JPH09141009A - Gravity filter and starting method of backward washing siphon in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more miniaturize a vacuum generating tank than before and to effectively perform backward washing. SOLUTION: To plural branch pipes 17b of a communicative pipe 17 connected to a vacuum generating tank 16, small diameter siphons 15a-15c functioning as a backward washing waste water passing part constituting a backward washing siphon 15 are connected, respectively. Negative pressure generated by the vacuum generating tank 16 is used for only the small diameter siphon 15a which first starts the siphon 15, and for the other small diameter siphons 15b, 15c, negative pressure generated by the small diameter siphon 15a which has been operated is used to start them. The vacuum generating tank 16 is miniaturized because it is enough to only the small diameter siphon 15a.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gravity type filtration device.

[0002]

2. Description of the Related Art Known gravity type filtration devices are disclosed in, for example, Japanese Utility Model Publication No. 61-43527 and Japanese Patent Publication No. 2-550851. As shown in FIG. 3, the gravity type filtration device 100 includes a plurality of filtration basins 101 arranged in a row, a common raw water inflow conduit 102 provided above the filtration basin 101, and the raw water inflow conduit 102. A raw water distribution chamber 104 provided on the side corresponding to each filter basin 101 via a partition 103, and a raw water inflow chamber 106 provided adjacent to the raw water distribution chamber 104 via a water seal 105.
And the backwash drainage drainage conduit 107b provided adjacent to the filter basin 101 and further provided outside the backwash drainage drainage conduit 10b.
7, a backwash drainage ditch 107a, a filter bed 108 provided in the filtration basin 101, a filtered water collection chamber 109 provided below the filtered bed 108, and filtered water that has passed through the filtered water collection chamber 109 join together. Filtered water outlet 110 and filtered water outlet outlet 111
have.

Further, a vacuum generating tank 112 communicating with the raw water inlet 102 through a valve 112a and a valve 113a are interposed, one end of which is connected to the vacuum generating tank 112, and the other end of which is backwashed and drained. A drainage pipe 113 facing the inside of the backwash drainage staying in the backwash drainage retention drain 107a that constitutes the drain 107 and sealed with water, and a raw water inlet 102 and a raw water distribution chamber 104 separated by a partition wall 103. And a raw water inflow siphon 115 that is connected to the vacuum generation tank 112 by a communication pipe 114 having a valve 114a that is interposed, and a filtration basin 10 that is separated by a partition 116.
1 and the backwash drainage ditch 107a, and the backwash siphon pipe 117 is connected to the vacuum generation tank 112 by a communication pipe 114 having an intervening valve 114b.
And

In the case of filtering, first, the communication pipe 1
14 valve 114c is closed and valve 114a and drain pipe 113 are closed.
The drain valve 113a is opened to drain the water in the vacuum generation tank 112 from the drain pipe 113. As a result, the air in the raw water inflow siphon 115 is sucked into the vacuum generation tank 112, and the air pressure in the raw water inflow siphon 115 sealed by the raw water inflow conduit 102 and the raw water distribution chamber 104 is rapidly reduced.
The water surface in the raw water inflow siphon 115 rises and the siphon is activated. As a result, the raw water in the raw water inflow conduit 102 flows through the raw water inflow siphon 115 into the raw water distribution chamber 104, the raw water inflow chamber 106, the raw water pipe 118, and the filtration pond 101, and further passes through the filter bed 108 to be filtered water. It flows out to the filtered water collection chamber 109, the filtered water drainage 110, and the filtered water drainage drain 111.

On the other hand, when the filtration is continued in this way, the filter bed 108 is clogged and the water level in the filter basin 101 gradually rises, so that backwashing is performed. In this case,
First, the valve 114a is closed and the valve 114c is opened, air is introduced into the raw water inflow siphon 115, and the inflow of raw water into the filter basin 101 is interrupted. Next, the valve 114d of the communication pipe 114 is closed, the valve 114b and the drain valve 113a of the drain pipe 113 are opened, and the water in the vacuum generation tank 112 (water is replenished in the vacuum generation tank 112 during the filtration). ) Is drained. As a result, the air pressure in the backwash siphon pipe 117 is reduced, and the water in the filter basin 101 is discharged to the backwash drainage ditch 107a via the backwash siphon pipe 117. Then, although the water level in the filtration basin 101 decreases, the filtration culvert 11
The water level of 0 is constant because it communicates with other filtration basins (not shown), and the filtered water in the filtered drain 110 flows back due to the head difference to backwash the filter bed 108. The water flows into the filtration basin 101, and passes through the backwash siphon pipe 117, and the backwash drainage retention drain 107a and the backwash drainage drain 10
It flows out to 7b and backwashing is performed.

