JP6963806B2 - Bioelectrochemical system - Google Patents

Description

The present invention relates to a bioelectrochemical system.

For livestock farmers, the treatment of wastewater from the barn requires a great deal of cost and labor, which is a heavy burden. In addition, in order to prevent impacts on the environment, it is required to develop new wastewater treatment technology that responds to the recycling of livestock biomass and stricter wastewater treatment standards. The development of new technologies that can realize proper treatment of organic wastewater and recovery of resources from organic wastewater is required not only in the livestock field but also in a wide range of fields such as food processing, brewing, and sewage treatment in urban areas. There is.

In recent years, a new technology called Bioelectrochemical System (BES) has attracted attention. The bioelectrochemical system is a general term for devices (bioreactors) that utilize living organisms as catalysts that promote reactions on electrodes. Examples of bioelectrochemical systems include microbial fuel cells (MFCs), microbial electrolysis cells (MECs), and devices that produce or decompose microbial electrochemical or enzymatic electrochemical substances. Etc. are included. In microbial fuel cells and microbial electrolytic cells, microorganisms play a role of decomposing organic substances by redox reaction under anaerobic conditions and passing electrons generated at that time to an anode (negative electrode).

A microbial fuel cell is a bioreactor that generates power (energy recovery) by recovering excess reducing power (electrons) generated by decomposition (oxidation) of organic substances by microorganisms under anaerobic conditions at the anode (negative electrode). .. In a microbial fuel cell, hydrogen ions generated by decomposition of organic matter move to the cathode (positive electrode) side. On the other hand, the electrons generated by the decomposition of organic matter are collected at the anode and move to the cathode via an external circuit. On the cathode surface, water is generated by the reaction of hydrogen ions and electrons that have moved from the anode side with oxygen.

The microbial electrolysis cell is a bioreactor that recovers excess reducing power (electrons) generated by decomposition (oxidation) of organic substances by microorganisms under anaerobic conditions as hydrogen at the cathode (positive electrode). In the microbial electrolysis cell, hydrogen ions generated by decomposition of organic substances move to the cathode (positive electrode) side. On the other hand, the electrons generated by the decomposition of the organic substance are recovered at the anode by applying a voltage between the anode (negative electrode) and the cathode (positive electrode), and move to the cathode via an external circuit. On the cathode surface, hydrogen gas is generated by the reaction of hydrogen ions and electrons. By recovering this hydrogen, energy can be recovered. Since the amount of energy obtained as hydrogen is larger than the amount of energy input as a voltage application, the energy of the entire microbial electrolysis cell is recovered from the wastewater. As described above, in the microbial electrolytic cell, it is necessary to apply a voltage between the anode and the cathode by a voltage application unit (a power source, a potentiostat, etc.) connected to the anode and the cathode.

Bioelectrochemical systems such as microbial fuel cells and microbial electrolytic cells can treat various types of organic wastewater. Since the organic matter in the wastewater is decomposed by this treatment, the bioelectrochemical system also has a function of purifying the wastewater (removing the organic matter). In this way, the bioelectrochemical system is expected as a new technology in the future because it can purify wastewater and recover energy from the wastewater at the same time.

By the way, as a method for removing organic matter in wastewater, a standard activated sludge method and a sprinkling filter method, which are both performed in an aerobic state, are widely used. In the standard activated sludge method, air bubbles are sent to a treatment liquid that is a mixture of sludge containing aerobic microorganisms (activated sludge) and wastewater to bring the treatment liquid into an aerobic state, and the aerobic microorganisms remove organic substances from the wastewater. The method. The sprinkling filter method is a method in which wastewater is sprinkled on a filter medium to which aerobic microorganisms are attached, and the aerobic microorganisms remove organic substances in the wastewater while the wastewater passes through the filter medium.

Removal of nitrogen in wastewater is also important for purification of wastewater. As the removal of nitrogen, an intermittent aeration method and a method of adding a reagent for removing nitrogen, which are both performed in an anaerobic state, are known. The intermittent aeration method involves intermittent aeration of the treatment tank to react ammonia to nitric acid or nitrite in an aerobic state, and nitric acid or nitrite to nitrogen in a gas form by denitrifying bacteria in an anaerobic state. , Is a method of repeating.

Microbial-catalyzed reactions on electrodes in bioelectrochemical systems proceed in an anaerobic state. Therefore, the decomposition of organic matter by the bioelectrochemical system is also performed in an anaerobic state. The present inventors have found that even if an aeration device is combined with a bioelectrochemical system, the reaction on the electrodes proceeds, and at this time, the efficiency of removing organic substances is increased (see Patent Document 1). At this time, the present inventors have also found that if the aeration device intermittently aerates the liquid of the bioelectrochemical system, the aerobic state and the anaerobic state are repeated, and the efficiency of nitrogen removal is also improved.

Japanese Unexamined Patent Publication No. 2016-091805

Hong Liu, and Bruce E. Logan, "Electricity Generation Using an Air-Cathode Single Chamber Microbial Fuel Cell in the Presence and Absence of a Proton Exchange Membrane", Environ. Sci. Technol., Vol. 38, pp. 4040-4046 ..

As mentioned above, bioelectrochemical systems are expected not only to generate electricity but also to remove organic matter in wastewater for purification treatment. In addition, the treatment of wastewater requires not only the removal of organic matter but also the removal of nitrogen. However, the conventional bioelectrochemical system has a lower ability to remove organic substances than the activated sludge method or the like. Therefore, the development of a microbial fuel cell having a high ability to decompose organic substances is expected.

As described in Patent Document 1, if an aeration device is combined with a bioelectrochemical system to intermittently aerate the liquid of the bioelectrochemical system, the efficiency of removing organic substances is increased and the efficiency of removing nitrogen is also increased. Can be done. However, there is always a demand for the development of methods that can remove organic matter and nitrogen in wastewater with lower power consumption. In addition, in bioelectrochemical systems, there is always a demand for higher energy recovery efficiency. The energy recovery efficiency can be evaluated, for example, by the Coulomb efficiency.

The present invention has been made in view of this point, and bioelectricity can remove organic substances and nitrogen in waste water with lower power consumption, and can significantly improve the energy recovery efficiency evaluated by Coulomb efficiency and the like. The purpose is to provide a chemical system.

The present invention relates to the following bioelectrochemical systems.

