Water treatment method, water treatment device, and design method for water treatment device

Abstract

To increase an efficiency of decomposing an organic matter and suppress an increase of hydrogen peroxide.SOLUTION: A water treatment method includes: removing dissolved oxygen from water to be treated, which contains dissolved oxygen and an organic matter, by a first deoxygenation device 33; irradiating the treated water from the first deoxygenation device 33 with ultraviolet light by an ultraviolet irradiation device 34; and passing the treated water from the ultraviolet irradiation device 34 through an ion exchanger filling device 35 filled with at least anion exchanger A. The ion exchanger filling device 35 removes hydrogen peroxide generated by irradiation of ultraviolet rays from the ultraviolet irradiation device 34 from the treated water of the ultraviolet irradiation device 34, and the treated water from the ultraviolet irradiation device 34 is passed through the anion exchanger A in the ion exchanger filling device 35 at a space velocity of less than 160 ( / h).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water treatment method, a water treatment device, and a method for designing a water treatment device. [Background technology]

[0002] As the demand for high quality pure water becomes more evident, in recent years, various methods for decomposing and removing trace amounts of organic matter contained in pure water have been considered. Patent Document 1 discloses a water treatment device in which a degassing membrane device, a UV oxidation device (hereinafter referred to as an ultraviolet irradiation device), and an ion exchanger are arranged in series. Patent Document 1 further describes that the efficiency of decomposing organic matter in the ultraviolet irradiation device is increased by lowering the dissolved oxygen concentration in the water to be treated by the ultraviolet irradiation device to a predetermined range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-175837 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application have found that lowering the dissolved oxygen concentration in water to be treated by an ultraviolet irradiation device increases the hydrogen peroxide concentration in the water being treated by the ultraviolet irradiation device. The present invention aims to provide a water treatment method that can increase the efficiency of decomposing organic matter and suppress an increase in the hydrogen peroxide concentration. [Means for solving the problem]

[0005] The water treatment method of the present invention includes removing dissolved oxygen from water to be treated, which contains dissolved oxygen and organic matter, by a first deoxygenation device, irradiating the treated water of the first deoxygenation device with ultraviolet light by an ultraviolet irradiation device, and passing the treated water of the ultraviolet irradiation device through an ion exchanger-packed device packed with at least an anion exchanger. The ion exchanger-packed device removes hydrogen peroxide generated by irradiation of ultraviolet light from the ultraviolet irradiation device from the treated water of the ultraviolet irradiation device, and the treated water of the ultraviolet irradiation device is passed through the anion exchanger of the ion exchanger-packed device at a space velocity of less than 160 ( / h).

[0006] Another water treatment method of the present invention includes removing dissolved oxygen from water to be treated containing dissolved oxygen and organic matter by a first deoxygenation device, irradiating the treated water by the first deoxygenation device with ultraviolet light by an ultraviolet irradiation device, and passing the treated water by the ultraviolet irradiation device through an ion exchanger-filled device filled with an ion exchanger. The first deoxygenation device adjusts the dissolved oxygen concentration in the treated water by the first deoxygenation device so that the hydrogen peroxide concentration in the treated water by the ion exchanger-filled device is lower than a predetermined value. Effect of the Invention

[0007] According to the present invention, it is possible to provide a water treatment method capable of increasing the efficiency of decomposing organic matter and suppressing an increase in the concentration of hydrogen peroxide. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a water treatment device according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic configuration diagram of a water treatment device according to a second embodiment of the present invention. [Diagram 3] FIG. 11 is a schematic configuration diagram of a water treatment device according to a third embodiment of the present invention. [Figure 4] FIG. 1 is a graph showing the relationship between the dissolved oxygen concentration in the water to be treated by the ultraviolet irradiation device and the hydrogen peroxide concentration and TOC in the water at the outlet of the ion exchange resin loading device. [Diagram 5]FIG. 1 is a schematic diagram of a test device used in Examples 1 and 2. [Figure 6] 1 is a graph showing the relationship between SV and the hydrogen peroxide concentration of the treated water. [Figure 7] 1 is a graph showing the relationship between the dissolved oxygen concentration in the inlet water of the ultraviolet irradiation device and the TOC reduction rate. [Figure 8] FIG. 1 is a schematic diagram of a test device used in Example 3. [Figure 9] 1 is a graph showing the relationship between the dissolved oxygen concentration in water to be treated by an ultraviolet irradiation device and the hydrogen peroxide concentration and TOC in water treated by an ion exchange resin filling device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the water treatment method and water treatment device of the present invention will be described with reference to the drawings. In the following description, "treated water" means water treated by a certain device and usually means the outlet water of the device, but in a context where a specific property of the treated water (e.g., dissolved oxygen concentration or organic matter concentration) is an issue, it includes water at any position downstream of the device as long as the specific property does not change substantially. FIG. 1 shows a schematic configuration of a water treatment device 1 according to a first embodiment of the present invention. The water treatment device 1 has a pretreatment device 2 on the upstream side and a pure water production device 3 (primary system) on the downstream side. The water treatment device 1 constitutes an ultrapure water production device together with a downstream subsystem (secondary system). The raw water supplied to the pretreatment device 2 contains dissolved oxygen and organic matter. In the following description, upstream and downstream are defined with respect to the flow direction D of the water to be treated or the treated water.