[0006]

However, the gravity type filtration device described above has the following problems. First,
In order to effectively backwash the filter bed, it is necessary to pass a predetermined amount of filtered water at a predetermined flow rate, but in the above-described conventional gravity type filtration device, each filter bed 108 is used for backwashing. Since only one siphon tube is provided, it is necessary to set the diameter of the backwash siphon tube according to the area of the filter basin in order to secure the flow rate and flow velocity required for backwashing. For example, if the cross-sectional area of one filtration pond is 70～80M ² is usually disposed those having a diameter of about 0.9 m, flow rate of the backwash siphon tube about 1.2～1.5M / It is operated so as to be about s. However, in order to activate the backwash siphon tube with a diameter of about 0.9 m, it is necessary to increase the capacity of the vacuum generation tank that generates negative pressure by discharging the water stored inside. However, when the above-mentioned backwash siphon tube is used, it must have a capacity of about 8 m ³ . Therefore, it is desired to reduce the size.

On the other hand, when the filter bed is washed, there is a lump of sand or the like accumulated in the form of a mat on the surface of the filter bed. ,
It may sink to the bottom of the filtration basin, which may result in insufficient backwashing.Usually, there are multiple backplanes placed above the filter bed from before the backwashing until a certain time after the backwashing. Water is sprayed from a nozzle (not shown), and the lumps are crushed for surface washing. For this reason, both surface washing and backwashing are performed for a certain period of time from the start of backwashing. However, since only one backwash siphon tube is used for each filtration pond, when the backwash siphon tube is activated to backwash the filter bed, the filter bed is washed. Since the flow rate of the filtered water passing through is fast and constant as described above, when backwashing is started, the filtered water passes through the filter bed at a predetermined flow rate from the beginning. As a result, from the beginning of backwashing, the filter bed itself rises in a piston shape while maintaining its layered form, and the filtered water injection for surface washing is performed while both surface washing and backwashing are performed. The nozzle's injection port rises like a piston and is located inside the filter bed, requiring surface washing for the required time,
May not be effective.

Further, as described above, the backwash siphon pipe used in the conventional gravity type filtration device is generally quite thick, and its manufacture is very difficult.
There was also a problem that manufacturing costs were high.

The present invention has been made in order to solve the above-described problems, and provides a backwash siphon that can make the vacuum generation tank smaller than the conventional one and can also effectively perform surface washing. An object of the present invention is to provide a gravity type filtration device equipped with the device. It is another object of the present invention to provide a gravity type filtration device that can use a siphon tube having a diameter smaller than that of a conventional one as a siphon tube constituting a backwash siphon. Furthermore, it aims at providing the starting method of the backwash siphon in such a gravity type filtration apparatus.

[0010]

In order to achieve the above object, the gravity type filtration device of the present invention is connected to a vacuum generation tank through a valve and a communication pipe, and is activated when water in the vacuum generation tank is discharged. In a gravity type filtration device having a backwash siphon that causes backwash drainage in a filtration pond to flow into a backwash drain, a main pipe connected to a vacuum generation tank and a plurality of main pipes are provided in the main pipe. While having a branch pipe, the backwash siphon has a plurality of backwash drainage passages, each backwash drainage passage is connected to each branch pipe via a valve, respectively. And

The backwash siphon is composed of at least one large-diameter siphon tube in which a plurality of backwash drainage passages are partitioned by a partition wall provided inside along the length direction. It is possible to use one that is provided with a plurality of small-diameter siphon pipes that are provided independently and that each function as a backwash drainage passage. In each case, the plurality of backwash drainage passages may have the same diameter, but the diameters are different from each other, and it is preferable that the plurality of backwash drainage passages are arranged so that the diameter increases according to the order of activation.

Further, the method for activating the backwash siphon in the gravity type filtration device of the present invention is connected to the vacuum generation tank through the valve and the communication pipe, and is activated when the water in the vacuum generation tank is discharged to start the filtration tank. A method of activating a backwash siphon in a gravity filtration apparatus having a backwash siphon that causes the backwash drainage to flow to a backwash drain, a main pipe connected to a vacuum generation tank as the communication pipe, A main pipe having a plurality of branch pipes is used, and as the backwash siphon, a plurality of backwash drainage passage parts are provided, and each backwash drainage passage part is provided with each of the branch pipes. Use the negative pressure generated in the vacuum generation tank only for one of the backwash drainage passages that are connected via a valve and first start the siphon, and use the other backwash drainage passages. For backwash drainage that is already siphoning By utilizing the negative pressure generated by the passage portion, characterized in that to siphon starts.

