JP5750236B2 - Pure water production method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for producing pure water by ultraviolet oxidation treatment.

  Conventionally, pure water such as ultrapure water from which organic substances, ionic components, fine particles, bacteria, and the like have been highly removed has been used as an application for washing water and the like in the manufacturing process of a semiconductor device and the manufacturing process of a liquid crystal display device. . In particular, when manufacturing an electronic component including a semiconductor device, a large amount of pure water is used in the cleaning process, and the demand for the water quality is increasing year by year. Pure water used in the cleaning process of electronic component manufacturing is one of the water quality management items in order to prevent the organic matter contained in the pure water from carbonizing in the subsequent heat treatment process and causing poor insulation. There is a growing demand for extremely low levels of total organic carbon (TOC).

  As such high demands for pure water quality become apparent, various methods for decomposing and removing trace amounts of organic substances contained in pure water have been studied in recent years. As a representative example of such a method, a process for decomposing and removing organic substances by ultraviolet oxidation is being introduced.

In general, when organic substances are decomposed and removed by ultraviolet oxidation treatment, for example, an ultraviolet oxidation apparatus including a stainless steel reaction tank and a tubular ultraviolet lamp installed in the reaction tank is used. The water to be treated is introduced into the water and irradiated with ultraviolet rays. As the ultraviolet lamp, for example, a low-pressure ultraviolet lamp that generates ultraviolet rays having wavelengths of 254 nm and 185 nm, or a low-pressure ultraviolet lamp that generates ultraviolet rays having wavelengths of 254 nm, 194 nm, and 185 nm is used. When the water to be treated is irradiated with ultraviolet rays having a wavelength of 185 nm, oxidizing species such as hydroxyl radicals (.OH) are generated in the water to be treated, and trace organic substances in the water to be treated are oxidized by the oxidizing power of the oxidizing species. Decomposes into carbon and organic acids. The treated water obtained by subjecting the water to be treated in this way to the ultraviolet oxidative decomposition treatment is then sent to an ion exchange device disposed in the subsequent stage to remove carbon dioxide and organic acid. At this time, hydrogen peroxide (H ₂ O ₂ ) is generated from the hydroxyl radical generated in the water to be treated but not consumed in the oxidation reaction of the organic substance, for example, by the reaction shown in the formula (1).

When H ₂ O ₂ is contained in pure water, for example, if the pure water is used in a semiconductor device manufacturing process, H ₂ O _{2 in the} pure water may affect the semiconductor device manufacturing process. In addition, the concentration of H ₂ O ₂ is required to be extremely low.

As a general technique for removing H ₂ O ₂ from water to be treated, for example, as shown in Patent Document 1, it is known to bring water to be treated into contact with a palladium catalyst. It is supported on a resin.

Patent Document 2 discloses an ultrapure water production apparatus provided with a catalytic oxidizing substance decomposing apparatus for decomposing an oxidizing substance such as H ₂ O ₂ contained in water flowing out from the ultraviolet oxidizing apparatus after the ultraviolet oxidizing apparatus. It is shown. In this ultrapure water production apparatus, a deaeration device, a mixed bed type ion exchange device, and a fine particle separation membrane device are further provided in this order after the catalytic oxidative substance decomposition device. The water flowing out from the apparatus is supplied to the point of use as pure water from which impurities are highly removed. In addition, the ultrapure water production apparatus of Patent Document 2 is configured as a circulation type subsystem, and of the pure water from the fine particle separation membrane apparatus, surplus that has not been supplied to the use point is stored in a tank called a sub tank. After that, it is returned to the ultraviolet oxidizer. In order to supplement the pure water used at the point of use and keep the amount of water in the circulatory system constant, the sub-tank also contains water from which organic substances have already been removed to some extent as treated water (also called primary pure water) Have been supplied. The catalytic oxidizing substance decomposition apparatus has a noble metal catalyst such as metal palladium (Pd), a palladium compound, or platinum (Pt).

  Similarly, Patent Document 3 discloses an ultrapure water production apparatus configured as a circulation type sub-system, which is provided in a non-regenerative ion exchange apparatus at a stage subsequent to an ultraviolet oxidation apparatus, and is a non-regenerative ion exchange apparatus. Are filled with an ion exchange resin and a palladium catalyst. In this ultrapure water production apparatus, the palladium catalyst is supported on a resin.

In Patent Document 4, in an ultrapure water production apparatus, a hydrogen peroxide decomposition apparatus having a hydrogen peroxide decomposition catalyst is provided downstream of an ultraviolet oxidation apparatus in order to remove H ₂ O ₂ from water to be treated. In order to remove dissolved oxygen generated by decomposition of H ₂ O _{2 or} the like, it is disclosed to provide a membrane deaerator. As the hydrogen peroxide decomposition catalyst, a catalyst in which platinum group metal nanocolloid particles are supported on a carrier is used.

For example, when H ₂ O ₂ is decomposed by a catalyst having a platinum group metal, oxygen (O ₂ ) is generated as a reaction product and becomes a dissolved oxygen component in the pure water after the treatment. In pure water, it is desirable that dissolved oxygen also has a very low concentration. However, Patent Document 5 discloses that water to be treated is irradiated with ultraviolet light by an ultraviolet irradiation device and then passed through a palladium-supported catalyst resin tower. Thus, it is disclosed that dissolved oxygen can be chemically removed by a reducing agent such as hydrogen generated in an ultraviolet irradiation device.

JP-A-60-71085 Japanese Patent Laid-Open No. 2002-210494 JP 2006-192352 A JP 2007-185587 A JP-A-8-168756 JP-A-5-305297 Japanese Patent Laid-Open No. 10-277572 JP-A-11-99394 Japanese Patent No. 2500968 JP 7-284799 A Japanese Examined Patent Publication No. 6-47105 JP 2002-306976 A JP 2009-62512 A

For example, pure water used in the manufacturing process of a semiconductor device and from which TOC and H ₂ O ₂ are highly removed is manufactured by a circulating type pure water manufacturing apparatus also called a subsystem. The circulating pure water production apparatus includes at least an ultraviolet oxidation apparatus that oxidatively decomposes TOC components in the water to be treated and a hydrogen peroxide removal apparatus that removes H ₂ O ₂ contained in the effluent water from the ultraviolet oxidation apparatus. A part of the pure water from which the TOC and H ₂ O ₂ have been removed is supplied to the use point and consumed, and the rest returns to the sub tank.

