JP2019195761A - Washing method of filtration module and filtration device - Google Patents

Abstract

To provide a washing method of a filtration module capable of sufficiently suppressing the reduction of filtration efficiency by enhancing the washing effect of a plurality of hollow fiber membranes caused by backwashing.SOLUTION: A washing method of a filtration module according to one aspect of the present invention is a washing method of an immersion type or external pressure type filtration module having a plurality of hollow fiber membranes aligned in one direction and includes a step of stopping the filtration of a liquid to be treated and a step of backwashing the plurality of hollow fiber membranes by backwashing water after the stopping step. In the backwashing step, the flow rate of the backwashing water supplied to the filtration module is controlled so as to keep the flow rate of the backwashing water constant.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for cleaning a filtration module and a filtration apparatus.

  2. Description of the Related Art As a solid-liquid separation processing apparatus in a manufacturing process such as sewage treatment or medicine, a filtration apparatus including a filtration module having a plurality of hollow fiber membranes aligned in one direction is used. The filtration device performs filtration by preventing permeation of impurities contained in the liquid to be treated by the surface of the hollow fiber membrane and allowing other impurities to permeate into the hollow fiber membrane.

  However, since this filtration device prevents the impurities contained in the liquid to be treated from being permeated by the surface of the hollow fiber membrane, impurities that have not been permeated to the inside adhere to the surface of the hollow fiber membrane. For this reason, in this filtration device, there is a risk that the filtration efficiency of the liquid to be originally filtered is reduced by the impurities attached to the surface of the hollow fiber membrane.

  Therefore, in this filtration apparatus, membrane fouling is prevented by performing filtration treatment operation intermittently and backwashing a plurality of hollow fiber membranes during the filtration treatment operation. However, in the above filtration device, even when back washing is performed between the filtration treatment operations, residual impurities accumulate on the surfaces of the plurality of hollow fiber membranes as the filtration treatment operation is performed, and the filtration efficiency is likely to decrease.

  Therefore, today, in order to suppress the accumulation of residual impurities on the surface of a plurality of hollow fiber membranes, an inverter is connected to the backwash pump, and the backwash pump is subjected to PID control (Proportional-Integral-Differential Control). A method of controlling the flow rate of backwash water supplied to the water is employed (see JP 2013-212497 A).

JP 2013-212497 A

  However, according to feedback control using an inverter or the like as described in the above publication, it is necessary to adjust the output (frequency) of the motor a plurality of times. The hollow fiber membrane of the book cannot be back cleaned. Therefore, according to this cleaning method, it takes time to adjust the flow rate of the backwash water, so that the backwash time becomes longer and the filtration time becomes relatively shorter, so that it is difficult to sufficiently increase the filtration efficiency. Furthermore, the backwash water may use filtered water that has passed through the filtration module. However, if the backwash time is increased, the consumption of filtered water increases, leading to a reduction in the final water treatment amount.

  In addition, it is conceivable that the output of the motor is controlled to be constant by an inverter. In this case, the flow rate of the backwash water supplied to the filtration module due to accumulation of residual impurities on the surface of the plurality of hollow fiber membranes is considered. Decreases over time.

  The present invention has been made on the basis of such circumstances, and it is possible to clean a filtration module that can sufficiently suppress a decrease in filtration processing efficiency by enhancing the cleaning effect of a plurality of hollow fiber membranes by reverse cleaning. It is an object to provide a method and a filtration device.

  The method for cleaning a filtration module according to one aspect of the present invention made to solve the above problem is a method for cleaning an immersion type or external pressure type filtration module having a plurality of hollow fiber membranes aligned in one direction. A backwashing step of stopping filtration of the liquid to be treated and a step of backwashing the plurality of hollow fiber membranes with backwashing water after the stopping step, and supplying the filtration module in the backwashing step. Control to keep the water flow constant.

  Further, a filtration device according to one aspect of the present invention made to solve the above problems is a filtration device including an immersion type or external pressure type filtration module having a plurality of hollow fiber membranes aligned in one direction. A filtration stopping mechanism for stopping the filtration of the liquid to be treated; and a back washing mechanism for back washing the plurality of hollow fiber membranes with back washing water after the filtration is stopped by the filtration stopping mechanism. A constant flow valve for maintaining a constant flow of backwash water supplied to the filtration module;

  The filtration method and filtration device for a filtration module according to an embodiment of the present invention can sufficiently suppress a reduction in filtration treatment efficiency by enhancing the washing effect of a plurality of hollow fiber membranes by back washing.

It is a flowchart which shows the washing | cleaning method of the filtration module which concerns on one Embodiment of this invention. It is a schematic diagram which shows the filtration apparatus which can implement the washing | cleaning method of the filtration module of FIG. It is a flowchart which shows the washing | cleaning method of the filtration module which concerns on embodiment different from the washing | cleaning method of the filtration module of FIG. It is a schematic diagram which shows the filtration apparatus which can implement the washing | cleaning method of the filtration module of FIG.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  A cleaning method for a filtration module according to an aspect of the present invention is a method for cleaning an immersion type or external pressure type filtration module having a plurality of hollow fiber membranes aligned in one direction, and stops filtration of a liquid to be treated. And a step of backwashing the plurality of hollow fiber membranes with backwashing water after the stopping step, and controlling the flow of backwashing water supplied to the filtration module to be constant in the backwashing step. To do.

