JP4461288B2 - Filtration membrane abnormality detection method and apparatus - Google Patents

Description

The present invention relates to a method for detecting an abnormality in a filtration membrane such as a UF membrane or an MF membrane used in a water treatment device, and an apparatus used in the method. In addition, the present invention relates to a method for detecting an abnormality of a filtration membrane that is easier and more reliable by applying the diffusion flow rate test method for detecting an abnormality of the filtration membrane, and an apparatus used for the method. Furthermore, the present invention is a method for detecting an abnormality of a filtration membrane that is easier and more reliable by measuring the amount of water to be pushed out by injecting pressurized air from the primary side of the filtration membrane, and The present invention relates to an apparatus used for the method.

In the water purification field, UF (ultrafiltration) membranes and MF (microfiltration) membranes are used as filtration membranes as membrane filtration systems to remove microorganisms and suspended solids in raw water (hereinafter also referred to as treated water). There was a system that was. These are very effective systems for removing pathogenic microorganisms such as Cryptosporidium that cannot be removed by conventional coagulation sedimentation, sand filtration, and chlorine disinfection.
Currently, membrane filtration systems are beginning to spread in the water purification field with the primary purpose of removing pathogenic microorganisms, so even if there is an abnormality in the membrane, such as when the membrane is broken, the membrane is used to purify the water. If provided, the main purpose cannot be achieved, so a technique for reliably detecting the abnormality is required.

One of the detection techniques known so far is a method of measuring filtration water particulates and turbidity to know abnormalities in the filtration membrane. Although this method enables continuous monitoring, the detection sensitivity is limited due to particles formed by collecting particles in the pipe that are smaller than the membrane holes present in the membrane filtered water on the secondary side of the membrane. There is. In that respect, the detection sensitivity is more than 10 times that of the method of measuring fine particles and turbidity of filtered water without depending on the turbidity of raw water, and a diffusion flow test (air flow test) is a highly reliable method ( Non-patent document 1). This test method utilizes the fact that in order for air to pass through the pores of a wet MF membrane or UF membrane, a pressure greater than the capillary suction force of the pores (pressure above the bubble point) is required. Injecting air (e.g., about 100 kPa) pressurized below the bubble point to the primary side of the membrane, the flow rate of air necessary to maintain a constant pressure, i.e., exiting to the secondary side of the membrane It is a test method that measures the amount of air going.
In the case of a film (normal film) in which no abnormality is found such as no breakage, the pressurized air does not pass through the pores of the film except that the air diffuses into the water. Therefore, a small amount of air flow is required to keep the pressure on the primary side of the membrane constant.
On the other hand, in the case of abnormal membranes (ruptured membranes) such as when there is a rupture, air is ejected from the ruptured location to the secondary side of the membrane. You must continue to supply air.

FIG. 3 is a flowchart of a conventional membrane filtration apparatus with a membrane breakage detection function.
In the normal operation of the filtration device, the treated water injection valve 3 and the treated water drain valve 4 are opened, and the treated water is caused to flow into the membrane module 1 via the treated water injection valve 3. Is taken out from the treated water drain valve 4.
Of the conventional methods of injecting air into the membrane and detecting the breakage of the membrane, there are the following two methods for measuring the flow rate of the injected air.
(1) In FIG. 3, the flow rate of pressurized air injected from the primary side of the membrane module 1 through the air injection valve 10 from the compressor 8 through the pressure reducing valve 9 is changed to the air injection on the primary side of the membrane module 1. A method of measuring with an air flow meter 12 arranged on a pipe 11 (Non-patent Document 3).
(2) In FIG. 3, the drain pipe 16 connected to the secondary side of the membrane module 1 via the drain valve 15 is connected with the flow rate of the air injected from the primary side of the membrane module 1 in the same procedure as described above. A method of measuring the amount of water pushed out by the air leaked to the secondary side of the membrane module 1 with the water flow meter 17 disposed above (Non-patent Document 2).
Among these, in the case of the above (1) in which the air flow meter 12 is installed and the air flow rate is measured, whether the flowing air amount is the amount that is missing on the secondary side of the membrane module 1, There is a drawback that it cannot be determined whether the amount of air injected to increase the pressure on the primary side of the membrane module 1 is measured.

