JP4154879B2 - Hydrophilization method and submersion method of rotating flat membrane - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of hydrophilizing a rotating flat membrane and a water immersion method, and more particularly to a method of hydrophilizing a rotating flat membrane and a water immersion method in a rotating flat membrane separator for filtering water and waste water.
[0002]
[Prior art]
In recent years, many membrane separators have been put into practical use as solid-liquid separators for filtration. There are various module shapes such as a hollow fiber type, a spiral type, and a flat membrane type in the membrane separation apparatus, and they are properly used depending on the application. In the rotating flat membrane module, a rotating flat membrane disc having a rotating flat membrane coated on the disc is mounted on a rotating shaft, and filtration is performed while rotating the rotating flat membrane disc. Since this rotating flat membrane module obtains the membrane surface flow rate by rotation to prevent the dirt layer from adhering to the surface of the rotating flat membrane, the other membrane module obtains the membrane surface flow rate by the circulation flow rate of the liquid to be treated. Unlike, it can be operated with low power.
[0003]
By the way, in order to obtain a simple storage method, the rotating flat membrane disk before use is treated by applying glycerin on the surface of the rotating flat membrane to prevent alteration of the polymer and stored in a dry state. Yes. The rotating flat membrane disk at the time of use is subjected to a filtration treatment after the rotating flat membrane stored in a dry state is wetted by hydrophilization.
[0004]
The procedure for hydrophilizing the rotating flat membrane coated with glycerin is that the rotating flat membrane disc mounted on the rotating shaft is rotated at a low rotation (peripheral speed of about 0.5 m / s) while a hydrophilizing agent (for example, ethanol). A nozzle for spraying the solution) is inserted between each rotating flat membrane disk. In this state, the glycerin applied to the rotating flat membrane is removed by spraying the hydrophilizing agent from the nozzle onto the surface of the rotating flat membrane. When the hydrophilization treatment is performed, the surface of the rotating flat membrane changes from white to translucent, and this can be confirmed visually.
[0005]
[Problems to be solved by the invention]
However, since the distance between the rotating flat membrane disks is narrow, it is actually impossible to confirm whether the rotating flat membrane near the rotating shaft has been hydrophilicized. Does not permeate, reducing the effective area contributing to filtration. Therefore, for the sake of safety, an excess amount of the hydrophilizing agent is sprayed more than the actual amount required for hydrophilization, not only the hydrophilizing agent is wasted, but also the amount of waste liquid generated is increased and the hydrophilicity is increased. There is a disadvantage that the time required for the conversion process becomes longer.
[0006]
Also, after exchanging the rotating flat membrane, or evacuating the membrane separation tank, removing the rotating flat membrane, reattaching the rotating flat membrane after inspection, and starting the operation of the rotating flat membrane separator, or for some reason After the air enters from the treated water piping side, when the rotating flat membrane disk in the air is submerged again, the air accumulates inside the rotating flat membrane (disk side). The hydrophilized rotating flat membrane permeates water but does not permeate air, so that air accumulated inside the rotating flat membrane does not escape from the membrane surface. Further, since the suction for filtration is performed through the rotation shaft at the center of the rotating flat membrane, the air accumulated above the rotation shaft portion cannot be sucked and is very difficult to remove. As a result, there has been a problem that the rotating flat membrane swells in water due to the accumulated air, and the rotating flat membranes adjacent to each other are rubbed and damaged when the rotating flat membrane rotates. In this case, if the suction is continued without rotating the rotating flat membrane, the air gradually escapes. However, if the rotating flat membrane is not rotated, the rotating flat membrane is blocked during that time.
[0007]
The present invention has been made in view of such circumstances. The entire rotating flat membrane can be reliably hydrophilized in a short time and the amount of the hydrophilizing agent used during the hydrophilizing treatment can be reduced. An object of the present invention is to provide a hydrophilic method and a water immersion method for a rotating flat membrane that can prevent the rotating flat membrane from being damaged or clogged because air can be prevented from accumulating inside the rotating flat membrane during water immersion.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is directed to a membrane separation tank having a hollow rotating shaft in which a plurality of disk-shaped rotating flat membrane disks each having a rotating flat membrane coated thereon are arranged at predetermined intervals. The raw water to be treated supplied to the membrane separation tank is filtered by the rotating flat membrane disk, and the filtrate is guided from the rotating flat membrane disk to the inside of the rotating shaft. In the method of hydrophilizing the rotating flat membrane in the rotating flat membrane separator for discharging to the inside of the rotating flat membrane disk during the hydrophilization process of spraying a hydrophilizing agent to the rotating flat membrane to hydrophilize the rotating flat membrane. It is characterized by a reduced pressure state.
