Microbial power generation device and water treatment equipment

Abstract

To provide a microbial power generation device which has simple and easily-scaled up configuration, and therefore can be introduced into existing water treatment facilities at a low cost, and to provide water treatment equipment which can exhibit sufficient water treatment capacity while performing power generation by the microbial power generation device.SOLUTION: A microbial power generation device 1 includes an anode region 3 in which an anode 31 is disposed and a cathode region 4 in which a cathode 41 is disposed in a treated water tank 2 from which inflow treatment-target water can flow out as treated water. The anode 31 is connected to an external resistor 5 via an anode conductor 51. The cathode 41 is connected to the external resistor 5 via a cathode conductor 52. The treatment-target water has a microorganism group including electroactive bacteria, being aerated by an aeration member 6 in the cathode region 4, and in which a flow exists at least from the anode region 3 to the cathode region 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a microbial power generation technology that uses electrodes to recover the reducing power generated when microorganisms decompose organic matter. [Background technology]

[0002] As so-called microbial power generation technology that generates electricity by utilizing the metabolic reactions of microorganisms, for example, the power generation device disclosed in Patent Document 1 and the microbial fuel cell disclosed in Patent Document 2 are known.

[0003] Patent Document 1 describes a liquid catholyte type and an air cathode type power generating device.

[0004] The liquid catholyte type power generation device includes two anode chambers each having a conductive filler that holds a microorganism group and filled with a stock solution containing an electron donor, and a cathode chamber disposed between the two anode chambers. The cathode chamber is filled with a cathode solution containing potassium ferricyanide. The boundary between the anode chamber and the cathode chamber is separated by a proton exchange membrane.

[0005] In the air cathode type power generation device, the cathode chamber is disposed on the outer surface of the single anode chamber. Air containing oxygen as an electron acceptor is introduced into the cathode chamber. As in the liquid catholyte type, the boundary between the anode chamber and the cathode chamber is partitioned by a proton exchange membrane.

[0006] The microbial fuel cell of Patent Document 2 includes an anode tank that is equipped with an anode that supports a group of microorganisms and that retains an organic substrate that serves as an electron acceptor, and a cathode cassette that is housed in the anode tank and into which oxygen-containing air is introduced as an electron acceptor. The side of the cathode cassette that faces the anode is sealed by an ion-permeable membrane that corresponds to the proton exchange membrane. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-152091 A [Patent Document 2] JP 2009-093861 A [Patent Document 3] JP 2015-109288 A [Non-patent literature]

[0008] [Non-Patent Document 1] Matsumoto et. Al. 2012, Environ. Sci. Technol. 2012, 46, 18, 10175-10181 Summary of the Invention [Problem to be solved by the invention]

[0009] The liquid catholyte type power generation device requires the installation of a new frame or reconstruction of the inside of the tank, which is costly, and there is a risk of the tank structure collapsing due to the rupture of the proton exchange membrane.

[0010] The air cathode type power generation equipment also requires the installation of a new structure or the restructuring of the tank, which is costly. In addition, the larger the scale, the higher the water pressure becomes, which inhibits the diffusion of oxygen from the air cathode. Furthermore, there is a risk that the air cathode will be damaged by the water pressure.

[0011] Microbial fuel cells equipped with the cathode cassette have a risk of water quality deterioration due to the short hydraulic retention time caused by the increased volume occupied by the electrode unit. In addition, the larger the scale, the higher the water pressure becomes, which hinders oxygen diffusion from the cathode cassette, as in the air cathode type power generation device, and furthermore, there is a risk of the cathode cassette being damaged.

[0012] In view of the above, the present invention aims to provide a microbial power generation device that can be introduced into existing water treatment facilities at low cost due to its simple configuration that allows for easy scale-up, and to provide a water treatment device that can demonstrate sufficient water treatment capacity while generating electricity using the microbial power generation device. [Means for solving the problem]

[0013] Therefore, one aspect of the present invention is a microbial power generation device having a treatment water tank into which the flow-in water to be treated can flow out as treated water, an anode region in the treatment water tank in which an anode is placed, and a cathode region in the treatment water tank in which a cathode is placed, the water to be treated having a microbial group including electroactive bacteria, aerated in the cathode region by an aeration member, and there is a flow of the water to be treated at least from the anode region to the cathode region.

