Water treatment system, water quality measurement device, and water quality measurement method

Abstract

The water treatment system comprises: a water treatment device 1 that treats water to be treated to produce a treated water having a resistivity of at least 0.10 MΩ·cm; a concentration device 2 that is disposed separately from the water treatment device 1 and that, by the passage therethrough of at least a part of a treated water 1b produced by the water treatment device 1, concentrates a prescribed component in at least a part of the treated water; a measurement instrument 3 that continuously measures the concentration of a prescribed component in the concentrated water concentrated by the concentration device 2; and a monitoring section 11 that monitors the water quality of the treated water 1b on the basis of the measured value from the measurement instrument 3.

Description

Water treatment system, water quality measuring device, and water quality measuring method

[0001] The present invention relates to a water treatment system, a water quality measuring device, and a water quality measuring method.

[0002] In the manufacturing process of semiconductor devices and liquid crystal devices, pure water (including ultrapure water) from which organic matter, ionic components, particulates, bacteria, etc. have been highly removed is used as cleaning water. To produce such pure water for cleaning, it is required that the quality of the pure water be constantly maintained at a stable, high purity. To meet this requirement, it is preferable to manage the operating conditions in the pure water manufacturing process by checking the quality of the pure water on-site using an online water quality meter.

[0003] However, the minimum detectable concentration of chlorine compounds with general-purpose water quality instruments is generally high, limiting the ability to directly measure pure water quality on-site. Therefore, pure water is collected in a pre-cleaned sampling bottle in an environment that minimizes contamination, such as a clean room, and the bottle is then sent to an external specialized analysis laboratory for analysis. Specialized analysis laboratories have special analysis equipment that can measure concentrations down to low quantitation limits, making it possible to analyze pure water quality.

[0004] As another technique, Patent Document 1 discloses a method for measuring the water quality at the inlet side of a water treatment device and predicting (simulating) the concentration of components leaking to the outlet side of the water treatment device based on the measured value and a preset removal rate of the water treatment device. Patent Document 2 describes a continuous monitoring device for test water. This monitoring device includes a reverse osmosis (RO) membrane separation means, a return means, an analysis means, and a calculation means. The return means returns a portion of the concentrated water from the RO membrane separation means to the inlet side of the RO membrane separation means. The analysis means measures the concentration of the analyte in the remaining concentrated water. The calculation means calculates the concentration of the analyte in the test water based on the measurement results. By concentrating the test water using the RO membrane separation means, the analysis means can measure the concentration of the analyte in the test water at an ultrapure water level. Furthermore, by circulating a portion of the concentrated water, the flow rate on the RO membrane surface increases. This allows the analyte in the test water to be concentrated at a high concentration rate.

[0005] JP 2017-131846 A JP 2009-156692 A JP 10-232226 A

[0006] The method using sampling bottles requires a clean environment and sampling equipment, which increases facility costs. It also requires skilled technicians with advanced sampling techniques. Furthermore, analysis at specialized analytical laboratories is costly and time-consuming.

[0007] The method described in Patent Document 1 measures the water quality at the inlet side of the water treatment device. Therefore, it is difficult to accurately determine the performance degradation of the water treatment device itself. The device described in Patent Document 2 measures the water quality of test water. Therefore, it is difficult to continuously measure the water quality of pure water discharged from the water treatment device on-site. Even if the device described in Patent Document 2 were applied to a water treatment device and configured to measure the water quality of pure water on-site, it would be difficult to accurately measure the water quality of pure water discharged from the water treatment device because a portion of the concentrated water would be circulated. Until now, no water treatment system or water quality measuring device has been provided that can accurately detect the water quality of pure water-level treated water discharged from the water treatment device on-site using an online meter.

[0008] An object of the present invention is to provide a water treatment system and a water quality measuring device that can accurately detect the quality of treated water at a pure water level on-site.

[0009] In order to achieve the above object, according to one aspect of the present invention, there is provided a water treatment system comprising: a water treatment device that treats water to be treated to produce treated water with a resistivity of 0.10 MΩ·cm or more; a concentrating device disposed separately from the water treatment device through which at least a portion of the treated water produced by the water treatment device passes and which concentrates specific components in the at least a portion of the treated water; a measuring instrument that continuously measures the concentration of the specific component in the concentrated water concentrated by the concentrating device; and a monitoring unit that monitors the water quality of the treated water based on the measurements taken by the measuring instrument.

[0010] According to another aspect of the present invention, there is provided a water quality measuring device used to monitor the quality of treated water produced by a water treatment device that treats water to be treated and produces treated water with a resistivity of 0.10 MΩ cm or more, the water quality measuring device comprising: a concentrating device through which at least a portion of the treated water passes and concentrates a specific component in the at least a portion of the treated water; and a measuring instrument that continuously measures the concentration of the specific component in the concentrated water concentrated by the concentrating device, wherein the concentrating device is an electric concentrating device.

[0011] According to the present invention, the quality of treated water at a pure water level can be accurately detected on-site. The above and other objects, features, and advantages of the present application will become apparent from the following detailed description taken in conjunction with the accompanying drawings illustrating the present application.

[0012] 1 is a block diagram showing the configuration of a water treatment system according to a first embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of a water treatment system according to a second embodiment of the present invention. FIG. 3 is a schematic diagram showing a first example of an electric concentrator. FIG. 4 is a schematic diagram showing a second example of an electric concentrator. FIG. 5 is a schematic diagram showing a third example of an electric concentrator. FIG. 6 is a schematic diagram showing a fourth example of an electric concentrator. FIG. 7 is a schematic diagram showing a fifth example of an electric concentrator. FIG. 8 is a schematic diagram showing a sixth example of an electric concentrator. FIG. 9 is a diagram for explaining an example of a method for calculating the concentration factor of the concentrator 2. FIG. 10 is a diagram for explaining another example of a method for calculating the concentration factor of the concentrator 2. FIG. 11 is a block diagram showing a water treatment system according to a first embodiment. FIG. 12 is a diagram for explaining changes in silica concentration before and after adjustment. FIG. 13 is a block diagram showing a water treatment system according to a second embodiment. FIG. 14 is a diagram for explaining changes in silica concentration before and after chemical regeneration. FIG. 15 is a block diagram showing a water treatment system according to a third embodiment. FIG. 16 is a diagram showing changes in silica concentration. FIG. 17 is a block diagram showing a water treatment system according to a fourth embodiment. FIG. 18 is a diagram showing changes in boron concentration. FIG. 19 is a block diagram showing a water treatment system according to a sixth embodiment. FIG. 19 is a diagram showing changes in IC concentration. FIG. 28 is a diagram for explaining an example of a method for calculating the concentration ratio of an RO membrane separation device. FIG. 29 is a diagram showing the measurement results of sodium and silica. FIG. 29 is a diagram showing an example of measurement values ​​of a silica meter in the case where a concentrator is not provided. FIG. 29 is a diagram showing an example of measurement values ​​of a silica meter in the case where a concentrator is provided. FIG. 30 is a block diagram showing the configuration of a water treatment system according to a third embodiment of the present invention. FIG. 31 is a schematic diagram showing an example of the configuration of a concentrator. FIG. 32 is a schematic diagram showing another example of the configuration of a concentrator. FIG. 33 is a block diagram showing the configuration of a water treatment system according to a comparative example. FIG. 34 is a diagram showing an example of measurement data of the water quality measurement device shown in FIG. 27. FIG. 35 is a block diagram showing the configuration of a water treatment system according to a fourth embodiment of the present invention.

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the components described in the embodiments are merely examples and are not intended to limit the scope of the present invention.

[0014] First Embodiment FIG. 1 is a block diagram showing the configuration of a water treatment system according to a first embodiment of the present invention. Referring to FIG. 1 , the water treatment system of this embodiment includes a water treatment device 1, a water quality measurement device 10, and a monitoring unit 11. The water treatment device 1 treats water to be treated 1a to produce treated water 1b. The treated water 1b is, for example, pure water (or ultrapure water) having a specific resistance of, for example, 0.10 MΩ·cm or more (conductivity of 10 μS / cm or less). The treated water 1b produced by the water treatment device 1 is branched into two parts: one is supplied as treated water 1c to a point-of-use or a downstream treatment device, and the other is supplied as treated water 1d to the water quality measurement device 10. The water treatment device 1 includes, for example, at least one of a reverse osmosis (RO) membrane separation device, a regenerative ion exchange resin device, a non-regenerative ion exchange resin device, and an electro-deionized water production device (EDI). The water treatment device 1 may include other devices for water treatment as long as it can produce treated water having a resistivity of 0.10 MΩ·cm or more.

[0015] The water quality measuring device 10 includes a concentrator 2 and a measuring instrument 3. The concentrator 2 is configured to pass treated water 1d, which is a portion of treated water 1b produced by the water treatment device 1. The concentrator 2 concentrates a specific component (a component to be concentrated) contained in the treated water 1d. The concentrator 2 supplies a signal indicating the concentration ratio to the monitoring unit 11. The concentrator 2 is, for example, a desalination device that produces at least concentrated water 2a and desalinated water 2b. The removal rate (densification rate) of the specific component is 90% or more, preferably 95% or more, and more preferably 99% or more. The concentration ratio of the concentrated water 2a relative to the water to be treated 1d is 3 times or more, preferably 10 times or more, and more preferably 20 times or more. In this embodiment, the removal rate (densification rate) is 90% or more, and the concentration ratio is in the range of 3 to 20 times. The concentrated water 2a is supplied to the measuring instrument 3. The desalinated water 2b is combined with treated water 1c and supplied to a point of use. The concentrated water that has passed through the measuring instrument 3 is basically discarded, but from the viewpoint of utilization efficiency, it may be returned to the upstream or downstream of the water treatment device 1, or may be used in another system. Note that the desalinated treated water 2b may be sent in a separate system without being merged with the treated water 1c, if the piping connections are too time-consuming or the configuration becomes complicated.

