JP2024058775A - Filter media cleaning device - Google Patents

Abstract

To provide a low-cost and lightweight filter material washing device that kneads and washes filter material inside a filtration tank or the like with a rotating screw placed therein.
[Solution] A filter material cleaning device 200 for a filtration device 100 that has a layer of filtration material 110 inside a filtration tank 106 or the like and filters supplied raw water by passing it through the layer of filtration material 110, the filter material cleaning device 200 having a spiral screw 204 arranged upright within the layer of filtration material 110 and screw driving means 206, 208 for rotating the screw 204 around the screw axis, in which the filter material cleaning device 200 rotates to knead and clean the filter material 110, does not include an outer tube surrounding the screw 204, and the filter material 110 is transported upward while the outer peripheral edge of the screw 204 is directly in contact with the layer of filtration material 110.
[Selected Figure] Figure 1

Description

The present invention relates to a device for cleaning filter media in a filtration device that purifies raw water by passing it through the filter media.

Conventionally, as shown in, for example, Patent Documents 1 and 2, filtration devices that purify raw water by filtering (filtering) are known. This filtration device basically has a layer of filter material inside a filter tank made of metal or the like, and the raw water supplied is filtered by passing it through the layer of filter material. With repeated use of this type of filtration device, the filter material becomes dirty with captured fine suspended matter, etc., so the filter material must be discarded or washed as appropriate. Conventionally, methods widely used for cleaning this filter material include surface washing, in which the surface of the filter material layer is washed by tapping it with a water flow sprayed from a nozzle, and backflow washing, in which purified water is injected into the filter material layer from below and the filter material is rubbed and washed.

However, the above-mentioned surface washing and backwash washing have been recognized to have problems such as a weak cleaning effect and therefore a long cleaning time is required. Therefore, the applicant has previously proposed and put into practical use a filter media washing device that can solve the above-mentioned problems, for example, a device that washes filter media using a screw conveyor, as shown in the above-mentioned Patent Documents 1 and 2. This filter media washing device basically has a helical screw (more specifically, the screw blade portion) arranged vertically within the layer of filter media, and a screw driving means that rotates this screw around the screw axis, and by rotating the screw, the filter media is kneaded and washed while being transported from the bottom to the top.

Here, the filter cleaning device using the screw conveyor is described in detail with reference to FIG. 6, taking the device shown in Patent Document 1 as an example. First, the filter device 1 in which the filter cleaning device 14 is installed will be described. Note that in the figure, some parts are shown in a schematic manner, such as by showing the cross-sectional shape of a thick member with a single straight line. As shown in the schematic side shape in the figure, the filter device 1 has a substantially cylindrical filter tank 2 closed at the top and bottom, a filter bed 4 with many fine holes (not shown) arranged at the inside lower part of the filter tank 2, and filter material 6 stacked on the filter bed 4. A plurality of support legs 8 (only one is shown in the figure) are attached to the filter tank 2, and the filter tank 2 is installed on the floor surface 10 by this. Note that a plurality of short cylindrical filters 12 made of ceramic with fine holes are installed in the filter bed 4. The filters 12 allow only purified water 16 to permeate below the filter bed 4.

A circular mounting opening 22 is formed in the center of the upper wall 20 of the filtration tank, and the filter media cleaning device 14 is attached to this mounting opening 22. The periphery of the mounting opening 22 is formed into a mounting rim 24. A base 28 to which a motor 26 and a reduction mechanism 27 are attached is attached on the rim 24. A holding section 36 having bearings 30 in three places is formed on this base 28, and the three bearings 30 are configured to support the rotating shaft 34 of the screw conveyor 32 so that it can rotate freely without wobbling.

The cylindrical tubular member 38 that constitutes the cleaning tank body in the filter media cleaning device 14 has a disk-shaped partition wall 29 at its upper part. A flange 31 on the outer periphery of the partition wall 29 is attached to the rim 24, and is attached to the rim 24 together with the base 28 by bolts. In this way, the upper part of the tubular member 38 is attached to the rim 24, and substantially the entire tubular member 38 hangs down from the upper wall 20. A hole 33 that fits tightly into the retaining portion 36 is formed in the center of the flange 31. This makes it possible to maintain a sealed state inside the filtration tank 2 during filtration.

