JP2022035725A - Pure water production system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pure water production system capable of stably supplying water from which a hardness component has been removed to an EDI device in a system in which a water softening device is installed between a reverse osmosis membrane device and an EDI device. SOLUTION: The pure water production system 1 according to the present invention has a back-penetration film device 10 that separates raw water into permeated water and concentrated water by a back-permeation film, and an intermediate treatment in which hardness is removed from the permeated water by ion exchange. The water softening device 20 for producing water, the EDI device 40 for producing treated water in which ions are removed from the intermediate treated water by electroregenerative desalination, and the outlet hardness detection for detecting the hardness of the intermediate treated water flowing out from the water softening device 20. It includes a device 32 and a control device having a hardness reference control unit 341 that causes the water softening device 20 to perform a regeneration operation when the detected value of the outlet hardness detector 32 becomes a predetermined hardness set value or more. [Selection diagram] Fig. 3

Description

The present invention relates to a pure water production system.

Conventionally, a system for producing pure water using an EDI device (Electro Deionization Device) is known. Although the EDI device can remove ions to a high degree, it cannot remove nonionic impurities and the amount of ions that can be removed is small. Therefore, the nonionic impurities in the raw water can be removed and the ion concentration can be removed. Requires pretreatment to reduce to a certain degree. In particular, if the hardness component is brought into the EDI device, it may form a scale and adhere to the inside of the EDI device to hinder electric regeneration, resulting in a problem that the processing performance is significantly deteriorated. Pretreatment for EDI equipment is often performed using reverse osmosis membrane equipment, but usually, reverse osmosis membrane equipment is arranged in multiple stages to reduce the ion concentration of raw water to the extent that it can be processed by EDI equipment. It is necessary to do.

As a pretreatment facility for an EDI device, it has been proposed to arrange a water softening device for ion exchange in front of the reverse osmosis membrane device instead of a configuration in which the reverse osmosis membrane device is arranged in multiple stages (for example, patent). See Document 1). As described above, by using the water softening device, the equipment cost and the operating cost can be reduced as compared with the case where the reverse osmosis membrane device is provided in multiple stages.

Japanese Unexamined Patent Publication No. 2011-20029

Since the reverse osmosis membrane device is a device that separates the water to be treated into permeated water and concentrated water by a reverse osmosis membrane, it is a part of the water to be treated that is costly treated by the reverse osmosis membrane device or the water softening device in the previous stage. Is discharged to the outside of the system as concentrated water. If the discharge of concentrated water is suppressed in order to increase the recovery rate (ratio of permeated water to the amount of untreated water supplied) of the reverse osmosis membrane device, stains and scale components will adhere due to overconcentration, and the reverse osmosis membrane will be adhered. It can be rather inefficient due to the increased frequency of cleaning.

In view of such circumstances, a system configuration in which a water softening device is installed between the reverse osmosis membrane device and the EDI device can be considered. By installing a water softening device between the reverse osmosis membrane device and the EDI device, the entire amount of intermediate treated water from which the hardness is removed by the water softening device from the permeated water of the reverse osmosis membrane device can be supplied to the EDI device. The utilization efficiency of the water softener is high, and pure water can be produced at a relatively low cost.

However, since the hardness removing performance of the water softening device is limited, leakage of the hardness will occur unless regeneration is performed at an appropriate timing. In a system in which a water softening device is installed between a reverse osmosis membrane device and an EDI device, the hardness leaked from the water softening device is supplied to the EDI device as it is, which is a cause of fatal damage to the EDI device. Can be.

An object of the present invention is to provide a pure water production system capable of stably supplying water from which hardness is removed to an EDI device in a system in which a water softening device is installed between a reverse osmosis membrane device and an EDI device.

The pure water production system according to one aspect of the present invention uses a back-penetration membrane device that separates raw water into permeated water and concentrated water by a back-permeation membrane, and intermediate-treated water from which the hardness is removed from the permeated water by ion exchange. A water softening device to be manufactured, an EDI device for manufacturing treated water in which ions are removed from the intermediate treated water by electroregenerative desalination, and an outlet hardness detector for detecting the hardness of the intermediate treated water flowing out of the soft water device. A control device having a hardness reference control unit for causing the water softening device to perform a regeneration operation when the detection value of the outlet hardness detector becomes a predetermined hardness set value or more.

