JP2022034249A - Purification treatment method for methane fermentation digestion liquid and purification treatment system for methane fermentation digestion liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purification treatment method for methane-fermented digestive liquid capable of efficiently treating methane-fermented digestive liquid produced by methane-fermenting organic waste without requiring a large-scale treatment facility or power source. It is an object of the present invention to provide a purification treatment system for methane fermentation digestive juice. SOLUTION: 10 parts by weight or more, preferably 30 parts by weight or more of livestock manure is mixed with 100 parts by weight of methane fermentation digestive liquid to generate a mixed liquid having a BOD / N ratio of 3 or more. The mixed liquid is separated into a filtered liquid and a solid substance by the solid-liquid separating device 40, and the filtered liquid is further treated with activated sludge to obtain a detoxified biological treatment liquid. [Selection diagram] Fig. 1

Description

The present invention relates to a method for purifying methane-fermented digestive juice and a system for purifying methane-fermented digestive juice. Specifically, a purification treatment method for methane-fermented digestive juice that can efficiently treat methane-fermented digestive juice produced by methane-fermenting organic waste without the need for large-scale treatment equipment or power sources, and It is related to the purification treatment system of methane fermentation digestive juice.

Conventionally, in livestock facilities such as cattle and pigs, a method has been adopted in which livestock manure (hereinafter referred to as “livestock manure”) is purified and then discharged into a river. However, in recent years, the construction site of livestock facilities has been shifting to the mountains due to bad odors, etc., and the treated water from the livestock facilities is discharged near the river headwaters, and the amount of wastewater is increased due to the increase in the scale of livestock farmers. Purification treatment of facilities There is a problem that the quality of final treated water deteriorates beyond the range of purification capacity of facilities.

On the other hand, livestock manure is an organic resource of biological origin, and since it contains elements such as nitrogen, phosphorus, and potassium necessary for plant growth, it should be reused as fertilizer or an auxiliary material for compost production. It is attracting attention because it can be used. Many techniques relating to a method for producing compost from livestock manure are disclosed (for example, Patent Document 1 and Patent Document 2).

Generally, compost made from livestock manure as a main raw material is composted over a long period of time by mixing livestock manure with auxiliary materials and stacking them in the open. Nowadays, due to legal regulations and problems with bad odors, livestock manure is piled up on the floor of a covered facility, fermentation progresses, and when it reaches a predetermined temperature, it is repeatedly cut back (reversed) and fully ripened while removing bad odors. It is made to let. Among livestock manure, it takes about 120 to 150 days to obtain ripe compost of cow dung.

In this way, it takes a lot of time and effort to produce compost from livestock manure, and since the compost surplus has become a serious situation due to the recent reduction in the area of agricultural land, livestock manure is not returned to farmland. , Part of it has been incinerated, and it is not always used effectively.

By the way, methane gas obtained by methane fermentation treatment of livestock manure is known to be an excellent fuel for recovering electricity and heat. Therefore, in recent years, methane fermentation treatment as a treatment method other than compost of livestock manure has attracted attention. However, since the methane fermentation digested liquid generated after the methane fermentation treatment is also a waste, the purification treatment method of this methane fermentation digested liquid becomes an issue.

In this regard, since methane-fermented digestive juice is made from livestock manure and contains a large amount of fertilizer components (nitrogen, phosphorus, potassium) like compost, methane-fertilized digestive juice is sprayed on fields in some agriculturallands. Agricultural land is returned as liquid fertilizer. However, as mentioned above, due to the recent reduction in the area of agricultural land, there is a limit to the amount of methane fermentation digestive juice that can be accepted by agricultural land, and in some areas it is not possible to return the entire amount of livestock manure generated in that area to agricultural land. In some cases. Therefore, it is conceivable to incinerate the surplus methane fermentation digestive juice, but since the methane fermentation digestive juice is in the form of a slurry in which a large amount of water (about 90% by weight or more) and a small amount of solid content are mixed, the total amount It cannot be said that it is a preferable method for incineration because of the high cost of incineration equipment and fuel.

