JP2020182896A - Repair method of hollow fiber membrane module - Google Patents

Abstract

To provide a repair method of a hollow fiber membrane module capable of more reliably suppressing leakage of raw water to the filtrate water side.SOLUTION: A repair method of a hollow fiber membrane module is a method of inserting a repairing needle into a hollow part of fractured hollow fiber membrane of a number of hollow fiber membranes to repair the hollow fiber membrane module, in an external pressure filtration type hollow fiber membrane module having a number of hollow fiber membrane module. The method includes a process of preparing the repair needle made of one material selected from a group consisting of stainless steel and titanium, and having a rate of a needle diameter to an inner diameter of the hollow fiber membrane of 105 to 120%, and a process of inserting the repair needle into the hollow part from an opening from which filtrate water flows out as an opening of the fractured hollow fiber membrane and closing the opening with the repair needle.SELECTED DRAWING: Figure 6

Description

The present invention relates to a method for repairing a hollow fiber membrane module.

Conventionally, a hollow fiber membrane module has been used in various water purification treatments such as pure water recovery and drinking water production. The hollow fiber membrane module has an element in which a large number of hollow fiber membranes are bundled and a housing for accommodating the element, and the raw water introduced into the housing is permeated through the hollow fiber membrane and filtered. Here, the membrane may break in a part of a large number of hollow fiber membranes during use of the module, and in this case, the hollow fiber membrane module is repaired in order to prevent leakage of raw water to the filtered water side. You will need it. For example, Patent Documents 1 and 2 describe a technique for repairing such a hollow fiber membrane module.

Patent Document 1 houses a hollow fiber membrane bundle composed of a plurality of hollow fiber membranes, a resin portion for fixing the plurality of hollow fiber membranes at both ends of the hollow fiber membrane bundle, and the hollow fiber membrane bundle. A method for repairing a membrane module provided with a casing and comprising a sealing step of inserting an opening sealing member into an opening of a hollow fiber membrane in which a leak has occurred is described. In this method, an opening sealing member made of a flexible resin such as polyethylene or polypropylene is used. Further, Patent Document 2 describes that an object having a cylindrical shape, a conical shape, or a composite shape of both is used for sealing the unit opening of the damaged hollow fiber.

Japanese Patent No. 6290616 Japanese Unexamined Patent Publication No. 51-32487

As a result of diligent studies by the present inventors, when an opening sealing member made of a flexible material as described in Patent Document 1 is used, it is necessary to sufficiently seal the opening of the hollow fiber membrane. It became clear that it can be difficult. For this reason, conventionally, it is difficult to prevent the leakage of raw water to the filtered water side even after the opening sealing member is inserted, and there is a problem that the repair effect becomes insufficient. Further, the repair technique described in Patent Document 2 also has a similar problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for repairing a hollow fiber membrane module capable of more reliably suppressing leakage of raw water to the filtered water side. ..

A method for repairing a hollow fiber membrane module according to one aspect of the present invention is to use an external pressure filtration type hollow fiber membrane module having a large number of hollow fiber membranes in a hollow portion of the hollow fiber membrane that is broken among the large number of the hollow fiber membranes. This is a method of repairing the hollow fiber membrane module by inserting a repair needle into the hollow fiber membrane module. This method comprises a step of preparing a repair needle in which the ratio of the needle diameter to the inner diameter of the hollow fiber membrane is 105% or more and 120% or less, which is made of one material selected from the group consisting of stainless steel and titanium, and is broken. The process includes a step of inserting the repair needle into the hollow portion through the opening of the hollow fiber membrane through which the filtered water flows out, and closing the opening with the repair needle.

According to the method for repairing the hollow fiber membrane module, the hollow fiber membrane is made of one material selected from the group consisting of stainless steel and titanium, and the ratio of the needle diameter to the inner diameter of the hollow fiber membrane (hereinafter, also referred to as “diameter ratio”) is 105. By inserting a repair needle of% or more and 120% or less into the hollow portion through the opening of the broken hollow fiber membrane to close the opening, leakage of raw water to the filtered water side after repair can be more reliably suppressed. Can be done. Therefore, the repair effect of the hollow fiber membrane module can be further improved.

Further, since impurities and the like adhere to the membrane surface during use of the hollow fiber membrane module, it is common to periodically carry out chemical cleaning with an oxidizing agent, an acidic solution, an alkaline solution or the like. For this reason, the material of the repair needle is required to have chemical resistance. As described above, by selecting one material selected from the group consisting of stainless steel and titanium as the material of the repair needle, the repair needle at the time of chemical cleaning is selected. It is possible to suppress the deterioration of.

