A multi-chamber microbial fuel cell and a method for purifying wastewater with a high C / N ratio

Abstract

The invention discloses a multi-chamber microbial fuel cell, comprising a plurality of electrode chambers, wherein the plurality of electrode chambers comprise a plurality of anode chambers and a plurality of cathode chambers of the same number, wherein the anode chambers and the cathode chambers are alternately arranged to form a sequence, wherein the electrode chamber at the front position is sealed and fixedly connected to the electrode chamber at the back position, wherein the first position of the sequence is the anode chamber, and the last position of the sequence is the cathode chamber, and the last position cathode chamber is connected to the first position anode chamber to form a cyclic sequence; in the invention, ammonia nitrogen in the anode chamber at the front position migrates to the cathode chamber at the back position through a cation exchange membrane, ammonia nitrogen undergoes nitrification reaction in the cathode chamber at the back position, nitrite and nitrate migrate to the anode chamber at the back position through anion exchange membrane for denitrification and denitrification, and during denitrification and denitrification, anaerobic microorganisms in the anode chamber at the back position can be used to decompose CO2, protons and electrons generated by the metabolism of a large amount of carbon-containing organic matter in sewage, thereby finally achieving simultaneous purification of organic matter and ammonia nitrogen in sewage with a high C / N ratio.

Description

Technical Field

[0001] The invention relates to the field of sewage treatment, and in particular to a multi-chamber microbial fuel cell and a method for purifying sewage with a high C / N ratio. Background Art

[0002] Microbial fuel cells are devices that use the catalytic action of microorganisms to degrade organic matter such as organic acids, proteins, and sugars, and directly convert chemical energy into electrical energy. They are highly efficient and pollution-free. Using microbial fuel cells to treat sewage can effectively generate electricity while removing pollutants. In recent years, the use of microbial fuel cell technology to degrade organic matter and remove nitrogen has become a research hotspot.

[0003] However, most of the membrane microbial fuel cells currently developed are traditional dual-chamber structures, and the water quality of the anode chamber and the cathode chamber is mostly different. The effluent from the anode chamber often needs to be treated in combination with other processes, and the treated water is used as the inlet water for the cathode chamber.

[0004] In the form of free ammonia (NH3) and ammonium ions (NH4 + ) is called ammonia nitrogen. Ammonia nitrogen is a nutrient in water bodies, which can cause eutrophication of water. It is the main oxygen-consuming pollutant in water bodies and is toxic to fish and some aquatic organisms.

[0005] At present, the main ammonia nitrogen removal process is the biofilm method, which first uses nitrifying bacteria to convert ammonia nitrogen into nitrate nitrogen or nitrite nitrogen, and then uses denitrifying bacteria to convert nitrate nitrogen or nitrite nitrogen into nitrogen gas, thereby achieving the purpose of denitrification. Based on this denitrification principle, there is a dual-chamber microbial fuel cell with cathode nitrification coupled anode denitrification in the prior art, in which nitrification reaction is carried out in the cathode chamber and denitrification reaction is carried out in the anode chamber to purify sewage.

[0006] For a dual-chamber microbial fuel cell with cathode nitrification coupled with anode denitrification, when a cation exchange membrane is used as the separator, the nitrification products in the cathode chamber cannot be effectively removed due to the barrier of the cation exchange membrane; when an anion exchange membrane is used as the separator, the ammonia nitrogen in the anode chamber cannot be effectively removed under anaerobic conditions due to the barrier of the anion exchange membrane.

[0007] Moreover, when the dual-chamber microbial fuel cell with cathode nitrification coupled with anode denitrification treats wastewater with a high C / N ratio, the heterotrophic microorganisms in the cathode chamber will multiply in large numbers, and the growth rate of heterotrophic microorganisms is lower than that of autotrophic microorganisms. Therefore, the autotrophic nitrifying bacteria cannot obtain sufficient dissolved oxygen and are inhibited. Therefore, when the dual-chamber microbial fuel cell with cathode nitrification coupled with anode denitrification treats wastewater with a high C / N ratio, it is actually difficult to achieve effective simultaneous removal of organic matter and ammonia nitrogen. Summary of the invention

[0008] The purpose of the present invention is to provide a multi-chamber microbial fuel cell and a method for purifying high C / N ratio sewage, so as to solve the technical problem that it is difficult to achieve effective simultaneous removal of organic matter and ammonia nitrogen when treating high C / N ratio sewage using a double-chamber microbial fuel cell with cathode nitrification coupled with anode denitrification in the prior art.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A multi-chamber microbial fuel cell, characterized in that it comprises a plurality of electrode chambers, wherein the plurality of electrode chambers comprises a plurality of anode chambers and a plurality of cathode chambers of the same number, wherein the anode chambers and the cathode chambers are alternately arranged to form a sequence, wherein the electrode chambers at the front position are sealed and fixedly connected to the electrode chambers at the rear position, wherein the first position of the sequence is the anode chamber, and the last position of the sequence is the cathode chamber, and the last position cathode chamber is connected to the first position anode chamber to form a cyclic sequence;

[0011] Each electrode chamber is equipped with an electrode assembly. In the order of sequence, the electrode assemblies in the two adjacent electrode chambers are connected by electrical wires. At the same time, the electrode assembly in the last cathode chamber is also connected to the electrode assembly in the first anode chamber by electrical wires.

[0012] The side wall of each electrode chamber is provided with two ion channels, and in sequence, the ion channels of the adjacent two electrode chambers correspond to each other and are connected;

[0013] In sequence order, a cation exchange membrane is installed between the ion channel connecting the anode chamber at the front position and the cathode chamber at the rear position adjacent thereto, an anion exchange membrane is installed between the ion channel connecting the cathode chamber at the front position and the anode chamber at the rear position adjacent thereto, and an anion exchange membrane is installed between the ion channel connecting the last cathode chamber and the first anode chamber.

[0014] The multi-chamber microbial fuel cell disclosed in the present invention can simultaneously remove organic matter and ammonia nitrogen in the anode chamber. The cation exchange membrane and the anion exchange membrane are alternately arranged between the anode chamber and the cathode chamber. The ammonia nitrogen in the front-order anode chamber migrates to the back-order cathode chamber through the cation exchange membrane. The ammonia nitrogen undergoes a nitrification reaction in the back-order cathode chamber and is converted into nitrite and nitrate. The nitrite and nitrate migrate to the back-order anode chamber through the anion exchange membrane for denitrification. During denitrification, anaerobic microorganisms in the back-order anode chamber can be used to decompose CO2, protons and electrons generated by the metabolism of a large amount of carbon-containing organic matter in sewage, thereby ultimately achieving simultaneous purification of organic matter and ammonia nitrogen in sewage with a high C / N ratio.

[0015] Preferably, a double electrode assembly is arranged in each electrode chamber, and in the same electrode chamber, two electrode assemblies are respectively installed on the top wall of the electrode chamber near the cation exchange membrane and the anion exchange membrane. This can reduce the electrode spacing between adjacent anode chambers and cathode chambers, effectively increase the channel for electrons to be transmitted from the anode to the cathode, increase the current between the cathode and the cathode while improving the transfer rate, and thus enhance the catalytic activity of the microorganisms.

[0016] Preferably, the electrode assembly includes graphite felt and titanium wire, the graphite felt is in sheet form and is vertically arranged inside the electrode chamber; one end of the titanium wire is inserted into the graphite felt, one end of the titanium wire and the middle section of the titanium wire are fixed to the top wall of the electrode chamber, and the other end of the titanium wire is exposed outside the top wall of the electrode chamber, and the electrical conductor is connected to the titanium wire exposed outside the top wall of the electrode chamber; a resistor is arranged on the electrical conductor.

[0017] The electric wire is located outside each electrode chamber. Specifically, the end of the electric wire has an alligator clip, and the electric wire is connected to the titanium wire through the alligator clip. The electric wire is preferably a copper wire with good electrical conductivity.

