JP6618708B2 - Method for operating hollow fiber membrane module and filtration device - Google Patents

Description

  The present invention relates to a method for operating a hollow fiber membrane module and a filtration device used in the method.

  In recent years, the development of separation technology using hollow fiber membranes has progressed, and it is widely used for various applications including water filtration. However, in the process of filtration with a hollow fiber membrane, solid substances such as suspended solids in a stock solution called SS adhere to the surface of the hollow fiber membrane or penetrate into the microporous membrane, and the permeation flux decreases with time. . Therefore, in order to continue the filtration operation stably over a long period of time, it is indispensable to develop a method for washing the hollow fiber membrane and a method for operating the filtration device in washing simultaneously with setting of the filtration conditions.

  Conventionally, various methods have been proposed as a method for cleaning a hollow fiber membrane module, and these can be roughly classified into a physical cleaning method and a chemical cleaning method.

  As a physical cleaning method, a liquid backwashing method for passing a liquid such as water or filtered water from the filtrate side to the stock solution side, a gas backwashing method for passing a pressurized gas from the filtrate side to the stock solution side (Patent Document 1, Patent Document 2 etc.), a variety of methods such as a bubbling method in which bubbles are ejected from the bottom of a module on the stock solution side, an ultrasonic method, and the like have been proposed. Further, as a chemical cleaning method, a method is known in which a deposit is dissolved or decomposed with a chemical solution such as an acid, an alkaline aqueous solution, an oxidizing agent, or a cleaning agent.

  In general, when a conventionally known physical cleaning method is used, the cleaning effect is not always satisfactory. For example, when the filtration process and the cleaning process are continuously operated by sequence control or the like, it is several days to several months. There was a problem that the permeation flux was greatly reduced. In order to solve this problem, Patent Document 3 proposes a physical cleaning method in which a gas having a pressure lower than the pressure at which bubbles are released from the raw liquid side of the hollow fiber membrane is introduced from the filtrate side of the hollow fiber membrane. .

JP-A-53-108882 Japanese translation of PCT publication 1-500732 Japanese Patent Laid-Open No. 10-286441

  By using the physical cleaning method disclosed in Patent Document 3, undiluted SS solution, undiluted solution that is unlikely to be clogged by filtration, or filtration with a low filtration flux enables long-term continuous filtration operation. . On the other hand, filtration of high turbidity stock solution with a large amount of SS in the stock solution, filtration of stock solution that has been subjected to agglomeration treatment to prevent membrane clogging, or filtration with a high filtration flux that is the filtration flow rate per unit membrane area In this case, SS attached to the surface of the hollow fiber membrane by membrane filtration cannot be discharged by physical washing, and SS gradually accumulates on the surface of the hollow fiber membrane to become filtration resistance. It is often difficult to continue driving. Therefore, in order to enable a continuous filtration operation for a long period of time in a filtration operation with a high turbidity undiluted solution, a stock solution requiring a coagulation treatment as a pretreatment, and a high filtration flux, an effective operation method in physical cleaning is required. Development is necessary.

  An object of the present invention is to provide a method of operating a hollow fiber membrane module and a filtration device capable of reducing the deposition of SS on the hollow fiber membrane as compared with a conventional method.

  The operation method of the hollow fiber membrane module of the present invention that solves the above problems has the following characteristics.

(1) An operation method of a hollow fiber membrane module used in an external pressure filtration system in which a stock solution is supplied to the outer surface side of a hollow fiber membrane and a filtrate is taken out from the inner surface side of the hollow fiber membrane, A filtration step for filtering the stock solution and a pressurization step for pressurization with gas or liquid from the filtrate side of the hollow fiber membrane, and then a gas from the filtrate side of the hollow fiber membrane between the subsequent filtration step Alternatively, without repeating the pressurizing step of pressurizing with the liquid , the gas washing step of washing the hollow fiber membrane stock solution side with bubbles, the draining step of discharging the liquid in the module out of the system, and the hollow fiber membrane stock solution side The water filling step for filling the liquid is repeated twice or more between the filtration step and the subsequent filtration step.

