Water treatment method and apparatus

Abstract

To provide a water treatment device which increases decomposition efficiency of organic matter in water to be treated with little influence on downstream devices.SOLUTION: A water treatment device which decomposes and removes organic matter in water to be treated comprises: hydrogen peroxide addition means (a hydrogen peroxide source 101) to add hydrogen peroxide to the water to be treated; an ultraviolet oxidation device 103 which irradiates the water to be treated with the hydrogen peroxide added thereto with ultraviolet light; and a hydrogen peroxide removal device 105 which removes the hydrogen peroxide included in outlet water from the ultraviolet oxidation device 103. The hydrogen peroxide removal device 105 comprises: an anode 11 and a cathode 12; and a hydrogen peroxide removal chamber 23 which is disposed between the anode 11 and the cathode 12 and has a metal catalyst having a hydrogen peroxide decomposing ability provided therein. A direct current is applied between the anode 11 and the cathode 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water treatment method and apparatus for decomposing and removing organic matter in water to be treated. [Background technology]

[0002] Conventionally, pure water such as ultrapure water, from which organic matter, ionic components, fine particles, bacteria, etc. have been highly removed, has been used as cleaning water in the manufacturing processes of semiconductor devices and liquid crystal display devices. In particular, when manufacturing electronic components including semiconductor devices, a large amount of pure water is used in the cleaning process, and the requirements for water quality are increasing year by year. The pure water used in the cleaning process of electronic component manufacturing is required to have an extremely low concentration of total organic carbon (TOC), which is one of the water quality control items, in order to prevent the organic matter contained in the pure water from carbonizing in the subsequent heat treatment process, causing insulation failure, etc.

[0003] In response to these demands for higher quality pure water, various methods for decomposing and removing trace amounts of organic matter (TOC components) from pure water have been investigated in recent years. One such method is the decomposition and removal of organic matter using ultraviolet oxidation. Typically, UV oxidation involves an ultraviolet oxidation system, typically consisting of a stainless steel reactor and a tubular low-pressure ultraviolet lamp installed within the reactor. The water to be treated is then introduced into the reactor and irradiated with ultraviolet light. For example, low-pressure ultraviolet lamps emitting ultraviolet light with wavelengths of 254 nm and 185 nm are commonly used. When the water is irradiated with ultraviolet light containing wavelengths of 185 nm, ultraviolet decomposition of the water progresses, generating oxidizing species such as hydroxyl radicals (·OH) in the water. The oxidizing power of these oxidizing species decomposes the trace organic matter in the water into carbon dioxide (CO2) and organic acids. The treated water obtained by subjecting the water to ultraviolet oxidation treatment in this manner is then sent to an ion exchange device disposed downstream, where carbon dioxide and organic acids are removed.

[0004] However, typical TOC oxidative decomposition methods using ultraviolet oxidation equipment use low-pressure ultraviolet lamps. These lamps are very expensive, but their UV intensity decreases over time, requiring replacement, for example, approximately once a year. Therefore, reducing running costs, such as the cost of replacing the UV lamps and reducing energy consumption, is a key issue in oxidative decomposition of TOC components using ultraviolet oxidation equipment. To improve the decomposition efficiency of TOC components, Patent Document 1 proposes adding a predetermined amount of hydrogen peroxide (H2O2) upstream of the ultraviolet oxidation equipment using a low-pressure ultraviolet lamp. The 254 nm ultraviolet light emitted from the low-pressure ultraviolet lamp reacts with H2O2 to generate hydroxyl radicals (OH·).

[0005] Hydroxyl radicals generated by the decomposition of hydrogen peroxide also contribute to the decomposition of TOC components, so by adding hydrogen peroxide to the water to be treated prior to the ultraviolet oxidation treatment, the efficiency of the decomposition of TOC components is improved.

[0006] The above describes the removal of TOC components from wastewater discharged from various processes by adding hydrogen peroxide to water, such as tap water, and then subjecting it to ultraviolet oxidation treatment to produce pure or ultrapure water. However, there is also a demand for the removal of TOC components from wastewater discharged from various processes. In recent years, there has been a growing demand for more efficient use of water resources, and water conservation is strongly desired, for example, in semiconductor device manufacturing plants, which use a large amount of ultrapure water. To achieve water conservation, recovering and reusing used water is an effective method. To increase water recovery rates, technologies (wastewater treatment technologies, wastewater recovery treatment technologies) for treating wastewater with high TOC concentrations after use at points of use and further recovering and treating it for reuse are being studied. To recover and reuse wastewater with high TOC concentrations as raw water for ultrapure water production, it is necessary to reduce the TOC concentration to a level that does not incur energy costs and does not deteriorate the quality of the final ultrapure water. One technology for treating water with high TOC concentrations includes adding an oxidizing agent, such as hydrogen peroxide or ozone, to the water and oxidizing and decomposing TOC by ultraviolet irradiation. In this case, the TOC concentration in the water to be treated is assumed to be on the order of mg / L, and since the water to be treated originally contains a large amount of various impurities, UV irradiation is carried out using, for example, an open reaction vessel.The UV source generally used is a low-pressure or high-pressure UV lamp that generates light at a wavelength of 254 nm.

[0007] As a water treatment method that can also be used to remove organic components when wastewater from a process is treated and reused, Patent Document 2 discloses that in order to improve the efficiency of decomposition of organic matter and increase the TOC removal rate, hydrogen peroxide is added to the water to be treated and then the water is subjected to ultraviolet oxidation treatment, and the amount of hydrogen peroxide added is adjusted depending on the dissolved oxygen concentration of the water at the outlet of the ultraviolet oxidation treatment.

[0008] Related to the present invention is a technology for reducing the concentration of hydrogen peroxide in water to be treated. Known methods for reducing the concentration of hydrogen peroxide in water to be treated, including adding a reducing agent, contacting activated carbon, and contacting a metal-supported catalyst, are available. In the method of adding a reducing agent, a reducing agent such as sodium sulfite, sodium bisulfite, or sodium thiosulfate is added to the water to be treated. The reaction rate between the reducing agent and hydrogen peroxide is very high, enabling reliable decomposition and removal of hydrogen peroxide; however, it is difficult to adjust the amount of reducing agent added. Furthermore, in the method of adding a reducing agent, an excessive amount of reducing agent is required to reliably remove hydrogen peroxide, which increases the amount of ions in the treated water and may result in deterioration of the water quality. In the method of contacting the water to be treated with activated carbon, a packed column of activated carbon is typically installed and the water is passed through it. However, this method has the drawback of requiring a large-scale device due to the slow reaction rate, which makes it difficult to increase the space velocity of the water passing through. There is also a concern that the activated carbon itself may be oxidized during the decomposition of hydrogen peroxide, resulting in particle disintegration.

