JP2001113140A - Spiral type membrane element and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spiral membrane element capable of performing a stable filtration operation while maintaining a high permeation flux for a long period of time, and a method of operating the same. SOLUTION: A spiral membrane element 1 is produced using a separation membrane having a high back pressure strength. At the time of backwashing, washing water 21 is introduced from the end of the water collecting pipe 5 through the permeated water outlet 14, and backwashing is performed at a back pressure of 0.05 to 0.3 MPa. At the same time, the raw water 31 is supplied from the raw water inlet 13 to the pressure vessel 10.
Into the first liquid chamber 18. The raw water 31 flows axially inside the spiral membrane element 1 toward the other end, and contaminants separated from the separation membrane are pushed down from one end of the spiral membrane element 1 to the other end by the raw water 31, The water is discharged into the second liquid chamber 19 together with the washing water 21, and taken out of the pressure vessel 10 through the concentrated water outlet 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spiral type membrane element used for a membrane separation device such as a reverse osmosis membrane separation device, an ultrafiltration membrane separation device, and a microfiltration membrane separation device, and a method for operating the same.

[0002]

2. Description of the Related Art In recent years, the application of membrane separation technology to water purification and wastewater treatment has been widened, and the application of membrane separation technology to liquid quality, which has been difficult in the past, has been performed. In particular, there is a strong demand for recovery and reuse of industrial wastewater using membrane separation technology.

As a form of a membrane element used for such a membrane separation, a hollow fiber membrane element is often used in view of a membrane area per unit volume (volume efficiency). However, the hollow fiber membrane element has a drawback that the membrane is easily broken, and if the membrane is broken, the raw water mixes with the permeated water and the separation performance is reduced.

Therefore, instead of the hollow fiber type membrane element,
It has been proposed to apply spiral membrane elements. This spiral type membrane element has an advantage that a membrane area per unit volume can be increased as in the hollow fiber type membrane element, separation performance can be maintained, and reliability is high.

[0005]

Since wastewater contains many suspended substances, colloidal substances or dissolved substances, if such wastewater is subjected to membrane separation, these suspended substances, colloidal substances or dissolved substances are removed. The toxic substances accumulate on the film surface as contaminants, causing a decrease in the rate of water permeation.

[0006] Cross-flow filtration is performed to prevent the deposition of contaminants on the membrane surface. In the cross-flow filtration, raw water is caused to flow in parallel to the membrane surface to prevent the accumulation of contaminants on the membrane surface by utilizing the shearing force generated at the interface between the membrane surface and the fluid. Further, contaminants deposited on the film surface are removed by backwashing. This backwashing is generally performed in a hollow fiber membrane element.

[0007] Application of backwashing to a spiral type membrane element has been proposed, for example, in Japanese Patent Publication No. 6-98276. However, the separation membrane of the conventional spiral-type membrane element has a low back pressure strength. Therefore, if a back pressure is applied to the separation membrane during backwashing, the separation membrane may be damaged. Therefore, according to the above publication, the spiral type membrane element has a thickness of 0.1 to 0.5 kg / cm ² (0.01 to 0.05 kg / cm ² ).
It is said that it is preferable to perform backwashing at a low back pressure of MPa).

However, according to the experiment of the present inventor, when backflow cleaning was performed at such a back pressure in a spiral membrane element, a high permeation flux could not be maintained for a long time.

On the other hand, the present inventor has disclosed in Japanese Patent Laid-Open No. 10-2256.
No. 26 proposes a structure and a manufacturing method of a separation membrane having a back pressure strength of 2 kgf / cm ² or more. However,
When a spiral-wound membrane element is manufactured using a separation membrane having such a back pressure strength, what kind of back pressure can actually be used for backflow cleaning, and what kind of back pressure It has not been sufficiently verified that a high permeation flux can be maintained over a long period of time when backflow washing is performed under pressure.

[0010] Even when such a separation membrane having a high back pressure strength is used, unless the optimum washing conditions and washing methods are applied, the spiral membrane element is stable without causing a decrease in permeation flux over a long period of time. Filtration operation cannot be continued.

An object of the present invention is to provide a spiral-wound membrane element capable of performing a stable filtration operation while maintaining a high permeation flux for a long period of time.

Another object of the present invention is to provide a method of operating a spiral membrane element capable of performing a stable filtration operation while maintaining a high permeation flux for a long period of time.

[0013]

The spiral-type membrane element according to the present invention is a spiral-type membrane element in which a bag-shaped separation membrane is wound around the outer peripheral surface of a perforated hollow tube. 0.3MPa higher than 0.05MPa
Backwashing is possible with a back pressure of a or less.

In the spiral membrane element according to the present invention, at the time of cleaning, a cleaning liquid is introduced from at least one open end of the perforated hollow tube. The washing liquid is led out from the outer peripheral surface of the perforated hollow tube into the bag-like separation membrane, and permeates through the separation membrane in a direction opposite to that during filtration. As a result, the separation membrane is backwashed, and contaminants deposited on the surface of the separation membrane are separated from the separation membrane.

In this case, the pressure is higher than 0.05 MPa.
Since the separation membrane can be backwashed with a back pressure of 3 MPa or less, a required amount of washing solution can be flowed in a short time.
Thus, the contaminants deposited on the surface of the separation membrane can be effectively removed. As a result, a stable filtration operation can be performed while maintaining a high permeation flux over a long period of time.

