JPH0255084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for starting and stopping a siphon tube for backwashing in a gravity filtration device.

Conventionally, when starting the siphon of a gravity-type filtration device, a vacuum pump or ejector was connected to the top of the siphon tube, and the vacuum pump or ejector reduced the air pressure in the siphon tube to start the siphon, but the power source However, there is a disadvantage that an expensive vacuum pump and pressure water pump for the ejector must be provided.

The present invention compensates for these conventional drawbacks and makes it possible to reliably start and stop a backwashing siphon pipe without the need for a special power source, with low production costs and operation management costs, and with simple operation. purpose.

That is, the present invention has a filter basin 3 which is partitioned by a partition wall 14 into a floor 6 and a backwash wastewater inflow chamber 13, which are adjacent to and separated from the backwash wastewater inflow chamber 13, so that the backwash water in the floor 6 overflows. a backwash drainage retention culvert 16 that maintains the water level below the water level at which the backwash water overflows; The backwash wastewater inlet chamber 13 and the backwash wastewater retention conduit 16 are connected to each other by an inverted U-shaped pipe having a bent portion above the water level of the filter basin 3, and both ends of which are sealed with water. The water in the backwash drainage inflow chamber 13 is discharged by the backwash siphon pipe 5, and the water head held by the overflow channel 9 causes the overwater to flow back to the floor 6. In the gravity-type filtration device, when starting and stopping the backwashing siphon pipe 5, the water surface of the backwash wastewater inflow chamber 13 when the backwashing siphon pipe 5 is about to start, and the water surface for backwashing The distance H ₁ from the top of the siphon pipe 5 and the distance H 2 between the low level water level in the water tank 19 and the water seal water level in the backwash wastewater retention conduit 16 of the suction/drainage pipe 23 attached to the water tank ₁₉ are H ₁ <
_H2 , and the distance between the high level water level in the water tank 19 and the water seal water level of the suction and drainage pipe 23.
The closed water tank 19 is installed so that H ₅ and the distance H ₄ between the upper part of the backwashing siphon pipe 5 and the water surface of the backwashing wastewater retention conduit 16 satisfy the relationship H ₅ < H ₄ . An automatic valve connects the upper part of the washing siphon pipe 5 and the water tank 19.
A siphon stop automatic release valve V ₂ is provided in the upper part of the backwashing siphon pipe 5 or in the communication pipe 20 between the automatic valve V ₁ and the backwashing siphon pipe ₅ . , A water stop valve consisting of an automatic valve or a manual valve is installed in the suction and drainage pipe 23.
V ₄ is provided, and the water tank 19 is further provided with a supply pipe 21 having an inflow valve V ₃ consisting of an automatic valve or a manual valve,
Further, the water tank 19 is provided with a water surface detection meter 25 for detecting a high level water level in the water tank 19.
5 and the automatic valve _V1 , and when the capacity of the water tank 19 is discharged from the suction and drainage pipe 23 from the high water level to the low water level, the backwash siphon pipe 5 and the communication pipe 20, the water in the backwash wastewater inflow chamber 13 is sucked up to a capacity that allows the backwash siphon pipe 5 to start, and the first backwash siphon pipe is When starting 5,
Close the water stop valve V ₄ and inflow valve V ₃ , automatic valve
V ₁ , open the siphon stop automatic release valve V ₂ ,
Fill the water tank 19 with water up to the high water level, and when the water level reaches the high water level, close the inflow valve _V3 and the siphon stop automatic release valve _V2 ,
Next, by opening the water stop valve V ₄ and the automatic valve V ₁ and discharging the water in the water tank 19 from the suction/drainage pipe 23 according to the water head difference, the backwashing siphon pipe 5 is activated, and even after activation, the automatic valve is closed. V ₁ and the water stop valve V ₄ are opened, water is sucked up from the suction and drainage pipe 23 by the negative pressure generated at the upper part of the backwashing siphon pipe 5, and when the water level reaches the above-mentioned high level, the automatic valve V ₁ is opened. close,
Water is held in the water tank 19, and the water in the water tank 19 is used as starting water for the next backwashing siphon pipe 5, and the siphon stop automatic release valve _V2 is opened and started while the automatic valve _V1 is closed. To stop the current backwashing siphon pipe 5 and start the next backwashing siphon pipe 5, close the siphon stop automatic release valve V ₂ and open the automatic valve V ₁ to open the suction and drainage pipe 23. The backwashing siphon pipe 5 is started by discharging the sucked water in the water tank 19 according to the water head difference, and even after starting, the automatic valve V ₁ is opened and the negative pressure generated at the upper part of the backwashing siphon pipe 5 is used. Water is sucked up from the suction and drainage pipe 23, and when the water level reaches the above-mentioned high level, the automatic valve _V1 is closed to retain the water in the water tank 19, and the water in the water tank 19 is used as a siphon for backwashing from the next time onwards. A siphon tube for backwashing of a gravity-type filtration device, characterized in that it is used as starting water for the siphon tube 5, and thereafter the activation of the siphon tube 5 for backwashing in the next time and the stopping of the siphon tube 5 for backwashing are sequentially repeated. This relates to how to start and stop the .

