JP2760358B2 - Filtration tower using long fiber bundle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention relates to various recovered waters such as water supply and sewage water, sewage, river water, lake water, coagulated sedimentation supernatant water, intermediate water for various processes, and recovered water in a papermaking process. The present invention relates to a filtration tower using a long fiber bundle for removing a suspended matter in a stock solution such as various wastewaters, treated water of a biological treatment apparatus or a liquid containing valuables, sake, oil, or the like at a high flow rate.

<Prior Art> The applicant of the present application has previously described Japanese Patent Application Laid-Open No.
No. 131715 discloses a filtration tower using a long fiber bundle.

As shown in FIG. 3, the filtration tower has a support (b) such as a perforated plate provided horizontally below the filtration tower (b), and the lower end of the long fiber bundle (c) is placed on the support (b). The filter is fixed and its upper end is set as a free end. A long fiber bundle (c) is erected on the whole inside of the filtration tower (a). When filtering the undiluted solution containing the suspension, the valve (d) and the valve ( E) and the undiluted solution flows in from the undiluted solution inflow pipe (f) and the long fiber bundle (c)
, The undiluted solution is passed in a downward flow, the suspended matter is trapped in the void portion of the long fiber bundle, and the filtrate is taken out from the filtrate outflow pipe (g) provided below the support (b). Things.

When the pressure loss increased due to the trapping of the suspended matter, the valve (d) and the valve (e) were closed, and the valves (h) and (l) were opened, and compressed air was introduced from the air inlet pipe (nu). And agitate and oscillate the long fiber bundle (c). Then, with the compressed air flowing in, or stop the flow and open the valve (l) to flow backwash water from the quick-wash water inlet pipe (ヲ). Then, the suspension is discharged from the backflow water discharge pipe (W).

The filtration tower is usually an acrylic fiber having a thickness of 10 μ to 80 μ,
A long fiber bundle of 0.4 m to 3.0 m long, which is a polymer of non-twisted monofilaments of polyester fiber and polyamide fiber towers, is filled up relatively tightly in the filtration tower so as to be upright. The suspension can be filtered at a high flow rate without increasing the size.

In addition, since the lower end of the long fiber bundle is fixed, when high-speed compressed air or backwash water flows in ascending flow at the time of backwashing, the long fiber bundle becomes like a streamer with the lower end fixed. Since the long fiber bundle vibrates as it elongates, the captured suspension can be effectively removed.

However, as shown in FIG. 4, the lower end of the long fiber bundle was fixed at the beginning of the development of this filtration tower, the long fiber bundle (c) was bent, the bent portion was gathered by a ring (f), and the support (b)
Position the bent portion so as to cover each hole (Y), and use a bolt (T) communicating with the ring (F) to support the long fiber bundle (C) with the support rod (Le) and nut (S). Since it had a fixed structure, it had the following drawbacks.

That is, in the case of such a structure, the long fiber bundles gathered by the ring (f) are quite dense and the liquid always passes through the part during the filtration, so that the suspended matter is collected in the dense part. The suspension was easily clogged, and once the suspension was clogged, it was not possible to remove the backwash even if the above-mentioned back washing was performed.

This is because, in the structure shown in FIG. 4, even when a fluid such as compressed air or backwash water is passed through each hole (Y), the upper surface of the perforated plate (B) and the long fiber bundle (C) are not This is because the fluid preferentially passes through the contact portion, and it is difficult for the fluid to pass through the essential portion, that is, the dense portion. When the nut (so) is strongly tightened to increase the degree of contact between each hole (Y) and the long fiber bundle (C), the long fiber bundle (C) in which the dense portion is relatively free from clogging with the suspension. The fluid preferentially passes through the hole (Y) having the flow path, and the fluid does not pass through the hole (Y) having the long fiber bundle (C) in which the suspended portion is clogged with the portion to be washed, that is, the dense portion. A phenomenon also occurs.

Also, the vicinity of the lower end fixing portion of the long fiber bundle (c) is not originally a portion that vibrates so much due to the inflow of the cleaning fluid.
Even if the washing fluid flows ideally, it is difficult to remove the suspended matter trapped in this part, and it is inevitable that the clogging of the part will gradually progress while continuing filtration well. .