[0016] The measuring instrument 3 continuously measures the concentration of a specific component contained in the concentrated water 2a discharged from the concentrating device 2. The measuring instrument 3 supplies a signal indicating the measurement value to the monitoring unit 11. The measuring instrument 3 is, for example, an instrument that measures the concentration of any of the following components: silica, boron, metal ions (sodium, aluminum, calcium, magnesium, etc.), carbonate, IC (inorganic carbon), and TOC (total organic carbon). Note that these instruments are merely examples, and instruments that measure the concentration of other components may also be used.

[0017] The monitoring unit 11 monitors the water quality of the treated water 1b based on the measurement values ​​of the measuring instrument 3. The monitoring unit 11 has a treated water concentration calculation unit 4, an adjustment unit 5, and an alarm output unit 6. The treated water concentration calculation unit 4 calculates the concentration value (conversion value) of a specific component in the treated water 1b by dividing the measurement value of the measuring instrument 3 by the concentration ratio of the concentrating device 2. The concentration value (conversion value) is supplied to the adjustment unit 5 and the alarm output unit 6. Furthermore, the concentration ratio may be a preset value, or may be a value constantly calculated from the values ​​of each flow meter installed in the concentrating device 2.

[0018] The adjustment unit 5 adjusts the treatment state of the water treatment device 1 for the specific component based on the concentration value (converted value) of the specific component in the treated water 1b. The adjustment unit 5 is configured to be able to adjust at least one of, for example, flow rate adjustment, chemical regeneration, ion exchange resin replacement, current adjustment, water temperature adjustment, and pH adjustment. These adjustments will be described in detail in the examples below. Note that these adjustments may also be performed by an administrator.

[0019] The alarm output unit 6 outputs an alarm based on the concentration value (converted value) of a specific component in the treated water 1b. For example, the alarm output unit 6 outputs an alarm when the concentration value (converted value) of the specific component in the treated water 1b exceeds a threshold value or when a trend indicating a decrease in treatment performance for the specific component is detected. The alarm output unit 6 may include a display device that displays a message indicating the alarm, a speaker that outputs an alarm sound, or the like.

[0020] The water treatment system of this embodiment provides the following advantageous effects. Because the concentration of a specific component in pure-water-level treated water 1b is lower than the lower limit of the concentration measurable by the measuring instrument 3, it is difficult to accurately measure the concentration of the specific component in treated water 1b using the measuring instrument 3. In this embodiment, the measuring instrument 3 measures the concentration of the specific component in concentrated water 2a, which is obtained by concentrating treated water 1d, a portion of treated water 1b. The concentration of the specific component in concentrated water 2a is higher than the lower limit of the concentration measurable by the measuring instrument 3. Therefore, the measuring instrument 3 can accurately measure the concentration of the specific component in concentrated water 2a. The measured value of concentrated water 2a can be converted to the concentration value of the specific component in treated water 1b by dividing it by the concentration factor of the concentrator 2. This makes it possible to obtain the concentration (converted value) of the specific component in pure-water-level treated water 1b.

[0021] Furthermore, since the concentration of a specific component in the treated water 1b can be continuously obtained on-site using an online meter, the water treatment device 1 can be continuously and stably operated and managed. For example, if a trend indicating a decrease in the treatment performance of the water treatment device 1 for a specific component (e.g., an increasing trend) is detected, a performance recovery process for the water treatment device 1 can be immediately implemented. This stabilizes the performance of the water treatment device 1, and as a result, the water quality of the treated water 1b can be stably maintained.

[0022] In addition, compared to using a specialized analytical laboratory, the following advantages are achieved. When using a specialized analytical laboratory, the quality of the treated water produced by the water treatment device cannot be analyzed on-site immediately. Therefore, if a problem such as a performance degradation of the water treatment device occurs, it takes time to identify the cause. Furthermore, if the performance of the water treatment device deteriorates before the cause is identified, operation will continue in that state. In this case, the treated water may no longer meet the water quality requirements for cleaning water in semiconductor manufacturing equipment or liquid crystal manufacturing equipment. Using treated water that does not meet the required water quality as cleaning water may cause fatal damage to the semiconductor manufacturing equipment or liquid crystal manufacturing equipment. According to this embodiment, the quality of the treated water can be analyzed on-site, allowing problems such as a performance degradation of the water treatment device 1 to be immediately detected and addressed. Therefore, treated water that meets the required water quality for cleaning water can be consistently provided.

[0023] Furthermore, when using specialized analytical laboratories, performance recovery treatment of water treatment devices is typically performed with a margin of error. For example, when the water treatment device is a regenerative ion exchange resin device, it is common to perform regeneration with a margin of error, before performance degradation progresses. According to the present embodiment, such a margin of error is not required, and performance recovery treatment can be performed at the optimal timing. For example, in a regenerative ion exchange resin device, by identifying a trend in performance degradation at an early stage, it becomes possible to continue operation until the very limit of performance degradation, thereby enabling a more optimal regeneration frequency to be achieved.

[0024] Furthermore, when using a specialized analysis laboratory, the water quality can be analyzed at the time of sampling, but it is difficult to grasp fluctuations in water quality. According to this embodiment, by constantly monitoring the water quality on-site using online instruments, fluctuations in water quality can be grasped and more appropriate operation management can be implemented. Furthermore, according to this embodiment, a clean environment and sampling equipment are not required, which also reduces equipment costs.

[0025] Although analytical instruments capable of analyzing low concentrations are available, such instruments are expensive, and from the viewpoint of equipment costs, it is not practical to use such expensive analytical instruments. According to this embodiment, since the concentration of the substance to be measured is high, a general-purpose, inexpensive instrument can be used as the measuring instrument 3, thereby making it possible to significantly reduce equipment costs.

[0026] In the present embodiment, the adjustment unit 5 is configured to perform the performance recovery process for the water treatment device 1, but this is not limiting. An administrator may perform the necessary work for the performance recovery process in response to the alarm (message or alarm sound) from the alarm output unit 6.

[0027] Second Embodiment Figure 2 is a block diagram showing the configuration of a water treatment system according to a second embodiment of the present invention. As shown in Figure 2, the water treatment system of this embodiment includes a water treatment device 1, a water quality measurement device 10, and a monitoring unit 11. The water treatment device 1 and the monitoring unit 11 are the same as those described in the first embodiment. The water quality measurement device 10 is also basically the same as that described in the first embodiment, but differs from the first embodiment in that the concentrator 2 is configured to pass treated water 1b produced by the water treatment device 1 through it. In Figure 2, the same components are designated by the same reference numerals, and detailed description thereof will be omitted.

[0028] The concentrator 2 concentrates specific components (components to be concentrated) contained in the treated water 1b. The concentrator 2 is, for example, a desalination device that produces at least concentrated water 2a and desalinated water 2b. The specific configuration of the concentrator 2 is as described in the first embodiment. The concentrated water 2a discharged from the concentrator 2 is supplied to a measuring instrument 3. The desalinated water 2b discharged from the concentrator 2 is supplied to a point-of-use or a downstream treatment device.

[0029] The water treatment system of this embodiment also achieves the effects described in the first embodiment. Furthermore, in the water treatment system of the first embodiment, the concentrator 2 is provided in a branch line for the treated water. In contrast, in the water treatment system of this embodiment, the concentrator 2 is provided in the main line for the treated water, and no branch line is provided. This allows for a slimmer facility compared to the first embodiment. In other words, when a concentrator is installed in the main line, the concentrated water device must have the capacity to handle all of the treated water in the main line. Therefore, while the water treatment system of the first embodiment is suitable for a large water treatment device 1, the water treatment system of this embodiment is suitable for a small water treatment device 1.

[0030] In the water treatment systems of the first and second embodiments described above, the concentrator 2 is preferably an electrical regeneration type deionized water production device (hereinafter referred to as an electrical concentrator). An electrical concentrator has a cation exchange membrane and an anion exchange membrane disposed between a cathode and an anode. The electrical concentrator has a cationic component concentration chamber on the cathode side of the cation exchange membrane and a deionization chamber on the anode side, and / or an anionic component concentration chamber on the anode side of the anion exchange membrane and a deionization chamber on the cathode side. At least the deionization chamber is filled with ion exchange resin, and continuous concentration is performed by passing a direct current between the cathode and the anode.

[0031] Specific examples of electric concentrators used as the concentrator 2 are described below. (Electric concentrator 1) Fig. 3 is a schematic diagram showing a first example of an electric concentrator. Referring to Fig. 3, the electric concentrator 2 has an anode 23a and a cathode 23b. Between the anode 23a and the cathode 23b, there are deionization compartments 20a, 20b, concentration compartments 21a, 21b, electrode compartments 22a, 22b, the anode 23a, the cathode 23b, anion exchange membranes 24a to 24d, and cation exchange membranes 25a, 25b.

[0032] Deionization compartment 20a is located on the anode side of anion exchange membrane 24a, and deionization compartment 20b is located on the cathode side of anion exchange membrane 24a. Deionization compartment 20a is filled with anion exchange resin. Deionization compartment 20b has a first region on the upstream side and a second region on the downstream side with respect to the flow direction of the water to be treated flowing through deionization compartment 20b. The first region is filled with cation exchange resin, and the second region is filled with anion exchange resin.

