Solid-liquid separation device, organic waste treatment system, and organic waste treatment method

Abstract

Solid-liquid separation device capable of achieving separation of digestive fluid at low cost, organic waste treatment system, and organic waste treatment method [Solution] A solid-liquid separation device that separates digestive fluid into solids and liquids comprises a solid-liquid separation vessel including an outer cylinder extending along the vertical direction and at least one inner cylinder provided inside the outer cylinder, and at least one upward flow generating section that generates an upward flow containing air bubbles in an outer flow space formed between the outer cylinder and the inner cylinder or an inner flow space formed inside the inner cylinder, the inner flow space and the outer flow space are connected at the upper and lower sides of the inner cylinder and are configured to be capable of forming a circulation flow path for circulating the digestive fluid and air bubbles, and the upward flow generating section is configured to be capable of stopping the circulation of the digestive fluid and air bubbles.

Description

[Technical field]

[0001] The present invention relates to a solid-liquid separation device, an organic waste treatment system, and an organic waste treatment method. [Background technology]

[0002] Conventionally, there has been known an organic waste treatment apparatus that includes an anaerobic tank that separates organic waste into biogas and treated water, an MF membrane that filters the treated water obtained in the anaerobic tank, a reverse osmosis membrane (RO membrane) that performs membrane separation on the treated water filtered by the MF membrane, and an evaporative concentrator that evaporates and concentrates the treated water separated by the reverse osmosis membrane (Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-192953 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the organic waste treatment device described in Patent Document 1, although filtration using an MF membrane is performed as a pretreatment for membrane separation of treated water using a reverse osmosis membrane, the filtration using the MF membrane alone is insufficient to remove solids contained in the treated water, which causes clogging of the reverse osmosis membrane. In addition, clogging requires frequent replacement of the reverse osmosis membrane, which results in high running costs.

[0005] The present invention relates to a solid-liquid separation device capable of achieving separation of digestive liquid at low cost, an organic waste treatment system, and an organic waste treatment method. [Means for solving the problem]

[0006] The solid-liquid separation device of the present invention is a solid-liquid separation device that separates a digestive fluid into solids and liquids, and comprises a solid-liquid separation vessel including an outer cylinder extending along a vertical direction and at least one inner cylinder provided inside the outer cylinder, and at least one upward flow generating unit that generates an upward flow containing air bubbles in an outer flow space formed between the outer cylinder and the inner cylinder or an inner flow space formed inside the inner cylinder, the inner flow space and the outer flow space are connected to each other on the upper and lower sides of the inner cylinder and are configured to be capable of forming a circulation flow path that circulates the digestive fluid and air bubbles, and the upward flow generating unit is configured to be capable of stopping the circulation of the digestive fluid and air bubbles.

[0007] In the solid-liquid separation apparatus according to the present invention, the outer cylinder may have at least one solid outlet capable of discharging the solid, and at least one liquid outlet capable of discharging the liquid.

[0008] In the solid-liquid separation apparatus according to the present invention, the upward flow generating section may be provided with at least one gas release section that releases gas into the outer flow space or the inner flow space, below a vertical middle section of the solid-liquid separation vessel.

[0009] The solid-liquid separation device according to the present invention may include a top plate portion provided opposite an upper opening of the inner cylinder, and the lower surface of the top plate portion may have an inclined surface that slopes downward at the center in a planar direction.

[0010] The solid-liquid separation apparatus according to the present invention may include at least one of an inner swirling flow generating section that causes the flow in the inner flow space to become a swirling flow, and an outer swirling flow generating section that causes the flow in the outer flow space to become a swirling flow.

[0011] In the solid-liquid separation apparatus according to the present invention, the inner swirling flow generating section and the outer swirling flow generating section may each have a plurality of blade portions arranged at a predetermined interval, and the plurality of blade portions may have a shape curved in the circumferential direction of the inner cylinder.

[0012] In the solid-liquid separation apparatus according to the present invention, the blade portion may be configured to be non-rotatable.

[0013] The organic waste treatment system according to the present invention is an organic waste treatment system for treating organic waste, and includes a generation tank in which the organic waste is reacted with anaerobic microorganisms to produce biogas and digested sludge, a digested sludge separation device that separates the digested sludge into solids and digested liquid, a solid-liquid separation device that further separates the digested liquid separated in the digested sludge separation device into solids and liquid, and a concentration device that concentrates the liquid separated in the solid-liquid separation device. The solid-liquid separation device includes a solid-liquid separation container including an outer cylinder extending along a vertical direction and at least one inner cylinder provided inside the outer cylinder, and at least one upward flow generating unit that generates an upward flow containing air bubbles in an outer flow space formed between the outer cylinder and the inner cylinder or an inner flow space formed inside the inner cylinder, and the inner flow space and the outer flow space are connected to each other at the upper and lower sides of the inner cylinder, and are configured to be capable of forming a circulation flow path that circulates the digested liquid and air bubbles, and the upward flow generating unit is configured to be capable of stopping the circulation of the digested liquid and air bubbles.

[0014] The organic waste treatment method according to the present invention is an organic waste treatment method for treating organic waste, and includes a generating step of reacting the organic waste with anaerobic microorganisms to generate biogas and digested sludge, a digested sludge separation step of separating the digested sludge into a solid and a digestive liquid, a solid-liquid separation step of further separating the digestive liquid separated in the digested sludge separation step into a solid and a liquid, and a concentrating step of concentrating the liquid separated in the solid-liquid separation step, and the solid-liquid separation step includes an inflow step of inflowing the digestive liquid into a solid-liquid separation vessel including an outer cylinder extending along a vertical direction and at least one inner cylinder provided inside the outer cylinder, a circulation step of circulating the digestive liquid and air bubbles by generating an upward flow containing air bubbles in an outer flow space formed between the outer cylinder and the inner cylinder or an inner flow space formed inside the inner cylinder, and a stop step of stopping the circulation of the digestive liquid and air bubbles. Effect of the Invention

[0015] According to the solid-liquid separation device, organic waste treatment system, and organic waste treatment method of the present invention, separation of digestive liquid can be realized at low cost. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing an organic waste treatment system according to an embodiment of the present invention. [Diagram 2] 1 is a schematic cross-sectional view showing a solid-liquid separation device according to an embodiment of the present invention. [Diagram 3] 1 is an enlarged view showing a part of a solid-liquid separation device according to an embodiment of the present invention. [Figure 4] 1 is an enlarged view showing a part of a solid-liquid separation device according to an embodiment of the present invention. [Diagram 5] 3 is a schematic plan view showing a lower blade portion according to the embodiment. FIG. [Figure 6] 4 is a schematic bottom view showing the upper wing portion according to the embodiment. FIG. [Figure 7] FIG. 2 is a schematic diagram showing the flow of solid-liquid separation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. In addition, in the present embodiments, the scale and dimensions of each component may be exaggerated, and some components may be omitted.

