JPH10328538A - Method for cleaning hollow yarn membrane filtration tower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently clean a hollow yarn membrane filter to prolong the service life of the hollow yarn membrane filter. SOLUTION: At the time of cleaning the hollow yarn membrane filter 51 in the hollow yarn membrane filtration tower provided with a parting plate 4, which divides the inside of a tower main body 1 into a lower section 2 and an upper section 3, and a hollow yarn membrane module 5, upper end of which is fixed to the parting plate 4 and which vertically hangs in the tower main body 1, and formed so as to filter raw water flowing-in to the lower section 2 with many numbers of the hollow yarn membrane filters 51 in the hollow yarn membrane module 5 and to make the filtrate to flow-out to the upper section 3, the cleaning method of the hollow yarn membrane filtration tower is performed by supplying a liquid chemical for cleaning to the upper section 3, making the liquid chemical for cleaning to flow in to the lower section 2 through the hollow yarn membrane filter 51 and filling the inside of the lower section 2 with the liquid chemical for cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a hollow fiber membrane filtration tower, and more particularly, for example, to a nuclear power plant,
The present invention relates to a method for cleaning a hollow fiber membrane filtration tower suitably used for water treatment of a thermal power plant, wastewater treatment for general industry, and the like.

[0002]

2. Description of the Related Art Hollow fiber membrane filtration towers (hereinafter simply referred to as "filtration towers").
Called. ) Will be described by taking, for example, a one-end water collecting type. The hollow fiber membrane filtration tower includes, for example, a tower main body, a partition plate that divides the inside of the tower main body into a lower chamber serving as a primary chamber and an upper chamber serving as a secondary chamber, and a plurality of pieces hanging down from the partition board to the lower chamber. And a hollow fiber membrane module. The hollow fiber membrane module has a large number of hollow fiber membrane filters, and the upper end of each hollow fiber membrane filter is open in the upper chamber in the tower body. Therefore, during the treatment of raw water, the raw water flowing into the lower chamber permeates from the outside (primary side) to the inside (secondary side) of each hollow fiber membrane filter in the hollow fiber membrane module, and the raw water passes through each hollow fiber membrane filter. During the permeation, suspended substances such as inorganic substances such as iron oxide and insoluble organic substances in the raw water are captured on the outer surface of the hollow fiber membrane filter, and the filtered water flows out to the upper chamber through the inside of the hollow fiber membrane filter. It has become.

[0003] When the filtration is continued for a predetermined period of time, the suspended solids are deposited in a compacted state on the outer surface of the hollow fiber membrane filter, and the resistance when the raw water permeates the sediment increases. The differential pressure between them gradually increases, and the filtering function gradually decreases. Therefore, the filtration tower is washed and the function of the hollow fiber membrane filter is restored. When washing the filtration tower, for example, air is flowed into each hollow fiber membrane module in a state where the lower chamber is filled with water, and when air is bubbled through the hollow fiber membrane module, each hollow fiber membrane filter vibrates, The suspended substance is separated from each hollow fiber membrane filter, and each hollow fiber membrane filter is washed.

However, when a large amount of suspended solids accumulate in each hollow fiber membrane filter in a compacted state and gaps between the hollow fiber membrane filters are clogged with suspended solids, or when sticky suspended solids accumulate, simply Only bubbling air in the hollow fiber membrane module may not be enough to remove suspended matter from the hollow fiber membrane filter. In this case, after filling the lower chamber with a cleaning chemical having a high cleaning effect, bubbling air into the cleaning chemical as described above, and further immersing the hollow fiber membrane module in the cleaning chemical for a predetermined time. . Further, thereafter, air is bubbled into the cleaning solution to remove suspended substances from the hollow fiber membrane filter.

