JPH11319782A - Methane fermentation process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat more efficiently organic waste by applying the UASB process. SOLUTION: Flowing organic waste 5 formed of a plurality of kinds mixed together and having an adjusted concentration is introduced as an upward flow into an anaerobic fermentation tank 10 in which granules 9 are formed by the self-immobilization of anaerobic microbes, and the anaerobic microbes in the floating state are kept in the tank by filtrating a fermentation liquid 15 flowed out of tank upper section, and the organic waste 5 is methane- fermented under the presence of anaerobic microbes of high concentration and generated gas 17 containing methane gas is recovered. Also, in the case the state in the anaerobic fermentation tank 10 is unstabilized and the granules 9 are not formed, still the anaerobic microbes are kept in the tank to methane ferment efficiently the organic waste 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a methane fermentation method for treating a plurality of types of organic wastes having different properties and concentrations and recovering useful substances in a methane fermentation method.

[0002]

2. Description of the Related Art Conventionally, organic waste has been recycled. For example, Japanese Patent Application Laid-Open No. Hei 9-201699 discloses that human waste, septic tank sludge, sewage sludge, agricultural sludge, livestock manure, garbage and foods are disclosed. Organic waste with different properties and concentrations, such as waste, is treated in the same system to collect useful substances,
A method for recycling is disclosed.

This method is as shown in FIG. 4. In this method, human waste, septic tank sludge, agricultural sludge, sewage sludge, and livestock manure are removed in a removing step # 31, and a solid-liquid separation step # 3 is performed.
In 2, the liquid waste 31 and the dewatered sludge 32 are separated,
The liquid waste 31 is subjected to BOD decomposition and denitrification as necessary in the biological treatment step # 33, and suspended matter is removed in the solid-liquid separation step # 34. COD, pigment components, iron and manganese are removed in the advanced treatment step # 35. Heavy metals such as are removed and disinfected for effluent or reused water.

On the other hand, garbage and food waste are crushed in a crushing / separating step # 36, plastic bags and trays are separated, and then mixed with the above-mentioned dewatered sludge 32.
The fermentation is performed in the anaerobic fermentation step # 37, the generated methane gas 33 is collected, and used in the form of electricity or heat in the power generation step # 38 or the like.
Is converted into a dewatered sludge 35 in a dehydration step # 39, sent to a composting step # 40 and the like to be collected as fertilizer, solid fuel and dried sludge, and the dehydrated filtrate 36 is sent to a biological treatment step # 33 for processing.

[0005]

When anaerobic fermentation is carried out, an organic substance having a relatively low solids concentration is introduced into a fermentation apparatus and kept at a medium temperature (37 ° C.) or a high temperature (55 ° C.). It is a conventional technique to stay for about 30 days to generate biogas (including about 60% methane gas) by the action of methane bacteria.

An anaerobic fermentation process with a high concentration of organic waste #
In the above-described processing system supplied to the 37, the water is added to
The concentration is adjusted to 2 to 12%.
The amount of inflow into the fermentation apparatus increases, and the size of the fermentation apparatus must be increased in order to secure a certain number of staying days.

On the other hand, in the field of wastewater treatment, a UASB method using granules, that is, anaerobic microorganisms naturally formed into bead-like clumps, is performed, and the microorganisms are maintained at a high concentration in a fermenter. Therefore, high-speed, high-efficiency processing is possible, the methane gas concentration in the generated gas is high, and extremely good processing results are obtained even under high load conditions.

The present invention has been made in view of the above circumstances, and has as its object to more efficiently treat organic waste by employing the UASB method.

[0009]

Means for Solving the Problems To solve the above problems, the methane fermentation method according to claim 1 of the present invention treats a plurality of types of organic wastes having different properties and concentrations and recovers useful substances. In a treatment system, a plurality of types of mixed and fluidized organic waste whose concentration is adjusted are introduced as an upward flow into an anaerobic fermenter in which granules are formed by self-immobilization of anaerobic microorganisms, and The anaerobic microorganisms in a suspended state are retained in the tank by filtering the fermentation liquor flowing from the upper part, and methane fermentation of organic waste in the presence of high concentration of anaerobic microorganisms produces methane-containing gas. Is to be collected.

[0010] In the methane fermentation method according to the second aspect, the fermented liquid flowing out of the anaerobic fermenter is filtered by a solid-liquid separation means outside the tank, and the concentrated liquid having an increased concentration of microorganisms is returned to the anaerobic fermenter. It is something to do.

In the methane fermentation method according to a third aspect, as the solid-liquid separation means, an external pressure type separation membrane is immersed and installed, and a membrane separation tank provided with a stirring means for stirring the liquid in the tank is used. is there.

