JP2019000815A - Hollow fiber membrane filtration device and cleaning method therefor - Google Patents

Abstract

To provide a hollow fiber membrane filtration device in which a hollow fiber membrane can be effectively cleaned with a simple device configuration, and a method for cleaning the same.SOLUTION: A hollow fiber membrane filtration device comprises a hollow fiber membrane module 10 of an external pressure filtration type. The hollow fiber membrane module 10 has: a hollow fiber membrane bundle 15; a housing 13 having an internal space in which the hollow fiber membrane bundle 15 is accommodated; and a pipe member 5C which is provided with an upper opening part 5B and a lower opening part 5C. The hollow fiber membrane filtration device comprises a gas supply part which supplies a gas to an in-pipe space 5A. The gas supply part is so configured as to supply the gas of which a flow rate and a pressure are adjusted so that raw water, which flows into the in-pipe space 5A from a space in the housing 13 through the lower opening part 5C, is so made as to rise to an upper side with respect to a liquid level 11B of raw water together with the gas, and is ejected into the space in the housing 13 together with the gas through the upper opening part 5B which is positioned on an upper side with respect to the liquid level 11B of raw water.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a hollow fiber membrane filtration device and a cleaning method thereof.

  Conventionally, in a water treatment for removing impurities in water, a hollow fiber membrane module having a plurality of bundled hollow fiber membranes has been used. In the filtration process of water treatment, raw water (water before filtration) is supplied into the module through the raw water inlet provided in the hollow fiber membrane module, and the filtered water that has passed through the membrane passes outside the module through the filtered water outlet provided in the module. To be discharged.

  In the hollow fiber membrane module, when a water treatment filtration step is performed, a substance (suspended solids (SS)) removed from the water is deposited on the membrane surface. As described above, it is one of important issues to efficiently remove the suspended pollutant deposited on the film surface.

  In general, removal of suspended contaminants is performed by so-called backwashing (backpressure washing). In the backwashing process, a fluid flow in the opposite direction to the filtration process is formed in the module in order to float the suspended contaminants from the membrane surface. That is, a fluid such as gas or liquid is supplied into the module through the filtered water outlet, and the fluid that has passed through the membrane is discharged out of the module through the raw water inlet.

  The suspended pollutant that has partially floated from the film surface by the backwashing process is peeled off from the film surface by the subsequent bubbling process. In this bubbling process, gas is supplied into the filled module, and the membrane fluctuates due to bubbles, so that the suspended contaminants are peeled off from the membrane surface.

  Patent Documents 1 and 2 disclose a hollow fiber membrane module having a configuration for dispersing a gas in the module in a bubbling process. In the hollow fiber membrane module described in Patent Document 1, an air supply header and an air distributor are provided below the lower end of the hollow fiber membrane, and the air supplied from the air supply header is dispersed by the air distributor. Be guided. In the hollow fiber membrane module described in Patent Document 2, pores are formed on the lower side surface of a pipe disposed at the center of the hollow fiber membrane bundle, and gas is supplied into the housing through the pores.

  Patent Document 3 describes a hollow fiber membrane module having a configuration capable of cleaning the upper end of the hollow fiber membrane. This hollow fiber membrane module includes a plurality of nozzles that vertically penetrate a fixing portion that fixes the upper end of the hollow fiber membrane, and is capable of ejecting washing water from an ejection hole provided at the nozzle tip. Thus, the turbidity at the upper end of the hollow fiber membrane can be removed.

Japanese Patent Laid-Open No. 11-33367 JP-A-7-136469 Japanese Patent Laying-Open No. 2015-226884

  In the hollow fiber membrane modules described in Patent Documents 1 and 2, the gas can be dispersed in the housing and the surface of the hollow fiber membrane can be cleaned with bubbles, but the cleaning effect is not sufficient. Moreover, in patent document 3, it is necessary to make the nozzle for washing | cleaning penetrate the fixing | fixed part which fixes the upper end of a hollow fiber membrane, and there exists a problem that a module structure becomes complicated.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a hollow fiber membrane filtration device capable of effectively washing a hollow fiber membrane with a simple device configuration and a cleaning method thereof. It is.

  A hollow fiber membrane filtration device according to one aspect of the present invention includes an external pressure filtration type hollow fiber membrane module. The hollow fiber membrane module is formed with a hollow fiber membrane bundle having a plurality of bundled hollow fiber membranes and an internal space in which the hollow fiber membrane bundle is accommodated, and for discharging gas from the internal space to the outside A housing provided with a gas discharge port; a tube member disposed so as to extend along a longitudinal direction of the hollow fiber membrane; and a space in the tube which is a space inside the tube member, and a space in the housing An upper opening that communicates with the pipe member, and the pipe member that is provided below the upper opening and that has a lower opening that communicates the space in the tube and the space in the housing. doing. The hollow fiber membrane filtration device further includes a gas supply unit that supplies gas to the space in the tube. The gas supply unit causes raw water flowing from the space in the housing to the space in the pipe through the lower opening to be higher than the level of the raw water located between the upper opening and the lower opening. It is configured to supply a gas whose flow rate and pressure are adjusted so that the gas is raised together with the gas, and jetted into the space in the housing together with the gas through the upper opening located above the liquid level. .

  According to the hollow fiber membrane filtration device, the hollow fiber membrane can be effectively washed using a so-called air lift effect as follows. That is, by supplying a gas whose flow rate and pressure are appropriately adjusted from the gas supply unit to the pipe space, the raw water flowing into the pipe space from the space in the housing through the lower opening is made higher than the liquid level of the raw water. And the gas can be ejected from the upper side of the liquid level to the space inside the housing through the upper opening. Thereby, since it becomes possible to wash | clean by applying raw | natural water and gas to the surface of a hollow fiber membrane, a cleaning effect can be heightened compared with normal bubbling washing | cleaning. Moreover, the air lift effect as described above can be realized with a simple device configuration. Therefore, according to the said hollow fiber membrane filtration apparatus, a hollow fiber membrane can be wash | cleaned effectively with a simple apparatus structure.

  The said hollow fiber membrane filtration apparatus WHEREIN: The said gas supply part may have the gas supply port which supplies gas to the said pipe | tube space in the position above the said lower side opening part.

  According to this configuration, it is possible to prevent the gas supplied from the gas supply port to the pipe inner space from leaking out of the pipe through the lower opening.

  In the hollow fiber membrane filtration device, the hollow fiber membrane module may further include an air diffuser that disperses gas in the internal space at a position below the lower end of the hollow fiber membrane.

  According to this configuration, when the gas dispersed by the air diffusing member rises from the lower end of the hollow fiber membrane and the hollow fiber membrane swings, the suspended contaminants attached to the membrane surface can be peeled off.

