JPH119970A - Method for cleaning hollow-yarn membrane filtration tower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently disperse a chemical solution for cleaning which adheres to the respective hollow-yarn membrane filters of a hollow-yarn membrane module due to immersion of the hollow-yarn membrane filters in the solution for a prescribed immersion time in rinsing to the outside of the hollow-yarn membrane module and to significantly lower the discharge amount of cleaning wastewater used for cleaning off the chemical solution for cleaning. SOLUTION: In this method for cleaning hollow-yarn membrane filtration tower, a rinsing process of cleaning off a cleaning chemical solution out of a tower main body of a hollow-yarn membrane filtration tower, where raw water flowing into a lower chamber 2 of the tower main body 1 is filtered by a large number of hollow- yarn membrane filters 51 of hollow-yarn membrane modules 5 and the filtered water is made to flow out to an upper chamber 3 of the main body, comprises a water-filling process to fill the lower chamber 2 with water, a scrubbing process to stir the water in the respective hollow-yarn membrane modules 5 by supplying air to the lower chamber 2 after the chamber 2 is filled with water and to disperse the chemical solution for cleaning from the surfaces of the respective hollow-yarn membrane filters 51, and water-discharging process to discharge rinsing wastewater out of the lower chamber 2 after the scrubbing process is carried out.

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 which is suitably used for water treatment of nuclear power plants and thermal power plants and wastewater treatment for general industry, for example. The present invention relates to a method for cleaning a hollow fiber membrane filtration tower capable of reducing the amount of waste liquid.

[0002]

2. Description of the Related Art Hollow fiber membrane filtration towers (hereinafter simply referred to as "filtration towers").
Called. ) Is, for example, a tower main body, and a partition plate that divides the inside of the tower main body into a lower chamber that is a primary chamber and an upper chamber that is a secondary chamber.
A plurality of hollow fiber membrane modules hanging down from the partition plate to the lower chamber. The hollow fiber membrane module has a large number of hollow fiber membrane filters, the upper end of each hollow fiber membrane filter is open in the upper chamber in the tower body, and the lower end is closed. Therefore,
During the treatment of the raw water, the raw water flowing into the lower chamber permeates from the outside to the inside of each hollow fiber membrane filter in the hollow fiber membrane module, and while the raw water passes through each hollow fiber membrane filter, such as iron oxide in the raw water. Suspended substances such as inorganic substances and insoluble organic substances are captured on the outer surface of the hollow fiber membrane filter, and the filtered water flows out to the upper chamber via the inside of the hollow fiber membrane filter.

[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, after filling the lower chamber with water, air is supplied into each hollow fiber membrane module, and suspended substances are removed from each hollow fiber membrane filter by bubbles generated by bubbling air. After peeling, 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 able to almost completely remove suspended substances that cause a rise in the membrane differential pressure from the hollow fiber membrane filter. In this case, a chemical cleaning operation using a cleaning chemical having a high cleaning effect is performed. In this chemical cleaning operation, first, the cleaning chemical is filled in the lower chamber, air is supplied into each hollow fiber membrane module in the cleaning chemical, and the cleaning chemical is uniformly hollowed by bubbles generated by bubbling of air. The hollow fiber membrane module is dispersed in the fiber membrane module and the filtration tower, and the hollow fiber membrane module is immersed in a cleaning chemical for a predetermined time to decompose the deposited suspended substance. Thereafter, air is bubbled into the hollow fiber membrane module in the cleaning chemical to remove suspended substances from the surface of the hollow fiber membrane filter, and then the cleaning waste liquid is discharged from the lower chamber to complete the chemical cleaning operation. Next, the lower chamber is filled with pure water, for example, and the hollow fiber membrane filters are immersed for a predetermined time to rinse each hollow fiber membrane filter, and the cleaning chemicals attached to each are washed off. "Rinse wastewater"
Called. ), Which is a so-called rinsing operation.

