JP2003251319A - Treatment method for organic waste and treatment apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method for organic waste capable of efficiently and certainly treating the organic waste containing an organic substance in a high concentration, and a treatment apparatus therefor. <P>SOLUTION: The treatment method for the organic waste includes a dehydration process for separating a mixture of the organic waste and concentrated sludge into a dehydrated separation liquid and dehydrated sludge, a methane fermentation process for subjecting the dehydrated separation liquid to a methane fermentation treatment in a methane fermentation tank to obtain a fermentation treated liquid, a membrane separation process for subjecting the fermentation treated liquid to a membrane separation treatment to obtain a membrane separation liquid and concentrated sludge and a return process for returning the concentrated sludge obtained in the membrane separation process to the dehydration process and the methane fermentation process. By returning the concentrated sludge to the dehydration process, the clogging or the like of a membrane can be prevented and, by treating the highly concentrated fermentation treated liquid, methane fermentation sludge can be sufficiently concentrated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to human waste, livestock manure,
The present invention relates to a method and a device for treating organic waste such as septic tank sludge and raw garbage, and more particularly to a method and a device for treating these organic waste by methane fermentation.

[0002]

2. Description of the Related Art As a technique for treating organic waste, a treatment method in which a methane fermentation treatment is performed and then a membrane separation treatment is known is known (for example, Japanese Patent Laid-Open No. 10-286591). In this treatment method, a high molecular weight organic substance is decomposed into a low molecular weight organic acid, and further decomposed into methane gas (CH ₄ ) and carbon dioxide gas (CO ₂ ), so that solid waste can be reduced. is there. In addition, since the generated methane gas can be used as a fuel for power generation and heat supply, it is attracting attention as a resource recovery process.

[0003]

However, when treating organic waste such as human waste, livestock excrement, septic tank sludge, raw garbage, etc. containing a large amount of contaminants by the above-mentioned conventional treatment method, the following problems are encountered. was there.

That is, the decomposition rate of organic substances in methane fermentation treatment is not always sufficient, and when these organic wastes containing high concentrations of organic substances are treated, contaminants remaining in the fermentation solution are generated. As a result, phenomena such as accumulation of foreign substances in the methane fermentation tank, clogging of pipes, clogging and damage of membranes are likely to occur. Also, in order to obtain a sufficient decomposition rate of organic substances, it is necessary to make the residence time of organic waste in the methane fermentation tank very long, resulting in a very large capacity of the methane fermentation tank. .

The present invention has been made in view of the above problems of the prior art, and is an organic waste which can efficiently and surely treat organic waste containing a high concentration of an organic substance. An object of the present invention is to provide a method and an apparatus for treating an object.

[0006]

In order to solve the above problems, the method for treating organic waste according to the present invention separates a mixture of organic waste and concentrated sludge into dehydrated separation liquid and dehydrated sludge. A dehydration step, a methane fermentation step of subjecting the dehydrated separated liquid to a methane fermentation treatment in a methane fermentation tank to obtain a fermentation processed liquid, a membrane separation step of performing a membrane separation of the fermentation processed liquid to obtain a membrane separated liquid and concentrated sludge, and a membrane It is characterized by including a returning step of returning the concentrated sludge obtained in the separation step to a dehydration step and a methane fermentation step.

According to the treatment method of the present invention, the dehydrated separated liquid separated from the mixture of organic waste and concentrated sludge is subjected to methane fermentation treatment to give a fermentation treated liquid, and further subjected to membrane separation to obtain a clear membrane. It becomes a separated liquid. At this time, by returning the concentrated sludge obtained by the membrane separation step to the dehydration step and the methane fermentation step, it is possible to sufficiently reduce the concentration of impurities in the methane fermentation tank, and as a result, in the membrane separation device. It is possible to prevent clogging and damage of the membrane.

Further, according to the conventional method, if the concentration of impurities in the methane fermentation tank becomes high, it becomes very difficult to concentrate the methane fermentation sludge by membrane separation, but according to the present invention, the concentration of impurities is reduced as described above. Therefore, the methane fermentation sludge can be sufficiently concentrated by membrane-separating the high-concentration fermentation treatment liquid.

