JP2004167461A - Method and apparatus for anaerobic digestion process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially advantageous method for anaerobic digestion process suppressing the membrane blockage at a minimum, decomposing/digesting an organic matter rapidly with a high decomposition rate, and efficiently producing methane and fertilizer simultaneously in the high efficient anaerobic digestion processing method of organic waste water and/or waste utilizing a solid/liquid separation membrane. <P>SOLUTION: In the anaerobic digestion processing method, the organic waste water and/or organic waste are/is subjected to the anaerobic digestion process, and an obtained digestion liquid is separated by the solid/liquid separation membrane. The anaerobic digestion process is performed in the presence of an anaerobic digestion microorganisms immobilization carrier. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to organic waste such as wastewater and garbage discharged from households, restaurants and food factories, organic sludge and livestock discharged from wastewater treatment facilities and sewage treatment plants such as household septic tanks and factories. The present invention relates to an anaerobic digestion treatment method for livestock excrement discharged from industry, organic waste discharged from fisheries, and the like, and an apparatus for performing the method.
[0002]
[Prior art]
Anaerobic digestion (methane fermentation) has been used as an energy recovery organic wastewater and / or waste treatment technology. As a high-efficiency anaerobic digestion treatment method for organic wastewater and waste, a method has been proposed in which solid-liquid separation membranes are used to maintain a high concentration of degrading microorganisms such as methanogens in an anaerobic digestion tank. (Patent Document 1).
However, the anaerobic digestion treatment method using the solid-liquid separation membrane has a problem that microscopic particles such as microorganisms are liable to be clogged in the pores of the membrane in the membrane separation step and are likely to be clogged. Although the membrane separation performance can be recovered by washing the clogged membrane, cleaning the membrane requires operations such as stopping the membrane separation device and injecting a chemical solution, which results in complicated maintenance and increased costs. Therefore, there is a demand for a technique that does not easily cause blockage of the membrane.
[0003]
In order to solve such a problem of membrane clogging, a method has been proposed in which a gas in an anaerobic digestion tank is aerated to cause a gas-liquid multiphase flow to act as a scavenging flow on the membrane surface (Patent Literature) 2).
However, this method also has a problem that the membrane is clogged because the concentration of microorganisms and suspended matter in the anaerobic digestion tank is high.
[0004]
On the other hand, as a method of maintaining a high concentration of microorganisms in a methane fermentation tank, a method of equipping a methane fermentation tank with a carrier for immobilizing microorganisms has been proposed (Patent Document 3).
This method has the advantage that the microorganism concentration can be maintained high because the microorganisms are immobilized on the carrier, but unlike the method using a solid-liquid separation membrane, there are also microorganisms that are not immobilized on the carrier, Furthermore, undecomposed organic matter particles are not fixed to the carrier and are not maintained in the methane fermentation tank and are discharged out of the system. For this reason, there was a problem that the decomposition rate of the organic matter was not so improved.
[0005]
Further, the membrane separation method is a method in which microorganisms are concentrated by a membrane separation device provided outside the methane fermentation tank, and the concentrated microorganisms are returned to the methane fermentation tank, thereby maintaining a high concentration of microorganisms in the methane fermentation tank. What you are trying to do. On the other hand, the immobilization method is a method of immobilizing microorganisms on a carrier inside a methane fermentation tank without using an external separation device, thereby maintaining a high concentration of microorganisms in the methane fermentation tank.
Therefore, conventionally, these methods are different methods used independently, and there has never been an idea to combine the two methods.
[0006]
[Patent Document 1] Japanese Patent No. 2885737 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-024661 [Patent Document 3] Japanese Patent Application Laid-Open No. 09-038686 [0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances of the prior art, and in the method for highly efficient anaerobic digestion treatment of organic wastewater and / or waste using a solid-liquid separation membrane, membrane clogging is minimized. Provided is an industrially advantageous anaerobic digestion treatment method and apparatus that can suppress and can decompose and digest organic substances quickly and at a high decomposition rate, and can efficiently produce methane and fertilizers at the same time. The purpose is to:
[0008]
[Means for Solving the Invention]
The present inventor has conducted intensive studies to solve the above problems, and as a result, when the membrane separation method and the immobilized carrier method are combined, the clogging of the membrane is suppressed to a minimum, and organic substances are rapidly decomposed at a high decomposition rate. They have found that they can be decomposed and digested, and at the same time can efficiently produce methane and fertilizers, and have completed the present invention.
