JPH09892A - Method for cleaning filtration membrane - Google Patents

Abstract

PURPOSE: To achieve a long life of a membrane and to prevent damage thereto by a method wherein a filtration membrane is constituted of a hydrophilic material and a pneumatic pressure is applied to a liquid passed through the membrane and held at a filtration membrane loading part through a liquid outlet port so that the filtration membrane can be surely cleaned and a pneumatic pressure required when the membrane is cleaned can be reduced. CONSTITUTION: During a filtration operation, a flow line 7 and flow line 8 are switched by a line switching three-way valve 6 so that both the valves communicate with each other. As a result, a liquid which is filtrated by a hollow fiber membrane module 100 and filled in a hollow fiber membrane bundle loading part 106 flows out of a liquid outlet port 109. And in the case of backward washing, a flow line 9 is brought into communication with the line 7 by means of the valve 6. Consequently compressed air pressure is applied onto the surface of the liquid filled in the part 106 of the module 100 so that the liquid is discharged through a raw liquid inlet port 7, whereby foreign matters attached and accumulated on the raw liquid side (inner side) of membrane wall of a hollow fiber membrane 102 are removed so that the membrane 102 is cleaned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a filtration membrane of a so-called cross-flow type membrane module, and particularly to wash the filtration membrane by causing a liquid to flow backward from the permeate side of the membrane wall of the filtration membrane to the raw solution side. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, as a cross-flow type membrane module, for example, there is a hollow fiber membrane module as shown in FIG.

In this hollow fiber membrane module 100, a bundle 103 of a large number of hollow fiber membranes 102 is loaded as a filtration membrane in a housing 101, and both ends of each hollow fiber membrane 102 are opened at both ends of the housing 101. While maintaining the gap between the hollow fiber membranes 102 and the gap between the hollow fiber membranes 102 and the housing 101, the potting material 104 as a sealing material.
The hollow fiber membrane bundle 103 is separated from the housing 101 and the outside of the housing 101 by the sealing portion 105, and the permeated liquid filtered by the hollow fiber membrane bundle loading portion 106 does not leak out. It is configured as such.

The housing 101 has a stock solution inlet 107 at one end of the hollow fiber membrane 102 on the opening side, and the hollow fiber membrane 10.
There is a stock solution outlet 108 at the other end on the opening side, and a permeate solution outlet 109 near the stock solution outlet 108 on the side wall where the hollow fiber membrane bundle loading section 106 is located.

In the hollow fiber membrane module 100 thus constructed, the stock solution is passed from the stock solution inlet 107 through the hollow fiber membrane bundle loading section 106 to the stock solution outlet 108.
The hollow fiber membrane bundle 103 in the hollow fiber membrane bundle loading unit 106 filters the filtered permeate, and the filtered permeate is filled in the hollow fiber membrane bundle loading unit 106.
It is held inside and flows out through the permeate outlet 109.

That is, the hollow fiber membrane module 100
Is the stock solution of each hollow fiber membrane 102 of the hollow fiber membrane bundle loading unit 106.
When flowing from one open end (on the side of the undiluted solution inlet 107) to the other open end (on the side of the undiluted solution outlet 108), part of the undiluted solution permeates through the membrane wall from the inside of the hollow fiber membrane 102 and is filtered. This is a so-called cross-flow type filtration.

The hollow fiber membrane module 100 is used in the system 200 shown in FIG.

In the figure, 201 is a stock solution tank for storing the stock solution, 202 is a pressurizing pump, and the pressurizing pump 202 feeds the stock solution from the stock solution tank 201 to the hollow fiber membrane module 10.
It is for supplying 0.

The hollow fiber membrane module 100 is installed vertically, and the stock solution inlet 107 of the housing 101 is arranged on the lower side in the figure, and the stock solution outlet 108 is arranged on the upper side in the figure. As a result, the permeated liquid outlet 109 also becomes the upper side in the figure. Further, a stock solution outlet pressure adjusting valve 203 is provided on the side of the stock solution outlet 108, whereby the pressure of the stock solution passing through the hollow fiber membrane module 100 is
The filtration pressure is adjusted to a predetermined level.

