Water treatment system and water quality measurement method

Abstract

The concentration of non-volatile dissolved substances in the water flowing through the water treatment system must be properly managed. [Solution] The water treatment system 1 has a measuring device 5 that introduces the water flowing through the water treatment system 1 as the water to be measured and measures the water quality of the water to be measured. The measuring device 5 has an evaporation unit 52 that evaporates the water to be measured to form residual particles, and a measuring unit 53 that measures the number of residual particles.

Description

Technical Field

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

Background Art

[0002] In a water treatment system, there is a method of determining the water quality of the water flowing through the water treatment system based on the number of fine particles contained in the water flowing through the water treatment system (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The water flowing through the water treatment system may contain, in addition to particles, non-volatile dissolved substances that become particulate residues upon drying. Such non-volatile dissolved substances may be harmful depending on the use of pure water. For example, in the cleaning and drying process of semiconductor wafers, non-volatile dissolved substances may precipitate due to the evaporation of ultrapure water and become residues on the wafers.

[0005] An object of the present invention is to provide a water treatment system capable of appropriately controlling the concentration of non-volatile dissolved substances contained in the water flowing through the water treatment system.

Means for Solving the Problems

[0006] The water treatment system of the present invention has a measuring device that introduces the water flowing through the water treatment system as measurement target water and performs water quality measurement of the measurement target water. The measuring device has an evaporation unit that evaporates the measurement target water to form residual particles, and a measurement unit that measures the number of residual particles.

Effects of the Invention

[0007] According to the present invention, it is possible to provide a water treatment system that can appropriately control the concentration of non-volatile dissolved substances contained in the water flowing through the water treatment system. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of the water treatment system according to the first embodiment. [Figure 2] This is a schematic diagram of the measuring device. [Figure 3] This is a schematic diagram of the water treatment system according to the second embodiment. [Figure 4A] This is a schematic diagram of the water treatment system according to the third embodiment (when the ion exchange device is in operation). [Figure 4B] This is a schematic diagram of the water treatment system according to the third embodiment (when the ion exchange device is started up). [Figure 5] This graph shows the relationship between the TOC concentration of the cationic resin eluate and the number of residual particles. [Figure 6] This graph shows the relationship between the TOC concentration and the number of residual particles in a PSS standard solution. [Figure 7] This graph shows the relationship between the TOC concentration of the anionic resin eluate and the number of residual particles. [Modes for carrying out the invention]

[0009] Embodiments of the water treatment system of the present invention will be described with reference to the drawings. In the following description, pure water means water with an electrical resistivity of 0.1 MΩ·cm or higher, and ultrapure water is pure water with an electrical resistivity of 15 MΩ·cm or higher (the maximum value is 18.24 MΩ·cm for theoretically pure water). In the following description, when it is not necessary to distinguish between pure water and ultrapure water, the term "pure water" will be used simply. Also, since no distinction is made between fine particles and particles in this specification, fine particles and particles are used interchangeably.

[0010] (First embodiment) Figure 1 shows a schematic configuration of a water treatment system 1 according to the first embodiment. The water treatment system 1 includes a primary pure water system 2 that produces pure water from raw water, and a secondary pure water system (hereinafter referred to as a subsystem) 3 that further removes impurities from the pure water produced by the primary pure water system 2 to produce ultrapure water of the water quality required at the use point 4. The primary pure water system 2 includes a raw water tank, a heat exchanger, a turbidity removal membrane device, an activated carbon tower, a decarbonation membrane device, a reverse osmosis membrane device, an ultraviolet irradiation device, a degassing membrane device, etc. (not shown).

[0011] Subsystem 3 comprises a pure water tank 31, a pure water supply pump 32, an ultraviolet oxidation device 33, a hydrogen peroxide removal device 34, a non-regenerative mixed-bed first ion exchange device 35 (cartridge polisher), a membrane degasser 36, a booster pump 37, a non-regenerative mixed-bed second ion exchange device 38 (cartridge polisher), and an ultrafiltration membrane device 39. These are arranged in this order along the main pipe L1 and in series along the flow direction D of the water to be treated. Ultrapure water not used at use point 4 is returned to the pure water tank 31 by a return line L2 connected to the main pipe L1. The pure water tank 31 stores the pure water produced by the primary pure water system 2.

