WO2018092832A1

WO2018092832A1 - Water treatment method and device

Info

Publication number: WO2018092832A1
Application number: PCT/JP2017/041215
Authority: WO
Inventors: 一重高橋; 菅原　広
Original assignee: オルガノ株式会社
Priority date: 2016-11-18
Filing date: 2017-11-16
Publication date: 2018-05-24
Also published as: TW201821371A; JP6752693B2; JP2018079448A; CN109906206B; KR102233505B1; CN109906206A; KR20190066059A; TWI732970B

Abstract

This water treatment device, which subjects, to decomposition treatment, organic matter included in water to be treated, is provided with: a hydrogen peroxide addition device which adds hydrogen peroxide to the water to be treated, in order to improve the organic matter decomposition efficiency, and achieve a high TOC removal rate; an ultraviolet irradiation device which irradiates, with ultraviolet, the water to be treated to which the hydrogen peroxide has been added; a dissolved oxygen measurement means which measures the dissolved oxygen concentration in outlet water of the ultraviolet irradiation device; and a control means which controls the addition amount of the hydrogen peroxide on the basis of the dissolved oxygen concentration measured by the dissolved oxygen measurement means.

Description

Water treatment method and apparatus

The present invention relates to a water treatment method and apparatus for decomposing organic substances contained in water to be treated which is water to be treated.

Conventionally, pure water such as ultrapure water from which organic substances, ionic components, fine particles, and bacteria have been highly removed has been used as cleaning water used in the manufacturing process of semiconductor devices and the manufacturing process of liquid crystal display devices. Yes. 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 insulation failure. There is a 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 (TOC components) contained in pure water have been studied in recent years. As a typical example of such a method, a process for decomposing and removing organic substances by ultraviolet oxidation treatment is used.

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 is used. When the water to be treated is irradiated with ultraviolet rays having a wavelength of 185 nm, oxidized species such as hydroxyl radicals (.OH) are generated in the treated water, and trace amounts of organic substances in the treated water are oxidized by the oxidizing power of the oxidized species. Decomposes into carbon and organic acids. The treated water obtained by subjecting the water to be treated in this way to the ultraviolet oxidation treatment is then sent to an ion exchange device disposed in the subsequent stage to remove carbon dioxide and organic acid.

However, in the oxidative decomposition method of TOC by a general ultraviolet oxidation apparatus, an ultraviolet lamp is used. However, although the ultraviolet lamp is very expensive, the ultraviolet intensity decreases with the lapse of the usage period. For example, replacement is required about once a year. Therefore, in the oxidative decomposition treatment of the TOC using the ultraviolet oxidation apparatus, it is a problem to reduce the running cost such as the replacement cost of the ultraviolet lamp and the energy consumption.

In order to increase the decomposition efficiency of TOC, for example, in Patent Document 1, oxygen gas is added to the water to be treated as a water treatment device that removes the TOC in the water to be treated using a low-pressure ultraviolet oxidation device. The thing which provided the dissolved oxygen concentration adjustment process to do is proposed. The low-pressure ultraviolet oxidizer is an oxidizer using a low-pressure ultraviolet lamp. Patent Document 2 proposes that a predetermined amount of hydrogen peroxide (H ₂ O ₂ ) is added to the water to be treated before the low-pressure ultraviolet oxidation apparatus.

By the way, in recent years, in order to cope with the depletion and deterioration of water resources, there is a strong demand for saving water even in semiconductor factories and the like that use a lot of ultrapure water. In order to save water, it is effective to collect and reuse the water once used. To increase the water recovery rate, for example, wastewater with a high TOC concentration after use at the point of use is treated. Furthermore, studies on techniques for collecting and processing are underway. Such a technique is generally called a wastewater treatment technique, a wastewater recovery treatment technique, or the like. In order to recover and reuse wastewater with a high TOC concentration as raw water for the production of ultrapure water, it is necessary to reduce the TOC concentration to a level that does not degrade the quality of the ultrapure water at the end without incurring energy costs. is there. As a technique for treating the water to be treated having a high TOC concentration, there is a technique in which an oxidant such as hydrogen peroxide or ozone (O ₃ ) is added to the water to be treated, and the TOC is oxidized and decomposed by ultraviolet irradiation. In this case, it is assumed that the TOC concentration in the water to be treated is on the order of mg / L, and since the water to be treated originally containing a large amount of various impurities is targeted, for example, an open reaction vessel Is used for UV irradiation. As an ultraviolet ray source, a low-pressure ultraviolet lamp or a high-pressure ultraviolet lamp that generates a wavelength of 254 nm is generally used.