On the other hand, the liquid flowing out from the undiluted solution outlet 108 of the hollow fiber membrane module 100 has the undiluted solution outlet pressure adjusting valve 203.
The liquid is returned to the stock solution tank 201 through the flow path, and the solution is circulated through the flow path 204 connecting the above-mentioned components.

Then, the filtration is performed as follows.

The stock solution stored in the stock solution tank 201 is hollowed from the stock solution inlet 107 of the housing 101 below the hollow fiber membrane module 100 at a predetermined filtration pressure set by a pressurizing pump 202 and a stock solution outlet pressure adjusting valve 203. The hollow fiber membrane bundle loading unit 10 is supplied to the fiber membrane bundle loading unit 106.
The hollow fiber membrane bundle 103 in 6 is filtered as described above,
The filtered permeate is held in the hollow fiber membrane bundle loading unit 106 and flows out from the permeate outlet 109. On the other hand, the unfiltered undiluted solution is returned from the undiluted solution outlet 108 to the undiluted solution tank 201 via the undiluted solution outlet pressure adjusting valve 203, is stored in the undiluted solution tank 201, and the above-mentioned filtration is repeated. Therefore, the housing 1 of the hollow fiber membrane module 100
The hollow fiber membrane bundle loading unit 106 in 01 is always filled with the permeated liquid.

However, when the hollow fiber membrane module 100 is used for a long period of time, foreign matter and oil contained in the undiluted solution adhere to and deposit on the inner membrane surface of the hollow fiber membrane 102, which lowers the permeation flow rate and causes the hollow fiber membrane to become hollow. The thread film 102 is contaminated.

Therefore, in order to prevent contamination (do not reduce the permeation flow rate), the system 200 has a hollow fiber membrane 1
A cleaning means for cleaning 02 is provided.

This cleaning method is a so-called back-flow cleaning in which the pressurized liquid is back-flowed from the outside to the inside of the hollow fiber membrane 102 to remove the deposits on the inner membrane surface.

This cleaning means will be described with reference to FIG. 3. In the figure, 205 is a permeate tank for temporarily storing the permeate that has flowed out from the permeate outlet 109, and 206 is provided downstream of the permeate tank 205. With the pump that is used, 207
Is the permeated liquid in the permeated liquid tank 205.
It is a four-way valve for switching the flow path of flowing to the outside and flowing to the outside or to the hollow fiber membrane module 100 side.

The passage switching four-way valve 207 has a passage 208 communicating with the permeate outlet 109 of the hollow fiber membrane module 100, a passage 209 communicating with the inlet side of the permeate tank 205, and a permeate. Outlet side of tank 205 and pump 206
A flow path 210 that communicates with each other and a flow path 211 that communicates with the outside are respectively connected.

In this system 200, during the filtration operation, the flow passage switching four-way valve 207 is used to set the flow passage 208 and the flow passage 20.
9 and the flow path 210 and the flow path 211 are switched to communicate with each other (see solid line arrow in the figure). Thus, the hollow fiber membrane module 100 filters the hollow fiber membrane bundle loading unit 1
The permeate filled with 06 is temporarily stored in the permeate tank 205 from the permeate outlet 109 through the flow passage 208, the flow passage switching four-way valve 207 and the flow passage 209, and then the pump 20.
6, the flow path 210, the flow path switching 4-way valve 207 and the flow path 2
It is discharged to the outside through 11.

At the time of backflow cleaning, the flow path switching four-way valve 207 is switched so that only the flow path 210 and the flow path 208 are communicated with each other (see the dotted arrow in the figure). As a result, the permeated liquid stored in the permeated liquid tank 205 is pumped by the pump 20.
A pressure is applied by 6 to the flow path 210 and the flow path switching four-way valve 20.
7 and the flow path 208, and flows into the hollow fiber membrane bundle loading section 106 through the permeate outlet 109, and the pressurized permeate is transferred from the permeate side (outside) of the hollow fiber membrane 102 to the stock solution side (outside). It is washed by backflowing to the inside) and removing the deposits on the inside film surface.

