Drain treatment method, ultrapure water production method, and drain treatment device

Abstract

The hardness components in the desalted drainage generated in the desalination process in the ultrapure water production process are replaced by the ion exchange components of the weakly acidic cation exchange resin for acid drainage, and the hardness components adsorbed on the weakly acidic cation exchange resin are replaced by the regeneration components, thereby regenerating the weakly acidic cation exchange resin. The regeneration components are the regeneration components contained in the used-up drainage generated after the ultrapure water produced in the ultrapure water production process is used.

Description

Technical Field

[0001] The present disclosure relates to a drainage treatment method, an ultrapure water production method, and a drainage treatment apparatus. Background Art

[0002] In recent years' ultrapure water production systems, it has been required to produce ultrapure water of higher purity. For example, it is required to produce ultrapure water with a TOC (Total Organic Carbon) concentration of 5 μgC / L or less and a resistivity of 17.5 MΩ·cm or more.

[0003] Therefore, the stabilization of each device in the ultrapure water production system is also required to be more strict. For example, Japanese Patent Application Laid-Open No. 2010-36160 discloses a method and an apparatus that can suppress the propagation of microorganisms even when the drainage is highly concentrated, thereby preventing the separation membrane from being clogged due to the generation of mucus. Japanese Patent Application Laid-Open No. 2003-154362 discloses a water treatment apparatus and a water treatment method. The water treatment apparatus treats the concentrated water filtered by a reverse osmosis filtration (RO) membrane and / or a nanofiltration membrane (NF membrane) that has been previously subjected to solid-liquid separation by a softening treatment method and / or an organic matter removal method, so that fouling or scale can be suppressed even during high recovery operation. Thus, it is necessary to highly suppress the generation of products that cause unstable operation of the device. Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] The ultrapure water production apparatus included in the ultrapure water production system mainly includes, for example:

[0006] · A pretreatment unit that removes suspended substances in raw water to obtain pretreated water;

[0007] · A primary pure water production unit that removes TOC components and ionic components in the pretreated water to produce primary pure water; and

[0008] · A secondary pure water production unit that removes extremely minute impurities in the primary pure water to produce ultrapure water.

[0009] Moreover, in the ultrapure water production apparatus, in most cases, the primary pure water production unit includes desalination treatment apparatuses such as a reverse osmosis apparatus and a nanomembrane filtration apparatus. For example, from the viewpoints of cost reduction, effective utilization of water resources, and miniaturization of the drainage treatment process, it is preferable to reuse the concentrated liquid generated by these desalination treatment apparatuses.

[0010] However, if the concentrate is to be returned to the ultrapure water production process, it is necessary to highly remove impurities that may be the cause of the above-mentioned products. For example, removal of cations as described in Japanese Patent Application Laid-Open No. 2010-36160, softening treatment as described in Japanese Patent Application Laid-Open No. 2003-154362, removal of organic substances, etc.

[0011] In the concentrate produced by the desalination treatment device provided upstream of the ultrapure water production device, the concentrations of impurities such as general salts and organic substances are usually high. The concentrate also contains components that cause scale formation, and the concentration of this component is close to the precipitation limit concentration.

[0012] In order to highly remove impurities from this concentrate, a device that divides the water to be treated into treated water with impurities removed and concentrate with impurities further concentrated is sometimes used. For example, a reverse osmosis device or an electrodeionization (EDI) device is used. When using such a reverse osmosis device or electrodeionization device, in order to suppress scale formation, it is impossible to increase the recovery rate (the ratio of the amount of treated water to the amount of water to be treated) of the device.

[0013] In addition, a treatment of adding a dispersant (also called a scale inhibitor) described later to the water to be treated is also performed. This scale inhibitor is a dispersant that increases the precipitation limit concentration by suppressing crystal growth of impurities. However, even when a scale inhibitor is added to the water to be treated, it is difficult to significantly increase the precipitation limit concentration. Therefore, the increase in the above-mentioned recovery rate is limited.

[0014] On the other hand, for the reasons described later, the ultrapure water production system is also required to be non-chemical type without using chemical substances such as acids and alkalis.

[0015] Thus, from the viewpoint of making the ultrapure water production system non-chemical type, treatment devices and operating conditions that require the use of chemical substances (especially highly dangerous acids and alkalis) cannot be adopted in the ultrapure water production system. For example, ion exchange resins that require the addition of acids and alkalis during regeneration cannot usually be used. In addition, since the dispersant (also called a scale inhibitor) is also a chemical substance, it is preferably not added.

[0016] As a result of the above, in the concentrate produced by the desalination treatment device provided upstream of the ultrapure water production system, even if there is concentrate that can be returned to the ultrapure water production process, it is limited to a very small part. How to improve the reuse rate of such concentrate has become an issue.

[0017] On the other hand, in manufacturing plants of devices that use ultrapure water, such as semiconductors, liquid crystal panels, and displays, a large amount of acidic wastewater is generated. Examples of acidic wastewater include cleaning wastewater using acids, etching wastewater, resist removal wastewater, and CMP wastewater.

[0018] Part of this acidic wastewater is reused, but how to improve its reuse rate has also become one of the issues.

[0019] In addition, if the acidic wastewater is to be discharged to the outside, it is necessary to neutralize the acidic wastewater, and for this purpose, an alkali needs to be added as required. However, due to cost and the increasing demand for a chemical-free type similar to the ultrapure water manufacturing process, how to reduce the amount of alkali added has also become one of the issues.

[0020] Thus, more appropriate treatment of the wastewater generated in the ultrapure water manufacturing process is required.

[0021] The purpose of the present disclosure is to appropriately treat the wastewater generated in the ultrapure water manufacturing process.

[0022] Means for Solving the Issues

[0023] In the wastewater treatment method of the first aspect, the hardness component, which is the hardness component of the demineralized wastewater generated by the desalination treatment in the ultrapure water manufacturing process, is replaced with the ion exchange component of the weakly acidic cation exchange resin; the hardness component adsorbed on the weakly acidic cation exchange resin is replaced with the regeneration component, thereby regenerating the weakly acidic cation exchange resin, and the regeneration component is the regeneration component contained in the used-up wastewater generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used.

[0024] In this wastewater treatment method, the hardness component of the demineralized wastewater generated by the desalination treatment in the ultrapure water manufacturing process is replaced with the ion exchange component of the weakly acidic cation exchange resin. As a result, the hardness component in the demineralized wastewater becomes less.