[1] The container, a watering device for spraying a liquid containing an organic substance on the container, a liquid containing an electrolyte contained in the container, and a position where the liquid sprayed from the watering device comes into contact with each other. An anode carrying an electron-donating microorganism on the surface, which is placed in contact with the liquid contained in the container, and the contained liquid so as to be in contact with the contained liquid or across a cation-permeable diaphragm. A bioelectrochemical system having a cathode arranged adjacent to and.
[2] The bioelectrochemical system according to [1], wherein the watering apparatus adjusts watering and stopping, or the amount of watering according to an electric current flowing between the anode and the cathode.
[3] The bioelectrochemical system according to [1] or [2], wherein the liquid contained in the container further contains an organic substance, and the watering device sprays the liquid contained in the container.
[4] The bioelectrochemical system according to any one of [1] to [3], wherein the shape of the anode is brush-like, fibrous, or a combination thereof.
[5] The bioelectrochemical system according to any one of [1] to [4], wherein the bioelectrochemical system is a microbial fuel cell.
[6] The bioelectrochemical system according to [5], wherein the aeration device is driven by an electric current flowing between the anode and the cathode.
[7] The bioelectrochemical system is a microbial electrolysis cell, further comprising a voltage application section for applying a voltage between the anode and the cathode so that electrons flow from the anode to the cathode. 1] The bioelectrochemical system according to any one of [4].
[8] The organism according to any one of [1] to [7], further comprising an ammeter for measuring the current flowing between the anode and the cathode, wherein the bioelectrochemical system is a water quality sensor. Electrochemical system.

According to the present invention, there is provided a bioelectrochemical system capable of removing organic substances and nitrogen in waste water with lower power consumption and significantly improving the energy recovery efficiency evaluated by the Coulomb efficiency and the like.

FIG. 1 is a schematic cross-sectional view showing the configuration of a microbial fuel cell according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the configuration of a microbial electrolytic cell according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing the configuration of another microbial electrolytic cell according to an embodiment of the present invention. FIG. 4 is a graph showing changes over time in the current in the microbial electrolytic cell used in the experiment. FIG. 5 is a graph showing changes over time in chemical oxygen demand (COD) in the microbial electrolysis cell used in the experiment. FIG. 6 is a graph showing changes over time in the concentration of total nitrogen (TN) in the microbial electrolysis cell used in the experiment.

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

[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing the configuration of a microbial fuel cell 100 according to an embodiment of the present invention.

As shown in FIG. 1, the microbial fuel cell 100 has a container 110, a sprinkler 120, a liquid 130, an anode 140, a membrane electrode assembly (MEA) 150, a lead wire 170 and an ammeter 175. The watering device 120 includes a pumping pipe 122, a pump 124, a water pipe 126, a watering device 128, and a control unit 129. The liquid 130 contains an electrolyte. The anode 140 carries an electron-donating microorganism 142. The membrane electrode assembly 150 includes a diaphragm 152, a cathode 154 and a float 156. The anode 140 and the cathode 154 are electrically connected by a conducting wire 170 that constitutes an external circuit. An ammeter 175 is installed on the conductor 170.

The container 110 constitutes the main body of the microbial fuel cell 100 and houses the liquid 130. The material, shape and size of the container 110 are not particularly limited and may be appropriately set according to the intended use. In the microbial fuel cell 100 according to the present embodiment, unlike the conventional microbial fuel cell, the container 110 may be opened to the outside because the anaerobic condition is not always set.

In this embodiment, the container 110 has a stirrer 115 that facilitates agitation of the liquid 130. When the liquid 130 is sufficiently agitated by watering, the stirrer 115 is unnecessary.

The watering device 120 has a pumping pipe 122, a pump 124, a water pipe 126, a watering device 128, and a control unit 129, and sprays a liquid containing an organic substance into a container 110 (anode 140). The organic substance is an organic substance that serves as a fuel for the electron-donating microorganism 142 carried by the anode 140, and is not particularly limited as long as the electron-donating microorganism 142 can be metabolized. Organic matter used as fuel includes not only useful resources such as alcohol, monosaccharides, polysaccharides, and proteins, but also unused resources (organic waste) such as agricultural industrial waste, organic waste liquid, urine, sludge, and food residue. Can be used. As the liquid containing an organic substance, various wastewaters may be used as they are, or an organic substance as a fuel for maintaining and multiplying the electron-donating microorganism 142 and for continuously operating the microbial fuel cell 100 as necessary. May be added. In the present embodiment, the liquid 130 contained in the container 110 contains an organic substance as a fuel, and the watering device 120 sprays the liquid 130 contained in the container 110.

The pumping pipe 122 is a water channel pipe that guides the liquid 130 contained in the container 110 to the pump 124. The shape and configuration of the pumping pipe 122 is not particularly limited as long as the amount of liquid 130 to be sprayed can be conducted to the pump 124. In order to agitate the liquid 130, the pumping pipe 122 preferably pumps the liquid 130 on the bottom side of the liquid 130 and guides it to the pump 124, from a depth on the bottom side rather than half the depth of the liquid 130. It is preferable to pump the liquid 130 and guide it to the pump 124.

The pump 124 pumps the liquid 130 in the container 110 through the pumping pipe 122 and supplies it to the sprinkler 128. The type of the pump 124 is not particularly limited, and can be appropriately selected depending on the required amount of the liquid 130 to be sprayed and the like.

The water pipe 126 is a water pipe that guides the liquid 130 from the pump 124 to the watering nozzle 128. The shape and configuration of the water pipe 126 are not particularly limited as long as the amount of liquid 130 to be sprayed can be conducted to the watering nozzle 128.

The sprinkler 128 is arranged at the top of the container 110 and sprays the liquid 130 supplied from the pump 124 toward the bottom surface of the container 110. The watering device 128 can be, for example, a rotary or fixed watering device having a plurality of watering nozzles.

The control unit 129 controls the supply or stop of the liquid from the pump 124 to the watering nozzle 128, and the supply amount of the liquid from the pump 124 to the watering nozzle 128. The control unit 129 may continuously operate the pump 124, but may intermittently operate the pump 124 from the viewpoint of easily adjusting the balance between the power generation capacity and the decomposition capacity of organic matter. Further, the control unit 129 may operate the pump 124 so that the amount of liquid supplied to the watering nozzle 128 is constant, but the control unit 129 operates the pump 124 so that the amount of liquid supplied to the watering nozzle 128 fluctuates. You may let me.

