JP2008238078A - Methane fermentation processing method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methane fermentation processing method capable of increasing fungus concentration inside a methane fermentation tank, thereby accelerating a processing speed without using a concentrating apparatus or a carrier. <P>SOLUTION: In the methane fermentation processing method, the precipitation time for solid-liquid separation is provided by stopping an agitation apparatus 8 and an agitation apparatus 12 when mixing and agitating organic waste 4 and acid producing bacteria inside a first fermentation tank 1 and lower fatty acid and methane fermentation bacteria inside a second fermentation tank 2. By the means, the fungus concentration inside the first fermentation tank 1 and the second fermentation tank 2 is increased to improve the throughput. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic waste treatment apparatus, and more particularly to a methane fermentation treatment method centering on moss having a high solid content.

  At present, aerobic treatment, which is the mainstream wastewater treatment, has problems such as being unable to decompose difficult-to-decompose substances such as harmful volatile organic pollutants in addition to a large amount of excess sludge produced in the process. I have it.

  On the other hand, the anaerobic treatment is not only a general organic sludge substance in industrial wastewater, but also has a capability of decomposing toxic substances, so that the use value is increasing as a means for regenerating industrial wastewater. Furthermore, while the methane gas generated by fermentation is used as electricity and heat, the digested sludge after methane fermentation can be composted into fertilizer in the process of being discarded, or reused as solid fuel, dry sludge, etc. Yes and economical.

Methane fermentation is roughly divided into a two-stage biochemical reaction, a solubilization process by hydrolyzing bacteria and acid-producing bacteria, and a methane fermentation process by methane fermentation bacteria. High molecular organic compounds such as proteins, carbohydrates, and fats are first reduced in molecular weight by hydrolyzing bacteria to become higher fatty acids, amino acids, and saccharides. Next, it is decomposed into H ₂ , CO ₂ , and lower fatty acids (acetic acid, butyric acid, propionic acid, pyruvic acid, formic acid, lactic acid, succinic acid, etc.) by acid producing bacteria, etc. Generate.

  Thus, the solubilization process and the methane fermentation process have completely different types of active microorganisms, and the optimum pH value is different from 5.5 to 6.5 for the solubilization process and 7 to 8 for the methane production process. In many cases, a so-called solubilization tank and a methane fermentation tank are separated from each other and a method called a two-phase system is employed to increase fermentation efficiency (see, for example, Patent Document 1).

  In this patent document 1, in order to prevent the activity fall of methane fermentation bacteria, paying attention to pH, the process water return process is provided. In other words, it is an idea of improving the quality (activity) of bacteria, not the number of bacteria, and sufficiently solubilizing.

  In this way, if the fermentation liquid in the first fermentor is transferred to the second fermenter without sufficiently solubilizing, substances that cannot be decomposed by the methane fermentation bacteria accumulate in the second fermentor, and the methane fermentation apparatus fails. There is a fear.

  In the present specification, “solubilization” includes not only the reduction of molecular weight of organic substances by the action of microorganisms and the conversion to lower fatty acids, but also the refinement of solid particles by various physicochemical methods. It is out.

  In addition, various methods for improving the processing efficiency in methane fermentation have been studied.

  FIG. 3 shows an example in which sludge containing methane fermentation bacteria is concentrated in order to increase fermentation efficiency.

  Organic waste 102, mainly moss, is crushed by a crusher 101, and then introduced into a first fermenter 104 by a pump 105 and an inflow pipe 103, and mainly unspecified microorganisms present in the waste. It is solubilized under relatively mild conditions such as working and stirring, and produces lower fatty acids and low-molecular organic substances that are raw materials for methane fermentation.

  The slurry solubilized product is sent to the second fermenter 111 by the pump 110 and the inflow / outflow pipe 109, and biogas of 50 to 65% methane and about 35 to 50% carbon dioxide is produced by the action of the methane fermentation bacteria. Is done.

  In the second fermenter 111, various bacteria that solubilize in addition to methane fermentation bacteria coexist, so that organic substances other than lower fatty acids are also decomposed and converted into lower fatty acids to become raw materials for methane fermentation.

  The generated biogas is stored in the gas holder 113 via the gas outflow pipe 112 and then used mainly as fuel. In the second fermentation tank 111, sludge is extracted by the pump 116 and the outflow pipe 114 in accordance with the inflow amount of the solubilizing liquid containing a large amount of lower fatty acids, and the liquid level in the tank is kept constant.

