JP2002126472A - Solid-liquid separation membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane for solid-liquid separation, which produces a large amount of permeated liquid and exhibits high SS separation performance. SOLUTION: The membrane for the solid-liquid separation is formed from a composite membrane composed of a base material membrane having polygonal holes, each being at least triangle, and a polymer film. The shape of each hole is such that each angle part of the polygon being at least triangle has a roundish shape. Further, the membrane for the solid-liquid separation satisfies such requirements that (a) the average hole diameter is 10 to 90 μm and the hole diameter distribution defined by formula: (L-M)/M}×100 (L is the diameter of the smallest hole and M is an average hole diameter) is within ±20%, (b) the opening ratio is 15 to 60% and (c) the thickness is 50 to 300 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a solid-liquid separation membrane capable of stably exhibiting S (suspended particle) separation performance for a long period of time and a method for producing a solid-liquid separation membrane suitable for producing the solid-liquid separation membrane.

[0002]

2. Description of the Related Art
In a solid-liquid separation treatment of a liquid containing SS, such as a suspension or sludge, an inexpensive nonwoven fabric having a high water permeation rate has been used as a filtering material. For example, Japanese Patent Application Laid-Open No. 61-17491
No. 2 discloses a filter cloth having a nap portion made of synthetic fiber, having a directional index of 1.2 to 10, a concavo-convex index of 0.5 or less, and a specific surface area of the napped synthetic fiber of 9 × 10 ^3. cm
There is disclosed a filter cloth for solid-liquid separation of ² / g or more.

[0003] However, when a liquid containing a high concentration of SS such as a suspension or activated sludge is generally subjected to solid-liquid separation treatment using a nonwoven fabric, the pore diameter (gap) of the nonwoven fabric is larger than the SS diameter to be separated. Therefore, the solid-liquid separation becomes insufficient and the SS concentration in the permeate increases, and the SS penetrating into the nonwoven fabric causes clogging, so-called fouling occurs, and the permeate amount is significantly reduced.

[0004] On the other hand, a dynamic filtration method is known as a filtration method for reducing clogging of a nonwoven fabric at the time of solid-liquid separation of activated sludge liquid. In this filtration method, solid-liquid separation is not achieved by a filter material, but a dynamic layer made of activated sludge formed on a filtration surface substantially performs solid-liquid separation. By employing this method, a high permeate volume and excellent SS removal can be achieved at the same time.

Japanese Patent No. 2888581 discloses a solid-liquid separation method in which a bag-shaped filter made of a water-permeable sheet is immersed in an aeration tank above the aeration tank. Is disclosed in
No. 75 discloses a hollow filtration having a separation particle size of 30 μm or more and a thickness of 2 mm or less, having an inflow portion made of a water-permeable supporting material as at least a part of a peripheral wall and an outflow portion as an opening. There is disclosed a sewage treatment apparatus in which a body is immersed and filtered by a head difference from a subsequent tank. In these prior arts, a nonwoven fabric is used as a filter.

However, even if such a dynamic filtration method is employed, the nonwoven fabric has various sizes of fiber gaps, so that clogging inside the nonwoven fabric due to particles of activated sludge or the like is liable to occur. It becomes remarkable in the region. For this reason, it is desired to have a filter medium for solid-liquid separation that has a high permeate volume and can maintain the initial permeate volume for a long period of time without causing clogging as much as possible.

Kiso et al. Presented at the 1998 Japan Society of Civil Engineers 53rd Annual Scientific Lecture on dynamic filtration of activated sludge using nylon nets with openings of 100 μm and 150 μm. Among these, it has been concluded that those having a mesh size of 100 μm are the best. However, in order to lower the concentration of SS contained in the permeate, it is considered that a net having a smaller opening is required. However, if the opening is made smaller, clogging generally tends to occur.

Accordingly, an object of the present invention is to provide a solid-liquid separation membrane capable of stably exhibiting a high permeate volume and excellent SS removal for a long period of time because clogging is extremely unlikely to occur. .

[0009]

Means for Solving the Problems The present inventors, in addition to the requirement that the shape of the holes is rounded, as well as the requirement of adjusting the filtration performance, include three requirements of the average pore diameter, the porosity and the thickness.
By selecting the requirements and associating these three requirements with each other so as to exhibit the maximum filtration capability, it has been found that these requirements act synergistically to greatly improve the solid-liquid separation capability.

That is, according to the present invention, the shape of the hole is a shape in which the corners of a polygon of three or more are rounded, (a) the average hole diameter is 10 to 90 μm, and the following formula: (L -M)
/ M × 100 (L is the minimum pore size, M is the average pore size), the pore size distribution is within ± 20%, and (b) the aperture ratio is 1
Provided is a solid-liquid separation membrane having each requirement of 5 to 60% and (c) a thickness of 50 to 300 μm.

