Mixing tank

Abstract

To provide a stirring tank configured so that sludge or the like deposited on a bottom part can be stirred.SOLUTION: A stirring tank 2, which is configured so that received sludge is stirred by circulation flow while the received sludge flows in a flowing direction, is provided with a hollow space forming member 7 extending along a bottom surface 6i formed on a bottom part of the stirring tank 2 and having an ejection port 7b formed at an end part in an extending direction, and a discharge port 81 through which fluid is discharged to an internal space S1 defined by an inner surface 7i of the space forming member 7. The space forming member 7, in which a lower opening 7d separated from the bottom surface 6i is formed at a lower portion thereof, is extended in a direction in which an angle with respect to the flowing direction is 30 degrees or more and 150 degrees or less in a planar view. The lower opening 7d suctions liquid around the port into the internal space S1 when fluid is ejected from the ejection port 7b. The ejection port 7b forms circulation flow by ejecting fluid discharged from the discharging port 81 as well as liquid suctioned through the lower opening 7d.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an agitation tank for agitating received liquid. [Background technology]

[0002] In wastewater treatment facilities that treat wastewater such as sewage and rainwater, aerobic biological treatment is performed to remove nitrogen, phosphorus, etc. from wastewater. In recent years, advanced treatments have also been performed in which anaerobic biological treatment or biological treatment in an anoxic state in which nitric acid or the like is added is performed before the aerobic biological treatment to efficiently remove nitrogen, phosphorus, etc. Each biological treatment is performed in an agitation tank that has a function of agitating the stored wastewater so that garbage and sludge contained in the wastewater do not accumulate in the same place and putrefy. Some agitation tanks agitate the wastewater by discharging a fluid from a discharge port arranged in the stored wastewater to form a circulating flow of wastewater. In addition, some agitation tanks that perform aerobic biological treatment form a circulating flow of wastewater by discharging the wastewater while supplying air, thereby mixing the air and the wastewater. As an agitation tank for performing such aerobic biological treatment, a cylinder having a discharge port for discharging air and wastewater and openings at both ends in the discharge direction is installed near the bottom of the agitation tank, and the air and wastewater are mixed inside the cylinder while the flow of the air discharged from the discharge port circulates the wastewater (see, for example, Patent Documents 1 and 2). Agitation tanks are sometimes used for purposes other than biological treatment, such as mixing two or more types of fluids or uniformly dispersing various powders and chemicals in a fluid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 50-98158 [Patent Document 2] Japanese Patent Application Laid-open No. 50-107769 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in an agitation tank in which a cylinder is installed, the flow of fluid is difficult to enter the gap between the bottom surface of the agitation tank and the cylinder, so that a circulation flow is difficult to form in the gap. In particular, when sewage and air are discharged from the discharge port, the mixed fluid of air and sewage that has passed through the cylinder is likely to move upward due to the buoyancy of the air contained in the mixed fluid, so that even if a circulation flow is formed above the cylinder, it is difficult to form a circulation flow below the cylinder. If a circulation flow is not formed below the cylinder, or if a circulation flow is formed, the flow of the circulation flow is weak, the sludge that has settled below the cylinder will remain without being agitated and may rot.

[0005] SUMMARY OF THE PRESENT EMBODIMENT In view of the above circumstances, an object of the present invention is to provide an agitation tank capable of agitating sludge and the like that has settled to the bottom. [Means for solving the problem]

[0006] The agitation tank of the present invention, which solves the above-mentioned problems, is an agitation tank that agitates a received liquid by a circulating flow while the liquid flows in a flow direction, and a hollow space forming member extending along a bottom surface formed on the bottom of the mixing vessel and having a discharge port provided at an end in the extending direction; a discharge port that discharges a fluid in the extension direction into an internal space defined by an inner surface of the space forming member, The space forming member has a lower opening formed in a lower portion thereof separated from the bottom surface, and extends in a direction at an angle of 30 degrees or more and 150 degrees or less with respect to the flow direction in a plan view, the lower opening sucks surrounding liquid into the internal space when fluid is discharged from the discharge port; The discharge port forms the circulating flow by discharging the fluid discharged from the discharge port and the liquid sucked in from the lower opening.

[0007] The agitation tank of the present invention, which solves the above-mentioned problems, is an agitation tank that agitates a received liquid by a circulating flow while the liquid flows in a flow direction, and a hollow space forming member extending along a bottom surface formed on the bottom of the mixing vessel and having a discharge port provided at an end in the extending direction; a discharge port that discharges a fluid in the extension direction into an internal space defined by an inner surface of the space forming member, The space forming member has a lower opening formed in a lower portion thereof and spaced apart from the bottom surface, and extends in a direction perpendicular to the flow direction in a plan view, the lower opening sucks surrounding liquid into the internal space when fluid is discharged from the discharge port; The discharge port forms the circulating flow by discharging the fluid discharged from the discharge port and the liquid sucked in from the lower opening.

[0008] The space forming member may be disposed in an area partitioned by a partition wall. Effect of the Invention

[0009] According to the present invention, it is possible to provide an agitation tank capable of agitating sludge and the like that has settled to the bottom. [Brief description of the drawings]

[0010] [Figure 1] 1 is a plan view of an advanced treatment facility equipped with a stirring tank according to an embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of the advanced treatment facility shown in FIG. 1 along the line AA. [Diagram 3] 2A is an enlarged view of part C in FIG. 1, and FIG. 2B is an E-E cross-sectional view of FIG. 1A. [Figure 4] 2A is an enlarged view of a portion D in FIG. 1, and FIG. 2B is a cross-sectional view taken along line FF of FIG. 1A. [Diagram 5] FIG. 3 is a B-B cross-sectional view of the anaerobic tank shown in FIG. 2. [Figure 6] 3 is a cross-sectional view showing an aspect corresponding to FIG. 2 in the advanced treatment facility 1 of the second embodiment. [Figure 7] 4(a) is a cross-sectional view showing a modified example of one end portion of the space forming member shown in FIG. 3(b), and FIG. 4(b) is a cross-sectional view showing a modified example of the other end portion of the space forming member shown in FIG. 4(b). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings. An agitation tank according to one embodiment of the present invention is disposed in a wastewater treatment facility and performs biological treatment to remove nitrogen, phosphorus, and the like from wastewater.

