CN115485245A - Method for treating wastewater, method for producing ultrapure water, and wastewater treatment apparatus - Google Patents

Method for treating wastewater, method for producing ultrapure water, and wastewater treatment apparatus Download PDF

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CN115485245A
CN115485245A CN202180029928.0A CN202180029928A CN115485245A CN 115485245 A CN115485245 A CN 115485245A CN 202180029928 A CN202180029928 A CN 202180029928A CN 115485245 A CN115485245 A CN 115485245A
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wastewater
water
ultrapure water
component
cation exchange
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中村清一
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Nomura Micro Science Co Ltd
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Nomura Micro Science Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/58—Multistep processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D19/00—Degasification of liquids
    • B01D19/0031—Degasification of liquids by filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • B01D61/026—Reverse osmosis; Hyperfiltration comprising multiple reverse osmosis steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/145—Ultrafiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/147—Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • B01D61/46—Apparatus therefor
    • B01D61/48—Apparatus therefor having one or more compartments filled with ion-exchange material, e.g. electrodeionisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J39/00—Cation exchange; Use of material as cation exchangers; Treatment of material for improving the cation exchange properties
    • B01J39/04—Processes using organic exchangers
    • B01J39/07—Processes using organic exchangers in the weakly acidic form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J49/00—Regeneration or reactivation of ion-exchangers; Apparatus therefor
    • B01J49/50—Regeneration or reactivation of ion-exchangers; Apparatus therefor characterised by the regeneration reagents
    • B01J49/53—Regeneration or reactivation of ion-exchangers; Apparatus therefor characterised by the regeneration reagents for cationic exchangers
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/20—Treatment of water, waste water, or sewage by degassing, i.e. liberation of dissolved gases
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/42—Treatment of water, waste water, or sewage by ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4693—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis
    • C02F1/4695—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis electrodialysis electrodeionisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Abstract

The acid wastewater is regenerated by replacing the hardness component in desalted wastewater generated by the desalting treatment in the ultrapure water production process with the ion exchange component of a weakly acidic cation exchange resin, and replacing the hardness component adsorbed to the weakly acidic cation exchange resin with a regenerated component, which is a regenerated component contained in used wastewater generated by using ultrapure water produced in the ultrapure water production process.

Description

Method for treating wastewater, method for producing ultrapure water, and wastewater treatment apparatus
Technical Field
The present disclosure relates to a wastewater treatment method, an ultrapure water production method, and a wastewater treatment apparatus.
Background
In recent ultrapure water production systems, it has been desired to produce ultrapure water of higher purity, for example, ultrapure water having a TOC (Total Organic Carbon) concentration of 5. Mu.g C/L or less and a specific resistance of 17.5 M.OMEGA.cm or more.
Therefore, the stability of each apparatus in the ultrapure water production system is also becoming more stringent. For example, japanese patent application laid-open No. 2010-36160 describes a method and an apparatus that can suppress the propagation of microorganisms even if drainage is highly concentrated, thereby preventing a separation membrane from being clogged due to the production of slime. Japanese patent application laid-open No. 2003-154362 describes a water treatment apparatus and a water treatment method, which can suppress fouling (fouling) or scale even in a high recovery rate operation by treating concentrated water, which has been subjected to solid-liquid separation in advance and has been filtered through a Reverse Osmosis (RO) membrane and/or a Nanofiltration (NF) membrane, with a softening treatment method and/or an organic matter removal method. Thus, it is necessary to highly suppress the generation of products that cause unstable operation of the apparatus.
Disclosure of Invention
Problems to be solved by the invention
An ultrapure water production system includes, for example, mainly:
a pretreatment section for removing suspended matter in the raw water to obtain pretreated water;
a first-stage pure water producing unit for removing a TOC component and an ion component in the pretreated water to produce first-stage pure water; and
a second pure water producing unit for removing an extremely small amount of impurities from the first pure water to produce ultrapure water.
Further, in many cases, the ultrapure water production apparatus includes a desalination treatment apparatus such as a reverse osmosis apparatus or a nano-membrane filtration apparatus in the first-stage ultrapure water production unit. For example, from the viewpoint of cost reduction, effective utilization of water resources, and small-scale wastewater treatment processes, it is preferable to reuse the concentrated solution generated by these desalination treatment apparatuses.
However, if the concentrated solution is returned to the ultrapure water production process, it is necessary to highly remove impurities that may cause the production of the product, for example, the removal of cations described in japanese patent application laid-open No. 2010-36160, the softening treatment described in japanese patent application laid-open No. 2003-154362, and the removal of organic substances.
Concentrated water produced by a desalination treatment apparatus disposed upstream of an ultrapure water production apparatus generally contains a component causing scale generation and a component having a concentration close to a precipitation limit concentration, and the concentration of impurities such as salts and organic substances is high.
In order to remove impurities from the concentrated water to a high degree, a device for dividing the water to be treated into treated water from which the impurities are removed and concentrated water from which the impurities are further concentrated, for example, a reverse osmosis device or an Electrodeionization (EDI) device, may be used. When such a reverse osmosis apparatus or an electrodeionization apparatus is used, the recovery rate (the ratio of the amount of treated water to the amount of water to be treated) of the apparatus cannot be increased in order to suppress the generation of scale.
In addition, a treatment is also performed in which a dispersant (also referred to as a scale inhibitor) described later is added to the water to be treated. The scale inhibitor is a dispersant which can improve the precipitation limit concentration by inhibiting the crystal growth of impurities. However, even if an antiscalant is added to the water to be treated, it is difficult to increase the precipitation limit concentration significantly, and therefore, the improvement of the recovery rate is limited.
On the other hand, for the reason described later, the ultrapure water production system is also required to be a Non-chemical type (Non-chemical type) system which does not use chemicals such as acids and alkalis.
