JP2020011167A - Sedimentation basin and sand collection method - Google Patents

Abstract

To provide a sedimentation basin which enables efficient collection of sand, and to provide a sand collection method.SOLUTION: A sedimentation basin 2 includes: a main trough 8 provided at a basin bottom part and extending in a predetermined direction; a trough first discharge port 831a which discharges a fluid in the predetermined direction in water accumulated in the main trough 8; a bottom flat surface 71 provided at the basin bottom part and connected to the main trough 8; a discharge port 911 which discharges a fluid for causing sand accumulated on the bottom flat surface 71 to flow from the side wall W side of the sedimentation basin 2 toward the main trough 8 into the atmospheric air; and a first cover member 13 which covers a periphery of a vertical axis extending from a center of the trough first discharge port 831a in the predetermined direction and has an opening 13a at a lower end portion.SELECTED DRAWING: Figure 5

Description

  TECHNICAL FIELD The present invention relates to a sand basin in which sand contained in received water sinks to the bottom of the pond, and a sand collecting method for collecting the settled sand.

  The sewage treatment facility receives sewage such as sewage and rainwater, and the sand contained in the sewage settles on the bottom of the pond and in the trench provided at the bottom of the pond, and then deposits on the bottom and in the trench. Some have a sand basin that collects sand in a sand collection pit and removes it from wastewater. After discharging the sewage in the sand basin and exposing the sand deposited on the bottom surface to the atmosphere, this sand basin discharges fluid from a plurality of discharge ports provided near the side wall of the sand basin, and the sand is discharged by the fluid. Is provided with a sand collecting means for flowing water toward a groove. The groove is formed of a long member having a U-shaped or arc-shaped cross section, extends in a direction orthogonal to the pond width direction, and has a rear end connected to the sand collecting pit. Further, the groove is inclined downward toward the sand collecting pit, and is deepest on the sand collecting pit side. The sand deposited in the groove is transported to the sand collecting pit by the flow of the fluid discharged into the groove from the tip of the groove. During transport, the flow of the fluid supplied into the groove toward the sand collecting pit is assisted by the inclination of the groove. Thereby, the sand in the groove is easily moved to the sand collecting pit side. The sand transported to the sand collection pit is discharged to the outside of the sand basin by a sand pump installed in the sand collection pit. As a sand basin having a plurality of discharge ports and the like provided in the vicinity of such grooves and side walls, for example, those described in Patent Documents 1 and 2 are known.

JP-A-2017-127871 JP 2018-39007 A

  However, when the fluid discharged into the groove from the tip side of the groove collides with the sand accumulated in the groove, the fluid and the sand may scatter in the pond width direction. If the sand scatters, the sand returns to the bottom surface that has been washed away, and the sand collecting efficiency is reduced. In addition, since the flow of the fluid generated by the discharge is weakened by the collision between the fluid and the sand, the sand collecting efficiency also decreases in this respect.

  In view of the above circumstances, an object of the present invention is to provide a sand basin and a sand collecting method capable of collecting sand efficiently.

The sand basin of the present invention that solves the above object is a sand basin in which the sand contained in the received water sinks to the bottom of the pond,
A groove provided in the bottom of the pond and extending in a predetermined direction;
A first discharge port for discharging a fluid in the predetermined direction in the water accumulated in the groove;
A bottom surface provided at the bottom of the pond and connected to the trench;
A second discharge port for discharging a fluid for flowing sand deposited on the bottom surface from the side wall side of the sand basin toward the groove, into the atmosphere;
A cover member that covers the periphery of the virtual axis extending in the predetermined direction from the center of the first discharge port and has an opening at a lower end portion.

  Here, the covering member may have an inclined surface which is inclined downward in the width direction of the groove in an upper portion thereof. This inclined surface may be formed as a flat surface or may be formed as a curved surface. When the inclined surface is formed as a curved surface, it is preferable that the curved surface has a curved shape with a convex upper part. Further, the covering member may have a cylindrical shape having an opening at a lower end.

  According to this sand basin, the fluid discharged in the predetermined direction from the first discharge port is prevented from diffusing in the radial direction orthogonal to the predetermined direction by the cover member, and creates a strong flow of the fluid in the cover member. This flow causes a pressure difference between the inside and outside of the covering member, and the sand accumulated in the groove is sucked into the inside of the covering member from the opening at the lower end portion of the covering member. Then, the sucked sand is transported by the flow of the fluid in the covering member. That is, since the flow of the fluid discharged from the first discharge port can be effectively used for conveyance, the sand accumulated in the groove can be efficiently conveyed.

  In this sand basin, the opening of the covering member may be arranged below the center of the groove in the height direction.

  According to this aspect, since the opening of the covering member and the sand deposited below the groove approach each other, the sand accumulated in the groove can be easily sucked into the covering member.

Further, the sand collecting method of the present invention for solving the above-mentioned object is a sand settling tank in which sand contained in received water is settled in a pond bottom having a groove extending in a predetermined direction and a bottom surface connected to the groove. In the method for collecting sand deposited on the bottom of the pond,
An underwater discharge step of discharging a fluid from the first discharge port in the predetermined direction in the water accumulated in the groove;
Discharging the fluid for flowing the sand deposited on the bottom surface from the side wall side toward the groove from the second discharge port into the atmosphere,
The underwater discharge step is a step of discharging a fluid into a space covered by a covering member having an opening at a lower end portion and extending around a virtual axis extending in the predetermined direction from the center of the first discharge port. It is characterized by the following.

  Here, the underwater discharge step may be a step performed in a state where the inside of the cover member is filled with a fluid, or may be a step performed in a state where the air remains in the cover member. Further, the underwater discharge step may be a step performed in a step in which the first discharge port is completely submerged in water. The process may be performed in a state of being exposed to the surface.

  According to this sand collecting method, the fluid discharged in the predetermined direction from the first discharge port in the underwater discharge step creates a strong flow of the fluid in the covering member, and removes the sand accumulated in the groove from the covering member. Since it is sucked in and transported in a predetermined direction, sand can be transported and collected efficiently. Further, the fluid discharged into the atmosphere from the second discharge port in the discharge step into the atmosphere does not receive the resistance of water, so that the sand deposited on the bottom surface can flow efficiently.

Further, in this sand collecting method, the underwater discharging step is a step performed in a state where a water level is maintained above the covering member,
The atmospheric discharge step may be a step performed in a state where a water level is maintained below the bottom surface.

  In the underwater discharge step, the fluid is discharged into the water from the first discharge port in a state where the inside of the cover member is filled with the fluid, so that a loss of the discharge pressure is small and a strong fluid flow can be created in the cover member. . In addition, in the atmospheric discharge step, since the sand deposited on the bottom surface is exposed to the atmosphere, even if the discharge pressure of the fluid discharged from the second discharge port is weak, the sand deposited on the bottom surface can flow. it can.

  In this sand collecting method, the process of executing the underwater discharging process after the execution of the atmospheric discharging process may be performed as a set of sand collecting processes, and the sand collecting process may be performed a plurality of times.

  If the sand that has flowed into the groove during the air discharge process remains in the groove, the sand that has flowed into the groove during the next air discharge process will be added to the remaining sand, and a large amount of sand will flow into the groove. May accumulate. If a large amount of sand is accumulated, the sand may hinder the conveyance of the sand in the groove in the underwater discharge process. Further, even if it is attempted to flow sand into the groove in the next atmospheric discharge step, the inside of the groove may be filled with sand, and the overflowing sand may remain on the bottom surface. In this sand collecting method, the process of flowing into the groove by the air discharging process and the process of transporting the inside of the groove by the underwater discharging process are a set of sand collecting processes. The sand that has flowed into the groove during the sand treatment does not remain in the groove. This allows the sand to flow toward the groove from which the sand has been removed in the air discharging step in the next sand collecting process, thereby preventing the sand from overflowing from the groove. Further, in the underwater discharging step in the next sand collecting process, it is possible to prevent a large amount of sand accumulated in the groove from making it difficult to transport the sand in the groove.

  Further, in this sand collecting method, the underwater discharging step may be performed before performing the sand collecting process a plurality of times.

  Before the first sand collection process, the sand that has settled in the trench is transported by the underwater discharge process, so that in the atmospheric discharge process in the first sand collection process, the sand can flow toward the groove from which the sand has been removed. Therefore, it is possible to prevent the sand from overflowing from the groove. In addition, in the underwater discharging step in the first sand collecting process, it is possible to prevent a large amount of sand accumulated in the groove from making it difficult to transport the sand in the groove.

  ADVANTAGE OF THE INVENTION According to this invention, the sand basin and the sand collection method which can collect sand efficiently can be provided.

1 is a schematic cross-sectional view of a sewage treatment facility including a sand basin according to an embodiment of the present invention. It is the top view which looked at the sand basin corresponding to one embodiment of the present invention from the upper part. It is XX sectional drawing of the sand basin shown in FIG. FIG. 4A is an enlarged view showing a portion Z of FIG. 3 in an enlarged manner, and FIG. 4B is a schematic perspective view showing a first covering member and an upstream trough first nozzle. It is AA sectional drawing of the sand basin shown in FIG. It is an enlarged view which expands and shows the B section of FIG. (A) is sectional drawing for demonstrating the state in which one pipe | tube provided with the lap joint was couple | bonded with the other pipe | tube, (b) is one side provided with a lap joint by loosening a bolt. FIG. 4 is a cross-sectional view for explaining a state in which a tube is rotatable around the axial direction with respect to the other tube. FIG. 7A is a cross-sectional view taken along the line CC of FIG. 6, and FIG. 6B is a cross-sectional view similar to FIG. It is a water supply system diagram in a sewage treatment facility. It is explanatory drawing which shows the water level of a settling basin, and a water level sensor. It is a flow chart which shows a flow of sand removal operation in a sewage treatment facility. It is sectional drawing of a sand basin similar to FIG. 5 which shows the case where a sand collecting means is arrange | positioned at the upper part of a sand basin, and the case where sand collection means is arrange | positioned near the pond bottom of a sand basin. It is sectional drawing similar to FIG. 3 which shows the modification of a connection surface. (A) is a figure which shows the 1st modification of the supply pipe and the sand collecting nozzle shown in FIG. 8, and (b) is a figure which shows the 2nd modification of the supply pipe and the sand collecting nozzle shown in FIG. is there. It is sectional drawing similar to FIG. 5 which shows the modification of a main trough, a covering member, and a bottom plane. FIG. 16 is a cross-sectional view similar to FIG. 8A, showing a bottom plane near the upstream end of the sand basin and a bottom plane near the sand collection pit in the modification example shown in FIG. 15. It is explanatory drawing similar to FIG. 10 which shows the example of detection of the water level at the time of raising the height of a main trough.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A sand basin according to an embodiment of the present invention is disposed in a sewage treatment facility, and after sedimentation of sand contained in sewage such as sewage and rainwater, the settled sand is moved to a sand collecting pit and removed from the sewage. Things.

  FIG. 1 is a schematic sectional view of a sewage treatment plant including a sand basin according to an embodiment of the present invention.

  As shown in FIG. 1, the sewage treatment facility 1 includes a sand basin 2, a pump well 3, and a dam device 4. Sewage such as sewage and rainwater flows into the sewage treatment facility 1. The sewage treatment facility 1 receives sewage from the left side in FIG. The received sewage slowly flows toward the pump well 3 on the right side of the figure while sedimenting the sand contained in the sewage in the sand basin 2 (see the straight arrow shown in FIG. 1). Hereinafter, the upstream side of the received sewage flow is simply referred to as the upstream side, and the downstream side of the sewage flow is simply referred to as the downstream side.

  A dam device 4 is disposed upstream of the sedimentation basin 2 in the sewage treatment facility 1. The dam device 4 has an opening wall 41, an inflow gate 42, and a gate driving device 43. The wall surface on the downstream side of the opening wall 41 defines the upstream end of the sand basin 2. An inflow port 411 is open at a lower end portion of the opening wall 41. The inflow gate 42 is provided movably up and down along the wall surface on the upstream side of the opening wall 41. When the inflow gate 42 is at the lower position shown by the solid line in FIG. 1, the inflow gate 411 is closed to block the inflow of sewage upstream of the dam device 4 into the sand basin 2. When the inflow gate 42 is raised to the upper position indicated by the two-dot chain line in FIG. 1, the sewage is allowed to flow into the sand basin 2. The gate drive device 43 has a drive mechanism (not shown) therein, and moves the inflow gate 42 up and down in response to a command from a control device that controls the dam device 4. By this vertical movement, the inflow gate 42 is selectively disposed at any one of the upper position and the lower position.

