Wastewater treatment device, power generation device, desulfurization treatment device, 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 apparatus involving power generation or desulfurization treatment. The present invention also relates to a power generation apparatus and a power generation method for wastewater treatment. Furthermore, the present invention relates to a desulfurization treatment apparatus and a desulfurization method for wastewater treatment. BACKGROUND ART

[0002] Generally, as a method for treating wastewater containing organic matter, biological treatment using various microorganisms is known. In particular, biological treatment under an anaerobic environment (hereinafter referred to as "anaerobic treatment") is widely used because it has high advantages for introduction such as no requirement for aeration power and almost no generation of excess sludge. In addition, various treatment processes and techniques have also been combined with wastewater treatment by anaerobic treatment. For example, as one of the techniques associated with anaerobic treatment, it is known to generate power by using biogas such as methane generated by anaerobic treatment as fuel.

[0003] On the other hand, microbial fuel cells are known as a technique for generating power utilizing redox reactions by microorganisms. Microbial fuel cells obtain electrical energy by utilizing the metabolic capacity of microorganisms. More specifically, a microbial fuel cell has a configuration in which electrons generated in the process of oxidative decomposition of a substrate such as an organic substance by microorganisms are collected on the anode side, and electrons are moved to the cathode side to obtain an electric current.

[0004] For example, Patent Document 1 describes a power generation device in which one electrode of a pair is used as an anode and is in contact with a solution (suspension) containing microorganisms that can grow under anaerobic conditions and organic matter, and the other electrode is formed as a cathode from a material with structural voids and is in 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 surface of the anode. Furthermore, Patent Document 1 describes a power generation method using this power generation device in which an oxidation reaction by microorganisms using the organic matter at the anode as an electron donor and a reduction reaction using oxygen at the cathode as an electron acceptor are carried out. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2004-342412 [Overview of the project] [Problems that the invention aims to solve]

[0006] Power generation using microbial fuel cells, as described in Patent Document 1, has low energy conversion efficiency, and improving power output is a major challenge for practical application. This is presumed to be due to the fact that the transfer of mass to the electrodes is inhibited by the microorganisms, as the microorganisms are in direct contact with or supported on the electrodes, and the metabolic rate of the microorganisms becomes the rate-limiting factor.

[0007] Furthermore, in recent years, in order to reduce the power consumption required to drive equipment during wastewater treatment and to achieve superior energy conservation, there has been a demand for technologies that enable efficient energy recovery and utilization as an accessory to wastewater treatment. As one such technology, a technology that applies microbial fuel cells to wastewater treatment and generates electricity simultaneously is being considered, but as mentioned above, there is a challenge in obtaining sufficient power output.

[0008] Furthermore, in addition to efficient energy recovery and utilization, technologies for wastewater treatment also require the efficient removal of harmful substances from the treated water during treatment. In particular, such technologies require the efficient removal of hydrogen sulfide generated during wastewater treatment.

[0009] The 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 that enable more efficient energy recovery and utilization or desulfurization treatment as technologies associated with wastewater treatment. [Means for solving the problem]

[0010] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have discovered that by performing a reaction using reducing substances in the treated water during wastewater treatment, it becomes possible to efficiently recover and utilize energy through power generation and to desulfurize the treated water during wastewater treatment, thereby completing the present invention. In other words, 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 apparatus of the present invention, which solves the above problems, is a wastewater treatment apparatus that treats water to be treated and is characterized by generating electricity through a reaction in which reducing substances in the water to be treated are used as electron donors.

[0012] The wastewater treatment device of the present invention generates electricity by directly using reducing substances contained in the treated water as electron donors, thus preventing inhibition of mass transfer by microorganisms, and thus enabling efficient power generation. Furthermore, it is possible to miniaturize the equipment compared to power generation using microbial fuel cells.

[0013] Furthermore, another embodiment of the wastewater treatment apparatus of the present invention for solving the above problems is a wastewater treatment apparatus for treating water to be treated, characterized in that it performs desulfurization treatment by a reaction using reducing substances in the water to be treated as electron donors.

[0014] The wastewater treatment apparatus of the present invention can convert hydrogen sulfide, which is a reducing substance, into sulfur by directly using a reducing substance contained in the water to be treated as an electron donor to perform desulfurization treatment, thereby enabling efficient removal of hydrogen sulfide from the water to be treated.

[0015] Furthermore, one embodiment of the wastewater treatment apparatus of the present invention is characterized by the installation of electrodes in the water to be treated and the generation of electricity. This feature allows for power generation within the wastewater treatment process by directly installing electrodes in the water being treated before it is introduced into the wastewater treatment system. This enables efficient power generation without increasing the size of the equipment. Furthermore, during this process, an electrode reaction proceeds using hydrogen sulfide contained in the water being treated as an electron donor, converting it into sulfur. Therefore, efficient desulfurization can be performed without the need for separate desulfurization equipment.

[0016] Furthermore, one embodiment of the wastewater treatment apparatus of the present invention is characterized by having an ion exchanger placed between electrodes. This feature makes it possible to increase the efficiency of electron transfer between a pair of electrodes, thereby further improving power generation efficiency and desulfurization efficiency.

[0017] Furthermore, one embodiment of the wastewater treatment apparatus of the present invention is characterized by having a treatment tank for treating the water to be treated, and a power generation unit located downstream of the treatment tank, wherein reducing substances in the water to be treated after treatment by the treatment tank are introduced into the power generation unit to generate electricity. 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. This feature allows for the separation of the treatment tank that processes the water to be treated from the power generation unit that generates electricity. This avoids the trade-off between wastewater treatment efficiency and power generation efficiency, as wastewater treatment and power generation do not need to be performed simultaneously in one location. In particular, by using the reducing substances generated by the treatment of the water to be treated as electron donors, it becomes possible not only to generate electricity but also to oxidize (desulfurize) the reducing substances contained in the treated water after wastewater treatment, thereby improving the overall wastewater treatment efficiency.

[0018] Furthermore, one embodiment of the wastewater treatment apparatus of the present invention is characterized by providing a pH control means for dissolving reducing substances in the water to be treated. This characteristic allows for the retention of more reducing substances, whose solubility in the treated water varies depending on the pH, in the treated water. This increases the amount of reducing substances available for the reaction as electron donors. As a result, it becomes possible to improve power generation efficiency and desulfurization efficiency.

[0019] Furthermore, one embodiment of the wastewater treatment apparatus of the present invention is characterized by providing a temperature control means for a reaction in which a reducing substance in the water to be treated is used as an electron donor. This characteristic makes it possible to control the temperature in reactions using reducing substances as electron donors to improve mass transfer rates and reaction efficiency. This, in turn, makes it possible to increase power generation efficiency and desulfurization efficiency.

[0020] Furthermore, the present invention, which solves the above problems, is a power generation device installed in a wastewater treatment device that treats water to be treated, and is characterized by generating electricity using reducing substances in the water to be treated as electron donors. The power generation device of the present invention performs power generation by directly using reducing substances contained in water to be treated as electron donors, which avoids the inhibition of mass transfer caused by microorganisms, thereby enabling efficient power generation. In addition, it allows for miniaturization of the equipment compared with power generation by microbial fuel cells. Furthermore, by applying the present invention to an existing wastewater treatment apparatus, it becomes possible to update the wastewater treatment apparatus to one that can perform power generation without large-scale renovation of the entire wastewater treatment apparatus.

