WO2012039464A1

WO2012039464A1 - Microorganism fuel cell system, method for generating electricity, and method for processing organic substances

Info

Publication number: WO2012039464A1
Application number: PCT/JP2011/071660
Authority: WO
Inventors: 慶久日比; 太田　祐介
Original assignee: イビデン株式会社
Priority date: 2010-09-24
Filing date: 2011-09-22
Publication date: 2012-03-29

Abstract

Provided is a microorganism fuel cell system comprising: an anaerobic tank which has anaerobic microorganisms accommodated and an electrode provided therein; an aerobic tank which has aerobic microorganisms accommodated and an electrode provided therein; a separator which separates the anaerobic tank and the aerobic tank; and an external circuit which electrically connects the electrodes, the electrode provided in the anaerobic tank constituting a negative electrode and the electrode provided in the aerobic tank constituting a positive electrode. This microorganism fuel cell system does not require the addition of a mediator, and is capable of operating, without generating bad odours, whether low concentration organic substances are supplied or high concentration organic substances are supplied.

Description

Microbial fuel cell system, power generation method, and organic matter treatment method

The present invention relates to a microbial fuel cell system capable of purifying wastewater simultaneously with power generation, a power generation method, and a method for treating organic matter, and particularly relates to a microbial fuel cell system using anaerobic / aerobic microorganisms, a power generation method, and a method for treating organic matter. .

2. Description of the Related Art In recent years, in a method for treating sewage in which organic matter in sewage is decomposed by microorganisms, the sewage is characterized by taking out electrons from microorganisms that metabolize organic matter with an electron transfer agent, inhibiting cell synthesis and inhibiting microbial growth. A processing method has been reported (Patent Document 1).

Furthermore, there is a report relating to a microbial battery using a microbial carrier suitable for purification of domestic wastewater and / or river sludge as an electrode, and a sludge purification device that efficiently purifies sludge using the battery (Patent Document 2). .

Conventional microbial fuel cells use MB (methylene blue) or NR (neutral red), which are not electron transfer materials biosynthesized by microorganisms, as mediators to extract electrons from the microorganisms and generate electricity. As a result, cell division of the microorganism is also suppressed, and an increase in sludge can be prevented. As a result, sludge reduction is also achieved by suppressing the growth of microorganisms.

JP 2006-75791 A JP 2006-114375 A

However, the above-described conventional technology has the following problems. In the sewage treatment method of Patent Document 1, by adding an electron transfer substance (MB, NR, etc.) as a mediator from the outside, electrons generated when microorganisms take in organic substances into the body and decompose organic substances to convert energy. The mediator takes it and generates electricity by taking the electrons out of the body of the microorganism. As a result, cell division of microorganisms can be suppressed and sludge can be reduced. However, since the added electron transfer substance is not decomposed in the wastewater treatment, the added electron transfer substance becomes a surplus substance, and thus an apparatus or a processing method for excluding the electron transfer substance is separately required.

Moreover, in the sludge purification apparatus of patent document 2, using the electrode which used charcoal and bamboo charcoal to an anaerobic tank and an aerobic tank, respectively, while attaching microorganisms and taking out electricity simultaneously, sludge (sludge) Purification is the main. Therefore, the batch type sedimentation separation method is adopted, continuous operation is impossible, and waste water cannot be purified. Furthermore, since organic substances are not decomposed by both anaerobic treatment and aerobic treatment, electrons and protons cannot be obtained efficiently. Furthermore, when the organic matter-containing wastewater continuously flows in or when the organic matter-containing wastewater flows in a large amount, the anaerobic tank and the aerobic tank are mixed, and the organic matter-containing wastewater cannot be purified. In addition, the electromotive force is reduced and no power can be obtained.

Also, since only carbonized wood or bamboo is used as the electrode, the specific surface area is small, so the adhesion (accumulation) of microorganisms is poor, and the number of microorganisms present on the electrode surface is small. As a result, the number of electrons generated in the process of microorganisms decomposing and absorbing organic matter is reduced, and therefore cannot be used for power generation. Furthermore, since microorganisms decompose organic substances other than on the electrode surface, electrons are not delivered to the electrode, resulting in an electron loss. Gases (such as methane and hydrogen sulfide) that are ultimately produced by anaerobic microorganisms, including obligate anaerobic bacteria, are not treated (utilized), and at the same time, electrons are generated from the decomposition of organic matter. In other words, there is a problem of odor as well as high efficiency in which electricity cannot be obtained.

An object of the present invention is to provide a microbial fuel cell system that does not require the addition of a mediator, is not accompanied by generation of odor, and can cope with supply of low concentration or high concentration organic matter. Furthermore, an object of the present invention is to provide a power generation method and an organic matter treatment method (a method for purifying water and treating sludge generation by wastewater treatment) using such a microbial fuel cell system.

That is, the gist of the present invention is as follows.
[1] An anaerobic tank containing an anaerobic microorganism group and provided with an electrode, an aerobic tank containing an aerobic microorganism group and provided with an electrode, the anaerobic tank and the aerobic tank A separator to be separated, and an external circuit for electrically connecting the electrodes,
A microbial fuel cell system in which the electrode provided in the anaerobic tank is a negative electrode and the electrode provided in the aerobic tank is a positive electrode;
[2] A power generation method for taking out electricity via the external circuit using the microbial fuel cell system according to [1];
[3] An anaerobic tank containing an anaerobic microorganism group and provided with a negative electrode, an aerobic tank containing an aerobic microorganism group and provided with a positive electrode, the anaerobic tank and the aerobic tank And an external circuit that electrically connects between the negative electrode and the positive electrode,
A method for treating organic matter, comprising: supplying a liquid containing organic matter to the anaerobic tank; and discharging the treated liquid from the aerobic tank;

