JP5380688B2 - Water treatment member, septic tank, and water treatment device - Google Patents

Description

  The present invention relates to a water treatment member and a septic tank.

For example, Patent Document 1 discloses a fiber filter medium in which one end portions of a fiber bundle obtained by bundling a plurality of fibrous carriers composed of carbon fibers are connected to each other at a fixing portion.
Further, for example, Patent Document 2 discloses a microbial carrier used in a wastewater treatment apparatus, wherein the microbial carrier includes a plurality of support carriers, and the support carrier includes a support member and a fiber bundle arranged in a plurality of stages in the vertical direction on the support member. The fiber bundle is composed of a plurality of fiber filaments, one end or the middle is bundled and fixed to a support member, the other end or the end is a free end of the fiber filament, and a plurality of support carriers are arranged in parallel. Also disclosed is a microbial carrier in which the free ends of the fiber filaments of adjacent support carriers are arranged so as to partially overlap each other.
In addition, for example, in Patent Document 3, in a biological contact filter medium comprising a large number of string contact filter media that are installed in an aeration tank of a water treatment device and attached to a support frame in order to adhere microorganisms, A biological contact filter medium in which the biological carrier parts of the contact filter medium are discontinuously provided, and the biological carrier parts are arranged so that their heights are uneven with respect to the biological carrier part of the adjacent string-like contact filter medium.
For example, Patent Document 4 discloses a septic tank in which a plurality of flexible rocking members are provided radially around a string-like fixing member as a filter medium in an anaerobic biological treatment tank.

JP 2009-136737 A JP 2008-29945 A JP-A-5-237490 JP 2001-54796 A

  As described above, in each of Patent Documents 1, 2, 3, and 4, the fiber material is used for wastewater treatment to increase the sludge collection efficiency, but when the water in the tank is discharged, the fiber material adheres in large quantities. In addition to the risk of damaging the fiber material itself due to the sludge load, the suspended part or the connecting part may be damaged when the fiber material assembly is suspended. Moreover, if the amount of fiber material is increased in order to increase the supplement rate, the filter bed may be blocked by supplemental sludge. Further, the water treatment member needs to be easily charged and replaced. The present invention is simple and excellent in the effect of collecting sludge such as suspended solids in an anaerobic treatment section, hardly causes filter bed clogging, and can withstand the load load when draining water in the tank. And it aims at providing the water treatment apparatus and septic tank which provided this water treatment member.

  The water treatment member according to the present invention includes a support body having a hardness capable of maintaining a certain form in the air or water, and a plurality of fiber members projecting obliquely from the support body.

  Suitably, the said support body is rod-shaped and the fixing position of the said fiber member is helically provided in the said support body surface.

  Preferably, it further has a string-like or belt-like flexible member, and the plurality of fiber members are arranged in the flexible member, and the flexible member spirals around the support. Wrapped in a shape.

  Preferably, the fiber member is carbon fiber, and the long axis direction of the fiber member is substantially orthogonal to the long axis direction of the flexible member.

  Further, the septic tank according to the present invention spirally arranges a rod-like support having a hardness capable of maintaining a certain form in the air or in water and a plurality of fiber members projecting obliquely from the support. Thus, it has a water treatment member capable of efficiently collecting sludge such as suspended solids, and an anaerobic treatment tank formed so that the major axis direction of the support is the direction in which the treated water flows.

  Preferably, the fiber member is carbon fiber, and the long axis direction of the fiber member is substantially orthogonal to the long axis direction of the flexible member.

  In the water treatment method according to the present invention, a string-like or belt-like flexible member in which a plurality of fiber members are arranged is spirally wound around the surface of a rod-like support, and the flexible member is wound around the surface. The support is installed in the treated water.

  The water treatment member according to the present invention can efficiently collect sludge such as suspended solids, hardly clogs the filter bed, and can withstand the load applied when the water in the tank is discharged.

It is a figure which represents typically the whole structure of the septic tank. It is a figure which represents typically the whole structure of the water treatment member. It is a figure showing the sludge outflow amount from the anaerobic filter bed tank provided with various water treatment members. It is a figure showing the sludge retention amount in the anaerobic filter bed tank provided with various water treatment members. It is a figure which represents typically the whole structure of the septic tank. It is a figure which represents typically the whole structure of the septic tank. It is a figure which represents typically the whole structure of the water treatment member. It is a figure which represents typically the whole structure of the water treatment member. It is a principal part enlarged view of the water treatment member 124. FIG. It is a figure which represents typically the whole structure of the water treatment apparatus 400. FIG.