  In the hollow fiber membrane filtration device, the lower opening may be located below the lower end of the hollow fiber membrane.

  According to this configuration, as the raw water ejected from the upper opening flows toward the lower opening, the suspended contaminants removed from the membrane surface are moved below the lower end of the hollow fiber membrane by the raw water flow. Can carry up to. Thereby, it is possible to prevent floating contaminants from reattaching to the outer surface of the hollow fiber membrane.

  In the hollow fiber membrane filtration device, the hollow fiber membrane bundle may be a one-end free type in which the upper end of the hollow fiber membrane is fixed and the hollow fiber membranes are not fixed one by one at the lower end.

  According to this configuration, since the hollow fiber membrane can be easily swung by bubbling, compared with the case of using a both-end fixed type hollow fiber membrane module, the cleaning effect of the hollow fiber membrane can be further enhanced.

  A cleaning method for a hollow fiber membrane filtration device according to another aspect of the present invention includes a hollow fiber membrane bundle having a plurality of bundled hollow fiber membranes, and a housing in which an internal space in which the hollow fiber membrane bundle is accommodated is formed. An external pressure filtration system having a pipe member provided to extend along the longitudinal direction of the hollow fiber membrane and provided with an upper opening and a lower opening located below the upper opening, respectively. In the hollow fiber membrane filtration apparatus provided with the hollow fiber membrane module, the hollow fiber membrane is washed. This method includes supplying raw water into the housing, and in a state where the level of the raw water is located below the upper end of the hollow fiber membrane, gas is supplied to the inner space of the tube member. By supplying the raw water flowing into the pipe space from the space in the housing through the lower opening to the upper side above the liquid level together with the gas, the upper opening located above the liquid level And a step of ejecting the gas together with the gas into the space in the housing.

  According to the cleaning method of the hollow fiber membrane filtration device, the raw water flowing into the pipe space from the space in the housing through the lower opening is raised together with the gas above the liquid level of the raw water, and above the liquid level. The gas can be ejected into the space in the housing together with the gas through the upper opening located. Thereby, it becomes possible to wash | clean by applying raw | natural water and gas to the surface of a hollow fiber membrane, and can improve the washing | cleaning effect of a hollow fiber membrane compared with normal bubbling washing | cleaning. In addition, this method using the air lift effect can be performed using an apparatus having a simple configuration.

  As is apparent from the above description, according to the present invention, it is possible to provide a hollow fiber membrane filtration device and a cleaning method thereof that can effectively wash the hollow fiber membrane with a simple device configuration.

It is a figure which shows typically the structure of the hollow fiber membrane filtration apparatus in Embodiment 1 of this invention. It is a figure which shows typically the structure of the hollow fiber membrane module with which the said hollow fiber membrane filtration apparatus is provided. It is a schematic diagram for demonstrating the air lift washing | cleaning in the said hollow fiber membrane module. It is a figure which shows typically the planar structure of the aeration member with which the said hollow fiber membrane module is provided. It is a figure which shows typically the cross-sectional structure of the aeration member in alignment with line segment VV in FIG. It is a figure which shows the basic driving | operation program of the said hollow fiber membrane filtration apparatus. It is a figure which shows typically the structure of the hollow fiber membrane module in Embodiment 2 of this invention. It is a figure which shows typically the structure of the hollow fiber membrane module in Embodiment 3 of this invention. It is a schematic diagram for demonstrating the hollow fiber membrane module in other embodiment of this invention. It is a schematic diagram for demonstrating the air lift washing | cleaning in other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
<Hollow fiber membrane filtration device>
First, the configuration of the hollow fiber membrane filtration device 1 according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 schematically shows the overall configuration of the hollow fiber membrane filtration device 1. FIG. 2 schematically shows the configuration of the hollow fiber membrane module 10 provided in the hollow fiber membrane filtration device 1.

  The hollow fiber membrane filtration device 1 includes an external pressure filtration type hollow fiber membrane module 10 and is a device for obtaining a filtrate by filtering raw water with the hollow fiber membrane module 10. Here, the “external pressure filtration method” is a filtration method in which raw water is supplied to the outer surface side of the hollow fiber membrane and the filtrate that has passed through the membrane wall is taken out from the inner surface side of the membrane. As the hollow fiber membrane module 10, an external pressure total filtration type or an external pressure circulation filtration type can be used depending on the conditions of membrane separation treatment and required performance. From the viewpoint of membrane life, an external pressure circulation filtration type module that can perform membrane surface cleaning simultaneously with filtration is preferable. On the other hand, from the viewpoints of simplicity of equipment, installation cost, and operation cost, an external pressure total amount filtration module is preferable.

  As shown in FIG. 1, the hollow fiber membrane filtration device 1 includes a hollow fiber membrane module 10, a liquid feed pump 20, an air compressor 30, a pipe connecting them, an open / close valve provided in the pipe, a control The apparatus 40 is mainly provided.

  As shown in FIG. 2, the hollow fiber membrane module 10 accommodates a hollow fiber membrane bundle 15 in which a plurality of hollow fiber membranes 14 are fixed in a bundle shape by a fixing member 3 at an upper end 14 </ b> B, and a hollow fiber membrane bundle 15. It mainly includes a housing 13 in which an internal space S1 is formed, a pipe member 5 for supplying raw water into the housing 13, and an air diffuser member 4 for dispersing gas in the internal space S1.

  The hollow fiber membrane bundle 15 is fixed by the fixing member 3 in a state where the upper end 14B of the hollow fiber membrane 14 is open, and is sealed in a state where the lower ends 14A of the hollow fiber membranes 14 are not fixed one by one. belongs to. However, the hollow fiber membrane bundle is not limited to the one-end free type, and may be a both-end fixed type in which the upper end 14B and the lower end 14A are fixed.

  The fixing member 3 converges and fixes the upper ends 14B of the plurality of hollow fiber membranes 14. The fixing member 3 liquid-tightly partitions the space in the housing 13 into the raw water side spaces S1 and S3 and the filtrate side space S2 so that the hollow fiber membrane 14 functions as a filtration membrane. For the fixing member 3, a thermosetting resin such as an epoxy resin, an unsaturated polyester resin, or a polyurethane resin is used. Examples of the bonding method between the hollow fiber membrane bundle 15 and the fixing member 3 include a centrifugal bonding method and a stationary bonding method.

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

  The hollow fiber membrane 14 is preferably made hydrophilic. The hollow fiber membrane 14 is hydrophilized by containing, for example, 0.1 wt% or more and 10 wt% or less of a hydrophilic resin. As the hydrophilic resin, polyvinyl pyrrolidone, cellulose ester, ethylene-vinyl alcohol, polyvinyl alcohol, or the like can be used. The hollow fiber membrane 14 preferably contains polyvinyl alcohol, which is a particularly highly hydrophilic resin.