[0005]

However, in the rinsing operation after the chemical solution washing in the conventional washing method, the hollow fiber membrane filter adheres to each hollow fiber membrane filter in the hollow fiber membrane module simply by immersing the hollow fiber membrane filter in pure water for a predetermined time. The cleaning chemical solution thus obtained cannot be sufficiently diffused to the outside of the hollow fiber membrane module, and the concentration of the remaining cleaning chemical solution between the hollow fiber membrane filters is much higher than that outside each hollow fiber membrane module, Non-uniform concentration unevenness occurs, and it is particularly difficult to wash off the cleaning chemicals as the hollow fiber membrane filter is closer to the center of the hollow fiber membrane module. Conventionally, the cleaning chemical in the rinse waste liquid has a predetermined concentration (for example, about 100 ppb). ), The rinsing operation must be repeated a plurality of times, and as a result, there is a problem that a large amount of cleaning waste liquid is generated. In particular, since nuclear power plants use radioactive wastewater, the wastewater treatment system is a closed system, and it is necessary to minimize the amount of washing wastewater discharged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a method for cleaning a hollow fiber membrane filtration tower capable of remarkably reducing the discharge amount of a cleaning waste liquid and reducing a cleaning (rinsing) time. It is intended to provide.

[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. In a hollow fiber membrane filtration tower for filtering with a membrane filter and allowing the filtered water to flow to the secondary chamber, a chemical liquid washing step of washing the hollow fiber membrane filtration tower with a washing liquid as a washing step of the hollow fiber membrane filtration tower And a rinsing step of washing off the cleaning chemical from inside the tower body, and the rinsing step includes filling the primary chamber with water and filling the primary chamber during and / or after the water filling step. Supply air to each hollow fiber membrane module A scrubbing step of agitating the water in Lumpur, is characterized in that it has a drainage step of discharging the rinse wastewater in the primary chamber after the scrubbing.

[0008] The method for washing a hollow fiber membrane filtration tower according to claim 2 of the present invention provides the method according to claim 1, wherein
During the draining step, air is supplied into the primary chamber to stir the rinse wastewater to diffuse the cleaning chemical from the surface of each hollow fiber membrane filter into the rinse wastewater.

[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 shows the rinsing effect when the cleaning method of the present invention and the conventional cleaning method are used. FIG. 4 is a graph showing the relationship between the amount of rinse wastewater and the concentration of hydrogen peroxide in rinse wastewater.

First, a hollow fiber membrane filtration tower (hereinafter, simply referred to as a "filtration tower") in which the method for washing a filtration tower of the present invention is suitably used, for example, a single-end collecting type hollow fiber membrane filtration tower, is shown in FIG.
This will be described with reference to FIG. As shown in FIG. 1, the filtration tower includes a tower body 1 and a lower chamber 2 at an upper portion of the tower body 1.
And a partition plate 4 partitioned into an upper chamber 3, and a hollow fiber membrane module 5 described below hanging from the partition plate 4 to the lower chamber 2. An inflow pipe 6 through which raw water flows is connected to the bottom of the lower chamber 2, and an outflow pipe 7 through which filtered water flows out is connected to the top of the upper chamber 3.
Are connected, and valves 6A and 7A are attached to the pipes 6 and 7, respectively. 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. In addition, a drain pipe 14 is connected to the lower end of the tower main body 1, and the washing wastewater containing suspended substances is drained through the drain pipe 14. 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. At the upper end of the protective cylinder 52, an upper joint 53 is formed by bonding and fixing the upper ends of the hollow fiber membrane filters 51 with an adhesive or the like, and the lower end thereof is connected to the lower end of each hollow fiber membrane filter 51 by the upper end. A lower joining portion 54 joined and fixed in the same manner as described above is formed. 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, and the flow hole 54A is formed.
The air collected by the skirt portion 52B through A flows into the hollow fiber membrane module 5. Further, flow holes 52C and 52D are formed slightly below the upper joint portion 53 and slightly above the lower joint portion 54 of the protective cylinder 52, respectively, and the raw water flows through the hollow fiber membrane through these flow holes 52C and 52D. It flows into the module 5.

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. Further, 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 51 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 rises in the lower chamber 2 from around the distribution pipe 10 of the distribution mechanism 9 and the distribution mechanism 9, and each hollow It is distributed and supplied to the yarn membrane module 5. The distributed and supplied raw water passes through the protection holes 52C and 52D of the protection case 52 and the flow holes 54A of the lower connecting portion 54 and passes through each protection case 52.
Flows into. 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 for a predetermined period, a suspended substance accumulates on the outer surface of each hollow fiber membrane filter 51, and the differential pressure between the outside and the inside of the hollow fiber membrane filter 51 becomes a specified value or more, and subsequent filtration becomes difficult. .