[0033] Concentration compartment 21a is located on the anode side of dilution compartment 20a. Concentration compartment 21a is filled with a cation exchange resin. An anion exchange membrane 24b is located between concentration compartment 21a and dilution compartment 20a. Concentration compartment 21a can be called an anion concentration compartment, which concentrates anion components.

[0034] Concentration compartment 21b is located on the cathode side of deionization compartment 20b. Concentration compartment 21b is filled with anion exchange resin. An ion exchange membrane consisting of an anion exchange membrane 24c and a cation exchange membrane 25b is located between concentration compartment 21b and deionization compartment 20b. Cation exchange membrane 25b is located throughout the first and second regions of deionization compartment 20b. Anion exchange membrane 24c is located on the surface of cation exchange membrane 25b facing deionization compartment 20b (the side opposite concentration compartment 21b). The area of ​​anion exchange membrane 24c is smaller than the area of ​​cation exchange membrane 25b. Anion exchange membrane 24c faces the second region of deionization compartment 20b. Concentration compartment 21b can be called a cation concentration compartment that concentrates cationic components.

[0035] Electrode chamber 22a is disposed on the anode side of concentration chamber 21a. Electrode chamber 22a is filled with a cation exchange resin. A cation exchange membrane 25a is disposed between electrode chamber 22a and concentration chamber 21a. Electrode chamber 22b is disposed on the cathode side of concentration chamber 21b. Electrode chamber 22b is filled with an anion exchange resin. An anion exchange membrane 24d is disposed between electrode chamber 22b and concentration chamber 21b.

[0036] In the electrical concentrator 2 of this example, the feed water (treated water 1b, 1d) first passes through deionization chamber 20a and then through deionization chamber 20b. Deionization chamber 20b discharges desalinated water. A valve 26a is provided in the line for supplying the feed water to deionization chamber 20a. A valve 26b is provided in the line for the desalinated water discharged from deionization chamber 20b, and a flow meter FI1 is provided downstream of this valve 26b.

[0037] The desalinated water discharged from desalting chamber 20b branches upstream of valve 26b, and the branched desalinated water is supplied to concentrating chambers 21a and 21b, respectively. Valve 26c is provided on the branch line for the desalinated water, and flow meter FI2 is provided downstream of valve 26c. After flow meter FI2, the desalinated water line branches into two, one line communicating with concentrating chamber 21a and the other line communicating with concentrating chamber 21b. Concentrating chambers 21a and 21b each discharge concentrated water.

[0038] The desalinated water discharged from desalting chamber 20b is further branched before the branch point to concentrating chambers 21a and 21b. This branched desalinated water first passes through electrode chamber 22b and then through electrode chamber 22a. Electrode chamber 22a discharges electrode water. Valve 26d is provided in the branch line of the desalinated water to electrode chamber 22b, and flow meter FI3 is provided downstream of valve 26d.

[0039] Feed water is supplied to deionization compartments 20a and 20b, and a portion of the desalinated water discharged from deionization compartment 20 is supplied to concentration compartments 21a and 21b and electrode compartment 22b. The flow rate of the feed water can be adjusted using valve 26a. The flow rate of the desalinated water discharged from deionization compartment 20b can be adjusted using valve 26b. The flow rate of the desalinated water supplied to concentration compartments 21a and 21b can be adjusted using valve 26c. The flow rate of the desalinated water supplied to electrode compartment 22b can be adjusted using valve 26d.

[0040] A direct current is passed between the anode 23a and the cathode 23b. Ions move between the deionization compartment 20a and the concentration compartment 21a via the anion exchange membrane 24b, and the concentration compartment 21a discharges concentrated water containing concentrated anionic components. Ions move between the deionization compartment 20b and the concentration compartment 21b via the anion exchange membrane 24c and the cation exchange membrane 25b, and the concentration compartment 21b discharges concentrated water containing concentrated cation components. The concentrated water discharged from the concentration compartment 21a and the concentrated water discharged from the concentration compartment 21b join together and are supplied to the measuring instrument 3 shown in FIG. 1 (or FIG. 2).

[0041] (Electric concentrator 2) Figure 4 is a schematic diagram showing a second example of an electric concentrator. The electric concentrator 2 of this example has a deionization compartment 27 and a cation exchange membrane 25c instead of the deionization compartments 20a and 20b, anion exchange membranes 24a and 24c, and cation exchange membrane 25b shown in Figure 3. The configuration other than the deionization compartment 27 and the cation exchange membrane 25c is the same as that shown in Figure 3. The same components as those shown in Figure 3 are designated by the same reference numerals, and detailed description thereof will be omitted here.

[0042] Deionization compartment 27 is disposed between concentration compartment 21a and concentration compartment 21b. Anion exchange membrane 24b is disposed between deionization compartment 27 and concentration compartment 21a. Cation exchange membrane 25c is disposed between deionization compartment 27 and concentration compartment 21b. Deionization compartment 27 is filled with a cation exchange resin and an anion exchange resin. Specifically, deionization compartment 27 is filled with a mixed resin obtained by mixing a cation exchange resin and an anion exchange resin in a predetermined ratio.

[0043] In the electrical concentrator 2 of this example, the feed water (treated water 1b, 1d) is supplied to the deionization chamber 27. The deionization chamber 27 discharges desalinated water. As in the first example, the feed water line is provided with a valve 26a. The line for the desalinated water discharged from the deionization chamber 27 is provided with a valve 26e, and a flow meter FI1 is provided downstream of this valve 26e.

[0044] The desalinated water discharged from desalting chamber 27 branches upstream of valve 26e, and the branched desalinated water is supplied to concentration chambers 21a and 21b. Valve 26f is provided on the branch line of the desalinated water, and flow meter FI2 is provided downstream of valve 26f. After flow meter FI2, the desalinated water line branches into two, one line communicating with concentration chamber 21a and the other line communicating with concentration chamber 21b. Concentration chambers 21a and 21b each discharge concentrated water.

[0045] The desalinated water discharged from deionization chamber 27 is further branched before the branch point to concentration chambers 21a and 21b. This branched desalinated water first passes through electrode chamber 22b and then through electrode chamber 22a. Electrode chamber 22a discharges electrode water. Valve 26g is provided in the branch line of the desalinated water to electrode chamber 22b, and flow meter FI3 is provided downstream of valve 26g.

[0046] Feed water is supplied to deionization compartment 27, and a portion of the desalinated water discharged from deionization compartment 27 is supplied to concentration compartments 21a, 21b and electrode compartment 22b. The flow rate of the feed water can be adjusted using valve 26a. The flow rate of the desalinated water discharged from deionization compartment 27 can be adjusted using valve 26e. The flow rate of the desalinated water supplied to concentration compartments 21a, 21b can be adjusted using valve 26f. The flow rate of the desalinated water supplied to electrode compartment 22b can be adjusted using valve 26g.

[0047] A direct current is passed between the anode 23a and the cathode 23b. Ions move between the deionization compartment 27 and the concentration compartment 21a via the anion exchange membrane 24b, and ions move between the deionization compartment 27 and the concentration compartment 21b via the cation exchange membrane 25c. The concentration compartment 21a discharges concentrated water containing concentrated anionic components, while the concentration compartment 21b discharges concentrated water containing concentrated cation components. The concentrated water discharged from the concentration compartment 21a and the concentrated water discharged from the concentration compartment 21b join together and are supplied to the measuring instrument 3 shown in FIG. 1 (or FIG. 2).

[0048] (Electric concentrator 3) Figure 5 is a schematic diagram showing a third example of an electric concentrator. The electric concentrator 2 of this example has concentrating chambers 28a and 28b instead of the concentrating chambers 21a and 21b shown in Figure 4. The rest of the configuration is the same as that shown in Figure 4. The same components are given the same reference numerals, and detailed description thereof will be omitted here.

[0049] Concentrating compartment 28a is disposed on the anode side of dilution compartment 27, and concentrating compartment 28b is disposed on the cathode side of dilution compartment 27. Anion exchange membrane 24b is disposed between concentrating compartment 28a and dilution compartment 27. Cation exchange membrane 25c is disposed between concentrating compartment 28b and dilution compartment 27. Concentrating compartments 28a and 28b are filled with a mixed resin comprising a cation exchange resin and an anion exchange resin mixed in a predetermined ratio. Although not shown, valves 26a, 26e, 26f, and 26g and flow meters FI1 to FI3 are disposed in the same manner as in the second example.

[0050] In the electric concentrator 2 of this example, the feed water (treated water 1b, 1d) is supplied to the deionization compartment 27, and a portion of the deionized water discharged from the deionization compartment 27 is supplied to the concentration compartments 28a, 28b and the electrode compartment 22b. The concentration compartments 28a, 28b each discharge concentrated water.

[0051] A direct current is passed between the anode 23a and the cathode 23b. Ions move between the deionization compartment 27 and the concentration compartment 28a via the anion exchange membrane 24b, and ions move between the deionization compartment 27 and the concentration compartment 28b via the cation exchange membrane 25c. The concentration compartment 28a discharges concentrated water containing concentrated anionic components, while the concentration compartment 28b discharges concentrated water containing concentrated cation components. The concentrated water discharged from the concentration compartment 28a and the concentrated water discharged from the concentration compartment 28b join together and are supplied to the measuring instrument 3 shown in FIG. 1 (or FIG. 2).