[0012] The pure water stored in the pure water tank 31 is sent to the ultraviolet oxidation device 33 by the pure water supply pump 32. The ultraviolet oxidation device 33 irradiates the water to be treated with ultraviolet light to decompose organic matter contained in the water. The hydrogen peroxide removal device 34 is equipped with an ion exchanger on which a catalyst such as palladium (Pd) or platinum (Pt) is supported, and decomposes oxidizing substances (hydrogen peroxide) generated by ultraviolet irradiation in the ultraviolet oxidation device 33. This prevents the subsequent first ion exchange device 35 from being damaged by oxidizing substances. The first ion exchange device 35 is filled with a mixed bed of cation exchange resin and anion exchange resin and removes ionic components from the water to be treated. The membrane degasser 36 removes dissolved oxygen and carbon dioxide contained in the water to be treated. The booster pump 37 is provided to pressurize the water to be treated, for example, when the use point 4 is located at a high location. The second ion exchange device 38 is an example of a water treatment device and removes fine particles and particulate components contained in the water to be treated. The second ion exchange device 38 is a non-regenerative ion exchange device.

[0013] The ultrafiltration membrane device 39 is an example of a membrane filtration device. An example of an ultrafiltration membrane device 39 is one that uses a membrane with a molecular weight cutoff of approximately 4000 to 6000 (corresponding to a pore size of 2-4 nm), which makes it possible to remove fine particles with a particle size of 10 nm or larger with a high probability. The membrane may be a hollow fiber membrane, a flat membrane, or a pleated membrane. It is also possible to use a system in which the filtration membrane is packed into a pipe, or a tower-like structure with multiple cartridges attached. The ultrafiltration membrane is preferably one that has low impurity elution from the membrane itself, and polysulfone is suitably used. For example, fine particles flowing out from the resin of the first ion exchange device 35 are removed by the ultrafiltration membrane device 39, further improving the water quality of the ultrapure water supplied to the use point 4.

[0014] Although not shown in the diagram, another filtration membrane device may be provided downstream of the ultrafiltration membrane device 39, for example, having a retaining diameter of 5 nm or less, preferably 3 nm or less, and more preferably 1 nm or less. The retaining diameter is the particle size at which the particle removal efficiency (PRE) is 80% or more, preferably 90%, and the PRE is measured according to the SEMI (Semiconductor Equipment and Materials International) standard C89-0116 "TEST METHOD FOR PARTICLE ROMOVAL PERFORMANCE OF LIQUID DILTER RATED BELOW 30 nm WITH INDUCITIVELY COUPLED PLASMA-MASS SPECTROSCOPY (ICP-MS)".

[0015] The configuration of subsystem 3 described above is just one example, and the configuration of subsystem 3 can be changed as appropriate. For example, a heat exchanger can be installed upstream of the ultraviolet oxidation device 33 (between the pure water supply pump 32 and the ultraviolet oxidation device 33). At least one of the hydrogen peroxide removal device 34, the first ion exchange device 35, and the booster pump 37 can be omitted. The membrane degasser 36 and the second ion exchange device 38 may be swapped with each other.

[0016] Regarding the water quality management standards for pure water, it is common to use the concentrations of fine particles, total organic carbon (TOC), hydrogen peroxide, metals, anions, boron, etc. Fine particles originally existed as solids in pure water and are also referred to as native particles. However, although no management standards have been established, in recent years, it has been pointed out that fine particle precursors may contribute to the formation of residues on semiconductor wafers (for example, refer to the International Roadmap for Devices and Systems (IRDS (registered trademark))). Fine particle precursors are non-volatile dissolved substances, and the main source of fine particle precursors contained in pure water is considered to be high molecular weight organic substances eluted from resins, etc. In addition, high molecular weight substances that are not detected as particles due to the relationship of refractive index, such as viable bacteria, microorganisms, silicic acid, etc., substances that are usually dissolved in water but easily precipitate to form sediments, and substances that are completely dissolved in water, such as NaCl, KCl, etc., are also included in fine particle precursors. Fine particle precursors are dissolved in pure water, but they precipitate to form particulate residues when the surrounding water evaporates. In the cleaning and drying process of semiconductor wafers, since the semiconductor wafers are washed with ultrapure water and then dried, the fine particle precursors contained in the ultrapure water used for washing may become particulate residues due to the evaporation of water and remain on the wafer surface. Since fine particle precursors may not be removed even by an ultrafiltration membrane device 39, it is becoming increasingly important to appropriately manage and suppress the concentration of fine particle precursors.