Further, the treatment method of the present invention comprises the amount of dehydrated separated liquid supplied from the dehydration step to the methane fermentation step, the amount of concentrated sludge returned from the return step to the dehydration step, and the concentrated sludge from the return step to the methane fermentation step. The retention time of the solid matter in the methane fermentation tank may be controlled by controlling the return amount of the above-mentioned and the outflow amount of the membrane separation liquid from the membrane separation step. As a result, the solids residence time can be sufficiently lengthened without increasing the capacity of the methane fermentation tank, and as a result, the effect of improving the decomposition rate of the organic substance can be achieved at a higher level.

The solids retention time (Solid
ds Retention Time (SRT) means an average time during which a suspended matter such as an organic substance stays in the methane fermentation tank. In the present invention, the mass of all suspended matter in the methane fermentation tank is 1
It is obtained by dividing by the mass of dehydrated sludge discharged from the dehydration process per day.

Further, the first organic waste treatment apparatus of the present invention comprises dehydration means for separating a mixture of organic waste and concentrated sludge into dehydrated separated liquid and dehydrated sludge, and methane fermentation of the dehydrated separated liquid. A methane fermentation tank for treating to obtain a fermentation treatment liquid, a membrane separation means for obtaining a membrane separation liquid and a concentrated sludge by membrane separation of the fermentation treatment liquid, a concentrated sludge obtained by the membrane separation means for a dehydration means and a methane fermentation And a return means for returning to the tank.

Further, the second organic waste treatment apparatus of the present invention is a dehydration means for separating a mixture of organic waste and concentrated sludge into dehydrated separated liquid and dehydrated sludge, and methane fermentation of the dehydrated separated liquid. A methane fermentation tank that is processed to obtain a fermentation treatment liquid, and a membrane separation unit that is housed in the methane fermentation tank and that separates the fermentation treatment liquid into a membrane separation liquid and concentrated sludge to obtain a membrane separation unit. And a return means for returning the concentrated sludge thus obtained to the dehydration means.

According to the first and second processing devices as described above, the processing method of the present invention can be effectively implemented.

In the second treatment apparatus, the concentrated sludge obtained by the membrane separation means stays in the methane fermentation tank and is used again in the methane fermentation process. Therefore, the concentrated sludge is returned to the methane fermentation tank. It is possible to realize the returning step according to the processing method of the present invention without separately providing the returning means.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be denoted by the same reference signs,
A duplicate description will be omitted.

FIG. 1 is a flow chart showing an organic waste treatment apparatus according to the first embodiment of the present invention. The organic waste treatment device shown in FIG. 1 is for sucking the latter side of the membrane separation device to perform membrane separation of the fermentation treatment liquid. The mixture of the organic waste and the concentrated sludge is separated into the dehydrated separation liquid and the dehydrated sludge. A dehydrator 1 for separating organic matter in the dehydrated separated liquid into a methane fermentation tank 2, and a membrane separator 3a for separating the fermented liquid into a membrane separated liquid and concentrated sludge. 1 and the methane fermentation tank 2, and the methane fermentation tank 2 and the membrane separation device 3a are connected by lines L2 and L3, respectively.

Lines L1 and L4b are connected to the dehydrator 1, and organic wastes such as human waste, livestock excrement, septic tank sludge, and garbage are added to the line L1, a membrane separation device 3a described later.
The concentrated sludge separated in step 1 is transferred to the dehydrator 1 through the line L4b. Then, a mixture of organic waste and concentrated sludge is separated into dehydrated separated liquid and dehydrated sludge by dehydration treatment, and coarse solids contained in the mixture (for example, straw or sawdust contained in livestock excreta) ) Is contained in the dehydrated sludge and discharged from the line L5. As such a dehydrator 1, a centrifugal separator, a belt press, a filter press, a multiple disc dehydrator or the like is used.