The present invention will be explained in detail below with reference to the drawings.

The drawing is a longitudinal cross-sectional view showing an example of an embodiment of a gravity-type filtration device using the method for starting and stopping a backwashing siphon pipe of the present invention. A filter pond 3 is provided, and a raw water inflow conduit 2 common to each filter pond 3 is provided above the filter pond 3. Also, on the side of the raw water inlet 2, a raw water distribution chamber 4 is provided corresponding to each filter pond 3.
Further, a raw water inflow chamber 15 is provided outside the raw water distribution chamber 4 via a water seal weir 27, and
The raw water distribution chamber 4 and the raw water inlet conduit 2 are connected via a water passage siphon pipe 22. In addition, the filter pond 3 is partitioned into two chambers by a partition wall 14, one chamber is used as a backwash wastewater inflow chamber 13, and the chamber 13 and the raw water inflow chamber 15
The raw water pipe 24 communicates with the raw water pipe 24. Further, a support bed 7 is provided below the other chamber of the overflow basin 3, and a floor 6 is formed above the support bed 7, and above the bed 6 and opposite to the height of the upper end of the partition wall 14. A plurality of wash drainage gutters 12 are provided, and one end of the backwash drainage gutters 12 on the partition wall 14 side is opened. In addition, an overwater collection chamber 8 is provided below the support bed 7, and the chamber 8 is further connected to an overwater channel 9, so that the overwater flowing out from each overwater pond 3 is passed through the overwater collection chamber 8 and sent to the overwater channel 9. Let them merge. In addition, the overwater drain 9 is communicated with the overwater drain 10 via the overflow weir 11, and the overflow weir 1 is connected to the overflow drain 10.
1 is provided so as to be higher than the upper end of the backwash drainage gutter 12, and the water level of the overflow drain 9 is kept almost constant at the height of the overflow weir 11.

Further, a water surface detector 26 is attached to the over pond 3.

In addition, a backwash wastewater retention conduit 16 is arranged adjacent to and separated from the backwash wastewater inflow chamber 13, and the backwash wastewater retention conduit 16 and the backwash wastewater inflow chamber 13 of the filter pond 3 are connected to each other. Communication is provided through a backwashing siphon tube 5, which is an inverted U-shaped tube that has a bent portion above the water level and is sealed with water at both ends. Furthermore, a backwash wastewater outflow pipe 18 is provided further outside the backwash wastewater retention pipe 16.
The backwash wastewater retention conduit 16 and the backwash wastewater outflow conduit 18 are connected to a water seal weir 1 whose height is lower than the partition wall 14.
7 to keep the water level of the backwash drainage retention conduit 16 constant at the height of the water seal weir 17.

In addition, the sealed water tank 19 is backwashed to the waste water retention conduit 16.
Distance H ₁ between the water surface of the backwash wastewater inflow chamber 13 and the upper part of the backwash siphon pipe 5 when the backwash siphon pipe 5 is to be activated,
As will be described later, the distance H ₂ between the low level water level D in the water tank 19 and the water surface of the backwash wastewater retention conduit 16 has a relationship of H ₁ <H ₂ , and the high level water level A in the water tank 19
and the distance H ₅ from the water seal water level of the suction and drainage pipe 23, which will be described later.
and the distance H ₄ between the upper part of the backwashing siphon pipe 5 and the water surface of the backwashing wastewater retention conduit 16 are provided so that H ₅ <H ₄ . Note that the capacity of the water tank 19 will be described later.

