JP6924300B1 - Wastewater treatment method, ultrapure water production method and wastewater treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately treat wastewater generated in a process of producing ultrapure water. SOLUTION: The hardness component of drainage after desalting generated in the desalting treatment in the ultrapure water production process is replaced with an ion exchange component of a weakly acidic cation exchange resin, and the hardness component adsorbed on the weakly acidic cation exchange resin. Is replaced with a regenerated component contained in the used wastewater after using the ultrapure water produced in the ultrapure water production process to regenerate the weakly acidic cation exchange resin. [Selection diagram] Fig. 1

Description

The present application relates to a wastewater treatment method, an ultrapure water production method, and a wastewater treatment apparatus.

In recent ultrapure water production systems, it is required to produce ultrapure water having a higher purity, for example, a TOC (Total Organic Carbon) concentration of 5 μg C / L or less and a specific resistivity of 17.5 MΩ · cm or more. Has been done.

Therefore, stabilization of each device in the ultrapure water production system is also required more strictly. For example, Patent Document 1 describes a method and an apparatus capable of suppressing the growth of microorganisms and preventing clogging of the separation membrane due to the generation of slime even if the waste water is highly concentrated. Patent Document 2 describes a high recovery rate by treating concentrated water of a reverse osmosis filtration (RO) membrane and / or a nanofiltration membrane (NF membrane) separated in advance by a softening treatment method and / or an organic substance removal method. A water treatment device and a water treatment method that can suppress fouling and scale even during operation are described. As described above, the generation of products leading to the instability of the operation of the device needs to be highly suppressed.

Japanese Unexamined Patent Publication No. 2010-36160 Japanese Unexamined Patent Publication No. 2003-154362

The ultrapure water production equipment of the ultrapure water production system is, for example,
・ Pretreatment part that removes suspended solids in raw water to obtain pretreatment water ・ Primary pure water production part that removes TOC components and ionic components in pretreatment water to produce primary pure water ・ In primary pure water It is mainly composed of a secondary pure water production unit that produces ultrapure water by removing a very small amount of impurities.

In many cases, the ultrapure water production apparatus includes a desalting treatment apparatus such as a reverse osmosis apparatus and a nanomembrane filtration apparatus in the primary pure water production unit. The concentrates of these desalination treatment devices are preferably reused from the viewpoints of cost reduction, effective use of water resources, and downsizing of wastewater treatment steps, for example.

However, when returning this concentrated solution to the ultrapure water production process, for example, cation removal as described in Patent Document 1, softening treatment and organic substance removal as described in Patent Document 2, etc. The removal of impurities that can cause the generation of products needs to be highly performed.

The concentrated water of the desalination treatment equipment installed upstream of the ultrapure water production equipment generally has a high concentration of impurities such as salts and organic substances, and also contains components that cause scale at a concentration close to the precipitation limit concentration. There is.

When removing impurities from this concentrated water to a high degree, a device that divides the water to be treated into treated water from which impurities have been removed and concentrated water in which impurities have been further concentrated, such as a reverse osmosis device and an electrodeionization device. (EDI) may be used. When such a reverse osmosis device or an electrodeionization device is used, the recovery rate of the device (the ratio of the amount of treated water to the amount of water to be treated) cannot be increased in order to suppress the generation of scale.

Further, a dispersant also called a scale inhibitor, which will be described later, is also added to the water to be treated. This scale inhibitor is a dispersant for improving the precipitation limit concentration by suppressing the crystal growth of impurities. However, even if a scale inhibitor is added to the water to be treated, it is difficult to significantly improve the precipitation limit concentration, so that there is a limit to the improvement of the recovery rate described above.

On the other hand, for the reason described later, there is also a demand for a non-chemical type of ultrapure water production system that does not use chemicals such as acids and alkalis.

From the viewpoint of making the ultrapure water production system non-chemical type, processing equipment and operating conditions that require the use of chemical substances, especially high-risk acids and alkalis, cannot be adopted for the ultrapure water production system. .. For example, an ion exchange resin that requires the addition of an acid or alkali for regeneration cannot generally be used. Further, it is preferable that the dispersant, which is also called a scale inhibitor, is not added because it is a chemical agent.

As a result of the above, only a small part of the concentrated water of the desalination treatment device installed upstream of the ultrapure water production system can be returned to the ultrapure water production process. One of the challenges is to increase the reuse rate of such concentrated water.

On the other hand, in equipment where ultrapure water is used, for example, in semiconductor, liquid crystal panel, and display manufacturing plants, a large amount of acid wastewater is generated. Examples of acid effluent include cleaning effluent using acid, etching effluent, resist removal effluent, and CMP effluent.

Some of these acid wastewaters are reused, but improving the reuse rate is also an issue.

In addition, when acid wastewater is discharged to the outside, it is necessary to neutralize it, and for that purpose, it is necessary to add alkali as necessary. However, due to the cost aspect and the increasing demand for non-chemical type as in the ultrapure water production process, reduction of the addition amount is also one of the issues.

As described above, it is required to treat the wastewater generated in the process of producing ultrapure water more appropriately.

The purpose of the present application is to appropriately treat the wastewater generated in the process of producing ultrapure water.

In the wastewater treatment method of the first aspect, the hardness component of the desalted wastewater generated in the desalting treatment in the ultrapure water production process is replaced with the ion exchange component of the weakly acidic cation exchange resin, and the weakly acidic cation exchange resin is used. The weakly acidic cation exchange resin is regenerated by substituting the hardness component adsorbed on the water with a regenerated component contained in the used wastewater after using the ultrapure water produced in the ultrapure water production step.

In this wastewater treatment method, the hardness component of the desalted wastewater generated by the desalination treatment in the ultrapure water production process is replaced with the ion exchange component of the weakly acidic cation exchange resin. As a result, the hardness component in the wastewater after desalting is reduced.

