JPH03224697A - Separating membrane-combined methane fermentation device - Google Patents

Abstract

PURPOSE:To enhance methane fermentation efficiency by dividing the methane fermentation device to an acid fermentation tank and the methane fermentation tanks, providing a separating membrane between the two tanks, packing the microorganisms deposited on specific non-woven fabrics into both tanks and providing circulating means for forming upward flow in both tanks. CONSTITUTION:The methane fermentation device is divided into the anaerobic fermentation tank 104 and the methane fermentation tank 115 and the separating membrane 109 is installed between the two tanks. The water permeated through the separating membrane 109 is admitted into the methane fermentation tank 115 and the concentrated water is returned to the lower part of the acid fermentation tank 104. Further, the microorganisms deposited on the non-woven fabrics consisting of plastic fibers of >=1.0 sp. gr. are respectively packed into the acid fermentation tank 104 and the methane fermentation tank 115. In addition, circulating pumps 112, 117 for forming the upward flow are respectively provided in the acid fermentation tank 104 and the methane fermentation tank 115. As a result, the methane fermentation efficiency is improved and the quality of the treated water is greatly improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a methane fermentation device suitable for the treatment of wastewater containing organic matter, and more particularly to a methane fermentation device capable of carrying out efficient methane fermentation.

[Problems to be solved by conventional techniques and inventions] Currently,
Organic matter-containing wastewater discharged from cities, factories, etc. in Japan is mainly treated using aerobic organisms. However, in recent years, anaerobic methane fermentation treatment has attracted attention, and anaerobic treatment equipment for industrial wastewater has been put into practical use. The reasons for this include: ■ less electricity is required for treatment than aerobic treatment, ■ it is possible to recover effective energy through gasification, and ■ the amount of surplus sludge is small, reducing sludge treatment costs. This is because it enables energy-saving wastewater treatment.

Methane fermentation usually involves "hydrolysis → acid fermentation → methane fermentation"
It consists of a three-element biochemical reaction in which high-molecular substrates such as proteins and carbohydrates are reduced to lower molecules to become higher fatty acids, which are further converted to lower fatty acids to produce methane, carbon dioxide, etc. In this biochemical reaction process, the growth rate of methane-fermenting bacteria is extremely low, so it is necessary to avoid leaking the bacterial cells out of the system. Under these circumstances, in order to enable high-speed methane fermentation, it is necessary to maintain a high concentration of methane-fermenting bacteria in the bioreactor. In order to achieve high-speed methane fermentation, a bioreactor is filled with microbial carriers, the microbial cells are attached, and the microbial cells are washed out.
It is necessary to increase the bacterial cell concentration in the bioreactor and carry out efficient methane fermentation by inhibiting this phenomenon.

Currently, microbial carriers include inorganic carriers such as porous ceramic sand, activated carbon, and diatomaceous materials, as well as organic carriers such as plastic temporary or particles, and Raschig rings, but none of them are satisfactory because they cannot sufficiently attach bacterial cells. No results have been obtained.

[Means to solve the problem]

Therefore, the present inventors conducted intensive research with the aim of realizing a high-performance bioreactor for methane fermentation that solved the above problems, and found that the bioreactor was divided into an acid fermentation tank and a methane fermentation tank, and there was a gap between the two tanks. A separation membrane is installed, and the permeated water of the separation membrane flows into the methane fermentation tank, and the concentrated water is returned to the lower part of the acid fermentation tank.Furthermore, each type is filled with a specific nonwoven fabric as a microbial carrier, and the carrier is used for methane fermentation. We discovered that methane fermentation efficiency could be greatly increased and the quality of treated water could be greatly improved by using materials that carried bacteria and providing each type with circulation means to form an upward flow. The present invention was completed based on this.

