Leak detection method for hollow fiber membrane module, and leak detection device therefor

Abstract

To provide a leak detection method and a leak detection device for a hollow fiber membrane module that reduce a risk of contamination of filtrate with microbes.SOLUTION: There is provided a method for detecting a leak in a hollow fiber membrane module used to manufacture purified water. The method includes the steps of: filling all of a primary-side space, an in-film pore space, and a secondary-side space of each hollow fiber membrane module, and the inside of a piping system including detection means arranged nearby a secondary-side space exit with heated pure water; or filling all of the primary-side space, the in-film pore space, and the secondary-side space of each hollow fiber membrane module, and the inside of the piping system including the detection means arranged nearby the secondary-side space exit with the pure water and then heating the whole system filled with the pure water instead of the step; supplying a gas of predetermined pressure to the primary side filled with the heated pure water; and detecting air bubbles leaking to the secondary side filled with the heated pure water by the detection means.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for detecting leaks in a hollow fiber membrane module.

Background Art

[0002] Hollow fiber membrane modules are widely used for separating various gases, liquids, and solids, such as the production of pure water, the sterilization and turbidity removal of service water, wastewater treatment, degassing, dehydration, and gas separation.

[0003] In the manufacturing process of hollow fiber membranes, if defects or damages occur in the hollow fiber membranes, the system using the hollow fiber membrane module cannot exhibit the desired performance. Therefore, the leak test of the hollow fiber membrane module is an essential process for using the hollow fiber membrane module.

[0004] For example, Patent Document 1 discloses a leak test method in which, after wetting the inside of the membrane wall of a hydrophilic polymer-containing hollow fiber membrane with water, the space inside the hollow fiber membrane is pressurized with a gas, and the gas leaking through the hollow fiber membrane is detected. In this leak test method, the water is characterized by being warm water.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the method described in Patent Document 1, the water used for wetting the hollow fiber membrane is not water that has undergone purification treatment. Therefore, even though it is heated, sterilization is not sufficient, and there may be a case where microorganisms survive, resulting in a risk of contamination by microorganisms. In addition, since the method described in Patent Document 1 is a method of pressurizing the space inside the wetted hollow fiber membrane with gas, air was present on the treated water supply port side (in one aspect, the primary side) of the hollow fiber membrane module and on the filtrate outlet side (in one aspect, the secondary side or the filtrate side) of the hollow fiber membrane module. In the method described in Patent Document 1, there is a possibility of causing contamination by microorganisms derived from air. In particular, when a membrane leak is detected, there is a problem that foreign substances such as microorganisms captured by the membrane may mix into the secondary side and contaminate the filtrate.

[0007] An object of the present invention is to provide a method and an apparatus for detecting a leak in a hollow fiber membrane module that reduce the risk of contamination of the filtrate by microorganisms.

Means for Solving the Problems

[0008] The gist of the present invention is as follows.

[0009] <<Aspect 1>> A method for detecting a leak in a hollow fiber membrane module used for producing purified water, comprising the following steps: A step of filling all of the primary side space, the pore space inside the membrane, and the secondary side space of each hollow fiber membrane module, as well as the inside of the piping system including the detection means disposed near the outlet of the secondary side space, with heated pure water; or, instead of this step, a step of filling all of the primary side space, the pore space inside the membrane, and the secondary side space of each hollow fiber membrane module, as well as the inside of the piping system including the detection means disposed near the outlet of the secondary side space, with pure water and heating the entire system filled with the pure water; A step of supplying a gas at a predetermined pressure to the primary side filled with the heated pure water; and A step of detecting, by the detection means, bubbles leaked to the secondary side filled with the heated pure water; A leak detection method comprising the above steps. <<Aspect 2>> The leak detection method according to Aspect 1, wherein the temperature of the heated pure water is 55°C or higher and 95°C or lower. <<Aspect 3>> The temperature of the heated pure water is 80°C or higher and 95°C or lower. The leak detection method according to Embodiment 1 or 2. <<Embodiment 4>> The detection means detects bubbles based on ultrasonic attenuation or propagation efficiency. The leak detection method according to any one of Embodiments 1 to 3. <<Embodiment 5>> The detection means detects bubbles based on an image inside the piping system. The leak detection method according to any one of Embodiments 1 to 4. <<Embodiment 6>> Leak detection is performed in an apparatus system provided with the detection means for each of a plurality of hollow fiber membrane modules. The leak detection method according to any one of Embodiments 1 to 5. <<Embodiment 7>> The purified water is water for injection. The leak detection method according to any one of Embodiments 1 to 6. <<Embodiment 8>> Leak detection of the hollow fiber membrane module is performed while performing filtration by the hollow fiber membrane module. The leak detection method according to any one of Embodiments 1 to 7. <<Embodiment 9>> A leak detection device for detecting a leak in a hollow fiber membrane module used for producing purified water, comprising a heating means, a gas supply means, a detection means, a pump, and a piping system connecting these, The pump fills all of the primary side space, the intracapillary pore space, and the secondary side space of each hollow fiber membrane module, and the piping system including the detection means disposed near the outlet of the secondary side space with pure water, The heating means is a means for heating the pure water filled in all of the piping system, The gas supply means is a means for supplying a gas at a predetermined pressure to the primary side filled with the heated pure water, and The detection means is a means for detecting bubbles leaked to the secondary side filled with the heated pure water. A leak detection device. <<Embodiment 10>> The heating means heats the pure water to 55°C or higher and 95°C or lower. The leak detection device according to Embodiment 9. <<Aspect 11>> The leak detection device according to Aspect 9 or 10, wherein pure water is heated to 80°C or higher and 95°C or lower by the heating means. <<Aspect 12>> The leak detection device according to any one of Aspects 9 to 11, wherein the detection means detects bubbles based on ultrasonic attenuation or propagation efficiency. <<Aspect 13>> The leak detection device according to any one of Aspects 9 to 12, wherein the detection means detects bubbles based on an image inside the piping system. <<Aspect 14>> The leak detection device according to any one of Aspects 9 to 13, comprising the detection means for each of a plurality of hollow fiber membrane modules. <<Aspect 15>> The leak detection device according to any one of Aspects 9 to 14, wherein the purified water is water for injection. <<Aspect 16>> The leak detection device according to any one of Aspects 9 to 15, wherein leak detection of the hollow fiber membrane module is performed while filtration by the hollow fiber membrane module is carried out.

