Method for strengthening performance of anaerobic membrane bioreactor by coupling internal electron circulation with external electric field

Abstract

The invention relates to the technical field of biological treatment of wastewater, in particular to a method for enhancing the performance of an anaerobic membrane bioreactor by coupling internal electron circulation with an external electric field. The method comprises the following steps: preparing a surface conductive flat sheet membrane assembly, wherein the surface conductive flat sheet membrane assembly is formed by alternately coating a stainless steel mesh and a titanium mesh on the surface of a flat sheet membrane unit; the method comprises the following steps: constructing an electrochemical anaerobic membrane bioreactor, and connecting a surface conductive flat membrane assembly serving as a cathode and an anode of the electrochemical anaerobic membrane bioreactor to a direct-current power supply through a wire; preparing a carbonized MIL-53 (Fe) micro-electric field material, wherein the carbonized MIL-53 (Fe) micro-electric field material is powder with the particle size ranging from 1 micron to 10 microns; dispersing the carbonized MIL-53 (Fe) micro electric field material in an anaerobic digestion solution of an electrochemical anaerobic membrane bioreactor in a powder form; the anaerobic digestion liquid and the carbonized MIL-53 (Fe) micro-electric field material are uniformly mixed in a mechanical stirring or anaerobic digestion gas stirring mode. The membrane pollution of the anaerobic membrane bioreactor is efficiently controlled, and the anaerobic digestion efficiency is remarkably enhanced.

Description

Technical Field

[0001] This application relates to the field of wastewater biological treatment technology, and in particular to a method for enhancing the performance of an anaerobic membrane bioreactor by coupling an internal electron circulation with an external electric field. Background Technology

[0002] Anaerobic membrane bioreactor (AnMBR) is a wastewater treatment process that combines anaerobic digestion and membrane filtration technologies. It converts biodegradable organic compounds into biogas through three stages: hydrolysis and fermentation, hydrogen and acetic acid production, and methanogenesis. Solid-liquid separation is then achieved through membrane filtration, allowing wastewater to be recycled as a "resource and energy carrier." Simultaneously, the selective permeability of the membrane modules effectively retains anaerobic sludge within the reactor, completely separating sludge retention time (SRT) and hydraulic retention time (HRT), thus enhancing the stability of the anaerobic system.

[0003] Despite its numerous advantages, AnMBR still faces several limitations. Membrane fouling and low anaerobic digestion efficiency are the main limiting factors. Adding exogenous mediators is one effective method to address the low anaerobic digestion efficiency of AnMBR. Current research typically involves adding conductive materials to promote electron transfer rates between anaerobic microorganisms and provide attachment sites for microbial growth. Simultaneously, studies have found that exogenous mediators with capacitive properties can store excess electrons produced by acid-producing bacteria during anaerobic digestion and slowly release them to methanogens, thereby regulating the metabolic imbalance between acid-producing and methanogenous bacteria and effectively alleviating reactor acidification. However, these materials can only play a "passive" role in regulating electron transfer between anaerobic microorganisms, and their electron transfer performance remains limited. Summary of the Invention

[0004] This application provides a method for enhancing the performance of an anaerobic membrane bioreactor by coupling an internal electron circulation with an external electric field, in order to solve the above-mentioned problems.

[0005] In a first aspect, this application provides a method for enhancing the performance of an anaerobic membrane bioreactor by coupling an internal electron circulation with an external electric field, the method comprising:

[0006] S1. Prepare a surface conductive flat sheet film assembly, wherein the surface conductive flat sheet film assembly is formed by alternately covering the surface of a flat sheet film unit with stainless steel mesh and titanium mesh;

[0007] S2. Construct an electrochemical anaerobic membrane bioreactor, wherein the surface conductive flat sheet membrane assembly serves as the cathode and anode of the electrochemical anaerobic membrane bioreactor and is connected to a DC power supply via wires;

[0008] S3. Prepare carbonized MIL-53(Fe) micro-electric field material, wherein the carbonized MIL-53(Fe) micro-electric field material is a powder with a particle size range of 1 micrometer to 10 micrometers;

[0009] S4. Disperse the carbonized MIL-53(Fe) micro electric field material in powder form in the anaerobic digestion liquid of the electrochemical anaerobic membrane bioreactor;

[0010] S5. The anaerobic digestion liquid is uniformly mixed with the carbonized MIL-53(Fe) micro-electric field material by mechanical stirring or anaerobic digestion gas stirring.

[0011] By incorporating micro-electric field materials and coupling alternating membrane electric fields into the anaerobic membrane bioreactor, highly efficient control of membrane fouling and significant enhancement of anaerobic digestion efficiency are achieved. This simultaneously and efficiently solves the problems of membrane fouling and low anaerobic digestion efficiency, enabling long-term stable operation of the anaerobic membrane bioreactor. Furthermore, by constructing a novel, highly efficient surface-conductive flat-plate membrane module using a metal mesh coating method and alternately setting it as the cathode and anode, a more uniform electric field gradient is formed in the spacer region of the flat-plate membrane. This also simplifies the fabrication process and effectively reduces costs.

[0012] Optionally, the stainless steel mesh and titanium mesh have a wire diameter of 0.02 mm to 0.03 mm and a mesh size of 0.2 mm to 0.3 mm.

[0013] The above technical solutions help reduce obstruction of the effective filtration area of ​​the membrane surface, thereby maintaining a high membrane flux. Simultaneously, the fine filament diameter and mesh size ensure a tight fit between the metal mesh and the flat sheet membrane unit surface, forming a uniform conductive layer. This results in a more uniform electric field distribution on the membrane surface when an electric field is applied, effectively suppressing membrane fouling. Furthermore, this mesh structure provides additional attachment sites for anaerobic microorganisms, promoting biofilm formation and growth, and ultimately improving anaerobic digestion efficiency.

[0014] Optionally, the output voltage range of the DC power supply is 0.4V to 1.0V.

[0015] The above technical solution establishes a stable and uniform alternating electric field between the cathode and anode of the surface conductive flat sheet membrane module. This electric field effectively prevents negatively charged pollutants (such as extracellular polymeric substances, EPS) from adsorbing and accumulating on the membrane surface through electrostatic repulsion, thereby significantly mitigating membrane fouling. Simultaneously, a moderate electric field strength can also promote interspecies electron transfer (IET) among anaerobic microorganisms, accelerating the degradation of organic matter and the generation of methane, thus improving anaerobic digestion efficiency.

[0016] Optionally, the carbonized MIL-53(Fe) micro-electric field material is prepared by pyrolysis of MIL-53(Fe) under a nitrogen atmosphere at 750°C to 900°C.

[0017] The above technical solution endows the carbonized MIL-53(Fe) micro-electric field material with excellent conductivity. At the same time, the pyrolysis under a nitrogen atmosphere can effectively inhibit the oxidation of the material at high temperature, ensure the purity and structural integrity of the carbonization products, and avoid the formation of non-conductive impurities such as amorphous carbon or iron oxide. This makes the carbonized MIL-53(Fe) micro-electric field material not only have good conductivity, but also have micro-electric field effect and charge regulation performance, which can actively induce electron transfer between anaerobic microorganisms and significantly improve the efficiency of anaerobic digestion.

[0018] Optionally, the amount of the carbonized MIL-53(Fe) micro-electric field material added to the electrochemical anaerobic membrane bioreactor is from 0.5 g / L to 2.0 g / L.

[0019] By employing the above technical solutions, a balance is struck between material costs and the improvement in anaerobic digestion performance. This allows the carbonized MIL-53(Fe) micro-electric field material to generate sufficient micro-electric field effects or provide sufficient electron transfer sites while reducing material costs. This effectively promotes electron transfer between anaerobic microorganisms, accelerates the degradation of organic matter and the generation of methane.