The term "average pore diameter" used in the present invention refers to the diameter when the pore is circular, and the diameter of the inscribed circle when the pore is polygonal.

In the present invention, the shape of the hole is a circle or a shape similar to the circle, and the following formula: 1 ≦ R / r <√2
(R is the maximum value from the center point of the hole to the peripheral wall portion, and r is the minimum value from the center point of the hole to the peripheral wall portion). When the shape of the hole is elliptical, R is the major axis and r is the minor axis.

Further, the solid-liquid separation membrane in each of the above-mentioned inventions is preferably 3
It is preferably formed of a composite film of a base film having a polygonal or more polygonal hole and a polymer film.

Further, according to the present invention, when the solid-liquid separation membrane is the above-mentioned composite membrane, the surface of a substrate membrane having triangular or more polygonal pores made of a material selected from metals other than iron and synthetic fibers is provided. Provided is a method for producing a solid-liquid separation membrane which is treated with a polymer solution for forming a film.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The solid-liquid separation membrane of the present invention has a polygonal shape in which the corners of a polygon having a triangle or more, preferably a rectangle or more are rounded. The shape is a circle or a shape close to a circle, and the following formula: 1 ≦ R / r
It is preferable to satisfy the relationship of <√2 (R indicates the maximum value from the center point of the hole to the peripheral wall portion, and r indicates the minimum value from the center point of the hole to the peripheral wall portion).

The solid-liquid separation membrane of the present invention further comprises:
It satisfies the three requirements of (a) average pore diameter, (b) porosity, and (c) thickness.

The average pore diameter of (a) is 10 to 90 μm, preferably 30 to 80 μm, and has the following formula: (LM) / M
The pore size distribution defined by × 100 (L represents the minimum pore size and M represents the average pore size) is within ± 20%, preferably within ± 15%.

The porosity of (b) is 15 to 60%, preferably 20 to 50%.

The thickness of (c) is 50 to 300 μm, preferably 60 to 200 μm.

The solid-liquid separation membrane of the present invention is preferably composed of a composite membrane of a substrate membrane having polygonal pores of at least triangular, preferably at least quadrangular, and a polymer membrane.

The substrate film having polygonal holes of three or more triangles is preferably selected from metals and synthetic resins except for iron, and includes nets and nonwoven fabrics. Nets are preferable.

Examples of the metal include stainless steel, aluminum, copper, silver, copper and the like, and stainless steel is preferable. As the synthetic resin, polyester, polystyrene,
Polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, poly (meth) acrylate, cellulose derivatives such as viscose rayon and cellulose acetate, polyolefins such as polyethylene and polypropylene, polycarbonate, polyamide, polyesteramide, polyimide, Examples thereof include polyether esters, copolymers, blends and cross-linked products thereof. Polyester, polyethylene, polypropylene and nylon are preferred, and stainless steel, polyester and polyethylene are preferred.

The net can be provided with antibacterial properties,
As a method of imparting antibacterial properties, materials having antibacterial properties,
For example, in addition to silver, copper, and copper alloys, a method using silver or copper plating, an antibacterial agent (including an antifungal agent), for example, an imidazole-based, thiazole-based, iodine-based, nitrile-based, or phenol-based compound A method of kneading, impregnating or applying fibers with antibacterial zeolite, titanium oxide or the like can be applied.

The polymer film is preferably made of a hydrophilic or hydrophobic polymer in order to suppress the adhesion of clogging substances derived from sludge.

The hydrophilic polymer has a contact angle with water of 60 °.
Examples of the following polymers include polymers such as polyvinyl alcohol, polyacrylonitrile, and polymethacrylic acid, and copolymers thereof, and polyvinyl alcohol is preferable.

The hydrophobic polymer has a contact angle with water of 100.
° or higher, and examples thereof include polyvinylidene chloride, polytetrafluoroethylene, polydimethylsiloxane, and modified polymers thereof, and polytetrafluoroethylene and modified polymers thereof are preferable.

The solid-liquid separation membrane of the present invention preferably has regularly arranged holes, and more preferably has holes arranged in a lattice.

When the solid-liquid separation membrane of the present invention is used as the above-mentioned composite membrane, the surface of a substrate membrane having triangular or more polygonal pores made of a metal selected from metals other than iron and synthetic fibers is treated as a film. It can be produced by treating with a polymer solution to be formed.