FIG. 1 is a diagram schematically illustrating the entire configuration of the septic tank 1.
As illustrated in FIG. 1, the septic tank 1 includes an anaerobic filter bed first chamber 10, a solubilization tank 20, an anaerobic filter bed second chamber 30, a contact aeration tank 40, a treated water tank 50, and a disinfectant. And a tank 60.

  The anaerobic filter bed first chamber 10 is a place where sewage such as domestic wastewater or human waste is first introduced. The inflowing sewage flows from the top to the bottom in the anaerobic filter bed first chamber 10, and the sludge contained in the sewage is attached to the solid material 110 in the middle. The solid material 110 is a kind of water treatment member, and various microbial populations are formed in a film form (hereinafter referred to as “microbe membrane”) on the surface. The sludge substance adhering to the solid material 110 is decomposed and purified by this microbial film. Then, the sewage obtained by decomposing and purifying the sludge material is then sent to the anaerobic filter bed tank second chamber 30. The sludge substance that does not adhere to the solid material 110 and accumulates at the bottom of the anaerobic filter bed first chamber 10 is sucked up by the air lift pump and sent to the solubilization tank 20.

  The solubilization tank 20 is provided with a water treatment member 120 (described later with reference to FIG. 2). The sewage sent to the solubilization tank 20 is circulated up and down in the solubilization tank 20 by the action of a pump provided at the bottom of the solubilization tank 20. By this circulation, the sludge substance contained in the sewage sent to the solubilization tank 20 is promoted to dissolve in the sewage. Moreover, the sludge substance contained in sewage adheres to the water treatment member 120 by this circulation. An anaerobic microbial membrane is formed on the surface of the water treatment member 120. The sludge substance adhering to the water treatment member 120 is decomposed and purified by this microbial membrane. The water treatment member 120 has a surface area larger than that of the solid material 110, and can attach and disassemble and purify many sludge substances at a time. In particular, in the case of carbon fiber, it can be expected that an anaerobic microbial film having high bioaffinity is formed at an early stage. Then, the sewage obtained by decomposing and purifying the sludge material is then sent to the anaerobic filter bed tank second chamber 30.

  The anaerobic filter bed second chamber 30 is provided with a water treatment member 120. The sewage sent to the anaerobic filter bed second chamber 30 flows from the bottom to the top, and the sludge contained in the sewage is attached to the water treatment member 120 in the middle. As in the case of the solubilization tank 20, the water treatment member 120 decomposes and purifies the attached sludge substance by the microbial film formed on the surface. Then, the sewage obtained by decomposing and purifying the sludge substance is then sent to the contact aeration tank 40.

  The contact aeration tank 40 is provided with a contact material 130 and an air diffuser 140 that constantly discharges air bubbles toward the contact material 130. An aerobic microbial film is formed on the surface of the contact material 130. The pollutant contained in the sewage is decomposed and purified by the catalytic oxidation action by the microbial membrane. Furthermore, the inside of the contact aeration tank 40 has a biological filtration part 135, and a backwashing air diffuser 145 is arranged in the lower part thereof. This biological filtration unit 135 has a solid material 115, and physically filters and captures solid matter floating in the sewage, and decomposes and purifies residual pollutants by a microbial film formed on the surface. . Normally, the backwashing diffuser 145 does not release air, and automatic backwashing (air release) is performed once to several times a day, and the solid matter captured by the biological filtration unit 135 is collected. To prevent complete blockage. Then, the sewage obtained by decomposing and purifying the pollutant is sent to the treated water tank 50 and further to the disinfection tank 60.

  The disinfection tank 60 finally disinfects the decomposed and purified sewage and discharges it to a river or the like. Moreover, the treated water tank 50 sends the sewage sent from the contact aeration tank 40 to the anaerobic filter bed tank first chamber 10 as circulating water by a pump. In some cases, it may be sent to the anaerobic filter bed tank second chamber 30.

  As described above, the water treatment member 120 according to the present embodiment is provided in the septic tank 1 and performs sewage treatment.

