JP6943402B2 - Anaerobic processing system - Google Patents

Description

The present invention relates to an anaerobic treatment system for biologically treating organic waste under anaerobic conditions. In particular, it relates to an anaerobic treatment system equipped with a digestion tank for digesting organic waste.

The method of anaerobic methane fermentation treatment of organic waste is attracting attention as a highly useful technology because the amount of waste can be reduced and the generated methane can be used as energy. For example, Patent Document 1 describes an organic waste treatment apparatus and an organic waste, which are characterized in that organic waste and a conductive substance are introduced into a treatment tank and subjected to biochemical anaerobic treatment. The processing method of is described.
Further, Patent Document 1 also describes that the treatment speed of the anaerobic treatment can be improved and maintained for a long period of time by adding a conductive substance.

Japanese Unexamined Patent Publication No. 2016-203029

In a treatment system such as Patent Document 1, the conductive substance added to the organic waste in the treatment tank is discharged to the outside of the system together with the treatment liquid, so that it is necessary to constantly supply a new conductive substance. .. On the other hand, in order to reduce the cost of treatment, it is required that the conductive substance can act repeatedly in the treatment tank.

An object of the present invention is an anaerobic treatment capable of maintaining a conductive substance in a system, improving treatment efficiency and reducing running costs when treating organic waste by methane fermentation using a conductive substance. To provide a system.

As a result of diligent studies on the above problems, the present inventor has found that by fixing a conductive substance in the digestive tub, it becomes possible to maintain the conductive substance in the system, and complete the present invention. bottom.
That is, the present invention is the following anaerobic treatment system.

The anaerobic treatment system of the present invention for solving the above-mentioned problems is an anaerobic treatment system for biologically treating organic waste under anaerobic conditions, and is provided with a digestion tank for digesting organic waste. Is characterized by providing a stirring unit for stirring the inside of the digestion tank and a fixing part for fixing the conductive substance in the digestion tank.
In the anaerobic treatment system of the present invention, by providing a fixing portion for fixing the conductive substance in the digestive tub, the conductive substance is not discharged to the outside of the digestive tub together with the treatment liquid, so that the running cost can be reduced.

Further, in one embodiment of the anaerobic treatment system of the present invention, the fixed portion is characterized in that it is located above the stirring portion.
According to this feature, it is possible to secure the bottom flow velocity in the digestion tank without hindering the stirring operation of the stirring part, and the organic waste and the microorganism are effectively mixed to improve the reaction rate. It becomes possible to make it. In addition, it is possible to prevent the solid residue from accumulating on the bottom of the digestion tank.

Further, one embodiment of the anaerobic treatment system of the present invention is characterized in that an addition portion to which a conductive substance is added is provided separately from the fixing portion.
According to this feature, the reaction rate can be further improved by the presence of a conductive substance that is directly added to the organic waste in addition to the fixed conductive substance.

Further, one embodiment of the anaerobic treatment system of the present invention is characterized in that the addition portion is provided in the front stage of the digestive tub.
According to this feature, by mixing the organic waste and the conductive substance in advance in the stage before the digestion tank, it is possible to treat the organic waste in the digestion tank in a state of high mixing efficiency. Further, especially in an anaerobic treatment system in which a concentration tank is provided in front of the digestion tank, the conductive substance functions as a coagulant in the concentration tank, and the treatment efficiency of organic waste can be improved by increasing the concentration. It will be possible.

Further, in one embodiment of the anaerobic treatment system of the present invention, the particle size of the conductive substance added from the addition portion is smaller than the particle size of the conductive substance fixed in the fixing portion. ..
According to this feature, the specific surface area of the conductive substance that is directly mixed with the organic waste is increased, so that the contact efficiency with the microorganism is increased and the reactivity is improved. Further, the conductive substance from the addition portion is partially adsorbed to the conductive substance in the fixed portion and stays in the digestion tub, so that the loss due to the discharge of the conductive substance can be reduced.

