JP2008104945A - Membrane leak detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out with an efficient and simple constitution a membrane leak detection of a hollow fiber membrane, a discrimination of whether the membrane is reworkable or scrapped after the membrane leak confirmation, and an appropriatizing of operation conditions by a leak position estimation. <P>SOLUTION: The constitution comprises a straight run of pipe and a tapered part, which are connected by a visible cap constituted by a transparent material and has a filtration membrane module which separates a supply liquid supplied by a plurality of hollow fiber membranes into a filtrate and a concentrated liquid, and a filtrate pipe which is a pipe arrangement distributing the filtrate from the filtration membrane module are provided. Air is supplied to the filtration membrane module, and a view of bubbles in the filtrate generated from the hollow fiber membrane specifies the leaked membranes and the number, and specifies the leak positions from the relation of a gas supply time and a leak confirming time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a filtration membrane module using a hollow fiber membrane, and particularly relates to a membrane leak detection method for an external pressure type hollow fiber membrane module having excellent detection performance.

  There is a filtration device that performs water treatment to purify a large amount by microfiltration or ultrafiltration device using river water, lake water, groundwater, seawater or the like as a raw solution. In such a filtration device, in order to eliminate suspended substances adhering to the filtration membrane in order to maintain the filtration capacity, the external pressure filtration membrane module regularly performs air bubbling operation for supplying gas such as air to the supply water side. Implemented. A method for detecting a membrane leak of a hollow fiber membrane provided in a filtration device in accordance with the air bubbling operation has been proposed (see, for example, Patent Document 1).

  In the configuration of Patent Document 1, the presence or absence of bubbles in the hollow body of the hollow fiber membrane is determined by visually confirming the presence or absence of bubbles in the tubular body of the joint member during or after the air bubbling operation.

JP-A-11-311596

  However, in the above-described conventional example, the membrane leak is detected only when the gas is supplied for the purpose of detecting the membrane leak, and it is not possible to detect whether the membrane leak has occurred during the normal operation. For this reason, when a membrane leak occurs while the membrane leak detection test is not performed, there is a problem that bacteria and contaminants are mixed in the filtered water for a long period of time.

  In addition, by checking the cylindrical body of the joint member by supplying gas, it can be confirmed whether there is a membrane leak in the hollow fiber membrane, but at which position of which hollow fiber membrane the membrane leak occurs Could not be identified. For this reason, when it is confirmed that a membrane leak has occurred, it is necessary to remove the caps for all the filtration membrane modules and confirm the presence or absence of the membrane leak again. Then, it was necessary to identify that a film having a small film leak was repaired and a film having a large film leak was discarded and replaced. For this reason, it was necessary to work more efficiently.

  In addition, in order to check the occurrence of bubbles due to a membrane leak in the detection of a membrane leak that supplies gas, it is necessary to collect water on the hollow fiber cutting end surface, and connect a special part or remove the module. It was necessary to check in the aquarium.

  Further, in the case of a casing storage type membrane module, it is disassembled to specify the leak position, and the cause is estimated by looking at the leak status, and it took a very long time to take countermeasures.

  The present invention solves the above-mentioned problems, and the object of the present invention is to detect the membrane leak of the hollow fiber membrane and to identify whether it can be repaired or discarded after confirming the membrane breakage. What is to be done in the configuration and to implement measures immediately.

The present invention includes:
(1) In an external pressure filtration membrane module that encloses a plurality of hollow fiber membranes and filters the supplied water from the outside to the inside of the hollow fiber membrane, the filtration water side of the membrane module is composed of a straight pipe portion and a tapered portion. It is composed of a visual recognition cap made of a transparent material, and this visual recognition cap is pressurized with gas from the supply water side or the filtrate water side is decompressed using a filtration membrane module fixed by a separate connecting member. A membrane leak detection method for identifying a leak hollow fiber from the position of bubbles generated from the filtrate water side while lowering the liquid level around the hollow fiber,
(2) The leak position in the vertical direction of the hollow fiber membrane is specified by measuring the pressurized pressure of the gas or the reduced pressure on the filtered water side, and measuring the time required to generate bubbles. This is a film leak detection method.