[0014] In one aspect of the present invention, in the microbial power generation device, the flow of the treated water is only from the anode region to the cathode region.

[0015] In one aspect of the present invention, in the microbial power generation device, the flow of the water to be treated further includes a flow from the cathode region to the anode region.

[0016] One aspect of the present invention is a water treatment device equipped with the above-mentioned microbial power generation device. Effect of the Invention

[0017] According to the present invention, it is possible to provide a microbial power generation device that can be introduced into existing water treatment facilities at low cost due to its simple configuration that allows for easy scale-up. It is also possible to provide a water treatment device that can demonstrate sufficient water treatment capacity while generating electricity using the microbial power generation device. [Brief description of the drawings]

[0018] [Figure 1] A longitudinal cross-sectional view showing the concept of the microbial power generation device of the present invention. [Diagram 2]FIG. 1 is a longitudinal cross-sectional view of a microbial power generation device according to embodiment 1, one aspect of the present invention. [Diagram 3] A longitudinal cross-sectional view of a modified example of a microbial power generation device of embodiment 1, which is one aspect of the present invention. [Figure 4] (a) A longitudinal cross-sectional view of a microbial power generation device of embodiment 2, which is one aspect of the present invention, and (b) a transverse cross-sectional view of the device. [Diagram 5] (a) A longitudinal cross-sectional view of a modified microbial power generation device of embodiment 2, which is one aspect of the present invention, and (b) a transverse cross-sectional view of the device. [Figure 6] 4 shows the distribution of dissolved oxygen concentration and organic matter concentration in a treatment water tank according to embodiment 2 of the present invention. [Figure 7] FIG. 1 is a vertical cross-sectional view of an example according to a first embodiment of the present invention. [Figure 8] FIG. 11 is a vertical cross-sectional view of an example according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] As shown in Fig. 1, the microbial power generation device 1 of the present invention has an anode region 3 in which an anode 31 is arranged, and a cathode region 4 in which a cathode 41 is arranged, in a treatment water tank 2 into which the inflowing water to be treated can flow out as treated water. The anode 31 is connected to an external resistance 5 via an anode conductor 51. The cathode 41 is connected to the external resistance 5 via a cathode conductor 52.

[0021] The water to be treated contains a microorganism group including electroactive bacteria, and is aerated by the aeration member 6 in the cathode region 4. The water to be treated may or may not contain a microorganism group including electroactive bacteria before it flows into the treatment tank. If the water to be treated does not contain the microorganism group, a microorganism group including electroactive bacteria may be added after the water to be treated flows into the treatment tank.

[0022] Furthermore, within the treatment tank 2, there is a flow of the water to be treated at least from the anode region 3 to the cathode region 4. The flow of the water to be treated may be the entire water to be treated or only a portion of it may flow, but from the viewpoint of improving power generation efficiency and water treatment efficiency, it is preferable that the entire water to be treated flows as much as possible. In this specification, "flow" refers to the main movement (flow) of the water to be treated in the treatment tank, and secondary movements (flows) that do not affect the main movement (flow) of the water to be treated are ignored.

[0023] As the conductive substrate constituting the anode 31 and the cathode 41, carbon-based materials (graphite felt, carbon cloth, etc.) and metal-based materials (SUS mesh) are used in consideration of conductivity, corrosion resistance, and microbial adhesion (Non-Patent Document 1).

[0024] Examples of the anode 31 include an electrode in which a conductive base material such as a SUS mesh is coated with a conductive paint (Patent Document 3), and an electrode made of a carbon material such as graphite felt or carbon cloth, or a conductive material in which a conductive base material is coated with a carbon film. Of these, from the viewpoint of improving power generation efficiency, a carbon-coated SUS mesh or graphite felt is preferred.

[0025] The anode region 3 in which the anode 31 is disposed refers to the space in the treatment water tank 2 in which the anode 31 exists and its surroundings, specifically the space formed by a plane including the upper end face of the anode 31, a plane including the lower end face, and the inner wall surfaces of the treatment water tank intersecting these planes. The higher the ratio of the volume occupied by the anode 31 in the anode region 3 (anode filling rate), the higher the power generation efficiency tends to be.

