Water treatment device, pure water production device, ultrapure water production device, and water treatment method

Abstract

A water treatment device according to the present invention is provided with: a regenerative double-bed ion exchange tower filled with an anion exchanger and a cation exchanger; and a catalyst tower which is located on the downstream side of the regenerative double-bed ion exchange tower and is filled with a platinum group catalyst carrier, and which removes anions from water to be treated containing hydrogen peroxide and anions.

Description

This application is a divisional application of the original application with national application number 202180040719.6 and invention name “Water treatment device, ultrapure water production device and water treatment method”, which entered the Chinese national phase of the PCT international application with an international application date of May 24, 2021. Technical Field

[0001] The present invention is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-107736, filed on June 23, 2020, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a water treatment device, an ultrapure water production device and a water treatment method. Background Art

[0003] With the increasing demand for pure water quality, various methods for decomposing and removing trace organic matter in pure water have been under investigation in recent years. A representative method of this type is the introduction of an organic matter decomposition and removal process based on ultraviolet oxidation. To improve the efficiency of organic matter decomposition and removal, hydrogen peroxide is sometimes pre-added to the treated water. Ultraviolet radiation generates hydroxyl radicals from hydrogen peroxide, which promote the oxidative decomposition of organic matter. Furthermore, even when ultraviolet radiation is applied without the addition of hydrogen peroxide, hydrogen peroxide will also be generated in the treated water.

[0004] However, because excess hydrogen peroxide can affect the quality of the treated water, it is desirable to remove it as much as possible. Patent Specifications No. 5045099 and No. 5649520 disclose catalyst towers filled with a mixture of anion resins for removing decomposition products resulting from the decomposition of organic matter and catalyst supports for decomposing hydrogen peroxide. Patent Specification No. 5649520 further discloses that such catalyst towers can be filled with catalyst supports on the inflow side of the treated liquid and with a double bed of anion resins on the outflow side. Alternatively, a catalyst tower filled with a catalyst support and an anion exchange tower filled solely with anion resins can be arranged in that order. Summary of the Invention

[0005] The inventors of the present invention have found that it is difficult to improve the removal efficiency of hydrogen peroxide using the methods disclosed in Patent No. 5045099 and Patent No. 5649520. An object of the present invention is to provide a water treatment device that can improve the removal efficiency of hydrogen peroxide.

[0006] The water treatment apparatus of the present invention includes: an anion removal unit for removing anions from water to be treated containing hydrogen peroxide and anions; and a platinum group catalyst support located downstream of the anion removal unit.

[0007] According to the present invention, it is possible to provide a water treatment apparatus capable of improving the removal efficiency of hydrogen peroxide.

[0008] The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the accompanying drawings which illustrate the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A This is a schematic configuration diagram of a pure water production apparatus according to Embodiment 1A. Figure 1B This is a schematic diagram of the configuration of a pure water production apparatus according to Embodiment 1B. Figure 1C This is a schematic diagram of the structure of the pure water production apparatus according to Embodiment 1C. Figure 2A This is a schematic diagram of the configuration of a pure water production apparatus according to Embodiment 2A. Figure 2B This is a schematic diagram of the configuration of a pure water production apparatus according to Embodiment 2B. Figure 3A This is a schematic diagram of the configuration of a pure water production apparatus according to Embodiment 3A. Figure 3B This is a schematic diagram of the configuration of a pure water production apparatus according to Embodiment 3B. Figure 4 This is a schematic diagram of the test device used in Example 1. Figure 5 This is a graph showing the relationship between the pH of the water to be treated and the urea removal rate in Example 1. Figure 6 This is a graph showing the relationship between the hypobromous acid concentration in the water to be treated and the urea removal rate in Example 1. Figure 7A This is a schematic diagram of the test apparatus used in Example 2. Figure 7B This is a schematic diagram of the test apparatus used in Example 2. Figure 8A This is a schematic diagram of the test apparatus used in Example 3. Figure 8B This is a schematic diagram of the test apparatus used in Example 3. Figure 9A This is a schematic diagram of the test apparatus used in Example 3. Figure 9B This is a schematic diagram of the test apparatus used in Example 3. DETAILED DESCRIPTION

[0010] (Embodiments 1A to 1C) Embodiments of the water treatment apparatus and water treatment method of the present invention are described below with reference to the accompanying drawings. The embodiments and examples described below relate to a pure water production apparatus and a pure water production method for producing pure water from treated water. However, the present invention is also widely applicable to water treatment apparatuses other than pure water production apparatuses that use recycled water or wastewater as treated water, and to water treatment methods other than pure water production methods that use recycled water or wastewater as treated water. Figure 1A The schematic diagram shows the structure of a pure water production apparatus 1A according to Embodiment 1A of the present invention. The pure water production apparatus 1 (primary system), along with an upstream pretreatment system and a downstream subsystem (secondary system), constitutes an ultrapure water production apparatus. The raw water produced by the pretreatment system (hereinafter referred to as treated water) contains organic matter including urea.