  Since the filtration method of the filtration module is controlled so as to keep the flow rate of the backwash water supplied to the filtration module constant in the backwash process, the backwash water caused by impurities adhering to the surfaces of the plurality of hollow fiber membranes is controlled. A decrease in the flow rate can be easily and reliably prevented. Therefore, the cleaning method of the filtration module can enhance the cleaning effect of the plurality of hollow fiber membranes by back cleaning, and can sufficiently suppress the decrease in filtration processing efficiency.

  In the back washing step, it is preferable to supply bubbles to the outside of the plurality of hollow fiber membranes. Since the filtration method of the filtration module is controlled to keep the flow rate of the backwash water supplied to the filtration module in the backwashing step as described above, the outside of the plurality of hollow fiber membranes in the backwashing step is controlled. Even when air bubbles are supplied to the water, the flow rate of backwash water does not decrease due to the supply pressure of the air bubbles. Therefore, the plurality of hollow fiber membranes can be effectively washed in a short time by backwashing water and bubbles.

  The cleaning time in the reverse cleaning step is preferably 15 seconds or more and 80 seconds or less. In feedback control using a conventional inverter, it takes time to adjust the flow rate of the backwash water, and thus it is difficult to obtain a desired flow rate within the time range described above. On the other hand, since the cleaning method of the filtration module controls the flow rate of the backwash water supplied to the filtration module in the backwashing process to be constant, the washing time in the backwashing process is within the above range. However, the cleaning effect of the plurality of hollow fiber membranes can be sufficiently enhanced.

  The backwash water may contain a drug. Thus, when the backwash water contains a chemical, impurities attached to the surfaces of the plurality of hollow fiber membranes can be more reliably removed.

  Further, a filtration device according to another aspect of the present invention is a filtration device including an immersion type or external pressure type filtration module having a plurality of hollow fiber membranes aligned in one direction, and filters the liquid to be treated. A filtration stopping mechanism for stopping, and a back washing mechanism for back washing the plurality of hollow fiber membranes with back washing water after the filtration is stopped by the filtration stopping mechanism. It has a constant flow valve that keeps the flow rate of washing water constant.

  Since the filtration device has a constant flow valve that keeps the flow rate of the backwash water supplied to the filtration module by the backwashing mechanism constant, the flow rate of the backwash water caused by impurities adhering to the surface of the plurality of hollow fiber membranes Can be easily and reliably prevented. Therefore, the said filtration apparatus can improve the washing | cleaning effect of the multiple hollow fiber membrane by back washing | cleaning, and can fully suppress the fall of filtration process efficiency.

  In the present invention, the “immersion type” refers to a method in which the inner peripheral surface side of the hollow fiber membrane is set to a negative pressure and the liquid to be treated is transmitted to the inner peripheral surface side, and is also referred to as “suction type”. The “external pressure type” refers to a method in which the liquid to be treated is permeated to the inner peripheral surface side of the hollow fiber membrane by setting the outer peripheral surface side of the hollow fiber membrane to a high pressure.

[Details of the embodiment of the present invention]
Hereinafter, a cleaning method and a filtration device for a filtration module according to each embodiment of the present invention will be described in detail with reference to the drawings.

[First embodiment]
<Cleaning method for filtration module>
The method for cleaning the filtration module in FIG. 1 is a method for cleaning an external pressure filtration module having a plurality of hollow fiber membranes aligned in one direction. The method for washing the filtration module includes a step of stopping filtration of the liquid to be treated (stopping step), and a step of backwashing the plurality of hollow fiber membranes with backwashing water after the stopping step (backwashing step). Prepare. The filtration method for the filtration module is controlled so that the flow rate of the backwash water supplied to the filtration module is kept constant in the backwashing step.

  Since the filtration method of the filtration module is controlled so as to keep the flow rate of the backwash water supplied to the filtration module in the backwashing step constant, the backwash caused by impurities adhering to the surfaces of the plurality of hollow fiber membranes is controlled. It is possible to easily and reliably prevent a decrease in the flow rate of the washing water. Therefore, the cleaning method of the filtration module can enhance the cleaning effect of the plurality of hollow fiber membranes by back cleaning, and can sufficiently suppress the decrease in filtration processing efficiency. Further, since the filtration method of the filtration module is controlled so as to keep the flow rate of the backwash water supplied to the filtration module in the backwashing step constant, it does not take time to adjust the flow rate of the backwash water. Therefore, the filtration method of the said filtration module can suppress the usage-amount of filtered water at the time of using filtered water as backwash water, and can suppress the fall of the final water treatment amount.

