JP2023008823A - Pure water production apparatus and its operational method - Google Patents

Abstract

To suppress temperature rise due to circulation of pure water at a lower cost.SOLUTION: A pure water production apparatus 1 consists of a tank 2 for storing pure water, a circulation line L1 for circulating pure water in the tank 2, a pump 3 installed in the circulation line L1 for distributing pure water in the tank 2 to the circulation line L1, a water delivery line L2 downstream of the pump 3 and connected to a use point 7 through a branch from the circulation line L1, and a control means 10 for switching the speed of the pump 3 based on the results of directly or indirectly detecting whether or not pure water is distributed to the water delivery line L2 or a change in the flow rate of pure water flowing through the water delivery line L2.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a pure water production apparatus and an operating method thereof.

As a device that produces pure water (purified water) for pharmaceutical manufacturing and biochemical analysis and supplies it to the point of use, it circulates the pure water along the circulation line and supplies part of it to the point of use as needed. There is known a pure water manufacturing apparatus that supplies water (see, for example, Patent Document 1). In such a device, even if the supply of pure water to the point of use is stopped for a long period of time, such as at night or on holidays when there is no demand for pure water at the point of use, it is necessary to suppress the generation of viable bacteria due to stagnation. Circulation operation of pure water is performed.

JP 2006-095479 A

When the pure water is circulated for a long period of time, the temperature of the pure water may rise and exceed the proper use temperature (set temperature) at the point of use due to heat generated by the pump and ultraviolet sterilizer installed in the circulation line. be. For example, relatively small water purifiers, which are often used in research institutions, require a pump with a relatively large capacity (maximum discharge flow rate) relative to the maximum amount of water that can be held in the tank, in order to support a variety of uses. It is often used, and such a temperature rise is likely to occur remarkably. As a countermeasure against such a temperature rise, it is conceivable to install a cooling means such as a heat exchanger in the circulation line as described in Patent Document 1. However, in a relatively small pure water production apparatus, It is not realistic in terms of device size and cost. Moreover, even in relatively large-sized pure water production apparatuses installed in various plants, the installation of cooling means in the circulation line may be postponed from an economical point of view. Therefore, in many pure water production apparatuses, a certain amount of circulating pure water is blown and newly replenished in order to lower the temperature of the pure water below the set temperature. However, such wasteful disposal of pure water is also undesirable because it results in an increase in cost.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a pure water production apparatus and a method of operating the same at a lower cost that suppresses temperature rise due to circulation of pure water.

In order to achieve the above object, the pure water production apparatus of the present invention comprises a tank for storing pure water, a circulation line for circulating the pure water in the tank, and a system provided in the circulation line to circulate the pure water in the tank. The pump that circulates in the circulation line, the water supply line that branches from the circulation line on the downstream side of the pump and is connected to the point of use, the presence or absence of pure water circulation in the water supply line, and the flow rate change of the pure water flowing through the water supply line. and control means for switching the rotation speed of the pump based on the directly or indirectly detected results.

Further, the method of operating the pure water production apparatus of the present invention includes the step of circulating the pure water stored in the tank along the circulation line by means of a pump provided in the circulation line; Directly or indirectly detected the process of sending the pure water circulating in the circulation line to the point of use through the water supply line, whether or not the pure water is flowing to the water supply line, or the change in the flow rate of the pure water flowing through the water supply line. and C. switching the speed of the pump based on the result.

According to such a pure water production apparatus and its operating method, it is possible to suppress temperature rise due to circulation of pure water by switching the rotation speed of the pump, so that pure water is not wasted. Furthermore, compared to the case where the pump is always operated at the same number of revolutions, the power consumption of the pump can be suppressed and the running cost can be reduced.

As described above, according to the present invention, temperature rise due to circulation of pure water can be suppressed at a lower cost.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the structure of the pure-water production apparatus which concerns on the 1st Embodiment of this invention. It is a schematic diagram showing the configuration of a pure water production apparatus according to a second embodiment of the present invention. It is a schematic diagram showing the configuration of a pure water production apparatus according to a third embodiment of the present invention. It is a schematic diagram showing the configuration of a pure water production apparatus according to a fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, as the pure water producing apparatus of the present invention, a cabinet-type pure water producing apparatus that is suitably used together with analyzers such as automatic blood analyzers in research institutions and medical institutions is exemplified. is not limited to The pure water production apparatus of the present invention can be installed in various plants, for example, as long as it is not provided with means for actively adjusting the temperature of circulating pure water (for example, a heat exchanger). It may be a large-sized pure water production apparatus.