The lower part of the tubular member 38 is an open circular lower opening 40, and multiple upper openings 42 are formed at the upper part. The multiple upper openings 42 are formed at a predetermined interval around the circumference of the tubular member 38, and each extends in the vertical direction. The positional relationship between the lower opening 40 and the filter material 6 is determined so that it is located inside the filter material 6. A screw conveyor 32 is arranged inside the tubular member 38. The screw conveyor 32 is formed from a rotating shaft 34, for example, a hollow pipe-like rotating shaft whose upper and lower parts have different diameters, and a spiral screw blade portion 43 fixed to the outer circumferential surface of the lower part (relatively large diameter part) of the rotating shaft 34. The screw blade portion 43 is formed up to the lower end 44 of the rotating shaft 34.

The upper end of the rotating shaft 34 of the screw conveyor 32 is connected to the reduction mechanism 27 of the motor 26 via a joint 52. When the screw blade portion 43 is thus arranged inside the tubular member 38, the upper end of the screw blade portion 43 is located near the lower edge 42a of the upper opening 42. In addition, the lower end portion 35 of the screw conveyor 32 protrudes downward from the lower opening 40 of the tubular member 38, and the lower end 44 of the rotating shaft 34 is located near the filter bed 4. Therefore, when the filter material 6 is washed, the filter material 6 near the filter bed 4 is also efficiently transported upward by the screw blade portion 43 and washed.

A purified water discharge pipe 60 extending downward is attached to the center of the curved bottom wall 58 of the filtration tank 2, and water purified by passing through the filtration material 6, filter bed 4, and filter 12 is discharged through this purified water discharge pipe 60. In addition, on the right side of the filtration tank 2 in the figure, there is a raw water inlet (turbidity discharge means) 62 for injecting raw water, i.e., water before filtration 16, into the filtration tank 2 during filtration, and a water level adjustment port 64 installed below it. The water level adjustment port 64 also functions as a discharge port for discharging water 16 in order to adjust the optimal water level for washing the filtration material 6.

An inspection hatch 68 is provided on the top wall 20 of the filtration tank 2, and is used to check the condition inside the filtration tank 2, such as the top surface 66 of the filtration material 6. An air vent valve 70 is located to the left of the top wall 20 of the filtration tank 2. In addition, a filtration material insertion port 72 for inserting the filtration material 6 is provided on the side of the filtration tank 2.

Next, filtration and cleaning of the filter material in the filter tank 2 will be described. First, raw water to be filtered is pumped in through the raw water inlet 62 by a pump (not shown). As the water level 74 rises, air in the filter tank 2 is discharged through the air vent valve 70. In this embodiment, the water level 74 is set so that it exceeds the raw water inlet 62 and reaches the top of the filter tank 2, that is, so that the filter tank 2 is almost entirely filled with water (raw water) 16. The water level 74 shown in FIG. 1 indicates a midway position before it is full. The water 16 permeates the filter material 6 and also enters the tubular member 38 through the upper opening 42 to permeate the filter material 6 in the tubular member 38, so that filtration can be performed even within the tubular member 38. The water that has permeated the filter material 6 and been filtered is discharged to the outside from the purified water discharge pipe 60 at the bottom of the filter tank 2 and is available for use.

Next, a method of cleaning the filter material 6 by the filter material cleaning device 14 when the filter material 6 becomes clogged after long-term use will be described. When the motor 26 is driven and the screw conveyor 32 rotates, the filter material 6 is pushed up into the upper tube member 38 by the blade portion 43 of the screw conveyor 32, particularly the blade portion 43 of the portion exposed below the tube member 38. The particles of the pushed up filter material 6 rub against each other and rise while being rubbed and washed by the rotation of the blade portion 43, and are discharged from the upper opening 42 into the filtration tank 2. The impact of the filter material 6 falling onto the surface of the water 16 promotes the separation of the turbidity from the filter material 6. The dropped filter material 6 is pushed up again into the tube member 38 by the blade portion 43 and rubbed and washed. In this way, the filter material 6 is repeatedly washed in the tube member 38, and the contaminants are separated. As mentioned above, the lower end 44 of the screw conveyor 32 is located near the filter bed 4, so the filter media 6 close to the filter bed 4 are also pushed up, and all of the filter media 6 are evenly washed.

