JP2004008981A - Membrane separation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane separation apparatus having a membrane filtration performance stabilized for a long time by preventing sludge or the like from being accumulated around hollow fibers of a hollow fiber membrane cartridge. <P>SOLUTION: This membrane separation apparatus is composed of the hollow fiber membrane cartridge and a gas diffusing unit. The hollow fiber membrane cartridge is arranged vertically in this apparatus, which comprises many hollow fiber membranes, both ends of which are glued and fixed and which has openings of hollow fibers in the upper part and in the lower part a skirt-structured part for introducing a gas and gas introducing holes for introducing the gas into the outer surfaces of the hollow fibers. The gas diffusing unit is arranged below the skirt-structure part of the hollow fiber membrane cartridge, which has a plurality of gas diffusing holes per one hollow fiber membrane cartridge. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a membrane separation device used for water treatment.
[0002]
[Prior art]
Conventionally, for water purification treatment, industrial wastewater treatment, sewage treatment, and the like, a physical solid-liquid separation method such as coagulation sedimentation, sand filtration, and sedimentation separation has been performed. Highly treated solid-liquid separation by membrane separation has attracted attention in recent years because of the quality of treated water, safety of water quality, ease of management, and the like. In particular, in the case of membrane filtration raw water having high turbidity, a method of directly immersing the separation membrane in a tank, a tank, a pit, or the like containing the raw water and performing suction or gravity filtration is promising. The feature of such a membrane separation device is that turbidity on the membrane surface can be removed by diffusing gas from below. Japanese Patent Application Laid-Open No. 2000-107573 discloses a tank-type filtration membrane washing apparatus provided with a restricting orifice for uniformly supplying gas or liquid from the lower part of a hollow fiber in a tank-type filtration device in which a hollow fiber is suspended and supported. An apparatus is disclosed. Although this device is extremely effective as a tank type membrane filtration device, when the gas flow rate is large, the pressure loss of the gas flow is large, and depending on the flow rate, there is a problem that a blower having a low discharge pressure cannot be used.
[0003]
Japanese Patent Application Laid-Open No. Hei 5-277345 discloses a membrane filtration device comprising a cylindrical casing in a vertical direction and a filtration membrane element, and a tubular casing of 500 mm or more and 2000 mm or less and an air blowing port provided below the element. ing. Since a zone for dispersing air is provided in the lower casing portion, a space of 500 mm or more is required below the membrane element, and there is a problem that the depth direction cannot be used effectively.
[0004]
[Problems to be solved by the invention]
The present invention uniformly disperses the gas necessary for such membrane surface cleaning, prevents the accumulation of sludge and the like around the hollow fiber of the hollow fiber membrane cartridge, and provides a membrane separation exhibiting stable membrane filtration performance for a long time. It is intended to provide a device.
[0005]
[Means for Solving the Problems]
The present inventors have conducted intensive studies and as a result, have formed a large number of hollow fiber membranes, both ends are adhered and fixed, a hollow fiber opening is provided at the top, a skirt structure for introducing gas is provided at the bottom, and the gas is hollow. In a vertically installed hollow fiber membrane cartridge having a gas introduction hole to be introduced into the outer surface of a yarn and a membrane separation device having a gas diffusion hole at a lower portion of the skirt structure, the gas diffusion hole is formed per hollow fiber membrane cartridge. By using a plurality of membrane separation devices, a membrane filtration device exhibiting stable filtration performance for a long time has been invented.
[0006]
That is, the present invention is as follows.
1. It consists of a number of hollow fiber membranes, both ends are bonded and fixed, has an opening for the hollow fiber in the upper part, and has a skirt structure for introducing gas and a gas introduction hole for introducing the gas to the outer surface of the hollow fiber in the lower part. And a hollow fiber membrane cartridge installed vertically and a gas diffuser having a gas diffusion hole and installed at a lower portion of the skirt structure portion, wherein one hollow fiber membrane cartridge is provided. A membrane separation device comprising a plurality of gas diffusion holes per unit.
