TWI732970B - 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 organic matter contained in the water to be treated, which is the water to be treated.

Conventionally, as washing water used in the manufacturing steps of semiconductor devices and liquid crystal display devices, pure water such as ultrapure water from which organic matter, ion components, particles, bacteria, and the like have been removed to a high degree has been used. Especially when manufacturing electronic parts including semiconductor devices, a large amount of pure water is used in the washing step, and the requirements for the water quality are also increasing. For the pure water used in the washing step of electronic parts manufacturing, in order to prevent the organic matter contained in the pure water from being carbonized in the subsequent heat treatment step and causing insulation failure, the total organic carbon ( TOC; Total Organic Carbon) concentration is extremely low.

With such a high demand for pure water quality, various methods have been studied in recent years to decompose and remove trace amounts of organic matter (TOC components) contained in pure water. As a representative of such a method, an organic matter decomposition and removal step by ultraviolet oxidation treatment is used.

Generally speaking, when the organic matter is decomposed and removed by ultraviolet oxidation treatment, for example, an ultraviolet oxidation device equipped with a reaction tank made of stainless steel and a tubular ultraviolet lamp installed in the reaction tank is used, and the water to be treated is introduced into the reaction tank. The treated water is irradiated with ultraviolet rays. As for 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 with a wavelength of 185nm, oxide species such as hydroxyl radicals (･OH) are generated in the treated water, and the trace organic matter in the treated water is decomposed into carbon dioxide and organic acid due to the oxidation ability of the oxide species. In this way, the treated water is subjected to ultraviolet ray oxidation treatment to obtain the treated water, and then sent to the ion exchange device arranged in the subsequent stage to remove carbon dioxide and organic acids.

However, the general oxidative decomposition method of TOC using ultraviolet oxidizers uses ultraviolet lamps, which are very expensive. However, the intensity of ultraviolet rays will still decrease as the period of use passes, so it needs to be replaced about once a year, for example. Therefore, the oxidative decomposition treatment of TOC using the ultraviolet oxidizer has problems such as the reduction of the replacement cost of the ultraviolet lamp and the reduction of energy consumption, such as the reduction of operating costs.

In order to improve the decomposition efficiency of TOC, for example, in Patent Document 1, regarding a water treatment device that uses a low-pressure ultraviolet oxidation device to remove TOC in the water to be treated, it is proposed to install a device that adds oxygen to the water to be treated before the low-pressure ultraviolet oxidation device. Those who adjust the concentration of dissolved oxygen. The low-pressure ultraviolet oxidizer is an oxidizer using low-pressure ultraviolet lamps. In addition, Patent Document 2 proposes to add a predetermined amount of hydrogen peroxide (H ₂ O ₂ ) to the water to be treated before the low-pressure ultraviolet oxidizer.

In recent years, in order to cope with the depletion and deterioration of water resources, there is also a strong desire to save water in semiconductor factories that use a large amount of ultrapure water. In order to save water, it is effective to recover and reuse the used water. In order to increase the water recovery rate, for example, it is studied to treat the discharged water with high TOC concentration after use at the end of use, and further recover and treat it. Technology. Such technology is generally also referred to as discharge water treatment technology, discharge water recovery treatment technology, etc. In order to recover and reuse the discharged water with high TOC concentration as raw water for generating ultrapure water, the TOC concentration needs to be reduced to a level that does not consume energy costs and does not deteriorate the quality of the ultrapure water at the end. The technology for treating water with high TOC concentration includes adding _{oxidants such as hydrogen peroxide and ozone (O 3} ) to the water to be treated, and oxidizing and decomposing TOC by ultraviolet irradiation. At this time, it is assumed that the TOC concentration of the water to be treated is on the order of mg/L, and the water to be treated originally contains many various impurities as the object, so for example, an open system reaction vessel is used for ultraviolet irradiation. In addition, as for the ultraviolet source, a low-pressure ultraviolet lamp or a high-pressure ultraviolet lamp that generates a wavelength of 254 nm is generally used. [Prior Art Document] [Patent Document]