Therefore, if such a state continues, the suspension gradually remains at or near the dense portion, that is, near the fixing portion of the long fiber bundle, and therefore the initial differential pressure in the filtration gradually increases, and in some cases, the filtration step It will have a serious hindrance to itself.

Further, the above-mentioned filtration tower has another problem as follows.

In the filtration tower, the quality of the obtained filtrate and the degree of the pressure loss differ depending on the thickness of each single fiber of the long fiber bundle used, and these relationships are as follows.

In other words, when a long fiber bundle, which is an aggregate of relatively thin single fibers, is used, although the quality of the filtrate is improved, the fiber itself is weak and the long fiber bundle is captured as the suspended matter is captured during filtration. Uprights cannot be maintained, and the pressure loss rises faster due to the consolidation of long fiber bundles, especially in the lower part of the filtration tower, resulting in shorter filtration times and, in some cases, insufficient washing. have.

On the other hand, when a long fiber bundle, which is an aggregate of relatively thick single fibers, is used, since the fibers themselves are strong, the consolidation of the long fiber bundle does not occur so much, the pressure loss rises slowly, and the filtration time is long. However, it has a drawback that the quality of the filtrate decreases.

Therefore, it has been difficult to meet the demand to improve the quality of the filtrate as much as possible and to increase the filtration time.

<Problems to be Solved by the Invention> The present invention solves the above-mentioned problems in a conventional filtration tower using a long fiber bundle, and the residual and accumulation of the suspended matter near the fixed portion of the long fiber bundle. It is an object of the present invention to provide a filtration tower capable of reliably preventing contamination by water.

Another object of the present invention is to provide a filtration tower capable of preventing the contamination in the long fiber bundle fixing portion, improving the quality of the filtrate as much as possible, and extending the filtration time. It is in.

<Means for Solving the Problems> In a filtration tower using a long fiber bundle according to the present invention which has been made to achieve the above object, a lower end of the long fiber bundle is fixed to a support provided at a lower part in the tower. With the upper end as the free end, the undiluted solution flows in from above the filtration tower having a plurality of long fiber bundles erected throughout the inside of the tower, and the undiluted solution flows from the upper end to the lower end of the long fiber bundle. In a filtration tower for trapping a suspended material in a void inside the collector, a collector for collecting a filtrate is provided in the long fiber bundle group slightly above the support.

Further, according to the invention described in the second aspect, in the filtration tower having the above-described configuration, a first long fiber bundle composed of an aggregate of relatively thin single fibers is arranged in a central portion of the tower, and the first long fiber bundle is arranged around the first bundle. A collector for disposing a second long fiber bundle composed of an aggregate of single fibers thicker than the single fiber used for the one long fiber bundle, and collecting a filtrate in the first long fiber bundle group And a filtration tower using a long fiber bundle.

 Hereinafter, the present invention will be described in detail.

FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of a filtration tower of the present invention. A support 2 made of a perforated plate is provided horizontally below a filtration tower 1, and a long fiber bundle is provided on the support 2. 3 is fixed, and the upper end of the long fiber bundle 3 is a free end.
The long fiber bundle 3 is erected in the filtration tower 1 by packing the long fiber bundle 3 relatively densely in the tower.

Further, a stock solution inflow pipe 4 is provided above the filtration tower 1, and a backwash water discharge pipe 5 is branched and communicated with the stock solution inflow pipe 4.

Further, a backwash air inflow pipe 6 is communicated below the support 2 and a backwash water inflow pipe 7 is branched to communicate with the backwash air inflow pipe 6.

A feature of the present invention is that a collector 8 for collecting a filtrate is provided in the group of long fiber bundles 3 slightly above the support 2 in the filtration tower having the above configuration. The collector 8
Any shape may be used as long as it has a structure capable of collecting the filtrate, and a known collector, such as a hollow pipe having a number of water collection holes formed in the peripheral wall connected in a cross shape, may be used. FIG. 1 shows a collector having such a structure arranged laterally in a tower. Reference numeral 9 denotes a filtrate outflow pipe communicating with the collector 8. Note that 10
Reference numerals 14 each denote a valve.

According to the filtration tower of this embodiment, it is possible to reliably prevent contamination near the long fiber bundle fixing portion.

