JP2020099851A - Liquid treatment system - Google Patents

Abstract

To provide a liquid treatment system capable of easily performing maintenance of a negative electrode.SOLUTION: There are provided liquid treatment systems 1 and 1A which comprise an electrolyte tank 70 which holds an electrolyte 60 containing an organic matter and has an outflow port 72 through which an electrolyte flows out, a negative electrode 30 which holds an anaerobic microorganism and is in contact with an electrolyte and a positive electrode 20 electrically connected to the negative electrode. The liquid treatment systems further comprise at least an electrolyte stirring part 100 for stirring an electrolyte around the negative electrode, an opening/closing part 90 which is provided at the outflow port and opens and closes the outflow port and a control part 110 for controlling an opening/closing state of the opening/closing part. The control part makes the opening/closing part in a closed state when the electrolyte stirring part is operated and makes the opening/closing part in an opened state when the electrolyte stirring part is stopped.SELECTED DRAWING: Figure 2

Description

The present invention relates to liquid treatment systems.

In recent years, microbial fuel cells that generate electricity using biomass have been attracting attention as sustainable energy. The microbial fuel cell is a wastewater treatment device that converts chemical energy of organic matter contained in domestic wastewater and industrial wastewater into electric energy and at the same time oxidizes and decomposes the organic matter. Further, the microbial fuel cell has the characteristics that the generation of sludge is small and the energy consumption is small.

The microbial fuel cell has a negative electrode supporting microorganisms and a positive electrode in contact with a gas phase containing oxygen and an electrolytic solution. Then, an electrolytic solution containing an organic substance or the like is supplied to the negative electrode, and a gas containing oxygen is supplied to the positive electrode. The negative electrode and the positive electrode form a closed circuit by connecting to each other via a load circuit. At the negative electrode, hydrogen ions and electrons are generated from the electrolytic solution by the catalytic action of microorganisms. Then, the generated hydrogen ions move to the positive electrode, and the electrons move to the positive electrode via the load circuit. Hydrogen ions and electrons transferred from the negative electrode combine with oxygen in the positive electrode and are consumed as water. At that time, the electric energy flowing through the closed circuit is recovered.

For example, in Patent Document 1, a negative electrode that is immersed in an organic substrate to support anaerobic microorganisms, an outer shell formed of an ion-permeable diaphragm, and an inlet/outlet are enclosed together with an electrolytic solution in an enclosed hollow cassette. And a positive electrode that is inserted into an organic substrate. Then, in the microbial fuel cell, while supplying oxygen into the cassette via the inlet/outlet hole, electricity is taken out via a circuit electrically connecting the negative electrode and the positive electrode.

Here, when the microbial fuel cell is operated for a long period of time, the amount of electric energy that can be recovered decreases as the negative electrode deteriorates. Specifically, anaerobic microorganisms are supported on the negative electrode by a biofilm. When the microbial fuel cell is operated for a long period of time, the biofilm on the negative electrode is enlarged and the amount of recoverable electric energy is reduced. Therefore, in order to stably recover electric energy over a long period of time, it is necessary to maintain the negative electrode.

Japanese Patent No. 5164511

However, in the microbial fuel cell of Patent Document 1, it is necessary to take out the negative electrode to the outside of the microbial fuel cell every maintenance. Therefore, the conventional microbial fuel cell has a problem that the maintenance of the negative electrode is complicated.

The present invention has been made in view of the problems of the related art. And an object of the present invention is to provide a liquid processing system capable of easily performing maintenance of a negative electrode.

In order to solve the above problems, the liquid treatment system according to an aspect of the present invention holds an electrolytic solution containing an organic matter, an electrolytic solution tank including an outlet port through which the electrolytic solution flows out, and holds anaerobic microorganisms, and A negative electrode that is in contact with the electrolytic solution, a positive electrode that is electrically connected to the negative electrode, an electrolytic solution stirring unit that stirs at least the electrolytic solution around the negative electrode, and an opening/closing unit that is provided at the outlet and that opens and closes the outlet. And a control unit that controls the open/closed state of the open/close unit. The control unit performs control such that the opening/closing unit is closed when the electrolyte stirring unit is in operation, and the opening/closing unit is opened when the electrolyte stirring unit is stopped.

According to the present disclosure, it is possible to provide a liquid treatment system capable of easily performing maintenance of a negative electrode.

It is a perspective view which shows roughly an example of the liquid processing system which concerns on this embodiment. It is sectional drawing which followed the AA line in FIG. It is an exploded perspective view showing a layered product which laminates a positive electrode, a spacer member, and a plate member in a liquid treatment system concerning this embodiment. It is sectional drawing which shows the other example of the liquid processing system which concerns on this embodiment schematically. It is sectional drawing which shows the other example of the liquid processing system which concerns on this embodiment schematically. 6 is a flowchart for explaining control of an electrolytic solution stirring unit and an opening/closing unit in the liquid processing system according to the present embodiment.

Hereinafter, the liquid processing system according to this embodiment will be described in detail. It should be noted that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

As shown in FIG. 1, the liquid treatment system 1 according to the present embodiment includes an electrode unit 10 having a positive electrode 20 and a negative electrode 30 carrying a microorganism and electrically connected to the positive electrode 20. Further, the liquid processing system 1 includes an electrolytic solution tank 70 that holds an electrolytic solution 60 containing an organic substance therein and further that the electrode unit 10 is arranged so as to be immersed in the electrolytic solution 60.

[Electrode unit]
The electrode unit 10 includes a positive electrode 20 and a negative electrode 30, as shown in FIGS. In the electrode unit 10, the positive electrode 20 and the negative electrode 30 are arranged such that the surface 20b of the positive electrode 20 and the surface 30a of the negative electrode 30 face each other, and further, the surface 20b of the positive electrode 20 and the surface 30a of the negative electrode 30 are arranged. There is a void between them.

As shown in FIG. 3, the positive electrode 20 is laminated and fixed on the spacer member 40. The spacer member 40 is a U-shaped frame member that extends along the outer periphery of the surface 20 a of the positive electrode 20, and has an open top. That is, the spacer member 40 is a frame member in which the bottom surfaces of the two first columnar members 41 are connected by the second columnar member 42. Then, as shown in FIG. 2, the side surface 43 of the spacer member 40 is joined to the outer peripheral portion of the surface 20 a of the positive electrode 20, and the side surface 44 opposite to the side surface 43 is the outer peripheral portion of the surface 50 a of the plate member 50. It is joined with.

As shown in FIG. 1 and FIG. 2, the laminated body formed by laminating the positive electrode 20, the spacer member 40, and the plate member 50 is inside the electrolytic solution tank 70 so that the gas phase G communicating with the atmosphere is formed. Is located in. The electrolytic solution 60, which is waste water, is held inside the electrolytic solution tank 70, and the gas diffusion layer 22 of the positive electrode 20 and the negative electrode 30 are immersed in the electrolytic solution 60.

As will be described later, the positive electrode 20 includes a water-repellent layer 21 having water repellency, and the plate member 50 is made of a flat plate material that does not allow the electrolytic solution 60 to pass therethrough. Therefore, the electrolytic solution 60 held inside the electrolytic solution tank 70 is separated from the internal space formed by the positive electrode 20, the spacer member 40, and the plate member 50, and the internal space is in the gas phase G. In the liquid processing system 1, the gas phase G is opened to the outside air, or the gas phase G is supplied with air from the outside by, for example, a pump. Further, as shown in FIG. 2, the positive electrode 20 and the negative electrode 30 are electrically connected to the external circuit 80, respectively.

