Membrane filter

Abstract

The present invention addresses the problem of providing a membrane filter configured of flexible separation membrane elements and flexible water collecting tubes that connect the separation membrane elements and a water collecting pipe, the membrane filter making it possible to prevent a problem that the separation membrane elements adjacent to each other, water collecting tubes adjacent to each other or tube joints interposed in the water collecting tubes become worn and damaged as a result of coming into contact with each other under an aeration environment.　This membrane filter includes: separation membrane elements in which a separation membrane pair is bonded at a peripheral edge and a filtered water port for discharging filtered water is arranged in at least a part of the peripheral edge; a water collecting pipe for collecting filtered water from a plurality of the separation membrane elements; and a plurality of filtered water pipes that connect the filtered water ports and the water collecting pipe, the membrane filter being characterized in that a member for maintaining a constant distance between adjacent filtered water pipes is provided to the filtered water pipes.

Description

Membrane filter

[0001] The present invention relates to a membrane filter used in a membrane bioreactor.

[0002] The membrane bioreactor is a treatment method in which a separation membrane is immersed in an activated sludge tank and the activated sludge and treated water are separated by the membrane. In recent years, this method has been increasingly applied to water treatment fields such as drinking water production, water purification, and wastewater treatment, as well as the food industry.

[0003] Various configurations of membrane filters used in membrane bioreactors are known. Patent Document 1 discloses a membrane filter that houses multiple flexible, lightweight separation membrane elements without a support plate. An example of the membrane filter described in Patent Document 1 will be described with reference to FIG. 8 . Here, a membrane filter 101 houses multiple separation membrane elements 102 in a housing 124, and an air diffuser 123 is provided below the housing 124. Each separation membrane element 102 has a filtered water inlet 105 on its periphery, and each filtered water inlet 105 is connected to a water collection pipe 104 via a flexible water collection tube 107. The water collection tube has the advantage that if a specific separation membrane element is damaged, the connected water collection tube can be crushed with forceps or the like to prevent turbidity from flowing into the water collection pipe. Furthermore, if the water collection tube is transparent, the damaged separation membrane element can be identified by visually checking the color of the filtered water in the water collection tube. Patent Document 1 also discloses a configuration in which the water collection nozzles (corresponding to the filtrate water outlet 105 in Figure 8) of adjacent separation membrane elements are arranged in a staggered pattern, thereby narrowing the gap between adjacent separation membrane elements and enabling the separation membrane elements to be arranged more densely.

[0004] On the other hand, a disadvantage of connecting the filtrate outlet of the separation membrane element to the water collection pipe with a water collection tube is that a certain length of water collection tube is required to ensure the space necessary for inserting the water collection tube into the filtrate outlet or the water collection pipe. In this regard, Patent Document 2 discloses a configuration in which the filtrate outlet 205 and the water collection pipe 204 are connected via an L-shaped water collection tube 219 consisting of a horizontal tube 207, a vertical tube 208, and a tube joint 206, as shown in a membrane filter 201 schematically shown in Figures 9, 10, and 11. This connection configuration makes it possible to ensure the space necessary for the connection work between the water collection pipe and the filtrate outlet while minimizing the length of the water collection tube.

[0005] Japanese Patent No. 6164216 Japanese Patent Application Laid-Open No. 2022-101940

[0006] By combining the configurations of Patent Documents 1 and 2, it is possible to create a product configuration that obtains the benefits of the water collection tube described above while making the product more compact. However, when filtration is performed in an aeration environment from an aeration device, the separation membrane element and the water collection tube are flexible, and so both components will swing, which can cause problems such as adjacent separation membrane elements, particularly the filtrate outlet, coming into contact with the membrane of an adjacent separation membrane element and damaging the membrane, or tube fittings coming into contact with each other, causing wear and damage.

[0007] The object of the present invention is to provide a membrane filter that has no support plate, has multiple flexible and lightweight separation membrane elements arranged in a highly integrated manner, and has space secured between the water collection pipe and the filtrate outlet to facilitate connection of the water collection tube, and has a configuration that can prevent contact between adjacent separation membrane elements or tube joints.