  In order to achieve the above object, a first configuration according to the present invention includes an external pressure filtration membrane module that includes a plurality of hollow fiber membranes and separates a supplied liquid into a filtrate and a concentrated liquid. The filtered water side cap is transparent, and the hollow fiber leaked by membrane leak detection can be identified.

  In order to achieve the above object, the second configuration according to the present invention is based on the relationship between the gas pressurization or decompression pressure and the time required until bubble generation in addition to the first configuration, and the leak position in the vertical direction of the hollow fiber membrane. It is characterized by specifying.

  The present invention has the configuration as described above. In the first configuration, the filtration membrane module and the filtrate pipe are connected by a visual recognition cap that is constituted by a straight pipe portion and a tapered portion and is made of a transparent material. For this reason, when a membrane leak occurs, it can be confirmed that dirt is attached to the visual cap portion in the upper portion of the leaked membrane where filtrate water flows out, and that a membrane leak has occurred, and then the connecting member 12 is loosened. Rotate the contaminated part of the cap from the top of the leaked hollow fiber so that it can be confirmed by shifting it, supply pressurized air to generate bubbles from the hollow fiber membrane, and generate the bubbles from the outside of the visual cap The leaked hollow fiber can be identified by directly observing the facts and points.

  In addition, the membrane leak can be verified by loosening the connecting member 12 and rotating and shifting the contaminated portion of the cap from the upper part of the leaked hollow fiber and confirming that the contamination is similarly generated by continuing the operation again.

  It is preferable in terms of visibility that the cap can be rotatably fixed by the connecting member 12 when loosened.

  Further, in the second configuration, when the pressure of the supply water is lowered by pressurization with gas from the supply water side, the pressure pressure is kept constant, and the liquid level lowering rate due to time and filtration of the liquid in the module The leakage position in the longitudinal direction of the hollow fiber membrane is specified from the measurement of the time until the occurrence of leakage. That is, bubbles are not generated when the leak position is lower than the liquid level, but the position is specified from the pressure and time by utilizing the fact that bubbles are generated when the liquid level drops below the leak position.

  Examples of the method for lowering the liquid level on the supply water side include pressurization by gas from the supply water side, filtration by reducing the filtrate water side, drainage of liquid on the supply water side, and the like.

  In the case of pressure reduction on the filtered water side, when the leaked portion of the membrane reaches or exceeds the liquid level, bubbles are sucked from the leaked portion and bubbles are confirmed on the filtered water side.

  Furthermore, in order to increase the sensitivity, it is necessary to inspect at a high pressure (a high differential pressure between the supply water side and the filtrate water side). However, if the pressure is increased, the rate of liquid level drop due to filtration increases. The position error in the vertical direction increases. Therefore, it is possible to perform inspection at a high pressure by supplying a pressurized liquid to the module simultaneously with the gas, or by repeatedly pressing the liquid with a liquid after supplying a certain amount of gas.

  The pressure in this inspection needs to be carried out at a pressure below the bubble point in the liquid to be filtered in order not to dry the membrane.

  By this method, if the leak portion of the hollow fiber is the outer peripheral portion of the hollow fiber bundle, and it is determined that the leak is at the uppermost portion of the hollow fiber, measures such as mild operation conditions such as air bubbling are taken. If it is below the thread membrane bundle, it can be estimated that the pollutant discharge after physical cleaning has not been performed well, and it has been estimated that contaminants have accumulated, and measures such as changing discharge conditions after physical cleaning and strengthening pretreatment, etc. Since the cause can be estimated from past knowledge, it is possible to take immediate provisional measures.

  In the second configuration, when the filtrate water side is depressurized, the liquid level in the membrane module is lowered while suctioning the filtrate water side with a decompression pump or the like. At this time, in the case of the membrane module of the reduced pressure and the required time or the immersion type in the tank, the membrane leak position in the longitudinal direction of the hollow fiber can be specified by detecting the generation of bubbles simultaneously with the liquid level.