The methane fermentation tank 2 stores the dehydrated separated liquid,
Methane fermentation is performed under anaerobic conditions to decompose organic substances contained in the dehydrated separated liquid. In the methane fermentation tank 2, in addition to the line L2 described above, a line L3 for transferring the fermentation treatment liquid after methane fermentation to the membrane separation device 3a, and the concentrated sludge separated by the membrane separation device 3a are returned to the methane fermentation tank 2. Is connected to the line L4a. Further, the methane fermentation tank 2 is equipped with a level gauge G1 for measuring the liquid level of the contents.

As described above, the membrane separation device 3a is a device for performing membrane separation by sucking the subsequent stage side (line L6 side), whereby the fermentation treatment liquid from the methane fermentation tank 2 is separated into membrane separation liquid and concentrated sludge. Is separated into membranes. Although details of the membrane separation device 3a are not shown, the membrane separation device 3a includes a membrane separation tank for storing the fermentation treatment liquid and a separation membrane arranged in the membrane separation tank. A flat membrane, a permeable membrane and the like are preferably used.

The membrane separation device 3a is connected with lines L4 and L5 in addition to the line L3, and the separated clear membrane separation liquid flows out from the line L5. On the other hand, the line L4 is branched into a line L4a and a line L4b at a predetermined position, the line L4a is connected to the dehydrator 1 and the line L4b is connected to the methane fermentation tank 2. Membrane separation device 3a
The concentrated sludge drawn from the line L4 to the line L4a
Is returned to the methane fermentation tank 2 via the dehydrator 1 and the line L4b.

Pumps P1, P2, P3, P4 are provided in the lines L2, L3, L4b, L6, respectively, and a flow meter F is provided in each of the lines L2, L4b, L6.
1, F2, F3 are provided. And the pump P1
The feed amount of the dehydrated separated liquid from the dehydrator 1 to the methane fermentation tank 2, the feed amount of the fermentation treatment liquid from the methane fermentation tank 2 to the membrane separation device 3a by the pump P2, and the line L6 through the separation membrane by the pump P3. The outflow amount of the membrane separation liquid flowing out and the return amount of the concentrated sludge returned from the membrane separation device 3a to the dehydration device 1 are controlled by the pump P4. In addition, pump P4
By controlling the return amount of the concentrated sludge returned to the dehydrator 1 by means of, it is possible to control the return amount of the concentrated sludge returned to the methane fermentation tank 2 at the same time, and thereby the liquid in the methane fermentation tank 2 can be controlled. You can adjust the position.

More specifically, the pumps P1 and P3 are adjusted so that the supply amount of the dehydrated separation liquid measured by the flow meter F1 is larger than the outflow amount of the membrane separation liquid measured by the flow meter F3. . The pump P2 is adjusted so that its flow rate is 2 to 10 times the flow rate of the pump P3. Further, the pump P4 is adjusted so that the liquid level in the methane fermentation tank 2 is within a predetermined range.

The liquid level in the methane fermentation tank 2 (that is, the amount of the contents of the methane fermentation tank 2) is one of the factors that determines the solids residence time in the methane fermentation tank 2. Here, the membrane separation liquid flowing out from the line L6 is sufficiently clear and has a much lower solid content concentration than the concentrated sludge returned to the dehydrator 1, so that the solid content in the methane fermentation tank 2 is reduced. residence time, the following equation (1): SRT = in _{(V M × D M) /} (V S × D S) (1) [ formula (1), SRT represents the solids residence time (days)
V _M and D _M represent the amount (l) and solids concentration (mg / l) of the contents in the methane fermenter, respectively, and V _S and D _S
Represents the daily discharge amount (L / day) and the solid content concentration (mg / l) of the dehydrated sludge discharged from the dehydrator. ] It can be obtained according to. The solids retention time is preferably set to 30 days or longer.

The hydraulic retention time in the methane fermentation tank 2 is preferably set to 10 days or longer. The hydraulic retention time (Hydraulic Retention Tim
e, HRT) means the volume (m ³ ) in the methane fermentation tank 2,
The value (day) divided by the daily supply amount (m ³ / day) of the organic waste supplied to the dehydrator 1.

