TW201821371A - Water treatment method and apparatus - Google Patents

Abstract

The present invention provides a water treatment apparatus for decomposing an organic matter contained in the water to be treated. In order to improve decomposition efficiency of the organic matter and achieve a high TOC removal rate, the water treatment apparatus comprises a hydrogen peroxide addition device for adding hydrogen peroxide to the water to be treated, an ultraviolet irradiation device for irradiating ultraviolet to the water to be treated with hydrogen peroxide added, a dissolved oxygen measuring means for measuring dissolved oxygen concentration of outlet water for the ultraviolet irradiation device, and a controlling means for controlling the addition amount of hydrogen peroxide based on dissolved oxygen concentration measured by the dissolved oxygen measuring means.

Description

Water treatment method and water treatment device

The present invention relates to a water treatment method and device for decomposing and treating organic matter contained in water to be treated as water to be treated.

Conventionally, pure water, such as ultrapure water, which has been highly removed from organic substances, ionic components, particulates, and bacteria, has been used as washing water used in the manufacturing steps of semiconductor devices and the manufacturing steps of liquid crystal display devices. In particular, when manufacturing electronic parts including semiconductor devices, a large amount of pure water is used in the washing step, and the water quality requirements are also increasing. For pure water used in washing steps of electronic component manufacturing, etc., in order to prevent organic matter contained in the pure water from being carbonized in a subsequent heat treatment step and causing poor insulation, a total organic carbon (one of the water quality management items) is required ( TOC; Total Organic Carbon) concentration is extremely low.

With the increasing demand for pure water quality, various methods have been studied in recent years for decomposing and removing trace organic substances (TOC components) contained in pure water. A representative example of such a method is a step of decomposing and removing organic matter by ultraviolet oxidation.

In general, when organic matter is decomposed and removed by ultraviolet oxidation treatment, for example, an ultraviolet oxidation device having a reaction tank made of stainless steel and a tubular ultraviolet lamp installed in the reaction tank is used. The treated water is irradiated with ultraviolet rays. As the ultraviolet lamp, for example, a low-pressure ultraviolet lamp that generates ultraviolet rays having respective wavelengths of 254 nm and 185 nm is used. When the treated water is irradiated with ultraviolet rays having a wavelength of 185 nm, oxide species such as hydroxyl radicals (･ OH) are generated in the treated water. Based on the oxidizing ability of the oxide species, trace organic substances in the treated water are decomposed into carbon dioxide and organic acids. In this way, the treated water obtained by subjecting the treated water to ultraviolet oxidation treatment is sent to an ion exchange device arranged at a subsequent stage to remove carbon dioxide and organic acids.

However, in general, the oxidation decomposition method of TOC using an ultraviolet oxidizing device uses an ultraviolet lamp, which is very expensive. However, as the use period passes, the intensity of ultraviolet rays will still decrease, so it needs to be replaced about once a year, for example. Therefore, the oxidation decomposition treatment of TOC using an ultraviolet oxidizing device has problems such as reduction of the replacement cost of the ultraviolet lamp and reduction of energy consumption, thereby suppressing the running cost.

In order to improve the decomposition efficiency of TOC, for example, in Patent Document 1, for a water treatment device that removes TOC in treated water using a low-pressure ultraviolet oxidation device, it is proposed that a device for adding oxygen to the treated water be provided in front of the low-pressure ultraviolet oxidation device. Steps for adjusting dissolved oxygen concentration. The low-pressure ultraviolet oxidation device is an oxidation device using a low-pressure ultraviolet lamp. In addition, Patent Document 2 proposes adding a predetermined amount of hydrogen peroxide (H ₂ O ₂ ) to the water to be treated before the low-pressure ultraviolet oxidation device.

In recent years, in order to cope with the depletion and deterioration of water resources, water saving is also strongly desired in semiconductor factories and the like that use ultrapure water in large quantities. In order to save water, it is effective to recycle and reuse the used water. In order to improve the water recovery rate, for example, some people have studied the use of treated high-TOC concentration discharged water after use at the end of use, and further recycled and treated technology. Such a technology is also generally referred to as a drainage water treatment technology, a drainage water recovery treatment technology, and the like. In order to recover and reuse the discharged water with high TOC concentration as the raw water to generate ultrapure water, it is necessary to reduce the TOC concentration to a level that does not consume energy costs and does not deteriorate the quality of the ultrapure water at the end. Techniques for treating high-TOC-concentrated treated water include a technique of adding oxidant such as hydrogen peroxide and ozone (O ₃ ) to the treated water, and oxidizing and decomposing TOC by ultraviolet irradiation. At this time, it is assumed that the TOC concentration in the treated water is on the order of mg / L, and that the treated water originally contains many various impurities is used as an object. Therefore, for example, an open-type reaction container is used for ultraviolet irradiation. In addition, as the ultraviolet source, a low-pressure ultraviolet lamp or a high-pressure ultraviolet lamp which generates a wavelength of 254 nm is generally used. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2011-167633 [Patent Document 2] Japanese Patent Application Publication No. 2011-218248 [Patent Document 3] Japanese Patent Application Publication No. 5-305297

