JPH10216749A - Ultrapure water making apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the addition amt. of an alkali agent to the water to be treated of an org. matter oxidizing apparatus and to prevent an increase in the load of an ion exchange apparatus of a post stage when org. matter in water to be treated containing org. matter is removed by using the org. matter oxidizing apparatus oxidizing and decomposing the org. matter contained in water to be treated by adding ozone to water to be treated under an alkaline condition in an apparatus for making ultrapure water used in the washing of a silicon wafer in the semiconductor industry. SOLUTION: An org. matter oxidizing apparatus 38 adding ozone to water to be treated under an alkaline condition, an anion exchange apparatus 42 using an OH type strong basic anion exchanger resin and an electrodialytic apparatus wherein a desalting chamber is packed with a cation exchange resin are arranged to a route for removing org. matter of an ultrapure water making apparatus so that water to be treated is passed in this order and the alkaline concn. water of the electrodialytic apparatus 44 is added to the water to be treated of the org. matter oxidizing apparatus 38 to be used in the adjustment of the pH of the water to be treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to ultrapure water used for cleaning silicon wafers in the semiconductor industry, for example.
Regarding equipment for producing condensed water for condensate of thermal power plants and nuclear power plants, pure water and ultrapure water used in the pharmaceutical manufacturing industry, etc., more specifically, ozone is added to treated water under alkaline conditions. The present invention relates to an ultrapure water production apparatus that uses an organic matter oxidizing apparatus to improve the efficiency of organic matter removal in a path (for example, a recovery system or a secondary pure water system) that removes organic matter in treated water containing organic matter. In this specification,
In general, high-purity water described by terms such as pure water and ultrapure water, which are not necessarily clearly defined, is collectively referred to as “ultrapure water”.

[0002]

2. Description of the Related Art As shown in FIG. 6, an apparatus for producing ultrapure water used for cleaning a silicon wafer or the like generally includes a primary pure water system 2, a secondary pure water system (subsystem) 4, and a wastewater recovery system. A pure water drainage recovery system 6 is provided. The primary pure water system 2 is a path provided with, for example, a reverse osmosis membrane device, a vacuum deaerator, an ion exchange device, and the like, and a part of suspended substances and organic substances contained in raw water such as city water and industrial water is used. After being removed by a treatment system (not shown), the treated water 8 is supplied to the primary pure water system 2. The secondary pure water system 4 is a path provided with, for example, an ultraviolet oxidation device, a cartridge polisher, an ultrafiltration membrane device, and the like. It is supplied to the secondary pure water system 4. Part of the ultrapure water 12 obtained in the secondary pure water system 4 is sent to a use place 14 for use, and the remainder is circulated to a pure water storage tank 10. The pure water wastewater recovery system 6 is a path provided with, for example, an activated carbon filtration device, an ion exchange device, an ultraviolet oxidation device, and the like, and performs a treatment of the wastewater 16 generated by using ultrapure water at the use place 14. The treated water 18 of the pure water drainage recovery system 6 is returned to the primary pure water system 2 and reused.

[0003] In a general ultrapure water producing apparatus, as a wastewater recovery system for treating the ultrapure water wastewater 16 discharged from the place of use 14, the above pure water is returned to the primary pure water system after being appropriately treated. Depending on the cleanliness of the wastewater, a route to return directly to the primary pure water system without any treatment, or a route to be used as miscellaneous water after appropriate treatment (drainage for miscellaneous water) (Recovery system), and a route (wastewater treatment system) for discharging after appropriate treatment.

[0004]

In the process of cleaning silicon wafers and the like in the semiconductor industry, since organic cleaning agents such as isopropyl alcohol, methanol, and acetone are used, ultrapure water from the place of use is used. The generated wastewater usually contains a trace amount of organic matter, but the wastewater from this place of use has an extremely low impurity concentration as compared with city water, industrial water and the like. Therefore, if the organic matter concentration in the wastewater from the place of use is reduced as much as possible in the pure water wastewater recovery system of the ultrapure water production equipment and the treated water is returned to the primary pure water system, high purity ultrapure water can be obtained. It will be very advantageous. Therefore, in the wastewater recovery system for pure water, it is desired to remove organic substances as much as possible from the water to be treated.

[0005] In this case, as a method of removing organic substances in the pure water wastewater recovery system, conventionally, ozone or hydrogen peroxide as an oxidizing agent is added to the water to be treated (the wastewater generated by using ultrapure water). Further, a method is known in which the water to be treated containing ozone or hydrogen peroxide is irradiated with ultraviolet rays to oxidatively decompose organic substances.

