JP2006263501A - System and method for cleaning membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane cleaning system facilitating cleaning of a membrane and being capable of switching from an ordinary filtrating operation to a cleaning operation according to the degree of contamination of the membrane. <P>SOLUTION: The system has an injector 11 serving as a fine bubble generator started on the operation of cleaning a membrane module 10, in the upstream of the module 10, and the module 10 has a detector 30 detecting the degree of contamination of the membrane and a controller 32 starting the injector 11 according to the detected values. When the degree of contamination of the membrane detected by the detector 30 reaches or exceeds a predetermined standard, the controller 32 switches to the cleaning operation so as to cause fine bubbles to flow into the module 10 from the injector 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cleaning system and a cleaning method for a membrane such as a reverse osmosis membrane used in various fresh water generation facilities.

  In recent years, desalination equipment using reverse osmosis membranes for desalination has been increasing, and it has become widespread in various fields such as seawater desalination facilities, ultrapure water production facilities, and water facilities for electric power. Among them, the seawater desalination facility is a facility that desalinates infinite seawater to make drinking water, and as a plant that stabilizes the supply of drinking water from the perspective of responding to seasonal water shortages and emergency drinking water. It attracts attention. Today, environmental conservation is a problem on a global scale, and awareness of the treatment of river water and groundwater and the reuse of sewage and wastewater is increasing, and active research and development is being carried out in the field of water treatment. Yes.

  This reverse osmosis membrane is formed by forming a skin layer on a support layer made of a filter structure. As a filtration system using such a reverse osmosis membrane, the one shown in Patent Document 1 is known. ing. However, when such a reverse osmosis membrane is used for a long period of time, clogging of the membrane is inevitable, and the membrane must be cleaned.

For example, as a conventional cleaning method in a membrane module of a type that is used by being installed in a cylindrical vessel such as a spiral membrane module, a hollow fiber membrane module, etc., flushing that increases the surface flow rate on the membrane primary side to remove dirt, There were backwashing to remove dirt by flowing the permeate back from the secondary side of the membrane, or chemical washing to dissolve the dirt with chemicals such as sodium hypochlorite solution.
JP 2005-34723 A

  However, the above chemical cleaning cannot be performed during normal operation, and flushing and backwashing have been insufficient in effect. For this reason, conventionally, flushing and backwashing are automated and incorporated as a membrane filtration washing process to prevent accumulation of dirt on the membrane, and chemical washing is generally performed when dirt still accumulates. there were.

  In particular, most reverse osmosis membrane spiral-type membranes and hollow fiber membranes cannot be backwashed, and flushing is the main cleaning method incorporated in the normal process, making it difficult to increase the chemical cleaning interval. It was. Therefore, there has been a problem that the reverse osmosis membrane spiral type membrane and hollow fiber membrane can be used only for the filtration of clear water.

  The present invention has been proposed in order to solve the above-described problems of the prior art, and the object thereof is to facilitate the cleaning of a membrane such as a reverse osmosis membrane, which has been conventionally considered difficult. A further object is to provide a membrane cleaning system and a membrane cleaning method capable of switching from a normal filtration operation to a cleaning operation according to the degree of contamination of the membrane.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a reverse osmosis membrane cleaning system in which a skin layer is formed on a support layer made of a filter structure, the upstream side of the reverse osmosis membrane. Is provided with a fine bubble generating device that is activated during the cleaning operation of the reverse osmosis membrane. The reverse osmosis membrane includes a contamination degree detection device that detects the degree of contamination and the fine bubbles based on the detected value. A control device for starting the generator is provided, and when the contamination level of the reverse osmosis membrane detected by the contamination level detection device is equal to or higher than a preset reference value, the control device switches to a cleaning operation, The microbubble generator is configured to flow microbubbles to the reverse osmosis membrane.

  The invention according to claim 6 captures the invention according to claim 1 from the viewpoint of the method, and is a reverse osmosis membrane formed by forming a skin layer on a support layer comprising a filter structure. In this cleaning method, when the degree of contamination of the reverse osmosis membrane exceeds a predetermined reference value, the reverse osmosis membrane is controlled to flow by washing with fine bubbles. .

