Wastewater treatment apparatus, power generation apparatus, desulfurization treatment apparatus, power generation method and desulfurization method

Abstract

To provide a wastewater treatment apparatus, a power generation apparatus, a desulfurization treatment apparatus, a power generation method and a desulfurization method enabling further efficient energy recovery / utilization or desulfurization as a technique associated with wastewater treatment.SOLUTION: A wastewater treatment apparatus for treating water to be treated, a power generation apparatus, a desulfurization treatment apparatus, a power generation method and a desulfurization method in which power generation or desulfurization treatment is carried out by a reaction using a reducing substance contained in water to be treated, as an electron donor. This invention enables efficient power generation and desulfurization treatment, because there occurs no inhibition of mass transfer by microorganisms when power generation or desulfurization treatment is carried out by a reaction using a reducing substance contained in water to be treated, as a direct electron donor. In addition, this makes it possible to downsize a wastewater treatment facility compared to a case where a power generation facility using a microbial fuel cell and a desulfurization treatment facility are installed separately.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wastewater treatment device that generates power or involves desulfurization. The present invention also relates to a power generation device and a power generation method in wastewater treatment. The present invention further relates to a desulfurization device and a desulfurization method in wastewater treatment. [Background technology]

[0002] Generally, biological treatment using various microorganisms is known as a method for treating wastewater containing organic matter. In particular, biological treatment in an anaerobic environment (hereinafter referred to as "anaerobic treatment") is widely used due to the many advantages of its introduction, such as the absence of aeration power and the fact that it generates almost no excess sludge. In addition, various treatment processes and technologies are sometimes combined with wastewater treatment by anaerobic treatment. For example, one of the technologies that can be used in conjunction with anaerobic treatment is the generation of electricity using biogas, such as methane, generated by anaerobic treatment as fuel.

[0003] On the other hand, microbial fuel cells are known as a technology for generating electricity using redox reactions caused by microorganisms. Microbial fuel cells obtain electrical energy by utilizing the metabolic ability of microorganisms. More specifically, microbial fuel cells have a configuration in which electrons generated during the process of oxidative decomposition of substrates such as organic matter by microorganisms are collected on the anode side, and an electric current is obtained by transferring the electrons to the cathode side.

[0004] For example, Patent Document 1 describes a power generation device in which one of a pair of electrodes is used as an anode and brought into contact with a solution (suspension) containing microorganisms and organic substances capable of growing under anaerobism, and the other electrode is used as a cathode, made of a material having structural voids and brought into contact with air, and the anode and cathode are electrically connected to form a closed circuit. Patent Document 1 also describes attaching microorganisms to the anode surface. Patent Document 1 further describes a power generation method in which the power generation device causes an oxidation reaction by microorganisms in the anode using organic substances as electron donors, and a reduction reaction in the cathode using oxygen as an electron acceptor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-342412 A Summary of the Invention [Problem to be solved by the invention]

[0006] Power generation by a microbial fuel cell as described in Patent Document 1 has low energy conversion efficiency, and improving the power output is a major challenge for practical use. This is presumably because the microorganisms are directly in contact with or supported on the electrodes, and therefore the transfer of substances to the electrodes is inhibited by the microorganisms, and the metabolic rate of the microorganisms is rate-limiting.

[0007] In recent years, in order to reduce the power required to operate the equipment during wastewater treatment and to achieve excellent energy conservation, there has been a demand for technology that can efficiently recover and utilize energy as a technology to be attached to wastewater treatment. One such technology that has been considered is the application of microbial fuel cells to wastewater treatment to simultaneously treat wastewater and generate electricity, but as mentioned above, there is an issue that it is difficult to obtain sufficient power output.

[0008] Furthermore, in addition to efficient energy recovery and utilization, technologies that can be used in conjunction with wastewater treatment include those that can efficiently remove harmful substances from the water being treated during wastewater treatment. In particular, there is a demand for efficient desulfurization, which removes hydrogen sulfide generated during wastewater treatment.

[0009] An object of the present invention is to provide a wastewater treatment device, a power generation device, a desulfurization treatment device, a power generation method, and a desulfurization method, which enable more efficient energy recovery and utilization or desulfurization treatment, as a technology incidental to wastewater treatment. [Means for solving the problem]

[0010] As a result of extensive research into the above-mentioned problems, the inventors have discovered that by carrying out a reaction using reducing substances in the water to be treated in wastewater treatment, it is possible to efficiently recover and utilize energy through power generation in the wastewater treatment, and it is also possible to desulfurize the water to be treated, and have completed the present invention. That is, the present invention relates to the following wastewater treatment device, power generation device, desulfurization treatment device, power generation method, and desulfurization method.

[0011] The wastewater treatment device of the present invention, which has been adapted to solve the above problems, is a wastewater treatment device which treats water to be treated, and is characterized in that it generates electricity through a reaction in which reducing substances in the water to be treated act as electron donors.

[0012] The wastewater treatment device of the present invention generates electricity by directly using the reducing substances contained in the treated water as electron donors, and therefore, there is no inhibition of mass transfer by microorganisms, making it possible to generate electricity efficiently. In addition, it is possible to make the equipment smaller than that used for power generation by a microbial fuel cell.

[0013] Another aspect of the wastewater treatment device of the present invention for solving the above problems is a wastewater treatment device that treats water to be treated, and is characterized in that it performs desulfurization treatment by a reaction in which reducing substances in the water to be treated serve as electron donors.

[0014] The wastewater treatment device of the present invention performs desulfurization treatment by directly using reducing substances contained in the treated water as electron donors, thereby converting the reducing substance hydrogen sulfide into sulfur, thereby making it possible to efficiently remove hydrogen sulfide from the treated water.

[0015] Moreover, one embodiment of the wastewater treatment apparatus of the present invention is characterized in that electrodes are placed in the water to be treated to generate electricity. According to this feature, by installing electrodes directly in the water to be treated that is introduced into the wastewater treatment device, it becomes possible to generate electricity during the series of processes in the wastewater treatment. This makes it possible to generate electricity efficiently without increasing the size of the equipment. In addition, at this time, an electrode reaction using hydrogen sulfide contained in the water to be treated as an electron donor progresses, converting it to sulfur. Therefore, it becomes possible to carry out an efficient desulfurization process without providing a separate facility for desulfurization.

[0016] In one embodiment of the wastewater treatment device of the present invention, an ion exchanger is disposed between the electrodes. According to this feature, it is possible to increase the efficiency of electron transfer between the pair of electrodes, and therefore it is possible to further improve the power generation efficiency and the desulfurization treatment efficiency.

[0017] In addition, one embodiment of the wastewater treatment device of the present invention is characterized in that it has a treatment tank for treating the water to be treated and a power generation unit downstream of the treatment tank, and the reducing substances in the water to be treated after it has been treated in the treatment tank are introduced into the power generation unit to generate electricity. In power generation using microbial fuel cells, a conventional technology, it is known that increasing the concentration of microorganisms required for wastewater treatment causes the microorganisms to further inhibit the transfer of substances to the electrodes, resulting in a trade-off between wastewater treatment efficiency and power generation efficiency. According to this feature, by separating the treatment tank that treats the water to be treated from the power generation section that generates power, wastewater treatment and power generation are not performed simultaneously in one place, and it is possible to avoid a trade-off between wastewater treatment efficiency and power generation efficiency. In particular, by using the reducing substances generated by the treatment of the water to be treated as electron donors, it is possible to perform not only power generation but also oxidation treatment (desulfurization treatment) of the reducing substances contained in the water to be treated after wastewater treatment, making it possible to improve the overall efficiency of wastewater treatment.

[0018] Moreover, one embodiment of the wastewater treatment apparatus of the present invention is characterized in that it is provided with a pH control means for dissolving reducing substances in the water to be treated in the water to be treated. This feature allows the amount of reducing substances, the solubility of which changes depending on the pH level, to be retained in the water being treated, and increases the amount of reducing substances available for reaction as electron donors, thereby improving power generation efficiency and desulfurization efficiency.

[0019] Moreover, one embodiment of the wastewater treatment apparatus of the present invention is characterized in that it is provided with a temperature control means for a reaction in which a reducing substance in the water to be treated serves as an electron donor. According to this feature, it is possible to control the temperature so as to improve the mass transfer rate and the reaction efficiency in the reaction in which the reducing substance serves as the electron donor, thereby making it possible to increase the power generation efficiency and the desulfurization efficiency.

[0020] In addition, the power generation device of the present invention for solving the above problems is a power generation device to be installed in a wastewater treatment device that treats water to be treated, and has a feature in that it generates electricity using reducing substances in the water to be treated as electron donors. The power generation device of the present invention generates power by directly using the reducing substances contained in the water to be treated as electron donors, and thus generates power efficiently without the inhibition of mass transfer by microorganisms. In addition, the equipment can be made smaller than that of power generation using a microbial fuel cell. Furthermore, by applying the present invention to an existing wastewater treatment device, it is possible to update the wastewater treatment device to one that can generate power without large-scale updates to the entire wastewater treatment device.

