JP2000288360A - Filter membrane element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate a back washing and at the same time, improve the recovery rate a water permeation by the back washing and further, enable a stable filtering capability to be maintained for a long time by arranging a filtered water flow path and an injection channel under a filter membrane face and at the same time, not allowing at least the injection channel of a cleaning medium to come into contact with a filter membrane. SOLUTION: A filter membrane element 10 is formed in a four-tier structure and two flat membranes 14, 15 are firmly attached to the outside face of a support frame 12, and at the same time, other flat membranes 21, 22 are firmly attached to the inside face of the support frame 12. Further, a single filtered water flow path 30a is formed in a gap between both flat membranes 14, 21 and another filtered water flow path 30b is formed in a gap between both flat membranes 15, 22. In addition, an injection channel 31 of a cleaning medium is formed in a gap between both flat membranes 21, 22. Consequently, the filter membrane element 10 which is shared by only an inlet and an outlet for the supply of the cleaning medium and for the drainage of filtered water, can be constituted, although the filtered water flow path 30b and the injection channel 31 of the cleaning medium are mutually different, by connecting both filtered water flow paths 30a, 30b and the injection channel 31 of the cleaning medium to a single filtered water nozzle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtration membrane element suitable as a solid-liquid separation membrane used for treating activated sludge and the like.

[0002]

2. Description of the Related Art
In the solid-liquid separation treatment of a liquid containing SS (suspension material) such as a suspended solid or sludge, various techniques using a nonwoven fabric as a filter are known, for example, JP-A-5-185078, JP-A-10-108. It is also disclosed in Japanese Patent Publication No. 128375. In the case of filtration using such a nonwoven fabric, dynamic filtration for substantially performing solid-liquid separation is performed by a dynamic layer formed on the membrane surface.However, in order to prevent clogging of the nonwoven fabric membrane, periodic filtration is performed. Cleaning of the surface is required.

[0003] Japanese Patent Application Laid-Open No. 10-128373 discloses that the filtration is stopped intermittently and gas is supplied from a vent pipe provided below the filter in the biological reaction tank so that the surface of the filter is attached. A method of peeling a kimono layer is disclosed.
However, according to this method, not only a ventilation pipe for supplying gas is separately required, but also the dynamic layer formed on the film surface during cleaning is once broken. Therefore, when a nonwoven fabric having a small basis weight, that is, a nonwoven fabric having a large fiber gap is used as a filter, there is a possibility that the SS concentration in the permeated liquid becomes extremely high after the filtration is started again until the dynamic layer is formed. is there. In addition, SS penetrates into the nonwoven fabric and promotes clogging of the film. On the other hand, when a nonwoven fabric having a large basis weight, that is, a small fiber gap is used as a filter, high water permeability cannot be obtained.

Japanese Patent Application Laid-Open No. 10-192880 discloses that filtration is intermittently stopped, gas is supplied from a ventilation pipe provided below a filter in a biological reaction tank, and clean water is supplied into the filter. An activated sludge filtration device provided with a supply of clean water is disclosed. However, when a filter having a pore size of several tens of μm or more is backwashed with water, it is difficult to uniformly flow backwash water to the membrane surface because the pore size is large. For this reason, it is difficult to uniformly remove SS on the film surface.

[0005] An object of the present invention is to provide a filtration membrane element capable of maintaining stable filtration performance for a long period of time.

[0006]

According to the present invention, a permeated water flow path and a jet path of a cleaning medium are disposed below a surface of a filtration membrane, and at least the jet path of the cleaning medium is not in contact with the filtration membrane. Provide the element. Further, the present invention provides a filtration membrane element in which a permeated water flow path and a cleaning medium injection path each having a separate path are arranged between filtration membranes, and at least the cleaning medium injection path is not in contact with the filtration membrane. .