[0018] The graphite felt is a microbial carrier and current collecting electrode material, and has the dual functions of microbial attachment and electron enrichment. The titanium wire and copper wire have electron transfer functions. The titanium wire has good electrical conductivity, can reduce the internal resistance of the reactor, and improve the power generation capacity. The graphite felt in the anode chamber can enrich electrons and transfer the enriched electrons to the cathode chamber through the titanium wire and copper wire, thereby realizing the electron transfer function between the anode chamber and the cathode chamber. The resistor is used to adjust the magnitude of the current transmitted on the electric wire to control the reaction speed.

[0019] Preferably, each electrode chamber is provided with a reference electrode hole for installing a reference electrode, and the reference electrode is a silver / silver chloride reference electrode.

[0020] The reference electrode is used to measure the curve of electrode potential (vs. Ag / AgCl) changing with current density.

[0021] Preferably, an aeration device is installed in each cathode chamber.

[0022] This enables the cathode chamber to be in an aerobic or anoxic environment.

[0023] Preferably, a water inlet and outlet are provided on the top wall or side wall of each electrode chamber.

[0024] The water inlet and outlet are convenient for inputting sewage or buffer solution into the anode chamber and the cathode chamber during operation. The water inlet and outlet are also used to discharge water from each electrode chamber after the power generation cycle is completed.

[0025] Preferably, a sampling port is provided on the top wall of each anode chamber, and a dissolved oxygen detection port is provided on the top wall of each cathode chamber.

[0026] The sampling port is convenient for sampling and testing the liquid in each cathode chamber during operation so as to monitor the operating status. The dissolved oxygen detection port is used to insert a dissolved oxygen monitoring probe to monitor the dissolved oxygen in the first cathode chamber and the second cathode chamber.

[0027] A method for purifying wastewater with a high C / N ratio, using the multi-chamber microbial fuel cell according to claim 1, characterized in that it comprises the following steps:

[0028] S1, connecting the electrodes between adjacent polar chambers with electrical wires to form an electron transfer path;

[0029] S2. Inoculate the corresponding type of sludge in each electrode chamber and turn on the aeration device in each cathode chamber;

[0030] S3, inputting corresponding types of influent water into each electrode chamber;

[0031] S4, after the power generation cycle of each electrode chamber is completed, the effluent is discharged to complete the purification process of the high C / N ratio sewage in a sequential batch mode;

[0032] S5. Repeat steps S4 and S5 to achieve continuous purification of high C / N ratio wastewater.

[0033] Preferably, in step S2, one specific implementation method of inoculating the corresponding type of sludge in each electrode chamber is to inoculate anaerobic sludge in each anode chamber and seal each anode chamber; inoculate aerobic sludge in each cathode chamber; correspondingly, in step S3, inputting the corresponding type of influent into each electrode chamber means inputting equal amounts of high C / N ratio sewage into each anode chamber; and inputting equal amounts of buffer solution to the amount of sewage input into each anode chamber into each cathode chamber.

[0034] Preferably, in step S2, another specific implementation method of inoculating the corresponding type of sludge in each electrode chamber is to inoculate anaerobic sludge in each anode chamber and seal each anode chamber; inoculate heterotrophic nitrifying sludge in each cathode chamber; correspondingly, in step S3, inputting the corresponding type of influent into each electrode chamber means that equal amounts of high C / N ratio sewage are respectively input into each electrode chamber, and the influent water quality of the anode chamber and the cathode chamber is the same.

[0035] The present invention has the following beneficial effects:

[0036] The multi-chamber microbial fuel cell disclosed in the present invention can achieve the simultaneous removal of organic matter and ammonia nitrogen in sewage with a high C / N ratio. The cation exchange membrane and the anion exchange membrane are alternately arranged between the anode chamber and the cathode chamber. The ammonia nitrogen in the front-order anode chamber migrates to the back-order cathode chamber through the cation exchange membrane. The ammonia nitrogen undergoes a nitrification reaction in the back-order cathode chamber and is converted into nitrite and nitrate. The nitrite and nitrate migrate to the back-order anode chamber through the anion exchange membrane for denitrification. During denitrification, anaerobic microorganisms in the back-order anode chamber can be used to decompose CO2, protons and electrons generated by the metabolism of a large amount of carbon-containing organic matter in the sewage, thereby ultimately achieving the simultaneous purification of organic matter and ammonia nitrogen in sewage with a high C / N ratio.

[0037] The electrons generated in the multiple anodes of the multi-chamber microbial fuel cell disclosed by the present invention will achieve a higher oxidation rate on the multiple cathodes, enhance the current channel inside the microbial fuel cell, improve the power generation capacity of the microbial fuel cell, thereby increasing the operating power of the microbial fuel cell, increasing the power generation, and thereby improving the removal efficiency of organic matter and ammonia nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to make the purpose, technical solution and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0039] Figure 1 Schematic diagram of the structure of a four-chamber microbial fuel cell according to an embodiment of the present invention.

[0040] Figure 2 Schematic diagram of an ion channel according to an embodiment of the present invention.

[0041] Figure 3 for Figure 1 aa section view in .

[0042] Figure 4 for Figure 1 bb cross-section diagram in.

[0043] Figure 5 This is an equivalent circuit diagram of a four-chamber denitrification microbial fuel cell in an embodiment of the present invention.

[0044] Figure 6 Graph showing the voltage output of a microbial fuel cell in an embodiment of the present invention.

[0045] Figure 7 This is a polarization curve and power density diagram of a four-chamber denitrification microbial fuel cell in an embodiment of the present invention.

[0046] Figure 8 Schematic diagram of COD removal effect of each anode chamber of a four-chamber denitrification microbial fuel cell under different C / N ratios in an embodiment of the present invention.

[0047] Fig. 9 This is a schematic diagram of the change in nitrogen concentration in each electrode chamber of a four-chamber denitrification microbial fuel cell when the C / N ratio in sewage is simulated to be 5 in an embodiment of the present invention.

[0048] Fig.10 This is a schematic diagram of the change in nitrogen concentration in each electrode chamber of a four-chamber denitrification microbial fuel cell when the C / N ratio in sewage is simulated to be 7 according to an embodiment of the present invention.

[0049] Fig.11 This is a schematic diagram of the change in nitrogen concentration in each electrode chamber of a four-chamber denitrification microbial fuel cell when the C / N ratio in sewage is simulated to be 9 in an embodiment of the present invention.

[0050] Fig.12 This is a schematic diagram of the change in nitrogen concentration in each electrode chamber of a four-chamber denitrification microbial fuel cell when the C / N ratio in sewage is simulated to be 11 in an embodiment of the present invention.

[0051] Explanation of the reference numerals: 1. first anode chamber; 2. first cathode chamber; 3. second anode chamber; 4. second cathode chamber; 51. preceding ion channel; 52. succeeding ion channel; 61. first cation exchange membrane; 62. first anion exchange membrane; 63. second cation exchange membrane; 64. second anion exchange membrane; 71. first electrode; 72. second electrode; 81. titanium wire; 82. copper wire; 83. resistor; 9. water inlet and outlet; 11. aeration device installation port; 12. dissolved oxygen detection port; 13. sealing gasket; 14. screw; 15. nut; 16. reference electrode placement port; 17. sampling port; 18. fixing hole. DETAILED DESCRIPTION

[0052] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0053] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of the present invention, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the invention product is usually placed when used, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In addition, the terms "horizontal", "vertical", etc. do not mean that the components are absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] The invention solves the technical problem that it is difficult to effectively remove organic matter and ammonia nitrogen simultaneously when treating high C / N ratio sewage using a double-chamber microbial fuel cell with cathode nitrification coupled with anode denitrification in the prior art.

[0055] Based on the above technical problems to be solved, the present invention discloses a multi-chamber microbial fuel cell, comprising a plurality of electrode chambers, wherein the plurality of electrode chambers include a plurality of anode chambers and a plurality of cathode chambers of the same number, wherein the anode chambers and the cathode chambers are alternately arranged to form a sequence, wherein the leading electrode chamber and the trailing electrode chamber are sealed and fixedly connected via a connecting structure, wherein the first position of the sequence is the anode chamber, and the last position of the sequence is the cathode chamber, and the last cathode chamber is connected to the first anode chamber to form a cyclic sequence;

[0056] Each electrode chamber is equipped with an electrode assembly. In the order of sequence, the electrode assemblies in the two adjacent electrode chambers are connected by electrical wires. At the same time, the electrode assembly in the last cathode chamber is also connected to the electrode assembly in the first anode chamber by electrical wires.

