JP6019512B2 - Sand removal method for sand basin - Google Patents

Description

The present invention relates to a sand removal method for collecting earth and sand deposited in a sand basin of a sewage treatment facility in a sand collecting pit and removing the collected earth and sand together with water by a pump.

  Sand collected at the bottom of the sand basin by discharging low pressure water from the nozzle to the bottom of the sand basin while draining the water in the sand basin with a drain pump (drainage state) Patent Document 1 discloses a low pressure sand collection type sand removal device that collects sand and sand in the pit, pumps the collected earth and sand together with water by a sand pump installed in the sand collection pit, and transfers it to a sewage settling basin.

  A sand basin that performs low-pressure sand collection by the sand removal device has 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 of the sand basin is inclined so that the periphery of the sand collection pit is deepest, and the bottom of the sand basin A trough that extends in parallel with the water flow direction (hereinafter referred to as the main trough) is formed so that the sand collecting pit side is deeper, and in the longitudinal center of the bottom, it descends from the side walls on both sides of the sand basin to the bottom of the sand collecting pit. In addition, a large number of small troughs extending in parallel to the direction perpendicular to the water flow direction in the sand basin are formed on the bottom surface of the sand basin (hereinafter referred to as the sand collecting pit slope surface).

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

  Further, in order to perform low-pressure sand collection, pressurized water supplied from a water supply pump installed in a pump well connected downstream of the sand basin is supplied (flowed) to the trough nozzle, the stirring nozzle and the nozzle header. Or a switching valve group for stopping the supply (water stoppage), that is, a trough nozzle switching valve, a switching valve for each nozzle header, and a switching valve for a stirring nozzle. And the sand removal apparatus has the switching valve control means which makes the opening / closing switching operation | movement of these each switching valve in a predetermined order.

In preparation for the sand removal operation, a dam device provided upstream of the settling basin and opened to allow sewage such as rainwater and sewage to enter the settling basin is closed to prevent sewage from entering the settling basin. Thereafter, 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 transfers the water in the sand basin to a terminal treatment plant or the like. When the amount of water in the settling basin and the pump well decreases due to drainage by the drainage pump and the water level reaches the height of the upper surface of the weir provided between the settling basin and the pump well, the operation of the drainage pump is stopped. Thereby, the preparation for the sand removal operation is completed.

  Subsequently, when the sand removal device starts the sand removal operation, the sand pump control means starts the automatic operation mode of the sand pump. In automatic operation mode, the sand pump will automatically start operation when the water level sensor installed in the sand collection pit detects that the water level in the sand collection pit has exceeded the specified high water level. When the water level sensor detects that the water level in the sand collecting pit has reached a predetermined low water level by the operation of the pump, the operation is automatically stopped. That is, the sand pump operates so as to maintain the drainage state in which the water surface in the sand basin is located in the sand collection pit.

  Further, based on the start of the sand removal operation, the switching valve is controlled by the switching valve control means. However, conventionally, the control of the sand 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 starts operation immediately because the water level in the sand pit is higher than the high water level. When the water level drops to a predetermined low water level, the sand pump is stopped. On the other hand, the switching valve control means controls the switching valve as follows. Below, the case where the bottom face of a sand basin is divided into 4 areas is demonstrated to an example.

