Waste water treatment system

Abstract

To maintain fermentation efficiency of methane fermentation of a fermentation raw material containing much oil content.SOLUTION: A waste water treatment system 10 includes: a first solid-liquid separation device 30 for separating a first solid matter from first organic waste water containing garbage crushed by a disposer 20; a second solid-liquid separation device 80 for separating a second solid matter from second organic waste water having oil content concentration higher than that of the first organic waste water; a fat and oil degrading tank 100 for storing the second solid matter, to which fat and oil degrading microorganisms degrading the stored second solid matter are supplied; and a methane fermentation tank 120 for subjecting the first solid matter, and the second solid matter supplied from the fat and oil degrading tank 100 as a fermentation raw material to methane fermentation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wastewater treatment system. [Background technology]

[0002] A wastewater treatment system is known that includes a first solid-liquid separation device that separates first organic wastewater containing food waste crushed by a crusher into first solids and second organic wastewater, a second solid-liquid separation device that coagulates and separates the second solids from the second organic wastewater, a third solid-liquid separation device that separates the third solids from the third organic wastewater, and a wastewater treatment device that treats the first solids, the second solids, and the third solids as wastewater (see, for example, Patent Document 1).

[0003] Also known is a methane production method that involves adding lipase and / or microorganisms capable of producing lipase to organic waste containing triglycerides and / or fatty acids, stirring the mixture, and then subjecting the mixture to methane fermentation (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2023 / 95314 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-296214 Summary of the Invention [Problem to be solved by the invention]

[0005] When fermentation raw materials such as organic waste are detoxified by methane fermentation, if the fermentation raw materials have a high oil concentration, methane fermentation of the fermentation raw materials may be inhibited, resulting in a decrease in the fermentation efficiency of methane fermentation.

[0006] In consideration of the above, an object of the present invention is to maintain the fermentation efficiency of methane fermentation of a fermentation feedstock containing a large amount of oil. [Means for solving the problem]

[0007] The wastewater treatment system described in claim 1 includes a first solid-liquid separation device that separates first solids from first organic wastewater containing food waste crushed by a crusher; a second solid-liquid separation device that separates second solids from second organic wastewater having a higher oil concentration than the first organic wastewater; an oil-decomposition tank that stores the second solids and is supplied with oil-decomposing microorganisms that decompose the stored second solids; and a methane fermentation tank that performs methane fermentation on the first solids and the second solids supplied from the oil-decomposition tank as fermentation raw materials.

[0008] A wastewater treatment system according to claim 1 includes a first solid-liquid separator, a second solid-liquid separator, an oil / grease decomposition tank, and a methane fermentation tank. The first solid-liquid separator separates first solids from first organic wastewater containing food waste crushed by a crusher.

[0009] Meanwhile, the second solid-liquid separator separates second solids from the second organic wastewater, which has a higher oil concentration than the first organic wastewater. This second solids is stored in the oil / fat decomposition tank. The methane fermenter then performs methane fermentation on the first solids and the second solids supplied from the oil / fat decomposition tank as fermentation feedstocks. This converts the first solids and the second solids into biogas primarily composed of methane and carbon dioxide.

[0010] Here, fat-decomposing microorganisms that decompose the stored second solids are supplied to the fat-decomposing tank. This causes the fat-decomposing microorganisms to decompose, for example, higher fatty acids in the second solids into lower fatty acids. As a result, the oil concentration of the second solids supplied from the fat-decomposing tank to the methane fermentation tank is reduced. Therefore, the fermentation efficiency of methane fermentation of the fermentation feedstock with a high oil concentration in the methane fermentation tank can be maintained.

[0011] Furthermore, in the present invention, as described above, the second solid matter separated from the second organic wastewater, which has a higher oil concentration than the first organic wastewater, is decomposed by oil-degrading microorganisms. As a result, in the present invention, the oil concentration of the fermentation raw material in the methane fermentation tank can be reduced more efficiently than in the case where the first solid matter separated from the first organic wastewater is decomposed by oil-degrading microorganisms.

[0012] The wastewater treatment system according to a second aspect of the present invention is the wastewater treatment system according to the first aspect, further comprising an activation means for activating the oil-decomposing microorganisms in the oil-decomposing tank.

[0013] According to the wastewater treatment system of claim 2, the activation means activates the oil-decomposing microorganisms in the oil-decomposing tank.

