic pool and anaerobic pool. The activated sludge naturally experiences anoxic and anaerobic environment, and the effect of nitrogen removal and phosphorus removal is relatively good. After adopting variable aeration, under the variable aeration state in the membrane pool, one group of membrane groups obtains several times the scrubbing aeration volume, while the aeration volume of the other group is very low or even zero. There is an imbalance in the gas volume in the membrane pool area. The mixed liquid in the high aeration zone in the upper part of the membrane pool will flow to the low aeration zone or the non-aeration zone. There is also a mixed sludge outside the membrane pool that will flow back to the membrane pool. The imbalance of flow state and the change of the flow direction of the mixed sludge are not conducive to the formation of the anoxic and anaerobic environment required for activated sludge, affecting the nitrogen removal and phosphorus removal effect, resulting in unstable removal of total nitrogen and total phosphorus in the effluent. Summary of the invention

[0005] The object of the present invention is to provide an MBR sewage treatment system to achieve deep nitrogen and phosphorus removal, reduce the aeration energy consumption of the membrane pool, improve the flushing effect of the membrane assembly, and delay membrane pollution.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: an MBR sewage treatment system, comprising an anoxic tank, an anaerobic tank and an aerobic tank connected in sequence, the aerobic tank is also connected to multiple membrane tanks, multiple membrane tanks are connected to the anoxic tank, and also comprises membrane components, the membrane components are divided into multiple groups and arranged correspondingly in the multiple membrane tanks, the multiple groups of membrane components are respectively connected to a membrane component aeration device, and the multiple groups of membrane component aeration devices are connected to an air source through a diverter valve.

[0007] Optionally, two membrane pools are provided, and the anoxic pool is provided between the two membrane pools. The bottoms of the two membrane pools are interconnected and share the same bottom wall. The bottom wall of the anoxic pool is spaced apart from the bottom walls of the two membrane pools. A gas lift device supplied with gas by the gas source is provided in the anoxic pool, and the gas lift device passes through the bottom wall of the anoxic pool and is connected to the bottoms of the two membrane pools.

[0008] Optionally, the lower part of the anoxic tank is funnel-shaped and connected to the anaerobic tank. The gas lift device includes an air supply pipe and an air lift pipe coaxially arranged inside and outside. The water inlet of the air lift pipe is trumpet-shaped with a small top and a large bottom. The water outlet of the air lift pipe is located at the upper part of the anoxic tank, and the air inlet of the air supply pipe is connected to the air source.

[0009] Optionally, aeration and gas collecting devices are also provided in the plurality of membrane pools.

[0010] Optionally, each of the plurality of membrane modules is connected to a suction pump via a water collecting main pipe.

[0011] Optionally, the air source is connected to the perforated aeration pipe in the anaerobic tank and the microporous aeration pipe in the aerobic tank via the anaerobic tank aeration main pipe and the aerobic tank aeration main pipe respectively.

[0012] Optionally, the anoxic tank and the anaerobic tank are connected to the water inlet main pipe via an anoxic tank water inlet regulating valve and an anaerobic tank water inlet regulating valve respectively.

[0013] Optionally, a filler support is provided in the anaerobic tank, and a braided filler, an elastic fiber filler, or a composite filler is suspended on the filler support.

[0014] The present invention also aims to provide a control method for an MBR sewage treatment system to achieve deep nitrogen and phosphorus removal, reduce aeration energy consumption of the membrane pool, improve the flushing effect of the membrane assembly, and delay membrane pollution.

[0015] In order to achieve the above object, the present invention adopts the following technical scheme: a control method of an MBR sewage treatment system, comprising the following steps:

[0016] A. Supply activated sludge to the anoxic tank, anaerobic tank or aerobic tank, and supply sewage to the anoxic tank or anaerobic tank;

[0017] B. When the system operates stably, the circulating flow of the activated sludge is as follows: aerobic tank - multiple membrane tanks - anoxic tank - anaerobic tank - aerobic tank;

[0018] C. The number of membrane tanks is set to n (n > 1), and the aeration volume of the membrane module aeration device in each membrane tank is set to X m 3 / h, then the total aeration volume of the gas source to the membrane tanks is nX m 3 / h. During the operation of the system, through the shunt valve, the membrane module aeration devices in m (1 ≤ m < n) membrane tanks are intermittently stopped from working, then the aeration volume of the membrane module aeration devices in the remaining n - m membrane tanks becomes nX / (n - m) m 3 / h.