[0020] Optionally, the temperature in the electrochemical anaerobic membrane bioreactor is between 20°C and 40°C.

[0021] The above technical solutions ensure the activity and growth of anaerobic microorganisms, thereby achieving efficient organic matter degradation and methane production, and improving reactor stability.

[0022] Optionally, the hydraulic retention time in the electrochemical anaerobic membrane bioreactor is 6 to 12 hours.

[0023] The above technical solutions ensure that wastewater has sufficient residence time in the reactor, enabling anaerobic microorganisms to fully degrade organic pollutants, improve effluent quality and methanogenesis efficiency, and avoid unnecessary increases in operating costs.

[0024] Optionally, the flat sheet membrane unit of the surface conductive flat sheet membrane assembly is an organic flat sheet membrane or a ceramic flat sheet membrane.

[0025] The above technical solutions enable the surface conductive flat sheet membrane module to meet the needs of different wastewater treatment scenarios, improve wastewater treatment performance, make the surface conductive flat sheet membrane module easy to maintain and clean, and ensure the service life of the surface conductive flat sheet membrane module.

[0026] Optionally, the electrochemical anaerobic membrane bioreactor is equipped with a mechanical stirrer or an anaerobic digestion gas circulation pump; the mechanical stirrer stirs the anaerobic digestion liquid at a speed of 20 rpm to 50 rpm; the anaerobic digestion gas circulation pump circulates anaerobic digestion gas at a flow rate of 0.1 L / min to 0.5 L / min to maintain the uniform dispersion of the anaerobic digestion liquid and the carbonized MIL-53(Fe) micro electric field material.

[0027] The above technical solution ensures the uniform dispersion of anaerobic digestion liquid and carbonized MIL-53(Fe) micro-electric field material, allowing the uniformly dispersed micro-electric field material to maximize contact with anaerobic microorganisms, promote electron transfer, improve the degradation efficiency of organic matter, and effectively reduce membrane surface fouling through stirring. Shear force washes the membrane surface, preventing pollutants from accumulating in the membrane pores and on the membrane surface, thereby maintaining a high membrane flux.

[0028] Optionally, the sludge concentration in the electrochemical anaerobic membrane bioreactor is between 6000 mg / L and 12000 mg / L.

[0029] The above technical solutions ensure that a sufficient amount of active microorganisms are maintained in the reactor, thereby achieving efficient organic matter degradation and methane production, while avoiding operational problems caused by excessive sludge concentration.

[0030] Secondly, this application provides a method for preparing a carbonized MIL-53(Fe) micro-electric field material, the method comprising:

[0031] Terephthalic acid and ferric chloride hexahydrate are added to N,N-dimethylformamide (DMF) to prepare a solution, wherein the mass ratio of terephthalic acid, ferric chloride hexahydrate and N,N-dimethylformamide (DMF) is within a specific range;

[0032] The solution was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and the autoclave was placed in a constant temperature oven at 160 °C and heated for 6 hours.

[0033] Remove the autoclave from the oven and allow it to cool naturally to 25°C. Transfer the reaction solution to a centrifuge tube and centrifuge at 8000 rpm for 10 minutes. Discard the supernatant, add 20 mL of anhydrous ethanol, and sonicate for 5 minutes. Repeat the centrifugation and washing steps three times. Finally, dry the solution in a vacuum oven at 80°C for 8 hours to obtain MIL-53(Fe) powder.

[0034] The MIL-53(Fe) powder was placed in a quartz boat in a tube furnace, and high-purity nitrogen was introduced at a flow rate of 100 mL / min. The temperature was increased to 750°C to 900°C at a heating rate of 5°C / min and held at this temperature for 2 hours. Then, the furnace was cooled to 25°C, and the carbonized MIL-53(Fe) micro-electric field material was obtained.

[0035] Optionally, the amount of terephthalic acid is 1.328 g, the amount of ferric chloride hexahydrate is 2.164 g, and the amount of N,N-dimethylformamide (DMF) is 80 mL.

[0036] Optionally, the solution is heated at 160°C for 6 hours. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A flowchart illustrating a method for enhancing the performance of an anaerobic membrane bioreactor by coupling an internal electron loop with an external electric field, as provided in an embodiment of this application;

[0039] Figure 2 A flowchart illustrating a method for preparing a carbonized MIL-53(Fe) micro-electric field material according to an embodiment of this application;

[0040] Figure 3 A graph showing the transmembrane pressure difference of an electrochemical anaerobic membrane bioreactor under different electric field application methods, provided in an embodiment of this application.

[0041] Figure 4 The graph shows the changes in COD concentration and methane production in an anaerobic membrane bioreactor after adding different micro-electric field materials, according to an embodiment of this application. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0043] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0044] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0045] Despite its numerous advantages, AnMBR still faces several limitations. Membrane fouling and low anaerobic digestion efficiency are the main limiting factors. Adding exogenous mediators is one effective method to address the low anaerobic digestion efficiency of AnMBR. Current research typically involves adding conductive materials to promote electron transfer rates between anaerobic microorganisms and provide attachment sites for microbial growth. Simultaneously, studies have found that exogenous mediators with capacitive properties can store excess electrons produced by acid-producing bacteria during anaerobic digestion and slowly release them to methanogens, thereby regulating the metabolic imbalance between acid-producing and methanogenous bacteria and effectively alleviating reactor acidification. However, these materials can only play a "passive" role in regulating electron transfer between anaerobic microorganisms, and their electron transfer performance remains limited.

[0046] Based on this, this application provides a method for enhancing the performance of an anaerobic membrane bioreactor by coupling an internal electron circulation with an external electric field. By embedding a micro-electric field material within the anaerobic membrane bioreactor and coupling it with alternating membrane electric fields, efficient control of membrane fouling and a significant enhancement of anaerobic digestion efficiency are achieved. This invention simultaneously and efficiently solves the problems of membrane fouling and low anaerobic digestion efficiency, enabling long-term stable operation of the anaerobic membrane bioreactor. By constructing a novel, highly efficient surface-conductive flat-plate membrane assembly using a metal mesh coating method and alternately setting it as the cathode and anode, a more uniform electric field gradient is formed in the spacer region of the flat-plate membrane, while simplifying the fabrication process and effectively reducing costs.

[0047] Figure 1 This is a flowchart illustrating a method for enhancing the performance of an anaerobic membrane bioreactor by coupling an internal electron loop with an external electric field, as provided in an embodiment of this application. Figure 1 As shown, the method includes:

[0048] S1. Prepare a surface conductive flat sheet film assembly, which is formed by alternately covering the surface of a flat sheet film unit with stainless steel mesh and titanium mesh;

[0049] S2. Construct an electrochemical anaerobic membrane bioreactor, with a surface conductive flat sheet membrane module serving as the cathode and anode of the electrochemical anaerobic membrane bioreactor, and connected to a DC power supply via wires;

[0050] S3. Prepare carbonized MIL-53(Fe) micro-electric field material, wherein the carbonized MIL-53(Fe) micro-electric field material is a powder with a particle size range of 1 micrometer to 10 micrometers;

[0051] S4. Disperse the carbonized MIL-53 (Fe) micro electric field material in powder form in the anaerobic digestion liquid of the electrochemical anaerobic membrane bioreactor;

[0052] S5. The anaerobic digestion liquid and the carbonized MIL-53(Fe) micro-electric field material are uniformly mixed by mechanical stirring or anaerobic digestion gas stirring.