[0008] To solve these problems, the present invention has the following configurations. (1) A membrane filter in which a plurality of separation membrane elements are arranged with their separation function layer surfaces adjacent to each other, the peripheral portions of which are sealed and at least a portion of the peripheral portions has a filtrate outlet for discharging filtrate that has permeated through the permeate surface to the outside of the separation membrane pair, the separation membrane elements being arranged with their separation function layer surfaces adjacent to each other, and the filtrate outlets of each separation membrane element being connected to a water collection pipe via individual filtrate pipes, the membrane filter being characterized in that a member for maintaining a constant distance between adjacent filtrate pipes is provided on the filtrate pipes. (2) The membrane filter described in (1), in which the member is a clip member removably fixed to the filtrate pipes. (3) The membrane filter described in (1) or (2), in which at least a portion of the filtrate pipes are made of a material having a 100% modulus of 20 MPa or less. (4) The membrane filter described in any one of (1) to (3), in which the filtrate pipes are made of a tube and a tube fitting, and the filtrate outlet and the water collection pipe are connected in an L-shape. (5) The membrane filter according to any one of (2) to (4), characterized in that the clip member has 3 to 10 gripping portions. (6) The membrane filter according to any one of (1) to (5), characterized in that a resin portion is provided between the opposing permeate-side surfaces of the separation membrane pair of the separation membrane element (hereinafter referred to as "between the separation membrane pair"), the resin portion forming a filtrate flow path of a predetermined width between the separation membrane pair, and the filtrate flow path communicating with the inner cavity of the filtrate inlet. (7) The membrane filter according to any one of (1) to (5), characterized in that a nonwoven fabric or a net-like material is provided between the separation membrane pair, the nonwoven fabric or the net-like material forming a filtrate flow path of a predetermined width between the separation membrane pair, and the filtrate flow path communicating with the inner cavity of the filtrate inlet. (8) The membrane filter according to (4), characterized in that the tube fitting has a plurality of tube connecting portions so as to be connected to the filtrate inlets of a plurality of separation membrane elements, and the tube connecting portions are installed in the same phase as the filtrate inlets.

[0009] According to the present invention, in a membrane filter including a flexible separation membrane element and a flexible filtrate pipe connecting the separation membrane element to a water collection pipe, it is possible to suppress the oscillation of the separation membrane element and the filtrate pipe under an aerated environment, thereby preventing contact between adjacent separation membrane elements, contact between the filtrate port and the membrane of an adjacent separation membrane element, and contact between adjacent filtrate pipes, and preventing damage to the separation membrane elements.

[0010] 1 is a perspective view schematically showing an example of an embodiment of a membrane filter of the present invention. FIG. 1 is a perspective view showing an enlarged view of part A of FIG. 1. FIG. 1 is a perspective view showing an enlarged view of part B of FIG. 1. FIG. 1 is a perspective view showing an example of a connection state between a clip member of the present invention and a filtrate piping. FIG. 2 is a front view showing an example of a clip member of the present invention. FIG. 2 is a perspective view showing an example of a tube joint constituting the filtrate piping of the present invention. FIG. 3 is a front view showing an example of an internal structure of a separation membrane element of the present invention. FIG. 3 is a perspective view showing an example of an embodiment of a membrane filter of the prior art. FIG. 4 is a perspective view showing an example of an embodiment of another membrane filter of the prior art. FIG. 4 is a perspective view showing an enlarged view of part C of FIG. 9. FIG. 4 is a perspective view showing an example of an embodiment of another membrane filter of the prior art in which a plurality of membrane filters of FIG. 9 are assembled.