  By the way, the decomposition efficiency of the organic matter in the ultraviolet oxidation apparatus decreases as the concentration of the organic matter in the water to be treated decreases. Therefore, in the circulating type pure water production apparatus, as the level of the TOC concentration in the pure water to be obtained is lowered, the TOC concentration in the water to be treated supplied to the ultraviolet oxidation apparatus is also decreased, and the ultraviolet oxidation treatment is performed. The efficiency of decomposition and removal of the TOC is reduced, the amount of power required for the ultraviolet oxidation process is increased, and the running cost of the apparatus is increased. In addition, the reduction in efficiency in TOC decomposition and removal also leads to an increase in the required amount of ultraviolet irradiation, the ultraviolet lamp is expensive, and it is necessary to replace the ultraviolet lamp, for example, every year. Considering this, it will lead to further increase in running cost.

  Therefore, an object of the present invention is a pure water production method and apparatus for producing pure water while circulating the obtained pure water, and improves the organic matter decomposition efficiency even when pure water having an extremely low TOC concentration is obtained. An object of the present invention is to provide a pure water production method and apparatus that can reduce the size and speed of the apparatus, and can reduce running costs.

In a circulation type pure water production apparatus having a hydrogen peroxide removal device in the circulation system, pure water having a very low hydrogen peroxide (H ₂ O ₂ ) concentration is operated so that it can be circulated. , so that the concentration of H ₂ O ₂ is low the water to be treated is passed through. According to the experiments by the present inventors, even when the TOC concentration level in the water to be treated is the same, the hydrogen peroxide removing device in the circulation system is compared with the case where the hydrogen peroxide removing device is not provided in the circulation system. , The decomposition efficiency of TOC in the ultraviolet oxidation apparatus was lowered.

Therefore, in the present invention, an appropriate amount of H ₂ O ₂ that does not cause an increase in the residual H ₂ O ₂ concentration in the obtained pure water and does not adversely affect the operation of the hydrogen peroxide removing device is oxidized by ultraviolet rays. It is added to the water to be treated before the treatment, thereby improving the TOC decomposition efficiency.

  Therefore, the pure water production method of the present invention includes an irradiation step of irradiating the water to be treated with a TOC of 10 ppb or less, a removing step of removing hydrogen peroxide contained in the water to be treated after the irradiation step, In a pure water production method in which pure water is produced at least by using the water at the point of use and is circulated to the irradiation process as at least part of the water to be treated. It has the addition process which adds hydrogen peroxide with respect to treated water.

  The pure water production apparatus of the present invention includes an ultraviolet oxidation apparatus that performs ultraviolet oxidation treatment by irradiating water to be treated with a TOC of 10 ppb or less, and an excessive amount contained in the water to be treated that has flowed out of the ultraviolet oxidation apparatus. A hydrogen peroxide removal device that removes hydrogen oxide, and at least a pure water that is used at a point of use to generate pure water and circulate the pure water as at least part of the treated water to the UV oxidation device The pure water production apparatus further comprising a pipe line is characterized by having an adding means for adding hydrogen peroxide to the water to be treated in front of the ultraviolet oxidation apparatus.

In the present invention, although the addition of H ₂ O ₂ to the water to be treated in front of an ultraviolet oxidation device, H ₂ O ₂ produced by this the added H ₂ O ₂ and the ultraviolet oxidation device, ultraviolet oxidation device Since it is removed by the hydrogen peroxide removing device provided at the subsequent stage, the H ₂ O ₂ concentration in the finally obtained pure water is extremely low.

It should be noted that the addition of H ₂ O ₂ before the ultraviolet oxidation treatment is a technique for treating TOC in water to be treated having a relatively high organic concentration (for example, wastewater containing TOC components after use at a use point). Is already known. In these cases, the TOC concentration in the water to be treated is assumed to be on the order of ppm, and since the water to be treated originally contains a large amount of various impurities, it is generally an open system. UV irradiation is performed using a reaction vessel. As a UV source, a high-pressure UV lamp that generates a wavelength of 254 nm is generally used.

As an example of a technique for decomposing and removing TOC in water to be treated having a relatively high organic matter concentration, Patent Document 6 discloses reverse osmosis membrane separation of raw water having a TOC concentration of 2 ppm as a technique for treating acidic wastewater containing organic matter. An example is described in which 30 ppm of H ₂ O ₂ is added to the permeated water obtained through the apparatus (RO), followed by ultraviolet irradiation with a high-pressure ultraviolet lamp (high-pressure mercury lamp) to decompose and remove the TOC component. ing. In Patent Document 7, 30 ppm of H ₂ O ₂ is added to raw water having a TOC concentration of 1 ppm, and ultraviolet irradiation treatment is performed by a high-pressure ultraviolet lamp as a means for decomposing and removing organic substances in treated water in wastewater recovery and the like. An example is given. Patent Document 8 discloses a TOC concentration of 6 ppm as a pretreatment step for reducing the amount of organic substances in advance when decomposing and removing organic substances in water to be treated using a sulfur compound containing a peroxide group (for example, sodium peroxydisulfate). An example is described in which 60 ppm of H ₂ O ₂ is added to a certain water to be treated and irradiated with ultraviolet rays. Patent Document 9 describes that 71 ppm of H ₂ O ₂ is added to the water to be treated having a TOC concentration of 20 ppm and irradiated with ultraviolet rays. In Patent Document 10, a biological reaction tank and an ultraviolet oxidation treatment tank are combined as a pretreatment device arranged in front of a pure water production apparatus in order to produce pure water from tap water (city water). While circulating the water to be treated, in the ultraviolet oxidation tank, 5 ppm H ₂ O ₂ is added to the water to be treated, and ultraviolet light is irradiated from the medium pressure ultraviolet lamp, thereby treating the treated water having a TOC concentration of about 55 to 60 ppb. It is described that it was obtained. Further, Patent Document 11, for the production of pure water, was added O ₃ with respect to water to be treated TOC concentration is 18Ppb, an example of performing ultraviolet oxidation process are the shown, instead of the O ₃ It is described that H ₂ O ₂ can also be used. Than those described in Patent Document 11, in order to remove excess O _3, by irradiating the ultraviolet rays by adding hydrogen (H ₂₎ after UV oxidation process, and the water by reducing O _3.