A hardness component is adsorbed on the weakly acidic cation exchange resin, and this hardness component is replaced with a regenerated component contained in the used wastewater after using the ultrapure water produced in the ultrapure water production process. As a result, the weakly acidic cation exchange resin is regenerated. In this way, the used wastewater after using the ultrapure water produced in the ultrapure water manufacturing process is used as a regenerating agent for the regeneration of the weakly acidic cation exchange resin, so that the weakly acidic cation exchange resin can be regenerated. Therefore, it is not necessary to add acid. In addition, the amount of neutralizing alkali added required for the treatment of used wastewater is reduced by the amount of the regenerated components consumed in the neutralization reaction during regeneration.

In the second aspect, in the first aspect, the hardness component contains at least one of calcium ions and magnesium ions.

Therefore, it is possible to remove calcium ions and magnesium ions from the desalted wastewater by replacing them with the ion exchange components of the weakly acidic cation exchange resin.

In the third aspect, in the first or second aspect, the regenerated component comprises hydrogen ions.

The weakly acidic cation exchange resin can be regenerated by effectively using the hydrogen ions contained in the used wastewater.

In the fourth aspect, in any one of the first to third aspects, the weakly acidic cation exchange resin is regenerated by using the concentrated wastewater obtained by concentrating the regenerated components with respect to the used wastewater. ..

Since concentrated wastewater obtained by concentrating used wastewater is used, the weakly acidic cation exchange resin can be efficiently regenerated, and the amount of wastewater after being used for regeneration can be reduced.

In the fifth aspect, in the fourth aspect, the concentration treatment is performed a plurality of times on the used wastewater to concentrate the regenerated component.

By performing the concentration treatment multiple times, the concentration of the regenerated component of the concentrated wastewater can be increased as compared with the case where the concentration treatment is performed only once, and the weakly acidic cation exchange resin can be regenerated more effectively and is used for regeneration. The amount of drainage after being discharged can be reduced.

In the sixth aspect, in any one of the first to fifth aspects, a degassing treatment is performed to remove the gas component from the treated water in which the hardness component is replaced with the ion exchange component.

By removing the gas component from the treated water, the treated water can be easily reused.

In the seventh aspect, in any one of the first to sixth aspects, a salt removal treatment for removing salt is performed on the treated water in which the hardness component is replaced with the ion exchange component.

By removing the salt by performing a salt removal treatment on the treated water, the treated water can be easily reused and the amount of wastewater that is not reused can be reduced.

In the eighth aspect, in any one of the first to seventh aspects, the desalting treatment is carried out by infiltrating the reverse osmosis membrane with water to be treated.

By using the reverse osmosis membrane, the desalting treatment can be surely performed and the water to be treated can be desalted.

In the method for producing ultrapure water according to the ninth aspect, ultrapure water is produced by an ultrapure water production process including at least desalting treatment of raw water, and the hardness component of the drainage after desalting generated by the desalting treatment is weakened. Replaced with the ion exchange component of the acidic cation exchange resin, the hardness component adsorbed on the weakly acidic cation exchange resin is used as used wastewater after using the ultrapure water produced in the ultrapure water production process. The weakly acidic cation exchange resin is regenerated by replacing it with a contained recycled component, and the used wastewater that was not used for the regeneration of the weakly acidic cation exchange resin among the used wastewater is returned to the ultrapure water production process. ..

In this ultrapure water production method, ultrapure water is produced by performing an ultrapure water production process on raw water. Since the ultrapure water production process includes at least desalting treatment, in the ultrapure water production process, wastewater containing a hardness component is generated as wastewater after desalting.

The hardness component of the drainage after desalting is replaced with the ion exchange component of the weakly acidic cation exchange resin. As a result, the hardness component in the wastewater after desalting is reduced.

A hardness component is adsorbed on the weakly acidic cation exchange resin, and this hardness component is replaced with a regenerated component contained in the used wastewater after using the ultrapure water produced in the ultrapure water production process. As a result, the weakly acidic cation exchange resin is regenerated. In this way, the used wastewater after using the ultrapure water produced in the ultrapure water manufacturing process is used as a regenerating agent for the regeneration of the weakly acidic cation exchange resin, so that the weakly acidic cation exchange resin can be regenerated. Therefore, it is not necessary to add acid. In addition, the amount of neutralizing alkali added required for the treatment of used wastewater is reduced by the amount of the regenerated components consumed in the neutralization reaction during regeneration.

Of the used wastewater, the used wastewater that was not used to regenerate the weakly acidic cation exchange resin is returned to the ultrapure water manufacturing process, so the used wastewater can be effectively reused without wasting it, and the ultrapure water can be reused. Can be manufactured.

In the wastewater treatment device of the tenth aspect, a weakly acidic cation exchange device that replaces the hardness component of the reclaimed water generated by the demineralization treatment in the ultrapure water production process with an ion exchange component of a weakly acidic cation exchange resin, and a weakly acidic cation exchange device. The hardness component adsorbed on the weakly acidic cation exchange resin is replaced with a reclaimed water component contained in the reclaimed water after using the ultrapure water produced in the ultrapure water manufacturing process, and the weakly acidic cation is replaced. It has a reclaimed water supply device that supplies reclaimed water for reclaiming an ion exchange resin.

In the weakly acidic cation exchange device of this wastewater treatment device, the hardness component of the desalted wastewater generated by the desalting treatment in the ultrapure water production process is replaced with the ion exchange component of the weakly acidic cation exchange resin. As a result, the hardness component in the wastewater after desalting is reduced.

