KR20180110511A - Apparatus for bioelectrochemical anaerobic digestion using electrode coated with dielectric material - Google Patents

Abstract

An apparatus for bioelectrochemical anaerobic digestion of the present invention includes: an anaerobic reaction tank into which anaerobic microorganisms flow in; and an insulating electrode pair where an insulating positive electrode and an insulating negative electrode coated with a dielectric material are installed in a pair while being spaced apart from each other so as to face each other in the anaerobic reaction tank. A direct current power source is applied to the insulating positive electrode and the insulating negative electrode so that an electric field is formed between the insulating positive electrode and the insulating negative electrode; and when the anaerobic microorganisms are exposed to the electric field, electroactive microorganisms grow under the influence of the electric field. According to the present invention, the direct electron transfer between the electroactive microorganisms and methanogenic microorganisms is activated to improve the electron transfer rate and efficiency, thereby improving the anaerobic digestion performance.

Description

[0001] The present invention relates to a bioelectrochemical anaerobic digestion apparatus using an insulating electrode coated with a dielectric material,

The present invention relates to an anaerobic digestion technique for decomposing and stabilizing organic pollutants contained in organic wastewater, sewage sludge, agricultural and animal wastes, food waste, etc., in an anaerobic state and obtaining useful products such as methane, And an electric field is formed by applying a small voltage to an electroactive microorganism to activate an interelectronic electron transfer between the electroactive microorganisms and the methanogenic microorganisms, whereby a highly efficient anaerobic It is about bioelectrochemical anaerobic digestion technology that enables digestion.

Biological electrochemical anaerobic digestion is an anaerobic digestion technique in which an oxidizing electrode and a reducing electrode are installed in an anaerobic digestion tank and a potential difference is applied between the electrodes using an external power source.

Anaerobic digestion is a technique to decompose and stabilize organic pollutants such as organic wastewater, sewage sludge, agricultural and livestock waste, food waste, and to obtain useful products such as methane.

The anaerobic digestion process will be described with reference to FIG.

As shown in FIG. 3, complex organic matters constituting the organic waste are hydrolyzed into monomers such as amino acids, fatty acids, and monosaccharides, and products produced by hydrolysis are fermented by acid fermenting bacteria to produce a mixture of succinic acid, Hydrogen, and carbon dioxide. The low-molecular organic matter is fermented again by acetic acid-producing bacteria to produce acetic acid. The electrons generated during this fermentation process generate hydrogen / formic acid, or they are released directly to the outside through the cell wall and transferred to methanogenic bacteria. In conventional conventional anaerobic digestion tanks, mainly acetic acid - using methane - producing bacteria and hydrogen - using methane - producing bacteria produced methane by using acetic acid or indirect electron transfer pathway (2) using hydrogen / formic acid, respectively.

However, acetic acid-use or hydrogen-using methanogenic bacteria are slow in growth rate and susceptible to changes in environment and operating factors such as pH, temperature, organic loading rate, etc., and thus are often rate-controlling stages that govern the speed and performance of the total anaerobic reaction .

Therefore, when the methane production reaction is inhibited or the rate of the acid production reaction is relatively fast due to various environmental factors, the acetic acid or the hydrogen / formic acid produced in the fermentation process is not consumed sufficiently by the methanogenic bacteria, Lt; / RTI > At this time, the methanogenic bacteria have a substrate inhibitory effect, and the methanogenic reaction is further inhibited by accumulated acetic acid and hydrogen / formic acid. Particularly, hydrogen is low in solubility and exists mainly in a gas phase. The fermentation reaction of a low molecular organic material becomes thermodynamically possible only when the hydrogen partial pressure of the gas phase is within a limit value. This means that improving the rate of methanogenic reaction can improve anaerobic digestion efficiency.

Up to now, processes that can increase the biomass of methanogenic bacteria in the digestion tank have been studied mainly to improve the rate of methanogenic reaction to the anaerobic digestion tank. Upflow anaerobic sludge blanket reactor (UASB), anaerobic biofilm filtration Anaerobic filter (AF), and anaerobic membrane bioreactor (AnBR).