That is, according to the present invention, the following inventions are provided.
(1) An anaerobic digestion method in which organic wastewater and / or organic waste is subjected to anaerobic digestion and the obtained digested liquid is separated by a solid-liquid separation membrane. An anaerobic digestion treatment method for organic wastewater and / or organic waste, which is performed in the presence of an immobilized carrier.
(2) An anaerobic digestion treatment method for organic wastewater and / or organic waste, wherein (I) organic matter is converted into methane and carbon dioxide by anaerobic digestion microorganisms in the presence of an anaerobic digestion microorganism-immobilized carrier. Decomposing, (II) separating the digested liquid obtained in the decomposition step into a suspended particle concentrate and a desorbed liquid by a solid-liquid separation membrane, and (III) concentrating the suspended particles obtained in the separation step. An anaerobic digestion method comprising returning a liquid to an anaerobic digestion tank.
(3) The anaerobic digestion treatment method according to the above (2), wherein the methane-containing gas phase obtained in the step (I) is used as a fuel.
(4) The anaerobic digestion treatment according to the above (2), wherein the desorbed solution and / or the suspended particle concentrate obtained in the step (II) is used as a fertilizer and / or a raw material of the fertilizer. Method.
(5) An apparatus for anaerobic digestion of organic wastewater and / or organic waste, comprising a solid-liquid separation membrane means and an anaerobic digestion tank, wherein the anaerobic fire extinguishing tank has an anaerobic digestion microorganism-immobilized carrier. An apparatus for anaerobic digestion of organic wastewater and / or organic waste, characterized in that the wastewater is stored therein.
(6) An apparatus for anaerobic digestion of organic wastewater and / or organic waste comprising a solid-liquid separation membrane means and an anaerobic digestion tank, wherein (I) an anaerobic digestion microorganism-immobilized carrier is accommodated. Anaerobic digestion tank, (II) solid-liquid separation membrane means for separating the digested liquid obtained in the anaerobic digestion tank into a suspension particle concentrate and a separation liquid, and (III) separation by the solid-liquid separation membrane means. An anaerobic digestion treatment apparatus comprising: means for returning the concentrated suspended particle liquid to an anaerobic digestion tank.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
A feature of the present invention is that the conventional anaerobic digestion method using a solid-liquid separation membrane has a problem that the membrane is easily clogged and it is difficult to quickly decompose and digest organic substances at a high decomposition rate. In order to overcome this problem, an anaerobic digestion tank is provided with an anaerobic digestion microorganism-immobilized carrier.
[0010]
As described above, when the anaerobic digestion tank is preliminarily accommodated with the anaerobic digestion microorganism-immobilized carrier (hereinafter, also referred to as a carrier), the anaerobic digestion microorganism in the anaerobic digestion tank (hereinafter, also simply referred to as a microorganism) is contained. Even when the suspended particle concentrate that has been attached and fixed to the carrier and separated by the separation membrane is returned, the returned microorganisms are attached, fixed, and / or decomposed to the immobilized carrier, so that The suspended microorganisms can be reduced. In addition, when membrane separation of digested juice in which microorganisms are suspended is performed, since the concentration of microorganisms in the digested juice is low, clogging of pores by microorganisms that cause membrane blockage is significantly reduced, and membrane blockage is efficiently suppressed. It becomes possible. Furthermore, in the present invention, the concentration of microorganisms in the anaerobic digestion tank becomes a high concentration, which is the sum of the microorganisms fixed on the carrier and the microorganisms returned by membrane separation, and these are simultaneously involved in the decomposition reaction of organic substances. As a result, the decomposition reaction of organic matter into methane and carbon dioxide proceeds efficiently.
