Hollow fiber membrane module

Abstract

To provide a hollow fiber membrane module capable of suppressing tangling, damage and the like of a hollow fiber membrane while effectively removing a floating pollutant stuck on the surface of the hollow fiber membrane in a bubbling step.SOLUTION: A hollow fiber membrane module 10 comprises a housing 13 in which a fixing member 3 is fixed and an internal space S1 is formed, a plurality of hollow fiber membrane bundles 15 each having a plurality of hollow fiber membranes 14 and disposed in the internal space S1 in a state in which upper ends 14B of the plurality of hollow fiber membranes 14 are fixed to the fixing member 3, a gas supply part 2 that supplies a gas into the internal space S1 to clean the hollow fiber membrane bundles 15, and suppression members 100 individually provided for the respective hollow fiber membrane bundles 15. The suppression member 100 is configured, in the corresponding hollow fiber membrane bundle 15, to suppress splashing of lower ends 14A of the hollow fiber membranes 14 while allowing oscillation of the hollow fiber membranes 14 by the gas supplied into the internal space S1 from the gas supply part 2.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a hollow fiber membrane module including a plurality of hollow fiber membranes. [Background technology]

[0002] Conventionally, hollow fiber membrane modules with bundles of hollow fiber membranes have been used in water treatment to remove impurities from water. In the filtration process of water treatment, raw water (water before filtration) is supplied into the hollow fiber membrane module through a raw water inlet provided in the module, and the filtrate that has passed through the membrane is discharged out of the module through a filtrate outlet provided in the module.

[0003] In hollow fiber membrane modules, when the filtration process for water treatment is performed, substances removed from the water (suspended solids (SS)) accumulate on the membrane surface. Thus, one of the important challenges is to efficiently remove the suspended solids that have accumulated on the membrane surface.

[0004] Generally, the removal of suspended pollutants is carried out by a process known as backwashing (backpressure washing). In the backwashing process, a fluid flow is created inside the module in the opposite direction to the filtration process in order to lift suspended pollutants adhering to the membrane surface. That is, fluids such as gases and liquids are supplied into the module through the filtrate outlet, and the fluid that passes through the membrane from the inside to the outside is discharged out of the module through the raw water inlet.

[0005] The suspended pollutants partially floating on the membrane surface as a result of the backwashing process are then peeled off from the membrane surface by the bubbling process, in which a cleaning gas is supplied to the module filled with water, and the bubbles of the supplied cleaning gas shake the membrane, causing the suspended pollutants on the membrane surface to peel off.

[0006] In the bubbling process, in order to more effectively remove suspended pollutants accumulated on the membrane surface, it is necessary to vigorously rock the hollow fiber membranes. However, excessive rocking can cause friction between the hollow fiber membranes due to contact, breakage near the fixing parts of the hollow fiber membranes, and tangles between the hollow fiber membranes, making stable operation difficult. Patent Document 1 listed below discloses a hollow fiber membrane module equipped with a configuration for appropriately rocking the hollow fiber membranes in the bubbling process.

[0007] In the hollow fiber membrane module of Patent Document 1 below, a net-like object is provided so as to cover the entire hollow fiber membrane bundle in which a plurality of hollow fiber membranes are fixed at the upper ends in a bundle shape. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-262441 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, all hollow fiber membranes constituting the hollow fiber membrane module are bundled together as a single hollow fiber membrane bundle, and this single hollow fiber membrane bundle is entirely covered with a net-like material. In this case, the oscillation of all hollow fiber membranes during the bubbling process is restricted by the same net-like material, making it impossible to effectively remove suspended pollutants attached to the membrane surface. Furthermore, in a structure in which the entire hollow fiber membrane bundle is covered with a net-like material, there is a risk that the lower ends of the hollow fiber membranes will become entangled with the net-like material due to the oscillation during the bubbling process. In this case, the hollow fiber membranes may become entangled with the net-like material, causing problems such as damage to the hollow fiber membranes.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a hollow fiber membrane module that can effectively remove suspended pollutants adhering to the membrane surfaces of hollow fiber membranes during a bubbling process while suppressing entanglement and damage to the hollow fiber membranes. [Means for solving the problem]

[0011] A hollow fiber membrane module according to one aspect of the present invention comprises a housing having a fixing member fixed therein and forming an internal space, a plurality of hollow fiber membrane bundles each having a plurality of hollow fiber membranes and arranged in the internal space with the upper ends of the hollow fiber membranes fixed to the fixing member, a gas supply unit that supplies gas for cleaning the hollow fiber membrane bundles to the internal space, and a suppression member individually provided for each of the hollow fiber membrane bundles. Each of the suppression members is configured to suppress the lower ends of the hollow fiber membranes from flying up while allowing the hollow fiber membranes to oscillate in the corresponding hollow fiber membrane bundle due to the gas supplied from the gas supply unit into the internal space.

[0012] According to this hollow fiber membrane module, the hollow fiber membranes constituting the hollow fiber membrane module are divided into multiple hollow fiber membrane bundles with their upper ends fixed to a fixing member, and each of the multiple hollow fiber membrane bundles is individually provided with a suppression member. As a result, the hollow fiber membrane bundles are isolated from each other by the suppression member. Therefore, during the bubbling process in response to the supply of cleaning gas from the gas supply unit, the multiple hollow fiber membranes oscillate within the isolated hollow fiber membrane bundle. This causes suspended pollutants adhering to the membrane surfaces to peel off. Since the hollow fiber membrane bundles are isolated from each other by the suppression member, the suspended pollutants peeled off from the membrane surfaces of the multiple hollow fiber membranes within each hollow fiber membrane bundle can be discharged through the hollow fiber membrane bundles. This allows suspended pollutants adhering to the membrane surfaces of the hollow fiber membranes within each hollow fiber membrane bundle to be effectively removed. Furthermore, the suppression member keeps each hollow fiber membrane bundle independent of the others, thereby suppressing interference between hollow fiber membranes belonging to different hollow fiber membrane bundles, thereby preventing entanglement of hollow fiber membranes between hollow fiber membrane bundles and suppressing damage to the hollow fiber membranes that would otherwise occur.

[0013] Furthermore, the suppression member that keeps each hollow fiber membrane bundle independent is configured to suppress the lower ends of the hollow fiber membranes from flying up while allowing the hollow fiber membranes to swing within the hollow fiber membrane bundle. In this way, the suppression member suppresses the lower ends of the hollow fiber membranes from flying up within the hollow fiber membrane bundle, thereby restricting excessive movement of the hollow fiber membranes within the hollow fiber membrane bundle. This makes it possible to suppress excessive interference between the hollow fiber membranes, such as entanglement between hollow fiber membranes belonging to the same hollow fiber membrane bundle, and to suppress accompanying damage to the hollow fiber membranes.

[0014] In the hollow fiber membrane module described above, each of the suppression members may be configured as a mesh-like body having a plurality of meshes and extending in the vertical direction so as to cover the side surfaces of the corresponding hollow fiber membrane bundle. In this case, the lower ends of the suppression members are positioned so as to be able to suppress the lower ends of the hollow fiber membranes oscillating within the corresponding hollow fiber membrane bundle from flying up and to suppress the lower ends of the hollow fiber membranes from entering the meshes.

[0015] In this embodiment, the lower end of the suppression member, which is formed of a mesh-like body covering the side surface of the hollow fiber membrane bundle, is positioned to prevent the lower ends of the hollow fiber membranes oscillating within the hollow fiber membrane bundle from flying up and to prevent the lower ends of the hollow fiber membranes from entering the mesh. The suppression member prevents the lower ends of the hollow fiber membranes within the hollow fiber membrane bundle from flying up, thereby preventing the hollow fiber membranes from becoming entangled within the hollow fiber membrane bundle. Furthermore, by positioning the lower end of the suppression member so as to prevent the lower ends of the hollow fiber membranes from entering the mesh of the suppression member, it is possible to prevent the hollow fiber membranes from becoming entangled with the suppression member. This prevents damage to the hollow fiber membranes.