  According to the invention described in claim 1 or claim 6 having the above-described configuration, since the fine bubbles are caused to flow from the same direction as that in the normal filtration operation, the physical stress applied to the membrane is small. Further, the apparatus can be simplified as compared with the conventionally used backwashing, and the normal filtration operation can be shifted to the timely washing operation according to the degree of contamination of the membrane.

  According to a second aspect of the present invention, in the membrane cleaning system according to the first aspect, the reverse osmosis membrane is incorporated in a cassette-shaped module.

  The invention according to claim 7 captures the invention according to claim 2 from the viewpoint of the method, wherein the reverse osmosis membrane is in a cassette shape. It is characterized by being incorporated in the module.

  According to the invention described in claim 2 or claim 7 having the above-described configuration, even when the reverse osmosis membrane is incorporated in the cassette-like module, fine bubbles are formed from the same direction as in the normal filtration operation. The physical stress applied to the film is small. Further, the apparatus can be simplified as compared with the conventionally used backwashing, and the normal filtration operation can be shifted to the timely washing operation according to the degree of contamination of the membrane.

  The invention described in claim 3 is the membrane cleaning system according to claim 2, wherein the contamination degree detection device measures a differential pressure between an inlet side and an outlet side of a module incorporating the reverse osmosis membrane. The control device is configured to switch to the cleaning operation when the differential pressure becomes equal to or higher than a preset reference value.

  The invention described in claim 8 captures the invention described in claim 3 from the viewpoint of the method, and in the membrane cleaning method according to claim 7, an inlet of the module incorporating the reverse osmosis membrane. Measure the differential pressure on the outlet side and the outlet side, and if the differential pressure exceeds a preset reference value, determine that cleaning is necessary, and control the module to flow by washing with fine bubbles It is characterized by doing.

  According to the invention described in claim 3 or claim 8 having the above configuration, the degree of contamination of the membrane can be detected by the differential pressure between the inlet side and the outlet side of the module incorporating the reverse osmosis membrane. .

  According to a fourth aspect of the present invention, in the membrane cleaning system according to the second aspect, the contamination degree detection device measures a flow rate in a module incorporating the reverse osmosis membrane, and the flow rate is preset. In this case, the controller is configured to switch to the cleaning operation when the reference value is below the reference value.

  The invention described in claim 9 captures the invention described in claim 4 from the viewpoint of the method, and in the membrane cleaning method according to claim 7, the flow velocity in the module incorporating the reverse osmosis membrane Is measured, and when the flow rate is equal to or lower than a preset reference value, it is determined that the cleaning is necessary, and the module is controlled to flow with fine bubbles to be cleaned. is there.

  According to invention of Claim 4 or Claim 9 which has the above structures, the contamination degree of a film | membrane can be detected with the flow rate in the module incorporating the reverse osmosis membrane.

  According to a fifth aspect of the present invention, in the membrane cleaning system according to any one of the first to fourth aspects, the fine bubble generating device generates fine bubbles by mixing high-pressure water and compressed air. It is characterized by being.

  The invention according to a tenth aspect captures the invention according to the fifth aspect from the viewpoint of the method, and is the method for cleaning a film according to any one of the sixth to ninth aspects. The bubbles are generated by mixing high-pressure water and compressed air.

  According to the invention described in claim 5 or claim 10 having the above-described configuration, it is possible to generate very fine bubbles having a bubble diameter of about 10 to 40 μm, and the fine bubbles provide an excellent cleaning effect. Obtainable.

  According to the present invention, it is easy to clean a membrane such as a reverse osmosis membrane which has been conventionally difficult, and a membrane which can be switched from a normal filtration operation to a cleaning operation according to the degree of contamination of the membrane. A cleaning system and a film cleaning method can be provided.

  Hereinafter, an embodiment (hereinafter referred to as an embodiment) of a film cleaning system according to the present invention will be specifically described with reference to the drawings.

(1) Configuration The membrane cleaning system according to the present invention is configured as shown in FIG. That is, the raw water storage tank 1 is connected to a raw water pipe 2 for introducing raw water into the tank, and the raw water is supplied from the raw water storage tank 1 to the high-pressure filtration pump 4 via the first pipe 3. It is configured as follows.

