JP5795459B2 - Hollow fiber membrane for immersion filtration, hollow fiber membrane module for immersion filtration using the same, immersion filtration device, and immersion filtration method - Google Patents

Description

The present invention relates to a hollow fiber membrane for immersion filtration, a hollow fiber membrane module for immersion filtration, and an immersion filtration device using the same, which are suitable for immersion suction filtration of liquids with high pollution properties (particularly due to organic pollutants). The present invention relates to an immersion filtration method.
This application claims priority based on Japanese Patent Application No. 2006-313248 for which it applied on November 20, 2006, and uses the content here.

In recent years, in water and sewage treatment and industrial wastewater treatment, a “hollow fiber membrane filtration method” in which a hollow fiber membrane is immersed in water to be treated and impurities are separated and removed from the water to be treated has become widespread.
However, the “hollow fiber membrane filtration method” causes an adhesion layer of suspended substances and organic substances in the water to be treated on the outer surface of the hollow fiber membrane due to long-term operation, and the hollow fiber membrane is clogged or caused by solid matter. It has been pointed out that a channel blockage (fouling) occurs. Fouling causes an increase in transmembrane pressure, a decrease in filtration flux, and the like, which adversely affects the overall operation efficiency of the water treatment system.

  The decrease in operating efficiency of the water treatment system due to fouling can be eliminated by physical cleaning of the hollow fiber membrane. For example, it is possible to control the degree of fouling within a certain range by introducing an operation cycle method in which physical washing is performed after a filtration process for a predetermined time and the filtration process and physical washing are repeated. For physical cleaning, reverse flow cleaning that reverses membrane filtered water; cleaning by flushing the primary surface of the hollow fiber membrane, that is, the surface in contact with the water to be treated (flushing); air bubbling that vibrates the hollow fiber membrane with air, etc. There is a physical action to remove the adhered substances.

Flushing and air bubbling, which are the above-described physical cleaning methods, are effective means for reducing fouling and are indispensable for stabilizing the filtration operation. When the concentration of suspended solids in the water to be treated is high, it is necessary to increase the physical cleaning strength in order to obtain a sufficient cleaning effect.
However, if the physical washing is too strong, the hollow fiber membranes may come into contact with each other or the suspended substances in the water to be treated may be rubbed, resulting in scratches on the surface of the hollow fiber membranes. It was.

In order to solve this problem, improvement of the shape and strength of the hollow fiber membrane has been studied.
For the purpose of improving the shape of the hollow fiber membrane, Patent Document 1 discloses a hollow fiber membrane whose shape is changed in an inclined manner. According to Patent Document 1, by changing the shape of the hollow fiber membrane in an inclined manner, the flow pressure loss is reduced as compared with the conventional hollow fiber membrane, the permeate flow velocity distribution is smoothed, and the load and contamination on the membrane local part are further reduced. Therefore, the bubbling and backwashing properties during membrane cleaning are improved, and the filtration operation can be prolonged.
Further, for the purpose of improving the strength of the hollow fiber membrane, a polyethylene hollow fiber porous membrane having a specific viscosity average molecular weight and molecular weight distribution and a specific pore structure is described in Patent Document 2. Yes.
Japanese Patent Laid-Open No. 7-96152 JP 2001-269556 A

However, the hollow fiber membrane of Patent Document 1 can be expected to improve the permeate flow rate due to the inclined structure. However, Patent Document 1 does not have a specific disclosure regarding the improvement of the operation stability and the washing performance, and the long-term operation stability. Issues remain from the perspective of sex. Moreover, in order to obtain such a membrane, the hollow fiber membrane production process is inevitably complicated, and the productivity is low and the production cost is high.
Further, in the hollow fiber-like porous membrane of Patent Document 2, although it can be expected to improve the scratch resistance against suspended components in the liquid to be treated, wear due to contact between the hollow fiber-like porous membranes is expected to occur, and long-term operation is expected. From the point of view, it does not lead to a solution. Further, it is difficult to reduce the physical cleaning strength only by improving the strength of the film, and it does not lead to a fundamental solution.

  The present invention has been made in view of the above circumstances, and even when hollow fiber membrane filtration in a high-concentration suspension is continued, deposits are unlikely to accumulate on the membrane surface, and the filtration operation is performed with water permeability. It is an object of the present invention to provide a hollow fiber membrane for immersion filtration, a hollow fiber membrane module for immersion filtration using the same, an immersion filtration device, and an immersion filtration method that can be continued for a long period of time without lowering.