[0053] Anaerobic membrane bioreactors (AnMBRs) currently offer advantages in wastewater treatment, including the conversion of organic matter into biogas and solid-liquid separation. However, practical applications still face challenges such as membrane fouling and low anaerobic digestion efficiency. In existing technologies, conductive membranes used as cathodes or anodes require counter electrodes, making it difficult to create a uniform electric field. Furthermore, the fabrication of conductive membranes is complex, costly, and has poor conductivity. In addition, existing exogenous mediators only provide passive regulation of electron transfer in anaerobic microorganisms, leaving room for improvement in electron transfer efficiency. Traditional metal anodes also suffer from passivation issues. This invention aims to provide a method for enhancing the performance of anaerobic membrane bioreactors by coupling alternating membrane electric fields with an integrated micro-electric field material. This method simultaneously achieves efficient control of membrane fouling and a significant enhancement of anaerobic digestion efficiency, thereby enabling long-term stable operation of the anaerobic membrane bioreactor. Based on real-time signal processing and dynamic control theory, this invention combines the electric field interaction between membrane electrodes and the electron transfer function of the micro-electric field material to achieve precise anaerobic digestion and membrane fouling control. A surface-conductive flat-sheet membrane module, formed by alternating coatings of stainless steel and titanium mesh, serves as the cathode and anode of the electrochemical anaerobic membrane bioreactor, creating a uniform and effective electric field on the membrane surface under DC power. Carbonized MIL-53(Fe) micro-electric field material acts as an exogenous mediator, actively inducing electron transfer between anaerobic microorganisms. In operation, the surface-conductive flat-sheet membrane module 1 is first prepared, followed by the construction of the electrochemical anaerobic membrane bioreactor and connection to a DC power supply. Next, carbonized MIL-53(Fe) micro-electric field material with a particle size of 1 to 10 micrometers is prepared and dispersed in the anaerobic digestion liquid as powder. The mixture is then uniformly mixed using mechanical stirring or anaerobic digestion gas stirring, thereby enhancing anaerobic digestion performance and membrane fouling control. Through synergistic effects, the components achieve stable and efficient operation of the anaerobic membrane bioreactor.

[0054] This invention includes the following core steps: S1. Preparing a surface-conductive flat-plate membrane assembly, which is formed by alternately coating the surface of a flat-plate membrane unit with stainless steel mesh and titanium mesh. This alternating coating design allows the surface-conductive flat-plate membrane assembly to simultaneously serve as both a cathode and anode, forming a uniform and effective electric field on the membrane surface. S2. Constructing an electrochemical anaerobic membrane bioreactor, using the aforementioned surface-conductive flat-plate membrane assembly as both the cathode and anode of the electrochemical anaerobic membrane bioreactor, connected to a DC power supply via wires. This configuration can effectively mitigate membrane fouling under the action of an applied electric field through electrostatic repulsion and anodic oxidation. S3. Preparing a carbonized MIL-53(Fe) micro-electric field material, which is a powder with a particle size ranging from 1 micrometer to 10 micrometers. This material has excellent conductivity and capacitance properties, and can promote electron transfer between anaerobic microorganisms. S4. Dispersing the carbonized MIL-53(Fe) micro-electric field material in powder form in the anaerobic digestion liquid of the electrochemical anaerobic membrane bioreactor, ensuring sufficient contact between the anaerobic microorganisms. S5. The anaerobic digestion liquid is uniformly mixed with the carbonized MIL-53(Fe) micro-electric field material by mechanical stirring or anaerobic digestion gas stirring, ensuring that the micro-electric field material is uniformly dispersed in the reactor and maximizing its effect. This stirring method ensures effective contact between the micro-electric field material and anaerobic microorganisms, promotes electron transfer, and improves anaerobic digestion efficiency.

[0055] This invention achieves highly efficient control of membrane fouling and significantly enhanced anaerobic digestion efficiency in anaerobic membrane bioreactors by embedding micro-electric field materials within the reactor and coupling them with alternating membrane electric fields. This invention simultaneously and efficiently solves the problems of membrane fouling and low anaerobic digestion efficiency, enabling long-term stable operation of the anaerobic membrane bioreactor. By constructing a novel, highly efficient surface-conductive flat-plate membrane assembly using a metal mesh coating method and alternately setting it as the cathode and anode, a more uniform electric field gradient is formed in the spacer region of the flat-plate membrane, while simultaneously simplifying the fabrication process and effectively reducing costs.

[0056] In the above embodiments, the flat sheet membrane unit of the surface conductive flat sheet membrane assembly can be replaced with different materials, such as organic flat sheet membranes or ceramic flat sheet membranes, to adapt to different water quality conditions and treatment requirements. Organic flat sheet membranes have the advantages of low cost and easy processing, and are suitable for general wastewater treatment; ceramic flat sheet membranes have higher mechanical strength and chemical stability, and are suitable for the treatment of high-intensity or special wastewater. When constructing an electrochemical anaerobic membrane bioreactor, the output voltage range of the DC power supply can be finely adjusted between 0.4V and 1.0V to optimize the electric field strength and achieve the best membrane fouling control effect and anaerobic digestion efficiency. In the preparation method of carbonized MIL-53(Fe) micro-electric field material, the pyrolysis temperature of MIL-53(Fe) can be adjusted under a nitrogen atmosphere from 750℃ to 900℃. The materials obtained by pyrolysis at different temperatures may have differences in particle size distribution, specific surface area, and conductivity, thereby affecting their micro-electric field effect and electron transfer efficiency. For example, carbonization at 800℃ may yield the best micro-electric field material performance. The dosage of carbonized MIL-53(Fe) micro-electric field material 2 can be adjusted within the range of 0.5 g / L to 2.0 g / L to adapt to anaerobic digestion liquids with different sludge concentrations and organic loads. Optimizing the dosage can achieve the best methanogenesis rate and membrane flux. Furthermore, in step S5, in addition to mechanical stirring or anaerobic digestion gas stirring, other methods such as ultrasonic dispersion and hydraulic circulation can be used to ensure uniform mixing of the carbonized MIL-53(Fe) micro-electric field material in the anaerobic digestion liquid, improving its dispersion effect and efficiency. The flow rate of the anaerobic digestion gas and the rotation speed of the mechanical stirring can also be adjusted according to the actual conditions of the reactor to adapt to different sludge viscosities and reactor sizes.

[0057] In some embodiments, the stainless steel mesh and titanium mesh have a wire diameter of 0.02 mm to 0.03 mm and a mesh size of 0.2 mm to 0.3 mm.

[0058] The surface-conductive flat-sheet membrane module is formed by alternately coating stainless steel mesh and titanium mesh. The wire diameter of the stainless steel mesh and titanium mesh is 0.02 mm to 0.03 mm, and the mesh size is 0.2 mm to 0.3 mm. These serve as the cathode and anode of the electrochemical anaerobic membrane bioreactor, forming a uniform and effective electric field on the membrane surface under the action of a DC power supply. Carbonized MIL-53(Fe) micro-electric field material acts as an exogenous mediator, actively inducing electron transfer between anaerobic microorganisms. In the operation, the surface-conductive flat-sheet membrane module is first prepared, and then the electrochemical anaerobic membrane bioreactor 10 is constructed and connected to a DC power supply. Next, carbonized MIL-53(Fe) micro-electric field material with a particle size of 1 micrometer to 10 micrometers is prepared and dispersed in anaerobic digestion liquid in powder form. It is then uniformly mixed by mechanical stirring or anaerobic digestion gas stirring, thereby enhancing the anaerobic digestion performance and membrane fouling control effect. Through synergistic effects, the components achieve stable and efficient operation of the anaerobic membrane bioreactor.