a) The switching valve control means first opens the trough nozzle switching valve (sets the water flow state). Thereby, the water from a water supply pump is supplied to a trough nozzle, and water is discharged from the trough nozzle. The water discharged from the trough nozzle causes soil and water on the inclined surface of the main trough and the sand collecting pit to flow into the sand collecting pit, and the water level in the sand collecting pit rises. When the water level becomes higher than the high water level, the sand pump will start operation again.
b) At the same time as or immediately before the start of the operation of the sand pump, the switching valve control means opens the stirring nozzle switching valve.
c) After the passage of water through the trough nozzle switching valve, after the time Tx required for the earth and sand in the inclined surface of the main trough and sand collecting pit to flow into the sand collecting pit, the nozzles in the first region at the bottom of the sand basin The header switching valve is opened for a predetermined time T1.
d) After the predetermined time T1 has elapsed, the nozzle header switching valve in the first region is closed (water-stopped), and the nozzle header switching valve in the second region is opened for a certain time T2.
e) After the predetermined time T2 has elapsed, the nozzle header switching valve in the second region is closed, and the nozzle header switching valve in the third region is opened for a certain time T3.
f) After the fixed time T3 has elapsed, the nozzle header switching valve in the third region is closed, and the nozzle header switching valve in the fourth region is opened for a fixed time T4.
g) After the elapse of the predetermined time T4, the nozzle header switching valve in the fourth region is closed and the trough switching valve is closed.
The fixed times T1 to T4 are times necessary for flowing the sediment accumulation amount in the region.

  After closing the nozzle header switching valve in the fourth zone, the water in the sand basin flows into the sand collecting pit and the sand basin is drained, that is, when the water level sensor detects a low water level. The sand pump stops operating. Thereby, a series of sand removal operations is completed. When this series of sand removal operations is completed, the automatic operation mode of the sand pump is canceled.

Japanese Patent No. 3315489

  As described above, in the conventional sand removal device, the main trough and the sand collecting pit are discharged by the water discharged from the trough nozzle after starting the sand pump at the high water level or higher and stopping the sand pump at the low water level. Sediment and water in the sloping surface flow into the sand collection pit, and when the water level in the sand collection pit becomes higher than the high water level, the sand pump starts operation, and at the same time or just before that, starts discharging water from the stirring nozzle. Was. However, when the first water discharge from the trough nozzle, the largest amount of earth and sand is likely to collect in the sand collection pit, so when the sand pump starts operation when the water level in the sand collection pit exceeds the high water level, the sand pump May be buried in the earth and sand, causing clogging and a situation where sand removal cannot be performed.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a sand removal method in which a sand pump is not buried in earth and sand collected in a sand collection pit at the beginning of the sand removal operation. And

In order to achieve the above-mentioned object, the present invention drives the sand pump installed in the sand collection pit to maintain the drainage state in which the water level of the sedimentation basin can be collected at a low pressure , and from the trough nozzle to the main trough and the sand collection pit. causes spouted to the inclined surface, I row for each region the water discharge from the nozzle provided in the region formed by dividing into a plurality of bottom of the settling basin into settling pond water flow direction, said main trough the sediment deposited in the area flushed, and collected in a further collection sand pits, with stirring by jetting of the sediment collected on the collecting sand pit from agitation nozzles arranged in the vicinity of the suction port of the lifting sand pump, or after stirring, the fried the dehumidifying sand method, excluding pumped together with water by sand pump, at the same time before or start and to start water discharge from the nozzle of each region, Torafunozuru and stirring a predetermined time water discharge from the nozzle at the same time And wherein the Ukoto.

According to the present invention, before or simultaneously with the start to start spouting of water from the area nozzles in each area, is performed at the same time a predetermined time spouting from Torafunozuru and agitation nozzles jetting the main runner and Atsumarisuna pit inclined surface dividing sand It is possible to prevent the sand pump from being buried in the earth and sand collected in the sand collecting pit at the beginning of the operation .

It is a longitudinal cross-sectional view of the rainwater treatment facility including a sand basin. FIG. 2 is a partially omitted plan view of a range of XX in FIG. 1. FIG. 3 is a cross-sectional view taken along line Y1-Y1 of FIG. FIG. 3 is a sectional view taken along line Y2-Y2 of FIG. FIG. 3 is a cross-sectional view taken along line Y3-Y3 of FIG. It is a top view of the periphery of a sand collection pit. It is Z1-Z1 sectional drawing of FIG. It is Z2-Z2 sectional drawing of FIG. It is a water supply system diagram. It is a control system diagram which illustrates the control device in one embodiment. It is sectional drawing which shows the detection water level by the water level sensor of a sand collection pit. It is a flowchart of a sand pump control means. It is a flowchart of a switching valve control means. It is a flowchart of a switching valve control means.

