JPH0255085B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for starting and stopping a backwash siphon tube of 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.

It is an object of the present invention to compensate for these conventional drawbacks, and to reliably start and stop a backwash siphon pipe without requiring a special power source, at low production cost, and with simple operation.

That is, the present invention provides a filter basin 3 which is partitioned by a partition wall 14 into a floor 6 and a backwash wastewater inflow chamber 13, and is installed adjacent to and separated from the backwash wastewater inflow chamber 13, so that the backwash water on the floor 6 overflows. A backwash drainage retention culvert 16 that maintains a water level below the flowing water level, and an overwater culvert 9 that communicates with the bottom of the floor 6 and maintains a water level above the water level from which the backwash water of the floor 6 overflows. , consisting of an inverted U-shaped pipe that communicates the backwash wastewater inflow chamber 13 and the backwash wastewater retention conduit 16 with a bent part above the water level of the filter basin 3, and 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 overwater culvert 9 causes the overwater to flow back to the floor 6. In the gravity type filtration device configured as above, when starting and stopping the backwashing siphon pipe 5, the water surface of the backwash wastewater inflow chamber 13 when starting the backwashing siphon pipe 5 and the backwash 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 and 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.
Connected by a communication pipe 20 having V ₁ and a water tank 19
A siphon stop automatic release valve _V3 is installed in the upper part of the tank or in the communication pipe 20 between the water tank 19 and the automatic valve _V1 ,
Further, the water tank 19 is provided with a supply pipe 21 having an inflow valve V ₅ consisting of an automatic valve or a manual valve, and furthermore, the water tank 1
9 is provided with a water surface detector 25 for detecting a high level water level in the water tank 19, and the intake/discharge pipe 23 is provided with an automatic valve V ₂ that is linked to the water surface detector 25,
And the capacity of the water tank 19 is increased so that when the water in the water tank 19 is discharged from the suction/drainage pipe 23 from the high water level to the low water level, the air present inside the backwashing siphon pipe 5 and the communication pipe 20 is By suctioning, the water in the backwashing drainage inflow chamber 13 is sucked up to a capacity that allows the backwashing siphon pipe 5 to start. When starting the backwashing siphon pipe 5 for the first time, the automatic valve V ₂ is used. At the same time, the siphon stop automatic release valve V ₃ and the inflow valve V ₅ are opened to fill water into the water tank 19, and when the water level reaches the above-mentioned high level, the automatic valve V ₂ is closed and the inflow valve V is closed. _5. Close the siphon stop automatic release valve V ₃ , then open the automatic valve V ₁ and automatic valve V ₂ to open the water tank 1.
The backwashing siphon pipe 5 is activated by discharging the water in the water from the suction/discharge pipe 23 according to the water head difference.
Further, even after startup, the automatic valves V ₁ and V ₂ are opened, and water is sucked up from the suction and drainage pipe 23 by the negative pressure generated in the backwashing siphon pipe 5, and when the water level reaches the above-mentioned high level, Close the automatic valve _V2 to retain water in the water tank 19, and use the water in the water tank 19 as starting water for the next backwashing siphon pipe 5,
Also automatic valve V ₁ and siphon stop automatic release valve
Backwash siphon tube 5 activated by opening V ₃
Stop the siphon pipe 5 for the next backwash.
Automatic release valve stops the siphon when starting
V ₃ is closed, automatic valve V ₁ and automatic valve V ₂ are opened, and the water in the water tank 19 sucked up from the suction and drainage pipe 23 is discharged according to the water head difference, thereby removing the backwashing siphon pipe 5.
After starting, the automatic valve V ₁ and the automatic valve V ₂ are opened, and 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 the water level reaches the above-mentioned high level. At the point when the water has deteriorated, the automatic valve V ₂ is closed to retain the water in the water tank 19, and the water in the water tank 19 is used as starting water for the siphon pipe 5 for backwashing from the next time onwards. The present invention relates to a method for starting and stopping a siphon tube for backwashing in a gravity-type filtration device, characterized in that starting the siphon tube 5 and stopping the siphon tube 5 for backwashing are sequentially repeated.