JP 2011-167633 A JP 2011-218248 A Japanese Patent Laid-Open No. 5-305297

In order to decompose and remove the TOC component in the water to be treated, in general, a process of oxidizing the TOC component by irradiating with ultraviolet rays is performed, but when considering from the viewpoint of how much TOC in the water to be treated has been removed, Technology is not necessarily optimized. In particular, as shown in Patent Document 2, in the case of performing the ultraviolet oxidation treatment after adding hydrogen peroxide, it cannot be said that sufficient studies have been made on optimizing the addition amount of hydrogen peroxide. . Therefore, when trying to increase the TOC removal rate in the water to be treated, the amount of ultraviolet irradiation is excessively increased, the required power amount is increased, the energy cost is increased, and the apparatus scale is also increased. There is a problem.

An object of the present invention is to provide a water treatment method and apparatus capable of downsizing the apparatus, suppressing running costs including energy costs, and improving the decomposition efficiency of organic substances.

In the case where the organic substance in the water to be treated is decomposed by adding ultraviolet rays and irradiating with ultraviolet rays, the present inventors have obtained dissolved oxygen concentration and TOC removal rate after the ultraviolet oxidation treatment, and the amount of hydrogen peroxide added. The present invention was completed by finding a relationship that can optimally control the amount of hydrogen peroxide added. That is, the water treatment method of the present invention is a water treatment method for decomposing an organic substance contained in water to be treated, comprising a hydrogen peroxide addition stage for adding hydrogen peroxide to the water to be treated, and adding hydrogen peroxide. A step of irradiating the treated water with ultraviolet rays, and a step of measuring the dissolved oxygen concentration of the outlet water from the ultraviolet irradiation step, and adding hydrogen peroxide based on the measured dissolved oxygen concentration Control the amount of hydrogen peroxide added in the stage.

The water treatment apparatus of the present invention is a water treatment apparatus for decomposing organic matter contained in the water to be treated, wherein the hydrogen peroxide is added to the water to be treated, and the hydrogen peroxide is added. An ultraviolet irradiation device for irradiating the water to be treated with ultraviolet rays, a dissolved oxygen measuring means for measuring the dissolved oxygen concentration in the outlet water of the ultraviolet irradiation device, and hydrogen peroxide based on the dissolved oxygen concentration measured by the dissolved oxygen measuring means Control means for controlling the amount of hydrogen peroxide added in the adding device.

According to the present invention, the decomposition efficiency of the organic matter in the water to be treated can be improved and a high TOC removal rate can be achieved, whereby the apparatus can be downsized and the running cost can be reduced.

It is a figure which shows the basic composition of the water treatment apparatus based on this invention. It is a figure which shows another structural example of a water treatment apparatus. It is a figure which shows another structural example of a water treatment apparatus. It is a figure which shows another structural example of a water treatment apparatus. It is a figure which shows another structural example of a water treatment apparatus. It is a figure which shows another structural example of a water treatment apparatus. It is a figure which shows another structural example of a water treatment apparatus. It is a figure which shows the example of application of the water treatment apparatus based on this invention. It is a figure which shows the structure of the apparatus used in the Example.

Next, a preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a basic configuration of a water treatment apparatus according to the present invention. The water treatment apparatus shown in FIG. 1 is connected to a hydrogen peroxide addition apparatus 20 that adds hydrogen peroxide (H ₂ O ₂ ) to the water to be treated, and an outlet of the hydrogen peroxide addition apparatus 20, and hydrogen peroxide is added. An ultraviolet irradiation device 30 for irradiating the treated water with ultraviolet rays, a dissolved oxygen meter (DO meter) 41 which is a dissolved oxygen measuring means for measuring the dissolved oxygen concentration in the outlet water of the ultraviolet irradiation device 30, and a DO meter 41 And a control device 40 which is a control means for controlling the amount of H ₂ O ₂ added to the water to be treated based on the dissolved oxygen concentration measured in (1). The hydrogen peroxide addition device 20 includes a storage tank 21 for storing H ₂ O ₂ and a pulse control type pump 22 connected to the outlet of the storage tank 21, and a pulse from the pump 22 is generated by a signal from the control device 40. Controlled so that H ₂ O ₂ is mixed with the water to be treated. The control device 40 receives the measurement result of the dissolved oxygen from the DO meter 41, and based on this, sends a signal for controlling the pulse of the pump 22 in the hydrogen peroxide addition device 20 to the hydrogen peroxide addition device 20. Output.

