KR100655166B1 - W-type under-drain block - Google Patents

Abstract

A device for distributing an amount of backwashing water and collecting filtered water is provided to reduce dead zone in a filter media layer during filtration or backwashing and perform filtration and backwashing uniformly and equally along the entire plane surface of a filter basin. As a block composing an underdrain system of a gravitational filtering plant, a W-type perforated block for the underdrain system comprises unit blocks continuously arranged longitudinally and laterally under a granular filter media of the underdrain system, wherein the unit blocks comprise: a first horizontal channel(36) formed in a longitudinal direction to have a triangular sectional shape; second horizontal channels(38) longitudinally formed in an upper part of left and right sides of the first horizontal channel such that the second horizontal channels are separated from each other by inner sidewalls(34); a plurality of water circulation holes(80) longitudinally formed in the inner sidewalls; a plurality of air circulation holes(48) longitudinally formed in the inner sidewalls such that the air circulation holes are formed in an upper part of the sidewalls than the water circulation holes; outer sidewalls(32) formed at outer sides of the second horizontal channels; a block top plate(28) formed on an upper surface of the second horizontal channels; and a plurality of ejection holes(40) formed in the block top plate, wherein the ejection holes are arranged in such a manner that the ejection holes are formed at apexes of regular triangles.

Description

W-type perforated block of lower collecting device {W-type under-drain block}

Figure 1 shows the overall configuration of the 'low collection device equipped with a W-type pore block' of the present invention.

2 is a plan view of a unit block constituting the assembled 'W-type porous block of the lower collecting device'.

Figure 3 is a bottom view of the unit block constituting the assembled 'W-type perforated block of the lower collecting device'.

4 is a cross-sectional view taken along the line A-A 'of FIG.

5 is a cross-sectional view taken along line BB ′ of FIG. 2.

6 is a plan view illustrating the arrangement of the ejection holes by removing the upper reflector in FIG. 2.

FIG. 7 is a cross-sectional view illustrating a state in which a cement mortar support column in which the unit block constituting the 'W-type hole block of the lower collecting device' is disposed and fixed in parallel to the bottom of the lower collecting device is poured.

FIG. 8 illustrates a spray form of air or washing water sprayed from a unit block constituting the 'W-type hole block of the lower collecting device' and a block upper plate portion in which the unit blocks are continuously arranged.

FIG. 9 shows a part of a side appearance of a unit block constituting the 'W-type porous block of the lower collecting device'.
FIG. 10 is a partially enlarged view of FIG. 8, showing that the backwash jet water is radially diffused by the reflector.
FIG. 11 is a cross-sectional view taken along line CC ′ of FIG. 10 and illustrates the function of the reflector in detail.

The lower collecting device of the early stage of rapid filter development was a wheeler block type, which had a strut installed on the plane of the bottom of the filter paper structure, the concrete molded product was solidified thereon, and the pressure chamber was formed between the molded product and the bottom plate of the filter paper structure. On the upper surface of the molded article, a pyramidal vertex was placed downward, and a lower collecting device block having five or fourteen magnetic domains was placed therein. This type was widely used as a bottom catchment device in the early stage of rapid filter development.

Next, a strainer was attached to the pipe or support plate buried beneath the filter media, and the filtered and backwash water flowed in through the strainer. In case of attaching strainer to the pipe, water collecting and collecting should be installed at the center of filter paper. The pipe should be made of durable material, and if the strainer is attached to the pipe or plate, the concrete should be filled near the bottom of the strainer to eliminate the stagnation of water and to keep the strainer from falling out of the pipe or plate. It should be fixed. If the strainer spacing is too wide, filtration and backwashing will not be even. Too narrow is uneconomical. From experiences so far, 10 to 20 cm was appropriate. And the mounting height of the strainer should be the same. When the total cross-sectional area of the short pipe required for the strainer installation was 0.25 to 1.0% of the filtration area, it was possible to obtain a suitable and almost even flow of water in the plane when backwashing. In order to ensure that the strainer-type bottom catchment is well maintained, corrosion and blockage of the strainer must be prevented. Corrosion resistant metals or synthetic resins were used, and the slit width of the strainer was 0.25-0.75 mm. In order to prevent the blockage of the strainer, it is possible to prevent the fine particles from falling out by maintaining a gravel of a thickness and a moderate thickness of gravel suitable for the slit size of the strainer, or by avoiding excessive filtration rate during filtration. It is recommended that the shape of the strainer be sized so that it will not become clogged even if sand is dropped.

