Water treatment system, method for producing pure water, and water treatment method.

Abstract

To remove persistent organic matter further effectively.SOLUTION: A pure water producing system 1A (water treatment system) includes halogen oxo acid adding means 21 for adding halogen oxo acid to treated water containing organic matter, and an ion exchanger filling apparatus 14 which is located downstream of the halogen oxo acid adding means 21 and filled with at least an anion exchanger. Treated water to which halogen oxo acid is added is made to pass through the ion exchanger filling apparatus 14.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water treatment system, a method for producing pure water, and a water treatment method.

Background Art

[0002] With the increasing demand for high-quality pure water, in recent years, methods for decomposing and removing trace amounts of organic substances contained in pure water, particularly refractory organic substances such as urea, have been studied. Patent Documents 1 and 2 disclose a method for removing urea by adding sodium bromide and sodium hypochlorite to the water to be treated containing urea and allowing the water to be treated to stay in a reaction tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The methods disclosed in Patent Documents 1 and 2 require the water to be treated to stay in the reaction tank for a long time and cannot efficiently remove urea. An object of the present invention is to provide a water treatment system capable of more effectively removing refractory organic substances.

Means for Solving the Problems

[0005] The water treatment system of the present invention includes a halogen oxoacid adding means for adding a halogen oxoacid to the water to be treated containing organic substances, and an ion exchanger filling device located downstream of the halogen oxoacid adding means and filled with at least an anion exchanger. Between the halogen oxoacid adding means and the ion exchanger filling device, there is a water treatment device having a liquid contact part made of an organic material and removing impurities contained in the water to be treated. and activated carbon andIt is not provided. The water to be treated, to which halogen oxoacid has been added, is passed through the ion exchange packing device. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a water treatment system that can more effectively remove recalcitrant organic matter. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of the pure water production apparatus according to the first embodiment. [Figure 2] This is a schematic diagram of a pure water production apparatus according to the second embodiment. [Figure 3] This is a schematic diagram of a pure water production apparatus according to the third embodiment. [Figure 4] This is a schematic diagram of the pure water production apparatus according to the fourth embodiment. [Figure 5] This is a schematic diagram of a pure water production apparatus according to the fifth embodiment. [Figure 6] This is a schematic diagram of a pure water production apparatus according to the sixth embodiment. [Figure 7] This is a schematic diagram of the pure water production apparatus according to the seventh embodiment. [Figure 8] This graph shows the relationship between the spatial velocity of the treated water and the urea removal rate. [Figure 9] This graph shows the relationship between the water flow time and the urea removal rate. [Modes for carrying out the invention]

[0008] The water treatment system, pure water production method, and embodiments of the water treatment method of the present invention will be described below with reference to the drawings. Figure 1 shows a schematic configuration of a pure water production apparatus 1A according to the first embodiment of the present invention. The pure water production apparatus 1A is an example of a water treatment system. The pure water production apparatus 1A (primary system), together with the downstream subsystem (secondary system), constitutes an ultrapure water production apparatus. The raw water supplied to the pure water production apparatus 1A (hereinafter referred to as the water to be treated) contains organic matter including urea.

[0009] The pure water production apparatus 1A includes a filter 11, an activated carbon column 12, a first ion exchange apparatus 13, an ion exchange material packing apparatus 14, a reverse osmosis membrane apparatus 15, an ultraviolet irradiation apparatus (ultraviolet oxidation apparatus) 16, a second ion exchange apparatus 17, and a degasser 18, which are arranged in series along the main pipe L1 in this order from upstream to downstream with respect to the flow direction D of the water to be treated. After the water to be treated is pressurized by a raw water pump (not shown), relatively large particles of dust and other debris are removed in the filter 11, and impurities such as high molecular weight organic matter are removed in the activated carbon column 12. The configuration of the filter 11 is not limited, but in this embodiment a sand filter is used. The first ion exchange apparatus 13 includes a cation column (not shown) filled with cation exchange resin, a decarboxylation column (not shown), and an anion column (not shown) filled with anion exchange resin, which are arranged in series in this order from upstream to downstream. The treated water has its cation components removed in a cation tower, its carbon dioxide removed in a decarbonation tower, and its anionic components removed in an anionic tower.

[0010] The pure water production apparatus 1A has a halogen oxoacid addition means 21 for adding halogen oxoacids to the water to be treated, which contains urea. Halogen oxoacids may exist as ions or acids depending on the pH. Halogen oxoacids are a general term encompassing these forms. In this embodiment, the halogen oxoacid is hypohalous acid, but halogen acids, perhalous acids, halogenous acids, etc., may also be used. In terms of stability, hypohalous acid is preferred. In this embodiment, the hypohalous acid is hypobromous acid, but hypochlorous acid or hypoiodic acid may also be used. In addition to halogen oxoacids, substances that can be measured with a general residual chlorine meter, such as combined chlorine or combined bromine, can also be used, but halogen oxoacids are preferred in terms of urea removal efficiency. The halogen oxoacid addition means 21 includes a storage tank 21a for bromide salt (means for supplying bromide salt), a storage tank 21b for oxidizing agent (means for supplying oxidizing agent), a retention tank 21c for bromide salt and oxidizing agent (means for mixing bromide salt and oxidizing agent), and a transfer pump 21d. Examples of bromide salts include sodium bromide (NaBr) and potassium bromide. Examples of oxidizing agents include hypochlorite (e.g., sodium hypochlorite (NaClO)), permanganate, hydrogen peroxide, and persulfate. Since hypobromous acid is difficult to store for long periods, it is produced by mixing bromide salt and oxidizing agent according to the timing of use. The hypobromous acid produced in the retention tank 21c is pressurized by the transfer pump 21d and added to the water to be treated passing through the main pipe L1. Alternatively, the bromide salt and oxidizing agent may be directly supplied to the main pipe L1, and these may be agitated by the flow of the water to be treated in the main pipe L1 to produce hypobromous acid. The hypobromous acid may be added to the water to be treated continuously or intermittently. Alternatively, a line mixer or orifice may be installed in the main pipe L1, and turbulence may be created using these devices to mix the bromide salt and oxidizing agent to produce hypobromous acid. Only one type of halogen oxoacid may be added, or a mixture of two or more types of halogen oxoacids may be added.