Further, in this embodiment, water from the raw water inflow conduit 2 is used as the water for starting the siphon pipe for the first time, but the water is not limited to this, and other water may be used.
Further, a water-tight water intake and drainage pipe 23 is provided below the water tank 19, which has a water stop valve V ₄ consisting of an automatic valve or a manual valve, and whose lower end is opened below the water surface of the backwash drainage retention conduit 16 and is water-sealed. The relevant suction and drainage pipe 23
The diameter of the water tank 19 is set to be such that the water in the water tank 19 can be rapidly discharged and the water in the backwash drainage retention conduit 16 can be sucked up into the water tank 19 within a short time.

Further, one end of the communication pipe 20 is connected to the upper part of the water tank 19, and the other end is connected to the upper part of the backwashing siphon pipe 5 via an automatic valve _V1 . Also automatic valve
The communication pipe 20 in front of V ₁ is branched and connected to the siphon pipe 2 for water flow via automatic valve V ₅ as shown in the drawing.
It may be connected to the upper part of 2. Note that the communication pipe 20 in front of the automatic valve V ₁ can be further branched to communicate with a backwashing siphon pipe (not shown) and a water flow siphon pipe 22 (not shown) of other filter basins. . In addition, a siphon stop automatic release valve is installed in the communication pipe 20 between the automatic valve V ₁ and the siphon pipe 5 for backwashing.
Provide V ₂ . As mentioned above, when the other end of the communication pipe 20 is connected to the upper part of the water flow siphon pipe 22 via the automatic valve _V5 as shown in the drawing,
A siphon stop automatic release valve for water flow is provided in the communication pipe 20 between the automatic valve V ₅ and the siphon pipe 22 for water flow.
Provide _V6 . Note that the siphon stop automatic release valves V ₂ and V ₆ may be attached to the upper portions of the backwashing siphon pipe 5 and the water flow siphon pipe 22, respectively. In addition, the water tank 19 and the raw water inflow conduit 2
are communicated with each other via a supply pipe 21 having an inlet valve _V3 consisting of an automatic valve or a manual valve. However, as mentioned above, when water other than raw water from the raw water inlet conduit 2 is charged as the initial start-up water of the siphon pipe, , supply pipe 2
It goes without saying that the other end of 1 is connected to its supply source.

In addition, a water surface detection meter 25 is provided in the water tank 19, and the water surface detection meter 25 and automatic valve _V1 are linked to prevent water from flowing from the suction and drainage pipe 23 due to the negative pressure generated in the upper part of the backwashing siphon pipe 5, as will be described later. When the water surface of the water tank 19 reaches a high water level A by being sucked up, an automatic valve _V1 linked to the water surface detector 25 is closed, and the suction of water from the suction/discharge pipe 23 is stopped.

Further, the low level water level D of the water tank 19 mentioned above is lower than the high level water level A, and the water level D is lower than the high level water level A.
The water tank 19 has a capacity sufficient to suck and depressurize the air present inside the backwashing siphon pipe 5 and the communication pipe 20.
When the water inside is discharged through the suction/discharge pipe 23 with a water head difference, the backwashing siphon pipe 5 is configured to start while the water level reaches from A to D.

When carrying out filtration in such a filtration device 1, the water flow siphon pipe 22 is first activated, but as shown in the drawing, the other end of the communication pipe 20 is branched and the water flow siphon pipe ₂₂ is activated via the automatic valve V5. tube 22
When communicating with the upper part of the water tank 19, the water flow siphon pipe 22 can be started by using the water tank 19 used in the present invention. That is, the water stop valve V ₄ of the suction and drainage pipe 23 is closed, the automatic valve V ₁ and the siphon stop automatic release valve V ₂ are opened to open the water tank 19 to the atmosphere, and the inflow valve of the supply pipe 21 is closed.
V ₃ is opened and raw water, for example, is supplied to the water tank 19 from the raw water inlet conduit 2 as make-up water. The water tank 19
When the water level rises to the high water level A, the automatic valve _V1 linked to the water level detector 25 closes, and then the inflow valve _V3 is closed to stop the supply of makeup water.