Another method is a perforated tube type, which uses a pipe having an open hole, and installs a support on the floor so that the opening of the open hole faces downward. The pipe shall be made of materials with high corrosion resistance, durability and pressure resistance, and the plumbing hole shall be of equally open diameter and angle. The interval between the reservoir pipes is 30 cm or less and the length is 60 times or less of the diameter. If the length of the pipe is too long compared to the diameter, the pressure in the pipe becomes uneven during backwashing, making it difficult to uniformly wash it. Perforated tubular type is easy to vibrate when washed, so it should be sufficiently settled on the support. It is also a good idea to interconnect them in order to keep the pressure distribution in the collection pipe as even as possible when backwashing.

Next, an improved method is a porous block method in which a molding block having a dispersion chamber and a water-transmission chamber is connected in parallel to the bottom plate. This type is a two-stage structure through the orifice and has the equalizing effect, and expects the effect of uniform filtration and backwashing planarly by a number of catchers arranged open upward from the top of the block. Compared to the wheeler type, this porous block type is lighter in block itself and may not require posts, so it is easy to install and does not require a separate pressure chamber, so that the filter paper structure can be made shallow and easy to install flat. The larger the cross section of the water supply chamber, the more uniform pressure is maintained during the water transportation process. Therefore, even if the pore size of the water collector is increased, the uniformity of water dispersion can be maintained. . Porous block is made of porcelain or plastic with high corrosion resistance, durability and pressure resistance. In addition, a collection basin is installed at the center of the filter paper and at the corridor to allow water to flow in and out of the block. The cross-sectional area is 1% or more of the filter area (when the backwashing speed is 0.6 m / min). If the laying length of the block is too long, the pressure is unbalanced according to the position is generally about 5m limit. In addition, when backwashing, an upward force acts on a part of the block. Therefore, anchors should be installed and fixed at appropriate intervals.

Apparently, the above methods seem to be able to uniformly distribute the backwash water and collect the filtered water.However, the arrangement of the ejection holes for collecting the filtered water and squirting the backwash water, when viewed in plan view, ejects each square or rectangle vertex. There are many ways to place the ball. Therefore, microscopically, the distribution of jet water was not uniform over the entire filter paper plane, and a local sandwater was formed.

In the case of using a strainer-type block, a space is formed in the upper surface of the block under the filter medium, and then a spout is formed. The further away from the strainer along the direction, a partial shooter is formed between the higher part and the top of the block. The range of the backwash water ejected from the strainer is when the quarter circumference with the radius of the midpoint of the shortest distance between the strainer and the strainer is placed at each vertex of the quadrilateral. The lower part of the part contacting the conical funnel formed by being ejected from the adjacent ejection hole is formed with a shooter.

On the other hand, in the hole block type bottom collecting device, since the ejection holes are open only upward, the spacing intervals of the ejection holes are narrower than that of the strainer method. Since it is sprayed in the form of the upper part of the block plate, backwashing and filtration are performed within the contact range of the jet stream, but a partial shooter is formed outside the range of the conical funnel, and filtration and backwashing are insufficient. Thus, despite the fact that this approach attempted to reduce the catchment area by narrowing the hole spacing, there may be more actual catchers than the strainer method. In addition, since the ejection hole is open up and down and the filter medium smaller than the ejection pore other than the coarse gravel can easily pass through the ejection hole, the granular filter material passing through the gravel layer is likely to leak into the filtered water.