In the method for repairing the hollow fiber membrane module, the hollow fiber membrane includes an outer membrane portion including the outer surface of the hollow fiber membrane and an inner surface including the inner surface of the hollow fiber membrane and having a lower density than the outer membrane portion. The inner membrane portion may be compressed toward the outer membrane portion by the repair needle inserted into the hollow portion having a membrane portion. At this time, the inner membrane portion may be compressed by the repair needle from a state in which the passage of raw water is allowed before the repair needle is inserted to a state in which the passage of raw water is blocked. As a result, not only the leakage of raw water through the hollow portion of the hollow fiber membrane but also the leakage of raw water through the inner membrane portion of the hollow fiber membrane can be suppressed.

As is clear from the above description, according to the present invention, it is possible to provide a method for repairing a hollow fiber membrane module capable of more reliably suppressing leakage of raw water to the filtered water side.

It is a figure which shows typically the structure of the hollow fiber membrane module which is the object of carrying out the method of repairing the hollow fiber membrane module which concerns on embodiment of this invention. It is a figure which shows typically the cross section of the hollow fiber membrane in the said hollow fiber membrane module. It is an enlarged view in the region III in FIG. It is a figure which shows typically the structure of the repair needle used in the repair method of the said hollow fiber membrane module. It is a flowchart which shows the procedure of the repair method of the hollow fiber membrane module which concerns on embodiment of this invention. It is a figure which shows typically the state of inserting the repair needle into the hollow part of the hollow fiber membrane in the said method of repairing a hollow fiber membrane module. It is a schematic diagram for demonstrating the repair method of the hollow fiber membrane module in other embodiment of this invention.

Hereinafter, the method of repairing the hollow fiber membrane module according to the embodiment of the present invention will be described in detail with reference to the drawings.

(Hollow fiber membrane module)
First, the configuration of the hollow fiber membrane module 1 to be implemented in the method for repairing the hollow fiber membrane module according to the embodiment of the present invention will be described with reference to FIGS. 1 to 3. The hollow fiber membrane module 1 is used for various water purification treatments such as production of tap water and drinking water. As shown in FIG. 1, the hollow fiber membrane module 1 mainly includes a housing 10, a water pipe 20, an air diffuser 30, a membrane element 40, and a cap 50.

The membrane element 40 has a large number of hollow fiber membranes 41 (for example, about 10,000) and a resin fixing portion 42 for fixing the large number of hollow fiber membranes 41 in a bundle. The hollow fiber membrane 41 is a hollow cylindrical membrane for filtering raw water (water to be purified), extends in one direction (vertical direction), and has an upper end 41A and a lower end 41B. A hollow portion H1 (FIG. 2) is formed in the hollow fiber membrane 41 over the entire length direction, and an opening on the upper end 41A side is opened to the space inside the cap 50 and an opening on the lower end 41B side. Is sealed with resin or the like. The material of the hollow fiber membrane 41 is not particularly limited, but for example, hydrophilic treated polyvinylidene fluoride (PVDF; Polyvinylidene DiFluoride) or the like is used.

FIG. 2 shows a cross section when one hollow fiber membrane 41 is cut perpendicularly to the length direction. As shown in FIG. 2, the hollow fiber membrane 41 is provided with an outer surface 43 and an inner surface 44 facing the opposite side of the outer surface 43, and a hollow portion H1 defined by the inner surface 44 is provided. It is formed inside.

FIG. 3 is an enlarged view of region III in FIG. The hollow fiber membrane 41 includes an outer membrane portion 46 including an outer surface 43 and having a predetermined thickness in the radial direction, and an inner membrane portion 47 including an inner surface 44 and having a predetermined thickness in the radial direction. doing. The inner film portion 47 has a lower density than the outer film portion 46. That is, as schematically shown in FIG. 3, the pores 45 of the hollow fiber membrane 41 are larger in the inner membrane portion 47 than in the outer membrane portion 46. In other words, the inner film portion 47 has a larger porosity of the film than the outer film portion 46, for example, 20% or more. The inner membrane portion 47 occupies 50% or more of the entire cross section of the membrane, and is a portion through which raw water and air can pass along the length direction of the hollow fiber membrane 41. On the other hand, the outer membrane portion 46 is a portion through which raw water and air cannot pass along the length direction of the hollow fiber membrane 41. The outer membrane portion 46 functions as a dense layer that effectively separates impurities in the raw water by the small-diameter pores 45, while the inner membrane portion 47 functions as a support layer that supports the outer membrane portion 46 from the inside. ..

