JP2002320829A - Method for inspecting perfectibility of membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which perfectibility of a membrane module is more accurately inspected because a bubble leak in inspection due to defective wetting of membranes is not caused without using liquid chemicals of high concentration. SOLUTION: In the method for inspecting perfectibility of a membrane module 4, gaseous CO2 is substituted for the residual air in the membrane module 4 and water or water-containing liquid is filtered with the membrane module 4 or the membrane module is dipped in water or water-containing liquid and gaseous CO2 is substituted for the residual air in the membrane module, and then gas pressure is applied to the membrane module.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to purification of tap water such as well water and tap water, purification of sewage such as domestic wastewater and industrial wastewater,
The present invention relates to a method for inspecting the integrity of a membrane module used in an industrial process such as a pharmaceutical industry, an electronics industry, and a food industry.

[0002]

2. Description of the Related Art A microfiltration module is 10 μm or less.
In particular, it is a membrane module for efficiently removing fine particles and microorganisms of 1 μm or less, and has been widely used for various purposes. As a form of this microfiltration module,
In order to increase the membrane area and facilitate handling, a hollow fiber membrane module in which a hollow fiber membrane is formed in a cylindrical or screen shape, a pleated membrane module in which a flat membrane is pleated and formed into a cylindrical shape, There is a flat membrane module in which a flat membrane is formed in a screen shape.

[0003] In order to guarantee the separation performance, the microfiltration module is usually used to confirm whether there is no defect such as a pinhole in the microfiltration membrane and whether there is a defective seal at the bonded portion before use. An inspection is performed. As one of the integrity checking methods, there is a "bubble point method".

FIG. 3 is a schematic diagram showing the principle of the inspection method based on the bubble point method. As shown in FIG. 3, assuming a cylindrical capillary tube 1 as a pore model of a microfiltration membrane and placing it in a liquid tank 2, the following equation holds for the capillary phenomenon. ρh = 2σ cos θ / r In the above equation, r is the radius of the capillary, ρ is the specific gravity of the liquid,
h represents the height of the liquid ascending the capillary, σ represents the surface tension of the liquid, and θ represents the contact angle between the liquid and the microfiltration membrane.
The product of the height h of the raised liquid 3 and the specific gravity ρ is the capillary 1
Is equal to the capillary force per unit area, ie, the pressure p, and the following equation holds. p = ρh Therefore, the following relationship holds. d = 4σcos θ / p In the above equation, d represents the diameter of the capillary. Here, when the gas pressure p which overcomes this capillary force is applied, the capillary 1
The liquid 3 inside is pushed out, and gas is blown out from the capillary. The gas pressure p is the diameter d of the capillary 1
Gas is first blown out of the capillary tube having the largest diameter. The gas pressure p at this time is the “bubble point”. If a large diameter hole such as a pinhole is present in the microfiltration membrane, the bubble point is lower than that of a normal microfiltration membrane, and it is possible to detect an abnormality.

[0005] The "diffusion flow method" is generally used for integrity testing of microfiltration modules having large membrane areas. Even if a gas pressure lower than the bubble point is applied to the microfiltration membrane that is wet with the liquid and the pores are filled with the liquid, the liquid remains in the pores and keeps the pores closed. However, according to Henry's law, a gas dissolves in a liquid in proportion to its absolute pressure. Therefore, a difference occurs in the concentration of the gas that can be dissolved in the liquid between the entrance and the exit of the pore, and the gas dissolved at the entrance of the pore diffuses and reaches the exit side of the pore, where it is vaporized. In other words, the microfiltration membrane whose pores are completely filled with the liquid allows a small amount of gas to permeate even when a gas pressure lower than the bubble point is applied. The gas permeation flow rate (diffusion flow rate) Q follows the following equation. Q = DHPSφC / L In the above equation, H is the solubility of the gas in the liquid, D is the diffusion coefficient of the gas in the liquid, φ is the porosity of the film, L is the thickness of the film, S is the film area, and P is the film. Pressure difference between the primary and secondary sides of C
Is a coefficient due to the module structure.

Although the amount of permeation is difficult to measure with a small membrane area, it can be easily detected with a microfiltration module having a large membrane area. Further, if the structure of the microfiltration module is the same, a constant amount of permeation can be obtained. If the diffusion flow rate Q of the defect-free microfiltration module is known in advance,
By measuring the amount of gas permeation by applying a gas pressure slightly lower than the bubble point, it is possible to determine the presence or absence of gas permeation from a defective portion in addition to gas permeation by diffusion.