In order to improve these problems, a method of uniformly dispersing the jetted water by attaching a porous plate on the upper portion of the lower hole collecting device has been developed. This is a plate formed by granular material having a diameter of several mm, and is used as a pressure chamber by installing a support wall on the bottom plate and attaching a porous plate to the support wall to be used as a water collecting device. As the granular material of the porous plate, molten alumina (about 3 mm long), which has been cut into corners and adhered roundly, is mainly used. The properties required in the porous plate include the uniformity of the flowing water such as the filtered water and the backwash water as viewed in the longitudinal section or the cross section of the whole filter paper, along with the water permeability and the mechanical strength.

Perforated plates generally have a merit that the structure depth can be made shallow because the gravel layer can be omitted. However, the disadvantage of perforated plate type is that in the large area of filter paper, it is necessary to secure construction management such as leveling of plate. In addition, in the perforated plates installed in parallel, invalid parts of filtration and backwashing are formed in the joint portion between the perforated plate and the perforated plate in the form of a band, thereby reducing the filtration efficiency. In some cases, the perforated plate is blocked and loses its original function as a perforated plate. If a local blockage occurs, serious problems such as shooter problems in the filter layer may occur. In addition, the perforated plate price is considerably higher than other lower collecting devices.

Especially when backwashing with water and air, it is important to distribute the air evenly. Air is less viscous than water, and even if a slight pressure difference occurs, the amount of air to be ejected varies greatly. Therefore, water and air can be generated in the filter material layer above the lower collecting device by narrowing the spacing interval as much as possible. The lower collecting device should be selected so that it can be evenly distributed throughout the filter media layer.

It aims to pursue an apparatus for distributing backwash water and collecting filtrate so that there is less water catchment in the filter media layer during filtration or backwashing, so that it is uniformly filtered and evenly backwashed over the entire plane of the filter paper. .

If a local catchment zone is present in the filter paper, the final stage of water treatment, contaminants will leak into the filtered water at some point, resulting in poor filtration water quality, as well as the filtration capacity that the catchment zone would normally handle. This can lead to the most avoiding phenomena when managing filter paper, such as local overloads and mudballs in the shooters.

To date, the bottom catchment system may have dead zones in the filtration bed where backwash water, backwash, or both do not reach, to properly filter the filter media and gravel layer. No structure can create an ideal bottom catchment system to completely eliminate this catchment area, but the present invention is uniformly filtered over the entire plane of the filter paper while minimizing the problem of locally occurring catchments in the filter paper, and also backwashing. The purpose is to implement a structure that distributes the backwash water relatively uniformly.