[0021] Furthermore, the desulfurization treatment apparatus of the present invention for solving the above problems is a desulfurization treatment apparatus provided in a wastewater treatment apparatus that treats water to be treated, and is characterized in that reducing substances in the water to be treated are used as electron donors for desulfurization treatment. The desulfurization treatment apparatus of the present invention performs desulfurization treatment by directly using reducing substances contained in water to be treated as electron donors, which enables efficient desulfurization without discharging hydrogen sulfide out of the system. In addition, by applying the present invention to an existing wastewater treatment apparatus, it becomes possible to update the wastewater treatment apparatus to one that can perform desulfurization treatment without large-scale renovation of the entire wastewater treatment apparatus.

[0022] Furthermore, the power generation method of the present invention for solving the above problems is a power generation method for wastewater treatment that treats water to be treated, and is characterized by comprising 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 performs power generation by directly using reducing substances contained in water to be treated as electron donors, which avoids the inhibition of mass transfer caused by microorganisms, thereby enabling efficient power generation. In addition, it allows for miniaturization of the equipment compared with power generation by microbial fuel cells.

[0023] Furthermore, the desulfurization method of the present invention for solving the above problems is a desulfurization method for wastewater treatment that treats water to be treated, and is characterized by comprising a step of subjecting reducing substances in the water to be treated to desulfurization treatment using the same as electron donors. In the desulfurization method of the present invention, desulfurization treatment is performed using reducing substances contained in water to be treated directly as electron donors, thereby enabling efficient desulfurization without discharging hydrogen sulfide out of the system.

Effects of the Invention

[0024] According to the present invention, as a technology accompanying wastewater treatment, a wastewater treatment device, a power generation device, a desulfurization treatment device, a power generation method and a desulfurization method that enable more efficient energy recovery, utilization or desulfurization treatment can be provided.

Brief Description of Drawings

[0025] [Figure 1] It is a schematic explanatory diagram of the wastewater treatment device according to the first embodiment of the present invention. [Figure 2] It is a schematic explanatory diagram of the wastewater treatment device according to the second embodiment of the present invention. [Figure 3] It is a schematic explanatory diagram showing another aspect of the wastewater treatment device according to the second embodiment of the present invention. [Figure 4] It is a schematic explanatory diagram of the wastewater treatment device according to the third embodiment of the present invention. [Figure 5] It is a schematic explanatory diagram of the wastewater treatment device according to the fourth embodiment of the present invention. [Figure 6] It is a schematic explanatory diagram showing another aspect of the wastewater treatment device according to the fourth embodiment of the present invention. [Figure 7] It is a schematic explanatory diagram showing another aspect of the wastewater treatment device according to the fourth embodiment of the present invention. [Figure 8] It is a schematic explanatory diagram of the wastewater treatment device according to the fifth embodiment of the present invention. [Figure 9] It is a schematic explanatory diagram of the wastewater treatment device according to the sixth embodiment of the present invention. [Figure 10] It is a schematic explanatory diagram showing another aspect of the wastewater treatment device according to the sixth embodiment of the present invention. [Figure 11] It is a schematic explanatory diagram showing another aspect of the wastewater treatment device according to the sixth embodiment of the present invention. [Modes for carrying out the invention]

[0026] Hereinafter, embodiments of the wastewater treatment apparatus, power generation apparatus, desulfurization treatment apparatus, 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 in the present invention will be replaced by the description of the operation of the wastewater treatment apparatus, power generation apparatus, and desulfurization treatment apparatus according to the present invention. The wastewater treatment apparatus, power generation apparatus, desulfurization treatment apparatus, power generation method, and desulfurization method described in the embodiments are merely illustrative examples for illustrating the wastewater treatment apparatus, power generation apparatus, desulfurization treatment apparatus, power generation method, and desulfurization method according to the present invention, and are not limited thereto.

[0027] In the wastewater treatment apparatus of the present invention, the water to be treated is not particularly limited as long as it contains reducing substances. The reducing substances may be present in the water to be treated before it is introduced into the wastewater treatment apparatus, or they may be generated during the treatment process in the wastewater treatment apparatus and present in the water to be treated. Specific examples of water to be treated include industrial wastewater discharged from various factories such as food processing plants, chemical plants, and paper and pulp factories, as well as domestic wastewater such as sewage. In the following embodiments, the water to be treated will mainly consist of water that generates reducing substances through treatment, but the invention is not limited to this.

[0028] Furthermore, 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 or not a substance functions as an electron donor is relatively determined by its 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 is one that is more likely to release electrons than an electron acceptor, that is, one with a lower oxidation-reduction potential than an electron acceptor. For example, when oxygen is used as the electron acceptor, the reducing substance in the present invention is one with a lower oxidation-reduction potential than oxygen, and examples of such reducing substances include hydrogen sulfide, hydrogen, and ammonia.

[0029] [First Embodiment] (Wastewater treatment equipment) Figure 1 is a schematic diagram illustrating the structure of a wastewater treatment apparatus in a first embodiment of the present invention. As shown in Figure 1, the wastewater treatment device 1A in this embodiment comprises a treatment tank 2 and a power generation unit 3. The wastewater treatment device 1A also includes an introduction pipe L1 for introducing the water to be treated W into the treatment tank 2, a connecting pipe L2 for connecting the treatment tank 2 and the power generation unit 3, and a discharge pipe L3 for discharging the water to be treated W from the power generation unit 3. The water to be treated W is introduced into the power generation unit 3 after being treated in the treatment tank 2.

[0030] (Processing tank) Treatment tank 2 is a tank for treating the water to be treated W. The treatment performed in treatment tank 2 is not particularly limited as long as it is appropriate for the target substance contained in the water to be treated W and the treated water W contains reducing substances after treatment. Examples include biological treatment and chemical treatment (chemical additive, ozone treatment, etc.), but it is desirable to use biological treatment, which does not involve the use or generation of substances harmful to the human body and can be performed at a relatively low cost. Furthermore, examples of biological treatment include, for instance, anaerobic treatment in an anaerobic environment, such as methane fermentation by acid-producing and methane-producing bacteria, denitrification treatment using denitrifying bacteria to reduce nitrates and nitrites, and sulfate reduction treatment using sulfate-reducing bacteria to reduce sulfuric acid. In addition, examples of biological treatment in an aerobic environment include activated sludge treatment using activated sludge. From the viewpoint of treatment costs and the usefulness of the produced gas, anaerobic treatment is preferred as a biological treatment, and methane fermentation, which produces methane, is particularly preferred.

[0031] In treatment tank 2, when methane fermentation is performed as part of anaerobic treatment, in addition to methane, hydrogen sulfide, hydrogen, ammonia, etc., are generated in the treated water W. These products correspond to the reducing substances in this invention.

[0032] The treated water W, processed in the treatment tank 2, contains reducing substances and is introduced to the power generation unit 3 via the connecting pipe L2.

[0033] (Power Generation Section (Power Generation Equipment / Desulfurization Treatment Equipment)) The power generation unit 3 is for generating electricity using reducing substances in the treated water W as electron donors. Furthermore, in this embodiment, the power generation unit 3 can also perform desulfurization by using sulfur-containing compounds such as hydrogen sulfide as electron donors among the reducing substances in the treated water W. The structure of the power generation unit 3 of this embodiment will be described below from the perspective of power generation. Details of the desulfurization treatment by the power generation unit 3 of this embodiment will be described later.

[0034] As shown in Figure 1, the power generation unit 3 of this embodiment is located downstream of the processing tank 2 and comprises a first cell 31a and a second cell 31b, an ion exchanger 32 provided to partition the cells 31a and 31b, and electrodes 33a and 33b arranged in cells 31a and 31b, respectively. Here, the first cell 31a is formed so that the water to be treated W introduced from the processing tank 2 via the connecting pipe L2 comes into contact with the electrode 33a, and the electrode 33a placed in the first cell 31a functions as an anode. On the other hand, the second cell 31b is formed to store or supply electron acceptors, and the electrode 33b placed in the second cell 31b functions as a cathode. Furthermore, electrodes 33a and 33b are connected to an external circuit by a conductor (not shown). This makes it possible to recover and utilize the electrical energy generated in the power generation unit 3 by the action of reducing substances as electron donors.