[0011] The pure water production apparatus 1A includes a filter 11, an activated carbon tower 12, a first ion exchange device 13, a reverse osmosis membrane device 14, an ultraviolet irradiation device (ultraviolet oxidation device) 15, a second ion exchange device 16, and a degassing device 17, which are arranged in series along the main pipe L1 from upstream to downstream in the flow direction D of the treated water. After the treated water is pressurized by a raw water pump (not shown), the filter 11 removes large dust particles, while the activated carbon tower 12 removes impurities such as high-molecular organic matter. The first ion exchange device 13 includes a cation tower (not shown) filled with cation exchange resin, a decarbonation tower (not shown), and an anion tower (not shown) filled with anion exchange resin, which are arranged in series in this order from upstream to downstream. The cation tower removes cationic components from the treated water, the decarbonation tower removes carbonic acid, and the anion tower removes anionic components. The reverse osmosis membrane device 14 then removes ionic components from the treated water.

[0012] The pure water production device 1A has a hypohalous acid addition unit 21 for adding hypohalous acid to the treated water. In this embodiment, the hypohalous acid is hypobromous acid, but it can also be hypochlorous acid or hypoiodous acid. The hypohalous acid addition unit 21 includes: a storage tank 21a for sodium bromide (NaBr) (a supply unit for sodium bromide), a storage tank 21b for sodium hypochlorite (NaClO) (a supply unit for sodium hypochlorite), a stirring tank 21c for sodium bromide and sodium hypochlorite (a mixing unit for sodium bromide and sodium hypochlorite), and a transfer pump 21d. Hypobromous acid is difficult to store for a long time, so sodium bromide and sodium hypochlorite are mixed to generate hypobromous acid according to the time of use. The hypobromous acid generated in the stirring tank 21c (mixing unit) is pressurized by the transfer pump 21d and added to the treated water passing through the main pipe L1 between the reverse osmosis membrane device 14 and the ultraviolet irradiation device 15. Sodium bromide and sodium hypochlorite may be directly supplied to the main pipe L1 and stirred by the flow of the water to be treated in the main pipe L1 to generate hypobromous acid.

[0013] The ultraviolet irradiation device 15 located downstream of the hypohalous acid addition unit 21 irradiates the treated water with ultraviolet rays to which hypohalous acid has been added. As the ultraviolet irradiation device 15, for example, an ultraviolet lamp having a wavelength of at least one of 254 nm and 185 nm can be used. The ultraviolet rays preferably contain a wavelength component of 185 nm, which has high energy and excellent ability to decompose organic matter. By irradiating with ultraviolet rays, an effect of promoting the decomposition of organic matter (urea) based on hypobromous acid is obtained. However, hypochlorous acid is more easily decomposed by ultraviolet rays than hypobromous acid, so if a large amount of ultraviolet rays is irradiated, the decomposition reaction of hypochlorous acid will be promoted, and energy will be consumed unnecessary. In addition, insufficient hypochlorous acid for generating hypobromous acid may cause the generation reaction of hypobromous acid to be unable to proceed.

[0014] Conventional methods are known to add hydrogen peroxide to treated water to remove organic matter. Ultraviolet radiation is used to generate hydroxyl radicals from hydrogen peroxide, which then promote the oxidative decomposition of organic matter. However, as demonstrated in Example 1, hypohalous acid is far more effective than hydrogen peroxide in removing persistent organic matter such as urea. Therefore, according to this embodiment, the concentration of persistent organic matter such as urea in ultrapure water supplied to the point of use can be reduced.

[0015] Second ion exchange unit 16, located downstream of ultraviolet irradiation unit 15, is a regenerative ion exchange resin tower filled with anion exchange resin and cation exchange resin. Decomposition products of organic matter produced in the treated water by ultraviolet irradiation are removed by second ion exchange unit 16. Dissolved oxygen in the treated water is then removed by degassing unit 17.