Advantages of the Invention

[0010] According to the present invention, the risk of contamination by microorganisms during leak checking of the hollow fiber membrane module is reduced. Further, according to one aspect of the present invention, even when a defect in the hollow fiber membrane module is confirmed by leak checking, the risk of contamination by microorganisms on the secondary side is reduced.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments for implementing the present invention (hereinafter also referred to as the present embodiments) will be described in detail. Note that the present embodiments are not limited to the embodiments described below, and various modifications can be made and used within the indicated range.

[0013] The present embodiments will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a leak detection device for a hollow fiber membrane module employed in the present embodiments. Note that parts unnecessary for the description are omitted and only the illustrated parts are shown.

[0014] The leak detection device of the present embodiments includes a water to be treated tank 1, a pump 2, a heater 3 as heating means, a hollow fiber membrane module 4, a detection means 5, a gas supply means 6, a water quality inspection means 7, and a pipe 8 connecting these. In addition, the hollow fiber membrane module 4 according to the present embodiments includes a primary side space (not shown), an intracapillary pore space (not shown), and a secondary side space (not shown). The pump 2 fills all of the primary side space, intracapillary pore space, and secondary side space of each hollow fiber membrane module 4, and the pipe system including the detection means 5 disposed near the secondary side space outlet with pure water.

[0015] The leak detection method by the leak detection device according to the present embodiments will be described below.

[0016] The present embodiments are a method for detecting leaks in a hollow fiber membrane module used for the production of purified water is. The leak detection method of the present embodiments is a leak detection device equipped with a hollow fiber membrane module, and the following steps: (1) A step of filling all of the primary side space, intracapillary pore space, and secondary side space of each hollow fiber membrane module, and the pipe system including the detection means disposed near the secondary side space outlet with heated pure water; or Instead of step (1), a step of filling all of the primary-side space, the pore space inside the membrane, and the secondary-side space of each hollow fiber membrane module, and all inside the piping system including the detection means arranged near the secondary-side space outlet with pure water, and heating the entire system filled with the pure water; (2) A step of supplying a gas at a predetermined pressure to the primary side filled with the heated pure water; (3) A step of detecting, by the detection means, the bubbles leaked to the secondary side filled with the heated pure water; It is a method of carrying out.

[0017] ≪Step (1) and Step (1’)≫ Step (1) is a step of filling all of the primary-side space, the pore space inside the membrane, and the secondary-side space of each hollow fiber membrane module 4, and all inside the piping system including the detection means 5 arranged near the secondary-side space outlet with the heated pure water. In one aspect, instead of step (1), step (1’) can be carried out. Step (1’) is a step of filling all of the primary-side space, the pore space inside the membrane, and the secondary-side space of each hollow fiber membrane module 4, and all inside the piping system including the detection means 5 arranged near the secondary-side space outlet with pure water, and heating the entire system filled with the pure water.

