JP2003190985A - Microorganism carrier for anaerobic digestion and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microorganism carrier for anaerobic digestion capable of shortening a starting time and enhancing a treatment efficiency when a methane fermentation treatment is carried out, for example, as an anaerobic digestion treatment and a manufacturing method therefor. <P>SOLUTION: The microorganism carrier for anaerobic digestion is formed by retaining the microorganism for anaerobic digestion on a skin layer of a carrier. The microorganism for anaerobic digestion is deposited and retained on the carrier by centrifugally treating the mother liquid with the carrier. The microorganism for anaerobic digestion is deposited and retained on the carrier by injecting the mother liquid onto the carrier. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a microorganism for methane fermentation mainly as an anaerobic digestion microorganism.
The present invention relates to a microbial carrier for anaerobic digestion and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method of treating organic waste, methods such as landfill and incineration have been mainly adopted.
However, in recent years, due to problems of environmental pollution such as shortage of landfill sites, generation of dioxin due to incineration, and CO ₂ emission, conversion to these treatment methods has been attempted.

Against this background, methane fermentation is being re-recognized as a method for treating organic solid waste such as raw garbage and livestock waste from kitchens and the like. Methane fermentation is an anaerobic digestion process by methane bacteria in a methane fermentation tank, and since methane, which is a useful resource, can be recovered, its use is expected.

In the treatment of the above-mentioned organic solid waste, unlike the treatment of low-concentration organic wastewater, quantitative treatment of methane bacteria and the stable maintenance thereof are required to control the treatment amount and treatment speed. It is a factor that greatly influences. Therefore, in order to quantitatively secure methane bacteria and the like and stably maintain them, a porous carrier for immobilizing various microbial groups has been conventionally proposed.

When such a porous carrier is used for fixed bed type methane fermentation, it is common to immerse the porous carrier in a methane fermentation solution and wait for the methane bacteria to naturally adhere to the porous carrier. Is. Also, for example, Japanese Patent Laid-Open No. 1-20699
As disclosed in Japanese Patent Publication No. 3, a method is known in which a water-soluble gel-forming substance is dissolved in a high-concentration microorganism suspension to immobilize the microorganism on the carrier surface.

[0006]

However, in the case of the conventional porous carrier, the adhesion of methane bacteria and the growth thereof are, for example, 1
Since it takes a long time of about a week, when performing methane fermentation in a methane fermentation tank, it takes a long time to start up and the methane fermentation efficiency at the time of start up becomes low. In addition, in the method using a gel-forming substance, the gel-forming substance causes the cells to adhere to and be fixed on the surface of the carrier, but since the carrier is covered by the gel-forming substance, the surface area of the carrier is reduced, and the porosity As a result, the proliferability of the immobilized microorganisms is reduced, and the contact efficiency between the microorganisms and the object to be treated may reduce the treatment efficiency.

The present invention has been made in view of the above circumstances, and an object of the present invention is to shorten the start-up time and increase the treatment efficiency particularly when performing methane fermentation treatment as anaerobic digestion treatment. An object of the present invention is to provide a microbial carrier for anaerobic digestion and a method for producing the same.

[0008]

In the carrier for anaerobic digestion microorganisms of the present invention, the anaerobic digestion microorganisms are held on the surface layer of the carrier as the means for solving the above-mentioned problems. According to this anaerobic digestion microbial carrier, since the anaerobic digestion microorganisms are retained in the surface layer thereof, by using this as a fixed bed in the anaerobic digestion treatment tank, the anaerobic digestion treatment is started up. In some cases, for example, a preparatory period for attaching and growing methane bacteria on a carrier becomes unnecessary, and therefore sufficient treatment efficiency can be obtained from the initial stage of startup.

Further, in this anaerobic digestion microbial carrier, it is preferable that the carrier is made of a porous material. By doing so, the inside of the pores has a high anaerobic property with no oxygen, so that the anaerobic digestion microorganisms easily proliferate here. Therefore, by using this carrier, anaerobic digestion can be achieved. It is possible to improve the processing efficiency of the processing.