As a method for treating wastewater from such a methane-fermented digested liquid, first, a flocculant is added to the methane-fermented digested liquid, and then solid-liquid separation is performed into a liquid component and a solid component (residue). The solid content generated by solid-liquid separation is used as compost, and the remaining liquid content is released to rivers, etc. by removing organic matter and nitrogen components contained in the liquid content by biodegradation such as activated sludge treatment. (Patent Document 3).

Japanese Unexamined Patent Publication No. 2004-101109 Japanese Unexamined Patent Publication No. 2001-287995 Japanese Unexamined Patent Publication No. 2004-290921

On the other hand, in activated sludge treatment, the value obtained by dividing the biochemical oxygen demand (BOD) of the water to be treated by the total nitrogen amount (TN) (hereinafter referred to as "BOD / N ratio") is generally used. There is an aspect that denitrification is not promoted unless it is 3 or more.

In this respect, the methane fermentation digested liquid tends to have a BOD / N ratio of less than 3 in the water to be treated because it is a residue that has been biologically treated once by the methane fermentation treatment, and denitrification is not promoted. Even if an activated sludge treatment is applied, there is a problem that a nitrogen component exceeding a predetermined standard value remains as compared with the treatment of general organic wastewater. Further, the methane fermentation digestive liquid has poor reactivity with the flocculant, and the solid-liquid separation which is the pretreatment for the activated sludge treatment is not promoted, which makes the activated sludge treatment even more difficult.

The present invention was devised in view of the above points, and does not require a large-scale treatment facility or power source, and efficiently treats methane-fermented digestive juice produced by methane-fermenting organic waste. It is an object of the present invention to provide a purification treatment method for methane fermentation digestive juice, and a purification treatment system for methane fermentation digestive juice.

In order to achieve the above object, the method for purifying the methane-fermented digested liquid of the present invention is to add a predetermined amount of the methane-fermented digested liquid taken out by subjecting a part of the collected organic waste to methane fermentation to the organic. A step of mixing a predetermined amount of organic waste that is not subjected to the methane fermentation of the sex waste to generate a mixed liquid, a step of separating the mixed liquid into a solid substance and a separation liquid, and an activation of the separation liquid. It includes a step of sludge treatment and a step of discharging the treated water obtained by the activated sludge treatment.

Here, a predetermined amount of the organic waste that is not subjected to the methane fermentation among the organic wastes is added to a predetermined amount of the methane fermentation digestive juice taken out by subjecting a part of the collected organic waste to the methane fermentation. By providing a step of mixing to produce a mixed solution, the BOD / N ratio of the methane fermentation digested solution can be increased. Therefore, in the post-process of the methane fermentation treatment, solid-liquid separation is promoted, activated sludge treatment is promoted, and the methane fermentation digestive juice can be efficiently decomposed.

Further, by providing a step of separating the mixed liquid into a solid substance and a separated liquid, the suspended solid contained in the mixed liquid can be separated. The solid substance composed of suspended solids separated from the mixture can be dehydrated by a dehydrator such as a screw press and used as fertilizer.

Further, by providing a step of treating the separated liquid with activated sludge, it is possible to remove organic substances and nitrogen contained in the separated liquid and make them harmless.

Further, by providing a step of discharging the treated water obtained by the activated sludge treatment, the detoxified treated water can be discharged to the outside. At this time, the solid matter contained in the treated water can be used as compost.

Further, the separation step includes a step of solid-liquid separating the mixed liquid into a solid substance and a filtered solution, and a step of adding a flocculant to the filtered solution and dehydrating and separating the filtered solution into a dehydration separation solution and a solid substance. In addition, the water content of the solid can be significantly reduced by the solid-liquid separation in two steps. At this time, by adding a flocculant in the step of dehydration separation, the separation of the dehydration separation liquid and the solid substance becomes easy.

