WO2018203455A1

WO2018203455A1 - Liquid treatment system

Info

Publication number: WO2018203455A1
Application number: PCT/JP2018/014048
Authority: WO
Inventors: 雄也鈴木; 邦彦小野; 直毅吉川
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2017-05-01
Filing date: 2018-04-02
Publication date: 2018-11-08

Abstract

A liquid treatment system 100 comprising an electrolytic solution vessel 70 that holds an electrolytic solution 60 containing an organic substance and has an inflow opening 71 and an outflow opening 72 for the electrolytic solution. The liquid treatment system furthermore comprises a liquid treatment unit 1 provided with a negative electrode 20 that supports microorganisms and a positive electrode 10 that is electrically connected to the negative electrode, the negative electrode and positive electrode being immersed in the electrolytic solution, and at least portion of the positive electrode being exposed to a gas phase 2. The liquid treatment system also comprises a porous carrier 90 for filtering insoluble matter in the electrolytic solution, the porous carrier being provided within the electrolytic solution vessel. When the electrolytic solution flows from the inflow opening to the outflow opening, the porous carrier is disposed downstream from the liquid treatment unit and upstream from the outflow opening.

Description

Liquid processing system

The present invention relates to a liquid processing system. More particularly, the present invention relates to a liquid treatment system using a microbial fuel cell that can purify wastewater and generate electrical energy.

In recent years, microbial fuel cells that generate electricity using biomass have attracted attention as sustainable energy. A microbial fuel cell is a wastewater treatment apparatus that converts the chemical energy of an organic substance contained in domestic wastewater or factory wastewater into electrical energy and oxidizes and decomposes the organic substance. The microbial fuel cell is characterized by little generation of sludge and low energy consumption.

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. And while supplying the electrolyte solution containing an organic substance etc. to a negative electrode, the gas containing oxygen is supplied to a positive electrode. The negative electrode and the positive electrode are connected to each other through a load circuit to form a closed circuit. In the negative electrode, hydrogen ions and electrons are generated from the electrolytic solution by the catalytic action of microorganisms. And the produced | generated hydrogen ion moves to a positive electrode, and an electron moves to a positive electrode through a load circuit. Hydrogen ions and electrons transferred from the negative electrode are combined with oxygen at the positive electrode and consumed as water. At that time, the electric energy flowing in the closed circuit is recovered.

For example, Patent Document 1 encloses an electrolytic solution in a sealed hollow cassette having a negative electrode immersed in an organic substrate to carry anaerobic microorganisms, an outer shell formed of an ion-permeable diaphragm and an inlet / outlet hole. And a positive electrode for insertion into an organic substrate. And in the said microbial fuel cell, electricity is taken out via the circuit which electrically connects a negative electrode and a positive electrode, supplying oxygen in a cassette via an inlet / outlet.

Japanese Patent No. 5164511

In the microbial fuel cell of Patent Document 1, treated water treated by the negative electrode and the positive electrode is discharged to the outside as it is. However, since the treated water contains microorganisms and organic substances that have not been used by the microorganisms, the water quality may be insufficient. Further, as microorganisms flow out from the microbial fuel cell, the self-digestion of sludge by microorganisms becomes insufficient, and the reduction of sludge becomes difficult to proceed. Therefore, the amount of excess sludge may increase.

The present invention has been made in view of such problems of the conventional technology. An object of the present invention is to provide a liquid treatment system that can reduce the content of microorganisms and organic substances in the discharged treated water and improve the quality of the treated water.

In order to solve the above problems, a liquid processing system according to an aspect of the present invention includes an electrolytic solution tank that holds an electrolytic solution containing an organic substance and has an inlet and an outlet for the electrolyte. The liquid processing system includes a negative electrode carrying microorganisms and a positive electrode electrically connected to the negative electrode, the negative electrode and the positive electrode being immersed in an electrolyte solution, and a liquid processing unit in which at least a part of the positive electrode is exposed to the gas phase. Prepare. And a liquid processing system is provided in the inside of an electrolyte solution tank, and is provided with the porous support | carrier for filtering the insoluble matter in electrolyte solution. In the liquid processing system, when the electrolytic solution flows from the inlet to the outlet, the porous carrier is disposed downstream of the liquid processing unit and upstream of the outlet.

FIG. 1 is a schematic perspective view showing an example of a liquid processing system according to an embodiment of the present invention. FIG. 2 is a sectional view taken along line AA in FIG. FIG. 3 is a schematic plan view showing an example of a liquid processing system according to an embodiment of the present invention. FIG. 4 is an exploded perspective view showing a liquid processing unit in the liquid processing system. FIG. 5 is a schematic cross-sectional view showing another example of the liquid processing system according to the embodiment of the present invention. FIG. 6 is a schematic plan view showing another example of the liquid processing system according to the embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing another example of the liquid processing system according to the embodiment of the present invention. FIG. 8 is a schematic plan view showing another example of the liquid processing system according to the embodiment of the present invention.

Hereinafter, the liquid processing system according to the present embodiment will be described in detail. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

As shown in FIG. 1, the liquid processing system 100 according to this embodiment includes a liquid processing unit 1 that includes a positive electrode 10 and a negative electrode 20 that carries microorganisms and is electrically connected to the positive electrode 10. . Further, the liquid processing system 100 includes an electrolytic solution tank 70 that holds an electrolytic solution 60 containing an organic substance therein and is further disposed so that the liquid processing unit 1 is immersed in the electrolytic solution 60.