[4] Supplying a liquid containing an organic substance and an inorganic flocculant into a tank containing a liquid containing an anaerobic microorganism group, separating the tank into an anaerobic layer and an aerobic layer, and existing in the anaerobic layer A method of generating electricity through an external circuit that electrically connects the negative electrode provided in the tank and the positive electrode provided in the tank so as to exist in the aerobic layer; and [5] Liquid containing organic matter in a tank of a tank in which a positive electrode and a negative electrode are provided in a tank containing a liquid containing anaerobic microorganisms, and an external circuit for electrically connecting the electrodes. And supplying the inorganic flocculant,
Next, a method for treating an organic substance having a step of separating the inside of the tank into an anaerobic layer and an aerobic layer, wherein a negative electrode is provided in the tank so that the negative electrode exists in the anaerobic layer, and a positive electrode is provided It is related with the processing method of the organic substance which is provided in this tank so that it may exist in this aerobic layer.

It is a figure which shows schematic structure of an example of the microbial fuel cell system which concerns on embodiment of this invention. It is an electron micrograph of the surface structure of the negative electrode used in Example 1 before system operation. It is an electron micrograph of the surface structure of the negative electrode used in Example 1 after system operation for 2 days. It is a figure which shows schematic structure of another example of the microbial fuel cell system which concerns on embodiment of this invention.

In the present invention, the disadvantages of each other are compensated by using anaerobic microorganism group and aerobic microorganism group in combination. That is, even when wastewater containing high-concentration organic matter is supplied, the anaerobic microorganism group can decompose the organic matter and reduce the molecular weight. When the wastewater containing such high-concentration organic substances is decomposed only in the anaerobic tank, ammonia and sulfur compounds are accumulated in the anaerobic tank, and the growth environment is deteriorated by such self-generated organisms. The decomposition process of the organic matter in the tank is suppressed.

However, by using the microbial fuel cell electrode with the anaerobic tank side as the negative electrode (anode side), bacteria accumulate on the electrode surface and at the same time the anaerobic tank is in a turbulent state, facilitating the contact between the bacteria-accumulated electrode and organic matter Is done. As a result, the relationship “decomposition of organic matter = emission of electrons” is established. In the present invention, microorganisms using sulfur compounds as energy sources and microorganisms utilizing ammonia nitrogen are preferably present in the anaerobic tank. In such a case, the electrode and the waste liquid are efficiently in contact with each other. In addition to the decomposition and removal of substances that have been disposed of with ancillary equipment in anaerobic treatment, the amount of sludge due to sedimentation of residual organic matter can be reduced.

Furthermore, by providing an aerobic tank by using a separator or by making two treatment tanks, the organic matter is decomposed on the anaerobic tank side, and a low molecular weight organic acid is separated from the separator or measuring tank. It passes through and moves to the aerobic tank side and is decomposed on the aerobic tank side. As a result, substances that could not react on the surface of the negative electrode side are treated on the aerobic tank side, and at the same time, high-concentration organic substances that were impossible with conventional aerobic treatment on the aerobic tank side are disposed of. At the same time, the generation of electricity reduces the amount of excess sludge generated so far by 40-50%. In addition, in the already installed organic matter processing equipment, if the equipment is provided with an anaerobic tank and an aerobic tank, or if the equipment is divided into two tanks in the upper and lower layers, a large-scale modification of the equipment is involved. In addition, separators, electrodes, external circuits, and if necessary, aeration means and devices that generate turbulent flow in the tank can be retrofitted, so that it is possible not only to improve the efficiency of wastewater organic matter treatment but also to generate power It is.

In the present invention, the high-concentration organic substance means BOD (biochemical oxygen demand rate: unit: ppm) of 2000 ppm or more.

Furthermore, a power generation method that does not use a separator is also proposed.

Hereinafter, the microbial fuel cell system according to the first aspect of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of an example of a microbial fuel cell system according to an embodiment of the present invention.

The microbial fuel cell system 11 of the first aspect of the present invention includes an anaerobic tank 1 in which anaerobic microorganisms are accommodated and provided with an electrode, and an aerobic effect in which an aerobic microorganisms are accommodated and provided with an electrode. It is composed of a tank 2, a separator 3 for separating the anaerobic tank 1 and the aerobic tank 2, and an external circuit 4 for electrically connecting the electrodes, and the electrode provided in the anaerobic tank 1 is negative. The electrode 5 and the electrode provided in the aerobic tank 2 are the positive electrodes 6.

Also, the dissolved oxygen concentration in the aerobic tank is preferably higher.

In the microbial fuel cell system of the first aspect of the present invention, it is preferable to supply a liquid containing organic matter to the anaerobic tank. When organic wastewater is supplied to the anaerobic tank 1 containing anaerobic microorganisms, organic substances (proteins, lipids, carbohydrates, etc.) are present due to the presence of anaerobic bacteria (facultative anaerobic bacteria and obligate anaerobic bacteria). Can be reduced in molecular weight (change to organic acid, monosaccharide, etc.). Furthermore, the reaction proceeds due to the presence of obligate anaerobic bacteria, and some of them are decomposed to methane. As anaerobic bacteria, halophilic facultative anaerobic bacteria are preferable, and acid- and alkali-resistant halophilic facultative anaerobic bacteria are more preferable.

In such a two-step reaction process, that is, a process in which organic substances in wastewater are reduced to low molecular organic acids and the like, and further decomposed to methane and the like, hydrogen and electrons are generated. Since this reaction occurs on the anaerobic tank side, the anaerobic tank side is the negative electrode and the aerobic tank side is the positive electrode. The electrode used in this case is preferably porous carbon carrying a metal or metal compound such as Pt or Cu, porous carbon modified with carbon nanotubes (CNT), carbon felt, or the like. The positive electrode and the negative electrode may be the same or different. Preferably, the electrode used for the positive electrode is an electrode provided with a catalyst for reducing oxygen. A metal that reacts with fermented methane may also be provided on the negative electrode side.