[0014] As a result, in the present invention, compared to when the oil-decomposing microorganisms in the oil-decomposing tank are not activated, it is possible to reduce the amount of oil-decomposing microorganisms required to decompose higher fatty acids in the second solid matter into lower fatty acids, and to shorten the decomposition time.

[0015] The wastewater treatment system of claim 3 is the wastewater treatment system of claim 1 or claim 2, and further comprises a storage time control means for adjusting the amount of the second solid material supplied from the fat / oil decomposition tank to the methane fermentation tank and controlling the storage time of the second solid material in the fat / oil decomposition tank.

[0016] In the wastewater treatment system according to claim 3, the retention time control means adjusts the amount of the second solids supplied from the fat / oil decomposition tank to the methane fermentation tank, thereby controlling the retention time of the second solids in the fat / oil decomposition tank, thereby ensuring time for decomposing higher fatty acids in the second solids into lower fatty acids in the fat / oil decomposition tank. [Effects of the Invention]

[0017] As described above, according to the present invention, it is possible to maintain the fermentation efficiency of methane fermentation of a fermentation raw material containing a large amount of oil. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a system configuration diagram showing a wastewater treatment system according to an embodiment. [Figure 2] FIG. 10 is a partially enlarged system configuration diagram showing a modified example of the wastewater treatment system according to the embodiment. [Figure 3] FIG. 10 is a system configuration diagram showing a modified example of the wastewater treatment system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, this embodiment will be described with reference to the drawings.

[0020] (Wastewater treatment system) A wastewater treatment system 10 according to this embodiment is shown in Figure 1. As an example, the wastewater treatment system 10 is a disposer wastewater treatment system that is applied to a structure such as a commercial complex and treats food waste (garbage) and kitchen wastewater generated in the kitchens of multiple restaurants within the structure.

[0021] The wastewater treatment system 10 is not limited to applications in commercial complexes, but can also be applied to structures such as apartment buildings.

[0022] The wastewater treatment system 10 includes a disposer 20, a first solid-liquid separation device 30, a second solid-liquid separation device 50, a second solid-liquid separation device 80, an oil / fat decomposition tank 100, a wastewater treatment device 110, and a water treatment device 130.

[0023] (disposer) The disposer 20 is an example of a crusher that crushes food waste. The disposer 20 is installed, for example, under the sink in the kitchen of each restaurant, and discharges the crushed food waste together with water (tap water) into a first drain pipe 22. The disposer 20 generates disposer wastewater containing food waste (hereinafter referred to as "first organic wastewater").

[0024] The disposer 20 is connected to the first solid-liquid separation device 30 via the above-mentioned first drainage pipe 22. The first organic wastewater generated in this disposer 20 is supplied to the first solid-liquid separation device 30 via the first drainage pipe 22 by natural drainage (gravity drainage) or by a pump or the like (not shown).

[0025] The disposer 20 is not limited to being installed in a kitchen sink of a restaurant, but may also be installed under a household sink, for example. At least one disposer 20 is sufficient. Furthermore, the shredder is not limited to the disposer 20, but may be another type of shredder.

[0026] (First solid-liquid separator) The first solid-liquid separator 30 is, for example, a screen-type solid-liquid separator that separates first solids from the first organic wastewater. The first solid-liquid separator 30 has a separation tank 32. The separation tank 32 is connected to a first drainage pipe 22. The first organic wastewater is supplied to the separation tank 32 from the disposer 20 via the first drainage pipe 22. A screen 34 is provided inside the separation tank 32.

[0027] The screen 34 is formed, for example, in a slit or mesh shape. The screen 34 also divides the interior of the separation tank 32. The first organic wastewater is passed through the screen 34. As a result, the first organic wastewater is separated into first solids having a size equal to or larger than a predetermined value that do not pass through the screen 34, and organic wastewater containing solids having a size smaller than the predetermined value that pass through the screen 34 (hereinafter referred to as "residual solids") and liquid (hereinafter referred to as "separated organic wastewater").

[0028] The post-separation organic wastewater is wastewater obtained by removing the first solid matter from the first organic wastewater (disposer wastewater).

[0029] A raw material tank 112 of a wastewater treatment device 110 (described later) is connected to the separation tank 32 via a pipe 40. A pump 42 such as a slurry pump is provided in the pipe 40. When the pump 42 is operated, the first solid material in the separation tank 32 is supplied to the raw material tank 112 via the pipe 40.