[Problems to be Solved by the Invention] In order to decompose and remove TOC components in treated water, a process of irradiating ultraviolet rays to oxidize TOC components is generally performed, but from the viewpoint of how much TOC can be removed in the treated water, so far The technology is hard to say is optimized. In particular, when hydrogen peroxide is added as shown in Patent Document 2 and an ultraviolet oxidation treatment is performed, it is difficult to say that sufficient research has been conducted to optimize the amount of hydrogen peroxide added. Therefore, in order to increase the TOC removal rate in the water to be treated, there are problems in that the amount of ultraviolet radiation is excessively increased, the amount of electric power required is increased, the energy cost is increased, and the scale of the device is also increased.

The present invention aims to provide a water treatment method and device that can miniaturize the device, can reduce the running cost including energy cost, and can improve the decomposition efficiency of organic matter. [Means for solving problems]

The inventors of the present case have found that when hydrogen peroxide is added and ultraviolet irradiation is performed to decompose organic matter in the water to be treated, there is a correlation between the dissolved oxygen concentration after the ultraviolet oxidation treatment, the TOC removal rate, and the amount of hydrogen peroxide added. The present invention has been completed by finding out the relationship that can control the amount of hydrogen peroxide added to the optimum. That is, the water treatment method of the present invention is a water treatment method that decomposes organic matter contained in the water to be treated, and has a hydrogen peroxide addition stage in which hydrogen peroxide is added to the water to be treated, and hydrogen peroxide is added to the treated water. The ultraviolet irradiation stage in which the treated water is irradiated with ultraviolet rays, and the stage for measuring the dissolved oxygen concentration of the outlet water from the ultraviolet irradiation stage; based on the measured dissolved oxygen concentration, the amount of hydrogen peroxide added in the hydrogen peroxide addition stage is controlled.

The water treatment device of the present invention is a water treatment device that decomposes organic substances contained in the water to be treated, and includes: a hydrogen peroxide adding device for adding hydrogen peroxide to the treated water; and an ultraviolet irradiation device for adding peroxide The treated water of hydrogen is irradiated with ultraviolet rays; the dissolved oxygen measuring means measures the dissolved oxygen concentration of the outlet water of the ultraviolet irradiation device; and the control means controls the hydrogen peroxide in the hydrogen peroxide adding device based on the dissolved oxygen concentration measured in the dissolved oxygen measuring means. The amount of hydrogen peroxide added. [Effect of Invention]

According to the present invention, it is possible to improve the decomposition efficiency of the organic matter in the water to be treated, and to achieve a high TOC removal rate, thereby reducing the size of the device and reducing the running cost.

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 device shown in FIG. 1 includes a hydrogen peroxide adding device 20 for adding hydrogen peroxide (H ₂ O ₂ ) to the water to be treated, and an ultraviolet irradiation device 30 connected to the outlet of the hydrogen peroxide adding device 20. The treated water with hydrogen peroxide is irradiated with ultraviolet rays; it is a dissolved oxygen meter (DO meter) 41 for measuring dissolved oxygen, and measures the dissolved oxygen concentration at the outlet water of the ultraviolet irradiation device 30; it is a control device 40 for controlling means, according to the DO meter The measured dissolved oxygen concentration of 41 controls the added amount of H ₂ O _{2 in the} treated water. The hydrogen peroxide addition device 20 includes a storage tank 21 that stores H ₂ O ₂ and a pulse-controlled pump 22 connected to the outlet of the storage tank 21. The pulse of the pump 22 is controlled by a signal from the control device 40 so that H ₂ O ₂ is mixed with the treated water. The control device 40 receives the measurement result of the dissolved oxygen from the DO meter 41, and sends a signal for controlling the pulse of the pump 22 in the hydrogen peroxide addition device 20 based on the measurement result, and outputs the signal to the hydrogen peroxide addition device 20.