[0059] In the fabrication of surface-conductive flat-sheet membrane modules, this invention involves alternately coating the surface of a flat-sheet membrane unit with stainless steel and titanium meshes. The stainless steel and titanium meshes have wire diameters of 0.02 mm to 0.03 mm and mesh opening sizes of 0.2 mm to 0.3 mm. This specific wire diameter and mesh opening size design offers several technical advantages. First, the finer wire diameter (0.02 mm to 0.03 mm) helps reduce obstruction of the effective filtration area of ​​the membrane surface, thereby maintaining a high membrane flux. Simultaneously, the fine wire diameter and appropriate mesh opening size (0.2 mm to 0.3 mm) ensure a tight fit between the metal mesh and the flat-sheet membrane unit surface, forming a uniform conductive layer. This results in a more uniform electric field distribution on the membrane surface when an electric field is applied, effectively suppressing membrane fouling. Second, this mesh structure provides additional attachment sites for anaerobic microorganisms, promoting biofilm formation and growth, and improving anaerobic digestion efficiency. Furthermore, the alternating use of stainless steel and titanium mesh, combined with their specific wire diameters and mesh sizes, optimizes electrochemical performance. Stainless steel mesh provides excellent conductivity, while titanium mesh offers superior corrosion resistance. This combination improves the stability and lifespan of the surface-conductive flat-panel membrane assembly 1, avoiding the high costs associated with anodic passivation of traditional sacrificial electrode materials. The specific wire diameter and mesh size (0.02 mm to 0.03 mm wire diameter, 0.2 mm to 0.3 mm mesh size) ensure the uniformity of the electric field on the membrane surface, significantly reducing the membrane fouling rate.

[0060] In the above embodiments, the wire diameter and mesh size of the stainless steel and titanium meshes can be finely adjusted according to the specific membrane material and treatment requirements. For example, for scenarios treating high-concentration wastewater or requiring higher membrane flux, the mesh size can be appropriately increased to reduce hydraulic resistance while maintaining sufficient electric field uniformity. For scenarios requiring finer filtration or stronger antifouling capabilities, finer wire diameters and smaller mesh sizes can be considered, but their impact on membrane flux must be weighed. In practical applications, the wire diameter and mesh size can be optimized based on the viscosity of the anaerobic digester, suspended solids content, and target treatment efficiency. In addition to stainless steel and titanium meshes, other conductive and corrosion-resistant metal mesh materials, such as nickel mesh or carbon fiber mesh, can be explored to further optimize the performance of the surface conductive flat sheet membrane module 1. The selection of these alternative materials will affect the cost, lifespan, and electrochemical characteristics of the module and needs to be evaluated based on the specific application scenario.

[0061] In some embodiments, the output voltage range of the DC power supply is 0.4V to 1.0V.

[0062] The cathode and anode of the electrochemical anaerobic membrane bioreactor are connected to a DC power supply via wires, the output voltage of which ranges from 0.4V to 1.0V. Carbonized MIL-53(Fe) micro-electric field material, acting as an exogenous mediator, actively induces electron transfer between anaerobic microorganisms. In the operation, a surface-conductive flat-sheet membrane assembly is first prepared, followed by the construction of the electrochemical anaerobic membrane bioreactor and connection to the DC power supply. Next, carbonized MIL-53(Fe) micro-electric field material with a particle size of 1 to 10 micrometers is prepared and dispersed in the anaerobic digestion liquid in powder form. This dispersion is achieved through mechanical stirring or anaerobic digestion gas stirring, thereby enhancing anaerobic digestion performance and membrane fouling control. Through synergistic effects, the components achieve stable and efficient operation of the anaerobic membrane bioreactor.

[0063] In constructing the electrochemical anaerobic membrane bioreactor, the DC power supply's output voltage range is set to 0.4V to 1.0V. This voltage range is chosen based on a comprehensive consideration of membrane fouling control and anaerobic digestion efficiency optimization. Voltages below 0.4V may be insufficient to form an effective electric field gradient on the membrane surface, making it difficult to generate sufficient electrostatic repulsion to effectively suppress membrane fouling and failing to adequately promote microbial electron transfer. Voltages above 1.0V may lead to excessive energy consumption, even triggering hydrolysis side reactions, adversely affecting microbial activity and increasing operating costs. Within this 0.4V to 1.0V voltage range, the DC power supply ensures the establishment of a stable and uniform alternating electric field between the cathode and anode of the surface-conductive flat-plate membrane assembly. This electric field effectively prevents negatively charged pollutants (such as extracellular polymeric substances, EPS) from adsorbing and accumulating on the membrane surface through electrostatic repulsion, thereby significantly mitigating membrane fouling. Simultaneously, a moderate electric field strength can also promote interspecies electron transfer (IET) between anaerobic microorganisms, accelerating the degradation of organic matter and methane generation, thereby improving anaerobic digestion efficiency. The DC power supply has an output voltage range of 0.4V to 1.0V, ensuring the uniformity and effectiveness of the electric field on the membrane surface and significantly reducing the membrane fouling rate.

[0064] In the above embodiments, the output voltage range of the DC power supply is preferably 0.4V to 1.0V, but in practical applications, it can be fine-tuned according to the specific wastewater quality, organic load, membrane fouling degree, and target methanogenesis efficiency. For example, for high-concentration organic wastewater, a slightly higher voltage may be needed to enhance the electric field effect and promote organic degradation; while for low-concentration wastewater, a lower voltage is sufficient, saving energy. Furthermore, the application method of the DC power supply can be varied, such as using a pulsed DC electric field or a periodic reverse electric field to further optimize membrane fouling control and microbial activity. A pulsed electric field reduces energy consumption by applying the electric field intermittently, while utilizing the intervals between electric fields to promote the shedding of pollutants from the membrane surface; a periodic reverse electric field can more effectively remove charged pollutants adsorbed on the membrane surface and prevent electrode passivation. These alternatives can be adjusted and optimized based on actual operating data and system performance.

[0065] In some embodiments, the carbonized MIL-53(Fe) micro-electric field material is prepared by pyrolysis of MIL-53(Fe) powder 21 at a nitrogen atmosphere of 750°C to 900°C.

[0066] In this invention, the preparation method of the carbonized MIL-53(Fe) micro-electric field material is crucial. It is obtained by pyrolytic carbonization of MIL-53(Fe) powder under a nitrogen atmosphere at 750℃ to 900℃. The selection of this preparation condition is based on the optimization consideration of the material's conductivity, micro-electric field effect, and structural stability. First, MIL-53(Fe) is a metal-organic framework material containing iron in its framework. During high-temperature pyrolysis, the organic ligands decompose and carbonize, while the iron may be transformed into carbides or nano-iron particles with better conductivity, thus endowing the material with excellent conductivity. Second, pyrolysis under a nitrogen atmosphere can effectively inhibit the oxidation of the material at high temperatures, ensuring the purity and structural integrity of the carbonization products and avoiding the formation of non-conductive impurities such as amorphous carbon or iron oxide. The temperature range of 750℃ to 900℃ has been experimentally optimized. Below 750℃, carbonization may be incomplete, resulting in poor conductivity; above 900℃, the material structure may collapse, reducing the specific surface area and thus affecting its micro-electric field effect and its ability to adhere to microorganisms. This preparation method enables the carbonized MIL-53(Fe) micro-electric field material to not only have good conductivity, but also micro-electric field effect and charge regulation performance, which can actively induce electron transfer between anaerobic microorganisms and significantly improve anaerobic digestion efficiency.

[0067] The carbonized MIL-53(Fe) micro-electric field material is prepared by pyrolysis of MIL-53(Fe) powder at 750℃ to 900℃ in a nitrogen atmosphere, ensuring the material's conductivity and micro-electric field effect. The use of a metal mesh coating improves the stability of the conductive film and avoids the high costs associated with anodic passivation of traditional sacrificial electrode materials.

