Water quality purifier and water quality purification system

Abstract

To solve the problem of insufficient reaction at the cathode electrode when a cathode electrode is installed in an area with low dissolved oxygen levels.SOLUTION: A water quality purifier includes a container for holding a liquid containing organic matter and electrochemically active bacteria, an anode electrode disposed within the liquid, a hollow body for holding a gas containing oxygen, and a first surface in contact with the liquid and a second surface for permeating the oxygen contained in the gas held within the hollow body, a cathode electrode positioned across the liquid relative to the anode electrode, and a resistor electrically connecting the anode electrode and the cathode electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water purification device and a water purification system. [Background technology]

[0002] Water purification systems that improve the water quality of rivers and lakes are known. Patent Document 1 describes a bottom sediment improvement device as a water purification system. The bottom sediment improvement device improves the bottom sediment of rivers and other areas using a microbial fuel cell system. The bottom sediment improvement device improves water quality by removing phosphorus and other substances immobilized in the bottom sediment. The bottom sediment improvement device is equipped with an anode electrode and a cathode electrode. The cathode electrode reacts with dissolved oxygen in the water. The cathode electrode is made up of multiple carbon felt electrodes installed at different water depths. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-168560 Summary of the Invention [Problem to be solved by the invention]

[0004] When the cathode electrode is installed in a location where the amount of dissolved oxygen is low, the reaction at the cathode electrode may be insufficient. [Means for solving the problem]

[0005] The water purification device disclosed herein includes a container that contains a liquid containing organic matter and electrochemically active bacteria, an anode electrode that is placed in the liquid, a hollow body that contains a gas containing oxygen, a cathode electrode that has a first surface that contacts the liquid and a second surface that allows the oxygen contained in the gas contained in the hollow body to pass through, and is placed relative to the anode electrode via the liquid, and a resistor that is electrically connected to the anode electrode and the cathode electrode.

[0006] The water purification system disclosed herein is a water purification system that is installed in a liquid containing organic mud and electrochemically active bacteria, and includes an anode electrode that is placed in the liquid, a hollow body that contains a gas that contains oxygen, a cathode electrode that has a first surface that contacts the liquid and a second surface that allows the oxygen contained in the gas contained in the hollow body to pass through, and is placed relative to the anode electrode via the liquid, and a resistor that is electrically connected to the anode electrode and the cathode electrode. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a liquid treatment apparatus. [Figure 2] FIG. 2 is a diagram showing a schematic configuration of a cathode electrode. [Figure 3] FIG. 2 is a diagram showing a schematic configuration of a gas container. [Figure 4] FIG. 2 is a diagram showing a schematic configuration of a gas container. [Figure 5] FIG. 2 is a diagram showing a schematic configuration of a gas container. [Figure 6] FIG. 2 is a diagram showing a schematic configuration of a gas container. [Figure 7] FIG. 2 is a diagram showing a schematic configuration of a gas container. [Figure 8] FIG. 1 is a diagram showing a schematic configuration of a liquid treatment apparatus. [Figure 9] FIG. 1 is a diagram showing a schematic configuration of a liquid treatment apparatus. [Figure 10] FIG. 1 is a diagram showing a schematic configuration of a liquid treatment apparatus. [Figure 11] FIG. 1 is a diagram showing a schematic configuration of a liquid treatment apparatus. [Figure 12] FIG. 1 is a diagram showing the schematic configuration of a microbial fuel cell unit. [Figure 13] FIG. 1 is a diagram showing the schematic configuration of a microbial fuel cell unit. [Figure 14] FIG. 1 is a diagram showing the schematic configuration of a microbial fuel cell unit. [Figure 15] FIG. 1 is a diagram showing the schematic configuration of a microbial fuel cell unit. [Figure 16] FIG. 1 is a diagram showing the schematic configuration of a microbial fuel cell unit. [Figure 17] FIG. 1 is a diagram showing the schematic configuration of a microbial fuel cell unit. [Figure 18] FIG. 1 is a diagram showing the schematic configuration of a microbial fuel cell unit. DETAILED DESCRIPTION OF THE INVENTION

[0008] FIG. 1 shows a schematic configuration of a liquid treatment device 100. The liquid treatment device 100 is a device that purifies stored water L, such as domestic wastewater or industrial wastewater. Domestic wastewater, industrial wastewater, etc. contain organic matter. The stored water L corresponds to an example of a liquid. Domestic wastewater, industrial wastewater, etc. are collected from rivers, lakes, marshes, waterways, etc. The liquid treatment device 100 purifies the stored water L using microorganisms. The liquid treatment device 100 corresponds to an example of a water purification device.

[0009] 1 shows a first liquid treatment device 100a, which is an example of a liquid treatment device 100. The first liquid treatment device 100a includes a first microbial fuel cell unit 10a and a storage tank 50. The first microbial fuel cell unit 10a is an example of a microbial fuel cell unit 10.

[0010] The microbial fuel cell unit 10 uses microorganisms to decompose organic matter contained in the stored water L. The microbial fuel cell unit 10 produces energy, useful substances, etc. by electrochemically controlling the metabolism of the microorganisms. The microbial fuel cell unit 10 purifies the stored water L by electrochemically controlling the metabolism of the microorganisms. The microbial fuel cell unit 10 corresponds to an example of a water purification system. The microbial fuel cell unit 10 includes an anode electrode 11, a cathode electrode 13, a gas container 20, and a connection circuit 30.

[0011] 1 shows a first microbial fuel cell unit 10a. The first microbial fuel cell unit 10a includes a first gas container 20a, which is an example of a gas container 20.

[0012] The anode electrode 11 collects electrons generated when organic matter in the stored water L is oxidatively decomposed by microorganisms. The anode electrode 11 is placed in the stored water L. The electrons collected by the anode electrode 11 move to the cathode electrode 13 via the connection circuit 30. The anode electrode 11 comes into contact with the stored water L contained in the storage tank 50. On the anode electrode 11, the microorganisms contained in the stored water L decompose the organic matter and generate electrons and hydrogen ions. The electrons generated by the microorganisms are collected by the anode electrode 11.

[0013] The anode electrode 11 is made of a conductive material such as a metal material or a carbon material. Metal materials include iron, stainless steel, titanium, aluminum, copper, platinum, etc. Carbon materials include graphite, carbon fiber, carbon cloth, carbon mat, graphite felt, carbon paper, etc. The material of the anode electrode 11 is not particularly limited as long as it is a material that can receive electrons from microorganisms.

[0014] The cathode electrode 13 consumes electrons moving via the connection circuit 30 in a reduction reaction of the oxidant. The cathode electrode 13 is arranged with the reservoir water L interposed between it and the anode electrode 11. The electrons flow through the connection circuit 30 according to the gradient between the potential generated at the anode electrode 11 and the oxidation-reduction potential of the chemical reaction occurring at the cathode electrode 13. The cathode electrode 13 uses oxygen in the air as an oxidant. The oxygen permeates through the cathode electrode 13. The oxygen reacts with hydrogen ions moving through the reservoir water L. The configuration of the cathode electrode 13 will be described later.