[0013]

FIG. 1 shows an embodiment of the present invention.
And FIG. In the figure, reference numeral 1 denotes a gravity type filtration device according to the present embodiment, which has a filtration basin 3 and a backwash drainage inflow culvert 7 which are provided with a partition wall 2 therebetween.
The filter basin 3 further has a filter section 32 with a partition wall 31 interposed therebetween. The filter section 32 has a backwash drainage gutter 33, a filter bed 34, and a plurality of filter beds 34 that support the filter. The support floor 35 in which the filtered water circulation hole 35a was formed is provided. Below the support floor 35, a filtered water collection chamber 4 in which the filtered water that has passed through the filter bed 34 is collected is provided. The filtered water collection chamber 4 is formed in a substantially inverted L-shape in cross section in FIG. 1, and has a partition wall 41 having an outflow hole 41a at the upper part thereof and communicated with another filtration pond (not shown). A filtered drain 5 is formed. Further, the filtered water collection chamber 4, which functions as the overflow weir 42, and the outer wall of the filtered water culvert 5 are provided with the overflow weir 42 in order to obtain a water head difference that maintains a flow velocity necessary for backwashing.
The height of the upper end of the backwash drainage gutter 33 is set to be higher than that of the backwash drainage gutter 33. Therefore, the water level of the filtered water culvert 5 is kept substantially constant at the height of the overflow weir 42. In addition, the filtered water culvert 5 is separated from the overflow weir 42, and the filtered water outflow culvert 6 is provided.
And the filtered water overflowing from the overflow weir 42 flows out to a predetermined location.

The backwash drainage basin 7 is provided with a water sealing weir 71 having a height lower than the height of the partition wall 31 provided in the filtration basin 3, and the water sealing weir 71 is used as a boundary. A backwash drainage ditch 72 is provided near the backwash drainage ditch 73, and a backwash drainage ditch 73 is provided on the opposite side. The water level of the backwash drainage accumulated in the backwash drainage ditch 72 is kept constant at the height of the water sealing weir 71.

Here, reference numeral 8 denotes each of the filtration basins 3 provided above the plurality of filtration basins 3 arranged in a line in a certain direction.
It is a common raw water inflow conduit. Raw water inflow 8 to each filter 3
When the raw water is supplied to the raw water distribution chamber 9, the raw water distribution chamber 9 is provided in each filtration basin 3 through the raw water inflow conduit 8 and the partition wall 81, and a water sealing weir 91 having a predetermined height is provided with respect to the raw water distribution chamber 9. The raw water inflow chamber 10 is provided, and further, the raw water inflow chamber 10 is connected to the filtration pond 3
In order to supply raw water to the raw water inflow chamber 10, one end is connected to the raw water inflow chamber 10 and the other end is provided with a raw water pipe 10a which faces the inside of the filter basin 3. Further, a raw water inflow siphon 12 is arranged between the raw water inflow conduit 8 and the raw water distribution chamber 9. As a result, the raw water in the raw water inflow conduit 8 flows into the raw water distribution chamber 9 via the raw water inflow siphon 12, and when the water level exceeds the height of the water seal weir 91, it flows out to the raw water inflow chamber 10. , And the raw water pipe 10a
Is supplied to the inside of the filtration basin 3 via. The configuration up to this point is almost the same as the configuration of the conventional gravity type filtration device 100 shown in FIG.

Next, the backwash siphon 15 according to the present embodiment will be described with reference to FIGS. 1 and 2. The backwash siphon 15 includes three small-diameter siphon tubes 15a, 15 that function as backwash drainage passages, respectively.
b, 15c. The "small-diameter siphon tube" here is of course different in diameter depending on the area of the filter basin, etc., but it is a gravity-type filtration that uses only one backwash siphon described in the section of the prior art. When compared with the device, when the filtration area is the same, it means a siphon tube having a diameter smaller than the diameter of one backwash siphon required in this conventional gravity type filtration device. Indicates that the sum of the cross-sectional areas of the three small-diameter siphon tubes is approximately equal to the cross-sectional area of the conventional single siphon tube.

The small-diameter siphon tubes 15a to 15c are substantially inverted U
It has a letter-like shape, one end of which faces the raw water stored in the filtration basin 3, and the other end of which faces the backwash drainage accumulated in the backwash drainage ditch 72. It is arranged so as to straddle the partition wall 2 that separates it from the culvert 7 and along the partition wall 2 as shown in FIG. Note that, in order to facilitate understanding in FIG. 2, the partition walls 2 are divided into three for each of the small-diameter siphon pipes 15a to 15c and are shown side by side, but in reality, one partition wall 2 shown in FIG. On the other hand, the small-diameter siphon tubes 15a to 15c are arranged side by side in the depth direction in FIG.