[0009] As a method for decomposing and removing hydrogen peroxide by contacting it with a metal-supported resin, for example, a method has been proposed in which water to be treated containing hydrogen peroxide is brought into contact with a catalytic resin in which a palladium or platinum catalyst is supported on an ion exchange resin (Patent Document 3). In this method, hydrogen peroxide is decomposed by the reaction shown in the following formula: 2H2O2 → 2H2O + O2 [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-218248 [Patent Document 2] Japanese Patent Application Publication No. 2018-79448 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-185587 Summary of the Invention [Problem to be solved by the invention]

[0011] Regarding the addition of hydrogen peroxide to decompose and remove TOC components before subjecting the treated water to ultraviolet oxidation treatment, it cannot be said that sufficient consideration has been given to optimizing the amount of hydrogen peroxide added or the impact of hydrogen peroxide remaining in the water exiting the ultraviolet oxidation treatment on downstream equipment.In addition, the treated water from the ultraviolet oxidation equipment contains carbonate components (carbonate ions, bicarbonate ions, and free carbon dioxide), but the impact of these on the removal of hydrogen peroxide has not been fully considered.

[0012] An object of the present invention is to provide a water treatment method and apparatus that improves the efficiency of decomposing organic matter in water to be treated and that has little effect on downstream equipment. [Means for solving the problem]

[0013] The inventors have confirmed that when TOC components in water to be treated are decomposed by UV oxidation treatment using hydrogen peroxide and UV light, the treated water, i.e., the outlet water from the UV oxidation treatment, contains a certain concentration of hydrogen peroxide. Hydrogen peroxide is an oxidizing agent that can cause irreparable, fatal damage to devices containing ion exchange resins and degassing membranes. In particular, the ion exchange resins used in electrodeionization (EDI) water production systems are known to be susceptible to degradation in the presence of oxidizing agents. Therefore, in the present invention, the outlet water from the UV oxidation treatment is supplied to a specific hydrogen peroxide removal device for hydrogen peroxide removal. The treated water obtained by the hydrogen peroxide removal treatment is supplied to, for example, an EDI device, a membrane degassing device, or a non-regenerative ion exchange resin device (cartridge polisher).

[0014] Therefore, the water treatment method of the present invention is a water treatment method for decomposing organic matter contained in water to be treated, and includes a step of adding hydrogen peroxide to the water to be treated, an ultraviolet irradiation step of irradiating the water to be treated with ultraviolet light to which hydrogen peroxide has been added, and a hydrogen peroxide removal step of removing the hydrogen peroxide contained in the outlet water from the ultraviolet irradiation step.The hydrogen peroxide removal step includes a step of applying a direct current between an anode and a cathode, and a step of passing the water to be treated through a hydrogen peroxide removal chamber that is placed between the anode and the cathode and has a metal catalyst having the ability to decompose hydrogen peroxide.

[0015] The water treatment device of the present invention is a water treatment device that decomposes organic matter contained in water to be treated, and includes a hydrogen peroxide addition means that adds hydrogen peroxide to the water to be treated, an ultraviolet irradiation means that irradiates the water to be treated with ultraviolet light to which hydrogen peroxide has been added, and a hydrogen peroxide removal means that removes hydrogen peroxide contained in the outlet water from the ultraviolet irradiation means.The hydrogen peroxide removal means includes an anode and a cathode, and a hydrogen peroxide removal chamber that is positioned between the anode and the cathode and is provided with a metal catalyst that has the ability to decompose hydrogen peroxide, and a direct current is applied between the anode and the cathode.

[0016] In the present invention, a metal catalyst having hydrogen peroxide-decomposing ability is provided in the hydrogen peroxide removal chamber disposed between the anode and the cathode, and a direct current is applied between the anode and the cathode while the water to be treated is passed through the hydrogen peroxide removal chamber. The direct current may be applied continuously or intermittently during the period in which the water to be treated is passed through the hydrogen peroxide removal chamber. Alternatively, the direct current may be applied continuously or intermittently while the water to be treated is also passed through the hydrogen peroxide removal chamber intermittently. For example, in the water treatment method of the present invention, in the hydrogen peroxide removal step, the step of applying a direct current between the anode and the cathode and the step of passing the water to be treated through the hydrogen peroxide removal chamber may be performed simultaneously or separately. The outlet water of the ultraviolet irradiation means, which irradiates the water to be treated with ultraviolet light to perform ultraviolet oxidation treatment, contains carbon dioxide components and the like, which can inhibit the decomposition of hydrogen peroxide by the metal catalyst.However, according to the present invention, both the decomposition of hydrogen peroxide and the removal of carbon dioxide components and the like from the hydrogen peroxide removal chamber proceed, making it possible to maintain a stable, high level of hydrogen peroxide decomposition and removal performance over the long term.

[0017] In the present invention, it is preferable to provide the hydrogen peroxide removal chamber with an ion exchanger carrying a metal catalyst capable of decomposing hydrogen peroxide, by filling the chamber with the metal catalyst. When a metal catalyst is carried on the ion exchanger, carbonic acid components and the like are adsorbed onto the ion exchanger. However, by applying a voltage between the anode and cathode, the decomposition of hydrogen peroxide and the electrical regeneration of the ion exchanger proceed in parallel, making it possible to maintain a high level of hydrogen peroxide decomposition and removal performance over a long period of time.

[0018] In the present invention, examples of metal catalysts capable of decomposing hydrogen peroxide include platinum group metal catalysts such as palladium and platinum, as well as iron, manganese, nickel, gold, silver, copper, chromium, aluminum, and compounds thereof. Among these, platinum group metal catalysts are more preferably used due to their high catalytic activity for decomposing hydrogen peroxide. Platinum group metal catalysts are catalysts containing one or more metals selected from ruthenium, rhodium, palladium, osmium, iridium, and platinum. Platinum group metal catalysts may contain any of these metal elements alone or in combination of two or more of them. Among these, platinum, palladium, and platinum / palladium alloys have high catalytic activity and are therefore preferably used as platinum group metal catalysts.

[0019] The present invention is more advantageous when removing hydrogen peroxide from water to be treated that contains carbonates, which place a load on the anion exchanger, by using an anion exchanger supported on a platinum group metal catalyst as the metal catalyst. Furthermore, when the hydrogen peroxide removal chamber is partitioned by an anion exchange membrane on the anode side, the anions, i.e., carbonates, adsorbed from the water to be treated on the anion exchanger in the hydrogen peroxide removal chamber are desorbed from the anion exchanger by electrical regeneration and discharged in the form of anions from the hydrogen peroxide removal chamber via the anion exchange membrane on the anode side. In other words, the present invention not only produces treated water from which hydrogen peroxide has been removed, but also improves the quality of the treated water.