Next, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a rainwater treatment facility, which includes a sand basin 2 and a pump well 3 formed between side walls Wa and Wb (see FIG. 2). The settling basin 2 is connected to an inflow trough 4 from which sewage such as rainwater and sewage is collected from a sewage pipe not shown. A dam device 5 for allowing or preventing the inflow of sewage from the inflow trough 4 to the sand basin 2 is installed at the downstream end of the inflow trough 4. A contaminant capturing screen 6 is installed immediately before the upstream end of the screen.

  In the pump well 3, a drainage pump P <b> 1 described later and a water supply pump P <b> 2 that also serves as a staying water pump are installed. F of FIG. 1 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 sand collecting pit inclined surface 8b, and a plurality of bottom surfaces of the sand basin are arranged in the direction of the water flow in the sand basin on both sides of the main trough 8a (4 in FIGS. 2 and 6, total 8). The area nozzle 9b is installed at the upper end of the area divided into (1). A plurality of region nozzles 9b are installed at equal intervals on the nozzle header NH installed in each region in the vicinity of the side walls Wa and Wb. FIG. 5 shows an example using nozzle headers NH1, NH2,... Formed by attaching a plurality of area nozzles 9b to the mother pipe 10 at a predetermined interval. In the sand collection pit 7, a stirring nozzle 9c is installed. A plurality of stirring nozzles 9c (four in FIG. 2) are installed so as to discharge from two directions facing the lower part of the sand pump P3 at a position close to the tangential line around the lower part of the sand pump P3. Yes. In order to simplify the drawing, the stirring nozzle 9c is not shown in FIG. 4, and the sand pump P3 is not shown in FIG.

  And as illustrated in FIG.5 and FIG.6, the water from the water supply pump P2 of the pump well 3 is supplied to each said nozzle 9a, 9b, 9c (water flow), or the supply is stopped (water stop). There are provided switching valve groups VG1 and VG2 constituted by electromagnetic valves, that is, a trough nozzle switching valve Va, a nozzle header switching valve Vb, and a stirring nozzle switching valve Vc. 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 via a switching valve Vd in a pipe line connecting the water supply pump P2 and the switching valve groups VG1 and VG2, and 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 apparatus for carrying out the method of the present invention incorporates a drain pump control circuit PCON1, a feed water pump control circuit PCON2, and a sand pump control circuit PCON3. A control circuit VCON is incorporated. When a sand removal start switch (not shown) added to the operation panel 101 of the control device 100 is operated, a sand removal start signal is given to the control device 100.

  As illustrated in FIG. 10, the switching valve control circuit VCON includes a rank designation unit 102 that sequentially designates the ranks of the areas where water should be injected from the nozzle header, as will be described later, and one rank area. A rank determination unit 103 that determines whether or not the rank of the region designated by the rank designation unit 102 is the last order when the nozzle header switching valve is closed, and a first that controls opening and closing of the switching valve Vd of the relief circuit. 1 switching valve control unit 104, second switching valve control unit 105 for controlling the opening and closing of trough nozzle switching valves Va and Vc, and nozzle header switching valves Vb1 to Vb8 in the region in which the order is designated are opened, and a water level sensor described later And a third switching valve control unit 106 that closes based on the intermediate water level detection signal from 13. These control units give control signals for driving the opening and closing operations to the group of switching valves Va, Vb, Vc, and Vd in a predetermined order.

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

  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 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 to pump up the water in the pump well 3, and a terminal treatment plant or the like outside the figure It is transferred to.

