JP2009285532A - Hollow fiber membrane module, membrane separation method, and water treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the operation efficiency of a water treatment apparatus from degrading by suppressing the permeation capacity of a hollow fiber membrane from degrading, thereby performing an efficient membrane separation method. <P>SOLUTION: The hollow fiber membrane module is provided with a fixing member fixing a lower end of the hollow fiber membranes by vertically extending the plurality of the hollow fiber membranes in water for performing the membrane separation, and is formed with an air diffusion mechanism generating bubbles from a lower end of the hollow fiber membranes for diffusing air into the vertically extending hollow fiber membranes. The air diffusion mechanism is formed to generate bubbles from the central region in the region disposed with the hollow fiber membranes more than the bubbles generated in the outer region of the central region. The present invention provides the hollow fiber membrane module, the membrane separation method using the hollow fiber membrane module, and the water treatment apparatus provided with the hollow fiber membrane module. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hollow fiber membrane module used for membrane separation and a water treatment device, and in particular, for example, water purification treatment such as river water, lake water, ground water, seawater, or membrane separation treatment such as sewage and industrial wastewater. The present invention relates to a hollow fiber membrane module, a membrane separation method, and a water treatment device used for the above.

  In water treatment equipment, etc., where sewage purification using the membrane-separated activated sludge method is carried out, the hollow fiber membrane is moved vertically in the water to be treated (active sludge mixed liquid) that has been subjected to aerobic biological treatment in a biological reaction tank in recent years. So that the external pressure type hollow fiber membrane module can be used, which is immersed in a standing posture extended and held, and the inside of the hollow fiber membrane is sucked to perform membrane separation of treated water to obtain permeated water It has become to.

  And the hollow fiber membrane module used for membrane separation of this kind of water to be treated is liable to lower the permeation performance of the hollow fiber membrane due to floating solids or adhesive organic compounds in the water to be treated. When the permeation performance is lowered, the operation efficiency of the water treatment apparatus is also lowered. Conventionally, methods for suppressing this reduction in permeation performance have been widely studied.

As a method of suppressing the deterioration of the permeation performance, in the hollow fiber membrane module that performs membrane separation by extending the hollow fiber membrane in the vertical direction, aeration is performed on the lower end side of the hollow fiber membrane. There is known a method called air scrubbing that removes deposits on the surface of the hollow fiber membrane with bubbles generated by the above.
For example, air diffusion is performed with only the lower end side of the hollow fiber membrane fixed, and membrane separation is performed while the hollow fiber membrane is placed in an upright position in the water by the upward flow accompanying the rising of the bubbles, or Further, there is known a method of performing membrane separation by fixing both ends of a hollow fiber membrane to a fixing member that is spaced apart vertically and generating bubbles from the upper surface side of the lower fixing member. Yes.
As a hollow fiber membrane module having an air diffusion mechanism for carrying out such air diffusion, those described in Patent Documents 1 and 2 below are known.

The hollow fiber membrane modules described in Patent Documents 1 and 2 fix one end portion (upper end portion) of both ends of the hollow fiber membrane so that a plurality of hollow fiber membranes can be held in an upright posture. An upper fixing member and a lower fixing member for fixing the other end (lower end) are provided, and air scrubbing can be performed on the hollow fiber membrane by generating bubbles from the lower fixing member side in the water to be treated. It has a diffuser mechanism.
For this reason, the hollow fiber membrane module described in Patent Documents 1 and 2, for example, by immersing in water containing a large amount of organic compounds and floating solids, such as the activated sludge mixed solution, and performing membrane separation, The adhering matter on the surface of the hollow fiber membrane can be removed by air scrubbing, so that a decrease in permeation performance is prevented.

  However, the hollow fiber membrane modules described in Patent Documents 1 and 2 have not been sufficiently studied to effectively perform air scrubbing, and moreover need to generate bubbles more than necessary. is there.

That is, the conventional hollow fiber membrane module tends to cause a decrease in the permeation performance of the hollow fiber membrane, and it is difficult to carry out an efficient membrane separation method, thereby suppressing a decrease in the operating efficiency of the water treatment device. It has also become difficult.
In addition, the activated sludge mixed liquid is the object of membrane separation for suppressing the decrease in the permeation performance of the hollow fiber membrane and implementing the efficient membrane separation method to suppress the decrease in the operation efficiency of the water treatment device. This is not only a case but also a matter generally required for hollow fiber membrane modules, membrane separation methods or water treatment devices.

JP 2003-326140 A No. 2004-112944

  This invention makes it the subject to suppress the fall of the operating efficiency of a water treatment apparatus by suppressing the fall of the permeation | permeation performance of a hollow fiber membrane, and implementing an efficient membrane separation method.

As a result of intensive studies to solve the above problems, the present inventor found that, in the air scrubbing of the hollow fiber membrane module, the bubbles generated in the outer region in the region where the hollow fiber membrane is fixed are hollow. It has been found that since it is easily detached from the hollow fiber membrane module due to the water flow around the yarn membrane module, the number of times of contact with the surface of the hollow fiber membrane is small and it is not sufficiently effective in removing the deposits.
Then, by generating more bubbles in the central region of the region where the hollow fiber membranes are arranged and promoting the movement of the bubbles in the lateral direction through the hollow fiber membranes, the bubbles are formed in the hollow fiber membranes. The present invention has been completed by finding that it is possible to increase the number of times of contact with the surface of the film to improve the effect of removing deposits and the effect of suppressing the adhesion of suspended matter.

  That is, the present invention relating to the hollow fiber membrane module includes a fixing member that fixes a lower end portion of the hollow fiber membrane so that a plurality of hollow fiber membranes can be extended in water in the vertical direction to perform membrane separation. A hollow fiber membrane module in which an air diffusion mechanism for generating bubbles from the lower end side of the hollow fiber membrane is formed so that air can diffuse into the hollow fiber membrane extending in the vertical direction, The air diffusion mechanism is formed such that the amount of bubbles generated from the central region in the region where the hollow fiber membrane is disposed is larger than the amount of bubbles generated in the region outside the central region. It is said.