[0020] In the present invention, a deionization compartment filled with an ion exchanger may be provided adjacent to the cathode or anode side of the hydrogen peroxide removal compartment via an intermediate ion exchange membrane, and treated water from the hydrogen peroxide removal compartment may be passed through the deionization compartment. This configuration allows for the removal of hydrogen peroxide from the water to be treated and the desalination of the water to be treated simultaneously. [Effects of the Invention]

[0021] According to the present invention, it is possible to obtain a water treatment method and apparatus that improves the efficiency of decomposing organic matter in water to be treated and that has little effect on downstream devices. [Brief explanation of the drawings]

[0022] [Figure 1] 1(a) to 1(d) are all flow diagrams showing a water treatment device according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram showing the configuration of a hydrogen peroxide removal device according to a first configuration example. [Figure 3] FIG. 1 is a schematic diagram showing a specific example of a hydrogen peroxide removal device. [Figure 4] 4 is a schematic diagram showing an example of the flow of water in the hydrogen peroxide removal device shown in FIG. 3. FIG. [Figure 5] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 6] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 7] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 8] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 9] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 10] FIG. 4 is a schematic diagram showing the configuration of a hydrogen peroxide removal device according to a second configuration example. [Figure 11] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 12] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 13] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 14] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 15] FIG. 1 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. [Figure 16] 1 is a graph showing the results of Example 1. [Figure 17]1 is a graph showing the results of Comparative Example 1. [Figure 18] 1 is a graph showing the results of Example 2 and Comparative Examples 2 and 3. DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings.

[0024] FIG. 1(a) shows a water treatment device according to one embodiment of the present invention. This water treatment device decomposes and removes organic components from water to be treated by ultraviolet oxidation. The water treatment device comprises a hydrogen peroxide source 101 for supplying hydrogen peroxide (H2O2) to a pipe carrying the water to be treated; an ultraviolet oxidation device 103 for performing ultraviolet oxidation by irradiating the water to which hydrogen peroxide has been added with ultraviolet light; and a hydrogen peroxide removal device 105 for removing hydrogen peroxide from the water at the outlet of the ultraviolet oxidation device 103. The water at the outlet of the hydrogen peroxide removal device 105 is the treated water. The hydrogen peroxide source 101 stores, for example, an aqueous solution of hydrogen peroxide, which is added to the water to be treated, thereby adding hydrogen peroxide to the water. In this embodiment, hydrogen peroxide is added to the water to be treated in order to increase the decomposition efficiency of organic matter during ultraviolet oxidation, as disclosed in Patent Document 1. Therefore, for example, the one described in Patent Document 1, which is equipped with a low-pressure ultraviolet lamp that emits ultraviolet rays with wavelengths of 254 nm and 185 nm, can be used as the ultraviolet oxidation device 103. A high-pressure ultraviolet lamp that emits ultraviolet rays with a wavelength of 254 nm can also be used. Furthermore, a mercury lamp is used as the lamp that emits ultraviolet rays, but for example, an ultraviolet LED (light-emitting diode) can also be used.

[0025] As will be apparent from the examples and comparative examples described below, the outlet water from the ultraviolet oxidation device 103 contains hydrogen peroxide. Supplying this outlet water directly to downstream devices, such as an ion exchange device, EDI device, or membrane degasser, could potentially damage those devices. Therefore, in the device of this embodiment, the outlet water from the ultraviolet oxidation device 103 is treated by a hydrogen peroxide removal device 105 to remove hydrogen peroxide. Supplying the treated water from the hydrogen peroxide removal device 105 to downstream devices reduces the amount of hydrogen peroxide flowing into the downstream devices, thereby preventing damage to the downstream devices. In this embodiment, the hydrogen peroxide removal device 105 includes an anode, a cathode, and a hydrogen peroxide removal chamber disposed between the anode and cathode and containing a metal catalyst capable of decomposing hydrogen peroxide. A direct current is applied between the anode and cathode. The specific configuration of the hydrogen peroxide removal device 105 will be described below. This hydrogen peroxide removal device 105 can be equipped with not only a hydrogen peroxide removal function but also a desalination function. Decomposition and removal of organic matter by ultraviolet oxidation generates carbon dioxide and other carbonic acid components and organic acids. However, by providing the hydrogen peroxide removal device 105 with a demineralization function, it becomes possible to omit the ion exchange device that is installed downstream of the ultraviolet oxidation device to remove the carbonic acid components and organic acids. Furthermore, an ion removal device may be installed upstream of the ultraviolet oxidation device. Specifically, at least one of a reverse osmosis membrane separation device, an ion exchange device, an EDI device, or the like may be installed upstream of the ultraviolet oxidation device. By removing ionic organic components (organic acids) in advance using these devices installed upstream of the ultraviolet oxidation process, it is possible to reduce the amount of organic matter that must be treated by the ultraviolet oxidation device, thereby achieving a more compact ultraviolet oxidation device.

[0026] FIG. 1(b) shows the configuration of a water treatment device according to another embodiment of the present invention. As will become clear from the comparative example described below, when the dissolved oxygen (DO) concentration in the inlet water to the ultraviolet oxidation treatment is high, the TOC (total organic carbon) removal rate in the ultraviolet oxidation treatment does not increase even if the inlet water contains hydrogen peroxide. The results of the comparative example showed that when the dissolved oxygen concentration in the inlet water to the ultraviolet oxidation treatment exceeds 3 mg / L, adding hydrogen peroxide to the water to be treated did not increase the organic matter decomposition efficiency. Therefore, the water treatment device shown in FIG. 1(b) is the same as the water treatment device shown in FIG. 1(a), except that a membrane degassing device 104 is installed in the area where the water to be treated is received to remove dissolved oxygen from the water to be treated. The water at the outlet of the membrane degassing device 104 is supplied to the ultraviolet oxidation device 103 after adding hydrogen peroxide. The membrane degassing device 104 removes oxygen from the water to be treated so that the dissolved oxygen concentration in the outlet water is 3 mg / L or less. An oxygen removal device other than the membrane degassing device 104 may also be used. For example, hydrogen (H2) may be added to the water to be treated and then passed through a palladium (Pd) catalyst or a platinum (Pt) catalyst, causing the oxygen and hydrogen to react to form water, thereby deoxidizing the water.

