JP5872148B2 - Biological treatment method and method for producing microorganism group-supporting carrier - Google Patents

Description

  The present invention relates to a biological treatment method and a method for producing a microorganism group-supporting carrier. More specifically, the present invention relates to a biological treatment method represented by methane fermentation treatment and the like, and a method for producing a microorganism group-supporting carrier.

  Biological treatment methods such as substance treatment methods and substance production methods utilizing microorganisms have attracted attention in recent years as methods that have low environmental impact and can be implemented at low cost, and various research and development are being promoted. .

  A typical example is a technology for methane fermentation of organic waste such as garbage. The methane fermentation treatment is a method in which organic waste is introduced into a fermentation broth and subjected to fermentation treatment with an anaerobic condition using a methane-producing bacterium to decompose the organic waste into biogas such as methane gas. Since methane fermentation treatment can greatly reduce the volume of organic waste, it has been attracting attention as an extremely useful technology that can solve the recent problems of landfill disposal and that can recover methane gas as energy. Yes.

  Therefore, in recent years, various technologies related to methane fermentation treatment have been proposed. For example, in Patent Document 1, as a system for efficiently treating organic waste such as garbage with a methane fermentation method, the organic waste is pulverized into a paste and heated at a high temperature of 50 to 60 ° C. A system for treating with methane bacteria is disclosed. Specifically, using the fact that thermophilic methane bacteria are 2-3 times more active than mesophilic bacteria whose activity is increased at medium temperatures of 36 to 38 ° C., methane fermentation is performed with high temperature methane bacteria In order to improve the decomposition rate and digestibility.

Japanese Patent Laid-Open No. 10-137730

  In general, when a substance is processed by conversion (decomposition, oxidation, reduction, etc.) using microorganisms, if the concentration of an object to be processed that is processed by microorganisms reaches a certain level or higher, It is known that the function is lowered and the processing capacity is lowered. This is no exception in methane fermentation treatment, and under high load conditions with high organic matter loading rate and hydraulic residence time, methane fermentation tanks may suffer from rancidity and the like, and the methane fermentation treatment ability may be significantly reduced. . If it falls into such a situation, it will be necessary to reproduce | regenerate a methane fermentation tank, and a methane fermentation process will be overdue. Therefore, it is desired to establish a method capable of performing continuous processing without reducing processing capacity even under high load conditions.

  The present invention has been made in view of such demands, and an object of the present invention is to provide a biological treatment method that can be efficiently performed while exhibiting excellent treatment capacity even under high load conditions. .

  Another object of the present invention is to provide a method for producing a microorganism-supporting carrier that exhibits excellent processing ability even under high load conditions.

  In order to solve such a problem, the inventors of the present application have made extensive studies, and in a methane fermentation method in which organic waste is introduced into a fermentation broth to perform methane fermentation, carbon fiber is provided on one side of a plate-like carbon electrode. By carrying the methane fermentation while bringing the carrier-supporting electrode provided into contact with the fermented liquid together with the organic waste, and controlling the potential of the carrier-holding electrode to -0.8 V to -1.0 V based on the silver / silver chloride electrode potential reference It has been found that it exhibits excellent methane fermentation treatment capacity even under high-load operation conditions.

Based on these findings, the inventors of the present application controlled the potential of the carrier holding electrode to +0.3 V with respect to the potential at which electrons are supplied from the carrier holding electrode or the silver / silver chloride electrode potential for methane fermentation treatment. Thus, the inventors have found that the possibility of being able to be implemented efficiently by exhibiting excellent processing ability even under high load conditions has led to the completion of the present invention.

That is, the methane fermentation process of the present invention is the methane fermentation processes and organic substrates include microorganisms involved in the carrier holding electrode and the organic substrate and methane fermentation with at least a part sparse aqueous carrier of the electrode surface The methane fermentation solution is brought into contact, and the methane fermentation treatment is performed while controlling the potential of the carrier holding electrode to +0.3 V based on the potential at which electrons are supplied from the carrier holding electrode or the silver / silver chloride electrode potential.

Here, in the methane fermentation method of the present invention, the carrier holding electrode is used as a working electrode, the working electrode, the counter electrode, and the reference electrode are connected to a potentiostat , and the methane fermentation solution and the electrolytic solution are connected via an ion exchange membrane. Preferably, the working electrode and the reference electrode are brought into contact with the methane fermentation solution, the counter electrode is brought into contact with the electrolytic solution, and the potential of the working electrode is controlled by a three-electrode system. In addition, the carrier holding electrode is used as a working electrode, the working electrode, the counter electrode, and the reference electrode are connected to a potentiostat , and the methane fermentation broth and the counter electrode are brought into contact with each other through an ion exchange membrane, so that the working electrode is in contact with the methane fermentation broth. And the reference electrode are brought into contact with each other, and the potential of the working electrode is preferably controlled by a three-electrode system. In this case, the potential of the carrier holding electrode is preferably controlled to -0.8 V to -1.0 V (silver / silver chloride electrode potential reference), which is a potential at which electrons are supplied from the carrier holding electrode. The carrier is preferably carbon fiber.

Next, (a method for manufacturing a carrier microorganisms is carried) Preparation method of microorganisms supporting carrier of the present invention, the carrier holding electrode having at least a part hydrophobicity of the support surface of the electrode and the organic substrate and methane A methane fermentation solution containing a microorganism group involved in fermentation and containing an organic substrate for methane fermentation is brought into contact, and the potential of the carrier holding electrode is determined based on a potential at which electrons are supplied from the carrier holding electrode or a silver / silver chloride electrode potential reference. It is controlled to + 0.3V, and a microorganism group involved in methane fermentation is supported on the carrier and activated.

Further, a method for manufacturing a microorganisms supporting carrier of the present invention (a method for manufacturing a carrier microorganisms is carried) is at least partially provided with hydrophobicity of the support carrier holding electrode and the methanogens group and methane electrode surface Contact with a culture solution containing at least a substance that is a substrate for the bacteria group, control the potential of the carrier holding electrode to the potential at which electrons are supplied from the carrier holding electrode, and activate the carrier by supporting the methanogenic bacteria group on the carrier I try to let them. According to the present invention, hydrogen-utilizing methane bacteria and acetic acid-assimilating methane bacteria can be carried and activated as the methanogenic bacteria group. Therefore, when supporting and activating hydrogen-assimilating methane bacteria, carbon dioxide and hydrogen may be included in the culture solution as substrates, and when supporting and activating acetic acid-assimilating methane bacteria In addition, a lower fatty acid (VFA) such as acetic acid may be included in the culture solution.

Here, in the method for producing a microorganism group-carrying carrier of the present invention (a method for producing a carrier carrying a microorganism group) , the carrier holding electrode is used as a working electrode, and the working electrode, the counter electrode, and the reference electrode are connected to a potentiostat. The methane fermentation broth or culture solution and the electrolytic solution are brought into contact with each other through an ion exchange membrane, the working electrode and the reference electrode are brought into contact with the methane fermentation broth or culture solution, the counter electrode is brought into contact with the electrolytic solution, and the working electrode Is preferably controlled by a three-electrode system. In addition, the carrier holding electrode is used as a working electrode, the working electrode, the counter electrode, and the reference electrode are connected to a potentiostat , and the methane fermentation broth or the culture broth is brought into contact with the counter electrode via an ion exchange membrane. Alternatively, the working electrode and the reference electrode are preferably brought into contact with the culture solution, and the potential of the working electrode is preferably controlled by a three-electrode system. In this case, the potential of the carrier holding electrode is preferably controlled to -0.8 V to -1.0 V (silver / silver chloride electrode potential reference), which is a potential at which electrons are supplied from the carrier holding electrode. The carrier is preferably carbon fiber.

  “Activation” in the present specification basically means that the function of the microorganism group to be supported itself is enhanced, but in addition to this, the carrier microorganism is propagated to grow the carrier. The meaning of enhancing the function as a whole supported microorganism group to be supported may be included.

According to the methane fermentation method of the present invention, an excellent methane fermentation treatment ability can be exhibited, and the ability is exhibited even under a high load condition in which a large amount of organic waste or the like is introduced, and for a long time. It becomes possible to perform the methane fermentation treatment continuously and efficiently.

Furthermore, according to the method for producing a carrier for supporting a microorganism group of the present invention (a method for producing a carrier on which a microorganism group is supported) , a carrier activated by supporting a microorganism group useful for methane fermentation treatment on a carrier. Can be obtained. Therefore, this carrier by using methane fermentation treatment, exhibit excellent methane fermentation treatment capacity, its capacity becomes that can be exhibited even at high load conditions large quantities have been introduced organic waste, etc., long-term It is possible to perform the methane fermentation treatment efficiently continuously over a period of. In addition, by producing a microorganism group-supporting carrier in which a methanogenic bacterium group is supported on a carrier and activated, methane can be efficiently and continuously produced over a long period of time.

It is sectional drawing of the experimental apparatus used in Reference Example A-1. It is a figure which shows the driving | running condition (load condition) of the methane fermenter in Reference Example A-1. It is a figure which shows the relationship between the setting electric potential and gas generation rate which were obtained in Reference example A-1. It is a figure which shows the relationship between the setting electric potential obtained in Reference Example A-1, and a chemical oxygen demand (COD) removal rate. It is a figure which shows the relationship between the setting electric potential obtained in Reference Example A-1, and floating solid content (SS) removal rate. It is a figure which shows the relationship between the setting potential obtained in Reference Example A-1, and a lower fatty acid concentration. It is a figure which shows the quantitative PCR result of all the microbe of the fermented liquor fraction obtained in Reference Example A-2. It is a figure which shows the quantitative PCR result of the methanogen of the fermented liquor fraction obtained in Reference Example A-2. It is a figure which shows the quantitative PCR result of all the microbes of the carrier adhesion fraction obtained in Reference Example A-2. It is a figure which shows the quantitative PCR result of the methanogen of the carrier adhesion fraction obtained in Reference Example A-2. In Reference Example A-2, it is a figure which shows the result of having analyzed the bacterial community structure by T-RFLP. In Reference Example A-2, it is a figure which shows the result of having analyzed the bacterial community structure on the carbon plate in case setting potential is -0.6V by TA cloning. In Reference Example A-2, it is a figure which shows the result of having analyzed the archaeal community structure by T-RFLP. In reference example A-2, it is a figure which shows the result of having analyzed the archaea community structure on the carbon plate in case setting potential is -0.6V by TA cloning. In Reference Example A-3, it is a figure which shows the electric potential dependence of the methanogenic activity of a methanogen. In Reference Example A-4, it is a figure which shows the result of having experimented about the difference in the gas generation rate by the kind etc. of support | carrier. It is sectional drawing of the experimental apparatus used in Reference Example A-3. It is a figure which shows the driving | running condition (load condition) of the methane fermenter in Reference Example B-1. It is a figure which shows the relationship between the setting electric potential obtained in Reference Example B-1, and a gas production rate. It is a figure which shows the relationship between the setting electric potential obtained in Reference Example B-1, and a chemical oxygen demand (COD) removal rate. It is a figure which shows the relationship between the setting electric potential obtained in Reference Example B-1, and floating solid content (SS) removal rate. It is a figure which shows the relationship between the setting potential obtained in Reference Example B-1, and a lower fatty acid concentration. It is a figure which shows the quantitative PCR result of all the microbe of the fermented liquor fraction obtained in Reference Example B-2. It is a figure which shows the quantitative PCR result of the methanogen of the fermented liquor fraction obtained in Reference Example B-2. It is a figure which shows the quantitative PCR result of all the microbes of the carrier adhesion fraction obtained in Reference Example B-2. It is a figure which shows the quantitative PCR result of the methanogen of the carrier adhesion fraction obtained in Reference Example B-2. It is a figure which shows the result of having performed the voltammetric measurement of the simulated organic waste. In Reference Example B-2, it is a figure which shows the result of having analyzed the bacterial community structure by T-RFLP. In Reference Example B-2, it is a figure which shows the result of having analyzed the archaeal community structure by T-RFLP. It is sectional drawing which shows an example of the processing apparatus concerning 1st Embodiment A. It is sectional drawing which shows an example of the processing apparatus concerning 1st Embodiment B. It is sectional drawing which shows an example of the processing apparatus concerning 1st Embodiment C. It is sectional drawing which shows an example of the processing apparatus concerning 1st Embodiment D. It is sectional drawing which shows an example of the processing apparatus concerning 2nd embodiment. It is sectional drawing which shows an example of the other form of a processing apparatus. It is a figure which shows the driving | running condition (load condition) of the methane fermenter in Example 1. FIG. It is a figure which shows the time-dependent change of the gas production | generation speed | rate in Example 1. FIG. It is a figure which shows the time-dependent change of the methane gas content rate in the biogas in Example 1. FIG. It is a figure which shows the time-dependent change of the VFA density | concentration of the methane fermentation liquid in Example 1. FIG. It is a figure which shows the COD removal rate with respect to the organic substance load in Example 1. FIG. It is a figure which shows SS removal rate with respect to the organic substance load in Example 1. FIG. It is a figure which shows the quantitative PCR result of all the microbe of the fermentation liquid fraction obtained in Example 2. FIG. It is a figure which shows the quantitative PCR result of all the microbes of the carrier adhesion fraction obtained in Example 2. FIG. It is a figure which shows the quantitative PCR result of the methane microbe of the fermented liquor fraction obtained in Example 2. It is a figure which shows the quantitative PCR result of the methane microbe of the carrier adhesion fraction obtained in Example 2. In Example 2, it is a figure which shows the result of having analyzed the archaeal community structure by T-RFLP.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  In the biological treatment method of the present invention, a carrier holding electrode provided with a carrier capable of supporting microorganisms on at least a part of the electrode surface, a microbial community including at least a microorganism group to be supported on the carrier, and a culture solution are contacted, Biological treatment is performed while controlling the potential of the carrier holding electrode within the optimum range of the microorganism group to be supported. Moreover, by carrying out the biological treatment method of the present invention, it is possible to activate a carrier group to be supported on a carrier.