As described above, from the viewpoint of chemical-free type of ultrapure water production system, a processing apparatus and operating conditions that require the use of chemicals (particularly, highly dangerous acids and alkalis) cannot be adopted in an ultrapure water production system. For example, ion exchange resins that require the addition of acids or bases during regeneration cannot generally be used. Further, since the dispersant (also referred to as a scale inhibitor) is also a chemical, it is preferable not to add such a dispersant.
As a result, the concentrated water produced by the desalination treatment apparatus provided upstream of the ultrapure water production system is limited to a very small portion, even if the concentrated water can be returned to the ultrapure water production process. How to improve the reuse efficiency of such concentrated water has been a problem.
On the other hand, in a manufacturing plant of equipment using ultrapure water, such as semiconductors, liquid crystal panels, displays, and the like, a large amount of acidic wastewater is generated. Examples of the acidic wastewater include cleaning wastewater using an acid, etching (etching) wastewater, resist removal wastewater, and CMP wastewater.
Some of these acidic waste water is reused, but how to improve the reuse efficiency is also one of the issues.
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 necessary. However, it is also one of the problems to reduce the amount of alkali to be added because of the increased demand for non-chemical type production, which is the same as the ultrapure water production process, in terms of cost.
In this manner, it is necessary to perform more appropriate treatment of the wastewater generated in the process of producing ultrapure water.
The purpose of the present disclosure is to appropriately treat drainage water generated in a process for producing ultrapure water.
Means for solving the problems
In the wastewater treatment method of the first aspect, the hardness component of desalted wastewater produced by the desalting treatment in the ultrapure water production step is replaced with the ion exchange component of the weakly acidic cation exchange resin; the weakly acidic cation exchange resin is regenerated by replacing the hardness component adsorbed to the weakly acidic cation exchange resin with a regeneration component contained in used wastewater generated after the ultrapure water produced in the ultrapure water production step is used.
In this method for treating wastewater, the hardness component of desalted wastewater produced in the desalting step in the ultrapure water production step is replaced with the ion exchange component of a weakly acidic cation exchange resin. This reduces the hardness component in the desalted effluent.
The weakly acidic cation exchange resin has a hardness component adsorbed therein, and the hardness component is replaced with a regenerated component contained in used wastewater produced after the ultrapure water produced in the ultrapure water production step is used. Thereby, the weakly acidic cation exchange resin is regenerated. In this way, since used wastewater generated after the ultrapure water produced in the ultrapure water production process is used as a 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. Further, the amount of the alkali added for neutralization required when the used wastewater is treated reduces the amount of the regeneration component consumed in the neutralization reaction at the time of regeneration.
In a second aspect, according to the first aspect, the hardness component includes at least one of calcium ions and magnesium ions.
Therefore, calcium ions and magnesium ions can be removed from the desalted waste water by replacing them with the ion exchange component of the weakly acidic cation exchange resin.
In a third aspect, according to the first or second aspect, the regeneration component contains hydrogen ions.
The hydrogen ions contained in the used waste water can be effectively utilized to regenerate the weakly acidic cation exchange resin.
In a fourth aspect, according to any one of the first to third aspects, the regeneration of the weakly acidic cation exchange resin is performed using concentrated drain water obtained by concentrating the regenerated component by subjecting the used drain water to a concentration treatment.
Since the concentrated waste water obtained by concentrating the used waste water is used, the weakly acidic cation exchange resin can be regenerated efficiently, and the amount of waste water after regeneration can be reduced.
In a fifth aspect, according to the fourth aspect, the concentration process is performed a plurality of times on the used drain water to concentrate the regenerated component.
By performing the concentration treatment a plurality of times, the concentration of the regenerated component of the concentrated wastewater can be increased as compared with the case where only the concentration treatment is performed once, and the weakly acidic cation exchange resin can be regenerated more efficiently, and the amount of the wastewater after regeneration can be further reduced.
In a sixth aspect, according to any one of the first to fifth aspects, the treated water obtained by replacing the hardness component with the ion exchange component is subjected to degassing treatment for removing a gas component.
By removing the gas component from the treated water, the treated water can be easily reused.
In a seventh aspect, according to any one of the first to sixth aspects, the treated water obtained by replacing the hardness component with the ion exchange component is subjected to a salt removal treatment for removing salts.
By removing salt by subjecting the treated water to a salt removal treatment, the reuse of the treated water is facilitated, and the amount of the waste water that is not reused can be reduced.
In an eighth aspect, according to any one of the first to seventh aspects, the desalination treatment is performed by causing treated water to permeate a reverse osmosis membrane.
By using a reverse osmosis membrane, desalination treatment can be reliably performed, and water to be treated can be desalinated.
In the ultrapure water production method of the ninth aspect, ultrapure water is produced by subjecting raw water to an ultrapure water production step including at least desalination treatment; replacing a hardness component of desalted wastewater generated in the desalting treatment with an ion exchange component of a weakly acidic cation exchange resin; replacing the hardness component adsorbed to the weakly acidic cation exchange resin with a regenerative component contained in used wastewater produced after the ultrapure water produced in the ultrapure water production step is used, thereby regenerating the weakly acidic cation exchange resin; returning the used wastewater that is not used for the regeneration of the weakly acidic cation exchange resin among the used wastewater to the ultrapure water production process.
In this ultrapure water production method, ultrapure water is produced by subjecting raw water to an ultrapure water production step. Since the ultrapure water production step includes at least desalination treatment, wastewater containing hardness components is produced as desalted wastewater in the ultrapure water production step.
The hardness component of the desalted waste water is replaced by the ion exchange component of the weakly acidic cation exchange resin. This reduces the hardness component in the desalted wastewater.
The weakly acidic cation exchange resin has a hardness component adsorbed therein, and the hardness component is replaced with a regenerated component contained in used wastewater produced after the ultrapure water produced in the ultrapure water production step is used. Thereby, the weakly acidic cation exchange resin is regenerated. In this way, since the used wastewater produced after the ultrapure water produced in the ultrapure water production step is used as the regenerant in the regeneration of the weakly acidic cation exchange resin, it is not necessary to add an acid for the regeneration of the weakly acidic cation exchange resin. Further, the amount of the alkali added for neutralization required in the treatment of the used wastewater reduces the amount of the regeneration component consumed in the neutralization reaction at the time of regeneration.