The control unit 129 determines the supply or stop of the liquid from the pump 124 to the watering nozzle 128 and the amount of the liquid supplied from the pump 124 to the watering nozzle 128, the power generation capacity of the microbial fuel cell 100, the decomposition capacity of organic substances, and the liquid 130. It may be appropriately controlled according to the concentration of the organic substance contained in the watering nozzle. When the organic matter is sufficiently decomposed and the liquid 130 is purified, the electric power obtained by the power generation of the microbial fuel cell 100 is reduced. That is, the concentration of organic matter in the liquid 130 can be estimated from the current flowing between the anode 140 and the cathode 154 detected by the ammeter 175. Therefore, the control unit 129 may control the operation and stop interval of the pump 124 and the amount of liquid supplied from the pump 124 to the watering nozzle 128 according to the current flowing between the anode 140 and the cathode 154. .. Since the watering from the sprinkler 128 is performed to utilize the decomposition of the organic matter in the liquid 130, it is not necessary to sprinkle the water when the concentration of the organic matter in the liquid 130 decreases, and the viewpoint of improving the nitrogen removal efficiency is improved. From now on, it may be preferable not to sprinkle water in order to make it anaerobic. In such a case, the control unit 129 may stop the operation of the pump 124 when it detects a decrease in the current, or may reduce the amount of liquid supplied from the pump 124 to the watering nozzle 128. By doing so, it is possible to suppress the power consumption for operating the pump 124. Further, the control unit 129 may control the operation of the pump 124 so as to sprinkle water under a preset suitable condition.

When the ammonia concentration in the liquid 130 is high as measured by an ammonia concentration meter (not shown), watering may be promoted to promote the nitrification reaction. In this case, after the nitrification reaction, nitrogen can be removed by pouring a small amount of raw sewage as an electron donor into the container 110 to cause a denitrification reaction.

The liquid 130 is an aqueous solution containing one or more kinds of organic substances, electrolytes and electron transport intervening substances contained in a container 110. The type of electrolyte is not particularly limited as long as it is a substance that can be ionized in water. Examples of electrolytes include NaH ₂ PO ₄ / Na ₂ HPO ₄ , KH ₂ PO ₄ / K ₂ HPO ₄ , NaCO ₃ / NaHCO ₃ , NaCl, KCl, NH ₄ Cl and the like. Further, an electron transfer intervening substance such as an electron mediator or conductive fine particles may be further added to the liquid 130, if necessary.

In the present embodiment, the liquid 130 further contains an organic substance as a fuel and an electron donating microorganism 142. In the present embodiment, the liquid 130 contained in the container 110 is sucked up by the pump 124 and sprayed from the watering device 120. At this time, if the liquid 130 contains the electron-donating microorganism 142, the electron-donating microorganism 142 can be easily attached to and supported from the liquid 130 to the anode 140 when it is sprayed and comes into contact with the anode 140.

The anode 140 is arranged between the sprinkler 128 and the bottom surface of the container 110 so as to come into contact with the liquid 130 contained in the container 110. This allows the anode 140 to come into contact with both the liquid sprinkled from the sprinkler 128 and the liquid 130 contained in the container 110. In the present embodiment, the anode 140 is partially exposed to the outside of the liquid 130 contained in the container 110 and partially immersed in the liquid 130 contained in the container 110. The length of the part of the anode 140 exposed to the outside (height from the liquid surface to the top of the anode 140) and the length of the part immersed in the liquid 130 (depth from the liquid surface to the tip of the anode 140). ) Is not particularly limited. The length of the portion of the anode 140 exposed to the outside is preferable because the longer the length is, the more aerobic decomposition of organic substances is promoted. In reality, the length of the portion of the anode 140 exposed to the outside is usually about 1 m or more and 15 m or less, and preferably 4 m or more and 8 m or less, from the viewpoint of the physical strength of the electrode and the capacity of the pump. .. Further, the length of the portion of the anode 140 immersed in the liquid 130 is preferable because the longer the length is, the more anaerobic decomposition of organic substances and energy recovery by power generation are promoted. Therefore, the anode 140 is immersed in the liquid 130. It is preferable that the portion to be formed has a length up to the bottom surface of the container 110. In reality, the length of the portion of the anode 140 immersed in the liquid 130 is usually about 1 m or more and 10 m or less, and 3 m or more and 6 m or less, depending on the physical strength of the electrode and the capacity of the pump. Is preferable. Further, it is also preferable that the ratio of the area occupied by the anode 140 to the area of the liquid surface of the liquid 130 when the liquid 130 is viewed from above is also large, and the area occupied by the anode 140 in the liquid surface of the liquid 130 is , 50% or more, more preferably 70% or more, and even more preferably 90% or more.

An electron donating microorganism 142 is supported on the anode 140. The type of the electron donating microorganism 142 may be one kind or two or more kinds. When organic wastewater, sludge, or the like is sprayed from the watering nozzle 128, the electron-donating microorganisms inhabiting them can be used as they are without adding electron-donating microorganisms from the outside. For example, Pseudomonas and Geobacter inhabit all parts of the natural environment such as soil, fresh water, and seawater, so if organic wastewater or sludge is sprayed from the sprinkler 128, it can be used without being added from the outside. The electron donating microorganism 142 may be supported on the anode 140 in advance before the operation of the microbial fuel cell 100, or a liquid containing the electron donating microorganism 142 contained in the container 110 by operating the microbial fuel cell 100. The 130 may be supplied to the anode 140 by being supplied to the sprinkler 128 by the pump 124, sprayed from the sprinkler 128 and in contact with the anode 140.

Since the anode 140 can also retain microorganisms other than the electron-donating microorganism 142, it can also function as a microbial carrier that enhances the wastewater purification action.

The material and shape of the anode 140 are not particularly limited, and may be appropriately selected depending on the adhesion of the electron-donating microorganism 142, the degree of electron transfer from the electron-donating microorganism 142, and the like. Examples of the material of the anode 140 include carbon, metal, metal oxide and the like. Examples of the shape of the anode 140 include a planar shape such as a cloth and a three-dimensional shape such as a brush shape, a rod shape, a granular shape, and a fibrous shape. Since the liquid 130 contained in the container 110 supplies a sufficient amount of organic matter to the anode 140 when sprinkled, it is desirable that an appropriate water flow is generated. Therefore, the anode 140 has an appropriate degree of flexibility, or a gap is formed between the electrodes or between the fibers constituting the electrodes, so that the water flow generated in the liquid 130 contained in the container 110 is excessive. It is desirable not to interfere with. From the viewpoint of increasing the surface area to more easily support the electron-donating microorganism 142 and making it difficult to obstruct the appropriate water flow of the liquid 130, the shape of the anode 140 is brush-like, fibrous, mesh-like or folded. It is preferably a mesh-like shape, and it is preferable to combine these shapes, such as bundling fibers. Examples of materials for the anode 140 that have moderate suppleness and do not easily obstruct the water flow of the liquid 130 include carbon fiber, carbon paper, graphite plate, carbon cloth, carbon mesh, graphite felt, graphite particles, and activated graphite. Includes particles, carbon felt, reticulated graphitized carbon, carbon brushes, etc. Further, examples of the material of the anode 140 that does not easily obstruct the water flow of the liquid 130 because it has an appropriate gap include a stainless steel mesh and the like. These may be heat-treated. Whether or not heat treatment was performed depends on the concentration of each element on the surface of the anode 140 by energy dispersive X-ray spectroscopy (EDS / EDX) and 5 μm or more from the surface in the cross section exposed by cutting the anode 140. It can be confirmed by comparing the concentration of each element in the distant part (inside).