Further, when the step of producing the mixed solution includes a step of mixing approximately 10 to 100 parts by weight, more preferably 30 to 100 parts by weight of the organic waste with 100 parts by weight of the methane fermentation digested liquid, there is a case. It is possible to increase the BOD / N ratio of the mixed solution and promote the activated sludge treatment in the subsequent process.

If the amount of organic waste to be mixed is less than 10 parts by weight with respect to 100 parts by weight of the methane fermentation digestive liquid, the BOD / N ratio is a value of less than about 3, so activated sludge treatment is not promoted. A large-scale treatment facility is required to remove organic substances contained in the separation liquid and harmful substances such as nitrogen.

Further, when the amount of the organic waste to be mixed is less than 30 parts by weight with respect to 100 parts by weight of the methane fermentation digestive liquid, the BOD / N ratio is also small. Therefore, the filtrate becomes difficult to react with the flocculant, solid-liquid separation is not promoted, and the separated liquid contains a large amount of solid matter. Therefore, a large-scale treatment facility is also required for activated sludge treatment. ..

From the above, from the viewpoint of promoting solid-liquid separation and promoting activated sludge treatment, the amount of organic waste to be mixed should be 30 parts by weight or more with respect to 100 parts by weight of the methane fermentation digestive liquid. Is more preferable.

In addition, when organic waste is livestock manure, the solid matter produced in the treatment process can be used as compost, and the separation liquid can be detoxified and discharged, so that livestock manure can be effectively utilized. At the same time, livestock manure can be efficiently detoxified.

Further, when the step of treating the activated sludge includes a step of supplying a predetermined amount of methanol, it is possible to supply a BOD source which tends to be insufficient in the activated sludge treatment and promote the denitrification treatment.

In order to achieve the above object, the methane fermentation digestive liquid purification treatment system of the present invention has a waste storage tank in which organic waste is stored and an organic waste stored in the waste storage tank. A methane fermentation treatment tank that produces methane gas and methane fermentation digestive juice by methane fermentation treatment of the supplied organic waste, and a predetermined amount of methane fermentation generated in the methane fermentation treatment tank. A mixing tank in which a predetermined amount of organic waste stored in the waste storage tank is supplied to generate a mixed liquid with respect to the digested liquid, and a mixed liquid produced in the mixed tank are separated from a solid substance. It is provided with a solid-liquid separation device for separating into liquids and an activated sludge device for treating the separated liquid with activated sludge to generate treated water.

Here, by providing a waste storage tank in which organic waste is stored, for example, livestock manure generated and collected in a livestock facility or the like can be stored in the waste storage tank.

In addition, a part of the organic waste stored in the waste storage tank is supplied, and the supplied organic waste is methane-fermented to produce methane gas and methane fermentation digestive juice. By providing, a part of the organic waste stored in the waste storage tank can be taken out as methane gas and effectively used as fuel for power generation and the like.

Further, by providing a mixing tank in which a mixed liquid of methane fermentation digestive liquid and organic waste is stored, the methane fermentation digestive liquid and organic waste can be mixed in the mixing tank, so that methane fermentation digestion can be performed. The BOD / N ratio of the liquid can be increased. Therefore, the solid-liquid separation of the methane fermentation digestive juice is promoted, the activated sludge treatment is promoted, and the methane fermentation digestive juice can be efficiently decomposed.

Further, by providing a solid-liquid separation device that separates the mixed liquid into a solid substance and a separated liquid, the suspended solids contained in the mixed liquid can be separated. The solid substance consisting of suspended solids separated from the mixed solution is dehydrated by a dehydrator such as a screw press and used as fertilizer, and the separated solution can be detoxified by biological treatment such as activated sludge treatment. ..

In addition, by providing an activated sludge device that treats the separated liquid with activated sludge to generate treated water, the solid-liquid separated separated liquid is harmless by removing organic substances and nitrogen components contained in the separated liquid in the activated sludge device. Can be transformed into.

