Hollow fiber membrane element, hollow fiber membrane module, water treatment device, and water treatment method

Abstract

To provide a hollow fiber membrane element and a hollow fiber membrane module which are excellent in pressure resistance.SOLUTION: A hollow fiber membrane element has a hollow fiber membrane, a water collecting pipe, and an output port for taking out treatment water from the water collecting pipe, in which the hollow fiber membrane and the water collecting pipe are fixed to each other by a potting part, a water collecting path using the potting part and the water collecting pipe as a wall surface is provided inside the water collecting pipe, an end of the hollow fiber membrane communicates with the water collecting pipe, and a cross-sectional area in an arbitrary water collecting path cross section vertical to a longitudinal direction of the water collecting pipe is 100-350 mm2.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a hollow fiber membrane element, a hollow fiber membrane module, a water treatment device, and a water treatment method. [Background technology]

[0002] Hollow fiber membrane elements are widely used in the production of sterile water, drinking water, highly pure water, etc. A known hollow fiber membrane element, for example, has water collection pipes provided at both longitudinal ends of the hollow fiber membrane and tubular supports connected in a state of communication with the water collection pipes (Patent Document 1). In a hollow fiber membrane element such as that described in Patent Document 1, both ends of the water collection pipe are provided with tubular protrusions that communicate with the water collection section and are fitted into the ends of the tubular supports to connect them. In manufacturing the hollow fiber membrane element, for example, resin is injected around the protrusions with the water collection pipe facing up, and the end of the tubular support is inserted into the end of the water collection pipe so that the protrusions are inserted into the end of the tubular support, and the resin is then cured. By inserting the tubular support into the end of the water collection pipe with the resin injected around the protrusions, the gap between the tubular support and the protrusions inserted into the end of the tubular support is also filled with resin, resulting in a hollow fiber membrane element with excellent watertightness at the connection between the water collection pipe and the tubular support. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Chinese Utility Model No. 202006088 Summary of the Invention [Problem to be solved by the invention]

[0004] A hollow fiber membrane element with a small pressure loss is preferred in that it requires less energy for operation. Therefore, in a hollow fiber membrane element in which water is collected from the end of the hollow fiber membrane via a water collection pipe, it is preferable that the cross-sectional area of ​​the water channel inside the water collection pipe is large, since this reduces pressure loss. Hollow fiber membrane elements are usually used as a hollow fiber membrane module using multiple hollow fiber membrane elements. Thinner hollow fiber membrane elements improve membrane cleanability and make it easier to increase the amount of treated water per unit volume. Therefore, when installation space is limited, relatively thin hollow fiber membrane elements may be used. When using a thin hollow fiber membrane element, in order to prevent an increase in pressure loss, the cross-sectional area of ​​the water channel inside the water collection pipe has been increased by increasing the maximum length (height) between the bottom of the water collection pipe and the part of the potting section that is furthest from the bottom and that comes into contact with the wall of the water collection pipe.

[0005] As a method for cleaning hollow fiber membrane elements, for example, a backwashing method is known in which cleaning water is passed through the hollow fiber membranes from the water collection pipe side to eliminate fouling. When the height of the water channel inside the water collection pipe of a relatively thin hollow fiber membrane element was increased, backwashing at high pressure (e.g., 1 MPa or more) was examined, water leakage due to damage occurred, and it was found that there was room for improvement in pressure resistance.

[0006] An object of the present invention is to provide a hollow fiber membrane element and a hollow fiber membrane module that are excellent in pressure resistance. [Means for solving the problem]

[0007] The present invention has the following configuration. [1] A hollow fiber membrane element having a hollow fiber membrane, a water collection pipe, and an outlet for taking out treated water from the water collection pipe, the hollow fiber membrane and the water collection pipe are fixed by a potting portion, a water collection channel having the potting portion and the water collection pipe as wall surfaces inside the water collection pipe; an end of the hollow fiber membrane communicates with the water collection pipe; The cross-sectional area of ​​any water collection channel cross section perpendicular to the longitudinal direction of the water collection pipe is 100 to 350 mm 2A hollow fiber membrane element. [2] The hollow fiber membrane element according to [1], wherein the length of the cross section of the water collecting channel in the longitudinal direction of the hollow fiber membrane is 20 mm or less. [3] The hollow fiber membrane element according to [1] or [2], which has at least one of a deformation suppression member in contact with the wall of the water collection pipe and a deformation suppression member integrated with the water collection pipe. [4] The hollow fiber membrane element according to [3], wherein the deformation suppression member is a rib. [5] The hollow fiber membrane element according to any one of [1] to [4], wherein the water collection pipe has a step, and the step and the lower part of the potting part are bonded together. [6] The hollow fiber membrane element according to [5], wherein the step is 0.5 mm or more. [7] The water collection pipes consist of a first water collection pipe and a second water collection pipe, the second water collection pipe is located on the opposite side of the first water collection pipe in the longitudinal direction of the hollow fiber membrane, and the first water collection pipe and the second water collection pipe are connected by a support. The hollow fiber membrane element according to any one of [1] to [6]. [8] The hollow fiber membrane element according to [7], wherein the water passage inside the support is connected to the first water collection channel of the first water collection pipe and the second water collection channel of the second water collection pipe, respectively. [9] The hollow fiber membrane element according to [8], wherein the cross-sectional area of ​​the water collection pipe in any plane perpendicular to the longitudinal direction of the water collection channel is defined as b, and the cross-sectional area of ​​the support pillar in any plane perpendicular to the longitudinal direction of the water passage satisfies the relationship 0.5 × a≦b.

[10] The hollow fiber membrane element according to [9], which satisfies the following formulas (1) and (2): a / b1≧0.9 (1) a / b2≧0.9 (2) a: Any cross-sectional area of ​​the water passage of the support b1: Cross-sectional area of ​​the first collecting pipe in any plane perpendicular to the longitudinal direction of the first collecting channel b2: Cross-sectional area of ​​the second collecting pipe in any plane perpendicular to the longitudinal direction of the second collecting channel

[11] The hollow fiber membrane element according to [9] or

[10] , which satisfies the following formulas (3) and (4): 0.5×a≦b1 (3) 0.5×a≦b2 (4) a: Any cross-sectional area of ​​the water passage of the support b1: Cross-sectional area of ​​the first collecting pipe in any plane perpendicular to the longitudinal direction of the first collecting channel b2: Cross-sectional area of ​​the second collecting pipe in any plane perpendicular to the longitudinal direction of the second collecting channel

[12] A hollow fiber membrane module comprising a plurality of hollow fiber membrane elements according to any one of [1] to

[11] .

[13] A water treatment device comprising the hollow fiber membrane module according to

[12] and an air diffuser disposed below the hollow fiber membrane module.

[14] A water treatment method using the water treatment device according to

[13] .