[0018] [Overall configuration of organic waste treatment system] The organic waste treatment system according to the present embodiment is a system for treating organic waste. Examples of organic waste include digestive fluids as residues after fermentation in a biogas plant, but are not limited thereto. For example, any mixture of solids and liquids, such as livestock waste, food waste, processing residues or residual liquids of milk or beverages, sludge, and agricultural residues, may be used, and the organic waste is not limited to organic "waste". The solids may be organic or inorganic, and the ratio of solids to liquids is not particularly limited.

[0019] As shown in FIG. 1, the organic waste treatment system 1 includes a production tank 100 in which organic waste is reacted with anaerobic microorganisms to produce biogas and digested sludge, a gas storage tank 200 in which the biogas produced in the production tank 100 is stored, a sludge storage tank 300 in which the digested sludge produced in the production tank 100 is stored, a digested sludge separation device 400 (primary separation device) in which the digested sludge stored in the sludge storage tank 300 is separated into solids and digested liquid, a solid-liquid separation device 500 (digested liquid separation device, secondary separation device) in which the digested liquid separated in the digested sludge separation device 400 is further separated into solids and liquid, a concentrating device 600 in which the liquid separated in the solid-liquid separation device 500 is concentrated, a permeated liquid storage tank 700 in which the permeated liquid that has permeated the concentrating device 600 is stored, and a concentrated liquid storage tank 800 in which the concentrated liquid concentrated in the concentrating device 600 is stored.

[0020] Examples of the separation method used by the digested sludge separation apparatus 400 include a method of capturing solids with a filter, a method of precipitating solids, a method of floating solids, and a method of adsorbing solids to an adsorbent. Examples of the method of precipitating solids include static precipitation, coagulation precipitation in which a coagulant is added, and electroprecipitation in which solids are coagulated by charging. Examples of the method of floating solids include normal pressure flotation by adding a foaming agent or foam assistant, and pressurized flotation by injecting fine bubbles. In this embodiment, the digested sludge separation apparatus 400 is provided with a screen and is configured to capture solids with the screen.

[0021] In this embodiment, the digested sludge separation device 400 is described as being installed upstream of the solid-liquid separation device 500, but this is not limited to this and the digested sludge separation device 400 may be installed upstream and downstream of the solid-liquid separation device 500.

[0022] The concentrating device 600 is configured to include, for example, a known filtration membrane such as an MF membrane or an RO membrane, and to concentrate the liquid by the filtration membrane. Note that the concentrating device 600 may also be configured to include, for example, an evaporation means for evaporating the liquid, and to concentrate the liquid by the evaporation means.

[0023] The organic waste treatment system 1 also includes a gas supply passage 2 that supplies the biogas generated in the generation tank 100 to the gas storage tank 200, a first sludge supply passage 3 that supplies the digested sludge generated in the generation tank 100 to the sludge storage tank 300, a second sludge supply passage 4 that supplies the digested sludge stored in the sludge storage tank 300 to the digested sludge separation device 400, a digested liquid supply passage 5 that supplies the digested liquid separated in the digested sludge separation device 400 to the solid-liquid separation device 500, a liquid supply passage 6 that supplies the liquid separated in the solid-liquid separation device 500 to the concentrating device 600, a permeated liquid supply passage 7 that supplies the permeated liquid that has permeated the concentrating device 600 to the permeated liquid storage tank 700, and a concentrated liquid supply passage 8 that supplies the concentrated liquid concentrated in the concentrating device 600 to the concentrated liquid storage tank 800. The gas supply passage 2, the first sludge supply passage 3, the second sludge supply passage 4, the digested liquid supply passage 5, the liquid supply passage 6, the permeate supply passage 7 and the concentrated liquid supply passage 8 are each formed in a tubular shape having an internal space capable of allowing the flow of fluid.

[0024] In addition, since the configurations of the organic waste treatment system 1 other than the solid-liquid separation device 500 can be known configurations, in the following explanation, only the configuration of the solid-liquid separation device 500 will be explained, and the explanation of the other configurations will be omitted.

[0025] [Configuration of solid-liquid separation device] As shown in Figures 2 to 4, the solid-liquid separation device 500 includes a solid-liquid separation vessel 510 that separates the digestive fluid into solids and liquids, an ascending flow generating section 520 that generates an ascending flow containing air bubbles inside the solid-liquid separation vessel 510, a discharge section 530 that discharges the discharged material inside the solid-liquid separation vessel 510, a lower swirling flow generating section 540 provided below the inner cylinder 512 described later, and an upper swirling flow generating section 550 provided above the inner cylinder 512 described later.

[0026] <Configuration of solid-liquid separation vessel> As shown in FIGS. 2 to 4, the solid-liquid separation vessel 510 has an outer cylinder 511 extending along the vertical direction, and an inner cylinder 512 provided inside the outer cylinder 511.

[0027] In this specification, "vertical" includes both completely vertical and approximately vertical. "Approximately vertical" means a slight inclination with respect to the vertical, specifically, an inclination to the extent that does not impede the effect of the solid-liquid separation device 500.

[0028] The outer cylinder 511 is formed in a cylindrical shape with an open upper end and lower end. The outer cylinder 511 has an inlet 511a through which the digestive fluid can flow in, a solid outlet 511b through which solids obtained by separation of the digestive fluid can be discharged, and a liquid outlet 511c through which liquid obtained by separation of the digestive fluid can be discharged.

[0029] The inlet 511a, the solid discharge port 511b, and the liquid discharge port 511c are openings formed from the inner surface to the outer surface of the outer cylinder 511. Known valves may be provided in the inlet 511a, the solid discharge port 511b, and the liquid discharge port 511c, and the valves may be opened and closed at any timing. The inlet 511a is connected to the digestive fluid supply path 5 by a tube joint TJ. The liquid discharge port 511c is connected to the liquid supply path 6 by a tube joint TJ.

