CN105858902B - Plant compound bio cathode wetland type biological fuel cell and water purification produce electricity method - Google Patents

Abstract

The invention discloses a plant composite biological cathode wetland biofuel cell and a method for generating electricity by purifying water. The sewage enters the ceramsite support layer from the water inlet pipe for water distribution, and the biological carbon particle layer is constructed to rise and overflow from the top overflow weir. Water flows into the wetland-type biocathode chamber through the connecting water pipe of the anode and cathode chamber, passes through the ceramsite water distribution layer, flows from top to bottom through the structural biochar particle layer, the bottom ceramsite support layer, and is discharged through the bottom central drain; at the same time , Sewage undergoes hydrolysis acidification deep anaerobic reaction in the anode chamber, organic matter is decomposed from macromolecules into small molecules, electricity-producing bacteria generate electrons while decomposing organic matter, electrons are collected by anode activated carbon felt electrode materials, and transmitted to the external circuit through copper wires , flows through the load to reach the cathode activated carbon felt electrode material, and participates in the reduction reaction on the surface of the cathode activated carbon felt electrode material. The invention has the advantages of simple structure, synchronous production capacity of ecological treatment sewage, good landscape effect and the like, and is a novel microbial fuel cell.

Description

Plant composite biocathode wetland biofuel cell and water purification method for generating electricity

technical field

The invention belongs to the field of environmental protection and clean energy, and relates to a microbial fuel cell and a method for generating electricity by purifying water by utilizing plant composite biological cathodes in cooperation with anaerobic microbial anodes to treat sewage and recover energy synchronously.

Background technique

Microbial fuel cells are a special class of fuel cells. It follows the principle of bioelectrochemistry, uses microorganisms to degrade organic pollutants in sewage, and at the same time converts chemical energy in pollutants into electrical energy. In addition to theoretically high energy conversion efficiency, there are other fuel cells that do not Some characteristics: wide range of raw materials, can use a variety of organic matter that cannot be used by general fuel cells, even organic matter in sewage; mild operating conditions, generally work under normal temperature, normal pressure, and neutral conditions, which makes the battery safe and efficient. Low carbon, recyclable resources, low maintenance costs.

The working principle of the known microbial fuel cell: a fuel cell is a device that converts chemical energy into electrical energy through microorganisms. The mechanism of action is that organic matter is oxidized by microorganisms as fuel in an anaerobic anode chamber, and the electrons generated are captured by microorganisms and transferred to the battery. At the anode, electrons reach the cathode through the external circuit, thereby forming a circuit to generate current, while protons reach the cathode through the proton exchange membrane through internal diffusion and mass transfer, and react with the electron acceptor (oxygen) to generate water. Its anode and cathode reactions are as follows:

Anode reaction: (CH ₂ O)n+nH ₂ O =nCO ₂ +4ne ^- +4nH ⁺

Cathodic reaction: 4e ^- +O ₂ +4H ⁺ = 2H ₂ O

In the known microbial fuel cells, the cathode generally adopts the following chemical cathodes: (1) gas cathode, which uses oxygen in the air as an electron acceptor to complete the cathode reduction reaction; (2) liquid cathode, which aerates the cathode to increase dissolved oxygen The concentration of dissolved oxygen is used as the electron acceptor, or chemical electron acceptors such as nitrate nitrogen are added. In order to improve the catalytic reduction performance of the electrode, this type of chemical cathode needs to add noble metals such as pt as electrode materials. The high price of noble metals inhibits microbial fuels. Large-scale application and promotion of batteries.