In (2) above (1), wherein the filtration step more than a predetermined number of times, the pressurizing step, the gas cleaning process, draining step, after repeated filling of water step, the gas between the filtration step and the next filtration step You may repeat a washing | cleaning process, the said drainage process, and the said water filling process twice or more.

( 3 ) In any one of the above (1) to ( 2 ), as the hollow fiber membrane module, the upper ends of the hollow fiber membrane bundles are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one. A single-end free type hollow fiber membrane module may be used.

(4) Further, the filtration device according to the present invention includes a hollow fiber membrane module having a hollow fiber membrane element, a liquid feed pump for supplying a stock solution to the hollow fiber membrane module, and a gas for pressurizing the hollow fiber membrane module. Or it is a filtration apparatus provided with the pressurization apparatus which supplies a liquid, and the control apparatus which performs the operation control of the said liquid feeding pump and the said pressurization apparatus. The control device performs a filtration step of filtering the stock solution using a hollow fiber membrane, and a pressurization step of applying pressure with gas or liquid from the filtrate side of the hollow fiber membrane, and then between the subsequent filtration steps. Without repeating the pressurizing step of pressurizing with a gas or liquid from the filtrate side of the hollow fiber membrane , the gas washing step, the draining step, and the water filling step are performed between the filtration step and the subsequent filtration step. It is configured to repeat more than once.

( 5 ) In the filtration device, as the hollow fiber membrane module, the hollow fiber membrane bundle is fixed at one end at the upper end, and the lower end is a one-end free type hollow sealed without hollow fiber membranes being fixed one by one A thread membrane module may be used.

  Although the reason why the operation method of the hollow fiber membrane module of the present invention exhibits an excellent effect compared to the conventional operation method is not clear, the operation of the present invention that the present inventors have estimated at the present time, The external pressure filtration method shown in FIG. 1 will be described below as an example.

  FIG. 1 is a diagram schematically illustrating the adhesion, separation, and discharge of SS on the surface of the hollow fiber membrane in the filtration step, the pressurization step, the gas washing step, and the drainage step in the external pressure filtration method. The SS in the stock solution is separated from the treated water by filtration and adheres to the membrane surface. The SS adhering to the membrane surface is cracked by being pressurized with liquid or gas from the filtrate side of the hollow fiber membrane module in the subsequent pressurizing step, and partly peels off from the membrane surface. Furthermore, by ejecting bubbles from the bottom of the module in the gas cleaning step, the SS is peeled off from the membrane surface and discharged out of the module in the draining step. Here, when the SS concentration of the stock solution is high, when agglomeration is performed as a pretreatment to prevent membrane clogging, or when the filtration flux that is the filtration flow rate per unit membrane area is set high. Increases the amount of SS adhering to the membrane surface during the filtration process. For this reason, SS cannot be completely discharged in the pressurization step, gas cleaning step, and drainage step, and SS gradually accumulates on the surface of the hollow fiber membrane, resulting in a filtration resistance. As SS deposition progresses, the filtration flux gradually decreases, making it difficult to continue the filtration operation. Therefore, by filling the stock solution again after the draining step of the physical cleaning, performing the gas cleaning step, and performing the draining step again, the SS discharging effect can be enhanced. Even after SS is deposited on the surface of the hollow fiber membrane by repeated filtration and physical cleaning, the module is filled with the stock solution, the gas cleaning step is performed, and the draining step is repeated. The SS deposited on the film surface can be peeled off and discharged. That is, the method of refilling the stock solution after the draining step and draining it after the washing step has not been conventionally employed because the filtrate recovery efficiency is reduced. However, when filtering the stock solution with a large amount of SS attached, the replacement frequency of the hollow fiber membrane module is increased, so that the stock solution is charged again after the draining step and drained after the cleaning step. By adopting, it is possible to contribute to the overall cost reduction although there is a disadvantage that the recovery efficiency of the filtrate is lowered.

  As described above, the amount of attached SS can be reduced by the operation method and the filtration device of the hollow fiber membrane module of the present invention, and a continuous filtration operation can be stably performed for a long period of time.