However, this method has a drawback that the processing time is long because the decomposition rate of organic substances is low and the processing efficiency is low. In addition, the use of a high-pressure ultraviolet lamp increases the size of the apparatus, increases the cost of replacing the ultraviolet lamp, and increases running costs such as electricity costs, which is economically disadvantageous.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrapure water production apparatus which can efficiently remove organic substances in a path for removing organic substances from water to be treated.

[0008]

Means for Solving the Problems The inventors of the present invention irradiate ultraviolet rays when the water to be treated containing organic substances is treated using an organic oxidation apparatus for adding ozone to the water to be treated under alkaline conditions. It has been found that the organic matter in the water to be treated can be efficiently removed without any treatment. In this apparatus, organic substances are oxidized and decomposed by hydroxy radicals generated by the reaction between ozone and alkali.

However, in the above-described organic oxidation apparatus, the wastewater generated by using ultrapure water from a place of use which is usually acidic and contains an acid such as hydrofluoric acid is made alkaline, so that the wastewater is oxidized. A metal hydroxide such as NaOH is added as an alkaline agent into the water, but this adds new metal ions to the water to be treated, which increases the load on the subsequent ion exchange apparatus and increases the chemical cost. There was a problem.

On the other hand, the inventors of the present invention have conducted studies for solving the above-mentioned problems, and have obtained the following findings. In the organic matter oxidizing apparatus described above, an alkali agent is added to the water to be treated in order to make the water to be treated alkaline.
Cations derived from the alkaline agent leak into the treated water together with the cations originally contained in the treated water. Therefore, if the treated water of the organic matter oxidizing device is passed through an electrodialysis device filled with a cation exchange resin alone in the desalting chamber, almost all the cations present in the water to be treated move to the concentrated water, As a result that anions in the water to be treated hardly migrate into the concentrated water, alkaline concentrated water is obtained in the concentration chamber. Therefore, this concentrated water is added to the water to be treated in the organic matter oxidizer and used for pH adjustment. Thereby, it has been found that the amount of an externally added alkali agent to the water to be treated can be reduced.

In the above-described organic oxidation apparatus, the water to be treated is
Ionic impurities, especially Cl^-, F^-, SO_Four ^2-Etc. shade
Oxidative decomposition reaction of organic matter when ionic impurities are contained
, And the efficiency of removing organic substances decreases. Also,
In the organic matter oxidation device_Four ⁺NO by oxidation of_Three ^-,
NO_Two ^-Are generated, and these also cause the oxidative decomposition reaction of organic substances.
Inhibit. Therefore, as mentioned in the electrodialysis machine
When adding the concentrated water of
Indicates that Cl^-, F^-, SO_Four ^2-Etc. anions
NO generated by organic impurities and organic oxidation equipment_Three ^-, NO_Two ^-Contains
It is not desirable to be left. In this case, the cation exchange tree
In an electrodialysis machine filled with fat alone, anions are concentrated water
Although it is difficult to move inside, the more anions are
It is inevitable to move into concentrated water. Therefore,
The treated water of the equipment oxidation equipment is charged with cation exchange resin.
Strongly basic anion-exchange tree in OH form upstream of the gas dialysis machine
By passing water through an anion exchange device using fat,
Cl in the exchange unit^-, F^-, SO _Four ^2-, NO_Three ^-, NO_Two ^-etc
And remove them to the concentrated water of the electrodialyzer.
It has been found that it is possible to suppress the execution.

The present invention has been made on the basis of the above-mentioned findings, and includes the addition of ozone under alkaline conditions to the water to be treated in the ultrapure water production system in a path for removing organic substances. An organic matter oxidizer that oxidizes and decomposes organic matter, an anion exchanger using a strong basic anion exchange resin in the OH form, and an electrodialysis apparatus in which a desalination chamber is filled with a cation exchange resin are processed. Water is installed so as to pass in this order, and alkaline concentrated water obtained from the concentration chamber of the electrodialyzer is added to the water to be treated in the organic matter oxidizer and used for pH adjustment of the water to be treated. An ultrapure water production apparatus is provided.

[0013] The ultrapure water production apparatus of the present invention is provided with a path for removing organic substances, particularly organic substances in the water to be treated containing a trace amount of organic substances, such as a wastewater recovery system for pure water and a secondary pure water system. An organic oxidation device, an anion exchange device and an electrodialysis device were installed.