[0027] FIG. 1(c) shows the configuration of a water treatment device according to yet another embodiment of the present invention. As will become clear from the examples described below, the TOC removal rate varies depending on the hydrogen peroxide concentration in the water exiting the ultraviolet oxidation process. Therefore, it is preferable to adjust the amount of hydrogen peroxide added to the water to be treated based on the hydrogen peroxide concentration in the water exiting the ultraviolet oxidation process. Therefore, the water treatment device shown in FIG. 1(c) differs from the water treatment device shown in FIG. 1(a) in that it includes a hydrogen peroxide injection amount adjusting means 102 at the outlet of the hydrogen peroxide source 101 and a hydrogen peroxide concentration meter (H2O2 meter) 106 that measures the hydrogen peroxide concentration in the water exiting the ultraviolet oxidation device 103. The hydrogen peroxide injection amount adjusting means 102 is controlled based on the hydrogen peroxide concentration measured by the hydrogen peroxide concentration meter 106, thereby adding hydrogen peroxide to the water to be treated according to the hydrogen peroxide concentration in the water exiting the ultraviolet oxidation device 103. Specifically, it is preferable to adjust the amount of hydrogen peroxide added to the water to be treated so that the hydrogen peroxide concentration measured by the hydrogen peroxide concentration meter 106 is 500 μg / L or less. In the configuration shown in FIG. 1(c), the water at the outlet of the ultraviolet oxidation device 103 is directly supplied to the hydrogen peroxide removal device 105, so the hydrogen peroxide concentration in the water at the outlet of the ultraviolet oxidation device 103 is equal to the hydrogen peroxide concentration in the water at the inlet of the hydrogen peroxide removal device 105. However, if some equipment is installed between the outlet of the ultraviolet oxidation device 103 and the inlet of the hydrogen peroxide removal device 105, the hydrogen peroxide concentration may change due to that equipment. In such cases, the amount of hydrogen peroxide added to the water to be treated can be adjusted based on at least one of the hydrogen peroxide concentration in the water at the outlet of the ultraviolet oxidation device 103 and the hydrogen peroxide concentration in the water at the inlet of the hydrogen peroxide removal device 105. The hydrogen peroxide injection amount adjustment means 102 can be of any configuration as long as it can adjust the amount of hydrogen peroxide added from the hydrogen peroxide source 101 to the water to be treated, but for example, a chemical injection pump (chemical injection pump) can be used.

[0028] FIG. 1(d) shows the configuration of a water treatment device according to yet another embodiment of the present invention. As will become clear from the examples described below, the TOC removal rate varies depending on the dissolved oxygen concentration in the outlet water of the hydrogen peroxide removal process. Therefore, it is preferable to change the amount of hydrogen peroxide added to the water to be treated based on the dissolved oxygen concentration in the outlet water of the hydrogen peroxide removal process. Therefore, the water treatment device shown in FIG. 1(d) is the same as the water treatment device shown in FIG. 1(a), except that a hydrogen peroxide injection rate adjusting means 102 is provided at the outlet of the hydrogen peroxide source 101, as described above, and a dissolved oxygen concentration meter (DO meter) 107 is provided to measure the dissolved oxygen concentration in the outlet water of the hydrogen peroxide removal device 105. The hydrogen peroxide injection rate adjusting means 102 is controlled based on the dissolved oxygen concentration measured by the dissolved oxygen concentration meter 107, thereby adding hydrogen peroxide to the water to be treated according to the dissolved oxygen concentration in the outlet water of the hydrogen peroxide removal device 105. Specifically, it is preferable to adjust the amount of hydrogen peroxide added to the water to be treated so that the dissolved oxygen concentration measured by the dissolved oxygen concentration meter 107 is 0.3 mg / L or less. The means for measuring various concentrations, such as the dissolved oxygen concentration, may be a continuous measurement or a measurement on an as-needed basis. Furthermore, sampled water may be separately measured online, and the amount of hydrogen peroxide added may be adjusted based on the measured value.

[0029] Next, the configuration of a hydrogen peroxide removal device 105 that can be preferably used in the water treatment device shown in FIGS. 1(a) to 1(d) will be described. As described above, the hydrogen peroxide removal device 105 includes an anode, a cathode, and a hydrogen peroxide removal chamber disposed between the anode and cathode and containing a metal catalyst capable of decomposing hydrogen peroxide. A direct current is applied between the anode and cathode. The metal catalyst is typically supported on a carrier. Preferably, an ion exchanger such as an ion exchange resin is used as the carrier. In this case, the hydrogen peroxide removal chamber is filled with the ion exchanger, and at least a portion of the ion exchanger filled in the hydrogen peroxide removal chamber is the ion exchanger carrying the metal catalyst. The hydrogen peroxide removal chamber disposed between the anode and cathode is partitioned into an anode side and a cathode side. In this case, it is preferable to partition the hydrogen peroxide removal chamber using an ion exchange membrane. The cathode side of the hydrogen peroxide removal chamber can also be partitioned by the cathode itself. An example of the configuration of such a hydrogen peroxide removal device 105 will be described below. In the following description of the configuration of the hydrogen peroxide removal device 105, the water to be treated refers to the water supplied to the hydrogen peroxide removal chamber of the hydrogen peroxide removal device 105, and is typically the outlet water of the ultraviolet oxidation device 103 in the water treatment device shown in Figures 1(a) to (d).

[0030] FIG. 2 shows the configuration of a hydrogen peroxide removal apparatus according to a first exemplary configuration. The hydrogen peroxide removal apparatus includes at least one hydrogen peroxide removal chamber 23 between an anode chamber 21 equipped with an anode 11 and a cathode chamber 25 equipped with a cathode 12. The hydrogen peroxide removal chamber 23 is partitioned by a first ion exchange membrane located on the anode 11 side and a second ion exchange membrane located on the cathode 12 side. The hydrogen peroxide removal chamber 23 is filled with an ion exchanger carrying a metal catalyst capable of decomposing hydrogen peroxide. In the example shown in FIG. 2, the first ion exchange membrane located on the anode 11 side is an anion exchange membrane 32, and the second ion exchange membrane located on the cathode 12 side is a cation exchange membrane 33. The hydrogen peroxide removal chamber 23 is filled with an ion exchanger (IER) carrying a platinum group metal catalyst. In the figure, the ion exchanger carrying a platinum group metal catalyst is designated "Cat. IER." 2, an anode 11 and a cathode 12 face each other, and an anode chamber 21, a first concentrating chamber 22, a hydrogen peroxide removal chamber 23, a second concentrating chamber 24, and a cathode chamber 25 are arranged between the anode 11 and the cathode 12 in this order from the anode 11 side. The anode chamber 21 and the first concentrating chamber 22 are separated by a cation exchange membrane 31, the first concentrating chamber 22 and the hydrogen peroxide removal chamber 23 are separated by an anion exchange membrane 32, the hydrogen peroxide removal chamber 23 and the second concentrating chamber 24 are separated by a cation exchange membrane 33, and the second concentrating chamber 24 and the cathode chamber 25 are separated by an anion exchange membrane 34. The anode chamber 21, the first concentrating chamber 22, the second concentrating chamber 24, and the cathode chamber 25 are each filled with an ion exchanger that does not support a platinum group metal catalyst. Here, the ion exchanger may be either an anion exchanger or a cation exchanger, or both. When both an anion exchanger and a cation exchanger are used, the ion exchanger may be packed in a mixed bed configuration in which a mixture of anion exchanger and cation exchanger is packed, or in a multi-layer bed configuration in which a layer of anion exchanger and a layer of cation exchanger are packed separately.