[0019] There are two membrane tanks, and the anoxic tank is arranged between the two membrane tanks. The bottoms of the two membrane tanks are interconnected and share the same bottom wall;

[0020] The suction pump intermittently pumps water from the membrane tanks through the water collection main pipe. During the period when the suction pump is turned on, the normal aeration volume of the two membrane module aeration devices is X m 3 / h. During the period when the suction pump is turned off, through the shunt valve, the two membrane module aeration devices are alternately turned off, then the aeration volume of the non - turned - off membrane module aeration device is 2X m 3 / h.

[0021] Compared with the prior art, the present application has the following technical effects:

[0022] (1) Low energy consumption

[0023] By adopting variable aeration, the energy consumption is only 40 - 50% of that of the conventional MBR technology (0.8 - 0.9 kWh / m 3 ), reaching the international advanced level of the energy consumption of this technology (0.4 - 0.5 kWh / m 3 );

[0024] (2) Small floor area and excellent effluent quality

[0025] It reduces the floor area of equipment by more than 50% compared with the traditional activated sludge method, and saves 10 - 15% of the floor area compared with the conventional MBR equipment; the effluent quality stably reaches the first - level A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" GB18918 - 2002;

[0026] (3) Simple and convenient operation

[0027] The development of membrane pollution slows down, the frequency of membrane cleaning is low (once every six months for online cleaning), and the labor intensity is low. The operation is simple and convenient; the degree of automation is high, and unattended operation can be achieved;

[0028] (4) Strong adaptability

[0029] The unitized, modularized and standardized design makes it more suitable for large, medium and small sewage treatment projects, and is convenient for rapid promotion in large, medium and small towns and rural areas;

[0030] (5) Low construction cost and low operating cost

[0031] In short, the MBR sewage treatment system of this application has the characteristics of low energy consumption, high nitrogen and phosphorus removal efficiency, excellent effluent quality, small footprint, convenient operation, and strong impact load resistance. The unitized, modular, and standardized design of the membrane components makes it more suitable for various sewage treatment scales, greatly shortening the equipment production cycle and engineering cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A top view of the present invention;

[0033] Figure 2 for Figure 1 AA section view;

[0034] Figure 3 for Figure 1 BB cross-section diagram;

[0035] Figure 4 for Figure 1 CC profile of ;

[0036] Figure 5 for Figure 1 DD cross-section diagram.

[0037] Reference numerals:

[0038] 1. Anoxic tank; 2. Anaerobic tank; 3. Aerobic tank; 4. Membrane tank; 5. Membrane module; 6. Membrane module aeration device; 7. Diverter valve; 8. Gas source; 9. Gas lift device; 91. Gas supply pipe; 92. Gas lift pipe; 10. Water collection main pipe; 11. Suction pump; 12. Anaerobic tank aeration main pipe; 13. Aerobic tank aeration main pipe; 14. Perforated aeration pipe; 15. Microporous aeration pipe; 16. Anoxic tank water inlet regulating valve; 17. Anaerobic tank water inlet regulating valve; 18. Water inlet main pipe; 19. Filling bracket; 20. Aeration and gas collection device. DETAILED DESCRIPTION

[0039] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0040] like Figure 1 As shown, an MBR sewage treatment system provided by the present invention includes an anoxic tank 1, an anaerobic tank 2 and an aerobic tank 3 connected in sequence, the aerobic tank 3 is also connected to a plurality of membrane tanks 4, the plurality of membrane tanks 4 are connected to the anoxic tank 1, and also includes a membrane assembly 5, the membrane assembly 5 is evenly divided into a plurality of groups and arranged correspondingly in the plurality of membrane tanks 4, the plurality of groups of membrane assemblies 5 are respectively connected to a membrane assembly aeration device 6, and the plurality of groups of membrane assembly aeration devices 6 are connected to an air source 8 through a diverter valve 7.

