An MFC-A / O / A coupled wastewater treatment system, method, and application

Abstract

This invention relates to an MFC-A / O / A coupled wastewater treatment system, method, and application, comprising an A / O / A device and an MFC device connected in series. The A / O / A device includes an influent tank, an anaerobic tank, an aerobic tank, an anoxic tank, and a sedimentation tank connected in sequence. The MFC device includes: an anode disposed in the anaerobic tank; a cathode disposed in the aerobic tank; a resistor disposed outside the A / O / A device and connected to the anode and cathode; and a proton exchange membrane disposed between the anaerobic tank and the aerobic tank. Compared with the prior art, this invention uses enriched bacteria obtained from anaerobic and aerobic enrichment as the inoculum source for the MFC-A / O / A coupled system, which accelerates the system startup, shortens the startup time, and significantly improves the system's power generation performance.

Description

Technical Field

[0001] This invention relates to the fields of microbial fuel cell and wastewater treatment technology, and in particular to an MFC-A / O / A coupled wastewater treatment system, method and application. Background Technology

[0002] With accelerated urbanization and increasingly stringent environmental protection requirements, the energy consumption of wastewater treatment plants is becoming increasingly prominent. Traditional activated sludge processes and their variants, such as the anaerobic-aerobic (A / O) and anaerobic-anoxic-aerobic (A / A / O) processes, while effectively removing organic matter and nutrients from wastewater, suffer from high energy consumption (accounting for 1-3% of global electricity consumption), large greenhouse gas emissions, and high costs for residual sludge treatment. These processes treat wastewater primarily as a "treatment object" rather than a "resource carrier," making them unsustainable in the context of carbon neutrality. Against this backdrop, microbial fuel cell (MFC) technology, with its unique advantage of utilizing electrogenic bacteria to oxidize organic matter and simultaneously recover electricity, is considered a transformative solution. Theoretically, this technology could transform wastewater treatment plants from energy consumers into energy producers, aligning with the principles of a circular economy. However, the application of MFCs alone faces challenges such as low power output, high construction costs, and difficulty in achieving effluent quality standards. Therefore, coupling MFCs with traditional wastewater treatment processes to construct synergistic composite systems has become an important approach to achieving a balance between energy recovery and efficient treatment.

[0003] In the prior art, Chinese patent CN120637516A discloses a carbon-based composite anode material for microbial fuel cells. This material is prepared by copolymerizing aniline monomers with dopamine hydrochloride under acidic conditions to form a polyaniline / dopamine modifier, which is then modified onto the surface of a carbon felt electrode using cyclic voltammetry to obtain a PANI-DA / CF anode. Finally, flower-shaped Fe2O3 nanoparticles are loaded through hydrothermal synthesis and electrochemical deposition to obtain the Fe2O3 / PANI-DA / CF composite anode. This anode exhibits high specific surface area, excellent conductivity, and biocompatibility, demonstrating superior performance in microbial fuel cell applications, with a maximum power density of 4594±97 mW / m³. 2 Compared to unmodified carbon felt anodes, the degradation rate of phenol reached 99.4% after 96 hours, with an improvement of 83.1%, and long-term stable operation. However, this preparation process involves multiple chemical reactions and electrochemical deposition, making the process complex and requiring sophisticated equipment, which is not conducive to large-scale application. At the same time, Fe2O3 nanoparticles pose a risk of metal leaching, which may cause secondary pollution. Their long-term safety and stability in real wastewater environments still need to be verified.

[0004] Chinese patent CN204281413U proposes a dual-chamber microbial fuel cell wastewater treatment system combined with an A / O process. This system separates the anode and cathode chambers via a proton exchange membrane. The anode chamber houses the main anode and auxiliary anode packing, while the cathode chamber has an aeration device at its bottom and an internal cathode. A variable resistance box connects the cathode and anode to form a loop. The system utilizes multiple peristaltic pumps and a sedimentation tank to create a circulating flow, enabling continuous treatment of wastewater through denitrification in the anode chamber, nitrification in the cathode chamber, and organic matter degradation, while simultaneously generating electricity. This design effectively combines the A / O process with microbial fuel cell technology, utilizing a biological cathode to reduce costs. Optimization of operation is achieved by adjusting the hydraulic retention time and internal circulation ratio, resulting in both efficient nitrogen, phosphorus, and carbon removal and stable power generation. However, the system lacks an independent anoxic section, making it difficult to achieve sufficient denitrification, thus failing to meet high-standard emission requirements for nitrogen removal.