It is considered that the biofilm formed by supporting the electron-donating microorganism 142 on the anode 140 is in an anaerobic state because oxygen is consumed by aerobic bacteria near the surface thereof. Therefore, it is considered that the reaction on the electrode catalyzed by microorganisms proceeds inside the biofilm to produce an electric current (the principle is not limited to this). As a result, it is possible to generate an electric current inside the biofilm in an anaerobic state not only at the portion of the anode 140 that comes into contact with the liquid 130 but also at the portion exposed to the outside of the liquid 130.

The membrane electrode assembly 150 includes a diaphragm 152 having cation permeability and a cathode 154 having gas permeability. The diaphragm 152 and the cathode 154 are integrated to form a membrane electrode assembly 150. The membrane electrode assembly 150 is arranged so that the diaphragm 152 is in contact with the liquid 130 and the cathode 154 is in contact with the outside air. In the present embodiment, the diaphragm 152 is fixed to the lower side of the float 156 so as to close the through hole provided in the substantially rectangular parallelepiped float 156 having the through hole formed in the central portion in a plan view. The cathode 154 is laminated on the diaphragm 152 in the through hole. As a result, the membrane electrode assembly 150 is floated and arranged on the surface of the liquid 130. The membrane electrode assembly 150 is arranged so as to be parallel to the surface (liquid surface) of the liquid 130 in FIG. 1, but the surface (liquid) of the liquid 130 is prevented from staying under the diaphragm 152. It may be arranged so as to be inclined with respect to the surface).

The diaphragm 152 is a membrane capable of selectively permeating cations and is arranged between the liquid 130 and the cathode 154. As described above, in the present embodiment, the diaphragm 152 is fixed to the lower side of the float 156 so as to close the through hole formed in the substantially rectangular parallelepiped float 156. The type of diaphragm 152 is not particularly limited as long as it can selectively permeate cations. Examples of the diaphragm 152 include a proton exchange membrane. The proton exchange membrane is a membrane made of a proton-conducting ion-exchange polymer electrolyte. Examples of materials for proton exchange membranes include perfluorosulfonic acid-based fluoroion exchange resins and organic / inorganic composite compounds. The perfluorosulfonic acid-based fluorine ion exchange resin includes, for example, a copolymer containing a polymerization unit based on a perfluorovinyl ether having a sulfo group or a carboxyl group and a polymerization unit based on tetrafluoroethylene. Nafion (registered trademark) is known as such a fluorine ion exchange resin. The organic / inorganic composite compound is a substance composed of a compound in which a hydrocarbon polymer (for example, polyvinyl alcohol) and an inorganic compound (for example, tungsten acid) are compounded. Membranes made of these materials are commercially available.

The cathode (air cathode) 154 is arranged adjacent to the liquid 130 with the diaphragm 152 in between. As described above, in the present embodiment, the cathode 154 is laminated on the diaphragm 152 in the through hole formed in the substantially rectangular parallelepiped float 156. The material and shape of the cathode 154 are not particularly limited as long as they can achieve both gas permeability and conductivity. Examples of the material of the cathode 154 include carbon, metal and the like. Examples of the cathode 154 include carbon paper, carbon cloth, carbon mesh, graphite particles, activated graphite particles, carbon felt, reticulated vitrified carbon, stainless steel mesh and the like. These may be heat-treated. Further, an oxygen reduction catalyst such as platinum or activated carbon may be supported on these surfaces. Whether or not heat treatment was performed depends on the concentration of each element on the surface of the cathode 154 by energy dispersive X-ray spectroscopy (EDS / EDX) and 5 μm or more from the surface in the cross section exposed by cutting the cathode 154. It can be confirmed by comparing the concentration of each element in the distant part (inside).

The float 156 floats on the surface (liquid surface) of the liquid 130 and directly or indirectly supports the diaphragm 152 and the cathode 154. As a result, the anode 140 is placed floating in the liquid 130, and the diaphragm 152 and the cathode 154 are placed floating in the surface of the liquid 130. That is, the anode 140, the diaphragm 152, the cathode 154, and the float 156 form one floating body. The material and shape of the float 156 are not particularly limited as long as the anode 140, diaphragm 152 and cathode 154 can be floated in or on the surface of the liquid 130. For example, the float 156 is a foamed plastic such as Styrofoam, a hollow structure made of resin, metal, or the like. In the present embodiment, the float 156 is a substantially rectangular parallelepiped foamed plastic having a through hole.

The ammeter 175 is installed on the conductor 170 to measure the current flowing between the anode 140 and the cathode 154.

In addition, the microbial fuel cell 100 includes a thermometer for measuring the temperature of the liquid 130, a pH meter for measuring the pH of the liquid 130, a dissolved oxygen meter (DO meter) for measuring the dissolved oxygen concentration in the liquid 130, and ammonium ions in the liquid 130. Further, it may have instruments such as an ion sensor for measuring the concentration of pH and nitrate ions. In this case, the control unit 129 determines the temperature of the liquid 130 (correlates with the activity of the electron donating microorganism 142), the pH of the liquid 130 (correlates with the concentration of ammonia in the liquid 130), and the oxidation-reduction potential (ORP) of the liquid 130. Organic substances contained in the liquid 130 based on information such as the dissolved oxygen concentration of the liquid 130 (correlates with whether the liquid 130 is anaerobic or aerobic) and the dissolved oxygen concentration of the liquid 130 (correlates with whether the liquid 130 is anaerobic or aerobic). It becomes possible to detect the concentration of water with higher sensitivity, and it becomes possible to set watering conditions more appropriately.