[0052] (Electric concentrator 4) Fig. 6 is a schematic diagram showing a fourth example of an electric concentrator. The electric concentrator 2 of this example has a dilution compartment 29 instead of the concentration compartment 21b and dilution compartment 27 shown in Fig. 4. The rest of the configuration is the same as that shown in Fig. 4. The same components are denoted by the same reference numerals, and detailed description thereof will be omitted here.

[0053] Deionization compartment 29 is disposed between concentration compartment 21a and electrode compartment 22b. Anion exchange membrane 24b is disposed between deionization compartment 29 and concentration compartment 21a, and anion exchange membrane 24d is disposed between deionization compartment 29 and electrode compartment 22b. Deionization compartment 29 is filled with anion exchange resin. Although not shown, valves 26a, 26e, 26f, and 26g and flow meters FI1 to FI3 are disposed in the same manner as in the second example.

[0054] In the electric concentrator 2 of this example, the feed water (treated water 1b, 1d) is supplied to the deionization compartment 29, and a portion of the deionized water discharged from the deionization compartment 29 is supplied to the concentration compartment 21a and the electrode compartment 22b. The concentration compartment 21a discharges concentrated water.

[0055] A direct current is passed between the anode 23a and the cathode 23b. Ions are transferred between the deionization compartment 29 and the concentration compartment 21a via the anion exchange membrane 24b. The concentration compartment 21a discharges concentrated water containing concentrated anionic components. The concentrated water discharged from the concentration compartment 21a is supplied to the measuring instrument 3 shown in FIG. 1 (or FIG. 2).

[0056] 7 is a schematic diagram showing a fifth example of an electric concentrator 5. The electric concentrator 2 of this example has deionization compartments 30a and 30b, a concentration compartment 31, an anion exchange membrane 24e, and a cation exchange membrane 25d between an anode 23a and a cathode 23b.

[0057] Deionization compartment 30a is located on the anode side of concentration compartment 31. A cation exchange membrane 25d is located between deionization compartment 30a and concentration compartment 31. Deionization compartment 30b is located on the cathode side of concentration compartment 31. An anion exchange membrane 24e is located between deionization compartment 30b and concentration compartment 31. Deionization compartment 30a is filled with a cation exchange resin, and deionization compartment 30b is filled with an anion exchange resin. Concentration compartment 31 is filled with a mixed resin made by mixing a cation exchange resin and an anion exchange resin in a predetermined ratio. Deionization compartment 30a is configured to double as the anode side electrode chamber, and deionization compartment 30b is configured to double as the cathode side electrode chamber.

[0058] In the electrical concentrator 2 of this example, the feed water (treated water 1b, 1d) first passes through the distillation compartment 30b and then through the distillation compartment 30a, which discharges the desalted water.

[0059] The line for supplying the feed water to the deionization compartment 30a branches, and the branch line communicates with the concentration compartment 31. A portion of the feed water is supplied to the concentration compartment 31 via the branch line. The concentration compartment 31 discharges concentrated water.

[0060] A direct current is passed between the anode 23a and the cathode 23b. Ions move between the dilution compartment 30a and the concentration compartment 31 via the cation exchange membrane 25d, and ions move between the dilution compartment 30b and the concentration compartment 31 via the anion exchange membrane 24e. The concentration compartment 31 discharges concentrated water in which the anion and cation components have been concentrated. The concentrated water discharged from the concentration compartment 31 is supplied to the measuring instrument 3 shown in FIG. 1 (or FIG. 2).

[0061] Although not shown, the supply line and branch line for the feed water, the discharge line for the concentrated water, and the discharge line for the desalinated water are provided with valves and flow meters so that the flow rates of the feed water, concentrated water, and desalinated water can be adjusted. As with other examples of electric concentrators, the treated water may be branched and passed through the concentrating chamber, but in that case, there is a concern that air bubbles generated in the electrode chamber may be mixed in.

[0062] (Electric concentrator 6) Figure 8 is a schematic diagram showing a sixth example of an electric concentrator. The electric concentrator 2 of this example has concentration chambers 32a and 32b instead of the concentration chambers 21a and 21b and the anion exchange membrane 24c shown in Figure 3. The configuration other than these concentration chambers 32a and 32b is the same as that shown in Figure 3. The same components as those shown in Figure 3 are designated by the same reference numerals, and detailed description thereof will be omitted here.

[0063] Concentration compartment 32a is located on the anode side of deionization compartment 20a. An anion exchange membrane 24b is located between concentration compartment 32a and deionization compartment 20a. Concentration compartment 32a is filled with a mixed resin made by mixing a cation exchange resin and an anion exchange resin in a predetermined ratio. Concentration compartment 32b is located on the cathode side of deionization compartment 20b. A cation exchange membrane 25b is located between concentration compartment 32b and deionization compartment 20b. Concentration compartment 32b is filled with a mixed resin made by mixing a cation exchange resin and an anion exchange resin in a predetermined ratio. Although not shown, valves 26a, 26b, 26c, and 26d and flow meters FI1 to FI3 are arranged in the same manner as in the first example.

[0064] A direct current is passed between the anode 23a and the cathode 23b. Ions move between the dilution compartment 20a and the concentration compartment 32a via the anion exchange membrane 24b, and ions move between the dilution compartment 20b and the concentration compartment 32b via the cation exchange membrane 25b. The concentration compartment 32a discharges concentrated water containing concentrated anionic components, while the concentration compartment 32b discharges concentrated water containing concentrated cation components. The concentrated water discharged from the concentration compartment 32a and the concentrated water discharged from the concentration compartment 32b join together and are supplied to the measuring instrument 3 shown in FIG. 1 (or FIG. 2).

[0065] In the electrical concentrator 2 of this example, the flow rates of the feed water, desalted water, concentrated water, and electrode water can be adjusted, as in the first example. Note that a plurality of sections each consisting of the desalting compartments 20a, 20b, the concentration compartment 32b, the anion exchange membranes 24a, 24b, and the cation exchange membrane 25b may be provided between the anode 23a and the cathode 23b.

[0066] Next, a method for calculating the concentration ratio of the concentrator 2 in the water treatment system of the first or second embodiment will be specifically described.

[0067] Figure 9 is a diagram illustrating an example of a method for calculating the concentration ratio of the concentrator 2. In the example shown in Figure 9, feed water is supplied to the desalting compartment 40. The flow rate of the feed water supplied to the desalting compartment 40 is set to 150 L / h. The desalting compartment 40 discharges desalinated water. The flow rate of the desalinated water discharged from the desalting compartment 40 is set to 150 L / h.

[0068] A portion of the desalinated water discharged from the desalting compartment 40 is supplied to the concentration compartment 41 and the electrode compartment 42. The flow rate of the remaining desalinated water, after subtracting the amount supplied to the concentration compartment 41 and the electrode compartment 42, is set to 125 L / h. The concentration compartment 41 discharges concentrated water. The flow rate of the concentrated water discharged from the concentration compartment 41 is set to 15 L / h. The electrode compartment 42 discharges electrode water. The flow rate of the electrode water discharged from the electrode compartment 42 is set to 10 L / h.

[0069] In this example, the concentration ratio of the concentrator 2 can be calculated as follows based on the flow rate of the remaining desalinated water, the flow rate of the concentrated water, and the flow rate of the electrode water. The concentration (converted value) of the specific component in the treated water 1b can be calculated by dividing the measurement value of the measuring instrument 3 by the concentration factor. In some cases, the concentration chamber 41 also serves as the electrode chamber 42 due to the structure of the concentrating device 2. In such cases, the flow rate of the electrode water is omitted when calculating the concentration factor.

[0070] Figure 10 is a diagram illustrating another example of a method for calculating the concentration ratio of concentrator 2. In the example shown in Figure 10, feed water is supplied to deionization compartment 40, concentration compartment 41, and electrode compartment 42. The flow rate of feed water supplied to deionization compartment 40 is 125 L / h. Deionization compartment 40 discharges desalinated water. The flow rate of desalinated water discharged from deionization compartment 40 is 125 L / h. Concentration compartment 41 discharges concentrated water. The flow rate of concentrated water discharged from concentration compartment 41 is 15 L / h. Electrode compartment 42 discharges electrode water. The flow rate of electrode water discharged from electrode compartment 42 is 10 L / h.

[0071] In this example, the concentration ratio of the concentrator 2 can be calculated as follows. The concentration (converted value) of the specific component in the treated water 1b can be calculated by dividing the measurement value of the measuring instrument 3 by the concentration factor. In this example, as in the example of Figure 9, the concentration chamber 41 may also serve as the electrode chamber 42. In this case, the flow rate of the electrode water is omitted when calculating the concentration factor.

[0072] Next, an example using either the water treatment system of the first or second embodiment will be described.

[0073] Example 1 FIG. 11 is a block diagram showing a water treatment system according to a first example. The water treatment system of the first example is an application of the water treatment system of the second embodiment shown in FIG. 2. The water treatment device 1 was configured with a two-stage reverse osmosis (RO) membrane separation device 50, 51. Feedwater (water to be treated) 1a was supplied to the first-stage RO membrane separation device 50, and the permeate from the RO membrane separation device 50 was supplied to the second-stage RO membrane separation device 51. A concentrator 2 was installed in the permeate line of the second-stage RO membrane separation device 51. The concentrator 2 was the electric concentrator shown in FIG. 3, and its concentration ratio was set to approximately 11 times. An online silica meter 3a (High Sensitivity Silica Monitor SLIA-300, manufactured by Horiba Advanced Techno Co., Ltd.) was used as the measuring instrument 3. Desalinated water 2b discharged from the electric concentrator 2 was sent to the subsequent stage.

