JP2019076833A - Liquid treatment system - Google Patents

Abstract

To provide a liquid treatment system capable of accelerating propagation of microorganisms and enhancing design freedom.SOLUTION: Liquid treatment systems 100, 100A include a treatment tank 70 for holding a liquid 60 to be treated containing organic substances, one or more electrode units 1 provided in an inside of the treatment tank and including a cathode 10 reducing oxygen, and expanded graphite particles 20 which are provided in the inside of the treatment tank and electrically connected to the cathode and which are carried thereon with microorganisms; and at least a part of the liquid 60 to be treated flowing into the treatment tank 70 passes through an inside of the expanded graphite particles 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to liquid processing systems. In particular, the present invention relates to a liquid treatment system using a microbial fuel cell capable of purifying wastewater and producing 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 device that oxidizes and processes organic substances and nitrogen-containing compounds while converting the chemical energy of organic substances and nitrogen-containing compounds contained in domestic wastewater and industrial wastewater into electrical energy. . And a microbial fuel cell has the characteristics of little generation | occurence | production of a sludge, and also energy consumption is small.

  A microbial fuel cell has a negative electrode carrying a microorganism, 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 form a closed circuit by being connected to each other through 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 through the load circuit. The hydrogen ions and electrons transferred from the negative electrode combine with oxygen at the positive electrode to be consumed as water. At that time, the electrical energy flowing to the closed circuit is recovered.

  As a conventional microbial fuel cell, there is disclosed a microbial fuel cell having a diameter of 1.5 mm to 5 mm and using particulate graphite to which a microorganism (current producing bacteria) is attached as an anode and a ferricyanide aqueous solution as a cathode. (For example, refer to nonpatent literature 1). In Non-Patent Document 1, it is disclosed that particulate graphite is filled in the inside of a cylindrical container, and furthermore, an electrolytic solution is continuously supplied to the inside of the cylindrical container.

Korneel Rabaey et al., “Tubular Microbial Fuel Cells for Efficient Electricity Generation”, Environmental Science & Technology, 2005, 39 (20), pp 8077-8082

However, the particulate graphite used in the microbial fuel cell of Non-Patent Document 1 has a small specific surface area of 817 to 2720 m ² / m ³ . Therefore, there are few sites to which microorganisms adhere to particulate graphite, and there is a problem that growth of microorganisms is difficult to progress. Moreover, in order to reduce the contact resistance between the particulate graphite, it is necessary to closely pack the particulate graphite inside the cylindrical container. Therefore, since it is necessary to always apply external pressure load to particulate graphite using a cylindrical container, an outer wall, etc., there existed a problem that the design freedom of a microbial fuel cell was restricted.

  The present invention has been made in view of the problems of the prior art. And the object of the present invention is to provide a liquid processing system capable of promoting the growth of microorganisms and further improving the freedom of design.

  In order to solve the above problems, a liquid processing system according to an aspect of the present invention includes a processing tank that holds a liquid to be processed including an organic substance, and a positive electrode that is provided inside the processing tank and reduces oxygen. And one or more electrode units, and an expanded graphite particle group provided inside the processing tank, electrically connected to the positive electrode, and further supporting a microorganism. Then, at least a part of the liquid to be treated that has flowed into the treatment tank passes through the inside of the expanded graphite particle group.

  According to the present invention, it is possible to provide a liquid processing system capable of promoting the growth of microorganisms and further improving the freedom of design.

1 is a schematic perspective view showing an example of a liquid processing system according to an embodiment of the present invention. It is sectional drawing along the AA in FIG. It is a schematic plan view which shows an example of the liquid processing system which concerns on embodiment of this invention. It is a disassembled perspective view which shows the electrode unit in a liquid processing system. It is a photograph which shows an example of an expanded graphite particle group. It is a schematic plan view which shows the other example of the liquid processing system which concerns on embodiment of this invention. It is sectional drawing along the BB line in FIG. It is sectional drawing along the C-C line in FIG. It is a graph which shows the relationship between the steady-state output in the liquid processing system of an Example, a total organic carbon processing rate (TOC processing rate), and the operation days. It is a graph which shows the relationship between the steady-state output in the liquid processing system of a comparative example and an all-organic carbon treatment rate, and the number of days in operation.

  Hereinafter, the liquid processing system according to the present embodiment will be described in detail. The dimensional ratios in the drawings are exaggerated for the convenience of description, and may differ from the actual ratios.

  As shown in FIG. 1, the liquid processing system 100 according to the present embodiment includes an electrode unit 1 having a positive electrode 10, and an expanded graphite particle group 20 electrically connected to the positive electrode 10 and acting as a negative electrode. There is. In addition, the liquid processing system 100 holds the liquid to be treated 60 containing an organic substance inside, and further the treatment tank 70 arranged so as to immerse the electrode unit 1 and the expanded graphite particle group 20 in the liquid to be treated 60. Have.

[Electrode unit]
The electrode unit 1 is equipped with the electrode assembly 40 which consists of the positive electrode 10 and the ion transfer layer 30, as shown in FIGS. In the electrode unit 1, the positive electrode 10 is disposed in contact with the surface 30 b of the ion transfer layer 30. The gas diffusion layer 12 of the positive electrode 10 is in contact with the ion transfer layer 30, and the water repellent layer 11 is exposed to the gas phase 2 side. The expanded graphite particle group 20 is disposed in contact with the surface 30 a of the ion transfer layer 30 opposite to the surface 30 b.

  As shown in FIG. 4, the electrode assembly 40 is stacked on the cassette base 50. The cassette base 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 portion is open. That is, the cassette base 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. Then, as shown in FIG. 2, the side surface 53 of the cassette base 50 is joined to the outer peripheral portion of the surface 10 a of the positive electrode 10.