<Filtration device>
First, with reference to FIG. 2, an example of the filtration apparatus which can implement the washing | cleaning method of the said filtration module is demonstrated. The filtration device includes an external pressure filtration module 1 having a plurality of hollow fiber membranes 11 aligned in one direction. The filtration device may include only one filtration module 1 or may include a plurality of filtration modules 1. The filtration device includes a filtration stop mechanism 2 that stops filtration of the liquid X to be treated, and a backwashing mechanism 3 that backwashes the plurality of hollow fiber membranes 11 with backwash water P after the filtration by the filtration stop mechanism 2 is stopped. Prepare. In addition, the filtration device includes a treatment liquid supply mechanism 4 that supplies the treatment liquid X to the filtration module 1, a treatment liquid storage tank 5 that stores the treatment liquid X supplied to the filtration module 1, and backwash water. And a backwash water storage tank 6 for storing P. The backwash water storage tank 6 and the filtration module 1 are connected by a filtered water discharge pipe 7. The back washing mechanism 3 has a constant flow valve 3 a that keeps the flow rate of the back washing water P supplied to the filtration module 1 constant. In the present embodiment, as the backwash water P, filtered water that has passed through a plurality of hollow fiber membranes 11 is used. However, as the backwash water P, permeated water that has permeated through a plurality of hollow fiber membranes 11 and then permeated through another filtration membrane such as a reverse osmosis membrane may be used. Moreover, as this backwash water P, it is also possible to use water prepared separately from the filtered water which permeate | transmitted the several hollow fiber membrane 11, such as tap water.

  Since the filtration device includes the constant flow valve 3a that keeps the flow rate of the backwash water P supplied to the filtration module 1 by the backwashing mechanism 3, the filtration device is caused by impurities attached to the surface of the plurality of hollow fiber membranes 11. A decrease in the flow rate of the backwash water P can be easily and reliably prevented. Therefore, the said filtration apparatus can improve the washing | cleaning effect of the several hollow fiber membrane 11 by back washing | cleaning, and can fully suppress the fall of filtration process efficiency. Moreover, since the said filtration apparatus keeps the flow volume of the backwash water P supplied to the filtration module 1 with the constant flow valve 3a, it does not require time for adjustment of the flow volume of the backwash water P. FIG. Therefore, the said filtration apparatus can suppress the liquid quantity of the filtrate water used as the backwash water P, and can suppress the fall of the final water treatment amount. Furthermore, since the said filtration apparatus does not require the feedback control mechanism like the conventional filtration apparatus, the installation cost required for the back washing | cleaning mechanism 3 can be held down.

(Filtration module)
The filtration module 1 includes a plurality of hollow fiber membranes 11 aligned in the vertical direction, an upper holding member 12 that holds the upper ends of the plurality of hollow fiber membranes 11, and a lower end portion of the plurality of hollow fiber membranes 11. It has a lower holding member 13 for holding, and a casing 14 for storing a plurality of hollow fiber membranes 11, an upper holding member 12 and a lower holding member 13.

<Hollow fiber membrane>
The hollow fiber membrane 11 is preferably composed mainly of a thermoplastic resin. Examples of the main component of the hollow fiber membrane 11 include polyethylene, polypropylene, polyvinylidene fluoride, ethylene-vinyl alcohol copolymer, polyamide, polyimide, polyetherimide, polystyrene, polysulfone, polyvinyl alcohol, polyphenylene ether, polyphenylene sulfide, and cellulose acetate. , Polyacrylonitrile, polytetrafluoroethylene (PTFE) and the like. Among these, PTFE which is excellent in mechanical strength, chemical resistance, heat resistance, weather resistance, nonflammability and the like and is porous is preferable, and uniaxially or biaxially stretched PTFE is more preferable. The “main component” means a component having the largest content in terms of mass, for example, a component having a content of 50% by mass or more.

<casing>
The casing 14 has, for example, a cylindrical shape whose axis is parallel to the vertical direction. The upper opening 14 a of the casing 14 is connected to the filtered water discharge pipe 7. A lower opening 14 b of the casing 14 is connected to a liquid supply pipe 4 a to be processed, which will be described later, constituting the liquid supply mechanism 4 to be processed. The casing 14 has a discharge port 14c through which the liquid X to be processed that has not permeated the plurality of hollow fiber membranes 11, the backwash water P after backwashing, and the like can be discharged.

<Holding member>
The upper holding member 12 is disposed between the upper opening 14a and the discharge port 14c of the casing 14, and divides the internal space of the casing 14 in the vertical direction. The upper holding member 12 holds the plurality of hollow fiber membranes 11 with the upper openings of these hollow fiber membranes 11 protruding upward. Thereby, the filtrate water permeate | transmitted inside the multiple hollow fiber membrane 11 is stored in the backwash water storage tank 6 through the filtrate discharge pipe | tube 7 from the upper opening 14a of the casing 14. FIG. The lower holding member 13 has a plurality of fixing portions 13 a that are provided at intervals and fix the lower ends of the plurality of hollow fiber membranes 11. By fixing the lower end portions of the plurality of hollow fiber membranes 11 with the plurality of fixing portions 13a, the liquid X to be treated supplied into the casing 14 from the lower opening 14b becomes a plurality of hollow portions between the plurality of fixing portions 13a. It is introduced on the surface (outer peripheral surface) side of the thread film 11.

