JP6836285B2 - How to remove sand from a sand basin - Google Patents

Description

The present invention relates to a sand removal method in which sediment settled in a sand basin of a sewage treatment facility is collected in a sand collecting pit, and the collected earth and sand is pumped up by a sand lifting pump to be removed.

With the water in the sand basin discharged by a drainage pump (drainage state), low-pressure water is sprayed from the nozzle to the bottom of the sand basin to flush the sediment accumulated on the bottom of the sand basin, and the sand is collected at the bottom of the sand basin. Patent Document 1 discloses a low-pressure sand collecting type sand removing device that collects the collected sand in a pit, pumps the collected earth and sand together with water by a sand lifting pump installed in the sand collecting pit, and transfers the collected sand to a sewage settling basin.

The sand basin that collects low-pressure sand by the sand remover is provided with the following structure. That is, a sand collection pit is formed in a part of the bottom of the sand basin, for example, in the center, and the bottom surface of the sand basin is inclined so that the periphery of the sand basin is the deepest, and the bottom of the sand basin is inside the sand basin. A trough extending parallel to the water flow direction (hereinafter referred to as the main trough) is formed so that the sand collection pit side becomes deeper, and at the center of the bottom in the longitudinal direction, it slopes downward from the side walls on both sides of the sand basin to the bottom of the sand collection pit. A large number of small troughs extending in parallel with the water flow direction in the sand basin are formed on the bottom surface of the sand basin (hereinafter referred to as a sand collecting pit inclined surface).

In addition, a large number of nozzles are installed for low-pressure sand collection as follows. That is, nozzles are installed at the upper end of the main trough, the upper end of the inclined surface of the sand collection pit, the upper end of the area where the bottom surface of the sand basin is divided into a plurality of areas on both sides of the main trough, and the inside of the sand collection pit. There is. The nozzles provided at the upper end of the main trough and the upper end of the inclined surface of the sand collecting pit are hereinafter referred to as trough nozzles. A plurality of nozzles installed in the area (hereinafter referred to as area nozzles) are attached to nozzle headers installed along the side wall of the sand basin in each area at equal intervals. The nozzle installed in the sand collecting pit is for stirring the earth and sand in the sand collecting pit (hereinafter, referred to as a stirring nozzle), as will be described later.

Further, in order to collect low-pressure sand, pressurized water supplied from a water supply pump installed in a pump well connected to the downstream side of the sand sink is supplied (passed) to the trough nozzle, the stirring nozzle and the nozzle header. A switching valve group for stopping (stopping water) the supply thereof, that is, a switching valve for a trough nozzle, a switching valve for each nozzle header, and a switching valve for a stirring nozzle are provided. The sand removal device has a switching valve control means for switching the opening / closing operation of each of these switching valves in a predetermined order.

In preparation for the sand removal operation, the dam device installed on the upstream side of the sand basin, which was opened to allow sewage such as rainwater and sewage to enter the sand basin, is closed to prevent sewage from entering the sand basin. After that, when the sand removal device is started, the control device of the sand removal device starts the operation of the drainage pump installed in the pump well, and the water in the sand basin is transferred to the terminal treatment plant or the like. When the amount of water in the sand basin and the pump well decreases due to the drainage by the drainage pump and the water level reaches the height of the upper surface of the weir provided between the sand basin and the pump well, the operation of the drainage pump is stopped. This completes the preparation for the sand removal operation.

Subsequently, when the sand removing device is started to remove sand, the sand lifting pump control means starts the automatic rotation mode of the sand lifting pump. In the automatic operation mode, the sand lifting pump automatically starts operation when the water level sensor installed in the sand collecting pit detects that the water level in the sand collecting pit has exceeded a predetermined high water level, and sand is lifted. When the water level sensor detects that the water level in the sand collection pit has reached a predetermined low level due to the operation of the pump, the operation is automatically stopped. That is, the sand pump operates so that the water surface in the sand basin maintains the drainage state located in the sand collection pit.

Further, the switching valve is controlled by the switching valve control means based on the start of the sand removal operation. However, conventionally, the control of the sand lifting pump and the control of the switching valve have been performed independently.