In recent years, efforts have been made to improve the methanogenic reaction by using a bioelectrochemical anaerobic digester in which a bioelectrochemical device is installed in an anaerobic digestion tank. The bioelectrochemical device is composed of an oxidation electrode to which a small voltage of about 0.3-0.7 V is applied, a reduction electrode, and a DC power supply device for applying a voltage.

In the bioelectrochemical anaerobic digestion tank, when the potential of the oxidized electrode is higher than -0.486 V (Ag / AgCl) in the standard state as shown in Equation 1, the low molecular weight material is decomposed by the electroactive microorganisms adhering to the surface of the oxidized electrode, And carbon dioxide, and the generated electrons are directly transferred to the oxidation electrode. At this time, carbon dioxide reacts with alkaline water in water and is present as bicarbonate ion or the like.

When the reduction electrode potential is lower than -0.445 V (Ag / AgCl) as shown in Equation (2) in a standard state, methane is produced by reducing carbon dioxide or bicarbonate ions using electrons and protons.

Conventionally, a noble metal such as methane-producing bacteria or platinum adhering to the surface of the reducing electrode was used as a catalyst in order to improve the reaction rate of the carbon dioxide reducing reaction that generates methane in the reducing electrode.

It is known that bioelectrochemical anaerobic digesters can improve anaerobic digestion efficiency by about 50-80% compared to conventional anaerobic digesters.

On the other hand, the oxidizing electrode and the reducing electrode provided in the bioelectrochemical anaerobic digestion tank to induce the bioelectrochemical reaction must be inexpensive, have a large specific surface area, have high biocompatibility so that the anaerobic microorganism adheres and grow, and the environment of the anaerobic digestion tank High-conductivity materials that are not corroded and durable should be used.

Until now, carbon fiber has been mainly used as an electrode material by improving the conductivity by pretreating the surface of carbon fiber having high durability and biocompatibility with carbon nanotubes and graphene. However, since the carbon-based electrode materials have a limitation of conductivity that can be improved by surface treatment, the ohmic resistance increases in proportion to the size of the electrode. Therefore, the size of the electrode that can be used in the bioelectrochemical anaerobic digestion tank was limited. In order to eliminate the influence of the ohmic resistance, a metal collector having high conductivity and high corrosion resistance was indispensable.

The catalyst such as platinum which is also used as a reducing electrode catalyst is expensive noble metal and causes the electrode manufacturing cost to increase. Therefore, it is difficult to use in actual plant in the field and it is used only in laboratory research.

Also, in the process of installing and using in the anaerobic digestion tank, the material of the surface carbon-based electrode and the materials such as the carbon nanotubes used in the surface treatment are damaged by the turbulence due to the stirring of the contents of the digestion tank, Therefore, it is pointed out that the shortness of life of electrode is short.

In addition, since the performance of the anaerobic digester is proportional to the area of the electrodes installed in the anaerobic digestion tank, it is disadvantageous that a large area of the electrodes should be installed inside the anaerobic digestion tank.

Therefore, bioelectrochemical anaerobic digestion remains in the laboratory research stage due to various disadvantages related to the oxidizing electrode and the reducing electrode installed therein, and it has not been practically used yet.

Korean Patent No. 10-0895122

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a high-efficiency bioelectrochemical anaerobic digestion device capable of improving electron transfer rate and efficiency by activating direct electron transfer between species of electro- It has its purpose. That is, the present invention solves the disadvantages of carbon-based and metal electrodes installed in a conventional bioelectrochemical anaerobic reaction tank so that bioelectrochemical anaerobic digestion technology can be easily utilized in the field.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

To achieve the above object, an anaerobic digester of the present invention comprises an anaerobic reactor into which anaerobic microorganisms flow, an insulated anode coated with a dielectric material, and an insulated cathode, which are spaced apart from each other to face each other in the anaerobic reactor Wherein an electric field is formed between the insulating anode and the insulating cathode so that a direct current power is applied from the outside to the insulating anode and the insulating cathode to cause an electric field to be formed between the insulating anode and the insulating cathode, This grows.

The insulating electrode pair may be formed of a conductive metal or a carbon-based material, and a polymer or ceramic-based dielectric material covering the surface of the ground electrode.