[0068] In the above embodiments, the preparation method of carbonized MIL-53(Fe) micro-electric field materials can be modified and optimized in various ways. For example, in addition to a nitrogen atmosphere, pyrolysis carbonization can also be carried out under an inert gas atmosphere (such as argon) to further control the morphology and composition of the carbonization products. The heating rate and isothermal time of pyrolysis can also be adjusted to affect the crystallinity, pore structure, and conductivity of the material. For example, a faster heating rate or a longer isothermal time may lead to different degrees of carbonization and material properties. In addition to MIL-53(Fe) powder, other metal-organic frameworks (MOFs) can be explored as precursors, such as MOFs based on other transition metals (such as Co, Ni) or different organic ligands. These MOFs may form carbon-based materials with different micro-electric field effects and electron transport capabilities after pyrolysis. Other dopants (such as sulfur, phosphorus) can also be introduced during the pyrolysis process to further improve the conductivity and catalytic activity of the material.

[0069] In some embodiments, the amount of the carbonized MIL-53(Fe) micro-electric field material 2 added to the electrochemical anaerobic membrane bioreactor 10 is from 0.5 g / L to 2.0 g / L.

[0070] In this invention, the dosage of carbonized MIL-53(Fe) micro-electric field material in an electrochemical anaerobic membrane bioreactor is set to be between 0.5 g / L and 2.0 g / L. This dosage range has been experimentally optimized to balance material cost and the improvement in anaerobic digestion performance. Dosage below 0.5 g / L may result in an insufficient concentration of the micro-electric field material in the anaerobic digestion liquid, failing to create a sufficient micro-electric field effect or provide enough electron transfer sites, thus having a negligible effect on improving anaerobic digestion efficiency. While dosages above 2.0 g / L may further improve performance, they significantly increase material cost, and excessively high concentrations may lead to material agglomeration, affecting its dispersibility and effectiveness, and even increasing the viscosity of the anaerobic digestion liquid, adversely affecting stirring and membrane filtration. Within this dosage range of 0.5 g / L to 2.0 g / L, the carbonized MIL-53(Fe) micro-electric field material can fully utilize its micro-electric field effect and charge regulation performance, effectively promoting electron transfer between anaerobic microorganisms, accelerating the degradation of organic matter and the generation of methane.

[0071] In the above embodiments, the dosage of carbonized MIL-53(Fe) micro-electric field material can be dynamically adjusted according to the actual operating conditions of the anaerobic membrane bioreactor. For example, during the start-up phase or when treating high-concentration organic wastewater, the dosage can be appropriately increased to quickly establish microbial activity and enhance degradation efficiency; while during the stable operation phase or when treating low-concentration wastewater, the dosage can be appropriately reduced to save costs. Furthermore, in addition to direct addition in powder form, it is possible to explore immobilizing the carbonized MIL-53(Fe) micro-electric field material on certain carriers, or preparing it in granular or thin-film form, to improve its dispersibility, recoverability, and long-term stability in the anaerobic digestion liquid. This immobilization or modification method may further optimize the material utilization efficiency and reduce loss.

[0072] In some embodiments, the temperature in the electrochemical anaerobic membrane bioreactor 10 is between 20°C and 40°C.

[0073] In this invention, the temperature in the electrochemical anaerobic membrane bioreactor is set between 20°C and 40°C. This temperature range is suitable for anaerobic microorganisms, especially methanogens, to carry out efficient anaerobic digestion activities. Below 20°C, the metabolic activity of anaerobic microorganisms decreases significantly, leading to a slower rate of organic matter degradation and reduced methanogenesis, thus affecting anaerobic digestion efficiency. Above 40°C, although some thermophilic bacteria may exhibit high activity, the activity of most mesophilic anaerobic microorganisms is inhibited, or even leads to microbial inactivation, thereby compromising reactor stability. Therefore, controlling the temperature between 20°C and 40°C, especially within the mesophilic range (30°C-37°C), maximizes the activity and growth of anaerobic microorganisms, thereby achieving efficient organic matter degradation and methane production.

[0074] In the above embodiments, the operating temperature of the electrochemical anaerobic membrane bioreactor can be adjusted according to the actual application scenario and climatic conditions. For example, in cold regions, additional heating measures may be needed to maintain a temperature above 20°C; while in warm regions, cooling measures may be needed to prevent excessively high temperatures. Furthermore, phased operation within different temperature ranges can be explored; for example, a higher temperature can be used during the initial startup phase to accelerate microbial proliferation, followed by a lower temperature adjustment during the stable operation phase to save energy. Besides constant temperature control, temperature gradient or periodic temperature fluctuation strategies can also be considered to adapt to the temperature responses of different anaerobic microbial communities, thereby optimizing anaerobic digestion efficiency and stability.

[0075] In some embodiments, the hydraulic retention time in the electrochemical anaerobic membrane bioreactor 10 is 6 h to 12 h.

[0076] In this invention, the hydraulic retention time (HRT) in the electrochemical anaerobic membrane bioreactor is set to 6 to 12 hours. HRT is one of the key parameters affecting anaerobic digestion efficiency and reactor stability. A shorter HRT (e.g., less than 6 hours) may result in insufficient wastewater retention time in the reactor, leading to inadequate degradation of organic matter and reduced effluent quality and methanogenesis efficiency. While an excessively long HRT (e.g., more than 12 hours) may improve organic matter removal, it significantly increases reactor volume and operating costs, reduces treatment efficiency, and may even lead to decreased microbial activity. Therefore, controlling the HRT to 6 to 12 hours ensures sufficient retention time for wastewater in the reactor, allowing anaerobic microorganisms to fully degrade organic pollutants while avoiding unnecessary increases in operating costs.

[0077] In the above embodiments, the hydraulic retention time (HRT) can be dynamically adjusted based on the influent water quality (e.g., COD concentration, biodegradability), the target effluent water quality, and the actual operating conditions of the reactor. For example, for high-concentration organic wastewater, the HRT may need to be appropriately extended to ensure sufficient degradation; while for low-concentration wastewater, the HRT can be shortened to improve treatment efficiency. Furthermore, a staged HRT strategy can be adopted, i.e., setting different HRTs in different reactor units to optimize the performance of the entire treatment system. Besides a constant HRT, a variable HRT strategy can be explored, automatically adjusting the influent flow rate based on real-time monitoring data (e.g., effluent COD, methanogenesis) to achieve more precise operational control.

[0078] In some embodiments, the flat sheet film unit of the surface conductive flat sheet film assembly is an organic flat sheet film or a ceramic flat sheet film.

[0079] In this invention, the flat sheet membrane unit of the surface conductive flat sheet membrane assembly can be selected from organic flat sheet membranes or ceramic flat sheet membranes. This choice provides technical flexibility and adaptability, meeting the needs of different wastewater treatment scenarios. Organic flat sheet membranes, such as those made of polyvinylidene fluoride (PVDF) and polyethersulfone (PES), have the advantages of relatively low cost, moderate mechanical strength, and ease of processing and installation. They perform well in treating municipal sewage and general industrial wastewater and are easy to maintain through physical or chemical cleaning. Ceramic flat sheet membranes are known for their excellent chemical stability, high temperature resistance, corrosion resistance, high mechanical strength, and longer service life. Ceramic membranes can withstand more demanding operating conditions, such as wastewater with high concentrations of organic matter, strong acids and alkalis, or containing abrasive particles, and have longer cleaning cycles and stronger antifouling capabilities.

[0080] In the above embodiments, besides organic and ceramic flat sheet membranes, other types of flat sheet membrane materials can be explored as substrates for surface-conductive flat sheet membrane modules. For example, novel composite membranes or nanofiber membranes can be considered, which may have higher porosity, smaller pore size, or better surface hydrophilicity / hydrophobicity, thereby further improving membrane flux and antifouling performance. Furthermore, when coating the metal mesh, different coating methods, such as spraying, impregnation, or electrodeposition, can be tried to optimize the bonding strength and conductivity uniformity between the metal mesh and the membrane surface. For specific applications, membranes with specific functionalized coatings, such as membranes with antibacterial or self-cleaning capabilities, can be selected based on the characteristics of the wastewater to further enhance the performance and stability of the anaerobic membrane bioreactor.

