JP2000117071A - Flat membrane element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat membrane element superior in back washing property. SOLUTION: In the flat membrane element 10, both ends of nonwoven cloth- made bag shaped flat membrane 11 are supported and fixed with support members 20 having permeated water nozzles 21. Since the flat membrane element 10 can be back-washed from both the end sides, the whole surface of the bag shaped flat membrane 11 can be uniformly washed at lower pressure than it to a conventional element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat membrane element having excellent backwashing properties, and more particularly to a method for operating a membrane module capable of maintaining stable filtration performance.

[0002]

2. Description of the Related Art As a membrane module used for solid-liquid separation of activated sludge liquid or the like, a module in which a plurality of flat membrane elements are housed in a housing is used. The flat membrane element is formed by sandwiching a spacer serving as a permeated water channel material between two flat membranes, attaching a permeated water nozzle, and bonding the periphery of the flat membrane.

When the operation of the membrane module is continued, sludge or the like adheres to the membrane surface of the flat membrane element to reduce the filtration ability. Need to be backwashed. In this case, permeated water is often used for effective use of water resources. However, when a non-woven fabric membrane is used, the turbidity of permeated water is large, and when used as washing water as it is, suspended particles contained in the permeated water aggregate to form flocs larger than the pore size of the filtered membrane, The flock may damage the membrane.

[0004] When a non-woven fabric membrane is used, dynamic filtration is performed. However, it is difficult to uniformly clean the entire membrane surface by the conventional back washing method, so that the amount of sludge adhering to the membrane surface is controlled. It will also be difficult to do.

[0005] It is an object of the present invention to provide a flat membrane element having excellent backwashing properties, particularly when using a nonwoven fabric membrane. Another object of the present invention is to provide a method of operating a membrane module having a plurality of flat membrane elements, which can maintain stable filtration performance for a long period of time.

[0006]

SUMMARY OF THE INVENTION The present invention provides a flat membrane element in which both ends of the flat membrane are supported and fixed by a support member having a permeate nozzle.

[0007] The present invention also provides a method for operating a membrane module comprising a large number of flat membrane elements having permeated water nozzles housed in a housing, after filtering the permeated water through a membrane having a pore size smaller than that of the flat membrane element. The present invention provides a method for operating a membrane module for back washing a membrane module with the filtered permeated water.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the flat membrane element of the present invention will be described with reference to FIG. FIG. 1 is a front view of a flat membrane element.

The flat membrane element 10 has both ends of the flat membrane 11 supported and fixed by a support member 20 having a permeated water nozzle 21. The type of the flat membrane 11 is not particularly limited, but a bag-shaped flat membrane in which a mesh-shaped flow path holding material is sandwiched inside is preferable.

The bag-like flat membrane is preferably made of a nonwoven fabric. Examples of the nonwoven fabric include natural fibers such as cotton, hemp, and wool, polyester derivatives such as polyester, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly (meth) acrylate, viscose rayon, cellulose acetate, and methyl cellulose. Polyolefins such as polyethylene and polypropylene, polycarbonates,
Polyamide, polyester amide, polyether, polyimide, polyamide imide, polyether imide and those obtained by a conventional method from synthetic fibers comprising a mixture or copolymer of two or more thereof can be used. As such a nonwoven fabric, MF180 (trade name: fiber diameter 1)
0 μm polyester fiber nonwoven fabric; manufactured by Japan Vilene Co., Ltd .; trade name SB-35 (fiber diameter 10 μm polyester fiber nonwoven fabric; manufactured by Unitika Ltd.); trade name FC3105
(Nonwoven fabric made of polyester fiber having a fiber diameter of 10 μm; manufactured by Japan Vilene Co., Ltd.), trade name: NF felt (fiber diameter: 10 μm
Non-woven fabric made of polyester fiber of Nippon Felt Co., Ltd .; trade name FC302 (non-woven fabric of polyester fiber having a fiber diameter of 10 μm; made by Nippon Vilene Co., Ltd.); ), Trade name H8007 (nonwoven fabric made of polyester fiber having a fiber diameter of 10 μm; manufactured by Japan Vilene Co., Ltd.), and the like.

The support member 20 has therein a permeated water introduction passage for guiding permeated water filtered by the flat membrane element 10 to a permeated water nozzle 21. This support member 20
Since it is easy to confirm the degree of turbidity of the permeated water and the presence / absence of the blockage of the permeated water introduction passage, it is preferable that the permeated water be transparent.

When a bag-shaped flat membrane is used, the flat membrane element 10 is attached with an adhesive or the like so as to sandwich the bonding portion of the support member 20 at both short sides.
The edges 12 at both long sides of the flat membrane element 10 are sealed with an adhesive or the like.

Next, an embodiment of a method for operating a membrane module according to the present invention will be described with reference to FIGS. FIG.
1 is a perspective view of a membrane module of the present invention, with a part thereof being cut away.

A stock solution such as an activated sludge solution is supplied from a stock solution supply port of the membrane module 30 (not shown; provided on the bottom surface on the end surface 33 side of the housing 32).

The membrane module 30 is such that a plurality of flat membrane elements 10 whose both ends are supported by a support member 20 are housed in a rectangular parallelepiped housing 32. In the method for operating the membrane module of the present invention, a flat membrane element having only one end supported and fixed by the support member can be applied. However, as described above, both ends have the flat membrane element supported and fixed by the support member. Those are preferred. The flat membrane element 10 is preferably in the form of a bag and made of a nonwoven fabric.