[0025] The hardness component is adsorbed on the weakly acidic cation exchange resin, and the hardness component is replaced with the regeneration component contained in the used-up wastewater generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used. Thus, the weakly acidic cation exchange resin is regenerated. In this way, since the used-up wastewater generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used is used as the regenerant when regenerating the weakly acidic cation exchange resin, it is not necessary to add an acid for regenerating the weakly acidic cation exchange resin. In addition, the amount of alkali added for neutralization required for treating the used-up wastewater is reduced by the amount of the regeneration component consumed in the neutralization reaction during regeneration.

[0026] In a second aspect, according to the first aspect, the hardness component contains at least one of calcium ions and magnesium ions.

[0027] Therefore, by replacing calcium ions and magnesium ions with the ion exchange component of the weakly acidic cation exchange resin, calcium ions and magnesium ions can be removed from the drained water after desalination.

[0028] In a third aspect, according to the first aspect or the second aspect, the regeneration component contains hydrogen ions.

[0029] The hydrogen ions contained in the drained water after use can be effectively utilized to regenerate the weakly acidic cation exchange resin.

[0030] In a fourth aspect, according to any one of the first aspect to the third aspect, the weakly acidic cation exchange resin is regenerated using the concentrated drained water, which is obtained by concentrating the regeneration component by concentrating the drained water after use.

[0031] Since the concentrated drained water obtained by concentrating the drained water after use is used, the weakly acidic cation exchange resin can be efficiently regenerated, and at the same time, the amount of drained water after regeneration can be reduced.

[0032] In a fifth aspect, according to the fourth aspect, the drained water after use is subjected to the concentration treatment multiple times to concentrate the regeneration component.

[0033] By performing the concentration treatment multiple times, compared with the case of performing the concentration treatment only once, the concentration of the regeneration component in the concentrated drained water can be increased, the weakly acidic cation exchange resin can be regenerated more effectively, and at the same time, the amount of drained water after regeneration can be further reduced.

[0034] In a sixth aspect, according to any one of the first aspect to the fifth aspect, the treated water obtained by replacing the hardness component with the ion exchange component is subjected to a degassing treatment to remove the gas component.

[0035] By removing the gas component from the treated water, the reuse of the treated water becomes easier.

[0036] In a seventh aspect, according to any one of the first aspect to the sixth aspect, the treated water obtained by replacing the hardness component with the ion exchange component is subjected to a salt removal treatment to remove salts.

[0037] By performing the salt removal treatment on the treated water to remove salts, the reuse of the treated water becomes easier, and at the same time, the amount of drained water that is not reused can be reduced.

[0038] In an eighth aspect, according to any one of the first aspect to the seventh aspect, the desalination treatment is performed by allowing the water to be treated to permeate through a reverse osmosis membrane.

[0039] By using a reverse osmosis membrane, desalination treatment can be reliably performed to desalinate the water to be treated.

[0040] In the method for manufacturing ultrapure water according to the ninth aspect, ultrapure water is manufactured by performing an ultrapure water manufacturing process on raw water that includes at least desalination treatment; the hardness component, which is the hardness component of the desalinated drainage generated in the desalination treatment, is replaced with the ion exchange component of a weakly acidic cation exchange resin; the hardness component adsorbed to the weakly acidic cation exchange resin is replaced with a regeneration component to regenerate the weakly acidic cation exchange resin, and the regeneration component is the regeneration component contained in the used-up drainage generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used; the used-up drainage in the used-up drainage that is not used for regenerating the weakly acidic cation exchange resin is returned to the ultrapure water manufacturing process.

[0041] In this method for manufacturing ultrapure water, ultrapure water is manufactured by performing an ultrapure water manufacturing process on raw water. Since the ultrapure water manufacturing process includes at least desalination treatment, in the ultrapure water manufacturing process, drainage containing a hardness component is generated as desalinated drainage.

[0042] The hardness component of the desalinated drainage is replaced with the ion exchange component of a weakly acidic cation exchange resin. As a result, the hardness component in the desalinated drainage becomes less.

[0043] The hardness component is adsorbed to the weakly acidic cation exchange resin, and the hardness component is replaced with the regeneration component contained in the used-up drainage generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used. Thus, the weakly acidic cation exchange resin is regenerated. In this way, since the used-up drainage generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used is used as a regenerant when regenerating the weakly acidic cation exchange resin, there is no need to add acid for regenerating the weakly acidic cation exchange resin. In addition, the amount of alkali for neutralization required for treating the used-up drainage is reduced by the amount of the regeneration component consumed in the neutralization reaction during regeneration.

[0044] Since the used-up drainage in the used-up drainage that is not used for regenerating the weakly acidic cation exchange resin is returned to the ultrapure water manufacturing process, effective reuse can be performed without wasting the used-up drainage, thereby manufacturing ultrapure water.

[0045] In the drainage treatment device according to the tenth aspect, a weakly acidic cation exchange device and a regenerated water supply device are provided. Among them, the weakly acidic cation exchange device replaces hardness components with the ion exchange components of weakly acidic cation exchange resin, and the hardness components are the hardness components of the demineralized drainage generated in the desalination treatment in the ultrapure water manufacturing process. The regenerated water supply device supplies regenerated water, and the regenerated water is used to replace the hardness components adsorbed on the weakly acidic cation exchange resin with regenerated components, thereby regenerating the weakly acidic cation exchange resin. The regenerated components are the regenerated components contained in the used-up drainage generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used.

[0046] In the weakly acidic cation exchange device of this drainage treatment device, the hardness components are replaced with the ion exchange components of weakly acidic cation exchange resin, and the hardness components are the hardness components of the demineralized drainage generated in the desalination treatment in the ultrapure water manufacturing process. As a result, the hardness components in the demineralized drainage become less.

[0047] In the regenerated water supply device, regenerated water is supplied. The regenerated water is used to replace the hardness components adsorbed on the weakly acidic cation exchange resin with regenerated components, thereby regenerating the weakly acidic cation exchange resin. The regenerated components are the regenerated components contained in the used-up drainage generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used. The hardness components adsorbed on the weakly acidic cation exchange resin are replaced with the regenerated components of the regenerated water to regenerate the weakly acidic cation exchange resin. In this way, since the used-up drainage generated after the ultrapure water manufactured in the ultrapure water manufacturing process is used is used as a regenerant when regenerating the weakly acidic cation exchange resin, there is no need to add acid for the regeneration of the weakly acidic cation exchange resin. In addition, the amount of alkali added for neutralization required for treating the used-up drainage reduces the amount of regenerated components consumed in the neutralization reaction during regeneration.

