JP6889628B2 - Pure water production equipment and pure water production method - Google Patents

Description

The present invention relates to a pure water production apparatus and a pure water production method for performing reverse osmosis membrane treatment.

For pure water production equipment that produces pure water using an RO (Reverse Osmosis Membrane) device, EDI (Electro Deionization: Some are equipped with an electric deionized water production device (see Patent Document 1).

In the above pure water production apparatus, when the temperature of the raw water treated by the RO apparatus fluctuates, the amount of permeated water, which is the amount of permeated water that permeates the RO apparatus, changes. For example, the lower the temperature of raw water, the lower the amount of permeated water.

The EDI at the rear stage of the RO device may not operate normally when the amount of permeated water decreases. For example, in EDI, since electricity is passed through the permeated water of the RO device, the permeated water generates heat, but when the amount of permeated water decreases, the temperature of the permeated water and EDI rises due to the heat generation, which causes a failure. There is a risk of becoming. Further, in EDI, since bubbles are generated in the electrodes, if the amount of permeated water decreases, the bubbles do not flow, the flow path is filled with gas, and the permeated water does not flow.

For this reason, in a pure water production device equipped with EDI, a heating means for heating raw water is usually arranged in front of the RO device, and the temperature of the raw water flowing into the RO device is maintained constant by controlling the heating means. ing.

Japanese Unexamined Patent Publication No. 2006-255651

In a pure water production device that maintains a constant temperature of raw water using a heating means, when the heating means is stopped when the production of pure water is stopped, the temperature of the raw water becomes higher than the temperature at which EDI operates normally. It may be low. In this case, even if the heating means is restarted in order to restart the production of pure water, the EDI cannot be operated normally immediately, and the production efficiency of pure water is lowered.

In order to increase the efficiency of producing pure water, the heating means must be continuously driven even when pure water is not produced, which is costly. In particular, when a heat exchanger that transfers heat from a boiler used for various purposes to raw water is used as a heating means, the boiler is driven even when the boiler is not used for other purposes such as on holidays and at night. It has to be kept, and there is a lot of waste.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a pure water production apparatus and a pure water production method capable of improving the production efficiency of pure water while reducing the cost. To do.

The pure water production apparatus according to the present invention includes a reverse osmosis membrane apparatus that performs reverse osmosis membrane treatment on water to be treated and separates the water to be treated into permeated water and concentrated water, and deionization treatment on the permeated water. An electric deionized water producing apparatus for performing the above, a pump for sending the water to be treated to the reverse osmosis membrane apparatus, a first temperature detecting unit for detecting the temperature of the water to be treated, and a first temperature detecting unit. When the temperature falls below a predetermined temperature, the supply of the permeated water to the electric deionized water production apparatus is stopped, at least a part of the permeated water and the concentrated water is returned to the front stage of the pump, and the permeated water is heated by the pump. It has a control unit for executing the first circulation operation.

The pure water production method according to the present invention includes a reverse osmosis membrane device that performs reverse osmosis membrane treatment on water to be treated and separates the water to be treated into permeated water and concentrated water, and deionization treatment on the permeated water. This is a pure water production method using a pure water production device having an electric deionized water production device for performing the above and a pump for sending the water to be treated to the reverse osmosis membrane device, and detects the temperature of the water to be treated. When the step and the temperature fall below the first predetermined temperature, the supply of the permeated water to the electric deionized water production apparatus is stopped, and at least a part of the permeated water and the concentrated water is supplied to the pump. refluxed in front, and executing the first circulation operation you heat pump, the.

According to the present invention, it is possible to improve the production efficiency of pure water while reducing the cost.

It is a block diagram which shows the structure of the pure water production apparatus of 1st Embodiment of this invention. It is a block diagram which shows the structure of the pure water production apparatus of the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, those having the same function may be designated by the same reference numerals and the description thereof may be omitted.

(First Embodiment)
FIG. 1 is a configuration diagram showing a configuration of a pure water production apparatus according to the first embodiment of the present invention. The pure water production apparatus 100 shown in FIG. 1 includes a raw water tank 1, a pressurizing pump 2, a heat exchanger 3, an RO (reverse osmosis membrane) apparatus 4, three-way valves 5 and 6, a thermometer 7, and the like. It has an EDI (electric deionized water production apparatus) 8, a treated water tank 9, and a control panel 10.

The raw water tank 1 is a container for accommodating raw water (water to be treated) supplied from the outside of the pure water production apparatus 100. The pressurizing pump 2 is a pump that sends the raw water contained in the raw water tank 1 to the RO device 4.