The pure water production system includes an inlet hardness detector that detects the hardness of the permeated water introduced into the water softening device, and the permeated water introduced into the water softening device or the intermediate treated water derived from the water softening device. The control device further includes a flow rate detector for detecting the flow rate of the water, and the control device has a time integral value of the product of the detection value of the inlet hardness detector and the detection value of the flow rate detector of a predetermined total amount set value or more. It may further have a total amount reference control unit for causing the water softening device to perform a regeneration operation in the event of a failure.

The pure water production system according to another aspect of the present invention includes a back-penetration membrane device that separates raw water into permeated water and concentrated water by a back-permeation membrane, and intermediate treated water from which hardness is removed from the permeated water by ion exchange. An EDI device for producing treated water from which ions have been removed from the intermediate treated water by electroregenerative desalination, and an inlet hardness detector for detecting the hardness of the permeated water introduced into the water softening device. A flow rate detector that detects the flow rate of the permeated water introduced into the water softening device or the intermediate treated water derived from the water softening device, and the detection values of the inlet hardness detector and the detection values of the flow rate detector. A control device including a total amount reference control unit for causing the water softening device to perform a regeneration operation when the time-integrated value of the product with and is equal to or greater than a predetermined total amount set value is provided.

In the pure water production system, a plurality of the water softening devices are arranged in parallel, and when the control device causes the water softening device to perform the regeneration operation, at least one other water softening device is operated from the permeated water to the intermediate. Treated water may be derived.

When the water softening device is allowed to perform the regeneration operation, the control device may bypass the water softening device during the regeneration operation and mix the permeated water with the intermediate treated water derived from the other water softening device. good.

The pure water production system may further include a degassing device for removing dissolved gas from the intermediate treated water.

The water softening device may supply the regenerating liquid to a plurality of places during the regenerating operation.

The reverse osmosis membrane device may be controlled so that the flow rate of the permeated water becomes constant.

According to the present invention, in a system in which a water softening device is installed between a reverse osmosis membrane device and an EDI device, it is possible to provide a pure water production system capable of stably supplying water from which hardness is removed to the EDI device.

It is an overall block diagram of the pure water production system which concerns on one Embodiment of this invention. It is a detailed block diagram of the upstream part of the pure water production system of FIG. It is a detailed block diagram of the middle-flow part of the pure water production system of FIG. It is a detailed block diagram of the downstream part of the pure water production system of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of the pure water production system 1 of the present invention. FIG. 2 is a detailed configuration diagram of an upstream portion of the pure water production system 1. FIG. 3 is a detailed configuration diagram of the middle flow portion of the pure water production system 1. FIG. 4 is a detailed configuration diagram of a downstream portion of the pure water production system 1.

The pure water production system 1 of the present embodiment is arranged in parallel with a reverse osmosis membrane device 10 that separates raw water into permeated water and concentrated water by a reverse osmosis membrane, and each of them has a hardness component from the permeated water by ion exchange. A plurality of water softening devices 20 for producing the removed intermediate treated water and a degassing device 30 for removing dissolved gas from the intermediate treated water are arranged in parallel, and the intermediate treated water is each arranged by electroregenerative desalination. A plurality of EDI devices 40 for producing treated water from which ions have been removed from the water are provided.

As shown in FIG. 2, the pure water production system 1 is associated with the reverse osmosis membrane device 10 and has a raw water tank 11 for storing raw water and a raw water supply line for supplying raw water from the raw water tank 11 to the reverse osmosis membrane device 10. It is provided with L11, a permeation water lead-out line L12 that draws out permeated water from the reverse osmosis membrane device 10, and a concentrated water line L13 that discharges concentrated water from the reverse osmosis membrane device 10 to the outside of the system.