[0012] Fig. 1 is a plan view of an advanced treatment facility equipped with a stirring tank corresponding to one embodiment of the present invention. In Fig. 1, the advanced treatment facility is shown with the upper portion, such as a ceiling, omitted. Fig. 2 is a cross-sectional view taken along line AA of the advanced treatment facility shown in Fig. 1. In Fig. 2, an intermediate portion of a fluid supply pipe, which will be described later, is shown in a simplified form.

[0013] As shown in FIG. 1, the advanced treatment equipment 1 is a rectangular equipment in a plan view, and has a plurality of anaerobic tanks 2 for performing anaerobic biological treatment and aeration tanks 3 for performing aerobic biological treatment between a left side wall 11 and a right side wall 12. Hereinafter, the short side direction of the advanced treatment equipment 1 (the vertical direction in FIG. 1) is referred to as the width direction. This advanced treatment equipment 1 is an equipment that performs biological treatment on wastewater from which contaminants such as sand have been removed in a wastewater treatment facility. Wastewater such as sewage and rainwater that has been treated in a grit basin and a primary sedimentation basin (not shown) flows into this advanced treatment equipment 1. This wastewater corresponds to an example of a liquid. The advanced treatment equipment 1 receives wastewater from the left side in FIG. 1. The wastewater received by the advanced treatment equipment 1 contains fine garbage that cannot be removed in the grit basin and the like. In addition, in order to perform biological treatment, activated sludge containing a large amount of microorganisms is supplied to the anaerobic tank 2 from a final sedimentation basin (not shown) provided downstream of the advanced treatment equipment 1. Hereinafter, the above-mentioned garbage and activated sludge will be collectively referred to as sludge, etc. The wastewater received by the advanced treatment facility 1 flows slowly toward the right side in Fig. 1 in the anaerobic tank 2 and the aeration tank 3 (see the straight arrows in Fig. 1). Hereinafter, the upstream side of the flow of the received wastewater will be simply referred to as the upstream side, and the downstream side of the flow of the wastewater will be simply referred to as the downstream side.

[0014] On the upstream side of the advanced treatment facility 1, a total of eight anaerobic tanks 2 are provided in two rows parallel to the sewage flow direction, four in each row. Each of these anaerobic tanks 2 corresponds to an example of an agitation tank. On the downstream side of the advanced treatment facility 1, a total of four aeration tanks 3 are provided in two rows parallel to the sewage flow direction, two in each row. A central wall 13 is formed between each row, and this central wall 13 prevents the sewage received in the anaerobic tank 2 and aeration tank 3 of one row from flowing into the anaerobic tank 2 and aeration tank 3 of the other row. Partition walls 14 are provided between the anaerobic tanks 2, between the aeration tanks 3, and between the anaerobic tank 2 and the aeration tank 3 in the same row. This partition wall 14 separates the anaerobic tanks 2, between the aeration tanks 3, and between the anaerobic tank 2 and the aeration tank 3 in the same row. However, an inlet opening 14a (see FIG. 2) is formed in the widthwise central portion of the lower end of the partition wall 14. Wastewater received in the most upstream anaerobic tank 2 in each row passes through these inlet openings 14a and flows downstream. Since the anaerobic tanks 2 and aeration tanks 3 in each row are formed symmetrically with respect to the central wall 13, the following explanation will focus on the anaerobic tanks 2 and aeration tanks 3 in the upper row in FIG. 1, and will not include an explanation of the anaerobic tanks 2 and aeration tanks 3 in the lower row in FIG. 1.

[0015] Each aeration tank 3 is provided with a number of air diffusers 31 at its bottom. A support 33 is fixed to the bottom surface 32 of the aeration tank 3, and an air pipe 34 is attached on the support 33. Each air diffuser 31 is fixed to the air pipe 34, and air is supplied through the air pipe 34. The air diffuser 31 in this embodiment is a membrane type air diffuser. However, other types of air diffusers may be used. The air diffuser 31 is disposed close to the left wall 11. In this aeration tank 3, air sent from a blower (not shown) is made into fine bubbles by the air diffuser 31 and blown into the wastewater from the bottom of the aeration tank 3. The blown air bubbles rise toward the water surface, and the air lift effect at this time generates a force that moves the wastewater upward, generating an upward flow of wastewater on the left wall 11 side of the aeration tank 3. On the other hand, a downward flow is generated on the center wall 13 side. As a result, a circulating flow is formed in the aeration tank 3.

[0016] Each anaerobic tank 2 is provided at its bottom with a bottom inclined surface 5, a trough 6, a space forming member 7, and a nozzle 8 (see FIG. 3). The nozzle 8 corresponds to an example of a discharge member. The first three anaerobic tanks 2 from the most upstream are each provided with two troughs 6. The most downstream anaerobic tank 2 is provided with three troughs 6. The troughs 6 are gutter-shaped members extending in the width direction of the advanced treatment facility 1 from the vicinity of the left wall 11 to the vicinity of the central wall 13 at the bottom of the anaerobic tank 2. That is, each trough 6 extends in a direction perpendicular to the flow direction of the wastewater in the advanced treatment facility 1. Therefore, the width direction of each trough 6 coincides with the flow direction of the wastewater in the advanced treatment facility 1. Hereinafter, the width direction of the trough 6 is referred to as the groove width direction. One space forming member 7 and one nozzle 8 are disposed in each trough 6. The troughs 6, the space forming member 7, and the nozzles 8 will be described in detail later.

