JP2017148776A - Water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide water treatment equipment dispensing with input of electric energy, and capable of miniaturizing furthermore the equipment.SOLUTION: Water treatment equipment (100) includes a negative pole (20) not having a passive film on the surface, and containing iron, and a positive pole (10) comprising a gas diffusion electrode at least a part of which is exposed to a gas phase (90), and which includes an oxygen reduction catalyst. Further, the water treatment equipment includes an external circuit (110) connected electrically to the negative pole and the positive pole, and an electrolytic solution treatment tank (80) for holding an electrolytic solution containing a phosphorus compound.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment apparatus. Specifically, the present invention relates to a water treatment apparatus for removing phosphorus compounds contained in wastewater.

  Conventionally, various water treatment methods have been provided in order to remove phosphorus compounds contained in wastewater. As a method for removing a phosphorus compound, for example, an iron electrolysis method, an AOA method using microorganisms, an aggregation precipitation method by adding an aggregation material, and the like are known. In particular, the iron electrolysis method is advantageously used for wastewater treatment because it has an advantage that it can stably remove phosphorus compounds for a long period of time and can easily control the amount of dissolved iron.

  As a method for removing a phosphorus compound by such an iron electrolysis method, for example, a sewage treatment method described in Patent Document 1 is disclosed. The method of Patent Document 1 is a sewage treatment method in which metal ions are electrochemically eluted from a metal electrode and phosphorus compounds are removed by binding phosphorus compounds and metal ions contained in sewage. That is, by immersing a metal electrode made of one of iron and aluminum in sewage and energizing the immersed metal electrode, metal ions are electrochemically eluted from the metal electrode. And the phosphorus compound contained in waste water is removed by combining and eluting the eluted metal ion and the phosphorus compound contained in waste water.

Japanese Patent No. 3506697

  However, in the iron electrolysis type removal method as in Patent Document 1, it is necessary to throw electric energy in order to electrolyze the metal electrode. Furthermore, since it is necessary to provide a power source for flowing current to the metal electrode and the counter electrode, the conventional iron electrolysis type phosphorus removal method has a problem that the apparatus becomes large.

  The present invention has been made in view of such problems of the prior art. And the objective of this invention is providing the water treatment apparatus which does not need to throw electric energy and can further reduce an apparatus in size.

  In order to solve the above problems, a water treatment apparatus according to an aspect of the present invention has an oxygen reduction catalyst that does not have a passive film on the surface and is negatively exposed with iron, and at least part of the negative electrode is exposed to the gas phase. And a positive electrode made of a gas diffusion electrode. Further, the water treatment apparatus includes an external circuit that is electrically connected to the negative electrode and the positive electrode, and an electrolyte treatment tank that holds an electrolyte containing a phosphorus compound.

  ADVANTAGE OF THE INVENTION According to this invention, it is not necessary to throw an electrical energy and can obtain the water treatment apparatus which can reduce an apparatus further in size.

It is a perspective view which shows an example of the water treatment apparatus which concerns on embodiment of this invention. It is sectional drawing along the AA line in FIG. It is a disassembled perspective view which shows the water treatment unit in the said water treatment apparatus. It is a perspective view which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is sectional drawing along the BB line in FIG. It is sectional drawing which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a top view which shows the other example of the water treatment apparatus which concerns on embodiment of this invention.

  Hereinafter, the water treatment apparatus 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.

[First embodiment]
The water treatment apparatus 100 according to the present embodiment includes a water treatment unit 1 as shown in FIGS. 1 and 2. The water treatment unit 1 includes an electrode assembly 40 including a positive electrode 10, a negative electrode 20, and a separator 30. In the water treatment unit 1, the negative electrode 20 is disposed so as to contact one surface 30 a of the separator 30, and the positive electrode 10 is disposed so as to contact the surface 30 b opposite to the surface 30 a of the separator 30. The gas diffusion layer 12 of the positive electrode 10 is in contact with the separator 30, and the first water repellent layer 11 is exposed to the gas phase 90 side.

  As shown in FIG. 3, the electrode assembly 40 is laminated on the cassette base material 50. 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 substrate 50 is joined to the outer peripheral portion of the surface 10 a of the positive electrode 10, and the side surface 54 opposite to the side surface 53 is the outer periphery of the surface 60 a of the plate member 60. It is joined to the part.