  Further, the present invention related to the membrane separation method is provided with a fixing member for fixing the lower end portion of the hollow fiber membrane so that the membrane separation can be performed by extending a plurality of hollow fiber membranes in the vertical direction in water. A membrane separation method using a hollow fiber membrane module in which an air diffusion mechanism for generating air bubbles from the lower end side of the hollow fiber membrane is formed so that air can diffuse into the hollow fiber membrane extending in the vertical direction The amount of bubbles generated from the central region in the region where the hollow fiber membrane is disposed during or after membrane separation by the hollow fiber membrane is the amount of bubbles generated in the region outside the central region. It is characterized by carrying out the aeration by the aeration mechanism so as to increase more.

  Furthermore, the present invention relating to the water treatment apparatus is provided with a fixing member for fixing the lower end portion of the hollow fiber membrane so that a plurality of hollow fiber membranes can extend in the vertical direction in water to perform membrane separation. A membrane comprising a hollow fiber membrane module in which an air diffusion mechanism for generating bubbles from the lower end side of the hollow fiber membrane is formed so that air can diffuse into the hollow fiber membrane extending in the vertical direction A water treatment device having a separation device, wherein the membrane separation is performed by immersing the hollow fiber membrane module in a water tank in which water to be treated is accommodated, wherein the hollow fiber membrane is disposed. A hollow fiber membrane module having an air diffusion mechanism formed so that the amount of bubbles generated from the central region in a region that is present is larger than the amount of bubbles generated in a region outside the central region is used for the membrane separation device. It is characterized by being That.

In the present specification, the “region where the hollow fiber membrane is disposed” is intended to mean a “region formed by connecting the positions of the hollow fiber membranes arranged on the outermost side of the hollow fiber membrane module”. ing.
In order to clarify the definition of “center region”, in this specification, the term “center region” is located at the center of the “region where the hollow fiber membrane is disposed” and its size. Is intended to be used as a half (area ¼).
Therefore, draw a similar shape whose side length is 1/2 of the “region where the hollow fiber membrane is arranged” with the center overlapped with the center of the “region where the hollow fiber membrane is arranged”. Usually, the “central region” can be defined. For example, if the line connecting the positions of the outermost hollow fiber membranes is a substantially circular shape having a diameter of 10 cm, this case The “central region” means a region in a circle having a diameter of 5 cm that is concentric with the circle having a diameter of 10 cm.

  In addition, regarding “the amount of bubbles generated from the central region” and “the amount of bubbles generated outside the central region”, the volume of bubbles generated per unit time is totaled in each region, and this volume is calculated at room temperature. It is possible to determine which is more by comparing with normal pressure.

According to the present invention, since the amount of bubbles generated from the central region in the region where the hollow fiber membrane is disposed is larger than the amount generated in the region outside the central region, the conventional hollow fiber membrane module In comparison, more bubbles can be brought into contact with the surface of the hollow fiber membrane.
Therefore, since the deposit removal from the hollow fiber membrane is performed efficiently, a decrease in the permeation performance of the hollow fiber membrane can be efficiently suppressed. It is also possible to suppress the adhesion of the suspension to the surface of the hollow fiber membrane.
Therefore, an efficient membrane separation method can be implemented.
That is, a decrease in operating efficiency of the water treatment apparatus can be suppressed.
As a result, for example, as compared with a conventional hollow fiber membrane module, the frequency and time of air diffusion to the hollow fiber membrane can be reduced, and the frequency of chemical cleaning and the amount of chemicals used can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a state in which the hollow fiber membrane module of the first embodiment of the present invention is raised from the side surface direction, and reference numeral 10 in the drawing represents the hollow fiber membrane module.
2 is a diagram (a cross-sectional view taken along line AA) showing the arrangement of the hollow fiber membranes (hollow fiber membrane bundles) fixed to the upper fixing member in FIG. 1 from above, and FIGS. It is a figure (BB sectional view) which shows a mode that arrangement | positioning of the vent provided in the lower fixing member in 1 was seen from the lower surface side.

The hollow fiber membrane module 10 of the present embodiment is formed in a vertically long cylindrical shape as shown in FIG. 1, and is provided with a plurality of hollow fiber membranes 11 exposed at the middle in the vertical direction. It has been.
The hollow fiber membrane module 10 of the first embodiment includes a fixing member that fixes one end of both ends of a plurality of hollow fiber membranes 11 on the upper side and a fixing member that fixes the other end on the lower side. Two fixing members are used.
More specifically, the hollow fiber membrane module 10 includes a lower fixing member 20, an upper fixing member 30 positioned above the lower fixing member 20 at a predetermined interval, and the lower fixing member 20 and the upper fixing member 30. And a plurality of support members (not shown) extending in the vertical direction to support them while maintaining their spacing, and the plurality of hollow fiber membranes 11 are in a state where the membrane ends are sealed at the membrane ends The hollow fiber membrane module 10 is fixed to the lower fixing member 20 and fixed to the upper fixing member 30 with its upper end opened at its membrane end.
That is, the plurality of hollow fiber membranes 11 are provided in the hollow fiber membrane module 10 with their lengths extending in the vertical direction with both ends aligned.
As the hollow fiber membrane 11 constituting the hollow fiber membrane module 10, a microfiltration membrane or an ultrafiltration membrane can be used.
Moreover, the hollow fiber membrane module 10 of this embodiment has an air diffusion mechanism so that air bubbles can be generated from the lower fixing member side and air scrubbing can be performed on the hollow fiber membrane.

  The upper fixing member 30 includes a cylindrical body 31, a circular upper plate 32 having a permeate outlet 32a and attached to the upper side of the cylindrical body, and a circular lower plate having a membrane bundle through-hole and attached to the lower side of the cylindrical body. 33.

Inside the upper fixing member 30, there is provided a plate-like portion 34 that is arranged in the horizontal direction and partitions the internal space of the cylindrical body 31 into a circular upper plate side and a circular lower plate side.
The plate-like portion 34 is formed into a plate shape by solidifying an adhesive, and the hollow fiber membrane 11 is formed by penetrating the end portion from the lower surface side to the upper surface side of the plate-like portion 34. It is fixed to the shaped part 34.
The hollow fiber membrane 11 is fixed by the adhesive in a bundled state so that all of the hollow fiber membranes 11 are bundled, and the upper edge of the hollow fiber membrane 11 is flush with the upper surface of the plate-like portion 34. So that it is fixed.
Therefore, on the upper surface side of the plate-like portion 34, the adhesive portion 34a formed by the adhesive and the portion where the hollow fiber membrane 11 is opened are formed in a relatively uniformly dispersed state. Moreover, the open position of the hollow fiber membrane 11 is formed on the entire upper surface of the plate-like portion 34.
The adhesive for fixing the hollow fiber membrane 11 is filled and solidified to a substantially constant depth from the upper surface side to the lower surface side of the plate-like portion 34, so that the plate-like portion 34 has a substantially constant thickness. Is formed.