(First embodiment)
FIG. 1 is a schematic diagram showing the configuration of a pure water production apparatus according to one embodiment of the present invention. The illustrated configuration of the pure water production apparatus is merely an example, and does not limit the present invention.

The pure water production device 1 has a tank 2 , a pump 3 , an ultraviolet oxidation device 4 , an ion exchange device 5 and a separation membrane device 6 . These are housed in a cabinet and constitute a secondary pure water system (subsystem) that sequentially processes primary pure water produced in a primary pure water system (not shown) to produce pure water. to the point of use 7.

Pump 3 , ultraviolet oxidation device 4 , ion exchange device 5 , and separation membrane device 6 are provided on circulation line L<b>1 having both ends connected to tank 2 . A water supply line L2 branched from the circulation line L1 is connected to the point of use 7 via a solenoid valve V1, and the solenoid valve V1 is configured to open and close in response to a command signal (open/close command signal) sent from the point of use 7. It is In addition, a primary pure water supply line L3 is connected to the tank 2. For example, according to the water level in the tank 2 detected by a water level sensor (not shown), the primary pure water system (not shown) Pure water is supplied. Specifically, when the water level in the tank 2 falls below a predetermined water supply start water level, primary pure water is supplied to the tank 2 through the primary pure water supply line L3, and when the water level in the tank 2 reaches a predetermined upper limit water level. , the supply of primary pure water to the tank 2 is stopped.

The primary pure water (water to be treated) stored in the tank 2 is pumped by the pump 3 and supplied to the ultraviolet oxidizer 4, where it is irradiated with ultraviolet rays having a wavelength of 185 nm, and the total organic carbon (TOC) in the water to be treated is reduced. is decomposed. Thereafter, metals and the like are removed from the water to be treated by ion exchange treatment in the ion exchange device 5, and fine particles and the like are removed in the separation membrane device 6. FIG. The pure water thus obtained is returned to the tank 2 through the circulation line L1, but when the electromagnetic valve V1 is opened in response to a water sampling request from the point of use 7, part or all of it flows through the water supply line L2 to the point of use 7. supplied to Back pressure is generated in the circulation line L1 on the downstream side of the branch point B with the water supply line L2 in order to ensure that pure water flows from the circulation line L1 into the water supply line L2 when the solenoid valve V1 is opened. A back pressure valve V2 is provided as a means.

As the tank 2, the pump 3, the ultraviolet oxidation device 4, the ion exchange device 5, and the separation membrane device 6, those commonly used in subsystems of pure water production apparatuses can be used. For example, as the ion exchange device 5, a non-regenerative mixed bed ion exchange device (cartridge polisher) packed with a mixed bed of cation exchange resin and anion exchange resin can be used. Moreover, the separation membrane device 6 may include either a microfiltration membrane (MF membrane) or an ultrafiltration membrane (UF membrane). Instead of or in addition to the ultraviolet oxidation device 4, an ultraviolet sterilization device that sterilizes the water to be treated by irradiating ultraviolet rays with a wavelength of 254 nm may be provided.

In the pure water production apparatus 1, even when the water sampling operation (supply of pure water to the point of use 7) is stopped for a long period of time, such as at night or on holidays when there is no demand for pure water at the point of use 7, the accumulation of In order to suppress the generation of viable bacteria, a circulation operation is performed in which the manufactured pure water is returned to the tank 2 . If such pure water circulation operation continues for a long period of time, the temperature of the pure water will rise due to heat generation of the pump 3 and the ultraviolet oxidation device 4, and will exceed the proper use temperature (set temperature) at the point of use 7. There is In particular, in a cabinet-type pure water production apparatus as in the present embodiment, a pump having a relatively large capacity (maximum discharge flow rate) with respect to the maximum amount of water held in the tank is used in order to accommodate various uses. However, due to the equipment size and cost, no cooling means such as a heat exchanger is provided. Therefore, such a temperature rise is likely to occur remarkably. For example, when the manufactured pure water is used in an analyzer such as an automatic blood analyzer, the usage temperature at the point of use is 30 to 35°C. On the other hand, the temperature of pure water may exceed 35°C.