  As shown in FIG. 2, an electrode unit 1 formed by laminating two sets of electrode assemblies 40 and a cassette base 50 is formed inside the processing tank 70 so that the gas phase 2 communicated with the atmosphere is formed. Be placed. A liquid to be treated 60, which is a waste water, is held inside the treatment tank 70, and the gas diffusion layer 12 and the ion transfer layer 30 of the positive electrode 10 and the expanded graphite particle group 20 are immersed in the liquid to be treated 60.

  As described later, the positive electrode 10 is provided with a water repellent layer 11 having water repellency. Therefore, the liquid to be treated 60 held inside the treatment tank 70 and the inside of the cassette base 50 are separated, and the internal space formed by the electrode assembly 40 and the cassette base 50 is the gas phase 2 . Then, in the liquid processing system 100, 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. Further, as shown in FIG. 2, the positive electrode 10 and the expanded graphite particle group 20 are each electrically connected to the external circuit 80.

(Positive electrode)
As shown in FIG. 2, the positive electrode 10 according to the present embodiment is a gas diffusion electrode including a water repellent layer 11 and a gas diffusion layer 12 stacked so as to be in contact with the water repellent layer 11. By using such a thin plate-like gas diffusion electrode, it is possible to easily supply the oxygen in the gas phase 2 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 the movement of oxygen from the gas phase 2 to the liquid phase while satisfactorily separating the gas phase 2 and the liquid phase in the electrochemical system in the electrode unit 1. That is, while the water repellent layer 11 allows oxygen in the gas phase 2 to permeate and move to the gas diffusion layer 12, the liquid 60 can be inhibited from moving to the gas phase 2 side. Here, “separation” means to physically shut off.

  The water repellent layer 11 is in contact with the gas phase 2 containing oxygen and diffuses the oxygen in the gas phase 2. The water repellent layer 11 supplies oxygen to the gas diffusion layer 12 substantially uniformly in the configuration shown in FIG. Therefore, it is preferable that the water repellent layer 11 be a porous body so that the oxygen can be diffused. In addition, since the water repellent layer 11 has water repellency, it is possible to prevent the pores of the porous body from being blocked by condensation or the like and the decrease in the diffusion of oxygen being suppressed. Further, since the liquid 60 to be treated is difficult to permeate into the water repellent layer 11, oxygen can be efficiently circulated from the surface of the water repellent layer 11 in contact with the gas phase 2 to the surface facing the gas diffusion layer 12. It becomes possible.

  The water repellent layer 11 is preferably formed in a sheet shape. Further, the material constituting the water repellent layer 11 is not particularly limited as long as it has water repellency and oxygen in the gas phase 2 can be diffused. The material constituting the water repellent layer 11 is made of, for example, polyethylene, polypropylene, polybutadiene, nylon, polytetrafluoroethylene (PTFE), ethylcellulose, 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 also have high water repellency, it is possible to suppress clogging of pores and improve gas diffusivity. The water repellent layer 11 preferably has a plurality of through holes in the stacking direction Z of the water repellent layer 11 and the gas diffusion layer 12.

  As the water repellent layer 11, for example, a waterproof moisture permeable sheet can be used. As the waterproof moisture-permeable sheet, for example, Cellpore (registered trademark) manufactured by Sekisui Chemical Co., Ltd. and Breslon (registered trademark) manufactured by Nitoms Corporation can be used.

  The water repellent layer 11 may be subjected to a water repellent treatment using a water repellent, if necessary, in order to enhance the water repellency. Specifically, a water repellent agent such as polytetrafluoroethylene may be attached to the porous body constituting the water repellent layer 11 to improve the 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 made of a porous and conductive catalyst. By providing such a gas diffusion layer 12 on the positive electrode 10, it becomes possible to conduct electrons generated by a local cell reaction described later between the catalyst and the external circuit 80. That is, as described later, a catalyst is supported on the gas diffusion layer 12, 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 so that the catalyst can promote the oxygen reduction reaction by oxygen, hydrogen ions and electrons.

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

  In the positive electrode 10, in order to supply oxygen to the gas diffusion layer 12 efficiently, the water repellent layer 11 is preferably joined to the gas diffusion layer 12 via an adhesive. Thus, the diffused oxygen is directly supplied to the gas diffusion layer 12, and the oxygen reduction reaction can be efficiently performed. The adhesive is preferably provided at least in part between the water repellent layer 11 and the gas diffusion layer 12 from the viewpoint of securing the adhesiveness between the water repellent layer 11 and the gas diffusion layer 12. However, from the viewpoint of enhancing 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, the adhesive is the water repellent layer 11 and the gas diffusion layer More preferably, it is provided on the entire surface between 12 and 12.

  The adhesive is preferably one having oxygen permeability, and contains 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 made of, for example, one or more materials selected from the group consisting of carbon-based materials, conductive polymers, semiconductors, and metals. Here, the carbon-based substance refers to a substance having carbon as a component. Examples of carbon-based materials include, for example, graphite, activated carbon, carbon black, Vulcan (registered trademark) XC-72R, acetylene black, carbon powder such as furnace black and denka black, graphite felt, carbon wool, carbon woven fabric, etc. Carbon fiber, carbon plate, carbon paper, carbon disk, carbon cloth, graphite foil, carbon-based material obtained by compression molding of carbon particles can be mentioned. In addition, as an example of the carbon-based material, fine structure materials such as carbon nanotubes, carbon nanohorns, and carbon nanoclusters can also be mentioned.

  The conductive polymer is a generic term for polymer compounds having conductivity. As the conductive polymer, for example, a single monomer or a polymer of two or more monomers having aniline, aminophenol, diaminophenol, pyrrole, thiophene, paraphenylene, fluorene, furan, acetylene or derivatives thereof as a constitutional unit It can be mentioned. Specifically, examples of the conductive polymer include polyaniline, polyaminophenol, polydiaminophenol, polypyrrole, polythiophene, polyparaphenylene, polyfluorene, polyfuran, polyacetylene and the like. As a metal conductive material, a stainless steel mesh is mentioned, for example. In consideration of availability, cost, corrosion resistance, durability and the like, the conductive material is preferably a carbon-based material.

