CN111362401A - A Sewage Treatment Method Using Micron Fe3O4 Enhanced Anaerobic Dynamic Membrane Bioreactor - Google Patents

Abstract

The invention relates to the technical field of anaerobic dynamic membrane bioreactors, in particular to a sewage treatment method using micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactors. Micron Fe ₃ O ₄ and inoculated sludge are added into the dynamic membrane bioreactor, and the particle size of the inoculated sludge is larger than that of _micron Fe ₃ O _{4 ;} That is, magnetic anaerobic sludge is formed. 2) Place a membrane module in the reactor where the magnetic anaerobic sludge is formed, then feed sewage into the reactor and keep stirring, until the magnetic anaerobic dynamic membrane is formed, and enter the next stage. 3) When the flux of the membrane module drops to the set value, take out the membrane module and rinse it for the next cycle. The invention shortens the formation time of the anaerobic dynamic film by using the micron Fe ₃ O ₄ , improves the formed anaerobic dynamic film, and achieves the purpose of effectively controlling the film pollution and improving the treatment effect.

Description

A Sewage Treatment Method Using Micron Fe3O4 Enhanced Anaerobic Dynamic Membrane Bioreactor

technical field

The invention relates to the technical field of anaerobic dynamic membrane bioreactors, in particular to a sewage treatment method using micron Fe ₃ O ₄ to strengthen the anaerobic dynamic membrane bioreactor.

Background technique

The information disclosed in this Background of the Invention is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

The anaerobic sewage treatment process has received extensive attention in the field of water environment due to its advantages of low capital construction and operation cost, low sludge production, recyclable biogas energy, no need for aeration, and low energy consumption. However, the sludge loss problem has been a major problem since the development of anaerobic technology. Anaerobic membrane bioreactor (AnMBR) is a technology that applies membrane separation to traditional anaerobic biological treatment processes. Based on the advantages of anaerobic technology, this technology can achieve complete biomass retention by using the interception effect of membrane (microfiltration/ultrafiltration membrane), and solve the problem of sludge loss in traditional anaerobic processes. It has the advantages of strong impact ability and small footprint. But the high-cost membrane modules greatly increase the investment and operating costs of AnMBR.

Anaerobic dynamic membrane bioreactor (AnDMBR) is an emerging technology that combines dynamic membrane with anaerobic treatment and is applied to activated sludge process. Specifically, by replacing traditional microfiltration/ultrafiltration membranes with inexpensive large-pore filter materials, and using the anaerobic dynamic membrane (sludge layer) formed or re-formed on the filter material in the initial stage of the filtration process as the separation medium, the A technology similar to the solid-liquid separation effect of the MF/UF membrane in AnMBR. The coarse-pored filter material in AnDMBR greatly saves investment costs; the formed anaerobic dynamic membrane has small filtration resistance and simple cleaning method, which significantly reduces the operation and maintenance costs of the sewage treatment process. AnDMBR, which replaces expensive microfiltration/ultrafiltration membranes with lower-cost large-pore filter materials, is more suitable for wastewater treatment.

However, the inventors found that: AnDMBR still has the following deficiencies: the formation of anaerobic dynamic membrane is divided into two stages: the first stage is the formation stage of anaerobic dynamic membrane, and the anaerobic active pollutants in the reactor are divided into two stages. The sludge particles are deposited on the large-pore filter material to form a sludge layer, that is, an anaerobic dynamic membrane. However, the retention rate of particles and colloids in the formation stage of the anaerobic dynamic membrane is low, which makes AnDMBR poor in the initial interception effect and low effluent efficiency. It has been reported in the literature. The accumulation rate of sludge flocs is about 0-50 g/(m ² ·h), resulting in a long dynamic membrane formation time, generally ranging from 30 minutes to several hours. After the anaerobic dynamic membrane is formed, it enters the second stage. After the anaerobic dynamic membrane continues to operate stably for a period of time, finally due to the adsorption/deposition of anaerobic activated sludge particles and extracellular polymers (EPS) on the membrane module, anaerobic dynamic membrane The thickness of the oxygen dynamic membrane increases, the pore size becomes smaller, the filtration resistance increases, and the membrane pores are blocked, causing membrane fouling. In addition, due to the long generation period of anaerobic microorganisms and the slow proliferation rate, the efficiency of AnDMBR in treating sewage is low.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention proposes a sewage treatment method using micron Fe ₃ O ₄ to strengthen the anaerobic dynamic membrane bioreactor. The invention shortens the formation time of the anaerobic dynamic film by using the micron Fe ₃ O ₄ , improves the formed anaerobic dynamic film, and finally achieves the purpose of effectively controlling the film pollution and improving the treatment effect. For achieving the above object, the technical means adopted in the present invention are:

