JP3401541B2 - Membrane separation device and its operation method - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a membrane separation device and its operation.
Method , especially microfiltration (MF) membrane, ultrafiltration (U
F) When the stock solution is subjected to a membrane separation process using a membrane module equipped with a membrane or a reverse osmosis (RO) membrane, etc., leakage of the primary stock solution from the membrane surface to the secondary permeate side due to membrane damage is detected. Membrane separator that reliably prevents the resulting treated water from being contaminated
And its operating method .

[0002]

2. Description of the Related Art In recent years, with the development of membrane separation technology, membrane filtration has come to be applied in various fields.

That is, conventionally, membrane filtration has been widely used in fields such as turbidity removal and sterilization, but in recent years, filtration can be continued for a long time by a cross-flow type membrane module or regular backwashing operation. With the development of dead-end type membrane modules, the concentration range of the liquid to be treated (stock solution) to which membrane filtration can be applied has been expanded. By using these cross-flow type membrane modules and dead-end type membrane modules that perform regular backwashing, the filtration rate can be reduced to an unusable rate even if the turbidity of the stock solution changes. Membrane filtration can be continued without being performed.

For this reason, river water, industrial water and tap water are RO
As a pretreatment for membrane separation, it is possible to simplify the pretreatment process by performing membrane filtration with a UF membrane or an MF membrane instead of coagulation, precipitation and filtration.

However, when the filtered water (permeated water) is supplied to drinking water such as tap water, in order to reliably obtain treated water of high water quality, a safety device more than the above-mentioned use, that is, a membrane surface is used. The practical application of an economical device for detecting the leakage of the undiluted solution on the primary side into the permeated water on the secondary side was a problem.

Conventionally, as a means for detecting the leakage of the primary side stock solution from the membrane surface, a method of measuring the turbidity of permeated water has been a general method in the field of water purification treatment. However, MF membrane, UF
Since the permeated water of the membrane and the RO membrane does not contain turbidity in principle, it is impossible to optically detect turbidity and compare the water quality.

Therefore, even if a membrane such as an MF membrane, a UF membrane or an RO membrane is damaged and a small amount of the primary side stock solution leaks into the secondary side permeate, if the amount is very small, the turbidity will be high. Can not be detected as. On the contrary, when the turbidity of the permeate can be detected, the treated water system has a definite membrane damage, and it takes a lot of man-hours to repair and restore it.

When the permeated water is supplied to drinking water such as waterworks, it is important to detect the damage of the membrane early so that repair and restoration can be promptly performed even if the membrane is damaged. Therefore, the FI value measurement method developed as an index for determining the water quality of the water supplied to the RO membrane device is used as an MF membrane or UF membrane.
It can be diverted to determine the quality of permeated water such as membranes and RO membranes.
Currently being conducted.

When the FI value measuring method is used, the membrane permeated water is filtered with a membrane filter having a pore size of 0.45 μm and a membrane permeated water of 10 to 20 liters. Therefore, even if a slight amount of suspended matter is contained in the membrane permeated water, It can be captured on a membrane filter and its presence detected.

[0010]

However, it takes about 30 minutes for one sample to measure the FI value, and it requires a great deal of cost, labor and time to continuously measure a large amount of sample. And

Further, even if the leakage of a small amount of the primary side stock solution into the permeated water due to the membrane damage can be detected by the FI value or the like, it has already been detected that the secondary side permeated water is contaminated due to some accident. It does not prevent leakage.

Therefore, it is desired to develop a device that not only efficiently detects a small amount of undiluted solution on the primary side into the permeated water on the secondary side due to damage to the membrane, but at the same time prevents the leakage. It is the current situation.

For such a purpose, the permeated water of the first membrane module is passed through the second membrane module to obtain the first membrane module.
The method of preventing the suspended solids leaking from the second membrane module and detecting the pressure increase of the second membrane module has been proposed. In this method, the second membrane module is slightly larger than the first membrane module by 0.1-1 μm.
An MF membrane with a pore size of about m is used.

However, as described above, the present inventor
When the method for detecting the membrane damage by means such as value measurement was examined, it was found that the FI value was detected even in the MF membrane in the latter stage having a larger pore size than the membrane, even if the membrane had no abnormality. That is, even when the normal permeated water of the first membrane module having no abnormality in the membrane is passed through the MF membrane of the second membrane module, it is clear that the pressure increase of the second membrane module gradually occurs over time. became.