As a result of intensive studies, the inventors have provided a protrusion on the outer surface of the hollow fiber membrane so that the hollow fiber membrane can be washed on the outer surface of the hollow fiber membrane when applied to immersion filtration of a highly pollutant liquid. The present invention has been completed.
That is, the present invention is a hollow fiber membrane for immersion filtration having one or more protrusions on the outer surface, and the outer surface of the protrusions with respect to the outer surface of the hollow fiber membrane when the protrusions are excluded. It is a hollow fiber membrane for immersion filtration whose projected area ratio is in the range of 1 to 20% .
Further, the present invention is a hollow fiber membrane for immersion filtration having 8 or more protrusions on the outer surface, and the outer surface of the protrusions with respect to the outer surface of the hollow fiber membrane when the protrusions are excluded. It is a hollow fiber membrane for immersion filtration whose projected area ratio is in the range of 1 to 20% .

Further, the present invention is a hollow fiber membrane module for immersion filtration, wherein a plurality of the hollow fiber membranes for immersion filtration are bonded and fixed to a housing, and the outer surface of the hollow fiber membrane when the protrusions are excluded, It is a hollow fiber membrane module for immersion filtration, wherein the projected area ratio of the protrusions to the outer surface is in the range of 1 to 20% .
Furthermore, this invention is an immersion filtration apparatus in which the said hollow fiber membrane module for immersion filtration was installed in the immersion water tank.
The present invention also provides a submerged filtration hollow fiber membrane module in which a submerged water tank is filled with water to be treated, and a plurality of submerged filtration hollow fiber membranes having one or more protrusions on the outer surface are bonded and fixed to a housing. It is an immersion filtration method for immersing in treated water and obtaining filtered water from the hollow part of the hollow fiber membrane for immersion filtration , wherein the protrusion part has a protrusion with respect to the outer surface of the hollow fiber membrane when the protrusion part is excluded. The immersion filtration method has a ratio of a projected area on the outer surface of 1 to 20% .
The present invention also covers a hollow fiber membrane module for immersion filtration in which an immersion water tank is filled with water to be treated and a plurality of hollow fiber membranes for immersion filtration having 8 or more protrusions on the outer surface are bonded and fixed to a housing. It is an immersion filtration method for immersing in treated water and obtaining filtered water from the hollow part of the hollow fiber membrane for immersion filtration , wherein the protrusion part has a protrusion with respect to the outer surface of the hollow fiber membrane when the protrusion part is excluded. The immersion filtration method has a ratio of a projected area on the outer surface of 1 to 20% .

  By using a hollow fiber membrane having one or more protrusions on the outer surface for immersion filtration, the physical cleaning effect on the outer surface of the membrane is improved. As a result, even when membrane filtration in a high-concentration suspension is continued, it is difficult for deposits to accumulate excessively on the outer surface, and the filtration operation can be continued for a long time without reducing water permeability. it can.

It is the schematic which shows an example of embodiment of the hollow fiber membrane which has a projection part. It is the schematic which shows an example of embodiment of the hollow fiber membrane module which concerns on this invention. It is a figure which shows the processing flow of the immersion filtration test of an Example. It is a figure which shows the graph of the experimental result of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Fixing resin 3 Hollow fiber membrane 4 Water flow port 5 Protrusion part 6 Screen 7 Flow rate adjustment tank 8 Supply pump 9 Stirring motor 10 Stirring blade 11 Denitrification water tank 12 Circulation pump 13 Membrane immersion water tank 14 Circulating water flow meter 15 Supply Piping 16 Aeration pipe 17 Air flow meter 18 Blower 19 Hollow fiber membrane module 20 Backwash pump 21 Pressure gauge 22 Filtration pump 23 Membrane filtration water flow meter 24 Membrane treatment water tank 25 Denitrification water tank drain 26 Membrane immersion water tank drain 27 Blower supply valve 28 Membrane filtration valve 29 Backwash water valve

Hereinafter, the present invention will be specifically described focusing on its preferred form.
Drawing 1 is a figure showing an example of an embodiment of a hollow fiber membrane for immersion filtration which has a projection on the outer surface. It is important that the hollow fiber membrane 3 for immersion filtration is provided with a protrusion 5 on its outer surface.