[0030] A flocculation reaction tank 52 of a solid-liquid re-separation apparatus 50 (described later) is connected to the separation tank 32 via a pipe 44. A pump 46 such as a slurry pump is provided to the pipe 44. When the pump 46 is operated, the separated organic wastewater in the separation tank 32 is supplied to the flocculation reaction tank 52 via the pipe 44.

[0031] (Re-solid-liquid separator) The solid-liquid re-separator 50 is, for example, a screen-type solid-liquid separator that separates residual solids from the separated organic wastewater by flocculation. The solid-liquid re-separator 50 has a flocculation reaction tank 52 and a separation tank 54.

[0032] The coagulation reaction tank 52 is a tank in which a coagulant is added to the separated organic wastewater to coagulate the residual solids, as shown by arrow a. The separated organic wastewater containing the residual solids coagulated in the coagulation reaction tank 52 is supplied to a separation tank 54 via piping or the like (not shown).

[0033] The flocculant is added to the flocculation reaction tank 52 in a predetermined amount and at a predetermined timing, for example, by an operator. Examples of flocculants include aluminum salts and iron chloride polyferric chloride. The flocculation reaction tank 52 may be provided in the solid-liquid re-separation device 50 as needed, and may be omitted as appropriate.

[0034] A screen 56 is provided inside the separation tank 54. The screen 56 is formed, for example, in a slit or mesh shape. The screen 56 also divides the interior of the separation tank 54. The separated organic wastewater containing flocculated residual solids is passed through this screen 56. This separates the separated organic wastewater into residual solids of a predetermined size or larger that do not pass through the screen 56 and treated water that passes through the screen 56.

[0035] A raw material tank 112 of a wastewater treatment device 110 (described later) is connected to the separation tank 54 via a pipe 60. A pump 62 such as a slurry pump is provided in the pipe 60. When the pump 62 is operated, the residual solids in the separation tank 54 are supplied to the raw material tank 112 via the pipe 60.

[0036] Separation tank 54 is connected to water treatment device 130 via piping 64. Pipe 64 is provided with pump 66. When pump 66 is operated, treated water in separation tank 54 is supplied to water treatment device 130 via piping 64.

[0037] The solid-liquid re-separator 50 is not limited to a screen type, but may be a flotation type solid-liquid separator.

[0038] (Second solid-liquid separator) The second solid-liquid separator 80 is, for example, a flotation-type solid-liquid separator that flocculates and separates second solids from kitchen wastewater (hereinafter referred to as "second organic wastewater"). The second solid-liquid separator 80 has a flocculation reaction tank 82 and a separation tank (flotation tank) 84.

[0039] A drain outlet of a generation source 70, such as a kitchen washing area, is connected to the coagulation reaction tank 82 via a second drain pipe 72. Kitchen wastewater (kitchen wastewater) including wash water used to wash dishes and the like is drained from the generation source 70 via the second drain pipe 72 into this coagulation reaction tank 82.

[0040] The second organic wastewater (kitchen wastewater) has a higher oil concentration than the first organic wastewater (garbage disposal wastewater) and the separated organic wastewater. Furthermore, the second organic wastewater is generated in smaller quantities than the first organic wastewater and the separated organic wastewater, for example. In other words, the first organic wastewater and the separated organic wastewater have lower oil concentrations and are generated in larger quantities than the second organic wastewater.

[0041] The coagulation reaction tank 82 is a tank in which a coagulant is added to the second organic wastewater, as indicated by arrow b, to coagulate second solids contained in the second organic wastewater. The second solids, such as scum, coagulated in this coagulation reaction tank 82 contain higher fatty acids that inhibit methane fermentation of the fermentation raw material in a methane fermentation tank 120, which will be described later. The second solids are supplied to a separation tank 84 via piping or the like (not shown).

[0042] The flocculant is added to the flocculation reaction tank 82 in a predetermined amount and at a predetermined timing, for example, by an operator. Examples of flocculants include aluminum salts and iron chloride polyferric chloride. The flocculation reaction tank 82 may be provided in the solid-liquid re-separation device 50 as needed, and may be omitted as appropriate.