In the present invention, the permeated water flow path and the cleaning medium injection path mean a flow path or a path having an independent space for permeated water or a cleaning medium to pass therethrough. The present invention does not include a flow path of permeated water formed only by the mesh member. Also,
“Not in contact with the filtration membrane” means that the filtration membrane, that is, the membrane that directly contacts the liquid to be treated and performs filtration does not participate in the formation of the injection path of the cleaning medium. I do. However, for example, in the case of an element formed by bonding the peripheral portions of a filtration membrane (flat membrane) having a multi-layer structure or an element having a similar structure, the peripheral portion of the membrane that does not substantially perform filtration is sprayed with a cleaning medium. It may be in contact with the route.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The filtration membrane element of the present invention has a permeated water flow path and a cleaning medium injection path arranged below the filtration membrane surface. , Or the same route or separately isolated routes. However, at least the washing medium jet path is not in contact with the filtration membrane. Therefore, if the permeated water flow path and the washing medium jet path are the same, the permeated water flow path is also in contact with the filtration membrane. Absent. Here, as the cleaning medium used in the present invention, water or air is preferable.

[0009] The filtration element of the present invention may be of a flat membrane type or a tube type. In the case of the flat membrane type, as a four-layer membrane, the gap formed by the two inner flat membranes is used as the cleaning medium injection path, and the two gaps formed by the outer flat membrane and the inner flat membrane are used as the permeated water flow path. can do. In the case of tube type,
As a double-structured membrane, the inner membrane gap can be used as a jet path of the cleaning medium, and the gap composed of the outer and inner membranes can be used as the permeated water flow path. In these cases, when air is used as the cleaning medium, the inner membrane material is preferably a hydrophobic material such as an olefin polymer or a fluorine polymer.

[0010] Further, even when the filtration element of the present invention is a flat membrane type having a double membrane structure, a required number of pipes having a required number of pores on the peripheral surface are arranged between the two membranes. The tubing can be a permeate flow path and a jet path for the cleaning medium. At this time, by arranging the tubing in one system, it is possible to obtain the same filtration membrane element in which the permeated water flow path and the injection path of the cleaning medium are the same, arrange the tubing in two systems, and make one system the permeated water flow path. By using another system as the cleaning medium injection path, a filtration membrane element in which the permeated water flow path and the cleaning medium injection path are isolated can be obtained.

Further, the filtration membrane element of the present invention has a
When air is used as a cleaning medium even when the flat film type having a multilayer structure or the tube type having a single structure is used, contraction and expansion can be performed by taking in and out air between the films, and air is injected at a predetermined pressure. It is possible to adopt a structure in which a rubber-like elastic body in which pores are generated only when it is inserted. In the case of a filtration membrane element having such a structure, the rubber-like elastic body has pores formed only when air is injected at a predetermined pressure, and the air ejected from the pores is ejected from the outer surface of the membrane to form a membrane. Excess SS adhering to the outer surface is removed.

Further, in these flat membrane type and tube type filtration membrane elements, the permeated water flow path and the injection path of the washing medium may be completely isolated or only a part thereof may be shared. Good.

In the filtration membrane element of the present invention, in order to effectively spray the cleaning medium, the average pore diameter of the inner membrane is preferably smaller than the average pore diameter of the outer membrane. The average pore diameter of the membrane is 1/2 to 1 / 10,000, preferably 1/5 to the average pore diameter of the outer membrane.
It can be reduced to 1/5000, more preferably 1/10 to 1/500. The outer membrane has an average pore diameter of 10 μm.
m or more is preferable, and 50 μm or more is more preferable.

Furthermore, the outer membrane preferably has a basis weight of 1
0 to 1000 g / m ² , more preferably 20 to 900 g
/ M ² , the air permeability is preferably 0.1 to 200 cm ³ /
(Cm ² · s), more preferably 0.2 to 150 cm ³ /
(Cm ² · s).

The fiber diameter of the outer membrane and the inner membrane is
Preferably 0.5 to 30 μm, more preferably 1 to 10
μm, and the thickness is preferably 0.5 to 30 μm, preferably 100 to 2000 μm.