Thus, the conventional technology using both the addition of H ₂ O ₂ and ultraviolet irradiation is intended for a case where the TOC concentration in the water to be treated is relatively high, and the TOC concentration is 10 ppb or less. It is not intended for water to be treated, nor does it provide a guideline for H ₂ O ₂ addition conditions or UV oxidation treatment conditions.

In pure water used in the manufacturing process of semiconductor devices, it is necessary to make the concentration of H ₂ O ₂ extremely low. Therefore, the addition of H ₂ O ₂ accelerates the ultraviolet oxidation treatment of organic substances in the water to be treated. Even if the knowledge that it can be obtained has been obtained, it has not been considered so far to add H ₂ O ₂ in the production of pure water used in these applications.

The present invention is a recycle type pure water production apparatus in which a hydrogen peroxide removal device is provided at a subsequent stage of an ultraviolet oxidation apparatus, and is treated at a front stage of the ultraviolet oxidation apparatus on the premise that the hydrogen peroxide removal apparatus is removed. It is intended to add an appropriate amount of hydrogen peroxide to water, and by adding an appropriate amount of hydrogen peroxide, the TOC removal efficiency in the ultraviolet oxidation treatment is improved. In addition, an attempt is made to obtain pure water in which the H ₂ O ₂ concentration is suppressed to an extremely low level.

Hereinafter, the ultraviolet oxidation treatment when H ₂ O ₂ is added to the water to be treated will be described.

  In general, the reaction mechanism of decomposition and removal of organic substances by ultraviolet oxidation using a low-pressure ultraviolet lamp is such that the hydroxyl radical (OH radical) generated by the decomposition of water with light having a wavelength of 185 nm reacts with the TOC component in the treated water. It is considered that the TOC component is oxidatively decomposed. Light having a wavelength of 185 nm is very well absorbed by water and therefore hardly transmits. The low-pressure ultraviolet lamp emits light having a wavelength of 254 nm in addition to light having a wavelength of 185 nm. However, light having a wavelength of 254 nm can be transmitted without being absorbed by water.

When H ₂ O ₂ is added to the water to be treated, the light having a wavelength of 254 nm reacts with H ₂ O ₂ to generate OH radicals as shown in the formula (2). Since light having a wavelength of 185 nm also has higher energy than light having a wavelength of 254 nm, it can react with H ₂ O ₂ to generate OH radicals.

The generated OH radical can oxidatively decompose the TOC component, but has a short lifetime. OH radicals that could not encounter TOC component molecules, that is, organic molecules, and could not react with TOC components were converted to H ₂ O ₂ as shown in the above formula (1), which is the reverse reaction of formula (2). Return.

In order to improve the decomposition efficiency of organic matter, the amount of OH radicals generated should be increased. When the addition of H ₂ O ₂ and ultraviolet irradiation are used in combination, the reaction of formula (2) may be advanced to the right side in order to increase the amount of OH radicals produced. For that purpose, the H ₂ O ₂ concentration Must be increased, the amount of UV irradiation should be increased, or both. However, even if the amount of OH radicals generated is increased, the OH radicals that did not react with the TOC component without reacting with them are only returned to H ₂ O ₂ in the reaction shown in the formula (1). Will be used wastefully and will also increase the amount of H ₂ O ₂ to be removed from the water flowing out of the UV oxidizer, which may result in higher processing costs for pure water production. There is also. For these reasons, it is not preferable to add an excessive amount of H ₂ O ₂ to the water to be treated before the ultraviolet oxidation treatment. According to the study by the present inventors, the amount of H ₂ O ₂ added is preferably such that the H ₂ O ₂ concentration in the treated water after the addition is 10 ppb or more and 400 ppb or less.

According to the present invention, when pure water is generated using a circulating pure water production apparatus that includes at least an ultraviolet oxidation device and a hydrogen peroxide removal device, the water to be treated is treated before the ultraviolet oxidation device. By adding hydrogen oxide, the TOC decomposition efficiency can be greatly improved even when the TOC concentration of the water to be treated is low, and the TOC concentration and the H ₂ O ₂ concentration are maintained at extremely low levels. Purified water can be obtained. Thereby, the apparatus scale of the ultraviolet oxidation apparatus can be reduced, and the running cost including the power consumption cost and the lamp cost can be greatly reduced.

Also, H ₂ O ₂ generated by H ₂ O ₂ and UV oxidation apparatus added, in a hydrogen peroxide removal apparatus arranged downstream of the ultraviolet oxidation device, for example, by contacting with a platinum group metal catalyst, electrode Removed to low concentrations. As a result, when a subsequent ion exchange apparatus or the like is provided in the pure water production apparatus, adverse effects such as oxidative deterioration of the ion exchange resin due to the oxidizing substance can be ignored.

It is a figure which shows an example of a structure of the pure water manufacturing apparatus of one Embodiment of this invention. It is a figure which shows the structure of the pure water manufacturing apparatus of other embodiment of this invention. It is a figure which shows the structure of the pure water manufacturing apparatus of further another embodiment of this invention. It is a figure which shows the structure of the water treatment apparatus in an Example. It is a graph showing the relationship between the concentration of H ₂ O ₂ and TOC removal rate in the ultraviolet oxidation device inlet. It is a figure which shows another structure of the water treatment apparatus in an Example. It is a graph showing the relationship between the concentration of H ₂ O ₂ and TOC removal rate in the ultraviolet oxidation device inlet. It is a figure which shows another structure of the water treatment apparatus in an Example.

  Next, embodiments of the present invention will be described with reference to the drawings.

  The pure water production method according to the present invention generates pure water that is configured as a circulation system and is supplied to a use point, and the amount of pure water that exceeds the use amount at the use point passes through the circulation system. It circulates and is preferably applicable to, for example, pure water production in a system that generates secondary pure water from primary pure water, a so-called subsystem. In order to keep the amount of water in the circulation system constant, water is supplied from the outside according to the amount of use at the point of use. As water supplied from the outside, primary pure water level water that has been subjected to at least desalting treatment is assumed. The water supplied from the outside and the pure water circulating in the circulation system are combined to be treated water in the ultraviolet oxidation treatment, and the TOC concentration in the treated water is assumed to be 10 ppb or less. The lower limit of the TOC concentration in the water to be treated is, for example, 1 ppb. Accordingly, the pure water production method according to the present invention includes an irradiation step of irradiating the water to be treated having a TOC of 10 ppb or less with an ultraviolet ray, and a removing step of removing hydrogen peroxide contained in the water to be treated after the irradiation step. In a pure water production method in which pure water is produced at least by using the water at the point of use and is circulated to the irradiation process as at least a part of the water to be treated. It has the addition process which adds hydrogen peroxide with respect to treated water.