Therefore, after washing the hollow fiber membrane filter by air bubbling, the filtration tower is washed by the washing method of the present embodiment. The cleaning method of the present embodiment includes a chemical cleaning step of cleaning each hollow fiber membrane module 5 in the lower chamber 2 with a cleaning chemical to remove suspended substances deposited on the surface of each hollow fiber membrane filter, and after the chemical cleaning. A rinsing step of washing off the cleaning chemical remaining in each hollow fiber membrane module 5; the rinsing step is characterized by this embodiment. Hereinafter, the cleaning method of the present embodiment will be described.

When the cleaning method of the present embodiment is carried out, first, the valves 6A and 7A of the inflow pipe 6 and the outflow pipe 7 are closed to stop water flow. Thereafter, for example, a cleaning step of the hollow fiber membrane filter with air in the lower chamber 2 is performed according to the following procedure. In this cleaning step, the valves 12A and 13A of the air pipe 12 and the air pipe 13 are opened while the lower chamber 2 and the upper chamber 3 are full, and compressed air is supplied from the air pipe 12 into the lower chamber 2. A scrubbing operation for bubbling air into each hollow fiber membrane module 5 via the distribution mechanism 9 is performed. With this operation, each hollow fiber membrane filter 51 vibrates and the suspended matter in the surface layer is peeled off, but the suspended matter in the compacted state cannot be removed so much. After the scrubbing operation, the valves 13A and 14A are opened to supply compressed air from the air pipe 13, or the atmosphere is released to drain the raw water in the lower chamber 2 from the drain pipe 14, and the raw water from the lower chamber 2 is discharged from the lower chamber 2. , All valves are once closed, and the draining operation is terminated. After the scrubbing cleaning step with air, the valve 13A of the air pipe 13 is opened as necessary, compressed air is supplied from the air pipe 11 into the upper chamber 3 of the filtration tower, and the filtered water is supplied from the upper chamber 3 to the lower chamber 2. Backflow from the inside of the hollow fiber membrane filter to the outside, that is, after performing an air surge backwashing step of separating suspended substances adhering to the outside of the hollow fiber membrane filter, the backwash waste liquid is drained from the drain pipe 14. After discharging, the inside of the lower chamber 2 may be filled with water, and the scrubbing cleaning step using air may be performed again.

After the above-described step of cleaning the hollow fiber membrane filter with air, a chemical cleaning step of cleaning the condensed suspended substance of each hollow fiber membrane filter 51 is performed. In this chemical cleaning step, first, the valve 7A is closed and the valves 6A, 13
A is opened, and a cleaning chemical such as hydrogen peroxide or hydrochloric acid is supplied into the lower chamber 2 through the inflow pipe 6, and the lower chamber 2 is filled with the cleaning chemical. Next, the valve 6A is closed and the valve 12A is opened, and compressed air is supplied from the air pipe 12 for a predetermined time to perform a scrubbing operation. Then, the valves 12A are closed and each hollow fiber membrane filter 51 is placed in the cleaning chemical for a predetermined time. Immerse. When the suspended substance is loosened by the immersion operation, the valve 12A is opened again, compressed air is supplied from the air pipe 12 for a predetermined time to perform a scrubbing operation, and the suspended substance is separated from each hollow fiber membrane filter 51. And drain the washing waste water from the drain pipe 14. At this time, compressed air may be supplied from the air pipe 13 to promote drainage.

After the chemical cleaning step, a rinsing step, which is a feature of the present embodiment, is performed. In this rinsing step, the valve 6
A and 13A are opened, for example, pure water is supplied from the inflow pipe 6 into the lower chamber 2 to fill the lower chamber 2 with water, and each hollow fiber membrane module 5 is immersed. Next, the valve 6A is closed and the valve 12A is opened, and compressed air is supplied from the air pipe 12 for a predetermined time to bubble bubbles in the water in each hollow fiber membrane module 5 to scrub each hollow fiber membrane module 5. Further, the valve 13A may be opened during the water filling step to perform the above-described scrubbing operation. In this case, the valve 6A is closed as soon as the lower chamber 2 becomes full. During this scrubbing operation, the hollow fiber membrane filter 51 is vibrated by bubbles that bubble through the water in each hollow fiber membrane module 5. This vibration stirs the water between the hollow fiber membrane filters 51, promotes the diffusion of the remaining cleaning chemical solution from the surface of each hollow fiber membrane filter 51 into pure water, and rinses each hollow fiber membrane filter 51 while rinsing each hollow fiber membrane filter 51. The cleaning chemical remaining in the space between the fiber membrane filters 51 is diffused outside the hollow fiber membrane module 5, and the remaining cleaning chemical in the hollow fiber membrane module 5 is sufficiently washed away. After the scrubbing operation is completed in this manner, the valve 1
2A is closed and the valves 13A and 14A are opened, and the rinsing liquid is discharged from the drain pipe 14. At this time, compressed air may be supplied from the air pipe 13 to promote drainage.