  The method for producing the hollow fiber membrane for immersion filtration 3 having the projections 5 may be such that the projections 5 are polymerized later on the hollow fiber membrane having no projection structure, or at the time of producing the hollow fiber membrane 3 for immersion filtration. Although it may be shaped into a shape having the protrusions 5, it is preferable to shape at the time of producing the hollow fiber membrane 3 for immersion filtration because the production process and production cost can be reduced.

The shape of the protrusion 5 is not particularly limited as long as it has a protrusion on the outer surface of the immersion filtration hollow fiber membrane 3, but a large amount of the immersion filtration hollow fiber membrane 3 can be manufactured stably and continuously. Therefore, the structure as shown in FIG. 1 having at least one protrusion 5 having a shape continuous in the longitudinal direction on the outer surface of the hollow fiber membrane 3 for immersion filtration is particularly preferable.
The number of protrusions 5 having a shape that is continuous in the longitudinal direction is not particularly limited, but when a plurality of immersion filtration hollow fiber membranes 3 are arranged, the adjacent hollow fiber membranes are washed. In order to obtain the effect effectively, it is particularly preferable to have 8 or more.
On the other hand, when the number of the protrusions 5 is too large, there is a possibility that the filtration capacity may be reduced due to the reduction of the effective filtration area of the hollow fiber membrane 3 for immersion filtration. Therefore, the number of the protrusions 5 is a range in which the projected area ratio of the protrusions 5 to the outer surface of the hollow fiber membrane 3 for immersion filtration is 1 to 20% when the protrusions 5 are excluded. It is preferable to adjust so that it becomes.
This is because when the projected area ratio is 1% or more, an excellent cleaning effect by the protrusions 5 tends to be exhibited. More preferably, it is 5% or more.
Moreover, it is because it exists in the tendency for coexistence with the washing | cleaning effect by the projection part 5, and the above-mentioned filtration processing capability by making a projected area ratio into 20% or less. More preferably, it is 15% or less.

In addition, the protrusion 5 has a parallel shape from the root to the tip of the protrusion 5 or from the root to the tip so that the deposits deposited on the membrane surface of the hollow fiber membrane 3 can be easily separated and discharged by physical cleaning. Therefore, a shape whose width is reduced is preferable.
The protruding structure provided on the outer periphery of the hollow fiber membrane 3 for immersion filtration makes the deposit layer deposited on the outer surface discontinuous and excessively deposits on the outer surface of the adjacent hollow fiber membrane 3 for immersion filtration. It is for physically peeling and removing this by contacting the adhered matter. For this reason, since the adhering matter should not be deposited on the protrusion 5, it is preferable to have a structure in which the filtration function is remarkably reduced, and it is more preferable that the projection part 5 does not substantially have the filtration function.

The width of the protrusion 5 is not particularly limited, but is preferably 5 μm or more. This is because when the width of the protrusion 5 is set to 5 μm or more, the protrusion 5 is less likely to be deformed or damaged due to swinging of the immersion filtration hollow fiber membrane 3 or mutual collision during filtration. Because. Moreover, it is because the shape of the protrusion part 5 at the time of hollow fiber membrane manufacture is stable, and the productivity of the hollow fiber membrane 3 for immersion filtration tends to be good. More preferably, it is 15 μm or more.
Further, the width of the protrusion 5 is not particularly limited, but is preferably 50 μm or less. This is because by setting the thickness to 50 μm or less, an excellent membrane surface cleaning effect tends to be expected while maintaining the effective filtration area of the hollow fiber membrane 3 for immersion filtration. More preferably, it is 40 μm or less.

  The interval between the protrusions 5 can be appropriately selected as necessary. However, in consideration of uniform cleaning of the membrane surface, the protrusions 5 are arranged on the outer surface of the hollow fiber membrane 3 for immersion filtration at substantially equal intervals. It is preferable.

