Wastewater treatment device, electrode, and wastewater treatment method

Abstract

To provide a wastewater treatment apparatus, an electrode and a wastewater treatment method, enabling energy generated by electrode reaction to be recovered / utilized and reduction of electrode reaction efficiency to be suppressed in wastewater treatment.SOLUTION: A wastewater treatment apparatus and a wastewater treatment method performing treatment on treatment-object water are provided, the wastewater treatment apparatus comprising: an electric power generation unit which brings treated water obtained by treating the treatment-object water into contact with an electrode to perform electric power generation; and deaeration means removing gas included in the electrode. A deaerated electrode is also provided. According to the present invention, the electric power generation unit using the electrode is provided in the wastewater treatment apparatus, so that electric power generation can be executed in a series of treatment processes in wastewater treatment. Thus, efficient electric power generation is executed, and energy can be recovered / utilized. Further, the electrode is deaerated, so that efficiency reduction of electrode reaction due to reduction of a specific surface area inside the electrode is suppressed, which makes it possible to improve efficiency of electric power generation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wastewater treatment device and a wastewater treatment method.The present invention also relates to an electrode to be provided for the wastewater treatment device. [Background technology]

[0002] Various wastewater treatment methods are known for treating water to be treated. The wastewater treatment methods are selected taking into consideration the physical properties of the water to be treated itself, such as the components contained in the water to be treated and the amount of water to be discharged, and the characteristics of the facilities and operations for carrying out the wastewater treatment, such as the balance between treatment efficiency and cost. In addition, in wastewater treatment, efforts are being made to improve the efficiency of wastewater treatment by combining a plurality of different wastewater treatment methods.

[0003] For example, Patent Document 1 describes a wastewater treatment method in which a pair of electrodes are immersed in the water to be treated, electrochemical treatment is performed, and then the water is biologically treated to treat the water containing organic matter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-330182 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, in wastewater treatment combining electrochemical treatment and biological treatment, it is possible to proceed with reactions with good reaction efficiency for each treatment, thereby improving the treatment efficiency of the wastewater treatment as a whole. On the other hand, electrochemical treatment generally has a problem in that the running costs related to power consumption are high. It is said that the wastewater treatment described in Patent Document 1 can reduce the running costs more than electrochemical treatment alone. However, the wastewater treatment described in Patent Document 1 requires the supply of energy for the electrochemical treatment and biological treatment from outside the wastewater treatment system. Therefore, further energy saving during wastewater treatment is required.

[0006] In recent years, technologies that enable the recovery and utilization of energy during wastewater treatment have been investigated in order to reduce the power required to operate the equipment during wastewater treatment and to achieve excellent energy conservation. One such technology is the recovery of energy using biogas generated by biological treatment, but this requires additional facilities such as biogas storage and purification equipment, and equipment to convert the thermal energy obtained by burning the biogas into electrical energy using a gas engine or gas turbine. Therefore, there is a demand for technology that allows for simpler and more efficient energy recovery and utilization in wastewater treatment.

[0007] One possible technology for easily and efficiently recovering energy in wastewater treatment is to install electrodes in the wastewater treatment process and directly recover electrical energy through electrode reactions. In this case, electrochemical treatment of the treated water can be performed simultaneously with energy recovery through electrode reactions, which is expected to improve the efficiency of wastewater treatment and realize energy savings.

[0008] Here, it is expected that the efficiency of the electrode reaction will be improved by using an electrode with a large specific surface area. However, the present inventors have found that when an electrode reaction using an electrode is performed in a wastewater treatment device, if a porous electrode is used as it is as an electrode with a large specific surface area, there is a problem that the electrode reaction efficiency is lower than expected.

[0009] An object of the present invention is to provide a wastewater treatment device, an electrode, and a wastewater treatment method that enable the recovery and utilization of energy generated by electrode reactions in wastewater treatment and can suppress a decrease in the efficiency of the electrode reactions. [Means for solving the problem]

[0010] As a result of extensive research into the above-mentioned problems, the inventors have discovered that in wastewater treatment, energy can be efficiently recovered and utilized by generating electricity (electrode reaction) using components contained in the treated water after the treatment of the water to be treated, and that removing the gas contained in the electrode can increase the contact area between the treated water and the electrode, thereby preventing a decrease in the efficiency of the electrode reaction, and thus completed the present invention. That is, the present invention relates to the following wastewater treatment device, electrode, and wastewater treatment method.

[0011] The wastewater treatment device of the present invention, which is intended to solve the above problems, is a wastewater treatment device that treats water to be treated, and is characterized in that it is equipped with a power generation unit that brings the treated water after it has been treated into contact with an electrode to generate electricity, and a deaeration means that removes gas contained in the electrode.

[0012] The wastewater treatment device of the present invention is capable of generating electricity during a series of wastewater treatment processes by installing a power generation unit using electrodes in the wastewater treatment device. This makes it possible to generate electricity efficiently and recover and utilize energy without enlarging the size of the equipment. In addition, by carrying out an electrode reaction using components contained in the treated water after treating the water to be treated, it becomes possible to effectively utilize the components generated in the wastewater treatment process. Furthermore, by providing a degassing means for removing gas contained in the electrode, the problem of a decrease in the specific surface area inside the electrode can be solved. This makes it possible to suppress a decrease in the efficiency of the electrode reaction and improve the efficiency of power generation and electrochemical treatment.

[0013] In one embodiment of the wastewater treatment device of the present invention, the deaeration means is characterized by including chemical addition means for adding a chemical to the electrodes. According to this feature, the electrode can be degassed by the simple means of adding a chemical to replace the air bubbles inside the electrode, which makes it possible to prevent the size of the auxiliary equipment related to the electrode degassing from increasing and reduce the initial cost.