  The sedimentation basin 2 is provided with a dust remover 5 arranged on the upstream side thereof, a sand collecting pit 6 arranged near the middle stream, and a sand pump 61 for carrying sand in the sand collecting pit 6 out of the pond. Have been. A sand pump 64 is connected to the sand pump 61. The sand sucked by the sand pump 61 is sent to a sand separator (not shown) provided outside the sand basin 2 through the sand pipe 64. The dust remover 5 is for removing contaminants (residues) mixed in the sewage flowing into the sand basin 2. The configuration of the sand basin 2 will be described later in detail.

  A pump well 3 is formed downstream of the sedimentation basin 2 in the sewage treatment facility 1. In the pump well 3, sewage from which sand has been removed by the sand basin 2 is stored. The bottom of the pump well 3 is the deepest part in the sewage treatment facility 1. The pump well 3 is provided with a water pump 31 and a water supply pump 33. The pump 31 moves the sewage stored in the pump well 3 to the outside of the sewage treatment facility 1. The water pump 32 is connected to a water pump 32. The sewage sucked by the water pump 31 is sent through the water pipe 32 to a sedimentation basin (not shown) for performing the next-stage sewage treatment. The water supply pump 33 is arranged at a position closer to the bottom of the pump well than the water pump 31 described above. A water supply pipe 34 is connected to the water supply pump 33. The sewage sucked by the water supply pump 33 is sent to each nozzle and the like to be described later through the water supply pipe 34. The waste water sucked by the water supply pump 33 is referred to as a fluid in the following description.

  FIG. 2 is a plan view of a sand basin corresponding to one embodiment of the present invention as viewed from above. In FIG. 2, the dust remover is indicated by a two-dot chain line rectangle. The flow direction of the sewage is indicated by a straight arrow.

  As shown in FIG. 2, the sand basin 2 includes a dust remover 5, a sand collection pit 6, a bottom plane 71, a small trough 72, a connection surface 73, between a left side wall Wa and a right side wall Wb. The pond has a trough 8 and a sand collecting means 9 and has a substantially rectangular shape in plan view. The bottom plane 71 and the small trough 72 correspond to an example of a bottom surface. The main trough 8 corresponds to an example of a groove. Hereinafter, the left side wall Wa and the right side wall Wb may be collectively referred to as a side wall W. A projecting wall 10 for supporting the dust remover 5 is provided at a central part in the pond width direction on the upstream side of the sand basin 2. The sand collecting pit 6, the bottom plane 71, the small trough 72, the connection surface 73, and the main trough 8 are provided at the bottom of the sand basin 2 respectively. This bottom plane 71 is formed by the surface of concrete cast at the bottom of the pond. The main trough 8 extends in the longitudinal direction from near the upstream end of the sand basin 2, and has an upstream first main trough 815 and an upstream second main trough 816 whose rear ends are connected to the sand collection pit 6, and A downstream main trough 82 extending in the longitudinal direction from near the downstream end of the pond 2 and having a rear end connected to the sand collecting pit 6. The upstream first main trough 815 corresponds to an example of a first groove, and the upstream second main trough 816 corresponds to an example of a second groove. This sedimentation basin 2 discharges fluid to the bottom plane 71 and the small trough 72 while draining sewage in the sedimentation basin 2, and collects the sand that has settled on the bottom plane 71 and the small trough 72. It is a method of sand basin. Hereinafter, the long side direction of the sand basin 2 is referred to as a longitudinal direction, and the short side direction is referred to as a pond width direction. This longitudinal direction is also an orthogonal direction orthogonal to the pond width direction.

  Above the sedimentation basin 2 (on the front side of the paper in FIG. 2), there are cases where a building, piping, and the like (not shown) are arranged. The pillar 11 may be formed adjacent to the sand basin 2 for the purpose of supporting the building or the like. In the sand basin 2 shown in FIG. 2, a pillar 11 is formed near the left side wall Wa. In the left side wall Wa, a portion serving as a base of the pillar 11 is formed with a convex wall portion Wa1 protruding toward the center in the pond width direction. Conversely, in the left side wall Wa, in a portion where the column 11 does not exist on the left side wall Wa, it can be said that a concave wall portion Wa2 that is recessed outward in the pond width direction is formed. An inclined wall portion Wa3 that is inclined with respect to the longitudinal direction and the pond width direction is formed at a portion connecting the convex wall portion Wa1 and the concave wall portion Wa2. In addition, since the pillar 11 does not exist near the right side wall Wb, the right side wall Wb is formed substantially linearly in plan view.

  The sand collecting pit 6 is disposed at a position slightly downstream of the longitudinal center of the sand basin 2. The sand collecting pit 6 is constituted by a concave portion formed at the center of the sand basin 2 in the pond width direction. A sand pump 61 and a stirring nozzle 62 are disposed inside the sand collecting pit 6. The sand collecting pit 6 is the deepest and deepest part in the sand basin 2. The sand collecting pit 6 has a rectangular shape in plan view. Between the side wall W and the sand collecting pit 6, there is a sand collecting pit inclined surface 6b which is inclined so as to gradually become deeper toward the sand collecting pit 6 located in the central portion in the pond width direction.

  A total of four stirring nozzles 62 are arranged near each corner of the sand collecting pit 6. The stirring nozzle 62 is for stirring the sand collected in the sand collecting pit 6. By discharging the fluid from the discharge port 62a of the stirring nozzle 62 when the sand pump 61 is driven, the suction efficiency of the sand collected in the sand collecting pit 6 by the sand pump 61 can be increased. Two pit sand collecting nozzles 63 are arranged at each end of the sand collecting pit inclined surface 6b in the pond width direction. By discharging the fluid from the discharge port 63a of the pit sand collecting nozzle 63 in a state where the water level of the sedimentation basin 2 is lower than a predetermined value, the sand accumulated on the sand collecting pit inclined surface 6b is removed. Can be collected.

  The bottom plane 71 has a first bottom surface 711 formed between the left side wall Wa and the upstream first main trough 815, and a second bottom surface 712 formed between the right side wall Wb and the upstream second main trough 816. , A third bottom surface 713 formed between the left side wall Wa and the downstream main trough 82, and a fourth bottom surface 714 formed between the right side wall Wb and the downstream main trough 82. The bottom plane 71 and the small trough 72 are connected to the main trough 8 at the center of the sand basin 2 in the pond width direction. The bottom plane 71 is inclined downward by about 5 degrees from the side wall W at the outside end in the pond width direction toward the main trough 8 so that the end of the main trough 8 is deepest. On the other hand, the bottom plane 71 is formed horizontally in the longitudinal direction. The small trough 72 is a gutter-shaped cross section having a U-shape, and extends in the pond width direction from the vicinity of the side wall W. A plurality of small troughs 72 are arranged at equal intervals in the longitudinal direction. In the present embodiment, a total of 56 small troughs 72 are arranged on each of one side and the other side in the pond width direction with the main trough 8 interposed therebetween. Similar to the bottom plane 71, the small trough 72 is also inclined about 5 degrees downward from the side wall W toward the main trough 8 so that the portion connected to the main trough 8 is located closest to the pond bottom. I have.

  The upstream first main trough 815, the upstream second main trough 816, and the downstream main trough 82 are grooves formed by a trough formed body made of a stainless steel plate and having an arc shape with a 円 circle in cross section. . However, the upstream first main trough 815, the upstream second main trough 816, and the downstream main trough 82 may be made of concrete integrally with the bottom plane 71. The upstream first main trough 815, the upstream second main trough 816, and the downstream main trough 82 are horizontally arranged over the entire length in the longitudinal direction from near the end of the sand basin to a portion connected to the sand collecting pit 6. ing.

  As shown in FIG. 2, the upstream first main trough 815 is provided on the left side wall Wa side with respect to the center in the pond width direction, and extends in the longitudinal direction. The upstream second main trough 816 is provided on the right side wall Wb side with respect to the center in the pond width direction, and extends in the longitudinal direction. The upstream first main trough 815 and the upstream second main trough 816 both have a total length of 10 m and have the same shape. The downstream ends of the first upstream main trough 815 and the second upstream main trough 816 are connected to the sand collection pit 6. An upstream trough first nozzle 831 having a trough first discharge port 831a is provided at an upstream end portion of the upstream first main trough 815 (a distal end portion of the upstream first main trough 815). An upstream trough second nozzle 832 having a trough second discharge port 832a is provided at an upstream end portion of the upstream second main trough 816 (a distal end portion of the upstream second main trough 816). The first trough outlet 831a and the second trough outlet 832a correspond to an example of a first outlet. The first cover member 13 is disposed inside the upstream first main trough 815. The second cover member 14 is disposed inside the upstream second main trough 816. The first covering member 13 and the second covering member 14 extend along the upstream first main trough 815 and the upstream second main trough 816, respectively. The total length of the first covering member 13 and the second covering member 14 is substantially the same as the total length of the upstream first main trough 815 and the upstream second main trough 816. As shown in FIG. 2, the first covering member 13 extends from the upstream of the trough first discharge port 831 a to a little downstream of the upstream first main trough 815 beyond the portion connected to the sand collecting pit 6. Are there. Discharging the sand accumulated in the upstream first main trough 815 to the sand collecting pit 6 by discharging the fluid from the trough first discharge port 831 a in a state where the wastewater is accumulated in the upstream first main trough 815. Can be. In addition, the second covering member 14 extends from the upstream of the trough second discharge port 832a to slightly downstream of the upstream second main trough 816 beyond the portion connected to the sand collecting pit 6. By discharging fluid from the trough second discharge port 832 a in a state where sewage is accumulated in the upstream second main trough 816, sand deposited on the upstream second main trough 816 is moved to the sand collecting pit 6. Can be. The movement of the sand in the upstream first main trough 815 and the upstream second main trough 816, and the detailed description of the first covering member 13 and the second covering member 14 will be described later.

  The downstream main trough 82 extends linearly in the longitudinal direction at the center in the width direction of the sand basin 2. The overall length of the downstream main trough 82 is 5 m. The upstream end of the downstream main trough 82 is connected to the sand collecting pit 6. A downstream trough nozzle 84 having a trough third discharge port 84a is provided at a downstream end of the downstream main trough 82 (a tip portion of the downstream main trough 82). The third trough outlet 84a also corresponds to an example of the first outlet. The third covering member 15 is disposed inside the downstream main trough 82. The third covering member 15 extends along the downstream main trough 82. The entire length of the third covering member 15 is substantially the same as the entire length of the downstream main trough 82. As shown in FIG. 2, the third covering member 15 extends from the downstream of the third trough discharge port 84a to slightly upstream of a portion of the downstream main trough 82 connected to the sand collecting pit 6. ing. By discharging the fluid from the third trough discharge port 84a in a state where the waste water is accumulated in the downstream main trough 82, the sand deposited on the downstream main trough 82 can be moved to the sand collecting pit 6. The movement of the sand in the downstream main trough 82 and the detailed description of the third covering member 15 will be described later.

  A projecting wall 10 for supporting the dust remover 5 is formed between the upstream first main trough 815 and the upstream second main trough 816 and on the upstream side of the sand basin 2. The projecting wall 10 is a concrete wall rising up to near the upper end of the sand basin 2. The connection surface 73 is located between the upstream first main trough 815 and the upstream second main trough 816 and at the pond bottom downstream of the protruding wall 10. That is, the connection surface 73 is formed in a portion between the upstream first main trough 815 and the upstream second main trough 816 except for a region where the protruding wall 10 is provided. The connection surface 73 includes a ridge 731 extending along the longitudinal direction, a first connection surface 732 connecting the ridge 731 and the first upstream main trough 815, a ridge 731 and an upstream second main trough 815. And a second connection surface 733 that connects the trough 816. The extending direction of the ridge 731 may not be completely the same as the longitudinal direction, and may be, for example, a direction slightly inclined in the pond width direction and the vertical direction with respect to the longitudinal direction. In addition, the ridgeline portion 731 may meander slightly in the pond width direction and the vertical direction. That is, “extending along the longitudinal direction” is a concept that includes some inclination or meandering.

  FIG. 3 is an XX cross-sectional view of the sand basin shown in FIG. 2. In FIG. 3, the dust remover is not shown.