[0035] The first cell 31a is equipped with an electrode 33a and is formed so that the water to be treated W comes into contact with the electrode 33a; its material and shape are not particularly limited. For example, as shown in Figure 1, it may have a space that can temporarily store the water to be treated W introduced via a connecting pipe L2, and a discharge pipe L3 for discharging the water to be treated W after it has come into contact with the electrode 33a. In this way, the reducing substances in the water to be treated W donate electrons to the electrode 33a as electron donors and are then quickly discharged through the discharge pipe L3. Furthermore, a flow rate adjustment mechanism such as a valve may be provided in the connecting pipe L2 and / or the discharge pipe L3. This makes it possible to adjust the amount and flow rate of the water to be treated W that comes into contact with the electrode 33a, and to control the mass transfer rate to the electrode 33a.

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

[0037] The second cell 31b is equipped with an electrode 33b and is formed to store or supply electron acceptors to reducing substances in the water to be treated W, and is not limited in terms of material or shape.

[0038] Here, the electron acceptor may be in the form of either a gas or a liquid. The liquid may be a solution in which a solid drug is dissolved, or a solution in which a gas is mixed (dissolved). In this embodiment, specific examples of electron acceptors include, for example, gases such as oxygen and oxygen-containing gases. Oxygen-containing gases include those that contain oxygen as a mixture, such as air, and those that contain oxygen as an element constituting a compound, such as carbon dioxide. When a gas is used as an electron acceptor, there are advantages such as the fact that the treatment of waste products 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. Furthermore, other examples of electron acceptors in this embodiment include, for example, solutions containing dissolved oxygen or aqueous solutions of oxidizing agents such as potassium ferricyanide, as liquids. When a liquid is used as the electron acceptor, it has the advantage of making it easier to handle compounds (oxidizing agents) that are highly effective as electron acceptors, thereby further improving power generation efficiency. From the viewpoint of improving 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 Figure 1, the second cell 31b may be provided with an electron acceptor supply port 34a for supplying gaseous electron acceptors (oxygen, air, etc.) to the electrode 33b, and an electron acceptor outlet 34b for discharging the gas after the reaction. Another example of the second cell 31b is to provide a space in the second cell 31b that can store liquid, and to provide an electron acceptor supply port 34a and an electron acceptor outlet 34b that can supply the electron acceptor solution and discharge the solution after the reaction, respectively. As a result, electrons from electrode 33a can be received by the electron acceptor via electrode 33b, and an electric current flows between electrode 33a and electrode 33b to generate electricity. The electron acceptor after the reaction is quickly discharged to the outside of the power generation unit 3 via the electron acceptor outlet 34b. Furthermore, a flow rate adjustment mechanism such as a valve may be provided at the electron acceptor supply port 34a and / or electron acceptor outlet port 34b to adjust the concentration of the electron acceptor in the second cell 31b. In addition, a control mechanism may be provided to control the flow rate adjustment mechanism so that the electron acceptor concentration is maintained in proportion to the amount of electrons generated by the reaction at electrode 33a. This makes it possible to suppress the decrease in reaction efficiency related to electron transfer between electrode 33a and electrode 33b, and thereby suppress the decrease in power generation efficiency.

[0040] In Figure 1, the electron acceptor supply port 34a and electron acceptor outlet 34b are shown as one each, but the design is not limited to this. For example, multiple electron acceptor supply ports 34a and electron acceptor outlets 34b may be provided. In particular, when an oxygen-containing gas is used as the electron acceptor, water is produced by the reaction at electrode 33b, as will be described later. Therefore, when multiple electron acceptor outlets 34b are provided, for example, one can be provided to discharge gas and the other to discharge liquid.

[0041] The ion exchanger 32 can be any known configuration that allows ions to pass through, and is not particularly limited. In particular, it is preferable to use a cation exchange membrane that can allow hydrogen ions generated at electrode 33a (anode side) to pass through. This allows hydrogen ions to move from electrode 33a (anode side) to electrode 33b (cathode side), thereby increasing the reaction efficiency of the electron acceptor at electrode 33b and improving power generation efficiency. Furthermore, it is more preferable that the ion exchanger 32 has low oxygen permeability. This suppresses the movement of electron acceptors (oxygen) supplied to electrode 33b (cathode side) to electrode 33a, and prevents the reaction efficiency of the electron donor at electrode 33a from decreasing due to oxygen. In Figure 1, the ion exchanger 32 is shown as being provided separately from electrodes 33a and 33b, but this is not the only option. For example, the ion exchange material can be integrated with electrodes 33a and / or 33b. This makes it possible to miniaturize the entire power generation unit 3 and reduce the time required for maintenance work.

[0042] Electrode 33a is an electrode that recovers electrons from reducing substances in the water to be treated W, and functions as a so-called anode. In this embodiment, electrode 33a is placed in the first cell 31a so as to be in contact with the water to be treated W after it has been treated in the treatment tank 2.

[0043] The electrode 33a can function as an anode, and its material and shape are not particularly limited. The material and shape of the electrode 33a can be appropriately selected considering the cost of material procurement and processing, the reaction efficiency of reducing substances in the electrode 33a, etc. Examples of materials for the electrode 33a include carbon and metals (stainless steel, platinum, copper, etc.) which are widely used as electrode materials in the field of electrochemistry. Examples of shapes for the electrode 33a include flat plates, rods, meshes, etc.

[0044] In this embodiment, the electrode 33a does not have microorganisms in contact with or supported on its surface. Therefore, the mass transfer of reducing substances is not inhibited by microorganisms, the reaction efficiency as an electron donor (the mass transfer rate of reducing substances to the electrode 33a) can be improved, and the power generation efficiency can be improved. Furthermore, in this embodiment, electrode 33a does not recover electrons generated by the metabolism of microorganisms, but rather recovers electrons directly from reducing substances. Therefore, the metabolism of microorganisms does not become the rate-limiting factor, the reaction efficiency as an electron donor (the rate of electron recovery at electrode 33a) is improved, and the power generation efficiency can be improved.

[0045] Furthermore, in this embodiment, the electrode 33a does not require processing to make its structure suitable for retaining microorganisms, thus reducing the cost associated with manufacturing the electrode 33a. Also, considering the amount of microorganisms that can be retained by the electrode 33a and the reaction efficiency by the microorganisms, there is no need to enlarge the electrode 33a, which makes it possible to miniaturize the equipment related to the wastewater treatment device 1.

[0046] Electrode 33b is the counter electrode to electrode 33a and is the electrode that transfers electrons to the electron acceptor, functioning as a so-called cathode. Furthermore, in this embodiment, electrode 33b is located within the second cell 31b.

[0047] The electrode 33b can function as a cathode, and its material and shape are not particularly limited. The material and shape of the electrode 33b can be appropriately selected considering the cost of material procurement and processing, the reaction efficiency of the electron acceptor in the electrode 33b, etc. Examples of materials for the electrode 33b include carbon and metals (stainless steel, platinum, copper, etc.) which are widely used as electrode materials in the field of electrochemistry. Examples of shapes for the electrode 33b include flat plates, rods, meshes, etc.