[0014] In one embodiment of the wastewater treatment device of the present invention, the deaeration means is characterized by comprising an electrical treatment means for applying a voltage to the electrodes. According to this feature, the electrode can be degassed by generating gas through an electrode reaction and pushing out the gas bubbles inside the electrode to the outside of the electrode. In this case, there is no need to install additional equipment for degassing the electrode, and the initial cost can be significantly reduced.

[0015] In one embodiment of the wastewater treatment device of the present invention, the deaeration means is characterized by including a pressure reducing means for reducing the pressure of the electrodes. According to this feature, the electrode can be degassed by removing air bubbles inside the electrode through a depressurization process. In particular, by performing a depressurization process on the electrode installed in the power generation unit, it becomes possible to introduce treated water into the electrode, which increases the contact area between the treated water and the electrode and improves the electrode reaction efficiency. In addition, since there is no need to supply anything separately from the outside for degassing, the impact on the environment related to the electrode reaction in the power generation unit can be minimized.

[0016] In addition, the electrode of the present invention for solving the above problems is an electrode that is brought into contact with treated water after it has been treated in a wastewater treatment device that treats the water to be treated, and has the characteristic that a deaeration treatment has been performed. According to this feature, the problem of a decrease in the specific surface area inside the electrode can be solved by using an electrode that has been subjected to a degassing process to remove gas contained therein for generating electricity in a series of processes in wastewater treatment, thereby preventing a decrease in the efficiency of the electrode reaction and improving the efficiency of power generation and electrochemical treatment in the wastewater treatment device.

[0017] Further, as a wastewater treatment method of the present invention for solving the above problems, it is a wastewater treatment method for treating raw water to be treated, which includes a power generation step of bringing treated water after the raw water to be treated is treated into contact with an electrode to generate power, and a degassing step of removing gas contained in the electrode. The wastewater treatment method of the present invention enables power generation during a series of treatment processes in wastewater treatment by providing a power generation step using an electrode in wastewater treatment. Thereby, efficient power generation can be carried out without increasing the size of the equipment, and energy can be recovered and utilized. Also, by performing an electrode reaction using the components contained in the treated water after treating the raw water to be treated, it becomes possible to effectively utilize the components generated within the wastewater treatment process. Furthermore, by performing a degassing step of removing the gas contained in the electrode, the problem of the specific surface area inside the electrode decreasing can be solved. Thereby, it is possible to suppress a decrease in the efficiency of the electrode reaction, and it becomes possible to improve the efficiency of power generation and electrochemical treatment.

Effects of the Invention

[0018] According to the present invention, it is possible to provide a wastewater treatment apparatus, an electrode, and a wastewater treatment method that enable recovery and utilization of energy by an electrode reaction in wastewater treatment and suppress a decrease in the electrode reaction efficiency.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic explanatory view of a wastewater treatment apparatus in a first embodiment of the present invention. [Diagram 2] It is a schematic explanatory view showing a degassing means in the wastewater treatment apparatus of the first embodiment of the present invention. [Diagram 3] It is a schematic explanatory view showing another aspect of the degassing means in the wastewater treatment apparatus of the first embodiment of the present invention. [Figure 4] It is a schematic explanatory view showing another aspect of the degassing means in the wastewater treatment apparatus of the first embodiment of the present invention. [Diagram 5] It is a schematic explanatory view of a wastewater treatment apparatus in a second embodiment of the present invention. [Figure 6]FIG. 4 is a schematic explanatory diagram showing another aspect of the wastewater treatment device in the second embodiment of the present invention. [Figure 7] FIG. 11 is a schematic explanatory diagram of a wastewater treatment device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the wastewater treatment device and the wastewater treatment method according to the present invention will be described in detail with reference to the drawings. The wastewater treatment method in the present invention is replaced with the description of the operation of the wastewater treatment device in the present invention. The wastewater treatment device and the wastewater treatment method described in the embodiments are merely examples for the purpose of explaining the wastewater treatment device and the wastewater treatment method according to the present invention, and the present invention is not limited thereto.

[0021] In the wastewater treatment device of the present invention, the treated water to be treated is not particularly limited as long as it generates a substance capable of an electrode reaction through treatment. Examples of substances capable of an electrode reaction include reducing substances. Specific examples of the treated water 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 treated water will be mainly described as a water that generates a reducing substance through treatment, but is not limited thereto.

[0022] 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.

[0023] [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. As shown in Fig. 1, wastewater treatment device 1A in this embodiment includes a treatment tank 2, a power generation unit 3, and a deaeration means 4. Wastewater treatment device 1A also includes an inlet pipe L1 for introducing water W to be treated into treatment tank 2, a connection pipe L2 for connecting treatment tank 2 and power generation unit 3 and for supplying treated water W1 after the water W to be treated in treatment tank 2 to power generation unit 3, and a discharge pipe L3 for discharging treated water W2 after electrode reaction from power generation unit 3. Furthermore, a reaction tank 5 is connected downstream of discharge pipe L3.

[0024] (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 in the treated water W1 after treatment. 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. Furthermore, 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. Examples of biological treatments in an aerobic environment (aerobic treatments) include activated sludge treatments using activated sludge. Anaerobic treatments are preferred because of the many benefits of their introduction, such as no need for aeration power and almost no generation of excess sludge. Furthermore, methane fermentation, which produces methane, is particularly preferred from the standpoint of treatment costs and the usefulness of the generated gas.

[0025] 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.

[0026] The water W to be treated that has been treated in the treatment tank 2 becomes treated water W1 containing reducing substances, and is introduced into the power generation section 3 via a connection pipe L2.

[0027] (Power Generation Division) The power generation section 3 is for generating power by using reducing substances in the treated water W1 as electron donors. 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 35 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 treated water W1 introduced from the treatment tank 2 through the connection pipe L2 contacts 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 cathode. 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 use the electric energy generated by the action of the reducing substance as an electron donor in the power generation unit 3.

