JPH11253763A - Washing method for hollow fiber membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a washing method for a hollow fiber membrane module which allows easy and efficient washing. SOLUTION: A hollow fiber membrane module which is fixed on a fixing member whose cross section vertical to hollow fiber membranes 3 has a long, narrow, almost rectangular shape, is washed by back washing, a sponge ball, or ultrasonic waves, while at least one end parts of the hollow fiber membranes 3 are kept in an opened state. The use of the hollow fiber membrane module having a specific shape enables easy efficient washing to efficiently perform a recovery of a filtration function by washing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a hollow fiber membrane module, and more particularly to a cleaning method capable of easily and efficiently cleaning a hollow fiber membrane module having a specific structure and easily recovering a filtration function. About.

[0002]

2. Description of the Related Art Conventionally, hollow fiber membrane modules have been constructed using sterile water,
It has been widely used in the field of so-called microfiltration, such as the production of drinking water and high-purity water, and the purification of air. Various studies have been made for use in water treatment applications.

[0003] However, the hollow fiber membrane modules used in these fields are also of a cylindrical type in which hollow fiber membranes converged and arranged in a circular shape or concentric circles used in the field of conventional microfiltration. Was the most.
Even if improvements are made, there are many that only change the filling rate or filling form of the hollow fiber membrane.

[0004]

However, when such a conventional hollow fiber membrane module is used to filter high-polluting water (for example, SS ≧ 50 ppm, TOC ≧ 100 ppm), it is difficult to use the filter. The hollow fiber membranes are fixed (adhered) to each other through deposits such as organic substances attached to the surface of the hollow fiber membrane, thereby reducing the effective membrane area of the hollow fiber membrane in the module. A sharp decrease in the filtration flow rate was observed. In particular, this phenomenon was remarkable in the hollow fiber membrane at the center of the cylindrical module, and was more remarkable in a larger module.

[0005] In addition, even when the hollow fiber membrane module in which the hollow fiber membranes are fixed and integrated as described above is periodically cleaned and backwashed, the function of the module once fixed and integrated can be easily recovered. Instead, the cleaning efficiency was reduced.

SUMMARY OF THE INVENTION An object of the present invention is to use a hollow fiber membrane module having a specific structure in which a hollow fiber membrane is difficult to be fixed and integrated, which enables simple and efficient cleaning, and facilitates recovery of a filtration function. It is to provide a method.

[0007]

That is, the present invention relates to a fixing member in which at least one end of a hollow fiber membrane has an elongated and substantially rectangular cross section perpendicular to the hollow fiber membrane while keeping its end open. A method for cleaning a hollow fiber membrane module, comprising cleaning the fixed hollow fiber membrane module by backwashing.

Further, the present invention provides a hollow fiber membrane in which at least one end of the hollow fiber membrane is fixed to an elongate and substantially rectangular fixing member whose cross section perpendicular to the hollow fiber membrane is elongated while keeping its end open. A method for cleaning a hollow fiber membrane module, comprising cleaning the module with a sponge ball.

The present invention further provides a hollow fiber membrane in which at least one end of the hollow fiber membrane is fixed to an elongate and substantially rectangular fixing member whose cross section perpendicular to the hollow fiber membrane has an elongated shape while keeping its end open. A method for cleaning a hollow fiber membrane module, comprising cleaning the module by ultrasonic waves.

[0010]

Hereinafter, the hollow fiber membrane module used in the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a perspective view showing an example of a hollow fiber membrane module used in the present invention, and FIG. 2 is a sectional view thereof. This hollow fiber membrane module basically includes a housing 1, a fixing member 2, and a hollow fiber membrane 3. In addition to these, various accessory members such as the dispersing means 4 may be provided.

The housing 1 functions as a member for supporting the entire hollow fiber membrane module, and has an elongated, substantially rectangular opening. Any material may be used as long as it has mechanical strength and durability. For example, polycarbonate, polysulfone, polypropylene, acrylic resin, ABS
Resin, modified PPE resin and the like are exemplified. If incineration is required after use, it is preferable to use a hydrocarbon resin that can be completely burned without emitting toxic gas by combustion.