(Positive electrode)
As shown in FIG. 2, the positive electrode 20 according to the present embodiment is composed of a gas diffusion electrode including a water repellent layer 21 and a gas diffusion layer 22 that is stacked so as to contact the water repellent layer 21. By using such a thin plate-shaped gas diffusion electrode, it becomes possible to easily supply oxygen in the gas phase G to the catalyst in the positive electrode 20.

<Water repellent layer>
The water repellent layer 21 of the positive electrode 20 is a layer having both water repellency and oxygen permeability. The water-repellent layer 21 is configured to allow the movement of oxygen from the gas phase G to the liquid phase while favorably separating the gas phase G and the liquid phase in the electrochemical system in the electrode unit 10. That is, the water-repellent layer 21 allows oxygen in the vapor phase G to permeate and move to the gas diffusion layer 22, while suppressing the movement of the electrolytic solution 60 to the vapor phase G side. The term “separation” as used herein means to physically cut off.

The water-repellent layer 21 is in contact with the gas phase G containing oxygen and diffuses oxygen in the gas phase G. In the configuration shown in FIG. 2, the water repellent layer 21 supplies oxygen to the gas diffusion layer 22 substantially uniformly. Therefore, the water repellent layer 21 is preferably a porous body so that the oxygen can be diffused. Since the water-repellent layer 21 has water repellency, it is possible to prevent the pores of the porous body from being clogged due to dew condensation or the like to reduce the oxygen diffusivity. Further, since the electrolytic solution 60 is unlikely to soak into the water repellent layer 21, oxygen can be efficiently circulated from the surface of the water repellent layer 21 that contacts the gas phase G to the surface that faces the gas diffusion layer 22. Becomes

The water repellent layer 21 is preferably formed in a sheet shape. The material forming the water repellent layer 21 is not particularly limited as long as it has water repellency and can diffuse oxygen in the gas phase G. Examples of the material forming the water-repellent layer 21 include polyethylene, polypropylene, polybutadiene, nylon, polytetrafluoroethylene (PTFE), ethyl cellulose, poly-4-methylpentene-1, butyl rubber and polydimethylsiloxane (PDMS). At least one selected from the group can be used. Since these materials easily form a porous body and have high water repellency, it is possible to suppress clogging of pores and improve gas diffusivity. The water-repellent layer 21 preferably has a plurality of through holes in the stacking direction X of the water-repellent layer 21 and the gas diffusion layer 22.

As the water repellent layer 21, for example, a waterproof moisture permeable sheet can be used. As the waterproof and moisture-permeable sheet, for example, Serpore (registered trademark) manufactured by Sekisui Chemical Co., Ltd. and Breathlon (registered trademark) manufactured by Nitoms Co., Ltd. can be used.

The water-repellent layer 21 may be subjected to water-repellent treatment using a water-repellent agent, if necessary, in order to enhance water repellency. Specifically, water repellency may be improved by attaching a water repellent agent such as polytetrafluoroethylene to the porous body forming the water repellent layer 21.

<Gas diffusion layer>
The gas diffusion layer 22 in the positive electrode 20 preferably includes a porous conductive material and a catalyst carried by the conductive material. The gas diffusion layer 22 may be composed of a porous catalyst having conductivity. By providing such a gas diffusion layer 22 on the positive electrode 20, it becomes possible to conduct electrons generated by a local cell reaction, which will be described later, between the catalyst and the external circuit 80. That is, as will be described later, the gas diffusion layer 22 carries a catalyst, and the catalyst is an oxygen reduction catalyst. Then, the electrons move from the external circuit 80 to the catalyst through the gas diffusion layer 22, whereby the oxygen reduction reaction by oxygen, hydrogen ions and electrons can be advanced by the catalyst.

In the positive electrode 20, it is preferable that oxygen permeates the water repellent layer 21 and the gas diffusion layer 22 and is supplied to the catalyst in order to ensure stable performance. Therefore, it is preferable that the gas diffusion layer 22 is a porous body having a large number of pores through which oxygen permeates, from the surface facing the water repellent layer 21 to the surface opposite thereto. In addition, the shape of the gas diffusion layer 22 is particularly preferably a three-dimensional mesh shape. Such a mesh shape makes it possible to impart high oxygen permeability and conductivity to the gas diffusion layer 22.

In the positive electrode 20, in order to efficiently supply oxygen to the gas diffusion layer 22, the water repellent layer 21 is preferably bonded to the gas diffusion layer 22 with an adhesive. Thereby, the diffused oxygen is directly supplied to the gas diffusion layer 22, and the oxygen reduction reaction can be efficiently performed. From the viewpoint of ensuring the adhesiveness between the water repellent layer 21 and the gas diffusion layer 22, the adhesive is preferably provided on at least part of the water repellent layer 21 and the gas diffusion layer 22. However, from the viewpoint of enhancing the adhesiveness between the water repellent layer 21 and the gas diffusion layer 22 and stably supplying oxygen to the gas diffusion layer 22 for a long period of time, the adhesive is the water repellent layer 21 and the gas diffusion layer 22. It is more preferable that it is provided on the entire surface between 22 and 22.

The adhesive preferably has oxygen permeability and contains at least one selected from the group consisting of polymethylmethacrylate, methacrylic acid-styrene copolymer, styrene-butadiene rubber, butyl rubber, nitrile rubber, chloroprene rubber and silicone. A resin can be used.

Here, the gas diffusion layer 22 of the positive electrode 20 in this embodiment will be described in more detail. As described above, the gas diffusion layer 22 can be configured to include the porous conductive material and the catalyst carried by the conductive material.

The conductive material in the gas diffusion layer 22 can be composed of, for example, one or more materials selected from the group consisting of carbon-based substances, conductive polymers, semiconductors and metals. Here, the carbon-based substance means a substance containing carbon as a constituent component. Examples of carbon-based materials include carbon powders such as graphite, activated carbon, carbon black, Vulcan (registered trademark) XC-72R, acetylene black, furnace black, and denka black, graphite felt, carbon wool, carbon woven cloth, and the like. Examples thereof include carbon fibers, carbon plates, carbon paper, carbon disks, carbon cloth, carbon foil, and carbon-based materials obtained by compression-molding carbon particles. In addition, examples of the carbon-based material also include fine-structured materials such as carbon nanotubes, carbon nanohorns, and carbon nanoclusters.

The conductive polymer is a general term for polymer compounds having conductivity. Examples of the conductive polymer include aniline, aminophenol, diaminophenol, pyrrole, thiophene, paraphenylene, fluorene, furan, acetylene or a single monomer having a derivative thereof as a constituent unit or a polymer of two or more kinds of monomers. Can be mentioned. Specifically, examples of the conductive polymer include polyaniline, polyaminophenol, polydiaminophenol, polypyrrole, polythiophene, polyparaphenylene, polyfluorene, polyfuran, and polyacetylene. Examples of the conductive material made of metal include a stainless mesh. In consideration of availability, cost, corrosion resistance, durability, etc., the conductive material is preferably a carbon-based substance.

The shape of the conductive material is preferably a powder shape or a fiber shape. Moreover, the conductive material may be supported by a support. The support means a member which has rigidity itself and can give a certain shape to the gas diffusion electrode. The support may be an insulator or a conductor. When the support is an insulator, examples of the support include glass, plastic, synthetic rubber, ceramics, water-resistant or water-repellent treated paper, plant pieces such as wood pieces, bone pieces, animal pieces such as shells, and the like. .. Examples of the support having a porous structure include porous ceramics, porous plastics and sponges. When the support is a conductor, examples of the support include carbon papers, carbon fibers, carbon-based substances such as carbon rods, metals, and conductive polymers.