[0028] The first cell 31a may be any material or shape as long as it is provided with an electrode 33a and is formed so that the treated water W1 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 treated water W1 introduced from the treated water inlet 32a via the connection pipe L2, and may be provided with a discharge pipe L3 for discharging the treated water W2 from the treated water outlet 32b after contacting the electrode 33a. As a result, the reducing substances in the treated water W1 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 treated water W1 brought into contact with the electrode 33a and control the mass transfer rate to the electrode 33a.

[0029] The treated water W2 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 5 for further treating the treated water W2 may be provided downstream of the discharge pipe L3, and the treated water W2 may be discharged outside the system as treated water W3. The reaction tank 5 is not particularly limited as long as it can treat the treated water W2 to a water quality suitable for discharge outside the system or into a river. For example, an aeration tank, a pH adjustment tank, etc. may be mentioned.

[0030] The second cell 31b may be made of any material or have any shape 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 treatment water W1.

[0031] 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). In particular, the second cell 31b in which the electrode 33b is disposed is filled with the solution of the electron acceptor, which makes it possible to easily form the configuration related to the degassing means 4 (particularly, the electrical processing means 4B and the pressure reducing means 4C) described later.

[0032] 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.

[0033] As an example of the second cell 31b, as shown in FIG. 1, a space capable of storing a liquid is provided in the second cell 31b, and an electron acceptor supply port 34a and an electron acceptor discharge port 34b are provided that can supply a solution of the electron acceptor and discharge the solution after the reaction, respectively. Another example of the second cell 31b is that the second cell 31b is provided with an electron acceptor supply port 34a for supplying a gas and an electron acceptor discharge port 34b for discharging the gas after the reaction in order to supply a gaseous electron acceptor (oxygen, air, etc.) to the electrode 33b. 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. The electron acceptor after the reaction is quickly discharged to the outside of the power generation unit 3 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.

[0034] 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 the reaction at the electrode 33b. 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.

[0035] The ion exchanger 35 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 the power generation efficiency. In addition, it is more preferable that the ion exchanger 35 has low oxygen permeability. This makes it possible to suppress the electron acceptor (particularly 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 35 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 allows the time required for maintenance work to be shortened.

[0036] The electrode 33a is an electrode that collects electrons from reducing substances in the treated water W1, and functions as a so-called anode. In this embodiment, the electrode 33a is disposed in the first cell 31a so as to be in contact with the treated water W1 after being treated in the treatment tank 2.

[0037] The electrode 33a only needs to 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 in view of factors such as material procurement cost, processing cost, and reaction efficiency of the reducing substance in the electrode 33a. Examples of the material of the electrode 33a include, for example, carbon and metals (such as 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, for example, flat plate shape, rod shape, mesh shape, etc. In particular, in view of power generation efficiency, it is preferable to use a porous body as the electrode 33a in this embodiment. For example, as the electrode 33a, in addition to using carbon fibers such as carbon paper and carbon cloth which are porous bodies, foamed metal, porous metal, and metal mesh can also be used.

[0038] The electrode 33b is the counter electrode of the electrode 33a, and is an electrode that transfers electrons to the electron acceptor, functioning as a so-called cathode. Also, the electrode 33b in this embodiment is disposed within the second cell 31b.

[0039] The electrode 33b only needs to 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 in view of factors such as material procurement cost, processing cost, and reaction efficiency of the electron acceptor in the electrode 33b. Examples of the material of the electrode 33b include, for example, carbon and metals (such as 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, for example, flat plate shape, rod shape, mesh shape, etc. In particular, in view of power generation efficiency, it is preferable to use a porous body as the electrode 33b in this embodiment. For example, as the electrode 33b, in addition to using carbon fibers such as carbon paper and carbon cloth which are porous bodies, foamed metal, porous metal, and metal mesh can also be used.

[0040] When the electron acceptor supplied into the second cell 31b is a gas (air), one side of the electrode 33b contacts the gas, and the other side contacts the treated water W1. For this reason, the electrode 33b is preferably in a form suitable for use as a so-called air cathode. Examples of a form suitable for use as an air cathode include a form having both gas permeability and water impermeability. By making the electrode 33b in a form having gas permeability, it is possible to effectively react the gas, which is the electron acceptor, at the electrode 33b. In addition, by making the electrode 33b water impermeable, it is possible to prevent the treated water W1 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.

[0041] The power generation in the wastewater treatment device 1 will be described in detail below. The reactions and steps involved in power generation in the wastewater treatment device of the first embodiment of the present invention will be described with reference to Fig. 1. The reactions and steps involved in power generation in the piping of this embodiment will be described as using a reducing substance generated by anaerobic treatment of the water to be treated W as an electron donor, and using a solution containing oxygen and an oxidizing agent as an electron acceptor. 1 shows an example of power generation in this embodiment, and is not limited thereto. The following description 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 5) 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.

[0042] 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.

[0043] The treated water W1, 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, taking hydrogen sulfide 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

[0044] 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

[0045] As shown in formulas 1 and 2, in reaction R1, hydrogen sulfide contained in treated water W1 after treatment in treatment tank 2 donates electrons to electrode 33a, and hydrogen sulfide itself is oxidized to become harmless and odorless. Therefore, the wastewater treatment device of this embodiment has the effect of being capable of desulfurization and deodorization in addition to power generation. Note that reducing substances (ammonia, etc.), 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 odorless.

[0046] After the reaction at the electrode 33a proceeds according to 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 35 (Reaction R3).

[0047] On the other hand, an electron acceptor (solution) is introduced into the second cell 31b through the electron acceptor supply port 34a (step S3). Here, the electrons that have moved from the electrode 33a to the electrode 33b in 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 35 in reaction R3 also react with the electron acceptor. The reaction at the electrode 33b at this time (reaction R4) is shown by the following reaction formula (formula 3). Note that oxygen in formula 3 corresponds to the electron acceptor.

number

[0048] Based on the above-mentioned reactions R1 to R4 and steps S1 to S3, a current flows between the electrodes 33a and 33b, whereby power is generated in the wastewater treatment device 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.