  In addition, the material treatment method of the present invention comprises a carrier holding electrode provided with a carrier capable of supporting microorganisms on at least a part of the electrode surface, and a microbial community including at least a microorganism group having a substance conversion treatment ability as a supporting target microorganism group. A culture solution containing an object to be processed that is converted by the target microorganism group is brought into contact, and the object to be processed is converted while controlling the potential of the carrier holding electrode within the optimum range of the target microorganism group. Further, the substance production method of the present invention includes a carrier holding electrode provided with a carrier capable of supporting microorganisms on at least a part of the electrode surface, and a microorganism community including at least a microorganism group having substance production processing ability as a supporting target microorganism group. A substance is produced while contacting the culture solution containing the production source material of the product of the target microorganism group and controlling the potential of the carrier holding electrode within the optimum range of the target microorganism group. And by implementing the substance processing method of this invention, the microorganism group which has substance conversion processing ability can be carry | supported and activated on a support | carrier. Moreover, by carrying out the substance production method of the present invention, it is possible to activate a carrier by supporting a group of microorganisms having substance production processing ability.

  In the present invention, the entire microorganism group that can perform conversion treatment such as decomposition, oxidation, reduction, etc. on the object to be processed or the entire microorganism group that has the ability to produce a substance using a certain source material is supported. It can be a microorganism group.

  For example, decomposition of SS (solid suspended matter), decomposition removal of COD (chemical oxygen demand), decomposition removal of TOC (total organic carbon), removal of tetrachlorethylene (PCE), dichloroethylene (DCE) and vinyl chloride (VC) A known or new microorganism having a function of performing a chlorination treatment or the like can be used as a supported microorganism group. For example, microorganisms contained in sludge obtained from methane fermenters are used for SS (solid suspended solids) decomposition, COD (chemical oxygen demand) decomposition removal, and TOC (total organic carbon) decomposition removal. can do. Further, for the dechlorination of tetrachlorethylene (PCE), for example, Desulfitobacterium, Dehalococcoides, Dehalobacter, Geobacter and the like, and for the dechlorination of dichloroethylene (DCE) and vinyl chloride (VC), a microorganism group such as Dehalococcoides can be used. .

  Further, for example, known or novel microorganisms having a function of producing methane gas, hydrogen, amino acids, and various organic substances can be used as the supported microorganism group. For example, hydrogen-utilizing methanogens that produce methane gas using hydrogen and carbon dioxide as sources (for example, Methanothermobacter thermautotrophicus), acetic acid-assimilating methanogens that produce methane gas using acetic acid as a source (for example, Methanosarcina thermophila ), Clostridium acetobutylicum that produces ethanol, butanol, and acetone from glucose, but is not limited thereto.

  The carrier holding electrode used in the present invention can be used by appropriately selecting the nature of the carrier held on the electrode surface in accordance with the microbial reaction process. For example, when a microorganism that can adhere to a hydrophilic carrier is supported, a hydrophilic carrier may be used. When a microorganism that can adhere to a hydrophobic carrier is supported, a hydrophobic carrier may be used. That's fine. That is, the microorganism group can be supported in accordance with the microorganism reaction process by appropriately selecting the nature of the carrier without depending on the nature of the electrode. Therefore, for example, by holding both the hydrophilic carrier and the hydrophobic carrier on the surface of the electrode, it is easy to carry both the microorganisms attached to the hydrophilic carrier and the microorganisms attached to the hydrophobic carrier. Can be done. Moreover, it is preferable that a support | carrier is made into the form which can increase a surface area as a three-dimensional structure, such as a fibrous form, a porous body, and a granular material, and can increase the load of microorganisms.

  Here, when carrying out methane fermentation treatment or methane gas generation, it is preferable to use a hydrophobic carrier. As the hydrophobic carrier, for example, carbon fibers are preferably used, carbon fibers having a porosity of 25% to 98%, preferably carbon fibers having a porosity of 50 to 98%, and more preferably a porosity. 98% carbon fiber can be used, but the hydrophobic carrier is not limited to carbon fiber, and for example, a carrier such as a fiber made of polyethylene or polypropylene may be used. Carbon fiber is easy to secure a high porosity, and for example, a carbon fiber nonwoven fabric is suitable because it is easy to ensure a high porosity (98%) and can be obtained at low cost.

  The material used for the carrier holding electrode is not particularly limited, and any electrode capable of causing a reduction reaction on the electrode can be used. For example, although a carbon electrode is suitable, it is not limited to this.

  The carrier holding electrode used in the present invention may be provided with a carrier on at least a part of the electrode surface, but is preferably provided on one side of the electrode surface and provided on the entire electrode surface. Most preferably. The higher the carrier holding area on the electrode surface, the easier it is to support microorganisms. Examples of the method of providing the carrier on the electrode surface include adhesion by an adhesive, and a method of covering the electrode by covering the electrode with a bag or cylinder, but is not limited thereto.

  Here, it is preferable that the carrier capable of supporting the microorganism has liquid permeability capable of ensuring contact between the electrode and the methane fermentation broth. In this case, the microorganisms can be sufficiently loaded up to the vicinity of the electrode of the carrier, and the controllability of the potential in the vicinity of the electrode can be ensured to sufficiently activate the microorganism on the carrier. In other words, even if the carrier material is a conductive material such as carbon, if the porosity is increased in order to increase the amount of microorganisms supported, the conductivity performance will be substantially reduced and substantially reduced. If the carrier does not flow, but the carrier has liquid permeability that can ensure contact between the electrode and the methane fermentation broth, the potential of the methane fermentation broth that fills the gap in the carrier is controlled, and the potential environment of the carrier is reduced to microorganisms. Can be controlled within the optimum range.

As the culture solution, a normal culture solution used for culturing microorganisms may be used, and a substance that serves as an energy source for microorganisms, a substance for controlling the culture environment such as pH, and the like may be appropriately added. That's fine. The culture solution usually contains monovalent cations such as hydrogen ions, sodium ions (Na ⁺ ), and potassium ions (K ⁺ ), so that the culture solution itself has electrical conductivity and supports the carrier. The potential control of the electrode itself can be easily performed.

  The contact method between the carrier holding electrode, the target microorganism group and the culture solution is not particularly limited. For example, the carrier holding electrode and the microorganism group to be supported may be separately added to the culture solution, or the microorganism group including the microorganism group to be supported or the microorganism group to be supported is previously loaded on the carrier in the form of a biofilm, for example. You may make it carry | support and make this put into a culture solution. In any case, the target microorganism group can be supported by the carrier of the carrier holding electrode and activated. According to the present invention, it is possible to carry and activate a supported target microorganism group, and of the microorganism group including the supported target microorganism group, the supported target microorganism group is supported as a main component. Can be activated. That is, it is possible to activate a desired microorganism group as a main constituent from a microorganism group including a plurality of types of microorganism groups.

  The optimum range of the microorganism group to be supported is derived by the experimental method described below. That is, when a microorganism group having an ability to convert the object to be treated is to be supported, a certain amount of the object to be treated is added to the culture solution, and the microorganism includes at least the carrier holding electrode and the object microorganism group to be supported in the culture solution. By contacting the crowd and controlling the carrier holding electrode at various potentials for a certain period of time, the potential range in which the amount of the object to be treated contained in the culture solution is greatly reduced can be made the optimum range. When a microorganism group that produces a product is to be supported, a certain amount of a source material is added to the culture solution, and the culture solution is brought into contact with a carrier holding electrode and a microorganism community that includes at least the supported microorganism group. Thus, the carrier holding electrode can be controlled to various potentials for a certain period of time, and the potential range where the amount of product produced is large can be made the optimum range.

According to the present invention, the target microorganism group can be supported by the carrier of the carrier holding electrode and activated. Therefore, even if a material processing method or a material production method using microorganisms is performed under high load conditions, it can be efficiently performed with its excellent processing capacity. Moreover, according to the present invention, it may be possible to efficiently carry out the target treatment by inactivating or removing the microorganism group that inhibits the target treatment. In addition, in the biological treatment method of the present invention, even if carried out under high load conditions, for example, the following can be considered as one of the factors that can be carried out efficiently while exhibiting excellent treatment capacity. . That is, according to the biological treatment method of the present invention, while the carrier target microorganism group is supported on the carrier and activated, the proportion of the target microorganism group in the total bacteria in the culture solution can be increased, and the carrier One of the factors can be considered that the processing capacity of the entire processing tank including the holding electrode and the culture solution is improved. In any case, by taking the configuration of the present invention, it is possible to exhibit excellent processing capability.

  Hereinafter, the case where a methane fermentation process is implemented as a biological treatment method of the present invention will be specifically described.

  In the methane fermentation process, organic waste is reduced in volume by methane fermentation, and biogas containing methane gas is generated and recovered in the process.

  As the methane fermentation liquid, a methane fermentation liquid in a methane fermentation tank in which methane fermentation treatment such as organic waste is performed or a culture liquid to which methane fermentation sludge is added can be used. Moreover, the culture solution which added the microorganism community which cultured the microorganism group for performing methane fermentation artificially can also be used.

  Organic waste is introduced into the methane fermentation broth as an organic substrate. Examples of the organic waste include, but are not limited to, livestock waste, raw garbage, wastewater treatment sludge, rice cakes such as rice straw and wheat straw, paper waste, various biomass, and the like. In addition, the organic waste is subjected to a methane fermentation treatment after performing pretreatment such as crushing and fractionation, if necessary, depending on its properties.

  As described above, as the carrier holding electrode, an electrode such as one having a hydrophobic carrier such as carbon fiber provided on at least a part of the surface of the carbon plate is immersed in the methane fermentation broth.

  The potential of the carrier holding electrode is controlled to +0.3 V based on the potential at which a reduction reaction can occur at the carrier holding electrode or the silver / silver chloride electrode potential reference. The potential at which the reduction reaction can occur at the support holding electrode is generally about -0.5 V on the basis of the silver / silver chloride electrode potential for methane fermentation liquor. If it is made larger than 6V to the minus side, a reduction reaction may occur at the carrier holding electrode, but if it is made too large on the minus side, water electrolysis may occur vigorously and methane fermentation may be stopped. Since there is a possibility that a shift to hydrogen fermentation may occur, it is preferable to set a smaller potential. Specifically, if -1.0V is included and it is made larger than -1.0V to the minus side, there is a possibility that the transition from methane fermentation to hydrogen fermentation may occur, so it is smaller than -1.0V on an absolute value basis. It is preferable to do. Incidentally, if it is about -1.2V, electrolysis of water does not occur vigorously. In the case of an embodiment provided with an ion exchange membrane, which will be described later, even if it is increased to the minus side from -1.0 V, the shift to hydrogen fermentation does not occur. May be. By controlling the potential of the carrier holding electrode in this way, the microbial group involved in the methane fermentation treatment is activated by being carried on the carrier of the carrier holding electrode, and the SS decomposition treatment, which is a series of microbial reactions of the methane fermentation treatment, COD decomposition and removal treatment, lower fatty acid decomposition treatment and methane production proceed efficiently. In addition, according to the experiments by the inventors of the present application, the organic load is finally increased to 27.8 gCOD / l / day by continuously controlling the potential to the above value for 44 days while gradually increasing the load of organic matter. It was confirmed that the methane generation proceeded without any problem. Particularly, in the case where the set potential was set to -1.0 V, the potential was finally controlled by continuously controlling the potential for 54 days while gradually increasing the organic load. Even when methane fermentation was carried out at an organic load of 32.7 g COD / l / day, it was confirmed that methane production proceeded without problems. From this, the set potential is controlled to -0.8 V to -1.0 V or +0.3 V, preferably -1.0 V on the basis of the silver / silver chloride electrode potential, and the final organic load, for example, is 20 gCOD. By gradually increasing the organic load so that it becomes / l / day and acclimatizing for at least 44 days, the methane fermentation treatment is performed even under extremely high load operating conditions of at least 27.8 g COD / l / day. Can be produced.

  Here, the methane fermentation method of the present invention is implemented by, for example, the apparatus shown in FIGS. Hereinafter, the methane fermentation method according to the first embodiment will be described based on FIGS. 30 to 33, and the methane fermentation method according to the second embodiment will be described based on FIG. 34.

<First embodiment>
In the methane fermentation method according to the first embodiment, the working electrode, the counter electrode, and the reference electrode are defined by using a carrier holding electrode having a hydrophobic carrier capable of carrying microorganisms on at least a part of the electrode surface. Connect to the potential setting device, contact the methane fermentation broth and electrolyte through the ion exchange membrane, contact the methane fermentation broth, working electrode, and reference electrode, contact the counter electrode to the electrolyte, The potential is controlled by a three-electrode system.