In this case, the structure of the organic matter oxidizing apparatus is not limited, but it is preferable that the apparatus satisfies one of the following conditions, especially both. Ozone is added to the water to be treated by gas-liquid stirring and mixing means. Ozone is added to the water to be treated under alkaline conditions where the pH of the water to be treated is 9.7 or more.

That is, when ozone is added to the water to be treated, ozone has low solubility in water, so that it is not sufficiently dissolved in water by bubbling using a diffuser plate, and the oxidative decomposition reaction of organic substances is efficiently performed. Although it is difficult, ozone can be sufficiently dissolved in the water to be treated by using the gas-liquid stirring and mixing means, and the oxidative decomposition reaction of organic substances is efficiently performed. Therefore, it is preferable that the organic material oxidizing device has the following conditions.

Here, the gas-liquid stirring and mixing means means means for mixing a gas and a liquid while stirring them to dissolve the gas in the liquid. As a method for dissolving ozone using such a means, for example, water to be treated and ozone are introduced into the suction side of a pump equipped with a rotating blade, and the water to be treated and ozone are stirred and mixed by rotation of the rotating blade. Ozone is dissolved in the water to be treated by stirring and mixing, and the water to be treated in which the ozone is dissolved is sent to the treatment system through a pipe connected to the discharge side of the pump (ozone dissolving pump). Then, a pressurized water flow is supplied by an ejector or the like, and the water to be treated and ozone are stirred and mixed by the movement of the water flow to dissolve ozone in the water to be treated. Further, a line mixer having a stirring mechanism provided with a rotating blade inside a sealed container formed with a sealed blade in the middle of the pipe can also be used.

FIG. 5 shows the preparation of a plurality of waters containing organic substances (TOC concentration of 2000 ppb), the addition of alkali to each of them to adjust the pH to various values, and the addition of 9.6 ppm of ozone to oxidize the organic substances. This shows how the degree of decomposition changes depending on the initial pH value. TOC on the vertical axis of the graph indicates the residual TOC after 10 minutes from the ozone reaction. According to the figure, pH 9.7 or more,
Especially pH 9.7 to 11.0, especially pH 10.0 to 1
It can be seen that the decomposition rate of organic matter is high in the range of 0.5. Therefore, it is preferable that the organic material oxidizing device has the following conditions.

In the organic matter oxidation apparatus used in the present invention, the pH of the water to be treated may be adjusted before dissolving ozone in the water to be treated. The pH may be adjusted, and the pH adjustment of the water to be treated and the ozone dissolution in the water to be treated may be performed simultaneously. When ozone is added to the water to be treated under alkaline conditions, the oxidative decomposition reaction of the organic matter in the water to be treated starts immediately. However, by heating the water to be treated, the oxidative decomposition rate of the organic matter can be increased.

In the present invention, as an anion exchange device,
Is the one using strong basic anion exchange resin in OH form
Is used. This is due to the Cl contained in the water to be treated.^-, F^-,
SO _Four ^2-, NO_Three ^-, NO_Two ^-Good under alkaline conditions
In order to remove it. In this case, the anion exchange tree
As fats, for example, Amberlite (registered trademark, below)
IRA-402, IRA-402BL, IRA-
400 or the like can be used.

If an anion exchange device is provided downstream of the organic matter oxidizing apparatus as in the present invention, even when the organic matter is not decomposed into carbon dioxide by the organic matter oxidizing apparatus, the organic matter is converted into an ionic substance by the organic matter oxidizing apparatus. If the organic acid is decomposed into the organic acid, the ionic substance is removed by the anion exchange device on the downstream side, so that the organic matter is efficiently removed as a whole.

In the present invention, as the electrodialysis apparatus, a plurality of cation exchange membranes and anion exchange membranes are alternately arranged between the opposed electrode pairs, and the desalting chamber and the concentration chamber are alternately arranged. And a cation exchange resin alone filled in a desalination chamber for producing desalinated water. Thereby, alkaline concentrated water can be obtained from the concentration chamber (this point will be described later). The type of the cation exchange resin is not limited, and either a strongly acidic cation exchange resin or a weakly acidic cation exchange resin can be used. In addition, the form of the cation exchange resin may be any one such as granular or fibrous.