That is, the present invention provides a methane fermentation apparatus for methane fermentation of organic-containing wastewater, in which the methane fermentation apparatus is divided into an anaerobic acid fermentation tank and a methane fermentation tank, and a separation membrane is installed between the two tanks. The permeated water of the separation membrane flows into the methane fermentation tank, and the concentrated water is returned to the lower part of the acid fermentation tank, and each of the acid fermentation tank and the methane fermentation tank is provided with a nonwoven fabric made of plastic fibers with a specific gravity of 1.0 or more. A separation membrane-complexed methane membrane-compounded methane system, characterized in that microorganisms supported on a carrier are filled, and the acid fermenter and the methane fermenter are each equipped with a circulation means for forming an upward flow. The present invention provides a fermentation device.

Hereinafter, the present invention will be explained in detail with reference to the drawings. The apparatus of the present invention basically consists of two tanks, an acid fermenter and a methane fermenter, and a separation membrane. Figures 1 (a) to (C) show one embodiment of the acid fermenter used in the present invention;
Figure (a) is a top plan view of the acid fermenter, Figure 1 (b) is a longitudinal sectional view of the acid fermenter and a connection diagram with the separation membrane, and Figure 1 (
C) is a partially cutaway lower plan view of the acid fermenter. Moreover, FIGS. 2(a) to (C) show one embodiment of the methane fermentation tank used in the present invention, and FIG. 2(a) is a top plan view of the methane fermentation tank, and FIG. 2(C) is a longitudinal sectional view of the same methane fermentation tank, and FIG. 2(C) is a partially cutaway lower plan view of the same methane fermentation tank.

In the figure, reference numeral 1 denotes an acid fermentation tank, and the acid fermentation tank l usually has a cylindrical or square shape, and FIG. 1 shows a square shape. This acid fermenter 1 has a grating 2 in the upper part that prevents the nonwoven carrier from flowing out, which will be described later, and a grating 3 in the lower part to maintain the nonwoven carrier.
have.

These gratings 2 and 3 have the same external shape as the acid fermenter 1, and are slightly smaller in size than the acid fermenter 1. Here, the grating 2 and the grating 3, as shown in the figure, refer to grid-like gratings used for sewage gutters and the like.

Microorganisms supported on a nonwoven fabric carrier are filled between the gratings 2 and 3.

In the figure, numeral 4 is a layer filled with microorganisms supported on a nonwoven fabric carrier. Details of this nonwoven fabric carrier will be described later.

The filling rate of the nonwoven fabric carrier is preferably 50 to 90%, particularly 60 to 80%, of the volume between grating 2 and grating 3. If the filling rate is less than 50%, although sufficient flow occurs during backwashing, the amount of bacterial cells adhering to the nonwoven fabric carrier decreases, which is undesirable because the reaction efficiency decreases.

On the other hand, if the filling rate exceeds 90%, sufficient flow of the nonwoven fabric carrier will not be achieved when excess bacterial cells adhering to the nonwoven fabric carrier are peeled off by backwashing, and a sufficient cleaning effect will not be obtained, which is not preferable.

In the present invention, a wastewater supply pipe 5 and a wastewater supply pump 6 for supplying wastewater containing organic matter (raw wastewater) to the acid fermentation tank 1 are provided below the lower grating 3. Therefore, the waste water flows through the waste water supply pipe 5 and the waste water supply pump 6, and through the perforated pipe 7 installed under the lower grating 3 towards the top of the acid fermenter 1.

