JP2001157825A - Spiral membrane element and method for operating spiral membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spiral membrane element capable of performing stable filtering operation at a low cost while keeping a high transmission flux over a long period of time and a method for operating a spiral membrane module. SOLUTION: A spiral membrane module is equipped with a spiral filter element 1 having a separation membrane high in back pressure strength. At a time of filtering, a raw water outlet 15 is closed by closing the valves 30c, 30d of pipings 27, 27a and raw water 7 is supplied to the spiral membrane element 1 from one end surface thereof through a raw water inlet 13 to be filtered wholly. At a time of washing, washing water 21 is introduced into a water gathering pipe 5 from the end part thereof through a transmitted water outlet 14 to perform backwashing under back pressure of 0.05-0.3 MPa.

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 and a method for operating a spiral-type membrane module used in a membrane separation device such as a reverse osmosis membrane separation device, an ultrafiltration membrane separation device, and a microfiltration membrane separation device. .

[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. In particular, in the case of performing total filtration, contaminants easily accumulate on the membrane surface, the permeation rate of water is significantly reduced, and it is difficult to continue stable filtration operation.

[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. In such cross-flow filtration, it is necessary to obtain a sufficient film surface linear velocity to prevent the deposition of contaminants on the film surface. To this end, a sufficient flow of raw water is supplied in parallel to the film surface. Need to shed. However, if the flow rate of the raw water flowing parallel to the membrane surface is increased, the recovery rate per spiral type membrane element will be low, and the pump for supplying the raw water will be large, and the system cost will be very large.

On the other hand, contaminants deposited on the film surface are also removed by backwashing. Backwashing is generally performed for hollow fiber membrane elements.

The 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 an experiment conducted by the present inventors, it is difficult to sufficiently remove contaminants when backflow cleaning is performed with such a back pressure in a spiral-type membrane element, and high permeation over a long period of time. Flux could not be maintained.

On the other hand, the present inventor has disclosed in Japanese Patent Application 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. Furthermore, the operation method of the spiral-type membrane element having the separation membrane with high back pressure strength as described above and the operation method of the spiral-type membrane module provided with such a spiral-type membrane element have not been verified.

Even when such a separation membrane having a high back pressure strength is used, the spiral type membrane element and the spiral type membrane are required unless the optimal washing conditions and washing method are applied and the filtration operation is not performed by the optimal operating method. A stable filtration operation cannot be continued for a long period of time without causing a decrease in permeation flux in the module.

An object of the present invention is to provide a spiral-type membrane element and a method of operating a spiral-type membrane module which can perform a stable filtration operation at low cost while maintaining a high permeation flux for a long period of time. .

[0013]

Means for Solving the Problems and Effects of the Invention A method of operating a spiral type membrane element according to a first aspect of 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. An operation method of the membrane element, wherein at the time of filtration,
Supplying the undiluted solution into the spiral-type membrane element and performing total filtration, and introducing the cleaning liquid from at least one open end of the perforated hollow tube to discharge the cleaning liquid from at least one end of the spiral-type membrane element during washing. With 0.
This is to backwash the separation membrane at a back pressure higher than 05 MPa and not higher than 0.3 MPa.

In the method for operating a spiral type membrane element according to the present invention, at the time of washing, a washing 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 is backwashed at a back pressure of 3 MPa or less, a required amount of washing liquid can be flowed in a short time. Thereby,
Contaminants deposited on the surface of the separation membrane can be effectively removed. As a result, it is possible to perform a stable filtration operation while maintaining a high permeation flux over a long period of time even in a total amount filtration in which a contaminant is easily deposited on the membrane surface.

As described above, according to the operation method of the spiral type membrane element described above, since the total filtration can be performed stably, the permeated liquid can be obtained efficiently. In addition, it is not necessary to use a large pump for supplying the undiluted solution, and the scale of the system can be reduced. Thereby, the system cost is reduced.

A method for operating a spiral type membrane element according to a second aspect of the present invention is a method for operating a spiral type membrane element in which a bag-shaped separation membrane is wound around an outer peripheral surface of a perforated hollow tube. At times, a stock solution is supplied into the spiral membrane element and a part of the stock solution is always or intermittently flowed in the spiral membrane element in the axial direction.
A cleaning liquid is introduced from at least one open end of the perforated hollow tube and the cleaning liquid is discharged from at least one end of the spiral-type membrane element, so that the separation membrane has a back pressure higher than 0.05 MPa and 0.3 MPa or less. Is to be backwashed.

In the method for operating a spiral-wound membrane element according to the present invention, at the time of cleaning, the cleaning liquid introduced from at least one open end of the perforated hollow tube is separated from the outer peripheral surface of the perforated hollow tube in a bag-like manner. 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.
Since the separation membrane is backwashed at a back pressure of 3 MPa or less, a required amount of washing liquid can be flowed in a short time. Thereby,
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.

Here, in the above operation method, the stock solution is always or intermittently flowed in the spiral membrane element in the axial direction during the filtration. This makes it possible to suppress the contaminants in the stock solution from adhering to the membrane surface of the separation membrane of the spiral membrane element, and to discharge some of the contaminants to the outside together with the stock solution. . Therefore, a more stable filtration operation can be performed. Further, in this case, it is not necessary to use a large pump for supplying the undiluted solution, and the scale of the system can be reduced. Thereby, the system cost is reduced.

It is preferable that at least a part of the stock solution flowing in the spiral membrane element in the axial direction is returned to the supply side of the spiral membrane element. By circulating the stock solution in this way, it is possible to obtain a permeate at a high recovery rate.

The separation membrane may have a permeable membrane joined to one surface of the porous sheet material, and the permeable membrane may be joined to one surface of the porous sheet material in an anchored state. In such a separation membrane, the bonding between the porous sheet material and the permeable membrane is strengthened, and the back pressure strength of the separation membrane is improved. 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, 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 foam 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.

[0026] Thereby, it is possible to obtain a back pressure strength of 0.2 MPa or more, and at the same time, increase the permeation resistance and prevent peeling of the permeable membrane while securing the strength as a reinforcing sheet.

In a third aspect of the present invention, there is provided a method for operating a spiral type membrane module, wherein a spiral type membrane element formed by winding a bag-shaped separation membrane around an outer peripheral surface of a perforated hollow tube is provided in a pressure vessel having a stock solution inlet. A method for operating one or more spiral-type membrane modules accommodated in
The undiluted solution is supplied into the spiral membrane element through the undiluted liquid inlet of the pressure vessel, and the whole is filtered. At the time of washing, the washing liquid is introduced from at least one open end of the perforated hollow tube to at least one end of the spiral membrane element. The cleaning liquid is discharged from the pressure vessel and taken out of the pressure vessel.
This is to backwash the separation membrane at a back pressure higher than 05 MPa and not higher than 0.3 MPa.