[0010] The pretreatment device 2 includes a filter 21 for removing dust particles having a relatively large particle size, and an activated carbon tower 22 for removing impurities such as polymeric organic matter. For example, a sand filter can be used as the filter 21. The pure water production system 3 includes an ion removal device 31, a reverse osmosis membrane device 32, a first deoxygenation device 33, an ultraviolet irradiation device 34, an ion exchanger filling device 35, and a second deoxygenation device 36. These devices 21, 22, 31 to 36 are arranged in series in this order in the mother pipe L1 from upstream to downstream with respect to the flow direction D of the water to be treated. Although not shown in the figure, a tank for holding treated water from each device of the pretreatment device 2 and the pure water production system 3, for example, the activated carbon tower 22, the ion removal device 31, and the reverse osmosis membrane device 32, may be provided. In addition, although not shown in the figure, a circulation line for returning a part of treated water from any of the devices 31 to 36 of the pure water production system 3 to an upstream tank may be provided.

[0011] The ion removal device 31 has a cation tower (not shown) filled with a cation exchange resin, a decarbonation tower (not shown), and an anion tower (not shown) filled with anion exchange resin, which are arranged in series from upstream to downstream. A decarbonation membrane may be provided instead of the decarbonation tower. Instead of the ion removal device 31, it is also possible to arrange a softener that removes hardness components such as calcium and magnesium on the upstream side and an electrodeionized water production device (EDI) on the downstream side in series.

[0012] The reverse osmosis membrane device 32 removes impurities such as ions. In this embodiment, since the ion removal device 31 is provided upstream of the reverse osmosis membrane device 32, the reverse osmosis membrane device 32 mainly removes uncharged substances such as organic matter. Removing organic matter with the reverse osmosis membrane device 32 reduces the load on the ultraviolet irradiator 34 located downstream. If the total organic carbon (hereinafter also referred to as TOC) of the water to be treated is high, the TOC reduction effect of the ultraviolet irradiator 34 decreases.

[0013] The first deoxygenation device 33 removes oxygen from the water to be treated, and reduces the dissolved oxygen concentration in the water to be treated. Since the first deoxygenation device 33 is located upstream of the ultraviolet irradiation device 34, the water to be treated with a reduced (adjusted) dissolved oxygen concentration is supplied to the ultraviolet irradiation device 34. The type of the first deoxygenation device 33 is not limited as long as it can remove dissolved oxygen, and for example, a vacuum degassing device can be used. In general, in a vacuum degassing device, a gas-liquid contact material for increasing the surface area of ​​water is filled in a degassing tower, the gas pressure in the degassing tower is reduced by a vacuum pump, the pure water to be treated is placed in a vacuum state, and the dissolved oxygen is removed. The dissolved oxygen concentration can be adjusted (controlled) by adjusting (controlling) the degree of vacuum in the degassing tower using a vacuum pump. Furthermore, the degassing performance can be improved by inflowing nitrogen. In this case, the dissolved oxygen concentration can be adjusted (controlled) by adjusting (controlling) the degree of vacuum and the amount of nitrogen inflow (nitrogen partial pressure). A degassing membrane device may be used as the first deoxygenation device 33. In this case, a vacuum pump is used as in the vacuum degassing device, and the dissolved oxygen concentration can be adjusted (controlled) by adjusting (controlling) the degree of vacuum. These first deoxygenation devices 33 can reduce the dissolved oxygen concentration in the water and at the same time remove volatile organic matter and carbon dioxide into the gas phase (secondary side), thereby reducing the concentrations of these substances in the water. Adjusting (controlling) the degree of vacuum and the amount of nitrogen inflow in the first deoxygenation device 33 includes, for example, measuring the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34 with a measuring device (not shown), and automatically adjusting (controlling) the degree of vacuum and the amount of nitrogen inflow in the first deoxygenation device 33 based on the measured value by a control device (not shown), or manually adjusting (controlling) the degree of vacuum and the amount of nitrogen inflow in the first deoxygenation device 33 by an operator. As another first deoxygenation device 33, a platinum catalyst loading device carrying a platinum catalyst such as palladium (Pd) may be used. The dissolved oxygen concentration in the water to be treated can be reduced by contacting the water to which hydrogen has been added with a platinum catalyst. The above-described first deoxidizing device 33 may be of a single stage configuration, or may be of a multi-stage configuration in which a plurality of devices are connected in series.

[0014] The ultraviolet irradiator 34 irradiates the water to be treated with ultraviolet rays. As the ultraviolet irradiator 34, for example, a low-pressure ultraviolet irradiator that generates ultraviolet rays with at least one of the wavelengths of 185 nm and 254 nm can be used.