As shown in the examples to be described later, when the present inventors perform ultraviolet oxidation treatment on water to be treated with H ₂ O ₂ added, the dissolved oxygen concentration in the water to be treated has an effect on the TOC removal rate. It has been found that there is a correlation between the concentration of dissolved oxygen after UV oxidation, the TOC removal rate, and the amount of H ₂ O ₂ added. In particular, adding H ₂ O ₂ is that the when the amount is small additive remains also the dissolved oxygen concentration after ultraviolet oxidation treatment irrespective of the amount of H ₂ O ₂ less, and the addition of H ₂ O ₂ It has been found that the TOC removal rate is not necessarily improved when the amount of dissolved oxygen concentration after the ultraviolet oxidation treatment exceeds a certain value when the amount is increased. Therefore, the control device 40 adds the hydrogen peroxide addition device 20 so that H ₂ O ₂ is added to the water to be treated in a range where the dissolved oxygen concentration in the outlet water of the ultraviolet irradiation device 30 does not exceed, for example, 0.1 mg / L. Is preferably controlled.

As the ultraviolet irradiation device 30, it is preferable to use an ultraviolet oxidation device that performs ultraviolet oxidation treatment by irradiating ultraviolet rays containing a component having a wavelength of 185 nm or less. In the water treatment device shown in FIG. 1, the outlet water from the ultraviolet irradiation device 30 is treated by the water treatment device and supplied to the outside.

In a conventional water treatment apparatus that performs ultraviolet irradiation treatment by adding H ₂ O ₂ , a sterilization lamp that emits ultraviolet light having a wavelength of 254 nm or a high-pressure mercury lamp is generally used as the ultraviolet irradiation apparatus for ultraviolet irradiation treatment. Yes. In addition, the system described in Patent Document 2 described above is a system for producing ultrapure water by a circulation purification process, and uses a low-pressure ultraviolet oxidizer that generates ultraviolet rays containing a component having a wavelength of 185 nm. Ultraviolet oxidation is performed by adding H ₂ O ₂ . Ultraviolet light having a wavelength of 185 nm is generally generated by a low-pressure mercury lamp, but the low-pressure mercury lamp also generates ultraviolet light having a wavelength of 254 nm. The ratio is about 1: 9 in intensity ratio, and the component having the wavelength of 254 nm has higher intensity. Ultraviolet rays having a wavelength of 185 nm have an advantage that organic substances can be directly decomposed although they are low in intensity. On the other hand, ultraviolet rays having a wavelength of 254 nm react with H ₂ O ₂ to generate hydroxyl radicals (.OH) to decompose organic substances. In the ultraviolet irradiation apparatus used in the water treatment apparatus according to the present invention, for example, a mercury lamp that generates ultraviolet rays having a wavelength of 185 nm and a wavelength of 254 nm is used as an ultraviolet ray source. It is also possible to use an LED (light emitting diode).

By the way, when the dissolved oxygen concentration of the water to be treated is high, if the dissolved oxygen concentration in the outlet water of the ultraviolet irradiation device 30 is set to be, for example, 0.1 mg / L or less, a sufficient amount of H ₂ O necessary for the decomposition of the organic matter. ₂ can not be added, as a result, sometimes TOC removal rate is not improved. In such a case, it is preferable to provide a deoxygenation device that reduces the dissolved oxygen concentration of the water to be treated before the hydrogen peroxide addition device 20. The water treatment apparatus shown in FIG. 2 uses an ultraviolet oxidation apparatus 31 that generates ultraviolet rays containing a component having a wavelength of 185 nm as the ultraviolet irradiation apparatus 30 that performs ultraviolet oxidation treatment in the water treatment apparatus shown in FIG. The deoxygenation device 10 is provided in the preceding stage of the hydrogen oxide addition device 20. As the deoxygenation device 10, any device that can remove oxygen (O ₂ ) dissolved in water can be used. For example, a vacuum degassing device, a membrane degassing device, and a nitrogen degassing device can be used. Either can be used. Vacuum deaerators, membrane deaerators, and nitrogen deaerators can reduce dissolved oxygen concentration in water and at the same time remove volatile organics, carbon dioxide, etc. in the gas phase and reduce their concentration in water This is preferable. As another deoxygenation device, a device that removes oxygen by adding hydrogen (H ₂ ) and then reacting oxygen with hydrogen using a palladium (Pd) catalyst to form water can also be used.