[0016] In the hollow fiber membrane module described above, the upper ends of the suppression members may be fixed to the fixing members, and the lengths of the suppression members in the vertical direction may be set to satisfy the following formula (1): 0.7≦L1 / L2≦1.0 (1)

[0017] In the above formula (1), "L1" represents the length of the suppression member in the vertical direction, and "L2" represents the effective length of the hollow fiber membrane.

[0018] In this embodiment, the vertical length of the suppression member, which is composed of a mesh-like body covering the side surface of the hollow fiber membrane bundle, is set to satisfy the above formula (1). By setting the length of the suppression member to satisfy the left side of the above formula (1), "0.7≦L1 / L2," the lower end of the suppression member can be positioned at a position that can prevent the lower ends of the multiple hollow fiber membranes from flying up. On the other hand, by setting the length of the suppression member to satisfy the right side of the above formula (1), "L1 / L2≦1.0," the lower end of the suppression member can be positioned at a position that can prevent the lower ends of the multiple hollow fiber membranes from entering the mesh of the suppression member.

[0019] In the hollow fiber membrane module described above, each of the suppression members may have a function of separating the hollow fiber membrane bundles so as to form gaps between the plurality of hollow fiber membrane bundles.

[0020] In this embodiment, the suppression member forms gaps between the hollow fiber membrane bundles, so that suspended pollutants that are peeled off in response to the oscillation of the hollow fiber membranes within each hollow fiber membrane bundle during the bubbling process can be discharged through the gaps between the hollow fiber membrane bundles, thereby further enhancing the removal effect of suspended pollutants that have adhered to the membrane surfaces of the hollow fiber membranes.

[0021] In the above hollow fiber membrane module, the gas supply unit may be configured to include an air diffusing member that is disposed below the hollow fiber membrane bundle, has a shape that expands in the radial direction of the hollow fiber membrane bundle, and has a plurality of air diffusion vents formed at intervals in the radial direction. In this case, the air diffusing member includes: a plate-shaped main body that expands in the radial direction of the hollow fiber membrane bundle and has a plurality of air diffusion vents formed at intervals in the radial direction; and a gas receiving part that has a cylindrical shape with one end connected to the lower surface of the main body and the other end formed with a gas receiving port, and has dispersion holes formed therein for guiding the gas contained in the cylinder to the air diffusion vents.

[0022] In the hollow fiber membrane module described above, the gas receiving portion may have a shape in which the inner diameter increases from the one end toward the other end.

[0023] Furthermore, in the hollow fiber membrane module described above, the aeration vents may be arranged on a plurality of circumferences spaced apart in the radial direction in the main body, and the number of the aeration vents on each circumference may be a multiple of the number of the hollow fiber membrane bundles. [Effects of the Invention]

[0024] As described above, according to the present invention, it is possible to provide a hollow fiber membrane module that can effectively remove suspended pollutants adhering to the membrane surfaces of the hollow fiber membranes during the bubbling process while suppressing entanglement and damage to the hollow fiber membranes. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram illustrating a configuration of a filtering device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing the configuration of a hollow fiber membrane module according to a first embodiment of the present invention. [Figure 3] FIG. 2 is a diagram showing the planar structure of an air diffusing member provided in the hollow fiber membrane module. [Figure 4] 4 is a diagram showing a cross-sectional structure of the air diffusing member taken along line IV-IV in FIG. 3. FIG. [Figure 5] 3 is a diagram showing a cross-sectional structure of a water pipe taken along line VV in FIG. 2. FIG. [Figure 6] FIG. 3 is an enlarged view of a water pipe in region VI in FIG. 2. [Figure 7] FIG. 1 is a perspective view showing a state in which a suppression member is provided for each hollow fiber membrane bundle in a hollow fiber membrane module. [Figure 8] FIG. 10 is a top view of a hollow fiber membrane module in which a suppression member is provided for each hollow fiber membrane bundle. [Figure 9] FIG. 10 is a diagram showing a basic operation program of the filtration device. [Figure 10] FIG. 10 is a perspective view showing a state in which a suppression member is provided for each hollow fiber membrane bundle in a hollow fiber membrane module according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a perspective view showing a state in which a suppression member is provided for each hollow fiber membrane bundle in a hollow fiber membrane module according to a third embodiment of the present invention. [Figure 12] FIG. 10 is a perspective view showing a state in which a suppression member is provided for each hollow fiber membrane bundle in a hollow fiber membrane module according to a fourth embodiment of the present invention. [Figure 13] FIG. 10 is a perspective view showing a state in which a suppression member is provided for each hollow fiber membrane bundle in a hollow fiber membrane module according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0027] (First embodiment) [Filtration equipment, hollow fiber membrane module] First, the configuration of a filtration device 1 equipped with a hollow fiber membrane module 10 according to a first embodiment of the present invention will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a schematic diagram showing the configuration of the filtration device 1. Fig. 2 is a schematic diagram showing the configuration of the hollow fiber membrane module 10.

[0028] The filtration device 1 includes an external pressure filtration type hollow fiber membrane module 10, a liquid feed pump 20, an air compressor 30, piping connecting these modules with on-off valves provided on the piping, and a control device 40. The hollow fiber membrane module 10 is an external pressure filtration type module in which a raw liquid is supplied to the outer surface side of the hollow fiber membrane and a filtrate is taken out from the inner surface side.

[0029] As shown in FIG. 2, the hollow fiber membrane module 10 includes a housing 13 in which a fixing member 3 is fixed and which forms an internal space S1, a plurality of hollow fiber membrane bundles 15 arranged in the internal space S1, a water guide pipe (pipe member) 5 for introducing raw water into the internal space S1, a gas supply unit 2 for supplying gas (cleaning gas) for cleaning the plurality of hollow fiber membrane bundles 15 to the internal space S1, and a suppression member 100 individually provided for each of the plurality of hollow fiber membrane bundles 15.

[0030] Each of the hollow fiber membrane bundles 15 has a plurality of hollow fiber membranes 14, and the upper ends 14B of the hollow fiber membranes 14 are fixed to the fixing member 3 in an open state, while the lower ends 14A of the hollow fiber membranes 14 are sealed and not fixed individually, forming a one-end free type. The fixing member 3 converges and fixes the upper ends 14B of the hollow fiber membranes 14 for each hollow fiber membrane bundle 15. The fixing member 3 liquid-tightly divides the space within the housing 13 into an internal space S1 on the raw water side and a space S2 on the filtrate side to allow the hollow fiber membranes 14 to function as filtration membranes. A thermosetting resin such as epoxy resin, unsaturated polyester resin, or polyurethane resin is used for the fixing member 3. Methods for bonding each hollow fiber membrane bundle 15 to the fixing member 3 include centrifugal bonding and static bonding.

[0031] Various materials can be used as the material for the hollow fiber membrane 14, and are not particularly limited. For example, the hollow fiber membrane 14 preferably contains at least one selected from the group consisting of polyethylene, polypropylene, polyacrylonitrile, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, polytetrafluoroethylene, polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, polysulfone, cellulose acetate, polyvinyl alcohol, and polyethersulfone, and polyvinylidene fluoride (PVDF) is more preferable from the viewpoint of membrane strength and chemical resistance.

[0032] The hollow fiber membrane module 10 is of an external pressure filtration type, and may be of either an external pressure dead-end filtration type or an external pressure circulation filtration type depending on the conditions of the membrane separation process and the required performance. From the viewpoint of membrane life, the external pressure circulation filtration type is preferred because it allows simultaneous surface cleaning of the filtration membrane, while the external pressure dead-end filtration type is preferred from the viewpoint of simplicity of the equipment, installation costs, and operating costs.

[0033] In the hollow fiber membrane module 10, as the total number of hollow fiber membranes 14 constituting each hollow fiber membrane bundle 15 increases, the membrane area per module increases, so the filtration flow rate can be increased, but on the other hand, the efficiency of discharging suspended pollutants during cleaning decreases. Therefore, the outer diameter di (m) of the hollow fiber membrane 14, the total number n (units) of hollow fiber membranes 14, and the cross-sectional area S (m 2 ) The film filling factor 100πndi is calculated by 2 The / 4S (%) is preferably 10 to 60%, and more preferably 20 to 50%.