  The extracted sludge is sent to a sludge concentrator 117, and usually a flocculant 118 is added to separate the sludge into concentrated sludge (mainly bacterial cells) and desorbed water. The desorbed water is sent from the desorbed water pipe 119 to the waste water treatment device 115 and discharged after being subjected to final treatment by an aerobic activated sludge method or the like.

  On the other hand, the concentrated sludge is returned to the second fermenter 111 via the pump 120 and the switching valve 121, and partly via the concentrated sludge return pipe 123, and used to increase the bacterial cell concentration in the tank. The remaining concentrated sludge is discharged from the sludge discharge pipe 124 as excess sludge. The surplus sludge is often returned to the first fermenter 104 and re-fermented, or composted or incinerated.

  FIG. 4 shows an example in which a carrier is used as a methane fermentation tank in order to increase fermentation efficiency.

  The fixed bed type methane fermentation tank 130 is provided with a carrier packed layer 131 for holding bacteria therein, and a solubilized liquid is circulated and decomposed to generate biogas. That is, in the fixed bed type methane fermenter 130, since the concentration of bacteria can be maintained without returning the concentrated sludge, a flocculant and a concentrating device are unnecessary, and the operation is easy.

  Usually, the liquid is circulated by the pump 133, and an upward flow is formed in the fixed bed methane fermentation tank 130, and the treated water 134 flows out from the treated water pipe 135 as an overflow. Since the solid content of the treated water 134 is low due to the filter action of the carrier packed bed 131, the treated water 134 can be treated by the wastewater treatment device 115 without being concentrated and separated.

  On the contrary, a thick sludge (bacteria and undecomposed fine organic matter) is accumulated in the fixed bed bottom 136 below the carrier packed bed 131. This is surplus by a valve 137 and a sludge discharge pipe 138 as necessary. Discharge as sludge.

  Thus, since the fixed bed type | mold methane fermenter 130 can hold | maintain a microbial cell with a high density | concentration with a support | carrier, a process speed is quick and can make a fermenter compact.

  However, when organic waste such as soot with a relatively high solid content compared to sludge and wastewater is targeted, clogging of the fixed bed with coarse particles becomes a problem. It is necessary to perform solid-liquid separation after solubilization to remove coarse solid particles or to prevent clogging. As means for promoting solubilization, means such as enzyme addition, alkali addition, mechanical pulverization, ozone, ultrasonic treatment, high temperature and high pressure treatment are used.

It is also known to provide a separation membrane for preventing the outflow of microorganisms such as methane fermentation bacteria in the methane fermentation tank (see, for example, Patent Document 2).
JP 2000-167487 A JP 2001-170631 A

  When improving the processing efficiency of methane fermentation, there are roughly two types of prevention, such as prevention of activity reduction of methane fermentation bacteria as in Patent Document 1 and securing of the number of bacteria as in FIG. 3, FIG. 4 and Patent Document 2. There is a way.

  However, in either case, there is a problem that the methane fermenter is enlarged or a new apparatus is required for returning or concentrating (including a membrane), and the concentration work is very complicated. It is required to simplify the work.

  Further, in the conventional methane fermentation treatment method and apparatus as shown in FIG. 4, when the cell concentration is increased using a carrier, high solubilization is necessary to prevent clogging of the fermenter, and the solubilization process is complicated. There is a problem of increasing the cell concentration without using a carrier.

  The present invention solves such a conventional problem, does not provide a new device, prevents outflow of bacteria from each tank, and efficiently eliminates bacteria in the methane fermentation tank without complicating the process. An object of the present invention is to provide a methane fermentation treatment method and apparatus capable of increasing the body concentration, the contact opportunity between methane fermentation bacteria and lower fatty acids, and increasing the fermentation treatment rate.

  In order to achieve the above object, the methane fermentation treatment method and apparatus of the present invention provide a precipitation time for stopping the agitation device and performing solid-liquid separation when mixing and stirring the lower fatty acid and methane fermentation bacteria in the methane fermentation tank. That's what it meant.