  For example, when the upper fixing member 30 is assembled, the hollow fiber membrane 11 is passed through the circular lower plate 33 and the space between the hollow fiber membranes 11 is filled with an adhesive so that the upper end portion of the hollow fiber membrane 11 is embedded in the cylindrical body 31. Then, the circular lower plate 33 can be formed by being attached to the cylindrical body 31.

In the upper part of the upper fixing member 30, a water collection chamber 35 is formed on the upper side of the plate-like portion 34 to store permeated water. The water collection chamber 35 is formed of each hollow fiber membrane 11. It communicates with the opening at the upper end, and is defined by the lower surface of the circular upper plate 32, the inner wall surface of the cylindrical body 31, and the upper surface of the plate-like portion 34.
A pipe from a suction pump installed outside the biological reaction tank is connected to the permeate outlet 32 a connected to the water collection chamber 35.

  Further, the lower fixing member 20 has a cylindrical body 21 having the same inner diameter as the cylindrical body 31 of the upper fixing member 30 and a ventilation hole (eight in this embodiment) for air diffusion for air scrubbing. And a plate-like portion 22 having a disk shape attached to the upper side in the cylindrical body 21.

The plate-like portion 22 is arranged in the horizontal direction inside the cylindrical body 21, and the lower end portion of the hollow fiber membrane 11 is fixed to the upper surface side thereof.
In addition, the hollow fiber membrane 11 is fixed to the entire upper surface of the plate-like portion 22 except for the locations where the air holes 23 are formed, with the fixing positions distributed substantially uniformly.
The eight vent holes 23 are formed as through holes penetrating the plate-like portion 22 in the vertical direction (vertical direction), and open to the upper surface side and the lower surface side of the plate-like portion 22, respectively.
As shown in FIG. 3, the eight vent holes 23 in the plate-like portion 22 have a radiation angle (45 ° opening angle each) centered on the radial center of the lower fixing member 20 (plate-like portion 22). Are arranged so as to be equidistant from the radial center of the plate-like portion 22.
In addition, as shown in FIG. 4, the radius of the inner circumference circle (outer edge of the plate-like portion 22) of the cylindrical body 21 is “R”, and the virtual circle C having a radius “R / 2” concentric with this circle. All eight vent holes 23 are located in the inner region, that is, the central region of the region where the hollow fiber membrane 11 is disposed.

In addition, about this ventilation hole 23, by making the opening area small and raising the flow velocity of the air which passes the ventilation hole 23, a bubble can be made to contact the surface of the hollow fiber membrane 11 vigorously, and a high deposit | attachment A removal effect can be obtained.
On the other hand, if the opening area of the vent hole 23 is reduced, the vent hole 23 may be clogged while the air diffusion is stopped.
In this respect, the vent hole 23 is preferably formed so that the opening area per one is 0.5 to ⁵ cm ² , specifically, when the vent hole has a circular shape. The diameter is preferably 8 to 25 mm.
The vent hole 23 is preferably formed only in the central region in that the released bubbles can be effectively utilized by air scrubbing.
However, in this case, if the region where the hollow fiber membrane 11 is disposed is enlarged, the distance between the vent hole 23 and the outermost hollow fiber membrane is increased, and the effect of the air scrubbing is increased. There is a risk that it may be difficult to make the film sufficiently exhibited.
On the other hand, if the area where the hollow fiber membrane 11 is disposed is made too small, the bubbles released from the vent holes 23 will pass through the outermost hollow fiber membrane in a short time, so that the bubbles are air scrubbed. May be disadvantageous in terms of effective utilization.
Therefore, in the point that this air scrubbing effect can be exhibited to every corner of the arranged hollow fiber membrane while effectively utilizing the bubbles for air scrubbing, for example, the position of the outermost arranged hollow fiber membrane is When the connected line is substantially circular, the region where the hollow fiber membrane is disposed is preferably a circular region having a diameter of 120 to 250 mm.
Furthermore, the effective length of the hollow fiber membrane 11 (the length of the portion where the hollow fiber membrane is in contact with water) depends on the inner diameter of the hollow fiber membrane, but is preferably 400 to 2500 mm, for example, the inner diameter of the hollow fiber membrane. Is 0.5 to 1.2 mm, 500 to 1500 mm is preferable from the viewpoint of permeate water intake efficiency.

Since the plate-like portion 22 is located on the upper side in the cylindrical body 21, the lower fixing member 20 supplies a gas such as air used for air scrubbing to the lower surface side of the plate-like portion 22. The gas is accommodated in a space 24 (hereinafter also referred to as “gas accommodating portion 24”) surrounded by the lower surface of the plate-like portion 22 and the inner wall surface of the cylindrical body 21, and the accommodated gas is accommodated in the vent hole 23. It is formed so as to be released as bubbles on the upper surface side of the plate-like portion 22.
In other words, the lower fixing member 20 is formed with a gas containing portion 24 defined by the lower surface of the plate-like portion 22 and the inner wall surface of the cylindrical body 21.

  The air diffusion mechanism includes the air hole 23 provided in the plate-like portion 22, the gas accommodating portion 24, etc. together with the gas supply pipe 25 for supplying gas to the gas accommodating portion 24. It is formed to generate bubbles on the upper surface side of the plate-like portion 22.

In addition, as the hollow fiber membrane module 10 of the first embodiment, a module in which various improvements are added in addition to the above-described exemplary embodiment can be adopted.
This improvement will be described with reference to FIGS.
5, 6, 7, and 11 are views showing the arrangement of the air holes as in FIG. 3, and FIGS. 8 to 10 and 12 show the structure of the hollow fiber membrane module as in FIG. 1. It is sectional drawing shown (FIGS. 8-10 is only a lower fixing member side).

