JPH06285464A - Method and apparatus for treating recovered water to obtain recycled water - Google Patents

Abstract

PURPOSE:To provide a method for recycling effectively used high purity water by ionizing a nonionic silica component, which does not react with a molybdic acid reagent, contained in the water recovered from the used high purity water and removing the ionized silica component with a reverse osmosis membrane apparatus. CONSTITUTION:In a method for treating recovered water, an ionization apparatus 1 oxidizes the recovered water by a method in which the water recovered from ultra- high purity water used for washing semiconductor and others is introduced into an ozone diffusing tank 11 from its lower part while ozone gas being injected from the lower part. The recovered water from the upper part of the tank 11 is then introduced into an ultraviolet irradiation apparatus 12 from its lower part and irradiated with an ultraviolet lamp set in a transparent glass tube 13. In this way, a nonionic silica component, which does not react with a molybdic acid reagent, contained in the recovered water is ionized, while organic compounds in the recovered water is decomposed. The recovered water from the ionization apparatus 1 is fed into a reverse osmosis membrane apparatus 2, so that the water passed through the membrane is used as recycled water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is typically applied to high-purity water (generally pure water or ultrapure water) used for cleaning purposes in equipment for the semiconductor manufacturing industry, chemical manufacturing industry, etc. High-purity water, which is called pure water), is a method and device for treating recovered water that is effective when used as reused water in the attached equipment after use, or raw water used in the production of the high-purity water used in major equipment. The present invention relates to a method and an apparatus for treating recovered water, which is effective when reused as.

[0002]

BACKGROUND OF THE INVENTION Recently, it has become popular to use high-purity water, which is called pure water or ultrapure water, as washing water, as has been widely used recently in, for example, semiconductor manufacturing facilities. The standard of water quality required for these high-purity waters is that the content of impurities is usually below the ppm level even in the current industrial-scale manufacturing facilities. In the field where the improvement of the product cost and the reduction of the product cost are strictly demanded, it is required to use water which does not contain an extremely minute amount of impurities based on the level of several tens of ppb to several ppb. ing. For this reason, various proposals effective for producing high-purity water have been made.

Further, in the actual industrial manufacturing equipment that requires high-purity water as described above, water is also used for various purposes in the equipment attached to the main equipment. For example, it can be said in semiconductor manufacturing equipment. For example, various boilers and heat exchangers are usually used as auxiliary equipment, and in actual industrial equipment, water is used for various purposes other than this.

By the way, the high-purity water called pure water or ultrapure water used in the main production line is still compared to general industrial water or city water even after it is used for cleaning purposes. Since it is often good in water quality, it can be used as water for producing pure water or ultrapure water as described above, or as water used in devices industrially classified as auxiliary equipment such as heat exchangers, as described above. It is common practice to use the used wastewater as reused water after it has been used in the main production line of. This is also preferable from the viewpoint of reducing wastewater from industrial equipment as much as possible, and in industrial equipment that uses groundwater or the like as raw water, its use is often limited in quantity, so In industrial facilities in such areas, reuse of wastewater is strongly required.

However, since the water used for cleaning and the like is of course used to remove dust and the like adhering to the object to be cleaned, the water quality is lower than that of high-purity water before use,
If it is reused as it is, its use is greatly restricted. Therefore, in order to reuse the recovered water, a certain amount of treatment has been generally performed conventionally.

As a conventional treatment for reusing used waste water of such high-purity water, as shown in FIG. 4, for example, recovered water is passed through an activated carbon tank 101 to remove organic substances by adsorption. In addition, the ionic component is removed by passing through a desalting tower 102 filled with a strongly acidic cation exchange resin and a weakly basic anion exchange resin, whereby the total amount of organic matter (TOC) is about 1 ppm. The total cation content is about 500 ppm, and the recovered water is about 0.1 ppm in TOC.
It is often regenerated as reused water of about ppm.

[0007]

However, in the conventional treatment for producing such recycled water, for example, since the treatment capacity is limited to about SV5 to 10 due to the use of the activated carbon tank, a large amount of high water is required. When it is applied to a manufacturing facility that uses pure water, there is a problem that the facility for treating the recovered water is inevitably increased in size.