[0074] Operational management of the water treatment system of the first embodiment was carried out. The concentration of silica components contained in the concentrated water 2a discharged from the electric concentrator 2 was measured using a silica meter 3a. As the measurement results indicated a tendency for the silica concentration to be high, the pH at the second-stage RO inlet was adjusted to the alkaline side to improve the silica removal performance of the RO membrane.

[0075] Figure 12 is a diagram illustrating the change in silica concentration before and after adjustment. Figure 12(a) shows the silica measurement value, concentration ratio, converted value, and pH value at the second RO inlet before and after adjustment. Figure 12(b) shows the change in the silica converted value and the change in the pH value at the second RO inlet before and after adjustment. The broken line indicated by black squares shows the change in the silica converted value, and the broken line indicated by white circles shows the change in the pH value at the second RO inlet.

[0076] As can be seen from Figure 12, the online silica meter 3a was used to monitor changes in the silica concentration of the permeate discharged from the second-stage RO membrane separation device 51, and operation adjustments were made without overlooking small fluctuations, allowing the silica concentration to be stabilized at 3 μg / L or less. Furthermore, the conductivity (resistivity) of the RO permeate was 1.0 μS / cm (1.0 MΩ cm) before pH adjustment and 4.0 μS / cm (0.25 MΩ cm) after adjustment, a value of 5 μS / cm or less. This demonstrates that treated water (RO permeate) meeting the required water quality for use as wash water can be stably maintained.

[0077] Example 2 FIG. 13 is a block diagram showing a water treatment system according to a second example. The water treatment system of the second example is an application of the water treatment system of the first embodiment shown in FIG. 1. The water treatment device 1 is configured with a chemical regeneration type ion exchange resin device 60. The chemical regeneration type ion exchange resin device 60 is a regenerative type ion exchange resin device that regenerates ion exchange resin using chemicals. Feed water (water to be treated) 1a was supplied to the chemical regeneration type ion exchange resin device 60. A concentrator 2 was installed in a line branching from the treated water line of the chemical regeneration type ion exchange resin device 60. The concentrator 2 was the electric concentrator shown in FIG. 3, and its concentration ratio was set to 8 times. An online silica meter 3a (High Sensitivity Silica Monitor SLIA-300, manufactured by Horiba Advanced Techno Co., Ltd.) was used as the measuring instrument 3. The desalinated treated water 2b discharged from the electric concentrator 2 was sent to a downstream stage together with the treated water discharged from the chemical regeneration type ion exchange resin device 60.

[0078] Operational management of the water treatment system of this second embodiment was carried out. During this operational management, the resistivity of treated water 1b discharged from the chemical regeneration type ion exchange resin device 60 fluctuated between 13 and 18 MΩ cm. The concentration of silica components contained in concentrated water 2a discharged from the electric concentrator 2 was measured using a silica meter 3a.

[0079] Figure 14 is a diagram illustrating the change in silica concentration before and after chemical regeneration. As can be seen from Figure 14, immediately after chemical regeneration, the silica concentration began to decrease, and then reached an inflection point and began to increase. This increasing trend in silica concentration was captured and the timing of chemical regeneration was adjusted. This enabled optimal operation.

[0080] For example, when chemical regeneration is performed periodically using a timer, the interval between chemical regenerations is set with a safety margin. In contrast, according to the second embodiment, there is no need to ensure such a safety margin, so the size of the equipment can be significantly slimmed down. Furthermore, by identifying trends in performance deterioration or increase at an early stage, it is possible to approach a more optimal regeneration frequency.

[0081] Example 3 Figure 15 is a block diagram showing a water treatment system of Example 3. The water treatment system of Example 3 is an application of the water treatment system of the first embodiment shown in Figure 1. The water treatment device 1 was configured with a non-regenerative ion exchange resin device (CP) 61. Feed water (water to be treated) 1a was supplied to the non-regenerative ion exchange resin device 61. A concentrator 2 was placed on a line branching from the treated water line of the non-regenerative ion exchange resin device 61. The concentrator 2 was the electric concentrator shown in Figure 3, and its concentration ratio was set to approximately 7 times. An online silica meter 3a (High Sensitivity Silica Monitor SLIA-300, manufactured by Horiba Advanced Techno Co., Ltd.) was used as the measuring instrument 3. The desalinated treated water 2b discharged from the electric concentrator 2 was sent to the subsequent stage together with the treated water discharged from the non-regenerative ion exchange resin device 61.

[0082] Operational management of the water treatment system of the third embodiment was carried out. During this operational management, the resistivity of treated water 1b discharged from the non-regenerative ion exchange resin device 61 was stable at 18.2 MΩ cm. The concentration of silica components contained in concentrated water 2a discharged from the electric concentrator 2 was measured using a silica meter 3a.

[0083] Fig. 16 shows the change in silica concentration. As can be seen from Fig. 16, silica components were leaking from the non-regenerative ion exchange resin device 61 at a stable concentration, indicating that it was time to replace the resin. In this way, by measuring the concentration of the concentrated water 2a from the electrical concentrator 2, it was possible to confirm low concentrations of silica components that could not normally be measured on-site using an online meter.

[0084] Example 4 Figure 17 is a block diagram showing a water treatment system of Example 4. The water treatment system of Example 4 is an application of the water treatment system of the first embodiment shown in Figure 1. The water treatment device 1 is configured with an electrically regenerated deionized water production device (EDI device) 62. The EDI device 62 is configured so that its treatment performance improves as the value of the current supplied thereto increases.

[0085] Feed water (water to be treated) 1a was supplied to EDI device 62. A concentrator 2 was placed on a line branching off from the treated water line of EDI device 62. The electric concentrator shown in FIG. 4 was used as concentrator 2, and the concentration ratio was set to approximately 3 times. An online boron meter 3b (Sievers UPW Boron Analyzer manufactured by Suez) was used as measuring instrument 3. Desalinated treated water 2b discharged from electric concentrator 2 was sent to the subsequent stage together with treated water discharged from EDI device 62.

[0086] Operational management of the water treatment system of the fourth embodiment was carried out. During this operational management, the resistivity of treated water 1b discharged from EDI device 62 was fluctuating between 17.5 and 17.9 MΩ cm. The concentration of boron contained in concentrated water 2a discharged from electric concentrator 2 was measured using boron meter 3b.

[0087] FIG. 18 is a diagram illustrating changes in boron concentration. As can be seen from FIG. 18, it was found that the boron concentration of the treated water from the EDI device 62 fluctuated. Because the boron concentration was trending higher, the current value supplied to the EDI device 62 was increased. Specifically, the current value was increased from 4.0 A to 5.0 A. This adjustment reduced the fluctuation range of the boron concentration, confirming that the treatment performance of the EDI device 62 had improved. Note that, with the method of analyzing sampled water, it was difficult to grasp the fluctuations and trends in the boron concentration. It was also found that when the fluctuation range of the boron concentration was large, the correct concentration could not be grasped depending on the timing of sampling.

[0088] (Example 5) Figure 19 is a block diagram showing a water treatment system of Example 5. The water treatment system of Example 5 is an application of the water treatment system of the first embodiment shown in Figure 1. The water treatment device 1 is configured with an EDI device 63. The EDI device 63 is configured so that the treatment performance improves when the water temperature of the supply water (water to be treated) 1a is lowered.

[0089] Feedwater 1a was supplied to EDI device 63. A concentrator 2 was placed on a line branching off from the treated water line of EDI device 63. The electric concentrator shown in FIG. 4 was used as concentrator 2, and the concentration ratio was set to approximately 3 times. An online boron meter 3b (Sievers UPW Boron Analyzer, manufactured by Suez) was used as measuring instrument 3. Desalinated treated water 2b discharged from electric concentrator 2 was sent to the subsequent stage together with treated water discharged from EDI device 63.

[0090] Operational control of the water treatment system of the fifth embodiment was carried out. During this operational control, the concentration of boron contained in the concentrated water 2a discharged from the electric concentrator 2 was measured by the boron meter 3b.

[0091] FIG. 20 is a diagram illustrating changes in boron concentration. As can be seen from FIG. 20, the boron concentration of the treated water from the EDI device 63 remained high. For this reason, the temperature of the feed water 1a was lowered from 25°C to 20°C to improve the treatment performance of the EDI device 63. The resistivity of the treated water from the EDI device 63 was stable between 18.0 and 18.2 MΩ cm before and after the water temperature adjustment. It was confirmed that, because the water temperature can be adjusted while monitoring the boron concentration, it is possible to respond appropriately to an increase in the amount of boron inflow from the pretreatment device installed upstream of the EDI device 63.

[0092] (Example 6) Figure 21 is a block diagram showing a water treatment system of Example 6. The water treatment system of Example 6 is an application of the water treatment system of the first embodiment shown in Figure 1. The water treatment device 1 is configured with the EDI device 62 used in Example 4.

[0093] Feed water (water to be treated) 1a was supplied to an EDI device 62. A concentrator 2 was placed on a line branching off from the treated water line of the EDI device 62. The electric concentrator shown in FIG. 4 was used as the concentrator 2, and its concentration ratio was set to approximately 20 times. An online TOC meter 3c (Sievers m9e, manufactured by Suez) was used as the measuring instrument 3. Desalinated treated water 2b discharged from the electric concentrator 2 was sent to the subsequent stage together with the treated water discharged from the EDI device 62.