[0005] Chinese patent CN117886433A discloses an MFC-A / A / O coupling system and method for treating high-salt pharmaceutical wastewater. This system integrates a microbial fuel cell into the A... 2 The / O process includes an influent tank, an anaerobic tank, an anoxic tank, an aerobic tank, and a sedimentation tank connected in sequence. The MFC device includes a first electrode in the anaerobic tank, a second electrode in the anoxic tank, an external resistor connecting the two electrodes, and a proton exchange membrane between the two tanks. The first electrode enriches electrogenic bacteria to decompose organic matter and generate electrons and protons. Electrons are transferred to the second electrode via an external circuit, and protons pass through the exchange membrane into the anoxic tank, achieving simultaneous pollutant degradation and electrical energy output. This method, through three stages of sludge acclimation, pre-start-up, and continuous operation, introduces Shewanella suspension as an inoculum source, significantly shortening start-up time, increasing output voltage and power density, and enhancing total nitrogen removal. However, the system suffers from carbon source imbalance; excessive consumption of carbon source by polyphosphate-accumulating bacteria in the anaerobic section leads to insufficient electron donors for denitrification in the anoxic section, affecting total nitrogen removal and power generation stability. Low electron transfer efficiency and other factors limit its practical application. Summary of the Invention

[0006] To address at least one of the following shortcomings of traditional wastewater treatment processes—high energy consumption, poor performance of MFC alone, and inadequate denitrification, carbon source imbalance, complex electrode preparation leading to secondary pollution, long system start-up time, and low power generation and pollutant removal efficiency—this invention provides an MFC-A / O / A coupled wastewater treatment system, method, and application that significantly improves the system's power generation performance and denitrification and carbon removal capabilities. The invention first anaerobically and aerobically acclimates the microorganisms in the screened activated sludge; then, it pre-treats the electrodes; finally, it places the enriched anaerobic microorganisms and anolyte in the anode chamber of a microbial fuel cell reactor, and then adds the enriched aerobic microbial catholyte to the cathode chamber, resulting in a highly efficient power-generating microbial fuel cell.

[0007] The objective of this invention can be achieved through the following technical solutions: This invention provides an MFC-A / O / A coupled wastewater treatment system, characterized in that it includes a connected A / O / A device and an MFC device; The A / O / A device includes an inlet tank, an anaerobic tank, an aerobic tank, an anoxic tank, and a sedimentation tank connected in sequence. The MFC device includes: an anode disposed in the anaerobic tank; a cathode disposed in the aerobic tank; a resistor disposed outside the A / O / A device and connected to the anode and cathode; and a proton exchange membrane disposed between the anaerobic tank and the aerobic tank to separate them. Electrogenic bacteria are enriched on the anode, which degrade organic matter in the wastewater to produce electrons and protons. Electrons are transferred to the cathode via an external circuit, and protons pass through the proton exchange membrane into the aerobic tank.

[0008] Furthermore, the resistor is connected to the anode and the cathode respectively via titanium wire.

[0009] Furthermore, electric stirrers are installed in both the anaerobic tank and the anoxic tank.

[0010] Furthermore, the aerobic tank is equipped with several aeration devices.

[0011] Furthermore, the anaerobic tank, aerobic tank, anoxic tank, and sedimentation tank are connected in sequence by overflow.

[0012] Furthermore, the anode and cathode are either carbon fiber brushes or carbon fiber brushes prepared through a pretreatment activation process; The pretreatment activation process is any one or a combination of strong acid immersion activation process, strong alkali immersion activation process, or high temperature calcination activation process.

[0013] Furthermore, the strong acid immersion activation process involves immersing the carbon fiber brush in a 0.1~0.5 mol / L HCl solution for 12~24 h, rinsing it with deionized water until neutral, and drying it at 100~105℃ for 1~2 h. The strong alkali soaking and activation process involves brushing the carbon fiber into a 0.5~1.0 mol / L NaOH solution, soaking it for 12~24 h, rinsing it with deionized water until neutral, and drying it at 100~105 ℃ for 1~2 h. The high-temperature calcination activation process involves calcining the carbon fiber brush in a muffle furnace at 400-450°C for 15-30 minutes, and then removing it and cooling it to room temperature.

