JP2014050788A - Membrane module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane module that can prevent a breakage of a flat pre-filter, even if the inline cleaning is performed, and can suppress increase of consumption of a cleaning solution.SOLUTION: A membrane module 3 is an external pressure filtration type membrane module 3 with a flat pre-filter 15 covering a filtration membrane 7, and includes a suppression structure 17 for suppressing expansion of the flat pre-filter 15. The suppression structure 17 is a mesh-like body provided outside the flat pre-filter 15, and preferably, the mesh-like body is made of resin or metal.

Description

  The present invention relates to a membrane module, and more particularly to a membrane module in which a flat prefilter is provided on the surface of a filtration membrane.

  2. Description of the Related Art Conventionally, an external pressure filtration type submerged membrane separation apparatus has been used for filtering water to be treated including activated sludge and agglomerated sludge. The external pressure filtration type submerged membrane separation apparatus has a membrane module provided with a number of filtration membranes such as hollow fiber membranes or tubular membranes. Then, the submerged membrane separation device is immersed in the water to be treated stored in the tank, the negative pressure is applied to the membrane module, the water to be treated is sucked into the membrane module, and the water to be treated is filtered by the filtration membrane. To do.

  The submerged membrane separation apparatus is suitable for filtering various types of water to be treated. Among them, highly polluted water (for example, SS (Suspended Solid) concentration is higher than 50 ppm and TOC (Total Organic) is used. When treating wastewater whose carbon content is higher than 100 ppm, SS and organic substances are likely to be deposited on the film surface. When SS or organic matter is deposited on the film surface, SS or organic matter forms a lump, and adjacent films are fixed and integrated, so that the effective film area of the film is reduced, so-called interfiber clogging occurs. There was a problem that.

  When interfiber logging occurs, the filtration capacity of the membrane is extremely reduced, so it is desirable to prevent interfiber logging in advance. As a membrane module capable of preventing interfiber clogging, a membrane module in which the membrane is covered with a flat prefilter is known (for example, Patent Document 1).

Japanese Patent No. 3694536

  The membrane module of Patent Document 1 includes a flat prefilter that covers the hollow fiber membrane, and the flat prefilter captures SS and organic matter in advance to prevent them from adhering to the membrane. .

  Regarding the cleaning method for cleaning the membrane module configured by covering the membrane with a flat prefilter, there is no established technology yet, but the shape of the membrane module from the secondary side (filtered water side) to the primary side (from the filtered water side) It is considered that in-line cleaning in which a cleaning solution is flowed toward the treated water side) is effective. However, when performing in-line cleaning, the flat prefilter expands due to the pressure of the cleaning liquid, the flat prefilter is damaged, or the cleaning liquid oozes out from the flat prefilter, increasing the amount of cleaning liquid used. There's a problem.

  Therefore, the present invention has been made to solve the above-described problems, and even if in-line cleaning is performed, the flat prefilter can be prevented from being damaged, and an increase in the consumption of cleaning liquid is suppressed. An object of the present invention is to provide a membrane module including a flat prefilter that can be used.

  In order to solve the above-described problems, the present invention is an external pressure filtration type membrane module including a flat type prefilter that covers a filtration membrane, and includes a suppression structure that suppresses expansion of the flat type prefilter. .

  According to the present invention configured as described above, since the expansion of the flat prefilter can be suppressed by the suppression structure, the flat prefilter can be used when the pressure in the membrane module is increased by performing in-line cleaning. Expansion can be suppressed.

  In the present invention, preferably, the suppression structure is a net-like body provided outside the flat prefilter. In the present invention, preferably, the net is made of resin or metal.

  As described above, according to the present invention, even if in-line cleaning is performed, the flat prefilter can be prevented from being damaged, and an increase in the consumption of the cleaning liquid can be suppressed.

It is a perspective view which shows a membrane filtration apparatus provided with the membrane module by embodiment of this invention. It is a perspective view which shows the membrane module by embodiment of this invention. It is sectional drawing of the III-III cross section of FIG.

Hereinafter, a membrane module according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a membrane filtration device including a membrane module.

  As shown in FIG. 1, the membrane filtration device 1 includes a plurality of membrane modules 3 and a diffuser plate 5 disposed below the membrane modules 3. The plurality of membrane modules 3 are arranged at a predetermined interval so that their surfaces face each other. A diffuser plate 5 connected to an external blower is disposed below the membrane module 3.

  The diffuser plate 5 emits air over a wide range so that the air flowing from the blower hits all the membrane modules 3. The air released from the diffuser plate 5 passes between the adjacent membrane modules 3 and hits the membrane module 3 to physically wash the membrane module 3.

2 is a perspective view showing a membrane module of the membrane filtration device, and FIG. 3 is a cross-sectional view taken along the line III-III of FIG.
The membrane module 3 includes a plurality of filtration membranes 7 arranged in parallel, and a pair of housings 9 fixed to both ends of the filtration membrane 7.