In the reclaimed water supply device, the hardness component adsorbed on the weakly acidic cation exchange resin is replaced with the reclaimed water contained in the used wastewater after using the ultrapure water produced in the ultrapure water manufacturing process, and the reclaimed water is weakly acidic. Supply reclaimed water to regenerate the cation exchange resin. The hardness component adsorbed on the weakly acidic cation exchange resin is replaced with the reclaimed water component to regenerate the weakly acidic cation exchange resin. In this way, the used wastewater after using the ultrapure water produced in the ultrapure water manufacturing process is used as a regenerating agent for the regeneration of the weakly acidic cation exchange resin, so that the weakly acidic cation exchange resin can be regenerated. Therefore, it is not necessary to add acid. In addition, the amount of neutralizing alkali added required for the treatment of used wastewater is reduced by the amount of the regenerated components consumed in the neutralization reaction during regeneration.

In the present application, it is possible to appropriately treat the wastewater generated in the process of producing ultrapure water.

FIG. 1 is a configuration diagram showing an ultrapure water production system including the wastewater treatment apparatus of the first embodiment. FIG. 2 is a configuration diagram showing an ultrapure water production system of the first comparative example. FIG. 3 is a configuration diagram showing an ultrapure water production system of the second comparative example.

Hereinafter, the wastewater treatment apparatus 12 of the first embodiment and the ultrapure water production system 16 provided with the wastewater treatment apparatus 12 will be described with reference to the drawings. The ultrapure water production system 16 is a so-called non-chemical type ultrapure water production system that does not use chemicals in the process of producing ultrapure water. Since the ultrapure water production system 16 does not use chemicals, there are no problems associated with the use of chemicals, such as the influence of residual chemicals on the ultrapure water system, quality fluctuations of ultrapure water, and chemistry. It has the effects of avoiding the danger of handling chemicals, reducing the load on wastewater treatment, and reducing the load on the environment.

The ultrapure water production system 16 includes an ultrapure water production apparatus 14 for producing ultrapure water, a wastewater treatment apparatus 12 for treating the wastewater generated by the ultrapure water production apparatus 14, and a used one. It includes a wastewater recovery device 42 for recovering ultrapure water (acid drainage) and using it again for producing ultrapure water.

The ultrapure water production apparatus 14 has 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 has 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 deionizing device 30. The secondary pure water production unit 76 has a polisher 32.

The raw water tank 18 accommodates the raw water supplied to the ultrapure water production apparatus 14. Examples of raw water include industrial water, tap water, groundwater, river water and the like. This raw water is supplied to the sand filtration device 20.

The sand filtration device 20 is a device that removes fine foreign matter from the raw water by passing the supplied raw water through the filtered sand as a filter medium. In addition to the sand filtration device 20, for example, a coagulation sedimentation device may be used to precipitate foreign substances and 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 water to be treated.

The activated carbon device 22 has a structure in which a container is filled with particulate activated carbon. A large number of pores are formed in this activated carbon, and by passing the supplied water to be treated through the activated carbon, foreign matter that cannot be removed by the sand filtration device 20, for example, chlorine that causes deterioration of the subsequent device. Etc. are captured in the pores of activated carbon and removed or decomposed from the water to be treated. The water to be treated from which foreign substances have been removed by the activated carbon device 22 is supplied to the first membrane filtration device 24. The water containing a large amount of foreign matter removed by the activated carbon device 22 is filtered by the filtration device 36 and then sent to the wastewater utilization facility 38.

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

The first membrane filtration device 24 is, for example, a reverse osmosis device that desalinates the water to be treated by passing the water to be treated through the reverse osmosis membrane. By this desalting treatment, hardness components such as calcium ion (Ca ²⁺ ), magnesium ion (Mg ²⁺ ), and bicarbonate ion are removed from the water to be treated. Actually, the water to be treated is divided into water in which the hardness component is concentrated to a high concentration (hereinafter referred to as "drainage after desalting") and water in which the hardness component is diluted to a low concentration. The water in which the hardness component is diluted to a low concentration is supplied to the second membrane filtration device 26 as water to be treated. On the other hand, the desalted wastewater is supplied to the wastewater treatment device 12 as described later.

As the first membrane filtration device 24 that desalinates the water to be treated in this way, for example, a nanomembrane filtration device may be used. However, from the viewpoint of increasing the salt removal rate and the removal rate of other impurities contained in the water to be treated, the device using the reverse osmosis membrane described above is preferable.

In the second membrane filtration device 26, as an example, similarly to the first membrane filtration device 24, the water to be treated is re-demineralized by passing the water to be treated through the reverse osmosis membrane. The hardness component is further removed from the water to be treated by the re-salting treatment. The water in which the hardness component is diluted to a lower concentration is supplied to the degassing device 28 as water to be treated. On the other hand, the drainage after desalting in the second membrane filtration device 26 is returned to the raw water tank 18 because it has a low hardness component unlike the drainage after desalting by the first membrane filtration device 24, and the production of ultrapure water is performed again. Used for.

The degassing device 28 is, for example, a membrane degassing device using a gas separation film that does not allow moisture to permeate but allows gas to permeate. The degassing device 28 can remove gas in the water to be treated, particularly carbon dioxide gas. The water to be treated by the degassing device 28 has a low concentration of carbon dioxide gas and is supplied to the deionizing device 30 as water to be treated.

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

As the deionizing device 30, for example, an electric deionizing device (EDI) or a mixed bed type ion exchange resin device (MB) can be preferably used. An electrodeionizer is preferable from the viewpoint that it is not necessary to add a chemical for the regeneration of the ion exchange resin.

The electrodeionizer fills the voids formed by the anion exchange membrane and the cation exchange membrane with an ion exchange resin to form a desalting chamber and a concentration chamber, and applies a DC current to the liquid to be treated. It is configured to remove ions. In the electrodeionizer, for example, the water to be treated is supplied in parallel to the desalination chamber and the concentration chamber, and the mixture of the anion exchange resin and the cation exchange resin in the desalination chamber removes impurity ions in the liquid to be treated. Adsorb. The adsorbed impurity ions are transferred to the concentration chamber by the action of direct current. The concentrated water in the concentration chamber is returned to, for example, the raw water tank 18.