The separation membrane is formed by joining a permeable membrane to one surface of a porous sheet material. This makes it possible to sufficiently perform backflow cleaning at a back pressure higher than 0.05 MPa and not higher than 0.3 MPa without causing damage to the separation membrane of the spiral-wound membrane element.

In particular, it is preferable that the permeable membrane is joined to one surface of the porous sheet material in an anchored state. This allows
The bonding between the porous sheet material and the permeable membrane is strengthened, and the back pressure strength of the separation membrane is improved.

Particularly, the back pressure strength of the separation membrane is preferably 0.2 MPa or more. This makes it possible to perform backwashing at a high back pressure, and by performing sufficient membrane washing, stable membrane separation processing can be performed for a long period of time.

In particular, the porous sheet material is preferably made of a woven fabric, a nonwoven fabric, a mesh net or a foamed sintered sheet made of a synthetic resin.

Further, the porous sheet material has a thickness of 0.0
8mm or more and 0.15mm or less and density 0.5g / c
It is preferable to be formed of a nonwoven fabric having a m ^{3 of} 0.8 g / cm ³ or less.

[0021] Thereby, it is possible to obtain a back pressure strength of 0.2 MPa or more, and at the same time, to secure the strength as a reinforcing sheet, and to prevent an increase in permeation resistance and peeling of the permeable membrane.

The method for operating a spiral-type membrane element according to the present invention is a method for operating a spiral-type membrane element in which a bag-shaped separation membrane is wound around the outer peripheral surface of a perforated hollow tube. By introducing a cleaning liquid from at least one open end of the hollow tube and discharging the cleaning liquid from at least one end of the spiral membrane element, 0.05
This is to backwash the separation membrane at a back pressure higher than MPa and equal to or lower than 0.3 MPa.

In the method of operating a spiral-type membrane element according to the present invention, at the time of washing, the washing liquid introduced from at least one open end of the perforated hollow tube is separated into a bag-like form from the outer peripheral surface of the perforated hollow tube. It is led inside the membrane and permeates through the separation membrane in the opposite direction to that during filtration. As a result, the separation membrane is backwashed, and contaminants deposited on the surface of the separation membrane are separated from the separation membrane.

In this case, the pressure is higher than 0.05 MPa.
By backwashing the separation membrane at a back pressure of 3 MPa or less, a required amount of washing liquid can be flowed in a short time. Thus, the contaminants deposited on the surface of the separation membrane can be effectively removed. As a result, a stable filtration operation can be performed while maintaining a high permeation flux over a long period of time.

The stock solution is supplied from one end to the other end of the spiral membrane element during filtration, and the stock solution is flowed from one end to the other end of the spiral membrane element in the same direction as the stock solution during filtration during washing. Is also good.

In this case, the contaminants separated from the separation membrane at the time of washing are flushed from one end to the other end of the spiral type membrane element by the stock solution flowing in the same direction as the stock solution supply direction at the time of filtration, and the contaminants are spiraled together with the washing solution. It is discharged from the other end of the mold membrane element. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again.

As described above, by flowing the undiluted solution in the same direction as the filtration at the time of washing, the contaminants separated from the separation membrane can be quickly discharged out of the system.

The stock solution is supplied from one end to the other end of the spiral membrane element during filtration, and the stock solution is flowed from the other end to one end of the spiral membrane element in the direction opposite to the stock solution supply direction during filtration during washing. Is also good.

In this case, at the time of washing, the contaminants separated from the separation membrane are pushed away from the other end of the spiral membrane element to one end by the stock solution flowing in the direction opposite to the stock solution supply direction at the time of filtration, and are spirally wound together with the washing solution. It is discharged from one end of the mold membrane element. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again.

As described above, by flowing the undiluted solution in the opposite direction to the filtration at the time of washing, contaminants deposited particularly near one end of the spiral membrane element can be easily removed from the spiral membrane element and discharged. it can.

The stock solution is supplied from one end to the other end of the spiral membrane element at the time of filtration, and after washing, the stock solution is flowed from one end to the other end of the spiral membrane element in the same direction as the stock solution supply direction at the time of filtration. Is also good.

In this case, the contaminants separated from the separation membrane at the time of washing are flushed from one end to the other end of the spiral type membrane element by the stock solution flowing in the same direction as the stock solution supply during filtration after washing. It is discharged from the other end of the spiral type membrane element together with the cleaning liquid remaining inside the type membrane element. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again.

As described above, the contaminants separated from the separation membrane can be quickly discharged out of the system by flowing the undiluted solution after the washing in the same direction as the filtration.

At the time of filtration, the stock solution is supplied from one end to the other end of the spiral membrane element, and after washing, the stock solution is flowed from the other end of the spiral membrane element to one end in the direction opposite to the stock solution supply direction at the time of filtration. Is also good.

In this case, the contaminants separated from the separation membrane at the time of washing are washed away from the other end of the spiral type membrane element to one end by the undiluted solution flowing in the direction opposite to the undiluted solution supply direction at the time of washing. It is discharged from one end of the spiral type membrane element together with the cleaning liquid remaining inside the type membrane element. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again.

As described above, by flowing the undiluted solution in the direction opposite to the direction of filtration after washing, contaminants deposited especially near one end of the spiral membrane element can be easily removed from the spiral membrane element and discharged. it can.

[0037]

FIG. 1 is a partially cutaway perspective view showing an example of a spiral type membrane element according to the present invention.