According to the present invention, in an anaerobic treatment system for biologically treating organic waste under anaerobic conditions, the methane fermentation performance is improved and the residence time is shortened to enable miniaturization of the apparatus and in the digestive tub. By suppressing the discharge of the conductive substance to the outside of the system, it is possible to provide an anaerobic treatment system capable of reducing the running cost.

It is the schematic explanatory drawing of the anaerobic treatment system which concerns on 1st Embodiment of this invention. It is a schematic explanatory drawing which shows the structure of the digestive tub in the anaerobic treatment system which concerns on 1st Embodiment of this invention. It is a schematic explanatory drawing which shows the structure of the digestive tub in the anaerobic treatment system which concerns on the 2nd Embodiment of this invention. It is the schematic explanatory drawing of the anaerobic treatment system which concerns on 3rd Embodiment of this invention. It is the schematic explanatory drawing of the anaerobic treatment system which concerns on 4th Embodiment of this invention. It is the schematic explanatory drawing of the anaerobic treatment system which concerns on 5th Embodiment of this invention. It is the schematic explanatory drawing of the anaerobic treatment system which concerns on 6th Embodiment of this invention.

The anaerobic treatment system of the present invention is an anaerobic treatment system for biologically treating organic waste under anaerobic conditions, and is provided with a digestion tank for digesting organic waste. It is characterized by providing a stirring part for stirring and a fixing part for fixing a conductive substance in the digestive tub.

Examples of the organic waste to be treated include organic wastewater containing sludge, livestock manure, and surplus sludge. The organic waste is not limited to this, and any organic waste containing an organic substance that can be biologically treated under anaerobic conditions is the subject of the present invention.

Biotreatment under anaerobic means treatment by microorganisms under conditions that do not supply oxygen. The microorganism is not particularly limited as long as it decomposes an organic substance under the condition that oxygen is not supplied, and may be a facultative anaerobic microorganism as well as an absolutely anaerobic microorganism.

Examples of the anaerobic treatment include methane fermentation by methanogens, denitrification treatment in which nitric acid and nitrite are reduced by denitrifying bacteria, and sulfuric acid reduction treatment in which sulfuric acid is reduced by sulfuric acid reducing bacteria. .. From the viewpoint of usefulness as energy, methane fermentation that produces methane is preferable as the anaerobic treatment.

Hereinafter, embodiments of the anaerobic treatment system according to the present invention will be described in detail with reference to the drawings.
The anaerobic treatment system described in the embodiment is merely exemplified for explaining the anaerobic treatment system according to the present invention, and is not limited thereto.

[First Embodiment]
FIG. 1 shows a schematic explanatory view of an anaerobic treatment system according to the first embodiment of the present invention.
The anaerobic treatment system 1a according to the present invention is a treatment system for treating organic waste by methane fermentation, and as shown in FIG. 1, includes a digestion tank 2 for digesting organic waste S. The concentration tank 3 is provided in the front stage of the digestion tank 2, and the dehydration equipment 4 is provided in the rear stage of the digestion tank 2. A biogas utilization facility including a desulfurization apparatus and a gas storage tank for recovering and utilizing methane gas generated from the digestion tank may be provided.

The concentrating tank 3 is not particularly limited as long as it is a device for concentrating the solid content in the water to be treated. For example, a sedimentation separation tank for precipitating and concentrating the solid content or a centrifugal separation for separating the solid content by centrifugal force. Devices and the like can be mentioned. A flocculant or the like is added to the concentrating tank 3 as necessary in order to promote the separation of solid components.

The dehydration equipment 4 is an equipment for separating solids in the anaerobic-treated treatment liquid. For example, a centrifugal separator that separates solids by centrifugal force, a filtration device that separates solids by filtration, and the like can be mentioned. As the dehydrating device 4, a filtration device is preferable from the viewpoint of being excellent in the action of lowering the water content of the solid content. Further, it is preferable to provide a sedimentation separation tank, a centrifugal separation device, or the like in front of the filtration device. Further, in order to promote the separation of solid components, a coagulant or the like is added to the dehydration equipment 4 as needed. The solid component dehydrated by the dehydration facility 4 is processed by a drying facility, a carbonization facility, or the like.