It is a figure for demonstrating adhesion, peeling, and discharge | emission of SS on the surface of a hollow fiber membrane element in each process. It is a figure which shows an example of the external pressure type | mold hollow fiber membrane module used for the filtration apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the filtration apparatus which concerns on embodiment of this invention using an external pressure type | mold hollow fiber membrane module. It is a figure which shows the basic driving | operation program of the filtration apparatus shown in FIG. FIG. 4 is a diagram for explaining the order of steps in Example 1. FIG. 10 is a diagram for explaining the order of steps in Example 2. 10 is a diagram for explaining the order of each step in Comparative Example 1. FIG. It is a figure which shows transition of SS adhesion amount in Example 1, Example 2, and Comparative Example 1. FIG.

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

  Examples of the hollow fiber membrane used in the embodiment of the present invention include a polysulfone resin hydrophilized with a polyvinyl alcohol resin, a polyvinylidene fluoride resin, a polysulfone resin to which a hydrophilic polymer is added, and polyvinylidene fluoride. -Based resin, polyvinyl alcohol-based resin, polyacrylonitrile-based resin, cellulose acetate-based resin, a hydrophilic material such as a polyethylene-based resin that has been subjected to a hydrophilic treatment, has high hydrophilicity, so that the SS component hardly adheres, A hollow fiber membrane made of another material can also be used, although it is preferable in terms of excellent peelability of the attached SS component. For example, it is composed of organic polymer materials such as polyolefin, polysulfone, polyethersulfone, cellulose acetate, polyvinylidene fluoride, polyperfluoroethylene, polymethacrylate, polyester, and polyamide. Hollow fiber membranes, hollow fiber membranes made of inorganic materials such as ceramics, and the like can be selected according to use conditions, desired filtration performance, and the like. Here, a hollow fiber membrane comprising a polysulfone resin hydrophilized with a polyvinyl alcohol resin, a polyvinylidene fluoride resin, a polysulfone resin to which a hydrophilic polymer is added, a polyvinylidene fluoride resin, and a polyvinyl alcohol resin. Is particularly preferable because it is excellent not only in the above-described hydrophilicity but also in heat resistance. When an organic polymer material is used, it may be a copolymer obtained by copolymerizing other components in an amount of 30 mol% or less, or a blend of other materials in an amount of 30 wt% or less.

  When an organic polymer hollow fiber membrane is used, the method for producing the hollow fiber membrane is not particularly limited, and a method appropriately selected from known methods depending on the characteristics of the material and the desired hollow fiber membrane performance Can be selected. Generally, a melt spinning method, a wet spinning method, a dry / wet spinning method, or the like is employed. Further, from the viewpoint of water permeability, the hollow fiber membrane preferably has an inclined structure having a dense layer and a support layer. However, since hollow fibers generally produced by melt spinning have a symmetric structure, the dry and wet spinning method It is preferable to produce by a phase change method such as

  The pore diameter of the hollow fiber membrane used in the present embodiment is not particularly limited, but is preferably in the range of 0.001 to 5 microns because it has high water permeability and is less likely to reduce filtration efficiency. . Here, the pore diameter refers to the particle diameter of a reference material from which 90% is excluded when various reference substances with known particle diameters such as colloidal silica, emulsion, and latex are filtered through a hollow fiber membrane. The pore diameter is preferably uniform. In the case of an ultrafiltration membrane, it is impossible to determine the pore size based on the particle size of the reference material as described above, but when a similar measurement is performed using a protein having a known molecular weight, Those having a molecular weight of 3000 or more are preferred.

  From the viewpoint of the mechanical properties of the hollow fiber membrane and the membrane area as a module, the outer diameter of the hollow fiber membrane is preferably set in the range of 200 to 30000 microns, more preferably in the range of 500 to 2000 microns. . Similarly, the thickness of the hollow fiber membrane is more preferably in the range of 100 to 600 microns.