[0030] The inlet 511a, the solid outlet 511b, and the liquid outlet 511c may each be provided in one or more. In this embodiment, only one inlet 511a and one liquid outlet 511c are provided, and are provided near the middle part of the outer flow space 515 described later. By providing the liquid outlet 511c near the middle part of the outer flow space 515, the liquid obtained by separating the digestive liquid can be efficiently discharged. On the other hand, two solid outlets 511b are provided, one near the upper part and one near the lower part of the outer flow space 515. By providing the solid outlets 511b near the upper part and the lower part of the outer flow space 515, the solids obtained by separating the digestive liquid (floated solids and precipitated solids) can be efficiently discharged. In this embodiment, as described later, the lower end of the outer cylinder 511 is fitted into the bottom 513, and therefore the solid discharge outlet 511b provided near the lower part of the outer flow space 515 is formed by penetrating the bottom 513.

[0031] The inner cylinder 512 is formed in a cylindrical shape with an open upper end and lower end. The outer diameter of the inner cylinder 512 is smaller than the inner diameter of the outer cylinder 511. The length of the inner cylinder 512 in the vertical direction is shorter than the length of the outer cylinder 511 in the vertical direction. In this embodiment, only one inner cylinder 512 is provided, but this is not limiting, and two or more inner cylinders 512 may be provided.

[0032] The shapes of the outer cylinder 511 and the inner cylinder 512 are not limited to cylindrical shapes, and may be, for example, rectangular cylindrical, conical, or pyramidal. A convex or concave portion may be formed in a part in the vertical direction, or the cylinder may be formed in a bellows shape.

[0033] The solid-liquid separation container 510 has a bottom 513 that closes the lower end of the outer cylinder 511, and a top 514 that closes the upper end of the outer cylinder 511. The bottom 513 is formed in a bottomed cylindrical shape with an open upper end. The bottom 513 is configured to close the lower end of the outer cylinder 511 by fitting the lower end of the outer cylinder 511 into it. The top 514 is formed in a topped cylindrical shape with an open lower end. The top 514 is configured to close the upper end of the outer cylinder 511 by fitting the upper end of the outer cylinder 511 into it.

[0034] The solid-liquid separation vessel 510 also has an outer flow space 515 formed between the outer cylinder 511 and the inner cylinder 512, and an inner flow space 516 formed inside the inner cylinder 512. The outer flow space 515 and the inner flow space 516 communicate with each other at the upper and lower sides of the inner cylinder 512, and are configured to be able to form a circulation flow path CP that circulates the digestive fluid and air bubbles.

[0035] <Configuration of the upward flow generating section> 2 to 4, the upward flow generating section 520 has a gas generating section 521 that generates gas, a gas releasing section 522 that releases the gas generated in the gas generating section 521 into the outer flow space 515 or the inner flow space 516, a gas supplying section 523 that supplies the gas generated in the gas generating section 521 to the gas releasing section 522, and a connecting section 524 that connects the gas releasing section 522 and the gas supplying section 523. In this embodiment, only one upward flow generating section 520 is provided, but this is not limited thereto, and two or more may be provided.

[0036] The gas generating unit 521 is, for example, a fan or a blower. The gas generating unit 521 has a switch 521a that starts or stops the generation of gas. In other words, the switch 521a is configured to be able to start or stop the release of gas by the gas releasing unit 522.

[0037] The gas release section 522 is, for example, a tube, and is configured to allow gas to flow. One end of the gas release section 522 is connected to the connection section 524, and the other end of the gas release section 522 is connected to an attached section 543c of a support section 543, which will be described later. Therefore, the gas release section 522 according to this embodiment is configured to release gas into the inner flow space 516. Specifically, the gas release section 522 is configured to release gas into the inner flow space 516 via the support section 543, which will be described later.

[0038] From the viewpoint of generating an upward flow, the other end of the gas releasing section 522 may be located below the vertical middle part of the solid-liquid separation vessel 510, and may be connected to, for example, the outer cylinder 511 or the inner cylinder 512. When the other end of the gas releasing section 522 is connected to the outer cylinder 511, the gas releasing section 522 is configured to release the gas into the outer flow space 515.

[0039] The gas supply unit 523 is, for example, a tube, and is configured to be able to flow gas. One end of the gas supply unit 523 is connected to the gas generation unit 521, and the other end of the gas supply unit 523 is connected to the connection unit 524. The connection unit 524 is, for example, a tube joint, and is inserted into an opening (not shown) formed in the top 514.

[0040] The upward flow generating section 520 having the above configuration is configured to generate an upward flow containing air bubbles in the inner flow space 516 by the gas release section 522 releasing gas into the inner flow space 516. When the gas release section 522 releases gas into the outer flow space 515, the upward flow generating section 520 generates an upward flow containing air bubbles in the outer flow space 515.

[0041] Moreover, the upward flow generating section 520 is configured to stop the circulation of the digestive fluid and air bubbles in the circulation flow path CP at any or a predetermined timing by the switch 521a stopping the release of gas by the gas release section 522. The stop by the switch 521a may be performed manually or automatically. Examples of a method for automatically stopping by the switch 521a include a method of turning off the switch 521a after a predetermined time has elapsed since the switch 521a was turned on, and a method of turning off the switch 521a after a predetermined flow rate has been released since the switch 521a was turned on, but the method is not limited thereto.

[0042] <Exhaust section configuration> 2 and 3, the discharge unit 530 has a tube portion 531 that discharges the discharged material in the solid-liquid separation container 510, and a holding unit 532 that holds the tube portion 531. Examples of the discharged material include surplus material (e.g., gas, liquid, etc.) that exceeds the volume of the solid-liquid separation container 510.

[0043] The cylindrical portion 531 is formed in a tubular shape with both ends open, and is inserted into an opening (not shown) formed in the top portion 514. That is, the upper end of the cylindrical portion 531 is located outside the solid-liquid separation container 510, and the lower end of the cylindrical portion 531 is located inside the solid-liquid separation container 510. As shown in FIG. 2, the cylindrical portion 531 may be formed by connecting two or more tubes, or may be composed of one tube. In addition, the cylindrical portion 531 has a plurality of inflow holes 531a that allow the gas in the solid-liquid separation container 510 to flow into the cylindrical portion 531. The inflow holes 531a are provided in a portion of the cylindrical portion 531 that is located inside the solid-liquid separation container 510 (in this embodiment, below the axial middle portion of the cylindrical portion 531), and are provided along each of the axial and circumferential directions of the cylindrical portion 531.

