Fermentation apparatus

Abstract

To provide a fermentation apparatus capable of efficiently fermenting water to be treated.SOLUTION: A fermentation apparatus 1 includes a fermentation tank 2 for containing organic-containing water to be treated W and microorganisms that ferment the organic matter; an electrode 3 installed within the fermentation tank 2 for applying an electric current to the water to be treated W; and a gas discharge part 4 for discharging gas G generated from the electrode 3 by electrolysis of the water to be treated W to the outside of the fermentation tank 2. The gas discharge part 4 may include a gas collection part 41 provided above the electrodes 3 for collecting the gas G, and a gas discharge pipe 42 open into the gas collection part 41 for leading the gas G collected in the gas collection part 41 to the outside of the fermentation tank 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fermentation apparatus. [Background technology]

[0002] Fermentation by microorganisms has been used for the purpose of removing organic matter from water to be treated that contains organic matter, recovering resources, etc. For example, Patent Document 1 describes a method for promoting methane fermentation, which includes: (1) a bioelectrochemical treatment step in which a carrier-holding electrode having a carrier on at least a part of the electrode surface is brought into contact with an organic substrate and a methane fermentation liquid that contains a group of microorganisms involved in methane fermentation and that subjects the organic substrate to methane fermentation; and (2) a fixed film fermentation step in which the fermentation liquid obtained in the bioelectrochemical treatment step is brought into contact with a fixed film containing a conductive material. In the (1) bioelectrochemical treatment step in the method for promoting methane fermentation of Patent Document 1, a current of 3 μA / cm 2 Fermentation is carried out while controlling the current as follows: [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-057634 Summary of the Invention [Problem to be solved by the invention]

[0004] In the method for promoting methane fermentation described in Patent Document 1, when fermentation is carried out while an electric current is passed through the organic substrate, the water in the organic substrate is electrolyzed, which may generate hydrogen and oxygen. However, because methane fermentation by microorganisms is carried out in an anaerobic atmosphere, the generation of oxygen by electrolysis may reduce the efficiency of methane fermentation.

[0005] The present invention has been made in view of the above problems, and aims to provide a fermentation apparatus that can efficiently ferment water to be treated. [Means for solving the problem]

[0006] One aspect of the present invention is a fermentation tank that accommodates water to be treated containing organic matter and microorganisms that ferment the organic matter, an electrode installed in the fermenter for passing an electric current through the water to be treated; and a gas outlet portion that leads gas generated from the electrodes by electrolysis of the water to the outside of the fermenter. [Effects of the Invention]

[0007] The fermentation device has electrodes arranged in the fermentation tank, so that by passing an electric current through the water to be treated via the electrodes, it is possible to promote the fermentation of organic matter in the water to be treated by microorganisms.

[0008] The fermentation apparatus also has a gas outlet that leads gas generated from the electrodes by electrolysis of the water to the outside of the fermenter. The gas outlet leads gas that interferes with fermentation by microorganisms out of the fermenter, thereby maintaining an atmosphere suitable for fermentation in the fermenter. As a result, fermentation of organic matter by microorganisms can be carried out efficiently.

[0009] Therefore, according to the above-described embodiment, it is possible to provide a fermentation apparatus that can efficiently ferment the water to be treated. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram showing the main parts of the fermentation apparatus in the first embodiment. [Figure 2] FIG. 2 is an explanatory diagram of another aspect of the fermenter of the fermentation apparatus in the second embodiment. [Figure 3] FIG. 3 is an explanatory diagram showing the main parts of a fermentation apparatus equipped with two fermentation tanks according to the third embodiment. [Figure 4] FIG. 4 is an explanatory diagram of another aspect of a fermentation apparatus having two fermentation tanks in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Embodiment 1) An embodiment of the fermentation apparatus will be described with reference to Fig. 1. As shown in Fig. 1, the fermentation apparatus 1 of this embodiment includes a fermentation tank 2 that contains water to be treated W containing organic matter and microorganisms that ferment the organic matter, an electrode 3 that is installed in the fermentation tank 2 and that applies an electric current to the water to be treated W, and a gas outlet 4 that leads gas G generated from the electrode 3 by electrolysis of the water to be treated W to the outside of the fermentation tank 2.

[0012] The fermenter 2 in the fermentation apparatus 1 of this embodiment can take various forms as long as it can bring the water to be treated W into contact with microorganisms and ferment the organic matter in the water to be treated W. For example, the fermenter 2 may be configured to perform anaerobic fermentation or aerobic fermentation. The fermenter 2 may also be configured to generate biogas by fermenting organic matter, or to perform a dephosphorization treatment to recover phosphorus from the organic matter or a denitrification treatment to recover nitrogen from the organic matter by fermenting the organic matter. For example, the fermenter 2 of this embodiment is configured to produce biogas B from the organic matter in the water to be treated W by anaerobic fermentation.