[0021] In addition, the desulfurization treatment device of the present invention for solving the above problems is a desulfurization treatment device to be installed in a wastewater treatment device that treats water to be treated, and has a feature in that reducing substances in the water to be treated are supplied as electron donors to the desulfurization treatment. The desulfurization treatment device of the present invention performs desulfurization treatment by directly using a reducing substance contained in the water to be treated as an electron donor, thereby enabling efficient desulfurization without discharging hydrogen sulfide outside the system. Furthermore, by applying this device to existing wastewater treatment devices, it becomes possible to upgrade the wastewater treatment devices to ones capable of desulfurization treatment without requiring a large-scale upgrade of the entire wastewater treatment device.

[0022] In addition, the power generation method of the present invention for solving the above problems is a power generation method in wastewater treatment for treating water to be treated, and is characterized by including a step of generating power using reducing substances in the water to be treated as electron donors. The power generation method of the present invention uses the reducing substances contained in the treated water directly as electron donors to generate power, which allows efficient power generation without the inhibition of mass transfer by microorganisms. In addition, the equipment can be made smaller than that required for power generation using a microbial fuel cell.

[0023] Furthermore, the desulfurization method of the present invention for solving the above problems is a desulfurization method in wastewater treatment for treating water to be treated, and is characterized by including a step of subjecting reducing substances in the water to be treated as electron donors to the desulfurization treatment. The desulfurization method of the present invention performs desulfurization treatment by directly using a reducing substance contained in the water to be treated as an electron donor, thereby enabling efficient desulfurization without discharging hydrogen sulfide outside the system. Effect of the Invention

[0024] According to the present invention, it is possible to provide a wastewater treatment device, a power generation device, a desulfurization treatment device, a power generation method, and a desulfurization method, which enable more efficient energy recovery and utilization or desulfurization treatment, as a technology incidental to wastewater treatment. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic explanatory diagram of a wastewater treatment device according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic explanatory diagram of a wastewater treatment device according to a second embodiment of the present invention. [Diagram 3] FIG. 1 is a schematic explanatory view showing another aspect of a wastewater treatment device in a second embodiment of the present invention. [Figure 4] FIG. 11 is a schematic explanatory diagram of a wastewater treatment device according to a third embodiment of the present invention. [Diagram 5] FIG. 11 is a schematic explanatory diagram of a wastewater treatment device according to a fourth embodiment of the present invention. [Figure 6] FIG. 11 is a schematic explanatory view showing another aspect of the wastewater treatment device in the fourth embodiment of the present invention. [Figure 7] FIG. 11 is a schematic explanatory view showing another aspect of the wastewater treatment device in the fourth embodiment of the present invention. [Figure 8] FIG. 11 is a schematic explanatory diagram of a wastewater treatment device according to a fifth embodiment of the present invention. [Figure 9] FIG. 13 is a schematic explanatory diagram of a wastewater treatment device according to a sixth embodiment of the present invention. [Figure 10] FIG. 13 is a schematic explanatory diagram showing another aspect of a wastewater treatment device in the sixth embodiment of the present invention. [Figure 11] FIG. 13 is a schematic explanatory diagram showing another aspect of a wastewater treatment device in the sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, embodiments of the wastewater treatment device, power generation device, desulfurization treatment device, power generation method, and desulfurization method according to the present invention will be described in detail with reference to the drawings. The power generation method and desulfurization method according to the present invention are to be replaced with the description of the operation of the wastewater treatment device, power generation device, and desulfurization treatment device according to the present invention. The wastewater treatment device, power generation device, desulfurization treatment device, power generation method, and desulfurization method described in the embodiments are merely examples used to explain the wastewater treatment device, power generation device, desulfurization treatment device, power generation method, and desulfurization method of the present invention, and are not limited thereto.

[0027] In the wastewater treatment device of the present invention, the water to be treated is not particularly limited as long as it contains a reducing substance. The reducing substance may be contained in the water to be treated before being introduced into the wastewater treatment device, or may be generated during the treatment process in the wastewater treatment device and be present in the water to be treated. Specific examples of the water to be treated include industrial wastewater discharged from various factories such as food factories, chemical factories, and paper and pulp factories, and domestic wastewater such as sewage. In the following embodiment, the water to be treated will mainly be described as a water to be treated in which a reducing substance is generated through treatment, but is not limited thereto.

[0028] In the present invention, the reducing substance contained in the water to be treated is not particularly limited as long as it functions as an electron donor. Whether a substance functions as an electron donor is determined relatively depending on the combination with a substance that functions as an electron acceptor (hereinafter simply referred to as "electron acceptor"). In other words, the reducing substance in the present invention can be one that is more likely to release electrons than the electron acceptor, that is, one that has a lower redox potential than the electron acceptor. For example, when oxygen is used as the electron acceptor, the reducing substance in the present invention can be one that has a lower redox potential than oxygen, and examples of such reducing substances include hydrogen sulfide, hydrogen, and ammonia.

[0029] [First embodiment] (Wastewater treatment equipment) FIG. 1 is a schematic explanatory diagram showing the structure of a wastewater treatment device in a first embodiment of the present invention. 1, wastewater treatment device 1A in this embodiment includes a treatment tank 2 and a power generation unit 3. Wastewater treatment device 1A also includes an inlet pipe L1 for introducing water to be treated W into treatment tank 2, a connection pipe L2 for connecting treatment tank 2 and power generation unit 3, and a discharge pipe L3 for discharging water to be treated W from power generation unit 3. After being treated in treatment tank 2, water to be treated W is introduced into power generation unit 3.

[0030] (Treatment tank) The treatment tank 2 is a tank for treating the water W to be treated. The treatment carried out in the treatment tank 2 is not particularly limited as long as it is suitable for the treatment target contained in the water to be treated W and contains reducing substances after treatment in the water to be treated W. Examples include biological treatment and chemical treatment (addition of chemicals, ozone treatment, etc.), but it is preferable to use biological treatment, which does not involve the use or generation of substances harmful to the human body and allows for relatively low-cost treatment. Further, examples of biological treatments include biological treatments in an anaerobic environment (anaerobic treatments), such as methane fermentation by acid-producing bacteria and methanogenic bacteria, denitrification treatments in which nitrate and nitrite are reduced by denitrifying bacteria, and sulfate reduction treatments in which sulfate is reduced by sulfate-reducing bacteria. Furthermore, examples of biological treatments in an aerobic environment (aerobic treatments) include activated sludge treatments using activated sludge. From the viewpoints of treatment costs and the usefulness of the generated gas, anaerobic treatments are preferred as biological treatments, and methane fermentation that produces methane is particularly preferred.

[0031] In the treatment tank 2, when anaerobic treatment, particularly methane fermentation, is performed, hydrogen sulfide, hydrogen, ammonia, and the like are produced in addition to methane in the water to be treated W. These products correspond to the reducing substances in the present invention.

[0032] The water W to be treated that has been treated in the treatment tank 2 contains reducing substances, and is introduced into the power generation section 3 via the connection pipe L2.

[0033] (Power Generation Section (Power Generation Equipment / Desulfurization Equipment)) The power generation unit 3 generates power using reducing substances in the water to be treated W as electron donors. Moreover, the power generation unit 3 in this embodiment can also perform desulfurization by using sulfur-containing compounds such as hydrogen sulfide, among the reducing substances in the water to be treated W, as electron donors. The structure of the power generation section 3 of this embodiment will be described below from the viewpoint of power generation. The desulfurization process by the power generation section 3 of this embodiment will be described in detail later.

[0034] As shown in FIG. 1, the power generation unit 3 of this embodiment is provided at the rear of the treatment tank 2, and includes a first cell 31a and a second cell 31b, an ion exchanger 32 provided to separate the cells 31a and 31b, and electrodes 33a and 33b arranged in the cells 31a and 31b, respectively. Here, the first cell 31a is formed so that the water to be treated W introduced from the treatment tank 2 through the connection pipe L2 comes into contact with the electrode 33a, and the electrode 33a arranged in the first cell 31a functions as an anode. On the other hand, the second cell 31b is formed so as to store or supply an electron acceptor, and the electrode 33b arranged in the second cell 31b functions as a card. In addition, the electrodes 33a and 33b are connected to an external circuit by a conductor (not shown). This makes it possible to recover and utilize electrical energy generated by the action of the reducing substance as an electron donor in the power generation unit 3.

