KR20130120729A - Filtering system and method for cleaning hollow fiber membrane module - Google Patents

Abstract

Disclosed is a filtering system enabling improvement of the cleaning efficiency, reduction of the cleaning cost and prevention of the lifetime lowering of a hollow fiber membrane module through automation of the cleaning process, and a method for cleaning a hollow fiber membrane module. The filtering system according to the present invention comprises a hollow fiber membrane module; a first cleaning tub for storing the cleaning water for back washing of the hollow fiber membrane module; a control unit for controlling the flow of the cleaning water so as to perform the back washing; and a second cleaning tub for storing the cleaning-processed water produced upon the back washing, wherein the control unit controls the flow of the cleaning-processed water so that the filtering and cleaning of the hollow fiber membrane module is performed with the cleaning-processed water of the second cleaning tub after the back washing.

Description

Filtering System and Method for Cleaning Hollow Fiber Membrane Module

The present invention relates to a filtration system and a method for cleaning a hollow fiber membrane module, and more particularly, to a filtration system and a hollow hollow filter module for improving cleaning efficiency, reducing cleaning cost, and preventing the life of the hollow fiber membrane module through automation of the cleaning process. It relates to a cleaning method of the desert module.

As a water treatment method for purifying contaminants from a fluid, there is a method using heating or phase change or a method using a filtration membrane.

Since the desired quality of water can be stably obtained depending on the pore size of the filtration membrane, the method using the filtration membrane is advantageous in that the reliability of the process is higher than the method using heating or phase change. Further, when a filtration membrane is used, operation such as heating is not required, so that microorganisms can be prevented from being affected by heat in a separation step using microorganisms.

One of the separation methods using a filtration membrane is a method using a hollow fiber membrane. Traditionally, hollow fiber membranes have been widely used in the field of microfiltration such as sterile water, drinking water, and ultrapure water production. Recently, however, they have been used for treating sewage / wastewater, solid-liquid separation in septic tanks, removal of suspended solid (SS) Filtration of industrial water, filtration of pool water, and the like.

Filtration using the hollow fiber membrane can be classified into pressurized filtration and submerged filtration according to its operation.

In the case of pressurized filtration, pressure is applied to the fluid to be treated so that only the fluid except solid components such as impurities or sludge is selectively permeated through the surface of the hollow fiber membrane. Pressurized filtration requires an additional facility for fluid circulation, but has the advantage that the amount of permeate obtained in unit time is relatively large compared to submerged filtration.

In contrast, in the case of immersion type filtration, the hollow fiber membrane module is directly immersed in a bath in which the fluid to be treated is stored and a negative pressure is applied to the hollow of the hollow fiber membrane to remove a solid component such as impurities or sludge. Only allows selective transmission of the hollow through the hollow fiber membrane surface. Submerged filtration has the disadvantage that the amount of permeated water that can be obtained in a unit time is relatively less than that of immersion filtration, but it has the advantage that it does not need the equipment for the fluid circulation can reduce the installation cost or operating cost.

However, in the case of filtration using a hollow fiber membrane, as the filtration operation is performed, fouling phenomenon occurs in which impurities present in raw water to be treated stick to the surface of the hollow fiber membrane and contaminate the hollow fiber membrane. This fouling phenomenon reduces the filtration performance of the hollow fiber membrane. Therefore, in order to ensure the filtration performance of a hollow fiber membrane more than a predetermined | prescribed degree, the hollow fiber membrane should be wash | cleaned.

Cleaning of the hollow fiber membranes can be broadly classified into maintenance cleaning and recovery cleaning.

Maintenance cleaning is a physical cleaning that impacts the hollow fiber membranes to drop impurities adhering to the surface.Aeration cleaning performed continuously while the filtration is performed and backwashing performed when the filtration is stopped for a while. (reverse cleaning). Oxidizer cleaning is cleaning in which the air injected from below the hollow fiber membrane rises in raw water and impinges on the outer surface of the hollow fiber membrane to remove impurities. In the backwash, the treated water obtained through the filtration operation is removed from the hollow through the hollow fiber membrane. It is the washing | cleaning by which the impurity adhering to the outer surface of a hollow fiber membrane is removed by discharge | release.