The dissolved oxygen concentration in water is about 7 to 8 mg / L when saturated at atmospheric pressure. Even if ultra-pure water with a low dissolved oxygen concentration is exposed to the atmosphere, oxygen immediately dissolves and the dissolved oxygen concentration increases. Therefore, generally, the dissolved oxygen concentration in the waste water discharged from various processes exceeds 1 mg / L, and in many cases, becomes a value close to the saturation amount under atmospheric pressure. According to the knowledge of the present inventors, when the dissolved oxygen concentration exceeded 1 mg / L, the improvement in the TOC removal rate was not necessarily observed even when H ₂ O ₂ was added and the ultraviolet oxidation treatment was performed. Therefore, in the water treatment apparatus according to the present invention, when the deoxygenation apparatus 10 is provided, it is preferable that the dissolved oxygen concentration in the outlet water of the deoxygenation apparatus 10 is 1 mg / L or less. Since dissolved oxygen absorbs ultraviolet rays, when the dissolved oxygen concentration is high, the amount of ultraviolet rays that should originally be used for the decomposition reaction of organic matter decreases, and organic matter decomposition becomes difficult to proceed. On the other hand, by removing dissolved oxygen to some extent, the influence of absorption of ultraviolet rays can be reduced. As a result, the ultraviolet rays efficiently react with the organic matter, and the TOC removal rate is improved. In addition, ultraviolet rays and H ₂ O ₂ react efficiently to generate hydroxyl radicals, whereby the hydroxyl radicals react with organic substances and the TOC removal rate is improved. Therefore, by setting the dissolved oxygen concentration of the outlet water of the deoxygenation device 10 to 1 mg / L or less, as a guideline, the effect of the present invention is further improved by setting it to 1/10 or less of the saturation amount under atmospheric pressure. It will be demonstrated remarkably. More preferably, the dissolved oxygen concentration in the outlet water of the deoxygenation apparatus 10 is 0.5 mg / L or less, and more preferably 0.1 mg / L or less. Although dissolved oxygen may be reduced to an extremely low concentration, for example, μg / L, even if highly deoxygenated to the order of μg / L, there is no significant difference in the obtained TOC removal performance. Considering the cost-effectiveness composed of the cost required for the deoxygenation treatment and the TOC removal rate, it is preferable that the dissolved oxygen concentration in the outlet water of the deoxygenation apparatus 10 is 0.05 mg / L or more and 1 mg / L or less.

FIG. 3 shows another configuration example of the water treatment apparatus according to the present invention. Although the water treatment apparatus based on this invention decomposes | disassembles the TOC component in to-be-processed water by ultraviolet oxidation treatment, and removes TOC, when the TOC density | concentration in to-be-processed water is high, the load of ultraviolet-ray oxidation treatment is large. Therefore, it is preferable to reduce the TOC of the water to be treated before the ultraviolet oxidation treatment, specifically, before adding H ₂ O ₂ . The water treatment apparatus shown in FIG. 3 is the same as the water treatment apparatus shown in FIG. 2 except that a reverse osmosis device 15 is provided upstream of the deoxygenation device 10. The treated water is first supplied to the reverse osmosis device 15 where the TOC is reduced, and then supplied to the deoxygenation device 10. As a result, in the water treatment apparatus shown in FIG. 3, the load of removing the TOC in the ultraviolet oxidation apparatus 31 is reduced. As the reverse osmosis device 15, it is preferable to use a multistage treatment apparatus in which reverse osmosis membranes are installed in multiple stages. By using reverse osmosis membranes provided in multiple stages, it is possible to further eliminate TOC and reduce the load of ultraviolet oxidation treatment.

As the reverse osmosis membrane provided in the reverse osmosis device 15, it is preferable to use a reverse osmosis membrane having a high TOC removal capability, such as a high rejection rate used for seawater desalination, for example. Specifically, the permeation flux per effective pressure of 1 MPa is 0.5 m ³ / m ² / d or less. Examples of the reverse osmosis membrane that can be used in the water treatment apparatus according to the present invention include, for example, SWC series membrane by Hydranautics, TM800 series membrane by Toray, SW30 series membrane by DOW, HR by Kurita -RO series membranes. More specifically, as a reverse osmosis membrane, SWC5MAX (0.32 m ³ / m ² / d) manufactured by Hydranautics, SWC6MAX (0.43 m ³ / m ² / d) manufactured by Hydranautics, SW30ULE manufactured by DOW (0.39 m ³ / m ² / d), SW30HRLE (0.25 m ³ / m ² / d) manufactured by DOW, TM820V (0.32 m ³ / m ² / d) manufactured by Toray, manufactured by Toray TM820K (0.20 m ³ / m ² / d), Kurita Kogyo HR-RO (0.36 m ³ / m ² / d), and the like can be used. The numerical value parenthesized here is the permeation flux per effective pressure of 1 MPa in the reverse osmosis membrane.

The permeation flux is the permeated water amount divided by the membrane area. The “effective pressure” is an effective pressure acting on the membrane obtained by subtracting the osmotic pressure difference and the secondary side pressure from the average operating pressure described in JIS K3802: 2015 “Membrane terminology”. The average operating pressure is an average value of the pressure of the membrane supply water on the primary side of the membrane, that is, the operating pressure, and the pressure of the concentrated water, that is, the concentrated water outlet pressure, and is expressed by the following equation.