[0043] The second organic wastewater containing second solids such as scum flocculated in the flocculation reaction tank 82 is supplied to the separation tank 84. In this separation tank 84, the second solids floating near the liquid surface of the second organic wastewater are removed by a removal device (not shown). As a result, the second organic wastewater is separated into the second solids and treated water (liquid).

[0044] The removal device is connected to an oil / fat decomposition tank 100 via piping 90. A pump 92 such as a slurry pump is provided in the piping 90. When this pump 92 is operated, the second solid matter removed in the removal device is supplied to the oil / fat decomposition tank 100 via piping 90.

[0045] Separation tank 84 is connected to water treatment device 130 via piping 94. This piping 94 is provided with a pump 96. When this pump 96 is operated, treated water in separation tank 84 is supplied to water treatment device 130 via piping 94.

[0046] (Oil / fat decomposition tank) The fat / oil decomposition tank 100 is a tank for storing second solids such as scum. Furthermore, fat / oil decomposition microorganisms are supplied to the fat / oil decomposition tank 100 from a microorganism storage tank 140, which will be described later. These fat / oil decomposition microorganisms decompose higher fatty acids contained in the second solids stored in the fat / oil decomposition tank 100 into lower fatty acids such as straight-chain carboxylic acids.

[0047] The fat / oil decomposition tank 100 is provided with a temperature sensor (not shown). The fat / oil decomposition tank 100 is also provided with a heater 106 such as a heater. The heater 106 heats the fat / oil decomposition tank 100 based on the temperature inside the fat / oil decomposition tank 100 detected by the temperature sensor described above, and maintains the temperature at a level that facilitates activation of fat / oil decomposition microorganisms inside the fat / oil decomposition tank 100.

[0048] The fat / oil decomposition tank 100 is also connected via a pipe 102 to a raw material tank 112 of a wastewater treatment device 110, which will be described later. The pipe 102 is provided with a pump 104, such as a slurry pump. When the pump 104 is operated, the second solid matter in the fat / oil decomposition tank 100 is supplied to the raw material tank 112 via the pipe 102.

[0049] (Microbial reservoir) The microbial storage tank 140 is a tank for storing fat-decomposing microorganisms, a culture solution for cultivating the fat-decomposing microorganisms, and the like. The fat-decomposing tank 100 is connected to this microbial storage tank 140 via a pipe 142. The pipe 142 is provided with a pump 144 such as a liquid pump. When this pump 144 is operated, the culture solution containing the fat-decomposing microorganisms stored in the microbial storage tank 140 is supplied to the fat-decomposing tank 100 via the pipe 142.

[0050] Here, for example, the amount of fat-decomposing microorganisms required to decompose higher fatty acids contained in the second solids per unit amount into lower fatty acids is determined in advance through experiments, etc. Then, the amount of fat-decomposing microorganisms to be supplied from the microorganism storage tank 140 to the fat-decomposing tank 100 is adjusted by controlling the operation of the pump 144 in accordance with the amount of second solids supplied from the second solid-liquid separator 80 to the fat-decomposing tank 100.

[0051] As described above, the fat-decomposing microorganisms decompose higher fatty acids contained in the second solid matter into lower fatty acids. Examples of fat-decomposing microorganisms include lipase-producing bacteria such as Bacillus, Pseudomonas, and Burkholderia, yeasts such as Yarrowia, filamentous fungi such as Aspergillus, microorganisms such as the Syntrophomonadaceae family that decompose higher fatty acids, and microorganisms such as Clostridium that convert unsaturated fatty acids into saturated fatty acids.

[0052] (Wastewater treatment equipment) The wastewater treatment device 110 is a biological treatment device that decomposes the fermentation raw materials by methane fermentation using the first solid matter, the residual solid matter, and the second solid matter as fermentation raw materials. The wastewater treatment device 110 has a raw material tank 112 and a methane fermentation tank 120.

[0053] (Raw material tank) The raw material tank 112 is a storage tank that stores a mixture of the first solid material, the residual solid material, and the second solid material as a fermentation raw material. This raw material tank 112 is provided with a temperature sensor (not shown). The raw material tank 112 is also provided with a heater 114. The heater 114 heats the inside of the raw material tank 112 based on the temperature inside the raw material tank 112 detected by the temperature sensor described above, and maintains the fermentation raw material in the raw material tank 112 at a predetermined temperature (for example, 30°C to 40°C) at which the fermentation raw material is easily flowable.