  The shape of the conductive material is preferably in the form of powder or fiber. In addition, the conductive material may be supported by a support. The support refers to a member which itself is rigid and can give the gas diffusion electrode a certain shape. 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, paper treated with water or water resistance, water repellent or water repellent, plant pieces such as wood pieces, bone pieces, animal pieces such as shells, etc. . Examples of the support having a porous structure include porous ceramic, porous plastic, sponge and the like. When the support is a conductor, examples of the support include carbon paper, carbon fibers, carbon-based materials such as carbon rods, metals, conductive polymers, and the like.

  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) or 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 12 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 preferable that it is 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 particularly 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.

  The carbon-based material is preferably further doped with one or more nonmetallic atoms selected from nitrogen, boron, sulfur and phosphorus. The amount of nonmetal atoms doped in the carbon-based material may also 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 metal atoms and one or more nonmetal atoms selected from nitrogen, boron, sulfur and phosphorus It is obtained by

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

  The nonmetal atom may contain nitrogen, and the metal atom may contain at least one of cobalt and manganese. Also in this case, the carbon-based material can have particularly excellent catalytic activity. The nonmetal atom may be only nitrogen. In addition, 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-like shape. The dimensions of the carbon-based material having a sheet-like shape are not particularly limited, and, for example, the carbon-based material may have minute dimensions. The carbonaceous material having a sheet-like shape may be porous. It is preferable that the porous carbon-based material having a sheet-like shape has, for example, a woven-like shape, a non-woven-like shape or the like. Such a carbon-based material can constitute the gas diffusion layer 12 even without the conductive material.

  The carbon-based material configured as a catalyst in the gas diffusion layer 12 can be prepared as follows. First, a mixture containing, for example, a nonmetal 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. Then, the mixture is heated at a temperature of 800 ° C. or more and 1000 ° C. or less for 45 seconds or more and less than 600 seconds. Thereby, a carbon-based material configured as a catalyst can be obtained.

  Here, as the carbon source material, as described above, for example, graphite or amorphous carbon can be used. Further, the metal compound is not particularly limited as long as it is a compound containing a metal atom which can coordinately bond with a nonmetal atom doped in the carbon source material. Examples of metal compounds 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. In addition, when graphite is doped with cobalt, the metal compound preferably contains cobalt chloride. When manganese is doped to the carbon source material, the metal compound preferably contains manganese acetate. The amount of the metal compound used is preferably determined so that, for example, the ratio of metal atoms in the metal compound to the carbon source material is in the range of 5 to 30% by mass, and the ratio is further 5 to 20% by mass More preferably, it is determined to be within the range.

  The nonmetallic compound is preferably at least one nonmetallic compound selected from the group consisting of nitrogen, boron, sulfur and phosphorus as described above. Examples of nonmetal compounds include pentaethylenehexamine, ethylenediamine, tetraethylenepentamine, triethylenetetramine, ethylenediamine, octylboronic acid, 1,2-bis (diethylphosphinoethane), triphenyl phosphite, and benzyl disalc. At least one compound selected from the group consisting of Fides can be used. The amount of the nonmetallic compound used is appropriately set according to the doping amount of the nonmetallic atom to the carbon source material. The amount of the nonmetallic compound used is preferably determined such that the molar ratio of the metal atom in the metallic 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 in the range of 1: 1.5 to 1: 1.8.

  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, the catalyst can be prevented from being desorbed from the conductive material and the oxygen reduction characteristics can be prevented from being degraded. As the binder, it is preferable to use, for example, 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 a binder.

(Ion transfer layer)
The electrode unit 1 of the present embodiment is further provided with an ion transfer layer 30 provided between the expanded graphite particle group 20 acting as a negative electrode and the positive electrode 10 and having electrical insulation and proton permeability. Then, as shown in FIG. 1 and FIG. 2, the expanded graphite particle group 20 is separated from the positive electrode 10 via the ion transfer layer 30. The ion transfer layer 30 has a function of transmitting hydrogen ions generated in the expanded graphite particle group 20 and moving them to the positive electrode 10 side.

  As the ion transfer 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 Co., Ltd., and Flemion (registered trademark) and Seremion (registered trademark) manufactured by Asahi Glass Co., Ltd. can be used.

  Alternatively, as the ion transfer layer 30, a porous membrane having pores through which hydrogen ions can pass may be used. That is, the ion transfer layer 30 may be a sheet having a space (void) for hydrogen ions to move from the expanded graphite particle group 20 to the positive electrode 10. Therefore, it is preferable that the ion transfer layer 30 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 30 may be 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 obtained by laminating a plurality of these. Such a porous sheet has a large number of pores inside, so that hydrogen ions can be easily moved. The pore diameter of the ion transfer layer 30 is not particularly limited as long as hydrogen ions can move from the expanded graphite particle group 20 to the positive electrode 10.

  As described above, the ion transfer layer 30 has a function of transmitting hydrogen ions generated in the expanded graphite particle group 20 and moving them to the positive electrode 10 side. Therefore, for example, hydrogen ions can move from the expanded graphite particle group 20 to the positive electrode 10 if the expanded graphite particle group 20 and the positive electrode 10 are close to each other without being in contact with each other. Therefore, in the liquid treatment system 100, the ion transfer layer 30 is not an essential component. However, by providing the ion transfer layer 30, hydrogen ions can be efficiently transferred from the expanded graphite particle group 20 to the positive electrode 10. Therefore, the ion transfer layer 30 is preferably provided from the viewpoint of output improvement. A space may be provided between positive electrode 10 and ion transfer layer 30, and a space may be provided between expanded graphite particle group 20 and ion transfer layer 30.