[0008] The present invention may have the following alternative configurations. [A1] A hollow fiber membrane; a water collection pipe for collecting the treated water recovered by the hollow fiber membrane; an outlet for taking out treated water from the water collection pipe; A hollow fiber membrane element having the hollow fiber membrane and the water collection pipe are fixed by a potting portion, a water collection channel having the potting portion and the water collection pipe as wall surfaces inside the water collection pipe; the water collection pipe has a support extending parallel to the hollow fiber membrane, The support has a water passage therein that communicates with the water collection channel, The cross-sectional area of ​​the water collection channel in a plane perpendicular to the longitudinal direction of the water collection pipe is equal to or less than the cross-sectional area of ​​the water passage; Hollow fiber membrane element. [A2] If the cross-sectional area of ​​the water collection channel is b and the cross-sectional area of ​​the water passage channel is a, 0.5×a≦b The hollow fiber membrane element according to [A1], which satisfies the relationship: [A3] The maximum length between the wall surfaces of the water collection pipes facing each other at an interval in the short direction of the water collection pipes is W, Let H be the maximum length in the longitudinal direction of the hollow fiber membrane, perpendicular to the longitudinal direction of the water collection pipe, from the part of the potting portion in contact with the wall surface that is farthest from the bottom surface of the water collection channel to the bottom surface. The hollow fiber membrane element according to [A1] or [A2], which satisfies the relationship H≦1.2×W. [A4] The water collection pipe includes a first water collection pipe provided on one side of the hollow fiber membrane in the longitudinal direction and having a first water collection channel, and a second water collection pipe provided on the other side of the hollow fiber membrane in the longitudinal direction and having a second water collection channel, The hollow fiber membrane element according to any one of [A1] to [A3], wherein the first water collection pipe and the second water collection pipe are connected by the support, and the first water collection channel and the second water collection channel are in communication with the water passage. [A5] The hollow fiber membrane element according to any one of [A1] to [A4], wherein a rib is disposed at the lower part of the water collection pipe. [A6] The hollow fiber membrane element according to [A5], wherein the ribs are arranged over 70% or more of the length of the water collection channel in the longitudinal direction. [A7] A hollow fiber membrane; a water collection pipe for collecting the treated water recovered by the hollow fiber membrane; an outlet for taking out treated water from the water collection pipe; A hollow fiber membrane element having the hollow fiber membrane and the water collection pipe are fixed by a potting portion, a water collection channel having the potting portion and the water collection pipe as wall surfaces inside the water collection pipe; The end of the hollow fiber membrane is in communication with the water collection pipe, and The cross-sectional area of ​​the water collection channel in a plane perpendicular to the longitudinal direction of the water collection pipe is 100 to 350 mm 2 And, The length of the water collection channel in the longitudinal direction of the hollow fiber membrane in a plane perpendicular to the longitudinal direction of the water collection pipe is 20 mm or less. Hollow fiber membrane element. [A8] A hollow fiber membrane; a water collection pipe for collecting the treated water recovered by the hollow fiber membrane; an outlet for taking out treated water from the water collection pipe; A hollow fiber membrane element having the hollow fiber membrane and the water collection pipe are fixed by a potting portion, a water collection channel having the potting portion and the water collection pipe as wall surfaces inside the water collection pipe; The end of the hollow fiber membrane is in communication with the water collection pipe, and The cross-sectional area of ​​the water collection channel perpendicular to the longitudinal direction of the water collection pipe is 100 to 350 mm 2 And, A member that contacts and / or is integrated with the wall of the water collection pipe and suppresses deformation of the wall, Hollow fiber membrane element. [A9] The water collection pipes include a first water collection pipe and a second water collection pipe, The hollow fiber membrane element according to [A7] or [A8], wherein the second water collection pipe is located on the opposite side of the first water collection pipe in the longitudinal direction of the hollow fiber membrane, and the first water collection pipe and the second water collection pipe are connected by a support. [A10] The hollow fiber membrane element according to [A9], wherein the support is in communication with a water collecting section inside the first water collecting pipe and a second water collecting section inside the second water collecting pipe. [A11] The hollow fiber membrane element according to [A10], wherein the ratio a / b1 of the cross-sectional area a of the support column through which water passes to the cross-sectional area b1 of the first water collecting pipe through which water passes, and the ratio a / b2 of the cross-sectional area a of the support column through which water passes to the cross-sectional area b2 of the second water collecting pipe through which water passes, simultaneously satisfy formula (1) and formula (2). a / b1≧0.9 (1) a / b2≧0.9 (2) [A12] The hollow fiber membrane element according to any one of [A1] to [A11], wherein the surface roughness of the adhesive surface of the water collection pipe to be bonded to the potting portion is Ra 6.3 to 25. [A13] The hollow fiber membrane element according to any one of [A1] to [A12], wherein the surface of the water collection pipe that is bonded to the potting portion has irregularities. [A14] The hollow fiber membrane element according to any one of [A1] to [A13], wherein the water collecting pipe has a step at the bottom of the bonding surface with the potting portion. [A15] The hollow fiber membrane element according to [A14], wherein the step is 0.5 mm or more. [A16] A hollow fiber membrane module comprising a plurality of hollow fiber membrane elements according to any one of [A1] to [A15]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a hollow fiber membrane element and a hollow fiber membrane module that are excellent in pressure resistance. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing an example of a hollow fiber membrane element of the present invention. [Figure 2] FIG. 2 is a front view of the hollow fiber membrane element of FIG. [Figure 3] FIG. 3 is a cross-sectional view of the hollow fiber membrane element of FIG. 2 taken along line AA. [Figure 3A] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 3B] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 3C] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 3D] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 3E] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 3F] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 3G] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 3H] 1 is a modified example of the hollow fiber membrane element of the present invention. [Figure 4] FIG. 2 is a cross-sectional view taken along the line BB of the hollow fiber membrane element of FIG. [Figure 5] FIG. 5 is a CC cross-sectional view of the hollow fiber membrane element of FIG. [Figure 6] 1 is a modified example of the hollow fiber membrane element of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] When "~" is used to indicate a range of values, the values ​​before and after the "~" are included as the lower and upper limits. In addition, in the present invention, the term "arbitrary" is synonymous with "at least a part."

[0012] 1. Hollow fiber membrane element An example of the hollow fiber membrane element of the present invention will be described below with reference to the drawings. Note that the dimensions of the drawings shown in the following description are merely examples, and the present invention is not necessarily limited to these. Appropriate changes can be made within the scope of the present invention.