[0007] A "pressure retention method" is also used for integrity testing of microfiltration modules having large membrane areas. This method is similar in principle to the "diffusion flow method", except that a gas pressure lower than the bubble point is applied to the primary side of the membrane that is wetted with liquid and the pores are closed, and then the gas is supplied. This is a method of stopping and measuring the pressure drop for a predetermined time. The gas dissolves and diffuses in the liquid and penetrates from the higher pressure to the lower pressure, so that the pressure decreases in proportion to the amount of the diffused gas. Thus, a defect-free microfiltration module of the same structure will have a certain amount of pressure drop, and if it has a defect, it will have a greater pressure drop than a defect-free one.

[0008]

As described above, in the integrity inspection of the microfiltration module, the pores of the microfiltration membrane are filled with the liquid and the gas pressure is applied, and the permeation pressure and the permeation amount of the gas are measured. Measure. Therefore, if there is a portion of the pores of the microfiltration membrane that is not filled with the liquid, a large amount of gas permeates at a low pressure, and accurate measurement cannot be performed. In the microfiltration module, since many membranes are filled in a certain volume, when the microfiltration membrane is wet, air bubbles may interfere and create a place where the liquid does not get wet.
In particular, water, which is often used as a liquid, has a high surface tension, so that it is difficult for bubbles to escape.

For this reason, in JIS K3832 “Method for testing bubble point of microfiltration membrane element and module”, while discharging air from the primary side of the housing, a filtration differential pressure of 29.4 to 98.0 kPa is applied to the liquid to apply liquid. A method of wetting while filtering is proposed. However, even if the liquid is filtered under such conditions, the liquid cannot always be completely wetted, and the fluctuation may occur because the bubble point value becomes smaller than the original value or the diffusion flow rate becomes larger than the original value. It tends to be large. Therefore, there is a risk that a poor wetting and a defect of the microfiltration membrane cannot be distinguished, and a non-defective product is regarded as a defective product, and conversely, a defective product is mistaken for a non-defective product.

Therefore, a method has been proposed in which a chemical such as ethanol having a lower surface tension than water is used as a liquid for wetting the film. By using such a chemical solution, it is possible to completely wet the film, but depending on the type and concentration of the chemical solution used, there is a problem that the module component member is not applicable because it is not resistant, and there is also a problem that the chemical solution cost increases. is there.

The present invention has been made in view of such problems of the prior art, and has as its object to eliminate the use of a high-concentration chemical solution and to prevent air bubbles from leaking due to poor wetting of a film. It is an object of the present invention to provide a method for performing a more accurate inspection of the integrity of a membrane module.

[0012]

According to the present invention, the air remaining in the membrane module is replaced with carbon dioxide gas, and then water or a liquid containing water is filtered by the membrane module. A method for inspecting the integrity of a membrane module, comprising inspecting the integrity of the module.

Further, according to the present invention, the membrane module is immersed in water or a liquid containing water, and the air remaining in the membrane module is replaced with carbon dioxide gas. This is a method for inspecting the integrity of a membrane module, which comprises inspecting.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, there is no particular limitation on a method for replacing air remaining in a membrane module with carbon dioxide gas. For example, the membrane module may be left alone in a carbon dioxide gas atmosphere, but a simple method is to use a carbon dioxide gas cylinder while continuously supplying carbon dioxide gas from the primary or secondary side of the membrane module to replace the module. Is mentioned.

In the present invention, when filtration is performed with a membrane module or when a membrane module is immersed, water or a liquid containing water is used. The liquid containing water is a mixed solution of a liquid soluble in water and water. The surface tension of the liquid containing water is lower than that of water. In the present invention, the membrane can be sufficiently wetted with water by substituting with carbon dioxide and further filtering.However, by using a liquid containing water, the membrane can be more effectively reduced, for example, in a shorter time. Can be wet. A mixture of water and one or more solvents selected from the group consisting of ethanol, butanol, propanol, and methanol, and the like, may be used. Propanol and butanol may be isomers. The surface tension of water is 72 dyn / cm. For example, the surface tension of a mixed solution of water and ethanol is 56 dyn / cm (ethanol concentration: 5 vol%). As described above, since the liquid containing water has a lower surface tension than water, the film is easily wetted.
In the liquid containing water, the ratio between the water-soluble liquid and water may be appropriately determined as desired. Further, the proportion of the water-soluble liquid dissolved in water may be a part.