  During the transfer, earth and sand are precipitated from the sewage mixed with the earth and sand flowing into the sand basin 2 and deposited on the bottom surface 2a of the sand basin. When the accumulation amount reaches a predetermined value, the dam device 5 is closed and the inflow of sewage into the sand basin 2 is prevented. Then, when the water level of the sedimentation basin 2 and the pump well 3 is lowered by the drainage by the drainage pump P1, and the water level is equal to the upper surface of the weir provided between the sedimentation basin 2 and the pump well 3 (WL in FIG. 1), the drainage pump The control circuit PCON1 stops the operation of the drain pump P1.

  Further, when the water level 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 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). And it is investigated by the detection signal from the water level sensor 13 whether the water surface in the sand collection pit 7 is more than predetermined high water level HWL (S12). At this time, immediately after the operation of the drainage pump P1 is stopped, since the water surface of the sand basin 2 is at WL and is higher than the high water level HWL, the sand pump P3 starts operation immediately (S13). Thereby, the water surface in the sand collection pit 7 begins to fall from WL.

  On the other hand, as shown in FIG. 13, when the switching valve control circuit VCON is activated, 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, 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 immediately 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), 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. Thereby, the earth and sand of the main trough 8a and the sand collection pit inclined surface 8b are made to flow toward the sand collection pit 7 together with water.

  In the embodiment of the present invention, the switching valve control circuit VCON opens the stirring nozzle switching valve Vc at the same time as opening the trough nozzle switching valve Va (S22). Therefore, water discharge to the main trough 8a and the sand collecting pit inclined surface 8b, stirring in the sand collecting pit, and start of operation of the sand pump are performed almost simultaneously. Therefore, although the amount of earth and sand flowing into the sand collecting pit is particularly large at the beginning of the sand removal operation, sand removal is smoothly performed without the sand pump P3 being buried in the sand.

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 is lowered because the discharging amount of the sand pump P3 is larger than the discharging amount of the water supply pump P2. When the water level sensor 13 detects that the decreasing water level has reached a predetermined intermediate water level MWL (when S24 is Y), the rank specifying unit 102 of the switching valve control circuit VCON determines the rank of the sand collection target area, for example, +1 is designated in the first region B1 (S25), so that the third switching valve control unit 106 opens the nozzle header switching valve Vb (b1) in the first region B1 (S26). Water is jetted from the ground, and the earth and sand accumulated in the first region B1 is flowed toward the main trough together with the water, and further flows into the sand collecting pit 7. Thus, the sewage mixed with the earth and sand collected and stirred in the sand collecting pit 7 is pumped up by the sand pump P3 and transferred to the sewage settling basin. The water surface 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 again reached the intermediate water level MWL (Y in S27), the third switching valve control section closes the nozzle header switching valve Vb (b1). The order determination unit 103 checks the order designated at that time, and if it is not the last order, the process returns to S25 to open the nozzle header switching valve Vb (b2) in the next order (S26), and the water level sensor 13 When it is detected that the predetermined intermediate water level has been reached, the nozzle header switching valve Vb (b2) is closed by the third switching valve control unit. Then, S25 (order designation) to S28 (closure of the nozzle header switching valve) are repeated until the sand collection target region is in the last order. Moreover, the water discharge to the main trough 8a and the sand collection pit inclined surface 8b, the stirring in the sand collection pit, and the operation of the sand pump are repeated until the sand collection target region is in the last order. During this time, water discharge from the trough nozzle and the stirring nozzle is continued, and the water level repeatedly rises and falls.

  After the sand collecting operation is performed up to the eighth area B8 which is the last order area, when the water level sensor 13 detects that the water level LWL has become low (Y in S210), the first switching piece The control unit 104 to the third switching valve control unit 106 open the relief circuit switching valve Vd, close the trough nozzle switching valve Va, the stirring nozzle switching valve Vc, and the nozzle header switching valve Vb (b8). A series of switching valve control is completed. Further, the feed water pump control circuit PCON2 also stops the operation of the feed water pump P2.