[0009]
According to the present invention, since the hydrophilizing agent is sprayed with the inside of the rotating flat membrane disk in a reduced pressure state during the hydrophilic treatment of the rotating flat membrane, an attractive force for attracting the hydrophilizing agent into the rotating flat membrane is generated. . As a result, the sprayed hydrophilizing agent immediately enters the pores of the membrane surface without flowing through the membrane surface. In this case, an attractive force is also generated in the rotating flat membrane portion near the rotating shaft, so that the hydrophilizing agent spreads reliably over the entire rotating flat membrane, and the coating agent such as glycerin applied to the membrane surface is removed. As a result, the entire rotating flat membrane can be reliably hydrophilized in a short time and the amount of hydrophilizing agent used during the hydrophilization can be reduced.
[0010]
According to a second aspect of the present invention, in order to achieve the above object, a hollow rotating shaft in which a plurality of disc-shaped rotating flat membrane disks each having a rotating flat membrane coated on a disk are arranged in parallel at a predetermined interval, An apparatus that is rotatably disposed in a tank, filters raw water to be treated supplied into the membrane separation tank through the rotating flat membrane disk, and guides the filtrate from the rotating flat membrane disk to the inside of the rotating shaft. In the method of submerging the rotating flat membrane in the rotating flat membrane separator for discharging to the outside, the rotating flat membrane disc is decompressed before the rotating flat membrane disc is immersed in the raw water to be treated.
[0011]
According to the present invention, since the rotating flat membrane disk is depressurized before the rotating flat membrane disk is immersed in the raw water to be treated, air accumulated inside the rotating flat membrane (disk side) Can be removed. In this case, since the rotating flat membrane does not transmit air, once the accumulated air passes through, the air does not collect again inside the rotating flat membrane. Accordingly, if the rotating flat membrane is immersed in the raw water to be treated in this state, the rotating flat membrane does not swell with air. Thereby, breakage and blockage of the rotating flat membrane can be prevented.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of a hydrophilization method and a water immersion method according to the present invention will be described in detail with reference to the accompanying drawings.
[0013]
FIG. 1 is a perspective view in which a part of a rotating flat membrane separation apparatus to which the hydrophilizing method and water immersion method according to the present invention are applied is cut out, and FIG. 2 is an overall configuration diagram.
[0014]
As shown in these drawings, the rotary flat membrane separation apparatus 10 according to the present invention is mainly provided with two hollow rotary shafts 14 and 14 parallel to the left and right in the membrane separation tank 12 so as to be freely rotatable, A plurality of rotating flat membrane disks 16, 16... Having a disk shape are supported on each rotating shaft 14.
[0015]
The rotating flat membrane disk 16 is configured by coating a water-permeable disc 13 with a rotating flat membrane 15 such as a microfiltration membrane or an ultrafiltration membrane, and the filtered water filtered by the rotating flat membrane 15 is contained in the disc 13. Then, it is guided into the hollow rotary shaft 14 through a hole (not shown) that communicates the disk 13 and the rotary shaft 14. As the material of the rotating flat film 15, a polymer resin film such as polystyrene, polypropylene, polyethylene, and polyolefin can be used. The diameter of the rotating flat membrane disk 16 is, for example, 750 mm, and the diameter of a collar (not shown) is about 200 mm. Further, the rotating flat membrane disks 16 supported by the two rotating shafts 14 arranged side by side are configured such that a part of the adjacent rotating flat membrane disks 16 overlap and rotate in the same direction. . Due to the rotation in the same direction, the rotating direction is opposite in the overlapping portion of the rotating flat membrane disks 16 and turbulence is generated. In this case, it is preferable to change the number of rotations according to the size of the diameter of the rotating flat membrane disk 16.
[0016]
Both ends of the rotating shaft 14 extend outside the membrane separation tank 12, and water-tightness is ensured by the shaft sealing means 18 from the membrane separation tank 12. One of the rotating shafts 14 is connected to the motors 20 and 20, respectively, so that the rotating shaft 14 and the rotating flat membrane disk 16 are integrally rotated, and the other is connected to the filtrate pipe 22.