  As shown in FIG. 3, the first connection surface 732 is an inclined surface that is inclined downward toward the first upstream main trough 815. The second connection surface 733 is an inclined surface that is inclined downward toward the second upstream main trough 816. The first connection surface 732 and the second connection surface 733 are formed by concrete surfaces. The inclination angle of the first connection surface 732 and the second connection surface 733 is about 45 degrees with respect to the horizontal plane. Since the connection surface is inclined, sand settling on the connection surface 73 can be collected in the upstream first main trough 815 or the upstream second main trough 816 without remaining on the connection surface 73. . If the inclination angle of the first connection surface 732 and the second connection surface 733 is 15 degrees or more, most of the sand that settles in the sewage in the sand basin 2 to the connection surface 73 due to its own weight. Slide down. In addition, when the inclination angle of the first connection surface 732 and the second connection surface 733 is set to 30 degrees or more, the sand that settles on the connection surface 73 is more likely to slide down the connection surface 73, which is preferable. However, if the inclination angle is too large, the thickness of the concrete forming the connection surface 73 in the pond width direction becomes too thin in the vicinity of the ridge line portion 731, and the ridge line portion 731 portion is easily damaged. Therefore, the angle of the ridge 731 formed by the first connection surface 732 and the second connection surface 733 is set such that the angle of the ridge 731 formed by the first connection surface 732 and the second connection surface 733 is 30 degrees or more. Is preferred. Note that one or both of the first connection surface 732 and the second connection surface 733 need not be formed of a single plane, and may be formed of, for example, a plurality of surfaces having different inclination angles. In this case, the inclination angles of all the plurality of surfaces may be set to 15 degrees or more. Alternatively, one of the first connection surface 732 and the second connection surface 733 may be a vertical surface, and the other may be an inclined surface. However, by making each of the first connection surface 732 and the second connection surface 733 an inclined surface as in the present embodiment, the sand is distributed to the upstream first main trough 815 and the upstream second main trough 816 to slide down. Therefore, it is preferable to make each of them inclined surfaces. In addition, as in the present embodiment, by providing the ridge 731 at the center portion between the upstream first main trough 815 and the upstream second main trough 816, the upstream first main trough 815 and the upstream second main trough 815 are provided. The amount of sand sliding down the main trough 816 can be made uniform. By doing so, accumulation of a large amount of sand on one of the upstream first main trough 815 and the upstream second main trough 816 is suppressed, so that the upstream first main trough 815 and the upstream It is possible to prevent the sand from being unable to be conveyed to the sand collection pit 6 due to the conveyance resistance of the sand in the second main trough 816.

  FIG. 4A is an enlarged view showing a portion Z in FIG. 3 in an enlarged manner, and FIG. 4B is a schematic perspective view showing a first covering member and an upstream trough first nozzle. In FIG. 4A, the horizontal direction in the figure is the pond width direction, and the direction perpendicular to the paper is the longitudinal direction. In FIG. 4A, hatching indicating a cross section of the first upstream main trough and the first cover member is omitted.

  FIG. 4A shows the first upstream main trough 815, the first upstream trough nozzle 831, and the first covering member 13. The upstream second main trough 816, the upstream trough second nozzle 832, and the second cover member 14, and the downstream main trough 82, the downstream trough nozzle 84, and the third cover member 15 are connected to the bottom plane 71. Or, since they have the same shape except for the connection surface 73, the description is omitted. As described above, the upstream first main trough 815 of the present embodiment has a 、 ２ circle cross-sectional shape. That is, it has an arc shape centered on the trough arc center 815c, which is the center in the radial direction. However, the cross-sectional shape of the upstream first main trough 815 is not limited to an arc shape, and may be a U-shape, a V-shape, or the like. The upstream-side first main trough 815 has a shape in which a cylindrical body having an inner diameter of 300 mm is cut off above, and opens upward over the entire length thereof. Hereinafter, this open portion may be referred to as a first trough opening 815b. The small trough 72 is connected to the first trough opening 815b, and the position of the first trough opening 815b in the height direction is the same as the position of the lower end of the small trough 72 in the height direction. The upper part 815a of the upstream first main trough 815 above the trough arc center 815c has a width in the pond width direction narrowing toward the first trough opening 815b at the upper end. Thus, even if the sand rises in the upstream first main trough 815, the upper portion 815a acts as a barb, and the soared sand can be returned into the upstream first main trough 815.

  The first cover member 13 has a 5/6 circular cross-sectional shape having an opening 13a at a lower end portion. That is, it has an arc shape centered on the covering arc center 13c, which is the center in the radial direction. The first cover member 13 is formed by shaping a stainless steel plate material having a thickness of 3 mm into a circular arc shape having an inner diameter of 150 mm. The opening 13a is provided over the entire length of the first cover member 13. The first cover member 13 partitions the internal space of the upstream first main trough 815. The space inside the first covering member 13 is a transport space FS that is a space covered by the first covering member 13. Since the first covering member 13 has an arcuate shape in which the upper part is closed, the sand that has settled down in the sand basin 2 toward the upper part of the first covering member 13 is formed by the upper part of the first covering member 13. Easy to slide down the outer surface of The sand that has slipped down is deposited below the upstream first main trough 815. In addition, the transport space FS of the first covering member 13 below the covering arc center 13c is narrower in the pond width direction toward the lower opening 13a. The first cover member 13 is supported by a support 131 (see FIG. 5) fixed to a concrete poured into the bottom of the sand basin 2 by a chemical anchor. The height position of the upper end of the first cover member 13 is located at substantially the same height as the first trough opening 815b. It is desirable that the height position of the upper end of the first cover member 13 be substantially the same height as the first trough opening 815b or a position lower than the first trough opening 815b. By setting this position, if the upstream first main trough 815 is filled with water, the inside of the first cover member 13 can be filled with water. By filling the inside of the first covering member 13 with water when the fluid is discharged into the water from the trough first discharge port 831a, a strong flow of the fluid can be created inside the first covering member 13. The opening 13a of the first cover member 13 is disposed below the center 815h of the upstream first main trough 815 in the height direction. With this arrangement, the opening 13a of the first cover member 13 and the sand deposited below the upstream first main trough 815 can be brought close to each other. The sand accumulated in the first main trough 815 can be easily sucked into the first cover member 13. Since both ends of the first cover member 13 in the extending direction are open, if the water level of the sand basin 2 is higher than the upper end position of the first cover member 13, the atmosphere may not remain in the transport space FS. Instead, the transport space FS is filled with sewage. In addition, the first covering member 13 of the present embodiment has an arc-shaped cross section, but may have a polygonal cross section, or a shape in which an arc and a linear portion are continuous. It may be. However, it is desirable that the cross-sectional shape of the upper portion of the first cover member 13 be an inclined surface that is inclined downward in the width direction of the groove. By making the upper part of the first covering member 13 an inclined surface, the sand that has settled on the upper part of the first covering member 13 can easily slide down the upper part. It becomes easy to accumulate below.

  The trough first discharge port 831a is arranged in the transport space FS in the first cover member 13. The trough first discharge port 831a has a long hole shape obtained by flattening the tip of a pipe having an inner diameter of 80 mm from above and below. The maximum opening length in the pond width direction of the trough first discharge port 831a is 117 mm, and the maximum height in the vertical direction is 18 mm. The trough first discharge port 831a may have another shape such as a perfect circle. However, by forming the trough first discharge port 831a in a flat shape, the fluid can be discharged in a wider range than that of a true circle before being crushed. The discharge flow rate of the fluid discharged from the trough first discharge port 831a is preferably set to 8 m / sec or more. If the speed is less than 8 m / sec, the flow velocity may be insufficient, and the sand may not be moved a predetermined distance. Further, it is desirable that the discharge pressure of the fluid discharged from the trough first discharge port 831a be 0.05 MPa or more and 0.3 MPa or less. The center of the trough first discharge port 831a coincides with the covering arc center 13c. The trough first discharge port 831a discharges the fluid in the longitudinal direction, which is the direction in which the first cover member 13 extends. As shown in FIG. 4B, the first covering member 13 extends in the fluid discharge direction so as to cover the trough first discharge port 831a and cover the fluid discharged from the trough first discharge port 831a. ing. An axis extending in the flow direction of the fluid discharged from the trough first discharge port 831a with the center of the trough first discharge port 831a (the center of the covering arc 13c) as a starting point is the virtual axis VL. That is, the first cover member 13 extends so as to cover the virtual axis VL extending in the longitudinal direction from the center of the trough first discharge port 831a. The extending direction of the first cover member 13 and the discharge direction of the fluid discharged from the trough first discharge port 831a do not need to completely coincide with the longitudinal direction, but by making them coincide, the sand is transported more efficiently. it can. In addition, even if the discharge direction of the fluid discharged from the trough first discharge port 831a and the extending direction of the first cover member 13 are slightly different, the discharged fluid is guided by the first cover member. The flow direction of the fluid coincides with the extending direction of the first cover member. Therefore, the virtual axis VL in this case is the extending direction of the first cover member. However, in this case, since the fluid may collide with the first cover member and the flow may be weakened, the discharge direction of the fluid discharged from the trough first discharge port 831a and the extending direction of the first cover member 13 are matched. It is desirable. Further, the center of the trough first discharge port 831a may be located at a position different from the covering arc center 13c. For example, the center may be arranged below the covering arc center 13c and above the opening 13a. However, the loss of the flow of the fluid discharged from the trough first discharge port 831a can be minimized by making the center of the trough first discharge port 831a coincide with the covering arc center 13c. On the other hand, by arranging the center of the trough first discharge port 831a below the covering arc center 13c, it is possible to increase the suction force for sucking sand into the transport space FS from the opening 13a. Therefore, it is desirable that the center of the trough first discharge port 831a is disposed between the center 13c of the covering arc and the opening 13a of the first covering member 13.

  By discharging the fluid from the trough first discharge port 831a into the transport space FS, a fluid flow is generated in the transport space FS inside the first cover member 13. Then, a pressure difference occurs between the transport space FS and the outside of the first cover member 13 due to the flow of the fluid. That is, a negative pressure is generated in the transport space FS in which the flow of the fluid is generated. The sand deposited in the upstream first main trough 815 is sucked into the transport space FS from the opening 13a by the negative pressure as indicated by the curved arrow shown in FIG. Further, the fluid discharged from the trough first discharge port 831a is prevented from diffusing in the radial direction orthogonal to the longitudinal direction by the first covering member 13, so that the flow is maintained in the transport space FS over a long distance. The sucked sand is transported toward the sand collecting pit 6 by the flow of the fluid generated in the transport space FS. In this embodiment, by forming the transport space FS by the first cover member 13, the fluid can be used for transporting sand without impairing the flow of the fluid discharged from the trough first discharge port 831a. As a result, the sand accumulated in the first upstream main trough 815 can be efficiently transported toward the sand collection pit 6. As described above, the pond width direction becomes narrower toward the lower opening 13a below the covering arc center 13c in the transport space FS. By making the width of the opening 13a narrow in the pond width direction, the sand conveyed in the transport space FS is less likely to leak out of the transport space FS. Further, since the fluid in the transport space FS hardly flows out of the transport space FS, the flow of the fluid can be maintained for a long distance, and the sand can be moved farther. Then, the negative pressure in the transport space FS can be easily maintained even at a position distant from the trough first discharge port 831a.

  As shown in FIG. 2, two dust removers 5 are provided on the upstream side of the sand basin 2 in the pond width direction with the protruding wall 10 interposed therebetween. In other words, one dust remover 5 is disposed between the left side wall Wa and the protruding wall 10 and one between the right side wall Wb and the protruding wall 10. These two dust removers 5, 5 have the same configuration. The dust remover 5 is for removing contaminants (residues) mixed in the sewage flowing into the sand basin 2. One dust remover 5 shown in the upper part of FIG. 2 is supported by the left side wall Wa and the protruding wall 10, and the other dust remover 5 shown in the lower part of FIG. It is supported by the protruding wall 10. By arranging the two dust removers 5 and 5 side by side in the pond width direction, the width of each dust remover 5 in the pond width direction can be shortened. By reducing the width of the dust remover 5 in the pond width direction, the strength of the dust remover 5 is increased, and even if the amount and flow rate of the wastewater flowing into the sand basin 2 due to heavy rain or the like increase, the dust remover 5 is damaged. Can be suppressed.

  FIG. 5 is an AA cross-sectional view of the sand basin shown in FIG. 2. In FIG. 5, the pillar and the sand pump are not shown, and the shape of the protruding wall is shown by a two-dot chain line. The flow direction of the sewage is indicated by a straight arrow. The water surface WL of the sand basin fluctuates depending on the amount of rain and sewage flowing in, and the like. Located at medium height.

  As shown in FIG. 5, the dust remover 5 has an endless chain 51, a plurality of rakes 52 attached to the endless chain 51 at intervals, and a filtration screen 53. The endless chain 51 is provided in an upright state on both sides in the width direction of the sand basin 2, and is wound around a ground sprocket 511 and a bottom sprocket 512. The upper part of the endless chain 51 and the ground sprocket 511 are arranged on the ground part of the sand basin 2. When the ground side sprocket 511 is driven by a motor (not shown) in the rotation direction shown by the arcuate arrow R when the water surface WL is in the normal state, the endless chain 51 circulates, and the rake 52 enters and exits the water. FIG. 5 shows the water surface WL in a normal state. The protruding wall 10 protrudes above the water surface WL. However, when the projecting wall 10 is formed for a purpose other than supporting the dust remover 5, the projecting wall 10 may be lower than the water surface WL. The filtration screen 53 is arranged downstream of the endless chain 51. In the filtration screen 53, bars extending in the vertical direction are arranged at predetermined intervals (for example, 25 mm to 75 mm) in the pond width direction, and block the passage of contaminants having a size equal to or more than the predetermined interval. The contaminants blocked by the filtration screen 53 are scooped up by the rake 52, and the contaminated matters are placed on a conveyor such as a belt conveyor (not shown) on the ground side. In addition, the lower end of the pond bottom side sprocket 512 and the filtration screen 53 are arranged more upstream than the bottom plane 71 and the main trough 8. On the other hand, the upper ends of the ground-side sprocket 511 and the filtration screen 53 are located above the bottom plane 71 and the upstream portion of the main trough 8. That is, the upper portions of the endless chain 51 and the filtration screen 53 overlap the bottom plane 71 and the main trough 8 in the longitudinal direction. Note that FIG. 5 also shows a support 151 that supports the third covering member 15.