[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

[Problem to be solved by the invention] In order to decompose and remove the TOC component in the water to be treated, generally irradiated with ultraviolet rays to oxidize the TOC component, but from the viewpoint of how much TOC can be removed from the water to be treated, so far The technology is hard to say is the most optimized. In particular, when hydrogen peroxide is added and the ultraviolet oxidation treatment is performed as shown in Patent Document 2, it is difficult to say that sufficient research has been conducted on the optimization of the amount of hydrogen peroxide added. Therefore, when an attempt is made to increase the TOC removal rate in the water to be treated, the amount of ultraviolet radiation is excessively increased, the amount of power required increases, the energy cost increases, and the scale of the device also increases.

The present invention aims to provide a water treatment method and device that can miniaturize the device, reduce operating costs including energy costs, and improve the decomposition efficiency of organic matter. [Means to solve the problem]

The inventors of this case found that when hydrogen peroxide is added and ultraviolet radiation is applied to decompose the 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 best. That is, the water treatment method of the present invention is a water treatment method that decomposes the organic matter contained in the water to be treated. It has a hydrogen peroxide addition stage in which hydrogen peroxide is added to the water to be treated. The treated water is irradiated with ultraviolet rays during the ultraviolet irradiation stage, and the stage of measuring the dissolved oxygen concentration of the outlet water from the ultraviolet irradiation stage; according to 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 and treats the organic matter contained in the water to be treated. It has: a hydrogen peroxide addition device to add hydrogen peroxide to the water to be treated; an ultraviolet irradiation device for the addition of peroxide The treated water of hydrogen is irradiated with ultraviolet rays; the dissolved oxygen measurement means measures the dissolved oxygen concentration in the outlet water of the ultraviolet irradiation device; and the control means controls the hydrogen peroxide addition device based on the dissolved oxygen concentration measured in the dissolved oxygen measurement means The amount of hydrogen peroxide added. [Effects of Invention]

According to the present invention, the decomposition efficiency of organic matter in the water to be treated can be improved, and a high TOC removal rate can be achieved, whereby the miniaturization of the device and the reduction of operating costs can be achieved.

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

Figure 1 shows the basic structure of a water treatment device based on the present invention. The water treatment device shown in Fig. 1 includes: a hydrogen peroxide addition device 20 for adding hydrogen peroxide (H ₂ O ₂ ) to the water to be treated; an ultraviolet irradiation device 30 connected to the outlet of the hydrogen peroxide addition device 20 for adding The treated water with hydrogen peroxide is irradiated with ultraviolet rays; the dissolved oxygen meter (DO meter) 41 is a means of measuring dissolved oxygen, which measures the dissolved oxygen concentration of the outlet water of the ultraviolet irradiation device 30; the control device 40 is a control means, according to the DO meter 41 The measured dissolved oxygen concentration controls the amount of H ₂ O ₂ added in the water to be treated. The hydrogen peroxide addition device 20 includes a storage _{tank 21 for storing H 2} O ₂ and a pulse control 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 to make 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, based on the measurement result, sends out a pulse signal for controlling the pump 22 in the hydrogen peroxide addition device 20, and outputs the signal to the hydrogen peroxide addition device 20.

As shown in the following examples, the inventors of the present case found that _{when the water to be treated with added H 2} O ₂ is subjected to ultraviolet oxidation treatment, the concentration of dissolved oxygen in the water to be treated will affect the TOC removal rate, and the effect after the ultraviolet oxidation treatment There is a correlation between the concentration of dissolved oxygen, the TOC removal rate and the amount of H ₂ O _{2 added.} Especially when _{the addition amount of H 2} O ₂ is small, regardless of _{the addition amount of H 2} O ₂ , the dissolved oxygen concentration after ultraviolet oxidation treatment is also small. When the addition amount of H ₂ O ₂ is increased, after ultraviolet oxidation treatment When the dissolved oxygen concentration exceeds a certain value, the TOC removal rate may not necessarily increase. _{Therefore, the control device 40 preferably controls the hydrogen peroxide addition device 20 to add H 2} O ₂ to the water to be treated so that the dissolved oxygen concentration in the outlet water of the ultraviolet irradiation device 30 does not exceed 0.1 mg/L, for example.