The catalyst in the gas diffusion layer 22 is a platinum-based catalyst, a carbon-based catalyst using iron or cobalt, a transition metal oxide-based catalyst such as partially oxidized tantalum carbonitride (TaCNO) and zirconium carbonitride (ZrCNO), tungsten. Alternatively, a carbide-based catalyst using molybdenum, activated carbon or the like can be used.

The catalyst in the gas diffusion layer 22 is preferably a carbon-based material doped with metal atoms. The metal atom is not particularly limited, but titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium. It is preferably an atom of at least one metal selected from the group consisting of platinum and gold. In this case, the carbon-based material exhibits excellent performance, particularly as a catalyst for promoting the oxygen reduction reaction. The amount of metal atoms contained in the carbon-based material may be appropriately set so that the carbon-based material has excellent catalytic performance.

It is preferable that the carbon-based material is further doped with at least one non-metal atom selected from the group consisting of nitrogen, boron, sulfur and phosphorus. The amount of non-metal atoms doped in the carbon-based material may be appropriately set so that the carbon-based material has excellent catalytic performance.

The carbon-based material is based on a carbon source material such as graphite and amorphous carbon, and the carbon source material is doped with a metal atom and one or more non-metal atoms selected from nitrogen, boron, sulfur and phosphorus. It can be obtained.

The combination of metal atoms and non-metal atoms doped in the carbon-based material is appropriately selected. In particular, it is preferable that the non-metal atom contains nitrogen and the metal atom contains iron. In this case, the carbon-based material can have a particularly excellent catalytic activity. The non-metal atom may be only nitrogen, and the metal atom may be only iron.

The non-metal atom may include nitrogen and the metal atom may include at least one of cobalt and manganese. Also in this case, the carbon-based material can have a particularly excellent catalytic activity. The non-metal atom may be nitrogen only. Further, the metal atom may be only cobalt, only manganese, or only cobalt and manganese.

The shape of the carbon-based material is not particularly limited. For example, the carbon-based material may have a particle shape or a sheet shape. The size of the carbon-based material having a sheet shape is not particularly limited, and the carbon-based material may have a minute size, for example. The carbonaceous material having a sheet shape may be porous. The sheet-shaped and porous carbon-based material preferably has, for example, a woven cloth shape, a non-woven cloth shape, or the like. Such a carbon-based material can form the gas diffusion layer 22 without a conductive material.

The carbon-based material configured as the catalyst in the gas diffusion layer 22 can be prepared as follows. First, a mixture containing a non-metal compound containing at least one non-metal selected from the group consisting of nitrogen, boron, sulfur and phosphorus, a metal compound, and a carbon source material is prepared. Then, this mixture is heated at a temperature of 800° C. or higher and 1000° C. or lower for 45 seconds or more and less than 600 seconds. As a result, it is possible to obtain a carbon-based material configured as a catalyst.

Here, as the carbon source material, for example, graphite or amorphous carbon can be used as described above. Furthermore, the metal compound is not particularly limited as long as it is a compound containing a metal atom capable of coordinatively bonding with a non-metal atom doped in the carbon source material. Examples of the metal compound include inorganic metal salts such as metal chlorides, nitrates, sulfates, bromides, iodides, and fluorides, organic metal salts such as acetates, hydrates of inorganic metal salts, and organic metal salts. It is possible to use at least one selected from the group consisting of hydrates of For example, when graphite is doped with iron, the metal compound preferably contains iron(III) chloride. When the graphite is doped with cobalt, the metal compound preferably contains cobalt chloride. When the carbon source material is doped with manganese, the metal compound preferably contains manganese acetate. The amount of the metal compound used is preferably determined, for example, so that the ratio of the metal atom in the metal compound to the carbon source material is in the range of 5 to 30% by mass, and further, this ratio is 5 to 20% by mass. More preferably, it is determined to be within the range.

As described above, the non-metal compound is preferably at least one non-metal compound selected from the group consisting of nitrogen, boron, sulfur and phosphorus. Examples of the nonmetal compound include pentaethylenehexamine, ethylenediamine, tetraethylenepentamine, triethylenetetramine, ethylenediamine, octylboronic acid, 1,2-bis(diethylphosphinoethane), triphenylphosphite, and benzyldisal. At least one compound selected from the group consisting of fido can be used. The amount of the non-metal compound used is appropriately set according to the amount of the non-metal atom doped into the carbon source material. The amount of the non-metal compound used is preferably determined such that the molar ratio of the metal atom in the metal compound to the non-metal atom in the non-metal compound is in the range of 1:1 to 1:2. , 1:1.5 to 1:1.8 is more preferably determined.

In the gas diffusion layer 22, the catalyst may be bound to the conductive material using a binder. That is, the catalyst may be supported on the surface of the conductive material and inside the pores by using a binder. This can prevent the catalyst from being desorbed from the conductive material and deteriorating the oxygen reduction property. As the binder, it is preferable to use at least one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride (PVDF), and ethylene-propylene-diene copolymer (EPDM). It is also preferable to use NAFION (registered trademark) as the binder.

(Negative electrode)
The negative electrode 30 according to this embodiment has a function of supporting a microorganism described below, and further having a function of generating a hydrogen ion and an electron from at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 60 by the catalytic action of the microorganism. Therefore, the negative electrode 30 is not particularly limited as long as it has a configuration that causes such a function.

The negative electrode 30 has a structure in which microorganisms are carried on a conductive sheet having conductivity. The conductor sheet preferably comprises at least one selected from the group consisting of a porous conductor sheet, a woven cloth-like conductor sheet and a non-woven cloth-like conductor sheet. Further, the conductor sheet may be a laminated body in which a plurality of sheets are laminated. By using such a sheet having a plurality of pores as the conductor sheet of the negative electrode 30, hydrogen ions generated by a local cell reaction described later easily move toward the positive electrode 20, and the rate of the oxygen reduction reaction is increased. It is possible to raise it. From the viewpoint of improving the ion permeability, the conductor sheet of the negative electrode 30 preferably has a space (void) continuous in the stacking direction X of the positive electrode 20 and the negative electrode 30, that is, in the thickness direction.

The conductor sheet may be a metal plate having a plurality of through holes in the thickness direction. Therefore, as the material forming the conductor sheet of the negative electrode 30, for example, at least one selected from the group consisting of aluminum, copper, stainless steel, conductive metals such as nickel and titanium, and carbon paper and carbon felt is used. be able to.

A graphite sheet may be used as the conductor sheet of the negative electrode 30. In addition, it is preferable that the negative electrode 30 contains graphite, and that the graphene layers in the graphite are arranged along a plane in the direction YZ perpendicular to the stacking direction X of the positive electrode 20 and the negative electrode 30. By arranging the graphene layers in this manner, the conductivity in the direction YZ perpendicular to the stacking direction X is improved rather than the conductivity in the stacking direction X. Therefore, the electrons generated by the local battery reaction of the negative electrode 30 are easily conducted to the external circuit 80, and the efficiency of the battery reaction can be further improved.