  As shown in FIG. 2, the water treatment unit 1 formed by laminating the electrode assembly 40, the cassette base material 50, and the plate member 60 has an electrolyte treatment tank 80 so that a gas phase 90 communicating with the atmosphere is formed. Placed inside. An electrolytic solution 70 that is a liquid to be treated is held inside the electrolytic solution treatment tank 80, and the positive electrode 10, the negative electrode 20, and the separator 30 are immersed in the electrolytic solution 70.

  As will be described later, the positive electrode 10 includes a first water-repellent layer 11 having water repellency, and the plate member 60 is made of a flat plate material that does not transmit the electrolyte solution 70. Therefore, the electrolytic solution 70 held in the electrolytic solution treatment tank 80 is separated from the inside of the cassette base material 50, and the internal space formed by the electrode assembly 40, the cassette base material 50, and the plate member 60 is a gas phase. 90. The water treatment apparatus 100 is configured such that the gas phase 90 is opened to the outside air, or air is supplied to the gas phase 90 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 the external circuit 110, respectively.

(Positive electrode)
As shown in FIG. 2, the positive electrode 10 according to the present embodiment includes a first water-repellent layer 11 and a gas diffusion electrode 12 that is overlaid so as to be in contact with the first water-repellent layer 11. Become. By using such a thin plate-like gas diffusion electrode, oxygen in the gas phase 90 can be easily supplied to the catalyst in the positive electrode 10.

  The first water repellent layer 11 in the positive electrode 10 is a layer having both water repellency and oxygen permeability. The first water repellent layer 11 is configured to allow oxygen to move from the gas phase to the liquid phase while favorably separating the gas phase and the liquid phase in the electrochemical system in the water treatment unit 1. That is, the first water repellent layer 11 can suppress the movement of the electrolytic solution 70 toward the gas phase 90 while allowing oxygen in the gas phase 90 to pass through and moving to the gas diffusion layer 12. In addition, "separation" here means physical interruption | blocking.

  The first water repellent layer 11 is in contact with the gas phase 90 containing oxygen, and diffuses oxygen in the gas phase 90. In the configuration shown in FIG. 2, the first water repellent layer 11 supplies oxygen substantially uniformly to the gas diffusion layer 12. Therefore, the first water repellent layer 11 is preferably a porous body so that the oxygen can be diffused. Since the first water repellent layer 11 has water repellency, it can be suppressed that pores of the porous body are blocked due to condensation or the like and oxygen diffusibility is lowered. In addition, since the electrolytic solution 70 hardly penetrates into the first water repellent layer 11, oxygen is efficiently circulated from the surface in contact with the gas phase 90 in the first water repellent layer 11 to the surface facing the gas diffusion layer 12. It becomes possible to make it.

  The first water repellent layer 11 is preferably formed in a sheet shape from a woven fabric or a non-woven fabric. The material constituting the first water repellent layer 11 is not particularly limited as long as it has water repellency and can diffuse oxygen in the gas phase 90. Examples of the material constituting the first 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 consisting of 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 first water repellent layer 11 preferably has a plurality of through holes in the stacking direction X of the first water repellent layer 11 and the gas diffusion layer 12.

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

  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 110. 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 110 to the catalyst through the gas diffusion layer 12, so that the oxygen reduction reaction by oxygen, hydrogen ions and electrons can be advanced by the catalyst.

  In the positive electrode 10, it is preferable that oxygen is efficiently transmitted through the first water repellent layer 11 and the gas diffusion layer 12 and supplied to the catalyst in order to ensure stable performance. For this reason, 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 first water repellent layer 11 to the surface on the opposite side. 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 first 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 provided on at least a part between the first water repellent layer 11 and the gas diffusion layer 12 from the viewpoint of securing the adhesion between the first water repellent layer 11 and the gas diffusion layer 12. It is preferable. However, from the viewpoint of improving the adhesion between the first 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 first water repellent layer 11. More preferably, it is provided on the entire surface between the gas diffusion layer 12 and the gas diffusion layer 12.

  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.