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

In the conventional water treatment device that adds H ₂ O ₂ and performs ultraviolet irradiation treatment, the ultraviolet irradiation device used for the ultraviolet irradiation treatment generally uses germicidal lamps and high-pressure mercury lamps that generate ultraviolet rays with a wavelength of 254 nm. In addition, the system described in the above-mentioned Patent Document 2 is a system for producing ultrapure water by cyclic purification treatment. It uses a low-pressure ultraviolet oxidizer that generates ultraviolet rays containing components with a wavelength of 185 nm, and adds H ₂ O _{2 to the water to be treated.} Carry out ultraviolet oxidation treatment. Ultraviolet rays with a wavelength of 185nm are generally generated by low-pressure mercury lamps, which also generate ultraviolet rays 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 254nm is greater. Ultraviolet light with a wavelength of 185nm is of low intensity, but it has the advantage of directly decomposing organic matter. On the other hand, ultraviolet light with a wavelength of 254nm _{decomposes organic matter 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 far as ultraviolet sources are concerned, for example, a mercury lamp that generates ultraviolet rays with a wavelength of 185nm and a wavelength of 254nm is used, and other ultraviolet sources, such as ultraviolet rays, may also 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, it is impossible to add a sufficient amount of H ₂ O _{2 for the decomposition of organic matter.} As a result, there will be cases where the TOC removal rate cannot be improved. At this time, it is advisable to install a deoxidizer that reduces the dissolved oxygen concentration of the water to be treated before the hydrogen peroxide adding device 20. The water treatment device shown in FIG. 2 uses an ultraviolet oxidation device 31 that generates ultraviolet rays containing components with 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 A deoxygenation device 10 is provided before the device 20. As for the deaerator 10, _{any device can be used as long as it can remove oxygen (O 2} ) dissolved in water, 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 the water can be reduced, and the volatile organic compounds, carbonic acid, etc. can be removed into the gas phase at the same time, and the viewpoint of reducing the concentration equal to the water concentration, the vacuum degassing device, membrane degassing device and nitrogen degassing device are more suitable. good. As another deoxygenation device, one that adds hydrogen (H ₂ ) and reacts oxygen and hydrogen with a palladium (Pd) catalyst to generate water to remove oxygen can also be used.

The dissolved oxygen concentration in the water is about 7-8mg/L when saturated at atmospheric pressure. Even the ultrapure water with low dissolved oxygen concentration, when exposed to the atmosphere, oxygen will dissolve immediately and the dissolved oxygen concentration will increase. Therefore, generally speaking, 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 under atmospheric pressure. According to the findings of the inventors of the present application, if the dissolved oxygen concentration exceeds 1 mg/L, even if H ₂ O _{2 is added} and the ultraviolet oxidation treatment is performed, the TOC removal rate may not necessarily be improved. Therefore, in the water treatment device based on the present invention, when the deoxidizer 10 is installed, it is preferable that the dissolved oxygen concentration of the outlet water of the deoxidizer 10 is 1 mg/L or less. Dissolved oxygen absorbs ultraviolet rays. Therefore, when the dissolved oxygen concentration is high, the amount of ultraviolet rays that should be used for the decomposition reaction of organic substances is reduced, and the decomposition of organic substances becomes difficult to proceed. On the other hand, by removing the dissolved oxygen to a certain extent, the influence of UV 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 making the dissolved oxygen concentration of the outlet water of the deoxidizer 10 less than 1 mg/L, as a reference, by making it less than 1/10 of the saturation under atmospheric pressure, the effect of the present invention can be more remarkably exhibited . More preferably, the dissolved oxygen concentration of the outlet water of the deoxidizer 10 is 0.5 mg/L or less, and particularly preferably 0.1 mg/L or less. The dissolved oxygen can also be reduced to a very low concentration, for example, to μg/L, but even if a high level of deoxygenation is performed to the order of μg/L, the obtained TOC removal performance will not have a significant difference. Considering the cost of the deoxidation treatment and the TOC removal rate and the corresponding effects, the dissolved oxygen concentration of the outlet water of the deoxidizer 10 should be 0.05 mg/L or more and 1 mg/L or less.