[0017] As shown in FIG. 2, the bottom inclined surface 5 is disposed on the upstream side of the trough 6 and on the downstream side of the trough 6 so as to sandwich the trough 6. The bottom inclined surface 5 is connected to the edge of the groove 61 (see FIG. 3(b)) formed by the trough 6. The bottom inclined surface 5 is inclined downward toward the edge of the groove 61. As a result, a ridge 51, which is the top of the bottom inclined surface 5, is formed between adjacent troughs 6. The inclination angle of the bottom inclined surface 5 is 30 degrees with respect to the horizontal. This inclination angle may be 15 degrees or more. If the inclination angle of the bottom inclined surface 5 is 15 degrees or more, the sludge, etc. that has settled toward the bottom inclined surface 5 slides down the bottom inclined surface 5 and settles in the groove 61. In addition, if this inclination angle is 30 degrees or more, the sludge, etc. that has settled toward the bottom inclined surface 5 slides down the bottom inclined surface 5 more easily, and it is more preferable because it is possible to reliably prevent the sludge, etc. that has settled toward the bottom inclined surface 5 from depositing on the bottom inclined surface 5. The bottom inclined surface 5 in contact with the partition wall 14 is cut out at the center in the width direction so as not to block the inflow opening 14a. In this cut-out portion, an inflow path surface 52 formed as a horizontal surface extending between the inflow opening 14a and the groove 61 is provided.

[0018] Next, the configurations of the trough 6, space forming member 7, and nozzle 8 (hereinafter, the space forming member 7 and nozzle 8 are collectively referred to as the agitator) will be described with reference to Figures 3 and 4. The trough 6 and agitator provided in each anaerobic tank 2 have the same configuration, so in the following explanation, the trough 6 and agitator provided at the most downstream side among those shown in Figure 2 will be explained, and explanations of the other troughs 6 and agitators will be omitted.

[0019] FIG. 3(a) is an enlarged view showing a portion C in FIG.

[0020] As shown in FIG. 3(a), the space forming member 7 is composed of a main body 70 and one end portion 71. The space forming member 7 is hollow, and one end of the space forming member 7 in the extension direction is open toward the extension direction. This open portion becomes the suction port 7a. An inner surface 7i of the space forming member 7 defines an internal space S1 (see FIG. 3(b)). The one end portion 71 has a significantly shorter length in the extension direction (the vertical direction in FIG. 3(a)) than the main body 70. The main body 70 is supported together with the trough 6 by a support 65. The support 65 is fixed to the concrete, which is the framework of the anaerobic tank 2, by an anchor bolt 21. The one end portion 71 of the space forming member 7 is detachably attached to the main body 70 by a bolt (not shown). The one end portion 71 has a portion that protrudes toward the one end side beyond one end of the trough 6. One end portion 71 of the space forming member 7 has a one end side small diameter portion 711 connected to the main body portion 70, a one end side expanded diameter portion 712, and a one end side large diameter portion 713. The one end side small diameter portion 711 has the same cross-sectional shape as the main body small diameter portion 701 described later, and extends along the extension direction while continuing to the main body portion 70 (main body small diameter portion 701). The one end side expanded diameter portion 712 has a shape that gradually expands in the radial direction perpendicular to the extension direction of the space forming member 7 toward the suction port 7a. The one end side large diameter portion 713 is a portion located closer to the suction port 7a than the one end side expanded diameter portion 712, and extends parallel to the extension direction. The one end side large diameter portion 713 defines the suction port 7a. It is to be noted that the one end side large diameter portion 713 may not be provided, and the suction port 7a may be defined by one end of the one end side expanded diameter portion 712. A pair of support pieces 77 are provided on the inside of the large diameter portion 713 on one end side, protruding toward the center in the groove width direction.

[0021] The nozzle 8 is formed by flattening the tip of a round pipe. An outlet 81 is formed at the tip of the nozzle 8. The wastewater supplied from the fluid supply pipe 9 is discharged from the outlet 81. The wastewater discharged from the outlet 81 corresponds to an example of a fluid. As described above, the nozzle 8 is formed by flattening a round pipe, so that the discharge pressure of the wastewater passing through the nozzle 8 and discharged from the outlet 81 can be increased. In addition, the nozzle 8 is easy to manufacture because it can be manufactured simply by crushing a round pipe. A nozzle flange 8a is welded to the rear end of the nozzle 8. In addition, a pipe flange 9a is welded to the tip of the fluid supply pipe 9. The nozzle flange 8a and the pipe flange 9a are connected by a bolt (not shown). As a result, the nozzle 8 is detachably attached to the fluid supply pipe 9. Two mounting pieces 83, each protruding outward in the groove width direction, are fixed to the nozzle 8. The nozzle 8 is detachably attached to the space forming member 7 by connecting the mounting piece 83 to the support piece 77 of the space forming member 7 with bolts 95 (see FIG. 3(b)). By disconnecting the nozzle flange 8a from the pipe flange 9a and disconnecting the one end portion 71 of the space forming member 7 from the main body 70, the nozzle 8 can be removed together with the one end portion 71 from the main body 70 and the fluid supply pipe 9. Thereafter, by removing the bolts 95 connecting the one end portion 71 to the nozzle 8, it is possible to remove only the nozzle 8. This makes it easy to perform maintenance work such as removing scale, sludge, etc., when the nozzle 8 becomes clogged with scale, sludge, etc.

[0022] The nozzle 8 is held by a support piece 77 formed on the space forming member 7 in a state in which the discharge direction of the wastewater discharged from the discharge port 81 and the extension direction of the space forming member 7 are substantially aligned. The tip side of the nozzle 8 enters the internal space S1 (see FIG. 3(b)) formed by the space forming member 7 from the suction port 7a. Therefore, the discharge port 81 is disposed in the internal space S1. That is, the discharge port 81 is formed at the tip portion of the nozzle 8 whose tip side enters the internal space S1 from the suction port 7a of the space forming member 7. This allows all of the wastewater discharged from the discharge port 81 to be discharged into the internal space S1. However, the discharge port 81 does not have to enter the internal space S1 as long as it can discharge the wastewater into the internal space S1, and may be disposed, for example, on a surface formed by one end of the space forming member, that is, at the same position as the suction port 7a. Furthermore, if the discharge outlet 81 is positioned outside the internal space S1 and far away from the internal space S1, there is a risk that some of the sewage discharged toward the internal space S1 will not flow into the internal space S1, so it is desirable to position the discharge outlet 81 within the internal space S1 or close to the suction port 7a.

