JP2011143407A - Filter and filtering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter which has a simplified piping mechanism and is excellent in uniform detergency of a filter layer part by backwashing. <P>SOLUTION: The filter is configured to include: a filter layer part for filtering raw water; a plurality of rows of water collecting pipes for collecting water permeated through the filter layer part; and a pressure ditch for sending water with pressure to the plurality of rows of the water collecting pipes, so that the filter layer part is backwashed by water being transferred from the pressure ditch to the water collecting pipes. The filter is characterized in that a communicative part is installed making each water collecting pipe communicated with each other for the purpose of transferring, between the respective water collecting pipes, the water transferred from the pressure ditch to the water collecting pipes by the difference of pressures imparted to each water collecting pipe. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a filtration device and a filtration method, and includes, for example, a filter layer portion that filters raw water, and a plurality of water collecting pipes that collect permeated water that has passed through the filter layer portion. A filtration device comprising a pressure rod for pumping water to the water pipe, and configured to backwash the filter layer by transferring water from the pressure rod to the water collecting tube, and a filter of the filtration device The present invention relates to a filtration method including a step of washing a layer portion by backwashing.

  Conventionally, this type of filtration device has been used to obtain filtered pond treated water as purified water from land water such as river water.

  Such a filtration device is configured such that a plurality of orifices are dispersedly provided on the upper surface of the water collecting pipe, and the water filtered through the filter layer is transferred from the orifice into the water collecting pipe and collected. . In addition, when the filter layer is clogged due to accumulation of impurities contained in the raw water in the filter layer, water is pumped from the pressure trough to the water collecting pipe, and the water is supplied to the orifice. The filter layer is pumped to the filter layer and the filter layer is washed (backwashed) with the water (for example, Patent Document 1).

  By the way, as a countermeasure against Cryptosporidium, the former Ministry of Health and Welfare issued a provisional guideline “To maintain the turbidity of filtered basin treatment water below 0.1 degree” in October 1996. In order to maintain the turbidity of the filtered basin treatment water at 0.1 degrees or less, it is necessary to prevent impurities from accumulating in the filter layer. Therefore, in order to prevent impurities from accumulating in the filter layer part, the pressure of water applied to each orifice during backwashing is required to be uniform in order to clean the entire filter layer part more uniformly than before. Yes.

In order to stabilize the turbidity of the treated water, the flow rate of water for backwashing such as slow start and slow down is gradually increased and decreased so as not to disturb the particle size of the filter layer. Driving methods have been proposed.
Even when this operation method is adopted, the pressure uniformity of the backwash water at the initially set constant flow rate is not to be maintained, but the reverse is also observed in the changing flow rate, particularly in the low flow rate region. It is necessary to maintain the uniformity of the washing water pressure.

Japanese Examined Patent Publication No. 6-61411

  However, in the conventional water collection pipe, the uniformity of the pressure of the backwash water is not sufficient, and in particular, when the flow rate of the backwash water is changed as described above, the uniformity is further insufficient. As a result, there is a problem that the entire filter layer cannot be washed uniformly.

  By the way, as a measure for uniformly washing the entire filter layer, it is conceivable to shorten the distance from the pressure pump to the upstream end of the water collecting pipe.

  However, in such a filtering device, in order to perform water treatment in a large area, it is necessary to produce many combinations of water collecting pipes and pressure rods, and there is a problem that the piping mechanism becomes complicated.

  In view of the above problems, an object of the present invention is to provide a filtration apparatus and a filtration method that can simplify the piping mechanism and are excellent in the uniform washing performance of the filter layer portion by backwashing.

The present invention is provided with a filter layer section for filtering raw water, and a plurality of water collecting pipes for collecting permeated water that has permeated through the filter layer section, and a pressure trough for pumping water to the plurality of water collecting pipes. A filtration device configured to backwash the filter layer by transferring water from the pressure trough to the water collecting pipe,
A filtration device comprising a communication portion for communicating each water collecting pipe so that water transferred from the pressure trough to the water collecting pipe is transferred between the water collecting pipes due to a pressure difference applied to each water collecting pipe. is there.