[0016] As described in detail in Example 1, if the pH of the treated water is 8 or less, the urea removal rate is greatly improved. Therefore, the pure water production device 1A has a pH adjustment unit 22 on the upstream side of the ultraviolet irradiation device 15. The pH adjustment unit 22 has a storage tank 22a for a pH adjustment liquid such as sulfuric acid or hydrochloric acid, and a transfer pump 22b. The pH adjustment liquid is pressurized by the transfer pump 22b and is added to the treated water passing through the main pipe L1 between the reverse osmosis membrane device 14 and the ultraviolet irradiation device 15. The pH adjustment unit 22 adjusts the pH of the treated water to 8 or less, preferably to 7 or less, more preferably to 5 or less, and further preferably to 4 or less. From the perspective of urea removal rate, the lower limit of pH is not limited, but considering the impact on the subsequent equipment, it is preferably set to 3 or more.

[0017] As described in detail in Example 1, the TOC removal rate is significantly improved by adding hypohalous acid at a weight of 30 times or more, preferably 60 times or more, more preferably 120 times or more, and even more preferably 250 times or more, relative to the TOC of the treated water upstream of the hypohalous acid addition unit 21. Therefore, the pure water production apparatus 1A includes a TOC analysis unit 18, such as a TOC meter, for measuring the TOC of the treated water upstream of the hypohalous acid addition unit 21. The location of the TOC analysis unit 18 is not limited as long as it is upstream of the hypohalous acid addition unit 21, but it is preferably located just before the addition of hypohalous acid. Therefore, the TOC analysis unit 18 is located between the reverse osmosis membrane device 14 and the hypohalous acid addition unit 21. The amount of hypohalous acid added is not limited from the perspective of TOC removal rate, but considering the impact on subsequent equipment, it is preferably set to 2000 times or less of the TOC. Alternatively, a urea analysis unit, such as a urea concentration meter, can be used as the TOC analysis unit 18. In this case, the urea removal rate is significantly improved by adding hypohalous acid at a concentration of 5 times or more, preferably 12 times or more, more preferably 25 times or more, and even more preferably 50 times or more, by weight relative to the urea concentration of the water to be treated upstream of the hypohalous acid addition unit 21. The amount of hypohalous acid added is not limited from the perspective of urea removal rate, but is preferably set to 400 times or less by weight relative to the urea concentration in consideration of the impact on downstream equipment.

[0018] Figure 1B The following figure shows the schematic structure of a pure water production device 1B according to embodiment 1B of the present invention. In this embodiment, another ultraviolet irradiation device 15a is provided in series after the ultraviolet irradiation device 15, specifically between the ultraviolet irradiation device 15 and the second ion exchange device 16. The structure is otherwise the same as that of embodiment 1A. The ultraviolet irradiation device 15a at the subsequent stage removes the hypohalous acid remaining in the treated water by photolysis. Therefore, not only can the load on the second ion exchange device 16 be reduced, but the oxidative degradation of the resin in the second ion exchange device 16 can also be suppressed. As the other ultraviolet irradiation device 15a, as with the ultraviolet irradiation device 15, an ultraviolet lamp having a wavelength of at least one of 254nm and 185nm can be used.

[0019] Figure 1CThe schematic structure of the pure water production device 1C involved in embodiment 1C of the present invention is shown. In this embodiment, a reducing agent addition unit 23 is provided at the rear stage of the ultraviolet irradiation device 15, and a reverse osmosis membrane device 19 is provided at the rear stage of the reducing agent addition unit 23 and the front stage of the second ion exchange device 16. The structure other than this is the same as that of embodiment 1A. The reducing agent addition unit 23 removes hypohalous acid remaining in the treated water. As a reducing agent, hydrogen peroxide, sodium sulfite, etc. can be used. The reducing agent addition unit 23 has a storage tank 23a for the reducing agent and a transfer pump 23b. The reducing agent is pressurized by the transfer pump 23b and is added to the treated water passing through the main pipe L1 between the ultraviolet irradiation device 15 and the reverse osmosis membrane device 19. The reverse osmosis membrane device 19 removes the remaining reducing agent. The reducing agent removal unit can be an ion exchange resin, an electrodeionization device, etc. Alternatively, these reducing agent removal units can be combined in series.

[0020] The hypohalous acid removal unit is not limited to the embodiments 1B and 1C. It can also be a hypohalous acid removal unit (oxidant removal unit) that has the same effect of removing hypohalous acid as the other ultraviolet irradiation device 15a and the reducing agent addition unit 23. For example, a platinum group catalyst such as palladium (Pd) or activated carbon can be used. Alternatively, these hypohalous acid removal units can be connected in series.