  The sand collecting means 9 includes a first nozzle header 9a, a second nozzle header 9b, a third nozzle header 9c disposed on the left side wall Wa side of the sand basin 2, and a fourth nozzle header 9d disposed on the right side wall Wb side. , A fifth nozzle header 9e, and a sixth nozzle header 9f (see FIG. 2). FIG. 5 shows the sand collecting means 9 on the left side wall Wa side. Since the sand collecting means 9 on the right side wall Wb side has the same configuration, the description of the sand collecting means 9 on the right side wall Wb side is omitted. Each of the first nozzle header 9a, the second nozzle header 9b, and the third nozzle header 9c has ten sand collecting nozzles 91, a supply pipe 92, and a mother pipe 93. The supply pipe 92 is arranged to face the left side wall Wa, and extends in the longitudinal direction. The mother pipe 93 has a single pipe 931 extending above the sand basin 2 and a branch pipe 932 connected to an end of the single pipe 931 on the bottom side of the pond. The single pipe 931 and the branch pipe 932 are fixed to the left side wall Wa by a fixture (not shown).

  FIG. 6 is an enlarged view showing a portion B in FIG. 5 in an enlarged manner. In FIG. 6, the flow direction of the sewage is indicated by a straight arrow. FIG. 6 also shows the side wall. FIG. 6 shows one of the six nozzle headers, but the other five nozzle headers have the same configuration as the nozzle header shown in FIG.

  As shown in FIG. 6, the branch pipe 932 is connected to the single pipe 931 by a flange joint 933. The branch pipe 932 is bifurcated below the portion connected to the single pipe 931, and the branched portions extend in the longitudinal direction of the sand basin 2. A supply pipe 92 to which a lap joint 934 is fixed is connected to a tip portion of the branch portion. In the present embodiment, for one mother pipe 93, an upstream supply pipe 921 disposed upstream of the branch pipe 932, a downstream supply pipe 923 disposed downstream of the branch pipe 932, Three supply pipes 92 of an intermediate supply pipe 922 arranged between the upstream supply pipe 921 and the downstream supply pipe 923 are provided. The other ends of the upstream supply pipe 921 and the downstream supply pipe 923 opposite to the one end connected to the branch pipe 932 are closed by a lid 97. Both ends of the intermediate supply pipe 922 are connected to the branch pipe 932.

  Three sand collecting nozzles 91 are fixed to the upstream supply pipe 921 and the downstream supply pipe 923 at equal intervals, respectively. Further, four sand collecting nozzles 91 are fixed to the intermediate supply pipe 922 at equal intervals. The intervals at which these ten sand collecting nozzles 91 are arranged are all arranged at equal intervals. In addition, the interval between the most downstream sand collecting nozzle 91 of the first nozzle header 9a (see FIG. 2) and the most upstream sand collecting nozzle 91 of the second nozzle header 9b is also the same as that of the ten sand collecting nozzles described above. This is the same interval as the interval. That is, the sand collecting nozzles 91 are all arranged at equal intervals in the longitudinal direction of the sand basin 2. Note that the number of the sand collecting nozzles 91 arranged in each supply pipe 92 may be determined as appropriate according to factors such as the length of the supply pipe 92. A discharge port 911 is formed at the tip of each sand collecting nozzle 91. The outlet 911 corresponds to an example of a second outlet. Out of the outlets 911, the outlets 911 provided in the first nozzle header 9a (see FIG. 2) and the second nozzle header 9b correspond to an example of one side outlet, and the fourth nozzle header 9d and the fifth The ejection port 911 provided in the nozzle header 9e (see FIG. 2) corresponds to an example of the other ejection port. The fluid is discharged from the discharge port 911 into the atmosphere while the water level of the settling basin 2 is lowered below a predetermined value and the sand and the discharge port 911 deposited on the bottom flat surface 71 and the small trough 72 are exposed to the atmosphere. By doing so, the sand deposited on the bottom plane 71 and the small trough 72 shown in FIG. 2 and FIG. The discharge pressure of the fluid ejected from one discharge port 911 is, for example, 0.005 MPa, and preferably from 0.0002 MPa to 0.005 MPa. That is, the discharge pressure of the fluid discharged from the discharge port 911 is lower than the discharge pressure (0.05 MPa or more and 0.3 MPa or less) of the fluid discharged from the trough first discharge port 831a. In this way, an inexpensive and small-sized water supply pump 33 for supplying the fluid can be used while securing a flow rate that allows the sand deposited on the bottom plane 71 and the small trough 72 to flow through the main trough 8. it can.

  In the supply pipe 92, a portion facing the convex wall portion Wa1 and a portion facing the concave wall portion Wa2 have different distances from the supply pipe 92 to the left side wall Wa. That is, the supply pipe 92 has a first region 92a extending from the left side wall Wa at a first interval in the pond width direction and a second region extending from the left side wall Wa at a second interval in the pond width direction. There is an area 92b. Further, in the sand basin 2 of the present embodiment, since the inclined wall portion Wa3 is formed at a portion connecting the convex wall portion Wa1 and the concave wall portion Wa2, the supply pipe 92 includes the first region and the first region. There is a third area 92c that is an area connecting the second areas. Each sand collecting nozzle 91 and its discharge port 911 are arranged so as to face the left side wall Wa, and are fixed to the supply pipe 92 side by side in the longitudinal direction. In the second nozzle header 9b shown in FIG. 6, the upstream supply pipe 921 is arranged to face the convex wall Wa1. That is, the region where the upstream supply pipe 921 is located corresponds to the first region 92a. On the other hand, a region of the intermediate supply pipe 922 where the discharge port 911 is located at a position closest to the upstream supply pipe 921 is disposed to face the inclined wall Wa3. That is, the region corresponds to the third region 92c. Further, in the intermediate supply pipe 922, a region where three discharge ports 911 are arranged from the downstream supply pipe 923 side, and in the downstream supply pipe 923, two discharge ports 911 from the intermediate supply pipe 922 side are arranged. The arranged area is arranged to face the recessed wall Wa2. That is, those areas correspond to the second areas 92b. In the downstream supply pipe 923, a region where the most downstream discharge port 911 is arranged is arranged to face the inclined wall Wa3. That is, the region corresponds to the third region 92c. A direction changing unit using a lap joint 934 is provided between these regions.

  FIG. 7A is a cross-sectional view for explaining a state in which one pipe provided with a lap joint is connected to the other pipe. FIG. 7B is a cross-sectional view in which the lap joint is loosened by loosening bolts. It is sectional drawing for demonstrating the state in which one provided pipe | tube was rotatable centering on the axial direction with respect to the other pipe | tube. In FIG. 7, a supply pipe is shown as one pipe and a branch pipe is shown as the other pipe. However, the same configuration can be applied to a case where supply pipes are connected by providing a lap joint.

  As shown in FIGS. 7A and 7B, a lap joint 934 is welded to an end of the supply pipe 92. The lap joint 934 includes a small-diameter portion 934a welded to the supply pipe 92 and a large-diameter section 934b disposed on the branch pipe 932 side. The outer diameter of the small diameter portion 934a is formed to be the same as the outer diameter of the supply pipe 92. A free flange 935 is arranged on the outer periphery of the lap joint 934. The free flange 935 has a ring shape whose inner diameter is slightly larger than the outer diameter of the lap joint 934. In the free flange 935, eight free flange through holes 935a into which the bolts 95 are inserted are formed uniformly in the circumferential direction. The free flange 935 is coupled to the lap joint 934 so as to be rotatable with respect to the lap joint 934 and to be movable in the axial direction. A fixed flange 9322 is welded to an outer diameter portion of the tip of the branch pipe 932. The fixed flange 9322 is formed with eight fixed flange through holes 9322a into which the bolts 95 are inserted, similarly to the free flange 935. A ring-shaped packing 94 is arranged between the lap joint 934 and the fixing flange 9322. The packing 94 is for preventing the fluid passing through the supply pipe 92 and the branch pipe 932 from leaking when the supply pipe 92 and the branch pipe 932 are joined.

  The bolt 95 is inserted into the fixed flange through hole 9322 a of the fixed flange 9322 and the free flange through hole 935 a of the free flange 935. In a state where the bolt 95 and the nut 96 are tightened, the lap joint 934 is sandwiched by the fixing flange 9322 and the free flange 935 together with the packing 94 as in the supply pipe 92 shown in FIG. The supply pipe 92 is fixed to 932. On the other hand, when the bolt 95 is loosened, the supply pipe 92 becomes rotatable about the axial direction with respect to the branch pipe 932 as in the supply pipe 92 shown in FIG. 7B. That is, in the present embodiment, since the mother pipe 93 (see FIG. 5) and the supply pipe 92 are connected using the lap joint 934 and the free flange 935, the supply pipe 92 is centered on its axial direction. It is configured to be able to rotate steplessly with respect to the mother pipe 93. Note that the supply pipe 92 can be connected to the mother pipe 93 so as to be able to rotate in a stepless manner even if another loose flange such as a loose flange is used instead of the lap joint 934.

  Further, as shown in FIG. 6, between the discharge port 911 disposed in the first area 92a and the discharge port 911 disposed in the third area 92c, and between the discharge port 911 disposed in the second area 92b and the third port 911. A lap joint 934 is arranged between the discharge ports 911 arranged in the region 92c. Accordingly, the discharge ports 911 arranged in each of the first area 92a, the second area 92b, and the third area 92c are configured to be able to rotate steplessly around the axial direction of the supply pipe 92 independently of each other. With this configuration, the discharge direction of the fluid at the discharge port 911 of each region can be set according to the distance from the supply pipe 92 to the left side wall Wa. The lap joint 934 disposed between the discharge port 911 disposed in the first area 92a and the discharge port 911 disposed in the third area 92c corresponds to an example of a first direction changing unit. A lap joint 934 disposed between the discharge port 911 disposed in the second area 92b and the discharge port 911 disposed in the third area 92c corresponds to an example of a second direction changing unit. In the first region 92a of the supply pipe 92 shown in FIG. 6, the discharge directions of the fluids at the three discharge ports 911 arranged in the first region 92a can be changed at a time. Can be easily adjusted. In the supply pipe 92 shown in FIG. 6, in the second area 92b, the three discharge ports 911 arranged in the intermediate supply pipe 922 can be changed collectively, and the two discharge ports 911 arranged in the downstream supply pipe 923 can be changed. Since the outlets 911 can be changed collectively, the ejection direction in the second area 92b can be easily adjusted. That is, the lap joint 934 in a case where the discharge directions of the plurality of discharge ports 911 can be changed collectively corresponds to an example of a collective direction change unit. In addition, when the longitudinal direction of the third region 92c is short and the discharge port 911 does not exist in the third region 92c, or when the third region 92c does not exist, the wrapping is performed between the first region 92a and the second region 92b. What is necessary is just to arrange the joint 934.

  FIG. 8A is a cross-sectional view taken along the line CC of FIG. FIG. 8A also shows the side wall and the bottom plane.

  As described above, the left side wall Wa has the convex wall portion Wa1 and the concave wall portion Wa2. In FIG. 8A, the convex wall portion Wa1 is indicated by a solid line, and the concave wall portion Wa2 is indicated by a two-dot chain line. At the discharge port 911 indicated by a solid line in FIG. 8A, the discharge direction of the fluid is directed to the direction toward the center in the pond width direction rather than the direction (vertical direction) from directly below the center of the supply pipe 92. At this discharge port 911, the angle θ at which the fluid is discharged to the bottom plane 71 is set to about 50 degrees. By setting the angle θ to about 50 degrees, the fluid that has reached the bottom plane 71 can be divided into a direction toward the main trough 8 and a direction toward the convex wall Wa1. The angle θ may be any angle at which the discharged fluid diverges in the direction toward the main trough 8 and the direction toward the convex wall Wa1, and more specifically, 30 degrees or more and 60 degrees or less with respect to the bottom plane 71. I just need. By setting this angle, when the supply pipe 92 and the left side wall Wa are close to each other like the convex wall part Wa1, that is, in the first region 92a (see FIG. 6), the bottom between the supply pipe 92 and the left side wall Wa is set. The shunted fluid also reaches the sand deposited on the flat surface 71, and the sand can flow. Further, since the direction of discharge of the fluid is more toward the main trough 8 at the center of the pond width direction than the vertical direction of the supply pipe 92, the force of the fluid flowing toward the main trough 8 is greater than the force of the fluid flowing toward the left side wall Wa. Becomes stronger. Due to the momentum of the fluid, the sand deposited on the bottom flat surface 71 between the supply pipe 92 and the main trough 8 can be efficiently flowed toward the main trough 8.