On the other hand, in the method (2) in which the water flow meter 17 is installed, the flow rate of water that is an incompressible fluid is measured. However, this method also has the following problems. This problem will be described with reference to FIGS.
In these drawings, the configuration in which the hollow fiber membranes are arranged side by side is taken as an example, and the case where the treated water is injected into the straw-shaped central hole of the hollow fiber membranes and membrane filtrate water is obtained on the outside is taken as an example. .
First, FIG. 4 shows the state before the diffusion flow rate test in which the membrane primary side 19, the membrane primary side (hollow fiber membrane inner side) 20, and the membrane secondary side (hollow fiber membrane outer side) 21 are filled with water. .
Next, before injecting the pressurized air, the water on the membrane primary side 19 is drained from the primary drain valve 14 as shown in FIG. At this time, much water remains on the primary side (hollow fiber membrane inner side) 20 of the membrane. This can occur when the hollow fiber membrane is placed vertically but the inner diameter of the membrane is small.

And in the state which this water remained, as shown in FIG. 6, pressurized air is inject | poured into the primary side (hollow fiber membrane inner side) 20 of a film | membrane. At this time, the water on the primary side of the membrane (inside the hollow fiber membrane) 20 is pushed by the air and is filtered to the secondary side (outside of the hollow fiber membrane) 21 of the membrane. A large amount of water may flow. Therefore, it is necessary to wait for a certain time until the water on the primary side (inside the hollow fiber membrane) 20 of the membrane is completely pushed out.
The problem here is the thickness of a pipe (hereinafter also referred to as a pipe) that reaches the drain port 18. If this pipe is sufficiently thick, it takes only a few minutes until drainage is completed. However, when the filtration membrane used is a membrane with no abnormality, after the water on the primary side (inside the hollow fiber membrane) 20 of the membrane has been completely extruded, the air becomes the secondary side (outside the hollow fiber membrane) 21 of the membrane. The amount of water that flows due to leakage is very small, for example, several tens to several hundreds ml / min. In order to measure this with a flow meter, the thickness of the pipe must be about several millimeters in diameter.
However, when the piping is so thin, it takes a long time, for example several tens of minutes, to drain the residual water on the primary side (inside the hollow fiber) 20 of the membrane, which is not practical.

"Membrane Filtration Method Q & A in Waterworks" Corporation Water Purification Process Association: (Reference: p139) Diffusion flow test EPA 815-D03-008 “Membrane Filtration Guidance Manual”, pages 4-29 to 4-37, pages 4-33 to 4-37, US Environmental Protection Agency (EPA): (http://www.epa.gov/safewater/ available at lt2 / guides.html)) "Membrane rupture detection experiment in total filtration system" (Proceedings of the 54th National Waterworks Research Presentation, 15.5 p186)

  Accordingly, an object of the present invention is to drain a relatively large amount of water that is filtered from the primary side of the membrane (inside the hollow fiber membrane) to the secondary side of the membrane (outside the hollow fiber membrane) without taking a long time. Furthermore, it is an object of the present invention to provide a method capable of accurately measuring a relatively small amount of water that flows out when air leaks to the secondary side of the membrane (outside of the hollow fiber membrane). Moreover, it is providing the apparatus used for the method.

In order to accurately measure the relatively small amount of water that flows out due to air leaking to the secondary side of the membrane during various efforts to solve the above problems, the present inventors are relatively small. It is necessary to use a plurality of pipes with different inner diameters, such as using a pipe with a relatively large inner diameter when a pipe with a moderately large inner diameter is required and having a large amount of drainage. When using pipes, it is necessary to decide which pipe to use according to the amount of drainage. To avoid such inconvenience, the pipes are arranged in an inverted U-shape and have a larger inner diameter. When the piping was made so that the height of the discharge port was higher than the height of the discharge port of the pipe having a thinner inner diameter, the above-mentioned problem could be solved, and the present invention was finally reached.

The invention according to claim 1 of the present invention fills the inside of the filtration membrane with a liquid, discharges the liquid on the primary side of the filtration membrane, injects pressurized gas from the primary side of the filtration membrane, In the method of detecting an abnormality of the filtration membrane by measuring the amount of liquid pushed out from the side and flowing in the piping, the secondary side tube of the filtration membrane has at least one branch pipe and the branch pipe The inner diameter of the branch pipe is increased to a position higher than the branch pipe, and the flow rate of the branch pipe is measured. It is a filtration membrane abnormality detection method. Here, the phrase “the pipe having a large inner diameter is raised to a position higher than that of the branch pipe” means that the pipe having a large inner diameter is installed above the branch pipe.
The invention according to claim 2 of the present invention is characterized in that, in the above invention, the liquid flowing in the branch pipe is lower than the liquid flowing in the pipe having a large inner diameter. , Characterized by measuring the amount of drainage from the branch pipe when not drained from the pipe having a large inner diameter,
According to a fourth aspect of the present invention, in the above invention, the height of the discharge port of the pipe having a large inner diameter is set to be higher than the discharge port of the branch pipe, and the branch pipe and the pipe having a large inner diameter are provided. It is characterized in that a part or all of the pipes are arranged in an inverted U shape.

