JP2001300208A - Apparatus and method for gathering sand of sand sedimentation basin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for gathering sand, capable of gathering earth and sand accumulated in a sand sedimentation basin to a sand gathering pit using water. SOLUTION: The sand gathering apparatus 1 for the sand sedimentation basin 2 is constituted so as to discharge water to the bottom part 7 of the sand sedimentation basin 2 having the sand gathering pit 8 provided in the bottom part 7 thereof to gather earth and sand accumulated in the sand sedimentation basin 2 to the sand gathering pit 8. The sand sedimentation basin 2 is adapted to a sewage treatment equipment having a pump well 4 arranged on the downstream side thereof and the sewage treatment equipment has a first pump for pumping up sewage from the pump well 4 to discharge the same to the bottom part of the sand sedimentation basin 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sand collecting apparatus and a sand collecting method for collecting sediment deposited in a sand basin of a sewage treatment facility in a sand collecting pit provided at the bottom of the sand basin.

[0002]

2. Description of the Related Art A sedimentation basin is installed in a sewage treatment facility such as a terminal treatment plant, and is for sedimentation removal of sediment in the sewage.

[0003] Therefore, in a sand basin, it is necessary to discharge the sediment deposited on the bottom of the sand basin to the outside at an appropriate time, and the sediment deposited in the sand basin is collected in a sand collecting pit and various kinds of sand are collected. It is designed to be discharged out of the sand basin by the device.

In a conventional sand collecting apparatus for collecting deposited sediment in a sand collecting pit, for example, sewage stored in a pump well arranged downstream of a sand basin is converted into sewage in the sand basin. There is one that moves earth and sand by spraying it from a nozzle located, and the earth and sand that has settled widely at the bottom of a sand basin can be collected in a sand collection pit.

However, in such a conventional sand collecting device, it is necessary to move the sediment deposited on the bottom of the sand basin in which the sewage is stored, overcoming the water pressure. High pressure.

[0006]

In a conventional sand collecting apparatus of this type, when sewage is jetted from the nozzle at high pressure, mist of sewage is generated and sewage stored in a sand basin is agitated. , Not only is the soil spread,
Causes offensive odor.

The present invention has been made in view of such circumstances, and provides a sand collecting apparatus and a sand collecting method capable of collecting sediment deposited in a sand basin in a sand collecting pit using water. It is the purpose.

[0008]

In order to achieve this object, the invention according to claim 1 is a sand basin having a sand collecting pit at the bottom, wherein water is discharged to the bottom of the sand basin. In a sand collection device of a sand basin that collects the sediment deposited in the sand basin in the sand collection pit, the sand basin is of a sewage treatment facility in which a pump well is arranged on a downstream side thereof, and the sewage treatment facility includes: And a first pump for pumping sewage from the pump well and discharging the sewage to the bottom of the sand basin.

According to a second aspect of the present invention, there is provided a sand basin having a sand collecting pit at a bottom thereof, wherein water is discharged to the bottom of the sand basin to collect sediment deposited in the sand basin in the sand collecting pit. In a sand collecting device for a sand basin, a first pump that discharges water to the bottom of the sand basin and a second pump that draws water from the sand collecting pit are provided, and the discharge amount of the first pump is A sand collection device for a sand basin, wherein the discharge amount is smaller than the discharge amount of the second pump.

According to a fifth aspect of the present invention, there is provided a sand basin having a sand collecting pit at a bottom thereof, wherein water is discharged to the bottom of the sand basin to collect sediment deposited in the sand basin in the sand collecting pit. In a sand collecting device for a sand basin, a bottom portion in the sand basin is divided into a plurality of regions, and in the plurality of regions, a transfer control means for sequentially discharging water for each region and transferring sediment in the region. It is a sand collecting device for a sand basin, which is provided.

[0011]

According to the first aspect of the present invention, the sediment in the sand basin is transferred to the sand collecting pit by discharging the sewage discharged from the pump well disposed on the downstream side to the bottom of the sand basin. Since it can be collected, the earth and sand can be reliably collected as a whole toward the sand collection pit.

According to the second aspect of the present invention, while the sediment deposited on the bottom of the sand basin by the water discharged by the first pump is transferred, the water in the sand collecting pit is drawn by the second pump. However, the amount of water discharged by the first pump is smaller than the amount of water discharged from the sand collecting pit by the second pump. The water surface is not raised.