[0013] There are no particular limitations on the water to be treated W supplied to the fermenter 2 or the microorganisms used for fermentation, and water to be treated W and microorganisms can be used appropriately depending on the desired fermentation mode. For example, wastewater containing organic waste such as sewage sludge and food residues can be used as the water to be treated W. In addition, industrial wastewater containing organic matter, such as waste water-soluble coolant recovered from machining equipment, can also be used as the water to be treated W.

[0014] Furthermore, microorganisms that can be used include, for example, methanogens such as Methanobacterium and Methanosarcina, polyphosphate-accumulating bacteria, nitrifying bacteria, and denitrifying bacteria, depending on the desired mode of fermentation. For example, the microorganisms used for fermentation in this embodiment include at least methanogens. By using microorganisms including methanogens to ferment organic matter in the water to be treated W under an anaerobic atmosphere, a biogas B containing methane can be produced.

[0015] When the water to be treated W contains hydrocarbons such as mineral oil, it is more preferable that the microorganisms include methanogens, hydrolytic bacteria, and acidogenic bacteria. When the methanogens, hydrolytic bacteria, and acidogenic bacteria are brought into contact with hydrocarbons in the fermenter 2, the hydrocarbons are digested by the hydrolytic bacteria and acidogenic bacteria, producing acetic acid, hydrogen, and carbon dioxide. These products are then further digested by the methanogens, which is believed to enable more efficient production of biogas B containing methane.

[0016] From the viewpoint of ensuring the effect of promoting fermentation by electric current, it is preferable that the microorganisms in the sludge include organic matter-utilizing bacteria that have the ability to ferment organic matter in the water to be treated W, and electron-emitting bacteria that have the ability to transfer electrons received from outside to the organic matter-utilizing bacteria. In this case, electrons can be supplied to the electron-emitting bacteria by passing an electric current through the water to be treated W via the electrode 3. Furthermore, the electron-emitting bacteria that have received electrons can transfer the electrons to the organic matter-utilizing bacteria, thereby promoting the fermentation of organic matter by the organic matter-utilizing bacteria.

[0017] The type of organic matter-utilizing bacteria is not particularly limited. For example, organic matter-utilizing bacteria include methanogens. Electron-emitting bacteria have the property of receiving electrons from the outside and transferring them to organic matter-utilizing bacteria. Examples of microorganisms with this property include Morganella morganii and Proteus mirabilis.

[0018] The contact between the water to be treated W and the microorganisms in the fermenter 2 can take various forms. For example, the fermenter 2 may agitate a mixture of the water to be treated W and microorganisms or sludge containing microorganisms, thereby bringing the water to be treated W into contact with the microorganisms, thereby fermenting the organic matter in the water to be treated W. The fermenter 2 may also have, for example, a microbial carrier supporting microorganisms, and bring the water to be treated W into contact with the microbial carrier, thereby fermenting the organic matter in the water to be treated W. The fermenter 2 of this embodiment is configured to agitate a mixture of the water to be treated W and microorganisms or sludge containing microorganisms, thereby bringing the water to be treated W into contact with the microorganisms.

[0019] The fermenter 2 may further include a fermentation promotion unit 21 for promoting the fermentation of organic matter. For example, the fermenter 2 of this embodiment includes, as the fermentation promotion unit 21, an agitation unit 211 that agitates the water W to be treated in the fermenter 2 and further improves the contact efficiency between the organic matter and the microorganisms. Although not shown in the figure, the fermentation promotion unit 21 may also include a temperature adjustment unit that adjusts the temperature in the fermenter 2 to increase the activity of the microorganisms, or a pH adjustment unit that adjusts the pH in the fermenter 2 to increase the activity of the microorganisms, etc.

[0020] Electrodes 3 are provided in the fermenter 2 for passing a current through the water to be treated W. The number, shape, and arrangement of the electrodes 3 arranged in the fermenter 2 can take various forms. For example, one electrode 3 may be provided in the fermenter 2. In this case, a current can be passed through the water to be treated W by applying a voltage between the electrode 3 and the fermenter 2. Two or more electrodes 3 may be provided in the fermenter 2. In this case, a current can be passed through the water to be treated W by applying a voltage between the electrodes 3 so that some of the electrodes 3 serve as anodes and the remaining electrodes 3 serve as cathodes.

[0021] The electrode 3 may have various shapes such as a rod, a plate, or a mesh. The electrode 3 may extend in a direction parallel to the vertical direction of the fermenter 2, or in a direction perpendicular to the vertical direction. When the fermenter 2 has multiple electrodes 3, the anode and the cathode may be disposed opposite each other in the vertical direction of the fermenter 2, or may be disposed opposite each other in a direction perpendicular to the vertical direction of the fermenter 2.

[0022] The fermenter 2 of this embodiment has one anode 32 and one cathode 33 as electrodes 3. The anode 32 and the cathode 33 are arranged at an interval from each other in a direction perpendicular to the vertical direction of the fermenter 2. The anode 32 and the cathode 33 each have a rod-like shape and extend in a direction parallel to the vertical direction of the fermenter 2.