Further, in this anaerobic digestion microorganism carrier, it is preferable that the carrier comprises a sheet-like water-permeable substrate. By doing so, the anaerobic digestion microorganisms adhere to the water passages such as between the fibers or the mesh, and easily proliferate. Therefore, by using this carrier, it is possible to enhance the treatment efficiency of the anaerobic digestion treatment. .

In the method for producing a carrier for a microorganism for anaerobic digestion according to the present invention, a mother liquor of an anaerobic digesting microorganism and a carrier are placed in a centrifuge, and the mother liquor and the carrier are subjected to a centrifugal treatment to remove the carrier for anaerobic digestion. Adhering microorganisms was used as a means for solving the above problems. According to this production method, the mother liquor of the anaerobic digesting microorganism is forcibly brought into contact with the surface layer of the carrier by centrifugation, so that the obtained carrier is stable and sufficient for the surface layer of the anaerobic digesting microorganism. The amount will be retained.

In another method for producing a microbial carrier for anaerobic digestion of the present invention, the mother liquor of the microorganism for anaerobic digestion is jetted onto the carrier to attach the anaerobic digestive microorganism to the carrier, did. According to this production method, the mother liquor of the anaerobic digestive microorganism is forcibly adhered to the surface layer of the carrier by injection, so that the obtained carrier is stable and has a sufficient amount of the anaerobic digestive microorganism on the surface layer. It will be retained.

Further, in these manufacturing methods, it is preferable that the carrier is put into a water-permeable bag or a water-permeable container and subjected to centrifugal treatment or jetting treatment. In this way, after the centrifugal treatment or the jetting treatment, the water-permeable bag or the water-permeable container can be put into the anaerobic digestion treatment tank as it is and used as a fixed bed, and the workability is improved.

Further, in these manufacturing methods, the carrier is preferably made of a porous material. In this way, since the inside of the pores has a high anaerobic property without oxygen, the attached anaerobic digestive microorganisms easily grow in the pores, and therefore by using this carrier. It becomes possible to improve the processing efficiency of anaerobic digestion processing.

Further, in these manufacturing methods, the carrier is preferably made of a sheet-like water-permeable substrate. By doing so, the anaerobic digestion microorganisms adhere to the water passages between the fibers or the meshes and are easily proliferated. Therefore, by using this carrier, it is possible to enhance the treatment efficiency of the anaerobic digestion treatment. become.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The carrier for anaerobic digestion microorganisms of the present invention holds the microorganisms for anaerobic digestion on the surface layer of the carrier.

The carrier for holding the anaerobic digestive microorganisms is not particularly limited, and is, for example, a porous body such as calcium silicate or wood carbide, or a sheet-like water-permeable material such as non-woven fabric, woven fabric or mesh sheet. A substrate is used. Here, it is particularly preferable to use calcium silicate as the porous body. That is, this is installed as an anaerobic digestion treatment tank, for example, in a methane fermentation tank, and when used in a methane fermentation treatment, the alkaline components are eluted little by little, which makes methane that favors an environment in the weak alkaline to neutral range. This is because it creates an environment in which bacteria easily attach to the carrier and proliferate easily. When a porous body is used as the carrier, various shapes such as a columnar shape, a cylindrical shape, a truncated cone shape, a spherical shape, a lump shape, and a rectangular parallelepiped shape are used. A shape that does not hinder the flow of the object to be treated in the reaction tank when it is installed in the reaction tank, such as a cylindrical shape, is suitable.

The material for forming the sheet-like water-permeable substrate is not particularly limited, and chemical fibers, glass fibers, activated carbon fibers, metal fibers and the like are used. That is, a non-woven fabric or a woven fabric is formed of these fibers or the like, or is knitted in a mesh shape to form a sheet-like water-permeable substrate. The carrier composed of such a porous body or sheet-like water-permeable base material has a large specific surface area due to the presence of pores, fibers or meshes, and therefore anaerobic digestion of methane bacteria and the like. It is easy to attach and fix the microorganisms for use. In particular, when it is made of a porous body, the inside of the pores has a high anaerobic property without oxygen, so that the methane bacteria easily grow here, and therefore it is advantageous in improving the methane fermentation efficiency. Become.