[0015] The ion exchanger packing device 35 removes decomposition products of organic matter generated in the water to be treated by ultraviolet irradiation. The ion exchanger packing device 35 is packed with at least anion exchanger A, and may further be packed with cation exchanger K. The anion exchanger A is preferably of OH type. The anion exchanger A and the cation exchanger K are ion exchange resins, and the ion exchange resin may be either of gel type or MR type. When using an anion exchange resin and a cation exchange resin, either of a mixed bed type or a double bed type may be used. When using a double bed type, it is preferable that the anion exchange resin is located upstream of the cation exchange resin, since the cation exchange resin can remove a small amount of organic matter derived from the anion exchange resin that has eluted. The anion exchange resin and the cation exchange resin may be of either a regenerated type or a non-regenerated type. In the case of the regenerated type, it is preferable to use a double bed type because of ease of regeneration. Note that, for convenience, the anion exchanger A and the cation exchanger K are shown as a double bed type in FIG. 1, but FIG. 1 does not limit the configuration of the ion exchanger packing device 35. Monolithic or fibrous anion exchanger A and cation exchanger K can also be used. Alternatively, EDI packed with at least anion exchange resin can be used. Since EDI is a continuous regeneration type, a regeneration process for ion exchange resin is not required.

[0016] The second deoxygenation device 36 is located downstream of the ion exchanger filling device 35, and can have a configuration similar to that of the first deoxygenation device 33. The second deoxygenation device 36 removes dissolved oxygen, carbon dioxide, etc. from the water to be treated.

[0017] (Operation method of water treatment device 1) Next, a method of operating the water treatment device 1 described above will be described. First, the water to be treated (raw water) is supplied to the pretreatment device 2. The pretreatment device 2 removes impurities such as relatively large particle size dust and polymeric organic matter from the water to be treated. The cation tower, anion tower, and decarbonation tower of the ion removal device 31 remove cationic components, carbonates, and anionic components, respectively, from the water to be treated. The first deoxygenation device 33 removes a portion of the dissolved oxygen from the water to be treated that contains dissolved oxygen and organic matter. In this way, the water to be treated that contains organic matter and dissolved oxygen and has an adjusted dissolved oxygen concentration is supplied to the ultraviolet irradiation device 34.

[0018] The ultraviolet irradiation device 34, located downstream of the first deoxygenation device 33, irradiates the treated water from the first deoxygenation device 33 with ultraviolet rays. As shown in the following formula 1, the dissociated hydrogen radicals (·H) react with dissolved oxygen to become water, and the remaining OH radicals (·OH) decompose the organic matter. The OH radicals not used to decompose the organic matter recombine to become hydrogen peroxide. In other words, by irradiating the water to be treated with ultraviolet rays from the ultraviolet irradiation device 34, hydrogen peroxide is generated in the water to be treated (or the hydrogen peroxide concentration increases).

number

[0019] The treated water from the ultraviolet irradiation device 34 is passed through the ion exchanger packing device 35, which is located downstream of the ultraviolet irradiation device 34 and is packed with at least anion exchanger A. A part of hydrogen peroxide is decomposed into H2O and O2 (dissolved oxygen) on the surface of the anion exchanger A. That is, the ion exchanger packing device 35 removes a part of hydrogen peroxide generated by irradiation of ultraviolet light from the ultraviolet irradiation device 34 from the treated water from the ultraviolet irradiation device 34. The ion exchanger packing device 35 also removes organic matter remaining in the treated water from the ultraviolet irradiation device 34. The second deoxygenation device 36 removes dissolved oxygen generated when hydrogen peroxide is decomposed in the ion exchanger packing device 35. The treated water in which TOC is reduced and the increase in hydrogen peroxide is suppressed in this way is sent to the subsystem for further treatment.

[0020] Conventionally, platinum group catalysts have been used to remove hydrogen peroxide. Platinum group catalysts can decompose hydrogen peroxide with high efficiency, but are expensive. For this reason, when treating water containing a relatively high concentration of hydrogen peroxide, such as the treated water of the ultraviolet irradiation device 34, with a platinum group catalyst, the platinum group catalyst becomes large (i.e., a large amount of platinum group catalyst may be required), which may lead to an increase in the cost of the water treatment device 1. In this embodiment, hydrogen peroxide is decomposed by the anion exchanger A, so there is no need to use a platinum group catalyst, and an increase in operating costs can be suppressed. Note that the hydrogen peroxide concentration of the treated water of the ultraviolet irradiation device 34 is higher than the hydrogen peroxide concentration of the inlet water of the ultraviolet irradiation device 34, but the hydrogen peroxide concentration is on the order of several tens of μg / L as described in the examples below, and damage to the anion exchanger A, if any, is limited.

[0021] (Regarding the space velocity (SV) of the water to be treated passing through the ion exchanger packing device 35) As described above, hydrogen peroxide generated by irradiation of ultraviolet rays from the ultraviolet irradiation device 34 is removed by the ion exchanger packing device 35. However, the inventors of the present application have found that the efficiency of removing hydrogen peroxide from the water to be treated varies greatly depending on the conditions of water flow to the ion exchanger packing device 35. In this embodiment, the space velocity (SV) of the water treated by the ultraviolet irradiation device 34, which is passed through the anion exchanger A of the ion exchanger packing device 35, is controlled or adjusted to be less than 160 ( / h). The control or adjustment may be performed automatically or manually by an operator. This promotes the decomposition reaction of hydrogen peroxide by the anion exchanger A, and the increase in the hydrogen peroxide concentration can be suppressed. Although the lower limit of the SV is not particularly limited, if the SV is too low, the amount of organic matter eluted from the ion exchanger of the ion exchanger packing device 35 into the treated water per unit volume increases, leading to an increase in the TOC of the treated water. Therefore, the SV is preferably 40 ( / h) or more. Details of the SV will be described in the examples.