[0054] The heater 114 may be provided in the raw material tank 112 as needed, and may be omitted as appropriate.

[0055] A methane fermentation tank 120 is connected to the raw material tank 112 via a pipe 116. A pump 118 such as a slurry pump is provided in the pipe 116. When this pump 118 is operated, the fermentation raw material is supplied from the raw material tank 112 via the pipe 116 to the methane fermentation tank 120.

[0056] (methane fermentation tank) The methane fermentation tank 120 decomposes (detoxifies) the fermentation raw material by methane fermentation. During this process, biogas containing methane and carbon dioxide as its main components is generated. A pipe 122 is connected to the methane fermentation tank 120. The biogas generated in the methane fermentation tank 120 is supplied via the pipe 122 to a biogas utilization device such as a power generation device (not shown).

[0057] Furthermore, a pipe 124 is connected to the methane fermentation tank 120. A pump 126 is provided in the pipe 124. When the pump 126 is operated, treated water such as digestive fluid generated in the methane fermentation tank 120 is supplied to the water treatment device 130 via the pipe 124.

[0058] The methane fermentation method employed by the methane fermenter 120 is not particularly limited, and may be a mesophilic fermentation method in which the fermentation temperature is around 37° C., or a thermophilic fermentation method in which the fermentation temperature is around 55° C. Furthermore, the methane fermentation method employed by the methane fermenter 120 may be a wet method in which the amount of water is relatively high, or a dry method in which the amount of water is relatively low.

[0059] (Water treatment equipment) The water treatment device 130 has a second solid-liquid separation device 50, a second solid-liquid separation device 80, and a water treatment tank 132 that treats the treated water supplied from the methane fermentation tank 120. The treated water treated in the water treatment tank 132 is discharged via a pipe 134, for example, into a public sewer outside the structure.

[0060] (Wastewater treatment method) Next, an example of a wastewater treatment method using the wastewater treatment system 10 will be described.

[0061] In the wastewater treatment method according to this embodiment, first, in a first solid separation step, first organic wastewater containing food waste crushed by a disposer 20 is separated into first solids and separated organic wastewater by a first solid-liquid separator 30. Next, in a residual solid separation step, residual solids are coagulated and separated from the separated organic wastewater by a second solid-liquid separator 50.

[0062] Meanwhile, in the second solid separation step, the second solids are coagulated and separated from the second organic wastewater by the second solid-liquid separator 80. The second solid separation step may be carried out in parallel with the first solid separation step and the residual solid separation step, or may be carried out before or after the first solid separation step and the residual solid separation step.

[0063] Next, in the fat / oil splitting step, the higher fatty acids in the second solid matter stored in the fat / oil splitting tank 100 are decomposed into lower fatty acids by fat / oil splitting microorganisms.

[0064] Next, in the methane fermentation step, the first solid matter, the residual solid matter, and the second solid matter obtained by decomposing the higher fatty acids into lower fatty acids in the fat and oil decomposition step are subjected to methane fermentation in the methane fermentation tank 120.

[0065] (Action and effect) Next, the operation and effects of this embodiment will be described.

[0066] As shown in FIG. 1, the wastewater treatment system 10 according to this embodiment includes a first solid-liquid separation device 30, a second solid-liquid separation device 50, a second solid-liquid separation device 80, an oil / fat decomposition tank 100, a microbial storage tank 140, a raw material tank 112, and a methane fermentation tank 120.

[0067] The first solid-liquid separator 30 separates the first organic wastewater containing food waste crushed by the disposer 20 into first solids and separated organic wastewater. The second solid-liquid separator 50 separates the remaining solids from the separated organic wastewater.

[0068] Meanwhile, the second solid-liquid separator 80 separates second solids from the second organic wastewater, which has a higher oil concentration than the first organic wastewater. This second solids is stored in the fat / oil decomposition tank 100. The methane fermenter 120 then performs methane fermentation using the first solids, residual solids, and the second solids supplied from the fat / oil decomposition tank 100 as fermentation raw materials. This converts the fermentation raw material into biogas containing methane and carbon dioxide as main components, and decomposes (detoxifies) the organic matter in the fermentation raw material.

[0069] Here, if the oil concentration in the fermentation raw material is high, methane fermentation of the fermentation raw material may be inhibited, and the fermentation efficiency of methane fermentation may decrease.