As described above, in the first embodiment, the dehydrated separated liquid separated from the mixture of the organic waste and the concentrated sludge is
A methane fermentation treatment is performed to obtain a fermentation treatment liquid, and further membrane separation is performed to obtain a clear membrane separation liquid. At this time, by returning the concentrated sludge obtained by the membrane separation device 3a to the dehydration step and the methane fermentation step, the concentration of impurities in the methane fermentation tank 2 can be sufficiently reduced, and as a result, the membrane separation It is possible to prevent clogging and damage of the film in the device 3a. Further, by reducing the concentration of contaminants in this way, it is possible to sufficiently concentrate the methane fermentation sludge.

Further, in the apparatus shown in FIG. 1, the line L
4 (L4a, L4b) and the pump P4 realize a returning means for returning the concentrated sludge from the membrane separation device 3a to the dehydrator 1 and the methane fermentation tank 2. The pumps P1 to P4, or the flowmeters F1 to F3 and the level gauge G1 also have a function as control means of the solids retention time. That is, the amount of dehydrated separated liquid supplied from the dehydrator 1 to the methane fermentation tank 2, the amount of concentrated sludge returned from the membrane separator 3a to the dehydrator 1, and the amount of concentrated sludge returned from the membrane separator 3a to the methane fermentation tank 2. By controlling the amount and the outflow amount of the membrane separation liquid from the membrane separation device 3a as described above, a sufficiently long solids residence time in the methane fermentation tank 2 can be achieved, so that the decomposition rate of the organic substance is high. It becomes possible to improve.

In this embodiment, the fermentation treatment liquid from the methane fermentation tank 2 may be directly introduced into the membrane separation device 3a for membrane separation, but when the fermentation treatment liquid is transferred to the membrane separation device 3a. By adding a coagulant to the above to remove a small amount of undecomposed matter, it is possible to more reliably prevent the separation membrane from being clogged or damaged (the same applies to other embodiments described later).

The concentrated sludge from the membrane separator 3a is
The dehydrator 1 is returned to the dehydrator 1 and the methane fermentation tank 2,
A part of the concentrated sludge returned to is discharged from the dehydrator 1 as dehydrated sludge having a good dehydration property. As described above, according to the present embodiment, it is possible to reduce the amount of generated sludge and recover sludge suitable for incineration or composting (sludge having a low water content).

FIG. 2 is a flow chart showing an organic waste treatment apparatus according to the second embodiment of the present invention. In the device shown in FIG. 2, the pump P4 is not provided in the line L4a, and the three-way valve V is provided at the branch point between the line L4a and the line L4b.
1 is provided, and other configurations are the same as in FIG.
It is similar to the device shown in FIG.

That is, in the apparatus shown in FIG. 2, a return means for returning the concentrated sludge from the membrane separator 3a to the dehydrator 1 and the methane fermentation tank 2 is realized by the line L4 (L4a, L4b) and the three-way valve V1. Has been done. Then, by switching the three-way valve V1 and adjusting the flow rates of the pumps P1 to P3 so that the liquid level in the methane fermentation tank 2 is within a predetermined range, the dehydrated separated liquid from the dehydrator 1 to the methane fermentation tank 2 is obtained. Supply amount, the amount of concentrated sludge returned from the membrane separation device 3a to the dehydrator 1, the methane fermentation tank 2 from the membrane separation device 3a
The amount of concentrated sludge returned to the membrane and the amount of the membrane separation liquid flowing out from the membrane separation device 3a are controlled.

As described above, in the second embodiment, the pump P4
Only with the difference that a three-way valve V1 is used instead of, a sufficiently long solids residence time in the methane fermentation tank 2 can be easily and surely achieved, the decomposition rate of organic substances is improved, and the processing accuracy therewith is improved. As in the case of the first embodiment, the effects of improving the temperature, preventing the membrane from being clogged and broken, reducing the amount of sludge produced, and recovering sludge suitable for incineration or composting are achieved.