[0031] Next, the operation of the hydrogen peroxide removal apparatus shown in Figure 2 will be described. When removing hydrogen peroxide from water to be treated that contains hydrogen peroxide, feed water is passed through the anode chamber 21, first concentration chamber 22, second concentration chamber 24, and cathode chamber 25, and the water to be treated is passed through the hydrogen peroxide removal chamber 23 while a direct current is applied between the anode 11 and the cathode 12. When the water to be treated that contains hydrogen peroxide is passed through the hydrogen peroxide removal chamber 23, the hydrogen peroxide in the water to be treated is decomposed into water and oxygen by a catalytic reaction with a platinum group metal catalyst supported on the ion exchanger in the hydrogen peroxide removal chamber 23, and as a result, treated water from which hydrogen peroxide has been removed flows out of the hydrogen peroxide removal chamber 23. At this time, in the hydrogen peroxide removal chamber 23, a potential difference generated at the interface between the different ion exchange materials due to the applied current causes a water dissociation reaction (HO → H + +OH - ) occurs simultaneously, and hydrogen ions (H + ) and hydroxide ions (OH - ) is generated. The interface between different ion exchange materials is, for example, the interface between an anion exchange membrane and a cation exchanger, the interface between a cation exchange membrane and an anion exchanger, or the interface between a cation exchanger and anion exchanger. The hydrogen ions and hydroxide ions generated in this way exchange and desorb ion components that were previously adsorbed on the ion exchanger in the hydrogen peroxide removal chamber 23. Of the desorbed ion components, anions migrate through the anion exchange membrane 32 to the first concentrating chamber 22 closer to the anode 11 and are discharged from this first concentrating chamber 22 as concentrated water. Meanwhile, cations migrate through the cation exchange membrane 33 to the second concentrating chamber 24 closer to the cathode 12 and are discharged from this second concentrating chamber 24 as concentrated water. Ultimately, the ion components in the water to be treated that were supplied to the hydrogen peroxide removal chamber 23 migrate to the first concentrating chamber 22 and the second concentrating chamber 24 and are discharged, and at the same time, the ion exchanger in the hydrogen peroxide removal chamber 23 is regenerated. Electrode water is discharged from the anode chamber 21 and the cathode chamber 25. The application of DC current may be continuous or intermittent while the water to be treated is being passed through. Furthermore, the water to be treated may be passed through the hydrogen peroxide removal chamber 23 intermittently while the DC current is being applied continuously or intermittently.

[0032] The feed water passed through the concentration chambers 22, 24 and the electrode chambers (i.e., the anode chamber 21 and the cathode chamber 25) is not particularly limited; independent feed waters can be used, or the same feed water can be branched and used. Furthermore, the feed water can be the water to be treated or the treated water discharged from the hydrogen peroxide removal chamber 23, or a separate system of feed water that does not contain hydrogen peroxide can be passed through. In the figure, the flow of the feed water and the water to be treated in the electrode chambers, concentration chambers 22, 24, and hydrogen peroxide removal chamber 23 is parallel to each other, but the water can also flow countercurrently between adjacent chambers.

[0033] In the configuration shown in FIG. 2 , a basic configuration consisting of [concentration compartment (C) 22 | anion exchange membrane (AEM) 32 | hydrogen peroxide removal compartment (H) 23 | cation exchange membrane (CEM) 33 | concentration compartment (C) 24] is disposed between an anode 11 and a cathode 12. This basic configuration is called a cell set. In practice, a plurality of such cell sets (referred to as "N sets" in FIG. 2 ) can be juxtaposed between the electrodes, and the plurality of cell sets can be electrically connected in series with one end serving as the anode 11 and the other end as the cathode 12, thereby increasing the treatment capacity. In this case, adjacent cell sets can share adjacent concentration compartments. Therefore, the configuration of the hydrogen peroxide removal device according to the present invention can be configured as [anode chamber | CEM | C | X | X | · · · | X | AEM | cathode chamber], where X represents the repeating unit consisting of [AEM | H | CEM | C]. In such a series structure, for the hydrogen peroxide removal chamber 23 closest to the anode chamber 21, the anode chamber 21 itself can function as the concentration chamber 22 without an independent concentration chamber 22 interposed between the anode chamber 21 and the anode chamber 21. Similarly, for the hydrogen peroxide removal chamber 23 closest to the cathode chamber 25, the cathode chamber 25 itself can function as the concentration chamber 24 without an independent concentration chamber 24 interposed between the cathode chamber 25 and the anode chamber 21.

[0034] FIG. 3 shows another specific example of a hydrogen peroxide removal device, in which, in the configuration shown in FIG. 2, the anode chamber 21 is filled with a cation exchange resin (CER), the concentration chambers 22 and 24 and the cathode chamber 25 are filled with anion exchange resin (AER), and the hydrogen peroxide removal chamber 23 is filled with anion exchange resin (Cat. AER) carrying a platinum group metal catalyst.

[0035] 4 shows an example in which treated water from which hydrogen peroxide has been removed in the hydrogen peroxide removal chamber 23 is used as feed water to the anode chamber 21, the first concentrating chamber 22, the second concentrating chamber 24, and the cathode chamber 25 in the hydrogen peroxide removal apparatus shown in FIG. A portion of the treated water obtained from the hydrogen peroxide removal chamber 23 is passed through the first concentrating chamber 22 and the second concentrating chamber 24 and discharged as concentrated water. A portion of the treated water is passed through the cathode chamber 25, and the discharged electrode water is passed through the anode chamber 21. Using the treated water from which hydrogen peroxide has been removed as feed water to be passed through the concentrating chambers and the electrode chambers reduces the risk of oxidative degradation of the ion exchangers contained in the concentrating chambers and the electrode chambers.

[0036] In the hydrogen peroxide removal apparatus of the first configuration example, in addition to an anion exchanger (Cat. AER) supporting a platinum group metal catalyst, an ion exchanger not supporting a metal catalyst can be packed into the hydrogen peroxide removal chamber 23. Such an example will be described below. When the hydrogen peroxide removal chamber 23 is packed with an ion exchanger not supporting a metal catalyst, it is preferable to determine the arrangement of the ion exchangers so that the ion exchanger supporting a metal catalyst is placed in contact with the inlet of the hydrogen peroxide removal chamber 23 for the water to be treated, so that the ion exchanger is not deteriorated by hydrogen peroxide. In the following description, an anion exchange resin supporting a platinum group metal catalyst is also referred to as a catalyst-supported anion exchange resin (Cat. AER). The terms anion exchange resin (AER) and cation exchange resin (CER) simply refer to an anion exchange resin and cation exchange resin not supporting a metal catalyst, respectively.

[0037] 5, the hydrogen peroxide removal chamber 23 is filled with a mixture of a catalyst-supported anion exchange resin (Cat. AER) and an anion exchange resin (AER). Note that a cation exchange resin (CER) may be used instead of the anion exchange resin (AER). In this configuration, the amount of expensive platinum group metal catalyst used can be reduced compared to when only a catalyst-supported anion exchange resin (Cat. AER) is filled in the hydrogen peroxide removal chamber 23, thereby reducing costs.