[Liquid processing unit]
As shown in FIGS. 1 to 3, the liquid processing unit 1 includes an electrode assembly 40 including a positive electrode 10, a negative electrode 20, and an ion transfer layer 30. In the liquid processing unit 1, the negative electrode 20 is disposed so as to contact one surface 30 a of the ion moving layer 30, and the positive electrode 10 is disposed so as to contact the surface 30 b opposite to the surface 30 a of the ion moving layer 30. Has been. The gas diffusion layer 12 of the positive electrode 10 is in contact with the ion migration layer 30 and the water repellent layer 11 is exposed to the gas phase 2 side.

And as shown in FIG. 4, the electrode assembly 40 is laminated | stacked on the cassette base material 50. As shown in FIG. The cassette base material 50 is a U-shaped frame member along the outer peripheral portion of the surface 10 a of the positive electrode 10, and the upper part is open. That is, the cassette base material 50 is a frame member in which the bottom surfaces of the two first columnar members 51 are connected by the second columnar member 52. As shown in FIG. 2, the side surface 53 of the cassette base material 50 is joined to the outer peripheral portion of the surface 10 a of the positive electrode 10.

As shown in FIG. 2, the liquid processing unit 1 formed by laminating two sets of electrode assemblies 40 and the cassette base material 50 includes an electrolyte bath 70 so that a gas phase 2 communicating with the atmosphere is formed. Arranged inside. An electrolytic solution 60 that is water to be treated is held inside the electrolytic solution tank 70, and the gas diffusion layer 12, the negative electrode 20, and the ion moving layer 30 of the positive electrode 10 are immersed in the electrolytic solution 60.

As will be described later, the positive electrode 10 includes a water-repellent layer 11 having water repellency. Therefore, the electrolytic solution 60 held inside the electrolytic solution tank 70 is separated from the inside of the cassette base material 50, and the internal space formed by the electrode assembly 40 and the cassette base material 50 is in the gas phase 2. . The liquid processing system 100 is configured such that the gas phase 2 is opened to the outside air or air is supplied to the gas phase 2 from the outside by, for example, a pump. As shown in FIG. 2, the positive electrode 10 and the negative electrode 20 are electrically connected to an external circuit 80, respectively.

(Positive electrode)
As shown in FIG. 2, the positive electrode 10 according to the present embodiment includes a gas diffusion electrode including a water-repellent layer 11 and a gas diffusion layer 12 stacked to be in contact with the water-repellent layer 11. By using such a thin plate-like gas diffusion electrode, oxygen in the gas phase 2 can be easily supplied to the catalyst in the positive electrode 10.

<Water repellent layer>
The water repellent layer 11 in the positive electrode 10 is a layer having both water repellency and oxygen permeability. The water repellent layer 11 is configured to allow oxygen to move from the gas phase 2 toward the liquid phase while favorably separating the gas phase 2 and the liquid phase in the electrochemical system in the liquid processing unit 1. That is, the water repellent layer 11 can suppress the movement of the electrolytic solution 60 to the gas phase 2 side while allowing oxygen in the gas phase 2 to permeate and move to the gas diffusion layer 12. In addition, "separation" here means physical interruption | blocking.

The water repellent layer 11 is in contact with the gas phase 2 containing oxygen, and diffuses oxygen in the gas phase 2. In the configuration shown in FIG. 2, the water repellent layer 11 supplies oxygen to the gas diffusion layer 12 substantially uniformly. Therefore, the water repellent layer 11 is preferably a porous body so that the oxygen can be diffused. In addition, since the water repellent layer 11 has water repellency, it can suppress that the pores of a porous body are obstruct | occluded by dew condensation etc. and oxygen diffusibility falls. In addition, since the electrolytic solution 60 hardly penetrates into the water repellent layer 11, oxygen can be efficiently circulated from the surface in contact with the gas phase 2 to the surface facing the gas diffusion layer 12 in the water repellent layer 11. It becomes.

The water repellent layer 11 is preferably formed in a sheet shape from a woven fabric or a non-woven fabric. The material constituting the water repellent layer 11 is not particularly limited as long as it has water repellency and can diffuse oxygen in the gas phase 2. Examples of the material constituting the water repellent layer 11 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 are easy to form a porous body and also have high water repellency, they can suppress clogging of pores and improve gas diffusibility. The water repellent layer 11 preferably has a plurality of through holes in the stacking direction X of the water repellent layer 11 and the gas diffusion layer 12.

The water repellent layer 11 may be subjected to a water repellent treatment using a water repellent as necessary in order to enhance water repellency. Specifically, a water repellent such as polytetrafluoroethylene may be attached to the porous body constituting the water repellent layer 11 to improve water repellency.

<Gas diffusion layer>
The gas diffusion layer 12 in the positive electrode 10 preferably includes a porous conductive material and a catalyst supported on the conductive material. The gas diffusion layer 12 may be composed of a porous and conductive catalyst. By providing the positive electrode 10 with such a gas diffusion layer 12, electrons generated by a local battery reaction described later can be conducted between the catalyst and the external circuit 80. That is, as will be described later, the gas diffusion layer 12 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 12, whereby the oxygen reduction reaction by oxygen, hydrogen ions, and electrons can be advanced by the catalyst.

In the positive electrode 10, in order to ensure stable performance, it is preferable that oxygen permeate the water-repellent layer 11 and the gas diffusion layer 12 efficiently and be supplied to the catalyst. Therefore, the gas diffusion layer 12 is preferably a porous body having a large number of pores through which oxygen passes from the surface facing the water repellent layer 11 to the opposite surface. The shape of the gas diffusion layer 12 is particularly preferably a three-dimensional mesh. Such a mesh shape makes it possible to impart high oxygen permeability and conductivity to the gas diffusion layer 12.