Furthermore, in the filtration device according to the present invention, preferably, the water collecting pipe is constituted by an outer shell body having a hollow column shape in cross section, and an inner shell body provided in the outer shell body,
The inner shell body is configured to partition the outer shell body into a first flow portion and a second flow portion;
A first orifice is provided on the upper surface portion of the outer shell body, and the permeated water is transferred from the first orifice to the first circulation portion.
The inner shell is provided with a second orifice, and the permeated water of the first circulation part is transferred from the second orifice to the second circulation part,
At least a part of the side part of the second flow part is constituted by at least a part of the side part of the outer shell,
The communicating part is connected to the part of the side part of the second flow part constituted by at least a part of the side part of the outer shell.

  Moreover, this invention exists in the filtration method provided with the process of performing filtration using the filter layer part of the said filtration apparatus, and wash | cleaning this filter part by backwashing.

  As described above, according to the present invention, it is possible to provide a filtration device and a filtration method that can simplify the piping mechanism and are excellent in the uniform washability of the filter layer by backwashing.

The partially broken schematic perspective view of the filtration apparatus concerning one embodiment. The schematic diagram of the filtration apparatus concerning one embodiment. The partially broken schematic perspective view which shows the perforated block which comprises the water collecting pipe of the filtration apparatus which concerns on one Embodiment. Sectional drawing of the perforated block of the filtration apparatus which concerns on one Embodiment. Sectional drawing of the filtration apparatus which concerns on one Embodiment. Sectional drawing of the filtration apparatus which concerns on one Embodiment. The side view of the filtration device concerning one embodiment. Model of continuous equidistributed piping. Static pressure distribution at various k _d .

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a partially broken schematic perspective view of the filtration device, in which 100 denotes a filtration device, and 101 denotes a filtration tank body provided in the filtration device 100. .
Reference numeral 103 denotes a perforated block that is laid above the bottom plate portion 101a that forms the bottom surface of the filter tank body 101 and forms a plurality of water collecting pipes.
FIG. 2 is a schematic diagram showing the positional relationship between the water collecting pipe 2, the pressure rod 110 and the communication part 4 in the filtration device 100.
Further, FIG. 3 is a schematic perspective view including a partially broken view showing the structure of the perforated block 103, and FIG. 4 is a cross-sectional view of the perforated block 103 cut along a plane orthogonal to the axial direction.

As shown in FIGS. 1 and 2, the filtration device 100 according to the present embodiment includes a filtration tank body 101 in which raw water that is to be treated is stored, and the filtration so that the raw water is passed in a downward flow and filtered. The filtration layer body 102 formed in the tank body 101 and the filtration tank body to collect permeate (filtered water) that has passed through the filtration layer portion 102 and to diffuse the filtration layer portion 102. And a plurality of water collecting pipes 2 disposed above the bottom plate portion 101 a forming the bottom surface of 101 and below the filter layer portion 102.
Each of the water collecting pipes 2 is formed by connecting a perforated block 103 (see FIGS. 3 and 4) in a cylindrical shape and having a plurality of orifices formed on an upper surface thereof in an axial direction (longitudinal direction). The outer surface portion excluding the portion is fixed to the bottom plate portion 101a in a state of being embedded in the solidified mortar 108.
Further, the filtration device 100 of this embodiment includes a support material layer 105 for supporting the filter layer portion 102 between the filter layer portion 102 and the water collecting pipe 2.