There are no particular restrictions on the water used,
It is preferable to use degassed water from which dissolved gases in water have been removed. If gas is dissolved in the water to be used, the air remaining inside the membrane module is replaced with carbon dioxide, and then the dissolved gas in the water exchanges gas with carbon dioxide. For example, when it takes a long time to perform the treatment, the solubility of the bubbles in water may decrease. Therefore, it is preferable to use degassed water.

The method of filtering water or a liquid containing water by the membrane module may be a pressurization method or a suction method, and can be appropriately selected according to the type of the membrane module.

In the present invention, gas pressure is applied to the membrane module to check for the generation of bubbles from the membrane module. As the gas pressure, a pressure lower than the bubble point of the membrane is applied. The type of gas is not particularly limited, and for example, air, oxygen, nitrogen, or the like can be used. Examples of the method for inspecting the generation of bubbles include the above-described “pressure holding method”, “diffusion flow method”, visual observation, sound wave measurement, and the like.

In the integrity inspection method of the present invention, since the pores of the membrane can be completely filled in advance with the liquid, there is no bubble leakage at the time of inspection due to poor wetting of the membrane as in the prior art. Accurate inspection is possible regardless of the above.
As described above, the integrity test of a conventionally known microfiltration module is a method of measuring the permeation pressure and permeation amount of a gas by filling pores of a microfiltration membrane with a liquid and applying gas pressure. . Therefore, the method for testing the integrity of a membrane module according to the present invention is particularly useful as a test for checking the integrity of a microfiltration module.

The structure of the microfiltration module is not particularly limited as long as the membrane is a microfiltration membrane. For example, a hollow fiber membrane module having a hollow fiber membrane formed into a cylindrical shape, a screen shape, or the like, or a flat membrane having a pleated shape is used. And a pleated membrane module formed into a cylindrical shape, a flat membrane module formed from a flat membrane in a screen shape, and the like. As a microfiltration membrane,
As long as it has a pore diameter of about 0.01 to 10 μm, there are no particular restrictions on its form, structure, dimensions, material, etc., and it can be applied to various conventionally known microfiltration membranes. As the material of the hollow fiber membrane, for example, polyolefin, polysulfone, polyvinyl alcohol, cellulose, polyacrylonitrile, polyamide, polyimide,
Examples include polytetrafluoroethylene and polyvinylidene fluoride. Further, the hydrophobic hollow fiber membrane used for water filtration can be used after being subjected to a hydrophilic treatment.

Hereinafter, the integrity inspection method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram for explaining an example of the integrity inspection method of the present invention. The inspection line is roughly composed of a membrane module 4, a raw water pump 5, a raw water tank 6, a gas supply line 14, and a discharge line 12. The membrane module 4 is a pressurized hollow fiber membrane module. An element formed by fixing an end of a hollow fiber membrane 7 at a potting section 8 is accommodated in a housing 9.
The housing 9 has a raw water inlet 10 and a filtered water outlet 11, and a raw water side switching valve 13 is provided between the raw water inlet 10 and the discharge line 12.
A filtered water switching valve 15 is provided between the gas supply line 14 and the gas supply line 14. A pressure gauge 16 is mounted near the outlet of the filtered water.

First, the raw water side switching valve 13 is directed toward the discharge line 12 and the filtered water side switching valve 15 is directed toward the gas supply line 14. Then, a carbon dioxide gas is supplied from the gas supply line 14 to the membrane module 4, and the air remaining inside the membrane module 4 is replaced with the carbon dioxide gas.
Regarding the conditions for supplying carbon dioxide gas, it is preferable to increase the pressure and lengthen the time in order to completely replace the air,
In consideration of the pressure resistance and workability of the membrane module, the supply pressure is preferably 1 to 500 kPa and the supply time is preferably about 10 seconds to 30 minutes. A more preferable supply pressure is 1 to 300 kPa, and a more preferable supply time is 10 seconds to 10 minutes.