[0048] Advantages of the Invention

[0049] In the present disclosure, the drainage generated in the process of manufacturing ultrapure water can be appropriately treated. Description of the Drawings

[0050] Figure 1 It is a structural diagram of an ultrapure water manufacturing system including the drainage treatment device of the first embodiment.

[0051] Figure 2 It is a structural diagram of the ultrapure water manufacturing system of the first comparative example.

[0052] Figure 3 It is a structural diagram of the ultrapure water manufacturing system of the second comparative example. Detailed Description of the Invention

[0053] Hereinafter, the drainage treatment device 12 of the first embodiment and the ultrapure water production system 16 including the drainage treatment device 12 will be described with reference to the accompanying drawings. In addition, the ultrapure water production system 16 is a so-called chemical-free type ultrapure water production system that does not use chemicals during the production of ultrapure water. Since the ultrapure water production system 16 does not use chemicals, it has various effects listed below. In addition, these effects are merely illustrative.

[0054] · There are no adverse conditions caused by the use of chemicals, such as the impact on the ultrapure water system due to the residue of chemicals.

[0055] · There are no fluctuations in the quality of ultrapure water, etc.

[0056] · The risks associated with chemical treatment can be avoided.

[0057] · The load on drainage treatment can be reduced, and further, the load on the environment can be decreased.

[0058] The ultrapure water production system 16 includes: an ultrapure water production device 14 for producing ultrapure water, a drainage treatment device 12 for treating the drainage generated by the ultrapure water production device 14, and a drainage recovery device 42 for recovering the used ultrapure water (acidic drainage) and reusing it for ultrapure water production.

[0059] The ultrapure water production device 14 includes a raw water tank 18, a pretreatment unit 72, a primary pure water production unit 74, a secondary pure water production unit 76, and a use point 34. The pretreatment unit 72 includes a sand filtration device 20 and an activated carbon device 22. The primary pure water production unit 74 includes a first membrane filtration device 24, a second membrane filtration device 26, a degassing device 28, and a deionization device 30. The secondary pure water production unit 76 has a terminal filter (Polisher) 32.

[0060] The raw water tank 18 contains the raw water supplied to the ultrapure water production device 14. Examples of the raw water include industrial water, tap water, groundwater, river water, etc. This raw water is supplied to the sand filtration device 20.

[0061] The sand filtration device 20 is a device that allows the supplied raw water to pass through filter sand as a filter medium to remove fine foreign matters from the raw water. In addition to the sand filtration device 20, for example, a coagulation sedimentation device can also be used to precipitate foreign matters to remove them from the raw water. The water that has passed through the sand filtration device 20 is supplied to the activated carbon device 22 as the water to be treated.

[0062] The activated carbon device 22 has a structure in which particulate activated carbon is filled in a container. Multiple pores are formed in this activated carbon. By passing the supplied water to be treated through this activated carbon, foreign substances that cannot be removed in the sand filtration device 20 can be captured by the pores of the activated carbon. For example, chlorine that causes deterioration of subsequent devices can be captured by the pores of the activated carbon, etc., so as to remove or decompose the foreign substances from the water to be treated. The water to be treated from which foreign substances have been removed via the activated carbon device 22 is supplied to the first membrane filtration device 24. The water containing a large amount of foreign substances removed by the activated carbon device 22 is filtered by the filtration device 36 and then transported to the drainage utilization device 38.

[0063] As the filtration device 36, for example, a microfiltration membrane (MF membrane) device or a sand filtration device can be preferably used.

[0064] As an example, the first membrane filtration device 24 is a reverse osmosis device that desalinizes the water to be treated by passing the water to be treated through a reverse osmosis membrane. Through this desalination treatment, hardness components (i.e., calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ), bicarbonate ions, etc.) are removed from the water to be treated. In fact, the water to be treated is divided into water in which the hardness components are concentrated to a high concentration (hereinafter referred to as "desalted drainage") and water in which the hardness components are diluted to a low concentration. The water in which the hardness components are diluted to a low concentration is supplied to the second membrane filtration device 26 as the water to be treated. In contrast, the desalted drainage after the first membrane filtration device 24 is supplied to the drainage treatment device 12 as described later.

[0065] As the first membrane filtration device 24 that desalinizes the water to be treated in this way, for example, a nanofiltration device can also be used. However, from the viewpoint of improving the salt removal rate and the removal rate of other impurities contained in the water to be treated, a device using the above-mentioned reverse osmosis membrane is preferably used.

[0066] In the second membrane filtration device 26, as an example, the same as the first membrane filtration device 24, the water to be treated is passed through a reverse osmosis membrane, thereby desalinating the water to be treated again. Through the re-desalination treatment, the hardness components are further removed from the water to be treated. The water in which the hardness components are diluted to a low concentration is supplied to the degassing device 28 as the water to be treated. In contrast, the desalted drainage in the second membrane filtration device 26 is different from the desalted drainage in the first membrane filtration device 24, and the content of hardness components is lower, so it is returned to the raw water tank 18 to be reused for the production of ultrapure water.

[0067] The degassing device 28 is, for example, a membrane degassing device using a gas separation membrane that allows gas to pass through but not water. Through this degassing device 28, the gas (especially carbon dioxide) in the water to be treated can be removed. The water to be treated after being processed by the degassing device 28 becomes a state with a lower concentration of carbon dioxide and is supplied as the water to be treated to the deionization device 30.

[0068] The deionization device 30 is a device for removing impurity ions such as organic acids contained in the liquid to be treated.

[0069] As the deionization device 30, for example, an electro-deionization device (EDI) or a mixed-bed ion exchange resin device can be preferably used. From the viewpoint of not requiring the addition of chemicals for the regeneration of ion exchange resins, the electro-deionization device is preferred.