2. The gas diffusion holes of the air diffuser have a diameter equivalent to a circle of 5 to 30 mm, and the number of the gas diffusion holes is at least one per 40 square centimeters in the area of the upper part of the skirt structure. The membrane separation device as described in the above.
3. The gas introduction hole is a through hole having a circle equivalent diameter of 6 to 30 mm. Or 2. The membrane separation device as described in the above.
[0007]
In order to separate solids from a solution containing solids such as turbidity using a hollow fiber membrane and obtain a clear filtrate, gas is diffused from the bottom at the same time as filtration, and the scrubbing effect when the gas rises Thus, a membrane filtration device that gives a turbulent flow to the liquid flow on the surface of the membrane and removes suspended matter and the like is effective. In order to operate this membrane filtration stably for a long time, it is important to uniformly diffuse gas into the hollow fiber membrane. For this purpose, a hollow fiber membrane cartridge having a skirt structure and a gas introduction hole at the bottom has a high space utilization rate, and the diffused gas efficiently hits the surface of the hollow fiber membrane. The skirt structure is to distribute the gas diffused from the lower part to the gas introduction holes evenly, but if the gas flow rate increases or the gas ejection pressure increases, the gas is not sufficiently dispersed into the gas introduction holes. become. The present inventors have found that a membrane separation device having an air diffusion structure having a simple structure below the skirt structure is extremely effective in filtering raw water having high turbidity. By providing a plurality of gas diffusion holes in the gas diffusion device at the bottom of the skirt structure, the gas to be diffused can be dispersed and uniformly introduced into the gas introduction holes at the top, which can improve the membrane filtration performance for a long time. It is effective to keep it stable.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described focusing on its preferred embodiments.
The equivalent circle diameter of the gas diffusing holes of the diffusing device constituting the present invention is preferably 6 mm to 30 mm, though it depends on the type and amount of the turbid substance. The equivalent diameter of the gas diffusing hole is 6 mm or more in terms of preventing clogging of turbid gas diffusing holes and preventing pressure loss of gas diffusing, preventing pressure fluctuation of gas diffusing, preventing inflow of turbid gas diffusing holes. In this respect, the thickness is preferably 30 mm or less.
[0009]
Further, it is preferable that the number of gas diffusing holes is one or more per 40 square centimeters of the horizontal cross-sectional area of the skirt structure portion in order to uniformly disperse the diffused gas into the upper gas introducing holes. The “area of the upper part of the skirt structure” in the present application refers to the area of the skirt structure closest to the gas introduction hole in the module cross-sectional direction. It is structurally preferable to provide a plurality of gas diffusion holes having substantially the same circle equivalent diameter.
[0010]
In addition, although the direction of air diffusion of the gas diffusion holes is normally upward, air may be diffused downward. When the direction of air diffusion is downward, the gas diffusion holes are less likely to be closed.
The gas introduction hole of the present invention is preferably a through hole having an equivalent circle diameter of 6 to 30 mm. The gas introduction hole is for uniformly supplying the scattered gas to the hollow fiber, but the equivalent circle diameter of the gas introduction hole is to prevent clogging of turbid matter and maintain long-term stable membrane separation performance. Is preferably 6 mm or more and 30 mm or less from the viewpoint of uniformly supplying a gas to the hollow fibers and preventing turbidity from remaining between the hollow fibers.
[0011]
Further, the shape of the gas introduction hole is usually circular, but may be elliptical, triangular, quadrangular polygonal, or star-shaped.
The introduced gas here is air or oxygen when the raw filtered water is activated sludge, and becomes nitrogen gas or a reaction gas when the raw filtered water is a fermentation liquid.
[0012]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a hollow fiber membrane cartridge and an air diffuser constituting the membrane separation device of the present invention. Reference numeral 1 denotes a hollow fiber membrane, which is a membrane used for ordinary turbidity removal, such as a reverse osmosis membrane, an ultrafiltration membrane, and a microfiltration membrane. The material of the hollow fiber membrane 1 is not particularly limited, and polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyetherimide, polyamide, polyetherketone, polyetheretherketone, polyethylene, polypropylene, poly-4 methylpentene, Examples include hydrophilic polyethylene, cellulose, cellulose acetate, polyvinyl alcohol, polyvinylidene fluoride, polyethylene-tetrafluoroethylene copolymer, and polytetrafluoroethylene. Alternatively, these composite material films can also be used.