When a net is used as the substrate film, the average pore diameter is 10 to 150 μm, preferably 20 to 120 μm,
It is preferable to use one having a porosity of 20 to 60%, preferably 30 to 50%, a thickness of 50 to 300 μm, preferably 60 to 200 μm, and a wire diameter of 10 to 100 μm, preferably 20 to 70 μm. The shape of the hole in this net is
Although the polygon is a triangle or more, a quadrangle is preferable from the viewpoint of easy availability, and when a polygon of pentagon or more or hexagon (honeycomb) or more is used, the shape of the hole becomes more true. It can be approximated to a circle.

The polymer solution is an aqueous solution, an organic solvent solution, or an aqueous dispersion, and the concentration is determined in consideration of the type of the polymer, the ability to form a film, the workability of the treatment, and the like. Thus, a pore-shaped solid-liquid separation membrane satisfying the relationship of 1 ≦ R / r <√2 can be obtained.

As the surface treatment method using a polymer solution, a method of applying or spraying a polymer solution on a substrate film, a method of dipping the substrate film in the polymer solution, and the like can be applied. After the surface treatment, it can be dried at room temperature, cooled or heated.

The solid-liquid separation membrane of the present invention is not particularly limited in its shape and size, and may be appropriately modified into a plate shape, a bag shape, a spiral shape, a tube shape, or the like according to a use condition. Can be.

The solid-liquid separation membrane of the present invention is suitable for water treatment in which a dynamic membrane is formed and solid-liquid separation of activated sludge or suspension is performed.

As a mode of the solid-liquid separation apparatus using the module filled with the solid-liquid separation membrane of the present invention, the membrane module filled with the solid-liquid separation membrane is directly placed in a biological reaction tank or an activated sludge treatment drainage tank. An immersion-type solid-liquid separator for immersion or an externally-installed solid-liquid separator installed outside a biological treatment tank may be used.

The solid-liquid separation membrane of the present invention can be used for treatment of wastewater containing activated sludge and the like in sewage treatment plants, treatment of wastewater from various facilities and domestic wastewater, wastewater containing suspended matters, and purification of rivers, lakes and marshes. It can be applied to processing and the like.

[0036]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. In addition, each numerical value in the following was performed by each of the following methods. (1) Measurement of average pore diameter, pore diameter distribution and R / r value A 200-fold optical microscope photograph of a solid-liquid separation membrane having a cross-sectional area of 20 cm ² was taken, the diameter of 100 openings was calculated, and the average pore diameter and average were measured. The pore size distribution was determined. The R / r value was calculated by averaging and calculating the R / r value from the maximum value and the minimum value of the distance from the center in each of the ten openings. (2) Measurement of contact angle with water The polymer solution was applied on a glass slide and dried, and water was dropped with an automatic contact angle meter (manufactured by Kyowa Interface Science Co., Ltd .: CA-Z type) to make contact with water. The corner was measured. (3) Average permeate SS concentration and stable operation days Bag-like modules (membrane area 37 cm ² ) were prepared using various solid-liquid separation nets. The obtained bag-shaped module is immersed and arranged in a tank having a capacity of 2 liters, and the transmembrane pressure is 0.3 kP.
In 15a, filtration of activated sludge collected at the sewage treatment plant
Performed at 0 ° C. Backwashing with water was performed several times a day. Once a day permeate SS concentration and unit time,
The amount of permeated liquid (flux) per unit area was measured. The average permeate SS concentration was defined as the average value of the permeate SS concentration, and the number of stable operation days was defined as the time until the flux became half of the initial value.

Example 1 A plain woven stainless steel net shown in FIG.
A 10% by weight aqueous solution of polyvinyl alcohol (LM-10HD, manufactured by Kuraray Co., Ltd .; contact angle: 40 °) was applied to a wire diameter of 50 µm and an opening ratio of 37%, and dried at 80 ° C for 4 hours. The average pore size of the obtained solid-liquid separation membrane is 60 μm,
All pore diameters were within 10% of the average pore diameter, the aperture ratio was 30%, the thickness was 100 μm, and the R / r value was 1.1.
Using this solid-liquid separation membrane, the average permeate SS concentration and the number of stable operation days were determined. The results are shown in FIGS.

Examples 2A and 2B The same stainless steel net as used in Example 1 was coated on a fluororesin Bonflon (Asahi Glass Coat and Resin Co., Ltd.).
, W # 1500; contact angle 145 °) with water
The solution diluted twice was applied and dried at 80 ° C. for 1 hour.
The average pore size of the obtained solid-liquid separation membrane is 45 μm (applied with a 2-fold dilute Bonflon solution) shown in FIG. 3A and 66 μm (applied with a 3-fold dilute Bonflon solution) shown in FIG. 3B, respectively. It was present within 9% and 7%, the aperture ratio was 20% and 30%, respectively, the thickness was 100 μm, and the R / r values were 1.26 and 1.15. Among them, the average permeate SS concentration and the number of stable operation days were determined using a solid-liquid separation membrane having an average pore diameter of 66 μm. The results are shown in FIGS.