[0013] 1.1 Structure of hollow fiber membrane element As shown in FIGS. 1 and 2, the hollow fiber membrane element 1 of this embodiment has hollow fiber membranes 11, a water collection pipe, and outlets 40a and 40b for taking out treated water from the water collection pipe. 1 and 2, the water collection pipes are composed of a first water collection pipe 12 having a first water collection channel 20e therein and a second water collection pipe 14 having a second water collection channel 20f therein. The first water collection pipe 12 and the second water collection pipe 14 are arranged on opposite sides in the longitudinal direction of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10 in which a plurality of hollow fiber membranes 11 are bundled. The ends of the first water collection pipe 12 and the second water collection pipe 14 are connected to each other by a first tubular support 16 and a second tubular support 18, respectively. In the hollow fiber membrane element 1, outlets 40a, 40b are formed at both longitudinal ends of the second water collection pipe 14. The outlets may be located anywhere, even on the support columns, as long as they allow the treated water collected in the water collection pipe via the hollow fiber membranes to be taken out.

[0014] 1.2 Hollow fiber membrane The hollow fiber membranes 11 are usually used as a hollow fiber membrane sheet 10 in which a plurality of hollow fiber membranes 11 are bundled together to form a sheet. The first water collection pipe 12 is provided on the first open end 10a side in the longitudinal direction of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10. The second water collection pipe 14 is provided on the second open end 10b side, opposite the first open end 10a in the longitudinal direction of the hollow fiber membrane sheet 10.

[0015] The first tubular support 16 is disposed on one side in the width direction of the hollow fiber membrane sheet material 10, with a first end 17a of the first tubular support 16 connected to a first end 13a of the first water collecting pipe 12 and a second end 17b of the first tubular support 16 connected to a first end 15a of the second water collecting pipe 14. The second tubular support 18 is disposed on the other side in the width direction of the hollow fiber membrane sheet material 10, with a first end 19a of the second tubular support 18 connected to a second end 13b of the first water collecting pipe 12 and a second end 19b of the second tubular support 18 connected to a second end 15b of the second water collecting pipe 14. The hollow fiber membrane element 1 can be arranged with the first water collection pipe 12 on the lower side and the second water collection pipe 14 on the upper side, with the length direction of each hollow fiber membrane 11 of the hollow fiber membrane sheet 10 aligned vertically.

[0016] The hollow fiber membrane sheet 10 is formed by bundling a plurality of hollow fiber membranes 11 in parallel to one another into a sheet. The number of hollow fiber membranes 11 in the hollow fiber membrane sheet 10 is not particularly limited and can be set appropriately depending on the membrane area, for example, to 1,000 to 6,000, 2,000 to 5,000, or the like. The hollow fiber membrane sheet material 10 in this example is a laminate of a plurality of sheets, each of which is formed by aligning a plurality of hollow fiber membranes 11. In the present invention, the hollow fiber membrane sheet material may be a laminate of such a plurality of sheets, or may consist of a single sheet.

[0017] Examples of materials for the hollow fiber membrane include polysulfone resins, polyacrylonitrile, cellulose derivatives, polyolefins such as polyethylene and polypropylene, fluorine-based resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene, polyamides, polyesters, polymethacrylates, and polyacrylates. Substituents may be introduced into some of these resins. The hollow fiber membrane may be made of one type of material, or two or more types.

[0018] For example, a hollow fiber membrane sheet may be formed using a plurality of hollow fiber membranes 11 according to the method for producing a hollow fiber membrane sheet described in Japanese Patent No. 5919672, and then used.

[0019] 1.3 Water collection pipe As shown in Fig. 3, the first water collecting pipe 12 has a pair of elongated side walls 20a, 20b that face each other in the short direction of the first water collecting pipe 12 and extend in the longitudinal direction of the first water collecting pipe 12, and a semicircular cross-sectional bottom 20c that connects one end of the side walls 20a, 20b (the lower ends in Fig. 3). The cross section of the first water collecting pipe 12 perpendicular to the longitudinal direction is U-shaped. On the side of the first water collecting pipe 12 opposite the bottom 20c, a slit-shaped opening 20d is formed between the first end 13a and the second end 13b and extends in the longitudinal direction. The first open end 10a of the hollow fiber membrane sheet 10 is inserted into the opening 20d of the first water collecting pipe 12.

[0020] A pair of wall surfaces 50a, 50b that face each other and are spaced apart in the short-side direction of the first water collecting pipe 12 and extend in the long-side direction of the first water collecting pipe 12, and a bottom surface 50c that connects the lower ends of the pair of wall surfaces 50a, 50b are formed on the inside of the bottom portion 20c. The wall surfaces 50a and 50b are arranged at an interval of a maximum length W in the short-side direction of the first water collecting pipe 12. The cross section of the bottom surface 50c perpendicular to the long-side direction of the first water collecting pipe 12 is a semicircle with a radius of W / 2.

[0021] 3, the first open end 10a of the hollow fiber membrane sheet material 10 is housed in a potting case 23 and is inserted into the opening 20d of the first water collecting pipe 12 while being fixed to the potting case 23 by a potting part 23b made of a cured potting resin. The potting case 23 is fixed to the first water collecting pipe 12 by a potting part 22a made of a cured potting resin. Furthermore, the portion of the first open end 10a of the hollow fiber membrane sheet material 10 that is closer to the opening 20d than the potting case 23 is fixed to the first water collecting pipe 12 by the potting part 23a made of a cured potting resin. In this way, the hollow fiber membrane 11 and the first water collecting pipe 12 are fixed by the potting parts 22a, 23a, and 23b. The portion of the first water collecting pipe 12 closer to the bottom 20c than the potting parts 22a and 23b forms the first water collecting channel 20e (water collecting channel). In other words, the first water collecting pipe 12 has the first water collecting channel 20e inside, with the potting parts 22a and 23b and the first water collecting pipe 12 as its wall surfaces. At the first open end 10 a of the hollow fiber membrane sheet 10 , the inside of each hollow fiber membrane 11 communicates with the first water collecting channel 20 e of the first water collecting pipe 12 .

[0022] The cross-sectional area of ​​any first water collecting channel 20e perpendicular to the longitudinal direction of the first water collecting pipe 12 is 100 mm 2 ~350mm 2 and preferably 150 mm 2 ~300mm 2 and more preferably 250 mm 2 ~280mm 2 By setting the cross-sectional area within this range, it is possible to ensure excellent pressure resistance while suppressing the increase in flow resistance to an acceptable range. It is preferable that the cross-sectional area of ​​the first water collection pipe 12 be within the above range at any position in the longitudinal direction of the first water collection pipe 12. However, this is not limited thereto, and the cross-sectional area of ​​only a portion of the longitudinal direction of the first water collection pipe 12 may be within the above range.

[0023] The length H in the longitudinal direction of the hollow fiber membrane 11 in the cross section of the water collecting channel perpendicular to the longitudinal direction of the first water collecting pipe 12 (also referred to as the height H of the water collecting channel) is preferably 20 mm or less, more preferably 15 to 20 mm, even more preferably 16 mm to 20 mm, and particularly preferably 17 mm to 19 mm. Note that, as shown in Fig. 3, the length H is the distance from the end face of the potting portion 23b in contact with the wall surfaces 50a, 50b on the bottom surface 50c side to the bottom of the bottom surface 50c in the longitudinal direction of the hollow fiber membrane 11 in the cross section perpendicular to the longitudinal direction of the first water collecting pipe 12. If the height H of the water collection channel is 20 mm or less, the pressure resistance is further improved, and water leakage is less likely to occur even when backwashing is performed at high pressure.