The above-mentioned filter media cleaning device has the effect of efficiently cleaning dirty filter media in a short time of about 7 minutes, compared to the 15 minutes required for conventional surface cleaning or backflow cleaning. The above has been described as being applied to a filter tank, but filter basins such as those shown in Patent Document 3 are also publicly known, and the above-mentioned filter media cleaning device can also be applied to such filter basins, and in this case too, the filter media can be efficiently cleaned in a short time.

JP 2004-121885 A JP 2004-160432 A JP 2000-350994 A

In the past, it was thought that in constructing the above-mentioned screw conveyor, it was necessary to provide a cylindrical member (outer cylinder) that extends in the axial direction of the screw so as to surround the screw from the outside. This cylindrical member must be precisely formed so that its inner peripheral surface maintains a predetermined distance from the outer peripheral edge of the screw, and it is also required to be formed robustly so that it will not be broken even if it rubs against the filter material being transported. For these reasons, there is room for improvement in terms of cost and weight reduction in the conventional filter material washing device that uses a screw conveyor.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a filter media cleaning device that can be formed at low cost and with a lightweight structure.

The filter cleaning device according to the present invention comprises:
A filter cleaning device for a filtration device having a layer of filter material inside a filtration tank or filtration basin, which filters supplied raw water by passing it through the layer of filter material,
A filter material cleaning device having a helical screw arranged vertically within a layer of filter material and a screw driving means for rotating the screw about a screw axis, the device rotating the screw to knead and clean the filter material,
This is characterized by a configuration in which the filter material is transported upward while the outer periphery of the screw is in direct contact with the layer of filter material.

The phrase "while the outer periphery of the screw is in direct contact with the layer of filter material" means that a tubular member is present on the outer periphery of the screw, and the filter material that has entered between the tubular member and the screw does not come into contact with the outer periphery of the screw; in other words, the tubular member as described above is not provided. It is most desirable that the range in which no tubular member is provided extends over the entire length of the screw. However, this is not limited to this, and the tubular member may not be provided in only a portion of the entire length of the screw.

In the filter cleaning device of the present invention having the above configuration, the screw arranged upright in the layer of filter material is most preferably arranged upright in the vertical direction, but is not limited thereto and may be arranged at a slight angle inclined to the vertical direction. In that case, it is desirable for the angle of inclination to be at most about 10° (degrees).

In addition, in the filter media cleaning device of the present invention having the above configuration, it is preferable that a screw having a coil spring shape is used as the screw. More specifically, this "coil spring shape" refers to a shape in which the helical screw blade portion constituting the screw forms a ring at a position away from the screw axis on the outer circumferential side when viewed from the screw axial direction (the direction in which the screw axis extends).

The inventors discovered for the first time that when the filter material is transported upward by a rotating screw while being rubbed and washed, the filter material can be transported and washed even without the tubular member described above. Based on this finding, the filter material washing device of the present invention eliminates the tubular member, and as a result, while ensuring the same filter material washing effect as conventional devices, the omission of the tubular member makes it possible to form a low-cost, lightweight device. This effect is most noticeable when the area where the tubular member is not provided covers the entire length of the screw.

FIG. 1 is a schematic side view showing a filtration device having a filter media cleaning device according to a first embodiment of the present invention. FIG. 2 is a plan view showing a part of the filter media cleaning device of FIG. FIG. 11 is a schematic side view showing a filtration device having a filter media cleaning device according to a second embodiment of the present invention. A photograph showing a filter medium cleaned by the filter medium cleaning device of FIG. 1. A photograph showing a filter medium cleaned by the filter medium cleaning device of FIG. 3. FIG. 1 is a schematic side view showing a filtration device having a conventional filter media cleaning device. FIG. 1 is a schematic side view showing another example of a filtration device in which the filtration medium cleaning device of the present invention is used.