Further, depending on the use of the reused water, for example, when this water is used for a heat exchange device such as a cooling tower, an appropriate chemical is conventionally added to prevent scale adhesion. Minute amount of inorganic fine particles contained in
In particular, colloidal silica components, which have a great influence on scale generation, cannot be removed by the conventional processing apparatus shown in FIG. 4, and a device for removing them has been desired.

The present inventor proposes the present invention in view of the above-mentioned present situation, and one of the purposes thereof is to provide equipment using high-purity water and high-purity water after using it. The present invention provides a treatment method and apparatus suitable for treating water and effectively using it as recycled water.

Another object of the present invention is to use a colloidal silica component, which causes scale adhesion, when the above-mentioned reused water is used as feed water and make-up water for heat exchangers and boilers. It is an object of the present invention to provide a processing method and device that can be removed from

Still another object of the present invention is to improve the utilization rate and recovery / reuse rate of water in equipment using high-purity water to reduce running costs, effective use of resources, and influence on the surrounding environment. There is provided a processing method and apparatus capable of realizing the above.

Still another object of the present invention is to provide a treatment method and apparatus which are effective when the cleaning wastewater discharged from the main line of a semiconductor manufacturing facility or the like is reused as raw water used for the cleaning water of this main line. It is for the purpose of providing.

[0013]

In order to achieve the above-mentioned object, the present inventor has proposed a treatment method for recovering and reusing used waste water of high-purity water, especially a non-contained water contained in the recovered water. Since the ionic silica component is one of the major causes of scale, for example, the treatment method that can remove it as much as possible was earnestly studied.

As such a method, conventionally, for example,
Proposal to remove inorganic fine particles (colloidal substances) that cause evaporation residue in ultrapure water by forced oxidation with ozone to form solid oxide fine particles ("A Mechanistic Study of Ozone-
Induced Particle Destabilization ", JOURNAL AWWA, 19
91), but with this method, the proportion of colloidal silica components that become fine particles is small.

However, the present inventor has found that when the recovered water is treated by combining forced oxidation and ultraviolet irradiation, ionization of colloidal silica, which has hitherto not been expected, occurs.

The present invention has been made on the basis of such findings, and one of its characteristics is to collect used wastewater of high-purity water used for cleaning semiconductors and the like, and obtain molybdic acid contained in the recovered water. This is a treatment method of recovered water for obtaining recycled water by ionizing a nonionic silica component that does not react with a reagent, and then removing the ionic silica component by membrane removal with a reverse osmosis membrane device.

In the above, in order to ionize the nonionic silica component, a step of bringing recovered water into contact with ozone gas as an oxidant and a step of irradiating the recovered water with ultraviolet rays are carried out.
It may be carried out simultaneously or sequentially. When ozone gas is used, its concentration is 0.5 ppm or more, preferably 1 ppm or more, optimally 3 to 4 ppm, and the ultraviolet irradiation has an emission wavelength of 170 to 400 nm and a light amount of 0.35 WH / l or more. , Preferably 0.
It is preferable to set it to 7 WH / l or more. The oxidant can be injected directly into the recovered water pipe or into the recovered water storage tank, and the ultraviolet irradiation can be, for example, but not limited to, ultraviolet light in a transparent case. It is possible to preferably use a device that accommodates a light emitting lamp and allows collected water to flow near the periphery of the case.

The used waste water of high-purity water used as raw water in the above structure is not limited, but used cleaning water used in the plating process or cleaning process of semiconductor or liquid crystal device manufacturing equipment, Alternatively, in the chemical manufacturing industry, for example, water for washing ampoules can be cited as a representative example.

The recovered water as raw water which is treated by the present invention and used as recycled water is not particularly limited, but generally the total amount of organic matter (TO
C) is about 1 ppm, total cation is 500 ppm
It is preferable that the water quality is about the same.

Not reacting with molybdic acid reagent means JI
It refers to a reagent used in the measurement of SK 0101 by the molybdic acid yellow absorbance method.