The digestion tank 2 is a reaction tank for digesting organic waste. FIG. 2 shows the structure of the digestive tub 2 in the anaerobic treatment system 1a according to the first embodiment of the present invention.
As shown in FIG. 2, the digestion tank 2 is provided with a stirring unit 5 for stirring the inside of the digestion tank 2 and a fixing unit 6 for fixing the conductive substance 7 in the digestion tank 2.

The digestive tank 2 in the anaerobic treatment system 1a according to the first embodiment of the present invention is a reaction tank in which organic waste reacts with microorganisms to perform methane fermentation under anaerobic conditions, in order to maintain anaerobic condition. It is desirable to use a closed container.
Further, as shown in FIG. 2, the shape of the bottom of the digestion tank 2 is preferably inclined. This facilitates the recovery of the solid residue and improves the stirring efficiency at the bottom of the digestion tank.

The conductive substance 7 is a substance having an electrical resistivity of 1 mΩm or less, preferably 100 μΩm or less, and has an effect of promoting a methane production reaction from an organic acid called a symbiotic reaction in the reaction process of methane fermentation. Specific examples thereof include activated carbon, coal coke, graphite, magnetite, iron sulfide minerals, reduced iron and the like.
As a mechanism for promoting the symbiotic reaction by the conductive substance, it is considered that the reaction is promoted by inducing electrical symbiosis between the microorganisms by adhering to the conductive substance.

The shape of the conductive substance 7 is not particularly limited, and examples thereof include a granular shape, a plate shape, a sponge shape, a rod shape, a string shape, a tubular shape, and a honeycomb shape. Considering the contact efficiency with microorganisms, granules having a large specific surface area are preferable. When the granular conductive substance 7 is used, the particle size of the conductive substance 7 is preferably 1 mm or more in consideration of the ease of fixing to the fixing portion 6. Further, the shape of the conductive substance 7 may be a porous molded body. At this time, the size of the molded product is preferably more than 1 cm.

The fixing portion 6 has a structure capable of holding the conductive substance 7 and allowing the conductive substance 7 to come into contact with the organic waste S and microorganisms. Specific configurations include, for example, a container made of punching metal, a plate material to which the conductive substance 7 is fixed, a string, and the like, in addition to the net as shown in FIG. Considering the ease of installation in the digestion tank 2 and the ease of replacement of the conductive substance 7, it is preferable to use a container having holes such as a net and punching metal. As the container having holes such as a net and punching metal, a container having holes smaller than the size of the conductive substance 7 may be used so as not to flow out to the outside of the fixing portion 6.

The arrangement of the fixing portion 6 is not particularly limited as long as it can be arranged so that at least the organic waste S and the conductive substance 7 in the fixing portion 6 are in contact with each other. For example, it may be located at any height above, in the center, or at the bottom of the digestion tank 2, or at any position on the wall surface side or the center side of the digestion tank. As shown in FIG. 2, it is desirable that the fixing portion 6 is provided above the stirring portion 5. This makes it possible to secure the bottom flow velocity in the digestion tank 2 and prevent the accumulation of solid residue.

Further, the means for attaching the fixing portion 6 to the digestion tank 2 is not particularly limited as long as the stirring action of the stirring portion 5 can be ensured. For example, as shown in FIG. 2, it may be attached to the inner wall surface of the digestion tank 2, or a fixed portion may be suspended from the ceiling of the digestion tank 2. Further, the fixing portion 6 may be attached to the rotating shaft R in the digestion tank 2 so as to rotate together with the stirring blade 51. By attaching the fixing portion 6 to the inner wall surface of the digestion tank 2, a good stirring state can be obtained without interfering with the stirring operation by the stirring unit 5.