[0049] The electrode 33a in this embodiment directly collects electrons from reducing substances in the treated water W1. Therefore, by improving the contact efficiency between the electrode 33a and the reducing substances, the reaction efficiency as an electron donor (the electron collection speed at the electrode 33a) is improved, and it becomes possible to improve the power generation efficiency. Similarly, in the electrode 33b, by improving the contact efficiency between the electrode 33b and the electron acceptor, it becomes possible to improve the power generation efficiency.

[0050] On the other hand, when a porous body with a large specific surface area is used as the electrode 33a or electrode 33b in consideration of power generation efficiency, a space into which gas can enter is present inside the electrode. Therefore, if the electrodes 33a and 33b made of a porous body are directly placed in cells (first cell 31a and second cell 31b) that store liquid such as treated water, air bubbles will be present inside the electrodes 33a and 33b, and the contact area between the surfaces of the electrodes 33a and 33b and the liquid such as treated water will decrease. In this case, a problem occurs in that the efficiency of the electrode reaction (power generation) by the reducing substance and the electron acceptor decreases in the electrodes 33a and 33b.

[0051] (Degassing means) The degassing means 4 is for removing gas contained in the electrodes 33a and 33b in the power generation section 3, and suppressing a decrease in the electrode reaction efficiency. The degassing means 4 is not particularly limited as long as it can remove the gas contained in the electrodes 33a and 33b. In this embodiment, the degassing means 4 may be one that performs degassing while the electrodes 33a and 33b are installed in the power generation unit 3, or one that performs degassing of the electrodes 33a and 33b outside the power generation unit 3, such as before installation in the power generation unit 3 or after removal from the power generation unit 3. When degassing the electrodes 33a and 33b in the power generation unit 3, the electrodes 33a and 33b can be transported and installed as usual, and the degassing process can be easily performed between power generation processes. For this reason, it is possible to easily set the timing of operations related to the degassing process. On the other hand, when degassing the electrodes 33a and 33b outside the power generation unit 3, multiple electrodes can be treated at once without adding any equipment related to degassing to the power generation unit 3, and therefore the operating cost can be reduced. Therefore, the degassing means 4 may be located either inside or outside the power generation section 3, and can be appropriately selected in consideration of the degassing effect, working efficiency, and the like.

[0052] The degassing means 4 in this embodiment includes a chemical adding means 4A for adding a chemical to the electrodes. The chemical addition means 4A may be any means capable of removing gas contained in the electrodes by adding a chemical, such as a means for adding a chemical to the electrodes 33a and 33b outside the power generation unit 3, or a means for adding a chemical inside the power generation unit 3. By using the chemical addition means 4A as the degassing means 4, the electrodes can be degassed by the relatively simple means of adding a chemical. In this case, it is possible to prevent the ancillary equipment for degassing the electrodes from becoming too large, and to reduce the initial cost.

[0053] A specific example of the chemical supplying means 4A is a mechanism for supplying chemicals to the electrodes 33a and 33b disposed in the power generating unit 3. Fig. 2 is a schematic explanatory diagram of a mechanism for adding a chemical to the electrodes 33a and 33b in the power generation unit 3, as the chemical addition means 4A of this embodiment. Note that Fig. 2 is an enlarged view of the periphery of the power generation unit 3 in the wastewater treatment device 1A, and the treatment tank 2 and reaction tank 5 are not shown.

[0054] As shown in Fig. 2, the drug addition means 4A may be provided with drug supply ports 41a, 41b and drug supply means 42 in the first cell 31a and the second cell 31b, respectively, and arranged so that the drug comes into contact with the surfaces of the electrodes 33a and 33b. The dashed arrow in Fig. 2 indicates the inflow direction of the drug.

[0055] There is no particular limitation on the drug supplying means 42 as long as it can add a drug. For example, the drug supplying means 42 may include a storage unit for storing the drug, a control unit for determining and adjusting the amount of drug to be added, and the like.

[0056] Examples of the chemicals supplied from the chemical supply means 42 include those that replace the gas in the electrodes 33a, 33b and push the gas out of the electrodes 33a, 33b, those that dissolve the gas in the electrodes 33a, 33b, and those that break down the bubbles in the electrodes 33a, 33b. More specifically, examples of the chemicals include organic solvents such as alcohol, and substances known as defoamers. This makes it possible to remove the gas contained in the electrodes 33a, 33b arranged in the power generation unit 3.

[0057] 2, the chemical addition means 4A is not limited to providing chemical supply ports 41a, 41b and a chemical supply means 42 to the power generation unit 3. For example, the chemical supply means 42 may be connected to the connection pipe L2, and the chemical may be supplied from the treated water inlet 32a to the electrode 33a. This eliminates the need to provide a separate chemical supply port 41a, making it possible to simplify the device configuration.

[0058] Another embodiment of the drug addition means 4A is to provide equipment for adding drugs to the electrodes 33a, 33b outside the power generation unit 3, and after performing a degassing process all at once, to transport and place the electrodes 33a, 33b in a storage container filled with a storage solution to the power generation unit 3.

[0059] In this case, the preservation solution may be any liquid capable of preventing gas from flowing back into the electrodes 33a, 33b after the degassing process, and examples of such liquid include the chemical (solution) used in the degassing process, as well as pure water. It is preferable to use an aqueous solution such as pure water as the preservation solution. This allows the preservation solution to be easily replaced with the treatment water when the electrodes 33a, 33b are placed in the power generation unit 3, and even if the preservation solution flows out into the treatment water, it is possible to suppress the effect on the environmental conditions in the first cell 31a and the second cell 31b.

[0060] In this case, the storage container may be any container that can accommodate the electrodes 33a, 33b and the storage solution and prevent gas from flowing back into the electrodes 33a, 33b after the degassing process, and may be, for example, a box or bag made of a material that is neither breathable nor water-permeable. Specific examples of such storage containers include bags made of plastic film or thin metal film, and boxes made of plastic or metal plates.