[0048] When the electron acceptor supplied to the second cell 31b is a gas (air), one side of the electrode 33b is in contact with the gas, while the other side is in contact with the water to be treated W. For this reason, it is preferable that the electrode 33b be in a form suitable as a so-called air cathode. A suitable form for an air cathode is, for example, one that possesses both gas permeability and water impermeability. By making the electrode 33b gas permeable, it becomes possible to effectively react the gas, which is the electron acceptor, at the electrode 33b. Furthermore, by making the electrode 33b water impermeable, it becomes possible to suppress the water to be treated W in the first cell 31a from permeating through the electrode 33b and flowing into the second cell 31b. Specific examples of such an electrode 33b include one made of carbon fiber, or one in which a metal mesh surface has been treated by coating it with a material that has gas permeability and water impermeability, or by laminating a film. In this context, impermeability refers to the inability to allow water to pass through. For example, waterproofing, water-repellenting, hydrophobicating, or water-stopping the electrode 33b is also included in the definition of impermeability.

[0049] In this embodiment, the wastewater treatment device 1A uses a reducing substance in the water to be treated W as an electron donor and performs power generation or desulfurization treatment by electrochemical reaction (electrode reaction). Generally, when performing an electrochemical reaction, a problem arises in which the efficiency of the electrochemical reaction decreases due to the movement of electrons to parts other than the part where the electrochemical reaction actually takes place (power generation unit 3). Therefore, in this embodiment, it is preferable to insulate parts other than the part where the electrochemical reaction takes place (power generation unit 3) of the wastewater treatment device 1A. Specific examples of insulation treatment include, for example, installing the treatment tank 2 and reaction tank 4 on top of an insulator, constructing the outer or inner walls of the treatment tank 2 and reaction tank 4 with an insulator, or coating the outer or inner walls of the treatment tank 2 and reaction tank 4 with an insulating material. Furthermore, as for the insulation treatment of the introduction pipe L1, connecting pipe L2, and discharge pipe L3, for example, each pipe may be made of an insulator, or each pipe may be coated with an insulating material.

[0050] In the wastewater treatment apparatus 1A of the above embodiment, power generation or desulfurization treatment can be performed by a reaction using reducing substances in the treated water W as electron donors. The following provides a detailed explanation of the power generation and desulfurization treatment in wastewater treatment device 1A.

[0051] (Power generation and desulfurization treatment in wastewater treatment equipment) Based on Figure 1, the reactions and processes related to power generation and desulfurization in the wastewater treatment apparatus 1A of the first embodiment of the present invention will be described. The reactions and processes related to power generation in the wastewater treatment apparatus of this embodiment will be described in which a reducing substance produced by anaerobic treatment of the water to be treated W is used as an electron donor and air (oxygen) is used as an electron acceptor. In particular, the use of hydrogen sulfide as an electron donor corresponds to the reactions and processes related to desulfurization in the wastewater treatment apparatus of this embodiment. The description of the reactions and processes based on Figure 1 is an example of power generation and desulfurization treatment in this embodiment, and is not limited to this example. Furthermore, the following description concerns the reactions and processes from the treatment tank 2 to the power generation unit 3, and the reactions and processes related to other components (such as the introduction pipe L1, discharge pipe L3, and reaction tank 4) are omitted. In addition, the notations for reactions R1 to R4 and processes S1 to S3 are assigned for explanatory purposes only and do not specify the order of the reactions and processes.

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

[0053] The treated water W, which has been treated in the treatment tank 2 and contains reducing substances, is introduced into the first cell 31a in the power generation unit 3 via the connecting pipe L2 (step S2). Here, when the reducing substance (hydrogen, hydrogen sulfide, ammonia, etc.) comes into contact with the electrode 33a, the reducing substance functions as an electron donor and donates electrons to the electrode 33a. Taking hydrogen sulfide as an example of the reducing substance that functions as an electron donor, the reaction at the electrode 33a (reaction R1) is shown by the following reaction equation (equation 1).

number

[0054] Furthermore, some of the hydrogen sulfide reacts as hydrogen sulfide ions. This reaction is represented by the following reaction equation (Equation 2).

number

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

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

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

number

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

[0059] As described above, by using the wastewater treatment device of this embodiment, it is possible to improve power generation efficiency and desulfurization efficiency by eliminating inhibition of mass transfer by microorganisms and rate-limiting steps based on the metabolic rate of microorganisms. Furthermore, the equipment can be made smaller compared to power generation using microbial fuel cells. Moreover, it is possible to perform efficient desulfurization without installing separate equipment for desulfurization.

[0060] In conventional power generation using microbial fuel cells, 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 apparatus and power generation method of this embodiment can perform wastewater treatment and power generation separately. Therefore, in the wastewater treatment apparatus and power generation method of this embodiment, there is no trade-off between wastewater treatment efficiency and power generation efficiency, enabling efficient power generation.

[0061] Furthermore, the configuration of the power generation unit 3 in this embodiment can be made into an independent power generation device or desulfurization device according to the present invention. This power generation device or desulfurization device can be applied to existing wastewater treatment devices. This makes it possible to provide the wastewater treatment device of the present invention without extensively updating the entire wastewater treatment device. In addition, a power generation method or desulfurization method using this wastewater treatment device can be provided.

[0062] [Second Embodiment] Figure 2 is a schematic diagram illustrating a wastewater treatment apparatus in a second embodiment of the present invention. Figure 3 is a schematic diagram illustrating another embodiment of the wastewater treatment apparatus in a second embodiment of the present invention. The wastewater treatment apparatus 1B according to the second embodiment has a treatment tank 2 consisting of an acid generation tank 21 and a methane fermentation tank 22. The power generation unit 3 is installed on a circulation channel provided in the treatment tank 2 (acid generation tank 21 and methane fermentation tank 22). Here, the wastewater treatment apparatus 1B shown in Figures 2 and 3 each show the installation location of the power generation unit 3 in different places. The same configuration as that of the first embodiment will not be explained.

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

[0064] In this embodiment, the treatment tank 2 comprises an acid generation tank 21 and a methane fermentation tank 22. The acid generation tank 21 and the methane fermentation tank 22 are reaction tanks for anaerobic treatment of the water to be treated W by microorganisms contained inside. It is preferable that the acid generation tank 21 and the methane fermentation tank 22 have a ceiling and form a closed space in order to maintain anaerobic conditions.

[0065] The acid generation tank 21 takes the water to be treated W introduced through the introduction pipe L1 and performs an acid generation treatment by using acid-producing bacteria (mainly anaerobic acid-producing bacteria) contained inside to decompose solids and high molecular weight organic substances such as sugars, proteins, and oils, producing monosaccharides, amino acids, lower fatty acids, and acetic acid. The water to be treated W in the acid generation tank 21 is supplied to the methane fermentation tank 22 via the connecting pipe L4.

[0066] The acid generating tank 21 may also be equipped with means for adjusting the internal water temperature, means for adding a pH adjusting agent, and means for adding metals such as nitrogen, phosphorus, cobalt, and nickel, which are nutrients required by the bacteria (not shown).

[0067] The methane fermentation tank 22 performs methane fermentation, which generates methane from monosaccharides, amino acids, lower fatty acids, and acetic acid contained in the treated water W supplied by the connecting pipe L4 in the acid production tank 21. The methane fermentation is carried out in an anaerobic atmosphere without dissolved oxygen using methane-producing bacteria maintained by methods such as the suspension method, fixed bed method, fluidized bed method, UASB (Upflow Anaerobic Sludge Blanket) method, and EGSB (Expanded Granular Sludge Bed) method.