Next, when the automatic valve V ₅ and the water stop valve V ₄ of the water flow siphon pipe 22 are opened, the water in the water tank 19 is rapidly discharged from the suction and drainage pipe 23, and as the water level in the water tank 19 decreases, the water flow is continued. Water siphon tube 22
The air inside is sucked into the water tank 19 through the communication pipe 20, and the air pressure in the water-flowing siphon pipe 22, which is sealed by the raw water inflow conduit 2 and the raw water distribution chamber 4, decreases rapidly. The water level of 22 rises and the siphon is activated. In this way, the raw water in the raw water inflow conduit 2 flows through the water flow siphon pipe 22 into the raw water distribution chamber 4, then into the raw water inflow chamber 15, and further through the raw water pipe 24 into the backwash drainage inflow chamber 1 of the over pond 3.
3, passing over the bulkhead 14 and passing through the bed 6 in a downward flow, the excess water exits via the excess water collection chamber 8, the excess water culvert 9 and the excess water outflow culvert 10.

Note that the water flow siphon pipe 22 has an air capacity of about 100 ml compared to the backwash siphon pipe 5
Small as 1/12 and also a siphon tube for water flow 22
The distance H ₃ between the water surface on the inflow side and the top of the water flow siphon pipe 22 when trying to start the water flow is much smaller than H ₁ in a normal gravity-type filtration device, and H ₃ ≪H ₂
Therefore, by rapidly discharging the water in the water tank 19 as described above, the water flow siphon pipe 22 can be easily activated.

Additionally, when the water flow siphon tube 22 is activated,
Discharge of water from the suction/drainage pipe 23 of the water tank 19 is stopped, and the water level in the water tank 19 becomes constant. Next automatic valve
Close V ₅ and water stop valve V ₄ , open automatic valve V ₁ and siphon stop automatic release valve V ₂ , and then open the inflow valve
V ₃ is opened, make-up water is stored in the water tank 19 up to the high water level A as described above, and the automatic valve V ₁ is closed. At the same time, the inflow valve V ₃ is closed to start the siphon pipe 5 for backwashing for the first time. I'll wait.

If such filtration continues, the floor 6 will become clogged, so backwashing is performed. In other words, at the beginning of the overflow period, the water level in the overflow pond 3 is almost the same as the water level in the overflow channel 9, but as the floor 6 becomes clogged, the water level in the overflow pond 3 gradually rises until the water level reaches the water level. It reaches B of the detector 26. When this is achieved, open the siphon stop automatic release valve V ₆ and introduce air into the water flow siphon pipe 22.
Interrupt the flow of raw water into the over pond 3. Further, when the water sampling time set in advance by a timer (not shown) ends, the siphon stop automatic release valve _V6 may be opened to stop the water flow siphon pipe 22.
When the inflow of raw water is interrupted, the water in the over pond 3 passes through the floor 6 and flows out from the over water culvert 9, and the water level drops from B to C, which is slightly above the water level in the over water culvert 9. Draining is completed.

A water surface detector (not shown) is used to detect the end of water draining.
may be provided to detect that the water level has fallen to C, or the time for the water level to fall to C may be set in advance and detected using a timer (not shown).

After doing this, the first backwashing siphon tube 5
In this case, the siphon stop automatic release valve V ₂ of the backwash siphon pipe 5 is closed, and the automatic valve V ₁ and the water stop valve V ₄ are opened.

In this way, the water in the water tank 19 is rapidly discharged from the suction and drainage pipe 23, and as the water level in the water tank 19 decreases, the air in the backwashing siphon pipe 5 is sucked into the water tank 19 through the communication pipe 20. The air pressure in the backwashing siphon pipe 5, which is water-sealed by the backwashing wastewater inflow chamber 13 and the backwashing wastewater retention conduit 16, rapidly decreases, and the water level in the backwashing siphon pipe 5 rises, causing the siphon to drain. to start. In this way, the water in the filter basin 3 is discharged from the backwash wastewater inflow chamber 13 through the backwash siphon pipe 5, the backwash wastewater retention culvert 16, and the backwash wastewater outflow culvert 18, and the water level in the backwash wastewater inflow chamber 13 is reversed. The water drops below the washing drain gutter 12.