[0015] The cathode electrode 13 has an ion exchange surface S1 and an oxygen permeable surface S2. The ion exchange surface S1 contacts the stored water L. The ion exchange surface S1 corresponds to an example of a first surface. The oxygen permeable surface S2 contacts the gas contained in the gas container 20. The oxygen permeable surface S2 allows oxygen contained in the gas to pass through. The oxygen permeable surface S2 corresponds to an example of a second surface.

[0016] The gas container 20 contains a gas containing oxygen. The gas container 20 supports the cathode electrode 13. The gas container 20 supports the cathode electrode 13 in a state where the oxygen permeable surface S2 of the cathode electrode 13 can come into contact with the contained gas. The gas container 20 supplies oxygen to the cathode electrode 13. The gas container 20 is configured as a hollow cylindrical body with a bottom. The gas container 20 is configured in a cylindrical shape, a rectangular prism shape, or a polygonal shape. The gas container 20 corresponds to an example of a hollow body. By providing the gas container 20, oxygen is stably supplied to the cathode electrode 13. FIG. 1 shows a first gas container 20a, which is an example of the gas container 20. The configuration of the first gas container 20a will be described later.

[0017] The connection circuit 30 is an electric circuit that moves electrons from the anode electrode 11 to the cathode electrode 13. The connection circuit 30 is electrically connected to the anode electrode 11 and the cathode electrode 13. The connection circuit 30 has a resistor 31. The resistor 31 is electrically connected to the anode electrode 11 and the cathode electrode 13. The resistor 31 may be a variable resistor that switches its resistance value. The resistor 31 adjusts the amount of current flowing through the connection circuit 30.

[0018] The storage tank 50 stores the stored water L. The storage tank 50 may be connected to an inflow path and an outflow path. The inflow path is a path through which water such as domestic wastewater and industrial wastewater flows into the storage tank 50. The domestic wastewater, industrial wastewater, and other water is stored in the storage tank 50 as the stored water L. The outflow path is a path through which the stored water L flows out of the storage tank 50. The inflow path and the outflow path are not shown. The storage tank 50 corresponds to an example of a storage body.

[0019] The reservoir water L contains organic matter and microorganisms. As an example, the reservoir water L is water collected from lakes, rivers, etc. The reservoir water L may contain organic mud collected from lakes, etc. The organic mud settles in the reservoir tank 50 to form a bottom mud layer ML. The bottom mud layer ML contains the reservoir water L. The bottom mud layer ML corresponds to an example of an organic mud layer. The organic matter contained in the reservoir water L is consumed as fuel for the microorganisms.

[0020] The microorganisms are electrochemically active bacteria that decompose organic matter in the stored water L. The electrochemically active bacteria include bacteria of the genus Geobacter, Shewanella, Aeromonas, Geothrix, and Saccharomyces. The microorganisms may be contained in the stored water L in advance, or may be added to the stored water L. The microorganisms may be supported on the anode electrode 11 in the form of a biofilm or the like.

[0021] The first liquid treatment device 100a comprises a storage tank 50 that stores water L containing organic matter and electrochemically active bacteria, an anode electrode 11 placed in the water L, a first gas container 20a that stores a gas containing oxygen, a cathode electrode 13 that has an ion exchange surface S1 in contact with the water L and an oxygen permeable surface S2 that allows oxygen contained in the gas stored in the gas container 20 to pass through, and is placed relative to the anode electrode 11 via the water L, and a resistor 31 that is electrically connected to the anode electrode 11 and the cathode electrode 13. By providing the first gas container 20a, the first liquid treatment device 100a can stably supply oxygen to the cathode electrode 13. The oxidation-reduction reaction at the cathode electrode 13 is stabilized. The first liquid treatment device 100a stably purifies water.

[0022] Fig. 2 shows a schematic configuration of the cathode electrode 13. Fig. 2 shows a cross-sectional configuration of the cathode electrode 13. The cathode electrode 13 includes a substrate layer 131, a filter layer 133, and a water-repellent layer 135. The outer surface of the filter layer 133 is an ion exchange surface S1. The outer surface of the water-repellent layer 135 is an oxygen permeable surface S2.

[0023] The substrate layer 131 is made of a conductive material such as a metal material or a carbon material. The substrate layer 131 is preferably made of a carbon material. When made of a carbon material, the surface area is larger and the electrical conductivity is higher than when made of a metal material. Metal materials include iron, stainless steel, titanium, aluminum, copper, platinum, etc. Carbon materials include graphite, carbon fiber, carbon cloth, carbon mat, graphite felt, carbon paper, etc. The material of the substrate layer 131 is not particularly limited as long as it has a conductive structure. The substrate layer 131 is preferably porous. The substrate layer 131 is oxygen permeable.

[0024] The filter layer 133 prevents microorganisms from entering the base material layer 131. The filter layer 133 transfers hydrogen ions to the base material layer 131. The filter layer 133 is made of, for example, an ion exchange resin. Examples of ion exchange resins include NAFION manufactured by DuPont Corporation, Flemion manufactured by Asahi Glass Co., Ltd., and Selemion manufactured by Asahi Glass Co., Ltd. NAFION, Flemion, and Selemion are registered trademarks.

[0025] The filter layer 133 includes a catalytic material. The catalytic material functions as a catalyst for the oxidation-reduction reaction. Examples of the catalytic material include precious metals and precious metal alloys such as platinum, cobalt, ruthenium, and iridium. The catalytic material may be precious metal-supported carbon, precious metal alloy-supported carbon, or precious metal compounds such as platinum phthalocyanine and ruthenium phthalocyanine. The catalytic material may be metal compounds such as iron oxide, cobalt oxide, iron nitride, iron phosphide, and cementite, or metal complex compounds such as iron phthalocyanine, iron azaphthalocyanine, iron porphyrin, cobalt phthalocyanine, cobalt azaphthalocyanine, and cobalt porphyrin. The catalytic material is preferably a precious metal, a precious metal compound, or a metal compound.

[0026] The water-repellent layer 135 prevents the stored water L from adhering to the base layer 131. The water-repellent layer 135 has oxygen permeability and water repellency. The water-repellent layer 135 allows oxygen in the atmosphere to pass through to the base layer 131. The water-repellent layer 135 is made of a nonwoven fabric such as polyethylene or polypropylene, a film such as polytetrafluoroethylene (PTFE), a composite material film made by compounding polyurethane polymers, beeswax, or the like. As an example, the water-repellent layer 135 is made of a PTFE layer. The PTFE layer is produced by applying a 30 to 80% PTFE liquid to one surface of the base layer 131 and drying it.