  In particular, the method of reducing the pressure on the filtered water side improves the sensitivity by increasing the volume of the generated bubbles under reduced pressure, and increases the rising speed of the bubbles generated from inside the hollow fiber in the longitudinal direction. This is preferable because the error can be reduced in the position specification.

  With the first and second configurations, a transparent visual cap is attached to the filtration membrane module, and from the upper part of the filtration membrane module, the cap leaks due to membrane leakage and the generation and generation of bubbles from the hollow fiber membrane. The location can be directly viewed.

  Further, by measuring the leak inspection pressure and the required time or the liquid level, it is possible to specify the leak position in the vertical direction of the hollow fiber, and it is possible to take immediate measures against leaks.

  The filtration device using the hollow fiber membrane according to the present invention will be described with reference to the drawings. In the description, the schematic configuration of the filtration device 1 using a hollow fiber membrane, the detailed configuration of the filtration membrane module 10, the operation when the filtration device 1 operates, the operation during air bubbling operation, the operation during membrane leak detection, the visual recognition cap 11 The detailed configuration and the leak detection principle are performed in this order.

  FIG. 1 is a schematic explanatory diagram of a pressure membrane filtration device 1 that performs filtration by pressurizing supply water, and FIG. 2 is a submerged membrane filtration device that performs filtration by immersing the membrane in a tank and suctioning filtered water. 3 is a cross-sectional view of the filtration membrane module 10, FIG. 4 is a perspective view of the visual recognition cap 11 when a membrane leak is detected, and FIG. 5 is a top view and a cross-sectional view of the visual recognition cap 11. FIG. 6 is a diagram showing the principle of leak detection.

(Schematic configuration of pressurized membrane filtration device 1 using a hollow fiber membrane)
As shown in FIG. 1, a filtration device 1 using a hollow fiber membrane filters a supply liquid such as water containing a suspended substance by a filtration membrane module 10 in which a number of hollow fiber membranes are disposed. is there.

  The filtration device 1 includes a supply liquid tank 21 that stores a supply liquid to be supplied to the filtration membrane module 10, a supply liquid pump 22 that conveys the supply liquid in the supply liquid tank 21 to the filtration membrane module 10, and air filtration It has a compressor 23 that feeds out to the membrane module 10, and a filtrate tank 24 that stores the filtered filtrate.

  The downstream side of the supply liquid tank 21 and the upstream side of the filtration membrane module 10 are connected by a supply liquid pipe 41, and the downstream side of the compressor 23 and the upstream side of the filtration membrane module 10 are connected by an air pipe 42. The downstream side of the filtration membrane module 10 and the upstream side of the supply liquid tank 21 are connected by a concentrate pipe 43, and the downstream side of the filtration membrane module 10 and the upstream side of the filtrate tank 24 are connected by a filtrate pipe 44. The downstream side of the filtrate tank 24 and the filtrate pipe 44 are connected by a backwash liquid pipe 45.

The supply liquid pipe 41 is provided with a supply liquid valve 31 downstream of the supply liquid pump 22, the air pipe 42 is provided with an air valve 32, and the concentrate liquid pipe 43 is provided with a concentrate liquid valve 33. The filtrate pipe 34 is provided in the filtrate pipe 44, and the backwash liquid valve 36 is provided in the backwash liquid pipe 45.
(Schematic configuration of the immersion membrane filtration device 2 using a hollow fiber membrane)
As shown in FIG. 2, a filtration device 2 using a hollow fiber membrane is used to filter a supply liquid such as water containing a suspended substance by a filtration membrane module 10 in which a number of hollow fiber membranes are disposed. is there.

  The filtration device 2 includes a supply liquid pump 22 that conveys the supply liquid to the filtration membrane module 10, a membrane immersion tank 26 that immerses the filtration membrane module 10, a compressor 23 that sends air to the filtration membrane module 10, and a filtration And a filtrate tank 24 for storing the filtrate.