[0068] A granule layer containing anaerobic bacteria suitable for anaerobic treatment is formed in the methane fermentation tank 22. When the water to be treated W is introduced into the methane fermentation tank 22 from the acid production tank 21, methane fermentation is carried out by the anaerobic bacteria contained in the granule layer. As a result, gas mainly composed of methane and carbon dioxide is generated in the methane fermentation tank 22, and water to be treated W containing reducing substances is produced. 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 outside the tank or recovered (not shown). The water to be treated W produced in the methane fermentation tank 22 is discharged outside the treatment system via the discharge pipe L7.

[0069] Furthermore, the methane fermentation tank 22 may be equipped with various additional facilities. For example, it may be equipped with means for adjusting the internal water temperature, means for adding pH adjusters, and means for adding nutrients required by the bacteria, such as nitrogen, phosphorus, cobalt, and nickel (not shown).

[0070] The methane fermentation tank 22 is preferably equipped with means for recovering, purifying, and storing methane gas from the gas generated within the methane fermentation tank 22. This makes it possible to recover and effectively utilize methane gas, a useful energy source, from the treated water W, in addition to power generation by the power generation unit 3. Furthermore, the methane fermentation tank 22 may be equipped with means for recovering, purifying, and storing carbon dioxide gas from the gas generated in the methane fermentation tank 22, and may also be equipped with 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 utilize carbon dioxide gas as an electron acceptor and to reduce the supply cost of the electron acceptor.

[0071] Furthermore, the methane fermentation tank 22 in this embodiment is equipped with circulation piping L5 and / or circulation piping L6. Circulation piping L5 supplies the water to be treated W from the upper part of the methane fermentation tank 22 to the acid generation tank 21, forming a circulation channel between the acid generation tank 21 and the methane fermentation tank 22. Circulation piping L6 supplies the water to be treated W from the upper part of the methane fermentation tank 22 to the lower part of the methane fermentation tank 22, forming a circulation channel within the methane fermentation tank 22.

[0072] In this embodiment, the power generation unit 3 is provided on a circulation path formed by circulation pipes L5 and L6.

[0073] As shown in Figure 2, in the case where the power generation unit 3 is installed on the circulation piping L5, the water to be treated W from the methane fermentation tank 22 is supplied to the first cell 31a, and the water to be treated W after the reaction at electrode 33a is supplied to the acid generation tank 21 via the circulation piping L5. At this time, the water to be treated W after the reaction at electrode 33a has an increased hydrogen ion concentration and becomes a solution with an acidic pH, as shown in Equations 1 and 2. It is generally known that in order for the reaction in the acid generation tank 21 to proceed favorably, it is preferable for the pH in the acid generation tank 21 to be on the acidic side. Therefore, the water to be treated W discharged from the power generation unit 3 to the acid generation tank 21 may be used as a pH adjuster to allow the reaction in the acid generation tank 21 to proceed 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 installed on the circulation piping 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, it becomes possible to control the amount of water W flowing into the treated water W and control the pH of the treated water W, thereby suppressing inhibition of the reaction in the acid generation tank 21.

[0074] Furthermore, as shown in Figure 3, in the case where the power generation unit 3 is installed on the circulation pipe L6, the water to be treated W from the upper part of the methane fermentation tank 22 is supplied to the first cell 31a, and the water to be treated W after the reaction at electrode 33a is supplied to the lower part of the methane fermentation tank 22 via the circulation pipe L6. At this time, the water to be treated W after the reaction at electrode 33a becomes a solution with a reduced concentration of dissolved hydrogen sulfide, as shown in Equations 1 and 2. It is known that methanogenic bacteria contained in the granule layer in the methane fermentation tank 22 have their metabolism inhibited by hydrogen sulfide. Therefore, the water to be treated W discharged from the power generation unit 3 to the lower part of the methane fermentation tank 22 has the effect of being able to circulate within the methane fermentation tank 22 without inhibiting methane fermentation.

[0075] As described above, the wastewater treatment apparatus 1B in this embodiment can perform wastewater treatment under conditions suitable for each treatment (acid production treatment and methane fermentation) by configuring the treatment tank 2 with an acid production tank 21 and a methane fermentation tank 22, thereby further improving wastewater treatment efficiency. Furthermore, in this embodiment, the wastewater treatment device 1B is configured such that the power generation unit 3 is installed on a circulation channel provided in the treatment tank 2 (acid generation tank 21 and methane fermentation tank 22). This allows the water to be treated W supplied to the first cell 31a to be supplied back to the treatment tank 2 (acid generation tank 21 or methane fermentation tank 22) after the reaction. As a result, the water to be treated W is repeatedly treated, improving wastewater treatment even for the water to be treated W discharged from the power generation unit 3. Additionally, by reintroducing the water to be treated W discharged from the power generation unit 3 into the treatment tank 2 (acid generation tank 21 or methane fermentation tank 22), the reaction in the treatment tank 2 can be carried out under favorable conditions.

[0076] In this embodiment, the power generation unit 3 is installed on a circulation channel that circulates the treated water W above the methane fermentation tank 22. Therefore, it is presumed that the amount of microorganisms present in the treated water W within the circulation channel is relatively small. Consequently, the influence of microorganisms on the reaction in the power generation unit 3 can be suppressed, and the power generation efficiency can be improved.

[0077] In this embodiment of the wastewater treatment device 1B, the treated water W discharged through the discharge pipe L7 can be discharged directly into rivers or other bodies of water if it meets the water quality requirements for discharge into rivers or the like. Alternatively, a reaction tank 4, as shown in the first embodiment, may be provided downstream of the discharge pipe L7. This further improves the treatment efficiency of the treated water W by processing it in the reaction tank 4, making it possible to discharge the treated water W from the wastewater treatment device 1B to the outside of the system.

[0078] Furthermore, in the wastewater treatment apparatus 1B of this embodiment, power generation and desulfurization treatment can be performed by the same process as in the first embodiment.

[0079] [Third Embodiment] Figure 4 is a schematic diagram illustrating a wastewater treatment apparatus in a third embodiment of the present invention. As shown in Figure 4, the wastewater treatment apparatus 1C according to the third embodiment is configured such that, in the wastewater treatment apparatus 1A according to the first embodiment, the reaction tank 4 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 unit by a connecting pipe L8. Note that the same configuration as in the first embodiment will not be described.

[0080] In this embodiment, the wastewater treatment device 1C supplies treated water W1 from the aeration tank 41 to the power generation unit 3 and uses it as an electron acceptor in the power generation unit 3. Any treated water W1 other than that supplied to the power generation unit 3 via the connecting pipe L8 is discharged outside the system.

[0081] The aeration tank 41 uses an aeration device 42 to aerate the water to be treated W introduced into the tank with an oxygen-containing gas (oxygen, air, etc.), thereby promoting aerobic treatment by aerobic microorganisms and oxidation reactions by dissolved oxygen. In this embodiment, the aeration tank 41 is not limited to one in which the water to be treated W discharged from the first cell 31a of the power generation unit 3 is introduced and aeration is performed on the introduced water to be treated W, as shown in Figure 4. Other examples of the aeration tank 41 include, for example, one in which the water to be treated W is introduced directly 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 to be treated W in the aeration tank 41. For example, a combination of a blower and an aeration pipe is widely used in aeration treatment.

[0083] Since oxygen-containing gas is introduced into the aeration tank 41 by the aeration device 42, the treated water W1 in the aeration tank 41 is a liquid containing dissolved oxygen. Therefore, the treated water W1 introduced into the second cell 31b of the power generation unit 3 via the connecting pipe L8 becomes an electron acceptor in the power generation unit 3. This makes it possible to generate electricity by effectively utilizing the materials generated in the treatment process within 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 rivers or other bodies of water, it can be discharged as is. Alternatively, the discharged treated water W may be returned to the aeration tank 41 and subjected to aeration treatment again. This makes it possible to more reliably control the water quality of the treated water W1 discharged outside the system.