[0081] In some embodiments, the electrochemical anaerobic membrane bioreactor is equipped with a mechanical stirrer or an anaerobic digestion gas circulation pump; the mechanical stirrer stirs the anaerobic digestion liquid at a speed of 20 rpm to 50 rpm; the anaerobic digestion gas circulation pump circulates anaerobic digestion gas at a flow rate of 0.1 L / min to 0.5 L / min to maintain the uniform dispersion of the anaerobic digestion liquid and the carbonized MIL-53(Fe) micro electric field material.

[0082] In this invention, the electrochemical anaerobic membrane bioreactor is equipped with a mechanical stirrer or an anaerobic digester gas circulation pump to ensure uniform dispersion of the anaerobic digestate and the carbonized MIL-53(Fe) micro-electric field material. This stirring mechanism is key to the efficient operation of the anaerobic membrane bioreactor. First, the uniformly dispersed micro-electric field material can maximize contact with anaerobic microorganisms, promoting electron transfer and improving the degradation efficiency of organic matter. Second, the stirring action can effectively reduce membrane surface fouling by shearing the membrane surface, preventing the accumulation of pollutants in the membrane pores and on the membrane surface, thereby maintaining a high membrane flux. The mechanical stirrer stirs the anaerobic digestate at a speed of 20 rpm to 50 rpm. This speed range ensures thorough mixing while avoiding excessive shearing that could damage the microbial flocs and membrane. The anaerobic digester gas circulation pump circulates anaerobic digester gas at a flow rate of 0.1 L / min to 0.5 L / min. The rising movement of the bubbles disturbs the anaerobic digestate, achieving uniform mixing and membrane surface scouring as well.

[0083] In the above embodiments, in addition to mechanical stirrers and anaerobic digestion gas recirculation pumps, other stirring or mixing methods can be explored to adapt to anaerobic membrane bioreactors of different sizes and configurations. For example, jet stirrers, magnetic stirrers, or ultrasonic dispersion devices can be used to achieve more efficient or gentler mixing effects. The rotational speed of the mechanical stirrer (20 rpm to 50 rpm) and the flow rate of the anaerobic digestion gas recirculation pump (0.1 L / min to 0.5 L / min) can be dynamically adjusted according to the viscosity of the anaerobic digestate, sludge concentration, and membrane fouling degree. For example, in the early stages of membrane fouling or at high organic loads, the stirring intensity can be appropriately increased to enhance the membrane surface scouring effect and mass transfer efficiency. In addition, intermittent stirring or pulse stirring can be used to save energy and optimize the mixing effect.

[0084] In some embodiments, the sludge concentration in the electrochemical anaerobic membrane bioreactor 10 is between 6000 mg / L and 12000 mg / L.

[0085] In this invention, the sludge concentration in the electrochemical anaerobic membrane bioreactor is set between 6000 mg / L and 12000 mg / L. Sludge concentration is one of the key indicators of the operating efficiency of the anaerobic membrane bioreactor, directly affecting the organic matter removal rate and methanogenesis. A low sludge concentration (e.g., below 6000 mg / L) may result in insufficient active microorganisms in the reactor, hindering the effective degradation of high-concentration organic matter, thus reducing treatment efficiency and effluent quality. Conversely, an excessively high sludge concentration (e.g., above 12000 mg / L), while potentially increasing degradation capacity, significantly increases the viscosity of the anaerobic digester, leading to increased mass transfer resistance, affecting stirring efficiency and membrane flux, and possibly even exacerbating membrane fouling. Therefore, controlling the sludge concentration between 6000 mg / L and 12000 mg / L ensures a sufficient number of active microorganisms in the reactor, thereby achieving efficient organic matter degradation and methane production, while avoiding operational problems caused by excessively high sludge concentrations.

[0086] In the above embodiments, the sludge concentration of the electrochemical anaerobic membrane bioreactor can be dynamically adjusted according to the influent water quality, organic load, and target treatment efficiency. For example, when treating high-concentration organic wastewater or requiring rapid start-up, the sludge concentration can be appropriately increased to enhance degradation capacity; while during stable operation or when treating low-concentration wastewater, a lower sludge concentration can be maintained to save operating costs. Furthermore, the sludge concentration and activity within the reactor can be precisely controlled and optimized through sludge recirculation, the addition of exogenous sludge, or the cultivation of specific microbial communities. Sludge concentration monitoring can be performed using online sensors or periodic sampling and analysis to ensure it remains within the optimal operating range.

[0087] Figure 2This is a flowchart illustrating a method for preparing a carbonized MIL-53(Fe) micro-electric field material according to an embodiment of this application. The preparation method comprises two main stages: the synthesis of MIL-53(Fe) powder and the pyrolysis carbonization of the MIL-53(Fe) powder.

[0088] In the MIL-53(Fe) powder synthesis stage, terephthalic acid and ferric chloride hexahydrate were first added to N,N dimethylformamide (DMF) in a specific ratio to prepare a solution. This ratio is crucial for the formation of the MIL-53(Fe) crystal structure. The solution was then transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene (PTFE) and heated in a constant temperature oven at 160°C for 6 hours. The autoclave and PTFE liner ensured that the reaction was carried out under closed, high-temperature, and high-pressure conditions, which is beneficial for the growth of MIL-53(Fe) crystals. After heating, the mixture was naturally cooled to 25°C. Unreacted substances and impurities were removed by repeated steps of centrifugation, washing with anhydrous ethanol, and ultrasonic dispersion. Finally, the powder was dried in a vacuum oven at 80°C for 8 hours to obtain pure MIL-53(Fe) powder.

[0089] In the pyrolysis and carbonization stage of MIL-53(Fe) powder, the powder was placed in a quartz boat in a tube furnace, and high-purity nitrogen gas was introduced at a flow rate of 100 mL / min. The powder was heated to 750°C to 900°C at a heating rate of 5°C / min and held at this temperature for 2 hours. The nitrogen atmosphere ensured that the carbonization process took place in an inert environment, preventing oxidation. Precise control of the heating rate and the holding temperature ensured that the MIL-53(Fe) framework was fully carbonized, forming a carbonized MIL-53(Fe) micro-electric field material with excellent conductivity and micro-electric field effect. Finally, the powder was cooled to 25°C in the furnace and removed to obtain the target product.

[0090] In the above embodiments, the preparation method of carbonized MIL-53(Fe) micro-electric field material can be modified and optimized in various ways. For example, the mass ratio of terephthalic acid, ferric chloride hexahydrate, and N,N-dimethylformamide (DMF) can be fine-tuned to optimize the yield and crystal morphology of MIL-53(Fe) powder. The temperature and time of hydrothermal synthesis can also be adjusted according to actual needs, for example, shortening the reaction time to improve production efficiency, or adjusting the temperature to control crystal size. In addition to anhydrous ethanol, other organic solvents (such as methanol, acetone) or water can be tried as washing solvents for MIL-53(Fe) powder to optimize washing effect and cost. In the pyrolysis carbonization stage, the nitrogen flow rate, heating rate, and isothermal time can also be optimized to precisely control the degree of carbonization and the pore structure of the material. For example, a faster heating rate may result in a smaller grain size, while a longer isothermal time may result in a higher degree of carbonization. Furthermore, in addition to tube furnaces, muffle furnaces or other types of pyrolysis equipment can be used for carbonization.

[0091] In some embodiments, the amount of terephthalic acid is 1.328 g, the amount of ferric chloride hexahydrate is 2.164 g, and the amount of N,N-dimethylformamide (DMF) is 80 mL.