[0013]
The hollow fiber membrane cartridge is installed vertically, and filtered water is obtained from a water collecting pipe connected to the upper water collecting part 2 by pump suction, siphon or head pressurization.
In some cases, a membrane separation device as shown in FIG. 1 is immersed in raw water of high turbidity such as activated sludge and used. Reference numeral 6 shown in FIG. 1 denotes filtration raw water, which diffuses gas from a plurality of gas diffusion holes 5 of the diffusion device 7 to a lower portion of the skirt structure 3. The gas diffused is uniformly dispersed in the skirt structure while staying in the skirt structure, and is diffused through the gas introduction holes 4 to the outer surface of the upper hollow fiber. The filtered raw water is supplied to the hollow fiber from the peripheral portion by the gas lift effect of the diffused gas, and is filtered to obtain clear filtered water.
[0014]
【Example】
Embodiments of the present invention will be described below.
[0015]
Embodiment 1
As shown in FIG. 2, a membrane composed of a hollow fiber membrane cartridge having a gas introduction hole of 10 mm in the skirt structure portion and an air diffusion device having two gas diffusion holes having an inner diameter of 10 mm installed at the lower portion of the skirt structure portion. A separation device was prepared. The membrane area of the hollow fiber membrane was 7 square meters, and the material used was a microfiltration membrane made of polyvinylidene fluoride. The effective length was 1000 mm, the diameter of the resin portion of the hollow fiber bonding portion was 90 mm, and the area of the skirt structure was 64 square centimeters. That is, one gas diffusion hole is provided per 32 square centimeters. The membrane separation device was immersed in high-concentration activated sludge and filtered while diffusing air from below. While air of 5 Nm ³ / hr was diffused from the air diffuser, suction filtration was performed with a suction pump so that the membrane filtration flux became 0.6 m ³ / membrane area m ² / day. At this time, the transmembrane pressure was 20 kPa and was stable for one month.
[0016]
The concentration MLSS of the activated sludge tank during the evaluation period was 10,000 mg / L on average, and the temperature was 25 ° C.
As the treated water for the activated sludge, a synthetic sewage having the following composition was used, and the BOD-SS load was 0.03 kg / kg / day.
The synthetic sewage composition (g / L) was peptone 0.35, meat extract 0.23, urea 0.059, NaCL 0.059, KCL 0.015, CaCL ₂ 0.015, MgSO ₄ 0.012, K ₂ HPO ₄ 0.935, KH ₂ PO ₄ 0.117, and tap water 1 (L) were used.
[0017]
Embodiment 2
As shown in FIG. 3, a membrane separation device including a hollow fiber membrane cartridge having a gas introduction hole of 10 mm in a skirt structure portion and an air diffusion device having four gas diffusion holes with an inner diameter of 10 mm installed at a lower portion of the skirt. Was prepared. The membrane area of the hollow fiber membrane was 25 square meters, and the material used was a microfiltration membrane made of polyvinylidene fluoride. The effective length was 1000 mm, the diameter of the resin portion of the hollow fiber bonding portion was 167 mm, and the area of the skirt portion was 167 square centimeters. There will be one gas diffusing hole per 42 square centimeters. This hollow fiber membrane element was immersed in high-concentration activated sludge, and filtered while diffusing air from below. While aerating the air at 18 Nm ³ / hr from the air diffuser, suction filtration was performed using a suction pump such that the membrane filtration flux became 0.6 m ³ / membrane area m ² / day. At this time, the transmembrane pressure was 20 kPa and was stable for one month.
[0018]
The concentration MLSS of the activated sludge tank during the evaluation period was 10,000 mg / L on average, and the temperature was 25 ° C.