  As shown in FIG. 2, the liquid processing system 100 includes an external circuit 80 electrically connected to the positive electrode 10 and the expanded graphite particle group 20. However, in the liquid processing system, the positive electrode 10 and the expanded graphite particle group 20 may be electrically connected directly using the conductive member without the external circuit 80. In the electrode unit 1, the entire upper portion of the cassette base 50 is open, but may be partially open if air (oxygen) can be introduced into the inside, or the cassette base 50 is closed. It may be

[Treatment tank]
The liquid processing system 100 includes a substantially rectangular processing tank 70 that holds the liquid to be processed 60 containing an organic substance therein. The treatment tank 70 is provided with an inlet 71 for supplying the liquid to be treated 60 to the treatment tank 70, and an outlet 72 for discharging the liquid to be treated 60 after treatment from the treatment tank 70. In the present embodiment, the inlet 71 is provided at the lower part of the front wall 73 of the processing tank 70, and the outlet 72 is provided at the upper part of the rear wall 74 of the processing tank 70.

  The liquid to be treated 60 is continuously supplied to the inside of the treatment tank 70 through the inlet 71. Further, as shown in FIGS. 1 and 2, the electrode unit 1 and the expanded graphite particle group 20 are disposed inside the treatment tank 70 so as to be immersed in the liquid 60 to be treated. Therefore, the liquid to be treated 60 supplied from the inflow port 71 of the processing tank 70 flows in contact with the electrode unit 1 and the expanded graphite particle group 20, and is then discharged from the outflow port 72.

  In the liquid treatment system 100, the electrode units 1 are preferably arranged along the direction from the inflow port 71 to the outflow port 72 in plan view. Specifically, as shown in FIGS. 1 and 3, in the liquid processing system 100, the inlet 71 is provided on the front wall 73 of the processing tank 70, and the outlet 72 is provided on the rear wall 74 opposite to the front wall 73. It is done. Then, the electrode unit 1 is placed inside the processing tank 70 so that the film-like positive electrode 10 and the ion transfer layer 30 in the electrode unit 1 are substantially parallel to the direction (X direction) from the inflow port 71 to the outflow port 72. It is preferable that it is arrange | positioned. Thereby, as described later, even when the plurality of electrode units 1 are disposed inside the liquid processing system, the concentration of the organic substance in the liquid to be treated 60 in contact with each electrode unit 1 is made comparable. can do. As a result, it is possible to make the amount of power generation of each electrode unit 1 uniform.

Expanded Graphite Particles
The liquid processing system 100 includes an expanded graphite particle group 20 which acts as a negative electrode and contains expanded graphite. The expanded graphite particle group 20 has a function of supporting microorganisms and generating hydrogen ions and electrons from at least one of the organic substance and the nitrogen-containing compound in the liquid to be treated 60 by the catalytic action of the microorganisms.

  The microorganism supported by the expanded graphite particle group 20 is not particularly limited as long as it is a current generating bacterium that decomposes the organic substance or the nitrogen-containing compound in the liquid to be treated 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 organic substances in the liquid 60 to be treated. Therefore, the power required to feed the air can be significantly reduced. In addition, since the free energy obtained by microorganisms is small, it is possible to reduce the amount of sludge generated.

  When the microorganism supported by the expanded graphite particle group 20 is an anaerobic microorganism, in order to enhance the activity of the anaerobic microorganism, it is preferable to keep the periphery of the expanded graphite particle group 20 in an anaerobic atmosphere.

  Examples of aerobic microorganisms retained in the expanded graphite particle group 20 include E. coli, which is an Escherichia bacteria, P. niger, which is a Pseudomonas bacteria, and B. subtilis, which is a Bacillus bacteria. Moreover, it is preferable that the anaerobic microorganisms hold | maintained at the expanded-graphite particle group 20 are electric production bacteria which have an extracellular electron transfer mechanism, for example. Specifically, examples of anaerobic microorganisms include, for example, bacteria belonging to the genus Geobacter, bacteria belonging to the genus Shewanella, bacteria belonging to the genus Aeromonas, bacteria belonging to the genus Geothrix, and bacteria belonging to the genus Saccharomyces.

  A microorganism may be held in the expanded graphite particle group 20 by superimposing and fixing a biofilm containing the microorganism on the expanded graphite particle group 20. 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 retained in the expanded graphite particle group 20 without using the biofilm. The microorganism may be held not only on the surface of the expanded graphite particle group 20 but also on the inside.

  In the liquid treatment system 100, the liquid to be treated 60 flows inside the expanded graphite particle group 20 while being in contact with the surface of the expanded graphite. Therefore, the expanded graphite particle group 20 may be disposed so as to be filled in the entire flow path of the liquid to be treated 60, or may be disposed only in a part of the flow path of the liquid to be treated 60.

  Specifically, when the expanded graphite particle group 20 is provided between the electrode unit 1 and the processing tank 70, as shown in FIGS. 2 and 3, the electrode unit 1 and the left wall 75 of the processing tank 70. It is preferable to arrange the expanded graphite particle group 20 throughout the space. Similarly, the expanded graphite particle group 20 is preferably disposed in the entire area between the electrode unit 1 and the right wall 76 of the processing tank 70. However, the present embodiment is not limited to such an aspect, and the expanded graphite particle group 20 may be disposed in a part between the electrode unit 1 and the left wall 75 and the right wall 76 of the processing tank 70. .

  In the liquid treatment system 100, the upper end 21 of the expanded graphite particle group 20 is preferably arranged to be higher than the water surface of the liquid 60 to be treated. Specifically, as shown in FIG. 2, the inside of the treatment tank 70 such that the upper end 21 of the expanded graphite particle group 20 is higher than the water surface 61 of the liquid to be treated 60 and the upper end 21 is exposed from the liquid to be treated 60. It is preferred that the However, the present embodiment is not limited to such an aspect, and the upper end 21 of the expanded graphite particle group 20 may be lower than the water surface 61 of the liquid 60 to be treated.

  In FIG. 2, the lower end 22 of the expanded graphite particle group 20 is in contact with the bottom wall 77 of the processing tank 70. However, the present embodiment is not limited to such an aspect, and a gap may be present between the lower end 22 of the expanded graphite particle group 20 and the bottom wall 77 of the processing tank 70.