As shown in the examples described later, the inventors of the present invention found that when the treated water added with H ₂ O ₂ is subjected to ultraviolet oxidation treatment, the dissolved oxygen concentration in the treated water will affect the TOC removal rate, and the There is a correlation between the dissolved oxygen concentration and the TOC removal rate and the amount of H ₂ O ₂ added. Especially when the added amount of H ₂ O ₂ is small, the amount of H ₂ O ₂ is not added, and the dissolved oxygen concentration after the ultraviolet oxidation treatment is also small. When the added amount of H ₂ O ₂ is increased, the ultraviolet oxidation treatment is performed. When the dissolved oxygen concentration exceeds a certain value, the TOC removal rate does not necessarily increase. Therefore, it is preferable that the control device 40 controls the hydrogen peroxide addition device 20 to add H ₂ O ₂ to the water to be treated such that the dissolved oxygen concentration in the outlet water of the ultraviolet irradiation device 30 is, for example, not more than 0.1 mg / L.

The ultraviolet irradiation device 30 is preferably an ultraviolet oxidation device that irradiates ultraviolet rays containing a component having a wavelength of 185 nm or less to perform an ultraviolet oxidation treatment. In the water treatment apparatus shown in FIG. 1, the outlet water from the ultraviolet irradiation device 30 is water that is processed by the water treatment apparatus and supplied to the outside.

In a conventional water treatment apparatus that adds H ₂ O ₂ and performs ultraviolet irradiation treatment, as a ultraviolet irradiation device used for ultraviolet irradiation treatment, a germicidal lamp or a high-pressure mercury lamp that generates ultraviolet rays with a wavelength of 254 nm is generally used. The system described in Patent Document 2 above is a system for producing ultrapure water by cyclic refining. It uses a low-pressure ultraviolet oxidizing device that generates ultraviolet rays containing a component with a wavelength of 185 nm, and adds H ₂ O _{2 to the} water to be treated. UV-oxidation. Ultraviolet light with a wavelength of 185nm is generally generated by a low-pressure mercury lamp. Low-pressure mercury lamps also generate ultraviolet light with a wavelength of 254nm. The ratio is about 1: 9 in terms of intensity ratio, and the intensity of the component with a wavelength of 254 nm is large. Ultraviolet light with a wavelength of 185nm has low intensity, but has the advantage of directly decomposing organic matter. On the other hand, ultraviolet rays with a wavelength of 254 nm decompose organic substances by reacting with H ₂ O ₂ to generate hydroxyl radicals (･ OH). Based on the ultraviolet irradiation device used in the water treatment device of the present invention, as the ultraviolet source, for example, a mercury lamp that generates ultraviolet rays having both a wavelength of 185 nm and a wavelength of 254 nm can be used. LED (Light Emitting Diode).

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 to be, for example, 0.1 mg / L or less, a sufficient amount of H ₂ O ₂ required for the decomposition of organic substances cannot be added. As a result, there may be cases where the TOC removal rate cannot be improved. At this time, it is desirable to install a deoxidizing device in front of the hydrogen peroxide adding device 20 to reduce the dissolved oxygen concentration of the treated water. The water treatment device shown in FIG. 2 uses an ultraviolet oxidizing device 31 that generates ultraviolet rays containing a component having a wavelength of 185 nm as the ultraviolet irradiation device 30 that performs ultraviolet oxidation treatment in the water treatment device shown in FIG. 1 and adds hydrogen peroxide to the water treatment device. A deoxygenation device 10 is provided at the front of the device 20. The deoxidation device 10 may be any device that can remove oxygen (O ₂ ) dissolved in water, and any device can be used. For example, any of a vacuum degassing device, a membrane degassing device, and a nitrogen degassing device can be used. . Considering that the dissolved oxygen concentration in water can be reduced, and at the same time volatile organic compounds, carbonic acid, etc. can be removed into the gas phase, and the concentration equal to the water is reduced, the vacuum degassing device, membrane degassing device and nitrogen degassing device are more good. As another deoxidation device, it is also possible to use hydrogen (H ₂ ) and react with oxygen and hydrogen through palladium (Pd) catalyst to generate water to remove oxygen.