[0011] The concentration of halogen oxoacid is preferably 6 to 200 times the TOC (total organic carbon) in the treated water, and more preferably 30 times or more. Adding halogen oxoacid exceeding 200 times the TOC increases the load on downstream equipment. As shown in Example 5 below, depending on the required water quality, adding 6 times the weight of halogen oxoacid may be sufficient to achieve a sufficient urea removal effect. Also, as will be described in Example 4 below, the concentration of divalent anions in the treated water is preferably in the range of 0 to 0.4 mmol / L. The concentration of halogen oxoacid, TOC, and divalent anion concentration in the treated water are values ​​at the inlet of the ion exchanger packing device 14.

[0012] The connection point of the halogen oxoacid addition means 21 to the main pipe L1, that is, the point where halogen oxoacid is added to the water to be treated, is located between the first ion exchange device 13 and the ion exchanger packing device 14. In other words, the ion exchanger packing device 14 is located immediately downstream of the connection point of the halogen oxoacid addition means 21 to the main pipe L1, and the water to be treated to which halogen oxoacid has been added is immediately treated in the ion exchanger packing device 14. "Immediately downstream" means that there is no water treatment device having a wetted part made of organic material between the addition point of the halogen oxoacid addition means 21 and the ion exchanger packing device 14. The water treatment device is any device for removing impurities contained in the water to be treated, and includes filtration membranes such as reverse osmosis membranes, ultrafiltration membranes, and microfiltration membranes, as well as ion exchange devices and degassing devices, but does not include heat exchangers, pumps, valves, instruments, etc.

[0013] The ion exchanger packing device 14 is a column packed with at least an anion exchanger. The ion exchanger packing device 14 may also be further packed with a cation exchanger. In this case, the cation exchanger is packed in a mixed bed with the anion exchanger, but it may also be packed in a double bed, and in the latter case, it is preferable that the anion exchanger is upstream of the cation exchanger. As described in Example 1 below, from the viewpoint of urea removal efficiency, it is more preferable that the ion exchanger packing device 14 is packed with only anion exchangers. On the other hand, when the cation exchanger and anion exchanger are packed in a mixed bed, positively charged elutes flowing out from the anion exchanger can be adsorbed by the cation exchanger. Anion exchange resins and cation exchange resins are preferably used as the anion exchanger and cation exchanger, but monolithic or fibrous anion exchangers and cation exchangers can also be used. The ion exchange resin may be either gel type or MR type. The anion exchange resin is not limited and may be either a strongly basic resin or a weakly basic resin, and in the case of a strongly basic resin, it may be in OH form or Cl form, etc. Furthermore, the ion exchanger filling device 14 may be an electrodeionized water production device (EDI) filled with anion exchange resin.

[0014] By bringing the water to be treated, to which halogenated oxoacids have been added, into contact with anion exchangers packed in the ion exchanger packing device 14, urea can be efficiently removed in a short time. Most of the urea is removed in the few seconds to a few minutes that the water to be treated passes through the ion exchanger packing device 14. This is significantly faster than conventional reaction tanks, which require residence times on the order of several hours. Furthermore, while conventional reaction tanks require large equipment to ensure sufficient residence time for the water to be treated, the ion exchanger packing device 14 has a configuration similar to that of a general ion exchange device, making it more advantageous than a reaction tank in terms of installation space.

[0015] By contacting the treated water to which a halogen oxo acid, particularly hypohalous acid, is added with an anion exchanger in this way, the inventor considers the reason why urea can be efficiently removed in a short time as follows. When the halogen oxo acid contacts the anion exchanger, the halogen oxo acid ions are captured by the anion exchanger. As a result, the halogen oxo acid ions are concentrated inside the anion exchanger. In addition, since the treated water flows along the voids of the anion exchanger (in the case of resin, the gaps between the resins), urea tends to stay in the anion exchanger. From the above, the possibility of the halogen oxo acid ions contacting urea becomes high, and urea can be removed in a short time. Therefore, the ion exchanger filling device 14 needs to be filled with at least an anion exchanger in order to capture the halogen oxo acid ions.

[0016] A reducing agent adding means 22 is installed between the ion exchanger filling device 14 and the reverse osmosis membrane device 15. The reducing agent adding means 22 is a means for removing the halogen oxo acid remaining in the treated water. Hydrogen peroxide is used as the reducing agent, but a sulfite can be used. The reducing agent adding means 2 possess a storage tank 22a for the reducing agent and a transfer pump 22b. The reducing agent is pressurized by the transfer pump 22b and added to the treated water passing through the main pipe L1 between the ion exchanger filling device 14 and the reverse osmosis membrane device 15. The means for removing the halogen oxo acid is not limited to the reducing agent adding means 22 as long as it has the same effect, and for example, a platinum group metal catalyst carrier such as palladium (Pd), activated carbon, etc. may be used. Alternatively, these means for removing the halogen oxo acid may be combined in series.

[0017] The reverse osmosis membrane device 15 removes excess reducing agent. The reducing agent removal means may be an ion exchange resin, an electro-deionized water production device, an ultraviolet irradiation device, a platinum group metal catalyst carrier, etc., and these reducing agent removal means may be combined in series. The platinum group metal catalyst carrier is one in which a platinum group metal catalyst made of a platinum group metal is supported on an anion exchanger. As the anion exchanger, an anion exchange resin, a monolithic organic porous anion exchanger, etc. can be used. The platinum group metal catalyst decomposes a reducing agent such as hydrogen peroxide by its catalytic action. Examples of the platinum group metal include platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), etc., and one of these may be used alone, or two or more of them may be used in combination. Among these platinum group metals, Pt and Pd are preferred, and Pd is more preferred from the viewpoint of cost. The installation position of the platinum group metal catalyst carrier is not particularly limited as long as it is downstream of the reducing agent addition position, but the downstream of the second ion exchange device 17 described later is preferred. Since the anion component is removed by the second ion exchange device 17, the reducing agent removal performance of the platinum group metal catalyst is improved.