In the spiral type membrane element 1 shown in FIG. 1, an envelope membrane (bag-like membrane) 4 is formed by superimposing separation membranes 2 on both sides of a permeated water spacer 3 made of a synthetic resin net and bonding three sides. It is formed by attaching the opening of the envelope-shaped membrane 4 to the water collecting pipe 5 and spirally winding the outer peripheral surface of the water collecting pipe 5 together with the raw water spacer 6 made of a synthetic resin net. Spiral type membrane element 1
Is covered with an exterior material.

In this spiral type membrane element 1, backflow cleaning can be performed with a back pressure of 0.05 to 0.3 MPa by using a separation membrane 2 having a structure described later.

At the time of filtration, the raw water 7 is supplied from one end face of the spiral type membrane element 1. This raw water 7
Flows linearly in a direction parallel to the water collecting pipe 5 along the raw water spacer 6 and is discharged as concentrated water 9 from the other end face side of the spiral membrane element 1. While the raw water 7 flows along the raw water spacer 6, a part of the raw water 7 permeates the separation membrane 2 due to the pressure difference between the raw water side and the permeated water side, and the permeated water 8 flows along the permeated water spacer 3 into the collecting pipe 5. Flows into the
It is discharged from the end of the water collecting pipe 5.

FIG. 2 is a sectional view showing an operation method of the spiral membrane element according to the first embodiment of the present invention.
(A) shows an operation method at the time of filtration, and (b) shows an operation method at the time of backwashing.

As shown in FIG. 2, a pressure vessel (pressure vessel)
10 is a cylindrical case 11 and a pair of end plates 12a, 12
b. One end plate 12a has raw water inlet 1
3 and a concentrated water outlet 15 is formed in the other end plate 12b. A permeated water outlet 14 is provided at the center of the other end plate 12b. The structure of the pressure vessel is not limited to the structure shown in FIG. 2, and a pressure vessel having a side entry shape in which a raw water inlet and a concentrated water outlet are provided in a cylindrical case may be used.

The spiral-type membrane element 1 with the packing 17 attached to one end of the outer peripheral surface is attached to the cylindrical case 1.
1 and both open ends of the cylindrical case 11 are sealed with end plates 12a and 12b, respectively. One open end of the water collecting pipe 5 is fitted to the permeated water outlet 14 of the end plate 12b, and an end cap 16 is attached to the other open end. The inner space of the pressure vessel 10 is filled with a first liquid chamber 18 by a packing 17.
And the second liquid chamber 19. Thus, a spiral-type membrane module in which the spiral-type membrane element 1 is housed in the pressure vessel 10 is configured.

At the time of filtration, as shown in FIG. 2A, the raw water 7 is supplied from the raw water inlet 13 to the first liquid chamber 18 of the pressure vessel 10.
To be introduced. Raw water 7 is supplied from one end of the spiral type membrane element 1. The concentrated water 9 is discharged from the other end of the spiral membrane element 1 to the second liquid chamber 19 and taken out of the pressure vessel 10 through the concentrated water outlet 15.
Further, the permeated water 8 is discharged from the open end of the water collecting pipe 5, and taken out of the pressure vessel 10 through the permeated water outlet 14.

In this process, suspended substances, colloidal substances or dissolved substances contained in the raw water 7 are deposited as pollutants on the surface of the separation membrane.

At the time of backwashing, as shown in FIG. 2B, washing water 21 is introduced from the end of the water collecting pipe 5 through the permeated water outlet 14. As the washing water 21, for example, permeated water is used. The washing water 21 is led out from the outer peripheral surface of the water collecting pipe 5 to the inside of the separation membrane, and permeates the separation membrane in a direction opposite to that during filtration.
At this time, contaminants deposited on the surface of the separation membrane are separated from the separation membrane. Since the outer peripheral surface of the spiral type membrane element 1 is covered with the exterior material, the washing water 2 permeating the separation membrane is used.
1 is a spiral type membrane element 1 along the raw water spacer
Flows in the axial direction, is discharged from both ends of the spiral membrane element 1 into the first liquid chamber 18 and the second liquid chamber 19, and is taken out through the raw water inlet 13 and the concentrated water outlet 15, respectively.

Wash water 21 taken out from raw water inlet 13
Is discharged out of the system as wastewater. Alternatively, a part of the washing water 21 may be discharged to the outside of the system as wastewater, and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the cleaning water as raw water.

The washing water 2 taken out from the concentrated water outlet 15
In the case of 1, the entire amount is discharged outside the system as wastewater. Or
A part of the washing water 21 may be discharged as wastewater to the outside of the system and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the raw water as raw water.

In this case, the separation membrane has a thickness of 0.05 to 0.3 MP.
The pressure on the permeated water outlet 14 side, the pressure on the raw water inlet 13 side, and the pressure on the concentrated water outlet 15 side are set so as to apply the back pressure a. Thus, a required amount of the washing water 21 can be flowed in a short time, and contaminants deposited on the surface of the separation membrane can be effectively removed. Therefore, a stable filtration operation can be performed over a long period of time without causing a decrease in the permeation flux.

In the example of FIG. 2, the washing water 21 is discharged from both ends of the spiral membrane element 1 at the time of backwashing, and is taken out from the raw water inlet 13 and the concentrated water outlet 15, respectively. The pressure at the permeated water outlet 14 and the pressure at the raw water inlet 13 are set so that the water 21 is discharged from one end of the spiral membrane element 1 to the first liquid chamber 18 and taken out from the raw water inlet 13 to the outside. Is also good. In this case, the concentrate outlet 15 is closed. Alternatively, the pressure on the permeated water outlet 14 side and the concentrated water outlet 15 side such that the washing water 21 is discharged from the other end of the spiral membrane element 1 to the second liquid chamber 19 and taken out from the concentrated water outlet 15 to the outside. May be set. In this case, the raw water inlet 13 is closed.