Since the used wastewater that is not used for the regeneration of the weakly acidic cation exchange resin among the used wastewater is returned to the ultrapure water production process, the used wastewater can be effectively reused without wasting the used wastewater, and ultrapure water can be produced.
In the wastewater treatment apparatus of the tenth aspect, a weakly acidic cation exchange device and a regenerated water supply device are provided; wherein the weakly acidic cation exchanger replaces a hardness component of desalted wastewater produced by a desalting treatment in an ultrapure water production process with an ion exchange component of a weakly acidic cation exchange resin; the regenerated water supply device supplies regenerated water for replacing the hardness component adsorbed to the weakly acidic cation exchange resin with a regenerated component contained in used wastewater generated after the ultrapure water produced in the ultrapure water production process is used, thereby regenerating the weakly acidic cation exchange resin.
In the weakly acidic cation exchange device of the wastewater treatment apparatus, the hardness component of desalted wastewater produced in the desalting treatment in the ultrapure water production step is replaced with the ion exchange component of the weakly acidic cation exchange resin. This reduces the hardness component in the desalted effluent.
In the regenerated water supply device, regenerated water is supplied, the regenerated water is used for replacing hardness components adsorbed on the weak acid cation exchange resin by regenerated components, and the regenerated components are regenerated in used drainage generated after the ultrapure water produced in the ultrapure water production process is used. The hardness component adsorbed to the weakly acidic cation exchange resin is replaced with a regeneration component of the regeneration water to regenerate the weakly acidic cation exchange resin. In this way, when the weakly acidic cation exchange resin is regenerated, used wastewater produced after the ultrapure water produced in the ultrapure water production process is used as a regenerant, and therefore, it is not necessary to add an acid for the regeneration of the weakly acidic cation exchange resin. Further, the amount of the alkali added for neutralization required when the used wastewater is treated reduces the amount of the regeneration component consumed in the neutralization reaction at the time of regeneration.
Effects of the invention
In the present disclosure, the drainage water generated in the process of producing ultrapure water can be appropriately treated.
Drawings
FIG. 1 is a block diagram showing an ultrapure water production system including a wastewater treatment apparatus according to a first embodiment.
FIG. 2 is a block diagram showing an ultrapure water production system of a first comparative example.
FIG. 3 is a block diagram showing an ultrapure water production system of a second comparative example.
Detailed Description
Hereinafter, the wastewater treatment apparatus 12 according to the first embodiment and the ultrapure water production system 16 including the wastewater treatment apparatus 12 will be described with reference to the drawings. The ultrapure water production system 16 is a so-called chemical-free ultrapure water production system which does not use chemicals in the process of producing ultrapure water. The ultrapure water production system 16 does not use chemicals, and therefore has various effects as described below. In addition, these effects are merely illustrative.
There is no problem associated with the use of chemicals, for example, there is no influence on an ultrapure water system due to the remaining of chemicals.
Absence of quality fluctuations of ultrapure water, etc.
The risk associated with chemical handling can be avoided.
The load on the drainage treatment can be reduced, and the load on the environment can be reduced.
The ultrapure water production system 16 includes: an ultrapure water production apparatus 14 for producing ultrapure water, a wastewater treatment apparatus 12 for treating wastewater produced by the ultrapure water production apparatus 14, and a wastewater recovery apparatus 42 for recovering used ultrapure water (acidic wastewater) and reusing the same for ultrapure water production.
The ultrapure water production apparatus 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 (use point) 34. The pre-treatment section 72 includes the sand filter device 20 and the activated carbon device 22. The primary pure water production unit 74 includes the first membrane filtration device 24, the second membrane filtration device 26, the degasifier 28, and the deionizer 30. The secondary pure water producing unit 76 has a terminal filter (Polisher) 32.
The raw water tank 18 contains raw water to be supplied to the ultrapure water production system 14. Examples of the raw water include industrial water, tap water, underground water, and river water. The raw water is supplied to the sand filter 20.
The sand filter 20 is a device that removes fine foreign matter from raw water by passing the supplied raw water through filter sand as a filter medium. In addition to the sand filter device 20, for example, a coagulation sedimentation device may be used to sediment foreign matter to remove the foreign matter from the raw water. The water having passed through the sand filter 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 granular activated carbon. The activated carbon has a plurality of pores, and when the supplied water to be treated passes through the activated carbon, foreign matter that cannot be removed by the sand filter device 20 can be captured by the pores of the activated carbon, for example, chlorine that causes subsequent device deterioration can be captured by the pores of the activated carbon, and the foreign matter can be removed or decomposed from the water to be treated. The treated water from which foreign matter is removed via the activated carbon device 22 is supplied to the first membrane filtration device 24. The water containing a large amount of foreign matters removed by the activated carbon device 22 is filtered by the filter device 36 and then sent to the drain water utilization apparatus 38.
As the filtration device 36, for example, a Microfiltration Membrane (MF) device or a sand filtration device can be preferably used.
As one example, the first membrane filtration device 24 is a reverse osmosis device that performs desalination treatment on water to be treated by passing the water to be treated through a reverse osmosis membrane. By this desalting treatment, hardness components (i.e., calcium ions (Ca) 2+ ) Magnesium ion (Mg) 2+ ) Bicarbonate ions, etc.) are removed from the water being treated. In practice, the water to be treated is divided into water in which the hardness component is concentrated to a high concentration (hereinafter, referred to as "desalted drain") and water in which the hardness component is diluted to a low concentration. The water diluted to have a low concentration of the hardness component is supplied to the second membrane filtration device 26 as the water to be treated. On the other hand, the desalted wastewater is supplied to the wastewater treatment apparatus 12 as described later.
As the first membrane filtration device 24 for performing desalination treatment of the water to be treated, for example, a nano-membrane filtration device may be used. However, from the viewpoint of improving the salt removal rate and the removal rate of impurities contained in other water to be treated, an apparatus using the reverse osmosis membrane is preferred.