The height of the protrusion 5 is not particularly limited, but is preferably sufficiently higher than the deposit layer deposited on the outer surface of the hollow fiber membrane 3 for immersion filtration in order to obtain an excellent membrane surface cleaning effect. .
The deposit layer deposited on the outer surface of the hollow fiber membrane 3 for immersion filtration and the height thereof vary depending on the quality of the water to be treated. The height of the part 5 is preferably 5 μm or more. More preferably, it is 10 μm or more.
Moreover, although the height of the projection part 5 is not specifically limited, It is preferable to set it as 3 times or less of the width | variety of the root part. This is because, when the ratio is 3 times or less, the protrusion 5 is less likely to be deformed or damaged due to the swing of the hollow fiber membrane 3 for filtration during filtration or the mutual collision. More preferably, it is 2 times or less.
In addition, the height of the projection part 5 in this invention means the distance from the outer surface of a hollow fiber membrane to the front-end | tip of a projection part when a projection part is excluded.

  The hollow fiber membrane 3 for immersion filtration of the present invention preferably has an inner diameter in the range of 50 to 1000 μm from the viewpoint of shape stability and handleability, and the film thickness of the portion without the protrusions 5 is 5 to 300 μm. It is preferable to be in the range.

As the pore diameter of the hollow fiber membrane 3 for immersion filtration of the present invention, generally known reverse osmosis membranes, ultrafiltration membranes, microfiltration membranes and large pore membranes can be used, but preferably ultrafiltration membranes. The range of 0.005 to 5 μm can be used as a microfiltration membrane and a large pore membrane.
The material of the hollow fiber membrane 3 for immersion filtration is not particularly limited, and polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyetherimide, polyamide, polyetherketone, polyetheretherketone, polyethylene, polypropylene, poly- Examples include 4-methylpentene, cellulose, cellulose acetate, polyvinylidene fluoride, polyethylene-tetrafluoroethylene copolymer, and polytetrafluoroethylene. These composite materials can also be used.

  When the protrusion 5 is polymerized later on the hollow fiber membrane having no protrusion structure, each may be a different material, but considering the adhesion between the hollow fiber membrane and the protrusion 5 and the like It is preferable to use the same material for each.

FIG. 2 is a diagram showing an example of an embodiment of a hollow fiber membrane module for immersion filtration using the hollow fiber membrane for immersion filtration of the present invention.
In the hollow fiber membrane module 19 for immersion filtration of the present invention in FIG. 2, a plurality of hollow fiber membranes 3 for immersion filtration are bundled in a sheet shape, and at least one end of the hollow fiber membrane 3 for immersion filtration is kept open. As is, it can be obtained by a manufacturing method in which the hollow fiber membrane bundle is potted with a fixing resin 2 that is disposed in the housing 1 having the water flow port 4 and bonded and fixed to the housing 1.
At least one end of the housing 1 is provided with a pipe that is open to the outside and communicates with an internal path for passing a processing solution contained in the housing 1.

  As a hollow fiber membrane bundle used for the hollow fiber membrane module 19 for immersion filtration of the present invention, the hollow fiber membrane 3 for immersion filtration may be simply arranged, but from the point of workability of the hollow fiber membrane module 19, It seems that the hollow fiber membrane bundle is wound in a multi-threaded manner around the frame, the hollow fiber membrane 3 is used as a knitted fabric as a weft, or several knitted fabrics are laminated to form a laminate. Can be used suitably. The form of these hollow fiber membrane bundles can be appropriately selected according to the hollow fiber membrane 3 for immersion filtration used.

  The material of the housing 1 used for the hollow fiber membrane module 19 for immersion filtration of the present invention may be any material having mechanical strength and durability. For example, polycarbonate, polysulfone, polyolefin, PVC (polyvinyl chloride), acrylic Resin, ABS resin, modified PPE (polyphenylene ether) and the like can be used. When incineration is necessary after use, it is preferable to use a hydrocarbon-based resin such as polyolefin that can be completely burned without producing a toxic gas by combustion.

As described above, the hollow fiber membrane 3 for immersion filtration is fixed in the housing 1 with the fixing resin 2 while the opening surface communicates with the internal path while maintaining the opening surface.
As the fixing resin 2 used here, an epoxy resin, a urethane resin, an epoxy acrylate resin, a silicon resin, various hot-melt resins, and the like can be used, and can be appropriately selected.
The viscosity (20 ° C.) of the fixing resin 2 at the time of fixing the immersion filtration hollow fiber membrane 3 is not particularly limited, but the fixing resin 2 is easily impregnated between the plurality of immersion filtration hollow fiber membranes 3. Therefore, it is preferably set to 5000 mPa · s or less. More preferably, it is 3000 mPa · s or less.

