Wastewater treatment system and wastewater treatment method

Abstract

This wastewater treatment system includes: a first solid / liquid separation device that separates first organic wastewater, which includes kitchen waste crushed by a crusher, into first solid matter and second organic wastewater; a second solid / liquid separation device that aggregates and separates second solid matter from the second organic wastewater; a third solid / liquid separation device that separates third solid matter from third organic wastewater; and a wastewater treatment device for subjecting the first solid matter, the second solid matter, and the third solid matter to wastewater treatment.

Description

[Technical Field]

[0001] The technology disclosed in the present application relates to a wastewater treatment system and a wastewater treatment method. [Background technology]

[0002] A wastewater treatment system is known that uses a biological treatment device to treat disposer wastewater containing food waste crushed by a disposer (see, for example, Japanese Patent Application Laid-Open No. 2011-177637 and Japanese Patent Application Laid-Open No. 2021-122772). Summary of the Invention [Problem to be solved by the invention]

[0003] The wastewater treatment system disclosed in JP 2011-177637 A includes a first solid-liquid separation device and a second solid-liquid separation device. The first solid-liquid separation device separates solids (organic matter) from wastewater discharged from a garbage disposal. The solids separated by the first solid-liquid separation device are supplied to a biological treatment device where they are decomposed (detoxified).

[0004] The second solid-liquid separation device separates solid matter from a mixture of the garbage disposal wastewater discharged from the first solid-liquid separation device and the kitchen wastewater discharged from the kitchen washing area, etc. The solid matter separated by this second solid-liquid separation device is supplied to a biological treatment device where it is decomposed (made harmless).

[0005] In this way, in the wastewater treatment system disclosed in JP 2011-177637 A, the mixed wastewater from the garbage disposal and the kitchen wastewater is subjected to solid-liquid separation using a single second solid-liquid separation device. As a result, in the wastewater treatment system disclosed in JP 2011-177637 A, the number of solid-liquid separation devices can be reduced compared to when the mixed wastewater from the garbage disposal and the kitchen wastewater are separated into solid and liquid by separate solid-liquid separation devices.

[0006] Incidentally, in the second solid-liquid separation device, a flocculation treatment is also used in which, for example, a flocculant is added to the mixed wastewater of the garbage disposal wastewater and the kitchen wastewater to flocculate solid matter.

[0007] However, coagulation treatment is not necessarily required for both garbage disposal wastewater and kitchen wastewater. Even if coagulation treatment is required for both garbage disposal wastewater and kitchen wastewater, the oil concentration, amount of wastewater, and frequency of discharge differ between the garbage disposal wastewater and kitchen wastewater. Therefore, the amount of coagulant required to be added to the garbage disposal wastewater and kitchen wastewater differs.

[0008] Therefore, as mentioned above, when the mixed wastewater of garbage disposal wastewater and kitchen wastewater is subjected to solid-liquid separation using a single second solid-liquid separation device, there is a possibility that the flocculant added to the mixed wastewater will be wasted.

[0009] Therefore, the technology disclosed in the present application aims to optimize the amount of flocculant added. [Means for solving the problem]

[0010] The wastewater treatment system according to a first aspect 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 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.

[0011] In the wastewater treatment system according to the first aspect, the first solid-liquid separator separates the first organic wastewater containing food waste crushed by the crusher into a first solid and a second organic wastewater, and the second solid-liquid separator flocculates and separates the second solid from the second organic wastewater.

[0012] Meanwhile, the third solid-liquid separator separates the third solid matter from the third organic wastewater, and the first solid matter, the second solid matter, and the third solid matter are subjected to wastewater treatment in a wastewater treatment device.

[0013] In this manner, in this embodiment, the second solid-liquid separator separates the second solid matter from the second organic wastewater by flocculation, and the third solid matter is separated from the third organic wastewater by the third solid-liquid separator.

[0014] Therefore, in this embodiment, the amount of coagulant to be added to the second organic wastewater in the second solid-liquid separation device can be set based on the oil concentration of the second organic wastewater, the amount of wastewater, and the frequency of wastewater discharge, etc.

[0015] Therefore, in this embodiment, the amount of coagulant added to the second organic wastewater can be optimized compared to when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using a single solid-liquid separation device.

[0016] The wastewater treatment system according to the second aspect 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 separates the second solids from the second organic wastewater, a third solid-liquid separation device that coagulates and separates 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.

[0017] In the wastewater treatment system according to the second aspect, the first solid-liquid separator separates the first organic wastewater containing food waste crushed by the crusher into the first solid matter and the second organic wastewater, and the second solid-liquid separator separates the second solid matter from the second organic wastewater.

[0018] On the other hand, the third solid-liquid separator flocculates and separates the third solid matter from the third organic wastewater, and the first solid matter, the second solid matter, and the third solid matter are then subjected to wastewater treatment in a wastewater treatment device.

[0019] In this manner, in this embodiment, the second solid matter is separated from the second organic wastewater by the second solid-liquid separator, and the third solid matter is coagulated and separated from the third organic wastewater by the third solid-liquid separator.

[0020] Therefore, in this embodiment, the amount of coagulant to be added to the third organic wastewater in the third solid-liquid separation device can be set depending on the oil concentration of the third organic wastewater, the amount of wastewater, and the frequency of wastewater discharge, etc.

[0021] Therefore, in this embodiment, the amount of coagulant added to the third organic wastewater can be optimized compared to when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using a single solid-liquid separation device.

[0022] A wastewater treatment system according to a third aspect is the wastewater treatment system according to the first or second aspect, wherein the oil concentration of the third organic wastewater is higher than the oil concentration of the second organic wastewater.

[0023] In the wastewater treatment system according to the third aspect, the oil concentration of the third organic wastewater is higher than the oil concentration of the second organic wastewater. In such a case, the second organic wastewater and the third organic wastewater are likely to require different coagulation treatments.

[0024] Furthermore, even if coagulation treatment is required for both the second organic wastewater and the third organic wastewater, the difference between the amount of coagulant required to be added to the second organic wastewater and the amount of coagulant required to be added to the third organic wastewater is likely to be large.