  The pure water production apparatus according to the present invention has a structure suitable for producing pure water by the pure water production method according to the present invention. For example, a system for producing secondary pure water, a so-called subsystem. It is suitable for use in. Therefore, the pure water manufacturing apparatus based on this invention is contained in the to-be-processed water which irradiates the to-be-processed water whose TOC is 10 ppb or less, and performs an ultraviolet-oxidation process, and the to-be-processed water which flowed out of the ultraviolet-oxidation apparatus And at least a hydrogen peroxide removal device that removes the generated hydrogen peroxide, generates pure water, and circulates the pure water in excess of the amount used at the point of use to the UV oxidation device as at least part of the treated water In the pure water production apparatus further comprising a circulation pipe, an addition means for adding hydrogen peroxide to the water to be treated is provided upstream of the ultraviolet oxidation apparatus.

  In the pure water production method and apparatus according to the present invention, the resistivity of the water to be treated is preferably 1 MΩcm or more.

  Hereinafter, an embodiment of the present invention will be described by taking the case where the present invention is applied to a subsystem as an example.

Here, the amount of H ₂ O ₂ added to the water to be treated will be described. When the TOC concentration of the water to be treated is 10 ppb or less, H ₂ O ₂ is added so as to be 10 ppb or more and 400 ppb or less from the viewpoint of improving TOC removal efficiency without generating OH radicals unnecessarily. As will be apparent from the reference examples and comparative examples described later, when the TOC concentration of the water to be treated is 10 ppb or less, when a small amount of H ₂ O ₂ is added, that is, within a range of up to 400 ppb, The TOC removal efficiency is improved as compared with the case where H ₂ O ₂ is not added. However, when the H ₂ O ₂ concentration exceeds 400 ppb, the TOC removal efficiency is higher than the case where H ₂ O ₂ is not added. descend. In the present invention, therefore, it is preferable to adding H ₂ O ₂ to be within 400ppb following range of 10 ppb.

  FIG. 1 shows a pure water producing apparatus according to an embodiment of the present invention.

This apparatus includes a tank 11 for storing pure water, and a pump (P) 12 for sending pure water from the tank 11. To the pump 12, a heat exchanger 15, an ultraviolet oxidizer (UV) 16, H ₂ O ₂ removal device 17, membrane deaeration device (MD) 18, non-regenerative mixed bed ion exchange device (CP) 19 and ultrafiltration device (UF) 20 are connected in this order, and ultrafiltration device 20 Water is sent to the use point, and the water not used at the use point is returned to the tank 11 by the circulation pipe. In this apparatus, the pump 11 from the tank 11, the heat exchanger 15, the ultraviolet oxidation device 16, the H ₂ O ₂ removal device 17, the membrane deaeration device 18, the non-regenerative mixed bed ion exchange device 19 and the ultrafiltration device 20. A circulation system is formed to return to the tank 11 via Since the amount of water in the circulation system decreases according to the use of pure water at the point of use, water (supply water) from the outside is also supplied to the tank 11 in order to keep the amount of water in the circulation system constant. .
The supply water is, for example, primary pure water.

In this configuration, the TOC concentration of water supplied to the ultraviolet oxidizer 16 is 10 ppb or less. Further, in this system, an H ₂ O ₂ storage tank (H ₂ O ₂ ) 13 for storing H ₂ O ₂ is connected to a pipe connecting a heat exchanger 15 and an ultraviolet oxidation device 16, and water to be treated in the pipe is treated. and a, a pump (P) 14 for supplying H ₂ O ₂ from H ₂ O ₂ reservoir 13 so as adding H ₂ O ₂ relative. The pump 14 adds H ₂ O ₂ to the water to be treated so that the H ₂ O ₂ concentration in the water to be treated after the addition becomes, for example, 10 ppb or more and 400 ppb or less.

In such a system, pure water stored in the tank 11 is first sent to the heat exchanger 15 by the pump 12 as water to be treated, and the temperature is adjusted. Thereafter, H ₂ O ₂ is added, and ultraviolet rays are irradiated in the ultraviolet oxidizer 16. As a result, the TOC component in the for-treatment water is decomposed.

  The ultraviolet oxidation device 16 includes, for example, a sealed flow type reaction vessel in which an interface between the water to be treated and the gas phase is not formed, and an ultraviolet lamp that irradiates the water to be treated in the reaction vessel with ultraviolet rays. Preferably there is. As the ultraviolet lamp, for example, a low-pressure ultraviolet lamp that generates at least light having a wavelength of 185 nm can be used.

The light from the low-pressure ultraviolet lamp includes a component having a wavelength of 254 nm and a wavelength of 194 nm in addition to a component having a wavelength of 185 nm. When H ₂ O ₂ is not added, light with a wavelength of 185 nm mainly contributes to the decomposition of the TOC component. However, in this embodiment, by adding H ₂ O ₂ , light with a wavelength of 254 nm also decomposes the TOC component. Will be able to contribute.

Although it is possible to decompose the TOC component by using H ₂ O ₂ in combination with a high-pressure ultraviolet lamp that mainly emits light with a wavelength of 254 nm, the residence time of the water to be treated in the reactor is improved by improving the decomposition efficiency. In order to shorten the size and reduce the size of the apparatus, it is preferable to use a low-pressure ultraviolet lamp (radiating a component having a wavelength of 185 nm) for ultraviolet irradiation.

In this embodiment, it is preferable that the irradiation amount in ultraviolet irradiation is 0.3 kWh / m ³ or less. Since the TOC concentration in the water to be treated is low, even if a large amount of OH radicals are generated with a high irradiation dose, the OH radicals are consumed in the reaction shown in the formula (1). I can't. By setting the irradiation amount to 0.3 kWh / m ³ or less, efficient treatment can be performed without generating OH radicals in vain.

  By using a closed flow type reaction vessel in which the interface between the water to be treated and the gas phase is not formed as the reaction vessel of the ultraviolet oxidizer 16, the light having a wavelength of 254 nm that has passed through the water does not escape to the gas phase. It is effectively used for the OH radical production reaction represented by the formula (2). From the viewpoint of effective use of light having a wavelength of 254 nm, the inner surface of the reaction vessel is preferably made of a metal such as stainless steel (SUS) and mirror-finished.