Next, FIG. 2 is a schematic cross-sectional view showing an embodiment of the filtration tower according to the second claim of the present invention. The feature of the filtration tower 1 is as a long fiber bundle standing upright in the filtration tower 1. Using two types of long fiber bundles, each having a different fiber thickness, a first long fiber bundle 3A, which is an aggregate of relatively thin single fibers, is passed through a filtration tower 1
A long fiber bundle 3B composed of an aggregate of single fibers thicker than the single fibers used for the first long fiber bundle 3A is arranged around the center portion (outside in FIG. 2), Further, a collector 8 for collecting the filtrate is provided in the first long fiber bundle 3A group. In the filtration tower of the present embodiment, for example, a hollow tube having a large number of liquid collecting ports formed in the peripheral wall is used as the collector 8, and the hollow tube is connected to the first long fiber bundle as shown in FIG. It is good to stand almost in the center of the 3A group, and the reason will be described later.

The other parts are the same as those of the above-mentioned filtration tower, so that the detailed description is omitted.

According to the filtration tower of the present embodiment, as in the case of the filtration tower shown in FIG. 1, it is possible to prevent contamination near the long fiber bundle fixing portion and to improve the quality of the filtrate as much as possible. In addition, it is possible to simultaneously satisfy the requirement of increasing the filtration time.

<Operation> The operation of the present filtration tower will be described below.

First, when filtering the undiluted solution containing the suspension, the valve 10
And the valve 14 is opened and the other valves are closed to allow the stock solution to flow downward from the stock solution inflow pipe 4. The undiluted solution flows down along the long fiber bundle 3 erected in the tower, and the suspended matter is captured in the void formed by the long fiber bundle 3. The filtrate in which the suspension is captured enters the collector 8 from a collecting port (not shown) of the collector 8 provided slightly above the support 2 to which the long fiber bundle 3 is fixed. It flows out of the tower from the outflow pipe 9.

As described above, in the filtration tower of the present invention, the filtrate can be collected slightly above the support 2 and allowed to flow out of the tower. The flow does not have to be allowed to flow, so that the suspension does not become clogged near the fixing portion.

If the stock solution is a perishable liquid and retention of the solution in the lower part of the tower is not preferable, a part of the filtrate may be passed through the support 2 and taken out as in the related art. In this case, since the liquid passes near the fixed portion of the long fiber bundle 3, the suspension is more likely to be clogged in the vicinity of the fixed portion than in the above-described case, but allows the entire amount of the filtrate to pass as in the related art. Compared to the case, the degree is much smaller, and it is of such a degree that it can be sufficiently washed by back washing.

When a large amount of suspended matter is trapped in the voids of the long fiber bundle 3 due to the continuation of the filtration as described above, the pressure loss gradually increases,
With an increase in pressure loss, the long fiber bundle 3 standing upright from the lower part of the long fiber bundle 3 starts to bend, and a phenomenon that the upright height of the long fiber bundle 3 gradually decreases occurs.

When the increase in the pressure loss reaches a predetermined value, the valves 10 and 14 are closed to stop filtration, and the following backwashing is performed.

That is, the valves 11 and 13 are opened, and compressed air flows in from the backwash air inflow pipe 6.

Due to the inflow of the compressed air, the liquid in the filtration tower 1 is stirred and the long fiber bundle 3 vibrates, the voids formed between the fibers are destroyed, and the aggregate of the suspended matter is destroyed. The suspension adhered to the bundle 3 is peeled off.

Then, while the inflow of the compressed air is continued or the valve 13 is closed to stop the inflow of the compressed air, the valve 12 is opened and the valve 12 is opened, and the backwash water flows from the backwash water inflow pipe 7.

Since the lower end of the long fiber bundle 3 is fixed to the support 2 and the upper end is a free end, the long fiber bundle 3 causes the support 2 to Each fiber vibrates while elongating like a swept streamer.

Therefore, the suspended matter cannot remain in the long fiber bundle 3, the suspended matter is separated from the long fiber bundle 3, and the backwash wastewater containing a large amount of the suspended matter flows out from the backwash water outflow pipe 5. .

In addition, as the backwashing method, in addition to the above-described method, a method of intermittently flowing compressed air while flowing a certain amount of backwashing water in an upward flow may be used. It is effective in most cases.

The above operation is common to the filtration tower shown in FIG. 1 and the filtration tower shown in FIG. 2, and achieves the object of reliably preventing contamination near the fixed portion of the long fiber bundle 3. The same can be said about what can be done. However, the filtration tower shown in FIG. 2 has another effect as described below.

