WO2023195160A1

WO2023195160A1 - Organic waste treatment system and organic waste treatment method

Info

Publication number: WO2023195160A1
Application number: PCT/JP2022/017366
Authority: WO
Inventors: 恭平明田川; 典亮勝又; パトムアッタウィリヤヌパープ; 義規島田; 満片山; 章博大西
Original assignee: 三菱電機株式会社; 学校法人東京農業大学
Priority date: 2022-04-08
Filing date: 2022-04-08
Publication date: 2023-10-12
Also published as: JP7292535B1; JPWO2023195160A1

Abstract

This organic waste treatment system includes: a single treatment tank for treating organic waste using microorganisms; and a return means for returning liquid inside the treatment tank. The treatment tank includes: a solubilizing section for solubilizing organic waste by microorganisms and generating a first treated water; an acid generation section for generating an acid from the first treated water generated by the solubilization section and generating a second treated water; a solid-liquid separation section for separating the second treated water generated by the acid generation section into a solid component and a separation liquid; and a methane fermentation section for carrying out methane fermentation of the separation liquid separated by the solid-liquid separation section by methanogenic bacteria to convert the separation liquid into a third treated water and a gas. The return means has a first return means for returning the separation liquid separated by the solid-liquid separation section to the solubilization section.

Description

Organic waste treatment system and organic waste treatment method

The present disclosure relates to an organic waste treatment system and an organic waste treatment method.

Conventionally, organic waste containing solid organic matter such as sewage sludge, human waste, and food residue is fermented using microorganisms to produce methane gas or hydrogen gas, which is then converted into electrical energy using a generator. Efforts are being made to make effective use of it by converting it into heat or converting it into thermal energy using a heat exchanger.

The method of fermentation treatment of organic waste using microorganisms involves solubilizing organic waste, producing an organic acid or an acid such as acetic acid from the solubilized organic waste, and directly or hydrogen oxidation from the produced acid. It consists of a process that generates methane gas via gas. For example, Patent Document 1 discloses that the microorganisms that perform solubilization, acid production, and methane fermentation are separated and arranged to become the dominant species in each treatment tank, and sequence processing is performed. A high load and high speed methane fermentation system is disclosed.

JP2003-183908A

However, since the system disclosed in Patent Document 1 is composed of a plurality of processing tanks, a large number of pipes connecting the processing tanks or liquid feeding devices between the processing tanks are required, making the system complicated. Therefore, depending on the nature of the organic waste to be treated or the location where the system is applied, the system may become larger due to the influence of piping connecting each treatment tank or liquid delivery equipment between treatment tanks, resulting in increased equipment costs and operation management costs. There is a risk that it will become larger.

The present disclosure has been made to solve the above-mentioned problems, and provides an organic waste treatment system and organic waste treatment in which a high-load and high-speed methane fermentation system is constructed in a single treatment tank. The purpose is to provide a method.

An organic waste treatment system according to the present disclosure includes a single treatment tank for treating organic waste using microorganisms, and a return means for returning the liquid inside the treatment tank, The tank includes a solubilizing section that solubilizes the organic waste by the microorganisms to produce a first treated water, and a solubilizing section that generates an acid from the first treated water generated in the solubilizing section and a second treated water. an acid generation section that generates water; a solid-liquid separation section that separates the second treated water generated in the acid generation section into a solid content and a separated liquid; and the separated liquid separated in the solid-liquid separation section. and a methane fermentation section that performs methane fermentation using methane fermentation bacteria and converts it into third treated water and gas, and the return means returns the separated liquid separated in the solid-liquid separation section to the It has a first return means for returning it to the solubilization section.

The organic waste treatment method according to the present disclosure is a treatment method using the organic waste treatment system described above, in which the organic waste is solubilized by microorganisms to generate first treated water. a solubilization step, an acid generation step of generating an acid from the first treated water to generate second treated water, a solid-liquid separation step of separating the second treated water into a solid content and a separated liquid, and a solid-liquid separation step of separating the second treated water into solids and a separated liquid; A separated liquid return step of returning a predetermined amount of the separated liquid to the solubilization section out of the separated liquid separated in the liquid separation step, and a separation liquid returning step in which the separated liquid that is not returned to the solubilization section is treated with methane fermentation bacteria. The method includes a methane fermentation step in which methane is fermented and converted into third treated water and gas.

According to the present disclosure, since a return means is provided for returning the separated liquid separated in the solid-liquid separation section to the solubilization section, a high-load and high-speed methane fermentation system can be constructed with a single processing tank. .

1 is a schematic diagram showing the configuration of an organic waste treatment system according to Embodiment 1. FIG. 1 is a flowchart showing a method for treating organic waste according to Embodiment 1. FIG. FIG. 2 is a schematic diagram showing the configuration of an organic waste treatment system according to a second embodiment. 3 is a schematic diagram showing the configuration of an organic waste treatment system according to Embodiment 3. FIG. 7 is a flowchart showing a method for treating organic waste according to Embodiment 3. FIG.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will be omitted or simplified as appropriate. Furthermore, the shape, size, arrangement, etc. of the configurations shown in each figure can be changed as appropriate.

Embodiment 1.
FIG. 1 is a schematic diagram showing the configuration of an organic waste 7 treatment system 100 according to the first embodiment. As shown in FIG. 1, a treatment system 100 for organic waste 7 according to the first embodiment includes a single treatment tank 1 that processes organic waste 7 using microorganisms, and an interior of the treatment tank 1. and a first return means 2 for returning the liquid.

The processing tank 1 has a solubilization section 3, an acid generation section 4, a solid-liquid separation section 5, and a methane fermentation section 6 inside. In the solubilization section 3, the organic waste 7 is solubilized by microorganisms to generate first treated water 30. The acid generating section 4 generates an acid from the first treated water 30 generated in the solubilizing section 3 to generate second treated water 40 . In the solid-liquid separation section 5, the second treated water 40 generated in the acid generation section 4 is separated into a solid content 50 and a separated liquid 51. In the methane fermentation section 6, the separated liquid 51 separated in the solid-liquid separation section 5 is subjected to methane fermentation using methane-fermenting bacteria, and converted into third treated water 62 and gas 63. The methane fermentation section 6 includes a first transfer section 60 to which the separated liquid 51 separated by the solid-liquid separation section 5 is transferred, and a first storage section 61 in which methane fermentation bacteria are stored.