[0035] The first cell 31a may be of any material or shape as long as it is provided with an electrode 33a and is formed so that the water to be treated W comes into contact with the electrode 33a. For example, as shown in Fig. 1, the first cell may have a space capable of temporarily storing the water to be treated W introduced through a connection pipe L2, and may be provided with a discharge pipe L3 for discharging the water to be treated W after it comes into contact with the electrode 33a. As a result, reducing substances in the water to be treated W donate electrons to the electrode 33a as electron donors, and are then promptly discharged through the discharge pipe L3. A flow rate adjusting mechanism such as a valve may be provided in the connection pipe L2 and / or the discharge pipe L3, which makes it possible to adjust the amount and flow rate of the water W to be treated that is brought into contact with the electrode 33a, and to control the mass transfer rate to the electrode 33a.

[0036] The water to be treated W discharged through the discharge pipe L3 can be discharged as it is if it meets the water quality requirements for discharge into a river or the like. In addition, a reaction tank 4 for further treating the water to be treated W may be provided downstream of the discharge pipe L3. The reaction tank 4 is not particularly limited as long as it can treat the water to be treated W to a water quality suitable for discharge into a river. Examples of the reaction tank include an aeration tank and a pH adjustment tank.

[0037] The second cell 31b may be any cell as long as it is provided with an electrode 33b and is formed so as to store or supply an electron acceptor for the reducing substances in the water to be treated W, and there is no particular restriction on the material or shape.

[0038] Here, the electron acceptor may be in the form of either gas or liquid. The liquid may be a solution in which a solid drug is dissolved, or a solution in which a gas is mixed (dissolved). Specific examples of the electron acceptor in this embodiment include gases such as oxygen and gases containing oxygen. Incidentally, examples of gases containing oxygen include those containing oxygen as a mixture such as air, and those containing oxygen as an element constituting a compound such as carbon dioxide. When a gas is used as the electron acceptor, there are advantages in that the treatment of the gas discharged after the reaction is unnecessary (or easy) and the cost of obtaining the gas can be reduced. In order to make the most of these advantages, it is particularly preferable to use air as the electron acceptor. In addition, other examples of the electron acceptor in this embodiment include, for example, a liquid solution containing dissolved oxygen, an aqueous solution of an oxidizing agent such as an aqueous solution of potassium ferricyanide, etc. When a liquid is used as the electron acceptor, it is advantageous in that the compound (oxidizing agent) that is highly effective as an electron acceptor can be easily handled, and therefore the power generation efficiency can be further improved. From the viewpoint of improving the power generation efficiency, it is particularly preferable to use an aqueous solution of potassium ferricyanide as the electron acceptor.

[0039] As an example of the second cell 31b, as shown in FIG. 1, in order to supply a gaseous electron acceptor (oxygen, air, etc.) to the electrode 33b, an electron acceptor supply port 34a for supplying a gas and an electron acceptor discharge port 34b for discharging the gas after the reaction may be provided in the second cell 31b. Another example of the second cell 31b is to provide a space capable of storing a liquid in the second cell 31b, and provide the electron acceptor supply port 34a and the electron acceptor discharge port 34b that can supply a solution of the electron acceptor and discharge the solution after the reaction, respectively. This allows the electron acceptor to receive electrons from the electrode 33a via the electrode 33b, and a current flows between the electrodes 33a and 33b to generate electricity. In addition, the electron acceptor after the reaction is quickly discharged to the outside of the power generation unit via the electron acceptor discharge port 34b. A flow rate adjusting mechanism such as a valve may be provided at the electron acceptor supply port 34a and / or the electron acceptor discharge port 34b to adjust the concentration of the electron acceptor in the second cell 31b. Furthermore, a control mechanism may be provided to control the flow rate adjusting mechanism so that the electron acceptor concentration is maintained according to the amount of electrons generated by the reaction at the electrode 33a. This makes it possible to suppress a decrease in the reaction efficiency related to the electron transfer between the electrodes 33a and 33b and suppress a decrease in the power generation efficiency.

[0040] 1, one each of the electron acceptor supply port 34a and the electron acceptor discharge port 34b is shown, but the present invention is not limited thereto. For example, a plurality of electron acceptor supply ports 34a and electron acceptor discharge ports 34b may be provided. In particular, when a gas containing oxygen is used as the electron acceptor, water is generated by a reaction at the electrode 33b, as described below. Therefore, when a plurality of electron acceptor discharge ports 34b are provided, for example, one for discharging gas and one for discharging liquid may be provided separately.

[0041] The ion exchanger 32 may have a known structure that allows ions to pass through it, and is not particularly limited. In particular, it may be a cation exchange membrane that allows hydrogen ions generated at the electrode 33a (anode side) to pass through it. This allows hydrogen ions to move from the electrode 33a (anode side) to the electrode 33b (cathode side), thereby increasing the reaction efficiency of the electron acceptor at the electrode 33b and improving power generation efficiency. In addition, it is more preferable that the ion exchanger 32 has low oxygen permeability. This makes it possible to suppress the electron acceptor (oxygen) supplied to the electrode 33b (cathode side) from moving to the electrode 33a side, and to suppress the reaction efficiency of the electron donor at the electrode 33a from decreasing due to oxygen. 1, the ion exchanger 32 is shown as being provided separately from the electrodes 33a and 33b, but is not limited thereto. For example, a material having ion exchange ability may be integrated with the electrodes 33a and / or 33b. This allows the power generating unit 3 to be made smaller as a whole, and also shortens the time required for maintenance work.

[0042] The electrode 33a is an electrode that collects electrons from reducing substances in the water to be treated W, and functions as a so-called anode. In this embodiment, the electrode 33a is disposed in the first cell 31a so as to come into contact with the water to be treated W after being treated in the treatment tank 2.

[0043] The electrode 33a may be any material that functions as an anode, and there are no particular limitations on the material and shape. The material and shape of the electrode 33a may be appropriately selected in consideration of the costs involved in material procurement and processing, and the reaction efficiency of the reducing substance in the electrode 33a. Examples of the material of the electrode 33a include carbon and metals (stainless steel, platinum, copper, etc.) that are widely used as electrode materials in the field of electrochemistry. Examples of the shape of the electrode 33a include a flat plate, a rod, a mesh, etc.

[0044] In this embodiment, the electrode 33a does not have microorganisms in contact with or supported on the electrode surface. Therefore, mass transfer of the reducing substance is not inhibited by the microorganisms, and the reaction efficiency as an electron donor (the mass transfer rate of the reducing substance to the electrode 33a) can be improved, and the power generation efficiency can be improved. In addition, the electrode 33a in this embodiment does not collect electrons generated by the metabolism of the microorganism, but collects electrons directly from the reducing substance. Therefore, the metabolism of the microorganism is not rate-limiting, and the reaction efficiency as an electron donor (electron collection rate at the electrode 33a) is improved, thereby improving the power generation efficiency.

[0045] Furthermore, the electrode 33a in this embodiment does not need to be processed so that the structure of the electrode 33a is suitable for retaining microorganisms, which reduces the cost of producing the electrode 33a. In addition, in consideration of the amount of microorganisms retained on the electrode 33a and the reaction efficiency of the microorganisms, there is no need to enlarge the electrode 33a, which allows the equipment related to the wastewater treatment device 1 to be miniaturized.

[0046] The electrode 33b is a counter electrode of the electrode 33a, and is an electrode that transfers electrons to the electron acceptor, and functions as a so-called cathode. The electrode 33b in this embodiment is disposed in the second cell 31b.

[0047] The electrode 33b may be any material that functions as a cathode, and there are no particular limitations on the material and shape. The material and shape of the electrode 33b may be appropriately selected in consideration of the costs involved in material procurement and processing, and the reaction efficiency of the electron acceptor in the electrode 33b. Examples of the material of the electrode 33b include carbon and metals (stainless steel, platinum, copper, etc.) that are widely used as electrode materials in the field of electrochemistry. Examples of the shape of the electrode 33b include a flat plate, a rod, a mesh, etc.

[0048] When the electron acceptor supplied to the second cell 31b is a gas (air), one side of the electrode 33b contacts the gas, and the other side contacts the water W to be treated. For this reason, the electrode 33b is preferably in a form suitable for use as a so-called air cathode. For example, the electrode 33b may be in a form suitable for use as an air cathode, which may have both gas permeability and water impermeability. By making the electrode 33b in a form having gas permeability, the gas, which is the electron acceptor, can be effectively reacted at the electrode 33b. Furthermore, by making the electrode 33b water impermeable, it is possible to prevent the water W to be treated in the first cell 31a from passing through the electrode 33b and flowing into the second cell 31b. Specific examples of such an electrode 33b include one made of carbon fiber, and one in which a surface treatment such as coating a material having gas permeability and water impermeability or lamination of a film is performed on the surface of a metal mesh. In this case, impermeable refers to not allowing water to pass through. For example, making electrode 33b waterproof, water-repellent, hydrophobic, or water-stopping is also included in being impermeable.