The membrane used in the filtration membrane element is preferably a non-woven fabric. For example, in the case of a quadruple structure, the inner membrane may be a membrane other than the non-woven fabric. The nonwoven fabric is produced by a conventional method using natural or synthetic fibers. Examples of the natural or synthetic fibers include natural fibers such as cotton, hemp, wool, and the like, and polyester derivatives such as polyester, polystyrene, polyvinyl chloride, polyvinylidene chloride, poly (meth) acrylate, viscose rayon, cellulose acetate, and methylcellulose. And synthetic fibers composed of polyolefins such as polyethylene and polypropylene, polycarbonates, polyamides, polyesteramides, polyethers, polyimides, polyamideimides, polyetherimides, and mixtures or copolymers of two or more of these. Among them, those made of polyester, polyethylene, polypropylene or polycarbonate fibers are preferable, and those made of polyester fibers are particularly preferable. Examples of such a non-woven fabric include MF180 (trade name: polyester fiber non-woven fabric having a fiber diameter of 10 μm; manufactured by Japan Vilene Co., Ltd.), SB-35 (trade name: 10-μm polyester fiber non-woven fabric; manufactured by Unitika Ltd.), FC3 (trade name)
105 (a nonwoven fabric made of polyester fiber having a fiber diameter of 10 μm;
Nippon Vilene Co., Ltd., brand name NF felt (fiber diameter 1
0 μm polyester fiber non-woven fabric; Nippon Felt Co., Ltd .; trade name FC302 (10 μm fiber diameter polyester fiber non-woven cloth; Nippon Vilene Co., Ltd.); trade name S-0
30 (polypropylene fiber non-woven fabric having a fiber diameter of 10 μm;
Product name: H8007 (fiber diameter 10)
μm polyester fiber non-woven fabric; manufactured by Japan Vilene Co., Ltd.).

Further, since SS may be accumulated in the permeated water channel due to long-term filtration operation, a drain valve of an electric type or a pressure sensitive type for discharging SS is provided below the filtration membrane element. Is preferred.

Hereinafter, the filtration membrane element of the present invention will be described with reference to the drawings. FIG. 1 is a front view of a filtration membrane element,
2 is a cross-sectional view taken along line II-II of the filtration membrane element shown in FIG. 1, FIG. 3 is one end view of the filtration membrane element in FIG. 1, and FIG. 4 is one end view of another embodiment of the filtration membrane element. 5 is a conceptual diagram of a solid-liquid separation device using a filtration membrane element.

As shown in FIGS. 1 and 2, the filtration membrane element 10 has a quadruple structure, and two flat membranes 14 and 15 are fixed on an outer surface of a support frame 12 by an adhesive or the like, and Flat films 21 and 22 are fixed to the inner surface of the frame 12 with an adhesive or the like. 16 is a passage for collecting permeated water,
18 is a permeate nozzle. When the filtration membrane element 10 is housed in a housing, a drain pipe such as a plastic tube is connected to the permeate nozzle 18.

With such a quadruple structure, the gap formed by the flat membrane 14 and the flat membrane 21 can
a, the gap formed by the flat membranes 15 and 22 forms another permeate flow path 30b, and the gap formed by the flat membranes 21 and 22 forms the jet path 31 of the cleaning medium. At this time, a mesh member may be disposed in the permeated water flow paths 30a and 30b.

Then, as shown in FIG.
By connecting the water collecting passages 16a and 30b and the washing medium jetting path 31 to one permeated water nozzle 18, the permeated water flow path and the jetting path of the washing medium are different. The filtration membrane element 10 which shares only the inlet and outlet for supply of is obtained. At this time,
For example, an on-off valve that can be adjusted so that the cleaning medium flows only into the injection path 31 can be attached to a connection portion between each water collecting passage 16 and one permeate nozzle 18.

Further, as shown in FIG.
a, 30b through the permeated water nozzles 18a, 18
b, and by connecting the water collecting passage 16 in the cleaning medium injection path 31 to the cleaning medium supply nozzle 18c, the filtration membrane element 10 in which the permeated water flow path and the cleaning medium injection path are completely isolated can be obtained. .

Next, the operation of the solid-liquid separation device using the filtration membrane element as shown in FIGS. 1, 2 and 4 of the present invention will be described with reference to FIG.

The biological reaction tank 50 is filled with an activated sludge liquid as a liquid to be treated, and an aeration pipe 5 is provided at the bottom.
1 is installed. The processing liquid processed in the biological reaction tank 50 passes through the liquid sending line 53 by the circulation pump 70,
It is sent to the filtration membrane module 55. The filtration membrane module 55 has a required number of filtration membrane elements 10 housed in a housing.