  By this means, a methane fermentation treatment method and apparatus capable of increasing the cell concentration in the methane fermentation tank and increasing the treatment speed without using a concentrator can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the methane fermentation processing method and apparatus which have the effect that the process speed can be raised by raising the fungal | concentration density | concentration in a methane fermentation tank, without using a concentration apparatus and a support | carrier can be provided.

  Moreover, the methane fermentation processing method and apparatus which can maintain the contact opportunity of a methane fermentation microbe and a lower fatty acid without complicating a process can be provided.

  The present invention includes a first fermenter that decomposes organic waste into lower fatty acids by acid-producing bacteria, a second fermenter that further decomposes lower fatty acids into methane and carbon dioxide gas by methane-fermenting bacteria, In the methane fermentation treatment method in which the two fermenters are equipped with a stirrer, and organic waste and acid-producing bacteria are mixed in the first fermentor, and the lower fatty acid and methane fermenter are mixed and stirred in the second fermenter. It is intended to provide a sedimentation time to increase the bacterial cell concentration in the sedimentation section that has been stopped and solid-liquid separated, and the processing speed can be increased by increasing the bacterial cell concentration in the methane fermentation tank without using a concentrator. Has an effect.

  In addition, the stirrer has a stirring blade, and by fixing the stirring blade in the solid-liquid separated precipitation part, organic waste, acid-producing bacteria, and lower fatty acid and methane fermentation bacteria are mixed and stirred in the precipitation part. It is possible to mix and stir organic waste and acid-producing bacteria, and lower fatty acids and methane-fermenting bacteria in the precipitation part.

  In addition, a first fermentor having an inflow pipe for organic waste, a second fermenter having an outlet for discharging scum and supernatant, and a lower fatty acid produced in the first fermenter are subjected to second fermentation. An outflow / inflow pipe that is transferred to the tank, a stirrer for stirring the first and second fermenters, and a gas outflow for collecting biogas generated in the first and second fermenters The stirrer in the second fermentor is equipped with a pipe and a gas holder, and consists of a stirrer blade and a motor that drives the stirrer blade. The counterflow is generated and the outlet of the inflow / outflow pipe is arranged below the stirring blade of the second fermenter, so that the lower fatty acid and the methane fermentation bacteria can be mixed and stirred efficiently in the precipitation part. It can be precipitated in a short time compared to stirring in the entire tank It has the effect of kill.

  Moreover, the stirring device is stopped to provide a sedimentation time for increasing the bacterial cell concentration in the sedimentation part separated by solid-liquid separation, and the processing speed is increased by increasing the bacterial cell concentration in the methane fermentation tank without using a concentrator. It has the effect that it can be raised.

  The stirring device in the first fermenter is composed of a stirring blade and a motor for driving the stirring blade, and the stirring blade in the first fermenter is fixed in the precipitation portion separated into solid and liquid and generates a downward flow by rotation. In addition, the outlet of the inflow pipe is disposed below the stirring blade of the first fermenter, and organic waste and acid-producing bacteria can be efficiently mixed and stirred in the precipitation part. It has the effect | action that it can be made to precipitate in a short time compared with stirring.

  Moreover, it is supposed that the outlet of the second fermenter is arranged at the liquid level of the second fermenter, and has an effect of keeping the fermentation liquid level in the second fermenter constant.

  Further, the outlet of the inflow / outflow pipe in the first fermenter is arranged at the liquid level of the first fermentor, and has an effect of keeping the fermentation liquid level in the first fermenter constant.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of a methane fermentation apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, the present methane fermentation treatment apparatus is configured such that the first fermenter 1 and the second fermenter 2 are provided in the same tank, and a partition plate 3 divides the first fermenter 1 and the second fermenter 2.

  The first fermenter 1 includes an inflow pipe 5 for inflowing the organic waste 4 crushed by the crusher, a stirring blade 6 for agitating the fermented liquid in the first fermenter, and a motor 7 for driving this. The stirring device 8 is configured.

  The stirring blade 6 provided in the first fermenter 1 is fixed in a precipitation portion in a state where the fermentation liquid in the first fermenter is solid-liquid separated, and a downward flow is generated from the stirring blade 6 during rotation. . The outlet of the inflow pipe 5 is fixed below the stirring blade 6 of the first fermenter 1.