[0038] 6, hydrogen peroxide removal chamber 23 is filled with a multi-layered bed configuration in which layers of catalyst-supported anion exchange resin (Cat. AER) and layers of anion exchange resin (AER) are alternately arranged with the catalyst-supported anion exchange resin (Cat. AER) layer being located upstream along the water flow. In this hydrogen peroxide removal apparatus, hydrogen peroxide is decomposed and removed near the inlet for the water to be treated in hydrogen peroxide removal chamber 23, and anions are desalted throughout hydrogen peroxide removal chamber 23.

[0039] The hydrogen peroxide removal apparatus shown in Figure 7 is the same as the hydrogen peroxide removal apparatus shown in Figure 6, except that cation exchange resin (CER) is used instead of anion exchange resin (AER). Therefore, hydrogen peroxide removal chamber 23 is filled with a layer of catalyst-supported anion exchange resin (Cat. AER) and a layer of cation exchange resin (CER) in a multi-layered bed configuration, with the layer of catalyst-supported anion exchange resin (Cat. AER) located upstream along the water flow. In this hydrogen peroxide removal apparatus, hydrogen peroxide is decomposed and removed near the inlet for the water to be treated in hydrogen peroxide removal chamber 23, and desalination of anions and cations is also performed overall.

[0040] 8, a layer of catalyst-supported anion exchange resin (Cat. AER), a layer of cation exchange resin (CER), and a layer of anion exchange resin (AER) are packed in hydrogen peroxide removal chamber 23 in this order from upstream along the water flow in a multi-layered bed configuration. In hydrogen peroxide removal chamber 23 of this hydrogen peroxide removal apparatus, removal of hydrogen peroxide and desalination treatment of both anions and cations are also carried out, and at the same time, regeneration of each ion exchange resin is carried out.

[0041] In the hydrogen peroxide removal apparatus described using Figures 6 to 8, by making the hydrogen peroxide removal chamber 23 a multi-layer bed structure, the amount of expensive platinum group metal catalyst used can be reduced compared to when only catalyst-supported anion exchange resin (Cat. AER) is filled in the hydrogen peroxide removal chamber 23, thereby reducing costs.

[0042] As mentioned above, the anode chamber can function as a concentrating compartment without providing a concentrating compartment adjacent to the anode chamber, and similarly, the cathode chamber can function as a concentrating compartment without providing a concentrating compartment adjacent to the cathode chamber. In the hydrogen peroxide removal device shown in Figure 9, an anode 11, an anode chamber 26, an anion exchange membrane 32, a hydrogen peroxide removal chamber 23, a cation exchange membrane 33, a cathode chamber 27, and a cathode 12 are arranged in this order. Both the anode chamber 26 and the cathode chamber 27 function as concentrating compartments. The anode chamber 26 is filled with an anion exchange resin (AER) or a cation exchange resin (CER), the hydrogen peroxide removal chamber 23 is filled with a catalyst-supported anion exchange resin (Cat. AER), and the cathode chamber 27 is filled with an anion exchange resin (AER) or a cation exchange resin (CER). This hydrogen peroxide removal apparatus is the same as the hydrogen peroxide removal apparatus shown in Figure 3, except that anode chamber 26 and cathode chamber 27 respectively function as concentration chambers 22 and 24, and instead do not have concentration chambers 22 and 24. Therefore, the hydrogen peroxide removal apparatus shown in Figure 9 operates in the same way as the hydrogen peroxide removal apparatus shown in Figure 3.

[0043] Next, a second configuration example of a hydrogen peroxide removal apparatus will be described. In the hydrogen peroxide removal apparatus of the first configuration example, a deionization chamber can be provided adjacent to the hydrogen peroxide removal chamber 23 via an intermediate ion exchange membrane between the anode 11 and the cathode 12 on either the cathode or anode side of the hydrogen peroxide removal chamber 23. The treated water obtained by passing the water to be treated through the hydrogen peroxide removal chamber can be passed through the deionization chamber. The deionization chamber is filled with an ion exchanger. This configuration allows for simultaneous removal of hydrogen peroxide from the water to be treated and desalination, making it possible to produce highly pure water and ultrapure water. The intermediate ion exchange membrane can be an anion exchange membrane, a cation exchange membrane, or a composite membrane such as a bipolar membrane.

[0044] Figure 10 shows a second configuration example of a hydrogen peroxide removal device. The illustrated hydrogen peroxide removal device has an intermediate ion exchange membrane 36 instead of the second ion exchange membrane of the hydrogen peroxide removal device shown in Figure 2. A deionization compartment 28 filled with an ion exchanger is provided on the cathode 12 side of the intermediate ion exchange membrane 36, and a second ion exchange membrane is disposed between the deionization compartment 28 and the cathode compartment 25. Water treated in the hydrogen peroxide removal compartment 23 is passed through the deionization compartment 28. In the illustrated configuration, the anode 11, anode compartment 21, cation exchange membrane 31, first concentration compartment 22, anion exchange membrane 32, hydrogen peroxide removal compartment 23, intermediate ion exchange membrane 36, deionization compartment 28, cation exchange membrane 33, second concentration compartment 24, anion exchange membrane 34, cathode compartment 25, and cathode 12 are arranged in this order.

[0045] Figure 11 shows a specific example of the hydrogen peroxide removal apparatus of the second configuration example. The hydrogen peroxide removal apparatus shown in Figure 11 is the hydrogen peroxide removal apparatus shown in Figure 3, with deionization chamber 28 located between hydrogen peroxide removal chamber 23 and second concentrating chamber 24. Hydrogen peroxide removal chamber 23 and deionization chamber 28 are separated by cation exchange membrane 35, which is an intermediate ion exchange membrane, and deionization chamber 28 and second concentrating chamber 24 are separated by cation exchange membrane 33, which is a second ion exchange membrane. Water to be treated is supplied to hydrogen peroxide removal chamber 23, where hydrogen peroxide is decomposed and removed, and then the water is passed through deionization chamber 28. Treated water from which hydrogen peroxide has been removed and desalted is discharged from deionization chamber 28. In the hydrogen peroxide removal apparatus shown in FIG. 11 , the anion exchange membrane 32 to the second concentrating chamber 24 are defined as a repeating unit X, and multiple sets of repeating units X can be provided in series between the first concentrating chamber 22 adjacent to the anode chamber 21 and the anion exchange membrane 34 in contact with the cathode chamber 25.

[0046] The hydrogen peroxide removal apparatus shown in Figure 12 differs from the hydrogen peroxide removal apparatus shown in Figure 11 in that anion exchange resin and cation exchange resin are packed in a mixed bed (MB) configuration in deionization compartment 28. In Figure 12, the intermediate ion exchange membrane separating hydrogen peroxide removal compartment 23 and deionization compartment 28 is composed of anion exchange membrane 37.