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

The drawing is a longitudinal cross-sectional explanatory 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 plurality of filter ponds 3 are provided in a line, and a raw water inflow conduit 2 common to each of the filter ponds 3 is provided above the filter ponds 3. In addition, a raw water distribution chamber 4 is provided on the side of the raw water inlet 2 corresponding to each filter pond 3, and furthermore, a raw water distribution chamber 4 is provided on the side of the raw water inlet 2.
A raw water inflow chamber 15 is provided outside of the water seal weir 27, and the raw water distribution chamber 4 and the raw water inflow conduit 2
is read directly through the water passage siphon tube 22.
Further, 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 are communicated through a raw water pipe 24. In addition, a support bed 7 is provided below the other chamber of the over pond 3, and a floor 6 is formed above the support bed 7.
A plurality of backwash drainage troughs 12 are provided above the floor 6 and at the height of the upper end of the partition wall 14, and one end of the backwash drainage troughs 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. Further, the overwater drain 9 is communicated with the overwater outflow drain 10 via an overflow weir 11, and the overflow weir 11 is provided so as to be higher than the upper end of the backwash drainage gutter 12, so that the water level of the overwater drain 9 is is maintained approximately constant at the height of the overflow weir 11. Also Kagaike 3
A water surface detection meter 26 is attached to the.

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 _H2 between the low level water level D in the water tank 19 and the water surface of the backwash wastewater retention conduit 16 is _H1, respectively.
< _H2 , and the distance H5 between the high level water level A in the water tank 19 and the water seal water level of the suction and drainage pipe 23, which will be described later, and the distance between the upper part of the backwashing siphon pipe ₅ and the backwash wastewater retention conduit 16. The distance from the water surface is H ₄ and 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-sealed suction/drainage pipe 23 is provided below the water tank 19, which has an automatic valve V ₂ and whose lower end is opened below the water surface of the backwash wastewater retention conduit 16 and is water-sealed. Backwash drainage retention conduit 1 that can quickly drain water in 19 and return to water tank 19 in a short time
The thickness should be such that it can absorb 6 of the water.

Further, one end of a 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 V ₁
The communication pipe 20 in front of the pipe 20 may be branched and connected to the upper part of the water flow siphon pipe 22 via an automatic valve _V4 . Note that the communication pipe 20 in front of the automatic valve V ₁ can be further branched to communicate with a backwash siphon pipe (not shown) and a water flow siphon pipe (not shown) of other filter basins.

Additionally, a siphon stop automatic release valve _V3 is provided at the top of the water tank 19. The siphon stop automatic release valve V ₃ is connected to the communication pipe 2 between the water tank 19 and the automatic valve V ₁ .
There is no problem even if it is set to 0.

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 V ₂ are linked.
When the water surface reaches the high water level A, the automatic valve V ₂ linked to the water surface detector 25 closes, and the
Configure it so that it stops drawing water from it.
In addition, the water tank 19 and the raw water inlet culvert 2 are communicated via the supply pipe 21 having the inlet valve _V5 , which is an automatic valve or a manual valve. Needless to say, when water other than the above is to be filled, the other end of the supply pipe 21 is communicated with the supply source.

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 air having the capacity of the water tank 19 from water levels A to D is sucked inside the backwashing siphon pipe 5 and the communication pipe 20. When the water in the water tank 19 is discharged through the suction/drainage pipe 23 with a water head difference, while the water level reaches from A to D, the backwash siphon pipe 5 Configure it to start.

When carrying out filtration in such a filtration device 1, the siphon pipe 22 for water flow is first activated, but as shown in the drawing, the other end of the communication pipe 20 is branched and the water flow is carried out via the automatic valve _V4 . siphon tube 22
When the water tank 19 is in communication 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 automatic valve V ₂ of the suction and drainage pipe 23 is closed, the siphon stop automatic release valve V ₃ is opened, and the inflow valve V ₅ of the supply pipe 21 is opened to supply raw water, for example, as make-up water to the water tank 19 from the raw water inlet conduit 2. . When the water level of the water tank 19 rises to the high water level A, the inflow valve _V5 is closed and the supply of raw water is stopped. Also, after stopping the supply of raw water, close the siphon stop automatic release valve _V3 .