[0014] Furthermore, the anaerobic tank and the aerobic tank have the same volume, and the volume ratio of the anaerobic tank or aerobic tank to the anoxic tank is 1:(2~3).

[0015] The second objective of this invention is to provide an MFC-A / O / A coupled wastewater treatment method, which employs the MFC-A / O / A coupled system described above and includes the following steps: S1. After sedimentation, concentration and impurity removal, activated sludge is anaerobic stirred culture and aerated culture using simulated wastewater to obtain anaerobic sludge and aerobic sludge. Then, wastewater containing anaerobic sludge is connected to the anaerobic tank and the anoxic tank, and wastewater containing aerobic sludge is connected to the aerobic tank to complete the system inoculation. S2. The anaerobic microorganisms prepared in S1 were placed in an anaerobic basic medium containing phenazine-1-carboxylic acid for enrichment culture to obtain enriched mixed electrogenic bacteria. The aerobic microorganisms prepared in S1 were placed in a medium with ammonia nitrogen as the only nitrogen source and no or only a very small amount of organic carbon added for continuous aeration enrichment culture to obtain enriched mixed nitrifying bacteria. S3. Add the enriched mixed electrogenic bacteria prepared in S2 and the prepared simulated wastewater to the anaerobic tank, and add the enriched mixed nitrifying bacteria prepared in S2 and the prepared simulated wastewater to the aerobic tank; use a 30℃ constant temperature sequential batch operation of the MFC-A / O / A coupled system with a cycle of 6-8 days, and after 3 cycles of stable operation; start wastewater treatment and MFC operation by continuously feeding wastewater into the anaerobic tank.

[0016] Furthermore, during the enrichment process of aerobic dominant bacteria, the concentration of ammonia nitrogen in the culture medium was gradually increased, and the population dominance of nitrifying bacteria was further screened and enhanced through the principle of pollutant concentration gradient. The microbial strains in the anaerobic tank were electroactive bacteria. Proteobacteria or Firmicutes One or more combinations of these, while the microbial species in the aerobic and anoxic ponds enrich the symbiotic communities of nitrification / denitrification. Proteobacteria or Bacteroidetes One or more combinations thereof.

[0017] A third objective of this invention is the application of the MFC-A / O / A coupled wastewater treatment system described above, used for providing electrical energy and / or treating wastewater. The wastewater quality indicators in this application scenario are: Chemical Oxygen Demand (COD) concentration of 200 mg / L to 8000 mg / L, Ammonia Nitrogen (NH3-N) concentration of 10 mg / L to 800 mg / L, and Total Phosphorus (TP) concentration of 2 mg / L to 150 mg / L.

[0018] Compared with the prior art, the present invention has the following advantages: (1) The present invention uses the enriched strains obtained by anaerobic enrichment and aerobic enrichment as the inoculum source of the MFC-A / O / A coupling system, which accelerates the start-up of the system, shortens the start-up time, and significantly improves the power generation performance of the system.

[0019] (2) The present invention uses carbon fiber brushes as anode and cathode materials and microbial cathodes instead of chemical cathodes, which significantly reduces process costs and has practical application value.

[0020] (3) The overflow connection method of the present invention adopts the AOA process, which is conducive to achieving full denitrification, ensuring the removal effect of pollutants C, N, P in wastewater, and ensuring the reasonable allocation of carbon source. At the same time, the use of proton exchange membrane enables protons in the anaerobic tank to selectively and rapidly pass into the aerobic tank, thereby improving the power generation performance. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system of the present invention.

[0022] Figure 2 This is a flowchart illustrating the method of the present invention.

[0023] The numbers in the diagram indicate: 1-Inlet tank; 2-Anaerobic tank; 3-Aerobic tank; 4-Anoxic tank; 5-Sedimentation tank; 6-Inlet pump; 7-Electric stirrer; 9-Resistor; 10-Anode; 11-Cathode; 12-Aeration element; 14-Proton exchange membrane; 15-Voltage data acquisition system; 16-Control host computer. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0025] The following is in conjunction with the appendix Figure 1 The present invention will be described in detail below with specific embodiments. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0026] In the following embodiments, the activated sludge is derived from the secondary sedimentation tank of a chemical and pharmaceutical company's wastewater treatment plant.