Also, during this time, filtration is being carried out in other overflow basins, and the water level in the overflow culvert is kept constant at the height of the overflow weir 11, so the water level in the overflow culvert 9 and the upper edge of the backwash drainage gutter 12 are Due to the water head difference between the
The excess water flows back from the excess water collection chamber 8 to backwash the floor 6, and the backwash wastewater flows into the backwash wastewater inflow chamber 13 from the backwash drainage gutter 12. Also, the backwash wastewater flowing into the backwash wastewater inflow chamber 13 passes through the backwash siphon pipe 5, and is discharged from the backwash wastewater retention conduit 16 and the backwash wastewater outflow conduit 18 as described above.
The water level in the backwash drain is maintained below the backwash drain gutter 12 and above the water level of the backwash drain retention culvert 16.
Continue backwashing of floor 6.

On the other hand, when the backwashing siphon pipe 5 is activated, the discharge of water from the suction and drainage pipe 23 of the water tank 19 is stopped, and the water surface in the water tank 19 temporarily becomes a low water level D. After that, if the automatic valve V ₁ and the water stop valve V ₄ are kept open, backwash wastewater flows through the backwash siphon pipe 5, and the upper part of the backwash siphon pipe 5 is, for example, 4 to 5 m H ₂ A negative pressure of O is generated, and the air in the water tank 19 is sucked into the backwashing siphon pipe 5 through the communication pipe 20. As the air in the water tank 19 is sucked, backwash wastewater from the backwash wastewater retention conduit 16 is sucked up into the water tank 19 through the suction and drainage pipe 23. Then, the water level in the water tank 19 rises to the high water level A, but at this point, the automatic valve _V1 linked to the water surface detector 25 closes, and the flow of water into the water tank 19 is automatically stopped. Then, it is placed on standby for the next activation of the backwashing siphon tube 5. In this way, while the backwashing siphon pipe 5 is activated for the first time, the negative pressure generated in the upper part of the backwashing siphon pipe 5 is used to transfer the backwash wastewater from the backwash wastewater retention conduit 16 to the water tank 19.
Since it is possible to automatically suck up and fill the tank 19 with water, it is only necessary to supply make-up water such as raw water to the water tank 19 only when starting the siphon pipe 22 for water flow and the siphon pipe 5 for backwashing for the first time, and from the next time onwards. There is no need to separately secure the filling water required for starting up the backwashing siphon pipe each time, and there is no need to increase the amount of water discharged from the backwashing drainage retention conduit 16. The switching operation of the inflow valve V ₃ and water stop valve V ₄ is only required to start the siphon pipe for the first time, and after that, basically only the operation of the automatic valve V ₁ and the siphon stop automatic release valve V ₂ is required to switch the backwash siphon pipe. The pipe 5 can be started and stopped, and even when the communication pipe 20 is branched and communicated with the siphon pipe 22 for water flow, water can be passed only by operating the automatic valve V ₅ and the siphon stop automatic release valve V ₆ . The siphon tube 22 can be started and stopped.

Next, after backwashing has been performed for a predetermined period of time, the siphon stop automatic release valve _V2 is opened, air is introduced into the backwashing siphon pipe 5, and the discharge of backwash wastewater is stopped. Next, the siphon tube 22 for water passage is started again to carry out the water passage, but when starting the siphon tube 22 for water passage from the second time onward, it is preferable to perform the following operation. That is, in a normal gravity filtration device, the water flow siphon pipe 22 is replaced by the backwash siphon pipe 5.
The capacity of the siphon tube is much smaller than that of
Since H ₃ is much smaller than H ₁ , the siphon stop automatic release valve V ₆ of the water flow siphon pipe 22 is closed and the automatic valve V ₅ is opened to connect the water tank 19 with residual negative pressure via the communication pipe 20. By simply sucking the air inside the siphon tube 22 for water passage, the water surface of the siphon tube 22 for water passage can be raised to easily start the siphon, and the siphon can be started. In normal cases, the aforementioned water flow siphon pipe 22
The water tank 19 and the communication pipe 20 have a negative pressure of, for example, 1.5 to 3 m·H ₂ O when the system is started.

Further, after starting the water passing siphon pipe 22, the automatic valve _V5 of the water passing siphon pipe 22 is closed.