Thus, even if the membrane is normal, simply using the second membrane module provided with the MF membrane having a pore size of about 0.1 to 1 μm, which is slightly larger than the membrane of the first membrane module. The MF membrane of the second membrane module needs to be frequently replaced, which is economically disadvantageous. Therefore, it is desired to develop a more effective method.

The present invention has been made in view of the above-mentioned conventional circumstances, and the treatment obtained by surely detecting the leakage of the primary side stock solution from the membrane surface to the secondary side permeated water due to the damage of the membrane. It is an object of the present invention to provide a membrane separation device that prevents water contamination and does not require frequent membrane replacement, and an operating method thereof.

[0017]

SUMMARY OF THE INVENTION The membrane separation apparatus according to claim 1, the first membrane module and precision of membrane separation processes accept permeate of the first membrane module for membrane separation process accept stock A second membrane module having a filtration membrane;
A pipe for taking out the permeated water of the first membrane module from the upstream side of the microfiltration membrane directly to the outside of the system without permeating the microfiltration membrane, and the permeated water of the first membrane module. Selection of a flow path for taking out directly from the pipe to the outside of the system without permeating water, and flow path selection for performing a membrane separation process by passing permeated water of the first membrane module through a microfiltration membrane of the second membrane module. And a flow path switching means for switching the flow path to any one of the above.

The membrane separation device of claim 2 is the same as that of claim 1.
The flow channel switching means intermittently connects the first membrane module.
Immediately after the first membrane module was restarted.
The second membrane module is operated for a predetermined period afterwards,
The permeated water of the first membrane module is guided to the second membrane module.
Select the flow path for the membrane separation process to be performed within the specified period.
A pressure rise above a predetermined level is detected in the second membrane module.
If not, the permeate of the first membrane module is
From the upstream side of the microfiltration membrane of the membrane module of
Select the flow-out channel, and within the predetermined period, the second membrane module
If an increase in the differential pressure above a predetermined level is detected, the first
The permeated water of the membrane module of
Process without changing the flow path to be introduced into the second membrane module.
It is characterized by continuing the.

The method of operating the membrane separation device according to claim 3 is the same as the undiluted solution.
A first membrane module for receiving a membrane to perform a membrane separation treatment;
Membrane separation treatment is performed by receiving permeated water from the first membrane module.
A second membrane module having a microfiltration membrane,
Is the permeated water of the membrane module upstream of the microfiltration membrane?
Directly out of the system without passing through the microfiltration membrane
Pipe and the permeated water of the first membrane module is filtered by the precision filter.
Take it directly out of the system through the pipe without passing through the membrane.
The selection of the flow path to be output and the permeated water of the first membrane module
Membrane separation treatment by passing through the microfiltration membrane of the second membrane module
For switching the flow path to either
A method for operating a membrane separation device comprising a flow path switching means.
Then, the first membrane module is operated intermittently,
For a predetermined period immediately after the membrane module of
Operating the second membrane module to operate the first membrane module
Permeated water is introduced into the second membrane module for membrane separation treatment.
A second membrane module within the predetermined period
If no pressure rise above the predetermined level is detected,
The permeated water of the first membrane module is used for the purification of the second membrane module.
Select a flow path that takes out from the upstream side of the dense filtration membrane to the outside of the system
Within the predetermined period, the difference of the second membrane module is more than the predetermined value.
If an increase in pressure is detected, the first membrane module
Permeate is not discharged directly to the outside of the system,
The process continues with the flow path selected for
It is characterized by

[0020]

In the membrane separation apparatus and the method of operating the same of the present invention, the membrane separation treatment can be performed as follows.

That is, the first membrane module is intermittently operated, and the second membrane module is operated for a certain period immediately after the first membrane module is restarted to operate the first membrane module. The permeated water is introduced into the second membrane module to select a channel for membrane separation treatment.

At this time, for example, the differential pressure of the second membrane module is measured, and if no increase in pressure more than a predetermined value is detected within a predetermined period, the permeated water of the first membrane module is changed to The flow path to be taken out of the system from the upstream side of the MF membrane of the second membrane module is selected.