[0025] In such a case, this embodiment is particularly effective. That is, in this embodiment, the second solid matter is separated from the second organic wastewater by the second solid-liquid separator, and the third solid matter is separated from the third organic wastewater by the third solid-liquid separator.

[0026] As a result, in this embodiment, the amount of coagulant added to the second organic wastewater or the third organic wastewater can be optimized compared to when a mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using a single solid-liquid separation device.

[0027] A wastewater treatment system according to a fourth aspect is the wastewater treatment system according to the third aspect, wherein the wastewater treatment device has a methane fermentation tank for performing methane fermentation using the first solid material, the second solid material, the third solid material, and an additive as fermentation raw materials, and the additive adjusts the ratio of the concentration of normal hexane extractable substances in the fermentation raw materials to the loss on ignition of the fermentation raw materials to a predetermined value or less.

[0028] According to a fourth aspect of the wastewater treatment system, the wastewater treatment device includes a methane fermentation tank. The methane fermentation tank performs methane fermentation on the first solid material, the second solid material, the third solid material, and the additive as fermentation raw materials. This decomposes (detoxifies) the fermentation raw materials.

[0029] Here, if the fermentation feedstock has a high oil concentration, methane fermentation of the fermentation feedstock may be inhibited. Therefore, in this embodiment, an additive is added to the first solid material, the second solid material, and the third solid material to make the ratio of the concentration of normal hexane extractable substances in the fermentation feedstock to the loss on ignition of the fermentation feedstock equal to or less than a predetermined value.

[0030] In other words, by adding an additive to the first solid material, the second solid material, and the third solid material, the oil concentration of the fermentation raw material is reduced to a predetermined value or less, thereby enabling efficient methane fermentation of the fermentation raw material.

[0031] The amount of additive to be added is calculated based on, for example, the amounts of the first solid, the second solid, and the third solid supplied to the methane fermentation tank, their losses on ignition, and the concentrations of normal-hexane extractables. In this case, the losses on ignition and the concentrations of normal-hexane extractables of the first solid, the second solid, and the third solid are analyzed from samples collected from the first solid, the second solid, and the third solid, for example.

[0032] Here, when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using a single solid-liquid separator, the second solid matter and the third solid matter are mixed together, making it difficult to measure the amounts of the second solid matter and the third solid matter supplied to the methane fermentation tank, respectively.

[0033] Furthermore, when the second organic wastewater and the third organic wastewater are generated at different frequencies, the ratio of the second solids to the third solids in the mixture varies depending on the timing at which a sample is collected from the mixture of the second solids and the third solids. This variation causes the loss on ignition and the concentration of normal-hexane extractables of the mixture of the second solids and the third solids to also vary, making it difficult to accurately analyze the loss on ignition and the concentration of normal-hexane extractables of the mixture.

[0034] In contrast, in this embodiment, the amounts of the first solid, the second solid, and the third solid supplied to the methane fermentation tank can be measured separately. Also, in this embodiment, samples can be collected from each of the first solid, the second solid, and the third solid. Then, the ignition loss and the n-hexane extractables concentration of the first solid, the second solid, and the third solid collected can be analyzed separately from the samples.

[0035] Therefore, in this aspect, even if the second organic wastewater and the third organic wastewater are generated at different frequencies, the accuracy of calculating the amount of additive to be added to the first solid, the second solid, and the third solid can be improved. Therefore, in this aspect, the oil concentration of the fermentation raw material can be more reliably kept at or below a predetermined value.

[0036] A wastewater treatment system according to a fifth aspect is the wastewater treatment system according to the fourth aspect, wherein the wastewater treatment device has a raw material tank for storing the first solids and the second solids, and a mixture of the first solids and the second solids is supplied to the methane fermentation tank from the raw material tank.

[0037] In a wastewater treatment system according to a fifth aspect, the wastewater treatment device includes a raw material tank for storing a first solid material and a second solid material, and a mixture of the first solid material and the second solid material is supplied from the raw material tank to a methane fermentation tank.

[0038] By storing the first solid material and the second solid material in the raw material tank in this manner, a constant amount of the mixture of the first solid material and the second solid material can be continuously supplied from the raw material tank to the methane fermenter, thereby increasing the fermentation efficiency of the fermentation raw material in the methane fermenter.

[0039] A wastewater treatment system according to a sixth aspect is the wastewater treatment system according to the fourth or fifth aspect, further comprising a storage tank for storing the third solid material, and the third solid material is supplied to the wastewater treatment device from the storage tank.

[0040] In the wastewater treatment system according to the sixth aspect, the storage tank stores the third solid material, and the third solid material is supplied from the storage tank to the wastewater treatment device.

[0041] By storing the third solid material in the storage tank in this manner, a constant amount of the third solid material can be continuously supplied from the raw material tank to the wastewater treatment device, thereby improving the efficiency of wastewater treatment by the wastewater treatment device.

[0042] A wastewater treatment system according to a seventh aspect is the wastewater treatment system according to the sixth aspect, wherein the storage tank has a heater that heats the third solid material.

[0043] In the wastewater treatment system according to the seventh aspect, the storage tank has a heater that heats the third solid material.

[0044] Here, the oil concentration of the third organic wastewater is higher than the oil concentration of the second organic wastewater, and therefore the third solid matter is likely to have a higher oil concentration than the first solid matter and the second solid matter.

[0045] Therefore, by heating the third solids by the heater separately from the first and second solids, the fluidity of the third solids can be efficiently increased, and as a result, the third solids can be easily supplied from the storage tank to the wastewater treatment device.

[0046] The wastewater treatment system according to an eighth aspect is the wastewater treatment system according to any one of the fourth to seventh aspects, and further comprises a first flow rate measuring unit that measures the flow rate of the first solid, a second flow rate measuring unit that measures the flow rate of the second solid, and a third flow rate measuring unit that measures the flow rate of the third solid.

[0047] In the wastewater treatment system according to the eighth aspect, the flow rates of the first solid, the second solid, and the third solid are measured by the first flow rate measuring unit, the second flow rate measuring unit, and the third flow rate measuring unit, respectively.

[0048] Therefore, even if the occurrence frequencies of the first solid, the second solid, and the third solid are different, the accuracy of calculating the amount of additive to be added to the first solid, the second solid, and the third solid can be improved.