The opening of the housing 1 is required to be such that the shape of a cross section perpendicular to the hollow fiber membrane of the fixing member filled and fixed with the hollow fiber membrane therein is elongated and substantially rectangular. The length of the short side of this rectangle is preferably 30 mm or less, particularly preferably 15 mm or less. As described above, by developing the arrangement mode of the hollow fiber membranes as a flat sheet, the entire hollow fiber membrane bundle is fixedly integrated into one rod shape, and the effective membrane area of the hollow fiber membrane rapidly decreases. Can be prevented. Even if the hollow fiber membranes are fixed to each other, the thickness of the fixing portion of the hollow fiber membrane is small, and the fixing state can be easily recovered because the hollow fiber membrane is provided in a sheet shape. In addition,
There is no particular limitation on the length of the long side of the rectangle. It is not preferable. Usually, the length of the long side is about 100 to 2000 mm.

The fixing member 2 is filled and fixed in the opening of the housing 1, and collectively fixes each end of the large number of U-shaped hollow fiber membranes 3 while maintaining the open state. Functions as a filtration membrane in order to function as a filtration membrane. Fixing member 2
Is usually formed by curing a liquid resin such as an epoxy resin, an unsaturated polyester resin, or polyurethane.

As the hollow fiber membrane 3, various materials can be used, and for example, those made of various materials such as cellulose, polyolefin, polyvinyl alcohol, PMMA, and polysulfone can be used. However, in consideration of the ease of processing into a knitted fabric, a material having a high strength and elongation such as polyethylene is preferable. The pore diameter, porosity, film thickness, outer diameter and the like are not particularly limited as long as they can be used as a filtration membrane.

In order to store the hollow fiber membrane 3 in the elongated, substantially rectangular opening of the housing 1, it is necessary to use a laminate in which several knitted fabrics are formed by using the hollow fiber membrane as a warp, for example. It is suitable. In the case of the conventional cylindrical module, there was no difficulty in storing the hollow fiber membranes that had been skeined and bundled in the cylindrical housing. However, it is difficult to store the skeined hollow fiber membrane in the elongated rectangular opening,
The knitted fabric can be easily stored. When laminating knitted fabrics of hollow fiber membranes, hollow fiber membrane knitted fabrics having different performances can be used. For example, when a hollow fiber membrane module is manufactured by sandwiching a knitted fabric of a hydrophobic hollow fiber membrane with a knitted fabric of a hollow fiber membrane subjected to hydrophilic treatment and sandwiching the same, a hydrophobic hollow fiber membrane layer is formed. Can be used as a means for supplying bubbles during backwashing.

Instead of using a knitted fabric in which several knitted fabrics are laminated, a folded knitted fabric in which a knitted fabric of a hollow fiber membrane is folded in a zigzag shape in an elongated manner (arranged in a meandering shape) may be used. By employing this storage method, it is possible to prevent uneven placement of the hollow fiber membrane in the fixing member when the filling density of the hollow fiber membrane is relatively low.

In the hollow fiber membrane module used in the present invention, it is preferable that the hollow fiber membrane having a U-shape or the like is formed as an aggregate of small bundles of hollow fiber membranes. Here, the small bundle means a collection of hollow fiber membranes satisfying the following conditions. That is, the hollow fiber membrane contained in one small bundle is fixed, for example, in a state where both fixing portions corresponding to the base of the U-shape are close to each other on the fixing member (preferably within 1 cm ² ). Can be easily bundled (aligned) with the hollow fiber membranes belonging to the same small bundle, but other hollow fiber membranes in the vicinity of the hollow fiber membranes belonging to the other small bundles interfere with each other to form a bundle. It is difficult to do. More specifically, when only the hollow fiber membrane wound and converged on one skein is housed in one housing and fixed, all the hollow fiber membranes in the module are contained in the same bundle. Will be. On the other hand, for example, when a hollow fiber membrane knitted using ten plied hollow fiber membranes as wefts is housed and fixed in a housing, the whole of the previously stranded hollow fiber membranes becomes one piece. Make up one bundle,
The number of hollow fiber membranes included in one bundle is 10.

Therefore, when the U-shaped hollow fiber membrane is constituted as an aggregate of small bundles of hollow fiber membranes, the hollow fiber membranes are bundled for each small bundle and this is bundled with another small bundle. Since the hollow fiber membrane module can be easily separated from the body, forcible uniform dispersion and fixation of the hollow fiber membrane can be easily performed when using the hollow fiber membrane module. The number of hollow fiber membranes included in one of the small bundles depends on the thickness of the hollow fiber membrane, but is preferably 100 or less, more preferably 50 or less.