(Operation of microbial fuel cell)
Next, the operation of the microbial fuel cell 100 according to the present embodiment will be described.

When the liquid 130 contained in the container 110 is pumped by the pump 124 and supplied to the sprinkler 128 to operate the microbial fuel cell 100 according to the present embodiment, it is formed by the electron donating microorganism 142 supported on the anode 140. Inside the biofilm, hydrogen ions and electrons are generated when the electron-donating microorganism 142 decomposes an organic substance (for example, acetic acid) into carbon dioxide. The hydrogen ions generated by the decomposition of the organic matter move to the inside of the liquid 130 contained in the container 110 by the flow of the sprayed liquid 130, pass through the diaphragm 152, and move to the surface of the cathode 154. On the other hand, the electrons generated by the decomposition of the organic substance are collected at the anode 140 and move to the cathode 154 via an external circuit. Further, since the cathode 154 has air permeability, oxygen is also present on the surface of the cathode 154. In such a situation, on the surface of the cathode 154, hydrogen ions and electrons react with oxygen to generate water. Therefore, by supplying the organic substance into the container 110, the above cycle can be maintained and the electric power can be continuously supplied to the external circuit.

The microbial fuel cell 100 according to the present embodiment is mainly characterized in that a liquid containing an organic substance is sprayed on the anode 140. In the microbial fuel cell 100 according to the present embodiment, the anode 140 comes into contact with the liquid 130 containing an organic substance at a position where it comes into contact with the outside air. Therefore, in the microbial fuel cell 100 according to the present embodiment, in addition to power generation and decomposition of organic substances by anaerobic treatment inside the biofilm, organic substances are subjected to aerobic treatment in the region of the biofilm that comes into contact with the outside air. It can also be disassembled (see FIG. 5).

Further, since the microbial fuel cell 100 according to the present embodiment also uses aerobic treatment, it is possible to remove nitrogen, which was not possible with a conventional microbial fuel cell using only anaerobic treatment (see FIG. 6). .. The biofilm formed by supporting the electron-donating microorganism 142 on the anode 140 is in an aerobic state near the outer surface and in an anaerobic state inside. Therefore, at the anode 140, the reaction from ammonia to nitric acid or nitrite proceeds near the outer surface of the biofilm, and the reaction from nitric acid or nitrite to nitrogen in the gas form by the anaerobic bacterium denitrifying bacteria is the biofilm. It is thought that it proceeds inside the (the principle is not limited to this).

(effect)
As described above, in the microbial fuel cell 100 according to the present embodiment, by watering the liquid with the watering device 120, the portion of the anode 140 exposed from the liquid 130 becomes an aerobic state, and the decomposition and removal of organic substances and ammonia are eliminated. The reaction to nitric acid or nitrite can proceed. On the other hand, in the part of the anode 140 that comes into contact with the liquid 130, the inside of the biofilm formed by the electron donating microorganism 142 adhering to the anode 140, and the inside of the liquid 130 contained in the container 110, microorganisms due to an anaerobic state are introduced. The reaction on the electrode as a catalyst and the reaction of nitric acid or nitrite to nitrogen of the gas body can also proceed. In this way, the microbial fuel cell 100 according to the present embodiment can simultaneously and continuously produce electric current, remove organic substances, and remove nitrogen without performing intermittent aeration. Therefore, the microbial fuel cell 100 according to the present embodiment can continuously produce electric current, remove organic substances, and remove nitrogen, and it is easy to increase the processing speed of these.

Further, since the microbial fuel cell 100 according to the present embodiment operates while pumping and sprinkling the liquid by the watering device 120, the liquid 130 is appropriately agitated to appropriately equalize the concentrations of organic substances and nitrogen, and the electric current is generated. Production, removal of organic matter, and removal of nitrogen can be made more efficient.

Further, since the microbial fuel cell 100 according to the present embodiment can form an aerobic state on the surface of the anode 140 by watering with lower power consumption, power consumption becomes a problem when removing organic substances by the standard activated sludge method. Increase is suppressed. Further, since the microbial fuel cell 100 according to the present embodiment uses not only aerobic treatment but also anaerobic treatment, it is possible to reduce the amount of excess sludge generated as compared with the standard activated sludge method that does not use anaerobic treatment.

Further, the microbial fuel cell 100 according to the present embodiment has a feature that the current flowing through the conducting wire 170 flows through the conducting wire 170 in an amount corresponding to the amount of organic matter in the liquid 130 (see FIGS. 4 and 5). Therefore, the microbial fuel cell 100 according to the present embodiment is also useful as a water quality sensor that estimates the amount of organic matter in the liquid 130 by measuring the current flowing through the lead wire 170 with an ammeter 175.

Further, in the microbial fuel cell 100 according to the present embodiment, the anode 140, the diaphragm 152, and the cathode 154 float in or on the surface of the liquid 130 without forming a part of the wall surface of the container 110. Therefore, the container 110 can be enlarged, that is, the microbial fuel cell 100 can be scaled up without considering the destruction of the anode 140, the diaphragm 152, and the cathode 154 due to the increase in the pressure of the liquid 130. Further, regardless of the amount of the liquid 130, the entire surfaces of the anode 140 and the cathode 154 are always in contact with the liquid 130 directly or through the diaphragm 152, so that the external circuit is powered without being affected by the change in the amount of the liquid 130. Can be output stably.

Further, in the microbial fuel cell 100 according to the present embodiment, the anode 140 and the cathode 154 (membrane electrode assembly 150) need only be installed in the apparatus used in the conventional sprinkling filter method. Therefore, it is easy to introduce the microbial fuel cell 100 according to the present embodiment into an existing facility.

Further, in the present embodiment, the microbial fuel cell 100 having the float 156 for floating the cathode 154 in or on the surface of the liquid 130 has been described, but the float 156 is not an indispensable constituent requirement. For example, the diaphragm 152 or the cathode 154 may have a hollow structure so as to float themselves.

Further, in the present embodiment, the microbial fuel cell 100 having the diaphragm 152 has been described, but the diaphragm 152 is not an indispensable constituent requirement. That is, the cathode 154 must not be in contact with the anode 140, but may be in direct contact with the liquid 130. However, considering the practicality of the battery, it is preferable that the diaphragm 152 is present.