[0034] The housing 13 has a cylindrical shape and has an upper surface 13A, a lower surface 13C, and a side surface 13B connecting these. The housing 13 has an internal space S1 in which a plurality of hollow fiber membrane bundles 15 are accommodated, and the internal space S1 is divided into an upper space S11 in which the hollow fiber membranes 14 are located above the center in the longitudinal direction (vertical direction), and a lower space S12 in which the hollow fiber membranes 14 are located below the center in the longitudinal direction.

[0035] A filtrate pipe 51 for extracting filtrate is connected to the upper surface 13A of the housing 13, and the filtrate pipe 51 is provided with a filtrate outlet 52 and a filtrate-side gas inlet 53. A gas vent port 11 for discharging gas in the internal space S1 to the outside of the system is provided on the side surface 13B directly below the fixing member 3. The gas vent port 11 is an opening of the upper space S11. A drain outlet 12 for discharging liquid in the internal space S1 to the outside of the system is provided on the side surface 13B directly above the lower surface 13C. A diffuser gas inlet 7 for supplying gas into the internal space S1 is provided near the center of the lower surface 13C.

[0036] As shown in Figure 1, a gas vent pipe 61 is connected to the gas vent port 11, and gas within the housing 13 is discharged to the outside of the system via this. A gas discharge port valve 62 is provided on the gas vent pipe 61, and opening this valve allows gas to be discharged from within the housing 13. Furthermore, a drain pipe 41 is connected to the drain vent port 12, and liquid within the housing 13 is discharged to the outside of the system via this. A raw liquid discharge port valve 42 is provided on the drain pipe 41, and opening this valve allows liquid to be discharged from the housing 13.

[0037] Materials that can be used for the housing 13 include SUS, modified PPE, polyvinyl chloride, polysulfone, polycarbonate, polyolefin, and ABS resin. A so-called integrated module may be configured by adhesively fixing the fixing member 3 to the inner surface of the housing 13. Alternatively, an O-ring, packing, or the like may be attached to the outer periphery of the fixing member 3, and the fixing member 3 may be detachably and liquid-tightly attached to the housing 13. In this case, the fixing member 3 can be removed and each hollow fiber membrane bundle 15 replaced, allowing the housing 13 to be used repeatedly.

[0038] As shown in Figure 2, the water conduit 5 is disposed in a position where it penetrates the center of the lower surface 13C of the housing 13 and extends toward the upper surface 13A, and its upper end is connected to the fixing member 3. The water conduit 5 has a raw liquid inlet 9 at its lower end and a gas inlet 8 for the water conduit on its side. The water conduit 5 can supply only the unfiltered raw water introduced from the raw liquid inlet 9 into the housing 13, and can supply only the gas introduced from the gas inlet 8 for the water conduit into the housing 13, or can supply both raw water and gas into the housing 13. The water conduit 5 constitutes part of the gas supply unit 2.

[0039] The gas supply unit 2 has the above-mentioned water guide pipe 5 and the air diffusing member 4. The air diffusing member 4 is a member for dispersing the gas supplied into the housing 13 from the air diffusing gas inlet 7 provided on the lower surface 13C of the housing 13 so that the gas spreads in the radial direction of each hollow fiber membrane bundle 15. The air diffusing member 4 is disposed below the plurality of hollow fiber membrane bundles 15, and the water guide pipe 5 passes through the center of the air diffusing member 4. The detailed structures of the water guide pipe 5 and the air diffusing member 4 will be described later.

[0040] The suppression member 100 is individually provided for each of the plurality of hollow fiber membrane bundles 15. Each suppression member 100 is a member that controls the movement of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 when gas is being supplied to the internal space S1 of the housing 13 by the gas supply unit 2. The detailed structure of the suppression member 100 will be described later.

[0041] As shown in Fig. 1, the liquid feed pump 20 is connected to the raw liquid inlet 9 of the water conduit 5 via the raw liquid introduction pipe 21. The raw liquid introduction pipe 21 is provided with a raw liquid introduction valve 22 that switches between flowing and blocking of raw water in the pipe. The liquid feed pump 20 supplies raw water into the water conduit 5 via the raw liquid introduction pipe 21.

[0042] The air compressor 30 is connected to the filtrate-side gas inlet 53 via a first gas introduction pipe 31, to the aeration gas inlet 7 via a second gas introduction pipe 32, and to the water conduit gas inlet 8 via a third gas introduction pipe 33. The first gas introduction pipe 31 is provided with a first gas introduction valve 34 for switching between allowing and blocking gas flow within the pipe, and the second and third gas introduction pipes 32, 33 are similarly provided with second and third gas introduction valves 35, 36. In this manner, in this embodiment, the third gas introduction pipe 33 and the third gas introduction valve 36 as gas supply means for the water conduit 5, and the second gas introduction pipe 32 and the second gas introduction valve 35 as gas supply means for the aeration member 4 are separately provided.

[0043] The control device 40 controls the operation of the liquid feed pump 20 and the air compressor 30, and also controls the opening and closing of each valve. The control device 40 is configured, for example, by a personal computer. The control device 40 has a memory unit that stores sequence information for each step (filling with water, filtration, backwashing, bubbling, drainage, etc.) that is executed sequentially in the filtration process, and a control unit that controls the operation of each device and the opening and closing of the valves in accordance with the sequence information.

[0044] [Aeration components, water pipes] Next, the detailed structures of the air diffusing member 4 and the water conduit 5 will be described with reference to Figs. 2 to 5. Fig. 3 shows the planar structure of the air diffusing member 4. Fig. 4 shows the cross-sectional structure of the air diffusing member 4 taken along line IV-IV in Fig. 3. Fig. 5 shows the cross-sectional structure of the water conduit 5 taken along line VV in Fig. 2. In the hollow fiber membrane module 10, the gas supply unit 2 that supplies a gas (e.g., air) for cleaning the hollow fiber membranes 14 to the internal space S1 of the housing 13 while dispersing it has the air diffusing member 4 and the water conduit 5.

[0045] The diffusing member 4 is disposed below the lower ends 14A of the hollow fiber membranes 14 that make up each hollow fiber membrane bundle 15. The diffusing member 4 has a shape that extends in the radial direction of each hollow fiber membrane bundle 15. The diffusing member 4 has a plurality of diffusing vents 43 formed at intervals in the radial direction for diffusing gas within the housing 13.

[0046] The air diffusion member 4 has a disk-shaped main body 44 in which a plurality of air diffusion holes 43 are formed, a peripheral wall 47 connected to the peripheral edge of the main body 44, and a cylindrical gas receiving portion 45 connected to the underside of the main body 44, which are integrally formed.

[0047] The air diffusion holes 43 are formed to penetrate the main body 44 in the thickness direction. The air diffusion holes 43 are formed at intervals from one another in the radial and circumferential directions of the main body 44, and some of them are located radially outward of each hollow fiber membrane bundle 15. This allows gas to be diffused over a wide range in the radial direction relative to each hollow fiber membrane bundle 15. As shown in FIG. 3, the air diffusion holes 43 are arranged on multiple circumferences of the main body 44 that are spaced apart in the radial direction. In this case, the number of air diffusion holes 43 on each circumference is set to be a multiple of the number of hollow fiber membrane bundles 15. Specifically, the number of air diffusion holes 43 on each circumference is set to be a multiple of the number of hollow fiber membrane bundles 15 so that the number of air diffusion holes 43 corresponding to each hollow fiber membrane bundle 15 is the same. In addition, a through-hole 44A, through which the water guide pipe 5 passes, is formed in the center of the main body 44. The main body 44 is not limited to a disk shape as shown in FIG. 3, but may have various shapes.

[0048] The gas receiving portion 45 is a portion for temporarily storing the gas supplied into the housing 13 from the gas inlet 7 for aeration. The gas receiving portion 45 has a cylindrical shape, an upper end (one end) of which is connected to the lower surface of the main body portion 44, and a gas receiving port 45A is formed on the lower end (other end) side. In this embodiment, the gas receiving portion 45 is configured so that the inner diameter is approximately constant from the upper end to the lower end. Note that the gas receiving portion 45 may also be configured so that the inner diameter increases from the upper end to the lower end. The gas receiving portion 45 has an inner diameter larger than the outer diameter of the water conduit 5, and stores gas in the gap between it and the outer circumferential surface of the water conduit 5.