[0027] Fig. 3 shows a schematic configuration of the gas container 20. Fig. 3 shows a schematic configuration of a first gas container 20a, which is an example of the gas container 20. Fig. 3 shows the configuration of the first gas container 20a in a state in which the cathode electrode 13 has been removed. The cathode electrode 13 and a fixing jig 15 are attached to the first gas container 20a.

[0028] The first gas container 20a has a first container outer casing 21a. The first container outer casing 21a is an example of the container outer casing 21. The first container outer casing 21a is a cylindrical body having a bottom surface. The first container outer casing 21a has a side opening 23 and a top opening 25.

[0029] The side opening 23 is an opening provided in the first container-exterior body 21a. The side opening 23 is provided on a side surface of the first container-exterior body 21a. The side surface of the first container-exterior body 21a is a surface different from the bottom surface of the first container-exterior body 21a. The cathode electrode 13 is attached to the side opening 23. The cathode electrode 13 covers the side opening 23. By attaching the cathode electrode 13 to the side opening 23, the oxygen permeable surface S2 of the cathode electrode 13 can come into contact with the gas contained in the first gas container 20a. The side opening 23 corresponds to an example of a first opening.

[0030] The top opening 25 is an opening provided in the first container-exterior body 21a. The top opening 25 is provided on the top surface of the first container-exterior body 21a. The top surface of the first container-exterior body 21a is a surface that is located above along the vertical axis when the cathode electrode 13 is placed in the reservoir water L. When the cathode electrode 13 is placed in the reservoir water L, the top opening 25 is located outside the reservoir water L. The top opening 25 allows gas to circulate inside the first gas container 20a. The top opening 25 corresponds to an example of a second opening.

[0031] The cathode electrode 13 is attached to the first container outer casing 21a at the position of the side opening 23. By being attached to the first container outer casing 21a, the cathode electrode 13 constitutes part of the first container outer casing 21a. The ion exchange surface S1 of the cathode electrode 13 is capable of coming into contact with the stored water L. The cathode electrode 13 can come into contact with the stored water L at the ion exchange surface S1 and can come into contact with gas at the oxygen permeable surface S2.

[0032] The fixing jig 15 fixes the cathode electrode 13 to the first container-exterior body 21a. The fixing jig 15 contacts the outer periphery of the cathode electrode 13 and fixes the cathode electrode 13 to the first container-exterior body 21a. The fixing jig 15 is attached to the first container-exterior body 21a via the cathode electrode 13. The fixing jig 15 shown in FIG. 3 is configured to contact the outer periphery of the cathode electrode 13, but is not limited to this. The configuration of the fixing jig 15 is not limited as long as it is capable of fixing the cathode electrode 13 to the first container-exterior body 21a.

[0033] Fig. 4 shows a schematic configuration of the gas container 20. Fig. 4 shows a schematic configuration of a first gas container 20a, which is an example of the gas container 20. Fig. 4 shows the first gas container 20a to which the cathode electrode 13 is attached.

[0034] The cathode electrode 13 is attached to the first container outer casing 21a. The cathode electrode 13 is attached at a position where the side opening 23 is provided. The cathode electrode 13 is fixed to the first container outer casing 21a by a fixing jig 15. The cathode electrode 13 covers the side opening 23. By covering the side opening 23, the cathode electrode 13 can prevent the stored water L from entering the gas container 20.

[0035] The first gas container 20a is a cylindrical body having a side opening 23 and a top opening 25. The cathode electrode 13 is preferably attached to the side opening 23 and covers the side opening 23. By attaching the cathode electrode 13 to the side opening 23, the oxygen contained in the gas stored in the first gas container 20a can pass through the oxygen permeable surface S2 of the cathode electrode 13. Furthermore, by covering the side opening 23 with the cathode electrode 13, the stored water L is prevented from entering the first gas container 20a.

[0036] Fig. 5 shows a schematic configuration of the gas container 20. Fig. 5 shows a schematic configuration of a second gas container 20b, which is an example of the gas container 20. Fig. 5 shows the second gas container 20b to which the cathode electrode 13 is attached. The second gas container 20b has a sealing member 27. The second gas container 20b has the same configuration as the first gas container 20a, except that it has the sealing member 27.

[0037] The sealing member 27 covers the top opening 25. The sealing member 27 seals the top opening 25. The sealing member 27 seals the interior of the second gas container 20b. By providing the sealing member 27, the entire second gas container 20b can be immersed in the stored water L. The second gas container 20b can supply oxygen contained in the gas to the cathode electrode 13 while immersed in the stored water L. The sealing member 27 may be fixed to the first container exterior body 21a, or may be configured to be detachable. The sealing member 27 may be provided so as to be openable and closable relative to the first container exterior body 21a. The sealing member 27 corresponds to an example of a lid member.

[0038] The second gas container 20b preferably has a sealing member 27 that seals the top opening 25. By providing the sealing member 27, the entire second gas container 20b can be immersed in the stored water L. The second gas container 20b can supply oxygen contained in the gas to the cathode electrode 13 while immersed in the stored water L.

[0039] FIG. 6 shows a schematic configuration of the gas container 20. FIG. 6 shows a schematic configuration of a third gas container 20c, which is an example of the gas container 20. FIG. 6 shows the third gas container 20c to which the cathode electrode 13 is attached. The third gas container 20c has a sealing member 27. The third gas container 20c has a second container outer casing 21b, which is an example of the container outer casing 21. The third gas container 20c has the same configuration as the second gas container 20b, except for the configuration of the container outer casing 21 and the position of the cathode electrode 13.

[0040] The second container-exterior body 21b has a top opening 25 and a bottom opening 28. The second container-exterior body 21b does not have a side opening 23. The top opening 25 of the second container-exterior body 21b has the same configuration as the top opening 25 of the first container-exterior body 21a. The top opening 25 shown in FIG. 6 is sealed by a sealing member 27, but is not limited to this. The third gas container 20c does not need to include a sealing member 27. The second container-exterior body 21b shown in FIG. 6 has a different external shape from the first container-exterior body 21a shown in FIGS. 4 and 5, but is not limited to this. The second container-exterior body 21b may have the same external shape as the first container-exterior body 21a, or a different external shape.

[0041] The bottom opening 28 is an opening provided in the second container exterior body 21b. The bottom opening 28 is provided on the bottom surface of the second container exterior body 21b. The bottom surface of the second container exterior body 21b is the surface that is located downward along the vertical axis when the third gas container 20c is immersed in the stored water L. The bottom opening 28 is located in a position that faces the lower surface of the storage tank 50 or the bottom surface of a lake or marsh when the cathode electrode 13 is placed in the stored water L. The bottom opening 28 corresponds to an example of a first opening.