The anaerobic digestion microorganisms to be retained are not particularly limited as long as they are microorganisms used for anaerobic digestion treatment, and any microorganisms can be attached. It is preferably used for methane fermentation treatment.

Next, a method for producing such a microbial carrier for anaerobic digestion will be described. FIG. 1 is a diagram showing an example of an apparatus suitably used for producing a microbial carrier for anaerobic digestion, and reference numeral 1 in FIG. 1 is a microbial carrier producing apparatus. The microbial carrier manufacturing apparatus 1 includes a centrifugal device 2 and the centrifugal device 2
Supply tank 3 for supplying mother liquor of anaerobic digestion microorganisms to
And an inert gas source 4 for introducing an inert gas such as nitrogen into the centrifuge 2, and a vacuum pump 5 for evacuating the inside of the centrifuge 2.

The centrifuge 2 has a cylindrical container 6 that keeps the inside airtight, a lid 7 that seals the container 6 airtight, a cage 8 provided in the container 6, and the cage 8 And a rotating means (not shown) such as a motor for rotating the. The cage 8 has a water-permeable structure made of a net made of metal such as stainless steel or punching metal, and has a strength that does not cause deformation or the like when it is rotated at high speed by a rotating means. Is. The rotating means has a rotating plate (not shown) on which the basket 8 is placed, and rotates this rotating plate at an arbitrary speed from low rotation to high rotation, and particularly by rotating it at high speed. The body 8 is configured so that a high centrifugal force, for example, a centrifugal force of about 20,000 G can be applied.

In this centrifuge 2, the container 6 is provided with a pipe 9
The supply tank 3 is connected via the
The inert gas source 4 is connected through the pipe 11, and the vacuum pump 5 is further connected through the pipe 11.
The pipe 10 connected to the supply tank 3 is provided with a pressure pump (not shown) so that the mother liquor in the supply tank 3 described later is forcibly sent into the container 6.
An opening / closing valve 12 is provided in each of the pipes 9, 10 and 11, so that the inside and outside of the container 6 are airtightly blocked or communicated with each other.

An upper end portion of a jet nozzle pipe 13 is connected to an end portion inside the container 6 of the pipe 9 connected to the supply tank 3. This injection nozzle tube 13 is inside the container 6 and the cage 8
Which is disposed on the outside of the container and extends in the height direction of the container 6,
A large number of injection holes 14 are formed along the length direction. The injection hole 14 is opened toward the center side of the container 6, that is, toward the basket 8 side, and jets the liquid sent to the injection nozzle pipe 13 to the basket 8 side.

In order to manufacture the anaerobic digestion microorganism carrier of the present invention with such a manufacturing apparatus, first, the carrier 15 for holding microorganisms is put in the cage 8 of the container 6.
At this time, a large number of carriers 15 are attached to a water-permeable bag or a water-permeable container,
For example, it is preferable to put them in a mesh bag 16 made of chemical fiber and to carry out the processing collectively. The bag 16 is not particularly limited in size and shape, and any bag can be used, and the number thereof can be appropriately selected according to the volume of the basket 8. From the viewpoint of work efficiency, it is preferable that the side wall surface of the basket 8 is substantially covered and the bag 16 is not provided inside thereof.

When the bag 16 accommodating the carrier 15 is put into the cage 8, the lid 7 is closed and the vacuum pump 5 is operated to make the container 2
The inside of the support 15 is depressurized to a state close to a vacuum, whereby
The gas components such as air adhering to or adsorbing on are deaerated. Separately from this, the supply tank 3 is filled with a mother liquor of an anaerobic digestion microorganism, for example, methane bacteria. As the mother liquor, a seed solution obtained by filtering a methane fermentation solution with a filter, a concentrated bacterial solution obtained by concentrating the seed solution, or a solution produced and proliferated by culture is used.