The water to be treated receives the ultraviolet oxidation treatment by ultraviolet oxidation device 16 is then sent to the H ₂ O ₂ removing device 17, H ₂ O ₂ is removed. The H ₂ O ₂ removed here is treated by H ₂ O ₂ added by the pump 14 before the ultraviolet oxidizer 16 and not used in the ultraviolet oxidizer 16 and by ultraviolet irradiation in the ultraviolet oxidizer 16. Both H ₂ O ₂ generated in water.

A platinum group metal catalyst is provided in the H ₂ O ₂ removal device 17, and when the treated water comes into contact with the platinum group metal catalyst, the residue of H ₂ O ₂ is removed by catalytic decomposition. Activated carbon is also known as a decomposition catalyst for H ₂ O ₂ , but it is preferable to use a platinum group metal catalyst with little eluate in view of application in a pure water system. The platinum group metal here is ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), and one of these is used alone. You may use, and may use it in combination of 2 or more types. Among these platinum group metals, Pt and Pd can be preferably used, and Pd is preferable from the viewpoint of cost and the like.

Such a platinum group metal catalyst is supported on, for example, an anion exchanger in the H ₂ O ₂ removing device 17. The anion exchanger may be a granular anion exchange resin, or may be a monolithic organic porous anion exchanger formed by integrating the anion exchange resin. Monolithic organic porous anion exchangers that can be used here are described in, for example, Patent Document 12 and Patent Document 13. Supporting a platinum group metal catalyst on the anion exchanger is effective in exhibiting high catalytic ability and reducing the amount of eluate from the catalyst.

The H ₂ O ₂ removing device 17 having a platinum group metal catalyst is provided, by contacting with the platinum group metal catalyst with H ₂ O ₂ generated by H ₂ O ₂ and UV oxidation apparatus 16 is added to the water to be treated, H ₂ O ₂ can be removed to an extremely low concentration. Thereby, it is possible to prevent adverse effects such as oxidative deterioration of the ion exchange resin in the non-regenerative mixed bed ion exchange apparatus 19 in the subsequent stage due to the oxidizing substance H ₂ O ₂ .

The treated water flowing out from the H ₂ O ₂ removal device 17 is then sent to the membrane deaeration device 18 to remove dissolved oxygen (DO) and the like, and then sent to the non-regenerative mixed bed ion exchange device 19. It is done. The organic acid and carbon dioxide (CO ₂ ) produced by the ultraviolet oxidation treatment and contained in the for-treatment water are removed in the non-regenerative mixed bed ion exchanger 19. Furthermore, the water to be treated is sent to the ultrafiltration device 20 and becomes water from which impurities are highly removed, and is sent to the use point. The unused water is circulated and returned to the tank 11. In some cases, the membrane deaerator 18 can be omitted. In this configuration, pure water in which the TOC concentration and the H ₂ O ₂ concentration are suppressed to extremely low levels is obtained from the use point, and such pure water is also returned to the tank 11 through the circulation line.

FIG. 2 shows a pure water production apparatus according to another embodiment. The pure water production apparatus shown in FIG. 2 is obtained by reversing the connection order of the membrane deaerator (MD) 18 and the non-regenerative mixed bed ion exchanger (CP) 19 in the apparatus shown in FIG. Even if the connection order is changed in this way, pure water in which the TOC concentration and the H ₂ O ₂ concentration are suppressed to a very low level can be obtained from the use point.

  FIG. 3 shows a pure water producing apparatus according to still another embodiment.

The apparatus shown in FIG. 3 is the same as the apparatus shown in FIG. 1 except that hydrogen (H ₂ ) is added to remove dissolved oxygen (DO) and promote decomposition and removal of H ₂ O ₂ . In order to add H ₂ , a gas dissolution film device 22 is provided between the ultraviolet oxidation device 16 and the H ₂ O ₂ removal device 17, and the gas dissolution film device 22 includes H ₂ storage tank (H ₂ ) 21 to H ₂ is supplied. In this case, since the dissolved oxygen can be removed by the H ₂ O ₂ removal device 17, the membrane deaeration device 18 is not provided.

In this configuration, water from the ultraviolet oxidizer 16 is brought into contact with the platinum group metal catalyst after H ₂ is dissolved. A platinum group metal catalyst such as Pd or Pt can remove dissolved oxygen in the presence of dissolved hydrogen. By treating with a platinum group metal catalyst after dissolving H ₂ , removal of residual H ₂ O ₂ and removal of DO can be performed simultaneously.

In each of the above-described embodiments, even when the TOC concentration in the water to be treated is low, an ultraviolet oxidizer is added by adding an appropriate amount of H ₂ O ₂ to the water to be treated before the ultraviolet oxidizer 16. The TOC decomposition efficiency at 16 can be improved. Such an improvement in decomposition efficiency was remarkable when the TOC concentration in the water to be treated was 10 ppb or less, as will be apparent from the examples described later.

The present invention will be described in more detail based on examples performed by the present inventors in order to confirm the effects of the present invention. In the circulation type pure water production apparatus, since at least a part of the produced pure water circulates in the apparatus as treated water, the TOC concentration and H ₂ O ₂ concentration in the produced pure water are If a very long time has not elapsed since the start of operation, the value does not converge to a constant value, and the TOC concentration and H ₂ O ₂ concentration also change depending on the amount of pure water used at the use point. Therefore, for the purpose of confirming the effect of the present invention and obtaining the optimum value of the addition amount of H ₂ O ₂ , the non-circulation type configuration is used rather than using the data actually obtained in the circulation type pure water production apparatus. Since it is easier to understand using the acquired data, the present invention will be described below based on data acquired by a non-circular apparatus configuration. A person skilled in the art can easily obtain the effects of the present invention and the optimum value of the amount of H ₂ O ₂ when configured as a circulating pure water production apparatus from the following examples, comparative examples and reference examples. Can be recognized.