  The hollow fiber membrane 14 is preferably insolubilized in high-temperature water by acetalization. Thereby, the excessive elution of hydrophilic resin at the time of an extraction process and at the time of use can be prevented. Acetalization is performed by treating the hollow fiber membrane 14 in an acid aqueous solution containing an aldehyde compound. As the aldehyde, formaldehyde, glyoxal, glutaraldehyde, malondialdehyde, nonane dial and the like can be used. As the acid, it is preferable to use a strong acid such as sulfuric acid, hydrochloric acid or nitric acid.

  The hollow fiber membrane 14 is preferably a vinylidene fluoride resin porous hollow fiber membrane having a pure water permeation rate that satisfies the following formula (1).

(FLUXd / FLUXw) × 100 ≧ 40.0 (1)
In the above formula (1), “FLUXd” represents the pure water permeation rate (L / m ² / hr / 98 kPa) of the dry hollow fiber membrane, and “FLUXw” represents the pure water permeation rate of the wet hollow fiber membrane ( L / m ² / hr / 98 kPa).

  In the hollow fiber membrane module 10, pressure cleaning with air is performed from the secondary side. Here, when the pure water permeation rate of the hollow fiber membrane 14 does not satisfy the range of the above formula (1), the membrane may be dried, and the SS discharge property may be lowered. That is, when (FLUXd / FLUXw) × 100 is less than 40, the hollow fiber membrane 14 is dried during repeated use of the module. And since the water does not permeate into the dried membrane part, the filtration function is lost. On the other hand, the load on the membrane part having the filtration function is increased, and the discharge performance tends to be lowered.

The hollow fiber membrane 14 is preferably water permeation amount in transmembrane pressure 0.1MPa is 1000~40000L ^/ m 2 ^/ hr, more preferably ^{1000~30000L / m 2 / hr, 1000~20000L} / More preferably, it is m ² / hr. When there is too little water permeability, there exists a tendency for permeation | transmission performance to be inferior. On the other hand, when there is too much water permeability, there exists a tendency for a fractionation characteristic to fall. Therefore, the hollow fiber membrane 14 excellent in permeation performance and fractionation characteristics can be obtained by setting the water permeation amount within the above range.

  The water permeability of the hollow fiber membrane 14 can be measured as follows. First, a hollow fiber membrane module 10 in which 20 hollow fiber membranes 14 having an effective membrane length of 20 cm are bundled is produced. At this time, the hollow upper end 14B penetrates the fixing member 3, while the hollow portion of the lower end 14A is sealed with an epoxy resin. Using this hollow fiber membrane module 10, pure water is filtered from the outer surface side of the hollow fiber membrane 14, and filtered water is obtained from the inner surface side of the upper end 14B. At this time, the transmembrane differential pressure is adjusted to 0.1 MPa, and the permeation performance obtained at that time can be measured as the water permeability of the hollow fiber membrane 14 at the transmembrane differential pressure of 0.1 MPa.

The hollow fiber membrane bundle 15 has a larger membrane area per module as the number of the hollow fiber membranes 14 increases, so that the filtration flow rate can be increased. On the other hand, when the number of the hollow fiber membranes 14 is excessively increased, the discharge efficiency of the floating contaminants at the time of cleaning is lowered. Therefore, when the outer diameter of the hollow fiber membrane 14 is di (m), the number of the hollow fiber membranes 14 is n (pieces), and the sectional area of the housing 13 is S (m ² ), it is calculated by 100πndi ² / 4S. The film filling rate is preferably 10 to 60%, more preferably 20 to 50%.

  The housing 13 is a cylindrical container having an upper surface 13A and a lower surface 13C and a side surface 13B connecting them. The housing 13 has an internal space S1 in which the hollow fiber membrane bundle 15 is accommodated, and a space S3 below the internal space S1. The internal space S <b> 1 includes an upper space S <b> 11 in which an upper portion is located with respect to the longitudinal center of the hollow fiber membrane 14, and a lower space S <b> 12 in which a lower portion is located with respect to the longitudinal center of the hollow fiber membrane 14. .

  A filtrate pipe 51 for taking out the 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, respectively. A gas discharge port 11 for discharging gas from the internal space S1 to the outside is provided below the fixing member 3 on the side surface 13B. As shown in FIG. 2, the gas discharge port 11 is an opening of the upper space S11. When the gas is supplied to the internal space S1, the gas is discharged out of the module through the gas discharge port 11. For this reason, the level 11B of the raw water in the housing 13 is lower than the lower end 11A of the gas outlet 11 as shown in FIG.

  On the side surface 13B, a drain outlet 12 for discharging the raw water in the housing 13 to the outside of the module is provided just above the lower surface 13C. Near the center of the lower surface 13C, a gas inlet 7 for aeration for supplying gas into the housing 13 is provided. The drain port 12 and the gas inlet 7 for aeration are openings of the space S3.

  As shown in FIG. 1, a gas discharge pipe 61 is connected to the gas discharge port 11, and the gas in the housing 13 is discharged through this. The gas discharge pipe 61 is provided with a gas discharge port valve 62, and the gas is extracted from the housing 13 by opening the valve.

  A drain pipe 41 is connected to the drain outlet 12, and the raw water in the housing 13 is discharged through this. The drain pipe 41 is provided with a drain valve 42, and the raw water is drained from the housing 13 by opening the drain valve 42.

  As the material of the housing 13, SUS (JIS standard), modified PPE (Poly Phenylene Ether), polyvinyl chloride, polysulfone, polycarbonate, polyolefin, ABS (acrylonitrile butadiene styrene) resin, or the like is used. A so-called integrated module may be configured by fixing and fixing the fixing member 3 to the inner surface of the housing 13. Further, an O-ring, packing, or the like may be attached to the outer peripheral portion 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 housing 13 can be used repeatedly by removing the fixing member 3 and replacing the hollow fiber membrane bundle 15.

  The pipe member 5 supplies raw water into the housing 13, and has a structure through which raw water passes in a pipe inner space 5 </ b> A that is a space inside the pipe member 5. As shown in FIG. 2, the pipe member 5 penetrates the center of the lower surface 13C of the housing 13 and the air diffuser member 4, and the inner side (center) of the hollow fiber membrane bundle 15 extends toward the upper surface 13A. It arrange | positions so that it may extend along a direction and the upper end is connected to the fixing member 3. The upper end opening of the tube member 5 is closed by the fixing member 3. As the pipe member 5, for example, a cylindrical member can be used, but is not limited thereto. Further, the tube member 5 is not limited to the case of extending inside the hollow fiber membrane bundle 15, and may be arranged outside the hollow fiber membrane bundle 15 in the housing 13.