[0005]

However, when a large amount of suspended matter is deposited on the hollow fiber membrane filter in a compacted state,
The gap between the hollow fiber membrane filters becomes extremely narrow, and in some cases, the gap between the hollow fiber membrane filters may be clogged with the suspended substance, and the hollow fiber membrane filters may be bundled. In this state, even if the lower chamber is filled with the cleaning chemical, the cleaning chemical hardly penetrates into the inside of the bundle of the hollow fiber membrane filters, and the cleaning chemical cannot sufficiently contact the suspended substance, In extreme cases, the cleaning effect of the cleaning chemical can hardly be expected just by contacting the outer peripheral surface of the bundle of hollow fiber membrane filters, and even if air is bubbled into the cleaning chemical under such a condition. Most of the air bubbles escape along the outer peripheral surface of the bundle of hollow fiber membrane filters, and almost no bubbling effect of air can be expected, and the hollow fiber membrane filters cannot be sufficiently washed. There has been a problem that the time required for the membrane to reach the working differential pressure is short, and the number of backwashing increases. As a result, there is a problem that the life of the hollow fiber membrane filter is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can enhance the cleaning effect of a cleaning chemical to efficiently clean a hollow fiber membrane filter, thereby increasing the differential pressure of the hollow fiber membrane filter. It is an object of the present invention to provide a method for cleaning a hollow fiber membrane filtration tower, which can prevent the occurrence of the bleeding and extend the life.

[0007]

According to a first aspect of the present invention, there is provided a method for cleaning a hollow fiber membrane filtration tower, comprising: a partition member for partitioning the inside of the tower body into a primary chamber and a secondary chamber; A hollow fiber membrane module whose section is fixed and disposed in the primary chamber along the axis of the tower main body, and the raw water flowing into the primary chamber is provided with a plurality of hollow fibers in the hollow fiber membrane module. When the hollow fiber membrane filter is washed in the hollow fiber membrane filtration tower that filters the water through the membrane filter and allows the filtered water to flow out to the secondary chamber, a cleaning chemical is supplied to the secondary chamber, A chemical solution is caused to flow into the primary chamber through the hollow fiber membrane filter.

According to a second aspect of the present invention, there is provided a method for cleaning a hollow fiber membrane filtration tower, comprising a partition member for partitioning the inside of the tower body into a primary chamber and a secondary chamber, and an end fixed to the partition member. And a hollow fiber membrane module disposed in the primary chamber along the axis of the tower main body, and the raw water flowing into the primary chamber is passed through a number of hollow fiber membrane filters in the hollow fiber membrane module. When the hollow fiber membrane filter is washed in the hollow fiber membrane filtration tower that allows the filtered water to flow out to the secondary chamber, air is supplied to the primary chamber while supplying a cleaning chemical to the primary chamber. And supplying the primary chamber with the cleaning solution.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the embodiments shown in FIGS. In each of the drawings, FIG. 1 is a cross-sectional view showing the configuration of a hollow fiber membrane filtration tower used in one embodiment of the cleaning method of the present invention, and FIG. 2 is a hollow fiber used in the hollow fiber membrane filtration tower shown in FIG. Sectional view showing the configuration of the membrane module,
FIG. 3 is a cross-sectional view showing a double-end collecting hollow fiber membrane module used in another embodiment of the filtration tower of the present invention, and FIG. 4 is a schematic diagram for explaining a cleaning action according to an embodiment of the cleaning method of the present invention. In the figure, (a) is a cross-sectional view of the hollow fiber membrane filter showing the state immediately before the cleaning treatment in an enlarged manner, (b) is a cross-sectional view of the hollow fiber membrane filter showing the state in which suspended substances are separated by the cleaning,
5A and 5B are schematic views for explaining a cleaning action according to another embodiment of the cleaning method of the present invention. FIG. 5A is a cross-sectional view showing a hollow fiber membrane module during cleaning, and FIG. It is sectional drawing which expands and shows the hollow fiber membrane filter of a hollow fiber membrane module.