The mixed-bed ion exchange resin device has, for example, a structure in which a cylindrical closed container is filled with a mixed-bed ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed. The water from which impurity ions have been removed by the deionization device 30 is supplied to the polisher 32 as water to be treated.

The primary pure water production unit 74 is not limited to the above configuration. For example, in addition, an ultraviolet oxidizing device may be provided for the purpose of oxidatively decomposing organic substances in the water to be treated. Further, it has a degassing device having a configuration capable of removing dissolved oxygen as a gas in the water to be treated, in place of or in combination with the degassing device 28 having the above configuration for removing carbon dioxide gas as a gas in the water to be treated. May be. For example, a degassing device for removing carbon dioxide gas, an ultraviolet irradiation device, and a degassing device for removing dissolved oxygen may be provided in order from the upstream side of the flow of water to be treated.

The polisher 32 performs final treatment on the water to be treated, that is, removal of a very small amount of impurities in the primary pure water to obtain ultrapure water. The polisher 32 is, for example, a non-regenerative mixed bed type ion exchange resin device.

The secondary pure water production unit 76 may be provided with heat exchangers before and after the polisher 32 to adjust the temperature by heat exchange (heating or cooling) with respect to the water to be treated. Examples of the heat exchanger include a plate-type heat exchanger, but the specific structure is not particularly limited.

Further, in the secondary pure water production unit 76, various treatment devices are provided before and after the polisher 32 as necessary, such as taking measures against contamination of microorganisms by sterilizing means or the like, to obtain ultrapure water having a desired purity. You can also get it. Examples of such processing devices include an ultraviolet oxidizing device, a hydrogen peroxide removing device, a degassing device, and an ultrafiltration membrane device (UF).

The hydrogen peroxide removing device is a device for decomposing and removing hydrogen peroxide in water. For example, the hydrogen peroxide removing device includes a palladium-supporting resin device that decomposes and removes hydrogen peroxide with a palladium (Pd) -supporting resin, or a reducing resin having a sulfite group and / or a hydrogen peroxide group in a basic anion exchange resin. It is a filled reducing resin device or the like.

The ultrapure water obtained by the polisher 32 (ultrapure water production apparatus 14) is sent to the use point 34 where it is used. From the use point 34, the water after using the ultrapure water is discharged as used wastewater. This used wastewater is acid wastewater containing ^{hydrogen ions (H +).}

Examples of the use point 34 include manufacturing factories for semiconductors, liquid crystal panels, and displays. Examples of used wastewater include cleaning wastewater using acid, etching wastewater, resist removal wastewater, and CMP wastewater.

The wastewater recovery device 42 has a used drainage tank 44, an activated carbon device 46, and a membrane filtration device 48. The used wastewater discharged from the use point 34 is stored in the used drainage tank 44. Then, for example, when the used drainage tank 44 is full, the overflowing used drainage is sent to the activated carbon device 46.

The activated carbon device 46 removes foreign substances contained in the used wastewater by capturing them in the pores of the activated carbon. The used wastewater from which foreign substances have been removed by the activated carbon device 46 is sent to the membrane filtration device 48.

In membrane filtering device 48, as an example, by passing the spent effluent in the reverse osmosis membrane, the water to be treated, chloride ion (Cl ^-), nitrate ion (NO ₃ ^-), sulfate ion _(SO ^{4 2-} ), fluorine ion (F ^-) and phosphate ion _(PO ^{4 2-)} acid component or the like is eliminated. The used wastewater having a low acid component is returned to the raw water tank 18 and used again for the production of ultrapure water. The used wastewater having a high concentration of acid components concentrated in the membrane filtration device 48 has a high hydrogen ion concentration and is sent to the wastewater treatment device 12.

The wastewater treatment device 12 includes a high hardness water tank 54, a weakly acidic cation exchange device 56, a degassing device 58, a salt removing device 60, a concentration tank 62, and a membrane filtration device 64.

The high hardness water tank 54 of the wastewater treatment device 12 accommodates the desalted wastewater generated by the first membrane filtration device 24. The drainage after desalting is sent from the high hardness water tank 54 to the weakly acidic cation exchange device 56.

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 an ion exchange component, is in the form of particles or fibers, and is sealed in a container. When the weakly acidic cation exchange resin is touched by the drainage after desalting and passes through the weakly acidic cation exchange device 56, the calcium ions and magnesium ions, which are the hardness components of the drainage after desalting, are changed to the hydrogen ions of the weakly acidic cation exchange resin. Is replaced with. The desalted wastewater having a reduced hardness component is sent to the degassing device 58 as treated water.

The degassing device 58 removes dissolved gas such as carbon dioxide from the treated water. Examples of the degassing device 58 include, but are not limited to, a vacuum degassing device, a normal pressure degassing device, and a membrane degassing device.

From the viewpoint of reducing the cost, a normal pressure degassing device or a membrane degassing device is preferable, and a normal pressure degassing device is more preferable. Further, from the viewpoint of facilitating management, a membrane deaerator is preferable.

The treated water of the weakly acidic cation exchange device 56 contained carbonic acid gas generated by the neutralization reaction of bicarbonate ions contained in the wastewater after desalting and hydrogen ions contained as an ion exchange component. , It is an acidic liquid. By degassing the treated water, carbon dioxide gas can be efficiently removed without the need to add an acid.

The treated water from which the dissolved gas has been removed by the degassing device 58 is sent to the salt removing device 60.

The salt removing device 60 removes residual salts from the treated water. Examples of the salt removing device 60 include an electrodialysis device that removes salt with an electrodialysis membrane and a membrane filtration device that removes salt with a reverse osmosis membrane. The treated water from which salts have been removed by the salt removing device 60 is sent to the wastewater utilization facility 38 for use. Examples of the wastewater utilization equipment 38 include reclaimed water equipment such as scrubber equipment, cooling tower equipment, and toilet purification equipment.

The treated water from which salts have been removed by the salt removing device 60 is wastewater having a higher impurity concentration than the raw water supplied to the ultrapure water production system 16. The wastewater utilization facility 38 is a facility that can be used even for wastewater having such a high impurity concentration.