[0023] When the fermenter 2 has a plurality of electrodes 3, the electrodes 3 are preferably arranged so that their projected positions differ from one another when projected from above the fermenter 2. That is, the plurality of electrodes 3 are preferably arranged at positions that do not overlap one another in a top view from above the fermenter 2. In this case, it is possible to more easily prevent the gas G generated from each electrode 3 from mixing with one another during the period from when the gas G is generated from the electrode 3 by electrolysis of the water to be treated W until the gas G is recovered by the gas discharge part 4. Therefore, in this case, the gas G that inhibits microbial fermentation can be more easily guided to the outside of the fermenter 2, and the fermentation of organic matter by the microorganisms can be more efficiently carried out.

[0024] The fermentation apparatus 1 has a gas outlet section 4 that leads gas G generated from the electrodes 3 by electrolysis of the water to be treated W to the outside of the fermenter 2. The specific embodiment of the gas outlet section 4 is not particularly limited, and various embodiments are possible. The gas outlet section 4 only needs to be configured to lead at least the gas G that interferes with fermentation out of the gas G generated from the electrodes 3 by electrolysis to the outside of the fermenter 2.

[0025] For example, the gas outlet 4 of this embodiment is configured to be able to guide the gas G generated from the anode 32 to the outside of the fermenter 2. In the anode 32, oxygen-containing gas G is generated by electrolysis of the water to be treated W, and if the gas G generated from the anode 32 fills the fermenter 2, anaerobic fermentation by microorganisms may be hindered. Therefore, in a fermentation apparatus 1 that performs anaerobic fermentation, the gas G generated from the anode 32 is guided to the outside of the fermenter 2 by the gas outlet 4, so that anaerobic fermentation of organic matter by microorganisms can be carried out more efficiently.

[0026] Furthermore, the gas outlet part 4 may be configured to be able to guide the gas produced from the cathode 33 to the outside of the fermenter 2. In the cathode 33, a gas containing hydrogen is produced by electrolysis of the water to be treated W. Depending on the mode of fermentation in the fermenter 2, hydrogen may not be necessary for fermentation by microorganisms. Therefore, the gas outlet part 4 can also guide the gas produced from the cathode 33 to the outside of the fermenter 2 as needed.

[0027] The gas discharge section 4 in this embodiment is provided above the anode 32 serving as the electrode 3, and includes a gas collection section 41 that collects the gas G, and a gas discharge pipe 42 that opens into the gas collection section 41 and leads the gas G collected in the gas collection section 41 to the outside of the fermenter 2. The gas G generated by the electrolysis of the water to be treated W typically rises above the electrode 3 due to buoyancy. Therefore, by providing the gas collection section 41 above the electrode 3, the gas G generated from the electrode 3 can be easily collected. Furthermore, by providing the opening of the gas discharge pipe 42 in the gas collection section 41, the gas G collected in the gas collection section 41 can be reliably led to the outside of the fermenter 2.

[0028] The gas collecting unit 41 may take various forms as long as it is configured to be able to collect the gas G generated from the electrode 3 and store the gas inside the gas collecting unit 41. For example, the gas collecting unit 41 of this embodiment has a collecting cup 411 that covers the upper part of the electrode 3. The collecting cup 411 has a cup shape, and is attached to the fermenter 2 such that the opening of the collecting cup 411 faces downward in the fermenter 2. The collecting cup 411 is configured to be able to store the gas G generated from the electrode 3 inside the collecting cup 411.

[0029] One end of the gas outlet pipe 42 protrudes into the collecting cup 411, and the gas G in the collecting cup 411 can flow into the gas outlet pipe 42. The other end of the gas outlet pipe 42 is connected to, for example, a recovered gas tank or gas purification equipment (not shown), and the gas G that has flowed into the gas outlet pipe 42 can be guided to the outside of the fermenter 2.

[0030] The gas discharge pipe 42 preferably has a backflow prevention part 43 that prevents substances outside the fermenter 2 from flowing back into the fermenter 2. By providing the backflow prevention part 43 in the gas discharge pipe 42, an atmosphere suitable for fermentation can be more easily maintained inside the fermenter 2. The specific embodiment of the backflow prevention part 43 is not particularly limited, and various embodiments are possible. For example, the gas discharge pipe 42 of this embodiment has a check valve 431 as the backflow prevention part 43, and the check valve 431 can prevent substances from flowing back from the outside to the inside of the fermenter 2.

[0031] The fermenter 2 may have a biogas outlet 22 that leads biogas B produced by the fermentation of organic matter to the outside of the fermenter 2. The fermenter 2 of this embodiment has a biogas outlet pipe 221 as the biogas outlet 22 at its upper part. The biogas B led to the outside of the fermenter 2 by the biogas outlet 22 is used for various purposes depending on its composition. For example, biogas B containing methane may be used as fuel for generators. Furthermore, methane refined from biogas B may be used, for example, as a raw material for C1 chemistry or as a carbon source in carburization processes.

