JP7200606B2 - Membrane separator - Google Patents

Description

The present invention relates to a membrane separation device.

2. Description of the Related Art Conventionally, high-purity pure water containing no impurities is used in the manufacturing process of semiconductors, cleaning of electronic parts and medical equipment, and the like. This type of pure water is generally produced by subjecting raw water such as groundwater and tap water to reverse osmosis membrane separation treatment using a reverse osmosis membrane module (hereinafter also referred to as "RO membrane module").

As pure water is produced by reverse osmosis membrane separation processing using a reverse osmosis membrane module, contaminants such as suspended solids, humic substances, and proteins adhere to the reverse osmosis membrane module. Periodically or irregularly, it becomes necessary to clean the reverse osmosis membrane module. Such cleaning of reverse osmosis membrane modules is generally called flushing.

For example, Patent Literature 1 discloses a technique of performing a flushing operation after adjusting the osmotic pressure of supply water.

JP 2017-064599 A

However, in the past, flushing was finished after a certain amount of cleaning water had flowed for a certain amount of time. A case is also conceivable.

An object of the present invention is to provide a membrane separation device that is highly effective in saving water during flushing of an RO membrane module.

The present invention comprises a reverse osmosis membrane module that separates feed water including feed water into permeated water and concentrated water, a feed water line that feeds the feed water to the reverse osmosis membrane module, and the reverse osmosis membrane module. A permeated water line for sending permeated water, a concentrated water line for sending concentrated water separated by the reverse osmosis membrane module, a first flow rate measuring means for measuring the flow rate of the permeated water, and a flow rate of the concentrated water. a second flow rate measuring means for measuring; a recovery rate calculation section for calculating a recovery rate from the flow rate of the permeated water and the flow rate of the concentrated water; and a flushing control section for performing control to end the flushing process of the reverse osmosis membrane module. and an integrated water flow rate calculation unit that calculates the integrated water flow rate of the water supply and/or an integrated water flow rate calculation section that calculates an integrated water flow rate of the concentrated water as waste water by the second flow rate measuring means , wherein the flushing The control unit relates to a membrane separation device that terminates the flushing process when the cumulative water flow rate or the cumulative water discharge rate during flushing reaches a predetermined amount calculated based on the recovery rate.

In addition, the flushing control unit controls when the integrated water flow rate or the integrated water discharge amount during flushing reaches a predetermined amount calculated based on the recovery rate during water supply in addition to the recovery rate during flushing. , preferably to terminate the flushing process.

In addition, the flushing control unit increases the ratio of the recovery rate during flushing to the recovery rate during water supply, or the difference obtained by subtracting the recovery rate during flushing from the recovery rate during water supply, the larger the difference. It is preferable to reduce the predetermined amount.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the membrane separation apparatus with the high water-saving effect at the time of flushing of an RO membrane module.

1 is an overall configuration diagram of a membrane separation device according to an embodiment of the present invention; FIG. It is a figure which shows the relationship of the pressure and flow volume which concern on the flow control unit used by embodiment of this invention. It is a functional block diagram of a control unit included in the membrane separation device according to the first embodiment of the present invention. 4 is an example of a graph showing the relationship between the recovery rate during flushing and the amount of water required for flushing in the embodiment of the present invention. 4 is a flow chart showing the operation of the membrane separation device according to the first embodiment of the present invention; It is a functional block diagram of the control part contained in the membrane separation apparatus concerning the 2nd Embodiment of this invention. It is a flowchart which shows operation|movement of the membrane separation apparatus which concerns on the 2nd Embodiment of this invention. It is a functional block diagram of the control part contained in the membrane separation apparatus concerning the 3rd Embodiment of this invention. 4 is an example of a graph showing the relationship between the ratio of recovery rate during water supply to recovery rate during flushing and the amount of water required for flushing in the embodiment of the present invention. It is a flowchart which shows operation|movement of the membrane separation apparatus which concerns on the 3rd Embodiment of this invention.

[1 First embodiment]
[1.1 Configuration of Membrane Separation Apparatus]
A membrane separation device 1 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a membrane separation device 1 according to this embodiment. The membrane separation device 1 according to this embodiment is applied, for example, to a pure water production system that produces pure water from fresh water.