[Example 1]
A water treatment apparatus having the configuration shown in FIG. 4 was assembled. In this apparatus, by adding methanol (CH ₃ OH) as an organic substance to ultrapure water, water to be treated having a controlled TOC concentration is generated, and ultraviolet oxidation treatment is performed. The ultrapure water supplied to this apparatus contains H ₂ O ₂ produced in the process of producing the ultrapure water. Therefore, this apparatus is provided with an H ₂ O ₂ removal device 32 having a hydrogen peroxide removal catalyst, and this H ₂ O ₂ removal device 32 is bypassed when passing ultrapure water as supply water. By switching between cases, the concentration of H ₂ O _{2 in} the water to be treated supplied to the ultraviolet oxidation apparatus can be changed. The quality of the ultrapure water used here was 18 MΩ · cm or more in resistivity, 0.5 ppb or less in TOC, and 14 ppb in H ₂ O ₂ concentration.

A three-way valve 31 is provided for a pipe to which ultrapure water is supplied. An inlet of the H ₂ O ₂ removal device 32 is connected to one outlet of the three-way valve 31, and the other outlet of the three-way valve 31 is connected. It is connected to the outlet of H ₂ O ₂ removing device 32 so as to bypass the H ₂ O ₂ removing device 32. As the H ₂ O ₂ removing device 32, a PTFE (polytetrafluoroethylene) column having an inner diameter of 57 mm filled with a Pd monolith having a layer height of 10 mm (about 25 mL in volume) was used.

Methanol is supplied from a methanol storage tank (methanol) 33 through a pump (P) to the piping from the outlet of the H ₂ O ₂ removal device 32, and the ultrapure water to which methanol is added is sent to the membrane deaeration device 34. It is done. The water flowing out from the membrane deaerator 34 was treated water, and the TOC concentration in the treated water was measured online with a TOC meter 35 (A-1000XP TOC meter manufactured by ANATEL). The H ₂ O ₂ concentration of the water to be treated was measured with an absorptiometer using the phenol phthaline method after sampling as shown in the figure (S).

  A part of the water to be treated flowing out from the membrane deaerator 34 was branched and supplied to the ultraviolet oxidizer 37 via the flow meter 36. As the ultraviolet oxidation device 37, TFL-1 manufactured by Chiyoda Corporation was used. In the ultraviolet oxidizer 37, one low-pressure ultraviolet lamp (200W ultraviolet lamp SV-1500 manufactured by Chiyoda Corporation) that emits both light having a wavelength of 254 nm and light having a wavelength of 185 nm was installed as an ultraviolet lamp.

  A part of the treated water flowing out from the ultraviolet oxidizer 37 is branched and passed through the non-regenerative mixed bed ion exchanger (CP) 38 and the flow meter 39 in this order, and the TOC of the treated water flowing out from the flow meter 39. The concentration was measured with a TOC meter 40 (A-1000XP TOC meter manufactured by ANATEL). The non-regenerative mixed bed type ion exchange device 38 has a cylindrical container made of acrylic resin (inner diameter 25 mm, height 1000 mm), and this container is filled with 300 ml of mixed bed ion exchange resin (layer height of about 600 mm). What was done was used.

The TOC removal rate was determined by the following formula:
TOC removal rate (%) = ((TOC0−TOC1) / TOC0) × 100
Here, TOC0 is the TOC concentration of the water to be treated, that is, the TOC concentration measured by the TOC meter 35, and TOC1 is the TOC concentration of the treated water from the non-regenerative mixed bed ion exchanger 38, that is, the TOC meter 40. TOC concentration measured in

As treated water, methanol is added to ultrapure water so that the TOC concentration becomes 2.3 ppb for a water flow rate of 330 L / h, and dissolved oxygen (DO) is less than 10 ppb by the membrane deaerator 34. What was used was used. At this time, the H ₂ O ₂ concentration of the water to be treated was set to 14 ppb with the three-way valve 31 as a bypass side. In the ultraviolet oxidation device 37, ultraviolet oxidation treatment was performed so that the ultraviolet irradiation amount was 0.2 kWh / m ³ . The TOC concentration of the treated water from the non-regenerative mixed bed ion exchanger 38 was measured to calculate the TOC removal rate. The results are shown in FIG.

As shown in FIG. 5, the TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 0.66 ppb, and the TOC removal rate was 71%. By comparing with Comparative Example 1 described later, the presence of a small amount of H ₂ O ₂ improves the TOC removal efficiency even when pure water with a very low TOC concentration is treated water. I found out that

[Comparative Example 1]
Using the apparatus described in Example 1, using the three-way valve 31 as the H ₂ O ₂ removal apparatus 32 side, ultrapure water with reduced H ₂ O ₂ concentration is used as water to be treated, and the TOC concentration of water to be treated is 1 The test was performed under the same conditions as in Example 1 except that the density was 9 ppb. The H ₂ O ₂ concentration in the water to be treated at this time was 3.1 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Comparative Example 1 was 0.70 ppb, and the TOC removal rate was 63%.

[Example 2]
The test was performed under the same conditions as in Example 1 except that the TOC concentration of the water to be treated was 6.1 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Example 2 was 0.70 ppb, and the TOC removal rate was 89%.

[Comparative Example 2]
Except that the three-way valve 31 is the H ₂ O ₂ removal device 32 side, ultrapure water with reduced H ₂ O ₂ concentration is treated water, and the TOC concentration of treated water is 6.8 ppb. The test was performed under the same conditions as in Example 2. The H ₂ O ₂ concentration in the water to be treated at this time was 4.8 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 in Comparative Example 2 was 1.50 ppb, and the TOC removal rate was 78%.

[Example 3]
The test was performed under the same conditions as in Example 1 except that the TOC concentration of the water to be treated was 10.3 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Example 3 was 1.50 ppb, and the TOC removal rate was 85%.

[Comparative Example 3]
Except that the three-way valve 31 is the H ₂ O ₂ removal device 32 side, ultrapure water with reduced H ₂ O ₂ concentration is treated water, and the TOC concentration of treated water is 9.2 ppb. The test was performed under the same conditions as in Example 3. The H ₂ O ₂ concentration in the water to be treated at this time was 3.1 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 in Comparative Example 3 was 1.40 ppb, and the TOC removal rate was 84%.

[ Comparative Example 4-1 ]
The test was performed under the same conditions as in Example 1 except that the TOC concentration of the water to be treated was 28 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Comparative Example 4-1 was 10.3 ppb, and the TOC removal rate was 63%.