[0026] The cathode 41 is an electrode carrying an inorganic or organic catalyst having oxygen reduction ability, and examples thereof include a mixture of a powder having oxygen reduction ability and a binder carried on a conductive base material, a biocathode, and the like. Examples of the powder having oxygen reduction ability include Pt / C (a powder in which platinum nanoparticles are highly dispersed and carried on carbon particles), nitrogen-doped carbon-based powder, and Fe-doped metal-based powder. Examples of the binder include a compound that selectively transmits protons (e.g., Nafion (trade name)), PTFE (polytetrafluoroethylene), and PDMS (polydimethylsiloxane), and from the viewpoint of improving power generation efficiency, a compound that selectively transmits protons is preferable. The biocathode is a group of microorganisms having oxygen reduction ability, and is acclimatized during the operation of the treatment water tank 2.

[0027] The cathode region 4 in which the cathode 41 is disposed represents the space in the treatment water tank 2 in which the cathode 41 exists and its surroundings, specifically the space formed by a plane including the upper end face of the cathode 41, a plane including the lower end face, and the inner wall surface of the treatment water tank intersecting these planes. The higher the ratio of the volume occupied by the cathode 41 in the cathode region 4 (cathode filling rate), the higher the power generation efficiency tends to be.

[0028] The anode region 3 and the cathode region 4 may have the same or different volumes. For example, when the anode region 3 has a larger volume than the cathode region 4 under the same anode and cathode filling rates, the effect of improving power generation efficiency is expected. On the other hand, when the cathode region 4 has a larger volume than the anode region 3 under the same conditions, the effect of improving water treatment efficiency is expected.

[0029] The air diffusing member 6 injects air introduced from a blower 61 into the water to be treated in the cathode region 4 to supply dissolved oxygen (hereinafter, referred to as DO) required for the reduction reaction in the cathode 41. As the air diffusing member 6, a well-known air diffusing member in the water treatment technology is used.

[0030] When the treatment tank 2 is started up, a seeding microbial source such as activated sludge, paddy field soil, or maggrove forest bottom mud is added. In the anode region 3, the electroactive bacteria directly attach to the anode 31 in the process of decomposing organic matter, and transfer electrons to the anode 31. In addition, electrons are transferred to the anode 31 in the process of oxidation and reduction of mediators (organic or inorganic matter having electron transfer function) contained in the treatment water. The electrons provided to the anode 31 move to the cathode 41 via the anode conductor 51, the external resistor 5, and the cathode conductor 52. Then, oxygen remaining on the catalyst surface near the cathode 41 receives protons and the electrons and is reduced to hydrogen peroxide or water. In the process of electrons moving from the anode 31 to the cathode 41, a current is generated.

[0031] Specific embodiments of the present invention will be described below.

[0032] [Embodiment 1] The microbial power generation device 1 of embodiment 1 shown in Figure 2 uses an upward flow type treatment water tank 2, and the flow of the treated water is only from the anode region 3 at the lower side of the treatment water tank 2 to the cathode region 4 at the upper side of the treatment water tank 2.

[0033] The treated water tank 2 is provided with an inlet passage 21 through which the water to be treated flowing in from outside is supplied from near the bottom of the treated water tank 2, and an outlet passage 22 through which treated water that overflows from the top of the treated water tank 2 flows out.

[0034] The water to be treated, which is supplied from near the bottom of the treatment tank 2 through the inflow path 21, flows from the anode region 3 (anode 31) through the cathode region 4 (cathode 41) and overflows from the top of the treatment tank 2 and flows out from the outflow path 22 as treated water. The cathode region 4 is aerated by the aeration member 6, and the reduction reaction in the cathode 41 is promoted. The anode region 3 and the cathode region 4 of the treatment tank 2 are monitored for DO and ORP by a DO meter and an oxidation-reduction potential (hereinafter, ORP) meter, respectively, not shown, and the hydraulic retention time and aeration volume in the treatment tank 2 are adjusted so that the anode region 3 is anaerobic while the cathode region 4 is aerobic. The conditions cannot be generally defined because they depend on the size of the treatment tank 2, but for example, in the case of a lab-scale treatment tank of about 3 L, the hydraulic retention time is about 6 to 48 hours and the aeration volume is about 0.01 to 1 L / min.