[0019]
[Comparative Example 1]
A membrane separation device including the same hollow fiber membrane cartridge as in Example 1 and an air diffusion device as shown in FIG. 4 and having one gas diffusion hole with an inner diameter of 10 mm and installed below the skirt structure was prepared. The area of the skirt structure was 64 square centimeters. That is, one gas diffusion hole is provided per 64 square centimeters. While aerating ⁵ Nm ³ / hr of air from the lower air diffuser, suction filtration was performed with a suction pump such that the membrane filtration flow rate was 0.6 m ³ / membrane area m ² / day. The transmembrane pressure gradually increased from 20 kPa in one month and reached 50 kPa. When the hollow fiber membrane cartridge was observed, a part of the gas introduction hole was closed, and a large amount of sludge was attached around the hollow fiber membrane.
[0020]
The concentration MLSS of the activated sludge tank was 10,000 mg / L, and the temperature was 25 ° C.
[0021]
【The invention's effect】
It consists of a number of hollow fiber membranes, both ends are bonded and fixed, has an opening for the hollow fiber at the top, a skirt structure for gas introduction at the bottom and a gas introduction hole for introducing the gas to the outer surface of the hollow fiber. A hollow fiber membrane cartridge comprising a hollow fiber membrane cartridge having a gas diffusion hole and a gas diffusion hole and being provided at a lower portion of the skirt structure portion. By using a membrane separation device, which has a plurality of gas diffusion holes per unit, the gas required for cleaning the membrane surface is evenly dispersed, and sludge accumulates around the hollow fibers of the hollow fiber membrane cartridge. This makes it possible to realize stable membrane filtration performance for a long time.
[Brief description of the drawings]
FIG. 1 is a schematic diagram schematically illustrating an embodiment of the present invention, in which (a) is a cross-sectional view and (b) is a bottom view of a skirt structure portion.
FIGS. 2A and 2B are schematic diagrams schematically illustrating a membrane separation device used in Example 1, in which FIG. 2A is a horizontal cross-sectional view of an upper part of a skirt structure, FIG. c) is a side view thereof. Note that the broken line in (b) is an outline projection line of the skirt structure, and indicates the positional relationship between the gas diffusion holes and the skirt structure.
3A and 3B are schematic diagrams schematically illustrating a membrane separation device used in Example 2, (a) is a horizontal cross-sectional view of an upper part of a skirt structure, (b) is a plan view showing gas diffusion holes, c) is a side view thereof. Note that the broken line in (b) is an outline projection line of the skirt structure, and indicates the positional relationship between the gas diffusion holes and the skirt structure.
FIGS. 4A and 4B are schematic diagrams schematically illustrating the membrane separation device used in Comparative Example 1, in which FIG. 4A is a horizontal cross-sectional view of an upper part of a skirt structure, FIG. c) is a side view thereof. Note that the broken line in (b) is an outline projection line of the skirt structure, and indicates the positional relationship between the gas diffusion holes and the skirt structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hollow fiber 2 Filtration water collecting part 3 Skirt structure part 4 Gas introduction hole 5 Gas diffusion hole 6 Filtration raw water 7 Diffusion device 8 Induction gas 9 Filtration raw water + introduction gas

Claims (3)

It is composed of a number of hollow fiber membranes, both ends are bonded and fixed, the upper part has an opening for the hollow fiber, the lower part has a skirt structure for gas introduction and a gas introduction hole for introducing the gas to the outer surface of the hollow fiber. A hollow fiber membrane cartridge comprising a hollow fiber membrane cartridge having a gas diffusion hole and a gas diffusion hole and being provided at a lower portion of the skirt structure. A membrane separation device having a plurality of gas diffusion holes per unit. 2. The membrane according to claim 1, wherein the gas diffuser has a circle-equivalent diameter of 5 to 30 mm, and the number of gas diffusers is at least one per 40 square centimeters of the upper part of the skirt structure. Separation device. 3. The membrane separation device according to claim 1, wherein the gas introduction hole is a through hole having a circle equivalent diameter of 6 to 30 mm.

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