Water treatment system and method based on split anaerobic membrane bioreactor

Abstract

A water treatment system and method based on a split anaerobic membrane bioreactor, the water treatment system includes an anaerobic reactor for anaerobic fermentation and biogas production; a membrane tank, which is provided with a membrane assembly for discharging treated wastewater; and a gas circulation device for forming a biogas cycle in the anaerobic reactor and the membrane tank. The present invention can adapt to high-concentration organic wastewater, can achieve the advantages of stable process operation system, and short-term compliance of effluent water quality; the membrane separation technology is used to intercept large molecular weight pollutants in the sludge mixed liquid, increase the sludge concentration in the reactor, and stabilize the effluent water quality; the treatment device has a high degree of mixing and strong impact load resistance, especially for organic wastewater that is easily acidified.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment and new energy, and in particular relates to a water treatment system and method based on a split anaerobic membrane bioreactor. Background Art

[0002] With the promotion of garbage classification, the discharge of high-concentration organic wastewater, represented by kitchen waste and its fresh leachate, is at a high level. Anaerobic treatment can simultaneously recover energy and water resources, so it is necessary to develop on-site equipment. Taking kitchen waste leachate as an example, it is rich in carbohydrates and proteins, and the chemical oxygen demand (COD) can be as high as 40-50g·L -1 The solid content TS can reach 3-5%, and the total phosphorus and total nitrogen are 70-90 mg·L -1 and 1500-2000 mg·L -1 , with good biodegradability and suitable for anaerobic treatment.

[0003] Kitchen waste leachate wastewater is prone to hydrolysis and acidification. If the volatile fatty acids (VFAs) produced during operation cannot be quickly removed by methanogenication, they can easily inhibit anaerobic microorganisms to a certain extent, leading to the acidification and collapse of the reactor. At the same time, kitchen waste leachate wastewater is prone to cause sludge floating and loss during the anaerobic process. For example, its hydrolysis product, long-chain fatty acids (LCFAs), have anaerobic inhibition and hydrophobicity, which may cause sludge floating and loss. Therefore, the traditional anaerobic process for treating kitchen waste leachate has the disadvantages of limited COD removal rate and sludge loss.

[0004] The use of a split anaerobic reactor coupled with a membrane separation to form an external anaerobic membrane bioreactor can effectively enhance solid-liquid separation and reduce sludge loss; at the same time, it is conducive to maintaining a high volume load and reducing the risk of system acidification. AnMBR (anaerobic membrane bioreactor) is a new wastewater treatment process that combines anaerobic biological treatment units and membrane separation technology. It not only retains some of the advantages of anaerobic technology, but also the introduction of membrane components can completely intercept microorganisms, thereby achieving the decoupling of SRT (sludge retention time) and HRT (hydraulic retention time). Therefore, the anaerobic membrane bioreactor has the advantages of high pollutant removal rate and stable treatment effect. It shows a good application prospect in the treatment of high-concentration and complex organic wastewater. Due to the complete interception of suspended solids by the membrane and its high treatment efficiency, AnMBR can obtain good effluent water quality. Summary of the invention

[0005] In view of this, one of the main objectives of the present invention is to provide a water treatment system and method based on a split anaerobic membrane bioreactor, in order to at least partially solve at least one of the above technical problems.

[0006] In order to achieve the above object, as one aspect of the present invention, a water treatment system based on a split anaerobic membrane bioreactor is provided, comprising:

[0007] Anaerobic reactor, used for anaerobic fermentation and biogas production;

[0008] a membrane tank, in which a membrane module is arranged for discharging treated wastewater; and

[0009] The gas circulation device is used to form biogas circulation in the anaerobic reactor and the membrane tank.

[0010] As another aspect of the present invention, a water treatment method is also provided, using the water treatment system as described above, comprising:

[0011] Inoculating anaerobic sludge in an anaerobic reactor;

[0012] Introducing the wastewater to be treated into an anaerobic reactor for reaction;

[0013] The biogas generated in the anaerobic reactor is circulated between the membrane tank and the anaerobic reactor through a gas circulation device and excess gas is collected;

[0014] The water treatment is completed by circulating the liquid produced in the anaerobic reactor between the membrane tank and the anaerobic reactor and collecting the treated water.