In the present invention, treated water that has undergone acid fermentation passes through a pipe 8 and is supplied to a separation membrane 10 by a pump 9. The details of this separation membrane will be described later, but as the separation membrane 10, an ultrafiltration membrane or a precision filtration membrane is used. The separation membrane 10 prevents SS present during acid fermentation treatment, that is, microorganisms and solids contained in wastewater, from flowing into the methane fermentation tank. The permeated water 11 that has passed through the separation membrane 10 goes to the methane fermentation tank. Although the permeated water 11 has a clean appearance, it contains organic acids and the like. On the other hand, a part of the concentrated water 12 that did not pass through the separation membrane 1o passes through the piping 14 and circulates through the acid fermentation tank 1 as an upward flow through the perforated pipe 15, and most of the concentrated water 1
2 passes through the circulation pipe 13 and is again supplied to the separation membrane by the pump 9, where it is circulated. Here, the flow rate (the total flow rate of the raw water flow rate and the circulating water flow rate) of the early flow formed in the acid fermenter 1 by the above means is 6 to 8 m/hr or more before gas generation starts. It is necessary to do so. When the LV value is above this range, there is no dead zone within the acid fermentation tank 1, and the contact between the drainage water and circulating water and the microorganisms supported on the nonwoven fabric carrier is carried out extremely efficiently throughout the tank. Once gas starts to be generated from the acid fermenter 1, the LV value should be adjusted to 6 to 8 m/h to perform mixing with the gas.
It may be lowered below r.

Since the acid fermenter 1 uses a nonwoven fabric carrier as a fixed bed as described above, the carrier becomes clogged due to proliferation of bacterial cells. For this reason, it is necessary to backwash the carrier periodically.
The backwashing means for this purpose is the lower grating 3 of the acid fermentation tank 1.
It is located lower. Possible methods for backwashing include a method of increasing the upward flow velocity LV in the tank and a method of supplying blown gas into the tank.
Let's use both to clear the blockage.

Therefore, the backwashing means in a broad sense includes means for increasing the flow velocity LV of the upward flow in the tank, but here, the backwashing means in the narrow sense, that is, the means for supplying blown gas into the tank will be described.

As the blowing gas, inert gas such as nitrogen or gas generated from inside the tank is used. In the present invention, as shown in the figure, a backwashing gas pipe 16 and a sparger are installed at the bottom of the acid fermenter 1.
17, and the backwashing gas passes through the backwashing gas pipe 16 and is blown into the tank from the sparger F.

In the acid fermentation tank l having the above structure, organic matter in the wastewater undergoes an acid fermentation reaction by microorganisms, and the separation membrane 10
The permeated water 11 is led to the methane fermentation tank 21 in the latter stage. Further, the gas generated from the acid fermentation tank 1 is taken out from the gas pipe 18, and a part of it is used as the above-mentioned blowing gas for backwashing, if necessary.

Separately from the acid fermentation tank 1, a methane fermentation tank 21 is provided at a subsequent stage connected to the separation membrane 10. The methane fermentation tank 21 usually has a cylindrical or square shape, and FIG. 2 shows a square shape.

This methane fermentation tank 21 has almost the same structure as the acid fermentation tank 1 described above, but the carrier filling rate and the shape of the carrier used are usually different from those of the acid fermentation tank 1.

That is, the methane fermentation tank 21 has gratings 22. The upper grating 22 prevents the nonwoven fabric carrier from floating, and the lower grating 23 maintains the nonwoven fabric carrier. These gratings 22 and 23 are
These are similar to the gratings 2 and 3 in the acid fermenter 1.

Microorganisms supported on a nonwoven fabric carrier are filled between the grating 22 and the grating 23. In the figure,
Reference numeral 24 is a layer filled with microorganisms supported on a nonwoven fabric carrier.

The filling rate of the nonwoven fabric carrier filled into this methane fermentation tank 21 is 70 to 100% of the volume between the gratings 22 and 23. The reason is that methane fermentation tank 21
This is because the methane-fermenting bacteria within the membrane grow slowly, and the acid-fermenting bacteria are not sticky, so that the microorganisms can be removed even without fluidization of the nonwoven fabric carrier.

In the present invention, a separation membrane 10 is provided in the methane fermentation tank 21.
A supply pipe 25 is provided for supplying the permeated water that has passed through. This supply pipe 25 connects to the lower grating 23
It is located lower.