A sewage treatment method utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor, comprising the following steps:

(1) Magnetic anaerobic sludge formation stage: firstly add micron Fe ₃ O ₄ and anaerobic activated sludge into the closed anaerobic dynamic membrane bioreactor excluding membrane modules, and the particle size of anaerobic activated sludge larger than micron Fe ₃ O ₄ ; and then stirring to fully mix micron Fe ₃ O ₄ with anaerobic activated sludge, that is, to form magnetic anaerobic sludge.

(2) Magnetic anaerobic dynamic membrane formation stage (film hanging stage): place a membrane module in the reactor where magnetic anaerobic sludge is formed, and then feed sewage into the reactor and stir continuously until the magnetic anaerobic dynamic membrane is formed , enter the next stage.

(3) The stable operation stage of the magnetic anaerobic dynamic membrane: when the flux of the membrane module drops to the set value, one operation cycle ends, and the membrane module is taken out and washed for the next cycle.

Further, the anaerobic dynamic membrane bioreactor includes: a bioreactor and a membrane module, the bioreactor is a double-layer structure composed of an inner shell and an outer shell, the inner shell and the outer shell A water bath area is formed between the shells, and the water bath area forms a circulating connection with the constant temperature medium supply device through a suction pump. The reaction zone formed by the inner shell is connected with a peristaltic pump for water inflow, and a stirrer is arranged in the reaction zone to control the stirring rate of the anaerobic sludge mixed solution in the reactor. The membrane module is composed of a support structure and a filter medium coated on its surface. The outlet pipe is connected with the membrane module, and a flow meter is installed on the outlet pipe to determine the effluent flux.

Optionally, the filter medium includes any one of non-woven fabric, polyester mesh, nylon mesh, stainless steel mesh, etc., preferably polyester non-woven fabric. The support structure is cylindrical, and its material can be selected from PVC.

Optionally, the constant temperature medium supply device is a constant temperature water bath box heated by an electric heating rod, and hot water is circulated into the water bath area through a suction pump to control the temperature in the reactor to be constant. Optionally, maintain between 20-30°C.

Optionally, the bioreactor is made of plexiglass, and a transparent shell is formed to facilitate the observation of the mixing of micron Fe ₃ O ₄ and anaerobic activated sludge in the reactor, the treatment of sewage, and the like.

Further, a liquid level controller is also included, and the detection end of the liquid level controller is located in the reaction zone, and the liquid level controller is connected with the peristaltic pump, so as to control the influent water according to the change of the liquid level in the reactor.

Further, in step (1), the concentration of the micron Fe ₃ O ₄ is 0.2-0.8 g/L. It is preferably 0.8g/L, with COD and turbidity as detection indicators, the treatment effect of sewage is better at this concentration.

Further, in step (1), the average particle size of the micron Fe ₃ O ₄ is 2.70±0.01 μm, and the Fe ₃ O ₄ with a particle size in the micro scale accounts for more than 98% of the total content, and the micro Fe ₃ O ₄ is more stable than nano Fe ₃ O ₄ .

Further, in step (2), the turbidity of the effluent is less than 2NTU as a sign of the formation of the magnetic anaerobic dynamic film.

Further, in step (2), constant pressure gravity self-flowing water is adopted, and the head difference is set to 2.5-6.5 cm, so as to increase the pressure difference on both sides of the dynamic membrane and shorten the film hanging time.

Further, in step (3), the head difference is adjusted to 2.5-3.0 cm to prolong the stable operation period.

The role of micron Fe ₃ O ₄ in the sewage treatment of the present invention mainly has three aspects: (1) the micron Fe ₃ O ₄ and the inoculated sludge with larger particle size can form a magnetic anaerobic dynamic membrane with loose structure and uniform particles, The membrane has better filtration performance and low filtration resistance, thereby significantly enhancing the stable running time of the magnetic anaerobic dynamic membrane. (2) Adding micron Fe ₃ O ₄ can reduce the content of extracellular polymer (EPS) in the activated sludge mixture, reduce the filtration resistance of the membrane, and thus slow down the membrane fouling of the anaerobic dynamic membrane. (3) In the formation stage of anaerobic dynamic membrane, due to the flocculation of micron Fe ₃ O ₄ , the particle size of anaerobic activated sludge flocs can be increased, the aggregation property can be improved, and the formation time of anaerobic dynamic membrane can be shortened. (4) Since the existence of micron Fe ₃ O ₄ can promote the metabolism of anaerobic microorganisms, it also improves the biodegradation function of the sludge layer on the anaerobic dynamic membrane to a certain extent.