[0022] As described above, in addition to controlling or adjusting the space velocity (SV) of the treated water of the ultraviolet irradiation device 34, which is passed through the anion exchanger A of the ion exchanger filling device 35, to less than 160 ( / h), the water treatment device 1 may be designed so that the space velocity (SV) of the treated water of the ultraviolet irradiation device 34, which is passed through the anion exchanger A of the ion exchanger filling device 35, is less than 160 ( / h). For example, the water treatment device 1 includes a first deoxygenation device that removes dissolved oxygen from the water to be treated, which contains dissolved oxygen and organic matter, an ultraviolet irradiation device that is located downstream of the first deoxygenation device and irradiates the treated water of the first deoxygenation device with ultraviolet light, and an ion exchanger filling device that is located downstream of the ultraviolet irradiation device and is filled with at least an anion exchanger, and the water treatment device 1 is designed so that the space velocity of the treated water of the ultraviolet irradiation device, which is passed through the anion exchanger of the ion exchanger filling device, is less than 160 ( / h). In the water treatment device 1, as a method for designing so that the space velocity of the treated water in the ultraviolet irradiation device is less than 160 ( / h), for example, the flow rate of the water to be treated to the ion exchanger packing device 35 is determined based on the raw water flow rate, the treated water flow rate, the treated water quality, etc. Then, the amount of resin to be packed in the ion exchanger packing device 35 (for example, the cross-sectional area of ​​the ion exchanger packing device 35, the layer height of the ion exchange resin, etc.) and the number of columns of the ion exchanger packing device 35 when the ion exchanger packing devices 35 are arranged in parallel, etc. are determined so that the space velocity of the treated water in the ultraviolet irradiation device is less than 160 ( / h).

[0023] SV is calculated for anion exchanger A. For example, when only anion exchanger A is packed in the ion exchanger packing device 35, SV is calculated for the volume of the anion exchanger packed section. Specifically, the volume of the anion exchanger packed section is V(m 3 ), the flow rate of the treated water is q(m 3If the ion exchanger packing device 35 is packed with multiple beds of anion exchanger A and cation exchanger K, SV is calculated based on the volume of anion exchanger A only. If the ion exchanger packing device 35 is packed with mixed beds of anion exchanger A and cation exchanger K, SV is calculated based on the total volume of anion exchanger A, that is, based on the volume of anion exchanger A only when it is assumed that multiple beds of anion exchanger A and cation exchanger K are packed.

[0024] SV can be adjusted by several methods. If the flow area of ​​the anion exchanger-packed section is A and the height (layer thickness) of the anion exchanger-packed section in the flow direction is h, then V=A×h, and therefore SV=q / (A×h). Therefore, SV can be adjusted by adjusting at least one of the flow rate q, flow area A, and layer thickness h. Alternatively, although not shown, a circulation pipe may be provided that branches off from the mother pipe L1 downstream of the ion exchanger-packed device 35 and joins the mother pipe L1 upstream of the ion exchanger-packed device 35. During normal operation, a circulation operation is performed in which a part of the water to be treated is returned to the upstream side through the circulation pipe. When the SV of the ion exchanger-packed device 35 becomes equal to or greater than a predetermined value, the opening degree of the valve provided in the circulation pipe is adjusted to reduce the flow rate (or the valve is closed). The flow rate of the ion exchanger-packed device 35 decreases by the amount of the decrease in the flow rate of the circulation pipe, so that SV can also be adjusted by this method. The opening and closing of the valve and the opening degree may be adjusted by an operator or by a control device. As another method, a plurality of ion exchanger packing devices 35 may be installed in parallel, and water may be passed through only some of the ion exchanger packing devices 35 during normal operation. When the SV of the circulating ion exchanger packing device 35 reaches or exceeds a predetermined value, water may be passed through the other ion exchanger packing devices 35 as well.

[0025] (About dissolved oxygen concentration) Since the ultraviolet light irradiated from the ultraviolet light irradiation device 34 is easily absorbed by oxygen, if the dissolved oxygen concentration in the water to be treated is high, the reaction shown in formula (1) is difficult to occur, and the efficiency of generating OH radicals is reduced. The first deoxygenation device 33 adjusts the dissolved oxygen concentration in the water to be treated in the ultraviolet light irradiation device 34 to less than 1000 μg / L. This makes it difficult for the ultraviolet light to be consumed by the dissolved oxygen, improving the efficiency of generating OH radicals and improving the efficiency of decomposing organic matter. As will be described in the examples below, even if the dissolved oxygen concentration is reduced too much, the TOC reduction effect cannot be obtained. In addition, reducing the dissolved oxygen concentration may lead to an increase in the size of the first deoxygenation device 33 and an increase in operating costs. On the other hand, as can be understood from formula (1), a certain amount of dissolved oxygen or more is necessary to increase the efficiency of decomposing organic matter (or to efficiently generate OH radicals). From the above, the dissolved oxygen concentration is preferably 1 μg / L or more, and more preferably 5 μg / L or more. Details will be described in the examples.