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The configuration of the present invention is as follows.
The present invention relates to a block constituting the lower collecting device 12 of the gravity filtration system 10, consisting of a unit block that is continuously arranged longitudinally and horizontally under the granular filter material 14 of the lower collecting device (12). The unit block 16 may include a first horizontal horizontal path 36 formed in a longitudinal direction to have a triangular cross section; A second order horizontal path 38 formed in a longitudinal direction so as to be divided into an inner side wall 34 on each of left and right upper portions of the first order horizontal path 36; A plurality of water distribution holes 80 provided in the longitudinal direction on the inner side wall 34; A plurality of air distribution holes 48 provided in the longitudinal direction on the inner side wall 34 and positioned above the water distribution hole 80; An outer side wall 32 provided on an outer surface of the second order horizontal path 38; A block upper plate 28 provided on an upper surface of the second order horizontal path 38; And a plurality of ejection holes 40 provided in the block top plate 28, wherein the ejection holes 40 are arranged at vertices of an equilateral triangle.
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1 is a view showing the overall configuration of the 'low collection device equipped with a W-type porous block' of the present invention, Figure 2 is a plan view of a unit block constituting the assembled 'W-type porous block of the lower collection device' 3 is a bottom view of a unit block constituting the assembled 'W-type porous block of the lower collecting device'.
4 is a cross-sectional view taken along the line AA of FIG. 2 in a counterclockwise direction, and FIG. 5 is a cross-sectional view taken along line BB of FIG.
As shown in FIG. 1, the lower collecting device 12 of the gravity filtering facility 10 is composed of unit blocks 16 continuously arranged longitudinally and horizontally under the granular filter material 14.
The unit block 16 has end portions formed in the bell end 64 and end portions provided with the spigot end 68 at both sides in the longitudinal direction, respectively, so that the bell end 64 and the adjacent unit blocks 16 are mutually adjacent. The spigot end 68 is integrally coupled in an interlocking manner.
The unit block 16 is integrally coupled to the lower portion of the filter water is discharged and at the same time the washing water flows back when the backwash water inlet 22 and the backwash air inlet 24 is provided in the lower trough 20 do.
FIG. 2 is a plan view of the unit block constituting the assembled 'W-type hole block of the lower collecting device', and FIG. 4 is a cross-sectional view of the AA section of FIG.
As shown in FIG. 4, the unit block 16 has a first order horizontal path 36 formed in a longitudinal direction to have a triangular cross section, and a left and right sides of the first order horizontal path 36. Each of the second upper horizontal path 38 formed in the longitudinal direction so as to be divided into the inner side wall 34 is provided with one.
That is, the unit block 16 includes a first horizontal horizontal path 36 having a triangular cross section and two second horizontal horizontal paths 38 having an inverted triangle to form a symmetrical structure.
In other words, the unit block 16 is configured such that its cross section is wider at the top and narrower at the bottom thereof, and is provided at each of the outer side wall 32 and the upper left and right sides of the first horizontal horizontal line 36. The inner side wall 34 has a 'W' shape.
As shown in FIG. 5, the inner side wall 34, which is the boundary between the first horizontal horizontal path 36 and the second horizontal horizontal path 38, is provided with a plurality of water distribution holes 80 in the longitudinal direction. It becomes a passage of filtered water or backwash water flowing between the primary horizontal water passage 36 and the second horizontal horizontal passage 38. The water distribution hole 80 is disposed at regular intervals in the longitudinal direction of the unit block 16 at the lowest position of the inner side wall 34, and is used for collecting the filtered water and passing and distributing the backwash water.
Air distribution hole 48 is provided in the longitudinal direction on the inner side wall 34, as shown in Figure 5 is located above the water distribution hole (80).
As shown in FIG. 5, the water distribution hole 80 has only one row, and the air distribution hole 48 has three rows. However, the water distribution hole 80 is not necessarily limited to that shown in FIG. It is possible to freely change the diameter of the arrangement and the number of the 48 and the water distribution hole 80.
The outer side wall 32 is provided on the outer surface of the second horizontal horizontal path 38, and the block top plate 28 is provided on the upper surface.
The block top plate 28 is provided with a plurality of blow holes 40 as shown in Figures 2 and 6, characterized in that the blow holes 40 are arranged to be located at the vertex of the equilateral triangle.

The unit collecting block 16 of the lower collecting device 12 of the gravity filtering facility 10 should not come to pass through the gravel layer with the filtrate in the process of filtration to block the spout hole 40. The granular filter material 14 should not flow out with the filtered water. The filtered water passes through the first horizontal horizontal passage 38 through the second horizontal horizontal passage 38 and then enters the purified water through the backwash water inlet 22 of the lower trough 20 through a water purifier.