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

  As described above, the sand pump P3 automatically operates when the water level in the sand collection pit is higher than the high water level HWL in order to maintain the sand collection pit 7 in the drained 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 preceding region is closed to the last region. Since the switching valve for the nozzle header in the rear area is opened, the water surface in the sand collecting pit is stopped during the switching operation of these switching valves due to the closing operation of the nozzle header switching valve in the previous area. It fluctuates depending on the pumping up of the sand pump and the start of water injection by the opening operation of the nozzle header switching valve in the subsequent region. Therefore, an intermediate water level that is a temporal reference for the switching operation of the switching valve so that the low water level LWL is detected before the sand collection in the last region is finished and the sand pump P3 does not automatically stop operation. The water level in the sand collecting pit is set to a height position that 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 trough and each nozzle header, the cross-sectional area of the sand collecting pond, the discharge amount of the sand pump, and the like.

  If an automatic solenoid valve with a fast switching operation is used as the nozzle header switching valve, the water level in the sand collecting pit between the end of the water injection for the preceding region and the start of the water injection for the next region is reduced. Since the amount of decrease can be reduced, the accuracy in setting the intermediate water level MWL is relaxed. Moreover, since the load of the sand pump is stabilized, 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 fact that the water level sensor 13 detects the intermediate water level. Instead of using the timer provided in the switching valve control circuit VCON, when the predetermined time elapses, the nozzle header switching valve in the predecessor region is closed, and then when the water level sensor 13 detects the intermediate water level MWL, You may control to open the nozzle header switching valve in the forward region.

Also, at the same time immediately before or opening opening the nozzle header selector valve of each region, when the switching valve Va and stirred nozzle switching valve Vc troughs to be opened a predetermined time at the same time, Atsumarisuna efficiency is further improved.

Hereinafter, an embodiment in which a timer and a water level sensor are used will be described.
The switching valve control circuit VCON in this embodiment includes, as illustrated in FIG. 10 and, as will be described later, a rank designating unit 102 that sequentially designates the rank of the area where water should be injected from the nozzle header, and a postscript 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 rank of the region designated by the rank designation unit 102 is the last order, and a relief circuit switching valve When the determination result of the first determination valve control unit 104 that controls the opening / closing of Vd and the rank determination unit 103 when the sand removal operation start command is input or when the intermediate water level detection signal from the water level sensor 14 is input is not the last order The trough nozzle switching valve Va and the agitation nozzle switching valve Vc are opened for a predetermined time, and the nozzle header switching valves Vb1 to Vb in the regions in which the ranks are designated. And a third switching valve control unit 106 that opens 8 for a predetermined time, and gives a control signal for driving the opening and closing operations in a predetermined order to the group of switching valves Va, Vb, Vc, Vd. is there.

As shown in FIG. 14, the switching valve control circuit VCON starts a control program based on a sand removal operation start command input from the operation panel 101, and the first switching valve control unit 104 first switches the relief valve switching valve Vd. To prepare for driving the water supply pump P2 (step S31 in FIG. 14). Subsequently, after the second switching valve control unit 105 opens the trough nozzle switching valve Va and the earth and sand stirring nozzle switching valve Vc (S32), the first timer (not shown) is started (S33), and The one switching valve control unit 104 closes the switching valve Vd of the relief circuit 11 (S33 ′). When the first timer has timed, i.e., (Y at S34) when water from the water supply pump P2 is a predetermined time injected into the main trough 8a and Atsumarisuna pit inclined surface 8b from the trough nozzles 9a, Torafunozuru switch valve Va And the switching valve Vc for earth and sand stirring nozzle is closed (S35). Subsequently, since the rank designation unit 102 of the switching valve control circuit VCON increments (+1) the rank (S36), the third switching valve control unit 106 has a rank region designated by the rank designation unit 102, that is, this In this case, since the nozzle header switching valve Vb1 in the first region B1 is opened (S37), water is sprayed from each nozzle of the nozzle header NH1, and the sediment accumulated in the first region B1 is directed to the main trough 8a. And then flows into the sand collecting pit 7. Thus, the sewage mixed with the earth and sand collected and stirred in the sand collecting pit 7 is pumped up by the sand pump P3 and transferred to the sewage sand settling basin 13 through the sand settling separator 11.