Since the weakly acidic cation exchange device 56 has a low removal rate other than the hardness component, it is not generally used for the purpose of returning the desalted wastewater generated in the first membrane filtration device 24 to the ultrapure water production process. However, it can be suitably used for the purpose of producing wastewater that can be used in the wastewater utilization facility 38 described above.

The device configuration and operating conditions between the weakly acidic ion exchange device 56 and the wastewater utilization facility 38 can be appropriately determined in consideration of the required water quality of the wastewater utilization facility 38 and the like. For example, if it is not necessary to remove the salt remaining in the treated water of the weakly acidic cation exchange device 56, the salt removing device 60 may be omitted. If the wastewater utilization facility 38 is a reclaimed water facility such as a scrubber facility, a cooling tower facility, and a toilet purification facility as described above, it is preferable that a device configuration and operating conditions that are low cost and / or easy to manage can be applied.

The concentration tank 62 of the wastewater treatment device 12 accommodates used wastewater having a high hydrogen ion concentration in the membrane filtration device 48. The used wastewater contained in the concentration tank 62 is sent to the membrane filtration device 64. In the membrane filtration device 64, the used wastewater is passed through the reverse osmosis membrane in the same manner as in the membrane filtration device 48. As a result, in the used wastewater, that is, the component having a higher hydrogen ion concentration is extracted and returned to the concentration tank 62. That is, by circulating the used wastewater between the concentration tank 62 and the membrane filtration device 64, the hydrogen ion concentration of the used wastewater can be increased. In the membrane filtration device 64, the used wastewater after concentrating the hydrogen ion concentration is returned to the used drainage tank 44.

In this way, the used wastewater circulated between the concentration tank 62 and the membrane filtration device 64 to increase the hydrogen ion concentration is sent to the weakly acidic cation exchange device 56.

In the weakly acidic cation exchange device 56, the hydrogen ions of the weakly acidic cation exchange resin are replaced with the hardness component of the drainage after desalting, so that the hardness component is adsorbed on the weakly acidic cation exchange resin. On the other hand, the hydrogen ions contained in the used wastewater function as a regenerating component for regenerating the weakly acidic cation exchange resin by replacing the hardness component of the weakly acidic cation exchange resin. That is, by sending the used wastewater from the concentration tank 62 to the weakly acidic cation exchange device 56, the used wastewater is reused as a regenerating agent, and the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56 is used. Can be played. In particular, in the concentration tank 62, since the hydrogen ion concentration of the used wastewater is increased, the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56 can be efficiently regenerated.

In the weakly acidic cation exchange device 56, the used wastewater after being used for the regeneration of the weakly acidic cation exchange resin is obtained by neutralizing the remaining acid with alkali as necessary, and then in the wastewater treatment device 12. It is discharged to the outside. Further, the treated water that has not been sent from the salt removing device 60 to the wastewater utilization facility 38 is also discharged to the outside of the wastewater treatment device 12. Substantially, the wastewater from the weakly acidic cation exchange device 56 and the wastewater from the salt removing device 60 become the wastewater from the ultrapure water production system 16.

The method for regenerating the weakly acidic cation exchange resin using the regenerated component contained in the used wastewater after using ultrapure water is not limited to the method of the present embodiment.

For example, when the wastewater after use is wastewater after use having a high sodium concentration, a weakly acidic cation exchange resin may be regenerated into a Na type having an ion exchange component of sodium ions. Examples of such wastewater include regenerated wastewater after adding caustic soda to regenerate a mixed bed type ion exchange resin or anion exchange resin.

However, from the viewpoint of easy regeneration and the need for addition of chemicals for the regeneration process, hydrogen ions are used as the regeneration component, and the weakly acidic cation exchange resin is regenerated in the H type in which the ion exchange component is hydrogen ions. Is preferable.

From the viewpoint of easily concentrating the used wastewater to a concentration at which the weakly acidic cation exchange resin can be effectively regenerated, in the used wastewater discharged from the use point 34, for example, the concentration of the regenerated component is 40 ppm as CaCO. ₃ or more is preferable, and 100 ppm as CaCO ₃ or more is more preferable. The pH of the used wastewater is preferably 4 or less, more preferably 3 or less.

On the other hand, from the viewpoint of returning the used wastewater from which impurities have been removed by the wastewater recovery device 42 to the ultrapure water production process, in the used wastewater discharged from the use point 34, for example, the concentration of the regenerated component is 300 ppm as CaCO ₃ or less. Preferably, 250 ppm as CaCO ₃ or less is more preferable. Moreover, the pH of this used wastewater is preferably 2 or more.

From the viewpoint of effectively regenerating the weakly acidic cation exchange resin, in the used wastewater sent to the weakly acidic cation exchange device 56, for example, the concentration of the regenerated component _{is preferably 1% by weight as CaCO 3} or more. More preferably, it is ₃ % by weight as CaCO 3 or more. The pH of the used wastewater is preferably 2 or less, more preferably 1 or less.

On the other hand, from the viewpoint of suppressing the risk of resin breakage due to sudden volume change due to regeneration and the risk of corrosion of the members used in the device, the used wastewater sent to the weakly acidic cation exchange device 56 is used. For example, the concentration of the regenerated component _{is preferably 8% by weight as CaCO 3} or less, and more preferably 5% by weight as CaCO ₃ or less. Moreover, the pH of this used wastewater is preferably 0 or more.

Next, the operation of the ultrapure water production system 16 of the present embodiment, the wastewater treatment method, and the ultrapure water production method are described in the ultrapure water production system 82 of the first comparative example shown in FIG. 2 and the second shown in FIG. This will be described while comparing with the ultrapure water production system 92 of the comparative example. In addition, in FIG. 2 and FIG. 3, the same reference numerals are given to the same elements as those in FIG. Further, in FIGS. 1 to 3, the amount of water flowing through each portion in each ultrapure water production system is indicated by a number in a circle. The unit of each number is m ³ / h. The amount of water shown here is an example for convenience of explanation.

