JP2000107575A - Leak inspection method for permselective membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leak inspection method for a permselective membrane module whereby detection is facilitated; the concn. of a dye is reduced; and a membrane or a member of the module is prevented from staining by using a soln. of a fluorescent dye having a specified mol.wt. and by determining leak spots by detecting the fluorescence of the dye leaking from defects of the module. SOLUTION: This method is applicable to any permselective membrane module as far as it is a membrane module consisting mainly of a separation membrane capable of separating and concentrating a substance, though a reverse osmosis membrane and a nanofiltration membrane are pref. Any fluorescent dye is usable if it is soluble in some solvent, has fluorescent properties, and meets the requirements. The effective mol.wt. of the fluorescent dye is about 300-3,000 in terms of the capability of the membrane for hindering the dye. The detection of the dye can be easily made visible by the irradiation with ultraviolet rays. More specifically, a fluorescent dye soln. contg. a diaminostilbenedisulfonic acid deriv. or the like is used for the leak inspection of a permselective membrane module consisting of cellulose acetate or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selectively permeable membrane module used for purifying water and purifying wastewater, and more particularly to a method for inspecting a membrane module for separation, purification and recovery using pressure as a driving force. In particular, the present invention relates to a method for detecting a defective portion for specifying a leak portion of a membrane module of a reverse osmosis membrane and a nanofiltration membrane.

Reverse osmosis membranes are used for desalination of seawater and ultrapure water. Recently, applications for advanced treatment of tap water and high-grade water purifiers have been studied. Nanofiltration membranes with low desalination rates have been developed. Membrane modules often have defects such as defects during the manufacture of the film, scratches resulting from handling, and cracks generated at the bonding portion between the film and the container. On the other hand, even if a defect generated on the membrane surface is small, the separation performance is reduced and a leak of virus, endotoxin and the like is caused, thereby impairing the integrity of the membrane module. This defect can be repaired to produce a membrane module that is less expensive to supply as a complete membrane module. In order to repair a defective membrane module, it is necessary to specify the leak location.

[0003]

2. Description of the Related Art As a leak test, there are a method of using a gas leaking from a defect using a gas and a method of using an abnormal value of liquid permeability. Japanese Patent Application Laid-Open No.
In Japanese Patent Application Laid-Open Nos. 2-140607 and 63-84606, bubbles generated in water were observed.
In No. 5, the degree of vacuum retention was measured.
Measures the residual air pressure to determine the presence or absence of a leak.
The method for measuring the amount of permeation from the airflow resistance disclosed in Japanese Patent Application Laid-Open No. 61-249507 can also be used for leak detection. JP-A-61-22
0710 and JP-A-3-127614 detect the presence or absence of a leak by measuring the number of fine particles in a permeated flow of a gas containing suspended fine particles with a particle counter. In addition, a method has been devised in which a flow flowing out into the air is sensed by touch, or a difference in refractive index, a difference in density, and a difference in temperature are detected using various measuring instruments or by applying a visualization technique. A method utilizing an abnormal value of liquid permeability has also been devised. For example, Japanese Patent Application Laid-Open No. Sho 62-213811 describes the water quality of the filtrate, and Japanese Patent Application Laid-Open No. Sho 59-183807 describes the characteristic value fluctuation of the secondary liquid. Japanese Patent Application Laid-Open No. 60-25510 detects the presence or absence of a membrane leak by detecting a change in the pressure of the supply liquid. Japanese Patent Application Laid-Open No. Hei 6-182164 discloses a method in which a turbid substance in permeated water is filtered by a microfiltration membrane at a later stage to increase water flow resistance. JP-A-5-157654 determines the presence or absence of a leak by using a rise in the pressure of a filtration chamber when a liquid is sealed and gas is pressurized. A method of adding a solute or a suspension to a liquid to be supplied has also been devised. For example, Japanese Patent Application Laid-Open No. Hei 7-243959 discloses the presence or absence of leakage of a suspension of a magnetic substance or a conductive substance, and Japanese Patent Application Laid-Open No. 59-136631 Japanese Unexamined Patent Publication (Kokai) No. 6 (1994) discloses a labeled polymer (FITC-Dxt-T-200).
-254358 is an edible coloring matter, disclosed in JP-A-7-132215.
Detects leaks by measuring permeate properties and filtration performance of virus substitute particles. As other methods, JP-A-3-174225 describes the intensity of light scattering of transmitted light in the sealed portion, JP-A-3-174226 describes the intensity of reflected light, and JP-A-3-213129 describes the change in polarization of the transmitted light. The defect of the hollow fiber enclosing part is detected.
Has formed a coat layer to which a dye has been added, and disclosed in JP-A-7-1555.
Numeral 67 designates a hydrophobic or hydrophilic paint applied to the pervaporation film to specify a defective portion of the film. The method for measuring the potential difference between both surfaces of the membrane disclosed in JP-A-6-170186 and the method for measuring the virus removal rate described in JP-A-5-502164 can also be used for defect detection.