[0047] The hydrogen peroxide removal apparatus shown in Figure 13 differs from the hydrogen peroxide removal apparatus shown in Figure 11 in that it uses an anion exchange membrane 37 as an intermediate ion exchange membrane separating hydrogen peroxide removal compartment 23 and deionization compartment 28, and in that deionization compartment 28 is filled with a multi-layer bed configuration in which layers of cation exchange resin (CER) and layers of anion exchange resin (AER) are alternately arranged in this order along the direction of water flow. Deionization compartment 28 and concentration compartment 24 on the cathode 12 side are separated by a cation exchange membrane 33.

[0048] The hydrogen peroxide removal apparatus shown in Figure 14 is the same as the hydrogen peroxide removal apparatus shown in Figure 13, except that an auxiliary hydrogen peroxide removal chamber 29 is placed between the concentrating chamber 24 and the cathode chamber 25 on the cathode 12 side. This hydrogen peroxide removal chamber 29 is also filled with an anion exchanger (Cat. AER) supporting a platinum group metal catalyst, and water to be treated is supplied to it. The water discharged from the hydrogen peroxide removal chamber 29 is combined with the water discharged from the hydrogen peroxide removal chamber 23 and supplied to the deionization chamber 28. The concentrating chamber 24 and the hydrogen peroxide removal chamber 29 are adjacent to each other with an anion exchange membrane 34 in between, and the hydrogen peroxide removal chamber 29 and the cathode chamber 25 are adjacent to each other with an anion exchange membrane 38 in between. The hydrogen peroxide removal apparatus shown in Figure 14 has multiple hydrogen peroxide removal chambers 23, 29, allowing for more efficient removal of hydrogen peroxide.

[0049] In the hydrogen peroxide removal apparatus, the cathode chamber 25 can also be filled with an anion exchanger (Cat. AER) carrying a platinum group metal catalyst, allowing the cathode chamber 25 itself to function as a hydrogen peroxide removal chamber. The hydrogen peroxide removal apparatus shown in Figure 15 is the hydrogen peroxide removal apparatus shown in Figure 3, except that the cathode chamber 25 is also filled with a catalyst-carrying anion exchange resin (Cat. AER) and is supplied with water to be treated. The water discharged from the cathode chamber 25, i.e., cathode water, is combined with the water discharged from the hydrogen peroxide removal chamber 23 and discharged as treated water. This configuration is useful when the water to be treated contains carbonate components but no cations. In the configuration shown in Figure 15, the concentration chambers 22, 24, the hydrogen peroxide removal chamber 23, the cation exchange membranes 31, 33, and the anion exchange membrane 32 may not be provided, and the anode chamber 21, which is provided with the anode 11 and filled with a cation exchange resin (CER), may be adjacent to the cathode chamber 25 via the anion exchange membrane 34. [Example]

[0050] Next, the present invention will be described in more detail with reference to examples and comparative examples.

[0051] [Example 1] The water treatment device shown in Figure 1(a) was assembled. The ultraviolet oxidation device 103 was a Funatec Corporation-manufactured ultraviolet oxidation device (FOV type). The hydrogen peroxide removal device 105 used had the configuration shown in Figure 13, in which five sets of repeating units X (i.e., N = 5) were used. The dimensions of each chamber (anode chamber 21, concentration chambers 22 and 24, hydrogen peroxide removal chamber 23, cathode chamber 25, and deionization chamber 28) in the hydrogen peroxide removal device 105 were 160 mm x 280 mm x 8 mm. The operating current of the hydrogen peroxide removal device 103 was 3.0 A. Ultrapure water containing isopropyl alcohol added as a TOC component was used as the water to be treated. The flow rate of the water to be treated supplied to the ultraviolet oxidation device 103 was 570 L / h. Of the outlet water discharged from the ultraviolet oxidation device 103 at a flow rate of 570 L / h, 500 L / h was used as the water to be treated in the hydrogen peroxide removal device 105. At this time, the irradiation amount of the ultraviolet lamp in the ultraviolet oxidation device 103 is 1000 W·h / m 3 While changing the amount of hydrogen peroxide added, the water quality (resistivity), hydrogen peroxide concentration, TOC concentration, and dissolved oxygen concentration were measured at the inlet of the ultraviolet oxidation device 103, the inlet of the hydrogen peroxide removal device 105, and the outlet of the hydrogen peroxide removal device 105. The TOC removal rate was also calculated from the TOC concentrations at the inlet of the ultraviolet oxidation device 103 and the outlet of the hydrogen peroxide removal device 105. The results are shown in Table 1. The water temperature is the temperature of the water to be treated supplied to the ultraviolet oxidation device 103. Figure 16 shows the relationship between the hydrogen peroxide concentration at the inlet of the ultraviolet oxidation device 103 and the TOC removal rate.

[0052] [Table 1]

[0053] Table 1 and Figure 16 show that TOC removal performance, expressed as the TOC removal rate, is highest when the hydrogen peroxide concentration at the inlet of the ultraviolet oxidation device 103 is approximately 500 μg / L. Increasing the hydrogen peroxide concentration does not necessarily improve TOC removal performance; rather, when the hydrogen peroxide concentration exceeds 500 μg / L, TOC removal performance actually decreases. Furthermore, we found that to maintain a TOC removal rate of 80% or higher, it is necessary to adjust the amount of hydrogen peroxide added at the inlet of the ultraviolet oxidation device 103 so that the hydrogen peroxide concentration at the outlet of the ultraviolet oxidation device 103 is 500 μg / L or less and the dissolved oxygen concentration at the outlet of the hydrogen peroxide removal device 105 is 0.3 mg / L or less. The resistivity at the outlet of the hydrogen peroxide removal device 105 is close to the theoretical value for pure water, and we also found that the carbonic acid and organic acids generated by the ultraviolet oxidation process can be effectively removed by the hydrogen peroxide removal device 105. This means that the water treatment device according to the present invention does not need to have an ion exchange device in the downstream stage for removing carbonic acid components and organic acids generated in the ultraviolet oxidation treatment.

[0054] [Comparative Example 1] For the case where the dissolved oxygen concentration in the water to be treated supplied to the ultraviolet oxidation device 103 is high, an experiment similar to that in Example 1 was conducted using the same device as in Example 1. However, the flow rate of the water to be treated to the ultraviolet oxidation device 103 was set to 1390 L / h, and 750 L / h of the water at the outlet of the ultraviolet oxidation device 103 was supplied to the hydrogen peroxide removal device 105 as the water to be treated. The ultraviolet lamp irradiation amount in the ultraviolet oxidation device 103 was 410 W·h / m 3 The results are shown in Table 2 and FIG.

[0055] [Table 2]

[0056] From the results of Comparative Example 1, it was confirmed that when the dissolved oxygen concentration at the inlet of the ultraviolet oxidation device 103 exceeds 3 mg / L, the TOC removal efficiency does not improve even if hydrogen peroxide is added.