(Processed liquid supply mechanism)
The liquid supply mechanism 4 supplies the liquid X to the filtration module 1 when the liquid X is filtered. The processing liquid supply mechanism 4 includes a processing liquid supply pipe 4a connected to the processing liquid storage tank 5, and a processing liquid supply pump 4b and a valve 4c disposed in the processing liquid supply pipe 4a. The to-be-processed liquid supply pump 4b is configured so that the to-be-processed liquid X stored in the to-be-processed liquid storage tank 5 can be pumped to the filtration module 1 side. Further, the valve 4c is configured to be able to adjust the flow rate of the liquid X to be processed. The to-be-processed liquid supply mechanism 4 supplies the to-be-processed liquid X stored in the to-be-processed liquid storage tank 5 to the filtration module 1 by driving the to-be-processed liquid supply pump 4b with the valve 4c opened.

(Filtration stop mechanism)
The filtration stop mechanism 2 includes a suction pump 2a and a valve 2b disposed in the filtered water discharge pipe 7, and a filtration operation control unit 2c that drives and controls the suction pump 2a and the valve 2b. The filtration stop mechanism 2 stops driving the suction pump 2a under the control of the filtration operation control unit 2c, and stops the filtration of the liquid X to be processed by closing the valve 2b.

  The filtration operation control unit 2c includes a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and other memories. The filtration operation control unit 2c constitutes a single control unit 8 together with a backwash control unit 3e described later.

  In addition, the said filtration apparatus is provided with the filtration process mechanism which filters the to-be-processed liquid X by the filtration module 1. FIG. The filtration processing mechanism has the same configuration as the filtration stop mechanism 2. In other words, in the filtration device, the filtration stop mechanism 2 also serves as the filtration processing mechanism. In the state where the liquid X to be processed is supplied to the filtration module 1 by the liquid supply mechanism 4 to be processed, the filtration mechanism opens the valve 2b under the control of the filtration operation control unit 2c and drives the suction pump 2a. The filtration process by the filtration module 1 is performed. The filtered water treated by the filtration mechanism is stored in the backwash water storage tank 6 through the filtered water discharge pipe 7.

(Reverse cleaning mechanism)
The backwashing mechanism 3 includes a filtered water circulation pipe 3b connecting the backwash water storage tank 6 and the filtered water discharge pipe 7, the above-described constant flow valve 3a disposed in the filtered water circulation pipe 3b, and the filtered water circulation pipe 3b. A filtered water supply pump 3c and a drug supply pipe 3d are provided, and a backwash control unit 3e that performs drive control of the filtered water supply pump 3c and charge control of the drug Y through the drug supply pipe 3d. The constant flow valve 3a is disposed in the filtrate discharge pipe 7 on the downstream side of the filtrate supply pump 3c. The filtered water circulation pipe 3b is connected to the filtered water discharge pipe 7 on the filtration module 1 side from the positions where the suction pump 2a and the valve 2b are disposed. The backwashing mechanism 3 drives the filtered water supply pump 3c under the control of the backwashing control unit 3e while the valve 2b is closed, and the backwashing water P stored in the backwash water storage tank 6 is supplied at a constant flow rate. Supply to the filtration module 1. Moreover, the backwashing mechanism 3 throws the chemical | medical agent Y into the backwashing water P pumped by the filtration module 1 side from the chemical | medical agent supply pipe | tube 3d. Thereby, the filtration module 1 can be backwashed with the backwashing water P containing the chemical | medical agent Y. FIG. It is preferable that the chemical supply pipe 3d is disposed in the filtered water circulation pipe 3b on the upstream side (backwash water storage tank 6 side) with respect to the constant flow valve 3a. In the filtration device, the drug supply pipe 3d is arranged in the filtrate water circulation pipe 3b on the upstream side of the constant flow valve 3a, so that it is fixed by the backwash water P containing the medicine Y when the filtration module 1 is backwashed. The flow valve 3a can be cleaned simultaneously.

  Examples of the drug Y introduced from the drug supply pipe 3d include sodium hypochlorite, inorganic acid, organic acid, sodium hydroxide, and surfactant. Examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, sodium hydrogen sulfite and the like. Examples of the organic acid include citric acid and oxalic acid.

  Subsequently, each step of the method for cleaning the filtration module will be described in detail. In addition, the washing | cleaning method of the said filtration module is performed alternately with normal filtration process driving | operation. Therefore, the valve 2b is opened and the suction pump 2a is driven before the filtration module cleaning method is performed. As one operation time of the said filtration process operation, it can be 10 minutes or more and 60 minutes or less, for example.

(Stop process)
In the stop step (S01), the filtration of the liquid X to be processed is stopped. S01 is performed by the filtration stopping mechanism 2. In S01, the suction pump 2a is stopped by the control of the filtration operation control unit 2c, and the filtration of the liquid X to be processed is stopped by closing the valve 2b.

(Back washing process)
In the backwashing step (S02), the backwashing water P stored in the backwashing water storage tank 6 is supplied into the filtration module 1 from the upper opening side 14a. Back wash. S02 is performed by the reverse cleaning mechanism 3. In S02, the backwash water P in the backwash water storage tank 6 is pumped to the filtration module 1 side by driving the filtered water supply pump 3c under the control of the backwash control unit 3e with the valve 2b closed. . Since the back washing mechanism 3 has the constant flow valve 3a on the downstream side of the filtrate water supply pump 3c, the filtration module is washed by a constant flow rate in the filtration module 1 immediately after the start of S02. P can be supplied.