[0015] Based on the above technical solution, it can be seen that the water treatment system and method based on the split anaerobic membrane bioreactor of the present invention has at least one of the following advantages over the prior art:

[0016] 1. This treatment device can adapt to high-concentration organic wastewater, can achieve the advantages of stable process operation system and short-term compliance of effluent water quality;

[0017] 2. The membrane separation technology is used to intercept the large molecular weight pollutants in the sludge mixture, increase the sludge concentration in the reactor, and stabilize the effluent quality;

[0018] 3. This treatment device has high mixing degree and strong impact load resistance, especially good adaptability to easily acidified organic wastewater;

[0019] 4. This treatment device adopts partial heating, and forms a certain temperature gradient through gas-liquid upflow circulation, which saves energy, and can create different temperature environments in different areas, so that different types of microorganisms can reach higher activity in different areas; the gas production effect is good and the treatment efficiency is high;

[0020] 5. By counting the gas flow meter, the reactor load can be flexibly adjusted according to the gas production rate and the effluent COD concentration can be controlled, which is flexible in operation;

[0021] 6. Control membrane pollution through biogas aeration cycle, strengthen carbon dioxide mass transfer, increase the inorganic carbon TIC content of sludge mixed liquid, and have a better buffering effect on acidic organic wastewater;

[0022] 7. The high-concentration organic wastewater treatment device of the present invention has a compact structure, reduces the floor space of the wastewater treatment device, is easy to operate and maintain, is easy to realize automatic control, and is suitable for popularization and use;

[0023] 8. The present invention can be applied to high-concentration organic wastewater, such as agricultural and sideline food processing wastewater, fermentation and brewing wastewater, alcohol wastewater and livestock and poultry wastewater, to achieve treatment and discharge that meets the takeover standard in one step;

[0024] 9. The present invention has low cycle energy consumption, high volumetric load and stable effluent quality;

[0025] 10. The present invention can improve the COD removal rate of the anaerobic process, achieve the purpose of meeting the standards in a short process, and enable agricultural and sideline food processing wastewater, fermentation wastewater and kitchen wastewater to meet the takeover standards in one step. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the split anaerobic membrane bioreactor of the present invention;

[0027] Figure 2 It is a schematic diagram of the organic wastewater treatment process of the present invention.

[0028] Description of symbols in the accompanying drawings:

[0029] 100-first reaction chamber; 101-first three-phase separator; 102-water inlet container; 103-water inlet pump; 104-temperature control device; 200-second reaction chamber; 201-second three-phase separator; 202-overflow weir; 203-overflow weir outlet; 204-second reaction chamber reflux port; 205-gas collecting hood; 206-biogas outlet; 300-membrane pool; 301-membrane pool water inlet; 302-membrane pool water outlet; 303-flat membrane; 304-flat membrane outlet; 305-aeration port; 306-membrane pool outlet; 307-water outlet container; 308-water outlet pump; 309-pressure gauge; 310-liquid circulation pump; 400-gas circulation pump; 401-gas buffer bottle; 402-safety bottle; 403-gas flow meter. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0031] The purpose of the present invention is to provide a treatment device for high-concentration organic wastewater to achieve the advantages of effective stability of the entire treatment device, low treatment cost, and stable effluent quality, while realizing resource utilization of high-concentration organic matter in the wastewater.

[0032] The invention discloses a water treatment system, comprising:

[0033] Anaerobic reactor, used for anaerobic fermentation and biogas production;

[0034] a membrane tank, in which a membrane module is disposed, for discharging treated wastewater; and

[0035] The gas circulation device is used to form biogas circulation in the anaerobic reactor and the membrane tank.

[0036] In some embodiments of the present invention, the gas circulation device comprises:

[0037] A gas collection unit, used for separating and collecting biogas produced by the anaerobic reactor;

[0038] A gas circulation unit, used to introduce the biogas in the gas collection unit into the membrane tank for aeration; and

[0039] The gas reflux unit is used to return the biogas in the membrane pool to the gas collection unit.

[0040] In some embodiments of the present invention, the gas collection unit includes a gas collection hood;

[0041] In some embodiments of the present invention, the gas circulation unit comprises a gas circulation pump and a membrane pool aeration port arranged on the membrane pool;

[0042] In some embodiments of the present invention, a gas buffer bottle is provided between the gas circulation pump and the gas collection unit;

[0043] In some embodiments of the present invention, the gas reflux unit comprises a membrane pool exhaust port, and the membrane pool exhaust port is connected to a gas collecting hood.

[0044] In some embodiments of the present invention, the membrane pool is provided with a membrane pool water inlet for introducing the liquid in the anaerobic reactor into the membrane pool;

[0045] In some embodiments of the present invention, the membrane pool is provided with a membrane pool outlet for returning the liquid in the membrane pool to the anaerobic reactor.