That is, in the filtration tower shown in FIG. 2, as described above, as the long fiber bundle 3, two types of long fiber bundles having different fiber thicknesses are used, and the long fiber bundle 3 is formed of an aggregate of relatively thin single fibers. The first long fiber bundle 3A is disposed in the center of the filtration tower 1 and a second long fiber bundle formed of an aggregate of single fibers thicker than the single fibers used for the first long fiber bundle 3A around the first long fiber bundle 3A.
3B, and a collector 8 is provided in the first long fiber bundle 3A group, that is, substantially at the axis in the tower. Therefore, at the time of filtration, the undiluted solution flowing in the central part of the tower flows down almost along the first long fiber bundle 3A composed of a thin single fiber aggregate, and comes into contact with the long fiber bundle 3A to obtain a high quality filtrate. And liquid is collected by a collector 8 arranged at the axis of the tower. On the other hand, the undiluted solution flowing in the outer peripheral portion of the tower is arranged on the outer peripheral portion,
First, it flows down along a second long fiber bundle 3B composed of an aggregate of single fibers thicker than the single fiber used for the first long fiber bundle 3A,
Thereafter, the flow is directed toward the collector 8 disposed at the axis of the tower. The dotted line in FIG. 2 schematically shows such a flow of the liquid. In this case, the undiluted liquid first comes into contact with the second long fiber bundle 3B arranged on the outer peripheral portion of the tower, and relatively coarse filtration is performed. Given
Then, the second long fiber bundle 3B is brought into contact with the first long fiber bundle 3A and is subjected to relatively precise filtration, and finally a high quality filtrate is collected in the collector 8. Liquid.

The above-mentioned filtration tower of the present invention partially adopts the concept of so-called multilayer filtration in which two types of particulate filter materials having different particle sizes are laminated in the same tower, and the outer periphery of the filtration tower is Ideal filtration can be performed on the flowing undiluted solution, making the most of the characteristics of each long fiber bundle.

That is, according to the filtration tower shown in FIG. 2, the pressure loss of the entire tower is lower than that of the filtration tower in which only the first long fiber bundle 3A composed of an aggregate of thin single fibers is erected in the whole tower. And the filtration time can be extended, and a filtrate of almost the same quality as in the case of a filtration tower using only the first long fiber bundle 3A can be obtained.

As is clear from the above description, in the case of the filtration tower shown in FIG. 2, it is preferable that the filtrate be collected at the axis of the filtration tower 1 as much as possible. It is preferable to use such a collector vertically standing as shown in FIG.

Next, the long fiber bundle used in the filtration tower shown in FIG. 1 or FIG. 2 will be described. Although the lower part of the fiber bundle is slightly bent and its height is slightly reduced, and the bent part of the lower part increases due to the continuation of the liquid passing, and the upright height of the long fiber bundle gradually decreases, Synthesize acrylic fiber, polyester fiber, polyamide fiber, etc. Fibers or natural fibers such as cotton and wool can be used.

These synthetic fibers or natural fibers usually use an aggregate of non-twisted single fibers, and the thickness of the single fibers is preferably 1 to 80 μm, and the length of the fiber bundle is usually 1 to 3 m. Good to do.

In addition, the first long fiber bundle in the filtration tower shown in FIG.
3A and the thickness of each single fiber of the second long fiber bundle 3B,
Alternatively, the filling ratio of both long fiber bundles varies depending on the concentration of the suspension in the stock solution to be treated, the quality of the target filtrate, and the like, but is usually 1 to 43 μm in thickness as the first long fiber bundle. A long fiber bundle made of a single fiber is used, and a second long fiber bundle is used as a second long fiber bundle.
It is preferable to use a long fiber bundle consisting of single fibers of ~ 80μ, and the filling ratio of the first long fiber bundle is set to be 1/4 to 1/3 of the total filling amount, and the second long fiber bundle is used. The fiber bundle is arranged so as to have a weight of 3/4 to 2/3, or the first long fiber bundle is arranged at a central portion corresponding to about 1/4 of the cross-sectional area of the filtration tower, and the periphery thereof is arranged. It is preferable that the second long fiber bundle is arranged at a portion corresponding to about 3/4.

<Example> An example of the present invention will be described below.