[0070] The electro-deionization device is configured to fill ion exchange resins in the voids formed by anion exchange membranes and cation exchange membranes to form desalination chambers and concentration chambers, and a direct current is applied to remove ions in the liquid to be treated. In the electro-deionization device, for example, the water to be treated is supplied in parallel to the desalination chambers and the concentration chambers, and a mixture of anion exchange resins and cation exchange resins in the desalination chambers adsorbs the impurity ions in the liquid to be treated. The adsorbed impurity ions are transferred to the concentration chambers under the action of a direct current. The concentrated water in the concentration chambers is, for example, returned to the raw water tank 18.

[0071] The mixed-bed ion exchange resin device has, for example, the following structure: a mixed-bed ion exchange resin in which cation exchange resin and anion exchange resin are mixed is filled in a cylindrical closed container. The water obtained by removing impurity ions through the deionization device 30 is supplied as the water to be treated to the terminal filter 32.

[0072] The primary pure water production unit 74 is not limited to the above structure. For example, in addition, it may also have an ultraviolet oxidation device for oxidizing and decomposing organic substances in the water to be treated. In addition, a degassing device capable of removing the gas (especially dissolved oxygen) in the water to be treated may be provided instead of the degassing device 28 with the above structure for removing the gas (especially carbon dioxide) in the water to be treated, or a degassing device capable of removing the gas (especially dissolved oxygen) in the water to be treated may be provided and used in combination with the degassing device 28. For example, a degassing device for removing carbon dioxide, an ultraviolet irradiation device, and a degassing device for removing dissolved oxygen may be provided in sequence from the upstream side where the water to be treated flows.

[0073] In the terminal filter 32, the water to be treated is finally treated (i.e., extremely minute impurities in the primary pure water are removed) to obtain ultrapure water. The terminal filter 32 is, for example, a non-regenerative mixed-bed type ion exchange resin device.

[0074] In addition, in the secondary pure water production section 76, heat exchangers may be provided before and after the terminal filter 32 to adjust the temperature by heat-exchanging (heating or cooling) the water to be treated. As the heat exchanger, for example, a plate-type heat exchanger can be cited, but its specific structure is not particularly limited.

[0075] Furthermore, in the secondary pure water production section 76, as needed, various treatment devices for implementing measures such as microbial mixing strategy by sterilization means or the like may be provided before and after the terminal filter 32 to obtain ultrapure water with the required purity. Examples of such treatment devices include an ultraviolet oxidation device, a hydrogen peroxide removal device, a degassing device, and an ultrafiltration (UF) membrane device.

[0076] The hydrogen peroxide removal device is a device for decomposing and removing hydrogen peroxide in water. For example, the hydrogen peroxide removal device is a palladium-loaded resin device that decomposes and removes hydrogen peroxide by a palladium (Pd)-loaded resin, a reducing resin device in which a reducing resin having a sulfite group and / or a bisulfite group is filled in an alkaline anion exchange resin, or the like.

[0077] The ultrapure water obtained by the terminal filter 32 (ultrapure water production device 14) is sent to the point of use 34 as the place of use. The water generated after using the ultrapure water is discharged from the point of use 34 as the used-up drainage. This used-up drainage is acidic drainage containing hydrogen ions (H + ).

[0078] As the point of use 34, for example, semiconductor, liquid crystal panel, and display manufacturing factories can be cited. In addition, as the used-up drainage, for example, cleaning drainage using acid, etching solution drainage, resist removal drainage, and CMP drainage can be cited.

[0079] The drainage recovery device 42 includes a used-up drainage tank 44, an activated carbon device 46, and a membrane filtration device 48. The used-up drainage discharged from the point of use 34 is accommodated in the used-up drainage tank 44. And, for example, when the used-up drainage tank 44 is in a full state, the overflowing used-up drainage is sent to the activated carbon device 46.

[0080] In the activated carbon device 46, foreign matters contained in the used-up drainage are captured by the pores of the activated carbon and removed. The used-up drainage from which foreign matters have been removed by the activated carbon device 46 is transported to the membrane filtration device 48.

[0081] In the membrane filtration device 48, as an example, by passing the used-up drainage water through a reverse osmosis membrane, chloride ions (Cl - ), nitrate ions (NO3 - ), sulfate ions (SO4 2- ), fluoride ions (F - ), and phosphate ions (PO4 2- ) and other acid components are removed from the water to be treated. The used-up drainage water with low concentrations of acid components is returned to the raw water tank 18 and reused for the production of ultrapure water. For the used-up drainage water with high concentrations of acid components concentrated in the membrane filtration device 48, its hydrogen ion concentration is high and it is transported to the drainage treatment device 12.

[0082] The drainage treatment device 12 includes a high-hardness water tank 54, a weakly acidic cation exchange device 56, a degassing device 58, a salt removal device 60, a concentration tank 62, and a membrane filtration device 64.

[0083] In the high-hardness water tank 54 of the drainage treatment device 12, the desalted drainage water generated in the first membrane filtration device 24 is stored. This desalted drainage water is transported from the high-hardness water tank 54 to the weakly acidic cation exchange device 56.

[0084] The weakly acidic cation exchange device 56 has a weakly acidic cation exchange resin. This weakly acidic cation exchange resin has hydrogen ions (H + ) as the ion exchange component. The weakly acidic cation exchange resin is made into a particle shape or a fibrous shape and enclosed in a container. When the desalted drainage water contacts the weakly acidic cation exchange resin and passes through the weakly acidic cation exchange device 56 at the same time, the calcium ions and magnesium ions, which are the hardness components of the desalted drainage water, are replaced by the hydrogen ions of the weakly acidic cation exchange resin. The desalted drainage water with fewer hardness components is transported to the degassing device 58 as the treated water.

[0085] The degassing device 58 removes dissolved gases such as carbon dioxide from the treated water. As the degassing device 58, for example, a vacuum degassing device, an atmospheric degassing device, or a membrane degassing device can be cited, but it is not limited thereto.

[0086] From the perspective of cost reduction, an atmospheric degassing device or a membrane degassing device is preferred, and an atmospheric degassing device is more preferred. In addition, from the perspective of easy management, a membrane degassing device is preferred.

[0087] The treated water of the weakly acidic cation exchange device 56 becomes an acidic liquid containing carbon dioxide, which is generated by the neutralization reaction of the bicarbonate ions contained in the desalted drainage water and the hydrogen ions existing as the ion exchange component. By performing degassing treatment on this treated water, carbon dioxide can be efficiently removed without adding acid.