On the other hand, recovery washing is a chemical cleaning that initializes the filtration performance of the hollow fiber membrane using an acidic or basic compound, and is performed over a considerable time while the filtration operation is stopped.

Since the recovery rate of the desired hollow fiber membrane must be achieved by the recovery washing, in the conventional recovery washing, an excessively long time is arbitrarily allocated for the recovery washing, which leads to a decrease in the efficiency of the filtration operation. Moreover, since recovery cleaning is a chemical cleaning using an acidic or basic compound, recovery cleaning for an excessively long time not only leads to an increase in cleaning costs due to excessive compound consumption, but also damage to the hollow fiber membranes due to chemical reactions and This caused a decrease in the life of the hollow fiber membranes.

Accordingly, the present invention relates to a filtration system and a cleaning method of the hollow fiber membrane module which can prevent problems caused by the above limitations and disadvantages of the related art.

One aspect of the present invention is to provide a filtration system that can implement automation of the cleaning process, as well as improving the cleaning efficiency, reducing the cleaning cost, and preventing the life of the hollow fiber membrane module.

Another aspect of the present invention is to provide a method for cleaning a hollow fiber membrane module that can implement automation of the cleaning process, as well as to improve the cleaning efficiency, reduce the cleaning cost, and prevent the life of the hollow fiber membrane module from being lowered.

Other features and advantages of the invention will be set forth in the description which follows, or may be learned by those skilled in the art from the description.

According to one aspect of the invention as described above, hollow fiber membrane module; A first washing tank storing washing water for backwashing the hollow fiber membrane module; A control unit for controlling the flow of the washing water so that the backwash can be performed; And a second washing tank storing the washing treatment water generated as the backwashing is performed, wherein the controller may perform filtration washing of the hollow fiber membrane module with the washing treatment water of the second washing tank after the backwashing. A filtration system is provided which controls the flow of said rinsing treated water so that it is.

According to another aspect of the invention, the step of backwashing the hollow fiber membrane module with the washing water of the first cleaning tank; Storing the washing treatment water generated through the backwashing in a second washing tank; Stopping the backwash; And performing a filtration rinsing with the rinsing water of the second rinsing tank.

The foregoing general description of the present invention is intended to be illustrative of or explaining the present invention, but does not limit the scope of the present invention.

According to the present invention, since the backwashing and filtration cleaning are alternately performed for the recovery and washing of the hollow fiber membrane, the cleaning efficiency can be improved.

In addition, by measuring the pH of the washing water used for the backwashing in real time and by adjusting the amount of the compound to be added to the washing water based on the measured pH value, it is possible to optimize the amount of the compound consumed for recovery washing Can be.

In addition, during the filtration cleaning, the interlayer differential pressure of the hollow fiber membrane module may be measured in real time, and when the measured value is less than or equal to the preset interlayer differential pressure, the recovery washing may be stopped, thereby optimizing the time for the recovery washing. By optimizing the recovery cleaning time, it is possible to improve the cleaning efficiency, reduce the cleaning cost, and prevent the life of the hollow fiber membrane module from being lowered.

In summary, the present invention can improve the cleaning efficiency through the fully automated cleaning process, reduce the cleaning cost, and prevent the life of the hollow fiber membrane module from being degraded due to excessive recovery cleaning.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a cross-sectional view schematically showing a hollow fiber membrane module according to an embodiment of the present invention,
2 is a block diagram schematically illustrating a filtration system according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the cleaning method of the filtration system and the hollow fiber membrane module according to the present invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Therefore, the present invention encompasses all changes and modifications that come within the scope of the invention as defined in the appended claims and equivalents thereof.