Compared with the prior art, the present invention has at least the following beneficial effects:

(1) The flocculation of micron Fe ₃ O ₄ can improve the flocculation ability of anaerobic activated sludge, increase the size of sludge flocs, and shorten the formation time of magnetic anaerobic dynamic membrane by 10min.

(2) Adding micron Fe ₃ O ₄ slows down the membrane fouling of the anaerobic dynamic membrane layer, effectively inhibits the microorganisms in the anaerobic activated sludge mixture from secreting less EPS, reduces the filtration resistance of the anaerobic dynamic membrane and increases the flux , the formation of the magnetic anaerobic dynamic membrane filtration resistance growth rate decreased by an order of magnitude.

(3) The addition of micron Fe ₃ O ₄ can promote the metabolism of anaerobic microorganisms and improve the removal efficiency of pollutants. The average COD removal rate of the anaerobic dynamic membrane bioreactor enhanced by Fe ₃ O ₄ is increased by 15%.

(4) The addition of micron Fe ₃ O ₄ can strengthen the biodegradation function of the anaerobic dynamic membrane, and the average COD removal rate of the magnetic anaerobic dynamic membrane is significantly increased from the previous 9% to 22%.

(5) Compared with the existing technology of using Fe ₃ O ₄ nanoparticles to modify the ultrafiltration microfiltration membrane in AnMBR (for example, the patent document with the publication number of CN 108479429A), the present invention adopts Fe ₃ O ₄ to Accelerating the formation of anaerobic dynamic membranes in AnDMBR is a completely different technique. Because AnMBR is very different from AnDMBR, the ultrafiltration microfiltration membrane of AnMBR will "passively" deposit and attach some sludge layers during the filtration process, but the formation process of the sludge layer is not expected, it will Blocking of microfiltration and ultrafiltration membranes causes membrane fouling problems, so Fe ₃ O ₄ is used as an adsorbent to slow down membrane fouling. However, since AnDMBR is in the formation stage of anaerobic dynamic membrane (AnMBR does not have this process), anaerobic activated sludge agglomerates and adheres to the coarse pore filter material to form a sludge layer, which can play a role similar to microfiltration and ultrafiltration membrane. filtration, and during the mass transfer process, the pollutants in the water are in full contact with the microorganisms in the sludge layer, and the effective amount of microorganisms actually participating in the degradation of pollutants is much larger than that of the microfiltration ultrafiltration membrane, and the formation process of the sludge layer is expected to occur. However, the present invention utilizes the flocculation effect of micron Fe ₃ O ₄ to shorten the formation time of the anaerobic dynamic membrane and accelerate the formation of the sludge layer.

Description of drawings

The accompanying drawings forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention.

FIG. 1 is a schematic structural diagram of an anaerobic dynamic membrane bioreactor in an embodiment of the present invention.

The marks in the above drawings represent respectively: 1-bioreactor, 2-membrane module, 3-inner shell, 4-outer shell, 5-water bath area, 6-suction pump, 7- constant temperature medium supply device , 8-reaction zone, 9-peristaltic pump, 10-stirrer, 11-outlet pipe, 12-flow meter, 13-electric heating rod, 14-water inlet pipe, 15-liquid level controller, 16-micron Fe ₃ O _4. h-head difference.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, it only means that the directions of up, down, left and right are consistent with the drawings themselves, and do not limit the structure. It is for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element needs to have a specific orientation, is constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

Terminology explanation part: the terms "installation", "connection", "connection", "fixation" and other terms in the present invention should be understood in a broad sense, for example, it may be a fixed connection, a detachable connection, or an integrated; It can be a mechanical connection, it can also be an electrical connection, it can be a direct connection, it can also be indirectly connected through an intermediate medium, it can be an internal connection between two elements, or an interaction relationship between two elements, for those of ordinary skill in the art. , the specific meanings of the above terms in the present invention can be understood according to specific situations.