Next, when the automatic valves V ₄ and V ₂ of the water flow siphon pipe 22 are opened, the water in the water tank 19 is rapidly discharged from the water intake and drainage pipe 23, and as the water level in the water tank 19 decreases, the water flow is stopped. The air in the siphon pipe 22 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, and the water flow is stopped. The water level in the siphon tube 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 13 of the over pond 3.
The excess water flows downwardly through the bed 6 over the bulkhead 14 and exits via the collection chamber 8, the excess water culvert 9 and the excess water outflow culvert 10.

Note that the water flow siphon pipe 22 has a smaller air capacity in the siphon, for example, about 1/12, compared to the backwashing siphon pipe 5, and the air capacity on the inflow side when trying to start the water flow siphon pipe 22 is small. The distance _H3 between the water surface and the top of the water flow siphon pipe 22 is much smaller than _H1 in a normal gravity flow device
Since there is a relationship of H ₃ <<H ₂ , the water in the water tank 19 can be rapidly discharged by the above-described operation, and the water passage siphon pipe 22 can be easily activated.

On the other hand, when the water flow siphon pipe 22 is activated, the water discharge from the water intake and drainage pipe 23 of the water tank 19 is stopped.
The water level in the water tank 19 remains constant. Then automatic valve V ₂
At the same time, the automatic valve V ₄ is closed, the siphon stop automatic release valve V ₃ is opened, and the inflow valve V ₅ is opened to store the raw water in the water tank 19 up to the high water level A as described above, and then open the inflow valve. Close V ₅ and wait for the first activation of the backwashing siphon tube 5.

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. If you reach this way, the siphon will already stop automatically opening the valve V ₃
is open, the automatic valve _V4 is opened to introduce air into the water flow siphon pipe 22, and the flow of raw water into the filter pond 3 is interrupted. Also, when the water sampling time set in advance with a timer (not shown) ends,
The water flow siphon pipe 22 may be stopped by opening the automatic valve _V4 . 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, and the water in the over pond 3 is drained. ends.

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 automatic valve V ₄ of the water flow siphon pipe 22 and the siphon stop automatic release valve V ₃ are activated.
, and open the automatic valves V ₁ and V ₂ of the backwashing siphon pipe 5. In this way, the water in the water tank 19 is rapidly discharged from the suction and drainage pipe 23,
As the water level in the water tank 19 decreases, the air in the backwash 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 of the filter basin 3 and the backwash wastewater retention conduit 16. The air pressure in the backwashing siphon tube 5, which is sealed with water, rapidly decreases, the water level inside the backwashing siphon tube 5 rises, and the siphon is activated. 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 overwater basins, and the water level in overwater culvert 9 is kept constant at the height of overflow weir 11. Due to the water head difference with the edge, excess water in the excess water channel 9 flows back from the excess water collection chamber 8 to the floor 6.
Backwashing is performed, and the backwash wastewater flows into the backwash wastewater inflow chamber 13 from the backwash drainage gutter 12. In addition, the backwash wastewater flowing into the backwash wastewater inflow chamber 13 passes through the backwash siphon pipe 5, and then flows into the backwash wastewater retention conduit 16 as described above.
and backwash drainage from drain culvert 18, and the corresponding room 1
3 is maintained below the backwash drainage gutter 12 and above the water level of the backwash drainage retention culvert 16, so that the floor 6 is continuously backwashed.