In the positive electrode 10, the water repellent layer 11 is preferably bonded to the gas diffusion layer 12 via an adhesive in order to efficiently supply oxygen to the gas diffusion layer 12. Thereby, the diffused oxygen is directly supplied to the gas diffusion layer 12, and the oxygen reduction reaction can be performed efficiently. The adhesive is preferably provided on at least a part between the water-repellent layer 11 and the gas diffusion layer 12 from the viewpoint of ensuring the adhesion between the water-repellent layer 11 and the gas diffusion layer 12. However, from the viewpoint of improving the adhesion between the water repellent layer 11 and the gas diffusion layer 12 and supplying oxygen to the gas diffusion layer 12 stably over a long period of time, the adhesive is used as the water repellent layer 11 and the gas diffusion layer. It is more preferable that it is provided on the entire surface between the two.

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

Here, the gas diffusion layer 12 of the positive electrode 10 in the present embodiment will be described in more detail. As described above, the gas diffusion layer 12 can be configured to include a porous conductive material and a catalyst supported on the conductive material.

The conductive material in the gas diffusion layer 12 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 material means a material containing carbon as a constituent component. Examples of carbon-based materials include, for example, carbon powder such as graphite, activated carbon, carbon black, Vulcan (registered trademark) XC-72R, acetylene black, furnace black, Denka black, graphite felt, carbon wool, carbon woven cloth, etc. Carbon fiber, carbon plate, carbon paper, carbon disk, carbon cloth, carbon foil, and carbon-based material obtained by compression molding carbon particles are included. Examples of the carbon-based material also include fine-structured materials such as carbon nanotubes, carbon nanohorns, and carbon nanoclusters. Furthermore, as a conductive material in the gas diffusion layer 12, a metal material such as a mesh and a foam can also be used.

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

The shape of the conductive material is preferably a powder shape or a fiber shape. Further, the conductive material may be supported by a support. The support means a member that itself has rigidity 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 porous structure support include porous ceramics, porous plastics, and sponges. When the support is a conductor, examples of the support include carbon materials such as carbon paper, carbon fiber, and carbon rod, metals, conductive polymers, and the like. When the support is a conductor, the support can also function as a current collector by disposing a conductive material carrying a carbon-based material on the surface of the support.

The catalyst in the gas diffusion layer 12 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 catalyst using activated molybdenum, activated carbon, or the like can be used.

The catalyst in the gas diffusion layer 12 is preferably a carbon-based material doped with metal atoms. Although it does not specifically limit as a metal atom, Titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium , 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 as a catalyst for promoting the oxygen reduction reaction. What is necessary is just to set suitably the quantity of the metal atom which carbonaceous material contains so that carbonaceous material may have the outstanding catalyst performance.

It is preferable that the carbon-based material is further doped with one or more nonmetallic atoms selected from nitrogen, boron, sulfur, and phosphorus. What is necessary is just to set suitably the quantity of the nonmetallic atom doped by the carbonaceous material so that carbonaceous material may have the outstanding catalyst performance.

The carbon-based material is based on a carbon source material such as graphite and amorphous carbon, for example, 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. Can be obtained.

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

The nonmetallic atom may contain nitrogen, and the metallic atom may contain at least one of cobalt and manganese. Also in this case, the carbon-based material can have a particularly excellent catalytic activity. The nonmetallic atom may be only nitrogen. 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 particulate shape or may have a sheet shape. The dimension of the carbon-based material having a sheet-like shape is not particularly limited. For example, the carbon-based material may have a minute dimension. The carbon-based material having a sheet shape may be porous. It is preferable that the porous carbon-based material having a sheet shape has a shape such as a woven fabric shape or a nonwoven fabric shape. Such a carbon-based material can constitute the gas diffusion layer 12 even without a conductive material.

The carbon-based material configured as a catalyst in the gas diffusion layer 12 can be prepared as follows. First, for example, a mixture containing a nonmetallic compound containing at least one nonmetal selected from the group consisting of nitrogen, boron, sulfur, and phosphorus, a metal compound, and a carbon source material is prepared. And this mixture is heated at the temperature of 800 degreeC or more and 1000 degrees C or less for 45 second or more and less than 600 second. Thereby, the carbonaceous material comprised as a catalyst can be obtained.

Here, as the carbon source material, for example, graphite or amorphous carbon can be used as described above. Further, the metal compound is not particularly limited as long as it is a compound containing a metal atom capable of coordinating with a nonmetal atom doped in the carbon source material. Metal compounds include, for example, metal chlorides, nitrates, sulfates, bromides, iodides, fluorides, etc., inorganic metal salts, organic metal salts such as acetates, inorganic metal salt hydrates, and organic metal salts At least one selected from the group consisting of hydrates can be used. For example, when graphite is doped with iron, the metal compound preferably contains iron (III) chloride. Moreover, when 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 so that, for example, 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 nonmetallic compound is preferably at least one nonmetallic compound selected from the group consisting of nitrogen, boron, sulfur and phosphorus. Non-metallic compounds include, for example, pentaethylenehexamine, ethylenediamine, tetraethylenepentamine, triethylenetetramine, ethylenediamine, octylboronic acid, 1,2-bis (diethylphosphinoethane), triphenyl phosphite, benzyldisal At least one compound selected from the group consisting of fido can be used. The amount of the nonmetallic compound used is appropriately set according to the amount of the nonmetallic atom doped into the carbon source material. The amount of the nonmetallic compound used is preferably determined so that the molar ratio of the metal atom in the metal compound to the nonmetallic atom in the nonmetallic compound is in the range of 1: 1 to 1: 2. More preferably, it is determined to be within the range of 1: 1.5 to 1: 1.8.