More specifically, the pure water production system 1 includes a raw water quality detector 12, a raw water pump 13, an inverter 14, a permeated water flow rate detector 15, a concentrated water flow rate detector 16, and a concentrated water discharge control valve 17. , And a membrane separation control device 18. The raw water quality detector 12 is provided in the raw water tank 11 and detects the electric conductivity of the raw water. The raw water pump 13 is provided in the raw water supply line L11 and supplies the raw water to the reverse osmosis membrane device 10 by pressurizing the raw water. The inverter 14 supplies the raw water pump with electric power having a drive frequency corresponding to the input command signal. The permeated water flow rate detector 15 is provided in the permeated water lead-out line L12 and detects the flow rate of the permeated water flowing out from the reverse osmosis membrane device 10. The concentrated water flow rate detector 16 is provided in the concentrated water line L13, and detects the flow rate of the concentrated water discharged from the concentrated water line L13 to the outside of the system. The concentrated water discharge control valve 17 is provided in the concentrated water line L13, and regulates the flow rate of the concentrated water discharged from the concentrated water line L13 to the outside of the system. The membrane separation control device 18 outputs a command signal to the inverter 14 according to the detection values of the raw water quality detector 12, the permeated water flow rate detector 15, and the concentrated water flow rate detector 16, and also outputs a command signal to the inverter 14 and of the concentrated water discharge control valve 17. Adjust the opening.

Further, as shown in detail in FIG. 3, the pure water production system 1 is attached to the water softening device 20 from the permeated water tank 21 for storing the permeated water supplied through the permeated water lead-out line L12 and the permeated water tank 21. The permeated water supply line L21 that supplies the permeated water to each softening device 20, and the intermediate treated water lead-out line L22 that draws out the intermediate treated water from each softened water device 20 and merges the intermediate treated water and supplies it to the degassing device 30. , Bypassing a part of the permeated water from the permeated water supply line L21 to the intermediate treated water lead-out line L22 by bypassing the permeated water device 20, the bypass line L23 for mixing the permeated water with the intermediate treated water, and each softened water device 20. A sampling line L24 for sampling the intermediate treated water derived from the water softening device 20 and a regenerating liquid line L25 for supplying the regenerating liquid to each water softening device 20 are provided.

More specifically, the pure water production system 1 includes an inlet hardness detector 22, a permeation water pump 23, a plurality of intermediate treated water flow detectors 24, a plurality of intermediate treated water shutoff valves 26, and a bypass flow detector 27. A bypass flow control valve 28, a bypass shutoff valve 29, a plurality of sampling valves 31, an outlet hardness detector 32, a regenerating liquid tank 33, and a water softening control device 34 are provided.

The inlet hardness detector 22 is provided in, for example, the permeated water tank 21, and detects the hardness of the permeated water supplied to the water softening device 20. The inlet hardness detector 22 may be provided on the permeated water supply line L21. The permeated water pump 23 is provided in the permeated water supply line L21 and supplies the permeated water to the water softening device 20 by pressurizing the permeated water. The intermediate treated water flow rate detector 24 is provided in the intermediate treated water lead-out line L22, and detects the flow rate of the intermediate treated water led out from each of the soft water softening devices 20. The intermediate treated water flow rate adjusting valve 25 is provided in the intermediate treated water lead-out line L22, and adjusts the flow rate of the intermediate treated water led out from each of the water softening devices 20. The intermediate treated water shutoff valve 26 is provided in the intermediate treated water lead-out line L22, and shuts off the lead-out of the intermediate treated water from each of the soft water softening devices 20. The bypass flow rate detector 27 is provided on the bypass line L23 and detects the flow rate of the permeated water passing through the bypass line L23. The bypass flow rate adjusting valve 28 is provided on the bypass line L23 and regulates the flow rate of the permeated water passing through the bypass line L23. The bypass shutoff valve 29 is provided in the bypass line L23 and shuts off the supply of permeated water to the intermediate treated water lead-out line L22. The sampling valve 31 is provided in the sampling line L24 and enables introduction of the intermediate treated water derived from each water softening device 20 into the sampling line L24. The outlet hardness detector 32 is provided on the sampling line L24 and detects the hardness of the intermediate treated water flowing out from the water softening device 20. The regenerating liquid tank 33 is connected to the regenerating liquid line L25, and supplies the regenerating liquid to the water softening device 20 via the regenerating liquid line L25. The water softening control device 34 controls the operations of the water softening device 20, the intermediate treated water flow rate adjusting valve 25, the intermediate treated water shutoff valve 26, the bypass flow rate adjusting valve 28, the bypass shutoff valve 29, and the sampling valve 31.