  In S02, the drug Y is introduced from the drug supply pipe 3d into the backwash water P that is pumped to the filtration module 1 side. Thereby, the backwash water P contains the medicine Y. The filtration method for the filtration module can more reliably remove impurities adhering to the surface of the plurality of hollow fiber membranes 11 by supplying the backwash water P containing the drug Y to the filtration module 1. .

  In addition, the washing | cleaning method of the said filtration module is the process (discharge process) which discharges the backwash water P which permeate | transmitted the outer side of the several hollow fiber membrane 11 after completion | finish of S02 or in parallel with S02. You may have.

  The upper limit of the cleaning time by S02 is preferably 80 seconds, and more preferably 60 seconds. In feedback control using a conventional inverter, since it takes time to adjust the flow rate of backwash water, it is difficult to obtain a desired flow rate within a time equal to or less than the upper limit. On the other hand, since the washing | cleaning method of the said filtration module can maintain the flow volume of the backwash water P immediately after the start of S02, even when the washing time by S02 is made into the said upper limit or less, several hollow fiber The cleaning effect of the film 11 can be sufficiently enhanced. On the other hand, the lower limit of the cleaning time by S02 is preferably 15 seconds and more preferably 30 seconds from the viewpoint of sufficiently removing impurities adhering to the surface of the plurality of hollow fiber membranes 11.

  In S02, the flow rate of the backwash water P is constant from immediately after the start of backwashing to the end of backwashing. The lower limit of the flow rate of the backwash water P supplied to the filtration module 1 by S02 (that is, the flow rate after the control by the constant flow valve 3a) is preferably 30 LMH, more preferably 40 LMH. On the other hand, the upper limit of the flow rate is preferably 80 LMH, and more preferably 60 LMH. If the flow rate is less than the lower limit, impurities attached to the surface of the plurality of hollow fiber membranes 11 may not be sufficiently removed. Conversely, if the flow rate exceeds the upper limit, the amount of backwash water P used may be unnecessarily increased.

  The lower limit of the supply pressure of the backwash water P to the filtration module 1 in S02 (that is, the supply pressure after the flow control by the constant flow valve 3a) is preferably 80 kPa, and more preferably 100 kPa. On the other hand, the upper limit of the supply pressure is preferably 250 kPa, and more preferably 200 kPa. If the supply pressure is less than the lower limit, impurities attached to the surfaces of the plurality of hollow fiber membranes 11 may not be sufficiently removed. On the contrary, when the supply pressure exceeds the upper limit, the cleaning effect of the plurality of hollow fiber membranes 11 is not improved so much, while the output of the filtrate water supply pump 3c becomes unnecessarily large, and the cost required for reverse cleaning is high. There is a risk.

[Second Embodiment]
<Cleaning method for filtration module>
The method for cleaning the filtration module in FIG. 3 is a method for cleaning an external pressure filtration module having a plurality of hollow fiber membranes aligned in one direction. The method for washing the filtration module includes a step of stopping filtration of the liquid to be treated (stopping step), and a step of backwashing the plurality of hollow fiber membranes with backwashing water after the stopping step (backwashing step). Prepare. The filtration method for the filtration module is controlled so that the flow rate of the backwash water supplied to the filtration module is kept constant in the backwashing step. Moreover, the washing | cleaning method of the said filtration module supplies a bubble to the outer side of the said several hollow fiber membrane at the said back washing | cleaning process.

  Since the filtration method of the filtration module is controlled so as to keep the flow rate of the backwash water supplied to the filtration module constant in the backwashing step, bubbles are formed outside the plurality of hollow fiber membranes in the backwashing step. Even when supplied, the flow rate of backwash water does not decrease due to the supply pressure of bubbles. Therefore, the plurality of hollow fiber membranes can be effectively washed in a short time by backwashing water and bubbles. Moreover, since the flow rate of the backwash water does not decrease due to the supply pressure of the bubbles, the filtration method for the filtration module can easily increase the supply pressure of the backwash water and the supply pressure of the bubbles at the same time. It is easy to improve the cleaning effect of the backwash water and bubbles.