First, a hollow fiber membrane filtration tower (hereinafter, simply referred to as "filtration tower") suitably used in the method for washing a filtration tower of the present invention, for example, a single-end collecting hollow fiber membrane filtration tower, is shown in FIG. This will be described with reference to FIG. This filtration tower is shown in FIG.
As shown in FIG. 1, a tower body 1, a partition plate 4 partitioning an upper part of the tower body 1 into a lower chamber 2 and an upper chamber 3,
And a later-described hollow fiber membrane module 5 that hangs from the lower chamber 2 to the lower chamber 2. An inflow pipe 6 through which raw water flows in is connected to the bottom of the lower chamber 2, an outflow pipe 7 through which filtered water flows out is connected to the top of the upper chamber 3, and valves 6 A, 7 are connected to the respective pipes 6, 7.
A is attached respectively. The lower chamber 2 is formed as a primary chamber into which raw water flows, and the upper chamber 3 is formed as a secondary chamber from which filtered water flows. Each hollow fiber membrane module 5 is arranged on the partition plate 4 by forming a predetermined geometric pattern such as a honeycomb shape.

A baffle plate 8 is arranged at the bottom center of the lower chamber 2 so as to face the inlet of raw water, and the baffle plate 8 is used to disperse raw water flowing into the lower chamber 2. Also, this baffle plate 8
A distribution mechanism 9 is disposed between the hollow fiber membrane module 5 and the lower end of the hollow fiber membrane module 5.
To be distributed. That is, the distribution mechanism 9 has a flat cup shape as a whole and is formed to have an outer diameter smaller than the inner diameter of the lower chamber 2. The distribution mechanism 9 is provided with distribution pipes 10 facing the respective hollow fiber membrane modules 5, and distributes and supplies raw water from the periphery of the distribution pipes 10 and the distribution mechanism 9 to the respective hollow fiber membrane modules 5. It is like that.

The tower body 1 includes a hollow fiber membrane module 5.
Is connected to an air pipe used for washing suspended substances adhering to the hollow fiber membrane filter constituting the above. The air pipe includes an air pipe 11 connected to the top of the upper chamber 3, an air pipe 12 connected to a lower part of the lower chamber 2, and an air pipe 13 connected to an upper part of the lower chamber 2. . Air piping 1
1 branches into two branches, and each branch pipe has a valve 11A,
11B is attached. In addition, other air piping 1
Valves 12A and 13A are attached to 2 and 13, respectively. Further, a hole 10A is formed in each distribution pipe 10 of the distribution mechanism 9, and the air supplied into the lower chamber 2 accumulates below the distribution mechanism 9 and passes through the hole 10A. It is distributed and supplied to the lower end of the hollow fiber membrane module 5 above. A drain drain pipe 14 is connected to the lower end of the tower body 1.
The washing wastewater containing the suspended substance is withdrawn through the line 4. 14A is a valve attached to the drain pipe 14.

Next, the hollow fiber membrane module 5 will be described with reference to FIG. As shown in the drawing, the hollow fiber membrane module 5 includes about 100 to 50,000 hollow fiber membrane filters 51 and these hollow fiber membrane filters 5.
1 and a protective cylinder 52 for storing the bundle. Each hollow fiber membrane filter 51 is, for example, 0.01 to 0.3.
0.3 to 7 m outer diameter due to resin thin film with micro pores
m, and is formed as a hollow fiber having an inner diameter of 0.2 to 5 mm. A flange 52A is formed at the upper end of the protective tube 52, and the flange 52A hangs down from the partition plate 4. A skirt portion 52B is formed at a lower end portion of the protection cylinder 52, and the skirt portion 52B collects air flowing in at the time of cleaning. Then, the upper joint portion 5 in which the upper end portions of the hollow fiber membrane filters 51 are bundled and fixed at the upper end portion of the protective cylinder 52 with an adhesive or the like.
3 is formed, and a lower joint 54 is formed at the lower end of the hollow fiber membrane filter 51 by joining and fixing the lower end of each hollow fiber membrane filter 51 similarly to the upper end. At the upper joint 53, each hollow fiber membrane filter 51 is open, and at the lower joint 54, each hollow fiber membrane filter 51 is closed, and filtered water flows out of the upper end opening of the hollow fiber membrane filter 51 and flows into the upper chamber 3. To collect water. Further, a flow hole 54A is formed in the lower joint portion 54, so that air collected in the skirt portion 52B flows into the hollow fiber membrane module 5 through the flow hole 54A. Further, a flow hole 52 is provided slightly below the upper joint 53 of the protective cylinder 52 and slightly above the lower joint 54, respectively.
C and 52D are formed, and these circulation holes 52C and 52D are formed.
The raw water flows into the hollow fiber membrane module 5 via.