[0057] The side wall of each electrode chamber is provided with two ion channels, and in sequence, the ion channels of the adjacent two electrode chambers correspond to each other and are connected;

[0058] In sequence order, a cation exchange membrane is installed between the ion channel connecting the anode chamber at the front position and the cathode chamber at the rear position adjacent thereto, an anion exchange membrane is installed between the ion channel connecting the cathode chamber at the front position and the anode chamber at the rear position adjacent thereto, and an anion exchange membrane is installed between the ion channel connecting the last cathode chamber and the first anode chamber.

[0059] The multi-chamber microbial fuel cell disclosed in the present invention is suitable for purifying wastewater with a high C / N ratio and can remove organic matter and ammonia nitrogen at the same time. The multi-chamber microbial fuel cell disclosed in the present invention can also be applied to high-salt and high-concentration wastewater (such as mustard wastewater), and also shows potential application advantages in the removal of nutrient salts.

[0060] Specifically, the electrode assemblies in the adjacent two-electrode chambers are respectively connected by electrical wires, which means that the electrode assembly in the preceding electrode chamber is connected to the electrode assembly in the succeeding electrode chamber by electrical wires.

[0061] The two ion channels are respectively the leading ion channel and the trailing ion channel; the trailing ion channel of the leading electrode chamber in the sequence corresponds to and is connected with the leading ion channel of the trailing electrode chamber, the leading ion channel of the trailing electrode chamber corresponds to and is connected with the trailing ion channel of the leading electrode chamber, and the trailing ion channel of the last cathode chamber corresponds to and is connected with the leading ion channel of the first anode chamber.

[0062] Specifically, the multi-chamber microbial fuel cell disclosed in the present application document comprises n anode chambers and n cathode chambers, wherein n∈{2,3,4,...}, and the value of n can be determined empirically based on the amount and quality of water; a cation exchange membrane is installed between the subsequent ion channel of the i-th anode chamber and the preceding ion channel of the i-th cathode chamber, wherein i∈n, n∈{2,3,4,...}, and the cations in the anode chamber (such as NH4 + ) can pass through the cation exchange membrane into the cathode chamber, while the anions in the anode chamber cannot pass through the cation exchange membrane into the cathode chamber; an anion exchange membrane is installed between the subsequent ion channel of the i-th cathode chamber and the preceding ion channel of the i+1-th anode chamber, and the anions in the cathode chamber (such as NO2 - and NO3 - ) can pass through the anion exchange membrane into the anode chamber, where i∈n, n∈{2,3,4,...}; in addition, an anion exchange membrane is also installed between the subsequent ion channel of the last cathode chamber and the preceding ion channel of the first anode chamber, so that the anions in the last cathode chamber can pass through the anion exchange membrane into the anode chamber.

[0063] Specifically, an electron transfer channel can be formed between two adjacent electrode chambers connected by an electrical conductor, and the electrode in the i-th anode chamber and the electrode in the i-th cathode chamber form a closed loop to form an MFCi module, wherein i∈n, n∈{2,3,4,...}, and an electric current can be formed inside the electron transfer channel and flow and transfer through the electrical conductor, thereby realizing the transfer of electrons between different electrode chambers.

[0064] In specific operation, when the multi-chamber microbial fuel cell is running, water enters the anode chamber and the cathode chamber at the same time, the water source of the anode chamber is sewage, and the water source of the cathode chamber is buffer solution; the function of the buffer solution is to prevent the pH value of the solution in the cathode chamber from fluctuating greatly, and the cathode chamber buffer solution plays an intermediate transfer role, and the ammonia nitrogen in the previous anode chamber is transferred to the buffer solution in the subsequent cathode chamber through the cation exchange membrane for nitrification reaction, and the nitrite and nitrate after nitrification are transferred to the subsequent anode chamber through the anion exchange membrane for denitrification, and at the same time, the organic matter in the anode chamber can keep the cathode chamber in a low COD environment due to the barrier effect of the ion exchange membrane, and the autotrophic nitrifying bacteria can become the dominant strain, so the ammonia nitrogen migrated from the previous anode chamber can be efficiently removed in the subsequent cathode chamber. The buffer solution is preferably a phosphate buffer solution, and its components include K2HPO4·3H2O (concentration is 14.15g / L) and KH2PO4 (concentration is 5.166g / L).

[0065] Specifically, the domestic sewage with a high C / N ratio is divided into n parts, and the n parts of sewage are respectively input into each anode chamber from the water inlet and outlet of each anode chamber, and n parts of buffer solution are respectively input into each cathode chamber from the water inlet and outlet of each cathode chamber.

[0066] In a specific implementation, each anode chamber is inoculated with anaerobic microorganisms, and each cathode chamber is inoculated with aerobic microorganisms or heterotrophic nitrifying microorganisms.

[0067] After water enters each anode chamber and cathode chamber, the anode chamber operates under anaerobic environmental conditions and the cathode chamber operates under aerobic or anoxic environmental conditions. In this way, anaerobic reactions and denitrification reactions can occur in the anode chamber, so that the anode chamber has the functions of decomposing organic matter in sewage and denitrifying by denitrification.

[0068] The specific implementation method is that the inoculation of anaerobic microorganisms in the anode chamber can be achieved by inoculating anaerobic sludge that has been domesticated in advance in the anode chamber, wherein the anaerobic sludge contains denitrifying microorganisms, and the anaerobic sludge that has been domesticated in advance can react anaerobically and denitrify with organic matter; the inoculation of aerobic microorganisms in the cathode chamber can be achieved by inoculating aerobic sludge that has been domesticated in advance in the cathode chamber, and the aerobic sludge that has been domesticated in advance can react with NH4 + Nitration reaction occurs, NH4 +Converted to NO2 - and NO3 - The nitrifying bacteria in the aerobic sludge have a biocatalytic effect.

[0069] The anaerobic environmental condition means that during operation, the dissolved oxygen concentration in the aqueous solution in the anode chamber is less than or equal to 0.2 mg / L, the anoxic environmental condition means that during operation, the dissolved oxygen concentration in the aqueous solution in the cathode chamber is greater than 0.2 mg / L and less than or equal to 0.5 mg / L, and the aerobic environmental condition means that during operation, the dissolved oxygen concentration in the aqueous solution in the cathode chamber is greater than 2 mg / L.

[0070] The above-mentioned anaerobic reaction refers to the reaction of organic matter in sewage in the anode chamber, specifically refers to the reaction of decomposing macromolecular organic matter into small molecular organic matter under the action of anaerobic microorganisms. Anaerobic reaction is a conventional technology in the current sewage treatment field and is often used in A / O process and AAO process. The anaerobic reaction is roughly divided into four stages:

[0071] (1) Hydrolysis stage: Due to their large molecular volume, high molecular weight organic matter cannot directly pass through the cell wall of anaerobic bacteria and needs to be decomposed into small molecules by extracellular enzymes outside the microorganisms. Typical organic substances in sewage, such as cellulose, are decomposed into cellobiose and glucose by cellulase, starch is decomposed into maltose and glucose, and protein is decomposed into short peptides and amino acids. After decomposition, these small molecules can pass through the cell wall and enter the body of the cell for the next step of decomposition;

[0072] (2) Acidification stage: The above-mentioned small molecular organic matter enters the cell body and is converted into simpler compounds and distributed outside the cell. The main product of this stage is volatile fatty acids (VFA), and some alcohols, lactic acid, carbon dioxide, hydrogen, ammonia, hydrogen sulfide and other products are also produced;

[0073] (3) Acetogenesis stage: In this stage, the product of the previous step is further converted into acetic acid, carbonic acid, hydrogen and new cell substances;

[0074] (4) Methane production stage: In this stage, acetic acid, hydrogen, carbonic acid, formic acid and methanol are converted into methane, carbon dioxide and new cellular substances.

[0075] The nitrification reaction refers to the conversion of NH4 + The chemical equation for the conversion to nitrate nitrogen is as follows:

[0076] NH4 + +2O2→NO3 - +2H + +H2O;

[0077] The denitrification reaction refers to the process by which bacteria convert nitrate (NO3 - ) through a series of intermediate products (NO2 - The biochemical process of reducing nitrogen (NO, N2O) into nitrogen gas (N2). The bacteria involved in this process are collectively called denitrifying bacteria.

