JPH09155166A - Immersion type flat membrane separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue filtering for a long time while efficiently remove a cake on a membrane surface using a flexible flat membrane. SOLUTION: In an immersion type membrane separator wherein a plurality of flat membranes 11 each obtained by covering both surfaces of a flexible water permeable material with filter membranes are vertically and parallelly arranged in a separation tank 10 while the distance between the adjacent flat membranes 11 is held to a definite interval and permeated soln. taking-out parts 13, 14 are formed to both ends or single ends in the lateral direction of the vertically arranged flat membranes and an air diffusion means 15 is arranged under the flat membranes, a pair of holding plates holding a plurality of the flat membranes therebetween and capable of expanding and contracting the holding interval thereof are fitted to the entral part in the lateral direction of the vertically arranged flat membranes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane separation device, and more particularly to a submerged membrane separation device capable of efficiently separating a suspension in wastewater by a microfiltration membrane or an ultrafiltration membrane.

[0002]

2. Description of the Related Art In recent years, membrane separation has been accompanied by technological development, not only solid-liquid separation in chemical and food production lines, but also water production.
It is widely applied to the recovery of organic substances from wastewater, solid-liquid separation of tap water, gray water, and human waste, and is about to be applied to the treatment of sewage and industrial wastewater. As a low running cost method applicable to wastewater treatment, an immersion method has been developed in which the membrane is completely filtered while the membrane is immersed in a stock solution tank. this is,
Instead of giving the flow of the undiluted solution on the membrane surface, filtration is performed at a lower transmembrane pressure than the liquid circulation method to suppress the accumulation of cake on the membrane surface and to filter, which enables low power operation. is there. Further, since the structure is simple, there is an advantage that maintenance is easy. In order to generate a differential pressure between the membranes for filtration, the suction method is often used because it has less clogging than the pressure method and only requires the membrane to be immersed in the stock solution tank. The cake adhering to the film surface is peeled off and removed by bubbling while supplying air from an air diffusing tube or air diffusing plate provided in the lower part of the film.

The shape of the membrane used includes tubular membranes, hollow fiber membranes and flat membranes. Of these, tubular membranes are not suitable for large-scale processing because they cannot secure a large membrane area. Further, the hollow fiber membrane has high volume efficiency, but it is not disclosed in JP-A-4-265.
As disclosed in Japanese Patent Publication No. 128, etc., the suspension adheres or sticks to the inside of the bundle of hollow fiber membranes, which increases the filtration resistance, and it is extremely difficult to remove these suspensions by air bubbling. Have difficulty. On the other hand, the flat membrane is easy to wash the membrane surface by air bubbling because the suspended matter is not locally adhered to it unlike the hollow fiber membrane, and the volume efficiency is higher than that of the tubular membrane. From this point of view, it is desirable to use a flat membrane as the immersion type filtration method when filtering a liquid having a high suspension concentration.

However, when a flexible flat membrane is used, the bubbling of the membrane is also taken into account by air bubbling, and the cake on the membrane surface can be peeled off and removed, but the central portion of the transverse flat membrane is stretched. Since the degree is the smallest, there are the following problems.
In the central portion of the flat membrane, the fluctuation due to air bubbling is large, and the distance between the membranes, which is the distance between the membranes, tends to fluctuate more than both ends of the flat membrane in the lateral direction. Therefore, air bubbles may be difficult to enter where the distance between the films becomes small, and the cake adhering to the film surface may not be separated or removed. Thus, when a flexible flat membrane is used, cleaning by air bubbling still has problems to be improved.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, and uses a flexible flat membrane to efficiently remove the cake on the membrane surface while performing efficient filtration for a long time. It is an object of the present invention to provide an immersion type flat membrane separation device that can be continued.

[0006]

The submerged flat sheet membrane separating apparatus according to the present invention comprises a plurality of flat sheet membranes having a flexible water-permeable material coated with filtration membranes on both sides thereof in a tank vertically and adjacent to each other. Immersion type membrane in which the permeated liquid extraction parts are provided at both ends or one end in the horizontal direction of the flat membrane vertically arranged in parallel while keeping the distance between the flat membrane and the flat membrane. The separating apparatus is characterized in that it is provided with means for expanding / contracting the distance between the membranes at the central portion in the lateral direction of the plurality of vertically arranged flat membranes.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the flat membrane separation apparatus of the present invention,
The support inside the flat membrane filtration membrane is a flexible water permeable material. When air is bubbled from below the flat membrane to remove and remove the cake from the membrane surface, filtration is performed using a flat membrane that has both sides of this flexible water-permeable material coated with a filtration membrane. In order to intermittently apply pressure to the membrane surface by shaking and rising while meandering, the filtration membrane and the support together shake in the front-back direction of the flat membrane vertically dipped in the separation tank. That is, a flat membrane using a flexible support oscillates. However, in the central portion of the flat membrane in the lateral direction, the degree of tension is small, so that the distance between the membranes may be small, and it is difficult to supply bubbles from the lower portion of the flat membrane by air bubbling. As a solution to this problem, it is conceivable to make the bubble diameter of the air smaller depending on the distance between the membranes, but it is difficult to allow the bubbles to enter between the membranes because the cake adheres to the membrane surface.