[0024] It is preferable that the maximum length W of the short-side gap between the wall surfaces 50a, 50b and the height H of the water collection channel satisfy the relationship H≦1.2×W. When these values ​​are in this range, it becomes easier to prevent water from accumulating. In addition, if the maximum length W of the water collection channel is increased, more membranes can be packed into the collection pipe, increasing the amount of water that can be treated per unit time. Furthermore, the water inside the collection pipe is more easily renewed, and water that has accumulated at the bottom of the water collection channel flows out, improving water quality.

[0025] As another means for improving the pressure resistance of the first water collecting pipe 12, a deformation suppression member 21a that suppresses deformation of the wall of the first water collecting pipe 12 may be provided, as shown in Figures 3A to 3H. Furthermore, a member 21 that supports the deformation suppression member 21a may be further provided. The deformation suppression member 21a suppresses deformation of the water collecting channel that tends to expand outward even when backwashing is performed at high pressure, further improving pressure resistance and making it even less likely that water leakage will occur. Furthermore, by providing the deformation suppression member 21a, even if the hollow fiber membrane element 1 is hit, only the deformation suppression member 21a will be damaged, and the water collecting channel will be less likely to be damaged. The deformation suppression member 21a is preferably disposed over 70% or more of the length of the first water collection pipe 12 in the longitudinal direction. The deformation suppressing member 21a is preferably a reinforcing rib, but may be a reinforcing member other than a rib as long as it can suppress deformation of the wall of the first water collecting pipe 12.

[0026] The deformation suppression member 21a may be provided on the outside of the first water collection pipe 12, as shown in Figures 3A, 3B, and 3F to 3H, or may be provided on the inside of the first water collection pipe 12, i.e., on the side of the first water collection channel 20e, as shown in Figures 3C to 3E. Furthermore, the deformation suppression member 21a may be provided as a separate member from the first water collection pipe 12 so as to be in contact with the wall of the water collection pipe, or may be an integrated member connected to the first water collection pipe 12.

[0027] 3A to 3H, the deformation suppression member 21a is formed with a width that does not exceed the maximum width defined by the distance between the outer side surfaces of the pair of side wall portions 20a, 20b in a cross section perpendicular to the longitudinal direction of the first water collecting pipe 12. Therefore, the first water collecting pipe 12 having the deformation suppression member 21a does not have to have an increased overall dimension. For example, even if it is bumped during maintenance work, the structural reinforcement prevents damage, and the deformation suppression member 21a bears the impact of the bump, making it possible to replace the damaged part from the water collecting pipe with the deformation suppression member 21a.

[0028] As shown in Figure 3, the first water collection pipe 12 preferably has a step 20g on the inner surface of the pair of side wall portions 20a, 20b, with the lower part of the potting portion 22a bonded to the surface of the step 20g facing the opening 20d. The presence of such a step 20g is advantageous because it increases the area of ​​adhesion in the shear direction against the force that causes the water collection channel wall to expand outward when pressurized. Furthermore, the increased bonding area and improved adhesive strength increase the adhesive strength between the water collection pipe and the potting portion, making it easier to prevent peeling of the adhesive portion due to impact when it is hit. The width of the step 20g in the short-side direction of the first water collecting pipe 12 is preferably 0.5 mm or more, more preferably 1.5 mm or more, and more preferably 2.0 mm to 3.0 mm.

[0029] The surface roughness of the bonding surface of the first water collecting pipe 12 with the potting portion 22a is preferably Ra 6.3 to 25, as the arithmetic mean roughness Ra specified in JIS B 0601:2001. When the surface roughness is within this range, the adhesive strength between the first water collecting pipe 12 and the potting portion 22a is increased, the durability of the hollow fiber membrane element 1 is improved, and the element is more likely to withstand multiple high-pressure backwashings. In addition, the adhesive strength between the water collecting pipe and the potting portion is increased, making it easier to prevent peeling of the adhesive portion due to impact when the element is hit. Surface roughening can be performed on the water collection pipe itself or on the mold for the water collection pipe. For the water collection pipe itself, sandblasting and filing are examples, while for the mold for the water collection pipe, shot blasting and chemical corrosion treatment are examples.

[0030] The bonding surface of the first water collecting pipe 12 to the potting portion 22a preferably has projections and recesses. When the bonding surface has projections and recesses, the bonding strength between the first water collecting pipe 12 and the potting portion 22a increases, the durability of the hollow fiber membrane element 1 improves, and the element is more likely to withstand multiple high-pressure backwashings. In addition, the bonding strength between the water collecting pipe and the potting portion increases, making it easier to prevent the bonding portion from peeling off due to impact when the element is hit. The unevenness of the adhesive surface may be angular, wavy, or the like. The height of the unevenness (height difference) is preferably 0.3 mm to 1.0 mm, more preferably 0.4 mm to 0.6 mm. Having the unevenness within this range is preferable because it improves the adhesive strength of the potting liquid applied to the adhesive surface and makes it easier to prevent the potting liquid from flowing into the water collection channel when the potting liquid is poured.

[0031] The above explanation of the first water collecting pipe 12 in "1.3 Water Collection Pipe" also applies to the second water collecting pipe 14, including the manner in which the open end of the hollow fiber membrane sheet is inserted into the water collecting pipe, the cross-sectional area of ​​the water collection channel, etc. In the hollow fiber membrane element 1, the second water collecting pipe 14 is arranged on the opposite side of the hollow fiber membrane sheet 10 from the first water collecting pipe 12 in the longitudinal direction of each hollow fiber membrane 11, and is arranged upside down relative to the first water collecting pipe 12, i.e., with its opening facing downward. The second open end 10b of the hollow fiber membrane sheet 10 is inserted into the slit-shaped opening of the second water collecting pipe 14, and is fixed by a potting part with the end face of each hollow fiber membrane 11 open. The first water collection pipe 12 and the second water collection pipe 14 may be of the same embodiment or may be of different embodiments, but are preferably of the same embodiment.

[0032] The material of the water collection pipe is preferably one having excellent mechanical strength and durability, and examples thereof include polycarbonate, polysulfone, polyolefin, PVC (polyvinyl chloride), acrylic resin, ABS resin, modified PPE (polyphenylene ether), etc. The water collection pipe may be made of one type of material or two or more types of material.

[0033] Examples of potting resins that form the potting portion include epoxy resins, unsaturated polyester resins, polyurethane resins, silicone fillers, and various hot-melt resins. The potting portion may be formed of one type of potting resin or two or more types of potting resins.