Average operating pressure = (Operating pressure + Condensate outlet pressure) / 2
The permeation flux per effective pressure of 1 MPa can be calculated from information described in the catalog of the membrane manufacturer, for example, the amount of permeated water, membrane area, recovery rate during evaluation, NaCl concentration, and the like. In addition, when one or more pressure vessels are loaded with a plurality of membranes having the same permeation flux, information such as the average operating pressure / secondary pressure of the pressure vessel, raw water quality, amount of permeated water, number of membranes, etc. Thus, the permeation flux of the loaded membrane can be calculated.

The membrane shape of the reverse osmosis membrane is not particularly limited, and examples thereof include an annular type, a flat membrane type, a spiral type, and a hollow fiber type. The spiral type includes a 4-inch type, an 8-inch type, Any of a 16-inch type or the like may be used.

In the water treatment apparatus shown in FIG. 3, the reverse osmosis device 15 is provided in the preceding stage of the deoxygenation device 10, but the position of the reverse osmosis device 15 for reducing the load of the ultraviolet oxidation treatment is located at the hydrogen peroxide addition device. Any of the 20 entrance sides may be used. Therefore, as shown in FIG. 4, the positions of the deoxygenation device 10 and the reverse osmosis device 15 are switched, and the treated water is first supplied to the deoxygenation device 10, and the outlet water of the deoxygenation device 10 passes through the reverse osmosis device 15. You may make it supply to the hydrogen peroxide addition apparatus 20. FIG. Furthermore, it is effective to provide the reverse osmosis device 15 even in a configuration in which the deoxygenation device 10 is not provided. In FIG. 5, the reverse osmosis device 15 is connected to the inlet of the hydrogen peroxide addition device 20 without providing the deoxygenation device 10, and the water to be treated whose TOC is reduced by the reverse osmosis device 15 is supplied to the hydrogen peroxide addition device 20. 1 shows a water treatment device to be supplied.

In the present invention, an ion exchange device may be provided on the exit side of the ultraviolet irradiation device to remove ionic impurities derived from decomposition products and water to be treated in the ultraviolet oxidation treatment. In the water treatment device shown in FIG. 6, an ion exchange device 35 to which outlet water of the ultraviolet oxidation device 31 is supplied is further provided to the water treatment device shown in FIG. 3. The outlet water from the ion exchange device 35 is treated with this water treatment device and is supplied to the outside.

The organic matter contained in the water to be treated includes substances that are ionic from the stage prior to being subjected to the ultraviolet oxidation treatment, but various organic acids, carbonic acid, etc. are obtained by the ultraviolet oxidation treatment performed by adding H ₂ O _2. Ionic substances are produced. The ion exchange device 35 removes these ionic substances. The ion exchange device 35 is composed of, for example, an ion exchange tower filled with an ion exchange resin. When the concentration of ionic impurities in the outlet water of the ultraviolet oxidizer 31 is high, it is preferable to use a regenerative ion exchanger. Since the organic acid and carbonic acid which are reaction products by the ultraviolet oxidation treatment take the form of anions in water, the ion exchange resin used in the ion exchange device 35 is at least an anion exchange resin. Since organic acids and carbonic acids are weak acids, it is preferable to use a strongly basic anion exchange resin as an anion exchange resin in order to remove them reliably. Furthermore, by using a mixed resin of an anion exchange resin and a cation exchange resin as an ion exchange resin, or using a mixed bed type ion exchange tower filled with a mixed resin as an ion exchange tower, a high-purity treatment is performed. You can get water.

Incidentally, excessive H ₂ O ₂ contained in the outlet water of the ultraviolet oxidizer 31 may oxidize and degrade the ion exchange resin in the ion exchanger 35. Therefore, it is preferable to remove H ₂ O ₂ before the ion exchange device 35. The water treatment apparatus shown in FIG. 7 is provided with a hydrogen peroxide decomposition apparatus 37 for decomposing H ₂ O _{2 in} water between the ultraviolet oxidation apparatus 31 and the ion exchange apparatus 35 in the water treatment apparatus shown in FIG. Is. Hydrogen peroxide is removed from the outlet water of the ultraviolet oxidation device 31 through the hydrogen peroxide decomposition device 37, and then supplied to the ion exchange device 35. The hydrogen peroxide decomposition device 35 is, for example, a decomposition tower filled with activated carbon. It is preferable to use activated carbon as one that can effectively decompose H ₂ O ₂ at low cost. Alternatively, the hydrogen peroxide decomposition device 37 can decompose H ₂ O ₂ using a palladium (Pd) catalyst.

As mentioned above, although various structural examples were demonstrated to the water treatment apparatus based on this invention, these water treatment apparatuses, for example, have a TOC concentration of 0.1 mg / L or more and a dissolved oxygen concentration exceeding 1 mg / L. It can be used for decomposing organic matter in the treated water. According to the present invention, as will become clear from Examples described later, water to be treated containing TOC in the order of mg / L can be treated with a high TOC removal rate.