After the supply of the carbon dioxide gas is completed, the raw water side switching valve 13 is directed toward the raw water inlet 10 and the filtered water side switching valve 15 is directed toward the filtered water outlet 11. Next, the raw water pump 5 is started, the raw water in the raw water tank 6 is circulated through the membrane module 4, and the raw water is filtered by the membrane module 4. Water or a liquid containing water is used as raw water. By performing the filtration, air bubbles remaining on the membrane wall of the hollow fiber membrane and the like are easily removed. In addition, the bubbles remaining on the film wall and the like are carbon dioxide gas, and since the carbon dioxide gas has a higher solubility in water than air, the carbon dioxide gas in the form of bubbles easily dissolves in water to completely wet the film. be able to. Regarding the conditions for performing filtration, it is preferable to increase the filtration flux early and to increase the time in order to completely dissolve the carbon dioxide gas in water.
In consideration of clogging and workability of the membrane module, a filtration flux of 0.1 to 3 m / d and a filtration time of about 30 seconds to 30 minutes are preferable. A more preferred filtration flux is 0.1 to 2 m / d, and a more preferred filtration time is 30 seconds to 20 minutes.

After completion of the above-mentioned filtration, an integrity check is performed.
Hereinafter, the procedure of the integrity test by the “pressure holding method” will be described. The raw water side switching valve 13 is directed toward the discharge line 12 to discharge water outside the hollow fiber membrane in the membrane module 4.
Next, a pressurized gas is supplied from the gas supply line 14 to increase the pressure in the hollow portion of the hollow fiber membrane 7 to a set value. Thereafter, the filtered water side switching valve 15 is closed, and the pressure change for a predetermined time is measured by the pressure gauge 16. Measure.

As the gas pressure, when the membrane is a microfiltration membrane, the pressure may be lower than the bubble point of the microfiltration membrane. The time may be appropriately selected depending on the size and shape of the membrane module. However, if the time is too long, there is a risk that the microfiltration membrane dries and bubbles may leak again.
The pressure is preferably set to about 00 kPa and the time is about 30 seconds to 20 minutes, more preferably 1 to 300 kPa, and more preferably 30 seconds to 10 minutes. As the gas, for example, air, nitrogen gas, oxygen gas, or the like can be used.

If the integrity test is performed at a pressure below the bubble point of the microfiltration membrane after the membrane has been completely wetted, a certain amount of pressure drop will occur in the defect free microfiltration module. Thus, if a greater pressure drop occurs than a defect-free microfiltration module of the same structure, the microfiltration module can be considered defective.

In the above-described example, the water outside the hollow fiber membrane in the membrane module is discharged and the gas pressure is applied to the hollow part. However, the integrity inspection method of the present invention is not limited to this. For example, it may be carried out without discharging water in the membrane module, or gas pressure may be applied to the outside of the hollow fiber membrane. Further, in the above-described example, the integrity test was performed by the “pressure holding method”, but the integrity test method of the present invention is not limited to this. For example,
The integrity test may be performed by a “diffusion flow method” in which a constant gas pressure is applied to the membrane module to measure the diffusion flow rate.

Next, a case where a hollow fiber membrane module of the immersion suction type is used as the membrane module will be described. FIG. 2 is a schematic diagram for explaining an example of such an integrity inspection method of the present invention. The inspection line is roughly composed of a membrane module 4, a raw water pump 5, a raw water tank 6, a gas supply line 14, and a filtration line 17. The membrane module 4 is formed by fixing both ends of a hollow fiber membrane 7 to a potting section 8. In addition, the membrane module 4 is connected to the filtration line 17, and the filtration water side switching valve 1 on the way.
5 is connected to a gas supply line 14.

First, the membrane module 4 is placed in the raw water tank 6
Immerse in the water inside. As a result, most of the air remaining inside the membrane module is pushed out and replaced by the water. The immersion time may be appropriately selected depending on the size and shape of the membrane module, but is usually 1 to 30 minutes.
When a liquid containing water is used as raw water, the immersion time is usually 1 to 3 because the film is easily wetted and the immersion time can be shortened.
It takes about 20 minutes.