[0049] The wastewater treatment device 1A in this embodiment uses a reducing substance in the water W to be treated as an electron donor and performs power generation or desulfurization by electrochemical reaction (electrode reaction). In general, when performing an electrochemical reaction, the electrons move to a location other than the location where the electrochemical reaction actually occurs (the power generation unit 3), which causes a problem of a decrease in the efficiency of the electrochemical reaction. Therefore, in the wastewater treatment device 1A in this embodiment, it is preferable to insulate the location other than the location where the electrochemical reaction occurs (the power generation unit 3). Specific examples of the insulation treatment include, for example, placing the treatment tank 2 and the reaction tank 4 on top of an insulator, constructing the outer wall or inner wall of the treatment tank 2 and the reaction tank 4 from an insulator, or coating the outer wall or inner wall of the treatment tank 2 and the reaction tank 4 with an insulating material. In addition, examples of the insulation treatment of the introduction pipe L1, the connection pipe L2, and the discharge pipe L3 include making each pipe from an insulator, coating each pipe with an insulating material, and the like.

[0050] In the wastewater treatment device 1A in this embodiment described above, power generation or desulfurization can be performed by a reaction in which the reducing substances in the water to be treated W serve as electron donors. The power generation and desulfurization treatment in the wastewater treatment device 1A will be described in detail below.

[0051] (Power generation and desulfurization in wastewater treatment equipment) The reactions and steps involved in power generation and desulfurization in a wastewater treatment device 1A according to a first embodiment of the present invention will be described with reference to Fig. 1. The reactions and steps involved in power generation in the wastewater treatment device of this embodiment are described as using a reducing substance generated by anaerobically treating the water to be treated W as an electron donor and air (oxygen) as an electron acceptor. In particular, the reaction and steps using hydrogen sulfide as the electron donor correspond to the reactions and steps involved in the desulfurization in the wastewater treatment device of this embodiment. The explanation of the reactions and steps based on Fig. 1 shows an example of power generation and desulfurization treatment in this embodiment, and is not limited thereto. The following explanation describes the reactions and steps related to the treatment tank 2 to the power generation section 3, and the reactions and steps related to other components (such as the inlet pipe L1, the outlet pipe L3, and the reaction tank 4) are omitted. Furthermore, the notations of reactions R1 to R4 and steps S1 to S3 are numbered for the purpose of explanation, and do not specify the order of the reactions and steps.

[0052] As shown in Fig. 1, the water W to be treated introduced into the treatment tank 2 is anaerobically treated by anaerobic microorganisms (acid-producing bacteria and methanogens) in the treatment tank 2 (step S1). During this process, in addition to methane, reducing substances (hydrogen, hydrogen sulfide, ammonia, etc.) are produced.

[0053] The water to be treated W, which has been treated in the treatment tank 2 and contains reducing substances, is introduced into the first cell 31a of the power generation unit 3 via the connection pipe L2 (step S2). Here, the reducing substances (hydrogen, hydrogen sulfide, ammonia, etc.) come into contact with the electrode 33a, whereby the reducing substances function as electron donors and donate electrons to the electrode 33a. In this case, if hydrogen sulfide is taken as an example of a reducing substance that functions as an electron donor, the reaction (reaction R1) at the electrode 33a is represented by the following reaction formula (formula 1).

number

[0054] In addition, some of the hydrogen sulfide reacts as hydrogen sulfide ions. The reaction at this time is shown in the following reaction formula (Formula 2).

number

[0055] As shown in formulas 1 and 2, in reaction R1, hydrogen sulfide contained in the water to be treated W after treatment in the treatment tank 2 donates electrons to the electrode 33a, and hydrogen sulfide itself is oxidized to become harmless and deodorized. Therefore, the wastewater treatment device of this embodiment is capable of desulfurization and deodorization in addition to power generation. Note that reducing substances (such as ammonia), which are harmful substances and odorous substances other than hydrogen sulfide, also function as electron donors in the same way, and as the reaction progresses, they can be rendered harmless and deodorized.

[0056] After the reaction at the electrode 33a proceeds based on the reaction formulas shown in Equations 1 and 2, electrons move from the electrode 33a to the electrode 33b via the conductor (reaction R2). At this time, hydrogen ions generated by the reaction at the electrode 33a move to the second cell 31b side via the ion exchanger 32 (reaction R3).

[0057] Meanwhile, air (oxygen) is introduced as an electron acceptor into the second cell 31b from the electron acceptor supply port 34a (step S3). Here, the electrons that have moved from the electrode 33a to the electrode 33b by reaction R2 are received by the electron acceptor via the electrode 33b. At this time, the hydrogen ions that have moved to the second cell 31b side via the ion exchanger 32 by reaction R3 also react with the electron acceptor (oxygen). The reaction (reaction R4) at the electrode 33b at this time is shown in the following reaction formula (formula 3).

number

[0058] Based on the above-mentioned reactions R1 to R4 and steps S1 to S3, a current flows between the electrodes 33a and 33b. This causes a reaction in which the reducing substances in the water to be treated W serve as electron donors to proceed, and power generation and desulfurization are performed in the wastewater treatment device 1A of this embodiment. The electric energy obtained by the power generation can be recovered and used through an external circuit connected to the electrodes 33a and 33b. The use of the electric energy is not particularly limited. For example, the electric energy may be used to drive the equipment of the wastewater treatment device, or may be used outside the wastewater treatment device.

[0059] As described above, by using the wastewater treatment device of this embodiment, there is no inhibition of mass transfer by microorganisms, and no rate-limiting step based on the metabolic rate of microorganisms, and it is possible to improve the efficiency of power generation and desulfurization. In addition, the equipment can be made smaller than that used for power generation by a microbial fuel cell. Furthermore, it is possible to carry out efficient desulfurization without providing a separate facility for desulfurization.

[0060] In conventional power generation using microbial fuel cells, it is known that increasing the concentration of microorganisms required for wastewater treatment further inhibits mass transfer to the electrodes, resulting in a trade-off between wastewater treatment efficiency and power generation efficiency. On the other hand, the wastewater treatment device and power generation method of this embodiment can perform wastewater treatment and power generation separately. Therefore, in the wastewater treatment device and power generation method of this embodiment, there is no trade-off between wastewater treatment efficiency and power generation efficiency, and efficient power generation is possible.

[0061] The configuration of the power generation unit 3 in this embodiment can be made independent as a power generation device or desulfurization treatment device according to the present invention. This power generation device or desulfurization treatment device can be applied to an existing wastewater treatment device. This makes it possible to provide the wastewater treatment device of the present invention without large-scale renewal of the entire wastewater treatment device. In addition, it is possible to provide a power generation method and a desulfurization method using this wastewater treatment device.

[0062] [Second embodiment] Fig. 2 is a schematic explanatory diagram showing a wastewater treatment device in a second embodiment of the present invention, and Fig. 3 is a schematic explanatory diagram showing another aspect of the wastewater treatment device in the second embodiment of the present invention. In the wastewater treatment device 1B according to the second embodiment, the treatment tank 2 is composed of an acid production tank 21 and a methane fermentation tank 22. The power generation unit 3 is provided on a circulation flow path provided in the treatment tank 2 (the acid production tank 21 and the methane fermentation tank 22). The wastewater treatment device 1B shown in Figs. 2 and 3 has the power generation unit 3 installed at different locations. Note that a description of the same configuration as in the first embodiment will be omitted.

[0063] As shown in Figures 2 and 3, in the wastewater treatment device 1B of this embodiment, the treatment tank 2 consists of an acid production tank 21 and a methane fermentation tank 22 connected by a connection pipe L4, a circulation flow path is formed between the acid production tank 21 and the methane fermentation tank 22 by a circulation pipe L5, and a circulation flow path within the methane fermentation tank 22 is formed by a circulation pipe L6. In the wastewater treatment device 1B shown in Fig. 2, the power generation unit 3 is provided on the circulation pipe L5. On the other hand, in the wastewater treatment device 1B shown in Fig. 3, the power generation unit 3 is provided on the circulation pipe L6.

[0064] The treatment tank 2 in this embodiment includes an acid production tank 21 and a methane fermentation tank 22. The acid production tank 21 and the methane fermentation tank 22 are reaction tanks for anaerobically treating the water to be treated W by microorganisms contained therein. In order to maintain anaerobic conditions, the acid production tank 21 and the methane fermentation tank 22 preferably have a ceiling and form a closed space.

[0065] The acid production tank 21 performs an acid production process on the water to be treated W introduced through the inlet pipe L1 by using acid-producing bacteria (mainly anaerobic acid-producing bacteria) contained therein to decompose solids and polymeric organic matter such as sugars, proteins, and oils, and produce monosaccharides, amino acids, lower fatty acids, and acetic acid. The water to be treated W treated in the acid production tank 21 is supplied to the methane fermentation tank 22 through a connecting pipe L4.

[0066] In addition, the acid generation tank 21 may be equipped with an internal water temperature adjustment means, a means for adding a pH adjuster, and a means for adding metals such as nitrogen, phosphorus, cobalt, and nickel, which are nutrient sources required by the bacteria (not shown).