[0034] 1.4 Struts FIG. 4 is a BB cross-sectional view of the hollow fiber membrane element of FIG. As shown in Figure 4, the first tubular support 16 has a water passage 61, which is a portion through which water passes. The water passage 61 inside the first tubular support 16 is connected to the first water collection channel 20e inside the first water collection pipe 12 and the second water collection channel 20f inside the second water collection pipe 14, respectively. Similarly, the second tubular support 18 has a water passage, which is a portion through which water passes. The water passage inside the second tubular support 18 is connected to the first water collection channel 20e inside the first water collection pipe 12 and the second water collection channel 20f inside the second water collection pipe 14, respectively.

[0035] The cross-sectional area of ​​the collection channel of the water collection pipe is preferably equal to or smaller than the cross-sectional area of ​​the water passage of the support. If the cross-sectional area of ​​the collection channel of the water collection pipe is larger than the cross-sectional area of ​​the water passage of the support, in other words, if the cross-sectional area of ​​the water passage of the support is smaller than the cross-sectional area of ​​the collection channel of the water collection pipe, the suction pressure when the hollow fiber membrane collects the treated water through the water passage by operating a suction pump or the like and collects it into the collection channel is lost in the water passage and is not sufficiently applied to the collection channel, which may reduce permeability. On the other hand, if the cross-sectional area of ​​the collection channel of the water collection pipe is equal to or smaller than the cross-sectional area of ​​the water passage of the support, pressure loss in the water passage is suppressed, making it easier to maintain permeability. In this way, by making the cross-sectional area of ​​the water collection channel in a plane perpendicular to the longitudinal direction of the water collection pipe equal to or smaller than the cross-sectional area of ​​the water passage, it becomes easier to suppress pressure loss in the water passage and maintain water permeability. Furthermore, since the cross-sectional area of ​​the water collection channel can be secured without changing the size of the hollow fiber membrane element and dimensional margin in the height direction can be secured, it becomes easier to install a deformation suppression member below the water collection channel or water collection pipe.

[0036] If the cross-sectional area of ​​any plane perpendicular to the longitudinal direction of the water passage of the support is a and the cross-sectional area of ​​any plane perpendicular to the longitudinal direction of the water collection passage of the water collection pipe is b, it is preferable to satisfy the relationship 0.5 × a ≦ b. If the cross-sectional area b of the water collection passage is smaller than 0.5 × a, the pressure loss in the water collection passage may be large, resulting in a decrease in water permeability. Therefore, satisfying the relationship 0.5 × a ≦ b makes it easier to maintain the water permeability of each hollow fiber membrane 11.

[0037] The ratio a / b1 of the cross-sectional area a of the water passage 61 of the first tubular support 16 to the cross-sectional area b1 of the first water collection passage 20e of the first water collection pipe 12, and the ratio a / b2 of the cross-sectional area a of the water passage 61 of the first tubular support 16 to the cross-sectional area b2 of the second water collection passage 20f of the second water collection pipe 14 are each preferably 0.7 or more, more preferably 0.9 or more, and preferably satisfy equations (1) and (2) simultaneously. a / b1≧0.9 (1) a / b2≧0.9 (2) When the ratio a / b1 and the ratio a / b2 are each 0.7 or more, the pressure loss in the water passage 61 of the first tubular support 16 in the hollow fiber membrane element 1 tends to be smaller, which is preferable. The same is true for the ratio between the cross-sectional area of ​​the water passage of the second tubular support 18 and the cross-sectional area of ​​the first water collection passage 20e of the first water collection pipe 12, and the ratio between the cross-sectional area of ​​the water passage of the second tubular support 18 and the cross-sectional area of ​​the second water collection passage 20f of the second water collection pipe.

[0038] It is more preferable that the cross-sectional area a of the water passage 61 of the first tubular support 16, the cross-sectional area b1 of the first water collection channel 20e of the first water collection pipe 12, and the cross-sectional area b2 of the second water collection channel 20f of the second water collection pipe 14 simultaneously satisfy formulas (3) and (4). This makes it easier to maintain the water permeability of each hollow fiber membrane 11. 0.5×a≦b1 (3) 0.5×a≦b2 (4)

[0039] The cross-sectional area of ​​the water passage of the support is, for example, 150 mm 2 ~400mm 2 It can be said that: The shape of the support is not particularly limited, and examples thereof include a square tube shape, a cylindrical shape, and the like. The material of the support is not particularly limited, and examples thereof include stainless steel (SUS).

[0040] 1.5 Protrusion 4 and 5, the first end 13a of the first water collection pipe 12 includes a cylindrical portion 24a communicating with the first water collection channel 20e, a tubular protrusion 24b protruding toward the opening 20d of the cylindrical portion 24a, and a peripheral wall portion 24c surrounding the protrusion 24b. Two of the four peripheral wall portions 24c are provided on both sides of the protrusion 24b on the cylindrical portion 24a in the longitudinal direction of the first water collection pipe 12, facing each other at a distance from the protrusion 24b. The remaining two of the four peripheral wall portions 24c are provided on both sides of the protrusion 24b on the cylindrical portion 24a in the lateral direction of the first water collection pipe 12, facing each other at a distance from the protrusion 24b, and are continuous walls integral with the side walls 20a, 20b. Of the four peripheral walls 24c surrounding the protrusion 24b, the upper end of the peripheral wall 24c on the longitudinal center side of the first water collecting pipe 12, i.e., the side closer to the first open end 10a of the hollow fiber membrane sheet 10, is slightly lower than the upper ends of the side walls 20a, 20b. Furthermore, the upper ends of the remaining three peripheral walls 24c, i.e., the peripheral wall 24c on the end face side of the first water collecting pipe 12 and the pair of peripheral walls 24c facing each other in the lateral direction, are at the same height as the upper ends of the side walls 20a, 20b.

[0041] The tubular protrusion 24b provided at the first end 13a of the first water collection pipe 12 is a portion for connecting to the first tubular support 16. The inside of the protrusion 24b is in communication with the inside of the tubular portion 24a. The shape of the protrusion 24b is not particularly limited, and examples include a square tube shape, a cylindrical shape, etc.

[0042] The height of the protrusions 24b is preferably 5 to 30 mm, and more preferably 10 to 20 mm. If the height of the protrusions 24b is equal to or greater than the lower limit of the above range, it is easy to increase the connection strength between the protrusions 24b and the first tubular support 16. If the height of the protrusions 24b is equal to or less than the upper limit of the above range, excellent moldability is achieved.

[0043] The second end 13b of the first water collection pipe 12 has the same configuration as the first end 13a, and is provided with a tubular protrusion for connecting to the second tubular support 18, and the preferred configuration is also the same. The first end 15a and second end 15b of the second water collection pipe 14 may have the same configuration as the second end 13b of the first water collection pipe 12, and the preferred configurations are also the same.