The solubilizing section 3 and the acid generating section 4 are separated by a first separation wall 10 that rises upward from the inner bottom surface of the processing tank 1. The solubilizing section 3 and the acid generating section 4 communicate above the first separation wall 10. The acid generation section 4 and the solid-liquid separation section 5 are separated by a second separation wall 11 that rises upward from the inner bottom surface of the processing tank 1 . The acid generation section 4 and the solid-liquid separation section 5 communicate with each other above the second separation wall 11. The solid-liquid separation section 5 and the first transfer section 60 are separated by a third separation wall 12 that rises upward from the inner bottom surface of the processing tank 1 . The solid-liquid separation section 5 and the first transfer section 60 communicate with each other above the third separation wall 12. The first transfer section 60 and the first storage section 61 are separated by a fourth separation wall 13 that protrudes downward from the top surface of the processing tank 1 . The first transfer section 60 and the first storage section 61 communicate with each other below the fourth separation wall 13.

In the solubilization section 3, the organic waste 7 to be treated is input, and the organic waste 7 is hydrolyzed by microorganisms to dissolve a portion of the solid content, thereby forming the first treated water 30. The microorganism is a hydrolyzing bacterium that hydrolyzes the organic waste 7. The first treated water 30 is mainly composed of hydrolyzing bacteria, solid content of the undecomposed organic waste 7, and solubilized components of the decomposed organic waste 7. Note that the solubilizing section 3 is provided with a first stirring mechanism 31 that stirs the first treated water 30. Thereby, solubilization in the solubilizing section 3 can be performed efficiently. The first stirring mechanism 31 is, for example, a stirrer, but may have any other configuration as long as it can stir the liquid.

In the acid generation section 4, the first treated water 30 flows over the first separation wall 10 and flows in, and is treated mainly by acid-producing bacteria that generate organic acids or acids such as acetic acid from the solubilized components of the organic waste 7. , second treated water 40 is formed. The second treated water 40 is mainly composed of acid-producing bacteria, solid content of the organic waste 7 that has not been decomposed, and acid, and also contains hydrolytic bacteria and the possible organic waste 7. Also includes solubilized components. The solubilized components of the organic waste 7 are components that have not been converted into acid in the acid generating section 4. Note that the acid generating section 4 is provided with a second stirring mechanism 41 that stirs the second treated water 40. Thereby, acid generation in the acid generation section 4 can be performed efficiently. The second stirring mechanism 41 is, for example, a stirrer, but may have any other configuration as long as it can stir the liquid.

In the solid-liquid separation section 5, the second treated water 40 flows over the second separation wall 11 and is separated into a solid content 50 and a separated liquid 51. Separation in the solid-liquid separation section 5 is performed in such a way that the solid content 50 is formed in the lower part and the separated liquid 51 is formed in the supernatant by using gravity sedimentation of the solid content 50 from the viewpoint of reducing the number of liquid feeding equipment. It is desirable to do so. Note that the solid-liquid separation unit 5 only needs to be able to separate the second treated water 40 into the solid content 50 and the separated liquid 51, and other separation methods may be used. For example, a filtration membrane, which is a known technology, is used as the solid-liquid separation section 5, and the second treated water 40 is passed through the filtration membrane using a liquid feeding device to separate it into solid content 50 and separated liquid 51. Good too. The solid content 50 is mainly composed of acid-producing bacteria and the solid content of the undecomposed organic waste 7, and also includes hydrolytic bacteria. The separation liquid 51 is mainly composed of acid, and also contains solubilized components of the organic waste 7. The solubilized components of the organic waste 7 are components that have not been converted into acid in the acid generating section 4.

In the methane fermentation section 6 , the separated liquid 51 that has flowed over the third separation wall 12 and flowed into the first transfer section 60 flows from the lower part of the first transfer section 60 to the lower part of the first storage section 61 . The separated liquid 51 is mainly treated by methane-fermenting bacteria that generate gas such as methane gas from acid, and is converted into third treated water 62 and gas 63. The third treated water 62 is discharged from the upper part of the first storage section 61 to the outside of the treatment tank 1 (arrow A in FIG. 1). The gas 63 is discharged from the upper part of the first storage section 61 to the outside of the processing tank 1 (arrow B in FIG. 1), is stored in a gas storage section (not shown), and is used for power generation or as a heat source. Note that it is desirable to use granules, which are self-granulated products, as the methane-fermenting bacteria. By using granules as methane fermenting bacteria, the organic waste 7 treatment system 100 can reduce the size of the methane fermentation section 6, thereby suppressing the enlargement of the entire system.

The methane fermentation section 6 is provided with a third stirring mechanism 64 that stirs the third treated water 62. This is to efficiently perform methane fermentation in the first storage section 61. The third stirring mechanism 64 connects the upper and lower parts of the first storage section 61, and includes a circulation piping section 64a through which the third treated water 62 flows, and a circulation piping section 64a that supplies the third treated water 62 to the first storage section through the circulation piping section 64a. It has a pump 64b that draws out the third treated water 62 from above the first storage section 61 and returns the third treated water 62 to the bottom of the first storage section 61. The third stirring mechanism 64 is provided outside the processing tank 1 . That is, the third stirring mechanism 64 is configured to stir the third treated water 62 in the first storage section 61 by circulating the third treated water 62 via the circulation piping section 64a. Note that the circulation piping section 64a may be configured to connect the upper part of the first storage section 61 and the first transfer section 60. Further, the third stirring mechanism 64 is not limited to the illustrated configuration, and may have any other configuration as long as it can stir the liquid.

The first return means 2 is for returning the separated liquid 51 separated from the second treated water 40 in the solid-liquid separation section 5 to the solubilization section 3. The first return means 2 connects the solid-liquid separation section 5 and the solubilization section 3, and includes a first return piping section 20 through which the separated liquid 51 flows, and extracts the separated liquid 51 through the first return piping section 20. The pump 21 includes a pump 21 that returns a predetermined amount of the separated liquid 51 to the solubilizing section 3.