The technical idea of the present invention may be applied to the immersion type hollow fiber membrane module as well as the pressure type hollow fiber membrane module. Hereinafter, the present invention will be described in detail with reference to the pressure type hollow fiber membrane module for convenience of description.

1 is a cross-sectional view schematically showing a pressurized hollow fiber membrane module according to an embodiment of the present invention. As illustrated in FIG. 1, the hollow fiber membrane module 10 includes a plurality of hollow fiber membranes 11. The hollow fiber membranes 11 have a bundle form arranged in the longitudinal direction. The hollow fiber membranes 11 have a tube shape. The hollow fiber membrane 11 in the form of a tube has a hollow formed therein, and only pure water except impurities in raw water to be treated may pass through the hollow fiber membrane 11 and enter the hollow.

The upper end of each hollow fiber membrane 11 is fixed to the upper side in the module case 14 by the first fixing part 12. The upper end of each of the hollow fiber membranes 11 is in an open state. The hollow fiber membrane module 10 of the present invention further includes a sealing agent (not shown) between the first fixing part 12 on which the plurality of hollow fiber membranes 11 are potted and the inner surface of the module case 14. After passing through the hollow fiber membrane 11 and entering the hollow, the filtered water discharged through the open end of the hollow fiber membrane 11 may be prevented from being mixed with the raw water.

The first fixing part 12 may be made of a thermosetting resin, for example, an epoxy resin, a urethane resin, a silicone rubber, or the like. Optionally, by incorporating fillers such as silica, carbon black, carbon fluoride, and the like into these thermosetting resins, the strength of the first fixing portion 12 and reduction of cure shrinkage can be achieved.

On the other hand, the lower end portion of each hollow fiber membrane 11 is fixed to the lower side in the module case 14 by the second fixing portion 13. The lower end of each hollow fiber membrane 11 is closed and buried in the second fixing part 13.

Raw water to be filtered is introduced into the module case 14 through the raw water inlet 15. The raw water introduced into the module case 14 is pressurized by a pump, and a part of the raw water penetrates the hollow fiber membrane 11 and flows into the hollow of the hollow fiber membrane 11. The filtered water introduced into the hollow of the hollow fiber membrane 11 exits the open end on the side of the first fixing part 12 and is discharged to the outside through the filtered water outlet 16 of the module case 14. Raw water (hereinafter, referred to as "concentrated water") having a high concentration of contaminants of solid components is discharged to the outside through the concentrated water outlet 17.

During the filtration operation or after the filtration operation is stopped, air for cleaning the hollow fiber membrane 11 is introduced into the module case 14 through the air inlet 18. A plurality of through holes 13a are formed in the second fixing part 13 so that air introduced into the module case 14 through the air inlet 18 can be delivered to the hollow fiber membrane 11. .

Optionally, the raw water to be filtered and air for acid cleaning of the hollow fiber membrane 11 may be introduced into the module case 14 through one inlet 18. In this case, both the raw water to be filtered and the air for the acid cleaning are passed through the plurality of through holes 13a formed in the second fixing part 13.

On the other hand, the raw water in the module case 14 after the filtration work is finished and passes through the plurality of through holes 13a formed in the second fixing part 13 and is discharged out of the module case 14 through the drain hole 19. do.

Hereinafter, with reference to Figure 2 to look at the filtration system according to an embodiment of the present invention in detail.

As illustrated in FIG. 2, the filtration system according to an embodiment of the present invention includes a first washing tank in which the hollow fiber membrane module 10 and the washing water CW for backwashing the hollow fiber membrane module 10 are stored. 21, a control unit 30, and a second washing tank 22 in which the washing treatment water PW generated as the backwashing is performed is stored.

A pressurized hollow fiber membrane module 10 having a raw water inlet 15, a filtrate outlet 16, a brine outlet 17, and an air inlet 18 is illustrated in FIG. 2 as a hollow fiber membrane module, but having only a filtrate outlet. Immersion hollow fiber membrane modules can also be used in the filtration system of the present invention. In that case, the bath in which the immersion hollow fiber membrane module is immersed will perform the same function as the second cleaning tank 22.