  In order to prevent the hollow fiber membrane module 10 from becoming bulky, the length of the portion located in the housing 13 in the pipe member 5 is preferably 1 to 2 times the length of the hollow fiber membrane 14. More preferably, it is 1.5 times. Further, the inner diameter of the pipe member 5 is preferably determined so that the flux at the time of water flow is 4 m / s or less in order to reduce the pressure loss at the time of water flow, and is determined to be 3 m / s or less. It is more preferable.

  A raw water inlet 9 is provided at the lower end of the pipe member 5, through which raw water is supplied to the pipe inner space 5A. An insertion hole 8 into which a later-described third gas introduction pipe 33 is inserted is provided on the side surface of the pipe member 5 (the side surface of the portion protruding below the lower surface 13C of the housing 13).

  The pipe member 5 is provided with an upper opening 5B and a lower opening 5C positioned below the upper opening 5B. The upper opening 5 </ b> B is a hole provided so as to penetrate the wall portion of the pipe member 5, and communicates the pipe inner space 5 </ b> A and the upper space S <b> 11 of the housing 13. As shown in FIG. 2, the upper opening 5 </ b> B is located above the raw water liquid level 11 </ b> B and the lower end 11 </ b> A of the gas discharge port 11.

  Similarly to the upper opening 5B, the lower opening 5C is a hole provided so as to penetrate the wall portion of the tube member 5, and communicates the inner space 5A and the space S3 of the housing 13. As shown in FIG. 2, since the lower opening 5C is located below the liquid level 11B of the raw water, the liquid level 11B is positioned between the upper opening 5B and the lower opening 5C. Become. More specifically, the lower opening 5 </ b> C is located below the lower end 14 </ b> A of the hollow fiber membrane 14. The upper opening 5B and the lower opening 5C may be circular holes, for example, but the shapes are not particularly limited.

  The upper opening 5B and the lower opening 5C are holes of the same size. The inner diameters of the upper opening 5B and the lower opening 5C are preferably 30 mm or less. Further, the inner diameters of the upper opening 5B and the lower opening 5C are determined so that the discharge speed of the raw water is 4 m / s or less in order to reduce the pressure loss when the raw water is supplied from the pipe member 5 into the housing 13. It is preferable that it is determined to be 3 m / s or less.

  Eight upper openings 5B and five lower openings 5C are formed at equal intervals (45 ° intervals) in the circumferential direction of the pipe member 5. However, the number of the upper openings 5B and the lower openings 5C and the interval in the circumferential direction are not particularly limited. Further, the upper opening 5B and the lower opening 5C may be formed so that the number and the interval in the circumferential direction are different from each other.

  As shown in FIG. 1, the liquid feed pump 20 is connected to the raw water inlet 9 of the pipe member 5 via the raw water introduction pipe 21. The raw water introduction pipe 21 is provided with a raw water introduction valve 22 that switches between distribution and blocking of the raw water in the pipe. By operating the liquid feed pump 20, raw water can be supplied into the pipe member 5 through the raw water introduction pipe 21. Then, raw water is supplied into the housing 13 through the upper opening 5B and the lower opening 5C shown in FIG.

  As shown in FIG. 1, the air compressor 30 is connected to a filtrate side gas inlet 53 via a first gas introduction pipe 31, and a gas inlet 7 for air diffusion of the housing 13 via a second gas introduction pipe 32. And is connected to the pipe member 5 via the third gas introduction pipe 33. The first gas introduction pipe 31 is provided with a first gas introduction valve 34 for switching between flow and shutoff of gas (compressed air) in the pipe. Similarly, the second and third gas introduction pipes 32 and 33 are also provided with second and third gas introduction valves 35 and 36, respectively.

  As shown in FIG. 2, the third gas introduction pipe 33 is inserted into the pipe member 5 from the insertion hole 8 and extends upward along the axial direction of the pipe member 5. A gas supply port 33A is provided at the tip of the third gas introduction pipe 33, through which gas is supplied to the in-pipe space 5A. The gas supply port 33A opens in the pipe space 5A.

  As shown in FIG. 2, the lower opening 5C of the pipe member 5 is located below the gas supply port 33A. That is, the gas supply port 33 </ b> A supplies gas to the pipe inner space 5 </ b> A at a position above the lower opening 5 </ b> C of the pipe member 5. For this reason, the gas supplied from the gas supply port 33A is not released into the housing 13 through the lower opening 5C. In the present embodiment, the air compressor 30 that generates compressed air, the third gas introduction pipe 33 that guides the compressed air to the pipe inner space 5A, and the third gas introduction valve 36 provided in the third gas introduction pipe 36 provide the pipe inner space 5A. The gas supply part 2 which supplies gas is comprised.

  The control device 40 controls the operation of the liquid feed pump 20 and also controls the opening / closing operation of each valve. The control device 40 is configured by, for example, a personal computer. The control device 40 includes a storage unit that stores sequence information of each step (water filling, filtration, backwashing, bubbling, drainage, etc.) sequentially executed in the filtration and cleaning processes, and the liquid feed pump 20 according to the sequence information. An operation control unit for controlling the operation and opening and closing of the valve.

  The hollow fiber membrane filtration device 1 according to the present embodiment uses the so-called air lift effect to raise the raw water flowing into the pipe member 5 through the lower opening 5C to the upper side above the liquid surface 11B by the gas. A feature is that the vicinity of the upper end 14B of the hollow fiber membrane 14 can be effectively washed by ejecting the gas together with the gas toward the upper space S11 of the housing 13 through the upper opening 5B located above the surface 11B. Have.

  FIG. 3 schematically shows the flow of raw water and gas (compressed air) during the cleaning of the hollow fiber membrane 14 using the air lift effect. In FIG. 3, the flow of raw water is indicated by solid arrows, and the flow of gas is indicated by broken arrows.

  As shown in FIG. 3, gas is supplied from the gas supply port 33 </ b> A to the pipe inner space 5 </ b> A in a state where the raw water enters the housing 13 so that the liquid surface 11 </ b> B of the raw water is located below the upper end 14 </ b> B of the hollow fiber membrane 14. Is supplied, the raw water in the pipe rises with the gas to the upper side of the liquid surface 11B. That is, the raw water in the pipe is pushed up to the upper side of the liquid surface 11B by the pressure of the compressed air. And raw | natural water spouts into the upper space of the housing 13 with gas through the upper side opening part 5B located above the liquid level 11B. Thereby, since raw | natural water and gas are applied to upper end 14B vicinity of the hollow fiber membrane 14, it becomes possible to wash | clean the membrane surface effectively.