[0094] Operational management of the water treatment system of the sixth embodiment was carried out. During this operational management, the resistivity of the treated water 1b discharged from the EDI device 62 was fluctuating between 17.5 and 17.9 MΩ cm. The IC (inorganic carbon) concentration in the concentrated water 2a discharged from the electrical concentrator 2 was measured using the IC (inorganic carbon) measurement function of the TOC meter 3c.

[0095] 22 is a diagram for explaining changes in IC concentration. As can be seen from FIG. 22, the IC concentration of the treated water from the EDI device 62 was stable at a low value, but it was confirmed that it was on a downward trend. In this sixth example, the IC concentration was monitored without adjusting the current.

[0096] The IC (inorganic carbon C) value can be converted into the amount of carbon dioxide leaking into the treated water. C = 12 [g / mol], CO ２ = 44 [g / mol], IC [mg / L as C] × (44 / 12) = carbonic acid [mgL as CO ２ ] can be converted into

[0097] Since carbon dioxide is a component that places a load on the non-regenerative ion exchange resin device (CP) installed downstream of the EDI device 62, knowing its concentration more accurately is useful for optimizing the CP replacement frequency.

[0098] Other Examples In the above-described examples, an electric concentrator was used as the concentrator 2 in the water treatment system of the first or second embodiment, but an RO membrane separation device can also be used instead.

[0099] 23 is a diagram for explaining an example of a method for calculating the concentration ratio of an RO membrane separation device. In the example shown in FIG. 23, feed water is supplied to an RO membrane separation device 70. The flow rate of the feed water supplied to the RO membrane separation device 70 is 1.24 m 3 The RO membrane separation device 70 discharges concentrated water 2a and desalinated water (permeate) 2b. The flow rate of the concentrated water 2a discharged from the RO membrane separation device 70 is 0.12 m 3 The flow rate of the desalinated water 2b discharged from the RO membrane separation device 70 is 1.12 m 3 / h.

[0100] The concentration ratio of the RO membrane separation device 70 can be calculated as follows. By dividing the measured value of the measuring instrument 3 by the concentration factor, it is possible to calculate the concentration (converted value) of the specific component in the treated water 1b.

[0101] Note that among the components to be concentrated, there are some components with low rejection rates (removal rates) by the RO membrane. For components with low rejection rates, a large amount leaks into the RO permeate, so the concentration (converted value) calculated using the concentration factor may differ from the actual concentration. Regarding this point, the results of actual operation of the RO membrane separation device 70 will be specifically explained below, in comparison with an EDI device.

[0102] An 8-inch XLE-440 (manufactured by DuPont) element was used as the RO membrane. The flow rates of the feed water, concentrated water 2a, and desalinated water 2b were set under the conditions described above, and the RO membrane separation device 70 was operated so that the concentration ratio was 10.3 times. The feed water had a resistivity of 0.1 MΩ cm, a sodium concentration of 1.1 ppm, and a silica concentration of 1.6 ppm.

[0103] Figure 24 shows the measurement results for sodium and silica. The measured value of the Na concentration in the concentrated water was 7.2 ppm, and the equivalent concentration value obtained by dividing this measurement by the concentration factor was 0.7 ppm. It was found that this equivalent concentration value of 0.7 ppm is significantly different from the actual concentration (1.1 ppm). When the sodium concentration of the desalted water (RO permeate) was measured, it was found to be 0.4 ppm, and the desalination rate was found to be approximately 64%.

[0104] On the other hand, the measured silica concentration in the concentrated water was 15.2 ppm, and the equivalent concentration value obtained by dividing the measured value by the concentration factor was 1.5 ppm. It was found that this equivalent concentration value of 1.5 ppm is approximately consistent with the actual concentration (1.6 ppm). The silica concentration in the desalinated treated water (RO permeate) was measured and found to be 0.1 ppm, indicating a salt rejection rate of approximately 94%. As can be seen from the above, when an RO membrane separation device is used as the concentrator 2, it is difficult to accurately determine the concentration of components with low salt rejection rates (e.g., sodium) in the treated water discharged from the water treatment device 1. Therefore, there is a problem in that the components to be concentrated are limited.

[0105] In contrast, an electric concentrator has a rejection rate of 90% or more for both sodium and silica. Therefore, when an electric concentrator is used as the concentrator 2, it is possible to accurately determine the concentration of components such as sodium in the treated water discharged from the water treatment device 1, which is difficult to accurately determine using an RO membrane separation device. Therefore, compared to an RO membrane separation device, an electric concentrator has the advantage of being able to relax the restrictions on the components to be concentrated. Note that there are many different types of RO membranes, and some have a high sodium removal rate depending on the membrane selected. Therefore, selecting a membrane with high removal performance for the component to be measured may be sufficient.

[0106] The above describes a specific configuration example of the concentrator 2 and its effects. Next, we will explain in detail how the presence or absence of the concentrator 2 affects the measurement of the measuring instrument 3. Here, we will explain the effect of the presence or absence of the concentrator 2 on the measurement of the silica meter 3a using the water treatment system (chemical regeneration) shown in Figure 13 as an example.

[0107] Figure 25 shows an example of measurement using the silica meter 3a without the concentrator 2. Figure 25 shows the change in the measured silica concentration before and after chemical regeneration. In this example, the silica meter 3a was used to measure the silica concentration of treated water 1d, which is part of treated water 1b discharged from the chemical regeneration-type ion exchange resin device 60. The silica meter 3a was unable to measure silica concentrations below a lower limit of about 200 ppt.

[0108] Figure 26 shows an example of measurement using the silica meter 3a when the concentrator 2 is included. Figure 26 shows the change in silica concentration (converted value) before and after chemical regeneration. In this example, the silica meter 3a was used to measure the silica concentration of concentrated water 2a obtained by concentrating treated water 1d, which is a portion of treated water 1b discharged from the chemical regeneration-type ion exchange resin device 60. The silica concentration of concentrated water 2a was 200 ppt or higher, which could be measured using the silica meter 3a. This result demonstrates that by using the concentrator 2, silica concentrations below 200 ppt can be measured using the silica meter 3a, confirming the usefulness of the concentrator 2.

[0109] (Third Embodiment) Because the lower limit of detectable concentrations using general-purpose measuring instruments for measuring water quality is high, there are limitations to directly measuring the quality of pure-water-level treated water produced by a water treatment device. Therefore, a water quality measuring device has been proposed that concentrates treated water produced by a water treatment device, measures the concentration of specific components contained in the concentrate, and obtains the quality of the treated water based on the measured value and the concentration ratio. As an example of such a water quality measuring device, Patent Document 3 describes an underwater ion monitor equipped with an electrodialysis device (concentrator) that concentrates ions in water and an electrical conductivity meter (measuring instrument) that measures the electrical conductivity of the ion-concentrated water concentrated by the electrodialysis device. However, the water quality measuring devices described therein, including the underwater ion monitor described in Patent Document 1, have the following problems. The flow rate required for concentration measurement by the measuring instrument is fixed. Therefore, for example, if the concentrator performs concentration by 10 times or more, the treated water must be passed through the concentrator at a flow rate at least 10 times the flow rate required by the measuring instrument. The larger the flow rate of treated water passed through the concentrator, the larger the concentrator's size becomes. Therefore, the concentrator tends to be large in the above-mentioned water quality measuring device. An object of this embodiment is to provide a water quality measuring device, a water treatment system, and a water quality measuring method that can reduce the size of the concentrating device.

[0110] FIG. 27 is a block diagram showing the configuration of a water treatment system according to a third embodiment of the present invention. Referring to FIG. 27 , the water treatment system of this embodiment includes a water treatment device 1, a water quality measurement device 10, and a monitoring unit 11. The water treatment device 1 treats water to be treated 1a to produce treated water 1b. The treated water 1b is, for example, pure water (or ultrapure water) having a specific resistance of, for example, 0.10 MΩ·cm or more (conductivity of 10 μS / cm or less). The treated water 1b produced by the water treatment device 1 is branched into two parts: one is supplied as treated water 1c to a point-of-use or a downstream treatment device, and the other is supplied as treated water 1d to the water quality measurement device 10. The water treatment device 1 includes, for example, at least one of a reverse osmosis (RO) membrane separation device, a regenerative ion exchange resin device, a non-regenerative ion exchange resin device, and an electro-deionized water production device (EDI). The water treatment device 1 may also include other water treatment devices.

[0111] The water quality measuring device 10 includes a concentrator 2, a measuring instrument 3, a storage unit 7, a timer 8, a sensor 9, a control unit 12, and a water pump 13. The concentrator 2 is configured to pass treated water 1d, which is a portion of treated water 1b produced by the water treatment device 1. The concentrator 2 concentrates a specific component (a component to be concentrated) contained in the treated water 1d. The concentrator 2 supplies a signal indicating the concentration ratio to the monitoring unit 11. The concentrator 2 is, for example, a desalination device that produces at least concentrated water 2a and desalinated water 2b. The removal rate (density) of the specific component is 90% or more, preferably 95% or more, and more preferably 99% or more. The concentration ratio of the concentrated water 2a relative to the treated water 1d is 3 times or more, preferably 10 times or more, and more preferably 20 times or more. In this embodiment, the removal rate (density) is 90% or more, and the concentration ratio is in the range of 3 to 20 times. The concentrated water 2a is supplied to the storage unit 7. The desalinated treated water 2b is combined with the treated water 1c and supplied to a point of use. It is also possible to supply all of the treated water 1b produced by the water treatment device 1 to the concentrator 2 as treated water 1d.