The dissolved oxygen concentration in water is about 7 to 8 mg / L when saturated at atmospheric pressure. Even ultrapure water with a low dissolved oxygen concentration will immediately dissolve oxygen when exposed to the atmosphere, and the dissolved oxygen concentration will rise. Therefore, in general, the dissolved oxygen concentration in the discharged water discharged from various processes exceeds 1 mg / L, and in most cases it is a value close to the saturation amount at atmospheric pressure. According to the findings of the inventors of the present invention, if the dissolved oxygen concentration exceeds 1 mg / L, even if H ₂ O _{2 is added} and an ultraviolet oxidation treatment is performed, improvement of the TOC removal rate may not be observed. Therefore, in the water treatment device according to the present invention, when the deoxidizing device 10 is provided, the dissolved oxygen concentration of the water at the outlet of the deoxidizing device 10 should be 1 mg / L or less. Since dissolved oxygen absorbs ultraviolet rays, when the concentration of dissolved oxygen is high, the amount of ultraviolet rays that should be used for the decomposition reaction of organic substances decreases, and the decomposition of organic substances becomes difficult. On the other hand, by removing dissolved oxygen to some extent, the influence of ultraviolet absorption can be reduced. As a result, ultraviolet rays efficiently react with organic substances to improve the TOC removal rate. In addition, by efficiently reacting ultraviolet rays with H ₂ O ₂ to generate hydroxyl radicals, the hydroxyl radicals react with organic substances to improve the TOC removal rate. Therefore, by setting the dissolved oxygen concentration of the outlet water of the deoxidizing device 10 to 1 mg / L or less, as a reference, by making it 1/10 or less of the saturation amount at atmospheric pressure, the effect of the present invention can be more significantly exerted. . More preferably, the dissolved oxygen concentration of the outlet water of the deoxidizing device 10 is 0.5 mg / L or less, and even more preferably 0.1 mg / L or less. It is also possible to reduce the dissolved oxygen to a very low concentration, for example to μg / L, but even if highly deoxidized to the order of μg / L, there will be no significant difference in the TOC removal performance obtained. Considering the cost of the deoxidation treatment and the cost of the TOC removal rate and the corresponding effects, the dissolved oxygen concentration of the outlet water of the deoxygenation device 10 should be 0.05 mg / L or more and 1 mg / L or less.

Fig. 3 shows another configuration example of a water treatment device according to the present invention. According to the water treatment device of the present invention, the TOC component in the treated water is decomposed and the TOC is removed by the ultraviolet oxidation treatment. However, when the TOC concentration in the treated water is high, the load of the ultraviolet oxidation treatment becomes too large. Before the ultraviolet oxidation treatment, specifically, it is preferable to reduce the TOC of the treated water before adding H ₂ O ₂ . The water treatment device shown in FIG. 3 is provided with a reverse osmosis device 15 in front of the deoxidation device 10 in the water treatment device shown in FIG. 2. The water to be treated is first supplied to the reverse osmosis device 15, the TOC is reduced in the reverse osmosis device 15, and then supplied to the deoxidation device 10. As a result, in the water treatment apparatus shown in FIG. 3, the load of TOC removal in the ultraviolet oxidation apparatus 31 is reduced. The reverse osmosis device 15 is preferably a multi-stage treatment device in which a reverse osmosis membrane is provided in multiple stages. By using a multi-stage reverse osmosis membrane, TOC can be further excluded, and the load of ultraviolet oxidation treatment can be reduced.

As the reverse osmosis membrane provided in the reverse osmosis device 15, a reverse osmosis membrane having a high TOC removal ability, such as a reverse osmosis membrane having a high blocking rate for seawater desalination and the like, is preferably used. Specifically, the characteristic is that the permeation flux per effective pressure of 1 MPa is 0.5 m ³ / m ² / d or less. Examples of reverse osmosis membranes that can be used in a water treatment device according to the present invention include: SWC series membranes from Hydronautics, TM800 series membranes from Toray, SW30 series membranes from Dow, and HR- RO series film. More specifically, as the reverse osmosis membrane, SWC5MAX (0.32m ³ / m ² / d) manufactured by Hydronautics, SWC6MAX (0.43m ³ / m ² / d) manufactured by Hydronautics, and SW30ULE (0.39m manufactured by DOW) can be used. ³ / m ² / d), SW30HRLE (0.25m ³ / m ² / d) by Dow, TM820V (0.32m ³ / m ² / d) by Toray, TM820K (0.20m by Toray) ³ / m ² / d), HR-RO (0.36m ³ / m ² / d) manufactured by Kurita Industry Co., Ltd., and the like. Here, the numerical value in parentheses is the permeation flux per 1 MPa effective pressure of the reverse osmosis membrane.

In addition, the permeate flux is obtained by dividing the permeate amount by the membrane area. "Effective pressure" is the effective pressure acting on the membrane obtained by subtracting the osmotic pressure difference and the downstream pressure from the average operating pressure as described in "Membrane Terms" in JIS K3802: 2015. In addition, the average operating pressure is the average of the pressure of the membrane supply water on the upstream side of the membrane, that is, the operating pressure and the pressure of the concentrated water, that is, the outlet pressure of the concentrated water, and is expressed by the following formula. Average operating pressure = (operating pressure + concentrated water outlet pressure) / 2

The permeate flux per effective pressure of 1MPa can be calculated from the information recorded in the product catalog of the membrane manufacturer, such as the permeate volume, membrane area, recovery rate during evaluation, and NaCl concentration. When one or more pressure vessels are filled with multiple membranes with the same permeation flux, the filling can be calculated from the information such as the average operating pressure of the pressure vessel / downstream pressure, raw water quality, permeation volume, and the number of membranes. The permeation flux of the membrane.