[0044] The holding portion 532 is formed in a disk shape, and has a mounting hole 532a in the center for mounting the tube portion 531. The holding portion 532 also has insertion holes 532b in both radial ends for inserting protrusions 551c formed on the upper end of the top plate portion 551 described later. The holding portion 532 is configured to hold the tube portion 531 by inserting the lower end of the tube portion 531 into the mounting hole 532a. The holding portion 532 is also configured to be attached to the upper end of the top plate portion 551 by inserting the protrusions 551c into the insertion hole 532b. The holding portion 532 is attached to the upper end of the top plate portion 551, so that the inner tube 512 can be prevented from floating up. The holding portion 532 may be omitted, or may be formed integrally with the upper swirling flow generating portion 550 described later.

[0045] The discharge unit 530 having the above configuration is configured to discharge the discharged material that has flowed into the cylindrical portion 531 from the lower end of the cylindrical portion 531 and the inlet hole 531a of the cylindrical portion 531 to the outside of the solid-liquid separation container 510. The discharged material discharged from the discharge unit 530 can be supplied to, for example, any storage tank.

[0046] <Configuration of lower swirl flow generation section> As shown in Figures 2, 4 and 5, the lower swirling flow generating section 540 has a weight section 541 placed on the bottom surface of the bottom section 513, a plurality of (seven in this embodiment) blade sections 542 (lower blade sections) arranged at predetermined intervals around the circumferential direction of the inner tube 512, and a support section 543 capable of supporting the inner tube 512.

[0047] The blades 542 are provided on the upper surface of the weight portion 541 and are configured to be non-rotatable. Each blade 542 extends along the radial direction of the inner tube 512 and has a shape curved in the circumferential direction of the inner tube 512. That is, the blades 542 are provided radially with the axis of the inner tube 512 as the center.

[0048] The inner end of each of the blades 542 in the extension direction is located within the area of ​​the inner cylinder 512 in a plan view. On the other hand, the outer end of each of the blades 542 in the extension direction is located within the area between the outer cylinder 511 and the inner cylinder 512 in a plan view. Also, each of the blades 542 is formed so that its height increases from the outer side in the extension direction toward the inner side in the extension direction. This has the advantage that the flow from the outer flow space 515 or the flow from the inner flow space 516 can be swirled efficiently without being obstructed.

[0049] The support portion 543 is formed in a cylindrical shape with open upper and lower ends, and has a shape that tapers from the lower end to the upper end. The support portion 543 has an insertion groove 543a at its upper end into which the lower end of the inner tube 512 can be inserted. The insertion groove 543a is formed in a concave shape that is concave downward from the upper end of the support portion 543. The support portion 543 is configured to support the inner tube 512 by inserting the lower end of the inner tube 512 into the insertion groove 543a.

[0050] The support portion 543 has, at its lower end portion, an annular pipe portion 543b that surrounds the periphery of the blade portion 542. The support portion 543 also has a mounting portion 543c to which the gas release portion 522 is mounted.

[0051] The pipe section 543b is formed in a tubular shape having an internal space capable of flowing the gas supplied from the gas release section 522. Outlet holes 543d for discharging the gas supplied from the gas release section 522 are formed in the inner peripheral section (the end section on the blade section 542 side) of the pipe section 543b. In this embodiment, the outlet holes 543d are a plurality of openings formed at predetermined intervals in the circumferential direction of the pipe section 543b. The outlet holes 543d may be a single opening or may be an annular opening extending along the circumferential direction of the pipe section 543b.

[0052] The mounting portion 543c is formed to extend upward from a part of the circumferential direction of the pipe portion 543b, and is formed in a cylindrical shape with an open upper end and lower end. Therefore, the gas supplied from the gas release portion 522 flows through the mounting portion 543c and is supplied to the pipe portion 543b. The support portion 543 is configured to be connected to the gas release portion 522 by inserting the mounting portion 543c into the other end of the gas release portion 522.

[0053] The support part 543 having the above configuration is provided between the upper surface of the weight part 541 and the lower end of the inner tube 512, and is configured to communicate the outer flow space 515 and the inner flow space 516 between the lower end of the support part 543 and the upper surface of the weight part 541. Specifically, the support part 543 is attached to the weight part 541 by fixing a plurality of fixing parts (not shown) extending from the outer periphery (end part on the outer tube 511 side) of the tube part 543b to the outer edge part of the weight part 541. Note that, in the present embodiment, the configuration in which the support part 543 includes the tube part 543b and the attached part 543c has been described, but the present invention is not limited thereto, and the support part 543 may be configured not to include these.

[0054] <Configuration of the upper swirl flow generating section> As shown in Figures 2, 3 and 6, the upper swirling flow generating section 550 has a top plate section 551 arranged opposite the upper opening 512a of the inner tube 512, a plurality of (six in this embodiment) blade sections 552 (upper blade sections) arranged at predetermined intervals around the circumferential direction of the inner tube 512, and an attachment section 553 that can be attached to the inner tube 512.

[0055] The top plate portion 551 has a circular planar shape. The top plate portion 551 has an inclined surface 551a that is inclined downward at the center in the planar direction. That is, the top plate portion 551 has a shape in which the center in the planar direction is recessed downward, and is formed into a substantially conical shape as a whole. From the viewpoint of efficiently circulating the separation target and air bubbles, it is sufficient that at least the lower surface of the top plate portion 551 has the inclined surface 551a.

[0056] A communication hole 551b that communicates with the inner flow space 516 and the internal space of the tube portion 531 is formed in the center of the top plate portion 551 in the planar direction. In addition, a plurality of (in this embodiment, three) protrusions 551c that are inserted into the insertion holes 532b of the holder 532 are formed on the upper end of the top plate portion 551.

[0057] The blades 552 are provided on the lower surface of the top plate 551. Specifically, the blades 552 are formed to extend downward from the lower surface of the top plate 551, and are configured to be non-rotatable. Each blade 552 extends along the radial direction of the inner tube 512, and has a shape curved in the circumferential direction of the inner tube 512. That is, the blades 552 are provided radially around the axis of the inner tube 512.

[0058] The curved direction of wing portion 552 may be the same as or different from the curved direction of wing portion 542, but from the viewpoint of efficiently circulating the digestive fluids and air bubbles, it is preferable that they are the same.

[0059] The inner end of each of the blades 552 in the extension direction is located within the area of ​​the inner cylinder 512 in a bottom view. On the other hand, the outer end of each of the blades 552 in the extension direction is located within the area between the outer cylinder 511 and the inner cylinder 512 in a bottom view. Also, each of the blades 552 is formed so that its height decreases from the outer side in the extension direction toward the inner side in the extension direction. This has the advantage that the flow from the outer flow space 515 or the flow from the inner flow space 516 can be swirled efficiently without being obstructed.