[0088] The treated water from which the dissolved gas has been removed by the degassing device 58 is delivered to the salt removal device 60.

[0089] In the salt removal device 60, the residual salts are removed from the treated water. As the salt removal device 60, for example, an electrodialysis device that removes salts using an electrodialysis membrane or a membrane filtration device that removes salts using a reverse osmosis membrane can be cited. The treated water from which the salts have been removed by the salt removal device 60 is delivered to the drain utilization equipment 38 for utilization. As the drain utilization equipment 38, for example, a scrubber equipment, a cooling tower equipment, and a toilet purification equipment, etc., which are reclaimed water equipment, can be cited.

[0090] Compared with the raw water supplied to the ultrapure water production system 16, the treated water from which the salts have been removed by the salt removal device 60 is drain water with a higher impurity concentration. The drain utilization equipment 38 is equipment that can utilize even such drain water with a higher impurity concentration.

[0091] Since the weak acid cation exchange device 56 has a low removal rate for components other than the hardness components, it is not usually used for the purpose of returning the desalted drain water generated in the first membrane filtration device 24 to the ultrapure water production process. However, it can preferably be used for the purpose of manufacturing drain water that can be utilized in the above-mentioned drain utilization equipment 38.

[0092] The device structure and operating conditions between the weak acid ion exchange device 56 and the drain utilization equipment 38 can be appropriately determined in consideration of the required water quality of the drain utilization equipment 38, etc. For example, if it is not necessary to remove the salts remaining in the treated water of the weak acid cation exchange device 56, the salt removal device 60 can also be omitted. If the drain utilization equipment 38 is reclaimed water equipment such as the scrubber equipment, the cooling tower equipment, and the toilet purification equipment as described above, it is also preferable to apply a device structure and operating conditions that are low-cost and / or easy to manage.

[0093] The used drain water with a high hydrogen ion concentration in the membrane filtration device 48 is accommodated in the concentration tank 62 of the drain treatment device 12. The used drain water accommodated in the concentration tank 62 is delivered to the membrane filtration device 64. In the membrane filtration device 64, similar to the membrane filtration device 48, the used drain water is passed through a reverse osmosis membrane. As a result, the components in the used drain water (i.e., the components with an even higher hydrogen ion concentration) are extracted and returned to the concentration tank 62. By circulating the used drain water between the concentration tank 62 and the membrane filtration device 64, the hydrogen ion concentration of the used drain water can be increased. In the membrane filtration device 64, the used drain water with the hydrogen ion concentration concentrated is returned to the used drain water tank 44.

[0094] Thus, the used drainage whose hydrogen ion concentration has been increased by circulating between the concentration tank 62 and the membrane filtration device 64 is transported to the weakly acidic cation exchange device 56.

[0095] In the weakly acidic cation exchange device 56, since the hydrogen ions of the weakly acidic cation exchange resin are replaced by the hardness components of the desalted drainage, the hardness components are adsorbed in the weakly acidic cation exchange resin. In contrast, the hydrogen ions contained in the used drainage are replaced by the hardness components of the weakly acidic cation exchange resin, thereby acting as a regeneration component for regenerating the weakly acidic cation exchange resin. That is, by sending the used drainage from the concentration tank 62 to the weakly acidic cation exchange device 56, the used drainage can be reused as a regenerant to regenerate the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56. In particular, in the concentration tank 62, the hydrogen ion concentration of the used drainage increases, so that the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56 can be regenerated efficiently.

[0096] In the weakly acidic cation exchange device 56, for the used drainage after being used in the regeneration of the weakly acidic cation exchange resin, after neutralizing the remaining acid with alkali as needed, it is discharged to the outside of the drainage treatment device 12. In addition, the treated water that has not been transported from the salt removal device 60 to the drainage utilization device 38 is also discharged to the outside of the drainage treatment device 12. Substantially, the drainage from the weakly acidic cation exchange device 56 and the drainage from the salt removal device 60 become the drainage from the ultrapure water production system 16.

[0097] The method of regenerating the weakly acidic cation exchange resin using the regeneration components contained in the used drainage after using ultrapure water is not limited to the method of this embodiment.

[0098] For example, in the case where the used drainage has a high sodium concentration, the weakly acidic cation exchange resin can also be regenerated into the Na type with the ion exchange component being sodium ions. As an example of such drainage, the regeneration drainage after adding caustic soda for the regeneration treatment of the mixed bed ion exchange resin and the anion exchange resin can be cited.

[0099] However, from the viewpoints of easy regeneration and no need to add drugs during the regeneration treatment, it is preferable to use hydrogen ions in the regeneration components to regenerate the weakly acidic cation exchange resin into the H type with the ion exchange component being hydrogen ions.

[0100] From the viewpoint of easily concentrating the spent drainage after use to a concentration capable of effectively regenerating the weakly acidic cation exchange resin, in the spent drainage discharged from the use point 34, for example, the concentration of the regeneration component is preferably 40 ppm or more in terms of CaCO3, and more preferably 100 ppm or more in terms of CaCO3. In addition, the pH of the spent drainage is preferably 4 or less, and more preferably 3 or less.

[0101] On the other hand, from the viewpoint of returning the spent drainage from which impurities have been removed by the drainage recovery device 42 to the ultrapure water production process, in the spent drainage discharged from the use point 34, for example, the concentration of the regeneration component is preferably 300 ppm or less in terms of CaCO3, and more preferably 250 ppm or less in terms of CaCO3. In addition, the pH of the spent drainage is preferably 2 or more.

[0102] From the viewpoint of effectively regenerating the weakly acidic cation exchange resin, in the spent drainage transported to the weakly acidic cation exchange device 56, for example, the concentration of the regeneration component is preferably 1 wt% or more in terms of CaCO3, and more preferably 3 wt% or more in terms of CaCO3. In addition, the pH of the spent drainage is preferably 2 or less, and more preferably 1 or less.

[0103] On the other hand, from the viewpoints of suppressing the risk of resin breakage caused by a sharp volume change accompanying regeneration, the risk of corrosion of the used components of the device, etc., in the spent drainage transported to the weakly acidic cation exchange device 56, for example, the concentration of the regeneration component is preferably 8 wt% or less in terms of CaCO3, and more preferably 5 wt% or less in terms of CaCO3. In addition, the pH of the spent drainage is preferably 0 or more.