[0011]
Organic wastewater to be treated according to the present invention includes general organic wastewater from households, restaurants, food factories, fermentation factories, and the like.Organic wastes include those from households, restaurants, food factories, and the like. Includes discharged food residues, organic sludge generated during wastewater treatment in food factories, septic tanks, sewage treatment plants, etc., livestock excreta, fishery processing waste, and digested sludge discharged after anaerobic digestion. Is included.
[0012]
The solid-liquid separation membrane referred to in the present specification means a pore size of 0.01 to 1 μm, preferably 0.1 to 0.2 μm, such as a known immersion type flat membrane or hollow fiber membrane, It means a membrane that can efficiently separate and concentrate anaerobic digestive microorganisms. Such a separation membrane is disclosed in detail, for example, in JP-A-62-181772.
[0013]
The anaerobic digestion microorganism-immobilized carrier means a solid substance to which the anaerobic digestion microorganism can be attached and immobilized, and the material of the carrier can be any of a variety of organic and inorganic materials such as carbon fiber, polyurethane, rock wool, and loofah. The carrier can be used in the form of a conventionally used flat plate, cylinder, sphere, disk, or the like.
[0014]
The term "anaerobic digestive microorganism" as used herein is a general term for an acid-fermenting microorganism and a methane-producing microorganism. Acid-fermenting microorganisms refer to microorganisms that produce organic acids and the like in anaerobic digestion, and include Bacteroides sp. Clostridium sp. Bacillus sp. Lactobacillus sp. And the like. A methane-producing microorganism refers to a microorganism that produces methane in anaerobic digestion, and is described in Methanosarcina sp. , Methanosaeta sp. , Metanogeum sp. And the like. Both are well known in the past.
[0015]
Hereinafter, the method of the present invention will be specifically described.
In the method of the present invention, first, when anaerobically digesting organic wastewater and / or organic waste, it is necessary to accommodate the above-described carrier in an anaerobic digestion tank. The method for accommodating the carrier may be a fixed bed, a fluidized bed, or a combination thereof.
In this anaerobic digestion treatment, the organic matter content is adjusted to 0.001 to 30%, preferably 0.01 to 90% in an anaerobic digestion tank containing an anaerobic digestion microorganism and a carrier, and the reaction temperature is 10 to 100%. Anaerobic digestion treatment is carried out by medium temperature fermentation at preferably 30 to 35 ° C or high temperature fermentation at 50 to 60 ° C to decompose organic substances and generate methane. In this anaerobic digestion treatment step, no air and / or oxygen is supplied into the anaerobic digestion tank.
[0016]
Next, in the present invention, the digested liquid in which anaerobic digestive microorganisms and other microorganisms are suspended, the suspension liquid concentrated liquid and the desorbed liquid containing no suspended particles such as microorganisms by solid-liquid separation membrane means. To separate.
As the separation membrane, as described above, a conventionally known separation membrane such as an immersion type flat membrane or a hollow fiber membrane can be used, and the pore size is 0.01 to 1 μm, preferably 0.1 to 0.2 μm. Those having a size of μm are preferably used. In this solid-liquid separation step, it is desirable not to supply air and / or oxygen.
[0017]
Next, the suspended particle concentrate separated by the solid-liquid separation membrane is returned to the anaerobic digestion tank. It is desirable not to supply air and / or oxygen even in this returning step.
[0018]
In the method of the present invention, anaerobic digestion is performed in an anaerobic digestion tank containing a carrier, and the digested solution is separated into a suspended particle concentrate and a desorbed solution by a solid-liquid separation membrane device. Because of this, the concentration of microorganisms suspended in the digestive juice is low, and membrane clogging can be suppressed, so that maintenance and management of the device are facilitated. In the present invention, the concentration of microorganisms in the anaerobic digestion tank is a high concentration obtained by adding the microorganisms immobilized on the carrier and the microorganisms returned by membrane separation, and these are simultaneously involved in the decomposition reaction of organic substances. As a result, the decomposition reaction of organic matter into methane and carbon dioxide proceeds efficiently. Further, in the method of the present invention, since the decomposition rate of organic substances is improved as compared with the conventional anaerobic digestion method, the amount of generated residues is also reduced as compared with the conventional method.