Instead of the permeated liquid, a cleaning liquid that is clear enough not to block the pores in the membrane wall of the hollow fiber membrane 102 may be used, and compressed air may be used instead of the pump 206.

[0021]

However, the above-mentioned cross-flow type hollow fiber membrane module 100 has the following problems.
The pressure loss of the undiluted solution causes a pressure difference between the undiluted solution inlet 107 side and the undiluted solution outlet 108 side, and the pressure difference on the undiluted solution inlet 107 side becomes higher. Therefore, the hollow fiber membrane 102 on the stock solution inlet 107 side in the hollow fiber membrane bundle loading unit 106 is closer to the stock solution outlet 108.
Since it is more often used for filtration from the side, the amount of permeation increases, and the hollow fiber membrane 102 in that portion is significantly contaminated.

By the way, this hollow fiber membrane module 100
Is the stock solution inlet 107 in the system 200 described above.
Since the raw liquid outlet 108 and the permeated liquid outlet 109 are vertically placed on the lower side and on the upper side, the hollow fiber membrane 102 below the hollow fiber membrane bundle loading section 106 is significantly contaminated.

When backwashing is carried out in the system 200 described above, the permeate outlet 109 becomes the hollow fiber membrane bundle loading section 1
Since it is at the upper part of 06, the pressurized permeate (or cleaning liquid) almost flows out through the undiluted solution outlet 108 at the upper part of the uncontaminated hollow fiber membrane 102 in the hollow fiber membrane bundle loading part 106. , The hollow fiber membrane 102 to be washed originally
Liquid does not flow to the bottom of the and is not washed. As a result, the recovery rate of the permeation flow rate ((flow rate after washing-flow rate before washing) / (initial flow rate-
The flow rate before washing)) was low.

Therefore, in order to wash the lower part of the hollow fiber membrane 102, a large backflow velocity is required, so that the hollow fiber membrane 102 at the portion of the permeate outlet 109 which is the inlet of the liquid for washing is required. A high fluid pressure acts on the hollow fiber membrane 102.
Is causing the damage.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its purpose is to:
It is an object of the present invention to provide a method for cleaning a filtration membrane, which ensures cleaning of the filtration membrane, lowers the air pressure required for the permeated liquid at the time of cleaning, and prolongs the life of the membrane and prevents damage to the membrane.

[0026]

In order to achieve the above object, according to the present invention, a housing having a plurality of inflow / outflow ports is loaded with a filtration membrane for filtering an undiluted solution,
When passing the undiluted solution from the undiluted solution inlet to the undiluted solution outlet among the plurality of inflow and outflow ports of the housing through the filtration membrane loading section, a part of the undiluted solution passes through the membrane wall of the filtration membrane in the filtration membrane loading section, A membrane module that holds the permeate in the filtration membrane loading portion of the housing and then flows out through the permeate outlet of the plurality of inflow and outflow ports of the housing, from the permeate side of the membrane wall of the filtration membrane to the raw solution side. In the method of washing the filtration membrane by backflowing the liquid, the filtration membrane is made of a hydrophilic material, and permeate retained in the filtration membrane loading part is permeated by applying air pressure through the permeate outlet. The liquid is discharged at least from the stock solution inlet.

[0027]

According to the above method for cleaning the filtration membrane, air pressure is applied to the permeated liquid held in the filtration membrane loading portion in the housing through the permeated liquid outlet of the housing to discharge the permeated liquid from at least the raw liquid inlet of the housing. Therefore, under the liquid level of the permeated liquid held in the filtration membrane loading section, the permeate side of the membrane wall of the filtration membrane flows back to the undiluted liquid side, and it is deposited on the undiluted liquid side. Foreign substances are removed and the filtration membrane is washed. That is, the entire filtration membrane of the filtration membrane loading section can be reliably washed.