[0041] Compared with the prior art, the present invention sets an aerobic pool 3 and a plurality of membrane pools 4 after the anoxic pool 1 and the anaerobic pool 2. The plurality of groups of membrane module aeration devices 6 in the plurality of membrane pools 4 can realize variable aeration through the diverter valve 7, that is, all the gas volume is concentrated and supplied to a group of membrane module aeration devices 6 in turn through the diverter valve 7. In this way, the aeration volume can be relatively increased without increasing energy consumption to enhance the cleaning effect of the membrane module 5. In addition, the plurality of membrane pools 4 are separated from each other, so there will be no situation where the area with high aeration volume flows to the low aeration area or the non-aeration area, and there is no interference between the plurality of membrane pools 4. The mixed liquor in the multiple membrane pools 4 will not flow back to the aerobic pool 3. Even if it flows back, only a small part of the mixed liquor will flow back to the aerobic pool 3, among which the oxygen-rich mixed liquor is the aerobic environment required by the aerobic pool 3, and the mixed liquor will not flow back to the anaerobic pool 2 to affect its anaerobic environment. The activated sludge in the multiple membrane pools 4 is promptly transported to the anoxic pool 1, and the activated sludge forms a cycle of "aerobic pool 3-multiple membrane pools 4-anoxic pool 1-anaerobic pool 2-aerobic pool 3". The activated sludge can be continuously converted in aerobic, anoxic and anaerobic environments to achieve the purpose of deep nitrogen and phosphorus removal.

[0042] In some embodiments, two membrane pools 4 are sufficient. If too many membrane pools 4 are provided, when one of the membrane pools 4 is centrally aerated in turn, the time interval for the other membrane pools 4 to wait for central aeration will increase, which will be detrimental to the cleaning of the membrane assembly 5. The two membrane pools 4 are cleverly separated by the anoxic pool 1. There is still a connecting area at the bottom of the two membrane pools 4. This connecting area is used to allow the air lift device 9 to transport the activated sludge mixed liquid in the two membrane pools 4 to the anoxic pool 1 in one direction. When centrally aerated in turn, there may still be turbulence in the connecting area, but the connecting area occupies a small volume, and the air lift device 9 will also promptly transport the activated sludge mixed liquid in this area to the anoxic pool 1, so the impact of the turbulence can be ignored. In addition, the present application adopts the air lift device 9 to share the air source 8 with the membrane assembly aeration device 6, and there is no need to arrange an additional lifting pump or motor, etc., which effectively simplifies the device layout and saves costs.

[0043] In some embodiments, the lower part of the anoxic tank 1 is funnel-shaped and is connected to the anaerobic tank 2. The air stripping device 9 includes an air supply pipe 91 and an air stripping pipe 92 coaxially arranged inside and outside. The water inlet of the air stripping pipe 92 is trumpet-shaped with a small top and a large bottom. The water outlet of the air stripping pipe 92 is located at the upper part of the anoxic tank 1, and the air inlet of the air supply pipe 91 is connected to the air source 8. The high-intensity aeration of the air stripping device 9 generates a large air stripping cycle power, which causes the activated sludge mixed liquor to flow unidirectionally from the bottom of the two membrane tanks 4 to the upper part of the anoxic tank 1 through the air stripping pipe 92, and then the activated sludge mixed liquor undergoes anoxic reaction from top to bottom and then automatically flows to the anaerobic tank 2, and then returns to the membrane tank 4 through the aerobic tank 3, forming an activated sludge biological reaction cycle.

[0044] In some embodiments, a plurality of membrane pools 4 are further provided with an aeration and gas collecting device 20. The aeration and gas collecting device 20 is used to collect the waste gas generated in the membrane pool 4 and the excess gas when the membrane module aeration device 6 flushes the membrane module 5. Since the dissolved oxygen concentration in the anoxic pool 1 should not be too high, timely collecting the gas in the membrane pool 4 is beneficial to reducing the dissolved oxygen concentration of the activated sludge mixed liquor flowing to the anoxic pool 1.