  The conductive polymer is a general term for polymer compounds having conductivity. Examples of the conductive polymer include aniline, aminophenol, diaminophenol, pyrrole, thiophene, paraphenylene, fluorene, furan, acetylene, or a 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. The metal atom is not particularly limited, but titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, hafnium, tantalum, tungsten, rhenium, osmium, iridium It is preferably an atom of at least one metal selected from the group consisting of platinum, and gold. In this case, the carbon-based material exhibits excellent performance 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.

  The carbon-based material is preferably 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.

  A combination of a metal atom and a nonmetal atom 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 within the range of 5 to 30% by mass, and the 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.

  The 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.

  Further, the carbon-based material may be further subjected to acid cleaning. 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 compounds and metal crystals 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 according to the present embodiment supports microorganisms described later, and further generates hydrogen ions and electrons from at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 70 by the catalytic action of the microorganisms.

  And it is preferable that the negative electrode 20 does not have a passive film on the surface, and contains iron. As will be described later, in the water treatment apparatus 100 of the present embodiment, iron in the negative electrode 20 is eluted into the electrolyte solution 70 as iron ions, and the eluted iron ions and phosphate ions contained in the sewage are combined. To precipitate insoluble phosphorus compounds. For this reason, when a thin oxide film such as a passive film is present on the negative electrode surface, the elution of iron is inhibited, and therefore it is preferable that there is no passive film.

  The negative electrode 20 preferably has a structure in which microorganisms are supported on a conductive sheet having conductivity. And as a conductor sheet, the sheet which does not have a passive film on the surface and contains iron is used. In addition, as a conductor sheet, it is preferable to use the sheet | seat which consists of iron or carbon steel.

  The conductor sheet constituting the negative electrode 20 preferably has a plurality of pores. By using a sheet having a plurality of pores as the conductor sheet, hydrogen ions generated by the local battery reaction described later can easily move toward the separator 30, and the rate of the oxygen reduction reaction can be increased. Further, from the viewpoint of improving ion permeability, the conductor sheet of the negative electrode 20 may have a space (void) continuous in the stacking direction X of the positive electrode 10, the separator 30, and the negative electrode 20, that is, in the thickness direction. preferable.

  The microorganism supported on the negative electrode 20 is not particularly limited as long as it is a microorganism that decomposes an organic substance in the electrolytic solution 70 or a compound containing nitrogen 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 70. 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 microorganism 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.

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

(Separator)
The water treatment unit 1 of the present embodiment further includes a separator 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 via a separator 30. The separator 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 separator 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.

  Further, as the separator 30, a porous film having pores through which hydrogen ions can permeate may be used. That is, the separator 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, it is preferable that the separator 30 includes at least one selected from the group consisting of a porous sheet, a woven sheet, and a nonwoven sheet. Moreover, the separator 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 | stacking 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 separator 30 is not particularly limited as long as hydrogen ions can move from the negative electrode 20 to the positive electrode 10.

  As described above, the separator 30 has a function of transmitting the hydrogen ions generated in the negative electrode 20 and moving the hydrogen ions 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 water treatment apparatus 100 of the present embodiment, the separator 30 is not an essential component. However, since the provision of the separator 30 enables efficient movement of hydrogen ions from the negative electrode 20 to the positive electrode 10, it is preferable to provide the separator 30 from the viewpoint of improving the output. Note that a gap may be provided between the positive electrode 10 and the separator 30, and a gap may also be provided between the negative electrode 20 and the separator 30.

  As shown in FIG. 2, the water treatment apparatus 100 according to this embodiment includes an external circuit 110 that is electrically connected to the negative electrode 20 and the positive electrode 10. The external circuit 110 preferably includes a current control unit that controls a current value flowing between the negative electrode 20 and the positive electrode 10. By providing such a current control unit, the elution rate of iron ions from the negative electrode 20 can be controlled as will be described later. For example, a resistor can be used as the current control unit.

  Next, the effect | action of the water treatment apparatus 100 of this embodiment is demonstrated. When the electrode assembly 40 including the positive electrode 10, the negative electrode 20, and the separator 30 is immersed in the electrolytic solution 70, the gas diffusion layer 12, the separator 30, and the negative electrode 20 of the positive electrode 10 are immersed in the electrolytic solution 70, and the first water repellent layer 11 is exposed to the gas phase 90.