The first and second cleaning baths 21 and 22 may be located apart from each other, or may be located side by side with the partition wall therebetween.

The controller 30 controls the flow of the washing water CW so that the backwashing of the hollow fiber membrane module 10 can be performed, and after the backwashing, the controller 30 supplies the washing water PW of the second washing tank 22. The flow of the cleaning water PW is controlled so that the filtration cleaning of the hollow fiber membrane module 10 can be performed. Specifically, the backwashing operation is controlled through the first pump P1 and the filtration cleaning operation is controlled through the second pump P2.

Backwashing herein means cleaning performed by passing water through the hollow fiber membrane in the inside-to-outside direction, and filtration cleaning refers to the cleaning of water in the outside-to-inside direction. It means the cleaning performed by passing through the hollow fiber membrane.

According to the present invention, the filtrate FW generated by the filtration washing (the filtrate FW generated by passing at least a portion of the washing water PW through the hollow fiber membrane) is later used as the washing water CW for backwashing. It is stored in the first cleaning tank 21 so that.

In the filtration cleaning, i) a total amount of washing water (PW) introduced into the filtration cleaning is filtered water (FW) passing through the hollow fiber membrane to be stored in the first cleaning tank 21 (dead end filtration), or ii) Only a part of the washing water PW put into the filtration cleaning passes through the hollow fiber membrane to become the filtered water FW, and is stored in the first washing tank 21, and the rest of the washing water PW through the concentrated water outlet 17. It may be performed by a cross-flow filtration method which is discharged from the 10 and stored in the second cleaning tank 22 again.

The filtration system of the present invention further includes a compound supply portion 40 for supplying an acidic or basic compound to the washing water CW for backwashing. The acidic compound may be HCl, citric acid, and / or oxalic acid, and the basic compound may be NaOH or NaOCl. The acidic compound and the basic compound may be supplied alone or alternately to the washing water (CW).

Optionally, the filtration system may further include a mixer 50 for uniformly mixing the washing water CW provided from the first washing tank 21 with the compound provided from the compound supply 40. Backwashing is performed with a mixture of washing water (CW) and an acidic or basic compound to perform recovery and washing for the hollow fiber membranes.

According to the present invention, the washing treatment water (PW) generated by backwashing with a mixture of washing water (CW) and an acidic or basic compound is stored in the second washing tank 22 and used for filtration washing. The filtrate FW generated as this filtration washing is performed is stored in the first washing tank 21 to be used again as the washing water CW for backwashing.

As the backwashing and filtration washing are alternately performed, the concentration of the compound in the washing water CW stored in the first washing tank 21 is lowered. For example, when an acidic compound is used, the pH of the washing water CW stored in the first washing tank 21 becomes gradually higher than the initial value each time one cycle of backwashing and filtration washing is performed. .

Thus, as illustrated in FIG. 2, the filtration system according to one embodiment of the present invention provides a first cleaning bath 21 so that an appropriate amount of compound corresponding to the lowered compound concentration can be supplied to the washing water CW. It further includes a pH meter (pH-meter) 60 for measuring the pH of the washing water (CW) in the. The control unit 30 receiving the pH value of the washing water CW in the first cleaning tank 21 from the pH meter 60 is supplied to the mixer 50 from the compound supply unit 40 based on the pH value. Adjust the amount of. Thus, according to the present invention, the amount of compound supplied can be adjusted in real time and automatically in response to the pH change of the washing water (CW) used for backwashing.

Meanwhile, as the backwashing is performed, the solid particles attached to the hollow fiber membranes are separated from the hollow fiber membranes, and thus, many solid particles are mixed in the washing water PW generated in the backwashing process and stored in the second washing tank 22. There may be. In the case of filtration cleaning using a washing water (PW) containing a lot of solid particles, the cleaning effect of the hollow fiber membrane may be reduced. Thus, as illustrated in FIG. 2, the filtration system of the present invention may further include a microfilter 70 for removing solid particles from the washing process water PW to be used for filtration cleaning.