  The methane fermentation method according to the first embodiment is performed by, for example, the apparatus 1 shown in FIGS. That is, in the processing apparatus 1 shown in FIGS. 30 to 33, one of the two tanks partitioned by the ion exchange membrane 6 is used as the processing tank 7, and the other tank is used as the counter electrode tank 8. The methane fermentation liquid 4 is accommodated in the working electrode 9 and the reference electrode 11, and the counter electrode tank 8 is filled with the electrolytic solution 4a and the counter electrode 10 is immersed in the working electrode 9 and the counter electrode 10. Is connected to the constant potential setting device 12, and the potential of the working electrode 9 is controlled by a three-electrode system.

  In this way, by controlling the potential of the working electrode 9 by the three-electrode method, the potential of the working electrode 9 can be strictly controlled to the set potential. Specifically, a potential difference between the working electrode 9 and the reference electrode 11 is measured by a constant potential setting device (potentiostat) 12, and the working electrode 9 and the counter electrode 10 are adjusted so that the potential difference reaches the set potential. A current is passed between them so that no current flows through the reference electrode 11 serving as a reference. The details of the potential control by the three-electrode method are described in, for example, pages 6 to 9 of Electrochemical Measurement Method (above), Technical Bulletin Publishing Co., Ltd., 1st edition 15 printing, published in June 2004. ing.

  However, when the potential of the working electrode 9 can be controlled only by the voltage between the working electrode 9 and the counter electrode 10, the three-electrode system may not be used. 30 to 33, the carrier 9a capable of supporting microorganisms is provided only on one side of the working electrode 9, but it may be provided on a part of one side or on both sides. Is of course good.

  Moreover, in the processing apparatus 1 shown in FIGS. 30-33, the biogas containing the methane gas which retains in the space (head space) above the liquid level of the methane fermentation liquid 4 in the processing tank 7 is outside the processing tank 7 ( A gas exhaust pipe 15a leading to the outside of the processing apparatus 1 is provided, and the biogas in the processing tank 7 is recovered by a gas recovery means 15 that can be opened and closed by a valve 15b. However, the biogas recovery method is not limited to this method. For example, without providing the gas recovery means 15, an opening is provided in the upper part of the processing tank 7, and the opening is closed with an elastic material such as synthetic rubber (for example, silicone rubber), and the syringe is injected into the elastic material that closes the opening. You may make it collect | recover biogas from a head space with a needle. The elastic material such as synthetic rubber closes the hole when the injection needle is pulled out. Therefore, when the biogas is not collected, the biogas does not leak from the processing tank 7 even if the injection needle is pulled out.

  Furthermore, in the processing apparatus 1 shown in FIGS. 30 to 33, methane fermentation for guiding the methane fermentation solution 4 in the treatment tank 7 to the outside of the treatment tank 7 below the liquid level of the methane fermentation solution 4 in the treatment tank 7. A methane fermentation broth 4 is collected from the treatment tank 7 by a methane fermentation broth collecting means 16 that includes a liquid discharge pipe 16a and that can be opened and closed by a valve 16b. However, the method for collecting the methane fermentation broth 4 is not limited to this method. For example, without providing the methane fermentation broth collecting means 16, the processing tank 7 may be provided with an opening and closed with an elastic material such as synthetic rubber, and the injection needle of a syringe may be inserted to collect the methane fermentation broth 4. . Or you may make it connect to the syringe of one end of the pipe | tube with which both ends were opened, immerse the other end in the methane fermentation liquid 4, and extract | collect the methane fermentation liquid 4 through a pipe | tube. Also in these cases, the biogas does not leak from the treatment tank 7.

  In addition to the gas recovery means 15 and the methane fermentation broth collecting means 16, a means for adding and supplying substances to the methane fermentation broth 4 may be provided. Specifically, an openable / closable substance introduction pipe that can add and supply substances to the methane fermentation broth 4 from the outside of the treatment tank 7 may be provided. In this case, substances such as nutrient sources, neutralizing agents, and methane fermentation sludge can be added to the methane fermentation broth as necessary. Of course, the organic substrate can also be supplied from this introduction tube. Gas can also be supplied to keep the environment anaerobic. However, it is not always necessary to provide means for adding and supplying substances to the methane fermentation broth 4, and the gas recovery means 15 and the methane fermentation liquid collecting means 16 may be used together as means for adding and supplying substances to the methane fermentation broth 4. May be. Further, as described above, the injection needle of the syringe may be inserted into the elastic material to add and supply the substance to the methane fermentation solution 4.

  Hereinafter, the case where the processing apparatus shown in FIG. 30 is used will be described as a first embodiment A, the case where the processing apparatus shown in FIG. 31 is used will be described as a first embodiment B, and the processing apparatus shown in FIG. Will be described as the first embodiment C, and the case where the processing apparatus shown in FIG. 33 is used will be described as the first embodiment D.

(First embodiment A)
In the processing apparatus 1 shown in FIG. 30, a sealed container 20 is used as a processing tank 7, a sealed small container 21 that can be accommodated in the container 20 is used as a counter electrode tank 8, and the small container 21 is at least partly an ion exchange membrane. 6 and a gas discharge pipe 22 for discharging gas (gas generated from the counter electrode 10) to the outside of the container 20. In the processing apparatus 1 shown in FIG. 30, the wiring connecting the counter electrode 10 and the constant potential setting device 12 passes through the gas exhaust pipe 22. However, the wiring is not necessarily limited to this configuration. The constant potential setting device 12 may be connected without passing through the gas discharge pipe 22.

  Therefore, according to the processing apparatus 1 shown in FIG. 30, biogas does not leak from the processing tank 7. In addition, since the gas generated from the counter electrode tank 8 does not leak into the processing tank 7, the gas generated from the counter electrode tank 8 is mixed with the biogas to reduce the methane concentration of the biogas, or the counter electrode tank. The gas generated from 8 does not dissolve in the methane fermentation solution 4 and does not adversely affect the growth and function of the microorganism group involved in methane fermentation. Furthermore, since the processing tank 7 has a sealed structure, there is an advantage that the processing tank 7 can be easily controlled in an anaerobic environment.

  Moreover, by accommodating the small container 21 in the container 20, the small container 21 is immersed in the methane fermentation solution 4 accommodated in the container 20, and the ion exchange membrane 6 provided in at least a part of the small container 21 is Contact with methane fermentation solution 4. In other words, the methane fermentation solution 4 comes into contact with the electrolytic solution 4 a through the ion exchange membrane 6.

  The container 20 having a sealed structure as the processing tank 7 is a container having a size capable of accommodating the small container 21 having the sealed structure as the counter electrode tank 8, and the shape thereof is not particularly limited. Examples of the material of the container include, but are not limited to, glass, plastic, an insulating metal, concrete, and the like. Further, a container in which a gas-impermeable film material is formed into a bag shape by heat sealing or the like may be used as the processing tank 7.

  The small container 21 having a sealed structure as the counter electrode tank 8 is a container of a size that can be accommodated in the container 20 as the processing tank 7, and includes the ion exchange membrane 6 at least in part. Here, the small container 21 may be a bag-like container formed entirely by the ion-exchange membrane 6, but only one side of the bag-like container may be constituted by the ion-exchange membrane 6, or a part of one surface may be further formed. You may make it comprise only the ion exchange membrane 6. FIG. When the ion exchange membrane 6 is partially used, other portions may be made of the same material as that of the container 20, or may be made of a membrane material other than the ion exchange membrane 6, such as a gas-impermeable membrane material. It may be configured so that gas from the small container 21 (gas generated from the counter electrode tank 8) does not leak into the container 20.

  The organic substrate is added to the treatment tank 7.

  The electrolyte solution 4a accommodated in the counter electrode tank 8 may include, for example, sodium ions or potassium ions. In addition, since sodium ion, potassium ion, etc. are normally contained also in the methane fermentation liquid 4, it is also possible to use the methane fermentation liquid 4 as the electrolyte solution 4a.

  As the working electrode 9 and the counter electrode 10, for example, a conductive material such as a carbon plate can be used as appropriate. In the counter electrode 10, a reaction that complements the exchange of electrons with respect to the oxidation-reduction reaction in the working electrode 9 proceeds.

  The temperature of the treatment tank 7 (the temperature of the methane fermentation solution 4) may be 4 ° C to less than 100 ° C, but is preferably 40 ° C to 70 ° C, more preferably 50 ° C to 60 ° C, and even more preferably. 55 ° C.

  In the present embodiment, the methane fermentation treatment is performed while controlling the potential of the working electrode 9 to a potential at which a reduction reaction can occur at the working electrode 9. Alternatively, the methane fermentation treatment is performed while controlling the potential of the working electrode 9 to +0.3 V with reference to the silver / silver chloride electrode potential. At this time, microorganisms (for example, hydrogen-utilizing methane bacteria or acetic acid-assimilating methane bacteria) involved in methane fermentation are supported on the carrier 9a of the working electrode 9 and activated. That is, production of a microorganism group-supporting carrier is performed. The potential at which the reduction reaction can occur at the working electrode 9 will be described in detail. In order to cause the reduction reaction at the working electrode 9, the potential of the working electrode 9 is changed to a methane fermentation solution when no potential is applied to the working electrode 9. 4 is controlled to a potential larger on the minus side than the solution potential (oxidation-reduction potential). That is, the potential difference between the working electrode 9 and the reference electrode 11 when no potential is applied corresponds to the solution potential of the methane fermentation broth 4 when no potential is applied to the working electrode 9, and is therefore larger on the minus side than that value. By applying a potential to the working electrode 9, the reduction reaction can proceed at the working electrode 9. Specifically, since the methane fermentation liquid is generally about −0.5 V on the basis of the silver / silver chloride electrode potential, the potential of the working electrode 9 includes −0.6 V and is minus −0.6 V. You just need to make it bigger. On the other hand, it is considered that the potential of the present invention can be obtained more easily when the potential at which the reduction reaction is as strong as possible. However, if the potential of the working electrode 9 is increased too much to the minus side, water electrolysis occurs vigorously and methane Since there is a possibility that fermentation may stop and there is a possibility that transition from methane fermentation to hydrogen fermentation may occur, it is preferable to use a potential lower than that. However, when the ion exchange membrane 6 is provided as in this embodiment, the transition from methane fermentation to hydrogen fermentation hardly occurs. Moreover, if it is about -1.2V, electrolysis of water will not occur violently. Therefore, it can be considered that the effect of the present invention can be obtained by setting −0.6 V to −1.2, but −0.8 V to −1.0 V is preferable, and −1.0 V is preferable. More preferably.

  The effect of the present invention is easily obtained by providing the ion exchange membrane 6. That is, the microorganism group-supporting carrier of the present invention supplies microorganisms to the methane fermentation solution, and the methane fermentation solution originally contains microorganisms that are involved in methane fermentation, and includes the ion exchange membrane 6. The microorganisms present in the methane fermentation liquid 4 can be retained on the treatment tank 7 side without being moved (diffused) to the counter electrode tank 8. Therefore, since the electrons can be supplied from the working electrode 9 to the microorganism while preventing the electrons from being extracted from the microorganism due to the oxidation reaction of the counter electrode 10, the effect of the present invention can be obtained more easily. Furthermore, by putting the electrolytic solution in the counter electrode tank 8, the electron extraction reaction by the counter electrode tank 8 is completed with the electrolytic solution, so that the extraction of electrons from the microorganisms is reliably prevented.

  Further, by providing the ion exchange membrane 6, when the potential of the working electrode 9 is controlled, the flow of ion current between the methane fermentation solution 4 and the electrolytic solution 4a is allowed. The potential of the working electrode 9 can be continuously controlled while maintaining the charge balance.

  Here, in the present invention, since microorganisms adhere sufficiently to the carrier of the carrier holding electrode, if only the solution potential in the vicinity of the working electrode 9 can be controlled, the potential environment can be controlled to be optimal for the microorganisms supported on the carrier. The microbial community involved in methane fermentation can be stably maintained by supplying electrons to the microorganism. Therefore, it is not necessary to add any expensive reagents such as redox substances (quinone compounds such as iron ion complex, potassium ferrocyanide, sodium anthraquinone disulfonate, methyl viologen) that are generally used to control the solution potential. It is very excellent in terms.

(First embodiment B)

  In the processing apparatus 1 shown in FIG. 31, two tanks opened by partitioning a container 23 whose upper side is opened by an ion exchange membrane 6 are formed, and an upper open part of one tank as the processing tank 7 is a gas. It is assumed that it is blocked by an impermeable film or a gas impermeable member 24. That is, the processing apparatus 1 shown in FIG. 31 has the same configuration as that of FIG. 30 except that the gas generated from the counter electrode tank 8 does not leak into the processing tank 7. Therefore, the same effect as that obtained when the processing apparatus shown in FIG. 30 is used can be obtained.

  As the gas impermeable film or the gas impermeable member 24, those generally used in various fields can be appropriately used. For example, examples of the gas impermeable member include, but are not limited to, glass, plastic, an insulating metal, concrete, and the like. Further, as the gas impermeable membrane, for example, an ion exchange membrane 6 can be used, but is not limited thereto.

  The counter electrode tank 8 may be left open, but has a sealed structure like the processing tank 7 and includes a gas discharge pipe for discharging the gas generated in the counter electrode tank 8 out of the counter electrode tank 8. It may be. In this case, since the gas generated from the counter electrode tank 8 can be discharged from a desired position, it can be recovered and reused in some cases.