In the present invention, the water to be treated is derived from, for example, process waste water. The water treatment method of the present invention is used to collect and treat process wastewater, particularly wastewater discharged from a process using ultrapure water such as a semiconductor manufacturing process. The water treated by the water treatment method of the present invention can be used as raw water for producing ultrapure water. Therefore, the water treatment method of the present invention can be used to collect and treat waste water from the process of using ultrapure water and generate ultrapure water for circulation reuse.

FIG. 8 shows an application example of the water treatment apparatus according to the present invention. The water treatment device 81 according to the present invention uses recovered water collected from the ultrapure water use process 83, which is a process of using ultrapure water, as treated water, and generates recovered water with reduced organic matter by treating this water. . The ultrapure water used in the ultrapure water use process 83 is produced by the ultrapure water production apparatus 82 to which the primary pure water is supplied. The recovered water from which the organic substances from the water treatment apparatus 81 are reduced is the primary pure water. And supplied to the ultrapure water production apparatus 82. In the system shown in FIG. 8, the ultrapure water is recovered and reused through the water treatment device 81, and the primary pure water is consumed by the ultrapure water that is consumed in the ultrapure water use process 83 and cannot be recovered. Can be supplied to the ultrapure water production apparatus 82, so that significant water saving can be realized.

Next, the present invention will be described in more detail by explaining the results of experiments conducted by the present inventors in order to complete the present invention.

[Experimental Example 1]
An apparatus having the configuration shown in FIG. 7 was assembled. In this apparatus, after performing deoxygenation treatment by deaeration on pure water, isopropyl alcohol (CH ₃ CH (OH) CH ₃ ; IPA) is added, H ₂ O ₂ is further added, and IPA is added. And H ₂ O ₂ are added to the water. The pure water used here had a resistivity of 1 MΩ · cm or more, a TOC of 3 μg / L or less, a dissolved oxygen concentration of 7.8 mg / L, and a H ₂ O ₂ concentration of 1 μg / L or less. This device uses pure water containing IPA as an organic substance (TOC component) as water to be treated, and decomposes the organic matter contained in the water to be treated. Deoxygenation treatment is performed by membrane deaeration before adding IPA. Can be said to be a treatment for reducing the dissolved oxygen concentration of the water to be treated. In some membrane degassing given that the IPA in water is generally not removed by the apparatus shown in FIG. 9, by supplying the water to be treated containing the IPA to deoxygenated carrying out deoxygenation process, then H ₂ O ₂ The same result as that obtained when the ultraviolet oxidation treatment is performed after the addition is obtained.

In the apparatus shown in FIG. 7, pure water is supplied to the membrane deaeration module 11 which is a deoxygenation apparatus. As the membrane degassing module 11, “Lixel G284” manufactured by Celgard was used, and the gas phase side of the membrane degassing module 11 was depressurized by the pump 12, and the degassing treatment was performed so that the dissolved oxygen concentration became a predetermined concentration. A predetermined amount of IPA was added as a TOC component through the storage tank 51 and the pump 52 to the water having passed through the membrane degassing module 11 and having a reduced dissolved oxygen concentration. Thereby, the to-be-processed water with which dissolved oxygen concentration was reduced produced | generated. Further, a predetermined amount of H ₂ O ₂ was added to the water to be treated via the storage tank 21 and the pump 22. A part of the water to be treated to which H ₂ O ₂ was added was branched, and the dissolved oxygen concentration and the TOC concentration were measured online with a dissolved oxygen meter (DO meter) 56 and a TOC meter 57, respectively. A DO-30A manufactured by TOA Electronics was used as the DO meter 56, and a SIEVERS 900 TOC meter manufactured by Seaverse was used as the TOC meter 57. The dissolved oxygen concentration in the DO meter 56 is the dissolved oxygen concentration in the outlet water of the membrane degassing module 11, that is, the dissolved oxygen concentration at the inlet of the ultraviolet oxidizer 31. The TOC measurement value TOC0 at the TOC meter 57 is the TOC concentration of the water to be treated.

Of the water to be treated to which H ₂ O ₂ was added, the water that was not branched was supplied to the ultraviolet oxidizer 31. JPW-2 manufactured by Nippon Photo Science Co., Ltd. is used as the ultraviolet oxidizer 31, and the ultraviolet oxidizer 31 is a low-pressure ultraviolet lamp that generates both light of wavelength 254 nm and light of wavelength 185 nm. Four 165W ultraviolet lamps AZ-9000W (Science) were arranged. The dissolved oxygen concentration in the outlet water of the ultraviolet oxidizer 31 is measured by the DO meter 41, a part of the outlet water of the ultraviolet oxidizer 31 is branched and passed through the ion exchanger 35, and the outlet from the ion exchanger 35 The TOC concentration TOC1 of water, that is, the TOC concentration TOC1 of the treated water in this water treatment apparatus was measured. As the DO meter 41, DO-30A manufactured by TOA Electronics was used, and as the TOC meter 58, a SIEVERS900 type TOC meter manufactured by Seaverse was used.