Example 1 A perforated plate was attached to the lower part of a stainless steel filtration tower having a diameter of 650 mm and a height of 2,000 mm (linear portion).
μ, a long fiber bundle composed of an aggregate of acrylic non-twisted single fibers having a length of 1,500 mm is fixedly erected so as to have a packing density of 65 kg / m ³ (dry weight), and 300 mm from the perforated plate. A filtration tower as shown in FIG. 1 was constructed by horizontally arranging a collector formed by connecting porous hollow tubes in a cross shape in the upper long fiber bundle group, and a suspension (SS concentration) was placed in the filtration tower. ) Is 50mg / h on average and the papermaking wastewater is passed at a downward streamline speed of 50m / h, and all the filtered water is collected by the collector.
1.5 mg / filtered water was obtained.

When the filtration was continued for 3.5 hours, the differential pressure was 0.5 kg / cm.
² (initial differential pressure 0.06 kg / cm ² ), water flow was stopped, and then the rising flow velocity from the bottom of the filtration tower was 1,000 Nm ³ / m ²
Was washed with compressed air at the same flow rate and backwashing water of 100 m / H for 3 minutes, and further backwashed with only 100 m / H of backwashing water for 1 minute. Thereafter, it was performed the backwash and the filtration and the 30-day continuous processing of repeatedly performed draining, even differential pressure after backwashing recovered to 0.06 kg / m ² is the initial differential pressure after lapse of 30 days No clogging occurred at the long fiber bundle fixing portion.

Example 2 A perforated plate was attached to the lower part of a stainless steel filtration tower having a diameter of 650 mm and a height of 2,000 mm (linear portion), and a 14 μm thick, 1,500 mm long acrylic non-coated plate was provided almost at the center of the perforated plate. The lower end of the first long fiber bundle composed of an aggregate of twisted single fibers is fixed, and a second long fiber bundle composed of an aggregate of acrylic non-twisted single fibers having a thickness of 43 μm and a length of 1,500 mm is fixed to the outside thereof. The lower ends are fixed, and the upper ends are free ends.
A filtration tower as shown in FIG. 2 was constructed in which a collector consisting of a porous hollow tube was erected in the first long fiber bundle group 0 mm above. In this case, the total packing density of the long fiber bundle is
65 kg / m ³ (dry weight, the same applies hereinafter), the filling ratio of the first long fiber bundle and the second long fiber bundle is 1 /
3 and 2/3.

From above the filtration tower, the concentration of suspended solid (SS) is 50mg on average
When the papermaking wastewater / was passed at a downward streamline speed of 50 m / h, and all the filtered water was collected by the collector,
Filtered water with an SS concentration of 0.5 mg / or less was obtained stably.

At the time when the filtration was continued for 2.5 hours, the differential pressure was 0.5 kg / cm ²
(Initial pressure difference 0.06kg / cm ² )
Then, from the lower part of the filtration tower, compressed air with a rising streamline velocity of 1,000 Nm ³ / m ² for 1 minute, then compressed air with the same flow rate and 100 m / H backwash water for 3 minutes, and 100 m / H backwash water After only 1 minute of backwashing, the pressure difference in the filtration tower returns to the initial pressure difference, the suspended matter captured by the long fiber bundle can be completely removed, and the state before filtration can be recovered. Was.

Furthermore, was subjected to a continuous treatment of waste water by repeating the such filtration and backwashing, even the differential pressure after the back washing is recovered to 0.06 kg / cm ² is the initial differential pressure after lapse of 30 days, also No clogging occurred at the long fiber bundle fixing portion.

For comparison, the second long fiber bundle made of an aggregate of acrylic non-twisted monofilaments having a diameter of 43 μm and a length of 1,500 mm in a filtration tower having the same diameter and height as used in Examples. The ^third is that only the same long fiber bundle as above is erected at a packing density of 65 kg / m 3.
In a conventional filtration tower as shown in the figure (Comparative Example-1) and a filtration tower having the same diameter and height as used in the examples, a thickness of 14 mm was added.
μ, consisting of an aggregate of acrylic non-twisted single fibers having a length of 1,500 mm, only the same long fiber bundle as the second long fiber bundle,
To each well conventional filtration column consisting erected at a packing density of 65 kg / m ³ (Comparative Example - 2), and passing water to the same papermaking waste water as in Example descending flow line speed 50 m / h, and in this case Was taken out after passing the entire amount of filtered water through the perforated plate in the same manner as in the related art.
It was able 3.5 hours water passage to reach g / m ^2, SS of filtered water
The concentration was 1.5 mg /, and in Comparative Example-2, the SS concentration of the filtered water was as good as 0.5 mg / or less, but the differential pressure became 0.5 kg / cm ² within only one hour.