Therefore, in this embodiment, the pump 3 operates at a lower rotational speed during the circulation operation than during the water sampling operation in order to suppress the temperature rise due to the circulation of pure water. That is, the pump 3 operates at a first rotation speed during the circulation operation, and operates at a second rotation speed higher than the first rotation speed during the water sampling operation. For this purpose, the pure water production apparatus 1 has a control unit (control means) 10 including an inverter (not shown) that controls the rotation speed of the pump 3. The control unit 10 supplies pure water to the water supply line L2. The number of revolutions of the pump 3 is switched based on the presence or absence of the circulation of the water.

When the control unit 10 acquires the open command signal sent from the point of use 7 to the solenoid valve V1, the solenoid valve V1 opens and pure water begins to flow in the water supply line L2 (that is, the water sampling operation is started). ), and when a close command signal sent from the point of use 7 to the solenoid valve V1 is acquired, the solenoid valve V1 is closed and the flow of pure water to the water supply line L2 is stopped (that is, It indirectly detects that the water sampling operation has been stopped). When detecting that the water sampling operation has started, the control unit 10 switches the rotation speed of the pump 3 from the first rotation speed to the second rotation speed, and detects that the water sampling operation has been stopped. , the rotation speed of the pump 3 is switched from the second rotation speed to the first rotation speed. Note that the rotation speed of the pump 3 can be adjusted by controlling the drive output (motor output) of the pump 3 .

Here, the first rotation speed during circulation operation is appropriately set according to the actual device configuration, and is not particularly limited. preferably. The results of the actual verification will be described later, but in order to minimize the temperature rise due to the circulation of pure water, the driving output of the pump 3 corresponding to the first rotation speed is converted to the minimum amount of water held in the tank 2 of 1 L. It is preferable to set it to 5 W or less, and more preferably to set it to 2 W or less. Here, the minimum retained water amount is the retained water amount when the water level in the tank 2 is the lowest, that is, when it is at a predetermined water supply start water level. Note that if the total volume of the pipes forming the circulation line L1 is not so small as to be negligible compared to the volume of the tank 2, in setting the driving output of the pump 3 corresponding to the first rotation speed, The total volume of piping may be considered. That is, the volume corresponding to the minimum water content of the tank 2 plus the total volume of the pipe may be regarded as the minimum water content of the tank 2 . On the other hand, the second rotation speed during the water sampling operation is appropriately set according to the flow rate of pure water required at the point of use 7, and is not particularly limited.

As described above, according to the present embodiment, by switching the rotation speed of the pump 3 according to the presence or absence of supply of pure water to the point of use 7 through the water supply line L2, the rotation speed is relatively low during the circulation operation. Pump 3 can be activated. As a result, it is possible to suppress the temperature rise of the pure water during the circulation operation without wastefully discarding the pure water. Furthermore, when the pump 3 is operated at the same rotation speed during the circulation operation and the water sampling operation, that is, when pure water is circulated at the same flow rate, the power consumption of the pump 3 and the ion exchange in the ion exchange device 5 Consumption of resin can be suppressed, and as a result, running costs can also be reduced. In cabinet-type pure water production equipment intended for use in research institutions and medical institutions, pure water is often used for short periods of time and at high frequency, so the blowing process that accompanies the temperature rise of pure water is unnecessary. It is also advantageous in that pure water can be used whenever necessary.

As described above, the illustrated configuration of the pure water production apparatus 1 is merely an example, and needless to say, it can be changed as appropriate according to the intended use, application, and required performance of the apparatus. In particular, a tank 2 for storing pure water (primary pure water), a circulation line L1 for circulating the pure water in the tank 2, a pump 3 for circulating the pure water in the tank 2 to the circulation line L1, and the pump 3 One or more of the ultraviolet oxidation device 4, the ion exchange device 5, and the separation membrane device 6 is omitted as long as the water supply line L2 branched from the circulation line L1 and connected to the point of use 7 is provided on the downstream side. or all three may be omitted. In addition, two or more back pressure valves V2 may be provided in order to adjust the flow rate of pure water flowing through the water supply line L2 during the water sampling operation, or may be omitted in some cases.