[0019]
In contrast, the conventional anaerobic digestion method using only a solid separation membrane, as described above, can maintain a high concentration of microorganisms in the anaerobic digestion tank, but has a problem of membrane blockage and poor operability. There is a problem that it is difficult to maintain and manage, and as in the present invention, clogging of the membrane is minimized, and organic substances cannot be rapidly decomposed and digested at a high decomposition rate.
[0020]
Methane generated during this anaerobic digestion process can be used as fuel for boiler fuel, digestive gas power generation, micro gas turbines, or fuel cells after reforming to hydrogen.
[0021]
Since the anaerobic digestion residue and the membrane separation desorbed solution of digested juice contain a large amount of fertilizer components such as nitrogen and phosphorus and the fermentation is progressing, it can be used as it is and / or as a raw material of the fertilizer.
[0022]
Next, a processing apparatus for preferably carrying out the method of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory view of the anaerobic digestion treatment apparatus of the present invention.
In FIG. 1, 1 is an organic wastewater and / or organic waste storage tank, 2 is a raw material pipe, 3 is an anaerobic digestion tank, 4 is a digestive liquid pipe, 5 is a solid-liquid separation membrane device, and 6 is suspended particles. Concentrated liquid return pipe, 7 is a desorbed liquid pipe, 8 is a desorbed liquid storage tank, 9 is a digested gas pipe, 10 is a digested gas storage tank, 11 is a suspended particle concentrated liquid pipe, and 12 is a suspended particle concentrated liquid storage Each tank is shown.
[0023]
In order to carry out the method of the present invention by the apparatus shown in FIG. 1, an anaerobic decomposition is caused from a raw material storage tank 1 through a raw material pipe 2, and the anaerobic digestion tank 3 containing a carrier is treated with an organic substance to be treated. Supply and mix the wastewater and / or organic waste or the returned membrane separated solids.
[0024]
In the anaerobic digester 3, the organic matter is decomposed by immobilized microorganisms and suspended microorganisms under anaerobic conditions to produce methane and carbon dioxide. At this time, since the concentration of the anaerobic microorganisms in the anaerobic digestion tank 3 is high due to the carrier, the decomposition of the organic matter proceeds efficiently.
[0025]
The anaerobic digestion tank according to the present invention may be maintained under anaerobic conditions without oxygen, and may be provided with a stirring device as needed in order to stir the digestion solution in the tank and promote the fermentation reaction.
[0026]
On the other hand, the digestion fluid obtained in the anaerobic digestion tank 3 is introduced into the solid-liquid separation membrane device 5 through the digestion fluid pipe 4. The solid-liquid separation membrane device 5 is maintained in an anaerobic condition, and the digested liquid is separated by this solid-liquid separation membrane device 5 into a suspension particle concentrated solution and a desorption solution containing no suspended particles. At this time, since the microorganisms are immobilized on the immobilization carrier in the anaerobic digestion tank 3, the concentration of the suspended microorganisms in the digestive juice is low, so that the blockage of the solid-liquid separation membrane device is suppressed. The obtained suspended particle concentrate contains anaerobic digestive microorganisms and undecomposed organic substances, and is returned to the anaerobic digestion tank 3 by the suspended particle concentrate return pipe 6, and one of the returned anaerobic microorganisms is returned. The part is immobilized, and a part of the part remains suspended to participate in the decomposition reaction again, and the returned undecomposed organic matter is again subjected to the decomposition action into methane and carbon dioxide. Further, the desorbed liquid from the solid-liquid separation membrane device is transferred to a desorbed liquid storage tank 8 through a desorbed liquid pipe 7.
[0027]
The digestion gas containing methane generated in the solid-liquid separation membrane device 5 is stored in the digestion gas storage tank 10 through the digestion gas pipe 9. The digestion gas in this case usually contains 50 to 100 mol% of methane, 0 to 50 mol% of carbon dioxide, and 0 to 10 mol% of hydrogen.
[0028]
On the other hand, a part of the suspended particle concentrate obtained by the solid-liquid separation membrane device 5 passes through the suspended particle concentrate pipe 11 and is stored in the suspended particle concentrate storage tank 12.