[0104] Next, the operation of the ultrapure water production system 16 of the present embodiment, the drainage treatment method, and the ultrapure water production method will be compared with and described in relation to Figure 2 the ultrapure water production system 82 of the first comparative example shown in Figure 3 and the ultrapure water production system 92 of the second comparative example shown in Figure 2 and Figure 3 For the same components as those in Figure 1 , the same reference numerals are assigned. In addition, in Figures 1 to 3 , in each ultrapure water production system, the amount of water flowing through each part is indicated by the numbers in the circles. The unit of each number is m 3 / h. The amount of water shown here is an example for ease of explanation.

[0105] In addition, Table 1 shows the amounts of water at the main parts in the ultrapure water production systems of the present embodiment, the first comparative example, and the second comparative example.

[0106] [Table 1]

[0107]

[0108] In each of the ultrapure water production systems of the first embodiment, the first comparative example, and the second comparative example, the amount of ultrapure water used at the point of use 34 is 200 m 3 / h, and the amount of acidic drainage discharged from the point of use 34 is 50% of the ultrapure water used at the point of use 34 (i.e., 100 m 3 / h), and the amount of drainage utilized in the drainage utilization device 38 is 25% of the amount of ultrapure water used at the point of use 34 (i.e., 50 m 3 / h).

[0109] Figure 2 The ultrapure water production system 82 of the first comparative example shown does not provide the drainage treatment device 12 in the ultrapure water production system 16 of the first embodiment. Moreover, the desalted drainage generated in the first membrane filtration device 24 is discharged to the outside of the ultrapure water production system 82. In addition, a part of the used-up drainage is also discharged from the membrane filtration device 48 of the drainage recovery device 42 to the outside of the ultrapure water production system 82.

[0110] Figure 3 The ultrapure water production system 92 of the second comparative example shown is configured to introduce a dispersant between the activated carbon device 22 and the first membrane filtration device 24. A dispersant is also referred to as a scale inhibitor, and it has the effect of dispersing the hardness components in the water to be treated in the solvent to inhibit the crystal growth of impurities. And the desalted drainage discharged from the first membrane filtration device 24 is filtered by the membrane filtration device 94 and returned to the raw water tank 18, while a part of it is discharged to the outside of the ultrapure water production system 92.

[0111] As Figure 1 shown, in the ultrapure water production system 16 of the present embodiment, a part (9 m 3 / h) of the raw water (154.5 m 3 / h) transported to the raw water tank 18 is transported to the drainage utilization device 38, while the remaining raw water (145.5 m 3 / h) is transported to the raw water tank 18. As will be described later, the water to be treated (10 m 3 / h) returned from the second membrane filtration device 26, the water to be treated (10 m 3 / h) returned from the deionization device 30, and the used-up drainage (99.5 m 3 / h) returned from the membrane filtration device 48 are also accommodated in the raw water tank 18. And the raw water accommodated in the raw water tank 18 is sequentially transported to the sand filtration device 20 and the activated carbon device 22 (265 m 3 / h).

[0112] In the sand filtration device 20 and the activated carbon device 22, the water obtained by removing foreign substances from the raw water is transported as the water to be treated to the first membrane filtration device 24 (260 m 3 / h). Further, calcium ions, magnesium ions, bicarbonate ions, etc. are removed (desalted) from the water to be treated and transported to the second membrane filtration device 26 (220 m 3 / h). The desalted drainage water (water with a relatively high concentration of calcium ions and magnesium ions) generated in the first membrane filtration device 24 is transported to the high-hardness water tank 54 of the drainage treatment device 12 (40 m 3 / h).

[0113] In the second membrane filtration device 26, calcium ions, magnesium ions, bicarbonate ions, etc. are further removed from the water to be treated and transported to the degassing device 28 (210 m 3 / h). The water to be treated that is not transported from the second membrane filtration device 26 to the degassing device 28 returns to the raw water tank 18 (10 m 3 / h).

[0114] In the degassing device 28, the gas (especially carbon dioxide) in the water to be treated is removed, and the water to be treated after carbon dioxide removal is transported as the water to be treated to the deionization device 30 (210 m 3 / h). In the deionization device 30, impurity ions are removed from the liquid to be treated, and the liquid to be treated is transported to the terminal filter 32 (200 m 3 / h). At the same time, the water to be treated that is not transported to the terminal filter 32 returns to the raw water tank 18 (10 m 3 / h). In the terminal filter 32, the water to be treated is finally treated, and the obtained ultrapure water is transported to the point of use 34 (200 m 3 / h). The ultrapure water is used at the point of use 34, and the used water is discharged as the used-up drainage water. The used-up drainage water is stored in the used-up drainage water tank 44 of the drainage recovery device 42. As described later, the used-up drainage water also returns from the membrane filtration device 64 to the used-up drainage water tank 44 (10.5 m 3 / h).

[0115] In the drainage recovery device 42, the used-up drainage water in the used-up drainage water tank 44 is transported to the activated carbon device 46 (110.5 m 3 / h). In the activated carbon device

[0116] The desalted drainage water generated in the first membrane filtration device 24 of the ultrapure water production device 14 is stored in the high-hardness water tank 54 of the drainage treatment device 12. This desalted drainage water is transported to the weakly acidic cation exchange device 56. And calcium ions and magnesium ions, which are the hardness components of the desalted drainage water, are replaced by hydrogen ions of the weakly acidic cation exchange resin. The hardness components of the desalted drainage water become less, and it is transported to the degassing device 58 as treated water. In the degassing device 58, dissolved gases such as carbon dioxide are removed from the treated water, and then the treated water is transported to the salt removal device 60 to further remove salts. Moreover, the treated water is transported to the drainage utilization equipment 38 (36 m 3 / h) for utilization, and the treated water that is not transported to the drainage utilization equipment 38 is discharged outside the drainage treatment device 12 (4 m 3 / h).