The heat exchanger 3 is provided between the raw water tank 1 and the RO device 4, and is a heating unit that heats the raw water sent to the RO device 4 to adjust the temperature of the raw water. Specifically, the heat exchanger 3 heats the raw water by transferring the heat from the boiler 200 to the raw water. The boiler 200 may be a general-purpose boiler, and may be shared not only with the pure water production device 100 but also with other devices (not shown). The heating unit (heat exchanger 3) may be provided in front of the raw water tank 1. Further, the heating unit is preferably a heat exchanger as in the present embodiment, but may be another device such as an electric heater.

The RO device 4 performs a reverse osmosis membrane treatment on the raw water sent by the pressurizing pump 2 to remove impurities in the raw water, thereby concentrating the raw water with the permeated water from which the impurities have been removed and the impurities. Separate into concentrated water. The amount of permeated water in the RO device 4 varies depending on the temperature of the raw water and the like. Specifically, the lower the temperature of the raw water, the smaller the amount of permeated water. The permeated water separated by the RO device 4 is sent to the three-way valve 5. A part of the concentrated water separated by the RO device 4 is returned to the raw water tank 1 for water saving, and the rest is sent to the three-way valve 6.

The three-way valve 5 is a switching unit that switches the destination of the permeated water from the RO device 4 to either the raw water tank 1 or the EDI8. The three-way valve 6 is a switching unit that switches the destination of the concentrated water from the RO device 4 to either the raw water tank 1 or the outside of the pure water production device 100. The switching unit is not limited to the three-way valve as long as it can switch the destination of the permeated water or the concentrated water.

The thermometer 7 is a first temperature detection unit that detects the temperature of raw water. In the present embodiment, the thermometer 7 is provided between the RO device 4 and the three-way valve 5 and detects the temperature of the permeated water as the temperature of the raw water, but between the pressurizing pump 2 and the RO device 4. The temperature of the raw water supplied to the RO device 4 may be directly detected. It is desirable that the thermometer 7 be provided as close as possible to the RO device 4.

The EDI8 deionizes the permeated water of the RO device 4 to separate the treated water from which the ions in the permeated water have been removed and the ion-concentrated water in which the ions are concentrated. The treated water separated by EDI8 is sent to the treated water tank 9. In order for the EDI8 to operate normally, a certain amount of water is required for the permeated water. A part of the ion-concentrated water is returned to the raw water tank 1 to save water, and the rest is drained to the outside of the pure water production apparatus 100.

The treated water tank 9 is a container for accommodating the treated water from the EDI 8. The treated water tank 9 is provided with a water level gauge 9a for measuring the water level of the treated water contained in the treated water tank 9. The treated water contained in the treated water tank 9 is sent to the use point as needed.

The control panel 10 is a pure water production apparatus based on the temperature of raw water detected by the thermometer 7, the state of the heat exchanger 3, the water level in the treated water tank 9 detected by the water level gauge 9a, and the like. It is a control unit that controls 100.

For example, when the heat exchanger 3 is in the driving state, the control panel 10 operates normally. In normal operation, the control panel 10 drives the pressurizing pump 2, the destination of the permeated water by the three-way valve 5 is EDI8, and the destination of the concentrated water by the three-way valve 6 is the outside. As a result, the permeated water of the RO device 4 is sent to the EDI 8 via the three-way valve 5. Further, a part of the concentrated water of the RO device 4 is discharged to the outside through the three-way valve 6, and the rest is returned to the raw water tank 1.

Then, the control panel 10 controls the heat exchanger 3 so that the temperature of the raw water detected by the thermometer 7 falls within a predetermined set temperature range. The set temperature range is a temperature range in which the amount of permeated water that permeates the RO device 4 is the amount of water that allows the EDI8 to operate normally. In this embodiment, the set temperature range is 22 ° C to 28 ° C.

During normal operation, when the water level in the treated water tank 9 detected by the water level gauge 9a exceeds the first predetermined water level, the control panel 10 stops the pressurizing pump 2 to stop the normal operation. After that, when the treated water in the treated water tank 9 is used, that is, the water is sent to the use point, and the water level in the treated water tank 9 falls below the second predetermined water level lower than the first predetermined water level, the control panel 10 Drives the pressurizing pump 2 to resume normal operation.