[0023] Fig. 3(b) is an E-E cross-sectional view of Fig. 3(a). In Fig. 3(b), the large diameter portion on one end side is shown smaller in size to make the drawing easier to see. Also, in Fig. 3(b), the nozzle flange and the pipe flange are omitted.

[0024] As shown in FIG. 3(b), the trough 6 is formed by bending a stainless steel plate material so that the cross section is in an arc shape with the trough center 6c as the center point. The trough 6 forms a groove 61 at the bottom of the anaerobic tank 2. In other words, the groove 61 is defined by the inner surface 6i of the trough 6. The trough 6 may be made of concrete or other materials such as resin. The cross-sectional shape of the trough 6 is not limited to an arc shape, and may be a U-shape, a V-shape, or the like. The trough 6 of this embodiment is a cylinder with an inner diameter of 300 mm with the upper 1 / 3 cut out, and opens upward. The upper end side of the groove 61 that is connected to the opening of the trough 6 becomes narrower as it approaches the opening.

[0025] The space forming member 7 extends along the inner surface 6i of the trough 6. Therefore, the space forming member 7 extends in a direction perpendicular to the direction of the wastewater flow in the advanced treatment facility 1. If the extension direction of the space forming member 7 is made parallel to the direction of the wastewater flow, a circulating flow is formed in the direction of the wastewater flow in the advanced treatment facility 1 when the wastewater is discharged from the discharge port 81, and there is a risk that the wastewater will be moved more than necessary to the downstream anaerobic tank 2 or aeration tank 3. It is desirable that the extension direction of the space forming member 7 in a plan view is at an angle of 30 degrees or more and 150 degrees or less with respect to the flow of the wastewater. The main body 70 and one end portion 71 of the space forming member 7 are formed so that the cross section is arc-shaped by bending a stainless steel plate material. A lower opening 7d that opens downward is formed in the lower part of the space forming member 7. The radial center of the cross section of the space forming member 7 coincides with the trough center 6c, which is the radial center of the trough 6. Hereinafter, the center in the radial direction in the cross section of the space forming member 7 is simply referred to as the center of the space forming member 7. The center of the space forming member 7 may be disposed at a position different from the trough center 6c, but it is preferable to dispose the center so that the lower opening 7d is at a position below the opening of the trough 6. The center of the discharge port 81 also coincides with the trough center 6c. By aligning the center of the space forming member 7 with the center of the discharge port 81, it is possible to prevent the wastewater discharged from the discharge port 81 from colliding with the inner surface 7i of the space forming member 7 and weakening the flow. However, the center of the space forming member 7 and the center of the discharge port 81 may be disposed at different positions. For example, the center of the discharge port 81 may be disposed below the center of the space forming member 7 and above the lower opening 7d. This arrangement can increase the force of sucking wastewater, settled sludge, etc. from the lower opening 7d into the internal space S1, which will be described later. In other words, it is preferable to dispose the center of the discharge port 81 between the center of the space forming member 7 and the lower opening 7d of the space forming member 7.

[0026] The space forming member 7 divides the inside of the groove 61 and forms an internal space S1. The internal space S1 is a space in which the portion above the lower end is closed. The main body 70 of the space forming member 7 is composed of a main body small diameter portion 701 and an other end side expanded diameter portion 702 (see FIG. 4) described later. The main body small diameter portion 701 and the one end side small diameter portion 711 have a cross-sectional shape of a 5 / 6 arc with the lower end portion of a cylinder with an inner diameter of 150 mm cut out. In addition, the lower end of the one end side small diameter portion 711, the lower end of the one end side expanded diameter portion 712, and the lower end of the one end side large diameter portion 713 are located at the same height position. That is, the one end portion 71 has a shape in which the entire lower end is cut horizontally. As a result, the one end side large diameter portion 713 has a cross-sectional shape of about 2 / 3 arc with the lower end portion of a cylinder with an inner diameter of 300 mm cut out. The suction port 7a (see FIG. 3(a)) is formed in a portion surrounded by one end of the one-end large diameter portion 713, and has a circular shape with a diameter of 300 mm with a missing lower end portion. The lower opening 7d formed in the lower end portion of the space forming member 7 acts as a suction port that sucks the wastewater and settled sludge in the groove 61 into the internal space S1. The lower opening 7d is formed over the entire area in the extension direction of the space forming member 7. Therefore, the lower opening 7d is also formed in the one-end enlarged diameter portion 712 and the one-end large diameter portion 713. There may be a portion in the extension direction of the space forming member 7 where the lower opening 7d is not formed, but in that portion, the wastewater and settled sludge cannot be sucked into the internal space S1, and there is a risk that the settled sludge will remain. Therefore, it is preferable to form the lower opening 7d over the entire area in the extension direction. The lower opening 7d formed in the main body small diameter portion 701 and the one end portion 71 is formed to have a length of 80 mm in the groove width direction. The lower opening 7d of the one end side large diameter portion 713 is formed to have a length of about 270 mm in the groove width direction. The lower opening 7d is disposed in the groove 61 except for both end portions where the space forming member 7 protrudes from the groove 61 in a plan view. Therefore, the lower opening 7d is disposed below the upper end edge of the groove 61. The lower opening 7d is also spaced apart from the inner surface 6i of the trough 6. In detail, the lower opening 7d is disposed at a position where the distance in the height direction from the lowest portion 6b of the inner surface 6i of the trough 6 is 84 mm. The distance in the height direction from the lowest portion 6b to the lower opening 7d is preferably 40 mm or more and 200 mm or less.If it is less than 40 mm, the gap between the edge of the lower opening 7d and the trough 6 becomes too narrow, and larger garbage that has passed through the grit chamber or the like for some reason may get stuck in the gap. If it is more than 200 mm, the lowest part 6b and the lower opening 7d are too far apart, so that sludge that has settled near the lowest part 6b cannot be sucked into the internal space S1 through the lower opening 7d. The relative position of the height direction of the space forming member 7 with respect to the trough 6 may be freely adjusted. By making the height direction position of the space forming member 7 freely adjustable, the space forming member 7 can be placed at an optimal position corresponding to the wastewater treatment facility. The inner surface 6i, the inflow road surface 52, and the bottom inclined surface 5 (see FIG. 2) of the trough 6 correspond to an example of the bottom surface. The outer surface of the space forming member 7 is arc-shaped, so that the part above the center of the circle that has this arc as a part of its circumference is inclined downward as it moves outward in the groove width direction. Therefore, sludge and the like that has settled toward the outer surface of the space forming member 7 easily slides down along the outer surface of the upper part of the space forming member 7 toward the bottom of the groove 61. This makes it possible to prevent sludge and the like from accumulating in the upper part of the space forming member 7. In addition, due to the lower part of the space forming member 7, the lower end part of the internal space S1 that is connected to the lower opening 7d becomes narrower as it approaches the lower opening 7d. Therefore, sludge and the like that has once been sucked into the internal space S1 is less likely to leak out of the internal space S1.