(First embodiment C)
In the processing apparatus 1 shown in FIG. 32, two containers 25a and 25b each having an opening below the liquid level of the liquid to be accommodated are connected to each other through the opening via the ion exchange membrane 6, and a U-shaped container 25 is used. The one container 25a is used as a processing tank 7 with a sealed structure, and the other container 25b is opened as a counter electrode tank 8. In this case, the methane fermentation solution 4 and the electrolyte solution 4a are in contact with each other via the ion exchange membrane 6, and the space above the liquid surface of the methane fermentation solution 4 in the treatment tank 7 and the solution of the electrolyte solution 4a in the counter electrode tank 8 are used. The space above the surface is spaced apart by the U-shaped structure of the container 25 itself. And since one container 25a is made into the airtight structure, the biogas generated from the processing tank 7 leaks from the processing tank 7 while preventing the gas generated from the counter electrode tank 8 from entering the processing tank 7. Can be prevented. Therefore, the same effect as that obtained when the processing apparatus shown in FIG. 30 is used can be obtained.

  In addition, the opening of the other container 25b in the processing apparatus 1 shown in FIG. 32 means that, for example, when the end of the other container 25b is completely opened, the sealing structure is the same as that of the one container 25a. This also includes the case where a gas discharge pipe for discharging the gas generated in the counter electrode tank 8 to the outside of the counter electrode tank 8 is provided. When the gas discharge pipe is provided, the gas generated from the counter electrode tank 8 can be discharged from a desired position, so that it can be easily recovered and reused.

(First embodiment D)
In the processing apparatus 1 shown in FIG. 33, two containers 26a and 26b each having an opening below the liquid level of the liquid to be accommodated are connected by an opening through the ion exchange membrane 6, and an H-shaped container 26 is provided. The one container 26a has a sealed structure as the processing tank 7, and the other container 26b is opened as the counter electrode tank 8. In this case as well, the methane fermentation solution 4 and the electrolyte solution 4a are in contact with each other through the ion exchange membrane 6, and the space above the liquid surface of the methane fermentation solution 4 in the treatment tank 7 and the electrolyte solution 4a in the counter electrode tank 8 are used. The space above the liquid level is spaced apart by the H-shaped structure of the container 26 itself. And since one container 26a of the H-shaped container 26 is made into the sealed structure, the processing tank 7 becomes a sealed structure. Therefore, it is possible to prevent the biogas generated from the processing tank 7 from leaking from the processing tank 7 while preventing the gas generated from the counter electrode tank 8 from entering the processing tank 7. Therefore, the same effect as that obtained when the processing apparatus shown in FIG. 30 is used can be obtained.

  In the present embodiment, the opening of the other container 26b is not limited to the case where the container 26 is completely opened. This also includes the case where a gas discharge pipe for discharging outside the electrode tank 8 is provided. When the gas discharge pipe is provided, the gas generated from the counter electrode tank 8 can be discharged from a desired position, so that it can be easily recovered and reused.

<Second Embodiment>
In the methane fermentation method according to the second embodiment, a carrier holding electrode including a hydrophobic carrier capable of supporting microorganisms on at least a part of an electrode surface is used as a working electrode, and a working electrode, a counter electrode, and a reference electrode are defined. It is connected to the potential setting device, the methane fermentation broth and the counter electrode are brought into contact with each other through an ion exchange membrane, the working electrode and the reference electrode are brought into contact with the methane fermentation broth, and the potential of the working electrode is controlled by a three-electrode system. I have to. That is, the methane fermentation method in the first embodiment is different from the methane fermentation method only in that the counter electrode is brought into direct contact with the ion exchange membrane without using an electrolytic solution.

  However, an ion current flows between the working electrode 9 and the counter electrode 10 via the ion exchange membrane 6 without using the electrolytic solution 4a as in the first embodiment. Further, the effect of retaining the microorganisms in the methane fermentation solution 4 in the treatment tank 7 without moving (diffusing) to the counter electrode 10 side is also obtained. Therefore, according to the methane fermentation method according to the second embodiment, the same effect can be obtained under the same potential control conditions as in the first embodiment.

  The methane fermentation method according to the second embodiment is performed by, for example, a processing apparatus shown in FIG. The processing apparatus 1 shown in FIG. 34 has a working electrode 9 and a reference electrode 11 arranged in a sealed container 5 having at least a part of an ion exchange membrane 6, and a counter electrode 10 arranged outside the container 5. 5, the working electrode 9 and the reference electrode 11 are immersed in the methane fermentation solution 4, and the ion exchange membrane 6 of the container 4 is at least when the methane fermentation solution 4 is stored in the container 5. The counter electrode 10 is disposed in contact with at least a part of the surface of the ion exchange membrane 6 opposite to the contact surface of the methane fermentation broth 4, provided in a position where a part can be in contact with the ion exchange membrane 6. It is supposed to be. In the processing apparatus 1 shown in FIG. 34, an opening 5 a is provided below the liquid level of the methane fermentation solution 4 in the container 5, the opening 5 a is closed with the ion exchange membrane 6, and ion exchange outside the container 5 is performed. It is assumed that the counter electrode 10 is disposed in contact with at least a part of the surface of the film 6. That is, in the processing apparatus 1 shown in FIG. 34, the entire container 5 functions as the processing tank 7.

  Therefore, according to the processing apparatus 1 shown in FIG. 34, biogas does not leak from the container 5. Further, since the gas generated from the counter electrode 10 does not leak into the container 5, the gas generated from the counter electrode 10 is mixed into the biogas to reduce the methane concentration of the biogas, or from the counter electrode 10. The dissolved gas does not dissolve in the methane fermentation solution 4 and does not adversely affect the growth and function of the microorganism group involved in methane fermentation. Furthermore, since the container 5 has a sealed structure, there is an advantage that the inside of the container 5 can be easily controlled in an anaerobic environment.

  In addition, although the processing apparatus 1 shown in FIG. 34 includes the gas recovery means 15 and the methane fermentation liquid collection means 16 as in the first embodiment, as described above, the gas recovery method, the methane fermentation liquid The collection method is not limited to those using these means. Moreover, you may make it provide the means to add and supply a substance to the methane fermentation liquid 4 similarly to 1st embodiment.

  Hereinafter, the details of the processing apparatus 1 shown in FIG. 34 will be described. However, configurations other than those described below are substantially the same as those in the first embodiment, and a description thereof will be omitted.

  The container 5 has a sealed structure including at least a part of the ion exchange membrane 6. Examples of the material of the container 5 include, but are not limited to, glass, plastic, metal subjected to insulation treatment, concrete, and the like. In FIG. 34, the opening 5a provided below the liquid surface of the methane fermentation solution 4 of the sealed container 5 is closed by the ion exchange membrane 6. However, the form and structure of the container 5 are not particularly limited. It is not limited. For example, the entire container 5 may be a bag-shaped container formed of the ion-exchange membrane 6, or only one surface of the bag-shaped container may be formed of the ion-exchange membrane 6, or a part of one surface may be ion-exchanged. You may make it comprise only with the film | membrane 6. FIG. When the ion exchange membrane 6 is partially used, the other portions may be made of the above-mentioned material such as glass, or other membrane materials other than the ion exchange membrane 6, such as the methane fermentation broth 4 and the methane fermentation broth 4 You may comprise with the film | membrane material which does not permeate | transmit both of the component (including microorganisms). In short, the methane fermentation solution 4 accommodated in the container 5 may be a container having a structure that can come into contact with the ion exchange membrane 6 constituting at least a part of the container 5.

  The counter electrode 10 is brought into contact with at least a part of the surface opposite to the contact surface of the ion exchange membrane 6 with the methane fermentation solution 4. In the present embodiment, the counter electrode 10 is a plate-like carbon electrode, but the shape and material of the counter electrode 10 are not limited to this, and the shape is that the contact with the ion exchange membrane 6 is essential. And a material capable of proceeding with a reaction that complements the exchange of electrons with respect to the oxidation-reduction reaction at the working electrode 9, that is, the oxidation reaction can proceed when the reduction reaction occurs at the working electrode 9. A material electrode may be used. In the present embodiment, the counter electrode 10 has a larger area than the ion exchange membrane 6 so that the entire ion exchange membrane 6 is completely covered with the counter electrode 10, and the ion exchange membrane 6 and the counter electrode 10 are covered. Although it is made to contact, if the counter electrode 10 is made to contact at least one part of the surface on the opposite side to the contact surface of the ion exchange membrane 6 with the methane fermentation liquid 4, methane fermentation will be carried out via the ion exchange membrane 6. Since ions are transmitted from the liquid 4 to the counter electrode 10, the ion exchange membrane 6 and the counter electrode 10 do not necessarily have to be in contact with each other so that the entire ion exchange membrane 6 is completely covered with the counter electrode 10. However, by completely covering the entire ion exchange membrane 6 with the counter electrode 10, the counter electrode 10 can function as a protective material for the ion exchange membrane 6, and the ion transmission surface from the methane fermentation solution 4 is increased. As a result, there is an advantage that the potential controllability of the methane fermentation broth 4 can be improved, which is preferable. As a method of completely covering the entire ion exchange membrane 6 with the counter electrode 10, for example, ion exchange is performed by closing the opening 5 a by applying an adhesive around the opening 5 a of the container 5 and bonding the counter electrode 10. The entire membrane 6 and the counter electrode 10 may be brought into contact with each other, or an ion exchange membrane formed by applying an adhesive around the opening 5a of the container 5 and applying it to at least a part of the surface of the counter electrode 10 By bonding 6, the counter electrode 10 may be brought into contact with the entire ion exchange membrane 6 that closes the opening 5 a while closing the opening 5 a with the ion exchange membrane 6. Examples of the agent for coating and forming the ion exchange membrane 6 include a Nafion dispersion, but are not limited thereto. Alternatively, a Nafion dispersion may be applied to the surface of the counter electrode 10 and the ion exchange membrane 6 may be attached before the Nafion dispersion is dried. In this case, the adhesion and contact properties of the ion exchange membrane 6 to the surface of the counter electrode 10 can be made sufficient.

  Here, the counter electrode 10 is preferably a porous body. In this case, the gas generated at the contact surface between the ion exchange membrane 6 and the counter electrode 10 can easily pass through the surface opposite to the contact surface. In addition, the counter electrode 10 is made a porous body, and the ion exchange membrane 6 is attached using a Nafion dispersion liquid, whereby the ion exchange membrane 6 and the counter electrode 10 are separated by the penetration of the Nafion dispersion liquid into the pores of the porous body. The contact area can be increased to facilitate the progress of the electrochemical reaction, which is preferable.

  Here, in the first embodiment and the second embodiment described above, the microbial fermentation treatment is performed, and at the same time, the microorganism group-supporting carrier is also produced. It is preferable that the microorganism group-supporting carrier is used as the working electrode 9 while being kept in contact with the methane fermentation solution 4 and performing the methane fermentation treatment of the present invention. In this case, the methane fermentation treatment can be continued as it is without taking out the produced microorganism group-supporting carrier. Moreover, since the quantity and distribution of microorganisms inhabiting the methane fermentation liquid 4 are also suitable for methane fermentation by controlling the potential, the methane fermentation treatment can be performed while receiving the benefits. Of course, the microorganism group-supported carrier prepared as described above may be once taken out and placed in a methane fermentation solution in another methane fermentation tank to perform methane fermentation treatment. You may make it perform a fermentation process.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, as shown in FIG. 35, for example, the processing apparatus for carrying out the present invention is not an ion-exchange membrane 6 but an impervious member 40 that does not allow ions or microorganisms to permeate through the methane fermentation solution 4 and the electrolyte 4a. Or the treatment tank 7 and the counter electrode tank 8 are formed in separate containers, and the methane fermentation solution 4 and the electrolyte 4a are brought into contact with each other through a salt bridge 41 (agar or the like containing a saturated electrolyte solution such as KCl). (Liquid junction) may be used. Also in this case, since the movement of microorganisms in the methane fermentation broth 4 to the counter electrode tank 8 can be prevented, the extraction of electrons from the counter electrode 10 can be prevented, and the flow of ion current by the salt bridge can be prevented. Is acceptable. In addition, since the redox material 3 contained in the methane fermentation broth 4 does not pass through the counter electrode tank 8, the controllability of the solution potential of the methane fermentation broth 4 is also ensured.

  In the above-described embodiment, the carrier holding electrode including a carrier capable of supporting microorganisms is used on at least a part of the electrode surface. However, a carrier capable of supporting microorganisms is provided on a part of the electrode surface. Alternatively, the biological treatment method or the methane fermentation treatment method of the present invention may be performed separately from the electrode (that is, by dispersing the carrier in the culture solution or the fermentation solution without adhering to the electrode). In this case as well, by controlling the solution potential with the electrode, it is possible to exhibit an excellent processing capability even under a high load condition and to efficiently perform the target processing, as in the present invention.

  Furthermore, in the above-described embodiment, while using a carrier holding electrode provided with a carrier capable of supporting microorganisms on at least a part of the electrode surface, the carrier capable of supporting microorganisms is dispersed in a culture solution or a fermentation solution, and the present invention is performed. The biological treatment method or the methane fermentation treatment method may be carried out. Thus, by providing a carrier capable of supporting microorganisms in the culture solution or both in the fermentation broth and on the electrode surface, the microorganisms are activated in the culture solution or in both the fermentation broth and the electrode surface, It may be possible to exhibit an excellent processing capacity even under higher load conditions and to perform the target processing more efficiently.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  First, as a reference example, the experimental results when using an electrode that does not hold a carrier capable of supporting microorganisms are shown below.