[0057] [Example 2, Comparative Examples 2 and 3] The water exiting the UV oxidation treatment contains carbon dioxide and organic acids produced by the oxidation of organic components, as well as hydrogen peroxide produced by the oxidation of water. Conventionally, non-regenerative ion exchange devices (cartridge polishers: CPs) and palladium-loaded ion exchange resin columns (Pd-loaded ion exchange resin columns) have been used to remove these components. Cartridge polishers primarily remove carbon dioxide and organic acids, while Pd-loaded ion exchange resin columns primarily remove hydrogen peroxide. Therefore, the hydrogen peroxide removal performance of these devices was compared with that of the hydrogen peroxide removal device used in the water treatment device of the present invention.

[0058] Test water was prepared by adding hydrogen peroxide and carbon dioxide to water that had passed through two reverse osmosis (RO) membrane devices connected in series. The hydrogen peroxide concentration in the test water was 40-50 μg / L, and the carbon dioxide concentration was 2.8-3.2 mg / L (as CO2). In Example 2, test water was passed through the same device as in Example 1 at a treatment flow rate of 750 L / h, and the change in the hydrogen peroxide concentration in the treated water discharged as outlet water was examined. The operating current of the hydrogen peroxide removal device was 3.0 A. In Comparative Example 2, a cartridge polisher containing 5 L of resin was prepared, in which anion exchange resin and cation exchange resin were mixed in a 2:1 ratio (volume ratio). The same test water as in Example 2 was passed through the cartridge polisher at a flow rate of 500 L / h, and the change in the hydrogen peroxide concentration in the treated water discharged as outlet water was examined. In Comparative Example 3, a Pd-loaded ion exchange resin column with a resin volume of 0.5 L was prepared, and the same test water as in Example 2 was passed through it at 50 L / h to examine the change in the hydrogen peroxide concentration in the treated water discharged as outlet water. The results of Example 2 and Comparative Examples 2 and 3 are shown in Figure 18.

[0059] Figure 18 shows that the cartridge polisher of Comparative Example 2 was unable to remove almost all hydrogen peroxide, allowing it to pass through. The Pd-loaded ion exchange resin column of Comparative Example 3 was able to remove hydrogen peroxide immediately after starting operation, but the amount of hydrogen peroxide leakage increased as operation continued. This is thought to be due to the adsorption of carbonate ions and bicarbonate ions onto the ion exchange resin on which Pd was loaded, i.e., the catalyst-loaded anion exchange resin (Cat. AER). In contrast, the hydrogen peroxide removal device used in the water treatment device of Example 2, i.e., the present invention, was found to be able to stably remove hydrogen peroxide over a long period of time from the start of operation, with little hydrogen peroxide leakage. This is thought to be due to the hydroxide ions generated by the water dissociation reaction that occurs when an electric current is applied, maintaining the Pd-loaded ion exchange resin, i.e., the catalyst-loaded anion exchange resin (Cat. AER), in its regenerated state. [Explanation of symbols]

[0060] 11 Anode 12 Cathode 21,26 Anode chamber 22,24 Concentration chamber 23,29 Hydrogen peroxide removal chamber 25,27 Cathode chamber 28 Desalination room 31,33,35 Cation exchange membrane (CEM) 32,34,37,38 Anion exchange membrane (AEM) 36 Intermediate ion exchange membrane 101 Hydrogen Peroxide Source 102 Hydrogen peroxide injection amount adjustment means 103 Ultraviolet oxidation device 104 Membrane degassing device 105 Hydrogen peroxide removal device 106 Hydrogen peroxide concentration meter 107 Dissolved oxygen concentration meter

Claims

1. A water treatment method for decomposing organic matter contained in water to be treated, comprising: adding hydrogen peroxide to the water to be treated; an ultraviolet irradiation step of irradiating the water to be treated with hydrogen peroxide with ultraviolet light; a hydrogen peroxide removal step for removing hydrogen peroxide contained in the outlet water from the ultraviolet irradiation step; and The hydrogen peroxide removal step includes a step of applying a direct current between an anode and a cathode, and a step of passing the water to be treated through a hydrogen peroxide removal chamber that is disposed between the anode and the cathode and has a metal catalyst having hydrogen peroxide decomposition ability, the hydrogen peroxide removal chamber is partitioned by an ion exchange membrane at least on the anode side, The water treatment method, wherein the metal catalyst is a platinum group metal catalyst, and the hydrogen peroxide removal chamber is filled with an ion exchanger carrying the platinum group metal catalyst.

2. 2. The water treatment method according to claim 1, further comprising the step of removing oxygen from the water to be treated so that the dissolved oxygen concentration in the water at an inlet to the ultraviolet irradiation step is 3 mg / L or less.

3. 3. The water treatment method according to claim 1, wherein the amount of hydrogen peroxide added to the water to be treated is adjusted according to at least one of the dissolved oxygen concentration in the outlet water of the hydrogen peroxide removal process, the hydrogen peroxide concentration in the outlet water of the ultraviolet irradiation process, and the hydrogen peroxide concentration in the inlet water of the hydrogen peroxide removal process.

4. 3. The water treatment method according to claim 1, wherein the amount of hydrogen peroxide added to the water to be treated is adjusted so that the dissolved oxygen concentration in the outlet water of the hydrogen peroxide removal step is 0.3 mg / L or less.

5. 3. The water treatment method according to claim 1, wherein the amount of hydrogen peroxide added to the water to be treated is adjusted so that the hydrogen peroxide concentration in at least one of the outlet water of the ultraviolet irradiation step and the inlet water of the hydrogen peroxide removal step is 500 μg / L or less.

6. A water treatment device that decomposes organic matter contained in water to be treated, a hydrogen peroxide adding means for adding hydrogen peroxide to the water to be treated; an ultraviolet irradiation means for irradiating the water to be treated with added hydrogen peroxide with ultraviolet light; a hydrogen peroxide removal means for removing hydrogen peroxide contained in the outlet water from the ultraviolet irradiation means; and The hydrogen peroxide removal means an anode and a cathode; a hydrogen peroxide removal chamber disposed between the anode and the cathode and provided with a metal catalyst having hydrogen peroxide decomposition ability; the hydrogen peroxide removal chamber is partitioned by an ion exchange membrane at least on the anode side, The water treatment device, wherein the metal catalyst is a platinum group metal catalyst, and the hydrogen peroxide removal chamber is filled with an ion exchanger carrying the platinum group metal catalyst.

7. The water treatment device according to claim 6, further comprising a means for removing oxygen from the water to be treated, provided upstream of the ultraviolet irradiation means.

8. 8. The water treatment device according to claim 6, further comprising a hydrogen peroxide injection amount adjusting means for adjusting the amount of hydrogen peroxide to be added to the water to be treated in accordance with at least one of the dissolved oxygen concentration in the outlet water of the hydrogen peroxide removal means, the outlet water of the ultraviolet irradiation means, and the hydrogen peroxide concentration in the inlet water of the hydrogen peroxide removal means.

Images