[0042] The cathode electrode 13 is attached to the bottom opening 28. The cathode electrode 13 covers the bottom opening 28. The cathode electrode 13 is fixed to the second container outer casing 21b by a fixing jig 15 (not shown). By attaching the cathode electrode 13 to a position that covers the bottom opening 28, the cathode electrode 13 is disposed in a position facing the lower surface of the storage tank 50 or the bottom surface of a lake or marsh or the like.

[0043] FIG. 7 shows a schematic configuration of the gas container 20. FIG. 7 shows a schematic configuration of a fourth gas container 20d, which is an example of the gas container 20. FIG. 7 shows the fourth gas container 20d to which the cathode electrode 13 is attached. The fourth gas container 20d has a sealing member 27. The fourth gas container 20d has a third container outer casing 21c, which is an example of the container outer casing 21. The fourth gas container 20d has the same configuration as the first gas container 20a, except for the configuration of the first container outer casing 21a and the position of the cathode electrode 13.

[0044] A first cathode electrode 13a and a second cathode electrode 13b are attached to the fourth gas container 20d. The first cathode electrode 13a and the second cathode electrode 13b are each an example of the cathode electrode 13. The first cathode electrode 13a and the second cathode electrode 13b are connected to a connection circuit 30 (not shown).

[0045] The third container-exterior body 21c has a side opening 23, a top opening 25, and a second side opening 29. The side opening 23 of the third container-exterior body 21c has the same configuration as the side opening 23 of the first container-exterior body 21a. The top opening 25 of the third container-exterior body 21c has the same configuration as the top opening 25 of the first container-exterior body 21a. The top opening 25 shown in FIG. 7 is sealed by a sealing member 27, but is not limited to this. The fourth gas container 20d does not need to include a sealing member 27. The third container-exterior body 21c shown in FIG. 7 has a different external shape from the first container-exterior body 21a shown in FIGS. 4 and 5, but is not limited to this. The third container-exterior body 21c may have the same external shape as the first container-exterior body 21a, or a different external shape.

[0046] A first cathode electrode 13a, which is an example of a cathode electrode 13, is attached to the side opening 23. The side opening 23 is covered by the first cathode electrode 13a. By attaching the first cathode electrode 13a to the side opening 23, the first cathode electrode 13a can come into contact with the gas contained in the fourth gas container 20d. The first cathode electrode 13a is fixed to the position of the side opening 23 of the third container outer casing 21c by a fixing jig 15 (not shown).

[0047] The second side opening 29 is an opening provided in the third container-exterior body 21c. The second side opening 29 is provided on a side surface of the third container-exterior body 21c. The second side opening 29 is provided on a side surface at a position different from the side surface on which the side opening 23 is provided. A second cathode electrode 13b, which is an example of a cathode electrode 13, is attached to the second side opening 29. The second side opening 29 is covered by the second cathode electrode 13b. By attaching the second cathode electrode 13b to the second side opening 29, the second cathode electrode 13b can come into contact with the gas contained in the fourth gas container 20d. The second cathode electrode 13b is fixed to the position of the second side opening 29 of the third container-exterior body 21c by a fixing jig 15 (not shown). The second side opening 29 corresponds to an example of a first opening.

[0048] 7 has a side opening 23, a top opening 25, and a second side opening 29, but is not limited to this. The third container-exterior body 21c may also be provided with openings such as a bottom opening 28 and a third side opening (not shown). A cathode electrode 13 is attached to each opening. Each opening is covered by the cathode electrode 13.

[0049] Figure 8 shows a schematic configuration of a liquid treatment device 100. Figure 8 shows a second liquid treatment device 100b, which is an example of the liquid treatment device 100. The second liquid treatment device 100b includes a second microbial fuel cell unit 10b and a storage tank 50. The second microbial fuel cell unit 10b is an example of the microbial fuel cell unit 10. The storage tank 50 of the second liquid treatment device 100b has the same configuration as the storage tank 50 of the first liquid treatment device 100a.

[0050] The second microbial fuel cell unit 10b comprises a first anode electrode 11a, a second anode electrode 11b, a cathode electrode 13, a first gas container 20a, and a connection circuit 30. The cathode electrode 13 and the first gas container 20a of the second microbial fuel cell unit 10b have the same configuration as the cathode electrode 13 and the first gas container 20a of the first microbial fuel cell unit 10a, respectively.

[0051] The first anode electrode 11a and the second anode electrode 11b are each an example of an anode electrode 11. The first anode electrode 11a and the second anode electrode 11b collect electrons generated when organic matter in the stored water L is oxidatively decomposed by microorganisms. The second microbial fuel cell unit 10b includes two anode electrodes 11. By including two anode electrodes 11 in the second microbial fuel cell unit 10b, the surface area of the anode electrode 11 that contacts the stored water L is larger than the surface area of the ion exchange surface S1 of the cathode electrode 13. The amount of electrons collected by the anode electrode 11 per unit surface area is smaller than the amount of electrons consumed by the cathode electrode 13 per unit area. As the surface area of the anode electrode 11 increases, the amount of electrons collected by the anode electrode 11 increases. As the amount of electrons collected by the anode electrode 11 increases, the maximum output power of the second microbial fuel cell unit 10b increases. The water purification ability of the second microbial fuel cell unit 10b is improved.

[0052] The second microbial fuel cell unit 10b includes, but is not limited to, two anode electrodes 11. The second microbial fuel cell unit 10b may include three or more anode electrodes 11. The second microbial fuel cell unit 10b includes, but is not limited to, two anode electrodes 11, thereby increasing the surface area of the anode electrodes 11. One anode electrode 11 having a larger surface area than the cathode electrode 13 may also be used.

[0053] The connection circuit 30 connects the first anode electrode 11a, the second anode electrode 11b, and the cathode electrode 13. The resistor 31 electrically connects the first anode electrode 11a, the second anode electrode 11b, and the cathode electrode 13. The connection circuit 30 transfers electrons collected by the first anode electrode 11a and the second anode electrode 11b to the cathode electrode 13.

[0054] The surface area of the contact surface of the anode electrode 11 that comes into contact with the stored water L is preferably larger than the surface area of the ion exchange surface S1 of the cathode electrode 13. The maximum output power of the second microbial fuel cell unit 10b increases as the supply of electrons at the anode electrode 11 increases, improving the water purification capacity of the second microbial fuel cell unit 10b.

[0055] Fig. 9 shows a schematic configuration of a liquid treatment device 100. Fig. 9 shows a third liquid treatment device 100c, which is an example of the liquid treatment device 100. The third liquid treatment device 100c includes a third microbial fuel cell unit 10c and a storage tank 50. The third microbial fuel cell unit 10c is an example of the microbial fuel cell unit 10. The storage tank 50 of the third liquid treatment device 100c has the same configuration as the storage tank 50 of the first liquid treatment device 100a.