  On the other hand, the supply pipe 92 and the left side wall Wa are separated from each other at the concave wall portion Wa2 indicated by the two-dot chain line in FIG. For this reason, in the discharge direction of the discharge port 911 shown by the solid line, even if the discharged fluid diverges, it does not reach the vicinity of the recessed wall portion Wa2, or even if it reaches, only a very small amount of the fluid. If the amount of the fluid that reaches the vicinity of the concave wall portion Wa2 is small, the sand that is located between the supply pipe 92 and the concave wall portion Wa2 and that is near the concave wall portion Wa2 cannot be sufficiently flown.

  In the present embodiment, since the supply pipe 92 is configured to be rotatable around its axial direction, the discharge direction of the fluid from the sand collecting nozzle 91 can be freely changed. In FIG. 8A, a sand collecting nozzle 91 in which the discharge direction of the fluid discharged from the discharge port 911 is adjusted corresponding to the position of the recessed wall portion Wa2 is indicated by a two-dot chain line. In the sand collecting nozzle 91 indicated by the two-dot chain line, the discharge direction of the fluid discharged from the discharge port 911 is more outward in the pond width direction than the direction (vertical direction) from directly below the center of the supply pipe 92. I have. By adjusting the discharge direction of the fluid discharged from the discharge port 911 according to the distance from the supply pipe 92 to the left side wall Wa, the supply pipe 92 and the left side wall Wa are adjusted as in the second region 92b (see FIG. 6). Even if is separated, the sand deposited near the left side wall Wa can sufficiently flow. In the present embodiment, the mother pipe 93 and the supply pipe 92 or the supply pipes 92 are connected to each other using the lap joint 934 and the free flange 935. Can be rotated in stages. Since the rotation can be performed in a stepless manner, the supply pipe 92 (third region 92c) located at a position facing the inclined wall portion Wa3 (see FIG. 2) between the convex wall portion Wa1 and the concave wall portion Wa2 has the configuration shown in FIG. 3), the discharge direction of the fluid may be set to an intermediate direction between the discharge direction of the sand collection nozzle 91 indicated by the solid line and the discharge direction of the sand collection nozzle 91 indicated by the two-dot chain line.

  Further, in the present embodiment, since the main pipe 93 is provided with the branch pipe 932, a total of three upstream supply pipes 921, intermediate supply pipes 922, and downstream supply pipes 923 are provided for one mother pipe 93. Are connected side by side in the longitudinal direction of the sand basin 2. In contrast, when there is no branch pipe 932 and the supply pipe 92 is connected to the single pipe 931, at most two supply pipes 92 are provided in the longitudinal direction of the sand basin 2 with respect to one mother pipe 93. can not connect. That is, there are two supply pipes 92 extending from the tip of the mother pipe 93 to the upstream side of the sand basin 2 and the supply pipe 92 extending to the downstream side. The discharge direction of the fluid discharged from the discharge port 911 can be set for each supply pipe 92. Therefore, when the branch pipe 932 is provided, the discharge direction of the fluid discharged from the discharge port 911 can be adjusted at many locations in the longitudinal direction of the sand basin 2 as compared with the case where the branch pipe 932 is not provided. It is possible to flexibly cope with the shape of the side wall W.

  FIG. 8B is a cross-sectional view similar to FIG. 8A for explaining a change in the discharge direction by the sand collecting nozzle. FIG. 8B also shows a side wall and a bottom plane.

  As shown in FIG. 8B, the sand collecting nozzle 91 is bent at an intermediate portion, and in a state shown by a solid line, is formed in an inverted letter shape when viewed in the longitudinal direction. Since the sand collecting nozzle 91 indicated by the solid line is rotated by 180 degrees about the axis L of the attachment portion with the supply pipe 92 because it is formed in an inverted letter shape, as indicated by the two-dot chain line. In addition, the discharge direction of the fluid can be changed from the center in the pond width direction to the outside in the pond width direction. By forming the sand collecting nozzle 91 in an inverted letter shape and making the connecting portion between the sand collecting nozzle 91 and the supply pipe 92 rotatable, the discharge direction of the fluid can be changed for each discharge port 911. become. That is, the configuration of the sand collecting nozzle 91 and the configuration in which the sand collecting nozzle 91 can rotate with respect to the supply pipe 92 in the present embodiment correspond to an example of an individual direction changing unit.

  FIG. 9 is a diagram of a water supply system in a sewage treatment facility.

  As shown in FIG. 9, the water supply pump 33 feeds the water in the pump well 3 with the stirring nozzle 62, the sand collecting nozzle 63 for pits, the first upstream trough nozzle 831, the second upstream nozzle 832, the downstream trough nozzle 84, And it is selectively supplied to the sand collecting means 9. The water supply pipe 34 connected to the water supply pump 33 has a supply switching valve Va for switching whether or not to supply the fluid to each of the nozzles and the sand collecting means 9, and a pump well for supplying the fluid sucked up by the water supply pump. 3 is provided with a relief switching valve Vb for switching whether or not to return to 3. In a pipeline between the supply switching valve Va and the stirring nozzle 62, a stirring switching valve Vc for switching whether or not to supply a fluid to the stirring nozzle 62 is provided. In a pipeline between the supply switching valve Va and the pit sand collection nozzle 63, a pit sand collection switching valve Vd for switching whether or not to supply a fluid to the pit sand collection nozzle 63 is provided. An upstream trough first switching valve Ve1 that switches whether or not to supply the fluid to the upstream trough first nozzle 831 is provided in a pipeline between the supply switching valve Va and the upstream trough first nozzle 831. In a pipeline between the supply switching valve Va and the upstream trough second nozzle 832, an upstream trough second switching valve Ve2 for switching whether or not to supply the fluid to the upstream trough second nozzle 832 is provided. In a pipeline between the supply switching valve Va and the downstream trough nozzle 84, a downstream trough switching valve Vf that switches whether to supply the fluid to the downstream trough nozzle 84 is provided. In addition, in each pipeline between the supply switching valve Va and each nozzle header 9a, 9b, 9c, 9d, 9e, 9f of the sand collecting means 9, each nozzle header 9a, 9b, 9c, 9d, 9e, 9f is provided. Sand collecting switching valves Vg1, Vg2, Vg3, Vg4, Vg5, Vg6 for switching whether or not to supply a fluid are provided, respectively. These switching valves are constituted by solenoid valves, and the opening and closing of the valves are controlled by a control device (not shown).

  FIG. 10 is an explanatory diagram showing a water level of a sand basin and a water level sensor.

  As shown in FIG. 10, a water level sensor 99 is disposed in the sand collection pit 6 of the sand basin 2. The water level sensor 99 includes a first high water level HHWL in which the water level of the sand basin 2 is above the bottom plane 71, and an upper end position 13b of each of the covering members 13, 14, 15 (below the first high water level HHWL). The upper end 8b of the trough 8, that is, the same position as the opening of the main trough 8, and the lower end 72b of the small trough 72 are also substantially the same position.) And the second high water level THWL above and the respective cover members 13, 14. , 15 near the upper end position 13b, a first intermediate water level TMWL between the second high water level THWL and the first low water level TLWL, and a main lower trough 8 below the upper end 8b. The third high water level HWL above the lower end 8a of the trough 8, the second low water level LWL below the sand collecting pit 6, and the second high water level LWL between the third high water level HWL and the second low water level LWL Intermediate water level MWL and second low water level LWL And outputs to detect respectively that it has become to a lower interlock level LLWL.

  FIG. 11 is a flowchart showing a flow of the sand removing operation in the sewage treatment facility.

  The operation of the sewage treatment plant 1 having the above-described configuration will be described with reference to FIGS. The sewage treatment facility 1 performs an operation of removing the deposited sand at a predetermined time when the sand has been deposited to some extent at the bottom of the sand basin 2. This time may be regular, for example, once a month, or may be when the total flow rate of the sewage flowing into or discharged from the sand basin 2 becomes constant. In the sand removing operation, first, the inflow gate 411 of the dam device 4 shown in FIG. 1 is driven to close the inflow port 411, and the inflow of sewage into the sand basin 2 is stopped (step S1). Next, the water pump 31 is driven to lower the water level of the sand basin 2. When the water level of the pump well 3 drops to a predetermined value, the pump 31 is stopped (step S2). Then, the water supply pump 33 is driven for several minutes to discharge the fluid from the stirring nozzle 62 shown in FIG. After stopping the water supply pump, the sand pump 61 is driven. When the water level of the sedimentation basin 2 drops to the second high water level THWL (see FIG. 10), the water supply pump 33 is driven again to discharge the fluid from the stirring nozzle 62 shown in FIG. Then, the drive of the sand pump 61 is set to the operation mode A described below (step S3). The sand pump 61 operates in one of the operation mode A and the operation mode B. In the operation mode A, the driving is stopped according to the output indicating the first low water level TLWL (see FIG. 10) from the water level sensor 99, and the driving is restarted according to the output indicating the second high water level THWL (see FIG. 10). Is automatically executed. This operation mode A is a mode in which the water level is maintained so as to be higher than the upper end position 13b of each of the covering members 13, 14, 15. Accordingly, in the operation mode A, each of the covering members 13, 14, 15, the first trough discharge port 831a, the second trough discharge port 832a, and the third trough discharge port 84a are in a state of being submerged in water. In the operation mode B, the operation of the sand pump 61 is stopped according to the output indicating the second low water level LWL (see FIG. 10) from the water level sensor 99, and the output is changed to the output indicating the third high water level HWL (see FIG. 10). Control for resuming driving is automatically executed accordingly. The operation mode B is a mode in which the water level is maintained below the lower end 72b of the small trough 72. Therefore, the bottom plane 71, the small troughs 72, the sand deposited thereon, and the sand collecting means 9 are exposed to the atmosphere. On the other hand, the water supply pump 33 shown in FIG. 1 is continuously driven until the sand removing operation ends. The sand conveyed to the sand collecting pit 6 is carried by the sand pump 61 to a sand separator (not shown) outside the sand basin 2 when the sand pump 61 is driven. When the water level sensor 99 detects that the water level has reached the first high water level HHWL or the interlock water level LLWL (see FIG. 10), it is considered that some abnormality has occurred. Stop the sand removal operation.