  In this embodiment, the hollow fiber membrane is modularized and used for filtration. The form of the module can be appropriately selected according to the filtration method, filtration conditions, washing method, and the like, and a hollow fiber membrane module may be configured by mounting one or a plurality of hollow fiber membrane elements. As the form of the module, for example, a bundle of dozens to hundreds of thousands of hollow fiber membranes is formed into a U shape in the module, one end of the hollow fiber bundle is collectively sealed with an appropriate sealing material, Examples include one in which one end of a hollow fiber bundle is sealed in a state where it is not fixed one by one with a suitable sealing material (free state), and one in which both ends of the hollow fiber bundle are opened. Further, the form of the hollow fiber membrane module is not particularly limited, and may be, for example, cylindrical or on a screen. In the cleaning method of the present embodiment, since SS discharge is important, it is particularly preferable to use a “one end free” type module in which one end of each hollow fiber fiber bundle is sealed in a free state.

  Examples of the filtration method using the hollow fiber membrane module used in the present embodiment include external pressure total filtration, external pressure circulation filtration, and the like, and can be appropriately selected according to desired treatment conditions and treatment performance. From the viewpoint of membrane life, a circulation system capable of performing filtration and cleaning of the membrane surface at the same time is preferable, and from the viewpoint of simplicity of equipment, installation cost, and operation cost, a total filtration system is preferable.

  In the present embodiment, a pressurizing step of pressurizing with a gas or a liquid from the filtrate side of the hollow fiber membrane is performed. Examples of the gas used in the pressurizing step include air, nitrogen, etc., and the liquid includes pure water and membrane filtration. Examples thereof include water, and chemicals such as sodium hypochlorite, acid, and alkali may be added. The pressure of the gas or liquid used in the pressurizing step is selected within a range that does not exceed the burst pressure of the hollow fiber membrane, but when the burst pressure is higher than 0.5 MPa, the pressure of the pressurized gas or liquid is 0. It is preferably in the range of 10 MPa to 0.50 MPa, more preferably in the range of 0.15 MPa to 0.30 MPa.

  The time for performing the pressurizing step with the gas or liquid needs to be longer than the time at which the liquid on the filtrate side of the hollow fiber membrane module can be completely discharged or replaced, but the unit time of the pressurized gas or liquid The time required for the pressurizing step varies depending on the amount of permeation and the volume of the hollow fiber membrane module on the filtrate side. In addition, it is necessary to set the pressurization time in consideration of the internal volume of the hollow fiber membrane.

  In the pressurizing step with gas, when a gas having a pressure smaller than the pressure at which the gas is released from the raw liquid side of the hollow fiber membrane is introduced from the filtrate side of the hollow fiber membrane, Backwashing is performed by the filtrate filled in the pipe connecting the pipes and the hollow fiber membrane module. For example, the amount of liquid at the time of backwashing can be increased by providing a retention part such as a permeate tank in the middle part of the pipe.

In this embodiment, the liquid side of the hollow fiber membrane module is washed with air bubbles while the liquid side is filled with the liquid. The gas used in this gas washing step includes air, nitrogen, and the like. . The supply amount of the gas is not particularly limited, membrane cleaning effect is high, there is since a risk of film damage is small, in the range of area 1 m ² per 5-1000 normal liters / h of supply quantity hollow fiber membrane gas It is more preferable that it is in the range of 10 to 500 normal liters / hour. When the above-mentioned “one end free” type module is used, SS peeled off from the hollow fiber membrane is easily discharged, and the membrane cleaning effect by gas becomes extremely high.

  After the reverse cleaning, the hollow fiber membrane can be washed with a chemical solution to dissolve and remove organic substances and inorganic substances adhering to the hollow fiber membrane. Here, as a chemical cleaning method, a method of treating with an alkali such as an aqueous sodium hydroxide solution to remove organic substances, inorganic materials, a method of treating with an acid such as an acid aqueous solution to remove metals, and a cleaning agent There is a method of treating with, and a method of continuously carrying out a combination of these, whereby the hollow fiber membrane can be regenerated.