[0017] To address this issue, subsystem 3 includes a sampling line L3 that branches off from the main pipe L1 between the ultrafiltration membrane device 39 and the use point 4, and a measuring device 5 connected to the sampling line L3, which introduces the treated water from the ultrafiltration membrane device 39 and measures the water quality of the treated water. The sampling line L3 separates the treated water flowing between the ultrafiltration membrane device 39 and the use point 4. The measuring device 5 introduces the water flowing through the water treatment system 1 (subsystem 3 in this embodiment) (in this embodiment, the treated water from the ultrafiltration membrane device 39 flowing between the ultrafiltration membrane device 39 and the use point 4) as the water to be measured, and measures the water quality of the water to be measured. In this embodiment, a configuration in which the treated water flowing between the ultrafiltration membrane device 39 and the use point 4 is separated by the sampling line L3 and introduced into the measuring device 5 is illustrated, but for example, the treated water flowing between the ultrafiltration membrane device 39 and the use point 4 may be sampled in a container or the like and introduced into the measuring device 5. If another filtration membrane device is installed downstream of the ultrafiltration membrane device 39, a sampling line L3 can be provided between the other filtration membrane device and the use point 4. The measuring device 5 is a water quality measuring device using the spray drying method, and pure water flows continuously into the sampling line L3, and the measuring device 5 continuously measures the water quality of the incoming pure water. The sampling line L3 can be formed from metal or resin piping, resin tubes, etc. The measuring device 5 has a spray unit 51, an evaporation unit 52, a measurement unit 53, and a determination unit 54. In this embodiment, the spray unit 51, the evaporation unit 52, and the measurement unit 53 are a single unit, and the determination unit 54 is a device independent of the spray unit 51, the evaporation unit 52, and the measurement unit 53. An example of a unit consisting of the spray unit 51, the evaporation unit 52, and the measurement unit 53 is the STPC-3 from KANOMAX. The configuration of the measuring device 5 is not limited to this, and for example, the spray unit 51, the evaporation unit 52, the measurement unit 53, and the determination unit 54 may be a single unit. Since the determination unit 54 includes an arithmetic circuit, it can be configured as a personal computer, or as part of the control device (not shown) of subsystem 3.

[0018] Figure 2 shows the schematic configuration and measurement principle of the measuring device 5. The spraying unit 51 has a pure water introduction line 55 that is the measurement target, a nitrogen gas introduction line 56, and a spray nozzle 57. The spray nozzle 57 sprays the pure water, which is the measurement target, using the driving force of nitrogen gas to atomize the pure water into droplets. It is also possible to use purified air from which impurities such as organic substances and moisture have been removed instead of nitrogen gas.

[0019] The evaporation unit 52 evaporates the treated water to form residual particles. That is, the evaporation unit 52 heats the droplets W generated by spraying to evaporate the moisture. The inherent particles P1 exist in the pure water in a size and shape close to or the same as when the pure water is removed. The inherent particles that existed in the pure water are dried by the evaporation of the surrounding water by the evaporation unit 52 to form an aerosol. The fine particle precursor is dissolved in the pure water, but precipitates as particulate residue P2 due to the evaporation of the surrounding water, also forming an aerosol. Therefore, the residual particles P include both the inherent particles P1 formed by removing moisture by the evaporation unit 52 and the particulate residue P2 (precipitated) formed by removing moisture by the evaporation unit 52.