[0032] The fermentation apparatus 1 may have a voltage control unit 31 that adjusts the voltage applied to the electrodes 3. In this case, the voltage applied to the electrodes 3 can be adjusted within an appropriate range, and excessive progress of electrolysis of the water to be treated W can be easily prevented.

[0033] The fermentation apparatus 1 of this embodiment has electrodes 3 arranged in the fermenter 2. Therefore, by passing an electric current through the water to be treated W via the electrodes 3, the fermentation of organic matter in the water to be treated W by microorganisms can be promoted.

[0034] The fermentation apparatus 1 also has a gas outlet 4 that leads gas G generated from the electrodes 3 by electrolysis of the water to be treated W to the outside of the fermenter 2. The gas outlet 4 leads gas G that interferes with fermentation by microorganisms out of the gas G generated by electrolysis of the water to be treated W to the outside of the fermenter 2, thereby maintaining an atmosphere suitable for fermentation inside the fermenter 2. As a result, fermentation of organic matter by microorganisms can be carried out efficiently.

[0035] Therefore, the fermentation apparatus 1 of this embodiment can efficiently ferment the water to be treated W.

[0036] (Embodiment 2) In this embodiment, another example of a fermenter will be described. Note that, among the symbols used in the following embodiments, the same symbols as those used in the previous embodiments represent the same components as those in the previous embodiments, unless otherwise specified. As shown in FIG. 2, the fermenter 202 in the fermenter 102 of this embodiment is a down-flow hanging sponge (DHS) reactor. More specifically, the fermenter 202 has a partition plate 24 that divides its internal space 23 into an upper space 231 and a lower space 232, a plurality of microorganism carriers 25 that are arranged in the upper space 231 and support microorganisms, a treated water spraying section 26 that sprays the treated water W onto the microorganism carriers 25, and a treated water discharge section 27 that has a treated water discharge pipe 271 that opens into the lower space 232 and discharges the treated water W stored in the lower space 232 to the outside of the fermenter 102. An electrode 3 is disposed in the lower space 232 of the fermenter 202 .

[0037] The fermenter 202 configured as a DHS reactor as in this embodiment has a large number of microbial carriers 25 therein, and can support a large number of microorganisms on these microbial carriers 25. Therefore, by fermenting the water to be treated W using the fermenter 202 of this embodiment, the water to be treated W and the microorganisms can be brought into sufficient contact with each other, and the fermentation of organic matter in the water to be treated W can be carried out more efficiently. Furthermore, the fermenter 202 of this embodiment can carry out fermentation efficiently even when water to be treated W having a high concentration of organic matter is used.

[0038] The shape and size of the fermenter 202 in the fermenter 102 of this embodiment can take various forms. For example, the shape of the fermenter 202 in this embodiment is cylindrical with a diameter of 2 m. The height of the fermenter 202 is 2 m. The fermenter 202 is configured to produce biogas B by anaerobic fermentation.

[0039] The fermenter 202 is provided with a partition plate 24 that divides the internal space 23 into an upper space 231 and a lower space 232. The partition plate 24 is configured to allow the water W to flow through.

[0040] The microorganism carrier 25 is placed on the partition plate 24 in the upper space 231 of the fermenter 202. For example, a porous body such as a resin sponge, a cylindrical body such as a plastic body molded into a cylindrical shape, a framed porous body in which a plastic frame is provided around a porous body, etc. can be used as the microorganism carrier 25. Specifically, the microorganism carrier 25 of this embodiment is a framed porous body in which a plastic frame is provided around a resin sponge.

[0041] The untreated water spraying unit 26 is configured to be able to spray the untreated water W onto the microorganism carriers 25. The specific form of the untreated water spraying unit 26 is not particularly limited, and various forms are possible. For example, the untreated water spraying unit 26 may be, for example, a spray nozzle configured to be able to spray the untreated water W into the fermenter 202, or a spray pipe with small holes for discharging the untreated water W.

[0042] The arrangement of the untreated water spraying unit 26 is not particularly limited. For example, the untreated water spraying unit 26 in this embodiment is arranged above the microbial carriers 25 and is configured to spray the untreated water W from above the microbial carriers 25. By arranging the untreated water spraying unit 26 above the microbial carriers 25 in this way, the untreated water W can be more easily sprayed over the entire microbial carriers 25 in the fermenter 202, and the fermentation of organic matter in the untreated water W can be more efficiently carried out. Furthermore, although not shown in the figure, the untreated water spraying unit 26 may be arranged along the side surface in the upper space 231 of the fermenter 202 and configured to spray the untreated water W from the side of the microbial carriers 25.

[0043] In the upper space 231 of the fermenter 202 of this embodiment, a biogas outlet 22 is provided that leads the biogas B produced by the fermentation of the organic matter to the outside of the fermenter 202.

