Method for driving a solid-liquid separator

Abstract

To provide a driving method of a solid-liquid separator capable of efficiently separating a solid and a liquid.SOLUTION: A driving method of a solid-liquid separator 1 that transports sand in a concentrated liquid by driving a transport device 5 comprises: a filling step of raising a liquid level in a concentrated liquid tank 4 to fill the inside of a liquid sending pipe 6 with waste water; and a driving step of driving the transport device 5 at a speed that does not allow liquid components contained in the concentrated liquid to reach a dropping part 52 and transporting solids collected at a lower end, wherein the solid-liquid separator comprises: a concentration container 3 that receives a sand-containing liquid; a concentrated liquid tank 4 that stores the concentrated liquid with an increased sand concentration; a transport device 5 that is provided with a dropping part 52 near an upper end of a transport path extending diagonally upward; and a liquid feeding pipe 6 that has an inflow entrance 611 connected to the concentration container 3 and a water outlet 62 disposed below the inflow entrance 611, and the filling step and the driving step are executed simultaneously.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for driving a solid-liquid separator that separates a liquid from a liquid containing a solid. [Background technology]

[0002] A sewage treatment facility is provided with a grit basin for removing sand from wastewater and a sedimentation basin for removing sludge from wastewater. In the grit basin, sand contained in the wastewater flowing in is collected in a sand collection pit at the bottom of the basin, and then the sand-mixed water containing the collected sand is sucked up by a sand pump and transferred to a solid-liquid separation device installed on the ground. This solid-liquid separation device receives the transferred sand-mixed water, separates the sand and wastewater from the sand-mixed water, and returns the wastewater to the grit basin. In addition, the sedimentation basin collects sludge contained in the received wastewater in a sludge pit at the bottom of the basin, and then transfers the sludge-mixed water containing the sludge collected in the sludge pit to a solid-liquid separation device installed above the sedimentation basin by a sludge pump. The solid-liquid separation device installed above the sedimentation basin also receives the transferred sludge-mixed water, separates the wastewater from the sludge-mixed water, and returns it to the sedimentation basin. Furthermore, solid-liquid separation devices that separate liquid from a mixed liquid containing a solid mixed in the liquid are used in places other than sewage treatment facilities. Such solid-liquid separation devices include, for example, devices that separate water and metal powder from industrial wastewater, and devices that separate sediment and the like that has flowed into a reservoir such as a dam lake from water. Hereinafter, sand, sludge, and screen residue contained in wastewater, metal powder contained in industrial wastewater, and sediment and the like that flows into a reservoir together with water may be collectively referred to as solids. Liquids that have solids mixed in them may be collectively referred to as mixed liquids.

[0003] As such a solid-liquid separation device, one equipped with a concentration container, a concentrated liquid tank, and a conveying device is known (see, for example, Patent Document 1, etc.). The concentration container in Patent Document 1 is disposed above the concentrated liquid tank, and is connected to a sand lifting pump disposed in the settling basin by a sand lifting pipe. The concentration container receives the sand-mixed water transferred from the settling basin by the sand lifting pump, and discharges the concentrated liquid, in which the sand concentration relative to the wastewater is higher than that of the sand-mixed water, from an outlet provided in the concentration container. The concentrated liquid tank receives and stores the concentrated liquid discharged from the concentration container. The conveying device is connected to the lower end portion of the concentrated liquid tank, and extends obliquely upward from the connected portion. The sand that has settled in the lower end portion of the concentrated liquid tank is conveyed obliquely upward by the conveying device while being drained, and is sent to the outside of the concentrated liquid tank. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-21483 A Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, however, there has been a demand for more efficient separation of solids and liquids.

[0006] In view of the above circumstances, an object of the present invention is to provide a method for driving a solid-liquid separator capable of efficiently separating a solid from a liquid. [Means for solving the problem]

[0007] The present invention provides a method for driving a solid-liquid separation apparatus that achieves the above object, the method comprising: a concentration container that receives a mixed liquid in which solids are mixed into a liquid and discharges from an outlet a concentrated liquid in which the concentration of solids in the liquid has increased; a concentrated liquid tank having the outlet disposed within the tank and storing the concentrated liquid obtained in the concentration container; a transport device having a transport path whose lower end portion extends obliquely upward and is connected to the bottom of the concentrated liquid tank, whose upper end portion is disposed above the outlet and which is provided with a drop portion extending downward from near the upper end of the transport path; and a liquid delivery pipe whose inlet is connected to the concentration container and whose outlet is disposed outside the concentrated liquid tank and below the inlet, the method comprising the steps of: collecting solids in the concentrated liquid at the lower end portion; driving the transport device to transport the solids obliquely upward along the transport path; and sending the liquid in the mixed liquid received by the concentration container to the outside of the concentrated liquid tank through the liquid delivery pipe, a filling step of raising the liquid level in the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container; a driving step of driving the conveying device at a speed at which a liquid component contained in the concentrated liquid does not reach the dropping portion, and conveying the solids collected in the lower end portion; The filling step and the driving step are performed simultaneously. Effect of the Invention

[0008] According to the present invention, it is possible to provide a method for driving a solid-liquid separator capable of efficiently separating a solid from a liquid. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a solid-liquid separation device according to one embodiment of the present invention. [Diagram 2] 1A is a plan view of the concentration vessel, and FIG. 1B is a cross-sectional view taken along line AA in FIG. [Diagram 3] 1A is a plan view showing the concentration container and the concentrated liquid tank, FIG. 1B is a front view showing the concentration container and the concentrated liquid tank, and FIG. 1C is a cross-sectional view taken along line BB in FIG. [Figure 4] 2 is a flowchart showing the operation of the solid-liquid separation device shown in FIG. [Diagram 5] 3(a) is a front view similar to FIG. 3(b) showing a modified example of the solid-liquid separator shown in FIG. 1, and FIG. 3(b) is a cross-sectional view taken along CC in FIG. 3(a). [Figure 6] 6(a) is a front view similar to FIG. 3(b) of a solid-liquid separator of a modified example different from the modified example shown in FIG. 5, and (b) is a DD cross-sectional view of FIG. [Figure 7] FIG. 5 is a front view similar to FIG. 3(b) of a solid-liquid separator according to a second embodiment. [Figure 8] 8 is a flowchart showing the operation of the solid-liquid separation device shown in FIG. [Figure 9] 8 is a front view similar to FIG. 7, showing a modification of the solid-liquid separator shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of this embodiment, an example is used in which the driving method of the present invention is applied to a solid-liquid separation device to which wastewater containing sand is transferred from a grit basin. The grit basin is disposed upstream of a sewage treatment facility to remove sand from wastewater such as sewage or rainwater. The wastewater from which sand has been removed in the grit basin is sent to a sedimentation basin or the like located downstream.

[0011] Fig. 1 is a schematic diagram showing a solid-liquid separation device according to one embodiment of the present invention, which also shows a grit basin.

[0012] As shown in FIG. 1, the grit basin 9 of this embodiment is a basin equipped with a pump well 91, a trough 92, a sand collecting nozzle 93, and a sand collecting pit 94. Wastewater flows into the grit basin 9 from the right side of the figure. The flowing wastewater flows slowly toward the left side of the figure. In the grit basin 9, the sand contained in the wastewater settles toward the bottom of the basin while the wastewater flows. The pump well 91 is disposed at the most downstream side of the grit basin 9. The pump well 91 stores the wastewater from which sand has been removed. A lifting pump 911 is provided inside the pump well 91. The lifting pump 911 discharges the wastewater stored in the pump well 91 to the outside of the grit basin 9. A lifting pipe 912 is connected to the lifting pump 911. The wastewater sucked by the lifting pump 911 is sent to a sedimentation basin (not shown) through the lifting pipe 912. Note that FIG. 1 also shows the water level WL1 of the wastewater. The position of the pond water surface WL1 varies depending on the amount of wastewater flowing into the grit basin 9, within a range of, for example, 1 m to 5 m from the bottom of the trough 92.

[0013] The trough 92 is formed in the pond bottom upstream of the pump well 91, in the center in the pond width direction. This trough 92 extends along the direction in which the wastewater flows in the grit basin 9. On both sides of the pond bottom in the pond width direction of the trough 92, pond bottom slopes 95 are formed, which slope downward toward the trough 92. Sand contained in the wastewater that flows into the grit basin 9 settles toward the pond bottom and slides down the pond bottom slopes 95 or is directly deposited in the trough 92.

[0014] The sand collection nozzle 93 is disposed at the upstream end of the trough 92. Wastewater pumped up from the settling basin is supplied to the sand collection nozzle 93. The wastewater supplied to the sand collection nozzle 93 is discharged from the tip of the sand collection nozzle 93 toward the downstream side of the settling basin 9. The downstream end of the trough 92 is connected to a sand collection pit 94. Sand deposited in the trough 92 is collected in the sand collection pit 94 by the flow of water discharged from the sand collection nozzle 93. The sand collection pit 94 is formed between the pump well 91 and the trough 92. The sand collected in the sand collection pit 94 is transported together with the wastewater to the solid-liquid separation device 1 and separated into a solid (sand) and a liquid (wastewater).