The invention according to claim 5 of the present invention includes means for filling the inside of the filtration membrane with liquid, means for discharging the liquid on the primary side of the filtration membrane, means for injecting gas from the primary side of the filtration membrane, and two of the filtration membranes. In an apparatus for detecting an abnormality of a filtration membrane provided with a means for measuring the amount of liquid extruded from the secondary side and flowing through the piped pipe, at least one pipe through which the liquid extruded from the secondary side of the filtration membrane flows And a pipe having an inner diameter larger than the inner diameter of the branch pipe and from which the branch pipe is branched. The pipe having the larger inner diameter is raised to a position higher than the branch pipe, and the branch pipe Is a filtration membrane abnormality detection device characterized by being a pipe for measuring the flow rate,
According to a sixth aspect of the present invention, in the above invention, the pipe having a large inner diameter is raised to a position higher than the branch pipe so that the liquid flowing in the branch pipe is located below the liquid flowing in the pipe having a large inner diameter. It is characterized by
The invention according to claim 7 is provided such that the discharge port of the pipe having a large inner diameter is positioned higher than the discharge port of the branch pipe, and part or all of the branch pipe and the pipe having the large inner diameter. It is characterized by being piped so as to have an inverted U shape.

Hereinafter, the present invention will be described in detail.
The filtration membrane of the present invention is typically a filtration membrane used when obtaining purified water, such as a UF membrane or an MF membrane, but membranes other than the purpose of obtaining purified water are also applicable. In the present invention, the above-described UF membranes, MF membranes, and other filtration membranes are generally combined into a membrane module, which is generally used for water purification treatment.
Water to be treated (hereinafter sometimes referred to as raw water) is injected into the membrane module from the primary side of the membrane, filtered, and the treated water is taken out from the secondary side of the membrane, and sent to the next step. The method is generally done.

In the present invention, when a membrane abnormality such as a breakage of the filtration membrane in the membrane module is detected, the membrane module is filled with water, and then the primary drainage of the membrane module is performed. Then, although pressurized air is inject | poured from the primary side of a film | membrane, it is preferable to make it below a bubble point. Since water remains inside the hollow fiber in the membrane module, the water on the primary side of the membrane module is pushed out to the secondary side by pressurized air, and a large amount of leaked water is drained from the membrane module through the drain pipe. (Hereinafter sometimes referred to as residual water). If pressurized air is continuously injected, the amount of leaked water flowing through the drainage pipe also decreases.
After almost all of the residual water has been pushed out, the water leaked from the primary side of the membrane to the secondary side of the membrane by diffusion diffuses and drains the water on the secondary side of the membrane.

  In the present invention, at least two kinds of pipes having different inner diameters are used as the drainage pipe. That is, when the leaked water flowing out from the drain pipe is relatively large, a pipe having a relatively large inner diameter is used so that the drain can be drained in a short time. On the other hand, when the amount of leaked water flowing out from the drainage pipe is relatively small, a pipe having a relatively small inner diameter is used so that the amount of leaked water can be accurately measured. Here, the size of the inner diameter is not limited at all, and may be appropriately determined depending on the amount of water to be discharged. However, a pipe having a small inner diameter needs to have an inner diameter that requires accurate measurement of the leaked water even if the leaked water is relatively small. If the amount of leaked water is large, the number of drainage pipes may be increased in order to drain the leaked water. The increased inner diameter of the pipe may be the same as or different from the inner diameter of the pipe that drains the leaked water.

Furthermore, in this invention, the part near the discharge port of the drainage pipe is made into a substantially inverted U shape. Here, the substantially inverted U shape means a shape in which a part of the tube has an inverted U shape or a similar shape, as shown in FIG. 1 or FIG.
And it installs so that the height of the discharge port of each drainage pipe may be almost the same or different. In particular, it is preferable that the outlet of the drainage pipe having a large inner diameter is set higher than the height of the outlet of the drainage pipe having a small inner diameter.
With such a configuration, when there is a large amount of leaked liquid, the leaked liquid is drained from all drainage pipes, but as the leaked liquid gradually decreases, the leaking soot is drained from the drainage pipe with a smaller inner diameter. become.