Therefore, the acid fermentation treated water is guided to the supply pipe 25, and the perforated pipe 2 installed under the lower grating 23
6 and flows toward the upper part of the methane fermentation tank 21.

Furthermore, in the present invention, a circulation means for forming an upward flow in the methane fermentation tank 21 is provided below the lower grating 23. Specifically, this circulation means consists of a circulation pipe 27 and a circulation pump 28, and the treated water above the upper grating 22 is passed through the circulation pipe 27 and the circulation pump 28, and then the treated water is pumped through a perforated pipe 29. Circulate some.

Here, the flow rate of the upward flow formed by the above means (the total flow rate of the flow rate of methane fermentation water and the flow rate of circulating water) LV is:
It is necessary to set the speed to 6 to 8 m/hr or more before gas generation begins. When the LV value is above this range, there is no dead zone in the methane fermentation tank 21, and the contact between the waste water (methane fermentation water) and circulating water and the microorganisms supported on the nonwoven fabric carrier is extremely efficient. well done. When gas starts to be generated from the methane fermentation tank 21, the LV value may be lowered to 6 to 8 m/hr, since mixing by the gas is performed.

Like the acid fermenter 1, the methane fermenter 21 uses a nonwoven fabric carrier as a fixed bed, and therefore, over a long period of time, the carrier becomes clogged due to the proliferation of bacterial cells.

Therefore, it is necessary to periodically backwash the carrier, and a backwashing means for this purpose is provided below the lower grating 23 of the methane fermentation tank 21. The backwashing method is similar to the backwashing method of the acid fermentation tank 1, and the flow rate L of the upward flow in the tank is
This is done by increasing V and supplying blowing gas into the tank.

Here, a backwashing gas pipe 30 and a sparger 31 are provided at the lowest part of the methane fermentation tank 21 in order to supply blown gas into the tank. A blowing gas using an inert gas such as nitrogen or a gas generated from inside the tank passes through a backwashing gas pipe 30 and is blown into the tank from a sparger 31.

In the present invention, organic matter in wastewater undergoes acid fermentation by microorganisms in an acid fermentation tank 1, solid matter is removed by a separation membrane 10, and the permeated water is converted into gas such as methane in a methane fermentation tank 21. It is taken out from the gas pipe 33. Furthermore, the methane fermentation treated water is discharged to the outside through the treated water pipe 32.

Now, regarding the nonwoven fabric carrier used as a microorganism carrier in the present invention, this nonwoven fabric carrier is made of a nonwoven fabric having countless complicated spaces. This nonwoven fabric material is made of plastic fibers with a specific gravity of 1.0 or more, which is higher in specific gravity than water.

Acid fermentation and methane fermentation have different bacterial flora that control each reaction, so it is necessary to choose materials that match the bacterial flora. Specific examples include polyvinylidene chloride, polyvinyl chloride, nylon, vinylon, etc.
Among these, polyvinylidene chloride is preferred because it is easily attached to both microorganisms involved in acid fermentation and microorganisms involved in methane fermentation.

In addition, we found that it is preferable that the opening of the nonwoven fabric carrier filled in the bioreactor for acid fermentation is 2 to 9 mm, and that the opening of the nonwoven fabric carrier filled in the bioreactor for methane fermentation is preferably 0.6 to 3 IIm. For details, please see the special request
No. 3-6836. ).

In the present invention, the shape of the nonwoven fabric carrier is preferably one that allows continuous production and is produced at low cost. The shapes of commonly used nonwoven fabric carriers are shown in FIGS. 3(a) to (e). Fig. 3 (a) is cylindrical, Fig. 3 et al.) is prismatic, Fig. 3 (C
) shows a spherical module, FIG. 3(d) shows a hollow cylindrical module, and FIG. 3(e) shows a cubic module in which plastic substrates and nonwoven fabrics are alternately combined.