In the method for operating a spiral-wound membrane module 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 from the outer peripheral surface of the perforated hollow tube in a bag-like manner. 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.
Since the separation membrane is backwashed at a back pressure of 3 MPa or less, a required amount of washing liquid can be flowed in a short time. Thereby,
Contaminants deposited on the surface of the separation membrane can be effectively removed. As a result, it is possible to perform a stable filtration operation while maintaining a high permeation flux over a long period of time even in a total amount filtration in which a contaminant is easily deposited on the membrane surface.

As described above, according to the above-described method of operating the spiral type membrane module, since the total filtration can be performed stably, the permeated liquid can be obtained efficiently. In addition, it is not necessary to use a large pump for supplying the undiluted solution, and the scale of the system can be reduced. Thereby, the system cost is reduced.

According to a fourth aspect of the present invention, in the method for operating a spiral membrane module, the spiral membrane element in which a bag-shaped separation membrane is wound around the outer peripheral surface of a perforated hollow tube has a stock solution inlet and a stock solution outlet. A method for operating a spiral-type membrane module in which one or more spiral-type membrane modules are housed in a pressure vessel, wherein during filtration, a stock solution is supplied into a spiral-type membrane element through a stock solution inlet of the pressure vessel, and the stock solution is constantly or intermittently supplied. A part of the spiral type membrane element flows in the axial direction in the spiral type membrane element, is taken out of the pressure vessel from the undiluted solution outlet, and at the time of cleaning, a cleaning liquid is introduced from at least one open end of the perforated hollow tube to form the spiral type membrane element. 0.3MP higher than 0.05MPa by draining the cleaning liquid from at least one end and taking it out of the pressure vessel
This is to backwash the separation membrane at a back pressure of not more than a.

According to the spiral membrane module operating method of the present invention, at the time of cleaning, the cleaning liquid introduced from at least one open end of the perforated hollow tube is formed into a bag-like shape from the outer peripheral surface of the perforated hollow tube. It is led inside the separation membrane, and permeates through the separation membrane in the 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 is backwashed at a back pressure of 3 MPa or less, a required amount of washing liquid can be flowed in a short time. Thereby,
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.

Here, in the above operating method, the stock solution is always or intermittently flowed in the spiral membrane element in the axial direction during the filtration. Therefore, it is possible to suppress the contaminants in the stock solution from adhering to the membrane surface of the separation membrane of the spiral membrane element, and it is possible to take out some of the contaminants together with the stock solution to the outside of the pressure vessel. become. Therefore, a more stable filtration operation can be performed.

In this case, it is not necessary to use a large pump for supplying the undiluted solution, and the size of the system can be reduced. Thereby, the system cost is reduced.

It is preferable that at least a part of the stock solution taken out of the pressure vessel is supplied again to the stock solution inlet. By circulating the stock solution in this way, it is possible to obtain a permeate at a high recovery rate.

In the method for operating the spiral membrane module according to the third and fourth aspects, at least a part of the cleaning liquid taken out of the pressure vessel may be supplied again to the stock solution inlet. By circulating the washing liquid in this way, it is possible to obtain a permeate at a high recovery rate.

At the time of washing, the stock solution is supplied into the spiral membrane element from the stock solution inlet of the pressure vessel in parallel with the backwashing, and the stock solution flows in the spiral membrane element in the axial direction. May be taken out of the pressure vessel. Alternatively, at the time of washing, after performing backwashing, the stock solution is supplied into the spiral membrane element from the stock solution inlet of the pressure vessel, the stock solution flows in the spiral membrane element in the axial direction, and the stock solution flowing in the axial direction is supplied to the pressure vessel. May be taken out of the device.

As described above, by flowing the stock solution in the spiral membrane element in the axial direction at the time of cleaning, the contaminants separated from the separation membrane are pushed away from one end of the spiral membrane element to the other end, and together with the cleaning liquid, the spiral membrane element is removed. It is discharged from the other end of the membrane element and taken out of the pressure vessel. This makes it possible to quickly discharge the contaminants separated from the separation membrane to the outside of the system, thereby preventing the contaminants from adhering to the separation membrane again.

Further, at least a part of the stock solution that has flowed in the axial direction at the time of washing may be supplied again to the stock solution inlet. By circulating the stock solution in this way, it is possible to obtain a permeate at a high recovery rate.

[0041]

FIG. 1 is a schematic sectional view showing an example of a spiral type membrane module according to an embodiment of the present invention.

As shown in FIG. 1, the spiral-type membrane module has a spiral-type membrane element 1 housed in a pressure vessel (pressure-resistant vessel) 10. The pressure vessel 10 includes a cylindrical case 11 and a pair of end plates 12a and 12b. A raw water inlet 13 is formed on one end plate 12a, and a raw water outlet 15 is formed on the other end plate 12b. A permeated water outlet 1 is provided at the center of the other end plate 12b.
4 are provided. The structure of the pressure vessel is not limited to the structure shown in FIG. 1, and a pressure vessel having a side entry shape in which a raw water inlet and a raw water outlet are provided in a cylindrical case as described later 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.

Raw water inlet 13 of spiral type membrane module
Is connected to a raw water tank 500 through a pipe 25. A valve 30a is inserted in the pipe 25, and a pipe 26 in which a valve 30b is inserted is connected downstream of the valve 30a. On the other hand, raw water outlet 15
Is connected to a pipe 27 in which a valve 30c is inserted, and a pipe 27a in which a valve 30d is inserted is connected to the pipe 27 upstream of the valve 30c. The raw water outlet 15 is connected to the raw water tank 500 via the pipe 27a. The permeated water outlet 14 is connected to a pipe 28 in which a valve 30e is inserted, and a pipe 29 in which a valve 30f is inserted is connected upstream of the valve 30e.

FIG. 5 is a partially cutaway perspective view of a spiral membrane element used in the spiral membrane module of FIG.

As shown in FIG. 5, the spiral-type membrane element 1 has a permeated water spacer 3 made of a synthetic resin net.
An envelope-shaped membrane (bag-shaped membrane) 4 is formed by superimposing the separation membrane 2 on both sides of the substrate and bonding the three sides thereof, and the opening of the envelope-shaped membrane 4 is attached to the water collecting pipe 5, and a synthetic resin net is formed. The raw water spacer 6 is spirally wound around the outer peripheral surface of the water collecting pipe 5. The outer peripheral surface of the spiral-type membrane element 1 is covered with an exterior material.