  The series of steps of the filtration step, the pressurization step, the water filling step, the gas washing step, and the drainage step that have been described so far can be sequence-controlled by the control device. For example, after performing filtration for a certain period of time, after performing a pressurization process, a water filling process, a gas washing process, and a draining process, a series of performing a water filling process, a gas washing process, and a draining process, followed by a filtration process It is possible to perform the process automatically and continuously by sequence control. Thereby, it becomes possible to continue the operation stably for a long time while alternately repeating the filtration and the washing process of the hollow fiber membrane. It is possible to change the number of repetitions of the filling process, the gas cleaning process, and the draining process. Although the cleaning effect is increased by increasing the number of repetitions, the recovery rate of the filtrate is decreased by increasing the number of repetitions, and therefore it is preferably in the range of 2 to 5 times. Moreover, after repeating a filtration process, a pressurization process, a gas washing process, and a drainage process more than a fixed number of times, a series of processes which repeat a water filling process, a gas washing process, and a drainage process twice or more can also be performed by sequence control. It is possible to change the number of repetitions of the filtration step, pressurization step, gas washing step, and drainage step. Although the cleaning effect is enhanced by reducing the number of repetitions, the recovery rate of the filtrate is reduced by reducing the number of repetitions, and therefore it is preferably within the range of 20 to 500 times. It is possible to change the number of repetitions of the water filling process, the gas washing process, and the drainage process. Increasing the number of repetitions increases the cleaning effect. However, increasing the number of repetitions decreases the filtrate recovery rate. It is preferably within the range of times to 30 times.

  The cleaning method of the hollow fiber membrane module of the present embodiment, in which the cleaning effect superior to the conventional cleaning method is expressed regardless of the material constituting the hollow fiber membrane and the shape of the module, is extremely wide use. It is possible to perform stable filtration continuously for a long period of time with a permeation flux higher than that of the prior art. For example, in the food industry field, sterilization / turbidity / iron removal / manganese removal of raw water, sterilization / fine particle removal / recovery of washing water, sterilization / fine particle removal of natural water, sterilization / purification of soy sauce, Sterilization and purification, vinegar sterilization and purification, mirin purification and seasoning sterilization and purification, product recovery from brewing and folding, sugar solution sterilization and fine particle removal and purification, honey purification, enzyme and protein Purification / concentration, purification of fermentation broth, recovery and purification of protein from cheese poye, production of high-protein milk by concentration of milk, recovery of protein from fishery processing wastewater, concentration of fish protein, recovery of meat protein from meat processing waste Separation of red blood cells from pig blood, concentration and purification of albumin and globulin in blood, recovery and purification of bioactive substances from soybean whey, protein recovery from soybean broth, removal of oily protein toxins and protein concentration, potato Starch industrial waste Recovery of useful proteins from, recovery and purification of the natural pigments can be used in applications such as the purification of fermentation liquid by the recovery of bacterial cells and metabolites. Also, in the medical field, pure water used as a stock solution, pretreatment of ultrapure water production equipment, pyrogen removal of backwash water, injection water production, dialysis water production, dialysate purification, vaccines / enzymes / viruses / nucleic acids / proteins It can be used for applications such as separation / concentration / purification of hormones, purification of hormones, production of artificial blood, concentration and purification of polysaccharides, sterilization of hospital hand washing water, and sterilization of surgical instrument washing water. In the electronics industry, reverse osmosis membrane pretreatment, ultrapure water final filter, ultrapure water use point filter, ultrapure water unit built-in filter, cleaning water particulate removal, polishing wastewater recovery, dicing wastewater It can be used for purposes such as recovery. Also, in the chemical industry, paint concentration / recovery, oil separation / recovery, emulsion separation / recovery, colloid separation / recovery, fine powder washing and purification, washing water particulate removal, plating solution purification, electrodialysis It can be used for purposes such as pre-processing. In the field of textile and dyeing processing, it can be used for applications such as closing PVA desizing drainage, recovery and reuse of textile processing oil, recovery of lanolin from hair washing wastewater, and recovery of sericin from silk processing wastewater. is there. In the steel and machining field, barrel polishing wastewater recovery, buffing wastewater recovery, rolling oil wastewater treatment, water-soluble cutting oil wastewater treatment, animal and vegetable oil processing wastewater treatment, degreasing wastewater, It can be used for applications such as recovery, removal of rinse water emulsion / rinse water recovery, and removal of inks from screen plate cleaning agents.