When using a porous electrode, that is, a large specific surface area, many microorganisms adhere to the surface of the negative electrode. It is considered that when the attached microorganism group forms a network, the cytochrome C substance synthesized by the microorganism itself becomes a conductive nanowire, functions as an electron transfer substance, and passes electrons to the negative electrode. On the other hand, the protons generated at the same time move to the aerobic tank through a solution (waste liquid) containing a low molecular weight organic substance.

With this function, it is not necessary to add an electron mediator called a mediator from the outside, and at the same time, electrons are transmitted through the microorganism itself, so that wastewater treatment (water purification) is advanced (for example, mediator). Can be accompanied by a process of removing).

Furthermore, since methane, mercaptan, hydrogen sulfide, etc. produced by anaerobic bacteria are decomposed using a noble metal element (Pt, Rh, or Au) or a metal element (Cu) as a catalyst, generation of odor can be suppressed. In addition, when there are microorganisms that take in sulfur compounds as nutrients in anaerobic bacteria, the generation of odors can be more effectively suppressed, and at the same time, the electrons generated when decomposing organic substances are transferred to the electrodes with high efficiency. Is preferable. Methane is decomposed using Pt or the like supported on the negative electrode as a catalyst, and exhibits the same reaction as a normal fuel cell. Hydrogen sulfide, which is an odorous substance other than methane, reacts because Cu is carried by the negative electrode, releases hydrogen and electrons, and the electrons are transferred to the negative electrode in the same manner as described above. This reaction makes it possible to acquire electrons with high efficiency at the same time as the reduction of the mercaptan odor substance (odor suppression).

Since such an electrode has high conductivity, it is desirable that it is carbon, and it is desirable that the electrode be porous because microorganisms easily adhere to it. Specifically, the specific surface area is desirably 16,000cm ² / g or more electrodes, the specific surface area is more desirable 360,000cm ² / g or more electrodes. It is desirable that at least pores having a pore diameter of 100 nm or more, more preferably 1 μm or more are opened on the surface of the electrode. More preferably, it is desirable that pores are distributed throughout the interior. This is because, when these carbons carry microorganisms, the above-mentioned noble metal elements or metal elements of the catalyst as catalysts, they are difficult to peel off. In addition, the conductivity is improved because the network of cytochrome C is dense between the accumulated microorganisms. In addition, since the microorganisms can easily enter, the pore diameter is desirably 5 μm or less.

Separation between the anaerobic tank and the aerobic tank is, for example, from the side where the proton and organic acid can pass and the anaerobic microorganism group and the aerobic microorganism group cannot pass (separator), or from the anaerobic tank side It is performed by the overflow of Kaminagamizu. Examples of the separator include a water treatment MF (Microfiltlation Membrance) membrane, filter paper, porous unglazed plate, and the like. These separators preferably have pores of 1 μm or less. This is because the size of the microorganism group is 1 μm or more, so that the microorganism group does not pass and protons and organic acids can pass. The pore diameter of the separator is more preferably 0.1 to 0.5 μm. From the viewpoint of allowing the organic acid to pass through effectively, the pore diameter of the separator is preferably 0.1 μm or more, and since there are microorganisms exceeding 0.5 μm, the pore diameter is preferably 0.5 μm or less.

Furthermore, by using two tanks, an anaerobic tank and an aerobic tank, in the separator or enclosure tank, general wastewater and industrial wastewater containing high-concentration wastewater are first allowed to flow into the anaerobic tank side, and organic matter is reduced in the anaerobic tank. After decomposition to an organic acid or the like, a liquid containing protons or organic acids is leached from the anaerobic tank side to the aerobic tank side. In the aerobic tank, the protons are reduced to water by making the dissolved oxygen concentration high (2-5 mg / L) by air aeration, etc., and the organic acid is also decomposed and removed by aerobic bacteria to purify the wastewater. Is done. The treated liquid is preferably discharged from the aerobic tank. Thus, by making two tanks, an anaerobic tank and an aerobic tank, continuous inflow treatment of wastewater becomes possible, and even when a large amount of wastewater is supplied, the liquid in the anaerobic tank and the liquid in the aerobic tank There is no mixing.

The organic acid decomposed into low molecules in the wastewater flowing into the aerobic tank through this separator is purified by aerobic bacteria and decomposed into water and carbon dioxide. However, in the case of only an anaerobic tank, growth suppression is caused by the high concentration of ammonia components produced by the anaerobic bacteria themselves in the process of anaerobic bacteria decomposing organic matter. As a result, the anaerobic treatment (anaerobic bacteria decompose organic substances) itself deteriorates. Therefore, by providing an aerobic tank through the separator in the anaerobic layer, ammonia components, sulfide ions, and the like move from the anaerobic layer to the aerobic tank through the separator and are decomposed in the aerobic tank. When a bacterial group using sulfur compounds or ammonia nitrogen as a nutrient source exists, such a bacterial group accumulates on the electrode surface by placing the electrode in an anaerobic tank. As a result, the phenomenon that has been the rate-limiting factor in the anaerobic tank is improved. At the same time, by providing the anaerobic tank and the aerobic tank as described above, after the wastewater is treated in the anaerobic tank, the wastewater (residual ammonia component, sulfide ions, etc.) is further treated in the aerobic tank. The system eliminates the rate-limiting factor in anaerobic processing. Furthermore, since the aerobic tank side is the positive electrode side, the electrons passed to the negative electrode are supplied to the positive electrode through an external circuit that electrically connects these electrodes, and the electrons from the positive electrode to the aerobic tank Is released. By obtaining the released electrons by the aerobic bacteria, the activity of the aerobic bacteria is maintained and the wastewater treatment efficiency is improved by supplementing the electrons lost when the aerobic bacteria take in the organic acid and convert the energy.