FIG. 3 is a sectional view showing a method of operating a spiral type membrane element according to a second embodiment of the present invention. FIG. 3 shows an operation method during backwashing. The operation method at the time of filtration is the same as the operation method shown in FIG.

At the time of backwashing, as shown in FIG. 3, washing water 21 is introduced from the end of the water collecting pipe 5 through the permeated water outlet 14. The washing water 21 led out from the outer peripheral surface of the water collecting pipe 5 to the inside of the separation membrane permeates the separation membrane. At this time, contaminants deposited on the surface of the separation membrane are separated from the separation membrane.

In this case, 0.05 to 0.3 MP is applied to the separation membrane.
The pressure on the permeated water outlet 14 side, the pressure on the raw water inlet 13 side, and the pressure on the concentrated water outlet 15 side are set so as to apply the back pressure a. Thus, a required amount of the washing water 21 can be flowed in a short time, and contaminants deposited on the surface of the separation membrane can be effectively removed.

At the same time, the raw water 31 is introduced from the raw water inlet 13 into the first liquid chamber 18 of the pressure vessel 10. The raw water 31 is supplied from one end of the spiral membrane element 1 and flows in the spiral membrane element 1 in the axial direction toward the other end. As a result, the contaminants separated from the separation membrane are washed away from one end of the spiral membrane element 1 by the raw water 31 to the other end, and together with the washing water 21, from the other end of the spiral membrane element 1 to the second liquid chamber 19. And is taken out of the pressure vessel 10 through the concentrated water outlet 15.

The washing water 2 taken out from the concentrated water outlet 15
In the case of 1, the entire amount is discharged outside the system as wastewater. Or
A part of the washing water 21 may be discharged as wastewater to the outside of the system and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the raw water as raw water.

As described above, by flowing the raw water 31 in the same direction as the supply direction of the raw water at the time of the backflow washing, the contaminants separated from the separation membrane in the spiral membrane element 1 can be quickly discharged out of the system. Can be. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again. Therefore, a stable filtration operation can be performed over a long period of time without causing a decrease in the permeation flux.

FIG. 4 is a sectional view showing a method of operating a spiral type membrane element according to a third embodiment of the present invention. FIG. 4 shows an operation method during backwashing. The operation method at the time of filtration is the same as the operation method shown in FIG.

At the time of backwashing, as shown in FIG. 4, washing water 21 is introduced from the end of the water collecting pipe 5 through the permeated water outlet 14. The washing water 21 led out from the outer peripheral surface of the water collecting pipe 5 to the inside of the separation membrane permeates the separation membrane. At this time, contaminants deposited on the surface of the separation membrane are separated from the separation membrane.

In this case, 0.05 to 0.3 MP is applied to the separation membrane.
The pressure on the permeated water outlet 14 side, the pressure on the raw water inlet 13 side, and the pressure on the concentrated water outlet 15 side are set so as to apply the back pressure a. Thus, a required amount of the washing water 21 can be flowed in a short time, and contaminants deposited on the surface of the separation membrane can be effectively removed.

At the same time, the raw water 41 is introduced from the concentrated water outlet 15 into the second liquid chamber 19 of the pressure vessel 10. Raw water 41 is supplied from the other end of the spiral membrane element 1 and flows in the spiral membrane element 1 in the axial direction toward the one end. As a result, the contaminants separated from the separation membrane are flushed from the other end of the spiral membrane element 1 to the one end by the raw water 41, and from the one end of the spiral membrane element 1 together with the washing water 21 to the first liquid chamber 18. It is discharged and taken out of the pressure vessel 10 from the raw water inlet 13.

Wash water 21 taken out from raw water inlet 13
Is discharged out of the system as wastewater. Alternatively, a part of the washing water 21 may be discharged to the outside of the system as wastewater, and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the cleaning water as raw water.

As described above, by flowing the raw water 41 in the reverse direction to the supply direction of the raw water at the time of backwashing, contaminants deposited on the side of the spiral membrane element 1 near the first liquid chamber 18 can be easily removed. It becomes possible to remove and discharge. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again. Therefore, a stable filtration operation can be performed over a long period of time without causing a decrease in the permeation flux.

The operation method of FIG. 3 and the operation method of FIG. 4 may be performed in order. Thereby, the contaminants distributed throughout the spiral membrane element 1 can be uniformly removed and discharged.

FIG. 5 is a sectional view showing a method of operating a spiral type membrane element according to a fourth embodiment of the present invention.
(A) shows the operation method at the time of backwashing, and (b) shows the operation method after the backwashing. The operation method during filtration is shown in FIG.
Is the same as the operation method shown in FIG.

At the time of backwashing, as shown in FIG. 5A, washing water 21 is introduced from the end of the water collecting pipe 5 through the permeated water outlet 14. The washing water 21 led out from the outer peripheral surface of the water collecting pipe 5 to the inside of the separation membrane permeates the separation membrane. At this time, contaminants deposited on the surface of the separation membrane are separated from the separation membrane.