[0067] The methane fermentation tank 22 performs a methane fermentation process to produce methane from monosaccharides, amino acids, lower fatty acids, acetic acid, etc. contained in the water to be treated W treated in the acid production tank 21 supplied through a connecting pipe L4. The methane fermentation process is carried out in an anaerobic atmosphere without dissolved oxygen by methanogens retained by a floating method, a fixed bed method, a fluidized bed method, an upflow anaerobic sludge blanket (UASB) method, an expanded granular sludge bed (EGSB) method, or the like.

[0068] In the methane fermentation tank 22, a granule layer is formed in which anaerobic bacteria suitable for anaerobic treatment exist. When the water W to be treated is introduced from the acid generation tank 21 into the methane fermentation tank 22, methane fermentation is carried out by the anaerobic bacteria contained in the granule layer. As a result, in the methane fermentation tank 22, gas mainly composed of methane and carbon dioxide is generated, and the water W to be treated containing reducing substances is generated. Note that a settler 23, which is a gas-solid-liquid separation means, may be provided inside the methane fermentation tank 22. The gas generated in the methane fermentation tank 22 is released or recovered outside the tank (not shown). The water W to be treated generated in the methane fermentation tank 22 is discharged outside the treatment system via a discharge pipe L7.

[0069] The methane fermentation tank 22 may further be provided with various additional equipment. For example, the tank may be equipped with an internal water temperature adjustment means, a pH adjuster supply means, and a means for adding metals such as nitrogen, phosphorus, cobalt, and nickel, which are nutrient sources required by the bacteria (not shown).

[0070] The methane fermentation tank 22 preferably includes a means for recovering, purifying, and storing methane gas generated in the methane fermentation tank 22. This makes it possible to recover methane gas, which is a useful energy source, from the water to be treated W and to make effective use of it, in addition to generating electricity in the power generation unit 3. Furthermore, the methane fermentation tank 22 may include means for recovering, purifying, and storing carbon dioxide gas from the gas generated in the methane fermentation tank 22, and may include means for introducing carbon dioxide gas into the second cell 31b from the electron acceptor supply port 34a in the power generation unit 3. This makes it possible to effectively use carbon dioxide gas as an electron acceptor, thereby reducing the supply cost of the electron acceptor.

[0071] Furthermore, the methane fermentation tank 22 in this embodiment is equipped with a circulation pipe L5 and / or a circulation pipe L6. The circulation pipe L5 supplies the water to be treated W in the upper part of the methane fermentation tank 22 to the acid production tank 21, and forms a circulation flow path between the acid production tank 21 and the methane fermentation tank 22. The circulation pipe L6 supplies the water to be treated W in the upper part of the methane fermentation tank 22 to the lower part of the methane fermentation tank 22, and a circulation flow path is formed within the methane fermentation tank 22.

[0072] The power generating section 3 in this embodiment is provided on a circulation flow path formed by the circulation pipes L5 and L6.

[0073] As shown in FIG. 2, in the case where the power generation unit 3 is provided on the circulation pipe L5, the water W to be treated from the methane fermentation tank 22 is supplied to the first cell 31a, and the water W to be treated after the reaction at the electrode 33a is supplied to the acid generation tank 21 through the circulation pipe L5. At this time, the hydrogen ion concentration of the water W to be treated after the reaction at the electrode 33a increases as shown in Equation 1 and Equation 2, and the solution has an acidic pH. It is generally known that in order to favorably proceed with the reaction in the acid generation tank 21, it is preferable that the pH in the acid generation tank 21 is on the acidic side. Therefore, the water W to be treated discharged from the power generation unit 3 to the acid generation tank 21 may be used as a pH adjuster to proceed with the reaction in the acid generation tank 21 under favorable conditions. In addition, a flow rate adjustment mechanism such as a valve or an adsorption treatment means such as activated carbon may be provided on the circulation pipe L5 on the acid generation tank 21 side. As a result, if the treated water W discharged from the power generation unit 3 flows into the acid generation tank 21 and the pH range in the acid generation tank 21 falls outside the appropriate range, the inflow amount of the treated water W and the pH of the treated water W can be controlled, making it possible to suppress inhibition of the reaction in the acid generation tank 21.

[0074] As shown in FIG. 3, in the case where the power generation unit 3 is provided on the circulation pipe L6, the water W to be treated is supplied from the upper part of the methane fermentation tank 22 to the first cell 31a, and the water W to be treated after the reaction at the electrode 33a is supplied to the lower part of the methane fermentation tank 22 via the circulation pipe L6. At this time, the water W to be treated after the reaction at the electrode 33a becomes a solution with a reduced concentration of dissolved hydrogen sulfide as shown in Equation 1 and Equation 2. It is known that the metabolism of methane bacteria contained in the granule layer in the methane fermentation tank 22 is inhibited by hydrogen sulfide. Therefore, the water W to be treated discharged from the power generation unit 3 to the lower part of the methane fermentation tank 22 can be circulated in the methane fermentation tank 22 without inhibiting methane fermentation.

[0075] As described above, in the wastewater treatment device 1B of this embodiment, the treatment tank 2 is composed of the acid production tank 21 and the methane fermentation tank 22, so that wastewater treatment can be performed under conditions suitable for each treatment (acid production treatment and methane fermentation), thereby further improving the wastewater treatment efficiency. In addition, in the wastewater treatment device 1B of this embodiment, the power generation unit 3 is installed on a circulation flow path provided in the treatment tank 2 (acid production tank 21 and methane fermentation tank 22), so that the water to be treated W supplied to the first cell 31a side is supplied again to the treatment tank 2 (acid production tank 21 or methane fermentation tank 22) after reaction. Therefore, the water to be treated W is repeatedly treated, so that it is possible to improve the wastewater treatment of the water to be treated W discharged from the power generation unit 3. In addition, by reintroducing the water to be treated W discharged from the power generation unit 3 at this time into the treatment tank 2 (acid production tank 21 or methane fermentation tank 22), it is possible to achieve the effect of allowing the reaction in the treatment tank 2 to proceed under favorable conditions.

[0076] The power generation unit 3 in this embodiment is provided on the circulation flow path that circulates the water to be treated W in the upper part of the methane fermentation tank 22, so it is assumed that the amount of microorganisms present in the water to be treated W in the circulation flow path is relatively small. Therefore, it is possible to suppress the effect of microorganisms on the reaction in the power generation unit 3 and improve the power generation efficiency.

[0077] In the wastewater treatment device 1B of this embodiment, the water to be treated W discharged through the discharge pipe L7 can be discharged as it is if the water quality satisfies the water quality requirements for discharge into a river or the like. In addition, the reaction tank 4 shown in the first embodiment may be provided downstream of the discharge pipe L7. This allows the water to be treated W to be further treated by being treated in the reaction tank 4, thereby improving the treatment efficiency, and allowing the water to be treated W to be discharged from the wastewater treatment device 1B to the outside of the system.

[0078] Moreover, in the wastewater treatment device 1B of this embodiment, it is possible to generate electricity and perform desulfurization treatment through the same steps as in the first embodiment.

[0079] [Third embodiment] FIG. 4 is a schematic explanatory diagram showing a wastewater treatment device according to a third embodiment of the present invention. 4, in the wastewater treatment device 1C according to the third embodiment, the reaction tank 4 in the wastewater treatment device 1A according to the first embodiment is replaced with an aeration tank 41, and the aeration tank 41 is connected to the electron acceptor supply port 34a provided in the second cell 31 of the power generation section by a connection pipe L8. Note that a description of the same components as those in the first embodiment will be omitted.

[0080] In the wastewater treatment device 1C of this embodiment, the treated water W1 in the aeration tank 41 is supplied to the power generation unit 3 and used as an electron acceptor in the power generation unit 3. Note that the treated water W1 other than that supplied to the power generation unit 3 through the connection pipe L8 is discharged outside the system.

[0081] The aeration tank 41 aerates the water to be treated W introduced into the tank with an oxygen-containing gas (oxygen, air, etc.) using an aeration device 42, thereby promoting aerobic treatment by aerobic microorganisms and oxidation reactions by dissolved oxygen. 4, the aeration tank 41 in this embodiment is not limited to one into which the water to be treated W discharged from the first cell 31a of the power generation section 3 is introduced and aeration is performed on the introduced water to be treated W. Other examples of the aeration tank 41 include one into which the water to be treated W is directly introduced from the treatment tank 2 and aeration is performed.

[0082] The aeration device 42 is not particularly limited as long as it can supply oxygen-containing gas to the water W to be treated in the aeration tank 41. For example, a device consisting of a combination of a blower and an aeration pipe is widely used in aeration treatment.

[0083] Since an oxygen-containing gas is introduced into the aeration tank 41 by the aeration device 42, the treated water W1 in the aeration tank 41 becomes a liquid containing dissolved oxygen. Therefore, the treated water W1 introduced into the second cell 31b of the power generation section 3 via the connection pipe L8 serves as an electron acceptor in the power generation section 3. This makes it possible to generate power by effectively utilizing the materials generated in the treatment process in the wastewater treatment device 1C.