FIG. 3 is a flow chart showing an organic waste treatment apparatus according to the third embodiment of the present invention. The apparatus shown in FIG. 3 is equipped with a membrane separation apparatus 3b that pressurizes the front side (line L3 side) to separate the fermentation treatment solution into membranes.
3 is provided with a pump 2 that supplies the fermentation treatment liquid so that the surface of the separation membrane is pressurized, and a flow meter F4 that measures the supply amount. A tubular membrane, a spiral membrane, a plate membrane, or the like is preferably used as the separation membrane of the membrane separation device 3b. In addition, dehydrator 1, methane fermentation tank 2, lines L1 to L4 (L4a, L4b), pump P
1, P4, the flow meters F1, F2, and the level gauge G1 have the same configurations as in the apparatus shown in FIG.

That is, in the apparatus shown in FIG. 3, the membrane separation apparatus 3 is constituted by lines L4a, L4b and pump P4.
Returning means for returning the concentrated sludge from b to the dehydrator 1 and the methane fermentation tank 2 is realized. Then, the pumps P1, P2, and P4 supply the dehydrated separated liquid from the dehydrator 1 to the methane fermentation tank 2, the amount of concentrated sludge returned from the membrane separator 3a to the dehydrator 1, the membrane separator 3a to the methane fermentation tank. Return amount of concentrated sludge to 2 and membrane separation device 3a
The outflow rate of the membrane separation liquid from the membrane is controlled.

As described above, the third embodiment is different from the third embodiment only in that the pressure type membrane separation device 3b is used, and a sufficiently long solids residence time in the methane fermentation tank 2 is easily and surely achieved. As a result, the decomposition rate of organic substances is improved and the treatment accuracy is improved accordingly, further prevention of clogging and damage of the membrane, reduction of the amount of sludge produced, and sludge suitable for incineration or composting. The point that an effect such as collection is achieved is the same as in the above-described embodiment.

In FIG. 3, the pump P4 is connected to the line L4a.
Although the apparatus provided with is shown, the second embodiment and the line L
A return device may be configured by disposing a three-way valve at a branch point between the line 4a and the line L4b.

FIG. 4 is a flow chart showing an organic waste treatment apparatus according to the fourth embodiment of the present invention. In the apparatus shown in FIG. 4, a membrane separator 3 is installed in the tank after the dehydrator 1.
A methane fermentation tank 2 accommodating a is provided, and the methane fermentation tank 3 and the dehydrator 1 are connected via a line L7. In addition, the pump P1 and the flow meter F are connected to the line L2.
1. The point that the pump P3 and the flow meter F3 are provided in the line L6 is the same as that of the first embodiment, and the pump P5 and the flow meter F5 are also provided in the line L7.

In the apparatus shown in FIG. 4, after the dehydration treatment liquid from the dehydration apparatus 1 is subjected to methane fermentation treatment in the methane fermentation tank 3, the latter side of the membrane separation apparatus 3a is sucked by the pump P3 and the membrane separation solution is fed into the line. It flows to L6. On the other hand, the concentrated sludge produced by this membrane separation accumulates in the methane fermentation tank 2, is drawn to the line L7 by the pump P5, and is returned to the dehydrator 1.

Here, the pumps P1 and P3 are the flowmeters F1.
The supply amount of the dehydrated separation liquid measured in step 3 is adjusted to be larger than the outflow amount of the membrane separation liquid measured in the flow meter F3. Further, the pump P5 adjusts the returned amount of the concentrated sludge measured by the flow meter F5 to be equal to the difference between the supply amount of the dehydrated sludge and the outflow amount of the membrane separation liquid, or the level gauge G.
The liquid level in the methane fermentation tank 2 measured at 1 is adjusted to fall within a predetermined range.

As described above, in the fourth embodiment, the line L7
The pump P5 realizes a returning means for returning the concentrated sludge from the methane fermentation tank 2 to the dehydrator 1. Then, by adjusting the flow rates of the pumps P1, P3, and P5, the amount of the dehydrated separated liquid supplied from the dehydrator 1 to the methane fermentation tank 2, the amount of the concentrated sludge returned from the methane fermentation tank 2 to the dehydrator 1, and the membrane separator 3a. By controlling the outflow amount of the membrane separation liquid from the methane fermentation tank 2, a sufficiently long solids residence time in the methane fermentation tank 2 can be easily and reliably achieved. Therefore, also in the present embodiment, improvement of the decomposition rate of the organic substance and improvement of treatment accuracy therewith, further prevention of clogging and damage of the membrane, reduction of the amount of sludge produced and sludge suitable for incineration or composting. The same effect as the above-described embodiment such as collection is obtained.