  Further, a second pipe 5 is connected to the downstream side of the high-pressure filtration pump 4, and a three-way switching valve 6 is attached to the tip of the second pipe 5, and the third pipe 7 and the fourth pipe. 8 is connected. The third pipe 7 is provided with a water supply regulating gate valve 9, and a membrane module 10 such as a spiral membrane module or a hollow fiber membrane module is connected to the downstream side thereof. The fourth pipe 8 connected to the three-way switching valve 6 is connected to an injector 11 and a fifth pipe 12 which will be described later, thereby forming a bypass path for the third pipe 7.

  The water supply adjustment gate valve 9 is provided to adjust the supply pressure of raw water to the membrane module 10. Usually, raw water is supplied to the membrane module 10 at a certain pressure. However, when the pressure of the high-pressure filtration pump 4 is excessive or when the membrane disposed in the membrane module 10 is clean at the initial stage of operation. Since the required amount of permeated water can be secured even at a low pressure, the supply pressure to the membrane module 10 can be lowered using this water supply adjusting gate valve 9 so as to be operated softly. On the other hand, when high pressure is required to obtain a required amount of permeated water due to contamination of the membrane, the operation can be performed by increasing the supply pressure to the membrane module 10.

  Further, a sixth pipe 13 through which treated water (permeated water) purified by the membrane module 10 flows and a seventh pipe 14 through which concentrated drainage flows are connected to the downstream side of the membrane module 10. A purified treated water storage tank 15 is connected to the sixth pipe 13, and treated water purified by the membrane module 10 is introduced into the purified treated water storage tank 15 via the sixth pipe 13. Furthermore, it is configured to be supplied to the customer through the eighth pipe 16. On the other hand, the seventh pipe 14 connected to the downstream side of the membrane module 10 is configured so that the waste water after being used for cleaning the membrane module 10 can be discharged to the outside.

  The seventh pipe 14 is provided with a pressure regulating valve 17 and a bypass circuit 18 that bypasses the pressure regulating valve 17. The bypass circuit 18 is provided with an automatic flushing valve 19. Yes. The pressure applied to the entire membrane module can be increased by restricting the pressure adjusting valve 17, and the amount of permeated water can be adjusted by appropriately adjusting the pressure adjusting valve 17. . In addition, as the membrane module 10, a membrane module of a type in which a spiral membrane or a hollow fiber membrane is incorporated in a cylindrical vessel is used.

  The injector 11 is connected to a compressor 22 serving as a high pressure air supply source via a ninth pipe 21 having a high pressure air valve 20. In the injector 11, the raw water supplied by the high-pressure filtration pump 4 through the three-way switching valve 6 and the air compressed by the compressor 22 are mixed to generate microbubbles. . Here, the microbubble refers to a very fine bubble having a bubble diameter of about 10 to 40 μm.

  In this injector 11, a part of the air mixed with the raw water (pressure water) is dissolved, and a part of the air flows into the membrane module as it is pulverized and dispersed in the raw water. Then, dissolved air is generated as fine bubbles in the membrane module, and ultrasonic waves are generated when the bubbles are further dissolved and crushed in the membrane module. The ultrasonic waves generated in this way become a driving force that removes dirt from the membrane surface, and the microbubbles enclose the dirt and make it easy to peel off from the membrane surface, and at the same time, carry the encased dirt out of the membrane module. To make it easier. Further, the dispersed bubbles increase the cleaning effect by increasing the shearing force on the membrane surface when the raw water flows through the membrane module.

  In addition, the membrane module 10 is provided with a detection device 30 that detects the degree of contamination in the membrane module 10. In other words, the detection device 30 determines whether or not the detected value exceeds a predetermined threshold value. For example, a determination device 31 that determines whether or not to switch to the cleaning operation is connected. Further, the determination device 31 is connected to a control device 32 that switches the three-way switching valve 6 and opens and closes the flushing automatic valve 19 and the high-pressure air valve 20 based on the determination result.

  The detection device 30 for detecting the degree of contamination in the membrane module 10 includes, for example, a membrane clogging sensing pressure sensor for measuring the differential pressure between the inlet and the outlet of the membrane module 10, and the permeation flow rate at the same operating pressure. An anemometer that measures the change can be used. That is, in the case where the membrane clogging sensing pressure sensor is used, an increase in the differential pressure between the inlet and the outlet of the membrane module 10 means an increase in the degree of contamination in the membrane module, and in the case where a velocimeter is used, A decrease in the permeation flow rate means an increase in the degree of contamination in the membrane module.