In addition, after the predetermined period of time has passed, the next backwash is performed again, but first, as described above, open the siphon stop automatic release valve V ₆ of the water passing siphon pipe 22, and then Air is introduced to interrupt the inflow of raw water.

The next activation of the backwashing siphon tube 5 is performed as follows.

i.e. close the siphon stop automatic release valve V ₂ ,
The automatic valve _V1 is opened to discharge the water in the water tank 19 that was sucked up when the above-mentioned first backwash siphon pipe was activated by the difference in water head. As the water level in the water tank 19 decreases, the air in the backwashing siphon pipe 5 is sucked into the water tank 19 through the communication pipe 20, and the air is sucked into the water tank 19 through the communication pipe 20, and the air is sucked into the water tank 19 through the backwash wastewater inflow chamber 13 and the backwash wastewater retention conduit 19. The water level in the water-sealed backwashing siphon pipe 5 rises and the siphon is activated.

In addition, after the siphon is started, if the automatic valve V ₁ is left open, the siphon pipe 5 for backwashing will be activated and the siphon pipe 5 will be Due to the negative pressure generated in the upper part, water in the backwash drainage retention conduit 16 is sucked up into the water tank 19 via the suction and drainage pipe 23. Furthermore, the water level of the water sucked into the water tank 19 rises to the high water level A, but at this point the automatic valve _V1 closes and the flow of water into the water tank 19 is automatically stopped.

The water thus sucked into the water tank 19 is used as starting water for the backwashing siphon pipe 5 from the next time onwards.

The method for starting and stopping a siphon pipe for backwashing of the present invention is to discharge water from a water tank with a water head difference greater than the water head difference in the siphon pipe, and to start the siphon by sucking air in the siphon pipe that communicates with the water tank. In addition, since the siphon is stopped by opening the siphon stop automatic release valve and introducing air into the siphon pipe for backwashing, there is no need for a special power source such as a vacuum pump, and it is possible to open and close small-diameter automatic valves. The siphon can be reliably started or stopped with a simple operation, and the siphon can be reliably started and stopped with a simple operation at low manufacturing cost.

In addition, filling water into the water tank 19 requires external water for the first activation of the backwashing siphon pipe, but from the next time onwards, the negative pressure generated by the activation of the backwashing siphon pipe 5 is used. Since the water can be sucked up into the water tank through the suction/drainage pipe 23, the amount of water drained from the drainage device does not increase.

[Brief explanation of the drawing]

The figure is a longitudinal cross-sectional view of a self-cleaning powered filtration device using a method for starting and stopping a backwashing siphon pipe according to an embodiment of the present invention. 1...Gravity filtration device, 2...Raw water inlet, 3...
Water pond, 4... Raw water distribution room, 5... Backwash siphon pipe, 6... Floor, 7... Support floor, 8... Super water collection room,
9... Overwater drain, 10... Overwater outflow drain, 11... Overflow weir, 12... Backwash drainage gutter, 13... Backwash drainage inlet chamber,
14... Partition wall, 15... Raw water inflow chamber, 16... Backwash wastewater retention culvert, 17... Water seal weir, 18... Backwash wastewater outflow culvert,
19... Water tank, 20... Communication pipe, 21... Supply pipe, 22
...Water flow siphon pipe, 23...Suction and drainage pipe, 24...
Raw water pipe, 25, 26...Water surface detection meter, 27...Water seal weir, _V1 , _V5 ...Automatic valve, _V2 , _V6 ...Siphon stop automatic release valve, _V3 ...Inflow valve, _V4 ...Water stop valve .

Claims (1)