[0015] A sand lifting pump 941 is disposed inside the sand collection pit 94 near the bottom of the sand collection pit 94. The sand lifting pump 941 corresponds to an example of a pump. A sand lifting pipe 942 is connected to the sand lifting pump 941. The sand lifting pump 941 sucks up the sand collected inside the sand collection pit 94 together with the wastewater, and transfers the wastewater mixed with the sand to the solid-liquid separation device 1 through the sand lifting pipe 942. The ratio of sand and wastewater transferred to the solid-liquid separation device 1 by the sand lifting pump 941 varies depending on the amount of sand collected inside the sand collection pit 94, etc., but is about 5% sand and about 95% wastewater. The sand-mixed water, in which sand is mixed into the wastewater and transferred by the sand lifting pump 941, corresponds to an example of a mixed liquid. The sand in the sand-mixed water corresponds to an example of a solid, and the wastewater in the sand-mixed water corresponds to an example of a liquid.

[0016] The solid-liquid separation device 1 includes a concentration container 3, a concentrated liquid tank 4, a conveying device 5, and a liquid feed pipe 6. The concentration container 3, the concentrated liquid tank 4, and the conveying device 5 are disposed on the ground near the grit basin 9. The concentration container 3 is disposed in the tank of the concentrated liquid tank 4. The concentration container 3 separates a part of the wastewater in the transferred sand-containing water from the sand and sends it to the liquid feed pipe 6. Hereinafter, the wastewater separated from the sand-containing water is referred to as separated water. The concentration container 3 also discharges a concentrated liquid in which the concentration of sand relative to the wastewater is increased by removing a part of the wastewater, into the concentrated liquid tank 4. The wastewater contained in this concentrated liquid also corresponds to an example of a liquid. The separated water sent out from the concentration container 3 is returned to the grit basin 9 through the liquid feed pipe 6. The liquid feed pipe 6 has one end portion 61 (see FIG. 2) inserted into the concentration container 3, a horizontal portion extending horizontally above the concentration container 3, and a vertical portion bent from the horizontal portion and extending downward. An outlet 62 formed at the lower end of the vertical portion is disposed above the grit basin 9, which is below the concentration vessel 3 and outside the concentrated liquid tank 4. The concentration vessel 3 and concentrated liquid tank 4 will be described in detail later.

[0017] The conveying device 5 extends obliquely upward from the lower end of the concentrated liquid tank 4. The conveying device 5 has a screw conveyor 51, a throwing part 52, and a cylindrical part 53 that covers the outside of the screw conveyor 51. The screw conveyor 51 is disposed in the cylindrical part 53. The axial direction of the screw conveyor 51 coincides with the extending direction of the conveying device 5. The screw conveyor 51 forms a conveying path that extends obliquely upward. The lower end part of this conveying path is connected to the bottom of the concentrated liquid tank 4. The upper end part of the conveying path is disposed above the discharge port 331 (see FIG. 2(b)) of the concentration container 3. The sand contained in the concentrated liquid discharged into the concentrated liquid tank 4 settles in the concentrated liquid tank 4 and collects at the lower end of the concentrated liquid tank 4. The sand that has collected at the lower end of the concentrated liquid tank 4 is conveyed obliquely upward by the rotation of the screw conveyor 51, and is conveyed while being drained at the upper end part of the conveying path of the conveying device 5. The dropping part 52 is a tube extending downward from near the upper end of the screw conveyor 51, and a drop port 52a is formed at the lower end. The upper end of the dropping part 52 is connected to an opening formed at the lower part near the upper end of the cylindrical part 53. The sand drained by the transport by the screw conveyor 51 is dropped downward from the drop port 52a through the dropping part 52. That is, the conveying device 5 conveys the sand contained in the concentrated liquid received by the concentrated liquid tank 4 to the outside of the concentrated liquid tank 4. Note that, instead of the screw conveyor 51, other conveying mechanisms such as a belt conveyor or a flight conveyor may be used. Note that, an opening and closing lid that can freely close and open the dropping part 52 may be provided on the dropping part 52, and the dropping part 52 may be closed when the conveying device 5 is not driven. The blocking lid is preferably formed at the upper end of the dropping part 52, i.e., between the dropping part 52 and the cylindrical part 53, but may be provided near the drop port 52a. By providing the opening and closing lid, even if the tank water level WL2 rises above the upper end of the input part 52, the concentrated liquid can be prevented from leaking out from the input part 52.

[0018] Fig. 2(a) is a plan view of the concentration container, and Fig. 2(b) is a cross-sectional view taken along line AA in Fig. 2(a). Fig. 2(a) and Fig. 2(b) also show one end portion of the liquid delivery pipe.

[0019] As shown in FIG. 2(b), the concentration container 3 includes a fluid inlet 31, a throttle section 32, a discharge section 33, a fluid inlet pipe 34, and a pair of mounting sections 36. The concentration container 3 of this embodiment is a so-called fluid cyclone device. The fluid inlet 31 is provided in the upper part of the concentration container 3. The upper end of the throttle section 32 is connected to the lower end of the fluid inlet 31. The upper end of the discharge section 33 is connected to the lower end of the throttle section 32. The inner circumferential surface 3a of the concentration container 3 is composed of the inner circumferential surface 31a of the fluid inlet 31, the inner circumferential surface 32a of the throttle section 32, and the inner circumferential surface 33a of the discharge section 33. The inner circumferential surface 3a of the concentration container 3 defines an internal space X1. That is, the fluid inlet 31, the throttle section 32, and the discharge section 33 form a hollow tank having an internal space X1.

[0020] The fluid introduction section 31 includes a cylindrical section 311 having a cylindrical inner circumferential surface 31a, and a lid 312 closing the upper end of the cylindrical section 311. The cylindrical section 311 is a steel plate having a thickness of 3.2 mm that is processed into a cylindrical shape with an inner diameter of 500 mm. The lid 312 is a steel plate having a thickness of 6.0 mm that is processed into a ring shape with an outer diameter of 586 mm and an inner diameter of 114 mm. The shape, material, and thickness of the cylindrical section 311 and the lid 312 may be appropriately selected according to the size of the internal space X1, etc. The cylindrical section 311 may be a cone-shaped or dome-shaped section in which the cross-sectional area of ​​the internal space X1 increases downward. The cylindrical section 311 may be a cone-shaped or dome-shaped section in which the cross-sectional area of ​​the internal space X1 increases downward in the upper part where the receiving port 341 described later is formed, and the lower part may be a cylindrical section. A pair of mounting portions 36 are fixed to the outer circumferential surface of the cylindrical portion 311. The mounting portions 36 are used to fix the concentration container 3 to the concentrated liquid tank 4 shown in FIG.

[0021] In addition, the fluid inlet pipe 34 is connected to the upper part of the cylindrical part 311. The sand lifting pump 941 and the fluid inlet pipe 34 shown in FIG. 1 are connected via a sand lifting pipe 942. The sand lifting pipe 942 and the fluid inlet pipe 34 are detachably connected by fastening the flanges provided at the connection ends with bolts. The fluid inlet pipe 34 is a pipe with an inner diameter of 100 mm. As shown in FIG. 2(b), a receiving port 341 is formed at the connection part between the fluid inlet pipe 34 and the cylindrical part 311. As shown by the straight arrow in FIG. 2(a), the sand-mixed water sucked up by the sand lifting pump 941 is introduced into the internal space X1 from the tangential direction of the inner circumferential surface 31a of the cylindrical part 311 through the receiving port 341. Therefore, the sand-mixed water received by the concentration container 3 is introduced between the outer circumferential surface of one end part 61 of the liquid supply pipe 6 and the inner circumferential surface 31a of the cylindrical part 311. As a result, a swirling flow of sand-mixed water is formed in the internal space X1.

[0022] The throttled portion 32 is disposed between the receiving port 341 and the discharge portion 33. In this throttled portion 32, the cross-sectional area of ​​the internal space X1 decreases toward the discharge portion 33. In other words, the throttled portion 32 has an inverted cone-shaped inner peripheral surface 32a that gradually decreases in diameter as it moves away from the cylindrical portion 311. The throttled portion 32 may have a cross-sectional area of ​​the internal space X1 that gradually decreases toward the discharge port 331. That is, the throttled portion 32 is formed so that the cross-sectional area of ​​the internal space X1 is smaller on the discharge port 331 side than on the receiving port 341 side. The throttled portion 32 is formed by processing a steel plate with a plate thickness of 3.2 mm into a cone shape, and the upper end is formed to have an inner diameter of 500 mm and the lower end is formed to have an inner diameter of 100 mm. The material and thickness of the throttled portion 32 may be appropriately selected according to the size of the internal space X1, the amount of throttling, and the like. In this embodiment, the cross-sectional area of ​​the lower end of the throttle section 32 is made to match the cross-sectional area of ​​the receiving port 341, but the cross-sectional area of ​​the lower end of the throttle section 32 may be larger or smaller than the cross-sectional area of ​​the receiving port 341. However, if the cross-sectional area of ​​the lower end of the throttle section 32 is made too small, the pressure loss in the concentration vessel 3 increases, so the cross-sectional area of ​​the lower end of the throttle section 32 is preferably equal to or larger than the cross-sectional area of ​​the receiving port 341.