In the second membrane filtration device 26, as an example, the water to be treated is passed through a reverse osmosis membrane, similarly to the first membrane filtration device 24, to thereby perform desalination treatment again on the water to be treated. By the desalting treatment again, the hardness components are further removed from the water to be treated. The water diluted to have a low concentration of the hardness component is supplied to the degasifier 28 as the water to be treated. In contrast, the desalted wastewater from the second membrane filtration device 26 is returned to the raw water tank 18 to be reused for the production of ultrapure water because the hardness component content is low, unlike the desalted wastewater from the first membrane filtration device 24.
The degasifier 28 is, for example, a membrane degasifier using a gas separation membrane which does not allow moisture to permeate but allows gas to permeate. The degasifier 28 can remove gas (particularly, carbon dioxide) in the water to be treated. The water to be treated by the deaerator 28 is supplied to the deionizer 30 as water to be treated in a state where the concentration of carbon dioxide is low.
The deionization unit 30 is a unit that removes impurity ions such as organic acids contained in the liquid to be treated.
As the Deionization unit 30, for example, an Electrodeionization (EDI) unit or a Mixed Bed Ion Exchange Resin (Mixed Bed Ion Exchange Resin) unit can be preferably used. From the viewpoint of not requiring the addition of chemicals for the regeneration of the ion exchange resin, an electrodeionization device is preferable.
The electrodeionization apparatus is configured such that a gap formed between an anion exchange membrane and a cation exchange membrane is filled with an ion exchange resin to form a desalting chamber and a concentrating chamber, and a direct current is applied to the desalting chamber and the concentrating chamber to remove ions in a liquid to be treated. In the electrodeionization apparatus, for example, water to be treated is supplied to a desalting chamber and a concentrating chamber in parallel, and impurity ions in a liquid to be treated are adsorbed by a mixture of an anion exchange resin and a cation exchange resin in the desalting chamber. The adsorbed impurity ions are transferred to the concentration chamber under the action of the direct current. The concentrate water in the concentrating compartment is returned to the raw water tank 18, for example.
The mixed bed type ion exchange resin apparatus has, for example, the following structure: a cylindrical closed container is filled with a mixed bed type ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed. The water obtained by removing the impurity ions by the deionization apparatus 30 is supplied to the final filter 32 as the water to be treated.
The primary pure water producing unit 74 is not limited to the above configuration. For example, an ultraviolet oxidation device may be provided to oxidize and decompose organic substances in the water to be treated. Instead of the degasifier 28 having the above-described configuration for removing gas (particularly carbon dioxide) in the water to be treated, a degasifier capable of removing gas (particularly dissolved oxygen) in the water to be treated may be provided, or a degasifier capable of removing gas (particularly dissolved oxygen) in the water to be treated may be provided in combination with the degasifier 28. For example, a degasifier for removing carbon dioxide, an ultraviolet irradiation device, and a degasifier for removing dissolved oxygen may be provided in this order from the upstream side of the flow of the water to be treated.
In the final filter 32, the water to be treated is subjected to final treatment (i.e., removal of an extremely small amount of impurities in the primary pure water) to obtain ultrapure water. The end filter 32 is, for example, a non-regenerative type mixed bed ion exchange resin device.
In the secondary pure water production unit 76, heat exchangers may be provided before and after the final filter 32, and the temperature of the water to be treated may be adjusted by heat exchange (heating or cooling). The heat exchanger may be a plate-type heat exchanger, for example, but the specific structure is not particularly limited.
In the secondary pure water production unit 76, various processing devices for implementing a microorganism contamination strategy or the like by a sterilization means or the like may be provided before and after the end filter 32 as necessary, so that ultrapure water having a desired purity can be obtained. Examples of such treatment apparatuses include an ultraviolet oxidation apparatus, a hydrogen peroxide removal apparatus, a degasser, and an Ultrafiltration (UF) membrane apparatus.
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-supported resin device that removes hydrogen peroxide by decomposition of a palladium (Pd) -supported resin, a reducing resin device that fills a basic anion exchange resin with a reducing resin having a sulfurous acid group and/or a sulfurous acid hydrogen group, or the like.
The ultrapure water obtained by the final filter 32 (ultrapure water production apparatus 14) is sent to a use point 34 as a use place. Water produced by using ultrapure water is discharged from the use point 34 as used water. The used waste water contains hydrogen ions (H) + ) The acidic drainage of (3).
Examples of the use point 34 include a manufacturing factory of a semiconductor, a liquid crystal panel, and a display. Examples of the used wastewater include cleaning wastewater using an acid, etching solution wastewater, resist removal wastewater, and CMP wastewater.
The drain recovery unit 42 includes a used drain tank 44, an activated carbon unit 46, and a membrane filtration unit 48. The used drain from the point of use 34 is contained in a used drain tank 44. And, for example, when the used drain tank 44 is in a full state, the overflowed used drain is sent to the activated carbon device 46.
In the activated carbon device 46, foreign matter contained in used drain water is captured by the fine pores of the activated carbon and removed. The used drain water from which foreign matter has been removed by the activated carbon device 46 is sent to the membrane filtration device 48.
In the membrane filtration device 48, as one example, the used drainage water is passed through a reverse osmosis membrane to remove chloride ions (Cl) from the water to be treated - ) Nitrate ion (NO) 3 - ) Sulfate ion (SO) 4 2- ) Fluorine ion (F) - ) And phosphate ion (PO) 4 2- ) And the like. The used waste water having a low acid content is returned to the raw water tank 18 and reused for producing ultrapure water. For acid in the membrane filtration unit 48The used wastewater having a high concentration of the concentrated components is sent to the wastewater treatment apparatus 12 with a high concentration of hydrogen ions.
The wastewater treatment apparatus 12 includes a high-hardness water tank 54, a weak acid cation exchange device 56, a degasifier 58, a salt remover 60, a concentration tank 62, and a membrane filtration device 64.