  Further, the liquid is supplied to the membrane immersion tank 26 from the downstream side of the supply liquid tank 21 and the upstream side of the filtration membrane module 10 through the supply liquid pipe 41, and the downstream side of the compressor 23 and the upstream side of the filtration membrane module 10 are connected to the air. The pipe 42 is connected, and the downstream side of the filtration membrane module 10 and the upstream side of the filtrate tank 24 are connected by a filtrate pipe 44.

  The supply liquid pipe 41 is provided with a supply liquid valve 31 on the downstream side of the supply liquid pump 22, the air pipe 42 is provided with an air valve 32, and the filtrate pipe 44 is provided with a filtrate valve 34. Is disposed.

(Detailed configuration of filtration membrane module 10)
As shown in FIG. 3, the filtration membrane module 10 is arranged upright so that the supply liquid is supplied from the lower part, the filtrate is discharged from the upper part, and the concentrated liquid is discharged from the upper side part. Is done.

  A visual recognition cap 11 is fitted to the upper end of the cylindrical module body 10a of the filtration membrane module 10, and a lower cap 13 is fitted to the lower end thereof, and connected and fixed by connecting members 12, 14 such as nuts, respectively. .

  In the case of the immersion membrane module, there is no housing, and the supply liquid is supplied not only from the lower part but also from the outer peripheral part of the hollow fiber.

  A large number of hollow fiber membranes 16 are disposed inside the module body 10a. The hollow fiber membrane 16 has a closed end 16a that is closed and fixed at the lower end, and an open end 16b that is open at the upper end. In FIG. 3, the number of the hollow fiber membranes 16 is three for the sake of explanation, but in actuality, many hollow fiber membranes 16 are bundled.

(Operation when the filtration device is activated)
With the above configuration, the following operation is performed when the filtration device is activated.

  First, in the pressurized membrane filtration device 1, the supply liquid stored in the supply liquid tank 21 enters from the lower cap 13 of the filtration membrane module 10 by the pump 22. The supply liquid circulates from the lower part to the upper part in the module main body 10a as indicated by an arrow indicated by a thick line in FIG. Here, the fine holes on the surface of the hollow fiber membrane 16 do not allow the suspended substances in the supply liquid to pass but allow liquids such as water to pass. For this reason, in the process of flowing from the lower part to the upper part in the module main body 10a, a part of the supply liquid enters into the hollow fiber membrane 16 as indicated by the broken line arrow in FIG. What has entered the hollow fiber membrane 16 becomes the filtrate and is led to the filtrate pipe 44.

  In the submerged membrane filtration device 2, the supply liquid is supplied to the membrane immersion tank 26 by the pump 22 and enters from the lower part of the filtration membrane module 10 and the outer periphery of the hollow fiber. The filtration of the supply liquid by the module is the same as that of the pressure membrane module, and the infiltrated into the hollow fiber membrane 16 becomes the filtrate and is led to the filtrate pipe 44.

  On the other hand, in the supply liquid that has circulated through the module body 10a without being filtered by the hollow fiber membrane 16, the suspended substance is concentrated by the amount excluding the filtrate. In the case of a submerged membrane, it returns to the supply liquid tank 21 through the condensate tube 43 in the case of a pressurized membrane. In the membrane immersion tank 26. This operation is repeated to separate the clean filtrate and concentrate from the supply liquid.

(Operation during air bubbling operation)
Next, an example of air bubbling operation will be described. The air bubbling operation is performed in order to exclude suspended substances attached to the hollow fiber membrane 16.

  During the air bubbling operation, the supply valve 31, the concentrate valve 33, and the filtrate valve 34 are closed, while the air valve 32, the backwash liquid valve 36, and the drain valve 37 are opened. In this state, air is supplied from the compressor 23 into the supply liquid pipe 41. In addition, the filtrate stored in the filtrate tank 24 is supplied to the filtrate pipe 44 using the backwash pump 25.