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

  Since the discharge amount of the sand pump P3 is designed to be larger than the discharge amount of the water supply pump P2, the water surface in the sand collecting pit 7 rises temporarily 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 level in the sand collection pit has reached a predetermined intermediate water level (Y in S311), the rank determination unit 103 of the switching valve control circuit VCON then ranks. It is determined whether or not the order specified in the specification unit 102 is the last order (S312).

If it is not the last order, the process returns to S22 and the second switching valve control unit 105 discharges water (S32-S35) for a predetermined time to the main trough 8a and the sand collecting pit inclined surface 8b, and then the rank specifying unit 102 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 it is detected again by the water level sensor 14 that the water level in the sand collection pit has reached the predetermined intermediate water level MWL , it is then determined whether or not the order is the last order (S312). That is, until the water injection target area is the last order, a predetermined time from the main trough 8a and Atsumarisuna predetermined time of the water discharge into the pit inclined surface 8b (S32-S35) and the nozzle headers from the trough nozzle 9a with respect to the region spouting (S37-S310) is repeated. As a result, the earth and sand in the entire area of the bottom surface of the sand basin is caused to flow along with the water to the main trough 8 a and to the sand collecting pit 7.

  When the rank determining unit 103 determines the last order, that is, the fourth region B4 (Y in S312), the water level sensor 14 detects that the water level in the sand collecting pit has become a predetermined low water level. At (when Y in S313), the first switching valve control unit 104 of the switching valve control circuit VCON performs control to open the switching valve Vd of the relief circuit, and the series of switching valve control is completed. Further, the feed water pump control circuit PCON2 also stops the operation of the feed water pump P2.

Immediately before or simultaneously with the start opening the nozzle header selector valve of each area, the switching valve Va and the switching valve Vc stirrer nozzle troughs to run the open predetermined time simultaneously, in FIG. 14 by the switching valve control means VCON Instead of performing the control of S32 and S35, in S37, the trough switching valve Va and the stirring nozzle switching valve Vc are set to a predetermined value immediately before or simultaneously with the opening of the nozzle header switching valve (Vb) in the region of the order. Control that opens at the same time may be performed.

DESCRIPTION OF SYMBOLS 1 Rainwater treatment facility 2 Sand basin 2a Bottom surface of sand basin 3 Pump well 7 Sand collection pit P1 Drainage pump P2 Water supply pump P3 Sand collection pump 8a Main trough 8b Sand collection pit slope 8c Small trough
9a Trough nozzle
9b area nozzle
9c Stirrer nozzles NH1 to NH8 Nozzle header 13 Water level sensor HWL High water level MWL Intermediate water level LWL Low water level Va, Vb, Vc, Vd selector valve

Claims (1)

While maintaining the drainage state of the water level of the sand basin can low current sand drives the Agesuna pump installed in Atsumarisuna pit, causes spouted into the main trough and Atsumarisuna pit inclined surface from Torafunozuru, the grit chamber I row for each region the water discharge from the nozzle provided in the region formed by dividing the plurality of bottom surface grit pond water flow direction, flow of sediment deposited in the area in the main trough, collect more collections sand pits, while stirring the water discharged from the agitation nozzles arranged in the vicinity of the suction opening before KiAge sand pump the condensed sand pit collected sediment, or after stirring, removing sand excluding pumped together with water by the Agesuna pump in the method, at the same time before or start and to start spouting from the nozzle of each region, and performs the Torafunozuru and water discharge from the stirring nozzle predetermined time simultaneously dividing Method.

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