[0044] In the lower space 232 of the fermenter 202, there are arranged a water-to-be-treated discharge section 27, an electrode 3, and a gas outlet section 4. The specific form of the water-to-be-treated discharge section 27 is not particularly limited, and various forms are possible. For example, the water-to-be-treated discharge section 27 in this embodiment has a water-to-be-treated discharge pipe 271 that opens into the lower space 232. The water-to-be-treated discharge pipe 271 can guide the water-to-be-treated W stored in the lower space 232 to the outside of the fermenter 202.

[0045] The electrode 3 is installed upright on the bottom of the fermenter 202 in the lower space 232. The fermenter 102 of this embodiment has two electrodes 3, an anode 32 and a cathode 33, and the anode 32 and the cathode 33 are arranged at positions spaced apart from each other.

[0046] Above the anode 32 in the lower space 232, a gas discharge part 4 is provided, which includes a gas collecting part 41 and a gas discharge pipe 42. In addition, a check valve 431 serving as a backflow prevention part 43 is provided in the gas discharge pipe 42.

[0047] The water to be treated W that has come into contact with the microbial carriers 25 in the upper space 231 of the fermenter 202 configured as a DHS reactor passes through the partition plate 24 and flows into the lower space 232. At this time, some of the microorganisms attached to the microbial carriers 25 also flow into the lower space 232 together with the water to be treated W. The microorganisms that have flowed into the lower space 232 in this way are not inactivated and may still have the ability to ferment organic matter in the water to be treated W. Therefore, by passing an electric current through the water to be treated W stored in the lower space 232, fermentation by the microorganisms can be promoted.

[0048] Furthermore, a gas outlet 4 is provided above the anode 32 in the fermenter 202. Therefore, the gas G generated from the anode 32 by the electrolysis of the water to be treated W can be led to the outside of the fermenter 202, making it easy to maintain an atmosphere inside the fermenter 202 suitable for anaerobic fermentation.

[0049] (Embodiment 3) In this embodiment, an example of a fermentation apparatus equipped with two fermenters will be described. As shown in Fig. 3, the fermentation apparatus 103 of this embodiment has two fermenters: a first fermenter 203 and a second fermenter 204. The first fermenter 203 has an electrode 3 and a gas outlet part 4. The gas outlet part 4 is configured to introduce the gas G discharged from the first fermenter 203 into the second fermenter 204.

[0050] The specific aspects of the first fermenter 203 and the second fermenter 204 are not particularly limited and may take various forms. For example, the first fermenter 203 of this embodiment is configured, similar to the fermenter 2 of embodiment 1, to bring the water to be treated W and the microorganisms into contact with each other by stirring a mixture of the water to be treated W and the microorganisms, and to generate biogas B through anaerobic fermentation of organic matter. The first fermenter 203 also has a stirring unit 211 as the fermentation promoter 21, two electrodes 3 including an anode 32 and a cathode 33, and a biogas discharge unit 22 equipped with a biogas discharge pipe 221. The configurations of these parts of the first fermenter 203 are the same as the configurations of the corresponding parts of the fermenter of embodiment 1.

[0051] A gas outlet section 4 including a gas collector 41 and a gas outlet pipe 42 is provided above the anode 32 in the first fermenter 203. A first end 421 of the gas outlet pipe 42 opens into the gas collector 41, allowing the gas collected by the gas collector 41 to flow into the gas outlet pipe 42. A second end 422 of the gas outlet pipe 42 opens into the second fermenter 204. This allows the gas G generated by electrolysis at the anode 32 in the first fermenter 203 to be introduced into the second fermenter 204 via the gas outlet pipe 42.

[0052] Furthermore, the gas discharge pipe 42 of this embodiment has a gas retention section 432 as the backflow prevention section 43. The gas retention section 432 is provided between the first end 421 and the second end 422 of the gas discharge pipe 42, and is positioned above the water surface of the water W to be treated in the first fermentation tank 203 and the water surface of the water W to be treated in the second fermentation tank 204. Furthermore, the second end 422 of the gas discharge pipe 42 extends below the water surface of the water W to be treated in the second fermentation tank 204.

[0053] In this way, by providing a gas stagnation section 432 in the gas discharge pipe 42 and extending the second end 422 of the gas discharge pipe 42 below the water surface of the water to be treated W in the second fermentation tank 204, the second end 422 of the gas discharge pipe 42 can be sealed with the water to be treated W in the second fermentation tank 204.

[0054] Furthermore, when the gas G is collected by the gas collector 41 of the first fermenter 203, the pressure inside the gas discharge pipe 42 increases, and the water level of the water to be treated W in the second fermenter 204 inside the gas discharge pipe 42 can be pushed down. When the water level of the water to be treated W inside the gas discharge pipe 42 reaches the second end 422, the gas G that has accumulated in the gas retention section 432 flows into the second fermenter 204. Therefore, by providing the gas retention section 432 in the gas discharge pipe 42 and extending the second end 422 of the gas discharge pipe 42 below the water level of the water to be treated W in the second fermenter 204, it is possible to prevent substances in the second fermenter 204 from flowing back into the first fermenter 203, and to guide the gas G collected by the gas collector 41 into the second fermenter 204.