  Next, an example of the filtration device of the present embodiment will be described with reference to the drawings. FIG. 2 is a schematic configuration diagram of an example of a filtration apparatus using an external pressure type hollow fiber membrane module that can be used for performing the above-described cleaning method. In this filtration device, the inside of the hollow fiber membrane module 1 in which the hollow fiber membrane element 4 is housed is partitioned by the adhesive end 2 so that the upper part is the filtrate side A and the lower part is the stock solution side B. The filtrate side A is provided with a filtrate outlet 5 and a pressurized gas introduction port 6, and the stock solution side B is provided with a stock solution introduction port 7, a gas discharge port 8, a gas introduction port 9 and a stock solution drain port 10. ing. On the stock solution side B, the hollow fiber membrane element 4 is arranged, and on the lower side of the hollow fiber membrane element 4, the diffuser plate 3 is arranged. The stock solution introduced into the stock solution side B from the stock solution introduction port 7 passes through the hollow fiber membrane element 4 to become a filtrate, and the filtrate is led to the filtrate side A.

  Next, an example of the operation method of the present embodiment will be described with reference to FIGS. 3 and 4 by taking an external pressure total filtration method in the case of pressurizing with gas in the pressurizing step as an example. FIG. 4 shows the correlation between each process and the opening / closing of the operation valve in the basic operation method of the filtration device illustrated in FIG. Here, in FIG. 4, when the circle is attached, it means that the valve is open.

  The filtration device of the present embodiment includes a hollow fiber membrane module 1, a liquid feed pump 29 that supplies a stock solution to the hollow fiber membrane module 1, and an air compressor 30 as a pressurizing device for pressurizing the inside of the hollow fiber membrane module 1. And a control device 40. The control device 40 can perform drive control of the liquid feed pump 29 and the air compressor 30 and open / close control of each valve. The control device 40 performs control for sequentially executing each process by sequence control. Note that the control device 40 may be omitted, and manual switching of valves may be sequentially performed so that each process is sequentially performed.

  In the filtration device of this embodiment, from the state where all the valves are closed, the gas discharge port valve 24 and the stock solution introduction port valve 21 are opened, and the liquid feed pump 29 is operated (a water filling step). As a result, the stock solution is introduced into the stock solution side B of the filtration container 25 (stock solution side B of the hollow fiber membrane module 1). After the stock solution overflows from the gas outlet 8 (gas outlet valve 24), the filtrate outlet valve 23 is opened and the gas outlet valve 24 is closed to start filtration (filtration step). In the filtration step, the SS component adheres to the membrane surface of the hollow fiber membrane element 4 as the filtration time elapses, and the filtration capability is lowered.

  That is, after the liquid feed pump 29 is stopped, the stock solution inlet valve 21 and the filtrate outlet valve 23 opened in the filtration step are closed to stop the filtration, and then the stock solution discharge valve 27 and the addition port are operated while the air compressor 30 is operated. The pressurized gas inlet valve 22 is opened to introduce pressurized gas (pressurized fluid) from the pressurized gas inlet 6 to the filtrate side A of the filtration container 25 (filtrate side A of the hollow fiber membrane module 1). Do. At this time, the filtrate in the filtrate side A and the hollow fiber membrane is pushed out to the stock solution side B through the wall surface of the hollow fiber membrane, and is discharged to the outside from the stock solution drain port 10 (stock solution outlet valve 27).

  Subsequently, the gas discharge port valve 24 and the stock solution inlet valve 21 are opened to open the filtrate side pressure release valve 31 to lower the pressure on the filtrate side A and raise the liquid level on the stock solution side D which has been lowered by the pressurization process. . Further, the liquid feed pump 29 is operated to introduce the stock solution to the stock solution side B again (water filling step). After the stock solution overflows from the gas discharge port 8 (gas discharge port valve 24), the liquid feed pump 29 is stopped, the stock solution introduction port valve 21 is closed, and the water filling process is stopped.

  Further, a gas draining step is performed in which the gas inlet valve 28 is opened and a gas cleaning process (bubbling) is performed for a predetermined time, and after the gas inlet valve 28 is closed, the stock solution outlet valve 27 is opened to discharge the stock solution B on the stock solution side. Do.