  The first fermenter 1 is connected to the second fermenter 2 by an inflow / outflow pipe 9, and the inlet of the outflow / inflow pipe 9 arranged in the first fermenter 1 is at the level of the fermented liquid in the first fermenter. Fix it.

  The second fermenter 2 flows out the agitator blade 10 for agitating the fermented liquid in the second fermenter and the stirrer 12 composed of a motor 11 for starting it, and the waste liquid 13 which is the supernatant of the second fermenter. The outflow pipe 14 is constituted.

  The agitating blade 10 provided in the second fermenter 2 is fixed in a precipitation portion in a state where the fermentation liquid in the second fermenter is solid-liquid separated, and has a structure for generating a downward flow from the agitating blade 10 during rotation. . Moreover, the outlet of the outflow / inflow pipe 9 is fixed below the stirring blade 10 of the second fermenter 2, and the inlet of the outflow pipe is fixed at the liquid level of the fermentation liquid in the second fermenter to be retained.

  Moreover, the first fermenter 1 and the second fermenter 2 are provided with a gas outflow pipe 16 for transferring biogas 15 generated in each tank to a gas holder (not shown).

  The process of methane fermentation in the above configuration will be described in detail.

  The organic waste 4 centering on the straw is crushed to about 20 mm or less by a crusher, and flows into a position below the stirring blade 6 in the settling portion of the first fermenter 1 through the inflow pipe 5. At this time, in order to prevent the organic waste 4 from being mixed with the supernatant of the first fermenter 1 and flowing out into the second fermenter 2 as much as possible before the decomposition into lower fatty acids by the acid-producing bacteria is completed, The outlet of the inflow pipe 5 is preferably closer to the bottom surface of the first fermenter 1.

  When the pulverized organic waste 4 completes the flow into the first fermenter 1, the stirrer 8 composed of an appropriate stirrer blade 6 and a motor 7 installed in the first fermenter 1 is started at a low speed, Only the precipitation part is mixed and stirred without taking in the supernatant of the fermentation liquid in the first fermentor.

  Since the pulverized organic waste 4 that has flowed into the position below the stirring blade 6 in the settling part stays in the settling part, it is unspecified mainly with acid-producing bacteria compared to the entire stirring including the supernatant. The opportunity for contact with microorganisms increases and the precipitation time for solid-liquid separation also decreases.

  FIG. 2 shows an example of a proper stirring blade 6. FIG. 2A is a configuration diagram of the stirring blade 6 viewed from above, and FIG. 2B is a configuration diagram of the stirring blade 6 viewed from the side, in which the stirring blade 6 is configured by four blade plates 17. It is.

  When the fermenter is cylindrical, the blade diameter D is 40% of the diameter, the width W of the blade plate 17 is 10% of the fermenter diameter, and the blade 17 has an inclination angle θ of 25 °. When the stirring device 8 having the rotating device was rotated at 50 rpm so as to generate a downward flow from the stirring blade 6 in the settling portion, it was possible to maintain efficient stirring of the settling portion without taking in the supernatant liquid for about 5 minutes. It was confirmed.

  The numerical values of the stirring blades are examples of combinations, and there are many combinations that provide appropriate stirring strength by increasing or decreasing each numerical value.

  In actual stirring, the stirring device 8 was stopped after about 1 minute from the start of the stirring device 8, and the fermented liquid was allowed to settle for about 5 minutes until the next organic waste 4 was introduced. .

  When the entire fermentation broth is stirred, it takes time to separate the solid and liquid. However, when the stirring device 8 having the proper stirring blade 6 as described above is operated at a low rotation, stirring is performed only in the precipitation portion, so that the supernatant liquid is obtained. Thus, the precipitation part and the organic waste can be efficiently stirred in a short time without taking in water, and the efficiency of solid-liquid separation can be further increased.

  The organic waste 4 that has flowed into the first fermenter 1 is solubilized mainly under the relatively mild conditions such as the action of unspecified microorganisms present in the waste and the degree of stirring. Produces fatty acids and low molecular weight organic substances.

  Although the fermentation liquid in the first fermentation tank overflows to the second fermentation tank 2 due to the rise in the liquid level in the fermentation liquid in the first fermentation tank proportional to the amount of the organic waste 4 that has flowed into the first fermentation tank 1, As described above, because only the inside of the precipitation part is stirred, the solid-liquid separation of the fermentation liquid in the first fermenter is promoted even if the precipitation time is short, and the supernatant of the fermentation liquid in the first fermenter is mainly used for the overflow. It becomes.