The membrane shape of the reverse osmosis membrane is not particularly limited, and examples thereof include a ring type, a flat membrane type, a spiral type, and a hollow fiber type. The spiral type may be 4 inches, 8 inches, 16 inches, etc. Any of them.

In the water treatment device shown in FIG. 3, the reverse osmosis device 15 is provided in front of the deoxidation device 10, but the position of the reverse osmosis device 15 for reducing the load of ultraviolet oxidation treatment is provided in the hydrogen peroxide addition device 20. The entrance side can be any position. Therefore, as shown in FIG. 4, the positions of the deoxidizing device 10 and the reverse osmosis device 15 may be exchanged. The treated water is first supplied to the deoxidizing device 10, and the outlet water of the deoxidizing device 10 is supplied to the hydrogen peroxide addition through the reverse osmosis device 15.装置 20。 Device 20. Further, in a configuration in which the deoxidizing device 10 is not provided, it is also effective to provide a reverse osmosis device 15. FIG. 5 shows the following water treatment device: the deoxygenation device 10 is not provided, the inlet of the hydrogen peroxide addition device 20 is connected to the reverse osmosis device 15, and the treated water whose TOC is reduced by the reverse osmosis device 15 is supplied to the hydrogen peroxide addition device 20.

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

Organic matter contained in the treated water also contains ionic substances at a stage before being subjected to the ultraviolet oxidation treatment, and ultraviolet oxidation treatment by adding H ₂ O ₂ generates various ionic substances such as organic acids and carbonic acid. The ion-exchange device 35 removes this plasma substance. The ion exchange device 35 is configured by, for example, an ion exchange column filled with an ion exchange resin. When the concentration of ionic impurities in the outlet water of the ultraviolet oxidizing device 31 is large, a regeneration-type ion exchange device is preferably used. Organic acids and carbonic acid, which are reaction products produced by ultraviolet oxidation treatment, are in the form of anions in water, so the ion exchange resin used in the ion exchange device 35 is at least an anion exchange resin. Organic acids and carbonic acid are weak acids. Therefore, in order to remove them reliably, it is preferable to use a strong basic anion exchange resin. Further, by using a mixed resin of an anion exchange resin and a cation exchange resin as the ion exchange resin, or a mixed bed type ion exchange tower filled with the mixed resin as the ion exchange tower, high-purity treated water can be obtained.

Excess H ₂ O ₂ contained in the outlet water of the ultraviolet oxidation device 31 may cause the ion exchange resin in the ion exchange device 35 to oxidize and deteriorate. Therefore, it is suitable to remove H ₂ O _{2 at the} front stage of the ion exchange device 35. The water treatment device shown in FIG. 7 is a hydrogen peroxide decomposition device 37 that decomposes H ₂ O _{2 in} water between the ultraviolet oxidation device 31 and the ion exchange device 35 in the water treatment device shown in FIG. 6. The water at the outlet of the ultraviolet oxidizing device 31 passes through the hydrogen peroxide decomposition device 37 to remove hydrogen peroxide, and is then supplied to the ion exchange device 35. The hydrogen peroxide decomposition device 35 is, for example, a decomposition tower filled with activated carbon. For those that can efficiently decompose H ₂ O ₂ at low cost, activated carbon is preferably used. Alternatively, H ₂ O _{2 may} be decomposed in a hydrogen peroxide decomposition device 37 using a palladium (Pd) catalyst.

In the foregoing, various configuration examples of the water treatment device according to the present invention have been described. Such water treatment devices can be used, for example, in treated water having a TOC concentration of 0.1 mg / L or more and a dissolved oxygen concentration of more than 1 mg / L. Organic matter is decomposed. As can be seen from the examples described later, according to the present invention, to-be-treated water containing TOC in the order of mg / L can be treated with a high TOC removal rate.

The treated water in the present invention is, for example, a person who discharges water from a process. The water treatment method of the present invention can be used for recovering and treating discharged water from a process, and can be particularly used for recovering and treating discharged water discharged from a process using ultrapure water such as a semiconductor manufacturing step. The water treated by the water treatment method of the present invention can be used as raw water for generating ultrapure water. Therefore, the water treatment method of the present invention can be used to recover, treat, and reuse the discharged water from a process using ultrapure water to generate ultrapure water.