FIG. 2 is a diagram schematically illustrating the entire configuration of the water treatment member 120.
As illustrated in FIG. 2, the water treatment member 120 includes a support body 210 and a carrier member 220. In the present embodiment, the water treatment member 120 further includes a fixing member 240.

The support 210 has a hardness capable of maintaining a certain form in the air or water, and supports the carrier member 220 wound around the support 210. The shape of the support 210 is not particularly limited as long as the support member 220 in a state where sludge is held can be supported at least as a structure, and can be wound around the support member 220. Good. For example, the support 210 may be formed in a substantially cylindrical shape, a substantially conical shape, a substantially spherical shape, a substantially polygonal column shape, a substantially cone shape, or the like.
In this embodiment, the support 210 is formed in a substantially cylindrical rod shape. The outer diameter of the vertical cross section with respect to the axis of the support 210 according to the present embodiment is not particularly limited, but the fibrous carrier 320 of the carrier member 220 that is wound around is moderately spread, so that the water flow is not hindered. Thus, it is preferable that it is 5-80 mm.
Further, the support 210 is preferably formed of a corrosion-resistant material that can withstand the water flow in the septic tank 1, and is formed of a lightweight material in consideration of replacement or maintenance of the support 210. It is more preferable. For example, the support 210 may be formed of a material such as vinyl chloride.

The carrier member 220 is obtained by fixing a plurality of fibrous carriers 320 to a base member 310 formed in a string shape or a belt shape. The means for fixing the fibrous carrier 320 to the base material 310 is not particularly limited. For example, the fibrous carrier 320 may be bonded to the basic material 310 by adhesion or welding, or the fibrous carrier 320 and the basic member 310 may be integrally formed. In addition, the inclination of the fibrous carrier 320 with respect to the axial direction of the basic member 310 when the fibrous carrier 320 is fixed to the basic material 310 is not particularly limited.
In this embodiment, the fibrous carrier 320 is fixed in a state of being substantially orthogonal to the basic member 310. The fibrous carrier 320 is flexible and bends obliquely downward due to gravity. Thereby, the carrier member 220 can reduce the shearing force which acts on the fibrous carrier 320 by the load applied vertically downward when the water in the tank is discharged.
The material of the basic member 310 and the fibrous carrier 320 is not particularly limited, and may be, for example, carbon fiber, nylon fiber, polyester fiber, polyvinylidene chloride fiber, polypropylene fiber, or the like. Among these, carbon fibers are preferable because they are excellent in durability, light in weight, and excellent in biocompatibility.

Further, the carrier member 220 is wound around the support 210 and fixed to the support 210. The means for fixing the carrier member 220 to the support 210 is not particularly limited. For example, the carrier member 220 may be fixed to the support 210 by being hooked on a hook-shaped member provided on the support 210 or tightened by a belt-shaped member. Further, the carrier member 220 is preferably fixed at a plurality of locations of the support 210. Thereby, the carrier member 220 can disperse the load applied vertically downward when the water in the tank is discharged to a plurality of locations fixed to the support 210.
In the present embodiment, the carrier member 220 is fixed to the support body 210 at a plurality of locations by fastening members 230. The fastening member 230 may be anything as long as it can fasten the carrier member 230 to the support 210. For example, the tightening member 230 is a rubber band or a belt.

  Moreover, the shape in which the carrier member 220 wraps around the support 210 is not particularly limited, but is preferably a spiral shape as illustrated in FIG. When the carrier member 220 is spirally wound and fixed around the support 210, the water flow in the vertical direction passing between the carrier members 220 is spirally spiraled. Thereby, since treated water repeatedly contacts with the fibrous carrier 320 without short-circuiting, the water treatment member 120 can efficiently attach sludge to the fibrous carrier 320. Further, since the carrier member 220 is spirally wound around the support 210, even if the arrangement interval of the support 210 is shortened, there are few lap joint portions of the adjacent carrier members 220, and the water flow path in the vertical direction. Therefore, filter bed blockage due to sludge growth is unlikely to occur. In this case, the axial direction of the support 210 is preferably parallel to the water flow direction.