[0061] If the chemical addition means 4A is configured to perform degassing treatment using a chemical outside the power generation unit 3, the chemical is not directly added to the power generation unit 3, which has the advantage that there is little change in the environment within the first cell 31a and the second cell 31b, and the impact on the electrode reaction (power generation) can be suppressed.

[0062] Another aspect of the degassing means 4 in this embodiment is one equipped with an electrical processing means 4B that applies a voltage to the electrodes. The electrical treatment means 4B may be any means capable of applying a voltage to the electrodes while they are immersed in a solution such as the treatment water, and examples of such means include providing an electrochemical device that controls the voltage and current between the electrodes 33a and 33b arranged in the power generation unit 3, or providing equipment equipped with an electrochemical device that controls the voltage and current applied between the electrodes 33a and 33b outside the power generation unit 3. In particular, by providing the electrical treatment means 4B as the degassing means 4 within the power generation unit 3, the amount of newly added equipment configuration is reduced, and the equipment can be made smaller.

[0063] Fig. 3 is a schematic explanatory diagram when the electrical treatment means 4B of this embodiment is one that applies a voltage between the electrodes 33a and 33b in the power generation unit 3. Note that Fig. 3 is an enlarged view of the periphery of the power generation unit 3 in the wastewater treatment device 1A, and the treatment tank 2 and reaction tank 5 are not shown.

[0064] As shown in FIG. 3, the electric treatment means 4B may be a voltage / current control device 43 connected to the electrodes 33a and 33b, and may perform electrochemical treatment. More specifically, a voltage may be applied so that an electrode reaction in which gas is generated from the electrodes 33a and 33b proceeds. As a result, the gas contained in the electrodes 33a and 33b is pushed out of the electrodes 33a and 33b by the gas generated by the electrode reaction, and the electrodes can be degassed. At this time, the electrode reaction in which gas is generated may be electrolysis of the aqueous solution (water) stored in the first cell 31a and the second cell 31b. Hydrogen and oxygen are generated by electrolysis of water in the power generation unit 3, and the hydrogen and oxygen are released to the outside of the electrodes 33a and 33b together with the gas contained in the electrodes 33a and 33b, and the electrodes can be degassed. As a result, it is almost unnecessary to add new equipment as the degassing means 4, and it is possible to significantly reduce equipment costs.

[0065] Another aspect of the degassing means 4 in this embodiment is one equipped with a decompression means 4C for applying a decompression treatment to the electrodes. The pressure reducing means 4C may be any means capable of reducing the pressure inside the cells (first cell 31a and / or second cell 31b) with the electrodes 33a and 33b disposed inside the power generating unit 3, or a means for reducing the pressure inside the cells (first cell 31a and / or second cell 31b) after reducing the pressure outside the power generating unit 3, and storing the electrodes 33a and 33b in a storage container while maintaining the reduced pressure. By using the pressure reducing means 4C as the degassing means 4, the electrodes can be degassed without changing the environmental conditions (pH, concentrations of various compounds, etc.) inside the first cell 31a and the second cell 31b.

[0066] Fig. 4 is a schematic explanatory diagram of the case where the pressure reducing means 4C in this embodiment reduces the pressure inside the first cell 31a and the second cell 31b with the electrodes 33a and 33b disposed in the power generation section 3. Fig. 4 is an enlarged view of the power generation section 3 and its surroundings in the wastewater treatment device 1A, and the treatment tank 2 and the reaction tank 5 are not shown.

[0067] As shown in FIG. 4, the pressure reducing means 4C may include flow rate adjustment valves 44a to 44d and a pressure reducing device 45. An example of the pressure reducing means 4C of this embodiment will be described with reference to FIG. 4. In the pressure reducing means 4C shown in FIG. 4, flow rate control valves 44a and 44b are provided on the connection pipe L2 and discharge pipe L3 that introduce and discharge the treated water W1 to the first cell 31a, and flow rate control valves 44c and 44d are provided on the connection pipe L10 and discharge pipe L11 that connect to the electron acceptor supply port 34a and the electron acceptor discharge port 34b that introduce and discharge the electron acceptor to the second cell 31b. This makes it possible to separate the first cell 31a and the second cell 31 from other equipment (treatment tank 2, reaction tank 5, etc.) related to the wastewater treatment device 1A by opening and closing the flow rate control valves 44a to 44d. In order to reduce the pressure in the partitioned space, the pressure reducing means 4C shown in FIG. 4 is provided with a pressure reducing device 45 that is connected to the first cell 31a and the second cell 31b. This reduces the pressure in the partitioned space, that is, the first cell 31a and the second cell 31b, by driving the pressure reducing device 45. At this time, the gas contained in the electrodes 33a and 33b is released to the outside of the electrodes 33a and 33b, so that the electrodes can be degassed.

[0068] The pressure reducing device 45 is not particularly limited as long as it can reduce the pressure in the first cell 31a and the second cell 31b. For example, the pressure reducing device 45 may be a device known as a pressure reducing pump.

[0069] The pressure reducing means 4C is not limited to the configuration shown in Fig. 4. For example, when the electron acceptor supplied to the second cell 31b is a gas and degassing is not required at the electrode 33b, the pressure reducing means 4C may be provided only on the first cell side. In this case, the pressure reducing means 4C may be provided with flow control valves 44a, 44b and a pressure reducing device 45 connected only to the first cell 31a. This allows degassing to be performed only on the electrode 33a side that comes into contact with the treated water W1 and requires gas removal, making it possible to simplify the wastewater treatment device 1A as a whole. On the other hand, if the pressure reducing means 4C is provided only in either the first cell 31a or the second cell 31b and degassing is performed by reducing pressure, the electrodes 33a, 33b and the ion exchanger 35 may be damaged due to the pressure difference between the cells. Therefore, when the pressure reducing means 4C is used as the degassing means 4, it is more preferable to partition the space to include both the first cell 31a and the second cell 31b by providing flow rate control valves 44a to 44d as shown in Fig. 4, and to reduce the pressure in the partitioned space. This makes it possible to stably perform the degassing of the electrodes 33a and 33b.