As described above, in the solubilizing section 3, the organic waste 7 is solubilized by hydrolysis of microorganisms, which are hydrolyzing bacteria, and the first treated water 30 is formed. The first treated water 30 is mainly composed of hydrolyzing bacteria, solid content of the undecomposed organic waste 7, and solubilized components of the decomposed organic waste 7. The solubilized components are a wide variety of soluble organic substances depending on the type of hydrolyzing bacteria, and include, for example, proteins, sugars, and lipids. Soluble organic matter is a low molecular weight organic matter. The efficiency of this hydrolysis of the organic waste 7 into solubilized components decreases as the concentration of the solubilized components contained in the first treated water 30 increases, and the decomposition of the organic waste 7 by the hydrolytic bacteria decreases. It becomes difficult to progress. Therefore, in the organic waste 7 treatment system 100 according to the first embodiment, by returning a predetermined amount of the separated liquid 51 from the solid-liquid separation unit 5 to the solubilization unit 3, The concentration of solubilized components is adjusted. As described above, the separation liquid 51 is mainly composed of the acid generated in the acid generation section 4. That is, in the organic waste 7 treatment system 100 according to the first embodiment, by returning the separated liquid 51 to the solubilization section 3, the solubilized components in the first treated water 30 are diluted with acid. It can be flushed into the generation section 4, and the concentration of the solubilized components in the first treated water 30 can be adjusted to suppress a decrease in the efficiency of hydrolyzing the organic waste 7 into the solubilized components.

In a processing system configured with a plurality of processing tanks as in the prior art, piping connecting each processing tank or liquid feeding equipment between the processing tanks can be installed. The liquid feeding device is, for example, a pump or the like. The liquid feeding device is, for example, a liquid feeding device capable of adding clean water or treated water to the solubilization tank, and a liquid feeding device from the solubilization tank to the acid generation tank. In this conventional system, the amount of liquid such as clean water or treated water sent to the solubilization tank is adjusted by adjusting the power input to the liquid delivery device. The concentration of the solubilized component in the solubilization tank can be adjusted by setting a margin for the volume of the solubilization tank.

However, in a processing system configured with a single processing tank, unlike the conventional technology, there is no piping connecting each processing tank or liquid feeding equipment between the processing tanks. Therefore, in this system, when clean water or treated water is added to the solubilizing section 3, the added volume is filled with the acid generating section 4, which communicates with the solubilizing section 3, and the solid-liquid. It flows continuously to the separation section 5 and the methane fermentation section 6, and affects the processing time in each section of the solubilization section 3, acid generation section 4, and methane fermentation section 6. In other words, the concentration adjustment of the solubilized component and the processing time of each compartment influence each other. Therefore, in this system, it is not possible to both adjust the concentration of the solubilized component and secure processing time for the organic waste 7, and there is a risk that the processing of the organic waste 7 will fail.

On the other hand, in the organic waste 7 treatment system 100 according to the first embodiment, the separated liquid 51 of the solid-liquid separation section 5 is returned to the solubilization section 3, so that the solubilization section 3, the acid generation section 4, and The liquid is circulated in the solid-liquid separation section 5, and the increase or decrease in the amount of the separated liquid 51 is not directly affected by the treatment time to the solubilization section 3 and acid generation section 4. Note that the separated liquid 51 is mainly composed of acid, but also partially contains solubilized components of the organic waste 7 that have not been converted into acid in the acid generating section 4. Therefore, the separated liquid 51 is less effective in suppressing a decrease in the efficiency of hydrolysis from the organic waste 7 to the solubilized components, compared to clean water or treated water that does not contain the solubilized components. However, in the organic waste 7 treatment system 100 according to the first embodiment, the concentration of the solubilized components is adjusted by returning the separated liquid 51 to the solubilization section 3, so that the efficiency of hydrolysis can be sufficiently improved. The reduction can be suppressed, and a system including a single processing tank 1 can be established.

The first return means 2 is located at a position immediately before the separated liquid 51 flows into the first transfer section 60, and is configured to pull out the separated liquid 51 from above the solid-liquid separation section 5 and return it to the solubilization section 3. It is desirable to do so. In the solid-liquid separation section 5, a part of the solubilized components of the organic waste 7 that have not been converted into acids in the acid generation section 4 are converted into acids. Therefore, by withdrawing the separated liquid 51 from the end of the solid-liquid separation section 5, that is, from the position immediately before the separated liquid 51 flows into the first transfer section 60, it is possible to prevent the separated liquid 51 from becoming an acid in the acid generating section 4. The amount of the solubilized components of the organic waste 7 can be reduced, and the effect of suppressing a decrease in the efficiency of hydrolysis from the organic waste 7 to the solubilized components can be easily obtained. Moreover, the reason why the solid content 50 should be drawn from above the solid-liquid separation part 5 is that if it is not above the solid-liquid separation part 5, the solid content 50 may flow into the first return piping part 20, and the first return piping part 20 This is because there is a risk of blockage within 50 minutes.

Moreover, in the generation of the first treated water 30, the second treated water 40, and the third treated water 62, it is known that the generation of the first treated water 30 is the most rate-limiting. Therefore, the amount of organic waste 7 to be input into the treatment tank 1 is determined by the weight of the organic waste 7 per effective volume of the solubilization section 3 or the COD (which is an index of the amount of organic matter in the organic waste 7). It is desirable to set the amount using the chemical oxygen demand) amount. The amount of organic waste 7 to be input into the treatment tank 1 is determined by the type of organic waste 7 and is not particularly limited, but if the weight of organic waste 7 is 20 kg/m ³ days or more. , and 200 kg/m ³ ·day or less, more preferably 50 kg/m ³ ·day or more and 100 kg/m ³ ·day or less. If the weight of the organic waste 7 is smaller than the above range, there is a risk that the system will become excessively large compared to the amount of organic waste 7 to be input. On the other hand, if the weight of the organic waste 7 is larger than the above range, the organic waste 7 cannot be properly treated in the treatment tank 1, and the third treated water 62 discharged outside the treatment tank 1 is left untreated. There is a risk that the amount of solid content 50 will increase as the solubilizing component or acid of decomposition is included. Furthermore, for the same reason, the COD amount is preferably 5 kg/m ³ ·day or more and 40 kg/m ³ ·day or less, and more specifically, 12.5 kg/m 3·day or more and 25 kg/m ³ ·day or more. More preferably, it is less than m ³ days.