A voltage is applied to the pair of insulated electrodes using an external direct current power supply so that a value obtained by dividing the voltage applied to the insulated electrode pair by the distance between the insulated positive electrode and the insulated negative electrode is between 0.01 and 1.5 V / can do. However, when the voltage applied to the insulating electrode pair divided by the distance is 1.5 V / cm or more, the growth of the electroactive microorganisms is rather inhibited.

And the anaerobic microorganisms are allowed to stand on the electric field between the pair of insulating electrodes so that the anaerobic microorganisms are continuously exposed to the electric field.

Wherein the anaerobic digester further comprises an agitating propeller for agitating the contents of the anaerobic reactor and an electric motor for rotating the agitator propeller so that the contents of the anaerobic reactor are agitated through the agitating propeller, So that the anaerobic microorganisms are allowed to pass periodically through the electric field formed between the pair of insulating electrodes so that the exposure of the anaerobic microorganisms inside the anaerobic reactor to the electric field can be averaged.

According to the present invention, by inserting insulation electrodes coated with a dielectric material in a bioelectrochemical anaerobic digestion device in pairs so as to face the anaerobic digestion tank, the direct electron transfer between the electroactive microorganisms and the methanogenic bacteria is activated, There is an effect that the efficiency can be improved.

1 is a schematic view of a bioelectrochemical anaerobic digester according to an embodiment of the present invention.
2 is a view showing the shape of an insulating electrode according to an embodiment of the present invention.
FIG. 3 is a diagram showing interspecific direct electron transfer pathways for methane production in bioelectrochemical anaerobic digestion using dielectric materials coated with a dielectric material of the present invention and interspecies indirect electron transfer pathways for methane production in a conventional anaerobic digester .
FIG. 4 is a graph showing a comparison between cumulative methane production amounts of a conventional bioelectrochemical anaerobic digestion tank and a bioelectrochemical anaerobic digestion tank of the present invention.
FIG. 5 is a graph showing a comparison of accumulated hydrogen production amounts of a conventional bioelectrochemical anaerobic digestion tank and a bioelectrochemical anaerobic digestion tank of the present invention.
FIG. 6 is a chart comparing the anaerobic digestion performance of a conventional bioelectrochemical anaerobic digestion tank and a bioelectrochemical anaerobic digestion tank of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted in an ideal or overly formal sense unless expressly defined in the present application Do not.

In the following description of the present invention with reference to the accompanying drawings, the same components are denoted by the same reference numerals regardless of the reference numerals, and redundant explanations thereof will be omitted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention is intended to improve the disadvantages of carbon-based and metal electrodes used in bioelectrochemical anaerobic digestion tanks, such as ohmic resistance, durability, shape and size limitation, and high cost,

An insulating electrode pair covering the surface of the conductive electrode material as a base electrode is provided as a dielectric material in the anaerobic reactor so as to face each other with a gap therebetween.

1 is a schematic view of a bioelectrochemical anaerobic digester according to an embodiment of the present invention.

1, an anaerobic digester 1 comprises an anaerobic digester 1, an insulated anode 2, an insulated cathode 3, a DC power supply 4, a conductor 5, ), An electric motor (7), and a stirring propeller (8).

As shown in FIG. 1, the bioelectrochemical anaerobic digestion apparatus of the present invention is installed in an anaerobic digestion tank 1 in a pair so as to face the insulated electrodes, and is installed between the opposing insulated electrodes Voltage is applied to form an electric field 11.

2 is a view showing the shape of an insulating electrode according to an embodiment of the present invention.

As shown in FIG. 2, the insulating electrode is formed in such a manner that the surface of an electrode material (hereinafter referred to as " background electrode ") having high conductivity is covered with a dielectric material.

Referring to FIG. 2, there is shown a background electrode 21, which is a conductive electrode material, and a dielectric material 22, which is coated with a background electrode 21.

The network electrode 23, the plate electrode 24, and the linear electrode 25 are illustrated as exemplary embodiments of the insulating electrode.

FIG. 3 is a diagram showing interspecific direct electron transfer pathways for methane generation in bioelectrochemical anaerobic digestion using dielectric materials coated with a dielectric material of the present invention and interspecies indirect electron transfer pathways for methane production in a conventional anaerobic digester .

3, when the anaerobic microorganisms are exposed to an electric field in the anaerobic digestion tank 1 of the present invention, the growth of the electroactive microorganisms among the anaerobic microorganisms is promoted and the direct electron transfer between the electroactive microorganisms and the methanogenic bacteria The methane production reaction by the methane is activated.