  During the operation of the water treatment apparatus 100, the electrolytic solution 70 containing at least one of an organic substance and a nitrogen-containing compound is supplied to the negative electrode 20, and air or oxygen 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 shown in FIG. 2, air diffuses through the gas diffusion layer 12 through the first 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 70 by the catalytic action of microorganisms. The generated hydrogen ions permeate the separator 30 and move to the positive electrode 10 side. Further, the generated electrons move to the external circuit 110 through the conductor sheet of the negative electrode 20 and further move from the external circuit 110 to the gas diffusion layer 12 of the positive electrode 10. Hydrogen ions and electrons are combined with oxygen by the action of the catalyst supported on the gas diffusion layer 12 and consumed as water.

Here, the oxygen reduction reaction of the positive electrode 10 is represented by the following chemical reaction formula (1), and the standard electrode potential is 1.23V. On the other hand, the oxidation reaction of iron in the negative electrode 20 is represented by the following chemical reaction formula (2), and the standard electrode potential is 0.44V. Therefore, when the positive electrode 10 and the negative electrode are electrically connected, the electromotive force of this battery becomes positive and proceeds spontaneously. As a result, iron contained in the negative electrode 20 becomes divalent iron ions and is eluted in the electrolytic solution 70.
[Chemical 1]
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (E ° = 1.23 V vs SHE) (1)
Fe → Fe ²⁺ + 2e ⁻ (E ° = 0.44 V vs SHE) (2)

The divalent iron ions (Fe ²⁺ ) eluted in the electrolytic solution 70 are oxidized by oxygen in the electrolytic solution 70 as shown in the chemical reaction formula (3) below, and trivalent iron ions (Fe ^3+). ) Then, as shown in the chemical reaction formula (4), the trivalent iron ions react with phosphate ions (PO ₄ ³⁻ ), which are phosphorus compounds in the electrolytic solution 70, and insoluble iron phosphate (FePO ₄ ). Is generated. Since insoluble iron phosphate aggregates and precipitates in the electrolytic solution 70, the phosphorus in the electrolytic solution 70 can be reduced by removing the iron phosphate.
[Chemical formula 2]
Fe ²⁺ → Fe ³⁺ + e ⁻ (3)
Fe ³⁺ + PO ₄ ³⁻ → FePO ₄ (4)

  Furthermore, the water treatment apparatus 100 according to the present embodiment allows carbon dioxide or nitrogen to be generated together with hydrogen ions and electrons from at least one of the organic substance and the nitrogen-containing compound in the electrolytic solution 70 by metabolism of the microorganisms supported on the negative electrode 20. Is generated. Thus, since the organic substance and nitrogen-containing compound in the electrolytic solution 70 come into contact with the negative electrode 20 and are oxidatively decomposed, the organic substance and nitrogen-containing compound in the electrolytic solution 70 can also be removed.

The water treatment apparatus 100 can also remove sulfur such as sulfate ions contained in the electrolytic solution. That is, sulfate ions are decomposed by microorganisms to generate hydrogen sulfide (H ₂ S), and the hydrogen sulfide is ionized to HS ⁻ in water. As shown in the following chemical reaction formulas (5) and (6), HS ^{− in} water reacts with divalent iron ions or trivalent iron ions eluted from the negative electrode 20 to form a hardly soluble sulfide (for example, It precipitates as iron sulfide (FeS) or atomic sulfur (S ⁰ ). Therefore, it is possible to reduce the sulfur content in the electrolytic solution 70 by removing the precipitate. In addition, since hydrogen sulfide generated by being decomposed by microorganisms is ionized to HS ⁻ , the amount of released hydrogen sulfide to the outside of the water treatment apparatus 100 can be reduced.
[Chemical formula 3]
HS ⁻ + Fe ²⁺ → FeS + H ⁺ (5)
HS ⁻ + 2Fe ³⁺ → S ⁰ + 2Fe ²⁺ + H ⁺ (6)