The hollow fiber membrane module 5 is a one-end water collecting type, but a so-called double-end collecting type module that collects water from both ends of each hollow fiber membrane filter can also be used as the hollow fiber membrane module. As shown in FIG. 3, the double-ended water collecting hollow fiber membrane module 5A has two types of hollow fiber membrane filters, a hollow fiber membrane fine fiber filter 51 and a hollow fiber membrane thick fiber filter 51A, as hollow fiber membrane filters. I have. Each of the hollow fiber membrane thin fiber filter 51 and the hollow fiber membrane thick fiber filter 51A has both upper and lower ends open.
In particular, the openings at the respective lower ends communicate with the filtration water collecting chamber 55 provided below the lower joining portion 54, and collect the filtered water from the hollow fiber membrane filters 51 and 51A in the filtration water collecting chamber 55. It has a structure. Each hollow fiber membrane fine fiber filter 51
The filtrate filtered on the lower side of the filter is once guided to the filtration and collection chamber 55, and then flows out of the upper junction 53 from the filtration and collection chamber 55 through the inside of the hollow fiber thick thread filter 51A. The water is collected within 3. In addition, the filtered water filtered on the upper side of each hollow fiber membrane fine fiber filter 51 flows out of the upper joint portion 53 via the inside of the hollow fiber membrane fine fiber filter 51A as it is and is collected in the upper chamber 3. It is so. The hollow fiber membrane fine fiber filter 51 here is the same as the hollow fiber membrane filter 51 used in the single-end water collecting type hollow fiber membrane module 5.

Next, the filtering operation will be described. When filtering raw water, the valves 6A and 7A of the inflow pipe 6 and the outflow pipe 7 arranged above and below the tower main body 1 are opened, respectively.
Close other valves. When supplying raw water in this state,
Raw water flows into the lower chamber 2 from the inflow pipe 6 and is dispersed in the baffle plate 8. The dispersed raw water is distributed and supplied to each hollow fiber membrane module 5 from the distribution pipe 10 of the distribution mechanism 9 and around the distribution mechanism 9. You. The distributed and supplied raw water flows into each of the protection cylinders 52 via the circulation holes 52C and 52D of the protection cylinder 52 and the circulation hole 54A of the lower joint 54. The raw water permeates from the outside to the inside of each hollow fiber membrane filter 51 in each protection cylinder 52, and at this time, the suspended matter contained in the raw water is captured on the outer surface of the hollow fiber membrane filter 51. The filtered water is obtained inside each hollow fiber membrane filter 51, and the filtered water rises in each hollow fiber membrane filter 51 and flows out from the upper end opening of each hollow fiber membrane filter 51 into the upper chamber 3, where Water is collected, and subsequently flows out of the tower through the outflow pipe 7.

When the filtration is continued, the trapped suspended matter C is deposited on the outer surface of each hollow fiber membrane filter 51 as shown in the enlarged view of FIG. And the differential pressure gradually rises. When the pressure difference is equal to or higher than the specified value, the membrane pressure difference is usually recovered by backwashing. If the gaps are clogged with suspended material or sticky suspended material accumulates, it is almost impossible to remove the suspended material from the hollow fiber membrane filter simply by bubbling air through the hollow fiber membrane module. Thus, by washing the filtration tower using the washing method of the present invention, the suspended substance C in the hollow fiber membrane filter 51 can be removed, and the membrane differential pressure can be recovered. In FIG. 4A, W is raw water and W1 is filtered water.