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

FIGS. 2 and 3 are schematic sectional views showing an example of an operation method of the spiral membrane module according to the present invention. In the operation method of this example, the spiral membrane module of FIG. 1 is used, FIG. 2 shows an operation method at the time of filtration, and FIG. 3 shows an operation method at the time of washing.

As shown in FIG. 2, at the time of filtration,
The valve 30a of the pipe 28 and the valve 30e of the pipe 28 are opened.
0c, the valve 30d of the pipe 27a and the valve 30f of the pipe 29 are closed.

Raw water 7 taken from raw water tank 500
Is supplied from the raw water inlet 13 to the inside of the pressure vessel 10 through the pipe 25. In the spiral membrane module, the supplied raw water 7 is supplied from the raw water inlet 13 to the pressure vessel 10.
Of the spiral-type membrane element 1 from one end of the spiral-type membrane element 1.
Supplied inside.

As shown in FIG. 5, in the spiral type membrane element 1, raw water 7 supplied from one end face side is provided.
Flows linearly along the raw water spacer 6 toward the other end face in a direction (axial direction) parallel to the water collecting pipe 5. 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 a pressure difference between the raw water side and the permeated water side. The permeated water 8 flows into the water collecting pipe 5 along the permeated water spacer 3 and is discharged from the end of the water collecting pipe 5.
On the other hand, the remaining raw water 7a that has not passed through the separation membrane 2 is discharged from the other end face side of the spiral membrane element 1.

The permeated water 8 discharged from the end of the water collecting pipe 5
Is taken out of the pressure vessel 10 from the permeated water outlet 14 through the pipe 28 as shown in FIG. On the other hand, the raw water 7 a discharged from the other end face side of the spiral membrane element 1 is led out to the second liquid chamber 19. in this case,
Since the valve 30c of the pipe 27 and the valve 30d of the pipe 27a connected to the raw water outlet 15 are closed, the permeation of the separation membrane 2 in the spiral membrane element 1 is promoted, and the total filtration is performed.

In the above-mentioned filtration process, suspended substances, colloidal substances or dissolved substances contained in the raw water are deposited on the membrane surface of the separation membrane 2 of the spiral membrane element 1 as pollutants. In particular, contaminants are likely to be deposited on the membrane surface of the separation membrane 2 in total filtration. Since the accumulation of such contaminants causes a reduction in the water transmission rate, the following cleaning is performed to remove the contaminants.

As shown in FIG. 3, at the time of cleaning, first, the valve 30a of the pipe 25, the valve 30e of the pipe 28, and the valve 30d of the pipe 27a are closed, and the valve 30b of the pipe 26, the valve 30f of the pipe 29, and the pipe 27 are closed.
Is opened to perform backwashing.

At the time of backwashing, the pipes 29 and 28
The washing water 21 is supplied from the permeated water outlet 14 to the opening end of the water collecting pipe 5, and the washing water 21 is introduced into the water collecting pipe 5. As the washing water 21, for example, permeated water is used. The washing water 21 introduced into the water collecting pipe 5 is led out from the outer peripheral surface of the water collecting pipe 5 to the inside of the separation membrane 2 and permeates the separation membrane 2 in a direction opposite to that during filtration. At this time, the contaminants deposited on the surface of the separation membrane 2 are separated from the separation membrane 2. Since the outer peripheral surface of the spiral-wound membrane element 1 is covered with the exterior material, the washing water 21 that has passed through the separation membrane 2 flows inside the spiral-wound membrane element 1 along the raw water spacer 6 in the axial direction. First from both ends of the membrane element 1
Is discharged to the liquid chamber 18 and the second liquid chamber 19. Further, the wash water 21 is taken out of the raw water inlet 13 and the raw water outlet 15 through pipes 26 and 27, respectively.

In this case, the separation membrane 2 has a thickness of 0.05 to 0.3M.
The pressure on the permeated water outlet 14 side, the pressure on the raw water inlet 13 side, and the pressure on the raw water outlet 15 side are set so that a back pressure of Pa is applied. Thus, a required amount of the washing water 21 can be flowed in a short time, and contaminants deposited on the film surface of the separation membrane 2 can be effectively removed. Further, it is possible to prevent the separated contaminants from being captured by the raw water spacer 6 before being discharged from the end of the spiral membrane element 1,
Contaminants can be effectively removed.

In this embodiment, the entire amount of the washing water 21 taken out from the raw water inlet 13 is discharged as waste water to the outside of the system. Part of the raw water 7 may be reused. For example, by further providing a pipe downstream of the valve 30b of the pipe 26 and connecting this arrangement to the raw water tank 500, a part of the washing water 21 can be removed from the raw water tank 50.
It may be returned to 0.

Further, in this embodiment, the entire amount of the washing water 21 taken out from the raw water outlet 15 is discharged out of the system as waste water, but a part of the washing water 21 is discharged out of the system as waste water. Part of the raw water 7 may be reused. For example, the valve 30c of the pipe 27 and the valve 30d of the pipe 27a may be opened, and a part of the washing water 21 may be returned to the raw water tank 500 through the pipe 27a.

In the example of FIG. 3, the washing water 21 is discharged from both ends of the spiral membrane element 1 at the time of backflow washing, and taken out from the raw water inlet 13 and the raw water outlet 15 through the pipe 26 and the pipe 27, respectively. However, the washing water 21 is discharged from one end of the spiral-type membrane element 1 to the first liquid chamber 18 and is taken out from the raw water inlet 13 through the pipe 26 to the outside.
Side pressure and the raw water inlet 13 side pressure may be set. In this case, the valve 30c of the pipe 27 is closed, and the raw water outlet 15 is closed. Alternatively, the pressure of the permeated water outlet 14 and the pressure of the raw water outlet 1 are set such that the cleaning 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 raw water outlet 15 through the pipe 27.
The pressure on the fifth side may be set. In this case, the valve 30b of the pipe 26 is closed, and the raw water inlet 13 is closed.

After the backwashing as described above, the valve 30b of the pipe 26 and the valve 30f of the pipe 29 are closed and the valve 30a of the pipe 25 is opened. As a result, the raw water 31 taken from the raw water tank 500 is supplied from the raw water inlet 13 into the pressure vessel 10 through the pipe 25, and is introduced into the first liquid chamber 18. The raw water 31 is supplied from one end of the spiral membrane element 1 to the inside, flows along the raw water spacer 6 in the spiral membrane element 1 in the axial direction, and is discharged from the other end. As a result, the contaminants separated from the separation membrane 2 are washed away from one end of the spiral membrane element 1 together with the raw water 31 to the other end, and together with the washing water 21 remaining inside the spiral membrane element 1, the spiral membrane element 1 is removed. From the other end to the second liquid chamber 19. Further, the contaminants are taken out of the pressure vessel 10 through the pipe 27 from the raw water outlet 15 together with the raw water 31.

