JP2008237971A - Method for operating membrane filtration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a membrane filtration system where, among a plurality of filtration membrane modules provided at a water feed line in series, capable of regulating the flow rate of concentrated water from the filtration membrane modules on the downstream side of the filtration membrane module provided on the uppermost stream. <P>SOLUTION: The method for operating a membrane filtration system 1 includes the steps of: disposing a first filtration membrane module 3 and a second filtration membrane module 4 in a water feed line 2 to an apparatus in series; constituting such that water fed from one side to the respective filtration membrane modules 3, 4 is separated into treatment water and concentrated water, so as to be made to flow out from the other side; adjusting the flow rate of the fed water to the respective filtration membrane modules 3, 4 such that the flow rate of the treatment water is made into the set flow rate, and further; adjusting the flow rate of the concentrated water at least from the second filtration membrane module 4, wherein the flow rate of the treatment water from the first filtration membrane module 3 is set to the flow rate obtained by adding the flow rate of the treatment water and the flow rate of the drainage of the concentrated water from the second filtration membrane module. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for operating a membrane filtration system in which a plurality of filtration membrane modules are provided in series on a water supply line to an apparatus.

  2. Description of the Related Art Conventionally, as a membrane filtration system in which a plurality of filtration membrane modules are provided in series on a water supply line to equipment, for example, a membrane filtration system that supplies pure water to equipment such as a semiconductor cleaning device is known (for example, Patent Document 1). reference). In this membrane filtration system, a reverse osmosis membrane is used as a filtration membrane of the filtration membrane module, and impurities are removed by filtration through this reverse osmosis membrane.

  In each filtration membrane module, feed water is supplied from one side by a feed water pump provided on the upstream side of each filtration membrane module, and treated water and concentrated water flow out from the other side.

  Here, the flow rate of the treated water from each of the filtration membrane modules varies greatly depending on the viscosity of the water and the change in membrane characteristics depending on the water temperature. The treated water flow rate decreases as the water temperature decreases, and increases as the water temperature increases. Therefore, in order to always ensure a constant treated water flow rate without being affected by fluctuations in the water temperature, a treated water flow rate sensor is provided in each of the water supply lines on the downstream side of each of the filtration membrane modules, and detection of the treated water flow rate sensor is performed. Based on the value, it is conceivable to control the rotation speed of each water supply pump so that the treated water flow rate from each filtration membrane module becomes a set flow rate (constant flow rate control).

By the way, in the patent document 2, the applicant of the present application is a membrane filtration system in which a filtration membrane module is provided in a water supply line to equipment, in order to prevent clogging of the filtration membrane in the filtration membrane module and maintain the quality of treated water The filtration based on the water temperature of the water supplied to the filtration membrane module, the treated water from the filtration membrane module and the concentrated water from the filtration membrane module, or the quality of the water supplied to the filtration membrane module A method for operating a membrane filtration system that adjusts the flow rate of concentrated water from the membrane module is proposed. In addition, in the patent document 3, the applicant of the present invention is a membrane filtration system in which a filtration membrane module is provided in a water supply line to an apparatus, and suppresses the precipitation of scale due to the hardness in the filtration membrane module. In order to prevent clogging and to maintain the treated water at a predetermined quality, it is based on the hardness of any one of water supplied to the filtration membrane module, treated water from the filtration membrane module and concentrated water from the filtration membrane module. Thus, a method of operating a membrane filtration system for adjusting the flow rate of concentrated water from the filtration membrane module has been proposed.
JP-A-5-309237 JP 2006-305499 A JP 2006-305500 A

  However, when the membrane filtration system operating method described in Patent Documents 2 and 3 is applied to the membrane filtration system in which a plurality of the filtration membrane modules are provided in series in the water supply line, it is provided in the uppermost stream. Even if an attempt is made to adjust the flow rate of the concentrated water from the filtration membrane module downstream from the filtered membrane module, the flow rate of the treated water from the filtration membrane module upstream from the filtration membrane module to be adjusted. If the constant flow rate control is constant, the concentrated water flow rate cannot be adjusted. That is, when performing constant flow control in the membrane filtration system in which a plurality of the filtration membrane modules are provided in series in the water supply line, the filtration membrane module upstream from the most downstream filtration membrane module is controlled by constant flow control. Therefore, the flow rate of the concentrated water from the filtration membrane module on the downstream side of the filtration membrane module provided in the uppermost stream cannot be adjusted.

  A problem to be solved by the present invention is that a plurality of filtration membrane modules are provided in series in a water supply line to an apparatus, and water is supplied to each filtration membrane module so that the flow rate of treated water from each filtration membrane module becomes a set flow rate. In the membrane filtration system for adjusting the flow rate, it is possible to adjust the flow rate of the concentrated water from the filtration membrane module on the downstream side of the filtration membrane module provided in the uppermost stream.