  Thus, the water treatment apparatus 100 of this embodiment has a passive film on the surface, a negative electrode 20 containing iron, and a gas that is at least partially exposed to the gas phase 90 and includes an oxygen reduction catalyst. And a positive electrode 10 made of a diffusion electrode. The water treatment apparatus 100 further includes an external circuit 110 that is electrically connected to the negative electrode 20 and the positive electrode 10, and an electrolytic solution treatment tank 80 that holds an electrolytic solution 70 containing a phosphorus compound. As described above, in the water treatment apparatus 100, the battery reaction proceeds without applying electric energy, and iron ions are eluted from the negative electrode 20 to the electrolytic solution 70. Therefore, since a precipitate of the phosphorus compound is generated by the eluted iron ions, the concentration of the phosphorus compound in the electrolytic solution can be reduced by removing the precipitate. Furthermore, since a device for throwing electric energy becomes unnecessary, the water treatment device 100 can be downsized. Moreover, since the organic substance and the nitrogen-containing compound are oxidatively decomposed by the microorganisms in the water treatment apparatus 100, the organic substance and the nitrogen-containing compound in the electrolytic solution can also be reduced.

  The aerobic microorganism and the anaerobic microorganism described above are preferably carried on the surface of the negative electrode 20. However, even if these microorganisms are only contained in the electrolytic solution 70, the effects of the present embodiment can be exhibited. Therefore, in the water treatment apparatus 100, it is preferable that at least one of the negative electrode 20 and the electrolytic solution 70 holds at least one of an aerobic microorganism and an anaerobic microorganism.

  1 to 3, the water treatment unit 1 forms the gas phase 90 by joining the positive electrode 10 to the side surface 53 of the cassette base material 50 and joining the plate member 60 to the side surface 54 opposite to the side surface 53. doing. However, the present embodiment is not limited to this aspect. For example, a water treatment unit 1A in which two electrode assemblies 40 are stacked with a cassette base material 50 interposed therebetween may be used as in the water treatment apparatus 100A shown in FIGS. In the water treatment unit 1 </ b> A, the side surface 53 and the side surface 54 of the cassette base material 50 are joined to the outer peripheral portion of the surface 10 a of the positive electrode 10, and the electrolyte solution enters the cassette base material 50 from the outer peripheral portion of the surface 10 a of the positive electrode 10. 70 is preventing leakage. The positive electrode 10 and the negative electrode 20 in the two electrode assemblies 40 are each electrically connected to the external circuit 110. Thus, by using the water treatment unit 1A using the two electrode assemblies 40, the elution amount of iron ions from the negative electrode 20 increases, and the phosphorus compound can be removed more efficiently. Become.

  As described above, if hydrogen ions can move from the negative electrode 20 to the positive electrode 10, the battery reaction proceeds, and iron ions are eluted from the negative electrode 20 to the electrolytic solution 70, so that the concentration of the phosphorus compound in the electrolytic solution is increased. Can be reduced. Therefore, like the water treatment unit 1B in the water treatment apparatus 100B illustrated in FIG. 6, the negative electrode 20 may not contact the separator 30, and a gap may exist between the negative electrode 20 and the separator 30.

  For example, the negative electrode 20 according to the present embodiment may be modified with an electron transfer mediator molecule. Alternatively, the electrolytic solution 70 in the electrolytic solution treatment tank 80 may contain electron transfer mediator molecules. Thereby, the electron transfer from an anaerobic microorganism to the negative electrode 20 is accelerated | stimulated, and more efficient liquid processing is realizable.

  Specifically, in the metabolic mechanism by anaerobic microorganisms, electrons are transferred between cells or with the final electron acceptor. When a mediator molecule is introduced into the electrolytic solution 70, 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 70. 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.

  In the water treatment unit 1 shown in FIG. 3, the cassette base material 50 is open at the entire upper part, but may be partially opened if air (oxygen) can be introduced into the inside, It may also be closed.

  The electrolytic solution treatment tank 80 holds the electrolytic solution 70 therein, but may be configured such that the electrolytic solution 70 circulates. For example, as shown in FIG. 1 and FIG. 2, in the electrolytic solution treatment tank 80, a liquid supply port 81 for supplying the electrolytic solution 70 to the electrolytic solution treatment tank 80 and the treated electrolytic solution 70 are treated with the electrolytic solution. A liquid discharge port 82 for discharging from the tank 80 may be provided. The electrolytic solution 70 is preferably continuously supplied through the liquid supply port 81 and the liquid discharge port 82.

[Second Embodiment]
Next, the water treatment apparatus according to the second embodiment will be described in detail based on the drawings. In addition, the same code | symbol is attached | subjected to the same structure as 1st embodiment, and the overlapping description is abbreviate | omitted.