The filtration device 100 of the present embodiment is configured to collect the permeated water that is connected to the water collecting pipe 2 and flows into the water collecting pipe 2 and to feed water back to the water collecting pipe 2 during backwashing. The pressure rod 110 is configured to be discharged from the pressure rod 110 to the outside of the filtration tank body 101 through the water distribution pipe 111, and further, water is pumped from the pressure rod 110 to the water collecting pipe 2. The filter layer 102 is configured to be backwashed.
Further, the filtration device 100 of the present embodiment includes a drainage trough 106 for discharging water (washing drainage) ejected to the upper surface side of the filter layer portion 102 by backwashing from the filtration tank body 101, and the drainage trough 106. And a drainage pit 107 into which the cleaning wastewater flows.
Furthermore, the filtration device 100 of the present embodiment has a gas supply pipe 104 that supplies air into the perforated block 103 in order to perform aeration by the perforated block 103 for back washing of the filter layer portion 102 and the like. It has.

The filtration tank main body 101 is formed with a bottom plate portion 101a having a rectangular shape in plan view, and has a substantially rectangular parallelepiped shape by side walls 101b ₁ , 101b ₂ , 101b ₃ , 101b ₄ erected on the periphery of the bottom plate portion 101a. A space is formed.
The bottom board 101a is formed by placing and solidifying a cement composition such as mortar or concrete.

The filter layer portion 102 is configured in the same manner as a filter layer in a conventionally known filtration device, and particles (filter medium) such as sand, anthracite, activated carbon, and plastic filter material are arranged in the depth direction of the filter tank body 101. It is filled and formed to have a constant thickness.
If necessary, microorganisms can be attached to the surface of the filtration medium.
The support material layer 105 is also configured similarly to the support material layer in a conventionally known filtration device, and in this embodiment, a perforated plate is used.
As the porous plate, for example, a plate-like structure constituted by joining a large number of beads having a diameter of several mm can be used.
As the beads forming the perforated plate, ceramics, sintered metals, etc. can be used in addition to plastics such as polyolefin resin such as polyethylene.
It is also possible to form gravel instead of the perforated plate to form the support material layer 105. When gravel is used, gravel having a particle size larger than the granular material forming the filter layer portion 102 is filtered. It can be filled and formed to have a constant thickness in the depth direction of 101.

  The pressure rod 110 is arranged below the most downstream part of the water collecting pipe 2 (specifically, the part near the one end side of the water collecting pipe 2 and the part where the opening is provided on the lower surface of the perforated block 103). In order to further collect the water collected in each of the water collecting pipes 2, it is formed so as to be dug further downward than the water collecting pipes 2.

  As shown in FIG. 2, the filtration device 100 of the present embodiment is configured so that the water transferred from the pressure rod 110 to the water collection pipe 2 due to the pressure difference applied to each water collection pipe 2 is transferred between the water collection pipes 2. A communication part 4 for communicating the water collecting pipe 2 is provided.

The portion of the water collecting pipe 2 where water is transferred by the communication portion 4 (that is, the portion where the communication portion 4 is provided) is preferably a location where water is pumped from the pressure rod 110 (that is, the pressure rod). 110 is connected to the upstream tip of the water collecting pipe 2 and is formed at a point that is less than half the distance. That is, the portion where water is transferred by the communication portion 4 is formed near the location where water is pumped between the location where water is pumped from the pressure rod 110 and the upstream tip. By having such a configuration, the filtration device 100 of the present embodiment has an advantage that the pressure applied to the orifices can be made more uniform, so that the cleaning efficiency of the filter layer portion 102 by backwashing can be further increased. In particular, when the distance from the point where water is pumped from the pressure rod 110 to the upstream end of the water collecting pipe 2 is 4 m or more, such a configuration is preferably applied to the filtering device 100 of the present embodiment. .
Further, the portion is more preferably formed at a point of a distance of 1/3 or less from the location to the upstream tip and a location separated by 200 mm or more from the location. The filtration device 100 according to the present embodiment has a configuration in which the portion is formed at a distance of 200 mm or more from the location, so that the bottom area of the portion connected from the pressure rod 110 to the water collecting pipe 2 is reduced. There is an advantage that the strength deficiency due to the reduction can be solved. (In this regard, in detail, the perforated block 103 spanning the end of the pressure rod 110 is loaded with a heavy material such as an upper filter layer or a support material layer 105. Therefore, it is preferable to avoid the opening of the perforated block 103 in the vicinity of the perforated block 103 in view of the load resistance of the perforated block 103. Therefore, the filtration device 100 of this embodiment has the above-described configuration. Having the above advantages.) Further, in the filtration device 100 of the present embodiment, the portion is formed at a point having a distance of 1/3 or less from the location to the upstream tip, so that the pressure applied to the orifices is further increased. Since it becomes more uniform, there exists an advantage that the washing | cleaning efficiency of the filter layer part 102 by backwashing can further be improved further. Such a configuration is preferably applied to the filtering device 100 of the present embodiment, particularly when the distance from the pressure pump 110 to the upstream end of the water collecting pipe 2 from the location where water is pumped is 6 m or more. .