[0017]
The filtrate pipe 22 is composed of branch pipes 24 and 24 connected to the two rotating shafts 14 respectively, and a trunk pipe 26 where the branch pipes 24 merge. One of the trunk pipes 26 is air via a three-way valve 27. The pipe 25 and the other are connected to the filtrate water pipe 31. A suction pump 28 is provided in the filtrate pipe 31 and a vacuum pump 29 is provided in the air pipe 25. The connection between the rotating shaft 14 and the branch pipe 24 is connected via connecting devices 30 and 30 for preventing the rotation of the rotating shaft 14.
[0018]
A nozzle 36 for spraying a hydrophilizing agent is disposed between the rotating flat membrane disks 16 and between the rotating flat membrane disks 16 and the wall of the membrane separation tank 12. To the hydrophilizing agent supply device 32.
[0019]
Next, when the rotary flat membrane 15 of the rotary flat membrane separator 10 configured as described above is subjected to a filtration operation, a hydrophilization treatment method in which the rotary flat membrane 15 is hydrophilized and then immersed in the raw water to be treated; The flooding method will be described.
[0020]
First, in a state where raw water to be treated does not flow into the membrane separation tank 12, the rotary flat membrane disk 16 is rotated at a low rotational speed of about 10 rpm, and the vacuum pump 29 is operated with the three-way valve 27 on the air pipe 25 side. As a result, the inside of the rotating flat membrane disk 16 is in a reduced pressure state, and in this state, a hydrophilizing agent such as a 30% ethanol solution is sprayed onto the rotating flat membrane 15 from the nozzle 36. Since the attracting force for attracting the hydrophilizing agent into the rotating flat membrane 15 is generated by this decompression, the sprayed hydrophilizing agent immediately enters the pores of the membrane surface without flowing through the membrane surface of the rotating flat membrane 15. . In this case, an attracting force is also generated in the rotating flat film 15 near the rotating shaft 14, so that the hydrophilizing agent spreads over the entire rotating flat film 15 and removes the coating agent such as glycerin applied to the rotating flat film 15. To do. When the hydrophilic treatment is finished, the vacuum pump 29 is stopped. Thereafter, the rotating flat membrane disk 16 is washed with water, and the hydrophilizing agent remaining in the rotating flat membrane 15 is dissolved in water and removed. Thereby, the whole rotation flat film 15 can be reliably hydrophilized in a short time, and the amount of the hydrophilizing agent used during the hydrophilization treatment can be reduced.
[0021]
Next, when the hydrophilic treatment of the rotary flat membrane 15 is completed, the raw water to be treated is fed into the membrane separation tank 12 from the raw water pipe 38 while the vacuum pump 29 is operated again and the rotary flat membrane disk 16 is kept in a reduced pressure state. Let it flow. As a result, the rotary flat membrane disk 16 is submerged in the raw water to be treated in a state in which the air accumulated inside the rotary flat membrane 15 (disk side) is removed. Will not swell. Once the suction by the vacuum pump 29 is performed, the rotating flat membrane 15 does not transmit air, so the accumulated air can be easily removed, and once removed, the air will not accumulate again inside the rotating flat membrane 15. . Therefore, when the rotating flat membrane disk 16 is immersed in the raw water to be treated and the filtration operation is performed, the rotating flat membrane 15 does not swell due to air, so that the rotating flat membranes 15 come into contact with each other by the rotation of the rotating flat membrane disk 16. The rotation flat membrane 15 can be prevented from being damaged. Further, since it is not necessary to stop the rotation of the rotating flat membrane disk 16 at the start of the filtering operation in order to remove the air accumulated inside the rotating flat membrane 15 as in the prior art, the rotating flat membrane at the start of the filtering operation is not necessary. 15 is not blocked.
[0022]
In the above-described method for immersing the rotating flat film 15, even if the vacuum pump 29 is operated in a state where part or all of the rotating flat film 15 is submerged, the inside of the disk 13 is not depressurized and the pressure is not reduced. Air remains. Therefore, it is important to operate the vacuum pump 29 in a state where no part of the rotating flat membrane 15 is submerged.