[0046] In some embodiments of the present invention, the membrane module comprises a flat sheet membrane;

[0047] In some embodiments of the present invention, the flat membrane is provided with a flat membrane water outlet for outputting separated water.

[0048] In some embodiments of the present invention, a first reaction chamber and a second reaction chamber are provided in the anaerobic reactor.

[0049] In some embodiments of the present invention, a first three-phase separator is disposed in the first reaction chamber;

[0050] In some embodiments of the present invention, a second three-phase separator is disposed in the second reaction chamber.

[0051] In some embodiments of the present invention, the first three-phase separator is a double-layer inverted triangle structure;

[0052] In some embodiments of the present invention, the second three-phase separator is a single-layer inverted cone structure; in some embodiments of the present invention, a throat-shaped hoop is provided at the lower part of the cone;

[0053] In some embodiments of the present invention, the exhaust pipe of the first three-phase separator extends into the interior of the inverted cone;

[0054] In some embodiments of the present invention, an overflow weir and an overflow weir outlet are provided on the second reaction chamber, and the liquid in the second reaction chamber flows into the membrane pool through the overflow weir outlet.

[0055] In some embodiments of the present invention, the anaerobic reactor further comprises an external circulation unit for returning the liquid in the membrane tank to the first reaction chamber;

[0056] In some embodiments of the present invention, the external circulation unit includes an external circulation pipeline;

[0057] In some embodiments of the present invention, the anaerobic reactor is cylindrical, and the height-to-diameter ratio of the anaerobic reactor is 8-20.

[0058] In some embodiments of the present invention, the water treatment system further comprises a temperature control device for regulating the anaerobic reactor;

[0059] In some embodiments of the present invention, the water treatment system further comprises a water inlet device, and the water inlet device is connected to the anaerobic reactor;

[0060] In some embodiments of the present invention, the water treatment system further comprises a drainage device, wherein the drainage device is connected to the membrane pool;

[0061] In some embodiments of the present invention, the drainage device includes a water outlet container and a water outlet pump;

[0062] In some embodiments of the present invention, the water treatment system further comprises an exhaust device, wherein the exhaust device is connected to the gas circulation device;

[0063] In some embodiments of the present invention, the exhaust device includes a safety bottle and a gas flow meter.

[0064] The present invention also discloses a water treatment method, which uses the water treatment system as described above, comprising:

[0065] Inoculating anaerobic sludge in an anaerobic reactor;

[0066] Introducing the wastewater to be treated into an anaerobic reactor for reaction;

[0067] The biogas generated in the anaerobic reactor is circulated between the membrane tank and the anaerobic reactor through a gas circulation device and excess gas is collected;

[0068] The water treatment is completed by circulating the liquid produced in the anaerobic reactor between the membrane tank and the anaerobic reactor and collecting the treated water.

[0069] In an exemplary embodiment, the split anaerobic membrane bioreactor treatment system of the present invention includes an anaerobic reactor, an external membrane tank 300 , a forced circulation system and a temperature control device 104 .

[0070] The anaerobic reactor is an internal circulation split anaerobic reactor, including a first reaction chamber 100 and a second reaction chamber 200. The anaerobic reactor is connected to the membrane pool 300 through a gas circulation device and a liquid circulation device.

[0071] The bottom of the first reaction chamber 100 is a water inlet pipe connected to the water inlet container 102, and the upper part of the first reaction chamber 100 is provided with a first three-phase separator 101;

[0072] The first three-phase separator 101 is disposed at the lower part of the second reaction chamber 200, the upper part of the second reaction chamber 200 is provided with a second three-phase separator 201, and the bottom of the second reaction chamber is provided with a reflux port 204;

[0073] The first three-phase separator 101 is connected to the gas-water separation pipe through the gas collecting tank, and the second three-phase separator is connected to the top gas-water separator through the gas-water collecting pipe;

[0074] An overflow weir 202 and an overflow weir outlet 203 are provided on the upper part of the second reaction chamber 200, a gas collecting hood 205 is provided on the upper part of the overflow weir 202, the overflow weir outlet 203 is connected to the membrane pool water inlet 301, and the membrane pool water outlet 302 is connected to the second reactor bottom reflux port 204. A biogas outlet 206 is provided on the top of the gas-water separator, and the biogas outlet 206 is connected to the aeration pipe 305 of the membrane assembly, i.e., the flat membrane 303, through a gas circulation pump 400. The reactor and the membrane pool 300 are aerated and flushed by the gas circulation pump 400, and part of the gas-liquid mixture is pushed to form an external circulation between the reactor and the membrane pool 300, and a controllable mixed liquid forced circulation is formed between the membrane pool water outlet 302 and the second reaction chamber reflux port 204 by a liquid circulation pump 310.