[0021] (Embodiment 2A-2B) Figure 2AThe schematic structure of a pure water production apparatus 2A according to embodiment 2A of the present invention is shown. In this embodiment, hydrogen peroxide is used for the oxidative decomposition of compounds such as organic matter. The treated water contains anions in addition to any compounds oxidized and decomposed by the hydrogen peroxide. The pure water production apparatus 2A comprises a filter 11, an activated carbon column 12, a first ion exchange unit 13, a reverse osmosis membrane unit 14, an ultraviolet irradiation unit 15, a second ion exchange unit 16, and a degassing unit 17, arranged in series along a main pipe L1 from upstream to downstream in the flow direction D of the treated water. These devices 11-17 have the same structure as in embodiments 1A-1C. In this embodiment, a hydrogen peroxide addition unit 24 is provided between the reverse osmosis membrane unit 14 and the ultraviolet irradiation unit 15. The hydrogen peroxide addition unit 24 comprises a hydrogen peroxide storage tank 24a and a transfer pump 24b. The hydrogen peroxide is pressurized by the transfer pump 24b and added to the treated water passing through the main pipe L1 between the reverse osmosis membrane unit 14 and the ultraviolet irradiation unit 15. Ultraviolet radiation is applied to the treated water after hydrogen peroxide has been added using ultraviolet radiation from an ultraviolet irradiation device 15. This generates hydroxyl radicals from the hydrogen peroxide, which promote the oxidative decomposition of organic matter. As mentioned above, hydrogen peroxide is inefficient in removing recalcitrant organic matter such as urea, but it is effective in the oxidative decomposition of common, less recalcitrant compounds. A catalyst tower 20 filled with a platinum-group catalyst carrier is located downstream of the second ion exchange device 16 (anion removal device), i.e., between the second ion exchange device 16 and the degassing device 17.

[0022] The second ion exchange device 16 is an ion exchange tower filled with at least an anion exchanger such as an anion exchange resin, which removes at least anions from the treated water after hydrogen peroxide is added. The ion exchange tower is preferably a regenerative type. In this embodiment, the second ion exchange device 16 is filled with anion exchange resin. The second ion exchange device 16 can also be filled with cation exchange resin. In this case, the anion exchange resin and the cation exchange resin can be filled in a double bed or a mixed bed. In particular, a regenerative double bed ion exchange tower is preferred because the regeneration operation is easy. In the case of a double bed filling, either the anion exchange resin or the cation exchange resin can be arranged on the upstream side of the flow direction D of the treated water. Alternatively, the anion tower filled with the anion exchange resin and the cation tower filled with the cation exchange resin can be separated. As long as the second ion exchange device 16 functions as an anion removal unit for removing anions from the treated water containing hydrogen peroxide and anions, the structure is not limited.

[0023] The platinum group catalyst carrier filled in the catalyst tower 20 is obtained by carrying a platinum group catalyst consisting of a platinum group metal on an anion exchanger (anion exchange resin in the present embodiment). The platinum group catalyst carrier removes the hydrogen peroxide contained in the treated water after the anions have been removed. As an anion exchanger, a monolithic organic porous anion exchanger can also be used. The platinum group catalyst decomposes hydrogen peroxide based on its catalytic action. As platinum group metals, platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir) etc. can be listed, and one of them can be used alone, or two or more can be used in combination. Among these platinum group metals, Pt and Pd are preferred, and from the perspective of cost, Pd is more preferred.

[0024] The remaining hydrogen peroxide added to the treated water that is not used to decompose the compounds comes into contact with the platinum-group catalyst, decomposing it into water and oxygen, which are then removed. As described in Example 2 below, the less anionic components the treated water contains, the more efficient the platinum-group catalyst is in removing hydrogen peroxide. Therefore, in this embodiment, a second ion exchange device 6 is positioned upstream of the platinum-group catalyst.

[0025] Previously, it was believed that hydrogen peroxide would cause oxidative degradation of ion exchangers, so platinum-group catalysts were placed upstream of the ion exchangers to reduce the amount of hydrogen peroxide that came into contact with them. However, the experiments conducted this time revealed little damage to the anion exchangers caused by hydrogen peroxide. This is believed to be because the concentration of hydrogen peroxide used in pure water production is low and not at a level that would damage the anion exchangers. Furthermore, since hydrogen peroxide is ultimately decomposed by the platinum-group catalyst, it does not affect the quality of the ultrapure water supplied to the point of use.