The inside of the container 2 is depressurized to a predetermined pressure, and the carrier 15
After removing the air and the like adhering to, the on-off valve 12 of the pipe 11 is closed. Then, the cage 8 is rotated at low speed by the rotating means. Next, the open / close valve 1 of the pipe 9
Open two. Then, since the inside of the container 6 is depressurized to a state close to a vacuum, the pressure difference causes the supply tank 3
The mother liquor therein is sucked into the container 6 through the pipe 9, whereby the mother liquor is injected from each of the injection holes 14 of the injection nozzle pipe 13 into the cage 8.
It is jetted toward the carrier 15 inside. By receiving the injection of the mother liquor in this way, the mother liquor of methane bacteria (microorganism for anaerobic digestion) is forcibly attached to the surface layer of the carrier.
Since the injection holes 14 are formed in a large number in the length direction of the injection nozzle tube 13 and the cage 8 is rotated at a low speed by the rotating means, a large number of carriers 15 put in the cage 8 are provided. Are uniformly and sufficiently injected with the mother liquor.

After the appropriate amount (for example, about half the volume of the container 6) of mother liquor is jetted and supplied into the container 6 in this way, the opening / closing valve 12 of the pipe 9 is closed. Then, if necessary, the opening / closing valve 12 of the pipe 10 is opened to supply an inert gas into the container 6 to return the inside of the container 6 to the normal pressure. Then, the rotating means is operated to rotate the cage 8 at a high speed this time, and a high centrifugal force of about 20000 G is applied to the cage 8. Then, the mother liquor subjected to the centrifugal force is forcibly brought into contact with the carrier 15, so that the mother liquor of methane bacteria (anaerobic digestion microorganism) is forcibly attached to the surface layer of the carrier 15.
Therefore, a sufficient amount of methane bacteria (anaerobic digestion microorganisms) is retained on the carrier 15 together with the attachment by the above-mentioned spraying treatment, and the carrier becomes the anaerobic digestion microorganism carrier of the present invention.

When the anaerobic digestion microbial carrier of the present invention is manufactured in this manner, the gas in the container 6 is filled with, for example, the pipe 10.
The mother liquor or water is supplied from the supply tank 3 to the container 6 by a pressure pump while the carrier 15 is immersed in the liquid. Then, the lid 7 is opened, and the carrier 15 is put together with the bag 16 in a container (not shown) filled with mother liquor, water or the like prepared in advance. Then, by carrying this container to a tank in which anaerobic digestion treatment such as methane fermentation is actually carried out and immersing the bag 16 in the tank and setting it as a fixed bed, the anaerobic digestion microbial carrier of the present invention is anaerobically digested. Provide for processing. At this time, since the injection process and the centrifugal process are performed with the carrier 15 placed in the water-permeable bag 16, after the process, the carrier 15 can be moved and installed in the anaerobic digestion treatment tank together with the bag 16. This improves workability. Further, even when the activity of the microorganisms attached to the carrier 15 decreases, the bag can be replaced with the newly manufactured anaerobic digestion microorganism carrier.

The anaerobic digestion microorganism carrier thus obtained is sufficiently sprayed with methane bacteria (anaerobic digestion microorganisms) on the surface layer of the carrier 15 by undergoing both jetting treatment and centrifugation treatment. Since the amount is retained, using this as a fixed bed in the anaerobic digestion treatment tank eliminates the need for a preparation period for attaching methane bacteria to the carrier and growing it at the start of the anaerobic digestion treatment. Therefore, the start-up time can be significantly shortened as compared with the related art, and sufficiently high processing efficiency can be obtained from the initial stage of start-up.

In the above example, the production apparatus 1 was used to perform both the mother liquor injection treatment and the centrifugal treatment, but the anaerobic digestion microbial carrier of the present invention does not perform both treatments as described above. The anaerobic digestion microorganisms may be attached and forcibly retained by performing either one of the treatments. Further, as the manufacturing apparatus 1 for carrying out the manufacturing method of the present invention, a plurality of injection nozzle tubes 13 may be provided so that the mother liquor can be supplied and injected more efficiently. Further, the container 6 may be provided with a heating means such as a heater so that the treatment can be performed at a desired temperature.