[0029]
The desorbed liquid (waste water) usually has a low concentration of dissolved organic substances and dissolved inorganic substances, is used as a liquid fertilizer, and is discharged after advanced treatment of waste water by an activated sludge method as required. Since the suspended particle concentrate has sufficiently decomposed organic substances and contains a large amount of ammonia and phosphoric acid at the same time, it can be used as a raw material for organic fertilizer and / or fertilizer as it is. Further, the solid content after dehydration may be used as it is or as a raw material of an organic fertilizer or a soil improvement material, and may be incinerated because the water content is reduced and the amount is sufficiently reduced.
[0030]
【The invention's effect】
In the method of the present invention, since the microorganisms are immobilized on the immobilization carrier, the concentration of the microorganisms suspended in the digestive juice is low, and the membrane is not easily blocked. Therefore, the operation and maintenance of the anaerobic digester become easy. In the anaerobic digestion tank, the immobilized anaerobic digestion microorganisms and the suspended anaerobic digestion microorganisms separated and returned by the solid-liquid separation membrane are simultaneously involved in the decomposition reaction. The conversion rate and conversion rate to carbon dioxide are improved. As a result, more methane gas is generated, the amount of residue generated is reduced, and the final residual sludge throughput is reduced.
[Brief description of drawings]
FIG. 1 is an explanatory view of an apparatus for anaerobic digestion of organic sludge according to the present invention.
[Explanation of symbols]
1. Raw material storage tank 2. 2. Raw material piping Anaerobic digester 4. Digestion fluid piping5. 5. Solid-liquid separation membrane device 6. Suspended particle concentrate return pipe Desorption liquid piping8. Desorption liquid storage tank 9. Digestion gas piping 10. Digestion gas storage tank 11. 11. Suspended particle concentrate liquid piping Suspended particle concentrate storage tank

Claims (6)

An anaerobic digestion treatment method for anaerobic digestion of organic wastewater and / or organic waste and separating the obtained digestion liquid by a solid-liquid separation membrane, wherein the anaerobic digestion treatment is carried out by an anaerobic digestion microorganism-immobilized carrier. An anaerobic digestion treatment method for organic wastewater and / or organic waste, which is carried out in the presence of water. An anaerobic digestion treatment method for organic wastewater and / or organic waste, wherein (I) a step of decomposing organic matter into methane and carbon dioxide by anaerobic digestion microorganisms in the presence of an anaerobic digestion microorganism-immobilized carrier (II) a step of separating the digested solution obtained in the decomposition step into a suspension particle concentrate and a separation liquid by a solid-liquid separation membrane, and (III) anaerobic treatment of the suspension particle concentrate obtained in the separation step. An anaerobic digestion method comprising returning the product to an anaerobic digestion tank. The anaerobic digestion treatment method according to claim 2, wherein the gaseous phase containing methane obtained in the step (I) is used as fuel. The anaerobic digestion treatment method according to claim 2, wherein the desorbed liquid and / or the suspended particle concentrate obtained in the step (II) is used as a fertilizer and / or a raw material of the fertilizer. An anaerobic digestion treatment apparatus for organic wastewater and / or organic waste, comprising a solid-liquid separation membrane means and an anaerobic digestion tank, wherein the anaerobic fire extinguishing tank contains an anaerobic digestion microorganism-immobilized carrier. An apparatus for anaerobic digestion of organic wastewater and / or organic waste, comprising: An apparatus for anaerobic digestion of organic wastewater and / or organic waste, comprising a solid-liquid separation membrane means and an anaerobic digestion tank, wherein (I) an anaerobic digestion apparatus containing an anaerobic digestion microorganism-immobilized carrier. Digestion tank, (II) solid-liquid separation membrane means for separating the digested liquid obtained in the anaerobic digestion tank into a suspension particle concentrate and a separation liquid, and (III) a suspension separated by the solid-liquid separation membrane means. An anaerobic digestion treatment apparatus comprising: means for returning a suspended particle concentrate to an anaerobic digestion tank.

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