In the aerobic tank 2, it is preferable that an aeration means 7 for increasing the dissolved oxygen concentration is further provided. By providing such aeration means, the dissolved oxygen concentration is preferably 2 to 5 mg / L, more preferably 3 to 5 mg / L, and the effect of further improving the ability to decompose and remove organic matter is exhibited. Wastewater can be purified with high efficiency. Specific examples of the aeration means are not particularly limited, and examples include aeration means known in the wastewater treatment field such as an aerator.

A stirring means 8 may be provided in at least one of the anaerobic tank 1 and the aerobic tank 2. By providing the stirring means 8, the power generation efficiency and the organic matter processing efficiency can be improved. Examples of such a stirrer include one that rotates a blade, an ejector, and an injector.

In the microbial fuel cell system according to the first aspect of the present invention, if necessary, another waste liquid treatment means is provided in the previous stage of the anaerobic tank, between the anaerobic tank and the aerobic tank, or in the subsequent stage of the aerobic tank. Also good.

In the first power generation method of the present invention, electricity can be taken out via an external circuit that electrically connects the negative electrode 5 and the positive electrode 6 using the microbial fuel cell system of the present invention. That is, the microbial fuel cell system of the present invention is driven as a microbial fuel cell.

When generating power using the microbial fuel cell system of the first invention, hydrogen ions and electrons are generated by the anaerobic microorganism group at the negative electrode 5 provided in the anaerobic tank 1. The generated hydrogen ions permeate the separator 3 and move from the anaerobic tank 1 side to the aerobic tank 2 side, the electrons move from the negative electrode 5 to the positive electrode 6 via the external circuit 4, and the hydrogen ions and electrons are The positive electrode 6 is combined with oxygen to form water. At that time, energy is recovered by taking out electricity flowing in the external circuit 4.

The organic matter treatment method of the first aspect of the present invention comprises an anaerobic microorganism group containing an anaerobic microorganism group and a negative electrode, and an aerobic tank containing an aerobic microorganism group and a positive electrode. A step of separating the anaerobic tank from the aerobic tank, and an external circuit for electrically connecting the negative electrode and the positive electrode, and supplying a liquid containing organic matter to the anaerobic tank; and It has the process of discharging | emitting the processed liquid from this aerobic tank. The organic matter treatment method can utilize the microbial fuel cell system of the present invention.

Examples of the step of supplying the liquid containing organic matter to the anaerobic tank include a step of supplying the liquid containing organic matter contained in the tank to the anaerobic tank by a pump or the like.

Also, the step of discharging the treated liquid from the aerobic tank includes a step of discharging the liquid from the aerobic tank. The aerobic tank is preferably further provided with aeration means. By providing such aeration means, the dissolved oxygen concentration can be increased.

It can be said that the decomposition of organic acids and the like is uptake of microbial nutrients. However, energy is consumed in order to advance the reaction at the same time as taking in energy. At that time, electrons emitted from the positive electrode side are supplemented as energy, so that the microorganisms are always activated and the number of microorganisms increases. As a result, the processing efficiency of organic matter is improved. Therefore, according to the microbial fuel cell system of the present invention, the treatment efficiency of organic matter is improved, so that undecomposed substances that have been excessive sludge until now are also decomposed and the generation of excessive sludge is reduced.

Furthermore, conventionally, reactions have progressed from organic acids to methane and carbon dioxide, and the activity of microorganisms has been suppressed by sulfides and ammonia generated in the reaction process, and incidental facilities for removing these substances have been required. However, the improvement of organic acid treatment efficiency not only suppresses the generation of sludge but also reduces the generation of sulfides and ammonia.

Next, the power generation method and the organic matter processing method of the second aspect of the present invention will be described. This is based on the microbial fuel cell system, the power generation method, and the organic matter treatment method of the first aspect of the present invention without using a separator. And it is an aspect which does not need to divide a tank into an anaerobic tank and an aerobic tank.

According to the second power generation method and organic matter treatment method of the present invention, it is possible to continuously purify 240 to 450 m ³ / day even if the liquid has a high BOD of 2000 ppm to 5000 ppm.

Generally, a liquid having a high BOD requires a large amount of oxygen by microorganisms for decomposing, so that the liquid in the entire tank tends to become anaerobic and the inside of the tank is difficult to become aerobic. When such a liquid flows in a large amount, the liquid in the tank tends to become anaerobic.

In order to make the liquid in the tank that tends to be anaerobic aerobic, for example, by adding an inorganic flocculant to the liquid in the tank containing an organic substance, flocks (flocculated precipitates: Flocks) are formed. Can be used. Examples of the inorganic flocculant used in such a method include oxides of calcium, magnesium, silicon, and the like that are conventionally used, such as diatomaceous earth, obsidian, and lime.

As a result, in one tank, there are many precipitates at the bottom of the tank, and no precipitate is formed at the top of the tank.

The sediment in the lower part of the tank is anaerobic and anaerobic because it has little contact with liquid and approaches anoxic conditions. On the contrary, since the upper part of the layer has less precipitate than the lower part, it comes into much contact with the liquid, oxygen is easily supplied, becomes aerobic, and becomes an aerobic layer.

The bacteria contained in the activated sludge are facultative anaerobic bacteria. When oxygen is present, it acts as an aerobic bacterium and becomes anaerobic when it becomes anoxic.

In the power generation method of the second aspect of the present invention, even if the BOD is 2000 ppm or more, as in the power generation method of the first aspect of the present invention, a positive electrode is provided on the upper and aerobic tank (layer) side, and the lower and anaerobic tank By providing a negative electrode on the (layer) side, electricity can be taken out via an external circuit that electrically connects the electrodes.