In the hollow fiber membrane module 10, the plate-like portion 22 having eight vent holes 23 is illustrated in the lower fixing member 20. For example, the plate-like portion having nine or more vent holes is used. It may be formed on the lower fixing member.
FIG. 5 is a plan view showing a state where the ninth vent hole 23a is formed in the plate-like portion 22 illustrated in FIGS.
As shown in FIG. 5, by having the vent hole 23a opened at the center of the region where the hollow fiber membrane is arranged, the hollow fiber membrane arranged at the center portion can surely diffuse air. Can be.

  Conversely, the number of vent holes may be less than eight. For example, as shown in FIG. 6, only a single vent hole 23b formed at the center of the region where the hollow fiber membrane is arranged is provided. It is also possible to provide the lower fixing member with the plate-like portion 22 having the same.

  In the first embodiment, the hollow fiber membrane module 10 has been described by taking an example in which the vent hole 23 is formed only in the central region in that the released bubbles can be effectively utilized by air scrubbing. As shown in FIG. 7, even when the vent hole 23c arranged outside the central region is provided, the amount of bubbles generated from the vent hole 23 in the central region is reduced from the vent hole 23c in the region outside the central region. As long as the air scrubbing is performed so as to be larger than the amount of bubbles generated, it is within the range intended by the present invention, and the arrangement of the air holes can be the embodiment illustrated in FIG. It is.

The air diffusion mechanism is arranged so that air scrubbing is performed so that the amount of bubbles generated from the vent hole 23 in the central region is larger than the amount of bubbles generated from the vent hole 23c in the region outside the central region. As a specific means for forming, there is a method in which the total opening area of the vent holes 23 in the central region is larger than the total opening area of the vent holes 23c outside the central region.
Thus, in the case where the air diffusion mechanism is formed so that the opening area opened in the central region of the vent hole is larger than the opening area in the region outside the central region, complicated control is required. Without this, it is possible to easily increase the amount of bubbles generated from the central region more than the amount of bubbles generated outside the center region.

If necessary, for example, as shown in FIG. 8, the center portion of the lower surface of the plate-like portion 22 of the lower fixing member 20 is recessed in a mortar shape toward the upper side. It is also possible to adopt a mode in which bubbles are generated only from 23.
In this case, there is no particular limitation on the relationship between the opening area of the vent hole 23 in the central region and the opening area of the vent hole 23c in the region outside the central region.
That is, even if the opening area of the vent hole 23c in the region outside the central region is formed to be larger than the opening area of the vent hole 23 in the central region, the gas storage portion 24 does not supply the gas. Since it is formed so as to be concentrated at the center of the lower surface of the shape portion 22, it is possible to increase the amount of bubbles generated from the central region rather than the amount of bubbles generated in the region outside the central region.

Further, in this case, for example, as shown in FIG. 9, when necessary, the gas supply amount from the gas supply pipe 25 is increased to increase the gas storage amount in the gas storage unit 24, thereby increasing the outside of the central region. Bubbles can be generated from the air holes 23c in the region.
That is, as shown in FIG. 8, the lower surface side is provided with a plate-like portion 22 in which a portion corresponding to the central region is recessed upward, thereby more reliably reducing the amount of bubbles generated from the central region from the outside. In addition, the amount of bubbles generated from the outer region can be adjusted as necessary.

Further, as shown in FIG. 10, a branch pipe portion 25a is provided at the tip of the gas supply pipe 25, and the tip end portion of the branch pipe portion 25 ′ is not only the vent hole 23 in the central region but also the vent hole outside the central region. It is also possible to supply gas directly to these vent holes 23 and 23c by connecting to 23c.
In this case, the bubble generation amount from the central region can be adjusted to be larger than the generation amount in the region outside the central region by adjusting the pipe diameter of the branch pipe portion 25a.
Moreover, the gas supply amount to each vent hole can be adjusted by a flow rate adjusting valve or the like.
In an embodiment in which such a gas supply pipe with an adjusted gas supply amount is used, the supply of gas to the vent hole is directly controlled, so that it is easy to adjust the bubble generation status. After that, fine control such as observing the state of deposit formation on the surface of the hollow fiber membrane and readjusting the gas supply based on the result can be performed.

Heretofore, the hollow fiber membrane module 10 having vent holes having a circular cross-sectional shape has been illustrated in the drawings. However, the present invention is also applicable to the case of having an oblong vent hole 23d as shown in FIG. Furthermore, the present invention can also employ a vent having a cross-sectional shape such as a polygon or an indeterminate shape, and the shape is not particularly limited.
As shown in FIG. 11, a vent hole 23d opened so as to extend from the central region to the outside of the central region can also be employed.
When such a vent 23d is employed, for example, a thick plastic film or the like is used to produce a cylinder whose cross-sectional shape is the same as that of the central region (virtual circle C). Installing on the upper surface, separating the bubbles generated on the upper surface side of the plate-like portion 22 into bubbles generated from the central region and bubbles generated in the region outside the central region, and comparing the generated amount It is possible to determine which amount of generation is large.

If necessary, for example, as shown in FIG. 12, the vent hole is not formed in the plate-like portion 22 of the lower fixing member 20. Instead, the open end of the gas supply pipe 25 is placed on the upper surface side of the plate-like portion 22. Alternatively, air bubbles may be generated from the lower end side of the hollow fiber membrane 11 extended in the vertical direction by releasing air from the opening end.
In this case, the amount of diffused air can be directly controlled, and the relative position between the region where the hollow fiber membrane 11 is arranged and the open end of the gas supply pipe 25 can be adjusted. The location where bubbles are generated can be changed according to the state of occurrence of deposits on the surface.
Therefore, a decrease in permeation performance of the hollow fiber membrane can be further suppressed, and an efficient membrane separation method can be implemented.

In addition to these, the technical matters employed in the conventionally known hollow fiber membrane module can be employed for the hollow fiber membrane module of the first embodiment as long as the effects of the present invention are not significantly impaired.
For example, instead of taking permeated water from the upper fixing member side, the plate-like portion of the lower fixing member has a hollow structure, and the hollow fiber membrane module is opened in the hollow portion of the plate-like portion from the lower fixing member side. Permeated water may be taken.
Further, the hollow fiber membrane module of the first embodiment exemplifies the case where the region where the hollow fiber membrane module is arranged is circular, but the region where the hollow fiber membrane module is arranged is elliptical or polygonal. And so on.