Each of the water collecting pipes 2 is configured by connecting a plurality of perforated blocks 103 in the longitudinal direction.
As shown in FIGS. 3 and 4, the perforated block 103 has a rectangular cross section and an outer shell body 13a having a cylindrical shape, and the two partition walls disposed in the outer shell body 13a are reversed in cross section. And an inner shell body 13b formed in a V shape.
The inner shell body 13b is arranged in the outer shell body 13a so as to partition the inside of the outer shell body 13a into two first circulation portions 13g and a second circulation portion 13f.
Specifically, the inner shell 13b has an inverted V-shaped top formed by the partition wall abutted along the substantially central portion of the inner surface of the upper surface portion 13c of the outer shell, and is reversed from the top. One of the two partition walls extending in a V shape is brought into contact with the tip of one side 13b ₁ along the substantially central portion of the inner surface of _one side 13d ₁ of the side surface part 13d of the outer shell 13a, and the other side 13b. the _second tip into contact along a substantially central portion of the inner surface of the side surface portions 13d ₂ that faces the side surface portion 13d ₁ of the one and are arranged in the outer shell body 13a.
As a result, the lower half of the side portions 13d ₁ and 13d ₂ facing each other, the lower surface portion 13e of the outer shell body 13a, and the inner shell body 13b form a central passage that is formed in a cross-section inverted home base shape. The perforated block 103 is formed with two flow portions 13f and first flow portions 13g that are side passages formed on the upper left and right sides of the central passage 13f.

The cross-sectional area of the first flow part 13g is preferably 1.0 × 10 ^{−2 to} 2.0 × 10 ⁻² m ² , more preferably 1.0 × 10 ^{−2 to} 1.7 × 10 ^{−. 2} m ² .

The cross-sectional area of the second flow part 13f is preferably 3.0 × 10 ^{−2 to} 6.0 × 10 ⁻² m ² , more preferably 3.4 × 10 ^{−2 to} 6.0 × 10 ^{−. 2} m ² .

In the present embodiment, a perforated plate 13p forming the support material layer 105 is attached to the perforated block 103 so as to cover the upper surface portion 13c of the perforated block 103.
That is, the perforated plate 13p is attached to the perforated block 103 of the present embodiment so that the support material layer 105 can be formed simultaneously by arranging the perforated block 103 above the bottom plate portion 101a. ing.

  The water collecting pipe 2 is provided with a first orifice 24a on the upper surface of the outer shell 13a so that the permeated water flowing down the filter layer portion 102 is transferred from the first orifice 24a to the first circulation portion 13g. It is made up of.

The first orifice 24a preferably has an opening ratio (ratio (%) of the total orifice area per plane area (m ² ) of the filter layer portion 102) of 0.5 to 1.5%, more preferably 0. .78 to 1.45%. The first orifice 24a at that time has a diameter of 4.5 to 6.0 mm when the cross-sectional shape of the orifice mouth is circular, and the cross-sectional area of the mouth is 15 when the cross-sectional shape of the orifice mouth is elliptical. .9 to 28.3 mm ² .

  The water collecting pipe 2 is configured such that a second orifice 24b is provided in the inner shell 13b, and the permeated water of the first circulation part 13g is transferred from the second orifice 24b to the second circulation part 13f. It becomes.