Further, as shown in detail in FIG. 4, the pure water production system 1 is attached to the EDI device 40 and supplies the degassed intermediate treated water flowing out from the degassing device 30 to each EDI device 40. It includes a supply line L41, a treated water line L42 that draws out treated water from each EDI device 40, and a treated water tank 41 that stores the treated water led out from the treated water line L42.

The membrane separation control device 18 preferably controls the reverse osmosis membrane device 10 so that the flow rate of the permeated water becomes constant. By controlling the reverse osmosis membrane device 10 so that the flow rate of the permeated water becomes constant, the capacity of the permeated water tank 21 for storing the permeated water can be reduced. Specifically, it is preferable that the membrane separation control device 18 feedback-controls the output frequency of the inverter 14 that drives the raw water pump 13 so that the flow rate of the permeated water detected by the permeated water flow rate detector 15 becomes constant.

Further, the membrane separation control device 18 determines the recovery rate of the reverse osmosis membrane device 10 (the ratio of the flow rate of the permeated water to the flow rate of the raw water supplied from the raw water tank 11) to the water quality of the raw water (in this embodiment, the raw water quality detector). The value may be adjusted to a value set according to the electrical conductivity detected by 12. As a result, scaling of the reverse osmosis membrane on the membrane surface can be prevented, and stable operation of the water softening device 20 and the EDI device becomes possible, so that high-quality pure water can be produced. Specifically, the membrane separation control device 18 sets the target value of the recovery rate to a smaller value as the electric conductivity detected by the raw water quality detector 12 is higher, and the detection value of the permeated water flow rate detector 15 and the concentrated water. It is preferable to adjust the opening degree of the concentrated water discharge adjusting valve 17 so that the ratio of the detected value of the permeated water flow detector 15 to the sum of the detected values of the flow detector 16 is maintained at the set target value.

The water softening device 20 has an exchange layer formed of an ion exchanger that replaces a hardness component (for example, calcium ion, magnesium ion, etc.) in the inflowing permeated water with sodium ion or the like. When the ion exchanger releases all the sodium ions, the hardness component cannot be removed any more. Therefore, the regenerated liquid is supplied from the regenerating liquid line L25 to replace the hardness component adsorbed by the ion exchanger with sodium ions. It is necessary to perform the regeneration operation of the water softening device 20.

The water softening control device 34 is a detection value of the intermediate treatment water flow rate detector 24 corresponding to the opening degree of each intermediate treatment water flow rate adjusting valve 25 so that the amount of the intermediate treatment water flowing out from each water softening device 20 is constant. Adjust based on.

The water softening control device 34 opens a plurality of sampling valves 31 in order, and supplies a sample of the intermediate treated water flowing out of the water softening device 20 to the outlet hardness detector 32. The sampling of this intermediate treatment water is sufficiently small compared to the entire flow rate of the intermediate treatment water. Instead of providing the sampling line L24, an outlet hardness detector 32 may be provided in the outlet flow path of each water softening device 20.

The water softening control device 34 has a hardness reference control unit 341 that causes the water softening device 20 to perform a regeneration operation when the detection value of the outlet hardness detector 32 is equal to or higher than a predetermined hardness set value, and a detection value of the inlet hardness detector 22. It has a total amount reference control unit 342 that causes the water softening device to perform a regeneration operation when the time integrated value of the product of the intermediate treated water flow rate detector 24 and the detected value becomes equal to or more than a predetermined total amount set value.

The hardness reference control unit 341 performs a regeneration operation for restoring the ion exchange capacity to the water softening device 20 that flows out the intermediate treated water having a high hardness when the hardness of the intermediate treated water flowing out from any of the water softening devices 20 becomes high. By doing so, it is possible to prevent the EDI device 40 from being accidentally supplied with water having a high hardness and causing trouble.

Further, the total amount reference control unit 342 is configured to regenerate the ion exchanger in the regenerating device when the cumulative amount of the hardness components flowing into each water softening device 20 exceeds the total amount set value. The breakthrough of 20 can be predicted in advance to keep the hardness of the intermediate treated water supplied to the EDI apparatus at a lower level.

In the water softening control device 34, the hardness reference control unit 341 and the total amount reference control unit 342 monitor the ion exchange capacity of the water softening device 20 according to different standards, and one of them states that the ion exchange capacity of the water softening device 20 is reduced. If it is determined, the water softening device 20 may be configured to perform a regeneration operation. Further, the water softening control device 34 may simultaneously perform control or the like to cause the water softening device 20 to perform a regeneration operation at regular time intervals.