Therefore, in the present invention, in consideration of the flexibility of the flat membrane itself, a means for expanding / contracting the distance between the membranes in the central portion of the flat membrane is provided. As means for expanding / contracting the distance between the membranes, air jetting means extending in a direction orthogonal to the flat membrane and / or
Alternatively, a means for giving an additional swing to the flat membrane by sandwiching the flat membrane may be used. More specifically, it is installed below the flat membrane,
An air ejection pipe extending in the direction orthogonal to the flat membrane, an air ejection pipe installed in the upper part of the flat membrane, extending in the direction orthogonal to the flat membrane, and ejecting air downward in water, or a plurality of flat membranes are sandwiched in the center part. There is a pair of sandwich plates that can expand and contract the sandwiching interval, and these means can be provided alone or in combination.

[0009]

Next, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic system diagram of an immersion type flat sheet membrane separator showing a first embodiment of the present invention. As a flexible water-permeable material used as a support, it is desired that the water resistance is significantly lower than that of a filtration membrane in order to secure a water passage. For example, a non-woven fabric made of natural fibers or synthetic fibers such as polyester, a mesh body, etc. Can be used.
In the flat sheet membrane separation device shown in FIG. 1, a flat sheet membrane 11 in which both sides of a flexible water-permeable material are covered with filtration membranes is vertically placed in a separation tank 10, and a plurality of flat sheet membranes are arranged at equal intervals at a set intermembrane distance. Both ends or one end thereof was potted with a synthetic resin or the like and then cut, and permeated liquid outlets 13 and 14 were provided with a vinyl chloride pipe or the like so that only the permeated liquid could be taken out. Reference numeral 12 is a membrane seal portion. The whole flat membrane 11 is surrounded by a frame 18 and both ends of the permeated liquid withdrawing portions 13 and 14 are fixed and movable with an adjusting screw 19, so that the tension of the flat membrane 11 can be adjusted to form a membrane module in the separation tank 10. Soaked in. further,
A sandwiching plate 21 is provided as a means for expanding / contracting the distance between the flat films 11.

A stock solution inlet 16 for supplying a stock solution and a concentrated solution is provided in the lower part of the separation tank 10, and a circulating water is uniformly overflowed in the upper part so that the circulating water does not drift in the separation tank 10. However, a circulating water outlet 17 is provided for further draining. Also, the separation tank 1
The bottom of 0 is inclined so that the concentrate outlet 20 is the lowest so that the concentrate containing the precipitated suspension can be easily discharged. The air diffuser 15 is provided below the flat film 11, but may be provided between the films. As the air diffuser 15, a normal air diffuser, an air diffuser, or the like can be used, and it is preferable that the air diffuser 15 is not easily clogged. The air for air bubbling can be supplied from below the flat film 11 by using a blower 33.

FIG. 2 is an explanatory view of the means for expanding and contracting the intermembrane distance in a structure (a form shown in FIG. 1) in which a flat membrane is sandwiched by a pair of sandwich plates, and FIG. 3 is surrounded by a circle in FIG. It is an enlarged view of a part.
The pair of sandwich plates 21 are flat plates 11 arranged in parallel in the lateral direction.
It is provided at a position adjacent to the central portion of the outer membrane of the sandwich plate 21, and the height of the sandwich plate 21 is made higher than that of the flat membrane 11. Also, the sandwich plate 2
As shown in FIG. 3, the lower part of 1 connects the sandwiching plates 21 at both ends of the flat film 11 with the rotating shafts 22 and 23, and the rotation of them can expand or contract the distance between the pair of sandwiching plates 21, and thus the intermembrane distance. It has a structure.