[Comparative Example 4-2 ]
Comparative Example 4 except that the three-way valve 31 is the H ₂ O ₂ removal device 32 side, ultrapure water with reduced H ₂ O ₂ concentration is treated water, and the TOC concentration of treated water is 29 ppb. The test was performed under the same conditions as for -1 . The H ₂ O ₂ concentration in the water to be treated at this time was 3.5 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Comparative Example 4-2 was 12 ppb, and the TOC removal rate was 59%.

[Example 5]
A water treatment apparatus having the configuration shown in FIG. 6 was assembled. This apparatus is the same as that shown in FIG. 4, but by removing the three-way valve 31, it is ensured that the ultrapure water that is the supply water passes through the H ₂ O ₂ removing apparatus 32, and further, Methanol is supplied from a methanol storage tank 33 through a pump (P) to a pipe between the H ₂ O ₂ removal device 32 and the membrane deaeration device 34 so that the H ₂ O ₂ concentration in water can be arbitrarily set. In addition, H ₂ O ₂ is supplied from the H ₂ O ₂ storage tank (H ₂ O ₂ ) 41 via the pump (P). Ultrapure water to which methanol and H ₂ O ₂ have been added is well mixed in the membrane deaerator 34. The quality of the ultrapure water used here was 18 MΩ · cm or more in resistivity and 0.5 ppb or less in TOC. In other respects, the apparatus shown in FIG. 6 has the same configuration as the apparatus shown in FIG.

As water to be treated, methanol and H ₂ O ₂ were added to ultrapure water so that the TOC concentration was 6.1 ppb and the H ₂ O ₂ concentration was 17 ppb with respect to a water flow rate of 400 L / h. What used dissolved oxygen (DO) less than 10 ppb by the deaeration apparatus 34 was used. When the water flow rate was 400 L / h, the ultraviolet irradiation amount in the ultraviolet oxidation device 37 was 0.17 kWh / m ³ . The TOC concentration of the treated water from the non-regenerative mixed bed ion exchanger 38 was measured to calculate the TOC removal rate. The results are shown in FIG.

As shown in FIG. 7, the TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 was 0.68 ppb, and the TOC removal rate was 89%. By comparing with Comparative Example 5 described below, the presence of a small amount of H ₂ O ₂ improves the TOC removal efficiency even when pure water having a very low TOC concentration is treated water. I found out that

[Example 6]
The test was performed under the same conditions as in Example 5 except that the H ₂ O ₂ concentration of the water to be treated was 33 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Example 6 was 0.57 ppb, and the TOC removal rate was 91%.

[Comparative Example 5]
Tested under the same conditions as in Example 5 except that H ₂ O ₂ was not added from the H ₂ O ₂ storage tank 41 to the ultrapure water and that the TOC concentration of the water to be treated was 7.25 ppb. Went. The H ₂ O ₂ concentration of the treated water at this time was 3.4 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 in Comparative Example 5 was 0.97 ppb, and the TOC removal rate was 87%.

[Example 7]
The test was performed under the same conditions as in Example 5 except that the TOC concentration of the water to be treated was 6.3 ppb and the H ₂ O ₂ concentration was 79 ppb. The results are shown in FIG. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchanger 38 in Example 7 was 0.60 ppb, and the TOC removal rate was 90%.

[Examples 8-1 to 8-5]
A water treatment apparatus having the configuration shown in FIG. 8 was assembled. This apparatus is the same as that shown in FIG. 6 except that no H ₂ O ₂ removal device 32 for removing H ₂ O ₂ from ultrapure water as supply water is provided. The line mixer 42 is provided in place of the device 34, and the connection order of the non-regenerative mixed bed ion exchange device 38 and the flow meter 39 to the outlet of the ultraviolet oxidation device 37 is reversed. 6 is different from that shown in FIG. 6 in that an H ₂ O ₂ removal device 43 is provided between the non-regenerative mixed bed ion exchange device 38. In addition, sampling is performed as shown in the figure (S) at the outlet of the non-regenerative mixed bed ion exchanger 38, and the residual H ₂ O ₂ concentration in the water flowing out of the non-regenerative mixed bed ion exchanger 38 is phenol. It was measured with an absorptiometer using the phthaline method.

As the H ₂ O ₂ removing device 43, an acrylic resin cylindrical container (inner diameter 25 mm, height 300 mm) having 100 ml of catalyst resin (layer height of about 200 mm) filled in this container was used. As the catalyst resin, an anion exchange resin carrying Pd and having a Pd loading of 100 mg-Pd / LR (gel form, OH form: 95% or more) was used.

  In the apparatus shown in FIG. 8, if the water flowing out from the non-regenerative mixed bed ion exchange apparatus 38 is circulated as ultrapure water as supply water, the basic structure of the pure water production apparatus according to the present invention will be described. It becomes the composition.

As the water to be treated, the TOC concentration is 10 ppb with respect to the water flow rate of 1.1 m ³ / h, and the H ₂ O ₂ concentration is 50, 100, 200, respectively for Examples 8-1 to 8-5. Methanol and H ₂ O ₂ were added to ultrapure water so as to be 300 and 400 ppb and mixed with the line mixer 42. Then, in the ultraviolet oxidation device 37, the ultraviolet oxidation treatment was performed so that the ultraviolet irradiation amount became 0.06 kWh / m ³ . The TOC concentration of the treated water from the non-regenerative mixed bed ion exchanger 38 was measured to calculate the TOC removal rate. The results are shown in Table 1.

As shown in Table 1, the TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 in Example 8-1 was 2.40 ppb, and the TOC removal rate was 76%. Similarly, in Example 8-2, the TOC concentration was 2.08 ppb and the TOC removal rate was 79%, and in Example 8-3, the TOC concentration was 2.12 ppb and the TOC removal rate was 79%, and Example 8-4. Then, the TOC concentration was 2.35 ppb and the TOC removal rate was 77%. In Example 8-5, the TOC concentration was 2.53 ppb and the TOC removal rate was 75%. In any case, the residual H ₂ O ₂ concentration in the treated water at the outlet of the non-regenerative mixed bed ion exchanger 38 was less than 1 ppb.

It was found that the TOC removal efficiency was improved when H ₂ O ₂ was added in a small amount, that is, in the range up to 400 ppb, as compared with Comparative Examples 6-1 to 6-2 described later.