As described above, according to the present embodiment,
After the chemical liquid washing step, in the rinsing step of washing off the remaining cleaning chemical liquid from the inside of the tower main body 1, during the water filling step of filling the lower chamber 2 and / or after filling the lower chamber 2, compressed air is supplied into the lower chamber 2 to supply After the water between the hollow fiber membrane filters 51 in the hollow fiber membrane module 5 is stirred to perform a scrubbing for diffusing the cleaning chemical from the surface of each hollow fiber membrane filter 51,
Since the rinsing wastewater in the lower chamber 2 is continuously discharged, each hollow fiber membrane filter 51 in the hollow fiber membrane module 5 is removed.
The cleaning chemical solution on the surface is diluted, so that the cleaning chemical solution can be efficiently removed from the hollow fiber membrane filter 51. The number of rinsing operations after the chemical liquid cleaning can be reduced, and the amount of cleaning wastewater can be significantly reduced. . Therefore, when the waste liquid treatment is a closed system such as a nuclear power plant, the amount of discharged radioactive waste liquid can be significantly reduced.

Further, another embodiment of the cleaning method of the present invention is characterized by a drainage step performed in the rinsing step of the above embodiment. In this drainage step, while rinsing wastewater is being discharged from the lower chamber 2, compressed air is supplied into the rinse wastewater to stir the rinse wastewater, thereby promoting diffusion of the cleaning chemical solution from the surface of each hollow fiber membrane filter 51. . That is, after rinsing each hollow fiber membrane filter 51 in each hollow fiber membrane module 5 in the tower main body 1 in the scrubbing step in the rinsing step, compressed air is supplied from the air pipe 12 while the valve 12A is kept open from the scrubbing step. To discharge the rinse wastewater in the lower chamber 2 while bubbling bubbles in water to vibrate each hollow fiber membrane module 5. Otherwise, the cleaning chemicals attached to each hollow fiber membrane filter 51 are washed away by the same method as in the above embodiment.

Therefore, according to the present embodiment, since the rinse wastewater is discharged from the lower chamber 2 while bubbling bubbles into the rinse wastewater, the water surface ripples when the bubbles are released from the water surface, and the rinse wastewater is discharged from the lower chamber 2. As the water is discharged from the lower chamber 2, the wavy water surface falls in the lower chamber 2, and the hollow fiber membrane filter 51 in each hollow fiber membrane module 5 in contact with the wave of the descending water surface
By vibrating the surface vigorously, the cleaning chemical liquid that could not be sufficiently diffused by the scrubbing operation when the water is full can be further diffused to further increase the rinsing efficiency.

Next, a specific embodiment will be described. Example 1 In this example, the following hollow fiber membrane module for a test was installed in a 7-L filtration tower, and 1 mL of a cleaning chemical solution was placed in the filtration tower.
% Hydrogen peroxide solution, the hollow fiber membrane module in the tower is immersed in the cleaning chemical for 3 hours, then a scrubbing operation is performed, and then the cleaning chemical is discharged, and the hollow fiber membrane after the chemical cleaning is removed. Almost the same state as the module was set. Thereafter, a rinsing operation based on the first embodiment was performed.
That is, after filling the inside of the filtration tower with pure water, the compressed air is supplied from the lower end of the hollow fiber membrane module under the following conditions to perform a scrubbing operation, and the hollow fiber membrane filter is rinsed with pure water.
This rinse wastewater was discharged from the filtration tower. Then, the concentration of hydrogen peroxide in the discharged rinse wastewater was measured, and the result is indicated by ■ in FIG. In FIG. 4, for example,
(1.0E + 07) represents 1.0 × 10 ⁷ . [Washing conditions] Hollow fiber membrane module (1) Number of hollow fiber membrane filters: 170 (2) Inner diameter of hollow fiber membrane filter: 0.7 mm (3) Outer diameter of hollow fiber membrane filter: 1.2 mm (4) Micropore diameter of hollow fiber membrane filter: 0.1 μm (5) Effective length of hollow fiber membrane filter: 2200 mm (6) Effective membrane area of hollow fiber membrane filter: 1.43 m ² Rinse process conditions (1) Air flow rate: 3 L / min (2) Scrubbing time: 10 minutes