[0117] In the weakly acidic cation exchange device 56, as described above, hydrogen ions of the weakly acidic cation exchange resin are replaced by calcium ions and magnesium ions of the high-hardness water, and the used drainage water with increased hydrogen ion concentration (0.5 m 3 / h) is transported from the concentration tank 62 to the weakly acidic cation exchange device 56. Hydrogen ions of this used drainage water are replaced by calcium ions and magnesium ions of the weakly acidic cation exchange resin, thereby regenerating the weakly acidic cation exchange resin. In the weakly acidic cation exchange device 56, for the used drainage water after being used in the regeneration of the weakly acidic cation exchange resin, the remaining acid is neutralized with alkali as needed and discharged outside the drainage treatment device 12 (0.5 m 3 / h). When the weakly acidic cation exchange resin is regenerated, the amount of acid remaining in the used drainage water is reduced by the neutralization reaction during this regeneration.

[0118] Thus, in the present embodiment, the hardness components of the desalted drainage water generated in the ultrapure water production process of the ultrapure water production device 14 are removed in the weakly acidic cation exchange device 56. Moreover, when regenerating the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56, since the used drainage water after being used at the use point 34 is effectively used, it is not necessary to add acid for the regeneration of the weakly acidic cation exchange resin. In addition, the amount of alkali added for neutralizing the used drainage water after being used when regenerating the weakly acidic cation exchange resin reduces the amount of regeneration components consumed in the neutralization reaction during regeneration. The drainage from the ultrapure water production system 16 is only the drainage from the weakly acidic cation exchange device 56 and the drainage from the salt removal device 60. Therefore, compared with the ultrapure water production system 16 that does not have the structure of the drainage treatment device 12, the amount of drainage of the entire system can be reduced.

[0119] As shown in Table 1, in the ultrapure water production system 16 of the present embodiment, in order to obtain 200 m 3 / h of ultrapure water used at the point of use 34 and 50 m 3 / h of drainage used in the drainage utilization device 38, 154.5 m 3 / h of raw water is used. And the total drainage from the ultrapure water production system 16 is 4.5 m 3 / h.

[0120] In contrast, in the ultrapure water production system 82 of the first comparative example shown in Figure 2 , 45 m 3 / h of the 200 m 3 / h of raw water is transported to the drainage utilization device 38, and 155 m 3 / h of raw water is transported to the raw water tank 18. 10 m 3 / h of the treated water returns from the second membrane filtration device 26 to the raw water tank 18, 10 m 3 / h of the treated water returns from the deionization device 30 to the raw water tank 18, and 90 m 3 / h of the used-up drainage returns from the membrane filtration device 48 to the raw water tank 18. 265 m 3 / h of raw water is transported from the raw water tank 18 to the sand filtration device 20 and is transported to the activated carbon device 22, and as a part of it, 5 m 3 / h of raw water is transported to the drainage utilization device 38 via the filtration device 36.

[0121] In the first membrane filtration device 24, the transported 260 m 3 / h of the treated water is desalted, and the desalted 220 m 3 / h of the treated water is transported to the second membrane filtration device 26. At the same time, 40 m 3 / h of the treated water is discharged to the outside of the ultrapure water production device 14.

[0122] 210 m 3 / h of the treated water is transported from the second membrane filtration device 26 to the degassing device 28 and the deionization device 30, and 200 m 3 / h of the treated liquid is transported from the deionization device 30 to the terminal filter 32. At the same time, 10 m 3 / h of the treated liquid returns to the raw water tank 18.

[0123] Among the ultrapure water used at the point of use 34, 100 m 3 / h is recovered and transported to the used-up drainage tank 44, the activated carbon device 46, and the membrane filtration device 48. After being filtered by the membrane filtration device 48, 90 m 3The drained water after use at [X] m³ / h returns to the raw water tank 18. 3 The drained water after use at [X] m³ / h is discharged to the outside of the ultrapure water production device 14.

[0124] As shown in Table 1, in the ultrapure water production system 82 of the first comparative example, in order to obtain 200 m³ / h of ultrapure water used at the use point 34 and 50 m³ / h of drained water used in the drainage utilization device 38, 200 m³ / h of raw water is used. And the total drained water from the ultrapure water production system 82 is 50 m³ / h. 3 / h of ultrapure water, and 50 m 3 / h of drained water used in the drainage utilization equipment 38, 200 m 3 / h of raw water is used. And the total drained water from the ultrapure water production system 82 is 50 m 3 / h.

[0125] In Figure 3 the ultrapure water production system 92 of the second comparative example shown, a dispersant is added to the water to be treated between the activated carbon device 22 and the first membrane filtration device 24. Therefore, 40 m³ / h of drained water from the first membrane filtration device 24 is filtered by the membrane filtration device 94 (reverse osmosis device), so that 20 m³ / h of the water to be treated can return to the raw water tank 18, and the substantial drained water from the first membrane filtration device 24 is 20 m³ / h. 3 / h of drained water, so that 20 m 3 / h of the water to be treated can return to the raw water tank 18, and the substantial drained water from the first membrane filtration device 24 is 20 m 3 / h.

[0126] As shown in Table 1, in the ultrapure water production system 92 of the second comparative example, in order to obtain 200 m³ / h of ultrapure water used at the use point 34 and 50 m³ / h of drained water used in the drainage utilization device 38, 180 m³ / h of raw water is used. And the total drained water from the ultrapure water production system 92 is 30 m³ / h. 3 / h of ultrapure water, and 50 m 3 / h of drained water used in the drainage utilization equipment 38, 180 m 3 / h of raw water is used. And the total drained water from the ultrapure water production system 92 is 30 m 3 / h.

[0127] It can be seen that compared with either the ultrapure water production system 82 of the first comparative example or the ultrapure water production system 92 of the second embodiment, the amount of drained water in the ultrapure water production system 16 of this embodiment is reduced.

[0128] Moreover, the reduced drained water is utilized in the drainage utilization device 38 and the like, and correspondingly, the amount of raw water used is reduced.

[0129] That is to say, in the ultrapure water production system 16 of this embodiment, in order to obtain 200 m³ / h of ultrapure water and 50 m³ / h of drained water used in the drainage utilization device 38, the amount of raw water required is reduced by approximately 23% compared with the ultrapure water production system 82 of the first comparative example and by approximately 14% compared with the ultrapure water production system 92 of the second comparative example. 3 / h of ultrapure water and 50 m 3 / h of drained water used in the drainage utilization equipment 38, the amount of raw water required is reduced by approximately 23% compared with the ultrapure water production system 82 of the first comparative example and by approximately 14% compared with the ultrapure water production system 92 of the second comparative example.