In this case, 0.05 to 0.3 MP is applied to the separation membrane.
The pressure on the permeated water outlet 14 side, the pressure on the raw water inlet 13 side, and the pressure on the concentrated water outlet 15 side are set so as to apply the back pressure a. Thus, a required amount of the washing water 21 can be flowed in a short time, and contaminants deposited on the surface of the separation membrane can be effectively removed. The washing water 21 is discharged from the other end of the spiral membrane element 1 to the second liquid chamber 19, and is taken out of the pressure vessel 10 through the raw water inlet 13 and the concentrated water outlet 15.

The washing water 2 taken out from the concentrated water outlet 15
In the case of 1, the entire amount is discharged outside the system as wastewater. Or
A part of the washing water 21 may be discharged as wastewater to the outside of the system and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the raw water as raw water.

After the backwashing, as shown in FIG.
Raw water 51 is introduced from the raw water inlet 13 into the first liquid chamber 18 of the pressure vessel 10. The raw water 51 is supplied from one end of the spiral membrane element 1,
Flows axially toward the other end. As a result, the contaminants separated from the separation membrane are washed away from one end of the spiral membrane element 1 by the raw water 51 to the other end, and together with the cleaning water remaining inside the spiral membrane element 1, The liquid is discharged from the end into the second liquid chamber 19 and taken out of the pressure vessel 10 through the concentrated water outlet 15.

Raw water 51 extracted from the concentrated water outlet 15
Is discharged out of the system as wastewater. Alternatively, a part of the raw water 51 may be discharged out of the system as wastewater and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the raw water as raw water.

As described above, by flowing the raw water 51 in the same direction as the supply direction of the raw water during the filtration after the backwashing, the contaminants separated from the separation membrane in the spiral membrane element 1 can be quickly discharged out of the system. Can be. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again. Therefore, a stable filtration operation can be performed over a long period of time without causing a decrease in the permeation flux.

During the backwashing, the washing water 21 may be discharged from one end of the spiral membrane element 1 to the first liquid chamber 18 and taken out of the pressure vessel 10 through the raw water inlet 13, or the backwashing may be performed. Occasionally, the washing water 21 is discharged from one end and the other end of the spiral membrane element to the first liquid chamber 18 and the second liquid chamber 19, and then to the outside of the pressure vessel 10 through the raw water inlet 13 and the concentrated water outlet 15, respectively. You may take it out.

FIG. 6 is a sectional view showing a method of operating a spiral type membrane element according to a fifth embodiment of the present invention.
(A) shows the operation method at the time of backwashing, and (b) shows the operation method after the backwashing. The operation method during filtration is shown in FIG.
Is the same as the operation method shown in FIG.

At the time of backwashing, as shown in FIG. 6A, washing water 21 is introduced from the end of the water collecting pipe 5 through the permeated water outlet 14. The washing water 21 led from the outer peripheral surface of the water collecting pipe 5 to the inside of the separation membrane permeates the separation membrane. At this time,
Contaminants deposited on the surface of the separation membrane are separated from the separation membrane.

In this case, 0.05 to 0.3 MP is applied to the separation membrane.
The pressure on the permeated water outlet 14 side, the pressure on the raw water inlet 13 side, and the pressure on the concentrated water outlet 15 side are set so as to apply the back pressure a. Thus, a required amount of the washing water 21 can be flowed in a short time, and contaminants deposited on the surface of the separation membrane can be effectively removed. The washing water 21 is discharged from the one end and the other end of the spiral membrane element 1 to the first liquid chamber 18 and the second liquid chamber 19, and goes out of the pressure vessel 10 through the raw water inlet 13 and the concentrated water outlet 15, respectively. Taken out.

Wash water 21 taken out from raw water inlet 13
Is discharged out of the system as wastewater. Alternatively, a part of the washing water 21 may be discharged to the outside of the system as wastewater, and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the cleaning water as raw water.

The washing water 2 taken out from the concentrated water outlet 15
In the case of 1, the entire amount is discharged outside the system as wastewater. Or
A part of the washing water 21 may be discharged as wastewater to the outside of the system and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the raw water as raw water.

After the backwashing, as shown in FIG.
Raw water 61 is introduced from the concentrated water outlet 15 into the second liquid chamber 19 of the pressure vessel 10. The raw water 61 is supplied from the other end of the spiral membrane element 1 and flows in the spiral membrane element 1 in the axial direction toward the one end. As a result, the contaminants separated from the separation membrane are washed away from the other end of the spiral membrane element 1 by the raw water 61 to one end, and together with the cleaning water remaining inside the spiral membrane element 1, one end of the spiral membrane element 1 The liquid is discharged from the section to the second liquid chamber 19 and taken out of the pressure vessel 10 through the raw water inlet 13.

Raw water 61 extracted from the raw water inlet 13
Is discharged out of the system as wastewater. Alternatively, a part of the raw water 61 may be discharged out of the system as wastewater, and returned to a raw water supply facility such as a raw water tank in order to reuse a part of the raw water.

As described above, by flowing the raw water 61 in the direction opposite to the supply direction of the raw water at the time of filtration after the backwashing, contaminants deposited on the side of the spiral membrane element 1 near the first liquid chamber 18 can be easily removed. It becomes possible to remove and discharge. Thus, the contaminants separated from the separation membrane are prevented from attaching to the separation membrane again. Therefore, a stable filtration operation can be performed over a long period of time without causing a decrease in the permeation flux.

The washing water 21 may be discharged from one end of the spiral membrane element 1 to the first liquid chamber 18 at the time of backwashing, and may be taken out of the pressure vessel 10 through the raw water inlet 13 or at the time of backwashing. The washing water 21 may be discharged from the other end of the spiral membrane element 1 to the second liquid chamber 19 and taken out of the pressure vessel 10 through the concentrated water outlet 15.