As mentioned above, some of the existing AnDMBR still have long anaerobic dynamic membrane formation time, short stable operation time, increased anaerobic dynamic membrane thickness in the later stage of operation, smaller pore size, increased filtration resistance, and membrane fouling caused by membrane pore blockage, etc. insufficient. Therefore, the present invention proposes a sewage treatment method using micron Fe ₃ O ₄ to strengthen the anaerobic dynamic membrane bioreactor; the present invention will now be further described with reference to the accompanying drawings and specific embodiments.

first embodiment

An anaerobic dynamic membrane bioreactor, as shown in FIG. 1 , includes: a bioreactor 1 and a membrane module 2 . The bioreactor is a double-layer structure composed of an inner shell 3 and an outer shell 4 made of plexiglass, and a water bath area 5 is formed between the inner shell and the outer shell, and the water bath area 5 is pumped. The suction pump 6 forms a cyclic connection with the constant temperature medium supply device 7. The constant temperature medium supply device 7 is a constant temperature water bath box heated by the electric heating rod 13, and hot water is circulated into the water bath area 5 through the suction pump 6 to control the temperature in the reactor. The temperature was constant at 25±2°C.

The airtight reaction zone 8 formed by the inner shell is connected with a peristaltic pump 9 for water intake through the water inlet pipe 14, and the reaction zone 8 is provided with a stirrer 10, and the rotating shaft of the stirrer 10 passes through the cylindrical membrane module and reaches the bottom of the reactor. , the stirring rate of the anaerobic sludge mixed solution in the reactor can be controlled by the agitator 10, and the effective volume of the reaction zone 8 is 3.8L.

The membrane module 2 is composed of a cylindrical support structure made of PVC and a polyester non-woven fabric covered on its surface, with a specification of 200g/m ² and an effective filtering area of 0.11m ² . The upper part of the membrane module is provided with a water outlet, which is connected with a water outlet pipe 11, and a flow meter 12 is installed on the water outlet pipe, and the change of the water outlet flow is measured by the flow meter to determine the change of the water outlet flux. The detection end of the liquid level controller 15 is located in the reaction zone 8, and the liquid level controller 15 is connected to the peristaltic pump 9, so as to control the influent water according to the change of the liquid level in the reactor.

Second Embodiment

A sewage treatment method utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor, firstly, pre-experiment is carried out to determine the optimum dosage of micron Fe ₃ O ₄ , including the following steps:

Four identical anaerobic bottles were used, and 800 mL of activated sludge mixture was added to each anaerobic bottle (the seeded sludge was anaerobic activated sludge obtained from Qingdao Municipal Wastewater Treatment Plant, and the sludge MLSS was 4g/L) . Then, different mass of micron Fe ₃ O ₄ was added to each anaerobic flask, so that the Fe ₃ O ₄ concentrations in the 4 anaerobic flasks were 0.2g/L, 0.4g/L, 0.6g/L and 0.8g/L respectively. L, put the anaerobic bottle in the shaking incubator for mixing, shaking time is 20min, shaking frequency is 120rpm, let it settle for 30min, measure the COD and turbidity of the supernatant, and determine the optimal dosage of micron Fe ₃ O ₄ The dosage is 0.8g/L.

Third Embodiment

A sewage treatment method using micron Fe ₃ O ₄ to strengthen the anaerobic dynamic membrane bioreactor, using the anaerobic dynamic membrane bioreactor described in the first embodiment as the treatment site, and during the entire treatment period and through the water bath zone, the reaction The reaction temperature of the vessel is maintained between 25±2°C, specifically, including the following steps:

(1) Magnetic anaerobic sludge formation stage: first add inoculated sludge (anaerobic activated sludge obtained from Qingdao Municipal Wastewater Treatment Plant, sludge MLSS is 4g/L) in the reaction zone of the reactor; then Add micron Fe ₃ O ₄ 16 into the reaction zone (the average particle size is 2.70±0.01 μm, and the Fe ₃ O ₄ with particle size in the micron scale accounts for more than 98% of the total content), and the micron Fe ₃ O ₄ is added The concentration is 0.8g/L. Adjust the stirrer at a speed of _150rpm to fully mix the micron _Fe3O4 with the anaerobic activated sludge, and finally form magnetic anaerobic sludge.