In the filtration membrane module 55, filtration is performed by a predetermined transmembrane pressure, and the permeated water flows through the permeated water passage 30.
a, 30b, flows into the water collecting passage 16, is discharged from a water distribution pipe connected to the permeated water nozzles 18a, 18b (a drain line 60), and is stored in a permeated water tank 61.

When the filtration treatment is continued for a long time, excessive SS adheres to the outer surface of the filtration membrane element 10, so that the amount of permeated water decreases as it is. Therefore, backwashing is performed to maintain a stable amount of permeated water. In the reverse cleaning, after the filtration process is temporarily stopped, the cleaning medium supply nozzle 1
From 8c, a liquid such as permeated water or air is press-fitted. As a guide at the time of this back washing, the amount of permeated water is 1 to 8 of the initial value.
It is desirable to carry out the treatment when it reaches 0%, preferably 2 to 70%. Although the backwashing time is not particularly limited, it is 10-1.
About 20 seconds is desirable.

When permeated water is used as a washing medium,
The backwash pump 71 is driven to press-in the permeated water in the permeated water tank 61. The permeated water thus injected flows into the injection path 31 and is injected from the flat membranes 21 and 22 toward the inner surfaces of the flat membranes 14 and 15. The injected permeate reaches the outer surfaces of the flat membranes 14 and 15 and adheres to the excessive SS.
Is removed. When air is used as the cleaning medium, air is injected from an air supply source. In FIG. 5, 80, 8
1 is a flow meter, 82 is a pressure gauge, 85-88 is an opening / closing valve.

The filtration membrane element of the present invention can be used for solid-liquid separation treatment, particularly for treatment of wastewater containing activated sludge in a sewage treatment plant, wastewater from various facilities and domestic wastewater, and purification treatment of natural waters such as rivers and lakes. Can be applied to

[0029]

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. The following numerical values were obtained by the following methods.

(1) Average Pore Size Electron micrographs of 100 times and 10000 times the surface of the filtration membrane were photographed, and a total of 3 places having an area of 2 × 2 cm were processed by an image processor to calculate an average pore size. (2) Water permeation rate The water permeation rate was determined from the effective membrane area of the filtration element and the amount of water permeated for a certain period of time. (3) Permeate SS concentration A solid content contained in a predetermined volume of permeate water is reduced to a pore size of 0.4 μm.
It was filtered through a glass filter of m, dried, and weighed. (4) Permeability rate recovery rate It was defined and calculated as the ratio of the permeability rate immediately after backwashing to the initial permeability rate.

Example 1 A filtration membrane element having the structure shown in FIGS. 1, 2 and 4 was manufactured. The two outer membranes are nonwoven fabric H8007 (average pore size 100 μm, basis weight 75 g / m ² , air permeability 60 cc / (c
m ² · s), a polyester fiber with a fiber diameter of 10 μm; manufactured by Japan Vilene Co., Ltd., and the inner two membranes are microfiltration membranes made of polytetrafluoroethylene (average pore diameter 0.2 μm, manufactured by Millipore) Was. The effective membrane area of the filtration membrane element was 78 cm ² . The two filtration membrane elements were housed in a housing (volume: 0.5 L), and subjected to a filtration treatment by a solid-liquid separator shown in FIG. As the liquid to be treated, wastewater containing activated sludge collected at a plant in Himeji City (MLSS concentration 10,000 mg / L) is used, and the transmembrane pressure is 0.3 kP.
a, Solid-liquid separation was performed at a temperature of the liquid to be treated of 18 to 23 ° C. In addition, water backwashing is performed at a rate of 60 L / (mi) once every 12 hours.
n · m ² ) for 1 minute.