In the present invention, the shapes of the nonwoven fabric carriers may be the same in the acid fermenter 1 and the methane fermenter 21, but preferably different shapes are used. That is, from the viewpoint of reaction efficiency, the shape shown in FIG. 3(e) is good, but this shape is inferior to the shape shown in FIG. 3(a) in terms of fluidity.

Therefore, the acid fermenter 1, which particularly requires fluidity when washing the carriers, should have a cylindrical shape as shown in Fig. 3(a), or it should be covered with a perforated plastic film around the circumference to further improve fluidity. It is preferable to use a methane fermenter having a shape as shown in FIG. 3(e) for the methane fermentation tank 21.

Next, the separation membrane used in the present invention will be described.

As this separation membrane 10, an ultrafiltration membrane or a precision filtration membrane is used. Conventional filtration uses porous filter media to
Although solids of more than m were separated, ultrafiltration membranes (UF)
Generally, substances with a diameter of 100 to lnm are filtered using microfiltration membranes (M
F) can usually separate substances of 10-0.1 μm. The pressure to be applied is 0.5 to 10 kg/ UF.
cIIN, MFT: 0.1-2 kg/ci.

Materials for the separation membrane include organic materials and inorganic materials such as ceramic membranes, but any material can be used in the present invention. Further, there are various types of separation membranes such as flat membrane type, spiral type, hollow fiber type, etc., and any type can be used in the present invention.

Membranes that can separate fine substances, such as the separation membrane of the present invention, usually undergo gel polarization that forms a gel layer on the membrane. Formation of a gel layer is prevented by flowing circulating water through the utility pipe 13.

In this way, by installing the separation membrane 10 after the acid fermenter 1, it became possible to increase the bacterial cell concentration in the acid fermenter 1 and to confine SS contained in the raw water in the acid fermenter 1. . Among the SS, organic ones are solubilized in the acid fermenter 1 and converted into organic acids. Therefore, it becomes possible to efficiently utilize the organic matter contained in the wastewater in the next methane fermentation tank 21. On the other hand, if a separation membrane is not used,
SS contained in wastewater may flow into the methane fermentation tank while remaining partially undecomposed in the acid fermentation tank, and the solubilization and acid fermentation reactions of SS may not occur in the methane fermentation tank where methane fermentation should normally take place. This reduces the efficiency of methane fermentation. Furthermore, in the fixed-bed two-tank fermentation process of the present invention, installing a separation membrane after the acid fermenter leads to an increase in the amount of permeated water passing through the separation membrane, and therefore it is possible to reduce the membrane area of the separation membrane. There are great economic benefits as well. That is, it has been proven that the amount of water permeated through a separation membrane generally tends to decrease as the concentration of SS present in raw water increases. In a fixed-bed fermenter, most of the bacterial cells are attached to the nonwoven fabric carrier in the fermenter, so the treated water that has undergone acid fermentation and is sent to the separation membrane contains bacterial cells and bacteria that have detached from the nonwoven fabric carrier. Only the SS originally contained in the wastewater is present. Therefore, the SS concentration in this treated water is extremely high compared to the SS1 degree contained in treated water treated in a normal floating fermenter, that is, the total amount of bacterial cells and the total amount of SS originally contained in the wastewater. It is low. Therefore, by installing a separation membrane after the fixed bed fermenter, the required membrane area of the separation membrane can be significantly reduced.

By using the configuration of a fixed bed fermenter, a separation membrane, and a fixed bed methane fermenter as in the present invention, the device is superior in terms of methane fermentation efficiency, treated water quality, and separation membrane efficiency. There is. Therefore, the methane fermentation process using this device is naturally much more sophisticated than the conventional process.

〔Example〕

Next, the present invention will be explained by examples, but the present invention is not limited thereto unless it exceeds the scope of the present invention.