(Experimental example) Porous calcium silicate and woody carbide (charred charcoal) were prepared as carriers. The size and shape of the calcium silicate was 5 cm × 1.8 cm × 0.8 mm plate-shaped. In addition, as the wood carbide (smear charcoal), a continuous porous ceramic charcoal manufactured by Sugiyama Kowtech Co., Ltd. was used. This is 85% carbon, ash is lime, iron,
It consists of potassium and sodium. The shape was columnar, and the height was 30 to 60 mm and the diameter was 1.8 mm. The internal surface area was 220 mm ² / g. Next, put each of these carriers in a centrifuge tube, and further put the culture solution in the latter stage of methane fermentation as a mother liquor into the centrifuge tube,
After that, the centrifuge tube was rotated at high speed by a centrifuge to forcibly attach methane bacteria to each carrier. As the obtained microorganism carrier, one using calcium silicate was used as Example 1, and one using wood charcoal was used as Example 2.

As the methane fermentation-treated product, there was prepared a product to be treated, in which the raw garbage discharged from the kitchen was minced and uniformly mixed. About 90% of this object was water. In addition, as a component in the solid content, oil and fat content is 20
%, Carbohydrate was 50%, and protein was about 6%. The prepared material to be treated was aerobically solubilized for 2 days under alkali (pH 8) before being put into the methane fermentation tank.

Cylindrical reactor made of glass (80 mm diameter x
In a height of 180 mm), a predetermined amount of the methane fermentation-treated product and 400 ml of decalcified tap water were added, and the microbial carrier of Example 1 to which the methane bacteria had been attached was added.
The fermentation treatment was performed by maintaining the temperature at 5 ° C. and stirring. Also,
The fermentation treatment was similarly performed on the microbial carrier of Example 2. Further, for comparison, a fermentation process was similarly performed without adding a carrier and simply adding a culture solution in the latter stage of methane fermentation, and this was used as a comparative example. In each fermentation process, the total amount of generated gas and the amount of methane gas in the generated gas were examined. The obtained results are shown in FIGS. 2 (a) and 2 (b).
Shown in. The amount of methane gas was measured by analyzing the generated gas by gas chromatography.

3 (a) to 3 (c) show the results of examining the number of days elapsed from the start of the fermentation process and the gas composition (CH ₄ , H ₂ and CO ₂ ) at that time. Figure 3 (a)
Shows the gas composition in the fermentation treatment of Example 1, FIG. 3 (b) shows the gas composition in the fermentation treatment of Example 2, and FIG. 3 (c) shows the gas composition in the fermentation treatment of Comparative Example.

From the results shown in FIGS. 2 (a) and 2 (b), Examples 1 and 2 using the microbial carrier of the present invention occurred particularly at the start-up, as compared with Comparative Examples using no carrier. It was confirmed that the total amount of gas and the amount of methane gas were sufficiently large, and thus Examples 1 and 2 were effective in increasing the efficiency of the methane fermentation treatment. Also, FIGS. 3 (a) to 3 (c)
From the results shown in Example 1, Examples 1 and 2 have a high ratio of methane gas in the total generated gas from the first day after the fermentation treatment. It was also confirmed that it was effective in increasing the efficiency of the treatment.

Although not shown in FIGS. 2 and 3, the carrier used in Examples 1 and 2 is subjected to a forced attachment treatment by centrifugation using the culture solution in the latter stage of methane fermentation. Instead, it was put in the fermentation treatment tank as it was, and the fermentation treatment was carried out under the same conditions as in the comparative example. As a result, it became almost the same as that of the comparative example, and therefore, it was found that the carrier without the forced attachment of microorganisms was not effective in improving the fermentation efficiency at the start-up.

[0037]

As described above, the carrier for anaerobic digestion microorganisms of the present invention holds the anaerobic digestion microorganisms in the surface layer of the carrier, so that it can be used in an anaerobic digestion treatment tank. By using it as a fixed bed, it is possible to eliminate the preparatory period such as attaching methane bacteria to the carrier and allowing it to grow when starting the anaerobic digestion process, and thus significantly shortening the start-up time compared to the conventional method. It is possible to obtain sufficient processing efficiency from the initial stage of startup. Further, since sufficient treatment efficiency can be obtained from the initial stage of startup, methane can be generated stably from the initial stage of startup.