[0020] The measurement unit 53 continuously measures the number (concentration) of residual particles P contained per unit volume of water to be measured. The measurement unit 53 includes an alcohol supply unit 58 and an agglutination particle counter 59. The alcohol supply unit 58 supplies, for example, n-butyl alcohol to form supersaturated alcohol vapor around the residual particles P. The supersaturated alcohol vapor cools and condenses, causing alcohol droplets to condense and grow with the residual particles P as nuclei. The agglutination particle counter 59 counts the number of alcohol droplets A using the light scattering method. This makes it possible to detect residual particles P that are too small to be directly detected by the light scattering method. The agglutination particle counter 59 allows setting the minimum detectable particle size of alcohol droplets A, measures the number (concentration) of alcohol droplets A corresponding to the set minimum detectable particle size, and transmits the result to the determination unit 54. The measurement unit 53 may also include a display device that displays the number (concentration) of alcohol droplets A. Since alcohol without residual particles does not grow sufficiently as droplets, the agglutination particle counter 59 mainly counts the number of alcohol droplets A containing residual particles. By multiplying the obtained measurement value by a pre-calibrated coefficient, the number (concentration) of residual particles in pure water can be obtained.

[0021] Thus, because the measuring device 5 includes the processes of evaporation and drying, it can measure the concentration of both the intrinsic particles P1 that originally existed in the liquid as a solid and the particulate residue P2 derived from non-volatile dissolved matter. Since the residual particles P form alcohol droplets, this method can, in principle, measure residual particles down to a particle size of about 2.5 nm, which is the detection limit of the aggregated particle counter 59, and has the advantage that the measurement results are not affected by the refractive index or shape of the intrinsic particles or residual particles.

[0022] For example, in the case of STPC-3, the agglomerated particle counter 59 can be set to have a minimum detection particle size of residual particles P of 3 nm or more, 9 nm or more, or 15 nm or more. That is, the agglomerated particle counter 59 can measure the number of residual particles with a particle size of 3 nm or more, the number of residual particles with a particle size of 9 nm or more, and the number of residual particles with a particle size of 15 nm or more. The agglomerated particle counter 59 cannot distinguish between intrinsic particles and particulate residue, but most of the residual particles with a particle size of 3 nm or more are thought to be particulate residue derived from the microparticle precursor, and most of the residual particles with a particle size of 15 nm or more are thought to be intrinsic particles. Therefore, in order to control the concentration of the microparticle precursor, it is preferable to measure the concentration of residual particles with a particle size of 3 nm or more.

[0023] The determination unit 54 determines whether the number of residual particles P measured by the measurement unit 53 exceeds a reference value. The determination unit 54 has a reference value stored in advance and compares the measured number with the reference value. When the determination unit 54 determines that the number of residual particles P exceeds the reference value, it generates at least one of the following: a signal indicating that the number of residual particles P exceeds the reference value, or a signal prompting the exchange of the ion exchanger.

[0024] Next, the operation method of subsystem 3 and the method for measuring the water quality of the water flowing through water treatment system 1 (subsystem 3) will be described. As described above, during operation, the pure water stored in the pure water tank 31 becomes ultrapure water by passing through the pure water supply pump 32, ultraviolet oxidation device 33, hydrogen peroxide removal device 34, first ion exchange device 35, membrane degasser 36, booster pump 37, second ion exchange device 38, and ultrafiltration membrane device 39, and is supplied to use point 4. If the quality of the ion exchange material is poor or the ion exchange material deteriorates, polymeric organic matter (particulate precursor) that constitutes the matrix will leach from the ion exchange material, typically an ion exchange resin, packed in the second ion exchange device 38. The water flowing through water treatment system 1 (treated water from the second ion exchange device 38) is introduced into the measuring device 5 as the water to be measured. The measuring device 5 evaporates the water to be measured to form residual particles P, and continuously measures the number (concentration) of residual particles P contained per unit volume of the water to be measured.

[0025] When the number of measured residual particles P exceeds a standard value, the determination unit 54 generates at least one of the following: a signal indicating that the number has exceeded the standard value, or a signal prompting the replacement of the ion exchanger. The measuring device 5 can notify the outside as an alarm by any means, such as a message or voice. Based on the alarm, the operator can determine that the ion exchanger may have deteriorated and take appropriate measures such as isolating the second ion exchanger 38, replacing the second ion exchanger 38, or replacing the ion exchanger.