[0035] According to the microbial power generation device 1 of the above-mentioned embodiment 1, since the configuration is simple, it is possible to reduce costs compared to conventional techniques, and it is possible to provide a microbial power generation device that is easy to scale up. Furthermore, when the microbial power generation device 1 of embodiment 1 is scaled up, economies of scale are expected, such as improved cathode performance (oxygen reduction efficiency) due to an increase in oxygen dissolution efficiency in the cathode region, improved anode performance (electroactive bacteria take precedence among the microbial group) due to a decrease in ORP as the water depth of the treatment tank increases, and utilization of reducing power (electrons) that tends to accumulate at the bottom of the treatment tank.

[0036] As a modified example of the first embodiment, for example, there is a treated water tank 2 of a microbial power generation device 1 shown in Fig. 3. The treated water tank 2 of this embodiment comprises an upward flow type anode treated water tank 2a having an anode region 3, and an upward flow type cathode treated water tank 2b having a cathode region 4.

[0037] The anode treatment tank 2a is equipped with an inlet passage 21a that supplies the treated water flowing in from the outside to the anode region 3 from near the bottom of the treatment tank 2, and an outlet passage 22a that drains the treated water that overflows from the top of the treatment tank 2.

[0038] The cathode treatment tank 2b is equipped with an inlet passage 21b that supplies the treated water flowing in from the anode treatment tank 2a to the cathode region 4 from near the bottom of the treatment tank 2, and an outlet passage 22b that discharges treated water that overflows from the top of the cathode treatment tank 2b.

[0039] The above-mentioned modified example also enables cost reduction compared to the conventional technology, and is expected to achieve economies of scale along with microbial power generation that is easy to scale up, as in the embodiment of Fig. 2. In this modified example, the efficiency of water treatment can be improved by providing a return flow path (not shown) for the treated water from the cathode treatment water tank 2b to the anode treatment water tank 2a.

[0040] [Embodiment 2] The microbial power generation device 1 of embodiment 2 shown in Figure 4 employs a swirling flow type treatment water tank 2, and the flow of the water to be treated includes a flow from the cathode region 4 to the anode region 3, in addition to a flow from the anode region 3 to the cathode region 4. Note that the embodiment shown in the figure has one anaerobic tank 23 and four aerobic tanks 24, but in this embodiment, the numbers of anaerobic tanks 23 and aerobic tanks 24 in the treatment water tank 2 are not limited to this.

[0041] The treated water tank 2 is partitioned by a partition wall 25 into an anaerobic tank 23 into which the untreated water flows in and an aerobic tank 24 into which the untreated water that has flowed in from the anaerobic tank 23 flows out as treated water.

[0042] The anaerobic tank 23 has an anode region 3 in which an anode 31 is disposed at the lower side of the treatment water tank 2, and a cathode region 4 in which a cathode 41 is disposed at the upper side of the treatment water tank 2. The water to be treated in the anaerobic tank 23 is appropriately stirred by a submersible aerator or agitator (not shown). An aeration member 6 is disposed between the anode 31 and the cathode 41, and the inside of the anaerobic tank 23 is aerated as necessary.

[0043] The aerobic tank 24 is further divided by partitions 25 so that a plurality of compartments, for example, four compartments (compartments (1) to (4)), communicate in series from the upstream side to the downstream side. The anaerobic tank 23 and the most upstream compartment (1) in the treatment water tank 2 communicate with each other via a notch 251 in the partition wall 25 on the lower side of the treatment water tank 2. Compartment (1) and compartment (2) on the downstream side communicate with each other via a notch 252 in the partition wall 25 on the upper side of the treatment water tank 2. Compartment (2) and compartment (3) on the downstream side communicate with each other via a notch 253 in the partition wall 25 on the lower side of the treatment water tank 2. Compartment (3) and compartment (4) on the downstream side communicate with each other via a notch 254 in the partition wall 25 on the upper side of the treatment water tank 2.