FIG. 8 shows an application example of the water treatment device according to the present invention. According to the water treatment device 81 of the present invention, the recovered water recovered from the ultrapure water use process 83, which is a process using ultrapure water, is treated as the water to be treated, and this is used to generate recovered water with reduced organic matter. The ultrapure water used in the ultrapure water production process 83 is produced by the ultrapure water manufacturing device 82 that supplies pure water once. The recycled water from the water treatment device 81 that reduces organic matter is mixed with the primary pure water and supplied. To ultra-pure water manufacturing device 82. In the system shown in FIG. 8, the ultra-pure water is recovered and reused by the water treatment device 81, and only one-time pure water of the amount of ultra-pure water consumed in the ultra-pure water use process 83 and cannot be recovered is supplied to the ultra-pure water. The pure water manufacturing device 82 is sufficient, and a large amount of water can be saved. [Example]

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

[Experimental Example 1] An apparatus having the configuration shown in Fig. 9 was assembled. This device performs deoxygenation treatment on pure water by membrane degassing, and then adds isopropanol (CH ₃ CH (OH) CH ₃ ; IPA), further adds H ₂ O ₂ , and adds IPA and H ₂ O ₂ water is subjected to ultraviolet oxidation treatment. In terms of the quality of the pure water used here, the electrical resistance is 1 MΩ ･ cm or more, the TOC is 3 μg / L or less, the dissolved oxygen concentration is 7.8 mg / L, and the H ₂ O ₂ concentration is 1 μg / L or less. This device uses pure water containing IPA as an organic substance (TOC component) as the water to be treated, and decomposes the organic matter contained in the water to be treated. The device is deoxidized by membrane degassing before IPA is added. It can be said that it is a treatment for reducing the dissolved oxygen concentration in the water to be treated. If it is considered that IPA in water cannot generally be removed by membrane degassing, the device shown in FIG. 9 can be used to supply the treated water containing IPA to the deoxidation treatment for deoxidation treatment, and then add H ₂ O ₂ and The same results were obtained when the ultraviolet oxidation treatment was performed.

In the apparatus shown in FIG. 9, pure water is supplied to the membrane degassing module 11 of the deoxidation system. "Liqui-Cel G284" manufactured by Celgard was used as the membrane degassing module 11. The gas phase side of the membrane degassing module 11 was decompressed by a pump 12, and degassing treatment was performed so that the dissolved oxygen concentration became a predetermined concentration. For the water having the dissolved oxygen concentration reduced by the membrane degassing module 11, a predetermined amount of IPA is added as a TOC component through the storage tank 51 and the pump 52. Thereby, to-be-processed water which reduced the dissolved oxygen concentration was produced. Further, a predetermined amount of H ₂ O _{2 is} added to the water to be treated by the storage tank 21 and the pump 22. Part of the treated water to which H ₂ O ₂ was added was shunted out, and the dissolved oxygen concentration and the TOC concentration thereof were measured online using a dissolved oxygen meter (DO meter) 56 and a TOC meter 57, respectively. The DO meter 56 uses DO-30A manufactured by TOA Electronics, and the TOC meter 57 uses a SIEVERS900 type TOC meter manufactured by Sievers. The dissolved oxygen concentration measured by 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 oxidation device 31. The TOC measurement value TOC0 measured by the TOC meter 57 is the TOC concentration of the treated water.

The water on the undivided side of the treated water to which H ₂ O ₂ is added is supplied to the ultraviolet oxidation device 31. The ultraviolet oxidizing device 31 uses JPW-2 manufactured by Japan Photoscience Corporation. In the ultraviolet oxidizing device 31, four low-pressure ultraviolet lamps (wavelength of 165W manufactured by Japan Science Corporation) are arranged to generate both light having a wavelength of 254 nm and light having a wavelength of 185 nm. AZ-9000W) as an ultraviolet lamp. The DO meter 41 was used to measure the dissolved oxygen concentration in the outlet water of the ultraviolet oxidizing device 31, and a part of the outlet water of the ultraviolet oxidizing device 31 was shunted out and passed to the ion exchange device 35. The TOC meter 58 was used to measure the The outlet water is the TOC concentration TOC1 of the treated water of the water treatment device. As DO meter 41, DO-30A manufactured by TOA Electronics was used, and as TOC meter 58, a SIEVERS900 type TOC meter manufactured by Sievers was used.

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

The TOC removal rate in the water treatment device is defined according to the following calculation formula: TOC removal rate (%) = ((TOC0-TOC1) / TOC0) × 100

As mentioned above, TOC0 is the TOC concentration of the treated water, that is, the TOC concentration measured by the TOC meter 57 and TOC1 is the TOC concentration of the treated water from the ion exchange device 35, that is, the TOC concentration measured by the TOC meter 58 .