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The granular filter material 14 should be cleaned regularly to maintain optimal performance of the gravity filtration system 10. This is achieved by regularly supplying the washing water at a constant pressure and through the lower collecting device 12, and upwardly through the granular filter material layer 14 while desorbing foreign matter particles attached to the granular filter material 14 during this backwashing process. Backwash.
In the washing method, washing with only water and washing with water and air are common. In case of washing with water alone or water and air at the same time, the washing flow of water is as follows.
In FIG. 4, a water distribution hole 80 is provided on an inner side wall 34 that separates the first horizontal horizontal path 36 and the second horizontal horizontal path 38, and the blower plate 40 is provided in the block upper plate 28. ) Is arranged to be located at the vertex of the equilateral triangle, is installed to be spaced apart from the top of each blow hole 40 is provided with a reflecting plate 43 larger than the diameter of the blow hole (40).
In the case of washing water alone, when water is injected into the first horizontal horizontal passage 36, the water is introduced into the second horizontal horizontal passage 38 through the water distribution hole 80 in the first horizontal horizontal passage 36. This flows to the block top plate 28 with the process water (26). The block top plate 28 has a blowing hole 40, and has a loss head adequately enough to pass through the blowing hole 40, and is uniformly sprayed. Water passing through the jet hole 40 is directed upward, but impinges on the reflecting plate 43 directly above the jet hole 40, the direction of jet of the jet water is switched to the horizontal direction, and the jet hole 40 is centered. It spreads radially and rises uniformly and slowly over the whole plane of the granular filter material 14, and perfect backwashing is achieved.

FIG. 10 shows that the jetted water is radially diffused by the reflecting plate 43, and FIG. 11 illustrates the function of the reflecting plate 43 in more detail in side view, taken along line C-C 'of FIG.

In addition, washing with air alone begins before washing water and air in combination or before washing with water alone. In this case, both the unit block 16 and the granular filter material 14 thereon are immersed in the process water 26. 4 illustrates the case of air washing alone in more detail. When compressed air is injected into the first horizontal horizontal path 36, an interface 46 between water and air is formed in the first horizontal horizontal path 36. In particular, the air distribution hole 48 is provided in the inner side wall 34 that separates the first horizontal horizontal path 36 and the second horizontal horizontal path 38. The air flows into the second horizontal horizontal path 38 through the air distribution hole 48 from the first horizontal horizontal path 36, where the air flows toward the block top plate 28 in a bubble state. The block top plate 28 has a loss head suitable for passing the ejection hole 40 from the air blanket or air pocket 50 formed in the lower portion of the total ejection hole 40 according to the size and spacing of the ejection hole 40. It is sprayed evenly. Similar to water backwashing, the direction of the air passing through the jet hole 40 is directed upward, but the direction of the air is changed in the horizontal direction by the reflector plate 43 directly above the jet hole 40 to spread radially. It rises uniformly to the filtration layer of the granular filter material 14. This dispersion is described in FIG. 8.

As described above, in order to maintain a proper head of water in the unit block 16 of the lower collecting device 12 during rinsing at high speed only with water, the blow holes 40 of the upper plate 28 are appropriately sized and spaced. It must be maintained. It is important to minimize the dispersion of the hydraulically uneven state by maintaining the equilibrium head loss of the blower hole 40. The opening ratio of the blower hole is within 1%.
9 shows a baffle 62 is provided inside the second order horizontal path 38 proximate the bell end 64 of the lower collector block 16. The baffles 62 are partitions formed to protrude from the lower surface of the block top plate 28 into the second horizontal horizontal path 38, and a plurality of baffles 62 are provided along the longitudinal direction of the second horizontal horizontal path 38. .

The baffle 62 protrudes downward in the second horizontal horizontal path 38, and the lower end of the baffle 62 is positioned below the interface 54 between water and air. The baffle 62 has a function of a pressure equalizing chamber that prevents sudden uneven movement of air in the lower portion of the block upper plate 28. In other words, when backwashing only with air, water is prevented from being partially drawn up from the water surface near the jet hole 40 due to the water level difference due to the hydraulic inclination line at the interface 54 between the water and the air. In order to prevent air leakage, the baffle 62 is attached to the upper portion of the second horizontal water path 38 at regular intervals to function as a pressure equalizing chamber to equalize the pressure between the sections by the baffle 62 in the pressure chamber.