Next, one embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, a large number of hollow fiber membrane filters 51 in each hollow fiber membrane module 5 are provided.
When cleaning is performed, the cleaning liquid L is transferred to the upper chamber 3, which is the secondary chamber.
(See FIG. 4B), and the cleaning chemical L is allowed to permeate from the upper chamber 3 through the hollow fiber membrane filters 51 to the lower chamber 2 as the primary chamber, and the inside of the lower chamber 2 is cleaned. Cleaning is performed by filling with a chemical solution L. Prior to this washing, first, an operation of extracting raw water in the tower main body 1, that is, a so-called draining operation is performed.

When draining the raw water from the tower body 1, first, the valves 6A and 7A of the inflow pipe 6 and the outflow pipe 7 are closed to stop the water flow, and then the lower chamber 2 and the upper chamber 3 are closed. The valve 12A of the air pipe 12 and the air pipe 13 in a full state,
13A is opened, compressed air is supplied from the air pipe 12 into the lower chamber 2, and each hollow fiber membrane module 5 is distributed via the distribution mechanism 9.
Bubble air inside. However, as shown in FIG. 4A, only a very narrow gap δ is left in each hollow fiber membrane filter 51 or there is no gap. Can hardly remove the suspended matter C from the water. Alternatively, the water in the lower chamber 2 may simply be drained without performing this operation. After this operation, the valves 11A and 14A are opened to supply compressed air from the air pipe 11, or the air is opened to the atmosphere and the filtered water in the upper chamber 3 flows back to the lower chamber 2 while the raw water in the lower chamber 2 is removed. Is gradually discharged from the drain pipe 14, and after all the filtered water and the raw water are discharged, all the valves are once closed, and the drain drain operation is completed.

After the above draining operation, the cleaning method of the present invention is performed. First, the valve 7A is opened and the valves 11A and 11B are opened to supply the cleaning chemical L such as hydrochloric acid and hydrogen peroxide into the upper chamber 3 through the cleaning chemical supply pipe 15 and the outflow pipe 7. Then, the inside of the upper chamber 3 is filled with the cleaning liquid L. Alternatively, a cleaning chemical supply pipe may be separately provided on the upper chamber 3 side, and the cleaning chemical L may be supplied to the upper chamber 3 therefrom. Next, after closing the valves 11A and 11B and opening the valve 13A, the supply of the cleaning chemical L from the outflow pipe 7 continues, as shown by the arrow in FIG. It flows down in each hollow fiber membrane filter 51 in the membrane module 5 and gradually permeates from inside to outside and flows out to the lower chamber 2. At this time, the cleaning liquid L uniformly contacts the suspended substance C from the inside of the suspended substance C attached to the outer surface of the membrane, and the side of the deposited layer of the suspended substance C that is in contact with the hollow fiber membrane filter 51 ( Suspended substance C with cleaning solution L from inside)
Is gradually loosened. At the same time, the cleaning liquid L gradually comes into contact with the suspended substance C from the inside to the outside, flows out into the lower chamber 2, and gradually fills the lower chamber 2 with the cleaning liquid L. As described above, in this embodiment, the cleaning liquid L and the suspended liquid C deposited on the surface of each hollow fiber membrane filter 51 and the cleaning liquid L pass through the hollow fiber membrane filter 51 from the inside to the outside. And the suspended substance C is in contact with the cleaning solution L.
, So that it can be peeled off.