[0023] The discharge section 33 is connected to the side of the throttle section 32 opposite to the side where the fluid introduction section 31 is provided. In other words, the discharge section 33 is connected to the lower end of the throttle section 32. The discharge section 33 has a cylindrical shape with a flange formed at the lower end and an inner diameter the same as the lower end of the throttle section 32. The opening at the lower end of this discharge section 33 becomes the discharge port 331. Note that the discharge section 33 may be omitted. In that case, the opening at the lower end of the throttle section 32 becomes the discharge port.

[0024] One end portion 61 of the liquid supply tube 6 penetrates the lid 312 of the fluid introduction part 31 in the vertical direction. This one end portion 61 extends from below the lower end of the lid 312 to above the upper end of the lid 312 along the radial center axis of the cylindrical part 311, and is joined to the lid 312 in a watertight state by welding. Therefore, the lower part of the one end portion 61 protrudes into the internal space X1. However, the lower part of the one end portion 61 does not have to protrude into the internal space X1, and for example, the lower surface of the lid 312 and the lower end of the one end portion 61 may be on the same plane. The one end portion 61 has a tubular shape with an inner diameter of 100 mm. The lower end of this one end portion 61 becomes one end of the liquid supply tube 6, and the opening of the one end becomes the inlet 611. Therefore, the one end portion 61 and the inlet 611 (one end of the liquid supply tube 6) are connected to the concentration container 3. Moreover, the inlet 611 of this embodiment is disposed in the internal space X1. The separated water separated from the sand-containing water is returned to the grit basin 9 through the inlet 611 and the liquid supply pipe 6. The inlet 611 is disposed below the receiver 341. The part of the liquid supply pipe 6 other than the one end part 61 and the one end part 61 are detachably connected by fastening with a bolt. The length of the one end part 61 in the extending direction is arbitrary, and for example, the lower part of the one end part 61 (the part in the internal space X1) may be formed longer than the fluid introduction part 31. In this case, the inlet 611 is formed in a region of the internal space X1 that is defined by the inner circumferential surface 32a of the throttle part 32. Although an example has been shown in which the cross-sectional area of ​​the inlet 611 is equal to the cross-sectional area of ​​the lower end of the throttle part 32, it is preferable that the cross-sectional area of ​​the inlet 611 is equal to or larger than the cross-sectional area of ​​the discharge port 331. This increases the amount of separated water discharged from the inlet 611, and further reduces the pressure loss in the concentration vessel 3.

[0025] Next, the operation of the concentration container 3 will be described mainly with reference to FIG. 2. As described above, by driving the sand-raising pump 941 (see FIG. 1), the sand-containing water flows into the internal space X1 from the receiving port 341, and a swirling flow of the sand-containing water is formed in the internal space X1. The sand contained in the sand-containing water has a larger specific gravity than the wastewater, and is pressed against the inner peripheral surface 3a of the concentration container 3 by centrifugal force, and gradually falls downward while rotating along the inner peripheral surface 3a. Meanwhile, separated water from which sand has been removed from the sand-containing water is collected in the radial center of the cylindrical portion 311. The separated water is discharged from the inlet 611. However, since the size of the receiving port 341 and the outlet 331 of the concentration container 3 of this embodiment is the same, it is necessary to provide a concentrated liquid tank 4, which will be described in detail later, in order to discharge the separated water from the inlet 611, although it depends on the amount of sand-containing water received from the receiving port 341 per unit time. As shown in FIG. 1, the separated water is discharged toward the grit basin 9 through the outlet 62 formed at the other end of the liquid supply pipe 6 through the liquid supply pipe 6. The outlet 62 formed at the other end of the liquid supply pipe 6 is disposed below the inlet 611 formed at one end of the liquid supply pipe 6. Therefore, when the liquid supply pipe 6 is filled with liquid, the sand-mixed water (separated water) in the internal space X1 is forced to flow out of the inlet 611 into the grit basin 9 due to the principle of a siphon. This produces an effect that the sand-mixed water can be transported to the concentration vessel 3 even if the power of the sand lifting pump 941 is small. The other end of the liquid supply pipe 6 may be extended below the water level WL1 of the grit basin 9 so that the outlet 62 is submerged in water. An intermediate tank may be provided between the concentration vessel 3 and the grit basin 9, and the separated water flowing out from the outlet 62 may be stored in the intermediate tank. By providing the intermediate tank, the state of the separated water can be confirmed by the separated water stored in the intermediate tank. Furthermore, even if a small amount of sand is sent out from the inlet 611 together with the separated water, the sand can be allowed to settle in the intermediate tank and the supernatant liquid of the intermediate tank returned to the settling basin 9, thereby further preventing the sand from being returned to the settling basin 9.

[0026] FIG. 3(a) is a plan view showing the concentration container and the concentrated liquid tank, FIG. 3(b) is a front view showing the concentration container and the concentrated liquid tank, and FIG. 3(c) is a cross-sectional view taken along line BB in FIG. 3(b).

[0027] As shown in FIG. 3(a) and FIG. 3(b), the concentrated liquid tank 4 has a side wall 41 that is disposed outside the outer peripheral side surface 3b of the concentration container 3 and extends above the discharge port 331. As shown in FIG. 3(c), in this embodiment, the side wall 41 extends above the upper end 6c of the liquid supply pipe 6. The concentration container 3 is detachably fixed in the concentrated liquid tank 4 by connecting the mounting portion 36 with a bolt to a pair of arms 42 that are fixed at one end to the inner peripheral surface of the side wall 41 and extend inward. As shown in FIG. 3(b) and FIG. 3(c), the liquid supply pipe 6 and the sand lifting pipe 942 penetrate the side wall 41 of the concentrated liquid tank 4. The penetrating portions of the liquid supply pipe 6 and the sand lifting pipe 942 are welded to the side wall 41, and the penetrating portions are watertight.

[0028] The concentrated liquid tank 4 is a tank having a substantially square shape in a plan view, with two tank inclined surfaces 41a formed on the lower part. The lower end of the concentrated liquid tank 4 is cut out obliquely upward at the same angle as the inclination angle of the conveying device 5. The tank inclined surface 41a is formed at a certain height from the lower end of the concentrated liquid tank 4. The lower end of this tank inclined surface 41a is connected to the conveying device 5. Sand contained in the concentrated liquid discharged from the discharge port 331 of the concentration container 3 slides down the tank inclined surface 41a and is deposited in the conveying device 5 connected to the lower end of the concentrated liquid tank 4. As described above, the sand deposited in the conveying device 5 is conveyed obliquely upward by the screw conveyor 51 and is dropped from the drop part 52 (see FIG. 1) at the upper end part. As shown in FIG. 3(c), an overflow port 43 is formed above the discharge port 331 and slightly below the upper end of the concentrated liquid tank 4. This overflow outlet 43 allows the supernatant liquid of the concentrated liquid to flow out of the concentrated liquid tank 4 when too much concentrated liquid is discharged from the discharge outlet 331. The supernatant liquid flowing out from the overflow outlet 43 is returned to the grit basin 9 (see FIG. 1) through the overflow pipe 7. Providing this overflow outlet 43 prevents the concentrated liquid from overflowing from the upper end of the side wall 41 of the concentrated liquid tank 4.

[0029] FIG. 4 is a flowchart showing the operation of the solid-liquid separation apparatus shown in FIG.

[0030] The operations of the grit basin 9 and the solid-liquid separator 1 are centrally controlled by a control device (not shown). Note that the grit basin 9 and the solid-liquid separator 1 may each be provided with a control device, and configured to be capable of transmitting and receiving information or commands to each other. At a predetermined time when the amount of sand accumulated on the bottom surface of the grit basin 9 shown in FIG. 1 reaches a certain amount, the grit basin 9 discharges wastewater from a sand collection nozzle 93 to collect the sand in a sand collection pit 94. After the sand collection operation, the solid-liquid separator 1 starts a solid-liquid separation operation. The predetermined time may be, for example, periodically, such as once a month, or when the total flow rate of wastewater flowing into the grit basin 9 or the total flow rate of wastewater discharged from the grit basin 9 reaches a certain amount. Note that the solid-liquid separation operation may be started while the sand is being collected in the sand collection pit 94.