[0075] The first three-phase separator 101 is a double-layer inverted triangle structure, with a gas collecting groove on the top to collect the gas in the first reaction chamber 100 and connect it to the exhaust pipe to pass into the second three-phase separator 201 .

[0076] Among them, the second three-phase separator 201 is a single-layer inverted cone structure, and a throat-shaped hoop is provided at the lower part of the cone to achieve gas-water separation. The exhaust pipe of the first three-phase separator 101 extends into the interior of the inverted cone, so that the gases in the first reaction chamber 100 and the second reaction chamber 200 are mixed and then enter the top gas-water separator.

[0077] Among them, the membrane component is biogas circulating aeration, and the membrane component uses biogas circulating aeration to control membrane pollution.

[0078] Among them, the membrane pool outlet pipe is equipped with a regulating valve to control the flow.

[0079] Among them, the split anaerobic membrane bioreactor is cylindrical with a height-to-diameter ratio of 8~20.

[0080] The temperature control device 104 only controls the temperature of the first reaction chamber 100 of the split anaerobic reactor.

[0081] Among them, the water inlet of the split anaerobic reactor is located at the bottom of the reactor, and the mixed liquid flows out from the overflow weir at the top of the split anaerobic reactor, flows into the membrane pool 300 through the liquid circulation pump 310, and the sludge and some pollutants are intercepted by the flat membrane 303 and retained in the membrane pool to enhance biodegradation; the membrane effluent is sucked out by the effluent pump 308, and a pressure gauge 309 is provided on the membrane effluent pipeline.

[0082] Among them, after the mixed liquid in the reactor enters the membrane pool 300, a part of it passes through the membrane pool gas outlet 306 at the top of the membrane pool 300 and returns to the top of the split anaerobic reactor through the biogas push flow, and then flows into the bottom of the first reaction chamber 100 through the external circulation pipe of the split anaerobic reactor for a second reaction, forming a first reaction chamber circulation; a part of the mixed liquid flows back to the bottom of the second reaction chamber 200 of the split anaerobic reactor through the membrane pool water outlet 302 below the membrane pool gas outlet 306 to form a circulation.

[0083] Among them, the internal circulation volume of organic wastewater is distributed and controlled by adjusting the aeration volume of the biogas cycle or the flow rate of the membrane pool outlet.

[0084] Among them, the internal circulation volume of organic wastewater is supplemented by forced circulation driven by a circulation pump.

[0085] The internal circulation volume of organic wastewater is controlled by adjusting the aeration volume of biogas circulation or the reflux volume of the membrane pool outlet. The membrane components are cleaned by controlling the aeration volume of biogas circulation.

[0086] The split anaerobic reactor provided by the present invention has the following process flow for treating organic wastewater:

[0087] A) inoculating anaerobic sludge in the first reaction chamber 100 and the second reaction chamber 200;

[0088] B) The organic wastewater is transported to the first reaction chamber 100 through the water inlet pipe, passes through the first three-phase separator 101, the second reaction chamber 200, the second three-phase separator 201 and the top gas-water separator in sequence, enters the membrane pool 300, and then flows back to the top of the reactor and the bottom of the second reaction chamber 200 from the membrane pool water outlet 302 and the membrane pool gas outlet 306 respectively to form an internal circulation. During the circulation process, the mixed liquid is separated through the flat membrane 303 to obtain output water;

[0089] C) The biogas generated in the first reaction chamber 100 and the second reaction chamber 200 is respectively enriched by the first three-phase separator 101 and the second three-phase separator 201, and enters the safety bottle 402 after passing through the top gas-water separator. The generated biogas is measured and counted by the gas flow meter 403;

[0090] D) After separation by the top gas-water separator, part of the biogas produced is supplied to the flat membrane 303 assembly under pressure, and then flows back to the top of the reactor through the membrane pool outlet 306, forming biogas circulation aeration.

[0091] The technical solution of the present invention is further described below by means of specific embodiments in combination with the accompanying drawings. It should be noted that the following specific embodiments are only used as examples, and the protection scope of the present invention is not limited thereto.