Example A bench plant using a methane fermentation device (separation membrane composite fixed bed methane fermentation bioreactor) having an acid fermenter, a methane fermenter, and a separation membrane was installed in an oil and protein manufacturing factory to produce long-term continuous anaerobic methane. A field test of fermentation was conducted. This wastewater has a BOD of approximately 1000mg/I!
The equipment was designed under the conditions of a flow rate of 7.5 rrf/day and a water temperature of 30°C.

The details of the experiment will be explained below according to the flow sheet shown in FIG.

(]) Description of Flow Sheet Wastewater (raw water) is stored in a regulating tank 101 and then passed through a raw water supply pipe 103 by a raw water pump 102 to an acid fermenter 1.
04. The inside of the acid fermentation tank 104 is filled with a nonwoven fabric carrier. The inside of the acid fermenter 104 flows in an upward flow, and the residence time is 3.2 hours based on raw water. Acid fermenter 104
The acid fermentation treated water flowing out from the upper part passes through the conduit 105 and is stored in the separation membrane storage tank 10. Thereafter, it passes through a separation membrane supply pump 107 and a separation membrane circulation pump 108, and is supplied to a separation membrane 109. The separation membrane permeate water 114 flows into the methane fermentation tank 115, while most of the concentrated water flows through the conduit 11.
1, and is circulated by a separation membrane circulation pump 108. The remaining concentrated water passes through a conduit 110 to the circulation pump 1 for the acid fermenter.
12, it is circulated again to the acid fermenter 104. Further, a part of the acid fermentation treated water is circulated through the acid fermenter circulation pump 112 and the conduit 103, but this is the line used for this experiment, and normally only the conduit 110 is sufficient. The methane fermentation tank 115 is filled with a nonwoven carrier like the acid fermentation tank 104, and part of the methane fermentation treated water is circulated in an upward flow through a conduit 116 by a circulation pump 117. After a residence time of 6.4 hours based on raw water, the overflowed methane fermentation treated water is transferred to conduit 118.
The water is then stored in the treated water tank 119 and discharged by the treated water pump 120 as appropriate. In addition, microorganisms that proliferate in the bioreactor are added to the acid fermentation tank 1o as excess sludge.
From the lower part of each 4° methane fermentation tank 115, pipe 12
8129 so that it can be pulled out as appropriate.

On the other hand, the gas generated from the bioreactor passes through gas pipes 122 and 123, respectively, and flows into desulfurization towers 124 and 124° filled with an iron oxide catalyst, where malodorous components such as hydrogen sulfide are removed. Next, the gas exiting the desulfurization towers 124 and 124' is led to a cleaning tower 126, where trace amounts of remaining malodorous components are absorbed by an aqueous solution containing alkali as the main component. A cushion tank 125 located between the desulfurization tower 124, 124'' and the cleaning tower 126 is used to remove sludge, etc.
A small amount of generated gas is stored to prevent the bioreactor from becoming negative pressure and sucking in the atmosphere. The generated gas from which malodorous components have been removed in this way can be used as energy.

(2) Experimental Apparatus The main equipment of the experimental apparatus shown in the flow sheet of FIG. 4 will be explained.

■Adjustment tank 2.000 mmφX2,000 mmH, volume 6.3
rrf, effective volume 5.0 μ x 2 fixed bed methane fermentation bioreactor [acid fermenter] A structure shown in FIG. 1 was used.

a) Dimensions: 0 900 mm x 750 mm x 1,800 mmH
, volume 1.2rrf.

Effective volume 1. Volume of upper and lower grating spacing: 900 mm x 75
0 mmX1.05On+mH, volume 0.71 rrr
b) Non-woven fabric carrier shape Cylindrical carrier (50mmφX50mm
L) covered with a perforated plastic film around the circumference (plastic film hole diameter: 7.8 nun
φ.

A plastic film with a porosity of 30% was used.

C) Nonwoven fabric carrier filling amount and ratio filling amount 0.54 rrr Filling rate per volume of grating interval 76% d) Opening of nonwoven fabric carrier A nonwoven fabric carrier with an opening of 3.6 mm was used.