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 filtration after the backflow washing, the contaminants separated from the separation membrane 2 in the spiral membrane element 1 are quickly discharged out of the system. can do. Thereby, the contaminants separated from the separation membrane 2 can be prevented from attaching to the separation membrane 2 again.

According to the operation method at the time of washing as described above,
Since the contaminants deposited on the separation membrane 2 during the filtration can be effectively removed, even in the case of total filtration in which the contaminants are easily deposited on the membrane surface, the permeation flux does not decrease over a long period of time without causing a reduction in the permeation flux. It is possible to perform driving.

In this example, the raw water 3
1 flows in the axial direction.
1 may flow in the axial direction. For example, in the above, the valves 30a, 30 of the pipes 25, 26, 27, 29 at the time of cleaning.
b, 30c and 30f are simultaneously opened, and washing water 2
1 and the raw water 31 may be supplied from the raw water side. In this case, an effect similar to that obtained when the raw water 31 is flown after the backwashing as described above can be obtained.

In this embodiment, the raw water 31 is supplied from the raw water inlet 13 and taken out from the raw water outlet 15.
Raw water may be supplied from the raw water outlet 15 and taken out from the raw water inlet 13, and the raw water may flow inside the spiral membrane element 1 in a direction opposite to the supply direction of the raw water at the time of filtration. In this case, an effect similar to the effect obtained when the raw water 31 flows in the same direction as the supply direction of the raw water at the time of filtration as described above can be obtained.

In the case where the raw water flows in the same direction as the supply direction of the raw water at the time of filtration, in particular, the contaminants deposited on the spiral membrane element 1 on the side close to the second liquid chamber 19 are easily removed. It is possible to discharge. On the other hand, when the raw water flows in the direction opposite to the supply direction of the raw water at the time of filtration, the contaminants deposited especially on the side of the spiral membrane element 1 near the first liquid chamber 18 are easily removed and discharged. It is possible to

The raw water may be flowed sequentially in the same direction as the supply direction of the raw water at the time of filtration and in the opposite direction. In this case, it is possible to uniformly remove contaminants distributed throughout the spiral membrane element 1 and discharge the contaminants.

Further, in this embodiment, the entire amount of the raw water 31 taken out from the raw water outlet 15 is discharged out of the system as waste water, but a part of the raw water 31 is discharged out of the system as waste water and a part thereof is discharged. It may be reused as raw water. For example, in the above, the valve 30c of the pipe 27 and the valve 30d of the pipe 27a may be opened, and a part of the raw water 31 may be returned to the raw water tank 500 through the pipe 27a.

As described above, according to the operation method of the present embodiment shown in FIGS. 2 and 3, the contaminants deposited on the film surface of the spiral type membrane element 1 can be sufficiently removed. In the spiral type membrane module, it is possible to stably perform total filtration while maintaining a high permeation flux, and to efficiently obtain permeated water 8. In this case, since the entire amount is filtered, it is not necessary to use a large pump for supplying the raw water 7, and the scale of the system can be reduced. Thereby, the system cost is reduced.

FIG. 4 is a schematic sectional view showing another example of the operation method of the spiral type membrane module according to the present invention. FIG. 4 shows an operation method at the time of filtration. In this example, the spiral type membrane module of FIG. 1 is used. The operation method at the time of cleaning in this example is the same as the operation method of FIG. 3 described above.

As shown in FIG. 4, at the time of filtration,
Valve 30a, valve 30e of pipe 28 and pipe 2
The valve 30d of the pipe 7a is opened, and the valve 30b of the pipe 26, the valve 30c of the pipe 27, and the valve 30f of the pipe 29 are closed.

In this case, as in the example of FIG.
Raw water 7 taken from 00 is introduced into the first liquid chamber 18 of the pressure vessel 10 from the raw water inlet 13 through the pipe 25. Further, raw water 7 is supplied from one end of the spiral membrane element 1 into the spiral membrane element 1.

As shown in FIG. 5, in the spiral membrane element 1, part of the raw water permeates through the separation membrane 2, flows into the water collecting pipe 5, and is discharged as permeated water 8 from the end of the water collecting pipe 5. You. On the other hand, the remaining raw water 7a that has not passed through the separation membrane 2 is discharged from the other end face side of the spiral membrane element 1.

The permeated water 8 discharged from the end of the water collecting pipe 5
Is taken out of the pressure vessel 10 from the permeated water outlet 14 through the pipe 28 as shown in FIG. On the other hand, the raw water 7a discharged from the other end face side of the spiral-wound membrane element 1 is drawn out to the second liquid chamber 19, then taken out of the raw water outlet 15 through the pipe 27a, and returned to the raw water tank 500. . Thus, in this example,
Filtration is performed in the spiral membrane module while taking out part of the raw water 7a from the raw water outlet 15 to the outside. This makes it possible to suppress the accumulation of the liquid in the gap between the outer peripheral surface of the spiral membrane element 1 and the inner peripheral surface of the pressure vessel 10. Spiral membrane element 1
Is formed inside the inside of the pressure vessel 10 while an axial flow of raw water from one end to the other end is formed. Can be discharged.

In the above, the raw water 7a is taken out by always opening the valve 30d. However, the raw water 7a may be taken out by opening the valve 30d intermittently. Also in this case, as in the case where the raw water 7a is always taken out,
It is possible to suppress the contaminant from adhering to the separation membrane 2.

In the above description, the entire amount of the raw water 7a taken out of the pressure vessel is returned to the raw water tank 500, but a part of the taken out raw water 7a may be discharged outside the system. For example, the valve 30c is opened and the valve 30c is opened.
And a part of the raw water 7a may be discharged out of the system through the pipe 27.

Also in this example, at the time of cleaning, backflow cleaning is performed at a high back pressure and the raw water 31 is introduced by the cleaning operation method shown in FIG. This makes it possible to effectively remove contaminants deposited on the separation membrane 2 during filtration.

As described above, according to the operation method in this example, the contaminants deposited on the film surface can be sufficiently removed, and therefore, the permeation flux does not decrease over a long period of time without causing a decrease. Driving can be performed.