[0045] In some embodiments, each of the plurality of membrane modules 5 is connected to a suction pump 11 via a water collecting main pipe 10, and the suction pump 11 is operated to collect purified water.

[0046] In some embodiments, the gas source 8 is connected to the perforated aeration pipe 14 in the anaerobic tank 2 and the microporous aeration pipe 15 in the aerobic tank 3 through the anaerobic tank aeration main pipe 12 and the aerobic tank aeration main pipe 13. The anaerobic tank 2 is aerated intermittently through the perforated aeration pipe 14 to ensure that the sludge in the anaerobic tank 2 can be evenly mixed and flowed, which is conducive to the occurrence of anaerobic reaction. The aerobic tank 3 is aerated through the microporous aeration pipe 15 to ensure the dissolved oxygen concentration of the aerobic tank 3, which is conducive to the occurrence of aerobic reaction.

[0047] In some embodiments, the anoxic tank 1 and the anaerobic tank 2 are connected to the water inlet main 18 via the anoxic tank inlet regulating valve 16 and the anaerobic tank inlet regulating valve 17 respectively, and the water volume is regulated by the anoxic tank inlet regulating valve 16 and the anaerobic tank inlet regulating valve 17.

[0048] In some embodiments, a filler support 19 is provided in the anaerobic tank 2, and a braided filler, an elastic fiber filler, or a composite filler is hung on the filler support 19. In actual application, fillers can be arranged in the anaerobic tank 2 or the anoxic tank 1 to facilitate the aggregation and growth of microorganisms and improve the nitrogen removal and phosphorus removal effect.

[0049] A control method for an MBR sewage treatment system comprises the following steps:

[0050] A. Supply activated sludge to the anoxic tank 1, anaerobic tank 2 or aerobic tank 3, and supply sewage to the anoxic tank 1 or anaerobic tank 2;

[0051] B. When the system operates stably, the circulating flow of the activated sludge is as follows: aerobic tank 3 - multiple membrane tanks 4 - anoxic tank 1 - anaerobic tank 2 - aerobic tank 3;

[0052] C. The number of membrane tanks 4 is set to n (n > 1), and the aeration volume of the membrane module aeration device 6 in each membrane tank 4 is set to X m 3 / h, then the total aeration volume of the gas source 8 for the membrane tanks 4 is nX m 3 / h. During the operation of the system, through the shunt valve 7, the membrane module aeration devices 6 in m (1 ≤ m < n) membrane tanks 4 are intermittently stopped from working, then the aeration volume of the membrane module aeration devices 6 in the remaining n - m membrane tanks 4 becomes nX / (n - m) m 3 / h.

[0053] Compared with the prior art, by adopting the above variable aeration method, without increasing energy consumption, the aeration volume of the membrane module aeration device 6 can be intermittently increased, thereby strengthening the flushing effect of the membrane module 5, further delaying membrane fouling, and correspondingly reducing the cost of cleaning or replacing the membrane; the activated sludge in multiple membrane tanks 4 is timely transported into the anoxic tank 1, and the activated sludge forms a cycle of "aerobic tank 3 - multiple membrane tanks 4 - anoxic tank 1 - anaerobic tank 2 - aerobic tank 3", and the activated sludge can continuously convert in aerobic, anaerobic, and anoxic environments to achieve the purpose of deep nitrogen and phosphorus removal.

[0054] The suction pump 11 intermittently pumps water from the membrane tank 4 through the water collection main pipe 10. During the period when the suction pump 11 is turned on, the normal aeration volume of the two membrane module aeration devices 6 is X m 3 / h. During the period when the suction pump 11 is turned off, through the shunt valve 7, the two membrane module aeration devices 6 are alternately turned off, then the aeration volume of the non - turned - off membrane module aeration device 6 is 2X m 3 / h. By adopting this adjustment method, while ensuring the normal aeration volume, the轮流集中曝气 can strengthen the aeration flushing effect on the membrane module 5, and the aeration volume is twice the normal aeration volume, thereby preventing dirt from adhering to the membrane module 5 during the period when the suction pump 11 is turned off.