The unit blocks 16 of the lower collecting device 12 are interconnected in the following manner. Each unit block 16 has a spigot end 68 and a bell end 64, respectively. This is illustrated in FIGS. 5 and 9. The bell end 64 includes a straight alignment protrusion 70 into which the trough 72 for straight alignment is to be placed on the spigot end 68. The straight alignment protrusions 70 and the straight alignment grooves are provided at both ends in the longitudinal direction of the unit block 16, respectively. Spigot end 68 accepts bell end 64 and tab 74 is provided at spigot end 68 to receive window 76 at bell end 64. The tab 74 is housed in the window 76 and then screwed on the top. The interlocking portions of the unit blocks 16 of the lower collecting device 12 are inserted into the spigot end 68 close to the tab 74 in order to maintain airtightness and watertightness, such as an O-ring. You can also keep it.

As described above, the water distribution hole 80 is disposed at regular intervals in the longitudinal direction of the unit block 16 at the lowest position of the inner side wall 34, and used for collecting the filtered water and passing and distributing the backwash water. do.

During backwashing with water, the backwashing water enters the first horizontal waterway 36 and enters the second horizontal waterway 38 through the water distribution hole 80. By compensating for the flow in the second order horizontal path 38 in a direction opposite to the flow in the first horizontal path 36, the distribution of the non-uniform backwash water in the lower collecting device 16 can be minimized. Furthermore, baffles 66 for controlling the flow of backwash water are attached to the first horizontal horizontal path 36 at appropriate intervals in order to control the non-uniform distribution. The baffle 66 attached to the first horizontal horizontal path 36 is formed at a constant height along the inner side wall 34, unlike the baffle 62 provided inside the second horizontal horizontal path 38. You can check its shape at. From the second horizontal water path 38, the backwash water rises upward through the jet hole 40 and is redispersed horizontally by the reflecting plate 43, and then goes upward into the granular filter material 14, and the granular filter material 14 Will be cleaned or transported to the upper part. Collection of the filtrate is a reverse process.

Meanwhile, during backwashing with air, the backwashing air enters the first horizontal water passage 36 and enters the second horizontal water passage 38 through the air distribution hole 48. As with water, the distribution of the non-uniform backwash air in the bottom catchment device 16 can be minimized by compensating the flow in the secondary horizontal path 38 in the reverse direction to the flow in the primary horizontal path 36. The backwashing air rises upwardly through the dispersion hole 40 from the second horizontal water path 38 and is redispersed horizontally by the reflecting plate, and then the filter medium is stirred while entering the filter medium 14 upward. Therefore, it is important to uniformly utilize all of the dispersion holes 40 during backwashing. Typically, backwash water is pressurized by pumps or supplied from backwash baths during backwash.
7 is a unit block so that when the unit block 16 and the unit block 16 of the lower collecting device 12 are installed in parallel, the unit block 16 is firmly adhered to the concrete floor 18 at the bottom. (16) The upper part was wide and the lower part was narrowly narrowed. The width of the unit block 16 is narrowed toward the lower portion is the shape of the concrete support column 92 between the unit block 16 and the unit block 16 of the lower collecting device 12, the lower side is the width When the concrete mortar is filled in the space between the outer side walls 32 of the adjacent unit blocks 16, the concrete support column 92 and the unit blocks 16 are closely fixed to each other and are also separately fixed to the concrete floor 18. The block 16 can be firmly installed on the floor without facilities.

In addition, the outer side wall 32 is provided with a plurality of outwardly protruding hooks 31 can further strengthen the coupling with the concrete support column (92).

The lower collecting device 12 of the gravity filtering facility 10 has a main function of collecting the filtered water uniformly and sending it to a water purifier, but as a function thereof, the backwashing water and the backwashing air are equally discharged to the spout 40. In order to allow the passage, the first and second horizontal paths 36 and 38 were constructed. In addition, by uniformly distributing the ejection hole 40 in the entire plane of the block top plate 28, the backwash water and the backwash air are placed on the granular filter material 14 located above the unit block 16 of the lower collecting device 12. It was washed uniformly and washed less water.