[0049] A wastewater treatment system according to a ninth aspect is the wastewater treatment system according to any one of the fourth to seventh aspects, and further comprises a mixed flow rate measuring unit that measures the flow rate of the mixture of the first solid and the second solid, and a third flow rate measuring unit that measures the flow rate of the third solid.

[0050] In the wastewater treatment system according to the ninth aspect, the mixture flow rate measuring unit measures the flow rate of the mixture of the first solid and the second solid, and the third flow rate measuring unit measures the flow rate of the third solid.

[0051] Therefore, even if the amount or frequency of occurrence of the mixture of the first solid and the second solid differs from that of the third solid, the accuracy of calculating the amount of additive to be added to the first solid, the second solid, and the third solid can be improved.

[0052] A wastewater treatment method according to a tenth aspect includes a first solid separation step of separating first organic wastewater containing food waste crushed by a crusher into first solids and second organic wastewater, a second solid separation step of flocculating and separating the second solids from the second organic wastewater, a third solid separation step of separating third solids from the third organic wastewater, and a wastewater treatment step of treating the first solids, the second solids, and the third solids as wastewater.

[0053] In a wastewater treatment method according to a tenth aspect, in a first solid separation step, a first organic wastewater containing food waste crushed by a crusher is separated into a first solid and a second organic wastewater by a first solid-liquid separator, and then, in a second solid separation step, the second solid is separated from the second organic wastewater by flocculation by the second solid-liquid separator.

[0054] Meanwhile, in the third solid separation step, a third solid is separated from the third organic wastewater by a third solid-liquid separator. The third solid separation step may be carried out in parallel with the first solid separation step and the second solid separation step, or may be carried out before or after the first solid separation step and the second solid separation step.

[0055] Next, in the wastewater treatment step, the first solid matter, the second solid matter, and the third solid matter are subjected to wastewater treatment.

[0056] In this manner, in this embodiment, the second solid-liquid separator separates the second solid matter from the second organic wastewater by flocculation, and the third solid matter is separated from the third organic wastewater by the third solid-liquid separator.

[0057] Therefore, in this embodiment, the amount of coagulant to be added to the second organic wastewater in the second solid-liquid separation device can be set based on the oil concentration of the second organic wastewater, the amount of wastewater, and the frequency of wastewater discharge, etc.

[0058] Therefore, in this embodiment, the amount of coagulant added to the second organic wastewater can be optimized compared to when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation in a single solid-liquid separation device.

[0059] The wastewater treatment method according to an eleventh aspect includes a first solid separation step of separating first organic wastewater containing food waste crushed by a crusher into first solids and second organic wastewater using a first solid-liquid separation device; a second solid separation step of separating second solids from the second organic wastewater using a second solid-liquid separation device; a third solid separation step of flocculating and separating third solids from the third organic wastewater using a third solid-liquid separation device; and a wastewater treatment step of treating the first solids, the second solids, and the third solids as wastewater.

[0060] In the wastewater treatment method according to the eleventh aspect, in the first solid separation step, first organic wastewater containing food waste crushed by a crusher is separated into first solids and second organic wastewater by a first solid-liquid separator, and then in the second solid separation step, the second solids are separated from the second organic wastewater by a second solid-liquid separator.

[0061] On the other hand, in the third solid separation step, the third solid is flocculated and separated from the third organic wastewater by a third solid-liquid separator. The third solid separation step may be performed in parallel with the first solid separation step and the second solid separation step, or may be performed before or after the first solid separation step and the second solid separation step.

[0062] Next, in the wastewater treatment step, the first solid matter, the second solid matter, and the third solid matter are subjected to wastewater treatment.

[0063] In this manner, in this embodiment, the second solid matter is separated from the second organic wastewater by the second solid-liquid separator, and the third solid matter is coagulated and separated from the third organic wastewater by the third solid-liquid separator.

[0064] Therefore, in this embodiment, the amount of coagulant to be added to the third organic wastewater in the second solid separation process can be set depending on the oil concentration of the third organic wastewater, the amount of wastewater, and the frequency of wastewater discharge, etc.

[0065] Therefore, in this embodiment, the amount of coagulant added to the third organic wastewater can be optimized compared to when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using a single solid-liquid separation device.

[0066] A wastewater treatment method according to a twelfth aspect is the wastewater treatment method according to the tenth or eleventh aspect, wherein an oil concentration of the third organic wastewater is higher than an oil concentration of the second organic wastewater.

[0067] According to the wastewater treatment method of the twelfth aspect, the oil concentration of the third organic wastewater is higher than the oil concentration of the second organic wastewater. In such cases, the second organic wastewater and the third organic wastewater tend to require different levels of coagulation treatment.

[0068] Furthermore, even if coagulation treatment is required for both the second organic wastewater and the third organic wastewater, the difference between the amount of coagulant required to be added to the second organic wastewater and the amount of coagulant required to be added to the third organic wastewater is likely to be large.

[0069] In such a case, this embodiment is particularly effective. Second solid-liquid separator separating the second solids from the second organic wastewater by Third solid-liquid separator The third solids are separated from the third organic wastewater by

[0070] As a result, in this embodiment, the amount of coagulant added to the second organic wastewater or the third organic wastewater can be optimized compared to when a mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using a single solid-liquid separation device.

[0071] A thirteenth aspect of the present invention relates to the wastewater treatment method of the twelfth aspect, wherein in the wastewater treatment step, the first solid material, the second solid material, the third solid material, and an additive are used as a fermentation raw material, and the fermentation raw material is subjected to methane fermentation in a state in which a ratio of a concentration of normal hexane extractable substances in the fermentation raw material to a loss on ignition of the fermentation raw material is set to a predetermined value or less.

[0072] In the wastewater treatment method according to the thirteenth aspect, the wastewater treatment step uses the first solid, the second solid, the third solid, and the additive as fermentation raw materials, and performs methane fermentation on the fermentation raw materials while keeping the ratio of the concentration of normal hexane extractable substances in the fermentation raw materials to the loss on ignition of the fermentation raw materials at or below a predetermined value, thereby decomposing (detoxifying) the fermentation raw materials.