[0027] The preservation method for the enriched bacterial strains was as follows: 0.75 mL of bacterial solution was added to 0.25 mL of 60% glycerol and mixed thoroughly to obtain a mixture; the mixture was then placed at room temperature for 30 minutes and transferred to an ultra-low temperature freezer for cryopreservation. The anaerobic tank microbial strains were electroactive bacteria. Proteobacteria or FirmicutesOne or more combinations of these, while the microbial species in the aerobic and anoxic ponds enrich the symbiotic communities of nitrification / denitrification. Proteobacteria or Bacteroidetes One or more combinations thereof.

[0028] In the following embodiments, chemical oxygen demand (COD) was measured using rapid digestion spectrophotometry (HJ399-2007); ammonia nitrogen (NH3-N) was measured using Nessler's reagent spectrophotometry (HJ535-2009); total nitrogen (TN) was measured using alkaline potassium persulfate digestion ultraviolet spectrophotometry (HJ636-2012); the MFC-A / O / A coupling system was connected to the LANBTS battery testing system (acquisition progress 5 min; voltage range 0-5V), and voltage data were recorded.

[0029] Example 1 This embodiment provides an MFC-A / O / A coupling system for microbial anodes and cathodes, the structure of which can be found in [reference needed]. Figure 1 As shown, it includes an A / O / A device and an MFC device connected to the A / O / A device; The A / O / A device comprises an inlet tank 1, an anaerobic tank 2, an aerobic tank 3, an anoxic tank 4, and a sedimentation tank 5, connected in sequence. The volumes of the anaerobic tank 2, aerobic tank 3, and anoxic tank 4 are 2L, 2L, and 6L, respectively, with a volume ratio of 1:1:3. An inlet pump 6 is installed between the inlet tank 1 and the anaerobic tank 2. Enriched mixed electrogenic bacteria and prepared simulated wastewater are added to the anaerobic tank, enriched mixed nitrifying bacteria and prepared simulated wastewater are added to the aerobic tank, and cultured anaerobic sludge and prepared simulated wastewater are added to the anoxic tank.

[0030] The MFC device includes an anode 10 located in the anaerobic tank 2, a cathode 11 located in the aerobic tank 3, a resistor 9 located outside the A / O / A device and connecting the anode 10 and cathode 11, and a proton exchange membrane located between the anaerobic tank 2 and the aerobic tank 3 to separate them. The anode 10 and cathode 11 are connected by titanium wire, and a 1000Ω resistor 9 is connected externally to the titanium wire. A voltage data acquisition system 15, i.e., the LANBTS battery testing system, is then connected to the anode 10 and cathode 11 via the titanium wire, and the voltage is acquired by a control computer 16. Electric stirrers 7 are installed in both the anaerobic tank 2 and the anoxic tank 4. Several aeration elements 12 are installed in the aerobic tank 3.

[0031] In this embodiment, both the cathode and anode materials are carbon fiber brushes. Before use, the brushes are soaked in 0.1 mol / L HCl solution for 24 hours, rinsed with deionized water, and then soaked in 1.0 mol / L NaOH solution for another 24 hours. After being removed, the brushes are rinsed until neutral, dried at 105°C for 2 hours, and finally calcined in a muffle furnace at 450°C for 30 minutes to improve the hydrophilicity of the carbon fiber brushes.

[0032] In this embodiment, the proton exchange membrane is a proton exchange membrane (CMI-7000 (20 cm × 16 cm, CEM, Membranes International Inc, US). Before use, the proton exchange membrane (CMI-7000 (20 cm × 16 cm, CEM, Membranes International Inc, US) is boiled in hydrogen peroxide and then soaked in a 5 wt% sodium chloride solution.

[0033] During wastewater treatment, a 30℃ constant-temperature sequential batch MFC-A / O / A coupled system was used with a cycle of 7 days. After three cycles of stable operation, biofilm formation was achieved in anaerobic tank 2 and aerobic tank 3. Simulated wastewater was continuously fed into anaerobic tank 2 at an influent flow rate of 10.42 m³ / min, with an average hydraulic retention time of 16 h. The dissolved oxygen concentration in the anaerobic tank was controlled below 0.2 mg / L, in the anoxic tank below 0.5 mg / L, and in the aerobic tank below 2-5 mg / L. The operating pH was 7.5, and the electric stirrer was maintained at 70 rpm / min.