[0011] In the present invention, the separation membrane element is an element having a flat membrane structure, in which a pair of separation membranes is bonded together with their permeation-side surfaces facing each other and their peripheral edges sealed, with a filtrate outlet provided as a water collection section in part of the peripheral edge of the membrane, and the peripheral edge other than the filtrate outlet being sealed. The pair of separation membranes may be two independent separation membranes with the opposing edges sealed, or may be a single folded separation membrane with the opposing edges sealed.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0013] An example of an embodiment of the membrane filter of the present invention is shown in Figure 1. The membrane filter 1 basically comprises a plurality of separation membrane elements 2 arranged so that their separation function layer sides (raw water sides) are adjacent to one another, a plurality of filtrate pipes 19 for extracting filtrate from the elements, water collection pipes 4 connected to the filtrate pipes 19 and collecting the filtrate, and clip members 9 fixed to the filtrate pipes 19.

[0014] Figure 2 is an enlarged schematic diagram of part A in Figure 1. Spacers 10 with a hole in the center are placed between each separation membrane element and fixed with long bolts 11 together with membrane protection plates 3 for protecting the membrane surfaces, ensuring space between adjacent separation membrane elements 2 and forming a raw water flow path.

[0015] 3 is a schematic enlarged view of part B in Fig. 1, in which the separation membrane element 2 has a filtrate outlet 5 on part of its periphery, to which a filtrate pipe 19 is connected. In Fig. 3, the filtrate pipe 19 is a water collection tube that is made up of a vertical tube 8, a tube joint 6, and a horizontal tube 7, and forms a flow path that guides the filtrate discharged from the filtrate outlet 5 to the water collection pipe 4, but the water collection tube (filtrate pipe) according to the present invention is not limited to this configuration.

[0016] Generally, to achieve high membrane integration in a membrane filter 1, the separation membrane elements 2 are thinned while maintaining a constant width of the raw water flow path. However, there is a limit to how thin the filtrate inlet 5 can be made due to the flow resistance of the filtrate water. As a result, the width of the filtrate inlet 5 limits the packing pitch of the separation membrane elements 2. In the membrane filter 1 shown in this figure, the filtrate inlets 5 are staggered to achieve even higher integration. Staggered arrangement refers to an arrangement pattern in which the elements are not aligned vertically or horizontally but are shifted vertically, left and right, etc., while maintaining a constant spacing between each element. Figure 3 corresponds to an arrangement pattern in which, in a configuration in which multiple separation membrane elements are arranged in parallel, the position of the filtrate inlet of the next separation membrane element is shifted vertically from the position of the filtrate inlet of the previous separation membrane element. Therefore, a staggered arrangement of the filtrate inlets 5 corresponds to a state in which the position of the filtrate inlet 5 for each adjacent separation membrane element 2 is regularly shifted. There are no particular limitations on the distance by which they are shifted, but it is preferable that there is a gap large enough for a finger to fit between adjacent filtered water ports to make it easy to insert and remove the water collection tube, and work can be done efficiently if the vertical distance between adjacent filtered water ports is 20 to 100 mm.

[0017] In one embodiment of the present invention, a resin portion is provided as a flow path material between a pair of sealed separation membranes of a separation membrane element (between the opposing permeate-side surfaces of the pair of separation membranes), and the resin portion forms a filtrate flow path of a predetermined width, which preferably communicates with the lumen of the filtrate inlet. A separation membrane element 2 is generally configured with a flow path material disposed between two separation membranes, and FIG. 7 shows an example of a schematic internal diagram of a separation membrane element. Here, a plurality of dots 17 are disposed in the separation membrane as the resin portion to form the flow path material, and the spaces between the dots function as flow paths for filtrate. There are no particular limitations on the method for forming the dots 17, and general-purpose plastic plates, adhesives, hot-melt resins, etc. can be preferably used.

[0018] Other examples of thin separation membrane elements that can be suitably used in the present invention include those that use nets, nonwoven fabrics, plastic cardboard, etc. as flow path materials.