Such a hollow fiber membrane module can also be formed, for example, by modifying an existing hollow fiber membrane module.
The conventional hollow fiber membrane module either generates air bubbles evenly in the entire region where the hollow fiber membranes are arranged or generates more air bubbles in the region outside the central region. Although a vent hole is provided, for example, even in such a conventional hollow fiber membrane module, a vent hole that generates bubbles in the center region and a vent hole that generates bubbles in the region outside the center region In such a case, the vents that generate bubbles in the outer area are reduced in diameter or closed, and the amount of bubbles generated from the vents is reduced compared to before the renovation. By doing so, the hollow fiber membrane module can be repaired so that the amount of bubbles generated from the central region is larger than the amount of bubbles generated in the region outside the central region.
In this way, when forming a hollow fiber membrane module in which the amount of bubbles generated from the central region is larger than the amount of bubbles generated outside the central region, the existing equipment can be used as it is. In addition, an efficient membrane separation method can be carried out by suppressing a decrease in the permeation performance of the hollow fiber membrane with a simple repair work.

Next, a second embodiment will be described with reference to FIGS.
FIG. 13: is sectional drawing which shows the structure of 2nd embodiment of the hollow fiber membrane module of this invention, The same code | symbol is used for the location which shows the same structure as 1st embodiment, and description is abbreviate | omitted.
14 is a diagram (cross-sectional view taken along the line C-C) showing the arrangement of the hollow fiber membranes (hollow fiber membrane bundles) fixed to the upper fixing member in FIG. 13, and FIG. 15 shows the lower fixing member in FIG. It is a figure (DD sectional view) which shows arrangement | positioning of the provided vent hole.

  In the hollow fiber membrane module 10 ′ of the second embodiment, a plurality of hollow fiber membranes 11 extending in the vertical direction are bonded together by bundling a predetermined number of the upper fixing member 30 and the lower fixing member 20 together. It is different from the hollow fiber membrane module 10 of the first embodiment in that the hollow fiber membrane bundle 12 is formed.

And the plate-like part 34 which divides the internal space of the said cylindrical body 31 into a circular upper board side and a circular lower board side is the hollow fiber membrane bundle coupling | bond part 12a in which the several hollow fiber membrane bundle 12 was couple | bonded with the adhesive agent. And an adhesive portion 34 a for fixing the hollow fiber membrane bundle 12.
Moreover, in this embodiment, as shown in FIG. 14, the plurality of hollow fiber membrane bundles 12 are on the radiation centering on the radial center of the upper fixing member 30 (in this embodiment, including the radial center position). Are arranged on eight radiations L11 to L18 each having a 45-degree opening angle.
On the other hand, the eight vent holes 23 formed in the lower fixing member 20 have a phase angle of 22.5 degrees with respect to the radiation L11 to L18 in the upper fixing member 30 in the plate-like portion 22, as shown in FIG. They are provided on the radiation (L11 ′ to L18 ′) shifted by a distance and at positions equidistant from the radial center.

Therefore, when the arrangement of the air holes 23 and the hollow fiber membrane bundle 12 is viewed from the lower surface side of the plate-like portion 22 of the lower fixing member 20, the relationship is as shown in FIG.
That is, the region where the hollow fiber membrane is arranged in the first embodiment is the entire upper surface side of the plate-like portion, but the region where the hollow fiber membrane is arranged in the second embodiment is shown in FIG. This is a regular octagonal region indicated by the virtual line E1.
In addition, the vent hole 23 in the hollow fiber membrane module 10 ′ of the second embodiment is represented by a regular octagon (virtual line E2) having the same center point as the regular octagon and having a half of one side. All are arranged in the region (central region).
That is, the hollow fiber membrane module 10 ′ of the second embodiment and the hollow fiber membrane module 10 of the first embodiment are common in that air scrubbing bubbles are generated in the central region.

In addition, from the viewpoint of suppressing the adhering matter of the hollow fiber membrane, even when the same number of hollow fiber membranes is used, the individual hollow fiber membranes are arranged even at the fixed ends. It is preferable that the hollow fiber membrane is arranged like the hollow fiber membrane module 10 of the first embodiment.
Or even if it is set as the aspect bundled to the hollow fiber membrane bundle 12 like the hollow fiber membrane module 10 'of said 2nd embodiment, the fixed state of the upper end part by the upper fixing member 30 is at least in the lower fixing member 20 side. As in the hollow fiber membrane module 10 of the first embodiment, it is preferable to form a fixed portion of the hollow fiber membrane by being distributed almost uniformly on the upper surface of the plate-like portion 22.

  Although not described in detail here, it is the same as the hollow fiber membrane module 10 of the first embodiment in that various improvements can be made to the hollow fiber membrane module 10 ′, and is shown in FIGS. Such a mode can also be applied to the hollow fiber membrane module 10 ′ of the second embodiment.

Next, a water treatment device and a membrane separation method carried out in this water treatment device will be described with reference to FIGS. 17 and 18.
FIG. 17 is a configuration explanatory view showing an embodiment of a water treatment device using the hollow fiber membrane module 10 of the first embodiment (or the hollow fiber membrane module 10 ′ of the second embodiment).

In this embodiment, the water treatment apparatus 40 performs water purification treatment of river water that is to-be-treated water.
As shown in FIG. 17, the water treatment apparatus 40 includes a water tank 42 to be treated to which water to be treated (river water) from a water supply line 41 to be treated is supplied.
Further, the water treatment apparatus 40 of the present embodiment includes a plurality of hollow fiber membrane modules 10 (10 ′) arranged so as to be immersed in a standing water in the water to be treated in the water tank 42 to be treated, and these hollow fibers. To connect the membrane module 10 (10 ′) and have a suction pump 43a, and suck the inside of the hollow fiber membrane by the suction pump 43a to perform solid-liquid separation by membrane filtration of the water to be treated and take out permeate. The permeated water extraction line 43 is provided.
Furthermore, in the water treatment apparatus 40 of the present embodiment, a blower 44a for causing an air scrubbing mechanism of the hollow fiber membrane module 10 (10 ′) to perform air scrubbing, and the gas supply pipe that conveys air from the blower 44a. 25 (see FIG. 1 and the like), an air supply line 44 for supplying air to the gas storage unit 24 and a sediment discharge line 45 for discharging the sediment in the water tank 42 to be treated are provided.