As mentioned above, if an excessively long time is arbitrarily allocated for recovery cleaning, problems such as lowering the efficiency of the filtration operation, increasing the cleaning cost, and thereby reducing the life of the hollow fiber membrane. Thus, as illustrated in FIG. 2, the filtration system of the present invention has manometers 81, 82 for measuring the transmembrane pressure of the hollow fiber membrane module 10 when filtration cleaning is performed. It may further include. In this case, the controller 30 calculates the interlayer differential pressure of the hollow fiber membrane module 10 by using the pressure values provided from the pressure gauges 81 and 82, and determines whether to stop backwashing and filtration cleaning based on this. .

That is, according to the present invention, whether or not the recovery rate of the desired hollow fiber membrane is achieved is measured in real time while the recovery cleaning is performed, and the recovery cleaning can be stopped as soon as this predetermined recovery rate is achieved. As a result, problems such as a decrease in the efficiency of the filtration operation due to excessive recovery cleaning, an increase in the cleaning cost, and a decrease in the lifespan of the hollow fiber membrane due to this can be prevented.

Optionally, when the interlayer differential pressure of the hollow fiber membrane module 10 is lowered to a predetermined value, backwashing the hollow fiber membrane module 10 with pure water without an acidic or basic compound for a predetermined time is performed in the hollow fiber membrane. The remaining compounds may be completely removed.

Hereinafter, the cleaning method of the hollow fiber membrane module 10 executed under the control of the controller 30 of the present invention will be described in more detail.

In the cleaning method of the present invention, backwashing the hollow fiber membrane module 10 with the washing water CW of the first washing tank 21 may include washing the washing water PW generated through the backwashing with the second washing machine. Storing in the washing tank 22, stopping the backwashing, and performing filtration washing with the washing water PW of the second washing tank 22.

In detail, the controller 30 operates the first pump P1 to allow the washing water CW of the first washing tank 21 to flow into the hollow fiber membrane module 10 through the filtered water outlet 16. . The washing water (CW) introduced into the hollow fiber membrane module 10 passes through the hollow fiber membrane after entering the hollow of the hollow fiber membrane, and in this process, impurities attached to the hollow fiber membrane are separated from the hollow fiber membrane. After the impurity separated from the hollow fiber membrane is mixed with the washing water (CW) passing through the hollow fiber membrane, the washing treatment water (PW) is discharged from the hollow fiber membrane module 10 through the concentrated water outlet 17 and then discharged. Stored in the bath 22.

After the backwashing is performed for a predetermined time, the controller 30 stops the backwashing by stopping the first pump P1 and operates the second pump P2 to clean the treated water PW of the second washing tank 22. ) Is introduced into the hollow fiber membrane module 10 through the raw water inlet 15. Filtration rinsing is performed by passing only the hollow water of the washing water PW introduced into the hollow fiber membrane module 10 through the hollow fiber membrane.

Subsequently, the filtered water FW obtained in the hollow of the hollow fiber membrane by filtration washing is discharged from the hollow fiber membrane module 10 through the filtered water outlet 16 and then stored in the first washing tank 21. The filtered water FW stored in the first washing tank 21 is used as the washing water CW in a backwashing process to be performed later.

The backwashing and filtration cleaning described above are alternately performed until the interlayer differential pressure of the hollow fiber membrane module 10 is lowered to a predetermined value.

The cleaning method according to an embodiment of the present invention further includes mixing an acidic or basic compound with the washing water (CW) before the washing water (CW) for backwashing flows into the hollow fiber membrane module 10. can do. In this case, the pH of the washing water CW of the first washing tank 21 may be measured, and the amount of the compound mixed with the washing water CW may be adjusted based on the pH value thus measured.

On the other hand, in the cleaning method of the present invention, in order to maximize the efficiency of the filtration cleaning, before the washing treatment water PW stored in the second cleaning tank 22 flows into the hollow fiber membrane module 10 for filtration cleaning. The method may further include removing solid particles from the washing water PW.