Embodiment 2 In this embodiment, the same operation as in Embodiment 1 is performed, and when rinsing wastewater is discharged from the filtration tower, the rinsing wastewater is drained while scrubbing with air, and the discharged rinsing wastewater is discharged. The concentration of hydrogen peroxide was measured, and the results are shown in FIG.
Indicated by

Comparative Example 1 In this comparative example, the same hollow fiber membrane module as in Example 1 was used. The hollow fiber membrane module was filled with pure water in the filtration tower in the same manner as in Example 1, and then the scrubbing operation was performed. Without performing, a conventional rinsing step was performed in which the rinse wastewater was discharged from the filtration tower. Then, the concentration of hydrogen peroxide in the discharged rinsing wastewater was measured, and the results are indicated by □ in FIG.

As is clear from the results shown in FIG. 4, for example, when the hydrogen peroxide concentration of the rinsing waste water is reduced to 100 ppb, the rinsing generated per 1 m ² of the membrane area of the hollow fiber membrane filter in the first embodiment. The amount of wastewater discharged is 0.
It was 025m ³ / m ^2, Example 2, 0.023m ³ /
m ² . However, in Comparative Example 1, the drainage amount of the rinse wastewater generated per 1 m ² of the membrane area of the hollow fiber membrane filter was 0.093 m ³ / m ² . Therefore, Examples 1 and 2
Is about 30% of the waste water amount of Comparative Example 1, and it was found that the waste water amount can be remarkably reduced in the case of the cleaning method of the present invention as compared with the conventional cleaning method. From these results, it was found that the cleaning method of the present invention was extremely effective in a closed wastewater treatment plant such as a nuclear power plant.

The present invention is not limited to the above embodiments, and the cleaning method of the present invention is a rinsing step of washing the cleaning chemical solution from the inside of the tower body 1 during the water filling step or in the lower chamber after the water filling. Air is supplied into each of the hollow fiber membrane filters 5 to stir the water in each hollow fiber membrane module 5.
A cleaning method including a scrubbing step of diffusing a cleaning chemical solution into water from the surface of 1 is sufficient, and a method of performing scrubbing in a drainage step of discharging rinse wastewater in the lower chamber 2 after the scrubbing step may be used. Any cleaning method including such a scrubbing step is included in the present invention.

[0027]

According to the first or second aspect of the present invention, it is possible to provide a method for cleaning a hollow fiber membrane filtration tower capable of remarkably reducing the amount of cleaning waste liquid discharged. .

[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.

FIG. 4 is a graph showing a rinsing effect when the cleaning method of the present invention and a conventional cleaning method are used, and is a graph showing the relationship between the amount of rinse wastewater and the concentration of hydrogen peroxide in the rinse wastewater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tower main body 2 Lower chamber 3 Upper chamber 4 Divider (partition member) 5 Hollow fiber membrane module 51 Hollow fiber membrane filter

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. A washing step of washing the hollow fiber membrane filtration tower with a washing chemical as a washing step of the hollow fiber membrane filtration tower, and a rinsing step of washing the washing chemical from the inside of the tower main body, and The rinsing step is a water filling step of filling the primary chamber with water, a scrubbing step of supplying air into the primary chamber during and / or after the water filling step to agitate the water in each of the hollow fiber membrane modules, Rear primary room A method for cleaning a hollow fiber membrane filtration tower, comprising: a drainage step of discharging rinsing wastewater from the inside. 2. In the draining step, while rinsing the rinsing wastewater, air is supplied into the primary chamber to agitate the rinsing wastewater, and the cleaning chemical is removed from the surface of each of the hollow fiber membrane filters. The method for washing a hollow fiber membrane filtration tower according to claim 1, wherein the filtration step is performed.