The concentration of the solubilized component in the first treated water 30 that is adjusted in the solubilization section 3 can be set as appropriate depending on the type of organic waste 7 or the type of hydrolyzing bacteria. However, it is desirable to understand and set the concentration during the acclimatization of the microorganisms, which is carried out at the time of starting up the system. The specific details of setting the concentration of the solubilized component by acclimatization are as follows.

The methane-fermenting bacteria in the methane-fermenting section 6 cannot proliferate without the acid produced by the acid-producing bacteria in the acid-producing section 4. Furthermore, acid-producing bacteria cannot proliferate without solubilized components produced from organic waste 7 by hydrolyzing bacteria in solubilizing section 3 . Therefore, start by acclimating the hydrolytic bacteria. First, hydrolytic bacteria prepared by culturing in advance in laboratory equipment is introduced into the solubilization section 3, and organic waste 7 is introduced into the solubilization section 3 in an amount smaller than the prescribed input amount. . In the process of gradually increasing the input amount of organic waste 7 toward the specified input amount, the degree of hydrolysis progress is determined by changing the input amount of organic waste 7 and the first treated water 30. The concentration of the solubilized component in the first treated water 30 is determined by the weight of the solid content of the organic waste 7 that remains without being decomposed. Thereby, it is possible to grasp the concentration of the solubilized component in the first treated water 30 at which hydrolysis proceeds efficiently. The concentration of the solubilized component at this time may be determined by directly measuring a specific substance such as protein or sugar. It should be noted that evaluation using COD is preferable because it is possible to integrate a wide variety of soluble organic substances depending on the type of hydrolyzing bacteria and use it as an index of the concentration of the solubilized component. By doing so, the amount of the separated liquid 51 returned to the solubilization section 3 can be adjusted so that the concentration of the solubilized component in the first treated water 30 becomes the set value.

The concentration of the solubilized components in the first treated water 30 is actually set by adjusting the amount of separated liquid 51 returned to the solubilization section 3, and controlling the degree of progress of hydrolysis by adjusting the amount of organic waste. It is also possible to do this indirectly by determining the input amount of the organic waste 7 and the weight of "the solid content of the organic waste 7 that remains without being decomposed" in the first treated water 30. The operation of the first return means 2 may be carried out continuously or intermittently in accordance with the timing of increase in the concentration of the solubilized component in the first treated water 30 according to the progress of hydrolysis by the hydrolyzing bacteria. It may be carried out separately.

Furthermore, the type of microorganism is not particularly limited, but for example, a dominant microorganism may be used. This is because the dominant microorganism is a microorganism species that can use the organic waste 7 as a substrate depending on the type of organic waste 7 during the habituation of the microorganism. Specifically, in the solubilization section 3, depending on the type of organic waste 7, hydrolytic bacteria that can use the organic waste 7 as a substrate proliferate and become the dominant species. Subsequently, in the acid generation section 4, depending on the type of organic waste 7, acid-producing bacteria that can use the solubilized components generated from the organic waste 7 as a substrate are the dominant species. Become. In the methane fermentation section 6, depending on the type of organic waste 7, methane-fermenting bacteria, which can use as a substrate the acid produced by the acid-producing bacteria from the solubilized components, become the dominant species.

FIG. 2 is a flowchart showing a method for treating organic waste 7 according to the first embodiment. The method for treating organic waste 7 according to the first embodiment uses the treatment system 100 described above. The method for treating organic waste 7 includes a solubilization step (step S1), an acid generation step (step S2), a solid-liquid separation step (step S3), a separated liquid return step (step S4), and a methane fermentation step. step (step S5).

In the solubilization step (step S1), the organic waste 7 to be treated, which has been input into the solubilization section 3, is solubilized by microorganisms to generate the first treated water 30. Specifically, the first treated water 30 is formed by hydrolyzing the organic waste 7 by the hydrolyzing bacteria in the solubilizing section 3 and dissolving a part of the solid content in the organic waste 7. . The first treated water 30 is mainly composed of hydrolyzing bacteria, solid content of the undecomposed organic waste 7, and solubilized components of the decomposed organic waste 7.

Next, in the acid generation step (step S2), acid is generated from the first treated water 30 that has flowed over the first separation wall 10 and flowed into the acid generation section 4, and the second treated water 40 is generated. Specifically, the second treated water 40 is mainly formed by acid-producing bacteria that produce organic acids or acids such as acetic acid from the solubilized components of the organic waste 7 . The second treated water 40 is mainly composed of acid-producing bacteria, the solid content of the organic waste 7 that has not been decomposed, and acids, and also contains hydrolytic bacteria and solubilized components of the organic waste 7. included. The solubilized component is a component that did not become an acid in the acid generating section 4.

Next, in the solid-liquid separation step (step S3), the second treated water 40 that has flown over the second separation wall 11 and flowed into the solid-liquid separation section 5 is separated into solid content 50 and separated liquid 51. The solid content 50 is mainly composed of acid-producing bacteria and the solid content of the organic waste 7 that has not been decomposed, and also includes hydrolytic bacteria. The separation liquid 51 is mainly composed of acid, and also contains solubilized components of the organic waste 7.

Next, in the separated liquid return step (step S4), a predetermined amount of the separated liquid 51 of the separated liquid 51 separated in the solid-liquid separation step is returned to the solubilization section 3. Thereby, the concentration of the solubilized components in the first treated water 30 can be adjusted, and a decrease in the efficiency of hydrolysis from the organic waste 7 to the solubilized components can be suppressed.

The methane fermentation step (step S5) is performed in parallel with the separated liquid return step (step S4). In the methane fermentation step (step S5), the separated liquid 51 that has overflowed the third separation wall 12 and flowed into the first storage section 61 of the methane fermentation section 6 is used as a source of methane fermentation bacteria that mainly produces gas such as methane gas from acid. The third treated water 62 and gas 63 are converted into third treated water 62 and gas 63.

As described above, the organic waste 7 treatment system 100 according to the first embodiment includes a single treatment tank 1 that processes the organic waste 7 using microorganisms, and a liquid inside the treatment tank 1. and a first return means 2 for returning the. The treatment tank 1 includes a solubilization unit 3 that solubilizes organic waste 7 with microorganisms to generate a first treated water 30, and generates acid from the first treated water 30 generated in the solubilization unit 3. An acid generation section 4 that generates second treated water 40, a solid-liquid separation section 5 that separates the second treated water 40 generated in the acid generation section 4 into a solid content 50 and a separated liquid 51, and a solid-liquid separation section. It has a methane fermentation section 6 which performs methane fermentation on the separated liquid 51 separated in step 5 using methane fermentation bacteria and converts it into third treated water 62 and gas 63. The first return means 2 is configured to return the separated liquid 51 separated by the solid-liquid separation section 5 to the solubilization section 3.