[0049] The gas receiving portion 45 is located radially outward of the gas inlet 7 for diffusion, thereby allowing the gas supplied into the housing 13 from the gas inlet 7 for diffusion to be contained within the cylinder. As shown in Fig. 2, a gap is formed between the lower end of the gas receiving portion 45 and the lower wall of the housing 13, allowing liquid inside the housing 13 to flow through this gap. This makes it possible to prevent liquid from pooling at the bottom of the housing 13.

[0050] A plurality of dispersion holes 46 are formed at intervals in the circumferential direction in a portion on the upper end side of the gas receiving portion 45. The dispersion holes 46 are formed so as to penetrate the gas receiving portion 45. The dispersion holes 46 allow the gas contained in the gas receiving portion 45 to escape radially outward from the gas receiving portion 45 and be guided to the air diffusion vents 43. The dispersion holes 46 may be formed at equal intervals in the circumferential direction, or may be formed at unequal intervals.

[0051] The peripheral wall portion 47 has a cylindrical shape that extends downward from the peripheral edge of the main body portion 44. The peripheral wall portion 47 can prevent the gas released from the dispersion holes 46 to the outside of the gas receiving portion 45 from spreading outward beyond the main body portion 44. This allows the gas to be retained on the underside of the main body portion 44 before being dispersed through the air diffusion vents 43.

[0052] In the bubbling process, the air diffusion member 4 allows the gas supplied from the diffusion gas inlet 7 into the housing 13 to be temporarily stored in the gas receiving portion 45, then released to the outside through the diffusion holes 46, and then dispersed into the lower space S12 through the air diffusion vents 43. That is, in this embodiment, the air diffusion vents 43 function as a lower gas supply portion that diffuses the gas into the housing 13 at a position lower than the lower space S12.

[0053] The water conduit 5 is disposed so as to extend vertically through the center of the housing 13. The water conduit 5 has a cylindrical shape, but is not particularly limited to this. As shown in FIG. 2, the water conduit 5 passes through the aeration member 4 (main body 44), and its lower end is fixed to the concentrate introduction pipe 21 (FIG. 1) via an optional sealing member (not shown). The method of fixing the water conduit 5 is not limited to this. A separate pipe may be provided that protrudes above the upper surface of the main body 44, and the water conduit 5 may be placed on the upper surface of the main body 44 so that the protruding portion is located inside the water conduit 5.

[0054] A plurality of pipe vents 54 are formed at intervals along the entire longitudinal direction (vertical direction) of the water conduit 5 in a portion that protrudes above the upper surface of the main body 44. More specifically, a plurality of pipe vents 54 are formed at intervals in the portion of the water conduit 5 located in the upper space S11, and a plurality of pipe vents 54 are also formed at intervals in the portion of the water conduit 5 located in the lower space S12. These pipe vents 54 allow a bubbling gas (cleaning gas) to be supplied into the housing 13, and also allow raw water to be filtered by the hollow fiber membrane 14 to be supplied into the housing 13. The pipe vents 54 may be formed at equal intervals along the longitudinal direction, or at unequal intervals. The pipe vents 54 are circular, but are not particularly limited to a circular shape.

[0055] The multiple pipe vents 54 are formed to have the same size in the longitudinal direction of the water conduit 5. The inner diameter of the pipe vents 54 is preferably designed to be 30 mm or less to enhance the bubbling effect. Furthermore, in order to reduce pressure loss during water passage, the inner diameter of the pipe vents 54 is preferably designed so that the total discharge flow rate of raw water from each hole is 4 m / s or less, and more preferably 3 m / s or less.

[0056] 2, the pipe vent 54A formed at the top of the water conduit 5 is located above the lower surface 11A of the gas vent port 11, and the second pipe vent 54B from the top is located below the lower surface 11A. In other words, the water conduit 5 has the pipe vents 54A and 54B formed at positions that sandwich the lower surface 11A of the gas vent port 11 in the vertical direction.

[0057] 5, four pipe vent holes 54 are formed at equal intervals in the circumferential direction of the water conduit 5. In this embodiment, four pipe vent holes 54 are formed at 90° intervals in both the portion located in the upper space S11 and the portion located in the lower space S12, but the number and circumferential spacing of the pipe vent holes 54 are not particularly limited. Furthermore, the number and circumferential spacing of the pipe vent holes 54 may differ between the portion located in the upper space S11 and the portion located in the lower space S12.

[0058] Fig. 6 is an enlarged view of the water conduit 5 in region VI in Fig. 2. The open area ratio of the pipe vents 54 in the water conduit 5 can be defined as follows. As shown in the shaded area in Fig. 6, when the area of ​​the outer peripheral surface of the water conduit 5 in the range from the mid-height position of the uppermost pipe vent 54A to the mid-height position of the pipe vent 54B below it is defined as S1, and the total open area of ​​all the pipe vents 54A, 54B formed on the outer peripheral surface in this range is defined as S2, the open area ratio of the pipe vents can be defined as S2 / S1 × 100. In this embodiment, the open area ratio is preferably designed to be 1% or more and 20% or less.

[0059] The water conduit 5 allows raw water to be supplied into the housing 13 through the pipe vent 54, and also allows gas introduced through the water conduit gas inlet 8 to rise by buoyancy and be dispersed into the housing 13 through the pipe vents 54A and 54B located in the upper space S11. That is, in this embodiment, the pipe vents 54A and 54B function as upper gas supply sections that disperse gas into the housing 13 at the position of the upper space S11.

[0060] The length of the water pipe 5 inserted into the housing 13 is preferably 1 to 2 times, and more preferably 1 to 1.5 times, the length of the hollow fiber membranes 14 so as to prevent the hollow fiber membrane module 10 from becoming bulky.

[0061] In order to reduce pressure loss during water flow, the inner diameter of the water conduit 5 is preferably designed so that the flow rate during water flow is 4 m / s or less, and more preferably 3 m / s or less.

[0062] [Restraining member] Next, the detailed structure of the suppression member 100 will be described with reference to Fig. 7 and Fig. 8 in addition to Fig. 2. In the hollow fiber membrane module 10 according to this embodiment, the hollow fiber membranes 14 constituting the hollow fiber membrane module 10 are divided into a plurality of hollow fiber membrane bundles 15 with their upper ends 14B fixed to the fixing member 3. The plurality of hollow fiber membrane bundles 15 are arranged in the internal space S1 of the housing 13 at equal intervals in the circumferential direction so as to surround the water conduit 5. In the example shown in Fig. 8, six hollow fiber membrane bundles 15 are arranged so as to surround the water conduit 5, but the number of hollow fiber membrane bundles 15 arranged is not particularly limited as long as it is two or more.

[0063] The suppression member 100 is provided individually for each of the plurality of hollow fiber membrane bundles 15. As a result, each hollow fiber membrane bundle 15 is isolated from one another by the suppression member 100. Therefore, during the bubbling step in which cleaning gas is supplied to the internal space S1 of the housing 13 by the gas supply unit 2, the plurality of hollow fiber membranes 14 oscillate within the hollow fiber membrane bundles 15 which are isolated from one another.

[0064] As the hollow fiber membranes 14 within each hollow fiber membrane bundle 15 oscillate, suspended pollutants adhering to the membrane surfaces are peeled off. During this process, the suppression member 100 keeps each hollow fiber membrane bundle 15 independent of one another, allowing the suspended pollutants peeled off from the membrane surfaces of the hollow fiber membranes 14 within each hollow fiber membrane bundle 15 to be discharged through the gaps between the hollow fiber membrane bundles 15. This allows the suspended pollutants adhering to the membrane surfaces of the hollow fiber membranes 14 within each hollow fiber membrane bundle 15 to be effectively removed. Furthermore, the suppression member 100 keeps each hollow fiber membrane bundle 15 independent of one another, thereby preventing interference between the hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15. This prevents the hollow fiber membranes 14 from becoming entangled between the hollow fiber membrane bundles 15 and also prevents damage to the hollow fiber membranes 14 that would otherwise occur.