At this time, since the filtration membrane is made of a hydrophilic material, air does not pass through to the undiluted solution side, so that the permeation efficiency does not decrease due to the inclusion of air.

When the membrane module is placed vertically with the undiluted solution inlet of the housing on the lower side, the contamination of the lower membrane in the filtration membrane loading section, which is the undiluted solution inlet side where the filtration pressure becomes high, becomes remarkable. According to this, since the permeated liquid held in the filtration membrane loading part is discharged from the raw liquid inlet, the filtration membrane is washed, so that the liquid surface of the permeated liquid is lowered as the cleaning progresses. The cleaning time at the bottom of the filtration membrane, which is the most polluted, can be extended.

As described above, since the cleaning time of the heavily contaminated part can be taken long, the permeated liquid retained in the filtration membrane loading part can be cleaned at a low pressure, whereby damage to the membrane can be prevented and the membrane can be prevented. It is possible to extend the life of the.

[0031]

EXAMPLE A method for cleaning a filtration membrane according to an example of the present invention will be described below.

First, a hollow fiber membrane module as a cross-flow type membrane module to which the method for cleaning a filtration membrane is applied will be described. Since this hollow fiber membrane module is the same as that shown in FIG. 2 described in the prior art,
The same components will be described with the same reference numerals.

In the hollow fiber membrane module 100, a bundle 103 of a large number of hollow fiber membranes 102 is loaded as a filtration membrane in a housing 101, and both ends of each hollow fiber membrane 102 are opened at both ends of the housing 101. While maintaining the gap between the hollow fiber membranes 102 and the gap between the hollow fiber membranes 102 and the housing 101, the potting material 104 as a sealing material.
The hollow fiber membrane bundle 103 is separated from the housing 101 and the outside of the housing 101 by the sealing portion 105, and the permeated liquid filtered by the hollow fiber membrane bundle loading portion 106 does not leak out. It is configured as such.

The housing 101 has a plurality of inflow and outflow ports, and a stock solution inlet 107 is provided at one end of the hollow fiber membrane 102 on the opening side and a stock solution inlet 107 is provided at the other end of the hollow fiber membrane 102 on the opening side. The stock solution outlet 108 is located near the stock solution outlet 108 on the side wall where the hollow fiber membrane bundle loading section 106 is located.
9 are provided.

In the hollow fiber membrane module 100 thus constructed, the stock solution is passed from the stock solution inlet 107 through the hollow fiber membrane bundle loading section 106 to the stock solution outlet 108.
The hollow fiber membrane bundle 103 in the hollow fiber membrane bundle loading unit 106 filters the filtered permeate, and the filtered permeate is filled in the hollow fiber membrane bundle loading unit 106.
It is held inside and flows out through the permeate outlet 109.

That is, this hollow fiber membrane module 100
Is the stock solution of each hollow fiber membrane 102 of the hollow fiber membrane bundle loading unit 106.
When flowing from one open end (on the side of the undiluted solution inlet 107) to the other open end (on the side of the undiluted solution outlet 108), part of the undiluted solution permeates through the membrane wall from the inside of the hollow fiber membrane 102 and is filtered. This is a so-called cross-flow type filtration.

The hollow fiber membrane module 100 is used in the system 1 shown in FIG.

In the figure, 2 is a stock solution tank for storing the stock solution, 3 is a pressurizing pump, and the pressurizing pump 3 is for supplying the stock solution from the stock solution tank 2 to the hollow fiber membrane module 100. .

The hollow fiber membrane module 100 is vertically installed, and the stock solution inlet 107 of the housing 101 is arranged on the lower side in the figure and the stock solution outlet 108 is arranged on the upper side in the figure. As a result, the permeated liquid outlet 109 also becomes the upper side in the figure. Further, a stock solution outlet pressure adjusting valve 4 is provided on the side of the stock solution outlet 108, so that the pressure of the stock solution passing through the hollow fiber membrane module 100 is adjusted to a predetermined filtration pressure.