According to the fifth aspect of the present invention, the bottom in the sand basin is divided into a plurality of regions, and water is discharged sequentially for each region and the sediment in the region is transferred, so that a pump, a trough, etc. By smoothing the burden of sand, sand can be collected smoothly.

Further, by setting the inside of the sand basin in a drainage state in which the surface of the water staying therein is located in the sand collecting pit, the water discharged from the nozzle agitates the sewage in the sand basin as in the related art. The generation of foul odors is reduced.

Further, since the water pressure due to the sewage does not act on the sediment deposited in the sand basin as in the prior art, the discharge pressure of the water from the nozzle can be made lower than in the prior art, thereby preventing the generation of sewage mist. This also reduces the generation of odor.

Then, the water flowing out of the nozzle is pumped out of the sand collecting pit, thereby maintaining the water surface in the sand basin in a drained state. It can be washed away and collected as a whole.

According to the present invention, there is provided a sand collecting apparatus and a sand collecting method capable of collecting earth and sand deposited in a sand basin using water in a sand collecting pit.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment showing an embodiment of the present invention in the drawings.
The first embodiment will be described with reference to FIG.

This embodiment is applied to rainwater treatment equipment at a pumping station in a terminal treatment plant.

As shown in FIG. 1, the rainwater treatment facility 1 of this embodiment has a first rainwater sedimentation basin 2 and a second rainwater sedimentation basin 3, and these two rainwater sedimentation basins 2, Numeral 3 is arranged in parallel between an upstream inflow channel (not shown) and a pump well 4 described later.

Since the rainwater basins 2 and 3 have the same construction, the following description of the structure of the sand basin will be made only for the first rainwater basin 2.

That is, in the rainwater treatment equipment 1 passing through the first rainwater sedimentation basin 2, the first rainwater sedimentation basin 2 is connected to the downstream side of the inflow culvert (not shown) via a gate (not shown). The downstream side of the rainwater sedimentation basin 1 is connected to a pump well 4 provided with a rainwater pump 5 to constitute the whole (FIG. 2).
reference).

Then, on the downstream side of the gate (not shown),
A dam device 6 is installed at a position on the upstream side immediately adjacent to the first rainwater sedimentation basin 2.

The dam device 6 is a bag made of, for example, an air-tight nylon woven fabric, and is capable of undulating in about several minutes by expanding and contracting the bag.
By raising this dam device 6, sewage such as rainwater from the upstream side is prevented from entering the first stormwater sedimentation basin 2, and by damping this dam device 6, rainwater is removed from the first stormwater basin 2. It leads to 2. In the figure, L1
Is the highest water level by the dam device 6.

[0025] The first device installed downstream of the dam device 6
A sand collecting pit 8 is formed at the center of the bottom 7 of the rainwater sedimentation basin 2, and a sand pump 11 is installed in the sand collecting pit 8. (FIG. 3).

It is to be noted that the present invention can be embodied by installing the second pump of the present invention separately from the sand pumping device such as the sand pump 11 or the like.

The sand collecting pit 8 is provided in the first rainwater settling basin 2.
The sediment separated from the rainwater and settled throughout the bottom 7 is collected therein, and the sediment is collected from the first sedimentation basin 2.
It is for discharging to outside.

Therefore, the sand collecting pit 8 becomes the deepest part at the bottom 7 of the first rainwater settling basin 2, and the overall shape of the bottom 7 is inclined toward the sand collecting pit 8 so that the surrounding bottom 7 becomes deeper. It is formed.

The shape of the bottom 7 will be specifically described.
It is as follows.

That is, at the bottom 7 of the first storm sedimentation basin 2 of this embodiment, a first trough 12 that crosses the bottom 7 in the width direction is formed at the center in the longitudinal direction of the rainwater basin 2. A second trough 13 is formed at the center in the width direction of the rainwater sedimentation basin 2, and the sand collecting pit 8 is formed at the intersection of the first and second troughs 12 and 13. (FIG. 3).

In the first trough 12, both sides of the sand collecting pit 8 are inclined so that the sand collecting pit 8 side becomes deeper (see FIG. 6). Similarly, both sides of the sand pit 8 are inclined such that the sand collecting pit 8 side becomes deeper (see FIG. 4).

The bottom 7 of the first storm sedimentation basin 2
The first trough 12 and the second trough 13 are divided into four regions, and each of these regions formed on the bottom 7 is located below the second trough 13 in FIG. As shown, a region upstream of the first trough 12 is referred to as a region A, and a region downstream of the first trough 12 is referred to as a region B.