A communication pipe 17 connected to the vacuum generating tank 16 is connected near the tops of the small-diameter siphon pipes 15a to 15c. The communication pipe 17 is composed of a main pipe 17a directly connected to the vacuum generating tank 16 and a plurality of branch pipes 17b provided in the main pipe 17a. In the present embodiment, as shown in FIG. Of these, each of the three branch pipes 17b is connected to each of the small-diameter siphon pipes 15a to 15c. In addition, valves V1 and V are provided in each branch pipe 17b.
2 and V3 are interposed, and by opening and closing the valves V1 to V3, the vacuum generation tank 16 and the small-diameter siphon tubes 1 are provided.
5a to 15c can be individually communicated with each other, or conversely, the communication state can be blocked.

As shown in FIG. 1, one of the branch pipes 17b provided in the communication pipe 17 is connected to the vicinity of the top of the raw water inflow siphon 12 via a valve V5. . Therefore, the vacuum generating tank 16 is used as a starting source of the raw water inflow siphon 12 together with the backwash siphon 15 described above.

The vacuum generating tank 16 is arranged above the backwash drainage ditch 72 and is constructed as a closed tank having a predetermined capacity capable of accumulating water therein, and communicates with the vicinity of the upper portion thereof as described above. A main pipe 17a of the pipe 17 is connected to the bottom portion thereof, and a drain pipe 18 is provided at the bottom thereof, which is water-sealed so as to face the backwash drainage whose open end is stored in the backwash drainage ditch 72. In addition, the drainage pipe 18 includes a vacuum generation tank 16
A drain valve V6 that controls the discharge of the water inside is disposed.

A valve V7 is provided in the main pipe 17a of the communication pipe 17 connected to the vacuum generating tank 16.
The valve V7 is maintained in an open state when the backwash siphon 15 or the raw water inflow siphon 12 is activated, but the backwash drainage is supplied to the vacuum generation tank 16 via the drain pipe 18 as described later. When a predetermined amount of gas has flown into the inside, it is closed and used to control the amount of inflow.

The vacuum generating tank 16 is further connected to an air discharge pipe 19 having an air discharge valve V8 and a supply pipe 20 having a raw water supply valve V9 whose one end is connected to the raw water inflow conduit 8. . A liquid level detector 16a that detects the water level and controls the operation of each valve is also provided in the vacuum generation tank 16.

The vacuum generation tank 16 supplies the raw water from the raw water inlet 8 via the supply pipe 20 or opens the raw water supply valve V9 or takes in the backwash drainage from the drain pipe 18. The water level to the high level water level A by
A predetermined negative pressure is generated by draining this water by a water head difference and lowering it to a low level water level B. Therefore, the vacuum generation tank 16 is disposed above the backwash drainage ditch 72 as described above, but the backwash siphon 15 is used.
Small-diameter siphon pipes 15a to 15 constituting the backwash siphon 15 and the water surface in the filtration basin 3 when starting the
The distance H1 from the upper part of c and the distance H2 from the low level water level B in the vacuum generation tank 16 to the water surface of the backwash drainage ditch 72 are:
They are arranged so as to satisfy the relationship of H1 <H2. Also,
High-level water level A of the vacuum generation tank 16 and backwash drainage ditch 72
Distance H3 from the water surface of each of the small-diameter siphon tubes 15a to 15
The distance H4 between the top of c and the backwash drainage ditch 72 is H3.
<H4 is provided.

The distance H5 between the top of the raw water inflow siphon 12 and the water surface of the raw water inflow culvert 2 is much smaller than the above H1 in an ordinary gravity type filtration device, and naturally H5 <H.
It is kept in a relationship of 2.

Further, the capacity of the vacuum generating tank 16 may be any capacity capable of generating a negative pressure for activating one of the small diameter siphon tubes 15a to 15c. In the present embodiment, as will be described later, this is also performed by using the negative pressure generated near the top of the small-diameter siphon tube (for example, reference numeral 15a) that has been activated in advance, and the next small-diameter siphon tube (for example, reference numeral This is because 15b) is activated.

Next, the operation of the present embodiment will be described. First, the raw water inflow siphon 12 is activated. At this time, the valves V1 to V of the branch pipes 17b connected to the small-diameter siphon pipes 15a to 15c forming the backwash siphon 15 are connected.
3, valve V7 of main pipe 17a of communication pipe 17 and vacuum generation tank 1
The valve V6 of the drainage pipe 18 of No. 6 is closed, the air discharge valve V8 is opened, and the raw water supply valve V9 is opened to supply the raw water from the raw water inflow conduit 2 into the vacuum generation tank 16. When the water level rises to the high level water level A, the raw water supply valve V9 is closed, the supply of the raw water to the vacuum generating tank 16 is stopped, and the air discharge valve V
Close 8.