When the water softening device 20 is allowed to perform the regeneration operation, the water softening control device 34 supplies the permeated water to at least one other water softening device 20 to derive the intermediate treated water. Preferably, the water softening control device 34 prevents the plurality of water softening devices 20 from simultaneously performing the regeneration operation. As a result, even if the buffer tank is not provided on the downstream side of the water softening device 20, it is not necessary to stop the supply of the intermediate treated water to the degassing device 30 and thus the EDI device 40 by the regeneration operation of the water softening device 20. Further, even if it is provided between the water softening device 20 and the EDI device 40, the capacity of the buffer tank can be reduced, so that the equipment cost can be reduced.

Further, when the water softening control device 34 causes the water softening device 20 to perform the regeneration operation, the permeated water is led out from the other water softening device 20 by bypassing the water softening device 20 during the regeneration operation via the bypass line L23. The bypass shutoff valve 29 is controlled so as to be mixed with the treated water. When any of the soft water devices 20 performs the regeneration operation, the permeated water having a flow rate corresponding to the intermediate treated water from the soft water device 20 is mixed with the intermediate treated water flowing out from the other soft water device 20, so that each soft water is softened. While the flow rate of the device 20 is kept constant, the flow rate of the intermediate treated water supplied to the degassing device 30 and thus the EDI device 40 can be kept constant. As a result, the operation of the EDI device 40 can be continued at a constant flow rate without providing a buffer tank on the downstream side of the water softening device 20. Therefore, the water softening control device 34 opens the bypass flow rate adjusting valve 28 so as to adjust the flow rate of the permeated water mixed with the intermediate treated water from the bypass line L23 according to the number of the water softening devices 20 performing the regeneration operation. It is desirable to adjust the degree based on the detection value of the bypass flow rate detector 27.

It is preferable that the water softening device 20 performs split flow regeneration in which the regeneration liquid is supplied to a plurality of locations during the regeneration operation. Specifically, in the water softening device 20, it is preferable that the regenerated liquid is supplied to both the upper end portion and the lower end portion of the exchange layer, and the regenerated liquid is discharged from the substantially central portion of the exchange layer. In this way, by dividing the exchange layer into a plurality of portions and inserting the regenerating liquid, the ion exchanger can be efficiently regenerated.

By removing the dissolved gas from the intermediate treated water, the degassing device 30 can suppress the deterioration of the performance of the EDI device 40 due to the dissolved gas. As the deaeration device 30, a decarboxylation device is typically used. The pure water production system 1 may include a plurality of degassing devices 30 installed in multiple stages, or may include a plurality of degassing devices installed in parallel.

The EDI device 40 is arranged in parallel in a number capable of processing the entire amount of the intermediate treated water supplied from the water softening device 20 via the degassing device 30. Each EDI device 40 separates the intermediate treated water into treated water (pure water) from which ions have been removed and concentrated water in which ions have been concentrated.

The pure water production system 1 is configured to supply the EDI device 40 with the intermediate treated water from which the ions have been removed from the permeated water of the reverse osmosis membrane device 10 by the water softening device 20, so that the total amount of the intermediate treated water flowing out from the water softening device is reached. Can be supplied to the EDI device 40. Therefore, the pure water production system 1 has high utilization efficiency of the water softening device 20, and can produce pure water at a relatively low cost.

In the pure water production system 1, the water softening control device 34 causes the water softening device 20 to perform a regeneration operation for recovering the ion exchange capacity when the hardness of the intermediate treated water becomes high, so that the hardness of the EDI device is erroneously increased. It is prevented from being supplied with high water and causing trouble.

The pure water production system 1 includes a plurality of water softening devices 20 arranged in parallel, and the water softening control device 34 may stop the supply of intermediate treated water at the same time by all the water softening devices 20 due to the regeneration of the ion exchanger. Since the permeated water is supplied from the bypass line L23 to the downstream side so as to compensate for the decrease in the flow rate of the intermediate treated water due to the soft water device 20 which is controlled so as not to be regenerated and is being regenerated, the intermediate treatment is performed on the EDI device even if there is no buffer tank. Water can be supplied continuously.

Although the preferred embodiments of the pure water production system of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be appropriately modified.