Fig. 3 shows another configuration example of the water treatment device based on the present invention. Based on the water treatment device of the present invention, the TOC component in the water to be treated is decomposed and removed by ultraviolet oxidation treatment. However, when the TOC concentration in the water to be treated is high, the load of the ultraviolet oxidation treatment becomes too large. Therefore, it is suitable Before the UV oxidation treatment, specifically, it is advisable to reduce the TOC of the water to be treated before _{adding H 2} O _2. The water treatment device shown in FIG. 3 is provided with a reverse osmosis device 15 before the deoxidizer 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 deoxidizer 10. As a result, in the water treatment device shown in FIG. 3, the load of TOC removal in the ultraviolet oxidation device 31 is reduced. The reverse osmosis device 15 is preferably a multi-stage treatment device in which a reverse osmosis membrane is arranged in multiple stages. By using reverse osmosis membranes arranged in multiple stages, TOC can be further eliminated and the load of ultraviolet oxidation treatment can be reduced.

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

In addition, the permeable flux is obtained by dividing the permeable water volume by the membrane area. "Effective pressure" is the effective pressure applied to the membrane by subtracting the average operating pressure from the osmotic pressure difference and the downstream pressure as described in JIS K3802:2015 "membrane terminology". In addition, the average operating pressure is the average value of the pressure of the membrane feed 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, expressed by the following formula. Average operating pressure = (operating pressure + concentrated water outlet pressure)/2

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

The membrane shape of the reverse osmosis membrane is not particularly limited. For example, ring type, flat membrane type, spiral type, hollow fiber type, etc. can be mentioned. The spiral type can 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 installed before the deoxidizer 10, but the position of the reverse osmosis device 15 for reducing the load of the ultraviolet oxidation treatment, as long as it is in the hydrogen peroxide addition device 20 The entrance side can be any position. Therefore, as shown in Figure 4, the position of the deoxidizer 10 and the reverse osmosis device 15 can be exchanged. The water to be treated is first supplied to the deoxidizer 10, and the outlet water of the deoxidizer 10 is supplied to the hydrogen peroxide addition via the reverse osmosis device 15.装置20。 Device 20. Furthermore, it is also effective to provide a reverse osmosis device 15 in a configuration where the deoxidizer 10 is not provided. Figure 5 shows the following water treatment device: without the deoxidizer 10, the inlet of the hydrogen peroxide adding device 20 is connected to the reverse osmosis device 15. The reverse osmosis device 15 reduces the TOC and the treated water is supplied to the hydrogen peroxide adding 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 can also be installed on the outlet side of the ultraviolet irradiation device. In the water treatment device shown in FIG. 6, the water treatment device shown in FIG. 3 is further provided with an ion exchange device 35 for supplying the outlet water 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 supplied to the outside.

The organic matter contained in the water to be treated also contains ionic substances in the stage before receiving the ultraviolet oxidation treatment, and _{the ultraviolet oxidation treatment by adding H 2} O ₂ will generate various organic acids and carbonic acid ionic substances. The ion exchange device 35 removes this plasmonic substance. The ion exchange device 35 is constituted by, for example, an ion exchange tower filled with ion exchange resin. When the concentration of ionic impurities in the outlet water of the ultraviolet oxidation device 31 is large, it is advisable to use a regenerative ion exchange device. The organic acid and carbonic acid, which are reaction products produced by the 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, so in order to remove them reliably, it is preferable to use a strongly basic anion exchange resin as an anion exchange resin. Furthermore, by using a mixed resin of anion exchange resin and cation exchange resin as the ion exchange resin, or using a mixed bed ion exchange tower filled with the mixed resin as the ion exchange tower, high-purity treated water can be obtained.