[0055] The aeration volume of the two membrane module aeration devices 6 is X / 2 m 3 / h, this aeration volume is half of the normal one, and the corresponding energy consumption will also be reduced by half. During the period when the suction pump 11 is turned off, through the shunt valve 7, the two membrane module aeration devices 6 are alternately turned off, then the aeration volume of the non - turned - off membrane module aeration device 6 is X m 3 / h. By adopting this adjustment method, while reducing the normal power consumption, the normal aeration volume of X m 3 / h can be achieved through the way of轮流集中曝气.

[0056] The following are the specific embodiments of the present invention:

[0057] It should be noted that the term "轮流集中曝气" in the translation is a literal translation of the Chinese phrase which may not be a commonly used technical term in English. It might need to be adjusted to a more appropriate expression according to the specific technical context, such as "alternate concentrated aeration".The gas supply from the gas source 8 is divided into four routes, one of which is connected to the two sets of membrane module aeration devices 6 via the diverter valve 7; another is connected to the perforated aeration pipe 14 via the anaerobic tank aeration main pipe 12; the third is connected to the microporous aeration pipe 15 via the aerobic tank aeration main pipe 13; and the fourth is connected to the gas supply pipe 91 via the regulating valve.

[0058] MBR sewage treatment system commissioning: fill the tank with water to ensure that the tank is leak-proof. After the tank is in good condition, inject clean water into the connecting pipe of the suction pump 11, and conduct a single-machine test run of the air source 8 and the suction pump 11 to ensure that the pipeline and the connection between the pipeline and the equipment are leak-proof. Check whether the four-way air supply of the air source 8 is uniform and normal, otherwise, repair until the aeration system is qualified. Start the suction pump 11 and start the regulating valve to make the pumping flow equal to the set value.

[0059] Operation of MBR sewage treatment system: Add activated sludge into the reaction tank and start sewage debugging. First, set the control state to automatic operation, and the water output of the suction pump 11 can be debugged and operated at a small flux of 1 / 4-1 / 2 of the full load; adjust the anoxic tank inlet regulating valve 16 and the anaerobic tank inlet regulating valve 17 on the water inlet main 18 so that the water inlet distribution of the anoxic tank 1 and the anaerobic tank 2 meets the design requirements; at the same time, adjust the air supply of each line to ensure that the DO of the anoxic tank 1 is below 0.3mg / L, and the DO of the anaerobic tank 2 is below 0.1mg / L, ensuring that the anoxic tank 1 and the anaerobic tank 2 are in anoxic and anaerobic environments respectively; start the automatic program, the suction pump 11 runs intermittently, and the intermittent operation and stop time are set to 4-13min:1.5-2min;

[0060] The membrane module aeration devices 6 in the two membrane pools 2 perform the full closing and full opening actions in turn once during a single shutdown period of the suction pump 11; or one of the membrane module aeration devices 6 performs concentrated aeration work during the first shutdown period of the suction pump 11, and the other membrane module aeration device 6 performs concentrated aeration work during the second shutdown period of the suction pump 11, and so on, the two membrane module aeration devices 6 perform the full closing and full opening actions in turn once during the two shutdown periods.

[0061] The reaction tank is set with three liquid levels: high, medium and low. When the liquid level is medium, the lifting pump of the regulating tank is turned on to replenish water to the reaction tank through the water inlet main 18. When the liquid level reaches the high level, the lifting pump is stopped to replenish water; when the liquid level is low, the system stops running and alarms. When the sludge concentration rises to 6g / L, it can be increased to full load operation; when the sludge concentration exceeds 9-12g / L, sludge can be discharged periodically, and the amount of sludge discharged is based on the set sludge age.

[0062] Cleaning of membrane assembly 5: The cleaning method of dismantling the membrane is as follows: 0.3% sodium hypochlorite solution is prepared in the chemical cleaning tank, the membrane is taken out and rinsed with clean water, and then immersed in the chemical cleaning tank for about 24 hours to complete the in vitro immersion chemical cleaning of the membrane.