On the other hand, the liquid flowing out from the raw liquid outlet 108 of the hollow fiber membrane module 100 returns to the raw liquid tank 201 via the raw liquid outlet pressure adjusting valve 4, and the liquid connects the above-mentioned components. It circulates through the flow path 5.

Then, the filtration is performed as follows.

The stock solution stored in the stock solution tank 2 is hollowed from the stock solution inlet 107 of the housing 101 below the hollow fiber membrane module 100 at a predetermined filtration pressure set by the pressure pump 3 and the stock solution outlet pressure adjusting valve 4. Thread film bundle loading unit 106
And is filtered by the hollow fiber membrane bundle 103 in the hollow fiber membrane bundle loading section 106 as described above, and the filtered permeate is retained in the hollow fiber membrane bundle loading section 106 and It flows out from the outlet 109. On the other hand, the unfiltered undiluted solution is returned from the undiluted solution outlet 108 to the undiluted solution tank 2 via the undiluted solution outlet pressure adjusting valve 4, and is stored in the undiluted solution tank 2, and the above-mentioned filtration is repeated. Therefore, the hollow fiber membrane bundle loading section 106 in the housing 101 of the hollow fiber membrane module 100 is always filled with the permeated liquid.

However, when the hollow fiber membrane module 100 is used for a long period of time, foreign matter and oil contained in the undiluted solution adhere and deposit on the inner membrane surface of the hollow fiber membrane 102, and the permeation flow velocity decreases and the hollow fiber membrane becomes hollow. The thread film 102 is contaminated.

Therefore, in order to prevent contamination (do not reduce the permeation velocity), the system 1 has a hollow fiber membrane 102.
A cleaning means is provided for cleaning the.

This cleaning method is a so-called backflow cleaning in which the pressurized liquid is backflowed from the outside to the inside of the hollow fiber membrane 102 to remove the deposit on the inner membrane surface.

This cleaning means will be described with reference to FIG. 1. In the figure, reference numeral 6 is a three-way valve for switching the flow path of flowing permeate to the outside or flowing compressed air to the hollow fiber membrane module 100 side. .

The flow path switching 3-way valve 6 has a flow path 7 communicating with the permeate outlet 109 of the hollow fiber membrane module 100.
, And a flow path 8 for flowing the permeated liquid to the outside and a flow path 9 through which compressed air flows are connected to each other.

In this system 1, during the filtration operation,
The flow path switching three-way valve 6 is switched so that the flow path 7 and the flow path 8 communicate with each other (see the solid arrow in the figure). As a result, the permeated liquid that has been filtered by the hollow fiber membrane module 100 and filled in the hollow fiber membrane bundle loading section 106 is filtered by the permeated liquid outlet 109.
Through the flow path 7, the flow path switching 3-way valve 6 and the flow path 8 to the outside.

Then, at the time of backwashing, the flow path switching three-way valve 6 is switched so that the flow path 9 and the flow path 7 communicate with each other (see the dotted arrow in the figure). As a result, pressure is applied by the compressed air to the liquid surface of the permeated liquid filling the hollow fiber membrane bundle loading unit 106 of the hollow fiber membrane module 100,
Since the permeated liquid is discharged from the undiluted liquid inlet 107, it flows backward from the permeated liquid side (outside) of the membrane wall of the hollow fiber membrane 102 to the undiluted liquid side (inner side) below the liquid surface of the permeated liquid and adheres to the undiluted liquid side membrane surface. The accumulated foreign matter is removed, and the hollow fiber membrane 102 is washed.

Accordingly, the entire surface of the hollow fiber membrane 102 in the hollow fiber membrane bundle loading section 106 is reliably washed from the upper portion to the lower portion. As a result, the recovery rate of the permeation flow rate due to cleaning ((flow rate after cleaning-flow rate before cleaning) / (initial flow rate-flow rate before cleaning)) can be improved.