_{The excess H 2} O ₂ contained in the outlet water of the ultraviolet oxidation device 31 may oxidize and deteriorate the ion exchange resin in the ion exchange device 35. Therefore, it is preferable to remove H ₂ O _{2 in the} preceding stage of the ion exchange device 35. The water treatment device shown in FIG. 7 is provided with 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 outlet water of the ultraviolet oxidation device 31 passes through the hydrogen peroxide decomposition device 37 to remove hydrogen peroxide, and then is supplied to the ion exchange device 35. The hydrogen peroxide decomposition device 35 is, for example, a decomposition tower filled with activated carbon. _{As far as H 2} O ₂ can be effectively decomposed at low cost, activated carbon is suitable. Alternatively, in the hydrogen peroxide decomposition device 37, H ₂ O _{2 may} be decomposed by using a palladium (Pd) catalyst.

Above, various structural examples of the water treatment device based on the present invention have been described. These water treatment devices can be used, for example, to treat water with 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 following examples, according to the present invention, the treated water containing TOC on the order of mg/L can be treated with a high TOC removal rate.

The water to be treated in the present invention is, for example, the water discharged from the process. The water treatment method of the present invention can be used to recover and treat process discharge water, in particular, it can be used to recover and process discharge water discharged from processes that use ultrapure water such as semiconductor manufacturing steps. 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 recycle the discharged water from a process using ultrapure water to generate ultrapure water.

Fig. 8 shows an application example of the water treatment device based on the present invention. Based on 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 used as the water to be treated, and it is processed to generate recovered water with reduced organic matter. The ultrapure water used in the process 83 is produced by the ultrapure water producing device 82 that supplies pure water once. The recovered water from the water treatment device 81 with reduced organic matter is mixed with the pure water and supplied To ultrapure water manufacturing device 82. In the system shown in Figure 8, the ultrapure water is recycled and reused by the water treatment device 81, and only the primary pure water of the amount of ultrapure water that is consumed in the ultrapure water use process 83 and cannot be recovered is supplied to the ultrapure water. The pure water production device 82 is sufficient, and therefore, a significant water saving can be achieved. [Example]

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

[Experimental Example 1] The device with the configuration shown in Fig. 9 was assembled. This device deoxidizes pure water by membrane degassing, 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. As far as the water quality of the pure water used here is concerned, the resistance is 1MΩ･cm or more, the TOC is 3μg/L or less, the dissolved oxygen concentration is 7.8mg/L, and the H ₂ O ₂ concentration is 1μg/L or less. The device uses pure water containing IPA as the organic matter (TOC component) as the water to be treated, and decomposes the organic matter contained in the water to be treated. Deoxidation by membrane degassing before adding IPA, It can be said to be used to reduce the dissolved oxygen concentration of the water to be treated. Considering that the IPA in the water is generally not removed by membrane degassing, the device shown in Figure 9 can be used to obtain and supply the treated water containing IPA to the deoxygenation treatment for deoxygenation treatment, and then add H ₂ O ₂ and The same result was obtained when UV oxidation treatment was carried out.

In the device shown in Fig. 9, pure water is supplied to the membrane degassing module 11 of the deoxidizing device. Celgard "Liqui-Cel G284" is used as the membrane degassing module 11, the gas phase side of the membrane degassing module 11 is depressurized by the pump 12, and degassing treatment is applied to make the dissolved oxygen concentration a predetermined concentration. For the water whose dissolved oxygen concentration has been 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. This produces water to be treated with a reduced concentration of dissolved oxygen. Furthermore, to the water to be treated, a predetermined amount of H ₂ O _{2 is} added through the storage tank 21 and the pump 22. Part of the water to be treated with H ₂ O ₂ added is diverted, and the dissolved oxygen concentration and TOC concentration are measured on-line with a dissolved oxygen meter (DO meter) 56 and a TOC meter 57, respectively. The DO meter 56 used DO-30A manufactured by TOA Electronics, and the TOC meter 57 used a SIEVERS900 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 measured value TOC0 measured by the TOC meter 57 is the TOC concentration of the water to be treated.