(Reference Example A-1)
1. Experimental Apparatus and Experimental Method FIG. 1 shows a cross-sectional view of the experimental apparatus used in this reference example. One of two 250 mL glass vials (manufactured by Duran) is the methane fermentation tank 26a, the other is the counter electrode tank 26b, and the two vials via a cation exchange membrane (Nafion K) at the lower opening. Were connected to form an H-shaped container 26. Moreover, the discharge part 51 and the supply part 52 were provided in the methane fermentation tank 26a. The methane fermentation tank 26a was covered, and a silicone rubber stopper was provided on the upper surface of the lid to ensure a sealed product when wiring and electrodes were passed. Further, the pipe 33 is passed through the silicone rubber stopper on the upper surface of the lid, and the gas in the space (head space) above the liquid level of the fermentation liquid 4 in the methane fermentation tank 26a is discharged from one end of the pipe 33, and the other end of the pipe Gas was collected in the bag 34 connected to the.

  The counter electrode tank 26b accommodated the electrolyte solution 4a and the counter electrode 10 (2.5 cm × 7.5 cm × 0.3 cm plate-like carbon electrode), and was immersed in the electrolyte solution 4a. The counter electrode tank 26b was also covered, and a silicone rubber plug was provided on the upper surface of the cover, and the gas discharge pipe 22 was passed through the silicone rubber plug. Then, a wiring 31 for connecting the counter electrode 10 and the potential control device 12 was passed through the gas exhaust pipe 22. Both ends of the gas discharge pipe 22 are opened, and the gas generated in the counter electrode tank 26b is arranged so that one end is disposed inside the counter electrode tank 26b and the other end is disposed outside the counter electrode tank 26b. It was made to discharge to the outside of 26b.

  The working electrode 9 (2.5 cm × 7.5 cm × 0.3 cm plate-like carbon electrode) is housed in the methane fermentation tank 26a and immersed in the fermentation broth 4, and the wiring from the working electrode 9 to the potential control device 12 is silicone. It was pulled out of the methane fermentation tank 26a through a rubber stopper. The reference electrode 11 (silver / silver chloride electrode) was inserted into a silicone rubber stopper from the outside of the methane fermentation tank 26a and brought into contact with the fermentation broth 4. The working electrode 9, the counter electrode 10, and the reference electrode 11 were connected to a three-electrode potential controller (potentiostat) 12 to control the potential of the working electrode 9.

The composition of the fermented liquid 4 accommodated in the methane fermenter 26a is KH ₂ PO ₄ 1.135 g / l, K ₂ HPO ₄ 1.740 g / l, NiCl ₂ · 6H ₂ O 0.403 mg / l, CoCl ₂ · 6H ₂ O 0.484 mg / l. In addition, anthraquinone-2,6-disulfonic acid (AQDS) was added as a redox substance to a final concentration of 0.2 mM to ensure the potential controllability of the methane fermentation broth 4. The composition of the electrolytic solution 4a was NaCl 5.844 g / l.

  To the fermentation liquid 4, a microbial community obtained from seed sludge accumulated by performing methane fermentation with simulated raw garbage was added. During the experiment, the pH of the fermentation broth 4 was maintained at 7.4 to 7.9, and the temperature was maintained at 55 ° C. Moreover, the fermented liquid 4 and the electrolyte solution 4a continued stirring with the stirring bar.

Further, in this reference example, the operation was performed while applying the load shown in FIG. 2 (organic matter load amount OLR, hydraulic retention time HRT). The operation of the methane fermentation tank was performed by the fill and draw method. In other words, a certain amount of fermentation broth was discarded and the operation was performed by adding the same amount of substrate. The substrate, dog food (Nippon pet manufactured food) to 100 g / l (10 wt%), KH ₂ PO ₄ and _{1.135 g / l, K 2 HPO} 4 and _{1.740 g / l, NiCl 2 ·} 6H 2 O and 0.403 mg / l, a simulated food waste substrate of CoCl ₂ · 6H ₂ O containing 0.484 mg / l was used.

  The potential of the working electrode 9 was +0.6 V, +0.3 V, −0.3 V, and −0.6 V based on the silver / silver chloride electrode potential standard as the reference electrode 11, and the methane fermentation treatment was performed. As a comparative experiment, methane fermentation treatment was performed without energizing the working electrode 9. The fermented liquid 4 to which the working electrode 9 and the microbial community had been added was brought into contact several days before the start of the experiment, and a few microbial communities were supported on the working electrode 9 in advance before the experiment.

  Since the potential of the methane fermentation broth 4 was about −0.5 V, when the potential of the working electrode 9 was +0.6 V, +0.3 V, and −0.3 V, the oxidation reaction was performed at the working electrode 9. This occurs, and a reduction reaction occurs at -0.6V. This can be confirmed from the fact that the cathode current flows in the working electrode 9 at −0.6 V, and the anode current flows in the working electrode 9 at +0.6 V, +0.3 V, and −0.3 V. .

2. Analysis method (1) Chemical analysis method The composition (methane, hydrogen, carbon dioxide) of the gas discharged from the methane fermentation tank 26a is a thermal conductivity detector (GC390B, manufactured by GL Science) and an activated carbon packed column (manufactured by GL Science). Was measured by gas chromatography equipped with

  The lower fatty acid concentration analysis of the fermentation broth 4 was performed by an analysis method: liquid chromatography (manufactured by GL Science, apparatus name: GL-7400).

  The analysis of COD (chemical oxygen demand) was performed according to the analysis method: Japanese Industrial Standard (JIS) K 0102-20 (HACH, apparatus name: DR800).

  The analysis of SS (floating solid content) was performed by an analysis method: JIS K 0102-14.1 (manufactured by Yamato, apparatus name DN63).

(2) Biological analysis method The copy number of 16S rRNA gene of the microorganism group adhering to the working electrode 9 and the microorganism group contained in the methane fermentation broth 4 was quantitatively analyzed using real-time PCR. Specifically, a solution in which the microorganism group adhering to the working electrode 9 is suspended or the methane fermentation solution 4 is centrifuged to settle the microorganism group, and a Tris-EDTA buffer solution (pH 8.0, 100 mM Tris). HCl, 40 mM EDTA). DNA was extracted by repeated collision of beads from the microbial population in the presence of sodium dodecyl sulfate and phenol-chloroform-isoamyl alcohol solution (25: 24: 1 v / v), and the extracted DNA was then extracted with the QIAamp DNA micro kit (Qiagen). Purified). This was subjected to TaqMan real-time PCR to quantitatively analyze the copy number of the 16S rRNA gene of the microorganism group. The primer / probe set was as follows. And the quantitative analysis result regarding a methane bacterium was added to the quantitative analysis result regarding a prokaryote, and the copy number of 16S rRNA gene of the whole microorganism group was calculated | required. The primer / probe set used in the experiment is described in the following paper (Takai, K., K. Horikoshi (2000). "Rapid detection and quatification of members of archaeal community by quantitative PCR using fluorogenic probes. "Appl. Environ. Microbiol. 66 (11): 5066-5072., Sawayama, S., Tsukahara K, Yagishita T (2006)." Phylogenetic description of immobilized methanogenic community using real-time PCR in a fixed- bed anaerobic digester. "Bioresour. Technol. 97 (1): 69-76.).
Prokaryotic primer / probe set:
Uni340F / Uni806R / Uni516F
・ Primer / probe set for methane bacteria:
SP-MArch-0348-Sa-17 / SD-Arch-0786-Aa-20 / SP-MArch-0515-Sa-25

  Further, by analyzing the terminal fragment length polymorphism (T-RFLP), the community structure of bacteria excluding archaea out of all bacteria and the community structure of archaea excluding bacteria among all bacteria were analyzed. Specifically, Ba27f labeled with 6-FAM at the 5 'end is used as a bacterial forward primer, Ba907 is used as a reverse primer, Ar109f is used as an archaeal forward primer, and the 5' end is used as a reverse primer. PCR was performed in a 50 μL reaction mixture using Ar912rt labeled with 6-FAM in to obtain a PCR amplicon. The PCR amplicon was purified by Wizard SV Gel and PCR Clean-Up System (Promega), MspI (New England BioLabs) was used as a bacterial restriction enzyme, and TaqI (New England BioLabs) was used as an archaeal restriction enzyme. England BioLabs). The DNA size standard GeneScan-500 ROX Size Standard (Applied Biosystems) was used as an internal size standard for this purified digest. Terminal fragment length polymorphism analysis was performed using 3130xl Genetic Analyzer (Applied Biosystems). Ingredients below 2% were removed from the data.

  Furthermore, clonal analysis was performed on archaea except bacteria. Specifically, PCR was performed under the same conditions as for T-RFLP, and the PCR product was purified and ligated into a pGEM-T Easy vector (Promega). The plasmid was incorporated into Escherichia coli JM109 cells, and clones were randomly selected and sequenced by ABI 3130xl sequencer (Applied Biosystems) using BigDye Terminator cycle sequencing chemistry.

3. Experimental Results (1) Relationship between Set Potential and Gas Generation Rate FIG. 3 shows changes with time in the gas generation rate at various set potentials. In addition, 50 to 70% of the gas obtained in this experiment was methane gas. When the set potential was +0.6 V, the gas generation rate decreased at an organic load of 11.2 g COD / l / day (final gas generation rate of 1000 ml / l / day). In addition, when the operation was continued under high load conditions (organic matter load: 26.9 g COD / l / day), a decrease in gas generation rate was observed when the set potential was -0.3 V and when there was no energization. (Final gas production rate is 2300 ml / l / day). On the other hand, in the case of + 0.3V and -0.6V, even if the operation was continued under a high load condition (organic matter load 26.9 g COD / l / day), no decrease in gas generation rate was observed (final) (The gas generation rate is 6800 ml / l / day for both).

(2) Relationship between set potential and COD removal rate FIG. 4 shows changes with time in the COD removal rate at various set potentials. When the set potential was +0.6 V, the COD removal rate did not increase with the increase in the organic load (final COD removal rate 3.1 g COD / l / day). Further, when the set potential is −0.3 V, no energization, +0.3 V, and −0.6 V, the COD removal rate increases with an increase in the organic load, and the organic load is 26.9 g COD / The COD removal rate also increased when increased to 1 / day. In particular, the increase in the COD removal rate was significant when the set potential was −0.6 V and +0.3 V. The final COD removal rates were 16.1 g COD / l / day (set potential −0.6 V), 12.0 g COD / l / day (no energization), 12.6 g COD / l / day (set potential −0.1 V). 3V), 15.4 g COD / l / day (set potential +0.3 V).

(3) Relationship between set potential and SS removal rate FIG. 5 shows changes with time in the SS removal rate at various set potentials. When the set potential is +0.3 V or -0.6 V, the SS removal rate tends to increase as the organic load increases, and the organic load increases 26.9 g COD / l / day. Also, an increase in the SS removal rate was observed. The final SS removal rates were 4.8 g / l / day (set potential −0.6 V) and 5.0 g / l / day (set potential +0.3 V). In addition, when the set potential was −0.3 V and no current was supplied, no significant increase in the SS removal rate accompanying an increase in the organic load was observed. The final SS removal rate was 3.3 g / l / day (set potential −0.3 V) and 3.0 g / l / day (no power supply).

(4) Relationship between set potential and lower fatty acid concentration FIG. 6 shows changes with time in lower fatty acid concentrations (acetic acid, butyric acid, propionic acid) at various set potentials. When the set potential was +0.6 V, accumulation of lower fatty acids was already observed around the 20th day. Further, when the operation was continued at (organic substance loading 26.9 g COD / l / day), accumulation of lower fatty acids was observed when the set potential was −0.3 V and when no current was supplied. On the other hand, when the set potential was +0.3 V and −0.6 V, accumulation of lower fatty acids was not observed. From this result, it was clarified that when the set potential was set to +0.3 V and −0.6 V, the methane fermentation treatment can be performed over a long period of time by preventing the methane fermentation tank from being spoiled.

(Reference Example A-2)
After the experiment of Reference Example A-1 was completed, the fermented liquid fraction and the carrier-adhered fraction were subjected to genetic analysis, and the state of microbial adhesion and the state of microbial population distribution were examined.

1. Quantitative PCR Results for Whole Bacteria and Methane Bacteria After completion of the experiment in Reference Example A-1, a fraction of the fermentation broth and a carrier-attached fraction were obtained, and the copy numbers of the whole bacteria and methane bacteria were measured by quantitative PCR. The results are shown in FIGS. FIG. 7 shows the copy number of all the bacteria in the fermentation broth fraction, FIG. 8 shows the copy number of methane bacteria in the fermented liquid fraction, FIG. 9 shows the copy number of all bacteria in the carrier-attached fraction, and FIG. Is the copy number of methane bacteria in the carrier-attached fraction. As a result, it has been clarified that in any fraction, when the set potential is +0.3 V and −0.6 V, the number of copies is greatly increased as compared with the case where no power is supplied. In addition, as for the fermented liquor fraction, the carrier-adhered fraction was not changed in the case of no energization and the set potential was +0.3 V and -0.6 V, although the copy number changed only about 2 to 5 times. It has been clarified that the copy number varies by 400 to 900 times between the case of no energization and the case where the set potential is + 0.3V and −0.6V. From this, it was clarified that the maintenance or improvement effect of the methane fermentation treatment performance under the high load condition seen in Reference Example A-1 is caused by a significant increase in the fraction adhered to the carrier.