Further, in the present embodiment, the microbial fuel cell 100 in which the liquid 130 contained in the container 110 is pumped by the pump 124 and sprayed from the sprinkler 128 has been described, but the liquid containing an organic substance is contained in the container 110. Wastewater may be supplied to the sprinkler 128 from the outside by a pump 124 and sprayed instead of the liquid 130. At this time as well, the electron donating microorganism 142 may be supported on the anode 140 in advance before the operation of the microbial fuel cell 100, or by operating the microbial fuel cell 100, waste water from the outside is sprinkled by the pump 124. It may be applied to the anode 140 by being supplied to the vessel 128, sprayed from the sprinkler 128, and in contact with the anode 140.

[Second Embodiment]
FIG. 2 is a schematic cross-sectional view showing the configuration of the microbial electrolytic cell 200 according to the embodiment of the present invention. The microbial electrolysis cell 200 includes a container 210, a sprinkler 220, a liquid 230, an anode (negative electrode, working electrode) 240, a cathode (positive electrode, counter electrode) 250, a reference electrode 280, a potentiostat 292, a hydrogen recovery unit 294, and a hydrogen storage unit 296. , Has a lead wire 270 and a current meter 275. Have. The anode 240, cathode 250 and reference electrode 280 are electrically connected to the potentiostat 292. Liquid 230 contains organic matter and electron donating microorganisms 242.

The container 210 constitutes the main body of the microbial electrolysis cell 200 and houses the liquid 230. The material, shape and size of the container 210 are not particularly limited and may be appropriately set according to the intended use.

Also in this embodiment, the container 210 has a stirrer 215 that promotes agitation of the liquid 230. When the liquid 230 is sufficiently agitated by watering, the stirrer 215 is unnecessary.

The watering device 220 sprays a liquid containing an organic substance into the container 210. The organic substance is an organic substance that serves as a fuel for the electron-donating microorganism 242 carried by the anode 240, and is not particularly limited as long as the electron-donating microorganism 242 can be metabolized. Organic matter used as fuel includes not only useful resources such as alcohol, monosaccharides, polysaccharides, and proteins, but also unused resources (organic waste) such as agricultural industrial waste, organic waste liquid, urine, sludge, and food residue. Can be used. As the liquid containing an organic substance, various wastewaters may be used as they are, or an organic substance as a fuel for maintaining and growing the electron-donating microorganism 242 and for continuously operating the microbial electrolysis cell 200, if necessary. May be added. The watering device 220 has the same structure as the watering device 220 of the microbial fuel cell 100 according to the first embodiment, and has a pumping pipe 222, a pump 224, a water pipe 226, a watering device 228, and a control unit 229. It is controlled in the same way.

The liquid 230 is contained in a container 210 and contains an organic substance as an energy source and an electron donating microorganism 242. The liquid 230 is the same as the liquid 130 of the microbial fuel cell 100 according to the first embodiment.

The anode 240 is arranged between the sprinkler 228 and the bottom surface of the container 210 so as to come into contact with the liquid 230 contained in the container 210. This allows the anode 240 to come into contact with the liquid 230 sprinkled from the sprinkler 228. In the present embodiment, the anode 240 is partially exposed to the outside of the liquid 230 contained in the container 210 and partially immersed in the liquid 230 contained in the container 210. Since the shape, arrangement position, and material of the anode 230 can be the same as those in the first embodiment, detailed description thereof will be omitted.

The cathode 250 is arranged so as to be in contact with the liquid 230. In this embodiment, the cathode 250 is immersed in the liquid 230. The material of the cathode 250 is not particularly limited as long as it has conductivity and is chemically stable. The shape of the cathode 250 is not particularly limited, and can be appropriately selected depending on the ease of recovery of hydrogen gas and the like. Examples of the material of the cathode 250 include carbon, metal, metal oxide and the like. Examples of the cathode 250 include carbon cloth, carbon felt, stainless steel mesh, platinum mesh and the like. These may be heat-treated. Further, an oxygen reduction catalyst such as platinum or activated carbon may be supported on these surfaces. Whether or not heat treatment was performed depends on the concentration of each element on the surface of the cathode 250 by energy dispersive X-ray spectroscopy (EDS / EDX) and 5 μm or more from the surface in the cross section exposed by cutting the cathode 250. It can be confirmed by comparing the concentration of each element in the distant part (inside).

The reference electrode 280 is arranged so as to be in contact with the liquid 230. In this embodiment, the reference electrode 280 is immersed in the liquid 230. The type of the reference electrode 280 is not particularly limited and may be appropriately selected. Examples of the reference electrode 280 include a silver-silver chloride electrode, a standard hydrogen electrode, a calomel electrode and the like.

The potentiostat 292 is electrically connected to the anode 240, the cathode 250 and the reference electrode 280, and has an electrode potential of the anode (working electrode) 230 of −0.4 V (vs. Ag / AgCl) (Ag / AgCl: silver). -Silver chloride electrode) The above, preferably -0.2 to 2.0 V (vs. Ag / AgCl) is controlled. A reference electrode 280 is used as a reference for controlling the electrode potential, and the electrode potential of the anode (working electrode) 230 is kept constant by passing electrons through the cathode (counter electrode) 250. As a result, the potentiostat 292 applies a voltage between the anode (working electrode) 230 and the cathode (counter electrode) 250, and the electrons generated by the decomposition of the organic substance transfer the potentiostat 292 from the anode (working electrode) 230. Finally, it flows to the cathode 250, and hydrogen gas is generated on the surface of the cathode 250. As described above, the electrode potential of the anode (working electrode) 240 is always lower than the electrode potential of the cathode 250 by a predetermined potential difference.

The hydrogen recovery unit 294 recovers the hydrogen gas generated on the surface of the cathode 250. The configuration of the hydrogen recovery unit 294 is not particularly limited as long as the above object can be achieved. In this embodiment, the hydrogen recovery unit 294 is a funnel-shaped member arranged above the cathode 250 in the liquid 230. The hydrogen recovery unit 294 sends the recovered hydrogen gas to the hydrogen storage unit 296. When the microbial electrolysis cell 200 is used for the purpose of removing organic substances and nitrogen in the water quality sensor and wastewater, but the main purpose is not to recover energy, the microbial electrolysis cell 200 is the hydrogen recovery unit 294. It is not necessary to have.

The hydrogen storage unit 296 stores the hydrogen gas recovered by the hydrogen recovery unit 294. The configuration of the hydrogen storage unit 296 is not particularly limited as long as the above object can be achieved. Examples of the hydrogen storage unit 296 include a gas holder and the like.

The ammeter 275 is installed on the conductor 270 and measures the current flowing between the anode 240 and the cathode 250.