[0027] Fig. 4(a) is an enlarged view of part D in Fig. 1, and Fig. 4(b) is a cross-sectional view taken along line FF of Fig. 4(a). In Fig. 4(b), the outer diameter of the discharge port is shown smaller than normal to make the drawing easier to see.

[0028] As shown in FIG. 4(a), the other end portion of the space forming member 7 protrudes further from the other end of the trough 6 toward the other end side. The other end of the space forming member 7 in the extension direction is open toward the extension direction. This open portion becomes the discharge port 7b. The other end portion of the space forming member 7 is formed with an other end side expanded diameter portion 702 having a shape that gradually expands in the radial direction perpendicular to the extension direction of the space forming member 7 as it approaches the discharge port 7b. This other end side expanded diameter portion 702 is formed symmetrically with the one end side expanded diameter portion 712 with a plane perpendicular to the extension direction of the space forming member 7 as a symmetrical plane. Therefore, as shown in FIG. 4(b), the discharge port 7b is formed in a part surrounded by the other end of the other end side expanded diameter portion 702, and has a circular shape with a diameter of 300 mm with a missing lower end portion. In other words, the discharge port 7b has the same shape as the intake port 7a.

[0029] Fig. 5 is a cross-sectional view taken along line B-B of the anaerobic tank shown in Fig. 2. In Fig. 5, the intermediate portion of the fluid supply pipe is shown in a simplified form.

[0030] As shown in FIG. 5, the suction port 7a faces the lower end portion of the left wall surface 111, which is the inner surface of the left side wall 11. This left wall surface 111 corresponds to an example of a first wall surface. The discharge port 7b faces the lower end portion of the central wall surface 131, which is the left side surface of the central wall 13. This central wall surface 131 corresponds to an example of a second wall surface. The lower end portion of the left wall surface 111 is formed with a first inclined surface 111a that approaches the suction port 7a as it goes downward. Sludge, etc. that has settled toward this first inclined surface 111a slides down the first inclined surface 111a due to the inclination and settles near the suction port 7a. In addition, when sewage is discharged from the discharge port 81, a flow of sewage is generated near the first inclined surface 111a toward the suction port 7a along the inclination of the first inclined surface 111a, as shown by an arc-shaped arrow in the lower right of FIG. 5. Due to this flow of wastewater, sludge and the like that has settled near the suction port 7a moves toward the suction port 7a. Due to this flow and the ejector effect of the space forming member 7, the settled sludge and the like is sucked into the internal space S1 (see FIG. 3(b)) in the space forming member 7, so that the sludge and the like can be prevented from settling near the lower end of the left wall surface 111 and remaining there. Although the first inclined surface 111a in this embodiment has a circular arc shape that is concave downward, it may also be flat.

[0031] A second inclined surface 131a is formed at the lower end portion of the central wall surface 131, which approaches the discharge port 7b as it goes downward. When the wastewater is discharged from the discharge port 81, the wastewater is discharged from the discharge port 7b. The wastewater discharged from the discharge port 7b smoothly rises upward along the second inclined surface 131a as shown by the arc-shaped arrow in the lower left of FIG. 3, and a strong circulating flow is formed above the space forming member 7 by this rising wastewater. The second inclined surface 131a may be flat. However, by forming the second inclined surface 131a in a circular arc shape concave downward, the flow of the wastewater discharged from the discharge port 7b in a generally horizontal direction can be converted upward more smoothly than in the case of a flat shape, so that there is an effect of reducing the loss of the flow compared to a flat shape.

[0032] The fluid supply pipe 9 extends upward from the bottom of the anaerobic tank 2 along the left wall surface 111. A flow rate control valve 91 and an electric valve 92 are installed on the upper end side of the fluid supply pipe 9. Note that in FIG. 5, the fluid supply pipe 9 above the flow rate control valve 91 is omitted. This fluid supply pipe 9 is connected to a pump (not shown) arranged in the advanced treatment facility 1. By opening the electric valve 92, wastewater sucked up by the pump (not shown) is supplied to the nozzle 8 through the fluid supply pipe 9, and the wastewater is discharged from the discharge port 81 provided in the nozzle 8. Note that, similar to the inflow opening 14a, two upper inflow ports 14b through which wastewater can pass are provided on the upper part of the partition wall 14.