[0070] To address this issue, in this embodiment, oil-decomposing microorganisms are supplied from the microorganism storage tank 140 to the oil-decomposition tank 100 in which the second solids are stored. This causes the oil-decomposing microorganisms to decompose, for example, higher fatty acids in the second solids into lower fatty acids. As a result, the oil concentration of the second solids supplied from the oil-decomposition tank 100 to the methane fermentation tank 120 decreases. This makes it possible to maintain the fermentation efficiency of methane fermentation of the fermentation feedstock in the methane fermentation tank 120, which has a high oil concentration.

[0071] As described above, the second organic wastewater has a higher oil concentration than the first organic wastewater. The second solid matter separated from the second organic wastewater is decomposed by oil-degrading microorganisms. As a result, in this embodiment, the oil concentration of the fermentation raw material in the methane fermentation tank 120 can be more efficiently reduced than in the case where the first solid matter separated from the first organic wastewater is decomposed by oil-degrading microorganisms.

[0072] Furthermore, in this embodiment, a heater 106 is provided in the fat / oil decomposition tank 100. By heating the inside of the fat / oil decomposition tank 100 with this heater 106, the temperature inside the fat / oil decomposition tank 100 is adjusted (maintained) at a temperature at which fat / oil decomposition microorganisms are easily activated.

[0073] As a result, in this embodiment, compared to when the temperature in the fat / oil decomposition tank 100 is not adjusted, it is possible to reduce the amount of fat / oil decomposition microorganisms required to decompose higher fatty acids in the second solid matter into lower fatty acids, and to shorten the decomposition time.

[0074] Furthermore, by heating the second solids in the fat / oil decomposition tank 100 with the heater 106, the fluidity of the second solids is increased. Therefore, the second solids can be easily supplied from the fat / oil decomposition tank 100 to the methane fermentation tank 120 via the raw material tank 112.

[0075] Furthermore, as described above, the second solids have a higher oil concentration than the first solids and the residual solids. Therefore, in the fat / oil decomposition tank 100, by heating the second solids by the heater 106 separately from the first solids and the residual solids, the fluidity of the second solids can be efficiently increased.

[0076] The second solids are supplied from the fat / oil decomposition tank 100 to the raw material tank 112. By storing the second solids in the fat / oil decomposition tank 100 in this manner, higher fatty acids in the second solids can be decomposed into lower fatty acids, while a constant amount of the second solids can be continuously supplied from the fat / oil decomposition tank 100 to the raw material tank 112. This further increases the fermentation efficiency of the fermentation raw material in the methane fermenter 120.

[0077] Here, as a method for reducing the oil concentration of the fermentation raw material in the methane fermenter 120, for example, it is possible to add a secondary material (additive) that reduces the oil concentration of the fermentation raw material to the raw material tank 112 or the methane fermenter 120.

[0078] However, the amount of the secondary material to be added is set according to the total amount of the first solid, the residual solid, and the second solid, which increases the required capacity (required volume) of the raw material tank 112 and the methane fermenter 120.

[0079] In contrast, in this embodiment, no secondary materials are added to the raw material tank 112 or the methane fermentation tank 120, and the higher fatty acids in the second solid matter stored in the fat / oil decomposition tank 100 are decomposed into lower fatty acids by the fat / oil decomposition microorganisms. Therefore, in this embodiment, the required capacities of the raw material tank 112 and the methane fermentation tank 120 can be reduced compared to when secondary materials are added to the raw material tank 112 and the methane fermentation tank 120.

[0080] Therefore, this embodiment is particularly effective when there are restrictions on the installation space for the raw material tank 112 and the methane fermentation tank 120, or when renovating an existing wastewater treatment system 10. In this embodiment as well, secondary materials may be added to the raw material tank 112 and the methane fermentation tank 120 as needed.

[0081] In this embodiment, as described above, the solid-liquid re-separator 50 separates the residual solids from the separated organic wastewater by flocculating them. Therefore, in this embodiment, the amount of flocculant to be added to the separated organic wastewater in the flocculation reaction tank 52 of the solid-liquid re-separator 50 can be set based on the oil concentration of the separated organic wastewater, the amount of wastewater, the frequency of wastewater discharge, etc.