  The water treatment apparatus according to this embodiment includes a water treatment unit 1 as in the first embodiment. And the said water treatment apparatus is further provided with the organic substance processing part for removing the organic substance contained in electrolyte solution. The organic substance processing unit does not have the function of removing the phosphorus compound as the water treatment unit 1 described above, but has the function of decomposing the organic substance contained in the electrolytic solution. By further providing such an organic substance processing unit, in order to remove the organic substance in the organic substance processing unit in addition to the water treatment unit 1, it is possible to more efficiently remove the phosphorus compound and the organic substance. It becomes possible.

  If the organic substance processing part which concerns on this embodiment can decompose the organic substance contained in the electrolyte solution 70, the structure will not be specifically limited. As an organic substance processing part, it can be set as the structure shown, for example in FIG. The organic substance processing unit 120 includes a second water-repellent layer 121 that has both water repellency and oxygen permeability and is in contact with the gas phase 90. Then, the organic substance in the electrolytic solution 70 is decomposed by oxygen that has passed through the second water repellent layer 121.

  As shown in FIG. 7, the organic substance processing unit 120 has two second water-repellent layers 121 facing each other with a gap therebetween, and further holding them apart between the second water-repellent layers 121. By providing the cassette base material 50, the gas phase 90 is formed inside. That is, as described above, the cassette base material 50 is a U-shaped frame member that extends along the outer peripheral portion of the second water repellent layer 121, and the upper portion is open. The side surface 53 and the side surface 54 of the cassette base material 50 are joined to the outer peripheral portion of the second water-repellent layer 121, thereby forming a gas phase 90 inside. The gas phase 90 of the organic substance processing unit 120 is not filled with the electrolyte solution 70 and is open to the outside air, so that air can be supplied to the second water repellent layer 121. However, the organic substance processing unit 120 is not limited to such a mode as long as the organic substance in the electrolytic solution 70 can be decomposed in contact with the gas phase. For example, the organic substance processing unit 120 may have a bag shape in which the periphery of the two second water repellent layers 121 is joined and the upper part is opened so as to have the gas phase 90 inside.

  From the viewpoint of further promoting the decomposition of the organic substance in the electrolytic solution 70, it is preferable that the holding body 122 for holding aerobic microorganisms is overlaid on the second water-repellent layer 121 in the organic substance processing unit 120. . The holding body 122 is preferably laminated on the surface of the second water repellent layer 121 on the electrolyte solution 70 side. By using the holding body 122 that holds aerobic microorganisms, the remaining organic substance can be efficiently decomposed even when the concentration of the organic substance in the electrolytic solution 70 is reduced downstream as described later. Is possible. Further, since the holding body 122 is provided on the surface of the second water-repellent layer 121 having oxygen permeability, the oxygen for the growth is sufficiently supplied to the aerobic microorganism through the second water-repellent layer 121. Is possible.

  The aerobic microorganism is a microorganism having a metabolic mechanism based on oxygen, and is not particularly limited as long as the organic substance in the electrolytic solution 70 can be decomposed. Examples of the aerobic microorganisms include Escherichia bacteria, Escherichia bacteria, Pseudomonas bacteria, Bacillus bacteria, Bacillus bacteria. In addition, as the holding body 122 that holds aerobic microorganisms, for example, a nonwoven fabric-like or sponge-like structure can be used. The holding body 122 can be made of, for example, one or more materials selected from the group consisting of polyethylene, polypropylene, polyethylene glycol, polyurethane, and polyvinyl alcohol.

  In the water treatment apparatus 100C shown in FIG. 7, the organic substance treatment unit 120 is disposed inside the electrolytic solution treatment tank 80A so that a gas phase 90 communicating with the atmosphere is formed. An electrolytic solution 70 that is a liquid to be treated is held inside the electrolytic solution treatment tank 80 </ b> A, and the holding body 122 is immersed in the electrolytic solution 70. The electrolytic solution treatment tank 80A includes a liquid discharge port 82 and a communication pipe 83 that communicates with the electrolytic solution treatment tank 80 in which the water treatment unit 1 is disposed.