[0026] Figure 2BThe schematic structure of the pure water manufacturing device 2B involved in embodiment 2B of the present invention is shown. In this embodiment, the second ion exchange device 16a is filled with an anion exchanger and a platinum group catalyst carrier, and the structure is the same as that of embodiment 2A. That is, in embodiment 2A, the second ion exchange device 16 and the catalyst tower 20 are separated, but in this embodiment, the anion exchanger and the platinum group catalyst carrier are filled in one ion exchange tower (second ion exchange device 16a). This can achieve the compactness of the pure water manufacturing device 2B. As in embodiment 2A, the second ion exchange device 16a can also be filled with a cation exchanger. That is, the second ion exchange device 16a can be a regeneration type ion exchange tower after the anion exchanger, cation exchanger and platinum group catalyst carrier are filled separately from each other. In this case, as long as the platinum group catalyst carrier is located on the downstream side of the anion exchanger, the position of the cation exchanger is not limited. Specifically, the anion exchanger, cation exchanger and platinum group catalyst carrier can be filled in the second ion exchange device 16a in the following order from upstream to downstream in the flow direction D of the treated water. (1) Anion exchanger / platinum group catalyst support / cation exchanger (2) Cation exchanger / anion exchanger / platinum group catalyst carrier (3) Anion exchanger / cation exchanger / platinum group catalyst carrier

[0027] As described above, the platinum group catalyst support is an anion exchanger. Therefore, it is preferable to pack the platinum group catalyst support and the anion exchanger adjacent to each other ((1) or (2)). This allows the platinum group catalyst support and the anion exchanger to be handled together during regeneration, thereby simplifying the regeneration process. In addition, it is also easy to use an existing ion exchange column by replacing part of the area filled with the existing anion exchanger with the platinum group catalyst support.

[0028] exist Figure 2A 、 2B In the illustrated embodiment, a hydrogen peroxide addition unit 24 is provided upstream of the ultraviolet irradiation device 15, but this unit can be omitted. Ultraviolet radiation from the ultraviolet irradiation device 15 generates hydrogen peroxide in the treated water, thereby achieving the same effect as the second ion exchange devices 16 and 16a. Although not shown, an electrodeionization device in which a platinum-group catalyst carrier is filled in the desalination chamber can also be used as the second ion exchange devices 16 and 16a.

[0029] (Third Embodiment 3A-3B) Embodiments 3A and 3B have a configuration that combines Embodiments 1A to 1C with Embodiments 2A and 2B. Therefore, regarding the configuration and effects of each device, reference can be made to the above-described embodiments. Figure 3A The schematic structure of the pure water production device 3A involved in embodiment 3A of the present invention is shown. The pure water production device A includes a filter 11, an activated carbon tower 12, a first ion exchange device 13, a reverse osmosis membrane device 14, an ultraviolet irradiation device 15, a second ion exchange device 16, a catalyst tower 20 (platinum group catalyst carrier) and a degassing device 17, which are arranged in series along the main pipe L1 from upstream to downstream in the flow direction D of the treated water. These devices 11 to 17, 20 have the same structure as embodiment 2A. In addition, the pure water production device 3A has a hypohalous acid addition unit 21 for adding hypohalous acid to the treated water. The hypohalous acid addition unit 21 has the same structure as embodiments 1A to 1C, and adds hypohalous acid to the treated water between the reverse osmosis membrane device 14 and the ultraviolet irradiation device 15. Furthermore, the pure water production device 3A has a pH adjustment unit 22 on the upstream side of the ultraviolet irradiation device 15, as in embodiments 1A to 1C. Furthermore, the pure water production apparatus 3A includes a TOC analysis unit 18 such as a TOC meter for measuring TOC of the water to be treated on the upstream side of the hypohalous acid addition unit 21, similarly to the embodiments 1A to 1C.