[Reference example]
The test was conducted under the same conditions as in Example 8-1 except that H ₂ O ₂ was not intentionally added to the water to be treated. At this time, by that contains H ₂ O ₂ in ultrapure water supplied, H ₂ O ₂ concentration in the water to be treated supplied to the ultraviolet oxidation device 37 was 12 ppb. The results are shown in Table 1. The TOC concentration at the outlet of the non-regenerative mixed bed ion exchange apparatus 38 was 2.72 ppb, and the TOC removal rate was 73%.

[Comparative Examples 6-1 and 6-2]
The test was performed under the same conditions as in Example 8-1 except that the H ₂ O ₂ concentration of the water to be treated was 600 ppb and 1000 ppb, respectively. The results are shown in Table 1. The TOC concentrations at the outlet of the non-regenerative mixed bed ion exchanger 38 were 2.89 ppb and 3.72 ppb, respectively, and the TOC removal rates were 71% and 63%, respectively. When H ₂ O ₂ was added excessively, the TOC removal rate was decreased as compared with the case where H ₂ O ₂ was not added.

11 Tank 12, 14 Pump (P)
13,41 H ₂ O ₂ storage tank 15 heat exchanger 16,37 UV oxidation equipment (UV)
17, 32, 43 H ₂ O ₂ removal device 18, 34 Membrane deaeration device (MD)
19,38 Non-regenerative mixed bed ion exchanger (CP)
20 Ultrafiltration equipment (UF)
21 H ₂ storage tank 22 Gas dissolution membrane device 31 Three-way valve 33 Methanol storage tank 36, 39 Flow meter 35, 40 TOC meter 42 Line mixer

Claims (11)

Produced pure water comprising at least an irradiation step of irradiating the water to be treated with a TOC of 10 ppb or less with an ultraviolet ray and a removing step of removing hydrogen peroxide contained in the water to be treated after the irradiation step In the pure water production method, the pure water that exceeds the usage amount at the use point is circulated to the irradiation step as at least a part of the treated water.
The irradiation step is a step of irradiating the ultraviolet ray with a low-pressure ultraviolet lamp, and irradiating an ultraviolet ray having a wavelength of 185 nm so that an ultraviolet ray irradiation amount is 0.3 kWh / m ³ or less,
Pure water characterized by having an addition step of adding hydrogen peroxide to the treated water so that the hydrogen peroxide concentration in the treated water is 10 ppb or more and 400 ppb or less before the irradiation step. Production method. Produced pure water comprising at least an irradiation step of irradiating the water to be treated with a TOC of 10 ppb or less with an ultraviolet ray and a removing step of removing hydrogen peroxide contained in the water to be treated after the irradiation step In the pure water production method, the pure water that exceeds the usage amount at the use point is circulated to the irradiation step as at least a part of the treated water.
Before the irradiation step, there is an addition step of adding hydrogen peroxide from the H ₂ O ₂ storage tank so that the hydrogen peroxide concentration in the water to be treated is 10 ppb or more and 400 ppb or less with respect to the water to be treated. And
The irradiation step is a step of irradiating the ultraviolet by the low-pressure ultraviolet lamp, ultraviolet irradiation amount ultraviolet rays including a wavelength 185nm is characterized in that it is a step of irradiating such that 0.3 kWh / m ³ or less Pure water production method.   The pure water production method according to claim 1 or 2, wherein the removing step is a step of decomposing hydrogen peroxide in the water to be treated by bringing the water to be treated into contact with a platinum group metal catalyst.   The method for producing pure water according to claim 3, further comprising a step of dissolving hydrogen in the water to be treated between the irradiation step and the removal step.   The pure water manufacturing method of any one of Claims 1 thru | or 4 which further includes the process of performing an ion exchange process with respect to the said to-be-processed water after the said irradiation process. An ultraviolet oxidation apparatus that performs ultraviolet oxidation treatment by irradiating ultraviolet rays to water to be treated having a TOC of 10 ppb or less, and peroxidation that removes hydrogen peroxide contained in the water to be treated that has flowed out of the ultraviolet oxidation apparatus A dehydrating device, and at least a circulation line that circulates the pure water in excess of the amount used at a use point to the ultraviolet oxidation device as at least part of the treated water. In the pure water production equipment provided,
The ultraviolet oxidation apparatus includes a low-pressure ultraviolet lamp that irradiates the water to be treated with ultraviolet light, and irradiates the water to be treated with ultraviolet light having a wavelength of 185 nm so that the amount of ultraviolet radiation is 0.3 kWh / m ³ or less. ,
An addition means for adding hydrogen peroxide to the treated water so that a concentration of hydrogen peroxide in the treated water is 10 ppb or more and 400 ppb or less with respect to the treated water. Water production equipment. An ultraviolet oxidation apparatus that performs ultraviolet oxidation treatment by irradiating ultraviolet rays to water to be treated having a TOC of 10 ppb or less, and peroxidation that removes hydrogen peroxide contained in the water to be treated that has flowed out of the ultraviolet oxidation apparatus A dehydrating device, and at least a circulation line that circulates the pure water in excess of the amount used at a use point to the ultraviolet oxidation device as at least part of the treated water. In the pure water production equipment provided,
There is an addition means for adding hydrogen peroxide from the H ₂ O ₂ storage tank to the front stage of the ultraviolet oxidizer so that the hydrogen peroxide concentration in the water to be treated is 10 ppb or more and 400 ppb or less. And
The ultraviolet oxidation device includes a low-pressure ultraviolet lamp that irradiates the water to be treated with ultraviolet light, and irradiates the water to be treated with ultraviolet rays having a wavelength of 185 nm so that the amount of ultraviolet irradiation is 0.3 kWh / m ³ or less. The pure water manufacturing apparatus characterized by the above-mentioned .   The pure water producing apparatus according to claim 6 or 7, wherein the hydrogen peroxide removing apparatus has a platinum group metal catalyst, and the treated water is brought into contact with the platinum group metal catalyst.   The pure water production apparatus according to claim 8, wherein the platinum group metal catalyst is supported on an anion exchanger.   10. The pure water production apparatus according to claim 8, further comprising a gas dissolving film device that dissolves hydrogen in the water to be treated between an outlet of the ultraviolet oxidation device and an inlet of the hydrogen peroxide removing device.   The ion exchange apparatus which is provided between the exit of the said ultraviolet oxidation apparatus, and the said use point, and further performs an ion exchange process with respect to the said to-be-processed water, The any one of Claim 6 thru | or 10 Pure water production equipment.

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