The above-mentioned reverse osmosis membrane device for removing the ionic silica component from the membrane is not necessarily uniformly determined by the performance of the membrane, but it is necessary to use a device having an excellent ability to remove the ionic silica component from the membrane. According to the reverse osmosis membrane device described in the examples below, it is preferable to use a device capable of removing ionic silica components with high efficiency of 60% or more, preferably 80% or more. The reverse osmosis membrane device may be provided with the membrane module in one stage or in two stages.

The feature of the present invention as an apparatus for carrying out such a treatment method is that the waste water of used high-purity water generated in a facility using high-purity water is collected and sent to the recovered water treatment means. Means, a recovered water treatment means for treating the recovered water that has been sent, and a water distribution means for distributing the treated water that has passed through the recovered water treatment means to the subsequent facility as reused water. An ionization treatment device that ionizes nonionic silica components that do not react with the molybdic acid reagent contained in the recovered water that has been sent, and a membrane removal capability for the ionic silica components in the collected water that is installed after this ionization treatment device. In addition to the reverse osmosis membrane device, the ionization treatment device includes an oxidant injection unit for injecting ozone gas into the recovered water and an ultraviolet irradiation unit for irradiating the recovered water with ultraviolet rays. There where the eggplant.

The means for distributing recycled water of this apparatus is, for example, a makeup water supply pipe for a heat exchanger such as a cooling tower provided as an accessory device in a semiconductor manufacturing facility, a makeup water supply pipe for various kinds of miscellaneous water, and various boilers. It is connected to the make-up water supply pipe to the. It can also be circulated and reused as a part of raw water for a high-purity water manufacturing apparatus such as ultrapure water in a semiconductor manufacturing facility.

In the above treatment apparatus of the present invention, a reducing agent (sodium thiosulfate or sodium sulfite) is provided between the ionization treatment apparatus and the reverse osmosis membrane apparatus by providing an activated carbon tank or a palladium catalyst filling tank. Etc.) may be added to remove residual ozone.

[0025]

The present invention will be further described below with reference to the drawings. Example 1 FIG. 1 is a diagram showing an example of an apparatus according to the present invention,
For example, used cleaning water after using ultrapure water (not shown) for cleaning semiconductors or the like is collected and sent to the ionization processing apparatus 1 via the water supply pipe 3.

In this example, a measuring device 4 is provided in the middle of the path of the water pipe 3 to measure, for example, the electric conductivity and TOC concentration of the recovered water, and when these values are below a predetermined reference value. Although it is sent to the above-mentioned ionization treatment device 1, if it exceeds the reference value, it is provided to switch the opening and closing of the switching valves 5 and 6 so that the water is drained as it is as unsuitable for reuse. Such a configuration is not essential.

The ionization processing apparatus 1 in this example is
While passing the recovered water from the lower part to the upper part of the ozone diffusion tank 11, ozone gas is injected from the lower part of the tank 11 to oxidize the recovered water. Next, the recovered water discharged from the upper part of the ozone diffusing tank 11 is irradiated with ultraviolet rays by the ultraviolet light emitting lamp built in the transparent glass tube 13 while flowing from the lower part to the upper part of the ultraviolet irradiation device 12. . As described above, the non-ionic silica component contained in the recovered water is ionized, and the organic matter contained in the recovered water is decomposed.

The recovered water that has left the ionization treatment device 1 is then supplied to the reverse osmosis membrane device 2, and the treated water that has permeated the membrane is reused water, such as the cooling tower 20 shown in FIG.
Is supplied to the makeup water pipe as makeup water.

The cooling tower 20 shown in FIG. 2 is a known one, and the medium in the piping system 22 is appropriately cooled by the cooling water circulating with the heat exchanger 21, and the tower in which this cooling water circulates. Since scale adheres to the bottom portion 23, the inside of the pipe 24, or the pipe of the heat exchanger, a scale inhibitor or the like is usually dosed to prevent this, but the scale treated with the device shown in FIG. When replenishing water for use, the amount of silica in the water is extremely small, so that scale adhesion can be reduced as it is, and the amount can also be greatly reduced when injecting chemicals.