[0018] The ultraviolet irradiation device 16 irradiates the water to be treated with ultraviolet rays. As the ultraviolet irradiation device 16, for example, an ultraviolet lamp including at least any one of the wavelengths of 254 nm, 185 nm, and 172 nm can be used. The anion exchanger (and cation exchanger) filled in the ion exchanger filling device 14 deteriorates by contacting with a halogen oxoacid which is an oxidizing agent, and organic substances flow out into the water to be treated. These organic substances are decomposed by the reverse osmosis membrane device 15, the ultraviolet irradiation device 16, and the second ion exchange device 17 (cation exchanger). This will be described in detail below.

[0019] Halogenated oxoacids such as hypobromous acid have a strong oxidizing effect and can easily degrade membranes formed from organic materials, for example. Therefore, in principle, contacting halogenated oxoacids with organic structures such as anion exchangers, as in this embodiment, is undesirable because it easily leads to a deterioration of the water quality of the treated water due to the peeling of organic materials. On the other hand, the inventors of this application have discovered that urea can be removed quickly and efficiently by contacting the treated water to which halogenated oxoacids have been added with an anion exchanger. For this reason, in this embodiment, despite the problem of increased possibility of peeling of organic materials, the treated water to which halogenated oxoacids have been added is deliberately contacted with an anion exchanger. Then, in order to remove any organic matter that may be generated as a result in a subsequent process, a reverse osmosis membrane device 15, an ultraviolet irradiation device 16, and a second ion exchange device 17 are provided.

[0020] In other words, it can also be explained as follows. In this embodiment, the anion exchanger is essential for removing urea, so the anion exchanger in the ion exchanger packing device 14 is deliberately brought into contact with halogen oxoacid. However, other water treatment devices (such as organic membranes) that have wetted parts made of organic materials do not contribute to the removal of urea, or contribute little to the removal of urea, even when they are in contact with halogen oxoacid. Furthermore, contact with halogen oxoacid degrades the organic material, reducing the treatment performance of other components. For this reason, these water treatment devices are placed downstream of the ion exchanger packing device 14 so as not to come into contact with high concentrations of halogen oxoacid. In other words, in this embodiment, there is no water treatment device with wetted parts made of organic materials that comes into contact with the water to be treated to which halogen oxoacid has been added, between the part where halogen oxoacid is added to the water to be treated and the ion exchanger packing device 14. Downstream of the ion exchanger packing device 14, the halogen oxoacid concentration in the treated water decreases significantly due to the consumption of halogen oxoacids in the ion exchanger packing device 14 and the decomposition of halogen oxoacids by the reducing agent. Therefore, any deterioration of the water quality of the treated water due to the peeling or leaching of organic materials from each water treatment device downstream of the ion exchanger packing device 14, particularly downstream of the reducing agent addition means 22, is limited, if any. In short, in this embodiment, by limiting the water treatment devices having wetted parts made of organic materials that come into contact with halogen oxoacids to only those that are essential for urea removal, both the efficiency of urea removal and the suppression of organic material outflow are achieved.

[0021] The second ion exchange device 17, located downstream of the ultraviolet irradiation device 16, is a regenerative ion exchange resin tower filled with anion exchange resin and cation exchange resin. Decomposition products of organic matter generated in the water to be treated by ultraviolet irradiation are removed by the second ion exchange device 17. Subsequently, dissolved oxygen, carbon dioxide, etc., in the water to be treated are removed by the degasser 18.

[0022] Next, other embodiments of the pure water production apparatus of the present invention will be described with reference to Figures 2 to 7. The configurations and effects that are not described are the same as in the first embodiment. As can be seen from the second to sixth embodiments, the halogen oxoacid addition means 21 and the ion exchange packing device 14 are incorporated into the pure water production apparatus as an inseparable set, and the installation position of this set has a high degree of flexibility.

[0023] (Second embodiment) Figure 2 shows a schematic configuration of the pure water production apparatus 1B according to the second embodiment. Halogenated oxoacids are added to the treated water of the activated carbon column 12. Accordingly, the ion exchange packing device 14 is provided between the halogenated oxoacid addition section and the first ion exchange device 13. That is, on the main pipe L1, the activated carbon column 12, halogenated oxoacid addition section, ion exchange packing device 14, reducing agent addition section, and first ion exchange device 13 are arranged in series in this order from upstream to downstream with respect to the flow direction D of the water to be treated. In this embodiment as well, since there is no water treatment device having a wetted part made of organic material between the halogenated oxoacid addition section and the ion exchange packing device 14, deterioration of the water quality of the water to be treated due to peeling or leaching of organic material is prevented. Furthermore, components derived from the oxidizing agent (in this embodiment, bromide ions, chloride ions, and Na ions) and components derived from the reducing agent can be removed not only by the reverse osmosis membrane device 15 and the second ion exchange device 17, but also by the first ion exchange device 13. Therefore, the load on the water treatment device downstream of the first ion exchange device 13 can be reduced.