  In the supernatant of the fermentation liquid in the first fermenter, there are few organic wastes that are not decomposed into lower fatty acids, and there are also fewer acid-producing bacteria, so the load on the second fermenter 2 can be suppressed, It is possible to prevent the acid-producing bacteria in one fermenter from flowing out to the second fermenter and increase the cell concentration of the acid-producing bacteria. That is, acid generation is promoted, and for the same processing amount, the processing time can be shortened or the processing tank can be downsized.

  Next, the solubilized liquid containing a large amount of lower fatty acids flows into the position below the stirring blade 10 in the precipitation part of the second fermenter 2 through the inflow / outflow pipe 9. At this time, as in the case of the first fermenter, in order to prevent the lower fatty acid from mixing with the supernatant of the second fermenter 2 and flowing out before the decomposition to the biogas 15 by the methane fermentation bacteria is completed as much as possible. The outlet of the inflow / outflow pipe 9 is preferably closer to the bottom surface of the second fermenter 2.

  When the inflow of the solubilized liquid containing a large amount of lower fatty acids into the second fermenter 2 is completed, the stirring device 12 including the appropriate stirring blade 10 and the motor 11 installed in the second fermenter 2 is started at a low speed. Then, only the precipitation part is mixed and stirred without taking in the supernatant of the fermentation liquid in the second fermenter, and the solubilized liquid containing a large amount of lower fatty acids and the chance of contact with unspecified microorganisms mainly composed of methane fermentation bacteria are increased.

  The solubilized liquid containing a large amount of lower fatty acid, which was flowed to a position below the stirring blade 10 in the precipitation part, moved mainly from the lower part in the precipitation part to the upper part by stirring. Contact with unspecified microorganisms.

  In addition, even when the inside of the precipitation part rises to the supernatant liquid side without contact, the lower fatty acid has a higher specific gravity than the supernatant liquid, so it stays at the boundary between the precipitation part and the supernatant liquid and is unspecified mainly consisting of methane fermentation There is an opportunity for contact with other microorganisms, and the contact opportunity increases compared to the whole agitation.

  Furthermore, the fermentation liquid in the second fermenter overflows out of the apparatus from the outflow pipe 14 due to the rise in the liquid level in the fermentation liquid in the second fermentor proportional to the amount of the solubilized liquid flowing into the second fermenter 2. However, as described above, because of stirring only in the precipitation part, solid-liquid separation of the fermentation liquid in the second fermenter is promoted even if the precipitation time is short, and what overflows is the supernatant of the fermentation liquid in the second fermenter Is the main.

  The supernatant of the fermented liquid in the second fermenter contains few lower fatty acids that have not been decomposed into methane-fermenting bacteria, and there are also few methane-fermenting bacteria. The cell concentration of methane fermentation bacteria can be increased.

  In other words, methane fermentation is promoted by increasing the cell concentration and increasing the chance of contact between methane-fermenting bacteria and lower fatty acids. For the same amount of processing, the processing time is shortened or the processing tank is downsized. realizable.

  When about 1 minute has elapsed since the start of the stirring device 12, the stirring device 12 is stopped, and the fermentation solution is allowed to settle for about 5 minutes until the next solubilizing solution is introduced. Here, the conditions of the suitable stirring blade 10 are the same as the stirring blade 6 of the said 1st fermenter.

  The solubilized liquid flowing into the second fermenter 2 is decomposed into biogas 15 containing 50 to 65% methane and about 35 to 50% carbon dioxide by the action of methane fermentation bacteria.

  The generated biogas 15 is stored in a gas holder (not shown) via the gas outflow pipe 16 and then used mainly as fuel.

  The supernatant liquid of the second fermenter 2 that has overflowed from the outflow pipe is processed as a waste liquid 13 by a wastewater treatment device without being concentrated and separated.

  Here, since the 2nd fermenter 2 is on the mere container which does not have structures, such as a fixed bed, the obstruction | occlusion by a coarse particle does not become a problem.