[0092] In this invention, the amounts of key components in the preparation method of carbonized MIL-53(Fe) micro-electric field material are precisely defined: 1.328 g of terephthalic acid, 2.164 g of ferric chloride hexahydrate, and 80 mL of N,N dimethylformamide (DMF). These precise proportions are fundamental to the successful synthesis of MIL-53(Fe) powder and the attainment of an ideal crystal structure and yield. Terephthalic acid serves as the organic ligand, ferric chloride hexahydrate provides the metal center, and DMF acts as the solvent and reaction medium. These components self-assemble under hydrothermal synthesis conditions (160°C, 6 h) to form MIL-53(Fe) crystals with a regular channel structure. Precise control of the component amounts ensures optimal stoichiometry between the reactants, thereby maximizing the yield of MIL-53(Fe) and guaranteeing the purity and crystallinity of the product. Any adjustment that deviates from these proportions may lead to a decrease in yield, irregular crystal morphology, or the generation of byproducts, which in turn may affect the conductivity and micro-electric field effect of the subsequent carbonized MIL-53(Fe) micro-electric field material 2.

[0093] In the above embodiments, the amounts of terephthalic acid, ferric chloride hexahydrate, and N,N-dimethylformamide (DMF) can be fine-tuned according to the target yield, crystal size, and morphology. For example, while maintaining a specific molar ratio, the amounts of all components can be increased or decreased proportionally to prepare larger or smaller batches of MIL-53(Fe) powder. Furthermore, in addition to DMF, other solvents, such as water, ethanol, or other organic amines, can be explored as reaction media, which may affect the crystallization process of MIL-53(Fe) and the morphology of the final product. In industrial production, to improve efficiency and reduce costs, these parameters can be further optimized, for example, by using a continuous flow reactor instead of an autoclave for the synthesis of MIL-53(Fe).

[0094] In some embodiments, the solution is heated at 160°C for 6 hours.

[0095] In this invention, the MIL-53(Fe) powder synthesis step in the method for preparing carbonized MIL-53(Fe) micro-electric field materials involves heating the solution in a constant-temperature oven at 160°C for 6 hours. This temperature and time parameter are key control conditions for the hydrothermal synthesis of MIL-53(Fe) crystals. The temperature of 160°C provides sufficient energy to promote the dissolution and reaction of terephthalic acid and ferric chloride hexahydrate in DMF solvent, accelerating the nucleation and growth of MIL-53(Fe) crystals. Heating for 6 hours ensures sufficient time for the reaction to proceed completely, resulting in high-yield and highly crystalline MIL-53(Fe) powder. If the heating temperature is too low or the time is too short, the reaction may be incomplete, resulting in products containing more impurities or poor crystallinity, affecting the performance of subsequent carbonized products. Conversely, if the temperature is too high or the time is too long, excessive crystal growth, irregular morphology, or even decomposition may occur, which is also detrimental to obtaining the target product. Therefore, the combination of 160℃ and 6h is optimized to ensure the efficient synthesis of MIL-53(Fe) and to provide a high-quality precursor for the subsequent pyrolysis carbonization step.

[0096] In the above embodiments, the heating temperature and time during the synthesis of MIL-53(Fe) powder can be fine-tuned according to specific needs. For example, to obtain MIL-53(Fe) crystals of different sizes or morphologies, the heating temperature can be adjusted or the heating time extended / shortened. In some cases, to accelerate the reaction process, short-time heating at a temperature slightly above 160°C can be attempted, but this may require a trade-off between product purity and crystallinity. Furthermore, the heating method for hydrothermal synthesis can be modified in various ways, such as using microwave heating or electromagnetic heating, to achieve faster and more uniform heating, thereby improving synthesis efficiency.

[0097] Figure 3 The diagram shows the transmembrane pressure difference changes of an electrochemical anaerobic membrane bioreactor under different electric field application methods, and the comparison diagram shows the changes in membrane electrodes after the operation cycle, as provided in an embodiment of this application. The processing procedure described in this embodiment includes the following steps:

[0098] (1) Simulated wastewater with COD of 600 mg / L was introduced into an electrochemical anaerobic membrane bioreactor, and the reactor temperature was controlled at 37℃, the reactor sludge concentration was 8000 mg / L, and the hydraulic retention time was maintained at 10 h.

[0099] (2) Four control reactors were set up respectively. In reactor R1, a hollow flat ceramic membrane module without electrode mesh was placed and not connected to a DC power supply. In reactor R2, a surface conductive flat membrane module covered with stainless steel mesh was placed and connected to the negative terminal of a DC power supply (i.e., the conductive membrane was used as the cathode only). In reactor R3, a surface conductive flat membrane covered with titanium mesh and a surface conductive flat membrane covered with stainless steel mesh were placed alternately and connected to the positive and negative terminals of a DC power supply respectively (i.e., the conductive membrane was used as the anode and cathode alternately). In reactor R4, a surface conductive flat membrane module covered with titanium mesh was connected to the positive terminal of a DC power supply (i.e., the conductive membrane was used as the anode only).

[0100] (3) The DC power supply of the four reactors is started at the same time, and the voltage is adjusted to 0.8V.

[0101] (4) The four reactors were run continuously for 35 days. At the same time, the changes in transmembrane pressure difference of different reactors were continuously monitored, and the morphological changes of membrane electrodes before and after the reaction were recorded.

[0102] Experimental results:

[0103] 1. For example Figure 3 As shown in Figure a, under constant flux operating conditions, the change in transmembrane pressure difference (TMP) over time reflects the membrane fouling characteristics of the anaerobic membrane bioreactor. Clearly, in reactor R3, where conductive membranes alternately act as anodes and cathodes, the fouling levels of both membranes are significantly lower than in the control reactor R1. Meanwhile, in reactor R2, where the conductive membrane acts only as the cathode, membrane fouling is less severe than in the control reactor R1, but the degree of reduction is significantly less than in R3. In reactor R4, where the conductive membrane acts only as the anode, membrane fouling is initially more severe than in R1, consistent with the theory of anodic electrostatic attraction. However, over time, a tendency for fouling to increase is observed in the later stages of membrane filtration. This may be because anodic oxidation on the anode surface gradually oxidizes the fouling layer, thus mitigating membrane fouling. Overall, the membrane fouling rate in reactor R3, where the metal mesh-coated conductive membranes alternately act as anodes and cathodes, is significantly lower than in reactors R2 and R4, where only the conductive membrane is used as a cathode or anode.

[0104] 2. For example Figure 3 As shown in b, the metal mesh covered by the conductive film remained largely unchanged and undamaged after the entire experimental cycle, demonstrating that the conductive film prepared by this method has superior stability compared to traditional sacrificial electrode materials.

[0105] Therefore, the above results indicate that a good and stable electric field is formed in the electrochemical anaerobic membrane bioreactor with the conductive film on the surface of the metal mesh alternating as the anode and cathode, while the membrane fouling problem is effectively alleviated. This method contributes to the stable operation of the anaerobic membrane bioreactor.

[0106] Figure 4This is a graph showing the changes in COD concentration and methane production in an anaerobic membrane bioreactor after adding different micro-electric field materials, provided in one embodiment of this application. The treatment process described in this embodiment includes the following steps:

[0107] (1) Simulated wastewater with COD of 600, 1300 and 2000 mg / L was introduced into an anaerobic membrane bioreactor. The reactor temperature was controlled at 37℃, the reactor sludge concentration was 8000 mg / L, and the hydraulic retention time was maintained at 10h.

[0108] (2) The carbonization precursor (MIL-53(Fe)) was prepared according to the material preparation method described in the invention. Then, it was carbonized at temperatures of 500, 800, and 1050 °C to obtain three different micro-electric field materials, and their effects on the performance of the anaerobic membrane bioreactor were tested.