  Thereafter, fluid is discharged from the stirring nozzle 62, the upstream trough first nozzle 831 and the upstream trough second nozzle 832 shown in FIG. 2 for a certain period of time, and the sand deposited on the upstream first main trough 815 and the upstream second main trough 816 Flow into the sand collecting pit 6 (step S4). In this step S4, the fluid may be ejected from one of the upstream trough first nozzle 831 and the upstream trough second nozzle 832 for a certain time, and then the fluid may be ejected from the other for a certain time. When the discharge of the fluid from the stirring nozzle 62, the upstream trough first nozzle 831, and the upstream trough second nozzle 832 is stopped, the sand pump 61 is switched to the operation mode B (step S5). Then, when it is detected that the water level is equal to or lower than the third high water level HWL, the fluid is discharged from the discharge port 911 (see FIG. 6) provided in the fifth nozzle header 9e. By this discharge, the sand deposited on the bottom flat surface 71 and the small trough 72 between the right side wall Wb near the fifth nozzle header 9e and the upstream second main trough 816 is transferred to the upstream second main trough. 816. After a lapse of a predetermined time during which the sand can be sufficiently flown, the sand pump 61 is switched to the operation mode A while continuing to discharge the fluid from the discharge port 911 provided in the fifth nozzle header 9e. Thereafter, when it is detected that the water level is equal to or higher than the first intermediate water level TMWL, the discharge of the fluid from the discharge port 911 provided in the fifth nozzle header 9e is stopped (Step S6). Then, the fluid is discharged from the stirring nozzle 62 and the upstream trough second nozzle 832 for a certain period of time, and the sand flowing in the upstream second main trough 816 is sent to the sand collecting pit 6 (step S7). When the discharge of the fluid from the stirring nozzle 62 and the upstream trough second nozzle 832 is stopped, the sand pump 61 is switched to the operation mode B (step S8). Then, when it is detected that the water level is equal to or lower than the third high water level HWL, the fluid is discharged from the discharge port 911 provided in the second nozzle header 9b. After a lapse of a predetermined time during which sand accumulated on the bottom flat surface 71 and the small trough 72 between the left side wall Wa near the second nozzle header 9b and the upstream first main trough 815 has passed, the second The sand pump 61 is switched to the operation mode A while continuously discharging the fluid from the discharge port 911 provided in the two-nozzle header 9b. Thereafter, when it is detected that the water level is equal to or higher than the first intermediate water level TMWL, the discharge of the fluid from the discharge port 911 provided in the second nozzle header 9b is stopped (Step S9). Of these, the discharge port 911 near the concave wall portion Wa2 and the inclined wall portion Wa3 changes the fluid discharge direction so that a certain amount of fluid reaches the left side wall Wa according to the distance from the supply pipe 92 to the left side wall Wa. Has been adjusted. Therefore, all the sand deposited on the bottom flat surface 71 and the small trough 72 between the left side wall Wa near where the second nozzle header 9b is arranged and the upstream first main trough 815 is transferred to the upstream first main trough. 815. After the discharge of the fluid from the discharge port 911 provided in the second nozzle header 9b is stopped, the fluid is discharged from the stirring nozzle 62 and the upstream trough first nozzle 831 for a certain period of time, and is caused to flow to the upstream first main trough 815. The sand is sent to the sand collecting pit 6 (step S10). When the discharge of the fluid from the stirring nozzle 62 and the upstream trough second nozzle 832 is stopped, the sand pump 61 is switched to the operation mode B (step S11). Thereafter, similarly to the operations in steps S6 to S10 described above, the fluid is discharged from the discharge port 911 provided in the fourth nozzle header 9d and the mode is switched to the operation mode A after a lapse of a predetermined time (step S12). 62 and discharge of fluid from the upstream trough second nozzle 832 (step S13), switching to the operation mode B (step S14), discharge of fluid from the discharge port 911 provided in the first nozzle header 9a and elapse of a predetermined time By switching to the operation mode A later (step S15) and discharging the fluid from the agitation nozzle 62 and the upstream trough first nozzle 831 (step S16) in this order, the bottom of the pond upstream of the sand collection pit 6 All the deposited sand is carried out of the sand basin 2. The order in which the fluids are ejected from the nozzle headers 9a, 9b, 9d, 9e may be in any order. However, when the sand deposited on the side far from the sand collecting pit 6 flows first, the sand deposited on the side near the sand collecting pit 6 together with the sand to be washed down collapses into the main trough 8 and the sand is deposited in the main trough. May accumulate, making it difficult to send the sand in the main trough 8 to the sand collecting pit 6. Therefore, after the fluid is discharged from the second nozzle header 9b and the fifth nozzle header 9e on the side closer to the sand collecting pit 6, the fluid is discharged from the first nozzle header 9a and the fourth nozzle header 9d far from the sand collecting pit 6. Is desirably discharged.

  After removing the sand deposited on the upstream side by the above-described operation, the fluid discharged from the stirring nozzle 62 and the downstream trough nozzle 84 for a certain period of time causes the sand deposited on the downstream main trough 82 to flow into the sand collecting pit 6 (step S1). S17). After stopping the discharge of the fluid from the stirring nozzle 62 and the downstream trough nozzle 84, the sand pump 61 is switched to the operation mode B (step S18). Then, when detecting that the water level is equal to or lower than the third high water level HWL, the fluid is discharged from the discharge port 911 provided in the sixth nozzle header 9f. After a lapse of a predetermined time during which the sand deposited on the bottom flat surface 71 and the small trough 72 between the right side wall Wb near the sixth nozzle header 9f and the downstream main trough 82 can sufficiently flow, the sixth nozzle The sand pump 61 is switched to the operation mode A while the fluid discharge from the discharge port 911 provided in the header 9f is continued. Thereafter, when it is detected that the water level is equal to or higher than the first intermediate water level TMWL, the discharge of the fluid from the discharge port 911 provided in the sixth nozzle header 9f is stopped (Step S19). Then, the fluid is discharged from the stirring nozzle 62 and the downstream main trough 82 for a certain period of time, and the sand flowing in the downstream main trough 82 is sent to the sand collecting pit 6 (step S20). When the discharge of the fluid from the stirring nozzle 62 and the downstream main trough 82 is stopped, the sand pump 61 is switched to the operation mode B (step S21). Then, similarly to the operations in steps S19 and S20 described above, the fluid is discharged from the discharge port 911 provided in the third nozzle header 9c and the mode is switched to the operation mode A after a lapse of a predetermined time (step S22). And the discharge of the fluid from the downstream trough nozzle 84 (step S23), the sand deposited on the bottom of the pond downstream from the sand collecting pit 6 is all carried out of the sand basin 2. Finally, by discharging a fluid from the pit sand collecting nozzle 63, the sand deposited on the sand collecting pit inclined surface 6b flows into the sand collecting pit 6 (Step S24). When all these operations are completed, the water supply pump 33 is stopped, and the sand pump 61 is also stopped after a predetermined time has elapsed.

  In this sand removing operation, when the sand pump 61 is switched from the operation mode A to the operation mode B, the supply of the fluid to the sand basin 2 is performed until the water level is detected to be equal to or lower than the third high water level HWL. Has stopped. As a result, the rate of decrease in the water level can be increased. At that time, in order to stop the supply of the fluid to the sand basin 2, the supply switching valve Va shown in FIG. 9 is closed and the relief switching valve Vb is opened, and the fluid pumped by the water supply pump 33 is returned to the pump well 3. I have. In this way, the supply of the fluid to the sand basin 2 can be stopped while driving the water supply pump 33 is continued. Each of steps S4, S7, S10, S13, S16, S17, S20, and S23 in the sand removing operation described so far corresponds to an example of the underwater discharging process. Steps S6, S9, S12, S15, S19, and S22 each correspond to an example of an atmospheric discharge process. That is, in the present embodiment, the process of performing the underwater discharge process after the execution of the atmospheric discharge process is a set of sand collection processes (steps S6 and S7, S9 and S10, S12 and S13, S15 and S16, S19 and S20, As each combination of S22 and S23), the sand collecting process is executed a plurality of times. Before the first sand collection process (steps S6 and S7), the underwater discharge step (step S4) is executed. If sand remains in the main trough 8 during the atmospheric discharge process, the sand that has flowed into the main trough 8 by the atmospheric discharge process is added to the remaining sand, and a large amount of sand remains in the main trough 8. Sand may accumulate. Further, at the time of the atmospheric discharge process, the inside of the main trough 8 may be filled with sand, and the overflowing sand may remain on the bottom plane 71. In the present embodiment, since the sand flowing from the bottom plane 71 to the main trough 8 is transported to the sand collecting pit 8 during a set of sand collecting processing, sand may remain in the main trough 8. There is no. Also, since the underwater discharge process (steps S4 and S17) is performed before the first sand collection process (each combination of steps S6 and S7 and S19 and S20), the first sand collection process is also performed. No sand remains in the main trough 8.

  In the present embodiment, when the above-described sand removal operation is being performed, the amount of fluid pumped by the sand pump 61 is set to be slightly larger than the amount of fluid pumped by the water supply pump 33. ing. Therefore, the sand pump 61 repeatedly stops and restarts a plurality of times during the execution of the removing operation. However, when the sand pump 61 repeats driving and stopping, the rush current at the start of driving shortens the pump life. As a countermeasure, the change in the water level in the sand removing operation may be minimized by making the pumping capacity of the water supply pump 33 close to the pumping capacity of the fluid in the sand pump 61. Further, when the water level sensor 99 detects that the fluid level has dropped to the first intermediate water level TMWL in the operation mode A and to the second intermediate water level MWL in the operation mode B, in addition to the nozzle that is discharging the fluid at that time, the other nozzles Alternatively, a fluid may be additionally discharged. By increasing the number of nozzles that discharge the fluid, the load (throttle resistance) on the flow of the fluid is reduced, so that the fluid sucked up by the water supply pump 33 is increased, and as a result, a large amount of fluid can be supplied to the sand basin 2. As a result, the first low water level TLWL or the second low water level LWL is less likely to be attained, so that the number of times the sand pump 61 stops and restarts can be reduced. Here, it is preferable that the other nozzle is a sand collecting nozzle 91 provided in a nozzle header to be discharged next. By discharging the fluid from the nozzle header which is to be discharged next, the sand in the bottom plane 71 and the small trough 72 to be flown next can be preliminarily flown, so that the residual sand can be further suppressed. it can. Further, the fluid to be additionally discharged may be a fluid stored in another facility. Further, even when the first low water level TLWL or the second low water level LWL is reached, the sand pump 61 is not stopped, and instead of stopping the sand pump 61, the fluid stored in other equipment is added to the fluid pumped by the water supply pump 33. You may comprise so that it may supply to the sand basin 2. In the case of such a configuration, the supply of the fluid stored in other equipment to the sand basin 2 may be stopped when the fluid reaches the second high water level THWL or the third high water level HWL. By reducing the number of times the sand pump 61 repeats stopping and driving, deterioration of the sand pump 61 can be suppressed and the life can be extended.

  By the way, in this embodiment, the discharge port 911 is arranged near the bottom of the sand basin 2. On the other hand, for example, in Japanese Patent Application Laid-Open No. 2011-245391, a sand collecting means 9 having a discharge port 911 is arranged on the upper part of the sand basin 2 and discharges fluid toward the side wall W, and the wall surface of the side wall W Has been proposed.

  FIG. 12 is a cross-sectional view of a sand basin similar to FIG. 5 showing a case where sand collecting means is arranged on an upper portion of a sand basin and a case where sand collecting means is arranged near the bottom of the sand basin. In FIG. 12, the sand collecting means arranged in the upper part of the sand basin is indicated by a two-dot chain line. In addition, of the lines indicating the pipes and the side walls, the lines intersecting with the sand collecting means arranged on the upper part of the sand basin are omitted from the intersection.

  FIG. 12 shows a virtual upper nozzle header 90 in the upper part of the sand basin 2. This upper nozzle header 90 is used in place of the first nozzle header 9a. At an upstream end of the sand basin 2, a dust remover 5 that stands upright is disposed. The sand collecting means 9 needs to be arranged so as not to interfere with the dust remover 5. Therefore, the upper nozzle header 90 arranged on the upper part of the sand basin 2 is located on the downstream side as compared with the case where it is arranged near the bottom of the sand basin 2 as shown in FIG. In other words, the upper nozzle header 90 has to be disposed downstream of the first nozzle header 9a by the distance S. As described above, the upper portions of the endless chain 51 and the filtration screen 53 constituting the dust remover 5 overlap the bottom plane 71 and the main trough 8 in the longitudinal direction. For this reason, even if the fluid is discharged from the upper nozzle header 90, a portion where the discharged fluid does not reach the most upstream portion of the bottom plane 71 is generated. If the dust remover 5 and the upper nozzle header 90 are arranged on the upstream side by the distance S from the positions shown in FIGS. 5 and 12, the fluid can reach the most upstream portion of the bottom plane 71. However, in that arrangement, the longitudinal length of the sand basin 2 becomes long. As a result, the sand basin 2 becomes large, requiring a large area for the installation of the sand basin 2, and the sand basin 2 becomes expensive. In the sand basin 2 of the present embodiment, since the first nozzle header 9a is arranged near the bottom of the sand basin 2, compared with the case where the upper nozzle header 90 arranged on the upper part of the sand basin 2 is used, There is an effect that the enlargement of the sand basin 2 is suppressed and the sand basin 2 can be provided at low cost.

  Next, a modified example of the connection surface 73 will be described. In the modified example described below, differences from the embodiment shown in FIGS. 1 to 11 will be mainly described, and components having the same names as the components in the embodiment shown in FIGS. 1 to 11 will be described. Will be described using the same reference numerals as used above, and redundant description will be omitted.

  FIG. 13 is a sectional view similar to FIG. 3 showing a modification of the connection surface.

  This modification is different from the example shown in FIG. 3 in that the connection surface 73 is formed as a curved surface. The connection surface 73 includes a ridge 731 extending along the longitudinal direction, a first connection surface 732, and a second connection surface 733. As shown in FIG. 13, the first connection surface 732 and the second connection surface 733 have a cross-section of a quarter circle. That is, the connection surface 73 is formed of a semi-cylindrical surface that protrudes upward as a whole. The ridge line portion 731 is constituted by a line at the upper end of the semi-cylindrical shape. Also in this modified example, as in the example shown in FIG. 3, the sand that settles in the sewage in the sand basin 2 to the connection surface 73 easily slides down from the connection surface 73 due to its own weight. However, in the vicinity of the ridge 731, the inclination angle of the tangent plane of the connection surface 73 becomes small, and there is a possibility that sand remains in the vicinity. On the other hand, since the thickness of the concrete forming the connection surface 73 in the pond width direction is thick even in the vicinity of the ridge 731, the ridge 731 is less likely to be damaged. In addition, one of the first connection surface 732 and the second connection surface 733 is formed in a planar shape as in the example shown in FIG. 3, and the other is formed in a curved surface as in the modification shown in FIG. It may be formed. Further, one or both of the first connection surface 732 and the second connection surface 733 may be formed as a combined surface of a curved surface and a flat surface.