In FIG. 3, the area above the second trough 13 and upstream of the first trough 12 is called area C, and the area downstream of the first trough 12 is area D I mean.

In these regions A, B, C, and D, the surface of the bottom 7 is a plane inclined substantially along both the inclination of the first trough 12 and the inclination of the second trough 13. The surface of the bottom 7 of each region has its maximum inclination line directed substantially toward the sand collecting pit 8.

A large number of small troughs 14 are formed on the surface of the bottom 7 in each of these regions in parallel with the first trough 12, and the bottom 7 between these small troughs 14 is formed. On the surface, water supply nozzles 15 are respectively installed at positions along the side wall of the rainwater basin 2.

This is because the water from the individual water supply nozzles 15 does not impair the cleaning function of the bottom 7 by colliding with water from the adjacent water supply nozzles 15 and interfering with each other. The soil from the water supply nozzles 15 is used to remove the sediment deposited on the entire
4. This is for sharing the area of each water supply nozzle 15 to be cleaned as collected in the sand collecting pit 8 via the second trough 13.

In this embodiment, the sand pump 11 installed in the sand collecting pit 8 is a so-called underwater sand pump capable of sucking water mixed with earth and sand. It is a submersible pump.

At the downstream end of such a rainwater sedimentation basin 2,
A filter 16 is installed similarly to a well-known storm sedimentation basin, and the pump well 4 is installed further downstream thereof (FIG. 2).
reference).

The pump well 4 is provided with sewage such as rainwater obtained by separating earth and sand in the first rainwater settling basin 2 and the second rainwater settling basin 3 as described above, to a discharge culvert by a rainwater pump 5 which is a drainage pump. The bottom of the pump well 4 is set lower than the bottom 7 of the sand basin 2 so that the rainwater pump 5 has a sufficient water depth to facilitate the draining operation.

In this embodiment, a stagnant water pump 18 is installed in the pump well 4 separately from the rainwater pump 5.

The accumulated water pump 18 corresponds to the first pump according to the present invention. As described later, water from the accumulated water pump 18 is guided to the water supply nozzle 15, and Sedimentation of the sediment deposited inside is performed. Each of the water supply nozzles 1 is controlled by the accumulated water pump 18.
The amount of water discharged from 5 is set smaller than the discharge amount of the sand pump 11 and the discharge pressure thereof is
The pressure is lower than 3 kg / cm ² . This is because if the discharge pressure of water from each water supply nozzle 15 is higher than 3 kg / cm ² , some sewage mist will be generated.

In the above-mentioned rainwater treatment equipment 1, a sand removal device for discharging the sediment deposited in the first and second rainwater sedimentation basins 2 and 3 is as shown in FIG.

At the discharge side of the accumulated water pump 18, a first
A first water supply system 21 for supplying water to the rainwater sedimentation basin 2 and a second water supply system 22 for supplying water to the second rainwater sedimentation basin 3 are connected in parallel. A relief circuit 24 connected to the sewage basin 23 is provided.

The first water supply system 21 and the second water supply system 22
Since the circuit configuration is the same as that described above, the first water supply system 21 will be described below, and the description of the second water supply system 22 will be omitted. In FIG. 1, a corresponding portion of the second water supply system 22 is indicated by adding a dash to a reference number of a corresponding portion of the first water supply system 21.

After the pipeline from the accumulated water pump 18 is branched to the first water supply system 21, the pipeline is further branched into five, and the five branch pipes are provided with a sand collecting valve comprising an electric valve. Are installed respectively.

The first sand collecting valve 25 interrupts the supply of water to the water supply nozzles 15 in the area A, and the second sand collection valve 26 interrupts the water supply to the water supply nozzles 15 in the area B. Third
Sand collecting valve 27 is provided with the first and second troughs 12 and 13.
The fourth sand collection valve 28 supplies water to the group of water supply nozzles 15 in the area D, and the fifth sand collection valve 29 supplies water to the group of water supply nozzles 15 in the area C. Is intermittent.

The pipe 31 extending from the discharge side of the sand pump 11 is guided to a sewage basin 23, and the sediment discharged from the stormwater basins 2 and 3 is sent to the sewage basin 23. .