FIG. 5 is a flow chart showing an organic waste treatment apparatus according to the fifth embodiment of the present invention. The apparatus shown in FIG. 5 is suitably used for treating organic wastes (surplus sludge of human waste, etc.) with relatively few impurities, and is highly advanced after the membrane separation apparatus 3a of the apparatus shown in FIG. Water treatment device 4,
The solid-liquid separation tank 5 is provided in this order, and the advanced water treatment device 4 and the solid-liquid separation tank 5 are connected via a line L8. The solid-liquid separation tank 5 has lines L9 and L1 respectively.
0 is connected, and line L10 is line L4.
Connected with.

The advanced water treatment device 4 is a device for performing ammonia stripping treatment, activated sludge treatment, coagulation sedimentation treatment, or a combination of two or more of these treatments, and TS (contained in the membrane separation liquid by such treatment is Total Soli
d), nitrogen content (eg ammoniacal nitrogen content), BOD,
Chromaticity components, phosphorus, etc. are sufficiently removed. The treatment liquid from the advanced water treatment device 4 contains activated sludge, coagulated sludge, etc.
The treated liquid is separated in the solid-liquid separation tank 5 into treated water and separated sludge. The separated treated water flows out of the system through the line 9, while the separated sludge drawn to the line L10 is mixed with the concentrated sludge from the membrane separation device 3a and returned to the dehydrator 1 or the methane fermentation tank 2. To be done.

As described above, in the fifth embodiment, in addition to the effect of improving the decomposability of the organic substance obtained in the first embodiment,
The effect of further improving the quality of treated water can be obtained.

In the device shown in FIG. 5, activated sludge, coagulated sludge and the like from the advanced water treatment device 4 are produced in addition to the concentrated sludge from the membrane separation device 3a. To increase. In this case, if a chemical such as a polymer flocculant is injected during the dehydration treatment in the dehydrator 1, the recovery rate of solids can be improved.

[0044]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto.

Example 1 An organic waste (livestock manure) was treated using the apparatus shown in FIG. That is, a mixture of organic waste and concentrated sludge is sequentially subjected to dehydration treatment, methane fermentation treatment, and membrane separation treatment under the treatment conditions shown in Table 1, and the concentrated sludge produced by the membrane separation is dehydrated in the dehydrator 1 and the methane fermentation tank 2. Sent back to. Table 1 shows the decomposition rates of the organic substances at this time.

[Comparative Example 1] Organic matter was treated in the same manner as in Example 1 except that the treatment conditions were as shown in Table 1 and the concentrated sludge generated by the membrane separation was not returned to the dehydrator 1 and the methane fermentation tank. The waste was treated. Table 1 shows the decomposition rate of the organic substances and the water content of the dehydrated sludge generated by the dehydration treatment at this time.

[0047]

[Table 1] As shown in Table 1, in Example 1, when the dehydrated separated liquid contained an organic substance at a high concentration (solids concentration: 5.55%)
Even in this case, the retention time of the solid substance in the methane fermentation tank could be sufficiently lengthened, and the organic substance could be decomposed efficiently with a high decomposition rate. In addition, during these processing,
The separation membrane was not clogged or damaged.

Example 2 An organic waste was treated by using the apparatus shown in FIG. The treatment conditions in the dehydration treatment, methane fermentation treatment and membrane separation treatment were the same as in Example 1, and ammonia stripping, activated sludge treatment and coagulation sedimentation treatment were sequentially performed in the advanced water treatment device. Table 2 shows the water amounts of the dehydrated separation liquid, the fermentation treatment liquid, the membrane separation liquid, and the discharged water (treated water was diluted 2-fold), and their TS concentration, BOD concentration, and total nitrogen content concentration.