As shown in FIG. 1, the membrane separation device 1 according to the present embodiment includes a pressure pump 2, a pressure side inverter 3, an RO membrane module 4 as a reverse osmosis membrane module, a flow rate adjustment unit 5, and a waste water flow rate A drain flow rate adjustment valve 7 (proportional control valve) as adjustment means, a water supply pump 12, a water supply side inverter 13, a water supply pressure adjustment valve 14 (proportional control valve) as water supply pressure adjustment means, and a first flow rate detection means. a flow rate sensor FM1 as a flow rate sensor, a flow rate sensor FM2 as a second flow rate detection means, and a control section 30. The illustration of electrical connection lines between the control unit 30 and the device to be controlled is omitted.

The membrane separation device 1 also includes a feed water line L1, a feed water line L2, a permeated water line L3, a first concentrated water line L41, and a second concentrated water line L42. The term "line" used herein is a general term for lines through which fluid can flow, such as channels, routes, and pipelines.

The water supply line L<b>1 is a line that supplies the water supply W<b>1 to the pressure pump 2 . The upstream end of the water supply line L1 is connected to a supply source (not shown) of the water supply W1. A water supply pump 12 is provided on the upstream side of the water supply line L1.

The water supply pump 12 is a device that sucks the water supply W<b>1 flowing through the water supply line L<b>1 and pumps (discharges) it toward the pressure pump 2 . The water supply pump 12 is supplied with drive power whose frequency has been converted from the water supply side inverter 13 . The water supply pump 12 is driven at a rotational speed corresponding to the frequency of the supplied (input) driving power (hereinafter also referred to as "driving frequency").

The water supply side inverter 13 is an electric circuit (or a device having such a circuit) that supplies drive power whose frequency is converted to the water supply pump 12 . The water supply side inverter 13 is electrically connected to the controller 30 . A command signal is input to the water supply side inverter 13 from the control unit 30 . The water supply-side inverter 13 outputs to the water supply pump 12 drive power having a drive frequency corresponding to the command signal (current value signal or voltage value signal) input from the control unit 30 . In this embodiment, the control unit 30 controls the water supply side inverter 13 so that the water supply pump 12 discharges the water supply W1 at a predetermined constant pressure value.

The water supply pressure regulating valve 14 is a proportional valve that adjusts the pressure of the water supply W1 supplied to the pressurizing pump 2 by adjusting the degree of opening substantially steplessly. The water supply pressure regulating valve 14 is electrically connected to the control unit 30 , and the degree of opening is adjusted by control from the control unit 30 .

The feed water line L2 is a line that supplies the feed water W1 to the RO membrane module 4 as the feed water W2. The upstream end of the water supply line L2 is connected to the pressure pump 2 . The downstream end of the feed water line L2 is connected to the primary side inlet port of the RO membrane module 4 . A pressure pump 2 and an RO membrane module 4 are provided in order from the upstream side to the downstream side of the feed water line L2.

The pressure pump 2 is provided in the supply water line L2. The pressurizing pump 2 is a device that sucks the feed water W1 in the feed water line L2 and pumps (discharges) it toward the RO membrane module 4 as the feed water W2. The pressurizing pump 2 is supplied with drive power whose frequency has been converted from the pressurizing inverter 3 . The pressurizing pump 2 is driven at a rotational speed corresponding to the frequency of the supplied (input) driving power (hereinafter also referred to as "driving frequency").

The pressurization-side inverter 3 is an electric circuit (or a device having such a circuit) that supplies the pressurization pump 2 with drive power whose frequency has been converted. The pressure-side inverter 3 is electrically connected to the controller 30 . A command signal is input to the pressure-side inverter 3 from the control unit 30 . The pressurization-side inverter 3 outputs to the pressurization pump 2 drive power having a drive frequency corresponding to the command signal (current value signal or voltage value signal) input from the control unit 30 .

The RO membrane module 4 is equipment for membrane separation treatment of the feed water W2 discharged from the pressure pump 2 into permeated water W3 from which dissolved salts have been removed and concentrated water W41 from which dissolved salts have been concentrated. The RO membrane module 4 includes single or multiple RO membrane elements (not shown). The RO membrane module 4 membrane-separates the feed water W2 using these RO membrane elements to produce permeated water W3 and concentrated water W41.

The permeated water line L3 is a line through which the permeated water W3 separated by the RO membrane module 4 is delivered. The upstream end of the permeate line L3 is connected to the secondary port of the RO membrane module 4 . A flow rate sensor FM1 is provided in the permeated water line L3.