Such a sand removing device is controlled by a microcomputer (not shown), and when the sand collecting operation is started, the sand removing device performs the operation according to, for example, the procedures shown in FIGS. Step 1 First, first and second
Device 6 installed in each of the rainwater settling basins 2 and 3
Compressed air from a compressor (not shown) is supplied to the dams (referred to as dam 1 and dam 2 in FIG. 7) to be in an upright state. As a result, intrusion of sewage and the like into each of the rainwater sedimentation basins 2 and 3 is prevented. Step 2 Next, the accumulated water pump switching valve 19 is opened. The water from the stagnant water pump 18 is transferred to
Preparation for transfer to 3. Step 3 accumulated water pump 18
Start driving. As a result, the rainwater in the pump well 4 is transferred to the sewage sedimentation basin 23 to reduce the amount of rainwater stored in the sand basin 2, and at the same time, the level of the sewage such as the rainwater stored in the pump well 4 Adjust Step 4 When the water level of the sewage such as rainwater in the pump well 4 reaches the required height L2, the operation of the accumulated water pump 18 is stopped. Step 5 Since the amount of rainwater in the first sand basin 2 is reduced in step 4 and the adjustment of the height of the sewage such as rainwater in the pump well 4 is completed, the sewage is transferred to the sewage basin 23. It becomes unnecessary and the accumulated water pump switching valve 19 is closed. Step 6 Since the preparation is completed in step 5, in step 6, a predetermined sand removal operation in the first rainwater sedimentation basin 2, which will be described in detail later, is performed (see FIG. 8). Step 7 When the sand removing operation of the first sand basin 2 is completed in Step 6, the sand removing operation of the second rainwater sand basin 3 is performed subsequently. The sand removal operation of the second rainwater settling basin 3 is performed by the first rainwater settling basin 2.
Since the operation is the same as the sand removal operation in, the detailed description is omitted. Step 8 When the sand removal operation in the second rainwater sedimentation basin 3 is completed in Step 7, the accumulated water pump switching valve 19 is opened. This is a preparation operation for transferring sewage from the pump well 4 in step 9.
Step 9 After this, the operation of the accumulated water pump 18 is started,
The sewage remaining in the pump well 4 is transferred to the sewage sedimentation basin 23.

This is because if the sewage such as rainwater remains in the pump well 4, the stagnant water rots and produces an odor, which is alleviated. Step 10 After the rainwater or the like in the pump well 4 has decreased to a predetermined small amount, the operation of the accumulated water pump 18 is stopped.

As a result, the inside of the pump well 4 is dried, and the generation of offensive odor is reduced. Step 11 Step 1
After the inside of the pump well 4 is dried at 0, the accumulated water pump switching valve 19 is closed.

The specific contents of the first rainwater settling basin treatment performed in step 6 are as shown in FIG. Step 101 When the process of the first rainwater basin 2 is started, first, the automatic operation of the sand pump 11 installed in the first rainwater basin 2 is started.

The sand pump 11 maintains the surface of the water remaining in the first rainwater settling basin 2 in a drainage state located in the sand collecting pit 8. When the water level is higher than a certain level, the operation is automatically performed, and when the water level becomes lower than that, the operation is automatically stopped.

After the driving of the sand pump 11 by this automatic operation is stopped and the water level in the sand collecting pit 8 becomes lower than a certain level, the process proceeds to step 102. Step 102 In step 102, the third sand collection valve 27 is opened to prepare for driving the accumulated water pump 18. Step 103 In step 103, the operation of the accumulated water pump 18 is started. Thereby, a relatively low pressure (for example, 1 k) is applied from each water supply nozzle 15 disposed at the outer end of the first and second troughs 12 and 13.
g / cm ² ), and the sediment deposited in the first and second troughs 12 and 13 is transferred to the sand collecting pit 8.

Accordingly, the water level in the sand collecting pit 8 rises, so that the sand pump 11 starts to be driven appropriately, and the sediment collected in the sand collecting pit 8 is discharged into the sewage basin 23.
Is transferred to

Since the discharge amount of the accumulated water pump 18 is smaller than the discharge amount of the sand pump 11,
1 automatically stops when the water level in the sand collecting pit 8 falls to a predetermined position.

The above operation of the sand pump 11 is automatically performed in each of the following steps independently of the flowchart. Step 104 After step 103, the first sand collection valve 25 is opened. As a result, the sediment deposited in the area A is washed away from the surface of the bottom portion 7 by the water supply from the water supply nozzle group 15, and is collected in the sand collecting pit 8 through the small trough 14 and the second trough 13, and the sand is collected. It is discharged by the pump 11. Step 105
After the elapse of the time T1, the first sand collecting valve 25 is closed, and the second sand collecting valve 26 is opened.