In order to solve the problems of proton exchange membrane fouling and high transmembrane resistance in the known microbial fuel single cell, some scholars have recently proposed a single cell plant deposition wetland biofuel cell. The fuel cell adopts the design that the anode and the cathode are in the same chamber, and the proton exchange membrane is cancelled. In this design, the roots of wetland plants are located in the anode area, forming a plant deposition wetland fuel cell. This type of fuel cell uses the rhizosphere microorganisms of wetland plants to participate in anodic oxidation, and uses rhizosphere enzymes secreted by roots to promote the anode catalytic oxidation reaction. In order to promote proton mass transfer, the upflow single-flow operation mode of bottom water inlet and top water outlet is adopted, and the proton exchange membrane is cancelled. The upflow mode also effectively inhibits the diffusion of dissolved oxygen in the top air to the lower anode. However, the production efficiency is low and the operation is unstable.

At present, the problems of the known membraneless wetland fuel cells are:

1. The integrated design of the cathode and anode leads to interference between the cathode and the anode, which reduces the Coulombic efficiency.

2. The cathode of the battery is a chemical cathode or a microbial cathode, and the oxygen in the cathode is oxygenated by artificial aeration, which consumes a lot of energy.

3. When the root system of the plant is located in the anaerobic zone, the oxygen secreted by the rhizosphere will lead to anode poisoning. If there is no strict anaerobic zone cooperation, the COD concentration of the influent should not be too high, otherwise it will inhibit the growth of wetland plants and even cause plant death. The low COD concentration also limits the nutrient source of electricity-producing bacteria, and the electricity production efficiency is low.

4. The remaining organic matter (COD) that is not fully degraded enters the cathode area, consumes the dissolved oxygen of the cathode, and leads to a decrease in power generation efficiency.

Contents of the invention

Aiming at the problems of the known microbial fuel cell and single-cell plant deposition wetland type biofuel cell, the present invention provides a plant composite biocathode wetland type biofuel cell and a water purification method for generating electricity.

The purpose of the present invention is achieved through the following technical solutions:

A wetland-type biofuel cell with a plant composite biocathode adopts a double-chamber membrane-free design, and mainly includes an anode chamber, a wetland-type biocathode chamber, a water pipe connected to the cathode chamber of the anode chamber, an external circuit, a load, and a copper wire, wherein;

The anode chamber is an anaerobic reaction chamber, including a water inlet pipe, a ceramsite support layer, a structural biological carbon particle layer, an overflow weir and multiple groups of anode activated carbon felt electrode materials;

The wetland type biological cathode chamber includes wetland plants, ceramsite cloth water layer, structural biochar particle layer, bottom ceramsite supporting layer, drainage pipe and cathode activated carbon felt electrode material;

Sewage enters the ceramsite support layer water distribution through the water inlet pipe located at the bottom center of the anode chamber, forming an upflow from bottom to top, and then overflows from the overflow weir at the top through the upflow of the structural bio-carbon particle layer, and flows in through the water pipe connecting the anode and cathode chambers In the wetland type biocathode chamber, water overflows from the top of the wetland type biocathode chamber to form falling water, which passes through the ceramsite cloth water layer to distribute water, from top to bottom, flows through the structural biocarbon particle layer, the bottom ceramsite supporting layer, It is discharged through the central drain pipe at the bottom to complete the material flow;

At the same time, the sewage undergoes hydrolysis and acidification deep anaerobic reaction in the anode chamber, and the organic matter is decomposed from macromolecules into small molecules. Electrogenic bacteria generate electrons while decomposing organic matter, and the electrons are collected by multiple groups of anode activated carbon felt electrode materials arranged vertically and parallel. It is transmitted to the external circuit through copper wires, flows through the load and reaches multiple groups of cathode activated carbon felt electrode materials arranged vertically and parallel in the wetland type biological cathode chamber, and participates in the reduction reaction on the surface of the cathode activated carbon felt electrode material.