Further, when the heat exchanger 3 is stopped, the control panel 10 stops the pressurizing pump 2. Then, when the temperature of the raw water detected by the thermometer 7 falls below the first predetermined temperature, the control panel 10 performs a circulation operation (first circulation operation). The first predetermined temperature is preferably equal to or lower than the lower limit of the set temperature range, and more preferably the lower limit of the set temperature range. In the present embodiment, the first predetermined temperature is the lower limit value (22 ° C.) of the set temperature range.

In the circulation operation, the control panel 10 drives the pressurizing pump 2 by setting the destination of the permeated water by the three-way valve 5 and the destination of the concentrated water by the three-way valve 6 to the raw water tank 1, respectively. As a result, the control panel 10 returns the permeated water and the concentrated water of the RO device 4 to the raw water tank 1 in front of the pressurizing pump 2. Therefore, the raw water sent from the raw water tank 1 is returned to the raw water tank 1, and a circulating flow is generated in the pure water production apparatus 100. It is desirable that all of the permeated water and the concentrated water be returned to the raw water tank 1 as in the present embodiment, but at least a part of the permeated water and the concentrated water may be returned to the raw water tank 1.

Since the circulating flow in the pure water production apparatus 100 is heated by the operating heat of the pressurizing pump 2, the temperature of the circulating flow rises, and as a result, the temperature of the raw water detected by the thermometer 7 also rises. Then, when the temperature of the raw water exceeds the second predetermined temperature, the control panel 10 stops the pressurizing pump 2. The second predetermined temperature is equal to or higher than the first predetermined temperature, and is preferably the upper limit of the set temperature range. In the present embodiment, the second predetermined temperature is the upper limit value (28 ° C.) of the set temperature range.

The state of the heat exchanger 3 may be automatically detected by measuring the temperature of steam from the boiler 200 or the like, or may be input by the manager of the pure water production apparatus 100.

Next, the operation will be described.

When the heat exchanger 3 is in the driving state, the control panel 10 sets the destination of the permeated water by the three-way valve 5 to EDI8 and the destination of the concentrated water by the three-way valve 6 to the outside. The control panel 10 determines whether or not the water level detected by the water level gauge 9a exceeds the first predetermined water level.

When the water level does not exceed the first predetermined water level, the control panel 10 performs normal operation. That is, the control panel 10 drives the pressurizing pump 2 and controls the heat exchanger 3 so that the temperature of the raw water detected by the thermometer 7 falls within the set temperature range.

As a result, the raw water is sent from the raw water tank 1 to the RO device 4 via the heat exchanger 3 by the pressurizing pump 2. The raw water is separated into permeated water and concentrated water by the RO device 4. A part of the concentrated water is returned to the raw water tank 1, and the rest is drained to the outside through the three-way valve 6. The permeated water is sent to the EDI 8 via the three-way valve 5. Since the permeated water sent to the EDI8 is heated so that the raw water falls within the set temperature range when passing through the heat exchanger 3, the EDI8 operates normally, and the permeated water is ion-concentrated with the treated water. Separate with water. A part of the ion-concentrated water is returned to the raw water tank 1, and the rest is drained to the outside. The treated water is sent to the treated water tank 9 and stored in the treated water tank 9.

On the other hand, when the water level exceeds the first predetermined water level, the control panel 10 stops the pressurizing pump 2. Then, when the treated water in the treated water tank 9 is used and the water level falls below the second predetermined water level, the control panel 10 performs normal operation.

When the heat exchanger 3 is stopped, the control panel 10 stops the pressurizing pump 2. Then, when the temperature of the raw water falls below the first predetermined temperature, the control panel 10 performs a circulation operation. That is, the control panel 10 drives the pressurizing pump 2 by setting the destination of the permeated water by the three-way valve 5 and the destination of the concentrated water by the three-way valve 6 as the raw water tank 1.

As a result, the raw water is sent from the raw water tank 1 to the RO device 4 via the heat exchanger 3 by the pressurizing pump 2. The raw water is separated into permeated water and concentrated water by the RO device 4. A part of the concentrated water is directly returned to the raw water tank 1, and the rest is returned to the raw water tank 1 via the three-way valve 6. The permeated water is also returned to the raw water tank 1 via the three-way valve 5. Therefore, the raw water sent from the raw water tank 1 is returned to the raw water tank 1, and a circulating flow is generated in the pure water production apparatus 100. At this time, the circulating flow is heated by the operating heat of the pressurizing pump 2, and the temperature of the raw water rises.