In particular, in this embodiment, as shown in FIG. 4, by removing a part of the raw water 7a to the outside of the pressure vessel 10 at the time of filtration, it is possible to prevent the contaminants in the raw water from settling on the film surface while preventing contamination. A part of the substance is mixed with the raw water 7a in the pressure vessel 10
Can be discharged to the outside, so that a more stable filtration operation can be performed. In this case, since the raw water 7a taken out from the raw water outlet 15 is circulated through the pipe 27a, the permeated water 8 can be obtained at a high recovery rate. Further, it is not necessary to use a large pump for supplying the raw water 7, so that the size of the system can be reduced. Thereby, the system cost is reduced.

In the above description, the case of operating a spiral type membrane module having one spiral type membrane element has been described. However, the operating method according to the present invention includes a plurality of spiral type membrane elements. The present invention is also applicable to a spiral type membrane module.

FIG. 6 is a schematic sectional view showing still another example of the operation method of the spiral membrane module according to the present invention.

As shown in FIG. 6, the spiral-type membrane module of this embodiment has a plurality of spiral-type membrane elements 1 housed in a pressure vessel 100. The pressure vessel 100
A cylindrical case 111 and a pair of end plates 120a, 120b
It consists of. A raw water inlet 130 is formed at the bottom of the cylindrical case 111, and a raw water outlet 131 is formed at the top. Thus, the pressure vessel 100 has a side entry shape. The raw water outlet 131 is also used for air release. Further, a permeated water outlet 140 is provided at the center of the end plates 120a and 120b.

A plurality of spiral membrane elements 1 in which the water collecting pipes 5 are connected in series by an interconnector 116 are accommodated in a cylindrical case 111, and both open ends of the cylindrical case 111 are connected to end plates 120a and 120b, respectively. Sealed. Here, the spiral type membrane element 1 of FIG. 5 is used. Spiral membrane element 1 at both ends
One end of the water collecting pipe 5 is fitted to the permeated water outlet 140 of the end plates 120a and 120b via the adapter 115, respectively. A packing 170 is attached near one end of the outer peripheral surface of each spiral membrane element 1, and the packing 170 separates the internal space of the pressure vessel 100 into a plurality of liquid chambers.

Raw water inlet 13 of spiral type membrane module
0 is connected to a raw water tank 500 through a pipe 55. A valve 60a is inserted in the pipe 55, and a pipe 56 in which a valve 60b is inserted is connected downstream of the valve 30a. On the other hand, raw water outlet 13
1 is connected to a pipe 57 in which a valve 60c is inserted, and further to a pipe 57a in which a valve 60d is inserted.
Is connected to the upstream side of the valve 60c of the pipe 57. The raw water outlet 131 is connected to the raw water tank 50 via the pipe 57a.
Connected to 0. Permeated water outlet 14 on end plate 120a side
0 is connected to a pipe 58a in which a valve 60e is inserted, and a valve 60g is provided upstream of the valve 60e.
Is connected to the pipe 59a. On the other hand, the permeated water outlet 140 on the end plate 120b side is connected to a pipe 58b in which a valve 60f is inserted.
A pipe 59b in which a valve 60h is inserted is connected to the upstream side of f.

At the time of filtration of the spiral type membrane module,
While opening the valve 60a of the pipe 55, the valve 60e of the pipe 58a, and the valve 60f of the pipe 58b,
6 valve 60b, pipe 59a valve 60g, pipe 5
The valve 60h of 9b, the valve 60c of the pipe 57, and the valve 60d of the pipe 57a are closed.

Raw water 7 taken from raw water tank 500
From the raw water inlet 130 through the pipe 55
0 is supplied inside. In the spiral membrane module, the raw water 7 supplied from the raw water inlet 130 is introduced into the spiral membrane element 1 from one end face of the spiral membrane element 1 located at the end on the end plate 120a side. . In the spiral membrane element 1, as shown in FIG. 5, a part of the raw water permeates through the separation membrane 2 and flows into the water collecting pipe 5, and is discharged as permeated water 8 from the end of the water collecting pipe 5. . On the other hand, the remaining raw water 7a that has not passed through the separation membrane 2 is discharged from the other end face side. The discharged raw water 7a is introduced into the spiral membrane element 1 from one end face side of the latter spiral membrane element 1, and is separated into the permeated water 8 and the raw water 7a in the same manner as described above. In this way, membrane separation is performed in each of the plurality of spiral-type membrane elements 1 connected in series. In this case, the valve 6 of the pipe 57
Since 0c and the valve 60d of the pipe 57a are closed, the permeation of the separation membrane 2 in each spiral membrane element 1 is promoted and the total filtration is performed in the spiral membrane module as in the example of FIG.

In the above-mentioned filtration process, contaminants contained in the raw water accumulate on the membrane surface of the separation membrane 2 of each spiral membrane element 1. In particular, when the total filtration is performed in the spiral membrane module provided with the plurality of spiral membrane elements 1 as described above, contaminants tend to accumulate on the membrane surface of the separation membrane 2. Since the accumulation of such contaminants causes a reduction in the water transmission rate, the following cleaning is performed to remove the contaminants.

At the time of cleaning, first, the valve 60 of the pipe 55
a, the valve 60e of the pipe 58a, and the valve 6 of the pipe 58b
0f and the valve 60d of the pipe 57a are closed, and the valve 60b of the pipe 56 and the valve 60 of the pipe 57 are closed.
(c) Open the valve 60g of the pipe 59a and the valve 60h of the pipe 59b, and perform backwashing.

At the time of backwashing, on the side of the end plate 120a,
The washing water 21 is supplied from the permeated water outlet 140 to one end of the water collecting pipe 5 through the pipe 59a and the pipe 58a. On the side of the end plate 120b, the washing water 21 is supplied from the permeated water outlet 140 to the other end of the water collecting pipe 5 through the pipe 59b and the pipe 58b. Thus, the washing water 2
1 is introduced into the inside of the water collecting pipe 5 from both ends of the water collecting pipe 5. The washing water 21 introduced into the water collecting pipe 5 is led out from the outer peripheral surface of the water collecting pipe 5 to the inside of the separation membrane 2 in each spiral type membrane element 1, and is separated from the separation membrane 2 in a direction opposite to the filtration.
Through. At this time, the contaminants deposited on the surface of the separation membrane 2 are separated from the separation membrane 2. The washing water 21 that has passed through the separation membrane 2 flows in the inside of the spiral membrane element 1 along the raw water spacer 6 in the axial direction, and is discharged from both ends of each spiral membrane element 1. The discharged washing water 21 is taken out from the raw water inlet 130 and the raw water outlet 131 through pipes 56 and 57 to the outside.