  Then, air is supplied from the lower part in the module main body 10a, and the filtrate is supplied from the upper part in the module main body 10a to the outside through the hollow fiber membrane 16, so that the inside of the module main body 10a. Air bubbles and filtrate will be supplied to. Then, due to the action of supplying the bubbles and the filtrate, on the one hand, the bubbles hit the suspended matter adhering to the side surface of the hollow fiber membrane 16, and on the other hand, the hollow fiber membrane 16 vibrates. As a result, the suspended substance is peeled off from the hollow fiber membrane 16. The separated suspended substance is discharged from the drain valve 37 together with the filtrate, and the suspended substance adhering to the hollow fiber membrane 16 can be excluded from the inside of the filtration device 1.

(Leak detection in pressurized membrane)
Next, the membrane leak detection of the hollow fiber membrane 16 will be described. The membrane leak detection of the present embodiment is detected by contaminating the visual cap with contaminants that have flowed out to the filtered water side due to membrane leaks during normal filtration operation that does not perform an operation specifically for detection. . Further, the leaked hollow fiber can be identified by using the same configuration as in the air bubbling operation. For this reason, even if it is the structure which detects a film leak, the number of members does not increase.

  In this respect, the same applies to the pressure membrane module and the immersion membrane module.

  To identify the leaked hollow fiber, if the visual cap 11 is contaminated, loosen the connecting member 12, shift the contaminated portion of the visual cap 11, and tighten the connecting member 12 again. The valve 31 and the concentrate valve 33 are closed. Then, the air valve 32 is opened to supply air from the compressor 23 from the lower part of the module body 10a. Then, first, while bubbles are mixed in the supply liquid in the module body 10a, a part of the supply liquid becomes a filtrate and passes through the hollow fiber membrane 16. If this operation is continued, air accumulates in the module main body 10a. On the other hand, it remains the same that a part of the supply liquid passes through the hollow fiber membrane 16 as a filtrate.

  In this state, the filtrate flows through the hollow fiber membrane 16, and the outer periphery of the hollow fiber membrane 16 is covered with air. Here, if there is a filtrate inside, the hollow fiber membrane 16 is covered by the surface tension of the filtrate, and the surrounding air does not pass through the holes.

  However, if the hollow fiber membrane 16 leaks, air enters the hollow fiber membrane 16 from the defective portion. The air that has entered the hollow fiber membrane 16 becomes bubbles A and rises in the filtrate, and moves from the open end 16b of the hollow fiber membrane 16 to the filtrate tube 44 side. This bubble A can be visually recognized from the outside through a transparent visual recognition cap 11 described later, as shown in FIG.

(Leak detection in immersion film)
In order to identify the leaked hollow fiber, when the visual cap 11 is contaminated, the connecting member 12 is loosened, the contaminated part of the visual cap 11 is rotated and shifted, and the connecting member 12 is tightened again. Thereafter, the supply liquid valve 31 is closed. When the backwash pump 25 is operated, the liquid in the membrane immersion tank 26 is filtered and the liquid level is lowered.

  In this state, the filtrate flows through the hollow fiber membrane 16, and the outer periphery of the hollow fiber membrane 16 is gradually covered with air from above. Here, if there is a filtrate inside, the hollow fiber membrane 16 is covered by the surface tension of the filtrate, and the surrounding air does not pass through the holes.

  However, if the hollow fiber membrane 16 leaks, air enters the hollow fiber membrane 16 from the defective portion. The air that has entered the hollow fiber membrane 16 becomes bubbles A and rises in the filtrate, and moves from the open end 16b of the hollow fiber membrane 16 to the filtrate tube 44 side. This bubble A can be visually recognized from the outside through the transparent visual recognition cap 11, as shown in FIG.