Next, pipes are connected, the filtered water side switching valve 15 is directed toward the gas supply line 14, and carbon dioxide gas is supplied from the gas supply line 14 to the membrane module 4.
As a result, air remaining on the membrane wall or the like of the hollow fiber membrane due to poor wetting and serving as a gas passage is replaced with carbon dioxide gas. At this time, fine bubbles of carbon dioxide gas are leaked from the site. The supply conditions of the carbon dioxide gas may be the same pressure and time as in the example described with reference to FIG.

After the supply of the carbon dioxide gas is completed, the filtered water side switching valve 15 is directed to the filtration line 17, then the raw water pump 5 is started, and the raw water in the raw water tank 6 is filtered by the membrane module 4. The conditions for the filtration may be the same filtration flux and time as in the example described with reference to FIG. This filtration operation allows the membrane to be completely wetted.

After the filtration, the filtered water side switching valve 1
5 is directed to the gas supply line 14 side, and then pressurized gas is supplied from the gas supply line 14 to apply gas pressure from the hollow portion of the hollow fiber membrane. As a method of the integrity test, the above-mentioned “pressure holding method” or “diffusion flow method” can be used.However, in the case of the immersion suction type membrane module as in this example, the hollow fiber membrane is not used. Because it is exposed, the generation of bubbles from the damaged portion of the membrane can be visually inspected.

[0033]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

<Production Example of Hollow Fiber Membrane Modules 1-4> As a filtration membrane, a hydrophilic polyethylene porous hollow fiber membrane (EX410TS manufactured by Mitsubishi Rayon Co., Ltd., average pore size 0.1 μm)
m, inner diameter 270 μm, outer diameter 410 μm).
A microfiltration module 1 (membrane area 10 m ² ) having the structure shown in FIG. Further, a screen-shaped microfiltration module 2 (membrane area: 5.6 m ² ) having a structure as shown in FIG. 2 was prepared using the same hollow fiber membrane.

As the filtration membrane, a hydrophilic polyvinylidene fluoride porous hollow fiber membrane (average pore diameter: 0.1 μm, inner diameter: 8 μm) was used.
(00 μm, outer diameter 1250 μm), a screen-shaped microfiltration module 3 (membrane area 5.6 m ² ) having the structure shown in FIG. 2 was produced.

As a filtration membrane, a polyethylene porous hollow fiber membrane (EHF410TA manufactured by Mitsubishi Rayon Co., Ltd., average pore diameter 0.1 μm, inner diameter 270 μm, outer diameter 410 μm)
Was used to produce a screen-shaped microfiltration module 4 (membrane area: 5.6 m ² ) having a structure as shown in FIG.

<Example 1> Cylindrical microfiltration module 1
Using (membrane material: hydrophilic polyethylene), an integrity test was performed as follows using the test line shown in FIG. Water was used as raw water. First, carbon dioxide was supplied to the microfiltration module, and the air remaining inside was replaced with carbon dioxide (pressure 50 kPa, time 5 minutes). Subsequently, pressure filtration is performed (filtration flux 0.5 m / d, time 15 minutes). After the filtration is completed, water outside the hollow fiber membrane is discharged, and the water is discharged to the hollow side of the hollow fiber membrane in accordance with the "pressure keeping method". Pressurized air (pressure 100kP
An integrity check was performed by feeding a) and measuring the pressure drop after 5 minutes. Table 1 shows the results.

<Example 2> As a raw water, a mixed solution of water and ethanol (ethanol concentration: 10 vol.) Was used instead of water.
%) And the integrity test was performed in the same manner as in Example 1 except that the filtration time was set to 10 minutes. Table 1 shows the results.

Example 3 Using a screen-shaped microfiltration module 2 (membrane material: hydrophilic polyethylene), FIG.
The integrity test was carried out as follows using the test line shown in FIG. First, the microfiltration module was immersed in water for 5 minutes. Next, carbon dioxide gas was supplied to the hollow portion side of the hollow fiber membrane, and the air remaining inside was replaced with carbon dioxide gas (pressure 5).
0 kPa, time 5 minutes). Next, suction filtration is performed (filtration flux: 0.5 m / d, time: 15 minutes), and after completion of the filtration, pressurized air (pressure: 50 kPa, time: 5 minutes) is supplied to visually check for air bubble leakage from the hollow fiber membrane module. Inspection by
An integrity check was performed. Table 2 shows the results.

Example 4 Instead of water, a mixed solution of water and ethanol (ethanol concentration: 10 vol) was used as raw water.
%) And the integrity test was carried out in the same manner as in Example 3 except that the filtration time was set to 10 minutes. Table 2 shows the results.