After that, the control panel 10 stops the pressurizing pump 2 when the temperature of the raw water exceeds the second predetermined temperature. As a result, the circulating flow is stopped and operating heat is not generated from the pressurizing pump 2, so that the temperature of the raw water decreases. After that, when the temperature of the raw water falls below the first predetermined temperature, the control panel 10 performs a circulation operation.

As described above, according to the present embodiment, when the temperature of the raw water falls below the first predetermined temperature, the control panel 10 stops the supply of the permeated water to the EDI8, and at least a part of the permeated water and the concentrated water. Is executed in the first circulation operation in which the water is returned to the front stage of the pressurizing pump 2. As a result, a circulating flow is generated in the pure water production apparatus 100, and the circulating flow is heated by the operating heat of the pressurizing pump 2, so that the temperature of the raw water rises. Therefore, even if there is no heating unit in front of the RO device 4, or even if the heating unit is stopped, the temperature of the raw water can be maintained within a certain range. It becomes possible to improve the manufacturing efficiency.

Further, in the present embodiment, the control panel 10 stops the pump when the temperature of the raw water exceeds the first predetermined temperature or higher and the second predetermined temperature during the first circulation operation. Therefore, it is possible to prevent the temperature of the raw water from becoming too high, and it is possible to further improve the production efficiency of pure water.

(Second Embodiment)
FIG. 2 is a configuration diagram showing a configuration of a pure water production apparatus according to a second embodiment of the present invention. The pure water production device 100a shown in FIG. 2 further includes an ultraviolet sterilizer 11 and a three-way valve 12 in addition to the configuration of the pure water production device 100a of the first embodiment shown in FIG.

The ultraviolet sterilizer 11 is provided between the EDI 8 and the treated water tank 9, and performs an ultraviolet sterilization treatment on the treated water from the EDI 8. The ultraviolet sterilization treatment is a treatment of sterilizing the treated water by irradiating the treated water with ultraviolet rays by an ultraviolet lamp (not shown) provided in the ultraviolet sterilizer 11.

The ultraviolet sterilizer 11 has a thermometer 11a. The thermometer 11a is a second temperature detection unit that detects the temperature of the treated water during the ultraviolet sterilization treatment. The thermometer 11a may detect the temperature of the treated water before and after the ultraviolet sterilization treatment.

In the three-way valve 12, the destination of the treated water that has been subjected to the UV sterilization treatment from the UV sterilizer 11 (hereinafter, may be referred to as the sterilized treated water) is either the raw water tank 1 or the treated water tank 9. It is a switching unit that switches to. This switching unit is not limited to the three-way valve as long as it can switch the destination of the sterilized treated water.

In the present embodiment, when the heat exchanger 3 is in the driving state, the control panel 10 performs normal operation as in the first embodiment. Specifically, the control panel 10 drives the pressurizing pump 2, the destination of the permeated water by the three-way valve 5 is EDI8, the destination of the concentrated water by the three-way valve 6 is the outside, and the treated water by the three-way valve 12 is used. The water supply destination is the treated water tank 9.

Further, when the heat exchanger 3 is stopped, the control panel 10 stops the pressurizing pump 2. Then, when the temperature of the raw water falls below the first predetermined temperature, the control panel 10 performs the first circulation operation as in the first embodiment. Specifically, the control panel 10 drives the pressurizing pump 2 by setting the destination of the permeated water by the three-way valve 5 and the destination of the concentrated water by the three-way valve 6 as the raw water tank 1. At this time, since there is no water to be treated flowing into the three-way valve 12, the destination of the water to be treated by the three-way valve 12 may be anywhere, but here, the raw water tank 1 is used.

In the first circulation operation, there is no inflow and outflow of the treated water to the ultraviolet sterilizer 11, and the treated water remains in the ultraviolet sterilizer 11. Switching the on / off of the ultraviolet lamp provided in the ultraviolet sterilizer 11 shortens the life of the ultraviolet lamp. Therefore, the ultraviolet sterilizer 11 usually continues to operate even when pure water is not produced. In this case, in the first circulation operation, since the treated water remains in the ultraviolet sterilizer 11, the temperature of the treated water in the ultraviolet sterilizer 11 rises, and the temperature of the ultraviolet sterilizer 11 rises accordingly. , May cause failure. Therefore, the control panel 10 interrupts the first circulation operation for a predetermined period of time, and performs the second circulation operation of supplying water to the ultraviolet sterilizer 11.

In the second circulation operation, the control panel 10 changes the destination of the permeated water by the three-way valve 5 to EDI8. That is, in the control panel 10, the destination of the permeated water by the three-way valve 5 is the EDI8, the destination of the concentrated water by the three-way valve 6 is the raw water tank 1, and the destination of the water to be treated by the three-way valve 12 is the raw water tank 1. To do.