Further, in the mixing tank, 10 to 100 parts by weight, more preferably 30 to 100 parts by weight of the organic waste supplied from the waste storage tank is used with respect to 100 parts by weight of the methane fermentation digested liquid supplied from the methane fermentation treatment tank. In the case of parts by weight, the BOD / N ratio of the mixed solution can be increased to promote the activated sludge treatment in the activated sludge apparatus.

If the amount of organic waste to be mixed is less than 10 parts by weight with respect to 100 parts by weight of the methane fermentation digestive liquid, the BOD / N ratio is a value of less than about 3, so activated sludge treatment is not promoted. , Organic substances contained in the separation liquid, and harmful substances such as nitrogen cannot be removed.

Further, when the amount of the organic waste to be mixed is less than 30 parts by weight with respect to 100 parts by weight of the methane fermentation digestive liquid, the BOD / N ratio is also small, so that the filtrate does not easily react with the flocculant. Since solid-liquid separation is not promoted, the water content in the solid matter increases.

From the above, from the viewpoint of promoting solid-liquid separation and promoting activated sludge treatment, 30 parts by weight of organic waste is added to 100 parts by weight of the methane fermentation digestive liquid as the mixed liquid produced in the mixing tank. It is preferable to have more than one part.

The methane fermentation digestive juice purification treatment method and the methane fermentation digestive liquid purification treatment system according to the present invention do not require a large-scale treatment facility or power source, and methane fermentation produced by methane fermentation of organic waste. Digestive juice can be processed efficiently.

It is a block diagram of the purification treatment system of the methane fermentation digestion liquid which concerns on embodiment of this invention.

Hereinafter, embodiments of the present invention relating to a method for purifying a methane-fermented digestive juice and a purifying treatment system for a methane-fermented digestive juice will be described with reference to the drawings, and the present invention will be understood.

First, the purification treatment system 1 for the methane fermentation digestive juice according to the embodiment of the present invention will be described with reference to FIG. The purification treatment system 1 for methane fermentation digestive juice is composed of a waste storage tank 10, a methane fermentation treatment tank 20, a mixing tank 30, a solid-liquid separation device 40, and an activated sludge device 50.

[Waste storage tank]
The waste storage tank 10 is a device for pulverizing livestock manure, which is organic waste generated from a livestock facility, into a paste and storing it in a slurry.

[Methane fermentation treatment tank]
The methane fermentation treatment tank 20 is a device for methane fermentation treatment of livestock manure, and is connected to the waste storage tank 10 by a pipe. A certain amount of the slurry-like livestock manure stored in the waste storage tank 10 is supplied to the methane fermentation treatment tank 20 via, for example, a supply pump.

In this methane fermentation treatment tank 20, a fixed filter bed or the like filled with immobilized microorganisms to which anaerobic microorganisms such as methane bacteria are attached and carried is installed, and methane fermentation of livestock manure is performed here and anaerobic. Livestock manure is decomposed by sex microorganisms. The temperature in methane fermentation is not particularly limited, but for example, by performing the fermentation in a temperature range of about 50 to 70 ° C., fermentation with a more active high-temperature methane bacterium can be performed, so that the decomposition rate of livestock manure can be increased. It can be further improved.

In the methane fermentation treatment tank 20, the slurry is stirred by a stirring blade or the like (not shown). As a method for stirring the slurry, the slurry may be circulated by a pump, or a part of the biogas may be blown into the lower part of the methane fermentation treatment tank 20 by a pump to bubbling and stirring.

The methane fermentation digested liquid obtained by the methane fermentation treatment in the methane fermentation treatment tank 20 is discharged from the methane fermentation treatment tank 20 and sent to the mixing tank 30. At this time, the methane fermentation digestive juice discharged from the methane fermentation treatment tank 20 is discharged in substantially the same amount as the livestock manure supplied from the waste storage tank 10 to the methane fermentation treatment tank 20, so that the methane fermentation treatment tank 20 is discharged. The inside is always filled with a certain amount of livestock manure. The biogas produced by the methane fermentation treatment is recovered in a gas holder (not shown) and effectively used as fuel for a generator such as a fuel cell power generation device or a gas engine or a boiler.