  In the water treatment apparatus 100 </ b> C having the above configuration, first, the electrolytic solution 70 is continuously supplied from the liquid supply port 81 of the electrolytic solution treatment tank 80, and the phosphorus compound and the organic substance are removed by the water treatment unit 1. Then, the electrolytic solution 70 purified by the water treatment unit 1 is transferred to the electrolytic solution treatment tank 80A through the communication pipe 83. The transferred electrolytic solution 70 is decomposed and removed by aerobic microorganisms held in the organic substance processing unit 120. Then, the electrolytic solution purified by removing the phosphorus compound and the organic substance is discharged to the outside through the liquid discharge port 82.

  As described above, in the water treatment apparatus 100C of the present embodiment, the water treatment unit 1A is arranged in the upstream electrolytic solution treatment tank 80 having a large organic substance content, and the downstream electrolytic process having a small organic substance content is performed. An organic substance processing unit 120 is provided in the liquid processing tank. Thereby, the upstream water treatment unit 1A efficiently decomposes a large amount of organic substances, and the organic substance that could not be decomposed by the water treatment unit 1A is decomposed by the downstream organic substance treatment unit 120. Therefore, it becomes possible to decompose the organic substance in the electrolytic solution 70 more efficiently.

  In the water treatment apparatus 100C shown in FIG. 7, one water treatment unit 1A is arranged in the electrolyte treatment tank 80, and one organic substance treatment unit 120 is arranged in the electrolyte treatment tank 80A. However, the present embodiment is not limited to this aspect. For example, a plurality of water treatment units 1A may be arranged in the electrolyte treatment tank 80, and a plurality of organic substance treatment units 120 are arranged in the electrolyte treatment tank 80A. May be.

  Further, as shown in FIG. 8, a plurality of water treatment units 1 </ b> A and organic substance treatment units 120 may be arranged inside one electrolyte treatment tank 80. In the water treatment apparatus 100D of FIG. 8, the water treatment unit 1A and the organic substance treatment unit 120 are arranged such that the electrolyte 70 flows in a wave shape inside the electrolyte treatment tank 80 as indicated by an arrow C. Specifically, the plurality of water treatment units 1A and the organic substance treatment unit 120 are arranged along the stacking direction X. At this time, the plurality of water treatment units 1A and the organic material treatment unit 120 are configured such that the side surface 1a of the water treatment unit 1A and the side surface 120a of the organic material treatment unit 120 correspond to the left wall 80a and the right wall 80b It arrange | positions so that it may touch alternately. In the water treatment apparatus 100, the electrolyte solution 70 flows in a wave shape, thereby increasing the contact rate between the electrolyte solution 70 and the negative electrode 20 and the contact rate between the electrolyte solution 70, the second water repellent layer 121, and the holding body 122. As a result, the purification efficiency can be further improved.

  In addition, in the water treatment apparatus 100C and the water treatment apparatus 100D of FIG.7 and FIG.8, the water treatment unit 1A which laminated | stacked the two electrode assemblies 40 shown in FIG.4 and FIG.5 is used as a water treatment unit. However, in the water treatment apparatus 100C and the water treatment apparatus 100D, the water treatment unit 1 in which one electrode assembly 40 illustrated in FIGS. 1 and 2 is stacked may be used. Moreover, in the water treatment apparatus 100C and the water treatment apparatus 100D of FIG.7 and FIG.8, the water treatment unit 1A is arrange | positioned in the upstream of the electrolyte solution 70, and the organic substance processing part 120 is arranged downstream from the water treatment unit 1A. It is arranged. However, the organic substance processing unit 120 may be arranged on the upstream side of the electrolytic solution 70, and the water treatment unit 1A may be arranged on the downstream side of the organic substance processing unit 120.

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

[Production of water treatment equipment]
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, a 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 further 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.

  And this sample was packed in the one end part of a quartz tube, and the inside of this quartz tube was substituted by argon subsequently. The quartz tube was pulled out 45 seconds after being placed in a furnace at 900 ° C. 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 an iron base material were installed in the container. As the iron substrate, an iron plate having an iron purity of 99.5% was used. Furthermore, after installing a nonwoven fabric between the positive electrode and the negative electrode, the electrolytic solution was filled in the container so as to be in contact with the positive electrode, the negative electrode, and the nonwoven fabric. The electrolytic solution contains 800 mg / L organic substance, 15 mg / L nitrogen compound, and 10 mg / L phosphorus compound as total organic carbon (TOC). In addition, soil microorganisms were planted in the electrolyte solution as an anaerobic microorganism source for power generation. And the residence time of electrolyte solution was continuously supplied to the container as 24 hours. Furthermore, the water treatment apparatus of this example was obtained by connecting a positive electrode and a negative electrode to a load circuit.