  When the determination device 31 determines that the differential pressure between the inlet and outlet of the membrane module 10 exceeds a certain value, or the permeation flow rate at a certain operation pressure is less than a certain ratio compared to the permeation flow rate at the initial stage of operation. If it is determined that the operation has been lowered, it is determined that the operation should be switched to the cleaning operation, and the switching operation and the opening degree adjusting operation by the control device 32 are performed.

(2) Operation The membrane cleaning system of the present embodiment having the above configuration operates as follows.

(2-1) During filtration operation During normal filtration operation, the second pipe 5 and the third pipe 7 are connected by the first three-way switching valve 6 as shown by the thick line in FIG. The raw water supplied by 2 is introduced into the membrane module 10 via the high-pressure filtration pump 4. During the filtration operation, the flushing automatic valve 19 and the high-pressure air valve 20 are closed.

  Then, the treated water purified by the membrane module 10 is introduced into the purified treated water storage tank 15 through the sixth pipe 13 and further supplied to the customer through the eighth pipe 16. On the other hand, the concentrated waste water discharged from the membrane module 10 is discharged to the outside through the seventh pipe 14.

(2-2) At the time of washing | cleaning operation During normal filtration driving | operation as mentioned above, the contamination degree of the film | membrane in the membrane module 10 becomes high, and the detection value by the detection apparatus 30 is detected by the determination apparatus 31. If it is determined that the predetermined threshold has been exceeded, the cleaning operation is switched. That is, as shown by the thick line in FIG. 3, the first three-way switching valve 6 is switched by the control device 32 to connect the second pipe 5 and the fourth pipe 8, and the flushing automatic valve 19 and the high-pressure air are connected. Valve 20 is opened.

  As a result, the raw water supplied by the raw water pipe 2 is introduced into the injector 11 through the high-pressure filtration pump 4, and the air compressed by the compressor 22 is introduced into the injector 11, and both are mixed to form a microbubble. Is generated. By introducing the microbubbles into the membrane module 10, the membrane can be washed. At that time, by opening the flushing automatic valve 19 provided in the bypass circuit 18, a large amount of water is passed to the primary side, and dirt is discharged to the outside.

  After the cleaning with microbubbles is performed in this way, when the determination device 31 determines that the detection value by the detection device 30 has become a predetermined threshold value or less, the control device 32 performs the first three-way switching valve. 6 and at the same time, the flushing automatic valve 19 and the high-pressure air valve 20 are closed to return to the normal operation.

(3) Effect As described above, according to the membrane cleaning system of the present embodiment, the effect of physical cleaning of a spiral membrane of a reverse osmosis membrane and a hollow fiber membrane, which could be dealt with only by flashing, which is less effective in the past, has been greatly improved. Can be improved. In addition, highly accurate cleaning can be performed with a smaller amount of water than flushing.

  In addition, the backwashing that has been used in the past must extrude water from the opposite direction to that of normal filtration operation, and structurally applies pressure from the side that is weak to the pressure, thereby damaging the membrane. There was a drawback that it was easy. On the other hand, the membrane cleaning system of the present embodiment has an advantage that the physical stress applied to the membrane is small because the microbubbles flow from the same direction as in the normal filtration operation. Furthermore, as compared with backwashing, the apparatus can be simplified, and since the normal filtration operation can be immediately shifted to the washing operation, less time is wasted.

  Further, in the cleaning method using the membrane cleaning system of the present embodiment, a sufficient cleaning effect can be obtained without using chemicals, and it is effective for dirt that cannot be removed by simple physical cleaning. By using it, it exhibits a better cleaning effect. Furthermore, the membrane cleaning system of the present embodiment can be easily added and incorporated as a cleaning system for an existing membrane filtration device.

  As described above, according to the membrane cleaning system of the present embodiment, the raw water and air are mixed and dissolved by the injector, and the mixed water is introduced into the membrane module, thereby cleaning the ultrasonic waves when the fine bubbles further collapse. Due to the improvement of the peeling and removal effect of the contaminated components due to the generation of force and fine bubbles, and the increase of the cleaning effect of the membrane surface due to the coarse bubbles, a very large cleaning effect can be obtained as compared with the conventional flushing.