[0004]

However, the method using gas is basically a test method for a microfiltration membrane, and a method using the generation of air bubbles is used for a leak test of a reverse osmosis membrane or a nanofiltration membrane. High pressure is required to generate air bubbles. Because of this, they are deformed or damaged, so that they cannot be applied to leak inspection of reverse osmosis membranes or nanofiltration membranes. The other method using gas is essentially a method in which the location of the leak cannot be specified and cannot be applied. The method of visualizing the permeation (leak) of gas has the disadvantage that the equipment becomes large, it is difficult to detect with a pinhole, and the area to be repaired becomes large, so that the permeation performance of the membrane module is impaired. The method using a solution or suspension always involves membrane blockage and membrane module contamination, and when using various solutes, it cannot be detected unless the concentration is high, and even if the leak location can be identified, Because of the contamination of the membrane module, the permeability of the membrane module is often impaired, and the cleanliness, aesthetics and safety of the membrane module are also impaired. In the method using a polymer substance solution, the polymer is larger than the pore size of the target membrane, which is likely to contribute to membrane contamination, it takes time and effort to clean after a leak test, and often impairs the membrane performance. It has the disadvantage of overlooking a leak. In the case of a solution of a dye or a dye, the solution is reactive with the film, and the detection of the dye requires a relatively high concentration. As mentioned above,
In order to repair the membrane module, it is necessary to specify the leak location, but there has been almost no suitable method.

[0005]

Means for Solving the Problems The present inventors have made intensive studies and found the following novel leak inspection method. That is,
In a leak test of a selectively permeable membrane module, a leak test is performed by using a fluorescent dye solution having a molecular weight of 300 to 3000 to detect a dye leaking from a defect of the membrane module with fluorescence to identify a leak portion. The method further includes detecting a food dye leaking from a defect in the membrane module using a water-soluble food dye having a fluorescent ability with fluorescence, and specifying a leak portion of the selectively permeable membrane module.

Hereinafter, the present invention will be described in detail. In the present invention, the permselective membrane module may be any membrane module assembled with a separation membrane capable of separating and concentrating a substance as a main element of separation, and is preferably a reverse osmosis membrane or a nanofiltration membrane. As a film forming method, any of a homogeneous film, an asymmetric film, and a composite film manufactured by casting, coating, surface modification, interfacial polymerization, wet spinning, semi-wet spinning, dry spinning, or the like may be used. The material of the support membrane of the homogeneous membrane or asymmetric membrane and the composite membrane is not particularly limited, and examples include various polyolefins, cellulose acetate, cellulose triacetate, polyamide, polyimide, polyacrylonitrile, polysulfone, polyfluoroethylene, Polymers such as polyethersulfone and derivatives thereof, and products using these copolymers are exemplified. The membrane material constituting the separation active layer of the composite membrane is not particularly limited, and examples thereof include polymers such as cellulose acetate, cellulose triacetate, polyamide, polyimide, polyacrylonitrile, polysulfone, polyethersulfone and derivatives thereof. And those using these copolymers. Preferred film materials include various polyamides, cellulose triacetate, and cellulose acetate. The perm-permeable membrane module is a product obtained by processing these membranes into a required shape, storing them in a container of an appropriate shape, and assembling them with an adhesive or the like. It can be applied to any of the used spiral wind type, multilayer lamination type, hollow fiber type, tubular membrane type, etc., but is most effective for the leak inspection of the hollow fiber type membrane module.