[0019] The filtrate water pipe 19 is not particularly limited as long as it has at least a portion that is flexible. However, materials such as polyvinyl chloride and polyurethane are preferred. The effects of the present invention can be fully achieved with a 100% modulus (according to JIS K 7311, 23°C, tensile speed 300 mm / min) of 20 MPa or less. A 100% modulus of 20 MPa or more is insufficient, making connection to the filtrate water outlet difficult. Furthermore, the filtrate water pipe 19 does not oscillate during filtration operation in an aerated environment, reducing the benefits of the present invention. Furthermore, to form the filtrate water pipe 19 in an L-shape, a configuration in which an L-shaped tube fitting 6 is installed inside the water collection tube, as shown in FIG. 3, can also be preferably used. This configuration allows for a compact membrane filter 1 with a small bottom projected area and also improves the ease of installing the clip member 9 on the filtrate water pipe 19. In this case, it is preferable to align the phases of the tube connection portion of the tube fitting 6 with the filtrate outlet. In Figure 3, the tube fitting shown in Figure 6 is used, in which the phases of the upper filtrate outlet tube connection portion 14 and the lower filtrate outlet tube connection portion 15 are offset to match the pitch of the filtrate outlets 5. By using a tube fitting with tube connection portions that match the horizontal and vertical distances between adjacent filtrate outlets, connection can be made without placing a load on the filtrate piping or the separation membrane element connected to the filtrate piping. This tube fitting also includes a tube connection portion 16 for the water collection pipe. The tube fitting 6 is not particularly limited as long as it allows filtrate water to flow through it. However, it is preferable that the tube fitting 6 be made of a general-purpose plastic, such as polyvinyl chloride or polypropylene, which is harder than the materials used for the connection portions to the water collection pipe 4 and the filtrate outlet 5, and that the outer shape of the tube connection portion be bamboo-shoot shaped, as this allows for easy installation of the tube fitting within the filtrate piping 19.

[0020] The form of the member that maintains a constant distance between adjacent filtered water pipes is not particularly limited. Examples include a form in which a plate-shaped member is adhesively fixed to each filtered water pipe, a form in which a plate-shaped member with a row of recesses is fitted into protrusions provided on each filtered water pipe to fix the plate-shaped member to the filtered water pipe, and a form in which the teeth of a comb-shaped member are inserted between each filtered water pipe. The embodiment of Figure 1 illustrates a clip-shaped member, but this is preferably used because it is easily detachable and makes it easy to ensure the space required for connection work between the water collection pipe and the filtered water outlet.

[0021] The clip member 9 is not particularly limited as long as it has a configuration that allows it to be removably installed on the filtered water pipe 19, but preferred specifications will be exemplified below.

[0022] Figure 4 is a schematic diagram showing the installation portion of the clip member 9 on the tube fitting 6 shown in Figure 3. The clip member 9 is composed of a semicircular gripping portion and a connecting portion that connects multiple gripping portions. The material of the clip is not particularly limited, but examples include general-purpose plastics such as polyvinyl chloride and polypropylene. When installing the tube fitting 6, using the same material as the tube fitting is preferable in terms of durability against wear and the like. The clip member 9 stores the tube fitting within the gripping portion by pushing it laterally against the tube fitting 6 while spreading the opening of the gripping portion outward. After storage, the opening elastically deforms and returns to its original position, securing the gripping portion and the tube fitting.

[0023] FIG. 5 is a schematic diagram showing a front view of a clip member 9, in which multiple gripping portions 12 are fixed to a single connecting portion 13. This configuration allows the pitch of the tube fittings 6 fixed to the gripping portions 12 of the clip member 9 to be maintained constant, and by restricting the movement of the tube fittings, the oscillation of the separation membrane element can be suppressed. While the number of gripping portions 12 fixed by the connecting portion 13 is not limited, if there are too many, the separation membrane element, which is flexible, may be damaged when simultaneously fitted into multiple tube fittings. If there are too few, the effect of suppressing the oscillation of the separation membrane element and tube is reduced. Therefore, it is preferable to fix three to ten gripping portions with the connecting portion. For example, in a membrane filter with 25 filtered water pipes, one clip member may have five gripping portions, and five clip members may be installed in the entire membrane filter. It is preferable that the inner diameter 22 of the gripping portion be the same as or slightly smaller than the diameter of the tube fitting, as this ensures strong fixation when connected. On the other hand, the length 21 of the opening needs to be smaller than the diameter of the tube fitting, but if it is too small, it becomes difficult to insert the tube fitting into the opening 20, and the clip member becomes difficult to remove, which results in time-consuming replacement of the separation membrane element in the membrane filter. Therefore, the length 21 of the opening is preferably set in the range of 60% to 95% of the inner diameter 22 of the gripping portion.