The shape of the negative electrode 30 according to this embodiment is not particularly limited. In addition, the microorganisms supported on the negative electrode 30 are not particularly limited as long as they are microorganisms that decompose organic substances or nitrogen-containing compounds in the electrolytic solution 60 to generate hydrogen ions and electrons. As such a microorganism, for example, an aerobic microorganism that requires oxygen for growth or an anaerobic microorganism that does not require oxygen for growth can be used, but it is preferable to use an anaerobic microorganism. Anaerobic microorganisms do not require air for oxidatively decomposing the organic matter in the electrolytic solution 60. Therefore, the electric power required to send the air can be significantly reduced. Moreover, since the free energy acquired by the microorganisms is small, the amount of sludge generated can be reduced.

When the microorganisms carried on the negative electrode 30 are anaerobic microorganisms, it is preferable to keep the periphery of the negative electrode 30 in an anaerobic atmosphere in order to enhance the activity of the anaerobic microorganisms. Further, the anaerobic microorganisms retained on the negative electrode 30 are preferably, for example, electro-producing bacteria having an extracellular electron transfer mechanism. Specifically, examples of the anaerobic microorganisms include Geobacter genus bacteria, Shewanella genus bacteria, Aeromonas genus bacteria, Geothrix genus bacteria, and Saccharomyces genus bacteria.

The microorganisms may be retained in the negative electrode 30 by stacking and fixing the biofilm containing the microorganisms on the negative electrode 30. Specifically, a biofilm containing microorganisms may be fixed to the surfaces 30a and 30b of the negative electrode 30 that are in direct contact with the electrolytic solution 60. In addition, a biofilm generally refers to a three-dimensional structure including a microbial population and an extracellular polymeric substance (EPS) produced by the microbial population. However, the microorganism may be retained on the negative electrode 30 without depending on the biofilm. The microorganisms may be retained not only on the surface of the negative electrode 30 but also inside.

The negative electrode 30 may be modified with, for example, an electron transfer mediator molecule. Alternatively, the electrolytic solution 60 in the electrolytic solution tank 70 may include electron transfer mediator molecules. As a result, electron transfer from the microorganisms to the negative electrode 30 is promoted, and more efficient liquid treatment can be realized.

Specifically, in the metabolic mechanism of microorganisms, electrons are exchanged intracellularly or with the final electron acceptor. When the mediator molecule is introduced into the electrolytic solution 60, the mediator molecule acts as the final electron acceptor for metabolism, and transfers the received electron to the negative electrode 30. As a result, it becomes possible to increase the rate of oxidative decomposition of organic substances in the electrolytic solution 60. Such an electron transfer mediator molecule is not particularly limited. As the electron transfer mediator molecule, for example, at least one selected from the group consisting of neutral red, anthraquinone-2,6-disulfonic acid (AQDS), thionine, potassium ferricyanide, and methyl viologen can be used.

(Ion transfer layer)
The electrode unit 10 may be further provided with an ion transfer layer 25 having proton permeability, which is provided between the positive electrode 20 and the negative electrode 30. As shown in FIG. 4, in the liquid treatment system 1A, the positive electrode 20 is disposed so as to contact one surface 25a of the ion transfer layer 25, and the surface 25a of the ion transfer layer 25 opposite to the surface 25a thereof is disposed. Are arranged so that the negative electrode 30 contacts. The negative electrode 30 is separated from the positive electrode 20 via the ion transfer layer 25. The ion transfer layer 25 has an electrical insulation property, and further has a function of transmitting hydrogen ions generated in the negative electrode 30 and moving them to the positive electrode 20 side.

As the ion transfer layer 25, for example, an ion exchange membrane using an ion exchange resin can be used. As the ion exchange resin, for example, NAFION (registered trademark) manufactured by DuPont Co., Ltd., and Flemion (registered trademark) and Selemion (registered trademark) manufactured by Asahi Glass Co., Ltd. can be used.

Further, as the ion transfer layer 25, a porous film having pores through which hydrogen ions can permeate may be used. That is, the ion transfer layer 25 may be a sheet having a space (void) for hydrogen ions to move from the negative electrode 30 to the positive electrode 20. Therefore, the ion transfer layer 25 preferably includes at least one selected from the group consisting of a porous sheet, a woven sheet and a non-woven sheet. Further, the ion transfer layer 25 can use at least one selected from the group consisting of a glass fiber membrane, a synthetic fiber membrane, and a plastic non-woven fabric, and may be a laminate formed by laminating a plurality of these. Since such a porous sheet has many pores inside, hydrogen ions can easily move. The pore size of the ion transfer layer 25 is not particularly limited as long as hydrogen ions can move from the negative electrode 30 to the positive electrode 20.

As described above, the ion transfer layer 25 has a function of transmitting hydrogen ions generated in the negative electrode 30 and moving them to the positive electrode 20 side. Therefore, for example, if the negative electrode 30 and the positive electrode 20 are close to each other without contacting with each other, hydrogen ions can move from the negative electrode 30 to the positive electrode 20. Therefore, in the liquid processing system of this embodiment, the ion transfer layer 25 is not an essential component. However, by providing the ion transfer layer 25, hydrogen ions can be efficiently transferred from the negative electrode 30 to the positive electrode 20, and therefore the ion transfer layer 25 is preferably provided from the viewpoint of improving the output. It should be noted that a gap may be provided between the positive electrode 20 and the ion transfer layer 25, or a gap may be provided between the negative electrode 30 and the ion transfer layer 25.

In the electrode unit 10, the entire upper part of the spacer member 40 is open, but it may be partially open or closed if it is possible to introduce air (oxygen) into the interior. Good.

[Electrolyte tank]
The liquid processing system 1 includes a substantially rectangular parallelepiped electrolytic solution tank 70 that holds an electrolytic solution 60 containing an organic substance therein. The front wall 73 of the electrolytic solution tank 70 is provided with an inflow port 71 for supplying the electrolytic solution 60 to the electrolytic solution tank 70. The rear wall 74 of the electrolytic solution tank 70 is provided with an outlet 72 for discharging the treated electrolytic solution 60 from the electrolytic solution tank 70.

The electrolytic solution 60 is continuously supplied into the electrolytic solution tank 70 through the inflow port 71. Further, as shown in FIGS. 1 and 2, the electrode unit 10 is arranged inside the electrolytic solution tank 70 so as to be immersed in the electrolytic solution 60. Therefore, the electrolytic solution 60 supplied from the inflow port 71 of the electrolytic solution tank 70 flows while contacting the electrode unit 10, and is then discharged from the outflow port 72.

[External circuit]
As shown in FIGS. 2 and 4, an external circuit 80 is electrically connected to the positive electrode 20 and the negative electrode 30. As will be described later, due to the catalytic action of the anaerobic microorganisms carried on the negative electrode 30, the organic substances in the electrolytic solution 60 are decomposed to generate electrons. The electrons generated in the negative electrode 30 move to the external circuit 80, and further move from the external circuit 80 to the positive electrode 20. At this time, the external circuit 80 can recover the electric energy flowing in the closed circuit. Further, the external circuit 80 has a function of measuring at least one of current and voltage between the positive electrode 20 and the negative electrode 30 and transmitting the measurement result to the control unit 110 described later.