[0065] Furthermore, the suppression member 100, which keeps each hollow fiber membrane bundle 15 independent, is configured to prevent the lower ends 14A of the hollow fiber membranes 14 from flying up while allowing the hollow fiber membranes 14 to swing within the hollow fiber membrane bundle 15. In other words, the hollow fiber membranes 14 are prevented from bending to the extent that the lower ends 14A of the hollow fiber membranes 14 are positioned above the lower end 100A of the suppression member 100. The suppression member 100 prevents the lower ends 14A of the hollow fiber membranes 14 from flying up within the hollow fiber membrane bundle 15, thereby restricting excessive movement of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15. This makes it possible to prevent excessive interference between the hollow fiber membranes 14, such as entanglement between hollow fiber membranes 14 belonging to the same hollow fiber membrane bundle 15, and also to prevent damage to the hollow fiber membranes 14 that would otherwise occur.

[0066] Furthermore, each suppression member 100 has the function of separating the hollow fiber membrane bundles 15 so as to form gaps between the plurality of hollow fiber membrane bundles 15. By forming gaps between the hollow fiber membrane bundles 15 in this way by the suppression members 100, suspended pollutants that are peeled off in accordance with the oscillation of the plurality of hollow fiber membranes 14 within each hollow fiber membrane bundle 15 during the bubbling process can be discharged through the gaps between the hollow fiber membrane bundles 15. This further enhances the effect of removing suspended pollutants that have adhered to the membrane surfaces of the hollow fiber membranes 14.

[0067] As shown in FIG. 7 , each suppression member 100 has a plurality of meshes 101 and is configured as a mesh-like body extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle 15. In this case, the material for the suppression member 100 is not particularly limited and various materials can be used. Examples include polyethylene and polypropylene. The suppression member 100 configured as a mesh-like body has elasticity according to the deformation of the shape of the meshes 101. When the plurality of hollow fiber membranes 14 oscillate within the hollow fiber membrane bundle 15 during the bubbling process, the shape of the meshes 101 deforms and expands and contracts, thereby causing the suppression member 100 to oscillate the plurality of hollow fiber membranes 14 appropriately.

[0068] The lower ends 100A of the suppression members 100, which are formed of a mesh-like body, are each located within an appropriate lower end range that can prevent the lower ends 14A of the multiple hollow fiber membranes 14 oscillating within the corresponding hollow fiber membrane bundle 15 from flying up and can prevent the lower ends 14A of the multiple hollow fiber membranes 14 from entering the mesh 101. The appropriate lower end range is a range in which the lower ends 100A of the suppression members 100 are spaced downward from the upper ends 14B of the hollow fiber membranes 14 by a distance that is 0.7 to 1.0 times the effective length L2 of the hollow fiber membranes 14. The effective length L2 of the hollow fiber membranes 14 is the vertical length of the portion of the hollow fiber membranes 14 that is exposed to the internal space S1 of the housing 13.

[0069] The suppression member 100 suppresses the lower ends 14A of multiple hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 from flying up, thereby suppressing entanglement of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15. Furthermore, by setting the position of the lower end 100A of the suppression member 100 so as to suppress the lower ends 14A of the hollow fiber membranes 14 from entering the mesh 101 of the suppression member 100, it is possible to prevent the hollow fiber membranes 14 from becoming entangled with the suppression member 100. This suppresses damage to the hollow fiber membranes 14.

[0070] In this embodiment, the upper ends 100B of the restricting members 100 formed of a mesh-like body are fixed to the upper ends 14B of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15, and are also fixed to the fixing member 3. Specifically, the upper ends 100B of the restricting members 100 and the upper ends 14B of the plurality of hollow fiber membranes 14 are fixed to the fixing member 3 so that their height positions in the vertical direction are the same. By fixing the upper ends 100B of the restricting members 100 to the fixing member 3, the side surfaces of the hollow fiber membrane bundle 15 can be stably covered.

[0071] The vertical length L1 of the suppression member 100 made of a mesh body is preferably set to satisfy the following formula (1): In the formula (1), "L1" represents the vertical length of the suppression member 100, and "L2" represents the effective length of the hollow fiber membrane 14. 0.7≦L1 / L2≦1.0 (1)

[0072] By setting the vertical length L1 of the suppression member 100 to satisfy the left side of the above formula (1), "0.7≦L1 / L2," the lower end 100A of the suppression member 100 can be positioned within the appropriate lower end range, which can prevent the lower ends 14A of the plurality of hollow fiber membranes 14 from flying up. On the other hand, by setting the vertical length L1 of the suppression member 100 to satisfy the right side of the above formula (1), "L1 / L2≦1.0," the lower end 100A of the suppression member 100 can be positioned within the appropriate lower end range, which can prevent the lower ends 14A of the plurality of hollow fiber membranes 14 from entering the mesh 101 of the suppression member 100.

[0073] [How to clean hollow fiber membrane modules] Next, the filtration operation by the filtration device 1 and the method for cleaning the hollow fiber membrane module 10 performed during the operation will be described with reference to Fig. 9. Fig. 9 shows the relationship between each step and the open / closed state of the valves in the basic operation method of the filtration device 1 shown in Fig. 1. A circle in Fig. 9 indicates that the corresponding valve is open.

[0074] First, a water filling process (before filtration) is carried out. In this process, all valves of the filtration device 1 are closed, and then the control device 40 opens the raw liquid introduction valve 22 and the gas outlet valve 62, and operates the liquid feed pump 20. As a result, raw water is introduced from the liquid feed pump 20 into the water conduit 5 via the raw liquid introduction piping 21, and the raw water is supplied into the housing 13 through the pipe vent 54. As a result, the internal space S1 of the housing 13 is filled with water.

[0075] Next, the filtration process is carried out. In this process, after the raw water overflows from the gas vent port 11, the control device 40 opens the filtrate outlet valve 71 and closes the gas discharge port valve 62. Then, the raw water filled in the internal space S1 permeates from the outer surface side of the hollow fiber membrane 14 through the wall surface to the inner surface side, and is extracted as filtrate from the filtrate-side space S2.

[0076] As the filtration time passes, suspended contaminants in the raw water adhere to the outer surfaces of the hollow fiber membranes 14, which reduces the filtration capacity. Therefore, after filtration has been performed for a certain period of time, the membrane surfaces of the hollow fiber membranes 14 are cleaned by carrying out the cleaning method for the hollow fiber membrane module 10 described below.

[0077] First, the backwashing process is performed. In this process, the control device 40 opens the raw liquid outlet valve 42 and the first gas introduction valve 34 and operates the air compressor 30. This introduces gas (e.g., air) into the filtrate-side space S2 of the housing 13 through the filtrate-side gas inlet 53, and the gas pressurizes the filtrate. The filtrate is pushed from the inner surface side to the outer surface side of the hollow fiber membrane 14, and as a result, a portion of the liquid in the internal space S1 is discharged to the outside of the system through the drain outlet 12. In this manner, the hollow fiber membrane 14 is backwashed. Thereafter, the filtrate-side pressure relief valve 81 is opened to reduce the pressure in the filtrate-side space S2.

[0078] Next, a water filling process (before lower bubbling) is carried out. In this process, in order to raise the liquid level in the internal space S1 that was lowered in the backwashing process, the control device 40 opens the gas outlet valve 62 and the raw liquid introduction valve 22 and operates the liquid feed pump 20. This introduces liquid into the internal space S1, causing the liquid level to rise. Thereafter, the liquid feed pump 20 is stopped, the raw liquid introduction valve 22 is closed, and the supply of liquid is stopped.