That is, in the organic waste 7 treatment system 100 according to the first embodiment, the separated liquid 51 of the solid-liquid separation section 5 is returned to the solubilization section 3, so that the solubilization section 3, the acid generation section 4, and Since the liquid is circulated in the solid-liquid separation section 5, the increase or decrease in the amount of the separated liquid 51 is not directly affected by the processing time of the solubilization section 3 and the acid generation section 4. Since the concentration of the solubilized component can be adjusted using the separated liquid 51 returned to the solubilization section 3, a decrease in the efficiency of hydrolysis can be suppressed. Therefore, in the organic waste 7 treatment system 100 according to the first embodiment, a high-load and high-speed methane fermentation system that had to be configured with a plurality of treatment tanks can be constructed with a single treatment tank 1. , the entire system can be downsized, and equipment costs and operation management costs can be suppressed.

Embodiment 2.
Next, with reference to FIG. 3, an organic waste 7 treatment system 101 according to the second embodiment will be described. FIG. 3 is a schematic diagram showing the configuration of a processing system 101 for organic waste 7 according to the second embodiment. Note that the same components as those of the organic waste 7 treatment system 100 described in Embodiment 1 are given the same reference numerals, and the description thereof will be omitted as appropriate.

In the organic waste 7 treatment system 101 according to the second embodiment, as shown in FIG. A holding member 35 for holding 34 is provided. The solubilization unit 3 includes a second storage unit 32 in which hydrolysis bacteria, which are microorganisms, are stored, and a first treated water that is disposed below the second storage unit 32 and that is generated by solubilizing in the second storage unit 32. 30. The holding member 35 is provided between the second storage section 32 and the second transfer section 33, holds the deposit 34, and partitions the second storage section 32 and the second transfer section 33. The solubilizing section 3 and the acid generating section 4 are separated by a fifth separation wall 14 that protrudes downward from the top surface of the processing tank 1. The second transfer section 33 and the acid generation section 4 communicate with each other below the fifth separation wall 14 . The other points have the same configuration as the organic waste 7 treatment system 100 of the first embodiment.

In the organic waste 7 treatment system 101 according to the second embodiment, by putting the organic waste 7 into the second storage section 32, the hydrolyzing bacteria of the deposit 34 hydrate the organic waste 7. Disassemble. The first stirring mechanism 31 is installed so as to be able to stir the inside of the second storage section 32. The deposit 34 is held inside the second storage section 32 by a holding member 35 .

In the second storage section 32, the organic waste 7 is hydrolyzed by hydrolyzing bacteria, a part of the solid content is dissolved, and the first treated water 30 is formed. The holding member 35 is configured to have a property of not allowing solid components to pass therethrough, but allowing liquefied solubilized components to pass therethrough. Therefore, the first treated water 30 is mainly composed of the solubilized components of the decomposed organic waste 7 and flows into the second transfer section 33 by the holding member 35 . That is, in the organic waste 7 treatment system 101 according to the second embodiment, unlike the configuration of the first embodiment, the deposit 34 to which hydrolytic bacteria have adhered and the organic waste 7 that has not been decomposed are removed. The solid content remains in the second storage section 32 by the holding member 35. Note that the first treated water 30 that has flowed into the second transfer section 33 flows into the acid generation section 4 .

In the acid generation section 4, the first treated water 30 flows in from the second transfer section 33, and is treated with the second treatment water by acid-producing bacteria that mainly generate organic acids or acids such as acetic acid from the solubilized components of the organic waste 7. Treated water 40 is formed. The second treated water 40 in the second embodiment differs from the first embodiment in that it is mainly composed of acid-producing bacteria and acids, and also contains solubilized components of the organic waste 7. The solubilized component is a component that did not become an acid in the acid generating section 4.

In the solid-liquid separation section 5, the second treated water 40 flows over the second separation wall 11 and is separated into solid content 50 and separated liquid 51. Unlike the first embodiment, the solid content 50 in the second embodiment is mainly composed of acid-producing bacteria. Further, the separation liquid 51 is mainly composed of acid, and also contains a solubilized component of the organic waste 7. The solubilized component is a component that did not become an acid in the acid generating section 4. The separated liquid 51 flows over the third separation wall 12 and is treated by methane fermentation bacteria in the methane fermentation section 6, and converted into third treated water 62 and gas 63.

In the organic waste 7 treatment system 101 according to the second embodiment, since the deposit 34 to which the hydrolytic bacteria have adhered is held inside the second storage section 32 by the holding member 35, the hydrolytic bacteria are 1 can be prevented from being contained in the treated water 30 and flowing out from the solubilizing section 3. Therefore, the organic waste 7 treatment system 101 according to the second embodiment can easily maintain a stable amount of hydrolyzing bacteria, can proceed with hydrolysis more efficiently, and can Since there is no need to consider the amount of bacteria, the solubilizing section 3 can be made smaller in size compared to the configuration of the first embodiment.

In the organic waste 7 treatment system 101 according to the second embodiment, a predetermined amount of the separated liquid 51 is returned to the second storage section 32 by the first return means 2, and the separated liquid 51 is solubilized in the first treated water 30. The concentration of the ingredients is adjusted. As with the first embodiment, the return amount of the separated liquid 51 can be set as appropriate depending on the type of organic waste 7 or the type of hydrolyzing bacteria. Note that it is desirable to determine and set the return amount of the separated liquid 51 during the acclimatization of microorganisms, which is performed at the time of starting up the system.

In the organic waste 7 treatment system 101 according to the second embodiment, the degree of progress of hydrolysis is determined based on the input amount of the organic waste 7 and the organic waste remaining in the second storage section 32 without being decomposed. The concentration of the solubilized component in the first treated water 30 is determined based on the weight of the solid content of the waste 7. Thereby, it is possible to grasp the concentration of the solubilized component in the first treated water 30 at which hydrolysis proceeds efficiently. The concentration of the solubilized component at this time may be determined by directly measuring a specific substance such as protein or sugar. However, if COD is used, a wide variety of soluble organic substances depending on the type of hydrolyzing bacteria can be integrated and used as an indicator of the concentration of solubilized components, so it is desirable to evaluate using COD.