After the backwash in FIG. 5A or FIG. 6A, the operation method in FIG. 5B and the operation method in FIG. 6B may be performed in order. Thereby, the contaminants distributed throughout the spiral membrane element 1 can be uniformly removed and discharged.

FIG. 7 is a sectional view of a separation membrane used in the spiral membrane element of FIG. The separation membrane 2 is formed by tightly integrating a permeable membrane 2b having a substantial separation function on the surface of a porous reinforcing sheet (porous sheet material) 2a.

The permeable membrane 2b may be made of one kind of polysulfone-based resin or a mixture of two or more kinds of polysulfone-based resins, or a copolymer of the polysulfone-based resin with a polymer such as polyimide or fluorine-containing polyimide resin, or Formed from a mixture.

The porous reinforcing sheet 2a is made of polyester,
It is formed of a woven fabric, a nonwoven fabric, a mesh net, a foamed sintered sheet, or the like made of polypropylene, polyethylene, polyamide, or the like, and a nonwoven fabric is preferable from the viewpoint of film forming properties and cost.

The porous reinforcing sheet 2a and the permeable membrane 2
b is an anchored state in which a part of the resin component constituting the permeable membrane 2b is filled in the inside of the hole of the porous reinforcing sheet 2a.

The back pressure strength of the separation membrane 2 lined with the porous reinforcing sheet 2a exceeds 0.2 MPa, and is 0.4 to 0.5 MPa.
It improved to about 5 MPa. The method of defining the back pressure strength will be described later.

In order to obtain a back pressure strength of 0.2 MPa or more using a nonwoven fabric as the porous reinforcing sheet 2a, the thickness of the nonwoven fabric is 0.08 to 0.15 mm and the density is 0.
It is preferably from ⁵ to 0.8 g / cm ³ . When the thickness is less than 0.08 mm or when the density is 0.5 g / cm
If it is smaller than ³ , the strength as a reinforcing sheet cannot be obtained, and it is difficult to secure the back pressure strength of the separation membrane 2 of 0.2 MPa or more. On the other hand, when the thickness is greater than 0.15 mm or the density is greater than 0.8 g / cm ³ ,
The filtration resistance of the porous reinforcing sheet 2a is increased, and the anchoring effect on the nonwoven fabric (porous reinforcing sheet 2a) is reduced, so that peeling easily occurs at the interface between the permeable membrane 2b and the nonwoven fabric.

Next, a method for manufacturing the separation membrane 2 will be described. First, a solvent, a non-solvent, and a swelling agent are added to polysulfone and dissolved by heating to prepare a uniform film forming solution.
Here, the polysulfone-based resin has the following structural formula (Formula 1)
As shown in the figure, at least one (-SO
There is no particular limitation as long as it has a _2- ) site.

[0089]

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Here, R represents a divalent aromatic, alicyclic or aliphatic hydrocarbon group, or a divalent organic group in which these hydrocarbon groups are bonded by a divalent organic bonding group.

Preferably, polysulfones represented by the following structural formulas (Formula 2) to (Formula 4) are used.

[0092]

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[0093]

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[0094]

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The solvent for the polysulfone is N-
It is preferable to use methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. Further, as the non-solvent, aliphatic polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol, and glycerin, lower aliphatic alcohols such as methanol, ethanol, and isopropyl alcohol, and lower aliphatic ketones such as methyl ethyl ketone are used. Is preferred.

The content of the non-solvent in the mixed solvent of the solvent and the non-solvent is not particularly limited as long as the obtained mixed solvent is uniform, but is usually 5 to 50% by weight, preferably 20 to 45% by weight.

The swelling agent used to promote or control the formation of the porous structure includes metal salts such as lithium chloride, sodium chloride and lithium nitrate, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid and the like. Or a metal salt thereof, formamide or the like. The content of the swelling agent in the mixed solvent is not particularly limited as long as the film forming solution is uniform, but is usually 1 to 50% by weight.

The concentration of polysulfone in the membrane forming solution is usually preferably from 10 to 30% by weight. When it exceeds 30% by weight, the water permeability of the obtained porous separation membrane becomes poor in practicality. When it is less than 10% by weight, the mechanical strength of the obtained porous separation membrane becomes poor and sufficient back pressure is obtained. Can't get strength.

Next, the above-mentioned film forming solution is formed on a nonwoven fabric support. That is, using a continuous film forming apparatus, a support sheet such as a non-woven fabric is sequentially sent out, and a film forming solution is applied to the surface thereof. As a coating method, a film forming solution is coated on a nonwoven fabric support using a gap coater such as a knife coater or a roll coater. For example, when a roll coater is used, a film-forming solution is stored between two rolls, the film-forming solution is applied on a nonwoven fabric support, and at the same time, the inside of the nonwoven fabric is sufficiently impregnated. In addition, a slight amount of water in the atmosphere is absorbed by the surface of the liquid film applied on the nonwoven fabric, and microphase separation is caused on the surface layer of the liquid film. Thereafter, the liquid film is immersed in a coagulation water bath to phase-separate and coagulate the entire liquid film, and the solvent is washed and removed in a water washing bath. Thereby, the separation film 2 is formed.