The flow rate sensor FM1 is a device that detects the flow rate of the permeated water W3 flowing through the permeated water line L3 as a detected flow rate value. The flow sensor FM1 is connected to the permeate line L3. The flow sensor FM1 is electrically connected to the controller 30 . A detected flow rate value of the permeated water W3 detected by the flow rate sensor FM1 is transmitted to the control section 30 as a detection signal. As the flow rate sensor FM1, for example, a pulse transmission type flow rate sensor having an axial flow impeller or a tangential impeller (not shown) arranged in a flow path housing can be used.

The first concentrated water line L41 is a line for sending out the concentrated water W41 separated by the RO membrane module 4 . The upstream end of the first concentrated water line L41 is connected to the primary outlet port of the RO membrane module 4 . Also, the downstream side of the first concentrated water line L41 is connected to the primary side of the flow rate adjustment unit 5 .

Also, the second concentrated water line L42 is a line for sending out the concentrated water W42 whose flow rate is adjusted by the flow rate adjustment unit 5 . The upstream end of the second concentrated water line L<b>42 is connected to the secondary side of the flow rate adjustment unit 5 . Further, the second concentrated water line L42 is provided with a waste water flow rate adjusting valve 7 as a waste water flow rate adjusting means and a flow rate sensor FM2 in this order.

In addition, henceforth, the 1st concentrated water line L41 and the 2nd concentrated water line L42 may be collectively called "concentrated water line L4." Also, the concentrated water W41 and the concentrated water W42 may be collectively referred to as "concentrated water W4".

The flow rate adjustment unit 5 has a constant flow rate element that circulates a substantially constant flow of concentrated water regardless of the differential pressure in the flow rate adjustment unit 5, and the concentration is substantially proportional to the differential pressure in the flow rate adjustment unit 5. and a proportional element with a high water flow rate. Specifically, the differential pressure in the flow rate adjusting unit 5 is the differential pressure between the water pressure of the first concentrated water line L41 and the water pressure of the second concentrated water line L42. A constant flow element maintains a constant flow value without the need for auxiliary power or external manipulation, and may be used, for example, under the name of a water governor. As the proportional element, for example, an orifice may be used.

FIG. 2 is a graph showing an example of the relationship between the inlet pressure of the RO membrane module 4 and the flow rate of concentrated water flowing through the flow rate adjusting unit 5. As shown in FIG. Since the flow rate adjusting unit 5 is provided with a constant flow rate element, the flow rate of the concentrated water flowing through the flow rate adjusting unit 5 rises to point A at once when the inlet pressure is generated. That is, approximately, the flow rate at the height of point A flows into the flow rate adjusting unit 5 at the same time as the inlet pressure is generated. At the same time, since the flow rate adjusting unit 5 has a proportional element, the flow rate of the concentrated water flowing through the flow rate adjusting unit 5 increases linearly as the inlet pressure rises.

In addition, in the flow rate adjustment unit 5, the constant flow rate element and the proportional element may be configured integrally or may be configured separately. When configured integrally, for example, the flow direction of the proportional element is aligned with the longitudinal direction of the flow rate adjustment unit 5, and the flow direction of the constant flow rate element is orthogonal to the longitudinal direction of the flow rate adjustment unit 5. It may be configured as Alternatively, the flow direction of the proportional element may be perpendicular to the longitudinal direction of the flow rate adjusting unit 5 and the flow direction of the constant flow rate element may be aligned with the longitudinal direction of the flow rate adjusting unit 5 . Alternatively, both the flow direction of the constant flow rate element and the flow direction of the proportional element may be configured to match the longitudinal direction of the flow rate adjustment unit 5 .

The drainage flow rate adjustment valve 7 is a valve capable of adjusting the drainage flow rate of the concentrated water W42 as the concentrated drainage discharged from the second concentrated water line L42 to the outside of the apparatus. The drainage flow rate adjustment valve 7 is electrically connected to the controller 30 . The valve opening degree of the drainage flow rate adjustment valve 7 is controlled by a drive signal transmitted from the control section 30 . A current value signal (eg, 4 to 20 mA) is sent from the control unit 30 to the drain flow rate adjustment valve 7 to control the valve opening, thereby adjusting the drain flow rate of the concentrated water W42.