The high-hardness water tank 54 of the drain water treatment device 12 contains the desalted drain water produced in the first membrane filtration device 24. The desalted drain water is sent from the high-hardness water tank 54 to the weak acid cation exchange device 56.
The weakly acidic cation exchange device 56 has a weakly acidic cation exchange resin. The weakly acidic cation exchange resin has hydrogen ion (H) + ) The weakly acidic cation exchange resin is formed into particles or fibers as an ion exchange component and sealed in a container. When the desalted wastewater passes through the weakly acidic cation exchange device 56 while being in contact with the weakly acidic cation exchange resin, calcium ions and magnesium ions as hardness components of the desalted wastewater are replaced with hydrogen ions of the weakly acidic cation exchange resin. The desalted drain water with a reduced hardness component is sent to the degasifier 58 as treated water.
The degasifier 58 removes dissolved gases such as carbon dioxide from the treated water. Examples of the degasifier 58 include a vacuum degasifier, an atmospheric degasifier, and a membrane degasifier, but are not limited thereto.
From the viewpoint of cost reduction, an atmospheric pressure degasser or a membrane degasser is preferable, and an atmospheric pressure degasser is more preferable. In addition, from the viewpoint of easy management, a membrane degassing apparatus is preferred.
The treated water of the weakly acidic cation exchanger 56 becomes an acidic liquid containing carbon dioxide generated by a neutralization reaction between bicarbonate ions contained in desalted drain water and hydrogen ions present as an ion exchange component. By degassing the treated water, carbon dioxide can be efficiently removed without adding an acid.
The treated water from which the dissolved gas has been removed by the degasser 58 is sent to a salt remover 60.
In the salt removing apparatus 60, the remaining salts are removed from the treated water. Examples of the salt removing device 60 include an electrodialysis device for removing salt with an electrodialysis membrane, and a membrane filtration device for removing 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 drain water utilizing facility 38 to be utilized. Examples of the drain utilization facility 38 include a scrubber facility, a cooling tower facility, and a water recovery facility such as a toilet cleaning facility.
The treated water from which salts have been removed by the salt removal device 60 is discharged water having a higher impurity concentration than the raw water supplied to the ultrapure water production system 16. The drain water utilization device 38 is a device that can utilize even drain water having a high impurity concentration.
Since the weak acid cation exchanger 56 has a low removal rate for components other than hardness components, it is not generally used for the purpose of returning desalted drain water generated in the first membrane filtration unit 24 to the ultrapure water production process. However, it can be preferably used for the purpose of producing drainage that can be utilized in the above-described drainage utilization apparatus 38.
The apparatus configuration and the operating conditions between the weakly acidic ion exchange apparatus 56 and the wastewater utilization facility 38 may be determined as appropriate 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 salts remaining in the treated water in the weakly acidic cation exchanger 56, the salt remover 60 may be omitted. If the drain utilization facility 38 is a reclaimed water facility such as a scrubber facility, a cooling tower facility, or a toilet cleaning facility as described above, it is preferable that the facility configuration and the operating conditions be applied at low cost and/or easy to manage.
The used wastewater having a high hydrogen ion concentration in the membrane filtration device 48 is stored in the concentration tank 62 of the wastewater treatment device 12. The used drain water contained in the concentration tank 62 is sent to the membrane filtration device 64. In the membrane filtration device 64, the used drain water is passed through a reverse osmosis membrane in the same manner as in the membrane filtration device 48. Thereby, the components in the used wastewater (i.e., the components having a further higher hydrogen ion concentration) are extracted and returned to the concentration tank 62. By circulating the used waste water between the concentration tank 62 and the membrane filtration device 64, the hydrogen ion concentration of the used waste water can be increased. In the membrane filtration device 64, the used drain water in which the hydrogen ion concentration is concentrated is returned to the used drain tank 44.
In this way, the used drain water having the hydrogen ion concentration increased by circulating between the concentration tank 62 and the membrane filtration device 64 is sent to the weakly acidic cation exchange device 56.
In the weak acid cation exchange device 56, since the hydrogen ions of the weak acid cation exchange resin are replaced with the hardness component of the desalted wastewater, the hardness component is adsorbed in the weak acid cation exchange resin. On the other hand, hydrogen ions contained in the used waste water are replaced with the hardness component of the weakly acidic cation exchange resin, and thus function as a regeneration component for regenerating the weakly acidic cation exchange resin. That is, the used drain is sent from the concentration tank 62 to the weakly acidic cation exchange device 56, and the used drain 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 concentration of hydrogen ions in the used wastewater increases, and therefore 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 regeneration of the weakly acidic cation exchange resin is neutralized with alkali as necessary, and then discharged to the outside of the wastewater treatment device 12. Further, the treated water that is not sent from the salt removing device 60 to the drain water utilizing apparatus 38 is also discharged to the outside of the drain water treatment device 12. Substantially, the wastewater from the weakly acidic cation exchanger 56 and the wastewater from the salt remover 60 are wastewater from the ultrapure water production system 16.
The method of regenerating the weakly acidic cation exchange resin by using the regeneration component contained in the used waste water after the use of ultrapure water is not limited to the method of the present embodiment.
For example, in the case where the after-use waste water has a high sodium concentration, the weakly acidic cation exchange resin may be regenerated to a Na form in which the ion exchange component is sodium ions. Examples of such drainage water include regeneration drainage water obtained by adding caustic soda to a mixed bed type ion exchange resin or anion exchange resin and performing regeneration treatment.
However, from the viewpoint of the easiness of regeneration and the fact that no chemical needs to be added during the regeneration treatment, it is preferable to use hydrogen ions as the regeneration component and regenerate the weakly acidic cation exchange resin into an H form in which the ion exchange component is hydrogen ions.
In the used wastewater discharged from the point of use 34, for example, the concentration of the regenerated component is preferably CaCO from the viewpoint of easily concentrating the used wastewater to a concentration at which the weakly acidic cation exchange resin can be regenerated efficiently 3 40ppm or more, more preferably CaCO 3 The content is more than 100 ppm. The pH of the used waste water is preferably 4 or less, and more preferably 3 or less.