The water on the undivided side of the water to be treated to which H ₂ O _{2 has been added is supplied to the ultraviolet oxidation device 31.} The ultraviolet oxidizer 31 uses JPW-2 made by Japan's PHOTOSCIENCE company. In the ultraviolet oxidizer 31, four low-pressure ultraviolet lamps (165W ultraviolet lamps made by Japan's PHOTOSCIENCE) are arranged to generate both light with a wavelength of 254nm and light with a wavelength of 185nm. AZ-9000W) as an ultraviolet lamp. The DO meter 41 is used to measure the dissolved oxygen concentration of the outlet water of the ultraviolet oxidation device 31, and at the same time, a part of the outlet water of the ultraviolet oxidation device 31 is shunted out and passed into the ion exchange device 35. The TOC meter 58 is used to measure the concentration of the water from the ion exchange device 35. The outlet water is the TOC concentration TOC1 of the treated water of the water treatment device. The DO meter 41 used DO-30A manufactured by TOA Electronics, and the TOC meter 58 used a SIEVERS900 TOC meter manufactured by Sievers.

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

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

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

The membrane degassing module 11 adjusts the dissolved oxygen concentration at the entrance of the ultraviolet oxidation device 31 to 50μg/L, and adjusts the amount of IPA added to make the TOC concentration of the water to be treated, that is, in the ultraviolet oxidation device 31 The TOC concentration at the entrance becomes 500μg/L. In this state, the amount of H ₂ O ₂ added is adjusted to 0 mg/L, 2.5 mg/L, 5.0 mg/L, and 10.0 mg/L, and 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. In addition, 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 treated liquid and the dissolved oxygen concentration at the inlet of the ultraviolet oxidation device 31 are constant, when _{H 2} O _{2 is excessively added,} On the contrary, the TOC removal rate will decrease, and the dissolved oxygen concentration at the outlet of the ultraviolet oxidation device 31 will increase. It can be seen from this that by measuring the dissolved oxygen concentration at the outlet of the ultraviolet oxidation device 31, the addition amount of _{H 2} O _{2 can be optimally controlled.}

Also, by skipping the membrane degassing module 11 separately, the dissolved oxygen concentration was adjusted to 7.8 _{mg/L, and the addition amount of H 2} O ₂ was set to 0 mg/L, and the TOC removal rate was measured. The concentration of dissolved oxygen at the outlet. The results are also shown in Table 1. The TOC removal rate at this time was 82%. It can be seen that the TOC removal rate is improved by reducing the dissolved oxygen concentration in the water to be treated and irradiating the treated water to _{which H 2} O _{2 is added with ultraviolet rays.}

【Table 1】

[Experimental example 2] The TOC concentration of the water to be treated, that is, the TOC concentration at the entrance of the ultraviolet oxidizer 31 is set to 1000 μg/L, and the addition _{amount of H 2} O _{2 is} 20.0 mg/L, except for this , The experiment was carried out under the same conditions as Experimental Example 1. The results are shown in Table 2. From this, the following results are also obtained: by reducing the dissolved oxygen concentration in the water to be treated and adding H ₂ O ₂ , the TOC removal rate is improved.

In addition, the dissolved oxygen concentration was adjusted to 7.8 _{mg/L by skipping the membrane degassing module 11 separately, and the addition amount of H 2} O ₂ was 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 its saturation under atmospheric pressure. However, when the dissolved oxygen concentration of the liquid to be treated is high, even if H ₂ O _{2 is added} , The TOC removal rate in UV oxidation treatment will not improve either.