A mixture containing a nonmetallic compound, a metal compound, and a carbon source material when preparing a carbon-based material configured as a catalyst is obtained, for example, as follows. First, a carbon source material, a metal compound, and a nonmetal compound are mixed, and if necessary, a solvent such as ethanol is added to adjust the total amount. These are further dispersed by an ultrasonic dispersion method. Subsequently, after heating them at an appropriate temperature (for example, 60 ° C.), the mixture is dried to remove the solvent. Thereby, the mixture containing a nonmetallic compound, a metal compound, and a carbon source raw material is obtained.

Next, the obtained mixture is heated, for example, under a reducing atmosphere or an inert gas atmosphere. Thereby, a non-metallic atom is doped to a carbon source raw material, and also a metallic atom is doped by the coordinate bond of a non-metallic atom and a metallic atom. The heating temperature is preferably in the range of 800 ° C. to 1000 ° C., and the heating time is preferably in the range of 45 seconds to less than 600 seconds. Since the heating time is short, the carbon-based material is efficiently produced, and the catalytic activity of the carbon-based material is further increased. In the heat treatment, the temperature rising rate of the mixture at the start of heating is preferably 50 ° C./s or more. Such rapid heating further improves the catalytic activity of the carbonaceous material.

In addition, the carbon-based material may be further acid cleaned. For example, the carbon-based material may be dispersed in pure water with a homogenizer for 30 minutes, and then the carbon-based material may be placed in 2M sulfuric acid and stirred at 80 ° C. for 3 hours. In this case, elution of the metal component from the carbon-based material can be suppressed.

By such a production method, a carbon-based material having a significantly low content of inert metal compound and metal crystal and high conductivity can be obtained.

In the gas diffusion layer 12, 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 using a binder. Thereby, it can suppress that a catalyst detaches | leaves from an electroconductive material and an oxygen reduction characteristic falls. As the binder, for example, at least one selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride (PVDF), and ethylene-propylene-diene copolymer (EPDM) is preferably used. Moreover, it is also preferable to use NAFION (registered trademark) as a binder.

(Negative electrode)
The negative electrode 20 in the present embodiment carries a microbe described later and further has a function of generating hydrogen ions and electrons from at least one of an organic substance and a nitrogen-containing compound in the electrolytic solution 60 by the catalytic action of the microbe. For this reason, the negative electrode 20 of the present embodiment is not particularly limited as long as it has such a function.

The negative electrode 20 of the present embodiment has a structure in which microorganisms are supported on a conductive sheet having conductivity. As the conductor sheet, it is possible to use at least one selected from the group consisting of a porous conductor sheet, a woven conductor sheet, and a nonwoven conductor sheet. The conductor sheet may be a laminate 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 20, hydrogen ions generated in the local battery reaction described later easily move toward the ion moving layer 30, and the oxygen reduction reaction The speed can be increased. Further, from the viewpoint of improving ion permeability, the conductor sheet of the negative electrode 20 has a space (void) continuous in the stacking direction X of the positive electrode 10, the ion moving layer 30 and the negative electrode 20, that is, in the thickness direction. It is preferable.

The conductor sheet may be a metal plate having a plurality of through holes in the thickness direction. Therefore, as a material constituting the conductor sheet of the negative electrode 20, for example, at least one selected from the group consisting of conductive metals such as aluminum, copper, stainless steel, nickel and titanium, carbon paper, and carbon felt is used. be able to.

As the conductor sheet of the negative electrode 20, a graphite sheet used in the positive electrode 10 may be used. In addition, the negative electrode 20 preferably contains graphite, and the graphene layer in the graphite is preferably arranged along a plane in the direction YZ perpendicular to the stacking direction X of the positive electrode 10, the ion moving layer 30 and the negative electrode 20. By arranging the graphene layers in this way, the conductivity in the direction YZ perpendicular to the stacking direction X is improved as compared with the conductivity in the stacking direction X. Therefore, the electrons generated by the local battery reaction of the negative electrode 20 can be easily conducted to the external circuit 80, and the efficiency of the battery reaction can be further improved.

The microorganism supported on the negative electrode 20 is not particularly limited as long as it is a microorganism that decomposes an organic substance or a nitrogen-containing compound in the electrolytic solution 60 to generate hydrogen ions and electrons. As such microorganisms, 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 an anaerobic microorganism is preferably used. Anaerobic microorganisms do not require air for oxidative decomposition of organic substances in the electrolyte solution 60. Therefore, the electric power required for sending air can be significantly reduced. Moreover, since the free energy which microbes acquire is small, it becomes possible to reduce the amount of sludge generation.

Examples of the aerobic microorganisms held in the negative electrode 20 include Escherichia bacterium, Escherichia bacterium, Pseudomonas bacterium, Bacillus bacterium, Bacillus bacterium. Moreover, it is preferable that the anaerobic microorganisms hold | maintained at the negative electrode 20 are the electric production bacteria which have an extracellular electron transmission mechanism, for example. Specifically, examples of the anaerobic microorganism include Geobacter genus bacteria, Shewanella genus bacteria, Aeromonas genus bacteria, Geothrix genus bacteria, and Saccharomyces genus bacteria.

Microorganisms may be held in the negative electrode 20 by superimposing and fixing a biofilm containing microorganisms on the negative electrode 20. The 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 microorganisms may be held on the negative electrode 20 without depending on the biofilm. Microorganisms may be held not only on the surface of the negative electrode 20 but also inside.

The negative electrode 20 according to this embodiment may be modified with, for example, an electron transfer mediator molecule. Alternatively, the electrolytic solution 60 in the electrolytic solution tank 70 may contain electron transfer mediator molecules. Thereby, the electron transfer from microorganisms to the negative electrode 20 is accelerated | stimulated, and more efficient liquid processing is realizable.