[0130] In addition, in the ultrapure water production system 16 of the present embodiment, the hardness components of the drainage water (i.e., the desalted drainage water) generated in the first membrane filtration device 24 are removed by the weakly acidic cation exchange device 56, and the used-up drainage water generated at the use point 34 is used to regenerate the weakly acidic cation exchange device 56 after the removal treatment.

[0131] At this time, since the hydrogen ions contained in the used-up drainage water are consumed, in the ultrapure water production system 16 of the present embodiment, for the used-up drainage water (0.5 m 3 / h) discharged to the outside, the addition amount of the alkali required for neutralization can be halved compared to the ultrapure water system 82 of the first comparative example and the ultrapure water system 92 of the second comparative example.

[0132] In addition, in the ultrapure water production system 16 of the present embodiment, the amount of drainage water generated when obtaining 200 m 3 / h of ultrapure water is reduced by 91% compared to the ultrapure water production system 82 of the first comparative example and reduced by 85% compared to the ultrapure water production system 92 of the second comparative example.

[0133] Moreover, in the drainage water treatment device 12 used in the ultrapure water production system 16 of the present embodiment, by circulating the used-up drainage water between the concentration tank 62 and the membrane filtration device 64, the hydrogen ion concentration of the used-up drainage water is increased. Since the used-up drainage water after concentrating hydrogen ions by performing multiple concentration treatments on the used-up drainage water is used, the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56 can be regenerated efficiently.

[0134] In the present embodiment, if only for removing the hardness components from the desalted drainage water, strongly acidic cation exchange resin can also be used instead of the weakly acidic cation exchange resin. However, if strongly acidic cation exchange resin is used, components other than the hardness components will also be removed from the desalted drainage water, and generally the amount of impurity ions removed per unit resin amount is also less than that when using the weakly acidic cation exchange resin (for example, 1 / 2 to 1 / 4), so the required amount of resin becomes larger. In addition, the regeneration of strongly acidic cation exchange resin is difficult and chemical agents such as acids must be added, so it generally cannot be used in chemical-free type equipment. In contrast, by using the weakly acidic cation exchange resin, the hardness components to be removed can be selectively and efficiently removed from the desalted drainage water, and at the same time, the regeneration of the weakly acidic cation exchange resin becomes easier.

[0135] As a regenerant for regenerating a weakly acidic cation exchange resin, it is not limited to the used drainage water after the hydrogen ions are concentrated as described above. By effectively utilizing the hydrogen ions contained in the used drainage water, it becomes a highly effective structure that contributes to reducing the drainage volume in the ultrapure water production system 16.

[0136] In particular, since the used drainage water is subjected to multiple concentration treatments, the used drainage water with a higher hydrogen ion concentration can be used to efficiently regenerate the weakly acidic cation exchange resin.

[0137] In the present embodiment, as a desalination treatment, the first membrane filtration device 24 is used to remove hardness components. In the desalination treatment, salts other than calcium ions and magnesium ions as hardness components may also be removed. If there are a large number of hardness components, scale may sometimes precipitate in the subsequent process (the downstream side where the liquid to be treated flows). By removing such scale-causing components, the generation of scale can be suppressed.

[0138] The entire disclosure of Japanese Patent Application No. 2020-75687 filed on April 21, 2020 is incorporated herein by reference in its entirety.

[0139] All documents, patent applications, and technical standards described in this application are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard incorporated by reference were specifically and individually described.

Claims

1. A drainage treatment method, in which the hardness components are replaced by the ion exchange components of a weakly acidic cation exchange resin, and the hardness components are the hardness components in the demineralized drainage water generated by the demineralization treatment in the ultrapure water production process, and the demineralized drainage water is water in which the hardness components are concentrated; the hardness components adsorbed on the weakly acidic cation exchange resin are replaced by the regeneration components, so as to regenerate the weakly acidic cation exchange resin, and the regeneration components are the regeneration components contained in the used-up drainage water generated after the ultrapure water produced by the ultrapure water production process is used; 2. The drainage treatment method according to claim 1, wherein, the hardness components include at least one of calcium ions and magnesium ions.

3. The drainage treatment method according to claim 1 or 2, wherein, The regeneration components contain hydrogen ions.

4. The drainage treatment method according to claim 1, wherein, The concentrated drainage water is used for regenerating the weakly acidic cation exchange resin, and the concentrated drainage water is obtained by concentrating the regeneration components by concentrating the used-up drainage water.

5. The drainage treatment method according to claim 4, wherein, The used-up drainage water is subjected to multiple times of the concentration treatment to concentrate the regeneration components.

6. The drainage treatment method according to claim 1, wherein, The treated water after replacing the hardness components with the ion exchange components is subjected to a degassing treatment to remove gas components.

7. The drainage treatment method according to claim 1, wherein, The treated water after replacing the hardness components with the ion exchange components is subjected to a salt removal treatment to remove salts.

8. The drainage treatment method according to claim 1, wherein, The demineralization treatment is performed by allowing the water to be treated to permeate a reverse osmosis membrane.

9. An ultrapure water production method, in which ultrapure water is produced by performing an ultrapure water production process on raw water that includes at least a demineralization treatment; the hardness components are replaced by the ion exchange components of a weakly acidic cation exchange resin, and the hardness components are the hardness components in the demineralized drainage water generated by the demineralization treatment, and the demineralized drainage water is water in which the hardness components are concentrated; the hardness components adsorbed on the weakly acidic cation exchange resin are replaced by the regeneration components, so as to regenerate the weakly acidic cation exchange resin, and the regeneration components are the regeneration components contained in the used-up drainage water generated after the ultrapure water produced by the ultrapure water production process is used; the used-up drainage water that is not used for regenerating the weakly acidic cation exchange resin in the used-up drainage water is returned to the ultrapure water production process.

10. A drainage treatment device, which includes: a weakly acidic cation exchange device that replaces the hardness components with the ion exchange components of a weakly acidic cation exchange resin, and the hardness components are the hardness components in the demineralized drainage water generated by the demineralization treatment in the ultrapure water production process, and the demineralized drainage water is water in which the hardness components are concentrated; and a regenerated water supply device that supplies regenerated water for replacing the hardness components adsorbed on the weakly acidic cation exchange resin with the regeneration components, so as to regenerate the weakly acidic cation exchange resin, and the regeneration components are the regeneration components contained in the used-up drainage water generated after the ultrapure water produced by the ultrapure water production process is used.

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