  Further, as shown in FIG. 3, the expanded graphite particle group 20 is preferably disposed upstream of the rear end 1 a of the electrode unit 1 in the flow direction (X direction) of the liquid to be treated 60. That is, the rear end 23 of the expanded graphite particle group 20 is preferably located upstream of the rear end 1 a of the electrode unit 1. However, the rear end 23 of the expanded graphite particle group 20 may be located downstream of the rear end 1 a of the electrode unit 1 without being limited to such an embodiment.

  As shown in FIG. 3, the expanded graphite particle group 20 is preferably located downstream of the front end 1 b of the electrode unit 1 in the flow direction of the liquid to be treated 60. That is, it is preferable that the front end 24 of the expanded graphite particle group 20 be located downstream of the front end 1 b of the electrode unit 1. However, the front end 24 of the expanded graphite particle group 20 may be located upstream of the front end 1 b of the electrode unit 1 without being limited to such an embodiment.

  As described above, in the liquid processing system according to the present embodiment, the expanded graphite particle group 20 including the plurality of expanded graphite particles is used as the conductive carrier supporting the microorganism. Expanded graphite is obtained by treating natural graphite with an acid such as sulfuric acid to form an intercalation compound, and rapidly heating the powder to expand the c-axis direction of the graphite 150 to 700 times. Therefore, expanded graphite has a very small bulk density compared to graphite, and has many pores supporting microbes.

  Here, FIG. 5 shows a state of expanded graphite particle groups obtained by forming expanded graphite particles used in Examples to be described later at different densities. FIG. 5 (a) shows expanded graphite particle groups molded to have a density of 0.00918 g / cc, and FIG. 5 (b) shows expansions molded to have a density of 0.01158 g / cc. Graphite particles are shown. In addition, the expanded graphite particle group of FIG. 5 is shape | molded so that it may become a cylinder about 5 cm in diameter.

Literature (Shoji Yoshimoto, one other person, "synthesis of expanded graphite", [online], December 2008, Aichi Industrial Research Institute, Internet <URL: http://www.aichi-inst.jp/sangyou /research/report/kougyo_2008_02.pdf> describes that the specific surface area of the expanded graphite particles is 10.6 m ² / g. When the specific surface area of the expanded graphite particles is 10.6 m ² / g, the specific surface area of the expanded graphite particle group shown in FIG. 5A is 84376 m ² / m ³ . Moreover, the specific surface area of the expanded graphite particle group shown to (b) of FIG. 5 will be 97308 m < ² > / m < ³ >. That is, the specific surface area of the expanded graphite particle group shown in FIG. 5 is increased by 10 times or more as compared with the particulate graphite of Non-Patent Document 1. The high specific surface area of the expanded graphite particle group means that the attachment site of microorganisms is increased. And, by increasing the attachment site of the microorganism, the growth of the microorganism can also be promoted. Therefore, when at least a part of the liquid to be treated 60 flowing into the treatment tank 70 permeates the inside of the expanded graphite particle group 20, the contact between the liquid to be treated 60 and the microorganisms is enhanced, and high water treatment performance and power generation performance It is possible to realize

  Furthermore, it can be seen from FIG. 5 that the expandable graphite particles used in the examples maintain their formability at a density of about 0.009 g / cc or more and can stand on their own. That is, the aggregate of the expanded graphite particles can stand by the expanded graphite particles themselves without using any supporting material. Since the expanded graphite particles have a structure in which the graphene layer is spread, the particles are generally easily entangled and can be formed without a binder. And such an effect is acting also in the expanded graphite particle group shown in FIG.

  And in the liquid processing system 100, since the expanded graphite particle group 20 acts as a negative electrode, it becomes possible to raise the design freedom of the liquid processing system 100 because the expanded graphite particle group 20 becomes independent. That is, when the particulate graphite or activated carbon particles of Non-Patent Document 1 which can not stand alone with the particle group is used as a negative electrode, it is necessary to closely pack in order to reduce the contact resistance between particles. Therefore, it is required to always apply external pressure to the particle group using a pipe, an outer wall or the like. Therefore, in general, there is required a structural design in which particulate graphite or activated carbon particles are filled into the inside of a tube or a box-like structure and external pressure is applied from the periphery by screwing or the like.

On the other hand, in the liquid processing system 100 of the present embodiment, the expanded graphite particle group can stand on its own without applying an external pressure at all times. Therefore, the expanded graphite particle group is filled in a tube or the like, and a structural design to apply an external pressure from the periphery by screwing or the like is not necessary, so that it can be easily applied to small to large size processing tanks. . Moreover, when the resistivity of the expanded graphite particle group shown in FIG. 5 was measured by the four probe method, it was 3.7 e ^<-2 > ohm * cm or less. From this, it can be seen that the expanded graphite particle group has low resistance sufficiently to obtain high power generation performance.

In this embodiment, the density of the expanded graphite particles 20 ^is preferably ^{0.001g / cm 3 ~0.1g / cm 3} . The density of the expanded graphite particles 20 ^is more preferably ^{0.001g / cm 3 ~0.05g / cm 3} , further preferably 0.001g / cm ³ ~0.03g / cm 3 . When the density of the expanded graphite particle group 20 is 0.001 g / cm ³ or more, the expanded graphite particle group 20 can stand on its own, and the design freedom of the liquid processing system can be further enhanced. Further, when the expanded graphite particle group 20 has a density of 0.1 g / cm ³ or less, the liquid to be treated 60 can easily pass through the inside of the expanded graphite particle group 20, so that the liquid 60 to be treated contacts microorganisms. Can be enhanced.