[Mixing tank]
The mixing tank 30 is a storage tank for storing a mixed solution of livestock manure and methane fermentation digestive juice. The mixing tank 30, the waste storage tank 10, and the methane fermentation treatment tank 20 are each connected by piping, and a predetermined ratio of livestock manure is discarded with respect to the methane fermentation digested liquid transferred from the methane fermentation treatment tank 20. It is pumped up from the storage tank 10 and transferred to the mixing tank 30.

[Solid-liquid separator]
The solid-liquid separation device 40 is a device that separates the mixture of livestock manure and methane fermentation digestion liquid transferred from the mixing tank 30 into a filtered liquid and a solid substance, for example, a screw press, a belt screen, a centrifugal concentration dehydrator, and the like. It can be appropriately selected from known solid-liquid separators such as a vacuum dehydrator.

In the methane fermentation in the methane fermentation treatment tank 20 described above, proteins and the like contained in a large amount in livestock manure can be decomposed into inorganic nitrogen such as ammoniacal nitrogen by a proteolytic enzyme, but all proteins are decomposed. It is difficult to decompose into inorganic nitrogen. In addition, the methane fermentation digestive juice contains a high concentration of nitrogen compounds having a complicated structure, and suspends methane fermenting bacteria, solid organic substances, or organic nitrogen having low solubility such as undecomposed proteins. It also contains suspended solids. The solid-liquid separation device 40 can effectively remove suspended solids such as methane-fermenting bacteria, solid organic substances, and organic nitrogen having low solubility in the methane-fermented digestive juice.

As a separation method using the solid-liquid separator 40, for example, a solid-liquid separator and a dehydrator are arranged in series, and the mixture is first separated into a filtrate and a residue which is a relatively large solid by the solid-liquid separator. Then, the filtrate may be separated into a dehydration separation liquid and a solid dehydration cake by a dehydrator. In this way, the two-step solid-liquid separation can separate more suspended solids contained in the mixed solution.

Further, it is preferable to add a polymer flocculant at the time of solid-liquid separation. Examples of the flocculant include iron salts such as ferric chloride and iron sulfate, inorganic flocculants such as polyaluminum chloride, and cationics such as polymethacrylic acid ester type, polyacrylic acid ester type and polyacrylamide type. Examples thereof include anionic and nonionic polymer flocculants, and these flocculants can be appropriately selected and used.

The amount of the flocculant added is preferably, for example, about 3 to 10% by weight with respect to the mixed solution, but this point can also be appropriately changed depending on the flocculant used. do.

The separation liquid separated by the solid-liquid separation device 40 is transferred to the activated sludge device 50 described later. On the other hand, the residue and the dehydrated cake separated by the solid-liquid separation device 40 are further dried to reduce the water content and then used as compost.

[Activated sludge device]
The separated liquid separated by the solid-liquid separating device 40 is treated with activated sludge. Here, the separation liquid contains a large amount of inorganic nitrogen that is dissolved as ions and organic nitrogen that is highly soluble. Ammonium ion, which is ammonia nitrogen (NH4-N) in methane fermentation digestive juice, and highly soluble organic nitrogen are biodecomposed into nitrite ion by nitrite bacteria, and biodecomposed into nitrate ion by nitrifying bacteria. Finally, nitrite ions and nitrate ions are biodegraded into nitrogen gas by denitrifying bacteria. This makes it possible to effectively remove inorganic nitrogen such as ammoniacal nitrogen and highly soluble organic nitrogen in the separation solution.