More specifically, when the automatic operation mode of the sand pump is started, the sand pump immediately starts operation because the water level in the sand collection pit is above the high water level, and thereby in the sand collection pit. When the water level of the sand drops to a predetermined low level, the sand pump stops operation. On the other hand, the switching valve control means controls the switching valve as follows. The case where the bottom surface of the sand basin is divided into four regions will be described below as an example.

a) The switching valve control means first opens the switching valve for the trough nozzle (makes the water flow state). As a result, water from the water supply pump is supplied to the trough nozzle, and water is discharged from the trough nozzle. Due to the water discharge from the trough nozzle, the sediment and water on the main trough and the slope of the sand collection pit flow into the sand collection pit, and the water level in the sand collection pit rises. When the water level rises above the high water level, the sand lifting pump starts operation again.
b) The switching valve control means opens the switching valve for the stirring nozzle at the same time as or immediately before the start of operation of the sand pump.
c) After switching the water flow of the switching valve for the trough nozzle, the nozzle in the first region on the bottom surface of the sand basin after the lapse of time Tx required for the earth and sand in the main trough and the inclined surface of the sand collecting pit to flow out to the sand collecting pit. Open the header switching valve T1 for a certain period of time.
d) After the lapse of T1 for a certain period of time, the nozzle header switching valve in the first region is closed (to stop water), and the nozzle header switching valve in the second region is opened T2 for a certain period of time.
e) After the lapse of T2 for a certain period of time, the nozzle header switching valve in the second region is closed, and the nozzle header switching valve in the third region is opened T3 for a certain period of time.
f) After the lapse of the fixed time T3, the nozzle header switching valve in the third region is closed, and the nozzle header switching valve in the fourth region is opened T4 for a fixed time.
g) After the lapse of T4 for a certain period of time, the switching valve for the nozzle header in the fourth region is closed, and the switching valve for the trough nozzle is closed.
The fixed time T1 to T4 is the time required to flow the sediment accumulation amount in the region.

After closing the switching valve for the nozzle header in the fourth region, the water in the sand basin flows down to the sand collection pit and is lifted when the sand basin is in a drainage state, that is, when the water level sensor detects a low water level. The sand pump shuts down. As a result, a series of sand removal operations is completed. When this series of sand removal operations is completed, the automatic operation mode of the sand lifting pump is released.

Japanese Patent No. 3315489

As described above, in the conventional sand removal device, the sand lifting pump is started at a high water level or higher, the sand lifting pump is stopped when the water level becomes low, and then the main trough and the sand collecting pit are discharged by water discharge from the trough nozzle. When the earth and sand and water in the inclined surface flow into the sand collection pit and the water level in the sand collection pit rises above the high water level, the sand lifting pump starts operation, and at the same time or immediately before that, water discharge from the stirring nozzle starts. Was. However, the largest amount of earth and sand tends to collect in the sand collection pit at the time of the first water discharge from the trough nozzle, so when the sand pump starts operation when the water level in the sand collection pit rises above the high water level, the sand pump Was buried in the earth and sand, causing a blockage, and there was a risk that the sand could not be removed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sand removal method for preventing the sand lifting pump from being buried in the earth and sand collected in the sand collection pit at the beginning of the sand removal operation. And.

In order to achieve the above object, the present invention injects low-pressure water into each of a plurality of regions that divide the bottom surface of the sand sedimentation pond by a water supply pump , and the earth and sand accumulated on the bottom surface of each region is discharged into the plurality of regions. while flowing the current sand pit via the main troughs which are adjacent to each, in removing the sand method to exclude sand basin sediment was flowed to the Atsumarisuna pit by Agesuna pump from the settling basin, the discharge of the water supply pump The discharge amount of the sand lifting pump is increased more than the amount, and the area nozzles that are arranged in each of the plurality of areas and inject the low-pressure water and are deposited on the main trough and the inclined surface of the sand collecting pit at the time of water discharge. and Torafunozuru the earth and sand flow toward the collector sand pits, the arranged suction near port of Agesuna pump, and a stirring nozzle for stirring the sediment flowing into the collector sand pits, said by the Agesuna pump In the process of removing sand in the sand collection pit, every time the water level of the sand collection pit drops to the intermediate water level, the area of the plurality of areas where sand is not collected in the sand collection pit By selecting any one region and injecting the low-pressure water from the region nozzle arranged in the selected region, the sediment accumulated on the bottom surface of the selected region is collected in the sand collection pit. The treatment is performed on all the regions of the plurality of regions while switching the selected regions, and water discharge from the region nozzle arranged in the selected region among the plurality of regions is started. It is characterized in that water is discharged from the trough nozzle and the stirring nozzle for a predetermined time immediately before or at the same time.