  This invention was made in order to solve the said subject, and the invention of Claim 1 provides the filtration membrane module in multiple stages in series in the water supply line to an apparatus, and is said to each said filtration membrane module from one side. The supplied water supply is configured to separate and flow out from the other side into treated water and concentrated water, and adjusts the water supply flow rate to the filtration membrane module so that the treated water flow rate becomes a set flow rate, and at least A method of operating a membrane filtration system that adjusts the flow rate of concentrated water from a filtration membrane module downstream from the most upstream filtration membrane module, and processing from a filtration membrane module upstream from the most downstream filtration membrane module In setting the water flow rate, the flow rate is set to the sum of the treated water flow rate and the concentrated water flow rate from the other filtration membrane module on the downstream side of one filtration membrane module to be set. Characterized in that it.

  Furthermore, the invention according to claim 2 is the operation method of the membrane filtration system according to claim 1, wherein the concentrated water from the filtration membrane module downstream from the filtration membrane module provided in the uppermost stream is supplied to the membrane filtration system. It is characterized by refluxing to the upstream side of the most upstream filtration membrane module.

  According to the first aspect of the present invention, in the case of performing constant flow control for adjusting the feed water flow rate to each filtration membrane module so that the treated water flow rate from each filtration membrane module becomes a set flow rate, The treated water flow rate from the filtration membrane module upstream of the most downstream filtration membrane module is equal to the treated water flow rate from the other filtration membrane module one downstream of the one filtration membrane module to set the treated water flow rate. The flow rate is set by adding the concentrated water flow rate. Thereby, even if the flow rate of concentrated water from the other filtration membrane module is increased, the flow rate of treated water from the one filtration membrane module is set accordingly. Accordingly, it is possible to adjust the flow rate of the concentrated water from the filtration membrane module on the downstream side of the filtration membrane module provided in the uppermost stream.

  According to the second aspect of the present invention, the concentrated water from the filtration membrane module on the downstream side of the most upstream filtration membrane module is returned to the upstream side of the upstream filtration membrane module, thereby saving water. be able to. Further, by setting the reflux point of the concentrated water upstream of the uppermost filtration membrane module, the refluxed concentrated water is supplied again to each of the filtration membrane modules as feed water to ensure as many times as possible to be filtered. Therefore, the final treated water quality, that is, the treated water quality from the most downstream filtration membrane module can be improved. Furthermore, since the concentrated water filtered in each filtration membrane module is refluxed, the quality of the water supplied to each filtration membrane module is improved, and also from this, treatment from the most downstream filtration membrane module is performed. Water quality can be improved.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
First, a first embodiment of a method for operating a membrane filtration system according to the present invention will be described. FIG. 1 is a schematic explanatory view showing an example of a membrane filtration system for carrying out the first embodiment of the present invention.

  A membrane filtration system 1 shown in FIG. 1 includes a first filtration membrane module 3 and a second filtration membrane module 4 provided in series in this order from the upstream side in a water supply line 2 to equipment (not shown) such as a semiconductor cleaning device. It has been. A reverse osmosis membrane (RO membrane) is used as the filtration membrane of each of the filtration membrane modules 3 and 4. This reverse osmosis membrane is a synthetic polymer membrane such as polyamide or polyether, and is a liquid separation membrane that can prevent permeation of a substance having a molecular weight of several tens. And by this reverse osmosis membrane, feed water is filtered and the impurity contained in feed water is removed.

  The first filtration membrane module 3 is supplied with feed water by a first feed water pump 5 provided on the upstream side of the first filtration membrane module 3. The second filtration membrane module 4 is supplied with water by a second water supply pump 6 provided in the water supply line 2 between the second filtration membrane module 4 and the first filtration membrane module 3. It has become. The first water supply pump 5 is connected to the first control unit 7 and the operation is controlled by the first control unit 7, and the second water supply pump 6 is connected to the second control unit 8 and connected to the first control unit 7. The operation is controlled by the second control unit 8. Here, the control units 7 and 8 are also connected to each other.

  In each of the filtration membrane modules 3 and 4, the feed water supplied from one side by the feed water pumps 5 and 6 is separated from the other side into treated water and concentrated water and flows out. . Then, the treated water flows out to the water supply line 2. On the other hand, a first concentrated water line 9 and a second concentrated water line 10 are connected to each of the filtration membrane modules 3 and 4, respectively, and the concentrated water from each of the filtration membrane modules 3 and 4 It flows out to the water lines 9 and 10, respectively, and is discharged out of the system.