When air is mixed into the hollow fiber membrane 102 during the backwashing, the permeation efficiency is lowered, and therefore the hollow fiber membrane 102 needs to be hydrophilic. Furthermore, it is preferable that the valve point is equal to or lower than the air pressure during backwashing. For example, polysulfone (fraction molecular weight 6000 ~ 1
00,000).

Here, the valve point is shown in FIG.
Description will be made based on (b).

When the liquid 300 is filtered, a repulsive force acts between the liquid 300 and the membrane material 301 to be filtered, and its strength is represented by the contact angle θ. If the contact angle θ is large, the force for closing the pores 302 for filtering with the liquid 300 is strong. The pressure at which this blockage is broken is the bubble point, which results in the holes 30 opening in the membrane 301.
Estimate a caliber of 2. The bubble point test is used to confirm the integrity of the film 301.

That is, the air is blown by the hollow fiber membrane 102 during backwashing.
Since it must be prevented from passing through the membrane wall, the valve point is set below the air pressure for backwashing. As a result, since the valve point of the contact portion between the air and the hollow fiber membrane 102 on the liquid surface of the permeated liquid during the backwashing is equal to or lower than the air pressure during the backwashing, the air does not permeate through the hollow fiber membrane 102.

In the cross-flow type hollow fiber membrane module 100, a pressure difference (tentatively 0.2 kg / cm ² G or more) between the raw solution inlet 107 side and the raw solution outlet 108 side is caused by the pressure loss of the raw solution flowing. It occurs and becomes higher on the side of the stock solution inlet 107. Therefore, the hollow fiber membrane 102 on the side of the stock solution inlet 107 of the hollow fiber membrane bundle loading unit 106 is closer to the stock solution outlet 108.
Since it is more often used for filtration from the side, the amount of permeation increases, and the hollow fiber membrane 102 in that portion is significantly contaminated.

That is, in the system 1 described above, the hollow fiber membrane module 100 is vertically installed so that the raw liquid inlet 107 is on the lower side and the raw liquid outlet 108 and the permeated liquid outlet 109 are on the upper side. Contamination of the hollow fiber membrane 102 below the bundle loading unit 106 becomes significant.

However, according to the present embodiment, the permeated liquid held in the hollow fiber membrane bundle loading section 106 can be accommodated in the housing 10.
Since it is a backflow cleaning method in which air pressure is applied through the permeate outlet 109 of No. 1, the liquid level of the permeate in the hollow fiber membrane loading section 106 is the upper part of the uncontaminated hollow fiber membrane 102 near the initial liquid level. As the cleaning progresses, the cleaning temperature decreases, and as a result, the cleaning time at the lower part of the hollow fiber membrane 102, which is the most contaminated, can be extended.

As described above, since the cleaning time can be extended, the hollow fiber membrane 102 in the heavily contaminated part can be effectively cleaned, so that the cleaning can be performed even when the air pressure to the permeate is low. As a result, a high recovery rate of the permeation flow velocity due to cleaning can be obtained even with low air pressure. Therefore, since the air pressure for backwashing can be set low, the hollow fiber membrane 1
02 will be less burdened and the life of the membrane will be extended.

In addition, since there is no effect of backwashing on the hollow fiber membrane 102 at the portion of the permeate outlet 109 which serves as an inlet for air pressure for washing, the hollow fiber membrane 102 is not damaged as in the prior art.

Further, according to the present invention, the permeated liquid retained in the hollow fiber membrane bundle loading section 106 is used as the cleaning liquid for the backwashing, and the permeated liquid is cleaned simply by applying air pressure with compressed air. Therefore, unlike the prior art, the tank for storing the permeated liquid is not necessary and the flow passage is not complicated, so that the device structure can be simplified as compared with the prior art.