[0024] (Third embodiment) Figure 3 shows a schematic configuration of a pure water production apparatus 1C according to the third embodiment. Halogenated oxoacids are added at two locations, upstream and downstream of the filtration device 11. Specifically, a halogenated oxoacid addition means 21 is connected downstream of the filtration device 11. A reaction tank 20 is provided upstream of the filtration device 11, and another halogenated oxoacid addition means 23 is connected to the reaction tank 20. Although not shown in the figure, another halogenated oxoacid addition means 23 may be connected upstream of the reaction tank 20. The halogenated oxoacid addition means 21 and the other halogenated oxoacid addition means 23 share storage tanks 21a, 21b, retention tank 21c, and transfer pump 21d, but these facilities may be provided separately for the halogenated oxoacid addition means 21 and the other halogenated oxoacid addition means 23. Halogenated oxoacids are added to the water to be treated in the reaction tank 20, and the water to be treated remains in the reaction tank 20 for a predetermined time before being sent to the filtration device 11. Although the filtration device 11 is supplied with water to be treated that has a high concentration of halogen oxoacids, since the filtration device 11 is a sand filtration device, no deterioration occurs due to contact with halogen oxoacids. Furthermore, since halogen oxoacids can be removed by the activated carbon column 12, there is no need to provide a reducing agent addition means 22.

[0025] The configuration of the reaction tank 20 is basically the same as that of a conventional reaction tank. That is, the reaction tank 20 is equipped with a flow channel (not shown) inside, and urea is removed as the water to be treated flows along the flow channel for a predetermined time. However, in this embodiment, halogenated oxoacid is added again to the water to be treated that has flowed out of the reaction tank 20, so it is not necessary to remove all the urea in the reaction tank 20. Generally, the urea removal efficiency tends to decrease as the urea concentration decreases. For example, the time required to reduce the urea concentration to 10% of the initial concentration is about the same as the time required to reduce it from 10% to 1%. In this embodiment, since the reaction tank 20 only needs to roughly remove the urea, a long residence time is not required. Therefore, urea can be processed in a shorter time than in the conventional method, and the size of the reaction tank 20 can also be reduced. On the other hand, the amount of urea processed by the ion exchange packing device 14 is significantly reduced by the reaction tank 20, so the load on the ion exchange packing device 14 is reduced. This reduces the frequency of anion exchange (and cation exchange) replacement and also reduces the amount of organic matter generated due to the degradation of the anion exchange (and cation exchange). In this embodiment, the halogen oxo acid addition means 21 is connected to the main pipe L1 at the outlet of the filtration device 11. However, the position of the connection part of the halogen oxo acid addition means 21 is not limited to this, and the halogen oxo acid addition means 21 may be connected to the main pipe L1 at a position in other embodiments.

[0026] The reaction vessel 20 can be omitted. Furthermore, either the halogen oxoacid addition means 21 or the other halogen oxoacid addition means 23 may be provided, or both may be provided. For example, if the reaction vessel 20 is provided and only the other halogen oxoacid addition means 23 is provided as the halogen acid addition means, the halogen oxoacid not consumed in the reaction vessel 20 can be brought into contact with the anion exchanger packed in the ion exchanger packing device 14. Also, in this embodiment, as in the second embodiment, components derived from the oxidizing agent and components derived from the reducing agent can be removed in the first ion exchanger 13.

[0027] (Fourth embodiment) Figure 4 shows a schematic configuration of the pure water production apparatus 1D according to the fourth embodiment. Halogenated oxoacids are added upstream of the filtration apparatus 11. Accordingly, an ion exchange packing apparatus 14 is provided between the halogenated oxoacid addition section and the filtration apparatus 11. That is, on the main pipe L1, the halogenated oxoacid addition section, the ion exchange packing apparatus 14, the filtration apparatus 11, the activated carbon column 12, and the first ion exchange apparatus 13 are arranged in series in this order from upstream to downstream with respect to the flow direction D of the water to be treated. Since the filtration apparatus 11 is a sand filter, it is less affected by halogenated oxoacids as described above. Therefore, the filtration apparatus 11 may be provided between the halogenated oxoacid addition section and the ion exchange packing apparatus 14. In this embodiment, if a small amount of crushed material flows out from the anion exchanger of the ion exchange packing apparatus 14, it can be removed by the downstream filtration apparatus 11. Also, since halogenated oxoacids can be removed by the activated carbon column 12, there is no need to provide a reducing agent addition means 22. In this embodiment, as in the third embodiment, the reaction tank 20 can be provided upstream of the ion exchange packing device 14. Also in this embodiment, as in the second embodiment, components derived from the oxidizing agent and components derived from the reducing agent can be removed by the first ion exchange device 13.

[0028] (Fifth embodiment) Figure 5 shows a schematic configuration of the pure water production apparatus 1E according to the fifth embodiment. The filtration apparatus is integrated with the ion exchanger packing apparatus 114. Specifically, sand and ion exchangers are packed in a common tower in a multi-bed mixed bed. In this embodiment, it is possible to reduce the cost and installation area of ​​the apparatus. Also, in this embodiment, as in the second embodiment, components derived from oxidizing agents and components derived from reducing agents can be removed in the first ion exchanger 13. Since halogen oxoacids can be removed in the activated carbon tower 12, there is no need to provide a reducing agent addition means 22.

[0029] (Sixth embodiment) Figure 6 shows a schematic configuration of the pure water production apparatus 1F according to the sixth embodiment. The pure water production apparatus 1F of this embodiment is equipped with means for adjusting dissolved oxygen (deoxygenation device 18A, dissolved oxygen meter 19). The deoxygenation device 18A is located upstream of the halogen oxoacid addition means 21, specifically between the first ion exchange device 13 and the ion exchange material filling device 14. The halogen oxoacid addition section is located between the deoxygenation device 18A and the ion exchange material filling device 14. The deoxygenation device 18A adjusts the dissolved oxygen concentration of the water to be treated at the inlet of the ion exchange material filling device 14 to between 0.1 mg / L and 1 mg / L. A dissolved oxygen meter 19 is provided between the deoxygenation device 18A and the ion exchange material filling device 14. The dissolved oxygen meter 19 measures the dissolved oxygen concentration of the water to be treated at the outlet of the deoxygenation device 18A. The dissolved oxygen concentration measured by the dissolved oxygen meter 19 is sent to the control device 24 of the deoxygenation device 18A. Based on this dissolved oxygen concentration, the control device 24 controls the deoxygenation device 18A so that the dissolved oxygen concentration measured by the dissolved oxygen meter 19 is between 0.1 mg / L and 1 mg / L. As a result, the dissolved oxygen concentration of the water to be treated at the inlet of the ion exchanger filling device 14 is controlled to 1 mg / L or less.