[0024] The membrane filter of the present invention can be used by placing an air diffuser that discharges air below the membrane filter 1 in Figure 1, but the membrane filter 1 of the present invention may also be loaded and used in a configuration in which multiple membrane filters 201 are loaded inside a housing 224 and an air diffuser 223 is placed below them, as in the conventional membrane filter of Figure 11.

[0025] DESCRIPTION OF SYMBOLS 1 Membrane filter 2 Separation membrane element 3 Membrane protection plate 4 Water collection pipe 5 Filtrate water outlet 6 Tube joint 7 Horizontal tube 8 Vertical tube 9 Clip member 10 Spacer 11 Long bolt 12 Grip portion 13 Connection portion 14 Tube connection portion for upper filtered water outlet 15 Tube connection portion for lower filtered water outlet 16 Tube connection portion for water collection pipe 17 Dot 18 Peripheral portion 19 Filtrate water piping 20 Opening 21 Length of opening 22 Inner diameter of grip portion 101 Membrane filter 102 Separation membrane element 104 Water collection pipe 105 Filtrate water outlet 107 Water collection tube 123 Aeration device 124 Housing 201 Membrane filter 202 Separation membrane element 203 Membrane protection plate 204 Water collection pipe 205 Filtrate water outlet 206 Tube joint 207 Horizontal tube 208 Vertical tube 219 Water collection tube 223 Air diffuser 224 Housing

Claims

1. A membrane filter comprising a pair of separation membranes arranged with their permeation-side surfaces facing each other and their peripheral edges sealed, with a plurality of separation membrane elements having filtrate ports on at least a portion of the peripheral edges for discharging filtrate that has permeated to the permeation-side surface to the outside of the pair of separation membranes, arranged with their separation function layer-side surfaces adjacent to each other, and each filtrate port of each separation membrane element connected to a water collection pipe via a separate filtrate pipe, characterized in that a member that maintains a constant distance between adjacent filtrate pipes is provided on the filtrate pipes.

2. The membrane filter according to claim 1, wherein the member is a clip member removably fixed to the filtered water pipe.

3. A membrane filter according to claim 1 or 2, characterized in that at least a portion of the filtrate water piping is made of a material having a 100% modulus of 20 MPa or less.

4. A membrane filter according to claim 1 or 2, characterized in that the filtered water piping is composed of a tube and a tube joint, and connects the filtered water outlet and the water collection pipe in an L-shape.

5. The membrane filter according to claim 2, wherein the clip member has 3 to 10 gripping portions.

6. A membrane filter according to claim 1 or 2, characterized in that a resin section is provided between the opposing permeation side surfaces of the separation membrane pair of the separation membrane element (hereinafter referred to as "between the separation membrane pair"), the resin section forms a filtrate flow path of a predetermined width between the separation membrane pair, and the filtrate flow path is connected to the inner cavity of the filtrate inlet.

7. A membrane filter according to claim 1 or 2, characterized in that a nonwoven fabric or net-like material is provided between the pair of separation membranes, the nonwoven fabric or net-like material forms a filtrate flow path of a predetermined width between the pair of separation membranes, and the filtrate flow path is connected to the inner cavity of the filtrate inlet.

8. A membrane filter as described in claim 4, characterized in that the tube fitting has a plurality of tube connection portions so as to be connected to the filtrate water inlets of a plurality of separation membrane elements, and the tube connection portions are installed in the same phase as the filtrate water inlets.

Images