In the microbial fuel cell system (power generation method) of the first invention, a separator is necessary, but in the power generation method of the second invention, a separator is not necessary.

This is because the inorganic flocculant separates the aerobic layer side and the anaerobic layer side in one tank, and hydrogen ions and low molecular weight organic acids float in the solution. This is because it becomes possible to move from the anaerobic tank (layer) side to the aerobic tank (tank) side.

In the power generation method of the second aspect of the present invention, it is preferable that the tank is aerated. When the tank is aerated, formation of an anaerobic layer is expected to be inhibited. However, an aerobic layer and an anaerobic layer could be formed unexpectedly regardless of the implementation of aeration.

As biological treatment in wastewater treatment, MLSS (active sludge suspended solids: Mixed liquor Suspended Solid) is preferably used as a bottom surface when it is controlled at a concentration of 15000 to 20000 mg / L, more preferably 20000 to 35000 mg / L. This is because a large amount of sludge accumulates in the lower part even when aeration is performed using an air diffuser. Therefore, the lower part becomes an anaerobic layer. And in the upper part of the tank, on the contrary, the floating floc is suspended, but the dissolved oxygen concentration is higher than the lower part (anaerobic layer), and it becomes a relatively aerobic tank. Because.

Next, a microbial fuel cell system used in the power generation method and organic matter processing method of the second aspect of the present invention will be described with reference to FIG.

The microbial fuel cell system 11 is a position where the anaerobic microorganism group is accommodated in the tank 9 and the anaerobic layer 13 is formed, for example, the position where the electrode 5 provided in the lower part of the tank and the aerobic layer 14 are formed. For example, an electrode 6 provided in the upper part of the tank and an external circuit 4 that electrically connects the electrodes, and the electrode provided in the anaerobic layer 13 is a negative electrode 5, and the aerobic layer 14 is the positive electrode 6.

Also, as the treatment time elapses, the aerobic layer has a higher dissolved oxygen concentration than the anaerobic layer. Therefore, an aerobic microorganism group exists in the aerobic layer.

In the microbial fuel cell system used in the second aspect of the present invention, it is preferable to supply a liquid containing an organic substance to the anaerobic tank (layer) 13. That is, since the anaerobic layer is formed below the tank, it is preferable to supply the liquid containing organic matter from the lower part of the tank. When organic wastewater is supplied to an anaerobic tank (layer) 13 containing anaerobic microorganisms, organic substances (proteins, lipids, sugars) are present due to the presence of anaerobic bacteria (facultative anaerobic bacteria / obligate anaerobic bacteria). Quality etc.) can be reduced in molecular weight (changed to organic acids, monosaccharides, etc.). Furthermore, the reaction proceeds due to the presence of obligate anaerobic bacteria, and some of them are decomposed to methane. As anaerobic bacteria, halophilic facultative anaerobic bacteria are preferable, and acid- and alkali-resistant halophilic facultative anaerobic bacteria are more preferable.

The waste liquid containing organic matter forms flocs by the addition of an inorganic flocculant, and as a result, a part of it is subjected to normal aerobic treatment, but most of it settles. Thereby, since the reaction mentioned above arises, it is also possible to supply waste liquid from the upper part.

In such a two-step reaction process, that is, a process in which organic substances in wastewater are reduced to low molecular organic acids and the like, and further decomposed to methane and the like, hydrogen and electrons are generated. However, when fermentation (decomposition) proceeds to methane, electrons are used for this reaction, and thus it is preferable to suppress the reaction of methane fermentation. Since this reaction occurs on the anaerobic tank (layer) 13 side, the anaerobic tank (layer) 13 side is used as the negative electrode, and the aerobic tank (layer) 14 is used as the positive electrode. As an electrode used at this time, porous carbon carrying a metal or a metal compound such as Pt or Cu, more preferably porous carbon modified with CNT, and the like are preferable. The positive electrode and the negative electrode may be the same or different. Preferably, a carbon electrode modified with CNT is used for the negative electrode, and porous carbon or the like carrying a metal catalyst (Pt, Ni, etc.) is preferable for the positive electrode.

When a porous electrode is used, many microorganisms adhere to the surface of the negative electrode. It is considered that the cytochrome C substance synthesized by the microorganism itself works as an electron transfer substance (conductive nanowire) and passes electrons to the negative electrode when the attached microorganism group forms a network. On the other hand, protons generated simultaneously float in the tank and move to the aerobic tank (layer) 14.

Furthermore, since methane, mercaptan, hydrogen sulfide, etc. produced by anaerobic bacteria are decomposed using a noble metal element (Pt, Rh, or Au) or a metal element (Cu) as a catalyst, generation of odor can be suppressed. In the anaerobic bacterium, when a bacterium using a sulfur compound as a nutrient source is present, the generation of odor is more effectively suppressed. Methane is decomposed using Pt or the like supported on the negative electrode as a catalyst, and exhibits the same reaction as a normal fuel cell. Hydrogen sulfide, which is an odorous substance other than methane, reacts because Cu is carried by the negative electrode, releases hydrogen and electrons, and the electrons are transferred to the negative electrode in the same manner as described above. This reaction makes it possible to acquire electrons with high efficiency at the same time as the reduction of the mercaptan odor substance (odor suppression). Furthermore, when bacteria using a sulfur compound as a nutrient source exist, electrons generated in a reaction process that takes in and decomposes a sulfur compound that is a source of an odorous substance can be further used, which is more preferable.

Since such an electrode has high conductivity, it is desirable to be carbon, and it is desirable to be porous because microorganisms are likely to adhere to it. It is desirable that at least pores having a pore diameter of 1 μm or more are open on the surface of the electrode. More preferably, it is desirable that pores are distributed throughout the interior. This is because these carbons do not easily peel off when the above-mentioned noble metal element or metal element of the catalyst is supported as a catalyst. Moreover, since a microorganism tends to enter inside, the pore diameter is desirably 5 μm or less.