[0044] 1.6 Outlet An outlet for taking out treated water is formed on the end face of at least one of the first water collection pipe 12 and the second water collection pipe 14. In this example, the opening 24d of the cylindrical portion 24a on the end face on the first end portion 13a side of the first water collection pipe 12 is closed by a cover member 25. The opening on the end face of the water collection pipe can also be used as an outlet for taking out treated water without being closed by a cover member.

[0045] 1.7 Tubular sleeve 4 and 5, the protrusion 24b of the first end 13a of the first water collecting pipe 12 is inserted into the first end 17a of the first tubular support 16 with the tubular sleeve 26 attached, but the tubular sleeve 26 can be omitted. Also, the tubular sleeve 26 may be molded integrally with the first water collecting pipe. When the tubular sleeve 26 is attached, the first end 17a of the first tubular support 16 is connected to the first end 13a of the first water collection pipe 12, with the inside of the first tubular support 16 and the first water collection channel 20e inside the first water collection pipe 12 communicating via the protrusion 24b and the tubular sleeve 26. Similarly, the protrusion on the second end 13b of the first water collection pipe 12, with a tubular sleeve attached, may be inserted into the first end 19a of the second tubular support 18, and the first end 19a of the second tubular support 18 and the second end 13b of the first water collection pipe 12 may be connected in a state in which the interior of the second tubular support 18 communicates with the first water collection channel 20e inside the first water collection pipe 12 via the protrusion and the tubular sleeve. The tubular sleeve may be omitted. Alternatively, the tubular sleeve 26 may be molded integrally with the second water collection pipe. The protrusion at the first end 15a of the second water collection pipe 14 may be inserted into the second end 17b of the first tubular support 16 with a tubular sleeve attached, and the second end 17b of the first tubular support 16 and the first end 15a of the second water collection pipe 14 may be connected with the interior of the first tubular support 16 communicating with the second water collection channel 20f inside the second water collection pipe 14 via the protrusion and the tubular sleeve. The protrusion on the second end 15b of the second water collection pipe 14 may be inserted into the second end 19b of the second tubular support 18 with a tubular sleeve attached, and the second end 19b of the second tubular support 18 and the second end 15b of the second water collection pipe 14 may be connected with the interior of the second tubular support 18 communicating with the second water collection channel 20f inside the second water collection pipe 14 via the protrusion and the tubular sleeve.

[0046] 1.8 Resin Resin 30 is filled around the first end 17a of the first tubular support 16 inside the peripheral wall portion 24c of the first end 13a of the first water collection pipe 12. As a result, the insertion portion 28 of the first tubular support 16 is fixed in place while being watertight sealed with the resin 30 so that the inside and outside are separated. It is preferable that the gap between the first tubular strut 16 and the protrusion 24b in the insertion portion 28 is sealed watertight with resin 30.

[0047] The resin 30 is not particularly limited, and any known curable resin can be used without any particular restriction. As the resin 30, a hard resin having a Shore A hardness of 80 or more measured in accordance with JIS C 2105 is preferred, as it has a stronger adhesive strength to the tubular support and excellent watertightness. When the resin 30 is a hard resin, the Shore A hardness is preferably 99 or less, as it makes the resin 30 less likely to break. However, a soft resin having a Shore A hardness of less than 80 may also be used as the resin 30.

[0048] Examples of hard resins include epoxy resins, unsaturated polyester resins, polyurethane resins, silicone-based fillers, and various hot-melt resins. Examples of soft resins include polyurethane resins, silicone-based fillers, and various hot-melt resins.

[0049] It is preferable that the protrusion 24b becomes thinner toward the tip. This makes it easier to insert the first tubular support 16 and also helps to prevent the resin 30 injected around the protrusion 24b from being peeled off when inserting the first tubular support 16. It also makes it easier to remove the first water collecting pipe 12 from the mold when manufacturing it by injection molding.

[0050] The outer surface of the first end 17a of the first tubular support 16 is preferably blasted. In the present invention, the outer surfaces of the ends of the first and second tubular supports are preferably blasted. The outer surfaces of the ends of the first and second tubular supports come into contact with a resin that fixes the insertion portions into which the protrusions are inserted, sealing them watertightly so as to separate the communicating interior and exterior. Blasting the outer surfaces of the ends of the first and second tubular supports improves adhesion between the tubular supports and the resin, thereby improving the strength of the hollow fiber membrane element. The method of blasting is not particularly limited.

[0051] 1.9 Blocks In this example, blocks 32 and 34 are provided on both longitudinal sides of the first end 17a of the first tubular support 16 inside the peripheral wall 24c of the first water collection pipe 12. The blocks 32 and 34 are provided in a state where they are embedded in the resin 30 that fills the inside of the peripheral wall 24c. This prevents the support from falling over and being damaged even when a load is applied to the support.

[0052] The shape of the block is not particularly limited, and examples thereof include a cylindrical body and a columnar body. The material of the block is not particularly limited, and examples thereof include the same materials as those listed as the materials of the water collection pipe. A part of the water collection pipe may be formed into a rectangular parallelepiped by integral molding so as to have the same function as the block.

[0053] In the present invention, it is also preferred that a first closing section for blocking the flow of treated water that has flowed into the water collection channel of the first water collection pipe through the first open end of the hollow fiber membrane sheet-like material toward the first tubular support is provided closer to the first end than the first open end of the hollow fiber membrane sheet-like material in the longitudinal direction of the first water collection pipe, and a second closing section for blocking the flow of treated water that has flowed into the water collection channel of the second water collection pipe through the second open end of the hollow fiber membrane sheet-like material toward the second tubular support is provided closer to the second end than the second open end of the hollow fiber membrane sheet-like material in the longitudinal direction of the second water collection pipe. This makes it possible to prevent uneven use of the hollow fiber membrane sheet-like material for treatment, and enables the hollow fiber membrane sheet-like material to be used for treatment efficiently overall.

[0054] 2, a first closing section 36 and a second closing section 38 are provided on the first end 13a side of the first open end 10a of the hollow fiber membrane sheet 10 in the longitudinal direction of the first water collecting pipe 12, and on the second end 15b side of the second open end 10b of the hollow fiber membrane sheet 10 in the longitudinal direction of the second water collecting pipe 14. Outlets 40a, 40b for taking out treated water are formed on the end faces of the first end 15a and the second end 15b of the second water collecting pipe 14.

[0055] The first closing section 36 is a section that blocks the flow of treated water that has flowed into the first water collection channel 20e through the first open end 10a of the hollow fiber membrane sheet 10 to the first tubular support 16. The second closing section 38 is a section that blocks the flow of treated water that has flowed into the second water collection channel 20f through the second open end 10b of the hollow fiber membrane sheet 10 to the second tubular support 18. The shapes of the first closing portion 36 and the second closing portion 38 are not particularly limited as long as they are capable of blocking the flow of treated water.