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.
The water surface in the water tank 19 temporarily becomes a low water level D. However, if the automatic valves V ₁ and V ₂ are left open after that, the activation of the backwashing siphon pipe 5 creates a negative pressure of, for example, 4 to 5 m H ₂ O in the upper part of the backwashing siphon pipe 5. occurs, so water tank 19
The air inside can be sucked into the backwashing siphon pipe 5 through the communication pipe 20. In addition, as the air is sucked, the backwash wastewater in the backwash wastewater retention conduit 16 is sucked up into the water tank 19 through the suction and drainage pipe 23, and the water level in the water tank 19 rises. When the water level rises to level A, the water surface detector 25 detects it and the automatic valve _V2 automatically closes. 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 suck up the backwash wastewater from the backwash wastewater retention conduit 16 into the water tank 19 and tension it. Therefore, only when starting the siphon pipe 22 for water flow and the siphon pipe 5 for backwashing for the first time,
It is only necessary to supply makeup water such as raw water to the water tank 19,
There is no need to separately secure the filling water required when starting up the backwashing siphon pipe from the next time onwards, and there is no need to increase the amount of water discharged from the backwashing drainage retention conduit 16. The switching operation of inflow valve V ₅ only requires starting the siphon pipe for the first time, and from then on, basically automatic valve V ₁
The backwashing siphon pipe 5 can be started and stopped only by operating the automatic valve V ₂ and the siphon stop automatic release valve V ₃ .

Next, after backwashing has been performed for a predetermined period of time, the backwashing siphon pipe 5 is stopped, but before that, the water flow siphon pipe 22 may be activated to start water flow. In other words, in a normal gravity filtration device, the air capacity of the siphon tube for water flow is much smaller than that for backwashing, and
Since H ₃ is much smaller than H ₁ , the automatic valve V ₄ of the water flow siphon pipe 22 is opened and the communication pipe 20 is connected to the water tank 19 which has the residual negative pressure generated by starting the backwashing siphon pipe 5. Siphon tube 2 for water flow through
By simply suctioning the air inside the siphon 2, the water level of the siphon tube 22 for water passage can be raised to easily activate the siphon, and filtration can be started. Also, when starting the water flow siphon pipe 22, the water tank 19 and the communication pipe 20 are, for example, 1.5 to 3 m long.
It has a residual negative pressure of H ₂ O, and it can be started with such residual negative pressure, but if you open the automatic valve V ₁ ,
Even by using the negative pressure generated in the upper part of the backwashing siphon tube 5, the air in the water passage siphon tube 22 is sucked, and the water passage siphon tube 22 can be easily activated.

In addition, after starting filtration, immediately close the automatic valve V ₄ of the siphon pipe 22 for water flow, then open the automatic valve V ₁ and the siphon stop automatic release valve V ₃ to introduce air into the siphon pipe 5 for backwashing. to stop the discharge of backwash wastewater.

After the filtration has been carried out for a predetermined period of time, the next backwash is carried out again, but first, as mentioned above, the automatic valve V ₄ of the water flow siphon pipe 22 is opened, and the siphon, which was left open in the previous process, is stopped. Air is introduced into the water flow siphon pipe 22 through the automatic release valve _V3 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 ₃ ,
Water tank 1 that was sucked up when opening the automatic valve V ₁ and automatic valve V ₂ and starting the siphon pipe for backwashing described above for the first time.
The water in 9 is discharged 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 automatic valves V ₁ and V ₂ are left open in the same way as the initial activation of the backwash siphon pipe 5 described above,
When the backwashing siphon pipe 5 is activated, negative pressure is generated in the upper part of the siphon pipe 5, and water in the backwash wastewater retention conduit 16 is sucked up into the water tank 19 via the suction/drainage pipe 23. Furthermore, the water level of the water sucked into the water tank 19 rises to the high level water level A, but at this point, the automatic valve V ₂ linked to the water level detector 25 closes, and the water automatically stops flowing into the water tank 19. Stop at.

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 the backwashing siphon pipe of the present invention is to discharge water from the water tank with a water head difference that is larger than the water head difference in the backwashing siphon pipe, and to suck air in the backwashing siphon pipe that communicates with the water tank. This method does not require a special power source such as a vacuum pump, and is a small and compact method. The siphon can be reliably started or stopped simply by opening and closing an automatic valve of the same diameter, and the siphon can be reliably started and stopped with 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 and drainage pipe 23, the amount of water discharged from the filtration device does not increase.