In the anaerobic digestion process, when the electron transfer process that generates methane by the interspecies direct electron transfer (1) is activated, the inter-species indirect electron transfer which generates methane via intermediates such as acetic acid, hydrogen / formic acid in the conventional anaerobic digestion process (2) the electron transfer rate is faster than the path, and the transfer loss is small, so that highly efficient anaerobic digestion of bioelectrochemical is possible.

1, in the bioelectrochemical anaerobic digester of the present invention, when a voltage is applied to a pair of insulated electrodes 2 and 3 coated with a dielectric material provided in an anaerobic digestion tank 1 by a DC power supply device 4, The surface of the coated insulating anode 2 is charged by Lorentz force with negative charges whose polarity is opposite to that of the electrode, and the surface of the insulating cathode 3 is charged with positive charges. Therefore, the electric field 11 is formed between the pair of insulating electrodes by the charged charges.

When the anaerobic microorganisms are exposed to the electric field 11 formed in the space between the pair of insulated electrodes 2 and 3 in the anaerobic digestion tank 1, the electro-active microorganisms are grown, and the direct interaction between the electroactive microorganisms and the methanogenic bacteria Electron transport is activated to improve methane production rate and methane yield in anaerobic digestion.

In one embodiment of the present invention, anaerobic microorganisms may be continuously exposed to the electric field 11 by keeping the anaerobic microorganisms in the electric field between the pair of insulated electrodes 2, 3.

The anaerobic digester of the present invention agitates the contents of the anaerobic reactor 1 through the agitating propeller 8 so that the anaerobic microorganisms periodically accumulate in the electric field 11 formed between the pair of insulated electrodes 2, So that the exposure of the anaerobic microorganisms inside the anaerobic tank 1 to the electric field 11 can be averaged.

2, a material used as a material of the ground electrode 21 of the insulating electrode coated with a dielectric material according to the present invention is a material having excellent conductivity and being inexpensive and easily manufactured in various shapes such as iron, stainless steel, aluminum And a carbon-based highly conductive material made of carbon nanotubes or graphene can be used.

In the present invention, the dielectric material 22 covering the surface of the backing electrode 21 is made of polyethylene, polypropylene, polycarbonate, polyvinyl chloride, polyester, or the like, which has a high dielectric constant and high corrosion resistance, , Polyurethane, epoxy, Teflon, polyvinylidene fluoride, or the like, or ceramic materials may be used. At this time, the thickness of the insulating material coated with the dielectric material is preferably as thin as possible in order to minimize the decrease in the strength of the electric field, but is preferably 0.05 mm or more in view of durability.

In FIG. 1, the insulating electrode pairs 2 and 3 coated with a dielectric material according to the present invention have various shapes irrespective of the shapes of the anaerobic reactors such as a completely mixed type, a plug flow type, an upward flow type, a downflow type, The same effect can be obtained even when the device is installed in an anaerobic reaction tank.

The insulating electrodes 2 and 3 covered with the dielectric material according to the present invention are installed in pairs in the anaerobic reaction tank 1 so as to face each other and the insulating electrode pairs 2 and 3 coated with the dielectric material provided are connected to an external DC power source The voltage applied to the pair of insulated electrodes 2 and 3 at this time is a value obtained by dividing a voltage applied by the distance between the pair of insulated electrodes 2 and 3 by a value of 0.01 - 1.5 V / cm.

In the present invention, it is preferable that the pair of insulating electrodes 2 and 3 coated with a dielectric material are spaced apart from each other in the anaerobic reaction tank 1 so that the anaerobic microorganisms can be exposed to the electric field 11 as much as possible Do.

In the conventional bioelectrochemical anaerobic reactor, the bioconjugation and specific surface area of the electrode surface as well as the electrical conductivity of the electrode were important because electroactive microorganisms adhere to the surface of the oxidizing electrode and the reducing electrode.

Therefore, in the conventional bio-electrochemical anaerobic reactor, electroactive microorganisms such as carbon fiber, graphite plate, and reticulated glass carbon, which are directly adhered to the surface, can participate in the oxidation and reduction reactions. However, the electrical conductivity of these carbon-based materials was much lower than that of metal materials, and it was difficult to process them in various shapes.