In this state, the raw water inflow siphon 12
The valve V4 of the main pipe 17a of the communication pipe 17 connected to the raw water inflow siphon 12 is closed by closing the open valve V4 attached to the upper part of the pipe.
7 and the valve V5 provided in the branch pipe 17b are opened, and the valve V6 of the drain pipe 18 is also opened. As mentioned above,
Because of the relationship of H5 <H2, by this operation, as the water level in the vacuum generation tank 16 decreases, the air in the raw water inflow siphon 12 is sucked through the communication pipe 17, and the air pressure in the raw water inflow siphon 12 is reduced. Decreases, the water surface in the raw water inflow siphon 12 rises, and the siphon is activated. As a result, the raw water in the raw water inflow conduit 8 flows into the raw water distribution chamber 9 corresponding to the filtration pond 3 and then to the raw water inflow chamber 10, and then flows into the filtration pond 3 via the raw water pipe 10a. When a predetermined amount of water flows in and reaches the water level above the partition wall 31 in the filtration basin 3,
It flows into the filtering section 32, passes through the filter bed 34 as a downward flow, and is discharged as filtered water through the filtered water collection chamber 4, the filtered water drainage pipe 5, and the filtered water drainage drainage port 6.

When the raw water inflow siphon 12 is activated, the discharge of the raw water from the drain pipe 18 of the vacuum generating tank 16 is stopped and the water level in the vacuum generating tank 16 becomes constant. Next, similar to the above, the valves V1 to V3 of each branch pipe 17b and the valve V6 of the drain pipe 18 connected to the small-diameter siphon pipes 15a to 15c are closed, and the communication pipe 17 connected to the raw water inflow siphon 12 is closed. The valve V7 and the valve V5 arranged in the branch pipe 17b connected to the raw water inflow siphon 12 are also closed. Further, the air discharge valve V8 is opened, and the raw water supply valve V9 is opened to supply the raw water from the raw water inlet 2 into the vacuum generation tank 16. When the water level rises to the high level water level A, the raw water supply valve V9 is closed and the supply of the raw water to the vacuum generation tank 16 is stopped. In this state, the vacuum generation tank 16 is kept in standby for starting the backwash siphon 15.

On the other hand, if the filtration is continued as described above, the filter bed 34 becomes clogged. That is,
The water level in the filtration basin 3 is 6 at the beginning of filtration.
However, when the filter bed 34 becomes clogged, the water level gradually rises. When it is detected by the liquid level detector 3a arranged in the filtration pond 3 that the water level reaches the C position, the opening provided in the branch pipe 17b connected to the raw water inflow siphon 12 is opened. Open the valve V4. By this operation, air is introduced into the raw water inflow siphon 12, the siphon operation is stopped, and the supply of raw water into the filtration basin 3 is interrupted. In addition, raw water inflow siphon 12
The stop of the siphon operation may be such that the opening valve V4 is automatically opened when the water level of the filtration basin 3 reaches the C position, and further, the raw water supply time preset by the timer is set. When the time has passed, the opening valve V4 may be opened.

When the supply of raw water is interrupted, the water in the filtration basin 3 passes through the filter bed 34 and flows out of the filtration basin 5, and the water level in the filtration basin 3 is slightly above the water in the filtration basin 5. The water is drained from the filter basin 3 after being lowered to the position. The detection of the end of water removal may be performed by detecting that the water level has reached the D position by the liquid level detector 3a, or by setting a time for the water level to drop in advance and using a timer.

When this state is reached, the backwash siphon 15 is activated to perform backwash. Specifically, first, each valve in the standby state described above is operated as follows. That is, the air exhaust valve V8 is closed, and among the valve V7 and the small-diameter siphon pipes 15a to 15c connected to the communication pipe 17,
First, the valve V1 of the branch pipe 17b and the drain valve V6 of the drain pipe 18 connected to the first small-diameter siphon pipe 15a to be activated are opened. As a result, the raw water in the vacuum generation tank 16 is rapidly discharged through the drain pipe 18. As a result, H1 <H
Since the water level in the vacuum generation tank 16 decreases, the air in the first small-diameter siphon pipe 15a is sucked into the vacuum generation tank 16 via the communication pipe 17 as the water level in the vacuum generation tank 16 decreases. The water surface in the small diameter siphon tube 15a rises and the siphon is activated. As a result, the raw water remaining in the filter basin 3 flows into the backwash drainage ditch 72 through the first small-diameter siphon pipe 15a, and is further discharged from the backwash drainage ditch 73, so that The water level of the water drops to below the backwash drain gutter 33.