  On the other hand, as the amount of raw water in the pipe decreases due to the jet of raw water, the raw water flows from the space in the housing 13 into the pipe inner space 5A through the lower opening 5C. And the raw | natural water which flowed into 5 A of pipe inner spaces raises by being pushed up with compressed air as mentioned above, and ejects with gas through the upper side opening part 5B. Thus, raw | natural water circulates between the upper side opening part 5B and the lower side opening part 5C. On the other hand, the gas ejected from the upper opening 5 </ b> B is discharged out of the module through the gas discharge port 11.

  As described above, the lower opening 5C functions as a suction port for sucking raw water from the space in the housing 13 toward the inner space 5A, and the upper opening 5B is directed from the inner space 5A toward the space in the housing 13. It functions as a gas-liquid jet outlet for jetting raw water and gas. Moreover, the bubble formed in 5 A of pipe | tube space becomes the magnitude | size which occupies the whole cross section of 5 A of pipe | tube space, or the magnitude | size close to it.

The gas supply unit 2 is configured to supply a gas (compressed air) whose flow rate and pressure are adjusted to the inner space 5 </ b> A in order to enable cleaning of the hollow fiber membrane 14 using the air lift effect as described above. ing. Specifically, the gas supply unit 2 supplies compressed air having a pressure of 0 MPa to 0.5 MPa and a flow rate of 0.1 m ³ / hr to 30 m ³ / hr from the gas supply port 33A to the pipe space 5A. It is comprised so that it may supply. These pressures and flow rates are defined by the capacity of the air compressor 30. The pressure of the compressed air is preferably 0.1 MPa or more and 0.3 MPa or less, and more preferably 0.1 MPa or more and 0.2 MPa or less. The flow rate of the compressed air is preferably 0.1 m ³ / hr or more and 20 m ³ / hr or less, and more preferably 1 m ³ / hr or more and 15 m ³ / hr or less.

Here, in the air lift, the following equation (2) is established as a theoretical equation. In the following equation (2), “η” is the pump efficiency (%) by air lift, “ρ _l ” is the density of water (kg / m ³ ), and “Q _l ” is the pumped amount (spout from the upper opening 5B). Raw water flow rate, l / min), “g” is weight acceleration (m / s ² ), “H _d ” is discharge head (height distance from liquid surface 11B to upper opening 5B, m), “P _s "Represents atmospheric pressure (kgf / m ² )," Q _g "represents the supply air amount (l / min), and" P _g "represents the supply air pressure (kgf / m ² ). As one calculation example, η = 10 (%), P _s = 10330 (kgf / m ² ), Q _g = 167 (l / min), P _g = 11000 (kgf / m ² ), ρ _l = 1000 ( Substituting kg / m ³ ), g = 9.8 (m / s ² ), and H _d = 0.05 (m) into the following equation (2), Q _l = 22.1 (l / min) It becomes. Therefore, it is considered that raw water can be ejected from the upper opening 5B at a flow rate of Q _l = 22.1 (l / min).

  As shown in FIG. 2, the air diffusing member 4 is located below the lower end 14A of the hollow fiber membrane 14, and gas is dispersed in the internal space S1 at this position. A tube member 5 penetrates through the center of the diffuser member 4. The air diffusing member 4 has a shape that expands in the radial direction of the hollow fiber membrane bundle 15, and the peripheral edge portion is located on the radially outer side of the hollow fiber membrane bundle 15. In the air diffusing member 4, a plurality of air vent holes 43 for dispersing gas in the housing 13 are formed at intervals in the radial direction. The air diffusion member 4 disperses the gas supplied into the housing 13 from the gas inlet 7 for air diffusion so as to spread in the radial direction of the hollow fiber membrane bundle 15.

  FIG. 4 shows a planar structure of the air diffusing member 4. FIG. 5 shows a cross-sectional structure of the air diffusing member 4 along the line VV in FIG. The air diffusion member 4 has a shape that expands in the radial direction of the hollow fiber membrane bundle 15, and has a disk-shaped main body 44 in which a plurality of air vent holes 43 are formed, and a peripheral portion of the main body 44. It has the connected surrounding wall part 47, and the cylindrical gas receiving part 45 connected to the lower surface of the main-body part 44, and these are integrally formed.

  The air diffusion hole 43 is formed so as to penetrate the main body 44 in the thickness direction. A plurality of ventilation holes 43 are formed at intervals in the radial direction and the circumferential direction of the main body portion 44, and a part thereof is located on the radially outer side than the hollow fiber membrane bundle 15. Thereby, gas can be disperse | distributed in the radial direction with respect to the hollow fiber membrane bundle 15 in a wide range. The main body portion 44 is formed with a through hole 44A through which the tube member 5 passes in the central portion. In addition, the main-body part 44 is not limited to a disk-shaped thing as shown in FIG. 4, A thing of various shapes may be sufficient.

  The gas receiving part 45 is a part for temporarily storing the gas supplied into the housing 13 from the gas inlet 7 for aeration. The gas receiving part 45 has a cylindrical shape, and an upper end (one end) is connected to the lower surface of the main body part 44, and a gas receiving port 45A is formed on the lower end (other end) side. In this embodiment, the gas receiving part 45 is comprised so that an internal diameter may become substantially constant toward a lower end from an upper end. The gas receiving part 45 has an inner diameter larger than the outer diameter of the tube member 5 and accommodates gas in a gap between the outer periphery of the tube member 5.

  As shown in FIG. 2, the gas receiving portion 45 is located radially outside of the gas diffusion inlet 7, thereby accommodating the gas supplied from the gas diffusion inlet 7 into the housing 13 in the cylinder. can do. Further, a gap is formed between the lower end of the gas receiving portion 45 and the lower wall of the housing 13, and the raw water in the housing 13 can flow through the gap. Thereby, the liquid pool in the lower part of the housing 13 can be prevented.

  As shown in FIG. 5, a plurality of dispersion holes 46 are formed at intervals in the circumferential direction at a portion on the upper end side of the gas receiving portion 45. The dispersion hole 46 is formed so as to penetrate the wall portion of the gas receiving portion 45. By the dispersion holes 46, the gas stored in the gas receiving part 45 can be released to the outer side in the radial direction and guided to the vent holes 43 for air diffusion. The dispersion holes 46 may be formed at equal intervals in the circumferential direction, or may be formed at different intervals.

  The peripheral wall portion 47 has a cylindrical shape extending downward from the peripheral edge portion of the main body portion 44. The peripheral wall portion 47 can suppress the gas released to the outside of the gas receiving portion 45 through the dispersion hole 46 from spreading outside the main body portion 44. Thus, the gas can be retained on the lower surface of the main body portion 44 before the gas is dispersed through the air diffusion hole 43.