[0078] The overall denitrification process can be expressed by the following chemical equation:

[0079] 2NO3 - +10e - +12H + →N2+6H2O,ΔG=-333kJ / mol.

[0080] This includes the following four reduction reactions:

[0081] Nitrate (NO3 - ) is reduced to nitrite (NO2 - ):2NO3 - +4H + +4e - →2NO2 - +2H2O;

[0082] Nitrite (NO2 - ) is reduced to nitric oxide (NO): 2NO2 - +4H + +2e - →2NO+2H2O;

[0083] Nitric oxide (NO) is reduced to nitrous oxide (N2O): 2NO+2H + +2e - →N2O+H2O;

[0084] Nitrous oxide (N2O) is reduced to nitrogen (N2): N2O+2H + +2e - →N2+H2O;

[0085] The above four reactions are all exothermic reactions, so under anaerobic or anoxic conditions, bacteria can convert nitrate (NO3 - ) acts as the final electron acceptor (TEA, terminal electron acceptor) of the electron transport chain (ETC) to complete the exchange of matter and energy.

[0086] The denitrifying bacteria described in the present application document refer to bacteria that can reduce nitrate or nitrite to nitrogen gas. Most denitrifying bacteria are heterotrophic bacteria, such as denitrifying micrococcus and denitrifying pseudomonas, which use organic matter as a nitrogen source and energy source and perform anaerobic respiration. A few denitrifying bacteria are autotrophic bacteria, such as denitrifying thiobacillus, which oxidize sulfur or nitrate to obtain energy, assimilate carbon dioxide, and use nitrate as the final electron acceptor for respiration. These are all commonly used bacteria in the prior art and can realize the denitrification reaction process.

[0087] The specific operation process of the multi-chamber microbial fuel cell disclosed in the present invention is as follows: domestic sewage with a high C / N ratio is divided into n parts, and n parts of sewage are respectively input into each anode chamber from the water inlet and outlet of each anode chamber, and n parts of buffer solution are respectively input into each cathode chamber from the water inlet and outlet of each cathode chamber. After water is input into each anode chamber and cathode chamber, anaerobic sludge is inoculated in the anode chamber, and aerobic sludge is inoculated in the cathode chamber, so that the anode chamber operates under anaerobic environmental conditions, and the cathode chamber operates under aerobic or anoxic environmental conditions. The electrodes between adjacent chambers are connected by electric wires to form an electron transfer channel, and the electron transfer can induce anion or cation transfer through the anion exchange membrane or the cation exchange membrane to maintain the charge neutrality of the system; in this way, the organic matter in the sewage undergoes an anaerobic reaction in each anode chamber, and a large amount of H is generated at the same time. + , while NH4 + It enters the cathode chamber through the cation exchange membrane and undergoes nitrification reaction under the action of aerobic microorganisms in the cathode chamber to produce NO2 - and NO3 - , the NO2 produced - and NO3 - Pass through the anion exchange membrane into the subsequent anode chamber, in the H + Under the action of electrons, organic matter and denitrifying bacteria, denitrification reaction occurs in the anode chamber, converting NO2 - and NO3 - Reduction to N2 to achieve the denitrification process. The multi-chamber microbial fuel cell disclosed in the present invention can simultaneously remove organic matter and ammonia nitrogen through the migration and transformation of ions in each electrode chamber, and discharge the effluent after the power generation cycle. At the end of the power generation cycle, the pollutant concentration in each electrode chamber of the multi-chamber microbial fuel cell is reduced to the minimum.

[0088] In specific implementation, in order to explore the change of electrode potential with current density, a reference electrode hole is provided in each electrode chamber. The reference electrode adopts a silver / silver chloride reference electrode (vs. Ag / AgCl), which is composed of metallic silver covered with silver chloride immersed in potassium chloride or hydrochloric acid solution. It has high temperature stability and excellent electrochemical stability. Since the outer shell is made of high-strength plastic, it can be used stably for a long time in complex environments such as seawater and soil.

[0089] As a preferred solution for the electrode assembly, a dual electrode assembly is arranged in each electrode chamber, and in the same electrode chamber, two electrode assemblies are respectively installed on the top wall of the electrode chamber near the cation exchange membrane and the anion exchange membrane. In this way, the installation position of one electrode assembly is close to the preceding ion channel, and the installation position of the other electrode assembly is close to the succeeding ion channel, which can reduce the electrode spacing between adjacent anode chambers and cathode chambers, effectively increase the channel for electrons to be transmitted from the anode to the cathode, and increase the current between the cathode and the cathode while improving the transfer rate, thereby enhancing the catalytic activity of the microorganisms.

[0090] As a preferred embodiment of the electrode assembly and the electric conductor, the electrode assembly includes graphite felt and titanium wire, the graphite felt is in sheet form and is vertically arranged inside the electrode chamber; one end of the titanium wire is inserted into the graphite felt, one end of the titanium wire and the middle section of the titanium wire are fixed to the top wall of the electrode chamber, and the other end of the titanium wire is exposed outside the top wall of the electrode chamber, and the electric conductor is connected to the titanium wire exposed outside the top wall of the electrode chamber.

[0091] The electric wire is located outside each electrode chamber. Specifically, the end of the electric wire has an alligator clip, and the electric wire is connected to the titanium wire through the alligator clip. The electric wire is preferably a copper wire with good electrical conductivity.

[0092] The graphite felt is a microbial carrier and current collecting electrode material, and has the dual functions of microbial attachment and electron enrichment. The titanium wire and the copper wire have an electron transfer function. The titanium wire has good electrical conductivity, can reduce the internal resistance of the reactor, and improve the power generation capacity. The graphite felt in the anode chamber can enrich electrons and transfer the enriched electrons to the cathode chamber through the titanium wire and the copper wire, thereby realizing the electron transfer function between the anode chamber and the cathode chamber.

[0093] Nitrifying bacteria can be attached to the graphite felt in the cathode chamber, and the rough surface of the graphite felt can increase the number of nitrifying bacteria. At the same time, since the graphite felt is in a flaky shape, it can also increase the contact area between nitrifying bacteria and ammonium ions, thereby improving the efficiency of the nitrification reaction. The nitrite and nitrate generated after nitrification migrate to the subsequent anode chamber through the cation exchange membrane, and denitrification is carried out using organic matter in the subsequent anode chamber to complete the denitrification process.

[0094] As a preferred solution for the electrical conductor, a resistor is also provided on the electrical conductor connecting the electrode assemblies of the two electrode chambers. Since the current of the microbial fuel cell is small and difficult to monitor, the output current of the microbial fuel cell is obtained by monitoring the voltage across the resistor using Ohm's law. When measuring the polarization curve and power density, the variable resistance method is used to obtain a curve of voltage versus current by changing the external resistance. Subsequent experiments can also explore the effect of current intensity on ion migration in the reactor by adjusting the external resistance.

[0095] In a specific implementation, the fixed resistor preferably has a resistance of 1000Ω.

[0096] As a preferred solution for convenient operation of the multi-chamber microbial fuel cell, a water inlet and outlet are provided on the top wall or the side wall of each electrode chamber.

[0097] The water inlet and outlet are convenient for inputting sewage or buffer solution into the anode chamber and cathode chamber during operation. The water inlet and outlet are also used to discharge water from each electrode chamber after the power generation cycle ends; the sampling port is convenient for sampling and testing the liquid in each electrode chamber during operation to monitor the operating status.

[0098] As a preferred solution for achieving an aerobic or anoxic environment in the cathode chamber, an aeration device is installed in each cathode chamber to place the cathode chamber in an aerobic or anoxic environment.

[0099] As one of the embodiments of the cathode chamber aeration device, the cathode chamber top wall or side wall is provided with an aeration device installation port, the aeration device is an aeration pipe connected to an aeration head, the aeration head and the aeration pipe extend from the aeration device installation port into the bottom of the cathode chamber, one end of the aeration pipe is fixedly connected to the aeration head, and the other end of the aeration pipe is connected to an aeration machine, the aeration machine can be a normal pressure aerator or an air compressor, and the gas output by the aeration machine is pure oxygen or air.