2. Comparison of bacterial community structure by T-RFLP By end fragment length polymorphism analysis (T-RFLP), the bacterial community structure of all bacteria except archaea was compared. The results are shown in FIG. From the results shown in FIG. 11, when the set potential was +0.3 V and −0.6 V, the proportion of microorganisms corresponding to 262 bp increased, and this tendency was particularly remarkable in the carbon plate. In addition, the electric potential in the parenthesis in FIG. 11 means the electric potential of the fermentation broth. That is, the potential of the working electrode 9 (carrier) and the potential of the fermentation broth are different.

  Next, the result of analyzing the structure of the bacterial community by TA cloning is shown in FIG. From this analysis result, it was revealed that a microorganism corresponding to 262 bp is a microorganism belonging to the Thermotogae gate. Therefore, it was considered that microorganisms belonging to the Thermotogae gate acted effectively in SS removal and COD removal. In addition, from this, a microbial community containing microorganisms belonging to Thermotogae is added to the culture solution, and the culture solution and a conductive carrier capable of supporting the microorganisms, for example, a carbon carrier, are brought into contact with each other. Is set to -0.6V or + 0.3V on the basis of the silver / silver chloride electrode potential, microorganisms belonging to Thermotogae can be supported on the conductive support and activated, and SS It was revealed that removal and COD removal can be carried out efficiently even under a high load environment.

  In addition, from the results shown in FIG. 11, when the set potential is +0.3 V and −0.6 V, the microorganisms corresponding to 210 bp are not detected, and thus the microorganisms corresponding to 210 bp are subjected to SS removal and COD removal. It is an inhibiting factor, and by setting the set potential to +0.3 V and -0.6 V, microorganisms corresponding to 210 bp are inactivated or removed, and SS removal and COD removal are efficiently performed even in a high load environment. This experiment also suggested the possibility of obtaining a practicable effect.

  Furthermore, it was suggested that microorganisms belonging to the Thermotogae gate are involved in the degradation of lower fatty acids, and that the degradation of lower fatty acids can be promoted by setting the set potential to +0.3 V and -0.6 V. . In addition, it was suggested that microorganisms corresponding to 210 bp promote accumulation of lower fatty acids, and that the accumulation of lower fatty acids can be suppressed by setting the set potential to +0.3 V and −0.6 V.

The result of further analysis, shows a relatedness to bacterial Bacteroidetes Gate microorganisms 95bp adhering to the carbon plate is considered to have a protein resolution when setting potential of -0.6 V, the 150bp It was confirmed that the bacteria are closely related to the bacteria of the Firmicutes, which are thought to specifically degrade food proteins and fiber. From this, it was also clarified that setting the set potential to −0.6 V has an effect of attaching a microorganism group effective for methane fermentation treatment of organic waste to the carrier.

3. Comparison of archaeal community structure by T-RFLP Comparison of archaea community structure excluding bacteria among all bacteria by end fragment length polymorphism analysis (T-RFLP). The archaebacteria contain methanogens. The results are shown in FIG. When the set potential was +0.3 V, the proportion of microorganisms corresponding to 92 bp increased, and the tendency was particularly remarkable in the carbon plate, but the proportion of microorganisms corresponding to 186 bp remained almost unchanged. . When the set potential was −0.6 V, a slight increase in the occupation ratio of microorganisms corresponding to 186 bp and a slight increase in the occupation ratio of microorganisms corresponding to 92 bp were observed on the carbon plate.

  Next, the results of analyzing the structure of the archaeal community by TA cloning are shown in FIG. From this result, it was clarified that the microorganism corresponding to 92 bp whose occupation ratio increased when the set potential was +0.3 V was Methanothermobacter thermautotrophicus, which is a hydrogen-assimilating methanogen. In addition, when the microorganism corresponding to 186 bp is Methanosarcina thermophila which is an acetic acid-assimilating methanogen and the set potential is +0.3 V and −0.6 V, the occupation ratio is the same as when no current is supplied or It was thought that this increased slightly, leading to the suppression of acetic acid accumulation, which is a lower fatty acid. That is, from the results of quantitative PCR, when the set potential is +0.3 V and −0.6 V, it is confirmed that the copy number of methanogenic bacteria on the carrier is significantly increased as compared with the case where no current is supplied. Therefore, acetic acid-assimilating methanogens increased with the growth of methanogens while maintaining their occupation ratio, and as a result, the accumulation of acetic acid, which is a lower fatty acid, was thought to have been suppressed. It was.

  Based on the above results, a microbial community containing Methanosarcina thermophila, which is an acetic acid-assimilating methanogen, is added to the culture solution, and a conductive carrier that can support the microorganism, for example, a carbon carrier, is brought into contact with the culture solution. It has been clarified that methane gas can be efficiently generated using acetic acid as a generation source by setting the potential of the active carrier to −0.6 V or +0.3 V based on the silver / silver chloride electrode potential.

  In addition, a microbial community containing Methanothermobacter thermautotrophicus, which is a hydrogen-utilizing methanogen, is added to the culture solution, and the culture solution is contacted with a conductive carrier that can support the microorganism, for example, a carbon carrier. It has been clarified that methane gas can be efficiently generated using hydrogen gas and carbon dioxide as a generation source by setting the potential to -0.6 V or +0.3 V on the basis of the silver / silver chloride electrode potential.

(Reference Example A-3)
We investigated whether Methanothermobacter thermautotrophicus, a hydrogen-utilizing methanogen, could increase the methane production rate by increasing the activity of the cell itself with a set potential.

  Experiments were performed using the experimental apparatus shown in FIG. A 250 mL glass vial (manufactured by Duran) was used as the culture container 5, and three openings were provided below the liquid level of the culture solution 4. The reference electrode 11 (manufactured by Toa DDK, HS-205C, silver / silver chloride electrode) was inserted into the first opening 5b, and the reference electrode 11 and the culture solution 4 were brought into contact with each other. The second opening 5c is provided to collect the culture solution 4, and the culture solution 4 can be collected by opening and closing the lid. The third opening 5a is closed with a porous plate-like carbon electrode (counter electrode 10), and 20% Nafion dispersion (DE2021) is applied to the lower half of the surface of one side of this plate-like carbon electrode. The ion exchange membrane 6 was formed by covering with N117, and the third opening 5a was blocked by the ion exchange membrane 6. The reason why the counter electrode 10 is made porous is that gas generated at the contact surface between the ion exchange membrane 6 and the counter electrode 10 can easily pass through the opposite surface of the counter electrode 10. A plate-like carbon electrode was immersed in the culture solution 4 as the working electrode 9 (conductive carrier). The working electrode 9, the counter electrode 10, and the reference electrode 11 were connected to a three-electrode potential control device (potentiostat) 12 so that the potential of the working electrode 9 (conductive carrier) could be strictly controlled. In addition, the culture solution 4 was put into the culture vessel 5 until about the eighth minute, and a head space was secured above the liquid level. The culture container 5 is provided with a lid 18, and an upper surface 18 a of the lid 18 is provided with a silicone rubber that is an elastic material. The syringe needle of the syringe can be inserted to collect a gaseous substance from the head space in the culture container 5, and The hole produced by inserting the injection needle was closed when the injection needle was removed.

The culture temperature was 55 ° C. Further, AQDS (anthraquinone-2,6-disulfonic acid) was added to the culture solution 4 so that the AQDS concentration was 0.5 mM. The culture solution 4 is stirred with a stir bar 19, two injection needles are inserted into the upper silicone rubber stopper, and H ₂ / CO ₂ = 80/20 mixed gas is aerated from one injection needle for 1 hour. The head space was replaced with a mixed gas of H ₂ and CO ₂ . The composition of the culture solution 4 was as follows. The pH of the culture solution 4 was 7.2.
<Culture solution composition (/ L)> KH ₂ PO ₄ 0.3 g, (NH ₄ ) ₂ SO ₄ 1.5 g, NaCl 0.6 g, MgSO ₄ .7H ₂ O 0.12 g, CaCl ₂ .2H ₂ O 0.08 g, FeSO ₄・ 7H ₂ O 4.0 mg, K ₂ HPO ₄ 0.15 g, Na ₂ CO ₃ 4.0 g, Trace vitamins 10.0 ml, Trace element solution 10.0 ml, L-Cysteine ・ HCl ・ H2O 0.5 g, Na ₂ S ・ 9H ₂ O 0.5 g, Resazurin 1.0 mg
<Vitamin solution (/ L)> Biotin 2.0 mg, Folic acid 2.0 mg, Pyridoxine-HCl 10.0 mg, Thiamine-HCl · 2H ₂ O 5.0 mg, Riboflavine 5.0 mg, Nicotinic acid 5.0 mg, Ca-pantothenate 5.0 mg, p- Aminobenzoic acid 1.0 mg, Vitamin B ₁₂ 0.01 mg
<Trace element solution (/ L)> Na ₂ · EDTA 0.64 g, MgSO ₄ · 7H ₂ O 6.2 g, MnSO ₄ · 4H ₂ O 0.55 g, NaCl 1.0 g, FeSO ₄ · 7H ₂ O 0.1 g, CoCl ₂ · 6H ₂ O 0.17 g, CaCl ₂・ 2H ₂ O 0.13 g, ZnSO ₄・ 7H ₂ O 0.18 g, CuSO ₄ 0.05 g, KAl (SO ₄ ) ₂・ 12H ₂ O 0.018 g, H ₃ BO ₃ 0.01 g, Na ₂ MoO ₄・ 12H ₂ O 0.011 g, NiCl ₂・ 6H ₂ O 0.025 g

  The results are shown in FIG. Note that the relative activity in FIG. 15 is a relative evaluation value where the amount of methane produced per cell under the condition where no current is supplied is 1. That is, by comparing these values, the methanogenic activity per methanogenic cell can be evaluated.

  From the results shown in FIG. 15, it is clear that setting the working potential of the working electrode 9 (conductive carrier) to −0.8 V improves the methane production activity by 3.5 times compared to the case where no current is supplied. became.

  From this experimental result, the potential of the conductive carrier is controlled to −0.6 V or +0.3 V, and the carrier is preferentially loaded with Methanothermobacter thermautotrophicus which is a hydrogen-assimilating methanogen. It was revealed that methane can be generated with extremely high efficiency by controlling the potential to -0.8V.

(Reference Example A-4)
The number of bacteria in the fermented liquid fraction was increased from the number of bacteria in the carrier-attached fraction, and the gas production rate was verified.

The experiment was performed by immersing a carrier under the following nine conditions in the fermentation broth. In addition, 200 ml of the fermented liquor was used by diluting seed sludge accumulated by performing methane fermentation with simulated raw garbage to 1/3 with deionized water.
(A) PE: polyethylene carrier (b) C: carbon carrier (c) PP: polypropylene carrier (d) PE + Bf : biofilm attached to polyethylene carrier (e) C + Bf : carbon (F) PP + Bf : Adhering biofilm to polypropylene carrier (g) No carrier

  The operating conditions were 0.95 g / l / day. In addition, even under the conditions where the biofilms (d) to (f) are attached, the fermentation liquid fraction has more bacteria than the carrier-supported fraction.

  The results are shown in FIG. Regarding the conditions (d) to (f), there was a tendency for the gas generation rate to gradually increase, but for other conditions, there was almost no increase in the gas generation rate. From these results, it was considered that the bacteria attached to the carrier had high activity and contributed to start-up.

  From the above results, it became clear that increasing the fraction adhered to the carrier has a very advantageous effect on the progress of the microbial reaction process. Therefore, as in the present invention, by controlling the potential of the conductive carrier and supporting and accumulating the target microorganism group in advance, or by supporting and accumulating while performing the treatment, the microbial reaction process can proceed extremely efficiently. It has become clear that the desired treatment can be carried out.

(Reference Example B-1)
1. Experimental Apparatus and Experimental Method An experiment was performed by changing the set potential using the same experimental apparatus and experimental method as in Reference Example A-1. Moreover, about the experiment on the one part set potential conditions implemented in Reference example A-1, it experimented again and confirmed reproducibility.

  Specifically, an experiment was newly conducted under the condition that the potential of the working electrode 9 was +0.0 V and −0.8 V based on the potential of the silver / silver chloride electrode as the reference electrode 11. The experiment at −0.8 V was performed three times.

  Moreover, the experiment which confirms the reproducibility of the result obtained by reference example A-1 about the conditions without electricity supply and the condition of -0.6V was implemented twice.

  Furthermore, an experiment was performed by increasing the organic load (OLR) under the conditions of -0.6V and -0.8V. Regarding the condition of −0.6 V, the organic load was increased to 31.8 g / l / day in the two experiments performed in this reference example. With respect to the condition of −0.8 V, the organic load was increased to 31.8 g / l / day for two of the three experiments performed in this reference example. The operation conditions (load conditions) of the methane fermenter in this reference example are shown in FIG.

  Incidentally, at -0.6 V and -0.8 V, a reduction reaction occurs on the working electrode 9. This could be confirmed from the fact that the cathode current flows in the working electrode 9 at −0.6V and −0.8V.