  According to the diffuser member 4, after the gas supplied into the housing 13 from the diffuser gas inlet 7 is temporarily accommodated by the gas receiving portion 45, it is released to the outside from the dispersion hole 46, and then the diffuser passage is passed. It can be dispersed toward the lower space S12 through the pores 43.

<Washing method for hollow fiber membrane filtration device>
Next, the raw water filtration operation by the hollow fiber membrane filtration device 1 and the method of cleaning the hollow fiber membrane filtration device according to the present embodiment, which is performed by interrupting the filtration operation, are performed along the process flow shown in FIG. I will explain. FIG. 6 shows the relationship between each step and the open / close state of the valve during the operation of the hollow fiber membrane filtration device 1 shown in FIG. In FIG. 6, a circle means the open state of the corresponding valve, and a blank means a closed state.

  First, a water filling step (before filtration) is performed. In this step, the raw water introduction valve 22 and the gas outlet valve 62 are opened by the control device 40 from the state where all the valves of the hollow fiber membrane filtration device 1 are closed, and the liquid feed pump 20 is operated. Thereby, raw water is introduced into the pipe member 5 from the liquid feed pump 20 via the raw water introduction pipe 21. Then, raw water is supplied into the housing 13 through the upper opening 5B and the lower opening 5C of the pipe member 5.

  Next, a filtration step is performed. In this step, after the raw water overflows from the gas outlet 11, the filtrate outlet valve 71 is opened and the gas outlet valve 62 is closed by the control device 40. Then, the raw water in the housing 13 passes through the membrane wall from the outer surface side of the hollow fiber membrane 14 and permeates into the inner surface side, and is taken out as filtrate from the filtrate-side space S2.

  In this filtration step, suspended contaminants in the raw water may adhere to the outer surface of the hollow fiber membrane 14 with the passage of filtration time, and the pores of the hollow fiber membrane 14 may be blocked. Thereby, the permeation | transmission flow rate of raw | natural water falls and the filtration capability by the hollow fiber membrane 14 falls. For this reason, after a certain time has elapsed from the start of filtration, the filtration operation is temporarily suspended, and the method for cleaning the hollow fiber membrane filtration device according to the present embodiment described below is performed. Thereby, the floating contaminants adhering to the outer surface of the hollow fiber membrane 14 during filtration are removed, and the filtration capability of the hollow fiber membrane 14 can be recovered.

  First, a backwash process is performed. In this step, the drain valve 42 and the first gas introduction valve 34 are opened by the control device 40. As a result, compressed air is introduced from the air compressor 30 into the filtrate-side space S2 in the housing 13 through the filtrate-side gas inlet 53, whereby the filtrate is pressurized. Then, the pressurized filtrate is pushed from the inner surface side of the hollow fiber membrane 14 to the outer surface side, and as a result, part of the raw water in the housing 13 is discharged out of the system through the drain outlet 12. As a result of the backwashing of the hollow fiber membrane 14 in this way, the suspended pollutant adhered during filtration floats from the membrane surface. Thereafter, the pressure in the filtrate-side space S2 is lowered by opening the filtrate-side pressure relief valve 81.

  Next, a water filling step (before lower bubbling) is performed. In this process, in order to raise the liquid level 11B in the housing 13 that has been lowered in the backwashing process, the control device 40 opens the raw water introduction valve 22 and the gas discharge valve 62 and activates the liquid feed pump 20. Thereby, raw | natural water is supplied in the housing 13 and the liquid level 11B of raw | natural water rises to the height position between the upper side opening part 5B and the lower side opening part 5C, as shown in FIG. Thereafter, the liquid feed pump 20 is stopped, the raw water introduction valve 22 is closed, and the supply of raw water is stopped.

  Next, a lower bubbling process is performed. In this step, the second gas introduction valve 35 is opened by the control device 40. As a result, gas (compressed air) is supplied from the air compressor 30 into the housing 13 through the gas inlet 7 for air diffusion. And after the said gas is accommodated in the gas receiving part 45, it is disperse | distributed toward the lower space S12 from the vent hole 43 for aeration. Then, the hollow fiber membrane 14 is swung by the bubbles rising from the lower end 14A to the upper end 14B of the hollow fiber membrane 14, and the suspended contaminants floating from the membrane surface are peeled off by the action.

  The amount of gas supply in the lower bubbling step is preferably 20000 NL / h or less, and more preferably 500 to 10000 NL / h. In the lower bubbling step, if the gas supply amount becomes excessive, the hollow fiber membranes 14 are entangled with each other and the membrane surface is damaged, and thus the upper limit of the gas supply amount is limited in this way.

  Next, an air lift cleaning process is performed. This step is an important step in the cleaning method of the hollow fiber membrane filtration device according to the present embodiment, and by performing this step, the upper end 14B of the hollow fiber membrane 14 that was not sufficiently cleaned in the lower bubbling step. Can be effectively cleaned.

  First, the control device 40 closes the second gas introduction valve 35 and opens the third gas introduction valve 36. Thus, gas (compressed air) is supplied from the gas supply port 33A to the pipe inner space 5A in a state where the liquid surface 11B of the raw water is located below the upper end 14B of the hollow fiber membrane 14 (FIG. 3). The gas flow rate and pressure at this time are as described above. Thereby, the raw | natural water in a pipe | tube is pushed up by the pressure of compressed air, and rises with a gas to the upper side rather than the liquid level 11B. And raw | natural water can be spouted toward upper space S11 with gas through the upper side opening part 5B located above the liquid level 11B.

  Further, as the amount of raw water in the pipe decreases due to the ejection of raw water, the raw water flows from the space S3 in the housing 13 into the pipe inner space 5A through the lower opening 5C. And as above-mentioned, this raw | natural water rises above the liquid level 11B with gas, and ejects with gas through the upper side opening part 5B. As a result, since the raw water and gas can be washed around the upper end 14B of the hollow fiber membrane 14, floating contaminants adhering to the membrane surface in the vicinity of the upper end 14B that could not be sufficiently removed in the lower bubbling step are removed. It can be removed reliably.

  Finally, a drainage process is performed. In this step, the control device 40 closes the third gas introduction valve 36 and opens the drain valve 42. Thereby, the raw water containing the suspended pollutant material peeled off from the membrane surface is discharged out of the system from the drain outlet 12. The hollow fiber membrane 14 is washed as described above.

  After the hollow fiber membrane 14 is washed as described above, the filtration process is started again. That is, the washing method of the hollow fiber membrane filtration device according to the present embodiment is performed between one filtration step and the next filtration step, and by carrying out this, in the next filtration step The apparatus can be operated with a high filtration capacity.

  Here, the features of the hollow fiber membrane filtration device 1 and the cleaning method thereof according to the present embodiment described above will be listed.