[0007] The fluorescent dye in the present invention refers to a substance which has some solvent which can be dissolved and has fluorescence.
Any substance that satisfies this condition is not restricted at all. Specifically, those having a CI Fluorescent Brightener number represented by the color index of the dye classification are all fluorescent dyes, and are preferably, and the representative numbers are 20, 24, 30, 32, 46, 48, 54,
71, 84, 85, 86, 87, 152, 156, 16
6, 225, 226, 260, 351, 19, 21, 2
2, 23, 31, 33, 35, 36, 37, 40, 7
2, 90 and 135. In addition, some dyes are generally classified as dyes and have fluorescent properties. Representative examples thereof include eosin, rhodamine B, and derivatives thereof. In addition, there are food colors having fluorescence and natural colors, and Food Red No. 3, Food Red No. 104, Food Red No. 106
No. 4, porphyrin derivatives such as sodium and potassium iron chlorophyllins, β-carotene, norbixin, biophoramine derivatives, vitamin B12 derivatives, and the like. Dyes having these fluorescent properties can also be used.

[0008] Among these, more preferred are the above-mentioned food dyes, CI Fluorescent Brightener 24, and CIFl.
uorescent Brightener 86, CI Fluorescent Bright
ener90, CI Fluorescent Brightener 260, eosin and its derivatives. The most preferred are food red 104 and food 106, and CIFluorescentBrigh
tener 24 and CI Fluorescent Brightener 86, C.
I. Fluorescent Brightener 260 is a 4,4'-diaminostilbene-2,2'-disulfonic acid derivative-based fluorescent dye, eosin and its derivatives.

The ability of the membrane to block the fluorescent dye depends on the molecular size of the fluorescent dye used. If the molecular size is small, the fluorescent dye penetrates the membrane, so the permeation can be seen from the entire surface of the opening of the membrane module, and no leak test can be performed.
If this is too large, the amount of leakage from the leak location will be small, and it will not be possible to detect it as a leak, and it will be impossible to detect a minute defect. Considering the ability of the film to block the fluorescent dye, the molecular weight of the fluorescent dye is effective from about 300 to 3000, preferably from 450 to 1800, and most preferably from 550 to 1200.

The detection of the fluorescent dye can be easily visualized by irradiation with ultraviolet light. That is, a desired place may be illuminated with ultraviolet light generated by an ultraviolet lamp. Since the fluorescence generated by irradiating ultraviolet rays is very bright, only a very small amount of fluorescent dye may be used. Any method may be used to identify the leak location, and the fluorescent dye is visualized with fluorescence in the flowing out stream and visually inspected, and the image is processed by capturing the fluorescence with a television camera or the like to determine the leak location. May be. A simple method is to apply the method described in JP-A-6-254358 to attach a detection medium to the permeated water outflow portion of the membrane module. Is a method for detecting the fluorescence generated by the spots of the fluorescent dye, and can be detected as fluorescent spots at the positions corresponding to the leak locations. Detecting by fluorescence makes the detection power 250 times higher than detecting by dyeing. For example, even at 20 μg / liter, it is possible to detect and specify a leak point. By increasing the affinity with the fluorescent dye by selecting the detection medium, it is easy to identify the leak location, and it is possible to detect minute defects such as peeling of the film surface and pin poles.

More specifically, a leak test of a permselective membrane module made of cellulose acetate or cellulose triacetate is performed by using a fluorescent dye solution made of one or a mixture of two or more diaminostilbene disulfonic acid derivatives. This is a leak test method in which a dye leaking from a defect in a membrane module is detected by fluorescence to identify a leak location.Furthermore, the separation active layer of the selectively permeable membrane is made of a polymer composed of piperazine and trimesic acid residues as main components. Leak testing of certain perm-permeable membrane modules involves using a solution of Food Red 104 or Food Red 106 or a dye solution that is eosin and / or a derivative thereof to leak from membrane module defects. This is a leak inspection method in which a dye is detected by fluorescence to specify a leak location.

The method of repairing the defective portion specifying the leak location differs depending on the type of the membrane module. There is no fixed method, and a known method may be applied. For example, apply an adhesive or sealant to the leak part for any type of membrane module, attach an impermeable sheet to the leak part, adhere to the leak part for the hollow fiber type etc. After performing processing such as shaving to improve the sealing property, sealing is performed with a sealant.Similarly, in the case of a hollow fiber type or a tubular type, there is, for example, closing an opening with an impermeable member. May be used.

[0013]

The present invention will be described below with reference to examples.