[0018] In this step, first, pure water PW is filled into all of the primary-side space, the pore space inside the membrane, and the secondary-side space of each hollow fiber membrane module 4, and all inside the piping system including the detection means 5 arranged near the secondary-side space outlet. In one aspect, pure water (Pure Water, hereinafter PW) is introduced into the primary-side space of each hollow fiber membrane module 4, and after passing through the primary-side space, it flows into the hollow fiber membrane, and the pure water PW flows from the inside of the hollow fiber membrane toward the outside of the hollow fiber membrane. In one aspect, pure water PW is introduced into the primary side space of each hollow fiber membrane module 4. After passing through the primary side space, it flows into the hollow fiber membrane, and the pure water PW flows from the outside of the hollow fiber membrane toward the inside of the hollow fiber membrane. The pure water PW that has flowed into the inside or outside of the hollow fiber membrane passes through the pore space inside the membrane of the hollow fiber membrane and fills the secondary side space. The pure water PW filled in the secondary side space reaches the detection means 5 arranged near the secondary side space outlet through the pipe 8, thereby filling the entire inside of the piping system. In one aspect, after filling the entire inside of the piping system with pure water PW, heating may be performed by the heater 3, or the pure water heated by the heater 3 may fill the entire inside of the piping system.

[0019] Step (2) is a step of supplying a gas at a predetermined pressure to the primary side filled with the heated pure water. In this step, a leak detection gas (gas, hereinafter referred to as g) is supplied from the gas supply means 6 to the primary side filled with the heated pure water so as to reach a predetermined pressure. Further, the gas g is introduced into the hollow fiber membrane module 4 through the pipe 8. A pressure gauge (not shown) for measuring the pressure of the leak detection gas is provided on the primary side of the hollow fiber membrane module 4.

[0020] Step (3) is a step of detecting, by the detection means 5, the bubbles leaked to the secondary side filled with the heated pure water. To the secondary side of the hollow fiber membrane module 4 filled with the heated pure water, the leak detection means 5 of the hollow fiber membrane is connected through a pipe 8 for recovering the filtrate. In this step, when gas is supplied to the primary side of the hollow fiber membrane module 4 within the range of the predetermined pressure described later, if there are no defects such as breaks or pinholes in the hollow fiber membrane, the gas passes through the hollow fiber membrane and does not flow into the secondary side space. However, if there is a break or the like in the hollow fiber membrane, gas flows into the secondary side space from the break point, and together with the filtrate, it becomes bubbles and is discharged from the pipe 8. When the detection means 5 detects bubbles, it is determined that there is a defect in the hollow fiber membrane, and the filtration by the hollow fiber membrane module 4 is stopped. On the other hand, when the detection means 5 does not detect bubbles, it is determined that there is no defect in the hollow fiber membrane, and the filtration is continued.

[0021] In this embodiment, by filling the entire inside of the piping system with pure water heated to a predetermined temperature, the growth of microorganisms can be suppressed, so the risk of contamination by microorganisms during the leak check of the hollow fiber membrane module 4 is reduced. Further, according to this embodiment, even if a defect is found in the hollow fiber membrane module 4 during the leak check, the risk of contamination by microorganisms on the secondary side is reduced because the secondary side is always filled with heated pure water.

[0022] From the viewpoint of improving the leak detection accuracy of the hollow fiber membrane module 4, the leak detection method of this embodiment may be carried out without performing the filtration process. Further, according to this embodiment, while filtering the water to be treated by the hollow fiber membrane module 4, the leak of the hollow fiber membrane can be detected. Thereby, since leak detection can be carried out while performing filtration, the workability of breakage detection of the hollow fiber membrane module 4 and the production efficiency of purified water are improved.

[0023] ≪Filtration process≫ As shown in FIG. 1, in the water to be treated tank 1, the water to be treated before filtration, that is, before being filtered by the hollow fiber membrane module 4, is stored. The water to be treated tank 1 is connected to the pump 2 via the pipe 8. The pump 2 supplies the water to be treated to the hollow fiber membrane module 4 at a predetermined pressure. The pump 2 is connected to the water supply port side (in one aspect, the primary side) of the hollow fiber membrane module 4 via the pipe 8.

[0024] By passing the water to be treated through the hollow fiber membrane module 4 for filtration, the substances to be separated (in one aspect, suspended substances, microorganisms, etc.) are separated to obtain purified filtrate. At least one hollow fiber membrane is accommodated in the hollow fiber membrane module 4.

[0025] The hollow fiber membrane module 4 is a hollow fiber membrane module including a hollow fiber membrane for filtering the water to be treated and a cylindrical casing (not shown) for housing the hollow fiber membrane. Inside the casing of the hollow fiber membrane module 4, a primary side space on the water to be treated supply port side, an inner pore space of the membrane, and a secondary side space on the filtrate outlet side are formed by the hollow fiber membrane which is a separation membrane.