  The hollow fiber membrane filtration device 1 includes an external pressure filtration type hollow fiber membrane module 10. The hollow fiber membrane module 10 includes a hollow fiber membrane bundle 15 having a plurality of bundled hollow fiber membranes 14 and an internal space S1 in which the hollow fiber membrane bundle 15 is accommodated, and discharges gas from the internal space S1 to the outside. And a tube member 5 disposed so as to extend along the longitudinal direction of the hollow fiber membrane 14, which is a space inside the tube member 5. And an upper opening 5B that communicates with the upper space S11, and a lower opening 5C that is located below the upper opening 5B and that communicates the inner space 5A and the space S3 of the housing 13 with each other. And a pipe member 5. The hollow fiber membrane filtration device 1 further includes a gas supply unit 2 that supplies gas to the inner space 5A. The gas supply unit 2 causes the raw water flowing into the pipe space 5A from the space S3 of the housing 13 through the lower opening 5C to be higher than the level 11B of the raw water positioned between the upper opening 5B and the lower opening 5C. It is configured to supply a gas whose flow rate and pressure are adjusted so that the gas is raised to the upper side together with the gas and ejected into the upper space S11 together with the gas through the upper opening 5B located above the liquid level 11B.

  The method for cleaning the hollow fiber membrane filtration device 1 according to the present embodiment includes a step of supplying raw water into the housing 13 (a water filling step (before lower bubbling)), and a liquid surface 11B of the raw water is By supplying gas to the pipe inner space 5A in a state positioned below the upper end 14B, the raw water flowing into the pipe inner space 5A through the lower opening 5C from the space S3 of the housing 13 is supplied from the liquid surface 11B together with the gas. And a step (air lift cleaning step) of jetting the gas into the upper space S11 together with the gas through the upper opening 5B located above the liquid level 11B.

  According to this feature, by supplying a gas whose flow rate and pressure are appropriately adjusted from the gas supply part 2 to the pipe inner space 5A, the raw water flowing into the pipe inner space 5A from the space S3 of the housing 13 through the lower opening 5C. Can be raised together with the gas to the upper side of the liquid surface 11B of the raw water, and can be jetted into the upper space S11 of the housing 13 together with the gas from the upper side of the liquid surface 11B through the upper opening 5B. Thereby, since it becomes possible to wash | clean by applying raw | natural water and gas to the surface of the upper end 14B vicinity of the hollow fiber membrane 14, a washing | cleaning effect can be heightened compared with normal bubbling washing | cleaning. Moreover, the air lift effect as described above can be realized with a simple device configuration.

  In the hollow fiber membrane filtration device 1, the gas supply unit 2 has a gas supply port 33A for supplying gas to the pipe space 5A at a position above the lower opening 5C. Thereby, it is possible to prevent the gas supplied from the gas supply port 33A to the pipe inner space 5A from leaking out of the pipe through the lower opening 5C.

  In the hollow fiber membrane filtration device 1, the hollow fiber membrane module 10 includes a diffuser member 4 that disperses gas in the internal space S <b> 1 at a position below the lower end 14 </ b> A of the hollow fiber membrane 14. Thereby, the gas dispersed by the air diffusing member 4 rises from the lower end 14A of the hollow fiber membrane 14 and the hollow fiber membrane 14 swings, so that the suspended contaminants attached to the membrane surface can be peeled off ( Lower bubbling).

  In the hollow fiber membrane filtration device 1, the lower opening 5 </ b> C is located below the lower end 14 </ b> A of the hollow fiber membrane 14. Thereby, as the raw water ejected from the upper opening 5B flows downward toward the lower opening 5C, the suspended contaminants removed from the membrane surface of the upper end 14B are moved below the lower end 14A by the raw water flow. Can carry up to. Thereby, it is possible to prevent the floating pollutant from reattaching to the outer surface of the hollow fiber membrane 14.

  In the hollow fiber membrane filtration device 1, the hollow fiber membrane bundle 15 is a one-end free type in which the upper end 14B of the hollow fiber membrane 14 is fixed and the hollow fiber membranes 14 are not fixed one by one at the lower end 14A. Accordingly, the hollow fiber membrane 14 can be easily swung by bubbling, compared with the case of using a both-ends fixed type hollow fiber membrane module, so that the cleaning effect of the hollow fiber membrane 14 can be further enhanced.

(Embodiment 2)
Next, a hollow fiber membrane filtration device according to Embodiment 2 of the present invention will be described. The hollow fiber membrane filtration device according to the second embodiment basically has the same configuration as the hollow fiber membrane filtration device 1 according to the first embodiment, except that the lower opening penetrates the wall portion of the tube member 5. Instead, it is different in that it is a tube end opening provided at the lower end of the tube member 5. Only differences from the first embodiment will be described below.

  As shown in FIG. 7, in Embodiment 2, the pipe member 5 is connected to the fixing member 3 so that a gap is formed between the lower end thereof and the lower wall of the housing 13. And the pipe end opening 5D is provided in the lower end of the pipe member 5, and raw | natural water flows in in a pipe | tube through this pipe end opening 5D. The pipe end opening 5D is located below the liquid level 11B of the raw water, and more specifically, is located below the lower end 14A of the hollow fiber membrane 14. The third gas introduction pipe 33 passes through the lower wall of the housing 13 and is inserted into the pipe member 5 so that the gas supply port 33A is positioned above the pipe end opening 5D.

  In the second embodiment, by supplying gas from the gas supply port 33A to the pipe inner space 5A, the raw water in the pipe is raised to the upper side of the liquid surface 11B together with the gas, as in the first embodiment, and through the upper opening 5B. It can be made to eject toward the upper end 14B of the hollow fiber membrane 14 with gas. As the amount of raw water in the pipe decreases, the raw water flows into the pipe inner space 5A through the pipe end opening 5D. According to the second embodiment, the configuration of the module can be further simplified, which is preferable from the viewpoint of cost reduction.

(Embodiment 3)
Next, a hollow fiber membrane filtration device according to Embodiment 3 of the present invention will be described. The hollow fiber membrane filtration device according to the third embodiment basically has the same configuration as the hollow fiber membrane filtration device 1 according to the first embodiment, but a tube end opening is formed at the lower end of the tube member 5 as shown in FIG. 5D is provided, and the difference is that a tube hole 5E is further formed below the upper opening 5B. Only differences from the first embodiment will be described below.

  As shown in FIG. 8, in the third embodiment, similarly to the second embodiment, a pipe end opening 5 </ b> D (lower opening) is provided at the lower end of the pipe member 5. Here, unlike the second embodiment, the tube end opening 5D is located above the lower end 14A of the hollow fiber membrane 14. That is, the tube member 5 is shorter than the hollow fiber membrane 14. The tube end opening 5D is located below the liquid level 11B of the raw water. The third gas introduction pipe 33 penetrates the lower wall of the housing 13 and the diffuser member 4 and is inserted into the pipe member 5 so that the gas supply port 33A is positioned above the pipe end opening 5D.