Conventionally, in order to improve the bio-affinity and electrical conductivity, it has been necessary to modify the surface with materials such as graphite carbon nanotubes and graphene. In order to increase the size of the electrode, a collector using an expensive corrosion- It was necessary separately. Therefore, in the conventional bio-electrochemical anaerobic reactor, the electrodes are exposed directly to the contents of the anaerobic reactor, so that it is difficult to prevent rapid deterioration or damage of the electrodes due to the use of the electrodes.

In addition, in conventional bioelectrochemical anaerobic reactors, ozone resistance of carbon-based electrodes has resulted in loss of efficiency of transfer of electrons from electroactive microorganisms to methanogenic bacteria.

These various disadvantages of the conventional bioelectrochemical anaerobic reactor have been obstacles to the practical application of bioelectrochemical anaerobic digestion technology.

As shown in FIG. 2, the shape of the insulating electrode coated with the dielectric material according to the present invention can be formed into various shapes according to the shape of the anaerobic reaction tank such as the mesh shape 23, the plate shape 24, and the linear shape 25, There is no restriction on the shape of the electrode. The effect of the present invention is determined by the electric field formed by the pair of insulating electrodes and the anaerobic microbe exposed to such an electric field.

When the anaerobic microorganisms in the anaerobic tank 1 according to the present invention are positioned between the insulating electrode pairs 2 and 3 coated with a dielectric material and continuously exposed to the electric field 11, have. A similar effect can also be obtained by stirring the contents of the anaerobic tank 1 through the agitating propeller 8 so that the anaerobic microorganisms are periodically exposed to the electric field 11. In addition, since the exposure of the anaerobic microorganisms present in the anaerobic tank 1 can be averaged by agitating the contents of the anaerobic tank 1, the activity of the electroactive microorganisms as a whole can be improved.

The insulating electrodes 2 and 3 coated with the dielectric material according to the present invention can be easily processed and manufactured into various shapes and sizes. When a metal material having excellent conductivity is used as the base electrode 21, a separate collector is not required Large electrodes can be made and used.

In addition, when a polymer dielectric material having high corrosion resistance such as an acid or a base is used as a covering material, deterioration can be prevented, and the life of the electrode can be greatly increased.

When insulation electrodes 2 and 3 coated with a dielectric material according to the present invention are installed in the anaerobic reaction tank 1 to stimulate the growth of electroactive microorganisms and induce direct direct electron transfer to methanogenic bacteria, It is possible to produce methane through an electron transfer rate and an electron transfer efficiency which are superior to those of conventional bioelectrochemical anaerobic reactors.

An experimental example of the present invention will be described below.

An insulating anode 2 and an insulating cathode 3 are provided in the anaerobic digestion tank 1 of the present invention and an insulating anode 2 and an insulating cathode 3 coated with a dielectric material by using a conductor 5, Is connected to an external direct-current power supply (4), and a voltage is applied between the anode and the cathode to form an electric field (11). Thereafter, the anaerobic sludge collected from the anaerobic digestion tank of the sewage treatment plant is imitated, the organic substance substrate is injected, and the stirring propeller 8 is rotated by the electric motor 7 at a constant temperature to operate the anaerobic digestion tank 1. As a result of direct exposure of the anaerobic microorganisms to the electric field 11 formed between the insulated anode 2 and the insulating cathode 3, an anaerobic microorganism having an electroactive property grows and direct electrons are transferred to the methanogenic bacteria The reaction is activated, and the methane production rate and methane yield are greatly increased. The improvement in methane production rate and methane yield according to the present invention is about 60% higher than the conventional anaerobic digestion.

An embodiment of the bioelectrochemical anaerobic digestion apparatus using the dielectric material coated with the dielectric material of the present invention is similar to the one in which the methane production rate, methane generation rate and yield of the bioelectrochemical anaerobic digestion tank using the electrode coated with the dielectric material according to the present invention are the same And comparing the conventional biochemical anaerobic digestion tank of the present invention with that of the conventional bioelectrochemical anaerobic digestion tank.