[0082] Similarly, in this embodiment, the second solids are coagulated and separated from the second organic wastewater by the second solid-liquid separator 80. Therefore, in this embodiment, the amount of coagulant to be added to the second organic wastewater in the coagulation reaction tank 82 of the second solid-liquid separator 80 can be set based on the oil concentration of the second organic wastewater, the amount of wastewater, the frequency of wastewater discharge, etc.

[0083] Therefore, in this embodiment, the amount of flocculant added to the separated organic wastewater and the second organic wastewater can be optimized compared to when the mixed wastewater of the separated organic wastewater and the second organic wastewater is subjected to solid-liquid separation using a single solid-liquid separation device.

[0084] As described above, the oil concentration of the second organic wastewater is higher than that of the separated organic wastewater. This embodiment is particularly effective in such cases. This is because, when the oil concentration of the second organic wastewater is higher than that of the separated organic wastewater, the difference between the required amount of flocculant added to the separated organic wastewater and the required amount of flocculant added to the second organic wastewater is likely to be large.

[0085] Furthermore, the wastewater treatment device 110 of this embodiment has a raw material tank 112 that stores the first solid matter, the residual solid matter, and the second solid matter. The fermentation raw material is supplied from this raw material tank 112 to a methane fermentation tank 120.

[0086] By storing the fermentation raw material in the raw material tank 112 in this manner, a constant amount of the fermentation raw material can be continuously supplied from the raw material tank 112 to the methane fermenter 120. Therefore, the fermentation efficiency of the fermentation raw material in the methane fermenter 120 can be improved.

[0087] (Variation) Next, a modification of the above embodiment will be described.

[0088] In the above embodiment, the activation means for activating the fat-decomposing microorganisms is the heater 106 that heats the second solid matter in the fat-decomposing tank 100. However, the activation means is not limited to the heater 106, and may be, for example, a pH adjustment means that adds a chemical or the like to the fat-decomposing tank 100 and adjusts the pH (potential hydrogen) in the fat-decomposing tank 100 to a value that makes it easy for the fat-decomposing microorganisms to be activated.

[0089] The activation means may also be, for example, an ORP adjustment means that aerates the separation tank (floatation tank) 84 of the second solid-liquid separator 80 and adjusts the ORP (Oxidation Reduction Potential) in the fat / oil decomposition tank 100 to a value that facilitates activation of the fat / oil decomposition microorganisms. Furthermore, the activation means may also be, for example, a nutrient addition means that adds a nutrient (additive) to the fat / oil decomposition tank 100 to activate the fat / oil decomposition microorganisms.

[0090] The wastewater treatment system 10 according to the above embodiment may also be provided with a retention time control means. The retention time control means controls the retention time of the second solids in the fat / oil decomposition tank 100 in accordance with the time required for the fat / oil decomposition microorganisms to decompose the higher fatty acids in the second solids into lower fatty acids (required decomposition time). For example, in the modified example shown in Fig. 2, the pump 104 and the control device 160 that controls the pump 104 function as the retention time control means.

[0091] Specifically, a flow rate measuring unit 150 is electrically connected to the control device 160. The flow rate measuring unit 150 is provided on a pipe 90 that supplies the second solids from the second solid-liquid separator 80 to the fat / oil decomposition tank 100. The flow rate measuring unit 150 measures the flow rate (supply amount) of the second solids that are supplied from the second solid-liquid separator 80 to the fat / oil decomposition tank 100, and outputs the measured flow rate of the second solids to the control device 160.

[0092] In addition, a storage amount measuring unit 152 is electrically connected to the control device 160. The storage amount measuring unit 152 is provided in the fat / oil decomposition tank 100. This storage amount measuring unit 152 measures the storage amount of the second solid matter stored in the fat / oil decomposition tank 100.

[0093] Specifically, the storage amount measuring unit 152 detects, for example, the liquid level of the second solids in the fat / oil decomposition tank 100, and calculates the storage amount of the second solids based on the detected liquid level of the second solids. The storage amount measuring unit 152 measures the storage amount of the second solids stored in the fat / oil decomposition tank 100, and outputs the measured storage amount of the second solids to the control device 160.

[0094] The control device 160 is electrically connected to a pump 104 that supplies the second solids from the fat / oil decomposition tank 100 to the raw material tank 112. The control device 160 adjusts the amount of the second solids supplied from the fat / oil decomposition tank 100 to the methane fermentation tank 120 via the raw material tank 112 using the pump 104, and controls the retention time of the second solids in the fat / oil decomposition tank 100.