[0073] Here, if the fermentation feedstock has a high oil concentration, methane fermentation of the fermentation feedstock may be inhibited. Therefore, in this embodiment, an additive is added to the first solid material, the second solid material, and the third solid material to make the ratio of the concentration of normal hexane extractable substances in the fermentation feedstock to the loss on ignition of the fermentation feedstock equal to or less than a predetermined value.

[0074] In other words, by adding an additive to the first solid material, the second solid material, and the third solid material, the oil concentration of the fermentation raw material is reduced to a predetermined value or less, thereby enabling efficient methane fermentation of the fermentation raw material.

[0075] The amount of additive to be added is calculated based on, for example, the amounts of the first solid, the second solid, and the third solid to be subjected to methane fermentation, the loss on ignition, and the concentration of normal-hexane extractables. In this case, the loss on ignition and the concentration of normal-hexane extractables of the first solid, the second solid, and the third solid are analyzed, for example, from samples collected from the first solid, the second solid, and the third solid.

[0076] Here, when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using one solid-liquid separator, the second solid matter and the third solid matter are mixed together, making it difficult to measure the amounts of the second solid matter and the third solid matter to be fermented by methane fermentation.

[0077] Furthermore, when the second organic wastewater and the third organic wastewater are generated at different frequencies, the ratio of the second solids to the third solids in the mixture varies depending on the timing at which a sample is collected from the mixture of the second solids and the third solids. This variation causes the loss on ignition and the concentration of normal-hexane extractables of the mixture of the second solids and the third solids to also vary, making it difficult to accurately analyze the loss on ignition and the concentration of normal-hexane extractables of the mixture.

[0078] In contrast, in this embodiment, the amounts of the first solid, the second solid, and the third solid to be subjected to methane fermentation can be measured separately, and the loss on ignition and the concentration of n-hexane extractables of the first solid, the second solid, and the third solid can be analyzed separately from samples collected from each of the first solid, the second solid, and the third solid.

[0079] Therefore, in this aspect, even if the second organic wastewater and the third organic wastewater are generated at different frequencies, the accuracy of calculating the amount of additive to be added to the first solid, the second solid, and the third solid can be improved. Therefore, in this aspect, the oil concentration of the fermentation raw material can be more reliably kept at or below a predetermined value. [Effects of the Invention]

[0080] According to the technology disclosed in the present application, the amount of flocculant to be added can be optimized. [Brief explanation of the drawings]

[0081] [Figure 1] 1 is a system configuration diagram showing a wastewater treatment system according to a first embodiment. [Figure 2] FIG. 10 is a system configuration diagram showing a wastewater treatment system according to a second embodiment. [Figure 3] FIG. 10 is a system configuration diagram showing a modified example of the wastewater treatment system according to the second embodiment. [Figure 4] FIG. 2 is a system configuration diagram showing a modified example of the wastewater treatment system according to the first embodiment and the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0082] (First embodiment) First, the first embodiment will be described.

[0083] (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.

[0084] The wastewater treatment system 10 is not limited to applications in commercial complexes, but can also be applied to structures such as apartment buildings.

[0085] The wastewater treatment system 10 includes a disposer 20, a first solid-liquid separation device 30, a second solid-liquid separation device 50, a third solid-liquid separation device 80, a storage tank 100, a wastewater treatment device 110, and a water treatment device 130.

[0086] (disposer) The disposer 20 is a crusher that crushes food waste. The disposer 20 is installed, for example, under the sink in the kitchen of each restaurant, and drains 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").

[0087] 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).

[0088] 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. At least one disposer 20 is sufficient. The disposer 20 is an example of a crusher.

[0089] (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.

[0090] 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. This separates the first organic wastewater into first solids having a size equal to or larger than a predetermined value that do not pass through the screen 34, and second organic wastewater containing second solids having a size smaller than the predetermined value and liquid that pass through the screen 34.

[0091] The second organic wastewater is wastewater obtained by removing the first solid matter from the first organic wastewater (disposer wastewater).

[0092] A raw material tank 112 of a wastewater treatment device 110 (described later) is connected to the separation tank 32 via a first pipe 40. A pump 42 such as a slurry pump is provided in the first 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 first pipe 40.

[0093] The separation tank 32 is connected to a coagulation reaction tank of a second solid-liquid separator 50 (described later) via a pipe 44. 52 The piping 44 is connected to a pump 46 such as a slurry pump. When the pump 46 is operated, the second organic wastewater in the separation tank 32 is pumped through the piping 44 to a coagulation reaction tank. 52are supplied to.

[0094] (Second solid-liquid separator) The second solid-liquid separator 50 is, for example, a screen-type solid-liquid separator that flocculates and separates the second solid matter from the second organic wastewater. The second solid-liquid separator 50 has a flocculation reaction tank 52 and a separation tank 54.

[0095] The coagulation reaction tank 52 is a tank in which a coagulant is added to the second organic wastewater to coagulate the second solid matter, as shown by arrow a. The second organic wastewater containing the second solid matter coagulated in the coagulation reaction tank 52 is supplied to a separation tank 54 via piping or the like (not shown).

[0096] The flocculant is added by, for example, an operator in a predetermined amount at a predetermined timing to the flocculation reaction tank 52. Examples of the flocculant include aluminum salts and iron chloride polyferric iron.

[0097] 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 second organic wastewater containing the flocculated second solids is passed through the screen 56. This separates the second organic wastewater into second solids having a size equal to or larger than a predetermined value that do not pass through the screen 56 and treated water that passes through the screen 56.

[0098] A raw material tank 112 of a wastewater treatment device 110 (described later) is connected to the separation tank 54 via a second pipe 60. A pump 62 such as a slurry pump is provided to the second pipe 60. When the pump 62 is operated, the second solid matter in the separation tank 54 is supplied to the raw material tank 112 via the second pipe 60.

[0099] 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.

[0100] (Third solid-liquid separator) The third solid-liquid separator 80 is, for example, a flotation-type solid-liquid separator that flocculates and separates third solids from the third organic wastewater. The third solid-liquid separator 80 has a flocculation reaction tank 82 and a separation tank (flotation tank) 84.