Through the membrane degassing module 11, the dissolved oxygen concentration at the inlet of the ultraviolet oxidation device 31 is adjusted to 50 μg / L, and the amount of IPA added is adjusted to make the TOC concentration of the treated water, that is, at the ultraviolet oxidation device 31. The TOC concentration at the inlet was 500 μg / L. In this state, the addition 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. The TOC removal rate, The dissolved oxygen concentration at the outlet of the ultraviolet oxidation device 31 is the measurement of the dissolved oxygen concentration measured by the DO meter 41. The results are shown in Table 1. The amount of water supplied to the ultraviolet oxidation device 31 was 800 L / hour. From this result, it can be seen that by adding H ₂ O ₂ , the TOC removal rate is improved, and if the TOC concentration of the liquid to be treated and the dissolved oxygen concentration at the inlet of the ultraviolet oxidation device 31 are fixed, when H ₂ O ₂ is excessively added, On the contrary, the TOC removal rate decreases, and the dissolved oxygen concentration at the outlet of the ultraviolet oxidizing device 31 increases. From this, it can be seen that by measuring the dissolved oxygen concentration at the outlet of the ultraviolet oxidation device 31, the amount of H ₂ O ₂ added can be controlled to be optimal.

In addition, by disregarding the membrane degassing module 11 separately, the dissolved oxygen concentration was adjusted to 7.8 mg / L, and the added amount of H ₂ O ₂ was set to 0 mg / L. The TOC removal rate was measured, and the UV oxidation device 31 was measured. Dissolved oxygen concentration at the exit. The results are also shown in Table 1. The TOC removal rate at this time was 82%. From this, it can be seen that the TOC removal rate is improved by reducing the dissolved oxygen concentration in the treated water and irradiating ultraviolet rays to the treated water to which H ₂ O ₂ is added.

【Table 1】

[Experimental Example 2] In addition to the case where the TOC concentration of the treated water, that is, the TOC concentration at the entrance of the ultraviolet oxidation device 31 is set to 1000 μg / L, and the addition amount of H ₂ O _{2 is} 20.0 mg / L, The experiment was performed under the same conditions as in Experimental Example 1. The results are shown in Table 2. From these, the following results were also obtained: By reducing the dissolved oxygen concentration in the water to be treated and adding H ₂ O ₂ , the TOC removal rate was improved.

In addition, by disregarding the membrane degassing module 11 separately, the dissolved oxygen concentration was adjusted to 7.8 mg / L, and the added amounts of H ₂ O ₂ were set to 0 mg / L and 2.5 mg / L, and the TOC removal rate was measured. These results are also shown in Table 2. It can be seen that skipping the membrane degassing module 11 does not reduce the dissolved oxygen concentration and almost maintains the saturation amount at atmospheric pressure. However, even when the dissolved oxygen concentration of the treated liquid is high, even if H ₂ O _{2 is added} , The removal rate of TOC in the ultraviolet oxidation treatment will not be improved.

【Table 2】

[Experimental Example 3] The dissolved oxygen concentration at the inlet of the ultraviolet oxidation device 31 was set to 500 μg / L, and the amount of H ₂ O ₂ added was set to 0 mg / L, 1.5 mg / L, 2.5 mg / L, and 5.0 mg / L. Other than that, the experiment was performed under the same conditions as in Experimental Example 1. The results are shown in Table 3.

【table 3】

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

【Table 4】

[Experimental Example 5] The dissolved oxygen concentration at the inlet of the ultraviolet oxidation device 31 was adjusted by the membrane degassing module 11 to 50 μg / L, and the amount of added IPA was adjusted so that the TOC concentration of the treated water (in the ultraviolet oxidation device) The TOC concentration at the inlet of 31) was 100 μg / L. In this state, the addition amount of H ₂ O ₂ was adjusted to 0 mg / L, 0.2 mg / L, and 0.4 mg / L, and the TOC removal rate was measured for each case. The amount of water supplied to the ultraviolet oxidation device 31 was 2000 L / hour. Other than that, the experiment was performed under the same conditions as in Experimental Example 1. The results are shown in Table 5.