(2) Magnetic anaerobic dynamic membrane formation stage (film hanging stage): place membrane module 2 in the reactor for forming magnetic anaerobic sludge, start the peristaltic pump, and pass the simulated synthetic sewage into the reaction through the influent peristaltic pump In the device, the inlet water C:N:P=100:5:1, the inlet water COD is controlled at about 300mg/L, and the pH is 6.8-7.2; the inlet water peristaltic pump is turned on to the maximum (150rpm), and the stirrer is adjusted at a rate of 120rpm The magnetic anaerobic sludge is in a state of suspension and agitation, and constant pressure gravity is used to flow out water, and the head difference is set to 6.0cm to increase the pressure difference on both sides of the dynamic membrane and shorten the film hanging time. The turbidity of the effluent is less than 2NTU as the magnetic anaerobic sludge Signs of oxygen dynamic film formation. In this stage, in addition to sampling, in order to ensure the proliferation and growth of anaerobic microorganisms with a long generation cycle, there is no sludge discharge in the whole stage, and the sludge age is close to infinity.

(3) The stable operation stage of the magnetic anaerobic dynamic membrane: After the magnetic anaerobic dynamic membrane is formed, it enters the stable operation stage. The influent peristaltic pump is adjusted to 20rpm, and the head difference h is adjusted to 2.5cm to prolong the stable operation period. The position controller controls the influent water, and the agitator keeps the magnetic anaerobic sludge in a suspended and agitated state at a rate of 60 rpm. The effluent flux and turbidity are relatively stable, and the pH of the sewage is maintained at 6.8-7.2. When the flux drops to 10L/m ² · When h is below, one operation cycle ends.

Fourth Embodiment

For the comparison of the third embodiment, the anaerobic dynamic membrane bioreactor was used as the treatment site, and the reaction temperature of the reactor was maintained between 25±2°C throughout the treatment period and through the water bath zone, the difference was that there was no reaction in the reactor. Add micron Fe ₃ O ₄ . Specifically, it includes the following steps:

(1) Anaerobic dynamic membrane formation stage (film hanging stage): Inoculated sludge is added to the reactor, the influent peristaltic pump is started, and then the simulated synthetic sewage (C:N:P=100:5:1, COD is controlled at About 300mg/L, pH is 6.8-7.2) pass into the reactor through the influent peristaltic pump, open the influent peristaltic pump to 150rpm, adjust the magnetic stirrer to make the anaerobic activated sludge in a state of suspension agitation at a rate of 120rpm, and use a constant The pressure gravity is self-effluent, and the head difference is set to 6.0cm to increase the pressure difference on both sides of the dynamic membrane and shorten the film hanging time. When the turbidity of the effluent is less than 2NTU, the anaerobic dynamic membrane is hung on the membrane module.

(2) Stable operation stage of anaerobic dynamic membrane: After the anaerobic dynamic membrane is formed, it enters the stable operation stage, the influent peristaltic pump is adjusted to 20rpm, and the head difference is adjusted to 2.5cm to prolong the stable operation period, which is controlled by the liquid level controller. Into the water, the agitator keeps the anaerobic sludge in a suspended and agitated state at a rate of 60rpm, and the effluent flux and turbidity are relatively stable. When the flux drops below 10L/m ² ·h, one operation cycle ends. In addition to sampling, in order to ensure the proliferation and growth of anaerobic microorganisms with a long generation cycle, there is no sludge discharge in the whole stage, and the sludge age is close to infinity.

effect test

For the fourth embodiment: in the film hanging stage, the formation time of the anaerobic dynamic film is 20min. The filtration resistance growth rate of the anaerobic dynamic membrane was 2.16×108m ^-1 h ^-1 within 10d during the stable operation. The stable running time of the anaerobic dynamic membrane is 10d, and the flux is maintained at about 10-20L/m ² ·h. The average particle size of the anaerobic activated sludge was 50.7 μm, and the average particle size of the anaerobic dynamic membrane layer was 63.1 μm. The effluent performance indicators after treatment are: the COD effluent concentration is 60.6±3.8mg/L, the average COD removal efficiency is 79.8%, the supernatant COD concentration is 87.6±4.2mg/L, and the average COD removal efficiency of the anaerobic dynamic membrane is 9 %. In addition, the soluble microbial metabolite (SMP) content of the anaerobic activated sludge mixture was 45.5 mg/g MLSS, and the extracellular polymer (EPS) content was 61.6 mg/g MLSS.