[Methane fermentation tank] The structure shown in FIG. 2 was used.

a) Dimensions: 0 900 mm x 900 mm x 3,000 mmH
, volume 2.4rrr.

Effective volume: 2.0 mm Volume between upper and lower gratings: 900 mm x 9
00 mmX2.050 mmH, volume 1.7rrfb
) Nonwoven Fabric Carrier Shape A cubic module in which a plastic substrate and a nonwoven fabric were combined as shown in FIG. 3(e) was used. Note that the plastic substrate used had an uneven surface. The thickness of this board is 0.7mm, the spacing between boards is 33mm, the thickness of the nonwoven fabric is 20mm, and the unit module size is 450m.
It was m x 450mm x 500mm.

C) Filling amount and ratio filling amount of nonwoven fabric carrier: 100% filling rate per volume of 1.7-vog grating interval d) Opening of nonwoven fabric carrier A nonwoven fabric carrier with an opening of 2.1 mm was used.

[Separation membrane]

Membrane type: External pressure capillary type membrane Material: Organic membrane (composite of polysulfone and polyvinyl alcohol) Capillary shape: Hollow fiber (outer diameter 1.35 mm, inner diameter 0, 80 mm) Molecular weight cut off: Approx. 15. OQQ membrane module shape: inner diameter 100mm, length 1,000
mm hollow fiber filling rate: approx. 60% membrane area per module: approx.
f [Desulfurization tower] The desulfurization towers 124 and 124'' used for the acid fermentation tank 104 and the methane fermentation tank 115 are of the same size (300 mmφ).
XI, 750 mmH, volume 120ffi) and filled with iron oxide 70e.

[Cushion tank] Volume 140! [Cleaning tower] 200 mmφX2,000 mmH, volume 60ffi
(3) Experimental method and results At the start of operation, the acid fermenter 10
4 and the methane fermentation tank 115. The pH of each type was controlled within the range of 6.0 to 6.7 for the former and 7.2 to 7.8 for the latter, and the temperature inside the tank was maintained at 30''C.
After half a year of operation without a separation membrane, in which microorganisms were grown in a device in which the acid fermentation treated water 113 was connected to the lower part of the methane fermentation tank 115, a steady state was reached. The average value of the experiment over a period of 2 months) was used.

The results are shown in Tables 1-3. Thereafter, experiments were conducted using the apparatus of the present invention in which a separation membrane was combined, and Tables 1 to 3 show the average values of the one month experiment after about six months.

Table 1 (BOD removal rate) *: Total gas recovery amount per bottle discharge (Nn+3/m') *2
: The amount of methane gas recovered per wastewater (Nm3/m3) As a result of long-term continuous experiments, the BOD load was approximately 2 kg BOD.
/m・day, the conventional activated sludge method (BOD load approx. 1
kgBOD/rIf/day) or higher and water temperature 3°C
Sufficient gas generation is possible under conditions of approximately room temperature, and the amount of gas recovered per 1 tank of waste water is 0.33 Nm3/m' without a separation membrane, and 0.0 when a separation membrane is installed in the middle. .478m3/m3, and the amount of methane gas recovered per one wastewater tank is also 0.30.
8m3/m3.0.37 Nm"/m", and it was found that extremely high energy could be recovered by installing a separation membrane between the acid fermenter and the methane fermenter. Furthermore, in terms of water quality, the BOD removal rate is approximately 92%.
．． 0%, and the BOD removal rate without a separation membrane is 60.
This was a significant improvement over 7%. The BOD removal rate is almost as high as that of the activated sludge method, and it is extremely revolutionary that approximately 92% BOD removal was achieved in methane fermentation, which does not require aeration power. . In particular, we were able to obtain good results despite treating wastewater with a relatively low concentration of BOD under conditions close to room temperature.
This means that it has been experimentally proven that the device of the present invention is superior.