  The concentrated water lines 9 and 10 are branched into a first drain line 11, a second drain line 12 and a third drain line 13. Each drain line 11, 12, 13 is provided with a first drain valve 14, a second drain valve 15, and a third drain valve 16, respectively. The drain valves 14, 15 and 16 in the first concentrated water line 9 are connected to the first control unit 7. The drain valves 14, 15, 16 in the second concentrated water line 10 are connected to the second control unit 8. The drain valves 14, 15, 16 are set to open / close in response to an open / close signal from the controllers 7, 8, and the drain valves 14, 15, 16 are opened / closed. By changing the state, the flow rate of the concentrated water from the concentrated water lines 9 and 10 is adjusted stepwise.

  A first flow sensor 17 is connected to the downstream side of the first filtration membrane module 3, specifically, to the water supply line 2 between the first filtration membrane module 3 and the second water supply pump 6. A second flow rate sensor 18 and an electrical conductivity sensor 19 are connected to the water supply line 2 on the downstream side of the second filtration membrane module 4. The first flow rate sensor 17 is connected to the first control unit 7, and the second flow rate sensor 18 and the electrical conductivity sensor 19 are connected to the second control unit 8.

  Now, an operation method of the membrane filtration system 1 will be described. In the membrane filtration system 1, the water supply pumps 5 and 6 are operated so that the flow rate of treated water from the filtration membrane modules 3 and 4 becomes a set flow rate. Specifically, the first control unit 7 controls the first flow rate sensor 17 so that the treated water flow rate from the first filtration membrane module 3 becomes the first treated water flow rate X1. The second control unit 8 controls the rotational speed of the first feed water pump 5 and the second flow rate sensor so that the treated water flow rate from the second filtration membrane module 4 becomes the second treated water flow rate X2. Based on the detected value of 18, the rotation speed of the second water supply pump 6 is controlled (flow rate feedback control).

  Here, the flow rate obtained by adding the treated water flow rate from the second filtration membrane module 4 and the concentrated water flow rate becomes the treated water flow rate from the first filtration membrane module 3. Accordingly, the first treated water flow rate X1 is set to a flow rate obtained by adding the second treated water flow rate X2 and the concentrated water flow rate from the second filtration membrane module 4 (second concentrated water flow rate Y2 described later). Further, the second treated water flow rate X2 is set to a desired flow rate according to the load of the device (not shown) to which water is supplied.

  Here, in the first embodiment, the most downstream filtration membrane module in the claims means the second filtration membrane module 4. Further, in the claims, one filtration membrane module which is upstream of the most downstream filtration membrane module and is intended to set the treated water flow rate is the first filtration membrane module in the first embodiment. Means 3. Furthermore, in the scope of the claims, the other filtration membrane module on the downstream side of one filtration membrane module for which the treatment water flow rate is to be set is the most downstream filtration membrane module in this second embodiment, that is, the above-mentioned The second filtration membrane module 4 is meant.

  In the membrane filtration system 1, the first control unit 7 controls the drain valves in the first concentrated water line 9 so that the concentrated water flow rate from the first filtration membrane module 3 becomes the first concentrated water flow rate Y1. The open / close state of 14, 15, 16 is set. Further, the second controller 8 controls the drain valves 14, 15, 16 in the second concentrated water line 10 so that the concentrated water flow rate from the second filtration membrane module 4 becomes the second concentrated water flow rate Y 2. Set the open / close state.

  Each concentrated water flow rate Y1, Y2 is determined according to the quality of raw water (for example, electrical conductivity) measured in advance, that is, according to the quality of the feed water supplied to the first filtration membrane module 3. In the vicinity of the surface of the reverse osmosis membrane (not shown) in No. 4, the flow rate is set so that impurities are not excessively concentrated. This set flow rate is a flow rate when the detected value of the electrical conductivity sensor 19 is greater than or equal to electrical conductivity E1 to E2 described later.

  In order to prevent impurities from being excessively concentrated near the surface of the reverse osmosis membrane when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2 during the operation of the membrane filtration system 1. The second control unit 8 outputs a flow rate setting signal to the drain valves 14, 15, 16 to increase the second concentrated water flow rate Y2. At this time, the second control unit 8 outputs the newly set second concentrated water flow rate Y21 and the second treated water flow rate X2 to the first control unit 7, and receives the first control unit 7 Then, the new second concentrated water flow rate Y21 and the second treated water flow rate X2 are added to calculate a new first treated water flow rate X11. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X11.

  Further, when the detection value of the electrical conductivity sensor 19 is lower than the electrical conductivity E1 (E1 <E2), it is possible to prevent the impurities from being excessively concentrated near the surface of the reverse osmosis membrane. In order to save water, the second controller 8 outputs a flow rate setting signal to the drain valves 14, 15, 16 to decrease the second concentrated water flow rate Y2. At this time, the second control unit 8 outputs the newly set second concentrated water flow rate Y22 and the second treated water flow rate X2 to the first control unit 7, and receives the first control unit. 7, the new second concentrated water flow rate Y22 and the second treated water flow rate X2 are added to calculate a new first treated water flow rate X12. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X12.