  Next, a modified example of the sand collecting means 9 will be described.

  FIG. 14A is a diagram showing a first modified example of the supply pipe and the sand collecting nozzle shown in FIG. 8, and FIG. 14B is a second modified example of the supply pipe and the sand collecting nozzle shown in FIG. FIG.

  In the first modified example, the supply pipe 92 is not provided with the lap joint 934, the supply pipe 92 and the branch pipe 932 are flange-coupled, and the sand collecting nozzle 91 is provided with a ball joint 912. This is different from the example shown in FIG. In FIG. 14A, the sand collecting nozzle 91 corresponding to the convex wall portion Wa1 is indicated by a solid line, and the sand collecting nozzle 91 corresponding to the concave wall portion Wa2 is indicated by a two-dot chain line. In this modification, a ball joint 912 is provided between the supply pipe 92 and each discharge port 911. With this ball joint 912, the discharge direction of the fluid can be changed steplessly not only in the rotation direction about the axis of the supply pipe 92 but also in various other directions. Therefore, fine adjustment of the ejection direction can be performed for each ejection port 911. Note that a lap joint 934 may be provided on the supply pipe 92 and a ball joint 912 may be provided on the sand collecting nozzle 91. In this case, the lap joint 934 corresponds to an example of a collective change unit, and the ball joint 912 corresponds to an example of an individual direction change unit.

  In the second modification, the supply pipe 92 is not provided with the wrap joint 934, and the supply pipe 92 and the branch pipe 932 are flange-coupled. The difference from the example shown in FIG. 8A is that a plurality of portions 924 are formed. In FIG. 14B, the sand collecting nozzle 91 corresponding to the convex wall portion Wa1 is indicated by a solid line, and the sand collecting nozzle 91 corresponding to the concave wall portion Wa2 is indicated by a two-dot chain line. In this modification, six mounting portions 924 of the sand collecting nozzle 91 are formed in the circumferential direction of the supply pipe 92. Thus, after the supply pipe 92 is fixed to the branch pipe 932, the sand collecting nozzle 91 can be mounted on any of the six mounting sections 924. Before the sand collecting nozzle 91 is attached, plug members are attached to all the attachment portions 924. When mounting the sand collecting nozzle 91, the plug member is removed, and then the sand collecting nozzle 91 is mounted. Note that a lap joint 934 may be provided in the supply pipe 92 and a mounting portion 924 may be formed in the supply pipe 92. In this case, the lap joint 934 corresponds to an example of a collective change unit, and the mounting unit 924 corresponds to an example of an individual direction change unit. In this modification, six mounting portions 924 are formed in the circumferential direction. However, the number of mounting portions 924 may be two or more and five or less, or seven or more.

  Next, modified examples of the main trough 8, the covering members 13, 14, 15 and the bottom plane 71 will be described.

  FIG. 15 is a cross-sectional view similar to FIG. 5 showing a modified example of the main trough, the cover member, and the bottom plane.

  This modified example is different from the example shown in FIG. 5 in that the main trough 8, the respective covering members 13, 14, 15 and the bottom plane 71 are inclined downward toward the sand collecting pit 6. . In FIG. 15, the inclination of the main trough 8, each of the covering members 13, 14, 15, and the bottom plane 71 is exaggerated for easy understanding of the inclination. As shown in FIG. 15, the bottom plane 71 is inclined downward by about 0.5 degrees in the longitudinal direction so that the end on the sand collecting pit 6 side becomes deepest toward the sand collecting pit 6. The upstream first main trough 815 and the downstream main trough 82 are also inclined about 0.5 degrees downward toward the sand collecting pit 6 like the bottom plane 71, and are connected to the sand collecting pit 6. The part is deepest. Further, the first cover member 13 and the third cover member 15 are also inclined downward by about 0.5 degrees toward the sand collecting pit 6, and the portion connected to the sand collecting pit 6 is the deepest. The upstream first main trough 815 and the second cover member 14 not shown in FIG. 15 are also inclined downward by about 0.5 degrees toward the sand collecting pit 6. In this modified example, by providing the cover members 13, 14, 15, not only is the sand transporting force in the main trough 8 increased, but also the main trough 8 and the cover members 13, 14, 15 are inclined. The flow of the fluid discharged into each of the covering members 13, 14, 15 is assisted. Thereby, the sand deposited on the main trough 8 can be transported for a longer distance. Note that the inclination angle may be appropriately set according to the length of the main trough 8.

  FIG. 16 is a cross-sectional view similar to FIG. 8A showing a bottom plane near the upstream end of the sand basin and a bottom plane near the sand collection pit in the modification shown in FIG. In FIG. 16, the side wall and the bottom plane are also shown.

  FIG. 16 shows the height direction of the bottom plane 71 when the bottom plane 71 is inclined downward toward the sand collection pit 6 so that the end of the sand collection pit 6 is deepest as shown in FIG. Shows the difference between the positions. In FIG. 16, the bottom plane 71 near the upstream end of the sand basin 2 is indicated by a solid line, and the bottom plane 71 near the sand collection pit 6 is indicated by a two-dot chain line. As shown in FIG. 16, in this case, the bottom plane 71 exists at a position lower in the vicinity of the sand collection pit 6 than in the vicinity of the upstream end of the sand basin 2. As shown in the figure, even if the fluid is discharged from the discharge port 911 located at the same position, the height of the bottom plane 71 in the height direction of the bottom plane 71 remains near the upstream end of the sand basin 2 and the sand collecting pit 6. Since the positions are different, a difference in the distance Y occurs at the point where the discharged fluid reaches the bottom plane 71. In particular, in the sand basin 2 whose length in the longitudinal direction is long, the distance Y becomes long, and even in the discharge direction optimal for one of the upstream end portion of the sand basin 2 and the vicinity of the sand collecting pit 6, the other is inefficient. It may be in the ejection direction. In the present embodiment, the discharge direction of the fluid from the discharge port 911 can be changed, so that the fluid can be changed in the optimal discharge direction in accordance with the height of the bottom plane 71 (the distance from the supply pipe 92 to the bottom plane 71). Can be discharged.

  Next, a modified example in which the height of the main trough 8 is increased will be described.

  FIG. 17 is an explanatory diagram similar to FIG. 10 showing an example of detecting the water level when the height of the main trough is increased.

  In the example shown in FIG. 10, each of the covering members 13, 14, and 15 is formed at a height exceeding half of the height of the main trough 8. The upper end position 13b of each of the cover members 13, 14, 15 was substantially the same as the lower end 72b of the small trough 72 (the upper end 8b of the main trough 8). As described above, since the operation mode A of the sand pump 61 is a control mode in which each of the cover members 13, 14, 15 is kept submerged in water, the upper end position 13b of each of the cover members 13, 14, 15 is set. It is necessary to set the first low water level TLWL above. Further, the operation mode B of the sand pump 61 is a control mode in which the water level is maintained so as to be lower than the lower end 72b of the small trough 72. 3 It is necessary to set the high water level HWL. In the example shown in FIG. 10, the first low water level TLWL is set above the upper end position 13b, and the third high water level HWL is set below the lower end 72b. Must also set the third high water level HWL below. As a result, there is no overlap between the water level maintenance ranges in the operation mode A and the operation mode B, and when switching from one mode to the other mode, a waiting time occurs until the water level falls within the range of the other mode. I was As shown in FIG. 17, when the height of the main trough 8 is increased and the respective cover members 13, 14, 15 are arranged on the lower portion of the main trough 8, the upper end positions of the respective cover members 13, 14, 15 13 b is located below the lower end 72 b of the small trough 72. Therefore, even if the above condition is satisfied, the third high water level HWL can be set above the first low water level TLWL. That is, a part of the water level range D1 in the operation mode A and a part of the water level range D2 in the operation mode B can be overlapped, so that the standby time after mode switching can be eliminated or reduced.

  The present invention is not limited to the above embodiments and modifications, and various modifications can be made within the scope described in the claims. For example, in the present embodiment, the present invention is applied to the sand basin 2 of the sewage treatment facility 1 into which sewage and rainwater flows, but the present invention can also be applied to a sand basin of rainwater treatment facilities into which only rainwater flows. In the present embodiment, after the sand deposited on the bottom plane 71 and the small trough 72 upstream of the sand collection pit 6 flows, the sand is deposited on the bottom plane 71 and the small trough 72 downstream of the sand collection pit 6. Although the sand that has flowed is used, the sand that has previously accumulated on the bottom plane 71 and the small trough 72 on the downstream side may be flown. In the present embodiment, the example in which the dust remover 5 and the protruding wall 10 are arranged at the upstream end of the sand basin 2 is shown, but the dust remover 5 and the protruding wall 10 are arranged at the downstream end of the sand basin 2. May be. When the dust remover 5 and the protruding wall 10 are arranged at the downstream end of the sand basin 2, two downstream main troughs 82 are provided, and the protruding wall 10 is arranged on the left side wall Wa side and the right side wall Wb side. do it. Then, a ridge portion, a first connection surface, and a second connection surface may be formed in a portion between the two downstream main troughs 82 and excluding a region where the protruding wall 10 is provided. Further, in the present embodiment, at the end portion (tip portion) of the main trough 8 opposite to the sand collecting pit 6, one discharge port for discharging the fluid to the transport space FS is provided one by one. A nozzle having a discharge port may be additionally provided at an intermediate position or the like in the extending direction of 13, 14, 15 in the extending direction. In particular, when the length of the covering members 13, 14, 15 in the extending direction is long or when the discharge pressure of the fluid is low, it is desirable to add a nozzle at an intermediate position or the like. Further, in the present embodiment, the fluid is discharged into the transport space FS in a state where each of the covering members 13, 14, 15 is completely immersed in the water, but a part of each of the covering members 13, 14, 15 is submerged in the water. If submerged, the fluid may be discharged in a state where the air remains in the transport space FS. Further, in the present embodiment, the fluid is discharged in a state where the first trough discharge port 831a, the second trough discharge port 832a, or the third trough discharge port 84a is completely submerged in water, but these discharge ports 831a, 832a , 84a may be submerged in water and the remaining part may be exposed to the atmosphere to discharge the fluid. However, in these cases, the flow of the fluid discharged particularly at the interface between the atmosphere and water causes a loss. Accordingly, in a state where each of the covering members 13, 14, 15 and the first trough discharge port 831a, the second trough discharge port 832a, and the third trough discharge port 84a are completely submerged, the discharge ports 831a, 832a, 84a are provided. It is desirable to discharge the fluid from the.

  According to this embodiment or its modification, sand can be efficiently collected. In addition, the sand deposited on the bottom plane 71, the small trough 72, and the connection surface 73 can be flowed with a fluid without remaining. Further, even in a sand basin in which the left side wall Wa or the right side wall Wb is not formed in a straight line, the straight supply pipe 92 can be used, so that the sand basin 2 can be provided at low cost. In addition, even if the shape of the side wall W is unknown when designing the sand basin 2 or creating the supply pipe 92, the discharge direction can be adjusted when the sand basin 2 is constructed. Can respond flexibly. Further, the sand that has settled on the connection surface 73 slides down the first connection surface 732 or the second connection surface 733 and deposits on the upstream first main trough 815 or the upstream second main trough 816, so that the upstream first Sand does not remain between the main trough 815 and the second upstream main trough 816. Further, in the present embodiment, the inclination angle of the first bottom surface 711 and the second bottom surface 712 is set to a gentle inclination angle (about 5 degrees) such that the deposited sand can flow with the fluid discharged from the discharge port 911. I have. Thus, the sand basin 2 can be created without having to dig deep into the ground. On the other hand, the connection surface 73 is formed at a steeper angle than the first bottom surface 711 and the second bottom surface 712, so that the fluid discharged from the discharge port 911 does not reach the connection surface 73. Can be deposited on the upstream first main trough 815 or the upstream second main trough 816.