[0026] (About TOC) If the TOC and dissolved oxygen concentration in the water to be treated by the ultraviolet irradiation device 34 are high, the hydrogen peroxide concentration in the water to be treated by the ultraviolet irradiation device 34 may become high. For this reason, it is preferable to adjust the dissolved oxygen concentration in the water to be treated by the ultraviolet irradiation device 34 as described above, and to adjust the TOC in the water to be treated by the ultraviolet irradiation device 34 to 5 μg / L or less. The TOC can be adjusted by an ion removal device located upstream of the ultraviolet irradiation device 34. Examples of ion removal devices include a reverse osmosis membrane device 32 and an ion removal device 31.

[0027] (Hydrogen peroxide removal rate) The hydrogen peroxide removal rate of the ion exchanger filling device 35 is preferably 10% or more. This can reduce the possibility that the hydrogen peroxide concentration at the point of use will exceed the allowable value, for example. Since the subsystem generally includes an ultraviolet irradiation device, if the hydrogen peroxide removal rate is lower than 10%, the TOC reduction effect of the ultraviolet irradiation device of the subsystem may decrease. This is because hydrogen peroxide may inhibit the TOC reduction effect of the downstream ultraviolet irradiation device. Generally, supplying hydrogen peroxide to the ultraviolet irradiation device promotes the generation of OH radicals, but the TOC reduction effect may decrease depending on the conditions. On the other hand, as described in the examples, the hydrogen peroxide removal rate can be increased by reducing the SV, but reducing the SV to increase the hydrogen peroxide removal rate may lead to an increase in the size of the ion exchanger filling device 35 and an increase in the TOC of the treated water. Therefore, the upper limit of the hydrogen peroxide removal rate is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less.

[0028] Second Embodiment FIG. 2 shows a schematic configuration of a water treatment device 1 according to a second embodiment of the present invention. The water treatment device 1 of this embodiment has a platinum group catalyst filling device 37 located downstream of the ion exchanger filling device 35 and upstream of the second deoxygenation device 36. The second embodiment is the same as the first embodiment except for this point. The platinum group catalyst filling device 37 supports a platinum group catalyst such as palladium (Pd) and can have the same configuration as the platinum group catalyst filling device described as an example of the first deoxygenation device 33. By contacting the water to be treated with the platinum group catalyst, the hydrogen peroxide concentration in the water to be treated can be further reduced. Note that a hydrogen addition section (not shown) may be provided upstream of the platinum group catalyst filling device 37 to reduce the dissolved oxygen concentration. As an alternative configuration, an ion exchanger supporting a metal catalyst such as palladium may be filled in the EDI. In this case, hydrogen generated at the cathode of the EDI can be used as hydrogen to be contacted with the metal catalyst.

[0029] As described above, platinum group catalysts are generally expensive, but most of the hydrogen peroxide is removed by the ion exchanger filling device 35 provided upstream of the platinum group catalyst filling device 37, thereby reducing the hydrogen peroxide concentration in the water supplied to the platinum group catalyst filling device 37 downstream of the ion exchanger filling device 35. This makes it possible to reduce the size of the platinum group catalyst filling device 37, and also prevents an increase in the cost of the water treatment device 1.

[0030] (Third embodiment) Next, the third embodiment will be described focusing on the differences from the first embodiment. The omitted configuration and effects are the same as those of the first embodiment. FIG. 3(a) shows a schematic configuration of a water treatment device 1 according to a third embodiment of the present invention. The water treatment device 1 of this embodiment has a dissolved oxygen concentration measuring device 38 that measures the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34, a hydrogen peroxide concentration measuring device 39 that measures the hydrogen peroxide concentration in the water to be treated in the ion exchanger filling device 35, and a TOC measuring device 40 that measures the TOC in the water to be treated in the ion exchanger filling device 35. The hydrogen peroxide concentration measuring device 39 and the TOC measuring device 40 are provided downstream of the second deoxygenation device 36, but they can also be provided between the ion exchanger filling device 35 and the second deoxygenation device 36. In this embodiment, it is also preferable to adjust the TOC in the water to be treated in the ultraviolet irradiation device 34 to 5 μg / L or less.

[0031] The ion exchanger filling device 35 is filled with ion exchangers. Unlike the first and second embodiments, the ion exchanger filling device 35 is mainly intended to remove organic matter, not hydrogen peroxide, and therefore preferably contains both an anion exchanger and a cation exchanger. However, the ion exchanger filling device 35 may contain only either an anion exchanger or a cation exchanger.

[0032] As shown in FIG. 3(b), in this embodiment, as in the second embodiment, a platinum group catalyst packing device 37 for removing hydrogen peroxide can be provided downstream of the ion exchanger packing device 35. In particular, when the ion exchanger packing device 35 contains an anion exchanger, hydrogen peroxide is removed by the ion exchanger packing device 35 as described above, so that the load of the platinum group catalyst packing device 37 for removing hydrogen peroxide is reduced. This enables treatment at a high flow rate (high SV), and reduces treatment costs. Although the hydrogen peroxide concentration measuring device 39 and the TOC measuring device 40 are provided downstream of the second deoxidizer 36, they can also be provided between the ion exchanger packing device 35 and the platinum group catalyst packing device 37 or between the platinum group catalyst packing device 37 and the second deoxidizer 36.