Example 1 Membrane Module Performance Evaluation Method I A circulating evaluation system for returning permeated water and concentrated water to a raw water tank using the membrane module evaluation apparatus shown in FIG. 1 was used. A temperature controller was attached to maintain a constant temperature, and the temperature was controlled to a specified value. The operating conditions were as follows: a 1500 mg / liter aqueous solution of sodium chloride was supplied at 25 ° C. and 30 kg / cm ² , and the recovery rate RC was 7%.
The valve was adjusted to 5%. In principle, the water permeability and the water quality were measured 2 hours after pressurization. For the measurement of water quality, the electric conductivity was measured, and the value was determined as the salt concentration. The water permeability FR and the desalination rate RJ of the membrane module were defined by the following equations. (Formula 1) RC = Qp / Qf × 100 (%) (Formula 2) FR = Qp × 1.44 (m ³ / day) (Formula 3) RJ = (Cf−Cp) / Cf × 100 (%) Qf (= Qp + Qb) is the amount of water supplied to the membrane module (liter / minute), and Qp is the amount of permeated water (liter / minute).
Min), Qb is the amount of concentrated water (liter / min), and Cf
Is the salt concentration of the feed water (mg / liter), and Cp is the salt concentration of the permeate water (mg / liter).

Method II for Evaluating Membrane Module Performance According to the above evaluation method, the operating conditions were changed to a 500 mg / liter aqueous solution of magnesium sulfate, 25 ° C., 5 kg / cm ² , and a recovery rate RC of 50%.

The E. coli removal test apparatus and operating conditions were performed according to the membrane module performance evaluation method. Time required for the operation to stabilize: After 2 hours, add the Escherichia coli culture solution that has been cultured and stored in advance.
After the elapse of 20 hours, an equal amount was added. After the elapse of 2 hours, permeated water and feed water were collected. E. coli culture
Escherichia coli, K-12 strain (IFO3206)
The cells were cultured in an HI liquid medium at 36 ° C. for 2 days or more. The addition was performed twice at a time of 20 ml per 300 l of raw water at the above-mentioned time.

Measurement of Escherichia coli Number The collected sample was measured as soon as possible, and when not possible, at 24 ° C. or less after refrigerated storage at 5 ° C. or less. This measurement was performed in accordance with JIS K0102-1993, the number of coliform bacteria in the test method for factory wastewater.

As a reverse osmosis membrane, a cellulose triacetate hollow fiber membrane module (trade name: HOLLOSEP HA5330,
Manufactured by Toyobo Co., Ltd.
Used for leak inspection. The permeability of this membrane module was evaluated by the evaluation method I of the membrane module by FR28.4 m ^3.
As a result of the E. coli removal test at 90.2% RJ / day, the permeated water was 1200 cells / cm ³ for the raw water of 3 million cells / cm ³ or more. Fluorescent dye, CI Fluorescent Brighten
er24 was dissolved in a 1 g / liter aqueous solution (20 cm ³⁾ in a 500 liter raw water tank (fluorescent dye concentration was 0.04 mg / liter).
Liter), a qualitative filter paper is inserted as a leak detection medium into the opening surface of this membrane module, and 10 kg / cm ² , 20 to 2
Operated at 5 ° C. for 1 hour. After the operation was completed, the filter paper was taken out, illuminated with a fluorescent lamp to generate fluorescent light, and the leak was examined. Fluorescent spots, that is, 43 leak locations were confirmed. The opening surface of the membrane module corresponding to the leak location was cut with a drill and sealed with an epoxy sealant. After the sealant was cured, the membrane module was evaluated again and the FR2
At 4.8 m ³ / day, RJ 93.1%, the removal of E. coli was 3 million raw water / cm ³ or more and 0 permeated water / cm ³ . After this, the membrane module was disassembled, but no spots or stains were found on the membrane.

Example 2 CI Fluorescent was used as a fluorescent dye.
The procedure was performed in the same manner as in Example 1 except that Brightener 86 was used. Table 1 shows the results.

Example 3 CI Fluorescent was used as a fluorescent dye.
The procedure was performed in the same manner as in Example 1 except that Brightener 260 was used. Table 1 shows the results.

(Comparative Example 1) Food dye No. 2 5m in fluorescent dye
g / liter and ion exchange filter paper DEA as the detection medium
Using E (manufactured by Toyo Roshi Kaisha), dyeing spots were visually observed instead of fluorescence, and the other steps were carried out in the same manner as in Example 1. Table 1 shows the results
Shown in In this method, the water permeability FR was greatly reduced, and the disassembled hollow fiber membrane was remarkably colored dark blue.

Comparative Example 2 JP-A-59-13 was used as a fluorescent dye.
6631, a fluorescently labeled polymer (FIT)
C-Dxt-T-200) was used, and the same operation as in Example 1 was performed except that ion-exchange filter paper CM (manufactured by Toyo Roshi) was used as a detection medium. Table 1 shows the results. Since the detection of fluorescent spots was not good, the concentration of dextran was 200 mg / liter, and the water permeation amount FR was significantly reduced.