The second orifice 24b preferably has an opening ratio (ratio (%) of the total orifice area per area (m ² ) of the filter layer portion 102) of 0.6 to 0.9%, more preferably 0. 70-0.85%. The second orifice 24b at that time has a diameter of 20 to 22 mm when the cross-sectional shape of the orifice mouth is circular, and a cross-sectional area of the mouth of 314 to 380 mm ² when the cross-sectional shape of the orifice mouth is elliptical. is there.

Further, each of the water collecting pipes 2 is configured such that at least a part of the side surface portion of the second circulation portion 13f is constituted by at least a part of the side surface portion of the outer shell body 13a, as shown in FIG. The communication part 4 is each provided in the side part of the 2nd distribution | circulation part 13f comprised by at least one part of the side part of this outer shell 13a, and is comprised.
The adjacent water collecting pipes 2 communicate with each other via the communication part 4 provided on the side surface part of the second circulation part 13f.

  The communication part 4 is formed such that the total pressure loss of water passing through the communication part 4 is smaller than the total pressure loss of water passing through the orifice.

The cross-sectional area of the communication part 4 is preferably 3.0 × 10 ^{−2 to} 6.0 × 10 ⁻² m ² , more preferably 3.0 × 10 ^{−2 to} 4.0 × 10 ⁻² m. ² .

  The filtration device of the present embodiment is configured as described above. Next, the filtration method of the present embodiment will be described.

  The filtration method of this embodiment is a method comprising a step of performing filtration using the filtration device 100 of this embodiment and washing the filter layer portion 102 by backwashing.

  Since the filtration device and the filtration method of the present embodiment are configured as described above, they have the following advantages.

  That is, in the filtration device 100 of the present embodiment, at least a part of the side surface portion of the second flow portion 13f is configured by at least a part of the side surface portion of the outer shell body 13a, and at least one of the side surface portions of the outer shell body 13a. There is an advantage that the mechanism of the communication part 4 can be further simplified by connecting the communication part 4 to the side part of the second flow part 13f constituted by the part.

  In addition, although the filtration apparatus and the filtration method of this embodiment had the said advantage by the said structure, the filtration apparatus and the filtration method of this invention are not limited to the said structure, A design change is possible suitably. .

For example, in the present embodiment, the perforated block 103 is configured such that at least a part of the side surface portion of the second flow portion 13f is constituted by at least a part of the side surface portion of the outer shell 13a. As shown in FIG. 6, the perforated block 103 may be in a form in which the side surface portion of the outer shell 13 a is not a component of the second flow portion 13 f. That is, the second flow portion 13f may be configured by the inner shell body 13b and the upper surface portion and the lower surface portion 13e of the outer shell body 13a.
Moreover, in such an aspect, as shown in FIG. 6, each communication part 4 is provided in the lower surface part 13e of the 2nd distribution | circulation part 13f, and each adjacent water collecting pipes 2 are 2nd distribution | circulation. You may be comprised so that it may mutually communicate via the communication part 4 provided in the lower surface part 13e of the part 13f.

  Furthermore, in the present invention, the position where the pressure rod 110 is disposed is not particularly limited, and may be below the vicinity of one end of the water collecting pipe 2 as shown in FIG. Moreover, as shown to (b), the center part lower part of the water collecting pipe 2 may be sufficient.

<About the model>
The filtration device and the filtration method of the present embodiment are configured so as to satisfy the above-described configuration, thereby simplifying the piping mechanism and increasing the cleaning efficiency of the filter layer portion by backwashing. This becomes clear from the results of the following model calculation. The model is described below.

  In general, when a pipe has a large number of branch pipes from the main flow path (main pipe), and a fluid flows out uniformly from the branch pipe, an approximate model with continuous uniform pipe is effective. (See Japan Society of Mechanical Engineers: Technical data, Fluid resistance of pipes and ducts (1979)).