[0034] In this embodiment, the initial influent simulated wastewater in the influent tank includes the following components at the following concentrations: 320 mg / L sodium acetate, 8.8 mg / L potassium dihydrogen phosphate, 38 mg / L ammonium chloride, 0.13 g / L potassium chloride, 6 mL / L vitamin solution, and 15 mL / L trace element solution, with deionized water as the solvent. The simulated wastewater has a chemical oxygen demand (COD) concentration of 200 mg / L, an ammonia nitrogen (NH3-N) concentration of 10 mg / L, and a total phosphorus (TP) concentration of 2 mg / L. Samples are taken every 72 hours to measure the effluent concentration.

[0035] Example 2 This embodiment provides a method for treating simulated high-concentration wastewater using a microbial anode-cathode MFC-A / O / A coupling system, which is the same as the method in Embodiment 1. The difference from Embodiment 1 is that the influent parameters for the simulated high-concentration wastewater are: chemical oxygen demand (COD) concentration of 8000 mg / L, ammonia nitrogen (NH3-N) concentration of 800 mg / L, and TP concentration of 150 mg / L. Samples are taken every 72 hours to measure the effluent concentration.

[0036] Example 3 This embodiment uses the same method as Embodiment 1. The difference is that the simulated high-concentration wastewater influent parameters are: COD concentration of 3000 mg / L, NH3-N concentration of 300 mg / L, and TP concentration of 38 mg / L. Samples are taken every 72 hours to measure the effluent concentration.

[0037] Example 4 This embodiment uses the same method as Embodiment 1. The difference is that the simulated high-concentration wastewater influent parameters are: COD concentration of 4000 mg / L, NH3-N concentration of 400 mg / L, and TP concentration of 50 mg / L. Samples are taken every 72 hours to measure the effluent concentration.

[0038] Example 5 This embodiment uses the same method as Embodiment 1. The difference is that the simulated high-concentration wastewater influent parameters are: COD concentration of 5000 mg / L, NH3-N concentration of 500 mg / L, and TP concentration of 80 mg / L. Samples are taken every 72 hours to measure the effluent concentration.

[0039] Example 6 This embodiment uses the same method as Embodiment 1, except that the simulated high-concentration wastewater influent parameters are: COD concentration of 7000 mg / L, ammonia nitrogen (NH3-N) concentration of 600 mg / L, and total phosphorus (TP) concentration of 100 mg / L. Samples are taken every 72 hours to measure the effluent concentration.

[0040] Comparative Example 1 This comparative example provides a method for treating simulated high-concentration wastewater using a microbial anode-cathode MFC-A / A / O coupled system, which is basically the same as the method in Example 1, except that its structure includes an A / A / O device and an MFC device connected to the A / A / O device; the A / A / O device includes an inlet tank, an anaerobic tank, an anoxic tank, an aerobic tank, and a sedimentation tank connected in sequence, with volumes of 2L, 2L, and 6L for the anaerobic tank, aerobic tank, and an anoxic tank, respectively; the anode of the MFC device is located in the anaerobic tank and the cathode is located in the aerobic tank.

[0041] The simulated high-concentration wastewater influent parameters were: COD concentration of 5000 mg / L, ammonia nitrogen (NH3-N) concentration of 500 mg / L, and total phosphorus (TP) concentration of 80 mg / L. Samples were taken every 72 hours to measure the effluent concentration.

[0042] Table 1. Comparison of effects between the examples and the comparative examples The data in the table above show that the MFC-A / O / A coupled systems in Examples 1-6 are significantly superior to the MFC-A / A / O coupled system in Comparative Example 1. This may be related to the unique process flow of the A / O / A-MFC system, which creates better substrate conditions and microbial niches. The electrogenic potential of MFC is generally increased by more than 40%, and the start-up time is shortened by about 40% to 50%. In addition, the removal rates of pollutants such as COD, ammonia nitrogen, and total phosphorus in wastewater are generally increased by 10 to 20 percentage points.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. An MFC-A / O / A coupled wastewater treatment system, characterized in that, Including connected A / O / A devices and MFC devices; The A / O / A device includes an inlet tank (1), an anaerobic tank (2), an aerobic tank (3), an anoxic tank (4), and a sedimentation tank (5) connected in sequence. The MFC device includes: an anode (10) disposed in the anaerobic tank (2); a cathode (11) disposed in the aerobic tank (3); a resistor (9) disposed outside the A / O / A device and connected to the anode (10) and the cathode (11); and a proton exchange membrane (14) disposed between the anaerobic tank (2) and the aerobic tank (3).