The fixing member 240 fixes the support body 210. The fixing member 240 may be only one of the upper part and the lower part, or may be both as shown in FIG. The means by which the fixing member 240 fixes the support 210 is not particularly limited. For example, the fixing member 240 may be fixed to the support 210 by fitting to the support 210 or supporting the periphery of the support 210. The fixing member 240 may be formed separately from the septic tank in which the water treatment member 120 is provided, and may be fixed to the septic tank, or may be formed integrally with the septic tank.
In this embodiment, the fixing member 240 is a plate provided with a plurality of holes slightly larger than the outer diameter of the support 210. Two fixing members 240 are provided in the septic tank in parallel so as to be positioned at both ends of the support 210. The support 210 is fixed at both ends by being inserted into the holes of the fixing member 240 provided in parallel.
In addition, the number of the support bodies 210 to which the fixing member 240 is fixed may be appropriately changed according to the capacity of the septic tank in which the water treatment member 120 is provided or the purification capacity.

With the configuration as described above, the water treatment member 120 reduces the load applied to the carrier member 220 when the water in the tank is discharged or irregularly changes in the flow rate, and the base material 310 is broken by the attached sludge. The member 220 is prevented from being damaged. Even when the fibrous carrier 320 is a carbon fiber that is weak against bending, the fibrous carrier 310 projects obliquely from the support 210, so that the fibrous carrier 320 hangs down by its own weight after draining the water in the tank. The bending angle of the fibrous carrier 320 with respect to the support 210 is reduced, and breakage prevention can be expected.
Further, the water treatment member 120 spirally winds the carrier member 220 around the support 210 to realize a spiral rectification effect and a sufficient spread of the fibrous carrier 320, and an improvement in purification capability can be expected. . Further, the water treatment member 120 facilitates replacement of each support 210 by the fixing member 240.

  FIG. 3 shows the results of an anaerobic treatment experiment in a 50 L small tank, and the SS concentration of the spilled sludge was measured when 5 L / day of sludge of suspended solids (SS) 3000 mg / L was flowed. . The “carbon fiber centipede type” in the graph is a carbon fiber that is installed as a carrier member 220 without being wrapped around and fixed to the support 210, and the “string-like fiber material” is a polyester fiber material that is supported by the carrier member 220. As described above, it is installed without being wrapped around the support 210 and fixed. The “carbon fiber spiral type” is a carbon fiber as a carrier member and is installed in a state of being wound around and fixed to the support 210 in a spiral manner. The amount of carbon fiber was the same.

  As illustrated in FIG. 3, the “carbon fiber centipede type” has a longer number of days until the outflow SS increases than the “string fiber material”, and the “carbon fiber spiral type” has a very large amount of outflow SS during the measurement period. There were few results.

  FIG. 4 shows the cumulative amount of sludge retained in the experimental tank, based on the difference between the inflow sludge amount and the outflow sludge amount, in the anaerobic treatment experiment shown in FIG. The “carbon fiber centipede type” in the graph is a carbon fiber that is installed as a carrier member 220 without being wrapped around and fixed to the support 210, and the “string-like fiber material” is a polyester fiber material that is supported by the carrier member 220. As described above, it is installed without being wrapped around the support 210 and fixed. The “carbon fiber spiral type” is a carbon fiber as a carrier member and is installed in a state of being wound around and fixed to the support 210 in a spiral manner.

  As illustrated in FIG. 4, the “carbon fiber centipede type” and the “carbon fiber spiral type” have a very high sludge retention amount compared to the “string fiber material”. Further, when the elapsed days have passed, the difference between the “carbon fiber spiral type” and the “carbon fiber spiral type” begins to appear, and it can be said that the “carbon fiber spiral type” can hold more sludge.

  From the graph demonstrated above, it turns out that the water treatment member 120 hold | maintains sludge efficiently, and decomposes | disassembles and purifies.

[Modification 1]
FIG. 5 is a diagram schematically illustrating the entire configuration of the septic tank 2.
As illustrated in FIG. 5, the septic tank 2 includes a separation septic tank 12, a solubilization tank 20, an anaerobic filter bed tank 32, a contact aeration tank 40, a treated water tank 50, and a disinfection tank 60. Note that, among the components shown in this figure, the same reference numerals are given to the components substantially the same as those shown in FIG.
In the following, the components different from those shown in FIG. 1 will be described among the components shown in FIG.

  The separation septic tank 12 is a place where sewage such as domestic wastewater or human waste is first introduced. The inflowing sewage precipitates sludge in the separation septic tank 12. The precipitated sludge material is decomposed and purified by anaerobic microorganisms. Then, the supernatant of the sewage in which the sludge substance is precipitated is sent to the anaerobic filter bed tank 32.