The present invention minimizes the catching water area by the ejection water by arranging the ejection holes 40 at each vertex of the equilateral triangle when viewed from the upper plane of the unit block 16 of the lower collecting device 12. That is, the conventional arrangement method up to now has adopted the method of arranging the ejection hole 40 at the vertex of a square or a rectangle. In the case where the ejection hole 40 is arranged at the vertex of the square, the shooter area is at least 21.5%, while the shooter area in the same condition has been reduced to about 9.5% by arranging the ejection hole 40 at the vertex of the equilateral triangle. In addition, the jet water passing through the jet hole 40 is changed to the horizontal direction by the reflector plate 43 on the upper side, so that the jet part of the jet water expands to the entire floor plane from the conventional shape, which is a vertex of the cone, upwards. As it proceeds, the size of the catchment water formed on the upper part of the block top plate 28 is much reduced compared to the conventional method in which the vertex of the conical shape is placed on the upper plate of the lower collector block in the conventional lower catchment unit block. That's the way. That is, since the jetted water and the sprayed air are ejected from the entire surface of the block top plate 28 of the unit block 16, the upper particulate filter material 14 particles can be uniformly backwashed evenly.

In addition, when the unit block 16 and the unit block 16 of the lower collecting device 12 are installed in parallel, the block 16 of the unit block 16 is firmly adhered to the lower concrete floor 18. The cross-sectional shape was such that the upper part was wider and the lower part was slightly narrower. Thus, the narrower the cross section of the unit block 16 toward the bottom, the shape of the concrete support column 92 between the lower collecting device 12 unit block 16 and the unit block 16, the lower side is larger Thus, when the concrete mortar is filled in the space between the outer side wall 32 of the adjacent unit block 16, the concrete support column 92 and the unit block 16 is fixed in close contact with each other without a separate fixing device on the concrete floor 18. The block 16 can be firmly installed on the floor.

Claims (6)

As a block constituting the bottom collecting device of the gravity filtration facility, Consists of unit blocks arranged continuously in the longitudinal and horizontal direction at the bottom of the granular filter material 14 of the lower collecting device 12, The unit block 16, A first horizontal horizontal path 36 formed in a longitudinal direction to have a triangular cross section; A second order horizontal path 38 formed in a longitudinal direction so as to be divided into an inner side wall 34 on each of left and right upper portions of the first order horizontal path 36; A plurality of water distribution holes 80 provided in the longitudinal direction on the inner side wall 34; A plurality of air distribution holes 48 provided in the longitudinal direction on the inner side wall 34 and positioned above the water distribution hole 80; An outer side wall 32 provided on an outer surface of the second order horizontal path 38; A block upper plate 28 provided on an upper surface of the second order horizontal path 38; And, A plurality of ejection holes 40 provided in the block upper plate 28; Consists of including W-hole hole block of the lower collecting device, characterized in that the ejection hole 40 is arranged to be located at the vertex of the equilateral triangle. In claim 1, A reflection plate 43 installed to be spaced apart from the upper portion of the blower hole 40 and larger than a diameter of the blower hole 40; Is provided, the back washing water or the back washing air passing through the spouting hole 40 collides with the reflecting plate 43, the radially spread around the spouting hole 40, characterized in that the lower collecting device W-type perforated block. In claim 2, A baffle (62) formed on the lower surface of the block top plate (28) so as to protrude into the second horizontal horizontal path (38), the plurality of baffles being provided along the longitudinal direction of the second horizontal horizontal path (38); W-type pore block of the lower collecting device, characterized in that it further comprises. In claim 3, The unit block 16, Its cross section is configured such that the upper portion is wider and narrower toward the lower portion, so that the inner side wall 34 provided in each of the outer side wall 32 and the left and right upper portions of the first horizontal horizontal line 36 is 'W'. W-type pore block of the lower collecting device, characterized in that the shape of the ruler. In claim 4, On the outer side wall 32, Outwardly protruding hooks 31; W-type porous block of the bottom collecting device, characterized in that the plurality is provided. delete

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