[0026] The membrane separation by the hollow fiber membrane is performed as follows. The water to be treated supplied from one end face side of the hollow fiber membrane module 4 through the pipe 8 flows through the primary side space and is discharged as a filtrate from the other end face side of the hollow fiber membrane module 4. In one aspect, after the water to be treated passes through the primary side space, it flows into the hollow fiber membrane and flows from the inside of the hollow fiber membrane toward the outside of the hollow fiber membrane. In one aspect, after the water to be treated passes through the primary side space, it flows into the hollow fiber membrane and flows from the outside of the hollow fiber membrane toward the inside of the hollow fiber membrane. The water to be treated flowing into the inside or outside of the hollow fiber membrane passes through the inner pore space of the hollow fiber membrane and is filtered, and seeps into the secondary side space as a filtrate. The filtrate is introduced into the water quality detection means 7 arranged at the secondary side space outlet through the pipe 8, and the water quality is inspected. If the filtrate meets the water quality standard, it is stored in a filtered water tank (not shown), and if it does not meet the water quality standard, it is returned to the water to be treated tank 1 through the pipe 8, and the same filtration is performed again.

[0027] <Hollow fiber membrane module> In one aspect, the hollow fiber membrane module 4 according to the present embodiment includes a primary side space, an inner pore space of the membrane, and a secondary side space by the hollow fiber membrane.

[0028] As the hollow fiber membrane and the casing provided in the hollow fiber membrane module 4, conventionally known ones can be adopted.

[0029] In one aspect, examples of the polymer for forming the hollow fiber membrane include cellulose acetate, polyamide, polyvinyl alcohol, polysulfone, etc., and polysulfone is preferable particularly from the viewpoint of heat resistance temperature. In one aspect, the molecular weight cut-off of the hollow fiber membrane module according to the present embodiment is preferably selected from the range of 3000 or more. In one aspect, the nominal pore size of the hollow fiber membrane module according to the present embodiment is preferably 1.0 μm or less.

[0030] The hollow fiber membrane provided in the hollow fiber membrane module 4 is not particularly limited, and for example, a reverse osmosis membrane, an ultrafiltration membrane, a microfiltration membrane, etc. can be adopted. As the hollow fiber membrane of the present embodiment, a microfiltration (MF) membrane, an ultrafiltration (UF) membrane, etc. are suitable, and an ultrafiltration (UF) membrane is particularly preferable. Also, in one aspect, the hollow fiber membrane can be used for filtration in the production of purified water, and it is particularly preferable to use an ultrafiltration (UF) membrane as the filtration in the final stage of the production of purified water.

[0031] In one aspect, the present embodiment is preferably a method for detecting a leak in the hollow fiber membrane module used in the final stage of the production of purified water. Also, in one aspect, it is preferably a method for detecting a leak in an ultrafiltration (UF) hollow fiber membrane module used in the production of purified water. Furthermore, in one aspect, the present embodiment is more preferably a method for detecting a leak in an ultrafiltration (UF) hollow fiber membrane module used in the final stage of the production of purified water.

[0032] In one aspect, one or more hollow fiber membrane modules 4 can be used in the production of purified water, for example, about 1 to 10 are used. Since the present embodiment has high leak detection accuracy, it is a method capable of detecting leaks in parallel even when a plurality of hollow fiber membrane modules 4 are used.

[0033] (Purified water) The hollow fiber membrane module according to the present embodiment is used in the production of purified water in one aspect. The water to be treated in the present disclosure is high-purity water that can be used for product applications such as industrial use. On the other hand, in pharmaceutical applications, water of higher purity than industrial water is required. Therefore, the water to be treated is passed through the hollow fiber membrane module 4 to obtain a filtrate. In one aspect, the purified water according to this embodiment may be this filtrate.

[0034] In one aspect, the final stage of manufacturing the purified water according to the present disclosure is the stage of passing the water to be treated through the hollow fiber membrane module 4 to produce the purified water as the final product as a filtrate. The purified water of the present disclosure refers to water having a viable count of 100 cfu (colony forming unit) or less per 1 mL. In one aspect, it is preferable that the purified water as the final product (for example, the final product for pharmaceutical use) of the present disclosure has a viable count of 10 cfu or less per 100 mL. In one aspect, as the use of the purified water of this embodiment, water for injection is suitable. When the purified water of this embodiment is water for injection, it is preferable that the viable count in 100 mL of water for injection is 10 cfu or less, more preferably 5 cfu or less, and particularly preferably 1 cfu or less.

[0035] The viable count in the purified water is measured as follows. Collect the purified water, dilute it with physiological saline or the like, inoculate the purified water diluted at each dilution ratio onto the agar medium in a petri dish, and culture it. Select a petri dish in which dozens to hundreds of colonies are formed from the agar medium inoculated with the liquid at each dilution ratio, and count the colonies to determine the viable count in the purified water.

[0036] [Method for manufacturing a hollow fiber membrane module] The method for manufacturing the hollow fiber membrane may be a known method. For example, a hollow fiber membrane can be manufactured by simultaneously discharging the membrane-forming stock solution and the core liquid from a die having a double slit tube structure. Thereafter, after passing through a predetermined water washing step, drying step, and crimping step, it is wound up, cut to an appropriate length, inserted into a case, and the ends are sealed with a potting material to be modularized.