In this case, each spiral membrane element 1
The pressure on the permeated water outlet 140 side, the pressure on the raw water inlet 130 side, and the pressure on the raw water outlet 131 side are set so that a back pressure of 0.05 to 0.3 MPa is applied to the separation membrane 2. Thus, a required amount of the washing water 21 can be flowed in a short time, and contaminants deposited on the film surface of the separation membrane 2 can be effectively removed. In addition, it is possible to prevent the separated contaminants from being captured by the raw water spacer 6 until the contaminated substances are discharged from the end of each spiral-type membrane element 1, and the contaminants can be effectively removed.

In the present embodiment, the entire amount of the washing water 21 taken out from the raw water inlet 130 is discharged out of the system as waste water, but a part of the washing water 21 is discharged out of the system as waste water. Part of the raw water 7 may be reused. For example, by further providing a pipe downstream of the valve 60 b of the pipe 56 and connecting this arrangement to the raw water tank 500, a part of the washing water 21 is supplied to the raw water tank 500.
May be returned.

In the present embodiment, the entire amount of the washing water 21 taken out from the raw water outlet 131 is discharged as waste water to the outside of the system. Part of the raw water 7 may be reused. For example, the valve 60c of the pipe 57 and the valve 60d of the pipe 57a may be opened, and a part of the washing water 21 may be returned to the raw water tank 500 through the pipe 57a.

In the example shown in FIG. 6, the washing water 21 is taken out from the raw water inlet 130 and the raw water outlet 131 through the pipe 56 and the pipe 57 to the outside during the backwashing. The pressure on the permeated water outlet 140 side and the pressure on the raw water inlet 130 side may be set so as to be taken out through 56. In this case, the valve 60c of the pipe 57 is closed, and the raw water outlet 131 is closed. Alternatively, the pressure on the permeated water outlet 140 side and the pressure on the raw water outlet 131 side may be set so that the washing water 21 is taken out from the raw water outlet 131 through the pipe 57 to the outside. In this case, the valve 60b of the pipe 56 is closed, and the raw water inlet 130 is closed.

After performing the backwashing as described above, the valve 60b of the pipe 56, the valve 60g of the pipe 59a, and the valve 60h of the pipe 59b are closed, and the pipe 5 is closed.
5. Open the valve 60a. As a result, the raw water tank 50
Raw water 31 taken from 0 is supplied into the pressure vessel 100 from the raw water inlet 130 through the pipe 55. In each spiral membrane element 1, raw water 31 is introduced into the spiral membrane element 1 from one end thereof, flows in the spiral membrane element 1 along the raw water spacer 6 in the axial direction, and then is discharged from the other end. Is done. Thereby,
The contaminants separated from the separation membrane 2 are washed away from one end of the spiral membrane element 1 by the raw water 31 to the other end, and the other end of the spiral membrane element 1 together with the washing water 21 remaining inside the spiral membrane element 1. Discharged from the department. Further, the contaminants and the washing water 21 are taken out of the pressure vessel 10 through the pipe 57 from the raw water outlet 131 together with the raw water 31.

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 filtration after the backflow washing, the contaminants separated from the separation membrane 2 in each spiral membrane element 1 can be quickly discharged out of the system. Can be discharged. Thereby, the contaminants separated from the separation membrane 2 can be prevented from attaching to the separation membrane 2 again.

In this example, the raw water 3
1 flows in the axial direction.
1 may flow in the axial direction. For example, in the above, at the time of cleaning, the valve 6 of the pipes 55, 56, 57, 59a, 59b
0a, 60b, 60c, 60g, 60h are simultaneously opened,
The cleaning water 21 may be supplied from the permeate side and the raw water 31 may be supplied from the raw water side. In this case, an effect similar to that obtained when the raw water 31 is flown after the backwashing as described above can be obtained.

In this embodiment, the raw water 31 is supplied from the raw water inlet 130 and taken out from the raw water outlet 131. However, the raw water is supplied from the raw water outlet 131 and supplied to the raw water inlet 130.
, And the raw water may flow inside the spiral membrane element 1 in a direction opposite to the supply direction of the raw water at the time of filtration. In this case, an effect similar to the effect obtained when the raw water 31 flows in the same direction as the supply direction of the raw water at the time of filtration as described above can be obtained. Alternatively, the raw water may flow sequentially in the same direction as the supply direction of the raw water at the time of filtration and in the opposite direction. In this case, it is possible to uniformly remove contaminants distributed throughout the spiral membrane element 1 and discharge the contaminants.

In this embodiment, the entire amount of the raw water 31 taken out from the raw water outlet 131 is discharged out of the system as waste water, but a part of the raw water 31 is discharged out of the system as waste water. May be reused as raw water 7.
For example, in the above, the valve 60c of the pipe 57 and the valve 60d of the pipe 57a may be opened, and a part of the raw water 31 may be returned to the raw water tank 500 through the pipe 57a.

According to the operation method at the time of washing as described above, it is possible to effectively remove contaminants deposited on the separation membrane 2 at the time of filtration.

As described above, according to the operation method in this example, since the contaminants deposited on the film surface can be sufficiently removed, high permeation can be obtained even in the total filtration in which the contaminants are easily deposited on the film surface. It is possible to operate stably while maintaining the flux, and to obtain the permeated water 8 efficiently. In this case, since the entire amount is filtered, it is not necessary to use a large pump for supplying the raw water 7, and the scale of the system can be reduced. Thereby, the system cost is reduced.

In the above description, the case of performing the total filtration using the spiral type membrane module of FIG. 6 as in the example of FIG. 2 has been described. However, the example of FIG. 4 using the spiral type membrane module of FIG. As described above, filtration may be performed while taking out part of the raw water 7a to the outside of the pressure vessel 100.

For example, at the time of filtration of the spiral type membrane module shown in FIG. 6, the valve 60d of the pipe 57a is opened constantly or intermittently to separate the separation membrane of the spiral type membrane element 1 from the raw water 7 supplied into the pressure vessel 100. A part of the raw water 7a that has not passed through
It may be taken out of the pressure vessel 100 through 7a and returned to the raw water tank 500. This makes it possible to suppress the accumulation of liquid in the gap between the outer peripheral portion of each spiral membrane element 1 and the inner peripheral surface of the pressure vessel 100. Further, since a flow of raw water in the axial direction from one end to the other end is formed inside each spiral type membrane element 1, a part of the contaminants is reduced while suppressing sedimentation of the contaminants in the raw water. It becomes possible to discharge to the outside of the pressure vessel together with 7a.