The following describes the embodiments of the present invention with reference to the drawings. FIG. 1 shows a schematic side view of a filtration device 100 having a filter cleaning device according to a first embodiment of the present invention. Note that the figure also shows some parts that are schematic, such as a cross-sectional shape of a thick member being shown by a single straight line. First, the filtration device 100 will be described. As shown in the schematic side view of the figure, the filtration device 100 has an upper end member 102 surrounding a circular opening, a substantially cylindrical filtration tank 106 having a bottom wall 104, a filter bed 108 having a large number of fine holes (not shown) arranged at the lower inside of the filtration tank 106, and a filter material 110 made of sand or the like having a specific gravity greater than that of water, which is layered on the filter bed 108. Note that the filter bed 108 is provided with a plurality of short cylindrical strainers 112 made of ceramic or the like having fine holes.

As an example, this filtration device 100 is a so-called upflow type filtration device, and has a raw water inlet chamber 114 between the filter bed 108 and the bottom wall 104 inside the filtration tank 106. A raw water inlet pipe 115 that opens at a position close to the peripheral wall on the left side of the figure and a backwash water inlet pipe 116 that opens at a position close to the peripheral wall on the right side of the figure are connected to this raw water inlet chamber 114. On the other hand, a treated water outlet pipe 118 that communicates with the inside of the filtration tank 106 is connected to a position slightly below the upper end member 102 of the filtration tank 106. In addition, a filter material outlet 120 that opens into the inside of the filtration tank 106 at a position slightly above the filter bed 108 is connected to the filtration tank 106. In addition, the filtration device 100 is provided with a horizontal cleaning port pipe that opens into the inside of the raw water inlet chamber 114, a water level adjustment outlet pipe that connects to the cleaning port pipe from above, etc., but these are not directly related to the present invention and may be formed in the same way as in conventional devices, so illustrations and detailed explanations are omitted. A filter cleaning device 200 according to the first embodiment of the present invention is attached to the center of the filter tank 106. Details of this filter cleaning device 200 will be described later.

In this filtration device 100, raw water to be filtered is sent from the raw water inlet pipe 115 into the raw water inlet chamber 114 under a predetermined pressure. This raw water passes through multiple strainers 112 and then through a layer of filter media 110 from bottom to top. During this process, contaminants contained in the raw water are captured by the filter media, and the raw water is filtered. After being filtered, the treated water 122 overflows the dam plate 124 and is discharged from the treated water outlet pipe 118 to the outside of the filtration tank 106.

Next, the filter cleaning device 200 will be described. The filter cleaning device 200 has a rotating shaft 203 that extends vertically through the center of the filtration tank 106, and a spiral screw blade portion 204 fixed to the outer circumferential surface of the rotating shaft 203. The rotating shaft 203 is composed of a relatively small-diameter upper shaft portion 201 and a relatively large-diameter lower shaft portion 202, and the screw blade portion 204 is specifically fixed to the outer circumferential surface of the lower shaft portion 202. The rotating shaft 203 and the screw blade portion 204 form a screw conveyor. Note that the screw blade portion 204 in this embodiment is composed of two screw blade portions that are not continuous with each other and are spaced apart from each other in the screw axial direction.

A motor 206 and a speed reducing mechanism 208 that reduces the speed of the motor 206 are disposed above the filtration tank 106. The motor 206 and the speed reducing mechanism 208 constitute a screw drive means, and the output shaft 208a of the speed reducing mechanism 208 is connected to the shaft upper portion 201 of the rotating shaft 203 via a joint 210. The motor 206 and the speed reducing mechanism 208 are integrated and held on the holding member 212. The holding member 212 is fixed to the filtration tank 106 via a plurality of supports 214 extending in the vertical direction and a support 216 fixed to the inside of the upper portion of the filtration tank 106. With the above configuration, the screw conveyor consisting of the rotating shaft 203 and the screw blade portion 204 is suspended in the filtration material 110 at the center of the filtration tank 106.