The process of using the above-mentioned plant composite biocathode wetland biofuel cell to purify water and generate electricity is as follows:

Sewage flows in from the central inlet pipe at the bottom of the anode chamber through the lift pump, distributes water through the ceramsite support layer, flows upwards, flows through the structural bio-carbon particle layer, overflows from the top overflow weir, and flows into the wetland through the connecting water pipe of the top anode and cathode chamber Type bio-cathode chamber, through the overflow and falling water, enters the wetland ceramsite cloth water layer, flows downward into the structural bio-carbon particle layer, and then passes down through the bottom ceramsite supporting layer, and is discharged from the central drainage pipe at the bottom of the cathode chamber to complete water purification cycle;

At the same time, the electrons generated by the anaerobic electricity-producing microorganisms in the anode chamber are collected by the anode activated carbon felt electrode material, passed through the copper wire to the external circuit, flow through the load to reach the cathode activated carbon felt electrode material, and participate in the reduction reaction on the surface of the cathode activated carbon felt electrode material , the power generation process is completed.

The plant composite bio-cathode wetland biofuel cell provided by the present invention is different from the currently known dual-chamber microbial fuel cell in that it adopts a dual-chamber design, the anode chamber and the cathode chamber are connected by pipes at the top, and there is no proton exchange membrane structure; the anode chamber It is an anaerobic reaction filter, and the cathode chamber is a plant-composite bio-cathode wetland cathode; the hydraulic flow state: the anode is upflow, and the cathode is downflow. Compared with known dual-chamber microbial fuel cells, the present invention has the following advantages:

1. The present invention has multi-strain layered combination from strict anaerobic bacteria to wetland micro-ecological system, multi-ecological combination operation and electricity production mode, can process and recover high-concentration organic sewage, and has the characteristics of high electricity production and energy efficiency.

2. The cathode of the fuel cell is a plant composite biocathode, which utilizes the dual catalytic reduction of rhizosphere microorganisms and rhizosphere enzymes, and utilizes rhizosphere secreted oxygen as an electron acceptor to realize the cathode reduction reaction. Wetland plants can effectively absorb CO ₂ , nitrogen, and P in sewage as nutrient sources, and produce oxygen while deeply purifying sewage.

3. High-efficiency conductive anode filter material and wetland matrix. Both the filter material and the matrix are constructed of biological carbon, with well-developed mesopores and dense and orderly micropores. The diffusion rate from anode to cathode reduces concentration polarization, reduces internal resistance, and improves battery efficiency. The developed mesopores are conducive to substrate mass transfer and biomass regulation, renew biofilm, and maintain microbial activity.

4. The anode chamber of the microbial fuel cell is a strict anaerobic reaction area, so that the fuel cell can use high-concentration organic sewage with a COD concentration greater than 1000mg/L, and also avoids the COD concentration of the water entering the ordinary wetland deposition fuel cell. The high problem has greatly increased the production capacity.

5. The fuel cell can realize the microbial operation mode of layered combination of polymorphic flora from deep anaerobic to wetland micro-ecological system. It has the advantages of simple structure, synchronous production capacity of ecological treatment sewage, and good landscape effect. It has the advantages of other biofuels. The technical advantage that the battery does not have is a new type of microbial fuel cell.

Description of drawings

Fig. 1 is the vertical layout of plant composite biocathode wetland biofuel cell;

Fig. 2 is A-A sectional view of plant composite biocathode wetland type biofuel cell;

In the figure, 1: anode chamber, 2: wetland type biocathode chamber, 3: anode chamber cathode chamber connected water pipe, 4: water inlet pipe, 5: overflow weir, 6: drain pipe, 7: external circuit, 8: load, 9: wetland plants, 10: copper wire, 1-1: anode activated carbon felt electrode material, 1-2: ceramsite support layer, 1-3: structural biological carbon particle layer, 1-5: sealing cover, 2- 1: Ceramsite cloth water layer, 2-2: Structural biochar particle layer, 2-3: Bottom ceramsite support layer, 2-4: Cathode activated carbon felt electrode material.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered by the present invention. within the scope of protection.