When the membrane of the first membrane module is damaged and the undiluted solution on the primary side leaks into the permeated water on the secondary side, the suspended matter is captured by the MF membrane of the second membrane module. Treated water discharged to the outside (permeate of the second membrane module)
Does not contain turbidity. In this case, since the differential pressure of the second membrane module rises within a predetermined period and the leakage of suspended matter is detected, the permeated water of the first membrane module is not directly discharged to the outside of the system, The process is continued with the flow path selected to be introduced into the membrane module.

As described above, when the primary side stock solution leaks into the secondary side permeated water due to the abnormality of the membrane of the first membrane module, this permeated water is treated by the MF membrane of the second membrane module. It is possible to prevent the suspended matter leaked from the first membrane module from being mixed into the treated water discharged to the outside of the system.

Further, when there is no abnormality in the membrane of the first membrane module and the rise of the differential pressure of the second membrane module is within the specified range, the processing by the second membrane module is not continued and the second membrane module is not processed. Since the operation of the membrane module is stopped, the membrane of the second membrane module does not cause unnecessary contamination.

Therefore, it is not necessary to frequently replace the MF membrane of the second membrane module.

In the membrane separation device of the present invention, the first
It is needless to say that the membrane module of (1) is not limited to the case where it is operated intermittently, and can be performed in continuous operation as described later.

[0028]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1 and 2 are system diagrams showing an embodiment of the membrane separation apparatus of the present invention.

In FIG. 1, 1 is a first membrane module,
2 is a second membrane module, which is membrane 1A, 2A, respectively
(2A is an MF membrane) with the stock solution chambers 1a and 2a and the permeate chamber 1
It is divided into b and 2b. 3 is an arithmetic unit, 1
Each code | symbol of 1-15 shows piping. V ₁ , V ₂ and V ₃ are valves, P ₁ and P ₂ are pumps, and PI is a pressure gauge (differential pressure gauge).

The second membrane module 2 is of a dead end filtration type, and the valves V ₁ and V ₂ provided on the upstream side and the downstream side of the second membrane module ₂ are automatic valves, 1 has an electric operation circuit that operates in conjunction with the filtration process of the membrane module 1.

In FIG. 1, the arithmetic unit 3 includes a pressure gauge PI.
Is input, and at the same time the operation and stop of the pump P ₂ and the opening / closing control signals of the valves V ₁ , V ₂ and V ₃ are output.

The membrane separation device shown in FIG. 1 has a pressure pump P ₁
And a suction pump P ₂ are used together to filter the first membrane module.

In order to carry out the treatment with such a membrane, the pumps P ₁ and P ₂ are operated to introduce the stock solution into the first membrane module 1 through the pipe 11 and take out the permeated water through the pipe 12. On the other hand, the concentrated water is taken out from the pipe 13.

Filtration by the first membrane module 1 is intermittently performed, and the cake layer of the membrane 1A of the first membrane module 1 is removed when the filtration is stopped. The cake layer is removed by scrubbing the membrane surface with a gas-liquid mixture, backwashing from the permeate side, or the like.

As described above, during the operation of the first membrane module 1, the valves V ₁ and V ₂ are automatically opened, and the permeated water of the first membrane module 1 is supplied to the second pipe 2 through the pipe 12 for a certain period.
Is introduced into the membrane module 2. Then, the permeated water of the second membrane module 2 is discharged out of the system through the pipe 14.

As described above, when the two-stage membrane separation process by the first membrane module 1 and the second membrane module 2 is performed for a certain period, the pressure gauge PI increases the differential pressure of the second membrane module 2. If it is less than the predetermined value, the arithmetic unit 3
A signal for opening the valve V ₂ and opening the valve V ₃ is output, and the permeated water of the first membrane module 1 is directly outside the system via the pipe 12, the stock solution chamber 2 a of the second membrane module 2 and the pipe 13. To discharge.

That is, in the second membrane module 2, when the rise of the differential pressure more than a predetermined value is not recognized, the membrane 1A of the first membrane module 1 is normal, and the primary membrane module 1 Side stock solution has not leaked into the secondary side permeate,
Since the permeated water of the first membrane module 1 is shown to be high quality permeated water, the permeated water of the first membrane module 1 is directly discharged to the outside of the system.