[0101] 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.

[0102] The oil concentration of kitchen wastewater (hereinafter referred to as "third organic wastewater") is higher than that of the first organic wastewater (garbage disposal wastewater) and the second organic wastewater. Moreover, the third organic wastewater is generated more frequently and in larger amounts than the first organic wastewater and the second organic wastewater.

[0103] The coagulation reaction tank 82 is a tank in which a coagulant is added to the third organic wastewater as shown by arrow b, and the third solid matter contained in the third organic wastewater is coagulated. The third solid matter coagulated in the coagulation reaction tank 82 is supplied to a separation tank 84 via a pipe or the like (not shown).

[0104] The flocculant is added by, for example, an operator in a predetermined amount at a predetermined timing to the flocculation reaction tank 82. Examples of the flocculant include aluminum salts and iron chloride polyferric iron.

[0105] The third organic wastewater containing third solids such as scum flocculated in the flocculation reaction tank 82 is supplied to the separation tank 84. In this separation tank 84, the third solids floating near the liquid surface of the third organic wastewater are removed by a removal device (not shown). As a result, the third organic wastewater is separated into the third solids and treated water (liquid).

[0106] The removal device is connected to a storage tank 100 via a pipe 90. A pump 92 such as a slurry pump is provided in the pipe 90. When the pump 92 is operated, the third solid matter removed by the removal device is supplied to the storage tank 100 via the pipe 90.

[0107] 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.

[0108] (storage tank) The storage tank 100 is a tank for storing third solids such as scum. The storage tank 100 is connected to a raw material tank 112 of a wastewater treatment device 110 (described later) via a third pipe 102. The third pipe 102 is provided with a pump 104 such as a slurry pump. When the pump 104 is operated, the third solids in the storage tank 100 are supplied to the raw material tank 112 via the third pipe 102.

[0109] (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 material, the second solid material, and the third solid material as fermentation raw materials. The wastewater treatment device 110 has a raw material tank 112 and a methane fermentation tank 120.

[0110] (Raw material tank) The raw material tank 112 is a storage tank that stores a mixture of the first solid material, the second solid material, and the third solid material as a fermentation raw material. The raw material tank 112 is provided with a heater 114. The heater 114 heats the mixture to a predetermined temperature (for example, 30°C to 40°C) at which the mixture is easy to flow.

[0111] 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.

[0112] (methane fermentation tank) The methane fermentation tank 120 decomposes (detoxifies) the fermentation raw material by methane fermentation. During this process, biogas containing methane 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).

[0113] 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.

[0114] 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.

[0115] (Water treatment equipment) The water treatment device 130 has a second solid-liquid separation device 50, a third 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.

[0116] (Wastewater treatment method) Next, an example of a wastewater treatment method using the wastewater treatment system 10 will be described.

[0117] 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 second organic wastewater by a first solid-liquid separator 30. Next, in a second solid separation step, second solids are coagulated and separated from the second organic wastewater by a second solid-liquid separator 50.

[0118] Meanwhile, in the third solid separation step, the third solid is flocculated and separated from the third organic wastewater by the third solid-liquid separator 80. The third solid separation step may be carried out in parallel with the first solid separation step and the second solid separation step, or may be carried out before or after the first solid separation step and the second solid separation step.

[0119] Next, in the wastewater treatment step, the first solid matter, the second solid matter, and the third solid matter are treated as wastewater by the wastewater treatment device 110.

[0120] (Action and effect) Next, the operation and effects of the first embodiment will be described.

[0121] As shown in FIG. 1, the first solid-liquid separator 30 separates the first organic wastewater containing the food waste crushed by the disposer 20 into a first solid and a second organic wastewater.

[0122] The second solid-liquid separator 50 separates the second solid matter from the second organic wastewater by flocculation, while the third solid-liquid separator 80 separates the third solid matter from the third organic wastewater by flocculation.

[0123] In this manner, in this embodiment, the second solid matter is coagulated and separated from the second organic wastewater by the second solid-liquid separator 50. Therefore, in this embodiment, the coagulation reaction tank of the second solid-liquid separator 50 is set based on the oil concentration of the second organic wastewater, the amount of wastewater, the frequency of wastewater discharge, etc. 52 In this step, the amount of the flocculant to be added to the second organic wastewater can be set.

[0124] Furthermore, in this embodiment, the third solid matter is flocculated and separated from the third organic wastewater by the third solid-liquid separator 80. Therefore, in this embodiment, the amount of flocculant to be added to the third organic wastewater in the flocculation reaction tank 82 of the third solid-liquid separator 80 can be set based on the oil concentration of the third organic wastewater, the wastewater volume, the wastewater frequency, and the like.

[0125] Therefore, in this embodiment, the amount of coagulant added to the second organic wastewater and the third organic wastewater can be optimized compared to when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using a single solid-liquid separation device.

[0126] Furthermore, the oil concentration of the third organic wastewater is higher than that of the second organic wastewater. This embodiment is particularly effective in such cases. This is because when the oil concentration of the third organic wastewater is higher than that of the second organic wastewater, the difference between the required amount of flocculant to be added to the second organic wastewater and the required amount of flocculant to be added to the third organic wastewater is likely to be large.

[0127] The wastewater treatment device 110 also has a methane fermentation tank 120. The methane fermentation tank 120 performs methane fermentation using the first solid matter, the second solid matter, and the third solid matter as fermentation raw materials, thereby decomposing (detoxifying) organic matter in the fermentation raw materials.

[0128] The wastewater treatment device 110 also has a raw material tank 112 that stores the first solid material, the second solid material, and the third solid material. The fermentation raw material is supplied from the raw material tank 112 to a methane fermentation tank 120.

[0129] 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.

[0130] Furthermore, the third solid material is supplied from the storage tank 100 to the raw material tank 112. By storing the third solid material in the storage tank 100 in this manner, Reservoir 100 A constant amount of the third solid material can be continuously supplied from the raw material tank 112 to the raw material tank 112. Therefore, the fermentation efficiency of the fermentation raw material in the methane fermenter 120 can be further improved.