According to such an operation method of filtering while taking out part of the raw water, the operation can be performed more stably without causing a decrease in the permeation flux for a long time. In this case, since the raw water 7a taken out is circulated through the pipe 57a, it is possible to obtain the permeated water 8 at a high recovery rate. Further, it is not necessary to use a large pump for supplying the raw water 7, so that the size of the system can be reduced. Thereby, the system cost is reduced.

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 a 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 0.1 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.

[0110]

Embedded image

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.

[0113]

Embedded image

[0114]

Embedded image

[0115]

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As the solvent for the polysulfone, 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.

Examples of the swelling agent used to promote or control the formation of the porous structure include 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 the 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, when the separation membrane 2 is used for the spiral type membrane element 1 shown in FIGS. 1 and 6, backflow cleaning is performed at a back pressure of 0.05 to 0.3 MPa. Even if it is performed, it is possible to prevent the separation membrane 2 from being damaged.

[0122]

EXAMPLES In the following Examples 1 and 2,
A spiral type ultrafiltration element 1 including an ultrafiltration membrane having a structure shown in FIG. 7 as a separation membrane 2 is produced, and the spiral type ultrafiltration module of FIG. To perform a continuous water filtration test.

Here, the ultrafiltration membrane used for the spiral type ultrafiltration membrane element 1 of Example 1 and Example 2 is as follows:
It was produced as follows.

First, polysulfone (P-35, manufactured by Amoco)
00), 16.5 parts by weight of N-methyl-2-pyrrolidone, 24.5 parts by weight of diethylene glycol and 1 part by weight of formamide were heated and dissolved to obtain a uniform film-forming solution. The impregnated coated film-forming solution to a thickness 0.1 mm, the surface of the polyester nonwoven fabric of density 0.8 g / cm ³ using a roll coater was adjusted coater gap 0.13 mm.

Thereafter, the relative humidity is 25% and the temperature is 30 ° C.
Through the atmosphere (low humidity atmosphere) at a predetermined speed,
After the microphase separation, the resultant was immersed in a coagulation water tank at 35 ° C. to remove the solvent and coagulate. Thereafter, the remaining solvent was washed and removed in a water washing tank to obtain a separation membrane 2. Here, the separation phase of the separation membrane 2 of Example 1 and Example 2 (time of passing through a low humidity atmosphere) is 4.5 seconds.

The ultrafiltration membrane produced as described above has a water permeability of 40 L / m ² · hr and a back pressure strength of 0.3 M
Pa, and the rejection of polyethylene oxide having an average molecular weight of 1,000,000 was 99%.

As for the back pressure strength, a membrane having a diameter of 47 mm was set in a back pressure strength holder (perforated diameter: 23 mm), and water pressure was gradually applied from the porous reinforcing sheet 2a side to form a permeable membrane 2b.
Is determined by the pressure at which the material is peeled off from the porous reinforcing sheet 2a or when the permeable membrane 2b and the porous reinforcing sheet 2a burst at the same time.

The rejection of polyethylene oxide was determined by passing 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.

Rejection (%) [1- (concentration of permeated liquid / concentration of undiluted solution)] × 100 Regarding the continuous water filtration test of the spiral membrane ultrafiltration membrane module provided with the ultrafiltration membrane thus produced. This will be described below.

[Example 1] In Example 1, raw water 7 was filtered at the time of filtration by the spiral type ultrafiltration membrane module shown in FIG.
Water having a turbidity of 20 NTU (pH 6-8, water temperature 1)
0 to 30 ° C.) and the operation method shown in FIG.
The whole volume was filtered for minutes. In this case, 5
The supply pressure of the raw water 7 was adjusted so that a permeate amount of L / min was obtained. After filtering the whole amount in this manner, washing was performed by the operation method shown in FIG. In this case, permeated water was used as the washing water 21 and backwashing was performed by supplying 10 L / min of washing water 21 at a back pressure of 0.2 MPa. The backwash time was 30 seconds. After backwashing,
The raw water 31 was supplied to the spiral type ultrafiltration membrane module, and the raw water 31 was flowed in the spiral type membrane element 1 in the same direction as the supply direction of the raw water 7 at the time of filtration.

The spiral ultrafiltration membrane element 1 was operated continuously for 30 days while repeating the filtration and washing as described above. The transmembrane pressure difference of the spiral type ultrafiltration membrane element 1 30 days after the start of the operation was measured and found to be 0.12 MPa.

Example 2 In Example 2, as the raw water 7 during filtration, industrial water having a turbidity of 50 NTU (pH 6 to 10) was used.
8, water temperature of 10 to 30 ° C.), and filtration and washing were performed in the spiral ultrafiltration membrane module by the same operation method as in Example 1 except that the operation was performed according to the operation method shown in FIG. Was. In this case, a part of the raw water 7a was taken out by always opening the valve 30d of the pipe 27a, and the raw water 7a was constantly circulated.

The spiral ultrafiltration membrane module was operated continuously for 30 days while repeating the above-mentioned filtration and washing. The transmembrane pressure of the spiral ultrafiltration membrane element 1 after 30 days from the start of the operation was measured, and was 0.17 MPa.

Comparative Example In the comparative example, a spiral type ultrafiltration membrane element 1 having a conventional ultrafiltration membrane having low back pressure resistance (NTU-3150- manufactured by Nitto Denko Corporation) was used.
A continuous water filtration test was performed using the spiral ultrafiltration membrane module of FIG. 1 provided with S4).

The back pressure strength of the ultrafiltration membrane of the spiral ultrafiltration membrane element 1 of the comparative example was 0.03 MPa, and the rejection of polyethylene oxide having an average molecular weight of 1,000,000 was 100%.

In the comparative example, the spiral type of FIG. 1 was operated in the same manner as in Example 1 except that the backflow was performed at a back pressure of 0.02 MPa because the back pressure resistance of the ultrafiltration membrane was low. Filtration and washing were performed in an ultrafiltration membrane module.

The spiral type ultrafiltration membrane module was operated for two consecutive days while repeating the filtration and washing as described above. The transmembrane pressure difference of the spiral ultrafiltration membrane element 1 after 2 days from the start of the operation was 0.5 MPa.