[0060] The mounting portion 553 is formed in an annular shape surrounding the periphery of the lower end of the blade portion 552. That is, the upper swirl flow generating portion 550 according to this embodiment is configured to communicate the outer flow space 515 and the inner flow space 516 between the lower surface of the top plate portion 551, the surface of the blade portion 552, and the inner peripheral portion of the mounting portion 553 (the end portion on the blade portion 552 side).

[0061] The mounting portion 553 has a mounting groove 553a into whose lower end the upper end of the inner tube 512 can be inserted. The mounting groove 553a is formed in a concave shape that is concave upward from the lower end of the mounting portion 553. The mounting portion 553 is configured to be attached to the inner tube 512 by inserting the upper end of the inner tube 512 into the mounting groove 553a.

[0062] <Configuration of the inner swirl flow generating section and the outer swirl flow generating section> In this embodiment, either the lower swirling flow generating section 540 or the upper swirling flow generating section 550 functions as an inner swirling flow generating section 560 that turns the flow in the inner flow space 516 into a swirling flow. The other either the lower swirling flow generating section 540 or the upper swirling flow generating section 550 functions as an outer swirling flow generating section 570 that turns the flow in the outer flow space 515 into a swirling flow.

[0063] Whether the lower swirling flow generating section 540 and the upper swirling flow generating section 550 function as the inner swirling flow generating section 560 or the outer swirling flow generating section 570 depends on the position where the upward flow generating section 520 generates an upward flow. Specifically, when the upward flow generating section 520 generates an upward flow in the inner flow space 516, the lower swirling flow generating section 540 functions as the inner swirling flow generating section 560, and the upper swirling flow generating section 550 functions as the outer swirling flow generating section 570. On the other hand, when the upward flow generating section 520 generates an upward flow in the outer flow space 515, the lower swirling flow generating section 540 functions as the outer swirling flow generating section 570, and the upper swirling flow generating section 550 functions as the inner swirling flow generating section 560.

[0064] [Organic waste treatment method] Next, an organic waste treatment method using the organic waste treatment system 1 will be described with reference to Fig. 7. The organic waste treatment method according to this embodiment includes a generation process in which organic waste is reacted with anaerobic microorganisms to generate biogas and digested sludge, a digested sludge separation process in which the digested sludge generated in the generation process is separated into a solid and a digested liquid, a solid-liquid separation process in which the digested liquid separated in the digested sludge separation process is further separated into a solid and a liquid, a drying process in which the solid separated in the solid-liquid separation process is dried, and a concentration process in which the liquid separated in the solid-liquid separation process is concentrated.

[0065] [Generation process] Organic waste is introduced into the production tank 100. The organic waste is then reacted with anaerobic microorganisms in the production tank 100 to produce biogas and digested sludge. The biogas produced in the production tank 100 is supplied to the gas storage tank 200 via the gas supply line 2, and is stored in the gas storage tank 200. Meanwhile, the digested sludge produced in the production tank 100 is supplied to the sludge storage tank 300 via the first sludge supply line 3, and is stored in the sludge storage tank 300.

[0066] [Digested sludge separation process] The digested sludge stored in the sludge storage tank 300 is supplied to the digested sludge separation device 400 via the second sludge supply line 4, and separated into solids and digested liquid in the digested sludge separation device 400. The digested liquid separated in the digested sludge separation device 400 is supplied to the solid-liquid separation device 500 via the digested liquid supply line 5.

[0067] [Solid-liquid separation process] The solid-liquid separation process according to this embodiment includes an inflow process of inflowing the digestive liquid into the solid-liquid separation container 510, a circulation process of circulating the digestive liquid and air bubbles, a stop process of stopping the circulation of the digestive liquid and air bubbles, a solid discharge process of discharging the solid obtained by separation of the digestive liquid, and a liquid discharge process of discharging the liquid obtained by separation of the digestive liquid.

[0068] <Inflow process> The digested liquid is made to flow into the solid-liquid separation vessel 510. Specifically, the digested liquid separated in the digested sludge separation apparatus 400 is made to flow into the solid-liquid separation vessel 510 from the inlet 511a. Note that although coarse solids contained in the digested sludge are removed in the digested sludge separation apparatus 400, many fine solids remain in the liquid flowing into the solid-liquid separation vessel 510.

[0069] <Circulation process> As shown in FIG. 7, an upward flow containing air bubbles B is generated in the inner flow space 516 (see arrow F1 in FIG. 7). Specifically, first, gas generation is started by the switch 521a of the gas generating unit 521, and the generated gas is supplied to the gas releasing unit 522 via the gas supply unit 523 and the connection unit 524. Next, the gas releasing unit 522 releases the gas into the inner flow space 516 via the support unit 543. As a result, an upward flow containing air bubbles B is generated in the inner flow space 516. Note that the gas released into the inner flow space 516 flows between the blades 542 and swirls, so that a swirling upward flow is generated in the inner flow space 516. That is, the digestive fluid and air bubbles B in the inner flow space 516 rise in the inner flow space 516 while swirling.

[0070] When the digestive fluid in the inner flow space 516 rises in the inner flow space 516, the digestive fluid in the outer flow space 515 is drawn into the inner flow space 516 (see arrow F2 in FIG. 7), and a downward flow is generated in the outer flow space 515 (see arrow F3 in FIG. 7). The digestive fluid drawn from the outer flow space 515 to the inner flow space 516 flows between the blades 542, and therefore, coupled with the swirling force of the gas released from the gas release section 522, the digestive fluid rises in the inner flow space 516 while swirling.

[0071] On the other hand, the digestive fluid and air bubbles B rising in the inner flow space 516 rise to the top plate portion 551, then flow along the inclined surface 551a of the top plate portion 551 to the outer flow space 515, and descend through the outer flow space 515 (see arrow F4 in FIG. 7). Note that the digestive fluid and air bubbles B flowing into the outer flow space 515 swirl as they flow between the blade portions 552, and thus a swirling downward flow is generated in the outer flow space 515. That is, the digestive fluid and air bubbles B in the outer flow space 515 descend through the outer flow space 515 while swirling.

[0072] The digestive fluid and the air bubbles B circulate through the circulation flow path CP in the above manner. During this circulation process, some of the suspended matter (solids) in the digestive fluid sinks down the outer flow space 515 and settles in the lower part of the outer flow space 515.