[0031] In the solid-liquid separation operation, first, the driving of the sand lifting pump 941 is started with the conveying device 5 stopped. This driving start starts the reception of sand-mixed water in the concentration container 3 shown in FIG. 3 (step S1). The conveying device 5 does not have to be completely stopped, and may be driven at a slow speed at which the liquid components contained in the concentrated liquid do not reach the dropping part 52 by the driving of the conveying device 5. That is, the conveying device 5 may be driven at a driving speed slower than a predetermined driving speed described later. If the internal space X1 (see FIG. 2(b)) of the concentration container 3 and the tank of the concentrated liquid tank 4 are empty before the driving of the sand lifting pump 941 starts, most of the sand-mixed water supplied to the internal space X1 is discharged from the discharge port 331. As the concentrated liquid discharged from the discharge port 331 is stored in the tank of the concentrated liquid tank 4, the tank water level WL2, which is the water level formed by the concentrated liquid stored in the concentrated liquid tank 4, gradually rises. This tank water level WL2 corresponds to an example of a liquid level. Also, sand contained in the concentrated liquid stored in the concentrated liquid tank 4 sinks toward the bottom of the concentrated liquid tank 4 due to its own weight, and gathers at the lower end of the conveying path of the conveying device 5. When the tank water level WL2 reaches the discharge port 331, the discharge port 331 is blocked by the concentrated liquid, and the amount of concentrated liquid discharged from the discharge port 331 decreases. That is, the resistance due to the reduction in the cross-sectional area of ​​the internal space X1 in the constricted section 32 and the water pressure of the concentrated liquid applied to the discharge port 331 combine to make it difficult for the concentrated liquid to be discharged from the discharge port 331, and the separated water starts to be sent out from the inlet 611 (see FIG. 2(b)). As the tank water level WL2 rises, the water pressure of the concentrated liquid applied to the discharge port 331 increases, so the amount of concentrated liquid discharged from the discharge port 331 decreases, and the amount of separated water sent out from the inlet 611 increases, and the liquid sending pipe 6 is filled with separated water (liquid). As described above, when the liquid supply pipe 6 is filled with separated water, the separated water acts as a siphon to flow out into the grit basin 9. In other words, due to the potential energy of the liquid in the sand-containing water and the liquid in the concentrated liquid, the separated water starts to be sent out of the concentrated liquid tank 4 through the liquid supply pipe 6. As a result, the amount of separated water sent out from the inlet 611 further increases, and the amount of concentrated liquid discharged from the outlet 331 further decreases.When the amount of sand-containing water supplied to the internal space X1 is, for example, 1.0 m3 / min, when the tank water level WL2 becomes slightly lower than the receiving port 341 (see FIG. 2(b)), almost only sand is discharged from the discharge port 331, and the tank water level WL2 stops rising. FIGS. 3(b) and 3(c) show the tank water level WL2 at this time. When the amount of sand-containing water supplied to the internal space X1 is, for example, 1.5 m3 / min, the amount of separated water discharged from the inlet 611 also increases, but concentrated liquid containing a certain proportion of wastewater is discharged from the discharge port 331, and the tank water level WL2 continues to rise. After the tank water level WL2 reaches the overflow port 43, the supernatant liquid of the sand-containing water flows out from the overflow port 43 at about 0.3 m3 / min. Furthermore, before the sand lifting pump 941 is driven, wastewater or tap water stored in the settling basin may be flowed into the concentrated liquid tank 4 to fill the concentrated liquid tank 4 with liquid. When the concentrated liquid tank 4 is filled with liquid, the internal space X1 is also filled with liquid to the same height as the concentrated liquid tank 4. Therefore, if liquid is stored so that the tank water level WL2 is equal to or higher than the height of the inlet 611, separated water can be sent from the inlet 611 almost simultaneously with the driving of the sand lifting pump 941. When the sand lifting pump 941 is driven for the second or subsequent times, separated water can be sent from the inlet 611 almost simultaneously with the driving of the sand lifting pump 941, as long as the liquid stored in the concentrated liquid tank 4 is not drained.

[0032] The driving of the sand lifting pump 941 continues until a first predetermined time has elapsed from the start of driving (step S2). Steps S1 and S2 described above correspond to an example of a filling step. This first predetermined time is a sufficient time to raise the tank water level WL2 above the discharge port 331 and fill the liquid supply pipe 6 with separated water. A water level sensor that detects when the tank water level WL2 has risen above the discharge port 331 may be provided in the concentrated liquid tank 4, and a water detection sensor that detects when the liquid supply pipe 6 has been filled with separated water may be provided in the liquid supply pipe 6. Then, instead of determining whether the first predetermined time has elapsed, it may be determined whether detection by these sensors has occurred.

[0033] After the first predetermined time has elapsed, the operation of the sand lifting pump 941 is stopped (step S3). Even after the operation of the sand lifting pump 941 is stopped, the concentrated liquid and the sand-mixed water still act to flow out through the liquid feed pipe 6 to the grit basin 9 due to the effect of the siphon principle described above. As a result, the supernatant liquid of the concentrated liquid and the sand-mixed water flows out through the liquid feed pipe 6 to the grit basin 9, and the tank water level WL2 drops. That is, the tank water level WL2 is lowered by sending the wastewater in the concentrated liquid stored in the concentrated liquid tank 4 to the outside of the concentrated liquid tank 4 through the liquid feed pipe 6 using the potential energy of the wastewater. Meanwhile, even while the tank water level WL2 is lowering, the sand contained in the concentrated liquid and the sand-mixed water gradually settles due to its own weight and gathers at the lower end of the transport path of the transport device 5. When the tank water level WL2 drops to the discharge port 331, air enters the liquid feed pipe 6 from the discharge port 331 through the concentration container 3, and the effect of the siphon principle ends. Until the second predetermined time has elapsed since the driving of the sand lifting pump 941 was stopped, the state immediately after the sand lifting pump 941 was stopped is maintained (step S4). Steps S3 and S4 described above correspond to an example of a liquid transfer process. This second predetermined time is the time for the tank water level WL2 to fall to the vicinity of the discharge port 331. Note that this second predetermined time may be shorter than the time for the tank water level WL2 to fall to the vicinity of the discharge port 331, as long as it is the time for the tank water level WL2 to fall to a position lower than the height of the upper end part of the transport path of the transport device 5. In addition, instead of determining whether the second predetermined time has elapsed, a water level sensor that detects that the tank water level WL2 has fallen to a position lower than the height of the upper end part of the transport path of the transport device 5 may be provided in the concentrated liquid tank 4, and it may be determined whether the detection has occurred. Furthermore, in steps S3 and S4, a small amount of sand-mixed water may be supplied to the concentration container 3 without completely stopping the driving of the sand lifting pump 941, as long as the amount is such that the tank water level WL2 falls.

[0034] After the second predetermined time has elapsed, the driving of the conveying device 5 is started (step S5). By driving the conveying device 5 at a predetermined driving speed, the sand collected at the lower end of the conveying path is conveyed to the upper end of the conveying path. At the time of starting this driving, the tank water level WL2 is lowered to a position lower than the upper end of the conveying path, so the sand conveyed by the screw conveyor 51 is conveyed while being drained at the upper end of the conveying path. Then, the sand that has reached the upper end of the dropping part 52 is dropped downward from the drop port 52a. The driving of the conveying device 5 continues from the start of driving until the third predetermined time has elapsed (step S6). The above-described steps S5 and S6 correspond to an example of the conveying process. This third predetermined time is the time during which most of the sand collected at the lower end of the conveying path can be conveyed and dropped from the drop part 52. Instead of determining whether the third predetermined time has elapsed, a sand presence / absence sensor that detects the presence or absence of sand at the lower end of the conveying path may be provided at the bottom of the concentrated liquid tank 4, and whether or not the detection has occurred may be determined. After the third predetermined time has elapsed, the driving of the transport device 5 is stopped (step S7), and the solid-liquid separation operation is terminated.

[0035] According to this driving method of the solid-liquid separator, the tank water level WL2 of the concentrated liquid tank 4 is lowered, and then the conveying device 5 is driven, so that even if the conveying path is short, the sand can be conveyed while being drained. That is, the height of the conveying path can be lowered from the normal level at least by the amount by which the tank water level WL2 is lowered in the above-mentioned steps S3 and S4. Since the conveying path extends obliquely upward, the width of the conveying device 5 can be shortened by lowering the height of the conveying device 5. As a result, the solid-liquid separator 1 can be made compact. In addition, in the above-mentioned steps S3 and S4, the potential energy of the wastewater in the concentrated liquid is used to send it to the outside of the concentrated liquid tank 4, so the liquid level of the concentrated liquid tank 4 can be lowered without providing a device such as a pump in the solid-liquid separator 1.