[0044] Similarly to the anaerobic tank 23, the sections (1) to (4) each have an anode region 3 in which an anode 31 is disposed at the lower side of the treated water tank 2, and a cathode region 4 in which a cathode 41 is disposed at the upper side of the treated water tank 2. Furthermore, the anodes 31 and the cathodes 41 are disposed in two rows as shown in FIG. 1B, separated by a plate-shaped detouring member 7 provided along the upstream side to the downstream side in the sections (1) to (4). An aeration member 6 is disposed between the anodes 31 and the cathodes 41 in one row. A well-known aeration member may be used as the aeration member 6. In addition, guide members 8 (not shown) that suppress retention of the treated water and promote swirling may be disposed on the bottom of the treated water tank 2 and on the four sides of the liquid surface from the upstream side to the downstream side. The shape of the guide member 8 may be any shape as long as it can suppress retention of the treated water and promote swirling.

[0045] The water to be treated flows into compartment (1) of aerobic tank 24 via anaerobic tank 23, passes through compartments (2) and (3), and is discharged as treated water from the downstream outlet of compartment (4).

[0046] In the anode 31 of the anaerobic tank 23, protons and electrons are generated by assimilation of organic matter by anaerobic electroactive bacteria contained in the water to be treated. The electrons are transmitted to the anode 31 and move to the cathode 41 via the anode conductor 51, the external resistor 5, and the cathode conductor 52. The inside of the anaerobic tank 23 is appropriately diffused with air by the air diffuser 6. Oxygen on the catalyst surface near the cathode 41 (including oxygen in the air supplied by the air diffuser 6) receives the protons and electrons and is reduced to hydrogen peroxide or water.

[0047] The water to be treated that flows from the anaerobic tank 23 into compartment (1) of the aerobic tank 24 through the notch 251 in the partition 25 on the lower side of the treatment water tank 2 moves to the upper side of compartment (1). The water to be treated that has moved to the upper side of compartment (1) flows into compartment (2) through the notch 252 in the partition 25. The water to be treated that has flowed into compartment (2) moves to the lower side of compartment (2). The water to be treated that has moved to the lower side of compartment (2) flows into compartment (3) through the notch 253 in the partition 25. The water to be treated that has flowed into compartment (3) moves to the upper side of compartment (3). The water to be treated that has moved to the upper side of compartment (3) flows into compartment (4) through the notch 254 in the partition 25.

[0048] In the sections (1) to (4) of the aerobic tank 24, the water flow generated by the aeration of the aeration member 6 bypasses the bypass member 7 to form a swirling flow. At this time, as shown in Figs. 4(a) and (b), the DO concentration is high in the upper part of the aerobic tank 24, while the DO concentration is low in the lower part. Also, as shown in Fig. 6, the DO concentration is low in the upstream to midstream areas of the aerobic tank 24, while the organic matter concentration is high. Here, electrons are transferred to the anode 31 during the process in which the aerobic electroactive bacteria decompose the organic matter in the anode region 3 of the aerobic tank 24 shown in Figs. 4(a) and (b) and the process in which the mediator contained in the water to be treated is oxidized and reduced. The electrons move to the cathode 41 of the cathode region 4 via the anode conductor 51, the external resistor 5, and the cathode conductor 52. Then, at the cathode 41, oxygen receives protons and the electrons and is reduced to hydrogen peroxide or water.

[0049] Current is generated in the process of electrons moving from the anode 31 to the cathode 41 in the anaerobic tank 23 and the aerobic tank 24. In particular, in the aerobic tank 24, power generation is efficient in the upstream to midstream regions where the DO concentration is low while the organic matter concentration is high.

[0050] As described above, the microbial power generation device 1 of the second embodiment can provide a microbial power generation device that can be easily introduced into a swirling-flow type treated water tank that is used as a reaction tank facility in an existing sewage treatment plant, and can be scaled up at a lower cost than conventional technology because of its simple configuration. When the microbial power generation device 1 of the second embodiment is scaled up, the performance (oxygen reduction efficiency) of the cathode 41 is improved by increasing the oxygen dissolution efficiency in the cathode region 4, the performance of the anode 31 is improved (electroactive bacteria take precedence among the microbial group) by decreasing the ORP as the water depth of the treated water tank 2 increases, and the reduction power (electrons) that tends to accumulate at the bottom of the treated water tank 2 can be utilized, which is expected to be a scale advantage. This scale advantage can be fully obtained when the microbial power generation device 1 of the second embodiment is applied to a reaction tank (deep-tank type reaction tank) with a particularly deep water depth among reaction tank facilities in an existing sewage treatment plant.