  And again, the liquid feeding pump 29 is operated and the stock solution is again introduced into the stock solution side B (water filling step). After the stock solution overflows from the gas discharge port 8 (gas discharge port valve 24), the liquid feed pump 29 is stopped, the stock solution introduction port valve 21 is closed, and the water filling process is stopped. Thereby, the following filtration process can be performed.

  Here, residual SS components can be reduced by repeating the gas cleaning step, the discharge step, and the water filling step. On the other hand, after repeating a filtration process, a pressurization process, a water filling process, a gas washing process, a drainage process, and a water filling process for a certain number of times, the gas washing process, the drainage process, and the water filling process are repeated within a certain number of times. Part of the SS component adhering to the module can be discharged.

  In addition to the basic operation method described above, other steps such as a step of washing the hollow fiber membrane surface and the inside of the hollow fiber membrane module by repeating drain discharge and water filling, or a flushing washing step as necessary It is also possible to add.

  The water filling step after the pressurization step may be performed as necessary when the liquid level of the stock solution on the outer surface side of the hollow fiber membrane is lowered after the pressurization step. It is also possible to omit the process.

  The filtration device of this embodiment is combined with post-treatment devices according to applications such as ion exchange resins, ion exchange membranes, reverse osmosis membranes, activated carbon adsorption devices, activated sludge treatment devices, and further purification and purification of the filtrate. It is also possible. In addition, it is possible to reduce the amount of waste by treating the concentrated liquid or drain discharged from the filtration device of the present embodiment with a precipitation tank, a flocculant addition device, a coagulation device comprising a reaction layer, an incineration device, or the like. .

  Hereinafter, an example of the present invention will be described in more detail by way of examples. From the results of Examples and Comparative Examples below, it is apparent that long-term stable filtration is possible according to an example of the present invention.

<Example 1>
As a hollow fiber membrane module, a one-end free type hollow fiber membrane module having a membrane area of 28 m ^{2 made} of a hollow fiber membrane made of a polyvinylidene fluoride resin hydrophilized with polyvinyl alcohol and having an average pore diameter of 0.02 microns. used. Using a model water containing 160 mg / L of ferric hydroxide as an SS component as a stock solution, the hollow fiber membrane module was subjected to constant flow filtration under a flow rate of 3500 L / h by an external pressure total filtration method. By the sequence control, a washing process and a washing process for washing the hollow fiber membrane element were performed once every 10 minutes in the filtration process. That is, the membrane element regeneration step was performed between the filtration step and the filtration step. As shown in FIG. 5, in the washing process, a pressurizing process in which a pressurized operation is performed for 10 seconds by sending compressed air having a pressure of 0.2 MPa from the filtrate side of the hollow fiber membrane module to pressurize the inside of the hollow fiber membrane module, A filling step for filling the stock solution on the side, a gas washing step for injecting air from the lower part of the stock solution side of the hollow fiber membrane module at a flow rate of 1700 NL / h for 30 seconds, a draining step for discharging the drain on the stock solution side, and the stock solution side A water filling step to fill the stock solution was performed. After this cleaning process, a re-cleaning process was performed in which the gas cleaning process, the drainage process, and the water filling process were performed once more under the same conditions. During the filtration operation period, the amount of SS attached to the hollow fiber membrane element was measured periodically, and the operation was continued for 7 days. As a result, the amount of SS attached was 66 g in dry weight.

<Example 2>
In the washing of the hollow fiber membrane, the washing step was performed once every 10 minutes in the filtration step. In the washing step, the pressure is applied to the filtrate side of the hollow fiber membrane module with air at a pressure of 0.2 MPa for 10 seconds, the water filling step, air is supplied from the lower part of the hollow fiber membrane module on the raw solution side to 1700 NL. A gas washing step of jetting for 60 seconds at a flow rate of / h and a draining step of discharging the stock solution side drain were performed. When the filtration step and the washing step were repeated 120 times, a rewashing step was performed. In the re-cleaning step, the gas cleaning step, the drainage step and the water filling step were repeated 10 times under the same conditions as in the above-described cleaning step. The other conditions were the same as in Example 1, and the model water was filtered. When the operation was continued for 7 days, the SS adhesion amount was 58 g in dry weight.