[0112] Here, the configuration of the concentrator 2 and its concentration ratio will be described in detail. Fig. 28 is a schematic diagram showing one configuration example of the concentrator 2. The concentrator 2 shown in Fig. 28 has a deionization compartment 40, a concentration compartment 41, and an electrode compartment 42. Feed water (treated water 1d) is supplied to the deionization compartment 40. The flow rate of the feed water supplied to the deionization compartment 40 is set to 20 L / h. The deionization compartment 40 discharges desalinated water. The flow rate of the desalinated water discharged from the deionization compartment 40 is set to 20 L / h.

[0113] A portion of the desalinated water discharged from the desalting compartment 40 is supplied to the concentration compartment 41 and the electrode compartment 42. The flow rate of the remaining desalinated water, after subtracting the amount supplied to the concentration compartment 41 and the electrode compartment 42, is set to 15 L / h. This remaining desalinated water corresponds to the desalinated water 2b shown in FIG. 27. The concentration compartment 41 discharges concentrated water 2a. The flow rate of the concentrated water 2a discharged from the concentration compartment 41 is set to 2 L / h. The electrode compartment 42 discharges electrode water. The flow rate of the electrode water discharged from the electrode compartment 42 is set to 3 L / h.

[0114] The concentration ratio of the concentrator 2 can be calculated as follows based on the flow rate of the remaining desalinated water 2b, the flow rate of the concentrated water 2a, and the flow rate of the electrode water. The concentration (converted value) of the specific component in the treated water 1b can be calculated by dividing the measurement value of the measuring instrument 3 by the concentration factor. In some cases, the concentration chamber 41 also serves as the electrode chamber 42 due to the structure of the concentrating device 2. In such cases, the flow rate of the electrode water is omitted when calculating the concentration factor.

[0115] Fig. 29 is a schematic diagram showing another example of the configuration of the concentrator 2. The concentrator 2 shown in Fig. 29 is composed of an RO membrane separation device 70. Feed water (treated water 1d) is supplied to the RO membrane separation device 70. The flow rate of the feed water supplied to the RO membrane separation device 70 is 1.24 m 3 The RO membrane separation device 70 discharges concentrated water 2a and desalinated water (permeate) 2b. The flow rate of the concentrated water 2a discharged from the RO membrane separation device 70 is 0.12 m 3 The flow rate of the desalinated water 2b discharged from the RO membrane separation device 70 is 1.12 m 3 / h.

[0116] The concentration ratio of the RO membrane separation device 70 can be calculated as follows. By dividing the measured value of the measuring instrument 3 by the concentration factor, it is possible to calculate the concentration (converted value) of the specific component in the treated water 1b.

[0117] Referring again to Figure 27, the storage unit 7 is configured to store the concentrated water 2a from the concentrating device 2 and supply the stored concentrated water 2a to the measuring instrument 3. In this embodiment, a water pump 13 is provided in the piping connecting the storage unit 7 and the measuring instrument 3, and this water pump 13 supplies the concentrated water 2a stored in the storage unit 7 to the measuring instrument 3. The storage unit 7 can be configured as a tank or a water tank, but is not limited to this. The storage unit 7 may have any structure as long as it can store the concentrated water 2a.

[0118] The measuring instrument 3 measures the concentration of a specific component contained in the concentrated water 2a supplied from the storage unit 7. The measuring instrument 3 supplies a signal indicating the measured value to the monitoring unit 11. The measuring instrument 3 is, for example, an instrument that measures the concentration of any of the following components: silica, boron, metal ions (sodium, aluminum, calcium, magnesium, etc.), carbonate, IC (inorganic carbon), and TOC (total organic carbon). Note that these instruments are merely examples, and instruments that measure the concentration of other components may also be used. The concentrated water that has passed through the measuring instrument 3 is generally discarded, but from the standpoint of utilization efficiency, it may be returned to an upstream or downstream stage of the water treatment device 1, or may be used in another system.

[0119] The control unit 12 controls the operation of the water pump 13. The control unit 12 operates the water pump 13 during the measurement period of the measuring instrument 3. Either the timer 8 or the sensor 9 can be used to control the water pump 13. The timer 8 measures the elapsed time. The control unit 12 operates the water pump 13 at predetermined time intervals based on the time measured by the timer 8. Here, the predetermined time may be, for example, the time required to store in the storage unit 7 an amount of water necessary for the concentration measurement by the measuring instrument 3.

[0120] Furthermore, sensor 9 detects the water level in storage unit 7. Controller 12 controls the operation of water pump 13 in accordance with the water level detected by sensor 9. Specifically, controller 12 operates water pump 13 when the water level detected by sensor 9 reaches a first level, and stops the water pump when the water level detected by sensor 9 reaches a second level lower than the first level. Here, the storage volume between the first level and the second level may be, for example, a storage volume corresponding to the amount required for concentration measurement by measuring instrument 3.

[0121] The monitoring unit 11 monitors the water quality of the treated water 1b based on the measurement values ​​of the measuring instrument 3. The monitoring unit 11 has a treated water concentration calculation unit 4, an adjustment unit 5, and an alarm output unit 6. The treated water concentration calculation unit 4 calculates the concentration value (conversion value) of a specific component in the treated water 1b by dividing the measurement value of the measuring instrument 3 by the concentration ratio of the concentrating device 2. The concentration value (conversion value) is supplied to the adjustment unit 5 and the alarm output unit 6. Furthermore, the concentration ratio may be a preset value, or may be a value constantly calculated from the values ​​of each flow meter installed in the concentrating device 2.

[0122] The adjustment unit 5 adjusts the treatment state of the water treatment device 1 for the specific component based on the concentration value (converted value) of the specific component in the treated water 1b. The adjustment unit 5 is configured to be able to adjust at least one of, for example, flow rate adjustment, chemical regeneration, ion exchange resin replacement, current adjustment, water temperature adjustment, and pH adjustment. These adjustments will be described in detail in the examples below. Note that these adjustments may also be performed by an administrator.

[0123] The alarm output unit 6 outputs an alarm based on the concentration value (converted value) of a specific component in the treated water 1b. For example, the alarm output unit 6 outputs an alarm when the concentration value (converted value) of the specific component in the treated water 1b exceeds a threshold value or when a trend indicating a decline in treatment performance for the specific component is detected. The alarm output unit 6 may include a display device that displays a message indicating the alarm, a speaker that outputs an alarm sound, or the like. In this case, the administrator can take the necessary steps to restore performance in response to the alarm (message or alarm sound) from the alarm output unit 6.

[0124] In the water treatment system of the present embodiment described above, the water quality measuring device 10 is configured so that the flow rate of concentrated water supplied from the storage unit 7 to the measuring device 3 is greater than the flow rate of concentrated water supplied from the concentrating device 2 to the storage unit 7 during the measurement period of the measuring device 3. This makes it possible to reduce the size of the concentrating device 2. Below, this effect will be specifically described in comparison with a water quality measuring device in a water treatment system of a comparative example.

[0125] Figure 30 is a block diagram showing the configuration of a water treatment system of a comparative example. The water treatment system shown in Figure 30 is the same as the water treatment system shown in Figure 27 except that it includes a water quality measuring device 10A instead of the water quality measuring device 10. The water quality measuring device 10A includes a concentrating device 2A and a measuring instrument 3A, but does not include the storage unit 7, timer 8, sensor 9, control unit 12, or water pump 13. The concentrating device 2A and measuring instrument 3A have the same configuration as the concentrating device 2 and measuring instrument 3 shown in Figure 27.

[0126] The specifications of the measuring instrument 3A are a measurement flow rate of 200 ml / min (=12 L / h), a measurement time of 5 minutes per measurement, and a required water volume of 1000 ml per measurement. The concentration ratio of the concentrator 2A is set to 10, and the measuring instrument 3A measures the concentration every 30 minutes. In this case, the flow rate required for measuring the concentration with the measuring instrument 3A is 12 L / h, so the treated water 1d needs to be passed through the concentrator 2A at a flow rate of 120 L / h, which is 10 times the flow rate required for measuring the concentration with the measuring instrument 3A. The larger the flow rate of the passed treated water 1d, the larger the size of the concentrator 2A. Therefore, in the water quality measuring device 10A of the comparative example, the concentrator 2A tends to be large.

[0127] In contrast, in the water quality measuring device 10 shown in FIG. 27 , concentrated water 2a discharged from the concentrator 2 is stored in the storage section 7, and by operating the pump 13 during the measurement period of the measuring instrument 3, the concentrated water 2a stored in the storage section 7 is supplied to the measuring instrument 3. The specifications of the measuring instrument 3 are the same as those of the measuring instrument 3A. In the water quality measuring device 10, the concentration ratio of the concentrator 2 is also set to 10, and concentration measurements are performed every 30 minutes using the measuring instrument 3. In this case, the required flow rate from the concentrator 2 to the storage section 7 is 2.00 L / h (1000 ÷ 30 = 33.3 ml / min). Here, the flow rate A supplied from the concentrator 2 to the storage section 7 is set to 2 L / h, and the flow rate required for concentration measurements using the measuring instrument 3 is set to 12 L / h. In this case, the treated water 1d is passed through the concentrator 2 at a flow rate of 20 L / h, which is 10 times the flow rate A (= 2 L / h). The water flow rate of the concentrator 2 (20 L / h) is significantly lower than the water flow rate of the comparative concentrator 2A (120 L / h). The size of the concentrator 2 can be reduced to one-sixth of that of the concentrator 2A.