The method for producing the hollow fiber membrane module used in the present invention is not particularly limited, but the following method is preferred. First, a knitted fabric using a hollow fiber membrane as a weft as shown in FIG. 3 is prepared. The specific method is disclosed in, for example, JP-A-62-57965 and JP-A-1-266258. Several sheets obtained by cutting the sheet-shaped knitted fabric into appropriate lengths are laminated.
Here, the term “lamination of knitted fabric” also includes a fabric obtained by folding and knitting a knitted fabric to an appropriate length without cutting it. The number of layers (folding) of the knitted fabric varies depending on the thickness of the knitted fabric, that is, the thickness of the hollow fiber membrane and the number of hollow fiber membranes when knitting the knitted fabric. It is preferable that the fixing member be configured so as to satisfy the limitation on the length of the short side of the rectangular cross section of the fixing member. One side of the knitted laminate is housed in a housing having an elongated, substantially rectangular opening,
After the storage portion is cured and fixed with a liquid resin (hereinafter referred to as potting), the cured resin is cut so that the open end of the hollow fiber membrane appears. In addition, as described above, a knitted fabric using a hollow fiber membrane as a weft may be folded into a zigzag shape to form a folded knitted fabric, and one side of the folded knitted fabric may be stored in the opening of the housing.

In manufacturing a hollow fiber membrane module, a method utilizing a centrifugal force is generally employed as a method for filling a liquid resin without gaps between hollow fiber membranes. However, when a hollow fiber membrane is potted in a housing having an elongated rectangular opening, a large and special shape such as a bucket used for centrifugal potting is required. Therefore, it is preferable to use potting using the vibration method described below, which is less affected by the size and shape of the housing. That is,
The knitted fabric of the hollow fiber membrane is housed in a housing, which is filled with a liquid resin. At that time, as in the case of the conventional method for manufacturing a hollow fiber membrane module, it is necessary to seal the end portion of the hollow fiber membrane bundle and perform processing so that the liquid resin does not enter the hollow portion of the hollow fiber membrane. Needless to say. Liquid resin is 1000
Those having a viscosity of about 2500 centipoise are optimal. While the liquid resin has fluidity, the housing containing the hollow fiber membrane bundle and the liquid resin is subjected to mechanical vibration to uniformly fill the resin. The frequency is 500 ~
Although about 12000 cycles are appropriate, vibration in the ultrasonic region may be applied. Details of the potting by the vibration method are disclosed in JP-A-3-114515. By using this potting method, the liquid resin is uniformly dispersed in the housing, and peeling between the hollow fiber membrane and the cured resin (fixing member) and leakage of the filtration fluid at the fixing member are prevented. The cutting of the end surface after the liquid resin has hardened (the formation of the open end of the hollow fiber membrane) and the like can be performed according to a general hollow fiber membrane module processing method.

When using this hollow fiber membrane module, a so-called pressure filtration method in which the module is disposed in a closed vessel and water to be treated is pressurized to allow the hollow fiber membrane to permeate can be adopted. It is preferable to dispose a hollow fiber membrane module in a precipitation tank or the like and use the suction filtration method for suctioning the side for collecting the treated water permeated through the hollow fiber membrane. Especially,
By adopting a so-called intermittent suction operation method in which temporary suction is periodically stopped, it is possible to efficiently prevent the film surface deposits from entering the inside of the film surface, and the frequency of the function recovery processing of the hollow fiber membrane module is reduced. Can be reduced.

The flow of the water to be treated in the suction filtration method is preferably made to flow substantially perpendicularly to the direction in which the hollow fiber membranes are provided, so that the effect of cleaning the membrane surface of the hollow fiber membranes is improved.