  The filtration membrane 7 is configured by processing a hollow fiber membrane made of, for example, a cellulose, polyolefin, polyvinyl alcohol, PMMA, or polysulfone material into a knitted fabric. Considering the ease of processing into a knitted fabric, a material having a high elongation such as polyethylene is preferable. In addition, there is no restriction | limiting in particular in a hole diameter, a porosity, a film thickness, an outer diameter, etc. if it can be used as a filtration membrane. Further, as the filtration membrane 7, it is preferable to use a single knitted fabric made of hollow fiber membranes as, for example, wefts, or a laminate in which several knitted fabrics are laminated. In the case of the conventional cylindrical module, there was no difficulty in housing the hollow fiber membrane that has been scraped and converged in the cylindrical structural material. On the other hand, it is difficult to store a hollow fiber membrane that has been trimmed into an elongated rectangular opening, but can be easily stored using a knitted fabric. In addition, the lamination | stacking of the knitted fabric here also includes what folded up and piled up to appropriate length, without cut | disconnecting a knitted fabric. The number of layers (folding) of the knitted fabric varies depending on the thickness of the knitted fabric, that is, the thickness of the hollow fiber membrane and the number of combined yarns of the hollow fiber membrane at the time of knitting the knitted fabric. It is preferable that the fixing member is configured to satisfy the limitation on the length of the short side of the rectangular cross section of the fixing member.

  The housing 9 is provided with an opening for receiving a bundle of a plurality of filtration membranes 7, filling the opening with a fixing resin, and fixing the bundle of filtration membranes 7 with the fixing resin. Both ends of the filtration membrane 7 are open, and the filtered water filtered by the filtration membrane 7 flows into the housing 9 through the filtration membrane 7. One of the pair of housings 9 includes a water intake 11 for taking out the filtered water, and the filtered water filtered by the membrane module 3 is discharged to the outside of the membrane filtration device 1 through the water intake 11. Is done.

  The material constituting the housing 9 may be any material having mechanical strength and durability, and examples thereof include polycarbonate, polysulfone, polypropylene, acrylic resin, ABS resin, and modified PPE resin. When incineration is necessary after use, it is preferable to use a hydrocarbon-based resin that can be completely burned without emitting toxic gas by combustion.

  As the fixing resin, it is preferable to use a resin obtained by curing a liquid resin such as an epoxy resin, an unsaturated polyester resin, or polyurethane.

  The water intake 11 of the housing 9 is connected to a cleaning device 13 for flowing a cleaning liquid into the membrane module 3. The cleaning device 13 flows the cleaning liquid into the membrane module 3 through the water intake 11 of the housing 9. The cleaning liquid is appropriately selected according to the properties of the sludge in the water to be treated.When the sludge in the water to be treated contains organic matter, an oxidizing agent such as a sodium hypochlorite solution is used. An acid solution such as oxalic acid, citric acid or hydrochloric acid is used. And the washing | cleaning apparatus 13 pours a washing | cleaning liquid in the membrane module 3, and wash | cleans the sludge adhering to the filtration membrane 7 by this.

  Further, a flat prefilter 15 for preventing interfiber clogging of the filtration membrane 7 is provided around the plurality of filtration membranes 7. The flat prefilter 15 is a filter provided so as to completely cover all the filtration membranes 7 of one membrane module 3, and prevents SS and organic matter from being deposited on the membrane surface. Prevent interfiber clogging.

  The flat prefilter 15 is a filter having a large number of micropores of, for example, 0.1 to 100 μm, and is made of a cellulose-based, acrylic-based, or polyolefin-based material. Further, the flat prefilter 15 may be constituted by a depth filter based on a nonwoven fabric or the like in consideration of the cost and the point that a cake layer is formed on the film surface and cake filtration is performed.

  By disposing the flat prefilter 15, the primary side (treated water side) of the filtration membrane 7 is completely covered by the flat prefilter 15.

  The membrane module 3 further includes a suppression structure 17 that suppresses the expansion of the flat prefilter 15. The suppression structure 17 is a net-like body disposed outside the flat prefilter 15. The suppression structure 17 is stretched between the pair of housings 9 and is disposed so as to surround the outer periphery of the flat prefilter 15. Specifically, the suppression structure 17 is formed so as to cover all exposed surfaces of the flat prefilter 15 and can resist expansion of the flat prefilter 15 when in-line cleaning is performed. It is fixed to the housing 9 with a certain degree of tension.

  The suppression structure 17 is not particularly limited as long as it does not substantially have filtration ability like the flat prefilter 15 and the filtration membrane 7 and does not excessively inhibit filtration by the flat prefilter 15. However, a mesh body made of stainless steel or hard plastic is preferably used. Moreover, the expansion of the flat prefilter 15 can be more reliably suppressed by further pressing the mesh body with a rod. The specification of the mesh body is not particularly limited as long as it does not damage the flat prefilter 15 and does not clog the mesh body itself or clog the flat prefilter 15.