The time when the detection of the abnormality of the filtration membrane is started is after the time when the amount of residual water gradually decreases and is eventually drained from the thin pipe. That is, the time for detecting the presence or absence of abnormality in the filtration membrane is after almost all of the residual water has been pushed out, and when the rate of change in the amount of leaked liquid drained from a pipe having a small inner diameter becomes almost zero. And Here, the rate of change is substantially 0 means that the amount of change per minute of the amount of leaked liquid is within 10 mL. An abnormal filtration membrane refers to a filtration membrane in which fine particles or protozoa that can be originally captured cannot be captured because a part of the filtration membrane is broken or broken.
As a simple method, a timer set at the start of pressurization is started, and when the set time comes, measurement for determining the presence or absence of breakage based on the amount of drainage is started. The set time is determined based on data obtained by preparing a membrane module made of a broken hollow fiber and performing a diffusion flow rate test in advance using the membrane module.

According to the present invention, it is possible to detect a membrane abnormality such as a filter membrane breakage with a relatively simple method in a relatively short time and with high reliability. Moreover, there is no troublesome operation. Furthermore, the abnormal film detection device of the present invention is a durable and cost-reduced device and is a very practical invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a main part of an example of a membrane module membrane abnormality detection device used in the present invention (using two tubes, a tube having a large diameter and a tube having a small diameter).
Water on the membrane primary side (hollow fiber membrane inner side) 20 and the membrane secondary side (hollow fiber membrane outer side) 21 passes through the drainage valve 15 and drainage pipes 22 and 16 to the outside of the system. Discharged. The drainage pipe 16 having a small inner diameter branched from the pipe is provided with a water flow meter 17 for measuring the amount of drainage flowing through the drainage pipe 16. A part of the drainage pipe 22 is piped in a substantially inverted U shape, and a part of the drainage pipe 16 is also piped in a substantially inverted U shape. The discharge port of the drainage pipe 22 is set higher than the discharge port of the drainage pipe 16 and is preferably set so as not to exceed the top of the drainage pipe 16. The difference in height between the discharge ports is preferably within a range of 5 to 10 cm. The inner diameter of the drainage pipe 16 is preferably 2 to 20 mm, and the inner diameter of the drainage pipe 22 is desirably about 5 to 10 times larger than the inner diameter of the drainage pipe 16.
Although not shown in the figure, the number of drain pipes can be further increased.

Here, as the thickness of the tube to be used, a thin tube is selected when the number of membrane modules to be measured at one time is small, and a thick tube is selected when the number is large. Further, the number of tubes may be increased.
This selection must be determined in consideration of the type, shape, and characteristics of the membrane, the number of membranes to be measured at one time, and the overall shape of the apparatus. The simplest determination method is to try several types at the trial production stage using an actually measuring device and select the combination that is most easily measured.

  When the abnormality of the filtration membrane is actually detected using the apparatus shown in FIG. 1, the effect shown in FIG. 2 can be obtained. That is, at the stage (2- (1)) where the water on the primary side (inside the hollow fiber membrane) 20 of the membrane of the membrane module 1 is first discharged, a large amount of water is discharged from the drainage pipes 22 and 16. . When the discharge is completed, the amount of water to be pushed out decreases, so the state of 2- (2) is reached, and almost no drainage is seen from the thick drainage pipe 22, and eventually, as shown in 2- (3) The drainage pipe 22 is not drained, but the drainage pipe 16 is drained. The head of the drainage pipe 22 settles at a position that is almost the same as the height of the discharge port of the drainage pipe 16 or a few centimeters higher.

Such a configuration has the following advantages.
By using the siphon effect, the optimum piping is automatically selected according to the change in the flow rate of water, and there is no need to use a valve for the selection.
Since machine parts are not required for the selection of piping, the durability and reliability of the equipment is improved.
The cost can be reduced,
Since drainage is performed quickly, the time used for testing can be shortened.