The time T1 is a time required to wash out the sediment deposited in the area A, and is, for example, about 1 minute, but is preferably adjusted as appropriate according to the amount of the deposited sediment. Step 106 After the elapse of time T2, the second sand collecting valve 26 is closed and the fourth sand collecting valve 28 is opened. The time T2 is a time required to wash out the sediment deposited in the area B.
After a lapse of time T3 in step 107, the fourth sand collecting valve 28 is closed, and the fifth sand collecting valve 29 is opened. The time T3 is a time required to wash out the sediment deposited in the area D. After a lapse of time T4 in step 108, the fifth sand collection valve 29 is closed.
Time T4 is a time required to wash out the earth and sand deposited in the area C. Step 109: After the elapse of the time T5, the driving of the accumulated water pump 18 is stopped, and the third sand collecting valve 27 is closed. Step 110 After the elapse of T6, the sand pump 1
The automatic operation 1 is canceled to stop the driving, and the processing of the first sand basin 2 is completed.

The time T6 is a time for draining the first rainwater sedimentation basin 2 without fail when rainwater or the like adhering to the bottom 7 flows down to the sand collecting pit 8.

In the sand removing apparatus of this embodiment, the water supply nozzles 15 in the area A and the water supply nozzles 15 in the area C
The group of water supply nozzles 15 in the area B and the group of water supply nozzles 15 in the area D are arranged in a positional relationship in which water discharge directions face each other, and serve as a second trough 13 as a flow path for sediment deposited in both areas. Are shared.

For this reason, in this embodiment, as shown in the flow chart of the processing of the storm sedimentation basin in FIG. 8, water is supplied to each area in order based on the transfer control means shown in steps 105 to 110. By preventing the second trough 13 from being clogged by earth and sand and leveling the load on the sand pump 11, even if the capacity of the second trough 13 or the sand pump 11 is relatively small, The sand is collected smoothly.

In the embodiment described above, it is preferable that the above-mentioned times T1 to T6 are respectively different optimum numerical values. However, the control may be simplified by uniformly setting them to constant values.

Further, in the embodiment described above, the bottom portions 7 serving as the respective regions are formed in a substantially planar shape. However, the present invention is not limited to this. For example, as shown in a cross section in FIG. Are formed by subdividing each stepwise,
A group of water supply nozzles 15 may be arranged for each step 7a.

FIG. 9 is a cross-sectional view corresponding to FIG. 5. Since the structure other than the above is the same as that of the above-described embodiment, the description will not be repeated.

In such a modification, each step 7a
If the sediment deposited on the top is washed down with water from the water supply nozzle 15 installed corresponding to the step 7a to the next lower step 7a, the transfer distance of the soil by each water supply nozzle 15 is reduced. Since it is small, the earth and sand can be transferred to the second trough 13 with a small amount of low-pressure water by sequentially supplying water to the water supply nozzle 15 of the lower step 7a.

Next, a second embodiment will be described with reference to FIG.

In the second embodiment, the sediment discharged from the first and second stormwater basins 2 and 3 by the sand pump 11 is
Instead of being transferred to the sewage sedimentation basin 23, the sediment is transferred to a sediment separator (sedimentation separator) 31, and the separated sediment is carried out through a hopper device 34 for disposal. The water is then collected by the water tank 33 and used together with the water W from the pump well 4 by the pressure pump 35 to supply water from the water supply nozzle 15 again.

In the second embodiment, the pressure pump 35
Corresponds to the first pump according to the present invention, and the discharge amount and discharge pressure of the pressure feed pump 35 satisfy the same conditions as those of the accumulated water pump 18 in the first embodiment.

Therefore, in the case of the second embodiment,
Since the water extracted by the sand pump 11 is circulated, a small amount of water is required for collecting the sediment deposited on the bottom 7. Therefore, in the second embodiment, there is an advantage that the cost is not so high even if the industrial water or the like is used as the water W in addition to the water from the pump well 4.

In the second embodiment, a filter device 32 is provided separately from the sedimentation / separation device 31, but the sedimentation / separation device 31 has a built-in filter 31a. The installation of the device 32 can be omitted.