Further, the filtration and the backwashing under the same conditions as in the example were repeatedly performed to continuously process the wastewater for 30 days. In the filtration tower of Comparative Example 1, the pressure difference after the backwash was increased by the initial pressure difference. pressure (0.06 kg / cm ²⁾ from 0.04 kg / cm ² increased to 0.1 kg / cm ^2, and the also the initial differential pressure in the filtration tower of Comparative example 2 (0.06
kg / cm ²⁾ from 0.14 kg / cm ² increased differential pressure after backwashing is 0.2 kg / cm
The phenomenon of reaching ² occurred, and it was visually confirmed that clogging occurred in the long fiber bundle fixing portion in any of the filtration towers.

<Effects> As described above, the filtration tower of the present invention can collect the filtrate above the support by providing the filtrate collector slightly above the support fixing the long fiber bundle. Since it is not necessary to pass the filtrate through the long fiber bundle fixing part as in the prior art, it is possible to reliably prevent the long fiber bundle fixing part from being clogged with the suspended matter in the undiluted solution and contaminating the part. Thus, even if filtration is performed for a long period of time, it is possible to stably obtain a filtrate of a constant quality with almost no increase in pressure loss.

Further, in addition to the above configuration, a first long fiber bundle composed of an aggregate of relatively thin single fibers is arranged in the center of the tower, and outside the single fiber used for the first long fiber bundle, According to the filtration tower in which the second long fiber bundle composed of the aggregate of the thick single fibers is arranged, and the collector is provided in the first long fiber bundle group, the following effects are obtained in addition to the effects described above. Another effect is also achieved.

That is, according to the filtration tower, for example, the pressure loss of the entire tower can be reduced as compared with a filtration tower in which only the first long fiber bundle composed of an aggregate of relatively thin single fibers is filled alone. Needless to say, in the filtration tower, as described above, a part of the stock solution, that is, the stock solution distributed on the outer peripheral side of the inside of the filtration tower is converted into two types of long fiber bundles each composed of an aggregate of single fibers having different diameters. Can be brought into contact with
Therefore, the effect of so-called multi-layer filtration is obtained for such a flow, and it is possible to obtain a filtrate having almost the same quality as that of a filtration tower in which only the first long fiber bundle is packed alone. In addition to this, there is an effect that the filtration time can be prolonged.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a filtration tower showing an example of an embodiment of the present invention, FIG. 2 is a schematic sectional view of a filtration tower showing another embodiment of the present invention, and FIG. FIG. FIG. 4 is an enlarged sectional view showing a fixing portion of the long fiber bundle. DESCRIPTION OF SYMBOLS 1 ... Filtration tower 2 ... Support 3 ... Long fiber bundle 4 ... Undiluted liquid inflow pipe 5 ... Backwash water discharge pipe, 6 ... Backwash air inflow pipe 7 ... Backwash water inflow pipe, 8 … Collector 9… Filtrate outflow pipe, 10-14… Valve

Claims (2)

(57) [Claims] An undiluted solution is fixed from above a filtration tower having a plurality of long fiber bundles erected on the whole inside of the tower, with the lower end of the long fiber bundle fixed to a support provided at the lower part in the tower and the upper end being a free end. By flowing the undiluted solution from the upper end to the lower end of the long fiber bundle, in the filtration tower that captures the suspended matter in the void portion in the long fiber bundle, the filtration tower is placed in the long fiber bundle group slightly above the support. A filtration tower using a long fiber bundle, provided with a collector for collecting a filtrate. 2. The filtration tower according to claim 1, wherein a first long fiber bundle composed of an aggregate of relatively thin single fibers is disposed in a central portion of the tower, and the first long fiber bundle is disposed around the first long fiber bundle. A second long fiber bundle composed of an aggregate of single fiber bundles thicker than the single fiber used in the first step, and a collector for collecting a filtrate is provided in the first long fiber bundle group. A filtration tower using a long fiber bundle.