As shown in FIG. 1, the housing 10 is a container having a long shape in the vertical direction and houses the membrane element 40. The upper portion 10A of the housing 10 is open, and the membrane element 40 can be inserted and removed from the opening. The space inside the housing 10 is a raw water space S1 into which raw water is introduced, and the raw water in the raw water space S1 is filtered by the hollow fiber membrane 41. Further, the outer peripheral surface of the resin fixing portion 42 is in close contact with the inner surface of the housing 10. The housing 10 is provided with a drainage port 11 for discharging raw water from the raw water space S1 at the lower portion, and an air introduction port 12 for introducing cleaning air for the hollow fiber membrane 41 at the lower portion, and also provides air. An air vent 13 for bleeding is provided at the upper part.

The water pipe 20 is a member for introducing raw water into the housing 10 (raw water space S1). As shown in FIG. 1, the water pipe 20 extends vertically inside the bundle-shaped hollow fiber membrane 41 in the housing 10, and the upper end thereof is fixed to the resin fixing portion 42. A large number of water flow holes 21 are formed in the water pipe 20 at intervals in the circumferential direction and the pipe axial direction (vertical direction), and the raw water in the water pipe 20 is introduced into the raw water space S1 through the water flow holes 21. Will be done.

The air diffuser 30 is a member that disperses the cleaning air introduced from the air introduction port 12 into the lower space in the housing 10 so as to spread in the radial direction of the membrane element 40. As shown in FIG. 1, the air diffuser 30 is arranged below the lower end 41B of the hollow fiber membrane 41 in the housing 10, and the water pipe 20 is inserted through the central portion thereof.

The cap 50 covers the upper opening of the housing 10 and is fixed to the upper part of the housing 10 by a predetermined fixture (not shown) such as a band. The upper end 41A of the hollow fiber membrane 41 penetrates the resin fixing portion 42, and the opening on the upper end 41A side communicates with the space inside the cap 50. The space inside the cap 50 is a filtered water space S2 into which the filtered water flowing out from the opening on the upper end 41A side of the hollow fiber membrane 41 flows in, and is liquid-tightly partitioned from the raw water space S1 by the resin fixing portion 42. There is. Further, a filtered water outlet 51 for taking out the filtered water to the outside of the module is provided on the upper portion of the cap 50.

With the hollow fiber membrane module 1 having the above configuration, raw water can be filtered as follows. First, the raw water introduced into the water pipe 20 by the water supply pump from the raw water tank (not shown) is introduced into the raw water space S1 in the housing 10 through the water passage hole 21. Then, the introduced raw water permeates from the outer surface 43 of the hollow fiber membrane 41 toward the inner surface 44, so that impurities in the raw water are removed. After that, clean filtered water flows through the hollow portion H1 (FIG. 2) toward the upper end 41A of the hollow fiber membrane 41, flows into the filtered water space S2 through the opening on the upper end 41A side, and then is hollow through the filtered water outlet 51. It is taken out of the filament membrane module 1. As described above, the hollow fiber membrane module 1 is an external pressure filtration type that allows raw water to permeate from the outer surface 43 toward the inner surface 44.

Here, as indicated by reference numeral B1 in FIG. 1, some of the hollow fiber membranes 41 out of a large number of hollow fiber membranes 41 may break during use of the hollow fiber membrane module 1. In this case, the raw water flows into the hollow portion H1 of the hollow fiber membrane 41 through the fractured portion B1 and flows into the filtered water space S2 while containing a large amount of impurities. Therefore, it is necessary to repair the hollow fiber membrane module 1 in order to prevent leakage of raw water to the filtered water side (mixed water of filtered water and raw water). Hereinafter, repair of such a hollow fiber membrane module 1 will be described.

(Repair needle for hollow fiber membrane module)
First, the configuration of the hollow fiber membrane module repair needle 60 (hereinafter, also simply referred to as “repair needle 60”) used in the method for repairing the hollow fiber membrane module according to the present embodiment will be described. The repair needle 60 is inserted into the hollow portion H1 of the broken hollow fiber membrane 41 (hollow fiber membrane 41 including the broken portion B1 in FIG. 1) among a large number of hollow fiber membranes 41 in the hollow fiber membrane module 1. This is for repairing the hollow fiber membrane module 1. Specifically, the repair needle 60 is for closing the upper end opening by inserting it into the hollow portion H1 from the opening on the upper end 41A side of the hollow fiber membrane 41 including the fractured portion B1.