2. Experimental Results (1) Relationship between Set Potential and Gas Generation Rate FIG. 19 shows changes over time in gas generation rate at various set potentials. In FIG. 19, x is a plot of three experimental results (one experimental result in Reference Example A-1 and two experimental results in the present Reference Example) under no-energization conditions. ○ is a plot of the average of three experimental results under the condition of -0.8 V. For data before increasing the organic load to 31.8 g / l / day, the standard deviation is the error bar. It showed in. □ is a plot of average values of three experimental results under the condition of −0.6 V (one experimental result in Reference Example A-1 and two experimental results in this Reference Example), and the organic load For data up to 31.8 g / l / day before increasing, the standard deviation is indicated by error bars. Δ is the experimental result under the condition of + 0.0V. The experimental results indicated by ◇ (−0.3V), ♦ (+ 0.3V) and ▲ (+ 0.6V) are the results obtained in Reference Example A-1 as they are.

  About the conditions without electricity supply and the conditions of -0.6V, the tendency similar to reference example A-1 was confirmed. In addition to the conditions of +0.3 V and -0.6 V, no decrease in gas generation rate was observed during the operation period under the condition of -0.8 V. In particular, under the conditions of -0.6 V and -0.8 V, no decrease in gas generation rate was observed even when the organic load was increased to 31.8 g / l / day.

(2) Relationship between set potential and COD removal rate FIG. 20 shows changes over time in the COD removal rate at various set potentials. In FIG. 20, x is a plot of average values of three experimental results (one experimental result in Reference Example A-1 and two experimental results in the present Reference Example) under the condition of no energization. Deviations are indicated by error bars. ○ is a plot of the average of three experimental results under the condition of -0.8 V. For data before increasing the organic load to 31.8 g / l / day, the standard deviation is the error bar. It showed in. □ is a plot of average values of three experimental results under the condition of −0.6 V (one experimental result in Reference Example A-1 and two experimental results in this Reference Example), and the organic load For data up to 31.8 g / l / day before increasing, the standard deviation is indicated by error bars. Δ is the experimental result under the condition of + 0.0V. The experimental results indicated by ◇ (−0.3V), ♦ (+ 0.3V) and ▲ (+ 0.6V) are the results obtained in Reference Example A-1 as they are.

  About the conditions without electricity supply and the conditions of -0.6V, the tendency similar to reference example A-1 was confirmed. Further, in addition to the conditions of +0.3 V and -0.6 V, the condition of -0.8 V continued to increase without decreasing the COD removal rate with the increase in the organic load. In particular, for the conditions of −0.6 V and −0.8 V, the COD removal rate continued to increase without decreasing even when the organic load was increased to 31.8 g / l / day.

(3) Relationship between set potential and SS removal rate FIG. 21 shows changes with time in the SS removal rate at various set potentials. In FIG. 21, x is a plot of average values of three experimental results (one experimental result in Reference Example A-1 and two experimental results in the present Reference Example) under the condition of no energization. Deviations are indicated by error bars. ○ is a plot of the average of three experimental results under the condition of -0.8 V. For data before increasing the organic load to 31.8 g / l / day, the standard deviation is the error bar. It showed in. □ is a plot of average values of three experimental results under the condition of −0.6 V (one experimental result in Reference Example A-1 and two experimental results in this Reference Example), and the organic load For data up to 31.8 g / l / day before increasing, the standard deviation is indicated by error bars. Δ is the experimental result under the condition of + 0.0V. The experimental results indicated by ◇ (−0.3V) and ♦ (+ 0.3V) are the results obtained in Reference Example A-1 as they are.

  About the conditions without electricity supply and the conditions of -0.6V, the tendency similar to reference example A-1 was confirmed. Further, in addition to the conditions of +0.3 V and −0.6 V, the condition of −0.8 V also continued to increase without decreasing the SS removal rate as the organic load increased. In particular, under the conditions of −0.6 V and −0.8 V, the SS removal rate continued to increase without decreasing even when the organic load was increased to 31.8 g / l / day.

(4) Relationship between set potential and lower fatty acid concentration FIG. 22 shows changes over time in the lower fatty acid concentration at various set potentials. In FIG. 22, x is a plot of average values of three experimental results (one experimental result in Reference Example A-1 and two experimental results in this reference example) under the condition of no energization. ○ is a plot of the average of three experimental results under the condition of -0.8 V. For data before increasing the organic load to 31.8 g / l / day, the standard deviation is the error bar. It showed in. □ is a plot of average values of three experimental results under the condition of −0.6 V (one experimental result in Reference Example A-1 and two experimental results in this Reference Example), and the organic load For data up to 31.8 g / l / day before increasing, the standard deviation is indicated by error bars. Δ is the experimental result under the condition of + 0.0V. The experimental results indicated by ◇ (−0.3V), ♦ (+ 0.3V) and ▲ (+ 0.6V) are the results obtained in Reference Example A-1 as they are.

  About the conditions without electricity supply and the conditions of -0.6V, the tendency similar to reference example A-1 was confirmed. Further, in addition to the conditions of +0.3 V and -0.6 V, the accumulation of lower fatty acids is hardly observed even under the condition of -0.8 V, and particularly with respect to the conditions of -0.6 V and -0.8 V. Even when the organic load was increased to 31.8 g / l / day, accumulation of lower fatty acids was hardly observed. From this result, in addition to the case where the set potential is set to +0.3 V and −0.6 V, also in the case of −0.8 V, it is possible to prevent the methane fermenter from being oxidized and to carry out the methane fermentation treatment over a long period of time. It became clear.

3. Summary From the above results, by setting the potential of the working electrode 9 to +0.3 V, −0.6 V, and −0.8 V on the basis of the potential of the silver / silver chloride electrode as the reference electrode 11, Even when the organic load is 26.9 g COD / l / day, a series of microbial reaction processes for methane fermentation without reducing the gas production rate, COD removal rate, SS removal rate, and without accumulating lower fatty acids It has become clear that it is possible to proceed. In particular, by setting the potential of the working electrode 9 to −0.6 V and −0.8 V based on the reference potential of the silver / silver chloride electrode as the reference electrode 11, an even higher load condition (organic load 31.8 g COD / 1 / day), it is possible to proceed with a series of microbial reaction processes of methane fermentation without reducing the gas generation rate, COD removal rate, SS removal rate, and without accumulating lower fatty acids. It became clear that there was.

  In addition, almost the same result was obtained when the set potential was set to -0.6V and -0.8V, and therefore the set potential was a value between -0.6V and -0.8V. It is estimated that almost the same result can be obtained even when set to. From this, by setting the set potential to +0.3 V or −0.6 V to −0.8 V, it is possible to proceed a series of microbial reaction processes of methane fermentation treatment even under high load conditions. I understood. And by making setting potential into -0.6V--0.8V, it becomes easy to acquire the improvement effect of SS removal rate, and the accumulation suppression effect of a lower fatty acid, and a series of microbial reaction processes of a methane fermentation process are advanced. It has been found suitable above.

(Reference Example B-2)
For the conditions newly added in Reference Example B-1, as in Reference Example A-2, each part of the fermentation broth and each part of the carrier adhering were subjected to genetic analysis, and the adhesion state of microorganisms and the distribution state of microorganism groups investigated.

1. Quantitative PCR Results for Whole Bacteria and Methane Bacteria After completion of the experiment of Reference Example B-1, a fraction of the fermentation broth and a carrier-attached fraction were obtained, and the copy numbers of whole bacteria and methane bacteria were measured by quantitative PCR. The results are shown in FIGS. FIG. 23 shows the number of copies of all bacteria in the fermented liquid fraction, FIG. 24 shows the number of copies of methane bacteria in the fermented liquid fraction, FIG. 25 shows the number of copies of all bacteria in the carrier-attached fraction, and FIG. Is the copy number of methane bacteria in the carrier-attached fraction. In FIG. 23 to FIG. 26, for the cases where the set potential is −0.3 V, +0.3 V, and −0.6 V, the results obtained in Reference Example A-2 are basically shown as they are. Some of the results were remeasured.

  As a result, for the carrier-attached fraction, in addition to the case where the set potential is +0.3 V and -0.6 V, the number of copies is greatly increased also in the case of -0.8 V compared to the case where no power is supplied. It became clear to do. However, for the fermented liquor fraction, it was revealed that the copy number decreased when the set potential was -0.8 V, unlike when the set potential was +0.3 V and -0.6 V.

  Thus, when the set potential was −0.8 V, unlike the cases where the set potential was +0.3 V and −0.6 V, there was a tendency for the number of copies to decrease for the fermentation broth fraction. Nevertheless, in Reference Example B-1, not only when the set potential is +0.3 V and −0.6 V, but also when the potential is −0.8 V, the maintenance or improvement of the methane fermentation treatment performance under high load conditions. The effect was confirmed. From this, it became clear that the carrier-adhered fraction contributes greatly to the effect of maintaining or improving the methane fermentation treatment performance under high load conditions. That is, it has been clarified that the effect of maintaining or improving the methane fermentation treatment performance under high load conditions can be surely obtained by increasing the copy number of the carrier-attached fraction.

  From the above results, it has been clarified that the carrier adhesion fraction can be increased when the set potential is −0.8 V in addition to the set potential of +0.3 V or −0.6 V. Further, since the carrier adhering fraction increased when the set potential was set to -0.8 V than when set to -0.6 V, the set voltage including -0.6 V and -0.6 V was exceeded. It was considered that the effect of increasing the fraction adhered to the carrier could be obtained by increasing the value to the minus side. In particular, when the set potential is set to -0.8V, the set voltage is set to -0.6V in view of the fact that the carrier adhering fraction of methane bacteria is greatly increased when set at -0.8V. It was considered that the effect of increasing the fraction adhering to the carrier was obtained and the effect of maintaining or improving the methane fermentation treatment performance under high load conditions was obtained. Here, the result of the voltammetric measurement of the simulated organic waste is shown in FIG. As shown in FIG. 27, it was confirmed that water splitting occurred when the set potential was increased to a minus side from −1.0V. That is, it was found that when the set potential is increased to the minus side from −1.0 V, gas is likely to be generated from the working electrode, and there is a possibility that an unintended reaction may occur. However, since the electrolysis of water does not occur so vigorously at about −1.2V, the present invention can be implemented even at about −1.2V, but the set potential is −0.6V to −1. It was found that the voltage was preferably 0.0 V, more preferably −0.6 V to −0.8 V, and even more preferably −0.8 V. Here, when the set potential is controlled to a potential larger than −0.6 V to the minus side, a reduction reaction occurs on the working electrode 9, so the set potential is set to a potential at which a reduction reaction can occur at the working electrode 9. It has been found that a potential that does not cause vigorous electrolysis of water is suitable.

2. Comparison of bacterial community structure by T-RFLP By end fragment length polymorphism analysis (T-RFLP), the bacterial community structure of all bacteria except archaea was compared. The results are shown in FIG. From the results shown in FIG. 28, in addition to the case where the set potential is +0.3 V and −0.6 V, the microorganism corresponding to 262 bp, that is, the microorganism belonging to the Thermotogae gate, even in the case of −0.8 V It became clear that the ratio which becomes large, and the tendency was remarkable especially in a carbon plate.

  Further, from the result shown in FIG. 28, in addition to the case where the set potential is + 0.3V and −0.6V, the microorganism corresponding to 210 bp is not detected even in the case of −0.8V.

  From the above results, it becomes clear that the bacterial community structure excluding archaea can be controlled when the set potential is set to -0.8 V in addition to the set potential set to +0.3 V or -0.6 V. It was.

  In addition, when the set potential was -0.6 V and -0.8 V, the bacterial community structure except archaea was similar, so the set potential was -0.6 V and -0. It was considered that almost the same result was obtained when the value was between 8V. Therefore, it was found that the bacterial community structure excluding archaea can be controlled by setting the set potential to +0.3 V or −0.6 V to −0.8 V.

The result of further analysis, closely related properties to bacteria Bacteroidetes Gate microorganisms 95bp adhering to the carbon plate is considered to have a protein resolution when setting potential of -0.6V and -0.8V The 150 bp bacterium was confirmed to be closely related to the bacteria of the Firmicutes phylum, which is thought to specifically decompose the protein and fiber components of garbage. From this, it was also clarified that setting the set potential to −0.6 V to −0.8 V has an effect of attaching a microorganism group effective for methane fermentation treatment of organic waste to the carrier.

3. Comparison of archaeal community structure by T-RFLP Comparison of archaea community structure excluding bacteria among all bacteria by end fragment length polymorphism analysis (T-RFLP). The archaebacteria contain methanogens. The results are shown in FIG. When the set potential is set to -0.8 V, the occupation ratio of Methanosarcina thermophila corresponding to 186 bp on the carbon plate increases as in the case where the set potential is set to -0.6 V. It became clear to do.

  In addition, in both the case where the set potential is set to -0.6 V and -0.8 V, the occupation ratio of the methanosarcina thermophila corresponding to 186 bp on the carbon plate may increase. Since it became clear, it was considered that almost the same result could be obtained even when the set potential was set to a value between -0.6V and -0.8V. Therefore, it was found that the occupation ratio of the acetic acid-assimilating methanogen (Methanosarcina thermophila) on the carbon plate can be increased by setting the set potential to −0.6 V to −0.8 V.

  As mentioned above, it becomes clear from the comparison result of the archaea community structure by T-RFLP that the archaea community structure can be controlled by setting the set potential to +0.3 V or −0.6 V to −0.8 V. It was. And, by setting the set potential to + 0.3V, the occupation ratio of hydrogen-utilizing methanogens on the carbon plate can be increased, and by setting the set potential to -0.6V to -0.8V. It was revealed that the occupation ratio of acetic acid-utilizing methanogens can be increased.