[0037] Examples of the shape of the hollow fiber membrane module include a linear both - ends - open type or a linear one - side - open type.

[0038] (Pure water) The pure water in the present disclosure refers to water purified by treating raw water that has not been purified with activated carbon, reverse osmosis membranes, electrically regenerated ion - exchange resins, etc., and refers to water with the number of viable bacteria in 1 mL of water being 10 cfu or less. In one aspect, the TOC (total organic carbon concentration) in pure water is 500 ppb (500 μg / L) or less. In one aspect, the electrical conductivity of pure water is 10 μS / cm or less.

[0039] From the perspective of suppressing the growth of microorganisms, the temperature of the pure water heated by the heater 3 is preferably 55°C or higher and 95°C or lower, and more preferably 80°C or higher and 95°C or lower. Also, in one aspect, from the perspective of suppressing the growth of microorganisms, it is preferable to fill all of the inside of the piping system with pure water, more preferably to fill all of the inside of the piping system with heated pure water, and particularly preferably to fill all of the inside of the piping system with pure water heated to a predetermined temperature. The leak detection method of the present embodiment only needs to satisfy a predetermined temperature when pure water is introduced into the inside of the piping system.

[0040] (Heating means) The heating means of the present embodiment is for heating the pure water filled in all of the inside of the piping system. The heating means is not particularly limited, and for example, the heater 3 etc. can be exemplified. Specifically, steam (steam, hereinafter s) introduced from outside the piping system is heated by the heater 3, and the pure water is heated by the heated steam. In one aspect, by the heating means of the present embodiment, the pure water may be heated and then the inside of the piping system may be filled with the heated pure water through the pipe 8, or the inside of the piping system may be filled with pure water through the pipe 8 and then the pure water filled in the entire inside of the piping system may be heated. Note that the temperature when heating the pure water is preferably 55°C or higher and 95°C or lower, and more preferably 80°C or higher and 95°C or lower.

[0041] (Gas supply means) The gas supply means 6 of this embodiment is for supplying the gas g for leak detection to the hollow fiber membrane module 4. In one aspect, the gas supply means 6 of this embodiment supplies a gas at a predetermined pressure to the primary side filled with heated pure water. Specifically, the on-off valve provided in the gas supply means 6 is opened to supply gas to the hollow fiber membrane module 4. The gas supply means 6 is not particularly limited, and for example, a compressor and a gas cylinder can be exemplified. Note that as the gas to be supplied to the hollow fiber membrane module 4, a gas that does not cause a chemical reaction with the hollow fiber membrane, such as an inert gas such as air or nitrogen, is preferable. The pressure at the time of supplying the gas is preferably within the range of 5 kPa to 400 kPa.

[0042] (Detection means) The detection means 5 of this embodiment is arranged near the secondary side space outlet. When there is a defect in the hollow fiber membrane, the gas supplied to the primary side moves to the secondary side through the hollow fiber membrane as bubbles. The detection means 5 of this embodiment detects the leak of the hollow fiber membrane by detecting the bubbles that have moved to the secondary side. In one aspect, the detection means 5 detects bubbles by the attenuation or propagation efficiency of ultrasonic waves. Specifically, a clamp-on ultrasonic flowmeter (product name FD-H, manufactured by Keyence Corporation) is used to detect the steepness (peak) of the ultrasonic signal when bubbles due to membrane leakage pass through, thereby detecting the bubbles. In one aspect, the detection means 5 detects bubbles by an image inside the piping system. Specifically, in the detection means 5, an image is taken by a photographing device (product name TG-6, manufactured by Olympus Corporation) equipped with a microscope lens to observe the bubbles. As the detection means 5 of this embodiment, for example, a transparent tube, an ultrasonic flowmeter, an optical sensor, a camera, etc. may be provided.

[0043] Figure 2 is a diagram showing a schematic view of the leak detection method of this embodiment when detecting a leak by an image inside the piping system. Note that parts unnecessary for the description are omitted and only the illustrated parts are shown. Open the on-off valve provided in the gas supply means 6, supply gas to the hollow fiber membrane module 4, and then close the on-off valve. Take an internal image of the pipe 8 with the imaging device provided in the detection means 5, and detect a leak in the hollow fiber membrane module 4 by checking for the presence or absence of air bubbles in the internal image of the pipe 8.

[0044] Regarding the leak detection method of this embodiment, for a plurality of hollow fiber membrane modules 4, if one or more detection means 5 are provided, a leak check of the hollow fiber membrane can be carried out. Also, from the viewpoint of improving the accuracy of the leak check, it is preferable to carry out leak detection with a device system in which the detection means 5 is provided for each of the plurality of hollow fiber membrane modules 4.