Specifically, in the metabolic mechanism by microorganisms, electrons are transferred between cells or with the final electron acceptor. When a mediator molecule is introduced into the electrolytic solution 60, the mediator molecule acts as a final electron acceptor of metabolism, and delivers received electrons to the negative electrode 20. As a result, it is possible to increase the rate of oxidative decomposition of the organic substance or the like 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 methylviologen can be used.

(Ion moving layer)
The liquid processing unit 1 of the present embodiment further includes an ion transfer layer 30 provided between the positive electrode 10 and the negative electrode 20 and having proton permeability. As shown in FIGS. 1 and 2, the negative electrode 20 is separated from the positive electrode 10 through an ion migration layer 30. The ion moving layer 30 has a function of transmitting hydrogen ions generated in the negative electrode 20 and moving the hydrogen ions to the positive electrode 10 side.

As the ion moving layer 30, 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, and Flemion (registered trademark) and Selemion (registered trademark) manufactured by Asahi Glass Co., Ltd. can be used.

Alternatively, a porous membrane having pores through which hydrogen ions can permeate may be used as the ion moving layer 30. That is, the ion moving layer 30 may be a sheet having a space (void) for hydrogen ions to move from the negative electrode 20 to the positive electrode 10. Therefore, the ion migration layer 30 preferably includes at least one selected from the group consisting of a porous sheet, a woven sheet, and a nonwoven sheet. Moreover, the ion migration layer 30 can use at least one chosen from the group which consists of a glass fiber membrane, a synthetic fiber membrane, and a plastic nonwoven fabric, and the laminated body formed by laminating these two or more may be used. Since such a porous sheet has a large number of pores inside, hydrogen ions can easily move. The pore diameter of the ion moving layer 30 is not particularly limited as long as hydrogen ions can move from the negative electrode 20 to the positive electrode 10.

Note that, as described above, the ion moving layer 30 has a function of transmitting hydrogen ions generated in the negative electrode 20 and moving them to the positive electrode 10 side. Therefore, for example, if the negative electrode 20 and the positive electrode 10 are close to each other without contact, hydrogen ions can move from the negative electrode 20 to the positive electrode 10. Therefore, in the liquid processing system 100 of the present embodiment, the ion moving layer 30 is not an essential component. However, since the provision of the ion moving layer 30 enables efficient movement of hydrogen ions from the negative electrode 20 to the positive electrode 10, it is preferable to provide the ion moving layer 30 from the viewpoint of improving the output. Note that a gap may be provided between the positive electrode 10 and the ion transfer layer 30, and a gap may also be provided between the negative electrode 20 and the ion transfer layer 30.

The liquid processing unit 1 includes an external circuit 80 that is electrically connected to the negative electrode 20 and the positive electrode 10 as shown in FIG. However, in the liquid processing unit 1, the negative electrode 20 and the positive electrode 10 may be directly electrically connected using a conductive member without using the external circuit 80. Further, in the liquid processing unit 1, the cassette base member 50 is entirely open at the top, but may be partially opened as long as air (oxygen) can be introduced into the cassette base member 50. You may do it.

[Electrolyte tank]
The liquid treatment system 100 includes a substantially rectangular parallelepiped electrolyte tank 70 that holds an electrolyte containing an organic substance therein. The electrolyte tank 70 is provided with an inlet 71 for supplying the electrolyte 60 to the electrolyte tank 70 and an outlet 72 for discharging the treated electrolyte 60 from the electrolyte tank 70. . The inlet 71 is provided on the upper part of the front wall 73 of the electrolytic solution tank 70, and the outlet 72 is provided on the upper part of the rear wall 74 of the electrolytic solution tank 70.

The electrolytic solution 60 is continuously supplied into the electrolytic solution tank 70 through the inlet 71. Moreover, as shown in FIG.1 and FIG.2, the liquid processing unit 1 is arrange | positioned inside the electrolyte solution tank 70 so that it may be immersed in the electrolyte solution 60. FIG. Therefore, the electrolytic solution 60 supplied from the inlet 71 of the electrolytic solution tank 70 flows while contacting the liquid processing unit 1, and is then discharged from the outlet 72.

[Porous carrier]
The liquid processing system 100 includes a porous carrier 90 that is provided inside the electrolytic solution tank 70 and filters insoluble matters in the electrolytic solution 60. By providing the porous carrier 90, it is possible to filter and remove microorganisms contained in the electrolytic solution 60 and fine organic substances that have not been used by the microorganisms. Therefore, it is possible to reduce the insoluble matter in the treated water discharged from the outlet 72 and improve the quality of the treated water.

The shape of the porous carrier 90 is not particularly limited as long as it is a shape capable of filtering microorganisms and solid organic substances contained in the electrolytic solution 60. The shape of the porous carrier 90 may be flat as shown in FIGS. 1 to 3, or may be hemispherical as shown in FIGS.

It is preferable to use a porous carrier 90 having a plurality of pores and capable of filtering the electrolytic solution 60 through the pores. The average pore diameter of the porous carrier 90 is not particularly limited as long as it can pass through the electrolytic solution 60 but is difficult for microorganisms and solid organic substances to pass through. The average pore diameter of the porous carrier 90 is preferably 500 μm or less, more preferably 100 μm or less, further preferably 50 μm or less, and particularly preferably 20 μm or less. In order to efficiently remove the microorganisms contained in the electrolytic solution 60 by the porous carrier 90, the average pore diameter of the porous carrier 90 is preferably 1 μm or less. Although the minimum of the average pore diameter of a porous support | carrier is not specifically limited, For example, it can be 500 nm.