FIG. 4 schematically shows the configuration of the repair needle 60. The repair needle 60 includes a base end 60A on the side gripped by the operator performing the repair work and a tip end 60B on the side inserted into the hollow portion H1 of the broken hollow fiber membrane 41, and the tip ends from the base end 60A. It has a shape extending in one direction toward 60B. More specifically, the repair needle 60 includes a base end 60A and is connected to a cylindrical needle body 61 extending in one direction with a constant diameter and a needle body 61 on the opposite side of the base end 60A. It has a truncated cone-shaped tip portion 62, which is gradually reduced in diameter toward the tip 60B.

When the repair needle is inserted into the hollow portion H1 of the broken hollow fiber membrane 41 to repair the hollow fiber membrane module 1, the present inventors more reliably leak the raw water to the filtered water side after the repair. In order to suppress it, a detailed study was conducted on the material and size of the repair needle. As a result, the present inventors have used a repair needle 60 which is made of one material selected from the group consisting of stainless steel and titanium and whose needle diameter ratio to the inner diameter of the hollow fiber membrane 41 satisfies a predetermined range. It was newly found that the repair effect (effect of suppressing leakage of raw water) of the hollow fiber membrane module 1 is remarkably improved.

"Stainless steel" is a general term for chromium or alloy steels containing chromium and nickel. For example, iron of 50% by mass or more, carbon of 1.2% by mass or less, and chromium of 10.5% by mass or more are used. It is contained and is indicated by the material symbol "SUS" in the JIS standard. Further, "titanium" means pure titanium or a titanium alloy. As the titanium alloy, those containing 80% by mass or more of titanium are preferable.

The repair needle 60 according to the present embodiment is made of one material selected from the group consisting of stainless steel and titanium, and the ratio of the needle diameter (diameter of the needle body 61) to the inner diameter of the hollow fiber membrane 41 is 105% or more. It is 120% or less. By inserting such a repair needle 60 into the hollow portion H1 through the opening on the upper end 41A side of the broken hollow fiber membrane 41, leakage of raw water after repair can be more reliably suppressed. The repair needle 60 is harder than the hollow fiber membrane 41 (inner membrane portion 47) to be repaired.

From the viewpoint of improving the leak suppressing effect of raw water, the repair needle 60 preferably has a tensile strength of 250 MPa or more, more preferably 290 MPa or more, further preferably 500 MPa or more, and 700 MPa or more. Is even more preferable. On the other hand, from the viewpoint of handleability, the tensile strength of the repair needle 60 is preferably 2000 MPa or less. The tensile strength of the repair needle 60 is defined in JIS Z2241: 2011.

The repair needle 60 made of stainless steel has a tensile strength of 520 MPa or more, for example, about 800 MPa. The repair needle 60 made of pure titanium has a tensile strength of 275 to 590 MPa or more, for example, about 300 MPa. The repair needle 60 made of a titanium alloy has a tensile strength of 800 to 10,000 MPa or more, for example, about 950 MPa.

According to the repair needle 60 in the present embodiment, raw water is compared with a repair needle made of stainless steel such as polyethylene or polypropylene and a material more flexible than titanium, or a repair needle having a diameter ratio of less than 105% or more than 120%. Leak suppression effect can be improved. When the diameter ratio is less than 105%, it is difficult to sufficiently seal the opening of the hollow fiber membrane 41. If the diameter ratio exceeds 120%, peeling occurs at the interface between the upper end 41A of the hollow fiber membrane 41 and the resin fixing portion 42 when the repair needle is inserted, which causes leakage of raw water. Therefore, the diameter ratio of the repair needle 60 is 105% or more and 120% or less, preferably 110% or more, and more preferably 115% or more.

(How to repair the hollow fiber membrane module)
Next, a method of repairing the hollow fiber membrane module according to the present embodiment will be described. This repair method is a method of repairing the hollow fiber membrane module 1 by inserting a repair needle 60 into the hollow portion H1 of the broken hollow fiber membrane 41 among a large number of hollow fiber membranes 41 in the hollow fiber membrane module 1. Yes, it is carried out according to the flowchart of FIG.