In the present invention, the alkaline concentrated water of the electrodialyzer is added to the water to be treated of the organic matter oxidizer and used for adjusting the pH of the water to be treated. In this case, if possible, the pH of the water to be treated in the organic matter oxidizing apparatus may be adjusted to an appropriate value only by adding the concentrated water of the electrodialysis apparatus. An alkaline agent may be added from the outside together with the concentrated water of the electrodialysis device. The water to be treated in the organic matter oxidizing apparatus is p
H 9.7 or more, especially pH 9.7 to 11.0, especially pH
It is preferable to adjust to a range of 10.0 to 10.5.
Further, the entire amount of the alkaline concentrated water of the electrodialysis apparatus may be added to the water to be treated of the organic matter oxidizing apparatus, or only a part thereof may be added as necessary.

In the apparatus for producing ultrapure water of the present invention, an ozone decomposing means for decomposing ozone in the water to be treated can be provided downstream of the organic matter oxidizing apparatus. Thereby, it is possible to prevent ozone remaining in the treated water of the organic matter oxidizing apparatus from adversely affecting the subsequent ion exchange apparatus and the like. Examples of the ozone decomposing means include a means for reducing the decomposition of ozone by passing treated water through activated carbon, and a means for reducing and decomposing ozone by injecting a reducing agent into the treated water. The ozone decomposing means is preferably provided immediately after the organic oxidizing device in order to prevent ozone from adversely affecting the subsequent device.

In the ultrapure water producing apparatus of the present invention, a deaerator can be provided downstream of the organic matter oxidizing apparatus. The deaerator is originally a device for removing dissolved oxygen in the water to be treated, but also removes a part of volatile organic substances present in the water to be treated when the dissolved oxygen is removed from the water to be treated. Therefore, by providing the deaerator on the downstream side of the organic matter oxidizing apparatus, it is possible to obtain treated water having a further reduced organic matter concentration. As the deaerator, for example, a vacuum deaerator, a membrane deaerator or the like can be used. Membrane deaerator is a system in which water to be treated flows into one chamber partitioned by a gas-permeable membrane, and the other chamber is decompressed to allow gas contained in the water to be treated to pass through the gas-permeable membrane to the other chamber. It is a device that moves and removes.

In the ultrapure water production apparatus of the present invention, an organic matter oxidizing apparatus, an anion exchange apparatus and an electrodialysis apparatus are installed in a pure water wastewater recovery system of a wastewater recovery system, and alkaline water obtained from a concentration chamber of the electrodialysis apparatus is obtained. The concentrated water is added to the water to be treated in the organic matter oxidizing apparatus and used for pH adjustment of the water to be treated,
Demineralized water obtained from the desalting chamber of the electrodialysis device can be introduced into the primary pure water system. In addition, the organic matter oxidizer, anion exchanger and electrodialyzer are installed without using a wastewater treatment system and without discharging ultrapure water wastewater from the place of use as raw water or miscellaneous water of ultrapure water. It may be a pure water drainage recovery system of a closed system ultrapure water production apparatus that is reused. By doing so, organic matter can be highly removed from the water to be treated in the wastewater recovery system for pure water, so that highly purified ultrapure water can be obtained by reusing the treated water. In this case, in the ultrapure water production apparatus of the present invention, anions in the water to be treated are removed by the anion exchange apparatus, and cations are transferred to the concentrated water in the electrodialysis apparatus. Ion concentration is low. Therefore, when the demineralized water from the electrodialysis apparatus is introduced into the primary pure water system, there is no problem even if the demineralized water is introduced downstream from the primary pure water system ion exchanger (eg, a two-bed, three-column pure water production system). However, this makes it possible to reduce the load on the primary pure water-based ion exchange device.

[0026]

FIG. 1 is a partially omitted flowchart showing an embodiment of an ultrapure water production apparatus according to the present invention. FIG.
22 is a pretreatment system, 24 is a primary pure water system,
Reference numeral 26 denotes a pure water drainage recovery system. The pretreatment system 22 is provided with a coagulation filtration device (F) and an activated carbon filtration device (CF). In the primary pure water system 24, from the upstream side to the downstream side, an activated carbon filtration device (CF) 28, a two-bed three-column pure water production device (2B3T) 30, a mixed-bed pure water production device (MBP)
32, vacuum degassing tower (VD) 34 and reverse osmosis membrane device (R
O) 36 are sequentially installed. The recovery system 26 includes, from the upstream side to the downstream side, an organic matter oxidation device 38, an activated carbon filtration device (CF) 40, an anion exchange device (AER) 42 using an OH-type strong basic anion exchange resin, a desalination chamber. Dialysis machine (EDI) 4 filled with cation exchange resin
4 are sequentially installed. In the recovery system 26, the alkaline concentrated water of the electrodialyzer 44 is supplied to the organic matter oxidizer 38.
A concentrated water introduction pipe 45 for adding to the water to be treated is provided.