[0055] The second fermentation tank 204 of this embodiment is configured to bring the water to be treated W into contact with the microorganisms by stirring the mixture of the water to be treated W and the microorganisms. The second fermentation tank 204 also has an agitation unit 212 as the fermentation promoter 21, and a water to be treated discharge unit 28 that discharges the water to be treated from the second fermentation tank 204. The water to be treated discharge unit 28 specifically has a water to be treated discharge pipe 281, and is configured so that the water to be treated W in the second fermentation tank 204 can be discharged to the outside via the water to be treated discharge pipe 281.

[0056] The fermentation apparatus 103 has a water-to-be-treated transfer unit 5 that transfers the water-to-be-treated W in either the first fermentation tank 203 or the second fermentation tank 204 to the other fermentation tank. The water-to-be-treated transfer unit 5 in this embodiment is configured to transfer the water-to-be-treated W after fermentation in the first fermentation tank 203 to the second fermentation tank 204 by the water-to-be-treated transfer unit 5. In this way, the water-to-be-treated W is fermented in one of the two fermentation tanks, and then further fermented in the other fermentation tank, thereby allowing the organic matter in the water-to-be-treated W to be sufficiently digested by microorganisms. As a result, the concentration of organic matter in the water-to-be-treated W can be further reduced.

[0057] The specific embodiment of the untreated water transfer unit 5 is not particularly limited and various embodiments are possible. For example, the untreated water transfer unit 5 in this embodiment has a untreated water transfer pipe 51 that connects the first fermentation tank 203 and the second fermentation tank 204, and a untreated water pump 52 that is provided in the untreated water transfer pipe 51 and sends the untreated water W in the first fermentation tank 203 to the second fermentation tank 204. The untreated water transfer unit 5 in this embodiment can transfer the untreated water W in the first fermentation tank 203 to the second fermentation tank 204 by operating the untreated water pump 52.

[0058] The fermentation apparatus 103 of this embodiment is configured to introduce gas G generated at the electrode 3 of the first fermentation tank 203 into the second fermentation tank 204. Therefore, by introducing gas G, which is generated from the electrode 3 of the first fermentation tank 203 and interferes with fermentation, into the second fermentation tank 204, the atmosphere in the first fermentation tank 203 can be easily adjusted to an atmosphere suitable for fermentation, and the fermentation of organic matter in the first fermentation tank 203 can be carried out more efficiently.

[0059] When the fermentation apparatus 103 has two fermenters, it is preferable that the fermentation apparatus 103 is configured to perform anaerobic fermentation in one of the first fermenter 203 and the second fermenter 204, and to perform aerobic fermentation in the other fermenter. For example, when anaerobic fermentation is performed in the first fermenter 203, oxygen-containing gas G generated from the electrode 3 hinders anaerobic fermentation. On the other hand, oxygen generated in the first fermenter 203 can promote aerobic fermentation in the second fermenter 204. Therefore, by introducing the gas G unnecessary for fermentation generated at the electrode 3 of the first fermenter 203 into the second fermenter 204, the atmosphere inside the second fermenter 204 can be adjusted to be suitable for fermentation. As a result, fermentation of organic matter can be performed more efficiently in both the first fermenter 203 and the second fermenter 204.

[0060] (Embodiment 4) In this embodiment, another example of a fermentation apparatus having two fermenters will be described. As shown in Fig. 4, the fermentation apparatus 104 of this embodiment has two fermenters, a first fermenter 203 and a second fermenter 205, and a water-to-be-treated transfer unit 5 that transfers the water-to-be-treated W in the first fermenter 203 to the second fermenter 205. The first fermenter 203 is configured to agitate a mixture of the water-to-be-treated W and the microorganisms to bring the water-to-be-treated W into contact with the microorganisms and generate biogas B by anaerobic fermentation. The first fermenter 203 also has an agitation unit 211 as a fermentation promoter 21, two electrodes 3 including an anode 32 and a cathode 33, and a biogas outlet unit 22 equipped with a biogas outlet pipe 221.

[0061] A gas outlet section 4 including a gas collector 41 and a gas outlet pipe 42 is provided above the anode 32 in the first fermenter 203. The gas outlet pipe 42 is also provided with a check valve 431 as a backflow prevention section 43. The configurations of these sections in the first fermenter 203 are similar to the configurations of the corresponding sections in the fermenter 2 of the first embodiment.

[0062] The treated water transfer section 5 has a treated water transfer pipe 51 that connects the first fermentation tank 203 and the second fermentation tank 205, and a treated water pump 52 that is provided in the treated water transfer pipe 51 and sends the treated water W in the first fermentation tank 203 to the second fermentation tank 205.

[0063] The second fermenter 205 is configured to agitate a mixture of the water to be treated W and the microorganisms to bring the water to be treated W into contact with the microorganisms and perform aerobic fermentation. The second fermenter 205 also has an agitation section 212 as the fermentation promoter 21, and a water to be treated discharge section 28. The configurations of these sections in the second fermenter 205 are similar to the configurations of the corresponding sections in the second fermenter 204 of the third embodiment.