As described above, since the separation membrane 2 has a high back pressure strength, even when the back flow cleaning is performed at a back pressure of 0.05 to 0.3 MPa when the separation membrane 2 is used for the spiral type membrane element 1 of FIG. The occurrence of breakage of the separation membrane 2 is prevented.

[0101]

EXAMPLE A spiral type ultrafiltration membrane element was prepared using an ultrafiltration membrane having a back pressure strength of 0.3 MPa as the separation membrane 2, and industrial water was supplied as raw water to conduct a continuous water filtration test. . In this filtration test, the initial filtration speed was 1 m
³ / m ² / day is set for quantitative operation and back pressure 0.2M
Backwashing was performed with Pa once every 20 minutes for 30 seconds. Here, the operation method of the first embodiment was performed.

For comparison, a spiral type ultrafiltration membrane element of a comparative example was prepared using an ultrafiltration membrane having a back pressure strength of 0.05 MPa as a separation membrane, and industrial water was supplied as raw water. A water filtration test was performed. In this filtration test, the initial filtration rate was set to 1 m ³ / m ² / day, and a quantitative operation was performed, and backwashing was performed at a back pressure of 0.05 MPa once every 20 minutes for 30 seconds.

The ultrafiltration membrane used for the spiral type ultrafiltration membrane element of the example was produced as follows. The spiral type ultrafiltration membrane element of the comparative example includes:
Conventional ultrafiltration membrane (NTU-315 manufactured by Nitto Denko Corporation)
0) was used.

First, polysulfone (P-3 manufactured by Amoco Co., Ltd.)
500) was heated and dissolved at 16.5 parts by weight, N-methyl-2-pyrrolidone at 58 parts by weight, diethylene glycol at 24.5 parts by weight, and formamide at 1 part by weight to obtain a uniform film-forming solution. Then, the coater gap is set to 0.13
using a roll coater adjusted to 0.1 mm in thickness,
A film forming solution was impregnated and applied to the surface of a polyester nonwoven fabric having a density of 0.8 g / cm ³ .

Thereafter, the relative humidity was 25% and the temperature was 30 ° C.
Through the atmosphere (low humidity atmosphere) at a predetermined speed,
After the microphase separation, the resultant was immersed in a coagulation water bath at 35 ° C. to remove the solvent and coagulate. Thereafter, the remaining solvent was washed and removed in a water washing bath to obtain a separation membrane. here,
The separation membrane of the example has a microphase separation time (time of passing through a low humidity atmosphere) of 4.5 seconds.

The ultrafiltration membrane used in the spiral type ultrafiltration membrane element of the example and the ultrafiltration membrane used in the spiral type ultrafiltration membrane element of the comparative example were measured for the surface of the membrane observed by a scanning electron microscope. Average pore size, water permeability,
The rejection and back pressure strength of polyethylene oxide having an average molecular weight of 1,000,000 were measured. Table 1 shows the results.

[0107]

[Table 1]

Here, the rejection of polyethylene oxide was determined by permeating a polyethylene oxide solution having a concentration of 500 ppm at a pressure of 1 kgf / cm ² from the concentrations of the stock solution and the permeated solution according to the following equation.

Inhibition ratio (%) = [1- (concentration of permeate / concentration of undiluted solution)] × 100 The back pressure strength was determined by setting a membrane having a diameter of 47 mm in a back pressure strength holder (effective diameter 23 mm). Reinforcement sheet 2
Water pressure is gradually applied from the side a, and the pressure is defined by the pressure at which the permeable membrane 2b peels off from the porous reinforcing sheet 2a or the permeable membrane 2b and the porous reinforcing sheet 2a burst at the same time.

As shown in Table 1, the ultrafiltration membrane used in the spiral type ultrafiltration membrane element of the example had an average pore diameter on the surface of 0.02 μm and a polyethylene oxide rejection of 90% or more. It showed excellent separation performance. Further, the back pressure strength was 0.2 MPa or more, and had excellent mechanical strength.

When the cross section of the membrane was observed with an electron microscope (SEM), the separation membrane of the example had an asymmetric structure in which the pore diameter was continuously increased from the surface in the film thickness direction. Moreover, the voids of the nonwoven fabric were impregnated with the film-forming solution, a part of which reached the back surface of the nonwoven fabric, and the membrane (permeable membrane) was bonded to the nonwoven fabric in an anchored state.

On the other hand, the ultrafiltration membrane used for the spiral ultrafiltration membrane element of the comparative example has a typical ultrafiltration in which a discontinuous dense layer is formed on the surface and finger-like cavities exist inside the membrane. It had the structure of a filtration membrane, and had a structure different from that of the separation membrane used for the spiral ultrafiltration membrane element of the example.

Further, in the separation membrane in the spiral type ultrafiltration membrane element of the comparative example, the minimum pore size layer was present near the interface between the permeable membrane and the nonwoven fabric, and a cavity was formed at the interface. This cavity is considered to have been generated by shrinkage during solidification due to microphase separation occurring near the interface of the nonwoven fabric, and it is presumed that the back pressure strength was reduced due to this.

Further, the separation membrane in the spiral type ultrafiltration membrane element of the embodiment was set in a holder for measuring the back pressure strength, and a state in which a back pressure of 0.2 MPa was applied and a state in which no back pressure was applied were cycled for 6 seconds. Repeated back pressure fatigue tests were performed. As a result, no separation occurred in the separation membrane in the spiral ultrafiltration membrane element of the example even after 100,000 tests.