  As a method of potting the hollow fiber membrane bundle with the fixing resin 2 and bonding and fixing it to the housing 1, known methods such as a centrifugal bonding method and a stationary bonding method are used. When it is desired to improve the curing shrinkage and strength of the fixing resin 2, the fixing resin 2 can contain fibrous materials such as glass fibers and carbon fibers, and fine powders such as carbon black, alumina, and silica.

  When the immersion filtration hollow fiber membrane module 19 of the present invention is installed in an immersion filtration apparatus and the immersion filtration is performed, it is preferable to provide an air diffuser at the lower part of the immersion filtration hollow fiber membrane module 19. As a result, suspended substances concentrated in the vicinity of the membrane surface by immersion filtration are easily discharged out of the module by air bubbling.

  In this case, since immersion filtration is stable for a long period of time and the physical washing of the hollow fiber membrane tends to be performed more reliably, the hollow fiber membrane module 19 for immersion filtration preferably has no casing. The distance between the housings 1 is preferably fixed by a support or the like that connects the adhesive fixing portions at both ends.

In the hollow fiber membrane module 19 for immersion filtration of the present invention, the filling rate of the hollow fiber membrane 3 for immersion filtration is in the range of 25 to 70% in order to increase the filtration capacity per volume and increase the cleaning efficiency by air bubbling. Is preferable.
Further, in order to give the hollow fiber membrane for immersion filtration 3 moderate rocking property and obtain an excellent membrane surface cleaning effect, the relaxation rate of the hollow fiber membrane for immersion filtration 3 between the housings 1 is 0. It is preferably 5% or more. On the other hand, if the film is too relaxed, bending or damage of the hollow fiber membrane 3 for immersion filtration tends to occur during immersion filtration. Therefore, the relaxation rate is preferably 5% or less.

When air bubbling is performed from the lower part of the hollow fiber membrane module 19 for immersion filtration in order to sufficiently swing the hollow fiber membrane 3 for immersion filtration and obtain a physical cleaning effect, the particle concentration in the water to be treated is relatively low. In high sewage drainage applications, it is preferable that the air supply amount per projected floor area of the module is 50 m ³ / m ² / h or more. On the other hand, excessive air bubbling causes bending and damage of the hollow fiber membrane 3 for immersion filtration and tends to increase energy consumption. Therefore, the air supply amount is set to 200 m ³ / m ² / h or less. Is preferred.
Air bubbling can be performed continuously during immersion filtration. Moreover, you may employ | adopt the cycle driving | operation which performs immersion filtration and air bubbling repeatedly by a fixed space | interval as needed.

In the hollow fiber membrane module 19 for immersion filtration of the present invention, it is important that the protrusion 5 is provided on the outer surface of each hollow fiber membrane 3 for immersion filtration. Due to the vibration of the hollow fiber membrane 3 for immersion filtration by air bubbling, the projections 5 come into contact with the deposits excessively deposited on the outer surface of the adjacent hollow fiber membrane 3, and this is effectively removed. be able to.
When the plurality of submerged filtration hollow fiber membranes 3 are swung by the protrusions 5, the effective filtration portions of the adjacent hollow fiber membranes are not easily brought into direct contact with each other. It is possible to prevent the deposits from being firmly fixed to the fine pores of the effective filtration portion, and to easily peel and remove the deposits on the film surface.
Moreover, the effective filtration part in a hollow fiber membrane circumferential direction can be formed discontinuously by forming the projection part 5.
As a result, the deposit on the effective filtration portion also becomes discontinuous in the circumferential direction of the hollow fiber membrane, and the cohesive force between the deposits decreases, so that the deposit tends to be easily peeled and removed by air bubbling or the like. is there.

  The present invention can be applied to various immersion filtration methods, and can be used for, for example, immersion pressure filtration. However, as described above, the present invention is more suitable for immersion suction filtration for a highly contaminated liquid. is there. The present invention can be suitably used particularly in water and sewage treatment applications and industrial wastewater treatment applications. By immersing the hollow fiber membrane module for immersion filtration of the present invention in water to be treated and reducing the pressure of the hollow part of the hollow fiber membrane for immersion filtration, filtered water can be obtained from the hollow part.