Example 5 The same as Example 4 except that a mixed solution of water and 1-propanol (concentration of 1-propanol: 10 vol%) was used as raw water instead of a mixed solution of water and ethanol. And an integrity check was performed.
Table 2 shows the results.

<Embodiment 6> A screen-type microfiltration module 3 is used instead of the screen-type microfiltration module 2.
An integrity test was performed in the same manner as in Example 4, except that (membrane material: hydrophilic polyvinylidene fluoride) was used.
Table 2 shows the results.

<Embodiment 7> A screen-type microfiltration module 4 is used instead of the screen-type microfiltration module 2.
Example 4 was repeated except that the ethanol concentration of the mixed solution was changed to 35 vol% using (membrane material: polyethylene).
An integrity check was performed as described above. Table 2 shows the results.

<Comparative Example 1> An integrity test was performed in the same manner as in Example 1 except that carbon dioxide gas substitution was not performed. Table 1 shows the results.

<Comparative Example 2> An integrity test was performed in the same manner as in Example 2 except that the module was filled with raw water without performing filtration. Table 1 shows the results
Shown in

<Comparative Example 3> An integrity test was performed in the same manner as in Example 3 except that the filtration was not performed. Table 2 shows the results.

<Comparative Example 4> An integrity test was performed in the same manner as in Example 4 except that the carbon dioxide gas substitution was not performed. Table 2 shows the results.

[0048]

[Table 1]

[0049]

[Table 2]

The hollow fiber membrane modules of Comparative Examples 1 to 4 were completely hydrophilized with ethanol for confirmation, and re-examined. In this case, the generation of bubbles from the hollow fiber membrane and the like disappeared. It was confirmed. Thereby, Comparative Examples 1 to 4
It can be seen that the bubble generation and the pressure drop are caused by insufficient wetting of the film. That is, from the results shown in Tables 1 and 2, it can be seen that in the example, no bubbles were generated in the integrity test, the film was completely wet, and an accurate integrity test could be performed.

[0051]

As described above, according to the present invention, the integrity test of a membrane module can be performed more accurately without using a high-concentration chemical solution, without air bubbles leaking due to poor wetting of the membrane. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an integrity inspection method according to the present invention.

FIG. 2 is a schematic diagram illustrating an example of an integrity inspection method according to the present invention.

FIG. 3 is a schematic diagram illustrating the principle of the bubble point method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical capillary 2 Liquid tank 3 Liquid sucked in the capillary 4 Membrane module 5 Raw water pump 6 Raw water tank 7 Hollow fiber membrane 8 Potting part 9 Housing 10 Raw water inlet 11 Filtration water outlet 12 Drain line 13 Raw water side switching valve 14 Gas supply line 15 Filtration water side switching valve 16 Pressure gauge 17 Filtration line

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Shinya Sueyoshi 4-160 Sunadabashi, Higashi-ku, Nagoya-shi, Aichi F-term in Product Development Laboratory Mitsubishi Rayon Co., Ltd. 4D006 GA07 HA01 HA21 HA41 HA71 KD28 LA03 MA01 MA02 MA03 MC16 MC22 MC29 MC30 MC33 MC39 MC54 MC58 MC62 NA58 PB05 PB06 PB08 PC01 PC11 PC42

Claims (5)

[Claims] 1. The method according to claim 1, wherein the air remaining in the membrane module is replaced with carbon dioxide gas, and then water or a liquid containing water is filtered by the membrane module, and then the integrity of the membrane module is checked by applying gas pressure. Characteristic integrity testing method for membrane modules. 2. After immersing the membrane module in water or a liquid containing water, and then replacing the air remaining in the membrane module with carbon dioxide, applying gas pressure to check the integrity of the membrane module. Characteristic integrity testing method for membrane modules. 3. The method for inspecting the integrity of a membrane module according to claim 1, wherein the integrity is inspected by generation of air bubbles, pressure change or diffusion flow rate. 4. The method according to claim 1, wherein the membrane module is a microfiltration module. 5. The integrity of the membrane module according to claim 1, wherein the liquid containing water is a mixture of at least one solvent selected from the group consisting of ethanol, butanol, propanol and methanol with water. Inspection methods.