In addition, Table 1 shows the amount of water in the main part in the ultrapure water production system of the present embodiment, the first comparative example and the second comparative example.

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 use point 34 is 200 m ³ / h, and the ultrapure water is discharged from the use point 34. ^{The amount of acid drainage is 100 m 3} / h, which is 50% of the ultrapure water used at use point 34, and the amount of wastewater used at the wastewater utilization facility 38 is that of the ultrapure water used at use point 34. It is set to 50 m ³ / h, which is 25% of the amount.

The ultrapure water production system 82 of the first comparative example shown in FIG. 2 is not provided with the wastewater treatment device 12 in the ultrapure water production system 16 of the first embodiment. Then, the drainage after desalting generated in the first membrane filtration device 24 is discharged to the outside of the ultrapure water production system 82. Further, a part of the used wastewater is also discharged to the outside of the ultrapure water production system 82 from the membrane filtration device 48 of the wastewater recovery device 42.

In the ultrapure water production system 92 of the second comparative example shown in FIG. 3, a dispersant is charged between the activated carbon device 22 and the first membrane filtration device 24. The dispersant, also called a scale inhibitor, has an action of dispersing the hardness component in the water to be treated in a solvent and suppressing the crystal growth of impurities. Then, the demineralized 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, and a part of the drainage is discharged to the outside of the ultrapure water production system 92.

As shown in FIG. 1, a part of the ultrapure water production system 16 of the present embodiment, the raw water fed to the raw water tank ^{18 (154.5m 3 / h) (} 9m 3 / h) is sent to the wastewater utilizing facility 38 However, the rest (145.5 m ³ / h) is sent to the raw water tank 18. The raw water tank 18, as described later, the treated water back from the second membrane filtration device 26 ^(10m 3 / h), treated water back from the deionizer 30 ^(10m 3 / h), and the membrane filtering device 48 Used drainage (99.5 m ³ / h) returning from is also housed. Then, the raw water contained in the raw water tank 18 is sequentially sent to the sand filtration device 20 and the activated carbon device 22 (265 m ³ / h).

The water from which foreign substances in the raw water have been removed by the sand filtration device 20 and the activated carbon device 22 is sent to the first membrane filtration device 24 as ^{water to be treated (260 m 3} / h), and further, calcium ions and magnesium from the water to be treated. Ions, bicarbonate ions, etc. are removed (demineralized) and sent to the second membrane filtration device 26 (220 m ³ / h). The desalted wastewater (water having a high concentration of calcium ions and magnesium ions) generated in the first film filtration device 24 is sent to the high hardness water tank 54 of the wastewater treatment device 12 (40 m ³ / h).

In the second membrane filtration device 26, calcium ions, magnesium ions, bicarbonate ions and the like are further removed from the water to be treated and sent to the degassing device 28 (210 m ³ / h). The water to be treated that has not been sent from the second membrane filtration device 26 to the degassing device 28 is returned to the raw water tank 18 (10 m ³ / h).

In the degassing device 28, the gas in the water to be treated, particularly carbon dioxide gas, is removed, and the water to be treated after removing the carbon dioxide gas is sent to the deionizing device 30 as water to be treated (210 m ³ / h). In the deionization device 30, impurity ions are removed from the liquid to be treated, the liquid to be treated is sent to the polisher 32 (200 m ³ / h), and the water to be treated that was not sent to the polisher 32 is returned to the raw water tank 18. (10m ³ / h). In the polisher 32, the final treatment of the water to be treated is performed, and the obtained ultrapure water is sent to the use point 34 (200 m ³ / h). Ultrapure water is used at use point 34, and the water after use is discharged as used wastewater. The used wastewater is stored in the used drainage tank 44 of the wastewater recovery device 42. As will be described later, the used drainage is returned to the used drainage tank 44 from the membrane filtration device 64 (10.5 m ³ / h).

In the wastewater recovery device 42, the used wastewater from the used drainage tank 44 is sent to the activated carbon device 46 (110.5 m ³ / h), and the activated carbon device 46 removes foreign substances contained in the used wastewater. Further, the used wastewater is sent to the membrane filtration device 48 to generate used wastewater having a low concentration of hydrogen ion components and used wastewater having a high concentration of hydrogen ions. The used wastewater having a low hydrogen ion concentration is returned to the raw water tank 18, and the used wastewater having a high hydrogen ion concentration is sent to the concentration tank 62 of the wastewater treatment apparatus 12.

The high hardness water tank 54 of the wastewater treatment apparatus 12 contains the desalted wastewater generated by the first membrane filtration apparatus 24 of the ultrapure water production apparatus 14. The drainage after desalting is sent to the weakly acidic cation exchange device 56. Then, the calcium ions and magnesium ions, which are the hardness components of the drainage after desalting, are replaced with the hydrogen ions of the weakly acidic cation exchange resin. After desalting, the hardness component of the wastewater is reduced, and the treated water is sent to the degassing device 58. In the degassing device 58, dissolved gas such as carbon dioxide gas is removed from the treated water, and then the treated water is sent to the salt removing device 60 to further remove salts. Then, the treated water is sent to the wastewater utilization facility 38 (36 m ³ / h) and used, but the treated water that is not sent to the wastewater utilization facility 38 is discharged to the outside of the wastewater treatment device 12. (4m ³ / h).

In the weakly acidic cation exchange device 56, as described above, the hydrogen ions of the weakly acidic cation exchange resin are replaced with the calcium ions and magnesium ions of the high hardness water. Used wastewater with an increased hydrogen ion concentration is sent from the concentration tank 62 (0.5 m ³ / h). The weakly acidic cation exchange resin is regenerated by substituting the hydrogen ions of the used wastewater with the calcium ions and magnesium ions of the weakly acidic cation exchange resin. In the weakly acidic cation exchange device 56, the used wastewater after being used for the regeneration of the weakly acidic cation exchange resin is neutralized with alkali as necessary for the remaining acid, and is outside the wastewater 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 wastewater is reduced by the neutralization reaction in this regeneration.