  When filtering the water to be treated by the membrane filtration device 1 described above, first, the membrane filtration device 1 is immersed in a tank in which the water to be treated is stored. And a negative pressure is made to act in the membrane module 3 by operating the pump connected to the water intake 11 of the membrane module 3. Thereby, the water to be treated around the membrane module 3 is first filtered by the flat prefilter 15. As a result, SS and part of the organic matter in the water to be treated adhere to the surface of the flat prefilter 15. The treated water that has passed through the flat prefilter 15 flows from the treated water side (primary side) of the filtration membrane 7 toward the filtered water side (secondary side) and passes through the filtration membrane 7. Thus, the water to be treated is filtered, and the filtered water passes through the housing 9 and is discharged from the water intake 11 to the outside of the membrane filtration device 1.

  Further, the membrane filtration device 1 physically cleans the filtration membrane 7 periodically by in-line cleaning that releases air from the diffuser plate 5 toward the filtration membrane 7 to operate aeration or aeration and the cleaning device 13. .

  When the filtration membrane 7 is cleaned by the cleaning device 13, the cleaning device 13 is operated to allow the cleaning liquid to flow into the membrane module 3 through the water intake port 11 at a predetermined pressure. Accordingly, the cleaning liquid flows from the casing 9 into the filtration membrane 7 and flows from the filtrate water side (secondary side) of the filtration membrane 7 toward the treated water side (primary side). Thereby, the sludge adhering to the surface of the filtration membrane 7 is chemically washed. At this time, since the cleaning liquid that has flowed to the treated water side of the filtration membrane 7 flows into the flat prefilter 15 that completely covers the filtration membrane 7, the flat prefilter 15 has a secondary side to a primary side. A pressure to expand the flat prefilter 15 acts on the surface. Therefore, the suppression structure 17 suppresses the expansion of the flat prefilter 15. Thereby, damage to the flat prefilter 15 due to expansion can be prevented. Further, by suppressing the expansion of the flat prefilter 15, the concentration of the cleaning liquid in the membrane module 3 can be maintained, whereby the consumption of the cleaning liquid can be suppressed.

  EXAMPLES Hereinafter, although the Example demonstrates the implementation method of this invention further in detail, these Examples aim at the illustration of this invention, and do not limit this invention.

Example 1 (module covered with net)
Fabrication of membrane module Hydrophilic polyethylene porous hollow fiber membrane EX540VS (manufactured by Mitsubishi Rayon Co., Ltd., inner diameter: 350 μm, outer diameter: 540 μm, material: polyethylene) and two-component curable urethane resin C4403 / N4224 as fixing resin (Nippon Polyurethane Co., Ltd.) was used to fix to the housing. Further, a non-woven fabric was installed so as to cover the hollow fiber membrane part and the housing, and a hollow fiber membrane module with a flat prefilter (hereinafter referred to as a membrane module) shown in FIG. 1 was produced. The outer dimensions of the membrane module were 550 mm × 250 mm × 30 mm, the effective membrane area of the flat prefilter was 0.22 m ² , the average effective length of the hollow fiber membrane was 200 mm, and the hollow fiber membrane area was 5 m ² .

Installation of net A high-density polyethylene net (thickness 2.1 mm, mesh pitch 10 × 10 mm) with a length of 600 mm and a width of 300 mm is installed so as to cover the surface of the flat prefilter of this membrane module, and the outer periphery is bound with polyethylene. Fixed with a band.

Measurement of volume inside membrane module A hole having a diameter of 10 mm was formed in a flat prefilter of the membrane module, and a tube fitting was installed. After the entire membrane module was submerged in tap water and the air in the membrane module was expelled, air was blown from the tube fitting portion at a flow rate of 5 L / min. The inner volume of this membrane module was found to be 3.8L. Further, when the aeration flow rate was gradually increased, the flat prefilter was not damaged even when the atmospheric pressure in the membrane module reached 250 kPa.

Comparative example 1 (module not covered by net)
Production of Membrane Module A membrane module similar to that of Example 1 was produced except that no net was provided.

Measurement of volume inside membrane module A hole having a diameter of 10 mm was made in the prefilter of this membrane module, and a tube fitting was installed. After submerging the entire membrane module in tap water and expelling the air in the membrane module, when air was blown from this tube fitting portion at a flow rate of 5 L / min, air began to blow out from the prefilter surface 83 seconds after the start of ventilation. The inner volume of this membrane module was found to be 6.9L. Further, when the air flow rate was gradually increased, the flat prefilter was damaged from the bonded portion when the atmospheric pressure in the membrane module reached 180 kPa.

DESCRIPTION OF SYMBOLS 1 Membrane filtration apparatus 3 Membrane module 7 Filtration membrane 13 Cleaning apparatus 15 Flat type prefilter 17 Suppression structure

Claims (3)

An external pressure filtration type membrane module having a flat prefilter covering the filtration membrane,
The membrane module provided with the suppression structure which suppresses expansion | swelling of the said flat type pre filter.   The membrane module according to claim 1, wherein the suppression structure is a mesh body provided outside the flat prefilter.   The membrane module according to claim 2, wherein the mesh body is made of resin or metal.

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