[0030] The deoxygenation device 18A removes oxygen from the water to be treated, thereby reducing the dissolved oxygen concentration of the water. It is the same as or similar to the deaeration device 18 in the first to fifth embodiments. For this reason, the deaeration device 18 is omitted in this embodiment, but it can also be provided in the same position as in the first to fifth embodiments. The type of deoxygenation device 18A is not limited; for example, a vacuum deaeration device can be used. Generally, in a vacuum deaeration device, a gas-liquid contact material to increase the surface area of ​​water is filled into the deaeration tower, the gas pressure inside the deaeration tower is reduced by a vacuum pump, the pure water to be treated is placed under vacuum, and dissolved oxygen is removed. The dissolved oxygen concentration can be controlled by adjusting the vacuum level inside the deaeration tower using a vacuum pump. Furthermore, the deaeration performance can be improved by introducing nitrogen. In this case, the dissolved oxygen concentration can be controlled by adjusting the vacuum level and the nitrogen inflow rate (nitrogen partial pressure). A deoxygenation device using a deaeration membrane may also be used. In this case as well, a vacuum pump is used, similar to a vacuum deaeration device, and the dissolved oxygen concentration can be controlled by adjusting the vacuum level. These deoxygenation devices 18A may be installed in series in two or more stages. As another deoxygenation device 18A, a configuration in which hydrogen (H2) is added to the water to be treated and the water to be treated is brought into contact with a palladium (Pd) catalyst can be used. Oxygen can be removed by the reaction of oxygen with hydrogen in the palladium catalyst to form water.

[0031] Since the resin packed into the ion exchanger packing device 14 is a wetted part made of organic material, when an oxidizing agent such as halogen oxoacid comes into contact with such a wetted part, the resin in the wetted part oxidizes and deteriorates, reducing the quality of the treated water. In addition, the swelling of the resin due to oxidative deterioration increases the differential pressure of the water flow. The inventors have found that when the dissolved oxygen concentration exceeds 1 mg / L, oxidation by the oxidizing agent is promoted, resulting in a decrease in water quality and an increase in the differential pressure of the water flow. By adjusting the dissolved oxygen concentration of the water to be treated to 1 mg / L or less, the oxidizing power of the oxidizing agent is reduced, and the oxidative deterioration of the resin can be mitigated. There is no particular lower limit to the dissolved oxygen concentration of the water to be treated, but 0.1 mg / L or higher is preferable. If the dissolved oxygen concentration is less than 0.1 mg / L, the effect of preventing oxidative deterioration of the wetted part is small, or at least limited. Furthermore, lowering the dissolved oxygen concentration to less than 0.1 mg / L would lead to an increase in the size of the vacuum pump of the deoxygenation device 18A and an increase in the power cost of the vacuum pump, which is undesirable.

[0032] Although several embodiments have been described above, the pure water production apparatus of the present invention is not limited to these. For example, in the first to sixth embodiments, the first ion exchange device 13 may be omitted, and an EDI may be provided between the reverse osmosis membrane device 15 and the ultraviolet irradiation device 16. Also, in all of the above embodiments, multiple reverse osmosis membrane devices 15 may be provided in multiple stages or in series. In this case, a halogen oxoacid addition means 21, an ion exchanger packing device 14, and a reducing agent addition means 22 may be provided in this order between the preceding reverse osmosis membrane device and the succeeding reverse osmosis membrane device. In the sixth embodiment, the location of the dissolved oxygen adjustment means (deoxygenation device 18A, dissolved oxygen meter 19) is not particularly limited. For example, multiple reverse osmosis membrane devices 15 may be provided in series, with the dissolved oxygen adjustment means, halogen oxoacid addition means 21, ion exchanger packing device 14, and reducing agent addition means 22 provided in between. In other words, in Figure 6, another reverse osmosis membrane device 15 may be provided between the first ion exchange device 13 and the deoxygenation device 18A. In this case, the first ion exchange device 13 may be omitted.

[0033] Furthermore, for example, the halogen oxoacid addition means 21, the ion exchanger packing device 14, and the reducing agent addition means 22 may be provided downstream of the reverse osmosis membrane device 15. The second ion exchange device 17 may be an electrodeionized water production device (EDI). The present invention can also be used for the treatment of recovered water and wastewater.

[0034] (Seventh Embodiment) Furthermore, the technical concept shown in the sixth embodiment can be extended to water treatment systems that add oxidizing agents containing halogen oxoacids or oxidizing agents other than halogen oxoacids to the water to be treated. In other words, general water treatment equipment used in water treatment systems (reverse osmosis membranes, ion exchange resins, etc.) undergoes oxidative degradation when oxidizing agents flow in, significantly reducing their treatment performance. For this reason, it is common to install oxidizing agent removal means such as activated carbon towers upstream of the water treatment equipment or downstream of the part where the oxidizing agent is added to the water to be treated. However, activated carbon deteriorates over time, reducing its oxidizing agent removal performance, which can lead to the oxidizing agent flowing into downstream water treatment equipment. In addition, activated carbon itself can deteriorate oxidatively, causing organic matter to leach out and potentially burdening downstream equipment. This can lead to deterioration of downstream water treatment equipment and a decrease in the quality of pure water. Furthermore, disinfectants (oxidizing agents) are sometimes passed through water treatment equipment to the extent that they do not deteriorate, for the purpose of sterilizing the water treatment equipment. However, under certain conditions, the water treatment equipment may deteriorate oxidatively due to the disinfectant. Unlike activated carbon towers, methods that remove oxidizing agents by adding reducing agents have a lower likelihood of equipment deterioration over time; however, residual reducing agents can burden downstream water treatment equipment. In accelerated oxidation treatment (AOP) using oxidizing agents, residual oxidizing agents can also degrade resins and other components in downstream water treatment equipment.