(Operation of microbial electrolysis cell)
Next, the operation of the microbial electrolysis cell 200 according to the present embodiment will be described.

The pump 224 pumps the liquid 230 contained in the container 210 and supplies it to the sprinkler 228, and the potentiostat 292 keeps the electrode potential of the anode (working electrode) 240 at a predetermined value (for example, −0. When a voltage is applied between the anode 240 and the cathode 250 using the reference electrode 280 as a reference so as to be 2V (vs. Ag / AgCl)) and the microbial electrolysis cell 200 is operated, it is carried on the anode 240. When an organic substance (for example, acetic acid) is decomposed into carbon dioxide by the electron donating microorganism 242, hydrogen ions and electrons are generated. The hydrogen ions generated by the decomposition of the organic matter move to the inside of the liquid 230 contained in the container 210 by the flow of the sprayed liquid 230, and move to the surface of the cathode 250. On the other hand, the electrons generated by the decomposition of the organic substance are collected at the anode 240 and move to the cathode 250 via an external circuit. In such a situation, hydrogen gas is generated by the reaction of hydrogen ions and electrons on the surface of the cathode 250. Therefore, by supplying the organic substance into the container 210, the above cycle can be maintained and hydrogen gas can be continuously generated.

(effect)
As described above, in the microbial electrolytic cell 200 according to the present embodiment, by watering the liquid with the watering apparatus 220, the portion of the anode 240 exposed from the liquid 230 becomes an aerobic state, and the decomposition and removal of organic substances and ammonia are achieved. Can proceed with the reaction to nitric acid or nitrite. On the other hand, in the portion of the anode 240 that comes into contact with the liquid 230, the inside of the biofilm formed by the electron donating microorganism 222 adhering to the anode 240, and the inside of the liquid 230 contained in the container 210, microorganisms due to an anaerobic state are introduced. The reaction on the electrode as a catalyst and the reaction of nitric acid or nitrite to nitrogen of the gas body can also proceed. In this way, the microbial electrolytic cell 200 according to the present embodiment can simultaneously and continuously produce electric current, remove organic substances, and remove nitrogen without performing intermittent aeration. Therefore, the microbial electrolytic cell 200 according to the present embodiment can continuously produce electric current, remove organic substances, and remove nitrogen, and it is easy to increase the processing speed of these.

Further, in the microbial electrolysis cell 200 according to the present embodiment, similarly to the microbial fuel cell 100 according to the first embodiment, the liquid 230 is appropriately agitated to appropriately equalize the concentrations of organic substances and nitrogen. Increases the efficiency of electric current production, organic matter removal, and nitrogen removal, suppresses the increase in power consumption due to the ability to form an aerobic state with low power by watering, and the amount of excess sludge generated by using anaerobic treatment. It has characteristics such as reduction of the electric power, use as a water quality sensor for estimating the amount of organic substances in the liquid 230 by measuring the current flowing through the lead wire 270 with a current meter 275, and the like.

Further, in the microbial electrolysis cell 200 according to the present embodiment, the anode 240, the cathode 250, the reference electrode 280, the potentiostat 292, the hydrogen recovery unit 294 and the hydrogen storage unit 296 are installed in the apparatus used in the conventional watering filter method. Just need it. Therefore, it is easy to introduce the microbial electrolysis cell 200 according to the present embodiment into an existing facility.

In the present embodiment, the microbial electrolysis cell 200 having the potentiometer 292 as the voltage applying portion for applying the voltage between the anode 240 and the cathode 250 has been described, but the power supply is used instead of the potentiometer 292 as the voltage applying portion. 298 may be arranged (see FIG. 3). In this case, the power supply 298 is electrically connected to the anode 240 and the cathode 250, and applies a voltage between the anode 240 and the cathode 250 so that electrons flow from the anode 240 to the cathode 250. The reference electrode 280 is unnecessary.

The power supply 298 is electrically connected to the anode 240 and the cathode 250, and a voltage is applied between the anode 240 and the cathode 250 so that the potential of the anode 240 is lower than the potential of the cathode 250. When a liquid 230 having a pH of 7 and 25 ° C. containing acetic acid is used as an organic substance, the electrode potential of the anode 240 is -0.3300 V (vs. NHE) (NHE: normal hydrogen electrode, standard hydrogen electrode), and it becomes a hydrogen ion. The electrode potential of the cathode 250 that passes electrons is -0.414V (vs. NHE). Therefore, theoretically, by applying a voltage of 0.114 V or more between the anode 240 and the cathode 250, electrons are finally transmitted from the anode 240 to the cathode 250 via an external circuit, and the surface of the cathode 250 is Will generate hydrogen. Actually, in consideration of overvoltage and reaction speed, it is preferable to apply a voltage of 0.13 V or more between the anode 240 and the cathode 250, and a voltage of 0.4 to 5.0 V is applied between the anode 240 and the cathode. It is more preferable to apply it between 250 and 250. When operating with an emphasis on hydrogen production, it is preferable to apply a small voltage of about 0.4 to 0.8 V, which has a small input energy. When operating with an emphasis on the decomposition of organic matter and the detection of the concentration of organic matter rather than the production of hydrogen, it is preferable to apply a voltage of 1.0 V or more.

Other configurations in the microbial electric field cell having the power supply 298 as the voltage applying portion may be similar to the microbial electric field cell having the potentiostat 292 as the voltage applying portion.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

1. 1. Preparation of Microbial Electrolyzed Cell Artificial wastewater was prepared by mixing a medium having the composition shown in the table below and activated sludge as a source of electron-donating microorganisms at a ratio of 5: 1. This artificial wastewater was inoculated as an inoculum by mixing a biofilm cultured on the negative electrode of another microbial fuel cell. 2.0 L of the obtained artificial wastewater was introduced into a container having a capacity of 3.0 L.

In the artificial waste water in the container, an electrode made by bundling carbon fibers with a length of 40 cm as an anode (working electrode, negative electrode), a platinum electrode as a cathode (counting electrode, positive electrode), and a silver-silver chloride electrode as a reference electrode are placed. Soaked. These electrodes are connected to the potentiostat. The anode was arranged so that 20 cm was lifted from the liquid surface, and the remaining 20 cm was suspended on the surface of artificial wastewater. A watering nozzle was installed directly above the anode. The artificial wastewater in the container was pumped up and supplied to the sprinkler, and sprayed toward the bottom of the container so that the sprayed artificial wastewater was brought into contact with the anode. Immediately above the cathode, a gas holder was installed to collect and store the hydrogen generated at the cathode.