By doing so, in the organic waste 7 treatment system 101 according to the second embodiment, the amount of the separated liquid 51 to be returned is adjusted so that the concentration of the solubilized component in the first treated water 30 becomes the set value. can be adjusted. Note that the concentration of the solubilized components in the first treated water 30 is determined by controlling the degree of progress of hydrolysis while adjusting the amount of separated liquid 51 returned to the solubilization section 3. It is also possible to set it indirectly by determining the input amount and the weight of "the solid content of the organic waste 7 remaining in the second storage section 32 without being decomposed."

Note that it is preferable that the first return means 2 includes a spraying means 22 for spraying the separated liquid 51 onto the deposits 34. The spraying means 22 is, for example, a water nozzle. Thereby, the solubilized component adsorbed on the surface of the deposit 34 can be efficiently flowed to the second transfer section 33, and a decrease in the efficiency of hydrolysis caused by the hydrolysis bacteria attached to the deposit 34 can be suppressed.

The holding member 35 allows the first treated water 30 to flow into the second transfer section 33 and allows the deposits 34 and the solid content of the undecomposed organic waste 7 to remain in the second storage section 32. It's fine as long as it's possible. For the holding member 35, for example, a commercially available filter or mesh can be used. Regarding the pore diameter, it is preferably 0.5 mm or more and 5 mm or less, and more preferably 1 mm or more and 3 mm or less. If the holding member 35 has a hole diameter smaller than this range, clogging with the organic waste 7 and the deposits 34 will easily occur. On the other hand, if the pore diameter of the holding member 35 is larger than this range, there is a high risk that the solid content of the organic waste 7 that has not been solubilized will flow out to the second transfer section 33.

The deposit 34 only needs to be able to retain hydrolytic bacteria, which are microorganisms. For the attachment 34, a known material capable of retaining microorganisms, such as a carrier or a straw, can be used. However, since it is desirable for the deposit 34 to have a large surface property capable of retaining microorganisms, it is desirable to use a material with a three-dimensional structure such as a porous material. The size of the deposit 34 may be smaller than the hole diameter of the holding member 35 depending on the hole diameter of the holding member 35 .

Next, a method for treating organic waste 7 according to the second embodiment will be described with reference to FIG. 2. The method for treating organic waste 7 according to the second embodiment uses the treatment system 101 described above. The method for treating organic waste 7 according to the second embodiment includes the solubilization step (step S1), the acid generation step (step S2), and the solid-liquid separation step (same as the structure of the first embodiment). Step S3), a separated liquid return step (Step S4), and a methane fermentation step (Step S5).

In the solubilization step (step S1), the organic waste 7 to be treated that has been input into the solubilization section 3 is solubilized by the microorganisms attached to the deposits 34, and the first treated water 30 is generated. Specifically, the organic waste 7 is hydrolyzed by the hydrolyzing bacteria attached to the deposit 34 to dissolve a part of the solid content in the organic waste 7, thereby converting the first treated water 30 into the first treated water 30. Form. The deposit 34 to which the hydrolytic bacteria have adhered is held inside the second storage section 32 by the holding member 35 . Therefore, hydrolysis bacteria can be prevented from being contained in the first treated water 30 and flowing out from the solubilizing section 3. The first treated water 30 is mainly composed of solubilized components of the decomposed organic waste 7.

Next, in the acid generation step (step S2), acid is generated from the first treated water 30 that has flowed over the first separation wall 10 and flowed into the acid generation section 4, and the second treated water 40 is generated. Specifically, the second treated water 40 is mainly formed by acid-producing bacteria that produce organic acids or acids such as acetic acid from the solubilized components of the organic waste 7 . The second treated water 40 is mainly composed of acid-producing bacteria and acids, and also contains solubilized components of the organic waste 7. The solubilized component is a component that did not become an acid in the acid generating section 4.

Next, in the solid-liquid separation step (step S3), the second treated water 40 that has flown over the second separation wall 11 and flowed into the solid-liquid separation section 5 is separated into solid content 50 and separated liquid 51. The solid content 50 is mainly composed of acid-producing bacteria. The separation liquid 51 is mainly composed of acid, and also contains solubilized components of the organic waste 7.

Next, in the separated liquid return step (step S4), a predetermined amount of the separated liquid 51 of the separated liquid 51 separated in the solid-liquid separation step is returned to the solubilization section 3. Thereby, the concentration of the solubilized components in the first treated water 30 can be adjusted, and a decrease in the efficiency of hydrolysis from the organic waste 7 to the solubilized components can be suppressed. Further, in the separated liquid return step (step S4), when the separated liquid 51 is returned to the solubilization section 3, the separated liquid 51 is sprayed onto the deposit 34 using the spraying means 22. Thereby, the solubilized component adsorbed on the surface of the deposit 34 can be efficiently flowed to the second transfer section 33, and a decrease in the efficiency of hydrolysis caused by the hydrolysis bacteria attached to the deposit 34 can be suppressed.

The methane fermentation step (step S5) is performed in parallel with the separated liquid return step (step S4). In the methane fermentation step (step S5), the separated liquid 51 that has not been returned to the solubilization section 3 and has flowed over the third separation wall 12 and into the first storage section 61 of the methane fermentation section 6 is mainly treated with methane-fermenting bacteria that generate gas such as methane gas from acid, and converted into third treated water 62 and gas 63.

Embodiment 3.
Next, with reference to FIG. 4, a processing system 102 for organic waste 7 according to the third embodiment will be described. FIG. 4 is a schematic diagram showing the configuration of the organic waste 7 treatment system 102 according to the third embodiment. Note that the same components as those of the organic waste 7

treatment systems

100 and 101 described in Embodiments 1 and 2 are given the same reference numerals, and the description thereof will be omitted as appropriate.