In an embodiment of the present invention, a dough made by mixing expanded graphite and carbon nanotubes with a Nafion solution was prepared to produce an electrode required for a bioelectrochemical anaerobic digestion tank, and screen printing was performed on a stainless steel mesh (STS 316L) , And thermocompression was performed to prepare a back electrode (6 cm x 10 cm). The surface of the prepared base electrode was covered with epoxy which is a dielectric substance easily obtainable from the periphery, thus completing the insulating electrode coated with the dielectric material of the present invention.

To verify the effect of the insulating electrode coated with the dielectric material of the present invention in bioelectrochemical anaerobic digestion, four effective volume 1L anaerobic batch reactors were prepared. In this case, in one anaerobic batch reactor, pairs of insulating electrodes coated with the dielectric material according to the present invention were installed so as to face each other at intervals of 5 cm. In the conventional bioelectrochemical anaerobic reactor used as the control 1, The electrodes were installed in the same way. In addition, a biogas outlet is installed on the top plate of all batch anaerobic reactors, and the amount of gas generated can be monitored by connecting the floating gas collector with a rubber tube. In addition, a biogas sampling port sealed with an n-butyl rubber stopper was installed on the upper surface of the batch type reactor, and the biogas on the upper side of the batch type reactor was sampled. Then, the gas chromatograph equipped with a thermal conductivity detector and Porapak- The change of gas composition was observed. Then, one conventional anaerobic batch reactor without an electrode installed therein was separately prepared and used as a second control for comparison purpose. However, in order to have the same fluid agitation characteristics as the reaction vessel equipped with the electrode, the non-conductive electrode model was formed in the same shape as the electrode and installed therein.

For the initial operation, anaerobic digestion sludge was collected from the anaerobic digestion tank at the sewage end treatment plant, sieved to remove impurities, and 0.4L was added to each of the prepared anaerobic reactors. In addition, the medium containing the substrate and the nutrient was filled to make the effective volume 1 L. The initial VSS and solubility COD of the impregnated anaerobic batch reactors were 5,630 mg / L and 3,284 mg / L, respectively. The initial substrate and nutrient concentrations in the batch reactor were 3 g / L of glucose, 2.45 g / L of Na2PO4, 4.58 g / L of Na2HPO4, 0.31 g / L of NH4Cl, 0.31 g / L of KCl, The element was 5 mL / L. The prepared anaerobic batch reactor was installed in a thermostatic chamber at 35 ° C, and a voltage of 0.5 V was applied between the anode and the cathode, and then the operation was started with magnetic bar stirring. Also, in order to correct the amount of methane generated from the sludge, one reaction tank without the initial substrate was prepared and operated in the same manner. During the operation of the anaerobic batch reactor, the composition and amount of biogas were monitored. When the biogas production was stopped, stirring was stopped, the contents were settled for 30 minutes, and the supernatant was replaced with fresh medium.

FIG. 4 is a graph showing the cumulative methane production of a conventional anaerobic bioreactor and anaerobic digestion tank of the present invention, and FIG. 5 is a graph showing the cumulative methane production of anaerobic anaerobic digestion tank of the present invention, And the cumulative hydrogen production of the chemical anaerobic digester.

In FIGS. 4 and 5, BEAD represents bioelectrochemical anaerobic digestion, DE represents electrode coated with dielectric material, and CE represents conventional electrode.

In FIGS. 4 and 5, BEAD w / DE represents experimental results in the anaerobic anaerobic digestion tank of the present invention, BEAD w / CE represents experimental results in a bioelectrochemical anaerobic digestion tank using conventional electrodes, and Control Shows experimental results in a conventional anaerobic digester.

As shown in FIG. 4, cumulative methane production in the reaction tank using the conventional bioelectrochemical anaerobic reactor and the dielectric material coated with the dielectric material sharply increased after a delay of about 3 days.

However, as shown in FIG. 5, during the period corresponding to the initial adaptation period, about 63.7 mL of hydrogen was generated in the conventional anaerobic reactor. However, it was 44.8 mL in conventional bio-electrochemical reactors and was lower than that of conventional anaerobic reactors. In the reactor using the electrode coated with the dielectric material according to the present invention, the amount of generated hydrogen was 41.3 mL, which was slightly lower than that of the conventional bioelectrochemical reactor.