[0030] In this embodiment, similar to Embodiments 1A to 1C, hypohalous acid is added to the treated water to remove persistent organic matter such as urea, and the pH of the treated water is then adjusted to 3 to 8, preferably 3 to 5, by a pH adjustment unit 22. The ultraviolet rays generated by the ultraviolet irradiation device 15 promote the decomposition of persistent organic matter (urea) by hypobromous acid. Hypohalous acid has a strong oxidizing power, so there is a possibility of oxidative degradation of the ion exchanger in the subsequent second ion exchange device 16. Therefore, hydrogen peroxide is added to the treated water to remove residual hypohalous acid. For this purpose, the pure water production apparatus 3A includes a hydrogen peroxide addition unit 24 located downstream of the ultraviolet irradiation device 15, more specifically, between the ultraviolet irradiation device 15 and the second ion exchange device 16. That is, the hydrogen peroxide addition unit 24 adds hydrogen peroxide to the treated water irradiated with ultraviolet rays. Similar to Embodiments 2A to 2C, the hydrogen peroxide addition unit 24 includes a peroxide water storage tank 24a and a transfer pump 24b. Hypohalous acid can also be removed using sulfites, for example, but this increases the load on the subsequent ion exchanger, so hydrogen peroxide is more preferable. After the hypohalous acid is removed using hydrogen peroxide, the remaining hydrogen peroxide is removed using a platinum group catalyst, similar to Embodiments 2A and 2B. In this case, since the anion components are pre-removed by the second ion exchange device 16, the efficiency of hydrogen peroxide removal using the platinum group catalyst is improved.

[0031] Figure 3B The schematic configuration of a pure water production apparatus 3B according to embodiment 3B of the present invention is shown. In this embodiment, the second ion exchange device 16a is filled with an anion exchanger and a platinum-group catalyst carrier. The configuration is otherwise the same as in embodiment 3A. That is, in this embodiment, as in embodiment 2B, the anion exchanger and the platinum-group catalyst carrier are filled in a single ion exchange column (second ion exchange device 16a). The second ion exchange device 16a may also be filled with a cation exchanger. For details, refer to embodiment 2B.

[0032] (Example 1) In order to confirm the effects of the embodiments 1A to 1C, the Figure 4 The test device shown was used to measure the urea removal rate. An oxidant was added to ultrapure water, and urea was added downstream as a persistent organic matter. The amount of urea added was adjusted so that the TOC of the treated water upstream of the ultraviolet irradiation device was 16 μg / L and the urea concentration was 80 μg / L. A ultraviolet irradiation device from Japan PHOTOSCIENCE Co., Ltd. was used at an irradiation rate of 0.70 kWh / m 3 Irradiated with ultraviolet rays. A non-regenerative mixed-bed ion exchange device (hereinafter referred to as the ion exchange device) with a capacity of 300 mL was set downstream of the ultraviolet irradiation device to remove the ion components. Urea measuring devices (ORUREA manufactured by ORGANO) were set on the inlet side of the ultraviolet irradiation device and the outlet side of the ion exchange device to measure the urea concentration. In Example 1, hypobromous acid was added as an oxidant at a concentration of 2 mg-Cl2 / L (chlorine conversion concentration). Hypobromous acid is generated by mixing NaBr and NaClO, as in embodiments 1A to 1C. The concentration of hypobromous acid was measured using a residual salt concentration meter (manufactured by HANNA) in a free chlorine reagent after adding glycine to the sample water to change free chlorine into combined chlorine. No oxidant was added in Comparative Example 1-1. In Comparative Example 1-2, hydrogen peroxide was added as an oxidant at a concentration of 2 mg / L. The pH of the treated water was set to 7. The urea removal rate was determined by (C1-C2) / C1×100(%), assuming that the urea concentration of the treated water at the inlet of the ultraviolet irradiation device was C1 and the urea concentration of the treated water in the ion exchange device was C2.

[0033] The urea removal rate was 61.5% in Example 1, 3.2% in Comparative Example 1-1, and 4.0% in Comparative Example 1-2. This demonstrates that the addition of hypobromous acid significantly improves the urea removal rate. Furthermore, while the addition of hydrogen peroxide improves the urea removal rate somewhat, the effect is limited compared to that of hypobromous acid.

[0034] Next, in order to evaluate the effect of the pH of the treated water on the urea removal rate, the urea removal rates were measured at pH values ​​of 4, 5, 7, 8, and 9. The pH was adjusted by adding sulfuric acid to the treated water, and the other conditions were the same as those in the above-mentioned embodiment. Figure 5 The results are shown in . The lower the pH, the higher the urea removal rate. The urea removal rate can be improved by setting the pH to 8 or less, preferably 7 or less, more preferably 5 or less, and further preferably 4 or less.