Embodiment 2 FIG. 3 shows an example in which the apparatus of FIG. 1 is applied to a cleaning water recovery system of a semiconductor manufacturing facility having an ultrapure water manufacturing apparatus. After manufacturing the ultrapure water by passing through the secondary pure water device 31 and the secondary pure water device 33 through the circulation tank 32 in this order, and using this for cleaning the semiconductor at the use point (UP) The collected water is collected and sent to the ionization treatment apparatus 1 through the water supply pipe 34 to perform ionization of the nonionic silica component by ozone diffusion and ultraviolet irradiation, and then the reverse osmosis membrane apparatus 2 eliminates the membrane to treat the treated water ( I try to get recycled water.

The treated water thus obtained can be used as makeup water for the apparatus shown in FIG. 2, but since the quality of the water is high, the primary system deionizer 31 or the secondary system deionized water is used. It may be circulated back to the pure water production line so as to be used as raw water for the apparatus, for example, returned to the position on the inlet side of the mixed bed polisher used as almost the final treatment step of the primary system pure water apparatus. .

Test Example Using the apparatus shown in FIG. 1, the recovered water was treated under the following conditions. Injected ozone concentration ・ ・ ・ 104 g / Mm ³ Ozone injection amount ・ ・ ・ 4 liters / mi
n Ozone concentration in sample water: 2.5-3 ppm Concentrated waste water (renewal chemical solution) used in the semiconductor manufacturing process was used as sample water. SU710 as reverse osmosis membrane
(Manufactured by Toray) was used. The total silica component was measured using an inductively coupled plasma mass spectrometer ICP-MS (manufactured by Yokogawa Electric Corp.), and the ionic silica component was a silica meter SA-.
It measured using 500 (made by Toray).

For comparison, a silica component in the case of no treatment, in which only ozone diffusion was performed and ultraviolet irradiation was not performed, or only ultraviolet irradiation was performed and ozone diffusion was not performed, was not performed. Were measured respectively. The results are shown in Table 1 below.

[0034]

[Table 1] From the results of Table 1, 500 pp in sample water
Although the nonionic silica of b exists, the ozone effusion only, the UV irradiation only, and no treatment did not change the ionic silica, and the reverse osmosis membrane treatment resulted in 300 ppb.
Non-ionic silica leaks.

On the other hand, in the present invention, the nonionic silica is reduced to 20 ppb by the ozone diffusion and the ultraviolet irradiation treatment, and the nonionic silica is reduced to 10 ppb by the reverse osmosis membrane treatment. It can be seen that the treated water in which the nonionic silica is greatly reduced can be obtained.

[0036]

According to the present invention, since used high-purity water can be treated and effectively used as recycled water, the utilization rate of water and the recovery / reuse rate are improved, and the recycled water is reused. This has the effect of effectively suppressing and reducing scale adhesion on heat exchangers and boilers. Therefore, it is possible to reduce the amount of scale-injecting agent conventionally used in a heat exchanger or the like, and to reduce running costs.

Further, by reusing the cleaning drainage discharged from the main line of the semiconductor manufacturing facility as the raw water used for the cleaning water of this main line, the water utilization efficiency is improved and the amount of drainage from the facility is reduced. There is also an effect that you can.

According to the treatment apparatus for recovered water of the present invention,
There is also an effect that the processing speed can be increased as compared with the conventional apparatus, and therefore the installation area per unit processing amount can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration outline of an embodiment of a recovered water treatment apparatus according to the present invention.

FIG. 2 is a view showing an example in which the reused water treated by the apparatus of FIG. 1 is used as makeup water for the cooling tower.

[Fig. 3] Fig. 3 is a diagram showing an outline of a configuration of equipment provided so as to treat water recovered from an ultrapure water producing apparatus.

FIG. 4 is a diagram showing an example of a conventional device for treating recovered water as reused water.

[Explanation of symbols]

1 ... Ionization treatment device, 2 ... Reverse osmosis membrane device, 1
1 ... Ozone diffuser, 12 ... Ultraviolet irradiation device.