The permeated water filtered in the flat membrane element 10 is discharged from the permeated water discharge pipe 34 (35) through the permeated water nozzle 21 of the support member 20. The permeated water may be discharged from either one of the permeated water discharge pipes 34 and 35 or from both.

When such a filtration process is continued, sludge or the like adheres to the membrane surface of the flat membrane element 10, and the filtration capacity is reduced. Therefore, the permeated water is sent from the permeated water discharge pipe 34 to the flat membrane element 10 for backwashing. At this time, in order to effectively use water resources, the permeated water is filtered into a membrane having a pore diameter smaller than that of the flat membrane element 10. And then backwash the membrane module with the filtered permeate.

The ratio of the pore size of the flat membrane element 10 to the membrane used for filtering the permeated water is not particularly limited as long as the object of the present invention can be achieved. It is preferable to use a membrane having a small pore size of about 90 to 10%.

Backwashing using the permeated water re-filtered in this manner improves the washing properties of the membrane. In addition, the particle size of the suspended particles contained in the re-filtered permeated water is sufficiently small to prevent agglomeration, or the floc formed by agglomeration is small in size to prevent the membrane from being damaged. it can.

The re-filtered permeated water is fed into the flat membrane element 10 from both the permeated water discharge pipes 34 and 35,
Back washing can also be performed. At this time, the permeated water discharge pipe 34
It is preferable to send back the permeated water that has been re-filtered alternately from steps 35 and 35 for backwashing.

In this way, when the backwashing is performed from both ends, the water pressure can be more uniformly applied to the entire membrane surface as compared with the case where the backwashing is performed from the one end side. It is easy to control the amount of adhesion. Furthermore, compared to the case of back washing from one end side,
Backwashing can be performed at lower pressure.

In the operation of the membrane module 30,
The concentrate is discharged from the concentrate outlet 36 and the housing 3
The sludge accumulated at the bottom of the second 2 is discharged from a sludge discharge port (not shown) provided at the bottom opposite to the concentrated liquid discharge port 36.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 A 1.4 mm thick polyethylene net (Dai Nippon Plastics Co., Ltd., Netron Sheet D) was placed between two nonwoven fabric membranes (FC3105, manufactured by Nippon Vilene Co., Ltd., average pore size: 15 μm).
6) The two sheets were sandwiched, and both long sides were sealed with a urethane adhesive (manufactured by Nippon Polyurethane Co., Ltd., main agent Coronate 4403, curing agent Nipporan 4235). Next, a support member having a permeated water nozzle was attached to both short sides, and a bag-shaped flat membrane element having support members at both ends as shown in FIG. 1 was obtained. The effective size of the membrane was 22 × 125 cm.
The flat membrane element was immersed in an MLSS 10,000 ppm activated sludge solution, and filtered at a speed of 1 m / day. 2
After the filtration operation for a period of time, permeated water was alternately sent from the both ends to the inside of the membrane at a rate of 2 liters / minute for 1 minute, and backwashed for a total of 2 minutes. The permeated water used for the back washing was obtained by re-filtering the obtained permeated water through a membrane having an average pore diameter of 10 μm. 2
Repeat the same backwashing operation every time the filtration operation is performed,
The filtration operation was performed for a total of 6 hours. After 6 hours, the filtration pressure was 10 kPa or less.

Comparative Example 1 A filtration operation was performed in the same manner as in Example 1 except that the permeated water used for the back washing was not refiltered. as a result,
After 6 hours, the filtration pressure was 15 kPa.

Comparative Example 2 A filtration operation was performed in the same manner as in Example 1 except that back washing was performed only from one end. As a result, after 4 hours, the filtration pressure reached 20 kPa.

[0027]

According to the present invention, the flat membrane element having the supporting members at both ends can be backwashed from both ends, so that the backwashing property is excellent, and the amount of sludge adhering to the membrane surface can be easily controlled. Particularly, it is suitable when a nonwoven fabric film is used. Further, according to the method for operating the membrane module of the present invention, since the backwashing property is excellent, stable filtration performance can be maintained for a long period of time.

[Brief description of the drawings]

FIG. 1 is a front view of a flat membrane element of the present invention.

FIG. 2 is a perspective view of a membrane module containing the flat membrane element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Flat membrane element 20 Support member 21 Permeated water nozzle 30 Membrane module 32 Housing 34, 35 Permeated water discharge pipe

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA02 HA53 JA04A JA04C JA07A JA07C JA08A JA08C JA14Z JA18A JA18C KA72 KB14 KC03 KC13 KE02Q KE08P KE12P KE24Q KE28Q MA03 MA22 MC11 MC14 MC16 MC18 MC22 MC23 MC48 MC42 MC28 MC59 PA02 PB08 PB20 PC64

Claims (6)

[Claims] 1. A flat membrane element in which both ends of the flat membrane are supported and fixed by a support member having a permeated water nozzle. 2. The flat membrane element according to claim 1, wherein the flat membrane is a bag-shaped flat membrane. 3. The flat membrane element according to claim 2, wherein the bag-shaped flat membrane is made of a nonwoven fabric. 4. When operating a membrane module in which a large number of flat membrane elements having a permeated water nozzle are housed in a housing, permeated water is filtered through a membrane having a pore diameter smaller than the pore diameter of the flat membrane element, and then filtered. A method for operating a membrane module in which the membrane module is backwashed with permeated water. 5. The method for operating a membrane module according to claim 4, which is a membrane module provided with the flat membrane element according to claim 1, 2, or 3. 6. The method for operating a membrane module according to claim 5, wherein backwashing is performed alternately or simultaneously from both ends of the flat membrane element.