Example 4 Using the membrane module used in Comparative Example 2, a fluorescent dye was used as a CI Fluorescent Brightener.
86, using a 0.04 mg / liter aqueous solution, except that the procedure was the same as in Example 1. Thirteen minute fluorescent spots remained, indicating that the detection power was insufficient in Comparative Example 2, and repair was performed again. Table 1 shows the results.

[0024]

[Table 1]

(Example 5) On a polysulfone hollow fiber porous membrane (inner diameter 200 µm, outer diameter 300 µm) as a nanofiltration membrane, piperazine and triethylenediamine (molar ratio 99: 1) were used as amine components, and trimesic acid chloride was used as an acid component. Then, interfacial polymerization was performed to produce a composite hollow fiber selectively permeable membrane, and a composite hollow fiber selectively permeable membrane module having an effective length of 185 mm and 6000 hollow fibers was assembled. The evaluation was performed using the evaluation method II of the membrane module. Among them, a membrane module having a lower permeation performance (expected performance FR:
250 liters / day, RJ: 70%, FR: 2
70 L / day or more, RJ: 55% or less). Permeability before leak test: FR: 285 liters / day, RJ: 44.0%, E. coli count: 3 million raw water /
cm ³ or more, using the permeate 2800 / cm ³ of Objects,
Food red No. 106 was used as the dye, and ion-exchange filter paper DEAE (manufactured by Toyo Roshi) was used as the leak detection medium. The results are shown in Table 2.

(Example 6) The same procedure as in Example 5 was carried out except that Edible Red No. 104 was used as the dye. Table 2 shows the results
Shown in

Comparative Example 3 An edible red No. 3 dye was used.
Other than that, it carried out similarly to Example 5. Table 2 shows the results. Edible Red No. 3 lacked detection power and contaminated the membrane module.

Example 7 The same procedure as in Example 5 was carried out except that eosin was used as the dye. Table 2 shows the results.

[0029]

[Table 2]

[0030]

The detection is facilitated by detecting the dye by fluorescence, and the dye used can be reduced in concentration. The contamination of the membrane and members of the permselective membrane module that was inspected was reduced,
You can do nothing.

[0031]

As a result, the water permeability of the permselective membrane module subjected to the leak test is not reduced, the aesthetic appearance of the permselective membrane module is maintained, and the permselective membrane module is further improved. When used, contaminated dye does not remain, and sanitary and safe permeated water can be obtained. Since the repair can be performed without impairing the water permeability of the membrane module, a highly water-permeable membrane module having no defect can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 shows a flow sheet of the evaluation device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Membrane module 2 Supply water piping 3 Permeated water piping 4 Concentrated water piping 11 Raw water tank 12 Pump 13 Valves

Continued on the front page F term (reference) 2G051 AB04 AB20 BA05 CB01 GA10 2G067 AA41 BB15 BB17 CC16 DD10 4D006 GA03 GA07 HA01 KE11P KE19P LA03 MA01 MA06 MC18X MC22 MC30 MC39 MC54X MC58 MC62X MC63 PA01 PB02 PB08

Claims (6)

[Claims] 1. In a leak test of a selectively permeable membrane module, a selectively dyeable portion is identified by detecting a dye leaking from a defect of the membrane module with fluorescence using a fluorescent dye solution having a molecular weight of 300 to 3000 to detect a leak location. Leak inspection method for membrane modules. 2. The method according to claim 1, wherein the permselective membrane module is a hollow fiber permselective membrane module. 3. The method according to claim 1, wherein the fluorescent dye is a water-soluble food dye having a fluorescent ability. 4. The method according to claim 1, wherein the permselective membrane module is made of cellulose acetate or cellulose triacetate, and the fluorescent dye is one or a mixture of two or more diaminostilbene disulfonic acid derivatives. 5. The method according to claim 1, wherein the separation active layer of the permselective membrane is a polymer composed mainly of piperazine and trimesic acid residues, and the fluorescent dye is Food Red No. 104 and / or Food Red No. 106. 2. The method according to 2. 6. The separation active layer of the permselective membrane is a polymer comprising piperazine and trimesic acid residues as main components,
3. The method according to claim 1, wherein the fluorescent dye is eosin and / or a derivative thereof.