[0079] Next, the lower bubbling process is carried out. In this process, with the internal space S1 filled with water, the control device 40 opens the second gas introduction valve 35 and activates the air compressor 30. As a result, gas is supplied from the diffusion gas inlet 7 into the housing 13 via the second gas introduction piping 32. The gas is then received in the gas receiving portion 45 and dispersed into the lower space S12 through the diffusion vents 43. The gas rising from the lower space S12 to the upper space S11 causes the multiple hollow fiber membranes 14 in each hollow fiber membrane bundle 15, which are isolated from one another by the suppression member 100, to vibrate, causing suspended pollutants adhering to the membrane surfaces to peel off. In this way, in the lower bubbling process, gas is dispersed within the housing 13 at a position below the multiple hollow fiber membrane bundles 15, and the gas is caused to rise to the upper space S11, thereby cleaning the hollow fiber membranes 14 located in the lower space S12 and the lower part of the upper space S11.

[0080] Suspended pollutants peeled off from the membrane surfaces of the hollow fiber membranes 14 within each hollow fiber membrane bundle 15 are discharged through the gaps between the hollow fiber membrane bundles 15. This makes it possible to effectively remove suspended pollutants adhering to the membrane surfaces of the hollow fiber membranes 14 within each hollow fiber membrane bundle 15. Furthermore, the suppression member 100 keeps each hollow fiber membrane bundle 15 independent of each other, thereby suppressing interference between the hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15. This makes it possible to suppress entanglement of the hollow fiber membranes 14 between the hollow fiber membrane bundles 15 and to suppress damage to the hollow fiber membranes 14 that would otherwise occur.

[0081] Furthermore, the suppression member 100 suppresses the lower ends 14A of the plurality of hollow fiber membranes 14 from flying up within the hollow fiber membrane bundle 15, thereby restricting excessive movement of the plurality of hollow fiber membranes 14 within the hollow fiber membrane bundle 15. This prevents excessive interference between the hollow fiber membranes 14, such as entanglement between the hollow fiber membranes 14 belonging to the same hollow fiber membrane bundle 15, and also prevents damage to the hollow fiber membranes 14 that would otherwise occur. Furthermore, by positioning the lower end 100A of the suppression member 100 so as to prevent the lower ends 14A of the hollow fiber membranes 14 from entering the mesh 101 of the suppression member 100, it is possible to prevent the hollow fiber membranes 14 from becoming entangled with the suppression member 100. This prevents damage to the hollow fiber membranes 14.

[0082] Next, the drainage process is carried out. In this process, the control device 40 closes the second gas introduction valve 35 and opens the raw liquid outlet valve 42. As a result, the liquid containing the suspended contaminants that have been removed from the membrane surface in the lower bubbling process is discharged outside the system via the drain outlet 12.

[0083] Next, a water filling step (before upper bubbling) is performed. In this step, the gas outlet valve 62 and the raw liquid introduction valve 22 are opened, and the liquid feed pump 20 is operated to fill the internal space S1 with liquid again.

[0084] Next, an upper bubbling step is carried out for the purpose of more reliably removing suspended contaminants adhering to the membrane surface at the upper end 14B of the hollow fiber membrane 14 that was not sufficiently cleaned in the lower bubbling step.

[0085] First, the control device 40 closes the raw liquid introduction valve 22 and opens the third gas introduction valve 36. This introduces gas into the water conduit 5 from the water conduit gas inlet 8 via the third gas introduction pipe 33. The gas then rises due to buoyancy within the pipe and is dispersed into the housing 13 through the pipe vents 54A and 54B located in the upper space S11. This allows for bubbling cleaning centered around the upper end 14B of the hollow fiber membrane 14, more reliably removing suspended contaminants adhering to the membrane surface around the upper end 14B that were not sufficiently removed in the lower bubbling step. In this way, in the upper bubbling step, the hollow fiber membrane 14 is cleaned by dispersing gas within the housing 13 at the position of the upper space S11.

[0086] In the upper bubbling step, immediately after the start of bubbling, the entire internal space S1 is filled with water, and therefore, bubbling cleaning can be performed with the gas discharged from the uppermost pipe vent 54A and the pipe vent 54B below it. After a certain time has passed since the start of bubbling, the gas-containing liquid is discharged from the gas vent port 11, and the liquid level in the internal space S1 drops to the lower surface 11A. Even in this state, the buoyancy of the gas supplied to the water conduit 5 causes the water in the water conduit 5 to be ejected together with the gas from the pipe vent 54A above the lower surface 11A of the gas vent port 11, and the water in the housing 13 to flow into the water conduit 5 from the pipe vent 54B below the lower surface 11A of the gas vent port 11. This allows the mixed fluid of liquid and gas to be continuously sprayed and bubbled from the pipe vent 54A above the lower surface 11A of the gas vent port 11, thereby effectively cleaning the hollow fiber membrane 14 up to the upper end 14B.

[0087] Next, the drainage step is carried out. In this step, the third gas introduction valve 36 is closed and the raw liquid outlet valve 42 is opened. As a result, the liquid containing suspended contaminants that have peeled off from the membrane surface in the upper bubbling step is discharged outside the system through the drain outlet 12. After the hollow fiber membrane module 10 has been cleaned in this manner, the filtration operation is resumed.

[0088] In both the upper and lower bubbling steps, the gas supply flow rate is preferably 12,000 NL / h or less, and preferably in the range of 1,500 to 12,000 NL / h. In the lower bubbling step, an excessive gas supply flow rate may cause the hollow fiber membranes 14 to become entangled, potentially damaging the membrane surface. In contrast, in the present embodiment, the suppression member 100 suppresses excessive oscillation of the hollow fiber membranes 14 for each hollow fiber membrane bundle 15 in the lower bubbling step, thereby enabling the upper limit gas supply flow rate in the lower bubbling step to be increased. Since such problems are generally less likely to occur in the upper bubbling step, the gas supply flow rate in the upper bubbling step may be set higher than in the lower bubbling step. However, the effect of the suppression member 100 makes it possible to supply gas in the lower bubbling step at a flow rate similar to that in the upper bubbling step.

[0089] (Second embodiment) Next, the structure of a hollow fiber membrane module 10 according to a second embodiment of the present invention will be described with reference to Fig. 10. The hollow fiber membrane module 10 according to the second embodiment basically has the same configuration and produces the same effects as the first embodiment, but differs from the first embodiment in the structure of the suppression members 100 individually provided on each of the plurality of hollow fiber membrane bundles 15.

[0090] In the hollow fiber membrane module 10 according to the second embodiment, each of the suppression members 100, as in the first embodiment, has a plurality of meshes 101 and is configured as a mesh-like body extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle 15. In the first embodiment, the upper end 100B of the suppression member 100 was fixed to the fixing member 3, but in the second embodiment, the upper end 100B of the suppression member 100 is located below the upper end 14B of the hollow fiber membranes 14. In other words, the upper end 100B of the suppression member 100 is spaced apart from the fixing member 3. In this case, the suppression member 100 is adhesively fixed to the side surface 13B of the housing 13, for example.

[0091] As in the first embodiment described above, the lower end 100A of the suppression member 100 is located within the appropriate lower end range, which can suppress the lower ends 14A of the multiple hollow fiber membranes 14 oscillating within the corresponding hollow fiber membrane bundle 15 from flying up and can also suppress the lower ends 14A of the multiple hollow fiber membranes 14 from entering the mesh 101.

[0092] The suppression member 100 suppresses the lower ends 14A of multiple hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 from flying up, thereby suppressing entanglement of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15. Furthermore, by setting the position of the lower end 100A of the suppression member 100 so as to suppress the lower ends 14A of the hollow fiber membranes 14 from entering the mesh 101 of the suppression member 100, it is possible to prevent the hollow fiber membranes 14 from becoming entangled with the suppression member 100. This suppresses damage to the hollow fiber membranes 14.

[0093] (Third embodiment) Next, the structure of a hollow fiber membrane module 10 according to a third embodiment of the present invention will be described with reference to Fig. 11. The hollow fiber membrane module 10 according to the third embodiment basically has the same configuration and produces the same effects as the first embodiment, but differs from the first embodiment in the structure of the suppression members 100 individually provided on each of the plurality of hollow fiber membrane bundles 15.