In this apparatus, the treated water of the pretreatment system 22 is introduced into the primary pure water system 24 after being stored in a tank 46. The treated water in the primary pure water system 24 is sent to a secondary pure water system (not shown), and the ultrapure water produced in the secondary pure water system is supplied to a place of use (not shown). The wastewater generated by using the ultrapure water at the place of use is sent to a tank 48 and further treated in a wastewater recovery system 26 for pure water. It is sent downstream of 30 and reused. In addition, in the ultrapure water production apparatus of this example,
The activated carbon filtration device 40 of the pure water drainage recovery system 26 corresponds to the ozone decomposing means on the downstream side of the organic matter oxidizing device described above, and the vacuum deaerator 34 of the primary pure water system 24 has the degassing downstream of the organic matter oxidizing device described above. It corresponds to a pneumatic device.

In the ultrapure water production apparatus of this embodiment, wastewater from the place of use is treated in the pure water wastewater recovery system 26 and the primary pure water system 24 as follows. That is, the wastewater from the place of use is first stored in the tank 48 once,
The organic matter is oxidized and decomposed in the organic oxidation device 38. The organic matter oxidizing device 38 is specifically shown in FIG.
Has the structure shown in FIG. That is, in FIG.
Is a line through which the water to be treated in the pure water drainage recovery system 26 flows, and this line 50 is connected to an alkali injection device 52 and an ozone supply device 54. Also, line 50
The injection pipe 56 of the alkali injection device 52 and the line 50
Immediately after the connecting portion 58, a concentrated water introducing pipe 45 for adding the alkaline concentrated water of the electrodialyzer 44 to the water to be treated of the organic matter oxidizing device 38 is connected. Further, a pH measuring section (not shown) is provided slightly behind the connecting section 58 and the connecting section 59 between the concentrated water introducing pipe 45 and the line 50, and the pH measuring section controls the pH of the water to be treated. It measures and outputs the measurement result as an electric signal to the alkali injecting device 52, based on which the amount of alkali injected into the water to be treated is automatically controlled.

As the ozone supply device 54, an ozone generation device having an ozone generation mechanism or an ozone tank filled with an ozone-containing gas produced by the ozone generation device is used. A gas-liquid stirring / mixing device 62 (for example, a line mixer or an ozone dissolving pump) is connected to the supply pipe 60 of the ozone supply device 54, and the gas-liquid stirring / mixing device 62 is connected to the line 50. A predetermined length of the line 50 on the outlet side of the gas-liquid stirring and mixing device 62 is configured as a reaction tube portion 66 in which an oxidative decomposition reaction of an organic substance is performed.

In the organic matter oxidizing apparatus 38 of this embodiment, first, alkali is injected into the water to be treated flowing through the line 50 from the alkali injecting device 52 and the concentrated water of the electrodialyzer 44 is injected from the concentrated water introducing pipe 45. , PH of water to be treated
Is adjusted to 9.7 or more, preferably 9.7 to 11.0. When the pH of the water to be treated can be adjusted to the above range only by adding the concentrated water of the electrodialysis device 44, the addition of the alkali from the alkali injection device 52 is stopped.

Next, ozone is supplied to the water to be treated from the ozone supply device 54, and the ozone and the water to be treated are stirred and mixed by the gas-liquid stirring / mixing device 62, and most of the ozone is dissolved in the water to be treated. Here, the amount of ozone added to the water to be treated is adjusted to 3 to 40 ppm, preferably 7 to 30 ppm. In the to-be-treated water, the oxidative decomposition reaction of the organic matter rapidly proceeds in the reaction tube section 66. The treated water obtained by the end of the oxidative decomposition reaction is introduced into the anion exchange device 42 after ozone is decomposed by the activated carbon filtration device 40.

The anion exchange device 42 uses an OH type strongly basic anion exchange resin. In the anion exchange device 42, Cl ⁻ ,
Anions such as F ⁻ , SO ₄ ²⁻ , NO ₃ ⁻ , NO ₂ ⁻ and organic acids generated in the organic oxidation device 38 are removed. The treated water of the anion exchange device 42 is introduced into the electrodialysis device 44.