The stirring unit 5 stirs the organic waste S to promote a reaction with microorganisms and increases the contact efficiency between the conductive substance and the microorganisms. As a specific configuration, as shown in FIG. 2, a rotating shaft R and a stirring blade 5a installed on the rotating shaft R are provided. The installation position of the stirring blade 5a is not particularly limited as long as a sufficient stirring action can be obtained in the digestion tank 2, and may be appropriately set according to the arrangement of the fixing portion 6 and the like. By arranging the fixing portion 6 from the center to the bottom side of the digestion tank 2, the fixing portion 6 can be arranged above, so that the flow velocity at the bottom of the digestion tank 2 can be secured and the accumulation of solid residue can be prevented. When the stirring blade 5a is arranged on the bottom side, the stirring force at the bottom of the digestion tank 2 can be increased. Further, when the stirring blade 5a is arranged in the center, the rotating shaft R is shortened, so that there is an effect that the load of the shaft fixing portion of the rotating shaft R is reduced and an effect that the power is reduced.

The stirring means of the stirring unit 5 is not particularly limited as long as it provides a sufficient stirring action in the digestion tank 2. In addition to the one including the rotating shaft R and the stirring blade 5a as shown in FIG. 2, gas stirring may be performed, for example, by supplying an inert gas such as nitrogen gas into the digestion tank 2 for stirring. ..

[Second Embodiment]
FIG. 3 is a schematic explanatory view showing the structure of the digestive tub 2 in the anaerobic treatment system 1b according to the second embodiment of the present invention.
The digestion tank 2 is provided with an addition portion 8 for adding a conductive substance 7a in addition to the fixing portion 6 to the digestion tank 2 in the anaerobic treatment system 1a of the first embodiment. As a result, the microorganism and the conductive substance are directly mixed, and the reaction efficiency can be further improved.

The structure of the addition unit 8 can use a known structure for adding powder, and is not particularly limited. For example, it may be like a hopper capable of automatically adding a predetermined amount.
Further, since the conductive substance 7a added from the addition section 8 is discharged to the outside of the system as the treatment progresses, the amount of the conductive substance 7a added should be reduced as much as possible in consideration of the desired reaction efficiency, cost, and the like. Is desirable. For example, it is preferably 0.01 kg / kg-DS (DS is the dry weight of organic waste) or less, and more preferably 0.001 kg / kg-DS or less.

It is desirable that the particle size of the conductive substance 7a added from the adding portion 8 is smaller than the particle size of the conductive substance 7 fixed to the fixing portion 6. At this time, it is preferable that the particle size of the conductive substance 7 fixed to the fixing portion 6 is 1 mm or more, and the particle size of the conductive substance 7a added from the addition portion 8 is 100 nm or less. As a result, the conductive substance 7a having a larger specific surface area is directly mixed with the microorganisms, the amount of the microorganisms adhering to the conductive substance increases, and the reaction is promoted. Further, the conductive substance 7a is adsorbed on the conductive substance 7 fixed to the fixed portion, and the discharge to the outside of the system can be suppressed.

Further, the conductive substance 7 and the conductive substance 7a may have the same composition or may have different compositions. Since the ratio of the conductive substances 7 and 7a may change due to continuous treatment, the conductive substances 7 and 7a have the same electrical resistivity (for example, the difference in electrical resistivity) in order to stabilize the reaction rate. Is preferably 10 μΩm or less), and particularly preferably has the same composition.

Since the conductive substance 7a flows out to the rear stage side of the digestion tank 2, the treatment efficiency in the dehydration equipment 4 can be improved by adding a conductive substance 7a that acts as a coagulant such as activated carbon. Further, when coal coke is used as the conductive substance 7a, it can also be used as a fuel for drying and carbonization including combustion in the dehydration equipment 4.

[Third Embodiment]
FIG. 4 is a schematic explanatory view showing the structure of the anaerobic treatment system 1c according to the third embodiment of the present invention.
In this anaerobic treatment system 1c, the addition part 8 of the second embodiment is provided in the concentration tank 3 which is the front stage of the digestion tank 2. The concentrating tank 3 is a reaction tank for concentrating the solid content of organic waste, and may be either a gravity type or a mechanical type. Further, the digestion tank 2 has the same structure as the digestion tank 2 in the anaerobic treatment system 1a of the first embodiment.
By mixing the conductive substance 7a in the front stage of the digestion tank 2 in this way, the treatment in the digestion tank 2 becomes possible in a state where the mixed state of the organic waste S and the conductive substance 7a is enhanced. Further, when activated carbon is used as the conductive substance 7a added from the addition unit 8, the activated carbon is excellent in agglutination action, so that the concentration efficiency in the concentration tank 3 can be improved.