[0100] Preferably, a sampling port is provided on the top wall of each anode chamber, and a dissolved oxygen detection port is provided on the top wall of each cathode chamber. The sampling port facilitates sampling and testing of the liquid in each anode chamber during operation so as to monitor the operation status, and the dissolved oxygen detection port is used to insert a dissolved oxygen monitoring probe to monitor the dissolved oxygen in the first cathode chamber and the second cathode chamber.

[0101] As one of the specific implementations of sealing and fixing the connection between the preceding electrode chamber and the succeeding electrode chamber, the sealing and fixing connection between the electrode chambers is achieved through a connection structure, and the connection structure includes a plurality of screws and nuts and a sealing gasket;

[0102] The screw has an external thread, the nut has an internal thread, and the top wall and the bottom wall of each electrode chamber are correspondingly provided with a plurality of fixing holes, the fixing holes are through-holes, and each screw penetrates the fixing holes of the top wall and the bottom wall of each electrode chamber in the horizontal and vertical directions, and parts of the screw with external threads can be exposed on both sides of the fixing holes, and the two ends of the screw with external threads exposed outside the side walls of the electrode chamber are fixedly connected by nuts;

[0103] The sealing gasket is installed between the side walls of the two electrode chambers on the surrounding side of the ion channel connecting the adjacent two electrode chambers, and the sealing gasket has an opening, which corresponds to the preceding ion channel and the succeeding ion channel. After the nut fixes each electrode chamber, the sealing gasket can be subjected to the pressure of the side walls of the two sides of the electrode chamber, thereby playing a sealing role to prevent the liquid in the electrode chamber from leaking out.

[0104] As a preferred material for the sealing gasket, the sealing gasket is preferably an epoxy rubber gasket.

[0105] The present invention also discloses a method for purifying sewage with a high C / N ratio, which uses a microbial fuel cell as described above to remove ammonia nitrogen from the sewage, comprising the following steps:

[0106] S1, connecting the electrodes between adjacent polar chambers with electrical wires to form an electron transfer path;

[0107] S2. Inoculate the corresponding type of sludge in each electrode chamber and turn on the aeration device in each cathode chamber;

[0108] S3, inputting corresponding types of influent water into each electrode chamber;

[0109] S4, after the power generation cycle of each electrode chamber is completed, the effluent is discharged to complete the purification process of the high C / N ratio sewage in a sequential batch mode;

[0110] S5. Repeat steps S4 and S5 to achieve continuous purification of high C / N ratio wastewater.

[0111] Preferably, in step S2, one specific implementation method of inoculating the corresponding type of sludge in each electrode chamber is to inoculate anaerobic sludge in each anode chamber and seal each anode chamber; inoculate aerobic sludge in each cathode chamber, and maintain the dissolved oxygen content in each cathode chamber by an aeration device. In this implementation method, the dissolved oxygen content in the cathode chamber is maintained at 5.5±0.5 mg / L.

[0112] Correspondingly, in step S3, inputting the corresponding type of influent water into each electrode chamber means inputting equal amounts of high C / N ratio sewage into each anode chamber respectively; and inputting equal amounts of buffer solution as the amount of sewage input into each anode chamber respectively into each cathode chamber.

[0113] The function of the buffer solution is to prevent the pH value of the solution in the cathode chamber from fluctuating too much. The buffer solution in the cathode chamber plays an intermediate transfer role. The ammonia nitrogen in the preceding anode chamber is transferred to the buffer solution in the succeeding cathode chamber through the cation exchange membrane for nitrification. The nitrite and nitrate after nitrification are transferred to the succeeding anode chamber through the anion exchange membrane for denitrification. At the same time, due to the barrier effect of the ion exchange membrane, the organic matter in the anode chamber can keep the cathode chamber in an environment with a low C / N ratio at all times, and the autotrophic nitrifying bacteria can obtain a good living environment. Therefore, the ammonia nitrogen migrated from the preceding anode chamber can be efficiently removed in the succeeding cathode chamber.

[0114] The buffer solution is preferably a phosphate buffer solution, whose components include K2HPO4·3H2O (concentration is 14.15 g / L) and KH2PO4 (concentration is 5.166 g / L).

[0115] In this way, the organic matter in the sewage undergoes anaerobic reaction in each anode chamber, and a large amount of H + , while NH4 + It enters the cathode chamber through the cation exchange membrane and undergoes nitrification reaction under the action of aerobic microorganisms in the cathode chamber to produce NO2 - and NO3 - , the NO2 produced - and NO3 - Pass through the anion exchange membrane into the subsequent anode chamber, in the H + Under the action of electrons, organic matter and denitrifying bacteria, denitrification reaction occurs in the anode chamber, converting NO2 - and NO3 - It is reduced to N2 to realize the denitrification process. Through the migration and transformation of ions in each electrode chamber, it can simultaneously remove organic matter and ammonia nitrogen.

[0116] Preferably, in step S2, another specific implementation method of inoculating the corresponding type of sludge in each electrode chamber is to inoculate anaerobic sludge in each anode chamber and seal each anode chamber; inoculate heterotrophic nitrification sludge in each cathode chamber, and maintain the dissolved oxygen content in each cathode chamber by an aeration device. In this implementation method, the dissolved oxygen content in the cathode chamber is maintained at 5.5±0.5 mg / L; the heterotrophic nitrification sludge includes heterotrophic nitrifying microorganisms, which can utilize organic matter and oxygen to achieve nitrification reaction.

[0117] Correspondingly, in step S3, inputting the corresponding type of influent into each electrode chamber means inputting equal amounts of high C / N ratio sewage into each electrode chamber respectively, and the influent water quality of the anode chamber and the cathode chamber is the same.

[0118] In this way, the organic matter in the sewage undergoes anaerobic reaction in each anode chamber, and a large amount of H + , while NH4 + It enters the cathode chamber through the cation exchange membrane and undergoes nitrification reaction under the action of heterotrophic nitrifying microorganisms in the cathode chamber, producing NO2 - and NO3 - , the NO2 produced - and NO3 - Pass through the anion exchange membrane into the subsequent anode chamber, in the H + Under the action of electrons, organic matter and denitrifying bacteria, denitrification reaction occurs in the anode chamber, converting NO2 - and NO3 - It is reduced to N2 to realize the denitrification process. Through the migration and transformation of ions in each electrode chamber, it can simultaneously remove organic matter and ammonia nitrogen.

[0119] During the specific implementation, in order to ensure that the amount of sewage input into each electrode chamber is the same, the high C / N ratio sewage is stored in a front buffer pool, and multiple sewage pumps are used to input equal amounts of high C / N ratio sewage into each electrode chamber. Each sewage pump has the same flow rate and the same start and close time.

[0120] The present invention has the following technical effects: the multi-chamber microbial fuel cell disclosed in the present invention adopts a multi-anode and multi-cathode structure in which the anodes and cathodes are arranged alternately, so that the electrons generated in the multiple anodes will achieve a higher oxidation rate on the multiple cathodes, thereby enhancing the current channel inside the microbial fuel cell, improving the power generation capacity of the microbial fuel cell, and thus increasing the operating power of the microbial fuel cell, increasing the power generation, and thus improving the removal efficiency of organic matter and ammonia nitrogen; compared with the multi-anode single cathode structure in the prior art, due to the limitation of the cathode area, the current generated by the anode is relatively small, which will limit the operating power of the microbial fuel cell.

[0121] By alternating the cation exchange membrane and the anion exchange membrane between the anode chamber and the cathode chamber, taking the first anode chamber as an example, the ammonia nitrogen in the first anode chamber migrates to the first cathode chamber through the cation exchange membrane, and the ammonia nitrogen undergoes nitrification reaction in the first cathode chamber to be converted into nitrite and nitrate, and the nitrite and nitrate migrate to the second anode chamber through the anion exchange membrane for denitrification. During denitrification, the anaerobic microorganisms in the second anode chamber can be used to decompose the CO2, protons and electrons generated by the metabolism of a large amount of carbon-containing organic matter in the sewage. At the same time, the weak electric field generated by the microbial fuel cell itself also enhances the catalytic activity of the anode and cathode microorganisms, ultimately achieving the simultaneous purification of organic matter and ammonia nitrogen in sewage with a high C / N ratio.