[0073] In addition, in the above circulation process, when the digestive fluid and air bubbles B are drawn from the outer flow space 515 to the inner flow space 516, the flow rate increases (the pressure decreases), and the air bubbles B are broken down into finer particles. The air bubbles B circulating through the circulation flow path CP are further broken down into finer particles by swirling in the inner flow space 516 and the outer flow space 515 and by being sheared by the blade portions 542 and 552. That is, the more the air bubbles B circulate through the circulation flow path CP, the more they are broken down into finer particles. Furthermore, fine solids contained in the digestive fluid are also broken down into finer particles by being sheared by the blade portions 542 and 552.

[0074] In this way, the solid-liquid separation device 500 according to this embodiment is configured to be capable of generating fine bubbles. By generating fine bubbles, the total surface area of ​​the bubbles generated in the solid-liquid separation container 510 increases, thereby improving the separation performance. Note that fine bubbles include microbubbles (bubbles with a diameter of 1 μm or more and less than 100 μm) and ultrafine bubbles (bubbles with a diameter of less than 1 μm).

[0075] <Stopping process> The generation of gas is stopped at any or a predetermined timing by the switch 521a of the gas generation unit 521. Then, the release of gas by the gas release unit 522 is stopped, and the circulation of the digestive fluid and the gas bubbles B in the circulation flow path CP is stopped.

[0076] When the circulation stops, the bubbles B rise in the inner flow space 516 and the outer flow space 515 while adsorbing suspended matter (solids) in the digestive fluid. As a result, settled solids (solids having a size and weight that cannot rise even by the buoyancy of the bubbles B) are present in the lower part of the inner flow space 516 and the outer flow space 515, floated solids (solids having a size and weight that can rise by the buoyancy of the bubbles B) are present in the upper part of the inner flow space 516 and the outer flow space 515, and liquid with little solids is present in the middle part of the inner flow space 516 and the outer flow space 515. In this way, the digestive fluid can be separated into solids and liquid.

[0077] <Solid discharge process and liquid discharge process> The solid obtained by separating the digestive liquid is discharged from the solid discharge port 511b. The liquid obtained by separating the digestive liquid is discharged from the liquid discharge port 511c. After the solid discharge step, the circulation step and the stopping step may be performed again to further concentrate the liquid.

[0078] [Drying process] The solid discharged from the solid-liquid separation vessel 510 is dried. The drying can be performed by any method, for example, drying in the sun. The dried solid can be used as a solid fertilizer.

[0079] [Concentration process] The liquid discharged from the solid-liquid separation vessel 510 is supplied to the concentrating device 600 via the liquid supply path 6, and is concentrated in the concentrating device 600. The permeated liquid that has permeated through the concentrating device 600 is supplied to the permeated liquid storage tank 700 via the permeated liquid supply path 7, and is stored in the permeated liquid storage tank 700. The permeated liquid stored in the permeated liquid storage tank 700 is circulated to the production tank 100 to be reused for new biogas generation. Meanwhile, the concentrated liquid concentrated in the concentrating device 600 is supplied to the concentrated liquid storage tank 800 via the concentrated liquid supply path 8, and is stored in the concentrated liquid storage tank 800. The liquid supplied to the concentrated liquid storage tank 800 is used as liquid fertilizer.

[0080] As described above, the concentration method by the concentrating device 600 can be a concentration method using an evaporation means in addition to a concentration method using a filtration membrane, but it is preferable to use a concentration method using a filtration membrane from the viewpoint of suppressing loss of fertilizer components contained in the liquid separated by the solid-liquid separation device 500. Incidentally, examples of the concentration method using an evaporation means include high-temperature drying, reduced-pressure distillation, hot air drying, and sun drying.

[0081] [Advantages of the solid-liquid separation device and organic waste treatment system according to this embodiment] The solid-liquid separation device 500 according to this embodiment is a solid-liquid separation device that separates a digestive liquid into a solid and a liquid, and is equipped with a solid-liquid separation vessel 510 including an outer cylinder 511 extending along the vertical direction and at least one inner cylinder 512 provided inside the outer cylinder 511, and at least one ascending flow generating section 520 that generates an ascending flow containing air bubbles in an outer flow space 515 formed between the outer cylinder 511 and the inner cylinder 512 or an inner flow space 516 formed inside the inner cylinder 512, the inner flow space 516 and the outer flow space 515 being connected to each other on the upper and lower sides of the inner cylinder 512, and configured to be capable of forming a circulation flow path CP that circulates the digestive liquid and air bubbles, and the ascending flow generating section 520 being configured to be capable of stopping the circulation of the digestive liquid and air bubbles.

[0082] According to the solid-liquid separation device 500 having such a configuration, among the solids contained in the digestive liquid, solids having a size and weight that cannot rise even by the buoyancy of the bubbles can be allowed to sink and settle at the bottom of the outer flow space 515 and the inner flow space 516. Furthermore, according to the above-mentioned solid-liquid separation device 500, among the solids contained in the digestive liquid, solids having a size and weight that can rise by the buoyancy of the bubbles can be caused to rise to the outer flow space 515 and the inner flow space 516 while being adsorbed by the bubbles. That is, according to the above-mentioned solid-liquid separation device 500, the digestive liquid can be separated into solids and liquids by circulating the digestive liquid and the bubbles. Furthermore, since the solid-liquid separation device 500 according to this embodiment can largely remove the solids contained in the digestive liquid, for example, when a filtration process using a filtration membrane is performed as a post-processing of the solid-liquid separation device 500, there is an advantage that clogging of the filtration membrane can be suppressed and the frequency of replacing the filtration membrane due to clogging, and thus the running cost, can be reduced.

[0083] Furthermore, in the solid-liquid separation apparatus 500 according to this embodiment, since there is no need to use a pressure pump or the like for pressurizing raw water to generate bubbles, separation of the digestive liquid can be realized at low cost, and there are also advantages in that it is highly reliable and durable. In addition, since there is no need to use a pressure pump, there is also no need to use a nozzle, which has the advantage of eliminating the need to replace the nozzle due to wear.

[0084] In the solid-liquid separation apparatus 500 according to this embodiment, the outer cylinder 511 has at least one solid outlet 511b capable of discharging solids and at least one liquid outlet 511c capable of discharging liquids. The solid-liquid separation apparatus 500 having such a configuration has an advantage that the solids can be used as solid fertilizer and the liquid can be used as liquid fertilizer.