[0045] (Water quality inspection means) The water quality inspection means 7 of this embodiment is arranged at the secondary side space outlet and is for inspecting the water quality of the filtrate introduced through the pipe 8. The water quality inspection means 7 is not particularly limited, and for example, a water quality measuring instrument etc. can be exemplified.

Example

[0046] Hereinafter, preferred embodiments of the present invention will be exemplarily and specifically described. However, the materials, contents, etc. described in this embodiment are not intended to limit the scope of the present invention only to them without particularly limiting descriptions, and are merely illustrative examples.

[0047] Inner diameter 0.8 mm, membrane area 4.7 m 2 A polysulfone ultrafiltration (UF) hollow fiber membrane module (product name: Microza VIP-3017, manufactured by Asahi Kasei Corporation) made of a polysulfone hollow fiber membrane with a molecular weight cut-off of 6000 was used.

[0048] Pure water PW and industrial water were each treated with a unit device (product name: 0600SHE, manufactured by Miura Industry Co., Ltd.) of a reverse osmosis membrane and an electrically regenerated ion exchange resin to obtain purified water of a desired water quality. The water quality of pure water PW was an electrical conductivity of 1.0 μS / cm and a TOC (organic matter concentration in pure water PW) of 50 μg / L. Also, the viable count in 1 mL of pure water PW was 1 cfu or less. The water quality of industrial water was an electrical conductivity of 180 μS / cm and a TOC (organic matter concentration in industrial water) of 1000 μg / L. Also, the viable count in 1 mL of industrial water was 100 cfu or less. Note that the electrical conductivities of the pure water PW and industrial water used for leak detection in this embodiment were measured with a HE-480C (manufactured by Horiba, Ltd.) under the condition of a water temperature of 25°C. The TOC in the pure water PW and industrial water was measured with a TOC5000A (manufactured by Shimadzu Corporation) under the condition of a water temperature of 25°C. The viable counts of the pure water PW and industrial water used for leak detection in this embodiment were measured as follows. The pure water and industrial water were sampled, diluted with physiological saline, etc., and the diluted pure water and industrial water at each dilution ratio were inoculated onto an agar medium in a petri dish and cultured. From the agar medium inoculated with the liquid at each dilution ratio, a petri dish in which dozens to hundreds of colonies were formed was selected, and the viable count in the pure water and industrial water was determined by counting the colonies.

[0049] As the hollow fiber membrane module 4, a hollow fiber membrane module having defects (defective product) and a hollow fiber membrane module without defects (non-defective product) were used. Using the leak detection device shown in FIG. 1, a polysulfone ultrafiltration (UF) hollow fiber membrane module 4 was subjected to a leak test by the method of this embodiment, and then the viable count in the filtrate was measured.

[0050] <Measurement of viable count in filtrate> The filtrate was sampled, diluted with physiological saline, etc., and the purified water diluted at each dilution ratio was inoculated onto an agar medium in a petri dish and cultured. From the agar medium inoculated with the liquid at each dilution ratio, a petri dish in which dozens to hundreds of colonies were formed was selected, and the viable count in the purified water was determined by counting the colonies.

[0051] (Example 1-1) Pure water PW was introduced into the entire piping system including the primary-side space, the intra-membrane pore space, the secondary-side space, and the detection means 5 from the inside of the hollow fiber membrane of a single good hollow fiber membrane module 4 toward the outside of the hollow fiber membrane through the pipe 8. The steam s introduced from outside the piping system was heated by the heater 3, and the pure water introduced into the entire piping system by the heated steam s was heated to 80 °C.

[0052] A compressor that supplies air was used as the gas supply means 6. The on-off valve provided in the gas supply means 6 was opened, and compressed air with a dew point of -25 °C was supplied from the compressor to the hollow fiber membrane module 4. The pressure of the air was pressurized so that the value measured by the pressure gauge was 300 kPa.

[0053] A clamp-on type ultrasonic flowmeter (product name FD-H, manufactured by Keyence Corporation) was used as the detection means 5. Detection of bubbles using ultrasonic waves, where the filtrate and the detection means 5 are non-contact, was carried out by the following method. The detection means 5 was attached to one location outside the pipe 8, and bubbles were detected by detecting the sharpness (peak) of the ultrasonic signal when bubbles passed through due to membrane leakage. As a result, since the sharpness of the ultrasonic signal was not detected, no bubbles were confirmed and no membrane leakage was detected. Also, when the viable bacteria count in the filtrate was measured, it was 0 cfu in 100 mL of the filtrate.

[0054] (Example 1-2) Detection of membrane leakage was performed in the same manner as in Example 1-1, except that an imaging device equipped with a microscope lens (product name TG-6, manufactured by Olympus Corporation) was used as the detection means 5 to take an image of the inside of the pipe. As a result, no bubbles were confirmed in the image and no membrane leakage was detected. Also, when the viable bacteria count in the filtrate was measured, it was 0 cfu in 100 mL of the filtrate.