In the above embodiment, the hollow fiber membrane module 100 as a membrane module is vertically placed with the undiluted solution inlet 107 of the housing 101 downward to create a pressure difference between the undiluted solution inlet side and the undiluted solution outlet side. As described above, it is possible to perform the cleaning in the same manner even when the pressure difference is not generated or when the pressure difference is set horizontally.

[0062]

As described above, in the present invention,
Since the permeated liquid retained in the filtration membrane loading section in the housing is subjected to air pressure through the permeate outlet of the housing to discharge the permeated fluid from at least the undiluted solution inlet of the housing, Under the liquid level of the permeated liquid retained, the permeated liquid side of the membrane wall of the filtration membrane flows back to the undiluted liquid side, foreign substances accumulated on the undiluted liquid side are removed, and the filtration membrane is washed. That is, the entire filtration membrane of the filtration membrane loading section can be reliably washed.

As a result, it is possible to improve the recovery rate of the permeation flow rate by cleaning.

Further, when the membrane module is placed vertically with the undiluted solution inlet of the housing facing downward, the lower membrane in the filtration membrane loading section, which is the undiluted solution inlet side where the filtration pressure becomes high, is remarkably contaminated. According to this, since the permeated liquid held in the filtration membrane loading part is discharged from the raw liquid inlet, the filtration membrane is washed, so that the liquid surface of the permeated liquid is lowered as the cleaning progresses. The cleaning time at the bottom of the filtration membrane, which is the most polluted, can be extended.

As described above, since the cleaning time can be extended, the filtration membrane in the heavily contaminated portion can be effectively cleaned.
Cleaning is possible even when the air pressure for the permeate is low. As a result, a high recovery rate of the permeation flow velocity due to cleaning can be obtained even with low air pressure. Therefore, the air pressure for backwashing can be set to be low, so that the burden on the filtration membrane is reduced and the life of the membrane can be extended.

In addition, since there is no effect of backflow cleaning on the filter membrane at the permeate outlet, which is the inlet of air pressure for cleaning, there is no damage to the filter membrane as in the prior art.

[Brief description of drawings]

FIG. 1 (a) is a schematic configuration diagram of a system showing a method for cleaning a filtration membrane according to an embodiment of the present invention, and FIG. 1 (b) is a schematic diagram for explaining bubble points. .

FIG. 2 is a cross-sectional view of a hollow fiber membrane module as a cross-flow type membrane module.

FIG. 3 is a schematic configuration diagram of a system showing a conventional method for cleaning a filtration membrane.

[Explanation of symbols]

 1 system 2 stock solution tank 3 pressurizing pump 4 stock solution outlet pressure adjusting valve 5, 7, 8, 9 flow path 6 flow path switching 3-way valve 100 hollow fiber membrane module 101 housing 102 hollow fiber membrane 103 hollow fiber membrane bundle 104 potting material 105 Sealing Part 106 Hollow Fiber Membrane Bundle Loading Part 107 Stock Solution Inlet 108 Stock Solution Outlet 109 Permeate Exit

Claims (1)

[Claims] 1. A filtration membrane for filtering a stock solution is loaded into a housing having a plurality of inflow / outflow ports, and the filtration membrane loading section is provided from a stock solution inlet to a stock solution outlet of the plurality of inflow / outflow ports of the housing. When passing the stock solution through
Part of the stock solution passes through the membrane wall of the filtration membrane in the filtration membrane loading section,
After holding the permeate in the filtration membrane loading part of the housing,
In a membrane module that flows out through a permeate outlet of a plurality of inflow and outflow ports of the housing, a method of backwashing a liquid from a permeate side of a membrane wall of the filtration membrane to a stock solution side to wash the filtration membrane, Filtration characterized in that the filtration membrane is made of a hydrophilic material, and air pressure is applied to the permeated liquid held in the filtration membrane loading part through the permeated liquid outlet to discharge the permeated liquid at least from the raw liquid inlet. Membrane cleaning method.