  According to the membrane filtration system 1 described above, even if the flow rate of concentrated water from the second filtration membrane module 4 is increased, the flow rate of treated water from the first filtration membrane module 3 is set accordingly. . Therefore, the flow rate of the concentrated water from the second filtration membrane module 4 can be adjusted.

  Incidentally, in the membrane filtration system 1, when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2, the electrical conductivity can be increased even if the concentrated water flow rate from the second filtration membrane module 4 is increased. When the detected value of the sensor 19 does not become the electrical conductivity E2 or less, the concentrated water flow rate from the first filtration membrane module 3 may be increased. Thereby, the quality of the treated water from the second filtration membrane module 4 can be improved. When the detected value of the electrical conductivity sensor 19 is lower than the electrical conductivity E1, the concentrated water flow rate from the second filtration membrane module 4 is decreased and the concentrated water flow rate from the first filtration membrane module 3 is decreased. May be reduced. Thereby, the quality of the treated water from said 2nd filtration membrane module 4 can be maintained, and further water saving can be aimed at.

(Second embodiment)
Next, a second embodiment of the operation method of the membrane filtration system according to the present invention will be described. FIG. 2 is a schematic explanatory view showing an example of a membrane filtration system for carrying out the second embodiment of the present invention. In FIG. 2, the same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the membrane filtration system 30 of the second embodiment, a third filtration membrane module 31 is provided in series in the water supply line 2 on the downstream side of the second filtration membrane module 4, and the filtration membrane module is provided in the water supply line 2. Are provided in three stages in series. The third filtration membrane module 31 also has the same configuration as each of the filtration membrane modules 3 and 4.

  Water is supplied to the third filtration membrane module 31 by a third water supply pump 32 provided in the water supply line 2 between the third filtration membrane module 31 and the second filtration membrane module 4. ing. The third water supply pump 32 is connected to a third control unit 33, and the operation is controlled by the third control unit 33. Here, the third control unit 33 is also connected to the second control unit 8.

  In the third filtration membrane module 31, when water is supplied from one side by the third water supply pump 32, treated water and concentrated water are supplied from the other side in the same manner as the filtration membrane modules 3 and 4. The treated water flows out through the water supply line 2 and is supplied to the equipment (not shown). On the other hand, the concentrated water flows out to the third concentrated water line 34 connected to the third filtration membrane module 31.

  The third concentrated water line 34 is branched into the first drainage line 11, the second drainage line 12, and the third drainage line 13 in the same manner as the concentrated water lines 9 and 10. The first drain valve 14, the second drain valve 15 and the third drain valve 16 provided in the drain lines 11, 12, 13 are connected to the third control unit 33, In response to the open / close signal from the third control unit 33, the open / close states of the drain valves 14, 15, 16 are set. Thereby, the flow rate of the concentrated water in the third concentrated water line 34 is adjusted stepwise.

  A third flow rate sensor 35 is connected to the water supply line 2 on the downstream side of the third filtration membrane module 31. The third flow sensor 35 is connected to the third control unit 33. In the membrane filtration system 30 of the third embodiment, the electrical conductivity sensor 19 is connected to the water supply line 2 on the downstream side of the third filtration membrane module 31.

  Now, an operation method of the membrane filtration system 30 will be described. In the following description, matters different from the operation method of the membrane filtration system 1 of the first embodiment will be described.

  In the membrane filtration system 30, the water supply pumps 5, 6, and 32 are operated so that the flow rate of treated water from the filtration membrane modules 3, 4, and 31 becomes a set flow rate. Then, the third control unit 33 determines the third treated water flow rate from the third filtration membrane module 31 to be the third treated water flow rate X3 based on the detected value of the third flow rate sensor 35. The rotational speed of the feed water pump 32 is controlled.

  Here, the flow rate obtained by adding the treated water flow rate from the third filtration membrane module 31 and the concentrated water flow rate becomes the treated water flow rate from the second filtration membrane module 4. Therefore, in this second embodiment, the treated water flow rate from the second filtration membrane module 4, that is, the second treated water flow rate X2, is the third treated water flow rate X3 and the concentrated water flow rate from the third filtration membrane module 31. It is set to a flow rate obtained by adding (third concentrated water flow rate Y3 described later). Then, the flow rate obtained by adding the second treated water flow rate X2 thus set and the concentrated water flow rate from the second filtration membrane module 4, that is, the second concentrated water flow rate Y2, is the first flow rate. It is set as the treated water flow rate from one filtration membrane module 3, that is, the first treated water flow rate X1.

  Further, the third treated water flow rate X3 is set to a desired flow rate according to the load of the device (not shown) to which the water supply is supplied.