[0056] In this embodiment, as shown in Figure 2, treated water collected from the lower portions of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10 into the first water collection channel 20e of the lower first water collection pipe 12 is sent through the second tubular support 18 to the second end 15b of the upper second water collection pipe 14 and taken out from the outlet 40b. Treated water collected from the upper portions of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10 into the second water collection channel 20f of the upper second water collection pipe 14 is sent to the first end 15a of the second water collection pipe 14 and taken out from the outlet 40a. This allows the hollow fiber membrane sheet 10 to be used for treatment efficiently overall.

[0057] Furthermore, for example, as shown in Figure 6, a first closing section 36 may be provided in the center of the first water collection pipe 12 in the longitudinal direction, a second closing section 38 may be provided in the center of the second water collection pipe 14 in the longitudinal direction, and outlets 40a, 40b for taking out treated water may be formed on the end faces of the first end 15a and the second end 15b of the second water collection pipe 14.

[0058] In this configuration, the first closing portion 36 blocks the flow of treated water that has flowed into the first water collection channel 20e through the first open end 10a of the hollow fiber membrane sheet 10 on the first end 13a side toward the second end 13b, and blocks the flow of treated water that has flowed into the first water collection channel 20e through the first open end 10a of the hollow fiber membrane sheet 10 on the second end 13b side toward the first end 13a. The second closing portion 38 blocks the flow of treated water that has flowed into the second water collection channel 20f through the second open end 10b of the hollow fiber membrane sheet 10 on the first end 15a side toward the second end 15b, and blocks the flow of treated water that has flowed into the second water collection channel 20f through the second open end 10b of the hollow fiber membrane sheet 10 on the second end 15b side toward the first end 15a.

[0059] 6, treated water collected from the lower portions of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10 on the first end 13a side into the first water collection channel 20e of the lower first water collection pipe 12 is sent through the first tubular support 16 to the first end 15a of the upper second water collection pipe 14 and taken out from the outlet 40a. Treated water collected from the upper portions of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10 on the first end 13a side into the second water collection channel 20f of the upper second water collection pipe 14 is sent to the first end 15a of the second water collection pipe 14 and taken out from the outlet 40a. Treated water collected from the lower portions of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10 on the second end 13b side into the first water collection channel 20e of the lower first water collection pipe 12 is sent through the second tubular support 18 to the second end 15b of the upper second water collection pipe 14 and taken out from the outlet 40b. Treated water collected from the upper portions of the hollow fiber membranes 11 of the hollow fiber membrane sheet 10 on the second end 13b side into the second water collection channel 20f of the upper second water collection pipe 14 is sent to the second end 15b of the second water collection pipe 14 and taken out from the outlet 40b. This allows the hollow fiber membrane sheet 10 to be used for treatment efficiently overall.

[0060] The hollow fiber membrane element of the present invention is not limited to the hollow fiber membrane element 1 described above. For example, the number and positions of the outlets are not limited to those described above, and can be set as appropriate. The hollow fiber membrane element may be used in a state where the length direction of each hollow fiber membrane of the hollow fiber membrane sheet is arranged horizontally.

[0061] 2. Manufacturing method of hollow fiber membrane element There are no particular limitations on the method for producing the hollow fiber membrane element of the present invention. As an example of the method for producing the hollow fiber membrane element of the present invention, a method for producing the hollow fiber membrane element 1 described above will be described below.

[0062] The hollow fiber membrane element 1 can be produced by a method including the following steps (a) to (e). Step (a): The first and second ends of a plurality of hollow fiber membranes 11 bundled into a sheet are inserted into a potting case, and potting resin is injected and hardened to fix the hollow fiber membrane sheet to the potting case. Step (b): The tip of the potting case to which the hollow fiber membrane 11 is fixed is cut off to obtain a hollow fiber membrane sheet 10. Step (c): The first tubular support 16 and the second tubular support 18 are connected to the protruding portions of the first end 13 a and the second end 13 b of the first water collecting pipe 12 . Step (d): The first tubular support 16 and the second tubular support 18 are connected to the protruding portions of the first end 15a and the second end 15b of the second water collecting pipe 14. Step (e): The first open end 10a of the hollow fiber membrane sheet 10 is inserted into the first water collecting pipe 12 and fixed with a potting part, and the second open end 10b of the hollow fiber membrane sheet 10 is inserted into the second water collecting pipe 14 and fixed with a potting part. If necessary, provide deformation suppression members on the water collection pipe.

[0063] 3. Hollow fiber membrane module The hollow fiber membrane module of the present invention comprises a plurality of hollow fiber membrane elements of the present invention. The hollow fiber membrane module of the present invention can adopt any known embodiment, except that it comprises a plurality of hollow fiber membrane elements of the present invention. In the hollow fiber membrane module of the present invention, for example, a plurality of hollow fiber membrane elements can be arranged so that the surfaces of the hollow fiber membrane sheets face each other and at intervals in a direction perpendicular to the surfaces of the hollow fiber membrane sheets. Alternatively, a plurality of units each having a plurality of hollow fiber membrane elements arranged in this manner can be formed, and these units can be stacked one on top of the other.

[0064] 4. Effects The hollow fiber membrane element of the present invention has a cross-sectional area of ​​the water collection channel in a plane perpendicular to the longitudinal direction of the water collection pipe of 100 to 350 mm 2 This provides excellent pressure resistance, preventing damage to the water collection pipe and causing water leakage even when pressure is applied to the inside of the water collection pipe during high-pressure backwashing. The uses of the hollow fiber membrane element and hollow fiber membrane module of the present invention are not particularly limited, and they may be used for wastewater treatment or for producing purified water such as sterile water, drinking water, highly pure water, etc. The hollow fiber membrane element of the present invention has excellent pressure resistance that can withstand backwashing, and is therefore particularly useful for producing purified water.

[0065] 5.Water treatment equipment The water treatment device of the present invention comprises the hollow fiber membrane module of the present invention and an air diffuser disposed below the hollow fiber membrane module. The air diffuser is not particularly limited, and any known air diffuser for membrane cleaning can be used without any restrictions. Examples of the water treatment device of the present invention include a device used in a membrane bioreactor (MBR) method and a water purification device for treating river water or the like.

[0066] 6. Water treatment methods The water treatment method of the present invention is a method of treating water using the water treatment device of the present invention. The water treatment method of the present invention is not particularly limited, and examples thereof include a membrane bioreactor (MBR) method and purification treatment of river water, etc. [Example]

[0067] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0068] [Example 1] A hollow fiber membrane element having the same configuration as the hollow fiber membrane element 1 illustrated in FIGS. 1 to 3 was produced. The cross-sectional area b1 of the first collection channel of the first collection pipe and the cross-sectional area b2 of the second collection channel of the second collection pipe are 300 mm 2 The height H of the first and second collection channels was set to 18 mm, and the ratios a / b1 and a / b2 were set to 1.28.