[0035] Figure 7 shows a schematic configuration of the pure water production apparatus 1G according to the seventh embodiment. In this embodiment, a softening device 25 is provided instead of the first ion exchange device 13 of the sixth embodiment. Also, a more general oxidizing agent adding means 27 is provided instead of the halogen oxoacid adding means 21. The softening device 25 is a device that removes hardness components such as calcium and magnesium, and is generally filled with ion exchange resin. Since the reverse osmosis membrane device 15 is generally susceptible to accelerated oxidative degradation due to residual chlorine and the like in the presence of hardness, the softening device 25 is installed upstream of the reverse osmosis membrane device 15. The location of the softening device 25 is not limited as long as it is upstream of the reverse osmosis membrane device 15. An EDI 26 is provided between the reverse osmosis membrane device 15 and the ultraviolet irradiation device 16. If an oxidizing agent leaks into the treated water of the reverse osmosis membrane device 15, the treated water containing the oxidizing agent is passed through the EDI 26. However, since the deoxygenation device 18A adjusts the dissolved oxygen concentration of the water to be treated to 1 mg / L or less, oxidative degradation of the resin packed in the EDI 26 is suppressed, and stable treated water quality can be obtained. Note that the softening device 25 and EDI 26 are not essential in this embodiment. Although not shown in the figures, the pure water production apparatus is provided in the following order: filter 11, activated carbon tower 12, first ion exchange device 13, deoxygenation device 18A, dissolved oxygen meter 19, reverse osmosis membrane device 15, ultraviolet irradiation device (ultraviolet oxidation device) 16, second ion exchange device 17, and degassing device 18, and an oxidizing agent addition means 27 may be provided between the dissolved oxygen meter 19 and the reverse osmosis membrane device 15.

[0036] Therefore, the water treatment system comprises a water treatment device having wetted parts made of organic material, an oxidizing agent adding means located upstream of the water treatment device for adding an oxidizing agent to the water to be treated, and a deoxygenation device located upstream of the water treatment device for adjusting the dissolved oxygen concentration at the inlet of the water treatment device to 1 mg / L or less. Examples of the water treatment device include a reverse osmosis membrane device, an ion exchange device filled with ion exchange resin, or an EDI. The water treatment method comprises adding an oxidizing agent to the water to be treated by the oxidizing agent adding means upstream of the water treatment device having wetted parts made of organic material, and adjusting the dissolved oxygen concentration at the inlet of the water treatment device to 1 mg / L or less by the deoxygenation device located upstream of the water treatment device. The oxidizing agent is not limited to halogen oxoacids such as hypohalous acid, but may also be permanganate, hydrogen peroxide, persulfuric acid, or a disinfectant used in the water treatment device. The water to be treated may also contain free chlorine, combined chlorine, combined bromine, etc.

[0037] Furthermore, the present invention can also be applied when the oxidizing agent addition means 27 is omitted, and the oxidizing agent is not added by the oxidizing agent addition means 27, but the water to be treated contains an oxidizing agent. Alternatively, in the sixth embodiment, it is possible to omit the halogen oxo acid addition means 21 and the reducing agent addition means 22. In this case, the oxidative degradation of the ion exchange resin packed in the reverse osmosis membrane device 15 and EDI 26 is suppressed by the dissolved oxygen adjustment means (deoxygenation device 18A, dissolved oxygen meter 19).

[0038] Therefore, the water treatment system comprises a water treatment device to which water to be treated containing an oxidizing agent is supplied and which has wetted parts made of organic material, and a deoxygenation device located upstream of the water treatment device that adjusts the dissolved oxygen concentration of the water to be treated at the inlet of the water treatment device to 1 mg / L or less. The water treatment method comprises supplying water to be treated containing an oxidizing agent to a water treatment device having wetted parts made of organic material, and adjusting the dissolved oxygen concentration of the water to be treated at the inlet of the water treatment device to 1 mg / L or less.

[0039] (Example 1) The urea removal rate was measured by passing treated water, prepared by adding a halogenated oxoacid to ultrapure water, through a column simulating an ion exchange apparatus. 100 mL of ion exchange resin was packed into the column, and the treated water was passed through at a flow rate of 12 L / h (SV120( / h)). The amount of urea added was adjusted to achieve a urea concentration of 80 μg / L. Hypobromous acid was added as the halogenated oxoacid at a concentration of 2 mg-Cl2 / L (chlorine equivalent). NaBr was selected as the bromide salt, and NaClO as the oxidizing agent. Hypobromous acid was produced by mixing NaBr and NaClO. The concentration of hypobromous acid was measured using a residual salt concentration meter (HANNA) with a free chlorine reagent after adding glycine to the sample water to convert free chlorine to bound chlorine. In Comparative Example 1, only 100 mL of cation exchange resin was packed into the column. In Example 1-1, 100 mL of anion exchange resin alone was packed into the column. In Example 1-2, anion exchange resin and cation exchange resin were mixed and packed into the column in a volume ratio of 2:1, totaling 100 mL. AMBERJET 1024 H type (manufactured by Organo Corporation) was used as the cation exchange resin, and AMBERJET 4002 OH type (manufactured by Organo Corporation) was used as the anion exchange resin. The urea removal rate was calculated as (C1-C2) / C1 × 100 (%), where C1 was the urea concentration of the treated water at the column inlet and C2 was the urea concentration of the treated water in the column. The urea concentration was measured using ICP-MS (inductively coupled plasma mass spectrometer). The urea removal rates were 98% in Example 1-1, 95% in Example 1-2, and 0.5% in the comparative example. From this, it was found that urea can be efficiently removed by bringing the water to be treated, which contains hypobromite, into contact with an anion exchanger.