As described above, in the present embodiment, the hardness component of the desalted wastewater generated in the ultrapure water production step of the ultrapure water production apparatus 14 is removed by the weakly acidic cation exchange apparatus 56. Then, in the regeneration of the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56, since the used wastewater after being used at the use point 34 is effectively used, the weakly acidic cation exchange resin can be regenerated. Therefore, it is not necessary to add acid. Moreover, the amount of alkali added for neutralizing the used wastewater after being used for the regeneration of the weakly acidic cation exchange resin is reduced by the amount of the regenerated components consumed in the neutralization reaction during the regeneration. Since the wastewater from the ultrapure water production system 16 is only the wastewater from the weakly acidic cation exchange device 56 and the salt removal device 60, the ultrapure water production system 16 having a configuration that does not have the wastewater treatment device 12 In comparison, it is possible to reduce the amount of wastewater in the entire system.

As shown in Table 1, in the ultrapure water production system 16 of the present embodiment, the ultrapure water of 200 m ^{3 / h used at the use point 34 and the drainage of 50 m 3} / h used at the wastewater utilization facility 38. In order to obtain this, 154.5 m ³ / h of raw water is used. The total amount of wastewater discharged from the ultrapure water production system 16 is 4.5 m ³ / h.

In contrast, in the ultrapure water production system 82 of the first comparative example shown in FIG. 2, among the raw water ^{200m 3 / h, 45m 3 /} h is fed to the waste water utilization facility 38, the raw water tank 18 is 155m ³ / h is sent. ^{The second membrane filtration device 26 returns 10 m 3} / h and the deionizer 30 ^{returns 10 m 3} / h of treated water to the raw water tank 18, and the ^{membrane filtration device 48 returns 90 m 3} / h of used wastewater. .. From the raw water tank 18, 265 m ³ / h of raw water is sent to the sand filtration device 20 and sent to the activated carbon device 22, and 5 m ³ / h, which is a part of the raw water, is sent to the drainage utilization facility 38 via the filtration device 36. Sent.

In the first membrane filtration device 24, the sent 260 m ³ / h of water to be treated is desalted, and the 220 m ³ / h of water to be treated after desalting is sent to the second membrane filter 26 and 40 m ³ The water to be treated at / h is discharged to the outside of the ultrapure water production apparatus 14.

From the second membrane filtration device 26, 210 m ³ / h of water to be treated is sent to the deaeration device 28 and the deionizer 30, and from the deionizer 30, 200 m ³ / h of the liquid to be treated is a polisher 32. At the same time, the ^{liquid to be treated at 10 m 3} / h is returned to the raw water tank 18.

Of the ultrapure water used at use point 34, 100 m ³ / h is recovered and sent to the used drainage tank 44, the activated carbon device 46, and the membrane filtration device 48. ^{The 90 m 3} / h used wastewater filtered by the membrane filtration device 48 is returned to the raw water tank 18, and the 10 m ³ / h used wastewater is discharged to the outside of the ultrapure water production device 14.

As shown in Table 1, in the ultrapure water production system 82 of the first comparative example, the ultrapure water of 200 m ^{3 / h used in the use point 34 and the ultrapure water of 50 m 3} / h used in the wastewater utilization facility 38. ^{200 m 3} / h of raw water is used to obtain drainage. The total amount of wastewater discharged from the ultrapure water production system 82 is 50 m ³ / h.

In the ultrapure water production system 92 of the second comparative example shown in FIG. 3, a dispersant is charged into the water to be treated between the activated carbon device 22 and the first membrane filtration device 24. ^{Therefore, by filtering 40 m 3} / h of wastewater from the first membrane filtration device 24 by the membrane filtration device 94 (reverse osmosis device), 20 m ³ / h of water to be treated can be returned to the raw water tank 18. The actual drainage from the first membrane filtration device 24 is 20 m ³ / h.

As shown in Table 1, in the ultrapure water production system 92 of the second comparative example, the ultrapure water of 200 m ^{3 / h used in the use point 34 and the ultrapure water of 50 m 3} / h used in the wastewater utilization facility 38. ^{180 m 3} / h of raw water is used to obtain drainage. The total amount of wastewater discharged from the ultrapure water production system 92 is 30 m ³ / h.

As described above, in the ultrapure water production system 16 of the present embodiment, the amount of wastewater discharged is compared with any of the ultrapure water production system 82 of the first comparative example and the ultrapure water production system 92 of the second embodiment. Can be seen to be reduced.

Then, the amount of raw water used is reduced by the amount that the reduced wastewater is used for the wastewater utilization facility 38 and the like.

That is, in the ultrapure water production system 16 of the present embodiment, the amount of raw water required to obtain ^{200 m 3} / h of ultrapure water and 50 m ^{3 / h of wastewater used in the wastewater utilization facility 38 is the first.} It is reduced by about 23% with respect to the ultrapure water production system 82 of the first comparative example, and is reduced by about 14% with respect to the ultrapure water production system 92 of the second comparative example.

Moreover, in the ultrapure water production system 16 of the present embodiment, the hardness component of the drainage after desalting, which is the wastewater generated by the first film filtration device 24, is removed by the weakly acidic cation exchange device 56, and after this removal treatment. The weakly acidic cation exchange device 56 of the above is regenerated using the used wastewater generated at the use point 34.

At that time, hydrogen ions contained in the used wastewater are consumed. Therefore, in the ultrapure water production system 16 of the present embodiment, the used wastewater (0.5 m ³ / h) discharged to the outside is treated with respect to the used wastewater (0.5 m 3 / h) discharged to the outside. The amount of alkali added for neutralization can be halved as compared with the ultrapure water system 82 of the first comparative example and the ultrapure water system 92 of the second comparative example.