  As described above, the apparatus configuration and operation method of this embodiment promotes solubilization by increasing the cell concentration of acid-producing bacteria, so that the solubilization is promoted as in the methane fermentation method using a carrier. It is not necessary to add chemicals such as alkali or to install special devices such as ultrasonic waves and ozone, so that the solubilization process is simplified, and the cost of the device and the chemicals can be reduced and the labor can be saved.

  Moreover, solubilization and methane fermentation are promoted by preventing outflow of acid-producing bacteria and methane-fermenting bacteria, resulting in a high-speed processing system that does not require special equipment and sludge concentration and return, with the same amount of processing compared to conventional methane fermentation equipment. If it is, each fermenter can be reduced in size.

  Furthermore, the discharge amount of solubilization residue and methane fermentation sludge can be reduced, the amount of final processed products to be composted and incinerated can be reduced, and the amount of biogas generated can be increased accordingly.

  In addition, in the said embodiment, although division | segmentation of the tank by the partition plate 3 was made into the example, when a water level difference cannot be utilized with another tank, even if it uses a pump, the same effect is acquired.

  The methane fermentation treatment method and treatment apparatus according to the present invention can be applied to the treatment of organic waste centering on moss having a high solid content.

The block diagram of the methane fermentation system which concerns on 1st Embodiment of this invention. The block diagram of the stirring blade which concerns on 1st Embodiment of this invention ((a) The block diagram which looked at the stirring blade from the top, (b) The block diagram which looked at the stirring blade from the side) System diagram of conventional methane fermentation system System diagram of conventional methane fermentation system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st fermenter 2 2nd fermenter 3 Partition plate 4 Organic waste 5 Inflow pipe 6, 10 Stirring blade 7, 11 Motor 8, 12 Stirrer 9 Outflow inflow pipe 13 Waste liquid 14 Outflow pipe 15 Biogas 16 Gas outflow pipe 17 slats

Claims (7)

A first fermenter that decomposes organic waste into lower fatty acids by acid-producing bacteria, a second fermenter that further decomposes the lower fatty acids into methane and carbon dioxide by methane-fermenting bacteria, the first fermenter, and the first In a methane fermentation treatment method in which a stirrer is provided in a two-fermentor, and the organic waste and acid-producing bacteria are mixed and stirred in the first fermentor, and the lower fatty acid and methane-fermenting bacteria are mixed in the second fermenter. A methane fermentation treatment method characterized by providing a sedimentation time for stopping the agitator and increasing the cell concentration in the sedimentation part separated by solid-liquid separation. The stirrer has a stirring blade, and the agitation blade is fixed in a solid-liquid separated precipitation part, whereby the organic waste, acid-producing bacteria, and the lower fatty acid and methane fermentation bacteria are mixed and stirred in the precipitation part. The methane fermentation treatment method according to claim 1, wherein: A first fermenter having an inflow pipe for organic waste, a second fermenter having an outlet for discharging scum and supernatant liquid, and lower fatty acids produced in the first fermenter by the second fermentation An inflow / outflow pipe that flows into the tank, a stirring device for stirring the inside of the first fermenter and the second fermenter, and biogas generated in the first fermenter and the second fermenter are collected. The stirrer in the second fermenter comprises a stirrer blade and a motor that drives the stirrer, and the stirrer blade in the second fermenter is placed in a solid-liquid separated precipitation section. The methane fermentation treatment apparatus is characterized in that it is fixed and generates a downward flow by rotation, and an outlet of the inflow / outflow pipe is disposed below the stirring blade of the second fermentation tank. The methane fermentation treatment apparatus according to claim 3, wherein a precipitation time is provided for increasing the bacterial cell concentration in the precipitation portion where the stirring device is stopped and solid-liquid separated. The stirrer in the first fermenter comprises a stirrer blade and a motor for driving the stirrer blade. The stirrer blade in the first fermenter is fixed in a precipitation portion separated into solid and liquid and generates a downward flow by rotation. The methane fermentation treatment apparatus according to claim 3, wherein the outlet of the inflow pipe is disposed below the stirring blade of the first fermentation tank. The methane fermentation treatment apparatus according to any one of claims 3 to 5, wherein an outlet of the second fermenter is disposed at a liquid level of the second fermenter. The methane fermentation treatment apparatus according to any one of claims 3 to 6, wherein an outlet / outlet of the inflow / outflow pipe in the first fermenter is disposed at a liquid level of the first fermenter.

Images