[0040] (Example 2) Using the same apparatus as in Example 1, the urea removal rate was determined using the space velocity of the water to be treated supplied to the column as a parameter. Specifically, the urea removal rate was determined for several SVs (120, 240, 500, 1000, 1200) (unit ( / h)) under the conditions of Example 1-1. The amount of anion exchange resin added was set to 100 mL for all SVs, and the flow rate of the water to be treated was varied. Figure 8 shows the relationship between SV and urea removal rate. The smaller the SV, the longer the contact time between the water to be treated and the anion exchanger, and therefore the higher the urea removal rate. The larger the SV, the lower the urea removal rate, but a removal rate of 44% was achieved even at SV 1200 ( / h), and depending on the required water quality of the pure water, this level may be sufficient. Therefore, it is preferable that the water to be treated is supplied to the ion exchange packing device 14 at a space velocity SV of 1200 ( / h) or less. If a urea removal rate of 70% or more is to be obtained, it is preferable that the SV be 500 ( / h) or less. If a urea removal rate of 90% or more is to be obtained, it is preferable that the SV be 240 ( / h) or less.

[0041] (Example 3) Using the same apparatus as in Example 1, the relationship between the urea removal rate and the time the treated water was passed through the ion exchange packing device 14 was determined. Specifically, urea and hypochlorous acid were added to ultrapure water under the same conditions as in Example 1-1 to prepare the treated water. This treated water was then subjected to BrO2. - Water was passed through at a flow rate of 120 L / h until the cumulative supply of urea reached approximately twice the ion exchange capacity of the anion exchange resin (the total flow time was approximately 700 hours). Figure 9 shows the relationship between the flow time and the urea removal rate. Although the anion exchange resin used was non-regenerative, it maintained a good urea removal rate even after prolonged water flow. Therefore, by making the ion exchanger packing device 14 non-regenerative, long-term operation is possible and regeneration is unnecessary.

[0042] (Example 4) Using the same apparatus as in Example 1, the relationship between the urea removal rate and the sulfate ion concentration of the treated water was determined. Specifically, 100 mL of ion exchange resin was packed into the column in the same manner as in Example 1-1, and the treated water was passed through at a flow rate of 12 L / h (SV120( / h)). The amount of urea added was adjusted so that the urea concentration was 80 μg / L. Hypobromous acid was added as a halogen oxoacid at a concentration of 2 mg-Cl2 / L (chlorine equivalent concentration). Furthermore, sulfuric acid was added to this treated water. This resulted in the divalent anion (SO4) being added to the treated water. 2- ) is included. The results are shown in Table 1. The urea removal rate decreases as the concentration of divalent anions increases. This is because when divalent anions are present, halogen oxoacids are less likely to be captured by the resin. However, a urea removal rate of 36% may be sufficient depending on the required water quality. Therefore, the concentration of divalent anions in the treated water is preferably 0.4 mmol / L or less, and more preferably 0.1 mmol / L or less.

[0043] [Table 1]

[0044] (Example 5) Using the same apparatus as in Example 1, the relationship between the urea removal rate and the halogen oxoacid concentration / TOC ratio (weight ratio) of the treated water was determined. Specifically, 100 mL of ion exchange resin was packed into the column in the same manner as in Example 1-1, and the treated water was passed through at a flow rate of 12 L / h (SV120( / h)). Hypobromous acid was used as the halogen oxoacid. Using urea and hypobromite, the ratio of the concentrations of urea and hypobromite was changed. The substance was added. The results are shown in Table 2. In the table, "Hypobromite / TOC ratio" is the halogen oxoacid concentration / TOC ratio, and the higher the hypobromite / TOC ratio, the better the urea removal rate. However, even a urea removal rate of 50% may be sufficient depending on the required water quality. Therefore, the halogen oxoacid concentration / TOC ratio of the treated water is preferably 6 times by weight or more, and more preferably 30 times by weight or more. As mentioned above, in order to suppress the impact on downstream equipment, it is preferable to keep the halogen oxoacid concentration / TOC ratio at 200 times by weight or less. Note that the TOC in this example is the value obtained by converting the urea concentration to TOC.

[0045] [Table 2]

[0046] (Example 6) Using the same apparatus as in Example 1, the relationship between dissolved oxygen concentration and the differential pressure through which the resin flows, and the relationship between dissolved oxygen concentration and TOC were determined. Specifically, the water to be treated, prepared by adding hypohalite to pure water, was passed through the column at a flow rate of 12 L / h (SV120( / h)) under the same conditions as in Example 1-1, and the urea removal rate was measured. The amount of urea added was adjusted so that the urea concentration was 80 μg / L. Hypobromous acid was added as hypohalite at a concentration of 2 mg-Cl2 / L (chlorine equivalent concentration). The differential pressure and the increase in TOC were measured after passing the water through for 250 hours, varying the dissolved oxygen concentration of the water to be treated. The increase in TOC was calculated by removing the urea-derived TOC from the TOC of the feed water and the TOC of the treated water, and then determining the difference between the TOC of the treated water (without urea-derived TOC) and the TOC of the feed water (without urea-derived TOC). The results are shown in Table 3. As mentioned above, the water flow differential pressure correlates with the degree of resin swelling; therefore, a low water flow differential pressure indicates that the resin is not swelling and is maintaining its integrity. Furthermore, lower water flow differential pressure also reduces the power cost of the pump. In all of Examples 6-1, 6-2, and Comparative Example 6, the urea removal rate was 90% or higher. By reducing the dissolved oxygen to 1 mg / L or less, the increase in TOC was suppressed, and no increase in water flow differential pressure was observed.