[0056] The third microbial fuel cell unit 10c includes an anode electrode 11, a cathode electrode 13, a third gas container 20c, and a connection circuit 30. The anode electrode 11 and connection circuit 30 of the third microbial fuel cell unit 10c have the same configuration as the anode electrode 11 and connection circuit 30 of the first microbial fuel cell unit 10a, respectively.

[0057] The cathode electrode 13 attached to the third gas container 20c is disposed along the bottom surface of the storage tank 50. The ion exchange surface S1 of the cathode electrode 13 is disposed facing the bottom surface of the storage tank 50. The cathode electrode 13 is disposed in the water L stored below the storage tank 50.

[0058] The anode electrode 11 is disposed at a position opposite the ion exchange surface S1 of the cathode electrode 13. The anode electrode 11 is disposed below the cathode electrode 13. The anode electrode 11 is disposed in the reservoir water L stored below the reservoir tank 50. The anode electrode 11 is disposed along the bottom surface of the reservoir tank 50. Because organic matter contained in the reservoir water L is heavier than water, the organic matter falls to the bottom of the reservoir tank 50. The content of organic matter contained in the reservoir water L increases toward the bottom of the reservoir tank 50. By disposing the anode electrode 11 and the cathode electrode 13 below the reservoir tank 50, the purification function of the third microbial fuel cell unit 10c for the reservoir water L is improved.

[0059] The third gas container 20c is placed in the stored water L. The third gas container 20c has a sealing member 27. The third gas container 20c has the sealing member 27, which prevents the stored water L from entering the third gas container 20c. The cathode electrode 13 is supplied with oxygen stably.

[0060] The anode electrode 11 is preferably disposed along the bottom surface of the storage tank 50, and the ion exchange surface S1 of the cathode electrode 13 is preferably provided at a position facing the anode electrode 11. The third microbial fuel cell unit 10c is capable of purifying the stored water L that has a high organic matter content.

[0061] Figure 10 shows a schematic configuration of a liquid treatment device 100. Figure 10 shows a fourth liquid treatment device 100d, which is an example of the liquid treatment device 100. The fourth liquid treatment device 100d includes a fourth microbial fuel cell unit 10d and a storage tank 50. The storage tank 50 of the fourth liquid treatment device 100d has the same configuration as the storage tank 50 of the first liquid treatment device 100a.

[0062] The fourth microbial fuel cell unit 10d comprises an anode electrode 11, a cathode electrode 13, a third gas container 20c, a connection circuit 30, and a fixing member 40. The anode electrode 11, the cathode electrode 13, the third gas container 20c, and the connection circuit 30 of the fourth microbial fuel cell unit 10d have the same configuration as the anode electrode 11, the cathode electrode 13, the third gas container 20c, and the connection circuit 30 of the third microbial fuel cell unit 10c, respectively.

[0063] The fixing member 40 fixes and supports the third gas container 20c in the stored water L. By fixing and supporting the third gas container 20c in the stored water L, the fixing member 40 positions the cathode electrode 13 at a predetermined position in the stored water L. Because the third gas container 20c contains gas, the specific gravity of the third gas container 20c is smaller than the specific gravity of the stored water L. It is difficult to maintain the third gas container 20c at a predetermined position in the stored water L due to buoyancy. By fixing and supporting the third gas container 20c with the fixing member 40, the position of the third gas container 20c is less likely to fluctuate. The fixing member 40 corresponds to an example of a support member. The fixing member 40 has a support net 41 and a plurality of weights 43.

[0064] The support net 41 is placed in the reservoir water L. The support net 41 supports the third gas container 20c. The support net 41 prevents the third gas container 20c from floating up and causing the position of the third gas container 20c to fluctuate. The support net 41 shown in FIG. 10 supports the third gas container 20c below the support net 41, but is not limited to this. The support net 41 may also support the third gas container 20c inside the support net 41.

[0065] The weight 43 secures the support net 41. The weight 43 is secured to the bottom surface of the storage tank 50. The weight 43 may be secured by the bottom mud layer ML. The weight 43 prevents the support net 41 from moving due to the flow of the stored water L, etc. The fixing member 40 shown in FIG. 10 has two weights 43, but is not limited to this. The fixing member 40 may have one weight 43 or three or more weights 43.

[0066] The anode electrode 11 of the fourth microbial fuel cell unit 10d shown in Figure 10 is placed in the bottom mud layer ML. The organic matter content in the bottom mud layer ML is greater than the organic matter content in the reservoir water L. By placing the anode electrode 11 in the bottom mud layer ML, the effect of water purification is improved.

[0067] The fourth liquid treatment device 100d preferably includes a fixing member 40 for disposing the cathode electrode 13 in the reservoir water L. By fixing and supporting the third gas container 20c with the fixing member 40, the position of the cathode electrode 13 attached to the third gas container 20c becomes less likely to fluctuate.

[0068] Fig. 11 shows a schematic configuration of a liquid treatment device 100. Fig. 11 shows a fifth liquid treatment device 100e, which is an example of the liquid treatment device 100. The fifth liquid treatment device 100e includes a fifth microbial fuel cell unit 10e and a storage tank 50. The fifth microbial fuel cell unit 10e is an example of the microbial fuel cell unit 10. The storage tank 50 of the fifth liquid treatment device 100e has the same configuration as the storage tank 50 of the first liquid treatment device 100a.

[0069] The fifth microbial fuel cell unit 10e includes a first anode electrode 11a, a second anode electrode 11b, a first cathode electrode 13a, a second cathode electrode 13b, a fourth gas container 20d, and a connection circuit 30.

[0070] The first anode electrode 11a is disposed in a position facing the first cathode electrode 13a. The second anode electrode 11b is disposed in a position facing the second cathode electrode 13b. By disposing the first anode electrode 11a and the second anode electrode 11b in positions facing the first cathode electrode 13a and the second cathode electrode 13b, respectively, hydrogen ions in the stored water L can easily move to the first cathode electrode 13a or the second cathode electrode 13b.

[0071] The fifth microbial fuel cell unit 10e shown in Figure 11 includes, but is not limited to, two anode electrodes 11 and two cathode electrodes 13. The fifth microbial fuel cell unit 10e may include three or more anode electrodes 11. The fifth microbial fuel cell unit 10e includes a cathode electrode 13 located opposite each of the three or more anode electrodes 11. Increasing the number of anode electrodes 11 and cathode electrodes 13 improves the water purification capacity of the fifth microbial fuel cell unit 10e.

[0072] Figure 12 shows a schematic configuration of a microbial fuel cell unit 10. Figure 12 shows the configuration of a microbial fuel cell unit 10 that is placed in lakes, rivers, etc. Figure 12 shows a first microbial fuel cell unit 10a, which is an example of the microbial fuel cell unit 10. Figure 12 shows a first microbial fuel cell unit 10a that is placed in a lake, which is an example of a lake, river, etc.