  The electrical resistivity of the expanded graphite particle group 20 used as the negative electrode is not particularly limited, but the lower one is preferable from the viewpoint of enhancing the power generation performance. Therefore, the electrical resistivity of the expanded graphite particle group 20 is preferably 0.001 Ω · cm to 0.1 Ω · cm. When the electrical resistivity of the expanded graphite particle group 20 is within this range, it is possible to secure a sufficiently low resistance as a negative electrode while making the expanded graphite particle group 20 stand alone. The electrical resistivity of the expanded graphite particle group 20 can be measured by the four-terminal method.

  The expanded graphite particle group 20 may be a structure in which only expanded graphite is collected. However, the expanded graphite particle group 20 may be mixed with other materials in addition to the expanded graphite. That is, the expanded graphite particle group 20 may be a structure including expanded graphite and at least one selected from the group consisting of a carbon material, a metal and a resin. The carbon material is preferably at least one selected from the group consisting of carbon paper, carbon felt, carbon fiber and graphite sheet. The metal is preferably at least one selected from the group consisting of aluminum, copper, stainless steel, nickel and titanium. The resin is preferably at least one selected from the group consisting of a thermosetting resin, a thermoplastic resin, and an elastomer. For example, a polyolefin resin or polytetrafluoroethylene (PTFE) can be used.

  As the expanded graphite particle group 20, for example, a sheet-like carbon material can be inserted into an aggregate of expanded graphite particles. Then, by electrically connecting the sheet-like carbon material and the external circuit 80, electrons generated by the microorganisms of the expanded graphite particle group 20 can be easily conducted from the external circuit 80 to the positive electrode 10, and power generation performance is improved. It is possible to

  Next, the operation of the liquid treatment system 100 of the present embodiment will be described. As described above, the processing tank 70 has the inlet 71 and the outlet 72 of the liquid to be treated 60, and the electrode unit 1 and the expanded graphite particle group 20 are disposed between the inlet 71 and the outlet 72. ing. Then, when the electrode assembly 40 composed of the positive electrode 10 and the ion transfer layer 30 is immersed in the liquid 60 to be treated, the gas diffusion layer 12 of the positive electrode 10 is immersed in the liquid 60 to be treated. Is exposed to the gas phase 2.

  At the time of operation of the liquid treatment system 100, the liquid to be treated 60 containing at least one of the organic substance and the nitrogen-containing compound is supplied to the expanded graphite particle group 20, and air is supplied to the positive electrode 10. At this time, air is continuously supplied through the opening provided at the top of the cassette base 50.

  Then, in the positive electrode 10, oxygen permeates the water repellent layer 11 and diffuses into the gas diffusion layer 12. In the expanded graphite particle group 20, hydrogen ions and electrons are generated from at least one of the organic substance and the nitrogen-containing compound in the liquid to be treated 60 by the catalytic action of microorganisms. The generated hydrogen ions permeate the ion transfer layer 30, move to the positive electrode 10 side, and reach the gas diffusion layer 12 in the positive electrode 10. The generated electrons move to the external circuit 80 through the expanded graphite particle group 20, and further move to the gas diffusion layer 12 of the positive electrode 10 from the external circuit 80. 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 external circuit 80 recovers the electrical energy flowing to the closed circuit. Thus, the electrode unit 1 can decompose at least one of the organic substance and the nitrogen-containing compound in the liquid to be treated 60 by the action of the microorganism in the expanded graphite particle group 20.

  And in this embodiment, the expanded-graphite particle group 20 which an expanded-graphite particle gathers is used as a negative electrode. The expanded graphite particle group 20 has a plurality of holes through which the liquid to be treated 60 can pass, and further, microorganisms are carried inside. Therefore, the contact between the liquid to be treated 60 and the microorganism is enhanced, and the organic substance in the liquid to be treated 60 can be efficiently decomposed by the microorganism to generate electric power. Further, in the expanded graphite particle group 20, the particles are easily entangled with each other, and can easily stand by itself. Therefore, since the structure which always applies an external pressure with respect to the expanded graphite particle group 20 becomes unnecessary, it becomes possible to improve the design freedom of the liquid processing system 100. FIG.

  Further, in the liquid treatment system 100, the liquid to be treated 60 is continuously supplied from the inflow port 71 of the treatment tank 70. The supplied liquid to be treated 60 contacts the expanded graphite particle group 20 and diffuses. Then, the organic substance in the liquid to be treated 60 is decomposed by the microbes supported by the expanded graphite particle group 20. As described above, since the liquid to be treated 60 is continuously supplied to the expanded graphite particle group 20 and the organic substance is decomposed by microorganisms, stable power generation characteristics can be obtained from the electrode unit 1.

  The liquid processing system according to the present embodiment may have a configuration in which one electrode unit 1 is provided inside one processing tank 70 as shown in FIGS. 1 to 3. However, the present embodiment is not limited to such a configuration. For example, a plurality of electrode units 1 may be provided in one processing tank 70. Specifically, as shown in FIGS. 6 to 8, five electrode units 1 may be provided in one processing tank 70. Such a configuration makes it possible to more efficiently perform power generation and wastewater purification by microorganisms.

  In the liquid processing system 100A shown in FIGS. 6-8, the inlet 71 is provided on the front wall 73 of the processing tank 70, and the outlet 72 is a rear wall facing the front wall 73, as in the liquid processing system 100 described above. Provided in 74. The five electrode units 1 are disposed inside the processing tank 70 such that the positive electrode 10 and the ion transfer layer 30 are substantially parallel to the direction (X direction) from the inflow port 71 toward the outflow port 72.

  The expanded graphite particle group 20 is provided between the adjacent electrode units 1 in addition to the space between the electrode unit 1 and the processing tank 70. By providing the expanded graphite particle group 20 between the adjacent electrode units 1, the to-be-treated liquid 60 can contact and diffuse the expanded graphite particle group 20, and the contact between the to-be-treated liquid 60 and microorganisms can be enhanced. Become.

  When the expanded graphite particle group 20 is provided between the adjacent electrode units 1, as shown in FIG. 6, the expanded graphite particle group is entirely formed between one electrode unit 1 and the other electrode unit 1. It is preferable to arrange 20. However, the present embodiment is not limited to such an aspect, and the expanded graphite particle group 20 may be disposed in a part between one electrode unit 1 and the other electrode unit 1.