2. Evaluation of microbial electrolysis cell At room temperature, while operating a pump to spray 130 mL / min of artificial wastewater from a sprinkler, the electrode potential of the anode is -0.2 V with respect to the potential of the silver-silver chloride electrode (reference electrode). A voltage was applied to the anode and the cathode so as to operate the prepared microbial electrolytic cell. Power was measured every 15 minutes. In addition, the concentration of total nitrogen (TN) in the artificial wastewater was measured immediately after the start of operation and 38 hours and 164 hours after the start of operation. In addition, the chemical oxygen demand (COD) of artificial wastewater was measured immediately after the start of operation, and 12 hours, 24 hours, 38 hours, 70 hours, and 158 hours after the start of operation. The COD was measured 3 times for each time, and the average value was used as the COD at each time. In addition, the total amount of current flowing through the lead wire (coulomb amount) within 24 hours after the start of operation with respect to the amount of coulomb required to consume the difference between the COD at the start of operation and the COD after 24 hours (COD consumption). ) Was calculated, and the ratio of the organic matter removed by the activity of the electron donating microorganism to the organic matter removed from the artificial wastewater within 24 hours from the start of operation (Coulomb efficiency) was calculated.

FIG. 4 is a graph showing changes over time in the current in the microbial electrolysis cell used in this experiment. From this graph, in the microbial electrolysis cell used in this experiment, a current was produced immediately after the start of the test, and the maximum current of 45 mA was obtained 19 hours later, and then decreased to about 0 mA 30 hours later. I understand.

FIG. 5 is a graph showing changes over time in COD in the microbial electrolysis cell used in this experiment. From this graph, it was found that in the microbial electrolysis cell used in this experiment, the COD decreased from about 740 mg / L immediately after the start of the test to about 150 mg / L 24 hours later, and the COD decreased by the operation of the microbial electrolysis cell for one day. It can be seen that the amount decreased by about 620 mg / L. Generally, wastewater treatment is required to reduce COD by 500 mg / L or more per day. Therefore, from this graph, it can be seen that the microbial electrolytic cell used in this experiment can be suitably used for wastewater treatment.

Further, from the comparison between FIGS. 4 and 5, it was found that when the COD decreased to about 200 mg / L or less, the current also decreased, and this microbial electric field cell functions as a real-time sensor of COD by measuring the current. You can also see what you can do.

FIG. 6 is a graph showing the time course of the TN concentration in the microbial electrolysis cell used in this experiment. From this graph, in the microbial electrolysis cell used in this experiment, the TN concentration decreased from 101 mg / L immediately after the start of the test to 53 mg / L 38 hours later, and to 30 mg / L after 164 hours. It can be seen that the operation of the microbial electrolysis cell was able to remove nitrogen in the artificial wastewater.

The Coulomb efficiency during 24-hour operation, calculated from the data used to create the graph shown in FIG. 4 and the graph shown in FIG. 5, was about 12.0%. The normal watering filter method without the action of electron-donating microorganisms does not remove about 13.9% of the organic matter, and 88.0% (100% -12.0%) of the removal of organic matter in this experiment. ), It is considered that organic matter is removed only at the rate of). Therefore, it is considered that the efficiency of removing organic matter in the microbial electrolytic cell used in this experiment is improved by about 14% (100 / 88.0) as compared with the usual sprinkling filter method. Since the Coulomb efficiency in the microbial electrolytic cell described in Patent Document 1 is about 0.1%, it can be seen that the Coulomb efficiency in the microbial electrolytic cell used in this experiment is remarkably high.

In addition, about 2.7 L of hydrogen gas was recovered by operating for 24 hours. From this, it can be seen that the microbial electrolysis cell used in this experiment can recover the generated energy as hydrogen.

The microbial fuel cell according to the present invention has a high ability to decompose organic substances while maintaining a power generation capacity, and is therefore useful in, for example, wastewater treatment in livestock barns and sewage purification treatment in urban areas.

100 Microbial fuel cell 110, 210 Container 115, 215 Stirrer 120, 220 Watering device 122, 222 Pumping pipe 124, 224 Pump 126, 226 Watering pipe 128, 228 Watering nozzle 129, 229 Control unit 130, 230 Liquid 140, 240 Anode 142, 242 Electron donating microorganisms 150 Membrane electrode assembly (MEA)
152 Diaphragm 154, 250 Cathode 156 Floating 170, 270 Conductor 175, 275 Ammeter 200 Microelectrolytic cell 280 Reference electrode 292 Potential stat 294 Hydrogen recovery 296 Hydrogen storage 298 Power supply

Claims (8)

With the container
A watering device that sprays a liquid containing organic matter into the container,
The electrolyte-containing liquid contained in the container and
An anode carrying an electron-donating microorganism on the surface, which is arranged in contact with the liquid contained in the container at a position in contact with the liquid sprayed from the watering apparatus.
A cathode placed in contact with the liquid contained in the container or adjacent to the liquid contained in the container with a cation-permeable diaphragm in between.
Have a,
The part of the anode exposed to the outside air is in an aerobic state, the part of the anode in contact with the liquid sprayed from the watering device, and the biofilm formed by the electron-donating microorganisms carried on the anode. The part covered with the water and the part in contact with the liquid contained in the container are anaerobic.
Bioelectrochemical system. The bioelectrochemical system according to claim 1, wherein the watering apparatus adjusts watering and stopping, or the amount of watering according to an electric current flowing between the anode and the cathode. The liquid contained in the container further contains an organic substance and contains an organic substance.
The bioelectrochemical system according to claim 1 or 2, wherein the watering device sprays a liquid contained in the container. The bioelectrochemical system according to any one of claims 1 to 3, wherein the shape of the anode is a brush shape, a fibrous shape, a mesh shape or a folded mesh shape, or a combination of these shapes. The bioelectrochemical system according to any one of claims 1 to 4, wherein the bioelectrochemical system is a microbial fuel cell. The bioelectrochemical system according to claim 5, wherein the watering apparatus is driven by an electric current flowing between the anode and the cathode. Further, a voltage application unit for applying a voltage between the anode and the cathode is provided so that electrons flow from the anode to the cathode.
The bioelectrochemical system is a microbial electrolytic cell,
The bioelectrochemical system according to any one of claims 1 to 4. It further comprises an ammeter that measures the current flowing between the anode and the cathode.
The bioelectrochemical system is a water quality sensor.
The bioelectrochemical system according to any one of claims 1 to 7.

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