[0064] In this embodiment, a second electrode 304 that passes an electric current through the water to be treated W is provided inside the second fermentation tank 205. The second electrode 304 can take various forms, similar to the electrode 3 provided in the first fermentation tank 203. For example, one second electrode 304 may be provided in the second fermentation tank 205, or two or more second electrodes 304 may be provided. The second electrode 304 can take various shapes, such as a rod, a plate, or a mesh. Furthermore, the arrangement of the second electrode 304 is not particularly limited.

[0065] For example, the second fermentation tank 205 of this embodiment has one second anode 34 and one second cathode 35 as the second electrode 304. The second fermentation tank 205 of this embodiment is configured so that a current can be passed through the water to be treated W in the second fermentation tank 205 by applying a voltage between the second anode 34 and the second cathode 35.

[0066] The second anode 34 and the second cathode 35 are disposed at an interval from each other in a direction perpendicular to the vertical direction of the second fermenter 205. The second anode 34 and the second cathode 35 each have a rod-like shape and extend in a direction parallel to the vertical direction of the second fermenter 205.

[0067] The second fermenter 205 has a second gas outlet 404 that leads the second gas G2 generated from the second electrode 304 by electrolysis of the water to be treated W to the outside of the second fermenter 205. The specific form of the second gas outlet 404 is not particularly limited, and various forms can be adopted, similar to the gas outlet provided in the first fermenter 203.

[0068] For example, the second gas discharge section 404 in this embodiment is provided above the second cathode 35 as the second electrode 304, and has a second gas collection section 44 that collects the second gas G2, and a second gas discharge pipe 45 that opens into the second gas collection section 44 and leads the second gas G2 collected in the second gas collection section 44 to the outside of the second fermentation tank 205.

[0069] More specifically, the second gas collecting unit 44 has a second collecting cup 441 that covers the upper part of the second cathode 35. The second collecting cup 441 has a cup-like shape, and is attached to the second fermenter 205 so that the opening of the second collecting cup 441 faces downward in the second fermenter 205. The second collecting cup 441 is configured to be able to store the second gas G2 generated from the second cathode 35 inside the second collecting cup 441.

[0070] A first end 451 of the second gas discharge pipe 45 opens into the second collecting cup 441, allowing the second gas G2 in the second collecting cup 441 to flow into the second gas discharge pipe 45. A second end 452 of the second gas discharge pipe 45 opens into the first fermenter 203. This allows the second gas G2 generated by electrolysis at the second cathode 35 of the second fermenter 205 to be introduced into the first fermenter 203 via the second gas discharge pipe 45.

[0071] The second gas discharge pipe 45 has a second backflow prevention part 46 that prevents substances outside the second fermenter 205 from flowing back into the second fermenter 205. This makes it easier to maintain an atmosphere suitable for fermentation inside the second fermenter 205. The specific embodiment of the second backflow prevention part 46 is not particularly limited, and various embodiments are possible.

[0072] For example, the second gas discharge pipe 45 of this embodiment has a gas retention section 461 as the second backflow prevention section 46. The gas retention section 461 is provided between the first end 451 and the second end 452 of the second gas discharge pipe 45, and is positioned above the water level of the water to be treated W in the first fermenter 203 and the water level of the water to be treated W in the second fermenter 205. The second end 452 of the second gas discharge pipe 45 extends below the water level of the water to be treated W in the first fermenter 203. By providing the gas retention section 461 in the second gas discharge pipe 45 and sealing the second end 452 of the second gas discharge pipe 45 with the water to be treated W in the first fermenter 203 in this way, it is possible to prevent substances in the first fermenter 203 from flowing back into the second fermenter 205, while guiding the second gas G2 collected by the second gas collection section 44 into the first fermenter 203.

[0073] The fermentation apparatus 104 of this embodiment is configured to introduce gas G generated at the anode 32 of the first fermentation tank 203 into the second fermentation tank 205. By introducing gas G, which interferes with anaerobic fermentation, into the second fermentation tank 205 in this way, the atmosphere inside the first fermentation tank 203 can be easily adjusted to an atmosphere suitable for anaerobic fermentation, and the fermentation of organic matter in the first fermentation tank 203 can be carried out more efficiently.

[0074] Furthermore, the fermentation apparatus 104 of this embodiment is configured to introduce the second gas G2 generated in the second cathode 35 of the second fermenter 205 into the first fermenter 203. The second gas G2 generated in the second cathode 35 contains hydrogen. Furthermore, hydrogen may be useful in promoting anaerobic fermentation. Therefore, by introducing the hydrogen-containing second gas G2 into the first fermenter 203, it is expected that the fermentation efficiency of organic matter in the first fermenter 203 will be further improved.