The flow rate sensor FM2 is a device that detects, as a detected flow rate value, the flow rate of the concentrated water W42 as the concentrated waste water discharged out of the apparatus from the second concentrated water line L42 after being adjusted by the waste water flow rate adjustment valve 7. The flow rate sensor FM2 is connected to the second concentrated water line L42. The flow rate sensor FM2 is electrically connected to the controller 30 . A detected flow rate value of the concentrated water W42 detected by the flow rate sensor FM2 is transmitted to the control section 30 as a detection signal. As the flow rate sensor FM2, for example, a pulse transmission type flow rate sensor in which an axial flow impeller or a tangential impeller (not shown) is arranged in a flow path housing can be used.

[1.2 Functional Blocks of Control Unit]
The control unit 30 has a CPU, a ROM, a RAM, a CMOS memory, etc., which are known to those skilled in the art and are configured to communicate with each other via a bus.

The CPU is a processor that controls the membrane separation device 1 as a whole. The CPU reads various programs stored in the ROM via the bus, and controls the entire membrane separation apparatus 1 according to the various programs, so that as shown in the functional block diagram of FIG. 301 , integrated water flow calculator 302 , and flushing controller 303 .

The recovery rate calculator 301 calculates the recovery rate in the membrane separation device 1 from the flow rate value of the permeated water W3 measured by the flow rate sensor FM1 and the flow rate value of the concentrated water W42 measured by the flow rate sensor FM2. In particular, the recovery rate calculator 301 calculates the recovery rate both during water supply and during flushing of the membrane separation device 1 .

The accumulated water flow calculation unit 302 calculates the accumulated water flow of the supply water W2 to the RO membrane module 4 during the flushing of the membrane separation device 1 . More specifically, the integrated water flow calculation unit 302 is triggered by a flushing start command in the membrane separation device 1, and thereafter calculates the flow rate of the permeate W3 measured by the flow sensor FM1 and the flow rate of the permeate W3 measured by the flow sensor FM2. and the flow rate value of the concentrated water W42, the integrated flow rate of the supply water W2 to the RO membrane module 4 is calculated.

The flushing control unit 303 terminates the flushing process based on the recovery rate calculated by the recovery rate calculation unit 301 during flushing of the membrane separation device 1 . In particular, in this embodiment, the flushing control unit 303 changes the integrated water flow during flushing calculated by the integrated water flow calculation unit 302 based on the recovery rate calculated by the recovery rate calculation unit 301. When the amount of water (first predetermined amount) required for , is reached, the flushing process is terminated.

FIG. 4 shows the relationship between the recovery rate calculated by the recovery rate calculator 301 and the amount of water required for flushing. Conventionally, it is known that the flushing effect increases as the recovery rate decreases due to a smaller amount of permeated water and an increased amount of concentrated wastewater. Specifically, the amount of water that flows from the primary side inlet to the primary side outlet without passing through the RO membrane is greater than the amount of water that permeates from the primary side inlet to the secondary side of the RO membrane module 4, and the RO membrane surface The flushing effect is enhanced by increasing the flow velocity at , and by increasing the degree of peeling off dirt adhered to the surface of the membrane. That is, the lower the recovery rate, the smaller the amount of water required to achieve the desired flushing effect. Therefore, the amount of water required for flushing monotonically increases as the recovery rate increases. In the graph of FIG. 4, when the recovery rate b during flushing is higher than the recovery rate a during flushing, the amount of water Qa required for flushing at the recovery rate a during flushing is less than the amount Qa required for flushing at the recovery rate b during flushing. The amount of water Qb required for is higher. In addition, in the graph of FIG. 4, the relationship between the recovery rate and the amount of water required for flushing is linear, but it is not limited to this.

In the membrane separation device 1 according to the present embodiment, the relationship between the recovery rate during flushing and the amount of water required for flushing illustrated in FIG. A predetermined amount of 1 may be calculated. Alternatively, in the membrane separation device 1, the relationship between the recovery rate during flushing and the amount of water required for flushing is derived in advance based on empirical rules, and the flushing control unit 303 calculates the first predetermined amount based on this relationship. may

[1.3 Operation of Membrane Separator]
FIG. 5 is a flow chart showing the operation of the membrane separation device 1. As shown in FIG.
In step S<b>1 , the flushing control unit 303 calculates a first predetermined amount based on the recovery rate during flushing calculated by the recovery rate calculation unit 301 .
In step S<b>2 , the cumulative water flow rate calculation unit 302 calculates the cumulative water flow rate to the RO membrane module 4 .