The porosity of the porous carrier 90 is not particularly limited, but can be set to, for example, 50 to 96% from the viewpoint of achieving both the strength of the porous carrier 90 and the high permeability of the electrolytic solution 60. In addition, although the measuring method of the average pore diameter and porosity of the porous support | carrier 90 is not specifically limited, For example, it can measure by the mercury intrusion method.

The material constituting the porous carrier 90 is not particularly limited, and for example, at least one of resin, metal, and ceramics can be used. The porous carrier 90 can be a woven fabric, a nonwoven fabric or a foam of these materials. The porous carrier 90 may be a single layer or a multilayer formed by laminating a plurality of layers.

The material constituting the porous carrier 90 is preferably a resin. As the resin constituting the porous carrier 90, at least one of a thermosetting resin, a thermoplastic resin, and an elastomer can be used.

Thermoplastic resins include polyvinyl alcohol resin, acrylic resin, methacrylic resin, vinyl acetate resin, vinyl chloride resin, vinylidene chloride resin, styrene resin, ethylene vinyl acetate resin, acrylonitrile-butadiene-styrene resin, polyethylene, polypropylene, polyacetal Polyamide resins, polyesters and copolymers thereof can be used. As the thermosetting resin, epoxy resin, unsaturated polyester resin, phenol resin, urea resin, melamine resin, polyurethane resin, silicone resin, diallyl phthalate resin and copolymers thereof can be used. Examples of the elastomer that can be used include styrene elastomers, polyolefin elastomers, polyurethane elastomers, polyester elastomers, polyamide elastomers, polybutadiene elastomers, and copolymers thereof.

In the liquid processing system 100, when the electrolytic solution 60 flows from the inlet 71 to the outlet 72, the porous carrier 90 is disposed on the downstream side of the liquid processing unit 1 and on the upstream side of the outlet 72. It is preferred that That is, the porous carrier 90 is preferably disposed between the liquid processing unit 1 and the outlet 72. By disposing the porous carrier 90 in this way, the electrolytic solution 60 processed by the liquid processing unit 1 passes through the pores of the porous carrier 90 and is then discharged through the outlet 72. Therefore, microorganisms and organic substances can be separated by the porous carrier 90 and the quality of the treated water can be improved.

Specifically, as shown in FIGS. 1 to 3, the porous carrier 90 is formed in a flat plate shape, and is further arranged so that the main surface of the porous carrier 90 is in contact with the rear wall 74 of the electrolyte bath 70. It is preferable. Thereby, the porous carrier 90 is disposed between the liquid processing unit 1 and the outlet 72, and the entire opening 72 a that is the inlet of the outlet 72 can be covered with the porous carrier 90. Therefore, the porous carrier 90 can efficiently filter microorganisms and organic substances.

In FIGS. 1 to 3, the porous carrier 90 is disposed so as to contact the rear wall 74 of the electrolyte bath 70. Further, in FIG. 2, the bottom surface of the porous carrier 90 is in contact with the bottom wall 77 of the electrolytic solution tank 70. In FIG. 3, the side surface of the porous carrier 90 is in contact with the left wall 75 and the right wall 76 of the electrolytic solution tank 70. However, the porous carrier 90 may be disposed on the rear wall 74 without contacting the left wall 75, the right wall 76, and the bottom wall 77 of the electrolytic solution tank 70.

In the liquid processing system 100, the porous carrier 90 may be arranged so as not to contact the rear wall 74 of the electrolytic solution tank 70. Specifically, as shown in FIGS. 5 and 6, the porous carrier 90 may be formed in a flat plate shape, and may be further disposed between the negative electrode 20 and the outlet 72 of the liquid processing unit 1. At this time, as shown in FIG. 5, the bottom surface of the porous carrier 90 may be in contact with the bottom wall 77 of the electrolytic solution tank 70. Further, as shown in FIG. 6, the side surface of the porous carrier 90 may be in contact with the left wall 75 and the right wall 76 of the electrolytic solution tank 70. However, the porous carrier 90 may not be in contact with the rear wall 74, the left wall 75, and the right wall 76 of the electrolyte bath 70.

In the liquid processing system 100, it is preferable that the uppermost portion of the porous carrier 90 is arranged to be higher than the water surface of the electrolytic solution 60. Specifically, as shown in FIG. 2, the porous carrier 90 is arranged inside the electrolytic solution tank 70 so that the upper surface 91 is higher than the water surface 61 of the electrolytic solution 60 and the upper surface 91 is exposed from the electrolytic solution 60. It is preferred that Microorganisms and solid organic substances often float on the water surface 61 of the electrolytic solution 60. Therefore, by arranging the uppermost portion of the porous carrier 90 to be higher than the water surface of the electrolytic solution 60, microorganisms and organic substances floating on the water surface 61 of the electrolytic solution 60 are efficiently removed, It becomes possible to further improve the water quality of the electrolytic solution 60 discharged from the outflow port 72. The difference D between the upper surface 91 of the porous carrier 90 and the water surface 61 of the electrolytic solution 60 is not particularly limited, and is appropriately set so that microorganisms and organic substances floating on the water surface 61 of the electrolytic solution 60 can be removed. It is possible.

In the liquid processing system 100, it is preferable that the porous carrier 90 is installed so as to cover the entire inlet 72. Specifically, when the electrolytic solution 60 flows to the outlet 72, the porous carrier 90 covers the entire opening 72a that is the inlet of the outlet 72 so as to surely pass through the pores of the porous carrier 90. It is preferable that it is installed. Thereby, the porous carrier 90 can reliably filter microorganisms and organic substances.