  In the liquid processing system 100A shown in FIGS. 6 to 8, the expanded graphite particle group 20 is provided between the adjacent electrode units 1 in addition to between the electrode unit 1 and the processing tank 70. However, the present embodiment is not limited to such an aspect, and the expanded graphite particle group 20 is not provided between the electrode unit 1 and the treatment tank 70, and the expanded graphite particle group 20 is disposed only between the adjacent electrode units 1. May be provided. That is, in the liquid treatment system 100A, the expanded graphite particle group 20 is preferably provided in at least one of between the electrode unit 1 and the treatment tank 70 and between the adjacent electrode units 1.

  As described above, the liquid processing system 100, 100A according to the present embodiment includes the processing tank 70 holding the liquid to be treated 60 containing an organic substance, and the positive electrode 10 provided inside the processing tank 70 to reduce oxygen. And one or more electrode units 1 are provided. The liquid processing system 100, 100A further includes an expanded graphite particle group 20 provided inside the processing tank 70, electrically connected to the positive electrode 10, and further supporting a microorganism. Then, at least a part of the liquid to be treated 60 flowing into the treatment tank 70 passes through the inside of the expanded graphite particle group 20. In the liquid processing system 100, 100A, the porous expanded graphite particle group 20 is used as the negative electrode. And since the expanded graphite particle group 20 has many sites to which microorganisms adhere, and it is a high specific surface area, the growth of microorganisms tends to progress. Therefore, when the liquid to be treated 60 permeates the inside of the expanded graphite particle group 20, the contact between the liquid to be treated 60 and the microorganism is enhanced, and it is possible to realize high water treatment performance and power generation performance. In addition, the aggregate of the expanded graphite particles can stand with only the expanded graphite particles themselves without using supporting materials. Furthermore, the aggregate of expanded graphite particles has low resistance even without continuously applying a constant pressure from the outside. Therefore, since the expanded graphite particle group 20 has low electrical resistance while standing on its own, it is possible to increase the design freedom of the liquid processing system 100, 100A.

  Further, in the liquid treatment system 100, 100 </ b> A, the positive electrode 10 is preferably immersed in the liquid 60 to be treated, and at least a portion of the positive electrode 10 is exposed to the gas phase 2. As a result, oxygen is easily supplied from the gas phase 2 to the catalyst of the positive electrode 10, so that the oxygen reduction reaction at the positive electrode 10 can be promoted to further enhance the power generation performance.

  In the liquid treatment system 100, 100 </ b> A, the expanded graphite particle group 20 is provided in at least one of between the electrode unit 1 and the treatment tank 70 and between the adjacent electrode units 1. Then, the liquid to be treated 60 passes through the inside of the expanded graphite particle group 20 and comes into contact with the surface of the expanded graphite, and then flows to the outlet 72. Thereby, the liquid to be treated 60 can be diffused, contact between the liquid to be treated 60 and the microorganism can be enhanced, and power generation by the microorganism and purification of the liquid to be treated 60 can be efficiently performed. Further, in the liquid processing system 100, the plurality of electrode units 1 are arranged along the direction from the inflow port 71 toward the outflow port 72, whereby the organic substance in the liquid to be treated 60 in contact with each electrode unit 1 The concentration of As a result, it is possible to make the amount of power generation of each electrode unit 1 uniform.

  In the liquid treatment systems 100 and 100A, the electrode units 1 are arranged along the direction from the inflow port 71 to the outflow port 72 in plan view. That is, the electrode unit 1 is disposed inside the processing tank 70 so that the positive electrode 10 and the ion transfer layer 30 in the electrode unit 1 are substantially parallel to the direction (X direction) from the inflow port 71 to the outflow port 72. There is. However, the present embodiment is not limited to such an aspect. The electrode units 1 may be arranged along a direction perpendicular to the direction from the inflow port 71 toward the outflow port 72 in plan view.

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

[Example]
First, a silicone resin which is an adhesive agent is applied to a water repellent layer made of polyolefin and then a graphite foil which is a gas diffusion layer is joined to produce a laminated sheet consisting of water repellent layer / silicone adhesive / gas diffusion layer did. As the water repellent layer, Cellpore (registered trademark) manufactured by Sekisui Chemical Co., Ltd. was used. As a silicone resin, one-component RTV rubber KE-3475-T manufactured by Shin-Etsu Chemical Co., Ltd. was used. The graphite foil used was manufactured by Hitachi Chemical Co., Ltd.

Next, a gas diffusion electrode was produced by press-forming 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. In addition, the oxygen reduction catalyst was press-molded so that a basis weight might be 6 mg / cm < ² >.

  The 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 an ethanol solution of 0.15 M pentaethylenehexamine in a container. As carbon black, ketjen black ECP600 JD manufactured by Lion Specialty Chemicals Co., Ltd. was used. The amount of use of the 0.1 M aqueous solution of iron (III) chloride was adjusted so that the ratio of iron atoms to carbon black was 10% by mass. The total volume was adjusted to 9 mL by further adding ethanol to this mixture. Then, the mixture was ultrasonically dispersed and then dried at a temperature of 60 ° C. in a drier. This yielded a sample containing carbon black, iron (III) chloride, and pentaethylenehexamine.

  The sample was then packed into one end of a quartz tube, which was then purged with argon in the quartz tube. The quartz tube was put into a furnace at 900 ° C. and pulled out in 45 seconds. When inserting the quartz tube into the furnace, the temperature rising rate of the sample at the start of heating was adjusted to 300 ° C./s by inserting the quartz tube into the furnace over 3 seconds. Subsequently, the sample was cooled by flowing argon gas through the quartz tube. Thus, an oxygen reduction catalyst was obtained.