[0131] (Modification of the first embodiment) In the above embodiment, the oil concentration of the second organic wastewater is higher than the oil concentration of the first organic wastewater. However, the oil concentration of the second organic wastewater may be the same as or lower than the oil concentration of the first organic wastewater.

[0132] In the first embodiment, the wastewater treatment device 110 is a biological treatment device. However, the wastewater treatment device 110 is not limited to a biological treatment device, and may be a mechanical treatment device.

[0133] Second Embodiment Next, a second embodiment will be described. In the second embodiment, the same components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0134] (Wastewater treatment equipment) 2 shows a wastewater treatment system 140 according to a second embodiment. The wastewater treatment device 110 of this wastewater treatment system 140 has a methane fermentation tank 120. The methane fermentation tank 120 performs methane fermentation using the first solid material, the second solid material, the third solid material, and an additive as fermentation raw materials. As a result, the fermentation raw materials are decomposed (detoxified).

[0135] (Additives) Here, as the oil concentration of the fermentation raw material increases, the methane fermentation of the fermentation raw material is more likely to be delayed. Therefore, in this embodiment, in order to suppress the delay of the methane fermentation of the fermentation raw material, an additive (secondary material) is added to the fermentation raw material as shown by arrow c in Figure 2 so that the oil concentration of the fermentation raw material in the methane fermentation tank 120 is equal to or lower than a predetermined value.

[0136] Specifically, additives are added to the first solid, the second solid, and the third solid so that the n-Hex concentration / loss on ignition of the fermentation raw material in the methane fermentation tank 120 is below a predetermined value.

[0137] The n-Hex concentration / loss on ignition is an index that indicates the oil concentration of the fermentation raw material. The value of this n-Hex concentration / loss on ignition increases as the oil concentration of the fermentation raw material increases. On the other hand, the value of n-Hex concentration / loss on ignition decreases as the oil concentration of the fermentation raw material decreases.

[0138] "n-Hex" refers to normal hexane extractables, and "n-Hex concentration" refers to the concentration of normal hexane extractables. Furthermore, "n-Hex concentration / loss on ignition" refers to the ratio of the concentration of normal hexane extractables to the loss on ignition. In other words, "n-Hex concentration / loss on ignition" indicates the n-Hex concentration per unit of loss on ignition.

[0139] The additive is organic waste with a lower oil concentration than the third solid material. This additive is added to the raw material tank 112. The additive is not limited to being added to the raw material tank 112, but can be added to at least one of the raw material tank 112 and the methane fermentation tank 120.

[0140] Examples of additives include dried food waste (eco-feed), waste sugar liquid (e.g., organic waste liquid generated from canning factories), bread crumbs, waste paper (e.g., cardboard), waste starch, old rice flour, waste sugar, tofu lees (okara), seaweed (e.g., Ulva), blackstrap molasses, and waste glycerin.

[0141] The additive preferably has a lower oil concentration than the first solid material, and more preferably has a lower oil concentration than the second solid material.

[0142] Here, from the viewpoint of suppressing the delay of methane fermentation in the methane fermenter 120, the value of n-Hex concentration / loss on ignition of the fermentation raw material in the methane fermenter 120 is preferably 0.4 or less. Furthermore, from the viewpoint of reducing the material cost of additives, the value of n-Hex concentration / loss on ignition of the fermentation raw material in the methane fermenter 120 is preferably 0.2 or more. In other words, the value of n-Hex concentration / loss on ignition of the fermentation raw material in the methane fermenter 120 is preferably 0.2 or more and 0.4 or less.

[0143] (Calculation method for n-Hex concentration / ignition loss of fermentation raw materials) The n-Hex concentration / loss on ignition of the fermentation raw material in the methane fermenter 120 can be calculated, for example, from the following formula (1). n-Hex concentration of fermentation raw material / loss on ignition = (total amount of n-Hex in fermentation raw material) / (total amount of ignition loss in fermentation raw material) (1) however, Total amount of n-Hex in fermentation raw materials: Sum of the amount of n-Hex per unit time in the first solid material, second solid material, third solid material, and additives Total ignition loss of fermentation raw materials: The sum of the ignition losses per unit time of the first solid material, second solid material, third solid material, and additives is.

[0144] In this embodiment, for example, samples of the first solid, the second solid, and the third solid are collected from inspection ports (not shown) of the first pipe 40, the second pipe 60, and the third pipe 102. The n-Hex concentrations and ignition losses of the first solid, the second solid, and the third solid are analyzed from these samples.

[0145] The first pipe 40 is provided with a first flow rate measuring unit 150 that measures the flow rate of the first solid material supplied to the raw material tank 112. The first flow rate measuring unit 150 measures the flow rate of the first solid material flowing through the first pipe 40.

[0146] Then, based on the n-Hex concentration and loss on ignition of the analyzed first solid material and the flow rate of the first solid material measured by the first flow rate measuring unit 150, the amount of n-Hex per unit time and the loss on ignition of the first solid material supplied to the raw material tank 112 are determined.

[0147] The second pipe 60 is provided with a second flow rate measuring unit 152 that measures the flow rate of the second solid material supplied to the raw material tank 112. The second flow rate measuring unit 152 measures the flow rate of the second solid material flowing through the second pipe 60.

[0148] Then, based on the n-Hex concentration and loss on ignition of the analyzed second solid material and the flow rate of the second solid material measured by the second flow rate measuring unit 152, the amount of n-Hex and the amount of loss on ignition per unit time of the second solid material supplied to the raw material tank 112 are respectively determined.

[0149] The third pipe 102 is provided with a third flow rate measuring unit 154 that measures the flow rate of the third solid material supplied to the raw material tank 112. The third flow rate measuring unit 154 measures the flow rate of the third solid material flowing through the third pipe 102.

[0150] Then, based on the n-Hex concentration and loss on ignition of the analyzed third solid material and the flow rate of the third solid material measured by the third flow rate measuring unit 154, the amount of n-Hex and the amount of loss on ignition per unit time of the third solid material supplied to the raw material tank 112 are determined, respectively.