In order to accurately determine the timing of stopping the recovery cleaning, the recovery rate of the hollow fiber membrane module 10 needs to be measured in real time while the recovery cleaning is performed. Therefore, the step of measuring the interlayer differential pressure of the hollow fiber membrane module 10 when the filtration cleaning is performed, and the step of determining whether to stop backwashing and filtration cleaning based on the measured interlayer differential pressure can be further performed. That is, according to the present invention, whether or not the recovery rate of the desired hollow fiber membrane is achieved is measured in real time while the recovery cleaning is performed, and the recovery cleaning can be stopped as soon as this predetermined recovery rate is achieved. As a result, problems such as a decrease in the efficiency of the filtration operation due to excessive recovery cleaning, an increase in the cleaning cost, and a decrease in the lifespan of the hollow fiber membrane due to this can be prevented.

Optionally, when the interlayer differential pressure of the hollow fiber membrane module 10 measured during the filtration cleaning is lowered to a predetermined value, backwashing the hollow fiber membrane module 10 with pure water without an acidic or basic compound is filtered. By carrying out for a predetermined time immediately after this end, the compound which may remain in the hollow fiber membrane can be completely removed.

10: hollow fiber membrane module 21, 22: first and second cleaning tank
30: control unit 40: chemical supply unit
50: Mixer 60: pH Meter
70: microfilter 81, 82: pressure gauge

Claims (12)

Hollow fiber membrane module;
A first washing tank storing washing water for backwashing the hollow fiber membrane module;
A control unit for controlling the flow of the washing water so that the backwash can be performed; And
A second rinsing tank for storing the rinse water generated as the backwashing is performed,
And the control unit controls the flow of the washing water to perform filtration washing of the hollow fiber membrane module with the washing water of the second washing tank after the backwashing. The method of claim 1,
A filtration system, wherein the filtrate produced by the filtration scrubbing is stored in the first scrubber for use as the scrubbing water for the backwash. The method of claim 1,
A compound supply part for supplying an acidic or basic compound; And
And a mixer for uniformly mixing the washing water provided from the first washing tank and the compound provided from the compound supply unit.
The backwashing is carried out with a mixture of the washing water and the compound. The method of claim 3,
Further comprising a pH meter (pH-meter) for measuring the pH of the washing water in the first washing tank,
And the control unit adjusts the amount of the compound supplied from the compound supply unit to the mixer based on the pH value measured by the pH meter. The method of claim 1,
And a microfilter for removing solid particles from the rinse water to be used for the filtration rinse. The method of claim 1,
Further comprising manometers for measuring the transmembrane pressure of the hollow fiber membrane module when the filtration cleaning is performed,
And the control unit determines whether to stop the backwashing and the filtration cleaning based on the interlayer differential pressure of the hollow fiber membrane module measured by the pressure gauges. Performing backwashing the hollow fiber membrane module with the washing water of the first washing tank;
Storing the washing treatment water generated through the backwashing in a second washing tank;
Stopping the backwash; And
And performing a filtration rinsing with the rinsing treated water in the second rinsing tank. The method of claim 7, wherein
And storing the filtrate in the first rinsing tank so that the filtrate generated through the filtration rinsing can be used as the rinsing water for backwashing. The method of claim 7, wherein
And mixing an acidic or basic compound with the washing water for backwashing. 10. The method of claim 9,
Measuring a pH of the washing water of the first washing tank; And
And adjusting the amount of the compound mixed with the washing water based on the measured pH value of the washing water. The method of claim 7, wherein
And removing solid particles from the rinsing water to be used for the filtration rinsing. The method of claim 7, wherein
Measuring the interlayer differential pressure of the hollow fiber membrane module when the filtration cleaning is performed; And
And determining whether to stop the backwashing and the filtration cleaning based on the measured intermembrane pressure of the hollow fiber membrane module.

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