[0092] Reference Figure 1-2 A high-load anaerobic membrane bioreactor for high-concentration organic wastewater treatment includes an internal circulation anaerobic reactor, wherein a first reaction chamber 100 is provided at the bottom of the internal circulation anaerobic reactor, a second reaction chamber 200 is provided at the bottom, a first three-phase separator 101 is installed in the first reaction chamber 100, a second three-phase separator 201 is installed in the second reaction chamber 200, and an air pipe of the first three-phase separator 101 penetrates into the cone of the second three-phase separator 201, and is mixed with the gas of the second reaction chamber 200 and discharged from the top. A throat-shaped hoop is provided under the cone of the second three-phase separator for gas-liquid separation.

[0093] The mixed liquid flows out through the overflow weir 202 at the top of the second reaction chamber 200, and enters the bottom of the membrane pool 300 through the liquid circulation pump 310. The membrane pool 300 is a rectangular parallelepiped structure with a built-in flat membrane 303. The flat membranes 303 are spaced 5 mm apart, and a perforated aeration tube 305 is set at the bottom. A part of the mixed liquid flows into the top of the second reaction chamber 200 from the membrane pool gas outlet 306 at the top of the membrane pool 300, and then returns to the bottom of the first reaction chamber 100 through the external circulation pipeline. A part of the mixed liquid enters the bottom of the second reaction chamber 200 from the membrane pool water outlet 302, and forms a cycle in the second reaction chamber 200. By adjusting the opening of the two parts of the reflux pipeline, the amount of water entering the first reaction chamber 100 and the second reaction chamber 200 can be distributed, and then different circulation ratios can be adjusted according to different load conditions.

[0094] After the biogas is collected, it is discharged through the safety bottle 402 and then through the gas flow meter 403. When the water is discharged, the water outlet pump 308 is turned on, and the membrane water is discharged out of the reactor through negative pressure suction. The biogas enters the bottom of the membrane pool 300 through the buffer bottle 401 and the gas circulation pump 400, and is exposed from the perforated aeration port 305 to flush the flat membrane 303, and returns to the top of the reactor from the membrane pool outlet 306 for circulation.

[0095] The present invention can achieve its functions through the following operations:

[0096] Step 1: Turn on the water inlet pump 103 to let the organic wastewater enter the bottom of the first reaction chamber 100 of the reactor, and at this time, turn off the gas circulation pump 400 and the water outlet pump 308. When the water intake is completed, turn off the water inlet pump 103, turn on the liquid circulation pump 310, and the reactor mixed liquid passes through the overflow weir outlet 203 through the liquid circulation pump 301 to the membrane pool 300, and then from the membrane pool outlet 302 to the second reaction chamber 200 and the first reaction chamber 100 of the reactor, and the generated biogas is discharged through the gas flowmeter 403.

[0097] Step 2: After a certain reaction time, the gas production rate of the reactor decreases. At this time, the gas circulation pump 400 is turned on, and the water outlet pump 308 is turned on at the same time. The mixed liquid in the reactor is discharged through the flat membrane outlet 304 in an intermittent water outlet manner.

[0098] Step 3: After the water discharge is completed, turn off the gas circulation pump 400 and the water discharge pump 308. At this time, the liquid level in the reactor decreases. Turn on the water inlet pump 103 and repeat step 1.

[0099] Example

[0100] The split anaerobic membrane bioreactor of this embodiment is cylindrical with a height-to-diameter ratio of 10-12.

[0101] Anaerobic sludge is inoculated according to the different sludge concentrations of the first reaction chamber 100 and the second reaction chamber 200. The kitchen wastewater pumped from the water inlet container 102 through the water inlet pump 103 is transported to the first reaction chamber 100, and then passes through the first three-phase separator 101 of the first reaction chamber 100, the second reaction chamber 200, the second three-phase separator 201 of the second reaction chamber, and the gas-water separator in sequence, and then enters the membrane pool 300, and then flows back to the top of the reactor and the bottom of the second reaction chamber 200, respectively, to form an internal cycle. During the entire operation, the temperature of the split anaerobic membrane bioreactor is maintained at 33-37°C, and the sludge concentration in the first reaction chamber is higher than that in the second reaction chamber.