  A positive electrode was produced by providing an air intake as shown in FIG. 1 on the water repellent layer of the gas diffusion electrode obtained as described above. And as shown in FIG. 1, the said positive electrode was provided in the processing tank of 300 cc capacity | capacitance provided with the inflow port and the outflow port. On the surface of the positive electrode, a non-woven resin sheet made of resin as an ion transfer layer was disposed so that the expanded graphite particle group serving as the negative electrode and the positive electrode did not contact.

Next, expanded graphite particles were filled between the positive electrode and the treatment tank to form expanded graphite particle groups. As the expanded graphite particles, a product manufactured by Fuji Graphite Industry Co., Ltd. was used. In addition, although the expanded graphite particle group was first applied with pressure to be formed into a rectangular parallelepiped structure, thereafter, application of a constant pressure from the outside was not continued. Then, in order to recover the electrons from the current generating bacteria carried on the expanded graphite particle group, the expanded graphite sheet was disposed in the expanded graphite particle group. An expanded graphite sheet having a thickness of 0.38 mm and a density of 1.0 g / cm ³ was used.

  In the liquid processing system of the embodiment, the liquid to be treated flows into the expanded graphite particle group after entering the processing tank through the inlet, and is discharged from the outlet.

  Next, the treatment liquid was filled in the treatment tank so as to be in contact with the positive electrode, the ion transfer layer, and the expanded graphite particle group. The liquid to be treated was a model waste solution having a total organic carbon (TOC) of 800 mg / L. Furthermore, in order to stabilize the proton supply property of the liquid to be treated, sodium hydrogencarbonate was added as a buffer to a concentration of 20 mM. Furthermore, soil microorganisms were inoculated to the expanded graphite particle group as an anaerobic microorganism source for generating power.

  Then, the liquid to be treated was supplied to the treatment tank so that the hydraulic retention time was 24 hours. Furthermore, the liquid to be treated was adjusted to have a water temperature of 30 ° C. Then, the positive electrode and the expanded graphite sheet of the expanded graphite particle group were connected to an external circuit using a conducting wire to obtain the liquid processing system of this example.

[Comparative example]
The liquid treatment system of this example was obtained in the same manner as in the example except that the expanded graphite particle group was not installed. In this case, the expanded graphite sheet disposed for electron collection functions as a negative electrode.

[Evaluation]
The liquid treatment systems of Examples and Comparative Examples were operated for about 60 days, and the steady-state output of the liquid treatment system was measured. FIG. 9 shows the relationship between working days and steady output in the liquid processing system of the example, and FIG. 10 shows the relationship between working days and steady output in the liquid processing system of the comparative example. As shown in FIGS. 9 and 10, in each of the liquid treatment systems of the example and the comparative example, the output changed about 250 mW / m ² after several days after the start-up.

Furthermore, the total organic carbon concentration (TOC concentration) in the liquid to be treated before and after treatment with the liquid treatment system of the example and the comparative example was measured. The total organic carbon concentration was measured using a total organic carbon meter. Then, the treatment rate (TOC treatment rate) of total organic carbon was obtained from Formula 1. Changes in the TOC treatment rate when the liquid treatment systems of the example and the comparative example are operated for about 60 days are also shown in FIG. 9 and FIG.
(T: TOC treatment rate, T1: TOC concentration before treatment, T2: TOC concentration after treatment)

  As shown in FIG. 9, in the liquid treatment system of the example, the TOC treatment rate always exceeded 90%, and reached up to 97%. On the other hand, in the liquid processing system of the comparative example, the TOC processing rate is changing at 80 to 90%, and it can be seen that the TOC processing characteristics are lowered compared to the example. From this, by using the expanded graphite particle group as the negative electrode, a large number of current generating bacteria are supported on the expanded graphite particle group, and further, the liquid to be treated flows sufficiently in contact with them, resulting in good output characteristics and It can be seen that TOC processing characteristics can be obtained.

  As mentioned above, although this embodiment was described, this embodiment is not limited to these, A various deformation | transformation is possible within the range of the summary of this embodiment. Specifically, in the drawings, the positive electrode 10 and the ion transfer layer 30 are formed in a rectangular shape. However, these shapes are not particularly limited, and can be arbitrarily changed according to the size of the liquid treatment system, the desired purification performance, and the like. Also, the area of each layer can be arbitrarily changed as long as the desired function can be exhibited.

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

DESCRIPTION OF SYMBOLS 1 electrode unit 2 vapor phase 10 positive electrode 20 expanded graphite particle group 60 to-be-processed liquid 70 treatment tank 71 inlet 72 outlet 80 external circuit 100, 100A liquid processing system

Claims (7)

A treatment tank for holding a liquid to be treated containing an organic substance;
One or more electrode units provided inside the processing tank and including a positive electrode that reduces oxygen,
Expanded graphite particles which are provided inside the treatment tank, are electrically connected to the positive electrode, and further carry a microorganism.
Equipped with
The liquid treatment system, wherein at least a part of the liquid to be treated that has flowed into the treatment tank passes through the inside of the expanded graphite particle group.   The liquid processing system according to claim 1, wherein the expanded graphite particle group is self-supporting. The density of the expanded graphite particles is ^{0.001g / cm 3 ~0.1g / cm 3} , the liquid processing system according to claim 1 or 2.   The liquid treatment system according to any one of claims 1 to 3, wherein an electrical resistivity of the expanded graphite particle group is 0.001 Ω · cm to 0.1 Ω · cm. The treatment tank has an inlet and an outlet for the liquid to be treated,
The liquid processing system according to any one of claims 1 to 4, wherein the electrode unit and the expanded graphite particle group are disposed between the inlet and the outlet.   The liquid processing system according to any one of claims 1 to 5, wherein the expanded graphite particle group is provided in at least one of between the electrode unit and the processing tank, and between the adjacent electrode units.   The liquid processing system according to any one of claims 1 to 6, wherein the positive electrode is immersed in the liquid to be treated, and at least a part of the positive electrode is exposed to a gas phase.