In the pure water production system according to the present invention, either the hardness standard control unit or the total amount standard control unit may be omitted. In the pure water production system according to the present invention, each water softening device may have a bypass flow path for supplying permeated water to the downstream side without passing through the ion exchanger during the regeneration operation. Further, the pure water production system according to the present invention may be further provided with a further configuration that does not impair the effect of the present invention, such as a flow path for recirculating incompletely processed water flowing out at the start of each device to the upstream side. good.

1 Pure water production system 10 Reverse permeation membrane device 11 Raw water tank 12 Raw water quality detector 13 Raw water pump 14 Inverter 15 Permeated water flow rate detector 16 Concentrated water flow rate detector 17 Concentrated water discharge control valve 18 Film separation control device 20 Soft water device 21 Permeated water tank 22 Inlet hardness detector 23 Permeated water pump 24 Intermediate treated water flow rate detector 25 Intermediate treated water flow control valve 26 Intermediate treated water shutoff valve 27 Bypass flow rate detector 28 Bypass flow control valve 29 Bypass shutoff valve 30 Degassing device 31 Sampling valve 32 Outlet hardness detector 33 Regenerating liquid tank 34 Softening control device 341 Hardness standard control unit 342 Total amount standard control unit 40 EDI device 41 Treated water tank L11 Raw water supply line L12 Permeated water lead-out line L13 Concentrated water line L21 Permeated water Supply line L22 Intermediate treated water lead-out line L23 Bypass line L24 Sampling line L25 Recycled liquid line L41 Intermediate treated water supply line L42 Treated water line

Claims (8)

A reverse osmosis membrane device that separates raw water into permeated water and concentrated water using a reverse osmosis membrane.
A water softening device that produces intermediate treated water from which hardness is removed from the permeated water by ion exchange, and
An EDI device that produces treated water from which ions have been removed from the intermediate treated water by electroregenerative desalination, and
An outlet hardness detector that detects the hardness of the intermediate treated water flowing out of the water softening device, and
A control device having a hardness reference control unit that causes the water softening device to perform a regeneration operation when the detection value of the outlet hardness detector is equal to or higher than a predetermined hardness set value.
A pure water production system. An inlet hardness detector that detects the hardness of the permeated water introduced into the water softening device, and
A flow rate detector that detects the flow rate of the permeated water introduced into the water softening device or the intermediate treated water derived from the water softening device.
Further prepare
The control device is a total amount reference for causing the water softening device to perform a regeneration operation when the time integral value of the product of the detection value of the inlet hardness detector and the detection value of the flow rate detector becomes a predetermined total amount set value or more. The pure water production system according to claim 1, further comprising a control unit. A reverse osmosis membrane device that separates raw water into permeated water and concentrated water using a reverse osmosis membrane.
A water softening device that produces intermediate treated water from which hardness is removed from the permeated water by ion exchange, and
An EDI device that produces treated water from which ions have been removed from the intermediate treated water by electroregenerative desalination, and
An inlet hardness detector that detects the hardness of the permeated water introduced into the water softening device, and
A flow rate detector that detects the flow rate of the permeated water introduced into the water softening device or the intermediate treated water derived from the water softening device.
A control provided with a total amount reference control unit for causing the water softening device to perform a regeneration operation when the time integral value of the product of the detection value of the inlet hardness detector and the detection value of the flow rate detector becomes equal to or more than a predetermined total amount set value. With the device
A pure water production system. A plurality of the water softening devices are arranged in parallel,
The pure water production system according to any one of claims 1 to 3, wherein the control device causes at least one other water softening device to derive the intermediate treated water when the water softening device is allowed to perform the regeneration operation. When the water softening device is allowed to perform the regeneration operation, the control device bypasses the water softening device during the regeneration operation and mixes the permeated water with the intermediate treated water derived from the other water softening device. Item 4. The pure water production system according to Item 4. The pure water production system according to any one of claims 1 to 5, further comprising a degassing device for removing dissolved gas from the intermediate treated water. The pure water production system according to any one of claims 1 to 6, wherein the water softening device supplies a regenerated liquid to a plurality of locations during the regenerating operation. The pure water production system according to any one of claims 1 to 7, wherein the reverse osmosis membrane device is controlled so that the flow rate of the permeated water becomes constant.

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