The separation between the anaerobic tank (layer) 13 side and the aerobic tank (layer) 14 is performed by an inorganic flocculant as described above.

By separating the tank into two parts, the anaerobic tank (layer) 13 side and the aerobic tank (layer) 14, when general and industrial wastewater containing high-concentration wastewater is flowed into the tank, it is separated and anaerobic at the bottom After the organic matter is decomposed to low molecular organic acid or the like on the tank (layer) 13 side, a liquid containing protons or organic acids moves from the anaerobic tank (layer) 13 side to the aerobic tank (layer) 14. In the aerobic tank (layer) 14, protons are reduced to water by making the dissolved oxygen concentration high (2-5 mg / L) by air aeration, etc., and organic acids are decomposed and removed by aerobic bacteria. Waste water is purified. And it is preferable to discharge | emit the processed liquid from this aerobic tank (layer). Thus, by dividing the tank into two parts, an anaerobic tank and an aerobic tank, continuous inflow treatment of wastewater becomes possible, and even when a large amount of wastewater is supplied, the liquid in the anaerobic tank and the aerobic tank The liquid is separated.

Organic acids and the like decomposed into low molecules flowing into the aerobic tank (layer) 14 are purified by aerobic bacteria and decomposed into water and carbon dioxide. If only the anaerobic tank (layer) 13 is present, in the process of anaerobic bacteria decomposing organic matter, the ammonia component produced by the anaerobic bacteria itself is accumulated at a high concentration, thereby suppressing growth. As a result, the anaerobic treatment (anaerobic bacteria decompose organic substances) itself deteriorates.

Therefore, by separating the anaerobic tank (layer) 13 with an inorganic flocculant and providing the aerobic tank (layer) 14, ammonia components and sulfide ions do not accumulate in the anaerobic tank (layer) 13. It moves from the (layer) 13 to the aerobic tank (layer) 14 and is decomposed in the aerobic tank. As described above, after the anaerobic tank (layer) 13 and the aerobic tank (layer) 14 are provided and the waste water is treated in the anaerobic tank (layer) 13, ammonia components and sulfide ions are further added to the aerobic tank. By the system processed in (layer) 14, the rate-determining factor in the anaerobic process is eliminated. Further, since the aerobic tank (layer) 14 side is the positive electrode side, the electrons transferred to the negative electrode are supplied to the positive electrode through an external circuit that electrically connects these electrodes, and the positive electrode is positively supplied. Electrons are emitted to the air tank (layer) 14. By obtaining the released electrons by the aerobic bacteria, the activity of the aerobic bacteria is maintained and the wastewater treatment efficiency is improved by supplementing the electrons lost when the aerobic bacteria take in the organic acid and convert the energy.

The tank is preferably further provided with aeration means 7 for increasing the dissolved oxygen concentration. By providing such aeration means, the dissolved oxygen concentration is preferably 2 to 5 mg / L, more preferably 3 to 5 mg / L, and the effect of further improving the ability to decompose and remove organic matter is exhibited. Wastewater can be purified with high efficiency. Specific examples of the aeration means are not particularly limited, and examples include aeration means known in the wastewater treatment field such as an aerator. Such aeration means may be provided in the upper part of the tank, in the central part, or in the lower part.

Although not shown, at least one of the anaerobic tank (layer) 13 and the aerobic tank (layer) 14 may be provided with stirring means. By providing such a stirring means, it is possible to improve power generation efficiency and organic matter processing efficiency. As such a stirrer, a rotating blade, an ejector or an injector is a preferred example.

In the microbial fuel cell system used in the second aspect of the present invention, another waste liquid treatment means may be provided in the front stage of the anaerobic tank or the rear stage of the aerobic tank as necessary.

In the power generation method of the second aspect of the present invention, electricity can be taken out via an external circuit that electrically connects the negative electrode 5 and the positive electrode 6 using the microbial fuel cell system described above. That is, the microbial fuel cell system of the present invention is driven as a microbial fuel cell.

When generating electricity using the microbial fuel cell system according to the second aspect of the present invention, hydrogen ions and electrons are generated by the anaerobic microorganism group at the negative electrode 5 provided in the anaerobic tank (layer) 13. The generated hydrogen ions float in the tank and move from the anaerobic tank (layer) 13 side to the aerobic tank (layer) 14 side, and the electrons move from the negative electrode 5 to the positive electrode 6 via the external circuit 4, Hydrogen ions and electrons combine with oxygen at the positive electrode 6 to become water. At that time, energy is recovered by taking out electricity flowing in the external circuit 4. The aerobic tank is preferably further provided with aeration means. By providing such aeration means, the dissolved oxygen concentration can be increased.

The organic material treatment method of the second aspect of the present invention is a tank in which a positive electrode and a negative electrode are provided in a tank containing a liquid containing anaerobic microorganisms, and an external circuit that electrically connects the electrodes. A process for supplying an organic substance-containing liquid and an inorganic flocculant, and then a process for separating the tank into an anaerobic layer and an aerobic layer, wherein the negative electrode has a negative electrode It is provided in the tank so as to exist in the anaerobic layer, and a positive electrode is provided in the tank so as to exist in the aerobic layer. The organic matter treatment system can utilize the microbial fuel cell system of the present invention.

Examples of the step of supplying the liquid containing organic matter to the tank include a step of supplying the liquid containing organic matter in the tank to the tank by a pump or the like.

Also, the step of discharging the treated liquid from the tank includes a step of discharging the liquid from the aerobic tank. The aerobic tank is preferably further provided with aeration means. By providing such aeration means, the dissolved oxygen concentration can be increased.