As shown in Fig. 1-2, the wetland type biofuel cell of the plant composite biocathode provided by the present invention consists of an anode chamber 1, a wetland type biocathode chamber 2, an anode chamber cathode chamber connected to a water pipe 3, an external circuit 7, a load 8 and copper wires 10 composition, of which:

The anode chamber 1 is a rectangular pool body, including a water inlet pipe 4, a ceramsite support layer 1-2, a structural biological carbon particle layer 1-3, an overflow weir 5 and multiple groups of anode activated carbon felt electrode materials 1-1, Among them: a water inlet pipe 4 is arranged at the central position of the bottom, and a 3mm thick anode activated carbon felt electrode material 1-1 is arranged in parallel and vertically in the pool, and the width of the anode activated carbon felt electrode material 1-1 is the same as the elevation size of the pool body, and the height is bottom. The side is flush with the bottom of the pool, and the top is the top of the structural biological carbon particle layer 1-3; the bottom of the anode chamber 1 is filled with a ceramsite support layer 1-2 with a thickness of 5cm and a particle size of 3-5mm, and the ceramsite support layer 1-2 2. On the top is a structural biological carbon particle layer 1-3 with a thickness of not less than 50cm and a particle size of 2-3mm. An overflow weir 5 is arranged on the top of the anode chamber 1. The size of the pool can be designed according to the water volume and hydraulic retention time of sewage treatment. Sewage enters the ceramsite support layer 1-2 from the water inlet pipe 4 and distributes water, forming an upward flow from bottom to top, and then overflows from the overflow weir 5 at the top through the structural biochar layer 1-3, and passes through the anode chamber and the cathode chamber to connect to the water pipe 3 flows into the wetland type biological cathode chamber 2. The top of the anode chamber 1 is provided with a sealing cover 1-5 to ensure that the anode chamber 1 is an anaerobic reaction chamber. In the anode chamber 1, the organic matter is catalyzed and decomposed by anaerobic bacteria, and the anaerobic bacteria grow in the form of biofilm on the surface of the structured biological carbon particle layer 1-3 and the electrode surface of the anode activated carbon felt electrode material 1-1, and the anaerobic bacteria decompose the organic matter to produce Electrons, electrons are collected by the anode activated carbon felt electrode material 1-1, transferred to the external circuit 7 through the copper wire 10, and reach the surface of the cathode activated carbon felt electrode material 2-4 through the load 8 and the copper wire 10.

The wetland type biological cathode chamber 2 is designed to be parallel to the anode chamber 1, including wetland plants 9, ceramsite cloth water layer 2-1, structural biochar particle layer 2-2, bottom ceramsite supporting layer 2-3, Drainage pipe 6 and cathode activated carbon felt electrode material 2-4, wherein: the thickness of the ceramsite cloth water layer 2-1 is 5cm, the ceramsite particle diameter is 3-5mm, and the thickness below the ceramsite cloth water layer 2-1 is not less than 50cm , a structural biochar particle layer 2-2 with a particle size of 2-3mm, the bottom of the structural biocarbon particle layer 2-2 is a bottom ceramsite supporting layer 2-3 with a thickness greater than 5cm and a ceramsite particle size of 3-5mm, A drain pipe 6 is arranged at the center of the bottom of the wetland type biological cathode chamber 2 . There are multiple groups of 3mm thick cathode activated carbon felt electrode materials 2-4 vertically arranged in parallel in the wetland type biocathode chamber 2, the height of which is that the bottom reaches the bottom of the wetland type biocathode chamber 2, and the top reaches the ceramsite cloth water layer 2-4. 1 top, the width is equivalent to the width of the wetland type biological cathode chamber 2, the cathode activated carbon felt electrode material 2-4 is connected with the external circuit 7 and the load 8 through multiple copper wires 10; wetland plants 9 are planted on the top of the wetland type biological cathode chamber 2 , the root system of the wetland plant 9 is located in the structural biochar particle layer 2-2 and the bottom ceramsite support layer 2-3, and the rhizosphere of the wetland plant 9 secretes oxygen, which is an important source of the cathode electron acceptor of the fuel cell, and solves the problem of artificial aeration. Oxygen, reducing operating costs; the facultative oxygen zone at the bottom of the rhizosphere in wetlands uses trace organic matter secreted from the rhizosphere, uses nitrate nitrogen as the electron acceptor, and uses denitrifying bacteria to perform reduction reactions to achieve denitrification while completing the electrical cycle; wetland plants 9 provides oxygen for the cathode chamber through the root system secreting oxygen, and at the same time, the wetland plant 9 absorbs nitrogen and phosphorus in the water through the root system to purify the water quality and recycle resources.