[0033] 4 conceptually shows the relationship between the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34 and the hydrogen peroxide concentration and TOC in the outlet water of the ion exchanger filling device 35. As described above, ultraviolet light is easily absorbed by oxygen, so if the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34 is high, the reaction shown in formula (1) is less likely to occur. As a result, the efficiency of OH radical production decreases and the hydrogen peroxide concentration decreases. On the other hand, if the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34 is low, the reaction shown in formula (1) is promoted, and the OH radicals increase, causing the hydrogen peroxide concentration to increase.

[0034] In this embodiment, this principle is used to adjust the hydrogen peroxide concentration in the treated water of the ion exchanger filling device 35. The first deoxygenation device 33 adjusts the dissolved oxygen concentration measured by the dissolved oxygen concentration measuring device 38 based on the hydrogen peroxide concentration measured by the hydrogen peroxide concentration measuring device 39, specifically, so that the hydrogen peroxide concentration measured by the hydrogen peroxide concentration measuring device 39 is lower than a predetermined value. For example, when an operator manually operates the first deoxygenation device 33, if the hydrogen peroxide concentration measured by the hydrogen peroxide concentration measuring device 39 exceeds a target value or is determined to be likely to exceed the target value, the output of the vacuum pump of the first deoxygenation device 33 is reduced, and the dissolved oxygen concentration in the treated water of the first deoxygenation device 33 is increased. The change in the dissolved oxygen concentration can be confirmed by the dissolved oxygen concentration measuring device 38. When the first deoxygenation device 33 is operated automatically, a control device (not shown) adjusts the output (dissolved oxygen concentration) of the vacuum pump of the first deoxygenation device 33 according to the measurement value of the hydrogen peroxide concentration measuring device 39 so that the hydrogen peroxide concentration measured by the hydrogen peroxide concentration measuring device 39 is within an appropriate range.

[0035] On the other hand, if the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34 is too high, ultraviolet light is excessively absorbed by oxygen, and the efficiency of generating OH radicals decreases. As a result, if the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34 is higher than necessary, the TOC in the treated water in the ion exchanger filling device 35 increases, as shown in Figure 4. Conversely, if the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiation device 34 is low, the TOC in the treated water in the ion exchanger filling device 35 decreases. In other words, the hydrogen peroxide concentration and TOC in the treated water of the ion exchanger filling device 35 have a relationship in which an increase in one causes a decrease in the other.

[0036] The first deoxidizer 33 adjusts the dissolved oxygen concentration measured by the dissolved oxygen measuring device 38 based on the hydrogen peroxide concentration measured by the hydrogen peroxide concentration measuring device 39 and the TOC measured by the TOC measuring device 40, specifically so that both are equal to or less than a predetermined value. The predetermined value of the hydrogen peroxide concentration is preferably 40 μg / L. As described above, when an ultraviolet ray irradiation device is provided downstream, if the hydrogen peroxide concentration is high, the TOC reduction effect of the ultraviolet ray irradiation device downstream may be hindered. In addition, when a hydrogen peroxide removal means is provided downstream, the load on the hydrogen peroxide removal means increases. The predetermined value of the TOC is not particularly limited, but is preferably 2 μg / L, and more preferably 1 μg / L. The first deoxidizer 33 adjusts the dissolved oxygen concentration to 20 μg / L or more and 100 μg / L or less, more preferably 20 μg / L or more and 60 μg / L or less, and even more preferably 20 μg / L or more and 40 μg / L or less.

[0037] Example 1 The hydrogen peroxide removal performance was evaluated by irradiating ultraviolet rays to the water to be treated, which contained dissolved oxygen and organic matter, and then passing the ultraviolet-irradiated water through an ion exchange resin packing device. FIG. 5 is a schematic diagram of the test device. A first membrane degassing device 41 and a second membrane degassing device 42 were arranged in series, and an ultraviolet irradiation device 43 and an ion exchange resin packing device 44 were arranged downstream of the first membrane degassing device 42. A dissolved oxygen meter (Orbisphere, manufactured by HACH) was installed between the second membrane degassing device 42 and the ultraviolet irradiation device 43 to measure the dissolved oxygen concentration of the inlet water of the ultraviolet irradiation device 43. The ion exchange resin packing device 44 was packed with multiple beds of anion exchange resin (AMBERJET4002OH type, manufactured by Organo Corporation) on the upstream side and cation exchange resin (AMBERJET1024 H type, manufactured by Organo Corporation) on the downstream side. The TOC in the inlet water of the first membrane degassing device 41 was 2 μg / L, and the hydrogen peroxide concentration was 10 μg / L.