The shaft upper portion 201 of the rotating shaft 203 is rotatably supported by, for example, four bearings 218 arranged at a distance from each other in the axial direction. This allows the rotating shaft 203 to rotate without wobbling. Inside the filtration tank 106, there are provided filter material flow prevention plates 220 that surround the screw blade portion 204 from eight points on the outer periphery, as shown in FIG. 2, one of the set of planar cross-sectional shapes. These filter material flow prevention plates 220 are provided in three sets at a distance from each other in the direction in which the spiral of the screw blade portion 204 repeats, that is, in the axial direction of the rotating shaft 203. Each filter material flow prevention plate 220 is inclined with respect to the axial direction, but the direction of inclination is opposite to that of adjacent sets.

Next, the operation of the filter cleaning device 200 will be described. As described above, when raw water passes through the filter 110 and is filtered, the contaminants contained in the raw water are captured by the filter 110. Therefore, in order to continue using the filter 110 without discarding it, it is necessary to remove the contaminants from the filter 110, that is, to properly clean the filter 110. As one method of cleaning the filter, the filter device 100 of this example performs so-called backflow cleaning (backwashing). When performing this backwashing, during a period when the filtration of raw water is suspended, purified water as backwash water is sent from the backwash water inlet pipe 116 to the raw water inlet chamber 114 under a predetermined pressure. This purified water passes through the filter 110 from the bottom to the top and is discharged from the treated water outlet pipe 118 to the outside of the filtration tank 106. At that time, the contaminants captured by the filter 110 are peeled off from the filter 110 by the purified water and are discharged from the treated water outlet pipe 118 to the outside of the filtration tank 106 together with the purified water.

In addition to this backwashing, the filter media can also be cleaned by the filter media cleaning device 200 as appropriate. When cleaning the filter media by the filter media cleaning device 200, the motor 206 is driven during the period when the raw water filtration is stopped and the backwashing is being performed, and the rotational force is transmitted to the rotating shaft 203 of the screw conveyor via the reduction mechanism 208. When the rotating shaft 203 rotates in this manner, the helical screw blade portion 204 rotates, and the filter media 110 is transported upward by the screw blade portion 204. At that time, the individual filter media 110 are squeezed together, so that the captured contaminants are peeled off from the filter media 110. In this case, the contaminants are discharged from the filtration tank 106 together with the backwash water through the treated water outlet pipe 118.

In this embodiment, unlike conventional screw conveyors that perform kneading and washing of the filter material, there is no tubular member (outer tube) surrounding the screw blade portion 204 from the outside. Therefore, in this embodiment, the outer periphery of the screw, or more specifically, the outer periphery of the screw blade portion 204, is kneaded and washed while being directly in contact with the layer of filter material 110. In other words, unlike conventional devices, there is no tubular member on the outer periphery of the screw blade portion 204, and the filter material 110 that has entered between the tubular member and the screw does not come into contact with the outer periphery of the screw blade portion 204.

According to the inventor's research, even if the above-mentioned tubular member is not provided, the screw blade portion 204 can function as a component of the screw conveyor, and the filter medium 110 can be kneaded and washed while being transported upward by the rotating screw blade portion 204. This action is believed to be achieved as follows.

As the screw blade portion 204 continues to rotate within the layer of the filter material 110, the portion of the filter material 110 in contact with its outer periphery is scraped off, and a roughly cylindrical space is defined within the layer of the filter material 110. In other words, the screw blade portion 204 rotates within the space with its outer periphery facing the circumferential surface of the space. If the filter material 110 is mainly made of sand, the circumferential surface of the space becomes a wall that can be called a "sand wall," and functions just like a tubular member (outer tube) in a conventional device. Thus, the filter material 110 that is scattered outward due to the centrifugal force caused by the rotation of the screw blade portion 204 bounces off this "sand wall" and returns to the upper surface of the screw blade portion 204, and is rubbed and washed while being transported upward by the screw blade portion 204.

The peripheral surface of the above space (the space in which the screw blade portion 204 rotates) functions like the tubular member (outer cylinder) in the conventional device as described above, but is formed from the sand-like filter material 110, and therefore also exhibits the inherent properties of sand-like materials. That is, even if the filter material 110 scattered around the outer periphery of the screw blade portion 204 collides with this peripheral surface as described above, the peripheral surface is only slightly deformed, and the scattered filter material 110 is not crushed. In contrast, in a conventional device in which a tubular member (outer cylinder) is arranged to surround the screw blade portion from the outer periphery, the filter material scattered around the outer periphery from the screw blade portion may collide with the tubular member made of metal or the like and be crushed.