The electrodialysis apparatus 44 has a structure shown in FIG. That is, a plurality of cation exchange membranes 72 and anion exchange membranes 74 are alternately arranged between the electrode pairs 70, 70 opposed to each other at both ends, and a desalination chamber 76 is provided between these ion exchange membranes 72, 74. The concentration chambers 78 are alternately formed, only the cation exchanger is filled in the desalination chamber 76, and the space between the electrode 70 and the ion exchange membranes 72 and 74 is defined as an electrode chamber 80. In the electrodialysis apparatus 44 of the present example, the water to be treated 82 flows downflow into the desalination chamber 76 to obtain demineralized water 84 from the desalination chamber 76, and the water 82 to be treated flows upward into the concentration chamber 78. Then, the concentrated water 86 is obtained from the concentration chamber 78. In addition, in the electrodialysis apparatus 44 of this example, the concentrated water 86
Are used as electrode water 88. In addition, in the electrodialysis apparatus 44 of the present example, the water to be treated flows into the concentration chamber 78, but the water that flows into the concentration chamber 78 may be other water.

According to the electrodialyzer 44 of this embodiment in which only the cation exchange resin is filled in the desalting chamber 76, alkaline concentrated water 86 can be obtained from the concentration chamber 78. That is, a typical electrodialysis apparatus for producing pure water is one in which a desalting chamber is filled with both a cation exchange resin and an anion exchange resin. In the case of such an electrodialysis apparatus, when, for example, NaCl-containing water is flowed as the water to be treated into the desalination chamber, the cation exchange resin and the anion exchange resin are filled in the desalination chamber. Na ⁺ and Cl ⁻ move to the concentration chamber side at almost the same speed. Therefore, Na
Demineralized water from which most Cl has been removed is obtained, and concentrated water from which NaCl has been concentrated is obtained from the concentration chamber.

On the other hand, in the case of the electrodialysis apparatus used in the present invention, when, for example, NaCl-containing water is flowed into the desalting chamber as water to be treated, only the cation exchange resin is present in the desalting chamber. Certain Na ⁺ is mobile, but Cl ⁻ , an anion, is harder to mobile than Na ⁺ . Therefore, almost all of Na ⁺ moves to the concentration chamber, but part of Cl ⁻ moves to the concentration chamber, and the other part remains in the deionization chamber and leaks into the deionized water. Therefore, in the electrodialysis apparatus used in the present invention, desalinated water from which most of the cations have been removed is generated in the desalting chamber, and NaCl in an amount corresponding to Cl ⁻ moved from the desalting chamber is generated in the concentration chamber. And more Na ⁺ than Cl ^{− in the} concentrating chamber, so the remaining N
a ⁺ generates NaOH in the concentration chamber. That is, in this case, NaOH and a small amount of NaCl
Is obtained. In the above description, water containing Na ⁺ and Cl ⁻ has been taken as an example. However, in the present invention, an anion exchange device using a strong basic anion exchange resin of OH type is installed on the upstream side of the electrodialysis device. since, Cl in the for-treatment water ^- anions such are removed largely O
H ^- is converted to, and hence concentrate is obtained almost containing only NaOH from concentrating compartment of the electrodialysis apparatus.
However, not all anions are removed by the anion exchanger, and a small amount of anions leaks into the treated water of the anion exchanger.

[0036] In the present invention, most of the negative ions contained in the treated water of organic oxidizer by anion exchange apparatus OH ^- together into a further removing the organic acid or CO ₂ produced by the organic matter oxidizing device Concentrates the cations contained in the treated water of the organic matter oxidizer in the concentration chamber of the subsequent electrodialyzer to make the concentrated water alkaline, and uses the concentrated water for pH adjustment of the water to be treated in the organic matter oxidizer. However, in this case, in order to minimize the transfer of a small amount of anions leaking from the anion exchange device to the concentration room, an electrodialysis device in which the desalination room is filled with only a cation exchange resin is used. Is what you do.

In the ultrapure water producing apparatus of the present embodiment, the alkaline concentrated water of the electrodialyzer 44 is added to the water to be treated of the organic matter oxidizing apparatus 38 through the concentrated water introducing pipe 45, and as described above, It is used for pH adjustment. The demineralized water from the electrodialysis device 44 is introduced into the water to be treated in the primary pure water system 24 on the downstream side of the two-bed, three-column pure water production device 30 of the primary pure water system 24. Then, anions and trace cations remaining in the deionized water of the electrodialysis device 44 are removed by the ion exchange resin used in the mixed-bed-type pure water production device 32, and then in the vacuum degasification tower 34. Removal of dissolved oxygen and removal of a trace amount of organic substances are performed, and further, removal of impurities remaining in the reverse osmosis membrane device 36 is performed. Even when the treated water that has passed through the mixed-bed-type pure water production apparatus 32 contains volatile organic substances that could not be removed by the ion exchange resin, the volatile organic substances should be removed by the vacuum degassing tower 34. Can be.