<Filtration device>
With reference to FIG. 4, an example of the filtration apparatus which can implement the washing | cleaning method of the said filtration module is demonstrated. The filtration device includes an external pressure filtration module 1 having a plurality of hollow fiber membranes 11 aligned in one direction. The filtration device may include only one filtration module 1 or may include a plurality of filtration modules 1. The filtration device includes a filtration stopping mechanism 2 that stops filtration of the liquid X to be treated, and a back washing mechanism 23 that back-washes the plurality of hollow fiber membranes 11 with the back washing water P after the filtration is stopped by the filtration stopping mechanism 2. Prepare. In addition, the filtration device includes a treatment liquid supply mechanism 4 that supplies the treatment liquid X to the filtration module 1, a treatment liquid storage tank 5 that stores the treatment liquid X supplied to the filtration module 1, and backwash water. And a backwash water storage tank 6 for storing P. The backwash water storage tank 6 and the filtration module 1 are connected by a filtered water discharge pipe 7. The back washing mechanism 23 has a constant flow valve 3 a that keeps the flow rate of the back washing water P supplied to the filtration module 1 constant. In addition, about the structure except the back washing | cleaning mechanism 23, the said filtration apparatus can be made the same as that of the filtration apparatus of FIG. Therefore, only the reverse cleaning mechanism 23 will be described below. In the present embodiment, filtered water that has permeated through a plurality of hollow fiber membranes 11 is used as the backwash water P. However, as the backwash water P, permeated water that has permeated through a plurality of hollow fiber membranes 11 and then permeated through another filtration membrane such as a reverse osmosis membrane may be used. Moreover, as this backwash water P, it is also possible to use water prepared separately from the filtered water which permeate | transmitted the several hollow fiber membrane 11, such as tap water.

(Reverse cleaning mechanism)
The reverse cleaning mechanism 23 includes a filtered water circulation pipe 3b that connects the backwash water storage tank 6 and the filtered water discharge pipe 7, a constant flow valve 3a that is disposed in the filtered water circulation pipe 3b, a filtered water supply pump 3c, and a chemical supply. It has a tube 3d, and a reverse cleaning control unit 3e that performs drive control of the filtered water supply pump 3c and injection control of the drug Y through the drug supply pipe 3d. The reverse cleaning mechanism 23 includes a bubble supply pipe 23a that communicates with the lower opening 14b of the casing 14, and a bubble supply device 23b that is connected to the end opposite to the communication side of the lower opening 14b of the bubble supply pipe 23a. And a bubble supply controller 23c for driving and controlling the bubble supplier 23b. The end of the bubble supply pipe 23a on the side communicating with the lower opening 14b is connected to the liquid supply pipe 4a to be processed on the downstream side of the valve 4c. The reverse cleaning mechanism 23 can have the same configuration as the reverse cleaning mechanism 3 of FIG. 2 except that it includes a bubble supply pipe 23a, a bubble supply unit 23b, and a bubble supply control unit 23c.

  The type of the bubble supplier 23b is not particularly limited as long as it can supply bubbles. As the bubble supplier 23b, for example, a blower, a compressor, or the like can be used. The bubble supply control unit 23c is composed of a computer including a CPU and a memory such as a ROM and a RAM. The bubble supply control unit 23c constitutes a single control unit 28 together with the filtration operation control unit 2c and the backwash control unit 3e.

  Subsequently, each step of the method for cleaning the filtration module will be described in detail. The cleaning method for the filtration module is performed alternately with the normal filtration treatment operation. Therefore, the valve 2b is opened and the suction pump 2a is driven before the filtration module cleaning method is performed. One operation time of the filtration treatment operation can be the same as the filtration method of the filtration module in FIG. In addition, the stop process (S11) in the washing | cleaning method of the said filtration module can be performed in the procedure similar to the stop process (S01) of the washing | cleaning method of the filtration module of FIG. Therefore, only the back cleaning process (S12) will be described below.

(Back washing process)
In S12, the backwash water P stored in the backwash water storage tank 6 is supplied into the filtration module 1 from the upper opening side 14a, whereby the plurality of hollow fiber membranes 11 are backwashed with the backwash water P. In S12, simultaneously with the reverse cleaning, the bubble supply device 23b is driven to supply bubbles from the lower opening 14b into the filtration module 1, and the surface of the plurality of hollow fiber membranes 11 is rubbed by these bubbles. As a result, the plurality of hollow fiber membranes 11 are swung to remove impurities attached to the surface of the plurality of hollow fiber membranes 11.

  S <b> 12 is performed by the reverse cleaning mechanism 23. In S12, with the valve 2b closed, the backwash water supply pump 3c is driven under the control of the backwash control unit 3e to pump the backwash water P in the backwash water storage tank 6 to the filtration module 1 side. . In S12, the medicine Y is supplied from the medicine supply pipe 3d to the backwash water P fed to the filtration module 1 side, and the backwash water P mixed with the medicine Y is supplied to the filtration module 1.

  At the same time, in S12, with the valve 4c closed, the bubble supply device 23b is driven under the control of the bubble supply control unit 23c to supply bubbles into the filtration module 1 from the lower opening 14b side. Since the back washing mechanism 23 has the constant flow valve 3a on the downstream side of the filtrate water supply pump 3c, the filtration module is washed immediately after the start of S12 even when bubbles are supplied by the bubble supplier 23b. The backwash water P can be supplied to the filtration module 1 at a constant flow rate.

  In addition, the washing | cleaning method of the said filtration module is the process (discharge process) which discharges the backwash water P which permeate | transmitted the outer side of the several hollow fiber membrane 11 after completion | finish of S12 or in parallel with S12. You may have.