Comparative Example 1 Plain woven stainless steel net (opening 104 μm, wire diameter 50)
(μm, opening ratio: 44%), the average permeate SS concentration and the number of days of stable operation were determined. The results are shown in FIGS.
The R / r value of this stainless steel net was 1.52. Using this stainless steel net, the average permeate SS
The concentration and the number of stable operation days were determined. The results are shown in FIGS.

Comparative Example 2 Using the same stainless steel net as used in Example 1, the average permeate SS concentration and the number of stable operation days were determined. The R / r value of this stainless steel net was 1.50.
The results are shown in FIGS.

Comparative Example 3 Twill-woven stainless steel net (mesh size 45 μm, wire diameter 40 μm)
m, opening ratio 27%) to determine the average permeate SS concentration and the number of stable operation days. The results are shown in FIGS. This R / r value was 1.45.

[0042]

[Table 1]

As can be seen from FIGS. 4 and 5, it can be seen that the use of the solid-liquid separation membrane composed of the composite membrane of the base material membrane and the polymer membrane enables the low permeate SS concentration and the water permeation rate to be maintained for a long time. Was.

[0044]

By using the solid-liquid separation membrane of the present invention, in particular, a solid-liquid separation membrane composed of a composite membrane of a base film and a polymer film, a low permeate SS concentration can be obtained in the solid-liquid separation of activated sludge and the like. In addition, the water permeability can be maintained for a long period of time.

[Brief description of the drawings]

FIG. 1 is an optical micrograph of the plain woven stainless steel net used in Example 1 at a magnification of 200 times (1 scale = 10 μm).

FIG. 2 is an optical micrograph of the solid-liquid separation membrane obtained in Example 1 at a magnification of 200 times (1 scale = 10 μm).

FIG. 3A is an optical microscope photograph of the solid-liquid separation membrane obtained in Example 3 at a magnification of 200 times (1 scale = 10 μm).

FIG. 3B is an optical microscope photograph of the solid-liquid separation membrane obtained in Example 3 at a magnification of 200 times (1 scale = 10 μm).

FIG. 4 is a graph showing the relationship between the average pore diameter of the solid-liquid separation membrane of Example 1 and the average permeate SS concentration.

FIG. 5 is a graph showing the relationship between the average pore diameter of the solid-liquid separation membrane of Example 1 and the number of stable operation days.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA02 HA21 HA41 HA61 HA93 KA01 KB21 KD30 MA02 MA03 MA16 MA21 MA22 MA23 MB09 MB10 MC02 MC09 MC28 MC28X MC33 MC33X NA64 PB04 PB15 PC64

Claims (9)

[Claims] 1. The shape of a hole is a shape in which a corner portion of a polygon of three or more is rounded, and (a) the average hole diameter is 10 to 90 μm, and the following formula: (LM) / M × 100
(L is the minimum pore size, M is the average pore size), and the pore size distribution is within ± 20%, (b) the aperture ratio is 15 to 60%, and (c) the thickness is 50 to 300 μm. Solid-liquid separation membrane. 2. The shape of the hole is a circle or a shape similar to the circle, and the following formula: 1 ≦ R / r <√2 (R is the maximum value from the center point of the hole to the peripheral wall portion, and r is the The minimum value from the center point to the peripheral wall portion) is satisfied.
The solid-liquid separation membrane according to the above. 3. The solid-liquid separation membrane according to claim 1, wherein the solid-liquid separation membrane comprises a composite film of a base film having three or more polygonal holes and a polymer film. 4. The solid-liquid separation membrane according to claim 3, wherein the substrate membrane is selected from a metal other than iron and a synthetic resin. 5. The solid-liquid separation membrane according to claim 3, wherein the polymer film is made of a hydrophilic or hydrophobic polymer. 6. The solid-liquid separation membrane according to claim 1, wherein the solid-liquid separation membrane has holes arranged regularly. 7. The solid-liquid separation membrane according to claim 1, wherein the solid-liquid separation membrane has pores arranged in a lattice pattern. 8. A water treatment for forming a dynamic membrane to perform solid-liquid separation of activated sludge or suspended matter.
A solid-liquid separation membrane according to any one of claims 1 to 7. 9. The method according to claim 3, wherein the surface of the substrate film having triangular or more polygonal holes made of a material selected from metals other than iron and synthetic fibers is treated with a polymer solution for forming a film. A method for producing a solid-liquid separation membrane according to any one of the preceding claims.