[0036] In addition, in the above-mentioned step S2, the discharge port 331 is blocked by the liquid stored in the concentrated liquid tank 4, so that the water pressure of the liquid stored in the tank of the concentrated liquid tank 4 is generated at the discharge port 331. This water pressure makes it difficult for the concentrated liquid to be discharged from the discharge port 331, so that the amount of separated water sent out through the liquid sending pipe 6 can be increased. That is, the ratio of the separated water sent out from the inlet 611 to the concentrated liquid discharged from the discharge port 331 increases, so that the separation efficiency in the concentration container 3 is improved. In addition, since the concentrated liquid discharged to the concentrated liquid tank 4 is small, the concentrated liquid tank 4 can be made smaller. Furthermore, even if the throttling amount (amount of reduction in the cross-sectional area) in the throttling section 32 is reduced, the amount of concentrated liquid discharged from the discharge port 331 can be suppressed. By reducing the throttling amount in the throttling section 32, the pressure loss in the concentration container 3 can be reduced, so that the power of the sand lifting pump 941 can be reduced. Furthermore, the concentrated liquid discharged from the discharge port 331 does not scatter, and the sand contained in the concentrated liquid easily settles to the bottom of the concentrated liquid tank 4 in a short time. In addition, because the separated water acts like a siphon to flow out of the inlet 611 into the grit basin 9, the power required for the sand lifting pump 941 can be further reduced. Also, because the transport device 5 is connected to the concentrated liquid tank 4 and the concentrated liquid tank 4 and the concentration container 3 are arranged so as to overlap each other in the height direction, the overall height of the solid-liquid separation apparatus 1 can be reduced. And because the concentration container 3 can be arranged close to the ground, the head required for the sand lifting pump 941 is reduced, and the mixed water can be transferred to the concentration container 3 with even less power.

[0037] In this embodiment, the side wall 41 of the concentrated liquid tank 4 extends above the upper end of the internal space X1, so that the liquid can be stored in the concentrated liquid tank 4 up to above the upper end of the internal space X1. By storing the liquid up to the upper end of the internal space X1, the water pressure applied to the outlet 331 is increased, and the force of the wastewater in the sand-mixed water in the internal space X1 trying to flow out of the outlet 331 due to gravity can be countered. This further reduces the amount of wastewater discharged from the outlet 331, and the concentration of sand in the concentrated liquid can be further increased. In addition, the amount of concentrated liquid discharged from the outlet 331 to the concentrated liquid tank 4 is reduced, so that the size of the concentrated liquid tank 4 can be reduced. Furthermore, the amount of reduction in the throttle section 32 can be reduced to further reduce pressure loss. Furthermore, since the height of the side wall 41 of the concentrated liquid tank 4 is set higher than the upper end 6c of the liquid supply pipe 6, even if the amount of throttling of the throttling section 32 is drastically reduced, once the tank water level WL2 reaches the upper end 6c of the pipe, the liquid supply pipe 6 will be filled with separated water, and the effect of the siphon principle can be obtained.

[0038] Next, a modified example of the solid-liquid separation device of the present embodiment will be described. In the following description, the names of components that are the same as those of components described so far may be assigned the same reference numerals as those used so far, and duplicate descriptions may be omitted.

[0039] FIG. 5(a) is a front view similar to FIG. 3(b) showing a modification of the solid-liquid separator shown in FIG. 1, and FIG. 5(b) is a cross-sectional view taken along CC in FIG. 5(a).

[0040] As shown in FIG. 5(a), the solid-liquid separation device 1 of this modification is different from the solid-liquid separation device 1 shown in FIGS. 1 to 4 in that a fine bubble water supply pipe 8 is connected to the sand lifting pipe 942 and the height of the concentrated liquid tank 4 is low. In this modification, nanobubble water generated by a nanobubble water generator (not shown) is supplied to the sand lifting pipe 942 through the fine bubble water supply pipe 8. However, microbubble water may be supplied to the sand lifting pipe 942 instead of nanobubble water, or micro-nano bubble water, which is a mixture of nanobubble water and microbubble water, may be supplied to the sand lifting pipe 942. This fine bubble water supply pipe 8 corresponds to an example of a fine bubble supplying means. Nanobubble water means water containing air bubbles with a particle size on the order of nanometers. Microbubble water means water containing air bubbles on the order of micrometers. Note that water containing oxygen bubbles on the order of nanometers may be used as the nanobubble water. Similarly, water containing oxygen bubbles on the order of micrometers may be used as the microbubble water. Also, the fine bubble water supply pipe 8 may be directly connected to the concentration container 3. That is, the fine bubble water supply pipe 8 may be connected between the sand lifting pump 941 (see FIG. 1) and the discharge port 331. Nanobubble water and microbubble water have a cleaning effect, so that adding them to sand-mixed water can clean the sand and dirty water contained in the sand-mixed water. By adding nanobubble water or microbubble water to the sand-mixed water between the sand lifting pump 941 (see FIG. 1) and the discharge port 331, the sand-mixed water can be cleaned with a high cleaning effect in the internal space X1 (see FIG. 2) of the concentration container 3. That is, the nanobubbles and microbubbles are mixed with the sand-mixed water in the internal space X1 by the swirling flow generated in the internal space X1, so that a high cleaning effect can be achieved.

[0041] The side wall 41 of the concentrated liquid tank 4 extends to a height above the upper end of the concentration container 3 and below the upper end 6c of the liquid supply pipe 6. If the side wall 41 of the concentrated liquid tank 4 is made higher as in the previous embodiment, the tank water level WL2 of the concentrated liquid tank 4 can be made higher than the upper end 6c of the liquid supply pipe 6. As described above, the water pressure applied to the discharge port 331 increases according to the height of the tank water level WL2, so that the tank water level WL2 is higher in terms of further increasing the concentration of sand in the concentrated liquid and reducing pressure loss. However, if the side wall 41 of the concentrated liquid tank 4 is made too high, the height of the entire solid-liquid separation device 1 will also increase, and the manufacturing cost of the concentrated liquid tank 4 will also become high, so in this sense it is preferable that the height of the side wall 41 of the concentrated liquid tank 4 is low. If the side wall 41 extends above the discharge port 331, the discharge port 331 can be blocked by the liquid stored in the concentrated liquid tank 4, but in this modified example, the side wall 41 is set at a height that prioritizes the balance between the overall height of the solid-liquid separation apparatus 1 and the water pressure applied to the discharge port 331. The overflow port 43 can be positioned appropriately depending on the height of the side wall 41, but in this modified example, it is set at the same height as the receiving port 341 (see FIG. 2(b)).

[0042] Next, a modification of the solid-liquid separator shown in FIG. 1, which is different from the modification shown in FIG. 5, will be described.

[0043] FIG. 6(a) is a front view similar to FIG. 3(b) of a solid-liquid separator of a modified example different from the modified example shown in FIG. 5, and FIG. 6(b) is a DD cross-sectional view of FIG. 6(a).

[0044] The solid-liquid separation apparatus 1 shown in FIG. 6(a) and FIG. 6(b) differs from the solid-liquid separation apparatus 1 shown in FIG. 1 to FIG. 4 in that the constriction vessel 3 is not provided with the constriction section 32 and the discharge section 33, the height of the concentrated liquid tank 4 is low, and the position of the overflow port 43. The concentration vessel 3 is formed with the fluid inlet section 31. Therefore, the internal space X1 is defined only by the inner peripheral surface 31a of the fluid inlet section 31. The lower end of the concentration vessel 3 is the lower end of the cylindrical section 311, and the opening of the lower end is the discharge port 331. This discharge port 331 is an opening with a diameter of 500 mm, which is considerably larger than the receiving port 341 (see FIG. 2(b)). Therefore, in this modification, there is almost no pressure loss in the concentration vessel 3. The concentrated liquid tank 4 is formed lower by the total height of the constriction section 32 and the discharge section 33 compared to the concentrated liquid tank 4 shown in FIG. 3. In addition, the receiving port 341 formed in the concentration container 3 is disposed at a position close to the lower end of the concentrated liquid tank 4 by the total height. The length (height) of the conveying device 5 can also be reduced by the amount that the height of the concentrated liquid tank 4 is reduced. That is, by lowering the height of the concentration container 3, the overall height of the solid-liquid separation device 1 can be reduced, and the solid-liquid separation device 1 can be made smaller in size. In addition, since the receiving port 341 is disposed at a position close to the ground, the lift required for the sand lifting pump 941 is reduced, and the mixed water can be transferred to the concentration container 3 with even less power. The overflow port 43 is disposed at the same height as the receiving port 341. However, the overflow port 43 may be disposed at a position higher than the receiving port 341 or at a position higher than the upper end 6c of the liquid supply pipe 6. By disposing the overflow port 43 at a higher position, the liquid can be quickly stored in the concentrated liquid tank 4 up to a position higher than the upper end 6c of the liquid supply pipe 6, and the time from when the sand-mixed water starts to be supplied to the internal space X1 until the effect of the siphon principle is generated can be shortened.