In a methane fermentation method according to a fourth aspect of the present invention, a gas stirrer for circulating and supplying gas generated in an anaerobic fermenter is used as stirring means. The above-described method of introducing the liquid to be treated as an upward flow into the anaerobic fermenter in which the granules are formed is the UASB method, but according to the configuration of claim 1, at the time of startup or in the anaerobic fermenter. The anaerobic microorganisms are retained in the tank even when the inside conditions are unstable and granules are difficult to form, so methane fermentation of organic waste efficiently in the presence of high concentrations of anaerobic microorganisms be able to.

According to the second aspect of the present invention, the anaerobic fermenter can hold the anaerobic microorganisms without obstructing the flow, and the solid-liquid separation means outside the tank allows the anaerobic fermenter to start from the top of the anaerobic fermenter. Since the effluent, ie, the supernatant, is filtered, clogging hardly occurs.

According to the third aspect of the present invention, since the membrane surface of the separation membrane can be washed by the stirring flow of the stirring means, the clogging can be further avoided and the filtration can be performed efficiently. According to the configuration of the fourth aspect, the generated gas can be used effectively without affecting the recovery rate of the methane gas.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, organic waste mainly consisting of solid matter, such as food waste and food waste, is introduced into a coarse crushing step # 1 in a garbage bag and coarsely crushed by a coarse crusher.

The coarsely crushed organic waste 1 is mixed with a slurry-like organic waste such as human waste, septic tank sludge, sewage sludge, agricultural sludge, livestock manure, etc., and is introduced into a pulper crushing step # 2. Then, a vortex is formed by the liquid component contained in the mixture, and the mixture is stirred and mixed to crush organic solid components.

When the amount of the organic waste in the form of slurry is larger than that of the organic waste 1 which has been coarsely crushed and the amount of the liquid component is too large, the organic waste in the form of slurry is removed by a centrifugal dehydrator, a belt press type. Solid-liquid separation is performed by a dehydrator such as a dehydrator, a filter press, a rotating disk type dehydrator, or a concentration screen or a gravity concentration tank, and a part of the separated liquid is introduced into the biological treatment process # 3 to decompose BOD. If necessary, the wastewater is denitrified into biologically treated water 2, and the excess sludge 3 is led to a pulper crushing step # 2. Conversely, when the amount of the organic waste in the slurry state is small and the liquid content is too small, the dilution water is mixed so as to form a vortex.

Next, the paste form derived from the pulper
Introduce organic waste 4 into the compression crushing process # 4 and compress and crush
Compression crushing at high pressure in a machine. The compression crusher is shown in FIG.
Is input from the input port 111.
Sent into the chamber 113 by the feeder 112
The crushed object extracted is
200-250kg / cm to load instantaneously ^TwoHigh pressure
Crushed discharge holes formed into a mesh by compression
(Not shown) by extruding into fine particles
It is discharged through the crushed material discharge port 115, and the residue remains separately.
It is configured to be taken out from the distillate discharge port 116.

Therefore, the paste-like organic waste 4
The paste-like organic waste 5 containing fine particles having a particle size of 1 to 2 mm or less has a large specific gravity due to crushing by a pulper, and may have a high compressibility in the chamber 113. The unfermentable residue 6 such as non-crushable residue, plastics, metals, and stones and sands are automatically separated by remaining.

Next, the pasty organic waste 5 derived from the compression crusher is subjected to anaerobic fermentation in the anaerobic fermentation step # 5, and the generated gas 7 containing methane gas and the digested sludge 8 are recovered in the same manner as before. Or lead to subsequent processing.

The apparatus used in the anaerobic fermentation step # 5 is as follows:
As shown in FIG. 3, a methane fermentation tank 10 in which granules 9 are deposited at the bottom and a membrane module 12 in which an external pressure type separation membrane 11 such as a tubular ceramic membrane is arranged are immersed and installed. And a membrane separation tank 14 provided with a gas stirring device 13.

In such a configuration, the concentration of the paste-like organic waste 5 is adjusted by adding dilution water as necessary, and then the upward flow of the granule 9 is prevented from flowing into the methane fermentation tank 10 at a speed that does not destroy the granules 9. Methane fermentation by contact with the granules 9, the supernatant fermentation liquid 15 is allowed to flow to the membrane separation tank 14, a part of the generated gas 16 is supplied to the gas stirring device 13, and the remaining The generated gas 17 is recovered.

In the membrane separation tank 14, the fermented liquid 15 in the tank is stirred by the generated gas ejected from the gas stirring device 13, and the efficiency of the separation membrane 11 is improved in a state where the separation membrane 11 is washed. The fermentation broth 15 is filtered well and the permeate 18
The concentrated liquid 15a concentrated thereby and the generated gas 16a rising in the tank are returned to the methane fermentation tank 10. The surplus sludge 15b is appropriately pulled out.

By performing the treatment in this way, the anaerobic microorganisms can be held in the methane fermentation tank 10 without obstructing the flow. Is difficult to form,
Organic waste can be efficiently methane fermented in the presence of a high concentration of anaerobic microorganisms.