[0033] Next, the action of discharging wastewater from the discharge port 81 will be described mainly with reference to FIG. 3 and FIG. 5. In the anaerobic tank 2, wastewater is always discharged from the discharge port 81 except for special circumstances such as during maintenance. In this embodiment, the discharge pressure of the wastewater discharged from the discharge port 81 is 0.09 MPa, and the discharge water volume is 1.5 m3 / min. However, as described later, the discharge pressure may be 0.001 MPa or more, and the discharge water volume may be 0.3 m3 / min or more. In addition, the discharge flow velocity of the wastewater is preferably 2 m / sec or more and 32 m / sec or less. If the discharge flow velocity is less than 2 m / sec, the circulating flow in the anaerobic tank 2 formed by the wastewater discharged from the discharge port 7b is weak, and there is a risk that sludge and the like cannot be circulated. If the discharge flow velocity exceeds 32 m / sec, the flow of the circulating flow becomes too strong, and air is sucked in at the water surface, and air is supplied to the wastewater. When the wastewater is discharged from the discharge port 81 into the internal space S1, a flow of wastewater is generated in the internal space S1. At that time, a pressure difference due to the flow of wastewater occurs between the inside of the internal space S1 and the outside of the internal space S1 due to the flow of wastewater. That is, a negative pressure is generated in the internal space S1 where the flow of wastewater is generated. The sludge, etc. that has settled in the groove 61 is sucked into the internal space S1 from the lower opening 7d by the negative pressure together with the surrounding wastewater, as shown by the curved arrow in FIG. 3(b). In order to obtain the negative pressure required to suck in the sludge, etc., it is preferable that the flow velocity of the wastewater flowing in the internal space S1 is 0.1 m / sec or more. In addition, the wastewater discharged from the discharge port 81 is prevented from diffusing in the radial direction perpendicular to the extension direction of the space forming member 7 by the space forming member 7, so that the flow is maintained in the internal space S1 over a long distance. The sewage and sludge sucked into the internal space S1 move toward the outlet 7b while being mixed with the sewage due to the flow of sewage occurring in the internal space S1, and are discharged from the outlet 7b. If the discharge pressure is less than 0.001 MPa, the sludge moving in the internal space S1 is likely to leak out from the lower opening 7d. Similarly, if the discharge water rate is less than 0.3 m3 / min, the sludge moving in the internal space S1 is likely to leak out from the lower opening 7d.In consideration of the pump capacity and power consumption, the discharge pressure is preferably 0.3 MPa or less, and the discharge water volume is preferably 3.0 m3 / min or less. As described above, the wastewater discharged from the discharge port 7b smoothly rises upward along the second inclined surface 131a, forming a strong circulating flow above the space forming member 7.

[0034] According to this embodiment, by discharging wastewater from the discharge port 81 into the internal space S1, the sludge and other substances that have settled in the grooves 61 can be sucked into the internal space S1, stirred and moved, and then discharged from the discharge port 7b. Then, the wastewater discharged from the discharge port 7b, mixed with the sludge and other substances, can be circulated in the anaerobic tank 2 by being placed in a circulating flow. Therefore, the sludge and other substances that have settled in the grooves 61 can be stirred.

[0035] Next, the anaerobic tank 2 of the second embodiment will be described. In the following description, components having the same names as components described so far will be assigned the same reference numerals as those used so far, and duplicate descriptions may be omitted.

[0036] Fig. 6 is a cross-sectional view of the advanced treatment facility 1 of the second embodiment similar to Fig. 2. In Fig. 6, the left side of the figure is the upstream side, and the right side is the downstream side.

[0037] The advanced treatment facility 1 shown in FIG. 6 is different from the advanced treatment facility 1 shown in the previous embodiment in the shape of the bottom of the anaerobic tank 2. As shown in FIG. 6, the bottom inclined surface 5 and the trough 6 are not formed on the bottom of this anaerobic tank 2, and the bottom surface 50 composed of a flat surface is formed on the bottom. In addition, in this embodiment, more space forming members 7 are arranged than in the previous embodiment. Specifically, the anaerobic tanks 2 from the most upstream to the third one each have three space forming members 7. And the anaerobic tank 2 on the most downstream side has five space forming members 7. The lower opening 7d of the space forming member 7 is separated from the bottom surface 50. In detail, the lower opening 7d is arranged at a position where the distance in the height direction from the bottom surface 50 is 84 mm. Note that, for the same reason as in the previous embodiment, the distance in the height direction between the lower opening 7d and the bottom surface 50 is preferably 40 mm or more and 200 mm or less. Each space forming member 7 has an outlet 81 for discharging a fluid into the internal space S1.

[0038] In the anaerobic tank 2 of this embodiment, wastewater is discharged from the discharge port 81 to form a circulating flow above the space forming member 7. Sludge and the like that are below the space forming member 7 and that are deposited near the space forming member 7 are sucked into the internal space S1 from the lower opening 7d by negative pressure together with the surrounding wastewater, as shown by the curved arrow in FIG. 6. The sucked sludge and the like then circulates along the circulating flow formed above. However, if the interval between adjacent space forming members 7 is wide, there is a risk that the sludge and the like that has settled on the bottom surface 50 at the intermediate position between the adjacent space forming members 7 will remain deposited. As a countermeasure against this, by arranging many space forming members 7 as described above, the interval between adjacent space forming members 7 is narrowed to prevent the sludge and the like that has settled on the bottom surface 50 at the intermediate position from remaining deposited. Instead of increasing the number of space forming members 7, a linear motion mechanism that moves the space forming member 7 and the discharge port 81 in the direction of the wastewater flow by an electric motor such as a motor may be provided. When this linear motion mechanism is provided, it is preferable to move the space forming member 7 together with the discharge port 81 from the vicinity of the upstream end to the vicinity of the downstream end of the anaerobic tank 2 while discharging the wastewater from the discharge port 81. In addition, a rotation mechanism may be provided that rotates the space forming member 7 along the bottom surface 50 by an electric motor around the center of the extension direction of the space forming member 7. When this rotation mechanism is provided, it is preferable to rotate the space forming member 7 parallel to the bottom surface 50 while discharging the wastewater from the discharge port 81. In this operation, it is preferable to rotate the space forming member 7 clockwise and counterclockwise by an angle of less than 150 degrees each. If it is rotated by 150 degrees or more, a circulating flow is formed in the flow direction of the wastewater, and there is a risk that the wastewater will be moved more than necessary to the downstream anaerobic tank 2 or aeration tank 3. In the embodiment in which the linear motion mechanism or the rotation mechanism is provided, the entire bottom surface 50 of the anaerobic tank 2 can be covered by a single space forming member 7, so that all sludge and the like deposited on the bottom surface 50 can be sucked up and stirred simply by arranging one space forming member 7 for each anaerobic tank 2. According to this embodiment, the sludge and the like that has settled on the bottom surface 50 can be stirred even if the inclined bottom surface 5 or the trough 6 is not formed in the anaerobic tank 2.

[0039] Next, a modified example of the anaerobic tank 2 that has been described thus far will be described, focusing on the differences from the configurations that have been described thus far.