Here, the test result of verifying how much the temperature of the pure water circulating in the circulation line rises due to the heat generated by the pump will be described.

(Test 1-1)
Using a test apparatus simulating the pure water production apparatus shown in FIG. 1, pure water was continuously circulated, and changes in the temperature of pure water (water temperature) over time were measured. Then, the period during which the water temperature rose the most was specified throughout the operation period, and the water temperature rise rate (water temperature rise amount per unit time) was calculated from that period (time) and the water temperature rise amount at that time. Note that this test apparatus has the same configuration as the pure water production apparatus shown in FIG. are doing. A tank with a maximum holding water volume of 60 L was used, and a magnet gear pump (model: MDG-M4S6A100) manufactured by Iwaki Co., Ltd. was used as a pump. The pure water circulation operation was performed with the motor output of the pump set to 200 W and the tank filled with 60 L of pure water.

(Test 1-2)
The measurement was performed under the same conditions as Test 1-1, except that the tank was filled with 40 L of pure water and the circulation operation was performed.

(Test 1-3)
The same conditions as Test 1-1, except that a tank with a maximum water volume of 20 L was used and the tank was filled with water, that is, the tank was filled with 20 L of pure water and the circulation operation was performed. was measured.

(Test 2-1)
Measurement was performed under the same conditions as in Test 1-1, except for the following points. A vortex turbine pump (model: 15DNL03ZM-V) manufactured by Nikuni Co., Ltd. is used as the pump, and an inverter manufactured by Mitsubishi Electric Corporation (model: FR-D710W-0.75K) is used as the inverter for driving the motor of the pump. board. The pure water circulation operation was performed with the motor output of the pump set to 110 W and the tank filled with 60 L of pure water.

(Test 2-2)
Measurement was performed under the same conditions as in Test 2-1, except that the motor output was set to 165 W and circulating operation was performed.

(Test 2-3)
Measurement was performed under the same conditions as in Test 2-1, except that the motor output was set to 235 W and circulating operation was performed.

(Test 2-4)
The measurement was performed under the same conditions as Test 2-1, except that the tank was filled with 40 L of pure water and the circulation operation was performed.

(Test 2-5)
The measurement was performed under the same conditions as Test 2-2, except that the tank was filled with 40 L of pure water and the circulation operation was performed.

Table 1 shows the calculation results of the water temperature rise rate in each test. For reference, Table 1 also shows the amount of water held in the tank, the motor output of the pump, and the motor output of the pump per liter of water held in the tank.

In all tests except Test 1-3, it was confirmed that the water temperature rise rate was suppressed to 1.6 ° C / h or less. 1 was confirmed to give particularly good results. Therefore, from the viewpoint of suppressing the temperature rise due to the circulation of pure water, the motor output of the pump is preferably 5 W or less, more preferably 2 W or less, in terms of 1 L of water held in the tank. it is conceivable that.

(Second embodiment)
FIG. 2 is a schematic diagram showing the configuration of a pure water production apparatus according to a second embodiment of the present invention. In the following, configurations similar to those of the first embodiment are denoted by the same reference numerals in the drawings, description thereof is omitted, and only configurations different from those of the first embodiment are described.

As described above, when the solenoid valve V1 is opened in response to a water sampling request from the point of use 7, some or all of the pure water flowing through the circulation line L1 is supplied to the point of use 7 through the water supply line L2. At this time, on the downstream side of the branch point B in the circulation line L1, a pressure drop occurs as the pure water flow rate drops. can be detected indirectly. In this embodiment, in order to detect such a pressure drop, a pressure switch 11 is provided downstream of the branch point B in the circulation line L1 and upstream of the back pressure valve V2. The pressure switch 11 is configured to output a detection signal when the pressure of the pure water flowing downstream of the branch point B in the circulation line L1 falls below a specified pressure (predetermined value). Then, when the detection signal is received, the control unit 10 assumes that the water sampling operation is started and pure water begins to flow in the water supply line L2, and changes the rotation speed of the pump 3 from the first rotation speed to the second rotation speed. It is designed to switch to the number of revolutions. As a result, even in the present embodiment, it is possible to suppress the temperature rise of the pure water during the circulation operation without wastefully discarding the pure water, and it is possible to reduce the running cost.