[Effects of the Invention] In the present invention, the methane fermentation apparatus is divided into an acid fermentation tank and a methane fermentation tank, and a separation membrane is installed between the two tanks. Furthermore, both of these tanks are filled with microorganisms supported on specific nonwoven fabric carriers, and both of these tanks are each equipped with circulation means for forming an upward flow. Therefore, when organic matter-containing wastewater is treated using this separation membrane composite methane fermentation device, the methane fermentation efficiency can be significantly increased, and the quality of the treated water can be significantly improved.

[Brief explanation of drawings]

Figures 1 (a) to (C) show one embodiment of the acid fermenter used in the present invention, where Figure 1 (a) is a top plan view of the acid fermenter, and Figure 1 (b) is a top plan view of the acid fermenter. 1 is a longitudinal sectional view of the acid fermenter and a connection diagram with a separation membrane, and FIG. 1(C) is a partially cutaway lower plan view of the acid fermenter. In addition, Fig. 2 (a) to (
C) shows one embodiment of the methane fermentation tank used in the present invention, FIG. 2(a) is a top plan view of the methane fermentation tank, FIG. Second
Figure (C) is a partially cutaway bottom plan view of the same methane fermentation tank. In addition, in the figure, code 1 is the acid fermenter, code 2 is (upper part)
Grating, code 3 is (lower) grating, code 4
1 is a microorganism carrier packed bed, 5 is a wastewater supply pipe, 6 is a wastewater supply pump, 7 and 15 are perforated pipes, 9 is a pump, 10 is a separation membrane, 12 is concentrated water, and 1
3 is a circulation pipe, 16 is a backwashing gas pipe, 17 is a sparger, 18 is a gas pipe, 21 is a methane fermentation tank, 22 is an (upper) grating, 23 is a (lower) grating, Reference numeral 24 is a microorganism carrier packed bed, 25 is a supply pipe, 26 and 29 are perforated pipes, and 2
7 is a circulation pipe, 28 is a circulation pump, 3o is a backwashing gas pipe, 31 is a sparger 1, and 32 is a treated water pipe. 3(a) to 3(C) show various shapes of the nonwoven fabric carrier, FIG. 3(a) is cylindrical, FIG. 3(d) is hollow cylindrical, and FIG. 3(e) is cylindrical. shows a cubic module made of alternating plastic substrates and nonwoven fabrics. FIG. 4 is a flow sheet in an embodiment of the present invention. In the figure, numeral 101 is a regulating tank, numeral 102 is a raw water pump,
103 is a raw water supply pipe, 104 is an acid fermentation tank, 106 is a separation tank, 107 is a separation membrane supply pump,
108 is a circulation pump for separation membrane, 109 is a separation membrane, 115 is a methane fermentation tank, 117 is a circulation pump, 119 is a treated water tank, 120 is a treated water pump, 122 and 123 are gas pipes, respectively. , code 12
4 and 124' are desulfurization towers, 125 is a cushion tank, and 126 is a cleaning tower.

Claims (2)

[Claims] (1) In a methane fermentation device that performs methane fermentation of wastewater containing organic matter, the methane fermentation device is divided into an anaerobic acid fermentation tank and a methane fermentation tank, and a separation membrane is installed between the two tanks. The permeated water of the separation membrane flows into the methane fermentation tank, and the concentrated water is returned to the lower part of the acid fermentation tank.The acid fermentation tank and the methane fermentation tank are each equipped with a nonwoven fabric carrier made of plastic fibers with a specific gravity of 1.0 or more. A separation membrane composite methane fermentation device filled with supported microorganisms, and wherein the acid fermenter and the methane fermenter are each equipped with circulation means for forming an upward flow. . (2) Claim (1) wherein the separation membrane installed between the acid fermenter and the methane fermenter is an ultrafiltration membrane or a precision filtration membrane.
The separation membrane composite methane fermentation device described above.