  With such a configuration and operation, a film leak is detected. That is, even during a normal operation in which no film leak detection is performed, the presence or absence of a film leak can be determined to some extent from the contamination state of the visual recognition cap. During the membrane leak detection operation, if bubbles are not visible from the outside of the visual recognition cap 11, it can be confirmed that no membrane leak has occurred in the hollow fiber membrane 16, and if bubbles are visible from the outside of the visual recognition cap 11, the membrane of the hollow fiber membrane 16 is confirmed. It can be confirmed that a leak has occurred.

(Detailed configuration of visual recognition cap 11)
Next, an example of a detailed configuration of the visual recognition cap 11 which is a characteristic part of the present invention will be described with reference to FIG.

  5A is a top view of the visual recognition cap 11, and FIGS. 5B and 5C are cross-sectional views of the visual recognition cap 11.

  As shown in FIG. 5, the visual recognition cap 11 is provided with a lower opening 11a having a diameter substantially the same as the diameter of the module body 10a and an upper opening 11b having a diameter substantially the same as the diameter of the filtrate pipe 44. . The shape of the visual recognition cap 11 includes a straight pipe portion 11c having the same diameter as the upper opening 11b and a tapered portion 11d whose diameter gradually decreases from the diameter of the lower opening 11a to the diameter of the upper opening 11b. Further, there is a groove 11e for fixing to the filtration membrane module 10 around the lower opening 11a, and a plurality of ribs 11f for maintaining strength are disposed on the groove 11e.

  The visual recognition cap 11 is made of a transparent or translucent member so that the internal bubbles A can be visually recognized. For example, glass or a resin member can be used. Here, if air bubbles adhere to the inner surface of the taper portion 11d, the inside of the taper portion 11d is blocked and the inside cannot be visually recognized, and it is difficult to grasp where the air bubbles A generated from the hollow fiber membrane 16 are located. Become.

  For this reason, it is preferable to use a thermoplastic resin member to which bubbles are not easily attached as the material of the visual recognition cap 11. Specifically, polyvinyl chloride, methyl methacrylate resin, polystyrene resin, fluorine resin, polycarbonate, polysulfone, polyether sulfone, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polychlorofluoroethylene Etc. are preferred.

  As described above, the tapered portion 11d has a certain inclination so that the diameter gradually decreases from the diameter of the lower opening 11a to the diameter of the upper opening 11b. Thereby, the filtrate discharged from the open end 16b of the hollow fiber membrane 16 is smoothly guided to the upper opening 11b and the filtrate pipe 44. Here, it is desirable that the angle formed by the contact between the straight pipe portion and the taper portion of the cap and the contact where the visual recognition cap comes into contact with the membrane module adhesion end face is 5 degrees or more and less than 50 degrees.

  If this angle is too large, the contamination of the cap due to film breakage is reduced and the detection sensitivity is deteriorated. On the other hand, if it is too small and too close to the end face of the membrane, it becomes difficult to identify the hollow fiber that has been cut off due to the generation of bubbles. Furthermore, in order to specify the hollow fiber that has been cut from the taper portion 11d, the ratio of the inner diameter of the connecting member 12 to the outer diameter of the upper opening 11b is 1.5 times or more, and the straight pipe portion 11c is 10 mm or more. desirable. This is because most of the membrane leak occurs near the outer periphery of the hollow fiber bundle in the membrane module, and it is necessary to improve the visibility of this portion.

  By satisfying this relationship, the operator can look over the entire surface of the lower opening 11a through the straight pipe portion 11c and the taper portion 11d, and has excellent visibility. Thereby, even when the bubble A is generated from the open end 16b of the hollow fiber membrane 16 at the center of the lower opening 11a, the bubble A can be surely recognized and the membrane leak can be detected. .

  As described above, by attaching the transparent visual recognition cap 11 on the filtration membrane module 10, it is possible to directly visually confirm the contamination state of the visual recognition cap 11 from the open end 16b of the hollow fiber membrane 16 and the generation of bubbles A. become able to. For this reason, it is possible to reliably detect the film leak. Further, since the position where the bubble A is generated can be directly recognized, it is possible to grasp which hollow fiber membrane 16 has a membrane leak or how many membrane leaks have occurred. .