[0023]
When the hydrophilization treatment of the rotating flat membrane 15 and the inundation into the raw water to be treated are finished, the three-way valve 27 is switched to the suction pump 28 side and the filtration operation is started. The filtration operation is performed by operating the suction pump 28 while rotating the rotating flat membrane disk 16 by the motor 20. That is, by operating the suction pump 28, the inside of the rotating flat membrane disk 16 is decompressed via the filtrate pipe 22 and the rotating shaft 14, and the liquid to be treated in the membrane separation tank 12 is sucked into the rotating flat membrane disk 16. Filtration is performed to remove deposits in the liquid to be treated, and a cake layer (not shown) is formed on the surface of the rotating flat membrane disk 16. The filtered water that has passed through the rotary flat membrane disk 16 is drawn out of the rotary flat membrane separator 10 through the rotary shaft 14 and the filtrate pipe 22.
[0024]
In the present embodiment, an example in which the rotating flat membrane disk 16 is hydrophilized before the rotating flat membrane separator 10 is used has been described. The hydrophilic treatment method of the present invention can also be applied when spraying a high-concentration ethanol solution onto the rotating flat membrane disk 16 when the surface of the membrane disk 16 is dry and cannot pass water. Furthermore, in the present embodiment, the example of the hydrophilic treatment of the rotating flat membrane disk 16 has been described. However, the present invention is not limited to this, and other types of membrane modules may be used. By maintaining in a reduced pressure state, the amount of the hydrophilizing agent used for the hydrophilization treatment can be reduced, and the hydrophilization time can be shortened.
[0025]
【The invention's effect】
As described above, according to the hydrophilizing method and the water immersion method of the rotating flat membrane according to the present invention, the entire rotating flat membrane can be reliably hydrophilized in a short time and the amount of the hydrophilizing agent used during the hydrophilizing treatment can be reduced. In addition, air can be prevented from accumulating inside the rotating flat membrane when the rotating flat membrane is submerged, so that the rotating flat membrane can be prevented from being damaged or blocked.
[Brief description of the drawings]
FIG. 1 is a perspective view in which a part of a rotating flat membrane separator to which a hydrophilizing method and a water immersion method according to the present invention are applied is cut away. FIG. 2 is a rotating flat membrane separator to which the present invention is applied. Overall configuration diagram [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Rotating flat membrane separator, 12 ... Membrane separation tank, 13 ... Disc, 14 ... Rotating shaft, 15 ... Rotating flat membrane, 16 ... Rotating flat membrane disc, 18 ... Shaft sealing means, 20 ... Motor, 22 ... Filtrate Pipe, 24 ... Branch pipe, 25 ... Air pipe, 26 ... Trunk pipe, 27 ... Three-way valve, 28 ... Suction pump, 29 ... Vacuum pump, 30 ... Connecting device, 31 ... Filtrated water pipe, 32 ... Hydrophilizing agent supply device 34 ... Supply pipe 36 ... Nozzle 38 ... Raw water piping

Claims (2)

A hollow rotating shaft in which a plurality of disc-shaped rotating flat membrane disks each having a rotating flat membrane coated on a disk are arranged in parallel at a predetermined interval is rotatably disposed in the membrane separation tank and supplied into the membrane separation tank. Of the rotary flat membrane in the rotary flat membrane separator for filtering the raw water to be treated with the rotary flat membrane disc and guiding the filtrate from the rotary flat membrane disc to the inside of the rotary shaft and discharging it outside the device. In the method
A method of hydrophilizing a rotating flat membrane, wherein the rotating flat membrane disk is depressurized during a hydrophilization treatment in which a hydrophilizing agent is sprayed onto the rotating flat membrane to make the rotating flat membrane hydrophilic. A hollow rotating shaft in which a plurality of disc-shaped rotating flat membrane disks each having a rotating flat membrane coated on a disk are arranged in parallel at a predetermined interval is rotatably disposed in the membrane separation tank and supplied into the membrane separation tank. Of the rotary flat membrane in the rotary flat membrane separator for filtering the raw water to be treated with the rotary flat membrane disc and guiding the filtrate from the rotary flat membrane disc to the inside of the rotary shaft and discharging it outside the device In
A method for immersing a rotating flat membrane, wherein the rotating flat membrane disc is depressurized before the rotating flat membrane disc is immersed in the raw water to be treated.

Images