The wetland type biocathode chamber 2 communicates with the anode chamber 1 at the top through the anode chamber cathode chamber connecting water pipe 3, and the water flows into the overflow weir 5 through the anode chamber cathode chamber connecting water pipe 3 and overflows into the wetland type biocathode chamber 2. Water overflows from the top of the wetland type biocathode chamber 2 to form falling water, which distributes water through the ceramsite water distribution layer 2-1, and flows through the structural biocarbon particle layer 2-2 and the bottom ceramsite supporting layer 2 from top to bottom. -3, discharged through the drain pipe 5 to complete the material flow.

The structure of the fuel cell adopts a double-cell design, the anode chamber and the cathode chamber are arranged in parallel separately, and are connected by a pipeline without a proton exchange membrane; the anode chamber is an anaerobic filter structure, the cathode is a wetland structure, and the plants are located in the cathode chamber; Effectively increase the concentration of organic substrate (COD) in the influent and increase production capacity.

The anode filter material and cathode wetland matrix material of the fuel cell are both supported by ceramsite for water distribution and filled with biochar. According to the concentration of influent organic substrate (COD), the structure of biochar has developed mesopores, dense micropores and Orderly and well-developed mesopores are conducive to dissolved oxygen and substrate mass transfer, improving mass transfer performance. Dense and orderly micropores are conducive to reducing internal resistance and improving electrical conductivity. At the same time, micropores are conducive to the formation of rich biofilms. Regulates biomass.

The operation mode adopts dual-flow operation: the anode is up-flow operation, and the cathode is down-flow operation, specifically: water enters the center of the bottom of the anode chamber, distributes water through the ceramsite supporting layer, flows through the structural biological carbon particle layer to reach the top, The upflow mode of the water outlet through the overflow weir, the top outlet water is discharged into the top of the wetland-type bio-cathode chamber through the anode chamber cathode chamber connected to the water pipe, forming a small drop at the top of the wetland, increasing the concentration of dissolved oxygen in the air, and entering water from the top. Evenly distribute water through the ceramsite water distribution layer, flow down through the structural biochar particle layer, the ceramsite support layer at the bottom, and drain in the center of the bottom to form a downflow operation mode and a dual-flow design. On the one hand, it inhibits the diffusion of dissolved oxygen into the anode. Chamber, on the other hand, reduces the interference of the cathode to the anode.

The electrode material of the fuel cell is activated carbon felt electrode material, and the copper wire is connected with the activated carbon felt electrode material to transfer electrons to the external circuit.

The process of the process section is:

1. The water containing organic matter flows in through the central water inlet pipe at the bottom of the anode chamber, and distributes water evenly through the ceramsite support layer 1-2 in the form of upward flow; the upward flow enters the organic carbon particle layer 1-3 and the anode activity In the anaerobic reaction zone composed of carbon felt electrode material 1-1, the organic matter in this area is hydrolyzed and acidified, deeply anaerobic, and the insoluble organic matter of large molecules becomes dissolved organic matter of small molecules, and finally most of the organic matter degrades, producing NH ⁴ + , CO ₂ , water, a small amount of CH ₄ , etc. generate electrons at the same time, and the electrons are collected by the anode activated carbon felt electrode material 1-1, transferred to the external circuit 7 through the copper wire 10, and reach the cathode activated carbon felt electrode through the load 8 2-5; Part of the undegraded organic matter (COD) ammonia nitrogen aqueous solution flows out through the top overflow weir 5, and flows into the top of the wetland type biocathode chamber 2 through the anode and cathode chamber connecting water pipe 3.