[0122] Moreover, the multi-chamber microbial fuel cell disclosed in the present invention is provided with two electrodes in each electrode chamber, and the electrodes are respectively close to the cation exchange membrane and the anion exchange membrane of each electrode chamber, so that there are electrodes on both sides of the cation exchange membrane and the anion exchange membrane, which reduces the electrode spacing between the anion and cation exchange membranes. Moreover, having two anodes in the anode chamber can increase the effective reaction area of ​​the anode chamber without increasing the volume of the anode chamber, thereby improving the anode coulomb efficiency.

[0123] In addition, the multi-chamber microbial fuel cell structure disclosed in the present invention separates the nitrification and denitrification processes, making it highly resistant to high C / N ratio sewage. During operation, the C / N ratio in the cathode chamber can be reduced to less than 0.25, making the nitrifying bacteria in the cathode chamber the dominant species, making the nitrification effect more significant, and being suitable for the purification of high C / N ratio sewage. The COD and ammonia nitrogen removal rates in the anode chamber of the present invention are both above 90%.

[0124] In summary, the present invention effectively solves the deficiencies and defects of the prior art, does not require an external mediator, has the characteristics of low cost, high efficiency in denitrification, strong power generation capacity, and suitability for long-term intermittent operation, while achieving the separation of anode denitrification and cathode nitrification, and further improving operability and safety.

[0125] The multi-chamber microbial fuel cell disclosed in the present invention is suitable for the denitrification treatment of organic wastewater with a high C / N ratio and containing ammonia nitrogen, and is suitable for sequencing batch operation and long-term intermittent operation. It has a wide range of applicable scenarios. The multi-chamber microbial fuel cell disclosed in the present invention integrates sewage power generation and efficient denitrification, and has the significance of energy saving and emission reduction.

[0126] Example

[0127] As one of the specific implementations of the above technical solution, Figures 1 to 4 As shown, the multi-chamber microbial fuel cell described in this embodiment has a total of four electrode chambers, and the arrangement order of the electrode chamber sequence is respectively a first anode chamber 1, a first cathode chamber 2, a second anode chamber 3 and a second cathode chamber 4. The four electrode chambers are connected in sequence according to the above arrangement order to form a four-chamber microbial fuel cell with a square shape as shown in the figure.

[0128] Specifically, a sealed fixed connection between each electrode chamber is achieved through a connection structure, and the connection structure includes a plurality of screws 14 and nuts 15 and a sealing gasket 13; the screws 14 have external threads, the nuts 15 have internal threads, and the top and bottom walls of each electrode chamber are correspondingly provided with a plurality of fixing holes 18, the fixing holes 18 are through-holes, and each screw 14 respectively penetrates the fixing holes 18 of the top and bottom walls of each electrode chamber in the horizontal and vertical directions, and can expose a portion of the screw 14 with external threads on both sides of the fixing holes 18, and the two ends of the screw 14 with external threads exposed outside the side walls of the electrode chamber are fixedly connected by nuts 15;

[0129] The sealing gasket 13 is installed between the side walls of the two electrode chambers on the surrounding side of the ion channel connecting the adjacent two electrode chambers, and the sealing gasket 13 has an opening, which corresponds to the preceding ion channel 51 and the succeeding ion channel 52. After the nut 15 fixes each electrode chamber, the sealing gasket 13 can be subjected to the pressure of the side walls of the two electrode chambers, thereby playing a sealing role to prevent the liquid in the electrode chamber from leaking out.

[0130] As a preferred material of the sealing gasket 13, the sealing gasket 13 is preferably an epoxy rubber gasket.

[0131] like Figure 2 As shown, two ion channels are provided on the side walls of each electrode chamber, and in the sequence order, the ion channels of the adjacent two electrode chambers correspond to each other and are connected; the two ion channels are respectively a leading ion channel 51 and a trailing ion channel second electrode 52, and the trailing ion channel second electrode 52 of the leading electrode chamber in the sequence corresponds to and is connected to the leading ion channel 51 of the trailing electrode chamber, the leading ion channel 51 of the trailing electrode chamber corresponds to and is connected to the trailing ion channel second electrode 52 of the leading electrode chamber, and the trailing ion channel second electrode 52 of the trailing cathode chamber corresponds to and is connected to the leading ion channel 51 of the first anode chamber.

[0132] Specifically, the second electrode 52 of the subsequent ion channel of the first anode chamber 1 is connected to the previous ion channel 51 of the first cathode chamber 2, and a first cation exchange membrane 61 is installed between the two ion channels; the second electrode 52 of the subsequent ion channel of the first cathode chamber 2 is connected to the previous ion channel 51 of the second anode chamber 3, and a first anion exchange membrane 62 is installed between the two ion channels; the second electrode 52 of the subsequent ion channel of the second anode chamber 3 is connected to the previous ion channel 51 of the second cathode chamber 4, and a second cation exchange membrane 63 is installed between the two ion channels; the second electrode 52 of the subsequent ion channel of the second cathode chamber 4 is connected to the previous ion channel 51 of the first anode chamber 1, and a second anion exchange membrane 64 is installed between the two ion channels.

[0133] Each electrode chamber is equipped with double graphite felt electrodes, namely, a first electrode 71 and a second electrode 72, which are respectively close to the preceding ion channel 51 and the succeeding ion channel 52 of their respective electrode chambers, and are both located inside their respective electrode chambers. One end of a titanium wire 81 is inserted into the top of the first electrode 71 and the second electrode 72, respectively, and the middle section of the titanium wire 81 is fixed to the top wall of each electrode chamber, and the other end of the titanium wire 81 is clamped by a copper wire 82 with an alligator clip, the second electrode 72 of the first anode chamber 1 is connected to the first electrode 71 of the first cathode chamber 2 through the copper wire 82, the second electrode 72 of the first cathode chamber 2 is connected to the first electrode 71 of the second anode chamber 3 through the copper wire 82, the second electrode 72 of the second anode chamber 3 is connected to the first electrode 71 of the second cathode chamber 4 through the copper wire 82, and the second electrode 72 of the second cathode chamber 4 is connected to the first electrode 71 of the first anode chamber 1 through the copper wire 82.

[0134] Specifically, a resistor 83 is installed on the copper wire 82 to control the current in the copper wire 82 , that is, to control the electron transfer speed in the copper wire 82 .

[0135] Specifically, the first anode chamber 1 and the second anode chamber 3 are also equipped with reference electrodes for measuring the battery potential.

[0136] Specifically, a reference electrode placement port 16 is opened on the top wall of the first anode chamber 1 and the second anode chamber 3. After the reference electrodes are placed in the first anode chamber 1 and the second anode chamber 3 through the reference electrode placement port 16, they are fixed with rubber stoppers to maintain an anaerobic environment in the first anode chamber 1 and the second anode chamber 3.

[0137] Specifically, water inlets and outlets 9 are provided above the first anode chamber 1, the second anode chamber 3, the first cathode chamber 2 and the second anode chamber 3. A sampling port 17 is also provided on the top wall of the first anode chamber 1 and the second anode chamber 3. During operation, the water inlets and outlets 9 and the sampling port 17 are fixed with rubber stoppers to maintain an anaerobic environment in the first anode chamber 1 and the second anode chamber 3; the water inlets and outlets 9 are used to input sewage and buffer solution into the anode chamber and the cathode chamber respectively, and the sampling port 17 is used to sample and detect water samples in the anode chamber and the cathode chamber.

[0138] Specifically, the top walls of the first cathode chamber 2 and the second cathode chamber 4 are further provided with a dissolved oxygen detection port 12 , and the dissolved oxygen detection port 12 is used to insert a dissolved oxygen monitoring probe to monitor the dissolved oxygen in the first cathode chamber 2 and the second cathode chamber 4 .