  Conventionally, when it was confirmed that a membrane leak occurred, it was necessary to remove the caps from all the filtration membrane modules and check again whether there was a membrane leak. In addition, it was necessary to identify that those with little film leak were repaired and those with much leak were discarded and replaced. However, according to the present embodiment, it is possible to identify a part of the membrane module in which a lot of membrane leaks are attached to the filtration device, so that labor and cost can be reduced.

  The visual recognition cap 11 also serves as a piping between the filtration membrane module 10 and the filtrate pipe 44. For this reason, it is possible to detect the film leak with a simple configuration without adding a new component for detecting the film leak as in the prior art, and it is possible to reduce the number of members and the cost.

(Identification of leak position in the longitudinal direction of the hollow fiber membrane)
By the above method, it is possible to identify the leaked hollow fiber membrane 16 and the number of leaks.

  Next, a method for specifying the leak position in the vertical direction of the hollow fiber membrane 16 will be described with reference to FIGS.

  In FIG. 1, in order to identify the hollow fiber in which leakage occurred, when the visual cap 11 is contaminated, the connecting member 12 is loosened, the contaminated portion of the visual cap 11 is shifted, and the connecting member 12 is tightened again. Thereafter, the supply liquid valve 31 and the concentrated liquid valve 33 are closed. In the case of a casing-contained pressurized membrane module, the air valve 32 is opened to supply air from the compressor 23 from the lower part of the module body 10a. Then, first, while bubbles are mixed in the supply liquid in the module body 10a, a part of the supply liquid becomes a filtrate and passes through the hollow fiber membrane 16. As this operation continues, air accumulates in the module body 10a. Then, as shown in FIG. 6, a layer of air is formed in the module main body from above, the liquid level moves downward, and bubbles are confirmed in the visual recognition cap 11 when reaching the leak portion of the membrane. . The speed at which this air accumulates, that is, the liquid level lowering speed in the module main body 10a is determined by the pressure and the filtration capacity of the hollow fiber membrane.

  As a specific identification method, air is supplied at a constant pressure from the lower part of the module body 10a, and the supply start time is set to 0 second.

  Next, the flowmeter instruction value on the filtrate side is confirmed, and the time A seconds until the liquid instruction in the module body 10a runs out and the flow instruction value becomes zero is measured.

  It can be seen that if the time until bubble generation is short, the film leaks in the upper part, and if close to A seconds, the film leaks in the lower part.

  The measurement condition is preferably a condition in which A second is long, that is, a pressure at which A second is about 60 seconds from the viewpoint of efficiency although the position can be specified more accurately as the pressure is lower.

  In the case of the submerged membrane module, suction is performed from the filtrate side with the filtration pump 27 or the decompression pump, and the leak position in the vertical direction of the hollow fiber membrane 16 is specified from the tank liquid level when bubbles are generated.

  Examples will be described in more detail below.

Asahi Kasei Chemicals' casing housing type hollow fiber microfiltration membrane module (model number UNA-620A, membrane area 50 m ² , hollow fiber length 2 m, PVDF hollow fiber membrane MF module, nominal pore size 0.1 micron) A module leaking from one hollow fiber was prepared, and a membrane leak detection test was conducted.

  The outer diameter of the upper opening 11b is 89.1 mm, the inner diameter of the connecting member 12 is 150 mm, the ratio is about 1.7 times, the straight pipe portion 11c is 4.4 cm, and the angle θ between the lower opening 11a and the tapered portion 11d is 20 degrees. A viewing cap was used.

Using this membrane module with a leaking cap attached to the leak, Fuji River river water with an average turbidity of 2 degrees was used as the membrane feed water, and operation was continued at a membrane filtration flux of 2 m ³ / m ² · day.

  Normally, a film leak detection test is carried out once every six months. In this experiment, adhesion of black-brown contaminants to the visual cap was observed after about one week. Thereby, the membrane leak which is not confirmed for 6 months at the longest was confirmed early.