According to the present invention, it is possible to prevent the sand lifting pump from being buried in the earth and sand collected in the sand collecting pit at the beginning of the sand removal operation.

It is a vertical cross-sectional view of a rainwater treatment facility including a sand basin. It is a partially omitted plan view of the range of XX of FIG. FIG. 2 is a cross-sectional view taken along the line Y1-Y1 of FIG. FIG. 2 is a sectional view taken along line Y2-Y2 of FIG. FIG. 2 is a sectional view taken along line Y3-Y3 of FIG. It is a top view around the sand collection pit. It is a cross-sectional view of Z1-Z1 of FIG. It is a cross-sectional view of Z2-Z2 of FIG. It is a water supply system diagram. It is a control system diagram which illustrates the control apparatus in 1 Embodiment. It is sectional drawing which shows the detected water level by the water level sensor of a sand collecting pit. It is a flowchart of the sand lifting pump control means. It is a flowchart of a switching valve control means. It is a flowchart of a switching valve control means.

Subsequently, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a rainwater treatment facility, which has a sand basin 2 and a pump well 3 formed between side walls Wa and Wb (see FIG. 2). The sand basin 2 is connected to an inflow culvert 4 in which sewage such as rainwater and sewage is collected from a sewer pipe (not shown). A dam device 5 is installed at the downstream end of the inflow culvert 4 to allow or prevent the inflow of sewage from the inflow culvert 4 to the sand basin 2, and on the downstream side of the dam device 5, the sand basin 2 is installed. A screen 6 for capturing contaminants is installed immediately before the upstream end of the dam.

A drainage pump P1 described later and a water supply pump P2 also serving as a stagnant water pump are installed in the pump well 3, and a sand lifting pump P3 described later is installed in the sand collecting pit 7. FIG. 1F is a filter installed at the downstream end of the sand basin 2.

Further, trough nozzles 9a are installed at the upper ends of the main trough 8a and the inclined surface 8b of the sand collecting pit, and a plurality of bottom surfaces of the sand basin are provided on both sides of the main trough 8a in the direction of water flow in the sand basin (4 in FIGS. A region nozzle 9b is installed at the upper end of the region divided into). A plurality of region nozzles 9b are installed at equal intervals in nozzle headers NH installed in the vicinity of the side walls Wa and Wb in each region. FIG. 5 shows an example in which nozzle headers NH1, NH2, ..., Which are formed by attaching a plurality of region nozzles 9b to the mother tube 10 at predetermined intervals, are used. A stirring nozzle 9c is installed in the sand collecting pit 7. A plurality of stirring nozzles 9c (4 in FIG. 2) are installed so as to discharge from two directions facing the lower part of the sand lifting pump P3 at a position close to the tangent line around the lower part of the sand lifting pump P3. There is. For the sake of simplification of the drawings, the stirring nozzle 9c is omitted in FIG. 4, and the sand lifting pump P3 is omitted in FIG.

Then, as illustrated in FIGS. 5 and 6, water from the water supply pump P2 of the pump well 3 is supplied (water flowed) to the nozzles 9a, 9b, 9c, or the supply is stopped (water stoppage). The switching valve groups VG1 and VG2, that is, the switching valve Va for the trough nozzle, the switching valve Vb for each nozzle header, and the switching valve Vc for the stirring nozzle are provided. As illustrated in FIGS. 2 and 9, when the bottom surface of the sand basin is divided into eight regions, eight nozzle header switching valves Vb (Vb1 to Vb8) are used.

A relief circuit 11 is provided in the pipeline connecting the water supply pump P2 and the switching valve groups VG1 and VG2 via the switching valve Vd to supply water from the water supply pump P2 when all the switching valves are closed. It is configured to escape to the sand basin 2.

As illustrated in FIG. 10, the control device 100 of the sand removal device that implements the method of the present invention includes a drainage pump control circuit PCON1, a water supply pump control circuit PCON2, and a sand pump control circuit PCON3, and further, a switching valve. The control circuit VCON is built-in. When the sand removal start switch (not shown) attached to the operation panel 101 of the control device 100 is operated, a sand removal start signal is given to the control device 100.