[0040] FIG. 7(a) is a cross-sectional view showing a modification of one end portion of the space forming member shown in FIG. 3(b).

[0041] As shown in FIG. 7(a), the space forming member 7 of this modification differs from the space forming member 7 shown in FIG. 3 in that the one end side expanded diameter portion 712 and the one end side large diameter portion 713 do not expand in the groove width direction, and the positions at which the support piece 77 and the mounting piece 83 are provided are different. That is, the one end side expanded diameter portion 712 and the one end side large diameter portion 713 have a shape that expands only upward relative to the one end side small diameter portion 711. The one end side large diameter portion 713 is provided on the inside with the support piece 77 protruding downward from the upper end portion. In addition, the nozzle 8 is fixed with the mounting piece 83 protruding upward from the upper end portion. The mounting piece 83 is connected to the support piece 77 by the bolt 95, so that the nozzle 8 is detachably attached to the one end portion 71 of the space forming member 7.

[0042] FIG. 7(b) is a cross-sectional view showing a modified example of the other end portion of the space forming member shown in FIG. 4(b).

[0043] As shown in Fig. 7(b), the space forming member 7 of this modification is different from the space forming member 7 shown in Fig. 4 in that the other end side expanded diameter portion 702 does not expand in the width direction. In other words, the other end side expanded diameter portion 702 has a shape that expands only upward relative to the main body small diameter portion 701. In this modification, since the one end side large diameter portion 713 expands only upward, a stronger circulating flow is likely to be formed above the space forming member 7 when wastewater is discharged from the discharge port 81.

[0044] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made within the scope of the claims. For example, in this embodiment, the stirring tank of the present invention is applied to the anaerobic tank 2, but it may be applied to the aeration tank 3 or anoxic tank. When applied to the aeration tank 3, another outlet that supplies sewage containing air or bubbles may be provided around or near the outlet 81, or air or bubbles may be added to the sewage midway through the fluid supply pipe 9 and discharged from the outlet 81. In this case, it is desirable that the bubbles are nanobubbles with a diameter of 1 μm or less. Nanobubbles have a large total surface area compared to bubbles with a large diameter of the same volume, so they can efficiently supply oxygen to aerobic bacteria. In addition, nanobubbles have almost no buoyancy, so they can circulate in the aeration tank 3 for a long time. When applied to the aeration tank 3, the flow rate of the sewage flowing in the internal space S1 of the aeration tank 3 may be faster than the flow rate of the sewage flowing in the internal space S1 of the anaerobic tank 2. When the flow rate of the wastewater flowing in the internal space S1 increases, the circulating flow becomes stronger, and air may be drawn in at the water surface and supplied to the wastewater, but it is preferable to supply air to the aeration tank 3. In other words, the flow rate of the wastewater flowing in the internal space S1 in the anaerobic tank 2 is preferably equal to or lower than the flow rate of the wastewater flowing in the internal space S1 in the aeration tank 3. When applied to an anoxic tank, a device for adding nitric acid or the like may be placed in the tank. Furthermore, the agitation tank of the present invention may be used in facilities other than wastewater treatment facilities, such as a tank for mixing two or more types of fluids or a tank for uniformly dispersing various powders, chemicals, and the like in a fluid.

[0045] According to the embodiment and modified examples described above, sludge and the like that has settled to the bottom can be sucked up and moved together with the wastewater into the internal space S1, thereby allowing the sludge and the like and the wastewater to be agitated.

[0046] In addition, even if a component is included only in the description of the embodiment or each modified example described above, that component may be applied to other embodiments or other modified examples.

[0047] The mixing vessel described above is a mixing vessel that mixes the received liquid, a hollow space forming member extending along a bottom surface formed at the bottom of the mixing vessel and having an intake port provided at one end in the extending direction and an exhaust port provided at the other end in the extending direction; a discharge port that discharges a fluid into an internal space defined by an inner surface of the space forming member, The space forming member may be characterized in that a lower opening is formed in a lower portion thereof and spaced apart from the bottom surface.

[0048] The mixing vessel described above is a mixing vessel that mixes the received liquid by circulating flow, a hollow space forming member extending along a bottom surface formed at the bottom of the mixing vessel and having an intake port provided at one end in the extending direction and an exhaust port provided at the other end in the extending direction; a discharge port that discharges a fluid into an internal space defined by an inner surface of the space forming member substantially in the extension direction, the space forming member has a lower opening provided along the extending direction and spaced apart from the bottom surface, the intake port and the lower opening suck surrounding liquid into the internal space when fluid is discharged from the discharge port; The discharge port forms the circulating flow by discharging the fluid discharged from the discharge port and the liquid sucked in from the suction port and the lower opening.

[0049] Here, the discharge port may be disposed within the internal space, or may be disposed outside the internal space. The lower opening may be formed along the extension direction. The lower opening may be formed over the entire length of the extension direction of the space forming member, or may be divided into a plurality of locations along the extension direction. In addition, the discharge port may discharge only liquid, or may discharge liquid containing bubbles. A second discharge port for discharging bubbles or liquid containing bubbles into the internal space may be provided separately from the discharge port. Furthermore, these bubbles may be nanobubbles having a diameter of 1 μm or less. The space forming member may have a cross-sectional shape of a circular arc. The internal space may be narrowed as the lower end portion connected to the lower opening approaches the lower opening.

[0050] According to this stirring tank, the fluid discharged from the discharge port into the internal space is prevented from diffusing in the radial direction perpendicular to the predetermined direction by the space forming member except for the part where the lower opening is formed, and a strong flow of fluid is created in the internal space. This flow creates a pressure difference between the inside and outside of the space forming member, and sludge, etc. that has settled at the bottom of the stirring tank is sucked into the internal space through the lower opening together with the liquid around the lower opening. The sucked sludge, etc. then moves through the internal space while being mixed with the liquid or fluid sucked in by the flow of fluid in the internal space, and is discharged from the discharge port together with the liquid, etc. A circulating flow is formed in the stirring tank by the liquid, etc., containing the discharged sludge, etc., and the sludge, etc. circulates in the stirring tank on the circulating flow. Therefore, the sludge, etc. that has settled at the bottom of the stirring tank can be reliably stirred.