[0070]

As described above, according to the present invention,
A sand collecting device and a sand collecting method capable of collecting earth and sand deposited in a sand basin using water in a sand collecting pit can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an entire circuit of a sand remover according to a first embodiment.

FIG. 2 is a schematic cross-sectional view of the rainwater treatment facility of the first embodiment.

FIG. 3 is a plan view of a rainwater sedimentation basin.

FIG. 4 is an enlarged sectional view of a main part of a rainwater sedimentation basin.

FIG. 5 is a sectional view taken along the line PP of FIG. 4;

FIG. 6 is a sectional view taken along the line QQ in FIG. 4;

FIG. 7 is a flowchart of the overall operation of the sand removal device of the first embodiment.

FIG. 8 is a flowchart of processing contents of a first rainwater sedimentation basin.

FIG. 9 is a sectional view showing a modification of the bottom of the first embodiment.

FIG. 10 is an overall schematic system diagram of a second embodiment.

[Explanation of symbols]

 2 First rainwater settling basin 3 Second rainwater settling basin 7 Bottom 8 Sand collection pit 11 Sand pump (second pump) 15 Water supply nozzle 18 Stagnant water pump (first pump)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihide Yoshihide 6-31-5 Ikegami, Ota-ku, Tokyo Inside the Tokyo Sewerage Bureau (72) Inventor Toshiharu Miki 547 Horinouchi, Kikugawa-cho, Ogasa-gun, Shizuoka Prefecture Asahi Tec Inside the corporation

Claims (10)

[Claims] 1. A sand basin having a sand collecting pit at a bottom thereof, wherein the sand is collected at the sand collecting pit by discharging water to the bottom of the sand basin. In the above, the sedimentation basin is of a sewage treatment facility having a pump well disposed downstream thereof, and the sewage treatment facility discharges sewage from the pump well and discharges sewage to a bottom of the sand basin. A sand collecting device for a sand basin, comprising the pump according to (1). 2. A sand basin having a sand collecting pit at a bottom thereof, wherein the sand is collected at the sand collecting pit by discharging water to the bottom of the sand basin. In the above, a first pump that discharges water to the bottom of the sand basin and a second pump that draws water out of the sand collecting pit are provided, and the discharge amount of the first pump is equal to that of the second pump. A sand collecting device for a sand basin, characterized in that the discharge amount is smaller than the discharge amount. 3. The sand collecting device for a sand basin according to claim 2, wherein the second pump is a sand pump. 4. The sand collecting device for a sand basin according to claim 1, wherein the water pumped by a second pump that draws water from the sand collecting pit is filtered, and then the sand basin is filtered. A sand collection device for a sand basin, wherein the water is returned to a water supply nozzle installed at the bottom of the sand basin. 5. A sand basin having a sand collecting pit at a bottom thereof, wherein the sand is collected at the sand collecting pit by discharging water to the bottom of the sand basin. In the above, the bottom in the sand basin is divided into a plurality of regions, and the plurality of regions are provided with transfer control means for sequentially discharging water for each region and transferring sediment in the region. Sand collection device for sand basin. 6. The sand collecting device for a sand basin according to claim 1, wherein a discharge pressure of water from a water supply nozzle installed at a bottom of the sand basin is less than 3 kg / cm ^2. A sand collecting device for a sand basin. 7. A sand basin having a sand collecting pit at the bottom, wherein water is discharged to the bottom of the sand basin to collect sediment deposited in the sand basin into the sand collecting pit. The method, wherein the settling basin is of a sewage treatment plant having a pump well located downstream thereof, wherein discharging water to the bottom of the settling basin supplies sewage pumped from the pump well. How to collect sand in a sand basin. 8. A sand basin having a sand collecting pit at the bottom, wherein sand is collected at the sand collecting pit by discharging water to the bottom of the sand basin. A method of collecting sand in a sand basin, comprising: dividing a bottom of the sand basin into a plurality of regions; and sequentially discharging water in each region to wash away sediment in the regions. 9. The sand collecting method for a sand basin according to claim 7, wherein a discharge pressure of water discharged from a plurality of water supply nozzles installed at a bottom of the sand basin is less than 3 kg / cm ^2. A method for collecting sand in a sand basin. 10. A sand pump for pumping sand and water out of a sand collecting pit, filtering the pumped water, and circulating the water through a water supply nozzle installed at the bottom of the sand basin, thereby obtaining sediment deposited in the sand basin. Collecting sand in the sand collecting pit.