[0051] As a modified example of embodiment 2, for example, there is the treated water tank 2 of the microbial power generation apparatus 1 shown in Figure 5. The anaerobic tank 23 of the treated water tank 2 of this embodiment does not have an aeration member 6, but is appropriately stirred by a submersible aerator or agitator (not shown). Only an anode 31 is disposed in the anaerobic tank 23. This anode 31 is connected to an external resistor 5 in parallel with the anode 31 in the section (1) of the aerobic tank 24. According to the above modified example, since the anaerobic tank 23 is not aerated, decomposition of organic matter by anaerobic bacteria is better than in the embodiment of Figure 4. EXAMPLES

[0052] [Example 1] Example 1 to which the treatment water tank 2 of the embodiment 1 is applied will be described.

[0053] The microbial power generation apparatus 1 of Example 1 shown in FIG. 7 comprises a raw water tank 11, a treated water tank 2, a thermostatic tank 12, a treated water storage tank 13, a control unit 14 and a potentiostat 15.

[0054] The raw water tank 11 stores the water to be treated. The raw water tank 11 can be continuously supplied from near the bottom of the treated water tank 2 by alternate operation of pumps P1 and P2 controlled by the control unit 14. The flow rate of air supplied from the blower 61 to the aeration member 6 in the treated water tank 2 is adjusted by a mass flow meter 62. The thermostatic tank 12 adjusts the liquid temperature in the treated water tank 2 to a constant value by a heater 17 controlled by the control unit 14. The treated water storage tank 13 stores the treated water overflowing from the treated water tank 2. The control unit 14 maintains the electromotive force by controlling the external resistance 5 in accordance with the acclimation of the electroactive bacteria in the treated water tank 2. The control unit 14 also records the value of the voltage generated by the power generation caused by the operation of the treated water tank 2 or transmits it to an external monitoring terminal via the network 16. The potentiostat 15 performs electrochemical analysis of the generated voltage and current.

[0055] The anode 31 and the cathode 41 of this embodiment will be described.

[0056] (Anode 31) In this example, a conductive paint was applied to a SUS mesh measuring 18 cm in length and 80 cm in width to form the anode 31. The SUS mesh used was a stainless steel plain weave wire mesh (SUS316, 100 mesh). The conductive paint used was carbon paste (JELCON CH-8) manufactured by Jujo Chemical Co., Ltd.

[0057] The procedure for producing the anode 31 will now be described. The conductive paint was applied to the SUS mesh using a commercially available paint roller, and the paint was dried to produce the anode 31. Next, a coated copper wire was fixed to the anode 31 with solder as the anode conductor 51, and the fixed part was waterproofed with epoxy resin. The electrode body of the anode 31 produced by the above procedure was folded into a bellows shape with a width of 4 cm, and fixed to a base so that the electrode body would not spread out.

[0058] (Cathode 41) In this example, an inorganic catalyst having oxygen reduction ability was applied to a SUS mesh substrate coated with the same conductive paint as the anode 31 to form the cathode 41. As the inorganic catalyst, a mixture of 20% Pt / C (manufactured by Tanaka Kikinzoku Kogyo Kogyo, Pt and C mixed ratio of 2:8) as a powder having oxygen reduction ability and 5% Nafion (trade name, manufactured by Sigma-Aldrich, dispersion solution, D-520) as a binder was used.

[0059] The procedure for producing the cathode 41 will be described. The SUS mesh substrate coated with the conductive paint was produced in the same manner as described in the procedure for producing the anode 31. After mixing 20% ​​Pt / C soaked in water and 5% Nafion, the mixture was applied to the SUS mesh substrate with a brush and dried to produce the cathode 41. 2 The mixture was prepared so that the amount of 20% Pt / C applied per electrode was 0.1 mg and the amount of 5% Nafion was 33 μL. Next, a coated copper wire was fixed to the cathode 41 as a cathode conductor 52 with solder, and the fixing part and the epoxy were waterproofed. The electrode body of the cathode 41 prepared by the above procedure was woven in a bellows pattern like the anode 31 and fixed with a cable tie.