[Opening and closing part]
As described above, the electrolytic solution tank 70 includes the outlet 72 for discharging the treated electrolytic solution 60 from the inside of the electrolytic solution tank 70. The liquid processing system 1 includes an opening/closing unit 90 that is provided at the outlet 72 of the electrolytic solution tank 70 and opens/closes the outlet 72. The opening/closing unit 90 adjusts the discharge of the electrolytic solution 60 through the outflow port 72 based on a command from the control unit 110, as described later. When the opening/closing part 90 is opened, the electrolytic solution 60 is discharged from the inside of the electrolytic solution tank 70 to the outside, and when the opening/closing part 90 is closed, the electrolytic solution 60 is discharged from the inside of the electrolytic solution tank 70 to the outside. It will not be done. The configuration of the opening/closing unit 90 is not particularly limited, but, for example, an electric valve or a solenoid valve can be used.

[Electrolyte stirring part]
In the liquid treatment system, the anaerobic microorganism may be supported on the negative electrode by a biofilm. However, when the liquid treatment system is operated for a long period of time, the biofilm on the negative electrode is enlarged, which may reduce the power generation efficiency of the liquid treatment system. The reason why the biofilm reduces the power generation efficiency of the liquid treatment system has not been sufficiently clarified, but power generation may be hindered by the biofilm formed by other microorganisms than the anaerobic microorganisms.

In order to remove such foreign matter such as the enlarged biofilm, there is a method of taking out the negative electrode from the electrolytic solution tank and peeling the foreign matter outside the electrolytic solution tank. However, in this method, it is necessary to stop the power generation of the liquid processing system in order to take out the negative electrode to the outside. Moreover, when the area of the negative electrode is large, it is necessary to secure a space for performing maintenance outside.

The liquid treatment system of the present embodiment includes an electrolytic solution stirring unit 100 that stirs at least the electrolytic solution 60 around the negative electrode 30 in order to remove foreign matter attached to the negative electrode 30 by a simple method. The electrolytic solution stirring unit 100 can stir the electrolytic solution 60 existing around the negative electrode 30, for example, the surface 30a of the negative electrode 30 facing the positive electrode 20 and/or the surface 30b opposite to the surface 30a. .. The electrolytic solution stirring unit 100 adjusts the stirring of the electrolytic solution 60 based on a command from the control unit 110, as described later.

The configuration of the electrolytic solution stirring unit 100 is not particularly limited as long as the electrolytic solution 60 around the negative electrode 30 can be stirred. For example, the electrolytic solution stirring unit 100 preferably includes a pump that generates a flow of the electrolytic solution 60 around the negative electrode 30. By using such a pump, it is possible to generate a flow of the electrolytic solution 60 around the negative electrode 30, and to remove foreign matters adhering to the surface of the negative electrode 30 by the water flow and/or the water pressure of the electrolytic solution. The pump that constitutes the electrolytic solution stirring unit 100 is not particularly limited, but a submersible pump or a submersible motor pump can be used. A submersible pump is a pump that has electrical components that are wholly or partially submerged in electrolyte 60 during normal use. The submersible motor pump is a pump that is used by putting the entire pump together with the electric motor in the electrolytic solution 60.

The electrolytic solution stirring unit 100 includes a pump arranged outside the electrolytic solution tank 70 and a pipe connected to the pump, and discharges the electrolytic solution 60 from the end of the pipe to surround the negative electrode 30. Alternatively, the flow of the electrolytic solution 60 may be generated.

The electrolytic solution stirring unit 100 is not limited to the pump described above. For example, it is also preferable that the electrolytic solution stirring unit 100 includes an air diffuser that diffuses the negative electrode 30. Specifically, as shown in FIG. 5, the air diffusing device 101 includes an air diffusing member 102 having holes for diffusing gas, and a gas supply member 103 for supplying gas to the holes. You can

The air diffuser member 102 is a member having a large number of holes through which gas can flow. The air diffusing member 102 is not particularly limited, but for example, a porous ceramic air diffusing plate obtained by joining coarse ceramic particles with a binder or the like, or a synthetic resin diffusing plate can be used. A membrane diffuser can also be used as the air diffuser 102.

The gas supply member 103 is a hollow member that holds the diffuser member 102 and further supplies gas to the holes of the diffuser member 102. Then, the gas supplied from the gas supply member 103 passes through the holes of the air diffusing member 102 to form bubbles, which diffuse into the electrolytic solution 60.

It is preferable that a pipe 104 for supplying gas from the outside of the electrolytic solution tank 70 is connected to the gas supply member 103. Specifically, it is preferable that the hollow pipe 104 is connected to the lower portion of the gas supply member 103. The pipe 104 penetrates the rear wall 74 of the electrolytic solution tank 70 and extends to the outside of the electrolytic solution tank 70. A compressor 105 for pumping gas is connected to the end of the pipe 104.

The gas diffused from the air diffuser 101 to the electrolytic solution 60 is not particularly limited. For example, air can be used as the gas. However, as described above, in order to enhance the activity of anaerobic microorganisms, it is preferable to keep the periphery of the negative electrode 30 in an anaerobic atmosphere. Therefore, the gas to be diffused is preferably a gas containing no oxygen, and for example, nitrogen is preferably used.

The electrolytic solution stirring unit 100 is preferably provided on the lower side of the negative electrode 30 in the vertical direction Y. Specifically, as shown in FIGS. 2 and 4, when the electrolytic solution stirring unit 100 includes a submersible pump or a submersible motor pump, the pump is located below the negative electrode 30 in the vertical direction Y. It is preferably provided. As a result, when the electrolytic solution stirring unit 100 operates, a water flow upward from the lower portion of the negative electrode 30 is generated, so that the biofilm is peeled from the lower end of the negative electrode 30 and the biofilm can be efficiently removed. It will be possible.

When the electrolytic solution stirring unit 100 includes a pump arranged outside the electrolytic solution tank 70 and a pipe connected to the pump, the end of the pipe discharged by the electrolytic solution 60 is arranged in the vertical direction Y, It is preferably provided on the lower side of the negative electrode 30.

When the electrolytic solution stirring unit 100 includes an air diffuser for diffusing the negative electrode 30, the air diffusing member 102 and the gas supply member 103 are arranged in the vertical direction Y in the negative electrode 30 as shown in FIG. Is preferably provided on the lower side. As a result, the air bubbles generated from the air diffuser 102 float along the surface of the negative electrode 30 and reach the water surface 61 of the electrolytic solution 60. At this time, the bubbles contact the surface of the negative electrode 30, so that the foreign matter on the negative electrode 30 can be removed.

[Control part]
The liquid processing system of the present embodiment includes a control unit 110 that controls the open/closed state of the open/close unit 90. As shown in FIGS. 2, 4 and 5, the control unit 110 is electrically connected to the opening/closing unit 90 provided at the outlet 72 of the electrolytic solution tank 70, and controls opening/closing of the opening/closing unit 90. .. Further, the control unit 110 is electrically connected to the electrolytic solution stirring unit 100, and preferably controls the operating state of the electrolytic solution stirring unit 100. When the liquid processing system includes the external circuit 80, the control unit 110 is preferably electrically connected to the external circuit 80. The control unit 110 includes at least one selected from the group consisting of CPU, RAM, ROM, and hard disk.

Next, the operation of the liquid processing system 1, 1A of this embodiment will be described. As shown in FIGS. 1 and 2, when the electrode unit 10 including the positive electrode 20 and the negative electrode 30 is immersed in the electrolyte solution 60, the gas diffusion layer 22 and the negative electrode 30 of the positive electrode 20 are immersed in the electrolyte solution 60, and the water repellent layer is formed. At least a part of 21 is exposed to the gas phase G.