[0063] Since the in vitro immersion cleaning operation can be carried out in batches, each batch can be limited to one group of membrane components, which will not affect the operation of other membrane components of the equipment and can meet the continuous operation requirements of the project.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An MBR sewage treatment system, characterized in that: The invention comprises an anoxic tank (1), an anaerobic tank (2) and an aerobic tank (3) which are connected in sequence, wherein the aerobic tank (3) is further connected to a plurality of membrane tanks (4), wherein the plurality of membrane tanks (4) are connected to the anoxic tank (1), and further comprises a membrane assembly (5), wherein the membrane assembly (5) is divided into a plurality of groups and arranged in the plurality of membrane tanks (4), wherein the plurality of groups of membrane assemblies (5) are respectively connected to a membrane assembly aeration device (6), and the plurality of groups of membrane assembly aeration devices (6) are connected to an air source (8) via a diverter valve (7); Two membrane pools (4) are provided, the anoxic pool (1) is provided between the two membrane pools (4), the bottoms of the two membrane pools (4) are interconnected and share a common bottom wall, the bottom wall of the anoxic pool (1) is spaced apart from the bottom walls of the two membrane pools (4), a gas stripping device (9) supplied with gas by the gas source (8) is provided in the anoxic pool (1), and the gas stripping device (9) passes through the bottom wall of the anoxic pool (1) and is connected to the bottoms of the two membrane pools (4); The lower part of the anoxic tank (1) is funnel-shaped and is connected to the anaerobic tank (2). The gas stripping device (9) comprises an air supply pipe (91) and an air stripping pipe (92) which are coaxially arranged inside and outside. The water inlet of the air stripping pipe (92) is trumpet-shaped with a small top and a large bottom. The water outlet of the air stripping pipe (92) is located at the upper part of the anoxic tank (1). The air inlet of the air supply pipe (91) is connected to the air source (8). The suction pump (11) intermittently pumps water from the membrane pool (4) through the water collecting main pipe (10). During the period when the suction pump (11) is turned on, the conventional aeration volume of the two membrane module aeration devices (6) is Xm 3 / h, during the period when the suction pump (11) is closed, the two membrane module aeration devices (6) are alternately closed through the diverter valve (7), and the aeration volume of the membrane module aeration device (6) that is not closed is 2Xm 3 / h; The gas source (8) is connected to the perforated aeration pipe (14) in the anaerobic tank (2) and the microporous aeration pipe (15) in the aerobic tank (3) via the anaerobic tank aeration main pipe (12) and the aerobic tank aeration main pipe (13) respectively.

2. The MBR sewage treatment system according to claim 1, characterized in that: An aeration and gas collecting device (20) is also provided in the plurality of membrane pools (4).

3. The MBR sewage treatment system according to claim 1, characterized in that: The plurality of groups of membrane modules (5) are connected to a suction pump (11) via a water collecting main pipe (10).

4. The MBR sewage treatment system according to claim 1, characterized in that: The anoxic tank (1) and the anaerobic tank (2) are connected to the water inlet main pipe (18) via the anoxic tank water inlet regulating valve (16) and the anaerobic tank water inlet regulating valve (17) respectively.

5. The MBR sewage treatment system according to claim 1, characterized in that: A filler support (19) is provided in the anaerobic tank (2), and braided fillers, elastic fiber fillers, or composite fillers are suspended on the filler support (19).

6. A control method for an MBR sewage treatment system according to any one of claims 1 to 5, characterized in that: The steps include: A. Supplying activated sludge to the anoxic tank (1), anaerobic tank (2) or aerobic tank (3), and supplying sewage to the anoxic tank (1) or anaerobic tank (2); B. When the system operates stably, the circulation flow of activated sludge is as follows: aerobic tank (3) - multiple membrane tanks (4) - anoxic tank (1) - anaerobic tank (2) - aerobic tank (3); C. The number of membrane pools (4) is set to 2, and the aeration volume of the membrane module aeration device (6) of each membrane pool (4) is set to Xm 3 / h, the total aeration volume of the air source (8) to the membrane pool (4) is 2Xm 3 / h. During the operation of the system, the membrane module aeration device (6) of one membrane tank (4) is intermittently stopped by the diverter valve (7), and the aeration volume of the membrane module aeration device (6) of the remaining membrane tank (4) becomes 2Xm 3 / h.

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