[0047] [Table 3]

[0048] (Example 7) Using the same apparatus as in Example 1, the relationship between dissolved oxygen concentration and the differential pressure through which the resin flows, and the relationship between dissolved oxygen concentration and TOC were determined. 100 mL of ion exchange resin was packed into the column, and the water to be treated was passed through at a flow rate of 12 L / h (SV120( / h)). Specifically, anion exchange resin and cation exchange resin were mixed and packed into the column in a volume ratio of 2:1, totaling 100 mL. 0.1 mg-Cl2 / L of hypochlorous acid was added to feedwater, which was pure water with dissolved oxygen, and passed through the column. AMBERJET 1024 H type (Organo Corporation) was used as the cation exchange resin, and AMBERJET 4002 OH type (Organo Corporation) was used as the anion exchange resin. The concentration of hypochlorous acid was measured using a residual salt concentration meter (HANNA). The TOC of the water to be treated at the column outlet was measured using a TOC meter (Sievers M9e). The differential pressure and TOC increment were measured by varying the dissolved oxygen concentration of the treated water. The TOC increment was calculated as the difference in TOC of the treated water at the column outlet and inlet. The results are shown in Table 4. In Examples 7-1 to 7-3, no increase in differential pressure was observed, and the TOC was 20 to 40 μg / L. In Comparative Example 7, a differential pressure of 0.2 MPa or more was generated, and the TOC was 100 μg / L.

[0049] [Table 4]

[0050] (Example 8) Using an EDI instead of an ion exchange resin column, the relationship between dissolved oxygen concentration and the differential pressure through the EDI, and the relationship between dissolved oxygen concentration and TOC were evaluated in the same manner as in Example 7. The EDI was equipped with a first desalination chamber and a second desalination chamber, and the water to be treated was passed through the first desalination chamber, followed by the second desalination chamber. The first desalination chamber was packed with anion exchange resin, and the second desalination chamber was packed with cation exchange resin. The concentration chamber was packed with a mixed bed of anion exchange resin and cation exchange resin. The flow rate through the first and second desalination chambers was 20 L / h, and the flow rate through the concentration chamber was 5 L / h, with a current value of 0.5 A. 0.1 mg-Cl2 / L of hypochlorous acid was added to feedwater, which was pure water with dissolved oxygen, and passed through the EDI. The results are shown in Table 5. The TOC increment was calculated as the difference in TOC of the water to be treated at the outlet and inlet of the EDI. In Examples 8-1 to 8-3, no increase in water flow differential pressure was observed, and the maximum increase in TOC was 2 μg / L. In Comparative Example 8, a water flow differential pressure of 0.1 MPa or more occurred, and the TOC was 14 μg / L.

[0051] [Table 5] [Explanation of symbols]

[0052] 1A~1G Pure water production equipment 11. Filter 12 Activated carbon tower 13. First ion exchange apparatus 14. Ion exchanger filling device 15 Reverse osmosis membrane equipment 16. Ultraviolet irradiation device (ultraviolet oxidation device) 17. Second ion exchange apparatus 18 Degassing device 18A Deoxygenation Unit 19. Dissolved oxygen meter 21. Means for adding halogen oxoacids 22. Means for adding reducing agent 23 Other methods for adding halogen oxoacids 27. Means for adding oxidizing agents

Claims

1. A halogen oxoacid addition method for adding halogen oxoacids to treated water containing organic matter, Located downstream of the halogen oxoacid addition means, the device includes an ion exchanger packing apparatus which is filled with at least an anion exchanger, Between the halogen oxoacid adding means and the ion exchange packing device, there is no water treatment device and activated carbon having a wetted part made of organic material that removes impurities contained in the water to be treated. A water treatment system in which the water to be treated, to which the halogen oxoacid has been added, is passed through the ion exchange packing device.

2. The water to be treated to which the halogen oxoacid has been added is supplied to the ion exchanger packing device at a space velocity of 1200 ( / h) or less, according to claim 1.

3. The water treatment system according to claim 1 or 2, wherein the ion exchanger filling device is of the non-regenerative type.

4. The water treatment system according to any one of claims 1 to 3, further comprising a halogen oxoacid removal means located downstream of the ion exchanger filling device.

5. The water treatment system according to any one of claims 1 to 4, wherein the dissolved oxygen concentration of the water to be treated at the inlet of the ion exchanger filling device is 1 mg / L or less.

6. The water treatment system according to claim 5, further comprising a deoxygenation device located upstream of the ion exchanger filling device, which adjusts the dissolved oxygen concentration of the water to be treated at the inlet of the ion exchanger filling device to 1 mg / L or less.

7. A dissolved oxygen meter for measuring the dissolved oxygen concentration of the water to be treated at the outlet of the deoxygenation device, A water treatment system according to claim 6, comprising: a control device that controls the deoxygenation device based on the dissolved oxygen concentration measured by the dissolved oxygen meter so that the dissolved oxygen concentration measured by the dissolved oxygen meter is 0.1 mg / L or more and 1 mg / L or less.

8. The water treatment system according to any one of claims 1 to 7, wherein the concentration of divalent anions in the water to be treated at the inlet of the ion exchanger filling device is 0.4 mmol / L or less.

9. The water treatment system according to any one of claims 1 to 8, wherein at the inlet of the ion exchanger-filling device, the concentration of the halogen oxoacid in the water to be treated is 6 to 200 times by weight of the total organic carbon in the water to be treated.

10. The water treatment system according to claim 9, wherein the water to be treated contains urea, and the total organic carbon of the water to be treated is the value obtained by converting the urea concentration in the water to be treated into total organic carbon.

11. The water treatment system according to any one of claims 1 to 10, wherein the halogen oxoacid is hypobromous acid.

12. By means of adding halogen oxoacids, halogen oxoacids are added to the water to be treated containing organic matter, The process involves passing the treated water to which the halogen oxoacid has been added through an ion exchanger filled with at least an anion exchanger, A method for producing pure water, wherein a water treatment device having a wetted part made of organic material for removing impurities contained in the water to be treated, and activated carbon are not provided between the halogen oxo acid adding means and the ion exchange packing device.

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