The permeate extraction line 43 in the membrane separation device of FIG. 17 includes a water collection pipe 43b connected to the permeate outlet 32a of each hollow fiber membrane module 10 (10 ′), a water collection header pipe 43c communicating with each water collection pipe 43b, A permeated water discharge pipe 43d is provided.
The air supply line 44 includes a blower 44a, an air transport pipe 44b for supplying air pressurized by the blower 44a, an air transport branch pipe 44d branched from the air transport pipe 44b, and each of the air transport branches. The distal end portion of the tube 44d is constituted by a gas supply tube 25 positioned on the lower end side of the cylindrical body 21 of each hollow fiber membrane module 10 ′.
In addition, each hollow fiber membrane module 10 (10 ') is installed so that the whole upper fixing member 30 may be located below the water surface.

In the water treatment apparatus 40 configured as described above, the water to be treated is membrane-separated (filtered) by the hollow fiber membrane by suctioning the inside of the hollow fiber membrane by the suction pump 43a. In addition, a membrane separation method can be implemented in which the permeate is discharged through the permeate take-out line 43 and the suspended matter or the like adhering to the surface of the hollow fiber membrane is removed by aeration by an aeration mechanism.
The membrane separation of the water to be treated by the hollow fiber membrane and the aeration by the aeration mechanism can be carried out at an appropriate timing from the viewpoint of the removal performance of the deposits.
For example, in the backwashing process after the membrane separation process is completed by alternately performing the membrane separation process for filtering the water to be treated and the backwashing process for backwashing the permeated water to backwash the hollow fiber membrane. A membrane separation method that performs only aeration.
In this case, reverse cleaning and air scrubbing by aeration are performed at the same time, and deposits adhering to the surface of the hollow fiber membrane can be effectively removed.

In addition, for example, a membrane separation method in which aeration is always performed while the membrane separation step and the backwashing step are performed, that is, a membrane separation method different from the above is mentioned.
In this case, since aeration is performed even during membrane separation, it is easy to increase the amount of aeration compared to the example of the membrane separation method described above. Therefore, the deterioration of the permeation performance of the hollow fiber membrane can be further prevented.
By performing aeration after such membrane separation or during membrane separation, a decrease in permeation performance of the hollow fiber membrane can be prevented, and an efficient membrane separation method can be implemented.

More specifically, in the air diffusion, the blower 44a, the air transport pipe 44b, the air transport branch pipe 44d, and the gas supply pipe 25 are below the lower fixing member 20 of the hollow fiber membrane module 10 (10 ′). Air is supplied to the hollow fiber membrane module 10 (10 '), and bubbles are generated in the region where the hollow fiber membrane 11 is disposed.
The generated bubbles rise between the hollow fiber membranes 11 due to their buoyancy.
Moreover, the generated bubbles pass through between the adjacent hollow fiber membranes 11 and rise while moving from the central region to the periphery thereof.
Eventually, the air bubbles move further outward than the outermost hollow fiber membrane, and are pushed away by the water flow of the water in the tank (water to be treated) of the water tank 42 to be treated. (10 ') will be detached.

In the water treatment device 40 of the present embodiment, more bubbles are generated in the central region of the region where the hollow fiber membrane 11 is disposed in the hollow fiber membrane module 10 (10 ′).
Since the bubbles generated in the central region move through more hollow fiber membranes until the bubbles are generated and detached from the hollow fiber membrane module 10 (10 ′), they are hollow. It can be made to act particularly effectively for the removal of deposits on the surface of the thread membrane.

In general, deposits on hollow fiber membranes can be broadly classified into adherents such as sticky organic substances that can be dissolved and removed by chemical cleaning, and deposits such as suspended solids that are difficult to remove by chemical cleaning. If a location where the effect of air scrubbing is insufficient is formed, deposits that are difficult to remove by chemical cleaning will adhere to and accumulate on this location. This creates a situation where the deposit is not sufficiently removed.
As a result, deposition of the deposit is accelerated, and in some regions, the hollow fiber membranes are integrated by the deposit, and the function as a separation membrane can be completely lost.
On the other hand, the water treatment apparatus provided with the hollow fiber membrane module of the present invention can effectively utilize bubbles for removing deposits, and the permeation performance of the hollow fiber membrane is reduced as compared with the conventional hollow fiber membrane module. Can be suppressed.
In addition, the chemical cleaning effect can be improved as compared with the conventional case, and a synergistic effect can be exhibited in the prevention of deposits (preventing deterioration in permeation performance).

Therefore, by further providing a chemical cleaning mechanism that performs chemical cleaning on the hollow fiber membrane, it is possible to more significantly prevent the permeation performance of the hollow fiber membrane from being deteriorated.
And by adopting such a hollow fiber membrane module in a membrane separator, an excellent effect is exhibited in preventing a decrease in operating efficiency of the water treatment device.

Next, another embodiment of the water treatment apparatus will be described with reference to FIG.
FIG. 18 is a configuration explanatory view showing another embodiment of the water treatment apparatus, and the water treatment apparatus 50 of the present embodiment performs a sewage purification process of treated water containing organic substances such as sewage and wastewater. It is performed by the membrane separation activated sludge method.
As shown in FIG. 18, the water treatment device 50 includes a biological reaction tank 52 as a water tank to be treated to which primary treated water is supplied from a water supply line 51 to be treated, and water to be treated in the biological reaction tank 52 ( An activated sludge mixed solution).
The membrane separation device is connected to a plurality of hollow fiber membrane modules 10 (10 ′) disposed so as to be immersed in the activated sludge mixed solution in a standing posture, and these hollow fiber membrane modules 10 (10 ′). And a permeate discharge line 53 for taking out the permeate by performing solid-liquid separation by membrane filtration of the water to be treated by suctioning the inside of the hollow fiber membrane with the suction pump 53a. ing.
Further, the water treatment device 50 includes an air supply line 54 for supplying air scrubbing air to the hollow fiber membrane module 10 (10 ′) by the blower 54a, and the hollow fiber membrane module 10 (10 in the biological reaction tank 52). A) an air diffuser 56 disposed below and a sludge discharge line 55 for discharging the sludge in the biological reaction tank 52.