[0045] The operation of the solid-liquid separator 1 of this modification is similar to that of the solid-liquid separator 1 shown in Figs. 1 to 4, but the behavior of the sand-mixed water and the concentrated liquid in steps S1 and S2 shown in Fig. 4 is slightly different, so these behaviors will be mainly described. When the inner space X1 of the concentration container 3 and the inside of the concentrated liquid tank 4 are empty, the sand-mixed water starts to be supplied to the inner space X1 when the sand pump 941 shown in Fig. 1 is driven. In this modification, the sand-mixed water is supplied to the inner space X1 at a rate of 2.0 m3 / min. The sand-mixed water is introduced into the inner space X1 from the tangential direction of the inner circumferential surface 31a of the cylindrical portion 311 through the receiving port 341 (see Fig. 2(b)), so that a swirling flow of the sand-mixed water is formed in the inner space X1. The sand contained in the sand-mixed water has a larger specific gravity than the wastewater, so it is pressed against the inner circumferential surface 31a of the cylindrical portion 311 by centrifugal force and gradually falls downward while swirling along the inner circumferential surface 31a. Meanwhile, separated water from which sand has been removed remains near the center of the diameter of the cylindrical portion 311. When the amount of liquid stored in the concentrated liquid tank 4 is small, all of the sand-containing water supplied to the internal space X1 is discharged from the outlet 331 as concentrated liquid. The concentrated liquid discharged from the outlet 331 is stored in the tank of the concentrated liquid tank 4, and the tank water level WL2 gradually rises. When the tank water level WL2 reaches the outlet 331, the outlet 331 is blocked by the concentrated liquid, and as the tank water level WL2 rises, the water pressure of the concentrated liquid applied to the outlet 331 increases. In this modified example, the throttle portion 32 shown in FIG. 2(b) is not present, and the outlet 331 is sufficiently large relative to the receiving port 341, so that even after the outlet 331 is blocked by the concentrated liquid, all of the sand-containing water supplied to the internal space X1 is discharged from the outlet 331 until the tank water level WL2 reaches a predetermined height. Thereafter, when the tank water level WL2 reaches the overflow port 43, the supernatant liquid of the concentrated liquid flows out from the overflow port 43, but the tank water level WL2 continues to rise because the amount of sand-containing water supplied by the sand lifting pump 941 is greater than the supernatant liquid flowing out from the overflow port 43 by gravity. When the tank water level WL2 reaches the lower end 6d of the liquid supply pipe 6, the separated water begins to be sent out through the liquid supply pipe 6.When the tank water level WL2 reaches the upper end 6c of the pipe, the liquid supply pipe 6 is filled with liquid, and the sand-mixed water acts like a siphon to flow out of the inlet 611 into the grit basin 9, causing the amount of separated water sent out of the inlet 611 to increase further, and the tank water level WL2 stops rising, then drops and stabilizes at a constant position. Figures 6(a) and 6(b) show the tank water level WL2 at this time. When the tank water level WL2 is stable, supernatant liquid flows out of the overflow port 43 at a rate of about 1.2 m3 / min.

[0046] The solid-liquid separation apparatus 1 of this modification also has the same effects as the solid-liquid separation apparatus 1 shown in Fig. 1. Furthermore, the amount of concentrated liquid discharged from the discharge port 331 can be suppressed even without the throttle unit 32 due to the water pressure at the discharge port 331 generated by the liquid stored in the concentrated liquid tank 4. Since there is no throttle unit 32, the pressure loss in the concentration container 3 is almost zero, and the power of the sand lifting pump 941 can be reduced. Furthermore, even when there is no liquid in the liquid supply pipe 6, simply driving the sand lifting pump 941 makes it possible to make the tank water level WL2 reach the height of the pipe upper end 6c and fill the liquid supply pipe 6 with liquid, so that the action based on the siphon principle can be easily produced.

[0047] From the above-described embodiments and modified examples, a solid-liquid separation device is provided which includes a concentration container which receives a mixed liquid in which solids have been mixed into a liquid and which discharges from an outlet a concentrated liquid in which the concentration of the solids in the liquid has increased; a concentrated liquid tank which is disposed within the tank and which stores the concentrated liquid obtained in the concentration container; a transport device which has a lower end portion connected to the bottom of the concentrated liquid tank and an upper end portion of the transport path which extends obliquely upward and is disposed above the outlet; and a liquid delivery pipe which has an inlet connected to the concentration container and an outlet disposed outside the concentrated liquid tank and below the inlet, and which collects solids in the concentrated liquid at the lower end portion, and drives the transport device to transport the solids obliquely upward along the transport path, and sends the liquid in the mixed liquid received by the concentration container through the liquid delivery pipe to the outside of the concentrated liquid tank, the concentration container receives the mixed liquid while the conveying device is stopped, so that the liquid level of the concentrated liquid tank rises above the discharge port and the liquid supply pipe is filled with the mixed liquid, the liquid delivery pipe delivers the liquid in the concentrated liquid stored in the concentrated liquid tank to the outside of the concentrated liquid tank by utilizing potential energy of the liquid in the concentrated liquid, The transport device starts operation after the liquid level in the concentrated liquid tank drops as a result of the liquid feed pipe sending the liquid in the mixed liquid to the outside of the concentrated liquid tank, and transports the solids collected in the lower end portion, which is a solid-liquid separation apparatus.

[0048] Next, a solid-liquid separator according to a second embodiment will be described.

[0049] FIG. 7 is a front view similar to FIG. 3(b) of the solid-liquid separator of the second embodiment.

[0050] The solid-liquid separation apparatus 1 shown in FIG. 7 differs from the solid-liquid separation apparatus 1 shown in the previous embodiment mainly in that the concentration container 3 is not provided. This solid-liquid separation apparatus 1 includes a storage tank 40, a conveying device 5, and a liquid supply pipe 6. The storage tank 40 has the same configuration as the concentrated liquid tank 4 in the previous embodiment. However, this storage tank 40 differs from the concentrated liquid tank 4 in the previous embodiment in that it receives and stores sand-mixed water without passing through the concentration container 3 shown in the previous embodiment, and sends the supernatant liquid (corresponding to the separated water in the previous embodiment) from the inlet 611 without passing through the concentration container 3. A sand-pumping pump 941 is connected to one end of the sand-pumping pipe 942, and a supply port 9421 is formed at the other end of the sand-pumping pipe 942. The sand-mixed water sucked by the sand-pumping pump 941 is directly poured into the storage tank 40 from the supply port 9421. The sand lifting pipe 942 in the second embodiment is inserted into the storage tank 40 from the opening at the top end of the storage tank 40. However, the sand pipe 942 may be inserted into the storage tank 40 by penetrating the side wall 401 of the storage tank 40. Note that although the sand lifting pump 941 is actually disposed in the sand collection pit 94 shown in Fig. 1, in order to simplify the drawing, it is shown to the side of the solid-liquid separation device 1 in Fig. 7.

[0051] The liquid supply pipe 6 has one end portion 61 disposed in the tank of the storage tank 40, a horizontal portion extending horizontally, and a vertical portion bent from the horizontal portion and extending downward. An inlet 611 is formed at one end (the tip of the one end portion 61). This inlet 611 is disposed in a lower portion of the storage tank 40. A cap-shaped cover member 612 that spreads around the inlet 611 in a plan view is attached to the one end portion 61 slightly above the inlet 611. This cover member 612 prevents sand contained in the sand-mixed water poured into the tank of the storage tank 40 from being sucked into the inlet 611 while it is sinking in the sand-mixed water stored in the tank of the storage tank 40. The peripheral portion of the cover member 612 may be disposed below the inlet 611. Furthermore, the cover member 612 may be disk-shaped. When a disk-shaped member is used, the cover member 612 may be at the same height as the inlet 611. That is, the cover member 612 may be provided above the inlet 611 or around the inlet 611. In other words, the cover member 612 may be provided between the supply port 9421 and the inlet 611. If a disk-shaped member that spreads horizontally is used as the cover member 612, sand will accumulate on the cover member 612, so it is preferable to use a cap-shaped member. An outlet 62 is formed at the lower end of the vertical part of the liquid supply pipe 6. This outlet 62 is located below the inlet 611 and above the grit basin 9 (see FIG. 1) that is outside the storage tank 40.

[0052] The operation of the solid-liquid separator 1 of the second embodiment is similar to that of the solid-liquid separator 1 of the previous embodiment, but the behavior of sand-mixed water is different. Below, differences from the previous embodiment will be mainly described with reference to Figs. 7 and 8.

[0053] FIG. 8 is a flowchart showing the operation of the solid-liquid separation apparatus shown in FIG.