As the ion exchange device 35, a mixed bed type ion exchange device was used. The mixed bed type ion exchange apparatus has a cylindrical container made of acrylic resin (inner diameter 25 mm, height 1000 mm), and 300 mL of mixed bed ion exchange resin (EG-5A: manufactured by Organo Corporation) is filled in the container. It is. At this time, the height of the ion exchange resin layer was about 600 mm.

The TOC removal rate in this water treatment device is defined by the following calculation formula:
TOC removal rate (%) = ((TOC0−TOC1) / TOC0) × 100
As described above, TOC0 is the TOC concentration of the water to be treated, that is, the TOC concentration measured by the TOC meter 57, and TOC1 is measured by the TOC concentration of the treated water from the ion exchange device 35, that is, the TOC meter 58. TOC concentration.

The membrane deaeration module 11 adjusts the dissolved oxygen concentration at the inlet of the ultraviolet oxidizer 31 to 50 μg / L, and adjusts the amount of IPA added to adjust the TOC concentration of the water to be treated, that is, at the inlet of the ultraviolet oxidizer 31. In this state, the amount of H ₂ O ₂ was adjusted to 0 mg / L, 2.5 mg / L, 5.0 mg / L, and 10.0 mg / L. In each case, the TOC removal rate and the dissolved oxygen concentration at the outlet of the ultraviolet oxidizer 31, that is, the dissolved oxygen concentration measured by the DO meter 41 were measured. The results are shown in Table 1. The amount of water supplied to the ultraviolet oxidizer 31 was 800 L / hour. From this result, if the TOC removal rate is improved by adding H ₂ O ₂ , and if the TOC concentration of the liquid to be treated and the dissolved oxygen concentration at the inlet of the ultraviolet oxidizer 31 are constant, H ₂ O _{On the other hand} , it was found that when ₂ was added too much, the TOC removal rate was lowered and the dissolved oxygen concentration at the outlet of the ultraviolet oxidizer 31 was increased. From this, it can be seen that the amount of H ₂ O ₂ added can be optimally controlled by measuring the dissolved oxygen concentration at the outlet of the ultraviolet oxidizer 31.

Separately, the membrane deaeration module 11 is bypassed to adjust the dissolved oxygen concentration to 7.8 mg / L, the H ₂ O ₂ addition amount is set to 0 mg / L, and the TOC removal rate and the ultraviolet light are adjusted. The dissolved oxygen concentration at the outlet of the oxidizer 31 was measured. The results are also shown in Table 1. Since the TOC removal rate in this case was 82%, the TOC removal rate was reduced by reducing the dissolved oxygen concentration in the treated water and irradiating the treated water added with H ₂ O ₂ with ultraviolet rays. It turns out that it improves.

[Experiment 2]
Same as Experimental Example 1 except that the TOC concentration of the water to be treated, that is, the TOC concentration at the inlet of the ultraviolet oxidizer 31, was 1000 μg / L, and the H ₂ O ₂ addition amount was 20.0 mg / L. The experiment was conducted under conditions. The results are shown in Table 2. From these results, it was found that the TOC removal rate was improved by reducing the dissolved oxygen concentration in the water to be treated and adding H ₂ O ₂ .

Separately, by adjusting the dissolved oxygen concentration to 7.8 mg / L by bypassing the membrane degassing module 11, the addition amount of H ₂ O ₂ is set to 0 mg / L and 2.5 mg / L. The TOC removal rate was measured. These results are also shown in Table 2. Bypassing the membrane deaeration module 11 means that the dissolved oxygen concentration is not reduced and the saturated amount at atmospheric pressure is maintained, but when the dissolved oxygen concentration of the liquid to be treated is high as described above. It was found that even when H ₂ O ₂ was added, the TOC removal rate in the ultraviolet oxidation treatment was not improved.

[Experiment 3]
The experiment was conducted except that the dissolved oxygen concentration at the entrance of the ultraviolet oxidizer 31 was 500 μg / L, and the H ₂ O ₂ addition amount was 0 mg / L, 1.5 mg / L, 2.5 mg / L, 5.0 mg / L. The experiment was performed under the same conditions as in Example 1. The results are shown in Table 3.