The above-described embodiment shows an example of an anaerobic treatment system. The anaerobic treatment system according to the present invention is not limited to the above-described embodiment, and the anaerobic treatment system according to the above-described embodiment may be modified without changing the gist described in the claims.

For example, in the anaerobic treatment system of the present embodiment, the addition portion 8 may be provided in the settling tank at the subsequent stage of the digestion tank 2. Since the precipitated digested sludge is returned to the digestion tank 2 as seed sludge, the conductive substance 7a added to the settling tank can be charged into the digestion tank 2 to improve the treatment efficiency of the anaerobic treatment. Further, since the conductive substance 7a also acts as a coagulant and a combustion aid, it is possible to increase the processing efficiency of the dehydration treatment in the dehydration equipment 4 located at the subsequent stage of the digestion tank 2.

Further, in the anaerobic treatment system of the present embodiment, the fixing portion 6 in the digestion tank 2 may be a structure composed of a plurality of units. For example, FIGS. 5 to 7 show other aspects of the fixing portion 6 and the conductive substance 7.

[Fourth Embodiment]
FIG. 5 is a schematic explanatory view showing the structure of the anaerobic treatment system 1d according to the fourth embodiment of the present invention.
The anaerobic treatment system 1d includes a string-shaped fixing portion 6a fixed to the ceiling portion of the digestion tank 2 and a granular conductive substance 7 fixed to the fixing portion 6a. According to this system, there is an effect that the contact efficiency between the organic substance and the conductive substance 7 is high.

The fixing portion 6a is fixed to the ceiling portion and suspended inside the digestion tank 2. The fixing portion 6a is a string-shaped member, for example, a string made of natural fibers such as a paper string, a linen string, and a cotton string, a string made of synthetic fibers such as a polypropylene string, a polyethylene string, an acrylic string, and a nylon string. be. If the lower end of the string-shaped member swings, it may get entangled with the rotating shaft R or the like of the stirring unit 5. Therefore, the swing may be suppressed by fixing the lower end or attaching a weight to the lower end. Further, the string may be wound around a core material such as a wire or the string may be bundled to impart a predetermined rigidity to the string-shaped member to suppress the swing.

As another aspect of the fixing portion suspended from the ceiling portion, for example, a rod-shaped or plate-shaped member may be suspended from the ceiling portion in addition to the string-shaped member.

The means for fixing the conductive substance 7 to the fixing portion 6a is not particularly limited, but for example, it may be fixed with an adhesive or the like, or it may be fixed by being entwined with fibers. Further, in the case of a rod-shaped or plate-shaped member, the conductive substance 7 may be attached to the surface of the member, or the conductive substance 7 may be molded to form a rod-shaped or plate-shaped member.

[Fifth Embodiment]
FIG. 6 is a schematic explanatory view showing the structure of the anaerobic treatment system 1e according to the fifth embodiment of the present invention.
The anaerobic treatment system 1e includes a plate-shaped fixing portion 6b fixed to the rotating shaft R and a granular conductive substance 7 fixed to the surface of the fixing portion 6b. According to this system, since the organic substance and the conductive substance 7 are attached to each other, it is possible to prevent the conductive substance 7 from flowing out from the digestion tank 2 together with the treated water.

The fixing portion 6b is a plate-shaped member fixed to the rotating shaft R of the stirring portion 5, and rotates together with the rotating shaft R. The material of the plate-shaped member is not particularly limited, and examples thereof include a metal plate such as stainless steel and a synthetic resin plate such as hard plastic. The shape of the plate-shaped member is not particularly limited, and examples thereof include a plate-shaped member having a disk-shaped shape and a rectangular shape, and a plate-shaped member made of a net, a mesh, or the like.
As another aspect of the fixing member fixed to the rotating shaft R, a rod-shaped or string-shaped member may be attached to the rotating shaft R in addition to the plate-shaped member.