Thereafter, the valves 12A and 13A are opened, compressed air is supplied from the air pipe 12 for a predetermined time, and the cleaning liquid L is stirred by the air. The cleaning liquid L between the surface of the suspended substance C or the film surface of the suspended substance C is renewed, the cleaning action is enhanced, and the suspended substance C is more easily peeled off. After supplying air for a predetermined time, the cleaning liquid L is left full for a predetermined time to impregnate the cleaning liquid L into the suspended substance C,
Further, when air is supplied for a predetermined time, air bubbles enter from the flow holes 54A of the lower joint portion 54 of each hollow fiber membrane module 5, and the suspended substance C deposited on the surface of each hollow fiber membrane filter 51 Air bubbles come into contact with. Since the suspended substance C is in a state that can be sufficiently peeled by the operation according to the present embodiment, almost only the suspended substance C can be peeled as shown in FIG. The separated suspended substance C can be discharged out of the tower by a draining operation. The cleaning method according to the present embodiment was specifically performed under the conditions described in Example 1 described later.

As described above, according to the present embodiment,
When cleaning a large number of hollow fiber membrane filters 51 in each hollow fiber membrane module 5, the cleaning liquid L is supplied to the upper chamber 3, which is a secondary chamber, and the cleaning liquid L is supplied from the upper chamber 3 to each of the upper chamber 3. Permeate to the lower chamber 2 which is the primary chamber through the hollow fiber membrane filter 51,
Since the inside of the lower chamber 2 is filled with the cleaning liquid L, the suspended substance C accumulates in a compacted state on each hollow fiber membrane filter 51, and furthermore, the accumulated amount increases and each hollow fiber membrane filter 51 becomes suspended. Even when the cleaning liquid L permeates from the inside to the outside of the hollow fiber membrane filter 51 even when the cleaning liquid L permeates from the inside to the outside through the substance C, the suspension liquid C Is gradually loosened, the suspended substance C is reliably removed from each hollow fiber membrane filter 51, and the pressure difference can be largely recovered, and the filtration performance of the filtration tower can be recovered. The life of the module 5 can be extended.

In another embodiment of the cleaning method of the present invention, when the hollow fiber membrane filter 51 in the hollow fiber membrane module 5 is cleaned, as shown in FIGS. While supplying the cleaning liquid L to the lower chamber 2 in the tower main body 1, air is supplied into each hollow fiber membrane module 5, and the air is used to stir the cleaning liquid L inside each hollow fiber membrane module 5 while stirring. This is a method of filling the inside of the chamber 2 with the cleaning liquid L.

First, backwashing of the hollow fiber membrane module 5 and draining of the inside of the tower body 1 are performed in the same manner as in the above embodiment. Next, after opening the valves 6A and 13A, the cleaning liquid L is supplied from the inflow pipe 6. When compressed air is supplied from the air pipe 12 by opening the valve 12A from the time when the liquid level of the cleaning liquid L reaches each hollow fiber membrane module 5, this air is distributed by the distribution mechanism as shown in FIG. Bubbles A are generated from the distribution pipe 9 and its surroundings, and the surface of the cleaning chemical liquid L is violently ruffled. Due to the undulation, the portion of the hollow fiber membrane filter 51 in each hollow fiber membrane module 5 which is in contact with the particularly undulating liquid surface vibrates violently in the lateral direction as shown by the arrow in FIG. At this time, even if the hollow fiber membrane filters 51 are adhered to each other by the suspended substance C, this vibration causes the hollow fiber membrane filters 51
The suspended substance C is gradually loosened in conjunction with the cleaning action of the cleaning liquid L. That is, vibration is applied to each hollow fiber membrane filter 51 by the waving of the cleaning liquid L at the time of bubbling of air, and the cleaning liquid L is supplied while loosening the suspended substance C. The cleaning liquid L easily penetrates into the suspended substance C between the thread membrane filters 51, and the contact area between the suspended substance C and the cleaning liquid L gradually increases, and the cleaning action of the cleaning liquid L is improved. Suspended substance C
Effectively. In addition, by supplying air while supplying the cleaning chemical liquid L, the wavy liquid surface moves upward from below the hollow fiber membrane module 5, and is uniformly applied to the entire hollow fiber membrane filter 51. Vibration can be applied.