On the other hand, within the above-mentioned period, when an increase in the differential pressure above the predetermined level is detected in the second membrane module 2, the processing of the second membrane module 2 is continued as it is,
The permeated water of the first membrane module 1 is transferred to the second membrane module 2
After two-stage treatment with, it is discharged out of the system.

That is, in the second membrane module 2, when the rise of the differential pressure more than a predetermined value is recognized, the membrane 1A of the first membrane module 1 is abnormal and the primary side of the first membrane module 1 is in the abnormal state. Since the undiluted solution leaked into the secondary side permeate and showed that the permeate of the first membrane module 1 contained suspended matter, the permeate of the first membrane module 1 was treated with the second membrane module. Then, it is discharged out of the system.

In this case, an alarm signal for stopping the operation of the first membrane module 1 is issued if necessary.

In the membrane separation device shown in FIG. 2, the filtration of the first membrane module 1 is performed only by the pressure pump P ₁ .
Further, this membrane separation device includes a permeated water tank 4 that stores permeated water of the first membrane module 1 and the second membrane module 2,
Means for back-flowing the permeated water in the permeated water tank 4 into the permeated water chamber 1b of the first membrane module 1 for backwashing (pipe 1
6, a pump P ₃ and a valve V ₄ ).

Also in this membrane separation apparatus, the membrane separation treatment can be carried out similarly to the membrane separation apparatus shown in FIG. Then, when the operation of the first membrane module 1 is stopped, the valve V ₄ is opened and the pump P ₃ is operated to cause the permeated water in the permeated water tank 4 to flow back, if necessary. Can be backwashed.

In both of the membrane separation devices of FIGS. 1 and 2, when the membrane 1A of the first membrane module 1 is abnormal, the permeated water of the first membrane module 1 is treated by the second membrane module 2. By doing so, it is possible to reliably prevent turbidity from mixing into the treated water, while the membrane 1A of the first membrane module 1 has no abnormality, and the permeated water of the first membrane module has sufficiently high water quality. To stop the second membrane module and
Unnecessary contamination of the membrane 2A of the membrane module 2 can be prevented.

In the above description, the case where the first membrane module is operated intermittently has been described, but the membrane separation apparatus of the present invention is not limited to intermittent operation, and the first membrane module can be operated continuously. Needless to say. In this case, while the first membrane module is continuously operated, the second membrane module is operated at regular intervals for a predetermined time, and the increase in differential pressure is examined. If no increase in differential pressure is observed, If only the first membrane module is treated again, and if an increase in the differential pressure is observed, then it is a two-stage treatment of the first membrane module and the second membrane module, and the membrane separation device is stopped if necessary. Then, the membrane of the first membrane module may be replaced.

In the present invention, as the membrane of the first membrane module, any of MF membrane, UF membrane and RO membrane can be used. The filtration method of the first membrane module is not particularly limited, and the membrane module is immersed in a water passage method such as dead end filtration or cross-flow filtration, or a module stack in which unit modules are connected, a water tank, or the like. It is possible to adopt various methods such as a method of performing.

On the other hand, as the MF membrane of the second membrane module, it is preferable to use an MF membrane having a pore diameter of about 0.3 to 0.8 μm. When the pore diameter of the MF membrane exceeds 0.8 μm, the pressure loss in the normal state is extremely small, but the pressure loss is small even when the suspended matter leaks out, and it becomes difficult to detect the rise in the differential pressure. On the other hand, if the pore diameter is less than 0.3 μm, the pressure loss during normal operation is extremely large and it cannot be put to practical use. It is considered that such an increase in pressure loss during normal operation is due to a partial blocking phenomenon of the dissolved organic matter that flows out without being blocked by the first membrane module.

In the present invention, the filtration system of the second membrane module is preferably dead end filtration.

Of the embodiments shown in FIGS. 1 and 2, the membrane shown in FIG. 1 has a suction pump P ₂ provided in the permeated water extraction pipe of the first membrane module 1. By providing the pump P ₂ , one pump can share the driving force for suction filtration of the first membrane module 1 and the driving force for pressure filtration of the second membrane module 2, which is advantageous in simplifying the apparatus. is there.

The membrane separators shown in FIGS. 1 and 2 are all embodiments of the present invention, and the present invention is not limited to the illustrated ones as long as the gist thereof is not exceeded.
For example, in both of FIGS. 1 and 2, the permeated water of the first membrane module 1 is configured to be taken out of the system through the stock solution chamber 2a of the second membrane module 2. The permeated water of No. 1 can be directly discharged to the outside of the system by providing a pipe branching to the pipe 12 (pipe 20 shown by a broken line in FIGS. 1 and 2).