[0054] In the solid-liquid separation operation, first, the sand lifting pump 941 is started to be driven while the conveying device 5 is stopped, and the sand-mixed water is received in the storage tank 40 (step S11). The conveying device 5 does not have to be completely stopped, and may be driven at a slow speed at which the liquid component contained in the sand-mixed water does not reach the dropping part 52 by the driving of the conveying device 5. That is, the conveying device 5 may be driven at a driving speed slower than a predetermined driving speed. After that, the water level WL3 formed by the sand-mixed water stored in the storage tank 40 gradually rises. This water level WL3 corresponds to an example of a liquid level. The sand contained in the sand-mixed water stored in the storage tank 40 sinks toward the bottom of the storage tank 40 due to its own weight and gathers at the lower end part of the conveying path of the conveying device 5. When the water level WL3 rises above the lower end of the horizontal part of the liquid supply pipe 6, the supernatant liquid (polluted water) of the sand-mixed water starts to flow out of the outlet 62 through the liquid supply pipe 6. This supernatant liquid also corresponds to an example of liquid. When the water level WL3 rises and reaches the height of the upper end 6c of the liquid supply pipe 6, the liquid supply pipe 6 is filled with the supernatant liquid of the sand-mixed water, and the effect of the siphon principle occurs, increasing the amount of the supernatant liquid that flows out. In other words, the potential energy of the liquid in the sand-mixed water causes the supernatant liquid of the sand-mixed water to be sent out of the storage tank 40 through the liquid supply pipe 6. Due to this effect, a force that sucks in the sand-mixed water is generated near the inlet 611, but the sand that settles near the inlet 611 slides down on the cover member 612 and falls from the edge of the cover member 612, so it is moved away from the inlet 611. This prevents the sand that settles near the inlet 611 from entering the inlet 611. When the water level WL3 rises further and reaches the overflow port 43, the supernatant liquid of the sand-mixed water flows out of the overflow port 43 together with the liquid supply pipe 6, preventing the water level WL3 from rising any further. The operation of the sand lifting pump 941 continues until a fourth predetermined time has elapsed from the start of operation (step S12). Steps S11 and S12 described above correspond to an example of the receiving process. This fourth predetermined time is a sufficient time to raise the water level WL3 above the uppermost end of the liquid supply pipe 6.A water level sensor may be provided in the storage tank 40 to detect when the water level WL3 rises above the uppermost end of the liquid supply pipe 6, and a water detection sensor may be provided in the liquid supply pipe 6 to detect when the inside of the liquid supply pipe 6 is filled with supernatant liquid. Instead of determining whether the fourth predetermined time has elapsed, it may be determined whether detection by these sensors has occurred.

[0055] After the fourth predetermined time has elapsed, the operation of the sand lifting pump 941 is stopped (step S13). Even after the operation of the sand lifting pump 941 is stopped, the sand-containing water still acts to flow out through the liquid supply pipe 6 to the grit basin 9 due to the effect of the siphon principle described above. As a result, the supernatant of the sand-containing water flows out through the liquid supply pipe 6 to the grit basin 9, and the water level WL3 drops. That is, the supernatant of the sand-containing water stored in the storage tank 40 is sent to the outside of the storage tank 40 through the liquid supply pipe 6 by utilizing the potential energy of the supernatant, thereby lowering the water level WL3. When the water level WL3 drops to the inlet 611, air enters the liquid supply pipe 6 from the inlet 611, and the effect of the siphon principle ends. The state immediately after the sand lifting pump 941 is stopped is maintained until the fifth predetermined time has elapsed after the operation of the sand lifting pump 941 is stopped (step S14). The above-described steps S13 and S14 correspond to an example of the liquid transfer process. The fifth predetermined time is the time for the water surface WL3 to fall to the vicinity of the inlet 611. The fifth predetermined time may be shorter than the time for the water surface WL3 to fall to the vicinity of the inlet 611, as long as it is the time for the water surface WL3 to fall to a position lower than the height of the upper end part of the transfer path of the transfer device 5. Instead of determining whether the fifth predetermined time has elapsed, a water level sensor that detects that the water surface WL3 has fallen to a position lower than the height of the upper end part of the transfer path of the transfer device 5 may be provided in the storage tank 40, and it may be determined whether the detection has occurred. Furthermore, in steps S13 and S14, a small amount of sand-mixed water may be supplied to the storage tank 40 without completely stopping the drive of the sand lifting pump 941, as long as the amount is such that the water surface WL3 falls. Hereinafter, steps S15 to S17 are the same as steps S5 to S7 in the previous embodiment, and therefore will not be described.

[0056] This method of driving the solid-liquid separator also drives the transport device 5 after lowering the water level WL3 in the storage tank 40 by the siphon principle, so that the height of the transport path can be lowered and the solid-liquid separator 1 can be made smaller.

[0057] FIG. 9 is a front view similar to FIG. 7, showing a modification of the solid-liquid separator shown in FIG.

[0058] As shown in FIG. 9, the solid-liquid separation apparatus 1 of this modification is different from the solid-liquid separation apparatus 1 shown in FIG. 7 in the configuration of the liquid feed pipe 6 and the cover member 612. The liquid feed pipe 6 is composed of a horizontal part that extends horizontally and a vertical part that bends from the horizontal part and extends downward. In this modification, the opening at the end of the horizontal part of the liquid feed pipe 6 opposite to the side connected to the vertical part becomes the inlet 611. The cover member 612 is attached to the inner surface of the side wall 401 of the storage tank 40 and protrudes toward the inside of the storage tank 40 in parallel with the liquid feed pipe 6. As shown in the view of arrow E in FIG. 9, the cover member 612 is composed of a plate material with a V-shaped cross section that covers the upper part of the inlet 611. The cover member 612 prevents sand that settles near the inlet 611 from entering the inlet 611. Even in this modified example, during the period from the middle of step S12 described above until the water level WL3 drops to the inlet 611 after step S14, the potential energy (weight) of the liquid in the sand-mixed water causes the supernatant liquid of the sand-mixed water to be sent out of the storage tank 40 through the liquid delivery pipe 6.

[0059] From the second embodiment and its modified example described above, a solid-liquid separation device is provided which includes a storage tank for storing a mixed liquid in which solids are mixed into a liquid, a liquid transfer pipe having an inlet arranged within the storage tank and an outlet arranged outside the storage tank and below the inlet, and a transport device having a lower end portion of a transport path extending obliquely upward and connected to the bottom of the storage tank and an upper end portion of the transport path arranged above the inlet, and which collects solids in the mixed liquid at the lower end portion, transports the solids obliquely upward along the transport path by driving the transport device, and sends the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid transfer pipe, the storage tank receives the mixed liquid in a state in which the transport device is substantially stopped, thereby receiving the mixed liquid up to a level above an uppermost end of the liquid sending tube; the liquid supply pipe supplies the mixed liquid received in the storage tank up to a level above the uppermost end of the liquid supply pipe to the outside of the storage tank by utilizing potential energy of liquid in the mixed liquid, The transport device starts operating after the liquid level in the storage tank drops as a result of the liquid feed pipe sending the liquid in the mixed liquid to the outside of the storage tank, and transports the solids collected in the lower end portion, which is a solid-liquid separation device.

[0060] In this solid-liquid separation apparatus, a supply port for supplying the mixed liquid to the storage tank is provided above the inlet, The storage tank may have a cover member disposed between the supply port and the inlet.

[0061] In addition, the covering member may be provided above the inlet or around the inlet to prevent solids in the mixed liquid supplied from the supply port from entering the inlet during settling.

[0062] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, in the present embodiment, the solid-liquid separation device 1 is installed in a grit basin 9, but the solid-liquid separation device 1 may be installed in a sedimentation basin or a reservoir such as a dam lake. The solid-liquid separation device 1 may also be used to separate water and metal powder from industrial wastewater generated in a factory or the like.

[0063] According to the embodiment and modified examples described above, it is possible to provide a method for driving a solid-liquid separator that can realize miniaturization of the solid-liquid separator.

[0064] In addition, even if a constituent element is included only in the description of each of the embodiments and modified examples described above, that constituent element may be applied to other embodiments or modified examples.

[0065] The conveying device of the solid-liquid separation apparatus disclosed in Patent Document 1 has a conveying path that extends from the lower end of the concentrated liquid tank to a position considerably above the concentrated liquid tank. The conveying device conveys sand while draining water in a portion of the conveying path that is located above the water level of the concentrated liquid tank. The conveying device extends the distance over which the sand is conveyed while draining water, thereby preventing wastewater in the concentrated liquid stored in the concentrated liquid tank from being sent out of the concentrated liquid tank together with the sand. However, extending the distance over which the sand is conveyed while draining water results in a problem that the conveying path of the conveying device becomes longer, resulting in an increase in the size of the solid-liquid separation apparatus.