  As a minimum of the supply pressure of the bubble by bubble supply device 23b, 150 kPa is preferred and 200 kPa is more preferred. The method for cleaning the filtration module keeps the flow rate of the backwash water P supplied to the filtration module 1 constant, so even if the supply pressure of the bubbles by the bubble supply device 23b is equal to or higher than the lower limit, it is caused by the rising pressure of the bubbles. Thus, the backwashing effect by the backwashing water P is unlikely to decrease. Therefore, the washing | cleaning method of the said filtration module can heighten the washing | cleaning effect by backwashing water P and a bubble simultaneously by making the said supply pressure more than the said minimum. On the other hand, the upper limit of the supply pressure of the bubbles is preferably 300 kPa, and more preferably 250 kPa. When the supply pressure of the bubbles exceeds the upper limit, the cleaning effect of the plurality of hollow fiber membranes 11 is not improved so much, and the cost required for back cleaning may increase.

  As a minimum of the flow volume of the bubble supplied in filtration module 1, 150 L / min is preferred and 200 L / min is more preferred. Since the flow rate of the backwashing water P supplied to the filtration module 1 is kept constant in the washing method of the filtration module, even if the flow rate of the bubbles supplied into the filtration module 1 is set to the above lower limit or more, the backwashing water P is reversed. The cleaning effect is difficult to decrease. Therefore, the washing | cleaning method of the said filtration module can heighten the washing | cleaning effect by backwashing water P and a bubble simultaneously by making the said flow volume into the said minimum or more. On the other hand, the upper limit of the flow rate is preferably 300 L / min, and more preferably 250 L / min. When the flow rate exceeds the upper limit, the cleaning effect of the plurality of hollow fiber membranes 11 is not improved so much, and the cost required for back cleaning may increase.

  As a minimum of supply pressure of backwash water P to filtration module 1 by S12, 120 kPa is preferred and 150 kPa is more preferred. The filtration method of the filtration module is that the supply pressure of the backwash water P is set to the above lower limit or more even when bubbles are supplied into the filtration module 1 from the lower opening 14b side in parallel with the supply of the backwash water P. The flow rate of the backwash water P can be increased sufficiently, and as a result, the cleaning effect of the backwash water P and bubbles can be enhanced at the same time. On the other hand, the upper limit of the supply pressure is preferably 250 kPa, and more preferably 220 kPa. When the supply pressure exceeds the upper limit, the cleaning effect of the plurality of hollow fiber membranes 11 is not improved so much, and the cost required for back cleaning may increase.

  In addition, about the washing | cleaning period by S12, and the flow volume of the backwash water P, it can be the same as that of the washing | cleaning method of the filtration module of FIG.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  For example, in the above-described embodiment, the configuration using the external pressure filtration module has been described, but the filtration method for the filtration module can also be used for washing the immersion filtration module. Moreover, the said filtration apparatus can also be comprised as a filtration apparatus provided with an immersion type filtration module.

  In the method for cleaning the filtration module, the plurality of hollow fiber membranes do not necessarily have to be back-washed with the backwash water mixed with the drug. Moreover, even if the washing | cleaning method of the said filtration module uses the backwashing water with which the chemical | medical agent was mixed, you may use the chemical | medical solution prepared separately from filtered water as backwashing water.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[Example]
[No. 1]
The backwashing process was performed alternately with the filtration treatment operation for 25 minutes using the filtration apparatus of FIG. The permeation flux of the liquid to be treated during the filtration treatment operation was 40 LMH. In the backwashing step, after the filtration treatment operation is stopped (that is, after the above-mentioned stopping step), the backwashing water is obtained by mixing the drug (sodium hypochlorite solution) with filtered water at a concentration of 5 mg / L for 60 seconds. Backwashing and supply of bubbles into the filtration module by the bubble supplier were performed simultaneously. The flow rate of backwash water supplied to the filtration module in the backwashing process was constant at 48 LMH. Moreover, after this back washing | cleaning process, the liquid in a casing was discharged | emitted in 30 second, and the filtration process driving | operation was restarted after 30 seconds of filtration preparations. In addition, as a filtration module, the pore membrane (Sumitomo Electric Industries Ltd.) pressurization type membrane module "OPMW-12B100" by Sumitomo Electric Industries, Ltd. whose total membrane area of a plurality of hollow fiber membranes is 100 m ² is used as a constant flow valve. “Asahi Organic Materials constant flow valve C type” (nominal diameter 25 mm, differential pressure 30 to 200 kPa) manufactured by Asahi Organic Materials Co., Ltd. was used, and a filtered water circulation pipe having a piping size of 50 A was used. No. Table 1 shows the cleaning conditions in the first reverse cleaning step.

[No. 2]
No. Using the same filtration apparatus as in No. 1, a back washing process was performed alternately with the filtration treatment operation for 25 minutes. The permeation flux of the liquid to be treated during the filtration treatment operation was 40 LMH. No. In No. 2, after the filtration treatment operation was stopped, bubbles were supplied for 60 seconds using a bubble supplier, and then No. 2 was used as the backwashing process. The backwashing with the backwashing water similar to 1 was performed for 60 seconds (that is, in No. 2, bubbles are supplied in a process separate from the backwashing process, and no bubbles are supplied in the backwashing process) . The flow rate of backwash water supplied to the filtration module in the backwashing process was constant at 48 LMH. After the back washing step, the filtration operation was resumed after 30 seconds of filtration preparation. No. Table 1 shows the washing conditions of 2.