As shown in FIG. 4, in the organic waste 7 treatment system 102 according to the third embodiment, in addition to the configuration of the organic waste 7 treatment system 101 of the second embodiment, a methane fermentation unit 6 It is characterized by having a second return means 8 for returning the third treated water 62 to the acid generation section 4. The second return means 8 includes a second return pipe section 80 branched from the circulation pipe section 64a and connected below the acid generating section 4, and a solenoid valve 81 and a flow rate control valve provided in the second return pipe section 80. 82. The second return piping section 80 is connected to the circulation piping section 64a via a branch section 64c provided in the circulation piping section 64a. A timer 83 is connected to the solenoid valve 81 . The other points have the same configuration as the organic waste 7 treatment system 101 of the second embodiment.

In the organic waste 7 treatment system 102 according to the third embodiment, in parallel with the first return means 2 returning the separated liquid 51 of the solid-liquid separation section 5 to the solubilization section 3, the second return means 2 returns the separated liquid 51 to the solubilization section 3. The means 8 returns the third treated water 62 of the methane fermentation section 6 to the acid generation section 4. The third treated water 62 is returned from the methane fermentation section 6 to the acid generation section 4 through the second return piping section 80 using the third stirring mechanism 64 . Therefore, there is no need to provide additional liquid feeding equipment. Note that the means for returning the third treated water 62 of the methane fermentation section 6 to the acid generation section 4 is not limited to the configuration using the third stirring mechanism 64, and may be of other forms.

The third stirring mechanism 64 basically operates continuously and stirs the third treated water 62 of the methane fermentation section 6. Therefore, the return time and return timing of the third treated water 62 are controlled by the time when the solenoid valve 81 is opened and the timing when the solenoid valve 81 is opened and closed, which is controlled by the timer 83. Further, the return flow rate of the third treated water 62 is adjusted by a flow rate adjustment valve 82.

By the way, in Embodiment 1 and Embodiment 2, a single treatment tank 1 is used, and the inside of the treatment tank 1 includes a solubilization section 3, an acid generation section 4, a solid-liquid separation section 5, and a methane fermentation section. It is divided into 6. Therefore, the processing time of the separated liquid 51 in the methane fermentation section 6 is determined by the amount of solubilized components of the organic waste 7 in the first treated water 30 generated in the solubilization section 3. That is, the amount of organic waste 7 input into the solubilization section 3 and the processing time of the separated liquid 51 in the methane fermentation section 6 have a relationship, and cannot be managed independently.

By adjusting the processing time of the separated liquid 51 in the methane fermentation section 6 to an appropriate value, methane fermentation can proceed efficiently. However, as described above, there is a relationship between the amount of organic waste 7 input into the solubilization section 3 and the processing time of the separated liquid 51 in the methane fermentation section 6. In this case, the processing time of the separated liquid 51 in the methane fermentation section 6 may vary depending on the operational circumstances of the system installation site, such as when the input amount of organic waste 7 varies greatly. If the amount of processing time increases or decreases, there is a risk that it will not be possible to secure an appropriate processing time.

On the other hand, in the organic waste 7 treatment system 102 according to the third embodiment, in parallel with returning the separated liquid 51 of the solid-liquid separation section 5 to the solubilization section 3 by the first return means 2, It is possible to return the third treated water 62 of the methane fermentation section 6 to the acid generation section 4 by the second return means 8. Further, the acid generation section 4, the solid-liquid separation section 5, and the methane fermentation section 6 are in communication. Thereby, the amount of the third treated water 62 returned to the acid generating section 4 can be adjusted, so the processing time of the separated liquid 51 in the methane fermentation section 6 can be adjusted. Therefore, the processing time of the separated liquid 51 in the methane fermentation section 6 can be adjusted to an appropriate value independently of the input amount of organic waste 7, allowing the methane fermentation to proceed more efficiently and improving system operation. can be stabilized.

The processing time of the separated liquid 51 in the methane fermentation section 6 is appropriately set depending on the type of organic waste 7 and the type of separated liquid 51. Note that the processing time is not particularly limited, but is preferably, for example, one day or more and ten days or less, and more preferably three days or more and six days or less. If the treatment time is shorter than the above range, the separated liquid 51 will not undergo sufficient methane fermentation, the amount of gas 63 will decrease, and the gas 63 may be contained in the third treated water 62 discharged to the outside of the treatment tank 1. There is a risk that ingredients may be included. On the other hand, if the processing time is longer than the above range, the growth of methane-fermenting bacteria will be insufficient, the separated liquid 51 will not be sufficiently methane-fermented, the amount of gas 63 will decrease, and it will be discharged to the outside of the processing tank 1. There is a possibility that components that can become gas 63 may be contained in the third treated water 62.

The return flow rate of the third treated water 62 adjusted by the flow rate adjustment valve 82 is appropriately set according to the pipe diameter of the second return pipe section 80. Although the return flow rate is not particularly limited, it is generally desirable to set it so that the flow velocity in the pipe of the second return pipe section 80 is 1 or more and 3 m/s or less. Further, the opening time of the electromagnetic valve 81 controlled by the timer 83 may be determined according to the return flow rate of the third treated water 62 so that the processing time of the separated liquid 51 in the methane fermentation section 6 falls within the above range. good. The timing of opening and closing is appropriately set, such as once every hour.

Note that it is desirable that the means for returning the third treated water 62 of the methane fermentation section 6 to the acid generation section 4 utilizes the third treated water 62 above the methane fermentation section 6. In the methane fermentation section 6, the concentration of methane fermenting bacteria decreases from the bottom to the top. Therefore, if the methane fermenting bacteria are not the upper methane fermenting bacteria, there is a high risk that the methane fermenting bacteria will flow into the acid generating section 4 via the second return piping section 80 and the methane fermenting bacteria will die. Further, it is desirable that the methane fermentation section 6 is provided with a bacteria blocking mechanism 65 such as a baffle or a mesh. By providing the bacteria blocking mechanism 65, it is possible to suppress methane-fermenting bacteria from flowing into the acid generating section 4 via the second return piping section 80. However, the germ blocking mechanism 65 does not necessarily need to be provided and may be omitted.

FIG. 5 is a flowchart showing a method for treating organic waste 7 according to the third embodiment. The method for treating organic waste 7 according to the third embodiment uses the above-described treatment system 102. The method for treating organic waste 7 according to Embodiment 3 is the same as the method for treating organic waste 7 according to Embodiment 2 described above, except that it includes a solution return step (step S6). be. Therefore, the solubilization step (step S1), the acid generation step (step S2), the solid-liquid separation step (step S3), and the separated liquid return step (step S4) and the methane fermentation step (step S5) will not be described.