For example, as shown in FIGS. 1 to 3, it is preferable that the plate-like porous carrier 90 is disposed so as to contact the rear wall 74 of the electrolytic solution tank 70. Further, as shown in FIGS. 7 and 8, it is preferable that the hemispherical porous carrier 90 is disposed so as to contact the rear wall 74 of the electrolytic solution tank 70. Thereby, since the whole opening part 72a of the outflow port 72 is covered with the porous support |

carrier

90,90A, it becomes possible to filter microorganisms and an organic substance reliably, and to improve water quality.

As described above, since the porous carrier 90 has a large number of pores, it functions as a filter medium for filtering the solid content in the electrolytic solution 60. The porous carrier 90 may carry a microorganism. By supporting the microorganism, the organic substance or the nitrogen-containing compound in the electrolytic solution 60 can be decomposed in the porous carrier 90. As a result, the organic substance or nitrogen-containing compound in the electrolytic solution 60 can be removed, and the quality of the treated water can be further improved. The microorganisms supported on the porous carrier 90 are not particularly limited, and at least one of an aerobic microorganism and an anaerobic microorganism supported on the negative electrode 20 can be used. Further, the position of the porous carrier 90 where microorganisms are supported is not particularly limited, and may be supported on the inner surface of the pores of the porous carrier 90 or may be further supported on the outer surface of the porous carrier 90. .

Next, the operation of the liquid processing system 100 of this embodiment will be described. When the electrode assembly 40 including the positive electrode 10, the negative electrode 20, and the ion transfer layer 30 is immersed in the electrolytic solution 60, the gas diffusion layer 12 and the negative electrode 20 of the positive electrode 10 are immersed in the electrolytic solution 60, and the water repellent layer 11. At least a part of is exposed to the gas phase 2.

During the operation of the liquid processing system 100, the electrolyte 60 containing at least one of an organic substance and a nitrogen-containing compound is supplied to the negative electrode 20, and air is supplied to the positive electrode 10. At this time, the air is continuously supplied through an opening provided in the upper part of the cassette base material 50.

In the positive electrode 10, oxygen diffuses into the gas diffusion layer 12 through the water repellent layer 11. In the negative electrode 20, 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 microorganisms. The generated hydrogen ions pass through the ion moving layer 30 and move to the positive electrode 10 side, and reach the gas diffusion layer 12 in the positive electrode 10. Further, the generated electrons move to the external circuit 80 through the conductor sheet of the negative electrode 20, and further move from the external circuit 80 to the gas diffusion layer 12 of the positive electrode 10. The hydrogen ions and electrons are combined with oxygen by the action of the catalyst in the gas diffusion layer 12 and consumed as water. At this time, the electric energy flowing in the closed circuit is recovered by the external circuit 80. Thus, the liquid processing unit 1 can decompose at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 60 by the action of microorganisms in the negative electrode 20.

Here, in the liquid processing system 100, the electrolytic solution 60 is continuously supplied from the inlet 71 of the electrolytic solution tank 70. Then, at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 60 is decomposed by the microorganisms supported on the negative electrode 20 of the liquid processing unit 1. Thereafter, the electrolytic solution 60 passes through the pores of the porous carrier 90 arranged on the downstream side of the liquid processing unit 1 and on the upstream side of the outflow port 72, and then discharged by the outflow port 72. At this time, since solid microorganisms and organic substances contained in the electrolytic solution 60 are filtered and separated, the quality of the treated water discharged from the outlet 72 can be improved.

Further, by providing the porous carrier 90 in the electrolytic solution tank 70, it is possible to suppress the outflow of highly active microorganisms together with the electrolytic solution 60. Since highly active microorganisms remain in the electrolytic solution 60 in the electrolytic solution tank 70, sludge is reduced by self-digestion of the microorganisms, and it is possible to reduce the amount of excess sludge that accumulates in the electrolytic solution tank 70. It becomes.

Furthermore, when microorganisms are supported on the porous carrier 90, organic substances that could not be processed by the liquid processing unit 1 can be decomposed by the microorganisms supported on the porous carrier 90. As a result, the quality of the treated water discharged from the outlet 72 can be further improved.

As described above, the liquid processing system 100 according to the present embodiment includes the electrolytic solution tank 70 that holds the electrolytic solution 60 containing an organic substance and includes the inlet 71 and the outlet 72 of the electrolytic solution 60. Furthermore, the liquid processing system 100 includes a negative electrode 20 supporting microorganisms, and a positive electrode 10 electrically connected to the negative electrode 20, and the negative electrode 20 and the positive electrode 10 are immersed in the electrolytic solution 60, and at least a part of the positive electrode 10 is formed. A liquid processing unit 1 exposed to the gas phase 2 is provided. The liquid processing system 100 includes a porous carrier 90 that is provided inside the electrolytic solution tank 70 and filters insoluble matters in the electrolytic solution 60. In the liquid processing system 100, when the electrolytic solution 60 flows from the inlet 71 to the outlet 72, the porous carrier 90 is disposed downstream of the liquid processing unit 1 and upstream of the outlet 72. Is done. Further, the electrolytic solution 60 preferably flows to the outlet 72 after passing through the porous carrier 90. Thereby, since the microorganisms and organic substance contained in the electrolyte solution 60 can be removed through the porous carrier 90, the quality of the treated water discharged from the outlet 72 can be further improved.

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

[Example]
First, a silicone resin as an adhesive is applied to a polyolefin water repellent layer, and then a graphite foil as a gas diffusion layer is bonded to produce a laminated sheet composed of a water repellent layer / silicone adhesive / gas diffusion layer. did. In addition, Sekisui Chemical Co., Ltd. SELPORE (registered trademark) was used for the water repellent layer. As the silicone resin, one-component RTV rubber KE-3475-T manufactured by Shin-Etsu Chemical Co., Ltd. was used. A graphite foil manufactured by Hitachi Chemical Co., Ltd. was used.