It can be said that the decomposition of organic acids and the like is uptake of microbial nutrients. However, energy is consumed in order to advance the reaction at the same time as taking in energy. At that time, electrons emitted from the positive electrode side are supplemented as energy, so that the microorganisms are always activated and the number of microorganisms increases. As a result, the processing efficiency of organic matter is improved. Therefore, according to the microbial fuel cell system of the present invention, the treatment efficiency of organic matter is improved, so that undecomposed substances that have been excessive sludge until now are also decomposed and the generation of excessive sludge is reduced. Since the reaction does not proceed to methane fermentation due to the incorporation of the organic acid, the generation of sulfide ions, ammonia, etc. generated in the process is reduced.

Next, the embodiment will be described more specifically with reference to examples.

Example 1
The following microbial fuel cell system was produced using a U-shaped acrylic container as shown in FIG. The anaerobic tank 1 and the aerobic tank 2 were cylindrical chambers having a diameter of about 20 cm and a volume of about 3 liters, and their lower portions were connected by an acrylic pipe having a hole diameter of about 5 cm in diameter. A PVDF (polyvinylidene fluoride) film (trade name: MBR film, manufactured by Toray Industries, Inc.) as a separator 3 was provided at substantially the center of the pipe. In the anaerobic tank 1 and the aerobic tank 2, a stirring means 8 and an electrode (porous carbon supported by Pt, manufactured by Toray Industries, Inc., trade name: TGP-H-090) and a thermometer were installed. Further, the aerobic tank 2 was provided with an aerator as an aeration means, and air was supplied from the bottom of the aerobic tank 2.

Next, at the electronic component manufacturing plant wastewater treatment plant in Ogaki City, Gifu Prefecture, Japan, anaerobic sludge is applied from the bottom of the aeration tank that performs general wastewater treatment using the activated sludge method, and aerobic sludge from the top. obtained. The obtained anaerobic sludge was added to the

anaerobic tank

1, and 2 liters of the obtained aerobic sludge was added to the aerobic tank 2, respectively. Furthermore, 0.5 liter of hydrolyzate as a liquid containing organic substances was supplied to the anaerobic tank 1. After covering the upper part of the anaerobic tank 1 with a paraffin film so as not to come into contact with oxygen, each electrode and an electric resistance 1Ω ammeter as an external circuit were connected, and aeration and stirring were started.

The operation of the microbial fuel cell system was performed for 2 days. The results are shown in Table 1.

As shown in Table 1, the initial voltage was 0.8V, and the voltage after 2 days of operation was 0.8V. This shows that power can be generated throughout the operation period without adding a mediator called an electron transfer substance. Moreover, it can be seen that an inexpensive membrane (PVDF membrane) can be used as a separator as compared with a proton permeable membrane or an ion exchange membrane.

The measurement results of the BOD of the liquid in each tank showed that the initial BOD was 10000 ppm in the anaerobic layer and 700 ppm in the aerobic layer, but the BOD after 2 days of operation was 1400 ppm in the anaerobic layer. It was 45ppm. Thus, it can be seen that even when the liquid has a high BOD value, the organic matter can be effectively decomposed by the organic matter treatment method of the present invention in which the organic matter is first treated in an anaerobic tank. Moreover, it has been shown that by using two tanks, liquid containing organic substances can be supplied and processed not only in a batch system but continuously.

When the activated sludge in the anaerobic tank 1 after 2 days of operation was examined, Rhodobacter, which is an autotrophic bacterium, and Schwannella, an iron-reducing bacterium, were detected. Was shown to do. On the other hand, when the activated sludge in the aerobic tank 2 was examined in the same manner, a large number of fungal groups such as Bacillus bacteria, Paracoccus bacteria and Tauera bacteria, which are aerobic microorganisms, were detected. It was shown that the aerobic microorganism group exists in the aerobic tank 2 by operation of the system. Furthermore, when the dissolved oxygen concentration in the aerobic tank and the anaerobic tank after 2 days of operation was measured, the aerobic tank was 3 mg / L and the anaerobic tank was approximately 0 mg / L, respectively. The dissolved oxygen concentration was maintained at a high level.

Example 2
The microbial fuel cell system was operated under the same microbial fuel cell system and conditions as in Example 1 except that the electrodes in both tanks were changed to dense carbon (the one in which Cu was supported on dense carbon). I went for 2 days. As a result, the voltage in the initial state was 0.5 V, and the voltage after 2 days of operation was 0.5 V. As shown in Table 1, in Example 1 using the electrode made of porous carbon, the voltage in the initial state is 0.8V, and the voltage after operation for 2 days is 0.8V. Higher output power can be obtained.

From this result, it can be considered that the higher the electric power is, the more the microorganism is attached to the porous electrode and the larger the specific surface area, that is, the formation of the network due to the concentration of the microorganisms. This can be seen from the electron micrographs of FIGS. 2 is an electron micrograph of the surface structure of the negative electrode used in Example 1 before system operation, and FIG. 3 is an electron micrograph of the surface structure of the negative electrode of Example 1 after system operation for 2 days. It is. Thus, it is presumed that the microorganisms adhere to the carbon, so that the organic matter is efficiently decomposed and the electrons are transferred to the negative electrode.

Example 3
The following microbial fuel cell system was produced using a container as shown in FIG. The tank 9 has no separator but is divided into an anaerobic layer 13 and an aerobic layer 14.

The anaerobic layer 13 at the lower part of the tank 9 and the aerobic layer 14 at the upper part of the tank 9 have electrodes 5 and 6 (porous carbon supported by Pt, manufactured by Toray Industries, Inc., trade name: TGP- H-090) and a thermometer. Furthermore, the anaerobic layer 13 was provided with an aerator 7 as an aeration means, and air 12 was supplied from the bottom of the anaerobic layer 13. Each electrode and an electric resistance 1Ω ammeter as an external circuit 4 were connected.