[0038] The dissolved oxygen concentration in the inlet water of the ultraviolet irradiation device 43 was adjusted to 20 μg / L, 60 μg / L, and 100 μg / L. The adjustment of the dissolved oxygen concentration was performed using a method of bypassing either the first membrane degassing device 41 or the second membrane degassing device 42, a method of adjusting the degree of vacuum in the first membrane degassing device 41 and the second membrane degassing device 42 with a vacuum pump inverter, and a method of stopping the vacuum pump and supplying oxygen. The water to be treated thus prepared was supplied to the ultraviolet irradiation device 43. A low-pressure ultraviolet oxidation device JPW (manufactured by Japan Photoscience Co., Ltd.) was used as the ultraviolet irradiation device 43, and the irradiation amount was 0.07 kWh / m 3 The water to be treated was irradiated with ultraviolet rays. The flow rate of water passing through the ion exchange resin packing device 44 was changed using the blow line 45 provided at the inlet of the ion exchange resin packing device 44, and the SV for the anion exchange resin was changed to 60, 80, 100, 120, 140, 160, and 180 ( / h).

[0039] The hydrogen peroxide concentrations in the inlet water of the ion exchange resin charging device 44 and the treated water were measured to evaluate the hydrogen peroxide removal performance of the ion exchange resin charging device 44. The hydrogen peroxide concentration was measured by absorbance method using the phenolphthalein method. Figure 6 shows the relationship between SV and the hydrogen peroxide concentration in the treated water, and the relationship between SV and the hydrogen peroxide removal rate. The hydrogen peroxide removal rate was calculated using the formula shown in Figure 3 from the hydrogen peroxide concentration H1 of the inlet water of the ion exchange resin charging device 44 and the hydrogen peroxide concentration H2 of the treated water.

[0040] The hydrogen peroxide concentration H1 in the inlet water of the ion exchange resin filling device 44 (treated water of the ultraviolet irradiation device 43) was 41 μg / L when the dissolved oxygen concentration in the inlet water of the ultraviolet irradiation device 43 was 20 μg / L, 32 μg / L when the dissolved oxygen concentration was 60 μg / L, and 29 μg / L when the dissolved oxygen concentration was 100 μg / L. There was a tendency that the hydrogen peroxide concentration increased as the dissolved oxygen concentration decreased. However, by setting the SV for the anion exchanger to less than 160 ( / h), the hydrogen peroxide concentration H2 of the treated water could be reduced. By setting the SV to 120 ( / h) or less, the hydrogen peroxide removal rate was about 10% or more, and by setting the SV to 100 ( / h) or less, the hydrogen peroxide removal rate was about 20%. The SV is preferably 100 ( / h) or less, more preferably 90 ( / h) or less, and even more preferably 80 ( / h) or less.

[0041] Example 2 The SV for the anion exchanger was fixed at 80 ( / h), and the dissolved oxygen concentration was adjusted to 1, 5, 10, 20, 60, 100, 1000, and 8000 μg / L to evaluate the organic matter removal performance (TOC reduction rate). In the case of high dissolved oxygen concentration, oxygen was supplied to the treated water through a degassing membrane. Figure 7 shows the relationship between the dissolved oxygen concentration in the inlet water of the ultraviolet irradiation device 43 and the TOC reduction rate. The TOC reduction rate was calculated from the TOC T1 at the inlet of the ultraviolet irradiation device 43 and the TOC T2 of the treated water at the ion exchange resin filling device 44 using the formula shown in Figure 3. TOC was measured using a Sievers TOC meter M500e (manufactured by SUEZ). The TOC reduction rate did not change significantly when the dissolved oxygen concentration was 1000 to 8000 μg / L, but increased as the concentration decreased below 1000 μg / L, saturated at about 10 μg / L, and did not change significantly when the concentration was 1 to 10 μg / L. Therefore, the dissolved oxygen concentration in the inlet water of the ultraviolet irradiation device 43 is preferably less than 1000 μg / L, more preferably 100 μg / L or less, even more preferably 60 μg / L or less, and even more preferably 20 μg / L or less.

[0042] Example 3 Water to be treated, which contained dissolved oxygen and organic matter, was irradiated with ultraviolet light, and the ultraviolet-irradiated water to be treated was then passed through an ion exchanger packing device to evaluate the performance of removing hydrogen peroxide and organic matter. FIG. 8 is a schematic diagram of the test device. Using the same method as in Example 1, the dissolved oxygen concentration in the water to be treated in the ultraviolet irradiator 43 was adjusted to 20 μg / L, 50 μg / L, 100 μg / L, and 1000 μg / L. The SV of the ion exchanger packing device 44 was set to 50 ( / h). The same ultraviolet irradiator as in Examples 1 and 2 was used, with an irradiation dose of 0.07 kWh / m. 3 The water to be treated was irradiated with ultraviolet rays. The ion exchange resin packing device 44 was packed with multiple beds of the same cation exchange resin and anion exchange resin as in Example 1. The TOC in the inlet water of the first membrane degassing device 41 was 2 μg / L. The hydrogen peroxide concentration in the treated water of the ion exchange resin packing device 44 was measured with a hydrogen peroxide monitor meter (OROXIDE manufactured by Organo Corporation), and the TOC in the treated water of the ion exchange resin packing device 44 was measured with the same TOC meter as in Example 2.