During this time, filtration is being performed in another filtration pond (not shown), and the water level in the filtration drain 5 is the overflow weir 4
Since it is kept constant at a height of 1, the filtered water flows back through the filtered water collection chamber 4 due to the head difference between the water level of the filtered water drain 5 and the upper edge of the backwash drainage gutter 33, and the filtered bed 34 Backwashing is performed, and the backwash drainage flows from the backwash drainage gutter 33 into the filtration basin 3. The backwash drainage that flows in is the first small-diameter siphon pipe 15 described above.
It is discharged to the backwash drainage channel 7 through a.

As described above, the first small-diameter siphon pipe 15a is smaller than the diameter of the backwash siphon used when the filtering area is the same in the conventional gravity type filtering device. The pipe 15a alone cannot secure the flow velocity, the flow rate, etc. of the backwash drainage that passes through the filter bed 34, which is required to perform a complete backwash. Then, next, the branch pipe 17b connected to the second small-diameter siphon pipe 15b.
Open the valve V2. When the first small-diameter siphon tube 15a is activated, a predetermined negative pressure is generated near the top thereof. Therefore, when the valve V2 is opened, the small-diameter siphon pipes are also connected to each other through the communication pipe 17, so that the air in the second small-diameter siphon pipe 15b is sucked into the first small-diameter siphon pipe 15a, The water surface in the small diameter siphon tube 15b of No. 2 also rises, and the siphon is activated. Further, at a predetermined timing, the valve V3 of the branch pipe 17b connected to the third small-diameter siphon pipe 15c is opened, and similarly, the negative pressure generated near the top of the first small-diameter siphon pipe 15a is reduced. The third small-diameter siphon tube 15c is activated by using the negative pressure generated near the top of the second small-diameter siphon tube 15b. The switching operation of the valves V2 and V3 can be performed by setting a time with a timer or the like. All small diameter siphon 15
When a to 15c are activated, the required backwash drainage flow velocity and flow rate are secured according to the filtration area, and the backwash is effectively performed.
Therefore, for example, when one backwash siphon is used as in the conventional case, as described in the section of the related art, for example, when the cross-sectional area of one filter is 70 to 80 m ² , its diameter is Suppose about 0.9 m is required, the three small-diameter siphon pipes 15a to 15a are used as in the present embodiment.
When 5c is used, it is sufficient if each has a diameter of about 50 cm.

Here, the raw water in the vacuum generating tank 16 is the first small-diameter siphon pipe 15a constituting the backwash siphon 15.
When the water is activated, the discharge of water from the discharge pipe 18 is stopped and the water surface is at the low level water level B.
The valve V7 of 7b and the valve V6 of the drainage pipe 18 remain open. Further, a distance H2 between the low-level water level B in the vacuum generation tank 16 and the water surface of the backwash drainage ditch 72, and a distance H4 between the top of the first small-diameter siphon pipe 15a and the water level of the backwash drain ditch 72. From the above, since the above relationship is H2 <H4, the negative pressure generated at the top of the first small-diameter siphon tube 15a is larger than the negative pressure generated in the vacuum generation tank 16. Therefore, while the first small-diameter siphon tube 15a is operating, the air in the vacuum generation tank 16 is reversely connected to the communication tube 1
The suction water is sucked into the first small-diameter siphon pipe 15a via the drainage pipe 7, and the backwash drainage in the backwash drainage ditch 72 is sucked up into the vacuum generation tank 16 via the drainage pipe 18. The backwash drainage can be sucked up to the height corresponding to the top of the first small-diameter siphon pipe 15a from the water head difference, but when the water level reaches the high level water level A in the vacuum generation tank 16, the liquid level is detected. The valve V6 is closed based on the signal from the total 16a. As a result, the water necessary for activating the first small-diameter siphon pipe 15a is secured in the vacuum generation tank 16 when the backwash is performed next time.

That is, according to the present embodiment, as described above, the capacity of the vacuum generating tank 16 may be at least a capacity capable of generating the negative pressure necessary to activate the first small diameter siphon tube 15a. Moreover, siphon 1 for backwash
As for the water to be reserved inside for starting 5 as long as it is necessary to start the first small diameter siphon pipe 15a for the first time, by opening the raw water supply valve V9 and securing it from the raw water inflow conduit 8,
After that, the raw water supply valve V9 can be kept closed.