Aerobic sludge (3000 to 7000 mg / L as MLSS) from the upper part of an aeration tank that uses the activated sludge method at an electronic component manufacturing plant wastewater treatment plant in Ogaki City, Gifu Prefecture, Japan obtained. Then, sludge was put into the tank 9.

Then, Mg and containing silica, diatomaceous earth was added a powder of (2.5 g / m ³⁾ and obsidian (19 g / m ³⁾ as the inorganic flocculant in the tank 9, chemical further containing Ca like lime slurry in pH adjustment ( The activated sludge was agglomerated by adding 300 g / L) and settled below the tank 9.

In the microbial fuel cell system of Example 3, operation of waste water (BOD 2000 ppm to 3500 ppm, COD 2000 ppm to 3500 ppm) with a water volume of 300 L / day was performed for 7 days. As a result, the initial voltage was 0.8V, and the voltage after 7 days of operation was 0.8V. Finally, both BOD and COD dropped to 20ppm, and the wastewater was purified.

From the above, it can be seen that the microbial fuel cell system of Example 3 can purify a large amount of waste water at the same time as obtaining high output power.

Comparative Example 1
The following microbial fuel cell system 11 was produced using a container as shown in FIG. The tank 9 has no separator but is divided into an anaerobic layer 13 and an aerobic layer 14.

As in Example 3, the anaerobic layer 13 and the aerobic layer 14 are electrodes 5 and 6 (porous carbon supported by Pt, manufactured by Toray Industries, Inc., trade name: TGP-H-090). And a thermometer was installed. Furthermore, the anaerobic layer 13 was provided with an aerator 7 as an aeration means, and air 12 was supplied from the bottom of the anaerobic layer 13. Each electrode and an electric resistance 1Ω ammeter as an external circuit 4 were connected.

Next, aerobic sludge (3000 to 7000 mg / L as MLSS) from the upper part of the aeration tank that performs general wastewater treatment using the activated sludge method at the wastewater treatment plant in Ogaki City, Gifu Prefecture, Japan ) Was obtained.

And unlike Example 3, in the comparative example, the powder of diatomaceous earth and obsidian, and the chemical solution of the lime slurry were not added, so the activated sludge did not aggregate in the comparative example.

The operation of waste water (BOD 2000ppm to 3500ppm, COD 2000ppm to 3500ppm) of water volume 300L / day was performed on this microbial fuel cell system for 7 days. As a result, the voltage was 0 V and no change, and neither BOD nor COD was purified at 2000 to 3500 ppm.

From the above, the microbial fuel cell system of the comparative example could not perform continuous power generation and organic matter treatment.

According to the present invention, it is possible to provide a microbial fuel cell system capable of purifying waste water containing organic substances simultaneously with power generation.

DESCRIPTION OF SYMBOLS 1 Anaerobic tank 2 Aerobic tank 3 Separator 4 External circuit 5 Negative electrode 6 Positive electrode 7 Aeration means 8 Stirring means 9 Tank 11 Microbial fuel cell system 12 Air (bubble)
13 Anaerobic layer 14 Aerobic layer

Claims

An anaerobic tank containing an anaerobic microorganism group and provided with an electrode, an aerobic tank containing an aerobic microorganism group and provided with an electrode, a separator for separating the anaerobic tank and the aerobic tank And an external circuit that electrically connects the electrodes,
A microbial fuel cell system in which an electrode provided in the anaerobic tank is a negative electrode and an electrode provided in the aerobic tank is a positive electrode.
The microbial fuel cell system according to claim 1, wherein a liquid containing an organic substance is supplied to the anaerobic tank, and the treated liquid is discharged from the aerobic tank.
The microbial fuel cell system according to claim 1 or 2, wherein the aerobic tank has a higher dissolved oxygen concentration than the anaerobic tank.
The microbial fuel cell system according to any one of claims 1 to 3, wherein aeration means for realizing a high dissolved oxygen concentration in the aerobic tank is further provided in the aerobic tank.
A power generation method for taking out electricity via the external circuit using the microbial fuel cell system according to any one of claims 1 to 4.
An anaerobic tank containing anaerobic microorganisms and provided with a negative electrode, an aerobic tank containing an aerobic microorganisms and provided with a positive electrode, and separating the anaerobic tank and the aerobic tank Separator, and an external circuit that electrically connects between the negative electrode and the positive electrode,
An organic matter processing method comprising: supplying a liquid containing organic matter to the anaerobic tank; and discharging the treated liquid from the aerobic tank.
A liquid containing an organic substance and an inorganic flocculant are supplied into a tank containing a liquid containing an anaerobic microorganism group so that the inside of the tank is separated into an anaerobic layer and an aerobic layer so that the liquid exists in the anaerobic layer. A power generation method for extracting electricity via an external circuit that electrically connects a negative electrode provided in the tank and a positive electrode provided in the tank so as to exist in the aerobic layer.
The power generation method according to claim 7, wherein aeration is performed by aeration means in the tank.
Liquid containing organic matter and inorganic agglomeration in a tank provided with a positive electrode and a negative electrode in a tank containing a liquid containing anaerobic microorganisms, and an external circuit for electrically connecting the electrodes Supply process of supplying the agent,
Next, a method for treating an organic substance having a step of separating the inside of the tank into an anaerobic layer and an aerobic layer, wherein a negative electrode is provided in the tank so that the negative electrode exists in the anaerobic layer, and a positive electrode is provided A method for treating an organic substance, which is provided in the tank so as to exist in the aerobic layer.
The organic matter processing method according to claim 9, wherein aeration is performed by the aeration means in the tank.