【table 5】

10‧‧‧Deoxygenation device

11‧‧‧ membrane degassing module

12, 22, 52‧‧‧ Pump

15‧‧‧ reverse osmosis device

20‧‧‧ Hydrogen peroxide adding device

21, 51‧‧‧ storage tank

30‧‧‧ ultraviolet irradiation device

31‧‧‧ultraviolet oxidation device

35‧‧‧ion exchange device

37‧‧‧Hydrogen peroxide decomposition device

40‧‧‧control device

41, 56‧‧‧ dissolved oxygen meter (DO meter)

57, 58‧‧‧TOC

81‧‧‧water treatment equipment

82‧‧‧Ultra-pure water manufacturing equipment

83‧‧‧Ultra-pure water production process

FIG. 1 is a diagram showing a basic configuration of a water treatment apparatus according to the present invention. FIG. 2 is a diagram showing another configuration example of a water treatment device. FIG. 3 is a view showing still another configuration example of the water treatment device. Fig. 4 is a diagram showing still another configuration example of the water treatment device. Fig. 5 is a view showing still another configuration example of the water treatment device. Fig. 6 is a view showing still another configuration example of the water treatment device. FIG. 7 is a view showing still another configuration example of the water treatment device. FIG. 8 is a diagram showing an application example of a water treatment device according to the present invention. [Fig. 9] A diagram showing the structure of a device used in the embodiment.

Claims (14)

A water treatment method for decomposing and treating organic matter contained in water to be treated, comprising: adding a hydrogen peroxide to the water to be treated; and adding hydrogen peroxide to the water to be treated to irradiate ultraviolet rays. An ultraviolet irradiation stage; and a stage for measuring the dissolved oxygen concentration of the outlet water from the ultraviolet irradiation stage; and based on the measured dissolved oxygen concentration, the amount of hydrogen peroxide added in the hydrogen peroxide addition stage is controlled. For example, the water treatment method according to item 1 of the patent application scope, wherein the amount of hydrogen peroxide added is controlled so that the dissolved oxygen concentration of the outlet water from the ultraviolet irradiation stage becomes 0.1 mg / L or less. For example, the water treatment method according to item 1 or 2 of the patent application scope, wherein in the ultraviolet irradiation stage, ultraviolet rays containing a component having a wavelength of 185 nm or less are irradiated. For example, before applying the water treatment method of item 1 or 2 of the patent scope, before the hydrogen peroxide addition stage, there is a stage of reducing the organic matter contained in the treated water by reverse osmosis treatment. For example, the water treatment method according to item 4 of the scope of patent application, wherein the permeation flux per 1 MPa effective pressure of the reverse osmosis membrane used in the reverse osmosis treatment is 0.5 m ³ / m ² / d or less. For example, the water treatment method of the first or second patent application scope, wherein the total organic carbon concentration of the treated water before the treatment using the water treatment method is 0.1 mg / L or more, and the dissolved oxygen concentration is more than 1 mg / L. For example, the water treatment method according to item 1 or 2 of the patent application scope, wherein the treated water comes from process wastewater. For example, the water treatment method of the seventh scope of the patent application, wherein the process discharge water is the water discharged from the process using ultrapure water, and the water treated by the water treatment method is used to generate the water used in the process. Use of raw water for pure water. A water treatment device for decomposing and treating organic matters contained in water to be treated, comprising: a hydrogen peroxide adding device for adding hydrogen peroxide to the water to be treated; an ultraviolet irradiation device for the hydrogen peroxide-added to be processed Water irradiates ultraviolet rays; dissolved oxygen measuring means for measuring the dissolved oxygen concentration of water at the outlet of the ultraviolet irradiation device; and control means for controlling the hydrogen peroxide in the hydrogen peroxide adding device based on the dissolved oxygen concentration measured in the dissolved oxygen measuring means. The amount of hydrogen oxide added. For example, the water treatment device of the ninth scope of the patent application, wherein the control means is to control the added amount of hydrogen peroxide so that the dissolved oxygen concentration of the water from the outlet of the ultraviolet irradiation device becomes 0.1 mg / L or less. For example, a water treatment device according to item 9 or 10 of the scope of application for a patent, wherein the ultraviolet irradiation device is an ultraviolet oxidation device that irradiates ultraviolet rays containing a component having a wavelength of 185 nm or less. For example, a water treatment device of the scope of application for a patent item 9 or 10 is provided with a reverse osmosis device having a reverse osmosis membrane on the inlet side of the hydrogen peroxide adding device and reducing organic matter contained in the water to be treated. For example, the water treatment device according to item 12 of the patent application scope, wherein the permeation flux per effective pressure of the reverse osmosis membrane is 0.5 m ³ / m ² / d or less. For example, the water treatment device of the scope of application for the item 9 or 10, wherein the total organic carbon concentration of the treated water supplied to the water treatment device is 0.1 mg / L or more, and the dissolved oxygen concentration exceeds 1 mg / L.