<Comparative Example 1>
In the washing of the hollow fiber membrane, the washing step was performed once every 10 minutes in the filtration step. In the washing step, a pressurizing step of pressurizing for 10 seconds by pressurizing the filtrate side of the hollow fiber membrane module with air at a pressure of 0.2 MPa, a filling step for filling the stock solution on the stock solution side, a stock solution side of the hollow fiber membrane module Only a gas washing step of blowing air from the lower part of the substrate at a flow rate of 1700 NL / h for 60 seconds and a draining step of discharging the stock solution side drain were performed. No re-cleaning process was performed. The other conditions were the same as in Example 1, and the model water was filtered. When the operation was continued for 7 days, the SS adhesion amount was 397 g in dry weight.

  As shown in FIG. 8, in the comparative example 1, the SS adhesion amount gradually increased, whereas in the examples 1 and 2, the SS adhesion amount does not increase and is stable over a long period of time. Therefore, a continuous filtration operation can be performed stably for a long time.

A: Filtrate side B: Stock solution side 1: Filtration vessel 2: Adhesive end 3: Diffusing plate 4: Hollow fiber membrane element 5: Filtrate outlet 6: Pressurized gas inlet 7: Stock solution inlet 8: Gas outlet 9 : Gas inlet 10: Stock solution outlet 21: Stock solution introduction valve 22: Pressurized gas introduction valve 23: Filtrate outlet valve 24: Gas outlet valve 25: Filtration container 26: Hollow fiber membrane element 27: Stock solution outlet valve 28: Gas inlet valve 29: liquid feed pump 30: air compressor 31: pressure relief valve

Claims (5)

An operation method of a hollow fiber membrane module used in an external pressure filtration system in which a stock solution is supplied to the outer surface side of a hollow fiber membrane and a filtrate is taken out from the inner surface side of the hollow fiber membrane, And a pressurizing step of pressurizing with a gas or liquid from the filtrate side of the hollow fiber membrane, and a gas or liquid from the filtrate side of the hollow fiber membrane between the subsequent filtration steps. without repeating pressurizing pressurizing step, satisfy a gas cleaning process for cleaning the stock side of the hollow fiber membrane in a bubble, the drainage step of discharging the liquid in the module out of the system, the liquid concentrate side of the hollow fiber membranes The operation method of the hollow fiber membrane module which repeats a water filling process twice or more between a filtration process and the following filtration process.   After the filtration process, the pressurization process, the gas washing process, the drainage process, and the water filling process are repeated a certain number of times or more, the gas washing process, the drainage process, and the charging are performed between the filtration process and the subsequent filtration process. The operation method of the hollow fiber membrane module according to claim 1, wherein the water step is repeated twice or more.   The hollow fiber membrane module is a single-end free type hollow fiber membrane module in which the upper ends of the hollow fiber membrane bundles are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one. The operating method of the hollow fiber membrane module of 2. A hollow fiber membrane module having a hollow fiber membrane element;
A liquid feed pump for supplying a stock solution to the hollow fiber membrane module;
A pressurizing device for supplying a gas or liquid for pressurization to the hollow fiber membrane module;
A control device for controlling the operation of the liquid feeding pump and the pressurizing device;
The control device performs a filtration step of filtering the stock solution using a hollow fiber membrane, and a pressurization step of applying pressure with gas or liquid from the filtrate side of the hollow fiber membrane, and then between the subsequent filtration steps. Without repeating the pressurizing step of pressurizing with a gas or liquid from the filtrate side of the hollow fiber membrane , the gas washing step, the draining step, and the water filling step are performed between the filtration step and the subsequent filtration step. A filtration device configured to be repeated more than once.   As the hollow fiber membrane module, a single-end free type hollow fiber membrane module in which the upper ends of the hollow fiber membrane elements are fixed together and the lower ends are sealed in a state where the hollow fiber membranes are not fixed one by one is used. The filtration device according to claim 4.

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