The detecting means for indirectly detecting that pure water has started to flow in the water supply line L2 is not limited to the pressure switch 11, and may be a pressure sensor. In other words, a pressure sensor may be used instead of the pressure switch 11 as long as it can detect that the pressure of pure water flowing downstream of the branch point B in the circulation line L1 has become equal to or less than a predetermined value. Further, in order to reliably detect that pure water has started to flow in the water supply line L2, it is preferable to cause a sufficient pressure drop downstream of the branch point B in the circulation line L1 at that time. Therefore, the back pressure valve V2 may not necessarily be provided in the first embodiment as described above, but is preferably provided in the present embodiment. Note that, instead of the back pressure valve V2, another back pressure generating means such as an orifice may be provided.

(Third embodiment)
FIG. 3 is a schematic diagram showing the configuration of a pure water production apparatus according to a third embodiment of the present invention. In the following, configurations similar to those of the above-described embodiment are denoted by the same reference numerals in the drawings, description thereof is omitted, and only configurations different from the above-described embodiment are described.

This embodiment is a modification of the second embodiment, and differs from the second embodiment in the method of detecting the presence or absence of pure water flowing through the water supply line L2. Specifically, in the second embodiment, the pressure switch 11 is provided in the circulation line L1 in order to indirectly detect that pure water has started to flow in the water supply line L2. In the form, a flow rate switch 12 is provided in the water supply line L2 in order to detect it directly. The flow rate switch 12 is configured to output a detection signal when the flow rate of pure water flowing through the water supply line L2 reaches or exceeds a specified flow rate (predetermined value). , the rotation speed of the pump 3 is switched from the first rotation speed to the second rotation speed. As a result, even in the present embodiment, it is possible to suppress the temperature rise of the pure water during the circulation operation without wastefully discarding the pure water, and it is possible to reduce the running cost.

In the second embodiment, if the pressure loss in the water line L2 changes, the pressure downstream of the branch point B in the circulation line L1 will increase when pure water starts to flow in the water line L2. In some cases, the pressure does not fall below the specified pressure of the switch 11 . Therefore, in the second embodiment, it is necessary to consider changes in pressure loss in the water supply line L2 and adjust the set pressure of the pressure switch 11 accordingly. This is advantageous in that changes need not be considered.

The detection means for directly detecting that pure water has started to flow in the water supply line L2 is not limited to the flow rate switch 12, and may be a flow rate sensor. In other words, a flow rate sensor may be used instead of the flow rate switch 12 as long as it can detect that the flow rate of pure water flowing through the water supply line L2 has reached or exceeded a predetermined value.

(Fourth embodiment)
FIG. 4 is a schematic diagram showing the configuration of a pure water production apparatus according to a fourth embodiment of the present invention. In the following, configurations similar to those of the above-described embodiment are denoted by the same reference numerals in the drawings, description thereof is omitted, and only configurations different from the above-described embodiment are described.

In the second embodiment, the rotational speed of the pump 3 is switched when a pressure drop in pure water that occurs downstream of the branch point B in the circulation line L1 is detected. However, such a drop in pure water pressure occurs not only when pure water begins to flow through the water supply line L2 after the circulation operation shifts to the water sampling operation, but also when the flow rate of the pure water flowing through the water supply line L2 during the water sampling operation also occurs when increases. Therefore, the rotation speed of the pump 3 may be switched based on the flow rate change of pure water flowing through the water supply line L2 during the water sampling operation, as in the present embodiment.

In the present embodiment, the water supply line L2 is branched into a plurality (three in the illustrated example), each of which is connected to a plurality of points of use 71 to 73 via solenoid valves V11 to V13. Water sampling requests from points of use 71 to 73 are made independently of each other. Therefore, even during the water sampling operation, the flow rate of pure water flowing through the water supply line L2 fluctuates greatly. It will increase significantly compared to the case where there is an individual request for water sampling from. In this embodiment, a pressure sensor 13 is provided on the downstream side of the branch point B in the circulation line L1 in order to indirectly detect such an increase in the pure water flow rate. The pressure sensor 13 is configured to output a detection signal when the pressure of the pure water flowing downstream of the branch point B in the circulation line L1 falls below a predetermined set value. When receiving this detection signal, the control unit 10 determines that the flow rate of pure water flowing through the water supply line L2 has increased, and switches the rotation speed of the pump 3 from the first rotation speed to the second rotation speed. It has become. As a result, the number of revolutions of the pump 3 can be switched according to the flow rate of the pure water required by the points of use 71 to 73. In this embodiment as well, the pure water is not wastefully discarded, and the A rise in the temperature of pure water can be suppressed, and running costs can also be reduced.