The switching valve control circuit VCON includes, as illustrated in FIG. 10, and as will be described later, an order designation unit 102 that sequentially specifies the order of regions in which water should be injected from the nozzle header, and a region of one rank. When the nozzle header switching valve is closed, the ranking determination unit 103 that determines whether or not the order of the region specified by the order specification unit 102 is the last order, and the release control valve Vd that controls the opening and closing of the relief circuit. 1 Open the switching valve control unit 104, the second switching valve control unit 105 that controls the opening and closing of the trough nozzle switching valves Va and Vc, and the nozzle header switching valves Vb1 to Vb8 in the designated area, and open the water level sensor described later. It includes a third switching valve control unit 106 that closes based on the intermediate water level detection signal from 13. These control units give a control signal for driving the opening operation or the closing operation to the group of switching valves Va, Vb, Vc, and Vd in a predetermined order.

Further, a water level sensor 13 (see FIGS. 10 and 11) for detecting the height of the water surface in the sand collecting pit 7 is electrically connected to the control device 100. The water level sensor 13 detects whether the water surface in the sand collecting pit 7 is at a predetermined high water level HWL or higher, an intermediate water level MWL, or a low water level LWL conceptually shown in FIG. 11, and detects a high water level detection signal. It outputs an intermediate water level detection signal or a low water level detection signal.

The operation of the above configuration will be described. When the dam device 5 is opened, the sewage flows into the sand basin 2 and further flows into the pump well 3, and the water level reaches a predetermined height. When the sand removal start switch is operated, the drainage pump control circuit PCON1 of the control device 100 operates the drainage pump P1 provided in the pump well 3, and the water in the pump well 3 is pumped up. Will be transferred to.

During the transfer, sediment is settled from the sewage mixed with sediment that has flowed into the sand basin 2 and is deposited on the bottom surface 2a of the sand basin 2. When the accumulated amount reaches a predetermined value, the dam device 5 is closed to prevent the inflow of sewage into the sand basin 2. Then, when the water levels of the sand sink 2 and the pump well 3 are lowered by the drainage by the drainage pump P1 and the water level becomes equal to the upper surface of the weir provided between the sand sink 2 and the pump well 3 (WL in FIG. 1), the drainage pump The control circuit PCON1 stops the operation of the drainage pump P1.

When the water surface of the sand basin 2 reaches the above water level (WL in FIG. 1), the control device 100 activates the water supply pump control circuit PCON2, the sand lifting pump control circuit PCON3, and the switching valve control circuit VCON.

The activated sand pump control circuit PCON3 starts the automatic operation mode of the sand pump P3 as shown in FIG. 12 (S11). Then, it is examined whether or not the water surface in the sand collecting pit 7 is equal to or higher than the predetermined high water level HWL by the detection signal from the water level sensor 13 (S12). At this point, immediately after the operation of the drainage pump P1 is stopped, the water surface of the sand basin 2 is at the WL and the water level is HWL or higher, so that the sand pump P3 immediately starts the operation (S13). As a result, the water surface in the sand collecting pit 7 starts to fall from the WL.

On the other hand, when the switching valve control circuit VCON is started as shown in FIG. 13, the first switching valve control unit 104 first opens the switching valve Vd of the relief circuit to prepare for driving the water supply pump P2 ( Step S21 in FIG. 13). Subsequently, immediately after the second switching valve control unit 105 opens the trough nozzle switching valve Va and the stirring nozzle Vc (S22), the water supply pump control circuit PCON2 starts the operation of the water supply pump P2, and then the first switching valve. Since the control unit 104 closes the switching valve Vd of the relief circuit (S23), the water from the water supply pump P2 is discharged from the trough nozzle 9a to the main trough 8a and the sand collecting pit inclined surface 8b. As a result, the earth and sand of the main trough 8a and the inclined surface 8b of the sand collecting pit are flown toward the sand collecting pit 7 together with water.

In the embodiment of the present invention, the switching valve control circuit VCON opens the switching valve Vc for the stirring nozzle at the same time as opening the switching valve Va for the trough nozzle (S22). Therefore, water discharge to the main trough 8a and the inclined surface 8b of the sand collection pit, stirring in the sand collection pit, and start of operation of the sand pump are performed almost at the same time. Therefore, although the amount of earth and sand flowing into the sand collection pit is particularly large at the beginning of the sand removal operation, the sand lifting pump P3 is not buried in the sand and the sand is smoothly removed.