The activated sludge device 50 is composed of, for example, a denitrification tank 51 and a nitrification tank 52, and the separated liquid is biologically treated and denitrified while the liquid in the nitrification tank 52 is returned to the denitrification tank 51. By this biological treatment, biodegradable organic substances and nitrogen compounds contained in the separation liquid can be decomposed and removed.

The activated sludge device 50 is not particularly limited as long as it can biodegrade organic substances into inorganic substances such as carbon dioxide and water by the action of sludge microorganisms. For example, the denitrification tank 51 and the nitrification tank 52 may be continuously configured, and in that case, the aerobic treatment and the anaerobic treatment may be repeated in a plurality of stages, and the water to be treated may be treated. It can be appropriately designed according to the contamination status such as the contamination component and the degree of contamination.

Further, the microorganism used in the activated sludge device 50 is a microorganism having an ability to proliferate using an organic substance contained in the water to be treated as a nutrient source under aerobic or anaerobic conditions and efficiently decompose and assimilate sludge. If so, it is not particularly limited. Such microorganisms live in the water to be treated and do not need to be added from the outside, but in order to smoothly treat the activated sludge, if necessary, they are highly decomposed with respect to the contaminated components of the water to be treated. It is also possible to appropriately select and add a specific microorganism having activity.

Further, when treating the separation liquid in which the organic matter does not sufficiently exist with respect to the nitrogen to be removed in the separation liquid, methanol is injected into the activated sludge apparatus 50, and this methanol is used as a carbon source for denitrification. It can also accelerate the progress of the reaction.

The settling tank 53 is configured to perform solid-liquid separation by gravity sedimentation of the biodegradation treatment liquid obtained by activated sludge treatment, the supernatant liquid is discharged to the outside of the system as final treatment water, and the solid component settles to the bottom. , Pulled out as sedimented sludge.

Here, it is not always necessary to have the settling tank 53. For example, instead of the settling tank 53, solid-liquid separation may be performed by a membrane separation device, a filtration separation device, or the like. In that case, for example, the membrane separation device may be provided inside or outside the activated sludge device 50, or both inside and outside.

For example, as a configuration in which a membrane separation device is provided inside or outside the active sludge device 50, an immersion type membrane separation device made of a microfiltration membrane is provided in the internal vitrification tank 52, and a reverse osmosis membrane or an NF membrane is provided outside. A membrane treatment device consisting of each is installed.

In the membrane separation device configured as described above, the biodegradation treatment liquid is first subjected to membrane separation treatment by the immersion type membrane separation device inside, and solid matter such as activated sludge is removed. The permeate that has passed through the immersion type membrane separation device is supplied to the membrane treatment device, and removes the chromaticity component and soluble biodegradable substances remaining in the permeate. At this time, for example, since the pore size of the reverse osmosis membrane is very small, about 1 nm to several nm, it is possible to highly remove soluble chromaticity components and biodegradable substances, and the permeate is a reverse osmosis membrane or Since the suspended substance that is a load on the NF membrane is completely removed, the membrane separation treatment by the reverse osmosis membrane or the NF membrane can be carried out under low pressure operating conditions.

Next, a method for purifying the methane fermentation digestive juice according to the embodiment of the present invention will be described.

[Generation of mixture]
The methane fermentation digested liquid methane-fermented in the methane fermentation treatment tank 20 and the livestock manure stored in the waste treatment tank 10 are each transferred to the mixing tank 30. In the mixing tank, a mixed solution of these methane fermentation digested solutions and livestock manure is produced.

At this time, the supply amount of the pump is regulated so that the livestock manure supplied from the waste treatment tank 10 is 10 to 100 parts by weight with respect to 100 parts by weight of the methane fermentation digestive juice. There is.