The set value (threshold value) of the pressure sensor 13 can be appropriately changed according to the flow rate of pure water required by each point of use 71-73. For example, only when some of the plurality of points of use 71 to 73 request water sampling at the same time, the number of rotations of the pump 3 is switched from the first number of rotations to the second number of rotations, and each of the points of use 71 to 73 When there is an individual request for water sampling from, the rotation speed of the pump 3 may be maintained at the first rotation speed without switching. If there is a difference in the flow rate of pure water required for each of the points of use 71 to 73, the number of revolutions of the pump 3 is set to the first speed only when a water sampling request is made from a point of use with a relatively large required flow rate. number of revolutions to a second number of revolutions.

In this embodiment, as in the third embodiment, it may be possible to directly detect an increase in the flow rate of pure water flowing through the water supply line L2. is preferable to use a flow rate sensor because the threshold value for switching the rotation speed of the pump 3 can be arbitrarily set.

1 pure water production device 2 tank 3 pump 4 ultraviolet oxidation device 5 ion exchange device 6 separation membrane device 7, 71 to 73 points of use 10 control section (control means)
11 pressure switch 12 flow rate switch 13 pressure sensor L1 circulation line L2 water supply line V1, V11 to V13 solenoid valve V2 back pressure valve (back pressure generating means)

Claims (10)

a tank for storing pure water;
a circulation line for circulating pure water in the tank;
a pump provided in the circulation line for circulating pure water in the tank through the circulation line;
a water supply line branched from the circulation line downstream of the pump and connected to a point of use;
and control means for switching the rotation speed of the pump based on the result of directly or indirectly detecting the presence or absence of pure water flowing through the water supply line or a change in the flow rate of pure water flowing through the water supply line. Water production equipment. The control means controls the number of rotations of the pump from a first number of rotations to the first number of rotations when pure water starts flowing through the water supply line or when the flow rate of pure water flowing through the water supply line increases. 2. The pure water production apparatus according to claim 1, wherein the number of revolutions is switched to a second number of revolutions exceeding the number of revolutions. detection means for directly or indirectly detecting that pure water has started to flow through the water supply line or that the flow rate of pure water flowing through the water supply line has increased, and outputting a detection signal;
3. The pure water production apparatus according to claim 2, wherein said control means switches the rotation speed of said pump from said first rotation speed to said second rotation speed when said detection signal is received. back pressure generating means provided on the downstream side of a branch point with the water supply line in the circulation line,
4. The pure water production apparatus according to claim 3, wherein said detection means outputs said detection signal when the pressure of pure water flowing downstream of said branch point in said circulation line falls below a predetermined value. 5. The pure water production apparatus according to claim 4, wherein said detection means is a pressure switch or a pressure sensor provided downstream of said branch point and upstream of said back pressure generation means in said circulation line. 4. The pure water production apparatus according to claim 3, wherein said detection means outputs said detection signal when the flow rate of pure water flowing through said water supply line reaches or exceeds a predetermined value. 7. The pure water producing apparatus according to claim 6, wherein said detection means is a flow rate switch or a flow rate sensor provided in said water supply line. 3. The apparatus according to claim 2, wherein the control means switches the rotation speed of the pump from the first rotation speed to the second rotation speed when an electromagnetic valve connecting the water supply line and the point of use is opened. A pure water production apparatus as described. 3. The control means adjusts the rotation speed of the pump to the first rotation speed by setting the driving output of the pump to 5 W or less per 1 L of the minimum retained water volume of the tank. 9. The pure water production apparatus according to any one of 8. A method for operating a pure water production apparatus,
a step of circulating pure water stored in a tank along the circulation line by a pump provided in the circulation line;
a step of sending pure water circulating in the circulation line to a use point through a water supply line branched from the circulation line on the downstream side of the pump;
switching the rotation speed of the pump based on the result of directly or indirectly detecting the presence or absence of pure water flowing through the water supply line or a change in the flow rate of pure water flowing through the water supply line; A method of operating a water production device.

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