[0070] In addition, when connecting the pressure reducing device 45 to the first cell 31a and the second cell 31b, a new pipe may be provided, or an existing pipe may be utilized. In particular, by utilizing an existing pipe, the device configuration can be simplified.

[0071] The degassing means 4 in the wastewater treatment device 1A of this embodiment is not limited to the above-mentioned chemical addition means 4A, electrical treatment means 4B, and pressure reduction means 4C, each of which is performed individually, but may be a combination of a plurality of the above-mentioned means 4A to 4C. This makes it possible to select and perform a suitable degassing means 4 depending on the shape and arrangement of the electrodes 33a and 33b, thereby achieving a higher degassing effect.

[0072] The conditions for degassing the electrodes by the degassing means 4 in this embodiment (such as the number of times it is performed and the timing of degassing) are not particularly limited. For example, each degassing means 4 (means 4A to 4C) may be performed only once before or after the electrodes are installed in the power generation unit 3, or may be repeated multiple times. Note that the degassing efficiency can be increased by repeatedly performing the degassing means 4, but the number of times it is performed can be set appropriately in consideration of the costs (chemical costs, power costs, etc.) related to driving the degassing means 4. In addition, the timing for performing the degassing means 4 may include, for example, the timing when a new electrode is used, such as when replacing the electrode, as well as the timing after maintenance (cleaning, etc.) of the electrode.

[0073] Moreover, the electrodes 33a, 33b degassed by the degassing means 4 of this embodiment can be configured as independent electrodes of the present invention. The electrodes of the present invention are not particularly limited in terms of form, etc., as long as they have been degassed by the degassing means 4. For example, the electrodes may be degassed by the degassing means 4 provided outside the power generation unit 3, and may be stored in a storage container or the like to be transportable. The electrode of the present invention is an electrode that is brought into contact with treated water (treated water W1 in this embodiment) after treatment in a wastewater treatment device (wastewater treatment device 1A in this embodiment) that treats water to be treated, and is used to generate electricity during a series of treatment processes in wastewater treatment, and can solve the problem of a decrease in the specific surface area inside the electrode. This makes it possible to suppress a decrease in the efficiency of the electrode reaction and improve the efficiency of power generation and electrochemical treatment in the wastewater treatment device.

[0074] The wastewater treatment device 1A in this embodiment uses a reducing substance in the water to be treated W as an electron donor, generates electricity through an electrochemical reaction (electrode reaction), and recovers and utilizes the energy. In general, when an electrochemical reaction is performed, 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 5 on top of an insulator, constructing the outer wall or inner wall of the treatment tank 2 and the reaction tank 5 from an insulator, or coating the outer wall or inner wall of the treatment tank 2 and the reaction tank 5 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.

[0075] As described above, the wastewater treatment device and wastewater treatment method of this embodiment make it possible to generate electricity during a series of wastewater treatment processes. This makes it possible to generate electricity efficiently and recover and use energy without enlarging the size of the equipment. In addition, by carrying out an electrode reaction using components contained in the treated water after treating the water to be treated, it becomes possible to effectively utilize the components generated in the wastewater treatment process. Furthermore, by providing a degassing means for removing gas contained inside the electrode, the problem of a decrease in the specific surface area inside the electrode can be solved. This makes it possible to suppress a decrease in the efficiency of the electrode reaction and improve the efficiency of power generation and electrochemical treatment.

[0076] In addition, the electrode of this embodiment suppresses a decrease in the specific surface area inside the electrode, and when power generation is performed in a series of processes in wastewater treatment, the efficiency of power generation and electrochemical treatment can be improved. In particular, when a power generation function is added to an existing wastewater treatment device, the use of the electrode of this embodiment suppresses a decrease in the efficiency of the electrode reaction, and makes it possible to perform power generation with high efficiency.

[0077] Hereinafter, other embodiments of the treatment tank 2, power generation section 3 and reaction tank 5 in the wastewater treatment device of the present invention will be illustrated.

[0078] [Second embodiment] Fig. 5 is a schematic explanatory diagram showing a wastewater treatment device in a second embodiment of the present invention, and Fig. 6 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. 5 and 6 has the power generation unit 3 installed at different locations. The degassing means 4 may be any of the degassing means 4 shown in the first embodiment, and is not particularly limited. The same configurations as those in the first embodiment will not be described.

[0079] As shown in Figures 5 and 6, 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. 5, 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. 6, the power generation unit 3 is provided on the circulation pipe L6.

[0080] 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.

[0081] 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.

[0082] 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).

[0083] 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.

[0084] 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 production 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 treated water W1 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). In addition, treated water W3 generated in the methane fermentation tank 22 is discharged outside the treatment system via a discharge pipe L7.

[0085] 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).

[0086] 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.

[0087] 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.

[0088] The power generating section 3 in this embodiment is provided on a circulation flow path formed by the circulation pipes L5 and L6.

[0089] As shown in FIG. 5, in the case where the power generation unit 3 is provided on the circulation pipe L5, the treated water W1 from the methane fermentation tank 22 is supplied to the first cell 31a, and the treated water W2 after the reaction at the electrode 33a is supplied to the acid generation tank 21 through the circulation pipe L5. At this time, the treated water W2 after the reaction at the electrode 33a becomes a solution in which the hydrogen ion concentration increases and the pH is acidic, as shown in Equation 1 and Equation 2. 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 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 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 W2 discharged from the power generation unit 3 flows into the acid generation tank 21 and causes the pH range in the acid generation tank 21 to deviate from the appropriate range, the inflow amount of treated water W2 can be controlled and the pH of the water W to be treated in the acid generation tank 21 can be controlled, making it possible to suppress inhibition of the reaction in the acid generation tank 21.