（Ｐ：出力、Ｖ：負荷の両端における電位差、Ｒ：負荷回路の抵抗値、Ｓ：正極面積） [Evaluation]
(output)
The output of the water treatment device was measured by measuring the potential difference across the load in the water treatment device. In addition, the output of the water treatment apparatus was calculated | required by Numerical formula 1 in the state where the output was stable. As a result, the output of the water treatment apparatus of this example was 60 mW / m ² .

(P: output, V: potential difference at both ends of load, R: resistance value of load circuit, S: positive electrode area)

（Ｔ：ＴＯＣ除去率、Ｔ１：処理前のＴＯＣ濃度、Ｔ２：処理後のＴＯＣ濃度） (Organic substance removal rate)
The total organic carbon concentration (TOC concentration) in the electrolyte before and after the treatment with the water treatment apparatus 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 2. As a result, the TOC removal rate of the water treatment apparatus of this example was 90%.

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

（Ｎ：窒素除去率、Ｎ１：処理前の窒素濃度、Ｎ２：処理後の窒素濃度） (Nitrogen removal rate)
The nitrogen concentration in the electrolytic solution before and after the treatment with the water treatment apparatus was measured. The nitrogen concentration was measured using a total nitrogen meter. And the nitrogen removal rate was calculated | required from Numerical formula 3. As a result, the nitrogen removal rate of the water treatment apparatus of this example was 82%.

(N: nitrogen removal rate, N1: nitrogen concentration before treatment, N2: nitrogen concentration after treatment)

（Ｑ：リン除去率、Ｑ１：処理前のリン濃度、Ｑ２：処理後のリン濃度） (Phosphorus removal rate)
The phosphorus concentration in the electrolytic solution before and after the treatment with the water treatment apparatus was measured. The phosphorus concentration was measured by a colorimetric method. And the phosphorus removal rate was calculated | required from Numerical formula 4. As a result, the phosphorus removal rate of the water treatment apparatus of this example was 95%.

(Q: phosphorus removal rate, Q1: phosphorus concentration before treatment, Q2: phosphorus concentration after treatment)

  From the above results, it can be seen that the water treatment apparatus of this example can efficiently remove phosphorus compounds, organic substances and nitrogen in wastewater without throwing electric energy.

  Although the present embodiment has been described above, the present embodiment is not limited to these, and various modifications can be made within the scope of the gist of the present embodiment. Specifically, in the drawing, the positive electrode 10, the negative electrode 20, and the separator 30 provided with the first water repellent layer 11 and the gas diffusion layer 12 are formed in a rectangular shape. However, these shapes are not particularly limited, and can be arbitrarily changed depending on the size of the water treatment device, 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 water treatment apparatus according to this embodiment can be widely applied to treatment of liquids containing organic substances and nitrogen-containing compounds, for example, wastewater generated from factories of various industries, organic wastewater such as sewage sludge, and the like. It can also be used to improve the water environment.

DESCRIPTION OF SYMBOLS 10 Positive electrode 20 Negative electrode 70 Electrolytic solution 90 Gas phase 100,100A, 100B, 100C, 100D Water treatment apparatus 120 Organic substance processing part

Claims (4)

There is no passive film on the surface, and the negative electrode containing iron,
A positive electrode comprising a gas diffusion electrode at least partially exposed to the gas phase and comprising an oxygen reduction catalyst;
An external circuit electrically connected to the negative electrode and the positive electrode;
An electrolytic solution treatment tank for holding an electrolytic solution containing a phosphorus compound;
A water treatment apparatus comprising:   The water treatment apparatus according to claim 1, wherein the external circuit includes a current control unit that controls a current flowing between the negative electrode and the positive electrode.   The water treatment apparatus according to claim 1 or 2, wherein at least one of the negative electrode and the electrolytic solution holds at least one of an aerobic microorganism and an anaerobic microorganism.   The water treatment apparatus according to any one of claims 1 to 3, further comprising an organic substance treatment unit for removing an organic substance contained in the electrolytic solution.

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