[0066] The above-described method for driving a solid-liquid separation device includes a concentration container that receives a mixed liquid in which solids are mixed into a liquid and discharges from an outlet a concentrated liquid in which the concentration of solids in the liquid is increased, a concentrated liquid tank having the outlet disposed within a tank and storing the concentrated liquid obtained in the concentration container, a transport device having a transport path extending obliquely upward at a lower end portion connected to a bottom of the concentrated liquid tank and an upper end portion of the transport path disposed above the outlet, and a liquid feed pipe having an inlet connected to the concentration container and an outlet disposed outside the concentrated liquid tank and below the inlet, the method comprising the steps of: collecting solids in the concentrated liquid at the lower end portion; driving the transport device at a predetermined drive speed to transport the solids obliquely upward along the transport path; and sending the liquid in the mixed liquid received by the concentration container to the outside of the concentrated liquid tank through the liquid feed pipe, a filling step of raising the liquid level of the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container while driving or stopping the conveying device at a driving speed slower than the predetermined driving speed; a liquid sending step of sending the liquid in the concentrated liquid stored in the concentrated liquid tank to the outside of the concentrated liquid tank through the liquid sending pipe by utilizing potential energy of the liquid in the concentrated liquid, thereby lowering the liquid level in the concentrated liquid tank to a position lower than the height of the upper end portion; and a transport step of driving the transport device at the predetermined drive speed after lowering the liquid level in the concentrated liquid tank by the liquid sending step, and transporting the solids collected in the lower end portion while draining them at the upper end portion.

[0067] The present invention also provides a method for collecting solids in the concentrated liquid by a liquid feed pipe having an inlet connected to the concentration container and an outlet connected to the bottom of the concentrated liquid tank, the method comprising the steps of: (a) collecting solids in the concentrated liquid by a liquid feed pipe having an inlet connected to the concentration container and an outlet connected to the bottom of the concentrated liquid tank; at a predetermined drive speed to transport the solids obliquely upward along the transport path, and to send the liquid in the mixed liquid received by the concentration container to the outside of the concentrated liquid tank through the liquid delivery pipe, a filling step of raising the liquid level of the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container while the conveying device is stopped or driven at a drive speed slower than the predetermined drive speed; a liquid sending step of sending the liquid in the concentrated liquid stored in the concentrated liquid tank to the outside of the concentrated liquid tank through the liquid sending pipe by utilizing potential energy of the liquid in the concentrated liquid, thereby lowering the liquid level in the concentrated liquid tank; The method may further include a transporting step of driving the transport device at the predetermined driving speed after lowering the liquid level in the concentrated liquid tank by the liquid sending step, and transporting the solids collected in the lower end portion.

[0068] According to this method for driving a solid-liquid separation apparatus, the conveying device is driven after the liquid level in the concentrated liquid tank is lowered, so that the conveying path in the conveying device can be shortened. As a result, the solid-liquid separation apparatus can be made compact. In addition, in the liquid conveying step, the potential energy of the liquid in the concentrated liquid is utilized to convey the liquid to the outside of the concentrated liquid tank, so that the liquid level in the concentrated liquid tank can be lowered without providing a device such as a pump in the solid-liquid separation apparatus.

[0069] In this method for driving a solid-liquid separation device, the filling process may be a process of receiving the mixed liquid into a cylindrical portion of the concentration container having a cylindrical inner surface from a tangential direction of the inner surface, and discharging the concentrated liquid from the discharge outlet.

[0070] In this way, a swirling flow can be generated within the cylindrical portion. The solids contained in the mixed liquid move downward while being pressed against the inner circumferential surface by the centrifugal force generated by the swirling flow. Meanwhile, the liquid in the mixed liquid is collected in the radial center portion of the cylindrical portion, improving the separation performance of the solids and the liquid. Here, the filling step may include a delivery step of delivering the liquid in the mixed liquid from the inlet located at the radial center of the cylindrical portion.

[0071] Furthermore, in the method for driving this solid-liquid separation device, the filling step may be a step of using, as the concentration container, a constriction portion between the cylindrical portion and the discharge outlet, in which the cross-sectional area of ​​the internal space of the concentration container is smaller on the discharge outlet side than on the cylindrical portion side.

[0072] By using the device having the throttle portion, the amount of concentrated liquid discharged from the outlet can be reduced and the amount of liquid delivered from the inlet can be increased. Here, the filling step may include a delivery step of delivering the liquid in the mixed liquid from the inlet disposed at the radial center of the throttle portion.

[0073] The above-described method for driving a solid-liquid separation device includes a storage tank for storing a mixed liquid in which solids are mixed into a liquid, a liquid transfer pipe having an inlet arranged within the storage tank and an outlet arranged outside the storage tank and below the inlet, and a transport device having a transport path extending obliquely upward and having a lower end portion connected to a bottom of the storage tank and an upper end portion of the transport path arranged above the inlet, the method comprising the steps of: collecting solids in the mixed liquid at the lower end portion; transporting the solids obliquely upward along the transport path by driving the transport device at a predetermined drive speed; and sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid transfer pipe, a receiving step of receiving the mixed liquid into the storage tank while the transport device is stopped or driven at a drive speed slower than the predetermined drive speed, thereby raising the liquid level of the storage tank above the uppermost end of the liquid delivery pipe; a liquid sending step of sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid sending pipe by utilizing potential energy of the liquid in the mixed liquid, thereby lowering the liquid level in the storage tank to a position lower than the height of the upper end portion; The method is characterized by having a transport process in which, after the liquid level in the storage tank is lowered by the liquid delivery process, the transport device is driven at the specified drive speed and the solids collected in the lower end portion are transported while being drained at the upper end portion.

[0074] Also, there is provided a method for driving a solid-liquid separation device comprising: a storage tank for storing a mixed liquid in which solids are mixed into a liquid; a liquid transfer pipe having an inlet disposed within the storage tank and an outlet disposed outside the storage tank and below the inlet; and a transport device having a transport path extending obliquely upward, a lower end portion of which is connected to the bottom of the storage tank and an upper end portion of which is disposed above the inlet, the method comprising the steps of: collecting solids in the mixed liquid at the lower end portion; transporting the solids obliquely upward along the transport path by driving the transport device at a predetermined drive speed; and sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid transfer pipe, a receiving step of receiving the mixed liquid into the storage tank while the transport device is stopped or driven at a drive speed slower than the predetermined drive speed, thereby raising the liquid level of the storage tank above the uppermost end of the liquid delivery pipe; a liquid sending step of sending the liquid in the mixed liquid stored in the storage tank to the outside of the storage tank through the liquid sending pipe by utilizing potential energy of the liquid in the mixed liquid, thereby lowering the liquid level in the storage tank; After the liquid level in the storage tank is lowered by the liquid sending step, the conveying device is driven by the predetermined drive. and a conveying step of driving the solid material collected at the lower end portion at a constant speed and conveying the solid material collected at the lower end portion.

[0075] This method of driving a solid-liquid separation apparatus also drives the transport device after lowering the liquid level in the concentrated liquid tank, so that the transport path in the transport device can be shortened. As a result, the solid-liquid separation apparatus can be made more compact. In addition, in the liquid transport step, the liquid is transported by utilizing the potential energy of the liquid in the concentrated liquid, so that the liquid level in the concentrated liquid tank can be lowered without providing a device such as a pump in the solid-liquid separation apparatus.

[0076] Furthermore, in the method for driving this solid-liquid separation apparatus, the receiving step may be a step performed in a state in which the solids settling from above the cover member are prevented from entering the inlet by a cover member provided above the inlet or around the inlet.

[0077] Since the solid is prevented from entering through the inlet, the solid-liquid separation performance can be improved.

[0078] According to the above, it is possible to provide a method for driving a solid-liquid separator that can realize miniaturization of the solid-liquid separator. [Explanation of symbols]

[0079] 1 Solid-liquid separator 2. Sand lifting pump 3 Concentration Container 4 Concentrate tank 5. Conveyor 6 Liquid delivery pipe 40 Reservoir 62 Outlet 331 Exhaust 611 Inlet

Claims

[Claim 1] a concentrated liquid tank having the outlet disposed within the tank and storing the concentrated liquid obtained in the concentrated liquid; a conveying device having a conveying path extending obliquely upward at a lower end portion connected to a bottom of the concentrated liquid tank, an upper end portion of the conveying path being disposed above the outlet and having a dropping section extending downward from near the upper end of the conveying path; and a liquid delivery pipe having an inlet connected to the concentrated liquid tank and an outlet disposed outside the concentrated liquid tank and below the inlet, the method comprising the steps of: collecting solids in the concentrated liquid at the lower end portion; driving the conveying device to convey the solids obliquely upward along the conveying path; and sending the liquid in the mixed liquid received by the concentrated liquid tank through the liquid delivery pipe to the outside of the concentrated liquid tank, a filling step of raising the liquid level in the concentrated liquid tank above the discharge port and filling the liquid supply pipe with the liquid contained in the mixed liquid received by the concentration container; a driving step of driving the conveying device at a speed at which a liquid component contained in the concentrated liquid does not reach the dropping portion, and conveying the solids collected in the lower end portion, The method for driving a solid-liquid separator, wherein the filling step and the driving step are performed simultaneously.

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