One of the preferred methods of using this hollow fiber membrane module is as follows, for each small bundle 5 of hollow fiber membranes described above.
Dispersing means 4 for expanding and holding and fixing each of the U-shaped tops
The embodiment shown in FIG. At this time, the U-shaped top is temporarily fixed to the U-shaped top by the warp when the hollow fiber membrane knit is formed, and the U-shaped top is engaged with the dispersing means 4 as shown in FIG. Is preferred. Of course, the warp during knitting of the knitted fabric for temporary fixing may be removed from the hollow fiber membrane module. The dispersing means 4 may be provided separately from the hollow fiber membrane module,
It may be provided integrally with the hollow fiber membrane module. Further, the dispersing means is not limited to the hook-shaped one as shown in the figure, and may be a rod-shaped one having a partition distribution plate, or may have a number of strings, and tie the U-shaped top with this string. It may be fixed. By disposing this dispersing means, even if the hollow fiber membrane module of the present invention is used for filtering highly polluted water, a high degree of dispersibility of the hollow fiber membrane can be maintained for a longer period of time.

Further, as one of the preferred methods of using the hollow fiber membrane module, there is a method of arranging the module on a rotating body and performing filtration while rotating the module. As a method of attaching the module to the rotating body, the module housing is arranged so as to extend radially in the horizontal direction around the rotating body, and the hollow fiber membrane is hung downward from each housing, or is arranged vertically. There is a mode in which housings of a plurality of modules are arranged so as to be oriented in the vertical direction with the provided rotating body as an axis, and the hollow fiber membranes extend radially in the horizontal direction from each of the modules.

The hollow fiber membrane module is particularly suitable for filtration of highly polluted water. Specific application fields include river water filtration, industrial water filtration, sewage solid-liquid separation, and wastewater treatment (for example, merger). Treatment in a septic tank).

In the present invention, in order to recover the function of the hollow fiber membrane module, washing by back washing, washing with a sponge ball, or washing with ultrasonic waves is performed. In the present invention, since the hollow fiber module having the specific form as described in detail above is used, each cleaning method can be easily and efficiently performed due to this.

In the present invention, when washing is carried out by backwashing, when the hollow fiber membrane is clogged with contaminants, pressure is applied in the opposite direction to ordinary filtration to reverse the flow of gas or liquid, thereby causing the hollow fiber membrane to flow backward. Just clean the module. As the pressurizing means, a conventionally known blower, compressor and pump can be used. This backwashing method is advantageous in that it can be easily performed.

When a conventional hollow fiber module is washed by backwashing, since the central portion is surrounded by the yarn, deposits on the membrane surface are not easily peeled off even when backwashing is performed. Further, even if it is once peeled, it is difficult to get out of the portion surrounded by the yarn, so that it is easy to deposit again when filtration is restarted. On the other hand, in the present invention, since the hollow fiber membrane module of a specific form in which the hollow fiber membrane is developed is used as described in detail above, the portion surrounded by the yarn is small, and the backwashing of the membrane surface is performed. It can be done efficiently.

In the present invention, when washing is carried out with a sponge ball, any conventionally known sponge balls, such as resin, cotton, silk, animal hair, sponge, etc., can be used to scrape off any deposits on the membrane surface. A sponge ball may be caused to collide with the surface of the membrane by applying a stream of water while being floated in the liquid, thereby performing physical cleaning.

In the case of a conventional cylindrical hollow fiber membrane module, it is almost impossible to insert a sponge ball or the like since the yarns interfere with each other at the center. On the other hand, in the present invention, as described above, since the hollow fiber module of the specific form in which the hollow fiber membrane is developed is used, the membrane surface can be easily cleaned using a sponge ball.

In the present invention, when cleaning is performed by ultrasonic waves, a vibration device may be installed in the water tank to vibrate, thereby generating ultrasonic waves in the liquid in the water tank and cleaning the hollow fiber membrane module. .

In the case of the conventional cylindrical hollow fiber membrane module, since the inner yarn is shaded by the outer yarn, the impact by the ultrasonic wave is hardly transmitted, and the whole cannot be effectively cleaned. On the other hand, in the present invention, as described in detail above, since the hollow fiber module of a specific form is used in which the shade of the inner yarn is minimized, the whole is efficiently made by ultrasonic waves. Can be washed. In addition, as in the case of the backwash, there is an advantage that the deposit is easily peeled off.