Here, the amount of livestock manure supplied from the waste treatment tank 10 does not necessarily have to be set to 10 to 100 parts by weight with respect to 100 parts by weight of the methane fermentation digestive juice. However, as a result of the examination by the inventors, when the amount of livestock manure supplied to 100 parts by weight of the methane fermentation digestive juice is less than 10 parts by weight, the BOD / N ratio becomes less than 3, and the activated sludge treatment, which is a subsequent step, is performed. There is a problem that it is not activated and the amount of suspended solids in the bioprocessed water increases.

As a result of further studies by the inventors, when the livestock manure supplied to 100 parts by weight of the methane fermentation digestive liquid is in the range of 10 parts by weight or more and less than 30 parts by weight, the activated sludge treatment is active. However, in the solid-liquid separation in the solid-liquid separation device 40, the reaction of the polymer flocculant added to the mixed solution becomes weak. Therefore, there arises a problem that solid-liquid separation is not promoted and the burden of activated sludge treatment, which is a subsequent process, increases.

From the above, from the viewpoint of promoting solid-liquid separation and promoting activated sludge treatment, livestock manure supplied to 100 parts by weight of methane fermented digestive juice is in the range of 30 parts by weight to 100 parts by weight. It is preferable to have.

[Solid-liquid separation]
When the mixed liquid is supplied from the mixing tank 30 to the solid-liquid separating device 40, the mixed liquid is separated into a solid component composed of a suspended substance and a liquid component composed of a filtered solution. At this time, as described above, if the amount of livestock manure is 30 parts by weight or more with respect to 100 parts by weight of the methane fermentation digested liquid as a component of the mixed liquid, the amount of suspended solids contained in the filtrate is reduced. Activated sludge treatment, which is a post-process, is promoted.

[Activated sludge treatment]
The filtered liquid, which is the liquid component separated by the solid-liquid separation device 40, is biologically treated by the activated sludge device 50. At this time, as described above, when the BOD / N ratio is 3 or more as a component of the mixed liquid, biological treatment is promoted and denitrification and activated sludge treatment can be realized.

The biologically treated water denitrified by the biological treatment is discharged to a river or the like as wastewater that meets the water quality standard that does not contain suspended solids through the settling tank 53 or the membrane treatment.

Using the methane-fermented digestive juice purification treatment system 1 configured as described above, continuous operation was performed using the methane-fermented digestive juice purification treatment method of the present invention for cattle manure as livestock manure.

<Example 1>
First, as Example 1, 4 L of livestock manure was added to 10 L of methane fermentation digestive liquid supplied to the mixing tank 30 to generate a mixed liquid. Table 1 shows each component of the mixed solution at this time.

As shown in Table 2, in the case of a mixed solution in which only 40 parts by weight of livestock manure is mixed with 100 parts by weight of methane fermentation digestive liquid, the BOD / N ratio is 4.1, which is a guideline for activated sludge treatment. It is larger than the N ratio of 3. At this time, the reaction to the flocculant supplied in the solid-liquid separation step was also improved, and the activated sludge treatment / denitrification reaction proceeded, and the treated water quality was also good.

<Example 2>
Next, as Example 2, 1 L of livestock manure was added to 10 L of the methane fermentation digested liquid supplied to the mixing tank 30 to generate a mixed liquid. Table 3 shows each component of the mixed solution at this time.

As shown in Table 3, in the case of a mixed solution in which only 10 parts by weight of livestock manure is mixed with 100 parts by weight of methane fermentation digestive liquid, the BOD / N ratio is 2.5, which is a guideline for activated sludge treatment. It is slightly lower than the N ratio of 3. At this time, as shown in Table 4, the effect of the flocculant was inferior, the inseparable BOD component remained, and the BOD value of the treated water increased as compared with Example 1. Moreover, since the BOD / N ratio was less than 3, the TN value did not reach the target value of 100 mg / L. The result was that it was necessary to add methanol, which is the shortage of BOD.

<Comparison example>
Next, as Comparative Example 1, 10 L of the methane-fermented digestive juice supplied to the mixing tank 30 was treated by the above-mentioned purification treatment method for the methane-fermented digestive juice without adding livestock manure. Table 5 shows each component of the methane fermentation digestive juice at this time.