[Experimental Example 4]
The experiment was conducted except that the dissolved oxygen concentration at the inlet of the ultraviolet oxidizer 31 was 1000 μg / L, and the H ₂ O ₂ addition amount was 0 mg / L, 1.5 mg / L, 2.0 mg / L, and 2.5 mg / L. The experiment was performed under the same conditions as in Example 1. The results are shown in Table 4.

[Experimental Example 5]
The membrane degassing module 11 adjusts the dissolved oxygen concentration at the inlet of the ultraviolet oxidizer 31 to 50 μg / L, and adjusts the amount of IPA added to adjust the TOC concentration of the water to be treated (at the inlet of the ultraviolet oxidizer 31). The TOC concentration was set to 100 μg / L. In this state, the amount of H ₂ O ₂ added was adjusted to 0 mg / L, 0.2 mg / L, and 0.4 mg / L, and the TOC removal rate was measured in each case. The amount of water supplied to the ultraviolet oxidizer 31 was 2000 L / hour. In addition, it experimented on the conditions similar to Experimental example 1 about other than that. The results are shown in Table 5.

DESCRIPTION OF SYMBOLS 10 Deoxygenation apparatus 15 Reverse osmosis apparatus 20 Hydrogen peroxide addition apparatus 30 Ultraviolet irradiation apparatus 31 Ultraviolet oxidation apparatus 40

Control apparatus

41,56 Dissolved oxygen (DO) meter

Claims

A water treatment method for decomposing organic matter contained in water to be treated,
A hydrogen peroxide addition step of adding hydrogen peroxide to the treated water;
An ultraviolet irradiation step of irradiating the water to be treated with hydrogen peroxide with ultraviolet rays;
Measuring the dissolved oxygen concentration in the outlet water from the ultraviolet irradiation step;
And a water treatment method for controlling an addition amount of hydrogen peroxide in the hydrogen peroxide addition step based on the measured dissolved oxygen concentration.
The water treatment method according to claim 1, wherein the amount of hydrogen peroxide added is controlled so that the dissolved oxygen concentration in the outlet water from the ultraviolet irradiation stage is 0.1 mg / L or less.
The water treatment method according to claim 1 or 2, wherein in the ultraviolet irradiation step, ultraviolet rays containing a component having a wavelength of 185 nm or less are irradiated.
The water treatment method according to any one of claims 1 to 3, further comprising a step of reducing organic substances contained in the water to be treated by reverse osmosis treatment before the hydrogen peroxide addition step.
The water treatment method according to claim 4, wherein the reverse osmosis membrane used in the reverse osmosis treatment has a permeation flux per effective pressure of 1 MPa of 0.5 m 3 / m 2 / d or less.
The water to be treated before being treated by the water treatment method has a total organic carbon concentration of 0.1 mg / L or more and a dissolved oxygen concentration of more than 1 mg / L. The water treatment method according to item.
The water treatment method according to any one of claims 1 to 6, wherein the water to be treated is derived from process wastewater.
The process wastewater is water discharged from a process using ultrapure water, and the water treated by the water treatment method is used as raw water for generating ultrapure water used in the process. Item 8. The water treatment method according to Item 7.
A water treatment apparatus for decomposing organic matter contained in water to be treated,
A hydrogen peroxide addition device for adding hydrogen peroxide to the treated water;
An ultraviolet irradiation device for irradiating the water to which the hydrogen peroxide is added with ultraviolet rays;
Dissolved oxygen measuring means for measuring the dissolved oxygen concentration of the outlet water of the ultraviolet irradiation device;
Control means for controlling the amount of hydrogen peroxide added in the hydrogen peroxide addition device based on the dissolved oxygen concentration measured by the dissolved oxygen measuring means;
A water treatment device.
The water treatment apparatus according to claim 9, wherein the control means controls the amount of hydrogen peroxide added so that the dissolved oxygen concentration in the outlet water from the ultraviolet irradiation stage is 0.1 mg / L or less.
The water treatment apparatus according to claim 9 or 10, wherein the ultraviolet irradiation apparatus is an ultraviolet oxidation apparatus that irradiates ultraviolet rays including a component having a wavelength of 185 nm or less.
The water treatment device according to any one of claims 9 to 11, further comprising a reverse osmosis device that has a reverse osmosis membrane and reduces organic substances contained in the water to be treated on an inlet side of the hydrogen peroxide addition device.
The water treatment apparatus according to claim 12, wherein the reverse osmosis membrane has a permeation flux per effective pressure of 1 MPa of 0.5 m 3 / m 2 / d or less.
The to-be-treated water supplied to the water treatment device has a total organic carbon concentration of 0.1 mg / L or more and a dissolved oxygen concentration of more than 1 mg / L, according to any one of claims 9 to 13. Water treatment equipment.