Hydrogen generation is related to the ratio of NADH / NAD + due to the accumulation of electrons generated during the fermentation process. In the conventional anaerobic reactor, the hydrogen production is lower than the electron production rate by acid fermentation bacteria and acetic acid fermentation bacteria. This is because the speed is low. The relatively low amount of hydrogen generated in conventional bioelectrochemical reactors indicates that the activity of methanogens rapidly increased in the bioelectrochemical reactor after the initial operation. However, in the reaction vessel using the electrode coated with the dielectric material according to the present invention, the amount of hydrogen generation was relatively small, which means that the activity of the methanogenic bacteria was activated more rapidly than the conventional bio-electrochemical reaction tank.

The increase in cumulative methane production in the anaerobic reactor using the electrode coated with the dielectric material according to the present invention and the conventional bioelectrochemical reactor showed almost the same tendency, but was higher than that of the conventional anaerobic digester.

The medium was replaced for 16 days with substrate depletion. In the second batch experiment, cumulative methane production increased rapidly after a short lag period. However, the generation of hydrogen was not observed in all reactors.

FIG. 6 is a chart comparing the anaerobic digestion performance of a conventional bioelectrochemical anaerobic digestion tank and a bioelectrochemical anaerobic digestion tank of the present invention. In FIG. 6, CODr stands for Chemical oxygen demand removed.

As shown in FIG. 6, the results of the modified Gompertz equation show that the final methane production and methane yield of the bioelectrochemical anaerobic digestion tank using the insulating material coated with the dielectric material according to the present invention were 948.1 mL and 283.1 mL / g CODr , Slightly higher than 936.1 mL and 279.4 mL / g CODr of a conventional biochemical anaerobic digester. However, it was about 61% and 46.5% higher than the conventional anaerobic digestion of 589.7 mL and 193.2 mL / g CODr, respectively. The maximum rate of methane generation in the bioelectrochemical anaerobic digester and the conventional bioelectrochemical reactor using insulating material coated with dielectric material according to the present invention was 231.8 mL / d and 238.0 mL / d, respectively, which was 171.9 mL / d of conventional anaerobic digestion . This result means that the bioelectrochemical anaerobic digestion method using the insulating electrode coated with the dielectric material according to the present invention is a technique that can replace the conventional bioelectrochemical anaerobic digestion technique.

While the present invention has been described with reference to several preferred embodiments, these embodiments are illustrative and not restrictive. It will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.

1 anaerobic digester 2 insulated anode
3 Isolated cathode 4 DC power supply
5 conductor 7 Electric motor
8 Propellers for agitation

Claims (5)

An anaerobic tank for generating methane from organic matter; And
An insulated anode coated with a dielectric material and an insulated negative electrode comprising a pair of insulating electrodes spaced apart from each other so as to face each other in the anaerobic reactor,
A direct current power source is externally applied to the insulating anode and the insulating cathode so that an electric field is formed between the insulating anode and the insulating cathode and when the anaerobic microbe is exposed to the electric field, Electrochemical anaerobic digester.
The method according to claim 1,
Wherein the insulating electrode pair comprises a ground electrode made of a conductive metal or a carbon-based material, and a polymeric or ceramic-based dielectric material covering the surface of the ground electrode.
The method according to claim 1,
A voltage is applied to the pair of insulated electrodes using an external direct current power supply so that a value obtained by dividing the voltage applied to the insulated electrode pair by the distance between the insulated positive electrode and the insulated negative electrode is between 0.01 and 1.5 V / Wherein the anaerobic digestion device is a biogeochemical anaerobic digestion device.
The method according to claim 1,
And the anaerobic microorganisms are allowed to stand on the electric field between the pair of insulating electrodes so that the anaerobic microorganisms are continuously exposed to the electric field.
The method according to claim 1,
The bioelectrochemical anaerobic digestion apparatus comprises:
A stirring propeller for stirring the contents of the anaerobic tank; And
Further comprising an electric motor for rotating the stirring propeller,
The contents of the anaerobic reactor are agitated through the agitating propeller so that the anaerobic microorganisms periodically pass through an electric field formed between the pair of insulating electrodes so that the anaerobic microorganisms inside the anaerobic reactor are exposed to the electric field, Characterized in that the anaerobic digestion system is an anaerobic digester.

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