[0035] Furthermore, the urea removal rate was measured when the concentration of hypobromous acid in the treated water was set to 0, 0.5, 1.0, 2.0, 4.0, and 6.0 mg-Cl2 / L. Figure 6 The results are shown in . The more the concentration of hypobromous acid increases, the greater the urea removal rate. The concentration of hypobromous acid is set to 0.5 mg-Cl2 / L or more, preferably to 1.0 mg-Cl2 / L or more, more preferably to 2.0 mg-Cl2 / or more, and further preferably to 4.0 mg-Cl2 / L or more, so that the urea removal rate can be improved. Among them, when the concentration of hypobromous acid is 4.0 mg-Cl2 / L or more, the urea removal rate does not change much. Figure 6 The weight ratio of hypobromous acid to TOC is also shown.

[0036] (Example 2) In order to confirm the effects of the embodiments 2A and 2B, Figure 7A 、 7B The test apparatus shown was used to measure the hydrogen peroxide concentration of the treated water. Figure 7A As shown in FIG. 2 , hydrogen peroxide was added to ultrapure water, and carbonic acid was added downstream as an anion load. The treated water was sequentially passed through a regenerative ion exchange device filled with a composite bed of anion exchange resin and cation exchange resin, and then a Pd catalyst carrier, and the hydrogen peroxide concentration of the treated water (Pd resin tower outlet water) was measured. In Example 2-2, as shown in FIG. Figure 7B As shown in FIG2-1, processed water is generated similarly and passed through a regenerative ion exchange device after filling an anion exchange resin, a Pd catalyst support, and a cation exchange resin in this order as a water flow sequence, and the hydrogen peroxide concentration of the processed water (regenerative ion exchange device outlet water) is measured. Comparative Example 2 omits the diagram, while the regenerative ion exchange device is omitted in Example 2-1. That is, without removing the anion component from the processed water, the processed water is passed through the Pd catalyst support, and the hydrogen peroxide concentration of the processed water (Pd catalyst support outlet water) is measured.

[0037] In Examples 2-1, 2-2, and Comparative Example 2, hydrogen peroxide and carbonic acid were added to achieve a hydrogen peroxide concentration of 100 μg / L and a carbonic acid concentration of 1.5 mg / L. The flow rate of treated water through the regenerative ion exchange device and the Pd catalyst support was set at 36 L / h. The hydrogen peroxide removal rate was calculated using (C1 - C2) / C1 × 100 (%), assuming the hydrogen peroxide concentration of the treated water at the inlet of the ion exchange device was C1 and the hydrogen peroxide concentration of the treated water in the Pd catalyst support (Example 2-1, Comparative Example 2) or the regenerative ion exchange device (Example 2-2) was C2. The hydrogen peroxide removal rate was 99% or higher in both Examples 2-1 and 2-2, and 60% in Comparative Example 2. This confirms that passing water through the Pd catalyst support after pre-removal of anionic components results in more efficient hydrogen peroxide removal.

[0038] (Example 3) In order to confirm the effects of the embodiments 3A and 3B, Figure 8A 、 8B Comparative Examples 3-1 to 3-5 and Examples 3-1 and 3-2 were carried out using the test apparatus shown in 9A and 9B. The summary is shown in Table 1.

[0039] [Table 1]

[0040] First, use Figure 8AComparative Examples 3-1 to 3-3 were carried out using the test apparatus shown. Urea was added to ultrapure water as a difficult-to-decompose organic matter, and carbonic acid was added as an anion load, and ultraviolet rays were irradiated to the treated water using an ultraviolet irradiation device. In Comparative Example 3-1, no oxidant was added to the treated water. In Comparative Example 3-2, hydrogen peroxide was added as an oxidant at a concentration of 2 mg / L, and in Comparative Example 3-3, hypobromous acid was added as an oxidant at a concentration of 2 mg-Cl2 / L. Hypobromous acid was produced by mixing NaBr and NaClO, as in Embodiments 3A to 3C. The urea concentration was set to 80 μg / L (TOC 16 μg / L), and the carbonic acid concentration was set to 2 mg / L. The urea concentration was measured using a urea concentration meter (ORUREA, manufactured by ORUREA Co., Ltd.). The process up to ultraviolet irradiation was the same as in Example 1. A regenerative double-bed ion exchange device (capacity 300 mL) was set downstream of the ultraviolet irradiation device to remove the ion components. The urea removal rate was calculated using the same method as in Example 1. The results were 3% for Comparative Example 3-1, 4% for Comparative Example 3-2, and 60% for Comparative Example 3-3, which are almost identical to those in Example 1. In Comparative Example 3-3, the hypobromous acid concentration in the treated water after ultraviolet irradiation was 1 mg-Cl2 / L. Meanwhile, the TOC, after subtracting the urea content measured by the urea meter (ORUREA), was 0.8 μg / L in Comparative Examples 3-1 and 3-2, and 40 μg / L in Comparative Example 3-3. This is because the residual hypobromous acid from the ultraviolet irradiation device degraded the ion exchanger in the subsequent ion exchange device.