The conductive substance 7 is fixed to the surface of the plate-shaped member with an adhesive or the like. Further, instead of the fixing portion 6b and the conductive substance 7, a rod-shaped or plate-shaped member obtained by molding the conductive substance 7 may be attached to the rotating shaft R.

The plate-shaped member may be attached so as to rotate together with the rotating shaft R as in the fifth embodiment, or may be attached to the rotating shaft R via a bearing or the like so that the fixing portion 6b does not rotate. You may. When rotating together with the rotation shaft R, the stirring action in the digestion tank 2 can be enhanced by the rotation of the fixing portion 6b. Further, when it does not rotate together with the rotating shaft R, the power for rotating the rotating shaft R can be reduced.

[Sixth Embodiment]
FIG. 7 is a schematic explanatory view showing the structure of the anaerobic treatment system 1f according to the sixth embodiment of the present invention.
The anaerobic treatment system 1f includes a plate-shaped fixing portion 6c attached to the inner wall surface of the digestion tank 2 and a thin-film conductive substance 71 fixed to the surface of the fixing portion 6c. The fixing portion 6c provided with the conductive substance 71 is installed both above and below the stirring portion 5. According to this system, since the conductive substance 71 is installed at a plurality of places, the organic waste and the conductive substance 71 can be brought into contact with each other in a wide range.

The fixing portion 6c is a plate-shaped member fixed to the inner wall surface of the digestion tank 2. The material of the plate-shaped member is not particularly limited, and examples thereof include a metal plate such as stainless steel and a synthetic resin plate such as hard plastic. The shape of the plate-shaped member is not particularly limited, and examples thereof include a plate member having a rectangular shape and the like, and a plate member made of a net, a mesh, or the like.
As another aspect of the fixing member fixed to the inner wall surface of the digestion tank 2, a rod-shaped or string-shaped member may be attached to the inner wall surface in addition to the plate-shaped member.
In addition, these members may be attached along the inner wall surface of the digestion tank 2 or may be attached so as to project from the inner wall surface of the digestion tank 2.

A thin-film conductive substance 71 is fixed to the surface of the plate-shaped member of the fixing portion 6c. The conductive substance 71 can be formed by molding the surface of the fixing portion 6c into a thin film. Further, instead of the fixing portion 6c and the conductive substance 71, a member obtained by molding the conductive substance into a rod shape, a plate shape, or the like may be directly fixed to the inner wall surface of the digestion tank 2.

The anaerobic treatment system of the present invention is utilized for biological treatment of organic waste under anaerobic conditions. For example, it is suitably used for sludge treatment generated in a water treatment process such as sewage treatment. Since the anaerobic treatment system of the present invention increases the treatment speed of biological treatment, it can be suitably used for methane fermentation having a slow treatment speed.

1a, 1b, 1c, 1d, 1e, 1f Anaerobic treatment system, 2 digestion tank, 3 concentration tank, 4 dehydration equipment, 5 stirring part, 5a stirring blade, 6,6a, 6b, 6c fixed part, 7,71, 7a Conductive substance, 8 Additives, R rotating shaft, S Organic waste

Claims (5)

In an anaerobic treatment system that biologically treats organic waste under anaerobic conditions
Equipped with a digestive tank that digests organic waste
Wherein the digester, a stirring portion for stirring the digestion tank, fixing part is provided for fixing the conductive material into the digestion tank,
The anaerobic treatment system includes an addition part for adding a conductive substance in addition to the fixing part.
The anaerobic treatment system is characterized in that the stirring unit stirs organic waste to promote a reaction with microorganisms and increases the contact efficiency between a conductive substance and microorganisms. The anaerobic treatment system according to claim 1, wherein the fixed portion is located above the stirring portion. The anaerobic treatment system according to claim 1 or 2, wherein the amount of the conductive substance added from the addition portion is 0.01 kg or less per 1 kg of dry weight of the organic waste. .. The anaerobic treatment system according to any one of claims 1 to 3, wherein the addition portion is provided in front of the digestion tank. The anaerobic substance according to any one of claims 1 to 4, wherein the particle size of the conductive substance added from the addition portion is smaller than the particle size of the conductive substance fixed in the fixing portion. Sex processing system.

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