[0055] (Example 2-1) The detection of membrane leakage was performed in the same manner as in Example 1-1, except that the defective hollow fiber membrane module 4 was used. As a result, since the sharpness of the ultrasonic signal was detected by the detection means 5, bubbles were confirmed and membrane leakage could be detected. When the viable cell count in the filtrate was measured, it was 0 cfu in 100 mL of the filtrate.

[0056] (Example 2-2) The detection of membrane leakage was performed in the same manner as in Example 1-2, except that the defective hollow fiber membrane module 4 was used. As a result, bubbles were confirmed in the image and membrane leakage could be detected. When the viable cell count in the filtrate was measured, it was 0 cfu in 100 mL of the filtrate.

[0057] (Example 3-1) The detection of membrane leakage was performed in the same manner as in Example 2-1, except that the heating temperature of the pure water introduced into all of the piping systems was changed from 80°C to 55°C. As a result, since the sharpness of the ultrasonic signal was detected by the detection means 5, bubbles were confirmed and membrane leakage could be detected. When the viable cell count in the filtrate was measured, it was 3 cfu in 100 mL of the filtrate.

[0058] (Example 3-2) The detection of membrane leakage was performed in the same manner as in Example 2-2, except that the heating temperature of the pure water introduced into all of the piping systems was changed from 80°C to 55°C. As a result, bubbles were confirmed in the image and membrane leakage could be detected. When the viable cell count in the filtrate was measured, it was 3 cfu in 100 mL of the filtrate.

[0059] (Example 4-1) The detection of membrane leakage was performed in the same manner as in Example 2-1, except that one defective hollow fiber membrane module 4 and two non-defective hollow fiber membrane modules 4 were used, and the detection means 5 was arranged at three locations for each hollow fiber membrane module 4. As a result, since a sharpness of the ultrasonic signal was detected in the detection means 5 near the defective hollow fiber membrane module 4, bubbles were confirmed and membrane leakage could be detected. Note that since no sharpness of the ultrasonic signal was detected in the two detection means 5 near the non-defective hollow fiber membrane module 4, no bubbles were confirmed and no membrane leakage was detected. Further, when the viable cell count in the filtrate was measured, it was 0 cfu in 100 mL of the filtrate.

[0060] (Example 4-2) Membrane leakage was detected in the same manner as in Example 2-2, except that one defective hollow fiber membrane module 4 and two non-defective hollow fiber membrane modules 4 were used, and the detection means 5 was arranged at three locations for each hollow fiber membrane module 4. As a result, bubbles were confirmed in the image taken by the detection means 5 near the defective hollow fiber membrane module 4, and membrane leakage could be detected. Note that no bubbles were confirmed in the images taken by the two detection means 5 near the non-defective hollow fiber membrane module 4, and no membrane leakage was detected. Further, when the viable cell count in the filtrate was measured, it was 0 cfu in 100 mL of the filtrate.

[0061] (Comparative Example 1) Membrane leakage was detected in the same manner as in Example 2-1, except that the heating temperature of the pure water PW was set to 50°C. As a result, since a sharpness of the ultrasonic signal was detected in the detection means 5, bubbles were confirmed and membrane leakage could be detected. Further, when the viable cell count in the filtrate was measured, it was 12 cfu in 100 mL of the filtered water.

[0062] (Comparative Example 2) Membrane leakage was detected in the same manner as in Example 2-1, except that the pure water PW was changed to industrial water. As a result, since a sharpness of the ultrasonic signal was detected in the detection means 5, bubbles were confirmed and membrane leakage could be detected. When the viable cell count in the filtrate was measured, it was 15 cfu in 100 mL of the filtered water.

[0063] (Comparative Example 3) The membrane leak was detected in the same manner as in Example 4-1, except that the detection means 5 was not arranged for each hollow fiber membrane module 4. As a result, for the defective hollow fiber membrane modules 4, bubbles were confirmed due to the sharpness of the ultrasonic signal, and membrane leaks could be detected. However, multiple leak inspections were required to identify the hollow fiber membrane modules with membrane leaks. Also, when the viable bacteria count in the filtrate was measured, it was 0 cfu in 100 mL of the filtrate.

[0064] According to Comparative Example 1, since the entire internal piping system was filled with pure water heated outside the predetermined temperature range, the growth of microorganisms could not be suppressed, and the risk of contamination of the filtrate by microorganisms during the leak check of the hollow fiber membrane module could not be reduced. Also, according to Comparative Example 2, since the entire internal piping system was filled with water other than pure water, the growth of microorganisms could not be suppressed, and the risk of contamination of the filtrate by microorganisms during the leak check of the hollow fiber membrane module could not be reduced. Furthermore, according to Comparative Example 3, since the detection means was not provided for each hollow fiber membrane module, in order to detect the defective hollow fiber membrane modules from among a plurality of hollow fiber membrane modules, leak checks had to be performed for the number of hollow fiber membrane modules used in the filtration. Also, since multiple leak checks were required, the time for which the hollow fiber membrane modules were exposed to air became longer, and there was also a risk that the hollow fiber membranes would dry out.