From the above description, the present invention can be described as follows.
(1) A membrane treatment device that removes turbidity of treated water by injecting treated water from the primary side of the membrane using UF membrane or MF membrane and obtaining filtered water from the secondary side of the membrane. An apparatus for detecting the breakage of the membrane, utilizing the fact that air is injected from the primary side of the membrane and water on the secondary side of the membrane is pushed out by the gas leaking to the secondary side of the membrane. Then, in the device for detecting an abnormality of the membrane by measuring the amount of water, the path through which the water on the secondary side of the membrane flows out is a thin pipe for measuring the flow rate and a thick pipe for draining a large amount of water. An apparatus for detecting an abnormality of a film, characterized in that there are at least two.
(2) In the anomaly detection device according to claim 1, the pipe that becomes the path through which water flows out has an inverted U shape, and the height of the drain outlet of the thick pipe is higher than the outlet of the thin pipe. An apparatus for detecting an abnormality of a film characterized by being.
(3) Filling the inside of the filtration membrane with liquid, discharging the liquid on the primary side of the filtration membrane, injecting pressurized gas from the primary side of the filtration membrane, being pushed out from the secondary side of the filtration membrane, and flowing in the pipe An abnormality detection method for a filtration membrane by measuring the amount of liquid, wherein the liquid flows through a pipe provided with at least one branch pipe having a different inner diameter.

The principal part of the membrane module membrane abnormality detection apparatus of this invention. Explanatory drawing of the drain pipe of the membrane module of this invention. The flowchart of the conventional membrane filtration apparatus with a membrane abnormality detector. Explanatory drawing of the conventional membrane module membrane abnormality detection method. (Before experiment) Explanatory drawing of the conventional membrane module membrane abnormality detection method. (During primary drainage) Explanatory drawing of the conventional membrane module membrane abnormality detection method. (Immediately after pressurized air injection)

Explanation of symbols

1. 1. Membrane module 2. Filtration pump 3. Water to be treated injection valve Treated water drain valve
5). Filtration tank
6). 6. Backwash pump Backwash valve
8). compressor
9. Pressure reducing valve
10. Air injection valve 11. Air injection tube 12. 12. Air flow meter Air release valve 14. Primary drain valve 15. Drain valve 16. Drain pipe (for measurement)
17. Water flow meter 18. Drain port 19. Membrane primary side 20. Primary side of membrane (inside hollow fiber membrane)
21. Secondary side of membrane (outside of hollow fiber membrane)
22. Drainage pipe (for initial drainage)

Claims (7)

Fill the filtration membrane with liquid, discharge the primary side liquid of the filtration membrane, inject the pressurized gas from the primary side of the filtration membrane, push out the secondary side of the filtration membrane, and the amount of liquid flowing in the pipe In the method for detecting an abnormality of a filtration membrane by measuring the flow rate, the pipe through which the liquid on the secondary side of the filtration membrane flows has at least one branch pipe and an inner diameter larger than the inner diameter of the branch pipe, and the branch pipe is An abnormality detection method for a filtration membrane, comprising: a branched pipe, wherein the pipe having a large inner diameter is raised to a position higher than the branch pipe, and the flow rate of the branch pipe is measured. 2. The filtration membrane abnormality detection method according to claim 1, wherein the liquid flowing in the branch pipe is below the liquid flowing in the pipe having a large inner diameter. 3. The filtration membrane abnormality detection method according to claim 1, wherein the amount of drainage from the branch pipe is measured when the pipe having a large inner diameter is not drained. The discharge port of the pipe having a large inner diameter is provided so that the height of the discharge port is higher than the discharge port of the branch pipe, and part or all of the branch pipe and the pipe having the large inner diameter are inverted U-shaped. The filtration membrane abnormality detection method according to claim 1, wherein the filtration membrane abnormality detection method is provided. Means for filling the inside of the filtration membrane with liquid, means for discharging the liquid on the primary side of the filtration membrane, means for injecting gas from the primary side of the filtration membrane, and liquid that is pushed out from the secondary side of the filtration membrane and flows in the pipe In the filtration membrane abnormality detection device comprising means for measuring the amount, the pipe through which the liquid pushed out from the secondary side of the filtration membrane has an inner diameter larger than the inner diameter of at least one branch pipe and the branch pipe. The branch pipe is constituted by a branch pipe, the pipe having a large inner diameter is raised to a position higher than the branch pipe, and the branch pipe is also a pipe for measuring a flow rate. Anomaly detection device. 6. The filtration according to claim 5, wherein the pipe having a larger inner diameter is raised to a position higher than the branch pipe so that the liquid flowing in the branch pipe is located below the liquid flowing in the pipe having a larger inner diameter. Membrane abnormality detection device. The discharge port of the pipe having a large inner diameter is provided so that the height of the discharge port is higher than the discharge port of the branch pipe, and part or all of the branch pipe and the pipe having the large inner diameter are inverted U-shaped. The filtration membrane abnormality detection device according to claim 5 or 6, wherein the filtration membrane abnormality detection device is piped.

Images