[0060] (Installation of anode 31 and cathode 41 in treatment water tank 2) First, a base with an anode 31 attached thereto was placed in a cylindrical treatment water tank 2. Next, a disk-shaped aeration member 6 was fixed to the top of the base. Then, a cathode 41 was placed on the upper surface of the aeration member 6. After that, the anode conductor 51 and the cathode conductor 52 were connected to an external resistor 5. An axial lead type resistor was used as the external resistor 5.

[0061] (Water to be treated) In this embodiment, the artificial sewage obtained by dissolving the following per liter in ion-exchanged water was supplied to the raw water tank 11. The water quality of the artificial sewage was about 400 mg / L in terms of CODcr. The trace metal salts used were prepared by dissolving 12.8 g of nitrilotriacetic acid (NTA) in deionized water, adjusting the pH to 6.5, and adding and dissolving trace metal salts (FeCl3·6H2O: 1.35 g, MnCl2·4H2O: 0.1 g, CoCl2·6H2O: 0.024 g, CaCl2·2H2O: 0.1 g, ZnCl2: 0.1 g, CuCl2·2H2O: 0.025 g, H3BO3: 0.01 g, Na2MoO4·2H2O: 0.024 g, NaCl: 1.0 g, NiCl2·6H2O: 0.12 g, Na2SeO3·5H2O: 0.026 g) and adjusting the volume to 1 L with deionized water.

[0062] (Operating conditions) Activated sludge was used as a source of inoculum microorganisms for the electroactive bacteria to be introduced into the treatment tank 2 .

[0063] The activated sludge and the artificial sewage, each having an MLSS concentration of about 5,000 mg / L, were added in a total of 3 L, each of 1.5 L. The liquid temperature in the treated water tank 2 was controlled to 30° C. by the heater 17. The aeration rate to the cathode 41 by the aeration member 6 was adjusted to 0.1 to 0.2 L / min by the mass flow meter 62. Here, the operation of the microbial power generation device 1 was started, which supplies the artificial sewage from the raw water tank 11 to the treated water tank 2 at a flow rate of 3 L / day and a hydraulic retention time of 24 hours by alternately operating the pumps P1 and P2. Then, the external resistance 5 was adjusted based on the internal resistance value calculated from the slope of the current-voltage curve obtained by the potentiostat 15, to acclimate the activated sludge. The activated sludge was removed after 2 weeks to 1 month.

[0064] (Evaluation of power generation and processing performance) Table 1 shows the power generation and processing performance under the above operating conditions.

[0065] [Table 1]

[0066] As shown in Table 1, operation was started with an external resistance value of 10 kΩ, and the voltage increased over time. On the sixth day of operation, the voltage was about 646 mV and the current value was 0.006 mA. On the tenth day of operation, the external resistance value was changed from 10 kΩ to 2 kΩ. On the eleventh and seventeenth days of operation, the voltage was about 388 mV and 252 mV, and the current value was about 0.194 mA and 0.126 mA. On the 21st day of operation, the external resistance value was changed from 2 kΩ to 1 kΩ. On the 24th and 31st days of operation, the voltage was 336 mV and 242 mV, and the current value was 0.336 mA and 0.242 mA. The CODcr removal rate averaged about 96.2% over the period, and fluctuated between 93.0 and 99.2%. The above examples show that power generation can be performed while treating the artificial sewage, which is the water to be treated, well.

[0067] [Example 2] Example 2 in which the treatment water tank 2 of the second embodiment is applied will be described.

[0068] The microbial power generation apparatus 1 of Example 2 shown in FIG. 8 is similar in configuration to the microbial power generation apparatus 1 of Example 1, except that the treatment water tank 2 is of a swirling flow type.

[0069] A detouring member 7 was installed in the center of the rectangular parallelepiped treatment tank 2 to divert the flow of the water to be treated in the height direction of the treatment tank 2. Triangular prism guide members 8 were installed on the bottom and four sides of the liquid surface of the treatment tank 2 to prevent the water to be treated from stagnating and promote swirling. An aeration member 6 was installed approximately in the center near the inner surface of the treatment tank 2 to facilitate the generation of a swirling flow of the water to be treated in the treatment tank 2. An anode 31 was installed on the lower side and a cathode 41 was installed on the upper side in the treatment tank 2 partitioned by the detouring member 7. An inlet channel 21 for the water to be treated was provided near the bottom of the treatment tank 2, and an outlet channel 22 for the water to be treated was provided at the top of the treatment tank 2.