FIG. 4 is a flowchart showing an embodiment of the ultrapure water production apparatus according to the present invention. The ultrapure water production system of the apparatus in FIG. 4 includes an activated carbon filtration device (CF), a two-bed three-column pure water production device (2B3T), a mixed-bed pure water production device (MBP),
Primary deionized water system equipped with vacuum degassing tower (VD) and reverse osmosis membrane device (RO), tank (TK), UV sterilizer (UV
_st ), a mixed-bed type cartridge polisher (CP) and a secondary pure water system equipped with an ultrafiltration membrane device (UF).

Further, in the apparatus shown in FIG. 4, as a wastewater recovery system for treating wastewater generated by using ultrapure water at the place of use, the primary pure water is directly treated without any treatment according to the cleanliness of the wastewater. Route to return to water system, route to return to primary pure water system after appropriate treatment (pure water drainage recovery system), route to appropriate treatment and supply to utility equipment as miscellaneous water (miscellaneous wastewater collection system) ), And a route (wastewater treatment system) for discharging after appropriate treatment. The criteria for separating the ultrapure water drainage discharged from the place of use into the above-mentioned routes are, for example, as shown in Table 1, and the separation is performed by the sorting mechanisms (1) to (3).

[0040]

[Table 1]

In the apparatus shown in FIG. 4, a first activated carbon filter (C) is installed in the pure water wastewater recovery system from upstream to downstream.
F), using an anion exchanger (WA) using a weakly basic anion exchange resin in the OH form, an organic matter oxidizer, a second activated carbon filter (CF), and a strongly basic anion exchange resin in the OH form An anion exchange unit (AER) and an electrodialysis unit (EDI) filled with a cation exchange resin in a desalting chamber are installed in order, and the concentrated water of EDI is added to the water to be treated in the organic matter oxidation unit. Is provided. The demineralized water of EDI is introduced into the water to be treated in the primary pure water system downstream of the primary pure water system 2B3T. The first activated carbon filtration device (CF) is installed for the purpose of removing hydrogen peroxide contained in the wastewater, and the anion exchange device (WA) is installed for removing the acid contained in the wastewater. ing. The wastewater treatment in the pure water wastewater recovery system of the apparatus of FIG. 4 is basically the same as that of the apparatus of FIG.

[0042]

[Example] Organic matter oxidizer, activated carbon filter (CF),
An anion exchange device (AER) using a strong basic anion exchange resin in OH form, an electrodialysis device (EDI) in which a cation exchange resin is filled in a desalination chamber, and a mixed-bed pure water production device (M
BP), vacuum degassing tower (VD) and reverse osmosis membrane device (RO)
Are connected in this order, and the wastewater generated by using ultrapure water is flowed into a device provided with a concentrated water introduction pipe for adding the concentrated water of the electrodialysis device to the water to be treated of the organic matter oxidizing device. The wastewater was treated in this manner. The desalinated water from the electrodialysis device was introduced into a mixed-bed type pure water production device. As the wastewater, those having the water qualities shown in Table 2 below were used.

[0043]

[Table 2]

In the organic matter oxidizing device 38, sodium hydroxide is added to the water to be treated from the alkali injecting device 52, and the concentrated water of the electrodialyzer 44 is injected from the concentrated water introducing pipe 45 to adjust the pH of the water to be treated. Was adjusted to 10.3, and ozone was added to the water to be treated by the gas-liquid stirring and mixing device 62 so that the amount of ozone added to the water to be treated was 21.0 ppm. In this case, in order to adjust the pH to 10.3 by adding only sodium hydroxide to the water to be treated, it is necessary to add 275 g / h of Na ⁺ at a flow rate described later. Since the concentrated water of the dialysis device was used together, the addition amount of Na ⁺ was only 55 g / h.

As the gas-liquid stirring and mixing device 62, an ozone dissolving pump was used. Amberlite IRA-402BL was used as the OH-type strong basic anion exchange resin of the anion exchange apparatus (AER), and the electrodialysis apparatus (EDI) was used.
Amberlite IR-12 as a cation exchange resin
Amberlite ESG4 obtained by mixing H type strongly acidic cation exchange resin and OH type strongly basic anion exchange resin as the ion exchange resin of the mixed bed type pure water production apparatus (MBP). The polyamide-based composite membrane ES-10 manufactured by Nitto Denko Corporation was used as a reverse osmosis membrane of a reverse osmosis membrane device (RO). The vacuum deaerator (VD) was operated at a vacuum of 22 Torr. N of flow rate in each device, inlet water of each device, etc.
Table 3 shows the measurement results of the a ⁺ concentration pH and the TOC concentration of the outlet water of each device.