  The anaerobic filter bed tank 32 is provided with a solid material 110. The sewage sent to the anaerobic filter bed 32 flows from the top to the bottom, and the sludge substance contained in the sewage is attached to the solid material 110 in the middle. The solid material 110 decomposes and purifies the attached sludge substance by an anaerobic microbial film formed on the surface. Then, the sewage obtained by decomposing and purifying the sludge substance is then sent to the contact aeration tank 40. In addition, the sludge substance that does not adhere to the solid material 110 and accumulates at the bottom of the anaerobic filter bed tank 32 is sucked up by the air lift pump and sent to the solubilization tank 20.

  The water treatment member 120 according to the above embodiment may be provided in the septic tank 2 as described above.

[Modification 2]
FIG. 6 is a diagram schematically illustrating the entire configuration of the septic tank 3.
As illustrated in FIG. 6, the septic tank 3 includes an anaerobic filter bed tank first chamber 14, an anaerobic filter bed tank second chamber 34, a contact aeration tank 40, a treated water tank 50, and a disinfection tank 60. Note that, among the components shown in this figure, the same reference numerals are given to the components substantially the same as those shown in FIG.
In the following, the components different from those shown in FIG. 1 will be described among the components shown in FIG.

  The anaerobic filter bed first chamber 14 is a place where sewage such as daily wastewater or human waste is first introduced, and is provided with a water treatment member 120. The sewage that has flowed into the first chamber 14 of the anaerobic filter bed flows from the bottom to the top in the first chamber 14 of the anaerobic filter bed, and the sludge contained in the sewage adheres to the water treatment member 120 in the middle. Let The water treatment member 120 decomposes and purifies the attached sludge substance by an anaerobic microbial film formed on the surface. Then, the sewage obtained by decomposing and purifying the sludge substance is then sent to the anaerobic filter bed tank second chamber 34.

  The anaerobic filter bed second chamber 34 is provided with a water treatment member 120. The sewage that has flowed into the second chamber 34 of the anaerobic filter bed flows from the bottom to the top in the second chamber 34 of the anaerobic filter bed, and the sludge contained in the sewage adheres to the water treatment member 120 in the middle. Let The water treatment member 120 decomposes and purifies the attached sludge substance by an anaerobic microbial film formed on the surface. Then, the sewage obtained by decomposing and purifying the sludge substance is then sent to the contact aeration tank 40. The sludge substance that does not adhere to the water treatment member 120 and accumulates at the bottom of the anaerobic filter bed tank second chamber 34 is sucked up by the air lift pump and sent to the anaerobic filter bed tank first chamber 14.

  The water treatment member 120 according to the above embodiment may be provided in the septic tank 3 as described above.

[Modification 3]
FIG. 7 is a diagram schematically illustrating the entire configuration of the water treatment member 122.
As illustrated in FIG. 7, the water treatment member 122 includes a carrier member 222 that is fixed in a state in which the fibrous carrier 320 is substantially orthogonal to only one direction on one side of the base material 310. By fixing the fibrous carrier 320 to the base material 310 in this way, the fibrous carrier 320 is on the lower side on average, compared to the fibrous carrier 320 of the water treatment member 120 illustrated in FIG. Become. Thereby, the water treatment member 122 can further reduce the load applied vertically downward when the water in the tank is discharged.

FIG. 8 is a diagram schematically illustrating the overall configuration of the water treatment member 124.
As illustrated in FIG. 8, the water treatment member 124 includes a support body 210 and a carrier member 224. In the present embodiment, the water treatment member 124 further includes a fixing member 240. It should be noted that among the components shown in this figure, those substantially the same as those shown in FIG.
In the following, the configuration different from the configuration shown in FIG. 2 will be described among the configurations shown in FIG.