Example 1
Novatec HD HY540 (manufactured by Nippon Polyethylene Co., Ltd.), a high-density polyethylene having a density of 0.96 g / cm ³ and a melt flow rate of 1.0 g / 10 min, has a double tube structure with a discharge port diameter of 25 mm and an inner ring slit width of 4.0 mm. And air is introduced by a self-priming method using a hollow fiber shaping nozzle having 12 notches on the outer periphery, and melt spinning is performed at a spinning temperature of 165 ° C. and a winding speed of 70 m / min. An unstretched hollow fiber having 12 protrusions continuous in the longitudinal direction on the outer periphery was obtained.
This unstretched hollow fiber is 80% cold-stretched, then hot-stretched between slit heaters heated to 113 ° C. until the total stretch amount reaches 600%, and further heated with the slit heater heated to the same temperature. It became porous.
The hollow fiber membrane thus obtained had an inner diameter of 354 μm, a film thickness of 100 μm at the portion without the protrusion, a porosity of 72%, a height of the protrusion of 19 μm, and a width of the protrusion of 20 μm.
At this time, the ratio of the projected area of the protrusion to the outer surface with respect to the outer surface of the hollow fiber membrane when the protrusion was excluded was 14%.
4800 hollow fiber membranes for immersion were bundled to produce a hollow fiber membrane module for immersion filtration having an effective membrane length of 403 mm and a membrane area of 3 m ² shown in FIG.
At this time, the filling rate in the most dense place of the hollow fiber membrane was 60%, and the relaxation rate was 1.5%.

(Comparative Example 1)
A hollow fiber shaping nozzle having a double tube structure with a discharge port diameter of 25 mm and an inner ring slit width of 4.0 mm was used. Other conditions were the same as in Example 1, with an inner diameter of 354 μm, a film thickness of 100 μm, and a porosity of 72. % Hollow fiber membrane without protrusions was obtained.
This hollow fiber membrane was bundled to produce a hollow fiber membrane module for immersion filtration under the same conditions as in Example 1.

[Immersion filtration test]
Using a unit in which 20 hollow fiber membrane modules of Example 1 and Comparative Example 1 were arranged and integrated with each other at an interval of 18 mm, an immersion filtration test was carried out in a sewage treatment facility with a treatment flow shown in FIG.
In FIG. 3, the raw water that has flowed into the screen 6 is temporarily stored in the flow rate adjusting tank 7 after impurities are removed, and then supplied to the denitrification water tank 11 using the supply pump 8. The raw water supplied to the denitrification water tank 11 enters the membrane immersion water tank 13 via the supply pipe 15 and is circulated by the circulation pump 12 at a predetermined circulation magnification.
The raw water is biologically purified by activated sludge in the denitrification water tank 11 and the membrane immersion water tank 13. Removal of the nitrogen component in the raw water is performed by a so-called nitrification denitrification reaction by circulating sludge between the denitrification water tank 11 and the membrane immersion tank 13. Organic matter (BOD) in the raw water is aerobically oxidized and decomposed by the air discharged mainly from the air discharge portion of the air diffuser 16 disposed in the membrane immersion water tank 13.
Further, air is always discharged by the air diffuser 16 by the blower 18 and is also used as a physical cleaning means for the hollow fiber membrane module 19.
The purified water is separated from the activated sludge by membrane filtration by the hollow fiber membrane module 19. The filtered water is supplied to the membrane treatment water tank 24 by the filtration pump 22, and after being disinfected as necessary, it is discharged as treated water.
In this test, the suction side of the treated water is intermittently sucked by the filtration pump 22 to perform filtration, intermittent suction filtration is adopted, and the operation is performed with one cycle of intermittent suction filtration with a filtration time of 7 minutes and a stop time of 1 minute. Carried out.
In the immersion filtration test, the activated sludge concentration in the experiment was 8000 mg / L, the filtration flow rate per membrane area was 0.23 m ³ / m ² / d, and the air bubbling for cleaning was 120 m ³ / m ² / h per projected floor area. It went continuously. In addition, the unit in which the hollow fiber membrane module of Example 1 or Comparative Example 1 was integrated was operated in parallel in the same immersion water tank under the same operating conditions, and the membrane differential pressure at that time. Changes were measured. The result is shown in FIG.