For the third embodiment: in the film hanging stage, the formation time of the magnetic anaerobic dynamic film is 10 minutes, which is 10 minutes shorter than that without adding micron Fe ₃ O ₄ . The filtration resistance growth rate of the magnetic anaerobic dynamic membrane was 7.6×10 ⁷ m ^-1 h ^-1 within 10 days of stable operation, that is, the filtration resistance growth rate decreased by an order of magnitude compared with the previous one, indicating that the filtration resistance growth was significantly slower. The stable running time of the anaerobic dynamic membrane is 15d, and the flux is maintained at about 20-35L/m ² ·h. The average particle size of the magnetic anaerobic activated sludge was 60.6 μm, and the average particle size of the magnetic anaerobic dynamic membrane layer was 68.5 μm. The performance indicators of effluent after treatment are: COD effluent concentration is 13.8±2.7mg/L, average COD removal efficiency is 95.4%, supernatant COD concentration is 79.8±2.4mg/L, anaerobic dynamic membrane average COD removal efficiency is 22% . It can be seen that the addition of micron Fe ₃ O ₄ improves the sewage treatment performance of AnDMBR and increases the pollutant treatment capacity of the magnetic anaerobic dynamic membrane. In addition, the soluble microbial metabolite (SMP) content of the anaerobic activated sludge mixture was 38.5 mg/g MLSS, and the extracellular polymer (EPS) content was 53.3 mg/g MLSS. The addition of micron Fe ₃ O ₄ made SMP and The content of EPS decreased, which slowed down the membrane fouling of the anaerobic dynamic membrane.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a sewage treatment method utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor, is characterized in that, comprises the steps: (1) Magnetic anaerobic sludge formation stage: firstly add micron Fe ₃ O ₄ and anaerobic activated sludge into the closed anaerobic dynamic membrane bioreactor excluding membrane modules, and the particle size of anaerobic activated sludge larger than the micron Fe ₃ O ₄ ; then stir to fully mix the micron Fe ₃ O ₄ and the anaerobic activated sludge to form magnetic anaerobic sludge; (2) Magnetic anaerobic dynamic membrane formation stage: place a membrane module in the reactor where the magnetic anaerobic sludge is formed, then feed sewage into the reactor and stir continuously, until the magnetic anaerobic dynamic membrane is formed, enter the next stage ; (3) The stable operation stage of the magnetic anaerobic dynamic membrane: when the flux of the membrane module drops to the set value, one operation cycle ends. 2. The sewage treatment method of utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor as claimed in claim 1, wherein in step (1), the concentration of the micron Fe ₃ O ₄ is 0.2- 0.8g/L; preferably 0.8g/L. 3. The sewage treatment method of utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor as claimed in claim 1, wherein in step (1), the average particle size of the micron Fe ₃ O ₄ is 2.70±0.01μm, and the proportion of Fe ₃ O ₄ in the micron scale is more than 98% of the total content. 4. the sewage treatment method that utilizes micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor as claimed in claim 1, is characterized in that, in step (2), with effluent turbidity less than 2NTU as magnetic anaerobic dynamic membrane formed logo. 5. the sewage treatment method that utilizes micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor as claimed in claim 1, is characterized in that, in step (2), adopts constant pressure gravity self-flow water, and head difference is set to be 2.5-6.5cm. 6 . The sewage treatment method of utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor according to claim 1 , wherein, in step (3), the head difference is adjusted to 2.5-3.0 cm. 7 . 7. The sewage treatment method of utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor according to any one of claims 1-6, wherein the anaerobic dynamic membrane bioreactor comprises: a biological reaction The bioreactor is a double-layer structure composed of an inner shell and an outer shell, and a water bath area is formed between the inner shell and the outer shell, and the water bath area is connected to the water bath through a suction pump. The constant temperature medium supply device forms a circulating connection; the reaction zone formed by the inner shell is connected with a peristaltic pump for water intake, and the reaction zone is provided with a stirrer; the membrane module is composed of a support structure and a filter medium coated on its surface ; The outlet pipe is connected with the membrane module, and a flow meter is installed on the outlet pipe. 8. The sewage treatment method of utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor as claimed in claim 7, wherein the filter medium comprises non-woven fabrics, polyester nets, nylon nets, stainless steel nets Any one, preferably polyester non-woven fabric; Or; the support structure is cylindrical, and its material can be selected from PVC; Alternatively, the bioreactor is made of plexiglass. 9 . The sewage treatment method of utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor according to claim 7 , wherein the constant temperature medium supply device is a constant temperature water bath box heated by an electric heating rod. 10 . 10. The sewage treatment method of utilizing micron Fe ₃ O ₄ to strengthen anaerobic dynamic membrane bioreactor as claimed in claim 7, characterized in that, further comprising a liquid level controller, and the detection end of the liquid level controller is located in the reaction zone , and the level controller is connected to the peristaltic pump.

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