  Here, in the second embodiment, the most downstream filtration membrane module in the claims means the third filtration membrane module 31. Further, in the claims, the one filtration membrane module which is upstream of the most downstream filtration membrane module and is intended to set the treatment water flow rate is the first filtration membrane module in the second embodiment. 3 or the said 2nd filtration membrane module 4. Furthermore, in the scope of the claims, the other filtration membrane module on the one-stage downstream side of one filtration membrane module for which the treated water flow rate is to be set is, in this second embodiment, the one filtration membrane module is the first filtration membrane module. When it is one filtration membrane module 3, it means the second filtration membrane module 4, and when the one filtration membrane module is the second filtration membrane module 4, it means the third filtration membrane module 31.

  In the membrane filtration system 30, the concentrated water flow rate from the third filtration membrane module 31 is set to be the third concentrated water flow rate Y3. The third concentrated water flow rate Y3 is set in the same manner as the first concentrated water flow rate Y1 and the second concentrated water flow rate Y2. And the said 3rd control part 33 is said each drainage valve 14,15 in the said 3rd concentrated water line 34 so that the concentrated water flow rate from the said 3rd filtration membrane module 31 may become the 3rd concentrated water flow rate Y3. 16 open / close states are set.

  In the membrane filtration system 30, when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2 during operation, impurities are prevented from being excessively concentrated near the surface of the reverse osmosis membrane (not shown). In order to do so, the third control unit 33 outputs an open / close signal to the drain valves 14, 15, 16 to increase the third concentrated water flow rate Y3. At this time, the third control unit 33 outputs the newly set third concentrated water flow rate Y31 and the third treated water flow rate X3 to the second control unit 8, and receives the second control unit 8 Then, the new third concentrated water flow rate Y31 and the third treated water flow rate X3 are added to calculate a new second treated water flow rate X21. And the said 2nd control part 8 controls the rotation speed of said 2nd water supply pump 6 so that it may become this 2nd treated water flow volume X21.

  When a new second treated water flow rate X21 is set, the second control unit 8 outputs the newly set second treated water flow rate X21 and the second concentrated water flow rate Y2 to the first control unit 7. In response to this, the first control unit 7 adds the newly set second treated water flow rate X21 and the second concentrated water flow rate Y2 to calculate a new first treated water flow rate X111. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X111.

  Further, when the detected value of the electrical conductivity sensor 19 falls below the electrical conductivity E1 during the operation of the membrane filtration system 30, it is possible to prevent impurities from being excessively concentrated near the surface of the reverse osmosis membrane. In order to save water in a range where the water can be saved, the third control unit 33 outputs a flow rate setting signal to the drain valves 14, 15, 16 to reduce the third concentrated water flow rate Y3. At this time, the third control unit 33 outputs the newly set third concentrated water flow rate Y32 and the third treated water flow rate X3 to the second control unit 8, and receives the second control unit 33 In 8, the newly set third concentrated water flow rate Y32 and the third treated water flow rate X3 are added to calculate a new second treated water flow rate X22. And the said 2nd control part 8 controls the rotation speed of said 2nd water supply pump 6 so that it may become this 2nd treated water flow volume X22.

  When a new second treated water flow rate X22 is set, the second control unit 8 outputs a new second treated water flow rate X22 and a second concentrated water flow rate Y2 to the first control unit 7. The first control unit 7 adds the newly set second treated water flow rate X22 and the second concentrated water flow rate Y2, and calculates a new first treated water flow rate X112. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X112.

  Further, in the membrane filtration system 30, when the detection value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2 during operation, the flow rate of the concentrated water from the third filtration membrane module 31 is increased. When the detected value of the electrical conductivity sensor 19 does not become the electrical conductivity E2 or less, the concentrated water flow rate from the second filtration membrane module 4 may be increased. Thereby, the quality of the treated water from the third filtration membrane module 31 can be improved. Furthermore, when the detected value of the electrical conductivity sensor 19 is lower than the electrical conductivity E1, the concentrated water flow rate from the third filtration membrane module 31 is decreased and the concentrated water flow rate from the second filtration membrane module 4 is reduced. May be reduced. Thereby, the quality of the treated water from the third filtration membrane module 31 can be maintained and further water saving can be achieved. When the concentrated water flow rate from the second filtration membrane module 4 is increased or decreased in this way, the first control unit 7 sets the concentrated water flow rate from the second filtration membrane module newly set in the same manner as described above. And the second treated water flow rate X21 or X22 are added to calculate a new first treated water flow rate, and the rotational speed of the first feed water pump 5 is controlled so as to be the first treated water flow rate.