[0051] In this mixing tank, a groove is provided in the bottom portion and extends in the same direction as the extension direction; a bottom inclined surface provided at the bottom, connected to an edge of the groove, and inclined downwardly toward the edge of the groove; The lower opening may be disposed within the groove.

[0052] According to this aspect, sludge or the like that is attempting to settle on the inclined bottom surface is likely to slide down the inclined bottom surface and settle into the groove, and can be sucked into the internal space through the lower opening disposed in the groove, thereby preventing sludge or the like from settling on the inclined bottom surface and remaining there.

[0053] Furthermore, in this stirring vessel, the space forming member may have a shape at the one end portion that gradually widens in a radial direction perpendicular to the extending direction toward the suction port.

[0054] In this way, a larger amount of liquid can be sucked in through the suction port, so that a stronger circulating flow can be created. Note that the one end portion does not have to have a shape that expands in all directions in the radial direction, for example, a shape that expands only in the upward direction.

[0055] In this stirring tank, the space forming member may have a shape at the other end portion that gradually widens in a radial direction perpendicular to the extending direction toward the discharge port.

[0056] In this way, the liquid that reaches the other end portion is discharged from the discharge port while spreading in the radial direction, so that a circulating flow can be formed over a wider range. Note that the other end portion does not have to have a shape that spreads in all directions in the radial direction, for example, a shape that spreads only in the upward direction.

[0057] In addition, in this stirring vessel, the suction port is disposed opposite to a lower end portion of a first wall surface of the stirring vessel, A lower end portion of the first wall surface may have a first inclined surface that approaches the suction port as it extends downward.

[0058] Sludge, etc., which tends to settle on the first inclined surface slides down the first inclined surface and tends to settle near the suction port. In addition, since a flow of liquid generated near the first inclined surface when fluid is discharged from the discharge port moves toward the suction port along the inclination of the first inclined surface, sludge, etc., which has settled near the suction port moves toward the suction port along the flow of liquid and is likely to be sucked in from the suction port. This makes it possible to prevent sludge, etc., from settling near the lower end portion of the first wall surface and remaining there.

[0059] In addition, in this stirring tank, the discharge port is disposed opposite to a lower end portion of a second wall surface of the stirring tank, The lower end portion of the second wall surface may have a second inclined surface that approaches the discharge port as it extends downward.

[0060] The liquid discharged from the discharge port smoothly rises upward along the second inclined surface, so that flow loss is reduced and a stronger circulating flow can be formed above the space forming member.

[0061] The mixing tank described above is a mixing tank that mixes the received liquid by circulating flow. A tank comprising: The discharge pipe extends along the bottom surface formed at the bottom of the mixing vessel and is provided at the end of the extension direction. A hollow space forming member having a mouth; A fluid is injected into an internal space defined by an inner surface of the space forming member in the extending direction. and a discharge port for discharging the liquid, The space forming member is provided in the lower portion along the extending direction and spaced apart from the bottom surface. The lower opening is formed over the entire area in the extension direction, The lower opening allows surrounding liquid to flow into the internal space when fluid is discharged from the discharge port. It is something to inhale, The discharge port is configured to receive the fluid discharged from the discharge port and the fluid sucked in from the lower opening. The present invention is characterized in that the circulatory flow is formed by releasing the body.

[0062] Also, a mixing tank that mixes the received liquid by a circulating flow, The discharge pipe extends along the bottom surface formed at the bottom of the mixing vessel and is provided at the end of the extension direction. A hollow space forming member having a mouth; The air flows into the internal space defined by the inner surface of the space forming member in the direction substantially parallel to the extension direction. and a discharge port for discharging the body. The space forming member is provided in the lower portion along the extending direction and spaced apart from the bottom surface. A lower opening is formed, The lower opening allows surrounding liquid to flow into the internal space when fluid is discharged from the discharge port. It is something to inhale, The discharge port is configured to receive the fluid discharged from the discharge port and the fluid sucked in from the lower opening. The circulatory flow may be formed by releasing the body.

[0063] In addition, in this mixing tank, a groove is provided in the bottom portion and extends in the same direction as the extension direction; a bottom inclined surface provided at the bottom, connected to an edge of the groove, and inclined downwardly toward the edge of the groove; The lower opening may be disposed within the groove. [Explanation of symbols]

[0064] 1 Advanced treatment facilities 2 Anaerobic tank 6 Trough 6i Inside 7 Space forming members 7a Inlet 7b Outlet 7d Lower opening 50 Bottom 81 Discharge port S1 interior space

Claims

1. A mixing tank that mixes a received liquid by a circulating flow while the liquid flows in a flow direction, a hollow space forming member extending along a bottom surface formed on the bottom of the mixing vessel and having a discharge port provided at an end in the extending direction; a discharge port that discharges a fluid in the extension direction into an internal space defined by an inner surface of the space forming member, The space forming member has a lower opening formed in a lower portion thereof separated from the bottom surface, and extends in a direction at an angle of 30 degrees or more and 150 degrees or less with respect to the flow direction in a plan view, the lower opening sucks surrounding liquid into the internal space when fluid is discharged from the discharge port; The discharge port forms the circulating flow by discharging the fluid discharged from the discharge port and the liquid sucked in from the lower opening.

2. A mixing tank that mixes a received liquid by a circulating flow while the liquid flows in a flow direction, a hollow space forming member extending along a bottom surface formed on the bottom of the mixing vessel and having a discharge port provided at an end in the extending direction; a discharge port that discharges a fluid in the extension direction into an internal space defined by an inner surface of the space forming member, The space forming member has a lower opening formed in a lower portion thereof and spaced apart from the bottom surface, and extends in a direction perpendicular to the flow direction in a plan view, the lower opening sucks surrounding liquid into the internal space when fluid is discharged from the discharge port; The discharge port forms the circulating flow by discharging the fluid discharged from the discharge port and the liquid sucked in from the lower opening.

3. 3. The stirring vessel according to claim 1, wherein the space forming member is disposed in an area partitioned by a partition wall.

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