[Comparative example]
[No. 3]
4 except that the inverter was connected to the filtrate supply pump instead of the constant flow valve of the filtration device of FIG. A plurality of hollow fiber membranes were washed in the same manner as in 1.

[No. 4]
No. No. 3 except that the flow rate of backwash water was controlled to 48 LMH by an inverter using the same filtration device as in No. 3. A plurality of hollow fiber membranes were washed in the same manner as in 2.

<Permeation flux>
No. 1-No. For each of No. 4, the filtration treatment operation and the back washing step are alternately performed, immediately after the start of the filtration treatment operation (immediately after the start of the first filtration treatment operation), 200 hours, 500 hours, 1000 hours and 1800 from the first filtration treatment operation. The permeation flux [LMH] of the backwash water in the backwash process after the lapse of time was measured. The measurement results are shown in Table 2. The permeation flux is a value immediately before the end of the corresponding back washing process (60 seconds after the start).

<Membrane differential pressure>
No. 1-No. For each of 4, the membrane differential pressure [kPa] of the hollow fiber membrane at 25 ° C. at the time of resumption of the filtration treatment operation following the back washing step after 200 hours, 500 hours, 1000 hours and 1800 hours from the first filtration treatment operation. It was measured. The measurement results are shown in Table 3.

<Evaluation results>
As shown in Tables 2 and 3, No. 1 maintained the flow rate of backwash water supplied to the filtration module constant. 1 and no. No. 2 shows that the membrane differential pressure of the hollow fiber membrane is kept low even after 1800 hours have elapsed from the start of the filtration treatment, and the washing effect by back washing is sufficiently obtained. Among them, No. 1 in which bubbles were supplied into the filtration module at the same time as the backwashing with backwashing water. As shown in Table 1, the effect of the back washing process is further enhanced by increasing both the backwash water supply pressure to the filtration module and the bubble supply pressure by the bubble feeder as shown in Table 1. On the other hand, an inverter was connected to the filtered water supply pump, and the motor output was controlled to be constant by the inverter in the reverse cleaning process. 3 and No. 3 controlled by the inverter so that the flow rate of the backwash water becomes 48 LMH. No. 4 shows that the permeation flux of the backwash water becomes smaller with time. When 200 hours or more have elapsed from the start of the filtration treatment, the permeation flux of the backwash water cannot be sufficiently adjusted during the backwash time. No. 3 and no. No. 4 shows that when 200 hours or more have elapsed from the start of the filtration treatment, the membrane differential pressure of the hollow fiber membrane is No. corresponding to the decrease in the permeation flux of the backwash water. 1 and no. It is clearly larger than 2.

  As mentioned above, since the washing | cleaning method of the filtration module which concerns on embodiment of this invention can fully suppress the fall of filtration processing efficiency by improving the washing | cleaning effect of the multiple hollow fiber membrane by reverse washing, it is immersed. It is suitable as a cleaning method for the external and external pressure filtration modules.

DESCRIPTION OF SYMBOLS 1 Filtration module 2 Filtration stop mechanism 2a Suction pump 2b Valve 2c Filtration operation control part 3 Reverse washing mechanism 3a Constant flow valve 3b Filtrated water circulation pipe 3c Filtrated water supply pump 3d Chemical supply pipe 3e Reverse washing control part 4 To-be-treated liquid supply mechanism 4a Processed liquid supply pipe 4b Processed liquid supply pump 4c Valve 5 Processed liquid storage tank 6 Backwash water storage tank 7 Filtrated water discharge pipe 8 Control unit 11 Hollow fiber membrane 12 Upper holding member 13 Lower holding member 13a Fixed part 14 Casing 14a Upper opening 14b Lower opening 14c Discharge port 23 Reverse cleaning mechanism 23a Bubble supply pipe 23b Bubble supply device 23c Bubble supply control unit 28 Control unit P Backwash water X Liquid to be treated Y Chemical agent

Claims (5)

A method of cleaning an immersion type or external pressure type filtration module having a plurality of hollow fiber membranes aligned in one direction,
A step of stopping filtration of the liquid to be treated;
A step of backwashing the plurality of hollow fiber membranes with backwashing water after the stopping step,
A method for cleaning a filtration module, wherein the flow of backwash water supplied to the filtration module is controlled to be constant in the backwashing step.   The method for cleaning a filtration module according to claim 1, wherein bubbles are supplied to the outside of the plurality of hollow fiber membranes in the reverse cleaning step.   The cleaning method of the filtration module according to claim 1 or 2, wherein a cleaning time in the reverse cleaning step is 15 seconds or more and 80 seconds or less.   The method for cleaning a filtration module according to claim 1, wherein the backwash water contains a chemical. A filtration device comprising a submerged or external pressure filtration module having a plurality of hollow fiber membranes aligned in one direction,
A filtration stop mechanism for stopping the filtration of the liquid to be treated;
A backwashing mechanism for backwashing the plurality of hollow fiber membranes with backwashing water after the filtration is stopped by the filtration stopping mechanism,
The filtration device having a constant flow valve in which the back washing mechanism keeps the flow rate of back washing water supplied to the filtration module constant.

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