  According to the membrane filtration system 30 described above, even if the concentrated water flow rate from the third filtration membrane module 31 is increased, the treated water flow rate from the second filtration membrane module 4 is set accordingly. . Therefore, the flow rate of the concentrated water from the third filtration membrane module 31 can be adjusted.

  Further, even if the concentrated water flow rate from the second filtration membrane module 4 is increased, the treated water flow rate from the first filtration membrane module 3 is set accordingly. Therefore, the flow rate of the concentrated water from the second filtration membrane module 4 can be adjusted.

  Incidentally, in the membrane filtration system 30, when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2, the flow rate of the concentrated water from the first filtration membrane module 3 is changed as in the first embodiment. When the detected value of the electrical conductivity sensor 19 is lower than the electrical conductivity E1, the flow rate of the concentrated water from the first filtration membrane module 3 is decreased as in the first embodiment. May be.

(Third embodiment)
Next, a third embodiment of the operation method of the membrane filtration system according to the present invention will be described. FIG. 3 is a schematic explanatory view showing a membrane filtration system for carrying out the third embodiment of the present invention. In FIG. 3, the same components as those in the first and second embodiments are denoted by the same reference numerals and description thereof is omitted.

  The membrane filtration system 40 of the third embodiment has the same basic configuration as that of the first embodiment, includes the first filtration membrane module 3 and the second filtration membrane module 4, and the filtration membrane module in the water supply line 2 Are provided in two stages in series.

  In the membrane filtration system 40, the second concentrated water line 10 is connected to the water supply line 2 on the upstream side of the first filtration membrane module 3, and the concentrated water from the second filtration membrane module 4. Is refluxed to the upstream side of the first filtration membrane module 3. In the third embodiment, the second concentrated water line 10 has a portion branched into a first line 41, a second line 42, and a third line 43, and the lines 41, 42, 43 is provided with a first valve 44, a second valve 45 and a third valve 46. Each of the valves 44, 45, 46 is connected to the second control unit 8, and an open / close state is set in response to an open / close signal from the second control unit 8. And the flow rate of the concentrated water in the second concentrated water line 10 can be adjusted by changing the open / closed state of the valves 44, 45, 46 in this way.

  Now, an operation method of the membrane filtration system 40 will be described. In the following description, matters different from the membrane filtration systems 1 and 30 of the embodiments will be described.

  Also in the membrane filtration system 40, the flow rate obtained by adding the treated water flow rate from the second filtration membrane module 4 and the concentrated water flow rate becomes the treated water flow rate from the first filtration membrane module 3. Therefore, in this third embodiment, the treated water flow rate from the first filtration membrane module 3, that is, the first treated water flow rate X1, is the treated water flow rate from the second filtration membrane module 4, that is, the second treated water flow rate. The flow rate is set by adding X2 and the concentrated water flow rate from the second filtration membrane module 4, that is, the second concentrated water flow rate Y2.

  Incidentally, similarly to the first embodiment, the second treated water flow rate X2 is set to a desired flow rate according to the load of the device (not shown) to which water is supplied.

  Here, in the third embodiment, the most downstream filtration membrane module in the claims means the second filtration membrane module 4. Further, in the claims, the one filtration membrane module which is upstream of the most downstream filtration membrane module and is intended to set the treatment water flow rate is the first filtration membrane module in the third embodiment. Means 3. Furthermore, another filtration membrane module on the downstream side of one filtration membrane module whose processing water flow rate is to be set in the claims is the most downstream filtration membrane module in the third embodiment, that is, the first filtration membrane module. It means the two-filtration membrane module 4.

  In the membrane filtration system 40, when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2 during operation, the second control unit 8 outputs an open / close signal to the valves 44, 45, 46. The second concentrated water flow rate Y2 is increased. At this time, the second control unit 8 outputs the newly set second concentrated water flow rate Y21 and the second treated water flow rate X2 to the first control unit 7, and receives the first control unit 7 Then, the newly set second concentrated water flow rate Y21 and the second treated water flow rate X2 are added to calculate a new first treated water flow rate X11. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X11.

  When the detected value of the electrical conductivity sensor 19 falls below the electrical conductivity E1 during the operation of the membrane filtration system 40, the second control unit 8 sends a flow rate setting signal to each of the valves 44, 45, 46. Is output to decrease the second concentrated water flow rate Y2. At this time, the second control unit 8 outputs the newly set second concentrated water flow rate Y22 and the second treated water flow rate X2 to the first control unit 7, and receives the first control unit. 7, the newly set second concentrated water flow rate Y22 and the second treated water flow rate X2 are added to calculate a new first treated water flow rate X12. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X12.