During operation of the liquid processing systems 1 and 1A, the negative electrode 30 is supplied with the electrolytic solution 60 containing at least one of an organic substance and a nitrogen-containing compound, and the positive electrode 20 is supplied with air. At this time, the air is continuously supplied through the opening provided in the upper portion of the spacer member 40.

Then, in the positive electrode 20, oxygen permeates the water repellent layer 21 and diffuses into the gas diffusion layer 22. In the negative electrode 30, hydrogen ions and electrons are generated from at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 60 by the catalytic action of the microorganism. The hydrogen ions generated in the negative electrode 30 move to the positive electrode 20 side and reach the gas diffusion layer 22 in the positive electrode 20. As shown in FIG. 4, when the electrode unit 10 has the ion transfer layer 25, the hydrogen ions generated in the negative electrode 30 pass through the ion transfer layer 25 and move to the positive electrode 20 side, and the gas in the positive electrode 20 moves. It reaches the diffusion layer 22. Further, the generated electrons move to the external circuit 80 through the conductor sheet of the negative electrode 30, and further move from the external circuit 80 to the gas diffusion layer 22 of the positive electrode 20. Then, the hydrogen ions and electrons are combined with oxygen by the action of the catalyst in the gas diffusion layer 22, and are consumed as water. At this time, the external circuit 80 recovers the electric energy flowing in the closed circuit. As described above, the electrode unit 10 can decompose at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 60 by the action of the microorganisms on the negative electrode 30.

As described above, when the liquid processing system 1, 1A is operating, the electrolytic solution 60 is normally continuously supplied into the electrolytic solution tank 70 through the inflow port 71. Further, the electrolytic solution stirring unit 100 is in a stopped state and the opening/closing unit 90 is in an open state.

Here, when the liquid processing systems 1 and 1A operate for a long period of time and foreign matter such as a biofilm increases on the surface of the negative electrode 30, the control unit 110 controls the operation of the electrolytic solution stirring unit 100 and the opening/closing unit 90. .. Specifically, as shown in FIG. 6, control unit 110 determines whether it is necessary to stir electrolytic solution 60 around negative electrode 30 (step S1). Specifically, the external circuit 80 measures at least one of a current and a voltage between the positive electrode 20 and the negative electrode 30, and sends the measurement result to the control unit 110. The control unit 110 compares at least one of the received current and voltage with the reference value recorded in the storage unit. When at least one of the received current and voltage is less than the reference value, control unit 110 determines that the power generation efficiency has deteriorated, and determines that stirring of electrolytic solution 60 is necessary. Conversely, when at least one of the received current and voltage is equal to or higher than the reference value, control unit 110 determines that normal power generation is being performed, and determines that stirring is unnecessary. When it is determined that the stirring is not necessary, the control unit 110 performs control such that the electrolytic solution stirring unit 100 remains in the stopped state and the opening/closing unit 90 remains in the open state.

When the control unit 110 determines that the electrolytic solution 60 needs to be stirred, the control unit 110 transmits a command to operate the electrolytic solution stirring unit 100 (step S2). The control unit 110 further transmits a command to close the opening/closing unit 90 (step S3). That is, the control unit 110 controls the opening/closing unit 90 to be in the closed state when the electrolytic solution stirring unit 100 is in the operating state.

When the electrolytic solution stirring unit 100 operates, at least the electrolytic solution 60 around the negative electrode is stirred, and the water flow and/or the water pressure of the electrolytic solution 60 removes the foreign matter attached to the surface of the negative electrode 30. When the electrolytic solution stirring unit 100 includes an air diffusing device, bubbles are discharged from the air diffusing device to the electrolytic solution 60. Specifically, the compressor 105 is operated to send gas under pressure to the pipe 104. The gas fed under pressure passes through the inside of the pipe 104 and reaches the gas supply member 103. The gas supplied to the gas supply member 103 passes through the holes of the air diffusing member 102, becomes bubbles, and diffuses into the electrolytic solution 60.

The bubbles diffused from the air diffusing member 102 into the electrolytic solution 60 float along the surfaces 30a and 30b of the negative electrode 30 and reach the water surface 61 of the electrolytic solution 60. At this time, the bubbles contact the surfaces 30a and 30b of the negative electrode 30, so that the negative electrode 30 can be vibrated. Further, a swirl flow is generated near the surfaces 30a and 30b of the negative electrode 30 due to the rise of the bubbles. Due to the vibration of the negative electrode 30 and the swirling flow generated in the vicinity of the surfaces 30a and 30b of the negative electrode 30, the foreign matter on the surface of the negative electrode 30, that is, the enlarged biofilm is peeled off.

When the electrolytic solution stirring unit 100 operates and the electrolytic solution 60 is stirred, the enlarged biofilm is gradually peeled from the lower end of the negative electrode, and the biofilm floats in the electrolytic solution 60. At this time, both the lumpy biofilm and the micronized biofilm float in the electrolytic solution 60. Since the micronized biofilm has a smaller volume than the hole diameter of the outlet 72 of the electrolytic solution tank 70, it is difficult to block the outlet 72. Therefore, the miniaturized biofilm is discharged to the outside of the electrolytic solution tank 70 together with the electrolytic solution 60 in which the organic matter is reduced when the opening/closing section 90 is in the open state. However, since the bulk biofilm has a large volume, when the opening/closing part 90 is in the open state, the bulk biofilm may flow to the outflow port 72 and block the outflow port 72.

Therefore, in the present embodiment, the control unit 110 performs control to close the opening/closing unit 90 when the electrolytic solution stirring unit 100 is in operation (steps S2 and S3). As a result, even when the electrolytic solution stirring unit 100 operates and the biofilm floats in the electrolytic solution 60, the lumpy biofilm stays inside the electrolytic solution tank 70 and is hard to flow to the outflow port 72. Therefore, the blockage of the outflow port 72 due to the lumpy biofilm can be suppressed.

When the electrolytic solution stirring unit 100 operates and the removal of the foreign matter on the surface of the negative electrode progresses, the control unit 110 determines whether the stirring of the electrolytic solution 60 is further required (step S4). Specifically, the control unit 110 compares at least one of the current and the voltage received from the external circuit 80 with the reference value recorded in the storage unit. When at least one of the received current and voltage is less than the reference value, control unit 110 determines that stirring of electrolytic solution 60 is further necessary, and the operating state of electrolytic solution stirring section 100 and the closed state of opening/closing section 90 are determined. And maintain. Conversely, when at least one of the received current and voltage is equal to or higher than the reference value, control unit 110 determines that further stirring of electrolytic solution 60 is unnecessary.

When the control unit 110 determines that further stirring of the electrolytic solution 60 is unnecessary, the control unit 110 transmits a command to stop the operation to the electrolytic solution stirring unit 100 (step S5). The control unit 110 further transmits a command to open the open/close unit 90 (step S6). That is, the control unit 110 controls the opening/closing unit 90 to be in the open state when the electrolytic solution stirring unit 100 is in the stopped state.

When the electrolytic solution stirring unit 100 is stopped, the lumpy biofilm is quickly settled and settles on the bottom wall 75 of the electrolytic solution tank 70. Then, the miniaturized biofilm is discharged to the outside of the electrolytic solution tank 70 through the outlet 72 together with the electrolytic solution 60 in which the organic matter is reduced. By such steps, foreign matter on the negative electrode surface can be removed while suppressing clogging of the outlet 72 of the electrolytic solution tank 70.