In step S3, if the cumulative amount of water passing through the RO membrane module 4 is equal to or greater than the first predetermined value (S3: YES), the process proceeds to step S4. If the cumulative amount of water passing through the RO membrane module 4 is less than the first predetermined value (S3: NO), the process returns to step S1.

In step S4, the flushing control unit 303 terminates the flushing process and terminates the series of processes.

[1.4 Effects of the first embodiment]
According to the membrane separation device 1 according to the first embodiment described above, for example, the following effects can be obtained.
The membrane separation apparatus 1 according to the first embodiment includes a recovery rate calculation unit 301 that calculates the recovery rate from the flow rate of the permeated water W3 and the flow rate of the concentrated water W4, and the flushing process is terminated based on the recovery rate during flushing. and a flushing control unit 303 .
As a result, when the degree of concentration on the membrane surface decreases rapidly, that is, the amount of water that does not permeate the RO membrane from the primary side inlet to the primary side outlet is greater than the amount of water that permeates from the primary side inlet to the secondary side of the RO membrane module 4. When the flow rate of water increases, the flow velocity on the surface of the RO membrane increases, and the degree of peeling off dirt attached to the surface of the membrane increases. As a result, the amount of water required to achieve a predetermined flushing effect is small, so it is possible to perform flushing with a high water-saving effect.

The membrane separation device 1 further includes an integrated water flow calculation unit 302 that calculates the integrated water flow of the supply water W2. The flushing control unit 303 calculates the integrated water flow during flushing based on the recovery rate during flushing When the calculated predetermined amount is reached, the flushing process is terminated.
By determining the required amount of water during flushing according to the recovery rate during flushing, it is possible to perform flushing with a high water-saving effect.

[2 Second embodiment]
[2.1 Structure of Membrane Separation Apparatus]
Since the overall configuration of the membrane separation device 1A according to the second embodiment of the present invention is basically the same as that of the membrane separation device 1 according to the first embodiment, illustration and description thereof will be omitted. The control unit 30A provided in the membrane separation device 1A according to the second embodiment has a functional block different from that of the control unit 30 provided in the membrane separation device 1 according to the first embodiment. The membrane separation device 1A is different from the membrane separation device 1 according to the first embodiment.

[2.2 Functional Blocks of Control Unit]
FIG. 6 is a functional block diagram of the control section 30A. Unlike the control unit 30, the control unit 30A does not have the integrated water flow calculation unit 302, but has an integrated drainage amount calculation unit 304 instead. Further, the control section 30A has a flushing control section 303A instead of the flushing control section 303. FIG.

The accumulated wastewater amount calculation unit 304 calculates the accumulated amount of concentrated water discharge W42 as concentrated wastewater from the second concentrated water line L42 during flushing of the membrane separation device 1A. More specifically, the integrated waste water amount calculation unit 304 is triggered by a flushing start command in the membrane separation device 1A, and from the flow rate value of the concentrated water W42 measured by the flow sensor FM2 after this, from the second concentrated water line L42 Calculate the accumulated amount of the concentrated water W42 as the concentrated waste water.

The flushing control unit 303A terminates the flushing process based on the recovery rate calculated by the recovery rate calculation unit 301 during flushing of the membrane separation device 1A. In particular, the flushing control unit 303A determines that the accumulated amount of water during flushing calculated by the accumulated amount of water discharge calculation unit 304 is the amount of water required for flushing calculated based on the recovery rate calculated by the recovery rate calculation unit 301 (second When it reaches the predetermined amount), the flushing is terminated.

[2.3 Operation of Membrane Separator]
FIG. 7 is a flow chart showing the operation of the membrane separation device 1A.
In step S<b>11 , the flushing control unit 303</b>A calculates a second predetermined amount based on the recovery rate during flushing calculated by the recovery rate calculation unit 301 .
In step S12, the integrated drainage amount calculation unit 304 calculates the integrated amount of drainage from the second concentrated water line L42.

In step S13, if the cumulative amount of wastewater from the second concentrated water line L42 is equal to or greater than the second predetermined value (S13: YES), the process proceeds to step S14. If the cumulative amount of water discharged from the second concentrated water line L42 is less than the second predetermined value (S13: NO), the process returns to step S11.

In step S14, the flushing control unit 303A ends the flushing process and ends the series of processes.