2. Inflow of water containing a small amount of organic matter (COD) and ammonia nitrogen falls on the top of the wetland type biocathode chamber 2 to increase the concentration of dissolved oxygen, distribute water evenly through the ceramsite water distribution layer 2-1, and flow downward into the biochar formed by the structure The aerobic zone formed by the combination of granular layer 2-2 and 9 roots of wetland plants uses the 9 roots of wetland plants to secrete oxygen and dissolved oxygen as electron acceptors, and uses the biofilm that constructs biochar granular layer 2-2 as a catalyst to complete the cathode Microorganisms catalyze reduction reactions. At the same time, the adsorption of wetland substrates, the absorption of wetland plants, assimilation, and aerobic biochemistry are used to further reduce organic matter, ammonia nitrogen, and TP to purify water quality.

3. The water continues to flow downward into the ceramsite supporting layer 2-3 in the facultative zone. The nitrate nitrogen in this water acts as an electron acceptor, and the denitrifying bacteria use a small amount of COD secreted by the rhizosphere to complete the denitrification and denitrification reaction, and the water quality is improved. Fully purified, discharged through the central drain pipe 6 at the bottom, and the process of generating electricity and purifying water is completed.

The specific electrode reaction is as follows:

1. The main reaction of the anode:

C ₆ H ₁₂ O ₆ + 6H ₂ O –24e ^- (synergism between microorganisms and electrogenic bacteria) → 6CO ₂ + 24H ⁺

Second, the main reaction of the cathode:

6O ₂ + 24 e ^- +24H ⁺ → 12H ₂ O (oxygen comes from plant root oxygen secretion)

2NH ₄ ⁺ + 3O ₂ (nitrifying bacteria) → 2 NO ₃ ^- + 8H ⁺

2NO ₃ ^- + 12e ^- + 12H ⁺ → N ₂ + 6H ₂ O

3. Overall reaction:

C ₆ H ₁₂ O ₆ + 7O ₂ +NH ₄ → 6CO ₂ + 8H ₂ O+1/2N ₂

The above-mentioned plant composite biological cathode wetland biofuel cell provided by the present invention has a multi-ecological system combined operation power generation mode, can handle higher concentrations of organic sewage, and has the characteristics of higher electricity production efficiency, especially its wetland biocathode structure, forming a complex ecosystem composed of plants, wetland substrates, and substrate microorganisms. There are both bioreduction reactions with rhizosphere microorganisms as catalysts and reduction reactions with rhizosphere enzymes as catalysts, which greatly improves the reduction efficiency of the cathode; at the same time This cathode structure can use the rhizosphere to secrete oxygen to increase the oxygen concentration of the cathode electron acceptor, and use nitrate nitrogen as the electron acceptor in the facultative oxygen zone at the bottom of the rhizosphere to complete the denitrification reduction reaction. The catalytic reduction performance of the cathode, the cathode does not need artificial aeration and oxygenation, which is not available in other known microbial fuel cells.

Although the fuel cell adopts a double-chamber structure design, a non-separated ion-exchange membrane is used between the anode chamber and the cathode chamber, and the hydraulic flow state is used to suppress the influence of dissolved oxygen in the cathode chamber on the anaerobic power generation reaction in the anode chamber. Reduce the internal resistance of the battery and increase the effective output voltage.

The fuel cell can realize the multi-level purification process of sewage from deep anaerobic to wetland micro-ecological aerobic, and has a mode of microbial operation that combines anaerobic microorganisms attached to filter materials and microorganisms attached to wetland substrates to generate electricity and decontaminate. Fuel cells do not have.