By eliminating the above-mentioned tubular member provided in the conventional device, the filter media cleaning device 200 of this embodiment can be formed at a lower cost and with a lighter weight than the conventional device. In particular, the above-mentioned tubular member is usually formed from a metal such as stainless steel, and the distance between the screw blade portion and the tubular member must be precisely set to a predetermined value so that the filter media being rubbed and cleaned is not pinched between the inner surface of the tubular member and the screw blade portion and destroyed, which tends to increase costs. If such a tubular member can be eliminated, the effect of reducing costs will be particularly remarkable. Furthermore, if the filter media cleaning device 200 can be formed to be lightweight, the filtration device 100 equipped with it can naturally be made lighter as well.

Furthermore, if the weight can be reduced by eliminating the above-mentioned tubular member, which is usually made of metal, then when there is a weight limit on the screw conveyor, the overall length of the rotating shaft 203 and the screw blade portion 204, which together with the tubular member constitute the screw conveyor, can be set larger, which is advantageous in forming a longer filter tank 106.

In addition, in this embodiment, three sets of filter media flow prevention plates 220 are provided to surround the screw blade portion 204 from eight outer circumferential positions, thereby obtaining the following effects. That is, if raw water containing turbidity (pollutants) is continuously filtered by the filter media layer (layer of filter media 110), the turbidity gradually clogs the lower part of the layer, and pressure is applied to the filter media layer during filtration. When clogging progresses in this way and the filtration pressure increases, the filtration pressure increases further with the filter media 110 and the turbidity integrated at the bottom of the layer. Then, as the mass of the filter media 110 and the turbidity rises, a space (water space) is created in the filter media layer, and eventually the floating filter media 110 and the turbidity collapse and flow, causing the turbidity to leak. When this happens, proper filtration cannot be performed, leading to an inconvenient situation in which the turbidity is released all at once into the treated water 122 after filtration. On the other hand, by providing multiple sets of filter media flow prevention plates 220, it is possible to prevent the filter media 110 from flowing or floating up, thereby avoiding the occurrence of the above-mentioned inconveniences.

Next, referring to FIG. 3, a filter cleaning device 300 as a second embodiment of the present invention will be described. The filter cleaning device 300 is basically different from the filter cleaning device 200 in that the screw blade portion 204 is composed of one clew blade portion, whereas the screw blade portion 204 is composed of two clew blade portions in the filter cleaning device 200 of the first embodiment. The filter cleaning device 300 is provided in the filter device 150, and the filter device 150 is also different from the filter device 100 of FIG. 1 only in that the filter cleaning device 300 is used instead of the filter cleaning device 200. Therefore, in FIG. 3, the same elements as those in FIG. 1 are numbered the same as those in FIG. 1, and their explanation will be omitted unless otherwise necessary.

In the second embodiment of the filter cleaning device 300, the filter 110 is cleaned in the same manner as in the first embodiment of the filter cleaning device 200 shown in FIG. 1. However, in the first embodiment of the filter cleaning device 200, the screw blade portion 204 is composed of two clew blades, so the filter 110 can be transported and cleaned relatively efficiently, whereas in this embodiment, the screw blade portion 304 is composed of one clew blade, so the efficiency of the transport and cleaning of the filter 110 tends to be lower than in the first embodiment. The photographs shown in FIG. 4 and FIG. 5 show the actual state of the filter 110 transported by the screw blade portions 204 and 304, respectively.

In the first embodiment of the filter cleaning device 200, the screw blade portion 204 is composed of two clew blade portions, but three or more clew blade portions may be applied. In any case, applying multiple clew blade portions in this way is advantageous in improving the efficiency of transporting and cleaning the filter material 110 compared to applying a single clew blade portion.

The above describes an embodiment of a filter cleaning device installed in a filtration device having a filtration tank, but the filter cleaning device of the present invention is not limited to such filtration devices and can also be installed in a filtration tank. In addition, the filter cleaning devices 200 and 300 described above are applied to an upflow type filtration device, but the filter cleaning device of the present invention is not limited to this and can also be applied to a downflow type filtration device such as that shown in Figure 6.