As described above, the liquid processing systems 1 and 1A hold the electrolytic solution 60 containing an organic substance, the electrolytic solution tank 70 including the outlet 72 through which the electrolytic solution 60 flows out, hold the anaerobic microorganisms, and hold the electrolytic solution. The negative electrode 30 is in contact with the negative electrode 30, and the positive electrode 20 is electrically connected to the negative electrode 30. The liquid processing systems 1 and 1A further include an electrolytic solution stirring unit 100 that stirs at least the electrolytic solution 60 around the negative electrode 30, an opening/closing unit 90 that is provided at the outlet 72 and that opens and closes the outlet 72, and an opening/closing unit. And a control unit 110 that controls the open/closed state. The control unit 110 performs control such that the opening/closing unit 90 is closed when the electrolytic solution stirring unit 100 is in the operating state, and the opening/closing unit 90 is open when the electrolytic solution stirring unit 100 is in the stopped state.

In the liquid processing systems 1 and 1A, the electrolytic solution stirring unit 100 stirs the electrolytic solution 60 around the negative electrode 30 to remove foreign matter on the surface of the negative electrode 30. Therefore, it is not necessary to take out the negative electrode 30 to the outside of the liquid processing systems 1 and 1A each time maintenance is performed, and it is not necessary to stop the power generation of the liquid processing system. Further, since the foreign matter on the surface of the negative electrode is removed inside the electrolytic solution tank 70, the negative electrode 30 is not exposed to aerobic conditions. Therefore, maintenance can be performed without deteriorating the output characteristics of the liquid processing systems 1 and 1A. Furthermore, since foreign matter on the surface of the negative electrode is removed inside the electrolytic solution tank 70, it is not necessary to secure a space for performing maintenance outside. Therefore, in the liquid processing systems 1 and 1A, the maintenance of the negative electrode 30 can be easily performed.

In addition, in the liquid processing systems 1 and 1A, control is performed such that the opening/closing section 90 is closed when the electrolytic solution stirring section 100 is in operation, and the opening/closing section 90 is open when the electrolytic solution stirring section 100 is stopped. Therefore, clogging of the outflow port 72 of the electrolytic solution tank 70 with lumped foreign matter is suppressed, so that the electrolytic solution 60 can be efficiently discharged.

In the liquid processing systems 1 and 1A, it is preferable that the control unit 110 controls the timing at which the electrolytic solution stirring unit 100 removes foreign matter attached to the negative electrode 30. 2, 4, and 5, the control unit 110 is electrically connected to the external circuit 80. Then, the control unit 110 operates the opening/closing unit 90 and the electrolytic solution stirring unit 100 based on the value of at least one of the current and the voltage received from the external circuit 80 to remove the foreign matter attached to the negative electrode 30. That is, the control unit 110 adjusts the timing of removing the foreign matter attached to the negative electrode 30 by the electrolytic solution stirring unit 100 based on the value of at least one of the current and the voltage received from the external circuit 80.

In the liquid processing systems 1 and 1A, the control unit 110 does not have to be electrically connected to the external circuit 80, and based on the value measured by the external circuit 80, the electrolytic solution stirring unit 100 causes the negative electrode 30 to flow. It is not necessary to control the timing of removing the foreign matter attached to the. For example, it may be known in advance that a bloated biofilm is generated on the surface of the negative electrode 30 when the liquid processing system 1, 1A is operated for a certain period of time. In that case, the control unit 110 integrates the operating times of the liquid processing systems 1 and 1A, and adjusts the timing for removing the foreign matter adhering to the negative electrode 30 by the electrolytic solution stirring unit 100 based on the integrated value. Good.

The liquid processing systems 1 and 1A of the present embodiment are not limited to the above-mentioned configuration, and various modifications can be made within the scope of the gist of the present embodiment. For example, in FIGS. 2 and 4, the electrolytic solution stirring unit 100 is provided on the lower side of the negative electrode 30 in the vertical direction Y to generate a water flow upward from the lower side of the negative electrode 30. However, the electrolytic solution stirring unit 100 may be arranged so as to face the surface 30b of the negative electrode 30, and the water flow may be applied toward the surface 30b of the negative electrode 30. Even with such a configuration, it is possible to efficiently remove foreign matter on the negative electrode surface.

Further, in FIG. 6, the control unit 110 transmits a command to operate the electrolytic solution stirring unit 100, and then transmits a command to close the opening/closing unit 90 (steps S2 and S3). However, in the liquid processing systems 1 and 1A of the present embodiment, the control unit 110 closes the opening/closing unit 90 when the electrolytic solution stirring unit 100 is in operation, and opens the opening/closing unit 90 when the electrolytic solution stirring unit 100 is stopped. It is sufficient to control the state. Therefore, the control unit 110 may transmit a command to operate the electrolytic solution stirring unit 100 after transmitting a command to the opening/closing unit 90 to be in the closed state. In addition, the control unit 110 may send a command to the opening/closing unit 90 to be in the closed state and, at the same time, send a command to operate the electrolytic solution stirring unit 100.

In FIG. 6, the control unit 110 transmits a command to stop the operation to the electrolytic solution stirring unit 100, and then transmits a command to open the opening/closing unit 90 (steps S5 and S6). However, similarly to the above, the control unit 110 may transmit the command to stop the operation to the electrolytic solution stirring unit 100 after transmitting the command to open and close the opening/closing unit 90. In addition, the control unit 110 may send a command to the opening/closing unit 90 to open it and, at the same time, send a command to stop the operation to the electrolytic solution stirring unit 100.

In the liquid processing systems 1 and 1A of the present embodiment, the electrolytic solution 60 is preferably continuously supplied into the electrolytic solution tank 70 through the inflow port 71. Further, the electrolytic solution 60 may be continuously supplied to the inside of the electrolytic solution tank 70 even when the opening/closing part 90 is closed. However, control may be performed to stop the supply of the electrolytic solution 60 when the opening/closing unit 90 is in the closed state.

In the liquid processing system 1, 1A, the electrode unit 10 includes a spacer member 40 that forms a gas phase G that contacts the positive electrode 20. However, in the liquid treatment systems 1 and 1A of this embodiment, the spacer member 40 is not an essential component. That is, when the positive electrode 20 is in contact with the gas phase G and the negative electrode 30 is immersed in the electrolytic solution 60, electric energy can be obtained while decomposing the organic substance and/or the nitrogen-containing compound in the electrolytic solution 60. For example, by floating the positive electrode 20 on the water surface 61 and submerging the negative electrode 30 in the electrolytic solution 60, a part of the positive electrode 20 can come into contact with the gas phase G and the negative electrode 30 can come into contact with the electrolytic solution 60. In addition, in such a structure, the positive electrode 20 does not need to include the water-repellent layer 21.

In the drawing, the positive electrode 20, the negative electrode 30, and the ion transfer layer 25 are formed in a rectangular shape. However, these shapes are not particularly limited, and can be arbitrarily changed depending on the size of the liquid treatment systems 1 and 1A and desired power generation performance and purification performance. Also, the area of each layer can be arbitrarily changed as long as the desired function can be exhibited.

Hereinafter, the present embodiment will be described in more detail with reference to examples, but the present embodiment is not limited to these examples.

First, a water-repellent layer made of polyolefin is coated with a silicone resin that is an adhesive, and then a graphite foil that is a gas diffusion layer is joined to produce a laminated sheet composed of a water-repellent layer/silicone adhesive/gas diffusion layer. did. As the water-repellent layer, SERPUI (registered trademark) manufactured by Sekisui Chemical Co., Ltd. was used. As the silicone resin, one-pack type RTV rubber KE-3475-T manufactured by Shin-Etsu Chemical Co., Ltd. was used. The graphite foil used was made by Hitachi Chemical Co., Ltd.