[0043] 9 shows the relationship between the dissolved oxygen concentration of the water to be treated by the ultraviolet irradiation device 43 and the hydrogen peroxide concentration of the water to be treated by the ion exchange resin filling device 44. The hydrogen peroxide concentration was 33 μg / L when the dissolved oxygen concentration was 20 μg / L, 28 μg / L when the dissolved oxygen concentration was 50 μg / L, 23 μg / L when the dissolved oxygen concentration was 100 μg / L, and 21 μg / L when the dissolved oxygen concentration was 1000 μg / L, and there was a tendency for the hydrogen peroxide concentration to increase as the dissolved oxygen concentration was lowered. This shows that the hydrogen peroxide concentration of the water to be treated by the ion exchange resin filling device 44 can be adjusted by adjusting the dissolved oxygen concentration of the water to be treated by the ultraviolet irradiation device 43.

[0044] On the other hand, the TOC in the treated water from the ion exchange resin charging device 44 tended to decrease as the dissolved oxygen concentration of the water to be treated from the ultraviolet irradiation device 43 was reduced. If the target value of the hydrogen peroxide concentration in the treated water from the ion exchange resin charging device 44 was 30 μg / L and the target value of the TOC was 1.0 g / L, when the dissolved oxygen concentration of the water to be treated from the ultraviolet irradiation device 43 was 20 μg / L, the TOC was below the reference value but the hydrogen peroxide concentration exceeded the reference value. When the dissolved oxygen concentration of the water to be treated from the ultraviolet irradiation device 43 was 100 μg / L and 1000 μg / L, the hydrogen peroxide concentration was below the reference value but the TOC exceeded the reference value. When the dissolved oxygen concentration of the water to be treated from the ultraviolet irradiation device 43 was 50 μg / L, both the hydrogen peroxide concentration and the TOC were below the reference value. Note that the reference value is an example for explaining this embodiment, and as described above, it is preferable that the dissolved oxygen concentration is 20 μg / L or more and 100 μg / L or less.

[0045] Although the present invention has been described above with reference to the embodiment and examples, the present invention is not limited to these embodiment and examples. For example, the present invention can be applied to a subsystem of an ultrapure water production system. [Explanation of symbols]

[0046] 1 Water treatment equipment 33 First Deoxygenation Device 34 Ultraviolet irradiation device 35 Ion exchanger filling device 36 Second Deoxidizer 37 Platinum group catalyst filling equipment 38 TOC measuring device 39 Hydrogen peroxide concentration measuring device 40 TOC measuring device A Anion Exchanger K cation exchanger

Claims

1. Removing dissolved oxygen from water to be treated, the water containing dissolved oxygen and organic matter, by a first deoxygenation device; irradiating the treated water from the first deoxygenation device with ultraviolet light by an ultraviolet irradiation device; and passing the treated water from the ultraviolet irradiation device through an ion exchanger-packed device packed with at least an anion exchanger, The ion exchanger filling device removes hydrogen peroxide generated by irradiation of ultraviolet rays from the ultraviolet irradiation device from the treated water of the ultraviolet irradiation device, The water treated by the ultraviolet irradiation device is passed through the anion exchanger of the ion exchanger packing device at a space velocity of 40 ( / h) or more and less than 100 ( / h).

2. A water treatment method as described in claim 1, wherein the treated water from the ultraviolet irradiation device is passed through the anion exchanger of the ion exchanger filling device at a spatial velocity of 40 ( / h) or more and 90 ( / h) or less.

3. 2. The water treatment method according to claim 1, wherein the dissolved oxygen concentration in the water to be treated supplied from the first deoxygenation device to the ultraviolet irradiation device is less than 1000 μg / L.

4. 2. The water treatment method according to claim 1, wherein the dissolved oxygen concentration in the water to be treated supplied from the first deoxygenation device to the ultraviolet irradiation device is 1 μg / L or more and 100 μg / L or less.

5. 2. The water treatment method according to claim 1, wherein the total organic carbon in the water to be treated supplied to the ultraviolet irradiation device from an ion removal device located upstream of the ultraviolet irradiation device is 5 μg / L or less.

6. 2. The water treatment method according to claim 1, wherein the hydrogen peroxide removal rate of the ion exchanger-packed device is 10% or more.

7. 7. The water treatment method according to claim 1, wherein the treated water from the ion exchanger-packed device is treated in a second deoxygenation device located downstream of the ion exchanger-packed device.

8. a first deoxygenation device for removing dissolved oxygen from the water to be treated, the dissolved oxygen and organic matter being contained therein; an ultraviolet ray irradiation device located downstream of the first deoxygenation device and irradiating ultraviolet rays onto the treated water of the first deoxygenation device; an ion exchanger packing device that is located downstream of the ultraviolet irradiator and is packed with at least an anion exchanger, A water treatment device, wherein the space velocity of the treated water of the ultraviolet irradiator passed through the anion exchanger of the ion exchanger-packed device is 40 ( / h) or more and less than 100 ( / h).

9. A method for designing a water treatment device comprising: a first deoxygenation device for removing dissolved oxygen from water to be treated, the dissolved oxygen and organic matter being contained in the water; an ultraviolet irradiation device located downstream of the first deoxygenation device for irradiating treated water by the first deoxygenation device with ultraviolet light; and an ion exchanger packing device located downstream of the ultraviolet irradiation device and packed with at least an anion exchanger, A method for designing a water treatment device, comprising: designing the water treatment device so that the spatial velocity of the treated water of the ultraviolet irradiation device passed through the anion exchanger of the ion exchanger filling device is 40 ( / h) or more and less than 100 ( / h).

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