At this time, the paste-like organic waste 5 has a very large biodegradability due to the fine particles formed by compression crushing and the cell membrane being destroyed.
There is also the effect of mixing different components, such as trace elements (Fe, Ni, Co, etc.), of food waste and the like with human waste, septic tank sludge, sewage sludge, agricultural sludge, livestock manure, and the like. Ferment more efficiently and in a shorter number of days. In addition, organic waste that has been conventionally excluded as being difficult to crush and organic waste that has been removed by being attached to unsuitable fermentation materials 6 is also included in the paste-like organic waste 5. The recovery of organic components is very high.

In order to reliably form granules,
It is necessary to have a specific flow pattern caused by the liquid to be treated and the generated gas rising in the tank, and the COD volume load must be more than a certain limit and the SS load must be less than a certain limit. In addition, it is said that the application to methane fermentation requires the presence of lower volatile fatty acids as one component of the substrate.

In the above-described method, a plurality of types of mixed and fluidized organic waste whose concentration has been adjusted are introduced into the anaerobic fermenter as an upward flow, so that the COD volume load, S
The conditions of S loading and components of the substrate can be satisfied.

In the above, the anaerobic fermentation step #
By performing coarse crushing, pulper crushing, and compression crushing as pretreatment of the organic waste supplied to 5, the fermentation was promoted, and the treatment amount was increased. What kind of preprocessing should be selected.

For example, fermentation can be promoted by performing a solubilization treatment for liquefying and reducing the molecular weight of the organic waste which is difficult to ferment in advance. About 70-
Maintain at 80 ° C. for 3 days; maintain at 70 ° C., high temperature and high pressure of about 0.3 MPa; add alkali such as caustic soda or slaked lime to maintain at about 70 ° C .; blow ozone gas; maintain at 130 to 175 ° C. And various methods.

[0030]

As described above, according to the present invention, the fermentation liquid flowing out from the upper part of the anaerobic fermentation tank in which the granules are formed is filtered, and the anaerobic microorganisms in a floating state are also retained in the tank. When starting up, or when the condition in the tank becomes unstable and granules are difficult to form, organic waste can be removed at high speed and high efficiency in the presence of high concentration of anaerobic microorganisms. It can be processed and methane gas can be recovered.

Further, the fermentation liquid flowing out of the anaerobic fermenter is filtered by a solid-liquid separation means outside the tank, and the concentrated liquid having an increased concentration of microorganisms is returned to the anaerobic fermenter. The fermenter can retain anaerobic microorganisms while avoiding effects on the flow.

The external pressure type separation membrane is immersed and installed, and a membrane separation tank provided with a stirring means for stirring the liquid in the tank is used as a solid-liquid separation means. Clogging can be prevented and filtration can be performed efficiently.

By using the generated gas from the anaerobic fermenter as the gas stirring means, the generated gas can be used effectively without affecting the recovery rate of methane gas.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a methane fermentation method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a compression crusher used in the methane fermentation method.

FIG. 3 is an explanatory diagram showing a methane fermentation tank and a membrane separation tank used in the methane fermentation method.

FIG. 4 is a flowchart showing a conventional organic waste treatment flow.

[Explanation of symbols]

 9 Granules 10 Methane fermentation tank 15 Fermentation liquid 11 External pressure type separation membrane 13 Gas stirrer 14 Membrane separation tank 16, 17 Generated gas (methane gas)

Continuation of front page (72) Inventor Toshiyuki Shibata 2-47 Shishitsu Higashi 1-chome, Naniwa-ku, Osaka-shi, Osaka Kubota Corporation

Claims (4)

[Claims] 1. A treatment system for treating a plurality of types of organic wastes having different properties and concentrations and recovering useful substances, wherein a plurality of types of mixed, concentration-adjusted, flowable organic wastes are treated.
The anaerobic microorganisms are introduced into the anaerobic fermenter with granules formed by self-immobilization as an upward flow, and the fermentation liquor flowing out of the upper part of the tank is filtered to retain suspended anaerobic microorganisms in the tank. And subjecting the organic waste to methane fermentation in the presence of a high concentration of anaerobic microorganisms, and collecting generated gas containing methane gas. 2. The method according to claim 1, wherein the fermentation liquid flowing out of the anaerobic fermenter is filtered by a solid-liquid separation means outside the tank, and the concentrated liquid having an increased concentration of microorganisms is returned to the anaerobic fermenter. 2. The methane fermentation method according to 1. 3. The methane fermentation method according to claim 2, wherein the solid-liquid separation means is a membrane separation tank in which an external pressure type separation membrane is immersed and installed, and a stirring means for stirring the liquid in the tank is installed. 4. The methane fermentation method according to claim 3, wherein the stirring means is a gas stirring device to which the gas generated in the anaerobic fermenter is circulated and supplied.