Claims (9)

1. a kind of plant compound bio cathode wetland type biological fuel cell, it is characterised in that the fuel cell includes anode Room, wetland type biological-cathode room, anode chamber's cathode chamber connection water pipe, external circuit, load and copper conductor, wherein；

The anode chamber is the anaerobic reaction room that top is provided with sealing cover, including water inlet pipe, haydite supporting layer, construction biological carbon Granulosa, downflow weir and multigroup anode activated carbon-fiber felt electrode material；

Wetland type biological-cathode room includes wetland plant, haydite water distribution layer, construction biological carbon stratum granulosum, bottom haydite support Layer, drainpipe and cathode activity carbon felt electrode material；

Sewage positioned at the water inlet pipe of anode chamber's bottom center by entering haydite supporting layer water distribution, and formation flows up from bottom to top, through structure It makes biological carbon granulosa up-flow to be discharged from top weir overflow, being connected to water pipe by anode cathode room flows into wetland type biological-cathode Room, the top overflow in wetland type biological-cathode room, which is discharged, to form drop, is flowed through from top to bottom by haydite water distribution layer water distribution Biological carbon stratum granulosum, bottom haydite supporting layer are constructed, is discharged by bottom center drainpipe, material stream is completed；

Meanwhile in anode chamber hydrolysis acidification depth anaerobic reaction occurs for sewage, organic matter resolves into small molecule by macromolecular, produces electricity Bacterium generates electronics while decomposing organic matter, and electronics is received by multigroup anode activated carbon-fiber felt electrode material of vertical parallel arrangement Collection, external circuit is transmitted to by copper conductor, is flowed through load and is reached that multigroup vertical parallel to be arranged in wetland type biological-cathode indoor Cathode activity carbon felt electrode material participates in reduction reaction in cathode activity carbon felt electrode material surface.

2. plant compound bio cathode wetland type biological fuel cell according to claim 1, it is characterised in that the sun Pole room is rectangle pond body.

3. plant compound bio cathode wetland type biological fuel cell according to claim 1, it is characterised in that the pottery Grain supporting layer thickness be 5cm, grain size 3-5mm.

4. plant compound bio cathode wetland type biological fuel cell according to claim 1, it is characterised in that the structure The thickness for making biological carbon granulosa is not less than 50cm, grain size 2-3mm.

5. plant compound bio cathode wetland type biological fuel cell according to claim 1, it is characterised in that the pottery The thickness of grain water distribution layer is 5cm, haydite grain size is 3-5mm.

6. plant compound bio cathode wetland type biological fuel cell according to claim 1, it is characterised in that the structure The thickness for making biological carbon stratum granulosum is not less than 50cm, grain size 2-3mm.

7. plant compound bio cathode wetland type biological fuel cell according to claim 1, it is characterised in that the bottom The thickness of portion's haydite supporting layer is more than 5cm, haydite grain size is 3-5mm.

8. plant compound bio cathode wetland type biological fuel cell according to claim 1, it is characterised in that described the moon Pole activated carbon-fiber felt electrode material 3mm is thick, highly reaches cloudy wetland type biological-cathode room bottom for bottom, and top reaches haydite water distribution Layer top, width are suitable with wetland type biological-cathode room width.

9. a kind of plant compound bio cathode wetland type biological fuel cell using described in claim 1-8 any claims The method of water purification electricity production, it is characterised in that steps are as follows for the method：

The boosted pump of sewage is flowed into from anode chamber's bottom center water inlet pipe, by haydite supporting layer water distribution, is flowed up upwards, is flowed through structure Biological carbon granulosa is made, wetland type biological-cathode room, warp are flowed into through top anode cathode chamber connection water pipe by top weir overflow Overflow drop is crossed, construction biological carbon stratum granulosum is flowed downwardly into wetland haydite water distribution layer, still further below by bottom haydite support Layer is discharged by cathode chamber bottom center drainpipe, completes Water warfare cycle；

Meanwhile the electronics that anaerobism electricity-producing microorganism generates in anode chamber is collected by anode activated carbon-fiber felt electrode material, is led by copper Line is transmitted to external circuit and flows through load arrival cathode activity carbon felt electrode material, is participated in cathode activity carbon felt electrode material surface Reduction reaction, electricity generation process are completed.