On the other hand, from the viewpoint of returning the used wastewater from which the impurities have been removed by the wastewater recovery device 42 to the ultrapure water production process, the concentration of the regenerated component in the used wastewater discharged from the use point 34 is preferably CaCO, for example 3 300ppm or less, more preferably CaCO 3 The content is less than 250 ppm. The pH of the used drainage water is preferably 2 or more.
From the viewpoint of efficiently regenerating the weakly acidic cation exchange resin, the concentration of the regenerated component in the used wastewater sent to the weakly acidic cation exchange device 56 is preferably CaCO, for example 3 1% by weight or more, more preferably CaCO 3 3% by weight or more. The pH of the used waste water is preferably 2 or less, and more preferably 1 or less.
On the other hand, from the viewpoint of suppressing the risk of resin breakage due to a rapid volume change accompanying regeneration, the risk of corrosion of the members used in the apparatus, and the like, the resin is transported to the weakly acidic cation exchange apparatus56 in the used wastewater, the concentration of the regenerating component is preferably CaCO 3 Not more than 8% by weight, preferably CaCO 3 5 wt% or less. The pH of the used drainage water is preferably 0 or more.
Next, the operation, the drain treatment method, and the ultrapure water production method of the ultrapure water production system 16 of the present embodiment will be described in comparison with the ultrapure water production system 82 of the first comparative example shown in fig. 2 and the ultrapure water production system 92 of the second comparative example shown in fig. 3. In fig. 2 and 3, the same elements as those in fig. 1 are denoted by the same reference numerals. In fig. 1 to 3, the amounts of water flowing through the respective portions in the respective ultrapure water production systems are indicated by numbers in circles. The unit of each number is m 3 H is used as the reference value. The amount of water shown here is one example for ease of illustration.
Table 1 shows the amount of water in the main portions of the ultrapure water production systems according to the present embodiment and the first and second comparative examples.
[ Table 1]
Figure BDA0003900180310000121
In 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 was 200m 3 The amount of acidic wastewater discharged from the use point 34 is 50% (i.e., 100 m) of the ultrapure water used at the use point 34 3 H) the amount of the drainage water utilized in the drainage water utilization device 38 is 25% of the amount of ultrapure water used at the use point 34 (i.e., 50 m) 3 /h)。
An ultrapure water production system 82 of a first comparative example shown in FIG. 2 is not provided with the wastewater treatment apparatus 12 in the ultrapure water production system 16 of the first embodiment. The desalted wastewater produced 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 from the membrane filtration device 48 of the wastewater collection device 42 to the outside of the ultrapure water production system 82.
An ultrapure water production system 92 of a second comparative example shown in FIG. 3 is constituted such that a dispersant is introduced between the activated carbon unit 22 and the first membrane filtration unit 24. The dispersant is also called a scale inhibitor, and has an effect of dispersing hardness components in the water to be treated in the solvent to inhibit crystal growth of impurities. The desalted drain water discharged from the first membrane filtration unit 24 is filtered by the membrane filtration unit 94, returned to the raw water tank 18, and partially discharged to the outside of the ultrapure water production system 92.
As shown in FIG. 1, in the ultrapure water production system 16 of the present embodiment, raw water (154.5 m) fed to a raw water tank 18 is supplied 3 A fraction of (9 m)/h) 3 H) to the drain utilizing apparatus 38, and the remaining raw water (145.5 m) 3 H) to the raw water tank 18. As described later, the raw water tank 18 also accommodates water to be treated (10 m) returned from the second membrane filtration device 26 3 H), treated Water (10 m) returned from the deionization apparatus 30 3 H) and used drainage (99.5 m) returning from the membrane filtration unit 48 3 H) of the reaction. The raw water contained in the raw water tank 18 flows sequentially to the sand filter 20 and the activated carbon unit 22 (265 m) 3 H) conveying.
In the sand filter 20 and the activated carbon device 22, water obtained by removing foreign matters in raw water is sent to the first membrane filter 24 (260 m) as water to be treated 3 H), and further calcium ions, magnesium ions, bicarbonate ions, etc. are removed (desalted) from the water to be treated, and sent to the second membrane filtration device 26 (220 m) 3 H). The desalted drain water (water having a high concentration of calcium ions and magnesium ions) produced in the first membrane filtration unit 24 is sent to a high-hardness water tank 54 (40 m) of the drain water treatment unit 12 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 treated water which has not been sent from the second membrane filtration device 26 to the degasifier 28 is returned to the raw water tank 18 (10 m) 3 /h)。
In the degassing device 28, the water to be treatedIs removed, and the water to be treated after carbon dioxide removal is sent to the deionization apparatus 30 as water to be treated (210 m) 3 H). In the deionization unit 30, impurity ions are removed from the liquid to be treated, and the liquid to be treated is sent to a final filter 32 (200 m) 3 H) while the treated water not sent to the end filter 32 is returned to the raw water tank 18 (10 m) 3 H). In the final filter 32, the water to be treated is subjected to final treatment, and the resulting ultrapure water is supplied to a point of use 34 (200 m) 3 H). Ultrapure water is used at the use point 34, and the used water is discharged as used drain water. The used drain is accommodated in a used drain tank 44 of the drain recovery device 42. As described later, the used drain is also returned from the membrane filtration device 64 to the used drain tank 44 (10.5 m) 3 /h)。
In the drain recovery device 42, the used drain of the used drain tank 44 is sent to the activated carbon device 46 (110.5 m) 3 And/h), foreign matter contained in the used waste water is removed in the activated carbon device 46. The used wastewater is sent to the membrane filtration device 48, and used wastewater having a low hydrogen ion concentration and used wastewater having a high hydrogen ion concentration are produced. The used drain water having a low hydrogen ion concentration is returned to the raw water tank 18, and the used drain water having a high hydrogen ion concentration is sent to the concentration tank 62 of the drain water treatment apparatus 12.