  Further, the connecting member 12 of the membrane module was removed, the contaminated portion of the visual cap was rotated and shifted, and the connecting member 12 was attached again, and then the supply liquid valve 31 and the concentrated liquid valve 33 were closed. The air valve 32 was opened and air was supplied from the compressor 23 at a pressure of 200 kPa from the lower part of the module body 10a. As a result, the air that has entered the hollow fiber membrane 16 becomes bubbles A and rises in the filtrate, and moves from the open end 16b of the hollow fiber membrane 16 to the filtrate tube 44 side. As shown in FIG. 3, it can be visually recognized from the outside through the transparent visual recognition cap 11 without using the portion where the visibility is reduced, and the number of membrane leaks and the leaked hollow fiber membranes 16 can be reliably identified. It was possible.

At this time, since the time from the start of pressurization with air until the value of the flowmeter on the filtrate side reached 0 m ³ / hr was about 15 seconds, the same detection test was performed again at a pressure of 50 kPa. .

As a result, the time until bubble generation was 6 seconds, and the time until the value of the flowmeter on the filtrate side became 0 m ³ / hr was 58 seconds.

  From this result, it is estimated that it is 10 cm from the top of the 2 m long hollow fiber, and as a result of actually disassembling and checking the leak position, it is about 8 cm from the top, and it can be confirmed that it can be identified almost accurately. It was.

  The present invention can be used in a filtration device using a hollow fiber membrane, and can be effectively used particularly in a hollow fiber membrane.

The schematic explanatory drawing of the filtration apparatus 1. FIG. The schematic explanatory drawing of the filtration apparatus 2. FIG. 2 is a cross-sectional view of the filtration membrane module 10. FIG. The perspective view of the visual recognition cap 11 at the time of film | membrane leak detection. The top view and sectional drawing of the visual recognition cap 11. FIG. Fig. 2 is a principle diagram of membrane leak detection.

Explanation of symbols

A ... Bubble, 1 ... Pressure membrane filtration device, 2 ... Immersion membrane filtration device, 10 ... Filtration membrane module, 10a ... Module body, 11 ... Visual cap, 11a ... Lower opening, 11b ... Upper opening, 11c ... Straight pipe part 11d: Tapered portion, 11e: Groove, 11f: Rib, 12: Connecting member, 13: Lower cap, 14 ... Connecting member, 16 ... Hollow fiber membrane, 16a ... Closed end, 16b ... Open end, 21 ... Supply liquid tank , 22 ... Supply liquid pump, 23 ... Compressor, 24 ... Filtrate tank, 25 ... Backwash pump, 26 ... Membrane immersion tank, 27 ... Filtration pump, 31 ... Supply liquid valve, 32 ... Air valve, 33 ... Concentrated liquid valve 34 ... Filtrate valve, 36 ... Backwash valve, 37 ... Drain valve, 41 ... Supply liquid tube, 42 ... Air tube, 43 ... Concentrate tube, 44 ... Filtrate tube, 45 ... Reverse Wash pipe, 46 ... Diffuser

Claims (2)

In an external pressure filtration membrane module that encloses a plurality of hollow fiber membranes and filters the supplied water from the outside to the inside of the hollow fiber membranes,
A filtration membrane module in which the filtration water side of the membrane module is constituted by a visual recognition cap composed of a straight pipe portion and a taper portion and made of a transparent material, and the visual recognition cap is fixed by a separate connecting member. A membrane leak detection method for identifying a leaky hollow fiber from the position of bubbles generated from the filtered water side while lowering the liquid level around the hollow fiber by pressurizing with gas from the supply water side or reducing the liquid level around the hollow fiber.   2. The membrane leak according to claim 1, wherein the leak position in the vertical direction of the hollow fiber membrane is specified by measuring the pressurized pressure of the gas or the reduced pressure on the filtered water side, and measuring the time required until bubbles are generated. Detection method.

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