[0084] The treated water W1 after being used as an electron acceptor in the power generation unit 3 is discharged from the electron acceptor outlet 34b. At this time, if the discharged treated water W1 meets the water quality requirements for discharge into a river or the like, it can be discharged as is. The discharged treated water W may also be returned to the aeration tank 41 and aerated again. This makes it possible to more reliably control the water quality of the treated water W1 to be discharged outside the system.

[0085] As described above, the wastewater treatment device 1C in this embodiment can utilize the products produced during the treatment process carried out within the wastewater treatment device 1C as electron donors and electron acceptors in the power generation section 3, making it possible to reduce the running costs associated with power generation in particular.

[0086] Moreover, in the wastewater treatment device 1C of this embodiment, it is possible to generate electricity and perform desulfurization treatment through the same steps as in the first embodiment.

[0087] [Fourth embodiment] Fig. 5 is a schematic explanatory diagram showing a wastewater treatment device in a fourth embodiment of the present invention, and Figs. 6 and 7 are schematic explanatory diagrams showing other aspects of the wastewater treatment device in the fourth embodiment of the present invention. As shown in Figs. 5 to 7, wastewater treatment device 1D according to the fourth embodiment is configured by providing an insulation mechanism 5 for insulating the water to be treated W discharged from the first cell 31a in wastewater treatment device 1A according to the first embodiment. Note that explanations of the same configurations as those in the first embodiment will be omitted. Also, Figs. 5 to 7 are enlarged explanatory views of the power generation section 3 and its periphery of wastewater treatment device 1D, and configurations related to the treatment tank 2 and reaction tank 4 are omitted.

[0088] As described above, when an electrochemical reaction (electrode reaction) is carried out, it is preferable to insulate the area other than the area where the electrochemical reaction is carried out (power generation section 3). The wastewater treatment device 1D in this embodiment is provided with an insulating mechanism 5 that insulates the water W to be treated. This prevents electrons generated in the power generation unit 3 from flowing anywhere other than between the electrodes 33a and 33b, improving the electrode reaction efficiency. As a result, the power generation efficiency and the desulfurization treatment efficiency can be improved. Note that the wastewater treatment device 1D in this embodiment may also be configured to insulate the structures (treatment tank and piping) that constitute the wastewater treatment device as shown in the first embodiment. This provides an even greater insulation effect, making it possible to improve the power generation efficiency in the power generation unit 3.

[0089] The insulating mechanism 5 is not particularly limited as long as it can insulate the water to be treated W. Examples of the means for insulating the water to be treated W by the insulating mechanism 5 include eliminating electrical contact (liquid junction) between the electrode 33a of the power generation unit 3 and the water to be treated W or shortening the liquid junction time. Examples of such a liquid junction eliminating means or a means for shortening the liquid junction time include a means for making the flow of the water to be treated W discontinuous (intermittent), a means for interposing an insulator such as air in the water to be treated W, or a combination of these means.

[0090] FIG. 5 is a schematic explanatory diagram showing an insulation mechanism 5 of a wastewater treatment device 1D in this embodiment. As shown in FIG. 5, the insulation mechanism 5 in this embodiment includes a storage tank 51 and a sprinkling means 52 for sprinkling the water to be treated W into the storage tank 51.

[0091] The storage tank 51 stores the water to be treated W discharged from the power generation unit 3 via the discharge pipe L3. There are no particular limitations on the storage tank 51, so long as it is a tank capable of storing the water to be treated W. Since the air present in the storage tank 51 functions as an insulator for the water to be treated W, it is preferable to adjust the water level in the storage tank 51 so that the water level does not reach its maximum (full state). This makes it possible to further enhance the insulating effect of the water to be treated W.

[0092] The water sprinkling means 52 discharges the water to be treated W in the form of droplets. The air in the storage tank 51 is present as an insulator between the droplets of the water to be treated W discharged by the water sprinkling means 52, so that it is possible to eliminate liquid junctions or shorten the time for liquid junctions. The sprinkling means 52 is not particularly limited as long as it can turn the water W to droplets. A specific example of the sprinkling means 52 is a structure connected to the outlet of the discharge pipe L3 and having a plurality of holes like a shower head, as shown in Fig. 5. Another example of the sprinkling means 52 is a flat-plate-shaped structure provided in the storage tank 51 facing the outlet of the discharge pipe L3 and spaced a predetermined distance from it.

[0093] FIG. 6 is a schematic diagram illustrating another example of the insulation mechanism 5 of the wastewater treatment device 1D in this embodiment. As shown in FIG. 6, the insulation mechanism 5 in this embodiment includes a storage tank 53 and a water discharge means 54 for intermittently discharging the water W to be treated in the storage tank 53.

[0094] The storage tank 53 stores the water to be treated W discharged from the power generation unit 3 via the discharge pipe L3. The storage tank 53 may be any tank capable of storing the water to be treated W, and is not particularly limited. The water discharge means 54 is not particularly limited as long as it can intermittently discharge the water to be treated W in the storage tank 53. An example of the water discharge means 54 is a means for periodically opening and closing an electromagnetic valve 54a provided in a discharge pipe L9 for discharging the water to be treated W from the storage tank 53. This makes the flow of the water to be treated W discharged from the storage tank 53 through the discharge pipe L intermittent, thereby making it possible to eliminate liquid junctions of the water to be treated W or shorten the time of liquid junctions.

[0095] FIG. 7 is a schematic explanatory diagram showing another example of the insulation mechanism 5 of the wastewater treatment device 1D in this embodiment. As shown in FIG. 7, the insulation mechanism 5 in this embodiment is provided with a pipe diameter reduction means 55 for narrowing a portion of the pipe diameter of the exhaust pipe L3 on the exhaust pipe L3, and a gas supply means 56 for supplying gas into the exhaust pipe L3 from the upstream side of the pipe diameter reduction means 55.

[0096] The pipe diameter reducing means 55 is not particularly limited as long as it can partially narrow the pipe diameter of the discharge pipe L3. Examples of the pipe diameter reducing means 55 include a means for providing a structure for narrowing the pipe diameter inside the discharge pipe L3, a means for inserting a structure from the outside of the discharge pipe L3, and a means for deforming the discharge pipe L3 itself by pressing the discharge pipe L3 from the outside. The gas supply means 56 is not particularly limited as long as it can supply gas from the upstream side of the pipe diameter reduction means 55 into the discharge pipe L3. An example of the gas supply means 56 is one that supplies air into the discharge pipe L3 using a pump or the like that applies pressure to air. Note that the gas supplied by the gas supply means 56 is not limited to air. For example, biogas generated in the treatment tank 2 or exhaust gas after biogas combustion may be used in addition to air.

[0097] By supplying gas (air) from the upstream side of the pipe diameter reduction means 55 using the gas supply means 56, only gas flows intermittently into the portion narrowed by the pipe diameter reduction means 55, making it possible to discontinuously flow the flow of the water W to be treated in the discharge pipe L3. This makes it possible to eliminate liquid junctions of the water W to be treated in the discharge pipe L3 or shorten the time of liquid junction.

[0098] As described above, the wastewater treatment device 1D in this embodiment is provided with the insulating mechanism 5 that insulates the water to be treated W, thereby making it possible to eliminate the liquid junction or shorten the liquid junction time between the power generation unit 3 and the water to be treated W. This prevents the electrons generated in the power generation unit 3 from flowing to anywhere other than between the electrodes 33a and 33b, thereby preventing a decrease in the efficiency of the electrochemical reaction (electrode reaction), and improves the power generation efficiency and the desulfurization treatment efficiency.

[0099] Moreover, in the wastewater treatment device 1D of this embodiment, it is possible to generate electricity and perform desulfurization treatment through the same steps as in the first embodiment.

[0100] [Fifth embodiment] FIG. 8 is a schematic explanatory diagram showing a wastewater treatment device according to the fifth embodiment of the present invention. As shown in Fig. 8, wastewater treatment device 1E according to the fifth embodiment is configured by providing a pH control means 6 between the methane fermentation tank 22 and the power generation unit 3 in wastewater treatment device 1B according to the second embodiment. Note that wastewater treatment device 1E in this embodiment has a similar configuration to that of wastewater treatment device 1B shown in Fig. 3, and description of the same configuration as that of the second embodiment will be omitted.

[0101] As described above, in the methane fermentation tank 22, the water W to be treated, which is on the acidic side, is introduced from the acid production tank 21, and the methane fermentation process proceeds. At this time, in the methane fermentation tank 22, hydrogen sulfide, which is a reducing substance, is generated as the methane fermentation process proceeds. On the other hand, it is known that the solubility of hydrogen sulfide in a solution changes depending on the pH, and that the solubility increases when the solution is made alkaline, at pH 6 or higher, and the release of hydrogen sulfide out of the solution is suppressed. Therefore, by adjusting the pH of the water W to be treated, the solubility of reducing substances (particularly hydrogen sulfide) can be changed, and the reducing substances in the water W to be treated can be dissolved in the water W to be treated.