  The tube hole 5E (lower opening) is provided so as to penetrate the wall portion of the tube member 5, and communicates the space in the housing 13 and the tube space 5A. As shown in FIG. 8, the tube hole 5E is located below the lower end 11A of the gas outlet 11 and the liquid surface 11B of the raw water.

  In the third embodiment, by supplying gas from the gas supply port 33A to the pipe space 5A, the raw water in the pipe is raised to the upper side of the liquid surface 11B together with the gas, as in the first embodiment, and through the upper opening 5B. It can be made to eject toward the upper end 14B of the hollow fiber membrane 14 with gas. As the amount of raw water in the pipe decreases, the raw water in the housing 13 flows into the pipe inner space 5A through the pipe end opening 5D and the pipe hole 5E. That is, the tube end opening 5D and the tube hole 5E each function as a lower opening.

Moreover, when raw | natural water and gas are ejected through the upper side opening part 5B, the liquid level 11B will shake up and down with the momentum at the time of ejection. Here, since the pipe hole 5E is located directly below the liquid level 11B, the pipe hole 5E may be temporarily located above the liquid level 11B when the liquid level 11B is lowered. Therefore,
Raw water and gas can be ejected temporarily not only from the upper opening 5B but also from the tube hole 5E. In addition, in this case, since the height distance between the pipe hole 5E and the liquid surface 11B is extremely small, a large amount of raw water can be ejected by an air lift.

(Other embodiments)
Finally, other embodiments of the present invention will be described.

  In the first to third embodiments, the case where the hollow fiber membrane modules 10, 10 </ b> A, and 10 </ b> B include the aeration member 4 has been described, but the aeration member 4 may be omitted.

  In the second embodiment, the case where the third gas introduction pipe 33 is inserted into the pipe from the lower end of the pipe member 5 has been described. However, as shown in FIG. 9, the third gas introduction pipe 33 is inserted into the pipe member 5. Alternatively, the gas supply port 33A may be positioned below the tube end opening 5D.

  In the first embodiment, the third gas introduction pipe 33 may be directly connected to the side surface of the pipe member 5 from a position above the lower opening 5C.

  In the first embodiment, the case where the air lift cleaning process is performed after the lower bubbling process is performed has been described. However, the lower bubbling process may be performed after the air lift cleaning process, or these processes may be performed simultaneously. May be. However, when the lower bubbling step is performed after the air lift cleaning step, the upper end 14B of the hollow fiber membrane 14 is cleaned in the air lift cleaning step, and then the floating contaminants removed from the membrane surface in the lower bubbling step increase. Then, it reattaches to the upper end 14B. On the other hand, by performing the air lift cleaning process after the lower bubbling process, it is possible to prevent re-adhesion of suspended contaminants to the upper end 14B of the hollow fiber membrane 14 and to clean the entire hollow fiber membrane 14.

  As shown in FIG. 10, the air lift cleaning may be performed in a state where the liquid surface 11 </ b> B is lowered below the center of the hollow fiber membrane 14 in the longitudinal direction. In this case, in order to lower the liquid level 11B, a step of partially draining the raw water in the housing 13 may be further performed after the lower bubbling step and before the air lift cleaning step.

  In the first embodiment, the case where air is used as the bubbling gas has been described. However, the present invention is not limited to this. For example, an inert gas such as nitrogen may be used.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane filtration apparatus 2 Gas supply part 4 Aeration member 5 Pipe member 5A Inner space 5B Upper opening part 5C, 5D, 5E Lower opening part 10, 10A, 10B, 10C Hollow fiber membrane module 11 Gas exhaust port 11B Liquid Surface 13 Housing 14 Hollow fiber membrane 14A Lower end 14B Upper end 15 Hollow fiber membrane bundle 30 Air compressor 33 Third gas introduction pipe 33A Gas supply port S1 Internal space

Claims (6)

A hollow fiber membrane filtration device comprising an external pressure filtration type hollow fiber membrane module,
The hollow fiber membrane module is
A hollow fiber membrane bundle having a plurality of bundled hollow fiber membranes;
An internal space in which the hollow fiber membrane bundle is accommodated, and a housing provided with a gas discharge port for discharging gas from the internal space to the outside;
An upper opening that communicates a space in the tube that is an inner space of the tube member and a space in the housing, the tube member being arranged to extend along the longitudinal direction of the hollow fiber membrane, and the upper side The tube member provided with a lower opening that is located below the opening and communicates with the space in the tube and the space in the housing;
The hollow fiber membrane filtration device further comprises a gas supply unit for supplying gas to the space in the pipe,
The gas supply unit causes raw water flowing from the space in the housing to the space in the pipe through the lower opening to be higher than the level of the raw water located between the upper opening and the lower opening. It is configured to supply a gas whose flow rate and pressure are adjusted so that the gas is raised together with the gas, and jetted into the space in the housing together with the gas through the upper opening located above the liquid level. A hollow fiber membrane filtration device characterized by that.   The hollow fiber membrane filtration device according to claim 1, wherein the gas supply unit has a gas supply port for supplying gas to the space in the pipe at a position above the lower opening.   3. The hollow fiber according to claim 1, wherein the hollow fiber membrane module further includes an air diffuser that disperses gas in the internal space at a position below a lower end of the hollow fiber membrane. Membrane filtration device.   The said lower side opening part is located below the lower end of the said hollow fiber membrane, The hollow fiber membrane filtration apparatus of any one of Claims 1-3 characterized by the above-mentioned.   The hollow fiber membrane bundle is a one-end free type in which the upper end of the hollow fiber membrane is fixed and the hollow fiber membranes are not fixed one by one at the lower end. 2. A hollow fiber membrane filtration device according to item 1. A hollow fiber bundle having a plurality of bundled hollow fiber membranes, a housing in which an internal space in which the hollow fiber membrane bundle is accommodated is formed, and arranged to extend along the longitudinal direction of the hollow fiber membranes, A hollow fiber membrane filtration apparatus comprising an external pressure filtration type hollow fiber membrane module, each having an upper opening and a pipe member provided with a lower opening located below the upper opening. A method for washing a yarn membrane,
Supplying raw water into the housing;
In a state where the liquid level of the raw water is located below the upper end of the hollow fiber membrane, gas is supplied to the inner space of the tube, which is the space inside the tube member, thereby allowing the lower opening from the space in the housing. A step of raising the raw water flowing into the pipe space through the section to the upper side of the liquid surface together with the gas, and ejecting the raw water together with the gas into the space in the housing through the upper opening located above the liquid level; A method for cleaning a hollow fiber membrane filtration device.

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