[0085] In the solid-liquid separation apparatus 500 according to this embodiment, the upward flow generating section 520 is provided with at least one gas release section 522 that releases gas into the outer flow space 515 or the inner flow space 516 below the vertical middle section of the solid-liquid separation vessel 510. According to the solid-liquid separation apparatus 500 having such a configuration, an upward flow containing gas bubbles can be generated simply by releasing gas from the gas release section 522, and since the digestive liquid and gas bubbles can be circulated, the digestive liquid can be separated at low cost and without loss of fertilizer components contained in the digestive liquid, and the durability of the apparatus itself is also high.

[0086] The solid-liquid separator 500 according to this embodiment includes a top plate 551 provided opposite to an upper opening 512a of the inner cylinder 512, and the bottom surface of the top plate 551 has an inclined surface 551a that is inclined downward at the center in the planar direction. The solid-liquid separator 500 having such a configuration has the advantage that the rising digestive fluid flows along the inclined surface 551a, so that the digestive fluid can be circulated efficiently.

[0087] The solid-liquid separation device 500 according to this embodiment includes at least one of an inner swirling flow generating section 560 that causes the flow in the inner flow space 516 to swirl, and an outer swirling flow generating section 570 that causes the flow in the outer flow space 515 to swirl. The solid-liquid separation device 500 having such a configuration has the advantage that the swirling flow makes it easier to circulate the digestive liquid and air bubbles. In addition, since the air bubbles swirl, there is also the advantage that the air bubbles can be made finer. As the air bubbles are made finer, the total surface area of ​​the air bubbles increases, improving the separation performance.

[0088] In the solid-liquid separation device 500 according to the present embodiment, the inner swirling flow generating section 560 and the outer swirling flow generating section 570 are provided with a plurality of blades 542 (or blades 552) provided at a predetermined interval, and the plurality of blades 542 (or blades 552) have a shape curved in the circumferential direction of the inner cylinder 512. The solid-liquid separation device 500 having such a configuration has an advantage that a swirling flow can be generated simply by moving the sludge between the blades 542 (or blades 552). In addition, there is an advantage that the bubbles can be finely divided because the bubbles are sheared by the blades 542 (or blades 552). The fineness of the bubbles increases the total surface area of ​​the bubbles, and therefore the separation performance can be improved. In addition, there is an advantage that not only the bubbles but also the solids contained in the digestive liquid are sheared by the blades 542 (or blades 552), so that the solids are finely divided and easily floated.

[0089] In the solid-liquid separator 500 according to this embodiment, the blade portion 542 (or the blade portion 552) is configured to be non-rotatable. According to the solid-liquid separator 500 having such a configuration, a swirling flow can be generated without rotating the blade portion 542 (or the blade portion 552), which has the advantage of low costs (e.g., number of parts, power costs, costs associated with part replacement, etc.). In addition, since the blade portion 542 (or the blade portion 552) does not rotate, there is also the advantage that fine solids mixed in the digestive fluid are not caught by the blade portion 542 (or the blade portion 552).

[0090] The organic waste treatment system 1 according to this embodiment is an organic waste treatment system for treating organic waste, and includes a generation tank 100 for reacting organic waste with anaerobic microorganisms to produce biogas and digested sludge, a digested sludge separation device 400 for separating the digested sludge into solids and digested liquid, a solid-liquid separation device 500 for further separating the digested liquid separated in the digested sludge separation device 400 into solids and liquid, and a concentration device 600 for concentrating the liquid separated in the solid-liquid separation device 500. The solid-liquid separation device 500 includes an outer cylinder 511 extending vertically and a The solid-liquid separation vessel 510 includes at least one inner cylinder 512 provided therein, and at least one upward flow generating section 520 that generates an upward flow including air bubbles in an outer flow space 515 formed between the outer cylinder 511 and the inner cylinder 512 or in an inner flow space 516 formed inside the inner cylinder 512, the inner flow space 516 and the outer flow space 515 being connected to each other on the upper and lower sides of the inner cylinder 512 and configured to be capable of forming a circulation flow path CP that circulates the digestive liquid and air bubbles, and the upward flow generating section 520 is configured to be capable of stopping the circulation of the digestive liquid and air bubbles.

[0091] According to the organic waste treatment system 1 having such a configuration, the digested sludge separation device 400 can remove coarse solids, and the solid-liquid separation device 500 can remove fine and microscopic solids. Therefore, for example, when the concentrating device 600 is equipped with a filtration membrane, there is an advantage that clogging of the filtration membrane can be suppressed, and the frequency of replacing the filtration membrane due to clogging, and therefore the running cost, can be reduced. In addition, for example, when the concentrating device 600 is equipped with an evaporation means, there is an advantage that the loss of fertilizer components due to high temperature heating can be suppressed. In addition, according to the organic waste treatment system 1 of this embodiment, there is an advantage that the manufacturing cost and running cost are low because there is no need to use a flocculant or a pressure pump for solid-liquid separation.

[0092] [Variations] The solid-liquid separation device, organic waste treatment system, and organic waste treatment method according to the present invention are not limited to the above-described embodiments, and various modifications can be made within the scope that does not deviate from the technical concept of the present invention.

[0093] In the above-described embodiment, in addition to the solid-liquid separation apparatus 500, the digested sludge separation apparatus 400 and the thickening apparatus 600 are used, but this is not limited to this, and devices or means other than the digested sludge separation apparatus 400, the solid-liquid separation apparatus 500 and the thickening apparatus 600 may be used.

[0094] In the above-described embodiment, the upper swirl flow generating section 550 has been described as including the top plate portion 551, but is not limited thereto, and may not include the top plate portion 551. Moreover, the top plate portion 551 may not include the inclined surface 551a and may be formed in a flat shape.

[0095] In the above-described embodiment, the solid-liquid separation apparatus 500 has been described as including a lower swirling flow generating section 540 and an upper swirling flow generating section 550, but is not limited thereto and may include only one of them or neither of them.

[0096] In the above-described embodiment, the solid-liquid separation apparatus 500 has been described as having a top 514 that closes the upper end of the outer cylinder 511, and an exhaust section 530 that exhausts gas from within the solid-liquid separation container 510. However, the present invention is not limited to this, and the solid-liquid separation apparatus 500 may be configured as an open-to-atmosphere type in which the top 514 and exhaust section 530 are not provided, and the upper ends of the outer cylinder 511 and the inner cylinder 512 are open.