【Table 2】

[Experimental example 3] The dissolved oxygen concentration at the entrance 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, 5.0 mg/L, Except for this, 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 entrance 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, 2.5 mg/L, Except for this, 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 membrane degassing module 11 was used to adjust the dissolved oxygen concentration at the entrance of the ultraviolet oxidation device 31 to 50μg/L, and the amount of IPA added was adjusted to make the TOC concentration of the treated water (in the ultraviolet oxidation device) The TOC concentration at the entrance of 31) becomes 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 for each case. The amount of water supplied to the ultraviolet oxidation device 31 is 2000 L/hour. Except for this, 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 addition device 21、51‧‧‧Storage tank 30‧‧‧Ultraviolet radiation 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 meter 81‧‧‧Water treatment device 82‧‧‧Ultra-pure water manufacturing device 83‧‧‧Ultra-pure water use process

[Figure 1] is a diagram showing the basic structure of a water treatment device based on the present invention. [Figure 2] is a diagram showing another example of the structure of the water treatment device. [Figure 3] is a diagram showing yet another example of the structure of the water treatment device. [Figure 4] is a diagram showing yet another example of the structure of the water treatment device. [Figure 5] is a diagram showing yet another example of the structure of the water treatment device. [Figure 6] is a diagram showing yet another example of the structure of the water treatment device. [Figure 7] is a diagram showing yet another example of the structure of the water treatment device. [Figure 8] is a diagram showing an application example of the water treatment device based on the present invention. [Fig. 9] is a diagram showing the structure of the device used in the embodiment.

Claims (14)

A water treatment method that decomposes the 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 ultraviolet light is irradiated to the water to be treated with hydrogen peroxide added The ultraviolet irradiation stage; and the stage of measuring the dissolved oxygen concentration of the outlet water from the ultraviolet irradiation stage; according to 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 of item 1 in the scope of patent application, wherein the addition amount of the hydrogen peroxide 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 of item 1 or 2 of the scope of patent application, wherein, in the ultraviolet irradiation stage, ultraviolet rays containing components with a wavelength of 185 nm or less are irradiated. For example, the water treatment method of item 1 or 2 of the scope of patent application has a stage of reducing the organic matter contained in the water to be treated by reverse osmosis treatment before the hydrogen peroxide addition stage. For example, the water treatment method of item 4 in the scope of patent application, wherein the permeation flux per 1MPa effective pressure of the reverse osmosis membrane used in the reverse osmosis treatment is 0.5m ³ /m ² /d or less. For example, the water treatment method of item 1 or 2 of the scope of patent application, wherein the total organic carbon concentration of the treated water before the treatment by 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 of item 1 or 2 in the scope of patent application, wherein the treated water comes from process wastewater. For example, the water treatment method of item 7 of the scope of patent application, wherein the process discharge water is the water discharged from the process that uses ultrapure water, and the water treated by the water treatment method is used to generate the ultrapure water used in the process. The raw water of pure water is used. A water treatment device that decomposes the organic matter contained in the water to be treated, and has: a hydrogen peroxide addition device to add hydrogen peroxide to the treated water; an ultraviolet irradiation device for the treated water added with hydrogen peroxide The water 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 addition 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 item 9 of the scope of patent application, wherein the control means controls the addition amount of the hydrogen peroxide so that the dissolved oxygen concentration of the outlet water from the ultraviolet irradiation device becomes 0.1 mg/L or less. For example, the water treatment device of item 9 or 10 of the scope of patent application, wherein the ultraviolet irradiation device is an ultraviolet oxidation device that irradiates ultraviolet rays containing components with a wavelength of 185 nm or less. For example, the water treatment device of item 9 or 10 of the scope of patent application is equipped with a reverse osmosis device with a reverse osmosis membrane on the inlet side of the hydrogen peroxide addition device to reduce the organic matter contained in the water to be treated. For example, the water treatment device of item 12 of the scope of patent application, wherein the permeation flux per 1MPa effective pressure of the reverse osmosis membrane is ^{less than 0.5m 3} /m ² /d. For example, the water treatment device of item 9 or 10 of the scope of patent application, 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 is more than 1 mg/L.

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