First, the outline of continuous equidistributed piping is shown below. Consider a pipe as shown in FIG. 8 (model diagram of continuous uniform pipe). N branch pipes (also called “branch pipes”) are connected perpendicularly to the main pipe (also called “distribution pipe”), and water is discharged from the _nth branch pipe by q _n . . Here, let us consider a case where an infinite number of branch pipes exist and water flows out uniformly from all the branch pipes. Taking the x-axis along the axial direction of the main pipe from the inlet where water flows into the main pipe as the origin, the length of the main pipe (length in the axial direction) is L, the static pressure at x = L is p _e , If the density is ρ, the pipe friction coefficient is λ, the main length of the main pipe (equivalent diameter (inner diameter)) is D, and the static pressure and flow velocity at a certain x are p and V, respectively, the static pressure of the branch pipe (static pressure at x) ) The distribution of p is given by Equation 1 below.

Here, when the distribution pipe characteristic parameter k _{d is set} to the following formula 2, the static pressure distribution at various k _d is obtained, the result is as shown in FIG. As shown in FIG. 9, when k _d <0, the pressure increase due to the diffuser action is larger than the pressure drop due to pipe friction. Therefore, the pressure increases as the point is farther from the inlet.

The force that causes water to flow in a direction perpendicular to the flow direction is proportional to the static pressure. That is, in order to allow water to flow out uniformly in the backwashing process, the static pressure in the water channel must be uniform, and the absolute value of k _d can be reduced, or the dynamic pressure, that is, the flow rate can be reduced. It is valid.

  First, in order to confirm the presence or absence of a pressure gradient between a plurality of laterals (collecting pipes), an approximate model by continuous equal distribution was used in FIG. 8 with the main pipe as a pressure rod and the branch pipe as a lateral.

First, the following preconditions were assumed. That is, the pressure rod has a length (axial length) L of 9.0 m, a representative length (equivalent diameter (inner diameter)) D of 1.53 m, and a cross-sectional area of 2.75 m ² . It is assumed that water flows out at a rate of 0.7 m / min from a lateral (collection pipe) that branches off from the pressure tank. It is assumed that the flow velocity at the pressure inlet is 0.41 m / s by the same method as above. However, the density and viscosity coefficient of water are 1000 kg / m ³ and 0.001 Pa · s, respectively.
From the above preconditions, the Reynolds number Re is 6.23 × 10 ⁵ (−), so the pipe friction coefficient is expressed by the following formula 3 using the white formula, and the following formula 4. Therefore, the distribution characteristic parameter is expressed by the following formula 5. Then, since a pressure gradient close to k _d = −1 (−) in FIG. 9 is generated inside the pressure rod, water cannot be equally distributed. That is, a gradient also occurs in the flow rate between the laterals, and water cannot flow out uniformly.

  Below, the concrete effect of the communication block which is a communication part is verified. Table 1 shows the preconditions.

When operating under the conditions in Table 1, the pressure at the distribution pipe (perforated block inlet) point is 1.7 × 10 ⁴ Pa. On the other hand, since the dynamic pressure p at the inlet of the pressure rod where water flows into the pressure rod is 83 Pa, from Equation 1, the following Equation 6 is obtained, and the pressure difference between both ends of the pressure rod is about 0.5%. Next, the differential pressure between adjacent laterals is a maximum of about 5 Pa, which corresponds to about 0.03% of the pressure at the pressure inlet. If the communication block is regarded as an orifice, water flows at a maximum flow rate of 0.06 m / s between the lateral orifices. If the communication block is installed at a position 250 mm to 300 mm from the end of the pressure rod, it takes about 2.9 seconds for the inflow water to pass through the cross section of the communication block, so the amount of water that can pass through the communication block flows into the pressure rod. It can be expected that the pressure difference between adjacent laterals can be reduced almost completely because it is 50% or more with respect to the amount of water.