As illustrated in FIG. 9, the carrier member 224 is obtained by fixing a plurality of bundles (fiber bundles 322) of the fibrous carriers 320 in Example 1 to the base material 310 formed in a string shape or a band shape. It is. The means for fixing the fiber bundle 322 to the base material 310 is not particularly limited. For example, the fiber bundle 322 may be joined to the base material 310 by adhesion or welding, or the fiber bundle 322 and the base member 310 may be integrally formed. In addition, the inclination of the fiber bundle 322 with respect to the axial direction of the base member 310 when the fiber bundle 322 is fixed to the base material 310 is not particularly limited.
In this embodiment, the fiber bundle 320 is fixed in a state substantially orthogonal to the basic member 310. Further, the fiber bundle 322 has flexibility and bends downward due to gravity. Thereby, the carrier member 224 can reduce the load applied vertically downward when the water in the tank is discharged. Furthermore, the carrier member 224 can increase the surface area and retain a larger amount of sludge substance by fixing the fiber bundle 322 as compared with the water treatment member 120 illustrated in FIG.

FIG. 10 is a diagram schematically illustrating the overall configuration of the water treatment apparatus 400.
As illustrated in FIG. 10, the water treatment apparatus 400 includes a water supply pipe 410, a water treatment member 124, and a drain pipe 412. The liquid (raw water) flowing in from the water supply pipe 410 flows between the water treatment members 124 from the bottom to the top in the water treatment apparatus 400. At this time, the water treatment member 124 carries the microorganisms on the surface and treats the liquid by the action of the carried microorganisms. The liquid thus treated is discharged to the outside through the drain pipe 412. Further, the gas released in the process of processing the liquid is collected from the upper part of the water treatment device 400.
The water treatment apparatus 400 may be anything as long as it can process a liquid using microorganisms. Therefore, the septic tank is an example of the water treatment device 400.

  As described above, the water treatment member 124 according to the present embodiment is provided in the water treatment apparatus 400 and treats a liquid.

Other modifications will be described.
In the above embodiment, the mode in which the carrier member 220 is wound around the support 210 has been described. However, the present invention is not limited to this. For example, the fibrous carrier 320 is embedded obliquely with respect to the surface of the support 210. Alternatively, after integrally forming the support 210 and the fibrous carrier 320, the support 210 may be twisted, or the fibrous carrier may be bonded or sewn to the surface of a long thin bag, You may make it cover this support body 210 with this bag.

1 Septic Tank 2 Septic Tank (Modification 1)
3 Septic tank (Modification 2)
10 Anaerobic filter bed 1st chamber 12 Decomposition septic tank 14 Anaerobic filter bed 1st chamber (Modification 2)
20 Solubilization tank 30 Anaerobic filter bed 2nd chamber 32 Anaerobic filter bed (Modification 1)
34 Anaerobic filter bed second chamber (Modification 2)
40 Contact aeration tank 50 Treated water tank 60 Disinfection tank 110 Solid material 115 Solid material 120 Water treatment member 122 Water treatment member (Modification 3)
124 Water treatment member (Example 2)
DESCRIPTION OF SYMBOLS 130 Contact material 135 Biological filtration part 140 Air diffuser 145 Air diffuser for backwash 210 Support body 220 Carrier member 222 Carrier member (modification 3)
224 Carrier member (Example 2)
230 Tightening member 240 Fixing member 310 Base material 320 Fibrous carrier 322 Fiber bundle 400 Water treatment device 410 Water supply pipe 412 Drainage pipe

Claims (3)

A rod-like support disposed in parallel with the direction of the treated water flow ;
A fiber member made of carbon fiber ;
A string-like or belt-like flexible member;
Have
The plurality of fiber members are arranged in the flexible member such that the long axis direction of the fiber member is substantially orthogonal to the long axis direction of the flexible member,
A water treatment member in which the flexible member is spirally wound around the support and the fiber member protrudes obliquely from the support . A water treatment member;
Anaerobic treatment tank and
Have
The water treatment member is
A rod-shaped support;
A fiber member made of carbon fiber;
A string-like or belt-like flexible member;
Including
The plurality of fiber members are arranged in the flexible member such that the long axis direction of the fiber member is substantially orthogonal to the long axis direction of the flexible member,
The flexible member is spirally wound around the support, and the fiber member protrudes obliquely from the support;
The anaerobic treatment tank is a purification tank formed such that the major axis direction of the support is the direction in which treated water flows . A string-like or belt-like flexible member in which a plurality of fiber members made of carbon fiber are arranged is spirally wound around the surface of a rod-like support,
A water treatment method in which the support on which the flexible member is wound is installed in an anaerobic treatment tank so that the major axis direction of the support is a direction in which treated water flows .

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