FIGS. 8A and 8B show the first embodiment.
It is a figure which shows the time-dependent change of the transmembrane pressure difference of the spiral type ultrafiltration membrane element 1 in a comparative example. FIG. 8 (a)
As shown in (1), in Example 1, backflow cleaning is performed at a back pressure of 0.2 MPa, so that contaminants deposited on the membrane surface of the spiral type ultrafiltration membrane element 1 can be reliably removed. Thereby, the change in the transmembrane pressure in the spiral type ultrafiltration membrane element 1 was small, and stable operation could be continuously performed for a long time. In contrast,
As shown in FIG. 8B, in the comparative example, 0.02 MP
Since backflow cleaning is performed with the back pressure of a, the flow rate of the cleaning water 21 for discharging contaminants deposited on the film surface to the outside of the system cannot be secured, and contaminants accumulate on the film surface to increase the resistance of the film. I do. For this reason, the transmembrane pressure in the spiral ultrafiltration membrane element 1 increases. In such a spiral ultrafiltration membrane element 1, a stable filtration operation could not be continuously performed for a long period of time.

Further, as shown in Example 2, when the raw water 7a is filtered while taking out part of the raw water 7a outside the pressure vessel 10 at the time of filtration, and when the raw water 7 having a high turbidity is treated, the spiral type water is used. The change in the transmembrane pressure difference of the ultrafiltration membrane element 1 was small, and stable operation could be continuously performed for a long time.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating an example of an operation method of the spiral membrane module according to the present invention.

FIG. 3 is a cross-sectional view illustrating an example of an operation method of the spiral membrane module according to the present invention.

FIG. 4 is a cross-sectional view showing another example of an operation method of the spiral membrane module according to the present invention.

FIG. 5 is a partially cutaway perspective view of a spiral membrane element used in the spiral membrane module of FIG. 1;

FIG. 6 is a cross-sectional view showing still another example of the operation method of the spiral membrane module according to the present invention.

FIG. 7 is a cross-sectional view of a separation membrane used for the spiral-wound membrane element of FIG.

FIG. 8 is a graph showing the change over time of the transmembrane pressure of the spiral ultrafiltration membrane modules of Example 1 and 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 7,31 Raw water 8 Permeated water 10,100 Pressure vessel 13,130 Raw water inlet 14,140 Permeated water outlet 15,131 Raw water outlet 21 Cleaning water

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA03 GA06 GA07 HA61 HA65 HA95 JA03A JA03C KA63 KC02 KC03 KC12 KC13 KE05P KE06P KE06R KE07Q KE08Q KE09Q KE12P KE15P KE16P KE28Q MA03 MC06 MC31 MC40 NA05 NA10 NA13 NA14 NA46 PA01 PB02 PB08

Claims (11)

[Claims] 1. A method of operating a spiral membrane element comprising a bag-shaped separation membrane wound around an outer peripheral surface of a perforated hollow tube, wherein a stock solution is supplied into the spiral membrane element during filtration. The whole is filtered, and at the time of washing, the washing liquid is introduced from at least one open end of the perforated hollow tube and the washing liquid is discharged from at least one end of the spiral type membrane element. 3. A method for operating a spiral-type membrane element, comprising back-washing the separation membrane at a back pressure of 3 MPa or less. 2. A method for operating a spiral membrane element in which a bag-shaped separation membrane is wound around an outer peripheral surface of a perforated hollow tube, wherein a stock solution is supplied into the spiral membrane element during filtration. Along with constantly or intermittently flowing a part of the stock solution in the spiral membrane element in the axial direction, and at the time of washing, introducing a washing solution from at least one open end of the perforated hollow tube to at least remove the spiral membrane element. 0.05MP by draining the cleaning liquid from one end
A method for operating a spiral type membrane element, comprising backwashing the separation membrane with a back pressure higher than a and not more than 0.3 MPa. 3. The operation of the spiral membrane element according to claim 2, wherein at least a part of the stock solution flowing in the axial direction in the spiral membrane element is returned to the supply side of the spiral membrane element. Method. 4. The separation membrane, wherein a permeable membrane is joined to one surface of a porous sheet material, and the permeable membrane is joined to one surface of the porous sheet material in an anchored state. The method for operating the spiral membrane element according to claim 1. 5. A spiral-type membrane module comprising one or more spiral-type membrane elements each having a bag-shaped separation membrane wound on the outer peripheral surface of a perforated hollow tube and housed in a pressure vessel having a stock solution inlet. The method of claim 1, wherein at the time of filtration, the undiluted solution is supplied into the spiral-type membrane element through the undiluted solution inlet of the pressure vessel to perform total filtration, and at the time of washing, at least one open end of the perforated hollow tube. Backwashing the separation membrane at a back pressure of higher than 0.05 MPa and 0.3 MPa or less by discharging a cleaning liquid from at least one end of the spiral type membrane element and taking the cleaning liquid out of the pressure vessel. Operating method of a spiral type membrane module characterized by performing. 6. A spiral in which one or a plurality of spiral-type membrane elements in which a bag-shaped separation membrane is wound on the outer peripheral surface of a perforated hollow tube are housed in a pressure vessel having a stock solution inlet and a stock solution outlet. A method of operating a membrane element, comprising: supplying a stock solution into the spiral membrane element through the stock solution inlet of the pressure vessel during filtration;
A part of the stock solution is always or intermittently flowed in the spiral type membrane element in the axial direction and taken out from the stock solution outlet to the outside of the pressure vessel, and at the time of washing, at least one open end of the perforated hollow tube Backwashing the separation membrane at a back pressure of higher than 0.05 MPa and 0.3 MPa or less by discharging a cleaning liquid from at least one end of the spiral type membrane element and taking the cleaning liquid out of the pressure vessel. Operating method of a spiral type membrane module characterized by performing. 7. The method for operating a spiral membrane module according to claim 6, wherein at least a part of the stock solution taken out of the pressure vessel is supplied again to the stock solution inlet. 8. The method for operating a spiral type membrane module according to claim 5, wherein at least a part of the cleaning liquid taken out of the pressure vessel is supplied again to the stock solution inlet. 9. During washing, a stock solution is supplied into the spiral membrane element from the stock solution inlet of the pressure vessel in parallel with the backwashing, and the stock solution flows in the spiral membrane element in the axial direction. The method for operating a spiral type membrane module according to any one of claims 5 to 8, wherein the undiluted solution flowing in the axial direction is taken out of the pressure vessel. 10. At the time of washing, after performing the backwash, supplying a stock solution into the spiral membrane element from the stock solution inlet of the pressure vessel and flowing the stock solution in the spiral membrane element in the axial direction, The method for operating a spiral type membrane module according to any one of claims 5 to 8, wherein the undiluted solution flowing in the axial direction is taken out of the pressure vessel. 11. The spiral according to claim 9, wherein at least a part of the stock solution taken out of the pressure vessel by flowing in the spiral membrane element in the axial direction is supplied again to the stock solution inlet. How to operate the mold membrane module.