  From FIG. 4, in the unit in which the hollow fiber membrane module (Example 1) having a protrusion is integrated, compared to the unit in which the hollow fiber membrane module (Comparative Example 1) having no protrusion structure is integrated, Despite the same operating conditions, the increase in membrane differential pressure is suppressed, and by using hollow fiber membranes with protrusions on the outer surface of each hollow fiber membrane, membranes in a high concentration suspension It is confirmed that even if filtration is continued, the physical cleaning effect by air bubbling is enhanced, and excessive deposits are less likely to be deposited on the membrane surface, and operation can be continued without deteriorating water permeability. did it.

  According to the present invention, in the treatment of purified water, industrial water, sewage, human waste, industrial wastewater, etc., and immersion filtration in a combined septic tank, etc., adhesion of suspended substances and organic substances in raw water without using extra cleaning energy Hollow fiber membrane for immersion filtration, hollow fiber membrane module for immersion filtration using the same, immersion filtration device, and immersion, which can reduce membrane fouling due to layers, clogging, solid matter, and suppress differential pressure increase A filtration method is provided.

Claims (13)

A hollow fiber membrane for immersion filtration having one or more protrusions on the outer surface ,
The hollow fiber membrane for immersion filtration, wherein the projected area ratio of the projections to the outer surface of the hollow fiber membrane when the projections are excluded is in the range of 1 to 20% . A hollow fiber membrane for immersion filtration having 8 or more protrusions on the outer surface ,
The hollow fiber membrane for immersion filtration, wherein the projected area ratio of the projections to the outer surface of the hollow fiber membrane when the projections are excluded is in the range of 1 to 20% .   The hollow fiber membrane for immersion filtration according to claim 1 or 2, wherein the protrusion has a shape continuous in the longitudinal direction of the hollow fiber membrane.   The hollow fiber membrane for immersion filtration according to any one of claims 1 to 3, wherein the protrusion has a height of 5 µm or more.   The hollow fiber membrane for immersion filtration according to any one of claims 1 to 4, wherein the protrusion has a width of 5 µm or more. A plurality of hollow fiber membranes for immersion filtration, wherein a plurality of hollow fiber membranes for immersion filtration having one or more protrusions on the outer surface are bonded and fixed to a housing ,
The hollow fiber membrane module for immersion filtration, wherein the projected area ratio of the projections to the outer surface with respect to the outer surface of the hollow fiber membrane when the projections are excluded is in the range of 1 to 20% . A plurality of hollow fiber membranes for immersion filtration, wherein a plurality of hollow fiber membranes for immersion filtration having 8 or more protrusions on the outer surface are bonded and fixed to a housing ,
The hollow fiber membrane module for immersion filtration, wherein the projected area ratio of the projections to the outer surface with respect to the outer surface of the hollow fiber membrane when the projections are excluded is in the range of 1 to 20% . An immersion filtration apparatus in which the hollow fiber membrane module for immersion filtration according to claim 6 or 7 is installed in an immersion water tank. The immersion filtration apparatus according to claim 8 , further comprising an air diffuser at a lower part of the hollow fiber membrane module for immersion filtration. The immersion water tank is filled with the water to be treated, and a plurality of hollow fiber membranes for immersion filtration in which a plurality of hollow fiber membranes for immersion filtration having one or more protrusions on the outer surface are bonded and fixed to the housing are immersed in the water to be treated. , An immersion filtration method for obtaining filtered water from a hollow portion of the hollow fiber membrane for immersion filtration ,
The immersion filtration method, wherein the projected area ratio of the projection to the outer surface of the hollow fiber membrane when the projection is excluded is in the range of 1 to 20% . The immersion water tank is filled with the water to be treated, and a plurality of hollow fiber membranes for immersion filtration having 8 or more protrusions on the outer surface bonded and fixed to the housing are immersed in the water to be treated. , An immersion filtration method for obtaining filtered water from a hollow portion of the hollow fiber membrane for immersion filtration ,
The immersion filtration method, wherein the projected area ratio of the projection to the outer surface of the hollow fiber membrane when the projection is excluded is in the range of 1 to 20% . While air bubbling from the air diffuser apparatus, and filtration using the immersion filtration hollow fiber membrane, according to claim 1 0 or 1 1 Immersion filtration method according. Wherein by depressurizing the hollow portion of the immersion filtration hollow fiber membrane, said immersion performs filtration hollow fiber membrane suction filtration using, immersion filtration method according to any one of claims 1 0 to 1 2.

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