Example 2 A filtration membrane element having the structure shown in FIGS. 1, 2 and 4 was manufactured. The outer two membranes use non-woven fabric H8007, and the inner two membranes are non-woven fabric MF180 (average pore diameter 20 μm,
Weight per unit area: 180 g / m ² , air permeability: ² cc / (cm ² · s),
Polyester having a fiber diameter of 10 μm; manufactured by Japan Vilene Co., Ltd.). Effective membrane area of filtration membrane element is 78c
m ² . Example 1 using this filtration membrane element
Filtration treatment and back washing treatment were performed in the same manner as described above.

Example 3 A filtration membrane element having the structure shown in FIGS. 1, 2 and 4 was manufactured. The outer two membranes used nonwoven fabric MF180, and the inner two membranes used a polytetrafluoroethylene microfiltration membrane (average pore size 0.2 μm). The effective membrane area of the filtration membrane element was 78 cm ² . Using this filtration membrane element, a filtration treatment and a back washing treatment were performed in the same manner as in Example 1.

Example 4 A filtration membrane element having the structure shown in FIGS. 1, 2 and 4 was manufactured. The outer two membranes used nonwoven fabric H8007, and the inner two membranes used a polytetrafluoroethylene microfiltration membrane (average pore size 0.2 μm). The effective membrane area of the filtration membrane element was 78 cm ² . Using this filtration membrane element, filtration was performed in the same manner as in Example 1. However, air backwashing is performed once every 12 hours for 10 hours.
This was performed for 1 minute under the condition of 00 L / (min · m ² ).

[0035]

[Table 1]

As is evident from Table 1, in Examples 1 to 4, the water permeability recovery rate was 100%, and from this result, it was confirmed that the outer flat membrane surface was uniformly washed.

[0037]

The filtration membrane element of the present invention can maintain the filtration performance stably for a long period of time because the backwashing operation is easy and the rate of recovery of the water permeability by the backwashing is excellent.

[Brief description of the drawings]

FIG. 1 is a front view of one embodiment of a filtration membrane element.

FIG. 2 is a cross-sectional view taken along line II-II of the filtration membrane element shown in FIG.

FIG. 3 is an end view of the filtration membrane element in FIG. 1;

FIG. 4 is an end view of another embodiment of a filtration membrane element.

FIG. 5 is a conceptual diagram of a solid-liquid separation device using a filtration membrane element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Filtration membrane element 12 Support frame 14, 15 Flat membrane 16 Water collecting passage 18 Permeated water nozzle 18a, 18b Permeated water nozzle 18c Cleaning medium supply nozzle 21, 22 Flat membrane 30a, 30b Permeated water flow path 31 Cleaning medium injection path

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toyozo Hamada 2-45-45-201, Rikyumaemachi, Suma-ku, Kobe-shi, Hyogo Prefecture (72) Inventor Osamu Nakatsuka 79-11- 306 F term (reference) 4D006 GA07 HA22 HA42 KA17 KC03 KC13 KC14 MA02 MA03 MA06 MA07 MA22 MA40 MB06 MB18 MC16 MC18 MC22 MC23 MC24 MC27 MC30 MC48 MC49 MC54 MC58 MC59 MC90 PB08 PC64

Claims (7)

[Claims] 1. A filtration membrane element in which a permeated water flow path and an injection path of a cleaning medium are arranged below a surface of the filtration membrane, and at least an injection path of the cleaning medium is not in contact with the filtration membrane. 2. A filtration membrane element in which a permeated water flow path and a cleaning medium injection path, which are separate paths, are arranged between the filtration membranes, and at least the cleaning medium injection path is not in contact with the filtration membrane. 3. The filtration membrane is composed of a double membrane or a quadruple membrane, a jet path of the cleaning medium is formed between the inner membranes, and a permeated water path is formed between the inner membrane and the outer membrane. The filtration element of claim 2, wherein 4. The filtration membrane element according to claim 3, wherein the average pore size of the inner membrane is smaller than the average pore size of the outer membrane. 5. The filtration membrane element according to claim 3, wherein the outer membrane has an average pore diameter of 10 μm or more. 6. An outer membrane having a basis weight of 10 to 1000 g /
m ² , air permeability is 0.1 to 200 cm ³ / (cm ² · s)
The filtration membrane element according to claim 3, 4 or 5, wherein 7. The filtration membrane element according to claim 1, further comprising a drain valve communicating with the permeated water flow path.