The method for producing a microbial carrier for anaerobic digestion according to the present invention comprises placing a mother liquor of an anaerobic digesting microorganism and a carrier in a centrifuge, and centrifuging the mother liquor and the carrier to subject the carrier to anaerobic digestion. Since it is a method of attaching the microorganisms, by forcibly bringing the mother liquor of the anaerobic digesting microorganism into contact with the surface layer of the carrier by centrifugal treatment, the anaerobic digesting microorganism is added to the surface layer of the obtained carrier. It is possible to stably and retain a sufficient amount. Therefore, the anaerobic digestion microbial carrier in which a sufficient amount of the anaerobic digestion microorganisms is stably retained in this manner is a little air or acidic environment,
It also becomes resistant to inhibitors of anaerobic digestive microorganisms such as ammonia, salt, and temperature.

Another method for producing a microbial carrier for anaerobic digestion according to the present invention is to spray a mother liquor of an anaerobic digestive microorganism onto a carrier,
This is a method in which the mother liquor of the anaerobic digestion microorganisms is forcibly adhered to the surface layer of the carrier by attaching the anaerobic digestion microorganisms to the carrier. Microorganisms can be stably retained in a sufficient amount. Therefore, the anaerobic digestion microbial carrier also has resistance to the inhibitory factor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of an apparatus preferably used for producing the anaerobic digestion microbial carrier of the present invention.

2 (a) and 2 (b) show an experiment of methane fermentation in a case where a fermentation treatment was carried out using the anaerobic digestion microorganism carrier of the present invention and a case where the fermentation treatment was carried out without it. It is a graph which shows the result when it performs.

[Fig. 3] Similar to Fig. 2, when a methane fermentation experiment was carried out with a fermentation treatment using the anaerobic digestion microorganism carrier of the present invention and a fermentation treatment without using it. Is a graph showing the results of (a) shows the gas composition in the fermentation treatment of Example 1, (b) shows the gas composition in the fermentation treatment of Example 2, and (c) shows the gas composition in the fermentation treatment of Comparative Example. ing.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 11/04 B09B 3/00 D Z (72) Inventor Ei Fukunaga 1 Shin-Nakahara-cho, Isogo-ku, Yokohama, Kanagawa Address Ishi Kawashima Harima Heavy Industries Co., Ltd. Machinery and plant development center F-term (reference) 4D003 AA01 EA14 EA18 EA19 EA22 EA24 EA25 FA01 4D004 AA03 BA03 CA04 CA15 CA18 CA22 CB04 CB13 CB21 CB31 CC08 4D040 AA04 4D011 BA12 BA12 BA12 BA12 BA12 BA12 BA12 BA12 BA12 BA12 BA12 BA12 BA12 BA12

Claims (10)

[Claims] 1. A carrier for anaerobic digestion microorganisms, characterized in that an anaerobic digestion microorganism is retained on the surface layer of the carrier. 2. The anaerobic digestion microorganism carrier according to claim 1, wherein the anaerobic digestion microorganism is adhered to and retained by the carrier by centrifuging the mother liquor with the carrier. 3. The carrier for anaerobic digestion microorganisms according to claim 1, wherein the anaerobic digestion microorganisms are attached and retained on the carrier by spraying the mother liquor onto the carrier. 4. The microbial carrier for anaerobic digestion according to claim 1, wherein the carrier is a porous body. 5. The microbial carrier for anaerobic digestion according to claim 1, wherein the carrier is a sheet-like water-permeable substrate. 6. An anaerobic digestion characterized in that a mother liquor of an anaerobic digesting microorganism and a carrier are placed in a centrifuge and the mother liquor and the carrier are centrifuged to attach the anaerobic digesting microorganism to the carrier. Method for producing microbial carrier for use. 7. A method for producing a carrier for an anaerobic digestion microorganism, which comprises spraying a mother liquor of an anaerobic digestion microorganism onto a carrier to attach the anaerobic digestion microorganism to the carrier. 8. The method for producing a microbial carrier for anaerobic digestion according to claim 6 or 7, wherein the carrier is placed in a water-permeable bag or a water-permeable container and subjected to centrifugal treatment or jetting treatment. . 9. The method for producing a microbial carrier for anaerobic digestion according to claim 6, wherein the carrier is a porous body. 10. The method for producing a microbial carrier for anaerobic digestion according to claim 6, wherein the carrier is a sheet-like water-permeable substrate.