The communication block is a channel with an axial length (distance between laterals) of about 30 to 50 mm, compared to the width of the perforated block (side length) (axial length) (270 mm). In the following, it is considered as an orifice. When the flow coefficient of the orifice is 0.61 (-) and the flow velocity corresponding to the differential pressure of 5.2 Pa is obtained, it is 0.06 m / s. The cross-sectional area of the communication block opening is a rectangle of 0.08 (m) x 0.77 (m) = 6.2 x 10 ^-3 m ² and the water flowing into the opening from the pressure trough passes through the lateral cross section. Since this time is 0.77 (m) /0.27 (m / s) = 2.9 s, if the pressure difference can be relaxed within this time, the pressure difference caused by the pressure soot can be eliminated by the communication block.

Therefore, according to Bernoulli's theorem, the flow rate ratio is proportional to the 1/2 power of the pressure ratio, so from 5.2 (Pa) / 17000 (Pa) × 100 ≒ 0.03 (%) About 0.015%. More specifically, the relationship between the flow rate ratio (v ₁ / v ₂ ) and the pressure ratio (P ₁ / P ₂ ) is expressed by the following formula 7 according to Bernoulli's theorem, but P ₁ and P ₂ Since the values are very close to each other, P ₁ / P ₂ = (1 + 3 × 10 ⁻⁴ ) is very close to 1 (see Equation 8 below). Therefore, the flow rate, that is, the flow rate is 0.5 × 3 × 10 ⁻⁴ × 100 = 0.015% according to the above equation.

Therefore, the flow rate per lateral row is 1.9 × 10 ⁻² m ³ / s, and the equivalent of 0.015% is 2.9 × 10 ⁻⁶ m ³ / s. When water passes through the communication block cross section at 0.06m / s, the time required to alleviate the variation is about 8ms, which is extremely short compared to the time required to pass through the communication block cross section. .

  From the above, the communication block can relieve the pressure gradient generated in the pressure rod.

  In addition, consider the location of the communication block. As the communication block is installed closer to the pressure rod, the pressure difference between the laterals is suppressed in the block in front of the communication block, the difference in the amount of water passing through the water orifice is suppressed, and the flow becomes even more uniform. . Therefore, the communication block is preferably installed at a position closest to the pressure rod.

2: water collecting pipe, 4: communication portion, 13a: outer shell body, 13b: inner shell body, 13c: upper surface portion, 13d: side surface portion, 13e: lower surface portion, 13f: second flow portion, 13g: first flow portion , 13p: perforated plate, 24a: first orifice, 24b: second orifice 100: filtration apparatus 101: a filtration tank body, 101a: base plate _{portion, 101b 1, 101b 2, 101b} 3, 101b 4: side wall, 102: Filter layer part, 103: Perforated block, 104: Gas supply pipe, 105: Support material layer, 106: Drainage trough, 107: Drainage pit, 108: Mortar, 110: Pressure trough, 111: Water distribution pipe

Claims (3)

A filtration layer portion for filtering raw water is provided, a plurality of water collection pipes for collecting permeated water that has passed through the filtration layer portion are provided, and a pressure trough for pumping water to the plurality of water collection pipes is provided, A filtration device configured to backwash the filter layer by transferring water from the pressure trough to the water collecting pipe,
A filtration device comprising a communication portion for communicating each water collecting pipe so that water transferred from the pressure trough to the water collecting pipe is transferred between the water collecting pipes due to a pressure difference applied to each water collecting pipe. The water collecting pipe is constituted by an outer shell body having a columnar shape with a hollow cross section, and an inner shell body provided in the outer shell body,
The inner shell body is configured to partition the outer shell body into a first flow portion and a second flow portion;
A first orifice is provided on the upper surface portion of the outer shell body, and the permeated water is transferred from the first orifice to the first circulation portion.
The inner shell is provided with a second orifice, and the permeated water of the first circulation part is transferred from the second orifice to the second circulation part,
At least a part of the side part of the second flow part is constituted by at least a part of the side part of the outer shell,
The filtration device according to claim 1, wherein the communication portion is connected to the portions of the side surface portion of the second flow portion constituted by at least a part of the side surface portion of the outer shell.   A filtration method comprising the steps of performing filtration using the filtration device according to claim 1 and washing the filter layer portion by backwashing.

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