[0073] The first microbial fuel cell unit 10a purifies the water quality of lake water W. The first microbial fuel cell unit 10a shown in Figure 12 is installed in the lake water W. The first microbial fuel cell unit 10a purifies the lake water W on-site. The lake water W is an example of a liquid. The lake water W contains organic mud and microorganisms. The microorganisms include electrochemically active bacteria. A bottom mud layer ML, where organic mud is layered, is formed at the bottom of the lake. The bottom mud layer ML corresponds to an example of an organic mud layer. The organic mud contains organic matter. The first microbial fuel cell unit 10a purifies the water quality of the lake water W by decomposing the organic matter contained in the lake water W and the bottom mud layer ML.

[0074] The first microbial fuel cell unit 10a includes an anode electrode 11, a cathode electrode 13, a first gas container 20a, and a connection circuit 30. The first gas container 20a is an example of the gas container 20. In the first microbial fuel cell unit 10a shown in FIG. 12, the anode electrode 11 and the cathode electrode 13 are immersed in lake water W.

[0075] The anode electrode 11 collects electrons generated when organic matter in the lake water W is oxidized and decomposed by microorganisms. The electrons collected by the anode electrode 11 move to the cathode electrode 13 via the connection circuit 30. The anode electrode 11 comes into contact with the lake water W. On the anode electrode 11, the microorganisms contained in the lake water W decompose the organic matter and generate electrons and hydrogen ions. The electrons generated by the microorganisms are collected by the anode electrode 11.

[0076] The cathode electrode 13 consumes electrons moving via the connection circuit 30 in a reduction reaction of the oxidant. The cathode electrode 13 is placed with lake water W between it and the anode electrode 11. The electrons flow through the connection circuit 30 according to the gradient between the potential generated at the anode electrode 11 and the oxidation-reduction potential of the chemical reaction occurring at the cathode electrode 13. The cathode electrode 13 uses oxygen in the atmosphere as an oxidant. The oxygen permeates through the cathode electrode 13.

[0077] The cathode electrode 13 has an ion exchange surface S1 and an oxygen permeable surface S2. The ion exchange surface S1 contacts the lake water W. The oxygen permeable surface S2 contacts the gas contained in the first gas container 20a. The oxygen permeable surface S2 allows oxygen contained in the gas to pass through.

[0078] The first gas container 20a contains a gas containing oxygen. The first gas container 20a supports the cathode electrode 13. The first gas container 20a supports the cathode electrode 13 in a state where the oxygen permeable surface S2 of the cathode electrode 13 can come into contact with the contained gas. The first gas container 20a supplies oxygen to the cathode electrode 13. The first gas container 20a is configured as a hollow cylindrical body with a bottom. The first gas container 20a is configured in a cylindrical, rectangular prism, or polygonal shape. By providing the first gas container 20a, oxygen is stably supplied to the cathode electrode 13.

[0079] The connection circuit 30 is an electric circuit that moves electrons from the anode electrode 11 to the cathode electrode 13. The connection circuit 30 is connected to the anode electrode 11 and the cathode electrode 13. The connection circuit 30 has a resistor 31. The resistor 31 is electrically connected to the anode electrode 11 and the cathode electrode 13. The resistor 31 may be a variable resistor that switches its resistance value. The resistor 31 adjusts the amount of current flowing through the connection circuit 30.

[0080] The first microbial fuel cell unit 10a is installed in lake water W containing organic mud and electrochemically active bacteria. The first microbial fuel cell unit 10a comprises an anode electrode 11 placed in the lake water W, a first gas container 20a containing an oxygen-containing gas, a cathode electrode 13 having an ion exchange surface S1 in contact with the lake water W and an oxygen permeable surface S2 that allows the oxygen contained in the gas contained in the first gas container 20a to pass through, and placed relative to the anode electrode 11 via the lake water W, and a resistor 31 electrically connected to the anode electrode 11 and the cathode electrode 13. By providing the first gas container 20a, the first microbial fuel cell unit 10a can stably supply oxygen to the cathode electrode 13. The oxidation-reduction reaction at the cathode electrode 13 is stabilized. Water purification by the first microbial fuel cell unit 10a is stably performed.

[0081] Fig. 13 shows a schematic configuration of a microbial fuel cell unit 10. Fig. 13 shows the configuration of a microbial fuel cell unit 10 that is placed in lakes, rivers, etc. Fig. 13 shows an example of installation of a microbial fuel cell unit 10. Fig. 13 shows a first microbial fuel cell unit 10a, which is an example of a microbial fuel cell unit 10.

[0082] The anode electrode 11 and cathode electrode 13 included in the first microbial fuel cell unit 10a are arranged in the bottom mud layer ML. The ion exchange surface S1 of the cathode electrode 13 is arranged opposite the anode electrode 11. The bottom mud layer ML contains organic mud, electrochemically active bacteria, and lake water W. In the bottom mud layer ML, the electrochemically active bacteria decompose the organic matter contained in the organic mud to generate electrons and hydrogen ions. The anode electrode 11 collects the electrons generated by the electrochemically active bacteria. As the anode electrode 11 collects electrons, the decomposition of organic matter by the electrochemically active bacteria is continuously carried out. The first microbial fuel cell unit 10a can purify the lake water W by decomposing the organic matter contained in the bottom mud layer ML.

[0083] A bottom mud layer ML, in which organic mud is layered, is formed in the lake water W. The anode electrode 11 is disposed in the bottom mud layer ML. The ion exchange surface S1 of the cathode electrode 13 is disposed opposite the anode electrode 11. The first microbial fuel cell unit 10a can decompose organic matter contained in the bottom sludge layer ML. The first microbial fuel cell unit 10a can purify the lake water W by decomposing the organic matter contained in the bottom sludge layer ML.

[0084] Figure 14 shows a schematic configuration of a microbial fuel cell unit 10. Figure 14 shows the configuration of a microbial fuel cell unit 10 that is placed in lakes, rivers, etc. Figure 14 shows an example of installation of the microbial fuel cell unit 10. Figure 14 shows a third microbial fuel cell unit 10c, which is an example of the microbial fuel cell unit 10.

[0085] The anode electrode 11 included in the third microbial fuel cell unit 10c is placed in the bottom mud layer ML. The cathode electrode 13 is placed in the lake water W. The ion exchange surface S1 of the cathode electrode 13 is placed opposite the anode electrode 11. The anode electrode 11 and the cathode electrode 13 are placed opposite each other with the lake water W and the bottom mud layer ML interposed between them. In the bottom mud layer ML, electrochemically active bacteria decompose organic matter contained in the organic mud, generating electrons and hydrogen ions. The anode electrode 11 collects electrons generated by the electrochemically active bacteria in the bottom mud layer ML. As the anode electrode 11 collects electrons, the electrochemically active bacteria continuously decompose the organic matter. The third microbial fuel cell unit 10c can purify the lake water W by decomposing the organic matter contained in the bottom mud layer ML.