Next, a gas diffusion electrode was prepared by press-molding a catalyst layer formed by mixing an oxygen reduction catalyst and PTFE (manufactured by Aldrich) on the surface of the graphite foil opposite to the water-repellent layer. The oxygen reduction catalyst was press-molded so that the basis weight was 2 mg/cm ² .

The above oxygen reduction catalyst was prepared as follows. First, a mixed solution was prepared by placing 3 g of carbon black, a 0.1 M aqueous solution of iron(III) chloride, and a 0.15 M solution of pentaethylenehexamine in ethanol in a container. As the carbon black, Ketjenblack ECP600JD manufactured by Lion Specialty Chemicals Co., Ltd. was used. The amount of the 0.1 M iron(III) chloride aqueous solution used was adjusted so that the ratio of iron atoms to carbon black was 10% by mass. The total amount was adjusted to 9 mL by adding ethanol to this mixed solution. Then, this mixed solution was ultrasonically dispersed and then dried at a temperature of 60° C. by a dryer. As a result, a sample containing carbon black, iron (III) chloride, and pentaethylenehexamine was obtained.

Then, this sample was packed into one end of the quartz tube, and then the inside of the quartz tube was replaced with argon. This quartz tube was put in a furnace at 900° C. and then withdrawn in 45 seconds. When inserting the quartz tube into the furnace, the quartz tube was inserted into the furnace for 3 seconds to adjust the heating rate of the sample at the start of heating to 300° C./s. Then, the sample was cooled by circulating argon gas in the quartz tube. Thus, an oxygen reduction catalyst was obtained.

Next, as shown in FIG. 4, an electrode unit was obtained by laminating the obtained positive electrode made of a gas diffusion electrode, the ion transfer layer, and the negative electrode made of a carbon material on a U-shaped spacer member. A graphite foil was used as the carbon material forming the negative electrode. A non-woven fabric made of polyolefin was used as the ion transfer layer.

An electrolytic solution tank having an inlet and an outlet and a capacity of 300 cc was prepared, and a tube was installed on the bottom surface of the electrolytic solution tank. Then, one end of the tube was arranged below the negative electrode, and the other end was connected to a chemical transfer pump (manufactured by Thermo Fisher Scientific Co., Ltd.) as a liquid feeding device. Then, one end of the tube was fixed to the bottom surface of the electrolytic solution tank so that the electrolytic solution sent by using the solution sending device could contact the surface of the negative electrode.

Next, the electrolytic solution was filled in the electrolytic solution tank so as to contact the positive electrode, the negative electrode, and the ion transfer layer. As the electrolytic solution, a model waste solution having a total organic carbon (TOC) of 800 mg/L was used. Furthermore, as a source of anaerobic microorganisms for power generation, soil microorganisms were planted on the negative electrode. Then, the electrolytic solution was continuously supplied to the electrolytic solution tank so that the hydraulic retention time was 24 hours. Further, the electrolytic solution was adjusted so that the water temperature was 30°C. Then, the positive electrode and the negative electrode were connected to a load circuit (external circuit) to obtain the liquid treatment system of this example.

As a result of operating the obtained liquid treatment system for 165 days, an enlarged biofilm was visually confirmed on the surface of the negative electrode. Then, an acrylic resin blocking plate was installed at the outlet of the electrolytic solution tank as an opening/closing section, and then the liquid sending device was operated to flow the electrolytic solution onto the negative electrode surface at a flow rate of 1 L/min. Then, after stopping the liquid sending device, the blocking plate was opened.

[Evaluation]
(Visual observation)
Regarding the above-mentioned liquid processing system, the state immediately after the opening/closing part was installed at the outlet of the electrolytic solution tank was visually observed.

First, at the outlet of the electrolytic solution tank, after installing a blocking plate made of acrylic resin as an opening/closing part, the liquid feeding device was operated, and as a result, the electrolytic solution was discharged from one end of the tube, The electrolyte was stirred. Then, as the electrolyte solution was stirred, the enlarged biofilm gradually peeled from the lower end of the negative electrode, and the biofilm floated in the electrolyte solution. At this time, it was confirmed that both the massive biofilm and the micronized biofilm were suspended in the electrolytic solution.

Then, as a result of stopping the liquid feeding device and further opening the blocking plate as the opening/closing part, the lumpy biofilm was rapidly precipitated, but the micronized biofilm moved toward the outflow port and flowed together with the electrolytic solution. It was discharged from the outlet. At this time, the lumpy biofilm did not move toward the outlet, but moved downward, so that the outlet was not blocked by the biofilm.

(Output characteristics)
After operating the above-mentioned liquid treatment system for 165 days, the output characteristics before and after stirring the electrolytic solution were examined using the liquid feeding device. That is, first, the potential difference between both ends of the load circuit of the liquid processing system was measured before stirring the electrolytic solution around the negative electrode using the liquid sending device. Next, after stirring the electrolytic solution around the negative electrode using the liquid sending device, the potential difference between both ends of the load circuit of the liquid processing system was measured. Then, the output of the liquid treatment system was obtained based on the following Equation 1.
[Equation 1]
P=V ² /R
(P: output, V: potential difference between both ends of the load circuit, R: resistance value of the load circuit)

As a result, the output before stirring the electrolytic solution around the negative electrode was 0.15 mW/m ² . On the other hand, the output after stirring the electrolytic solution around the negative electrode was 2.1 mW/m ² . Thus, it can be seen that the power generation efficiency of the liquid treatment system is greatly improved by stirring the electrolytic solution around the negative electrode and peeling off the enlarged biofilm.

Although the present embodiment has been described above, the present embodiment is not limited to these, and various modifications can be made within the scope of the gist of the present embodiment.

1, 1A Liquid processing system 20 Positive electrode 30 Negative electrode 60 Electrolyte solution 70 Electrolyte solution tank 72 Outlet port 80 External circuit 90 Opening/closing section 100 Electrolyte solution stirring section 101 Air diffuser 110 Control section

Claims (5)

An electrolytic solution tank that holds an electrolytic solution containing an organic matter, and has an outlet through which the electrolytic solution flows out,
Holding the anaerobic microorganisms, and the negative electrode in contact with the electrolytic solution,
A positive electrode electrically connected to the negative electrode,
At least an electrolytic solution stirring section for stirring the electrolytic solution around the negative electrode,
An opening/closing unit provided at the outlet and opening/closing the outlet,
A control unit for controlling the open/closed state of the opening/closing unit,
Equipped with
The liquid processing system, wherein the control unit performs control such that the opening/closing unit is closed when the electrolyte stirring unit is in operation, and the opening/closing unit is opened when the electrolyte stirring unit is stopped. The liquid treatment system according to claim 1, wherein the electrolytic solution stirring unit includes a pump that generates a flow of the electrolytic solution around the negative electrode. The liquid treatment system according to claim 1, wherein the electrolytic solution stirring unit includes an air diffuser that diffuses air toward the negative electrode. The liquid treatment system according to any one of claims 1 to 3, wherein the electrolytic solution stirring unit is provided on the lower side of the negative electrode in the vertical direction. The liquid processing system according to claim 1, wherein the control unit controls a timing of removing foreign matter attached to the negative electrode by the electrolytic solution stirring unit.

Images