[0102] The main measure to alleviate the pollution of membrane components is biogas circulation aeration, which can also regulate the total reflux volume, thereby flexibly controlling the internal circulation volume of the first reaction chamber 100, forming a higher sludge concentration and good mixed mass transfer in the first reaction chamber 100. Through the coupling of high-load anaerobic degradation in the first reaction chamber 100 and the second reaction chamber 200 and the inner membrane interception of the membrane pool 300, the methanation rate of COD is increased, thereby achieving the purpose of reaching the effluent COD standard in one step.

[0103] The average COD concentration of kitchen wastewater entering the membrane circulation anaerobic reactor was 42080±3638 mg·L -1 The average COD concentration of membrane effluent was 213.3±12.5 mg·L -1 , the COD removal rate is 99.25±0.27%, and the COD organic pollutant removal effect is significant.

[0104] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A water treatment system, characterized in that: include: Anaerobic reactor, used for anaerobic fermentation and biogas production; A membrane tank, in which a membrane assembly is provided, for discharging treated wastewater; as well as A gas circulation device, used to form biogas circulation in the anaerobic reactor and the membrane tank; The anaerobic reactor is provided with a first reaction chamber and a second reaction chamber, wherein the first reaction chamber is arranged below the second reaction chamber; The anaerobic reactor also includes an external circulation unit for returning the liquid in the membrane tank to the first reaction chamber; Wherein, the external circulation unit comprises an external circulation pipeline; The membrane pool is provided with a membrane pool water outlet and a membrane pool gas outlet for returning the liquid in the membrane pool to the anaerobic reactor; The gas outlet of the membrane pool is connected to the top of the anaerobic reactor, and the water outlet of the membrane pool is connected to the bottom of the second reaction chamber; and A first three-phase separator is disposed in the first reaction chamber; A second three-phase separator is disposed in the second reaction chamber; The first three-phase separator is a double-layer inverted triangle structure; The second three-phase separator is a single-layer inverted cone structure; a throat-shaped hoop is provided at the lower part of the cone; the exhaust pipe of the first three-phase separator extends into the inside of the inverted cone, so that the gases in the first reaction chamber and the second reaction chamber are mixed and then enter the top gas-water separator; The second reaction chamber is provided with an overflow weir and an overflow weir outlet, and the liquid in the second reaction chamber flows into the membrane pool through the overflow weir outlet.

2. The water treatment system according to claim 1, characterized in that: The gas circulation device comprises: A gas collection unit, used for separating and collecting biogas produced by the anaerobic reactor; A gas circulation unit, used to introduce the biogas in the gas collection unit into the membrane tank for aeration; and The gas reflux unit is used to return the biogas in the membrane pool to the gas collection unit.

3. The water treatment system according to claim 2, characterized in that: The gas collection unit comprises a gas collection hood; The gas circulation unit comprises a gas circulation pump and a membrane pool aeration port arranged on the membrane pool; A gas buffer bottle is provided between the gas circulation pump and the gas collection unit; The gas reflux unit comprises a membrane pool exhaust port, and the membrane pool exhaust port is communicated with a gas collecting hood.

4. The water treatment system according to claim 1, characterized in that: The membrane pool is provided with a membrane pool water inlet for introducing the liquid in the anaerobic reactor into the membrane pool.

5. The water treatment system according to claim 1, characterized in that: The membrane assembly includes a flat membrane; Wherein, the flat membrane is provided with a flat membrane water outlet for outputting separated water.

6. The water treatment system according to claim 1, characterized in that: The anaerobic reactor is cylindrical, and the height-to-diameter ratio of the anaerobic reactor is 8-20.

7. The water treatment system according to claim 1, characterized in that: The water treatment system also includes a temperature control device for regulating the anaerobic reactor; The water treatment system further comprises a water inlet device, which is connected to the anaerobic reactor; The water treatment system further comprises a drainage device, wherein the drainage device is connected to the membrane pool; Wherein, the drainage device comprises a water outlet container and a water outlet pump; The water treatment system further comprises an exhaust device, wherein the exhaust device is connected to the gas circulation device; Wherein, the exhaust device includes a safety bottle and a gas flow meter.

8. A water treatment method, using the water treatment system according to any one of claims 1 to 7, comprising: Inoculating anaerobic sludge in an anaerobic reactor; Introducing the wastewater to be treated into an anaerobic reactor for reaction; The biogas generated in the anaerobic reactor is circulated between the membrane tank and the anaerobic reactor through a gas circulation device and excess gas is collected; The water treatment is completed by circulating the liquid produced in the anaerobic reactor between the membrane tank and the anaerobic reactor and collecting the treated water.

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