[0102] In the wastewater treatment device 1E of this embodiment, the pH control means 6 is provided to adjust the pH of the water to be treated W after methane fermentation treatment, thereby suppressing gasification of hydrogen sulfide and making it possible to dissolve hydrogen sulfide in the water to be treated W. This increases the amount of reducing substances in the water to be treated W and increases the amount of electron donors provided for the reaction, thereby making it possible to improve the power generation efficiency and desulfurization treatment efficiency in the power generation unit 3.

[0103] The pH control means 6 is not particularly limited as long as it can adjust the pH of the water W to be treated and dissolve reducing substances in the water W to be treated in the water W to be treated. As shown in FIG. 8, the pH control means 6 may include a storage section 61 for storing a pH adjuster, an addition section 62 for adding the pH adjuster to the water W to be treated, and a pH detection section 63.

[0104] The storage section 61 is not particularly limited as long as it can store a pH adjuster. The pH adjuster stored in the storage section 61 is also not particularly limited, and it is preferable to select the type of pH adjuster according to the pH dependency of the solubility of the reducing substance. For example, when the reducing substance is hydrogen sulfide, a pH adjuster that makes the pH of the water to be treated W more alkaline can be used to increase the solubility of hydrogen sulfide. More specifically, a hydroxide such as sodium hydroxide or calcium hydroxide can be used as the pH adjuster. An acid such as hydrochloric acid or sulfuric acid may also be used as the pH adjuster.

[0105] The addition unit 62 is for adding the pH adjuster in the storage unit 61 to the water to be treated W. In this embodiment, the addition unit 62 is provided on the circulation pipe L6 as shown in FIG. The adding unit 62 in this embodiment is not particularly limited as long as it has a structure capable of adding a pH adjuster to the water W in the circulation pipe L6. For example, it may be a pipe that connects the circulation pipe L6 and the storage unit 61 and has a flow rate adjustment function.

[0106] The position of the addition unit 62 is not particularly limited, but it is preferable to select a position where the pH of the water W to be treated can be adjusted and the solubility of the reducing substance can be appropriately controlled. For example, as shown in FIG. 8, the addition unit 62 can be provided on the circulation pipe L6 that circulates the water W to be treated from the power generation unit 3 to the methane fermentation tank 22 side. In this case, the circulation pipe L6 is connected to the middle part of the methane fermentation tank 22. As a result, in the lower part of the methane fermentation tank 22, the methane fermentation process proceeds in an environment that is more acidic, while the pH adjuster added by the addition unit 62 is introduced into the middle part of the methane fermentation tank 22 via the circulation pipe L6, so that the pH of the water W to be treated in the upper part of the methane fermentation tank 22 becomes more alkaline, and hydrogen sulfide generated in the methane fermentation tank 22 can be introduced into the power generation unit 3 in a state in which it is more reliably dissolved in the water W to be treated.

[0107] 8, it is preferable to provide a pH detection unit 63 on the circulation pipe L6 that circulates the water W to be treated from the methane fermentation tank 22 to the power generation unit 3, and to control the amount of pH adjuster added from the addition unit 62 according to the detection result of the pH detection unit 63. This makes it easier to adjust the pH of the water W to be treated, and enables it to be done at an appropriate timing. As a result, it is possible to increase the amount of reducing substances in the water W to be treated that is introduced into the power generation unit 3, and increase the amount of electron donor provided for the reaction, thereby improving the power generation efficiency and desulfurization treatment efficiency in the power generation unit 3. There is no particular limitation on the means for controlling the addition unit 62 in response to the detection result of the pH detection unit 63. For example, an operator may visually check the detection result of the pH detection unit 63 and manually operate the addition unit 62 in response to the result, or the pH detection unit 63 and the addition unit 62 may be controllably connected to automate the detection of the pH of the water to be treated W and the addition of the pH adjuster.

[0108] The structure of the wastewater treatment device 1E provided with the pH adjustment means 6 is not limited to the structure of the wastewater treatment device 1B shown in Fig. 3. As another example of the wastewater treatment device 1E provided with the pH adjustment means 6, for example, an addition unit 62 may be disposed on the connection pipe L2 of the wastewater treatment device 1A shown in Fig. 1 or on the circulation pipe L5 of the wastewater treatment device 1B shown in Fig. 2. This makes it possible to adjust the pH of the water to be treated W introduced from the treatment tank 2 (methane fermentation tank 22) to the power generation unit 3 and increase the amount of reducing substances introduced to the power generation unit 3.

[0109] As described above, the wastewater treatment device 1E in this embodiment is provided with a pH control means for dissolving the reducing substances in the water to be treated, so that the reducing substances, the solubility of which changes depending on the pH, can be retained in the water to be treated in a larger amount, and the amount of reducing substances to be provided to the reaction as electron donors can be increased, thereby making it possible to improve the power generation efficiency and the desulfurization efficiency.

[0110] Moreover, in the wastewater treatment device 1E of this embodiment, it is possible to perform power generation and desulfurization treatment through the same steps as those in the first embodiment.

[0111] [Sixth embodiment] Fig. 9 is a schematic explanatory diagram showing a wastewater treatment device in the sixth embodiment of the present invention, and Figs. 10 and 11 are schematic explanatory diagrams showing other aspects of the wastewater treatment device in the sixth embodiment of the present invention. As shown in Figures 9 to 11, wastewater treatment equipment 1F according to the sixth embodiment is the wastewater treatment equipment 1B according to the second embodiment, except that it is provided with a temperature control means 7. Note that the wastewater treatment equipment 1F in this embodiment has the same configuration as the wastewater treatment equipment 1B shown in Figure 3, and the description of the same components as those in the second embodiment will be omitted.

[0112] As described above, an electrode reaction using reducing substances in the water to be treated as electron donors proceeds in the power generation section 3. Generally, it is known that an increase in temperature in an electrode reaction improves the mass transfer rate and the reaction efficiency. Therefore, by controlling the temperature related to the electrode reaction in the wastewater treatment device 1F, it is possible to improve the efficiency of the electrode reaction, and thereby increase the power generation efficiency and the desulfurization treatment efficiency.

[0113] In the wastewater treatment device 1F of this embodiment, the temperature control means 7 is provided to enable adjustment of the temperature related to the power generation unit 3. This makes it possible to increase the efficiency of the reaction in which the reducing substance serves as an electron donor, and to increase the power generation efficiency and desulfurization treatment efficiency in the power generation unit 3.

[0114] The temperature control means 7 is not particularly limited as long as it can adjust the temperature of the power generation section 3. For example, it can adjust the temperature of the power generation section 3 itself, or adjust the temperature of the solution (the water to be treated W, etc.) introduced into the power generation section 3. As the temperature control means 7, a heat source may be newly installed or a heat source may be brought in from outside the wastewater treatment equipment 1F, but it is more preferable to use a heat source within the wastewater treatment equipment 1F. This makes it possible to reduce the initial cost and running cost of the equipment related to the wastewater treatment equipment 1F.

[0115] As the temperature control means 7 in this embodiment, an existing heat exchanger 71 installed to advance the methane fermentation treatment in the methane fermenter 22 may be used. For example, as shown in FIG. 9, the power generation unit 3 may be provided near the existing heat exchanger 71, and the power generation unit 3 may be arranged so that heat is supplied from the existing heat exchanger 71 to the cells (first cell 31a and second cell 31b) and electrodes (electrodes 33a and electrodes 33b) of the power generation unit 3, as well as the circulation pipe L6 and the electron acceptor supply port 34a, thereby heating the power generation unit 3 itself and the water to be treated W and the electron acceptor introduced into the power generation unit 3. This makes it possible to control the temperature of the site where the reaction using the reducing substance in the water to be treated W as the electron donor is carried out and the substance used in the reaction, without the need to install any new equipment related to temperature control.