[0090] As shown in FIG. 6, in the case where the power generation unit 3 is provided on the circulation pipe L6, the treated water W1 from the upper part of the methane fermentation tank 22 is supplied to the first cell 31a, and the treated water W2 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 treated water W2 after the reaction at the electrode 33a becomes a solution with a reduced concentration of dissolved hydrogen sulfide as shown in formulas 1 and 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 treated water W2 discharged from the power generation unit 3 to the lower part of the methane fermentation tank 22 can be effectively circulated in the methane fermentation tank 22 without inhibiting methane fermentation.

[0091] When the chemical agent adding means 4A is used as the degassing means 4 in the wastewater treatment device 1B of this embodiment shown in FIG. 6, the activity of bacteria contained in the granule layer in the methane fermentation tank 22 may be reduced by supplying the treated water W2 containing the chemical agent to the methane fermentation tank 22. Therefore, it is preferable to provide a branch pipe and a flow path switching mechanism on the circulation pipe L6 into which the treated water W2 is introduced, and to connect the branch pipe to the reaction tank 5. This allows the treated water W2 containing the chemical agent that reduces the activity of bacteria to be introduced into the reaction tank 5 via the branch pipe, thereby suppressing the reduction in the activity of bacteria in the methane fermentation tank 22. Note that the treated water W2 by the degassing means 4 other than the above can be introduced into the methane fermentation tank 22 and circulated, so that the introduction destination of the treated water W2 can be appropriately switched by the flow path switching mechanism to suppress the reduction in the wastewater treatment efficiency.

[0092] In the wastewater treatment device 1B of this embodiment, the treated water W3 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 5 shown in the first embodiment may be provided downstream of the discharge pipe L7. This further improves the treatment efficiency of the water W to be treated by subjecting it to treatment in the reaction tank 5, and makes it possible to discharge the water W to be treated from the wastewater treatment device 1B to the outside of the system.

[0093] Moreover, in the wastewater treatment device 1B of this embodiment, it is possible to generate electricity through the same steps as in the first embodiment.

[0094] As described above, in the wastewater treatment device 1B and the wastewater treatment method using the wastewater treatment device 1B in this embodiment, by configuring the treatment tank 2 with the acid production tank 21 and the methane fermentation tank 22, wastewater treatment can be performed under conditions suitable for each treatment (acid production treatment and methane fermentation), thereby further improving the wastewater treatment efficiency.

[0095] 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 treated water W1 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, and it is possible to improve the wastewater treatment of the treated water W2 discharged from the power generation unit 3. In addition, by reintroducing the treated water W2 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.

[0096] [Third embodiment] FIG. 7 is a schematic explanatory view showing a wastewater treatment device according to a third embodiment of the present invention. As shown in Fig. 7, in the wastewater treatment device 1C according to the third embodiment, the reaction tank 5 in the wastewater treatment device 1A according to the first embodiment is replaced with an aeration tank 51, and the aeration tank 51 is connected to the electron acceptor supply port 34a provided in the second cell 31b of the power generation section by a connection pipe L8. The degassing means 4 in the wastewater treatment device 1C according to this embodiment can be appropriately selected from the above-mentioned degassing means 4. Descriptions of the same configurations as those in the first embodiment will be omitted.

[0097] In the wastewater treatment device 1C of this embodiment, treated water W2 in the aeration tank 51 is supplied to the power generation unit 3 and used as an electron acceptor in the power generation unit 3. Note that treated water W2 other than that supplied to the power generation unit 3 through the connection pipe L8 is discharged outside the system as treated water W3.

[0098] The aeration tank 51 aerates the treatment water W2 introduced into the tank with an oxygen-containing gas (oxygen, air, etc.) using an aeration device 52, thereby promoting aerobic treatment by aerobic microorganisms and oxidation reactions by dissolved oxygen. 7, the aeration tank 51 in this embodiment is not limited to one into which treated water W2 discharged from the first cell 31a of the power generation section 3 is introduced and aeration is performed on the introduced treated water W2. Other examples of the aeration tank 51 include one into which treated water W1 is directly introduced from the treatment tank 2 and aeration is performed.

[0099] The aeration device 52 is not particularly limited as long as it can supply oxygen-containing gas to the treatment water W2 in the aeration tank 51. For example, a device consisting of a combination of a blower and an aeration pipe is widely used in aeration treatment.

[0100] Since an oxygen-containing gas is introduced into the aeration tank 51 by the aeration device 52, the treated water W2 in the aeration tank 51 becomes a liquid containing dissolved oxygen. Therefore, the treated water W2 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.

[0101] After being used as an electron acceptor in the power generation unit 3, the treated water W3 is discharged from the electron acceptor outlet 34b. At this time, if the discharged treated water W3 meets the water quality requirements for discharge into a river or the like, it can be discharged as is. The discharged treated water W3 may also be returned to the aeration tank 51 and aerated again. This makes it possible to more reliably control the water quality of the treated water W3 to be discharged outside the system.

[0102] Moreover, in the wastewater treatment device 1C of this embodiment, it is possible to generate electricity through the same steps as in the first embodiment.

[0103] As described above, the wastewater treatment device 1C and the wastewater treatment method using the wastewater treatment device 1C in this embodiment can utilize the products produced in 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.

[0104] The above-described embodiments are merely examples of the wastewater treatment device, the electrode, and the wastewater treatment method according to the present invention. The wastewater treatment device, the electrode, and the wastewater treatment method according to the present invention are not limited to the above-described embodiments, and the wastewater treatment device, the electrode, and the wastewater treatment method according to the above-described embodiments may be modified without departing from the gist of the claims.