[0085] As described above, the wastewater treatment device 1C in this embodiment can utilize the materials generated in the processing steps carried out within the wastewater treatment device 1C as electron donors and electron acceptors in the power generation unit 3, and in particular, it is possible to reduce the running costs related to power generation.

[0086] Furthermore, in the wastewater treatment apparatus 1C of this embodiment, power generation and desulfurization treatment can be performed by the same process as in the first embodiment.

[0087] [Fourth Embodiment] Figure 5 is a schematic diagram illustrating a wastewater treatment apparatus according to a fourth embodiment of the present invention. Figures 6 and 7 are schematic diagrams illustrating another aspect of the wastewater treatment apparatus according to the fourth embodiment of the present invention. The wastewater treatment apparatus 1D according to the fourth embodiment, as shown in Figures 5 to 7, is provided with an insulating mechanism 5 for insulating the treated water W discharged from the first cell 31a, as in the wastewater treatment apparatus 1A according to the first embodiment. Note that the same components as those in the first embodiment will not be explained. Furthermore, Figures 5 to 7 are enlarged explanatory diagrams of the area around the power generation unit 3 of the wastewater treatment apparatus 1D, and the configurations of the treatment tank 2 and reaction tank 4 are not shown.

[0088] As mentioned above, when performing an electrochemical reaction (electrode reaction), it is preferable to insulate areas other than the part where the electrochemical reaction takes place (power generation unit 3). The wastewater treatment device 1D in this embodiment is equipped with an insulating mechanism 5 that insulates the water to be treated W. This prevents electrons generated in the power generation unit 3 from flowing anywhere other than between electrodes 33a and 33b, thereby improving the electrode reaction efficiency. As a result, power generation efficiency and desulfurization treatment efficiency can be improved. In addition, the wastewater treatment device 1D in this embodiment may also incorporate insulation for the structures (treatment tank and piping) that constitute the wastewater treatment device, as shown in the first embodiment. This will provide an even greater insulating effect and make 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 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 liquid junction elimination means or liquid junction time shortening means include making the flow of the water to be treated W discontinuous (intermittent), interposing an insulator such as air between the water to be treated W and the water to be treated, or a combination of these means.

[0090] Figure 5 is a schematic diagram illustrating the insulation mechanism 5 of the wastewater treatment device 1D in this embodiment. As shown in Figure 5, the insulating mechanism 5 in this embodiment includes a storage tank 51 and a watering means 52 for spraying the water to be treated W into the storage tank 51.

[0091] The storage tank 51 stores the treated water W discharged from the power generation unit 3 via the discharge pipe L3. The storage tank 51 is not particularly limited and can be any tank capable of storing the treated water W. It is preferable to adjust the water level in the storage tank 51 so that it does not reach its maximum level (full). This further enhances the insulating effect of the treated water W.

[0092] The watering means 52 discharges the water to be treated W in droplet form. Since air from the storage tank 51 acts as an insulator between the droplets of water to be treated W discharged by the watering means 52, it is possible to eliminate liquid junctions or shorten the liquid junction time. The watering means 52 is not particularly limited and can be any means that can form the treated water W into droplets. A specific example of the watering means 52 is, for example, a structure connected to the outlet of the discharge pipe L3 and having multiple holes like a shower head, as shown in Figure 5. Another example of the watering means 52 is a flat, dish-shaped structure placed in the storage tank 51 opposite the outlet of the discharge pipe L3 and spaced a predetermined distance apart.

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

[0094] The storage tank 53 stores the treated water W discharged from the power generation unit 3 via the discharge pipe L3. The storage tank 53 is not particularly limited and can be any tank capable of storing the treated water W. The water discharge means 54 is not particularly limited, as long as it can intermittently discharge the water to be treated W from the storage tank 53. One example of the water discharge means 54 is to install a solenoid valve 54a in the water discharge pipe L9 that discharges the water to be treated W from the storage tank 53, and to periodically open and close the solenoid valve 54a. This makes the flow of the water to be treated W discharged from the storage tank 53 through the water discharge pipe L intermittent, thereby eliminating liquid entanglement of the water to be treated W or shortening the liquid entanglement time.

[0095] Figure 7 is a schematic diagram illustrating another aspect of the insulation mechanism 5 of the wastewater treatment device 1D in this embodiment. As shown in Figure 7, the insulating mechanism 5 in this embodiment includes a pipe diameter reduction means 55 on the discharge pipe L3 for narrowing a portion of the pipe diameter of the discharge pipe L3, and a gas supply means 56 for supplying gas into the discharge pipe L3 from the upstream side of the pipe diameter reduction means 55.

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

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

[0098] As described above, the wastewater treatment device 1D in this embodiment is equipped with an insulating mechanism 5 that insulates the water to be treated W, thereby enabling the elimination of liquid junctions between the power generation unit 3 and the water to be treated W, or shortening of the liquid junction time. This prevents electrons generated in the power generation unit 3 from flowing outside the space between electrodes 33a and 33b, thereby reducing the efficiency of the electrochemical reaction (electrode reaction) and improving the power generation efficiency and desulfurization treatment efficiency.

[0099] Furthermore, in the wastewater treatment apparatus 1D of this embodiment, power generation and desulfurization treatment can be performed by the same process as in the first embodiment.

[0100] [Fifth Embodiment] Figure 8 is a schematic diagram illustrating a wastewater treatment apparatus according to a fifth embodiment of the present invention. The wastewater treatment apparatus 1E according to the fifth embodiment, as shown in Figure 8, is a wastewater treatment apparatus 1B according to the second embodiment, with a pH control means 6 provided between the methane fermentation tank 22 and the power generation unit 3. In this embodiment, the wastewater treatment apparatus 1E has the same configuration as the wastewater treatment apparatus 1B shown in Figure 3, and the explanation of the same configuration as in the second embodiment is omitted.

[0101] As described above, in the methane fermentation tank 22, acidic treated water W is introduced from the acid generation tank 21, and the methane fermentation process proceeds. During this time, hydrogen sulfide, a reducing substance, is generated in the methane fermentation tank 22 as the methane fermentation process progresses. On the other hand, it is known that the solubility of hydrogen sulfide in a solution changes depending on the pH, and that increasing the pH to an alkaline level of 6 or higher increases its solubility and suppresses the release of hydrogen sulfide into the solution. Therefore, by adjusting the pH of the water to be treated W, the solubility of reducing substances (especially hydrogen sulfide) can be changed, making it possible to dissolve the reducing substances in the water to be treated W.

[0102] In the wastewater treatment apparatus 1E of this embodiment, the pH control means 6 is provided to adjust the pH of the treated water W after methane fermentation treatment, thereby suppressing the gasification of hydrogen sulfide and allowing hydrogen sulfide to remain dissolved in the treated water W. This increases the amount of reducing substances in the treated water W and increases the amount of electron donors used in the reaction, thereby improving 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 to be treated W and allow reducing substances in the water to be treated W to dissolve in the water to be treated W. As shown in Figure 8, the pH control means 6 includes a storage unit 61 for storing a pH adjusting agent, an addition unit 62 for adding the pH adjusting agent to the water to be treated W, and a pH detection unit 63.

[0104] The storage section 61 is not particularly limited as long as it is capable of storing a pH adjusting agent. Furthermore, the pH adjusting agent stored in the storage section 61 is not particularly limited, and it is preferable to select the type of pH adjusting agent according to the pH dependence of the solubility of the reducing substance. For example, if the reducing substance is hydrogen sulfide, a pH adjusting agent that makes the pH of the treated water W more alkaline can be used to increase the solubility of hydrogen sulfide. More specifically, hydroxides such as sodium hydroxide or calcium hydroxide can be used as pH adjusting agents. Acids such as hydrochloric acid or sulfuric acid may also be used as pH adjusting agents.