[0151] The amount of additive added to raw material tank 112 is set so that the n-Hex concentration / loss on ignition of the fermentation raw material is equal to or less than a predetermined value. That is, the amount of additive added is calculated based on the n-Hex concentration and loss on ignition of the first solid, second solid, and third solid analyzed from the sample, the n-Hex concentration and loss on ignition of the additive, and the flow rates of the first solid, second solid, and third solid measured by first flow rate measuring unit 150, second flow rate measuring unit 152, and third flow rate measuring unit 154.

[0152] The first flow rate measuring unit 150, the second flow rate measuring unit 152, and the third flow rate measuring unit 154 are, for example, flow rate measuring devices.

[0153] (Wastewater treatment method) Next, an example of a wastewater treatment method using the wastewater treatment system 140 will be described.

[0154] 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 second organic wastewater by a first solid-liquid separator 30. Next, in a second solid separation step, second solids are coagulated and separated from the second organic wastewater by a second solid-liquid separator 50.

[0155] In addition, in the third solid separation step, the third solid is flocculated and separated from the third organic wastewater by the third solid-liquid separator 80. The third solid separation step may be performed in parallel with the first solid separation step and the second solid separation step, or may be performed before or after the first solid separation step and the second solid separation step.

[0156] Next, in the wastewater treatment process, the wastewater treatment device 110 uses the first solid, the second solid, the third solid, and the additives as fermentation raw materials, and performs methane fermentation on the fermentation raw materials while keeping the ratio of the concentration of normal hexane extractable substances in the fermentation raw materials to the loss on ignition of the fermentation raw materials (n-Hex concentration / loss on ignition) below a predetermined value.

[0157] At this time, the n-Hex concentration / ignition loss of the fermentation raw material is adjusted by the amount of additive added to the raw material tank 112.

[0158] (Action and effect) Next, the operation and effects of the second embodiment will be described.

[0159] As mentioned above, a high oil concentration in the fermentation feedstock may inhibit methane fermentation of the fermentation feedstock. Therefore, in this embodiment, an additive is added to the first solid material, the second solid material, and the third solid material to set the ratio of the n-Hex concentration of the fermentation feedstock to the loss on ignition of the fermentation feedstock (n-Hex concentration / loss on ignition) to a predetermined value or less.

[0160] In other words, in this embodiment, by adding an additive to the first solid material, the second solid material, and the third solid material, the oil concentration of the fermentation raw material is reduced to a predetermined value or less, thereby enabling efficient methane fermentation of the fermentation raw material.

[0161] The amount of additive to be added is calculated based on, for example, the amounts of the first solid, the second solid, and the third solid to be subjected to methane fermentation, the loss on ignition, and the n-Hex concentration. In this case, the loss on ignition and the n-Hex concentration of the first solid, the second solid, and the third solid are analyzed from samples collected from the first solid, the second solid, and the third solid, for example.

[0162] Here, when the mixed wastewater of the second organic wastewater and the third organic wastewater is subjected to solid-liquid separation using one solid-liquid separator, the second solid matter and the third solid matter are mixed together, making it difficult to measure the amounts of the second solid matter and the third solid matter supplied to the methane fermentation tank 120, respectively.

[0163] Furthermore, the first organic wastewater (disposer wastewater) and second organic wastewater discharged from the disposer 20 differ in frequency of generation from the third organic wastewater (kitchen wastewater) discharged from a kitchen washing area or the like.

[0164] When the second organic wastewater and the third organic wastewater are generated at different frequencies, the ratio of the second solids to the third solids in the mixture varies depending on the timing at which a sample is collected from the mixture of the second solids and the third solids. This variation also causes the ignition loss and n-Hex concentration of the mixture of the second solids and the third solids to vary, making it difficult to accurately analyze the ignition loss and n-Hex concentration of the mixture.

[0165] In contrast, in this embodiment, the first flow rate measuring unit 150, the second flow rate measuring unit 152, and the third flow rate measuring unit 154 can separately measure the amounts of the first solids, the second solids, and the third solids supplied to the methane fermentation tank 120.

[0166] In this embodiment, samples of the first solid, the second solid, and the third solid can be collected from the first pipe 40, the second pipe 60, and the third pipe 102, respectively. The ignition loss and n-Hex concentration of the first solid, the second solid, and the third solid can be analyzed separately from the collected samples of the first solid, the second solid, and the third solid.

[0167] Therefore, in this embodiment, even if the second organic wastewater and the third organic wastewater are generated at different frequencies, the accuracy of calculating the amount of additive to be added to the first solid, the second solid, and the third solid can be improved. Therefore, in this embodiment, the oil concentration of the fermentation raw material can be more reliably kept at or below a predetermined value.

[0168] (Modification of the second embodiment) Next, a modification of the second embodiment will be described.

[0169] In the second embodiment, the additive is added to the raw material tank 112. However, the additive can be added to at least one of the raw material tank 112 and the methane fermentation tank 120.

[0170] In the second embodiment, the first pipe 40 is provided with a first flow rate measuring unit 150. The second pipe 60 is provided with a second flow rate measuring unit 152. However, for example, as in a modified example shown in FIG. 3, a mixed flow rate measuring unit 162 that measures the flow rate of the mixture of the first solid and the second solid may be provided in a collecting pipe 160 of the first pipe 40 and the second pipe 60. This is because the occurrence frequencies of the first solid and the second solid are basically similar.

[0171] On the other hand, the flow rate of the third solid is measured by the third flow rate measuring unit 154. This makes it possible to improve the accuracy of calculating the amounts of additive to be added to the first solid, the second solid, and the third solid, even if the occurrence frequency of the mixture of the first solid and the second solid differs from that of the third solid.

[0172] (Modifications of the first and second embodiments) Next, modified examples of the first embodiment and the second embodiment will be described. Note that, although various modified examples will be described below using the first embodiment as an example, these modified examples can also be applied to the second embodiment as appropriate.

[0173] In the first embodiment, the third solid material is supplied from the storage tank 100 to the raw material tank 112 via the third pipe 102. However, as in a modified example shown in Figure 4, the third solid material may be supplied from the storage tank 100 to the methane fermentation tank 120 via the third pipe 102.

[0174] Specifically, the storage tank 100 is connected to the methane fermentation tank 120 via a third pipe 102. A pump 104 provided in the third pipe 102 is operated to supply the third solid material from the storage tank 100 to the methane fermentation tank 120 via the third pipe 102.