  In many cases, the sand basin 2 has a length in the longitudinal direction of 20 meters or more. In the conventional sand basin 2, the main trough 8 is inclined downward, for example, once toward the sand collecting pit 6 side. For this reason, the sand collecting pit 6 side end (rear end) is deeper in proportion to the length of the sand basin 2 with respect to the depth position where the pond end (end) of the main trough 8 is arranged. Placed in the position. Further, since the bottom plane 71 is formed at the same inclination angle as the main trough 8, the bottom plane 71 is similarly arranged at a deep position on the sand collecting pit 6 side. When the length of the sand basin 2 in the longitudinal direction is long, the portion of the main trough 8 and the bottom plane 71 on the sand collecting pit 6 side is at a deeper position than in the case where the length of the sand basin 2 in the longitudinal direction is short. Will be placed. When constructing the sand basin 2, the ground is dug below the deepest position of the sand basin 2 and then the sand basin 2 is formed with concrete. When the main trough 8 and the bottom plane 71 are inclined, the sand collecting pit 6 is arranged at a deep position as compared with the case where the main trough 8 and the bottom plane 71 are not inclined. It takes. Also, when forming the bottom plane 71 with concrete from the dug-down position, it is necessary to gradually thicken the concrete from the sand collecting pit 6 side to the end of the sand basin in order to make the bottom plane 71 inclined. Used a lot of concrete. As a result, there is a problem that the sand basin 2 becomes expensive. In the present embodiment, since the sand collecting efficiency is enhanced by providing the covering members 13, 14, and 15, even if the inclination angle of the main trough 8 and the bottom plane 71 is reduced, the sand in the main trough 8 is collected by the sand collecting pit. 6 can be transported. This inclination angle is preferably from 0 degree to less than 1 degree, and more preferably from 0 degree to 0.5 degree. Since the inclination angle is reduced, it is not necessary to dig deep into the ground, and the amount of concrete used is small, so that the sand basin 2 can be formed at low cost.

  The following inventive concept can also be extracted from the sand basin of the present embodiment.

In the sand basin where the sand contained in the received water sinks,
A groove provided in the bottom of the pond below the side wall and extending in a predetermined direction;
A bottom surface provided at the bottom of the pond and connected to the trench;
A plurality of discharge ports for discharging a fluid for flowing sand settled on the bottom surface from the side wall side toward the groove,
A supply pipe provided with the discharge port,
The plurality of discharge ports are configured to discharge fluid toward the center in the pond width direction from the axis of the supply pipe provided with the discharge ports, and to the outside in the pond width direction relative to the axis of the supply pipe. A sand basin characterized in that it discharges fluid.

  Further, the following inventive concept can be extracted from the sand basin of the present embodiment.

In the sand basin where the sand contained in the received water sinks,
A groove provided in the bottom of the pond below the side wall and extending in a predetermined direction;
A bottom surface provided at the bottom of the pond and connected to the trench;
Having a discharge port for discharging a fluid for flowing the sand settled on the bottom surface from the side wall side toward the groove,
A settling basin, wherein a discharge direction of a fluid discharged from the discharge port can be changed.

In this sand basin,
A supply pipe provided with the discharge port,
A mother pipe for supplying a fluid to the supply pipe,
The supply pipe may be rotatable with respect to the mother pipe around an axial direction of the supply pipe.

In the above sand basin,
The supply pipe may have a plurality of discharge ports.

Further, in the sand basin,
Having a supply pipe provided with the discharge port,
The discharge port may be capable of changing a fluid discharge direction by a ball joint disposed between the supply pipe and the discharge port.

In addition, in the above sand basin,
The discharge port has a supply pipe detachably provided,
The supply pipe may have a plurality of mounting portions to which the discharge ports are mounted in a circumferential direction of the supply pipe.

  Further, the following inventive concept can be extracted from the sand basin of the present embodiment.

In the sand basin where the sand contained in the received water sinks,
A groove provided in the bottom of the pond below the side wall and extending in a predetermined direction;
A bottom surface provided at the bottom of the pond and connected to the trench;
A discharge port for discharging a fluid for flowing sand settled on the bottom surface from the side wall side toward the groove, and a discharge port arranged at a center side of the pond width direction from the side wall, and a plurality of the discharge ports are arranged in the predetermined direction. Supply pipe and
The supply pipe has a first region extending from the side wall at a first interval in the pond width direction, and a second region extending from the side wall at a second interval in the pond width direction. ,
A sand basin, wherein the discharge port arranged in the first area and the discharge port arranged in the second area can change the discharge direction of the fluid independently of each other.

  The first region may be provided with a plurality of discharge ports or a single discharge port. When there are a plurality of discharge ports provided in the first region, it is preferable that the discharge direction of the fluid from those discharge ports can be changed collectively. In addition, the number of discharge ports provided in the second region may be plural or one. Even when there are a plurality of discharge ports provided in the second region, it is preferable that the discharge direction of the fluid from those discharge ports can be changed collectively. The term “changeable in a lump” as used herein means that, for example, the portion of the first region and the portion of the second region of the supply pipe are separately rotated around the axial direction of the supply pipe. It is realized by doing. In addition, a rotatable portion may be provided at both ends of the first region of the supply pipe, and a rotatable portion may be provided at both ends of the second region. The supply pipe may be a straight pipe or a pipe provided with a slightly bent portion.

The supply pipe is provided with a third region connecting the first region and the second region,
The discharge port provided in the third region is capable of changing a fluid discharge direction separately from the discharge port provided in the first region and the discharge port provided in the second region. Is also good.

  The third region may be an inclined region in which the distance from the side wall gradually changes in the extending direction, or may be a region in which the distance gradually changes.

  In addition, the number of ejection ports provided in the third region may be plural or one. When there are a plurality of discharge ports provided in the third region, it is preferable that the discharge direction of the fluid from these discharge ports can be changed collectively. The term “changeable collectively” as used herein means, for example, that the portion of the third region of the supply pipe is separate from the portion of the first region and the second region. It is realized by rotating around the axial direction.

  Further, the following inventive concept can be extracted from the sand basin of the present embodiment.

In the sand basin where the sand contained in the received water sinks,
A groove provided in the bottom of the pond below the side wall and extending in a predetermined direction;
A bottom surface provided at the bottom of the pond and connected to the trench;
A plurality of discharge ports that are arranged to face the side wall and discharge a fluid for flowing sand settled on the bottom surface from the side wall toward the groove,
The side wall has a convex wall portion protruding toward the center of the pond width direction and extending in the predetermined direction, and a concave wall portion recessed outward in the pond width direction and extending in the predetermined direction,
The discharge port is disposed so as to face the convex wall portion and the concave wall portion, respectively.
The ejection direction of the fluid ejected from the ejection port arranged opposite to the concave wall portion is different from the ejection direction of the fluid ejected from the ejection port arranged opposite to the convex wall portion. A sand basin comprising a changeable direction changing means.

  Further, the following inventive concept can be extracted from the sand basin of the present embodiment.

In the sand basin where the sand contained in the received water sinks,
A groove provided in the bottom of the pond below the side wall and extending in a predetermined direction;
A bottom surface provided at the bottom of the pond and connected to the trench;
A supply pipe arranged opposite to the side wall and extending in the predetermined direction;
A plurality of discharge ports that are disposed on the supply pipe and discharge a fluid for flowing sand settled on the bottom surface from the side wall toward the groove,
The side wall has a convex wall portion protruding toward the center in the pond width direction and extending in the predetermined direction and a concave wall portion recessed outward in the pond width direction and extending in the predetermined direction,
The discharge port is disposed at a position facing the convex wall portion and a position facing the concave wall portion, respectively.
The supply pipe has a discharge direction of a fluid discharged from the discharge port between a discharge port arranged at a position facing the convex wall portion and a discharge port arranged at a position facing the concave wall portion. A sand basin, comprising a direction changing means capable of changing the direction of the sand.

In this sand basin,
The side wall has an inclined wall portion formed between the convex wall portion and the concave wall portion and extending in a direction inclined with respect to the predetermined direction and the pond width direction,
The discharge port is also arranged at a position facing the inclined wall portion,
The supply pipe has a discharge direction of a fluid discharged from the discharge port between a discharge port disposed to face the convex wall portion and a discharge port disposed to face the inclined wall portion. A first direction changing means that can be changed,
A discharge direction of a fluid discharged from the discharge port can be changed between a plurality of discharge ports arranged to face the concave wall portion and a discharge port arranged to face the inclined wall portion. It may have a second direction changing means.

  In addition, the following inventive concept can be extracted from the sand basin of the present embodiment.

In the sand basin where the sand contained in the received water sinks,
A groove provided in the bottom of the pond below the side wall and extending in a predetermined direction;
A bottom surface provided at the bottom of the pond and connected to the trench;
A plurality of discharge ports for discharging a fluid for flowing sand settled on the bottom surface from the side wall side toward the groove,
Batch direction changing means capable of changing a discharge direction of fluid discharged from at least two discharge ports of the plurality of discharge ports collectively;
A sand basin comprising: individual direction changing means for changing a discharge direction of a fluid discharged from the discharge port for each discharge port.

  Further, the following inventive concept can be extracted from the sand basin of the present embodiment.

In a sand basin that allows the received water to flow down in an orthogonal direction perpendicular to the pond width direction and settle the sand contained in the water, between the one side wall and the other side wall that constitute the end face in the pond width direction,
A first groove and a second groove which are provided at a bottom of the pond and are spaced apart in the pond width direction and respectively extend in the orthogonal direction;
A projecting wall formed between the first groove and the second groove and projecting upward from the bottom of the pond;
A ridge portion extending along the orthogonal direction at a portion of the pond bottom between the first groove and the second groove except for a region where the protruding wall is provided; A sand basin comprising a first connection surface connecting the first groove and a second connection surface connecting the ridge portion and the second groove.

The first connection surface is an inclined surface inclined downward from the ridge line portion toward the first groove,
The second connection surface may be an inclined surface that is inclined downward from the ridge line portion toward the second groove.

The first groove is provided on the one side wall side,
The second groove is provided on the other side wall side,
A first bottom surface formed between the one side wall and the first groove and inclined downward toward the first groove;
A second bottom surface formed between the other side wall and the second groove, and inclined downward toward the second groove;
The inclination angles of the first connection surface and the second connection surface may be steeper than the inclination angles of the first bottom surface and the second bottom surface.

One-side discharge port for discharging a fluid for flowing sand settled on the first bottom surface from the one side wall toward the first groove;
It may have a discharge port on the other side for discharging a fluid for flowing sand settled on the second bottom surface from the other side wall toward the second groove.

  Two dust removers may be provided between the one side wall and the protruding wall and between the other side wall and the protruding wall to remove contaminants contained in the received water.

  Further, the following inventive concept can be extracted from the sand basin of the present embodiment.

In a sand basin that allows the received water to flow down in an orthogonal direction perpendicular to the pond width direction and settle the sand contained in the water, between the one side wall and the other side wall that constitute the end face in the pond width direction,
A first groove and a second groove which are provided at a bottom of the pond and are spaced apart in the pond width direction and respectively extend in the orthogonal direction;
A sand collecting pit provided at the bottom of the pond, wherein the first groove is connected and the second groove is connected;
A projecting wall formed between the first groove and the second groove and projecting upward from the bottom of the pond;
A ridge portion extending along the orthogonal direction at a portion between the first groove and the second groove and between the sand collecting pit and the protruding wall in the bottom of the pond; A sand basin comprising a first connection surface connecting the first groove and a second connection surface connecting the ridge portion and the second groove.

  In addition, even if it is a component contained only in each of the description of the embodiment and each modification described above, the component may be applied to the embodiment and other modifications.

2 sedimentation basin 8 main trough 13 first covering member 13a opening 14 second covering member 15 third covering member 84a trough third discharge port 71 bottom plane 831a trough first discharge port 832a trough second discharge port 911 discharge port side wall W

Claims (6)

In the sand basin where the sand contained in the received water sinks to the bottom of the pond,
A groove provided in the bottom of the pond and extending in a predetermined direction;
A first discharge port for discharging a fluid in the predetermined direction in the water accumulated in the groove;
A bottom surface provided at the bottom of the pond and connected to the trench;
A second discharge port for discharging a fluid for flowing sand deposited on the bottom surface from the side wall side of the sand basin toward the groove, into the atmosphere;
A sand basin comprising: a cover member that covers a periphery of an imaginary axis extending from the center of the first discharge port toward the predetermined direction and has an opening at a lower end portion.   The sand basin according to claim 1, wherein the opening of the covering member is disposed below a center of the groove in a height direction. In a sand basin in which sand contained in received water is settled in a pond bottom having a groove extending in a predetermined direction and a bottom surface connected to the groove, a sand collecting method for collecting sand deposited on the bottom of the pond. So,
An underwater discharge step of discharging a fluid from the first discharge port in the predetermined direction in the water accumulated in the groove;
Discharging the fluid for flowing the sand deposited on the bottom surface from the side wall side toward the groove from the second discharge port into the atmosphere,
The underwater discharge step is a step of discharging a fluid into a space covered by a cover member having an opening at a lower end portion and surrounding a virtual axis extending from the center of the first discharge port toward the predetermined direction from the center of the first discharge port. A sand collecting method characterized by that: The underwater discharge step is a step performed in a state where the water level is maintained above the covering member,
4. The sand collecting method according to claim 3, wherein the discharging step in the atmosphere is performed in a state where a water level is maintained below the bottom surface. 5.   5. The sand collecting method according to claim 3, wherein the process of performing the underwater discharging process after the execution of the atmospheric discharging process is performed as a set of sand collecting processes, and the sand collecting process is performed a plurality of times.   The sand collecting method according to claim 5, wherein the underwater discharging step is performed before performing the sand collecting process a plurality of times.