The solution return process (step S6) is performed in parallel with the separated liquid return process (step S4) after converting the separated liquid 51 into the third treated water 62 and gas 63 in the methane fermentation process (step S5). . In the solution return process (step S6), the third treated water 62 produced in the methane fermentation process (step S5) is returned to the acid generation section 4. As a result, the processing time of the separated liquid 51 in the methane fermentation section 6 can be adjusted, so that the processing time of the separated liquid 51 in the methane fermentation section 6 can be adjusted to an appropriate value independently of the input amount of organic waste 7. This allows methane fermentation to proceed more efficiently and stabilizes system operation.

Although not shown in the drawings, the second return means 8, which is a feature of the organic waste 7 treatment system 102 and the organic waste 7 treatment method according to the third embodiment, is the same as that of the first embodiment. It may be applied to the configuration of

Although the organic waste 7 treatment system (100 to 102) and the organic waste 7 treatment method have been described above based on the embodiments, they are not limited to the configurations of the embodiments described above. For example, the organic waste 7 treatment system (100 to 102) is not limited to the configuration shown, and some components may be omitted or other components may be included. In short, the organic waste 7 treatment system (100 to 102) and the organic waste 7 treatment method are within the range of design changes and application variations that would normally be made by a person skilled in the art without departing from the technical concept thereof. This includes:

1 treatment tank, 2 first return means, 3 solubilization section, 4 acid generation section, 5 solid-liquid separation section, 6 methane fermentation section, 7 organic waste, 8 second return means, 10 first separation wall, 11 Second separation wall, 12 Third separation wall, 13 Fourth separation wall, 14 Fifth separation wall, 20 First return piping section, 21 Pump, 22 Spreading means, 30 First treated water, 31 First stirring mechanism, 32 2nd storage section, 33 2nd transfer section, 34 deposits, 35 holding member, 40 2nd treated water, 41 2nd stirring mechanism, 50 solid content, 51 separated liquid, 60 1st transfer section, 61 1st storage section , 62 Third treated water, 63 Gas, 64 Third stirring mechanism, 64a Circulation piping section, 64b Pump, 64c Branch section, 65 Bacteria isolation mechanism, 80 Second return piping section, 81 Solenoid valve, 82 Flow rate control valve, 83 Timer, 100, 101, 102 processing system.

Claims

a single treatment tank that processes organic waste using microorganisms;
A return means for returning the liquid inside the processing tank,
The processing tank is
a solubilizing unit that solubilizes the organic waste with the microorganism to generate first treated water;
an acid generation unit that generates an acid from the first treated water generated in the solubilization unit and generates second treated water;
a solid-liquid separation unit that separates the second treated water generated in the acid generation unit into a solid content and a separated liquid;
It has a methane fermentation section that performs methane fermentation on the separated liquid separated by the solid-liquid separation section using methane fermentation bacteria and converts it into third treated water and gas,
An organic waste treatment system, wherein the return means includes a first return means for returning the separated liquid separated in the solid-liquid separation section to the solubilization section.
The organic waste treatment system according to claim 1, wherein the solubilizing section is provided with a deposit to which the microorganism is attached and a holding member that holds the deposit.
The methane fermentation section includes a first transfer section to which the separated liquid separated by the solid-liquid separation section is transferred, and a first storage section in which the methane fermentation bacteria are stored,
The solubilization section includes a second storage section in which the microorganisms are stored, and a second storage section that is arranged below the second storage section and that transfers the first treated water produced by solubilization in the second storage section. 2 transfer parts;
The holding member is provided between the second storage section and the second transfer section,
A lower part of the second transfer part and a lower part of the acid generating part are in communication with each other,
The upper part of the acid generation part and the upper part of the solid-liquid separation part communicate with each other,
The upper part of the solid-liquid separation part and the upper part of the first transfer part communicate with each other,
The organic waste treatment system according to claim 2, wherein a lower part of the first transfer part and a lower part of the first storage part are in communication with each other.
The organic waste treatment system according to claim 2 or 3, wherein the first return means includes a spraying means for spraying the separated liquid onto the deposits.
The organic waste treatment system according to any one of claims 2 to 4, wherein the deposit is a three-dimensional structural material.
Any one of claims 1 to 5, wherein the first return means is configured to pull out the separated liquid from above the solid-liquid separation unit and return it to the solubilization unit, just before it flows into the methane fermentation unit. The organic waste treatment system according to item (1).
The organic waste treatment system according to any one of claims 1 to 6, wherein the methane-fermenting bacteria are self-granulated products of the microorganism.
The organic waste treatment system according to any one of claims 1 to 7, wherein the return means includes a second return means for returning the third treated water of the methane fermentation section to the acid generation section. .
The organic waste treatment system according to claim 8, wherein the second return means is configured to return the third treated water located above the methane fermentation section to the acid generation section.
The methane fermentation section is provided with a bacteria blocking mechanism that blocks the movement of the methane fermentation bacteria attempting to move above the methane fermentation section,
10. The organic waste treatment system according to claim 9, wherein the second return means is configured to return the third treated water located above the bacteria blocking mechanism to the acid generation section.
A treatment method using the organic waste treatment system according to any one of claims 1 to 10,
a solubilization step of solubilizing the organic waste with microorganisms to generate first treated water;
an acid generation step of generating an acid from the first treated water to generate second treated water;
a solid-liquid separation step of separating the second treated water into a solid content and a separated liquid;
A separated liquid return step of returning a predetermined amount of the separated liquid to the solubilization section out of the separated liquid separated in the solid-liquid separation step;
A method for treating organic waste, comprising a methane fermentation step in which the separated liquid that has not been returned to the solubilization section is subjected to methane fermentation using methane-fermenting bacteria to be converted into third treated water and gas.
In the solubilization step, the organic waste is solubilized by the microorganism attached to the deposit to generate the first treated water,
12. The organic waste treatment method according to claim 11, wherein in the separated liquid returning step, the separated liquid is sprayed onto the deposits when the separated liquid is returned to the solubilization section.
The organic waste treatment method according to claim 11 or 12, further comprising a solution return step of returning the third treated water produced in the methane fermentation step to the acid generation section.