Example 1
Adhere carbon fiber nonwoven fabric (carbon fiber nonwoven fabric (type: pitch, porosity: about 98%, diameter: 30.0 mm, height: 70.0 mm, thickness: 2.4 mm) to one side of the carbon plate of the working electrode 9. The same experiment as in the above Reference Example was performed, except that AQDS as a redox substance was not added to the methane fermentation broth 4. Therefore, the methane fermentation broth 4 The controllability of the solution potential is inferior to that of the above reference example, and the composition of the substrate is 100 g / L for dog food (manufactured by Nippon Pet Food), 0.8 g / L for rice straw, KH ₂ PO ₄ 1.135 g / l, K ₂ HPO ₄ 1.740 g / l, NiCl ₂ .6H ₂ O 0.403 mg / l, CoCl ₂ .6H ₂ O 0.484 mg / l.

  The operating conditions (temperature, pH, operating method) were the same as in the reference example. The organic load and the hydraulic residence time were as shown in FIG.

  The set potential was set to -0.8V and -1.0V. For comparison, an experiment was also conducted for the case where no potential control was performed (control).

  FIG. 37 shows changes with time in the gas generation rate. As for the control, when the organic load was 27.8 g CODcr / L / day, the gas generation rate started to decrease, whereas at -0.8 V, the gas generation rate did not decrease even at this organic load. It was confirmed that methane fermentation was in progress. Moreover, when it was set to -1.0V, it was confirmed that a high gas production | generation rate is obtained even if an organic substance load is 32.7gCODcr / L / day.

  Next, the methane gas content is shown in FIG. As for the control, when the organic load was 27.8 g CODcr / L / day, the methane gas content was greatly reduced. On the other hand, at -0.8V and -1.0V, the methane gas content does not decrease even at this organic load, and at -1.0V, the organic load is 32.7 g CODcr / L / day. No decrease in content was observed.

  Next, FIG. 39 shows changes with time in the VFA (lower fatty acid) concentration. For the control, when the organic load was 27.8 g CODcr / L / day, a significant increase in VFA concentration was observed. On the other hand, at −0.8 V and −1.0 V, no significant increase in VFA concentration was observed even with this organic loading, and for −1.0 V, the organic loading was 32.7 g CODcr / L / day. It was also confirmed that the VFA concentration could be maintained at a low concentration.

  Next, FIG. 40 shows the COD removal rate. Regarding the control, the COD removal rate is small compared to the cases of −0.8 V and −1.0 V, and when the organic load is 27.8 g CODcr / L / day, the COD removal rate tends to be greatly reduced. It was seen. On the other hand, at -0.8 V and -1.0 V, no decrease in COD removal rate was observed even at this organic load, and for -1.0 V, the organic load was 32.7 g CODcr / L / day. No reduction in COD removal rate was observed.

  Next, the SS removal rate is shown in FIG. Regarding the control, the SS removal rate is small compared to the cases of −0.8 V and −1.0 V, and when the organic load is 27.8 g CODcr / L / day, the SS removal rate tends to decrease. It was. On the other hand, at -0.8 V and -1.0 V, the SS removal rate of 40% or more can be maintained even at this organic load, and for -1.0 V, the organic load is 32.7 g CODcr / L / Even on a day, an SS removal rate of 40% or more was maintained.

  As described above, by providing a hydrophobic carrier capable of supporting microorganisms on the electrode surface, an organic load amount as high as 27.8 g CODcr / L / day, and further 32.7 g CODcr without adding a redox substance to the methane fermentation solution. It was revealed that the methane fermentation treatment can be stably performed even at an extremely high organic load of / L / day. That is, it has been confirmed that the methane fermentation treatment can be carried out efficiently and continuously even under high load conditions by adopting the configuration of the methane fermentation treatment of the present invention. In addition, in this example, although no redox substance was added, the controllability of the solution potential was low, but even at an organic load amount equal to or higher than that in the above reference example, The fermentation process could be performed stably. From this, it became clear that the methane fermentation treatment can be carried out efficiently and continuously without adding a redox substance. Furthermore, it became clear that an organic substrate containing lignocellulosic biomass that is difficult to be decomposed, such as rice straw, can be efficiently decomposed.

(Example 2)
In Example 1, the fermented liquid fraction and the carrier-adhered fraction at an organic substance load of 27.8 g CODcr / L / day (day 54), and the fermented liquid at an organic substance load of 32.7 g CODcr / L / day (day 62) The fraction and carrier-attached fraction (carbon fiber nonwoven fabric-attached fraction) are subjected to biological analysis in the same manner as in Reference Example A-1 (2), and the presence of microorganisms in the fermentation broth and carrier And the distribution state of the microorganism group was examined.

1. Quantitative PCR results of whole bacteria and methane bacteria Quantitative PCR results of whole bacteria and methane bacteria are shown in FIGS. FIG. 42 shows the number of copies of the whole bacteria in the fermented liquid fraction at the organic matter loading of 27.8 g CODcr / L / day, and FIG. 43 shows the copy of the whole bacteria in the carrier-adhered fraction at the organic loading of 27.8 g CODcr / L / day. 44 shows the number of copies of methane bacteria in the fermented liquid fraction at an organic matter loading of 32.7 gCODcr / L / day, and FIG. 45 shows the carrier-attached fraction at an organic matter loading of 32.7 gCODcr / L / day. This is the copy number of methane bacteria. Table 1 summarizes the quantitative PCR results for all bacteria and methane bacteria.

  As shown in FIG. 43 and FIG. 45, regarding the carrier-attached fraction, there was not much difference in the copy number depending on the presence or absence of energization in all the bacteria and methane bacteria. The reason for this was thought to be that the carbon fiber nonwoven fabric as the carrier had a high microorganism-retaining effect and it was difficult to produce a difference in the number of attached bacteria by controlling the potential.

  Further, as shown in FIG. 42, regarding the number of copies of all the bacteria in the fermented liquid fraction, when the organic matter load is 27.8 g CODcr / L / day, with energization (−0.8 V, −1.0 V) There was a tendency for the copy number to be slightly lower than when no current was applied. In the case of an organic substance loading of 32.7 g CODcr / L / day, the number of copies was the same or slightly increased in the presence of energization (−0.8 V, −1.0 V) compared to the absence of energization.

  In addition, as shown in FIG. 44, regarding the copy number of methane bacteria in the fermented liquor fraction, when the organic matter load is 27.8 g CODcr / L / day, with energization (−0.8V, −1.0V) There was a tendency for the number of copies to increase as compared to the case without electricity. On the other hand, when organic load was 32.7 g CODcr / L / day, the copy number tended to increase slightly at -0.8 V compared with no power supply, but at -1.0 V compared with no power supply. There was a tendency for the copy number to decrease slightly.

  Here, when the ratio of the copy number of methane bacteria to the total bacterial copy number is compared with respect to the fermented liquid fraction, in the case of an organic matter load of 27.8 g CODcr / L / day, it is about 15. It was about 21.3% at 7% and -1.0V, and a tendency to increase was observed as compared to the case without energization (about 8.2%). On the other hand, in the case of an organic substance load of 32.7 g CODcr / L / day, it is about 10.1% at -0.8V and about 6.3% at -1.0V, and when no power is supplied (about 8.2 %), There was almost no change.

2. Comparison of archaeal community structure by T-RFLP The endocrine polymorphism analysis (T-RFLP) was used to compare the archaeal community structure excluding bacteria. The results are shown in FIG.

  As a result of analysis, as in Reference Example A-2-3 and Reference Example B-2-3, four end restriction fragments (T-RFs) of 84 bp, 92 bp, 186 bp, and 779 bp corresponding to methanogens were detected. It was revealed that the archaeal flora of the fermented liquid fraction and the carrier-adhered fraction are all methanogens. Incidentally, 84 bp corresponds to Methanoculleus sp. Which is a hydrogen-utilizing methanogen, 92 bp corresponds to Methanothermobacter sp. Which is a hydrogen-utilizing methanogen, and 186 bp is Methanosarcina which is an acetic acid-assimilating methanogen. corresponds to sp., and 779 bp corresponds to Methanobacterium sp., which is a hydrogen-utilizing methanogen.

3. Summary From the results of quantitative PCR and terminal fragment polymorphism analysis, it was confirmed that methanogenic bacteria were attached to the carbon fibers provided on the surface of the working electrode. From this, by supplying electrons to the methanogenic bacteria group attached to the carbon fibers and activating them, the methane fermentation treatment ability was improved when energized (-0.8 V, -1.0 V) in Example 1. It is thought that it improved greatly. More specifically, by controlling the potential around the carbon fiber provided on the surface of the working electrode to a potential very close to the set potential, electrons can be easily supplied to the methane-producing bacteria group attached to the carbon fiber. It is thought that activation of the producing bacteria group was facilitated.

  Moreover, in Example 1, the outstanding methane fermentation processing capacity was confirmed when it supplied with electricity (-0.8V, -1.0V) as organic substance load amount 27.8gCODcr / L / day. Considering this result and the results obtained in quantitative PCR, it was suggested that an increase in the proportion of methane bacteria in the total bacteria in the fermented liquid fraction may contribute to the improvement of the methane fermentation processability. And as one of the causes of the increase of the ratio of the methane bacterium which occupies in all the bacteria in a fermentation liquid fraction, it is possible that the methane bacterium activated in the support | carrier was supplied to the fermentation liquid.

  Even when a hydrophobic carrier capable of supporting microorganisms is provided on the electrode surface, it is presumed that the same effect can be obtained by the potential at which an excellent effect is obtained in the above-mentioned reference example. In other words, even if the set potential is a potential at which the reduction reaction can occur at the working electrode and the electrolysis of water does not occur violently, or +0.3 V based on the silver / silver chloride electrode potential reference, methane bacteria are attached to the carrier. Thus, it is considered that the methane fermentation treatment can proceed efficiently without using a redox substance.

Claims (11)

At least a part comprises a sparse microorganisms involved in the carrier holding electrode and the organic substrate and methane fermentation with the aqueous carrier and the organic substrate of the electrode surface contacting the methane fermentation liquid methane fermentation process, the A methane fermentation method, wherein the methane fermentation treatment is performed while controlling the potential of the carrier holding electrode to +0.3 V based on the potential at which electrons are supplied from the carrier holding electrode or the silver / silver chloride electrode potential. The carrier holding electrode as a working electrode,
Connecting the working electrode, counter electrode and reference electrode to a potentiostat;
Contacting the methane fermentation broth and electrolyte through an ion exchange membrane;
Bringing the working electrode and the reference electrode into contact with the methane fermentation liquor,
Contacting the counter electrode with the electrolyte;
The methane fermentation method according to claim 1, wherein the potential of the working electrode is controlled by a three-electrode system. The carrier holding electrode as a working electrode,
Connecting the working electrode, counter electrode and reference electrode to a potentiostat;
Contacting the methane fermentation broth and the counter electrode through an ion exchange membrane;
Bringing the working electrode and the reference electrode into contact with the methane fermentation liquor,
The methane fermentation method according to claim 1, wherein the potential of the working electrode is controlled by a three-electrode system. The potential of the carrier holding electrode is controlled to -0.8 V to -1.0 V (silver / silver chloride electrode potential reference), which is a potential at which electrons are supplied from the carrier holding electrode. Methane fermentation method. The methane fermentation method according to any one of claims 1 to 4, wherein the carrier is carbon fiber. At least a part comprises a sparse microorganisms involved in the carrier holding electrode and the organic substrate and methane fermentation with the aqueous carrier and the organic substrate of the electrode surface contacting the methane fermentation liquid methane fermentation process, the the potential of the carrier holding electrode is controlled to the from the carrier holding electrode electrons by the potential or silver-silver electrode potential reference chloride supplied + 0.3V, by supporting the microorganisms involved in the methane fermentation in the carrier activation A method for producing a carrier on which a microorganism group is supported. The substance is at least in part on the sparse carrier holding electrode and the methanogens group and the methanogens group having the aqueous carrier substrate of the electrode surface in contact with at least containing culture medium, the potential of the carrier holding electrode A method for producing a carrier carrying a microorganism group, characterized by controlling the potential to which electrons are supplied from the carrier holding electrode and causing the carrier to carry and activate the methanogenic bacteria group. The carrier holding electrode as a working electrode,
Connecting the working electrode, counter electrode and reference electrode to a potentiostat;
The methane fermentation solution or the culture solution and the electrolyte solution are contacted via an ion exchange membrane,
Bringing the working electrode and the reference electrode into contact with the methane fermentation broth or the culture broth;
Contacting the counter electrode with the electrolyte;
The method for producing a carrier carrying a microorganism group according to claim 6 or 7, wherein the potential of the working electrode is controlled by a three-electrode system. The carrier holding electrode as a working electrode,
Connecting the working electrode, counter electrode and reference electrode to a potentiostat;
Contacting the methane fermentation broth or the culture with the counter electrode through an ion exchange membrane;
Bringing the working electrode and the reference electrode into contact with the methane fermentation broth or the culture broth;
The method for producing a carrier carrying a microorganism group according to claim 6 or 7, wherein the potential of the working electrode is controlled by a three-electrode system. The potential of the carrier holding electrode is controlled to -0.8 V to -1.0 V (silver / silver chloride electrode potential reference) which is a potential at which electrons are supplied from the carrier holding electrode. A method for producing a carrier carrying a microorganism group. The method for producing a carrier carrying a microorganism group according to any one of claims 6 to 10, wherein the carrier is carbon fiber.