Next, after backwashing for a predetermined time, the backwash siphon 15 is stopped, but it is preferable to activate the raw water inflow siphon 12 before that. That is, in this type of gravity type filtering device, the air capacity of the raw water inflow siphon 12 is considerably smaller than the air capacity of the small-diameter siphon pipes 15a to 15c constituting the backwash siphon 15, and as described above, Since H5 is much smaller than H2, each valve V1 for each small-diameter siphon pipe 15a-15c is
Even if V3 is closed, since the communication pipe 17 has the residual negative pressure generated by the activation of the small diameter siphon pipes 15a to 15c, the raw water inflow siphon 12 can be simply opened by opening the valve V5.
Can be easily activated. At this time, if the valves V1 to V3 for the small-diameter siphon pipes 15a to 15c are also opened, the negative pressure generated near the tops of the small-diameter siphon pipes 15a to 15c is used to utilize the raw water inflow siphon 12
Can also be activated. Therefore, if the raw water inflow siphon 12 is activated in this way, it is not necessary to generate a negative pressure in the vacuum generating tank 16 to activate the raw water inflow siphon 12 except for the first time.

When the filtration is started again, the valve V5 for the raw water inflow siphon 12 is closed, the valves V1 to V3 for the small diameter siphon pipes 15a to 15c and the air discharge valve V8 are opened, and the small diameter siphon pipe 15a is opened. Air is introduced into ~ 15c to stop discharge of backwash drainage. If the filter bed 34 becomes clogged by continuing the filtration for a predetermined time, the above-described operation is repeated and backwashing is performed again. However,
In backwashing after the second time, since the siphon starting water has already been taken into the vacuum generation tank 16, it is only necessary to discharge it by the head difference, and it is necessary to take in the raw water from the raw water inflow conduit 8 again. What has not been mentioned above.

On the other hand, the surface washing in this embodiment is performed as follows. A description will be given based on FIG. That is, the valve V10 for the surface-washing pump, which is interposed in the pipe 21 connected to the surface-washing pump (not shown), is opened, and the nozzle 22 for surface-washing disposed above the filter bed 34 is filtered. This is performed by spraying water onto the upper surface of the floor 34 and crushing the sand or the like that has solidified on the filter bed 34. This surface washing is performed for a preset time by a timer, but the valve V10 for the surface washing pump is opened before the above-described backwashing is started, for example, when the operation of the raw water inflow siphon 12 is stopped to perform the backwashing. From this point, it is carried out until a certain period of time has elapsed since the backwashing was started. Therefore, there is a time when the backwashing and the surface washing are repeated. However, according to the present embodiment, while the first small-diameter siphon tube 15a is operating, or the first and second small-diameter siphon tubes 15a and 15b are operated.
While a and 15b are operating, all small-diameter siphon tubes 15a to 15a corresponding to one conventional large-diameter backwash siphon are used.
Compared with the case where 15c is activated at the same time, the filter bed 34
The flow velocity and flow rate of backwash wastewater passing through are small. For this reason,
As in the conventional case, when the backwashing is started, the entire filter bed 34 becomes a piston shape, and at the same time when the backwashing is started, the sand layer rises above the injection port of the surface washing nozzle 22 and effective surface washing cannot be performed. Therefore, the surface washing water from the surface washing nozzle 22 is made to flow out from above the filter bed 34, and the filter bed 34 is sufficiently supplied.
It is possible to set the timing of the surface washing, and the surface washing efficiency is improved.

The gravity type filtration device of the present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the backwash siphon 15 is composed of a plurality of small-diameter siphon pipes 15a to 15c that function as backwash drainage passages. However, in the gravity filtration device described in the section of the prior art. As used, it is composed of one large-diameter siphon tube (not shown), and the inside is backwashed drainage (fluid)
A plurality of partition walls, for example, two partition walls may be formed along the flow direction, and thus a plurality of (for example, three) backwash drainage passage portions may be formed. In this case, for each backwash drainage passage, branch pipes branched from the communication pipe and provided with respective valves are connected. Then, by activating each backwash drainage passage part first, then two, and finally all, the same action and effect as the small-diameter siphon pipes 15a to 15c of the above-described embodiment can be obtained. .

That is, even in this case, since the diameter of each backwash drainage passage is smaller than that in the case where the conventional large-diameter siphon tube is used as it is, the capacity of the vacuum generating tank can be made smaller than that of the conventional one. The surface washing can also be effectively performed.
However, in this case, it is necessary to use a large-diameter siphon tube having the same diameter as the conventional one, which is inconvenient as compared with the above-described embodiment in which it is sufficient to use a small-diameter siphon tube. That is, in the above embodiment, the diameter 30
It is enough to use a siphon tube of about 60 cm, and a commercially available one can be obtained, but in the case of a large diameter siphon tube,
It is difficult to obtain a commercially available product, and it is usually disadvantageous in that a dedicated product must be newly manufactured.

A backwash siphon having a plurality of small-diameter siphon tubes described in the above embodiment, or
A backwash siphon having a plurality of backwash drainage passages in one large-diameter siphon pipe, in each case, not only one set,
Two or more sets may be provided depending on the filtration area and the like. Further, the number of backwash drainage passages (including small-diameter siphon pipes) can be appropriately changed depending on the filtration area and the like as long as it is 2 or more.