[0109] (3) Four control reactors were set up respectively. No micro electric field material was added to reactor R1; CMIL-500 micro electric field material carbonized at 500℃ was added to reactor R2; CMIL-800 micro electric field material carbonized at 800℃ was added to reactor R3; and CMIL-1050 micro electric field material carbonized at 1050℃ was added to reactor R4.

[0110] (3) The dosage of micro electric field material in all four reactors was 1 g / L.

[0111] (4) The four reactors were operated continuously for 90 days, and the COD concentration and methane production of different reactors were continuously monitored.

[0112] Experimental results:

[0113] 1. For example Figure 4 As shown in Figure a, the COD concentration of the control reactor R1 was consistently higher than that of the reactor with the added micro-electric field material, and the gap gradually widened as the organic load increased. When the influent COD concentration increased to 2000 mg / L, the effluent COD concentration of the control reactor R1 was 1.8, 2.3, and 1.9 times that of reactors R2, R3, and R4, respectively, demonstrating that the addition of different micro-electric field materials can improve the degree of hydrolysis of organic matter. Among them, the reactor with CMIL-800 added achieved a COD removal rate of 96.9%, significantly higher than the reactors with other materials. This proves that too low a carbonization temperature cannot form a good micro-electric field, while too high a temperature will destroy the effect of the micro-electric field. A suitable carbonization temperature (800℃) can form a good micro-electric field material, which can effectively improve the performance of anaerobic membrane bioreactors.

[0114] 2. For example Figure 4As shown in b, methane production gradually increased with increasing organic substrate concentration. By day 91 of reactor operation, the final net methane production of the four reactor groups were 226.3, 256.6, 332.8, and 285.8 mL / g COD, respectively. In contrast, the addition of CMIL-800 effectively improved the net methane production of the anaerobic membrane bioreactor, demonstrating that micro-electric field materials can promote electron transfer between anaerobic microorganisms. Furthermore, CMIL-800 carbonized at 800℃ can more effectively regulate the metabolic imbalance between acetogenic and methanogenic bacteria, thereby effectively improving the anaerobic digestion performance of the reactor.

[0115] 3. In addition, after the operating cycle ended, the anaerobic membrane bioreactor was shut down for 6 months and then restarted, and its COD concentration and methanogenesis performance were evaluated. Figure 4 As shown, the reactor with added CMIL-800 recovered rapidly, exhibiting excellent COD removal rates and a net methane yield exceeding 290 mL / g COD after only 10 days of operation. Conversely, even after 22 days of acclimatization, the performance of all other reactors was essentially lost. These results demonstrate that CMIL-800 carbonized at 800℃ can significantly stabilize the performance of anaerobic microorganisms and rapidly activate their metabolic functions after a prolonged dormancy period.

[0116] Therefore, the above results indicate that the micro-electric field material carbonized at a suitable temperature effectively promotes the anaerobic digestion performance of the anaerobic membrane bioreactor. Furthermore, this micro-electric field material possesses sufficient stability to maintain its promoting effect on anaerobic digestion performance over a long period.

[0117] Finally, it should be noted that the above embodiments are merely illustrative examples of the present invention and should not be considered as limitations on the method. The scope of protection of the present invention should be defined as the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for enhancing the performance of an anaerobic membrane bioreactor by coupling an internal electron circulation with an external electric field, characterized in that, include: S1. Prepare a surface conductive flat sheet film assembly, wherein the surface conductive flat sheet film assembly is formed by alternately covering the surface of a flat sheet film unit with stainless steel mesh and titanium mesh; S2. Construct an electrochemical anaerobic membrane bioreactor, wherein the surface conductive flat sheet membrane assembly serves as the cathode and anode of the electrochemical anaerobic membrane bioreactor and is connected to a DC power supply via wires; S3. Prepare carbonized MIL-53(Fe) micro-electric field material, wherein the carbonized MIL-53(Fe) micro-electric field material is a powder with a particle size range of 1 micrometer to 10 micrometers; S4. Disperse the carbonized MIL-53(Fe) micro electric field material in powder form in the anaerobic digestion liquid of the electrochemical anaerobic membrane bioreactor; S5. The anaerobic digestion liquid is uniformly mixed with the carbonized MIL-53(Fe) micro-electric field material by mechanical stirring or anaerobic digestion gas stirring.

2. The method according to claim 1, characterized in that, The stainless steel mesh and titanium mesh have a wire diameter of 0.02 mm to 0.03 mm and a mesh size of 0.2 mm to 0.3 mm.

3. The method according to claim 1, characterized in that, The output voltage range of the DC power supply is 0.4V to 1.0V.

4. The method according to claim 1, characterized in that, The carbonized MIL-53(Fe) micro-electric field material is prepared by pyrolysis of MIL-53(Fe) under a nitrogen atmosphere at 750°C to 900°C.

5. The method according to claim 1, characterized in that, The amount of the carbonized MIL-53(Fe) micro-electric field material added to the electrochemical anaerobic membrane bioreactor is from 0.5 g / L to 2.0 g / L.

6. The method according to claim 1, characterized in that, The temperature in the electrochemical anaerobic membrane bioreactor is between 20°C and 40°C.

7. The method according to claim 1, characterized in that, The hydraulic retention time in the electrochemical anaerobic membrane bioreactor is 6 to 12 hours.

8. The method according to claim 1, characterized in that, The flat sheet membrane unit of the surface conductive flat sheet membrane assembly is an organic flat sheet membrane or a ceramic flat sheet membrane.

9. The method according to claim 1, characterized in that, The electrochemical anaerobic membrane bioreactor is equipped with a mechanical stirrer or an anaerobic digestion gas circulation pump. The mechanical stirrer stirs the anaerobic digestion liquid at a speed of 20 rpm to 50 rpm; The anaerobic digestion gas circulation pump circulates the anaerobic digestion gas at a flow rate of 0.1 L / min to 0.5 L / min to maintain the uniform dispersion of the anaerobic digestion liquid and the carbonized MIL-53(Fe) micro electric field material.

10. The method according to claim 1, characterized in that, The sludge concentration in the electrochemical anaerobic membrane bioreactor is between 6000 mg / L and 12000 mg / L.

11. A method for preparing a carbonized MIL-53(Fe) micro-electric field material, characterized in that, include: Terephthalic acid and ferric chloride hexahydrate are added to N,N-dimethylformamide (DMF) to prepare a solution, wherein the mass ratio of terephthalic acid, ferric chloride hexahydrate and N,N-dimethylformamide (DMF) is within a specific range; The solution was transferred to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and the autoclave was placed in a constant temperature oven at 160 °C and heated for 6 hours. Remove the autoclave from the oven and allow it to cool naturally to 25°C. Transfer the reaction solution to a centrifuge tube and centrifuge at 8000 rpm for 10 minutes. Discard the supernatant, add 20 mL of anhydrous ethanol, and sonicate for 5 minutes. Repeat the centrifugation and washing steps three times. Finally, dry the solution in a vacuum oven at 80°C for 8 hours to obtain MIL-53(Fe) powder. The MIL-53(Fe) powder was placed in a quartz boat in a tube furnace, and high-purity nitrogen was introduced at a flow rate of 100 mL / min. The temperature was increased to 750°C to 900°C at a heating rate of 5°C / min and held at this temperature for 2 hours. Then, the furnace was cooled to 25°C, and the carbonized MIL-53(Fe) micro-electric field material was obtained.

12. The preparation method according to claim 12, characterized in that, The amount of terephthalic acid is 1.328 g, the amount of ferric chloride hexahydrate is 2.164 g, and the amount of N,N-dimethylformamide (DMF) is 80 mL.

13. The preparation method according to claim 12, wherein the solution is heated at 160°C for 6 hours.

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