Further, although the water level in the sand collecting pit 7 temporarily rises due to a large amount of earth and sand, the water level in the sand collecting pit 7 decreases because the discharge amount of the sand pump P3 is larger than the discharge amount of the water supply pump P2. When the water level sensor 13 detects that the falling water surface has reached a predetermined intermediate water level MWL (when Y in S24), the order designation unit 102 of the switching valve control circuit VCON sets the order of the sand collection target area, for example. Since the first region B1 is designated by +1 (S25), the third switching valve control unit 106 opens the nozzle header switching valve Vb (b1) in the first region B1 (S26), so that the nozzle of the nozzle header Water is jetted from the water, and the earth and sand accumulated in the first region B1 is washed away together with the water toward the main trough, and further flows into the sand collecting pit 7. In this way, the sewage mixed with earth and sand collected in the sand collection pit 7 and stirred is pumped up by the sand lifting pump P3 and transferred to the sewage settling basin. The water level in the sand collecting pit 7 temporarily rises above the intermediate water level MWL due to the inflow of earth and sand and water from the first region B1, but eventually falls.

When the water level sensor 13 detects that the water surface has reached the intermediate water level MWL again (when Y in S27), the nozzle header switching valve Vb (b1) is closed by the third switching valve control unit. The rank determination unit 103 checks the rank specified at that time, and if it is not the last order, returns to S25 and opens the nozzle header switching valve Vb (b2) in the next order region (S26), and the water level sensor 13 operates. When it is detected that the water level has reached a predetermined level, the nozzle header switching valve Vb (b2) is closed by the third switching valve control unit. Then, S25 (order designation) to S28 (closing of the nozzle header switching valve) are repeated until the sand collection target area is in the final order. Further, water discharge to the main trough 8a and the inclined surface 8b of the sand collection pit, stirring in the sand collection pit, and operation of the sand lifting pump are also repeated until the sand collection target area is in the final order. During this period, water discharge from the trough nozzle and the stirring nozzle is continued, and the water level repeatedly rises and falls.

Then, after the sand collection operation is performed up to the eighth region B8, which is the last region, when the water level sensor 13 detects that the water level has reached the low LWL (when Y in S210), the first switching piece The control unit 104 to the third switching valve control unit 106 opens the switching valve Vd of the relief circuit, closes the switching valve Va for the trough nozzle, the switching valve Vc for the stirring nozzle, and the switching valve Vb (b8) for the nozzle header. Complete a series of switching valve control. The water supply pump control circuit PCON2 also stops the operation of the water supply pump P2.

On the other hand, the sand lifting pump control circuit PCON3 constantly monitors the detection state of the water level sensor 13 from the start of operation of the sand lifting pump P3, and collects by closing the nozzle header switching valve Vb4 in the eighth region B8. Since the water level in the sand pit 7 drops to the low water level LWL (when Y in S14), the operation of the sand pump P3 is stopped (S15). After that, the sand pump control circuit PCON3 checks whether or not the control of the switching valve is completed (S16), and if it is not completed, returns to step S12, and when the high water level HWL is reached (when Y in S12). ) Starts the operation of the sand lifting pump P3 again, but after confirming the completion of the switching valve control (when Y in S16), the automatic operation mode of the sand lifting pump is released (S17).

As described above, the sand lifting pump P3 automatically operates when the water surface in the sand collecting pit is above the high water level HWL in order to maintain the inside of the sand collecting pit 7 in a drainage state when the automatic operation mode is started. When the water level drops to the low water level LWL, the operation is automatically stopped. In the method of the present invention, when the water level in the sand collecting pit drops to the intermediate water level MWL between the high water level HWL and the low water level LWL, the nozzle header switching valve in the first order region is closed until the last order region. Since the nozzle header switching valves in the rearward region are opened, the water surface in the sand collecting pit stops the water injection due to the closing operation of the nozzle header switching valves in the first region during the switching operation of those switching valves. It fluctuates due to the pumping of the sand pump and the start of water injection by the opening operation of the switching valve for the nozzle header in the posterior region. Therefore, the intermediate water level, which is the time reference for the switching operation of the switching valve, is prevented so that the low water level LWL is detected and the sand lifting pump P3 does not automatically stop the operation before the sand collection in the last region is completed. Is set to a height position where the water level in the sand collecting pit does not drop to the low water level LWL during the switching operation of the switching valve. The height position can be calculated from the injection amount of each nozzle 9a, 9b, 9c, the cross-sectional area of the sand basin, the discharge amount of the sand lifting pump, and the like.