[0139] Specifically, the top walls of the first cathode chamber 2 and the second cathode chamber 4 are also provided with an aeration device installation opening 11 for extending the aeration device into the first cathode chamber 2 and the second cathode chamber 4. The aeration device used in this embodiment is an aeration pipe connected to an aeration head, and the aeration head and the aeration pipe extend from the aeration device installation opening 11 into the bottom of the cathode chamber, one end of the aeration pipe is fixedly connected to the aeration head, and the other end of the aeration pipe is connected to the aerator.

[0140] The working process of the four-chamber microbial fuel cell disclosed in this embodiment is: the simulated sewage with a high C / N ratio is divided into two parts, and the two parts of the simulated sewage are respectively input into each anode chamber from the water inlet and outlet of each anode chamber, and the two parts of the buffer solution are respectively input into each cathode chamber from the water inlet and outlet of each cathode chamber. After the water enters each anode chamber and cathode chamber, anaerobic sludge is inoculated in the anode chamber, and aerobic sludge is inoculated in the cathode chamber, so that the anode chamber operates under anaerobic environmental conditions and the cathode chamber operates under aerobic or anoxic environmental conditions; a large number of electrogenic bacteria and non-electrogenic bacteria are attached to the graphite felt in the anode chamber, and the sewage can be A large amount of carbon-containing organic matter in the water is metabolized to produce CO2, protons and electrons. The electrons produced by the reaction in the anode chamber form an external current in the copper wire and are transferred to the cathode chamber through the external copper wire. The ammonia nitrogen in the first anode chamber is transferred to the first cathode chamber through the first cation exchange membrane, and the ammonia nitrogen in the second anode chamber is transferred to the second cathode chamber through the second cation exchange membrane, realizing biological nitrification in the cathode chamber; the nitrite and nitrate in the first cathode chamber and the second cathode chamber pass through the first anion exchange membrane and the second anion exchange membrane respectively, and are transferred to the second anode chamber and the first anode chamber respectively to realize biological denitrification.

[0141] The sewage purification effect verification of this example

[0142] The four-chamber microbial fuel cell disclosed in this embodiment was tested for its effect. First, the reaction conditions were set: the resistance values ​​of the four resistors on the conductive wires were set to 1000Ω, the ammonia nitrogen was set to 100 mg / L, the COD value was changed to 500, 700, 900, and 1100 mg / L, and the changes in nitrogen concentrations when the C / N ratios in the simulated sewage were 5, 7, 9, and 11 were compared.

[0143] The liquid input into the first anode chamber and the second anode chamber is simulated sewage, and its components include phosphate buffer solution (PBS), C6H 12O6 (concentration of 0.9368g / L), NH4Cl (concentration of 0.3824g / L), KCl (concentration of 0.1g / L), NaCl (concentration of 0.5g / L), CaCl2 (concentration of 0.015g / L), MgCl2·6H2O (concentration of 0.02g / L), trace elements and vitamins. The components of the phosphate buffer solution include K2HPO4·3H2O (concentration of 14.15g / L) and KH2PO4 (concentration of 5.166g / L). The influent of the first cathode chamber and the second cathode chamber does not contain organic matter and ammonia nitrogen, and its components include phosphate buffer solution, KCl (concentration of 0.1g / L), NaCl (concentration of 0.5g / L), CaCl2 (concentration of 0.015g / L), MgCl2·6H2O (concentration of 0.02g / L), trace elements and vitamins.

[0144] The trace elements shown in Table 1 and the vitamins shown in Table 2 were added to the inlet water of each electrode chamber at a ratio of 1L:1mL.

[0145] Table 1 Trace element formula

[0146] Element Concentration g / L Nitrilotriacetic acid 1.5 Magnesium sulfate 3.0 Manganese sulfate 0.5 Sodium chloride 1.0 Ferrous Sulfate Heptahydrate 0.1 Copper sulfate pentahydrate 0.01 Potassium aluminum sulfate dodecahydrate 0.01 Cobalt chloride hexahydrate 0.1 Calcium chloride dihydrate 0.1 Zinc chloride 0.13 Boric acid 0.01 Sodium molybdate 0.025 Nickel chloride hexahydrate 0.024 Sodium Tungstate Dihydrate 0.025

[0147] Table 2 Vitamin formula

[0148] Element Concentration mg / L Biotin 20 Folic acid 20 Vitamin B6 100 Thiamine 50 Riboflavin 50 niacin 50 Calcium Pantothenate 50 Vitamin B12 1 p-Aminobenzoic acid 50 Lipoic Acid 50

[0149] The equivalent connection circuit of the four-chamber microbial fuel cell disclosed in this embodiment is as follows Figure 5 As shown, the electrodes in the first anode chamber and the electrodes in the first cathode chamber form a closed loop to form the MFC1 module, the electrodes in the first cathode chamber and the electrodes in the second anode chamber form a closed loop to form the MFC2 module, the electrodes in the second anode chamber and the electrodes in the second cathode chamber form a closed loop to form the MFC3 module, and the electrodes in the second cathode chamber and the electrodes in the first anode chamber form a closed loop to form the MFC4 module. Any one of the MFC1 module, the MFC2 module, the MFC3 module and the MFC4 module shares the electrolyte with the other two adjacent module microbial fuel cells.

[0150] like Figure 6As shown, it is a voltage output diagram of the reactor of the present invention during the stabilization process. It can be seen from the figure that when the C / N ratio is 5, 7, 9, and 11, the power generation cycle is 103h, 128h, 162h, and 189h, respectively. When the C / N is 5, 7, 9, and 11, the peak voltage of the MFC1 module microbial fuel cell is 321mv, 317mv, 442mv, and 526mv, respectively, the peak voltage of the MFC2 module microbial fuel cell is 325mv, 318mv, 603mv, and 619mv, respectively, the peak voltage of the MFC3 module microbial fuel cell is 304mv, 314mv, 436mv, and 525mv, respectively, and the peak voltage of the MFC4 module microbial fuel cell is 313mv, 316mv, 603mv, and 619mv, respectively; that is, the power generation cycle of the four module microbial fuel cells increases with the increase of the C / N ratio, and the peak voltage shows an overall upward trend, as shown by Figure 6 The results showed that a four-chamber microbial fuel cell device with alternating cation exchange membranes and anion exchange membranes is feasible.

[0151] like Figure 7 As shown in the figure, it is the polarization curve of the four-chamber microbial fuel cell disclosed in this embodiment in the test. It can be seen from the figure that when C / N is 5, 7, 9, and 11, the maximum power density (compared to the electrode area) of the MFC1 module microbial fuel cell is 88.17 mw·m -2 、94.41mw·m -2 、152.55mw·m -2 and 224.45mw·m -2 The maximum power density of the MFC2 module microbial fuel cell is 130.05mw·m -2 、144.01mw·m -2 、154.71mw·m -2 and 236.02mw·m -2 The maximum power density of the MFC3 module microbial fuel cell is 136.53mw·m -2 、141.88mw·m -2 、149.33mw·m -2 and 206.94mw·m -2 The maximum power density of the MFC4 module microbial fuel cell is 66.67mw·m -2 、72.80mw·m -2 、178.94mw·m -2 and 242.00mw·m -2 ,Depend on Figure 7 The results show that the maximum power density of each module microbial fuel cell increases with the increase of C / N ratio.

[0152] When the test is completed, Figure 8 The COD removal rates of the first anode chamber and the second anode chamber shown increase with the increase of the C / N ratio. When C / N is 5, 7, 9, and 11, the COD removal rates of the first anode chamber are 85.24±0.48%, 90.94±0.22%, 93.69±0.07%, and 94.66±0.07%, respectively, and the COD removal rates of the second anode chamber are 86.28±0.67%, 91.15±0.07%, 94.20±0.25%, and 94.64±0.08%, respectively.