[0105] The additive section 62 is for adding the pH adjusting agent from the storage section 61 to the water to be treated W. In this embodiment, the additive section 62 is provided on the circulation piping L6, as shown in Figure 8. The additive unit 62 in this embodiment is not particularly limited, as long as it has a structure that allows a pH adjusting agent to be added to the treated water W in the circulation pipe L6. For example, it may consist of a pipe that connects the circulation pipe L6 and the storage unit 61 and has a flow rate adjustment function.

[0106] The placement of the additive unit 62 is not particularly limited, but it is preferable to select a location that can adjust the pH of the water to be treated W and appropriately control the solubility of reducing substances. For example, as shown in Figure 8, the additive unit 62 can be placed on the circulation pipe L6 that circulates the water to be treated W from the power generation unit 3 to the methane fermentation tank 22. In this case, the circulation pipe L6 is connected to the middle section of the methane fermentation tank 22. As a result, while the methane fermentation process proceeds in an acidic environment in the lower part of the methane fermentation tank 22, the pH adjusting agent added by the additive unit 62 is introduced to the middle section of the methane fermentation tank 22 via the circulation pipe L6, thereby making the pH of the water to be treated W in the upper part of the methane fermentation tank 22 more alkaline, and enabling the hydrogen sulfide generated in the methane fermentation tank 22 to be more reliably dissolved in the water to be treated W before being introduced to the power generation unit 3.

[0107] Furthermore, as shown in Figure 8, it is preferable to provide a pH detection unit 63 on the circulation pipe L6 that circulates the water to be treated W from the methane fermentation tank 22 to the power generation unit 3, and to control the amount of pH adjusting agent added from the additive unit 62 according to the detection result of the pH detection unit 63. This makes it easier to adjust the pH of the water to be treated W and to do so at the appropriate timing. As a result, it is possible to increase the amount of reducing substances in the water to be treated W introduced into the power generation unit 3 and increase the amount of electron donors used in the reaction, thereby improving the power generation efficiency and desulfurization efficiency in the power generation unit 3. Furthermore, the control means for the additive unit 62 in response to the detection result of the pH detection unit 63 is not particularly limited. For example, the detection result of the pH detection unit 63 could be visually confirmed by an operator, and the additive unit 62 could be operated manually according to the result, or the pH detection unit 63 and the additive unit 62 could be connected in a controllable manner to automate the pH detection of the water to be treated W and the addition of the pH adjusting agent.

[0108] The structure of the wastewater treatment apparatus 1E equipped with the pH adjustment means 6 is not limited to the structure of the wastewater treatment apparatus 1B shown in Figure 3. Another example of a wastewater treatment apparatus 1E equipped with the pH adjustment means 6 is to place the additive unit 62 on the connecting pipe L2 of the wastewater treatment apparatus 1A shown in Figure 1, or on the circulation pipe L5 of the wastewater treatment apparatus 1B shown in Figure 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 to increase the amount of reducing substances introduced to the power generation unit 3.

[0109] As described above, the wastewater treatment apparatus 1E in this embodiment is equipped with a pH control means for dissolving reducing substances in the water to be treated, thereby making it possible to retain more reducing substances in the water to be treated, whose solubility in the water to be treated changes depending on the pH, and increasing the amount of reducing substances used in the reaction as electron donors. This makes it possible to improve power generation efficiency and desulfurization treatment efficiency.

[0110] Furthermore, in the wastewater treatment apparatus 1E of this embodiment, power generation and desulfurization treatment can be performed by the same process as in the first embodiment.

[0111] [Sixth Embodiment] Figure 9 is a schematic diagram illustrating a wastewater treatment apparatus according to the sixth embodiment of the present invention. Figures 10 and 11 are schematic diagrams illustrating another aspect of the wastewater treatment apparatus according to the sixth embodiment of the present invention. The wastewater treatment device 1F according to the sixth embodiment, as shown in Figures 9 to 11, is a wastewater treatment device 1B according to the second embodiment, with the addition of a temperature control means 7. In this embodiment, the wastewater treatment device 1F has the same configuration as the wastewater treatment device 1B shown in Figure 3, and the explanation of the same configuration as in the second embodiment is omitted.

[0112] As described above, in the power generation section 3, an electrode reaction is proceeding with reducing substances in the treated water acting as electron donors. Furthermore, it is generally known that in electrode reactions, increasing the temperature leads to improvements in mass transfer rate and reaction efficiency. Therefore, by controlling the temperature related to the electrode reaction within the wastewater treatment device 1F, it is possible to improve the efficiency of the electrode reaction and enhance the power generation efficiency and desulfurization treatment efficiency.

[0113] In this embodiment, the wastewater treatment device 1F is provided with a temperature control means 7, which allows for temperature adjustment related to the power generation unit 3. This increases the efficiency of the reaction using reducing substances as electron donors, thereby improving the power generation efficiency and desulfurization efficiency in the power generation unit 3.

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

[0115] In this embodiment, the temperature control means 7 can be said to be the use of the existing heat exchange equipment 71 that is provided to carry out the methane fermentation process in the methane fermentation tank 22. For example, as shown in Figure 9, the power generation unit 3 is set up near the existing heat exchange equipment 71, and the cells (first cell 31a and second cell 31b) and electrodes (electrodes 33a and 33b) of the power generation unit 3, as well as the circulation piping L6 and electron acceptor supply port 34a, are arranged to receive heat from the existing heat exchange equipment 71, thereby heating the power generation unit 3 itself, as well as the water to be treated W and electron acceptors introduced into the power generation unit 3. This makes it possible to control the temperature of the part of the reaction that uses reducing substances in the water to be treated W as electron donors, and the substances used in the reaction, without installing new equipment related to temperature control.

[0116] Another example of the temperature control means 7 is to provide pipes 72 and 73 connecting the existing heat exchange equipment 71 and the power generation unit 3, as shown in Figure 10, and supply heat from the existing heat exchange equipment 71 to the power generation unit 3 by moving a heat transfer medium such as air or water through the pipes 72 and 73. This makes it possible to control the temperature of the power generation unit 3 and control the temperature at the point where a reaction takes place in which reducing substances in the treated water W are used as electron donors. The means of connecting the pipes 72 and 73 to the power generation unit 3 is not particularly limited. 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 be in contact with any one of the components of the power generation unit 3 (electrodes 33a and 33b, or the first cell 31a and the second cell 31b). Another example of the temperature control means 7 is to provide pipes 74 and 75 connecting the existing heat exchange equipment 71 and the circulation pipe L6, as shown in Figure 11. By moving a heat transfer medium such as air or water through the pipes 74 and 75, heat from the existing heat exchange equipment 71 is supplied to the water to be treated W in the circulation pipe L6. This allows for temperature control of the water to be treated W introduced into the power generation unit 3, and enables temperature control of the substance (reducing substance) used in the reaction that uses the reducing substance in the water to be treated W as an electron donor. Furthermore, instead of the circulation pipe L6, an electron acceptor supply port 34a may be used as the connection point for pipes 74 and 75. This allows for supplying heat from the existing heat exchange equipment 71 to the electron acceptor, and enables temperature control of the substance (electron acceptor) used in the reaction that uses the reducing substance in the water to be treated W as an electron donor. The temperature control means 7 shown in Figures 10 and 11 may be installed individually or in combination. The appropriate configuration can be selected considering the temperature control efficiency and equipment costs associated with the temperature control means 7.