Next, referring to FIG. 7, another example of a filtration device in which the filtration media cleaning device of the present invention is used will be described. In FIG. 7, the same elements as those in FIG. 1 are given the same numbers as in FIG. 1, and their description will be omitted unless otherwise necessary. The filtration device 400 shown in FIG. 7 is different from the filtration device 100 shown in FIG. 1 in that the shape of the filter bed 108A is different. That is, while the filtration device 100 in FIG. 1 uses a simple circular filter bed 108, the filter bed 108A in the filtration device 400 of this example has a "funnel-like" or "mortar-like" shape that is gradually tapered from the circular outer periphery toward the center and concaves downward.

By making the filter bed 108A in this shape, the filter material 110 that is being transported upward and kneaded by the rotating screw blade portion 204 of the filter material cleaning device 200, and the contaminants that are torn off from the filter material and discharged from the treated water outlet pipe 118, tend to naturally gather near the lower end of the screw blade portion 204. This makes it possible to more efficiently knead and wash the filter material 110 and discharge the contaminants.

In this case, the area of contact between the raw water before filtration and the filter media 110 through the filter bed 108A is larger than when the raw water contacts the filter media 110 through the circular filter bed 108, which is also advantageous in speeding up filtration.

In addition, in the present invention, the aforementioned backflow cleaning (backwashing) may be performed, but foam cleaning of the filter material may be performed in parallel with this backwashing, or independently as a substitute for this backwashing. This foam cleaning is a process in which foam cleaning water containing a large number of fine bubbles is flowed toward the filter material 110 from below the layer of the filter material 110. When this process is performed, the foam cleaning water flows between the filter materials 110, and the contaminants captured on the surface of each filter material 110 are peeled off by the vibration, impact, and contact caused by the passing of the bubbles. The foam cleaning water containing the peeled contaminants is discharged outside the filter tank 106 from the treated water outlet pipe 118, as in the case of backwashing.

When the foam washing described above is performed in parallel with the backwash, the effect of washing the filter material 110 is higher. In addition, since the backwash water can be reduced by the amount of foam washing, the consumption of backwash water can be reduced. The water for obtaining the foam washing water may be a part of the backwash water, or may be prepared separately from the backwash water. In order to include a large number of fine bubbles in the foam washing water, a non-positive displacement pump that rotates an impeller inside a casing can be used as a pump that pumps water toward the filter material 110, and the impeller can cut the water to generate bubbles. Alternatively, if finer bubbles, such as fine bubbles or microbubbles, are desired, a dedicated foam generator that generates such bubbles can be installed in the water pumping path.

100, 150, 400 Filtration device 102 Upper end member of filtration tank 104 Bottom wall of filtration tank 106 Filtration tank 108, 108A Filter bed 110 Filter material 112 Strainer 114 Raw water inlet chamber 115 Raw water inlet pipe 116 Backwash water inlet pipe 118 Treated water outlet pipe 120 Filter material outlet 122 Treated water 124 Weir plate 200, 300 Filter material cleaning device 203 Rotating shaft 204, 304 Screw blade portion 206 Motor 208 Reduction mechanism portion 210 Joint 212 Holding member 214, 216 Support 218 Bearing 220 Filter material flow prevention plate

Claims (3)

A filter cleaning device for a filtration device having a layer of filter material inside a filtration tank or a filtration basin, which filters supplied raw water by passing it through the layer of filter material,
A filter medium cleaning device having a helical screw arranged vertically within the layer of the filter medium and a screw driving means for rotating the screw about a screw axis, the filter medium being rubbed and washed by rotating the screw,
A filter medium cleaning device characterized in that the filter medium is transported upward while the outer periphery of the screw is in direct contact with the layer of the filter medium. The filter media cleaning device according to claim 1, wherein the screw is a screw having a coil spring shape in which the helical screw blade portion constituting the screw forms a ring at a position away from the rotation axis of the screw when viewed from the axial direction of the screw. The filter media cleaning device according to claim 1 or 2, wherein the area in which the outer periphery of the screw is in direct contact with the layer of filter media extends over the entire length of the screw.

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