[0049]

[Table 2] As shown in Table 2, in Example 2, BOD, total nitrogen, and the like were removed by performing the above-described advanced water treatment on the membrane separation liquid, and treated water of better water quality was obtained.

[0050]

As described above, according to the treatment method and apparatus of the present invention, the mixture of the organic waste and the concentrated sludge is sequentially subjected to the dehydration step, the methane fermentation step, and the membrane separation step. By returning the resulting concentrated sludge to the dehydration step and the methane fermentation step, it becomes possible to prevent clogging of the membrane and to process the high-concentration fermentation treatment liquid to sufficiently concentrate the methane fermentation sludge.

[Brief description of drawings]

FIG. 1 is a flow chart showing an organic waste treatment device according to a first embodiment of the present invention.

FIG. 2 is a flow chart showing an organic waste treatment device according to a second embodiment of the present invention.

FIG. 3 is a flowchart showing an organic waste treatment device according to a third embodiment of the present invention.

FIG. 4 is a flow chart showing an organic waste treatment device according to a fourth embodiment of the present invention.

FIG. 5 is a flow diagram showing an organic waste treatment device according to a fifth embodiment of the present invention.

[Explanation of symbols]

1 ... Dehydration device, 2 ... Methane fermentation tank, 3a, 3b ... Membrane separation device, 4 ... Advanced water treatment device, 5 ... Solid-liquid separation tank, L1-L
10 ... Line, P1 to P5 ... Pump, F1 to F5 ... Flowmeter, G1 ... Level gauge, V1 ... Three-way valve.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Ikumura             Sumitomo Heavy Industries, No. 15-15 Kyoritsutsumi, Hiratsuka City, Kanagawa Prefecture             Machine Industry Co., Ltd. Hiratsuka Office F term (reference) 4D004 AA02 AA03 BA03 CA18 DA02                       DA11                 4D040 AA12 AA13 AA14                 4D059 AA01 AA02 AA05 AA07 BA12                       BE07 BE08 BE16 BE19 EA02                       EB02 EB16

Claims (4)

[Claims] 1. A dehydration step of separating a mixture of organic waste and concentrated sludge into dehydrated separated liquid and dehydrated sludge, and methane fermentation treatment of the dehydrated separated liquid in a methane fermentation tank to obtain a fermentation treatment liquid. Fermentation step, membrane separation step to obtain a membrane separation liquid and concentrated sludge by membrane separation of the fermentation treatment liquid, and return the concentrated sludge obtained in the membrane separation step to the dehydration step and the methane fermentation step And a step of returning the organic waste. 2. The supply amount of the dehydrated separated liquid from the dehydration step to the methane fermentation step, the return amount of the concentrated sludge from the return step to the dehydration step, the return step to the methane fermentation step The solid retention time in the methane fermentation tank is controlled by controlling the amount of concentrated sludge to be returned and the amount of the membrane separation liquid flowing out from the membrane separation step. Of organic waste treatment. 3. A dehydration means for separating a mixture of organic waste and concentrated sludge into dehydrated separated liquid and dehydrated sludge, and a methane fermentation tank for subjecting the dehydrated separated liquid to methane fermentation to obtain a fermentation treated liquid. Membrane separation means for membrane-separating the fermentation treatment liquid to obtain membrane separation liquid and concentrated sludge, and returning means for returning the concentrated sludge obtained by the membrane separation means to the dehydration means and the methane fermentation tank. An organic waste treatment device comprising: 4. A dehydration means for separating a mixture of organic waste and concentrated sludge into dehydrated separated liquid and dehydrated sludge, and a methane fermentation tank for subjecting the dehydrated separated liquid to methane fermentation to obtain a fermented liquid. Membrane separation means, which is housed in the methane fermentation tank and obtains a membrane separation liquid and concentrated sludge by membrane separation of the fermentation treatment liquid, and the concentrated sludge obtained by the membrane separation means to the dehydration means. An organic waste treatment device comprising: a return means for returning.