[0026] (Second embodiment) Figure 3 shows a schematic configuration of the water treatment system 1 according to the second embodiment. This embodiment is the same as the first embodiment, except that the sampling line L3 branches off from the main pipe L1 between the second ion exchange device 38 and the ultrafiltration membrane device 39. In the first embodiment, the water quality of the treated water from the ultrafiltration membrane device 39 was measured by the measuring device 5, but in this embodiment, the water quality of the treated water from the second ion exchange device 38 is measured by the measuring device 5. The sampling line L3 separates the treated water flowing between the second ion exchange device 38 and the ultrafiltration membrane device 39 as the water to be measured.

[0027] In a water treatment system similar to the first and second embodiments, the number of residual particles with a particle size of 3 nm or larger was measured using STPC-3, and in the first embodiment, it was 7.8 × 10⁻⁶. 5 cells / mL, 7.9 × 10 in the second embodiment. 5 The concentration was 100 particles / mL. This means that almost no particulate precursors were eluting from the ultrafiltration membrane device 39. In order to measure and control the concentration of particulate precursors contained in the ultrapure water supplied to use point 4, there is little difference whether the measuring device 5 measures the water quality of the treated water from the ultrafiltration membrane device 39 or the treated water from the second ion exchange device 38. In other words, even in the first embodiment, the measuring device 5 can be considered to introduce the treated water from the second ion exchange device 38 as the target water and measure the water quality of said target water. However, the first embodiment may be more advantageous than the second embodiment in that it directly confirms the water quality of the ultrapure water supplied to use point 4.

[0028] If subsystem 3 is not equipped with a second ion exchange device 38, a sampling line L3 may be provided between the first ion exchange device 35 and the membrane degasser 36. That is, the measuring device 5 may introduce the treated water from the first ion exchange device 35 as the target water and perform water quality measurement on the said target water, with the first ion exchange device 35 being an example of a water treatment device. Alternatively, sampling lines L3 may be provided between the first ion exchange device 35 and the membrane degasser 36, and between the second ion exchange device 38 and the ultrafiltration membrane device 39. In this case, multiple measuring devices 5 may be provided to simultaneously measure the water quality of the treated water (target water) from the first ion exchange device 35 and the second ion exchange device 38. Alternatively, the water quality of the treated water (target water) from the first ion exchange device 35 and the second ion exchange device 38 may be measured with a single measuring device 5 while switching between the two sampling lines L3.

[0029] (Third embodiment) Figures 4A and 4B show a schematic configuration of the water treatment system 1 according to the third embodiment. Figure 4A shows the state of the second ion exchange devices 38A and 38B during normal operation, and Figure 4B shows the state of the second ion exchange device 38A during startup. In this embodiment, two second ion exchange devices 38A and 38B are provided in parallel. The main pipe L1 branches into two lines L1A and L1B, with the second ion exchange device 38A provided in line L1A and the second ion exchange device 38B provided in line L1B. Valves V1A and V1B are provided in lines L1A and L1B, respectively. Blow lines L4A and L4B branch from lines L1A and L1B, respectively, and valves V2A and V2B are provided in blow lines L4A and L4B, respectively. Blow lines L4A and L4B merge to form a single blow line L5, and a sampling line L3 branches from blow line L5. A measuring device 5, configured in the same manner as in the first embodiment, is provided on the sampling line L3. The number of second ion exchange devices is not limited, and three or more second ion exchange devices can be provided in parallel.

[0030] During normal operation of the second ion exchange units 38A and 38B, valves V1A and V1B are open and valves V2A and V2B are closed, as shown in Figure 4A. The ion exchange performance of the two second ion exchange units 38A and 38B is measured by resistivity meters (not shown) installed in lines L1A and L1B, respectively. For example, if it is determined that the second ion exchange unit 38A has reached the end of its lifespan or if an abnormal resistivity value is detected, the operation of the second ion exchange unit 38A is stopped, valve V1A is closed to stop the water flow to the second ion exchange unit 38A, and the second ion exchange unit 38A is replaced.

[0031] Since the water quality of the second ion exchange device 38A is unstable immediately after replacement, it is desirable to run water through it for a certain period of time (conditioning). Therefore, as shown in Figure 4B, valve V2A is opened and the entire amount of water that has been passed through the second ion exchange device 38A is blown out through blow lines L4A and L5. At this time, a portion of the water flowing through blow line L5 is supplied to sampling line L3, and the measuring device 5 introduces the treated water from the second ion exchange device 38A as the target water for measurement and measures the water quality of the target water.