[0175] 4, a heater 170 is provided in the storage tank 100. The third solid matter in the storage tank 100 is heated (for example, to 30°C to 40°C) by the heater 170, thereby increasing the fluidity of the third solid matter. Therefore, the third solid matter can be easily supplied from the storage tank 100 to the wastewater treatment device 110.

[0176] Furthermore, the third organic wastewater has a higher oil concentration than the first organic wastewater. Therefore, the third solids are likely to have a higher oil concentration than the first solids and the second solids. Therefore, by heating the third solids by heater 170 in storage tank 100 separately from the first solids and the second solids, the fluidity of the third solids can be efficiently increased.

[0177] On the other hand, the first solid and the second solid tend to have a lower oil concentration than the third solid. Therefore, the first solid and the second solid tend to maintain fluidity even at room temperature (e.g., 20°C). For this reason, in the modified example shown in Figure 4, the heater 114 (see Figure 2) of the raw material tank 112 is omitted. This allows the modified example shown in Figure 4 to reduce costs.

[0178] 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 solid material, the second solid material, and the third solid material 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 storage tank 100.

[0179] In the above embodiment, the third solid-liquid separation device 80 is connected to the wastewater treatment device 110 via the storage tank 100. However, the storage tank 100 may be omitted, and the third solid material may be supplied from the third solid-liquid separation device 80 to the wastewater treatment device 110.

[0180] Furthermore, in the above embodiment, the second solid matter is subjected to a flocculation treatment in the second solid-liquid separation device 50, and the third solid matter is subjected to a flocculation treatment in the third solid-liquid separation device 80. However, the flocculation treatment can be performed in at least one of the second solid-liquid separation device 50 and the third solid-liquid separation device 80. This is because the necessity of the flocculation treatment varies depending on the oil concentrations of the second organic wastewater and the third organic wastewater, etc.

[0181] In the above embodiment, the second solid-liquid separator 50 is a screen-type solid-liquid separator. However, the second solid-liquid separator 50 is not limited to the screen-type, and may be a flotation-type solid-liquid separator.

[0182] In the first embodiment, the crusher for crushing food waste is the disposer 20. However, the crusher is not limited to the disposer 20, and may be another type of crusher.

[0183] The above describes one embodiment of the technology disclosed in the present application. However, the technology disclosed in the present application is not limited to this embodiment, and one embodiment and various modified examples may be used in appropriate combination. Furthermore, it goes without saying that the technology disclosed in the present application can be embodied in various forms without departing from the gist of the technology.

Claims

1. a first solid-liquid separation device that separates first organic wastewater containing food waste crushed by the crusher into first solids and second organic wastewater; a second solid-liquid separation device that flocculates and separates second solids from the second organic wastewater; a third solid-liquid separation device that separates third solids from the third organic wastewater; a wastewater treatment device that treats the first solid material, the second solid material, and the third solid material; A wastewater treatment system comprising:

2. a first solid-liquid separation device that separates first organic wastewater containing food waste crushed by the crusher into first solids and second organic wastewater; a second solid-liquid separation device that separates second solids from the second organic wastewater; a third solid-liquid separation device that flocculates and separates third solids from the third organic wastewater; a wastewater treatment device that treats the first solid material, the second solid material, and the third solid material; A wastewater treatment system comprising:

3. The oil concentration of the third organic wastewater is higher than the oil concentration of the second organic wastewater; The wastewater treatment system according to claim 1 or 2.

4. the wastewater treatment device includes a methane fermentation tank that performs methane fermentation using the first solid material, the second solid material, the third solid material, and an additive as fermentation raw materials, The additive adjusts the ratio of the concentration of normal hexane extractable substances in the fermentation raw material to the ignition loss of the fermentation raw material to a predetermined value or less. The wastewater treatment system according to claim 3 .

5. the wastewater treatment device includes a raw material tank that stores the first solid material and the second solid material, The methane fermentation tank is supplied with a mixture of the first solid material and the second solid material from the raw material tank. The wastewater treatment system according to claim 4.

6. a storage tank for storing the third solid material; The third solid material is supplied to the wastewater treatment device from the storage tank. The wastewater treatment system according to claim 4 or 5.

7. the storage tank has a heater that heats the third solid material; The wastewater treatment system according to claim 6.

8. a first flow rate measuring unit that measures a flow rate of the first solid; a second flow rate measuring unit that measures the flow rate of the second solid; a third flow rate measuring unit that measures the flow rate of the third solid; The wastewater treatment system according to any one of claims 4 to 7, comprising:

9. a mixture flow rate measuring unit that measures a flow rate of the mixture of the first solid material and the second solid material; a third flow rate measuring unit that measures the flow rate of the third solid; The wastewater treatment system according to any one of claims 4 to 7, comprising:

10. a first solid separation step of separating the first organic wastewater containing the food waste crushed by the crusher into a first solid and a second organic wastewater; a second solid separation step of flocculating and separating second solids from the second organic wastewater; a third solid separation step of separating a third solid from the third organic wastewater; a wastewater treatment step of treating the first solid material, the second solid material, and the third solid material as wastewater; A wastewater treatment method comprising:

11. a first solid separation step of separating first organic wastewater containing food waste crushed by the crusher into first solids and second organic wastewater using a first solid-liquid separator; a second solid separation step of separating second solids from the second organic wastewater using a second solid-liquid separator; a third solid separation step of flocculating and separating third solids from the third organic wastewater using a third solid-liquid separator; a wastewater treatment step of treating the first solid material, the second solid material, and the third solid material as wastewater; A wastewater treatment method comprising:

12. The oil concentration of the third organic wastewater is higher than the oil concentration of the second organic wastewater; The wastewater treatment method according to claim 10 or 11.

13. In the wastewater treatment step, the first solid material, the second solid material, the third solid material, and an additive are used as fermentation raw materials, and the fermentation raw materials are subjected to methane fermentation in a state where a ratio of a concentration of normal hexane extractable substances in the fermentation raw materials to an ignition loss of the fermentation raw materials is set to a predetermined value or less. The wastewater treatment method according to claim 12.

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