(4) Other Embodiments The present invention is not limited to the above-described embodiment, and a known microbubble generator can be used as the microbubble generator. Also, without using the above three-way switching valve or bypass piping, a fine bubble generator such as an injector is installed on the cleaning processing line, which is provided upstream of the membrane module and separately from the filtration processing line. However, the filter processing line may be switched to the cleaning processing line depending on the detected degree of contamination of the membrane.

System flow diagram showing the configuration of the membrane cleaning system according to the present invention The system flow figure which shows the state at the time of normal operation of the film | membrane washing | cleaning system which concerns on this invention The system flow figure which shows the state at the time of washing | cleaning driving | operation of the film | membrane washing | cleaning system which concerns on this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Raw water storage tank 2 ... Raw water pipeline 3 ... 1st piping 4 ... High pressure filtration pump 5 ... 2nd piping 6 ... Three-way switching valve 7 ... 3rd piping 8 ... 4th piping 9 ... Water supply adjustment gate valve DESCRIPTION OF SYMBOLS 10 ... Membrane module 11 ... Injector 12 ... 5th piping 13 ... 6th piping 14 ... 7th piping 15 ... Purified water storage tank 16 ... 8th piping 17 ... Pressure regulating valve 18 ... Bypass circuit 19 ... Flushing Automatic valve 20 ... high pressure air valve 21 ... 9th piping 22 ... compressor 30 ... detection device 31 ... determination device 32 ... control device

Claims (10)

A reverse osmosis membrane cleaning system in which a skin layer is formed on a support layer made of a filter structure,
On the upstream side of the reverse osmosis membrane, a fine bubble generating device that is activated during the cleaning operation of the reverse osmosis membrane is provided,
The reverse osmosis membrane is provided with a contamination degree detection device that detects the contamination degree, and a control device that activates the fine bubble generation device based on the detection value,
When the contamination level of the reverse osmosis membrane detected by the contamination level detection device is equal to or higher than a preset reference value, the control device switches to a cleaning operation, and the fine bubble generating device finely changes the reverse osmosis membrane. A membrane cleaning system configured to flow air bubbles.   The membrane cleaning system according to claim 1, wherein the reverse osmosis membrane is incorporated in a cassette-shaped module. The contamination degree detection device measures a differential pressure between an inlet side and an outlet side of a module incorporating the reverse osmosis membrane;
The membrane cleaning system according to claim 2, wherein when the differential pressure becomes equal to or higher than a preset reference value, the controller is configured to switch to a cleaning operation. The contamination degree detection device measures a flow rate in a module incorporating the reverse osmosis membrane,
The membrane cleaning system according to claim 2, wherein when the flow velocity is equal to or lower than a preset reference value, the control device switches to a cleaning operation.   The membrane cleaning system according to any one of claims 1 to 4, wherein the microbubble generator generates microbubbles by mixing high-pressure water and compressed air. A method for cleaning a reverse osmosis membrane in which a skin layer is formed on a support layer made of a filter structure,
A method for cleaning a membrane, characterized in that when the degree of contamination of the reverse osmosis membrane exceeds a predetermined reference value, the reverse osmosis membrane is controlled to flow with fine bubbles.   The method for cleaning a membrane according to claim 6, wherein the reverse osmosis membrane is incorporated in a cassette-shaped module. Measure the differential pressure on the inlet side and outlet side of the module incorporating the reverse osmosis membrane,
8. The control according to claim 7, wherein when the differential pressure is equal to or higher than a preset reference value, it is determined that cleaning is necessary, and control is performed so that the module is cleaned by flowing fine bubbles. How to clean the membrane. Measure the flow rate in the module incorporating the reverse osmosis membrane,
8. The control according to claim 7, wherein when the flow velocity is equal to or lower than a preset reference value, it is determined that the cleaning is necessary, and the module is controlled so as to flow with fine bubbles. Method for cleaning the membrane.   The method for cleaning a film according to any one of claims 6 to 9, wherein the fine bubbles are generated by mixing high-pressure water and compressed air.

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