[0065] According to Examples 1 to 4, by filling the entire internal piping system with pure water heated to a predetermined temperature, the growth of microorganisms could be suppressed, and thus the risk of contamination of the filtrate by microorganisms during the leak check of the hollow fiber membrane module could be reduced. Also, according to Examples 2 to 4, even if a defect was found in the hollow fiber membrane module during the leak check, the risk of contamination of the filtrate by microorganisms on the secondary side could be avoided because the pure water heated on the secondary side was always filled. Furthermore, since the viable cell count in 100 mL of the filtrate treated in Examples 1 to 4 was 5 cfu or less, it was suitable as a method for detecting leaks in the hollow fiber membrane module used for the production of water for injection, which is the final product for pharmaceutical use. In addition, according to Example 4, since each hollow fiber membrane module was provided with a detection means, it was possible to detect a defective hollow fiber membrane module among a plurality of hollow fiber membrane modules at the time of the first leak check.

Explanation of symbols

[0066] 1 Water tank to be treated 2 Pump 3 Heater 4 Hollow fiber membrane module 5 Detection means 6 Gas supply means 7 Water quality inspection means 8 Pipe g Gas s Steam PW Pure water

Claims

1. A method for detecting leaks in a hollow fiber membrane module used for producing purified water, comprising the following steps: Filling all of the primary side space, the pore space inside the membrane, and the secondary side space of each hollow fiber membrane module, as well as the entire piping system including the detection means arranged near the outlet of the secondary side space, with heated pure water; or alternatively, instead of this step, filling all of the primary side space, the pore space inside the membrane, and the secondary side space of each hollow fiber membrane module, as well as the entire piping system including the detection means arranged near the outlet of the secondary side space, with pure water, and heating the entire system filled with the pure water; Supplying a gas at a predetermined pressure to the primary side filled with the heated pure water; and Detecting, by the detection means, the bubbles that have leaked to the secondary side filled with the heated pure water; A leak detection method comprising the above steps.

2. The leak detection method according to claim 1, wherein the temperature of the heated pure water is 55°C or higher and 95°C or lower.

3. The leak detection method according to claim 2, wherein the temperature of the heated pure water is 80°C or higher and 95°C or lower.

4. The leak detection method according to any one of claims 1 to 3, wherein the detection means detects bubbles by ultrasonic attenuation or propagation efficiency.

5. The leak detection method according to any one of claims 1 to 3, wherein the detection means detects bubbles based on an image inside the piping system.

6. The leak detection method according to any one of claims 1 to 3, wherein leak detection is carried out using a device system provided with the detection means for each of a plurality of hollow fiber membrane modules.

7. The leak detection method according to any one of claims 1 to 3, wherein the purified water is water for injection.

8. The leak detection method according to any one of claims 1 to 3, wherein leak detection of the hollow fiber membrane module is carried out while performing filtration by the hollow fiber membrane module.

9. A leak detection device for detecting leaks in a hollow fiber membrane module used for producing purified water, comprising a heating means, a gas supply means, a detection means, a pump, and a piping system connecting these; the pump fills all of the primary side space, the pore space inside the membrane, and the secondary side space of each hollow fiber membrane module, as well as the entire piping system including the detection means arranged near the outlet of the secondary side space, with pure water; the heating means is a means for heating the pure water filled in all of the piping system; The gas supply means is means for supplying a gas at a predetermined pressure to a primary side filled with the heated pure water, and The leak detection device, wherein the detection means is means for detecting bubbles leaked to a secondary side filled with the heated pure water. **Claim 10** The leak detection device according to claim 9, wherein the heating means heats the pure water to 55°C or higher and 95°C or lower. **Claim 11** The leak detection device according to claim 10, wherein the heating means heats the pure water to 80°C or higher and 95°C or lower. **Claim 12** The leak detection device according to any one of claims 9 to 11, wherein the detection means detects bubbles by ultrasonic attenuation or propagation efficiency. **Claim 13** The leak detection device according to any one of claims 9 to 11, wherein the detection means detects bubbles by an image inside the piping system. **Claim 14** The leak detection device according to any one of claims 9 to 11, comprising the detection means for each of a plurality of hollow fiber membrane modules. **Claim 15** The leak detection device according to any one of claims 9 to 11, wherein the purified water is water for injection. **Claim 16** The leak detection device according to any one of claims 9 to 11, wherein leak detection of the hollow fiber membrane module is carried out while performing filtration by the hollow fiber membrane module.

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