The permeated water extraction line 53 includes a water collection pipe 53b, a water collection header pipe 53c, a permeated water extraction pipe 53d, and a suction pump 53a.
The air supply line 54 includes a blower 54a, an air transport pipe 54b, an air transport branch pipe 54d, and a gas supply pipe 25.
In this embodiment, the air diffuser 56 is supplied through a pipe branched from the air transport pipe 54b by the pressurized air from the blower 54a.
The air diffuser 56 supplies oxygen by air bubbles (air) diffused from the air diffuser to perform activated sludge treatment (aerobic biological treatment), and collects undissolved air bubbles to collect the hollow fiber membrane module 10 ( 10 ′) for supplying the gas accommodating portion 24 to cause the upward flow generated by the air lift action of the rising bubbles to act on the membrane surface of the hollow fiber membrane module 10 (10 ′), and also to perform membrane surface cleaning. It is.
Each hollow fiber membrane module 10 (10 ′) is installed such that its upper fixing member 30 is positioned below the water surface.

According to the water treatment device 50 configured as described above, since the hollow fiber membrane module 10 (10 ′) described above is provided, the permeation performance of the hollow fiber membrane is reduced as compared with the conventional hollow fiber membrane module. Can be suppressed.
In addition, an efficient membrane separation method can be performed by the membrane separation apparatus.
In addition, the chemical cleaning effect can be improved as compared to the conventional case, and a synergistic effect can be exhibited in the prevention of deposits (prevention of deterioration in permeation performance).
Therefore, in this embodiment, the frequency of chemical cleaning can be reduced, and the risk of reducing the activity of microorganisms in the tank can also be reduced.
Therefore, the effect excellent also in prevention of the fall of the operation efficiency of the sewage purification treatment water treatment apparatus by a membrane separation activated sludge method can be exhibited.
In addition, by collecting undissolved bubbles that were not used among the bubbles supplied for aerobic biological treatment and supplying them to the gas storage part of the hollow fiber membrane module, the power of aeration to the hollow fiber membrane module Can be reduced.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Example 1)
Only in the central part of the plate-like part to which the lower end part of the hollow fiber membrane is fixed (within a radius of about 30 mm from the center) so that bubbles are generated only from the central region of the region where the hollow fiber membrane is arranged. A hollow fiber membrane module in which six vents are formed stands upright in a biological reaction tank (volume of about 932 L) containing an activated sludge mixed liquid with a suspended solids concentration (MLSS) of 1500 to 3000 mg / l. So that the membrane permeation flux was 0.75 m / day to 1.0 m / day.
At this time, the quality of the water to be treated supplied to the biological reaction tank has a total organic carbon concentration of about 1.5 mg / l and a turbidity of about 16 degrees, and the residence time of the treated water in the biological reaction tank. Was 36-50 minutes.
In addition, as shown in FIG. 19 (photograph of the state of the lower surface side of the plate-like portion), the hollow fiber membrane module used for the evaluation has 24 vent holes having an opening area of 11 mmφ provided in the entire plate-like portion. The existing hollow fiber membrane module is renovated with the other air holes closed except for the six air holes in the center of the hollow fiber membrane module.
The specification of the hollow fiber membrane module is that the hole diameter is nominally 0.1 μm, the length is 1 m, the area of the plate-like part to which the lower end of the hollow fiber membrane is fixed is about 0.0181 m ² (circular with a diameter of 152 mm), The membrane surface area was 25 m ² .
In the membrane separation, a reverse cleaning for 1 minute is performed every time the membrane is separated for 9 minutes, and only in the reverse cleaning, the total amount of bubbles generated from the six vent holes is 5 m ³ / h. Air scrubbing was performed.
As a result of carrying out this membrane separation for 33 days, it was confirmed that the increase in the differential pressure of the hollow fiber membrane module during membrane separation was only 8 kPa (0.24 kPa / day).

(Comparative Example 1)
The central region in the arrangement region of the hollow fiber membrane without using the vent hole to close (using a hollow fiber membrane module having 24 vent holes in which the arrangement locations are dispersed throughout the region where the hollow fiber membrane is arranged) The membrane separation was carried out in the same manner as in Example 1 except that more bubbles were generated in the outer region and the membrane separation was conducted for 7 days instead of 33 days.
As a result, the increase in the differential pressure of the hollow fiber membrane module is 8 kPa (1.15 kPa / day), which is the same as when the hollow fiber membrane module of Example 1 was used, even though the operation was only for 7 days. It was confirmed.

(Comparative Example 2)
Using the same hollow fiber membrane module as in Comparative Example 1, air scrubbing was performed so that the amount of bubbles generated was 5 m ³ / h even during 9 minutes of membrane separation (always performing air scrubbing) for 25 days. Membrane separation was performed in the same manner as in Example 1 except that membrane separation was performed.
As a result, it was confirmed that the increase in the differential pressure of the hollow fiber membrane module was 10 kPa (0.4 kPa / day).
That is, compared with the hollow fiber membrane module of Example 1, the increase in the differential pressure per day (0.4 kPa / day) while using 10 times as much air for air scrubbing resulted in the hollow fiber of Example 1. It was confirmed that it was larger than that of the membrane module (0.24 kPa / day).

  This also shows that according to this invention, the fall of the permeation | permeation performance of a hollow fiber membrane can be suppressed efficiently, and the fall of the operating efficiency of a water treatment apparatus can be suppressed.