Eventually, the lower chamber 2 is filled with the cleaning liquid L. At this time, the suspended substance C is considerably loosened by the waving of the liquid surface of the cleaning liquid L, and the cleaning liquid L is relatively easily introduced into the suspended substance C between the hollow fiber membrane filters 51. Penetrate into When each hollow fiber membrane module 5 is immersed in the cleaning liquid L by leaving the lower chamber 2 filled with the cleaning liquid L for a predetermined time, the cleaning liquid L permeated into the suspended substance C is obtained. , The suspended substance C is more easily loosened. Thereafter, when air is supplied again into the lower chamber 2 to vigorously bubble the cleaning liquid L, the suspended substance C is separated from each hollow fiber membrane filter 51. The separated suspended substance C can be discharged by a draining operation. Note that the cleaning method according to this embodiment was specifically performed under the conditions described in Example 2 described later.

As described above, according to the present embodiment,
Air is supplied into each hollow fiber membrane module 5 while supplying the cleaning liquid L to the lower chamber 2, and the lower chamber 2 is cleaned while stirring the cleaning liquid L inside each hollow fiber membrane module 5 with the air. Since the cleaning liquid L is filled with the cleaning liquid L, the liquid surface of the cleaning liquid L undulates, and the undulation moves from below to above the hollow fiber membrane filters 51 to thereby increase each hollow fiber membrane filter 51 of each hollow fiber membrane module 5. Vibration due to undulation is applied to the whole, and the cleaning liquid L can penetrate into the suspended substance C between the hollow fiber membrane filters 51 loosened by the vibration. Accordingly, the suspended substance C is deposited on each hollow fiber membrane filter 51 in a compacted state, and the deposition amount is increased, and the hollow fiber membrane filters 51 are adhered to each other via the suspended substance C to be in an integrated state. However, the cleaning liquid L penetrates into the suspended substance C between the hollow fiber membrane filters 51 and efficiently contacts the suspended substance C, and the suspended substance C is effectively removed from each hollow fiber membrane filter 51. By removing the filter, the initial pressure difference can be recovered and the filtration performance of the filtration tower can be restored, and the life of the hollow fiber membrane module 5 can be extended.

Example 1 In this example, the following filtration tower, which was treated with raw water for 10 days, was washed under the following conditions, and the suspended substance C separated by washing was washed.
The results shown in Table 1 below were obtained. still,
Since the air bubbling before performing the chemical cleaning does not directly affect the present invention, the operating conditions thereof are omitted. This is the same in Example 1 and Comparative Example 1. [Washing conditions] Filtration tower (1) Dimensions of tower body Outer diameter: 70 mm Inner diameter: 54 mm (2) Hollow fiber membrane module Number of hollow fiber membrane filters: 170 Hollow fiber membrane filter inner diameter: 0.7 mm Hollow fiber membrane filter outer diameter: 1.2 mm 2. Cleaning operation conditions (1) Cleaning chemical solution: 1N hydrochloric acid (2) Air bubbling Air flow rate: 3.3 NL / min Bubbling time: 10 minutes (3) Immersion time after bubbling: 3 hours (4) Air immersion after immersion Bubbling Air flow rate: 3.3 NL / min Bubbling time: 10 minutes

Example 2 In this example, the filtration tower used in Example 1 was washed under the following conditions, and the results shown in Table 1 below were obtained. [Washing conditions] Cleaning operation conditions (1) Cleaning chemical solution: 1N hydrochloric acid (2) Flow rate of cleaning chemical solution: 60 L / hour (3) Bubbling of air when supplying cleaning chemical solution Air flow rate: 3.3 NL / min Bubbling time: 5 minutes ( 4) Immersion time after filling: 3 hours (5) Bubbling of air after immersion Air flow rate: 3.3 NL / min Bubbling time: 10 minutes

COMPARATIVE EXAMPLE 1 In this comparative example, the same filtration tower as that used in each of the above-described embodiments was cleaned by a conventional cleaning method (after filling the lower chamber 2 with the cleaning solution, bubbling air and leaving it for a predetermined time). Then, the hollow fiber membrane module 51 was immersed, air was bubbled, and then draining was performed. As a result, the results shown in Table 1 below were obtained. [Washing conditions] Cleaning operation conditions (1) Chemical solution for cleaning: 1N hydrochloric acid (2) Immersion time after filling: 3 hours (3) Bubbling of air before immersion Air flow rate: 3.3 NL / min Bubbling time: 10 minutes