As shown in Table 5, when livestock manure is not mixed with the methane fermented digestive juice, the BOD / N ratio is 1.8 due to the large amount of nitrogen component, which is higher than the BOD / N ratio of 3 which is a guideline for activated sludge treatment. Is also significantly reduced. At this time, as shown in Table 6, the reaction rate to the flocculant supplied in the solid-liquid separation step deteriorates, and the treated water also deteriorates significantly as compared with Examples 1 and 2.

From the above Examples and Comparative Examples, by adding a predetermined amount of livestock manure to the methane fermented digestive juice, the BOD / N ratio, which is a guideline for promoting activated sludge treatment, becomes 3 or more, and solid-liquid separation and solid-liquid separation and Activated sludge treatment is promoted. In order to make the BOD / N ratio 3 or more, it is preferable to mix 10 parts by weight or more, preferably 30 parts by weight or more of livestock manure with 100 parts by weight of the methane fermentation digestive solution.

As described above, the methane fermentation digestive juice purification treatment method to which the present invention is applied and the methane fermentation digestive juice purification treatment system do not require a large-scale treatment facility or power source, and methane fermentation of organic waste. The resulting methane-fermented digestive juice can be efficiently processed.

1 Purification treatment system for methane fermentation digestive juice 10 Waste storage tank 20 methane fermentation treatment tank 30 Mixing tank 40 Solid-liquid separation device 50 Activated sludge device 51 Denitrification tank 52 Nitrification tank 53 Sedimentation tank

Claims (7)

A predetermined amount of organic waste that is not subjected to methane fermentation is mixed with a predetermined amount of methane fermentation digested liquid taken out by subjecting a part of the collected organic waste to methane fermentation. The process of producing a mixture and
The step of separating the mixed liquid into a solid substance and a separation liquid, and
The step of treating the separated liquid with activated sludge and
A method for purifying a methane fermentation digestive liquid, comprising a step of discharging the treated water obtained by the activated sludge treatment. The separation step is
The step of solid-liquid separating the mixed solution into a solid substance and a filtered solution,
The method for purifying a methane fermentation digested liquid according to claim 1, further comprising a step of adding a flocculant to the filtered liquid and dehydrating and separating the filtered liquid into a dehydrated separation liquid and a solid substance. The step of producing the mixed solution is
The methane fermentation according to claim 1 or 2, which comprises a step of mixing about 10 to 100 parts by weight, more preferably 30 to 100 parts by weight of the organic waste with 100 parts by weight of the methane fermentation digestive liquid. How to purify digestive juices. The method for purifying methane-fermented digestive juice according to any one of claims 1 to 3, wherein the organic waste is livestock manure. The step of treating the activated sludge is
The method for purifying methane fermentation digestive juice according to any one of claims 1 to 4, which comprises a step of supplying a predetermined amount of methanol. A waste storage tank in which organic waste is stored, and
A part of the organic waste stored in the waste storage tank is supplied, and the supplied organic waste is subjected to methane fermentation treatment to produce methane gas and methane fermentation digestive juice, and a methane fermentation treatment tank.
A mixing tank in which a predetermined amount of organic waste stored in the waste storage tank is supplied to generate a mixed liquid with respect to a predetermined amount of methane fermentation digested liquid produced in the methane fermentation treatment tank.
A solid-liquid separator that separates the mixed liquid produced in the mixing tank into a solid substance and a separated liquid,
A purification treatment system for methane fermentation digestive liquid, comprising an activated sludge device that treats the separated liquid with activated sludge to generate treated water. The mixing tank is
The amount of organic waste supplied from the waste storage tank is 10 to 100 parts by weight, more preferably 30 to 100 parts by weight, based on 100 parts by weight of the methane fermentation digestion liquid supplied from the methane fermentation treatment tank. The purification treatment system for methane fermentation digestive juice according to claim 6.

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