[0116] Another example of the temperature control means 7 is, as shown in FIG. 10, a method in which pipes 72 and 73 are provided to connect an existing heat exchanger 71 and the power generation unit 3, and a heat medium such as air or water moves through the pipes 72 and 73 to supply heat from the existing heat exchanger 71 to the power generation unit 3. This allows the temperature of the power generation unit 3 to be controlled, and the temperature of a portion where a reaction is carried out using a reducing substance in the water to be treated W as an electron donor. Note that there is no particular limitation on the means for connecting the pipes 72 and 73 to the power generation unit 3. For example, the pipes 72 and 73 may be arranged to surround the entire power generation unit 3, or the pipes 72 and 73 may be arranged to contact one of the components of the power generation unit 3 (the electrodes 33a and 33b, or the first cell 31a and the second cell 31b). As another example of the temperature control means 7, as shown in FIG. 11, pipes 74 and 75 are provided to connect an existing heat exchanger 71 and a circulation pipe L6, and a heat medium such as air or water moves through the pipes 74 and 75 to supply heat from the existing heat exchanger 71 to the water W to be treated in the circulation pipe L6. This allows the temperature of the water W to be introduced into the power generation unit 3 to be controlled, and the temperature of the substance (reducing substance) used in the reaction in which the reducing substance in the water W to be treated serves as the electron donor can be controlled. Furthermore, the point where the pipes 74 and 75 are connected can be the electron acceptor supply port 34a instead of the circulation pipe L6. This allows the heat from the existing heat exchanger 71 to be supplied to the electron acceptor, and the temperature of the substance (electron acceptor) used in the reaction in which the reducing substance in the water W to be treated serves as the electron donor can be controlled. 10 and 11 may be provided individually or in combination. It is possible to appropriately select the temperature control means 7 in consideration of the temperature control efficiency of the temperature control means 7 and the cost of the equipment.

[0117] Another example of the temperature control means 7 is to use exhaust heat from gas power generation using methane generated from the methane fermentation tank 22 instead of the existing heat exchange equipment 71. More specifically, a heat medium such as air or water heated using this exhaust heat is brought into contact with the power generation unit 3 or the circulation pipe L6 through a pipe to supply heat, thereby making it possible to control the temperature related to the reaction in which the reducing substances in the water to be treated W serve as electron donors. This improves the power generation efficiency and the desulfurization treatment efficiency, and enables the effective use of exhaust heat related to methane gas power generation.

[0118] The structure of the wastewater treatment device 1F provided with the temperature control means 7 is not limited to the structure of the wastewater treatment device 1B shown in Fig. 3. Other examples of the wastewater treatment device 1F provided with the temperature control means 7 include a structure capable of supplying heat from an existing heat exchanger 71 to those related to the reaction in which the reducing substance in the water to be treated W serves as an electron donor (power generation unit 3, connection pipe L2, etc.) in the wastewater treatment device 1A shown in Fig. 1, and those related to the reaction in which the reducing substance in the water to be treated W serves as an electron donor (power generation unit 3, circulation pipe L5, etc.) in the wastewater treatment device 1B shown in Fig. 2. This makes it possible to control the temperature related to the reaction in which the reducing substance in the water to be treated W serves as an electron donor, thereby improving the mass transfer rate and reaction efficiency related to the reaction.

[0119] As described above, the wastewater treatment device 1F in this embodiment is provided with a temperature control means for the reaction in which the reducing substance in the treated water serves as an electron donor, so that the temperature can be controlled so as to improve the mass transfer rate and reaction efficiency in the reaction in which the reducing substance serves as an electron donor, thereby making it possible to improve the power generation efficiency and the desulfurization treatment efficiency.

[0120] Moreover, in the wastewater treatment device 1F of this embodiment, it is possible to generate electricity and perform desulfurization treatment through the same steps as in the first embodiment.

[0121] The above-described embodiments are examples of the wastewater treatment device, power generation device, desulfurization treatment device, power generation method, and desulfurization method. The wastewater treatment device, power generation device, desulfurization treatment device, power generation method, and desulfurization method according to the present invention are not limited to the above-described embodiments, and the wastewater treatment device, power generation device, desulfurization treatment device, power generation method, and desulfurization method according to the above-described embodiments may be modified within the scope of the gist of the claims.

[0122] For example, when reducing substances are already contained in the water W to be treated, the wastewater treatment device in this embodiment may be configured so that the power generation unit 3 is provided upstream of the treatment tank 2. This makes it possible to perform pretreatment to reduce the reducing substances in the water W to be treated while generating electricity using the power generation unit 3. The wastewater treatment device in this embodiment may also include a plurality of power generation units (power generation devices). For example, the power generation unit shown in the first embodiment and the power generation unit shown in the second embodiment may both be included. This makes it possible to generate power at a plurality of locations by effectively utilizing the treatment in the wastewater treatment device, and also makes it possible to improve both the wastewater treatment efficiency and the power generation efficiency.

[0123] Furthermore, for example, the wastewater treatment device in this embodiment may be configured so that the electrodes 33a and 33b are provided in the settler 23 portion in the treatment tank 2 (methane fermentation tank 22) as the power generation unit 3. The electrodes 33a and 33b may be provided in the vicinity of the settler 23, or the settler 23 itself may be used as the electrodes 33a and 33b. This allows the power generation unit 3 to be incorporated in the treatment tank 2, making it possible to further reduce the size of the facility.

[0124] Furthermore, for example, in the wastewater treatment device of this embodiment, the electrode 33b may be provided in the aeration tank 41, and the aeration tank 41 may function as the second cell 31b of the power generation section 3. This allows the power generation section 3 and the reaction tank 4 (aeration tank 41) to be integrated, making it possible to further reduce the size of the equipment.

[0125] Furthermore, for example, the wastewater treatment device in this embodiment may be provided with a means for preventing adhesion and accumulation of microorganisms on the electrodes 33a and 33b. Examples of such a means include coating the electrode surfaces with a material that prevents adhesion of microorganisms, or making the electrode structure itself shaped to make it difficult for microorganisms to adhere to it. This makes it possible to suppress inhibition of the electrode reaction at the electrodes 33a and 33b by microorganisms even when microorganisms flow into the first cell 31a and the second cell 31b of the power generation unit 3.

[0126] Furthermore, for example, the wastewater treatment device in this embodiment may be configured such that some of the structures are omitted to further simplify the device structure. An example of a structure that can be omitted is the ion exchanger 32. This allows the power generation section 3 (power generation device / desulfurization treatment device) to be simplified and facilitates maintenance work. It becomes easy. Other examples of structures that can be omitted include the electron acceptor supply port 34a and the electron acceptor discharge port 34b in the second cell 31b. This allows the power generation unit 3 (power generation device / desulfurization treatment device) to be further simplified. In this case, one surface of the electrode 33b may be in contact with the water W to be treated or the ion exchanger 32, and the other surface may be in direct contact with the outside air (air) as a whole. Furthermore, it is preferable to provide a breathable material that is easily replaced or washed on the surface of the electrode 33b on the outside air side. This makes it possible to suppress the adhesion of solid impurities such as dust to the surface of the electrode 33b. [Industrial Applicability]

[0127] The wastewater treatment device, power generation method, and desulfurization method of the present invention are suitable for use in wastewater treatment for treating water to be treated that contains reducing substances, or in wastewater treatment in which reducing substances are generated by treating the water to be treated.

[0128] By applying the power generation device of the present invention to an existing wastewater treatment device, it is possible to provide the wastewater treatment device and the power generation method of the present invention without large-scale renewal of the entire wastewater treatment device. Furthermore, by applying the desulfurization treatment apparatus of the present invention to an existing wastewater treatment apparatus, it is possible to provide the wastewater treatment apparatus and desulfurization method of the present invention without requiring a large-scale renewal of the entire wastewater treatment apparatus. [Explanation of symbols]

[0129] 1A, 1B, 1C, 1D, 1E, 1F wastewater treatment device, 2 treatment tank, 21 acid generation tank, 22 methane fermentation tank, 23 settler, 3 power generation unit, 31a first cell, 31b second cell, 32 ion exchanger, 33a, 33b electrodes, 34a electron acceptor supply port, 34b electron acceptor discharge port, 4 reaction tank, 41 aeration tank, 42 ​​aeration device, 5 insulation mechanism, 51, 53 storage tank, 52 water spray means, 54 water discharge means, 54a solenoid valve, 55 pipe diameter reduction means, 56 gas supply means, 6 pH adjustment means, 61 storage unit, 62 addition unit, 63 pH detection unit, 7 temperature control means, 71 existing heat exchange equipment, 72 to 75 piping, L1 introduction piping, L2 connection piping, L3, L7 Discharge pipe, L4, L8 connection pipe, L5, L6 circulation pipe, L9 discharge pipe, W treated water, W1 treated water

Claims

1. A wastewater treatment device for treating water to be treated, The reducing substance in the water to be treated is hydrogen sulfide or hydrogen sulfide ions as an electron donor. A power generation unit that generates electricity and performs desulfurization by a reaction, The reducing substances in the water to be treated after anaerobic treatment are introduced into the power generation section, and power generation and desulfurization are performed. A wastewater treatment device comprising:

2. A power generation device provided in a wastewater treatment device that treats water to be treated, The reducing substance in the water to be treated is hydrogen sulfide or hydrogen sulfide ions as an electron donor. A power generation device which generates power and performs desulfurization.

3. A method for generating electricity in wastewater treatment for treating water to be treated, comprising the steps of: The reducing substance in the water to be treated is hydrogen sulfide or hydrogen sulfide ions as an electron donor. A power generation method comprising the steps of generating power and performing a desulfurization treatment.

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