  According to the membrane filtration system 40 described above, the same effect as that of the membrane filtration system 1 of the first embodiment can be obtained, and the concentrated water from the second filtration membrane module 4 is used as the first filtration membrane. By returning to the upstream side of the module 3, water can be saved. In addition, by setting the reflux point of the concentrated water upstream of the first filtration membrane module 3, the refluxed concentrated water is supplied again to the filtration membrane modules 3 and 4 as feed water and filtered as many times as possible. Since a large amount can be secured, the final treated water quality, that is, the treated water quality from the second filtration membrane module 4 can be improved. Furthermore, since the concentrated water filtered in each of the filtration membrane modules 3 and 4 is refluxed, the quality of the water supplied to each of the filtration membrane modules 3 and 4 is improved. The quality of the treated water from the filtration membrane module 4 can be improved.

  Incidentally, in the membrane filtration system 40, when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2, the flow rate of the concentrated water from the first filtration membrane module 3 is increased as in the above embodiments. In addition, when the detected value of the electrical conductivity sensor 19 is lower than the electrical conductivity E1, the flow rate of the concentrated water from the first filtration membrane module 3 may be reduced as in the above embodiments. Good.

(Fourth embodiment)
Next, a fourth embodiment of the operation method of the membrane filtration system according to the present invention will be described. FIG. 4 is a schematic explanatory view showing an example of a membrane filtration system for carrying out the fourth embodiment of the present invention. In FIG. 4, the same components as those of the first, second, and third embodiments are denoted by the same reference numerals, and description thereof is omitted.

  The membrane filtration system 50 of the fourth embodiment has the same basic configuration as the second embodiment, and includes the first filtration membrane module 3, the second filtration membrane module 4, and the third filtration membrane module 31, Three stages of filtration membrane modules are provided in the water supply line 2 in series.

  In the membrane filtration system 50, the second and third concentrated water lines 10 and 34 merge and are connected to the water supply line 2 on the upstream side of the first filtration membrane module 3. Accordingly, the concentrated water from the second filtration membrane module 4 and the third filtration membrane module 31 is refluxed to the upstream side of the first filtration membrane module 3. In the fourth embodiment, the third concentrated water line 34 has a portion branched into a first line 41, a second line 42, and a third line 43, similarly to the second concentrated water line 10. The first valve 44, the second valve 45, and the third valve 46 are provided in the lines 41, 42, and 43, respectively. The valves 44, 45, and 46 in the third concentrated water line 34 are connected to the third control unit 33, and an open / close state is set in response to an open / close signal from the third control unit 33. It has become so. Thus, the flow rate of the concentrated water in the third concentrated water line 34 can be adjusted by changing the open / closed state of the valves 44, 45, 46.

  Now, an operation method of the membrane filtration system 50 will be described. In the following description, matters different from the membrane filtration systems 1, 30, and 40 of the embodiments will be described.

  Also in the membrane filtration system 50, the flow rate obtained by adding the treated water flow rate from the third filtration membrane module 31 and the concentrated water flow rate becomes the treated water flow rate from the second filtration membrane module 4. Therefore, in the fourth embodiment, the treated water flow rate from the second filtration membrane module 4, that is, the second treated water flow rate X2, is the treated water flow rate from the third filtration membrane module 31, that is, the third treated water flow rate. The flow rate is set to a sum of X3 and the concentrated water flow rate from the third filtration membrane module 31, that is, the third concentrated water flow rate Y3. Then, the flow rate obtained by adding the second treated water flow rate X2 thus set and the concentrated water flow rate from the second filtration membrane module 4, that is, the second concentrated water flow rate Y2, is the first flow rate. It is set as the treated water flow rate from one filtration membrane module 3, that is, the first treated water flow rate X1.

  Incidentally, the third treated water flow rate X3 is set to a desired flow rate according to the load of the device (not shown) to which water is supplied, as in the second embodiment.

  Here, in the fourth embodiment, the most downstream filtration membrane module in the claims means the third filtration membrane module 31. Further, in the claims, one filtration membrane module which is upstream of the most downstream filtration membrane module and is intended to set the treatment water flow rate is the first filtration membrane module in the fourth embodiment. 3 or the said 2nd filtration membrane module 4. Furthermore, in the scope of the claims, the other filtration membrane module on the one-stage downstream side of the one filtration membrane module for which the treated water flow rate is to be set is, in this fourth embodiment, the one filtration membrane module is the first filtration membrane module. When it is one filtration membrane module 3, it means the second filtration membrane module 4, and when the one filtration membrane module is the second filtration membrane module 4, it means the third filtration membrane module 31.

  In the membrane filtration system 50, when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2 during operation, the third controller 33 controls the valves 44 and 45 as in the second embodiment. , 46 to output an open / close signal to increase the third concentrated water flow rate Y3. At this time, the third control unit 33 outputs the newly set third concentrated water flow rate Y31 and the third treated water flow rate X3 to the second control unit 8, and receives the second control unit 8 Then, the newly set third concentrated water flow rate Y31 and the third treated water flow rate X3 are added to calculate a new second treated water flow rate X21. And the said 2nd control part 8 controls the rotation speed of said 2nd water supply pump 6 so that it may become this 2nd treated water flow volume X21.