[0046]

[Table 3]

[0047]

According to the first aspect of the present invention, ozone is added to the water to be treated under alkaline conditions to thereby oxidize and decompose the organic matter contained in the water to be treated. When organic matter is removed from the treated water, the amount of the alkali agent added to the water to be treated in the organic matter oxidizing apparatus can be reduced, and the load on the subsequent ion exchange apparatus can be prevented from increasing.

According to the second aspect of the present invention, since the organic matter can be highly removed from the water to be treated in the pure water wastewater recovery system of the wastewater recovery system, high purity can be obtained by reusing the treated water. Ultrapure water can be obtained.

According to the third and fourth aspects of the present invention, the oxidative decomposition of organic substances in the organic substance oxidizing apparatus can be efficiently performed.

According to the fifth aspect of the present invention, it is possible to prevent dissolved ozone remaining in the treated water of the organic matter oxidizing apparatus from adversely affecting a subsequent apparatus, for example, an ion exchange resin of an ion exchange apparatus.

[Brief description of the drawings]

FIG. 1 is a partially omitted flowchart showing an embodiment of an ultrapure water production apparatus according to the present invention.

FIG. 2 is a flowchart showing an organic oxidation apparatus of the ultrapure water production apparatus shown in FIG.

FIG. 3 is a schematic diagram showing an electrodialysis apparatus of the ultrapure water production apparatus shown in FIG.

FIG. 4 is a flowchart showing an embodiment of the ultrapure water production apparatus according to the present invention.

FIG. 5 is a graph showing the relationship between the pH of water to be treated and the rate of oxidative decomposition of organic substances.

FIG. 6 is a flowchart showing an example of a conventional ultrapure water production apparatus.

[Explanation of symbols]

 22 Pretreatment system 24 Primary pure water system 26 Wastewater recovery system for pure water 38 Organic matter oxidizing device 40 Activated carbon filtration device 42 Anion exchange device 44 Electrodialysis device 45 Concentrated water introduction pipe

Claims (5)

[Claims] 1. An organic matter oxidizing apparatus that oxidizes and decomposes organic substances contained in water to be treated by adding ozone to the water to be treated under alkaline conditions in a path for removing organic substances in an ultrapure water production apparatus; An anion exchange device using a strong basic anion exchange resin in the form and an electrodialysis device filled with a cation exchange resin in a desalting chamber are installed so that the water to be treated flows in this order. An ultrapure water production apparatus characterized in that alkaline concentrated water obtained from a concentration chamber of an electrodialysis device is added to water to be treated in an organic matter oxidizing device and used for pH adjustment of the water to be treated. 2. An ultrapure water production apparatus comprising: a primary pure water system for processing raw water to produce primary pure water; a secondary pure water system for treating primary pure water to produce ultrapure water; A wastewater recovery system that treats wastewater generated by using ultrapure water produced in a pure water system at the place of use and returns it to the primary pure water system; an organic matter oxidizing device, an anion exchange device, and an electrodialysis device Is installed in the wastewater recovery system for pure water in the wastewater recovery system, and the alkaline concentrated water obtained from the concentration chamber of the electrodialysis apparatus is added to the water to be treated in the organic matter oxidizer and used for pH adjustment of the water to be treated. The ultrapure water production apparatus according to claim 1, wherein demineralized water obtained from a desalination chamber of the electrodialysis apparatus is introduced into the primary pure water system. 3. The pH of the water to be treated is adjusted to 9.7 or more by adding only the alkaline concentrated water of the electrodialysis apparatus and the alkaline agent or the alkaline concentrated water of the electrodialysis apparatus to the water to be treated in the organic matter oxidizing apparatus. The ultrapure water production apparatus according to claim 1. 4. The ultrapure water producing apparatus according to claim 1, wherein the organic substance oxidizing apparatus adds ozone to the water to be treated by gas-liquid stirring and mixing means. 5. Ozone decomposing means for decomposing ozone in the water to be treated is provided downstream of the organic matter oxidizing apparatus.
The ultrapure water production apparatus according to any one of the above.