[0117] Furthermore, another example of the temperature control means 7 is to use the waste heat from gas power generation using methane generated from the methane fermentation tank 22, instead of the existing heat exchange equipment 71. More specifically, by supplying heat to a heat transfer medium such as air or water heated using this waste heat and bringing it into contact with the power generation unit 3 and circulation pipe L6 through piping, it becomes possible to control the temperature related to the reaction in which reducing substances in the treated water W are used as electron donors. This improves power generation efficiency and desulfurization efficiency, as well as enabling the effective utilization of waste heat related to methane gas power generation.

[0118] The structure of the wastewater treatment apparatus 1F equipped with the temperature control means 7 is not limited to the structure of the wastewater treatment apparatus 1B shown in Figure 3. Other examples of the wastewater treatment apparatus 1F equipped with the temperature control means 7 include, for example, a structure that can supply heat from the existing heat exchange equipment 71 to the reactions related to the reaction using reducing substances in the treated water W as electron donors (power generation unit 3, connecting pipe L2, etc.) in the wastewater treatment apparatus 1A shown in Figure 1, or to the reactions related to the reaction using reducing substances in the treated water W as electron donors (power generation unit 3, circulation pipe L5, etc.) in the wastewater treatment apparatus 1B shown in Figure 2. This makes it possible to control the temperature related to the reactions using reducing substances in the treated water W as electron donors, thereby improving the mass transfer rate and reaction efficiency involved in the reaction.

[0119] As described above, the wastewater treatment apparatus 1F in this embodiment is equipped with a temperature control means for reactions using reducing substances in the treated water as electron donors, making it possible to control the temperature in such reactions that improve mass transfer rate and reaction efficiency. This makes it possible to improve power generation efficiency and desulfurization treatment efficiency.

[0120] Furthermore, in the wastewater treatment apparatus 1F of this embodiment, power generation and desulfurization treatment can be performed by the same process as in the first embodiment.

[0121] The embodiments described above are examples of wastewater treatment equipment, power generation equipment, desulfurization treatment equipment, power generation method, and desulfurization method. The wastewater treatment equipment, power generation equipment, desulfurization treatment equipment, power generation method, and desulfurization method according to the present invention are not limited to the embodiments described above, and the wastewater treatment equipment, power generation equipment, desulfurization treatment equipment, power generation method, and desulfurization method according to the embodiments described above may be modified without changing the gist of the claims.

[0122] For example, if the water to be treated W already contains reducing substances, the wastewater treatment device in this embodiment may have the power generation unit 3 placed before the treatment tank 2. This makes it possible to perform pretreatment to reduce the reducing substances in the water to be treated W, along with generating electricity using the power generation unit 3. Furthermore, the wastewater treatment device in this embodiment may be equipped with multiple power generation units (power generation devices). For example, it may be equipped with both the power generation unit shown in the first embodiment and the power generation unit shown in the second embodiment. This makes it possible to generate electricity at multiple locations by effectively utilizing the treatment within 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, in this embodiment, the wastewater treatment device may have electrodes 33a and 33b provided as the power generation unit 3 in the settler 23 portion within the treatment tank 2 (methane fermentation tank 22). Alternatively, electrodes 33a and 33b may be provided near the settler 23, or the settler 23 itself may be used as electrodes 33a and 33b. This allows the power generation unit 3 to be integrated into the treatment tank 2, enabling further miniaturization of the equipment.

[0124] Furthermore, for example, in this embodiment, the wastewater treatment device may have the electrode 33b installed in the aeration tank 41, and the aeration tank 41 may function as the second cell 31b of the power generation unit 3. This allows the power generation unit 3 and the reaction tank 4 (aeration tank 41) to be integrated, enabling further miniaturization of the equipment.

[0125] Furthermore, for example, the wastewater treatment device in this embodiment may be provided with means to prevent the attachment and accumulation of microorganisms on electrodes 33a and 33b. Such means include, for example, coating the electrode surface with a material that prevents the attachment of microorganisms, or making the structure of the electrodes themselves such that it is difficult for microorganisms to attach. This makes it possible to suppress the inhibition of the electrode reaction at 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 simplified by omitting some of its structures. An example of a structure that can be omitted is the ion exchanger 32. This allows for simplification of the power generation unit 3 (power generation device / desulfurization treatment device) and simplifies maintenance work. Furthermore, other examples of structures that can be omitted include the electron acceptor supply port 34a and electron acceptor outlet port 34b in the second cell 31b. This makes it possible to further simplify the power generation unit 3 (power generation device / desulfurization treatment device). In this case, one surface of the electrode 33b is in contact with the water to be treated W or the ion exchanger 32, and the other surface is in direct contact with the outside air. In addition, it is preferable to provide a breathable material that is easy to replace or clean on the surface of the electrode 33b facing the outside air. 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 apparatus, power generation method, and desulfurization method of the present invention are suitably used in wastewater treatment that treats water to be treated that contains reducing substances, and in wastewater treatment in which reducing substances are generated by treating water to be treated.

[0128] By applying the power generation device of the present invention to an existing wastewater treatment system, it is possible to provide a wastewater treatment system and a power generation method of the present invention without having to extensively renovate the entire wastewater treatment system. 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 having to extensively renovate the entire wastewater treatment apparatus. [Explanation of Symbols]

[0129] 1A, 1B, 1C, 1D, 1E, 1F Wastewater treatment equipment, 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 outlet, 4 Reaction tank, 41 Aeration tank, 42 ​​Aeration device, 5 Insulation mechanism, 51, 53 Storage tank, 52 Spraying means, 54 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, 72-75 Piping, L1 Inlet piping, L2 Connecting piping, L3, L7 Discharge piping, L4, L8; connecting piping, L5, L6; circulation piping, L9; discharge piping, W; treated water, W1; treated water

Claims

1. A wastewater treatment device for treating water to be treated, The system comprises a power generation unit that performs power generation and desulfurization treatment by a reaction using hydrogen sulfide or hydrogen sulfide ions as electron donors as reducing substances in the water to be treated, A wastewater treatment apparatus characterized by introducing reducing substances from the water to be treated after anaerobic treatment into the power generation section, and performing power generation and desulfurization treatment.

2. The wastewater treatment apparatus according to claim 1, characterized in that electrodes are installed in the water to be treated within the power generation unit and power is generated.

3. The wastewater treatment apparatus according to claim 2, characterized in that an ion exchanger is placed between the electrodes.

4. The wastewater treatment apparatus according to any one of claims 1 to 3, characterized in that a treatment tank for treating the water to be treated is provided in front of the power generation unit.

5. A wastewater treatment apparatus according to any one of claims 1 to 4, characterized in that it is provided with a pH control means for dissolving the reducing substance in the water to be treated in the water to be treated.

6. The wastewater treatment apparatus according to any one of claims 1 to 4, characterized by providing a temperature control means for a reaction in which a reducing substance in the water to be treated is used as an electron donor.

7. A power generation device installed in a wastewater treatment device that treats water to be treated, The unit comprises a power generation section that performs power generation and desulfurization treatment by a reaction using hydrogen sulfide or hydrogen sulfide ions as electron donors as reducing substances in the water to be treated, A power generation device characterized by introducing reducing substances from the water to be treated after anaerobic treatment into the power generation section, and performing power generation and desulfurization treatment.

8. A method for generating electricity in wastewater treatment, which involves treating water to be treated, The process includes a step of generating electricity and performing desulfurization treatment by a reaction in which hydrogen sulfide or hydrogen sulfide ions are used as electron donors as reducing substances in the water to be treated, A method for generating electricity, characterized in that, in the above step, a reducing substance is introduced into the water to be treated after anaerobic treatment, and power generation and desulfurization treatment are performed.

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