Furthermore, if the water flow siphon pipe 22 is branched into the communication pipe 20 and communicated with the water tank 19 used in the present invention, the water flow siphon pipe 22 can be easily started by simply switching the automatic valve _V4 . There is no need to separately provide a siphon stop automatic release valve for stopping the water flow siphon pipe, and the siphon can be stopped using the siphon stop automatic release valve _V3 of the backwashing siphon pipe 5.

[Brief explanation of the drawing]

The figure is a longitudinal cross-sectional view of a self-cleaning gravity-type 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... Water surface detection meter, 26... Water surface detection meter,
27...Water seal weir, _V1 , _V2 , _V4 ...Automatic valve, _V3 ...Siphon stop automatic release valve, _V5 ...Inflow valve.

Claims (1)

[Claims] 1 A filter basin 3 partitioned into a floor 6 and a backwash wastewater inflow chamber 13 by a partition wall 14, and a water level which 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 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 inlet 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 the top of the water tank 19 or the water tank 19
A siphon stop automatic release valve _V3 is provided in the communication pipe 20 between the automatic valve _V1 and the water tank 19, and a supply pipe 21 having an inflow valve _V5 consisting of an automatic valve or a manual valve is provided in the water tank 19. A water surface detector 25 is provided to detect a high level water level in the water tank 19, and an automatic valve _V2 that is linked to the water surface detector 25 is provided in the suction/discharge pipe 23, and the capacity of the water tank 19 is adjusted to When the water is discharged from the suction/drainage pipe 23 from the high water level to the low water level, the air inside the backwashing siphon pipe 5 and the communication pipe 20 is suctioned, thereby reducing the inside of the backwashing wastewater inflow chamber 13. The capacity is set so that the backwashing siphon pipe 5 can start by sucking up water, and when starting the backwashing siphon pipe 5 for the first time, an automatic valve is used.
V ₂ closes and shuts off the siphon with automatic release valve
V ₃ , the inflow valve V ₅ is opened to fill water into the water tank 19, and when the water level reaches the high level water level, the automatic valve V ₂ is closed, and the inflow valve V ₅ , the siphon stop automatic release valve V ₃ close, then automatic valve
By opening the automatic valve V ₁ and the automatic valve V ₂ and discharging the water in the water tank 19 from the suction and drainage pipe 23 according to the water head difference, the backwashing siphon pipe 5 is activated, and even after activation, the automatic valve V ₁ and the automatic valve The valve V ₂ is opened, and the negative pressure generated in the backwashing siphon pipe 5 sucks up water from the suction and drainage pipe 23. When the water level reaches the above-mentioned high level, the automatic valve V ₂ is closed and the water is removed from 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 backwashing is started by opening the automatic valve _V1 and the siphon stop automatic release valve _V3 . To stop the siphon pipe 5 for backwashing and start the siphon pipe 5 for backwashing next time, close the siphon stop automatic release valve V ₃ and open the automatic valves V ₁ and V ₂ to open the siphon pipe 23 from the suction and drainage pipe 23. The backwashing siphon pipe 5 is activated by discharging the sucked water in the water tank 19 according to the water head difference, and even after activation, the automatic valve V ₁ and the automatic valve V ₂ are opened and the water is discharged from the upper part of the backwashing siphon pipe 5. Water is sucked up from the suction and drainage pipe 23 by the generated negative pressure, and when the water level reaches the above-mentioned high level, the automatic valve V ₂ is closed to retain the water in the water tank 19, and the water in the water tank 19 is used from next time onwards. The gravity-type filtration device is characterized in that it is used as starting water for the backwashing siphon pipe 5, and thereafter, the starting of the next backwashing siphon pipe 5 and the stopping of the backwashing siphon pipe 5 are sequentially repeated. How to start and stop a backwash siphon tube.