[0032] The measurement unit 53 measures the number of residual particles in the same manner as in the first embodiment. When the number of residual particles falls below a standard value, the determination unit 54 generates at least one of the following signals: a signal indicating that the number of residual particles has fallen below a standard value, or a signal indicating that the startup of the second ion exchange device 38A is complete. The measuring device 5 can communicate these signals to the outside by any method, such as message or voice. Based on the notification, the operator can determine that the startup of the second ion exchange device 38A is complete and can restart the operation of the second ion exchange device 38A by closing valve V2A and opening valve V1A.

[0033] (Examples) A new cation exchange resin (product name: AMBERJET® ESG1024(H), manufactured by Organo Corporation) was mixed with 100 mL of pure water and shaken at 40°C for 16 hours to prepare an aqueous solution containing substances eluted from the cation exchange resin (hereinafter referred to as the cation resin eluate). Similarly, a new anion exchange resin (product name: AMBERJET® ESG4002(OH), manufactured by Organo Corporation) was mixed with 100 mL of pure water and shaken at 40°C for 16 hours to prepare an aqueous solution containing substances eluted from the anion exchange resin (hereinafter referred to as the anion resin eluate). Next, the TOC concentrations of the cation resin eluate and the anion resin eluate were measured using a TOC meter (Sievers M9e). The TOC concentration of the cation resin eluate was 78200 μg / L, and the TOC concentration of the anion resin eluate was 25867 μg / L.

[0034] Next, dilutions were prepared by diluting the cationic resin eluate 100-fold, 200-fold, and 300-fold with ultrapure water, and these were analyzed using KANOMAX's STPC-3. To determine the blank values, the ultrapure water used for dilution was also analyzed as a sample using the STPC-3. In addition to the samples, pure water, nitrogen gas (0.35 MPa), and 1-butanol (special grade, manufactured by Kanto Chemical Co., Ltd.) were supplied to the STPC-3. The analysis was performed using the batch mode of the STPC-3.

[0035] Figure 5 shows the relationship between TOC concentration and the number of residual particles measured by STPC-3. Multiple residual particle measurements were obtained for each TOC concentration, and the graph shows the average value of the measured residual particle numbers (Figures 6 and 7 are similar). The minimum detectable particle size for STPC-3 was set to 3 nm. As mentioned above, the cation resin eluate supplied to STPC-3 is diluted at a dilution ratio of 100 to 300 times (let's call it A), but the sample supplied to STPC-3 is further diluted inside STPC-3 at a dilution ratio (let's call it B) equal to the flow rate ratio of pure water to the sample. Therefore, the TOC concentration on the horizontal axis of Figure 5 is not the value actually measured by the TOC meter, but the value obtained by dividing the TOC concentration of the cation resin eluate measured by the TOC meter by the dilution ratio A × B. The flow rate of pure water was 100 mL / min, and the flow rate of the sample was determined from the sample addition time and weight change. Since the flow rate of the sample was approximately 0.2 mL / min, the dilution ratio B inside STPC-3 was approximately 500.

[0036] Figure 5 shows an exponential correlation between the TOC concentration of the sample and the number of residual particles. It is generally believed that polystyrene sulfonic acid (PSS) elutes from cation exchange resins, and this example confirms the possibility that PSS eluted from the cation exchange resin could be detected by STPC-3. PSS is a high-molecular-weight organic substance that is a source of particulate precursors. Therefore, to evaluate how much PSS elutes from the cation exchange resin, the cation resin eluate was analyzed by gel permeation chromatography (GPC). 126 mg / L of PSS with molecular weights of 2400-575, 39 mg / L of PSS with molecular weights of 575-310, and 20 mg / L of PSS with molecular weights of 310-180 were detected. A small amount of substances with molecular weights below 180 were also detected, but these are likely ions. From the above, it was found that virtually only PSS with a molecular weight of less than 2400 elutes from new cation exchange resin, and that it is highly likely that PSS eluted from the cation exchange resin was detected by STPC-3.