If an automatic solenoid valve with a fast switching operation is used for the switching valve for the nozzle header, the water surface in the sand collection pit between the end of the water injection for the first-order region and the start of the water injection for the next-order region. Since the amount of decrease can be reduced, the accuracy of setting the position of the intermediate water level MWL is relaxed. In addition, since the load of the sand lifting pump is stable, the life is extended.

In the above embodiment, the switching valve control circuit VCON sets the opening / closing timing of the nozzle header switching valve in each region based on the detection of the intermediate water level by the water level sensor 13, but only the water level sensor 13 is used. Instead of using it, the timer provided in the switching valve control circuit VCON is used to close the switching valve for the nozzle header in the pre-ordered region after a lapse of a predetermined time, and then when the water level sensor 13 detects the intermediate water level MWL, the next It may be controlled to open the switching valve for the nozzle header in the forward region.

Further, if the trough switching valve Va and the stirring nozzle switching valve Vc are opened for a predetermined time immediately before or at the same time as opening the nozzle header switching valve in each region, the sand collection efficiency is further improved. Further, as compared with the method in which the switching valve Va for the trough and the switching valve Vc for the stirring nozzle are always opened, the effect of reducing the operating time and the amount of water used by the water supply pump can be obtained.

An embodiment in the case of using the timer and the water level sensor will be described below.
The switching valve control circuit VCON in this embodiment includes a ranking designating unit 102 that sequentially designates the ranking of regions in which water should be injected from the nozzle header, as illustrated in FIG. 10, and as will be described later. Each time an intermediate water level detection signal from the water level sensor 14 is input, a rank determination unit 103 that determines whether or not the order of the region designated by the order designation unit 102 at that time is the last order, and a switching valve of the relief circuit. When the determination results of the first switching valve control unit 104 that controls the opening and closing of Vd and the ranking determination unit 103 after inputting the sand removal operation start command or when the intermediate water level detection signal from the water level sensor 14 is input are not in the final order. , The second switching valve control unit 105 that opens the switching valve Va for the trough nozzle and the switching valve Vc for the stirring nozzle for a predetermined time, and the third switching valve that opens the switching valves Vb1 to Vb8 for the nozzle header in the designated area for a predetermined time, respectively. The control unit 106 is included, and a control signal for driving the opening operation or the closing operation in a predetermined order is given to the group of switching valves Va, Vb, Vc, and Vd.

As shown in FIG. 14, the switching valve control circuit VCON activates the control program based on the input of the sand removal operation start command from the operation panel 101, and the first switching valve control unit 104 first activates the switching valve Vd of the relief circuit. To prepare for driving the water supply pump P2 (step S31 in FIG. 14). Subsequently, the second switching valve control unit 105 opens the switching valve Va for the trough nozzle and the switching valve Vc for the nozzle for agitating earth and sand (S32), and then starts the first timer (not shown) (S33). 1 The switching valve control unit 104 closes the switching valve Vd of the relief circuit 11 (S33'). When the time of the first timer is up, that is, when water from the water supply pump P2 is injected from the trough nozzle 9a onto the main trough 8a and the inclined surface of the sand collecting pit 8b for a predetermined time (Y in S34), the trough nozzle switching valve Va and The switching valve Vc for the stirring nozzle is closed (S35). Subsequently, the rank designation unit 102 of the switching valve control circuit VCON increments (+1) the rank (S36), so that the third switching valve control unit 106 has the rank region designated by the rank designation unit 102, that is, this In this case, in order to open the nozzle header switching valve Vb1 in the first region B1 (S37), water is sprayed from each nozzle of the nozzle header NH1 and the sediment accumulated in the first region B1 is directed toward the main trough 8a. It is washed away and then flows into the sand collecting pit 7. In this way, the sewage mixed with earth and sand collected and stirred in the sand collection pit 7 is pumped up by the sand lifting pump P3 and transferred to the sewage sedimentation basin 13 via the sand sedimentation separator 11.

When the nozzle header switching valve Vb1 in the first region B1 is opened, the second timer (not shown) is started, and the time is up with the passage of a preset predetermined time (Y in S39). The nozzle header switching valve Vb1 in the area B1 is closed.