Next, a gas diffusion electrode was produced 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 6 mg / cm ² .

The oxygen reduction catalyst was prepared as follows. First, 3 g of carbon black, 0.1 M iron (III) chloride aqueous solution, and 0.15 M pentaethylenehexamine ethanol solution were placed in a container to prepare a mixed solution. As carbon black, Ketjen Black ECP600JD manufactured by Lion Specialty Chemicals Co., Ltd. was used. The amount of 0.1M 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 the mixture. And this liquid mixture was ultrasonically disperse | distributed, and it was dried at the temperature of 60 degreeC with the 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 a quartz tube, and then the inside of this quartz tube was replaced with argon. The quartz tube was put into a furnace at 900 ° C. and pulled out in 45 seconds. When the quartz tube was inserted into the furnace, the quartz tube was inserted into the furnace over 3 seconds to adjust the rate of temperature rise of the sample at the start of heating to 300 ° C./s. Subsequently, the sample was cooled by flowing argon gas through the quartz tube. Thereby, an oxygen reduction catalyst was obtained.

Next, a positive electrode was produced by providing an air intake portion in the water repellent layer of the gas diffusion electrode obtained as described above. And the said positive electrode and the negative electrode which consists of carbon materials (graphite foil) were installed in the electrolyte tank provided with the inflow port and the outflow port. Furthermore, after installing the polyolefin nonwoven fabric between the positive electrode and the negative electrode, the electrolytic solution was filled in the electrolytic solution tank so as to be in contact with the positive electrode, the negative electrode, and the nonwoven fabric. The electrolytic solution contained 600 mg / L of an organic substance as total organic carbon (TOC), and soil microorganisms were inoculated as an anaerobic microorganism source for generating power. And the residence time of electrolyte solution was continuously supplied to the container as 24 hours. Furthermore, the liquid processing system of this example was obtained by connecting a positive electrode and a negative electrode to a load circuit.

Here, in this example, as shown in FIGS. 1 to 3, a porous carrier was installed on the downstream side of the positive electrode and the negative electrode and on the upstream side of the outlet of the electrolytic solution tank. As the porous carrier, a foam made of polyvinyl alcohol and having a pore diameter of 80 μm was used.

[Comparative example]
A liquid treatment system of this example was obtained in the same manner as in Example except that no porous carrier was installed.

[Evaluation]
The total organic carbon concentration (TOC concentration) in the electrolyte before and after the treatment with the liquid treatment system was measured. The total organic carbon concentration was measured using a total organic carbon meter. And the removal rate (TOC removal rate) of all the organic carbon was calculated | required from Numerical formula 1.

(T: TOC removal rate, T1: TOC concentration before treatment, T2: TOC concentration after treatment)

In the examples, the total organic carbon concentration before processing in the liquid processing system was 600 mg / L, and the total organic carbon concentration after processing was 43 mg / L. Therefore, the TOC removal rate of the liquid treatment system of the example was 93%. On the other hand, in the comparative example, the total organic carbon concentration before processing in the liquid processing system was 600 mg / L, and the total organic carbon concentration after processing was 69 mg / L. Therefore, the TOC removal rate of the liquid processing system of the comparative example was 89%.

From the above results, by disposing a porous carrier downstream from the liquid treatment unit and upstream from the outlet of the electrolytic solution tank, the removal rate of organic substances present in the treated water is increased, It turns out that the quality of treated water can be improved.

Although the present embodiment has been described above, the present embodiment is not limited to these, and various modifications are possible within the scope of the gist of the present embodiment. Specifically, in the drawing, the positive electrode 10, the negative electrode 20, and the ion migration layer 30 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 processing system, desired purification performance, and the like. Further, the area of each layer can be arbitrarily changed as long as a desired function can be exhibited.

The liquid treatment system according to this embodiment can be widely applied to treatment of a liquid containing an organic substance, for example, waste water generated from factories of various industries, organic waste water such as sewage sludge, and the like. It can also be used to improve the water environment.

The entire contents of Japanese Patent Application No. 2017-090991 (filing date: May 1, 2017) are incorporated herein by reference.

According to the present invention, it is possible to provide a liquid treatment system capable of reducing the content of microorganisms and organic substances in the discharged treated water and improving the quality of the treated water.

DESCRIPTION OF SYMBOLS 1 Liquid processing unit 2 Gas phase 10 Positive electrode 20 Negative electrode 60 Electrolyte 70 Electrolyte tank 71 Inlet 72

Outlet

90,90A Porous support 100 Liquid processing system

Claims

An electrolyte bath holding an electrolyte containing an organic substance and having an inlet and an outlet for the electrolyte, and
A liquid processing unit comprising a negative electrode supporting microorganisms and a positive electrode electrically connected to the negative electrode, wherein the negative electrode and the positive electrode are immersed in the electrolytic solution, and at least a part of the positive electrode is exposed to a gas phase; ,
A porous carrier provided inside the electrolytic solution tank for filtering insoluble matters in the electrolytic solution;
With
When the electrolytic solution flows from the inflow port to the outflow port, the porous carrier is disposed downstream of the liquid processing unit and upstream of the outflow port. .
The liquid processing system according to claim 1, wherein the electrolytic solution flows to the outlet after passing through the porous carrier.
The liquid processing system according to claim 1 or 2, wherein an uppermost part of the porous carrier is disposed so as to be higher than a water surface of the electrolytic solution.
The liquid processing system according to any one of claims 1 to 3, wherein the porous carrier is installed so as to cover the entire inlet of the outlet.