As a result, the control panel 10 supplies the permeated water of the RO device 4 to the EDI8, and supplies the sterilized treated water that has been sterilized by the ultraviolet sterilizer 11 to the raw water tank in front of the pressurizing pump 2. It will be refluxed to 1. Therefore, since the raw water sent from the raw water tank 1 is returned to the raw water tank 1, a circulating flow is generated in the pure water production apparatus 100a, and the circulating flow passes through the ultraviolet sterilizer 11. Therefore, since the treated water flows in and out of the ultraviolet sterilizer 11, the temperature inside the ultraviolet sterilizer 11 can be lowered. It is desirable that all the treated water is returned to the raw water tank 1 as in the present embodiment, but a part of the treated water may be returned to the raw water tank 1.

In the present embodiment, when the temperature of the treated water detected by the thermometer 11a reaches a third predetermined temperature higher than the second predetermined temperature, the control panel 10 interrupts the first circulation operation. The second circulation operation is started. Then, when the temperature detected by the thermometer 11a falls below the fourth predetermined temperature lower than the third predetermined temperature, the second circulation operation is stopped and the first circulation operation is restarted. Therefore, the predetermined period for performing the second circulation operation is the period from when the temperature of the treated water reaches the third predetermined temperature to when it falls below the fourth predetermined temperature. The third predetermined temperature is, for example, 35 ° C., and the fourth predetermined temperature is, for example, a temperature within the set temperature range (22 ° C. to 28 ° C.).

Next, the operation will be described. The operations related to the normal operation and the first circulation operation are the same as those in the first embodiment. However, in the case of normal operation, the treated water from the EDI8 was directly sent to the treated water tank 9 in the first embodiment, but in the present embodiment, the UV sterilization treatment is performed by the UV sterilizer 11. The sterilized treated water that has been subjected to the ultraviolet sterilization treatment is sent to the treated water tank 9 via the three-way valve 12.

In the first circulation operation, the control panel 10 monitors the temperature of the treated water detected by the thermometer 11a, and determines whether or not the temperature of the treated water has reached the third predetermined temperature. When the temperature of the treated water detected by the thermometer 11a reaches the third predetermined temperature, the control panel 10 interrupts the first circulation operation and starts the second circulation operation. That is, in the control panel 10, the destination of the permeated water by the three-way valve 5 is the EDI8, the destination of the concentrated water by the three-way valve 6 is the raw water tank 1, and the destination of the water to be treated by the three-way valve 12 is the raw water tank 1. To do.

As a result, the raw water is sent from the raw water tank 1 to the RO device 4 via the heat exchanger 3 by the pressurizing pump 2. The raw water is separated into permeated water and concentrated water by the RO device 4. A part of the concentrated water is directly returned to the raw water tank 1, and the rest is returned to the raw water tank 1 via the three-way valve 6. Further, the permeated water is sent to EDI 8 via the three-way valve 5, and is separated into treated water and ion-concentrated water by EDI. A part of the ion-concentrated water is returned to the raw water tank 1, and the rest is drained to the outside. The treated water is subjected to ultraviolet sterilization treatment by the ultraviolet sterilizer 11, and further returned to the raw water tank 1 via the three-way valve 12.

At this time, since the circulating flow in the pure water production apparatus 100a passes through the ultraviolet sterilizer 11, the temperature of the ultraviolet sterilizer 11 drops. Further, since the temperature of the permeated water is included in the set temperature range by the first circulation operation, the EDI8 operates normally. A part of the ion-concentrated water from EDI8 is discharged to the outside, but since the amount is small, the influence on the flow rate of the entire circulating flow is small and can be ignored.

After that, also in the second circulation operation, the control panel 10 monitors the temperature of the treated water detected by the thermometer 11a, and determines whether or not the temperature of the treated water has fallen below the fourth predetermined temperature. When the temperature of the treated water falls below the fourth predetermined temperature, the control panel 10 stops the second circulation operation and restarts the first circulation operation.

In the embodiment described above, the control panel 10 has started the second circulation operation when the temperature of the treated water reaches the third predetermined temperature, but every predetermined time (for example, every two hours). A second circulation operation may be started. Further, the control panel 10 may stop the second circulation operation and restart the first circulation operation when a predetermined operation time elapses from the start of the second circulation operation.