The high-hardness water tank 54 of the wastewater treatment apparatus 12 accommodates desalted wastewater generated in the first membrane filtration apparatus 24 of the ultrapure water production apparatus 14. The desalted drain water is sent to a weak acid cation exchange unit 56. Calcium ions and magnesium ions, which are hardness components of desalted wastewater, are replaced with hydrogen ions of the weakly acidic cation exchange resin. The hardness component of the desalted wastewater is reduced, and the wastewater is sent to the degasifier 58 as treated water. In the degasser 58, dissolved gases such as carbon dioxide are removed from the treated water, and then the treated water is sent to a salt remover 60 to further remove salts. Then, the treated water is sent to a drain utilization device 38 (36 m) 3 /h) The treated water which is not sent to the drain water utilization device 38 is discharged to the outside of the drain water treatment apparatus 12 (4 m) 3 /h)。
In the weakly acidic cation exchanger 56, as described above, the hydrogen ions of the weakly acidic cation exchange resin are replaced with calcium ions and magnesium ions of the water having high hardness, and the used wastewater (0.5 m) having an increased hydrogen ion concentration is sent from the concentration tank 62 to the weakly acidic cation exchanger 56 3 H). The hydrogen ions of the used waste 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, the used wastewater after being used for regeneration of the weakly acidic cation exchange resin is neutralized with alkali as necessary to discharge the residual acid to the outside of the wastewater treatment device 12 (0.5 m) 3 H). In the regeneration of the weakly acidic cation exchange resin, the amount of acid remaining in the used effluent is reduced by the neutralization reaction during the regeneration.
In this manner, in the present embodiment, the weak acid cation exchanger 56 removes the hardness components of the desalted wastewater generated in the ultrapure water production process of the ultrapure water production apparatus 14. Further, in the case of regenerating the weakly acidic cation exchange resin in the weakly acidic cation exchange device 56, since the used drain water after use at the use point 34 is effectively used, it is not necessary to add an acid for the regeneration of the weakly acidic cation exchange resin. Further, the amount of the alkali required for neutralization of the used drainage after use in regenerating the weakly acidic cation exchange resin reduces the amount of the regeneration component consumed in the neutralization reaction in regeneration. Since the wastewater from the ultrapure water production system 16 is only the wastewater from the weak acid cation exchange device 56 and the wastewater from the salt removal device 60, the amount of wastewater in the entire system can be reduced as compared with the ultrapure water production system 16 having no wastewater treatment device 12.
As shown in Table 1, in the ultrapure water production system 16 of the present embodiment, 200m was used at the use point 34 3 Ultrapure water/h and apparatus for utilizing waste water50m for use in preparation of 38 3 Drainage of 154.5 m/h 3 H of raw water. The total amount of the wastewater from the ultrapure water production system 16 was 4.5m 3 /h。
In contrast, in the ultrapure water production system 82 of the first comparative example shown in FIG. 2, 200m was used 3 45m in raw water/h 3 The raw water/h is sent to a drain utilization facility 38, where 155m is discharged 3 The/h raw water is delivered to the raw water tank 18. 10m 3 The treated water/h is returned from the second membrane filtration device 26 to the raw water tank 18, 10m 3 90m of treated water is returned from the deionization unit 30 to the raw water tank 18 3 The used off water/h is returned from the membrane filtration unit 48 to the raw water tank 18. 265m 3 The raw water/h is supplied from the raw water tank 18 to the sand filter 20 and is supplied to the activated carbon device 22, and 5m is a part of the activated carbon device 3 The/h raw water is transported to a drain utilization device 38 via a filter device 36.
In the first membrane filtration device 24, 260m of the fed liquid is 3 Per hour of desalination of the treated Water, 220m after desalination 3 The treated water was fed to the second membrane filtration device 26 at 40m 3 The water to be treated at/h is discharged to the outside of the ultrapure water production apparatus 14.
210m 3 H of the treated water is sent from the second membrane filtration device 26 to the degassing device 28 and the deionization device 30, 200m 3 The treated liquid/h was supplied from the deionizing unit 30 to the end filter 32 while 10m 3 The treated liquid/h is returned to the raw water tank 18.
In ultrapure water for use at point of use 34, 100m 3 The/h is recovered and sent to a used drain tank 44, an activated carbon unit 46 and a membrane filtration unit 48. 90m after filtration by the membrane filtration device 48 3 The used drainage water of/h is returned to the raw water tank 18, 10m 3 The used wastewater/h is discharged to the outside of the ultrapure water production apparatus 14.
As shown in Table 1, in the ultrapure water production system 82 of the first comparative example, 200m used at the use point 34 was obtained 3 Ultrapure water/h, and 50m used in the wastewater utilization facility 38 3 /h200m for drainage of 3 H of raw water. The total of the drainage from the ultrapure water production system 82 was 50m 3 /h。
In an ultrapure water production system 92 of a second comparative example shown in FIG. 3, a dispersant is put into the water to be treated between the activated carbon unit 22 and the first membrane filtration unit 24. Thus, 40m from the first membrane filtration device 24 was filtered with the membrane filtration device 94 (reverse osmosis device) 3 Water drainage of/h, thereby 20m 3 The treated water/h can be returned to the raw water tank 18 with a substantial discharge of 20m from the first membrane filtration unit 24 3 /h。
As shown in Table 1, in the ultrapure water production system 92 of the second comparative example, 200m was used at the use point 34 3 Ultrapure water/h, and 50m used in the wastewater utilization facility 38 3 Water drainage of 180m 3 H of raw water. The total amount of the wastewater from the ultrapure water production system 92 was 30m 3 /h。
From this fact, it is understood that the amount of water discharged in the ultrapure water production system 16 of the present embodiment is reduced as compared with the ultrapure water production system 82 of the first comparative example and the ultrapure water production system 92 of the second embodiment.
The reduced drain water is used for the drain utilization equipment 38 and the like, and the amount of used raw water is reduced accordingly.