[0105] For example, the wastewater treatment device in this embodiment may be provided with another mode other than the chemical addition means, the electrical treatment means, and the pressure reduction means as the degassing means. Another mode of the degassing means is, for example, a means for degassing by applying minute vibrations to the electrodes 33a and 33b in a solution such as the treated water. More specifically, an ultrasonic generator may be provided so that ultrasonic waves can be applied to the electrodes 33a and 33b arranged in the power generation unit 3. This allows the gas contained in the electrodes 33a and 33b to be broken down into smaller particles, and the gas in the electrodes 33a and 33b to be replaced with the liquid present around the electrodes 33a and 33b, making it possible to degas the electrodes. When degassing is performed using ultrasonic waves, the degassing efficiency of the electrodes can be improved and the impact on the environment related to the electrode reaction in the power generation unit 3 can be minimized.

[0106] Furthermore, for example, the wastewater treatment device in this embodiment may be provided with a plurality of power generation units. For example, the wastewater treatment device may be provided 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 power at a plurality of locations by effectively utilizing the treatment process of the water to be treated W in the wastewater treatment device, and to improve both the wastewater treatment efficiency and the power generation efficiency.

[0107] Also, for example, the electrodes 33a and 33b of the wastewater treatment device in this embodiment may be disposed in a housing with the surfaces of the electrodes 33a and 33b exposed, and may be provided in the power generation unit 3 as an electrode unit that can be removed from the power generation unit 3. This makes it easy to remove the electrodes 33a and 33b from the power generation unit 3 when degassing them, and also makes it easy to perform degassing treatment collectively by various degassing means 4, thereby making it possible to reduce the operating costs associated with the degassing treatment.

[0108] 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.

[0109] Furthermore, for example, in the wastewater treatment device of this embodiment, the electrode 33b may be provided in the aeration tank 51, and the aeration tank 51 may function as the second cell 31b of the power generation section 3. This allows the power generation section 3 and the reaction tank 5 (aeration tank 51) to be integrated, making it possible to further reduce the size of the equipment.

[0110] Furthermore, for example, the wastewater treatment device in this embodiment may be provided with an insulating mechanism. The insulating mechanism is not particularly limited as long as it can insulate treated water (treated water W2) other than the treated water W1 that reacts in the power generation unit 3. Examples of the insulating means using the insulating mechanism include eliminating electrical contact (liquid junction) between the electrode 33a of the power generation unit 3 and the treated water W2 or shortening the liquid junction time. Examples of such liquid junction eliminating means or shortening the liquid junction time include a means for making the flow of the treated water W2 discontinuous (intermittent), a means for interposing an insulator such as air in the treated water W2, or a combination of these means. This prevents electrons generated in the power generation unit 3 from flowing anywhere other than between the electrodes 33a and 33b, improving power generation efficiency. The wastewater treatment device in this embodiment may also be configured to insulate the structures (treatment tank and piping) constituting the wastewater treatment device as shown in the first embodiment. This provides a stronger insulation effect and improves the power generation efficiency of the power generation unit 3.

[0111] Furthermore, for example, the wastewater treatment device in this embodiment may have some of its structures omitted to further simplify the device configuration. An example of a structure that can be omitted is the ion exchanger 35. This allows the power generation section 3 to be simplified and facilitates maintenance work. Another example of a structure that can be omitted is 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 to be further simplified. In this case, one surface of the electrode 33b may be in contact with the treated water W1 or the ion exchanger 35, 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 prevent solid impurities such as dust from adhering to the surface of the electrode 33b. [Industrial Applicability]

[0112] The wastewater treatment device and the wastewater treatment method of the present invention are used for wastewater treatment in which water to be treated is treated, and are particularly suitable for use in wastewater treatment in which reducing substances are generated by treating the water to be treated. The electrode of the present invention is also suitably used as an electrode for generating electricity in a series of treatment processes in wastewater treatment for treating water to be treated. [Explanation of symbols]

[0113] 1A, 1B, 1C wastewater treatment device, 2 treatment tank, 21 acid generation tank, 22 methane fermentation tank, 23 settler, 24 pH adjustment means, 3 power generation unit, 31a first cell, 31b second cell, 32a treated water inlet, 32b treated water outlet, 33a, 33b electrodes, 34a electron acceptor supply port, 34b electron acceptor outlet, 35 ion exchanger, 4 degassing means, 4A chemical addition means, 4B electrical treatment means, 4C pressure reduction means, 41a, 41b chemical supply port, 42 chemical supply means, 43 voltage / current control device, 44a, 44b, 44c, 44d flow rate control valve, 45 pressure reduction device, 5 reaction tank, 51 aeration tank, 52 aeration device, L1 introduction pipe, L2, L10 connection pipe, L3, L7, L11 Discharge pipe, L4, L8, L9 connection pipe, L5, L6 circulation pipe, W treated water, W1, W2, W3 treated water

Claims

1. A wastewater treatment device that treats water to be treated, a power generation unit that generates power by contacting the treated water with an electrode after the treatment of the water to be treated; and a degassing means for removing gas contained in the electrodes by applying a voltage to the electrodes.

2. A wastewater treatment device that treats water to be treated, a power generation unit that generates power by contacting the treated water with an electrode after the treatment of the water to be treated; and a degassing means for removing gas contained in the electrodes by adding an organic solvent or a defoaming agent to the electrodes.

3. A method for storing an electrode that is in contact with treated water after treatment in a wastewater treatment device that treats water to be treated, comprising the steps of: a degassing step for degassing the electrodes by applying a voltage; A method for storing an electrode, comprising: a storage step of storing the electrode after the degassing step in a storage solution.

4. A wastewater treatment method for treating water to be treated, comprising the steps of: a power generation step of contacting the treated water with an electrode to generate power; a deaeration step of removing gas contained in the electrodes by applying a voltage to the electrodes.

5. A wastewater treatment method for treating water to be treated, comprising the steps of: a power generation step of contacting the treated water with an electrode to generate power; a deaeration step of removing gas contained in the electrodes by adding an organic solvent or an antifoaming agent to the electrodes.

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