Further, the backwash siphon used in the present invention has a backwash drainage passage (including a small-diameter siphon pipe), the first utilizing the negative pressure of the vacuum generating tank, and the second one. Using the negative pressure generated in the backwash drainage passage of the eye, the third is 1
Since the negative pressure generated in the second and second backwash drainage passages is used for activation, if the diameter of each backwash drainage passage is the same, it can be activated later. As much as possible, it will be started with a large negative pressure. Therefore, it is possible to use this fact in reverse, and to use the one having a smaller diameter as the one that is activated earlier. With such a configuration, the vacuum generation tank should activate the siphon of the backwashing drainage passage with the smallest diameter that is activated first among the multiple backwashing drainage passages (including small-diameter siphon pipes). The capacity of the vacuum generation tank can be further reduced as compared with the case where the respective backwash drainage passages are the same.

Further, the air exhaust valve V8 of the above-mentioned embodiment is also arranged at an appropriate position on the communication pipe if air can be taken in to stop the operation of the backwash siphon and the raw water inflow siphon. , Is not particularly limited. Further, the pipe connection for starting or stopping the backwash siphon pipe and the raw water inflow siphon pipe, the valve installation position and the number of valves installed are not limited to those in the above embodiment.
It goes without saying that various forms can be adopted without changing the gist of the present invention.

[0044]

According to the gravity type filtering device of the present invention and the method for activating the backwash siphon in the device, since it has the backwash siphon having a plurality of backwash drainage passages, the conventional large size The volume of the vacuum generating tank can be reduced as compared with the gravity type filtering device using only one diameter siphon tube. Further, since the plurality of backwash drainage passages are sequentially activated, surface washing can be effectively performed.

When the backwash siphon is composed of a plurality of small-diameter siphon pipes that function as backwash drainage passages, commercially available pipes or elbows can be used as siphon pipes. It is also possible to reduce the manufacturing cost of the entire gravity-type filtration device as compared with the case where a large-diameter siphon tube is manufactured again.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a gravity type filtration device according to the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a vacuum generation tank, a backwash siphon, and a frontwash nozzle for explaining the backwash and backwash methods of the gravity type filtration device according to the above embodiment.

FIG. 3 is a schematic cross-sectional view showing the configuration of a conventional gravity type filtration device.

[Explanation of symbols]

 1 Gravity Filter 3 Filter Pond 34 Filter Bed 4 Filtered Water Collection Room 5 Filtered Water Drain 7 Backwash Drainage Drain 72 Backwash Drainage Drain 8 Raw Water Inflow Drain 9 Raw Water Distribution Drain 12 Raw Water Inflow Siphon 15 Backwash Siphon 16 Vacuum Generation tank 17 Communication pipe 22 Nozzle for surface washing

Claims (5)

[Claims] 1. A backwash siphon that is connected to a vacuum generation tank via a valve and a communication pipe, is started when water in the vacuum generation tank is discharged, and drains the backwash drainage from the filtration pond to a backwash drain. In the gravity type filtration device having, the communication pipe has a main pipe connected to a vacuum generation tank and a plurality of branch pipes provided in the main pipe, and the backwash siphon has a plurality of backwash drainage passages. And a drainage passage for backwashing is connected to each of the branch pipes via a valve, respectively. 2. The backwash siphon is composed of at least one large-diameter siphon tube in which a plurality of backwash drainage passages are partitioned by a partition wall provided inside along the fluid flow direction. The gravity filtration device according to claim 1. 3. The gravity filtration device according to claim 1, wherein the backwash siphon is provided independently and is composed of a plurality of small-diameter siphon tubes each functioning as a backwash drainage passage. 4. The gravity type filtration device according to claim 2, wherein the plurality of backwash drainage passage portions have different diameters, and are arranged such that the diameters thereof become thicker in the order of starting. 5. A backwash siphon that is connected to a vacuum generation tank via a valve and a communication pipe, starts when water in the vacuum generation tank is discharged, and drains the backwash wastewater in the filter basin into a backwash drain. A method of activating a backwash siphon in a gravity-type filtration device having, wherein a communication pipe having a main pipe connected to a vacuum generation tank and a plurality of branch pipes provided in the main pipe is used. As the backwash siphon, one having a plurality of backwash drainage passages, each backwash drainage passage being connected to each of the branch pipes via a valve, is used to start the siphon first. Only for one of the backwash drainage passages, use the negative pressure generated in the vacuum generation tank, and for the other backwash drainage passages, use the siphon-operated backwash drainage passages. Characterized by activating the siphon using the negative pressure generated Starting the backwash siphon in that gravity filtration device.