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[Procedure amendment]

[Submission date] March 28, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

As a conventional treatment for reusing used waste water of such high-purity water, as shown in FIG. 4, for example, recovered water is passed through an activated carbon tank 101 to remove organic substances by adsorption. In addition, the ionic components are removed by passing through a desalting tower apparatus 102 filled with a strongly acidic cation exchange resin and a weakly basic anion exchange resin, whereby the total amount of organic matter (TOC) is 1 ppm. In many cases, the recovered water having a water quality of about 500 ppm of total cations is regenerated as recycled water of about 0.1 ppm in TOC and about 10 ppm of total cations.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

In the above, in order to ionize the nonionic silica component, a step of bringing recovered water into contact with ozone gas as an oxidant and a step of irradiating the recovered water with ultraviolet rays are carried out.
It may be carried out simultaneously or sequentially. When ozone gas is used, its concentration is 0.5 ppm or more, preferably 1 ppm or more, optimally 3 to 4 ppm, and the ultraviolet irradiation has an emission wavelength of 170 to 400 nm and a light amount of 30 WH / m ³ or more. Preferably 70W
H / m ³ or more is preferable. The oxidant can be injected directly into the recovered water pipe or into the recovered water storage tank, and the ultraviolet irradiation can be, for example, but not limited to, ultraviolet light in a transparent case. It is possible to preferably use a device that accommodates a light emitting lamp and allows collected water to flow near the periphery of the case.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Not reacting with molybdic acid reagent means JI
It means that it does not react with the reagent used for the measurement of SK 0101 by the molybdate yellow absorption method.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

The treated water thus obtained can be used as makeup water for the apparatus shown in FIG. 2, but since the quality of the water is high, the primary system deionizer 31 or the secondary system deionized water is used. It is circulated back to the pure water production line for use as raw water for the equipment . For example, it can be returned to the position on the inlet side of the mixed bed polisher used as almost the final treatment step of the primary water purifier.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

Test Example Using the apparatus shown in FIG. 1, the recovered water was treated under the following conditions. Injected ozone concentration ······· 104 g / N m ³ ozone injection amount ····· 4 liter / mi
n Ozone concentration in sample water: 2.5-3 ppm Concentrated waste water (renewal chemical solution) used in the semiconductor manufacturing process was used as sample water. SU710 as reverse osmosis membrane
(Manufactured by Toray) was used. The total silica component was measured using an inductively coupled plasma mass spectrometer ICP-MS (manufactured by Yokogawa Electric Corp.), and the ionic silica component was a silica meter SA-.
It measured using 500 (made by Toray).

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

[0034]

[Table 1] From the results shown in Table 1, although 5000 ppb of nonionic silica is present in the sample water, only ozone diffuser, UV
The irradiation does not change the ionic silica without treatment, and the reverse osmosis membrane treatment leaks 300 ppb of nonionic silica.

Claims (5)

[Claims] 1. A used wastewater of high-purity water used for cleaning semiconductors and the like is recovered, a nonionic silica component which does not react with a molybdic acid reagent contained in the recovered water is ionized, and then ionic silica. A method for treating recovered water for obtaining reused water, which comprises removing components by removing them with a reverse osmosis membrane device. 2. The reused water according to claim 1, wherein the ionization of the nonionic silica component comprises a step of bringing recovered water into contact with ozone gas and a step of irradiating the recovered water with ultraviolet rays. Method of processing recovered water to obtain water. 3. The method according to claim 1, wherein the recovered water as used waste water of the high-purity water is used cleaning water used in a plating step or a cleaning step of a semiconductor or liquid crystal device manufacturing facility. Reclaimed water treatment method to obtain reused water. 4. A water supply means for collecting wastewater of used high-purity water generated in equipment using high-purity water and sending it to the recovered-water treatment means, and a recovered-water treatment means for treating the sent-recovered water. And a water distribution means for distributing the treated water that has passed through the recovered water treatment means to the subsequent facility as reused water, wherein the recovered water treatment means is a non-ion which does not react with the molybdic acid reagent contained in the recovered water sent. With a reverse osmosis membrane device having an ionization treatment device for ionizing a water-soluble silica component, and a membrane removing ability of the ionic silica component in the recovered water, which is installed in a subsequent stage of the ionization treatment device, and the ionization treatment device comprises: An oxidant injection means for injecting an oxidant into the recovered water,
And an apparatus for irradiating the recovered water with an ultraviolet ray, the apparatus for treating recovered water for obtaining recycled water. 5. The treatment apparatus for recovered water for obtaining recycled water according to claim 4, wherein the oxidant injected into the recovered water by the oxidant injection means is ozone gas.