[0070] (anode 31, cathode 41, water to be treated, electroactive bacteria) The anode 31 and the cathode 41 used had the same specifications as those in Example 1. The water to be treated was artificial sewage with the same water quality as in Example 1. The electroactive bacteria introduced into the treatment water tank 2 was also activated sludge, which was a source of inoculated microorganisms, as in Example 1.

[0071] (Operating conditions) In Example 2, 1.0 L of the activated sludge with an MLSS concentration of about 3,000 mg / L and 2.5 L of the artificial sewage were added. The liquid temperature in the treated water tank 2 was controlled to a constant temperature of 30° C. by the heater 17. The aeration amount to the cathode 41 by the aeration member 6 was adjusted to 0.1 to 0.2 L / min by the mass flow meter 62. Here, the operation of the microbial power generation device 1 was started, which supplies the artificial sewage from the raw water tank 11 to the treated water tank 2 at a flow rate of 1.75 L / day and a hydraulic retention time of 48 hours by alternate operation of the pumps P1 and P2. After that, the supply amount of the artificial sewage was changed stepwise to continue the operation at a flow rate of 2.62 L / day and a hydraulic retention time of 36 hours. The aeration was changed from 0.2 L / min to 0.1 L / min on the 11th day of operation. Then, the external resistance 5 was adjusted based on the internal resistance value calculated from the slope of the current-voltage curve obtained by the potentiostat 15 to acclimate the activated sludge.

[0072] (Evaluation of power generation and processing performance) Table 2 shows the power generation and processing performance under the above operating conditions.

[0073] [Table 2]

[0074] As shown in Table 2, operation was started with an external resistance value of 10 kΩ, and the voltage increased over time. On the second day of operation, the external resistance was 2 kΩ, the voltage was about 684 mV, and the current value was 0.3 mA. On the third day of operation, the external resistance value was changed from 2 kΩ to 1 kΩ, and on the 43rd day of operation, the external resistance value was changed to 510 kΩ. From the third day to the 43rd day of operation, the voltage fluctuated between 400 and 600 mV, and the current value between 0.6 and 1.0 mA. The CODcr removal rate during the period from the third day to the 43rd day of operation was about 95.6% on average, and 94.9 to 96.6%. Continuous power generation was confirmed during the above period. According to the above Example 2, it was shown that power generation can be performed while treating the artificial sewage, which is the water to be treated, well. [Explanation of symbols]

[0075] 1. Microbial power generation device 2... treatment tank, 2a... anode treatment tank, 2b... cathode treatment tank, 21, 21a, 21b... inlet passage, 22, 22a, 22b... outlet passage, 23... anaerobic tank, 24... aerobic tank, 25... partition wall, 251 to 254... notches 3...anode region, 31...anode, 4...cathode region, 41...cathode 5...external resistor, 51...anode conductor, 52...cathode conductor 6... air diffusion member, 61... blower, 62... mass flow meter 7... Detour member 8...Guide member 11: raw water tank, 12: thermostatic tank, 13: treated water storage tank, 14: control unit, 15: potentiostat, 16: network, 17: heater, P1, P2: pump

Claims

1. a treatment water tank into which the inflowing water to be treated can be discharged as treated water; an anode region in which an anode is disposed within the treatment tank; a cathode region in which a cathode is disposed within the treatment water tank; having The water to be treated is It has a microbial community that includes electroactive bacteria. Aeration is performed in the cathode region by an aeration member, A microbial power generation device characterized in that there is a flow of the water to be treated at least from the anode region to the cathode region.

2. The microbial power generation device according to claim 1, characterized in that the flow of the treated water is only from the anode region to the cathode region.

3. The microbial power generation device according to claim 1, characterized in that the flow of the water to be treated further includes a flow from the cathode region to the anode region.

4. A water treatment device comprising the microbial power generation device according to any one of claims 1 to 3.

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