[2.4 Effect of Second Embodiment]
According to the membrane separation device 1A according to the second embodiment described above, the same effects as those of the membrane separation device 1 according to the first embodiment can be obtained.

In addition, the membrane separation device 1A further includes an integrated drainage volume calculation unit 304 that calculates the integrated drainage volume of the concentrated water W4, and the flushing control unit 303 calculates the integrated drainage volume during flushing based on the recovery rate during flushing. When the predetermined amount is reached, the flushing process is terminated.
By determining the required amount of water during flushing according to the recovery rate during flushing, it is possible to perform flushing with a high water-saving effect.

[3 Third Embodiment]
[3.1 Configuration of Membrane Separation Apparatus]
Since the overall configuration of the membrane separation device 1B according to the third embodiment of the present invention is basically the same as that of the membrane separation device 1 according to the first embodiment, illustration and description thereof will be omitted. The control unit 30B provided in the membrane separation device 1B according to the third embodiment has a functional block different from that of the control unit 30 provided in the membrane separation device 1 according to the first embodiment. The membrane separation device 1B is different from the membrane separation device 1 according to the first embodiment.

[3.2 Functional Blocks of Control Unit]
FIG. 8 is a functional block diagram of the control section 30B. Unlike the controller 30, the controller 30B has a flushing controller 303B instead of the flushing controller 303. FIG.

The flushing control unit 303 terminates the flushing process based on the recovery rate calculated by the recovery rate calculation unit 301 during flushing of the membrane separation device 1 . In particular, in this embodiment, the flushing control unit 303 changes the integrated water flow during flushing calculated by the integrated water flow calculation unit 302 based on the recovery rate calculated by the recovery rate calculation unit 301. When the amount of water (first predetermined amount) required for , is reached, the flushing process is terminated.

The flushing control unit 303B terminates the flushing process based on the recovery rate calculated by the recovery rate calculation unit 301 during flushing of the membrane separation device 1B. In particular, the flushing control unit 303B calculates the integrated water flow during flushing calculated by the integrated water flow calculation unit 302 based on the recovery rate during flushing and the recovery rate during water supply calculated by the recovery rate calculation unit 301. When the calculated amount of water required for flushing (third predetermined amount) is reached, flushing is terminated.

FIG. 9 shows the relationship between the ratio between the recovery rate during flushing and the recovery rate during water supply calculated by the recovery rate calculation unit 301 and the amount of water required for flushing. The concentration ratio of concentrated water is calculated by the following formula (1).
Concentration ratio = 1/(1-recovery rate/100) (1)
Therefore, it is known that the greater the gap between the recovery rate during flushing and the recovery rate during water supply, the greater the difference in the degree of concentration and the greater the flushing effect. That is, the smaller the recovery rate during flushing is compared to the recovery rate during water supply, the smaller the amount of water required to achieve a predetermined flushing effect. Therefore, the amount of water required for flushing monotonically increases as the ratio of the recovery rate during flushing to the recovery rate during water supply increases. In the graph of FIG. 9, when the ratio b of recovery rate during flushing/recovery rate during water supply is higher than the ratio a of recovery rate during flushing/recovery rate during water supply, the ratio a of recovery rate during flushing/recovery rate during water supply is higher. In the case of (b), the water amount Qb required for flushing is higher than the water amount Qa required for flushing. In the graph of FIG. 9, the relationship between the ratio of recovery rate during flushing/recovery rate during water supply and the amount of water required for flushing is linear, but is not limited to this.

In the membrane separation device 1B according to the present embodiment, the relationship between the ratio of recovery rate during flushing/recovery rate during water supply illustrated in FIG. 9 and the amount of water required for flushing is theoretically derived, A third predetermined amount may be calculated based on this relationship. Alternatively, in the membrane separation device 1B, based on empirical rules, the relationship between the ratio of recovery rate during flushing/recovery rate during water supply and the amount of water required for flushing is derived in advance, and based on this relationship, the flushing control unit 303B performs the second 3 may be calculated.

[2.3 Operation of Membrane Separator]
FIG. 10 is a flow chart showing the operation of the membrane separation device 1B.
In step S<b>21 , the flushing control unit 303</b>B calculates a third predetermined amount based on the recovery rate during flushing and the recovery rate during water supply calculated by the recovery rate calculation unit 301 .
In step S<b>22 , the integrated water flow rate calculation unit 302 calculates the integrated water flow rate to the RO membrane module 4 .