Since the discharge amount of the sand lifting pump P3 is designed to be larger than the discharge amount of the water supply pump P2, the water level in the sand collecting pit 7 initially temporarily rises due to the inflow of water and earth and sand, but eventually decreases. After that, when the water level sensor 14 detects that the water surface in the sand collecting pit has reached a predetermined intermediate water level MWL (when Y in S311), the order determination unit 103 of the switching valve control circuit VCON then. It is determined whether or not the rank designated by the rank designation unit 102 is the last order (S312).

If it is not the last order, the process returns to S22, and after the second switching valve control unit 105 discharges water (S32-S35) to the main trough 8a and the inclined surface of the sand collecting pit 8b for a predetermined time, the order designation unit 102 performs the water discharge. The next region is designated (S36), and the switching valve control circuit VCON opens the nozzle header switching valve Vb2 in the second region B2 for a predetermined time and then closes it. When the water level sensor 14 again detects that the water surface in the sand collecting pit has reached a predetermined intermediate water level MWL, it is determined at that time whether or not the order is the last order (S312). That is, until the water injection target area is in the final order, water is discharged from the trough nozzle 9a to the main trough 8a and the sand collecting pit inclined surface 8b for a predetermined time (S32-S35) and water is discharged from the nozzle header for a predetermined time (S32-S35). S37-S310) is repeated. As a result, the earth and sand in the entire area of the bottom surface of the sand basin is flushed to the main trough 8a together with water, and is flushed toward the sand collection pit 7.

When the ranking determination unit 103 determines the last order, that is, the fourth region B4 (when Y in S312), the water level sensor 14 detects that the water surface in the sand collection pit has reached a predetermined low water level LWL. At this time (when Y in S313), the first switching valve control unit 104 of the switching valve control circuit VCON controls to open the switching valve Vd of the relief circuit, and completes a series of switching valve control. The water supply pump control circuit PCON2 also stops the operation of the water supply pump P2.

To execute the opening of the trough switching valve Va and the stirring nozzle switching valve Vc for a predetermined time immediately before or at the same time as opening the nozzle header switching valve in each region, S32 and S35 in FIG. 14 by the switching valve control means VCON Instead of performing the control, in S37, control is performed to open the trough switching valve Va and the stirring nozzle switching valve Vc for a predetermined time immediately before or at the same time as opening the nozzle header switching valve (Vb) in the region of the relevant order. Just do it.

1 Rainwater treatment equipment 2 Sand basin 2a Bottom of sand basin 3 Pump well 7 Sand collection pit P1 Drainage pump P2 Water supply pump P3 Sand lifting pump 8a Main trough 8b Sand collection pit slope 8c Small trough 9a Traf nozzle 9b Area nozzle 9c Stirring nozzle NH1 ~ NH8 Nozzle header 13 Water level sensor HWL High water level MWL Intermediate water level LWL Low water level Va, Vb, Vc, Vd switching valve

Claims (1)

Low-pressure water is injected by a water supply pump into each of the plurality of regions that divide the bottom surface of the sand basin, and the sediment accumulated on the bottom surface of each region is passed through the main trough adjacent to each of the plurality of regions. while flowing the Atsumarisuna pit, in the dehumidifying sand method to exclude sand basin sediment was flowed to the Atsumarisuna pit by Agesuna pump from the settling basin,
The discharge amount of the sand lifting pump is increased more than the discharge amount of the water supply pump.
A region nozzle arranged in each of the plurality of regions and injecting the low-pressure water,
A trough nozzle that allows sediment accumulated on the main trough and the inclined surface of the sand collection pit to flow toward the sand collection pit at the time of water discharge.
It is provided with a stirring nozzle which is arranged near the suction port of the sand pump and stirs the earth and sand flowing into the sand collecting pit.
In the process of removing sand in the sand collection pit by the sand pump.
Each time the water level of the sand collecting pit drops to the intermediate water level, any one of the plurality of regions in which sand is not collected in the sand collecting pit is selected, and the selected region is selected. The process of collecting the earth and sand accumulated on the bottom surface of the selected area in the sand collecting pit by injecting the low-pressure water from the arranged area nozzle is performed while switching the selected area. In addition to doing it for all areas of
A sand basin characterized by executing water discharge from the trough nozzle and the stirring nozzle for a predetermined time immediately before or at the same time as starting water discharge from the region nozzle arranged in the selected region among the plurality of regions. Sand removal method.

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