  When a new second treated water flow rate X21 is set, the second control unit 8 outputs the newly set second treated water flow rate X21 and the second concentrated water flow rate Y2 to the first control unit 7. In response to this, the first control unit 7 adds the newly set second treated water flow rate X21 and the second concentrated water flow rate Y2 to calculate a new first treated water flow rate X111. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X111.

  Further, when the detected value of the electrical conductivity sensor 19 falls below the electrical conductivity E1 during the operation of the membrane filtration system 50, the third control unit 33 controls each valve in the same manner as in the second embodiment. An open / close signal is output to 44, 45, and 46 to decrease the third concentrated water flow rate Y3. At this time, the third control unit 33 outputs the newly set third concentrated water flow rate Y32 and the third treated water flow rate X3 to the second control unit 8, and receives the second control unit 33 In 8, the newly set third concentrated water flow rate Y32 and the third treated water flow rate X3 are added to calculate a new second treated water flow rate X22. And the said 2nd control part 8 controls the rotation speed of said 2nd water supply pump 6 so that it may become this 2nd treated water flow volume X22.

  When a new second treated water flow rate X22 is set, the second control unit 8 outputs a new second treated water flow rate X22 and a second concentrated water flow rate Y2 to the first control unit 7. The first control unit 7 adds the newly set second treated water flow rate X22 and the second concentrated water flow rate Y2, and calculates a new first treated water flow rate X112. And the said 1st control part 7 controls the rotation speed of said 1st water supply pump 5 so that it may become this 1st treated water flow volume X112.

  In the membrane filtration system 50, when the detected value of the electrical conductivity sensor 19 exceeds the electrical conductivity E2 during operation, the concentration from the third filtration membrane module 31 is the same as in the second embodiment. If the detected value of the electrical conductivity sensor 19 does not become equal to or lower than the electrical conductivity E2 even if the water flow rate is increased, the concentrated water flow rate from the second filtration membrane module may be increased. Furthermore, when the detected value of the electrical conductivity sensor 19 is lower than the electrical conductivity E1, the concentrated water flow rate from the third filtration membrane module 31 is decreased and the concentrated water flow rate from the second filtration membrane module 4 is reduced. May be reduced. As described above, when the flow rate of the concentrated water from the second filtration membrane module 4 is increased or decreased, the first control unit 7 receives the newly set second filtration membrane module 4 from the second filtration membrane module 4 in the same manner as described above. A new first treated water flow rate is calculated by adding the concentrated water flow rate and the second treated water flow rate X21 or X22, and the rotational speed of the first water supply pump 5 is controlled so as to be the first treated water flow rate. To do.

  According to the membrane filtration system 30 described above, it is possible to obtain the same effects as those of the above embodiments.

  As mentioned above, although this invention was demonstrated by embodiment, it cannot be overemphasized that this invention can be variously implemented in the range which does not change the main point.

1 is a schematic explanatory diagram illustrating an example of a membrane filtration system for carrying out a first embodiment of the present invention. It is a schematic explanatory drawing which shows an example of the membrane filtration system for implementing 2nd embodiment of this invention. It is a schematic explanatory drawing which shows an example of the membrane filtration system for implementing 3rd embodiment of this invention. It is a schematic explanatory drawing which shows an example of the membrane filtration system for implementing 4th embodiment of this invention.

Explanation of symbols

1, 30, 40, 50 Membrane filtration system 2 Water supply line 3 First filtration membrane module (filtration membrane module)
4 Second filtration membrane module (filtration membrane module)
31 Third filtration membrane module (filtration membrane module)

Claims (2)

A plurality of filtration membrane modules are provided in series in the water supply line to the equipment, and the supply water supplied from one side to each filtration membrane module is separated and discharged from the other side into treated water and concentrated water, Membrane filtration that adjusts the feed water flow rate to the filtration membrane module so that the treated water flow rate becomes a set flow rate, and also adjusts the concentrated water flow rate from the filtration membrane module downstream of the most upstream filtration membrane module A method of operating the system,
In setting the treatment water flow rate from the filtration membrane module on the upstream side of the most downstream filtration membrane module, from the other filtration membrane module on the one downstream side of one filtration membrane module for which the treatment water flow rate is to be set. A method for operating a membrane filtration system, characterized in that a flow rate obtained by adding the treated water flow rate and the concentrated water flow rate is set.   2. The membrane filtration system according to claim 1, wherein the concentrated water from the filtration membrane module downstream of the filtration membrane module provided in the uppermost stream is returned to the upstream side of the uppermost filtration membrane module. how to drive.

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