[0069] [Example 2] A hollow fiber membrane element having the same configuration as in Example 1 was produced, except that the configuration of the first and second water collecting pipes was changed to a configuration having a deformation suppression member as shown in Figure 3A, and the cross-sectional area, height H, ratio a / b1, and ratio a / b2 of the first and second water collecting channels were changed as shown in Table 1.

[0070] [Example 3] A hollow fiber membrane element having the same configuration as in Example 1 was produced, except that the configuration of the first and second water collecting pipes was changed to a configuration having a deformation suppression member as shown in Figure 3A, and the cross-sectional area, height H, ratio a / b1, and ratio a / b2 of the first and second water collecting channels were changed as shown in Table 1.

[0071] [Comparative Example 1] A hollow fiber membrane element having the same configuration as in Example 1 was produced, except that the configuration of the first and second water collecting pipes was changed to a configuration having a deformation suppression member as shown in Figure 3A, no supports were provided, and the cross-sectional areas and heights H of the first and second water collecting channels were changed as shown in Table 1.

[0072] Comparative Example 2 A hollow fiber membrane element having the same configuration as in Example 1 was produced, except that the cross-sectional area, height H, ratio a / b1 and ratio a / b2 of the first and second water collecting channels were changed as shown in Table 1.

[0073] [Pressure test] For each hollow fiber membrane element, each hollow fiber membrane was cut at the opening of the first and second water collection pipes, and the cut sections were sealed with potting resin. Water was then supplied to each water collection pipe, and the water pressure was gradually increased until the pipes were broken and water leaked. The water pressure at which water leakage occurred for each hollow fiber membrane element is shown in Table 1.

[0074] [Table 1]

[0075] As shown in Table 1, the hollow fiber membrane elements of Examples 1 to 3, in which the cross-sectional area of ​​the water collection pipe was within the appropriate range, had higher water pressure at the time of water leakage and were superior in pressure resistance compared to the hollow fiber membrane element of Comparative Example 1, in which the cross-sectional area of ​​the water collection pipe was small, and Comparative Example 2, in which the cross-sectional area of ​​the water collection pipe was large. Furthermore, the hollow fiber membrane elements of Examples 2 and 3, which were equipped with a deformation suppression member, were even superior in pressure resistance compared to the hollow fiber membrane element of Example 1, which was not equipped with a deformation suppression member. [Explanation of symbols]

[0076] 1...Hollow fiber membrane element, 10...Hollow fiber membrane sheet,...10a 1st open end, 10b...2nd open end, 11...hollow fiber membrane, 12...1st water collecting pipe (water collecting pipe), 13a...1st end, 13b...2nd end, 14...2nd water collecting pipe (water collecting pipe), 15a...1st end, 15b...2nd end, 16...1st tubular strut (support), 17a...first end, 17b...second end, 18...second tubular strut (support), 19a...first end, 19b...second end, 20a...side wall, 20b...side wall, 20c...bottom, 20d...opening, 20e...first collection channel (collection channel), 20f...second collection channel (Water collection channel), 20g...step, 21...member, 21a...deformation suppression member, 22a...potting portion, 23...potting case, 23a...potting portion, 23b...potting portion, 23c...interface, 24a...cylindrical portion, 24b...protrusion portion, 24c...peripheral wall portion, 24d...opening, 25...lid member, 26...tubular sleeve, 28...insertion portion, 30...resin, 32...block, 33...protective layer, 34...block, 36...first closing portion, 38...second closing portion, 40a, 40b...outlet, 61...water passage.

Claims

1. A hollow fiber membrane element having a hollow fiber membrane, a water collection pipe, and an outlet for taking out treated water from the water collection pipe, the hollow fiber membrane and the water collection pipe are fixed by a potting portion, a water collection channel having the potting portion and the water collection pipe as wall surfaces inside the water collection pipe; an end of the hollow fiber membrane communicates with the water collection pipe; The cross-sectional area of ​​any water collection channel cross section perpendicular to the longitudinal direction of the water collection pipe is 100 to 350 mm ２ and the water collection pipes include a first water collection pipe and a second water collection pipe; the second water collection pipe is located on the opposite side of the first water collection pipe in the longitudinal direction of the hollow fiber membrane, and the first water collection pipe and the second water collection pipe are connected by a support; the water passage inside the support is in communication with the first water collection channel of the first water collection pipe and the second water collection channel of the second water collection pipe, A hollow fiber membrane element that satisfies the following formulas (1) and (2): a / b 1 ≧0.9...(1) a / b 2 ≧0.9...(2) a: Cross-sectional area of ​​the water channel of the support in any plane perpendicular to the longitudinal direction b 1: Cross-sectional area of ​​the first water collecting pipe in any plane perpendicular to the longitudinal direction of the first water collecting channel b 2: Cross-sectional area of ​​the second collecting pipe in any plane perpendicular to the longitudinal direction of the second collecting channel

2. 2. The hollow fiber membrane element according to claim 1, wherein the length of the cross section of the water collecting channel in the longitudinal direction of the hollow fiber membrane is 20 mm or less.

3. 3. The hollow fiber membrane element according to claim 1, further comprising at least one of a deformation suppression member in contact with a wall of the water collection pipe and a deformation suppression member integrated with the water collection pipe.

4. The hollow fiber membrane element according to claim 3 , wherein the deformation suppressing member is a rib.

5. 5. The hollow fiber membrane element according to claim 1, wherein the water collection pipe has a step, and the step and a lower portion of the potting portion are bonded to each other.

6. The hollow fiber membrane element according to claim 5, wherein the step is 0.5 mm or more.

7. The hollow fiber membrane element according to any one of claims 1 to 6, wherein the relationship 0.5 × a ≦ b is satisfied, where b is the cross-sectional area of ​​the water collection pipe in any plane perpendicular to the longitudinal direction of the water collection channel, and a is the cross-sectional area of ​​the support pillar in any plane perpendicular to the longitudinal direction of the water passage channel.

8. The hollow fiber membrane element according to any one of claims 1 to 7, which satisfies the following formulas (3) and (4): 0.5×a≦b １ ・・・(3) 0.5×a≦b ２ ・・・(4) a: Any cross-sectional area of ​​the support waterway b １ : Cross-sectional area of ​​the first collecting pipe in any plane perpendicular to the longitudinal direction of the first collecting channel b ２ : Cross-sectional area of ​​the second collecting pipe in any plane perpendicular to the longitudinal direction of the second collecting channel

9. A hollow fiber membrane module comprising a plurality of hollow fiber membrane elements according to any one of claims 1 to 8.

10. A water treatment device comprising: the hollow fiber membrane module according to claim 9; and an air diffuser disposed below the hollow fiber membrane module.

11. A water treatment method using the water treatment device according to claim 10.

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