[0075] The present invention is not limited to the above-described embodiments and can be applied to various embodiments without departing from the spirit and scope of the present invention. For example, in Embodiments 3 and 4, examples of fermentation apparatuses in which both the first fermenter and the second fermenter are configured to ferment organic matter in the water to be treated by stirring the water to be treated with microorganisms are shown. However, the manner of contact between the water to be treated and the microorganisms in the first fermenter and the second fermenter is not limited to this. For example, the first fermenter may be configured to ferment organic matter in the water to be treated by contacting the water to be treated with a microbial carrier. The first fermenter may also be configured as the DHS reactor shown in Embodiment 2. Similarly, the second fermenter may be configured to ferment organic matter in the water to be treated by contacting the water to be treated with a microbial carrier, or may also be configured as a DHS reactor.

[0076] Although the third embodiment shows an example of a fermentation apparatus configured to perform anaerobic fermentation in the first fermentation tank 203, the fermentation apparatus may be configured to perform aerobic fermentation in the first fermentation tank 203. Similarly, the fourth embodiment shows an example of a fermentation apparatus configured to perform anaerobic fermentation in the first fermentation tank 203 and aerobic fermentation in the second fermentation tank 205, but the fermentation apparatus may be configured to perform aerobic fermentation in the first fermentation tank 203 and anaerobic fermentation in the second fermentation tank 205.

[0077] In the third and fourth embodiments, an example has been shown in which the water to be treated W is transferred from the first fermentation tank 203 to the second fermentation tanks 204 and 205 by the water to be treated transfer unit 5, but the water to be treated transfer unit 5 may be configured to transfer the water to be treated W from the second fermentation tanks 204 and 205 to the first fermentation tank 203. It is also possible not to provide the water to be treated transfer unit 5 between the first fermentation tank 203 and the second fermentation tanks 204 and 205, and to ferment different types of water to be treated in each fermentation tank. [Explanation of symbols]

[0078] 1, 102~104 Fermentation equipment 2. 202~205 Fermentation tanks 3 electrodes 4 Gas outlet section W Treated water G Gas

Claims

1. a fermenter containing water to be treated containing organic matter and microorganisms that ferment the organic matter; an electrode installed in the fermenter for passing an electric current through the water to be treated; a gas outlet section that leads gas generated from the electrodes by electrolysis of the water to the outside of the fermenter.

2. 2. The fermentation apparatus according to claim 1, wherein the gas discharge section comprises: a gas collection section provided above the electrode and configured to collect the gas; and a gas discharge pipe opening into the gas collection section and configured to guide the gas collected in the gas collection section to the outside of the fermentation tank.

3. 3. The fermentation apparatus according to claim 2, wherein the gas outlet pipe has a backflow prevention portion that prevents substances outside the fermentation tank from flowing back into the fermentation tank.

4. The fermenter includes a partition plate that divides the internal space of the fermenter into an upper space and a lower space; A plurality of microorganism carriers arranged in the upper space and carrying the microorganisms; a water-to-be-treated spraying unit that sprays the water to be treated onto the microorganism carrier; a treated water discharge section that is provided with a treated water discharge pipe that opens into the lower space and discharges the treated water stored in the lower space to the outside of the fermentation apparatus, The fermentation apparatus according to claim 1 , wherein a pair of the electrodes are disposed in the lower space.

5. The fermentation apparatus according to claim 1 , further comprising a voltage control unit that adjusts the voltage applied to the electrodes.

6. The fermentation apparatus according to any one of claims 1 to 5, wherein the fermentation apparatus has two fermentation tanks, namely, a first fermentation tank and a second fermentation tank, the first fermentation tank has the electrode and the gas outlet part, and the gas outlet part is configured to introduce the gas discharged from the first fermentation tank into the second fermentation tank.

7. The fermentation apparatus according to claim 6, wherein the second fermentation tank has a second electrode disposed therein for passing an electric current through the water to be treated.

8. 8. The fermentation apparatus according to claim 7, wherein the second fermenter has a second gas outlet portion that leads a second gas generated from the second electrode by electrolysis of the water to the outside of the second fermenter.

9. 9. The fermentation apparatus according to claim 8, wherein the second gas discharge section comprises: a second gas collection section provided above the second electrode and configured to collect the second gas; and a second gas discharge pipe opening into the second gas collection section and configured to guide the second gas collected in the second gas collection section to the outside of the second fermenter.

10. 10. The fermentation apparatus according to claim 9, wherein the second gas outlet pipe has a second backflow prevention part that prevents substances outside the second fermentation tank from flowing back into the second fermentation tank.

11. The fermentation apparatus according to claim 8 , wherein the second gas outlet section is configured to introduce the second gas discharged from the second fermenter into the first fermenter.

12. The fermentation apparatus according to claim 6 , wherein one of the first fermentation tank and the second fermentation tank is configured to perform anaerobic fermentation, and the other fermentation tank is configured to perform aerobic fermentation.

13. 7. The fermentation apparatus according to claim 6, further comprising a water-to-be-treated transfer unit that transfers the water to be treated in either the first fermentation tank or the second fermentation tank to the other fermentation tank.

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