[0128] Furthermore, the water treatment system of this embodiment can further achieve the following effects. An electrolytic deionized water production device (EDI device) can be used as the concentrator 2 (2A). With an EDI device, the water quality is not stable immediately after operation starts, and it takes time for the water quality to stabilize after operation starts. For this reason, when an EDI device is used as the concentrator 2, 2A, the EDI device needs to be operated constantly, not just during the measurement period of the measuring instrument 3. In the following, it is assumed that both the concentrator 2, 2A are EDI devices.

[0129] In the comparative water quality measuring device 10A shown in Figure 30, even when the measuring instrument 3A measures the concentration every 30 minutes, the concentrator 2A must be operated continuously. Therefore, in the comparative water quality measuring device 10A, concentrated water is constantly discharged from the concentrator 2A at a flow rate of 12 L / h. In contrast, in the water quality measuring device 10 shown in Figure 27, concentrated water is constantly discharged from the concentrator 2A at a flow rate of 2 L / h. In this case, the amount of concentrated water discharged from the concentrator 2 can be reduced to one-sixth of the amount of concentrated water discharged from the concentrator 2A.

[0130] Furthermore, the water treatment system of this embodiment can achieve the following additional effects. Because the concentration of a specific component in pure water-level treated water 1b is lower than the lower limit of the concentration measurable by the measuring instrument 3, it is difficult to accurately measure the concentration of the specific component in treated water 1b using the measuring instrument 3. In this embodiment, the measuring instrument 3 measures the concentration of the specific component in concentrated water 2a, which is obtained by concentrating treated water 1d, a portion of treated water 1b. The concentration of the specific component in concentrated water 2a is higher than the lower limit of the concentration measurable by the measuring instrument 3. Therefore, the measuring instrument 3 can accurately measure the concentration of the specific component in concentrated water 2a. The measured value of concentrated water 2a can be converted to the concentration value of the specific component in treated water 1b by dividing it by the concentration factor of the concentrator 2. This makes it possible to obtain the concentration (converted value) of the specific component in pure water-level treated water 1b.

[0131] Fig. 31 is a diagram showing the change in silica concentration at the outlet when an ion exchange resin device is used as the water treatment device 1. As can be seen from Fig. 31, by measuring the concentration of the concentrated water 2a from the concentrator 2, it was possible to confirm a low concentration (51 ppt in this case) of silica components that could not normally be measured on-site using an online meter.

[0132] (Fourth embodiment) Figure 32 is a block diagram showing the configuration of a water treatment system according to a fourth embodiment of the present invention. The water treatment system of this embodiment differs from the water treatment system of the third embodiment in that a switching valve 14 is provided in the water quality measurement device 10 to circulate concentrated water. In Figure 32, the same components as those in the water treatment system of the third embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0133] An outlet line 15a of the water pump 13 branches into a supply line 15b to the measuring instrument 3 and a circulation line 15c to the reservoir 7, and a switching valve 14 is provided at this branch point. The switching valve 14 connects the outlet line 15a to either the supply line 15b or the circulation line 15c.

[0134] The control unit 12 controls the operation of the switching valve 14. With the water pump 13 operating, the control unit 12 controls the switching valve 14 to connect the outlet line 15 a and the supply line 15 b during the measurement period of the measuring instrument 3, and controls the switching valve 14 to connect the outlet line 15 a and the circulation line 15 c outside the measurement period.

[0135] The switching valve 14 can be controlled using either the timer 8 or the sensor 9. Specifically, the control unit 12 controls the switching valve 14 so as to switch between a first state in which the outlet line 15 a and the supply line 15 b are connected and a second state in which the outlet line 15 a and the circulation line 15 c are connected at predetermined time intervals based on the time measured by the timer 8.

[0136] Furthermore, the control unit 12 controls the switching valve 14 to switch between the first state and the second state depending on the water level detected by the sensor. Specifically, the control unit 12 switches the switching valve 14 to the first state when the water level detected by the sensor 9 reaches the first level, and switches the switching valve 14 to the second state when the water level detected by the sensor 9 reaches a second level lower than the first level. Here, the storage amount between the first level and the second level may be, for example, a storage amount corresponding to the amount required for concentration measurement by the measuring instrument 3.

[0137] In addition to the effects described in the third embodiment, the water treatment system of this embodiment can achieve the following effects. During the measurement period of the measuring instrument 3, concentrated water discharged from the water supply pump 13 is supplied to the measuring instrument 3. Outside the measurement period, the concentrated water discharged from the water supply pump 13 is returned to the storage unit 7 via the circulation line 15c. If the storage unit 7 is a tank or a water tank, the concentration of the concentrated water stored in the storage unit 7 may differ between the upper and lower sides. By circulating the concentrated water via the circulation line 15c, the quality of the concentrated water stored in the storage unit 7 can be stabilized. As a result, the measurement accuracy of the measuring instrument 3 can be improved.

[0138] In the water treatment systems of the third and fourth embodiments described above, the illustrated configurations are merely examples and can be modified as needed. For example, in the water treatment system of the third embodiment, the water supply pump 13 is provided between the reservoir 7 and the measuring instrument 3, but this is not limiting. The water supply pump 13 may be provided inside the measuring instrument 3. In this case, a measuring instrument having a pump function may be used as the measuring instrument 3.

[0139] Furthermore, although the concentrated water is supplied from the reservoir 7 to the measuring instrument 3 using the water pump 13, this is not limiting. Any structure may be used as long as it can supply the concentrated water stored in the reservoir 7 to the measuring instrument 3. For example, a structure may be applied in which concentrated water is supplied from the reservoir 7 to the measuring instrument 3 using gravity. In this case, the flow rate and on / off of the concentrated water may be controlled using a valve.

[0140] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0141] This application claims priority based on Japanese Patent Application No. 2023-206112 filed on December 6, 2023, and Japanese Patent Application No. 2024-010924 filed on January 29, 2024, the disclosures of which are incorporated herein in their entireties.

[0142] 1 Water treatment device 1b Treated water 2 Concentration device 2a Concentrated water 3 Measuring instrument 11 Monitoring unit

Claims

1. A water quality measuring device used in a water treatment system that processes water to be treated to produce treated water, A concentration device that passes at least a portion of the treated water produced by the water treatment device through it and concentrates specific components in the treated water, A measuring instrument for measuring the concentration of the specific component in the concentrated water concentrated by the aforementioned concentration device, The device has a storage unit provided between the concentration device and the measuring instrument, which stores the concentrated water from the concentration device and supplies the stored concentrated water to the measuring instrument. A water quality measuring device characterized in that the flow rate of concentrated water supplied from the storage unit to the measuring instrument is greater than the flow rate of concentrated water supplied from the concentration device to the storage unit.

2. A water pump for supplying the concentrated water stored in the storage section to the measuring instrument, The system includes a control unit that controls the operation of the water supply pump, The water quality measuring device according to claim 1, wherein the control unit operates the water supply pump during the measurement period of the measuring instrument.

3. It has a timer that measures elapsed time, The water quality measuring device according to claim 2, wherein the control unit operates the water supply pump at predetermined intervals based on the measurement time of the timer.

4. The storage section has a sensor that detects the water level, The water quality measuring device according to claim 2, wherein the control unit controls the operation of the water supply pump according to the water level detected by the sensor.

5. The outlet line of the water supply pump is branched into a supply line to the measuring instrument and a circulation line to the storage unit, and a switching valve is provided at the branch to connect the outlet line to either the supply line or the circulation line. The water quality measuring device according to claim 2, wherein the control unit controls the switching valve to connect the outlet line and the supply line during the measurement period while the water supply pump is in operation, and controls the switching valve to connect the outlet line and the circulation line outside of the measurement period.

6. It has a timer that measures elapsed time, The water quality measuring device according to claim 5, wherein the control unit controls the switching valve to switch between a first state in which the outlet line and the supply line are connected and a second state in which the outlet line and the circulation line are connected at predetermined time intervals based on the measurement time of the timer.

7. The storage section has a sensor that detects the water level, The water quality measuring device according to claim 5, wherein the control unit controls the switching valve to switch between a first state in which the outlet line and the supply line are connected and a second state in which the outlet line and the circulation line are connected, according to the water level detected by the sensor.

8. A water treatment apparatus that processes water to be treated and produces treated water, A concentration device that passes at least a portion of the treated water produced by the water treatment device through it and concentrates specific components in the treated water, A measuring instrument for measuring the concentration of the specific component in the concentrated water concentrated by the aforementioned concentration device, The device has a storage unit provided between the concentration device and the measuring instrument, which stores the concentrated water from the concentration device and supplies the stored concentrated water to the measuring instrument. A water treatment system characterized by operating in such a way that the flow rate of concentrated water supplied from the storage unit to the measuring instrument is greater than the flow rate of concentrated water supplied from the concentration device to the storage unit.

9. A water quality measurement method performed in a water treatment apparatus that processes water to be treated to produce treated water, The steps include passing at least a portion of the treated water produced by the water treatment device through a concentration device to concentrate specific components in the treated water, The steps include storing the concentrated water concentrated by the aforementioned concentration device in a storage unit, The steps include supplying the concentrated water stored in the storage unit to a measuring instrument to measure the concentration of the specific component in the concentrated water, A water quality measurement method characterized by comprising the step of operating the device such that the flow rate of concentrated water supplied from the storage unit to the measuring instrument is greater than the flow rate of concentrated water supplied from the concentration device to the storage unit.