Reference Example 1 Porous polyethylene hollow fiber membrane (E
HF270T: trade name, inner diameter 270μm, outer diameter 380μ
m, manufactured by Mitsubishi Rayon Co., Ltd.) is a 10 mm ×
It was housed in a housing having an opening of 300 mm, and this housing was cured and fixed with a urethane resin by a vibration potting method to produce a hollow fiber membrane module having a structure as shown in FIG. The length of one hollow fiber membrane forming a loop is 760 m
m, the effective filtration area was 5 m ² .

Using this module, waste water treatment in the flow shown in FIG. 6 was performed. The hollow fiber membrane module was operated under the conditions of a suction pressure of 0.2 kg / cm ² and a suction cycle (suction for 9 minutes, stop for 1 minute). The explosive tank capacity was 800 liters, and the TOC volume load was 0.2 kg / m ^3.
-The day and MLSS were about 5000 ppm.

FIG. 7 shows the measurement results of the filtration flow rate of the hollow fiber membrane module when the wastewater treatment was performed for 30 days.

REFERENCE COMPARATIVE EXAMPLE 1 Polyethylene porous hollow fiber membrane (EHF270T: trade name, inner diameter 270 μm, outer diameter 38)
Using 0 μm, manufactured by Mitsubishi Rayon Co., Ltd.), the ends were solidified with urethane resin to produce a cylindrical module having a structure as shown in FIG. Length of one hollow fiber membrane forming a loop 76
0 mm and the effective filtration area was 5 m ² .

Except for using this cylindrical module, drainage treatment was performed in exactly the same manner as in Reference Example 1. FIG. 9 shows the measurement results of the filtration flow rate of the hollow fiber membrane module.

As is clear from the comparison between FIG. 7 and FIG. 9, the hollow fiber membrane module of Reference Example 1 has a higher flow rate and longer life in filtering highly polluted water than the cylindrical module. .

[0040]

The hollow fiber membrane module used in the present invention comprises:
Since more hollow fiber membranes are in direct contact with the water to be treated, the accumulation of organic substances between the hollow fiber membranes is suppressed, and adhesion and integration between the hollow fiber membranes are prevented, especially in the filtration of highly polluted water.
It is possible to maintain high filtration efficiency over a long period. Further, according to the cleaning method of the present invention, since the hollow fiber module having the specific form as described above is used, it is possible to easily and efficiently perform the cleaning due to the hollow fiber module, and to recover the filtration function by the cleaning. Processing can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a hollow fiber membrane module used in the present invention.

FIG. 2 is a cross-sectional view of the module of FIG.

FIG. 3 is a plan view showing a hollow fiber membrane knitted fabric suitable for use in manufacturing a hollow fiber membrane module.

FIG. 4 is a perspective view showing an example of how to use the hollow fiber membrane module.

FIG. 5 is a partially enlarged view showing an example of a use state of the hollow fiber membrane module.

FIG. 6 is a diagram showing a wastewater treatment flow when the hollow fiber membrane module is used for wastewater treatment.

FIG. 7 is a graph showing a measurement result of a filtration flow rate of the hollow fiber membrane module when the hollow fiber membrane module is used for drainage treatment in Reference Example 1.

FIG. 8 is a perspective view of a conventional cylindrical hollow fiber membrane module used in Comparative Reference Example 1.

FIG. 9 is a graph showing a measurement result of a filtration flow rate of the hollow fiber membrane module in Comparative Reference Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Fixing member 3 Hollow fiber membrane 4 Dispersing means 5 Small bundle 6 Temporary fixing 7 Hook

Claims (3)

[Claims] 1. A hollow fiber membrane module in which at least one end of a hollow fiber membrane is fixed to an elongated and substantially rectangular fixing member whose cross section perpendicular to the hollow fiber membrane has an elongated shape while keeping its end open. A method for cleaning a hollow fiber membrane module, comprising washing by backwashing. 2. A hollow fiber membrane module in which at least one end of a hollow fiber membrane is fixed to an elongated and substantially rectangular fixing member whose cross section perpendicular to the hollow fiber membrane has an elongated shape while keeping its ends open. A method for cleaning a hollow fiber membrane module, comprising cleaning with a sponge ball. 3. A hollow fiber membrane module in which at least one end of the hollow fiber membrane is fixed to a fixing member whose cross section perpendicular to the hollow fiber membrane has an elongated and substantially rectangular shape while keeping its end in an open state. A method for cleaning a hollow fiber membrane module, comprising cleaning with an ultrasonic wave.