FIG. 8 is a diagram showing the change over time in the filtration rate in a continuous water filtration test using the spiral ultrafiltration membrane element of the example. FIG. 9 is a diagram showing a temporal change in turbidity in a continuous water filtration test using the spiral ultrafiltration membrane element of the example. The horizontal axis in FIG. 8 is the number of operating days, and the vertical axis is the filtration rate (permeate flux). The horizontal axis in FIG. 9 is the number of operating days, and the vertical axis is turbidity.

As shown in FIGS. 8 and 9, even after 100 days from the start of operation, the same filtration rate and the same quality of filtered water as at the start of operation could be obtained. This is 0.2M
This is considered to be because a sufficient flow rate of the washing water could be secured by the backflow washing with the back pressure of Pa, and contaminants deposited on the membrane surface during the filtration time could be sufficiently discharged out of the system.

FIG. 10 is a diagram showing the change over time in the filtration rate in a continuous water filtration test using a spiral type ultrafiltration membrane element of a comparative example. The horizontal axis in FIG. 10 is the filtration time, and the vertical axis is the filtration speed.

As shown in FIG. 10, the filtration rate decreased over time. After a lapse of 20 hours from the start of the operation, the filtration rate decreased to 50% of that at the start of the operation. Stable filtration operation was difficult. This means that in the spiral type ultrafiltration membrane element of the comparative example, the backflow was performed at a back pressure of 0.05 MPa, so that the flow rate of the cleaning water enough to discharge contaminants deposited on the membrane surface to the outside of the system was reduced. It is considered that it is not possible to secure them.

As described above, according to the spiral membrane element and the operation method thereof according to the present invention, a stable filtration operation can be performed without causing a decrease in permeation flux over a long period of time.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an example of a spiral membrane element according to the present invention.

FIG. 2 is a cross-sectional view illustrating a method of operating the spiral-wound membrane element according to the first embodiment of the present invention.

FIG. 3 is a sectional view illustrating a method of operating a spiral-type membrane element according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a method of operating a spiral-type membrane element according to a third embodiment of the present invention.

FIG. 5 is a sectional view illustrating a method of operating a spiral-type membrane element according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view illustrating a method of operating a spiral-type membrane element according to a fifth embodiment of the present invention.

FIG. 7 is a cross-sectional view of a separation membrane using the spiral membrane element of FIG. 1;

FIG. 8 is a diagram showing a change over time of a filtration rate in a continuous water filtration test using a spiral ultrafiltration membrane element of an example.

FIG. 9 is a diagram showing a change over time in turbidity in a continuous water filtration test using a spiral ultrafiltration membrane element of an example.

FIG. 10 is a diagram showing a change over time in a filtration rate in a continuous water filtration test using a spiral type ultrafiltration membrane element of a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spiral type membrane element 2 Separation membrane 3 Permeated water spacer 4 Envelope membrane 5 Water collecting pipe 6 Raw water spacer 7 Raw water 8 Permeated water 9 Concentrated water 10 Pressure vessel 13 Raw water inlet 14 Permeated water outlet 15 Concentrated water outlet 21 Wash water 31, 41 , 51,61 Raw water

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4D006 GA03 GA06 GA07 HA61 KA63 KC02 KC03 KC12 KC13 KE05P KE06R KE07P KE08P KE13P KE24Q KE28Q MA03 MA06 MA22 MA25 MA31 MA40 MB02 MB06 MB16 MC22 MC23 MC48X MC54 NA58 MC62 PB02 PB08

Claims (6)

[Claims] 1. A spiral membrane element comprising a bag-shaped separation membrane wound around an outer peripheral surface of a perforated hollow tube, wherein the separation membrane is formed by joining a permeable membrane to one surface of a porous sheet material. A spiral-type membrane element characterized in that backflow cleaning is possible with a back pressure higher than 0.05 MPa and not higher than 0.3 MPa. 2. A method for operating a spiral-type membrane element comprising a bag-shaped separation membrane wound around the outer peripheral surface of a perforated hollow tube, wherein at least one of the open ends of the perforated hollow tube is opened during washing. Spiral type membrane, wherein the separation membrane is back-washed at a back pressure of higher than 0.05 MPa and 0.3 MPa or less by introducing a cleaning liquid and discharging the cleaning liquid from at least one end of the spiral type membrane element. Element operation method. 3. A stock solution is supplied from one end to the other end of the spiral membrane element during filtration, and one end of the spiral membrane element is supplied in the same direction as the stock solution supply direction during filtration during the washing. 3. The method for operating a spiral-type membrane element according to claim 2, wherein the undiluted solution is caused to flow into the section. 4. A stock solution is supplied from one end to the other end of the spiral membrane element during filtration, and one end from the other end of the spiral membrane element in the direction opposite to the stock solution supply direction during filtration during the washing. The method for operating a spiral-type membrane element according to claim 2 or 3, wherein the undiluted solution is caused to flow to the section. 5. A stock solution is supplied from one end to the other end of the spiral membrane element at the time of filtration, and after the washing, one end to the other end of the spiral membrane element in the same direction as the stock solution supply direction at the time of filtration. 3. The method for operating a spiral-type membrane element according to claim 2, wherein the undiluted solution is caused to flow into the section. 6. A solution is supplied from one end to the other end of the spiral membrane element at the time of filtration, and after the washing, one end is supplied from the other end of the spiral membrane element in a direction opposite to a stock solution supply direction at the time of filtration. The method for operating a spiral-type membrane element according to claim 2 or 3, wherein the undiluted solution is caused to flow to the section.