First, a step of identifying a broken hollow fiber membrane 41 among a large number of hollow fiber membranes 41 is performed (S10). In this step S10, the inside of the hollow fiber membrane module 1 (raw water space S1 and filtered water space S2) is filled with water, and the hollow fiber membrane 41 is pressurized from the outer surface 43 side by air. At this time, in the broken hollow fiber membrane 41, air flows into the hollow portion H1 through the broken portion B1, so that air escape from the opening on the upper end 41A side is confirmed. Therefore, the hollow fiber membrane 41 in which air release is confirmed is specified as the membrane to be repaired.

Next, a step of preparing the repair needle 60 is carried out (S20). In this step S20, a required number of repair needles 60 are prepared according to the number of hollow fiber membranes 41 to be repaired specified in step S10.

Next, a step of inserting the repair needle 60 into the hollow portion H1 of the hollow fiber membrane 41 is performed (S30). In this step S30, the repair needle 60 is inserted into the hollow portion H1 from the opening on the upper end 41A side of the damaged hollow fiber membrane 41 (the opening through which the filtered water flows out), and the opening is closed (sealed) by the repair needle 60. ). Specifically, with the cap 50 removed from the housing 10, the repair needle 60 is inserted from the tip 62B into the hollow portion H1 of the hollow fiber membrane 41 to be repaired, as shown in FIG. At this time, the repair needle 60 may be driven into the hollow portion H1 using, for example, a hammer.

In this step S30, as shown by the white arrows in FIG. 6, the inner film portion 47 (support layer) of the hollow fiber membrane 41 is compacted by the outer film portion 46 (dense) by the repair needle 60 inserted into the hollow portion H1. Compress (crush) radially outward toward the layer). More specifically, the inner membrane portion 47 is compressed by the repair needle 60 from a state in which the permeation of the raw water is allowed before the repair needle 60 is inserted to a state in which the permeation of the raw water is blocked. By press-fitting the repair needle 60 into the hollow portion H1 in this way, the inner membrane portion 47 is crushed by the outer peripheral surface of the repair needle 60 (needle body portion 61), and the porosity of the inner membrane portion 47 is reduced to the repair needle. It is smaller than before the insertion of 60.

As shown by the broken line arrow W1 in FIG. 6, even if the raw water flows into the hollow portion H1 from the raw water space S1 through the fractured portion B1, the raw water is filtered by closing the opening on the upper end 41A side with the repair needle 60. It can be prevented from flowing into the water space S2. On the other hand, as shown by the broken line arrow W2 in FIG. 6, even when the opening on the upper end 41A side of the hollow fiber membrane 41 is closed, the raw water passes through the inner membrane portion 47 toward the upper end 41A, so that the filtered water is filtered. Raw water may flow into the space S2. On the other hand, as described above, the inner membrane portion 47 is compressed by the repair needle 60 to prevent the passage of the raw water, so that the raw water leaks to the filtered water space S2 having the inner membrane portion 47 as the water passage route. Can be prevented.

Next, a step of confirming the repair effect of the hollow fiber membrane module 1 is carried out (S40). In this step S40, in the same manner as in the above step S10, the inside of the hollow fiber membrane module 1 is filled with water, and the hollow fiber membrane 41 is pressurized from the outer surface 43 side by air. Then, it is confirmed that air does not escape from the upper end 41A of the repaired hollow fiber membrane 41. The method for repairing the hollow fiber membrane module according to the present embodiment is carried out by the above procedure.

(Other embodiments)
Here, other embodiments of the present invention will be described.

The method for repairing the hollow fiber membrane module according to the above embodiment is carried out for the hollow fiber membrane module 1 in which the density of the inner membrane portion 47 is smaller than the density of the outer membrane portion 46, but is not limited thereto. .. As shown in FIG. 7, the hollow fiber membrane module has substantially the same density of the inner membrane portion 47 and the outer membrane portion 46, and the size of the pores 45 is substantially constant from the outer surface 43 to the inner surface 44. , May be subject to repair. In this case, since the inner membrane portion 47 does not allow the passage of raw water along the length direction of the hollow fiber membrane 41, the inner membrane portion 47 does not have to be compressed. Note that FIG. 7 is an enlarged view of a cross section of the hollow fiber membrane corresponding to FIG.