In the present embodiment, in the first circulation operation, the control panel 10 stops the supply of the permeated water of the RO device 4 to the EDI8, interrupts the first circulation operation for a predetermined period, and disperses the permeated water to the EDI8. A second circulation operation is performed in which at least a part of the treated water that has been subjected to the ultraviolet sterilization treatment by the ultraviolet sterilizer 11 is returned to the front stage of the pressurizing pump 2. As a result, even if the ultraviolet sterilizer 11 is continuously driven in order to prolong the life of the ultraviolet lamp, it is possible to suppress defects such as failures that occur in the ultraviolet sterilizer 11, so that the cost can be reduced.

In each of the above-described embodiments, the illustrated configuration is merely an example, and the present invention is not limited to that configuration.

For example, the water supply destinations of the three-way valves 5, 6 and 12 in the first circulation operation and the second circulation operation were the raw water tank 1 in each embodiment, but may be in the stage before the pressurizing pump 2. .. For example, the water supply destinations of the three-way valves 5, 6 and 12 may be a flow path between the raw water tank 1 and the pressure pump, or may be a pre-stage of the raw water tank 1.

1 Raw water tank 2 Pressurized pump 3 Heat exchanger 4 RO (reverse osmosis membrane) device 5, 6, 12 Three-way valve 7, 11a Thermometer 8 EDI (electric deionized water production device)
9 Treated water tank 9a Water level gauge 10 Control panel 11 Ultraviolet sterilizer 100, 100a Pure water production equipment 200 Boiler

Claims (10)

A reverse osmosis membrane device that performs reverse osmosis membrane treatment on the water to be treated and separates the water to be treated into permeated water and concentrated water.
An electric deionized water production device that deionizes the permeated water,
A pump that sends the water to be treated to the reverse osmosis membrane device,
A first temperature detection unit that detects the temperature of the water to be treated, and
When the temperature falls below the first predetermined temperature, the supply of the permeated water to the electric deionized water production apparatus is stopped, and at least a part of the permeated water and the concentrated water is returned to the front stage of the pump. is allowed, the water purifying system and a control unit for executing a first circulation operation heated in the pump. The pure water production apparatus according to claim 1, wherein the control unit stops the pump when the temperature exceeds a second predetermined temperature equal to or higher than the first predetermined temperature during the first circulation operation. .. It further has an ultraviolet sterilizer that performs ultraviolet sterilization treatment on the treated water, which is permeated water that has been deionized by the electric deionized water production apparatus.
The control unit interrupts the first circulation operation for a predetermined period of time, supplies the permeated water to the electric deionized water production apparatus, and performs the ultraviolet sterilization treatment by the ultraviolet sterilizer. The pure water production apparatus according to claim 1 or 2, wherein a second circulation operation is performed in which at least a part of the treated water is returned to the front stage of the pump. The pure water production apparatus according to claim 3, wherein the control unit starts the second circulation operation at predetermined time intervals. It further has a second temperature detection unit that detects the temperature of the treated water.
The pure water production apparatus according to claim 3, wherein the control unit starts the second circulation operation when the temperature of the treated water reaches a third predetermined temperature higher than the first predetermined temperature. Before SL control unit, the temperature of the treated water is below the first fourth predetermined temperature lower than the height rather the third predetermined temperature than a predetermined temperature, stopping the second circulation operation, The pure water production apparatus according to claim 5 , wherein the first circulation operation is restarted. The control unit stops the second circulation operation and restarts the first circulation operation when a predetermined operation time elapses from the start of the second circulation operation, claim 3 or. pure water production apparatus according to 4. Further having a heating part for heating the water to be treated,
The control unit executes any one of claims 1 to 7 when the heating unit is in a stopped state and the temperature falls below the first predetermined temperature. The pure water production apparatus described in 1. The pure water production apparatus according to claim 8, wherein the heating unit is a heat exchanger that transfers heat from a boiler to the water to be treated. A reverse osmosis membrane device that performs reverse osmosis membrane treatment on the water to be treated and separates the water to be treated into permeated water and concentrated water, and an electric deionized water production device that deionizes the permeated water. A method for producing pure water by a pure water producing apparatus having a pump for sending the water to be treated to the reverse osmosis membrane apparatus.
The step of detecting the temperature of the water to be treated and
When the temperature falls below the first predetermined temperature, the supply of the permeated water to the electric deionized water production apparatus is stopped, and at least a part of the permeated water and the concentrated water is returned to the front stage of the pump. is allowed, the pure water manufacturing method, comprising the steps of performing a first circulation operation you heated in the pump.

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