When performing the filtration operation using the separation apparatus shown in FIG. 1, first, the stock solution is supplied from the stock solution inlet 16 to fill the inside of the separation tank 10, and the stock solution is circulated from the circulating water outlet 17. Next, the suction pump 30 is operated, the flow rate control valve 39 is opened, and the permeated liquid withdrawing sections 13 and 14 perform suction filtration while observing the flow rate instruction controller 32. Suction filtration is often quantitatively filtered because the permeate is secured, that is, the amount of treated water is prioritized. The suspension in the stock solution is collected on the surface of the flat membrane 11 by suction filtration, adheres thereto, and becomes a cake layer while being deposited. During this time, the blower 33 is operated, the flow rate is adjusted by the flow rate control valve 36 in the air pipe while watching the flow meter 35, air is bubbled from the air diffuser 15, and air bubbles are supplied from the lower portion of the flat membrane 11 to the space between the membranes. . Since the bubbles rise while swinging between the membranes, the bubbles contact the cake on the membrane surface or swing the membrane to efficiently separate and remove the cake on the flat membrane 11. The air supply may be intermittent or continuous. In the initial stage of filtration, the transmembrane pressure difference is very low, so there is no problem, but since it increases after long-term filtration, the sandwich plate 21 is intermittently operated to swing the central portion of the flat membrane, Can accelerate the removal of the cake on the membrane surface.

FIG. 4 shows a second embodiment of the means for widening the intermembrane distance. In this case, an air diffusing tube 25 is installed below the flat membrane 11 in parallel with the flat membrane, and air extending in a direction orthogonal to the flat membrane 11 and the air diffusing tube 25 is provided in a lower portion corresponding to a central portion of the flat membrane 11. A jet pipe 26 is provided. Air is ejected from the air ejection pipe 26 to produce the flat film 11
Bubbles are allowed to enter between the membranes in the central portion of the membrane, the central portion of the flat membrane 11 is shaken, the distance between the membranes can be expanded and contracted, and the cake on the membrane surface can be easily removed. In the embodiment shown in FIG. 4, the air ejection pipe is provided below the flat membrane, but it may be provided above the flat membrane to eject air downward. Also,
Although two air ejection pipes 26 are shown in FIG. 4, the number is not limited to two, and one or two or more can be installed as required. Further, an air jet pipe may be provided below or above the flat membrane in addition to the first embodiment shown in FIGS.

[0014]

According to the flat membrane separation apparatus of the present invention, the cake on the membrane surface can be removed efficiently, and the suspended matter in the waste water containing the suspended matter can be efficiently separated over a long period of time. can do.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of an immersion type flat sheet membrane separator showing a first embodiment of the present invention.

FIG. 2 is an explanatory view of an inter-membrane distance widening means used in the first embodiment.

FIG. 3 is an enlarged view of a portion surrounded by a circle in FIG.

FIG. 4 is an explanatory view showing a second embodiment of the inter-membrane distance widening means used in the separation device of the present invention.

[Explanation of symbols]

 10 Separation Tank 11 Flat Membrane 13 Permeate Extraction Part 14 Permeate Extraction Part 15 Diffuser Part 18 Frame 19 Adjusting Screw 20 Condensate Discharge Port 21 Clamp Plate 22 Rotating Shaft 23 Rotating Shaft 25 Air Diffusing Pipe 26 Air Ejecting Pipe 30 Suction Pump 32 Flow rate indication controller 33 Blower 39 Flow rate control valve

Claims (4)

[Claims] 1. A plurality of flat membranes, each of which is coated with a filtration membrane on both sides of a flexible water-permeable material, are arranged vertically in a tank and in parallel with each other at a constant distance from adjacent flat membranes. In a submerged membrane separation device in which a permeate extraction part is provided at both ends or one end in the horizontal direction of a vertically arranged flat membrane, and a diffusing means is installed below the flat membrane, in the horizontal direction of a plurality of vertically arranged flat membranes. An immersion type flat sheet membrane separation device comprising means for expanding and contracting the distance between the membranes in the central part of the. 2. The immersion type flat sheet membrane separating apparatus according to claim 1, wherein the means for expanding / contracting the distance between the membranes is a pair of sandwich plates which sandwich a plurality of flat membranes and can expand / shrink the sandwiching intervals. 3. The submerged flat membrane separation apparatus according to claim 1, wherein the means for expanding / contracting the intermembrane distance is an air jet tube installed below the flat membrane and extending in a direction orthogonal to the flat membrane. 4. The immersion type as claimed in claim 1, wherein the means for expanding and contracting the intermembrane distance is an air ejection pipe which is installed on an upper portion of the flat membrane, extends in a direction orthogonal to the flat membrane, and ejects air downward in water. Flat membrane separator.