[0094] As shown in Figure 11, each suppression member 100 of the third embodiment is formed with a plurality of through holes 103 and is configured with a tubular body 102 extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle 15. While the suppression member 100 of the first embodiment is configured with a mesh body and has flexibility in response to deformation of the shape of the mesh 101, the suppression member 100 of the third embodiment has sufficient rigidity to prevent deformation of the shape of the through holes 103. This allows each suppression member 100 to more reliably keep each hollow fiber membrane bundle 15 independent of each other. Therefore, during the bubbling process, interference between hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 is more reliably suppressed.

[0095] The upper end 100B of the suppression member 100 of the third embodiment is fixed to the upper ends 14B of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15, and is also fixed to the fixing member 3. Similarly to the first embodiment, the lower end 100A of the suppression member 100 is located within the appropriate lower end range, which can prevent the lower ends 14A of the plurality of hollow fiber membranes 14 swaying in the corresponding hollow fiber membrane bundle 15 from flying up, and can prevent the lower ends 14A of the plurality of hollow fiber membranes 14 from entering the through-holes 103.

[0096] The suppression member 100 suppresses the lower ends 14A of multiple hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 from flying up, thereby suppressing entanglement of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15. Furthermore, by setting the position of the lower end 100A of the suppression member 100 so as to suppress the lower ends 14A of the hollow fiber membranes 14 from entering the through-holes 103 of the suppression member 100, it is possible to prevent the hollow fiber membranes 14 from becoming entangled with the suppression member 100. This suppresses damage to the hollow fiber membranes 14.

[0097] (Fourth embodiment) Next, the structure of a hollow fiber membrane module 10 according to a fourth embodiment of the present invention will be described with reference to Fig. 12. The hollow fiber membrane module 10 according to the fourth embodiment basically has the same configuration and produces the same effects as the first embodiment, but differs from the first embodiment in the structure of the suppression members 100 individually provided on each of the plurality of hollow fiber membrane bundles 15.

[0098] As shown in Fig. 12, each suppression member 100 of the fourth embodiment is formed of a spiral cord-like body wound around the side surface of the corresponding hollow fiber membrane bundle 15. The suppression members 100 formed of the spiral cord-like body make each hollow fiber membrane bundle 15 independent of each other when wound around the side surface of the hollow fiber membrane bundle 15. This prevents interference between hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 during the bubbling process.

[0099] The upper end 100B of the suppression member 100 of the fourth embodiment is fixed to the upper ends 14B of the plurality of hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15, and is also fixed to the fixing member 3. Similarly to the first embodiment, the lower end 100A of the suppression member 100 is located within the appropriate lower end range, which can prevent the lower ends 14A of the plurality of hollow fiber membranes 14 oscillating in the corresponding hollow fiber membrane bundle 15 from flying up, and can prevent the lower ends 14A of the plurality of hollow fiber membranes 14 from getting caught on the suppression member 100.

[0100] The suppression member 100 suppresses the lower ends 14A of multiple hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 from flying up, thereby suppressing entanglement of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15. Furthermore, by setting the position of the lower end 100A of the suppression member 100 so as to suppress the lower ends 14A of the hollow fiber membranes 14 from getting caught on the suppression member 100, it is possible to prevent the hollow fiber membranes 14 from becoming entangled with the suppression member 100. This suppresses damage to the hollow fiber membranes 14.

[0101] (Fifth embodiment) Next, the structure of a hollow fiber membrane module 10 according to a fifth embodiment of the present invention will be described with reference to Fig. 13. The hollow fiber membrane module 10 according to the fifth embodiment basically has the same configuration and produces the same effects as the first embodiment, but differs from the first embodiment in the structure of the suppression members 100 individually provided on each of the plurality of hollow fiber membrane bundles 15.

[0102] As shown in Figure 13, each suppression member 100 of the fifth embodiment is composed of a plurality of strips 104 wound around the side surface of a corresponding hollow fiber membrane bundle 15. The plurality of strips 104 are arranged at predetermined intervals in the vertical direction of the hollow fiber membrane bundle 15 and are adhesively fixed to, for example, the side surface 13B of the housing 13. The suppression member 100 composed of a plurality of strips 104 keeps each hollow fiber membrane bundle 15 independent from one another with each strip 104 wound around the side surface of the hollow fiber membrane bundle 15. This prevents interference between hollow fiber membranes 14 belonging to different hollow fiber membrane bundles 15 during the bubbling process.

[0103] The strip 104 located at the bottom of the plurality of strips 104 is located within the appropriate lower end range that can prevent the lower ends 14A of the plurality of hollow fiber membranes 14 oscillating within the corresponding hollow fiber membrane bundle 15 from flying up. The suppression member 100 prevents the lower ends 14A of the plurality of hollow fiber membranes 14 within the corresponding hollow fiber membrane bundle 15 from flying up, thereby preventing the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 from becoming entangled with each other.

[0104] [Example of the present invention] Next, examples illustrating the present invention more specifically will be described.

[0105] Example 1 The hollow fiber membrane bundle 15 has a membrane area of ​​40 m 2 The hollow fiber membrane 14 used was made of polyvinylidene fluoride resin that had been hydrophilized with polyvinyl alcohol, had an average pore size of 0.02 microns, and had a vertical length (effective length) L2 of 1035 mm.

[0106] A polypropylene mesh was used as the suppression member 100. The upper end of the mesh was fixed to the upper ends 14B of the hollow fiber membranes 14 in the corresponding hollow fiber membrane bundle 15 and to the fixing member 3, and the mesh had a vertical length L1 of 725 mm. In this case, the lower end of the mesh was located within an appropriate lower end range that could prevent the lower ends 14A of the hollow fiber membranes 14 from flying up and prevent the lower ends 14A of the hollow fiber membranes 14 from entering the mesh. The ratio (L1 / L2) of the mesh length L1 to the effective length L2 of the hollow fiber membranes 14 was 0.7.

[0107] The water conduit 5 used was a cylinder with a length of 1090.5 mm and an inner diameter of 48.6 mm. The water conduit 5 was placed in the center of the housing 13 and fixed together with the hollow fiber membrane bundle 15 by the fixing member 3. In this case, multiple hollow fiber membrane bundles 15 were arranged to surround the water conduit 5. Multiple pipe vents 54 (36 in total) were formed in the water conduit 5 at intervals of 100 mm, starting from a position 70 mm downward from the fixing member 3. The pipe vents 54 were formed at 90° intervals in the circumferential direction, and had a hole diameter of 10 mm.

[0108] The diffusing member 4 was attached at a position 1060.5 mm below the fixed member 3. The diffusing member 4 consists of a disk-shaped main body 44 with a plurality of diffusion holes 43 formed therein, a gas receiving portion 45, and a peripheral wall portion 47. A water pipe gas inlet 8 was provided as a gas supply port to the water pipe 5, and a diffusion gas inlet 7 was provided as a gas supply port to the gas receiving portion 45 of the diffusing member 4.

[0109] Using the hollow fiber membrane module 10 configured as described above, clean water was used as raw water and constant flow filtration was performed for 30 seconds using the external pressure total filtration method at a flow rate of 4000 L / h. After the filtration operation, backpressure cleaning was performed from the filtrate side of the hollow fiber membrane module 10 using compressed air at 0.2 MPa, followed by bubbling cleaning. This operation was repeated 300 times. The flow rate of the bubbling air (cleaning gas) on the aeration member 4 side was varied within a range of 1500 to 12000 NL / h. The flow rate of the bubbling air (cleaning gas) on the water conduit 5 side was kept constant at 10000 NL / h.

[0110] Example 2 The same procedure as in Example 1 was used, except that a mesh body with a vertical length L1 of 932 mm was used. In this case, the lower end of the mesh body was located within the appropriate lower end range. In addition, the ratio of the length L1 of the mesh body to the effective length L2 of the hollow fiber membrane 14 (L1 / L2) was 0.9.

[0111] Example 3 The same procedure as in Example 1 was used, except that a mesh body with a vertical length L1 of 1035 mm was used. In this case, the lower end of the mesh body was located within the appropriate lower end range. In addition, the ratio of the length L1 of the mesh body to the effective length L2 of the hollow fiber membrane 14 (L1 / L2) was 1.0.