Hereinafter, the present invention will be described in more detail based on Examples. However, the present invention is not limited to the following examples, and it is possible to carry out the present invention with appropriate modifications within a range that can be adapted to the gist of the preceding and following description, and all of them are the techniques of the present invention. It is included in the target range.

The hollow fiber membrane module 1 was repaired according to the following procedure. The inner and outer diameters of the hollow fiber membrane 41 are as shown in Tables 1 and 2 below (the inner diameter is 0.6 mm and the outer diameter is 1 mm (M02-100 manufactured by Kuraray Co., Ltd.), or the inner diameter is Those with a diameter of 0.75 mm and an outer diameter of 1.25 mm (using US02-125 manufactured by Kuraray Co., Ltd.). As the repair needles, as shown in Tables 1 and 2 below, those made of stainless steel, those made of pure titanium (tensile strength 300 MPa), those made of titanium alloy (tensile strength 950 MPa), and copper (tensile). Those made of polypropylene (PP, tensile strength 30 MPa) and those made of polypropylene (strength 200 MPa) were prepared respectively. For each of the above materials, repair needles having needle diameters of 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm and 1.0 mm were prepared, respectively. The tensile strength of the repair needle 60 made of a metal material is specified in JIS Z2241: 2011, and the tensile strength of the repair needle made of a resin material is specified in K 7161-1: 2014. ..

Then, the sample Nos. In Tables 1 and 2 below. With the combination of the repair needle and the hollow fiber membrane as shown in 1 to 30, as shown in FIG. 6, the repair needle 60 was inserted into the hollow portion H1 through the opening on the upper end 41A side of the broken hollow fiber membrane 41. After that, as described in the above step S40, the hollow fiber membrane 41 was pressurized from the outer surface 43 side by air, and the escape of air from the opening on the upper end 41A side was confirmed. In Tables 1 and 2 below, if air bleeding is not confirmed, mark "○" in the item column for repair availability, and if air bleeding is confirmed, mark "x" in the same item. The mark is written.

As shown in Tables 1 and 2 above, Sample No. 1 in which the material of the repair needle is PP. Sample Nos. 13 to 15 and 28 to 30, and the ratio of the diameter of the repair needle to the inner diameter of the hollow fiber membrane is less than 105% or more than 120%. In 1, 3, 4, 6, 7, 9, 18, 21 and 24, air escape from the upper end of the hollow fiber membrane was confirmed in the confirmation after repair. In addition, sample No. in which the material of the repair needle is copper. In 10-12 and 25-27, it was confirmed that the strength of the needle was insufficient when the needle was pushed in during repair, and the needle buckled, making repair difficult. On the other hand, the material of the repair needle is stainless steel or titanium, and the ratio of the diameter of the repair needle to the inner diameter of the hollow fiber membrane is in the range of 105% or more and 120% or less. In 2, 5, 8, 16, 17, 19, 20, 22 and 23, it was found that no air escape was confirmed in the confirmation after the repair, and a good repair effect was obtained.

It should be understood that the embodiments and examples disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Hollow fiber membrane module 41 Hollow fiber membrane 43 Outer surface 44 Inner surface 46 Outer membrane part 47 Inner membrane part 60 Repair needle for hollow fiber membrane module (repair needle)
H1 hollow part

Claims (3)

In an external pressure filtration type hollow fiber membrane module having a large number of hollow fiber membranes, a method of repairing the hollow fiber membrane module by inserting a repair needle into the hollow portion of the broken hollow fiber membrane among the large number of the hollow fiber membranes. And
A step of preparing a repair needle made of one material selected from the group consisting of stainless steel and titanium, and the ratio of the needle diameter to the inner diameter of the hollow fiber membrane is 105% or more and 120% or less.
Repair of a hollow fiber membrane module having a step of inserting the repair needle into the hollow portion through the opening through which the filtered water flows out at the opening of the broken hollow fiber membrane and closing the opening with the repair needle. Method. The hollow fiber membrane has an outer membrane portion including the outer surface of the hollow fiber membrane and an inner membrane portion including the inner surface of the hollow fiber membrane and having a density lower than that of the outer membrane portion.
The method for repairing a hollow fiber membrane module according to claim 1, wherein the inner membrane portion is compressed toward the outer membrane portion by the repair needle inserted into the hollow portion. The hollow fiber membrane module according to claim 2, wherein the inner membrane portion is compressed by the repair needle from a state that allows the passage of raw water before the repair needle is inserted to a state that prevents the passage of the raw water. Repair method.

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