[0097] In the above-described embodiment, the outer cylinder 511 and the bottom portion 513 are described as being formed independently, but the present invention is not limited thereto, and the outer cylinder 511 and the bottom portion 513 may be integrally formed. Also, for example, the outer cylinder 511, the bottom portion 513, the weight portion 541 and the blade portion 542 may be integrally formed, or the bottom portion 513, the weight portion 541 and the blade portion 542 may be integrally formed, or the weight portion 541 and the blade portion 542 may be integrally formed. Also, the weight portion 541 may not be provided.

[0098] It is apparent from the claims that the above-mentioned modifications are included within the scope of the present invention. [Explanation of symbols]

[0099] 1: Organic waste treatment system 2: Gas supply line 3: First sludge supply channel 4: Second sludge supply line 5: Digestive fluid supply channel 6:Liquid supply path 7: Permeate supply path 8: Concentrate supply path 100: Generation tank 200: Gas storage tank 300: Sludge storage tank 400: Digested sludge separator 500: Solid-liquid separation equipment 510: Solid-liquid separation container 511: Outer cylinder 511a: Inlet 511b :Solid discharge port 511c:Liquid outlet 512: Inner cylinder 512a: Upper side opening 513: Bottom 514:Top 515:Outer flow space 516:Inner flow space 520: Upward flow generation section 521: Gas generating section 521a: Switch 522: Gas release section 523: Gas supply section 524: Connection 530: Discharge section 531:Cylinder part 531a: Inflow hole 532: Holding part 532a: Mounting hole 532b: Insertion hole 540: Lower swirl flow generation section 541: Weight section 542: Wing 543: Support part 543a: Insertion groove 543b: Pipe section 543c: Attached part 543d:Outflow hole 550: Upper swirl flow generation section 551: Top plate 551a: Inclined surface 551b:Communication hole 551c:Protrusion 552: Wing 553: Mounting part 553a: Mounting groove 560: Inner swirl flow generating section 570:Outer swirl flow generation section 600: Concentrator 700: Permeate storage tank 800: Concentrated liquid storage tank B: Air bubbles CP: Circulation channel TJ: Tube joint

Claims

1. A solid-liquid separation device for separating a digestive liquid into solids and liquids, A solid-liquid separation vessel including an outer cylinder extending along a vertical direction and at least one inner cylinder provided inside the outer cylinder; at least one upward flow generating unit that generates an upward flow containing air bubbles in an outer flow space formed between the outer cylinder and the inner cylinder or in an inner flow space formed inside the inner cylinder; at least one of an inner swirling flow generating section which causes the flow in the inner flow space to swirl and an outer swirling flow generating section which causes the flow in the outer flow space to swirl; Equipped with The inner flow space and the outer flow space are connected to each other at the upper side and the lower side of the inner cylinder, and are configured to be able to form a circulation flow path that circulates the digestive fluid and air bubbles, The upward flow generating unit is configured to be capable of stopping the circulation of the digestive fluid and the air bubbles, The inner swirl flow generating portion and the outer swirl flow generating portion each include a plurality of blade portions provided at predetermined intervals, The plurality of blade portions have a shape curved in the circumferential direction of the inner cylinder. Solid-liquid separation equipment.

2. The outer cylinder is at least one solids outlet through which the solids can be discharged; At least one liquid outlet capable of discharging the liquid; Possesses The solid-liquid separation apparatus according to claim 1.

3. The upward flow generating section is provided with at least one gas releasing section that releases gas into the outer flow space or the inner flow space below a vertical middle portion of the solid-liquid separation vessel. The solid-liquid separation apparatus according to claim 1 or 2.

4. A top plate portion is provided opposite to an upper opening of the inner cylinder, The lower surface of the top plate portion has an inclined surface that is inclined downward at the center in the planar direction. The solid-liquid separation apparatus according to claim 1 or 2.

5. The blade portion is configured to be non-rotatable. The solid-liquid separation apparatus according to claim 1 or 2.

6. An organic waste treatment system for treating organic waste, comprising: a generation tank for reacting the organic waste with anaerobic microorganisms to generate biogas and digested sludge; a digested sludge separator for separating the digested sludge into a solid and a digested liquid; a solid-liquid separator for further separating the digestive liquid separated by the digested sludge separator into solids and liquids; a concentrating device for concentrating the liquid separated by the solid-liquid separation device; Equipped with The solid-liquid separation device is A solid-liquid separation vessel including an outer cylinder extending along a vertical direction and at least one inner cylinder provided inside the outer cylinder; at least one upward flow generating unit that generates an upward flow containing air bubbles in an outer flow space formed between the outer cylinder and the inner cylinder or in an inner flow space formed inside the inner cylinder; at least one of an inner swirling flow generating section which causes the flow in the inner flow space to swirl and an outer swirling flow generating section which causes the flow in the outer flow space to swirl; having The inner flow space and the outer flow space are connected to each other at the upper side and the lower side of the inner cylinder, and are configured to be able to form a circulation flow path that circulates the digestive fluid and air bubbles, The upward flow generating unit is configured to be capable of stopping the circulation of the digestive fluid and the air bubbles, The inner swirl flow generating portion and the outer swirl flow generating portion each include a plurality of blade portions provided at predetermined intervals, The plurality of blade portions have a shape curved in the circumferential direction of the inner cylinder. Organic waste treatment system.

7. An organic waste treatment method for treating organic waste, comprising: a generating step of reacting the organic waste with anaerobic microorganisms to generate biogas and digested sludge; a digested sludge separation step of separating the digested sludge into a solid and a digested liquid; a solid-liquid separation step for further separating the digestive liquid separated in the digested sludge separation step into solids and liquids; a concentration step for concentrating the liquid separated in the solid-liquid separation step; Including, The solid-liquid separation step includes: an inflow step of injecting the digestive liquid into a solid-liquid separation vessel including an outer cylinder extending along a vertical direction and at least one inner cylinder provided inside the outer cylinder; a circulation step of circulating the digestive liquid and the air bubbles by generating an upward flow containing air bubbles in an outer flow space formed between the outer cylinder and the inner cylinder or in an inner flow space formed inside the inner cylinder; a stopping step of stopping the circulation of the digestive liquid and the air bubbles; Including, In the circulating step, at least one of the flow in the inner flow space and the flow in the outer flow space is made to swirl by a plurality of blade portions provided at predetermined intervals, The plurality of blade portions have a shape curved in the circumferential direction of the inner cylinder. Organic waste treatment methods.

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