2. The MFC-A / O / A coupled wastewater treatment system according to claim 1, characterized in that, The resistor (9) is connected to the anode (10) and the cathode (11) respectively via titanium wire.

3. The MFC-A / O / A coupled wastewater treatment system according to claim 1, characterized in that, Electric stirrers are installed in the anaerobic tank (2) and the anoxic tank (4).

4. The MFC-A / O / A coupled wastewater treatment system according to claim 1, characterized in that, The aerobic tank (3) is equipped with several aeration devices.

5. The MFC-A / O / A coupled wastewater treatment system according to claim 1, characterized in that, The anaerobic tank (2), aerobic tank (3), anoxic tank (4), and sedimentation tank (5) are connected in sequence by overflow.

6. The MFC-A / O / A coupled wastewater treatment system according to claim 1, characterized in that, The anode and cathode are either carbon fiber brushes or carbon fiber brushes prepared through a pretreatment and activation process. The pretreatment activation process is any one or a combination of strong acid immersion activation process, strong alkali immersion activation process, or high temperature calcination activation process.

7. The MFC-A / O / A coupled wastewater treatment system according to claim 6, characterized in that, The strong acid immersion activation process involves immersing the carbon fiber brush in a 0.1~0.5 mol / L HCl solution for 12~24 h, rinsing it with deionized water until neutral, and drying it at 100~105℃ for 1~2 h. The strong alkali soaking and activation process involves brushing the carbon fiber into a 0.5~1.0 mol / L NaOH solution, soaking it for 12~24 hours, rinsing it with deionized water until neutral, and drying it at 100~105 ℃ for 1~2 hours. The high-temperature calcination activation process involves calcining the carbon fiber brush in a muffle furnace at 400-450°C for 15-30 minutes, and then removing it and cooling it to room temperature.

8. The MFC-A / O / A coupled wastewater treatment system according to claim 1, characterized in that, The anaerobic tank and the aerobic tank have the same volume, and the volume ratio of the anaerobic tank or aerobic tank to the anoxic tank is 1:(2~3).

9. A method for treating wastewater using an MFC-A / O / A coupling, characterized in that, It employs the MFC-A / O / A coupled wastewater treatment system as described in any one of claims 1-8, and includes the following steps: S1. After sedimentation, concentration and impurity removal, activated sludge is subjected to anaerobic stirring and aeration culture with simulated wastewater to obtain anaerobic sludge and aerobic sludge. Subsequently, wastewater containing anaerobic sludge was connected to the anaerobic tank and the anoxic tank, and wastewater containing aerobic sludge was connected to the aerobic tank to complete the system inoculation. S2. The anaerobic microorganisms prepared in S1 were placed in an anaerobic basic medium containing phenazine-1-carboxylic acid for enrichment culture to obtain enriched mixed electrogenic bacteria. The aerobic microorganisms prepared in S1 were placed in a medium with ammonia nitrogen as the only nitrogen source and no or only a very small amount of organic carbon added for continuous aeration enrichment culture to obtain enriched mixed nitrifying bacteria. S3. Add the enriched mixed electrogenic bacteria prepared in S2 and the prepared simulated wastewater to the anaerobic tank, and add the enriched mixed nitrifying bacteria prepared in S2 and the prepared simulated wastewater to the aerobic tank; use a 30℃ constant temperature sequential batch operation of the MFC-A / O / A coupled system with a cycle of 6-8 days, and after 3 cycles of stable operation; start wastewater treatment and MFC operation by continuously feeding wastewater into the anaerobic tank.

10. An application of the MFC-A / O / A coupled wastewater treatment system as described in any one of claims 1-8, characterized in that, Applications include providing electricity and / or treating wastewater.

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