[0153] like Fig. 9 As shown in the figure, the nitrogen concentration changes in each electrode chamber when the C / N ratio is 5, 7, 9, and 11. The ammonia nitrogen removal rate in the anode chamber is between 81.8% and 97.7%, and the removal rate increases with the increase of the C / N ratio. It can be seen from the figure that the nitrate in the cathode chamber first reaches a peak and then shows a downward trend. In the past, the nitrate in the cathode chamber of the cathode nitrification coupled anode denitrification double-chamber microbial fuel cell with a cation exchange membrane as a separator was difficult to be effectively removed under high dissolved oxygen conditions. And due to the barrier effect of the ion exchange membrane, most of the organic matter in the anode chamber is used for power generation and denitrification, and only a very small part diffuses into the cathode chamber. Therefore, the cathode chamber maintains a low COD environment, and autotrophic nitrifying bacteria can become the dominant species. The ammonia nitrogen in the previous anode chamber is transferred to the cathode chamber in the later sequence and is quickly converted into nitrate and nitrite. There is basically no accumulation of ammonia nitrogen in the cathode chamber. With the increase of the C / N ratio, the nitrate in the cathode chamber continues to decline, and finally only 2-3 mg / L NO3 — N. It can be seen that the reactor has a high resistance to sewage with a high C / N ratio and can achieve the purpose of synchronous degradation of organic matter and ammonia nitrogen in the anode chamber.

[0154] The four-chamber microbial fuel cell disclosed in this embodiment has an increasing power generation cycle as the C / N ratio increases from 5, 7, 9 to 11, and the power generation time increases from 103h to 189h. After the power generation cycle, the COD removal rate and ammonia nitrogen removal rate in the anode chamber increase with the increase of the C / N ratio, and the COD removal rate is between 84.7% and 94.7%, and the ammonia nitrogen removal rate is between 81.8% and 97.7%. The four-chamber microbial fuel cell disclosed in this embodiment can simultaneously remove organic matter and ammonia nitrogen through the migration and transformation of ions in each electrode chamber, and discharge the effluent after the power generation cycle. It is suitable for batch operation, suitable for long-term intermittent operation, and has a wide range of applicable scenarios.

[0155] The four-chamber microbial fuel cell disclosed in this embodiment adopts a dual-anode and dual-cathode structure in which the anodes and cathodes are arranged alternately, so that the electrons generated in multiple anodes will achieve a higher oxidation rate on multiple cathodes, thereby enhancing the current channel inside the microbial fuel cell, improving the power generation capacity of the microbial fuel cell, and thereby increasing the operating power of the microbial fuel cell, increasing the power generation, and thereby improving the removal efficiency of organic matter and ammonia nitrogen.

[0156] The four-chamber microbial fuel cell disclosed in this embodiment is provided with two electrodes in each electrode chamber, and the electrodes are respectively close to the cation exchange membrane and the anion exchange membrane of each electrode chamber, so that there are electrodes on both sides of the cation exchange membrane and the anion exchange membrane, which reduces the electrode spacing between the anion and cation exchange membranes. Moreover, having two anodes in the anode chamber can increase the effective reaction area of ​​the anode chamber without increasing the volume of the anode chamber, thereby improving the anode coulomb efficiency.

[0157] The four-chamber microbial fuel cell disclosed in this embodiment uses graphite felt with strong adsorption capacity as the electrode material, which can simultaneously realize the functions of increasing the microbial attachment area and electron current collection. The use of titanium wire with good conductivity as the conductor can reduce the internal resistance of the reactor and improve the power generation capacity; the alternating arrangement of the anode and cathode chambers and the anion and cation exchange membranes can improve the current channel inside the reactor and improve the power generation capacity; the four-chamber microbial fuel cell structure of double anode chambers and double cathode chambers can effectively increase the electron transmission channel and improve the power generation at the same time, so that the weak electric field generated by the system itself can stimulate the physiological activity of the anode and cathode microorganisms, and further improve the denitrification efficiency.

[0158] In summary, this embodiment effectively solves the shortcomings and defects of the prior art, does not require an external mediator, has the characteristics of low cost, high efficiency in denitrification, strong power generation capacity, and suitability for long-term intermittent operation, while achieving the separation of anode denitrification and cathode nitrification, and further improving operability and safety.

[0159] It is understood that the present invention is described by some embodiments, and those skilled in the art are aware that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. The embodiments described in the present invention are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all other embodiments obtained by ordinary technicians in the art without creative work based on the embodiments in the present invention belong to the scope of protection of the present invention.

Claims

1. A multi-chamber microbial fuel cell, characterized in that: It comprises a plurality of electrode chambers, wherein the plurality of electrode chambers comprises a plurality of anode chambers and a plurality of cathode chambers of the same number, wherein the anode chambers and the cathode chambers are alternately arranged to form a sequence, wherein the electrode chamber at the front position is sealed and fixedly connected to the electrode chamber at the rear position, wherein the first position of the sequence is the anode chamber, and the last position of the sequence is the cathode chamber, and the last position cathode chamber is connected to the first position anode chamber to form a cyclic sequence; A double electrode assembly is arranged in each electrode chamber, and in the same electrode chamber, two electrode assemblies are respectively installed on the top wall of the electrode chamber close to the cation exchange membrane and the anion exchange membrane; According to the sequence order, the electrode assemblies in the adjacent two-electrode chambers are connected by electrical wires, the electrode assemblies in the preceding electrode chamber are connected to the electrode assemblies in the succeeding electrode chambers by electrical wires, and the electrode assemblies in the last cathode chamber and the first anode chamber are also connected by electrical wires; the side wall of each electrode chamber is provided with two ion channels, and according to the sequence order, the ion channels in the adjacent two-electrode chambers are in corresponding positions and are connected; According to the sequence order, a cation exchange membrane is installed between the ion channel connecting the anode chamber at the front position and the cathode chamber at the back position adjacent thereto, an anion exchange membrane is installed between the ion channel connecting the cathode chamber at the front position and the anode chamber at the back position adjacent thereto, and an anion exchange membrane is installed between the ion channel connecting the last cathode chamber and the first anode chamber; anions in the last cathode chamber can pass through the anion exchange membrane and enter the first anode chamber; Anaerobic sludge is inoculated in each anode chamber, and each anode chamber is sealed; heterotrophic nitrification sludge is inoculated in each cathode chamber, and the dissolved oxygen content in each cathode chamber is maintained by an aeration device; high C / N ratio sewage is input into each electrode chamber in equal amounts, and the water quality of the anode chamber and the cathode chamber is the same; a water inlet and outlet are opened on the top wall or side wall of each electrode chamber, and the water inlet and outlet are used to input sewage into the anode chamber and the cathode chamber during operation, and the water inlet and outlet are also used to discharge water from each electrode chamber after the power generation cycle ends.

2. The multi-chamber microbial fuel cell according to claim 1, characterized in that: The electrode assembly includes graphite felt and titanium wire. The graphite felt is in sheet form and is vertically arranged inside the electrode chamber. One end of the titanium wire is inserted into the graphite felt, one end of the titanium wire and the middle section of the titanium wire are fixed to the top wall of the electrode chamber, and the other end of the titanium wire is exposed outside the top wall of the electrode chamber. The electric wire is connected to the titanium wire exposed outside the top wall of the electrode chamber. A resistor is arranged on the electric wire.

3. The multi-chamber microbial fuel cell according to claim 1, characterized in that: A reference electrode hole is provided in each electrode chamber for installing a reference electrode, and the reference electrode is a silver / silver chloride reference electrode.

4. The multi-chamber microbial fuel cell according to claim 1, characterized in that: The top wall of each anode chamber is also provided with a sampling port, and the top wall of each cathode chamber is also provided with a dissolved oxygen detection port.

5. A method for purifying wastewater with a high C / N ratio, using the multi-chamber microbial fuel cell as claimed in claim 1, characterized in that: The following steps are involved: S1, connecting the electrodes between adjacent polar chambers with electrical wires to form an electron transfer path; S2. Inoculate the corresponding type of sludge in each electrode chamber and turn on the aeration device in each cathode chamber; S3, inputting corresponding types of influent water into each electrode chamber; S4, after the power generation cycle of each electrode chamber is completed, the effluent is discharged to complete the purification process of the high C / N ratio sewage in a sequential batch mode; S5, repeating steps S3 and S4 to achieve continuous purification of high C / N ratio sewage; Among them, in step S2, anaerobic sludge is inoculated in each anode chamber, and each anode chamber is sealed; heterotrophic nitrifying sludge is inoculated in each cathode chamber; correspondingly, in step S3, inputting the corresponding type of influent into each electrode chamber means that equal amounts of high C / N ratio sewage are respectively input into each electrode chamber, and the influent water quality of the anode chamber and the cathode chamber is the same.

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