[0086] The third gas container 20c has a sealing member 27. The third gas container 20c is placed in the lake water W. The cathode electrode 13 is placed on the bottom surface of the third gas container 20c. By placing the third gas container 20c with the cathode electrode 13 attached in the lake water W, the ion exchange surface S1 of the cathode electrode 13 can be positioned at a predetermined distance from the anode electrode 11 in the bottom mud layer ML. Furthermore, by providing the third gas container 20c, oxygen can be supplied to the oxygen permeable surface S2 of the cathode electrode 13. The purification function of the lake water W by the third microbial fuel cell unit 10c is continuously maintained.

[0087] FIG. 15 shows a schematic configuration of a microbial fuel cell unit 10. FIG. 15 shows the configuration of a microbial fuel cell unit 10 that is placed in lakes, rivers, etc. FIG. 15 shows an example of installation of a microbial fuel cell unit 10. FIG. 15 shows a fourth microbial fuel cell unit 10d, which is an example of a microbial fuel cell unit 10. The fourth microbial fuel cell unit 10d includes an anode electrode 11, a cathode electrode 13, a third gas container 20c, a connection circuit 30, and a fixing member 40.

[0088] The anode electrode 11 is disposed in the bottom mud layer ML. The cathode electrode 13 is disposed in the lake water W. The ion exchange surface S1 of the cathode electrode 13 is disposed opposite the anode electrode 11. The anode electrode 11 and the cathode electrode 13 are disposed opposite each other with the lake water W and the bottom mud layer ML interposed therebetween.

[0089] The third gas container 20c has a sealing member 27. The third gas container 20c is placed in the lake water W. The cathode electrode 13 is placed on the bottom surface of the third gas container 20c. The third gas container 20c is installed in the lake water W by a fixing member 40.

[0090] The fixing member 40 fixes and supports the third gas container 20c in the lake water W. By fixing and supporting the third gas container 20c in the lake water W, the fixing member 40 supports the cathode electrode 13 at a predetermined position. The cathode electrode 13 is placed in the lake water W. By fixing and supporting the third gas container 20c with the fixing member 40, the position of the third gas container 20c is less likely to fluctuate. The fixing member 40 corresponds to an example of a support member. The fixing member 40 has a support net 41 and a plurality of weights 43.

[0091] The support net 41 is placed in the lake water W. The support net 41 supports the third gas container 20c. The support net 41 prevents the third gas container 20c from floating up and causing the position of the third gas container 20c to fluctuate. The support net 41 shown in FIG. 15 supports the third gas container 20c below the support net 41, but is not limited to this. The support net 41 may also support the third gas container 20c inside the support net 41.

[0092] The weights 43 secure the support net 41. The weights 43 are fixed to the bottom of the lake. As an example, the weights 43 are fixed by the bottom mud layer ML. The weights 43 prevent the support net 41 from moving due to the flow of lake water W, etc. The fixing member 40 shown in FIG. 15 has two weights 43, but is not limited to this. The fixing member 40 may have one weight 43 or three or more weights 43.

[0093] The anode electrode 11 of the fourth microbial fuel cell unit 10d shown in Figure 15 is placed in the bottom mud layer ML. The organic matter content in the bottom mud layer ML is greater than the organic matter content in the lake water W. By placing the anode electrode 11 in the bottom mud layer ML, the effect of water purification is improved.

[0094] It is preferable to provide a fixing member 40 for placing the cathode electrode 13 in the lake water W. By fixing and supporting the third gas container 20c with the fixing member 40, the position of the cathode electrode 13 attached to the third gas container 20c becomes less likely to fluctuate.

[0095] Fig. 16 shows a schematic configuration of a microbial fuel cell unit 10. Fig. 16 shows the configuration of a microbial fuel cell unit 10 that is placed in lakes, rivers, etc. Fig. 16 shows an example of installation of a microbial fuel cell unit 10. Fig. 16 shows a sixth microbial fuel cell unit 10f, which is an example of a microbial fuel cell unit 10.

[0096] The sixth microbial fuel cell unit 10f comprises an anode electrode 11, a cathode electrode 13, a second gas container 20b, and a connection circuit 30. The second gas container 20b is an example of the gas container 20. The anode electrode 11, the cathode electrode 13, and the connection circuit 30 included in the sixth microbial fuel cell unit 10f have the same configuration as the anode electrode 11, the cathode electrode 13, and the connection circuit 30 included in the first microbial fuel cell unit 10a, respectively. In the sixth microbial fuel cell unit 10f shown in FIG. 16, the anode electrode 11 and the cathode electrode 13 are immersed in lake water W.

[0097] The second gas container 20b has a sealing member 27. The second gas container 20b can be placed in the lake water W. By providing the second gas container 20b, it becomes possible to install the cathode electrode 13 below the lake water W. Furthermore, by providing the second gas container 20b, oxygen can be supplied to the oxygen permeable surface S2 of the cathode electrode 13. The sixth microbial fuel cell unit 10f can purify the lake water W below.

[0098] Figure 17 shows a schematic configuration of a microbial fuel cell unit 10. Figure 17 shows the configuration of a microbial fuel cell unit 10 that is placed in lakes, rivers, etc. Figure 17 shows an example of installation of a microbial fuel cell unit 10. Figure 17 shows an example of installation of a sixth microbial fuel cell unit 10f, which is an example of a microbial fuel cell unit 10.

[0099] The anode electrode 11 and cathode electrode 13 included in the sixth microbial fuel cell unit 10f are arranged in the bottom mud layer ML. The ion exchange surface S1 of the cathode electrode 13 is arranged opposite the anode electrode 11. In the bottom mud layer ML, electrochemically active bacteria decompose organic matter contained in the organic mud, generating electrons and hydrogen ions. The anode electrode 11 collects the electrons produced by the electrochemically active bacteria. As the anode electrode 11 collects electrons, the decomposition of organic matter by the electrochemically active bacteria is continuously carried out. The sixth microbial fuel cell unit 10f can purify the lake water W by decomposing the organic matter contained in the bottom mud layer ML.

[0100] Figure 18 shows a schematic configuration of the microbial fuel cell unit 10. Figure 18 shows the configuration of the microbial fuel cell unit 10 that is placed in lakes, rivers, etc. Figure 18 shows an example of installation of the microbial fuel cell unit 10. Figure 18 shows a seventh microbial fuel cell unit 10g, which is an example of the microbial fuel cell unit 10.