[0112] (Comparative Example 1) The procedure was the same as in Example 1, except that the provision of the mesh body on the hollow fiber membrane bundle 15 was omitted.

[0113] (Comparative Example 2) The same procedure as in Example 1 was used, except that a mesh body with a vertical length L1 of 518 mm was used. In this case, the lower end of the mesh body was located above the appropriate lower end range. In addition, the ratio of the length L1 of the mesh body to the effective length L2 of the hollow fiber membrane 14 (L1 / L2) was 0.5.

[0114] (Comparative Example 3) The same procedure as in Example 1 was used except that a mesh body having a vertical length L1 of 1242 mm was used. In this case, the lower end of the mesh body was located below the appropriate lower end range. In addition, the ratio (L1 / L2) of the length L1 of the mesh body to the effective length L2 of the hollow fiber membrane 14 was 1.2.

[0115] For the above Examples 1 to 3 and Comparative Examples 1 to 3, the occurrence of tangling or damage between the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 was visually evaluated. The evaluation results are shown in Table 1. "Good" in Table 1 indicates that there was almost no tangling or damage between the hollow fiber membranes 14 within the hollow fiber membrane bundle 15, and stable operation was possible. On the other hand, "Poor" in Table 1 indicates that there was significant tangling or damage between the hollow fiber membranes 14 within the hollow fiber membrane bundle 15, making it difficult to continue stable operation.

[0116] [Table 1]

[0117] As is clear from the results in Table 1, in Examples 1 to 3, when the flow rate of the cleaning gas on the aeration member 4 side was in the range of 1500 to 12000 NL / h, entanglement and damage of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 was suppressed. This is because the mesh structure suppressed the lower ends 14A of the plurality of hollow fiber membranes 14 within the hollow fiber membrane bundle 15 from flying up, thereby restricting excessive movement of the hollow fiber membranes 14.

[0118] Furthermore, in Examples 1 to 3, the lower ends of the mesh body were located within an appropriate lower end range that could prevent the lower ends 14A of the hollow fiber membranes 14 from flying up and could prevent the lower ends 14A of the hollow fiber membranes 14 from getting into the mesh. This is thought to have restricted entanglement of the hollow fiber membranes 14 with the mesh body and prevented damage to the hollow fiber membranes 14.

[0119] On the other hand, in Comparative Example 1, under conditions where the flow rate of the cleaning gas on the aeration member 4 side was 7000 NL / h or more, entanglement and damage of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 was significantly confirmed. This is because in Comparative Example 1, the installation of a mesh body was omitted, and therefore excessive movement of the multiple hollow fiber membranes 14 within the hollow fiber membrane bundle 15 was not restricted, causing the lower ends 14A of the multiple hollow fiber membranes 14 to fly up.

[0120] Furthermore, in Comparative Example 2, when the flow rate of the cleaning gas on the side of the diffusing member 4 was 10,000 NL / h or more, entanglement and damage of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 was significantly confirmed. This is because, in Comparative Example 2, the lower end of the mesh body was located above the appropriate lower end range that could prevent the lower ends 14A of the multiple hollow fiber membranes 14 from flying up within the hollow fiber membrane bundle 15. For this reason, in Comparative Example 2, when the flow rate of the cleaning gas on the side of the diffusing member 4 was 10,000 NL / h or more, the lower ends 14A of the multiple hollow fiber membranes 14 within the hollow fiber membrane bundle 15 flew up, which is thought to have resulted in entanglement and damage of the hollow fiber membranes 14.

[0121] Furthermore, in Comparative Example 3, when the flow rate of the cleaning gas on the aeration member 4 side was in the range of 1500 to 12000 NL / h, entanglement and damage of the hollow fiber membranes 14 within the hollow fiber membrane bundle 15 was significantly confirmed. This is because, in Comparative Example 3, the lower end of the mesh body was located below the appropriate lower end range that can prevent the lower ends 14A of the hollow fiber membranes 14 from entering the mesh 101 and was in contact with the aeration member 4. For this reason, in Comparative Example 3, the hollow fiber membranes 14 became entangled with the suppression member 100, causing damage to the hollow fiber membranes 14.

[0122] From the above results, it was found that in the above Examples 1 to 3, compared to Comparative Examples 1 to 3, excessive movement of the hollow fiber membranes 14 during the bubbling process was restricted, and entanglement and damage of the hollow fiber membranes 14 could be suppressed while ensuring the effect of removing suspended pollutants adhering to the membrane surface of the hollow fiber membranes 14.

[0123] The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0124] 2 Gas supply section 4. Aeration components 43 Diffuser vent 44 Main body 45 Gas receiving section 45A socket 46 Dispersion hole 10 Hollow fiber membrane module 13. Housing 14 Hollow fiber membrane 15 Hollow fiber membrane bundle 100 Restraining member S1 interior space

Claims

1. a housing in which the fixing member is fixed and which defines an internal space; a plurality of hollow fiber membrane bundles each having a plurality of hollow fiber membranes, the bundles being disposed in the internal space with upper ends of the hollow fiber membranes fixed to the fixing member; a gas supply unit that supplies a gas for cleaning the plurality of hollow fiber membrane bundles to the internal space; a suppression member individually provided for each of the plurality of hollow fiber membrane bundles, Each of the plurality of hollow fiber membrane bundles has a membrane packing ratio 100πdi 2 / 4S (%) calculated from the outer diameter di (m) of the hollow fiber membrane, the total number n (number of hollow fiber membranes) and the cross-sectional area S (m 2 ) of the housing, of 10% to 60% so that gaps are formed between the plurality of hollow fiber membranes; Each of the suppression members is fixed to a side surface of the fixing member or the housing so as to cover at least a portion of the side surface of the corresponding hollow fiber membrane bundle while maintaining the gaps between the plurality of hollow fiber membranes and being spaced from the side surface, and is configured to suppress the lower ends of the plurality of hollow fiber membranes from flying up within the corresponding hollow fiber membrane bundle while allowing the plurality of hollow fiber membranes to oscillate due to the gas supplied into the internal space from the gas supply unit.

2. each of the suppression members has a plurality of meshes and is configured as a mesh-like body extending in the vertical direction so as to cover the side surface of the corresponding hollow fiber membrane bundle; 2. The hollow fiber membrane module according to claim 1, wherein the lower ends of the suppression members are each positioned so as to suppress the lower ends of the plurality of hollow fiber membranes oscillating within the corresponding hollow fiber membrane bundle from flying up and to suppress the lower ends of the plurality of hollow fiber membranes from entering the meshes.

3. The upper ends of the suppression members are fixed to the fixing members, The hollow fiber membrane module according to claim 2 , wherein the lengths of the suppression members in the vertical direction are set so as to satisfy the following formula (1): 0.7≦L1 / L2≦1.0 (1) [In formula (1), "L1" represents the length of the suppression member in the vertical direction, and "L2" represents the effective length of the hollow fiber membrane.]

4. The hollow fiber membrane module according to any one of claims 1 to 3, wherein each of the suppression members has a function of separating the hollow fiber membrane bundles so as to form gaps between the plurality of hollow fiber membrane bundles.

5. the gas supply unit includes an air diffusion member that is disposed below the hollow fiber membrane bundle, has a shape that expands in a radial direction of the hollow fiber membrane bundle, and has a plurality of air diffusion holes formed at intervals in the radial direction; The air diffusing member is a plate-like main body portion having a shape expanding in a radial direction of the hollow fiber membrane bundle and having a plurality of the air diffusion holes formed at intervals in the radial direction; a gas receiving portion having a cylindrical shape with one end connected to the lower surface of the main body portion and the other end formed with a gas receiving port, and having formed therein dispersion holes for guiding the gas contained in the cylinder to the gas diffusion vent.

6. The hollow fiber membrane module according to claim 5 , wherein the gas receiving portion has an inner diameter that increases from the one end toward the other end.

7. The air diffusion holes are arranged on a plurality of circumferences spaced apart in the radial direction in the main body, 7. The hollow fiber membrane module according to claim 5, wherein the number of the air diffusion holes on each circumference is a multiple of the number of the hollow fiber membrane bundles.

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