[0037] Next, PSS standard samples with molecular weights of 246, 2010, and 9680 (sodium polystyrene sulfonate salt, manufactured by SAS Co., Ltd.) were diluted to a PSS concentration of 1000 μg / L, and the TOC concentration was measured. Additionally, samples were prepared by diluting the PSS standard samples to PSS concentrations of 10, 50, and 100 μg / L, and these were analyzed using STPC-3. As mentioned earlier, the samples were further diluted inside the STPC-3. Figure 6 shows the relationship between TOC concentration and the number of residual particles measured by STPC-3. The TOC concentration on the horizontal axis is not the value actually measured by the TOC meter, but rather the value obtained by proportionally converting the measured TOC concentration of the 1000 μg / L diluted solution according to the PSS concentration of the sample. In all cases, a correlation was observed between TOC concentration and the number of residual particles in the range of TOC concentration from 0.005 μg / L to 0.053 μg / L. Although PSS with a molecular weight of 9680 does not leach from new cation exchange resin, it was found that detection is possible even if PSS with a large molecular weight leaches for some reason. Generally, the detection accuracy of TOC meters is on the order of 0.1 μg / L (for this reason, the TOC concentration of the sample was calculated in this example as well), and it was difficult to control the concentration of PSS in the range of TOC concentration from 0.005 μg / L to 0.053 μg / L, but this example showed that it is possible.

[0038] Next, dilutions were prepared by diluting the anionic resin eluate 100, 200, and 300 times with pure water, and these were supplied to STPC-3 for analysis in the same manner as the cationic resin eluate. Figure 7 shows the relationship between TOC concentration and the number of residual particles measured by STPC-3. It is thought that mainly amines leach from the anionic resin eluate, and a similar trend was observed as with the cationic resin eluate, indicating that amine concentration can be detected using a similar method. Amines are high-molecular-weight organic substances that are the source of microparticle precursors. [Explanation of symbols]

[0039] 1. Water treatment system 4 Youth Points 5. Measuring device 38, 38A, 38B Second ion exchange device (water treatment device) 39. Ultrafiltration membrane apparatus (membrane filter apparatus) 52 Evaporation section 53 Measurement Unit 54 Judgment section

Claims

1. A water treatment system, The system includes a measuring device that introduces water flowing through the aforementioned water treatment system as the target water for measurement and performs water quality measurement on the target water, The measuring device is, An evaporation unit that evaporates the water to be measured to form residual particles, A water treatment system comprising a measuring unit for measuring the number of residual particles.

2. The water treatment system according to claim 1, wherein the residual particles include particles dissolved in the water to be measured and precipitated when the water to be measured is evaporated in the evaporation section.

3. The water treatment system according to claim 1, wherein the measuring device has a determination unit that determines whether the number measured by the measuring unit exceeds a standard value, and when the determination unit determines that the number exceeds the standard value, it generates a signal indicating that the number has exceeded the standard value.

4. The water treatment system is An ion exchange apparatus having an ion exchanger, A membrane filtration device is provided downstream of the ion exchange device, The system includes a sampling line that separates the water flowing between the membrane filtration device and a use point located downstream of the membrane filtration device as the water to be measured. The water treatment system according to claim 3, wherein the measuring device is connected to the sampling line.

5. The water treatment system is An ion exchange apparatus having an ion exchanger, A membrane filtration device is provided downstream of the ion exchange device, The system includes a sampling line that separates the water flowing between the ion exchange device and the membrane filtration device as the water to be measured, The water treatment system according to claim 3, wherein the measuring device is connected to the sampling line.

6. The water treatment system according to claim 4 or 5, wherein when the number of ions exceeds the reference value during operation of the ion exchange device, the determination unit generates a signal to prompt replacement of the ion exchange device.

7. The water treatment system according to claim 4 or 5, wherein when the number falls below the reference value during startup of the ion exchange device, the determination unit generates a signal indicating that the startup of the ion exchange device is complete.

8. The water treatment system according to claim 4 or 5, wherein the ion exchange device is a non-regenerative ion exchange device.

9. A water quality measurement method for measuring the water quality of water flowing through a water treatment system, The water flowing through the aforementioned water treatment system is introduced into the measuring device as the water to be measured, The water to be measured, introduced into the measuring device, is evaporated to form residual particles. A water quality measurement method comprising measuring the number of residual particles using the measuring device.

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