[0101] The seventh microbial fuel cell unit 10g comprises an anode electrode 11, a cathode electrode 13, an ion exchange membrane 19, a second gas container 20b, a connection circuit 30, and a support housing 45. The anode electrode 11, the cathode electrode 13, the second gas container 20b, and the connection circuit 30 included in the seventh microbial fuel cell unit 10g have the same configurations as the anode electrode 11, the cathode electrode 13, the second gas container 20b, and the connection circuit 30 included in the sixth microbial fuel cell unit 10f, respectively.

[0102] The anode electrode 11 and cathode electrode 13 included in the seventh microbial fuel cell unit 10g are disposed in the bottom mud layer ML. The ion exchange surface S1 of the cathode electrode 13 is disposed opposite the anode electrode 11. The anode electrode 11 collects electrons generated by the electrochemically active bacteria.

[0103] The second gas container 20b has a sealing member 27. The provision of the sealing member 27 prevents organic mud from entering the inside of the second gas container 20b. The second gas container 20b and the cathode electrode 13 attached to the second gas container 20b are disposed in the bottom mud layer ML.

[0104] The ion exchange membrane 19 allows hydrogen ions generated when the electrochemically active bacteria decompose organic matter to pass through. The ion exchange membrane 19 has the function of transferring the hydrogen ions from the anode electrode 11 to the cathode electrode 13. The ion exchange membrane 19 is disposed between the anode electrode 11 and the cathode electrode 13.

[0105] The ion exchange membrane 19 is made of, for example, an ion exchange resin. Examples of the ion exchange resin include NAFION manufactured by DuPont Corporation, Flemion manufactured by Asahi Glass Co., Ltd., and Selemion manufactured by Asahi Glass Co., Ltd. NAFION, Flemion, and Selemion are registered trademarks. The ion exchange membrane 19 may be made of a porous membrane having pores through which hydrogen ions pass. The ion exchange membrane 19 is made of a porous sheet, a woven sheet, or a nonwoven sheet.

[0106] The support housing 45 supports the anode electrode 11 and the second gas container 20b. The support housing 45 may support the ion exchange membrane 19. The support housing 45 supports the second gas container 20b, thereby supporting the cathode electrode 13. The support housing 45 supports the anode electrode 11 and the cathode electrode 13, thereby fixing the relative positions of the anode electrode 11 and the cathode electrode 13. The purification function of the lake water W by the seventh microbial fuel cell unit 10g is stabilized. The support housing 45 corresponds to an example of a support member.

[0107] 18 supports the anode electrode 11 and the cathode electrode 13 in the bottom mud layer ML, but is not limited to this. The support housing 45 may support the anode electrode 11 and the cathode electrode 13 in the lake water W. The support housing 45 can dispose the anode electrode 11 and the cathode electrode 13 in the lake water W or in the bottom mud layer ML.

[0108] The form of the support housing 45 is not limited as long as it is configured to support the anode electrode 11 and the cathode electrode 13. The support housing 45 may be configured from a mesh material that is permeable to lake water W but makes it difficult for organic mud to penetrate inside. By configuring the support housing 45 to make it difficult for organic mud to penetrate, it is possible to suppress positional fluctuations, deformation, etc. of the anode electrode 11, etc. due to the pressure of the organic mud.

[0109] The support housing 45 preferably supports the anode electrode 11 . The support housing 45 supports the anode electrode 11, thereby stabilizing the purification function of the lake water W by the seventh microbial fuel cell unit 10g. [Explanation of symbols]

[0110] 10...Microbial fuel cell unit, 10a...First microbial fuel cell unit, 10b...Second microbial fuel cell unit, 10c...Third microbial fuel cell unit, 10d...Fourth microbial fuel cell unit, 10e...Fifth microbial fuel cell unit, 10f...Sixth microbial fuel cell unit, 10g...Seventh microbial fuel cell unit, 11...Anode electrode, 11a...First anode electrode, 11b...Second anode electrode, 13...Cathode electrode, 13a...First cathode electrode, 13b...Second cathode electrode, 15...Fixing jig, 19...Ion exchange membrane, 20...Gas container, 20a...First gas container, 20b...Second gas container, 20c...Third gas container, 20d...Fourth gas container, 2 1...container outer casing, 21a...first container outer casing, 21b...second container outer casing, 21c...third container outer casing, 23...side opening, 25...top opening, 27...sealing member, 28...bottom opening, 29...second side opening, 30...connecting circuit, 31...resistor, 40...fixing member, 41...support net, 43...weight, 45...support housing, 50...storage tank, 100...liquid treatment device, 100a...first liquid treatment device, 100b...second liquid treatment device, 100c...third liquid treatment device, 100d...fourth liquid treatment device, 100e...fifth liquid treatment device, 131...substrate layer, 133...filter layer, 135...water-repellent layer, L...storage water, ML...bottom mud layer, S1...ion exchange surface, S2...oxygen permeable surface, W...lake water.

Claims

1. a container for containing a liquid containing organic matter and electrochemically active bacteria; an anode electrode disposed in the liquid; a hollow body containing an oxygen-containing gas; a cathode electrode having a first surface in contact with the liquid and a second surface that is permeable to the oxygen contained in the gas contained in the hollow body, the cathode electrode being disposed relative to the anode electrode with the liquid interposed therebetween; a resistor electrically connected to the anode electrode and the cathode electrode; A water purification device comprising:

2. a surface area of a contact surface of the anode electrode that contacts the liquid is larger than a surface area of the first surface of the cathode electrode; The water purification device according to claim 1.

3. the hollow body is a cylindrical body having a first opening and a second opening, the cathode electrode is attached to the first opening and covers the first opening; The water purification device according to claim 1.

4. The hollow body has a lid member that seals the second opening. The water purification device according to claim 3.

5. the anode electrode is disposed along the bottom surface of the container; the first surface of the cathode electrode is provided at a position facing the anode electrode; The water purification device according to claim 4.

6. a support member for disposing the cathode electrode in the liquid; The water purification device according to claim 1.

7. A water purification system installed in a liquid containing organic mud and electrochemically active bacteria, an anode electrode disposed in the liquid; a hollow body containing an oxygen-containing gas; a cathode electrode having a first surface in contact with the liquid and a second surface that is permeable to the oxygen contained in the gas contained in the hollow body, the cathode electrode being disposed relative to the anode electrode with the liquid interposed therebetween; a resistor electrically connected to the anode electrode and the cathode electrode; A water purification system equipped with:

8. a support member for disposing the cathode electrode in the liquid; The water purification system according to claim 7.

9. The support member supports the anode electrode. The water purification system according to claim 8.

10. In the liquid, an organic mud layer is formed in which the organic mud is layered, the anode electrode is disposed within the organic mud layer; The first surface of the cathode electrode is disposed opposite to the anode electrode. The water purification system according to claim 7.

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