[0041] Next, as Comparative Example 3-4, Figure 8B As shown, 2 mg / L of hydrogen peroxide was added to the treated water at the outlet side of the ultraviolet irradiation device, and the same measurement was performed. The urea removal rate was at the same level as that of Comparative Example 3-3. The concentration of hypobromous acid in the treated water after the addition of hydrogen peroxide was less than 0.01 mg-Cl2 / L. Based on the comparison between Comparative Examples 3-3 and 3-4, it can be seen that hypobromous acid has been removed by hydrogen peroxide. The hydrogen peroxide concentration at the inlet and outlet of the ion exchange device was 1 mg / L, and the TOC of the water treated by the ion exchange device after subtracting the amount of urea was 0.8 μg / L. Therefore, it is believed that at a hydrogen peroxide concentration of about 1 mg / L, TOC will not dissolve due to resin deterioration.

[0042] Next, as Comparative Examples 3-5, Figure 9AAs shown, a Pd catalyst support is placed before the ion exchange device. The hydrogen peroxide concentration in the outlet water of the Pd catalyst support and the treated water of the ion exchange device is 0.4 mg / L, resulting in a hydrogen peroxide removal efficiency of 60%. The carbonic acid concentration at the inlet of the Pd catalyst support is 2 mg / L. This indicates that the hydrogen peroxide removal efficiency (60%) is not as high as it would be if anions (carbonic acid) were not removed at the inlet of the Pd catalyst support.

[0043] Next, as Examples 3-1 and 3-2, Figure 9B The same measurements were performed using the test apparatus shown. In Example 3-1, a catalyst tower filled with a Pd catalyst carrier was installed after the ion exchange device. In Example 3-2, the ion exchange device was filled with a Pd catalyst carrier (anion exchange resin, Pd catalyst carrier, and cation exchange resin were filled in this order along the water flow direction). The hydrogen peroxide concentration at the outlet of the catalyst tower in Example 3-1 and at the outlet of the ion exchange device in Example 3-2 was both less than 0.01 mg / L, representing a hydrogen peroxide removal rate of over 99%. In Example 3-2, the carbonic acid concentration of the water treated by the ion exchange device was measured and found to be less than 1 μg / L, confirming that the anionic components had been removed by the ion exchange device.

[0044] Furthermore, the same measurement as in Example 1 was performed by changing the pH of the treated water and the concentration of hypobromous acid. As a result, the same results as in Example 1 were obtained.

[0045] It should be understood that although certain preferred embodiments of the present invention have been shown and described in detail, various changes and modifications may be made without departing from the spirit or scope of the claims. (Description of labels)

[0046] 1A~1C, 2A~2C, 3A~3C Pure water production equipment 15 Ultraviolet irradiation equipment 16, 16a, 16b Second ion exchange device (anion removal unit) 18 TOC meter (TOC analysis unit) 20 Catalyst Tower 21. Hypohalous acid addition unit 22 pH adjustment unit 23 Reducing agent addition unit 24 Hydrogen peroxide addition units.

Claims

1. A water treatment device comprising: a regenerative multi-bed ion exchange tower filled with anion exchangers and cation exchangers; and a catalyst tower, which is located on the downstream side of the regenerative multi-bed ion exchange tower and is filled with a platinum group catalyst carrier, The anion exchanger removes anions from the treated water containing hydrogen peroxide and anions.

2. A pure water production device comprising: The water treatment device according to claim 1; and The ultraviolet irradiation device is provided on the upstream side of the water treatment device.

3. An ultrapure water production device comprising: The pure water production device according to claim 2; a pre-treatment system, which is provided on the upstream side of the pure water production device; and The subsystem is arranged on the downstream side of the pure water production device.

4. A water treatment method comprising: a step of removing anions from the treated water containing hydrogen peroxide and anions using an anion exchanger; as well as The step of removing the hydrogen peroxide contained in the treated water after the anions are removed by using a platinum group catalyst, The anion exchanger and the cation exchanger are filled in a regenerative multi-bed ion exchange tower, and the platinum group catalyst carrier is filled in a catalyst tower.

5. The water treatment method according to claim 4, wherein: Before the anions are removed by the anion exchanger, the water to be treated is irradiated with ultraviolet rays by an ultraviolet irradiation device.

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