[0095] More specifically, the control device 160 controls the pump 104 based on the flow rate of the second solids measured by the flow rate measuring unit 150 and the storage amount of the second solids in the fat decomposition tank 100 measured by the storage amount measuring unit 152 so that the storage time of the second solids in the fat decomposition tank 100 is equal to or longer than a predetermined time.

[0096] For example, the required decomposition time of the second solids by the fat-decomposing microorganisms is set to two days, and the flow rate (average flow rate) of the second solids supplied from the second solid-liquid separator 80 to the fat-decomposing tank 100, i.e., the flow rate (average flow rate) of the second solids measured by the flow rate measuring unit 150, is set to 10 liters / day. In this case, the control device 160 controls the pump 104 so that the amount of the second solids stored in the fat-decomposing tank 100 becomes 20 liters.

[0097] This results in an average storage time of two days for the second solid material in the fat / oil decomposition tank 100. Therefore, it is possible to ensure sufficient time for decomposition of higher fatty acids in the second solid material into lower fatty acids in the fat / oil decomposition tank.

[0098] Furthermore, since the second organic wastewater is kitchen wastewater or the like, it is likely to be generated at a predetermined time, such as in the evening. In this way, when the timing of generation of the second organic wastewater is predictable, for example, the pump 104 may be operated after the second solids in the second organic wastewater generated at the predetermined timing have been stored in the fat / oil decomposition tank 100 and the required decomposition time for the second solids has elapsed. This makes it possible to make the storage time of the second solids in the fat / oil decomposition tank 100 longer than the required decomposition time for the second solids.

[0099] In the above embodiment, the second solid material is supplied from the fat / oil decomposition tank 100 to the raw material tank 112 via the pipe 102. However, as in a modified example shown in Figure 3, the second solid material may be supplied from the fat / oil decomposition tank 100 to the methane fermentation tank 120 via the pipe 102.

[0100] Specifically, the fat / oil decomposition tank 100 is connected to a methane fermentation tank 120 via a pipe 102. A pump 104 provided in this pipe 102 is operated to supply the second solid material from the fat / oil decomposition tank 100 to the methane fermentation tank 120 via the pipe 102.

[0101] In the above embodiment, the wastewater treatment device 110 is provided with the raw material tank 112. However, the raw material tank 112 may be omitted, and the first solids, residual solids, and second solids may be supplied to the methane fermentation tank 120 from the first solid-liquid separation device 30, the second solid-liquid separation device 50, and the fat / oil decomposition tank 100.

[0102] In the above embodiment, the wastewater treatment system 10 is provided with a solid-liquid re-separator 50. However, the solid-liquid re-separator 50 may be provided in the wastewater treatment system 10 as needed, and may be omitted as appropriate.

[0103] Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and one embodiment and various modified examples may be used in appropriate combination, and it goes without saying that the present invention can be implemented in various forms as long as it does not deviate from the gist of the present invention. [Explanation of symbols]

[0104] 10 Wastewater treatment system 20. Disposer (crusher) 30 First solid-liquid separator 80 Second solid-liquid separator 100 Oil and fat decomposition tank 104 Pump (retention time control means) 106 Heater (activation means) 120 Methane fermentation tank 140 Microbial Reservoir 160 Control device (retention time control means)

Claims

1. a first solid-liquid separation device that separates first solid matter from first organic wastewater containing food waste crushed by the crusher; a second solid-liquid separator that separates second solids from second organic wastewater having a higher oil concentration than the first organic wastewater; A fat / oil decomposition tank that stores the second solid material and is supplied with fat / oil decomposition microorganisms that decompose the stored second solid material; a methane fermentation tank for performing methane fermentation using the first solid material and the second solid material supplied from the fat / oil decomposition tank as fermentation raw materials; A wastewater treatment system comprising:

2. An activation means for activating oil-decomposing microorganisms in the oil-decomposing tank is provided. The wastewater treatment system according to claim 1 .

3. a storage time control means for adjusting the amount of the second solid material supplied from the fat / oil decomposition tank to the methane fermentation tank and controlling the storage time of the second solid material in the fat / oil decomposition tank; The wastewater treatment system according to claim 1 or 2.

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