[Claims] 1 A filter basin 3 that is partitioned into a floor 6 and a backwash wastewater inflow chamber 13 by a partition wall 14, and a water level that is installed adjacent to and separated from the backwash wastewater inflow chamber 13 and at which backwash water from the floor 6 overflows. a backwash drainage retention culvert 16 that maintains a water level lower than the above, an overwater culvert 9 that communicates with the bottom of the floor 6 and maintains a water level above the water level at which the backwash water of the floor 6 overflows; For backwashing, the wastewater inflow chamber 13 and the backwash wastewater retention conduit 16 are connected to each other by having a bent part above the water level of the filter basin 3, and are formed of an inverted U-shaped pipe whose both ends are sealed with water. The water in the backwash drainage inflow chamber 13 is discharged by the backwash siphon pipe 5, and the water head held by the overflow channel 9 causes the overwater to flow back into the floor 6. In the gravity-type filtration device, when starting and stopping the backwashing siphon pipe 5, the water surface of the backwash wastewater inflow chamber 13 and the backwashing siphon pipe when the backwashing siphon pipe 5 is about to be started. Distance from the top of 5 H ₁
and the distance H ₂ between the low level water level in the water tank 19 and the water seal water level in the backwash drainage retention conduit 16 of the suction/drainage pipe 23 attached to the water tank 19 has a relationship of H ₁ <H ₂ , and The distance _H5 between the high level water level and the water seal water level of the suction and drainage pipe 23, and the distance _H4 between the upper part of the backwashing siphon pipe 5 and the water surface of the backwashing wastewater retention conduit 16 are such that _H5 < _H4 A closed water tank 19 is installed so that the relationship is as follows, and a communication pipe 20 having an automatic valve V ₁ connects the upper part of the backwashing siphon pipe 5 and the water tank 19.
and a siphon stop automatic release valve V 2 is provided in the upper part of the backwashing siphon pipe 5 or in the communication pipe 20 between the automatic valve V ₁ and the backwashing siphon pipe ₅ , and an automatic A water stop valve V ₄ consisting of a valve or a manual valve is provided, and water tank 1
9 is provided with a supply pipe 21 having an inflow valve V ₃ consisting of an automatic valve or a manual valve, and a water tank 19 is provided with a supply pipe 21 having an inflow valve V 3 consisting of an automatic valve or a manual valve.
A water surface detector 25 is provided to detect a high level water level in the water tank 19, and the water surface detector 25 and the automatic valve _V1 are linked to each other, and the capacity of the water tank 19 is controlled so that the water in the water tank 19 is at that high level. When the water is discharged from the suction/drainage pipe 23 from the water level to the above-mentioned low water level, by suctioning the air present inside the backwashing siphon pipe 5 and the communication pipe 20, the water in the backwashing drainage inflow chamber 13 is sucked up and reversed. The capacity is such that the washing siphon pipe 5 starts, and the first backwashing siphon pipe 5
When starting the water tank 19, close the water stop valve _V4 and open the inflow valve _V3 , automatic valve _V1 , and siphon stop automatic release valve _V2 to fill the water tank 19 with water up to the high water level. When the water level reaches the above-mentioned high water level, the inflow valve V ₃ and the siphon stop automatic release valve V ₂ are closed, and then the water stop valve V ₄ and the automatic valve
By opening V ₁ and discharging the water in the water tank 19 from the suction and drainage pipe 23 with a head difference, the backwashing siphon pipe 5 is activated, and even after activation, the automatic valve V ₁ and the water stop valve V ₄ are activated. When opened, water is sucked up from the suction and drainage pipe 23 by the negative pressure generated in the upper part of the backwashing siphon pipe 5, and when the water level reaches the above-mentioned high level, the automatic valve _V1 is closed and the water is poured into the water tank 19. The water in the water tank 19 is used as starting water for the next backwashing siphon pipe 5, and the siphon stop automatic release valve _V2 is opened and started with the automatic valve _V1 closed. Stop the siphon tube 5,
Furthermore, when starting the siphon pipe 5 for backwashing next time, close the siphon stop automatic release valve V ₂ ,
By opening the automatic valve V ₁ and discharging the water sucked up from the suction and drainage pipe 23 in the water tank 19 according to the water head difference, the siphon pipe 5 for backwashing is activated, and even after activation, the automatic valve V ₁ is opened for backwashing. Water is sucked up from the suction/drainage pipe 23 by the negative pressure generated in the upper part of the siphon pipe 5, and when the water level reaches the high level water level, the automatic valve _V1 is closed to retain the water in the water tank 19,
The water in the water tank 19 is used as starting water for the backwashing siphon pipe 5 from the next time onward, and thereafter, the starting of the next backwashing siphon pipe 5 and the stopping of the backwashing siphon pipe 5 are sequentially repeated. A method for starting and stopping a siphon tube for backwashing in a gravity-type filtration device.