In step S23, when the integrated water flow rate is equal to or greater than the third predetermined value (S23: YES), the process proceeds to step S24. If the integrated water flow rate is less than the third predetermined value (S23: NO), the process returns to step S21.

In step S24, the flushing controller 303B terminates the flushing process and terminates the series of processes.

[3.4 Effect of Third Embodiment]
According to the membrane separation device 1B according to the third embodiment described above, effects similar to those of the membrane separation device 1 according to the first embodiment and the membrane separation device 1B according to the second embodiment are obtained.

Further, in the membrane separation apparatus 1B according to the third embodiment, the flushing control unit 303B terminates the flushing process based on the recovery rate during water supply in addition to the recovery rate during flushing. Further, the flushing control unit 303B reduces the third predetermined amount as the ratio of the recovery rate during flushing to the recovery rate during water supply is smaller.
As a result, depending on the level of flushing efficiency, it is possible to perform optimum flushing in terms of water saving effect.

[4 Modifications]
The degree of concentration may be determined by measuring the electrical conductivity in the membrane separation devices 1 to 1B, and the recovery rate calculation unit 301 may calculate the rate of recovery based on this degree of concentration.
Further, in the membrane separation apparatuses 1 to 1B, the amount of water required for flushing and the flushing time may be adjusted based on the water temperature of the feed water W1 or the supply water W2.
Further, in the membrane separation apparatuses 1 to 1B, the water saving effect may be further enhanced by performing a bubbling step in which air is supplied from the lower part of the RO membrane module 4 to rock the bundle of hollow fiber membranes.

Furthermore, in the membrane separation apparatus 1B according to the third embodiment, the flushing control unit 303B derives the amount of water required for flushing based on the ratio of the recovery rate during flushing/recovery rate during water supply. The amount of water required for flushing may be derived based on the difference between the recovery rate at the time of water supply and the recovery rate during water supply.
Further, in the membrane separation apparatus 1B according to the third embodiment, the flushing control unit 303B terminates the flushing process based on the comparison between the cumulative amount of water passing through the RO membrane module 4 and the third predetermined amount. , the flushing process may be terminated based on a comparison between the cumulative amount of water discharged from the second concentrated water line L42 and a third predetermined amount.

Reference Signs List 1, 1A, 1B Membrane separator 2 Pressure pump 3 Pressure-side inverter (inverter)
4 RO membrane module (reverse osmosis membrane module)
5 flow rate adjustment unit 7 drainage flow rate adjustment valve 12 water supply pump 13 water supply side inverter (inverter)
14 Water supply pressure regulating valve FM1, FM2 Flow rate sensor (flow rate detection means)
L1 feed water line L2 feed water line L3 permeated water line L4 concentrated water line L41 first concentrated water line L42 second concentrated water line

Claims (3)

a reverse osmosis membrane module that separates feed water, including feed water, into permeate and concentrate;
a feed water line that supplies feed water to the reverse osmosis membrane module;
a permeated water line for sending permeated water separated by the reverse osmosis membrane module;
a concentrated water line for delivering concentrated water separated by the reverse osmosis membrane module;
a first flow rate measuring means for measuring the flow rate of the permeated water;
a second flow rate measuring means for measuring the flow rate of the concentrated water;
a recovery rate calculation unit that calculates a recovery rate from the flow rate of the permeated water and the flow rate of the concentrated water;
a flushing control unit that performs control to end the flushing process of the reverse osmosis membrane module;
an integrated water flow rate calculation unit that calculates the integrated water flow rate of the water supply and/or an integrated water flow rate calculation section that calculates an integrated water flow rate of the concentrated water as waste water by the second flow rate measuring means ,
The flushing control unit terminates the flushing process when the cumulative water flow rate or the cumulative water discharge rate during flushing reaches a predetermined amount calculated based on the recovery rate. The flushing control unit performs flushing when the cumulative water flow rate or the cumulative water discharge rate during flushing reaches a predetermined amount calculated based on the recovery rate during water supply in addition to the recovery rate during flushing. The membrane separation device according to claim 1 , which terminates the process. The flushing control unit adjusts the predetermined amount as the ratio of the recovery rate during flushing to the recovery rate during water supply is smaller, or the difference obtained by subtracting the recovery rate during flushing from the recovery rate during water supply is larger. 3. The membrane separation device according to claim 2 , wherein .

Images