Further, in the ultrapure water production system 16 of the present embodiment ^{, the amount of wastewater generated when obtaining 200 m 3} / h ultrapure water is reduced by 91% as compared with the ultrapure water production system 82 of the first comparative example. It is reduced by 85% compared to the ultrapure water production system 92 of the second comparative example.

Moreover, in the wastewater treatment device 12 used in the ultrapure water production system 16 of the present embodiment, the used wastewater is circulated between the concentration tank 62 and the membrane filtration device 64 to increase the hydrogen ion concentration of the used wastewater. ing. Since the used wastewater in which hydrogen ions are concentrated by performing the concentration treatment on the used wastewater a plurality of times is used, the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56 can be efficiently regenerated.

In the present embodiment, it is also possible to use a strongly acidic cation exchange resin instead of a weakly acidic cation exchange resin only for removing the hardness component from the wastewater after desalting. However, when a strongly acidic cation exchange resin is used, in addition to removing components other than the hardness component from the drainage after desalting, the amount of impurity ions removed per unit resin amount is generally weakly acidic cation exchange resin. Since it is less (for example, 1/2 to 1/4), the amount of resin required is increased. In addition, it is difficult to regenerate a strongly acidic cation exchange resin, and it is essential to add a chemical such as an acid, so that it cannot be generally used in non-chemical type equipment. On the other hand, by using the weakly acidic cation exchange resin, the hardness component to be removed can be selectively and efficiently removed from the wastewater after desalting, and the weakly acidic cation exchange resin can be easily regenerated.

The regenerating agent for regenerating the weakly acidic cation exchange resin is not limited to the above-mentioned used wastewater in which hydrogen ions are concentrated, but by effectively using the hydrogen ions contained in the used wastewater, it is ultrapure. The configuration is highly effective in contributing to the reduction of the amount of wastewater in the water production system 16.

In particular, since the used wastewater is subjected to the concentration treatment a plurality of times, it is possible to efficiently regenerate the weakly acidic cation exchange resin by using the used wastewater having a high hydrogen ion concentration.

In the present embodiment, as the desalting treatment, the hardness component is removed by the first membrane filtration device 24. The desalting treatment may involve removal of salts other than calcium ions and magnesium ions, which are hardness components. If a large amount of the hardness component is contained, it may cause scale precipitation in a subsequent process (downstream side of the flow of the liquid to be treated). By removing the component that causes such scale, the generation of scale can be suppressed.

12 Wastewater treatment equipment 14 Ultra-pure water production equipment 16 Ultra-pure water production system 18 Raw water tank 20 Sand filtration equipment 22 Activated charcoal equipment 24 First-film filtration equipment 26 Second-film filtration equipment 28 Deaeration equipment 30 Deionization equipment 32 Polisher 34 Youth Point 36 Filtration device 38 Drainage utilization equipment 42 Drainage recovery device 44 Used drainage tank 46 Activated charcoal device 48 Film filtration device 52 Drainage reuse device 54 High hardness water tank 56 Weakly acidic cation exchange device 58 Degassing device 60 Desalting device 62 Concentration tank 64 Film filtration device 72 Pretreatment section 74 Primary pure water production section 76 Secondary pure water production section

Claims (10)

The hardness component of the drainage after desalting, which is water with concentrated hardness components generated by the desalination treatment in the ultrapure water production 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 a regenerated component contained in the used wastewater after using the ultrapure water produced in the ultrapure water manufacturing process, and the weakly acidic cation exchange resin is used. A wastewater treatment method that regenerates ion exchange resins. The wastewater treatment method according to claim 1, wherein the hardness component contains at least one of calcium ions and magnesium ions. The wastewater treatment method according to claim 1 or 2, wherein the regenerated component contains hydrogen ions. The wastewater treatment method according to any one of claims 1 to 3, wherein the weakly acidic cation exchange resin is regenerated by using the concentrated wastewater obtained by concentrating the recycled components with respect to the used wastewater. .. The wastewater treatment method according to claim 4, wherein the concentration treatment is performed a plurality of times on the used wastewater to concentrate the regenerated component. The wastewater treatment method according to any one of claims 1 to 5, wherein a degassing treatment for removing a gas component is performed on the treated water in which the hardness component is replaced with the ion exchange component. The wastewater treatment method according to any one of claims 1 to 6, wherein a salt removal treatment for removing salt is performed on the treated water in which the hardness component is replaced with the ion exchange component. The wastewater treatment method according to any one of claims 1 to 7, wherein the desalting treatment is performed by infiltrating the reverse osmosis membrane with water to be treated. Ultrapure water is produced by an ultrapure water production process that includes at least desalination of raw water.
The hardness component of the drainage after desalting, which is water in which the hardness component is concentrated , produced by the desalting treatment is replaced with an ion exchange component of a weakly acidic cation exchange resin.
The hardness component adsorbed on the weakly acidic cation exchange resin is replaced with a regenerated component contained in the used wastewater after using the ultrapure water produced in the ultrapure water manufacturing process, and the weakly acidic cation is replaced. Regenerate the exchange resin,
A method for producing ultrapure water, in which the used wastewater that has not been used for regenerating the weakly acidic cation exchange resin among the used wastewater is returned to the ultrapure water production process. A weakly acidic cation exchange device that replaces the hardness component of wastewater after desalting, which is water with a concentrated hardness component generated by desalting in the ultrapure water production process, with the ion exchange component of a weakly acidic cation exchange resin. ,
The hardness component adsorbed on the weakly acidic cation exchange resin is replaced with a reclaimed water component contained in the reclaimed water after using the ultrapure water produced in the ultrapure water manufacturing process, and the weakly acidic cation is replaced. A reclaimed water supply device that supplies reclaimed water for reclaiming ion exchange resins,
Wastewater treatment equipment with.

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