That is, in the ultrapure water production system 16 of the present embodiment, 200m is obtained 3 Ultrapure water/h and 50m used in the waste water utilization equipment 38 3 The amount of raw water required for the water discharge/h was reduced by about 23% with respect to the ultrapure water production system 82 of the first comparative example, and by about 14% with respect to the ultrapure water production system 92 of the second comparative example.
In the ultrapure water production system 16 of the present embodiment, the weak acid cation exchange device 56 is used to remove the hardness component of the wastewater (i.e., the desalted wastewater) generated in the first membrane filtration device 24, and the used wastewater generated at the use point 34 is used to regenerate the weak acid cation exchange device 56 after the removal treatment.
At this time, since hydrogen ions contained in the used wastewater are consumed, the used wastewater (0.5 m) discharged to the outside is used in the ultrapure water production system 16 of the present embodiment 3 H) the amount of alkali added required for neutralization can be halved with respect to 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, 200m was obtained 3 The amount of wastewater generated in the case of ultrapure water/h was reduced by 91% with respect to the ultrapure water production system 82 of the first comparative example and by 85% with respect to the ultrapure water production system 92 of the second comparative example.
In the wastewater treatment apparatus 12 used in the ultrapure water production system 16 of the present embodiment, the hydrogen ion concentration of the used wastewater is increased by circulating the used wastewater between the concentration tank 62 and the membrane filtration device 64. Since the used wastewater is concentrated with hydrogen ions by performing a plurality of times of concentration treatment on the used wastewater, the weakly acidic cation exchange resin of the weakly acidic cation exchange device 56 can be regenerated efficiently.
In the present embodiment, if only the hardness component is removed from the desalted wastewater, a strongly acidic cation exchange resin may be used instead of the weakly acidic cation exchange resin. However, if a strongly acidic cation exchange resin is used, components other than the hardness components are also removed from the desalted waste water, and the amount of impurity ions removed per unit resin amount is generally smaller (for example, 1/2 to 1/4) than when a weakly acidic cation exchange resin is used, so that the required resin amount increases. In addition, regeneration of a strongly acidic cation exchange resin is difficult, and chemicals such as acid must be added, and therefore, it is generally not applicable to a chemical-free type apparatus. On the other hand, by using a weakly acidic cation exchange resin, it is possible to selectively and efficiently remove a hardness component to be removed from desalted drain water, and to facilitate regeneration of the weakly acidic cation exchange resin.
The regenerant for regenerating the weakly acidic cation exchange resin is not limited to the used wastewater in which the hydrogen ions are concentrated, but has a structure that has a high effect of contributing to reduction of the amount of wastewater in the ultrapure water production system 16 by effectively utilizing the hydrogen ions contained in the used wastewater.
In particular, since the used wastewater is subjected to the concentration treatment a plurality of times, the weakly acidic cation exchange resin can be efficiently regenerated 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. In the desalting treatment, salts other than calcium ions and magnesium ions, which are hardness components, may be removed. If the hardness component is contained in a large amount, scale may be deposited in a post-step (downstream side of the flow of the treatment target liquid). By removing such scale-causing components, the generation of scale can be suppressed.
The disclosure of japanese patent application No. 2020-75687, filed on 21/4/2020, is hereby incorporated by reference in its entirety.
All documents, patent applications, and technical standards cited in the present application are incorporated by reference herein to the same extent as if the individual documents, patent applications, and technical standards incorporated by reference were specifically and individually described.

Claims (10)

1. A method for treating waste water, comprising,
replacing a hardness component in desalted wastewater produced by a desalting treatment in an ultrapure water production process with an ion exchange component of a weakly acidic cation exchange resin;
and replacing the hardness component adsorbed on the weakly acidic cation exchange resin with a regenerated component contained in used wastewater produced by using the ultrapure water produced in the ultrapure water production step, thereby regenerating the weakly acidic cation exchange resin.
2. The wastewater treatment method according to claim 1, wherein the hardness component comprises at least one of calcium ions and magnesium ions.
3. The method for treating wastewater according to claim 1 or 2, wherein the regenerative component contains hydrogen ions.
4. The wastewater treatment method according to any one of claims 1 to 3, wherein the regeneration of the weakly acidic cation exchange resin is performed using concentrated wastewater obtained by concentrating the regenerated component by performing a concentration treatment on the used wastewater.
5. The wastewater treatment method according to claim 4, wherein the concentration treatment is performed a plurality of times on used wastewater to concentrate the regenerated component.
6. The method for treating wastewater according to any one of claims 1 to 5, wherein the treated water after the hardness component is replaced with the ion exchange component is subjected to degassing treatment for removing a gas component.
7. The wastewater treatment method according to any one of claims 1 to 6, wherein a salt removal treatment for removing salts is performed on treated water after the hardness component is replaced with the ion exchange component.
8. The drainage treatment method according to any one of claims 1 to 7, wherein the desalting treatment is performed by allowing treated water to permeate a reverse osmosis membrane.
9. An ultrapure water production method, wherein, in the ultrapure water production method,
ultrapure water is produced by an ultrapure water production step including at least desalination of raw water;
replacing a hardness component in desalted wastewater produced by the desalting treatment with an ion exchange component of a weakly acidic cation exchange resin;
regenerating the weakly acidic cation exchange resin by replacing the hardness component adsorbed on the weakly acidic cation exchange resin with a regeneration component contained in used wastewater produced by using the ultrapure water produced in the ultrapure water production step;
returning the used wastewater that is not used for the regeneration of the weakly acidic cation exchange resin among the used wastewater to the ultrapure water production process.
10. A wastewater treatment device, comprising:
a weak acid cation exchanger for replacing a hardness component in desalted wastewater generated by a desalting treatment in the ultrapure water production process with an ion exchange component of a weak acid cation exchange resin; and
and a regenerated water supply device for supplying regenerated water for replacing the hardness component adsorbed to the weakly acidic cation exchange resin with a regenerated component contained in used wastewater generated by using the ultrapure water produced in the ultrapure water production process, thereby regenerating the weakly acidic cation exchange resin.
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