In FIGS. 1 and 2, one second membrane module is provided for each first membrane module, but a plurality of first membrane modules are provided in parallel. One or more second membrane modules may be provided for such a unit.

Further, the second membrane module is not limited to the measurement of the differential pressure, but the coloration degree of the membrane may be measured to detect the abnormality of the membrane of the first membrane module.

[0053]

As described above in detail, the membrane separation apparatus of the present invention
And according to the operating method thereof , when the primary side stock solution leaks into the secondary side permeated water due to the abnormality of the membrane of the first membrane module, this suspended matter is removed by the second membrane module to obtain high quality water. The treated water can be stably and reliably obtained. Moreover, since the operation of the second membrane module is performed only when necessary, the contamination of the MF membrane of the second membrane module is reduced, and it is not necessary to replace the membrane frequently.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a membrane separation device of the present invention.

FIG. 2 is a system diagram showing another embodiment of the membrane separation device of the present invention.

[Explanation of symbols]

1 first membrane module 1A membrane 1a Stock solution chamber 1b Permeate chamber 2 Second membrane module 2A MF membrane 2a Stock solution chamber 2b Permeate chamber 3 arithmetic unit 4 Permeate water tank

Claims (3)

(57) [Claims] 1. A first membrane module for receiving a raw solution for membrane separation treatment, and a second membrane module having a microfiltration membrane for receiving permeated water of the first membrane module for membrane separation treatment, said first membrane module comprising: A pipe for taking out the permeated water of the first membrane module from the upstream side of the microfiltration membrane directly to the outside of the system without permeating the microfiltration membrane, and the permeated water of the first membrane module permeating the microfiltration membrane. Either of selection of a flow path that is directly taken out of the system from the pipe without being carried out, or selection of a flow path in which the permeated water of the first membrane module is permeated through the microfiltration membrane of the second membrane module to perform a membrane separation treatment. A membrane separation device comprising a flow path switching means for switching the flow path. 2.The means for switching the flow path according to claim 1.
Is The first membrane module is operated intermittently, and the first membrane module is operated.
Just after the Joule restarted operation, the second
Operate the membrane module to permeate the first membrane module
Flow path for introducing water into the second membrane module for membrane separation treatment
Select Within the predetermined period, the second membrane module is pressurized to a predetermined pressure or more.
If no increase in G was detected, the first membrane module was detected.
Permeate water above the microfiltration membrane of the second membrane module
Select the flow path to take out of the system from the flow side, Within the predetermined period, the differential pressure of a second membrane module or more
If a rise is detected, the permeation of the first membrane module
The second membrane module without water being discharged directly to the outside of the system
The process should be continued with the flow path selected for
The membrane separation device according to claim 1, wherein 3.First to receive stock solution and perform membrane separation
Membrane module and permeate of the first membrane module
A second membrane module having a microfiltration membrane which is put in and subjected to membrane separation treatment
And the permeated water of the first membrane module
Do not allow the microfiltration membrane to permeate from the upstream side of the membrane.
And a pipe for directly taking it out of the system, and the first membrane module
The pipe without passing the permeated water of the microfiltration membrane
Straight from Selection of the flow path to be taken out of the contact system and the first membrane module
The permeated water of the second membrane module through the microfiltration membrane.
Flow path to either select the flow path for permeation and membrane separation treatment
Separation comprising flow path switching means for switching
A method of operating the device, The first membrane module is operated intermittently, and the first membrane module is operated.
Just after the Joule restarted operation, the second
Operate the membrane module to permeate the first membrane module
Flow path for introducing water into the second membrane module for membrane separation treatment
Select Within the predetermined period, the second membrane module is pressurized to a predetermined pressure or more.
If no increase in G was detected, the first membrane module was detected.
Permeate water above the microfiltration membrane of the second membrane module
Select the flow path to take out of the system from the flow side, Within the predetermined period, the differential pressure of a second membrane module or more
If a rise is detected, the permeation of the first membrane module
The second membrane module without water being discharged directly to the outside of the system
The process should be continued with the flow path selected for
And a method for operating a membrane separation device.