It is sectional drawing which shows the structure of 1st embodiment of the hollow fiber membrane module of this invention. It is a figure (AA sectional view taken on the line AA) which shows arrangement | positioning of the hollow fiber membrane bundle fixed to the upper fixing member in FIG. It is a figure (BB sectional view) which shows arrangement | positioning of the vent provided in the lower fixing member in FIG. It is a figure (BB sectional view) which shows the arrangement | positioning area | region of the vent provided in the lower fixing member in FIG. It is a figure which shows the example which improved arrangement | positioning of a vent hole. It is a figure which shows the example which improved arrangement | positioning of a vent hole. It is a figure which shows the example which improved arrangement | positioning of a vent hole. It is sectional drawing which shows the example of improvement of a lower fixing member (plate-shaped part). It is sectional drawing which shows the other usage method of the hollow fiber membrane module shown in FIG. It is sectional drawing which shows the example improved about the supply method of gas. It is a figure which shows the example which improved the shape of the vent hole. It is sectional drawing which shows the example which implements aeration with a gas supply pipe | tube, without using a vent hole. It is sectional drawing which shows the structure of 2nd embodiment of the hollow fiber membrane module of this invention. It is a figure (CC sectional view taken on the line C-C) which shows arrangement | positioning of the hollow fiber membrane bundle fixed to the upper fixing member in FIG. It is a figure (DD sectional view) which shows arrangement | positioning of the vent provided in the lower fixing member in FIG. It is a figure (DD sectional view) which shows the arrangement | positioning area | region of the vent provided in the lower fixing member in FIG. It is composition explanatory drawing which shows one Embodiment of the water treatment apparatus of this invention. It is a structure explanatory view showing another embodiment of the water treatment equipment of the present invention. The figure (appearance photograph) which shows the mode of the air vent of the hollow fiber membrane module used for evaluation as an Example (comparative example).

Explanation of symbols

10, 10 ': Hollow fiber membrane module, 11: Hollow fiber membrane, 12: Hollow fiber membrane bundle, 12a: Hollow fiber membrane bundle coupling part, 20: Lower fixing member, 21: Cylindrical body, 22: Plate-like part, 23 23a, 23b, 23c, 23d: vent hole, 24: gas accommodating part, 25: gas supply pipe, 25a: branch pipe part, 30: upper fixing member, 31: cylindrical body, 32: circular upper plate, 32a: permeation Water outlet, 33: circular lower plate, 34: plate-like part, 34a: adhesive part, 35: water collecting chamber, 40: water treatment device, 41: water to be treated supply line, 42: water tank to be treated, 43: permeation Water extraction line, 43a: Suction pump, 43b, water collection pipe, 43c: Water collection header pipe, 43d: Permeated water extraction pipe, 44: Air supply line, 44a: Blower, 44b: Air transport pipe, 44d: Air transport branch pipe 45: sediment discharge line, 50: water Science device, 51: treated water supply line, 52: biological reaction tank, 53: permeated water extraction line, 53a: suction pump, 53b: water collecting pipe, 53c: water collecting header pipe, 53d: permeated water taking pipe, 54: Air supply line, 54a: blower, 54b: air transport pipe, 54d: air transport branch pipe, 55: sludge discharge line, 56: air diffuser

Claims (6)

The hollow fiber extending in the vertical direction is provided with a fixing member for fixing a lower end portion of the hollow fiber membrane so that the membrane separation can be performed by extending a plurality of hollow fiber membranes in the vertical direction in water. A hollow fiber membrane module in which an air diffusion mechanism for generating bubbles from the lower end side of the hollow fiber membrane is formed so that air can be diffused in the membrane,
The air diffusion mechanism is formed such that the amount of bubbles generated from the central region in the region where the hollow fiber membrane is disposed is larger than the amount of bubbles generated in the region outside the central region. A featured hollow fiber membrane module.   The hollow fiber membrane module according to claim 1, wherein the air diffusion mechanism is formed so that the bubbles are generated only from the central region.   The fixing member is provided with a plate-like portion arranged in a horizontal direction, and a lower end portion of the hollow fiber membrane is fixed to the upper surface side of the plate-like portion and a passage for generating the bubbles is provided. One or more pores are opened in at least the central region, and a gas accommodating portion communicated with the vent hole is provided on the lower surface side of the plate-shaped portion, and the gas accommodating portion accommodates the gas to thereby store the gas. The air diffusion mechanism is formed so that bubbles can be generated from the vent hole, and the generation amount of bubbles from the central region is larger than the generation amount in the region outside the central region. The hollow fiber membrane module according to claim 1 or 2, wherein an opening area in which a vent hole opens in the central region is larger than a vent hole opening area in a region outside the central region.   The fixing member is provided with a plate-like portion arranged in a horizontal direction, and a lower end portion of the hollow fiber membrane is fixed to the upper surface side of the plate-like portion and a passage for generating the bubbles is provided. One or more pores are opened in at least the central region, and the gas supply pipe provided in the diffuser mechanism is connected to the vent hole so as to directly supply the gas for forming the bubbles to the vent hole. In addition, the gas supply pipe in which the amount of gas supply to the vent hole is adjusted so that the amount of bubbles generated from the central region is larger than the amount generated in regions outside the central region. The hollow fiber membrane module according to claim 1 or 2, wherein The hollow fiber extending in the vertical direction is provided with a fixing member for fixing a lower end portion of the hollow fiber membrane so that the membrane separation can be performed by extending a plurality of hollow fiber membranes in the vertical direction in water. A membrane separation method using a hollow fiber membrane module in which an air diffusion mechanism for generating bubbles from the lower end side of the hollow fiber membrane so that air can be diffused in the membrane,
During or after membrane separation by the hollow fiber membrane, the amount of bubbles generated from the central region in the region where the hollow fiber membrane is disposed is larger than the amount of bubbles generated in the region outside the central region. Thus, the membrane separation method characterized by implementing the aeration by the said aeration mechanism. The hollow fiber extending in the vertical direction is provided with a fixing member for fixing a lower end portion of the hollow fiber membrane so that the membrane separation can be performed by extending a plurality of hollow fiber membranes in the vertical direction in water. It has a membrane separation device provided with a hollow fiber membrane module in which an air diffusion mechanism for generating bubbles from the lower end side of the hollow fiber membrane so as to be diffused in the membrane, and accommodates water to be treated A water treatment apparatus in which the hollow fiber membrane module is immersed in a treated water tank and the membrane separation is performed,
A hollow fiber membrane having an air diffusion mechanism formed such that the amount of bubbles generated from a central region in a region where the hollow fiber membrane is disposed is larger than the amount of bubbles generated in a region outside the central region. A water treatment apparatus, wherein a module is used in the membrane separation apparatus.