[0029]

[Table 1] As is clear from the results shown in Table 1, in Example 1, the sequestration amount of the suspended substance C was much larger than in Comparative Example 1, and the differential pressure recovery ratio after washing was 2.5 times that of Comparative Example 1. You can see that it is. Further, in the case of Example 2, the cleaning effect is lower than that of Example 1, but the differential pressure recovery magnification is 1.
It reaches 5 times, and it turns out that it is considerably superior to the conventional cleaning method.

It is needless to say that the present invention is not limited to the above embodiments. For example, in the above embodiment, the single-end water collecting type filtration tower has been described.
The present invention can be applied to a hollow fiber membrane filter having both ends opened as shown in FIG. The operating conditions of the cleaning method of the present invention can be set appropriately according to the type of raw water.

[0031]

According to the first or second aspect of the present invention, the hollow fiber membrane filter can be efficiently cleaned by enhancing the cleaning effect of the cleaning chemical, and the hollow fiber membrane filter can be efficiently cleaned. The present invention can provide a method for washing a hollow fiber membrane filtration tower capable of preventing a rise in differential pressure and extending the life thereof.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a hollow fiber membrane filtration tower used in an embodiment of the filtration tower washing method of the present invention.

FIG. 2 is a sectional view showing a hollow fiber membrane module used in the hollow fiber membrane filtration tower shown in FIG.

FIG. 3 is a sectional view showing a double-end collecting hollow fiber membrane module used in another embodiment of the filtration tower of the present invention.

4A and 4B are cross-sectional views for explaining a cleaning action according to an embodiment of the method for cleaning a filtration tower of the present invention, wherein FIG. 4A is a diagram showing a state immediately before a cleaning process, and FIG. It is a figure which shows the state which peels off.

FIGS. 5A and 5B are views for explaining a cleaning action according to another embodiment of the method for cleaning a filtration tower of the present invention, wherein FIG. 5A is a cross-sectional view showing a hollow fiber membrane module during cleaning and FIG. It is sectional drawing which expands and shows the hollow fiber membrane filter of the hollow fiber membrane module shown to a).

[Explanation of symbols]

 1 Tower main body 2 Lower chamber (primary chamber) 3 Upper chamber (secondary chamber) 4 Partition plate (partition member) 5 Hollow fiber membrane module 51 Hollow fiber membrane filter C Suspended substance L Cleaning chemical

Claims (2)

[Claims] 1. A partition member for partitioning the inside of a tower body into a primary chamber and a secondary chamber, and a hollow member fixed to an end of the partition member and disposed in the primary chamber along an axis of the tower body. A hollow fiber membrane filtration tower that comprises a fiber membrane module, filters raw water flowing into the primary chamber through a number of hollow fiber membrane filters in the hollow fiber membrane module, and allows the filtered water to flow out to the secondary chamber. Supplying a cleaning chemical to the secondary chamber when the hollow fiber membrane filter is cleaned, and allowing the cleaning chemical to flow into the primary chamber through the hollow fiber membrane filter. A method for washing a membrane filtration tower. 2. A partition member for partitioning the inside of the tower body into a primary chamber and a secondary chamber, and a hollow member having an end fixed to the partition member and disposed in the primary chamber along the axis of the tower body. A hollow fiber membrane filter, comprising: a raw water flowing into the primary chamber through a number of hollow fiber membrane filters in the hollow fiber membrane module; and a filter water flowing out to the secondary chamber. In the tower, when cleaning the hollow fiber membrane filter, supplying air to the primary chamber while supplying a cleaning chemical to the primary chamber, and filling the primary chamber with the cleaning chemical. A method for cleaning a yarn membrane filtration tower.